Vanadium-doped Ni3S2 nanosheets for low-overpotential hydrogen evolution and sulfide removal

Replacing the sluggish anodic oxygen evolution reaction (OER) with the sulfide oxidation reaction (SOR), which possess a low thermodynamic oxidation potential, is an effective strategy to lower the energy consumption of the cathodic hydrogen evolution reaction (HER) while enabling the resource recovery of sulfide pollutants. However, enhancing the catalytic activity and stability of electrocatalysts for both the HER and SOR in sulfide-containing solutions remains a significant challenge. In this work, a nanoflower-like V-doped Ni 3 S 2 catalyst grown on nickel foam (V–Ni 3 S 2 /NF) was synthesized via a one-step hydrothermal method. Experimental results confirm that V doping effectively modulates the electronic structure of Ni 3 S 2 , thereby enhancing its intrinsic catalytic activity. As a consequence, the V–Ni 3 S 2 /NF-2 catalyst delivers an exceptionally low SOR overpotential of 0.283 V at a current density of 10 mA cm −2 , together with excellent long-term stability. In-situ Raman analysis unveils a stepwise sulfide oxidation pathway, where S 2− species are initially converted to short-chain polysulfides and subsequently oxidized to S 8 . Moreover, the electrode exhibits outstanding bifunctional characteristics toward HER and SOR, requiring only 0.442 V to simultaneously achieve hydrogen evolution and sulfide removal at 10 mA cm −2 , which is substantially lower than the energy required for overall water splitting (1.56 V). Prepared through a straightforward binder-free and noble-metal-free strategy, the V–Ni 3 S 2 /NF-2 catalyst combines low cost with potential practical applicability, presenting a promising approach for concurrent hydrogen production and sulfide valorization.