Regulating Electron Redistribution of Intermetallic Iridium Oxide by Incorporating Ru for Efficient Acidic Water Oxidation

Developing high-performance electrocatalysts to catalyze water splitting for the generation of sustainable hydrogen remains a challenge in proton exchange membrane (PEM) electrolyzers. However, the only applicable IrO x in PEM electrolyzers for oxygen evolution reaction (OER) with a multiproton-coupled process, requires a higher standard due to the weak oxygen bonding on Ir sites, which causes high overpotential and poor stability under oxidative and acidic conditions. Herein, the intermetallic Ru 1 Ir 1 O x is synthesized through incorporation of Ru into IrO x , which exhibits a record overpotential of 204 mV (10 mA cm −2 geo ) and excellent stability of 110 h (100 mA cm −2 geo ) with a high stability number (1.13 × 10 6 ) toward the acidic OER. Through fine characterizations, Ir sites with lower than +4 valence state are observed due to charge redistribution, in turn enhancing the acidic OER performance. Theoretical calculations reveal that incorporation of Ru effectively moves the Fermi level to the Ir 5d band center, thus enhancing the adsorption of oxygen intermediates and decreasing the energy barrier of the potential-determining step from 1.02 to 0.65 eV. The decreased valence states of Ir and enhanced valence state of Ru due to the charge redistribution significantly tunes the electronic structure of Ir sites, thereby drastically enhancing the OER performance.