Enriched Oxygen Coverage Localized within Ir Atomic Grids for Enhanced Oxygen Evolution Electrocatalysis

Abstract Inefficient active site utilization of oxygen evolution reaction (OER) catalysts have limited the energy efficiency of proton exchange membrane (PEM) water electrolysis. Here, an atomic grid structure is demonstrated composed of high‐density Ir sites (≈10 atoms per nm²) on reactive MnO_2–x support which mediates oxygen coverage‐enhanced OER process. Experimental characterizations verify the low‐valent Mn species with decreased oxygen coordination in MnO_2–x exert a pivotal impact in the enriched oxygen coverage on the surface during OER process, and the distributed Ir atomic grids, where highly electrophilic Ir─O^(II‐δ)− bonds proceed rapidly, render intense nucleophilic attack of oxygen radicals. Thereby, this metal‐support cooperation achieves ultra‐low overpotentials of 166 mV at 10 mA cm⁻² and 283 mV at 500 mA cm⁻², together with a striking mass activity which is 380 times higher than commercial IrO₂ at 1.53 V. Moreover, its high OER performance also markedly surpasses the commercial Ir black catalyst in PEM electrolyzers with long‐term stability.