Transformation of Metallic Ti to TiH2 Phase in the Ti/MgH2 Composite and Its Influence on the Hydrogen Storage Behavior of MgH2.

The current work explores the in-situ formation of TiH2 additive in a Ti/MgH2 nanocomposite system. Mild mechanical milling leaves Ti chemically unchanged, while formation of stable TiH2-x occurs upon strong mechanical milling. TiH2-x further transforms to TiH2 upon recycling the powder (dehydrogenation and subsequent hydrogenation) and lowers the activation energy of MgH2 to 89.4 kJ (mol H2 )(-1) [Ea of as-received MgH2 is 153 kJ (mol H2 )(-1) ]. This work also reiterates that metallic Ti additive mixed MgH2 requires strong mechanical milling for better H2 ab/de-sorption performance. The current observations support the view that lattice strain may be an important factor in the catalysis of additives incorporated MgH2 hydrogen storage systems.