Review of hydrogen storage in AB3 alloys targeting stationary fuel cell applications

Metal hydrides, particularly those based on intermetallic alloys, are effective, safe and efficient for storage of hydrogen. While their low gravimetric energy density is unsuited to mobile applications, this is seldom a problem for stationary hydrogen storage. In this review we focus on developments in the newest AB3 class of intermetallic hydrides, in the context of a renewable energy system in which hydrogen is supplied at relatively low pressure and delivered to a fuel cell. AB3 alloys are of interest because their characteristics are roughly speaking intermediate between those of the long-established AB5 and AB2 types. AB3 alloys offer promise of coming closer to satisfying important performance criteria than do the classic types, through tuning of their hydrogen absorption characteristics. Modification of the nominal composition by element substitution, leading to structural changes affecting all hydriding properties, is the most effective approach. After establishing performance criteria for the present application, conventional elemental and alloy hydrides are briefly compared, followed by a comprehensive survey of research on AB3 hydrides and the opportunities to tune their performance.