Preparation And Catalytic Properties Of Semiconductor Nanocrystalline Thin Films Of Visible Responding

In recent years, semiconductor photocatalysis has attracted increasing attention in the field of environmental protection due to its photodegradation of organics pollution in aqueous phase. Among all the various semiconductors used in photocatalysis, titanium dioxide (TiO2) has been proved to be one of the most promising photocatalysts with the advantages of low cost, nontoxicity, high oxidative power, high catalytic activity and chemical stability. Although TiO2 is used widely, the large bandgap of TiO2 is 3.2 eV, it makes the photocatalytic activity of TiO2 effectively works only under ultraviolet (UV) light irradiation, which accounts for only a small part (5%) of solar energy, while the visible light can not be used fully. Additionally, it is difficult to separate and recycle TiO2 nanoparticles from the suspension and nanoparticles is easy to agglomerate. In this paper, a iodine-doped TiO2 (I-TiO2) nanocrystalline film was prepared by using doctor-blade technique, in which I-TiO2 nanocrystals as film component were hydrothermally synthesized. The obtained films were characterized by field emission scanning electron microscope (FESEM) and UV-vis diffuse reflectance spectra.The photoactivity of I-TiO2 nanocrystalline films was evaluated in terms of the degradation of binary dyes (Flu/RhB and EO/RhB) in water at neutral pH upon visible-light irradiation. After the iodine was doped, the TiO2 nanocrystalline films have a significantly greater absorption and higher photoactivity than the pure TiO2 nanocrystalline films. When the I/Ti mole ratio is 10%, the film has the highest photoactivity. The photodegradation of RhB is enhanced significantly when Flu or EO, which played the role of photosensitizing agent, were introduced into the RhB solution. At the last, in order to ascertain the active species in the course of photocatalytic degradation, we added glycol, which acted as the·OH scavengers, into the Flu/RhB and EO/RhB systems. The result showed that the degradation rate of RhB, Flu, and EO all remarkably decreased. This suggeses that·OH radicals are the major oxidation species in the photodegradation reaction.The prepared iodine-doped TiO2 nanocrystalline film in this paper increased the absorption of visible light of TiO2 film and greatly enhanced the value of application in use of solar energy. In the binary dyes system, mutual interaction simultaneous and degradation occurred between two dyes, which significantly promoted the degradation of dyes. The method used in this paper has the advantages of high efficiency and low cost. It can be used for purification of industrial wastewater and the trace toxic bio-degradable organic wastewater of urban sewage.