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A perspective on increasing the efficiency of proton exchange membrane water electrolyzers– a review
... The same issues are currently affecting Proton Exchange Membrane Water Electrolysers (PEMWE). Having the same architecture as PEMFC, their technological development and market diffusion could benefit if stability of the components of the Membrane Electrode Assembly (MEA) would be improved, reducing initial investment costs and increasing a lifetime [6][7][8][9][10]. While costs are mainly related to the platinum-group precious metals (such as iridium and ruthenium), used as a catalyst for the Oxygen Evolution Reaction (OER) [11,12], reduction of catalyst stability over time is due to the high operating potentials at which water electrolyzers need to be run, inducing enhanced coarsening in the MEA [6]. ...
... The bipolar plates host the flow field (3, pitch 0.8 mm), the electrical connections (4), the cartridge used for heating the cell (5), and the thermocouples for controlling the cell temperature (6). Two silicone gaskets (7) are used to seal the MEA, while reactants and reaction products are fed and drained by four lateral pipes (8). At the centre of the flow field, in the channel for reactants distribution, a slit (0.8 mm × 1 mm) is drilled to allow beam passage across the cell, thus probing the MEA in the same operational conditions without compromising its performance. ...
... Proton exchange membrane water electrolyzers (PEMWEs) can convert surplus energy from the grid into chemical energy in the form of green hydrogen, which can then be used to generate electricity when the renewable supply is low [4,5]. However, PEMWEs still face several barriers to widespread commercialization regarding efficiency and cost [6,7]. The development of optimized porous materials and cell architectures plays a key role in increasing the performance and durability of PEMWEs. ...
The porous transport layer (PTL) plays a relevant role in the efficiency of polymer electrolyte membrane water electrolyzers (PEMWE). Extraction of good design guidelines for this porous component is necessary. In this regard, numerical modeling provides a versatile tool to examine large parameter set and determine optimal PTL conditions to be verified experimentally. Here, a hybrid model is presented to analyze two-phase transport of oxygen and water in the anode PTL of a PEMWE. Oxygen capillary transport is modeled with a multi-cluster invasion-percolation algorithm, while water convective transport is modeled with a continuum formulation that incorporates the blockage of gas saturation. The model is validated against in-operando X-ray computed tomography data of the oxygen saturation distribution at the rib/channel scale. Subsequently, a comprehensive parametric analysis is presented, considering the following variables: (i) PTL slenderness ratio, (ii) flow-field open area fraction, (iii) PTL isotropy, (iv) PTL average pore radius, and (v) PTL pore-size heterogeneity. Among other conclusions, the results show that the water transport resistance under the rib can lead to non-negligible mass transport losses at high current density. Water transport from the channel to the catalyst layer can be promoted by: (i) the use of PTLs with a slenderness ratio, defined as the PTL thickness to rib half-width ratio, around 0.5, (ii) the increase of the flow-field open area fraction, (iii) the design of highly anisotropic PTLs with a relatively large pore radius between , and (iv) increasing the homogeneity of the PTL microstructure.
... In this endeavor, the use of hydrogen as an energy vector is expected to play a role of paramount importance [1,2,3]. Among the different routes toward hydrogen generation, green hydrogen production with polymer electrolyte membrane water electrolyzers (PEMWEs) is regarded as an efficient technology to split water into hydrogen and oxygen using renewable power sources, such as solar, wind, or geothermal energies [4,5,6]. However, widespread adoption of PEMWE technology is hindered by the need to ensure high performance and durable operation, while reducing the use of noble metals. ...
Reducing the dependency of proton exchange membrane water electrolyzers (PEMWE) on precious metals, such as iridium (Ir), is necessary to develop a widespread green hydrogen system. This challenge requires a careful design of the interface between the anode porous transport layer (PTL) and the catalyst layer (CL). A comprehensive numerical analysis of relevant parameters that govern the behavior of the anode PTL/CL interface is presented. Calculations are also combined with an experimental characterization of the thickness and electrical conductivity of an unsupported CL as a function of Ir loading. The results show that the in-plane electrical resistance at the anode PTL/CL interface plays a critical role in cell performance. Reaching an acceptable electrical resistance at low Ir loading () can be accomplished through the incorporation of a micrometer-sized microporous layer (MPL) onto the PTL or the preparation of bimodal CLs with a secondary conductive phase (e.g., platinum black or NbOx/TiOx supported IrOx). Further reduction of the Ir loading to the ultra-low regime () may require the use of nanometer-sized MPLs with unsupported CLs or micrometer-sized MPLs with bimodal CLs. Furthermore, the decline of the volume reactive area at ultra-low Ir loading needs a maximization of the exchange current density and the specific electrochemical surface area, and a decrease of the catalyst oxygen coverage factor in the anode CL.
... Compared to traditional alkaline water electrolysis technology, PEM electrolysis operates at lower temperatures, reducing energy loss. Additionally, PEM systems are capable of responding quickly to load changes, making them well-suited for integration with intermittent renewable energy sources, such as wind and solar, thereby enhancing overall energy efficiency [103]. ...
As a clean energy source, hydrogen not only helps to reduce the use of fossil fuels but also promotes the transformation of energy structure and sustainable development. This paper firstly introduces the development status of green hydrogen at home and abroad and then focuses on several advanced green hydrogen production technologies. Then, the advantages and shortcomings of different green hydrogen production technologies are compared. Among them, the future source of hydrogen tends to be electrolysis water hydrogen production. Finally, the challenges and application prospects of the development process of green hydrogen technology are discussed, and green hydrogen is expected to become an important part of realizing sustainable global energy development.
... According to the "Polish Hydrogen Strategy until 2030", the production of 1 kg of hydrogen requires 9 L of water and about 50 kWh of electricity. This amount may change if a more efficient process is used [64]. The dependence of the monthly hydrogen production on the amount of electricity supplied to the electrolyzers is shown in Figure 1. ...
The article presents the application of the metalog family of probability distributions to predict the energy production of photovoltaic systems for the purpose of generating small amounts of green hydrogen in distributed systems. It can be used for transport purposes as well as to generate energy and heat for housing purposes. The monthly and daily amounts of energy produced by a photovoltaic system with a peak power of 6.15 kWp were analyzed using traditional statistical methods and the metalog probability distribution family. On this basis, it is possible to calculate daily and monthly amounts of hydrogen produced with accuracy from the probability distribution. Probabilistic analysis of the instantaneous power generated by the photovoltaic system was used to determine the nominal power of the hydrogen electrolyzer. In order to use all the energy produced by the photovoltaic system to produce green hydrogen, the use of a stationary energy storage device was proposed and its energy capacity was determined. The calculations contained in the article can be used to design home green hydrogen production systems and support the climate and energy transformation of small companies with a hydrogen demand of up to ¾ kg/day.
... PEM technology has benefited from intensive research for several years. Its operation in an acidic environment allows high current densities to be reached (>2 A/cm 2 for applied voltages below 2 V) [3]. In addition, PEM technology is well adapted to load variations, which is particularly suitable for renewable energy storage. ...
Anion exchange membrane water electrolyzers (AEMWEs) are attracting growing interest as a green hydrogen production technology. Unlike proton exchange membrane (PEM) systems, AEMWEs operate in an alkaline environment, allowing one to use less expensive, non-noble materials as catalysts for the reactions and non-fluorinated anion exchange polymer membranes. However, the performance and stability of AEMWEs strongly depend on the alkaline electrolyte concentration. In this work, a three-dimensional multi-physics model considering two-phase flow effects is applied to understand the impact of KOH electrolyte concentration and its flow rate on AEMWE performance, as well as on the current and gas volume fraction distributions. The numerical results were compared to experimental data published in the literature. For current densities above 1 A/cm2, a strongly non-uniform H2 and O2 gas volume distribution could be evidenced by the 3D simulations. Increasing the KOH electrolyte flow rate from 10 to 100 mL/min noticeably improves cell performance for current densities above 1 A/cm2. These results show the importance of accounting for the three-dimensional geometry of an AEMWE and two-phase flow effects to accurately describe its operation and performance.
... There are two types of electrolyser systems commercially available, the alkaline system (AEL) and the proton exchange membrane (PEM) system. Both technologies currently reach the same efficiencies and have sufficiently fast response time in the range of seconds [21]. The cold-start time for the PEM and alkaline system is less than 20 min and less than 60 min respectively [22]. ...
The seasonally varying potential to produce electricity from renewable sources such as wind, PV and hydropower is a challenge for the continuous supply of hydrogen for transport and mobility. Seasonal storage of energy allows to avoid the use of grid electricity when it is scarce; storage systems can thus increase the resilience of the energy system. For grid-neutral and renewable hydrogen production, an electrolyser is considered together with a Power-toGas seasonal storage system, which consists of a methanation, the gas grid as intermediate storage and a steam reformer. As feed stream, electricity from an own photovoltaic (PV) system is considered, and for some cases additional electricity from the grid or from a wind turbine. The dynamic operation of the plant during a year is simulated. It is possible to safely supply fuel cell vehicles with hydrogen from the grid-neutral plant without using electricity when it is scarce and expensive. To supply 135 kg H2 /day, unit sizes of 1 MW-2.9 MW for the PV system and 0.9 MW-2.6 MW for the electrolysis are required depending on the amount of available grid-electricity. The usage of grid-electricity increases the capacity factor of the electrolysis, which results in decreased unit sizes and in a better economic performance. Seasonal storage of energy is required, which results in an increased hydrogen production in summer of approximately 50% more than directly needed by the fuel cell vehicles. The overall efficiency from electricity to hydrogen is decreased due to the storage path by 10%-points to 56% based on the higher heating value. Assuming a cost-equivalent hydrogen price per driven kilometre in comparison to the actual diesel price and electricity costs of 10 Ct/kWh el from the grid, the revenues of the system are higher than the operating costs.
