Beyond single modulation: Synergistic Mo doping and S-vacancy engineering in NiS2 for efficient water electrolysis

The pursuit of efficient and cost-effective bifunctional electrocatalysts to replace precious-metal-based materials is crucial for sustainable hydrogen production through overall water splitting. While nickel disulfide (NiS 2 ) has shown promise as a candidate material, its practical application is hindered by inadequate electronic structure and poor electrical conductivity. Herein, we demonstrate a synergistic strategy involving molybdenum doping and sulfur vacancy engineering to substantially improve the electrocatalytic performance of NiS 2 . The resulting Mo-doped NiS 2 acts as an efficient bifunctional catalyst for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Impressively, the optimized catalyst achieves competitive overpotentials of 158 mV for OER (at 10 mA cm −2 in 1.0 M KOH) and 240 mV for HER (at 10 mA cm −2 in 0.5 M H 2 SO 4 ). Density functional theory (DFT) calculations further disclose that the synergy between Mo dopants and sulfur vacancies upshifts the d -band center towards the Fermi level and optimizes the adsorption free energy of key intermediates, thereby accelerating the reaction kinetics. This study not only demonstrates a superior bifunctional electrocatalyst, but more importantly, elucidates a universal synergistic mechanism of heteroatom-doping and vacancy engineering for precise electronic structure modulation, which provides a general design principle for advanced energy conversion materials. • Mo-NiS 2 with S vacancies was synthesized via one-step hydrothermal method. • Mo 0.01 -NiS 2 exhibits excellent OER/HER bifunctional activity. • DFT calculations reveal the synergy optimizes intermediate adsorption energy.