Lithium-Decorated Borospherene B40: A Promising Hydrogen Storage Medium

Abstract

The recent discovery of borospherene B₄₀ marks the onset of a new kind of boron-based nanostructures akin to the C₆₀ buckyball, offering opportunities to explore materials applications of nanoboron. Here we report on the feasibility of Li-decorated B₄₀ for hydrogen storage using the DFT calculations. The B₄₀ cluster has an overall shape of cube-like cage with six hexagonal and heptagonal holes and eight close-packing B₆ triangles. Our computational data show that Li_m&B₄₀(1-3) complexes bound up to three H₂ molecules per Li site with an adsorption energy (AE) of 0.11-0.25 eV/H₂, ideal for reversible hydrogen storage and release. The bonding features charge transfer from Li to B₄₀. The first 18 H₂ in Li₆&B₄₀(3) possess an AE of 0.11-0.18 eV, corresponding to a gravimetric density of 7.1 wt%. The eight triangular B₆ corners are shown as well to be good sites for Li-decoration and H₂ adsorption. In a desirable case of Li₁₄&B₄₀-42 H₂(8), a total of 42 H₂ molecules are adsorbed with an AE of 0.32 eV/H₂ for the first 14 H₂ and 0.12 eV/H₂ for the third 14 H₂. A maximum gravimetric density of 13.8 wt% is achieved in 8. The Li-B₄₀-nH₂ system differs markedly from the previous Li-C₆₀-nH₂ and Ti-B₄₀-nH₂ complexes.