An opinion on catalyst degradation mechanisms during catalyst support focused accelerated stress test (AST) for proton exchange membrane fuel cells (PEMFCs)

Accelerated stress test (AST) protocol meant to study the durability of catalyst support in a polymer electrolyte membrane fuel cell (PEMFC) electrode has been critically evaluated. For nanoparticulate catalysts supported on high surface area conductive materials (e.g. Pt/C), potential cycling meant to study the support durability causes significant impact on the catalyst particles presumed to be passivated due to formation of oxide layer. X-ray diffraction (XRD) patterns of pre-AST and post-AST samples suggest significant change in crystallite size during potential cycling between 1.0 and 1.6 V (vs. RHE), which may be considered to growth induced by dissolution/redeposition rather than particle growth through agglomeration due to support corrosion. Significant (∼50%) electrochemical surface area loss due to catalyst particle growth during support corrosion AST should be taken into account while development/screening of durable catalyst supports. To reduce such contribution, frequent observation cycle should be minimized.