Metal hydride alloys have received wide attention due to their various applications such as in hydrogen storage, in heat pumps, as negative electrodes in nickel/metal hydride batteries, in hydrogen puriÂźcation and in isotope separation. In recent years, study of the electrocatalytic activities of metal hydride alloys in alkaline solution has also attracted great interest [1±10]. Kitamura and coworkers [2±4] studied the hydrogen evolution reaction (HER) on LaNi5, MmNi5 etc. ingot-electrodes and found these ingotelectrodes to have highly electrocatalytic activities for hydrogen evolution, almost comparable to Pt and Pd electrodes. Hall and coworkers [5±6] also investigated the catalytic activities of the AB5-type porous electrodes in 30 wt% KOH at 80 C. Their experimental results indicated that the AB5-catalysed electrodes had highly electrocatalytic properties. The NiTi and NiZr alloys also exhibited good catalytic activities for HER after surface treatments with 1M HF aqueous solution [7±10]. However, hydrogen storage alloys easily suÂered from hydrogen-caused embrittlement during cathodization due to absorbing amounts of hydrogen and lattice expansion, especially during long-term polarization under high current density. In recent years, Ni±Mo alloys have been proved to be eÂective as electrocatalysts for HER in alkaline solution. However, the activity for HER on the Ni±Mo alloy electrodes is easily lost during intermittent electrolysis, especially after cell short-circuiting cases for more than two weeks. The reasons for degradation may be ascribed to the oxidized dissolution of the Mo component because of a reverse current caused by the cell short circuit [17, 18]. Hydrogen storage alloys can absorb amounts of hydrogen during electrolysis and release the hydrogen reversibly when oxidation current pass through the cathode. Therefore, development of a new class of cathode, which can overcome the above defects of Ni±Mo alloys and hydrogen storage alloys, is very important. The purpose of this work was to develop a new composite electrode composed of LaNi4:9Si0:1 hydride alloy and Ni/Mo alloy, and then evaluate its electrochemical properties such as activity for HER, durability under long-term electrolysis and stability against cell short-circuiting situations.