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Efficient reactant distribution and water removal are critical during polymer electrolyte fuel cell (PEFC) operation. The bipolar plate and its corresponding flow field design are vital among the PEFC components for enhancing reactant transport and water removal. The issues arising in the PEFC during the high current operation, such as reactant starvation and water removal, can be alleviated by improving the flow channel geometry. In this study, we analyze the variation in overall PEFC performance and corresponding reactant transport phenomenon for two independent design cases. The converging gradient design without channel traps at 0.4 V operating voltage exhibited a current density increment of 6.85% against the conventional design. Moreover, at 0.4 V, including channel traps enhanced the current density, as we observed a current density increment of 7.1% for the converging design with channel traps against the conventional design without channel traps. Likewise, at 0.4 V, the diverging design with channel traps exhibited a current density increment of 5.85% against the diverging design with no channel traps. Further, enhanced reactant distribution is observed in the catalyst layer upon introducing channel traps in the flow field design. [Display omitted] • Flow field design with the inclusion of channel traps is explored for performance. • Flow channel trap inclusion leads to cell performance increment. • Enhanced reactant distribution under the channel trap region is observed. • Converging design (case-2) attains a maximum current density of 1.38 A/cm2. • Converging (case-2) gains 7.0% current density compared to conventional design. [ABSTRACT FROM AUTHOR]

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) have emerged as a pivotal technology in the automotive industry, significantly contributing to the reduction of greenhouse gas emissions. However, the high material costs of the gas diffusion layer (GDL) and bipolar plate (BP) create a barrier for large scale commercial application. This study aims to address this challenge by optimizing the material and design of the cathode, GDL and BP. While deterministic design optimization (DDO) methods have been extensively studied, they often fall short when manufacturing uncertainties are introduced. This issue is addressed by introducing reliability-based design optimization (RBDO) to optimize four key PEMFC design variables, i.e., gas diffusion layer thickness, channel depth, channel width and land width. The objective is to maximize cell voltage considering the material cost of the cathode gas diffusion layer and cathode bipolar plate as reliability constraints. The results of the DDO show an increment in cell voltage of 31 mV, with a reliability of around 50% in material cost for both the cathode GDL and cathode BP. In contrast, the RBDO method provides a reliability of 95% for both components. Additionally, under a high level of uncertainty, the RBDO approach reduces the material cost of the cathode GDL by up to 12.25 $/stack, while the material cost for the cathode BP increases by up to 11.18 $/stack Under lower levels of manufacturing uncertainties, the RBDO method predicts a reduction in the material cost of the cathode GDL by up to 4.09 $/stack, with an increase in the material cost for the cathode BP by up to 6.71 $/stack, while maintaining a reliability of 95% for both components. These results demonstrate the effectiveness of the RBDO approach in achieving a reliable design under varying levels of manufacturing uncertainties. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) not only provide rapid dynamic response but also operate at low temperatures, which are desirable characteristics for transportation applications. However, metal bipolar plates in PEMFCs often deform under excessive clamping pressure, resulting in uneven pressure distribution. Rib-stiffened channels have been proposed to increase the structural stiffness of the bipolar plates, promoting durability. Parametric studies reveal that the supporting walls formed by the rib structure and a reduced top surface area contribute to better resistance against clamping force. Structural analysis and experimental assessments have confirmed the effectiveness of rib-stiffened channels in mitigating deformation. To ensure uniform compression of the gas diffusion layer during bolt assembly, a combined straight and rib-stiffened flow field has been designed and validated through structural simulations. Rib structures do not compromise fuel cell performance, as proved by computational fluid dynamics simulation with electrochemical reaction. [ABSTRACT FROM AUTHOR]

The efficiency of a proton exchange membrane fuel cell (PEMFC) could be increased dramatically if a cheap way to enhance sluggish kinetics of oxygen reduction at the cathode surface would be found. In this paper, a mathematical model to describe control of PEMFC operation by the sequence of laser pulses of a specific temporal shape applied to electrode surface is proposed. An optimization problem to find an optimal sequence of laser pulses to control electrode activity is formulated. [ABSTRACT FROM AUTHOR]

Improving the performance of polymer electrolyte fuel cells requires reducing the concentration overpotential at high current densities. Since liquid water accumulation in the gas diffusion layer (GDL) prevents oxygen diffusion to the catalyst layer, water management is a critical issue in fuel cell design and optimization. For such a purpose, the use of numerical simulation is desired. In the present study, a new macroscopic condensation model and a two-fluid model are developed. By using a condensation rate constant that depends on the relative humidity, the present simulation successfully predicts the liquid water content in the GDL quantitatively under a wide range of cell temperature and relative humidity conditions, which is experimentally validated using operando synchrotron X-ray radiography. The simulation also provides the state of water oversaturation. At 313 K, the relative humidity exceeds 100% extensively in the GDL except near the gas channel, while oversaturation is mitigated by higher temperatures. Thus, a simulation method incorporating finite phase change rates must improve prediction accuracy at lower cell temperatures and is expected to broaden the applicability of numerical prediction across various temperature and relative humidity conditions. • A new macroscopic condensation model and a two-fluid model are developed. • The model employs a condensation rate constant depending on the relative humidity. • The predicted liquid water content in GDL agrees well with experimental measurement. • The present model is effective under a wide range of temperature and RH conditions. • The state of oversaturation is reproduced, which is extensive at low temperature. [ABSTRACT FROM AUTHOR]

Near ambient pressure photoemission spectroscopy that uses hard X-rays (NAP-HAXPES) has been performed at BL36XU in SPring-8 and HAXPES measurements under atmospheric pressure have been achieved using a small diameter aperture recently. The main target of measurement using this system has been the operando measurement of fuel cell electrodes. We measured Pt/C and Pt3Co/C nanoparticle catalyst electrodes and obtained results on sulfur poisoning of the catalyst surface due to bias voltage changes. Recently, this system was moved to the upgraded HAXPES beamline “HAXPES II” (BL46XU). The beamline is publicly available, and it is expected to be used by users not only in Japan but also all over the world to promote HAXPES measurements on various samples and environments. [ABSTRACT FROM AUTHOR]

Preventing the accumulation of water in the gas diffusion layer (GDL) proves effective in enhancing the performance of polymer electrolyte fuel cells (PEFCs). To understand the water transport phenomena in GDLs and channels of PEFCs, cell hardware for operando synchrotron X-ray radiography was developed with a 100 mm channel length, facilitating the separate quantification of liquid water in the cathode and anode GDLs. The presence of liquid water in the cathode and anode GDLs was confirmed during operation with a supply of dry gas in a counter-flow configuration. Furthermore, the amount of liquid water in the cathode and anode GDLs increased toward the cathode inlet, while the amount of water in the cathode and anode channel regions increased toward each outlet. The liquid water distribution in the GDLs along the channel direction can be attributed to water transport from cathode to anode (back-diffusion), decreasing toward the anode outlet. Therefore, conducting radiography experiments aligned parallel to the GDLs and perpendicular to the channel could provide valuable insights for a more comprehensive understanding of water transport in cells.

