Electronic States of Ag and Au Atoms on Graphene/Rh(111)

Abstract

Supported single-metal atoms have attracted considerable interest as active centers in heterogeneous catalysis. Their unique electronic properties arise from their interactions with the support, ultimately influencing their catalytic activity. Graphene is widely used as a support material for metal atoms, and understanding how sp² carbon atoms influence the electronic state of these metal atoms is crucial for elucidating single-atom catalysis. Herein, we investigate the electronic states of individual Ag and Au atoms on a graphene layer using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. It was found that the 5s and 6s levels were split to form bonding and antibonding orbitals, leading to the emergence of an unoccupied state at 0.5−0.7 eV just above the Fermi level. As demonstrated by the adsorption of CO molecules, these levels play an important role in the interaction with gas molecules.