Ab Initio Study of the Effects of d-Block Metal (Mn, Re, Tc) Encapsulation on the Electronic, Phonon, Thermodynamic, and Gravimetric Hydrogen Capacity of BaXH₄ Hydride Perovskites

Hydrogen storage in metal hydrides is feasible since many metals react readily with hydrogen, forming a stable metal hydride. In this article, the structural, electrical, thermodynamic, phonon, and hydrogen storage properties of the perovskite hydride BaXH₄ (X = Mn, Re, or Tc) in its hexagonal form are examined by combining ab initio density functional theory using the generalized gradient approximation and Perdew–Burke–Ernzerhof exchange-correlation functional. The electronic characteristics of these hydrides were analyzed through band structure, total density of states (TDOS), and partial density of states (PDOS) analysis. Maximal conductivity at the Fermi level is revealed in the TDOS and PDOS, and the results were plotted against the energy of the incident radiations. The hydrogen storage properties of the material were also considered; the value of gravimetric hydrogen storage capacity was calculated to be 2.006 wt.%, 1.2124 wt.%, and 1.6517 wt.% for BaMnH₄, BaReH₄, and BaTcH₄, respectively. The formation energies obtained for BaMnH₄ and BaTcH₄were estimated to be −47.225 KJ mol⁻¹ and −47.331 KJ mol⁻¹, respectively, while the energy required to form BaReH₄perovskite hydride was −47.705 KJ mol⁻¹. This high formation energy indicates the compounds’ enhanced stability. Consequently, it is reasonable to assert that BaMnH₄, BaReH₄, and BaTcH₄ can be effectively employed as hydrides for hydrogen storage purposes. Furthermore, the calculated desorption temperature of the perovskite hydride BaMnH₄ was found to be T _des (K) = 361.32 K, while BaTcH₄ and BaReH₄ had estimated desorption temperatures of 362.13 K and 364.99 K, respectively. Notably, these values are within the recommended range of desorption temperatures (289–393 K) for practical applications, as proposed by the US Department of Energy (USDOE). This indicates that no significant barriers impede hydrogen desorption from BaXH₄ compounds, making them promising candidates for hydrogen release in various practical applications. The discussion above concludes that perovskite hydrides BaXH₄ (X = Mn, Re, or Tc) are suitable compounds for hydrogen storage because these materials are energetically stable and may be produced for hydrogen storage devices. Graphical Abstract: [Figure not available: see fulltext.].