Ahmet Kusoglu

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

PhD

About

169
Publications
24,592
Reads
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5,451
Citations
Citations since 2017
93 Research Items
4306 Citations
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201720182019202020212022202302004006008001,000
201720182019202020212022202302004006008001,000
Introduction
Research is on fundamental understanding of ion-containing polymeric materials and interfaces for electrochemical devices and related chemical-mechanical phenomena for energy applications. Our work focuses on modeling and diagnostics of ionomers and thin films, including their transport and mechanical properties, structure-function-performance relationships, chemical degradation and mechanical durability, as well as their morphological characterization through synchrotron X-ray techniques.
Additional affiliations
January 2014 - December 2014
University of California, Berkeley
Position
  • Lecturer
October 2013 - January 2020
Lawrence Berkeley National Laboratory
Position
  • Researcher
Description
  • Research on polymeric materials for energy and environmental applications, and related chemical-mechanical phenomena in electrochemical devices
January 2013 - January 2014
University of California, Berkeley
Position
  • Teaching
Description
  • Polymeric Materials Course
Education
April 2005 - January 2010

Publications

Publications (169)
Article
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Preprint
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...
Article
Full-text available
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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....
Article
Full-text available
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...
Article
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...
Preprint
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...
Conference Paper
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...
Article
Full-text available
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
Full-text available
The effects of film thickness and substrate composition on the ionomer structure in porous electrodes are critical in understanding pathways toward developing higher performance electrochemical devices, including fuel cells and batteries. Insights are gained into the molecular and nanostructural orientation dependence for thin Nafion films (12–300...
Preprint
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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-...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
Rapid improvements in fuel cell performance have been driven by the development of commercially available ionomers used as membranes and catalyst binders in membrane electrode assemblies (MEAs). Commercially available ionomers share a semi-crystalline polytetrafluoroethylene (PTFE) matrix, which imparts low gas permeability and high mechanical and...
Article
The performance of ion-conducting polymer membranes is complicated by an intricate interplay between chemistry and morphology that is challenging to understand. Here, we report on perfuoro ionene chain extended (PFICE) ionomers that contain either one or two bis(sulfonyl)imide groups on the side-chain in addition to a terminal sulfonic acid group....
Preprint
Full-text available
Grazing incidence x-ray scattering provides nanostructural information for thin film systems, but single images do not provide information on film thickness or the full complex index of refraction. X-ray reflectivity is a complementary technique that can provide this information, but it is most often done ex-situ. In this paper, we present an in-si...
Article
Mass-transport properties of electrosprayed catalyst-layers based on Pt/C and ionomer (Nafion) are studied with hydrogen limiting-current technique, water-vapor-uptake, scanning transmission microscopy (STEM), single-cell testing, and impedance spectroscopy. The hydrogen limiting-current technique provides the transport resistance of the layers (RC...
Article
Research activities and interests in electrochemical conversion devices (e.g., fuel cells, flow batteries, and electrolyzers, etc.) have been continuously increasing due to their great potential to provide clean and renewable energy technologies for stationary, transportation, and solid-state applications. At the heart of these devices is the polym...
Article
Impacts of processing, storage, and operation on thin-film perfluorosulfonic acid (PFSA) ionomer coatings used in electrodes of electrochemical devices remains unestablished. In this work, alteration of structure–function relationship in ionomers is achieved via exposure to elevated temperature and humidity (hygrothermal aging). Findings reflect a...
Chapter
In polymer-electrolyte fuel cells (PEFCs), ionomers play a key role not only as a proton exchange membrane (PEM) but also as nanometer-thick electrolyte “thin films” within porous catalyst layer (CL) structures, where they bind and cover the catalytic particles and provide transport pathways for the ions and reactant species. An ionomer’s propertie...
Article
Thin perfluorosulfonated ion-conducting polymers (PFSI ionomers) in energy-conversion devices have limitations in functionality attributed to confinement-driven and surface-dependent interactions. This study highlights the effects of confinement and interface-dependent interactions of PFSI thin-films by exploring thin-film thermal transition temper...
Article
Building on the recent demonstration of aqueous-dispersible hydrophobic pigments that retain their surface hydrophobicity after drying, we demonstrate the synthesis of surface modified Ti-Pure R-706 (denoted R706) titanium-dioxide-based pigments, consisting of a thin (1 - 3 monolayers) grafted poly-methylhydrosiloxane (PMHS) coating, which (i) are...
Article
Strong R&D progress and increased demand for hydrogen powered fuel-cell cars, is shifting Polymer Electrolyte Fuel Cells (PEFCs) to lower Platinum electrocatalyst loading and to Platinum-cobalt (Pt-Co) alloys that have demonstrated double the kinetic activity improvement [1]. Implementation of these catalysts can lower catalyst cost to $7/kW (from...
Article
Ion-conductive polymers (ionomers) have been widely used as the solid-electrolyte in energy conversion devices, such as polymer-electrolyte fuel cells (PEFCs) fuel cells, redox flow batteries and water-splitting devices. Ionomers, such as perfluorosulfonic-acid (PFSA), function as the separator-electrolyte in these devices due their high proton con...
Article
Redox flow batteries (RFBs) are poised at becoming one of the most promising technologies that are being explored for grid-scale energy storage from discontinuous power sources such as wind and solar.[1] This has resulted in a need for continued development and understanding of new redox couples and their supporting electrolyte counterparts, as wel...