ArticlePDF Available

Challenges and Opportunities in Green Hydrogen Adoption for Decarbonizing Hard-to-Abate Industries: A Comprehensive Review

January 2024
IEEE Access PP(99):1-1

DOI:10.1109/ACCESS.2024.3363869

License
CC BY-NC-ND 4.0

Authors:

Jayachandran Mohanasundaram

Puducherry Technological University

Ranjih Kumar Gatla

Institute of Aeronautical Engineering

Aymen Flah

École Nationale d'Ingénieurs de Gabès

Ahmad H. Milyani

King Abdulaziz University

Show all 8 authorsHide

The decarbonization of hard-to-abate industries is crucial for keeping global warming to below 2°C. Green or renewable hydrogen, synthesized through water electrolysis, has emerged as a sustainable alternative for fossil fuels in energy-intensive sectors such as aluminum, cement, chemicals, steel, and transportation. However, the scalability of green hydrogen production faces challenges including infrastructure gaps, energy losses, excessive power consumption, and high costs throughout the value chain. Therefore, this study analyzes the challenges within the green hydrogen value chain, focusing on the development of nascent technologies. Presenting a comprehensive synthesis of contemporary knowledge, this study assesses the potential impacts of green hydrogen on hard-to-abate sectors, emphasizing the expansion of clean energy infrastructure. Through an exploration of emerging renewable hydrogen technologies, the study investigates aspects such as economic feasibility, sustainability assessments, and the achievement of carbon neutrality. Additionally, considerations extend to the potential for large-scale renewable electricity storage and the realization of net-zero goals. The findings of this study suggest that emerging technologies have the potential to significantly increase green hydrogen production, offering affordable solutions for decarbonization. The study affirms that global-scale green hydrogen production could satisfy up to 24% of global energy needs by 2050, resulting in the abatement of 60 gigatons of greenhouse gas (GHG) emissions - equivalent to 6% of total cumulative CO ₂ emission reductions. To comprehensively evaluate the impact of the hydrogen economy on ecosystem decarbonization, this article analyzes the feasibility of three business models that emphasize choices for green hydrogen production and delivery. Finally, the study proposes potential directions for future research on hydrogen valleys, aiming to foster interconnected hydrogen ecosystems.

Comparison of properties of hydrogen with other fossil fuels [32]-[37]

…

Various pathways for hydrogen production and associated development research actions [42]-[64]

…

Figures - available via license: Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International

Content may be subject to copyright.

Available via license: CC BY-NC-ND 4.0

Content may be subject to copyright.

Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000.

Digital Object Identiﬁer 10.1109/ACCESS.2017.DOI

Challenges and Opportunities in Green

Hydrogen Adoption for Decarbonizing

Hard-to-Abate Industries: A

Comprehensive Review

M. JAYACHANDRAN1*, RANJITH KUMAR GATLA2, AYMEN FLAH3,4,8 AHMAD H. MILYANI5,

HISHAM M. MILYANI6, VOJTECH BLAZEK7, LUKAS PROKOP7, HABIB KRAIEM9,

1Department of Electrical and Electronics Engineering, Puducherry Technological University, Puducherry

2Department of Electrical and Electronics Engineering, Institute of Aeronautical Engineering, Hyderabad

3Processes, Energy, Environment, and Electrical Systems, National Engineering School of Gabes, University of Gabes, Gabes 6029, Tunisia

4MEU Research Unit, Middle East University, Amman, Jordan

5Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia

6Department of Business Administration, The Applied College, King Abdulaziz University, Jeddah 21589, Saudi Arabia

7ENET Centre, VSB-Technical University of Ostrava, Czech Republic

8College of Engineering, University of Business and Technology (UBT), Jeddah 21448, Saudi Arabia

9Department of Electrical Engineering, College of Engineering, Northern Border University, Arar, Saudi Arabia

“This work was supported by the following project TN02000025 National Centre for Energy II.”

ABSTRACT The decarbonization of hard-to-abate industries is crucial for keeping global warming

to below 2oC. Green or renewable hydrogen, synthesized through water electrolysis, has emerged as a

sustainable alternative for fossil fuels in energy-intensive sectors such as aluminum, cement, chemicals,

steel, and transportation. However, the scalability of green hydrogen production faces challenges including

infrastructure gaps, energy losses, excessive power consumption, and high costs throughout the value chain.

Therefore, this study analyzes the challenges within the green hydrogen value chain, focusing on the de-

velopment of nascent technologies. Presenting a comprehensive synthesis of contemporary knowledge, this

study assesses the potential impacts of green hydrogen on hard-to-abate sectors, emphasizing the expansion

of clean energy infrastructure. Through an exploration of emerging renewable hydrogen technologies, the

study investigates aspects such as economic feasibility, sustainability assessments, and the achievement of

carbon neutrality. Additionally, considerations extend to the potential for large-scale renewable electricity

storage and the realization of net-zero goals. The ﬁndings of this study suggest that emerging technologies

have the potential to signiﬁcantly increase green hydrogen production, offering affordable solutions for

decarbonization. The study afﬁrms that global-scale green hydrogen production could satisfy up to 24% of

global energy needs by 2050, resulting in the abatement of 60 gigatons of greenhouse gas (GHG) emissions

- equivalent to 6% of total cumulative CO2emission reductions. To comprehensively evaluate the impact of

the hydrogen economy on ecosystem decarbonization, this article analyzes the feasibility of three business

models that emphasize choices for green hydrogen production and delivery. Finally, the study proposes

potential directions for future research on hydrogen valleys, aiming to foster interconnected hydrogen

ecosystems.

INDEX TERMS Green or Renewable hydrogen, Renewable electricity storage, Decarbonization, Hard-to-

abate industries, Carbon neutrality

I. INTRODUCTION

A. BACKGROUND

Green hydrogen has emerged as a promising solution in the

global effort to achieve climate neutrality and meet the ambi-

tious target of limiting global warming to 1.5°C, particularly

in the industrial, shipping, and aviation sectors [1]. Produced

through water electrolysis using renewable electricity, green

hydrogen has the potential to signiﬁcantly reduce greenhouse

VOLUME 4, 2016 1

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

gas emissions and mitigate the adverse impacts of climate

change [2], [3]. However, there are several challenges that

must be addressed to realize the full potential of a green

hydrogen economy, including the high cost of renewable

electricity, elevated production costs, limited value chain

infrastructure, and the need for international standards [4].

Technological advancements in green hydrogen are crucial

for decarbonizing the hardest and most expensive industry

sectors and meeting the growing demand for renewable

power. Moreover, the integration of green hydrogen in the

transportation sector can provide signiﬁcant sustainability

beneﬁts, complementing the use of electric vehicles and

supporting the development of charging infrastructure. Con-

currently, the building sector faces the imperative of tran-

sitioning to 100% renewable heating sources [5], [6]. It is

worth noting that efﬁcient farming practices play a vital role

in mitigating agricultural emissions, particularly in the most

challenging agricultural sector [7].

In a prospective climate-neutral economy, hydrogen has

the potential to serve as a versatile energy carrier and fuel

for hard-to-abate sectors, a chemical feedstock for industrial

processes, a heat source for the building sector, and a medium

for inter-seasonal energy storage in the power sector [8], [9].

In achieving a 100% renewable future, renewable hydrogen

can facilitate emission-free operations in industries, heating,

and transportation. Furthermore, hydrogen has reemerged as

a promising solution to address the intermittency challenge

of renewable energy sources [10], [11].

B. LITERATURE SURVEY AND CONTRIBUTIONS

Hydrogen plays a pivotal role in various applications, in-

cluding methanol and ammonia production, oil reﬁning,

metal processing, fuel cell vehicles, and synthetic natu-

ral gas production [12]. Renewable hydrogen technologies,

such as Power-to-power, Power-to-gas, Power-to-fuel, and

Power-to-feedstock, hold promise in enabling the production

of hydrogen, methane, methanol, and ammonia, which are

crucial components of a low-carbon future [13]–[15]. The

integration of hydrogen into different energy sectors, encom-

passing production, storage, and re-electriﬁcation, is an area

of investigation [16]. Notably, hydrogen production from

renewable electricity is characterized by negligible negative

environmental impacts and presents opportunities to achieve

ambitious net-zero emission targets [17], [18]. The cost of

producing green hydrogen, which encompasses electricity

and electrolytes/catalysts for water electrolysis, is estimated

to be approximately ten dollars per kilogram, with conversion

efﬁciency ranging from 60-80% [19].

Hydrogen storage, transport, and delivery require signiﬁ-

cant space, with the option of storing hydrogen in liquid form

to minimize space requirements while maintaining it below

its freezing point at -253°C. Despite this, hydrogen remains

economically prohibitive due to factors such as lack of in-

frastructure and associated costs [20]. The development of

affordable decarbonization solutions is crucial for achieving

a sustainable and green energy transition in the long term.

This can be facilitated through advancements in technologies,

government policies, and strategic investments to enhance

the competitiveness of renewable hydrogen production com-

pared to carbon-based alternatives [21]. The storage and

delivery of hydrogen are crucial components for advancing

hydrogen and fuel cell technologies, which are applicable in

various domains such as stationary power, portable power,

and mobility applications [22], [23]. The establishment of

adequate infrastructure is essential to facilitate widespread

consumer adoption of hydrogen as an energy carrier. This in-

frastructure typically involves liquefaction plants, pipelines,

storage tanks, trucks, compressors, and dispensers at re-

fueling stations, which collectively enable the delivery of

hydrogen fuel to the point of consumption [24].

In comparison to rechargeable batteries, hydrogen regen-

erative fuel cells offer distinct advantages such as remote

energy storage, independence of discharge voltage from

stored energy levels (State of Charge or SoC), and tunable

recharge/discharge rates for mission-speciﬁc applications

[25]. Adopting green hydrogen as a fuel source in fuel-cell

electric vehicles (FCEVs) can lead to doubled mileage or

efﬁciency compared to hydrogen-based internal combustion

engines [26]. Recent technological and economic advance-

ments in heavy-duty transportation and heavy industries sug-

gest that hydrogen-powered FCEVs may become an ideal

choice for future transportation [27]. Ammonia has also

emerged as a potential eco-friendly alternative fuel with the

ability to enable a carbon-free economy, particularly in the

transportation industry [28]. While the utilization of ma-

ture and early-adoption technologies can signiﬁcantly reduce

emissions, ongoing research innovations and industrial scale-

up efforts may lead to further price reductions in electric

vehicles (EVs) and electrolyzers [29].

Table 1 provides a comprehensive overview of various

fuel properties, including hydrogen, highlighting its unique

characteristics. While hydrogen offers numerous advantages

over fossil fuels in terms of its environmental impact and

versatility, it is important to acknowledge that hydrogen

also presents inherent safety risks. These risks stem from

its high ﬂammability range, low ignition energy, low vis-

cosity, and low density. These inherent characteristics of

hydrogen can potentially lead to explosions. As a result, the

storage and delivery of hydrogen pose signiﬁcant challenges

from a safety perspective. [30], [31]. Green hydrogen has

the potential to signiﬁcantly reduce carbon emissions, but

there are several challenges that need to be addressed for

its widespread commercialization. These challenges include

sustainable production, cost-effectiveness, infrastructure de-

velopment, global market expansion, and recognition as a

comprehensive solution for transitioning to a hydrogen-based

energy system [38].

There is a lack of comprehensive reviews addressing

the knowledge gaps related to green hydrogen ecosystems.

Therefore, this review aims to provide a comprehensive

perspective on the sustainability and feasibility of renew-

able hydrogen production to delivery on the green hydrogen

2VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

TABLE 1. Comparison of properties of hydrogen with other fossil fuels [32]–[37]

Property Diesel Biodiesel Gasoline

Compressed

Natural

Gas (CNG)

Liqueﬁed

Natural

Gas (LNG)

Propane

(LPG) Ethanol Methanol Hydrogen

Energy content 35.8 MJ/L 38-42.6 MJ/kg 34.2 MJ/L 53.6 MJ/kg 55.5 MJ/kg 46.4 MJ/kg 26.8 MJ/L 19.9 MJ/L 141.8 MJ/kg

Lower heating

value (MJ/kg)) 42-45 37-39 43-48 47-53 50-56 46-50 23-29 19-20 120-142

Heat of evaporation

(kJ/kg)) 290-320 270-290 400-450 750-850 380-450 350-400 840-900 950-1100 440-460

Flammability

range (in air) 0.6-4.0% 1.0-6.0% 1.4-7.6% 5-15% 5-15% 1.5-10.1% 3.3-19% 4-75% 6-36%

Ignition energy (J) 0.8-1.6 0.7-0.9 0.25-0.3 0.17-0.25 0.25-0.35 0.2-0.25 0.2-0.3 0.3-0.5 0.017-0.05

Viscosity (cSt) 2-6 3.5-6.0 0.4-0.8 0.02-0.2 0.05-0.2 0.4-1.0 1.0-1.2 0.5-1.0 0.007

Density (kg/m3)830-860 860-900 700-800 0.67-0.9 420-470 540-580 789 792 0.089-0.090

Carbon content 264 g/L 0-79 g/MJ 235 g/L 30-90 g/MJ 25 g/MJ 73 g/MJ 35 g/MJ 107 g/MJ 0 g/kg

Sulphur content <15 ppm 0-20 ppm 0-10 ppm <1 ppm <1 ppm <1 ppm 0-17 ppm 0-5 ppm 0.1 ppm

Nitrogen content <15 ppm <10 ppm 0-8 ppm <1 ppm <1 ppm <1 ppm 0-62 ppm <1 ppm 0.1 ppm

(Source:https://afdc.energy.gov/fuels/properties)

network, while considering the nascent stages of modern

technological advancements. The review article discusses the

hurdles, opportunities, and advancements related to inter-

connected hydrogen ecosystems, including green hydrogen

production, storage, transport, distribution, and end-use lev-

els. Overcoming challenges for the large-scale adoption of

green hydrogen involves addressing critical aspects. Cost-

competitive production is a key hurdle, requiring the scaling

up of processes like electrolysis and photo-electrolysis while

improving efﬁciency for hard-to-abate industries. Catalysts

in hydrogen production and fuel cells need continuous inno-

vation for cost-effectiveness and mitigation of poisoning is-

sues. Transportation, distribution, and safety optimization are

crucial, involving infrastructure adaptation and material com-

patibility. Lowering component costs, balancing hydrogen

and carbonaceous fuels, and addressing storage challenges

are essential for a robust supply chain. Economic viability,

supportive policies, and regulatory frameworks are vital for

widespread adoption, helping reduce carbon-intensive prac-

tices and promote a low-carbon economy.

C. ORGANIZATION

The structure of the study is organized as follows: Section II

outlines the review methodology, explaining the systematic

approach employed to gather and analyze information on

green hydrogen technologies. Section III provides a tech-

nical overview of green hydrogen production, highlighting

signiﬁcant hurdles in cost reduction and scaling up in water

electrolyzers. Section IV examines the technological issues

related to hydrogen storage and highlights the challenges

that have hindered the development of a hydrogen economy

pathway. Section V investigates the existing hindrances to

hydrogen transportation and delivery, with a focus on modern

technical solutions. Section VI analyzes the commercial-

ization aspects of green hydrogen for end-use applications.

Section VII addresses unresolved scientiﬁc issues for fu-

ture developments in establishing interconnected hydrogen

ecosystems, followed by concluding observations. Figure 1

shows the research ﬂowchart of this investigation.

II. REVIEW METHODOLOGY

The methodology employed in this review involved a sys-

tematic approach to gather and analyze information on green

hydrogen technologies. A thorough literature review encom-

passed articles, research papers, and publications from rep-

utable sources, covering various aspects of green hydrogen

production, storage, transportation, distribution, and end-use

applications. Additionally, a patent analysis from 2014 to

2022 was conducted to identify trends in electrolyzer and fuel

cell technologies related to water electrolysis. A publication

analysis tracked research trends in fuel cells and hydrogen

production from 1996 to 2023. This methodological ap-

proach ensures a comprehensive exploration of challenges,

advancements, and opportunities in the green hydrogen do-

main.

Using patent information, a study is conducted to analyze

the trends and patterns of electrolyzer and fuel cell tech-

nologies related to water electrolysis from 2014 to 2022,

as shown in Figure 2. The results show the summary of

patent ﬁlings by the top 20 jurisdictions for international

water electrolysis patent families. China has emerged as the

global leader in patent ﬁlings for water electrolysis, followed

by the United States, Europe, and Japan. However, when it

comes to fuel cell technology, the United States takes the

lead, followed by Europe, Japan, and China. These ﬁndings

provide valuable insights into the geographical distribution

of innovation and research activities in these technologies,

as well as the dominance of certain jurisdictions in different

aspects of electrolyzer and fuel cell advancements. Figure 3

illustrates the number of publications in the ﬁeld of fuel cells

and hydrogen production sectors from 1996 to 2023, focusing

on Proton-exchange membrane fuel cells (PEMFC), Solid

oxide fuel cells (SOFC), Alkaline fuel cells (AFC), Alkaline

electrolysis (AEL), Proton exchange membrane electrolysis

(PEMEL), and Solid Oxide electrolysis (SOEL). The pub-

lication trend reveals a signiﬁcant increase in the number

of publications related to PEM technology, indicating rapid

advancements in this ﬁeld.

However, there is a scarcity of recent strategic research

VOLUME 4, 2016 3

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

FIGURE 1. Framework of this study

assessments in the literature on the commercialization of

green hydrogen. Therefore, this study aims to provide a com-

prehensive literature review on systematic research related to

sustainable hydrogen, with a focus on accelerating the expan-

sion of clean energy infrastructure towards carbon neutrality.

The primary objective of this study is to identify knowledge

gaps pertaining to the implications of green hydrogen on

hard-to-abate sectors in achieving climate neutrality. Addi-

tionally, the study addresses the challenges and opportunities

associated with commercial-scale green hydrogen production

and delivery and suggests potential business models.

III. RENEWABLES BASED GREEN HYDROGEN

PRODUCTION

The production of hydrogen through water electrolysis pow-

ered by renewable energy sources is currently expensive, but

there is a growing need for increased efﬁciency and cost

competitiveness in renewable hydrogen production routes.

This requires signiﬁcant development in electrolyzer tech-

nologies, including those supported by thermal dissociation

of water through photocatalysis, concentrated solar, and

biomass/biogas processes [39]. Water electrolysis is a well-

established technology for hydrogen production and has

been implemented at the megawatt (MW) scale in various

industries worldwide. Different types of electrolysis tech-

nologies, such as Alkaline electrolysis (AEL), Anion ex-

change membrane electrolysis (AEMEL), Proton exchange

membrane electrolysis (PEMEL), Proton conducting ceramic

electrolysis (PCCEL), and Solid oxide electrolysis (SOEL),

are being actively researched and developed to improve their

performance and cost-effectiveness in hydrogen production.

A. STRATEGIC RESEARCH AND INNOVATION IN

GREEN HYDROGEN PRODUCTION TECHNOLOGIES

The research and development of green hydrogen technolo-

gies are focused on various aspects, including reducing cap-

ital and operational costs, scaling up to larger sizes (up to

100 kW), achieving high power usage of 40 kWh/kg, devel-

oping new catalysts, minimizing environmental impact, and

extending the lifetime of the technologies, as summarized in

Table 2. These technological advancements contribute to the

establishment of a sustainable and low-carbon energy system

for the future [40], [41].

Among the promising technologies, Anion Exchange

Membrane (AEM) electrolysis combines the advantages

of Proton Exchange Membrane Electrolysis (PEMEL) in

terms of efﬁcient production of high-purity hydrogen, and

traditional Alkaline Electrolysis (AEL) in terms of cost-

effectiveness, making it a potential candidate for renewable

energy storage and fuel cell vehicle applications. Solid Oxide

Electrolysis (SOEL) technology eliminates the need for ex-

pensive and corrosive liquid electrolytes, making it suitable

for various applications such as renewable energy storage,

industrial hydrogen production, and energy-efﬁcient trans-

portation [65]. Highly efﬁcient Proton Conducting Ceramic

Electrolysis (PCCEL) technology ﬁnds applications in in-

dustrial hydrogen production, energy storage, grid stabiliza-

tion, and fuel cell vehicles [66]. Photoelectrochemical (PEC)

technology is a promising area of research with potential

applications in renewable energy storage and sustainable fuel

for fuel cell vehicles [67]. Biological (dark fermentation)

hydrogen production aims to develop a sustainable and cost-

effective technology that can provide a reliable source of

clean hydrogen for a wide range of applications, including

transportation and industrial processes [68]. Bioelectrochem-

ical (BEC) hydrogen production has several advantages over

4VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

FIGURE 2. The total number of patents ﬁled from 2014 to 2022 for hydrogen production and fuel cells based on water electrolysis.

