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Effective water management is crucial for the optimal operation of low‐temperature polymer electrolyte membrane fuel cells (PEMFCs). Excessive liquid water production can cause flooding in the gas diffusion electrodes and flow channels, limiting mass transfer and reducing PEMFC performance. To tackle this issue, a nature‐inspired chemical engineering (NICE) approach has been adopted that takes cues from the integument structure of desert‐dwelling lizards for passive water transport. By incorporating engraved, capillary microchannels into conventional flow fields, PEMFC performance improves significantly, including a 15% increase in maximum power density for a 25 cm2 cell and 13% for a 100 cm2 cell. Electro‐thermal maps of the lizard‐inspired flow field demonstrate a more uniform spatial distribution of current density and temperature than the conventional design. Neutron radiography provides evidence that capillary microchannels in the lizard‐inspired flow field facilitate the efficient transport and removal of generated liquid water, thereby preventing blockages in the reactant channels. These findings present a universally applicable and highly efficient water management strategy for PEMFCs, with the potential for widespread practical implementation for other electrochemical devices. [ABSTRACT FROM AUTHOR]

Reactant gas and liquid water transport phenomena in the flow channels are complex and critical to the performance and durability of polymer electrolyte membrane fuel cells. The polymer membrane needs water at an optimum level for proton conductivity. Water management involves the prevention of dehydration, waterlogging, and the cell’s subsequent performance decline and degradation. This process requires the study and understanding of internal two-phase flows. Different experimental visualization techniques are used to study two-phase flows in polymer electrolyte membrane fuel cells. However, the experiments have limitations in in situ measurements; they are also expensive and time exhaustive. In contrast, numerical modeling is cheaper and faster, providing insights into the complex multiscale processes occurring across the components of the polymer electrolyte membrane fuel cells. This paper introduces the recent design of flow channels. It reviews the numerical modeling techniques adopted for the transport phenomena therein: the two-fluid, multiphase mixture, volume of fluid, lattice Boltzmann, and pressure drop models. Furthermore, this work describes, compares, and analyses the models’ approaches and reviews the representative results of some selected aspects. Finally, the paper summarizes the modeling perspectives, emphasizing future directions with some recommendations. [ABSTRACT FROM AUTHOR]

Herein, a hybrid support of Nb-doped TiO 2 and carbon nanotubes (Nb x TO@CNT, x = Nb wt%) was successfully prepared by a facile hydrothermal method. Controlling the annealing temperature to form either anatase (ANb x TO@CNT) or rutile (RNb x TO@CNT) changed the effect of the Nb dopant in the TiO 2 structure. The Pt/RNb 10 TO@CNT electrocatalyst exhibits excellent oxygen reduction reaction activity and durability (E onset : 0.945 V vs. RHE; E 1/2 : 0.888 V vs. RHE; j L : −6.260 mA cm−2). Theoretical calculations predicted that the synergetic effect of Pt/RNb 10 TO@CNT improves the electrochemical performance. The strong metal-support interaction (SMSI) effect and the formation of oxygen vacancies due to the increased amount of Ti3+ was observed. Band-gap reorganization by the distortion of electronic structures was further confirmed by UV–visible spectrometry. Single-stack polymer electrolyte membrane fuel cell measurements showed the highly improved current density of Pt/RNb 10 TO@CNT (1.913 A cm−2 at 0.6 V) and low current degradation (6.3%) under identical conditions. We report a Nb-doped rutile TiO 2 @CNT hybrid catalyst support prepared by a facile method, namely RNb 10 TO@CNT, which exhibits enhanced activity and ultra-durability of Pt towards ORR by improved SMSI effect caused by Nb doping. [Display omitted] • Nb-doped rutile TiO 2 @CNT hybrid support was designed by a facile synthesis process. • Pt/Nb-doped rutile TiO 2 @CNT ORR catalyst showed reasonable activity and durability. • Nb doping not only controlled electronic structures but also enhanced SMSI effect. • Significantly improved sustainability was exhibited in a single-stack PEMFC cell. [ABSTRACT FROM AUTHOR]

Metal foam flow fields are considered as an alternative to conventional channel/rib flow field in polymer electrolyte membrane fuel cell (PEMFC) because of the advantages of three-dimensional pore structure. In this study, the effect of metal foam flow field with different manifold size on PEMFC performance was investigated, with a 25 cm2 unit cell. Polarization curve and electrochemical impedance spectroscopy results were analyzed to investigate the effects of gas stoichiometry and relative humidity on performance. The mass transfer loss was decreased with reduced manifold size. However, mass transfer loss was increased due to difficulty of water discharge in small manifold case. The metal foam flow field offer advantages in water discharge and mass transfer loss. At 100% relative humidity, performance was improved with increased air stoichiometry for different manifold size. At 25% relative humidity, performance was a little improved with increased air stoichiometry for small manifold case. Regardless of relative humidity, fuel cell performance with metal foam flow field was most improved in case of smallest manifold size based on air stoichiometry due to the high pressure drop. • The performances were not proportional to the size of the manifold. • Increasing air stoichiometry, the performance increase was highest for the smallest manifold size. • The mass transfer was mainly influenced by the size of the manifold. [ABSTRACT FROM AUTHOR]

Abstract Atomically dispersed metal and nitrogen co‐doped carbon (MNC) is a promising oxygen reduction reaction (ORR) catalyst for electrochemical energy storage and conversion applications but typically suffers from low durability and activity under the acidic conditions of practical polymer electrolyte exchange membrane fuel cells (PEMFCs). Recently, the performance of MNC nanocomposites under acidic ORR conditions has been enhanced by exploiting the synergistic coupling effects of their constituents (single‐atom sites, nanoclusters, and nanoparticles). The unique geometric structures formed by the coupling of diverse sites in these nanocomposites provide optimal electronic structures and efficient reaction pathways, thus resulting in high activity and long‐term durability. This work provides an overview of MNC nanocomposites as ORR electrocatalysts under practical PEMFC conditions, focusing on activity and durability enhancement methods and highlighting the strategies used to prepare electrocatalytically efficient MNC nanocomposites containing no or low amounts of platinum group metals. Progress in the development of advanced MNC nanocomposites as acidic ORR catalysts is discussed, and the pivotal role of synergistic effects resulting from the coupling sites within the nanocomposites is explored together with the characterization methods used to elucidate these effects. Finally, the challenges and prospects of developing MNC nanocomposites as next‐generation electrocatalysts are presented.