... Therefore, in recent years, many scholars have carried out a lot of research on the electrolyzer power sources [7], inputs [8], stack [9], components design, and control strategy [10] to improve the performance of alkaline electrolyzers. Additionally, researchers have explored new hybrid designs and other aspects of the electrolytic cell [11] to enhance its efficiency [12]. In alkaline electrolyzers, the main electrolytic unit's plate is often designed with a distinctive concave-convex shape, aiming to enhance both electrolytic efficiency and flow uniformity. ...
... The system operates under acidic conditions facilitated by a solid polymer membrane, typically Nafion ® , which ensures high proton conductivity. 2 When a cell voltage is applied across the electrodes, water at the anode undergoes oxidation, producing oxygen gas, protons (H+), and electrons. As shown in Fig. 4 the protons migrate through the proton exchange membrane to the cathode, where they combine with electrons (from the external circuit) to form hydrogen gas. ...
... The first of these reasons is the availability of technology for producing hydrogen from water using electrolytic methods [42]. Currently, the market offers electrolyzers with alkaline technology [13,[43][44][45], PEM [46][47][48][49][50], AEM [51,52], and SOE [53][54][55]. Another aspect is the availability of relatively cheap energy from renewable energy sources (RES) [56]. ...
Storing energy in hydrogen has been recognized by scientists as one of the most effective ways of storing energy for many reasons. The first of these reasons is the availability of technology for producing hydrogen from water using electrolytic methods. Another aspect is the availability of relatively cheap energy from renewable energy sources. Moreover, you can count on the availability of large amounts of this energy. The aim of this article is to support the decision-making processes related to the production of yellow hydrogen using a strategic model which exploits the metalog family of probability distributions. This model allows us to calculate, with accuracy regarding the probability distribution, the amount of energy produced by photovoltaic systems with a specific peak power. Using the model in question, it is possible to calculate the expected amount of electricity produced daily from the photovoltaic system and the corresponding amount of yellow hydrogen produced. Such a strategic model may be appropriate for renewable energy developers who build photovoltaic systems intended specifically for the production of yellow and green hydrogen. Based on our model, they can estimate the size of the photovoltaic system needed to produce the assumed hydrogen volume. The strategic model can also be adopted by producers of green and yellow hydrogen. Due to precise calculations, up to the probability distribution, the model allows us to calculate the probability of providing the required energy from a specific part of the energy mix.
... However, the application of high-pressure technology for storage, and the choice of short-term regulation capabilities, typically of only several hours, have allowed to facilitate the overcoming of this first problem. In addition, practical implementation of the technology has found two additional and important problems: the requirement of large amounts of catalysts made of noble metals and the necessity of high-quality water [19,20]. ...
... In particular, during the PEMWE process, water molecules undergo electrochemical separation into hydrogen and oxygen at their respective electrodes such as hydrogen at the cathode side and oxygen at the anode side. The electrochemical reaction begins by the transportation of water (H 2 O) to the anode, where it undergoes splitting into oxygen (O 2 ), protons (H + ), and electrons (e − ), the reaction equation as shown in Eq. (1). Subsequently, these protons are migrating along the electric field through the proton conducting membrane towards the cathode. ...
Proton exchange membrane (PEM) water electrolysis stands out as a promising technology for producing green hydrogen production by using intermittent renewable energy sources like wind or solar. Moreover, the growing demand for green energy and decarbonization has intensified interest in PEM water electrolysis, making it essential to compile and assess the
technology status and advancements. Therefore, this chapter comprehensively discusses state-of-the-art PEM water electrolysis technology and its cell components level. Additionally, it delves into the current technical status, challenges, and
advancements made in the development of essential components for PEM water electrolysis. Furthermore, we outline our vision for future research and development initiatives aimed at advancing PEM water electrolysis technology.
... In a perfect scenario, the combination of water decomposition and renewable energy sources could offer a practical approach to converting excess energy into hydrogen, a promising solution for both renewable energy storage and fluctuation challenges [2][3][4]. Proton-exchange membrane water electrolysis (PEMWE) stands out as a leading method for clean hydrogen production due to its compact design, high efficiency, and operational flexibility, which enable its direct coupling with renewable energy sources [5]. Nevertheless, the intermittency of and fluctuation in renewable energy sources can degrade the performance of proton-exchange membrane water electrolysers, potentially leading to increased voltage values in the electrolyzer [6]. ...
In this work, we focus on the degradation of membrane electrode assemblies (MEAs) in proton-exchange membrane water electrolysis (PEMWE) induced by different accelerated stress tests (ASTs), including constant-current mode, square-wave mode, and solar photovoltaic mode. In constant-current mode, at continuous testing for 600 h at 80 °C, a degradation of operating voltage increased by the enhanced current density from 22 µV/h (1 A/cm2) to 50 µV/h (3 A/cm2). In square-wave mode, we found that in the narrow fluctuation range (1–2 A/cm2), the shorter step time (2 s) generates a higher degradation rate of operating voltage, but in the wide fluctuation range (1–3 A/cm2), the longer step time (22 s) induces a faster operating voltage rise. In the solar photovoltaic mode, we used a simulation of 11 h sunshine duration containing multiple constant-current and square-wave modes, which is closest to the actual application environment. Over 1400 h ASTs, the solar photovoltaic mode lead to the most serious voltage rise of 87.7 µV/h. These results are beneficial to understanding the durability of the PEM electrolyzer and optimizing the components of MEAs, such as catalysts, membranes, and gas diffusion layers.
... Consequently, research efforts have shifted towards efficient energy extraction from renewable resources like solar, wind, and tidal power. The intermittent nature of renewable energy resources has prompted researchers to seek efficient energy carriers for storing and transporting surplus energy generated during periods of availability [1][2][3][4]. Hydrogen is a potential candidate for a sustainable and clean energy carrier owing to its desirable properties, including a high energy density (140 MJ/kg). The production of hydrogen can be accomplished through a variety of processes, depending on the primary source material. ...
Among water electrolysis methods, proton exchange membrane electrolyzers (PEMWEs) stand out for their potential to generate high-purity hydrogen with remarkable efficiency and dynamic response, making them a cornerstone technology for the sustainable hydrogen economy. However, a key bottleneck lies in the slow reaction rate of the oxygen evolution reaction (OER) at the anode, a four-electron transfer process that significantly throttles the system's full potential. This significantly impacts overall efficiency and calls for unfolding stable, durable, and highly active electrocatalysts that are cost-effective. However, the inherent acidity generated by the OER itself complicates this task. Noble metal catalysts like iridium (Ir) and ruthenium (Rh), pure or combined with other elements, exhibit excellent activity in the acidic OER environment. However, their high cost hinders large-scale PEMWE deployment. Therefore, extensive research has concentrated on non-noble metal alternatives, particularly transition metal oxides (monometallic and polymetallic) and carbon-based materials. This comprehensive review meticulously examines the emerging progress in non-noble metal electrocatalysts designed for low-pH OER conditions within PEMWEs. Following an introductory classification of water elec-trolyzer technologies, it explores how factors such as structure and synthesis route modulate the crucial performance parameters across diverse catalyst groups. Drawing upon these insights, the review also evaluates the current challenges and outlines promising avenues for future research.
Proton exchange membrane (PEM) electrolysis faces challenges associated with high overpotential and acidic environments, which pose significant hurdles in developing highly active and durable electrocatalysts for the oxygen evolution reaction (OER). Ir‐based nanomaterials are considered promising OER catalysts for PEM due to their favorable intrinsic activity and stability under acidic conditions. However, their high cost and limited availability pose significant limitations. Consequently, numerous studies have emerged aimed at reducing iridium content while maintaining high activity and durability. Furthermore, the research on the OER mechanism of Ir‐based catalysts has garnered widespread attention due to differing views among researchers. The recent progress in balancing activity, durability, and low iridium content in Ir‐based catalysts is summarized in this review, with a particular focus on the effects of catalyst morphology, heteroatom doping, substrate introduction, and novel structure development on catalyst performance from four perspectives. Additionally, the recent mechanistic studies on Ir‐based OER catalysts is discussed, and both theoretical and experimental approaches is summarized to elucidate the Ir‐based OER mechanism. Finally, the perspectives on the challenges and future developments of Ir‐based OER catalysts is presented.
Catalysts engineering focusing on industrialization, bridging the gap between academic research and industrial demands.
