Hydrogen evolution reaction on amorphous Ni–S–Co alloy in alkaline medium

Using an orthogonal design, i.e. the CoCl2 concentration, the current density, the temperature and the pH value as the factors, Ni–S–Co alloy was obtained through electrodeposition in a modified Watts bath by adding thiourea (TU) and CoCl2 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 amorphous Ni–S–Co 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–Co alloy obtained under the optimum conditions is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni–S electrode due to the higher sulfur content in such electrode, and heat treatment is harmful to its electrochemical activity.