Transition-metal-based hydrides for efficient hydrogen storage and their multiple bond analysis: A first-principles calculation

Hydrogen energy plays a growing role in the present energy market and attracts more attention in scientific researches and commercial application. Hydrogen energy has an increasing attractive in energy market due to its high energy density, pollution-free utilization usage and wide availability. Current challenge which obstructs large-scale application is safe and reliable hydrogen storage, which requires finding promising materials to promote hydrogen energy. Therefore, we have predicted three potential lithium-transition metal-based hydrides LiTM3LiH8 (TM = Sc, Ti V) for hydrogen storage based on first principles calculation. The stability analysis based on formation energy, elastic constants and phonon spectra confirms all hydrides are stable and feasible in practical application. Besides, they have a increasing ductility in the order of Sc, Ti and V. Among all studied materials, LiV3LiH8 has the best mechanical characteristics due to its excellent ductility and high Young's modulus (123.19 GPa), which are beneficial for resistance to adverse external surroundings. The electronic properties suggest that all hydrides metallic in band structures. Meanwhile, we analyzed how hydrogen was storage and the binding information from multiple perspectives, including the charge analysis, DOS, ELF and COHP. From multiple analyses of bond strengths, except the strong binding from transition metal, the centered Li atom is verified to possess greater influence than corner Li atom, which makes a viable regulation of hydrogen properties by substituting centered alkali metal atom in future. As concluded in this study, LiTi3LiH8 has a high storage capacity of 4.83 wt% along with a desorption temperature of 305.5 K, which is considered as a promising hydrogen storage material.