Agglomeration, support effects, and CO adsorption on Au/TiO2(110) prepared by ion beam deposition

The agglomeration behavior of 0.05 ML of An deposited as Au+ at 1 eV impact energy on rutile TiO2(110) was investigated by a combination of ion scattering, X-ray photoelectron spectroscopy (XPS), CO adsorption, and CO temperature-programmed desorption (TPD). Samples were studied over the temperature range between 115 K and 800 K, and on both near-stoichiometric UHV-annealed TiO2, and TiO2 with a high density of oxygen vacancies created by He+ bombardment. At low temperatures, An is atomically dispersed, shifting into complexes with oxygen vacancies for T-anneal around room temperature, and finally agglomerating into small clusters for T-anneal >= 450 K. CO adsorbed on dispersed atoms results in nearly 1 eV shift in the Au4f binding energy to higher energy, and CO desorption peaking at 280 K. CO adsorbs more weakly on Au-vacancy complexes and on An in clusters, as indicated by both TPD and XPS. Comparisons with experiments depositing thermal Au, and implications for size-selected CO oxidation on Au-n/TiO2 are discussed. (c) 2005 Elsevier B.V. All rights reserved.