FIGURE 3. The total number of publications from 1996 to 2023 related to Fuel cell and water electrolysis technology.

VOLUME 4, 2016 5

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

TABLE 2. Various pathways for hydrogen production and associated development research actions [42]–[64]

Technology Description Beneﬁts Limitations Development Research Action

PEMEL

[42]–[44]

PEM systems are

preferred where high

dynamic operation is

required, due to the

short start-up time

and wide load

ﬂexibility range.

PEMEL’s high current density and

compact design, and quick response

enable it to withstand high pressures.

This method has higher energy

efﬁciency (80–90%) and a greater

hydrogen generation rate with high

purity of gases (99.99%).

For decoupled water splitting,

a membrane-free ﬂow electrolyzer

has been designed.

The overall cost of PEM electrolyzer

accounts for the costs of rare metals

such as platinum-coated titanium

material for bipolar plates at the

stack level, iridium on the anode side,

platinum on the cathode side at

the cell level and system level.

The dearth of scarce metals can

hinder accelerated PEM electrolyzer

deployment and renewable hydrogen

consumption. To prevent this,

Iridium, Ruthenium, and other

precious Platinum group metal-free

catalysts must be invented with a

current density of 3A/cm2to

support 30-75 GW of the electrolyzer

capacity.

AEL

[45]

AEL is a mature,

affordable, and

commercialized

technology.

The energy efﬁciency

is 70-80%.

In comparison to a PEMEL,

AEL has a longer lifespan and

lower annual maintenance costs.

A high-performance alkaline

capillary-fed water electrolysis cell

leads to bubble-free operation at

electrodes.

The downsides of this technology are

low current densities, impure gases,

limited operating pressure (3-30 bar),

and low dynamic operation.

The formation of carbonates on

the electrode affects the performance

of the electrolyzer.

More compact stack design with 3D

electrodes, a high current density

of 1A/cm2, cell voltage biased at

1.51V, ruthenium-free metals for the

cathode, 98% energy efﬁciency, and

energy consumption of 40.4 kWh/kg

makes the development of affordable

renewable hydrogen.

SOEL

[46], [47]

SOEL is the promising

solution for energy

generation and storage

of synthetic fuels due to

its maximum conversion

efﬁciency (90–100%),

non-noble electrocatalysts,

and withstanding high

pressures.

Compared to AEL and PEMEL,

SOEL has small stack capacities

of less than 10kW. The current

density in solid oxide electrolysis

cells with bimodal-structured

nanocomposite oxygen electrodes

surpasses 3A/cm2.

The main issue with high-

temperature.

SOEL is material stability and

durability, despite its great

efﬁciency.

A pressurized stack must be designed

with a current density of 1.5A/cm2,

the reversible capacity of 40%, and

the efﬁciency of greater than 50%

using advanced manufacturing

technology.

AEMEL

[48]–[51]

AEMEL uses the

beneﬁts of PEMEL

and AEL systems to

produce hydrogen at

a potentially affordable

and sustainable way.

Reduced usage of IrOx and Pt/C

catalysts, KOH-based electrolytes

with lesser than 1%mol, the high-

current density of 1.5A/cm2,

novel membranes, and waste

minimization aids in the production

of inexpensive sustainable fuel.

Although several beneﬁts of AEMEL

technology, the challenges are the

mechanical and chemical stability of

the membrane, unstable operation,

and short lifetime.

Develop inexpensive porous

transport layers (PTLs), reduce

gas permeability in membranes

and ohmic losses, employ

perﬂuorinated sulfonic acid

(PFSA) membranes, and improve

membrane durability for AEM

electrolyzers.

PCCEL

[52]

PCCEL is a high-

temperature (500-

1000oC) electrolysis

system that uses a

proton-conducting

ceramic electrolytes

to produce hydrogen

gas from water.

Protonic ceramic electrochemical

cells use solid oxide proton

conductors to convert energy

between hydrogen and electricity

in a self-sustaining and reversible

manner.

PCCEL has several challenges that

need to be addressed, such as the

high operating temperature,

durability of the ceramic electrolyte,

and the cost of the materials.

A triple conducting oxide of

the perovskite-based electrode

has been developed for the

production of electricity and

water electrolysis.

Planar/tubular cells in enhanced

materials need to be designed for

scaling up to kW in PCCEL

technology.

Photoelectro

chemical

systems

(PEC)

[53]–[56]

PEC is inspired by

photosynthesis in plants

and uses solar energy to

split water.

Graphene oxide with oxygen

functionalization is a good

electrocatalyst for producing

hydrogen peroxide.

A hydrogel-protected photocathode

exhibits stability over 100 hours,

with 70% of its initial photocurrent,

and reduces the degradation rate to

prevent semiconductor photocorrosion

and improve the lifetime of

photoelectrochemical devices.

One signiﬁcant issue is the

development of efﬁcient and stable

photoelectrode materials capable

of producing enough electron-hole

pairs while also withstanding the

harsh electrolyte conditions.

Another issue is the development of

suitable electrolytes capable of

transporting charge effectively and

enabling the desired electrochemical

processes.

Although T iO2is the

most studied material for PEC

technology, its absorption is conﬁned

to UV due to its large band gap.

The development of PEC water

splitting requires contemporary

research efforts in nanotechnologies,

photovoltaics, and computational

materials to improve efﬁciency.

Biological

production

[57]–[60]

Biological hydrogen

production refers to the

use of microorganisms,

such as bacteria and

algae, to produce H2

through biological

processes.

Biohydrogen production

can be achieved through

two main pathways:

dark fermentation and

photofermentation.

Although the production cost is

around 2-3 USD/kg, biological

hydrogen production processes

should enhance biohydrogen yield

and rate.

A 100 m3bio-reactor should be

built to attain a high hydrogen

production rate of more than

15 kgH2/m3/day of reactor

volume employing technical solutions

such as inoculum conditioning and

feedstock pre-treatment.

Several challenges need to be

addressed to make biohydrogen

production of a viable commercial

technology, such as low efﬁciency

and low hydrogen yields, high costs,

and difﬁculty in controlling the

microbial community.

Biophotolysis, dark fermentation,

and photo fermentation technologies

have low hydrogen yield, are

inefﬁcient and require huge reactors.

Some of the key areas of research

and development including microbial

strain development, efﬁcient

bioreactor design, feedstock

optimization, integration with other

renewable energy systems, and

process control and monitoring.

Bioelectro

chemical

(BEC)

[61], [62]

BEC is a process that

use microorganisms

including wastewater,

agricultural waste,

and industrial waste

to generate hydrogen

through the use of

an electrochemical cell.

In contrast to conventional fuel cells,

BEC systems do not rely on expensive

precious metals as catalysts.

Biohydrogenesis is a method for

producing sustainable and efﬁcient

hydrogen gas from various organic

compounds as substrates under

anaerobic conditions.

Some of the main limitations of

BEC process including limited

microbial diversity,

environmental sensitivity, and

reactor design.

The R&D actions in BEC process

are focused on improving efﬁciency,

scalability, and cost-effectiveness of

the process and also explores its

potential applications in waste

treatment, renewable energy, and

hydrogen production.

Direct

Solar

[63], [64]

Utilizing photocatalysts

is crucial for effective

and efﬁcient charge

carrier separation.

Direct solar thermolysis

and photolysis are

promising methods

for using solar energy to

drive chemical reactions.

Intermittent solar irradiation,

low energy conversion efﬁciency

typically less than 10%, and high

cost of photovoltaic cells are some

of the main drawbacks of

solar-driven hydrogen production.

Thermolysis-based hydrogen

production technology suffers from

high capital costs, low conversion

efﬁciency (20-45%), Elements

toxicity, and corrosion issues.

The hydrogen generation process

in photolysis has poor efﬁciency

(0.06%) and a production cost of

approximately 8–10 USD/kg.

Innovative architectural designs,

composite materials, and collector/

reactor system designs need to be

employed to scale up

low-temperature thermochemical,

photolysis, and photocatalytic

water-splitting technologies.

6VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

other methods, such as utilizing a wide range of feedstocks,

including organic wastes and wastewater [69]. Solar-driven

hydrogen production has the potential to be a sustainable and

renewable method for hydrogen production, particularly in

regions with high levels of solar irradiation [70].

B. ENERGY LOSSES

In the production of green hydrogen, electrolysis, fermen-

tation, and steam reforming are commonly used processes.

However, electrolysis, which is an electrolytic method, faces

several challenges. These include signiﬁcant energy losses

of 30-35% at each stage of the value chain, low overall

efﬁciency ranging from 60-80%, the need for additional

onsite compressors, and a relatively short lifespan of fewer

than 5 years. Furthermore, during the conversion of hydrogen

derivatives such as ammonia, energy losses of 13-25% may

occur. Additionally, around 10-12% of hydrogen can be lost

during transportation, and utilization of hydrogen in fuel

cells may result in an additional energy loss of 40-50% [71].

On the other hand, the fermentation technique for hydrogen

production also has challenges, including poor hydrogen

generation yields, difﬁculties in scaling up microbial elec-

trolysis cell systems while maintaining production rates, and

overall efﬁciency limitations of around 40% [72]. Moreover,

steam reforming, which is another common process, faces

challenges such as high complexity, low overall efﬁciency,

and the need for reformer adaptation of various composite

materials [73]. These challenges need to be addressed in

order to improve the efﬁciency and sustainability of green hy-

drogen production processes and to enable their widespread

adoption as a clean energy source [74].

Research in the ﬁeld of water electrolysis should focus

on various aspects to enhance the commercial viability of

the technology. This includes designing large area and high-

pressure stacks, developing monitoring and control meth-

ods for electrolyzers, exploring reversible hydrogenation,

improving the balance of plant designs, integrating MW

scale electrolyzers into renewable generation and industrial

production plants, utilizing by-products, and exploring the

production of ammonia, methanol, and synthetic petrochemi-

cals using renewable hydrogen [56], [78], [79]. Furthermore,

continuous improvements are needed in electrolyzer tech-

nology, including enhancing efﬁciency through improved

surface catalysis and enhanced solar absorption, durability

and lifetime through protective surface coatings and rugged

materials, cost reduction through reduced scarce materials,

reversible electrolysis, co-electrolysis, connectivity of renew-

ables in the overall energy systems, water management, and

scale of deployment. After being produced at a large scale

and a competitive price, green hydrogen may then be further

transformed into energy carrier variants including ammonia,

methane, methanol, and liquid hydrocarbons [80]–[82].

For speciﬁc electrolysis technologies, research efforts are

targeted toward various aspects. For AEL, integrating porous

transport layers (PTLs) into electrodes and diaphragms can

lead to cost savings. Current research includes increasing

current densities and operating temperature limits, reducing

diaphragm thickness, redesigning catalyst compositions, de-

signing high-speciﬁc area electrodes, and developing novel

PTL/electrode concepts. For PEMEL, bipolar plates and

PTLs play a crucial role in cost reduction. Ongoing research

focuses on reducing membrane thickness and catalyst quan-

tities, eliminating expensive coating on PTLs, redesigning

catalyst-coated membranes, developing novel recombination

catalyst concepts, and exploring novel PTL/electrode con-

cepts. SOEL research is aimed at achieving the high efﬁ-

ciency and durability of electrodes. This includes improv-

ing electrolyte conductivity, equipping both electrodes with

matching thermal expansion coefﬁcients, minimizing reac-

tant crossover, and optimizing mechanical and chemical sta-

bility. For AEMEL, research efforts are focused on achieving

desirable membrane properties and ionomers, including high

mechanical and thermal stability, ionic conductivity, reduced

polymer degradation, and improved membrane and ionomer

conductivity. Critical performance metrics, including long-

term targets for each electrolysis technology, have been sum-

marized in a Table 3.

C. TECHNOLOGICAL BARRIERS TO GREEN

HYDROGEN COST REDUCTION: SCALING UP

ELECTROLYZERS:

Renewable hydrogen production through water electrolysis

using solar or wind energy is gaining momentum as a promis-

ing solution to replace fossil fuels in various industrial ap-

plications such as long-haul aviation, freight shipping, long-

distance trucking, oil reﬁning, ammonia production, and steel

manufacturing. However, signiﬁcant challenges remain to

achieve commercial viability. The high demand for renew-

able electricity to power electrolyzers is a major hurdle, with

electricity costs accounting for 80% of the overall production

cost [83]. The electrolyzer, being the most expensive com-

ponent, requires cost-effective solutions to drive down the

overall cost of green hydrogen production. The membrane

electrode unit, which constitutes 60% to 70% of the total cost,

presents another challenge due to the use of precious metals

[75]. Additionally, achieving the desired purity of hydrogen

at an affordable cost is a critical concern, as the conversion

process to more stable forms like ammonia can be expen-

sive. Furthermore, challenges in hydrogen transportation and

storage, such as the need for liquefaction at −253OC, add

to the overall cost of green hydrogen production. At the end-

user level, fuel cell vehicles, synthetic fuels for aviation, and

the cost of hydrogen tanks are more expensive than fossil

fuel counterparts [1]. To make green hydrogen production

economically viable, it is essential to reduce construction and

procurement costs, improve electrolyzer performance and

durability, and scale up from MW to GW scale. Long-term

targets for green hydrogen production include achieving a

cost of less than USD 200/kW, durability exceeding 50,000

hours, and approaching 80% efﬁciency [75]. Transitioning

from the potential to the reality of large-scale green hydrogen

production will require addressing these challenges through

VOLUME 4, 2016 7

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

TABLE 3. The critical performance metrics including the long-term targets for each of the four electrolysis technologies for the year 2050 [75]–[77]

Parameter AEL PEMEL SOEL AEMEL

Nominal current density (A/cm2)2 4-6 2 2

Voltage range (V) <1.7 <1.7 <1.48 <2

Operating temperature (oC)90 80 60 80

Cell pressure (bar) >70 >70 >20 >70

Load range (%) 5 – 300 5 – 300 5 – 200 5 – 200

H2purity (%) 99.99 99.99 99.99 99.99

Voltage efﬁciency (%) >70 >80 >85 >75

Electrical efﬁciency of stack (kWh/kg H2)<42 <42 <35 <42

Electrical efﬁciency of system (kWh/kg H2)<45 <45 <40 <45

Lifetime (khrs) 100-120 100-120 80 100

Stack unit size (MW) 10 10 0.2 2

Electrode area (cm2)>30000 >10000 >500 >1000

Cold start to nominal load (min) <30 <5<300 <5

Capital costs of stack (USD/kW) <100 <100 <200 <100

Capital costs of system (USD/kW) <200 <200 <300 <200

interdisciplinary collaboration and innovation in materials

science, electrochemistry, and renewable energy systems.

The challenges associated with cost reduction in water

electrolysis, as depicted in Figure 4, can potentially be over-

come through technological breakthroughs involving novel

materials, increased manufacturing capacity, and economies

of scale achieved through research [92]. These challenges fall

into several categories, including optimizing operation condi-

tions and electrolyzer structure, addressing material scarcity

issues, enhancing technological performance and durability,

exploring the stackability of electrolyzers with membranes,

developing novel approaches for solar-driven water splitting,

and managing plant requirements.

The optimal design of stack conﬁguration for each water

electrolysis technology, combined with scaling up plant ca-

pacity from MW to GW scale, has the potential to reduce

costs by up to 50% [93]. This can be achieved by avoiding the

use of scarce materials, such as iridium and platinum, in PEM

electrolyzers, which would enable cost savings and allow for

large-scale deployment of up to 100 GW [93]. Furthermore,

decentralized hydrogen production, facilitated by compact

electrolyzer modules, off-grid renewable energy sources, and

low capital expenditure (CAPEX) investment per unit of

electrolyzer capacity with minimal logistic expenses, has

emerged as a viable solution [63]. A combination of lower

electrolyzer unit capital costs, estimated at USD 130/kW,

along with reduced electricity prices of 20 USD/MWh, in-

creased lifetime of 20 years, improved efﬁciency of 76%,

and optimized electrolyzer operation with full load hours

of 4200 hours, could potentially alleviate up to 80% of the

production costs of green hydrogen. As a result, competitive

green hydrogen production costs of less than USD 1/kg could

be achieved, making it a cost-effective alternative to fossil

fuel-based hydrogen [94].

These ﬁndings highlight the potential for reducing the

cost of green hydrogen production through advancements

in stack design, scaling up of plant capacity, avoidance of

scarce materials, decentralized production approaches, and

optimization of key operational parameters.

D. FOSTERING INNOVATIONS IN WATER

ELECTROLYSIS FOR REDUCING THE COST OF

ELECTROLYZERS:

In order to achieve efﬁcient and cost-effective green hydro-

gen production through electrolysis, various factors related

to electrolyzer design and operation must be considered. For

instance, the use of thinner membranes, more active cata-

lysts, and reduced raw material requirements can enhance

efﬁciency, but may also impact electrolyzer stack durability,

leading to increased capital expenditure (CAPEX) annu-

ity. Strategies such as employing larger stacks, optimizing

manufacturing processes, and implementing quality control

measures can further improve efﬁciency and reduce CAPEX.

However, challenges such as low water quality, high-pressure

operation, and limited maintenance can result in higher

operational expenditure (OPEX) and decreased durability.

Therefore, ﬁnding a balance between enhancing efﬁciency

and minimizing costs remains a key challenge in the ﬁeld of

electrolysis for green hydrogen production. [92].

1) Cell operation conditions and structure:

Electrolyzer cost estimates vary based on the technology

used, with alkaline electrolyzers priced at approximately

$700-900 per kW and PEM electrolyzers being more ex-

pensive at $1300-1500 per kW. When operating PEM elec-

trolyzers, it’s crucial to maintain temperatures below 80°C to

prevent membrane degradation and ensure optimal efﬁciency.

Furthermore, an operating pressure of around 30 bar strikes

a balance between efﬁciency and hydrogen production. In-

creasing current density in PEM electrolyzers can offer cost-

saving beneﬁts by enhancing efﬁciency and reducing mate-

rial costs, but it necessitates advanced cooling systems to

manage the increased heat generation. Expanding the cell

area and stack height can also improve efﬁciency and reduce

the overall cost per kW of electrolysis capacity, though

practical limits need to be considered. These factors collec-

tively impact the design, operation, and cost-effectiveness of

electrolysis systems, which are pivotal in the development

and implementation of hydrogen production technologies.

Optimizing cell operation conditions and structure, such as

8VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

FIGURE 4. The technological obstacles to water electrolysis and explores six groups of sub-technologies for enhancing productivity and reducing overall electrolyzer costs [9], [16], [75], [83]–[92]

operating at higher pressures and temperatures, can enhance

the efﬁciency of electrolyzers without compromising mem-

brane performance and durability, resulting in lower costs for

green hydrogen production [95].

2) Stackability of electrolyzers (stacks):

For enhancing stack performance, it is essential to redesign

stacks for higher current density, efﬁciency, lifespan, and

durability while reducing the reliance on precious materi-

als. This improvement can be achieved by enhancing stack

components such as porous transport layers, bipolar plates,

electrodes, and membranes, as well as minimizing costly

protective coatings. Maximizing the cell area and increasing

the cell count within stacks can signiﬁcantly boost hydrogen

production. Moreover, extending stack lifespan and reduc-

ing material costs are critical for improving the economic

feasibility of hydrogen production via electrolysis. Scaling

up module sizes can further enhance production rates and

overall efﬁciency. However, challenges exist, including the

current and anticipated scarcity of electrolyzer stacks, as

well as the absence of gigawatt-scale stack production in

the supply chain, which must be addressed to facilitate

the widespread adoption of hydrogen production through

electrolysis. Advancements in bipolar plates, electrodes, and

porous transport layers can potentially lead to lower capital

costs for electrolyzer stacks. Transitioning from manual to

automated stack production at gigawatt (GW)-scale manu-

facturing plants may also result in signiﬁcant cost savings

[92].

