Structure and hydrogen sorption properties of multicomponent AB2 Laves type compounds derived from ZrVNb

A series of multicomponent pseudo-binary AB 2 Laves phase compounds was synthesized, starting from the base ZrVNb composition, by systematically substituting the B-site elements (V and Nb) with transition metals Cr, Mn, Fe, and Ni. Despite the significant compositional variation introduced by the substitution process, the vast majority of these alloys consists of the AB₂ compound with a hexagonal C14 Laves-type structure. The successful stabilization of the C14 type across a broad composition space highlights the versatility of the Laves type intermetallics. For the alloys that include Ni, the formation of a secondary ZrNi phase is observed. Increased substitution of V and Nb by Cr/Mn/Fe/Ni results in a significant contraction of the unit cell volume and in a less negative enthalpy of hydride formation. The most pronounced destabilization of the Laves-type hydride is observed for the alloy Zr(V 0.5 Nb 0.5 ) 0.25 (Cr 0.25 Mn 0.25 Fe 0.25 Ni 0.25 ) 1.75 , which at the temperature of 116 °C shows an equilibrium hydrogen pressure of 1 bar H 2 and a high reversible hydrogen storage capacity of 1.6 wt%. The hydrogenation results in an increase of the unit cell volume by 20.4%. The enthalpies of hydrogen absorption and desorption are Δ H abs o = − 36 ( 1 ) kJ mo l H 2 − 1 and Δ H des o = 36.7 ( 6 ) kJ mo l H 2 − 1 . The corresponding entropies are Δ S abs o = − 91 ( 2 ) J mo l H 2 − 1 K -1 and Δ S des o = 91.8 ( 14 ) J mo l H 2 − 1 K -1 . • Multicomponent alloys for hydrogen storage are synthesized starting from the parent compound ZrVNb • The C14 Laves structure is retained upon extended substitution of V and Nb with Cr, Mn, Fe and Ni • The unit cell volume decreases by 16% at the highest degree of substitution • The hydrogen desorption enthalpy can be reduced to 36 kJ/mol H 2 via substitution • The highest reversible hydrogen storage capacity is 1.6 wt%