Probing Sulfur‐Mediated Surface Dynamics in Oxomolybdate Nano‐Rods toward Efficient Oxygen Evolution

Abstract This study offers strategic approach to enhance oxygen evolution reaction (OER) by synthesis of sulfur‐doped nickel molybdate (S‐NiMoO 4 ) using a one‐pot hydrothermal approach. The optimized catalysts, featuring 10% S doping, reveals a remarkable activity with an overpotential of 289 mV at a current density of 10 mA cm −2 , with a high turnover frequency (TOF) of 0.465 s −1 and a low charge transfer resistance (6.6 Ω). Structural and surface analysis confirm successful sulfur incorporation and subsequent surface reconstruction during OER, leading to the formation of catalytically active SO 4 2 − species. DFT calculations reveal that S doping and subsequent SO 4 2 − adsorption, shift the d‐band center closer to the Fermi level, facilitating enhanced OH − adsorption and improve M─O binding interactions critical for OER. Further, the S‐NiMoO 4 improves the OER activity by modifying the electrode‐electrolyte interface and promoting Ni 3+ /Ni 4+ redox transitions. A volcano‐type relationship between surface charge accumulation and current density establishes 10% S doping as the ideal condition for balanced electronic and catalytic properties. Excellent durability over 30 h and faradic efficiency of 92% obtained. This study demonstrates the dual function of sulfur in surface reconstruction and lattice doping, providing a viable approach for creating long‐lasting and effective anion‐modified electrocatalysts.