Electrodeposition and Optimisation of Amorphous Ni_xS_y Catalyst for Hydrogen Evolution Reaction in Alkaline Environment

Anion exchange membrane (AEM) water electrolysers have shown their potential in green hydrogen production. One of the crucial tasks is to discover novel cost-effective and sustainable electrocatalyst materials. In this study, a low-cost Ni-S-based catalyst for hydrogen evolution reaction was prepared via a simple electrodeposition process from a modified Watts bath recipe. Physical characterisation methods suggest this deposit film to be amorphous. Optimisation of the electrodeposition parameters of the Ni_xS_y catalyst was carried out using a rotating disk electrode setup. The optimised catalyst exhibited excellent catalytical performance in 1 M KOH on a microelectrode, with overpotentials of 41 mV, 111 mV and 202 mV at 10, 100 and 1000 mA cm^-2 with Tafel slope of 67.9 mV dec^-1 recorded at 333 K. Long-term testing of the catalyst demonstrated steady performance over a 24 h period on microelectrode at 100 mA cm^-2 with only 71 mV and 37 mV overpotential increase at 293 K and 333 K respectively. Full cell testing with the optimised Ni_xS_y as cathode and NiFe(OH)₂ as anode showed 1.88 V after 1 h electrolysis at 500 mA cm^-2 in 1 M KOH under 333 K with FAA-3-30 membrane.