For polymer electrolyte fuel cells (PEFCs), platinum nanoparticles supported on carbon black (Pt/C) serve as the commonly used hydrogen anode catalyst, exhibiting high activity for the hydrogen oxidation reaction (HOR), while the carbon support is susceptible to corrosion under PEFC operation. Here, a highly active HOR anode catalyst of Pt nanorod supported on niobium (Nb)-doped ceria without using corrosive carbon support was developed, which exhibits high durability at high potentials associated with hydrogen starvation. The production of hydrogen peroxide (H2O2), which can degrade the polymer electrolyte membrane, was also found to be significantly suppressed on the Pt nanorod/doped ceria catalyst. Density functional theory (DFT) calculations suggests that the Pt nanorod geometry and interaction with Nb and Ce favor HOR activity and stability while suppressing H2O2 production by modulating the adsorption of key reaction intermediates. This new catalyst has the potential to be used as an anode for high-performance and high-durability PEFCs.

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) have emerged as a pivotal technology in the automotive industry, significantly contributing to the reduction of greenhouse gas emissions. However, the high material costs of the gas diffusion layer (GDL) and bipolar plate (BP) create a barrier for large scale commercial application. This study aims to address this challenge by optimizing the material and design of the cathode, GDL and BP. While deterministic design optimization (DDO) methods have been extensively studied, they often fall short when manufacturing uncertainties are introduced. This issue is addressed by introducing reliability-based design optimization (RBDO) to optimize four key PEMFC design variables, i.e., gas diffusion layer thickness, channel depth, channel width and land width. The objective is to maximize cell voltage considering the material cost of the cathode gas diffusion layer and cathode bipolar plate as reliability constraints. The results of the DDO show an increment in cell voltage of 31 mV, with a reliability of around 50% in material cost for both the cathode GDL and cathode BP. In contrast, the RBDO method provides a reliability of 95% for both components. Additionally, under a high level of uncertainty, the RBDO approach reduces the material cost of the cathode GDL by up to 12.25 $/stack, while the material cost for the cathode BP increases by up to 11.18 $/stack Under lower levels of manufacturing uncertainties, the RBDO method predicts a reduction in the material cost of the cathode GDL by up to 4.09 $/stack, with an increase in the material cost for the cathode BP by up to 6.71 $/stack, while maintaining a reliability of 95% for both components. These results demonstrate the effectiveness of the RBDO approach in achieving a reliable design under varying levels of manufacturing uncertainties.

A variety of electrochemical energy conversion technologies, including fuel cells, rely on solution-processing techniques (via inks) to form their catalyst layers (CLs). The CLs are heterogeneous structures, often with uneven ion-conducting polymer (ionomer) coverage and underutilized catalysts. Various platinum-supported-on-carbon colloidal catalyst particles are used, but little is known about how or why changing the primary particle loading (PPL, or the weight fraction of platinum of the carbon-platinum catalyst particles) impacts performance. By investigating the CL gas-transport resistance and zeta (ζ)-potentials of the corresponding inks as a function of PPL, a direct correlation between the CL high current density performance and ink ζ-potential is observed. This correlation stems from likely changes in ionomer distributions and catalyst-particle agglomeration as a function of PPL, as revealed by pH, ζ-potential, and impedance measurements. These findings are critical to unraveling the ionomer distribution heterogeneity in ink-based CLs and enabling enhanced Pt utilization and improved device performance for fuel cells and related electrochemical devices.

In this study, a three-dimensional single channel is numerically modeled to simulate the polymer electrolyte fuel cell (PEFC) with a homogeneous and inhomogeneous gas diffusion layer (GDL). The influence of interfacial contact resistance (ICR) between GDL and current collector ribs (GDL|CC) is also studied. In the present study, GDL is considered as a single component (homogeneous) in one case and inhomogeneous with varying electrical and flow properties to illustrate the inhomogeneity in another case. The inhomogeneity in GDL is primarily caused by localized deformation due to non-uniform contact pressure during fuel cell assemblies. The consideration of ICR is observed to have a significant effect on both the ohmic and mass transport regions of the polarization curve. Inhomogeneous GDL with ICR, considered close to a practical scenario, shows a ∼7% drop in performance evaluation at 0.3V. The study reveals increased consumption of reactants at higher current loads when ICR is assumed negligible. This study examines the effects of homogeneous GDL, inhomogeneous GDL, and the impact of ICR on the distributions of reactant concentration, water concentration, temperature, current density, and polarization curve in PEFC. This study presents the practical aspects of PEFC considering inhomogeneous GDL electrical and flow properties. [Display omitted] • The inhomogeneity of GDL electrical and flow properties are explored. • Slight variation in performance is predicted with GDL inhomogeneity in the absence of ICR. • The effect of inhomogeneous GDL with ICR led the performance to reduce overall by ∼7%. • GDL inhomogeneity has a significant influence on reactants and various transport characteristics. [ABSTRACT FROM AUTHOR]

Nickel foams feature superior structural and transport characteristics and are therefore strong candidates to be used as gas diffusion layers (GDLs) in polymer electrolyte fuel cells (PEFCs). In this work, the impact of compression on the key structural and transport properties has been investigated, including employing a specially designed compression apparatus and X-ray computed tomography. Namely, 20 equally spaced two-dimensional CT based images and numerical models have been used/developed to investigate the sensitivity of the key properties of nickel foams (porosity, tortuosity, pore size, ligament thickness, specific surface area, gas permeability and effective diffusivity) to realistic compressions normally experienced in PEFCs. Wherever applicable, the anisotropy in the property has been investigated. One of the notable findings is that, unlike porosity and ligament thickness, the mean pore size was found to decrease significantly with compression. The mean pore size is around 175 μm for uncompressed nickel foam and it decreased to around 110 μm for a 20% compression ratio and to around 70 μm for a 40% compression ratio. Further, unlike the effective diffusivity, the gas permeability was shown to be highly anisotropic with compression; this fact is of particular importance for PEFC modelling where the properties of GDLs are often assumed isotropic. All the computationally estimated properties have been presented, validated and discussed. [Display omitted] • Nickel foam was numerically evaluated as a potential GDL material for PEFCs. • X-ray CT images, 3D-printed compression device and numerical models were employed. • Structural and transport properties of nickel foam under compression were determined. • Anisotropy of nickel foam permeability significantly increases with compression. • Nickel foam has superior properties compared to conventional GDLs. [ABSTRACT FROM AUTHOR]

