Study On Preparation And Photocatalytic Properties Of Co-doped TiO₂for Degradation Of Methylene Blue

In the first chapter, a brief summary about nano-materials an photocatalytic nano-materials was firstlygiven. Secondly, we analyzed the structure and photocatalytic mechanisms of titanium dioxidephotocatalyst and evaluated the advantages and disadvantageous of titanium dioxide photocatalytic material.Then the main preparation methods of titanium dioxide were introduced. Moreover, the modificationmethods of improving the photocatalytic performance of TiO₂were reviewed in details, among whichmodifying TiO₂photocatalyst by doping was emphatically described. Finally, the purpose and significanceof this thesis were briefly given.In the second chapter, Iron or iodine single doped and their co-doped TiO₂nanocrystalline wereprepared by the sol-gel method and investigated by XRD, XPS, UV-Vis spectrum, respectively. Thephotocatalytic performances of the samples were evaluated by photocatalytic degrading methylene blue.XRD results show that all the samples compose of the anatase phase and the average grain sizes aredifferent from7to15nm. After the dopings, the absorption properties of the samples are significantenhanced. With the increase of Fe doping level, the photocatalytic activities of the codoped samplesincrease and then decrease gradually. The best photocatalytic property is presented in the codoped samplewith0.2%Fe doping level. The mechanisms of the photocatalytic property changes were further discussedby several factors such as grain size, absorption performance and band structure.In the third chapter, undoped, F-doped, Y-doped and （F, Y）-codoped TiO₂nanoparticles were preparedby the sol-gel method and investigated by XRD, TEM, XPS, UV-Vis spectrum and PL spectrum,respectively. The photocatalytic properties of the samples were evaluated by photocatalytic degradingmethylene blue. It is found that there is no visible absorbance edge shift after the dopings in TiO₂. That is tosay, the absorption performance can not be improved by the doping. With the increase of F doping level,the photocatalytic activity of TiO₂are gradually enhanced, resulting in an optimal doping level of10%. TheF doping sites can more easily trap the hydroxyl in the solution, which results in the formation of morehydroxyl radicals, enhancing the photocatalytic activity of the TiO₂photocatalyst. In the samples of （F,Y）-codoped TiO₂, the photocatalytic property is improved and then depressed with the increase of Y doping level. The best photodegrading efficiency is observed in the sample with0.05%Y doping level. Thephotocatalytic property changes in the codoped sample were interpreted by a competing mechanismbetween the photo-generated charge carrier recombination center and photocatalytic activity center, thedouble-role played by the Y doping induced oxygen vacancy.In the forth chapter, undoped, F-doped, Zn-doped and （F, Zn）-codoped TiO₂nanoparticles weresynthesized by the sol-gel method. XRD results reveal that the samples are anatase phase with the grainsize of10-14nm. From the UV-Vis spectra of the samples, it is found that the optical absorption propertyof TiO₂can not be obviously improved by the doping. The photocatalytic properties of the samples wereinvestigated by photocatalytic degrading methylene blue. The results show that the codoped sample with2%Zn doping level presents the best photocatalytic performance. Too large or too small zinc doping levelwill reduce the photocatalytic performance of TiO₂photocatalyst. The influence mechanisms of Zn dopinglevel on the photocatalytic activity of the codoped TiO₂is discussed in details.In the fifth chapter, a series of I-N codoped, single doped TiO₂nanoparticles and pure TiO₂werefabricated by the sol-gel method. The prepared photocatalytic materials were characterized by XRD,UV-Vis spectrum and photocatalytic activity measurement. XRD showed that all the samples are anatasephase with the grain size distribution of7-12nm; Ultraviolet-visible absorption spectra suggests that thevisible light absorption of the nitrogen doped and codoped samples are significantly enhanced. The bestphotocatalytic property is observed in the sample of1%I-N codoped TiO₂by photocatalytic degradation ofmethylene blue experiments. The photocatalytic activity of the N doped TiO₂is exactly enhanced by the Idoping.