Iron-Decorated VS _<b>2</b> 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-VS2) 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 VS2 nanosheets significantly enhances its bifunctional electrocatalytic activity for both the HER and OER in alkaline and natural seawater electrolytes. The optimized Fe(10)-VS2 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)-VS2 exhibits overpotentials of only 285 and 340 mV, respectively, at 200 mA cm–2. Further, overall water splitting using the optimized Fe-VS2 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 VS2 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.