N-doped graphene (NG) is a promising electrocatalyst for the oxygen reduction reaction (ORR) at the cathodes of Polymer Electrolyte Fuel Cells (PEFCs). The NG catalyst is generally supported on an electrode substrate composed of carbon materials. However, the influence of the carbon substrate on the ORR performance of the NG catalyst has not been systematically explored. In this study, we have systematically investigated the impact of the carbon substrate on the ORR activity of the NG catalyst using first-principles calculations based on density functional theory. Specifically, we have examined the ORR activity of the NG catalyst on graphene-based substrates with a van der Waals (vdW) interface. It has been revealed that the difference in work function between the substrate and the NG catalyst dominates the ORR activity; the maximum electrode potential (UMax) depends linearly on the work function difference. Such a linear relationship is derived from the fact that the net charge of the NG catalyst scales linearly with the work function of the substrate. Furthermore, UMax was predicted to show a volcano trend with respect to the work function difference. This is because the reaction step that determines UMax switches due to the change in the free energies of reaction intermediates by charge transfer across a vdW gap, indicating an optimal work function difference that maximizes the ORR activity of the NG catalyst supported on graphene-based substrates. The establishment of experimental techniques to control the work function difference at the substrate/NG catalyst interface will be key to achieving superior catalytic performance.

Mass transport limitations at high current densities hinder polymer electrolyte fuel cell (PEFC) performance due to inefficient water management and reactant distribution. Gas diffusion layer (GDL) perforation offers a potential solution as an alternative to complex flow-field modifications. However, understanding of how perforation impacts critical internal states like water distribution, local temperature and electrochemical reaction rates remains limited. This knowledge gap has prevented optimisation of GDL designs, with homogeneous patterns potentially exacerbating performance gradients. This study uses operando neutron imaging combined with synchronous thermal-electrical mapping to analyse water dynamics and their impact on PEFC performance with both homogeneous and heterogeneous GDLs. The approach enables detailed analysis of interactions between water, heat and electrochemical reactions, providing experimental validation beyond limited field-of-view techniques like X-ray tomography. Results demonstrate that a spatially tailored perforation pattern effectively balances in-plane saturation gradients and enhances peak power compared to both uniform patterns and non-perforated GDLs. This work establishes spatial engineering as a design principle for porous transport layers, offering a simpler and cost-effective solution to mass transport constraints in fuel cells and other electrochemical devices containing porous media.

Highly crystalline single-walled carbon nanotubes were employed as robust supports for carbon-encapsulated PtPd alloy electrocatalysts synthesized via a rapid, industrially scalable solution plasma method, enhancing long-term durability under frequent start-up/shut-down conditions. Electrochemical evaluation of PtPd@C/SWCNT as a cathode catalyst in a polymer electrolyte fuel cell (PEFC) membrane electrode assembly (MEA) demonstrated superior durability compared to commercial Pt/C and monometallic Pt@C/SWCNT under an accelerated durability test. PtPd@C/SWCNT maintained high performance for 5000 potential cycles and retained over 50% of its electrochemically active surface area (ECSA) after 10 000 cycles under the accelerated durability test of high-potential triangular pulses (1.0-1.5 V) simulating harsh conditions encountered during actual start-up/shut-down operations. Carbon encapsulation effectively inhibited nanoparticle agglomeration and suppressed the oxidation of the SWCNT support in close proximity to the nanoparticles during the durability test of 30 000 cycles. Raman spectroscopy confirmed the excellent corrosion resistance and maintained the crystallinity of the SWCNT support. The negligible thickness change observed in the PtPd@C/SWCNT cathode layer further highlights the benefit of the SWCNT support and carbon encapsulation in maintaining structural integrity under severe operating conditions. XPS analysis indicated a more stable, reduced state of Pt in PtPd@C/SWCNT compared to that of Pt/C. These results highlight the synergistic effects of the SWCNT support and carbon encapsulation in improving both catalyst stability and support durability for prolonged PEFC operation, particularly under demanding heavy-duty vehicle (HDV) conditions.

