DFT insights into the dynamically stable CaTcH3 and SrTcH3 perovskite hydrides: Promising candidates for solid-state hydrogen storage

A revolutionary change is necessary in storage technology to make hydrogen energy a viable mainstream answer. Among the new approaches that are being explored, the solid-state hydrogen storage stands out as especially promising. In this study, the structural, mechanical, lattice dynamic stability, vibrational, thermodynamic, hydrogen storage, and electronic properties of novel ATcH 3 (A = Ca, Sr) perovskite hydrides were investigated. The calculations are performed using density functional theory (DFT) calculations within the CASTEP module. The structural parameters are 3.646 Å for CaTcH 3 and 3.777 Å for SrTcH 3 . The formation energies −0.3297 eV/atom and −0.2420 eV/atom for CaTcH 3 and SrTcH 3 confirmed the thermodynamic stability. These compounds fulfill the Born stability criteria, so they are considered mechanically stable. The phonon dispersion curves show no imaginary frequencies, indicating that these compounds are dynamically stable. As these materials show no thermal fluctuation in AIMD simulations, these materials are considered thermally stable. The electronic property suggests that these materials are metallic in nature because there is no band gap around the Fermi level ( E g = 0). The thermoelectric behavior of these perovskites is also impressive. CaTcH 3 and SrTcH 3 offer gravimetric hydrogen storage capacities of 2.14 wt% and 1.60 wt%, respectively. While the volumetric hydrogen storage capacity of CaTcH 3 is 103.85 gH 2 /L, and SrTcH 3 is 93.26 gH 2 /L. Both of these materials meet the DOE target of volumetric capacity. The desorption temperatures are 243.15 K for CaTcH 3 and 178.52 K for SrTcH 3 . The desorption temperatures are quite low, and only the CaTcH 3 meets the DOE target set for operating conditions. Findings of this study reveal that the ATcH 3 hydrides could be promising materials for a solid-state hydrogen storage system.