Electrochemically Engineered Domain: Nickel–Hydroxide/Nickel Nitride Composite for Alkaline HER Electrocatalysis

Alkaline hydrogen evolution reaction (HER) is challenged by the inherent lack of readily available protons for hydrogen production. Since water is the reactant, electrocatalysts needed for Alkaline HER must have a sweet spot for water dissociation and a suitable binding energy for the intermediates. One approach to minimizing the energy requirement in the alkaline HER is by creating a water dissociation site on the catalyst's surface by utilizing site engineering strategies. In this study, cyclic voltammetry (CV) cycles are employed for electrochemical surface oxidation of nickel nitride. The incremental CV anodization led to the formation of a nickel hydroxide-nickel nitride composite which aids the water dissociation. The CV cycles were varied from 50-500 cycles for which 50 CV cycles were found to be the optimum. At 50 CV cycles, the nickel hydroxide-nickel nitride composite enhances the electrocatalytic ability of the precursor by reducing the overpotential from 172 mV to 164 mV and 207.27 mV to 192 mV at 50 and 100 mA/cm 2 respectively. The results also show that the charge transfer resistance drops from 8 to 6.5 Ω ohms and the kinetics marked by the Tafel slope also improves as marked by the decrease from 140 mV/dec to 100 mV/dec. This work shows that CV anodization can improve the kinetics of nickel-based pnictides by reconstructing the surface to favor the water dissociation reaction for alkaline HER. Figure 1