5/2 - Student-Invited Lecture (physical): John Yates, University of Virginia
John Yates - speaker's webpage
Department of Chemistry
University of Virginia
A New Kind of Active Site in Heterogeneous Catalysis on Au Nanoparticles
Gold, usually considered to be inactive chemically, becomes very active for heterogeneous catalysis when subdivided into nanometer-sized clusters and supported on reducible oxides such as TiO2. Such supported nanoparticles of Au feature sites at the interface between the Au and the TiO2 support which exhibit high catalytic activity for oxidation reactions. We have used transmission IR spectroscopy combined with DFT calculations to investigate the catalytic oxidation of CO and ethylene, finding that the sites responsible for activity are on the perimeter of the Au particles. Oxygen- molecule activation occurs by adsorption of an O2 molecule between a perimeter Au atom and a neighbor Ti4+ site, producing a Ti4+-O-O-Au species which is a strong oxidizer analogous to a peroxo species. These special surface sites are called dual- catalytic sites. I will show a combination of experimental and theoretical results which all point to the unique activity of the dual-catalytic sites at the Au particle perimeter. In addition, an exotic surface species, the ketenylidene species, Au2C=C=O, has been discovered when C2H4 is first oxidized to acetate and then to Au2C=C=O.