Perfluorosulfonic Acid Research Articles

Recent Progresses and Challenges to Determine Properties of Sulfonated Polyether Ether Ketone Based Electrolytes for Direct Methanol Fuel Cell Applications

AbstractThis review focuses on fillers, modifications, and methods used in the preparation and development of sulfonated poly(ether ether ketone) (sPEEK) membranes, specifically for direct methanol fuel cell (DMFC) applications as proton exchange membranes in recent years. The primary objective is to evaluate recent advancements by emphasizing key characteristics such as water uptake and swelling capacity, ionic conductivity, methanol permeability, and single cell polarization tests. Additionally, the review aims to provide insights for future researchers by discussing the preparation processes of electrolytes. It presents basic characterizations of membrane electrolytes, including evaluations of the sulfonation degree and ion exchange capacities of sPEEK. High performance of membrane electrolytes is essential for commercialization and to compete with established membranes like Nafion®, which has a perfluorosulfonic acid structure. Therefore, the review also covers detailed characterization methods for assessing long‐term stability when available in the related studies. Numerical results and indicators are categorized and tabulated for easy interpretation and comparative analysis.

Performance prediction of IPMC modified with SiO2-SGO based on backpropagation neural network

Ionic polymer–metal composites (IPMCs) constitute a new type of artificial muscle material that is commonly used in bionic soft robots and medical devices because of its small driving voltage and considerable deformation. However, IPMCs are limited by performance issues such as low output force and small operating time away from water. Silicon dioxide sulfonated graphene (SiO2-SGO) particles are often used to improve the performance of polymer membranes because of their hydrophilicity and high chemical stability. Reported here is the addition of SiO2-SGO particles prepared by in situ hydrolysis to perfluorosulfonic acid in order to improve the IPMC properties. Also, a predictive model was constructed based on a backpropagation neural network, with the SiO2-SGO doping amount and the IPMC excitation voltage in the input layer and the driving displacement in the output layer. The results show that the IPMC prepared with 1.0 wt. % doping content performed the best, with a maximum output displacement of 47.7 mm. The correlation coefficient (R2) was 0.9842 and the mean square error was 0.000 370 73, which show that the predictive model has high predictive accuracy and is suitable for predicting the performance of the SiO2-SGO-modified IPMC.

Advances in the Application of Sulfonated Poly(Ether Ether Ketone) (SPEEK) and Its Organic Composite Membranes for Proton Exchange Membrane Fuel Cells (PEMFCs)

This review discusses the progress of research on sulfonated poly(ether ether ketone) (SPEEK) and its composite membranes in proton exchange membrane fuel cells (PEMFCs). SPEEK is a promising material for replacing traditional perfluorosulfonic acid membranes due to its excellent thermal stability, mechanical property, and tunable proton conductivity. By adjusting the degree of sulfonation (DS) of SPEEK, the hydrophilicity and proton conductivity of the membrane can be controlled, while also balancing its mechanical, thermal, and chemical stability. Researchers have developed various composite membranes by combining SPEEK with a range of organic and inorganic materials, such as polybenzimidazole (PBI), fluoropolymers, and silica, to enhance the mechanical, chemical, and thermal stability of the membranes, while reducing fuel permeability and improving the overall performance of the fuel cell. Despite the significant potential of SPEEK and its composite membranes in PEMFCs, there are still challenges and room for improvement, including proton conductivity, chemical stability, cost-effectiveness, and environmental impact assessments.

High protonic resistance of hydrocarbon-based cathodes in PEM fuel cells under low humidity conditions: Origin, implication, and mitigation

Hydrocarbon-based electrodes for proton-exchange membrane fuel cells face challenges in closing the performance gap with electrodes based on perfluorosulfonic acid ionomers, particularly under low humidity conditions. Alongside increased oxygen transport resistance and higher kinetic-induced overpotentials, the protonic resistance of these fluorine-free electrodes is the primary hurdle to improved performance. This study systematically investigates the origin and impact of the cathode protonic resistance on fuel cell performance, utilizing sulfonated phenylated polyphenylenes as hydrocarbon ionomers. Electrochemical characterization at low relative humidity (≤50 %) reveal a high protonic resistance arising from both lower conductivity of the hydrocarbon thin film compared to the bulk membrane and increased cathode tortuosity at a gas transport-optimized ionomer to carbon (I/C) ratio of 0.2. The poor protonic resistance at low relative humidities leads to a non-homogeneous current distribution across the thickness of the cathode electrode, resulting in lower catalyst utilization. To address this issue, reducing the thickness of the cathode CL while maintaining a constant Pt loading (i.e., increasing the Pt on carbon ratio) significantly reduces protonic resistance. This improvement compensates for the kinetic disadvantages of highly loaded carbon particles and results in a considerable performance increase by 40 % at 0.75 V under low relative humidities.

Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach

Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.

Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach

Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.

Proton conductivity and durability of Ce-based hybrid proton exchange membranes synchronously enhanced by dual-function γ-AlOOH@Ti-supported CeO2 composite oxide

To enhance the proton conductivity and durability of Ce-based hybrid proton exchange membranes (PEMs), this study fabricates modified perfluorosulfonic acid (PFSA) hybrid membranes by incorporating the dual-function γ-AlOOH@Ti-supported CeO2 composite oxide (γ-AlOOH@Ti/CeO2). In addition to combining the inherent proton conductivity of γ-AlOOH with the excellent radical scavenging ability of CeO2, both the proton conductivity and durability of Ce-based PEMs are further improved by introducing Ti-dopant, which not only increases hydrogen vacancies on the surface of γ-AlOOH, which facilitate proton conduction, and induces electron transfer from γ-AlOOH@Ti to CeO2, which enhance free radical adsorption. As results shown, the proton conductivity and the fluoride release value of the resulting hybrid membrane are about 76 % higher and 35.25 % lower than those of the PFSA-CeO2 membrane, respectively. Moreover, the performance of cells shows that, after accelerated degradation testing, the PFSA-γ-AlOOH@Ti/CeO2 membrane exhibits the lowest peak power density decrease rate, the impedance increase rate and hydrogen crossover current density, with 11.79 %, 27.54 % and 3.04 mA cm−2, respectively. These results suggest that compared to CeO2-hybrid PEMs, γ-AlOOH@Ti/CeO2-based hybrid PEMs exhibit higher proton conductivity and superior chemical stability, indicating the potential application of γ-AlOOH@Ti/CeO2-based hybrid PEMs in proton exchange membrane fuel cells.

Orientation Control of Perfluorosulfonic Acid Films via Addition of 1,2,4-Triazole during Casting.

Perfluorosulfonic acid (PFSA) polymers are used as electrolyte membranes in polymer electrolyte fuel cells. To investigate the effect on proton conductivity through structural orientation control, we added 1,2,4-triazole to PFSA films during casting to impart anisotropy to the ion-cluster structure of the films. The proton conductivities of the films were found to be high in the film-surface direction and low in the film-thickness direction. Structural analysis using small-angle X-ray scattering suggested that the anisotropy in proton conductivity was due to anisotropy in the ion-cluster structure, which in turn was attributed to the formation of a phase-separated structure via strong bonding between sulfonic acid groups and 1,2,4-triazole during cast film formation and the surface segregation of fluorine. We expect the findings of this study to aid in the fabrication of PFSA films with controlled ion clusters.

PFOA and PFOS Pollution in Surface Waters and Surface Water Fish

Perfluoroalkyl and poly-fluoroalkyl substances (PFAS) are among the synthetic chemicals employed by various industries since the 1950s and the most critical persistent organic pollutants (POPs) that led to emerging concerns due to high persistency, toxicity, mobility, and environmental bioaccumulation. Although there are more than 5000 types of PFASs, perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS) are the two chemicals whose employment is highly restricted and banned by the Stockholm Convention. In the present study, certain water resources in the Marmara Region, the most densely populated and industrial region in Turkey, and the waters of Turkey’s two largest drinking water reserves, Beyşehir and Eğirdir lakes, were investigated. The study was carried out in two seasons, spring and autumn. The lowest and highest PFOA concentrations were determined between 1.77 ± 0.1 and 6.71 ± 2.9 ng/L in all surface waters, and the highest PFOS concentrations were between <LOQ and 3.27 ng/L. PFOA concentrations were higher when compared to PFOS concentrations in all water sources, and PFOA and PFOS concentrations were lower in spring compared to autumn. In some commercially procured fish from water resources, 7.48 ng/g PFOS was detected in Küçükçekmece Lake pike, and 2.5 ng/g PFOA was identified in Eğirdir Lake trout. PFOA and PFOS were not detected in other fish tissues.