Abstract Effective water management is crucial for the optimal operation of low‐temperature polymer electrolyte membrane fuel cells (PEMFCs). Excessive liquid water production can cause flooding in the gas diffusion electrodes and flow channels, limiting mass transfer and reducing PEMFC performance. To tackle this issue, a nature‐inspired chemical engineering (NICE) approach has been adopted that takes cues from the integument structure of desert‐dwelling lizards for passive water transport. By incorporating engraved, capillary microchannels into conventional flow fields, PEMFC performance improves significantly, including a 15% increase in maximum power density for a 25 cm2 cell and 13% for a 100 cm2 cell. Electro‐thermal maps of the lizard‐inspired flow field demonstrate a more uniform spatial distribution of current density and temperature than the conventional design. Neutron radiography provides evidence that capillary microchannels in the lizard‐inspired flow field facilitate the efficient transport and removal of generated liquid water, thereby preventing blockages in the reactant channels. These findings present a universally applicable and highly efficient water management strategy for PEMFCs, with the potential for widespread practical implementation for other electrochemical devices.

Polymer electrolyte membrane fuel cells (PEMFCs) suffer from severe performance degradation when operating under harsh conditions such as fuel starvation, shut‐down/start‐up, and open circuit voltage. A fundamental solution to these technical issues requires an integrated approach rather than condition‐specific solutions. In this study, an anode catalyst based on Pt nanoparticles encapsulated in a multifunctional carbon layer (MCL), acting as a molecular sieve layer and protective layer is designed. The MCL enabled selective hydrogen oxidation reaction on the surface of the Pt nanoparticles while preventing their dissolution and agglomeration. Thus, the structural deterioration of a membrane electrode assembly can be effectively suppressed under various harsh operating conditions. The results demonstrated that redesigning the anode catalyst structure can serve as a promising strategy to maximize the service life of the current PEMFC system. [ABSTRACT FROM AUTHOR]

This paper proposes a new control policy for optimal control of the 3-phase system of PEMFC connected to the grid. This also includes a 3-phase high step-up Interleaved Boost Converter (IBC) to amplify the PEMFC outputted voltage. To control the PEMFC system, Maximum Power Point Tracking (MPPT) based on Rigdelet Neural Networks (RNN) has been utilized, and to improve this controller, an improved version of the Satin Bowerbird Optimization (ISBO) algorithm has been utilized. The main advantage of the proposed improved version is modifying the convergence weakness and fixing convergence in chaos theory. The method is then validated by performing it one time on a standalone PEMFC system and another time on a grid-connected PEMFC system. Simulation results indicate that based o the IBC converter, better results with lower current ripples can be achieved. Also, the method has the ability to feed to both active and reactive powers by keeping stable the sudden temperatures. Final results have been also put in comparison with two different latest techniques to indicate the technique proficiency.

To efficiently mitigate the reversible performance degradation of polymer electrolyte membrane fuel cells, it is crucial to thoroughly understand recovery effects. In this work, the effect of operando performance recovery by temperature reduction is evaluated. The results reveal that operando reduction in cell temperature from 80 °C to 45 °C yields a performance recovery of 60–70% in the current density range below 1 A cm−2 in a shorter time (1.5 h versus 10.5 h), as opposed to a known and more complex non-operando recovery procedure. Notably, the absolute recovered voltage is directly proportional to the total amount of liquid water produced during the temperature reduction. Thus, the recovery effect is likely attributed to a reorganization/rearrangement of the ionomer due to water condensation. Reduction in the charge transfer and mass transfer resistance is observed after the temperature reduction by electrochemical impedance spectroscopy (EIS) measurement. During non-operando temperature reduction (i.e., open circuit voltage (OCV) hold during recovery instead of load cycling) an even higher recovery efficiency of >80% was achieved. [ABSTRACT FROM AUTHOR]

The viability of graphene-based microporous layers (MPLs) for polymer electrolyte membrane fuel cells is critically assessed through detailed characterisation of the morphology, microstructure, transport properties and electrochemical characterisation. Microporous layer composition was optimised by the fabrication of several hybrid MPLs produced from various ratios of graphene to Vulcan carbon black. Single cell tests were performed at various relative humidities between 25% and 100% at 80 °C, in order to provide a detailed understanding of the effect of the graphene-based MPL composition on the fuel cell performance. The inclusion of graphene in the MPL alters the pores size distribution of the layer and results in presence of higher amount of mesopores. Polarisation curves indicate that a small addition of graphene (i.e. 30 wt %) in the microporous layer improves the fuel cell performance under low humidity conditions (e.g. 25% relative humidity). On the other hand, under high humidity conditions (≥50% relative humidity), adding higher amounts of graphene (≥50 wt %) improves the fuel cell performance as it creates a good amount of mesopores required to drive excess water away from the cathode electrode, particularly when operating with high current densities. [Display omitted] • Microporous layers were fabricated with varying weight inclusions of graphene. • Composite MPLs were characterised by their morphology, microstructure and electrochemical properties. • Lower graphene concentrations (30%) improved cell performance in low humidity conditions. • Graphene concentration at 50 wt % or above enhances cell performance in high humidity conditions. [ABSTRACT FROM AUTHOR]

The primary issue for the commercialization of proton exchange membrane fuel cells (PEMFCs) is the carbon corrosion of support and dissolution agglomeration of platinum nanoparticles under start-up/shut-down (SU/SD) conditions. Carbon nanotubes (CNTs)-supported Pt nanowire (PtNW) catalyst toward the ORR was synthesized via the soft template method. Electrochemical characterization demonstrated that the PtNW/CNTs showed higher activity than Pt/C because the anisotropy of the 1D structure strengthened its ability to transport electrons. An accelerated stressed test between 1.0 and 1.5 V for carbon corrosion was performed to examine durability at a single cell under practical SU/SD conditions. After 5000 cycles, the voltage drop was 0.142 V, and the voltage decay rate was 0.0284 mV cycle−1 for the PtNW/CNTs catalyst at 1600 mA cm−2; the voltage drop was 0.417 V, and the voltage decay rate was 0.0834 mV cycle−1 for the Pt/C catalyst at 1600 mA cm−2. The Pt/C catalyst demonstrated severe Pt nanoparticle aggregation and growth with a wide size distribution, whereas the PtNW/CNTs catalyst showed a slight variation. The PtNW/CNTs catalyst showed remarkable durability after 5000 SU/SD cycles. Consequently, PtNW/CNTs is a promising electrocatalyst, which can replace traditional Pt/C catalyst in PEMFCs. • PtNW/CNTs were synthesized using the soft template method with CNTs as support. • The start-up/shut-down event was analyzed and simulated with a measurable protocol. • The ORR activity and the electrochemical stability of the PtNW/CNTs catalyst were remarkably improved. • The PtNW/CNTs catalyst has better performance and life of single cell than the Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Abstract Polymer electrolyte membrane fuel cells (PEMFCs) suffer from severe performance degradation when operating under harsh conditions such as fuel starvation, shut‐down/start‐up, and open circuit voltage. A fundamental solution to these technical issues requires an integrated approach rather than condition‐specific solutions. In this study, an anode catalyst based on Pt nanoparticles encapsulated in a multifunctional carbon layer (MCL), acting as a molecular sieve layer and protective layer is designed. The MCL enabled selective hydrogen oxidation reaction on the surface of the Pt nanoparticles while preventing their dissolution and agglomeration. Thus, the structural deterioration of a membrane electrode assembly can be effectively suppressed under various harsh operating conditions. The results demonstrated that redesigning the anode catalyst structure can serve as a promising strategy to maximize the service life of the current PEMFC system.

