Preparation And Electrochemical Energy Storage Of ZIFs@Polymer Based Carbon Nanofibers

This dissertation mainly uses electrospinning technology to mix polymers(one or a mixture of oil-soluble PAN,PAA and water-soluble PVA,PVP)with metal organic framework polymers(ZIF-8,ZIF-67)to prepare ZIFs@polymerization electrospun fiber.Then the ZIFs@polymer-based hierarchical pore flexible carbon fiber membrane material is obtained via pyrolysis carbonization,pickling and activation processes..Combined with a series of analysis and testing equipment,such as optical electron microscope,scanning electron microscope(SEM),X-ray powder diffractometer(XRD),infrared spectroscopy(FTIR)and thermogravimetric analyzer(TG),etc.,the morphology of the material,,composition content and physical and chemical properties were analyzed and charactered.Using carbon fiber membrane as electrode material,the relationship between carbon nanofiber structure and its electrochemical performance was investigated by AC impedance analysis,cyclic voltammetry and constant current discharge test.The main research is divided into the following aspects:(1)Preparation of nano ZIFs particles and two-dimensional nanosheets.ZIF particles with different sizes were prepared by room temperature synthesis method.By adjusting the reactant ratio,reaction conditions and structure control,nano materials with specific morphology and hierarchical porous structure were obtained and characterized.The results show that the prepared nanoparticles grow well,the purity can reach 95.6%,and the average particle size is about 200 nm.By adding crystal growth control agents,the synthesis process of ZIFs particles was explored.The results show that dodecyltrimethylammonium chloride with suitable oily chain length can adhere to the crystal surface of ZIFs during the growth process of ZIFs particles,which prevents the assembly of ZIFs along the transverse axis,so as to obtain two-dimensional ZIF-67 nano sheet materials of ZIFs grown in the longitudinal direction.(2)Preparation of ZIFs@polymer-derived carbon nanofibers.ZIFs@polymer nanofibers were prepared by blending method,external growth method and layerby-layer self-assembly method.Investigate the effect of different preparation methods on the electrospun fiber and the mechanism of action.Through SEM,IR,TG and other analysis tests,the morphology,composition and physical and chemical properties of the electrospun fiber are characterized.The results showed that the ZIFs particles in the ZIFs@polymer nanofibers prepared by the electrospinning method were clearly visible,the fiber continuity was good,and the diameter is 200-500 nm,and the ZIF-67@PVP nanofibers showed a "vein-like" structure.ZIFs@polymer-derived carbon nanofibers are obtained through subsequent carbonization and pickling treatments.SEM,TG and XRD were used to characterize the morphology,composition and physical and chemical properties of ZIFs@ polymer-derived carbon nanofibers.The results show that the prepared two-dimensional sheet-like ZIFs@polymer-based carbon fiber connects the twodimensional sheet-like ZIFs-based carbon through one-dimensional polymerbased carbon fiber to form a high electronic conductivity,narrow pore size distribution range,and high self-supporting three-dimensional network hierarchical porous carbon nanofiber membrane structure with performance advantages such as high specific surface area.(3)Investigation on the electrochemical energy storage behavior of ZIFs@polymer-derived carbon nanofibers.Using ZIFs@polymer-derived carbon nanofibers as electrode materials and ionic liquid as electrolyte,they are assembled into a simulated supercapacitor.Through AC impedance simulation circuit analysis,cyclic voltammetry analysis,constant current charge-discharge analysis and cycle life test,its electrochemical performance was tested.The results show that because ZIFs-based carbon has the characteristics of uniform pore size distribution,regular pore structure and fewer edge defects,it has the characteristics of high pore structure utilization,fast ion transmission rate and few electrochemical reaction active sites,making it an ideal double electric layer capacitor charge storage active material.The polymer-based carbon nanofibers have the characteristics of high electronic conductivity,good flexibility,and good structural tunability,and can be used as the connection and support material of ZIFs-based derived carbon particles.Among them,because the ZIF-67@PANbased carbon nanofibers supercapacitor has the characteristics of large specific surface area,uniform pore structure distribution and low resistance,it has a large specific capacitance(226.2 F/g)and low internal resistance.(0.31 ?)and good charge-discharge cycle stability(capacitance retention rate can reach 97.89% after1000 times).