DFT and AIMD predictions of Li2XBH6 (X = Li, Na, K) double perovskites for efficient hydrogen storage and photocatalytic applications

Abstract

Energy demand in today's world is increasing. So, to meet this energy demand and reduce reliance on fossil fuels, we need to look to renewable energy sources, and hydrogen storage can be one of them. This study conducted a magnificent investigation into the thermo-dynamical stability, optoelectronic properties, hydrogen storage capability, and photocatalytic activity of Li₂XBH₆ (X = Li, Na, K) Double perovskite hydrides (DPH) using a density functional theory (DFT)-based approach, with ab initio molecular dynamics (AIMD) simulations, which specifies that the compounds are thermally stable. The electronic structure analysis indicated that all compounds exhibit semiconductor behavior, with band gap energies of 1.79 eV for Li₂LiBH₆, 1.66 eV for Li₂NaBH₆, and 1.48 eV for Li₂KBH₆, suggesting their potential for efficient photonic and optoelectronic applications such as solar cell absorbers. This study shows a prominent initial theoretical GHSC, with Li₂LiBH₆ demonstrating the highest storage potential at 16.05 wt%, Li₂KBH₆ the lowest at 8.66 wt%, and Li₂NaBH₆ 11.25 wt% – all considerably surpassing the US-DOE target of ≥5.5 wt%. The study shows that these substances are promising theoretical candidates for advanced optoelectronic devices, hydrogen storage materials, and photocatalytic applications.