3) Separators (diaphragms, membranes):

Modifying the thickness of proton exchange membranes

(PEMs) and diaphragms in electrolyzers presents both ad-

vantages and challenges. In the case of PEMs, reducing their

thickness from 50 to 25 microns can yield a 40% decrease in

cell resistance and a 10% increase in current density, improv-

ing overall efﬁciency. However, this comes with potential

trade-offs, as thinner polymer/ceramic membranes may face

durability and mechanical stability issues. Redesigning mem-

branes or diaphragms with catalytic coatings, such as adding

a platinum layer to an anion exchange membrane (AEM),

can signiﬁcantly reduce hydrogen evolution overpotential by

75% and increase cell voltage by 40% at a given current

density, enhancing performance. Similarly, decreasing the

thickness of porous diaphragms from 1.5 mm to 0.5 mm

can reduce energy consumption by 40% and boost hydrogen

production rates by 20%. Nonetheless, thinner diaphragms

may be more susceptible to fouling or blockage, potentially

affecting both performance and durability. Balancing these

factors is crucial for optimizing the design and operation of

electrolyzer systems. Implementing effective mass transport

strategies, such as using thinner membranes like ceramic and

VOLUME 4, 2016 9

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

polymer electrolyte membranes, can enhance the efﬁciency

of electrolyzers and reduce electricity consumption [96].

4) Electrocatalyst materials:

Current benchmarks for precious group metal (PGM) loading

in PEM electrolyzers stand at around 0.5 mg/cm², ensuring

stable and efﬁcient performance. Utilizing a porous carbon

support with a thin PGM catalyst layer can signiﬁcantly re-

duce PGM loading while preserving performance, contribut-

ing to cost-efﬁciency. Scaling up production and exploring

alternatives to scarce materials like platinum and iridium are

essential to meet growing demand and reduce reliance on

limited resources. The exploration of earth-abundant cata-

lysts based on elements like cobalt, nickel, and iron holds

promise, but their long-term stability and scalability require

further investigation. Additionally, research into non-metallic

catalysts, such as carbon-based nanomaterials, metal-organic

frameworks, and 2D materials like graphene and molyb-

denum disulﬁde, is crucial to develop cost-effective, high-

performance catalysts and drive sustainability in hydrogen

production technologies. The scarcity of certain materials

poses a signiﬁcant barrier to the cost and scale-up of elec-

trolyzers. Developing alternative materials, such as non-

noble metal alloys and ceramics, could provide solutions

to mitigate this challenge and enable more cost-effective

electrolysis processes [97].

5) Balance of Plant

Enhancing the efﬁciency of hydrogen production through

electrolysis involves a multifaceted approach. This includes

improving rectiﬁer efﬁciency to over 98% to minimize power

losses, optimizing water treatment for energy efﬁciency and

reduced water consumption (less than 0.5 kWh/m³ of deion-

ized water circulation), reducing hydrogen compression en-

ergy consumption to less than 5 kWh/kg of hydrogen, and

optimizing buffer storage to match hydrogen production and

demand (targeting at least 24 hours of storage capacity).

Additionally, it entails minimizing energy consumption in the

compression and storage process (less than 10 kWh/kg of hy-

drogen), optimizing the cooling system for energy efﬁciency

(targeting less than 1 kWh/kg of hydrogen produced), and

designing the electrolyzer system to maximize the utilization

of renewable energy sources with a target of at least 50%

renewable energy incorporation. To enhance the overall efﬁ-

ciency and sustainability of the hydrogen production system,

a comprehensive approach is taken, encompassing various

aspects of the Balance of Plant [98].

6) Photoelectrolysis:

The development and implementation of photo-electrocatalytic

systems for solar-driven water splitting face several chal-

lenges. These include low photo-electrocatalyst efﬁciency,

with reported efﬁciencies ranging from less than 1% to

approximately 15%. Catalyst lifetimes are limited, typically

spanning from hundreds to thousands of hours, and the high

cost of photocatalysts, which can account for up to 90%

of the total system cost, poses a signiﬁcant challenge. To

address these issues, combining photocatalysts with different

absorption properties can expand the applicable wavelength

range, and specialized equipment, such as photo-reactors

and photo-electrochemical cells, is required, adding to the

complexity and cost. Furthermore, the stability of photocat-

alysts is a concern, potentially reducing the efﬁciency of

PV-electrolysis systems over time. Research suggests that

stability can be enhanced through structural modiﬁcation or

the use of protective coatings, offering potential solutions

to these challenges in the development of solar-driven water

splitting technologies. Despite the current challenges of tech-

nical maturity and route efﬁciency, photoelectrolysis offers

the potential to integrate electricity and hydrogen production

in a single process, which could lead to cost savings, in the

long run, [99]. Electrolyzers could be more cost-competitive

with photoelectrolysis when compared to fossil-based energy

sources.

In order to achieve more affordable pricing of electrolyz-

ers, continued research on anode and cathode catalysts is cru-

cial, as these catalysts signiﬁcantly contribute to the cost of

the stack by increasing surface area (over 50 m2/g) and uti-

lization (over 80%). Further research on anodic and cathodic

catalysts for both acidic and alkaline electrolyzers, which

are used in on-site hydrogen stations for water electrolysis,

can enable cost-effective refueling [100]. The development

of precious metal-free catalysts, particularly those that do

not contain iridium and titanium, with comparable activity

to electrodes at lower temperatures and improved durability

is of great importance [101]. Targeted research advancements

should focus on reducing interface resistances and mechani-

cal degradation of catalyst layers, minimizing contamination

issues related to sulfur dioxide (SO2) dissolution from the

stack, addressing thermal instability caused by electrode

and electrolyte mismatch, and scaling up stack units [102].

Additional improvements are needed to mitigate issues such

as nickel hydride (NiH) formation on the cathode, critical

degradation of catalysts, control of the oxidation state of

catalysts on the anode, and membrane poisoning/deactivation

by precious elements. Innovations in the design of recombi-

nation catalysts and enhancing the kinetics of oxygen and

hydrogen evolution with nickel-based alloys are necessary

for maintaining long-term stability [103].

In summary, Figure 4 comprehensively addresses the tech-

nological challenges and sub-technologies pertinent to ad-

vancing water electrolysis for hydrogen production. The six

categories cover diverse aspects, ranging from cell opera-

tion conditions and stackability to separators, electrocatalyst

materials, the balance of the plant, and photoelectrolysis.

These considerations span efﬁciency optimization, material

usage, cost reduction, and sustainability enhancements. The

outlined challenges and potential solutions underscore the

intricate landscape of water electrolysis, highlighting key

areas demanding attention for the progression and cost-

effectiveness of hydrogen production technologies.

10 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

IV. HYDROGEN STORAGE

Hydrogen is a promising method for storing renewable power

and mitigating greenhouse gas emissions, with hydrogen-

powered vehicles being a prominent application. However,

the main challenge in realizing a hydrogen economy is the

development of cost-effective, compact, conformable, and

safe hydrogen storage systems. Distinct standards for hydro-

gen storage and fuel cell vehicles are necessary for stationary

and mobility solutions. The hydrogen storage system must

meet stringent criteria, including safety, lightweight design,

compactness, cost-effectiveness, durability, long-term perfor-

mance, and efﬁcient refueling capabilities [104].

A. CHALLENGES OF STORING HYDROGEN

Hydrogen storage is a critical aspect of the hydrogen econ-

omy, with compression, cooling, or hybrid methods being the

primary approaches employed. However, several signiﬁcant

barriers hinder the effective storage of hydrogen. These chal-

lenges encompass energy-intensive compression processes,

stringent temperature and pressure requirements for solid

hydrogen storage, complex design considerations, social and

legal concerns, safety issues, high costs, and limited durabil-

ity of materials (metals, ﬁber, polymers, etc.), as well as the

need for puriﬁcation processes before end-use. Additionally,

bulk storage at geological formations such as abandoned

mines or salt caverns poses logistical challenges, and the

reliance on imports for fuel cell stacks, components, and

hydrogen storage materials further complicates the storage

landscape [105]. The multifaceted challenges associated with

hydrogen storage are highlighted in Figure 5.

Dormancy issues involve high-pressure requirements,

heavy containers, super insulation for cryo-compressed stor-

age, boil-off rates, and energy-intensive liquefaction. Safety

considerations revolve around hydrogen’s explosive poten-

tial, necessitating safe integration with propulsion and refu-

eling systems, effective insulation, and addressing concerns

with LH2 storage, including boil-off losses and embrittle-

ment. Hazards encompass potential rupture of high-pressure

storage containers due to high temperatures, risks associated

with larger tanks, steel embrittlement, and challenges in on-

board gas hydrogen storage. Charging and discharging rates

vary, requiring thermal management, faster refueling sys-

tems, and diverse responses. Material selection must account

for permeation, capacity, operating temperatures, reversibil-

ity, and the development of new materials. System weight and

volume entail heavy storage, thicker walls at high pressures,

lightweight solutions, increased storage capacity, and balance

of plant considerations. Energy efﬁciency differs with sys-

tem types and can degrade over time. Durability concerns

focus on material embrittlement, cracking, and degradation.

Uniform adoption of standards and regulations is critical,

including fuel quality standards and pressure relief device

codes. System costs, including expensive vehicular hydrogen

storage, highlight the need for cost-effective storage tech-

nologies, recyclable materials, and sustainability. Fuel costs

and the challenge of storing large hydrogen quantities at am-

bient conditions emphasize the importance of efﬁciency. Fuel

quality challenges address impurities like sulfur compounds,

requiring regulatory frameworks to mitigate safety risks [9],

[16], [84]–[91], [104], [105].

B. TECHNICAL BARRIERS IN HYDROGEN STORAGE

Hydrogen, a versatile energy carrier, can be stored in var-

ious forms such as solid, liquid, and gaseous, each with

unique advantages and challenges. Gaseous hydrogen is often

compressed to high pressures, typically up to 700 bars, and

stored in different types of tanks including Type I (metal),

Type II (metallic vessel hoop-wrapped with carbon ﬁber),

Type III (metallic liner fully wrapped with carbon ﬁber),

Type IV (polymeric liner fully wrapped with carbon ﬁber),

and Type V (all composite vessel without liner) to achieve

high volumetric density. Cryocompressed hydrogen storage,

achieved by cooling hydrogen to cryogenic temperatures,

also offers high volumetric and gravimetric efﬁciency [106],

[107].

Liquefaction, which involves compressing hydrogen to

high pressures and cooling it to cryogenic temperatures

(−253oC), is another storage option, but it incurs energy

losses due to the high power consumption of the liquefaction

process, estimated to be around 20-40% of the fuel energy.

Storage of liquid hydrogen at cryogenic temperatures and

near-ambient pressure (0.6 MPa) requires proper tank insu-

lation to prevent the leakage of evaporated gas. Additionally,

there are challenges associated with the long-term storage

and potential hydrogen loss during the liquefaction process.

However, it is considered to be the most efﬁcient storage

method currently available [83].

Hydrides, including metal, chemical, and complex hy-

drides, offer high gravimetric hydrogen storage capacity in

the solid form [108]. Despite their overall energy efﬁciency,

ammonia synthesis and breaking processes require signiﬁ-

cant energy input. Ammonia cracking is necessary as fuel

cells typically require pure hydrogen, and research efforts

have addressed the technical and economic challenges in

this stage. The reliability of the renewable ammonia supply

chain, including safe production, storage, and transportation,

has also been investigated [109]–[111]. Liquid ammonia,

stored in cryogenic tanks refrigerated to -33°C, is another

viable option for hydrogen storage at modest pressures due

to its higher energy density per volume compared to liquid

hydrogen. Liquid organic hydrogen carriers (LOHCs) are

potential candidates for long-term storage and long-distance

transportation of hydrogen, as they can store hydrogen at am-

bient pressure by saturating and desaturating hydrogen in the

hydrogenation and dehydrogenation processes, respectively.

Additionally, storage in suitable geological formations such

as salt caverns or abandoned mines, known as suburb stor-

age, can be a cost-effective option for compressed gaseous

hydrogen storage [112].

VOLUME 4, 2016 11

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

FIGURE 5. The technological issues associated with hydrogen storage [9], [16], [84]–[91], [104], [105]

1) Hydrogen liquefaction:

Superinsulated cryogenic tanks are utilized for the delivery of

liquid hydrogen, despite boil-off losses during storage. These

tanks have a high volume-to-surface ratio and are designed to

store cryogenic liquid hydrogen for industrial applications,

with temperatures as low as 200K and elevated pressures as

high as 500 bars. To limit boil-off losses during transport,

integrated refrigeration and storage systems are employed.

Advanced cooling materials and cryogenic containers for

hydrogen liquefaction are being developed to improve energy

efﬁciency and lower costs. It is anticipated that compressed

and liqueﬁed hydrogen for long-distance liquid renewable

transportation systems will become economically sustainable

in the future [83].

2) Liquid organic hydrogen carriers:

The effective storage and release of hydrogen as an energy

carrier is a critical requirement for its utilization. Hydrogen-

rich aromatic and alicyclic components have been inves-

tigated for their ability to absorb and release hydrogen

energy through the hydrogenation process. The feasibility

of distributing hydrogen from liquid organic hydrogen car-

rier storage technologies to hydrogen refueling stations has

garnered signiﬁcant research interest. Efforts to enhance

roundtrip efﬁciency and reduce costs in this context have

focused on the development of novel metal-based catalysts,

reduction of expensive raw materials, improved reactor tech-

nologies, and optimization of high-capacity CO2hydrogena-

tion/formic acid dehydrogenation facilities [113]. Further-

more, in backup power applications, metal-organic frame-

work adsorbents combined with fuel cells and electrolyzers

have been shown to be price competitive with modern energy

storage technologies [114].

3) Chemical hydrogen storage:

The utilization of hydrogen as a fuel has gained attention

due to its ability to be harvested, compressed, stored, and

used during periods of energy scarcity. Ammonia is cur-

rently being considered as a potential alternative to carbon-

12 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

based fuels, offering a means of delivering renewable energy

worldwide [109]. In this context, the development of new

catalysts for reforming and cracking processes has been

explored as a replacement for conventional Haber-Bosch-

based ammonia production plants. Electrochemical lithium-

mediated nitrogen reduction reactions have shown promising

results, achieving higher ammonia output rates of 150 nmol

s−1cm−2and nearly 100% current-to-ammonia efﬁciency

[115].

4) Underground H2storage facility:

Underground gas storage facilities are widely used for the

extensive seasonal storage of hydrogen, where enormous

amounts of hydrogen are preserved in salt or porous caverns.

The use of microporous metal-organic absorbers, which are

targeted to achieve a capital cost of $30 per kg, has been

explored as a potential solution for providing buffering func-

tions in such storage systems [116].

5) Compression, puriﬁcation, and separation:

The refueling of high-pressure storage tanks and managing

start-stop loads in hydrogen refueling stations (HRS) can

be achieved through various methods, including chemi-

cal, thermal, hydride, electrochemical, and turbo compres-

sion techniques. In particular, the development of plat-

inum group metal (PGM)-free catalysts for proton exchange

membranes in electrochemical and thermochemical puriﬁca-

tion/separation processes is of utmost importance in achiev-

ing high hydrogen purity levels of 99.99% [117].

High-pressure hydrogen storage is widely used in hydro-

gen delivery, onboard hydrogen storage (such as Type III or

Type IV tanks), and hydrogen storage at refueling stations

due to its economic and technological advantages. Low-

temperature liquid hydrogen storage is highly desirable for

long-distance and large-volume hydrogen storage, delivery,

and refueling stations, as it offers high hydrogen storage

density. For smaller-scale and short-distance hydrogen stor-

age and transportation with easy and safe operation, metal

hydride storage is a promising option. Future research in

hydrogen storage should prioritize nanoporous materials or

metal-organic frameworks with high gravimetric capacity,

graphene and composite materials for hydrogen storage,

high-pressure and lightweight hydrogen storage cylinders for

automotive applications, characterization of metal hydrides,

and complex hydrides for thermal management applications

[105], [118]–[123].

In summary, Figure 5 provides a comprehensive overview

of the multifaceted challenges associated with hydrogen

storage. These include dormancy, safety, hazards, charg-

ing rates, materials, fuel costs, energy efﬁciency, durability,

standards, fuel quality, and system weight/volume. High-

pressure containers, cryo-compressed storage, liquefaction

energy requirements, and safety concerns contribute to the

complexity of the storage landscape. Hazards such as rupture

risks and steel embrittlement, varying charging rates, and

material compatibility further add to the intricacies. Addi-

tionally, standards, fuel quality, and system weight/volume

considerations present challenges in the hydrogen storage

domain. Addressing these issues necessitates comprehensive

research and innovative solutions across various hydrogen

storage technologies to promote the development of effec-

tive, safe, and standardized systems, crucial for realizing a

hydrogen-powered future.

V. HYDROGEN TRANSPORTATION AND DISTRIBUTION

Pipelines have been widely recognized as the most cost-

effective mode of transportation for large quantities of hy-

drogen, ranging from 10-100 kilotonnes annually, over dis-

tances up to 1500 km [124]. However, for transportation of

hydrogen up to 4000 kg over longer distances to fueling

stations, liquid hydrogen in trucks has been identiﬁed as

the most economical option [125], [126]. Despite its cost-

effectiveness, the transportation of liquid hydrogen in ships

incurs signiﬁcant energy losses due to liquefaction, which

contributes to its high expense [127]. Comparatively, the

transportation costs of ammonia and compressed gaseous

hydrogen are similar. Among the various processes involved

in the hydrogen industry, ammonia synthesis and reformation

are considered the most expensive. Ammonia may become a

preferred option for long-haul oversea shipping [128]. Hy-

drogen pipelines and tank storage are identiﬁed as the most

expensive components in the compressed gaseous hydrogen

value chain. Pressurized tube trailers (200-500 bar) are found

to be ideal for transporting modest quantities of compressed

hydrogen over short distances [129]. However, to enable the

widespread use of hydrogen as a global energy carrier, rev-

olutionary advancements are needed in hydrogen transporta-

tion and distribution, considering its low volumetric density

and high energy content [130]. One potential solution for

hydrogen production involves utilizing completely exposed

palladium metal cluster catalysts to convert nitrogen hete-

rocycles into hydrogen. This catalytic reaction, which does

not require any observers, enhances reactivity and atomic

efﬁciency in the transportation and utilization of hydrogen

[131].

A. DIFFICULTIES OF HYDROGEN DELIVERY FROM AN

INFRASTRUCTURE, OPERATIONAL, TECHNICAL, AND

STANDARDS PERSPECTIVE

The transportation of hydrogen is primarily carried out

through gaseous tube trailers, pipelines, and liqueﬁed hydro-

gen tankers, which are widely used modes for delivering hy-

drogen to different destinations. However, the current hydro-

gen transmission pipeline infrastructure, which spans only

about 5000 km, is inadequate to meet the projected future

demand for hydrogen. Although liqueﬁed hydrogen is more

efﬁcient for transportation compared to high-pressure tube

trailers, there is a lack of infrastructure for the distribution

of hydrogen to end-user locations, such as hydrogen refu-

eling stations, which are limited in number (only 470), and

precise control of hydrogen ﬂow at refueling stations poses

VOLUME 4, 2016 13

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

challenges. Quick transfers of compressed hydrogen can

result in evaporation, leading to signiﬁcant losses, thermal

instability, and inefﬁcient usage of hydrogen. Additionally,

the conversion of existing natural gas pipelines to hydrogen

transportation presents difﬁculties. It is imperative to expand

the current infrastructure to accommodate the growing de-

mand for green hydrogen-based synthetic fuels.

FIGURE 6. The difﬁculties of hydrogen delivery from an infrastructure,

operational, technical, and standards perspective [9], [16], [84]–[91]

The key challenges associated with hydrogen transporta-

tion are summarized in Figure 6. These challenges encom-

pass aspects such as cost, energy efﬁciency, hydrogen purity,

boil-off, hydrogen leakage, safety, and environmental con-

cerns [132], [133].

a) Infrastructure: The establishment of a robust hydrogen

infrastructure faces several challenges, including a notable

shortage of hydrogen delivery infrastructure, the need for

substantial investments in new pipelines, and the devel-

opment of hydrogen refueling stations. Hydrogen pipeline

transport costs can vary widely, ranging from approximately

$1 to $10 per kilogram of hydrogen, contingent on factors

like transportation distance, pipeline diameter, and pressure.

To address these challenges and create an efﬁcient trans-

portation network for hydrogen, signiﬁcant investments, po-

tentially reaching $200 billion by 2050, may be required

for the development of a comprehensive hydrogen pipeline

network. This network aims to provide reliable and efﬁcient

hydrogen transportation, including integrated concepts that

utilize coastal and offshore renewable power sources for var-

ious applications, port infrastructure development to support

the transition of waterway vessels and coastal shipping to

hydrogen propulsion, and the creation of airport hydrogen

hubs to cater to local non-aviation consumers and liquid

hydrogen (LH2) fueling stations. These initiatives are crucial

for advancing the adoption and utilization of hydrogen as an

energy carrier in various sectors [134].

b) Technical requirements: Meeting the technical require-

ments for safe and efﬁcient hydrogen utilization and infras-

tructure development is essential. These include stringent

purity standards, demanding at least 99.999% purity with

less than 10 ppm impurities during hydrogen transportation.

