First-Principles study of Ti-Based X2TiH5 (X = Mg, Ca, Sr) hydrides for Advanced hydrogen storage applications

The potential solution to the urgent issue of hydrogen storage in mobile applications is in the potential contribution of solid materials. Moreover, extensive study has been carried out on perovskite hydride materials to improve their efficiency in the field of hydrogen storage. The present work focuses on the computational investigation of X2TiH5 (X = Mg, Ca, and Sr) perovskite-type hydrides, taking into account diverse physical properties and their potential uses in hydrogen storage. The thermodynamic stability of X2TiH5 (X = Mg, Ca, and Sr) was assessed by analyzing their negative formation equilibrium. The compounds exhibiting tetragonal structures with Sr2TiH5 have the highest computed lattice constants, namely a = b = 5.69 angstrom and c = 7.91 angstrom. The electrical properties unequivocally indicate that the molecules being investigated have a metallic nature. Furthermore, the metallic hydrides provide promising possibilities as potential contenders for hydrogen storage applications. Furthermore, the optical properties of all the compounds were quantified. Finally, the calculated hydrogen storage capacities are 4.97 wt% for Mg2TiH5, 3.78 wt% for Ca2TiH5 and 2.21 wt% for Sr2TiH5. This study demonstrated X2TiH5 (X = Mg, Ca and Sr) have the potential for hydrogen storage, although Mg2TiH5 and Ca2TiH5 are the only compounds that meets the US-DOE criterion for 2020.