Polymer electrolyte membrane fuel cells (PEMFCs) have reached the commercialization phase, representing a promising approach to curbing carbon emissions. However, greater durability of PEMFCs is of paramount importance to ensure their long-term viability and effectiveness, and catalyst development has become a focal point of research. Pt nanoparticles supported on carbon materials (Pt/C) are the primary catalysts used in PEMFCs. Accomplishing both a high dispersion of uniform metal particles on the carbon support and robust adhesion between the metal particles and the carbon support is imperative for superior stability, and will thereby, advance the practical applications of PEMFCs in sustainable energy solutions. Ultrasound-assisted polyol synthesis (UPS) has emerged as a suitable method for synthesizing catalysts with a well-defined metal-support structure, characterized by the high dispersion and uniformity of metal nanoparticles. In this study, we focused on the effect of ultrasound on the synthesis of Pt/C via UPS and the resulting enhanced stability of Pt/C catalysts. Therefore, we compared Pt/C synthesized using a conventional polyol synthesis (Pt/C_P) and Pt/C synthesized via UPS (Pt/C_U) under similar synthesis conditions. The two catalysts had a similar Pt content and the average particle size of the Pt nanoparticles was similar; however, the uniformity and dispersion of Pt nanoparticles in Pt/C_U were better than those of Pt/C_P. Moreover, ex/in-situ analyses performed in a high-temperature environment, in which nanoparticles tend to agglomerate, have revealed that Pt/C_U exhibited a notable improvement in the adhesion of Pt particles to the carbon support compared with that of Pt/C_P. The enhanced adhesion is crucial for maintaining the stability of the catalyst, ultimately contributing to a better durability in practical applications. Ultrasound was applied to the carbon support without the Pt precursor under the same UPS conditions used to synthesize Pt/C_U to identify the reason for the increased adhesion between the Pt particles and the carbon support in Pt/C_U, and we discovered that oxygen functional groups (C-O, C = O, and O-C = O) for anchoring site of Pt particles were generated in the carbon support. Pt/C_U displayed an increase in stability in an electrochemical accelerated stress test (AST) in an acidic electrolyte. The physical and chemical effects of ultrasound on the synthesis of Pt/C via UPS were identified, and we concluded that UPS is suitable for synthesizing carbon supported electrocatalysts with high stability.

Research and development on electrochemical energy storage and conversion (EESC) devices, viz. fuel cells, supercapacitors and batteries, are highly significant in realizing carbon neutrality and a sustainable energy economy. Component corrosion/degradation remains a major threat to EESC device's long‐term durability. Here, we provide a comprehensive account of the EESC device's corrosion and degradation issues. Discussions are mainly on polymer electrolyte membrane fuel cells, metal‐ion and metal‐air batteries and supercapacitors. Corrosion of bipolar plates/current collectors, carbon corrosion, electrode/electrocatalyst degradation, and various mitigation approaches are detailed. The collective information provided could help develop EESC devices with better durability. [ABSTRACT FROM AUTHOR]

The large deviations between the partial pressure of oxygen and hydrogen can lead to severe membrane damage, which reduces the life of the polymer electrolyte membrane fuel cell (PEMFC). The deviation of pressure can be restrained by effective control of partial pressure. Considering the actual operating environment of PEMFC, its control system is not only affected by load changes, but also affected by some unknown disturbances, such as system parameter variations, failures, etc. Considering the above factors, this paper has proposed a robust nonlinear adaptive pressure control (RNAPC) employing the perturbation estimation technique to suppress the deviations. The proposed controller does not need to identify or estimate the system parameters in real time like the conventional controller based on parameter estimation technology, nor does it need to rely on the fault diagnosis and isolation technology to detect and estimate the failures in real time. It only uses the variations of system state variables caused by failures to provide the required failure information for the controller. In the design of RNAPC, an observer is designed to estimate a perturbation term containing system uncertainties, nonlinearities, and disturbances. The estimation of perturbation is used for the compensation of actual perturbation. Then, an adaptive FLC of PEMFC system can be realized. Therefore, the RNAPC requires only a few state measurements and is independent of an accurate system model. Simulation results show that the RNAPC method has smaller deviations of partial pressure of oxygen and hydrogen and better dynamic performance than traditional PI control under load disturbance, and obtains higher robustness against uncertainties and sensor failures than traditional PI control and FLC. The maximum error of partial pressure can be limited within 0.5% under four different simulation scenarios under the RNAPC.

To reduce the environmental footprint of the aviation industry, aircraft with new propulsion systems are increasingly under consideration. In this paper, the potential of a fuel cell hybrid-electric aircraft (FCHEA) powered by hydrogen and kerosene is assessed. First, the methodology for the conceptual design of a single-aisle short-range FCHEA is developed and presented. Then, the environmental impact of this aircraft on its design mission is determined by means of a one-dimensional climate model and the climate metric sustained global temperature potential with a time horizon of 100 years. To complete the picture, the fleet adoption of the FCHEA concept is determined with the help of a fleet system dynamics model taking future air traffic development, fleet age, and production capacities into account. This makes it possible to analyze the potential of FCHEA to improve the environmental footprint of aviation considering the operational environment in the global aviation market. The results show that for a single FCHEA powered by liquid hydrogen produced via electrolysis with renewable energies, climate impact reductions of 15.2-17.8% can be achieved. The fleet uptake of the FCHEA made full use of the available production capacities, but still it was able to serve only 15.8% of total available seat kilometers. [ABSTRACT FROM AUTHOR]