Adaptations in sensors, compressors, and valves are neces-

sary to handle high pressure, low hydrogen viscosity, and pre-

vent leaks. Advances in carbon nanotubes can signiﬁcantly

improve hydrogen ﬂow rates and longevity, while advance-

ments in composite materials are crucial for constructing

lighter and safer vessel tanks. The shortage of technical

standards impedes the development of hydrogen-ready grids

and the repurposing of existing gas grids. It’s essential to

establish safety, operational, and maintenance requirements

for hydrogen infrastructure, along with developing energy

balance control mechanisms for hydrogen systems at the

Transmission System Operators (TSOs) and Distribution

System Operators (DSOs) levels. Addressing these technical

needs is paramount for the successful deployment and inte-

gration of hydrogen as an energy carrier [135], [136].

c) Standards: The standardization of hydrogen transporta-

tion and safety is paramount to ensure the widespread and

safe adoption of hydrogen as an energy carrier. This in-

cludes establishing standardized safety and pressure limits

for hydrogen transportation, which typically operates within

a range of 80 to 345 bar. Addressing the lack of standards

in bunkering compressed hydrogen for maritime use, hy-

drogen gas quality for pipelines, vessel tank pressure, tank

topology, and the use of ammonia as ship fuel is critical.

Developing standardized protocols and procedures for han-

dling and transporting compressed hydrogen is necessary to

ensure safety, quality control, and compatibility with existing

infrastructure. For liquid hydrogen, standard operating pro-

cedures for handling, including ﬁlling nozzles and volume

debits, and transportation through tunnels should be required.

Additionally, the creation of a regulatory framework for the

safe onward distribution of hydrogen and the implementation

of standardized hydrogen refueling infrastructure for all mo-

bility applications are essential steps in achieving a safe and

reliable hydrogen ecosystem [137].

d) Operational challenges: Hydrogen transportation

and operational challenges are signiﬁcant hurdles in the

widespread adoption of hydrogen as an energy carrier. These

challenges stem from hydrogen’s volatile and explosive na-

ture, with a wide explosive limit range, necessitating strin-

gent safety measures. The lack of harmonization and inte-

gration for pipelines and transport further complicates safe

and efﬁcient hydrogen transportation. Coordination across

the value chain is essential to control gas quality and quantity

and maintain hydrogen purity. The absence of a framework

for handling hydrogen gas quality at the Transmission Sys-

tem Operator (TSO) level is a major obstacle in hydrogen

14 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

adoption. Long-distance hydrogen transportation faces chal-

lenges related to cost reduction, enhanced energy efﬁciency,

hydrogen purity preservation, and the prevention of hydrogen

leakage risks. Additionally, the inadequate availability of

hydrogen refueling stations is a key challenge, which can be

addressed by identifying optimal refueling station locations,

developing standardized installation protocols, and ensuring

user accessibility to hydrogen fuel. Overcoming these chal-

lenges is vital for a successful transition to hydrogen as a

clean energy source [138].

Fiber-reinforced polymer (FRP) pipes are increasingly be-

ing employed for the transportation of hydrogen gas. How-

ever, the utilization of polymer materials in vehicle fuel sys-

tems presents signiﬁcant challenges due to pressure gradients

and heat transients that arise during fuel consumption and

reﬁlling operations. Polymers and polymer composites have

been utilized for sealing and bearing applications in liquid

hydrogen environments, addressing the unique requirements

of hydrogen transportation [139].

B. TECHNICAL CHALLENGES ASSOCIATED WITH

HYDROGEN REFUELING STATIONS (HRS):

High-capacity hydrogen refueling stations face technical

challenges, including the need for innovative interfacing

technological components to improve efﬁciency and reduce

CAPEX and OPEX. These challenges can be addressed

through the development of ﬂexible operation strategies

to accommodate variable renewable energy sources (RES),

enabling low inlet pressure, and implementing heavy-duty

nozzles, ﬂexibles, and chillers. Additionally, efforts should

be made to reduce the overall footprint of HRS and deploy

high-throughput HRS with multi-ton/day capacity. Standard-

ization and industrialization of reliable and safe heavy-duty

HRS equipment are also critical for the advancement of

hydrogen infrastructure [83]. Among various options for hy-

drogen transport and storage, the use of hydrogenated liquid

organic hydrogen compounds is considered cost-effective.

However, challenges exist in maintaining extremely low tem-

peratures around −253oC, which requires signiﬁcant energy

input for storage. Further demonstration of bulk hydrogen

storage is needed in various settings, including urban areas,

warehouses, refueling stations, and standalone systems, to

advance the adoption of this technology [112].

In summary, Figure 6 provides a comprehensive overview

of the difﬁculties associated with hydrogen delivery, span-

ning infrastructure, operational, technical, and standards per-

spectives. The challenges include an inadequate hydrogen

delivery infrastructure, high costs of hydrogen pipeline trans-

port, the necessity for substantial investments, and the im-

perative development of a comprehensive hydrogen pipeline

network. Technical challenges encompass stringent purity

standards, adaptations in sensors and valves, and the shortage

of technical standards for hydrogen-ready grids. Standard-

ization issues, such as pressure limits and bunkering pro-

cedures, add complexity to hydrogen transportation. Opera-

tional challenges arise from hydrogen’s explosive nature, the

lack of harmonization across the value chain, and inadequate

availability of hydrogen refueling stations. Overcoming these

challenges is crucial for the successful deployment and inte-

gration of hydrogen as an energy carrier. Addressing techni-

cal challenges in hydrogen refueling stations, including inter-

facing technological components, operational ﬂexibility, and

footprint reduction, is vital for advancing hydrogen infras-

tructure. Additionally, the utilization of hydrogenated liquid

organic compounds for cost-effective transport faces chal-

lenges related to energy input for extremely low-temperature

storage. To foster the widespread adoption of hydrogen tech-

nologies, it is imperative to invest in infrastructure develop-

ment, standardization, and innovative solutions that enhance

the efﬁciency, safety, and reliability of hydrogen transporta-

tion and distribution systems.

VI. GREEN HYDROGEN UTILIZATION: FUEL CELL

TECHNOLOGY

Fuel cells have diverse applications, such as large-scale

power plants, data center backup power, and light-duty and

heavy-duty vehicles. Proton-exchange membrane fuel cells

that utilize thin membranes (810 µm thick) operate at low

pressures of around 36 bar. To further improve the reliability

and affordability of PEMFCs, the development of new ma-

terials and catalysts is crucial. Solid oxide fuel cells with

reversible operation capability can potentially extend the

operating hours and maintain system temperature stability.

To successfully commercialize fuel cells, electrocatalysts for

oxygen reduction reactions must meet stringent performance

criteria, including high durability, fault-tolerance, and scal-

ability for high-volume production with consistent quality

[140]–[143].

A. HURDLES TO THE COMMERCIALIZATION ASPECTS

OF GREEN HYDROGEN

Although hydrogen fuel cells offer promising advantages

over battery systems for sustainable transportation, the

widespread commercialization of green hydrogen for various

end-use applications is hindered by several challenges. These

challenges include concerns related to fuel cell efﬁciency,

durability, size, robustness, state of health, current densities,

power, methods for monitoring system performance, thermal

and water management, volume and cost control, puriﬁca-

tion, and humidiﬁcation [144]–[146]. Major challenges asso-

ciated with green hydrogen utilization at the end-use level are

observed in transportation, industrial, heat generation, and

power sectors as well as in fuel cell applications, as depicted

in Figure 7 [144]–[146].

One key hurdle is the cost of hydrogen fuel cell systems

for electric vehicles, which currently stands at approximately

$100-200 USD per kilowatt (kW), making fuel cell electric

vehicles (FCEVs) 2-3 times more expensive to produce than

internal combustion engine (ICE) vehicles. However, it’s

essential to consider the long-term cost savings and envi-

ronmental beneﬁts. Advancements in technology are neces-

sary to reduce these costs. Another challenge is the limited

VOLUME 4, 2016 15

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

FIGURE 7. The key hurdles to the commercialization aspects of green

hydrogen [5], [9], [16], [84]–[91]

availability of hydrogen refueling stations (HRS), with each

HRS costing around $1-5 million, compared to the lower

costs of battery electric vehicle charging stations. Signiﬁcant

investment is required to establish HRS, and partnerships,

pilot projects, and technological advancements are crucial to

promote greater adoption of green hydrogen and ensure cost

competitiveness. Initiatives, government policies, incentives,

and collaboration between automakers and energy compa-

nies are also needed to address the challenges of FCEVs.

Additionally, addressing safety considerations is essential to

ensure the safe use of hydrogen in mobility and co-generation

applications, particularly at airports. Overcoming these chal-

lenges will be vital in the successful commercialization of

green hydrogen in the transport sector [147].

Combined heat and power (CHP) applications, speciﬁc

challenges arise in hydrogen utilization level, including

higher ﬂow volume due to hydrogen’s lower energy den-

sity, faster ﬂame speed, and increased NOx emissions from

higher ﬂame temperatures. These challenges can be mitigated

through appropriate infrastructure, equipment, and emission

control technologies. Additionally, for widespread adoption

of hydrogen-based CHP systems, it’s crucial to develop

hydrogen-capable prime movers and a robust hydrogen in-

frastructure, making it essential for all CHP prime movers to

be designed to be 100% hydrogen-capable, thus paving the

way for a sustainable and efﬁcient hydrogen-based energy

system [148].

For hydrogen to serve as a competitive long-term renew-

able energy storage solution, the levelized cost of hydrogen

fuel cells, which currently ranges from $0.12-0.68 per kWh,

must become more cost-competitive with lithium-ion-based

storage, which costs between $0.05-0.40 per kWh. Co-ﬁring

hydrogen at gas-ﬁred power plants faces technical barriers

related to fuel cell efﬁciency, technology cost, production, in-

frastructure, safety, and combustion system development. In

addition, the development of combustion systems for natural

gas and hydrogen mixtures up to 100% H2requires address-

ing challenges concerning combustion stability, emissions

control, fuel delivery, materials compatibility, and system

performance, underscoring the multifaceted nature of hydro-

gen integration and its economic feasibility [149], [150].

The cost of green hydrogen production from electrolysis is

currently around $3.5-7 per kilogram, while natural gas costs

about $1.5-2 per kilogram. Replacing steam-methane reform-

ing with renewable hydrogen production processes for indus-

trial demand faces technical barriers, including electrolysis

efﬁciency, scaling up hydrogen production, storage, trans-

portation, regulatory frameworks, partnerships, system inte-

gration, infrastructure investment, and cost-competitiveness

in production, storage, and transportation of green hydrogen

[21].

Cost challenges in the adoption of hydrogen fuel cells

are notable, with current costs ranging from $40 to $400

per kilowatt (kW) depending on the application. To promote

widespread use, it’s essential to address cost reductions, en-

hance system component production, and improve assembly

methods. Moreover, enhancing performance aspects of fuel

cells, including reliability, cold start capabilities, durability,

efﬁciency, control, power, and size & weight considerations,

is vital, particularly for increasing power density. Operation

considerations, such as installation, testing, system integra-

tion, and maintenance, are necessary to ensure the safe

and reliable operation of fuel cell systems. Additionally,

assessing the potential beneﬁts and drawbacks of hydrogen

fuel cells should account for their environmental effects,

emissions, hydrogen safety, energy security, and energy in-

dependence. These factors play a crucial role in the broader

adoption and success of hydrogen fuel cell technologies [16].

Small-scale electrolysis systems for residential use come

with a cost range of 2,000 to 7,000 per kilowatt (kW), which

varies depending on the system’s size and capacity. However,

challenges exist in terms of safety standards; current codes

and standards for hydrogen storage and handling require

improvement and updating to address the unique properties

of hydrogen. Moreover, the lack of hydrogen infrastructure

serves as a signiﬁcant barrier to the widespread adoption

of hydrogen in residential settings. To overcome this chal-

lenge, new infrastructure investments will be necessary to

support the deployment of small-scale electrolysis systems

and hydrogen storage tanks in residential areas, facilitating

the integration of hydrogen as an energy source in homes

[151].

High initial costs can be a barrier, as the upfront investment

required for fuel cells and electrolyzers can be daunting

for businesses. Infrastructure development, including pro-

duction, storage, and distribution, demands substantial in-

vestment and planning, slowing down the adoption process.

The development and implementation of regulatory frame-

16 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

works and standards is crucial but often complex and time-

consuming. Green hydrogen technologies face competition

from well-established alternatives, hindering their market

penetration. Ensuring economic viability in comparison to

cheaper, established alternatives is a persistent challenge.

Scalability, intermittency of renewable energy sources, pub-

lic perception, research and development, supply chain com-

plexity, and efﬁcient storage and transportation methods all

contribute to the multifaceted challenges of integrating green

hydrogen into various applications and industries. Overcom-

ing these challenges is vital for realizing the potential of

green hydrogen in decarbonizing the energy sector [152].

B. INNOVATIONS ON IMPROVING EFFICIENCY,

BOOSTING PRODUCTION CAPACITY OF

ELECTROLYZERS/FUEL CELLS

The inadequate interaction between electrodes and elec-

trolytes in ceramic fuel cells often leads to performance

degradation. To address this issue, the surface of high-

temperature annealed electrolytes can be treated with simple

acids to improve stability and efﬁcacy in decoupled electro-

chemical water splitting processes [153], [154]. Similarly, the

unsatisfactory performance of anion exchange ionomers and

membranes poses barriers in anion exchange membrane fuel

cells. However, the utilization of ﬂuorenyl aryl piperidinium-

based membranes and ionomers have shown high perfor-

mance in alkaline fuel cells [155]. Thermomechanical in-

stability remains a challenge in the commercialization of

solid oxide fuel cells. One potential solution is the use of

composite electrodes comprising cobalt-based perovskite and

negative-thermal-expansion materials, which have exhibited

high activity and stability when paired with the electrolyte

[156]. Another approach involves using perovskite nickelate

electrolytes with high initial ionic and electronic conduc-

tivity, low activation energy, and performance comparable

to the best-performing electrolytes in SOFCs at the same

temperature range [157].

Proton ceramic fuel cells have shown promise in using hy-

drogen and hydrocarbon fuels directly to generate power with

high potential efﬁciency for commercial applications. PCFCs

have demonstrated good performance and durability in long-

term testing with various fuel types without the need for

composition or architecture changes, showing resistance to

issues such as coking, sulfur poisoning, and temperature ﬂuc-

tuations [158]. Next-generation proton-exchange membrane

fuel cell technology based on nanomaterials is expected to

improve membrane electrode assembly, heat management,

and power density [159]. Recent research has shown that

water content in hydrocarbon polymer membranes in PEM-

FCs can be controlled by "nano cracks" that act as nanoscale

valves, preventing water desorption and maintaining ion con-

ductivity during dehumidiﬁcation. Such hydrocarbon fuel-

cell membranes with surface nano crack coatings exhibit re-

duced bulk resistance and improved ionic selectivity, leading

to superior electrochemical reaction performance [160].

One of the major challenges in fuel cell development is the

production of electrodes with high and durable electrocat-

alytic activity in a cost-effective and time-efﬁcient manner.

Metal nanoparticles on electrode architectures have shown

excellent performance in both fuel cells and electrolyzers,

and emerging nanomaterials offer the potential to integrate

fuel cells and electrolyzers into a single device [161].

C. COMMERCIAL-SCALE BUSINESS MODELS OF

GREEN HYDROGEN PRODUCTION AND DELIVERY

Understanding the commercial-scale business models associ-

ated with its production and delivery is critical for evaluating

its viability as an alternative energy source. This section an-

alyzes feasibility and sustainability of three distinct business

models for green hydrogen production and delivery, namely

onsite production, off-site production, and decentralized gen-

eration with district distribution.

For large-scale green hydrogen generation, “Onsite pro-

duction" is a commercially viable solution where the elec-

trolyzer is installed at the end-user site and powered by

solar or wind energy systems. This approach eliminates the

need for transportation infrastructure and associated costs.

However, challenges include limited production capacity and

ﬁnding the optimal balance between desired volumes and

generation capability. The medium to long-term solution

involves “Off-site production" and distribution of green hy-

drogen. In this model, large-scale electrolyzers are installed

near renewable energy sources, and hydrogen is transported

to end-users via pipelines or trucks. This approach allows for

wider consumer distribution and potentially lower production

costs due to economies of scale. The short-term solution

for green hydrogen production is the “Decentralized gener-

ation and district distribution". In this hybrid model, elec-

trolyzers are located close to end-user consumption points

and connected to the local electrical network, operating on

renewable energy. Beneﬁts include lower production costs

due to economies of scale and shorter development time for

the hydrogen grid. However, challenges exist in garnering

consensus to increase local volume consumption [94], [162].

This assessment will take into consideration critical fac-

tors such as capital investment, operational costs, revenue

generation, regulatory frameworks, and market demand. The

capital investment required for green hydrogen production

and delivery can vary signiﬁcantly depending on the project

scale, the technology used, and infrastructure requirements.

For instance, a large-scale green hydrogen production plant

using AEL is estimated to have a capital cost ranging from

$500 to $1400 per kg of hydrogen, PEMEL around $1100

to $1800 per kg of hydrogen, and SOEL $2800 to $5600

per kg of hydrogen. Operational costs are also subject to

variation due to factors such as energy prices, labor rates, and

maintenance requirements. For example, operational costs

for PEMEL can range from $2 to $6 per kg of hydrogen,

while for AEL, it can range from $1 to $3 per kg of hydrogen

[163], [164]. The ﬁndings of this study will provide valuable

insights into the viability and feasibility of these business

models, helping inform decision-making processes for the

VOLUME 4, 2016 17

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

adoption and implementation of green hydrogen technologies

in the transition towards a sustainable and low-carbon energy

future.

In summary, Figure 7 provides a comprehensive overview

of the hurdles obstructing the commercialization aspects of

green hydrogen utilization, particularly in fuel cell tech-

nology. These challenges span various sectors, including

transportation, heat generation, power generation, industrial

applications, fuel cell development, and residential usage.

Issues such as the cost of fuel cell systems, limited hy-

drogen refueling stations, and safety considerations hinder

the widespread adoption of green hydrogen in the transport

sector. In heat generation, challenges arise in handling higher

ﬂow volumes and emissions in hydrogen-based combined

heat and power systems. The power sector faces barriers

related to renewable energy storage and combustion system

development. The industrial sector encounters challenges in

achieving cost competitiveness and managing the transition.

Fuel cell technologies confront issues regarding cost, per-

formance aspects, operational challenges, and environmental

concerns. Additionally, the residential sector faces obstacles

in terms of cost range, safety standards, and infrastructure

barriers. Overcoming these multifaceted challenges is es-

sential for realizing the full potential of green hydrogen in

various applications and industries, necessitating technolog-

ical advancements, collaborative initiatives, and supportive

regulatory frameworks.

VII. DISCUSSION OF GREEN HYDROGEN ECOSYSTEM

ON THE PATH TO CLIMATE NEUTRALITY

The green hydrogen value chain encompasses several critical

research areas, including electrolysis technologies, renew-

able energy integration, storage and transportation, fuel cells

and applications, materials and catalysts, techno-economic

analysis, lifecycle analysis and sustainability, policy and

regulation, safety and standards, and education and outreach.

Table 4 provides an overview of global R&D activities in

the green hydrogen value chain and identiﬁes key develop-

ment research initiatives needed to bridge technology gaps.

Notably, cost-effective electrolyzers and renewable electric-

ity are crucial for competitive green hydrogen production,

while advancements in fuel cell technology, catalysts, mem-

branes, system components, and stack assembly are essential

for cost-competitive fuel cells in various sectors such as

transportation, logistics, heating, cooling, and power gen-

eration sectors [170]. The storage of hydrogen necessitates

the development of carbon composite and hydride cylinders

using indigenous materials. Furthermore, hydrogen distri-

bution infrastructure must be expanded with the installa-

tion of pipelines and dispensing stations. A comprehensive

ecosystem for hydrogen production, storage, and distribu-

tion needs to be established, catering to both stationary and

transport applications. In addition to technological advance-

ments, supportive policies, regulations, infrastructure, and

political backing are pivotal for a successful transition to

a clean hydrogen economy [74]. Achieving a sustainable,

decarbonized, and integrated energy system requires robust

scientiﬁc research and innovation efforts, encompassing ar-

eas such as repurposing natural gas infrastructure, novel pro-

duction methods, improved electrolyzers, safety and material

considerations, environmental impact, and cost-effectiveness

of clean hydrogen solutions.

