Relationship between hydrogen sorption properties and crystallography for TiMn2 based alloys

In order to develop suitable materials for a hydrogen storage tank or for electrochemical applications, TiMn2-based C14 Laves phase alloys were prepared. The effect of non-stoechiometry was first studied (TiMn2 exist as a single phase from TiMn1.6 to TiMn2.1 according to the Ti–Mn phase diagram). It was shown that maximum hydrogen storage capacity was obtained for the slightly under stoechiometric Ti0.95Zr0.05Mn1.95. Then, the substitution effect of transition metals such as Cr, V, Fe, Ni, Co (and Al) was also examined. It was found that Ni substitution led to an increase of the plateau pressure, Cr and Co substitutions did almost not influence the hydruration characteristics, Al was suitable to reduce the plateau pressure but also led to a huge decrease of the hydrogen storage capacity. Finally, we found that the best substitution effect was obtained with V which allowed us to decrease the plateau pressure and increase the hydrogen storage capacity. For each compound, a relationship was made with the lattice structures.