Preparation And Photocatalytic Properties Of Nano-Crystal TiO₂Through Sulotion Combustion Method

With its high photocatalytic activity, non-toxic and stablity, TiO₂has been used inmany fields, such as water decomposition, carbon and nitrogen fixation,decom-positionof organic materials. Recent studies show that TiO₂with mixed phases （including anatasephase and rutile phase） has much higher activity, however these studies are just few cases.Some researchers have synthesized nano-mixed TiO₂through sol-gel、hydrothermalmethod、microemulsion method by controlling temperature or adding some other ions. Butthese methods demand complict qualities, cost more energy and time, bring other elementsinto the products, so we need to think other ways to prepare the mixed-phases TiO₂powders.In this paper, we prepared the mixed-phases TiO₂through solution combustionmethod, controlling the crystalline proportion by adjusting the fuel ratio, improving thehard reunion and sintering phenomenon by adding dispersants, and further enhancing itslight catalytic performance of the mixed-phased TiO₂by doping V. With XRD, SEM,UV-vis, XPS and other means, the phase composition, grain size, eigen absorptionwavelength and each element state were characterized.TiO₂was successfully prepared by sol-gel and SCS methods. The powder preparedby sol-gel has a single phase-anatase phase, with average particle size of about20nm;while with the other method, TiO₂has two phases, including anatase phase and rutilephase, and their content ratio is about7:3, with average particle size of about20nm. Theeigenvalue of the absorption wavelength for them are425nm and415nm respectively.The methyl orange degradation rate of TiO₂powders prepared by sol-gel and SCS are79.8%and70.1%respectively under the uv lamp irradiation after5h.The light temperature and fuel ratio have important influences on the crystal phasesof TiO₂. The powders synthesized at600℃, with anatase phase as the main crystal and asmall amount of rutile TiO₂phase, and with no residual organic matter, have tiny uniformparticles and the average particle size is about20nm. Adjusting the fuel ratio can controlthe crystal proportion of TiO₂. When the fuel ratio Φ is0.25, TiO₂has a single anatase phase; along with the increase of the Φ, rutile phase begins to appear, and graduallyincrease; When Φ is up to1.5, the content of rutile phase is92.9%. The single anatasephase and mixed-phases TiO₂（fR: fAare about3:7） both show high catalytic activity, themethyl orange degradation rate are80.1%and70.1%respectively in the uv lightirradiation after5h.In the combustion synthesis process, the addition of appropriate amount of PEG andstarch can effectively improve the hard reunion and sintering phenomenon of TiO₂powders. When PEG content is0.5%wt or starch content is1%wt, TiO₂powders have tinyparticles and uniform distribution, and the average size is about15nm. the TiO₂powderssynthesized contain anatase phase and rutile phase, and their photo-catalytic degradationrate are99.4%and86.4%respectively.V doping can effectively improve the absorption eigenvalue of TiO₂, with theincreased amount of V doping, the absorption wavelength gradually increases, theabsorption of visible light also increases gradually. When the amount of V is3%, Theeigenvalue of the absorption wavelength expandes to625nm, and the band gap widthdown to1.87eV. when V doping is1%, the degradation rate reached the highest （95.8%）under the xenon lamp.