A comprehensive analysis of the requirements, technolog-

ical constraints, and economics of hydrogen utilization in

hard-to-abate sectors has been conducted, with a focus on the

entire hydrogen value chain. To accelerate the deployment

of hydrogen and build interconnected hydrogen ecosystems,

several scientiﬁc priorities and challenges are identiﬁed for

future research.

A. DEVELOPMENT OF ELECTROLYZERS:

Future research in electrolyzer technology should prior-

itize scaling up PEMEL and AEL, improving the ther-

mal connectivity of SOEL, developing spin-polarized cat-

alysts for energy-efﬁcient AEMEL, exploring PGM-free

catalysts and electrodes, synthesizing high-purity hydro-

gen from methanol and water, integrating electrolyzers into

steel plants for energy management, addressing safety is-

sues in electrolysis processes, developing intermetallic cata-

lysts with carbon nanotubes, advancing electrode/cell design

and membrane separation technologies, understanding per-

formance/durability mechanisms, evaluating environmental

impact and circularity of electrolyzers, and exploring the

possibility of impure/seawater electrolysis and direct air elec-

trolysis [171]–[175].

B. DEVELOPMENT OF HYDROGEN STORAGE AND

DISTRIBUTION:

Future research should focus on developing new concepts for

large-scale above and underground hydrogen buffer storage

to enable continuous industrial process output, characteriz-

ing and selecting polymer materials for cryogenic storage

systems, exploring advanced materials for hydrogen storage,

developing dedicated liquid hydrogen tanks for aircraft ap-

plications, and adopting a pluralistic approach for logistical

infrastructure to transport the hydrogen from potential renew-

able areas to demand centers [176], [177].

C. PROCESSES ADAPTATION IN THE INDUSTRY:

Future research directions in the industrial sector should in-

clude advancements in co-electrolysis processes, integration

of electrolyzers and hydrogen storage tanks, development

of hydrogen burners for boilers, modiﬁcation of melting

and smelting processes, conversion of combustion engines

from fossil fuels to efﬁcient internal combustion engines for

heavy-duty commercial hydrogen vehicles, hosting demon-

strations of hydrogen turbines, and design of dedicated tur-

bines for aircraft [178].

D. ALTERNATIVE HYDROGEN PRODUCTION:

Research on other routes of sustainable hydrogen produc-

tion for large-scale distributed plants, such as thermochem-

18 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

TABLE 4. Summary of key stakeholders and R&D activities happening globally in the green hydrogen value chain [165]–[169]

Country Government Consortia Research Research Activity

Canada

Natural Sciences and

Engineering Research

Council of Canada.

Natural Resources Canada.

Innovation, Science and

Economic Development

Canada.

Hydrogen Business

Council of

Canada.

Canadian Hydrogen

Fuel Cell

Association.

University of British

Columbia.

CanmetENERGY.

Ontario Tech

University.

McGill University.

National Research

Council .

Steam methane reforming with carbon capture and

storage and electrolysis using renewable energy sources,

Grid-scale energy storage, feedstock for the production

of clean ammonia, High-pressure or cryogenic storage,

Fuel cell electric vehicles, Hydrogen-powered buses,

Fuel cell vehicle systems.Stationary, portable, and

backup power. Developing new materials for fuel cells,

improving the performance and durability of fuel cells

China

Ministry of Science and

Technology.

Ministry of Industry and

Information Technology.

National Development and

Reform Committee.

NEC – National Energy

Commission.

China Society of

Automotive

Engineers.

China Hydrogen

Alliance.

Energy Research

Institute.

Chinese Academy of

Sciences .

Chinese Academy of

Engineering.

Tianjin University.

Zhejiang University.

Tsinghua University.

Hydrogen fuel cell vehicle components such as fuel cells,

hydrogen storage systems, and hydrogen refueling

systems. Steam methane reforming with carbon capture

and storage, electrolysis, and biomass gasiﬁcation,

solid-state hydrogen storage materials, hydrogen storage

in underground salt caverns, and hydrogen storage in

liquid organic hydrogen carriers, fuel cell electric

vehicles, fuel-cell buses, and fuel-cell backup power

systems.

France

Agency for Ecological

Transition.

National Research Agency.

France Hydrogène.

Europe:

Fuel Cells and

Hydrogen Joint

Undertaking.

Alternative Energies

and Atomic Energy

Commission.

Centre Nationale de

Recherche

Scientiﬁque.

Electrolysis using renewable energy sources, biomass

gasiﬁcation, and methane pyrolysis. Solid-state hydrogen

storage materials, hydrogen storage in metal hydrides,

and hydrogen storage in underground salt caverns,

Fuel cell technologies for stationary power and

transportation applications, Safe and efﬁcient

transportation and distribution of hydrogen

Germany

Ministry of Education and

Research.

Ministry of Economic Affairs

and Climate Action.

National Organisation

for Hydrogen and

Fuel Cell Technology .

Fuel Cells and Hydrogen

Joint Undertaking.

Helmholtz Association.

Fraunhofer Institute.

Electrolysis, fossil fuel conversion, biomass and waste

conversion, photochemical and photocatalytic, biological

production, thermal water splitting, compression and

liquefaction, chemical carriers, gas blending, transport,

electricity generation, and industrial processes.

India

Department of Science and

Technology.

Department of Scientiﬁc and

Industrial Research.

Ministry of New and

Renewable Energy.

Indian Hydrogen

Alliance.

Academy of Scientiﬁc

and Innovation

Research.

National Institute of

Technology.

Council of Scientiﬁc

& Industrial Research.

Electrolyser design, Storage & transport systems

(pipelines, tanks), FCEV components, systems/stacks,

re-fuelling stations, developing new materials and

technologies for fuel cells, improving the performance

and durability of fuel cells, and developing fuel cell-

based power systems for off-grid applications.

Japan

Japan Oil, Gas and Metals

National Corporation.

New Energy and Industrial

Technology Development

Organisation.

Japan Science and

Technology Agency.

Ministry of Economy, Trade

and Industry.

Clean Fuel Ammonia

Association.

Japan Hydrogen

Association.

Advanced Hydrogen

Energy Chain Association

for Technology

Development.

CO2-free Hydrogen

Energy Supply-chain

Technology Research

Association.

University of Tokyo.

Kyushu University.

Kyoto University.

National Institute of

Advanced Industrial

Science and

Technology

Water electrolyzer, liqueﬁed hydrogen carriers and

methylcyclohexane, fuel ammonia, synthetic methane,

ammonia fuel cells, ammonia cracking technologies,

ammonia-based power generation systems, fuel cell

vehicles, hydrogen liquefaction technologies, hydrogen-

based power generation systems,

Singapore

Development Board/Energy

Market Authority

Ministry of Trade and

Industry/Economic.

Singapore Energy

Centre.

Centre for Hydrogen

Innovations.

Nanyang Technological

University.

Agency for Science,

Technology and

Research.

Water electrolysis, steam methane reforming, biomass

gasiﬁcation, new catalysts and materials, solid-state

hydrogen storage materials and hydrogen carriers,

proton exchange membrane fuel cells, and solid oxide

fuel cells.

Republic of

Korea

National Research Council of

Science and Technology.

Ministry of Trade Industry

and Energy.

H2KOREA

HyNet Consortium

Korea Institute of

Energy Research .

Korea Advanced

Institute of Science

and Technology.

Development of hydrogen-powered trains and ships,

and the promotion of hydrogen as a fuel for aviation,

solid oxide fuel cells, hydrogen refueling stations,

and hydrogen production technologies,

Department of Energy:

Ofﬁce of Fossil Energy and

Carbon Management.

Ofﬁce of Nuclear Energy.

Ofﬁce of Science.

Ofﬁce of Clean Energy

Demonstrations.

Ofﬁce of Energy Efﬁciency &

Renewable Energy.

H2@Scale

Fuel cell and

Hydrogen Energy

Association.

21st Century Truck

Partnership.

DOE Hydrogen and

Fuel Cell Technologies.

Ofﬁce research

consortia.

Department of

Energy.

National laboratories.

Low and high-temperature electrolysis, thermochemical,

photoelectrochemical, and solar water splitting,

biological approaches, gasiﬁcation, pyrolysis, reforming,

coﬁring and modular systems, fuel cells and

combustions, high-pressure tanks, cryogenic vessels/

trucks, tube trailers, and reversible fuel cells.

UK Research and Innovation.

Department for Business,

Energy and Industrial

Strategy.

Engineering and Physical

Sciences Research Council.

UK Hydrogen and

Fuel Cell Association .

Imperial College London.

UK Research and

Innovation

Engineering and Physical

Sciences Council.

Electrolysis, steam methane reforming, autothermal

reforming, biomass gasiﬁcation, pyrolysis,

photoelectrochemical, high-temperature water splitting.

VOLUME 4, 2016 19

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

ical splitting, biomass & biowaste, electro-hydrogenesis,

water thermolysis, photocatalysis, and photoelectrocatal-

ysis, should be explored [179]. Additionally, substances

such as aluminum, zinc, and silicon that chemically react

with water for hydrogen production should be investigated

[39], [59], [139], [180], [181]. Promising methods, such as

photo-reforming of biodegradable oxygenates and PV/photo-

electrocatalytic cell integration technology, should be fur-

ther researched to enhance solar-to-hydrogen efﬁciency and

device lifespan [182]–[184]. Furthermore, liquid electricity,

such as eMethanol (electricity-to-methanol), could be ex-

plored as a green fuel for heavy-duty transport [185].

E. DEVELOPMENT OF FUEL CELL:

In the realm of hydrogen technology, advancing fuel cell

technology is pivotal. Research must prioritize critical ma-

terials and stack technologies for electrolysis and fuel cells,

with a focus on enhancing stack designs and materials to

improve overall system performance and cost-effectiveness.

Innovative fuel cell concepts tailored to heavy-duty vehicles

are needed to address unique challenges in this sector, such

as power output and durability. Enhancing the durability

and availability of fuel cell components, alongside the de-

velopment of advanced hydrogen puriﬁcation technologies,

is essential for long-term viability. [142], [186], [187]. Re-

search must also explore regenerative fuel cells for maritime

applications and address integration challenges in Power-to-

X systems such as onboard fuel cell storage and powertrain

integration, dedicated solid-oxide (SO) and proton exchange

membrane (PEM) fuel cell systems for aviation propulsion,

thin ﬁlm reversible solid-oxide fuel cells as energy storage

systems. Additionally, the utilization of ammonia as a fuel

source for solid-oxide fuel cells holds promise for various

applications [14], [80], [188]–[191]. These research priorities

and challenges are instrumental in accelerating the deploy-

ment of hydrogen technologies, particularly in hard-to-abate

sectors [192].

VIII. CONCLUSION

In the dynamic landscape of the green hydrogen economy,

achieving a Levelized Cost of Hydrogen (LCOH) production

of $1/kg at GW-scale requires targeted efforts. Emphasiz-

ing improvements in energy conversion efﬁciency, reducing

CAPEX/OPEX, and enhancing the durability of electrolyzer

systems are pivotal. Collaborative initiatives in research,

technology, and business model innovation are key elements

for shaping a sustainable energy future.

Government support is crucial for the entire hydrogen

production value chain, particularly in hard-to-abate sectors

where a harmonious blend of technology advancements and

market incentives is vital. Despite notable progress, per-

sistent economic scale challenges for crucial components

demand immediate attention. Overcoming these challenges

is essential for technology readiness, successful green hy-

drogen commercialization, and substantial contributions to

carbon neutrality.

Proposing future research directions, several key areas

demand exploration. Key directions include exploring large-

scale, sustainable energy conversion processes using novel

materials, prioritizing high-density solid-state materials for

hydrogen storage, developing highly efﬁcient power con-

verters, establishing regulatory frameworks, and innovatively

exploring sector coupling through hydrogen. This compre-

hensive approach aims to propel hydrogen and fuel cell

technologies into mainstream use, fostering a sustainable and

low-carbon future across diverse industries.

ACKNOWLEDGEMENT

The authors extend their appreciation to the Deputyship

for Research & Innovation, Ministry of Education in Saudi

Arabia, for funding this research work through the project

number NBU-FFR-2023-0058. The authors gratefully thank

the Prince Faisal bin Khalid bin Sultan Re- search Chair

in Renewable Energy Studies and Applications (PFCRE) at

Northern Border University for their support and assistance.

REFERENCES

[1] S. van Renssen, “The hydrogen solution?” Nature Climate Change,

vol. 10, no. 9, pp. 799–801, 2020.

[2] N. Mac Dowell, N. Sunny, N. Brandon, H. Herzog, A. Y. Ku, W. Maas,

A. Ramirez, D. M. Reiner, G. N. Sant, and N. Shah, “The hydrogen

economy: A pragmatic path forward,” Joule, vol. 5, no. 10, pp. 2524–

2529, 2021.

[3] F. Wang, J. D. Harindintwali, Z. Yuan, M. Wang, F. Wang, S. Li, Z. Yin,

L. Huang, Y. Fu, L. Li et al., “Technologies and perspectives for achieving

carbon neutrality,” The Innovation, vol. 2, no. 4, p. 100180, 2021.

[4] B. C. Tashie-Lewis and S. G. Nnabuife, “Hydrogen production, distribu-

tion, storage and power conversion in a hydrogen economy-a technology

review,” Chemical Engineering Journal Advances, vol. 8, p. 100172,

2021.

[5] H. Montazerinejad and U. Eicker, “Recent development of heat and

power generation using renewable fuels: A comprehensive review,” Re-

newable and Sustainable Energy Reviews, vol. 165, p. 112578, 2022.

[6] M. Jayachandran, C. Kalaiarasy, and C. Kalaivani, “Implementation

issues with large-scale renewable energy sources and electric vehicle

charging stations on the smart grid,” in Smart Grids for Renewable

Energy Systems, Electric Vehicles and Energy Storage Systems. CRC

Press, 2022, pp. 45–58.

[7] G. Luderer, M. Pehl, A. Arvesen, T. Gibon, B. L. Bodirsky, H. S. de Boer,

O. Fricko, M. Hejazi, F. Humpenöder, G. Iyer et al., “Environmental co-

beneﬁts and adverse side-effects of alternative power sector decarboniza-

tion strategies,” Nature communications, vol. 10, no. 1, pp. 1–13, 2019.

[8] A. M. Oliveira, R. R. Beswick, and Y. Yan, “A green hydrogen economy

for a renewable energy society,” Current Opinion in Chemical Engineer-

ing, vol. 33, p. 100701, 2021.

[9] C. B. Agaton, K. I. T. Batac, and E. M. Reyes Jr, “Prospects and chal-

lenges for green hydrogen production and utilization in the philippines,”

International Journal of Hydrogen Energy, 2022.

[10] M. Jayachandran, C. R. Reddy, S. Padmanaban, and A. Milyani, “Opera-

tional planning steps in smart electric power delivery system,” Scientiﬁc

Reports, vol. 11, no. 1, p. 17250, 2021.

[11] M. Jayachandran, K. P. Rao, R. K. Gatla, C. Kalaivani, C. Kalaiarasy,

and C. Logasabarirajan, “Operational concerns and solutions in smart

electricity distribution systems,” Utilities Policy, vol. 74, p. 101329, 2022.

[12] C. Mansilla, C. Bourasseau, C. Cany, B. Guinot, A. Le Duigou, and

P. Lucchese, “Hydrogen applications: Overview of the key economic

issues and perspectives,” Hydrogen Supply Chains, pp. 271–292, 2018.

[13] V. Maestre, A. Ortiz, and I. Ortiz, “Challenges and prospects of renewable

hydrogen-based strategies for full decarbonization of stationary power

applications,” Renewable and Sustainable Energy Reviews, vol. 152, p.

111628, 2021.

20 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

[14] I. Sorrenti, T. B. H. Rasmussen, S. You, and Q. Wu, “The role of power-

to-x in hybrid renewable energy systems: A comprehensive review,”

Renewable and Sustainable Energy Reviews, p. 112380, 2022.

[15] M. Ozturk and I. Dincer, “A comprehensive review on power-to-gas

with hydrogen options for cleaner applications,” International Journal of

Hydrogen Energy, vol. 46, no. 62, pp. 31 511–31 522, 2021.

[16] M. Yue, H. Lambert, E. Pahon, R. Roche, S. Jemei, and D. Hissel, “Hy-

drogen energy systems: A critical review of technologies, applications,

trends and challenges,” Renewable and Sustainable Energy Reviews, vol.

146, p. 111180, 2021.

[17] M. Hermesmann and T. Müller, “Green, turquoise, blue, or grey? environ-

mentally friendly hydrogen production in transforming energy systems,”

Progress in Energy and Combustion Science, vol. 90, p. 100996, 2022.

[18] M. Jayachandran, R. K. Gatla, K. P. Rao, G. S. Rao, S. Mohammed,

A. H. Milyani, A. A. Azhari, C. Kalaiarasy, and S. Geetha, “Challenges in

achieving sustainable development goal 7: Affordable and clean energy

in light of nascent technologies,” Sustainable Energy Technologies and

Assessments, vol. 53, p. 102692, 2022.

[19] S. S. Kumar and V. Himabindu, “Hydrogen production by pem water

electrolysis–a review,” Materials Science for Energy Technologies, vol. 2,

no. 3, pp. 442–454, 2019.

[20] O. Bachmann, “Large scale low-cost green hydrogen production using

thermal energy storage and polymer electrolyte membrane electrolysis

systems,” IET Renewable Power Generation, 2022.

[21] S. G. Nnabuife, J. Ugbeh-Johnson, N. E. Okeke, and C. Ogbonnaya,

“Present and projected developments in hydrogen production: A tech-

nological review*,” Carbon Capture Science & Technology, vol. 3, p.

100042, 2022.

[22] P. Ferreira-Aparicio and A. M. Chaparro, Portable Hydrogen Energy Sys-

tems: Fuel Cells and Storage Fundamentals and Applications. Academic

Press, 2018.

[23] B. Widera, “Renewable hydrogen implementations for combined energy

storage, transportation and stationary applications,” Thermal Science and

Engineering Progress, vol. 16, p. 100460, 2020.

[24] R. Moradi and K. M. Groth, “Hydrogen storage and delivery: Review

of the state of the art technologies and risk and reliability analysis,”

International Journal of Hydrogen Energy, vol. 44, no. 23, pp. 12 254–

12 269, 2019.

[25] B. Sundén, Hydrogen, batteries and fuel cells. Academic Press, 2019.

[26] G. J. Offer, D. Howey, M. Contestabile, R. Clague, and N. Brandon,

“Comparative analysis of battery electric, hydrogen fuel cell and hybrid

vehicles in a future sustainable road transport system,” Energy policy,

vol. 38, no. 1, pp. 24–29, 2010.

[27] V. Oldenbroek, S. Wijtzes, K. Blok, and A. J. van Wijk, “Fuel cell electric

vehicles and hydrogen balancing 100 percent renewable and integrated

national transportation and energy systems,” Energy Conversion and

Management: X, vol. 9, p. 100077, 2021.

[28] C. Kurien and M. Mittal, “Review on the production and utilization of

green ammonia as an alternate fuel in dual-fuel compression ignition

engines,” Energy Conversion and Management, vol. 251, p. 114990,

2022.

[29] Z. Liu, Z. Deng, G. He, H. Wang, X. Zhang, J. Lin, Y. Qi, and X. Liang,

“Challenges and opportunities for carbon neutrality in china,” Nature

Reviews Earth & Environment, vol. 3, no. 2, pp. 141–155, 2022.

[30] E. Abohamzeh, F. Salehi, M. Sheikholeslami, R. Abbassi, and F. Khan,

“Review of hydrogen safety during storage, transmission, and applica-

tions processes,” Journal of Loss Prevention in the Process Industries,

vol. 72, p. 104569, 2021.

[31] A. Kotchourko and T. Jordan, Hydrogen Safety for Energy Applica-

tions: Engineering Design, Risk Assessment, and Codes and Standards.

Butterworth-Heinemann, 2022.

[32] B. C. Tashie-Lewis and S. G. Nnabuife, “Hydrogen production, distribu-

tion, storage and power conversion in a hydrogen economy - a technology

review,” Chemical Engineering Journal Advances, vol. 8, p. 100172,

2021.

[33] R. Sakthivel, K. Ramesh, R. Purnachandran, and P. Mohamed Shameer,

“A review on the properties, performance and emission aspects of the

third generation biodiesels,” Renewable and Sustainable Energy Reviews,

vol. 82, pp. 2970–2992, 2018.

