Electric charge of single Au atoms adsorbed on TiO₂(110) and associated band bending

The influence of charge transfer from single Au atoms to TiO ₂(110) on the photostimulated desorption (PSD) of ¹⁸O ₂ has been studied using a measurement of the rate of hole transport which mediates PSD. Band bending effects observed experimentally and theoretically by density functional theory indicate that Au^σ+ atoms are present. The presence of atomically dispersed Au on the TiO ₂(110) surface with a constant coverage of preadsorbed ¹⁸O₂ depresses the photoinduced hole transport rate from the bulk to the TiO₂ surface and decreases the ¹⁸O ₂ PSD yield. This indicates that single Au atoms donate a fraction of an electron to the surface, causing downward band bending. DFT calculations show that ∼0.2 electron transfers from single Au atoms to the O ₂/TiO₂(110) surface and the valence and conduction bands bend ∼0.6 eV downward. With increasing Au coverage, the positive charge per Au atom decreases due to the formation of small Au clusters.