Structure and hydrogen storage properties of the hexagonal Laves phase Sc(Al1−xNix)2

The crystal structures of hydrogenated and unhydrogenated Sc(Al1−xNix)2 Laves phases have been studied by combining several diffraction techniques and it is shown that hydrogen is situated interstitially in the A2B2-sites, which have the maximum number of scandium neighbours. The hydrogen absorption/desorption behaviour has also been investigated. It is shown that a solid solution of hydrogen forms in the mother compound. The hydrogen storage capacity exceeds 1.7H/f.u. at 374K, and the activation energy of hydrogen desorption was determined to 4.6kJ/mol H2. It is shown that these compounds share the same local coordination as Frank–Kasper-type approximants and quasicrystals, which opens up the possibility of finding many new hydride phases with these types of crystal structures. The structure of ScNiAlDx, Sc atoms are shown in purple and Ni/Al atoms in blue and the iso-surfaces of deuterium in yellow. Revealed from refinements of neutron powder diffraction data. [Display omitted] ► The crystal structure of ScNiAl and ScNiAlDx is reported. ► We show the hydrogen storage properties of Sc(Al1−xNix)2. ► We discuss the possibility to store hydrogen in quasicrystals.