Paper SS1+NC-TuA5
Role of the Oxide Substrate on O₂ Dissociative Adsorption on Au Nanostructures: First Principle Studies

Tuesday, October 21, 2008, 3:00 pm, Room 208

In this work we apply the density functional theory calculations to explore the mechanism of high reactivity of Au nanoparticles on oxide substrates. We test the idea that the substrate – nanoparticle interaction makes the O2 dissociative adsorption favorable on this system, in contrast to bulk Au, and then the O atoms, so adsorbed, are consumed by reactants for further oxidation. We exploit the observation that the 1.5-layer Au film on TiOx displays an exceptionally high reactivity as compared to a monolayer Au film, as well as those with 2 or more layers.¹ We calculate the eneretics of dissociative adsorption of O2 on the surfaces 1.5, 2, 2.5, 3, 4.5, and 5 Au(001) layer structures in two environments: 1) free standing layers, 2) on TiO2 fragments (modeling a substrate). For all missing row n+0.5 Au structures under consideration, the total energy is found to decrease upon the O2 dissociative adsorption. However, analysis of entire pathway for this reaction suggests that the O2 dissociative adsorption is favorable only for 1.5Au/TiO2 structure. This result along with the experimental finding¹ point to the O2 dissociative adsorption as being the main mechanism for the observed reactivity of Au nanostructures. Calculated local densities of electronic states and local charges in the system will be presented for further insights into the nature of the effect.

¹M. S. Chen, D. W. Goodman, Science 306, 234 (2004). Work supported in part by DOE under grant # DE-FG02-03ER15842.