Toward modeling and mechanistic understanding of iridium oxide catalyst degradation in PEM water electrolysis

To achieve net-zero emissions by 2050, large-scale deployment of proton exchange membrane (PEM) water electrolysis for green hydrogen production is essential. Reliable estimates of hydrogen production costs and iridium (Ir) demand require a comprehensive understanding of iridium oxide anode degradation and the ability to predict catalyst lifetime under realistic operating conditions. This review builds on mechanistic insights from liquid-electrolyte studies and highlights differences in degradation behavior under device-relevant environments. We summarize key degradation mechanisms of Ir oxide catalysts, focusing on Ir dissolution, and review recent advances in analysis under cell-relevant conditions, including membrane electrode assembly (MEA) testing and gas diffusion electrode (GDE) approaches. We further discuss emerging modeling frameworks that link these regimes to predict catalyst degradation and performance loss. The insights and challenges identified here provide guidance for designing low-Ir electrodes and optimizing operating protocols toward durable and efficient PEM water electrolysis systems.