Enhanced Acidic Water Oxidation by Dynamic Migration of Oxygen Species at the Ir/Nb2O5−x Catalyst/Support Interfaces

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 Nb2O5−x supported iridium (Ir/Nb2O5−x) as a model catalyst, we uncovered the dynamic migration of oxygen species between IrOx and Nb2O5−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 over‐oxidation via spontaneously delivering excessive oxygen from IrOx to Nb2O5−x. The optimized Ir/Nb2O5−x thus demonstrated exceptional performance in scalable water electrolyzers, i.e., only need 1.839 V to attain 3 A cm−2 (surpassing the DOE 2025 target), and no activity decay during a 2000 h test at 2 A cm−2. The dynamic migration of oxygen species between oxide support and Ir catalyst during OER is uncovered. These migrations not only regulate the in situ Ir catalytic structure towards boosted activity, but also suppress Ir over‐oxidation via oxygen species transference, thereby ensuring overall high performance in PEM water electrolyzer.