• Synthesized Pt/CeO₂ scavenger to neutralize radicals and increase fuel cell durability. • The "intermixed" method is most effective for adding scavenger to the catalyst layer. • Optimal scavenger loading in the cathodic catalyst layer was identified as 1.0 wt.%. • Achieved max power density of ∼950 mW/cm² at 80°C and 50% relative humidity. • ADT shows a 19% performance loss of MEA containing scavenger versus 35% for the reference system after 48 hours. Polymer Electrolyte Fuel Cells (PEFCs) are a promising technology for clean energy conversion, but their long-term performance is often limited by fuel crossover, electrode degradation, and reactive species formation. In this study, the incorporation of radical scavengers into the cathodic catalyst layer (CL) was investigated as a strategy to enhance PEFC durability and performance. Different incorporation methods were tested, and the optimal scavenger loading was determined (0.5–1.5 wt.%). Membrane Electrode Assemblies (MEAs) in Catalyst Coated Membrane (CCM) configuration were electrochemically characterized in single-cell setups. Results show that the “intermixed” method—adding the scavenger directly to the catalyst ink—provides the most effective performance enhancement. The optimal loading of 1 wt.% resulted in a maximum power density of approximately 950 mW/cm² at 80 °C and 50% RH. Accelerated stress tests under open-circuit voltage conditions demonstrated significantly improved stability: at 0.5 A/cm², the scavenger-based MEA lost only 19% of its initial performance, compared to 35% for the reference MEA. These findings demonstrate that incorporating an optimized amount of radical scavenger into the cathodic CL effectively enhances both the performance and long-term durability of PEFCs.

Degradation Mechanism and Mitigation Strategy of Mesoporous Carbon-Supported Pt Catalysts during Realistic Startup and Air Confinement Shutdown in Polymer Electrolyte Fuel Cells

Development of fluorine-free microporous layer composed of thermosetting melamine resin via dry coating process for polymer electrolyte fuel cells

ABSTRACT This study examines the impact of gas diffusion layer (GDL) perforation characteristics—perforation size, center‐to‐center spacing, and location—on the performance and transport behaviors of polymer electrolyte fuel cells (PEFCs) under varying flow field configurations. Using both single‐channel serpentine and parallel flow fields, we demonstrate that perforating the cathode GDL, particularly under the gas flow channel, significantly improves water management by facilitating liquid water removal, thus enhancing mass transport and cell performance. The findings reveal that larger perforation sizes and smaller center‐to‐center spacings are more effective in high‐velocity regions, such as those found in serpentine flow fields, due to increased convective effects. However, in low‐velocity regions like parallel flow fields, these effects are less pronounced, resulting in only marginal improvements. Importantly, perforating only the cathode under the channel was shown to sufficiently enhance cell performance while maintaining design simplicity. Strategic perforation adjustments—denser perforations in high‐velocity regions and larger perforations in low‐velocity regions—can optimize water removal and mitigate mass transport limitations.

ABSTRACT Preferential oxidation of CO (CO‐PROX) is essential for supplying CO‐free hydrogen to polymer electrolyte fuel cells (PEFCs). We investigated the structure–performance relationship of Au catalysts supported on Mg─Al layered double hydroxides (LDHs) under H 2 ‐rich conditions. By combining catalytic measurements with in situ X‐ray absorption fine structure (XAFS), we demonstrated that cationic Au species and atomically dispersed Au(0) are not responsible for appreciable CO‐PROX activity. Instead, catalytic activity emerged after generating Au(0) clusters induced by thermal treatment under CO‐PROX conditions. The temperature required for Au cluster formation depended on the LDH crystallite size. According to in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), LDH nanoparticles (NPs) possessing abundant edge hydroxy groups stabilized atomically dispersed Au species more effectively than bulk LDH, but simultaneously promote H 2 O accumulation, blocking the active sites. In contrast, bulk LDH enabled the formation of active Au clusters at lower temperatures, while a moderate number of hydroxy groups allows regulation of the surface H 2 O quantity, thereby facilitating efficient removal of carbonate intermediates and accelerating CO oxidation. As a result, Au/bulk‐LDH achieved high CO oxidation activity and selectivity. These results provide mechanistic insights and design principles for Au‐based CO‐PROX catalysts operable at PEFC‐relevant temperatures.

