Ahmet Kusoglu

Lawrence Berkeley National Laboratory | LBL · Energy Storage and Distributed Resources Department

Mechanical and electrochemical phenomena exhibit many interesting multidirectional couplings in ion-exchange soft matter due to their intrinsic material physio-chemical states and responses to environmental stressors. In this perspective, such coupling is explored in terms of recent studies with a focus on the degradation of polymer-electrolyte fue...

Ion-conducting polymers (ionomers) have been extensively studied in solution, as membranes and substrate-supported thin films for various electrochemical energy-conversion devices, including fuel cells and electrolyzers. Formation of an ionomer film from a solution, however, is not well understood, despite its importance for fabrication of electrod...

Ionomer thin‐films (i.e., 20–100 nm) on supports serve as model systems to understand ionomer‐catalyst interfacial behavior as well as the confinement‐driven deviation in properties from bulk membranes. While ionomer thin‐films have been examined for proton exchange ionomers, the thin‐film properties of anion exchange ionomers (AEIs) remain largely...

The recent release of hydrogen economy roadmaps for several major countries emphasizes the need for accelerated worldwide investment in research and development activities for hydrogen production, storage, infrastructure and utilization in transportation, industry and the electrical grid. Due to the high gravimetric energy density of hydrogen, the...

Proton-exchange membrane (PEM) water electrolysis is a promising technology for producing clean hydrogen by electrochemically splitting water when paired with renewable energy sources. A major roadblock to improving electrolyzer durability is the mechanical degradation of the cell components, which requires an understanding of their mechanical resp...

Ionomers are important to electrode function in energy conversion devices, such as fuel cells and electrolyzers, as the catalyst‐binding nanometer‐thick films under confinement, which compromises mass transport of species. Mitigating confinement effects is necessary for improved performance of polymer electrolyte fuel cells. Studies on perfluorosul...

This article illustrates the key facts and figures about the transportation sector and its contribution to emissions, in particular the heavy-duty trucking, in terms of the current state of sector in the U.S. in light of increasing recent focus on decarbonization efforts with zero emission trucking. Heavy-duty trucks contribute significantly more t...

While significant advances have been made and early commercial fuel cell light-duty vehicles (LDVs) are starting to be produced, fuel cells in the heavy-duty-vehicle (HDV) transportation sector (including trucks, long-haul semitrailers, maritime, trains, etc.) are nascent, despite the fact that advantages of fuel cells compared to both diesel and e...

Electrochemical energy conversion devices such as polymer-electrolyte fuel cells, water-splitting or carbon dioxide reduction electrolyzers, utilize ionically-conductive polymers (ionomers) in their electrode structure where an ionomer forms interfaces with the catalysts. The ionomers exist as nanometer-thick film to cover the catalyst particles an...

Polymer electrolyte membrane fuel cells (PEMFCs) are being considered for heavy duty applications, and the DOE has established various performance and durability targets to enable their adoption. 1. The key differences between light and heavy-duty application of fuel cells is their increased durability and operating efficiency requirements for heav...

Use of solar irradiance to drive CO 2 reduction (CO 2 R) holds great promise for the sustainable generation of energy-dense fuels and chemicals, especially as it relates well to carbon capture technology. Multicarbon (C 2+ ) products ( e.g. , ethylene, ethanol, propanol) are particularly attractive because they have a large market size and can be f...

Anion-exchange membranes (AEMs) are a possible replacement for perfluorosulfonic-acid membranes in energy-conversion devices, primarily due to the hydroxide mobile ion allowing the devices to operate in alkaline conditions with less expensive electrocatalysts. However, the transport properties of AEMs remain understudied, especially electro-osmosis...

For the desired clean energy transition, hydrogen technologies are sought to play a critical role from electrolyzers to produce clean hydrogen from water to fuel cells to decarbonize heavy-duty transportation. Centerpiece to the successful operation of these technologies is the durable performance of the membrane-electrode assembly systems, which c...

Ion-conducting polymer, or ionomer, membranes play a key role as the ion-conducting electrolyte in electrochemical devices, including fuel cells and electrolyzers. The performance of ionomers, for example, its proton conductivity, is defined by its unique molecular structure and multiscale morphology. Perfluorinated sulfonic acid ionomers are the m...

