A Study Of Preparation And Properties On Magnetic Catalyst For Photocatalytic Reduction Of CO₂into Organic

We used the Fe3O4nanomaterials as the magnetic core, which was prepared by hydrothermal. Then, we used the meso-SiO2@TiO2as the basis, which was prepared by ultrasound-assisted method. Finally, the magnetic core/shell structure photocatalyst TiO2@SiO2@Fe3O4and Cu-TiO2@SiO-2@Fe3O4were synthesized through sol-gel method. The prepared catalysts were characterized by a variety of characterization. We use the photocatalytic reduction of CO2into methanol to evaluate the photocatalytic activity of the catalyst. The parameter of the photocatalytic reaction conditions and reuse performance were also studied.The results showed that:TiO2was successfully coated on meso-SiO2@TiO2by sol-gel method, and the thickness of TiO2is15～20nm. After coating, the specific surface area of the sample increased, but the pore volume and average pore diameter decreased. The TiO2@SiO2@Fe3O4catalyst has ordered mesoporous, and pore size is concentrate in4nm. The saturation magnetization of TiO2@SiO2@Fe3O4catalyst can reach to27.15emu/g. The methanol yield of TiO2@SiO2@Fe3O4catalyst grows linearly with UV irradiation time and CO2flow rate. The optimal condition parameters of the media system are0.1mol/L NaOH and O.lmol/L Na2SO3. After the six reusing cycles, the methanol yield of the TiO2@SiO2@Fe3O4catalyst can still reach to more than85%of the original test.We successfully prepared copper doped TiO2@SiO2@Fe3O4magnetic photocatalyst through adding copper nitrate in sol-gel process. The shape and size of sample’s Fe3O4characteristic diffraction peaks are basically unchanged, but the intensity of sample’s TiO2characteristic diffraction peaks decreased, position of TiO2peaks shifted. The space of101crystal plane decreased with increasing amount of copper doped, and copper ions doped into the TiO2lattice. The Cu-doped TiO2@SiO2@Fe3O4magnetic photocatalyst exhibits mesoporous structure. With increasing of copper ion content, the specific surface area of the sample increased, but the pore volume and average pore diameter decreased. Adding too much copper cause some copper ions enter into the pore of the shell, which affect CO2combined with binding sites, thereby influence the photocatalytic activity of the catalyst. The saturation magnetization of1%Cu-Ti02@Si02@Fe3O4catalyst can reach to25.96emu/g. The optimum of Cu/TiO2ratio in reaction system is1%. In this case, the yield of methanol is1265.784μmol/g. Compared with undoped TiO2@SiO2@Fe3O4catalyst the yield has increased69%. Under long-term UV irradiation, the methanol yield of1%Cu-TiO2@SiO2@Fe3O4catalyst increase with the irradiation time. After the six reusing cycles, the methanol yield of the1% Cu-TiO2@SiO2@Fe3O4catalyst can still reach to more than81%of the original test.