Operational Stability Factor: A Comprehensive Metric for Assessing Catalyst Durability in Dynamic Water Electrolyzer Conditions

The durability of water electrolyzer catalysts is a critical challenge for sustainable hydrogen production, particularly under dynamic operating conditions from renewable energy fluctuations. Conventional stability analyses fail to account for degradation mechanisms outside the oxygen evolution reaction (OER) range, particularly at low potentials during system downtime. In here, we reveal that degradation arises not only from OER activity but also from redox transitions of the support material at low potentials using iridium-supported manganese oxide (Ir-MnO 2 ) and IrOx as a model system. To address this gap, we propose the Operational Stability Factor (OSF), a metric that evaluates catalyst stability under dynamic (intermittent) operation scenarios. OSF provides critical insights into catalyst behavior during load fluctuations. Furthermore, OSF enables a quantitative assessment of catalyst lifespan, contributing to the feasibility of green hydrogen production. By integrating OSF into catalyst development and operational strategies, this study offers a transformative approach to designing more durable electrocatalysts and optimizing their operating conditions.