Reducing ionomer content in polymer electrolyte fuel cell catalyst layers is key to mitigating oxygen transport losses, yet current fabrication methods deposit ionomer in an uncontrolled manner, often requiring excess loadings to ensure proton conduction. Introducing well-defined proton-conducting functional groups directly onto catalyst supports offers a route to improve transport without relying on high ionomer fractions. Here, we demonstrate direct grafting of sulfonic acid groups onto Pt/Vulcan catalysts using diazonium chemistry. The grafting degree was systematically tuned by adjusting precursor concentration and quantified through water dispersibility measurements, zeta potential analysis, X-ray photoelectron spectroscopy, and acid-base titration. Electrochemical characterization revealed minor reductions in electrochemically active surface area and slight shifts in half-wave and onset potentials. In single-cell testing, however, grafted catalysts enabled improved performance at low ionomer loadings due to enhanced proton conductivity and increased catalyst-layer hydrophilicity, which together promote more efficient proton transport near Pt sites. At higher ionomer contents, performance gains diminished, likely due to unfavorable electrostatic interactions during catalyst-layer formation. Accelerated stress tests indicated that the grafted functionalities remained stable under fuel-cell operating conditions. Overall, diazonium-based sulfonic acid grafting provides a controllable and durable strategy to optimize proton transport and interfacial properties, enabling high performance at reduced ionomer contents.

In polymer electrolyte fuel cells (PEFCs), temperature gradients can exert a substantial influence on cell performance and durability. Monitoring these gradients without perturbing fuel cell operation is one of the main challenges. This study introduces a novel method for remotely mapping fuel cell temperature using ferromagnetic nanoparticles, such as nickel and iron. These nanomediators possess temperature-dependent magnetic properties, enabling neutron depolarization imaging (NDI) to provide insights into the internal fuel cell temperature. We extensively evaluated the main parameters pertaining to the utilization of these nanoparticles in powdered form for temperature sensing. This encompassed an assessment of the minimum detection concentration and temperature sensitivity. Our findings reveal that while the smallest nanoparticles yield the highest relative change in depolarization, they exhibit considerably lower absolute depolarization coefficients. Hence, larger particles emerge as strong candidates for signal detection. Despite the challenges posed by the considerable size of these sensors, which inhibits in-situ dispersion, there is an opportunity to enhance nanoparticle characteristics. Such improvements could be achieved by scaling up the size of the materials from the nanoscale while retaining high magnetic saturation and temperature sensitivity.

ABSTRACT Prognostics and health management are crucial for the reliability and lifetime assessment of polymer electrolyte fuel cells (PEFCs). Here, we review the current advances on this topic, focusing mainly on key degradation mechanisms and methodologies such as physics‐aware, data‐driven, and hybrid modeling approaches. Key open challenges are analyzed, including the need for more accurate degradation modeling, effective management of multi‐stack systems, and advancements in the currently underdeveloped action phase, in which diagnostic and prognostic insights are translated into real‐time system responses, such as dynamic load derating, thermal‐management adjustments, or automated maintenance triggers, to prevent failures and extend PEFC life. While notable strides have been made in recent years in diagnostics and remaining useful life estimation, it remains challenging to seamlessly integrate these insights into actionable strategies. Future directions highlight the need to address data scarcity and advance interdisciplinary research. Key focus areas include sensor integration, artificial intelligence, and digital twins. In addition, material innovations play a crucial role in bridging existing gaps. This work, therefore, intends to map the further development of prognostics and health management systems toward ensuring the viability of PEFCs in practical applications.

Polymer electrolyte fuel cells are paramount for future emission-free mobility. One of the vital challenges for prospering commercialization of PEFCs is water management in the cells. A microporous layer (MPL) is typically positioned between the gas diffusion layer (GDL) and the catalyst layer (CL) to boost the cell performance and facilitate water management. In this study, three different MPLs were investigated, namely, carbon black-based MPLs with different PTFE binder contents (20 wt % PTFE as a base case and 40 wt % PTFE), as well as perforated MPLs with micron-sized pores coated on the same GDL-Substrate (Freudenberg H14). The water content in the membrane, catalyst layers (CL), and MPLs was explored using operando scanning small- and wide-angle X-ray scattering (S/WAXS). At Tcell = 80 °C, relative humidity = 100%, pabs = 3 bar, the MPL with larger pores exhibits slightly higher performance than the base case, while a considerably lower cathode CL and MPL saturation levels were observed for the MPL. In contrast, the MPL with higher amounts of PTFE binder shows lower performance than the base case, with considerably higher cathode CL and MPL saturation levels. 3D representations of how the pores could be filled in the cathode CLs were obtained from operando SAXS profiles using representative structure modeling for the different materials and operating conditions.

