Lithium-Decorated Borospherene B40: A Promising Hydrogen Storage Medium

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 Lim&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.