Revolutionizing hydrogen storage: A first-principles investigation of XTiB2H6 (X= Li, Na and K) hydrides double perovskites for structural, optoelectronic, and mechanical properties

초록

In this study, density functional theory (DFT) calculations are employed to investigate gravimetric hydrogen storage capacities (GHSCs), structural, mechanical, and optoelectronic characteristics of double perovskite hydrides XTiB2H6 (X = Li, Na and K) for renewable energy production. The negative values of formation enthalpies (Delta H) for LiTiB2H6, NaTiB2H6, and KTiB2H6 are-9.031,-7.426, and-6.998 eV/atom, respectively. The overlapping valence and conduction bands across Fermi level provide evidence for the metallic nature of XTiB2H6 (X = Li, Na and K). The optical characteristics for XTiB2H6 (X = Li, Na and K) reveal that they are efficient absorbers of energy quanta in infrared and visible regions. The calculated values of GHSCs are 8.24, 6.64, and 5.60 wt% for LiTiB2H6, NaTiB2H6, and KTiB2H6, respectively. The mechanical stability of XTiB2H6 (X = Li, Na and K) is evident by the calculated elastic constants as they meet the conditions of Born stability criteria. The calculated values of Pugh's ratio for LiTiB2H6, NaTiB2H6, and KTiB2H6 are 2.645, 2.687, and 3.686, revealing their ductile nature. The ionic bonding in XTiB2H6 (X = Li, Na and K) is confirmed by positive values of Cauchy pressure C-y. The high gravimetric hydrogen storage capacities, thermodynamic stability favorable mechanical and electronic properties (ductility and metallic nature) as the distinguishing features that make XTiB2H6 a strong candidate for efficient hydrogen storage applications.

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