▎ 摘　　要

Density functional calculations of palladium absorbed on graphene have been performed to study the first stages of Pd coating and/or Pd cluster formation on the graphene surface, a question of great relevance to many experiments. We have found that palladium atoms deposited on graphene have a strong tendency to form clusters. Three-dimensional clusters are more stable than planar clusters and the transition from planar to three-dimensional Pd clusters adsorbed on graphene occurs very early as a function of cluster size, at Pd-4, as a consequence of the strong Pd-Pd interaction. Palladium might enhance hydrogen storage in porous materials by surface reactions. However, it is a heavy element and the formation of three-dimensional Pd clusters decreases the cluster surface and increases the cluster weight. Hence, a way should be found to prevent clusterization or to disperse finely the palladium atoms deposited on carbon materials. The adsorbed clusters are weakly magnetic, which may be of interest for some applications.