Buffering the Active State for Proton Exchange Membrane Water Electrolysis

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.