The formation of Au nanoclusters on rutile TiO2(110) has been studied with Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT). In the STM studies,1 three different TiO2(110) supports were used: (i) reduced TiO2 having bridging oxygen vacancies, (ii) hydrated TiO2 having bridging hydroxyl groups, and (iii) oxidized TiO2 having oxygen ad-atoms. At room temperature, gold nanoclusters nucleate homogeneously on the terraces of the reduced and oxidized supports, whereas on the hydrated TiO2(110) surface, clusters form preferentially at the step edges. The DFT studies1 show two different gold-TiO2(110) adhesion mechanisms for the reduced and oxidized supports. The adhesion of gold clusters is strongest on the oxidized support. The DFT studies2,3 further show that the excess oxygen atoms in the Au-oxidized TiO2 system are involved in the catalytic oxidation of CO under reaction conditions.
[1] D. Matthey, J.G. Wang, S. Wendt, J. Matthiesen, R. Schaub, E. Lægsgaard, B. Hammer, F. Besenbacher, Science, March 23rd (2007).
[2] J.G. Wang and B. Hammer, Phys. Rev. Lett. 97, 136107 (2006).
[3] J.G. Wang and B. Hammer, Topics in Catalysis, in press (2007). |