This study represents a comprehensive investigation of the performance of Artificial Hummingbird Algorithm for parameter estimation for Polymer Electrolyte Membrane Fuel Cell. With this purpose, four commercial fuel cell systems which were widely preferred in the literature such as NedStack PS6 (Case-I), 250 W fuel cell stack (Case-II), Horizon 500 W (Case-III), and BCS 500 W (Case-IV) were chosen. In order to compare the performance of this algorithm, seven well-known optimization techniques including Artificial Bee Colony, Salp Swarm Optimization, Particle Swarm Optimization, Gray Wolf Optimization, Genetic Algorithm, Harris Hawks Optimization, and Whale Optimization Algorithm were used. The sum of the squared errors, computational speed, and statistical measurements were calculated for the performance comparison. In this context, the best SSE values were found as 2.06556, 5.25017, 0.02477, 0.01170 for Case-I, Case-II, Case-III, and Case-IV, respectively. The best standard deviation value was found as 1 e −6 for the Case-III. Based on the obtained results, the Artificial Hummingbird Algorithm established itself as a competitive optimization technique for parameter estimation study of PEMFC in terms of computational speed and robustness. [ABSTRACT FROM AUTHOR]

Abstract Research and development on electrochemical energy storage and conversion (EESC) devices, viz. fuel cells, supercapacitors and batteries, are highly significant in realizing carbon neutrality and a sustainable energy economy. Component corrosion/degradation remains a major threat to EESC device‘s long‐term durability. Here, we provide a comprehensive account of the EESC device‘s corrosion and degradation issues. Discussions are mainly on polymer electrolyte membrane fuel cells, metal‐ion and metal‐air batteries and supercapacitors. Corrosion of bipolar plates/current collectors, carbon corrosion, electrode/electrocatalyst degradation, and various mitigation approaches are detailed. The collective information provided could help develop EESC devices with better durability.

To efficiently mitigate the reversible performance degradation of polymer electrolyte membrane fuel cells, it is crucial to thoroughly understand recovery effects. In this work, the effect of operando performance recovery by temperature reduction is evaluated. The results reveal that operando reduction in cell temperature from 80 °C to 45 °C yields a performance recovery of 60–70% in the current density range below 1 A cm−2 in a shorter time (1.5 h versus 10.5 h), as opposed to a known and more complex non-operando recovery procedure. Notably, the absolute recovered voltage is directly proportional to the total amount of liquid water produced during the temperature reduction. Thus, the recovery effect is likely attributed to a reorganization/rearrangement of the ionomer due to water condensation. Reduction in the charge transfer and mass transfer resistance is observed after the temperature reduction by electrochemical impedance spectroscopy (EIS) measurement. During non-operando temperature reduction (i.e., open circuit voltage (OCV) hold during recovery instead of load cycling) an even higher recovery efficiency of >80% was achieved.

Ultrathin films or particles of atomic layer deposition (ALD) on high surface can improve the activity and durability of catalyst fields, so depending on the surface state, the ALD growth mechanism on porous materials should be systematically investigated and optimized to improve their characteristics of catalysts. Herein, a Pt catalyst used in polymer electrode membrane fuel cell (PEMFC) applications is synthesized through fluidized‐bed‐reactor ALD on carbon black whose surface is modified through treatment with citric acid. The functional groups, analyzed through X‐ray photoelectron spectroscopy (XPS), are found to be maximized after 60 min of acid treatment with stirring. Compared with bare carbon (untreated), the acid‐treated carbon presents rich oxidized functional groups and abundant defects but lower surface areas and pore volumes. After ALD Pt deposition, highly dense, uniform, and well‐dispersed Pt nanoparticles (NPs) are observed on the carbon black subjected to acid treatment, because of the favorable surface modifications for ALD growth resulting from the acid treatment. The ALD‐Pt NPs on the acid‐treated carbon exhibit larger electrochemical active surface areas, improved oxygen reduction reactions, and PEMFC performances, when compared with that of NPs on bare carbon with similar Pt weight loading. [ABSTRACT FROM AUTHOR]

In this study, the effects of flow field types on the electrochemical properties of polymer electrolyte membrane fuel cells (PEMFCs) humidified with NaCl solution are systematically investigated. The parallel flow field and serpentine flow field were used to investigate the PEMFCs. Long-term stability was evaluated for 20 h using chronoamperometry. Fuel cells with both parallel and serpentine flow fields showed a decrease in performance because of the NaCl solution. Interestingly, the PEMFC with the serpentine flow field showed significantly more severe degradation during long-term stability evaluation compared to the fuel cell with the parallel flow field. Electrochemical impedance spectroscopy analysis showed that a significant increase in faradaic resistance caused the degradation of the performance. After long-term stability examinations, regenerations of fuel cells were performed with deionized water at a constant voltage (0.4 V). After the regeneration, the performance of the fuel cells with the serpentine flow field was improved more (52.96%) than the PEMFC with the parallel flow field (1.22%). [ABSTRACT FROM AUTHOR]

This study examined the effects of mist generated from NaCl solution on the electrochemical properties of polymer electrolyte membrane fuel cells. Mist-containing Na+ and Cl- ions were generated using a custom-made mist generator. The current density-voltage-power density curves and electrochemical impedance spectroscopy of fuel cells were systematically achieved. Furthermore, long-term stability experiments were carried out using chronoamperometry mode for 20 h with deionized water and NaCl solution. After the chronoamperometry measurement, the regeneration of fuel cells was performed with deionized water. The effects of regeneration methods on the performance of the fuel cell were evaluated. Due to the internally produced H2O, constant voltage regeneration was more effective than open circuit voltage regeneration. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multiphase, multicomponent model of PEFCs was developed using the MRT-LBM. • Meniscus channel film flow was approximated for two-phase channel flooding. • A two-phase flow regime and pressure drop multipliers were intensively validated. • Evaporation and condensation were visualized and quantified over fuel cell domains. • In-plane GDL permeability improved liquid water removal with less pressure drops. In this study, a reaction-coupled, multiphase, and multicomponent model was developed to simulate the multiphysics transport phenomena in polymer electrolyte membrane fuel cells. The model integrates electrochemical kinetics, hydrodynamics, species transport, and liquid flooding over the entire cell domain, with a specific focus on addressing channel liquid flooding during high-current operations. It also captures the phase transitions of water in fuel cells, that is, evaporation and condensation within the cell components. The multiple-relaxation-time lattice Boltzmann method was used to solve cell-scale reaction-coupled multiphase equations. Moreover, our model could predict a two-phase channel film flow with the formation of a capillary meniscus, which was validated against published experimental polarization curves, a two-phase flow regime, and two-phase pressure drop data. Numerical simulations were conducted under different operating conditions, that is, humidity, temperature, pressure, and stoichiometric flow ratio, to investigate the physicochemical correlations among the local cell performance, liquid distribution, and quantified phase change rates across the computational domain. Furthermore, various in-plane and through-plane absolute permeability combinations were compared to determine the anisotropic liquid transport characteristics in the porous gas diffusion layers. Based on cell performance and channel pressure drop, a figure of merit was established to optimize the fuel-cell operating conditions. This methodology offers an advanced pathway for balancing the dual challenges of water management, thus ensuring the hydration of the ionomeric phase and mitigating the accumulation of excess liquids. [ABSTRACT FROM AUTHOR]

