Surface and Interface Reactivity of Au Nanoparticles\nSupported on Rutile-TiO<sub>2</sub>(110) toward H<sub>2</sub>O, O<sub>2</sub>, CO, and CO<sub>2</sub>

Au\nnanoparticles with different coverages were deposited on a reduced\nrutile-TiO<sub>2</sub>(110) [r-TiO<sub>2</sub>(110)] surface. Their\nstructure and reactivity were probed with adsorption and reaction\nof H<sub>2</sub>O, O<sub>2</sub>, CO, and CO<sub>2</sub> using X-ray\nphotoelectron spectroscopy and temperature programmed desorption spectra.\nAu nanoparticles nucleate on bridge-bonded oxygen (BBO) vacancies\nof the r-TiO<sub>2</sub>(110) surface and quench the adsorption of\nprobing molecules on the BBO vacancies. Water facilely dissociates\nat the Au–TiO<sub>2</sub> interface of Au/r-TiO<sub>2</sub>(110) to subsequently produce H<sub>2</sub> above 200 K but not on\nthe r-TiO<sub>2</sub>(110) surface. The observed oxygen species on\nr-TiO<sub>2</sub>(110) and Au/r-TiO<sub>2</sub>(110) surfaces do not\nreact with coadsorbed CO whereas hydroxyl groups at the Au–TiO<sub>2</sub> interface of Au/r-TiO<sub>2</sub>(110) react with coadsorbed\nCO to produce CO<sub>2</sub>. Both the BBO vacancies and the Au–TiO<sub>2</sub> interface play vital roles in this reaction. These results\ngreatly help to fundamentally understand the structure of Au/TiO<sub>2</sub> catalysts and their catalytic activity in the reactions involving\nH<sub>2</sub>O, O<sub>2</sub>, CO, and CO<sub>2</sub>.