Impacts of Pt/Carbon Black Catalyst Surface Hydrophilicity on Ionomer Distribution and Durability during Water-Generating Load Cycling of Polymer Electrolyte Fuel Cells

The performance of polymer electrolyte fuel cells (PEFCs) is significantly influenced by the MEA structure and ionomer dispersibility. In this study, we modulated the catalyst surface hydrophilicity through surface treatment and assessed its impact on ionomer dispersibility and durability. The surface hydrophilicity was compared using nitrogen and water vapor adsorption measurements, while functional groups were analyzed using the surface-sensitive technique TOF-SIMS. Excessively hydrophilic catalysts with numerous functional groups demonstrated poor ionomer dispersion and reduced gas diffusivity due to water accumulation. Conversely, decreased hydrophilic catalysts with moderate functional groups displayed optimal ionomer dispersibility and superior I-V performance. Durability tests using water-generated load cycles revealed that a decreased hydrophilicity catalyst exhibited enhanced durability due to its moderate wettability. Our findings suggest that appropriate control of the catalyst surface condition can facilitate an improved MEA structure and its durability.