Abstract
Hydrogen (H2) is developing as a promising renewable energy carrier with the potential to reduce greenhouse gas emissions. Anion exchange membrane water electrolysis (AEMWE) provides a promising solution to the current human energy crisis by combining the advantages of both alkaline water electrolysis (AWE) and proton exchange membrane water electrolysis (PEMWE) and can be coupled with renewable energy sources to produce green H2. However, the AEMWE technology remains in the developmental stage and needs further research to compete with AWE, PEMWE, and solid oxide electrolysis cells (SOEC) regarding performance and durability. The current review discusses the recent progress of AWE, PEMWE, SOEC, and AEMWE with their associated challenges and drawbacks. A state-of-the-art critical analysis on anion exchange membranes (AEMs) with their mechanical properties, PGM and non-PGM based electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the performance of different electrolytes with non-PGM electrocatalysts in the AEMWE and the effect of various operating parameters such as temperature, pressure, and electrolyte flow rate on the performance of the AEMWE system are presented in detail. The techno-economic and environmental assessment of AEMWE technology for H2 production indicates that composite mixed matrix AEMs which could work at high temperature and pressure will provide sustainable opportunities in the automobile industry.
Machine Learning (ML) has emerged as a pivotal force in enhancing Proton Exchange Membrane Water Electrolyzer (PEMWE) devices. These devices are critical for transforming renewable electricity into hydrogen, a key clean energy vector. Despite their prospects, the broader implementation of PEMWE is hindered by cost and efficiency barriers. PEMWEs are inherently complex, involving multi-scale processes such as electrochemical reactions, reactant transportation, and thermo-electrical interactions. This complexity has previously limited optimizations to isolated components like electrocatalysts, membrane electrode assemblies (MEAs), Bipolar plates (BPs), and Gas Diffusion Electrodes (GDEs). ML presents a revolutionary pathway to address these obstacles by enabling system-wide optimization. In this paper, we offer an in-depth review of cutting-edge ML applications for improving PEMWE performance and efficiency. ML’s ability to process large datasets and identify intricate patterns accelerates the research and development of PEMWEs, thereby reducing costs and boosting efficiency. We describe a variety of algorithms, such as Artificial Neural Networks (ANN), Deep Learning (DL), Long Short-Term Memory (LSTM), Support Vector Machine (SVM), Categorical Boosting (CatBoost), and Light Gradient Boosting Machine (LightGBM), commonly used in PEMWE applications, highlighting their significance in enhancing PEMWE systems. Additionally, we explore hybrid methods that combine various ML techniques to further improve PEMWE performance and efficiency. The review provides a concise overview and forward-looking perspective on the role of ML in advancing PEMWE technology, marking a significant step towards their cost-effective and scalable deployment.
Under dynamic operating conditions, the proton exchange membrane water electrolyzers are prone to voltage overshoot, resulting in fluctuations under transient operation. In this paper, a three-dimensional, two-phase, non-isothermal model is developed to investigate the role of various factors on the dynamic response characteristics of electrolyzers. The results demonstrate that the overshoot phenomenon can be significantly mitigated by using a linear loading strategy and a multi-step loading strategy compared to a step loading strategy. Meanwhile, the effect of the flow field structure was examined, revealing that single-serpentine flow field exhibited excellent dynamic response performance. Additionally, calculated through multiple evaluation methods, it was found that the effect of loading magnitude was significantly greater than that of the other factors, including temperature, flow field structure and anode porous transport layer porosity. Finally, under combined variable load conditions, research revealed that whereas single-serpentine flow field shown benefits regarding dynamic response and energy dissipation.
This article presents a 3D model of a yellow hydrogen generation system that uses the electricity produced by a photovoltaic carport. The 3D models of all key system components were collected, and their characteristics were described. Based on the design of the 3D model of the photovoltaic carport, the amount of energy produced monthly was determined. These quantities were then applied to determine the production of low-emission hydrogen. In order to increase the amount of low-emission hydrogen produced, the usage of a stationary energy storage facility was proposed. The Metalog family of probability distributions was adopted to develop a strategic model for low-emission hydrogen production. The hydrogen economy of a company that uses small amounts of hydrogen can be based on such a model. The 3D modeling and calculations show that it is possible to design a compact low-emission hydrogen generation system using rapid prototyping tools, including the photovoltaic carport with an electrolyzer placed in the container and an energy storage facility. This is an effective solution for the climate and energy transition of companies with low hydrogen demand. In the analytical part, the Metalog probability distribution family was employed to determine the amount of monthly energy produced by 6.3 kWp photovoltaic systems located in two European countries: Poland and Italy. Calculating the probability of producing specific amounts of hydrogen in two European countries is an answer to a frequently asked question: In which European countries will the production of low-emission hydrogen from photovoltaic systems be the most profitable? As a result of the calculations, for the analyzed year 2023 in Poland and Italy, specific answers were obtained regarding the probability of monthly energy generation and monthly hydrogen production. Many companies from Poland and Italy are taking part in the European competition to create hydrogen banks. Only those that offer low-emission hydrogen at the lowest prices will receive EU funding.
Harvesting the renewable energy to split water offers an ideal approach to the production of clean hydrogen energy. Among various water electrolysis devices, proton exchange membrane water electrolyser (PEMWE) with...
The global energy sector is currently undergoing a fundamental transformation as it shifts away from fossil fuels towards renewable energy sources. Green hydrogen is one of the most promising energy carriers of the future in the worldwide effort to reduce the carbon footprint of energy systems. The advancement and uptake of green hydrogen technologies depend on various technological, environmental, and economic factors. In this paper, a comprehensive review of recent studies in green hydrogen energy systems (GHES) is conducted, highlighting technoeconomic aspects from the component to the technology and broader system level. Firstly, the technological principles and recent progress of different green hydrogen generation, storage, and utilization technologies are summarized. Subsequently, an in-depth analysis of various technoeconomic modeling and experimental activities focused on integrated GHES is undertaken. By examining applications in the stationary and transport sectors, this review paper offers an assessment of the current state-of-the-art in terms of development and integration options. The technical challenges, key factors, and future research directions of green hydrogen technologies and systems are outlined, demonstrating that an effective, intelligent, and innovative integration of GHES with other technologies will encourage a more efficient use of resources and enhanced energy system flexibility, resilience, and energy security.
Renewable energy‐driven proton exchange membrane water electrolyzer (PEMWE) attracts widespread attention as a zero‐emission and sustainable technology. Oxygen evolution reaction (OER) catalysts with sluggish OER kinetics and rapid deactivation are major obstacles to the widespread commercialization of PEMWE. To date, although various advanced electrocatalysts have been reported to enhance acidic OER performance, Ru/Ir‐based nanomaterials remain the most promising catalysts for PEMWE applications. Therefore, there is an urgent need to develop efficient, stable, and cost‐effective Ru/Ir catalysts. Since the structure‐performance relationship is one of the most important tools for studying the reaction mechanism and constructing the optimal catalytic system. In this review, the recent research progress from the construction of unsaturated sites to gain a deeper understanding of the reaction and deactivation mechanism of catalysts is summarized. First, a general understanding of OER reaction mechanism, catalyst dissolution mechanism, and active site structure is provided. Then, advances in the design and synthesis of advanced acidic OER catalysts are reviewed in terms of the classification of unsaturated active site design, i.e., alloy, core‐shell, single‐atom, and framework structures. Finally, challenges and perspectives are presented for the future development of OER catalysts and renewable energy technologies for hydrogen production.
The stability of catalyst layers and membranes in proton exchange membrane water electrolysis (PEMWE) cells represents an ongoing challenge, compounded by the dissolution of components and migration of elements within the catalyst‐coated membrane (CCM). Conventional microscopy methods often struggle to efficiently evaluate large cross‐sections of PEMWE membranes, which is essential for representative analysis of technical scale CCMs. Herein, synchrotron radiation‐based X‐Ray fluorescence microscopy is exploited to analyze the stability of CCMs with around 1 μm resolution and a field of view of ≈200 × 75 μm². Three application scenarios are investigated: 1) migration of catalyst elements, 2) dissolution of components, and 3) contaminated water supply containing Fe2+\left(\text{Fe}\right)^{2 +} ions. XRF is performed at three different X‐Ray energies (11.7, 11.4, and 11.0 keV), revealing the local elemental composition, including Pt, Ir, Ti, and Fe, under different stressing conditions. Notable observations include the distribution of Ir across the membrane and in the cathode catalyst layer, localization of Pt within the membrane, accumulation of Ti in the cathode catalyst layer, and minimal presence of Fe. XRF has been demonstrated to be a powerful analytical tool for accurate and high throughput imaging of catalyst degradation in PEMWE scenarios, particularly of technical scale devices.
In this work, the study of water uptake, ionic conductivity, and Donnan potential in systems with perfluorosulfonic acid membranes in H+, Li+, Na+, and K+ forms and solutions of inorganic electrolytes is presented. The properties of the commercial Aquivion E87-05S and Nafion 212 membranes, as well as the membranes prepared from the dispersions of Nafion 212 in the solvents of different nature (N,N-dimethylformamide, 1‑methyl-2-pyrrolidone, isopropyl alcohol–water mixtures in volume ratio of 80–20) were investigated. The influence of the number of functional groups, the length of the side chains of the polymer macromolecules, and the polymer morphology in the membranes on their equilibrium and transport properties depending on the counter-ion nature was revealed. The effect of the relaxation and electrophoretic factors on the alkali metal ion transfer through the system of pores and channels of the perfluorosulfonic acid membranes was discussed. The slope of the concentration dependencies of the Donnan potential for all highly hydrated membranes in the H+ form was close to the Nernstian one, while the selectivity to the alkali metal ions increased for the membranes with the highest ion-exchange capacity or the lowest amount of sorbed water and diffusion permeability due to the exclusion of the co-ions from the membrane phase.