With ever-growing need for decarbonization, the role of (clean) hydrogen in clean energy transition has been gaining more interest and recognized at many levels, from global and sectoral climate goals and targets to clean energy bills and many roadmaps to net-zero scenarios, all of which necessitate a clear, unambiguous definition for clean hydroge...

Materials are more easily damaged during accidents that involve rapid deformation. Here, a design strategy is described for electronic materials comprised of conducting polymers that defies this orthodox property, making their extensibility and toughness dynamically adaptive to deformation rates. This counterintuitive property is achieved through a...

The biggest obstacle to the widespread implantation of polymer electrolyte membrane fuel cells (PEMFCs) is the cost, primarily due to the use of platinum catalysts. The high intrinsic catalyst activity...

This article discusses the definition of “clean” hydrogen produced by various pathways with a focus on transitioning from color-coded definitions to one that is based on the emissions generated in its creation. Herein, we also discuss the limitations of color-coding by providing a refined critique and assessment. With increasing emphasis on decarbo...

Ion-conducting polymers (ionomers) are an important component of the heterogenous electrodes (catalyst layers, CL) in proton exchange membrane fuel cells (PEMFCs). In the CL, the nano-thin ionomer layer facilitates mass transport to and from the catalyst sites. Emerging chemistries have the potential to improve this mass transport by inserting addi...

Metal alloy catalysts, such as Pt-Co, reduce the activation energy of oxygen reduction reaction, leading to improved proton exchange membrane fuel cell (PEMFC) performance. However, leaching of non-noble elements contaminates the ionomer and membrane, which has a negative impact on the durability of PEMFCs [1,2]. For the commercial success of metal...

Ion conducting polymers used as membranes and catalyst binders in membrane electrode assemblies (MEAs) have driven continuous improvements in fuel cell performance. Commercially available membrane materials (e.g., Nafion ® ) impart low gas permeability, high chemical and mechanical stability thanks to their semi-crystalline polytetrafluoroethylene...

Water-splitting electrolyzers are a key technology for enabling the hydrogen economy and reshaping the renewable energy landscape. Among the most viable candidates for the low-temperature electrolyzers is the proton-exchange membrane (PEM) water-splitting electrolyzers (PEMWEs), which uses an ion-conductive polymer solid-electrolyte. For PEMWEs to...

Ionomers are used as the solid-electrolyte in many electrochemical energy conversion technologies where they offer many functionalities such as ion conduction, electrical insulation, and water transport. These ionomers are found as nanometer-thick electrolyte thin films within the catalyst layers of fuel cells, electrolyzers, and hydrogen-based red...

Hydrogen based proton-exchange-membrane fuel cells (PEMFCs) provide a sustainable, potentially decarbonized solution to meet the future energy needs for mobility applications especially heavy-duty vehicles. Water management plays a critical role in determining the performance and efficiency of PEMFCs. ¹ Low water content in the membrane-electrode a...

Perfluorosulfonated (PFSA) ionomer membranes owe their high conductivity and durability, which make them popular as proton-exchange membranes for fuel cells and electrolyzers, to their characteristic phase-separated morphology. The hydrophilic domains connecting the ionic moieties form the transport network for ions and water, while the hydrophobic...

Transport of protons and water through water-filled, phase-separated cation-exchange membranes occurs through a network of interconnected nanoscale hydrophilic aqueous domains. This paper uses numerical simulations and theory to explore the role of the mesoscale network on water, proton, and electrokinetic transport in perfluorinated sulfonic acid...

Metal alloy catalysts (e.g., Pt-Co) are widely used in fuel cells for improving the oxygen reduction reaction kinetics. Despite the promise, the leaching of the alloying element contaminates the ionomer/membrane, leading to poor durability. However, the underlying mechanisms by which cation contamination affects fuel cell performance remain poorly...

ConspectusThe electrochemical reduction of carbon dioxide (CO2R) driven by renewably generated electricity (e.g., solar and wind) offers a promising means for reusing the CO2 released during the production of cement, steel, and aluminum as well as the production of ammonia and methanol. If CO2 could be removed from the atmosphere at acceptable cost...

This short article presents a refined and updated view of the concept of the colors of hydrogen based on a survey of many recent reports and roadmaps on hydrogen. As a versatile, colorless molecular energy carrier with great potential to decarbonize multiple sectors and help reach net-zero emissions, there has been a renewed interest in improving a...

