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

Abstract

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 Å and c = 7.91 Å. 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.