Electronic and Vacancy Engineering of Mo–RuCoO_x Nanoarrays for High‐Efficiency Water Splitting

Abstract Exploring efficient strategies to achieve novel high‐efficiency catalysts for water splitting is of great significance to develop hydrogen energy technology. Herein, unique molybdenum (Mo)‐doped ruthenium–cobalt oxide (Mo–RuCoO_x) nanosheet arrays are prepared as a high‐performance bifunctional electrocatalyst toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through combining electronic and vacancy engineering. Theoretical calculations and experimental results reveal that the incorporation of Ru and Mo can effectively tune the electronic structure, and the controllable Mo dissolution coupling with the oxygen vacancy generation during surface reconstruction is able to optimize the adsorption energy of hydrogen/oxygen intermediates, thus greatly accelerating the kinetics for both HER and OER. As a result, the Mo–RuCoO_x nanoarrays exhibit remarkably low overpotentials of 41 and 156 mV at 10 mA cm⁻² for HER and OER in 1 m KOH, respectively. Furthermore, the two‐electrode electrolyzer assembled by the Mo–RuCoO_x nanoarrays requires a cell voltage as low as 1.457 V to achieve 10 mA cm⁻² for alkaline overall water splitting. This work holds great promise to develop novel and highly active electrocatalysts for future energy conversion applications.