Preparation Of Double Perovskite La₂XFeO₆?X=Bi,Co,Ni? And Study On Its Capacitance Performance And Degradation Of Dyes And Wastewater

With the rapid development of the research of perovskite type oxide?ABO₃?,double perovskite composite oxide has also attracted the attention of many researchers.Because of the unique lattice structure,makes it have a great magnetic dielectric effect and magneto-electric coupling performance,which will greatly reduce the resistance of the material so that it can be widely used in energy conversion materials,photocatalytic materials and energy storage materials.Nanofibrous materials Because of its unique one-dimensional structure and the characteristics of not easy to reunion have always been the research focus,and the current mainstream of nanofibers preparation method is electrospinning.In this thesis,we mainly studied the double-perovskite composite oxides in two aspects:Firstly,La₂BiFeO₆ and La₂CoFeO₆ nanofibers were synthesized by electrospinning using PAN as the polymer material,and they were used as electrode materials in the super Capacitor field.The results showed that the initial specific capacitance of La₂CoFeO₆ nanofibrous electrode was 142.86 F g^-11 at 1 A g^-1 current density,and its capacity retention was 70%after 1000 cycles,while La₂Bi FeO₆ nanofiber electrode,the initial specific capacitance of the material was 100.72F g^-1,with a capacity retention of only 50%after 1000 cycles.This shows that La₂CoFeO₆nanofibers have excellent electrochemical properties.The specific capacitance of La₂CoFeO₆nanofibers is mainly determined by the high specific surface area and porosity of nanofibers.The cyclic stability of La₂CoFeO₆ nanofibers is mainly determined by its high crystallinity.Second,based on the application of perovskite oxides in the field of photocatalysis,La₂NiFeO₆and La₂CoFeO₆ nanofibers were synthesized by electrospinning using PVP and PAN as polymeric materials,respectively,and using them as photocatalysts for methyl Orange solution was degraded to verify the photocatalytic oxidation of four materials properties.The results showed that PVP-La₂NiFeO₆,PAN-La₂NiFeO₆,PVP-La₂CoFeO₆ and PAN-La₂CoFeO₆nanofibers with a dosage of 1 g L^-1,a methyl orange solution of 5 to 6 and a sunlight of 2 h The degradation rates of the catalyst on 10 mg L^-1 methyl orange solution were 72%,54%,22%and15%,respectively.The conditions of photocatalytic degradation of methyl orange solution were optimized.The best experimental conditions of photocatalytic activity in sunlight were determined as follows:the pH value of methyl orange solution was 2,and the amount of catalyst added was 1.5 g L^-1.In this condition,the degradation rate of PVP-La₂NiFeO₆ nanofiber photocatalyst to 10 mg L^-1 methyl orange solution was 90%.Such excellent photocatalytic activity is mainly due to its complete nanofibrous structure increasing its specific surface area and further enhancing its reactive site.Subsequent cyclic catalysis experiments verified the photocatalytic stability of PVP-La₂NiFeO₆ nanofibers.After four cycles,the degradation rate of methyl orange solution decreased from 90%to 81%.This excellent photocatalytic stability mainly due to its high degree of crystallinity and unique one-dimensional structure.In this thesis,we have verified the double-perovskite composite oxide can be well applied in the fields of supercapacitors and photocatalysts by using it in different fields,and there are good performance in these fields.So,it is necessary to make further research for double perovskite composite oxide.