Gold atom and dimer adsorbed on perfect and defective graphene and boron nitride monolayer: A first-principles study

Energetic and structural properties of gold atom (Au) and gold dimer (Au dimer) adsorbed on pristine and defective graphene (Gra) and boron nitride monolayer (BN) are investigated using density functional theory. Substitutional doping models in the neutral charge state are considered by replacing the C site in graphene with B or N atom impurities (Gra-C_B and Gra-C _N) or by doping the B or N sites in the BN sheet by a C atom (BN-B_C and BN-N_C). It is shown that while the binding of Au/Au-dimer to a pristine support is weak, stronger binding could be achieved by introducing a defect in the surface indicating that defects can trap metal atoms. It is found that Gra-C_B and BN-N_C support Au/Au-dimer well and BN-N_C is more preferable from aspect of adsorption energy. Interaction between Au/Au-dimer and the BN-N_C substrates is explained by assigning appropriate partial charge densities of the valence band maximum (VBM) and conduction band minimum (CBM) at the point and projected densities of states (PDOS). The results demonstrate that both pristine and defective BN surfaces can no longer be treated as inert supports for Au/Au-dimer.