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Abstract: LiF-doped TiO2 was prepared by hydrolysis of tetrabutyl titanate in a mixed LiF–H2O–alcohol solution. The prepared LiF-doped TiO2 powders were characterized by X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectroscopy and photoluminescence spectra (PL). The photocatalytic activity was evaluated by the decomposition of trichloromethane (CHCl3). The results showed that LiF-doping increased the amount of OOH and oxygen vacancy (OV) on the surface of TiO2, which were beneficial to photocatalytic activity. LiF-doping inducted the new isolated energy band located above the valence band of TiO2, which extended the absorption region of TiO2 to visible light. The results of photocatalytic reaction showed that the photocatalytic activity of LiF-doped TiO2 was 2.5 times higher than that of pure TiO2. [Copyright &y& Elsevier]

Abstract: An overall comparative study was carried out on Li-doped, F-doped, and Li–F-codoped TiO2 powders in order to elucidate the roles of Li+ and F− ions in photocatalyst. The characteristic data were based on the analysis of XRD, XPS, and PL spectra. The effects of atomic ratio of Li/Ti and F/Ti on the photocatalytic activity were also investigated. As the results, Li doping accelerated the phase formation of rutile in lower temperature while F doping prevented the phase transition from anatase to rutile. Li doping inducted a large amount of OOH on the surface of TiO2, while F doping consumed much of OOH. Li+ ions acted as the roles of recombination center of electron–hole pairs while F doping could restrain the recombination of electron–hole pairs on the center of Li+ ions. The roles of Li+ and F− ions were also confirmed in the experimental section, where the photocatalytic activity of TiO2 was improved greatly by synergistic reaction of Li+ and F− ions. [Copyright &y& Elsevier]

Abstract: Photocatalysts nano A2Ti n O2n+1 (A=Li, Na, K) were prepared successfully by novel hydrothermal synthesis process. Powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) absorption spectra and field-emission scanning electron microscope (FE-SEM) measurements. These results showed that the compositions of lithium, sodium and potassium titanates were Li2TiO3, Na2Ti3O7 and K2Ti8O17, respectively. The nano crystals of Li2TiO3 were self-assembled as snowflakes while that of Na2Ti3O7 and K2Ti8O17 were nanorods. Photocatalytic properties of alkali titanates were also investigated. The results indicated that alkali titanates as prepared have higher photocatalytic activities compared with P25 TiO2 in the degradation of chloroform under UV light irradiation. A combination of K2Ti8O17 and NiO produces a photocatalyst effective for the degradation of chloroform in aqueous solution. The framework of the tunnel structure was suitable for accommodating cocatalysts such as NiO to induce a strong interaction between the active species and cocatalysts. Na2Ti3O7 has high photocatalytic activity under visible-light irradiation due to its strong absorption in the visible light region. The photocatalytic properties of Li2TiO3 are inferior to that of Na2Ti3O7 and K2Ti8O17 due to its mono-perovskite structure. [Copyright &y& Elsevier]

Abstract: Nanocrystalline tungsten oxide-doped titanium dioxide (WO x -TiO2) powders were prepared by a sol-mixing method. The photooxidation efficiencies of WO x -TiO2 catalysts were evaluated by conducting a set of experiments of photodegrading Methylene blue (MB) in aqueous solution. The experiments demonstrated that the MB in aqueous solution was successfully degraded using WO x -TiO2 under visible light irradiation, especially when the pH value of the solution was over 6. It was found that an optimal WO x dosage of 1% in WO x -TiO2 achieved the highest photocatalytic activity in the conditions of this experiment, on which MB was photooxided completely within 1h. Powders were characterized by X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), UV–vis absorption spectra, transmission electron micrograph (TEM) measurements. These results showed that tungsten oxides not only hindered the growth of TiO2 particles but greatly increased the transformation temperature (>800°C) from anatase to rutile during sintering; the dominant fraction of tungsten oxides was non-stoichiometric tungsten oxide (W x O y ) with W n+ (4< n <6), which could easily substitute Ti4+ in the lattice of TiO2 because of the similarity in the ion radius of W n+ and Ti4+ to form non-stiochiometric solid solution of W x Ti1−x O2. The light absorption band of TiO2 changed from the near UV to the visible light range (2.98eV in 1.0% WO x -TiO2) because of the tungsten impurity energy level induced by W x Ti1−x O2. [Copyright &y& Elsevier]