Excessive liquid water in the gas diffusion layer (GDL) of a polymer electrolyte fuel cell is known to degrade the performance. Cross-flow through the GDL is applied to reduce the liquid water in the GDL. However, cross-flow has a disadvantage with a high pressure drop and is difficult in practical use. Controlled cross-flow has the possibility to reduce the liquid water, while the pressure drop remains acceptable for application. This study experimentally quantifies the amount of liquid water in the GDL by operando synchrotron X-ray radiography and the cross-flow rate with different GDL thicknesses. The relationship between the cross-flow rate and the amount of liquid water indicates that liquid water could be reduced by a smaller pressure drop with a thicker GDL. In addition, vapor removal by cross-flow is evaluated, and the relative humidity of cross-flow does not increase to 100% after flowing through the GDL containing liquid water. [Display omitted] • Flow field with different inlet and outlet sizes for cross-flow through cathode GDL. • Cross-flow rate and the amount of liquid water was simultaneously quantified. • Liquid water could be reduced by a smaller pressure drop for a thicker GDL. • Vapor removal by cross-flow was evaluated. • Possibility of liquid water removal by cross-flow was suggested. [ABSTRACT FROM AUTHOR]

Concerning global warming, an energy-efficient power source must produce low or no pollutant emissions and provide an unlimited fuel supply. Proton Exchange Membrane fuel cell (PEMFC) is an electrochemical device that transforms chemical energy into electrical energy. The performance and durability of PEM fuel cells are affected by voltage reversals and fuel starvation. Oxygen Excess Ratio (OER) is a crucial factor in controlling the fuel starvation of the PEMFC system. First, this work identified the PEMFC as an integer order and fractional-order first order plus time delay models using the predictor error method and Grunwald–Letnikov simulation method based on a trust-region-reflect algorithm, respectively. Fractional order models more accurately represented the PEM fuel cell system dynamics. Then, robust fractional filters cascaded with PID controllers based on the Internal Model Control scheme (IMC) are designed for identified integer and fractional order models to regulate the OER by compressor voltage manipulation. The genetic Algorithm (GA) optimization technique is used to find the optimal fractional filter tuning parameters. The proposed controller's performance regarding Integral Absolute Error (IAE) and Total Variance (TV) is analyzed. Furthermore, the robustness of a perturbed plant and fragility with perturbed controllers are elucidated. The results show that a fractional filter cascaded with fractional order PID controller improves the performance compared to a fractional filter cascaded with integer order PID controllers. [ABSTRACT FROM AUTHOR]

The shelf-life of catalyst ink for fabricating polymer electrolyte fuel cells (PEFCs) is relevant for large-scale manufacturing with unforeseen production stops. In this study, the storage effects on the physicochemical characteristics of catalyst ink (Pt/C, Nafion, 2-propanol, water) and subsequently manufactured catalyst layers are investigated. Sedimentation analysis showed that catalyst particles are not fully stabilized by charge interaction induced by Nafion. Acetone was found to be an oxidation product, even in freshly prepared ink with platinum catalyzing the reaction. Rotating disk electrode analysis revealed that the electrochemically active surface area is, overall, minimally increased by storage, and the selectivity towards water formation (4-electron pathway) is unharmed within the first 48 h of storage. MEAs prepared from stored ink reach almost the same current density level after conditioning via potential cycling. The open-circuit voltage (OCV) increases due to increased catalyst availability. Scanning electron microscopy and mercury intrusion porosimetry showed that with increasing acetone content, the pore structure becomes finer, with a higher specific surface area. Electrochemical impedance spectroscopy revealed that this results in a more hindered mass transfer but lowered charge transfer resistance. The MEA with the highest OCV and power output and the lowest overall cell resistance was fabricated from catalyst ink stored for a duration of four weeks. [ABSTRACT FROM AUTHOR]

Because it is time‐consuming to optimize the design of a cathode catalyst layer (CCL), a numerical simulation to predict the reaction and mass transport characteristics without trial and error is desirable. This study used numerical analysis to investigate how the mass transport occurring in CCLs with flat and three‐dimensional (3D) structures influenced the performance. The simulations included the reconstruction of the CCLs and their electrochemical calculation using our multi‐block model. The simulation results showed the reduction of the proton resistance in the ionomer was a factor in improving the performance in the 3D structure in comparison with the flat structure. An increasing aspect ratio of the 3D structure improved the cell performance and decreased the proton resistance in the ionomer. These results were due to the shortened conductive path of the protons from the polymer electrolyte membrane to the gas diffusion layer side surface in the 3D structure. Finally, the cell performance with an increase in the ionomer content was predicted. This numerical analysis made it possible to understand the reaction of the 3D structure and mass transport and predict ways to optimize the structural design to improve cell performance. [ABSTRACT FROM AUTHOR]

The causes of coating irregularities in high-speed slot-die coating of catalyst slurries for polymer electrolyte fuel cells (PEFCs) have not been determined. Accordingly, in this study, slot-die-coating experiments and computer simulations of two-phase gas–liquid flow were conducted to explore coating instability in the high-speed coating of PEFC catalyst slurries applied through slot-die coating. The results obtained from experiments and simulations were consistent. A thinner target layer and a faster coating, causing non-uniform coating. This is caused by movement of the gas–liquid interface on the upstream side and side of the die, which entraps the gas phase. Viscosity and surface tension are important, and a lower ethanol content in the solvent increases surface tension and lowers viscosity, improving coating stability. [Display omitted] • PEFC catalyst slurry coating uniformity studied through experiments and simulations. • Results were consistent across experiments and simulations. • Coating is non-uniform at high speed, low thickness, and high ethanol ratio. • The coating occurs in a region with weak non-Newtonian behavior. [ABSTRACT FROM AUTHOR]

Abstract Because it is time‐consuming to optimize the design of a cathode catalyst layer (CCL), a numerical simulation to predict the reaction and mass transport characteristics without trial and error is desirable. This study used numerical analysis to investigate how the mass transport occurring in CCLs with flat and three‐dimensional (3D) structures influenced the performance. The simulations included the reconstruction of the CCLs and their electrochemical calculation using our multi‐block model. The simulation results showed the reduction of the proton resistance in the ionomer was a factor in improving the performance in the 3D structure in comparison with the flat structure. An increasing aspect ratio of the 3D structure improved the cell performance and decreased the proton resistance in the ionomer. These results were due to the shortened conductive path of the protons from the polymer electrolyte membrane to the gas diffusion layer side surface in the 3D structure. Finally, the cell performance with an increase in the ionomer content was predicted. This numerical analysis made it possible to understand the reaction of the 3D structure and mass transport and predict ways to optimize the structural design to improve cell performance.