Electrochemical carbon dioxide reduction (CO2R) provides a promising pathway for sustainable generation of fuels and chemicals. Copper (Cu) electrocatalysts catalyse CO2R to valuable multicarbon (C2+) products, but their selectivity depends on the local microenvironment near the catalyst surface. Here we systematically explore and optimize this mic...

Ion exchange membranes (IEMs) are a key component of electrochemical processes that purify water, generate clean energy, and treat waste. Most conventional polymer IEMs are covalently cross-linked, which results in a challenging tradeoff relationship between two desirable properties─high permselectivity and high conductivity─in which one property c...

Polymer-electrolyte membranes (PEMs) are a key component in electrochemical energy conversion devices where their main function is to selectively transport ionic species. Reducing PEM thickness is an effective strategy for improving performance by minimizing transport losses. However, how thickness affects the intrinsic properties of a membrane rem...

Transport phenomena are key in controlling the performance of electrochemical energy-conversion technologies and can be highly complex, involving multiple length scales and materials/phases. Material designs optimized for one reactant species transport however may inhibit other transport processes. We explore such trade-offs in the context of polym...

This study provides insights into structure-property relationships of Nafion membranes swollen with organic sorbates, revealing correlations between sorbate polarity, ionomer domain structure, and ionic conductivity. Swelling, nanostructure, and ionic conductivity of Nafion in the presence of short-chain alcohols and alkanes were studied by infrare...

p>This study provides insights into structure-property relationships of Nafion membranes swollen with organic sorbates, revealing correlations between sorbate polarity, ionomer domain structure, and ionic conductivity. Swelling, nanostructure, and ionic conductivity of Nafion in the presence of short-chain alcohols and alkanes was studied by infrar...

Cell voltage at high current densities (HCD) of an operating proton-exchange membrane fuel cell (PEMFC) suffers from losses due to the local-O 2 and bulk-H ⁺ transport resistances in the cathode catalyst layer (CCL). Particularly, the interaction of perfluorosulfonic acid (PFSA) ionomer with the carbon supported platinum catalyst plays a critical r...

Perfluorosulfonic acid (PFSA) ionomers are an important class of materials that many electrochemical devices rely on as their ion-conducting electrolyte. Often, PFSA films are prepared through solution-processing techniques. Previous research has demonstrated that the solvent environment affects PFSA dispersion conformation, but it is not clear to...

Commercial water electrolysis technologies, including proton exchange membrane electrolysis (PEMWE), are the only renewable hydrogen generation technologies that can achieve the U.S. Department of Energy (DOE) cost targets within the next ten years at the required scale, based on the supply chain maturity and materials performance. In particular, m...

Perfluorosulfonic-acid (PFSA) ionomers are a critical part of proton-exchange-membrane (PEM) fuel-cell catalyst layers (CLs). They serve both to bind the catalyst particles together, lending mechanical support, and provide pathways for ion transport. The CL fabrication process has garnered significant attention in recent years, with research effort...

Polymer electrolyte fuel cells (PEFCs) offer the prospects to revolutionize the transportation by powering not only automotive but also and heavy-duty vehicles. In PEFCs, ionomers are used to function as a proton-exchange membrane (PEM) facilitating ion transport between the catalyst layers (CLs). In addition, ionomer also function as an electrolyt...

During operation, polymer-electrolyte-membrane (PEM) fuel cells undergo mechanical and chemical degradation mechanisms, which behave synergistically and lead to accelerated membrane degradation over time. This study builds upon previous modeling work on mechanical degradation as described by a pinhole in the membrane and the effects of cerium on ch...

Grazing-incidence X-ray scattering is a common technique to elucidate nanostructural information for thin-film samples, but depth-resolving this nanostructure is difficult using a single or few images. An in situ method to extract film thickness, the index of refraction and depth information using scattering images taken across a range of incident...

One of the primary limiting factors for proton-exchange-membrane (PEM) fuel-cell lifetime is membrane degradation driven by operational stressors such as generation of highly reactive radical species, which result in cell failure and voltage decay. To extend the lifetime of the membrane, cerium ions are added to the membrane to mitigate the effects...

