Fabrication And Electrochemical Properties Of Three-dimensional Graphene And Polyaniline Composite

Supercapacitors are energy conversion and storage devices which have attracted much attention because of charge/discharging rates, convenience, environmental friendliness and long cycle life, and have raised enormous attention owing to their promising applications in energy field. The performance of supercapacitors depend principally on electrode materials. Graphene is a new emerging carbon material with huge specific surface area, high conductivity and excellent mechanical property, which can be regarded as one of the most promising candidate material for supercapacitor. The cycling stability and power density of graphene are outstangding while the specific capacitance is relatively low. As a conducting polymer, polyaniline(PANI) is widely applied in supercapacitor electrode materials due to its chemical stability, low cost, high theoretical capacitance and unique doping/dedoping properties. However, the electrochemical cycling stability and conductivity of PANI is poor. The combination of conducting graphene and PANI has been proposed as perfect electrode materials with good electrochemical properties for supercapacitors based on the synergistic effect of graphene and PANI. The dissertation focuses on the synthesis, the microstructure and electrochemical performance of graphene and PANI composite materials. The main results are summarized as follows:(1)The synthesis process of graphite oxide was accomplished based on pressurized oxidation, which was improved. First, we prepared expanded graphite by heating method of microwave furnace. Then the raw materials were mixxed at low temperature before high-temperature fabrication of GO. The results showed that the synthetic GO has abundant oxygen-containing functional groups, which shows a good dispersibility in water and N,N-dimethylformamide.(2)The paper proposed a facile and environmentally-friendly strategy for fabricating three-dimensional reduced graphene oxide(3D-rGO) porous structure with one step hydrothermal method using glucose as the reducing agent and CaCO3 as the template. The reducing process was accompanied by the selfassembly of two-dimensional graphene sheets into a 3D hydrogel which entrapped CaCO3 particle into the graphene network. After the removal of CaCO3 particle, 3D-rGO with interconnected porous structure was obtained. The 3D-rGO was further composted with PANI nanowire. Electrochemical test revealed that the 3D-rGO/PANI has high capacitance performance of 243 F/g at current charge–discharge current density of 1 A/g and an excellent capacity retention rate of 86% after 1000 cycles.(3)The paper reported a crosslinking method to prepare three-dimensional reduced graphene oxide(3D-rGO). F68(Triblock copolymers) were employed for chemically exfoliated graphite oxide, and reduced graphene oxide formed through in situ reduction by hydrazine. The formation of the stable aqueous copolymer-coated graphene solution is due to the noncovalent interaction between the hydrophobic PPO segments of F68 and the hydrophobic graphene surface, whereas the hydrophilic PEO chains extend into water. Supramolecular hydrogel(rGO/F68/CD) was formed withβ-cyclodextrin through the penetration of PEO chains into the cyclodextrin cavities, then this article further developed a facile and effective method to prepare three-dimensional reduced graphene oxide(3D-rGO) by high temperature removal of polymers. 3D-rGO/PANI composite was prepared via in situ polymerization. The composite exhibited high-capacitance performance(226 F/g at 1 A/g) and an excellent cycling stability.