▎ 摘　　要

As a candidate for hydrogen storage medium, geometric stability and hydrogen capacity of Ca decorated graphene with topological defects arc investigated using the first principle based on density functional theory (DET), specifically for the experimentally realizable single carbon vacancy (SV), 585 double carbon vacancy (585 DCV) and 555-777 double carbon vacancy (555-777 DCV) defects. It is found that Ca atom can be stabilized on above defective graphenes since Ca's binding energy on vacancy defect is much larger than its cohesive energy. Up to six H-2 molecules can stably bind to a Ca atom on defective graphene with the average adsorption energies of 0.17-0.39 eV/H-2. The hybridization of the Ca-3d orbitals with H-2-sigma-orbiLals and the electrostatic interaction between the Ca cation and the induced H-2 dipole both contribute to the H-2 molecules binding. Double-side Ca-decorated graphene with 585 DCV and 555-777 DCV defects can theoretically reach a gravimetric capacity of 5.2 wt% hydrogen, indicating that Ca-decorated detective graphene can be used as a promising material for high density hydrogen storage. (c) 2014 Elsevier B.V. All rights reserved.