Fabrication of high-performance pervaporation desalination composite membranes with study of its acid-base stability

In the process of industrial production will produce a lot of acid and alkaline waste liquid, how to effectively treat acid and alkali waste liquid is an important topic at present. At present, there are some problems about the treatment of acid and alkali waste liquid, such as large investment, complicated process and low efficiency. Pervaporation has the characteristics of mild operating conditions and no influence of osmotic pressure threshold, so it has great application potential in the concentration, reuse and reduction of acid and alkali waste liquid. However, at present, conventional pervaporation dense membrane materials cannot maintain long-term stability in strong acid and alkali environment, in order to achieve this performance, we use perfluorosulfonic acid resin with good acid and alkali resistance as the dense layer substrate. PFSA/PTFE/PP composite membrane was prepared by spraying process, and the final prepared composite membrane had a pure water flux of 45 ± 1.2 kg/(m2∙h) at 70 ℃. The acid and alkali resistance of the intrinsic membrane and the composite membrane was evaluated, and it was found that the feed liquid was concentrated to 20 wt% after 19 h long concentration operation at 70℃ and starting liquid was 5 wt% H2SO4 and 5 wt% NaOH. The retention rate of acid and alkali can be maintained above 99.9 %. During the concentration of H2SO4 solution, the dense layer structure is affected, and the pure water flux of the composite membrane is reduced, eventually maintaining around 32 kg/(m2∙h). In the process of concentrating NaOH solution, the pure water flux of the composite membrane increased first and then decreased, and the final pure water flux of the membrane remained near 40 kg/(m2∙h).

The Hybridization of Polymers with Metal Oxide Clusters for the Design of Non-Fluorinated Proton Exchange Membranes.

As the key component of various energy storage and conversion devices, proton exchange membranes (PEMs) have been attracting significant interest. However, their further development is limited by the high cost of perfluorosulfonic acid polymers and the poor stability of acid-dopped non-fluorinated polymers. Recently, a new group of PEMs has been developed by hybridizing polyoxometalates (POMs), a group of super acidic sub-nanoscale metal oxide clusters, with polymers. POMs can serve simultaneously as both proton sponges and stabilizing agents, and their complexation with polymers can further improve polymers' mechanical performance and processability. Enormous efforts have been focused on studying supramolecular complexation or covalent grafting of POMs with various polymers to optimize PEMs in terms of cost, mechanical properties and stabilities. This concept summarizes recent advances in this emerging field and outlines the design strategies and application perspectives employed for using POM-polymer hybrid materials as PEMs.

Degradation mechanism analysis of a fuel cell stack based on perfluoro sulfonic acid membrane in near-water boiling temperature environment

Perfluoro sulfonic acid (PFSA)-membrane fuel cells for heavy-duty vehicle applications require elevated operating temperature, which may negatively impact the durability of proton exchange membrane fuel cells (PEMFCs). This study evaluated a 10 kW stack by conducting a 100 h driving cycle test in near-water boiling temperature. Performance degradation varied in different regions of the membrane electrode assembly (MEA), with severe degradation observed near the coolant outlet (near-water boiling temperature) and the hydrogen inlet. The rapid degradation of the MEA was examined through an analysis of its electrochemical properties, morphology, pore size, mechanical properties, degree of graphitization, and elemental composition in different regions. It was found that elevated temperatures accelerated the degradation of the PEM, leading to polymer melting, corrosion of carbon support, and the aggregation and growth of Pt nanoparticles within the MEA, ultimately the MEA structural breakdown. the MEA supporting structural breakdown. The combination of high temperatures and the loss of fluoride ions from the MEA resulted in damage to the bipolar plate coatings. Under the collaborative influence of these factors, the average voltage degradation rate of the PEMFC stack was 1.44 %@1.0 A cm−2, and the single cell with the worst degradation was up to 8.6 %@1.0 A cm−2.