The effect of NO 2 , an air pollutant, on the durability of polymer electrolyte membrane fuel cells (PEMFCs) and the affected electrochemical processes in the PEMFC following the contamination were investigated. In-situ Electrochemical Impedance Spectroscopy (EIS) measurements were conducted on PEMFCs under different operating conditions of temperature and relative humidity (RH). NO 2 was introduced to the cathode inlet flow. Analyses of the EIS measurements were performed using a genetic algorithm called ISGP (Impedance Spectroscopy by Genetic Programming) to obtain the distribution function of relaxation times (DFRT, a.k.a. DRT) models. Utilizing ISGP enabled us to differentiate the various phenomena in PEMFC and study how they are affected by NO 2 contamination. Moreover, the experiments demonstrate the effectiveness of the mitigation method to flush the PEMFC and regenerate its performance after being contaminated, particularly at low operating temperatures. Energy-dispersive X-ray spectroscopy (EDS) technique is performed on the contaminated PEMFC to detect the presence of any nitrogen components in the FC's gas diffusion layer and the catalyst layer post the mitigation step. Cyclic Voltammetry is also performed on the contaminated cell to determine the effect of the contamination on the electrochemically active surface area of the cathode by evaluating the double-layer capacitance., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Ordered intermetallic alloys with significantly improved activity and stability have attracted extensive attention as advanced electrocatalysts for reactions in polymer electrolyte membrane fuel cells (PEMFCs). Here, recent advances in tuning intermetallic Pt- and Pd-based nanocrystals with tunable morphology and structure in PEMFCs to catalyze the cathodic reduction of oxygen and the anodic oxidation of fuels are highlighted. The fabrication/tuning of ordered noble metal-transition metal-bonded intermetallic PtM and PdM (M = Fe, Co) nanocrystals by using high temperature annealing treatments to promote the activity and stability of electrocatalytic reactions are discussed. Furthermore, the further improvement of the efficiency of this unique ordered intermetallic alloys for electrocatalysis are also proposed and discussed. This report aims to demonstrate the potential of the ordered intermetallic strategy of noble and transition metals to facilitate electrocatalysis and facilitate more research efforts in this field.

The high-voltage environment crucial for fuel cell efficiency also leads to performance degradation due to Pt oxide formation in the air electrode. We study the degradation and recovery mechanisms in a high-voltage operating environment using a unit cell with a 25-cm2 membrane electrode assembly (MEA). The study involves varying cell voltage between 0.8 V and 0.4 V for degradation and recovery, respectively. The 0.4-V recovery method, although improving performance, does not fully prevent degradation. Repeated voltage changes cause an increase in irreversible and total degradation, leading to gradual performance decline. In contrast, the N 2 purging method in the air electrode fully restores performance degraded at high voltages and maintains stability across degradation/recovery cycles. Employing an air-cutoff technique applied from the N 2 purging method effectively reverses high-voltage-induced MEA degradation. These findings demonstrate that chemical reduction of Pt oxides by H 2 gas during N 2 purging is more effective than electrochemical reduction at low voltages. This research contributes insights for material design and cell operation technology development, enhancing fuel cell efficiency and durability. • MEA degradation and recovery were observed by cycling voltage between 0.8 and 0.4 V. • The 0.4 V recovery method doesn't fully prevent degradation, leading to performance decline. • The air-cutoff technique effectively reverses high-voltage MEA degradation. • Chemical reduction of Pt oxides by H 2 gas during N 2 purging is crucial. • Combining chemical reduction with low-voltage electrochemical reduction enhances recovery. [ABSTRACT FROM AUTHOR]

Summary: The declining reserves and environmental concerns related to the use of fossil fuels have made the global think tanks to pursue for the technologies considered to be renewable as well as sustainable. Fuel cell technology is emerging and a green way to produce electricity, provided sufficient amount of hydrogen (fuel) is available that directly convert chemical energy to electrical energy. Despite of being an efficient and eco‐friendly source of energy, commercialization of fuel cells is still difficult to attain. Techno‐economic challenges like high manufacturing and assembly costs, water management, system size, nondurability, and instability of the system need to be addressed. In order to resolve these issues, considerable research has been carried out for the development of novel and inexpensive materials for the fuel cells. In this article, we have reviewed the development of electrodes and electrolyte materials for different types of fuel cells. A detailed description of applications, challenges, and improvement of electrodes/electrolytes materials of different types of fuel cells (polymer electrolyte membrane fuel cells, direct methanol fuel cells and solid oxide fuel cells) have been reported in this review article. A brief review of the development of materials for electrode of molten carbonate fuel cells has also been presented in the review. [ABSTRACT FROM AUTHOR]

This study provides evidence of the enhancement of the oxygen reduction reaction (ORR) activity of Pt/C and Pd-core Pt-shell catalysts upon ionic liquid modification. Under high potential at 1.15 V (vs. reversible hydrogen electrode), the lower coverage of the oxide species on the Pt surface modified with [7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD)][bis(trifluoromethylsulfonyl)imide (NTf2)] ionic liquid (IL) was confirmed by electrochemical analysis. Operando X-ray absorption spectra (XAS) of the ionic liquid-modified Pd-core Pt-shell catalyst displayed smaller 5d orbital vacancies than the naked catalyst. Shrinkage of Pt-Pt bond length was also displayed, indicating the suppression of oxidation. Thus, we conclude that the IL-modified systems are effective in avoiding the adsorption of oxide species on the Pt surface and improving the oxygen reduction activity.

