Ni/Ru Doping‐Induced Oxygen Vacancy of Cobalt Oxide Boosts Hydrogen Evolution Reaction for Water Splitting

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Cobalt oxide electrocatalysts often require Ru‐containing modification to overcome sluggish hydrogen evolution reaction (HER) kinetics. However, the enhanced water dissociation enabled by Ru may be accompanied by excessive adsorption of the adsorbed hydroxyl (OH ad ), leading to active‐site blocking and limited overall HER activity. Here, a dual cation‐doping strategy was proposed to balance water dissociation with OH ad desorption. Specifically, a Ni/Ru‐modified spinel Co 3 O 4 electrocatalyst (NiRuCoO x ) has been developed and demonstrated high efficiency for HER and water splitting. Dual metal incorporation induced oxygen vacancies and charge redistribution, thereby modulating the metal‐oxygen covalency and weakening the strong interaction between active sites and OH ad during the HER process. As a consequence, NiRuCoO x delivered a low HER overpotential of 29 mV at 10 mA cm −2 . It also exhibited good performance in oxygen evolution reaction (OER, 270 mV overpotential at 10 mA cm −2 ). For overall water splitting, the NiRuCoO x bifunctional electrode could reach 10 mA cm −2 with a low voltage of 1.538 V. This work offers valuable insights into oxygen vacancy‐accelerated HER kinetics and provides a new paradigm for designing efficient water‐spitting electrocatalysts.