Reframing water as a tunable design parameter in polymer electrolyte fuel cells by exploring multiscale perspectives

Effects of diameter ratio between fibers and grains for gas diffusion layer on transport properties via the Shan-Chen method

ABSTRACT The integration of hydrogen fuel cells into aerospace applications is limited by the weight and volume of fuel cell systems. Currently, bipolar plates account for 80 % of fuel cell stack mass and 60 % of its volume. Herein, we leverage a range of advanced manufacturing techniques to develop novel lightweight‐compact porous distributors with ultrahigh power densities. Research begins with a graphene‐coated nickel foam porous distributor, which enhances reactants transport and interfacial conductivity, achieving a power density of 1.52 W/cm 2 , ∼50 % improvement over conventional designs. To further boost gravimetric power density, titanium was adopted as a base material, and porous architectures were optimized using Computational Fluid Dynamics to ensure optimal reactant distribution and water management. To realize these porous titanium designs, two advanced manufacturing techniques were leveraged: laser powder bed fusion (LPBF) and laser micromachining. While the optimized LPBF lattice structure reached 1.36 W/cm 2 , the laser‐patterned non‐homogeneous architecture demonstrated a breakthrough performance of 1.62 W/cm 2 , translating to volumetric and gravimetric power densities of over 10 kW/L and 9 kW/kg, respectively. These values surpass current commercial benchmarks and exceed EU/UK 2030 targets. We demonstrate how integrating digital design, flow control, advanced materials, and manufacturing enables lightweight, high‐power fuel cells, with broader impact on electrolyzers, heat exchangers, and batteries.

Next-generation polymer electrolyte fuel cells (PEFCs)requirepolymer electrolyte membranes (PEMs) capable of operating at temperaturesabove the boiling point of water (100 °C) and under low-humiditybelow 40% RH. In this study, we synthesized poly­(8-(p-styryl)-1-octanephosphonic acid) (soPA), a polymer bearing phosphonicacid groups on the side chains connected via eight-carbon alkylenespacers. soPA was insoluble in water and formed a highly orientedlamellar phase-separated nanostructure with a 2.9 nm domain spacing,consisting of a hydrophobic phase formed by the alkylene spacers andthe polystyrene backbone, and a hydrophilic phase containing the phosphonicacid groups. Despite its lower acid group density compared with poly­(4-(p-styryl)-1-butanephosphonic acid) (sbPA) with shorter four-carbonspacers, the soPA membrane exhibited higher conductivities than sbPA.For instance, soPA achieved conductivities of 4.4 and 7.5 mS cm–1 at 120 °C under 20% and 40% RH, respectively,values which are approximately 4 and 2.9 times higher than those ofsbPA. These enhanced conductivities of soPA can be attributed to thehigher morphological and molecular ordering induced by the nanophaseseparation as well as the greater freedom of motion of the phosphonicacid groups provided by the flexibility of the longer alkylene spacers,which facilitate more efficient proton transfer between them.