In this review, the recent developments achieved in the electrochemical production of Bi-value-added chemicals
by replacing the conventional (oxygen evolution reaction) OER and (hydrogen evolution reaction) HER with
thermodynamically favorable reactions are summarized. Beyond conventional electrolysis used for the generation of a single value-added product at the anode or cathode, hybrid electrolysis opens a new avenue for the
simultaneous production of value-added concurrently at the anode and cathode. This new strategy can not only
increase the efficiency of value-added products, but also abolish the generation of explosive gaseous products by
eliminating conventional OER and HER. To construct a hybrid electrolyzer, various anodic oxidation reactions
including the oxidation of glucose, glycerol, CH4, 1,2-propanediol, 1-phenylethanol, isopropanol, benzyl alcohol,
biomass-derived HMF, syringaldehyde, and o-phenylenediamine are used to replace the anodic OER, whereas
CO2RR is mostly used to replace the cathodic HER. Furthermore, the collective efforts of the electrocatalyst,
device architecture, and fabrication method toward selective product formation are explained in detail.
Hydrogen is projected as a key energy vector to achieve aspiring global decarbonization goals mainly for those sectors where greenhouse gas emissions are highly challenging to reduce. Therefore, green hydrogen production using water PEM electrolysis has become the aim of numerous recent studies. One of the crucial challenges for improving hydrogen production is reaching a deep knowledge of the role of anodes electrocatalysts. In this investigation we studied and modeled the effect of different anode electrocatalysts and solid electrolyte’s configurations in a single-cell PEM electrolyzer performance, using EIS. We assembled and tested PEM electrolysis MEAs with two different configurations. MEA-1 comprises in catalyst-coated membrane (MEA)-type with a geometric area of 25 cm ² containing Nafion™ 115, 3.0 mg cm ⁻² IrRuOx as the anode, and 3.0 mg cm ⁻² PtB for the cathode. MEA-2 involves catalyst-coated membrane (MEA)-type with a geometric area of 25 cm ² containing Nafion™ 117, and 3.0 mg cm ⁻² PtB both for the anode and cathode. Sintered Ti plates were used as gas diffusion layers. After hydration and activation steps at room temperature, the polarization curve was performed. Hysteresis curves were achieved to provide information on thermal equilibrium during the measurements. The oxygen and hydrogen production rate were measured and compared to theoretical values. Experiments were carried out at 20 and 40 °C. EIS measurements were performed at different points of the polarization curve, sweeping a frequency range between 10 kHz and 10 mHz, with an amplitude of 5 mV and taking 10 points per decade. To avoid electrocatalysts area effects in charge transfer reaction, time constants were calculated. It can be clearly observed the trend of resistances and overpotentials according to different process control. Low onset potential for oxygen evolution reaction depicts for MEA-1 means that there will be less power consumption to achieve the same efficiency or same amount of gas generation rate compared to high onset potential case depicted for MEA-2. Although different membrane thicknesses would result in different electrochemical performances due to the change in the ionic resistance, for the thickness studied we did not observe a change in the ionic resistance. The experimental results show an increase in efficiency with temperature, reflected in higher currents for a given potential and lower time constants resulting in the EIS runs.
The development of renewable energy technologies is essential to achieve carbon neutrality. Hydrogen can be stably stored and transported in large quantities to maximize power utilization. Detailed understanding of the characteristics and operating methods of water electrolysis technologies, in which naturally intermittent fluctuating power is used directly, is required for green hydrogen production, because fluctuating power-driven water electrolysis processes significantly differ from industrial water electrolysis processes driven by steady grid power. Thus, it is necessary to overcome several issues related to the direct use of fluctuating power. This article reviews the characteristics of fluctuating power and its generation as well as the current status and issues related to the operation conditions, water electrolyzer configuration, system requirements, stack/catalyst durability, and degradation mechanisms under the direct use of fluctuating power sources. It also provides an accelerated degradation test protocol method for fair catalyst performance comparison and share of effective design directions. Finally, it discusses potential challenges and recommendations for further improvements in water electrolyzer components and systems suitable for practical use, suggesting that a breakthrough could be realized toward the achievement of a sustainable hydrogen-based society.
Hydrogen is an important alternative as a clean fuel for industry and power-to-gas energy storage. The water electrolysis process is a promising technology in green hydrogen production where proton exchange membrane (PEM) technology has been keenly interested. Industrial large-scale PEM electrolyzers need a high current power supply. When connected to an alternating current (AC) source, high current power rectifiers are used to convert AC to DC. Currently, the most commonly used topology in large-scale PEM electrolysis systems is the thyristor-based topology due to its technology maturity and low cost. However, this topology presents several drawbacks in terms of power quality and consequently leads to higher stack-specific energy consumption (SEC) and additional losses. In the present research, we demonstrate the potential power quality improvement for a 20 MW PEM water electrolysis system by rectifier topology upgrade. Rather than traditional thyristor-based topology, a 3-phase interleaved buck rectifier topology is proposed. The new topology presents advantages on both AC and DC sides via a validated simulation model, which is built using MATLAB/Simulink and then validated with experimental data from an industrial 20 MW PEM water electrolyzer at Air Liquide's Bécancour plant. Results show a great improvement in terms of power factor, Total Harmonic Distortion (THD), and DC-current ripple reducing the total losses and the SEC of the PEM stack, especially under partial load. Towards a higher power efficiency, the proposed rectifier topology may be considered in the construction of future large-scale PEM systems.
The urbanization and increase in the human population has significantly influenced the global energy demands. The utilization of non-renewable fossil fuel-based energy infrastructure involves air pollution, global warming due to CO2 emissions, greenhouse gas emissions, acid rains, diminishing energy resources, and environmental degradation leading to climate change due to global warming. These factors demand the exploration of alternative energy sources based on renewable sources. Hydrogen, an efficient energy carrier, has emerged as an alternative fuel to meet energy demands and green hydrogen production with zero carbon emission has gained scientific attraction in recent years. This review is focused on the production of hydrogen from renewable sources such as biomass, solar, wind, geothermal, and algae and conventional non-renewable sources including natural gas, coal, nuclear and thermochemical processes. Moreover, the cost analysis for hydrogen production from each source of energy is discussed. Finally, the impact of these hydrogen production processes on the environment and their implications are summarized.
Production of green hydrogen (H2) by water electrolysis is important for achieving the global mission of carbon neutrality. For this, acidic water electrolysis with a higher current density operation and energy conversion efficiency compared with alkaline water electrolysis has attracted much attention. The four‐electron‐transfer oxygen evolution reaction (OER) limits the overall efficiency of water electrolysis devices. In recent years, low‐dimensional OER catalysts have been extensively explored to increase the overall efficiency of such devices, but most of them work well only at low current density and show unsatisfied long‐term stability. In this review, recent progress in acidic OER is discussed and three aspects including intrinsic activity, high current density operation, and long‐term stability are focused upon. Strategies to improve these aspects including surface chemistry engineering, constructing porous structure, and protecting the active sites’ are comprehensively reviewed. Finally, prospects for developing high‐performance catalysts with high current density operation and long‐term stability for industrial applications are proposed.
Water electrolysis is an electrochemical process capable of producing high-purity hydrogen (H2 ≈ 100%). However, due to high anodic operating potentials, which are greater than 1.8 V in acidic media, they tend to degrade the components that are currently designed. One of the main components is the gas diffusion layer (GDL) of a proton exchange membrane water electrolyzer (PEMWE). A commonly used carbon GDL is coal. However, the acid medium increases the potential to 1.4 V, which causes the GDL to become oxidized and degrade; the above result is due to the generation of carbon products that poison the electrode and the blocking of active sites, all of which decrease the performance of the cell. In this work, the results of a morphological study on a modified titanium porous matrix are presented. The analysis includes the determination of the microstructural influence on mass transport through numerical simulation and statistical electrochemical characterization techniques. Two different microstructural attacks are performed to modify the porous matrix. These attacks consist of an acidic mixture of 17 and 27% v/v HCl/H2SO4 and an attack by a 0.1 M oxalic acid solution; these attacks were performed at different times. Afterward, the GDLs were characterized by scanning electron microscopy (SEM) at different magnifications to determine significant microstructural differences between the three matrices (the two that are modified and the one without modification) and their stochastic reconstruction. Subsequently, a surface area characterization is performed by the BET absorption technique to calculate the porosity of the different matrices.
In this study, an endurance test of 3000 h was conducted on four equivalent proton exchange membrane (PEM) electrolyzers to identify and quantify the impact of an electric ripple current on their durability. Three different typical power converter waveforms and frequencies were explored. Signals were added to the same direct current carrier and also tested for reference. Performance comparison based on polarization curves and electrochemical impedance spectroscopy (EIS) analysis revealed that the ripple current favors degradation. Triangular waveform and a frequency of 10 kHz were identified as the most degrading conditions, leading to a sharp increase in high-frequency resistance (HFR) and the emergence of mass transport limitations due to the enhanced degradation of titanium mesh. Moreover, reversible losses were observed and further explorations are needed to decorrelate them from our observations.
