Insights into the degradation mechanisms of anode catalyst accelerated by H2 crossover for thinner PEM water electrolyzer

Adopting thin proton exchange membranes (PEM) with low iridium loading to fabricate membrane electrode assemblies (MEAs) for PEM water electrolysis is the most efficient cost-reduction route by enhancing operating current density. However, the MEA degradation induced by thin membranes is critical to address. In this study, an IrO 2 /TiO 2 core-shell catalyst was synthesized via hydrolysis, and MEAs with 0.5 mg cm −2 iridium loading were prepared to investigate their durability under accelerated stress test (AST). The MEA based on thin NR212 showed a higher degradation rate (52 μV·h −1 ) than those based on N115 (16 μV·h −1 ) and N117 (−3 μV·h −1 ) membranes. Electrochemical analysis and BOT/EOT catalyst characterization revealed that hydrogen crossover through NR212 accelerated IrO 2 phase transformation into soluble metallic Ir and IrOOH, aggravated TiO 2 support corrosion and core-shell collapse, reduced catalytic layer conductivity, and thus accelerated performance degradation. This work elucidates the H 2 crossover-induced degradation mechanism of thin-film low-iridium MEAs and highlights the significance of H 2 crossover suppression for PEM electrolyzer cost reduction. • A low-iridium (0.5 mg cm −2 ) IrO 2 /TiO 2 core-shell ACL was constructed via the hydrolysis method. • Thinner PEM (NR212, 50 μm) promotes initial PEMWE performance but exhibits a much faster degradation rate (52 μV h −1 ) under a square-wave protocol. • Hydrogen crossover synergizes with high potential to induce IrO 2 phase transformation and TiO 2 corrosion, causing active site loss and increased catalytic layer resistance. • The synergistic effect of potential and hydrogen accelerated degradation of the low-Ir PEMWE performance.