Dynamic potentials of polymer electrolyte membrane fuel cells (PEMFCs) lead to the corrosion of metal bipolar plates and significantly increase their interfacial contact resistance (ICR). Herein, two nano-thin C/Ti coatings with different thicknesses are prepared on SS316L (C/Ti/SS) and examined under three types of polarization potential modes. The C 100 Ti 60 coating has improved corrosion resistance than C 20 Ti 140 coating. The C 100 Ti 60 coating exhibits a low ICR of 2.67 mΩ cm2 and a small corrosion rate of 1.47 μA/cm2, highlighting the high electrical conductivity and corrosion resistance. Moreover, C 100 Ti 60 /SS achieves a slight degradation of ICR after polarization at 0.67 V and cyclic polarization between 0.43 and 0.73 V. However, the high potential of 1.43 V induces severe delamination of C layer, resulting in a remarkable increase of ICR. Analysis suggests that the Ti layer improves the oxidation resistance and the C layer could provide effective protection when the potential is below 1.13 V. [Display omitted] • Two nano-thin C/Ti coatings with different thicknesses are prepared on SS316L. • Highly corrosion resistant and electrical conductive C 100 Ti 60 /SS is achieved. • Evolution of ICRs of C 100 Ti 60 /SS under three polarization modes are studied. • Anodic dissolution processes of C 100 Ti 60 /SS at different potentials are analyzed. • Correlation between ICR and negative current during cyclic polarization is discussed. [ABSTRACT FROM AUTHOR]

Commercial polymer electrolyte membrane fuel cells have relied on scares Platinum to catalyse the kinetically sluggish oxygen reduction reaction occurring at their anodes. Over the last decade organic materials, frequently based on graphitic structures have been demonstrated as promising alternative electrocatalysts to the noble metals. Researchers typically utilize ultrasonic treatment as part of the synthesis procedure to achieve homogeneous dispersion of graphitic carbon prior to. Herein we investigate the implications of the structural and compositional changes induced by the ultrasonication treatment on boron-doped reduced graphene oxide for oxygen reduction reaction. It is shown that ultrasonication pre-treatment prior to the boron doping and reduction of graphene oxide via hydrothermal process step leads to the increase of both substitutional B and electrocatalytic surface area, with associated reduction of average pore size diameter, leading to a significant improvement in the oxygen reduction reaction performance, with respect to the non-ultrasonicated material. It is proposed that the higher degree of substitutional doping of boron is a result of formation of the additional epoxy functionalities on graphitic planes, which act as a doping site for boric acid. • Ultrasonication enables higher doping of boron into Graphene oxide. • Longer ultrasonication times leads to higher substitutional boron. • Longer ultrasonication times leads to higher ORR activity. [ABSTRACT FROM AUTHOR]

Here, we report the growth of improved quality graphene thin film by a modified method using shellac as a low-cost and eco-friendly carbon source on three different substrates. We chose stainless steel (SS 316) plates used as a solid surface, nickel foam (NiF) representative of a solid porous substrate, and carbon fiber fabric (CFF) as a porous-flexible substrate. The graphene characteristic is found to be substrate-dependent in this single-step method. Uniform multilayer graphene is grown on SS316. In the case of Ni foam, the as-synthesized graphene exhibits high quality with relatively low defects. It was troublesome to grow uniform graphene on flexible CFF due to the low wettability of precursor solution. The substrate was required to modify with a thin (∼60 nm) layer of Ni deposition. The transfer-free method of graphene on CFF was assured by etching Ni via an acid treatment. Graphene coated SS316 used as bipolar plate exhibits superior corrosion resistance with corrosion current density I corr ∼1.2 μA/cm2 and much lower interfacial contact resistance ICR ∼7.7 mΩ cm2. Graphene coated Ni foam was utilized as electrodes in supercapacitors which show large areal capacitance ∼1.7 F/cm2. Besides, graphene coated CFF shows sheet resistance ∼50% lower than that of uncoated CFF. [Display omitted] • G/SS316, G/Ni foam and G/CFF were synthesized via a single-step method. • G/SS316 has long-term stability in a chloride environment. • DCG/SS316 bipolar plate has low Icorr ∼1.20 μA/cm2 and very low ICR ∼7.7 mΩ.cm2. • The supercapacitor with G/Ni foam electrode has high areal capacitance ∼1.7 F/cm2. • G/CFF has lower sheet resistance ∼13 Ω/□ compared to that (∼20 Ω/□) of bare CFF. [ABSTRACT FROM AUTHOR]

The catalysts performance degradation is a crucial issue in decay of the polymer electrolyte membrane fuel cell (PEMFC). The effect of Nafion content, dispersity of Pt nanoparticles and selected types of carbon support on the degradation of electrochemical surface area (ECSA) and double layer capacitance (DLC) were experimentally discussed by accelerated stress test (AST). The catalyst with 20wt% Nafion content exhibited better catalyst performance. i.e., the less DLC and ECSA degradation during AST. Catalysts with well Pt dispersity showed superior %ECSA (the percentage change of ECSA) retention. The heat-treated catalysts exhibited the lowest ECSA and DLC degradation rate due to the larger Pt particle and high carbon corrosion resistance. Moreover, a multi-order model describing the correlation between ECSA and DLC degradation was proposed, providing a vital reference for quantitatively investigating ECSA and DLC degradation in the catalysts with different catalysts structural parameters.

The nanostructure of Nafion and poly(vinylidene fluoride) (PVDF) blend membranes is successfully aligned through a mechanical uniaxial stretching method. The phase-separated morphology of Nafion molecules distinctly forms hydrophilic proton channels with increased connectivity, resulting in enhanced proton conductivity. Additionally, the crystalline phase of PVDF molecules undergoes a successful transformation from the α- to β-phase during membrane stretching, demonstrating an alignment of fluorine and hydrogen atoms with a TTTT(trans) structure. The aligned nanostructure of the blend film, combined with the dipole polarization of the β-phase PVDF, synergistically enhances the proton conduction through the membrane for operating proton-exchange membrane fuel cells (PEMFCs). The controlled structures of the blend membranes are thoroughly investigated using atomic force microscopy and small-angle X-ray scattering. Furthermore, the improved in-plane proton conductivity facilitates increased proton conduction at the interface between the membrane and catalyst layer in the membrane-electrode assembly, ultimately enhancing the power generation of PEMFCs.

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Abstract The influence of the surface modification of multi-walled carbon nanotubes (MWCNT) with nitrogen-containing compounds on the performance of 40 wt% Pt/MWCNT catalysts in the oxygen electroreduction reaction (ORR) was investigated using a rotating disk electrode (RDE) at 10–35 °C in 0.1 M HClO4 as electrolyte in electrochemical cell, and in a hydrogen–oxygen polymer electrolyte membrane fuel cell (PEMFC) at 82 °C. The catalysts were characterized by low-temperature nitrogen adsorption, XPS, TEM, gas-phase CO titration, electrooxidation of the adsorbed CO monolayer, and cyclic voltammetry. It was shown that the modification of MWCNT with melamine–formaldehyde resin leads to the surface nitrogen concentration up to 8.3 at.% (CNT-MF sample). The 40 wt% Pt/CNT-MF catalyst with 0.1 mg cm−2 Pt loading on the cathode showed a good performance in PEMFC (~ 0.61 W cm−2) and a high utilization ratio (0.84) of Pt in membrane electrode assembly as compared to Pt/CNT catalyst (~ 0.37 W cm−2 and utilization of 0.29). The higher power density of nitrogen-modified catalysts was ascribed to a higher utilization of Pt in the electrode layer.

