particles supported on pristine graphene-like cluster: A DFT cluster approach

Graphene is an only one-atom-thick bi-dimensional sheet with a unique electronic structure. It is a zero-gap semiconductor, where the electrons mimic massless relativistic particles. Because of its interesting electron properties, graphene is a promising material for supporting catalysts like palladium, silver, and Pd-Ag. The pristine graphene was modelled by using a 306 planar cluster, where Pd₆, Ag₈, and Pd₆/Ag₈ particles were adsorbed.

The geometry of a graphene cluster was optimized starting with a planar cluster and letting all the atoms fully free. After the geometry optimization, we observed that the cluster remained planar. Geometry optimization of silver on graphene was started with both silver and graphene having a planar geometry; after the geometry optimization, both remained planar. The silver planar cluster adsorbs very weakly on pristine graphene. The geometry optimization of palladium and graphene was started with both palladium and graphene having a planar geometry. It was observed that, during the optimization, palladium stacks, while graphene remains planar.

Charge transfer between Pd₆ and Ag₈ in the free Pd₆/Ag₈ particle was determined and compared with the charge transfer in the graphene-supported Pd₆/Ag₈. Charge transfer was determined via density difference analysis. In addition, NBO and natural population analysis were also reported.