First-principles study of high-capacity hydrogen storage on graphene with Li atoms

Developing safe and efficient hydrogen storage medium is essential for hydrogen economy since hydrogen is one of the ideal renewable energy sources. One possible way to store hydrogen can be realized by the adsorption of hydrogen molecules on the surface of low-weight material. In this paper, detailed studies for hydrogen storage on graphene with Li atoms have been carried out using the first-principles calculations based on density functional theory. With the Li coverage increasing from the (2×2) to (3×3) pattern on graphene, adsorbed Li atoms become more positively charged, which is opposite to that during the evolution of coverage from the (4×4) to (2×2) pattern. The binding energy of Li atom with the (3×3) pattern on graphene is larger than that with the (2×2) pattern. Results indicate that hydrogen storage capacity can be increased to 16 wt % by adjusting the coverage of Li atoms on graphene to the (3×3) pattern at both sides.