| Recently environment pollution has become more and more serious, which threatens the existence of human beings. Among them, organic dyes removal has recently attracted considerable attention because of their complex structure, poor biodegradability, and long-term environmental toxicity. In order to solve this problem, many researchers contribute their work to protect the environment. Semiconductor photocatalysis is an advanced technology that employing the electrons on conduction band and holes on valence band in photons excited semiconductor, pollutants can be removed via oxidization or reduction and hydrogen can be obtained via water-splitting. The focus of semiconductor photocatalysis is to develop photocatalysts with wide wavelength light response, high efficiency and stability. Highly active photocatalysts have the features of narrow band gap, high quantum efficiency, large specific surface area, high stability and can be easy recovered. Bismuth complex oxides with layered structure as a series new appealing photocatalysts have attracted considerable attention for their admirable photocatalytic properties under visible light irradiation. In this article,a series of bismuth complex oxides were prepared by hydrothermal method, which have superior visible light photocatalysis property. Physicochemical properties of the as-prepared materials were characterized by means of techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance and absorption spectroscopy (UV-vis), and fourier transform infrared spectroscopy (FT-IR). Photocatalytic activities of the as-fabricated samples were evaluated for the degradation of methylene blue (MB) and rhodamine(RhB) under visible-light illumination. The main results obtained in the present investigations are as follows:1. Monoclinic system Bi?WO6powder was prepared by hydrothermal method.The reaction temperature, reaction time, surfactant types and pH value of the reaction system had an important impact on particle morphology, absorption band edge and photocatalytic activity of the Bi22WO6product. When the reaction temperature is different, nonfixiform particles, sheet particles, flower-like aggregation and hierarchical globosity products can be obtained. With the reaction temperature rising, the absorption band edge of products brings red shift, energy gap decreases and photocatalytic activity increases. With the reaction time prolonging, the morphology of products changes from sheet particles accumulating and inserting, to sheet layer bodiness, to flower-like aggregation and then to hierarchical structure. The reaction time influences the absorption band edge and photocatalytic activity of products, but the effect has not a certain regular pattern. When reaction time is12h and24h respectively, energy gap of products is minimum and photocatalytic activity of products is the best. Near-spherical, flake, flower-like and hierarchical structure products can be obtained by changing surfactant types. Without surfactant, energy gap of products is minimum. With SDBS as surfactant, photocatalytic activity of products is best. pH value of the reaction system changes from acidity to neutrality and then to alkaline, the morphology of product changes from near-spherical to hierarchical structure and then to near-spherical structure composed by irregular morphology platy particle accumulating and inserting. When pH value is alkaline, energy gap of products is minimum. When pH value is neutrality, photocatalytic activity of products is the best.2. The Bi2WO6/PANI heterojunction photocatalysts were prepared by direct composite method and situ-composite method. The results show that the absorption band edge of composite powders occurs red shift and the energy gap decreases. When the doping quantity of PANI is1.5%(weight percentage content) by direct composite method, photocatalytic activity of products is the best. When the doping quantity of PANI is1.0%(weight percentage content) by situ-composite method, photocatalytic activity of products is the best. Photocatalytic activity of products prepared by situ-composite method is better than products prepared by direct composite method. In addition, photocatalytic activity of PANI composite powder synthesized in inorganic acid system is good.3. Monoclinic system BiVO4powder was prepared by hydrothermal method. The morphology of product is different with the different reaction temperature. With the reaction temperature rising, branched, rod-like, near-spherical reunited with granule products can be gotten, the absorption band edge of products brings red shift, energy gap decreases and photocatalytic activity increases. The reaction time has obvious effect on products morphology. With the reaction time prolonging, the morphology of product changes from rod-like to cosh with little draw ratio, and then to near-spherical particles, finally turning into large spherical grained assembled with granule. The reaction time has not obvious effect on energy gap. Photocatalytic efficiency of products reacted12h and18h is the highest. Near-spherical, rod-like and irregular morphology products can be obtained by changing surfactant types. With PVP as surfactant, energy gap of products is minimum and photocatalytic activity of products is the best. The morphology of products has obvious difference with different solvent types in the reaction system, such as near branched, near-spherical and rod-like. In addition, using water as solvent, energy gap of products is minimum and photocatalytic activity of products is the best.4. The BiVO4/ZnO composite powder was synthesized by hydrothermal method. The crystal form of BiV04transforms from monoclinic to tetragonal with ZnO adding, which was characterized by XRD. The absorption band edge of BiVO4arises red shift with ZnO adding, which was certified by UV-Vis diffuse reflection absorption spectra. When ZnO doping mass is7%(compared to BiVO4mass), red shift of the absorption band edge is the most, energy gap of products is minimum and photocatalytic efficiency of products is maximum.5. The flake and flowerlike Bi2MoO6were successfully prepared through hydrothermal method. The influence factors on Bi2MoO6morphology and size were discussed. The results show that the reaction temperature and surfactant types have an important impact on the size, morphology and photocatalytic efficiency of the Bi2MoO6products. The reaction temperature is higher, the energy gap of products is greater and photocatalytic efficiency is lower. With PVP as surfactant, energy gap of products is minimum and photocatalytic efficiency of products is maximum.6. The photocatalytic efficiency of Bi2MoO6changes with doping carbon element. The energy gap of products decreases and photocatalytic efficiency improves constantly with C doping amounts increasing. Meanwhile, the experiment results indicate that the energy gap of products and photocatalytic degradation rate are different with doping carbon source kinds. The molecular weight and carbon content of malt sugar are more than glucose’s, so photocatalytic property of products doping malt sugar is better. |
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