No abstract

Magnesium hydride (MgH2) and titanium hydride (TiH2) are two potential candidates for solid‐state hydrogen storage, but strong hydride formation energy in these hydrides undesirably results in their high dehydrogenation temperature. First‐principles calculations show that the metastable hydrides in the MgH2–TiH2 system have low hydrogen binding energy, which makes them more appropriate for low‐temperature hydrogen storage. In this study, severe plastic deformation (SPD) via the high‐pressure torsion (HPT) method is applied to the MgH2–TiH2 system to synthesize metastable hydrides. While MgH2 transforms to a high‐pressure orthorhombic γ phase, TiH2 does not exhibit any cubic‐to‐tetragonal phase transformation even by HPT processing at cryogenic temperature. Application of large strains by 400 HPT turns to the immiscible MgH2/TiH2 composite results in atomic‐scale mixing and formation of nanostructured ternary Mg–Ti–H hydride with the metastable FCC structure and lower dehydrogenation temperature than TiH2.