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

Using an orthogonal design, i.e. the LaCl 3 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 LaCl 3 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 i 0 and the activation energy Δ H * 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.