Interaction of Au with titania: the role of reduced Ti

摘要

The interaction of Au with oxide supports has been found to play a vital role in determining the unique properties of Au catalysts. In this study, the binding of Au with titania was investigated using scanning tunneling microscopy (STM) and ultra-violet photoemission spectroscopy (UPS). Two support systems, rutile TiO2(110) and an ordered TiO_x/Mo(l 12) thin film were used. On a highly defective TiO2(110) surface, Au particles were found to bind first on the oxygen vacancy sites. Complete wetting of the oxide by Au was found on an ordered and reduced Ti~(3+) O_x/Mo(112) film to form two ordered structures, a (1 X l)-monolayer and a (1X3)-Au/TiO_x/Mo(112) bi-layer. Detailed STM images confirm the proposed structural models. Reduced titania was found to enhance the binding of Au with Ti sites and promote electron donation from Ti~(delta+) to Au, leading to electron-rich Au and to enhanced CO bonding.