Preparation And Photocatalytic Property Of Complex Oxides

Since the water splitting on TiO2 electrode was discovered by Honda and Fujishima, an epoch for photocatalytic technic research have begun. TiO2 has been applied in many areas including degradation of organic and inorganic pollutants, water splitting, photocatalytic sterilization and photocatalytic synthesis. But the intrinsic defects of TiO2 have limited the industrial applications and development, such as low photon efficiency, narrow response spectrum and so on. Therefore, two forward topics about semiconductor photocatalysts, which are modification of the explored photocatalysts and exploiture of new photocatalysts, have been developed.On the basis of these, we prepared BiFeO3 and studied its photocatalytic property. At the same time, we designed a new type of photocatalyst Bi2Sn2O7 and investigated its photocatalytic property. The following is the main content of this thesis:Pure BiFeO3 has been synthesized by sol-gel method. TG-DTA, IR, SEM, XRD, DRS etc. have been used to characterize its structure and properties. Then the effect of synthesis conditions on phase structure and photocatalytic property has been investigated.The synthesis conditions include calcination temperature, calcination time, elevation rate, agglutinants, and so on. The results have shown that pure BiFeO3 sampled can be prepared more easily by tartaric acid than that prepared by malic acid. However, the impurity in the sample can improve the photocatalytic activity. The improvement of photocatalytic activity by ion-doped method can be realized by doping high-valent ions. The improvement mechanism is that the coulomb gravitation between the positive electrical charge on the the surfure of sample and the negative charge on methyl orange makes the absorption of methyl orange more easily, thus enhance the photocatalytic activity. Furthermore, based on the analysis of DRS,band gap structure, and SEM,we can ascribe the low photocatalytic activity to the existence of Fe3d, which is disadvantageous for the creating of photo-generated electrons and holes and also forms strong recombination sites of photogenerated electrons and holes. Additionally, the large grains size, which will decrease the number of the catalytic activity center sites and will extend the transfer distance of electron-hole pairs, also lowers the photocatalytic activity down.Bi2Sn2O7 has been prepared by co-precipitated method. XRD, IR, SEM, DRS, etc. have been used to characterize its phase structure and photocatalytic property. XRD results have shown that Bi2Sn2O7 can be formed at calcination temperature higher than 750℃and the grain size is in range of 90nm to 1μm. Its photocatalytic property has been evaluated by the degradation experiment of methyl orange. The photocatalytic results suggested that Bi2Sn2O7 exibit good photocatalytic activity and photostability under high pressure mercury lamp. However,its photocatalytic property decreased with elevated calcination temperature and prolonged calcination time.