Vanadium-Doped Ni₃S₂: Morphological Evolution for Enhanced Industrial-Scale Water and Urea Electrolysis

The development of an earth abundant, cost-effective, facile and multifunctional 3D-porous catalytic network for green hydrogen production is a tremendous challenge. Herein, we report the V-Ni₃S₂ self-supported catalytic network with optimized morphology grown directly on nickel foam (NF) by the one-step hydrothermal technique for water and urea electrolysis at industrial scale hydrogen generation. The morphology of Ni₃S₂ was modulated by doping of different concentrations of vanadium from granules to cross-linked wires to hierarchal nanosheets arrays, which is beneficial in electrochemical charge and mass transport, and generates more exposed active sites. The V-Ni₃S₂ catalyst requires the overpotential of 147 mV for hydrogen evolution reaction (HER). The OER and UOR half-cell reaction on V-Ni₃S₂ catalyst requires potential 1.57 V and 1.39 V (vs RHE), respectively to generate current 100 mA/cm². The water electrolysis cell developed by V-Ni₃S₂ as both anode and cathode generates 100 mA/cm² at cell voltage of 1.88 V in laboratory condition (1 M KOH, 25 °C) and 1.61 V at industrial condition (5 M KOH, 80 °C) and also shows considerable stability for 82 hr at current 300 mA/cm². The urea electrolysis cell with 1 M KOH and 0.33 M urea generates 100 mA/cm² at a cell voltage of 1.73 V, which is 150 mV less than that required for water electrolysis and demonstrate stability for 85 hr at a current of 100 mA/cm². The results provide an innovative plan for the considerate synthesis and design of bifunctional catalysts for energy storage and water splitting.