Establishing the Link Between Oxygen Vacancy and Activity Enhancement in Acidic Water Oxidation of Trigonal Iridium Oxide

Abstract Developing durable IrO 2 ‐based electrocatalysts with high oxygen evolution reaction (OER) activity under acidic condition is crucial for proton exchange membrane electrolyzers. While oxygen defects are considered potentially important in OER, their direct relationship with catalytic activity has yet to be established. In this study, we introduced abundant oxygen vacancies through Re doping in 2D IrO 2 (Re 0.03 Ir 0.97 O 2 ), demonstrating their decisive role in enhancing OER performance. The Re 0.03 Ir 0.97 O 2 catalyst exhibited excellent OER performance with an overpotential of 193 mV at 10 mA cm −2 and sustained activity for over 650 hours, significantly surpassing the undoped catalyst. Moreover, it maintained operation at a cell voltage of 1.70 V (~1200 mA cm −2 ) for over 140 hours without significant performance degradation. Theoretical calculations coupled with cyclic voltammetry, transient potential scanning and in situ characterizations confirmed the adsorbate evolving mechanism on Re 0.03 Ir 0.97 O 2 , as well as the critical role of Re‐induced oxygen vacancies in enhancing OER performance. These findings highlight that oxygen defects directly influence OER activity, providing guidance for the application of oxygen vacancy engineering in electrocatalyst design.