In this study, the cold-start process of a polymer electrolyte fuel cell has been numerically investigated under various ambient temperatures and operating currents, ranging from subzero to 283 K. The water desorbed from the electrolyte, when the cell temperature is below the freezing point, is assumed to exist in a state of either supercooled water or ice. The evolution of cell voltage, temperature, membrane water content, and the averaged volume fraction of supercooled water or ice in the catalyst layer and gas diffusion layer are presented. The results indicate that the cold-start process may fail due to ice blocking of the cathode catalyst layer when the desorbed water is in the form of ice and the ambient temperature is sufficiently low. However, when the desorbed water is in a supercooled state, it can diffuse from the cathode catalyst layer to the cathode gas diffusion layer, avoiding water clogging and enabling a successful cold-start process. During the cold-start process, as the ice undergoes a melting process, the membrane water content inside the membrane would increase rapidly, and a larger operation current with anode gas humidification is helpful to the cold-start process. [ABSTRACT FROM AUTHOR]

Abstract We measured the rotating ring-disk electrode (RRDE) voltammetry curves of a Pt catalyst supported on Marimo-like carbon (MC) to clarify the effect of carbon nanofilaments (CNFs) morphology and fine structures consisting of MC cathode material on the oxygen reduction reaction (ORR) activity for Polymer electrolyte fuel cells. The specific surface area and pore volume of MCs are influenced by their morphology and fine structures. MCs grown with Ni–Cu bimetal catalyst (represented as Ni80Cu20MC), having an octopus-like morphology, yielded four times larger total pore volume than that measured from the MC grown with Ni catalyst (Ni100MC). In the case of Ni80Cu20MC, coin-stacked graphenes perpendicular to the filament axis formed CNFs. Ni100MC consists of cup-stacked CNFs. The difference in the graphene stacked fine structure resulted in a different number of graphene edges covering the CNF surface; however, both supported Pt particle sizes and their distributions were similar. Linear sweep voltammetry with a RRDE revealed that the Pt/Ni80Cu20MC ORR onset potential was higher than that observed from the Pt/Ni100MC. This value is suggested to be correlates with the ORR activity. The origin of the ORR difference was discussed on the basis of the structural difference in the MCs.

An X-ray computed nano-tomography (nano-CT) system has been established at the BL33XU beamline of SPring-8. The optical system consists of pseudo-Köhler illumination with a sector condenser zone plate, an apodization Fresnel zone plate as the objective lens, and a Zernike phase plate. The imaging detector is a fiber-coupling type X-ray camera. The performance of the X-ray nano-CT system was confirmed by imaging an X-ray test chart. The system was subsequently applied to the observation of a microporous layer for polymer electrolyte fuel cells and a simulated microporous layer including liquid water. The nano-CT system, which can perform a computed tomography measurement in less than 4 min, allowed visualization of a spherical water droplet produced in the microporous layer. In the present study, the shape of water droplets in a nanoscale porous structure is investigated.

In the paper, the impact on durability of polymer electrolyte membrane fuel cells is investigated when varying operating conditions applied in accelerated stress tests. By this, the electric potential cycling protocol in given by a non-symmetric square profile. The electrochemical degradation of a catalyst layer is caused by platinum ion dissolution and oxide coverage. These mechanisms are described by the one-dimensional Holby–Morgan model with a modified Butler–Volmer equation for the reaction rates. For efficient numerical solution of the underlying nonlinear reaction-diffusion system, a variable time-step implicit-explicit method is suggested. Computer simulations predict durability for the catalyst by using a linear extrapolation up to the full platinum surface blockage. A parameter sensitivity analysis is presented on different time scales and measures how the platinum mass loss is impacted by the variation of specific parameters. • 1D Holby-Morgan model of platinum electrochemical degradation is applied. • The catalyst degradation is computed at non-symmetric square voltage cycling. • Simulations predict lifetime of Pt catalyst in low temperature PEM fuel cells. • Variance-based analysis of operating conditions on Pt mass loss is carried out. • Low temperature and ionomer ratio, high acidity and Pt size increase lifetime. [ABSTRACT FROM AUTHOR]

A three-dimensional single-flow channel computational model is used to investigate the performance characteristics of polymer electrolyte fuel cells (PEFC). The combined influence of non-uniform interfacial contact resistance (ICR) and inlet relative humidity (RH), along with the heterogeneous flow properties of the gas diffusion layer (GDL) on the PEFC performance is evaluated. The study considers combinations of full and partial humidification of anode and cathode reactants. Results reveal heterogeneous GDL with non-uniform ICR distribution results in a slight ∼4.4% reduction in current density at 0.3V compared to the homogeneous case. However, under same electrical/flow heterogeneities, the current density is observed to increase by ∼19% to ∼1.3A/cm2 under fully humidified anode and partially humidified cathode (i.e., RH a |RH c = 100%|60%) as compared to ∼1.1A/cm2 under symmetric RH a |RH c = 100%|100%. Interesting observations are made on the temperature distribution and cathodic water fractions. The variation in anodic inlet humidity is observed to have no impact on temperature distribution in the membrane, whereas variation in cathodic inlet humidity is effective in reducing the temperature in the channel regime with a 4K (kelvin) difference among all the cases. It is noted here that the overpotential map is not an indicator for performance loss, at least at full inlet humidity. This parameter is observed to depend on water concentration in the cathode. The study provides a detailed analysis of the distribution of reactant mass fraction, water concentration, current density, temperature, cathodic overpotential, and cell performance for all the simulated cases. • Effect of electrical/flow heterogeneity of GDL under different inlet humidification is simulated. • Heterogeneity lead to ∼4.4% reduction in current density (from ∼1.2A/cm2 to ∼1.15A/cm2) under full humidification. • ∼19% increase in current density (from ∼1.1A/cm2 to ∼1.3A/cm2) is observed with RH a.|RH c = 100%|60% • Temperature distribution in membrane is dependent function of cathode inlet humidity. • Overpotential is independent indicator of PEFC performance variation. [ABSTRACT FROM AUTHOR]

