Correlating Catalyst Growth with Liquid Water Distribution in Polymer Electrolyte Fuel Cells

This study investigates the impact of liquid water distribution in a polymer electrolyte fuel cell (PEFC) on the spatially heterogeneous platinum (Pt) catalyst degradation. The membrane electrode assemblies (MEAs) are aged using accelerated stress tests (ASTs) in varied cathode gas environments (N2 and air) to instigate Pt catalyst degradation. The study employs high‐resolution neutron imaging and synchrotron micro‐X‐ray diffraction (micro‐XRD) to map liquid water distribution and Pt particle size, respectively. Neutron radiographs reveal liquid water accumulation primarily within the diffusion media, especially under flow field lands, due to thermal resistance differences between channels and lands. Aged MEAs exhibit increased water retention, likely due to increased hydrophilicity of the diffusion media with aging. Synchrotron micro‐XRD maps unveil significant heterogeneity in Pt particle size distribution in the aged MEAs, correlated with preferential liquid water accumulation under flow field lands. This study highlights the critical role of flow field design and water distribution in catalyst degradation, underscoring the need for innovative strategies to enhance fuel cell durability and performance. This study examines how liquid water distribution in polymer electrolyte fuel cells impacts catalyst degradation. High‐resolution neutron imaging and synchrotron micro‐X‐ray diffraction quantify the liquid water distribution and platinum (Pt) catalyst growth, respectively. The results show that water accumulates under flow field lands, exacerbating Pt catalyst growth, and emphasize the role of flow field design in fuel cell durability.