During operation, polymer-electrolyte fuel cells undergo mechanical and chemical degradation, which behave synergistically and lead to accelerated membrane deterioration over time. This study builds upon previous modeling work on mechanical degradation, as described by a pinhole in the membrane, and chemical degradation mitigation by using cerium....

Perfluorosulfonic acids (PFSAs), are commonly used as solid polymer electrolyte membranes (PEMs) in electrochemical energy devices, where they are vulnerable to attack by hydroxyl radical species during operation, which reduces their effectiveness. A popular strategy to combat this problem is to introduce radical scavengers like cerium (Ce) ions th...

p>Limitations in fuel cell electrode performance have motivated the development of ion-conducting binders (ionomers) with high gas permeability. Such ionomers have been achieved by copolymerization of perfluorinated sulfonic acid (PFSA) monomers with bulky and asymmetric monomers, leading to a glassy ionomer matrix with chemical and mechanical prop...

Commercially available perfluorinated sulfonic acid ionomers (PFSAs), utilized as polymer electrolytes in membrane electrode assemblies (MEAs), have driven rapid improvements in fuel cell performance. These materials have a polytetrafluoroethylene (PTFE) backbone and semicrystalline matrix which imparts mechanical integrity and low gas permeability...

Multicomponent mass-transport in cation-exchange membranes involves the movement of multiple species whose motion is coupled one to another. This phenomenon mediates the performance of numerous electrochemical and water purification technologies. This work presents and validates against experiment a mathematical model for multicomponent mass transp...

We present and validate a mathematical model for multicomponent thermodynamic activity in phase-separated cation-exchange membranes (e.g., perfluorinated sulfonic-acid ionomers). The model consists of an expression for the free energy of the membrane and of the surrounding electrolyte solution. A modified Stokes-Robinson ionic solvation framework t...

Selectively tuning ion transport through redox flow battery separators is a promising approach toward increasing cell capacity, power density, and, ultimately, economic feasibility. However, this process is complex with numerous forces and coupled molecular interactions driving and impacting transport under different operating regimes. A fundamenta...

Cost and durability remain the two major barriers to widespread commercialization of polymer electrolyte membrane fuel cell (PEMFC)-based power systems, especially for the most impactful but challenging fuel cell electric vehicle (FCEV) application. Commercial FCEVs are now on the road; however, their PEMFC systems do not meet the cost targets esta...

The stability of ion-conductive membranes, such as perfluorosulfonic-acid (PFSA) membranes, as a solid-electrolyte separator in energy devices is strongly linked to their mechanical properties, the characterization of which presents challenges, especially in the presence of ionic interactions. Ionomer membranes’ elastic properties are affected by c...

Rapid improvements in polymer-electrolyte fuel-cell (PEFC) performance have been driven by the development of commercially available ion-conducting polymers (ionomers) that are employed as membranes and catalyst binders in membrane-electrode assemblies. Commercially available ionomers are based on a perfluorinated chemistry comprised of a polytetra...

Two-dimensional (2D) organic-inorganic (hybrid) perovskites are considered promising candidates to replace conventional three-dimensional (3D) perovskites for solar cell applications as they have good resistance against moisture and UV. However, the use of 2D perovskite is associated with a significant decrease in power efficiency resulting from th...

There is a critical need for higher performing proton exchange membranes for electrochemical energy conversion devices that would enable higher temperature and drier operating conditions to be utilized. A novel approach is to utilize multi-acid side chains in a perfluorinated polymer, maintaining the mechanical properties of the material, whilst dr...

Hydroxide-exchange membrane (HEM) fuel cells are emerging energy conversion technologies. A significant effort has been expended to develop new HEMs with enhanced transport functionality, which has driven the need for understanding how transport of hydroxide and other anions in these membranes is related to hydration and nano-morphology. In this wo...

Proton exchange membrane (PEM)-based devices are promising technologies for hydrogen production and electricity generation. Currently, the amount of expensive platinum catalyst used in these devices must be reduced in order to be cost-competitive with competing technologies. These devices typically contain Nafion® ionomer thin-films in the catalyst...

p>Rapid improvements in polymer-electrolyte fuel-cell (PEFC) performance have been driven by the development of commercially available ion-conducting polymers (ionomers) that are employed as membranes and catalyst binders in membrane-electrode assemblies. Commercially available ionomers are based on a perfluorinated chemistry comprised of a polytet...

