The influence of oxygen molecule (O-2) on the hydrogen storage process of Li-doped graphene has been investigated using the density functional theory (DFT) simulation. The results show that, the existence of the O-2 has a large influence on the hydrogen storage process of Li-doped graphene. Under the condition of coadsorption, each Li atom can only adsorb 3 H-2 (4 H-2 can be adsorbed without O-2) with a theoretical storage density of 2.6 wt.%. (C) 2014 Elsevier B. V. All rights reserved.