Unraveling the nanostructures and self-assembly behavior of perfluorosulfonic acid in water/ethanol solvent: Effect of EW and side-chain chemistry

The perfluorosulfonic acid (PFSA) ionomers are key materials for proton exchange membranes (PEMs) and catalyst layers (CLs). Their morphology is profoundly influenced by the chain assembly behavior of PFSA in dispersions. Hence, we combine the characterization techniques of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (Cryo-TEM) to study the nanostructures of PFSA dispersions, and provide a structure model for diverse PFSA ionomers in water/ethanol solvent. It is seen that PFSA ionomers self-assembly into a rod-like particle in dilute dispersion. As the concentration increases, the primary rod aggregates gradually assemble into a swollen- or Gaussian-network structure. Beyond this feature, we see that different PFSA ionomers show different nanostructures in dispersion. For the long-side-chain (LSC) PFSA ionomers, the 800-LSC PFSA tends to form monodisperse rod-like aggregates that is in a highly ordered arrangement with a rod diameter of 3.16 nm and a length of 28.72 nm. As the equivalent weight (EW) increases to 960, the poor solubility of the main chains in water/ethanol solvents leads to the “end-to-end” assemblies of the primary rod particles and dendritic secondary aggregates. The short-side-chain (SSC) PFSA ionomer that shares the same backbone with 960-LSC PFSA exhibit remarkable mono-dispersity and ordered arrangement of rod-like aggregates in water/ethanol solvents due to the strong electrostatic repulsion.

Preferential Partitioning of Per- and Polyfluoroalkyl Substances in Freshwater Ice.

Millions of lakes worldwide freeze, yet the fate of per- and polyfluoroalkyl substances (PFAS) in ice in freshwater systems is poorly understood. We quantified concentrations of 36 PFAS, dissolved organic carbon (DOC), and inorganic ions in ice and water in seven freshwater lakes to investigate the preferential exclusion of ions during freezing. PFAS concentrations in ice are typically lower than in the water column, demonstrating that these chemicals are excluded from ice as it freezes. However, there is preferential partitioning of both PFAS and DOC relative to cations with average sodium-normalized enrichment factors (EF) ranging from 2.74 for perfluorobutanoate (PFBA; a C4 perfluorocarboxylic acid) to 4.01 for perfluorooctanesulfonate (PFOS; a C8 perfluorosulfonic acid), with a similar EF value of 4.14 for DOC. Laboratory experiments and seasonal measurements of PFAS in the water column indicate that PFAS concentrations in ice are a function of aqueous PFAS concentrations, with lower EF values observed in waters with higher PFAS concentrations. Understanding PFAS behavior in freshwater ice is important for predicting contaminant fate during winter and spring periods, with implications for exposure to PFAS during the winter and release of PFAS when ice melts in freshwater systems.

(Invited) Mechanical Properties of Proton Exchange Membranes for Water Electrolysis Applications

Water electrolysers are critical to the advancement of sustainable hydrogen technologies. A key component of proton-exchange membrane water electrolysers (PEMWE) is the ionomer membrane which transports protons and water from the anode to the cathode and physically separates the H₂ and O₂ reaction products. Importantly, the barrier properties of the membrane must be maintained at high differential pressure over the lifetime of the PEMWE. To help predict the mechanical durability and operational safety of the PEMWE, it is important to understand the mechanical properties of the PEM as a function of temperature, differential pressure, and time.The main component of a typical modern PEM is a perfluorosulfonic acid (PFSA) ionomer. PFSAs have a hydrophobic perfluorinated backbone with pendant perfluorinated side chains terminating in sulfonic acid groups. The general chemical structure of PFSAs is understood to result in phase separation into hydrophilic, sulfonate-rich domains that act as transport pathways and hydrophobic, tetrafluoroethylene-rich domains that impart thermomechanical stability. In PEMWE applications, short-side chain PFSAs are a promising alternative to the benchmark Nafion, a long-side chain PFSA. At a given ion-exchange capacity (IEC), the ratio of perfluorinated backbone to sulfonic acid side chain increases as the side chain length decreases. Thus, short-side chain PFSAs may be more thermomechanically stable while maintaining good proton and water transport necessary for PEMWE efficiency.In this work, the mechanical properties of short-side chain PFSAs are investigated as a function of IEC, temperature, differential pressure, and time. Particular focus is given to compressive mechanical measurements to simulate the conditions experienced by the membrane in PEMWE applications. The findings are expected to help inform the design of next-generation membranes for hydrogen technology applications.

