Degradation behavior and mechanism of a reinforced high-temperature-stable PFSA membrane electrode assembly at 105 °C

Raising the operating temperature of proton exchange membrane fuel cells (PEMFCs) above 100 °C is an important route toward simplified thermal management and higher power density in heavy-duty and aviation applications, yet the durability of perfluorosulfonic acid (PFSA) membrane electrode assemblies (MEAs) in this regime remains a key challenge. Here, we report an approximately 350 h steady-state durability study of a reinforced, high-temperature-stable PFSA MEA operated at 105 °C and 1.6 A cm −2 . The cell exhibited a gradual voltage decay for approximately 262 h before transitioning to an accelerated degradation stage, defining a two-stage durability behavior resolvable from continuous voltage monitoring. Pre- and post-aging sensitivity mapping reveals region-dependent losses: hydrogen-crossover-induced mixed potentials and loss of electrochemical accessibility dominate at low current densities, whereas mass-transport resistance and triple-phase-boundary deterioration dominate at high current densities. Multiscale characterization links these signatures to a self-accelerating pathway: hydrogen crossover amplifies 11.9-fold as the membrane thins from 14.4 to 12.8 μm, the carbon support becomes disordered, and the glass-transition temperature rises by 6.2 °C. These results establish an experimentally grounded durability benchmark for reinforced high-temperature PFSA MEAs and pinpoint membrane defect tolerance and interfacial robustness as important design priorities for next-generation high-temperature fuel cells.