Pyrite copper nickel sulfide for stable hydrogen evolution reaction in alkaline media

The alkaline hydrogen evolution reaction is a promising solution to meet future energy demand due to the sustainable production of hydrogen via water electrolysis. The development of copper nickel sulfide (CuNiS) electrocatalysts for hydrogen evolution reaction (HER) relies on robust active sites without degradation. How-ever, the performance of CuNiS depends on the nature of sulfur precursors and complexing agents since the copper and sulfur oxidation states determine the adsorption and release of H2. The CuNiS synthesized with thioacetamide and 3-mercaptopropionic acid as sulfur source and complexing agent, respectively, at 100 degrees C for 10h delivered a lower overpotential of-96 mV to achieve a current density of-10 mA cm-2 in 1 M KOH electrolyte. The positive and negative shifts in binding energy peaks of Ni and S, respectively, caused charge redistribution and charge transfer between metals and S. The transfer of electrons from Ni to Cu atoms decreases the hydrogen binding energy and accelerates the Had desorption process, which leads to the subsequent formation of H2. Moreover, the negative shift in S improves the electron occupation, which helps with proton adsorption and the release of H2.