A Computational Study of Metal Hydrides Based on Rubidium for Developing Solid-State Hydrogen Storage

In this work, we explore the physical properties of RbXH3 (X=Cr, Zr) perovskite hydrides for solid-state hydrogen storage. The structural, mechanical, electronic, optical, and hydrogen storage properties were theoretically investigated using density functional theory and CASTEP software. The selected candidates were fully relaxed and optimized in the cubic phase space group Pm-3 m. The structural phase stability was verified by means of thermodynamic, dynamic and mechanical stabilities. Mechanical analyses based on Poisson's ratio (nu), G/B ratio, and Cauchy pressure show that RbCrH3 and RbZrH3 exhibit brittle behavior with preference of ionic bonding. The electronic structures unveil half-metallicity in RbCrH3 compound and metallic-like behavior in RbZrH3. Furthermore, optical calculations were also conducted to gain additional insights into the physical properties of RbXH3 compounds. The gravimetric hydrogen storage (Cwt %) capacities have been calculated as 2.09 wt % and 1.64 wt % for RbCrH3 and RbZrH3, respectively. The hydrogen desorption temperatures have been obtained as 545.11 K and 548.15 K for RbCrH3 and RbZrH3, respectively. Our calculation propose RbCrH3 hydride as potential material for hydrogen storage application. A novel cubic perovskite hydrides RbXH3 (X=Cr, Zr) are found to be thermodynamically and mechanically stable with promising gravimetric hydrogen storage capacities and desorption temperatures: RbCrH3 (2.09 wt %, 545.11 K) and RbZrH3 (1.64 wt %, 548.15 K). image