Baffles in flow field channels for air in a polymer electrolyte fuel cell are known to enhance the performance by inducing convective flow through the gas diffusion layer (GDL) with smaller pressure loss than interdigitated flow fields. This work experimentally correlates performance enhancement with the amount of liquid water in a GDL. A parallel flow field (PFF) that has different inlet and outlet opening sizes is applied to induce cross-flow in the GDL under the rib between adjacent air channels. Operando synchrotron X-ray radiography experiments are conducted to compare the amount of water in the GDL with that for a PFF having the same inlet and outlet sizes. The performance enhancement by application of different opening sizes increases with decreasing relative humidity and increasing air flow rate. A significant performance enhancement is observed when the amount of water in the GDL substrate under the rib becomes almost zero. No performance enhancement is observed under over-humidified conditions, although a decrease in the amount of water in the GDL is still observed, which suggests that the performance becomes insensitive to the difference in the liquid water saturation as the saturation increases.

Water management plays a key role in ensuring optimum polymer electrolyte fuel cell (PEFC) performance, and flow field design can influence the ability of a cell to balance maintaining hydration, whilst avoiding flooding and cell failure. This work deepens the understanding of water evolution in different PEFC flow channel designs, namely single serpentine (SS), double serpentine (DS) and parallel, using our novel high-speed neutron computed tomography method. We developed our previously-reported method by introducing continuous cell rotation, enabling 18 s per tomogram during 1 h holds at 300, 400 and 500 mA cm ^−2 . The volume of water evolved in the cathode, membrane electrode assembly and anode was quantified, and key mechanisms for water droplet formation in the different flow channel designs were elucidated. The parallel flow field design had the poorest water management, with 47% of the cathode flow channel becoming filled after 1 h at 400 mA cm ^−2 . This significant flooding blocked reactant sites and contributed to unstable cell performance and, ultimately, cell failure at higher current densities. The SS cell displayed the best water management, with only 11% of the cathode channel filled with water after 1 h at 500 mA cm ^−2 , compared with 28% of the DS cathode channel. 3D visualisation and analysis of droplet behaviour elucidated how water ‘slugs’ in the SS were removed in the gas stream, whereas three of the four parallel cathode flow channels became entirely filled with water plugs, blocking gas flow and exacerbating cell flooding. The new insights gained here are expected to extend to novel flow field designs and image-based models, with the use of operando neutron CT demonstrated as a powerful technique for both visualising and quantifying water management in operating PEFCs, as well as deepening the knowledge of droplet behaviour in different flow field types.

Accurate measurement of the gas diffusivity in a gas diffusion layer (GDL) for polymer electrolyte fuel cells (PEFCs) is extremely important in order to improve the performance of PEFCs and design fuel cell stacks. In the present study, in order to improve the accuracy in the determination of the gas diffusivity when uisng the simple and inexpensive method newly proposed by Yoshimune (2022), which uses an infrared absorption carbon dioxide sensor, three-dimensional (3D) simulations reproducing the experiments are performed. The results reveal that the gas transport resistance of the measurement apparatus is not small (approximately seven times higher than that of a commercial carbon paper (TGP-H060, Toray)), and the 3D simulation, which considers the resistance, reduces the error in the effective diffusion coefficient of the GDL by 25%. The effective diffusion coefficient for a new sample can be determined using the simulation results already obtained, when the apparatus is unchanged. In addition, a new one-dimensional (1D) model extended from the simple 1D model presented in Yoshimune (2022) is proposed. Since the extended model incorporates the gas transport resistance of the apparatus and dispenses with the generation of computational grids and the use of an expensive computer needed in conducting 3D simulations, this model enables us to obtain the accurate effective diffusion coefficient of a GDL with ease even when using a measurement apparatus with different sizes.

Degradation of a catalyst layer in polymer electrolyte membrane fuel cells is considered, which is caused by electrochemical reactions of the platinum ion dissolution and oxide coverage. An accelerated stress test is applied, where the electric potential cycling is given by a non-symmetric square profile. Computer simulations of the underlying one-dimensional Holby–Morgan model predict durability of the fuel cell operating. A sensitivity analysis based on the variance quantifies how loss of the platinum mass subjected to the degradation is impacted by the variation of fitting parameters in the model. [ABSTRACT FROM AUTHOR]

The flow field plate (FFP) design is a key factor for enhancing the electrochemical performance of Polymer Electrolyte Fuel Cells (PEFCs) through optimal reactants' distribution, low-pressure drops, and efficient water removal. The effect of geometrical features of the pin-type FFP design on the electrochemical performance of a 48 cm2 H 2 -fed Fuel Cell (FC) was assessed through polarization curves recording and current and temperature distribution maps along the electrode active area. The study was performed by changing excess air stoichiometry and cathode relative humidity (RH). Low-pressure drops were measured using pin-type FFPs; regardless of geometrical features, they were one order of magnitude lower than those of a single-channel serpentine FFP. Channel width and number of pins greatly influenced the current distribution along the active area and, consequently, the electrochemical performance of FCs. In particular, the best electrochemical performance was reached at air stoichiometry 4 and cathode RH = 100 % by using FFP with the highest coverage factor (65 %) and the lowest channel width (1 mm). Current distribution maps demonstrated that this FFP geometry led to an almost homogeneous current distribution and efficient water removal also at high current density values. On the contrary, low coverage factor (45 %) and high channel width led to worse electrochemical performances due to an uneven reactants distribution and an inefficient water removal, causing cell flooding. • Study of a fuel cell using different pin-type flow field plate designs is carried out. • Pin-type flow field experiences lower pressure drops than serpentine flow field. • Current and temperature distribution maps are recorded under several operating conditions. • Increasing coverage factor and decreasing channel width lead to more homogeneous current distribution. [ABSTRACT FROM AUTHOR]

The shelf-life of catalyst ink for fabricating polymer electrolyte fuel cells (PEFCs) is relevant for large-scale manufacturing with unforeseen production stops. In this study, the storage effects on the physicochemical characteristics of catalyst ink (Pt/C, Nafion, 2-propanol, water) and subsequently manufactured catalyst layers are investigated. Sedimentation analysis showed that catalyst particles are not fully stabilized by charge interaction induced by Nafion. Acetone was found to be an oxidation product, even in freshly prepared ink with platinum catalyzing the reaction. Rotating disk electrode analysis revealed that the electrochemically active surface area is, overall, minimally increased by storage, and the selectivity towards water formation (4-electron pathway) is unharmed within the first 48 h of storage. MEAs prepared from stored ink reach almost the same current density level after conditioning via potential cycling. The open-circuit voltage (OCV) increases due to increased catalyst availability. Scanning electron microscopy and mercury intrusion porosimetry showed that with increasing acetone content, the pore structure becomes finer, with a higher specific surface area. Electrochemical impedance spectroscopy revealed that this results in a more hindered mass transfer but lowered charge transfer resistance. The MEA with the highest OCV and power output and the lowest overall cell resistance was fabricated from catalyst ink stored for a duration of four weeks.

