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 \(\:{\text{B}}^{{\prime\:}}\) -site vacancy on hydrogen storage abilities of potassium-based K 2 LiAlH 6 double perovskite by employing the first-principles technique. For both K 2 LiAlH 6 and K 2 LiH 6 , 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 \(\:{\text{B}}^{{\prime\:}}\) -site. The mechanical properties imply that K 2 LiAlH 6 with or without the vacancy at \(\:{\text{B}}^{{\prime\:}}\) -site, the material possesses brittle characteristics. The electronic properties elaborates that K 2 LiAlH 6 possesses an indirect bandgap of 4.16 eV, whereas for K 2 LiH 6 metallic nature is observed. K 2 LiAlH 6 reveals stronger polarization in the high energy region, whereas K 2 LiH 6 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 \(\:\:{\uprho\:}\:\) (gH 2 /L) with the creation of \(\:{\text{B}}^{{\prime\:}}\) -site vacancy in K 2 LiAlH 6 . It ultimately fulfills the United States department of energy criteria and has indicated its capability to be utilized for hydrogen storage.