Morphology, Absorption Spectra, and Photocatalytic Activity of Nanosized Solid Solution Ti_(1-x)Eu_xO_(2-x)/2

摘要

Tremendous interest in titanium dioxide is caused by its important practical application as a photocata-lyst of oxidation of toxic and colored organic compounds dissolved in water, as well as of water disinfection. Titanium dioxide, is an environmentally safe compound. Its use is not associated with accumulation of wastes that should be utilized or disposed of. It is believed that the higher photocatalytic activity of ana-tase, as compared with rutile, is due to the higher position of the Fermi level, the better ability to adsorb oxygen, and stronger tendency to hydroxylation [1]. However, titanium dioxide with the anatase structure as a photocatalyst has disadvantages that limit its use. Because of the wide band gap (E = 3.2 eV), anatase is active only in the UV spectral range and absorbs an insignificant part of solar light (～5%) [2, 3]. The enhancement of the photocatalytic activity of titanium dioxide and its shift toward longer wavelength can be achieved by doping the metal and oxygen sub-lattices of titania, as well as by changing the size and morphology of particles and modifying their bulk and surface properties. The introduction of lanthanide ions into the anatase structure leads to narrowing of the band gap and considerably decreases the electron-hole pair recombination rate, which improves the anatase photocatalytic activity under visible light irradiation [4|. However, there are data that point to the lack of such a correlation since the absorption band edge of anatase doped with various lanthanides is not noticeably shifted [5|. The difficulty of describing the mechanism of photocatalysis for these objects, as well as the inconsistency of the optical and catalytic properties of doped titania, is due to that different methods of synthesis of the photocatalyst have been used, which leads to oxides of different morphology, dimension, micro-structure, and structure imperfection.