Effect of nitrogen induced defects in Li dispersed graphene on hydrogen storage

As a candidate for hydrogen storage medium, Li decorated graphene with experimentally realizable nitrogen defects was investigated for geometric stability and hydrogen capacity using density functional theory (DFT) calculations. Among the three types of defective structures, it is expected that Li metal atoms are well dispersed on the graphene sheets with pyridinic and pyrrolic defects without clustering as the bond strength of Li on pyridinic and pyrrolic N-doped graphene layers is higher than the cohesive energy of the Li metal bulk. The two stable structures were found to exhibit hydrogen uptake ability up to three H₂ per Li atom. The binding energies of the hydrogen molecules for these structures were in the range of 0.12–0.20 eV/H₂. These results demonstrate that a Li/N-doped graphene system could be used as a hydrogen storage material.