Laves type intermetallic compounds as hydrogen storage materials: A review

Abstract

Laves type AB2 intermetallics belong to the most abundant group of intermetallic compounds containing over 1000 compounds. A large variety of the chemical nature of A (Mg, Ca, Ti, Zr, Rare Earth Metals) and B (V, Cr, Mn, Fe, Co, Ni, Al) metals together with the existence of the extended solid solutions formed by mixing various selected components on both A and B sites dramatically extends the list the known binary and ternary individual compounds. A vast majority of the Laves type intermetallics crystallises with C15 / FCC MgCu2 and C14 / hexagonal MgZn2 types of structures, both formed for a large range of ratios between the atomic radii of the A and B components outside the ideal ratio rA/rB= 1.225. Their hydrogenation per- formance is defined by the chemical composition and structure of the alloys and proceeds according to the following alternative / parallel mechanisms: (a) Formation of the insertion type interstitial hydrides con- taining up to 6–7 at. H/f.u.AB2; (b) Amorphisation of the alloys on hydrogenation; (c) Disproportionation with the formation of a binary hydride of the A metal and depleted by A metal B-components based alloys/ hydrides.