Li decorated 6,6,12-graphyne: A new star for hydrogen storage material

•The hydrogen storage capacity of Li@6,6,12-graphyne is high up to 19.3 wt%.•Li atoms can bind to sp hybridization C atoms to avoid forming Li cluster.•The interaction originates from the polarization under the electric field.•The formation of hydrogen-hydrogen complex lowers the energy of system.

Based on ab initio calculations, we investigated the hydrogen storage capacity of Li decorated 6,6,12-graphyne (Li@GY). Due to the unique sp hybridization in GY, Li atoms can strongly bind to carbon atoms to avoid the formation of Li clusters on the surface of GY. It is found that the hydrogen storage capacity of Li@GY is high up to 19.3 wt% with the average adsorption energy of −0.230 eV which lying in the ideal adsorption energy range for practical application of hydrogen economy. The density of states and charge density difference demonstrated that the adsorption mechanism mainly depended on the electrostatic field produced by the Li ions on GY. Moreover, the formation of super hydrogen molecules induced by the electrostatic field around Li ions can further enhance the hydrogen absorption energy. Our results indicated that Li decorated 6,6,12-graphyne would be a potential material for hydrogen storage.