Oxidation at the sub-nanoscale: oxygen adsorption on graphene-supported size-selected Ag clusters

Abstract

The evolution of the aggregation of condensed matter from single atoms to three-dimensional structures represents an important topic in nanoscience, since it contains essential information to achieve tailor-made growth of nanostructured materials. Such an issue is particularly important in the case of the formation of nano-oxides, which have strong potentialities in heterogeneous catalysis reactions. Herein, we show that a low-nuclearity graphene supported Ag cluster (formed by 11 atoms) shows a local AgO₄ configuration, spatial charge distribution and two oxidation states that are similar to those of bulk AgO. This result indicates that bulk oxide conformations can start to develop already for extremely small atomic aggregates (<1 nm), differently from metallic clusters. This local conformation shows the lowest oxygen vacancy formation energy, which affords high efficiency in the ethylene epoxidation reaction with Ag and strongly supports the possibility of incorporating sub-nanometric clusters in important catalytic reactions.