Research On Synthesis And Photocatalytic Performance Of Lanthanum Ferrite Based Nanocomposites

Perovskite type material lanthanum ferrite（LaFeO₃）has attracted much attention due to its special crystal structure and stability.At present,LaFeO₃-based materials have received extensive attention in electrode,photocatalysis,gas sensor preparation and magnetic properties research.In this thesis,LaFeO₃ nanocomposites was prepared by different synthetic processes and its morphological characteristics were studied,which had an effect on photocatalysis and magnetic properties.Combined with characterizations,LaFeO₃-based materials are analyzed in the field of catalytic properties and magnetic properties.The main research contents are as follows:1)LaFeO₃ nanoparticles with high specific surface area were synthesized bychanging the pH value of solution and preparing calcined at high temperature in the process of sol-gel preparation.Combined with characterization methods,the effects of pH value on the microstructure,morphology and specific surface area of LaFeO₃samples were discussed in detail.According to the analysis of photocatalytic degradation of methylene blue（MB）and saturation magnetization（MS）,it is proposed that oxygen vacancy can effectively improve the photocatalytic performance and optimize the magnetic performance of LaFeO₃.2)LaFeO₃ nanoparticles were synthesized by ethylene glycol solvothermal method and high temperature calcination.The colloidal solution of g-C₃N₄ nanosheets was obtained by alkalization of block g-C₃N₄.g-C₃N₄/LaFeO₃ heterojunction photocatalyst was synthesized by electrostatic self-assembly.Combined with the characterization methods and the experimental results of photocatalytic degradation of tetracycline hydrochloride（TC HCl）,35%g-C₃N₄/LaFeO₃ has the best photocatalytic activity,and its degradation rate is about 97%.The results of stability and cycling test show that the catalyst has good stability.At the same time,the results of free radical capture show that·O^2-is the main active substance for photocatalytic degradation of TC HCl.Finally,according to the energy band distribution of LaFeO₃ and g-C₃N₄,the degradation mechanism of TC HCl by g-C₃N₄/LaFeO₃ is proposed.Under external light,the P-N heterojunction can realize the effective separation of photogenerated carriers,transfer electrons from LaFeO₃ conduction band to g-C₃N₄ conduction band,reduce the adsorbed oxygen to·O^2-,and improve the degradation efficiency.3)LaFe_1-xMn_xO₃/γ-Fe₂O₃ composites were prepared by controlling the proportion of Mn in solvothermal synthesis with ethylene glycol as solvent,which made it have better magnetic response.Combined the characterization and the experimental results of photocatalytic degradation of TC-HCl and MB,the photocatalytic degradation efficiency of is higher.Then,potassium bisulfate（PMS）is used to activate and catalyze the degradation of MB.The reaction mechanism of PMS activation and catalysis for the degradation of MB pollutants is proposed.The free radical capture experiment shows that·O^2-is the main active substances for catalytic degradation of MB.Finally,according to LaFe_1-xMn_xO₃ and LaFe_1-xMn_xO₃/γ-Fe₂O₃band distribution,the mechanism of LaFe_1-xMn_xO₃/γ-Fe₂O₃ degrading MB is proposed.