Lithium-Decorated Borospherene B40: A Promising Hydrogen Storage Medium

The recent discovery of borospherene B-40 marks the onset of a new kind of boron-based nanostructures akin to the C-60 buckyball, offering opportunities to explore materials applications of nanoboron. Here we report on the feasibility of Li-decorated B-40 for hydrogen storage using the DFT calculations. The B-40 cluster has an overall shape of cube-like cage with six hexagonal and heptagonal holes and eight close packing B-6 triangles. Our computational data show that Li-m&B-40(1-3) complexes bound up to three H-2 molecules per Li site with an adsorption energy (AE) of 0.11-0.25 eV/H-2, ideal for reversible hydrogen storage and release. The bonding features charge transfer from Li to B-40. The first 18 H-2 in Li-6&B-40(3) possess an AE of 0.11-0.18 eV, corresponding to a gravimetric density of 7.1 wt%. The eight triangular B-6 corners are shown as well to be good sites for Li-decoration and H-2 adsorption. In a desirable case of Li-14&B-40-42 H-2(8), a total of 42 H-2 molecules are adsorbed with an AE of 0.32 eV/H-2 for the first 14 H-2 and 0.12 eV/H-2 for the third 14 H-2. A maximum gravimetric density of 13.8 wt% is achieved in 8. The Li-B-40-nH(2) system differs markedly from the previous Li-C-60-nH(2) and Ti-B-40-nH(2) complexes.