Influence of Bʹ-site vacancy on hydrogen storage, structural, elastic, thermodynamic and optoelectronic attributes of potassium based double perovskite K2LiAlH6hydride for green energy applications

Materials with a greater propensity to store hydrogen have drawn a lot of attention in recent decade because of their possible uses in clean energy systems. By offering effective, sustainable, and eco-friendly substitutes for conventional fossil fuels, these materials are essential in tackling the world's energy problems. We have analyzed the influence of [Formula: see text]-site vacancy on hydrogen storage abilities of potassium-based K₂LiAlH₆ double perovskite by employing the first-principles technique. For both K₂LiAlH₆ and K₂LiH₆, structural and thermo-dynamical stability is attested by computing their volume optimization, tolerance factors and formation energies. The elastic constants reveal a significant reduction towards the external strains when vacancy is created at [Formula: see text]-site. The mechanical properties imply that K₂LiAlH₆ with or without the vacancy at [Formula: see text]-site, the material possesses brittle characteristics. The electronic properties elaborates that K₂LiAlH₆ possesses an indirect bandgap of 4.16 eV, whereas for K₂LiH₆ metallic nature is observed. K₂LiAlH₆ reveals stronger polarization in the high energy region, whereas K₂LiH₆ reports higher dispersion in the IR region as predicated via their optical analysis. The hydrogen storage abilities reveal a significant increase in the gravimetric densities which are evaluated from 4.83 to 6.17 wt% and a modest increase is noticed in volumetric densities, which are computed from 41.85 to 44.76[Formula: see text](gH₂/L) with the creation of [Formula: see text]-site vacancy in K₂LiAlH₆. It ultimately fulfills the United States department of energy criteria and has indicated its capability to be utilized for hydrogen storage.