In-situ X-ray Fluorescence Analysis of In-plane Cerium-ion Distribution Under Humidity Gradients in Proton Exchange Membrane

For the wide application of polymer electrolyte fuel cells, durability of more than 50,000 hours is necessary. Chemical degradation of the perfluorosulfonic acid (PFSA) membrane electrolyte is one of the degradation factors. Hydrogen peroxide generated from crossover gas reacts with impurities, and the resulting radicals break the chemical bonds in the electrolyte membrane. To quench the radicals, cerium ions are added to the membrane electrode assembly (MEA) as a radical quencher. However, cerium ions are known to move in the in-plane direction due to the humidity gradient during fuel cell operation. In areas where cerium ions are depleted, the chemical bonds of the PFSA are attacked by radicals. Therefore, it is necessary to understand the in-plane transport phenomena of cerium ions under fuel cell operating conditionsand incorporate into the development of MEAs. In this study, we developed an operando measurement cell that can track the change of cerium ion distribution over time by X-ray fluorescence spectroscopy (XRF) using high energy X-rays under fuel cell operation while controlling the in-plane humidity gradient. The in-plane transport of cerium ions, driven by the humidity and concentration gradients, was analyzed.Two gas inlets were connected to an end plate with an X-ray transmission window to control two humidity environments on the left and right sides with in-plane direction of MEA. For MEA, Pt/C catalyst layer was coated on PFSA membranes in which a part of sulfonic acids were exchanged with cerium ions. GDL without cerium was used. Operando XRF measurements were performed at beamline BL37XU on SPring-8. The incident energy was 60 keV X-rays, and Ce-Kα fluorescence X-rays were counted. The beam size was 0.5×0.5 mm2. The cell temperature was 60°C, the different relative humidity (RH) in the in-plane direction was set to 90% and 50% using N2 gas, then the RH of the whole MEA was set to 95% to measure the relaxation behavior of cerium.Fig. 1 shows the Ce intensity variation at the vertical center of the MEA under the condition of humidity difference with in-plane direction. The x-axis corresponds to the horizontal position of the MEA, with RH 90% on the left side and RH 50% on the right side. The y-axis corresponds to the time under the humidity gradient. The darker blue indicates weaker intensity of the Ce-Kα fluorescence X-ray and the white indicates stronger Ce intensity. This suggests that cerium ions move from the high humidity side to the low humidity side with the humidity gradient as the driving force. The time scale for this movement of a few millimeters was shown to be about tens of minutes. Acknowledgments The authors would like to thank M. Toida (Toyota Motor Corporation) for providing samples and for in-depth discussions. Figure 1

Enhancing Impregnability in Reinforced Composite Membrane Using Greener Dispersion

Perfluorosulfonic acid (PFSA) polymer commonly offer high ionic conductivity, chemical and physical properties, and rapid response, making them widely used in energy conversion technologies like fuel cell and water electrolysis. Industrial commercialization of the polymer electrolyte membranes for water electrolysis depends not only on sufficient electrochemical performance but also requires gas barrier properties and high dimensional stability. To improve the properties of these polymer electrolyte membranes selection of an appropriate dispersion solvent and optimization of its composition ratio are very important. However, PFSA polymer limits the types of dispersion solvents due to its unique structure, which consist of combining a hydrophilic perfluorovinyl ether side chain with sulfonate groups onto a hydrophobic tetrafluoroethylene backbone.Here, we have introduced a new greener mixture system for the fabrication of PFSA-reinforced composite membranes for water electrolysis and compared it with conventional solvent systems. Our solvent system not only produced a more densely packed support layer but also relaxed the anisotropy of the reinforced composite membrane. As a result, the compressive strength and tensile strain increased, making it possible to compensate for the shortcomings caused by the support. Also, this increased impregnability resulted in relatively low gas permeability and high ionic conductivity. The water electrolysis performance was comparable with those prepared using an NMP-based solvent. These results demonstrate a method for preparing PFSA dispersions for reinforced composite membrane and their potential to replace hazardous solvents used in fabrication processes.