The kinetically sluggish oxygen evolution reaction in proton exchange membrane water electrolyzers (PEMWEs) leads to high potentials of >1.5 V vs RHE at the anode electrode during operation. In contrast, an investigation with an in situ reference electrode indicates a much lower potential at the anode side of the bipolar plate which would allow the use of stainless steel and carbon as the bipolar plate materials. This decoupling is induced by the low conductivity of the circulating deionized water. In single cell electrolyzer tests, we show that carbon-coated 316L (C-316L) stainless steel is suitable as a bipolar plate material in contact with the anode and cathode sides of the PEMWE. The coating remains stable throughout the experiments, i.e., 720 h at the anode and 1000 h at the cathode side. Based on these results we regard carbon-coated stainless steel as a sustainable solution for the large-scale application of PEM water electrolysis since it might replace (Pt-coated) titanium in the bipolar plate.
In the literature, different energy carriers are proposed in future long-distance hydrogen value chains. Hydrogen can be stored and transported in different forms, e.g. as compressed dense-phase hydrogen, liquefied hydrogen and in chemically bound forms as different chemical hydrides. Recently, different high-level value chain studies have made extrapolative investigations and compared such options with respect to energy efficiency and cost. Three recent journal papers overlap as the liquid hydrogen option has been considered in all three studies. The studies are not fully aligned in terms of underlying assumptions and battery limits. A comparison reveals partly vast differences in results for chain energy efficiency for long-distance liquid hydrogen transport, which are attributable to distinct differences in the set of assumptions. Our comparison pinpoints the boiloff ratio, i.e. evaporation losses due to heat ingress, in liquid hydrogen storage tanks as the main cause of the differences, and this assumption is further discussed. A review of spherical tank size and attributed boiloff ratios is presented, for existing tanks of different vintage as well as for recently proposed designs. Furthermore, the prospect for further extension of tanks size and reduction of boiloff ratio is discussed, with a complementary discussion about the use of economic assumptions in extrapolative and predictive studies. Finally, we discuss the impact of battery limits in hydrogen value chain studies and pinpoint knowledge needs and the need for a detailed bottom-up approach as a prerequisite for improving the understanding for pros and cons of the different hydrogen energy carriers.
Water electrolysis is an eco-friendly method for the utilization of renewable energy sources which provide intermittent power supply. Proton exchange membrane water electrolysis (PEMWE) has a high efficiency in this regard. However, the two-phase flow of water and oxygen at the anode side causes performance degradation, and various operating conditions affect the performance of PEMWE. In this study, the effects of four control parameters (operating temperature, flow rate, cell orientation, and pattern of the channel) on the performance of PEMWE were investigated. The effects of the operating conditions on its performance were examined using a 25 cm2 single-cell. Evaluation tests were conducted using in situ methods such as polarization curves and electrochemical impedance spectroscopy. The results demonstrated that a high operating temperature and low flow rate reduce the activation and ohmic losses, and thereby enhance the performance of PEMWE. Additionally, the cell orientation affects the performance of PEMWE owing to the variation in the two-phase flow regime. It was observed that the slope of specific sections in the polarization curve rapidly increases at a specific cell voltage.
Hydrogen is a zero-carbon footprint energy source with high energy density that could be the basis of future energy systems. Membrane-based water electrolysis is one means by which to produce high-purity and sustainable hydrogen. It is important that the scientific community focus on developing electrolytic hydrogen systems which match available energy sources. In this review, various types of water splitting technologies, and membrane selection for electrolyzers, are discussed. We highlight the basic principles, recent studies, and achievements in membrane-based electrolysis for hydrogen production. Previously, the Nafion TM membrane was the gold standard for PEM electrolyzers, but today, cheaper and more effective membranes are favored. In this paper, CuCl-HCl electrolysis and its operating parameters are summarized. Additionally, a summary is presented of hydrogen production by water splitting, including a discussion of the advantages, disadvantages , and efficiencies of the relevant technologies. Nonetheless, the development of cost-effective and efficient hydrogen production technologies requires a significant amount of study, especially in terms of optimizing the operation parameters affecting the hydrogen output. Therefore, herein we address the challenges, prospects, and future trends in this field of research, and make critical suggestions regarding the implementation of comprehensive membrane-based electrolytic systems.
Developing cheap and highly durable non-noble metal catalysts for water electrolysis to sustainably produce hydrogen as alternatives to platinum-based catalysts is essential. Herein, we report graphene-encapsulated NiMo alloys as acid-stable non-noble metal catalyst electrodes. The graphene-encapsulated NiMo cathode showed a highly stable performance in the potential cycling test (10,000 cycles) from 0 to 5.0 A cm⁻² and 100 h of durability at a 2.2 V constant cell voltage. A balance between catalytic activity and corrosion in acidic environments was achieved by tuning the number of N-doped graphene layers. Through their application in a full-cell PEM-type water electrolyzer, we verify that noble metal catalysts can be replaced by non-noble metal catalysts. Such cheap acid-stable non-noble metal electrodes have promising practical applications in PEM-type water electrolysis.
Hydrogen is a clean, renewable secondary energy source. The development of hydrogen energy is a common goal pursued by many countries to combat the current global warming trend. This paper provides an overview of various technologies for hydrogen production from renewable and non-renewable resources, including fossil fuel or biomass-based hydrogen production, microbial hydrogen production, electrolysis and thermolysis of water and thermochemical cycles. The current status of development, recent advances and challenges of different hydrogen production technologies are also reviewed. Finally, we compared different hydrogen production methods in terms of cost and life cycle environmental impact assessment. The current mainstream approach is to obtain hydrogen from natural gas and coal, although their environmental impact is significant. Electrolysis and thermochemical cycle methods coupled with new energy sources show considerable potential for development in terms of economics and environmental friendliness.
Polymer electrolyte membrane water electrolysis (PEMWE) is the most promising technology for sustainable hydrogen production. However, it has been too expensive to compete with current state-of-the-art technologies due to the high cost of titanium bipolar plates (BPPs) and porous transport layers (PTLs). Here, we report a high-performance, durable and low-cost PEMWE cell with coated stainless steel (ss) BPPs and PTLs. When using uncoated ss components in the PEMWE cell, the cell depolarizes rapidly, reaching 2 V at only 0.15 A cm-2. After the application of non-precious metal coatings of Ti and Nb/Ti on ss-BPP and ss-PTL, respectively, the current density can be increased by a factor of 13 while maintaining the same performance. Extensive physical and electrochemical characterization supported by pore network modelling shows that the Nb/Ti coating on the ss-PTL leads to efficient water and gas transport at the interface with the anode. The PEMWE cell with coated ss components was evaluated in an accelerated stress test (AST) for more than 1000 h. No sign of Fe contamination in either the membrane or the electrodes is observed at the end of the test. With our results, we demonstrate that PEMWE can be manufactured almost entirely in ss, facilitating an unprecedented cost reduction in this technology and advancing the widespread use of green H2.
Dihydrogen (H 2 ), commonly named ‘hydrogen’, is increasingly recognised as a clean and reliable energy vector for decarbonisation and defossilisation by various sectors. The global hydrogen demand is projected to increase from 70 million tonnes in 2019 to 120 million tonnes by 2024. Hydrogen development should also meet the seventh goal of ‘affordable and clean energy’ of the United Nations. Here we review hydrogen production and life cycle analysis, hydrogen geological storage and hydrogen utilisation. Hydrogen is produced by water electrolysis, steam methane reforming, methane pyrolysis and coal gasification. We compare the environmental impact of hydrogen production routes by life cycle analysis. Hydrogen is used in power systems, transportation, hydrocarbon and ammonia production, and metallugical industries. Overall, combining electrolysis-generated hydrogen with hydrogen storage in underground porous media such as geological reservoirs and salt caverns is well suited for shifting excess off-peak energy to meet dispatchable on-peak demand.
The membrane electrode assembly was prepared by a catalyst coated membrane (CCM) with an effective active area of 10 × 10 cm2 in this work. Porous titanium plates with different diameters were used as anode collectors to study the polarization curve and electrochemical impedance spectroscopy (EIS) of the electrolyzer. The results show that the pore size of a porous titanium plate on the anode side has a significant effect on the performance of the electrolyzer. The best cell performance was obtained when the median diameter of the anode titanium plate was 12.3 um. When the current density is 1 A/cm2, the battery voltage is 2.253 V.
This paper presents the design, modelling and
control simulation of the Balance of Plant (BoP) for a medium-
size PEM (Proton Exchange Membrane) electrolyzer.
Taking into consideration the main chemical process that
occurs in the electrolysis of a PEM electrolyzer, the BoP
must be clearly divided into two main parts: water management
and hydrogen production. An exhaustive control
system is developed to test the working conditions that
will allow the PEM electrolyzer to generate hydrogen in a
safe and efficient way. The aim of this study is to find an
equilibrated solution between minimal BoP and a correct
performance, always into safety conditions of hydrogen
generation. Automation software is used to model the
system and perform a control logic, according to the desirable
operation of the PEM electrolyzer. The BoP developed,
along with the electrolyzer model and the control
logic proposed contribute the PEM electrolysis technology
to be expanded in the industrial market and the hydrogen
to be widely used as energy carrier, as part of the renewable
energy systems.
