▎ 摘　　要

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerenes, can be used for hydrogen storage. Alkali doping of these materials generally increases their H-2-storage density. In this study, the interaction of hydrogen molecules with Li-doped graphene nanoflakes was systematically investigated using density functional theory (DFT). A large polycyclic aromatic hydrocarbon composed of 37 benzene rings (referred to as GR) was used as a model of a graphene nanoflake, and GR-Li-(H-2) and GR-Li+-(H-2)(n), (n = 0-13) clusters were used as hydrogen storage systems. The first and second coordination shells of H2 around GR-Li were saturated at n = 3 and 7, respectively. The binding energy of H-2 to GR-Li decreased with increasing n, reaching a limiting value at n = 10. For GR-Li+-(H-2)(n), similar results were obtained and the Li atom on GR was shown to be activated by electron transfer from Li to GR. The diffusion barrier of Li+ on GR decreased upon addition of H-2 to Li+ from 6.35 (n = 0) to 3.62 kcal/mol (n = 4). The mechanism of H-2 addition is discussed herein based on the calculated results.