In this study, blended perfluorinated sulfonic acid (PFSA) ionomers with equivalent weights (EWs, g/mol) of ~1000, 980, and 830 are prepared. Catalyst layers (CLs), using blended PFSA ionomers, with different side chain lengths and EWs are investigated and compared to CLs using single ionomers. The ion exchange capacity results confirm that blended ionomers have the target EWs. As a result, blended ionomers exhibit higher ion conductivity than single ionomers at all temperatures due to the higher water uptake of the blended ionomers. This implies that blended ionomers have a bulk structure to form a competent free volume compared to single ionomers. Blended ionomers with short side chains and low EWs can help reduce the activation energy in proton conduction due to enhanced hydrophobic and hydrophilic segregation. In addition, when using the blended ionomer, the CLs form a more porous microstructure to help reduce the resistance of oxygen transport and contributes to lower mass transfer loss. This effect is proven in fuel cell operations at not a lower temperature (70 °C) and full humidification (100%) but at an elevated temperature (80 °C) and lower relative humidity (50 and 75%). Blended ionomer-based CLs with a higher water uptake and porous CL structure result in improved fuel cell performance with better mass transport than single ionomer-based CLs.

Herein, we report the oxygen transport phenomenon in the cathode catalyst layer of polymer electrolyte fuel cells. The oxygen transport resistance in the catalyst layer depended on the hot-pressing temperature of the fabrication procedure, suggesting morphological changes in the perfluorosulfonic acid ionomer of the catalyst layers. This work aims to highlight the importance of the manufacturing process in the oxygen transport properties of the catalyst layer.

Hydrogen isotopes are a valuable source of hydrogen energy through fusion reactions. The materials used in polymer electrolyte fuel cells (PEFCs), such as the hydrophobic support and Pt catalyst, are essentially the same to those used in the conventional isotope-separation method by water–hydrogen chemical exchange. Here, deuterium (D) separation was performed with a PEFC. A gas mixture of H 2 and D 2 was supplied while changing the humidity. The hydrogen gas and water vapor from the PEFC were analyzed to investigate the D mass balance. Without power generation, D was separated into the water vapor. This can be explained by the vapor-phase catalytic exchange reaction occurring on the platinum catalyst. The fuel-cell reaction enhanced D separation. A large amount of D (approximately 45%) was transferred to the water vapor during power generation. The present results demonstrate the synergistic effect of vapor-phase catalytic exchange and the PEFC on D separation. • Deuterium separation by polymer electrolyte fuel cell was studied. • The effect of the water vapor on the isotope separation was discussed. • The D mass balance clarified the breakdown of D/H ratio in the outlet gas and produced water. [ABSTRACT FROM AUTHOR]

We evaluated the power generation characteristics of a polymer electrolyte fuel cell (PEFC) composed of Pt-supported carbon nanowalls (CNWs) and a microporous layer (MPL) of carbon black on carbon paper (CP) as catalyst support materials. CNWs, standing vertically on highly crystallizing graphene sheets, were synthesized on an MPL/CP by plasma-enhanced chemical vapor deposition (PECVD) using inductively coupled plasma (ICP). Pt nanoparticles were supported on the CNW surface using the liquid-phase reduction method. The three types of voltage loss, namely those due to activated polarization, resistance polarization, and diffusion polarization, are discussed for the power generation characteristics of the PEFC using the Pt/CNWs/MPL/CP. The relationship between the height or gap area of the CNWs and the voltage loss of the PEFC is demonstrated, whereby the CNW height increased with the extension of growth time. The three-phase interface area increased with the increase in the CNW height, resulting in mitigation of the loss due to activated polarization. The gap area of the CNWs varied when changing the CH4/H2 gas ratio. The loss due to diffusion polarization was reduced by enlarging the gap area, due to the increased diffusion of fuel gas and discharge of water. The secondary growth of the CNWs caused the three-phase interface area to decrease as a result of platinum aggregation, impedance of the supply of ionomer dispersion solution to the bottom of the CNWs, and inhibition of fuel gas and water diffusion, which led to the loss of activated and diffuse polarizations. The voltage losses can be mitigated by increasing the height of CNWs while avoiding secondary growth. [ABSTRACT FROM AUTHOR]

In this study, the cold-start process of a polymer electrolyte fuel cell has been numerically investigated under various ambient temperatures and operating currents, ranging from subzero to 283 K. The water desorbed from the electrolyte, when the cell temperature is below the freezing point, is assumed to exist in a state of either supercooled water or ice. The evolution of cell voltage, temperature, membrane water content, and the averaged volume fraction of supercooled water or ice in the catalyst layer and gas diffusion layer are presented. The results indicate that the cold-start process may fail due to ice blocking of the cathode catalyst layer when the desorbed water is in the form of ice and the ambient temperature is sufficiently low. However, when the desorbed water is in a supercooled state, it can diffuse from the cathode catalyst layer to the cathode gas diffusion layer, avoiding water clogging and enabling a successful cold-start process. During the cold-start process, as the ice undergoes a melting process, the membrane water content inside the membrane would increase rapidly, and a larger operation current with anode gas humidification is helpful to the cold-start process.

