Interaction of silver with oxygen on sputtered pyrolytic graphite

Using core level spectra, it has been observed previously that the oxidation of silver nanoparticles deposited on sputter-damaged highly ordered pyrolytic graphite (HOPG) surfaces is very different from that taking place on surfaces composed entirely of silver. It is generally accepted that the final stage of the oxidation of silver is the formation of Ag2O/AgO. However, in the case of silver nanoparticles on HOPG, Ag2O/AgO can be further oxidized to give a species of unknown composition. In the present work it has been demonstrated that under these oxidizing conditions silver nanoparticles deposited on HOPG form silver carbonate. This implies that strong metal support interactions are responsible for the different behavior of silver nanoparticles on HOPG compared to that of silver in bulk. Carbonate formation is further suggested to be responsible for the deactivation of silver catalysts.

For Ag nanoparticles supported by sputtered HOPG, carbonate formation was observed under highly oxidizing conditions. This result implies that Ag, O and C of the support can react together forming a new species, which does not exist on the surface of pure Ag bulk. Carbonate formation is related to the deactivation of the Ag surface in heterogeneous catalysis.Figure optionsDownload as PowerPoint slide