During all the assembly stages of a polymer electrolyte membrane fuel cell (PEMFC) stack, gas diffusion layers (GDLs) endure clamping loads in the through-plane direction several times. Under such complicated assembly conditions, GDLs have to deform with the changes in structure, surface roughness, pore size, etc. A comprehensive understanding of the compressive performance of GDLs at different clamping phases is crucial to the assembly process improvement of PEMFCs. Two typical clamping compression was designed and performed to get close to the actual assembly conditions of PEMFCs. The results indicate that the initial clamping compression and the magnitude of the maximum clamping load have great impacts on the segmented compressive properties of GDLs. The nonlinear compressive performance of the GDL is mainly attributed to the unique microstructural information. The rough surface morphology contributes to the initial compressive characteristics where the big strain along with the small stress occurs, and the irreversible failures such as carbon fiber breakages and adhesive failures between fibers and binders account for the hysteresis between different compression stages. Importantly, it is found that the clamping compression hardly influences the small pore distribution below 175 μm but affects the large pore distribution over 200 μm.

In polymer electrolyte membrane fuel cells, carbon-supported platinum (Pt/C) catalyst particles require sufficient water condensation within the nanoscale pores to effectively utilize the interior Pt catalysts. Since experimental visualizations with nanoscale precision of this phenomenon are not yet possible, we utilized a Pt/C catalyst particle reconstructed from segmented nanoimaging of a catalyst powder, which served as the computational domain for lattice density functional theory (LDFT) simulation of water condensation. Paired with experimental water uptake data, LDFT successfully simulated high-resolution water condensation, capturing both thin-film and capillary water condensation phenomena. Using a simple proton movement method within the water network, we reproduced the Pt utilization data from a CO stripping experiment. Our findings highlight that at low relative humidity (RH), Pt utilization is influenced by thin water film formations, mainly dictated by the wettability properties of surfaces within primary pores and the Pt/C catalyst particle's exterior. Conversely, at high RH, Pt utilization is attributed to capillary water condensation in medium-to-large sized pores. This approach contributes a qualitative and quantitative discussion on hypotheses regarding the mechanism of Pt utilization, supporting recent studies (e.g., Girod, R.; Nat. Catal. 2023, 6, (5), 383-391).

The acid dissociation constant of three benzimidazoles, namely 2,2′-bibenzo[d]imidazole, 2,5′-bibenzo[d]imidazole, and 5,5′-bibenzo[d]imidazole, have been investigated by means of density functional theory calculations in gas phase and in aqueous solution. The theoretical approach was validated by the comparing of predicted and experimentally determined pKa values in imidazole, benzimidazole, and 2-phenylbenzimidazole. From the studied compounds, 2,2′-bibenzo[d]imidazole was found to be the most acidic, which made it a valuable candidate as a material for polymer electrolyte membrane fuel cells.

Developing a high electrically conductive and corrosion-resistant coating on metal bipolar plate is of prime importance for its application in polymer electrolyte membrane fuel cells. To achieve it and further improve its through-plane conductivity, we herein prepared a composite coating by introducing Au microdots onto TiN coated stainless steel (Au/TiN/SS). Au dots provide additional conduction paths and thus Au/TiN/SS exhibits a remarkably lower interfacial contact resistance than that of TiN/SS after 200 h of test, suggesting that incorporation of Au dots into TiN provides an effective approach to achieving dual merits of high conductivity and corrosion resistance. • A composite coating of Au/TiN was prepared on metal bipolar plates of PEMFCs. • Au/TiN delivers a remarkably enhanced through-plane electrical conductivity than TiN. • Au/TiN possesses the dual merits of high corrosion resistance and conductivity. • Correlation of sample's electrical conductivity and surface Au dot is built up. • Degradation mechanism of Au/TiN coating in dilute H 2 SO 4 solution is discussed. [ABSTRACT FROM AUTHOR]

The optimal operation of fuel cells in changing environmental and variable load conditions requires mathematical modeling. The electrochemical behavior of polymer electrolyte membrane fuel cells (PEMFC) is commonly described with a semi‐empirical model requiring fuel cell specific model parameter values. A large number of different nature inspired, heuristic optimization methods have been proposed for this PEMFC parameter estimation problem. In this study, those studies are listed and critically reviewed. In particular, the aim is to elaborate the generalization ability of the results and discuss the fair comparison of the algorithms used for the parameter estimation of the polarization curve. The observations made in this review could further increase the quality of future contributions in this particular area, as well as applications of heuristic optimization methods in other related problems in fuel cell systems. [ABSTRACT FROM AUTHOR]

The influence of hydrophobicity and porosity of the catalyst layer (CL) and cathode microporous layer (MPLC) on water distribution and performance of polymer electrolyte membrane fuel cell (PEMFC) is investigated. Hydrophobicity of the layers is altered with the addition of PTFE (polytetrafluoroethylene) and mono‐dispersed polymer particles are utilized to introduce the macro‐pores with a diameter of 0.5 µm and 30 µm within the CL and MPLC, respectively. The treated materials are implemented in a specially designed fuel cell with an active area of 8 cm2 to perform operando high‐resolution neutron tomography measurements. At high current density and humid operating conditions, MPLs with higher PTFE content increase the overall water content of the cell. The more hydrophobic MPL (40 wt.% PTFE) performs below the corresponding reference MPL (20 wt.% PTFE), whereas the performance result of double layer MPLC gives hint for further potential improvements of such design. The local water saturation beneath the land regions with the presence of perforated CL and MPLC is increased which is explained by lower capillary pressure barriers of bigger pores. Despite a higher water content, the perforated layers enhance the performance of the cell at both dry (RH 70%) and humid conditions (RH 120%), indicating that the parallel two‐phase flow is facilitated where the oxygen is transported through small pores and the water is preferentially transported through the bigger pores. [ABSTRACT FROM AUTHOR]

