| Core-shell structure microspheres is a novel kind of functional compositematerials with special structure and performance. It’s a high level of compositestructure materials consisting of a kind of micro/nano materials covered by anothernano material with physical or chemical force. Because of the special structure, itcan integrate the advantages of different materials and be applied in different fieldsas functional materials.SiO2@Cu core-shell microspheres are formed by a layer of Cu nanoparticlesfilm on the surface of SiO2microsphere. The electrical, magnetic, optical, mechanic,thermodynamics and chemical properties of Cu nano materials are different from thetraditional bulk materials and it shows many unique properties. So it can be used toproduce conductive material, catalyst, antibacterial agents and senior lubricating oiladditive, etc., and has potential application prospect in many fields, such as energy,electronic information, chemical industry, biological treatment, photonic crystals,super hydrophobic coating, national defense and military industry. And it is also ofgreat significance for energy saving and environmental protection.But compared with Au and Ag, nano Cu is relatively more active. Onceexposed to the air, it is really easy to be oxidized, so there still exists many problemssuch as poor stability and dispersity in the application process. SiO2@Cu, as a kindof typical inorganic core-inorganic shell composite material, has lots of advantagessuch as good dispersion, good stability, high catalytic activity, cyclic utilization andlow cost. But SiO2@Cu core-shell catalyst are not stable in structure and has lowcatalytic efficiency in the present practical application. Therefore, researchers aretrying to improve the catalytic performance of core-shell catalyst through a varietyof ways. Optimizing the preparation technology is the most effective method among them.Heterogeneous precipitation method, as one of the most common methods forthe preparation of core-shell structure composites, is not strict with laboratoryequipment and the prepared samples do not need heat treatment, so it can be used asa simple and feasible method. At the same time, papers and researches about theheterogeneous precipitation method and the catalytic mechanism of core-shellstructure composites are so few that the formation mechanism, the relationshipbetween morphology, performance and preparation process, practical applicationof core-shell structure composite are not clear. Thus, in this thesis，the heterogeneousprecipitation method was used to prepare SiO2@Cu core-shell catalyst.Firstly, we got cuprous oxide with the raw mterials of copper sulfate, sodiumhydroxide and glucose, and then coated copper nanoparticle layer on the surface ofthe homemade silica microsphere using heterogeneous precipitation to prepareSiO2@Cu core-shell catalyst. X-ray diffraction analyzer (X-ray diffraction, XRD),scanning electron microscope (SEM) and energy spectrum analyzer (EDS), fouriertransform infrared spectroscopy (FT-IR), fluorescence spectrum andultraviolet-visible (UV-vis) absorption were used to characterize the content,structure and purity, morphology, particle size and element composition, internalstructure, form of copper and oxide and catalytic performance of SiO2@Cucore-shell catalyst.The effects of pH value, mass ratio of SiO2/Cu2O, temperature of water bath anddosage of polyethylene glycol (PEG) on the structure and performance of SiO2@Cucore-shell catalyst were studied. The catalytic performances of the samples wereevaluated through the photocatalytic degradation of methyl orange (MO) solution.And the best parameters for the preparation of SiO2@Cu with good dispersion,uniform particle size, good catalytic performance were discussed. In addition, theinfluence of catalyst and UV light on the photocatalytic degradation behavior ofmethyl violet and methylene blue solution were also investigated; the preparationmechanism of core-shell structure was suggested; the optimum process to prepareSiO2@Cu core-shell catalyst which is easy to be applied is also determined. The single factor experiment results demonstrate that, the pH value of less than2or larger than3, SiO2/Cu2O mass ratio of1:6, water bath temperature of50°C,PEG amount of1.0mL is the optimized reaction condition for the formation of theSiO2@Cu core–shell catalyst with good dispersity, proper Cu loading, and goodphotocatalytic activity. And it showed good photocatalytic degradation performanceto methyl orange, methyl violet and methylene blue solution. In addition, the catalystand UV light have synergistic effect on the photocatalytic degradation behavior oforganic dyestuff. Adsorption layer media mechanism, the coulomb electrostaticgravity mechanism and the chemical bonding mechanism all contribute to theformation of SiO2@Cu core-shell catalyst. |
PDF Full Text Request