Adsorption and diffusion of Pt and Au on the stoichiometric and reducedTiO2rutile (110) surfaces

A comparative ab initio pseudopotential study of the adsorption and migration profiles of single neutral Pt and Au atoms on the stoichiometric and reduced $\mathrm{Ti}{\mathrm{O}}_2$ rutile (110) surfaces is presented. Pt and Au behave similarly with respect to (i) most favorable adsorption sites, (ii) the large increase in their binding energy when the surface is reduced, and (iii) their low migration barrier on the stoichiometric surface. Pt, on the other hand, binds more strongly (by $\sim 2\mathrm{eV}$) 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 $\mathrm{Au}-\mathrm{Ti}$ interactions playing a more important role. On the reduced surface, the migration barrier of Pt trapped at an O vacancy site is significantly larger compared to that of Au.