Preparation of Controllable Crystalline Titania and Study on the Photocatalytic Properties

Abstract

Nanocrystalline TiO₂ catalysts with different anatase/rutile ratios and high surface area (113−169 m²/g) have been prepared at low temperature by the microemulsion-mediated hydrothermal method. The samples were characterized by x-ray diffraction (XRD), Fourier transform (FT)-IR spectra, UV−vis diffuse reflectance spectra, and nitrogen adsorption−desorption methods. The contents of anatase and rutile phases in the TiO₂ powders have been successfully controlled by simply changing the proportion of Cl^- and SO₄^2- in the aqueous phase of the microemulsion. A proposed mechanism involving bidentately chelated sulfate is discussed to explain the variation of the crystalline phase in the TiO₂ powder. The photodegradation of methyl orange (MO) in water has been investigated over titanium dioxide consisting of different anatase/rutile ratios. The catalyst containing 74.2% anatase showed the highest photocatalytic activity, which is due to a synergistic effect between anatase and rutile. The synergism was also found for the photodegradation of MO with physically mixed anatase and rutile as catalysts.