Abstract: Replacing the energy-intensive oxygen evolution reaction with the thermodynamically more favorable sulfide oxidation reaction (SOR) is an effective strategy for achieving energy-saving hydrogen production while simultaneously recovering high-value sulfur products. However, uncontrollable solid sulfur deposition on the anode surface tends to cause active site passivation and sluggish reaction kinetics, severely impacting catalyst stability. Here, a cobalt‑molybdenum co‑doped nickel sulfide electrocatalyst with a unique "amorphous‑microcrystalline" heterostructure (CoMoNiS_x/NF) is fabricated on nickel foam via a two‑step hydrothermal method. Benefiting from an in‑situ constructed CoMoO₄/sulfide hydrophilic interface and abundant S₂^2- defect sites, the catalyst exhibits excellent SOR performance, delivering a current density of 100 mA·cm^-2 at an ultralow overpotential of just 0.28 V (vs. RHE) and operating stably for over 300 h. The in-situ generated polysulfides during the SOR process under alkaline conditions are soluble in the electrolyte system, which significantly suppresses the deposition of solid sulfur on the electrode surface and thus prevents electrode passivation. Furthermore, the assembled SOR||HER two‑electrode electrolyzer requires a cell voltage of only 1.0 V to reach 100 mA·cm^-2, achieving a Faradaic efficiency of 98.6% for hydrogen production.

Key words: sulfide oxidation reaction, hydrogen evolution reaction, amorphous-nanocrystalline heterostructure, disulfide defects, energy-saving hydrogen production and sulfur recovery