Strong Chemical Interactions Between Au and Off-Stoichiometric Defects on TiO₂ as a Possible Source of Chemical Activity of Nanosized Au Supported on the Oxide

The effect of off-stoichiometric point defects (oxygen vacancies or extra oxygen atoms at the metal−oxide interface) on oxide surfaces on the chemical activity of Au nanostructures supported on the oxide was studied using the density functional theory and ab initio thermodynamic calculations. We find that highly active Au sites are present on the Au nanostructures, when Au is anchored to the defects at the Au−oxide interface. Depending on the nature of the defect, we create electron-rich or electron-deficient Au. We show that the presence of the highly active Au sites does not correlate with the nominal charge on Au, and that the off-stoichiometric defects in the oxide play a critical role not only in anchoring metal particles, but also in inducing chemical activity on the particles.