Solvent-filled membranes, such as Nafion, are an important class of polymer electrolytes because the imbibed solvent imbues the material with high ionic conductivity, while still allowing the membrane to maintain its mechanical stability. Both of these attributes are essential for membrane electrolytes in numerous energy-storage and -conversion dev...

The performance of proton-conducting ionomer membranes used in electrochemical applications such as fuel cells is complicated by an intricate interplay between chemistry and morphology that is challenging to characterize and control. Here, we report on a class of perfluoro ionene chain extended (PFICE) ionomers that contain either one (PFICE-2) or...

Perfluorinated sulfonic-acid (PFSA) ion-conducting polymers (ionomers) serve as both a binder and active ion-transport material in electrochemical energy-conversion electrodes including fuel cells, electrolyzers, and redox-flow batteries. Within the catalyst layer of these devices, ionomer shuttles ionic and liquid or gaseous species to/from cataly...

To increase the energy density of hydrogen fuel, a common practice is through the production of high pressure hydrogen (up to 70 MPa). ¹⁻⁴ Furthermore, to ensure green or renewable hydrogen, water electrolysis from solar or wind resources is an attractive pathway, yet such technology has limitations on efficiency, especially when trying to deliver...

The heterogeneous microstructure of the electrode in polymer electrolyte-based electrochemical devices is not well understood. Due to its complex nature, it is challenging to investigate in a meaningful way. Model systems need to be designed to study controlled interfaces between polymer electrolytes and catalyst particles or surfaces. It is known...

Throughout the lifetime of a polymer-electrolyte fuel cell, the membrane undergoes chemical degradation that causes defects to form and grow, contributes to a loss of performance, and can lead to cell failure. A combination of accelerated stress tests (ASTs) ¹⁻² and modeling studies ³⁻⁴ have been performed on this topic to better understand membran...

The development of functionally complex mesoscale (nm - µm) materials requires comparable evolution in the analytical instruments and techniques in order to understand the physical and chemical structure-property relationships underlying their performance. Resonant X-Ray Scattering (ReXS) is a powerful technique due to its ability to statistically-...

Perfluorinated anion exchange membranes are promising materials for alkaline fuel cell applications. Our previous work indicates they have high conductivity of >100 mS/cm at 80ᵒC and 95%RH.(1) They have also displayed good fuel cell performance of 1W/cm ² .(2) We have also performed transmission small- and wide-angle X-ray scattering (SAXS/WAXS) of...

Anion exchange membrane (AEM) fuel cells are emerging energy conversion technologies. A significant challenge in these devices lies in the core component, the AEM, which must possess high ionic conductivity to minimize Ohmic losses and exhibit chemical stability in highly basic conditions. A significant amount of effort has been expended to develop...

Cerium enhances the durability of polymer electrolyte membrane (PEM) fuel cells by scavenging reactive radical species which are generated during operation. However, during cell fabrication, conditioning, discharge, and during fuel cell operation, Ce dissolves and is transported within the membrane-electrode-assembly (MEA) due to gradients in ionic...

The HydroGEN Energy Materials Network (EMN) supernode in low temperature electrolysis combines capabilities from the National Renewable Energy Laboratory (NREL), Lawrence Berkeley National Laboratory (LBNL), and Savannah River National Laboratory (SRNL) to perform relevant and ground-breaking research outside of EMN-funded projects. The low tempera...

Perfluorosulfonic acid (PFSA) membranes are the prototypical solid-electrolyte used in electrochemical devices such as polymer-electrolyte membrane fuel cells (PEMFCs) and electrolyzers [1]. To be commercially viable, polymer-electrolyte membranes (PEMs) in PEMFCs and electrolyzers must perform over a long operational time in both dry and wet envir...

Redox flow batteries (RFBs) remain one of the most promising technologies that are actively explored for grid-scale energy storage from discontinuous power sources such as wind and solar.[1] Proliferation of RFB technology has resulted in a need for continued development and understanding of new redox couples and improved separator membranes for RF...

Commercial water electrolysis technologies, including proton exchange membrane electrolysis (PEMWE), are the only renewable hydrogen generation technologies that can achieve the U.S. Department of Energy (DOE) cost targets within the next ten years at the required scale, based on the supply chain maturity and materials performance. In particular, m...