A STUDY OF THE ACTIVATION BEHAVIOR OF ZR-CR-NI-LA METAL HYDRIDE ELECTRODES IN ALKALINE-SOLUTION

The hydrogen absorption behaviour of ZrCrNi C14 Laves phase alloys pre-treated in various ways is studied during galvanostatic charging in KOH solution. It is found that the surface oxide layers prohibit hydrogen absorption. In order to investigate the effects of surface properties on the activation behaviours of ZrCrNi and ZrCrNiLa0.05 electrodes, their surfaces are analysed by means of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The surface property of ZrCrNiLa0.05 is identical to that of ZrCrNi except for La oxide at the surface. To investigate the effect of adding the element, Ti instead of La is added to ZrCrNi in excess. The Ti-containing alloy shows a poor activation behaviour in alkaline solution. From the results of the surface analysis on ZrCrNi, ZrCrNiLa0.05 and ZrCrNiTi0.05, alloys that show different activation behaviours in alkaline solution, it is suggested that the nature of the oxide layer formed on the surface plays a key role on the activation process of the metal hydrides in alkaline solution.