First principles investigation of perovskite hydrides XBH3 (X = Na, K, Rb): Novel materials for hydrogen storage applications

Alkali-based perovskite hydrides have flexible, stable structures, reversible features, higher capacity of hydrogen storage, and their adaptability makes them effective in hydrogen-driven technologies. The current work employs the WIEN2k software and FP-LAPW approach to investigate several physical characteristics and hydrogen storage capabilities of alkali-based perovskite hydrides XBH 3 (X = Li, Na, K, Rb). These thoroughly explored hydrides are estimated to be thermally stable, as evidenced by negative formation energies. The assessment of mechanical parameters reveals stability by satisfying Born's stability criteria, mechanical strength, and anisotropy. Electronic band profiles and density of states analysis indicate the overlapping states of conduction and valence band, evidencing metallic behavior. Additionally, thermodynamic characteristics, such as Debye temperature, sound velocities, and melting, were evaluated using the mechanical constants at standard temperature and pressure. Hydrogen storage capabilities are evaluated, which reveal exceptional gravimetric capacities of 8.21, 5.71, and 3.04 wt%, and volumetric capacities of 82.12, 57.13, and 30.45 g.H 2 /L for NaBH 3 , KBH 3 , and RbBH 3 , respectively. The desorption temperatures obtained by thy analysis of hydrogen storage aspects are 259 K for NaBH 3 , 298 K for KBH 3 , and 313 K for RbBH 3 . These aspects ensure that the potential of NaBH 3 and KBH 3 exceeds the target set by the US Department of Energy for 2025, making these hydrides excellent choices for hydrogen storage. The top chart represents the gravimetric storage capacity, and the bottom chart represents the desorption temperature. High values of H 2 storage capacity and low desorption temperature increase the significance of these materials for hydrogen storage applications. • NaBH 3 , KBH 3 , and RbBH 3 have H 2 storage capacities of 8.21, 5.71, and 3.04 wt%, respectively. • Low desorption temperatures 260 K, 297 K, and 312 K for NaBH 3 , KBH 3 , and RbBH 3 . • Structural, thermodynamic, and mechanical stability. • Ultralow Lattice thermal conductivity. • Ductile and anisotropic nature.