Phosphorus and sulfur co-doped nickel molybdate with rich-oxygen vacancies for efficient water splitting

The rational design of high-performance electrocatalysts is essential for promoting the industrialization of electrocatalytic water-splitting technology. Herein, phosphorus and sulfur co-doped nickel molybdate with rich-oxygen vacancies (P, S-NiMoO₄) was prepared as an efficient bifunctional self-supporting water-splitting catalyst from the perspective of enhancing the conductivity and optimizing the electronic configurations. The incorporation of P, S and oxygen vacancies greatly enhances the conductivity and charge-transfer efficiency of NiMoO₄. Additionally, P and S can serve as proton carriers and electron acceptors to enhance the catalytic activity by accelerating proton activation and high-valent metal generation in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As expected, P, S-NiMoO₄ demonstrates efficient bifunctional catalytic activity with an overpotential of only 31/206 mV at 10 mA cm^-2 for HER/OER in 1 M KOH. Meantime, the electrolyzer assembled with P, S-NiMoO₄ as electrodes requires a voltage of only 1.55 V to achieve a water-splitting current density of 50 mA cm^-2 along with good stability over 110 h. This work puts forward a novel approach based on elemental doping and vacancy engineering for the design of effective and enduring catalysts for water splitting.