This paper proposes the design of a LLC resonant converter to supply a proton exchange membrane (PEM) electrolyzer. The PEM requires a low voltage with high current, a reduced output voltage ripple, and an overdamped dynamic behavior of the converter to avoid voltage overshoots. The designed converter allows satisfying the design constraints, minimizing switching and reverse recovery losses; the efficiency is influenced mainly by the output rectifier's conduction losses.
To meet ambitious targets for greenhouse gas emissions reduction in the 2035-2050 timeframe, hydrogen has been identified as a clean “green” fuel of interest. In comparison to fossil fuel use the burning of hydrogen results in zero CO2 emissions and it can be obtained from renewable energy sources. In addition to zero CO2 emissions, hydrogen has several other attractive properties such as higher gravimetric energy content and wider flammability limits than most fossil fuels. However, there are practical limitations to its widespread use at present which include low volumetric energy density in the gaseous state and high well-to-wheel costs when compared to fossil fuel production and distribution. In this paper a review is undertaken to identify the current state of development of key areas of the hydrogen network such as production, distribution, storage and power conversion technology. At present high technology costs still are a barrier to widespread hydrogen adoption but it is envisioned that as scale of production increases, then costs are likely to fall. Technical barriers to a hydrogen economy adoption are not as significant as one might think as key technologies in the hydrogen network are already mature with working prototypes already developed for technologies such as liquid hydrogen composite cryotanks and proton exchange membrane fuel cells. It is envisioned that with continuous investment to achieve requisite scale that a hydrogen economy could be realised sooner rather than later with novel concepts such as turboelectric distributed propulsion enabled by a shift to hydrogen-powered network.
Hydrogen production with a proton exchange membrane (PEM)electrolyzer utilized with renewable energy power is considered to be an efficient and clean green technique, but the poor oxygen evolution performance results in high energy consumption and low efficiency. In this work, a strategy is reported for the construction of a support network of the anodic catalyst layer to simultaneously ameliorate its sluggish reaction kinetics and mass transport in order to realize highly efficient hydrogen production of the PEM electrolyzer. After in situ synthesis of IrO2 nanoparticles on N–doped TiO2 nanofibers, the as–prepared IrO2/N–TiO2 electrode shows substantially enhanced Ir utilization and accelerated mass transport, consequently decreasing the corresponding cell potential of 107 mV relative to pure IrO2 at 2 A cm−2. The enhanced activity of IrO2/N–TiO2 could be due to the fact that the N–TiO2 nanofiber support can form a porous network, endowing IrO2/N–TiO2 with a large reactive contact interface and favorable mass transfer characters. The strategy in this work supplies a pathway to develop high–efficiency interfacial reaction materials for diverse applications.
Sustainable energy demand drives innovation in energy production. Electrolysis of water can produce carbon-free hydrogen from renewable sources. This paper presents a bibliometric analysis of recent and highly referenced research on hydrogen electrolysers utilising the Scopus database to shed insight into future trends and applications. It has been discovered that the most frequently published type of study for top-ranked papers is the formulation of problems and simulations (38.3%), followed by a study of the state-of-the-art technology assessment (32.5%), laboratory research, design, and performance evaluation (24.2%), and reviews (5%). In general, 33.33% of articles focused on controlling hydrogen electrolyser efficiency. This study used different case studies from the global literature to conduct a complete evaluation of the electrolyser statistical analysis of the present state of the art, models or modes of operation, key challenges, outstanding issues, and future research. This evaluation will aid researchers in building a commercially successful hydrogen electrolyser.
Due to the ever-rising need for clean energy solutions, efficient utilizing of renewable sources is one of the most important research tasks. However, power generation from renewable sources is inevitably intermittent, which lowers the efficiency and obstructs practical use. The water electrolyzer has attracted much attention as a promising energy storage system in grid scale to solve the intermittency issue. The electrolyzer is a catalytic energy converter that converts electric energy into chemical energy in the form of hydrogen gas. Hydrogen gas production is also important because it is a clean energy carrier with zero emissions. Proton exchange membrane (PEM) based electrolyzer has better efficiency and produces hydrogen gas in higher pressure with a compact design compared to its alkaline counterpart. PEM water electrolyzer can produce pure hydrogen gas without CO impurity which is catalyst poison of Pt electrocatalyst in PEM fuel cells. Major efficiency loss of the electrolyzer comes from high overpotential at the anode reaction, oxygen evolution reaction (OER). A suitable electrocatalyst is needed to reduce the high overpotential. Ir is the only metal that can withstand the highly corrosive environment of the anode in acidic conditions with fine activity. However, Ir is even scarcer than Pt, thus development of Ir based efficient electrocatalysts is an urgent issue for the commercialization. Herein, we report our experimental results about tuning electrochemical property of Ir catalysts to enhance the performance of PEM water electrolyzer device.
Recently, it has been realized that the low cost of 3d metals such as Ni, or Cu can boost the OER activity of Ir oxide. To exploit the synergy, we made several shaped Ir-Ni bimetallic nanoparticles, Ir-Ni TL, Ir-Ni SC, and Ir-Ni LP. [1] The bimetallic nanoparticles exhibited enhanced OER performance in half-cell experiments; especially, Ir-Ni TL which greatly improved activity. However, they could not be applied to the PEM electrolyzer. Although, not only from our group, many other groups have also reported fancy Ir based alloy electrocatalysts with enhanced OER performance, their application to full electrolyzer has not been reported yet. Severe leaching of the secondary metal, Ni or Cu, from particles produce corresponding metal ions in the system. The leached metal ions contaminate PEM, and lower ion conductivity, which is fatal to cell performance.
We paid attention to adjusting the morphology of Ir oxide particles itself, considering its potential application to PEM water electrolyzers. As a result, we successfully synthesized one-dimensional ultrathin IrO 2 nanoneedles in gram scale. [2] It is known that one-dimensional structured electrocatalysts possess enhanced performance in various electrochemical reactions. The drawback of conventional one-dimensional electrocatalysts is its low surface area where the reaction would take place. By making ultrathin nanoneedles, sufficient surface area was exposed. The diameter of the nanoneedles was about 2 nm, which consists of 6~8 layers of (110) IrO 2 atomic planes. Molten salt method was applied to synthesize the nanoneedles, because it was hard to control the heterogeneous nucleation on the Ir surface and the homogeneous nucleation of the Ir nuclei in a solution using a conventional colloidal synthesis method. Moreover, the molten salt method does not require toxic chemicals and is readily scalable to gram scale. At higher temperatures above the melting point of the salt, NaNO 3 , Ir oxide particles were obtained in the liquid salt. When cysteamine was added together as an organic shaping agent, one-dimensional ultrathin IrO 2 nanoneedles were synthesized. NaNO 3 salt was used as an oxygen donor to produce oxide nanoparticles as well as a solvent. The aspect ratio of the nanoneedles was controlled by the concentration of the shaping agent. When larger amounts of cysteamine were used, thinner and longer IrO 2 nanoneedles were obtained.
Obtained ultrathin IrO 2 nanoneedles exhibited enhanced OER performance. The longer and thinner the particles, the higher electric conductivity and OER activity were observed. The conductivity was directly measured by the 4-point probe method. Also, the stability was enhanced compared to unshaped IrO 2 nanoparticles. Typically, there was an inverse relation between activity and stability for the OER electrocatalysts. The nanoneedles overcame the relation by its unique shape. When the nanoneedles were applied to PEM water electrolyzers, the efficiency and durability were enhanced compared to conventional unshaped counterparts.
We studied how morphology control of Ir based nanoparticles could affect OER property and PEM water electrolyzer performance. We believe our experimental findings will be valuable to researchers who are working on the development of OER electrocatalysts or PEM water electrolyzers.
[1] J. Lim et al. , Chem. Commun. 2016, 52, 5641-5644.
[2] J. Lim et al. , Adv. Funct. Mater. 2017, 1704796.
Figure 1
Hydrogen is now considered the most preferred medium for storing energyout of renewable, intermittent power sources because of its great advantages such as high energy density, low weight, environmental friendliness, etc. Water electrolysis is the most accessible hydrogen production method. Proton exchange membrane (PEM) water electrolysis is attracting much attention with its high efficiency. In a PEM electrolyzer cell (PEMEC), liquid/gas diffusion layers (LGDLs) are porous layers whose main functions are conducting electrons and heat and transporting reactants/products to and from the reaction sites. To achieve high efficiency, a PEMEC demands LGDLs with minimum intrinsic ohmic, thermal, and mass diffusion losses and also low interfacial contact resistances with other components. Thus, the morphologies and surface properties of LGDLs can greatly affect the cell performance.
In this research, anode LGDLs featuring pore sizes of approximately ten microns are fabricated by pulsed-laser micromachining (PLM). The effects of pore morphologies, including porosities and pore sizes, are characterized comprehensively ex-situ and in-situ . Electrochemical impedance spectroscopy (EIS) analysis is also carried out to investigate the impact of LGDL pore morphologies on the PEMEC performance. Results from this research can help the community better understand the relationship between LGDL morphology and PEMEC performance. A prediction of the performance at the design stage should also be available based on the morphology of an anode LGDL. Furthermore, an optimal design for anode LGDLs may be acquired.
