Lithium-decorated oxidized graphyne for hydrogen storage by first principles study

The geometric stability and hydrogen storage capacity of Li decorated oxidized γ-graphyne are studied based on the first-principles calculations. It is found that oxygen atoms trend to bond with acetylenic carbons and form C=O double bonds on both sides of graphyne. The binding energy of single Li atom on oxidized graphyne is 3.29 eV, owning to the strong interaction between Li atom and O atom. Meanwhile, the dispersion of Li is stable even under a relatively high density. One attached Li atom can at least adsorb six hydrogen molecules around. Benefitting from the porous structure of graphyne and the high attached Li density, a maximum hydrogen storage density 12.03 wt. % is achieved with four Li atoms in graphyne cell. The corresponding average binding energy is 0.24 eV/H₂, which is suitable for reversible storage. These results indicate that Li decorated graphyne can serve as a promising hydrogen storage material.