Study On The Photocatalytic Degradation Properties Of Titanium Oxide Film And Its Composite Films

TiO2 film and TiO2 composite films could accomplish the photocatalytic degradation of organic compounds under the radiation of UV. So they have a variety of application prospects in the field of environmental protection, indoor air cleaning, and self-cleaning coating, and so on.TiO2 films were prepared by mid-frequency AC reactive magnetron sputtering technique. The effects of processing parameters on photocatalytic degradation property of TiO2 film were systematically investigated. The influences of UV light source and reactor type on the photocatalytic performances of TiO2 film for methylene blue (MB) were discussed. And the other degradation objects such as methyl orange (MO), DDVP, and formaldehyde have been selected to verify the photocatalytic degradation property of TiO2 film. By growing the metal film or other metallic oxide film on TiO2 film or doing this before TiO2 film deposition, totally five kinds of composite films, namely, Ag/TiO2, Mo/TiO2, SnO2/TiO2, ZrO2/TiO2, and TiO2/ZrO2, have also been prepared by magnetron sputtering technique. TiO2: Mo film has been prepared by reactive magnetron sputtering technique using Ti-Mo (10at%) alloy target. The photocatalytic degradation properties of all these TiO2 composite films were investigated using MB as a degradation object.The results show that a stoichiometric TiO2 film mainly composed of anatase phase can be steadily grown by mid-frequency AC reactive magnetron sputtering under proper deposition conditions in Ar/O2 atmosphere with Ti metal target. Thus deposited TiO2 film shows excellent photocatalytic degradation performance for MB, formaldehyde etc., and has very good stability of photocatalytic degradation.The photocatalytic degradation rate of Ag/TiO2 composite film for MB prepared by magnetron sputtering obviously increased, for the highest by three time, as compared with that of TiO2 film with same thickness. The degradation results show that only when Ag on the surface of TiO2 film is composed of separating Ag particles, can it improve the photocatalytic degradation performance of TiO2 film. The reason for above results is that only if Ag is in a state of separating particles, can it be an effective capturer of photo-induced electron and reduce the recombination of photo-generated holes and electrons. Crystalline perfection of TiO2 film can be improved by a pre-deposited ZrO2 film. The photocatalytic degradation activity of TiO2/ZrO2 film increases by about 30 % than that of pure TiO2 film. The photocatalytic degradation activity of Mo/TiO2 film, SnO2/TiO2 film, and ZrO2/TiO2 film is lower than that of the TiO2 film with the same thickness. The main reason for this is that Mo, ZrO2 and SnO2 film is favorable to grow a continuous film to cover the surface of TiO2 film. Then these films will obstruct TiO2 film and degraded object from direct contact and photo-induced carriers from transferring to the surface.The photocatalytic degradation ability of TiO2: Mo composite film with a Ti to Mo atomic ratio of 7:1 gets poorer comparing with TiO2 film because of the presence of MoO3 phase in the composite film. MoO3 structure in the film can work as recombination centers of photo-generated holes and electrons as well as has strong absorbability to MB.The TiO2 film prepared by mid-frequency AC reactive magnetron sputtering has excellent photo-induced hydrophilicity and obvious antifogging action. Contact angle of water to Ag/TiO2 composite film can change from 120? to 0? under UV irradiation and resume quickly from 0? to 120? in dark.Based on the experimental results and theoretical analyse, a physical model for photocatalytic mechanisms of TiO2 film has been proposed.