Ir Single-Atom-Induced Localized Oxide Path Mechanism Enables Efficient and Stable Water Oxidation.

Alkaline anion exchange membrane water electrolyzers (AEMWEs), which combine the high current density of proton-exchange membrane electrolyzers with the low cost of alkaline electrolyzers, have emerged as a premier technology for scalable green hydrogen production. Overcoming the sluggish kinetics of the oxygen evolution reaction is critical to enabling sustainable hydrogen production. Herein, we present iridium single-atom catalysts supported on nickel-iron borides (Ir-NiFeB), in which isolated Ir atoms with Ir-O-Ni/Fe coordination trigger direct O-O radical coupling at oxygen-bridged dual-metal centers, thereby inducing a mechanistic transition from the adsorption evolution mechanism (AEM) to the localized oxide path mechanism (OPM). The Ir-mediated electron injection optimizes the d-band center and the electronic structure, as corroborated by a significant reduction in the reaction energy barrier under the OPM. This mechanistic optimization endows Ir-NiFeB with an overpotential of 190 mV at 10 mA cm-2 under alkaline media. The AEMWE with Ir-NiFeB at the anode achieved a cell voltage of 1.7 V at 1 A cm-2 and maintained stable operation exceeding 500 h. Remarkably, considering electricity consumption alone, the AEMWE achieves energy efficiencies of 87% and 73% at 1 A cm-2, based on the higher and lower heating values of hydrogen, respectively, thereby potentially producing hydrogen at an energy consumption of 45.2 kWh kg-1 and a cost of $0.90 per kg. This work demonstrates that atomic-scale coordination engineering can activate the OPM, overcoming AEM limitations and offering a scalable strategy for practical, high-performance electrolysis with minimal noble metal loading.