Adsorption and Diffusion of Pt and Au on the Stoichiometric and Reduced   TiO2 Rutile (110) Surfaces
  A comparative first principles pseudopotential study of the adsorption and migration profiles of single Pt and Au atoms on the stoichiometric and reduced TiO2 rutile (110) surfaces is presented. Pt and Au behave similarly with respect to (i) most favorable adsorption sites, which are found to be the hollow and substitutional sites on the stoichiometric and reduced surfaces, respectively, (ii) the large increase in their binding energy (by ~1.7 eV) when the surface is reduced, and (iii) their low migration barrier near 0.15 eV on the stoichiometric surface. Pt, on the other hand, binds more strongly (by ~2 eV) to both surfaces. On the stoichiometric surface, Pt migration pattern is expected to be one-dimensional, which is primarily influenced by interactions with O atoms. Au migration is expected to be two-dimensional, with Au-Ti interactions playing a more important role. On the reduced surface, the migration barrier for Pt diffusion is significantly larger compared to Au. 
Hakim Iddir, Serdar Ogut, Nigel D. Browning, Mark M. Disco