Morphology of size-selected Pt_n clusters on CeO₂(111)

Supported Pt catalysts and ceria are well known for their application in automotive exhaust catalysts. Size-selected Pt clusters supported on a CeO₂(111) surface exhibit distinct physical and chemical properties. We investigated the morphology of the size-selected Pt_n (n = 5-13) clusters on a CeO₂(111) surface using scanning tunneling microscopy at room temperature. Pt_n clusters prefer a two-dimensional morphology for n = 5 and a three-dimensional (3D) morphology for n ≥ 6. We further observed the preference for a 3D tri-layer structure when n ≥ 10. For each cluster size, we quantitatively estimated the relative fraction of the clusters for each type of morphology. Size-dependent morphology of the Pt_n clusters on the CeO₂(111) surface was attributed to the Pt-Pt interaction in the cluster and the Pt-O interaction between the cluster and CeO₂(111) surface. The results obtained herein provide a clear understanding of the size-dependent morphology of the Pt_n clusters on a CeO₂(111) surface.