Novel double hydride perovskites Li2TiF6-xHx as efficient materials for solid-state hydrogen storage: DFT insights

This study explores the potential of novel double hydride perovskites, Li2TiF6-xHx, for solid-state hydrogen storage using Density Functional Theory (DFT) within the WIEN2k software. Structural analysis shows tetragonal symmetry in each compound and a reduced unit cell volume as fluorine atoms are substituted by hydrogen. The compounds exhibit negative formation energies and satisfy Born's stability criteria, confirming their feasibility for experimental synthesis. Increasing hydrogen content enhances hydrogen storage properties, with Li2TiH6 showing a gravimetric capacity of 9.95 wt% and a volumetric density of 53.92 gH2/l, surpassing the Department of Energy (DOE) 2025 targets. It also demonstrates a low desorption temperature (315.52 K), suitable for practical hydrogen release. The findings reveal a reduction in bandgap from 6.294 eV for Li2TiF6 to 4.285 eV for Li2TiH6, with improved UV absorption and dielectric response. Thermal analysis shows decreased Debye and melting temperatures.