Synthesis、chracterization And Photocatalytic Activity Of Vanadate Composites

Photocatalytic technology as a new green technology performs well in solving the problem of environmental protection and energy. To find a stable, high efficiency and low cost photocatalyst is the focus in the field of photocatalysis. The strong response in the visible light region and its catalytic properties had been well known for researchers. However, there are some disadvantages, such as irregular shape, small specific surface area, poor adsorption performance, electrons and holes recombination, etc. which limit the application of vanadate. Therefore, it is necessary to improve the performance of the semiconductor by means of doping and composite, and broaden the light response region, modify the band structure, promote the electron hole separation, increase the utilization rate of the electron and hole, in order to obtain high efficient visible light catalyst. The main contents of this paper were shown as following:1. The In³⁺ doped BiVO₄ material were synthesized by the hydrothermal method, the pristine BiVO₄ and different concentrations of In³⁺ doping BiVO₄ were characterized by XRD, Raman, SEM, TEM, XPS, BET, UV-Vis DRS representation, to analyse the structure and composition of the samples. And the photocatalytic activity of different materials were detected through the degradation of methylene blue. The enhanced mechanism of the photocatalytic activity was summarized combine the characterization and analysis. Analysis results showed that the photocatalytic efficiency of the doped samples were better than that of pristine BiVO₄, and all the samples were well grown with single monoclinic phase. The introduction of In³⁺ lead to the crystalline distortion and the narrower band gap. So that the conductor could generate more electrons and holes in photocatalytic reaction, increasing the photocatalytic activity. Among them, the best photocatalytic performance was obtained with the BiVO₄ sample containing 5.0 mol% In ions.2 The rare earth element Eu-BiVO₄ composite photocatalyst was prepared by hydrothermal synthesis with polyethylene glycol（PEG-200） as template. The material were characterized by BET, Raman, UV-DRS, SEM, TEM and XRD. And methyl blue（MB） was used as an indicator to investigate the effect of Eu on the photocatalytic activity of BiVO₄. The results show that the Eu composite could change the crystal phase of BiVO₄ and inhibit the growth of tetragonal crystal, which makes the grain size smaller and the specific surface area increased. In the Eu composite samples, part of Eu3+ doped into lattice of BiVO₄ to instead of Bi3+, make the crystal distortion and benefit to the improvement of photocatalytic activity. When the content of Eu reached 50 mol%, the photocatalytic activity was the best. And the degradation efficiency after 120 min irradiation was 90%, which was significantly higher than that of pure BiVO₄.3. Because of the hydrogen production performance of SnO₂ and InVO₄, a new type of high efficient photocatalytic material is attempted to prepare by the two kinds of semiconductor composite. SnO₂/InVO₄ composite materials were prepared by simple hydrothermal method, characterized by some means and tested by hydrogen production. The experimental results show that the composite samples had a only strong response in the ultraviolet region, and have a certain degree of hydrogen production performance. The absorption edge of the composite sample were in the middle of two kinds of pristine samples, and the band gap can also be between two kinds of monomer band gap energy, but the hydrogen production of composite samples are better than the single one. When the molar ratio of In:Sn was 9:1, the optimum hydrogen yield was observed, and the ultraviolet irradiation of 5 h could produce 118.4 μmol hydrogen.