Enabling Rhenium Electrodeposition in Water-in-Salt Electrolytes through Isolated Anodic Reactions

Perfluorosulfonic Acid (PFSA)/Polytetrafluoroethylene (PTFE) copolymer and cation-exchange membranes were used to elongate the use water-in-salt electrolytes for rhenium electrodeposition. Water-in-salt electrolytes are a common technique used to minimize the amount of free water in solution by including high concentrations of salts, thus solvating the water molecules and lowering activity of the solution. This expands the electrochemical window in which deposition is possible and minimizes unnecessary hydrogen evolution reactions (HER) in the electrodeposition system by reducing available protons.Lithium chlorine (LiCl) is a common salt for this purpose due to low costs. However, in the LiCl electrolyte, the necessary oxygen evolution reaction (OER) competes with chlorine evolution, which increases water activity and is visually identifiable with a color change from clear to yellow. When chloride ions are depleted, further deposition is no longer possible, and the electrolyte breaks down.A solution to this issue is using membranes to isolate the anode and cathode, thus preventing the chlorine evolution reaction from occurring. Since rhenium is a system with a small electrochemical window, possible oxide intermediates, and an overpotential for hydrogen evolution, the system requires the use of a stable water-in-salt electrolyte for elongated deposition.In this experiment, three membranes were examined to compare the impact on rhenium depositions in an H-cell. To compare the impact of each membrane, the change of pH of the DI side of the H-cell was monitored across time alongside the volume changes on both sides of the H-cell as a function of time due to LiCl inclusion. The quality and thicknesses of the coatings was examined by SEM as well as the impact on the morphologies of the rhenium of the deposits between each of the membranes.

High Efficiency and High Durability Proton Exchange Membrane Water Electrolyzers for Hydrogen Production with Advanced Catalyst Coated Membranes

Water electrolyzers and fuel cells can be used to create a closed loop system for space exploration. Electrolyzers allow for reliable self-sustainable generation of hydrogen and oxygen for energy storage, followed by conversion into electrical energy in a fuel cell. A first-order safety concern for water electrolyzer operation is hydrogen crossover. Transport of hydrogen to the oxygen rich anode in proton exchange membrane (PEM) water electrolyzers poses safety concerns when the hydrogen concentration in the anode flow field approaches the hydrogen lower flammability limit (LFL). Hydrogen storage efficiency relies on high hydrogen pressure, leading to pressure-driven hydrogen crossover. Mitigation of hydrogen crossover through research and development of a platinum metal recombination layer has been demonstrated in high performing, durable PEMWEs.1-4 Ouimet4 explored the use of a novel dual recombination layer configuration to mitigate PEM water electrolyzer hydrogen crossover. In addition, the current state of the art for PEM fuel cells and water electrolyzers rely on perfluoro-sulfonated acid (PSFA) based membranes. There are significant challenges facing the use of PSFA-based membranes; namely, environmental contamination and performance limitations. The use of a hydrocarbon membrane allows for the development of a PSFA-free system that shows higher efficiency and durability. Investigation of hydrocarbon membranes pave way for developing a PEM water electrolyzer that will demonstrate improved gas permeability resistance, mechanical strength, and thermal stability.5-8 There is a need for both hydrogen crossover mitigation strategies and durability testing with hydrocarbon membranes.The research outlined in this work is focused on the development of PSFA-free PEM water electrolyzers with low hydrogen crossover. In this work, the dual recombination layer configuration will be incorporated into a hydrocarbon membrane for PEM water electrolysis. Polarization, electrochemical impedance spectroscopy, electrochemical equivalent circuits, distribution of relaxation times, and materials characterization will be used to investigate the cell performance and durability. References G. Mirshekari, R. Ouimet, Z. Zeng, H. Yu, S. Bliznakov, L. Bonville, A. Niedzwiecki, C. Capuano, K. Ayers, and R. Maric, “High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment,” international journal of hydrogen energy, vol. 46, no. 2, pp. 1526–1539, 2021.Z. Zeng, R. Ouimet, L. Bonville, A. Niedzwiecki, C. Capuano, K. Ayers, A. P. Soleymani, J. Jankovic, H. Yu, G. Mirshekari, et al., “Degradation mechanisms in advanced meas for pem water electrolyzers fabricated by reactive spray deposition technology,” Journal of The Electrochemical Society, vol. 169, no. 5, p. 054536, 2022.A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele, and R. Hanke-Rauschenbach, “Communication—proving the importance of ptinterlayer position in pemwe membranes for the effective reduction of the anodic hydrogen content,” Journal of The Electrochemical Society, vol. 168, no. 9, p. 094509, 2021.R. J. Ouimet, “Catalyst development by a novel fabrication process for energy applications,” University of Connecticut Doctoral Dissertation, 2021.P. Trinke, P. Haug, J. Brauns, B. Bensmann, R. Hanke-Rauschenbach, and T. Turek, “Hydrogen crossover in pem and alkaline water electrolysis: mechanisms, direct comparison and mitigation strategies,” Journal of The Electrochemical Society, vol. 165, no. 7, p. F502, 2018.P. Trinke, B. Bensmann, and R. Hanke-Rauschenbach, “Current density effect on hydrogen permeation in pem water electrolyzers,” International Journal of Hydrogen Energy, vol. 42, no. 21, pp. 14355–14366, 2017.H. Q. Nguyen and B. Shabani, “Proton exchange membrane fuel cells heat recovery opportunities for combined heating/cooling and power applications,” Energy Conversion and Management, vol. 204, p. 112328, 2020.C. Klose, T. Saatkamp, A. Münchinger, L. Bohn, G. Titvinidze, M. Breitwieser, K. D. Kreuer, and S. Vierrath, “All-hydrocarbon mea for pem water electrolysis combining low hydrogen crossover and high efficiency,” Advanced Energy Materials, vol. 10, no. 14, p. 1903995, 2020.

