Preparation And Super-capacitive Properties Carboxyl Graphene-based Conductive Polymer Composites

Supercapacitor play an increasingly important role in modern energy storage system due to its high energy density, high power density and long cycle life, Conducting polymers with high Faradaic pseudo-capacitor become important electrode materials for supercapacitor, however, the low electronic conductivity in dedoping state, poor electrochemical utilization and instability limit practical application of the Conducting polymers. The combination of conducting polymers and carboxylated graphene (CG) with high specific surface area, superior mechanical strength, good electronic conductivity has been proposed as composite materials with good electrochemical performance due to the synergistic effect of conducting polymers and CG.Therefore, this thesis is aimed at preparation, characterization of the CG-based conducting polymer composites and its super capacitor performance in order to obtain supercapacitor electrode materials with high specific capacitance and long cycle life. The main contents and results are as follows:1. Carboxyl Graphene (CG), containing functional group such as hydroxyl group, epoxy group, carboxyl group on the surface, it’s easy to form a stable suspension in an aqueous solvent and absorb monomer molecules to prepare composite materials. With this inherent advantage of CG, an in-situ polymerization was used in this chapter, CG was introduced in the polymerization of the pyrrole monomer to prepare a composite named CG/PPy. And CG/PPy were further characterized by transmission electron microscopy, Raman spectroscopy, infrared spectroscopy. X-ray diffraction and electrochemical tests. Change of the morphology, functional groups, current density, impedance, capacitance performance indicated that CG/PPy significantly improved the current response and reduced the resistance of the glassy carbon electrode in the electrolyte. The specific capacitance of the composite was up to584F/g and81%of the initial value was remained after1000cycles.2. CG/PANI was prepared by direct chemical synthesis using Carboxy Graphene (CG) and aniline (An) as raw materials, ammonium persulfate as the initiator. The experimental results showed that CG with nanometer size improved the oxidation-reduction reaction of polyaniline (PANI), at the same time, PANI improved the electric double layer capacitor and the sensor capacitor contributed by CG. Electrochemical studies showed that CG can improve charge transport of PANI in the charge-discharge process, specific capacitance of PANI in CG/PANI was up to579F/g, it’s higher than that of pure PANI.3. CG-PANI was prepared by a new synthesis method using an in-situ electrodeposition, the method is simple, effective, easy to operate without adding oxidant, so impact of oxidant was avoided. Specific capacitance of the CG-PANI was up to792.5F/g, which is higher than that prepared by direct chemical synthesis. The prepared composite has good electrochemical stability, it remained86%of the initial specific capacitance after1000cycles, which layed a solid foundation for the applicition of CG-PANI in the field of supercapacitor.4. PANI nanoparticles were prepared by an in-situ electrodeposition, morphology and properties were controlled by adjusting the deposition time. The experimental results proved that the optimum deposition time was600seconds, at that time, fibrous PANI nanoparticles were prepared. PANI with nanometer size shortened the distance of charge transfer, which was good for full utilization of the electrode materials. After1000cycles,86%of the initial specific capacitance was remained.