Structures of Pt clusters on graphene by first-principles calculations

The interactions between Pt-n clusters (n <= 13) and a graphene sheet have been investigated by first-principles calculations based on density functional theory. For single Pt-atom and Pt-2-dimer adsorptions, the stable adsorption sites are bridge sites between neighboring carbon atoms. When the number of Pt atoms in a cluster increases, the Pt-C interaction energy per contacting Pt atom becomes smaller. For smaller clusters (3 <= n <= 7), the adsorption as a vertical planar cluster is more stable than that as parallel planar or three-dimensional (3D) clusters, due to the stability of a planar configuration itself and the stronger planar-edge/graphene interaction, while the adsorption as a parallel planer cluster becomes stable for larger cluster (n >= 7) via the deformation of the planar configuration so as to attain the planar-edge/graphene contact. For much larger clusters (n >= 10), the adsorption as a 3D cluster becomes the most stable due to the stability of the 3D configuration itself as well as substantial Pt-C interactions of edge or corner Pt atoms. The interfacial interaction between a Pt cluster and graphene seriously depends on the shape and size of a cluster and the manner of contact on a graphene sheet. (C) 2009 Elsevier B.V. All rights reserved.