Electric Charge of Single Au Atoms Adsorbed on TiO2(110) and Associated Band Bending

The influence of charge transfer from single Au atoms to TiO2(110) on the photostimulated desorption (PSD) of O-18(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 delta+ atoms are present. The presence of atomically dispersed Au on the TiO2(110) surface with a constant coverage of preadsorbed O-18(2) depresses the photoinduced hole transport rate from the bulk to the TiO2 surface and decreases the O-18(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 similar to 0.2 electron transfers from single Au atoms to the O-2/TO2(110) surface and the valence and conduction bands bend similar to 0.6 eV downward. With increasing Au coverage, the positive charge per Au atom decreases due to the formation of small Au clusters.