| Recently, silver halides decorated with silver have become one class of promising plasmonic photocatalysts, due to high efficiency and stability. Nevertheless, in order to reduce the loss of nanophotocatalysts, a centrifugation step is required to recover the catalyst, which brings a great deal of inconvenience to the future practical application of photocatalysts. In view of the large specific surface area and good separation recycling characteristics of magnetic Fe3O4nanoparticles, we use Fe3O4as carrier to prepare magnetic Fe3O4@SiO2@AgCl:Ag nanocomposites, which not only have the high activity as a plasmonic photocatalysts, but also can be recovered completely form the treated solution through additional magnetic field.In this thesis, we synthesized Fe3O4nanospheres with good dispersion, uniformity size, strong magnetism through a polyol process, and then prepared Fe3O4@SiO2nanospheres by modified Stober method. Moreover, the crystalline structure, morphology and magnetic properties were analyzed. The hydrogen bonds between SiO2and PVP made AgCl strong attached to the Fe3O4@SiO2supports in polyol system, followed by photo reduction, a good Fe3O4@SiO2@AgCl:Ag magnetic nanophotocatalysts for dispersion is thus achieved. The results of XRD, UV-v/s spectra, SEM, HRTEM, EDS, and VSM showed that the magnetic photocatalyst displayed supported structure instead of a core-shell type. The as-achieved nanophotocatalyst exhibits high activity and stability toward decomposition of organic pollutant. It takes only4min to degrade Rhodamine B completely with the assistance of the magnetic nanophotocatalysts under visible-light irradiation. Furthermore, the catalyst can be reused8times without loss of activity. In addition, the photocatalytic degradation on MO and MB in aqueous solutions is also conducted. In order to ascertain the active species during the degradation process, a variety of scavengers were introduced to the reaction system. Tthe results indicate that h+or·OH plays a major role in the photo-oxidation reaction. In addition, we searched for the best synthesis process of the magnetic nanophotocatalyst by changing photoreduction time, magnetic fluid concentration and silica shell thickness. The wide applicability of the as-achieved Fe3O4@SiO2@AgCl:Ag magnetic photocatalyst was evaluated by testing the decomposition of typical pollutants, e.g., methyl red, malachite green, alizarin red, isopropyl alcohol, and heavy metal ions. We investigated the link between photooxidation of organics and photoreduction of heavy metal ions, and it was verified that there is a synergistic inhibition between them. Moreover, carbon dioxide was photocatalytically reduced to methanol, ethanol, and normal propyl alcohol under visible-light irradiation, with the total yield of the products reached16.656mmol/g-cat after5h.Finally, magnetic photocatalysts of Fe3O4@SiO2@AgBr:Ag and Fe3O4@SiO2@AgI:Ag have been synthesized via polyol precipitation. With the assistance of Fe3O4@SiO2@AgBr:Ag catalyst, carbon dioxide was photocatalytically reduced to methanol and ethanol under visible-light irradiation, with the total yield of the products reached4.792mmol/g-cat after5h. The results of XRD, TEM, XPS, and VSM showed that the Fe3O4@SiO2@AgI:Ag nanocomposite displayed capsule structure. Reduction of carbon dioxide was carried out under the same conditions for five times, with the highest total yield of products reached35.83mmol/g-cat, including methanol, ethanol, and normal propyl alcohol components. In addition, the effect of Ag0, photo, and I-has been investigated, and the reaction mechanism of photoreduction process has been explored. |
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