The poor stability of Ru-based acidic oxygen evolution (OER) electrocatalysts has greatly hampered their application in polymer electrolyte membrane electrolyzers (PEMWEs). Traditional understanding of performance degradation centered on influence of bias fails in describing the stability trend, calling for deep dive into the essential origin of inactivation. Here we uncover the decisive role of reaction route (including catalytic mechanism and intermediates binding strength) on operational stability of Ru-based catalysts. Using MRuOx (M = Ce4+, Sn4+, Ru4+, Cr4+) solid solution as structure model, we find the reaction route, thereby stability, can be customized by controlling the Ru charge. The screened SnRuOx thus exhibits orders of magnitude lifespan extension. A scalable PEMWE single cell using SnRuOx anode conveys an ever-smallest degradation rate of 53 μV h−1 during a 1300 h operation at 1 A cm−2.

Catalyst/support interaction plays a vital role in catalysis towards acidic oxygen evolution (OER), and the performance reinforcement is currently interpreted by either strain or electron donation effect. We herein report that these views are insufficient, where the dynamic evolution of the interface under potential bias must be considered. Taking Nb 2 O 5À x supported iridium (Ir/Nb 2 O 5À x ) as a model catalyst, we uncovered the dynamic migration of oxygen species between IrO x and Nb 2 O 5À x during OER. Direct spectroscopic evidence combined with theoretical computation suggests these migrations not only regulate the in situ Ir structure towards boosted activity, but also suppress its overoxidation via spontaneously delivering excessive oxygen from IrO x to Nb 2 O 5À x . The optimized Ir/Nb 2 O 5À x thus demonstrated exceptional performance in scalable water electrolyzers, i.e., only need 1.839 V to attain 3 A cm À 2 (surpassing the DOE 2025 target), and no activity decay during a 2000 h test at 2 A cm À 2 .