| Photocatalytic technology is a kind of green advanced oxidation technology, which had extensive study and application in environmental pollutant treatment and energy development. Visible-light-driven photocatalysts with high activity and stability had become a hot topic in the research field of photocatalysis. It was necessary to exploit right way to enhance the photo-generated electron-hole separation. In this paper, it was focused on the synthesis of BiOX-based composite visible-light-driven photocatalysts. BiOX was modified to enhance the separation rate of photo-generated electron-hole. The aim of this paper was also to obtain the information of the structure analyzed by various characterization techniques, as well to explain the relationship between the structure of the photocatalysts and photocatalytic activities. The photocatalytic mechanism of hybrid material was also discussed. In this paper, the research content and the achievements were mainly embodied in the following aspects:1. g-C3N4/BiOBr composite photocatalysts have been synthesized through solvothermal process in the presence of reactable ionic liquid1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br). The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmet-Teller (BET) and diffuse reflectance spectroscopy (DRS). The results indicated that ionic liquid [C16mim]Br played the role of solvent, reactant and template at the same time in the reactive process. The results of DRS analysis showed that the g-C3N4/BiOBr composite materials had significant optical absorption in the visible region and narrow energy gap. Moreover, the photocatalytic activities of g-C3N4/BiOBr composite structures were evaluated on the degradation of rhodamine B (RhB) under visible light irradiation. The photocatalytic activities of g-C3N4/BiOBr composite structures were found to depend largely on the g-C3N4content. In the ethylene glycol system, the optimum g-C3N4loading was found to be1wt%under visible light, respectively. RhB was completely mineralized for150min by g-C3N4/BiOBr in visible light irradiation, respectively. In the ethanol system, the optimum g-C3N4loading was found to be3wt%under visible light, respectively. The degradation rate in the case of the g-CsN4/BiOBr composite materials was higher than that of pure BiOBr and g-C3N4, respectively. The results of free radical trapping experiments showed that degradation process of composite material is mainly to hole oxidation process. The relationship between the structure of the photocatalyst and the photocatalytic activities were also discussed in details, it can be assumed that the enhanced photocatalytic activities of g-C3N4/BiOBr composite photocatalysts could be ascribed to a synergetic effect, including the energy band structure, the smaller particle size and light absorbance. The g-C3N4of g-C3N4/BiOBr composite photocatalysts was superior for the transfer of photogenerated electrons and holes, thereby improving the photocatalytic efficiency dramatically.2. g-C3N4/BiOCI microspheres composite photocatalysts have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl). The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、DRS. During the reactive process, ionic liquid [C16mim]Cl act as solvent, reactant and template at the same time, and also has a control action on the formation of microspheres. Moreover, the photocatalytic activities of g-C3N4/BiOCI composite photocatalysts on the degradation of rhodamine B (RhB) and methyl orange (MO) under visible light irradiation were evaluated. The results assumed that g-C3N4/BiOCI showed high photocatalytic activity for degradation of RhB and low photocatalytic activity for degradation of MO. It is indicated that the as-prepared sample has selective catalytic capacity. Experiments showed that the catalyst1%g-C3N4/BiOCl possessed the highest photocatalytic activity, after irradiation for90min, RhB were photodegraded completely. The introduction of g-C3N4can increase the light absorption range of the composite photocatalyst, improve its specific surface area, enhance the separation efficiency of the light-generated carriers, thus significantly enhance the performance of the photocatalytic activity.3. Fe/BiOCl microspheres composite photocatalysts have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid ([Omim]FeCl4). The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、DRS etc. XPS analysis showed that Fe element existed in form of Fe3+in the photocatalyst, BET analysis showed that the specific surface area of the photocatalyst was about64.3m2/g. In the presence of H2O2,73%and97%of RhB and MB were photodegraded by Fe/BiOC1microspheres after irradiation for30min, which was higher than the photocatalytic activity of pure BiOCI in the same experimental condition. The result showed that it is benefit to enhance the photocatalytic activity by introducing Fe. During the reaction process, optical fenton reaction might be occurred in the presence of Fe and H2O2.4. Composite photocatalysts Pt/BiOBr microspheres have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br).The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、DRS etc.During the reactive process, ionic liquid [C16mim]Br act as solvent, reactant and template at the same time,and also has a control action on the formation of microspheres.EG work as solvent and reductant during the reactive process,deoxidizing chloroplatinic acid to Pt Nano-particle. HRTEM demonstrate that during the tablets which assembly into microspheres, the surface of the crystal lattice spacing of0.132nm,corresponding to the Pt crystal [220] crystal plane, indicating that the Pt metal preferably dispersed in BiOBr microsphere surface.Photocatalytic studies have shown that doping amount of0.5%Pt/BiOBr material has the best photocatalytic activity by degradate rhodamine B under visible light irradiation. The reason is that the doped metal Pt has good ability of electron capture,it can timely separate the holes and photogenerated electrons in the conduction band (CB),which restrain the recombination of photo-generated electrons and holes. Therefore, it contribute to the conduct of photocatalytic degradation reaction.5. Composite photocatalysts MWCNT/BiOCl have been synthesized through EG-assisted solvothermal process in the presence of reactable ionic liquid1-octyl-3-methylimidazole chloridize.The as-prepared samples were characterized by XRD、SEM、TEM、EDS、BET、 DRS etc.SEM shows that MWCNT/BiOCl spherical structure material is self-assembled generated by irregular BiOCl nanoflake and a lot of MWCNT uniform disperse on the surface of BiOCI nanoflake. TEM analysis revealed that the MWCNT attached, embedded and interwoven on the suface of BiOCl nanosheets. This structure develop the the ability of electron conductivity and migrate of MWCNT/BiOCl material, promoting the efficiency of the photocatalytic. Experiments show that82%of RhB was photodegraded by the catalyst0.1%MWCNT/BiOCl after irradiation for30min. After further irradiation for60min,the intermediates were photodegraded completely. |
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