A comparative DFT study of adsorption and catalytic performance of Au nanoparticles at anatase and brookite TiO_2 surfaces

摘要

We have compared the adsorption properties of small Au_n (n = l-8) nanoparticles on the defect-free (stoichiometric) and defective (partially reduced) brookite TiO_2(210) and anatase TiO_2(101) surfaces using density functional theory calculations. The interaction between Au atoms and anatase TiO_2(101) was determined to be quite weak and small Au_n particles grown at defects (O vacancies) prefer extended 2D structures. By contrast, dispersion and 3D configurations appear to be favored at brookite TiO_2(210) for Au_n nanoparticles due to their strong interaction. Calculations of CO oxidation at Au_n (n = 6-8) particles supported at defective brookite TiO_2(210) show that occurrence of protruding low-coordinated Au atoms is essential for favorable CO adsorption and subsequent reaction with O_2. In particular, the configuration of the Au_n nanoparticles can determine the energetics in the formation of active Au atoms, and their mobility also affects the reaction between CO and O_2 (or O).