[34] F. Synak, K. Culik, V. Rievaj, and J. Gana, “Liqueﬁed petroleum gas as

an alternative fuel,” Transportation Research Procedia, vol. 40, pp. 527–

534, 2019, tRANSCOM 2019 13th International Scientiﬁc Conference

on Sustainable, Modern and Safe Transport.

[35] J. Jiao, J. Li, and Y. Bai, “Ethanol as a vehicle fuel in china: A review from

the perspectives of raw material resource, vehicle, and infrastructure,”

Journal of Cleaner Production, vol. 180, pp. 832–845, 2018.

[36] C. Bae and J. Kim, “Alternative fuels for internal combustion engines,”

Proceedings of the Combustion Institute, vol. 36, no. 3, pp. 3389–3413,

2017.

[37] A. Demirbas, “Importance of biodiesel as transportation fuel,” Energy

policy, vol. 35, no. 9, pp. 4661–4670, 2007.

[38] A. Trattner, M. Klell, and F. Radner, “Sustainable hydrogen society–

vision, ﬁndings and development of a hydrogen economy using the

example of austria,” International Journal of Hydrogen Energy, vol. 47,

no. 4, pp. 2059–2079, 2022.

[39] J. De Vrieze, K. Verbeeck, I. Pikaar, J. Boere, A. Van Wijk, K. Rabaey,

and W. Verstraete, “The hydrogen gas bio-based economy and the pro-

duction of renewable building block chemicals, food and energy,” New

biotechnology, vol. 55, pp. 12–18, 2020.

[40] X. Zhang, X. Gao, Y. Zheng, Y. Xu, E. Chung, and A. R. Sayed,

“Low-carbon oriented collaborative planning of electricity-hydrogen-

gas-transportation integrated system considering hydrogen vehicles,”

IEEE Transactions on Network Science and Engineering, 2023.

[41] I. Sorrenti, Y. Zheng, A. Singlitico, and S. You, “Low-carbon and cost-

efﬁcient hydrogen optimisation through a grid-connected electrolyser:

The case of greenlab skive,” Renewable and Sustainable Energy Reviews,

vol. 171, p. 113033, 2023.

[42] X. Yan, J. Biemolt, K. Zhao, Y. Zhao, X. Cao, Y. Yang, X. Wu, G. Rothen-

berg, and N. Yan, “A membrane-free ﬂow electrolyzer operating at high

current density using earth-abundant catalysts for water splitting,” Nature

Communications, vol. 12, no. 1, pp. 1–9, 2021.

[43] M. N. I. Salehmin, T. Husaini, J. Goh, and A. B. Sulong, “High-pressure

pem water electrolyser: A review on challenges and mitigation strategies

towards green and low-cost hydrogen production,” Energy Conversion

and Management, vol. 268, p. 115985, 2022.

[44] Y. Zhao, P. V. Kumar, X. Tan, X. Lu, X. Zhu, J. Jiang, J. Pan, S. Xi,

H. Y. Yang, Z. Ma et al., “Modulating pt-o-pt atomic clusters with

isolated cobalt atoms for enhanced hydrogen evolution catalysis,” Nature

communications, vol. 13, no. 1, pp. 1–11, 2022.

[45] A. Hodges, A. L. Hoang, G. Tsekouras, K. Wagner, C.-Y. Lee, G. F.

Swiegers, and G. G. Wallace, “A high-performance capillary-fed electrol-

ysis cell promises more cost-competitive renewable hydrogen,” Nature

communications, vol. 13, no. 1, pp. 1–11, 2022.

[46] H. Shimada, T. Yamaguchi, H. Kishimoto, H. Sumi, Y. Yamaguchi,

K. Nomura, and Y. Fujishiro, “Nanocomposite electrodes for high current

density over 3 a cm- 2 in solid oxide electrolysis cells,” Nature commu-

nications, vol. 10, no. 1, pp. 1–10, 2019.

[47] L. Ye, M. Zhang, P. Huang, G. Guo, M. Hong, C. Li, J. T. Irvine, and

K. Xie, “Enhancing co2 electrolysis through synergistic control of non-

stoichiometry and doping to tune cathode surface structures,” Nature

communications, vol. 8, no. 1, pp. 1–10, 2017.

[48] D. Li, E. J. Park, W. Zhu, Q. Shi, Y. Zhou, H. Tian, Y. Lin, A. Serov,

B. Zulevi, E. D. Baca et al., “Highly quaternized polystyrene ionomers for

high performance anion exchange membrane water electrolysers,” Nature

Energy, vol. 5, no. 5, pp. 378–385, 2020.

[49] I. Vincent, E.-C. Lee, and H.-M. Kim, “Comprehensive impedance inves-

tigation of low-cost anion exchange membrane electrolysis for large-scale

hydrogen production,” Scientiﬁc Reports, vol. 11, no. 1, pp. 1–12, 2021.

[50] W. H. Lee, Y.-J. Ko, J. H. Kim, C. H. Choi, K. H. Chae, H. Kim, Y. J.

Hwang, B. K. Min, P. Strasser, and H.-S. Oh, “High crystallinity design

of ir-based catalysts drives catalytic reversibility for water electrolysis

and fuel cells,” Nature Communications, vol. 12, no. 1, pp. 1–10, 2021.

[51] H. G. Kuppusamy, P. Dhanasekaran, N. Nagaraju, M. Neeshma, B. M.

Dass, V. M. Dhavale, S. M. Unni, and S. D. Bhat, “Anion exchange mem-

branes for alkaline polymer electrolyte fuel cells—a concise review,”

Materials, vol. 15, no. 16, p. 5601, 2022.

[52] H. Ding, W. Wu, C. Jiang, Y. Ding, W. Bian, B. Hu, P. Singh, C. J.

Orme, L. Wang, Y. Zhang et al., “Self-sustainable protonic ceramic

electrochemical cells using a triple conducting electrode for hydrogen

and power production,” Nature communications, vol. 11, no. 1, pp. 1–11,

2020.

[53] B.-W. Zhang, T. Zheng, Y.-X. Wang, Y. Du, S.-Q. Chu, Z. Xia, R. Amal,

S.-X. Dou, and L. Dai, “Highly efﬁcient and selective electrocatalytic hy-

drogen peroxide production on co-oc active centers on graphene oxide,”

Communications Chemistry, vol. 5, no. 1, pp. 1–7, 2022.

VOLUME 4, 2016 21

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

[54] J. Tan, B. Kang, K. Kim, D. Kang, H. Lee, S. Ma, G. Jang, H. Lee,

and J. Moon, “Hydrogel protection strategy to stabilize water-splitting

photoelectrodes,” Nature Energy, pp. 1–11, 2022.

[55] Y. Qi, Y. Zhang, L. Yang, Y. Zhao, Y. Zhu, H. Jiang, and C. Li, “Insights

into the activity of nickel boride/nickel heterostructures for efﬁcient

methanol electrooxidation,” Nature communications, vol. 13, no. 1, pp.

1–11, 2022.

[56] B. Zhou, X. Kong, S. Vanka, S. Chu, P. Ghamari, Y. Wang, N. Pant,

I. Shih, H. Guo, and Z. Mi, “Gallium nitride nanowire as a linker of

molybdenum sulﬁdes and silicon for photoelectrocatalytic water split-

ting,” Nature communications, vol. 9, no. 1, pp. 1–8, 2018.

[57] R. Silva, A. Abreu, A. Salvador, M. Alves, I. C. Neves, and M. Pereira,

“Zeolite addition to improve biohydrogen production from dark fermen-

tation of c5/c6-sugars and sargassum sp. biomass,” Scientiﬁc reports,

vol. 11, no. 1, pp. 1–14, 2021.

[58] F. Russo, V. Luongo, M. R. Mattei, and L. Frunzo, “Mathematical

modeling of metal recovery from e-waste using a dark-fermentation-

leaching process,” Scientiﬁc reports, vol. 12, no. 1, pp. 1–17, 2022.

[59] W. J. Martinez-Burgos, E. de Souza Candeo, A. B. P. Medeiros, J. C.

de Carvalho, V. O. de Andrade Tanobe, C. R. Soccol, and E. B. Sydney,

“Hydrogen: Current advances and patented technologies of its renewable

production,” Journal of Cleaner Production, vol. 286, p. 124970, 2021.

[60] J. C. Wood, J. Grové, E. Marcellin, J. K. Heffernan, S. Hu, Z. Yuan,

and B. Virdis, “Strategies to improve viability of a circular carbon

bioeconomy-a techno-economic review of microbial electrosynthesis and

gas fermentation,” Water Research, vol. 201, p. 117306, 2021.

[61] D. Ferraren-De Cagalitan and M. Abundo, “A review of biohydrogen

production technology for application towards hydrogen fuel cells,”

Renewable and Sustainable Energy Reviews, vol. 151, p. 111413, 2021.

[62] C. Santoro, P. Bollella, B. Erable, P. Atanassov, and D. Pant, “Oxygen re-

duction reaction electrocatalysis in neutral media for bioelectrochemical

systems,” Nature Catalysis, pp. 1–12, 2022.

[63] S. Guo, X. Li, J. Li, and B. Wei, “Boosting photocatalytic hydrogen

production from water by photothermally induced biphase systems,”

Nature communications, vol. 12, no. 1, pp. 1–10, 2021.

[64] D. W. Wakerley, M. F. Kuehnel, K. L. Orchard, K. H. Ly, T. E. Rosser,

and E. Reisner, “Solar-driven reforming of lignocellulose to h2 with a

cds/cdox photocatalyst,” Nature Energy, vol. 2, no. 4, pp. 1–9, 2017.

[65] P. S. Gaikwad, K. Mondal, Y. K. Shin, A. C. van Duin, and G. Pawar, “En-

hancing the faradaic efﬁciency of solid oxide electrolysis cells: progress

and perspective,” npj Computational Materials, vol. 9, no. 1, p. 149, 2023.

[66] H. Zheng, F. Han, N. Sata, and R. Costa, “Hydrogen production at

intermediate temperatures with proton conducting ceramic cells: Elec-

trocatalytic activity, durability and energy efﬁciency,” Journal of Energy

Chemistry, vol. 86, pp. 437–446, 2023.

[67] H. Liang, M. Li, Z. Li, W. Xie, T. Zhang, and Q. Wang, “Photoelec-

trochemical co2 reduction with copper-based photocathodes,” Journal of

CO2 Utilization, vol. 79, p. 102639, 2024.

[68] J. F. Soares, F. D. Mayer, and M. A. Mazutti, “Hydrogen production from

brewer’s spent grain hydrolysate by dark fermentation,” International

Journal of Hydrogen Energy, vol. 52, pp. 352–363, 2024.

[69] A. Y. Goren, I. Dincer, and A. Khalvati, “Comparative environmental

sustainability assessment of biohydrogen production methods,” Science

of The Total Environment, p. 166613, 2023.

[70] P. Lykas, N. Georgousis, E. Bellos, and C. Tzivanidis, “A comprehensive

review of solar-driven multigeneration systems with hydrogen produc-

tion,” International Journal of Hydrogen Energy, vol. 48, no. 2, pp. 437–

477, 2023.

[71] Y. Patcharavorachot, N. Chatrattanawet, A. Arpornwichanop, and D. Sae-

bea, “Comparative energy, economic, and environmental analyses

of power-to-gas systems integrating soecs in steam-electrolysis and

co-electrolysis and methanation,” Thermal Science and Engineering

Progress, vol. 42, p. 101873, 2023.

[72] B. D. Catumba, M. B. Sales, P. T. Borges, M. N. Ribeiro Filho, A. A. S.

Lopes, M. A. de Sousa Rios, A. S. Desai, M. Bilal, and J. C. S. dos Santos,

“Sustainability and challenges in hydrogen production: An advanced

bibliometric analysis,” International Journal of Hydrogen Energy, vol. 48,

no. 22, pp. 7975–7992, 2023.

[73] A. Di Nardo, M. Portarapillo, D. Russo, and A. Di Benedetto, “Hydrogen

production via steam reforming of different fuels: thermodynamic com-

parison,” International Journal of Hydrogen Energy, vol. 55, pp. 1143–

1160, 2024.

[74] E. Bianco and H. Blanco, “Green hydrogen: a guide to policy making,”

2020.

[75] I. R. E. Agency, “Green hydrogen cost reduction: Scaling up electrolysers

to meet the 1.5° c climate goal,” 2020.

[76] S. Shiva Kumar and H. Lim, “An overview of water electrolysis technolo-

gies for green hydrogen production,” Energy Reports, vol. 8, pp. 13 793–

13 813, 2022.

[77] S. G. Nnabuife, J. Ugbeh-Johnson, N. E. Okeke, and C. Ogbonnaya,

“Present and projected developments in hydrogen production: A techno-

logical review,” Carbon Capture Science & Technology, vol. 3, p. 100042,

2022.

[78] N. Meng, J. Shao, H. Li, Y. Wang, X. Fu, C. Liu, Y. Yu, and B. Zhang,

“Electrosynthesis of formamide from methanol and ammonia under

ambient conditions,” Nature Communications, vol. 13, no. 1, pp. 1–8,

2022.

[79] M. Jayachandran and G. Ravi, “Design and optimization of hybrid micro-

grid system,” Energy Procedia, vol. 117, pp. 95–103, 2017.

[80] G. Glenk and S. Reichelstein, “Reversible power-to-gas systems for

energy conversion and storage,” Nature communications, vol. 13, no. 1,

pp. 1–10, 2022.

[81] W. Li, Z. Yin, Z. Gao, G. Wang, Z. Li, F. Wei, X. Wei, H. Peng, X. Hu,

L. Xiao et al., “Bifunctional ionomers for efﬁcient co-electrolysis of co2

and pure water towards ethylene production at industrial-scale current

densities,” Nature Energy, vol. 7, no. 9, pp. 835–843, 2022.

[82] R.-P. Ye, J. Ding, W. Gong, M. D. Argyle, Q. Zhong, Y. Wang, C. K.

Russell, Z. Xu, A. G. Russell, Q. Li et al., “Co2 hydrogenation to high-

value products via heterogeneous catalysis,” Nature communications,

vol. 10, no. 1, pp. 1–15, 2019.

[83] F. Stöckl, W.-P. Schill, and A. Zerrahn, “Optimal supply chains and power

sector beneﬁts of green hydrogen,” Scientiﬁc reports, vol. 11, no. 1, pp.

1–14, 2021.

[84] A. J. Shih, M. C. Monteiro, F. Dattila, D. Pavesi, M. Philips, A. H.

da Silva, R. E. Vos, K. Ojha, S. Park, O. van der Heijden et al., “Water

electrolysis,” Nature Reviews Methods Primers, vol. 2, no. 1, pp. 1–19,

2022.

[85] A. Odenweller, F. Ueckerdt, G. F. Nemet, M. Jensterle, and G. Luderer,

“Probabilistic feasibility space of scaling up green hydrogen supply,”

Nature Energy, vol. 7, no. 9, pp. 854–865, 2022.

[86] J. Gong, “A commentary of green hydrogen in mit technology review

2021,” Fundamental Research, vol. 1, no. 6, pp. 848–850, 2021.

[87] H. Renaudineau, A. M. Llor, R. Cortés, C. A. Rojas, C. Restrepo, and

S. Kouro, “Photovoltaic green hydrogen challenges and opportunities:

A power electronics perspective,” IEEE Industrial Electronics Magazine,

vol. 16, no. 1, pp. 31–41, 2021.

[88] R. Raman, V. K. Nair, V. Prakash, A. Patwardhan, and P. Nedungadi,

“Green-hydrogen research: What have we achieved, and where are we

going? bibliometrics analysis,” Energy Reports, vol. 8, pp. 9242–9260,

2022.

[89] F. Eljack and M.-K. Kazi, “Prospects and challenges of green hydrogen

economy via multi-sector global symbiosis in qatar,” Frontiers in Sus-

tainability, vol. 1, p. 612762, 2021.

[90] A. Clerici and S. Furfari, “Challenges for green hydrogen development,”

in 2021 AEIT International Annual Conference (AEIT). IEEE, 2021,

pp. 1–6.

[91] X. Song, D. Liang, J. Song, G. Xu, Z. Deng, and M. Niu, “Problems and

technology development trends of hydrogen production from renewable

energy power electrolysis-a review,” in 2021 IEEE 5th Conference on

Energy Internet and Energy System Integration (EI2). IEEE, 2021, pp.

3879–3882.

[92] I. R. E. Agency, “Innovation trends in electrolysers for hydrogen produc-

tion,” 2022.

[93] J. Knöppel, M. Möckl, D. Escalera-López, K. Stojanovski, M. Bierling,

T. Böhm, S. Thiele, M. Rzepka, and S. Cherevko, “On the limitations

in assessing stability of oxygen evolution catalysts using aqueous model

electrochemical cells,” Nature communications, vol. 12, no. 1, pp. 1–9,

2021.

[94] S. Song, H. Lin, P. Sherman, X. Yang, C. P. Nielsen, X. Chen, and M. B.

McElroy, “Production of hydrogen from offshore wind in china and cost-

competitive supply to japan,” Nature communications, vol. 12, no. 1, pp.

1–8, 2021.

[95] J. Hughes, J. Clipsham, H. Chavushoglu, S. Rowley-Neale, and C. Banks,

“Polymer electrolyte electrolysis: A review of the activity and stability

of non-precious metal hydrogen evolution reaction and oxygen evolution

reaction catalysts,” Renewable and Sustainable Energy Reviews, vol. 139,

p. 110709, 2021.

22 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

[96] M. Maier, K. Smith, J. Dodwell, G. Hinds, P. Shearing, and D. Brett,

“Mass transport in pem water electrolysers: A review,” International

Journal of Hydrogen Energy, 2021.

[97] S. Saha, B. Rajbongshi, V. Ramani, and A. Verma, “Titanium carbide:

An emerging electrocatalyst for fuel cell and electrolyser,” International

Journal of hydrogen energy, vol. 46, no. 24, pp. 12 801–12 821, 2021.

[98] G. Sakas, A. Ibáñez-Rioja, V. Ruuskanen, A. Kosonen, J. Ahola, and

O. Bergmann, “Dynamic energy and mass balance model for an indus-

trial alkaline water electrolyzer plant process,” International Journal of

Hydrogen Energy, vol. 47, no. 7, pp. 4328–4345, 2022.

[99] S. Harrison and M. Hayne, “Photoelectrolysis using type-ii semiconduc-

tor heterojunctions,” Scientiﬁc Reports, vol. 7, no. 1, pp. 1–11, 2017.

[100] D. Wu, K. Kusada, S. Yoshioka, T. Yamamoto, T. Toriyama, S. Mat-

sumura, Y. Chen, O. Seo, J. Kim, C. Song et al., “Efﬁcient overall water

splitting in acid with anisotropic metal nanosheets,” Nature communica-

tions, vol. 12, no. 1, pp. 1–9, 2021.

[101] S. Pan, H. Li, D. Liu, R. Huang, X. Pan, D. Ren, J. Li, M. Shakouri,

Q. Zhang, M. Wang et al., “Efﬁcient and stable noble-metal-free catalyst

for acidic water oxidation,” Nature Communications, vol. 13, no. 1, pp.

1–10, 2022.

[102] B. Turan, J.-P. Becker, F. Urbain, F. Finger, U. Rau, and S. Haas,

“Upscaling of integrated photoelectrochemical water-splitting devices to

large areas,” Nature communications, vol. 7, no. 1, pp. 1–9, 2016.

[103] L. Fan, P. F. Liu, X. Yan, L. Gu, Z. Z. Yang, H. G. Yang, S. Qiu,

and X. Yao, “Atomically isolated nickel species anchored on graphitized

carbon for efﬁcient hydrogen evolution electrocatalysis,” Nature commu-

nications, vol. 7, no. 1, pp. 1–7, 2016.

[104] T. Egeland-Eriksen, A. Hajizadeh, and S. Sartori, “Hydrogen-based sys-

tems for integration of renewable energy in power systems: Achieve-

ments and perspectives,” international journal of hydrogen energy,

vol. 46, no. 63, pp. 31 963–31 983, 2021.

[105] A. Ahmed, S. Seth, J. Purewal, A. G. Wong-Foy, M. Veenstra, A. J.

Matzger, and D. J. Siegel, “Exceptional hydrogen storage achieved by

screening nearly half a million metal-organic frameworks,” Nature com-

munications, vol. 10, no. 1, pp. 1–9, 2019.

[106] J. Andersson and S. Grönkvist, “Large-scale storage of hydrogen,” Inter-

national Journal of Hydrogen Energy, vol. 44, no. 23, pp. 11 901–11 919,

2019.

