Hydrothermal synthesis of TiO2 photocatalysts in the presence of NH4F and their application for degradation of organic compounds

TiO2 photocatalysts were synthesized by hydrothermal method from tetraisopropyl orthotitanate (TPOT) in the presence of NH4F with different NH4F/Ti molar ratios (HT-TiO2) (F0, 0.01, 0.05, 0.25, and 1)). The formation of well-crystallized anatase phase of TiO2 and suppression of phase transition to rutile were observed even at high calcination temperature. The amount of employed NH4F influenced on the crystal size and surface area. XPS analysis showed that F- ions coordinated with Ti in the lattice. In comparison to the commercial TiO2 powder (P-25), the HT-TiO2 samples with high F- ion contents exhibited high absorption in the UV-visible range with a shift to the longer wavelength in the band gap transition. The measurement of the water adsorption ability suggested that the F- ion doping did not significantly influence on their hydrophobicity. The HT-TiO2 samples exhibited high photocatalytic activity for the degradation of i-BuOH diluted in water. The photocatalytic activities were apparently affected by surface area and crystallinity of TiO2 phase depending on the amount of employed NH4F. (C) 2007 Elsevier Ltd. All rights reserved.