Investigation of the Interaction Between Au and Brookite TiO2 Using Transmission Electron Microscopy and Density Functional Theory
Kohei Tada, Yoyo Hinuma, Satoshi Ichikawa, Shingo Tanaka
Abstract
Abstract Au/TiO2 systems are typical nano-gold catalysts and have been widely studied as models for functional nano-interfaces. The crystal shape is important for functional nano-interfaces and influences the activity and durability of Au/TiO2 catalysts. Of the three stable TiO2 crystal systems, rutile and anatase have been investigated thoroughly with respect to Au/TiO2 interfaces. However, knowledge of the Au/brookite TiO2 interaction is scarce. We prepared a Au/brookite TiO2 catalyst, which is active in low-temperature CO oxidation, and performed transmission electron microscopy (TEM) observation of its interface structure. TEM revealed that the Au nano-particles were adsorbed on brookite TiO2 (101). This new Au/TiO2 interface has not yet been investigated theoretically. The TiO2 (101) slab model was optimised using theoretical density functional theory calculations, and the Au/brookite TiO2 (101) interaction was investigated. The calculated results revealed that brookite TiO2 (101) can adsorb Au atoms more strongly than the other TiO2 surfaces can. In Au/brookite TiO2, an O2−-Au+-O2− linear coordination structure can be formed, and 2 eV stabilisation can be achieved by surface complex formation. This result indicates that Au atoms can be anchored even on stoichiometric and non-polar surfaces without defect sites or doping.