Exploring the structure and chemical activity of 2-D gold islands on graphene moiré/Ru(0001)

Au deposited on Ru(0001)-supported extended, continuous graphene moiré forms large 2-D islands at room temperature that are several nanometers in diameter but only 0.55 nm in height, in the apparent absence of typical binding sites such as defects and adsorbates. These Au islands conform to the corrugation of the underlying graphene and display commensurate moiré patterns. Several extended Au structure models on graphene/Ru(0001) are examined using density functional theory calculations. Close-packed Au overlayers are energetically more stable, but all interact weakly with the support. Preliminary tests found the Au islands/graphene/Ru(0001) surface to be active for CO oxidation at cryogenic temperature, which suggests that the Au itself is the locus of catalytic activity.