[107] A. M. Elberry, J. Thakur, A. Santasalo-Aarnio, and M. Larmi, “Large-

scale compressed hydrogen storage as part of renewable electricity stor-

age systems,” International journal of hydrogen energy, vol. 46, no. 29,

pp. 15 671–15690, 2021.

[108] M. Sahlberg, D. Karlsson, C. Zlotea, and U. Jansson, “Superior hydrogen

storage in high entropy alloys,” Scientiﬁc reports, vol. 6, no. 1, pp. 1–6,

2016.

[109] Z. Wan, Y. Tao, J. Shao, Y. Zhang, and H. You, “Ammonia as an effective

hydrogen carrier and a clean fuel for solid oxide fuel cells,” Energy

Conversion and Management, vol. 228, p. 113729, 2021.

[110] M. Hattori, S. Iijima, T. Nakao, H. Hosono, and M. Hara, “Solid solution

for catalytic ammonia synthesis from nitrogen and hydrogen gases at 50

c,” Nature communications, vol. 11, no. 1, pp. 1–8, 2020.

[111] P. Xie, Y. Yao, Z. Huang, Z. Liu, J. Zhang, T. Li, G. Wang, R. Shahbazian-

Yassar, L. Hu, and C. Wang, “Highly efﬁcient decomposition of ammonia

using high-entropy alloy catalysts,” Nature communications, vol. 10,

no. 1, pp. 1–12, 2019.

[112] P. Hu, E. Fogler, Y. Diskin-Posner, M. A. Iron, and D. Milstein, “A

novel liquid organic hydrogen carrier system based on catalytic peptide

formation and hydrogenation,” Nature communications, vol. 6, no. 1, pp.

1–7, 2015.

[113] D. Wei, R. Sang, P. Sponholz, H. Junge, and M. Beller, “Reversible hy-

drogenation of carbon dioxide to formic acid using a mn-pincer complex

in the presence of lysine,” Nature Energy, vol. 7, no. 5, pp. 438–447,

2022.

[114] P. Peng, A. Anastasopoulou, K. Brooks, H. Furukawa, M. E. Bowden,

J. R. Long, T. Autrey, and H. Breunig, “Cost and potential of metal–

organic frameworks for hydrogen back-up power supply,” Nature Energy,

vol. 7, no. 5, pp. 448–458, 2022.

[115] H.-L. Du, M. Chatti, R. Y. Hodgetts, P. V. Cherepanov, C. K. Nguyen,

K. Matuszek, D. R. MacFarlane, and A. N. Simonov, “Electroreduction

of nitrogen at almost 100% current-to-ammonia efﬁciency,” Nature, pp.

1–2, 2022.

[116] H. Li, L. Li, R.-B. Lin, G. Ramirez, W. Zhou, R. Krishna, Z. Zhang,

S. Xiang, and B. Chen, “Microporous metal–organic framework with

dual functionalities for efﬁcient separation of acetylene from light hy-

drocarbon mixtures,” ACS sustainable chemistry & engineering, vol. 7,

no. 5, pp. 4897–4902, 2019.

[117] Y. Sun, S. Polani, F. Luo, S. Ott, P. Strasser, and F. Dionigi, “Advance-

ments in cathode catalyst and cathode layer design for proton exchange

membrane fuel cells,” Nature communications, vol. 12, no. 1, pp. 1–14,

2021.

[118] D. P. Broom, C. Webb, G. S. Fanourgakis, G. E. Froudakis, P. N.

Trikalitis, and M. Hirscher, “Concepts for improving hydrogen storage in

nanoporous materials,” International journal of hydrogen energy, vol. 44,

no. 15, pp. 7768–7779, 2019.

[119] A. E. Baumann, D. A. Burns, B. Liu, and V. S. Thoi, “Metal-organic

framework functionalization and design strategies for advanced electro-

chemical energy storage devices,” Communications Chemistry, vol. 2,

no. 1, pp. 1–14, 2019.

[120] E. S. Cho, A. M. Ruminski, S. Aloni, Y.-S. Liu, J. Guo, and J. J. Urban,

“Graphene oxide/metal nanocrystal multilaminates as the atomic limit

for safe and selective hydrogen storage,” Nature communications, vol. 7,

no. 1, pp. 1–8, 2016.

[121] X. Zhang, Y. Sun, G. Xia, and X. Yu, “Light-weight solid-state hydrogen

storage materials characterized by neutron scattering,” Journal of Alloys

and Compounds, vol. 899, p. 163254, 2022.

[122] J. Barale, S. Deledda, E. M. Dematteis, M. H. Sørby, M. Baricco, and

B. C. Hauback, “Synthesis and characterization of magnesium-iron-

cobalt complex hydrides,” Scientiﬁc reports, vol. 10, no. 1, pp. 1–11,

2020.

[123] P. Schouwink, M. B. Ley, A. Tissot, H. Hagemann, T. R. Jensen,

L. Smrˇ

cok, and R. ˇ

Cern`

y, “Structure and properties of complex hydride

perovskite materials,” Nature communications, vol. 5, no. 1, pp. 1–10,

2014.

[124] A. Witkowski, A. Rusin, M. Majkut, and K. Stolecka, “Comprehensive

analysis of hydrogen compression and pipeline transportation from ther-

modynamics and safety aspects,” Energy, vol. 141, pp. 2508–2518, 2017.

[125] Y. Rong, S. Chen, C. Li, X. Chen, L. Xie, J. Chen, and R. Long, “Techno-

economic analysis of hydrogen storage and transportation from hydrogen

plant to terminal refueling station,” International Journal of Hydrogen

Energy, 2023.

[126] G. Di Lullo, T. Giwa, A. Okunlola, M. Davis, T. Mehedi, A. Oni,

and A. Kumar, “Large-scale long-distance land-based hydrogen trans-

portation systems: A comparative techno-economic and greenhouse gas

emission assessment,” International Journal of Hydrogen Energy, vol. 47,

no. 83, pp. 35 293–35319, 2022.

[127] Y. Ishimoto, M. Voldsund, P. Nekså, S. Roussanaly, D. Berstad, and S. O.

Gardarsdottir, “Large-scale production and transport of hydrogen from

norway to europe and japan: Value chain analysis and comparison of

liquid hydrogen and ammonia as energy carriers,” International Journal

of Hydrogen Energy, vol. 45, no. 58, pp. 32 865–32 883, 2020.

[128] C. J. McKinlay, S. R. Turnock, and D. A. Hudson, “Route to zero emis-

sion shipping: Hydrogen, ammonia or methanol?” International journal

of hydrogen energy, vol. 46, no. 55, pp. 28 282–28 297, 2021.

[129] K. Reddi, A. Elgowainy, N. Rustagi, and E. Gupta, “Techno-economic

analysis of conventional and advanced high-pressure tube trailer con-

ﬁgurations for compressed hydrogen gas transportation and refueling,”

International journal of hydrogen energy, vol. 43, no. 9, pp. 4428–4438,

2018.

[130] S. F. Ahmed, M. Moﬁjur, S. Nuzhat, N. Rafa, A. Musharrat, S. S.

Lam, and A. Boretti, “Sustainable hydrogen production: Technological

advancements and economic analysis,”International Journal of Hydrogen

Energy, vol. 47, no. 88, pp. 37 227–37 255, 2022.

[131] C. Dong, Z. Gao, Y. Li, M. Peng, M. Wang, Y. Xu, C. Li, M. Xu, Y. Deng,

X. Qin et al., “Fully exposed palladium cluster catalysts enable hydrogen

production from nitrogen heterocycles,” Nature Catalysis, pp. 1–9, 2022.

[132] “Hydrogen on the rise,” Nature Energy, vol. 1, no. 16127, 2016.

[133] X. Yang, C. P. Nielsen, S. Song, and M. B. McElroy, “Breaking the

hard-to-abate bottleneck in china’s path to carbon neutrality with clean

hydrogen,” Nature Energy, vol. 7, no. 10, pp. 955–965, 2022.

[134] C. Kim, S. H. Cho, S. M. Cho, Y. Na, S. Kim, and D. K. Kim, “Review

of hydrogen infrastructure: the current status and roll-out strategy,”

International Journal of Hydrogen Energy, vol. 48, no. 5, pp. 1701–1716,

2023.

[135] A. Aghakhani, N. Haque, C. Saccani, M. Pellegrini, and A. Guzzini,

“Hydrogen transportation and distribution,” in Towards Hydrogen Infras-

tructure. Elsevier, 2024, pp. 187–224.

[136] M. S. Ali, M. S. H. Khan, R. A. Tuhin, M. A. Kabir, A. K. Azad, and

O. Farrok, “Hydrogen energy storage and transportation challenges: A

VOLUME 4, 2016 23

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

review of recent advances,” Hydrogen Energy Conversion and Manage-

ment, pp. 255–287, 2024.

[137] S. Kumar, A. Nanan-Surujbally, D. P. Sharma, and D. Pathak, “Hydro-

gen safety/standards (national and international document standards on

hydrogen energy and fuel cell),” in Towards Hydrogen Infrastructure.

Elsevier, 2024, pp. 315–346.

[138] K. R. Simonsen, D. S. Hansen, and S. Pedersen, “Challenges in co2

transportation: Trends and perspectives,” Renewable and Sustainable

Energy Reviews, vol. 191, p. 114149, 2024.

[139] C.-L. Chang, W.-C. Lin, L.-Y. Ting, C.-H. Shih, S.-Y. Chen, T.-F.

Huang, H. Tateno, J. Jayakumar, W.-Y. Jao, C.-W. Tai et al., “Main-chain

engineering of polymer photocatalysts with hydrophilic non-conjugated

segments for visible-light-driven hydrogen evolution,” Nature Communi-

cations, vol. 13, no. 1, pp. 1–11, 2022.

[140] M. K. Debe, “Electrocatalyst approaches and challenges for automotive

fuel cells,” Nature, vol. 486, no. 7401, pp. 43–51, 2012.

[141] Z. Feng, J. Huang, S. Jin, G. Wang, and Y. Chen, “Artiﬁcial intelligence-

based multi-objective optimisation for proton exchange membrane fuel

cell: A literature review,” Journal of Power Sources, vol. 520, p. 230808,

2022.

[142] S. B. Beale, M. Andersson, C. Boigues-Muñoz, H. L. Frandsen, Z. Lin,

S. J. McPhail, M. Ni, B. Sundén, A. Weber, and A. Z. Weber, “Contin-

uum scale modelling and complementary experimentation of solid oxide

cells,” Progress in energy and combustion science, vol. 85, p. 100902,

2021.

[143] A. Harriman, “Electrochemical catalysts to meet the challenge for sus-

tainable fuel production from renewable energy,” Current Opinion in

Green and Sustainable Chemistry, vol. 30, p. 100492, 2021.

[144] P. Plötz, “Hydrogen technology is unlikely to play a major role in

sustainable road transport,” Nature Electronics, vol. 5, no. 1, pp. 8–10,

2022.

[145] S. Rashidi, N. Karimi, B. Sunden, K. C. Kim, A. G. Olabi, and O. Mahian,

“Progress and challenges on the thermal management of electrochemical

energy conversion and storage technologies: Fuel cells, electrolysers, and

supercapacitors,” Progress in Energy and Combustion Science, vol. 88, p.

100966, 2022.

[146] H. Q. Nguyen and B. Shabani, “Review of metal hydride hydrogen stor-

age thermal management for use in the fuel cell systems,” International

Journal of Hydrogen Energy, vol. 46, no. 62, pp. 31 699–31 726, 2021.

[147] M. Tahir, S. Hu, T. Khan, and H. Zhu, “Sustainable hybrid station design

framework for electric vehicle charging and hydrogen vehicle refueling

based on multiple attributes,” Energy Conversion and Management, vol.

300, p. 117922, 2024.

[148] S. Yu, Y. Fan, Z. Shi, J. Li, X. Zhao, T. Zhang, and Z. Chang, “Hydrogen-

based combined heat and power systems: A review of technologies and

challenges,” International Journal of Hydrogen Energy, 2023.

[149] Y.-K. Kim, J.-H. Kim, and S.-H. Yoo, “Public perspective on co-ﬁring

hydrogen with natural gas in power plants in south korea,” International

Journal of Hydrogen Energy, vol. 48, no. 11, pp. 4119–4128, 2023.

[150] Z. Xi, T. Lian, X. Shi, Z. Liu, S. Han, X. Yang, J. Zhang, W. Li, B. Mei,

and Y. Li, “Co-ﬁring hydrogen and dimethyl ether in a gas turbine

model combustor: Inﬂuence of hydrogen content and comparison with

methane,” International Journal of Hydrogen Energy, vol. 47, no. 90, pp.

38 432–38 444, 2022.

[151] D. Keiner, C. Thoma, D. Bogdanov, and C. Breyer, “Seasonal hydrogen

storage for residential on-and off-grid solar photovoltaics prosumer appli-

cations: Revolutionary solution or niche market for the energy transition

until 2050?” Applied Energy, vol. 340, p. 121009, 2023.

[152] F. Ferrada, F. Babonneau, T. Homem-de Mello, and F. Jalil-Vega, “The

role of hydrogen for deep decarbonization of energy systems: A chilean

case study,” Energy Policy, vol. 177, p. 113536, 2023.

[153] W. Bian, W. Wu, B. Wang, W. Tang, M. Zhou, C. Jin, H. Ding, W. Fan,

Y. Dong, J. Li et al., “Revitalizing interface in protonic ceramic cells by

acid etch,” Nature, vol. 604, no. 7906, pp. 479–485, 2022.

[154] J. Huang and Y. Wang, “Efﬁcient renewable-to-hydrogen conversion

via decoupled electrochemical water splitting,” Cell Reports Physical

Science, vol. 1, no. 8, p. 100138, 2020.

[155] N. Chen, H. H. Wang, S. P. Kim, H. M. Kim, W. H. Lee, C. Hu, J. Y.

Bae, E. S. Sim, Y.-C. Chung, J.-H. Jang et al., “Poly (ﬂuorenyl aryl

piperidinium) membranes and ionomers for anion exchange membrane

fuel cells,” Nature communications, vol. 12, no. 1, pp. 1–12, 2021.

[156] Y. Zhang, B. Chen, D. Guan, M. Xu, R. Ran, M. Ni, W. Zhou,

R. O’Hayre, and Z. Shao, “Thermal-expansion offset for high-

performance fuel cell cathodes,” Nature, vol. 591, no. 7849, pp. 246–251,

2021.

[157] Y. Zhou, X. Guan, H. Zhou, K. Ramadoss, S. Adam, H. Liu, S. Lee,

J. Shi, M. Tsuchiya, D. D. Fong et al., “Strongly correlated perovskite

fuel cells,” Nature, vol. 534, no. 7606, pp. 231–234, 2016.

[158] C. Duan, R. J. Kee, H. Zhu, C. Karakaya, Y. Chen, S. Ricote, A. Jarry,

E. J. Crumlin, D. Hook, R. Braun et al., “Highly durable, coking and

sulfur tolerant, fuel-ﬂexible protonic ceramic fuel cells,” Nature, vol. 557,

no. 7704, pp. 217–222, 2018.

[159] K. Jiao, J. Xuan, Q. Du, Z. Bao, B. Xie, B. Wang, Y. Zhao, L. Fan,

H. Wang, Z. Hou et al., “Designing the next generation of proton-

exchange membrane fuel cells,” Nature, vol. 595, no. 7867, pp. 361–369,

2021.

[160] C. H. Park, S. Y. Lee, D. S. Hwang, D. W. Shin, D. H. Cho, K. H. Lee,

T.-W. Kim, T.-W. Kim, M. Lee, D.-S. Kim et al., “Nanocrack-regulated

self-humidifying membranes,” Nature, vol. 532, no. 7600, pp. 480–483,

2016.

[161] J.-h. Myung, D. Neagu, D. N. Miller, and J. T. Irvine, “Switching on

electrocatalytic activity in solid oxide cells,” Nature, vol. 537, no. 7621,

pp. 528–531, 2016.

[162] D. Milani, A. Kiani, and R. McNaughton, “Renewable-powered hy-

drogen economy from australia’s perspective,” International Journal of

Hydrogen Energy, vol. 45, no. 46, pp. 24 125–24 145, 2020.

[163] Y. Li and F. Taghizadeh-Hesary, “The economic feasibility of green

hydrogen and fuel cell electric vehicles for road transport in china,”

Energy Policy, vol. 160, p. 112703, 2022.

[164] P. J. Megia, A. J. Vizcaino, J. A. Calles, and A. Carrero, “Hydrogen

production technologies: from fossil fuels toward renewable sources. a

mini review,” Energy & Fuels, vol. 35, no. 20, pp. 16403–16 415, 2021.

[165] B. Delaval, T. Rapson, R. Sharma, W. Hugh-Jones, E. McClure, M. Tem-

minghoff, and V. Srinivasan, “Hydrogen rd&d collaboration opportuni-

ties: Global report,” 2022.

[166] International Energy Agency (IEA), “Global hydrogen review 2022,”

2022.

[167] H. H. Cho, V. Strezov, and T. J. Evans, “A review on global warming

potential, challenges and opportunities of renewable hydrogen produc-

tion technologies,” Sustainable Materials and Technologies, vol. 35, p.

e00567, 2023.

[168] V. Panchenko, Y. Daus, A. Kovalev, I. Yudaev, and Y. Litti, “Prospects

for the production of green hydrogen: Review of countries with high

potential,” International Journal of Hydrogen Energy, vol. 48, no. 12, pp.

4551–4571, 2023.

[169] H. Ishaq, I. Dincer, and C. Crawford, “A review on hydrogen production

and utilization: Challenges and opportunities,” International Journal of

Hydrogen Energy, vol. 47, no. 62, pp. 26 238–26 264, 2022, sI: Progress

in Hydrogen Production, Storage and Distribution (Ahmadi).

[170] T. B. Ferriday and P. H. Middleton, “Alkaline fuel cell technology-a

review,” international journal of hydrogen energy, vol. 46, no. 35, pp.

18 489–18 510, 2021.

[171] S. Zhang, Y. Liu, M. Zhang, Y. Ma, J. Hu, and Y. Qu, “Sustainable

production of hydrogen with high purity from methanol and water at low

temperatures,” 2022.

[172] J. Zhang, L. Zhang, J. Liu, C. Zhong, Y. Tu, P. Li, L. Du, S. Chen,

and Z. Cui, “Oh spectator at irmo intermetallic narrowing activity gap

between alkaline and acidic hydrogen evolution reaction,” Nature com-

munications, vol. 13, no. 1, pp. 1–9, 2022.

[173] F.-Y. Gao, P.-C. Yu, and M.-R. Gao, “Seawater electrolysis technologies

for green hydrogen production: challenges and opportunities,” Current

Opinion in Chemical Engineering, vol. 36, p. 100827, 2022.

[174] G. K. Li, J. Guo, Y. Zhang, A. Zavabeti, K. Chen, Y. Guo, G. Hu, and

X. Fan, “Hydrogen production from the air,” 2021.

[175] F.-Y. Gao, P.-C. Yu, and M.-R. Gao, “Seawater electrolysis technologies

for green hydrogen production: challenges and opportunities,” Current

Opinion in Chemical Engineering, vol. 36, p. 100827, 2022.

[176] R. R. Barth, K. L. Simmons, and C. W. San Marchi, “Polymers for hydro-

gen infrastructure and vehicle fuel systems,” Sandia National Lab.(SNL-

CA), Livermore, CA (United States); Paciﬁc .. . , Tech. Rep., 2013.

[177] A. H. Azadnia, C. McDaid, A. M. Andwari, and S. E. Hosseini, “Green

hydrogen supply chain risk analysis: A european hard-to-abate sectors

perspective,” Renewable and Sustainable Energy Reviews, vol. 182, p.

113371, 2023.

[178] B. Shadidi, G. Najaﬁ, and T. Yusaf, “A review of hydrogen as a fuel in

internal combustion engines,” Energies, vol. 14, no. 19, 2021.

24 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

[179] Z. Wang, R. Roberts, G. Naterer, and K. Gabriel, “Comparison of

thermochemical, electrolytic, photoelectrolytic and photochemical solar-

to-hydrogen production technologies,” International journal of hydrogen

energy, vol. 37, no. 21, pp. 16 287–16 301, 2012.

[180] F. Kuttassery, S. Sagawa, S. Mathew, Y. Nabetani, A. Iwase, A. Kudo,

H. Tachibana, and H. Inoue, “Water splitting on aluminum porphyrins to

form hydrogen and hydrogen peroxide by one photon of visible light,”

ACS Applied Energy Materials, vol. 2, no. 11, pp. 8045–8051, 2019.

