Study On The Synthesis And Photocatalytic Properties Of Co-doped Nano-TiO₂

TiO2, has been widely studied because of its prominent behaviors such as low cost, good oxidation, chemical stability and no secondary pollution. Among all the photocatalytic materials, TiO2 has been widely used in many aspects, which is also a photocatalytic material with exploiture foreground. However, its wide band gap restricts the utilization of solar energy. Moreover, the high recombination rate of photogenerated electrons and holes also restricts its application. Many studies indicate that proper doping with metal or nonmetal as a promising approach can improve its absorbance and restrain recombination rate of photogenerated electrons and holes.In this dissertation, doped TiO2 was synthesized by sol-gel method with the dopant of Mn, Mo, Y and N. The crystal stucture, electron structure, optical property and photocatalytic activity were investigated by XRD, Raman spectra, XPS, UV-vis spectra and photocatalytic experiments, respectively. The significant results are listed as follows:1. The undoped TiO2, monodoped and codoped TiO2 with Mo and N were synthesized by sol-gel method. The results of XRD and Raman indicated that all the synthesized samples are of anatase phase. The average crystalline grain size is about 12-15 nm for all the codoped samples. The ability of optical absorption of doping TiO2 was improved markedly because of the energy band structure of the TiO2 is changed due to the dopings. The photocatalytic experiments indicated the photocatalytic activity of the codoped TiO2 decreased gradually with the increasing of concentration of the Mo dopant because of the increasing recombination rate of photogenerated charge carriers due to the increase of Mo doping level.2. The undoped TiO2, monodoped and codoped TiO2 with Y and N were synthesized by sol-gel method. The results of XRD and Raman indicated that all the synthesized samples are of anatase phase. The average crystalline grain size is about 12-16 nm for all the samples. The results showed that the Y cation and N anion had played significant synergistic effect on the photocatalytic activity of TiO2 , enhanced the photocatalytic activity of TiO2 effectively because the codoping with Y and N not only promoted the separation of photogenerated charge carriers but also expanded the optical absorption region of TiO2.3. The undoped TiO2, monodoped and codoped TiO2 with Mn and N were synthesized by sol-gel method. The results of XRD and Raman indicated that all the synthesized samples are of anatase phase. The average crystalline grain size is about 13-16 nm for all the codoped samples. The absorption performance of samples changed due to the codoping with Mn cation and N anion. It can be attributed to the sp-d spin—exchange interaction due to doping with Mn cation and the change of band structure of TiO2 due to the doping with N anion. Besides, The intensity of optical absorption in the visible light region increase with the increase of concentration of Mn cation due to the increasing disorder induced by doping. The photocatalytic experiments indicated the photocatalytic activity of the codoping TiO2 decreased because of the increasing of the recombination rate of photogenerated charge carriers with the increase of Mn doping level.