Enhanced hydrogen adsorption on Li-coated B₁₂C₆N₆

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.