Buffering the Active State for Proton Exchange Membrane Water Electrolysis

ABSTRACT Proton exchange membrane water electrolysis (PEMWE) is a key technology for renewable hydrogen production. In order to achieve large‐scale commercialization, acidic oxygen evolution reaction (OER) catalysts are required to simultaneously deliver high activity, long durability, and low noble‐metal loading. However, under realistic device operation, catalyst failure is mainly associated with the disruption of the active state, which is driven by coupled processes including active‐species redistribution, oxygen‐framework degradation, oxidative stress accumulation, proton‐transfer imbalance, and mechanistic drift. Accordingly, this review proposes a catalyst‐centered design framework that targets the root factors responsible for active‐species dissolution, buffering and sustaining the active state during PEMWE device operation. Within this framework, the buffering strategies are classified into five categories, including mobility and topology buffering, oxygen‐framework buffering, electron buffering, proton‐water‐ion programming, and the mechanistic dial. Finally, this review outlines how buffered active states can be rationally designed for Ir, Ru, and non‐platinum group metals (PGM) anodes, providing a forward‐looking roadmap for practical PEMWE catalyst development.