This research reports fabrication of three Polymer Electrolyte Membrane fuel cells (PEMFC) using composite of gold nanoparticles and nanotube graphene by varying concentration of Gold nanoparticles. The outer most layer of multiwall carbon nanotubes is un-zipped and nano ribbons of graphene are developed to attain a durable electrode. Moreover, the addition of gold nanoparticles adds benefit of better conductance over usual platinum electrodes. The effect of changing gold concentration on properties of composite material as well as fuel cell performance is investigated. The presence of gold nanoparticles and graphene nano-ribbons attached to carbon nanotubes are identified using SEM, TEM, and Raman analysis. Cyclic voltammetry analysis has showed that increase in concentration of gold nano particles improves the performance of fuel cell. EIS analysis reveled that the polarization resistance decreased by increasing the Au concentration. Thermal Gravimetric Analysis proved the thermal stability of composite material. Maximum power density of 242.29 mWcm−2 is achieved for the highest concentration of Gold nanoparticles. • A novel architecture of PEM fuel cell has been proposed. • The effect of gold concentration on properties of composite material as well as fuel cell performance is investigated. • Maximum power density of 242.29mWcm−2 is achieved for the highest concentration of gold nanoparticles. [ABSTRACT FROM AUTHOR]

Durability of catalyst support materials is one of the big challenges for long‐term fuel cell operation. The performance stabilities of stabilized carbons as cathode catalyst supports for polymer electrolyte membrane fuel cells (PEMFCs) are investigated. Homemade platinum (Pt) electrocatalysts are prepared on stabilized carbons and a traditional carbon black support. Subsequently, the characterization results of homemade catalysts are compared with a commercial catalyst. The characterization tools such as the measurement of electrochemical active surface areas (ECSAs), oxygen reduction reaction (ORR) activities, durability of both the Pt and the supports, and eventually membrane electrode assembly (MEA) single cell tests are implemented herein. The stabilized carbon supported catalysts show comparable ORR activities as well as improved corrosion resistance in terms of ECSA survival rates under accelerated stress conditions compared with the conventional supported catalysts. In addition, the dependency of MEA performances on the ionomer‐to‐carbon ratio on the catalyst layers is established. [ABSTRACT FROM AUTHOR]

TiO2-based catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs) are widely investigated and provide an alternative to corrosion-susceptible carbon-based catalyst supports. For PEMFCs, designing a catalyst support material with an optimal geometry is of high importance to provide high catalyst dispersion, long-term operation, and efficient fuel cell performance. In this work, we report on the use of spaced (SP) TiO2 nanotubes (NTs) as catalyst support for the cathode electrode of PEMFCs. We construct a vertically aligned Pt-TiO2 NT catalyst layer on the Nafion membrane by a three-step process: (i) growth of self-organized TiO2 nanotubes with defined intertube spacing and detachment from the Ti substrate, (ii) Pt catalyst decoration on tube walls by atomic layer deposition (ALD) or photodeposition (PD), and (iii) decal transfer of the Pt-TiO2 catalyst layer onto Nafion to fabricate a membrane-electrode assembly (MEA) by hot pressing. Such an MEA configuration based on vertically aligned high aspect ratio spaced TiO2 nanotubes with Pt catalyst decoration delivers a significantly higher fuel cell performance, compared with close-packed (CP) TiO2 nanotubes. The key for this excellent performance is that TiO2 NTs with a regular interspacing on the Nafion polymer membrane enable highly dispersed Pt catalyst decoration and provide strongly enhanced mass transport in the interspaces. [ABSTRACT FROM AUTHOR]

Local measurement of current was conducted using a segmented cell to understand local electrochemical characteristics of polymer electrolyte membrane fuel cell with counter flow channel under pressurized condition. We changed stoichiometry ratio (SR), relative humidity (RH), and operating temperature to examine the effect of operating parameters on the performance of fuel cell under pressurized condition. A segmented fuel cell with a divided active area of 25 cm2 was used to measure local current distribution to analyze complex relationships between SR, RH, temperature and pressure. The results show that RH and SR are the main factors for determining current distribution. High SR with low-RH reactants make the membrane of the inlet region more dried out, which leads to less electrochemical reaction. When SR is low, however, less water is evaporated and the effect of RH condition is minimized. On the other hand, current distribution at various RH and SR conditions at 3 bar is relatively similar among the results. Thus, the effects of RH and SR can be neglected for high operating pressure cases. When the temperature is high in pressurized condition, the Ohmic loss decreased and the overall cell performance improved. [ABSTRACT FROM AUTHOR]

We demonstrate an enhanced new architecture for fuel cell membrane electrode assemblies (MEAs), by deposition of the microporous layer (MPL) directly on the catalyst coated membrane (CCM), in order to reduce any gaps at the cathode catalyst layer (CCL) surface. A low bonding temperature Teflon was used to allow low temperature sintering of the CCM with the MPL. This modified structure enhances PEMFC performance by improving the electronic contact and minimizing water pooling at the CCL|MPL interface. The improvement in water management at the CCL|MPL is beneficial especially for thinner CCLs to fulfill the performance demand with low cathode catalyst loading MEAs (≤0.125 mgPt cm−2 as targeted by the US Department of Energy). [ABSTRACT FROM AUTHOR]

Fe‐N‐C catalysts containing atomic FeNx sites are promising candidates as precious‐metal‐free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The durability of Fe‐N‐C catalysts in fuel cells has been extensively studied using accelerated stress tests (AST). Herein we reveal stronger degradation of the Fe‐N‐C structure and four‐times higher ORR activity loss when performing load cycling AST in O2‐ vs. Ar‐saturated pH 1 electrolyte. Raman spectroscopy results show carbon corrosion after AST in O2, even when cycling at low potentials, while no corrosion occurred after any load cycling AST in Ar. The load‐cycling AST in O2 leads to loss of a significant fraction of FeNx sites, as shown by energy dispersive X‐ray spectroscopy analyses, and to the formation of Fe oxides. The results support that the unexpected carbon corrosion occurring at such low potential in the presence of O2 is due to reactive oxygen species produced between H2O2 and Fe sites via Fenton reactions. [ABSTRACT FROM AUTHOR]

PtRu and PtRuMo electrocatalysts supported on N-doped graphene nanoplatelets (N-GNPs) were synthesized by a polyol method and utilized as anodes in polymer electrolyte membrane fuel cells (PEMFCs) to measure their CO tolerance and stability. A higher structural stability of the N-GNP supported catalysts, presenting a lower metal loss and a lower particle growth than PtRu/C was observed. Tests in PEMFCs indicated both a higher CO tolerance and a higher electrochemical stability of N-GNP supported PtRu and PtRuMo catalysts than a commercial conventional carbon black (CB) supported PtRu. • PtRu and PtRuMo supported on N-doped graphene nanoplatelets by polyol method. • Higher structural stability of the N-GNP: lower metal loss and particle growth. • Higher CO tolerance and electrochemical stability of PtRu and PtRuMo/N-GNP. [ABSTRACT FROM AUTHOR]