First-principles evaluation of LiCaF3-αHα as an effective material for solid-state hydrogen storage

Hydrogen energy has attracted a lot of interest as a renewable and sustainable energy source, but there are a few technical impediments associated with its storage. Solid-state hydrogen storage is a catching-on and intensively researched alternative to other methods for storing hydrogen. Perovskite hydrides exhibit the ability to store solid-state hydrogen safely and effectively. This work employs the first-principles calculations to investigate the physical properties of LiCaF3_alpha H alpha (alpha = 0,1,2,3) perovskite compounds, aiming to elucidate insights into their potential in hydrogen storage applications. To assess the phase stability, we computed the formation enthalpies, which indicate that all compounds are stable and can be synthesized experimentally. Notably, the optimized lattice parameter decreased from 4.42 to 4.32 A when an impurity was added to pristine material. Additionally, the evaluation of the elastic stiffness constants manifests that all LiCaF3-alpha H alpha compounds are mechanically stable and brittle in nature. Investigations of electronic properties demonstrate the narrowing in the bandgap of the host compound with the inclusion of H. To gain insight into how the absorption edge shifts towards the valence band and causes the band gap to diminish, the Burstein-Moss shift and band gap renormalization were investigated. Interestingly, the gravimetric and volumetric hydrogen storage capacities have been improved up to 6.04 wt% and 61.77 gH2l- 1, respectively, which are fulfilling the target set by DOE for 2025. In short, this work suggests the applicability of LiCaH3 hydrides for effective hydrogen storage.