Structural Evolution of Pt Nanoclusters on Graphene Moire Superlattices

Moir & eacute; superlattices formed by graphene-covered Ru(0001) are known as excellent templates for the synthesis of monodispersed transition metal nanoclusters, but an accurate description of the structural evolution at the atomic level is still lacking. Herein, using first-principles calculations, we systematically explore the nucleation and growth of Pt nanoclusters (PtNCs) on such moir & eacute; superlattices. Our calculations reveal that, for the nucleation of PtNCs, FCC regions of the moir & eacute; superlattices are preferred compared with other regions due to the stronger C-sp(3) hybridization. Considering different shapes and stacking modes, monolayer PtNCs of regular hexagons and truncated triangles with three atoms removed from each corner and bilayer PtNCs of partially covered second layers with AA stacking are relatively stable. Comparing these stable configurations, we can find out that PtNC with 27 atoms is the critical size where the 2D growth mode will change to the 3D growth mode because of the weakening of Pt-C bonds caused by the inhibition of C-sp(3) hybridization. Our findings are of significance in revealing the structural evolution of metal nanoclusters on graphene moir & eacute; superlattices and other 2D templates.