| Chemical industry has major contribution to worldwide economic development, but it also causes many serious environmental problems. One of the most attractive concepts for pollution prevention is green chemistry, which is best defined as the utilization of a set of principles that reduces or eliminates the use or generation of hazardous materials, solvent, catalysts and byproducts in the design, manufacture, and applications of chemical products. The development and applications in organic synthesis of catalysts is proving to be a vital role in green chemistry. Catalysis can improve the efficiency of a reaction by lowering the energy input required, by avoiding the use of stoichiometric amount of reagents, and by greater product selectivity and yield. This implies less energy, less feedstock and less waste.Three different green catalysts including bimetal-modified carbon nanotubes electrode, bismuth oxide electrode and bismuth oxide powder catalyst were successfully fabricated based on the12classical principles of green chemistry. Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy, X-ray Diffraction and Electrochemical Workstations were used to characterize the structure and optical properties of the resulting catalytic materials.Carbon nanotubes modified by Ag-Co bimetal (Ag-Co/CNTs) were fabricated by reduction method. The characterization results indicated that the Ag-Co bimetallic nanoparticles with the size of3-6nm were evenly attached to the surface of carbon nanotubes. The structure consists of Ag-Co bimetallic and carbon nanotubes effectively promote the electrocatalytic performance of the carbon nanotubes.The obtained Ag-Co/CNTs electrode was used as the cathode for the selective oxidation of phenol in aqueous solution. The modified Ag-Co bimetallic carbon nanotubes significantly improved the efficiency of the selectivity and the yield. The yield of the Ag-Co/CNTs electrode (Ag:Co20wt%, Ag:Co atomic ratio=2:1) was1.7times higher than the pure CNTs. And the Ag-Co/CNTs obtained a satisfactory selectivity of benzodiazepine about91.8%in aqueous solution. The resultant Ag-Co/CNTs heterogeneous catalysts exhibited amazing catalytic reactivity towards the yield of benzoquinone, accomplishing with a reasonable conversion of phenol. The modified Ag-Co/CNTs electrode was performed in cyclic voltammetry as working electrode, and the effect of substrate concentration, metal mass fraction, oxygen content and scan rates on the cyclic voltammograms was investigated in this study. The possible electrocatalytic mechanism for Ag-Co/CNTs as catalyst was as follows:The modified electrode Ag-Co/CNTs could take advantage of oxygen effectively in situ with the assistance of electricity. At first, the oxygen was absorbed by bimetal Ag-Co, and then the absorbing oxygen atoms transfer to the active site on the surface of carbon nanotubes where selective oxidation of phenol will occur.The Bi2O3electrode and Bi2O3powder catalyst were successfully fabricated by electrodeposition method and hydrothermal method, respectively. The electrocatalytic property of Bi2O3was investigated in the synthesis of benzaldehyde by benzyl alcohol selective catalytic oxidation in aqueous solution. Results indicated that the benzaldehyde selectivity of Bi2O3electrode prepared by electrodeposition method was almost3times higher than that of Bi2O3electrode prepared by the dispensing method under the applied2V voltage, and the yield of benzaldehyde was9times higher. We found that the three-dimensional structures of Bi2O3nanoparticles favored the effective absorption and shift of the electrons.Various Bi2O3powder catalysts were investigated to evaluate the catalytic performance using benzyl alcohol as a model pollutant under the visible light irradiation. It was found that photocatalytic performance of Bi2O3powder prepared by nanocage hydrothermal method was superior to other Bi2O3powder catalysts under irradiation. The special "gathered structure" of Bi2O3nanoparticles with size of100-150nm exhibited higher efficiency of the transmission of photoelectron and molecule. Besides, several crystal forms were detected in the Bi2O3power including cuibic-Bi2O3and tetragonal-Bi2O3, which implied that the mixed crystal could transfer the photoelectron to the reaction more effectively. |
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