Lithium-based hydride perovskites LiXH3 (X = Mo, Tc, Rh) for hydrogen storage applications: a DFT study

Abstract

Contemporary research focuses on hydrogen storage as a clean energy source, opening new pathways for designing novel hydrogen storage materials. Among these materials, the simple perovskite compounds have emerged as central focus for exploring hydrogen storage applications. In this study, we investigate structural, mechanical, electronic, optical, thermodynamic, and hydrogen storage properties of the simple compounds LiXH 3 , (where X represents Mo , Tc , Rh ) to demonstrate their potential for hydrogen storage. These investigations employ ab initio calculations based on density functional theory using the GGA-PBE and mBJ methods within the WIEN2k simulation code. Structural optimizations of the studied compounds exhibit stable cubic crystal structures with lattice constants equal to 3.5224 Å, 3.4298 Å, and 3.3935 Å for LiMoH 3 , LiTcH 3 , and LiRhH 3 , respectively. The stability of these materials is further confirmed through elastic constants, phonon dispersion, and negative formation energies. The electronic calculations reveal a consistent metallic behavior of all compounds. In addition, we evaluated the thermodynamic properties, such as entropy, specific heat at constant volume, pressure, the Grüneisen parameter, and Debye temperature using the quasi-harmonic Debye model over a temperature range of 0 to 1000 K and a pressure range of 0 to 20 GPa. Finally, our analysis reveals gravimetric hydrogen storage capacities of 2.85 w t % , 2.80 w t % , and 2.68 w t % for LiMoH 3 , LiTcH 3 , and LiRhH 3 respectively. These results highlight the importance of these lithium-based hydride perovskite materials for hydrogen storage applications and their potential to provide clean and more sustainable energy sources. • DFT analysis reveals LiXH 3 (X = Mo, Tc, Rh) perovskites as hydrogen storage candidates. • Stability confirmed by elastic constants, phonon dispersion, and negative formation energy. • Metallic nature observed in LiXH 3 (X = Mo, Tc, Rh). • Achieved gravimetric storage capacities: 2.85%, 2.80%, and 2.68%, respectively. • LiMoH 3 , LiTcH 3 , and LiRhH 3 identified as suitable for energy harvesting and hydrogen storage.