Operando X-Ray Fluorescence Analysis of Dynamic Cerium Radical Quencher Motion Perpendicular to MEA

Polymer electrolyte fuel cells (PEFCs) are required to have a durability of over 50,000 hours. One of the degradation factors is chemical degradation of perfluorosulfonic acid (PFSA) electrolyte membrane. The reaction of hydrogen peroxide with iron impurities produces hydroxyl radicals that break the chemical bonds in the PFSA membrane. Cerium ions are added to electrolyte membranes to absorb these radicals and act as a radical quencher, contributing to improved membrane durability.1 However, cerium ions have been shown to move in both the planar and through-plane directions under fuel cell operating conditions.2,3 The spatial scale of migration in the membrane planar direction is large, and therefore the time scale is also large, where analysis of end-of-life samples has been reported. On the other hand, the observation of the movement in the membrane direction is not easy because the thickness of the electrolyte membrane is 10 micrometers, and it is estimated to be significantly different between the post-disassembly condition and the operating condition. Therefore, it is necessary to establish operando measurement technique for cerium ion concentration with high spatial and temporal resolution in the direction perpendicular to the membrane. We developed an operando X-ray fluorescence spectroscopy technique using a combination of high-energy X-rays and a focused microbeam, and analyzed the behavior of cerium concentration change under current-applied conditions.4 The distribution behavior of cerium ions in the membrane is significantly different depending on the current and humidity. In a high-humidity environment, the ions move in the membrane in the vertical direction in about 1 second. Therefore, in this study, we developed a method to continuously measure the cerium ion concentration in the membrane on a sub-second scale and were able to estimate the effective cerium diffusion coefficient. It was also found that cerium ions migrate to the cathode layer under current-applied conditions. This behavior is accelerated in low humidity environments. This is because the diffusion coefficient of cerium ions is smaller at lower humidity and the back-diffusion flux is smaller.This work is based on results obtained from the project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.[1] E. Endoh, ECS Trans., 16, 1229–1240 (2008).[2] Y. Lai, K. M. Rahmoeller, J. H. Hurst, R. S. Kukreja, M. Atwan, A. J. Maslyn,C. S. Gittleman, J. Electrochem. Soc., 165, F3217-F3229(2018).[3] S.M. Stewart, D. Spernjak, R. Borup, A. Datye, F. Garzon, ECS Electrochem. Lett., 3, F19-F22 (2014).[4] Y. Orikasa, A. Takezawa, K. Amemiya, Y. Tsuji, T. Asaoka, M. Ohki, O. Sekizawa, K. Nitta, ECS Trans., 109 109 (2022).