The transfer to renewable energy requires stable long-term storage of any surplus energy created by e.g. solar power. Water electrolysis is a simple method for conserving energy in the form of hydrogen gas. Offering several advantages compared to alkaline water electrolysis, the polymer electrolyte membrane water electrolyzers (PEMWEs) can respond more rapidly to fluctuations in the power grid and enables a more compact cell design[1]. However, the components used in PEM cells are more costly. As different cost-reduction measures are being implemented, the anode catalysts fraction of the total cost is increasing. This calls for reducing the amount of scarce and precious iridium catalyst for the oxygen evolution reaction (OER).
Galvanic exchange is a well-known way of producing metal thin-films on different metal substrates, where the substrate acts as both a reducing agent and template for a more noble metal. Applying iridium as a thin film on to a suitable substrate using galvanic exchange is a promising way of drastically reducing the iridium loading in PEMWE units. Although a substantial amount of effort has been made in producing core/shell electrocatalysts by galvanic exchange, not so much has been done on iridium structures[2]. A few groups have used nickel as a template for exchange in aqueous solution, either in the form of a thin metal foil[3, 4] or as nickel electrodeposited on to a glassy carbon electrode[5] or a nickel electrode[6]. Copper has also been used as a template in organic solvents [7, 8]. Although yielding promising results, the use of small-scale synthesis methods using expensive and toxic organic components is not feasible for industrial upscaling. Thus, we aim to use simple, scalable water-based methods for the synthesis of iridium electrocatalysts via galvanic exchange.
In this work, we have exchanged nickel and copper nanoparticles supported on metal oxides (MOx) for iridium by galvanic exchange in an aqueous iridium solution. The Ir:M’@MOx electrocatalysts (M’=Ni,Cu) have been evaluated for stability and activity towards the OER in acidic media. For comparison, Ir:M’ catalysts were also made from a simple organic phase synthesis of M’ nanoparticles[9], which were subjected to galvanic exchange by iridium using different methods. Figure 1 illustrates the first cycle during cyclic voltammetry in acidic media of Ir:Ni electrocatalysts synthesized from galvanic exchange between iridium and nickel in aqueous iridium solutions at different temperatures. As is clearly shown in the figure, the sample synthesized at 95⁰C displays voltammetric signatures consistent with the formation of iridium oxide at the substrate. In addition to outlining the conditions for the formation of iridium oxide, polarization data and other characteristics of iridium oxide made by galvanic displacement will be described. The discussion will emphasize the feasibility of manufacturing core/shell or other overlayer structures of iridium for application in PEM water electrolysis. Carmo, M., et al., A comprehensive review on PEM water electrolysis. International Journal of Hydrogen Energy, 2013. 38 (12): p. 4901-4934.
Papaderakis, A., et al., Electrocatalysts Prepared by Galvanic Replacement. Catalysts, 2017. 7 (3): p. 80.
Duca, M., et al., Activation of Nickel for Hydrogen Evolution by Spontaneous Deposition of Iridium. Electrocatalysis, 2013. 4 (4): p. 338-345.
Mellsop, S.R., A. Gardiner, and A.T. Marshall, Spontaneous Deposition of Iridium onto Nickel Substrates for the Oxygen Evolution Reaction. Electrocatalysis, 2016. 7 (3): p. 226-234.
Papaderakis, A., et al., Oxygen Evolution at IrO2 Shell–Ir−Ni Core Electrodes Prepared by Galvanic Replacement. The Journal of Physical Chemistry C, 2016. 120 (36): p. 19995-20005.
Vázquez-Gómez, L., et al., Hydrogen evolution on porous Ni cathodes modified by spontaneous deposition of Ru or Ir. Electrochimica Acta, 2008. 53 (28): p. 8310-8318.
Park, J., et al., Iridium-Based Multimetallic Nanoframe@Nanoframe Structure: An Efficient and Robust Electrocatalyst toward Oxygen Evolution Reaction. ACS Nano, 2017. 11 (6): p. 5500-5509.
Pei, J., et al., Ir–Cu nanoframes: one-pot synthesis and efficient electrocatalysts for oxygen evolution reaction. Chemical Communications, 2016. 52 (19): p. 3793-3796.
Manikandan, M., et al., In nascendi . 2017.
Captions
Figure 1: Cyclic voltammogram (1st cycle) of Ir:Ni electrocatalysts in acidic media. The Ir:Ni catalysts were synthesized by galvanic exchange between iridium and nickel in aqueous iridium solutions at different temperatures. As clearly shown, the temperature of the aqueous iridium solution strongly affects the oxidation state of the iridium in the resulting Ir:Ni catalyst.
Figure 1
Direct hydrogen production at high pressure by the proton exchange membrane (PEM) can improve the economy of the entire hydrogen-chain. A multi-physical model of a high pressure single-cell electrolyzer is established and the heat transfer, mass transfer, and electrochemical processes are described. The water permeation flow rate is simulated accurately using experimental data obtained under 0-700 bar pressure difference. The double layer effect and mass transfer lag effect are considered in the dynamic model in terms of different time constants. Polarization curves exhibit good consistency at different temperatures and high cathode pressure, and the average the sum of squares due to error (SSE) is less than 0.01. Different film thicknesses correspond to different safe operating zones (hydrogen concentration in oxygen below 2%). A membrane thickness of 250μm allows the cathode pressure to increase to approximately 120 bar, and the minimum operating current density should not be less than 0.2 A/cm2. Increasing the cathode pressure to 200 bar can reduce the water content on the hydrogen side by more than 19.5%. Finally, the temperature control model of circulating water in the electrolysis cell is calibrated and verified by experiments, and the steady-state error is less than 2.5%.
There is a strong need and hence specific challenges attached to this for data centers to bring holistic energy solutions for better operation, control and management in a more cost-effective, efficient and environmentally benign manner. The current study develops and investigates a solar-based novel integrated system to generate electricity and hence provide cooling in a sustainable way. The proposed system includes a parabolic trough-type concentrated solar plant with a Rankine cycle, bifacial photovoltaic plant, proton exchange membrane (PEM) fuel cell, PEM electrolyzer, Cu-Cl thermochemical hydrogen production cycle, Li-Br absorption refrigeration cycle. In order to prevent solar intermittency, thermal and chemical-based energy storage systems are integrated as molten salt cold and hot thermal energy storage tanks and hydrogen-based energy storage systems. The heat is recovered by the Rankine cycle and the Li-Br absorption refrigeration cycle in order to generate electricity and to provide cooling. The overall system is analyzed with thermodynamic approaches from the energy and exergy points of view. For further, the overall system is analyzed with the hourly ambient data in a time-dependent analysis for a data center in Calgary, Alberta, Canada. For the average ambient conditions, the energy and exergy efficiencies of the overall integrated system calculated as 35.98% and 31.24%, respectively. At least 10% of the overall energy efficiency is exceeded during a total of 8091 h of the year, whereas the overall exergy efficiency is exceeded 10% during the 7726 h in a year. Further to note that there are challenges for such systems to bring a holistic solution.
We review candidate long duration energy storage technologies that are commercially mature or under commercialization. We then compare their modularity, long-term energy storage capability and average capital cost with varied durations. Additional metrics of comparison are developed including land-use footprint and equivalent efficiency based on idle losses to account for emerging long-duration storage applications and use cases. The technology landscape may allow for a diverse range of storage applications based on land availability and duration need, which may be location dependent. These insights are valuable to guide the development of long-duration energy storage projects and inspire potential use cases for different long-duration energy storage technologies. This analysis also lays the foundation for future relevant modeling and decision-making studies that implement emerging long-duration energy storage.
Hydrogen production and liquefaction based on geothermal energy is a potential route for the future hydrogen economy. In the current study, a novel integrated system with power generation and cooling capabilities is designed which uses geothermal energy as a heat source and LNG stream as a heat sink. All the generated power by the system is delivered to the PEM electrolyzer to produce hydrogen and liquefied it through a Claude cycle. A comprehensive investigation is carried out to evaluate the performance of the system from a thermodynamic and economic points of view. The analysis shows that the hydrogen production rate is 106.8 kg/h if all the electricity is delivered to PEM electrolyzer. Also, PEM electrolyzer with 93.92 /h), 23.34%, respectively. At these conditions, cooling capacity and levelized cost of hydrogen are 5.25 MW and 1.827 $/ kg, correspondingly.
In the present work, an innovative solar-geothermal-natural gas-driven polygenration system is presented. It consists of using organic Rankine cycle, Internal Combustion Engine, Polymer Electrolyte Membrane, and Humidification-Dehumidification desalination plant to produce power, hydrogen, hot water, and freshwater. Energy, Exergy, Exergoeconomic, and Exergoenvironmental (4E) analyses have been performed for the proposed system. 4E analyses can provide a comprehensive overview of the proposed system. In addition, sensitivity analysis for the system's main parameters has been done to evaluate the system. Also, nine organic fluids were used and compared based on 4E analyses. The results show that energy and exergy efficiencies and total annual cost and environmental impacts of the system are 23.87%, 28.21%, 0.144 $/kWh, and 0.024 Pts/kWh. Also, the average production of freshwater is 4.67 m³/day, and the production of hydrogen and hot water is estimated at 1.85 kg/h and 1.31 kg/s, respectively. R141b is the best fluid for the organic Rankine section.