Polymer Electrolyte Fuel Cells (PEFCs) are increasingly recognized as a promising power source for electric vehicles (EVs) due to their high energy conversion efficiency and environmental benefits. Among the critical components of PEFCs, bipolar plates play a vital role in gas distribution, current collection, thermal management, and overall system durability. Conventional graphite bipolar plates suffer from limitations such as high cost, poor mechanical strength, corrosion issues, and difficulties in large-scale manufacturing. To overcome these challenges, this study investigates the suitability of metallic bipolar plates as alternatives for PEFC applications in EVs. A systematic evaluation of selected metallic materials—including 316, 310, 317L, and 316L austenitic stainless steels, along with gold-plated aluminium—was carried out using the Weighted Aggregated Sum Product Assessment (WASPAS) method. Key performance criteria such as specific stiffness (E¹ᐟ³/ρ), thermal stress resistance (σf/Eα), thermal diffusion (α/k), and electrical resistivity (µΩ·cm) were considered. Equal weights were assigned to all criteria to ensure unbiased comparison. Experimental characterization and normalization of data were performed, followed by weighted decision matrix construction and preference score calculation using both Weighted Sum Model (WSM) and Weighted Product Model (WPM). The results reveal that gold-plated aluminium achieved the highest overall rank, indicating superior performance under the selected criteria, while 310 austenitic stainless steel ranked lowest. The findings demonstrate the effectiveness of the WASPAS method in material selection and highlight the potential of metallic bipolar plates—particularly aluminium with protective coatings—for improving the performance, efficiency, and longevity of PEFC systems in electric vehicles.

Developing oxygen reduction reaction (ORR) catalysts with both high catalytic activity and durability is essential for the commercialization of polymer electrolyte fuel cells (PEFCs). One promising strategy to simultaneously enhance the catalytic activity and durability of Pt-based catalysts is surface modification with Au, which has led to substantial durability improvements in various catalysts such as bulk electrodes, nanowires, and core-shell structures. In this study, octahedral Pt-Ni nanoparticles (oct-Pt-Ni NPs), which are known to exhibit exceptionally high ORR activity, were synthesized and modified with Au using a continuous flow reactor to investigate the effects of Au modification on catalytic activity and durability. The flow synthesis enabled uniform Au deposition on individual nanoparticles owing to the rapid mixing and homogeneous contact between the Au precursor and Pt-Ni nanoparticles. Electrochemical measurements revealed that Au modification enhanced the specific activity (SA) by up to 1.5 times, while the mass activity (MA) remained nearly unchanged owing to the decrease in electrochemical surface area of Pt. The activity enhancement suggests that Au atoms promote the catalytic activity of the neighboring Au-free Pt-Ni sites as previously reported. In contrast, the MA of Au-modified oct-Pt-Ni NPs rapidly decreased within several hundred potential cycles along with the decrease in the SA, indicating that Au atoms on the Pt-Ni nanoparticles could not effectively suppress Ni leaching or morphological transformation. These results suggest that the beneficial effect of Au modification on durability is limited for shape-sensitive catalysts with numerous vulnerable edges and corners such as oct-Pt-Ni nanoparticles, unlike the spherical or nanowire catalysts with smooth or well-faceted surfaces.

Conventional physics‐based fuel cell models have faced limitation in explaining the through‐plane liquid water distributions observed by state‐of‐the‐art imaging techniques. To elucidate these experimental findings, we advance a temperature‐dependent phase separation model (TDPSM) framework by introducing separate liquid transport equations for each porous constituent. The proposed theoretical framework incorporates relative hydrophobicity at overlapping interfaces and employs a volume‐averaging scheme to reveal the physics underlying optical liquid visualization. A novel validation approach is proposed, enabling simultaneous prediction of through‐plane liquid profiles and conventional polarization curves with strong agreement to experimental data. Extensive numerical simulations comparing water transport scenarios with and without a microporous layer (MPL) integrate previously fragmented experimental findings on the MPL’s dual role. The study also presents water management strategies for two operating regimes: (i) low‐temperature high‐humidity (LTHH), where liquid flooding dominates, and (ii) high‐temperature low‐humidity (HTLH), where membrane dehydration presents an emerging industrial challenge. Under LTHH conditions, a hydrophobicity order of catalyst layer (CL) > MPL > gas diffusion layer (GDL) establishes an interfacial liquid pump that enables effective liquid removal. In contrast, under HTLH operation, a more hydrophobic MPL relative to the CL (MPL > CL) forms an interfacial barrier that sustains reliable membrane water retention. Overall, this theoretical framework redefines water management as a synergistic outcome of relative hydrophobic characteristics between adjacent porous layers, rather than as properties of isolated components.

Distribution of Water Molecules in Proton Exchange Membrane in Running Polymer Electrolyte Fuel Cell by Non–Linier Raman Scattering Spectroscopy