Atomistic simulations for electronic structure, mechanical stability and optical responses of sodium-based NaAH3 (A= Sc, Ti and V) metal hydride perovskites for hydrogen storage applications

Hydrogen storage serves a vital role in the advancement of hydrogen-based energy production for commercial use. Solid-state hydrogen storage has garnered significant interest and requires thorough investigation. This study involved the first-principles investigations to explore the phase stability, optoelectronic responses and hydrogen storage potential of Na-based metal perovskites NaAH₃ (A = Sc, Ti, V). The main scope of this study is to evaluate the possible applicability of metal perovskites NaAH₃ (A = Sc, Ti, V) hydrides for solid-state hydrogen storage. Initially, we assess the structural stability of NaAH₃ metal hydrides through calculations of formation enthalpies and phonon dispersion curves. The mechanical stability is assessed through elastic stiffness constants, indicating that NaAH₃ metal hydrides exhibit mechanical stability by satisfying the Born stability criteria. Calculations of the electronic band structure reveal that all NaAH₃ hydrides exhibit metallic properties. Further, we also investigated the optical responses of NaAH₃ hydrides in detail. The gravimetric hydrogen storage capacities of NaScH₃, NaTiH_3, and NaVH₃ hydrides are 4.09, 3.93, and 3.78 wt%, respectively. Furthermore, we have estimated the volumetric hydrogen storage capacities (C_V) for all NaAH₃ (A = Sc, Ti, V) metal perovskite hydrides. The obtained C_V values for NaAH₃ (A = Sc, Ti, V) are 78.99, 95.19, and 110.37 $g{H}_2{l}^{-1}$, respectively, meeting the US-DOE target established for 2025. In short, this study suggests that Na-based perovskite hydrides could serve as effective solid-state hydrogen storage materials.