The Markov model and the PEM electrolyzer system model for directly coupled photovoltaic are combined to construct an efficient and reliable working condition that fits the fluctuation characteristics of solar energy. The working condition is designed through genetic algorithm so that the average coupling efficiency of the system can reach 98.8%. Then, the durability and recovery test are conducted on the basis of the constructed conditions. It is found that the attenuation rate at the current density of 1A/cm² under the photovoltaic fluctuating condition reached 7.8mV/h, which is twice that under the constant current condition. The charge transfer impedance (Rct) is the main factor leading to the degradation. It is proved by the recovery experiment that the increase of Rct is related to the pollution of metal ions. After pickling to remove some metal ions, Rct can be significantly reduced by 46.8% and 65.2%, respectively. After the durability test, the voltammetric charges under the photovoltaic fluctuating condition and the constant current condition are reduced by 48.3% and 19.1% It indicates that the photovoltaic fluctuation condition will accelerate the attenuation of the effective reaction area of MEA, which is irreversible even after pickling. It can be observed from the SEM images that the catalyst layer of MEA has more obvious peeling under the photovoltaic fluctuation condition, which is not conducive to material transmission and destroys the transmission channel of ions and electrons. This result can provide a reliable reference for the coupling design of PEM electrolyzer and renewable energy in the future.
This study proposes and investigates a novel energy system based on biomass and solar energy. This plant is composed of a biomass unit, a solar unit, and a waste-heat recovery unit. This novel proposed integrated system can provide the needs such as electricity, hydrogen, freshwater, heating, and hot water production. For electricity generation, two gas turbines, one steam Rankine cycle, and one organic Rankine cycle are used. In contrast, for utilization of solar energy, a heliostat field, and for biomass conversion, a gasifier is used. In addition, the desalination unit and PEM electrolyzer are utilized to produce fresh water and hydrogen, respectively. Firstly, the present work aims to investigate the developed system from the exergoeconomic and environmental perspective. Multi-objective optimization is conducted to determine the maximum amount of exergetic efficiency and the minimum value of the cost rate. An artificial neural network (ANN) is employed as a mediator tool to accelerate the optimization process. The relation between objective functions and design parameters is studied utilizing ANN to obtain the plant optimal decision variables. Employing the Pareto Envelope-based selection algorithm II (PESA-II) method, the optimum amount for the total cost rate and exergy efficiency is found 224.1 $/h and 26.7%, respectively. In addition, three evolutionary-based optimization algorithms are applied to determine the optimum results of the suggested plant.
Electrochemical modeling is commonly used to model the characteristics of proton exchange membrane (PEM) electrolyzer cells where all losses caused during the electrolysis process are taken into account. The model has a nonlinear relationship between current density and voltage (
J–V
), with five model parameters that are subjected to change depending on the physical properties and chemical conditions of the PEM electrolyzer. In this article, a novel analytical approach based on the least square error method is proposed to estimate the model parameters and characterize the electrochemical behavior of the PEM electrolyzer under various operating conditions. The accuracy and validity of the proposed approach are tested under different case studies at various operating temperatures, output pressures, hydrogen production rates, and sizes of the dataset. Also, the relationship between the estimated parameters and the operating conditions of the PEM electrolyzer is explored. Finally, the superiority of the proposed approach is demonstrated by comparison to numerical and heuristic optimization parameter identification methods.
In this study, a techno-economic analysis for the bridging technology of hybrid methanol production based on tri-reforming of methane integrated with water electrolysis is performed. Focusing on the technical and economic parameters of three representative types of water electrolyzer (alkaline, proton exchange membrane, and solid oxide electrolysis), the process flow diagram for the targeted process is built and key economic parameters are confirmed. Based on the results of the simulation model and values of economic entries, itemized cost estimation reflecting the current status of water electrolyzers is conducted to evaluate the methanol production costs. Furthermore, the future production costs of methanol are estimated according to the projected values of system efficiencies, the lifetimes, and the future investment costs of three different water electrolyzer types. The results of methanol production costs in the present and the future are compared with the market prices of methanol in three different regions (U.S., Europe, and China) to verify the economic viability of the process. Considering the reported annual working hours of electrolyzers and the predicted decline of electricity prices generated from renewable energy sources such as photovoltaics and on-shore wind energy, operating hours of the plant and electricity prices for water electrolysis to be economically competitive are varied for more practical prediction for methanol production costs. In conclusion, the profitable operating conditions of the process to achieve a 20% margin in the regions in the present and the future are suggested concerning plant working hours and the levelized cost of electricity for each water electrolysis system.
The oxygen gas produced from electrolysis is both a good heat supplier and an oxidizing agent for the autothermal reforming (ATR) process. Thus, green hydrogen production could be achieved by integrating the biogas ATR and electrolysis processes directly with renewable power sources. Under the natural fluctuation of renewable power, the oxygen produced from electrolysis can be stored in a compressed or liquid state in an intermittent storage tank to buffer its production rate for steady-state operation of biogas ATR process. In this study, integrated systems have been newly proposed using compressed gas and liquid oxygen storage methods, which are denoted as PEMCOAR and PEMLOAR systems, respectively. Using the surrogate model based on polynomial chaos expansion methodology (PCE), the statistical moments of levelized cost of hydrogen (LCOH) of both proposed systems were optimized considering the uncertainties of renewable power, biogas composition, and electricity tariff. As a result, the mean and variance of LCOH is reduced by 11.9% and 37.8%, respectively. In case of renewable power and biogas price of 0.06 /MMBTU, it was observed that the average LCOH below the current green hydrogen market price at a renewable power scale of over 55 MW. In conclusion, the study suggests the optimal operating condition under uncertainties and simultaneously, prove the economic feasibility of integrating electrolysis and biogas ATR systems.
The integrated biomass gasification-Solid Oxide Fuel Cell (SOFC) technology combines the benefits of renewable and hydrogen energy-based systems. In this work, this system is incorporated with solar-powered hydrogen production and injection into the SOFC to provide higher hydrogen concentration in fuel mixture of the SOFC. Proton Exchange Membrane Electrolyzer (PEME) is employed for hydrogen production, meanwhile, its required power is generated by solar Photovoltaic-Thermal (PVT) panels. The proposed system with hydrogen injection is modeled and its performance is evaluated and compared with that of conventional integrated biomass gasification-SOFC system in terms of thermodynamics, environmental impacts and economics. In thermoeconomic assessment, the environmental damage costs resulted from CO2 emissions as the primary greenhouse gas is taken into account. Via conducting a parametric study the major design variables are determined and then, a tri-objective optimization is performed based on levelized product cost, CO2 emissions, and exergy efficiency. It is found that, the proposed system has significantly lower CO2 emissions compared to the conventional system. Under optimal operation, the proposed system with hydrogen injection yields lower CO2 emission by 12.9% and higher output power by 8.7% at the expense of 6.3 percentage points reduction in exergy efficiency, compared to the conventional system. Despite the additional costs associated with the solar PVT panels and electrolyzer, the proposed system yields almost the same product cost compared to the conventional system. This point can be accounted as an important and remarkable advantage for the proposed system in this work.
Water electrolysis is a process that can produce hydrogen in a clean way when renewable energy sources are used. This allows managing large renewable surpluses and transferring this energy to other sectors, such as industry or transport. Among the electrolytic technologies to produce hydrogen, proton exchange membrane (PEM) electrolysis is a promising alternative. One of the main components of PEM electrolysis cells are the bipolar plates, which are machined with a series of flow distribution channels, largely responsible for their performance and durability. In this work, AISI 316L stainless steel bipolar plates have been built by additive manufacturing (AM), using laser powder bed fusion (PBF-L) technology. These bipolar plates were subjected to ex-situ corrosion tests and assembled in an electrolysis cell to evaluate the polarization curve. Furthermore, the obtained results were compared with bipolar plates manufactured by conventional machining processes (MEC). The obtained experimental results are very similar for both manufacturing methods. This demonstrates the viability of the PBF-L technology to produce metal bipolar plates for PEM electrolyzers and opens the possibilities to design new and more complex flow distribution channels and to test these designs in initial phases before scaling them to larger surfaces.
The exponentially growing contribution of renewable energy sources in the electricity mix requires large systems for energy storage to tackle resources intermittency. In this context, the technologies for hydrogen production offer a clean and versatile alternative to boost renewables penetration and energy security. Hydrogen production as a strategy for the decarbonization of the energy sources mix has been investigated since the beginning of the 1990s. The stationary sector, i.e. all parts of the economy excluding the transportation sector, accounts for almost three-quarters of greenhouse gases (GHG) emissions (mass of CO2-eq) in the world associated with power generation. While several publications focus on the hybridization of renewables with traditional energy storage systems or in different pathways of hydrogen use (mainly power-to-gas), this study provides an insightful analysis of the state of art and evolution of renewable hydrogen-based systems (RHS) to power the stationary sector. The analysis started with a thorough review of RHS deployments for power-to-power stationary applications, such as in power generation, industry, residence, commercial building, and critical infrastructure. Then, a detailed evaluation of relevant techno-economic parameters such as levelized cost of energy (LCOE), hydrogen roundtrip efficiency (HRE), loss of power supply probability (LPSP), self-sufficiency ratio (SSR), or renewable fraction (fRES) is provided. Subsequently, lab-scale plants and pilot projects together with current market trends and commercial uptake of RHS and fuel cell systems are examined. Finally, the future techno-economic barriers and challenges for short and medium-term deployment of RHS are identified and discussed.