Synthesis Of Rare Earth Double Perovskite-Type La₂FeBO₆(B=Mn,Co,Zn) Catalysts And Studies Of Their Photocatalytic Degradation Properties

Presently, in order to improve the utilization ratio of solar and catalytic efficiency in the field of photocatalysis for wastewater degradation, it is becoming a research focus to explore and study the catalysts with highly efficient and available in visible light.In this thesis, rare-earth double perovskite-type catalysts La2FeBO6(B=Mn,Co,Zn) were synthesized by the citric acid complexing method and La2FeMnO6 was also prepared by other methods as comparison. Their structures, surface morphology, valence of ion, and so on, were characterized by XRD, XPS, BET, H2-TPR, SEM, and so on. Moreover, the effect of exchange interaction of B ions on the structure and photocatalytic character of rare-earth double perovskite-type catalysts was studied in visible light by using photocatalytic degradation of p-chlorophenol as a probe reaction.Characterization results showed that after calcined for 3h at 700℃, both of La2FeMnO6 and La2FeCoO6 prepared by citric acid complexing method exist with structure of single-phase double perovskite-type. However, the La-Fe-Zn-O catalyst exists with mixed oxides in marjory of LaFeO3. In the catalysts, the basic surface morphologies of La2FeMnO6 are spherical, the particles are relatively smaller and the specific surface is the largest. The degradation rate of p-chlorophenol catalyzed by La2FeMnO6 and La2FeCoO6 are 83% and 74% respectively after exposured for 5h in visible light, but degradation rate of p-chlorophenol is only 51% with La-Fe-Zn-O (LaFeO3) as the catalyst. It illustrated that structure of single-phase double perovskite-type and exchange interaction of B ions are the major influence factors in the reaction of p-chlorophenol degradation.Comparing the catalysts prepared by different methods, it was found that all of photocatalysts prepared by citric acid complexing, glucose complexing and IR-assisted citric acid complexing method exist with structure of single-phase double perovskite-type. In the catalysts, the La2FeMnO6 catalyst with the largest surface area(54.9 m2/g) prepared by glucose complexing method are laminar network, some small particles and a spot of Mn4+ and Fe4+ which can bring to charge imbalance of catalysts and oxygen vacancy easily disperse on their surface. Accordingly, double perovskite La2FeMnO6 synthesized by glucose complexing method has the best activity in degradation of p-chlorophenol, which can obtain 95% degradation rate after irradiationed 5h.In the end, the photocatalytic activity of single and double perovskite was compared. It was found that the activity of La2FeMnO6 is better than that of LaMnO3.