(116b) Simulation of Au Nanoparticles Deposited On Metal Oxide Support
Gold is a typically inert metal, but since the discovery that gold nanoparticles can be catalytically active, there has been intense research to understand the origin of this phenomena. The activity of gold nanoparticles can also change drastically depending on the support, usually a metal oxide, indicating that support effects are relevant. Au catalysts have application in oxidation of CO, the water-gas shift reaction, and several other oxidation reactions. There has been much debate about the nature of Au catalysts, and why certain systems (e.g. Au/TiO2 or Au/CeO2) are more reactive than others. Understanding the nature of nano-sized Au and support effects are crucial to developing better Au catalysts.
Au over metal oxide surfaces have been previously modeled, however the size of the Au particles have typically been limited to small clusters, perhaps up to 1 nm in size. Experimentally relevant systems often involve Au particles several nm in size. In this work we modeled Au nanoparticles deposited on metal oxide supports using density functional theory. We considered a range of Au particles, including relevant larger particles up to 219 atoms. Au particles deposited on TiO2 and MgO were simulated at the DFT and DFT+U level. We probed several reaction sites through model reactions CO oxidation and the water-gas shift reaction. Reaction sites considered include nanoparticle corners, steps, terraces, and interfacial sites between Au and metal oxide. From this work we have provided meaningful insights on the the role of the substrate, surface defects, particle size and shape.