Iron-Decorated VS ₂ Nanosheets as a Bifunctional Catalyst for Alkaline Water/Seawater Electrolysis

Development of resilient, stable, and cost-effective bifunctional electrocatalysts from earth-abundant materials for hydrogen and oxygen evolution reactions (HER and OER) under harsh alkaline and natural seawater conditions has gained significant attention for large-scale electrocatalytic water splitting toward sustainable green hydrogen production and usage technologies. In this work, we report the synthesis of highly active and durable iron-decorated vanadium sulfide (Fe-VS 2 ) nanosheets, supported on conductive nickel foam (NiF) via a simple one-pot hydrothermal method, as a promising bifunctional electrocatalyst for efficient alkaline/natural seawater electrolysis. The controlled incorporation of iron in VS 2 nanosheets significantly enhances its bifunctional electrocatalytic activity for both the HER and OER in alkaline and natural seawater electrolytes. The optimized Fe(10)-VS 2 electrocatalyst demonstrates low overpotentials of 256 and 216 mV at 20 mA cm –2 for HER in 1 M KOH and alkaline seawater (SW + 1 M KOH), respectively, along with a promising Tafel slope (114 mV dec –1 in alkaline natural seawater), close to the benchmark Pt/C catalyst. For OER, in the same electrolyte conditions, Fe(15)-VS 2 exhibits overpotentials of only 285 and 340 mV, respectively, at 200 mA cm –2 . Further, overall water splitting using the optimized Fe-VS 2 bifunctional electrocatalyst requires cell potentials of 1.93 and 1.97 V to achieve a current density of 100 mA cm –2 in 1 M KOH and SW + 1 M KOH, respectively, while maintaining excellent electrochemical stability under harsh electrolytic conditions. The superior performance arises from the synergistic effects of the nanosheet morphology with abundant active sites, Fe-induced electronic and structural activation of VS 2 and the conductive Ni foam substrate enabling charge transport. Moreover, the one-pot method offers a feasible and economical synthesis route, paving the way for the development of non-noble, low-cost electrocatalysts for industrial-scale seawater splitting applications.