In recent years, stainless steel has been used as a separator in polymer electrolyte fuel cells (PEFCs). An electrophoretic deposition (EPD) method has been developed as a surface treatment, in which titanium nitride (TiN) is coated on stainless steel to impart conductivity. Using the EPD method, the surface of SUS316L steel was coated with three types of TiNstyrene-butadiene rubber (SBR) with different TiN particle diameters and impurity contents to improve the contact resistance. A smaller impurity content in the TiN resulted in a lower contact resistance. Furthermore, when the TiN particle size was between 50 nm and 1.5 µm, a larger particle size provided a lower contact resistance. In the polarization curve measurements, no deterioration of the corrosion resistance was observed for TiNSBR. At the potential of an actual PEFC environment, low current densities were maintained in both the anodic and cathodic environments. Furthermore, scanning electron microscopy and electron probe microanalysis before and after the polarization test confirmed that there was no TiN detachment in the PEFC environment. The above results suggest that TiN-coated SUS316L steel is a promising separator for PEFCs. [ABSTRACT FROM AUTHOR]

The significance of under-rib convection in the flow field development of polymer electrolyte fuel cells (PEFCs) is increasingly recognized. This study quantitatively evaluates the interplay between mass transfer and reaction processes in adjacent channels, affected by under-rib convection. A comprehensive analysis identifies that oxygen mole fraction and current density profiles in the channel-rib direction are governed by five dimensionless moduli. The effectiveness factor, defined as the ratio of the integral average under-rib current density to that without mass transfer resistance, elucidates the potential for current density enhancement due to under-rib convection. Experimental results demonstrate a significant increase in the under-rib current density from 0.15 to 0.32 A cm⁻2 as the pressure difference between adjacent channels rises from 0 to 929 Pa at 0.60 V and 0.52 relative humidity. This corresponds to an increase in the effectiveness factor from 0.37 to 0.77 and a Péclet number increase from 0 to 34.8. Model predictions indicate that the maximum net power density is achieved at a Péclet number of 60, balancing under-rib convection benefits and pumping pressure. Validated by experimental results, the model aids in reaction kinetics analysis and polarization prediction, offering significant insights and practical guidelines for electrochemical reactor optimization. [Display omitted] • Under-rib convection affecting transport-reaction interactions is evaluated. • Dimensionless moduli determine the channel-rib oxygen and reaction profiles. • Polarization behaviors with varied pressure differences were measured and reproduced. • An optimal pressure difference maximizing the net power density is obtained. • The model demonstrates capability in kinetics analysis and polarization prediction. [ABSTRACT FROM AUTHOR]

To alleviate water flooding in cathode electrodes of polymer electrolyte fuel cells (PEFCs), it is essential to design the optimum channel/electrode structure for rapid water removal. This study presented a novel hybrid structure with the channel hydrophilization and electrode perforation for accelerating the through-plane water discharge and demonstrated the effect of its structure on the water transports in the cathode channel and gas diffusion layer (GDL) of a working PEFC with optical and X-ray imaging. The results revealed that the hydrophilization of the channel walls encourages the through-plane water suction form the GDL to the channel. Furthermore, the electrode perforation promotes the in-plane water discharge from the fine porous media to the large penetration grooves and holes. The synergistic effect of these two water transports in the hybrid structure effectively alleviates the flooding in the porous layers and enhances the oxygen diffusibility, resulting in significant improvement of the cell performance.

[Display omitted] • PEFC with channel length of 100 mm was developed for water visualization. • Water thickness in cathode and anode GDLs decreased toward cathode outlet. • Water thickness in cathode and anode channels increased toward each outlet. • Water distribution in GDLs is originated from back-diffusion. Preventing the accumulation of water in the gas diffusion layer (GDL) proves effective in enhancing the performance of polymer electrolyte fuel cells (PEFCs). To understand the water transport phenomena in GDLs and channels of PEFCs, cell hardware for operando synchrotron X-ray radiography was developed with a 100 mm channel length, facilitating the separate quantification of liquid water in the cathode and anode GDLs. The presence of liquid water in the cathode and anode GDLs was confirmed during operation with a supply of dry gas in a counter-flow configuration. Furthermore, the amount of liquid water in the cathode and anode GDLs increased toward the cathode inlet, while the amount of water in the cathode and anode channel regions increased toward each outlet. The liquid water distribution in the GDLs along the channel direction can be attributed to water transport from cathode to anode (back-diffusion), decreasing toward the anode outlet. Therefore, conducting radiography experiments aligned parallel to the GDLs and perpendicular to the channel could provide valuable insights for a more comprehensive understanding of water transport in cells. [ABSTRACT FROM AUTHOR]

The temporal stability and spatial homogeneity of current density are key factors in Polymer Electrolyte Fuel Cell (PEFC) performance and durability. Temporal and spatial variations of relative humidity, fuel concentration, and water droplets in the channels are the principal causes of non-homogeneous current density. A dynamic pseudo-3D model was previously proposed by the authors and has been extended and improved to perform the long-term and intensive simulations of PEFC with low computational cost, which allows to study of the performances homogeneity with different experimental configurations and flow field topologies. The model considers important phenomena in the homogeneity analysis, such as gases and liquid water movement in diffusion layers and flow field, electrochemical reactions, and others. Model validation has been performed using experimental data obtained from a 25 cm 2 cell with a single serpentine, which has allowed studying the model transient response and spatial representation. The simulations have been used to study the homogeneity and stability of 36 setups of PEFC, varying the rib/channel width ratio, the stoichiometric ratio, and the number of parallel serpentine channels. The results show the importance of a properly flow field design to control gas flow, remove the channels' liquid water, and keep a homogeneous feeding. The study evaluated a set of channel configurations that show the improved temporal voltage stability and current density spatial homogeneity. The results show the impact of channel gas speed and ratio channel/rib width in liquid droplets removal and the proper fuel spatial distribution; and how configurations with a lesser number of channels in serpentine design require a lower stoichiometric ratio to perform better temporal and spatial uniformity. In the case of the cell configurations simulated, the optimum design was achieved using between 5 and 7 parallel serpentine channels and a channel/rib ratio 3/5. • Pseudo-3D model of PEM fuel cell oriented to study the performance uniformity. • Temporal stability and spatial homogeneity studied for different flow field setups. • The methodology allows long-term simulations with low computational cost. • Stoichiometry is a key factor removing liquid water and increasing cell stability. • Balance of the number of channels and stoichiometry to proper liquid water removal. [ABSTRACT FROM AUTHOR]

