Investigating the physical and hydrogen storage properties of alkali metal-based cobalt hydrides

The perovskite-type hydride compounds are potential candidate materials in the field of hydrogen storage, which is essential for the transition to sustainable energy. This study investigates perovskite-type hydrides MCoH₃ (M = Na, K, Rb) as potential options for hydrogen storage applications by employing density functional theory (DFT). The analysis of formation energy and elastic constants indicates that the MCoH₃ compounds exhibit thermodynamic and mechanical stability. The calculation of Pugh's ratio reveals that these hydrides are brittle materials. Electronic properties reveal that MCoH₃ compounds exhibit metallic characteristics, while KCoH₃ and RbCoH₃ show half-metallic behavior. The phonon dispersion curves confirm dynamic stability. Thermodynamic analysis confirms the material's thermal stability at different temperature ranges. The compounds demonstrate significant gravimetric and volumetric hydrogen storage capacities, with NaCoH₃ exhibiting the highest value of 3.56 wt% and 129.94 g H₂/L, respectively. Optical characteristics suggest strong interactions with electromagnetic radiation. Thus, the study implies that MCoH₃ compounds can be considered for hydrogen storage.