Enhanced hydrogen adsorption on Li-coated B12C6N6.

Abstract

The hydrogen storage property of Li-coated B12C6N6 is investigated by density functional theory calculations. B12C6N6 is an electron deficient fullerene. Li atoms can be strongly bound to this cage by donating their valance electrons to the virtual 2p orbitals of carbon in the cluster. The binding energy (-2.90 eV) is much larger than the cohesive energy (1.63 eV) of bulk Li, and it prevents the Li atoms from aggregation. The coated Li atoms have large positive charges and the adsorbed hydrogen molecules can be moderately polarized by the Li+ ions. The computation shows that each Li atom coated on B12C6N6 can hold 2-3 H2 molecules with adsorption energies in the range of 0.21-0.24 eV/H2. The B12C6N6Li8 can adsorb 16 H2 and achieve a gravimetric hydrogen density of 8.63 wt. %. The present results indicate that alkali-metal atoms coated on electron deficient fullerenes can serve as hydrogen storage materials that can operate at ambient temperatures with high recycling storage capacity.