The solvent composition of the catalyst ink profoundly impacts both the porous structure and the efficiency of the mass-production process of the catalyst layer for polymer electrolyte fuel cells. However, the underlying mechanism remains far from elucidated. Here, we present the size of aggregate and the fractal dimension of the agglomerate structure as determined by ultra-small X-ray scattering (USAXS) of the catalyst inks with varied solvent composition. By examining the correlations between the structural properties provided by USAXS, rheological properties, and the quantity of ionomer adsorbed on the Pt/C, we elucidate the solvent's influence on the agglomerate structure. In highly polar solvents, akin to water, a considerable number of amphiphilic ionomers adsorb to the Pt/C particles, resulting in the formation of dispersed Pt/C aggregate particles approximately 200 nm in size that cannot be subdivided further into smaller particles even with the use of a homogenizer. As the polarity diminishes with the addition of alcohol content, ionomers desorb, and the affinity between the aggregates and the solvent decreases, leading to the evolution of agglomerates. The observed solvent effect can be rationally characterized by one of Hansen's solubility parameters, which specifies the polar interaction. [Display omitted] • Formation mechanism of the agglomerate structure in the catalyst ink of PEFC was investigated. • USAXS reveals changes in the agglomerate structure with varied solvent compositions. • In low-polarity solvents, ionomers desorb from Pt/C, facilitating agglomerate evolution. • Increased polarity leads to ionomer adsorption and dispersion of agglomerates into aggregates. • The observed solvent effects can be rationally characterized by HSP- δ P. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nb-doped ceria supported Pt nanorod catalyst is synthesized. • The Pt nanorod/Nb-CeO 2 catalyst exhibits high HOR activity and stability. • H 2 O 2 formation is suppressed on the Pt nanorod/Nb-CeO 2 catalyst. • Nanorod geometry and metal-support interactions promote the HOR catalysis. For polymer electrolyte fuel cells (PEFCs), platinum nanoparticles supported on carbon black (Pt/C) serve as the commonly used hydrogen anode catalyst, exhibiting high activity for the hydrogen oxidation reaction (HOR), while the carbon support is susceptible to corrosion under PEFC operation. Here, a highly active HOR anode catalyst of Pt nanorod supported on niobium (Nb)-doped ceria without using corrosive carbon support was developed, which exhibits high durability at high potentials associated with hydrogen starvation. The production of hydrogen peroxide (H 2 O 2), which can degrade the polymer electrolyte membrane, was also found to be significantly suppressed on the Pt nanorod/doped ceria catalyst. Density functional theory (DFT) calculations suggests that the Pt nanorod geometry and interaction with Nb and Ce favor HOR activity and stability while suppressing H 2 O 2 production by modulating the adsorption of key reaction intermediates. This new catalyst has the potential to be used as an anode for high-performance and high-durability PEFCs. [ABSTRACT FROM AUTHOR]

We clarify the issues to be addressed when inorganic materials are employed in the electrodes of low temperature fuel cells, which conventionally operate around 80 °C. The employed inorganic proton conductor is zirconium sulfophenyl phosphonate (ZrSPP), which is incorporated as an ionomer in the electrode catalyst layers by coating the Pt-supported carbon nanotubes with a ZrSPP layer (ZrSPP–Pt/CNTs). Compared with an MEA with an electrode comprising Nafion and Pt/CNT without a ZrSPP coating, a membrane–electrode assembly (MEA) with an electrode comprising ZrSPP–Pt/CNT exhibits an improved performance at elevated temperatures of 90 °C and 100 °C, illustrating an advantage of the inorganic proton conductors. However, a ZrSPP coating on the Pt/CNTs decreases the cell performance at 80 °C. A detailed in situ analysis using limiting-current measurements reveals that the oxygen transport resistance through the solid ionomers increases by approximately six times with the incorporation of the ZrSPP layer. These results indicate that the mass transport through the inorganic materials should be addressed when they are employed in electrodes. [Display omitted] • Issues of using inorganic proton conductors in the electrodes of PEFCs are clarified. • An inorganic proton conductor, ZrSPP, is coated on the surface of Pt/CNTs. • An MEA with ZrSPP-coated Pt/CNTs shows improved performance at 90 °C and 100 °C. • In situ analysis of mass transport properties in the cathode of MEAs is performed. • Oxygen transport resistance through the solid ionomers increases by ZrSPP coating. [ABSTRACT FROM AUTHOR]

[Display omitted] • [1 1 1]-oriented Pt nanorods were grown on polyhedral ceria by a colloidal strategy. • The Pt nanorods show strong atomic and electronic coupling with ceria support. • The coupling effects improve O 2 adsorption and activation on Pt sites. • The Pt nanorods/doped ceria catalyst exhibits excellent ORR activity and stability. Promoting the oxygen reduction reaction (ORR) performance is an urgent need to reduce the amount of Pt catalysts in fuel cells. One of the most promising strategies is interface engineering which takes advantage of the synergistic catalytic proficiencies of double or even multiple components. Herein, we synthesized the electrocatalyst that comprises Pt nanorods atomically oriented along the (1 1 1) nanofacets of Gd-doped cerium oxide polyhedra, which was much superior to commercial Pt/C catalyst for the four-electron ORR, with a 4-fold improvement of ORR intrinsic activity than Pt/C, as well as producing much less of the undesirable two-electron ORR product H 2 O 2. It also features a remarkable stability, with negligible activity degradation in 5000-cycle test. The exposure of Pt(1 1 1) facets and the oxygen vacancy-mediated interfacial PtCe alloying facilitate O 2 adsorption and dissociation together with desorption of OH ad , which can account for the exceptional ORR electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Fault diagnosis technology has been developed to improve the reliability of fuel cell systems in pursuit of successful commercialization. In this study, a hybrid fault diagnosis method is proposed to improve diagnosable fault magnitudes and diagnostic accuracy. Six types of faults in the air supply system of a proton exchange membrane fuel cell system were therefore defined and diagnosed according to the relevant components and locations as actuator, sensor, and piping faults. The proposed method applies an artificial neural network classifier as a data-based diagnostic tool within a model-based diagnosis method that relies upon residual patterns to address the limitations of the model-based diagnosis method (insufficient accuracy for initial fault diagnosis) and the data-based diagnosis method (need for a large dataset to generate a classifier). The proposed method is shown to improve the diagnostic accuracy and decrease the diagnosable fault magnitude compared to solely model-based and data-based methods. Moreover, the proposed method enables a faster diagnosis of air supply system faults, preventing loss of system efficiency and stack degradation. By providing fast and accurate diagnoses, the proposed method is expected to help develop an effective fuel cell health management system. • Fault components and locations in air supply systems are diagnosed. • The diagnosis involves a model-based method using residuals and a neural network. • The method improves both the diagnosable fault magnitude and diagnostic accuracy. • The hybrid method decreases the range and the amount of required training data. • The advanced method prevents system efficiency loss and stack degradation. [ABSTRACT FROM AUTHOR]