Study of amorphous Ni–S–Co alloy used as hydrogen evolution reaction cathode in alkaline medium

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 respectively. The contents of S and Co were measured by EPMA correspondingly. The electrochemical properties, including the hydrogen evolution overvoltages η (h.o.v.), the Tafel slope b and the exchange current density i0 of amorphous Ni–S–Co cathode were measured. The HER mechanism and the steady-state behavior of amorphous Ni–S–Co alloy in alkaline media were also investigated. The results indicate that the structure of Ni–S–Co alloy obtained is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni–S and Ni–S(La) electrodes partially due to the higher sulfur content in such electrode. The HER mechanism is a fast Volmer reaction following a slow Heyrovsky reaction and the high electrocatalytic HER property is mainly due to the large amount of adsorbed H atoms.