Research of the adsorption of Na on vacancy graphene

We investigate the charge densities, adsorption energies, densities of states and storage capacities of Na atoms on pristine graphene and vacancy graphene using the first-principles method of density functional theory combined with the pseudopotential approximation. The results indicate that the most stable sites are H site in two graphenes. The adsorption energy of Na on vacancy graphene is -2.46 eV, which is over 3.4 times that of Na on the pristine graphene. The orbital hybridizations can be observed in the vacancy graphene, while there is no orbital hybridization in the pristine graphene. Introducing each vacancy into graphene can adsorb up to five Na atoms, which is larger than that of pristine graphene. This work demonstrates that vacancy graphene is expected to be potential materials for storing Na. (authors)