| AVS 55th International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS1-WeA |
| Session: | Structure of Oxide Surfaces and Oxide Heterostructures |
| Presenter: | L.E. Walle, Norwegian University of Science and Technology, Norway |
| Authors: | L.E. Walle, Norwegian University of Science and Technology, Norway S. Plogmaker, Uppsala University, Sweden A. Borg, Norwegian University of Science and Technology, Norway A. Sandell, Uppsala University, Sweden |
| Correspondent: | Click to Email |
Gold has for a long time been regarded as an inert surface of little use as catalyst. However, in the last decade gold particles have begun to garner attention for their unique catalytic properties.1 Supported gold particles on metal oxides have been shown to be effective catalysts for several processes, including CO oxidation at remarkably low temperatures, down to 200 K. Most intriguing is the strong size dependence, particles below 5 nm in size are far superior to larger particles in terms of catalytic activity.2 The detailed mechanism behind the CO oxidation process on the Au/TiO2 system is still largely an enigma. Many studies have suggested under-coordinated Au atoms and the Au-TiO2 interface as reactive sites. A fundamental understanding of the growth mechanism of Au clusters on TiO2 and the nature of the Au/TiO2 bond is thus of great importance. Up till now most experimental studies of Au particles on single crystal TiO2 have been done on the rutile phase, due to the good availability of rutile single crystals. On the other hand, the anatase TiO2 polymorph seems to be the preferred phase when forming nanosized particles. In the last couple of years good quality anatase single crystals have become commercially available which has triggered an increased research interest. In this contribution we present a study of Au growth on single crystalline anatase TiO2(101) and TiO2(001) surfaces under UHV conditions using core level photoelectron spectroscopy. The data were obtained at the Swedish National Synchrotron Facility MAX II. A preliminary analysis gives that Au nucleates at steps on both surfaces. Regarding the (101) surface this is in agreement with a recent report by Gong et al.3 In addition, we have studied subsequent adsorption of CO at 120 K on the Au particles. Adsorption of CO induces a shift of the Au 4f core level by 1 eV, which is easily observed. The relative amount of Au atoms that can bond to CO varies with the amount of deposited Au. Since CO only bonds to under-coordinated Au atoms at 120 K the results thus give information regarding the geometrical properties of the Au particles.
1 M. Haruta, Catal. Today 36, 153 (1997).
2 M. Valden, X. Lai, and D. W. Goodman, Science 281, 1647 (1998).
3 X.-Q. Gong, A. Selloni, O. Dulub, P. Jacobson and U. Diebold, J. Am. Chem. Soc. 130, 370 (2008).