Reversible hydrogen adsorption on Li-decorated T-graphene flake: The effect of electric field.

In the present work, we have studied a new allotrope of graphene, denoted as T-graphene (TG) flake as a versatile material in hydrogen storage. Recently, the metallic character of TG has been revealed. Our results show that the Li-decoration has a significant effect on the electronic properties of TG flake. Our density functional theory (DFT) calculations exhibit that the energy band gap of TG flake is decreased by decorating of the Li atom. Hydrogen adsorption on Li-decorated TG flake (Li/TG) under the influence of different external electric fields (EFs) is also explored by DFT calculations. We found that the hydrogen adsorption on the Li/TG increases when the positive EF is applied. Our results also show that the adsorption energy of the hydrogen on the Li/TG can be gradually enhanced by increasing the applied positive external EF along with the charge transfer direction. Moreover, Li atom in the Li/TG shows the high hydrogen capacity up to six H2 molecules. On the other hand, the H2 adsorption on the Li/TG is remarkably decreased by applying the negative EFs to the Li/TG. Therefore, the H2 adsorption/release procedure on the Li/TG are reversible and can be tuned by applying the appropriate EFs. Our study exhibits that the Li/TG is a promising material for reversible adsorption and release of H2 .