Stabilization of 2D Raft Structures of Au Nanoclusters with up to 60 Atoms by a Carbon Support

Herein, the stabilization of 2D single-atom high gold rafts containing up to ≈60 Au atoms on amorphous carbon, fabricated by sputtering of atoms and imaged by aberration-corrected scanning transmission electron microscopy, is demonstrated. These rafts deviate from the established cluster transition from 2D to 3D Au structural motifs in free clusters, which occurs in the region of 10-14 atoms. The experimental findings are supported by explicit ab initio calculations of Au (n = 3-147) clusters on graphene and the role of cluster-surface interactions in the stabilization of the 2D single-atom high Au cluster rafts on graphene is revealed. The transition from equilibrium 2D-3D structures is delayed to n = 19, while metastable 2D single-atom high rafts compete with 3D structures up to about n = 60 atoms. The catalytic activity of supported nanoclusters depends strongly on their structure (and carbon-based supports are used for a number of reactions); therefore these results are relevant to the catalytic performance of nanocluster-based catalysts.