Post-Mortem Analysis of PEMFC Stacks after Accelerated and Long-Term Testing under Realistic Automotive Operating Conditions

This study presents post-mortem analyses of polymer electrolyte membrane fuel cell (PEMFC) stacks operated using previously published accelerated durability test (ADT) protocols. Each ADT, lasting 1,200 h, was derived from a 5,500 h automotive-relevant reference test and designed to isolate the effects of load cycling, operating temperature, and humidity cycling. All major membrane electrode assembly components, the membrane, catalyst layers, and gas diffusion layers (GDL), were characterized using SEM, EDX, IR thermography, contact angle measurements and XPS, and the results then correlated with prior in situ diagnostics. Elevated temperature and humidity cycling were identified as the most detrimental stressors under system-relevant operating conditions that included voltage clipping at 850 mV. These conditions led to accelerated carbon corrosion, increased platinum dissolution and cobalt leaching in the cathode catalyst layer, as well as a significant loss of hydrophobicity in the GDL. The membrane remained structurally stable, although localized stress indicators were observed. The results confirm that the applied ADT protocols successfully reproduce realistic degradation patterns and enable a differentiated assessment of stressor-specific aging phenomena. This provides a robust basis for refining accelerated stack testing methodologies and optimizing operating conditions for improved PEMFC stack durability.