Personnel:

Emily Coombs, M.S. 2008

Research Interests
DFT modeling of atomically dispersed gold in metal oxide

Activities
The oxidation of CO to CO₂ is an important process in many environmental and industrial applications, including both emission control and preventing catalyst poisoning. In particular, nanoscale metal oxides with small particles of Au or Pt are very promising catalysts for this reaction, including studying Au-carrying titania nanoparticles. However, although there is a lot of interest in this type of catalyst, there are many questions about what characteristics are important. Among several unsettled aspects of the CO oxidation mechanism, the role of the metal oxide and the nature of the Au species have all been heavily disputed.

Computational modeling is one tool to investigate the importance of different variables in this system. Not only does this include the size, role and electronic characteristics of the Au particles; it also includes the source of the oxygen used in the oxidation, which might either come from a reducible oxide or from the reaction gas, and the role of oxygen defects. As a reducible metal oxide, similar to other highly active catalysts, titania is both a good model for a reducible metal oxide support; yet it possesses characteristics that make it well suited to computer modeling compared to several of the other such oxides.

We are employing periodic, self-consistent density functional theory (DFT) calculations to address CO oxidation on small Au particles. An objective of this project is to use computational modeling to study the low temperature CO oxidation on a Au/TiO2 surface. Previous work has suggested that the active sites in similar catalysts are small particles of gold, strongly associated with the surface oxygen. Therefore we use are using DFT to investigate the thermodynamic and kinetic properties of intermediate elementary steps on the surface. From this data we can make conclusions about the stability of reaction intermediates and kinetic limitations of possible reaction pathways. Our goal is to ascertain the geometry and energetics of possible precursors on these surfaces, identify possible reaction pathways, and determine activation energies.

Education