Preparation And Photocatalytic Performance Of V-based Photocatalyst

In recent years, many researchers have attempted to research photodegradation of organic pollutants and photocatalytic hydrogen generation from water under visible light. Most investigations have focused on TiO2 because of its nontoxicity, chemical stability, high catalytic activity and low price. However, TiO2 has a large band gap (3.2eV) and absorbs only UV light which is less than 5% of ultraviolet light in solar-light spectrum. Hence, in order to make full use of the solar light, a visible light active photocatalyst is desired.In this thesis, we mainly investigate the potocatalytic activities of two types of V-based semiconductors (V2O5, Ag3VO4) and their modified composites.1,The photocatalyst V2O5/CeF3 was synthesized by the impregnation method. The photocatalytic activity of the samples was evaluated using the photocatalytic degradation of acetone. It was found that the contents of V2O5, the calcination temperature and gas flow had great effect on the photocatalytic activity. The 15% V2O5/CeF3 catalyst calcined at 450℃showed the best photocatalytic activity, with the acetone conversion of 85%. The photocatalytic activity decreased because of the occurrence of the CeVO4 phase which was formed with the increase of V2O5 content.2,Co3O4,Ag3VO4,Co3O4/Ag3VO4 were successfully prepared by the calcination of Co(NO3)2 solution, the precipitation method and the wetness impregnation method respectively. The photodegradation of RhB under visible light irradiation was used to investigate their photocatalytic performance. The test results exhibits that the photocatalytic activity of the composite is deeply affected by the Co3O4 contents and the calcination temperature. When the Co3O4 contents is 3% with the calcination temperature of 400℃, the photocatalyst shows the highest photocatalytic performance. The RhB solution can be decomposed completely in 80 min under visible light irradiation. Based on the results of the XRD, SEM-EDS and UV-Vis experiments, we believe that there exist coupling effect between Co3O4 and Ag3VO4. The photoexcited electrons can transfer from the conduction band of Ag3VO4 to that of Co3O4, while the holes in the valcene band of Co3O4 can transfer to the valence band of Ag3VO4. The charge transfer between the two semiconductor can retard the recombination of electron-hole pairs and promote the photocatalytic activity of Co3O4/Ag3VO4 composites. The concentration of Co3O4 and the caclination temperature can influence the charge transfer process. Therefore, there existed the optimal value of Co3O4 concentartion and calcination temperature. The photoabsorption performance of the Co3O4/Ag3VO4 composites might be another reason for the optimal values.