[181] G. Mussabek, S. A. Alekseev, A. I. Manilov, S. Tutashkonko, T. Nychy-

poruk, Y. Shabdan, G. Amirkhanova, S. V. Litvinenko, V. A. Skryshevsky,

and V. Lysenko, “Kinetics of hydrogen generation from oxidation of

hydrogenated silicon nanocrystals in aqueous solutions,” Nanomaterials,

vol. 10, no. 7, 2020.

[182] D. Banerjee, N. Kushwaha, N. P. Shetti, T. M. Aminabhavi, and E. Ah-

mad, “Green hydrogen production via photo-reforming of bio-renewable

resources,” Renewable and Sustainable Energy Reviews, vol. 167, p.

112827, 2022.

[183] P. Chatterjee, M. S. K. Ambati, A. K. Chakraborty, S. Chakrabortty,

S. Biring, S. Ramakrishna, T. K. S. Wong, A. Kumar, R. Lawaniya, and

G. K. Dalapati, “Photovoltaic/photo-electrocatalysis integration for green

hydrogen: A review,” Energy Conversion and Management, vol. 261, p.

115648, 2022.

[184] M. Rumayor, J. Fernández-González, A. Domínguez-Ramos, and

A. Irabien, “Perspectives for a sustainable implementation of super-green

hydrogen production by photoelectrochemical technology in hard-to-

abate sectors,” Cleaner Production Letters, vol. 4, p. 100041, 2023.

[185] F. Schorn, J. L. Breuer, R. C. Samsun, T. Schnorbus, B. Heuser, R. Peters,

and D. Stolten, “Methanol as a renewable energy carrier: An assessment

of production and transportation costs for selected global locations,”

Advances in Applied Energy, vol. 3, p. 100050, 2021.

[186] H. Xin, “Catalyst design with machine learning,” Nature Energy, pp. 790–

791, 2022.

[187] S. Zhai, H. Xie, P. Cui, D. Guan, J. Wang, S. Zhao, B. Chen, Y. Song,

Z. Shao, and M. Ni, “A combined ionic lewis acid descriptor and

machine-learning approach to prediction of efﬁcient oxygen reduction

electrodes for ceramic fuel cells,” Nature Energy, pp. 1–10, 2022.

[188] T. M. Gulotta, R. Salomone, F. Lanuzza, G. Saija, G. Mondello, and

G. Ioppolo, “Life cycle assessment and life cycle costing of unitized

regenerative fuel cell: A systematic review,” Environmental Impact As-

sessment Review, vol. 92, p. 106698, 2022.

[189] G. Shen, J. Liu, H. B. Wu, P. Xu, F. Liu, C. Tongsh, K. Jiao, J. Li,

M. Liu, M. Cai et al., “Multi-functional anodes boost the transient

power and durability of proton exchange membrane fuel cells,” Nature

communications, vol. 11, no. 1, pp. 1–10, 2020.

[190] S. S. Rathore, S. Biswas, D. Fini, A. P. Kulkarni, and S. Giddey, “Direct

ammonia solid-oxide fuel cells: A review of progress and prospects,”

International Journal of Hydrogen Energy, vol. 46, no. 71, pp. 35 365–

35 384, 2021.

[191] K. Dahal, S. Brynolf, C. Xisto, J. Hansson, M. Grahn, T. Grönstedt,

and M. Lehtveer, “Techno-economic review of alternative fuels and

propulsion systems for the aviation sector,” Renewable and Sustainable

Energy Reviews, vol. 151, p. 111564, 2021.

[192] D. Pivetta, C. Dall’Armi, P. Sandrin, M. Bogar, and R. Taccani, “The

role of hydrogen as enabler of industrial port area decarbonization,”

Renewable and Sustainable Energy Reviews, vol. 189, p. 113912, 2024.

JAYACHANDRAN. M has been researching

Green Energy since the late 2016s. He has pub-

lished many articles in journals and conferences

on the topic. He has a Bachelor’s degree (2006)

from Anna University and a doctorate (2021)

from Pondicherry University. He has currently

worked at Puducherry Technological University,

Puducherry, India. He has 10+ years of experience

in academia, research, teaching, and academic ad-

ministration. His current research interests include

Green and Sustainable Energy System.

RANJITH KUMAR GATLA is working as an

Associate Professor in the EEE Department and

Dean of Intellectual Property Management and

Commercialization at the Institute of Aeronautical

Engineering, Hyderabad, India. He received the

M.Tech. degree in power electronics from SRM

University, Chennai, India, and the Ph.D. degree

in power electronics from Wuhan University of

Technology, Wuhan, China, in 2008 and 2019, re-

spectively. Dr. Ranjith Kumar Gatla has 11+ years

of experience in academia, research, teaching, and academic administration.

His current research interests include the reliability of power electronics

systems, grid-connected PV systems, multilevel inverters, and electric ve-

hicle technologies. Dr. Ranjith Kumar Gatla is an IEEE Senior Member. He

is a Life-Member of ISTE, Associate Member of IE (I), and Member of

IAENG. He published 40+ research papers and 4+ patents. He is a frequent

reviewer, editorial board member and TPC member in ﬂagship conferences

and refereed journals.

AYMEN FLAH was born in Gabès, Tunisia, in

1983. He received the bachelor’s degree in elec-

trical engineering and the M.Tech. degree from

the ENIG, Tunisia, in 2007 and 2009, respectively,

and the Ph.D. degree from the Department of

Electrical Engineering, in 2012. He has academic

experience of 11 years. He has published over

40 research articles in reputed journals, and over

40 research papers in international conferences

and book chapters. His research interests include

electric vehicle, power systems, and renewable energy.

AHMAD H. MILYANI received the B.Sc with

distinction and the M.Sc degrees in Electrical and

Computer Engineering from Purdue University in

2011 and 2013, respectively, and the Ph.D. degree

in Electrical Engineering from the University of

Washington in 2019. He is currently an Associate

Professor with the Department of Electrical and

Computer Engineering, King Abdulaziz Univer-

sity, Jeddah, Saudi Arabia. His research interests

include power systems operation and optimiza-

tion, renewable and sustainable energy, power electronics, electric machines,

electric vehicles, and computational intelligence applications.

PLACE

PHOTO

HERE

Hisham M. Milyani received the Ph.D. degree

from Florida State University in 1983. He is cur-

rently an Associate Professor with the College of

Applied Studies, King Abdulaziz University, Jed-

dah, Saudi Arabia. His research interests include

economics, management, budgetary process, and

public policy.

VOLUME 4, 2016 25

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

VOJTECH BLAZEK was born in Czech Re-

public, in 1991. He received the Ing. degree

from the Department of Electrical Engineering,

VSB—Technical University of Ostrava, in 2016.

He is currently an Internal Doctoral Student and

a Junior Researcher with the Research Centre

ENET–Energy Units for Utilization of Non- Tra-

ditional Energy Sources, VSB—Technical Univer-

sity of Ostrava. His current work includes devel-

oping modern and green technologies in off-grid

systems with vehicle to home technologies.

LUKAS PROKOP graduated the Ing. degree ma-

joring in electrical power engineering from the

Faculty of Electrical Engineering and Communi-

cation, Brno University of Technology. He is an

Associate Professor at FEI TU Ostrava. Currently,

he is engaged in renewable energy sources, mod-

ern technologies, and methods in electrical power

engineering and electrical measurements. He is a

research team member of Czech and international

research projects. He serves as the Deputy Head of

the ENET Research Centre.

HABIB KRAIEM earned his Ph.D. in Electri-

cal Engineering from the National Engineering

School of Gabes, Tunisia, in October 2010. In

2012, he became a faculty member in the Elec-

trical Department at the Higher Institute of In-

dustrial Systems in Gabes, Tunisia. Since 2015,

he has been serving in the Department of Elec-

trical Engineering at the College of Engineering,

Northern Border University, Saudi Arabia. His

research primarily focuses on power electronics,

machine drives, automatic control, and the development of renewable energy

technologies.

26 VOLUME 4, 2016

This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and

content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2024.3363869

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/

Towards a Sustainable and Decarbonized Grid: Zimbabwe’s Readiness in Adopting Nuclear and Green Hydrogen Energies

Article

Full-text available

May 2025

Anesu Nicholas Charamba

A shift towards a sustainable and decarbonized power grid is one of Zimbabwe's main goals in the energy sector. This study comprehensively analyzes the country's readiness to implement green hydrogen and nuclear energy generation. Despite the extensive energy studies available in literature, the question of whether the country is ready to adopt these two technologies remains unanswered. The literature lacks information on how well the country is prepared for green hydrogen production for its industrial applications. Therefore, this paper begins with a synopsis of current electricity generation and consumption trends, followed by overviews of nuclear energy and green hydrogen generation, respectively. The country's readiness to adopt the technologies under study is then examined by considering the available infrastructure, economic status of the country, supporting policies, regulatory frameworks already in place, social acceptance and the potential positive and negative impacts. An analysis of strengths, weaknesses, opportunities, and threats analysis is implemented, emphasizing the critical factors that must be considered. Recommendations are outlined to enable a strategic and seamless adoption of green hydrogen and nuclear energy, specifically small modular reactors. The main findings indicate that Zimbabwe currently relies on thermal and hydroelectric energies, with an increasing demand for electricity, particularly in the mining sector. In addition, adopting green hydrogen and nuclear energy primarily results in improved grid resilience, reduced electricity supply-demand gap, economic growth through increased investments, and mitigation of poverty. However, insufficient policies and regulatory frameworks, as well as increased safety concerns, can hinder the implementation of these projects. However, these limitations can be effectively minimized by technological advances or international and regional collaborations. Hence, comprehensive economic reforms, supporting policies, and regulations are required, along with capacity-building investments. The study provides policymakers, investors, and stakeholders with insights into the substantial benefits of considering these energy sources for a decarbonized and sustainable energy future.

Hydrogen Energy Review: Challenges, Innovations, and Pathways to a Sustainable Future

Article

Mar 2025

Fahad Albalawi

Future of Connectivity: A Comprehensive Review of Innovations and Challenges in 7G Smart Networks

Article

Full-text available

Jan 2025

The evolution from 1G to 6G networks has transformed global communication, progressing from basic voice calls in 1G to the immersive, AI-enabled experiences of 6G. As emerging AI-driven applications like autonomous systems, the Internet of Everything (IoE), and immersive technologies demand unprecedented capabilities, 7G networks are set to redefine connectivity by overcoming the limitations of earlier generations. This paper comprehensively reviews the innovations and challenges in 7G networks, focusing on integrating advanced AI and machine learning paradigms such as meta-learning, incremental learning, distributed intelligence, and reinforcement learning to enhance adaptability, resource allocation, and edge performance. The review also examines the role of Large Language Models (LLMs) in enabling real-time actionable intelligence and optimizing edge devices within 7G. The paper highlights the use of technologies, including blockchain for decentralized security, quantum computing for robust encryption, terahertz communication for ultra-fast data transfer, zero-energy solutions for sustainability, and generative AI for intelligent network optimization and automation. By addressing these challenges and exploring cutting-edge strategies, this paper envisions 7G networks as the foundation for a secure, intelligent, and sustainable digital future, equipped to combat emerging cyber warfare threats, enhance resilience against technological disruptions, and support innovations across smart cities, autonomous systems, healthcare, and industrial IoT.

Green Hydrogen Sustainable Solution to Combat CO2 Emissions and Mitigate Climate Change

Chapter

Apr 2025

Jamal Mabrouki

The persistent increase in carbon dioxide (CO2) emissions from traditional fossil fuel-based energy production methods has led to significant environmental challenges, including climate change, ocean acidification, and biodiversity loss. This review examines the detrimental effects of CO2 on the environment and human health, highlighting the urgent need for a transition to cleaner energy sources. It explores the limitations of conventional energy systems and the ongoing efforts to adopt more sustainable practices. In this context, green hydrogen emerges as a promising alternative. Produced through water electrolysis using renewable energy, green hydrogen offers a clean and sustainable solution to reduce CO2 emissions across various sectors, including transportation, industry, and energy.

Optimizing CO2 and CH4 storage: the role of high skeletal density Activated Carbon in adsorption processes

Article

May 2025
COLLOID SURFACE A

Developing Green Hydrogen‐Based Regenerative Supply Chain Strategies for a Sustainable Future: An Empirical Study

Article

May 2025
Bus Strat Environ

Climate change poses a significant challenge for governments and businesses around the world. Amidst the increasing calls for decarbonization of the economy to combat climate change, policymakers and decision‐makers are carefully considering the advantages and disadvantages of green hydrogen. To enable a successful green hydrogen economy, all participants must emphasize the green hydrogen regenerative supply chain and prioritize the reconfiguration of tacit, rare, and socially complex resources. This concerted effort is essential for building green hydrogen regenerative supply chain capabilities. However, it is worth noting that the existing literature falls short in providing empirical evidence regarding the direct impact of such resources on organizational capabilities and the methods by which dynamic capabilities are cultivated to thrive in the rapidly changing business environment. Hence, the study firstly aims to identify and examine the effect of tactic resources, rare resources, and socially complex resources that help to build organization capabilities or zero‐level capabilities (i.e., pollution prevention capabilities and product stewardship capabilities). Second, the study investigates how the firm recombines or reconfigures its organization capabilities or zero‐level capabilities (i.e., pollution prevention capabilities and product stewardship capabilities) into first‐order capabilities or dynamic capabilities (i.e., green hydrogen regenerative supply chain capabilities) that better fit its environment. Thirdly, the study aims to understand how dynamic capabilities (i.e., green hydrogen regenerative supply chain capabilities) help to achieve enhanced operational performance. The data has been analyzed using empirical methods, and the findings provide interesting insights for research scholars, practitioners and policy makers.

Hardware-in-the-Loop of a Grid Forming Control Strategy Applied to a DC Off-Grid Green Hydrogen Production System

Conference Paper

Mar 2025

Recent advancements and future trends in the application of Perovskites as photo-catalysts, electro-catalysts and thermo-chemicals for sustainable green hydrogen production

Article

Apr 2025

Modelling and Simulation Analysis of Innovative Offshore Wind Energy Plant

Conference Paper

Dec 2024

Investigating the hydrogen renaissance in the global energy transition with AI integration

Article

Apr 2025

Abderrahim Lakhouit

Challenges in CO2 transportation: Trends and perspectives

Article

Full-text available

Nov 2023
RENEW SUST ENERG REV

Transportation of CO2 is essential for multiple applications in Carbon Capture, Utilisation and Storage (CCUS), e.g., for utilisation in methanol production, enhanced oil recovery, or permanent storage. Currently, the CCUS industry is still in its fancy, and the transportation regulation is still defined from project to project, where the existing quality specifications are tailored to the specific storage or utilisation site. It is estimated that transportation accounts for ∼25% of the total costs of a CCUS project, and commercialisation cannot be achieved with an infrastructure of high-grade steel together with high purity CO2. The current transportation infrastructure is based on point-to-point transport, where it is believed that it will be challenging to upscale CCUS without a common quality standard. This leaves a knowledge gap in the design, operation, and investment of CO2 transportation. This study includes an evaluation of the challenges that halt the progression in CO2 transportation based on a survey of the literature. Analysing the benefit of establishing an international quality standard for CO2 transportation for CCUS to become a global industry. A detailed description of the initiative policies within CCUS along with the challenges associated with designing the CO2 transportation infrastructure, which arises when chemical reactions form corrosive or scaling compounds. As a result, this study proposes a future action plan to make CO2 transport more feasible by forming a common CO2 quality specification and a material selection based on CO2 quality.

Hydrogen production via steam reforming of different fuels: thermodynamic comparison

Article

Full-text available

Nov 2023
INT J HYDROGEN ENERG

The role of hydrogen as enabler of industrial port area decarbonization

Article

Full-text available

Jan 2024
RENEW SUST ENERG REV

To meet environmental goals while maintaining economic competitiveness, worldwide ports have increased the amount of renewable energy production and have focused in optimizing performances and energy efficiency. However, carbon-neutral operation of industrial port areas (IPA) is challenging and requires the decarbonization of industrial processes and heavy transport systems. This study proposes a comprehensive review of decarbon-ization strategies for IPA, with a particular focus on the role that green hydrogen could play when used as renewable energy carrier. Much information on existing and future technologies was also derived from the analysis of 74 projects (existing and planned) in 36 IPAs, 80 % of which are in Europe, concerning hydrogen-based decarbonization strategies. The overall review shows that engine operation of ships at berth are responsible of more than 70 % of emissions in ports. Therefore, onshore power supply (OPS) seems to be one of the main strategies to reduce port pollution. Nevertheless, OPS powered by hydrogen is not today easily achievable. By overcoming the current cost-related and regulation barriers, hydrogen can also be used for the import/export of green energy and the decarbonization of hard-to-abate sectors. The technical and economic data regarding hydrogen-based technologies and strategies highlighted in this paper are useful for further research in the field of definition and development of decarbonization strategies in the IPA.

Hydrogen energy storage and transportation challenges: A review of recent advances

Chapter

Full-text available

Mar 2024

This chapter examines the latest technologies for efficient storage and transportation of hydrogen

Enhancing the Faradaic efficiency of solid oxide electrolysis cells: progress and perspective

Article

Full-text available

Aug 2023

To reduce global warming, many countries are shifting to sustainable energy production systems. Solid oxide electrolysis cells (SOECs) are being considered due to their high hydrogen generation efficiency. However, low faradaic efficiency in scaling SOEC technology affects costs and limits large-scale adoption of hydrogen as fuel. This review covers SOECs' critical aspects: current state-of-the-art anode, cathode, and electrolyte materials, operational and materials parameters affecting faradaic efficiency, and computational modeling techniques to resolve bottlenecks affecting SOEC faradaic efficiency. npj Computational Materials (2023) 9:149 ; https://doi.

Photoelectrochemical CO2 reduction with copper-based photocathodes

Article

Jan 2024

Techno-economic analysis of hydrogen storage and transportation from hydrogen plant to terminal refueling station

Article

Jan 2024
INT J HYDROGEN ENERG

Sustainable hybrid station design framework for electric vehicle charging and hydrogen vehicle refueling based on multiple attributes

Article

Dec 2023
ENERG CONVERS MANAGE

Hydrogen transportation and distribution-Towards Hydrogen Infrastructure

Chapter

Jan 2024

Hydrogen transportation and distribution, delivery methods cost, safety, policies and transport model.

Comparative environmental sustainability assessment of biohydrogen production methods

Article

Sep 2023
SCI TOTAL ENVIRON

As the energy crisis has been getting increasingly serious in recent years, the research on biohydrogen (bioH2) production as a renewable energy source has been a high-demanding subject. It aims to reduce the pressures set by CO2 emissions and the depletion of fossil fuel supplies. Though bioH2 science is still at the beginning, there have been a lot of reported works on lab and pilot-scale systems with promising futures. This paper presents various potential methods of bioH2 production using biomass resources and comparatively assesses them for environmental impacts with a special emphasis on biological processes. The environmental impact factors are then normalized with the feature scaling normalization methods to evaluate the environmental sustainability of each bioH2 production method. Results revealed that the photofermentation (PF) process was more environmentally sustainable than the other investigated biological and thermochemical processes, particularly regarding emissions, water-fossil-mineral uses, and health issues. The global warming potential (GWP) and acidification potential (AP) for the PF process are 1.88 kg-CO2 eq. and 3.61 g-SO2 eq., which are the lowest among all processes, including renewable energy-based H2 production processes. However, the dark fermentation-microbial electrolysis cell (DF-MEC) hybrid process is considered the most environmentally harmful technique, with the highest GWP value of 14.6 kg-CO2 eq. due to their superior electricity and heat requirements. The water conception potential (WCP) of 84.5 m3 and water scarcity footprint (WSF) of 3632.9 m3 for the DF-MEC process is also the highest compared to all other processes due to the huge amount of wastewater formation potential of the system. Overall rankings confirmed that biological processes are primarily promising candidates to produce bioH2 from an environmentally friendly point of view.

Challenges and Opportunities in Green Hydrogen Adoption for Decarbonizing Hard-to-Abate Industries: A Comprehensive Review

Abstract and Figures

Recommended publications

A review on hydrogen production and utilization: Challenges and opportunities

Advancing Sustainable Energy Transition Through Green Hydrogen Valleys

Hydrogen-Based Energy Systems: Current Technology Development Status, Opportunities and Challenges

Industrial symbiosis concept applied to green hydrogen production: a critical review based on biblio...

Technological Advancements in Adopting Green Hydrogen in the Power and Energy Sector