CATALYTIC EFFECT OF NICKEL, IRON AND PALLADIUM ON HYDRIDING TITANIUM AND STORAGE MATERIALS

Results of experiments on hydriding film samples of titanium and other metals, and titanium films covered with overlayers of various metals, indicate that the slow dissociation of H-2 molecules on film surfaces contaminated with O2 is a very important partial reaction step. A remarkable enhancement in H-2 dissociations is observed if nickel, iron or palladium acting as catalysts are present on the surface oxidized titanium or storage materials. This is demonstrated by experiments performed with titanium film samples using the volumetric Wagener technique or a piezoelectric quartz microbalance, and also by high pressure hydriding-dehydriding cycling tests with storage materials containing additions of palladium powder or an aluminium oxide suspended palladium catalyst. The development of storage materials with improved resistance against poisoning gas impurities in H-2 seems therefore to be mainly a problem of surface modification and/or catalysis. This aspect of the problem is discussed on the basis of relevant effects which have been measured.