Ni-S(La) alloy was obtained by electrodeposition from a modified Watts bath with an addition of thiourea (TU) and LaCl3 into the bath. The structure and morphology were determined by XRD and SEM methods, respectively. The electrochemical parameters, including the hydrogen evolution reaction (HER) overvoltages eta, the Tafel slope b, the exchange current density i(0), and the activation energy DeltaH* of Ni-S(La) cathode material were determined. The effect of heat treatment at various temperatures on Ni-S(La) alloy structure and electrochemical proper-ties was also determined. Furthermore, the stabilities of amorphous Ni-S alloy and Ni-S(La) alloy were investigated by measuring their sulfur contents before and after long-term electrolysis. The results indicate that the structure of Ni-S(La) alloy is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni-S electrode. The heat treatment is harmful to its electrochemical activity due to the damage of its amorphous structure. The stability of amorphous Ni-S(La) electrode is higher than that of the amorphous Ni-S electrode in view of its lower sulfur weight loss in the course of electrolysis. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.