One-Step Synthesis of Bifunctional TiO2Catalysts and Their Photocatalytic Activity

In this paper, we have investigated in detail the preparation of anatase TiO2 catalysts by the controlled thermal decomposition of ammonium titanyl sulfate ((NH4)2TiO(SO4)2) and their catalytic activity. The structures of anatase TiO2 catalysts have been characterized by powder X-ray diffraction, N2 adsorption−desorption isotherms, diffuse reflectance UV−vis spectroscopy, infrared spectroscopy, X-ray photoemission spectroscopy, NH3 temperature-programmed desorption, and solid-state MAS NMR spectrometer. We report for the first time that the anatase TiO2 catalyst prepared by calcination of (NH4)2TiO(SO4)2 at 600 °C (TiO2-600) is a very active bifunctional catalyst. TiO2-600 is doped with N and S and thus very active in the photodegradation of methyl orange under visible light illumination (λ > 420 nm); meanwhile, it also has a large number of Brönsted acid sites arising from the covalently bonded sulfuric acid groups and thus is active in the esterification of ethanol and acetic acid to ethyl acetate. The Pt/TiO2-600 photocatalysts with different Pt loadings were prepared via the incipient wetness impregnation method and their photocatalytic activity for the H2 production from water splitting was evaluated with methanol as a sacrificial electron donor under both all-wavelength light and visible light (λ > 400 nm) irradiation. All Pt/TiO2-600 photocatalysts show considerable photocatalytic activity of water splitting. The optimum Pt loading on TiO2-600 is 1 and 0.1 wt % for the all-wavelength light and visible light photocatalytic reaction, respectively. Our results demonstrate a facile method to prepare highly active bifunctional TiO2 catalysts promising in both visible-light-driven photocatalysis and acid catalysis.