First principles calculations of hydrogen storage on Cu and Pd-decorated graphene

Transition metals (TM) such as palladium (Pd) and copper (Cu) atom were introduced on defect-free graphene and graphene with a single vacancy (SV) defect, to investigate their potential hydrogen storage using first principles calculation. All calculations were performed using plane wave based density functional theory (DFT) as implemented in Quantum ESPRESSO (QE). Generalized gradient approximation (GGA) exchange-correlation function as described by Perdew-Burke-Ernzerhof (PBE) was used. The interaction between the valence electron and the ionic core was represented by ultrasoft pseudopotentials. In this study, the structure and geometry of complex hydrides were investigated, and the effect of a SV defect in graphene on hydrogen storage was explored. It was concluded that the introduction of a SV defect prevents the TM atom clustering and enables hydrogen molecule adsorption within the ideal usable range.