The heat-treatment effect of amorphous Ni–S(La) electrode on the hydrogen evolution reaction in an alkaline media

Ni–S(La) alloy was obtained by electrodeposition from a modified Watts bath with an addition of thiourea (TU) and LaCl3 into the bath. The structure and morphology were determined by XRD and SEM methods, respectively. The electrochemical parameters, including the hydrogen evolution reaction (HER) overvoltages η, the Tafel slope b, the exchange current density i0, and the activation energy ΔH∗ of Ni–S(La) cathode material were determined. The effect of heat treatment at various temperatures on Ni–S(La) alloy structure and electrochemical properties was also determined. Furthermore, the stabilities of amorphous Ni–S alloy and Ni–S(La) alloy were investigated by measuring their sulfur contents before and after long-term electrolysis. The results indicate that the structure of Ni–S(La) alloy is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni–S electrode. The heat treatment is harmful to its electrochemical activity due to the damage of its amorphous structure. The stability of amorphous Ni–S(La) electrode is higher than that of the amorphous Ni–S electrode in view of its lower sulfur weight loss in the course of electrolysis.