A study on the electrodeposited Ni–S alloys as hydrogen evolution reaction cathodes

Nickel–sulfur electrode was obtained in a modified Watts bath by adding thiourea (TU) into the bath. The effects of TU concentration, current density, temperature and pH value of electrodepositing solution on the sulfur content of Ni–S alloy were systematically studied. 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 Ni–S cathodes were measured. Results indicated that the main factors which influenced sulfur content in the Ni–S coatings were the TU concentration and the current density, and that Ni–S electrodes obtained showed much higher HER electrochemical activity than the mild steel or other nickel-based alloys. The structures of Ni–S coatings with various sulfur content were determined by XRD and the corresponding micrographs were obtained by SEM. Furthermore, the electrochemical behaviors in electrodepositing solutions with and without TU were studied and discussed.