Study of amorphous Ni-S(La) alloy used as HER cathode in alkaline medium

Using an orthogonal design, i.e. the LaCl3 concentration, the current density and the pH value as the factors, Ni-S(La) alloy was obtained through electrodeposition in a modified Watts bath by adding thiourea (TU) and LaCl3 into the bath. The structure and morphology were determined by XRD and SEM. The electrochemical properties, including the hydrogen evolution overvoltages η (h.o.v.), the Tafel slope b, the exchange current density i0 and the activation energy ΔH* of an amorphous Ni-S(La) cathode were measured. The effect of heat treatment under various temperatures on its structure and electrochemical properties were determined. The results indicate that the structure of Ni-S(La) alloy obtained under the optimum conditions is amorphous and it shows much higher electrochemical activity than other electrodes including the amorphous Ni-S electrode due to the higher sulfur content in such an electrode. Heat treatment is harmful to its electrochemical activity.