Unveiling Local Aging Patterns Following Accelerated Stress Testing of High-Performance Polymer Electrolyte Fuel...

This study presents an in-depth analysis of heterogeneous aging patterns in membrane electrode assemblies (MEAs) subjected to diverse accelerated stress test (AST) conditions, simulating carbon corrosion (CC AST) and Pt particle size growth in fully humidified (Pt AST-Wet) and underhumidified (Pt AST-Dry) H₂/N₂ atmospheres. Multimodal characterization techniques are used to focus on heterogeneous aging patterns, primarily examining the variations in current distributions and Pt particle size maps. The findings reveal distinct characteristics of current distributions for all the AST cases, with substantial changes and strong current gradients in the CC AST case, indicative of severe performance degradation. Notably, despite significant differences in Pt particle size growth at the end-of-life (EOL), the Pt AST-Wet and Pt AST-Dry cases show minor changes in spatial current distributions. Moreover, a preferential growth of Pt particles under serpentine flow field bends in the Pt AST-Wet case is observed for the first time. This study provides crucial insights into the role of mass transport properties in shaping fuel cell performance, and highlights the need to consider factors beyond electrochemically-active surface area (ECSA) when assessing fuel cell durability.