Calcium-decorated graphene for hydrogen storage: A van der Waals density functional study

► vdW-DF give a better description on the interactions between H2 molecules and Ca-graphene. ► H2 molecules are predicted to be weakly adsorbed (⩽100 meV/H2) by the Ca-decorated graphene using vdW-DF. ► The van der Waals interaction cannot be neglected in the studies of hydrogen storage materials.