Although iron-titanium is an excellent material for hydrogen storage, it becomes deactivated after repeated charge-discharge cycles. The mechanism of this phenomenon has been determined by J. H. Sanders and B. J. Tatarchuk of Auburn University, Alabama, U.S.A., who have also investigated the use of thin palladium films to protect the alloy from deactivation (Thin Solid Films, 1988, 166, 225–233; J. Phys. F: Met, Phys., 1988, 18, (11), L267–L270).

Deactivation is triggered by oxygen impurities in the hydrogen charging gas reacting with titanium in the surface layer of the iron-titanium matrix, forming titania and metallic iron crystallites which are inert to reversible hydrogen storage. However under the conditions of interest a thin 5nm layer of palladium provides an effective barrier to oxygen, preventing deactivation and so increasing the useful life of the alloy. The integrity of the coating has been verified by conversion electron Mössbauer spectroscopy.