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.
Wang et al. (Fri,) studied this question.