The Preparation And Photocatalytic Activity Of The Visible-light-induced Photocatalyst Loaded By Metal Elements

Semiconductor photocatalysis is one of the most promising methods for environment-organic-pollutant decontamination and energy production. The initial step of the photocatalytic process consists of the generation of electron-hole pair upon irradiation of a photon whose energy is equal to or higher than that of the band gap of a photocatalyst. Therefore, in order to search an effective photocatalyst, a tremendous amount of research have been devoted to study and discover the influencing factors of the photocatalytic activity. Ag3VO4 has been recognized as a photocatalyst for water splitting and pollutant degradation under visible light irradiation.In this paper, the photocatalyst Ag3VO4 is synthesized by precipitation method. Ag3VO4 doped with Gd3+, Nd3+, Fe3+photocatalysts are prepared by impregnation method. Moreover, the optical, physical and chemical properties of the Ag3VO4 series photocatalysts are studied by the way of different characterization such as XRD, DRS, SEM, EDS and XPS. In order to discuss the photocatalytic activities of Ag3VO4 doped by Gd3+, Nd3+ and Fe3+, Rhodamine B (RhB) dye and methylene blue (MB) are used for the object of degradation, respectively. Meanwhile, the effect of different experimental conditions on degradation of RhB and MB are researched. The mechanism by which metal ions enhance photocatalytic activities is also discussed. The experiment results are as follows:Gd2O3/Ag3VO4 photocatalysts are synthesized through impregnation method and characterized by XRD, XPS, SEM and DRS. It is shown that Gd3+ is dispersed on the surface of Ag3VO4 in the form of Gd2O3. The XRD analysis indicates the crystal structure of the catalyst has never changed after the introduction of Gd element. The DRS analysis indicates that the ability of visible light absorption of Gd2O3/Ag3VO4 catalysts is enhanced greatly. The photocatalytic activities of the samples are evaluated by the degradation of Rhodamine B dye under UV and visible light irradiation, respectively. The experimental results show that the role of Gd2O3 content has a significant impact on the photocatalytic activities of the samples. The mechanism of enhanced photocatalytic activity after the Gd3+ introduction is discussed. The photocatalytic degradation intermediates of the solution are identified by UV-vis and HPLC analysis.The Nd3+-Ag3VO4 heterojunction photocatalyst is also prepared by impregnation method. The characterization results indicate that the Nd3+ doping does not influence the crystal structures of Ag3VO4. According to the SEM-EDS and XPS results, the doped Nd3+ species exists as Nd2O3 clusters. The DRS spectra shows that the catalysts improves the ability of visible light absorption. The optimum conditions for Nd3+ doped is as follows:the doped quality of Nd3+ is 2 wt% and the calcination temperature of catalyst is 200℃. The photocatalyst doped with Nd2O3 exhibits the enhanced photocatalytic properties for degradation of Rhodamine B (RhB) under visible light irradiation. The mechanism of improved photocatalytic activity is also discussed.At last, Fe3+-Ag3VO4 is prepared by impregnation method. It is found that the crystal does not change after the doping of Fe3+, and the optimum conditions of Fe3+ doped is 1 wt%. The photocatalytic degradation efficiency is increased about 20% than the pure Ag3VO4. Absorption spectral analysis of MB shows the representation wavelength of MB has a obvious blue shift, and the manner of degradation of MB on Fe3+-Ag3VO4 is similar to the mineralization process.