The Synthesis And Photocatalytic Activity Of Nanocrystalline TiO₂ Based On Low Temperature

Semiconductor photocatalyst TiO2 has attracted worldwide research interest as their po-tential applications in the degradation of environmental pollutants and the conversion of solar energy.This dissertation developed the low temperature preparation method for TiO2 and fur-ther synthesized doped TiO2 to obtain excellent photocatalytic TiO2 and other special prosper-ity.The dissertation reviewed the phase structure,photocatalytic mechanism,synthesis meth-od,modified method and application of TiO2,and then systematically introduced low temper-ature methods to prepare mesoporous TiO2,rutile TiO2 nanorod superstructures with photo-catalytic activity,C-N-S-tridoped TiO2 nanocrystalline photocatalysts,and Ag/TiO2 with visible light photocatalytic activity.These resulting materials were characterized by XRD,XPS,TEM,photocatalytic activity test and antibacterial performance test.Around prepared inexpensive low-power and high photocatalytic activity of TiO2 pho-tocatalyst as the theme,the following research areas:1.It taked a non-aqueous sol-gel method to prepare mesoporous TiO2 using inexpensive TiCl4 as the titanium source and the PEG as template,and investigated their photocatalytic activity and discussion of the reaction mechanism.2.N-doped mesoporous titania was synthesized using polyethylene glycol(PEG)as template and dimethyl formamide(DMF)as nitrogen source.These photocatalysts exhibited excellent photocatalytic activity for methyl orange(MO)degradation under visible light irra-diation,which could be assigned to synergistic effect between the retained alkoxyls and the nitrogen doping.3.The pure rutile nanorods were synthesized under acidic conditions in the absence of surfactant as template at low temperature.The influence of 2-propanol/water ratio on the temperature and the influence of surfactant on the size and morphology of the rutile TiO2 samples have been studied.The prepared rutile TiO2 nanorod superstructures displayed ex-cellent photocatalytic activity on degradation of methyl orange(MO)under artificial solar light.Their activities were even 34%higher than that of the famous commercial photocatalyst P25.4.C-N-S-tridoped TiO2 nano-crystals with bicrystalline phases were prepared through the simple one-step alcohol-thermal method by addition of L-cysteine.The results indicate higher behavior of photocatalyst for methylene blue(MB)rationalization than the commercial P25 under the condition of visible light(??400 nm).The increased photo-catalytic activity of the prepared nano-crystals was mainly caused by the narrow band gap,the large surface area and the anatase-rutile mixed-phase of prepared TiO2.5.Mesoporous TiO2 materials adjusted with nanoparticles of Ag showed considerable capacity for the degradation of MB under visible light.Under visible light,the optimal pho-toactivity was obtained for the sample m-TiO2-Ag-2%.Investigations into the impact of Ag loadings upon the function of the catalyst and into the part of Ag nanoparticles in the degrada-tions of photocatalysis were conducted.6.The Langmuir-Hinshelwood model describe the TiO2 photocatalytic degradation reac-tion suspension,kinetic model is expressed as:r =-dc/dt = kKc/(1+Kc).Rate con-stants:k=(1-0.0388c0)(0.01571+0.02828e-pH/3.546)(3.19802×10-5M2-0.00241M +0.04367).7.TiO2 and N-TiO2 make a difference to the growth of Scenedesmus obliquus,which is due to the photocatalytic reaction to inhibit the growth of S.obliquus,but Scenedesmus obliquus can still relatively good growth,which indicates that the toxicity of TiO2 and N-TiO2 is very low.It can be inferred that TiO2 and N-TiO2 photocatalyst will not cause secondary pollution to the ecological environment.