Insights into the physical properties of Mg2TiH6 hydride double perovskite for solid-state hydrogen storage applications: A first-principles calculations

Abstract

Complex metal hydrides are promising candidates for hydrogen storage due to their exceptional hydrogen storage capacity. This study presents the first investigation of the Mg₂TiH₆ hydride to evaluate its potential for hydrogen storage. Using density functional theory (DFT), a detailed computational analysis is conducted to explore its structural, mechanical, electronic, and hydrogen storage properties. The thermodynamic stability of the cubic double perovskite Mg₂TiH₆ is evidenced by its negative formation energy, while mechanical stability is confirmed by elastic constants that satisfy Born's criteria. The calculated Cauchy pressure and Pugh's ratio further reveal its brittle nature. Regarding hydrogen storage capability, Mg₂TiH₆ demonstrates an excellent hydrogen capacity of approximately 5.90 wt%, aligning with the targets set by the U.S. Department of Energy (US-DOE). The hydrogen desorption temperature, derived from thermodynamic calculations, is approximately 630 K, indicating that hydrogen release from this compound requires moderately high thermal energy. Electronic structure analysis shows metallic character, implying high electrical conductivity. These findings position Mg₂TiH₆ material as a strong candidate for future hydrogen storage technologies.