The growth and thermal stability of Au clusters on a partially-reduced rutile TiO2 （110）-1 × 1 surface were investigated by high-resolution photoelectron spectroscopy using synchrotron- radiation-light. The valence-band photoelectron spectroscopy results demonstrate that the Ti^3＋3d feature attenuates quickly with the initial deposition of Au clusters, implying that Au clusters nucleate at the oxygen vacancy sites. The Au4f core-level photoelectron spectroscopy results directly prove the existence of charge transfer from oxygen vacancies to Au clusters. The thermal stability of Au clusters on the partially-reduced and stoichiometric TiO2（110） surfaces was also comparatively investigated by the annealing experiments. With the same film thickness, Au clusters are more thermally stable on the partially-reduced TiO2（110） surface than on the stoichiometric TiO2（110） surface. Meanwhile, large Au nanoparticles are more thermally stable than fine Au nanoparticles.
We developed a novel approach for the preparation of N-doped TiO2 photocatalysts by calcining ammonium titanium oxalate at different temperatures. The structures of N-TiO2 were characterized by powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, diffuse reflectance UV-Vis spectroscopy, and scanning electron microscope. The N-doped TiO2 photocatalysts calcined below 700 ℃ are the pure anatase phase but that calcined at 700 ℃ is a mixture of anatase and rutile phases. The doped N locates at the interstitial site of TiO2 which leads to the narrowing of bad gap of pure anatase N-TiO2. Among all photocatalysts, N-TiO2 photocatalysts calcined at 600 and 400 ℃ exhibit the best performance in the photodegradation of methyl orange under the UV light and all-wavelength light illuminations, respectively; however, because of the perfect crystallinity and the existence of anatase-rutile phase junctions, N-TiO2 photocatalyst calcined at 700 ℃ exhibits the highest specific photodegradation rate, i.e., the highest quantum yield, under both the UV light and all-wavelength light illuminations.
