| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 103 === The main idea of this thesis was to fabricate a flexible electrode with facile process for gel type supercapacitor. In-situ chemical polymerization of aniline was employed for the growth of PANI nanowire array on graphite foil with high surface area. We used SEM, TGA and electrochemical measurement including Galvanostatic charge discharge, cyclic voltammetry and EIS to characterize the PANI electrode that synthesized in different concentrations of aniline. The correlation between the capacitance and surface morphology of PANI polymerized in different aniline concentrations were investigated. When the concentration of aniline for reaction was 0.01 M, nanowire array was fabricated with the optimized specific capacitance reaching 737.29 F/g at 1 A/g and still remaining 474.60 F/g at 11 A/g.
To further improve the specific capacitance, PANI electrode was physisorbed with GQDs which were prominent in their oxygen-related chemical functionalities on the edge site. Accordingly, negative-charged GQDs could adsorb on positive-charged PANI easily as evidenced by FTIR-ATR. In addition, from TEM images, the surface of PANI/GQDs would not be reduced because of the small particle size and great dispersity of GQDs. Electrochemical measurements were also conducted to support the observed enhancement of capacitive performance. For PANI/GQD nanocomposites prepared by immersing PANI in 1.5 mg/ml GQDs suspension, the best specific capacitance obtained was 965.38 F/g at 1 A/g, ~30% higher than that without GQDs. EIS measurements also confirmed that both interface and electron charge transfer resistances were decreased significantly. It is believed that the GQDs on the PANI surface could serve as an electron funnel facilitating the charge transfer between the interfaces and enhancing faradaic redox reaction.
To overcome the leakage problem of liquid type electrolyte, we fabricated the gel type supercapapcitor with PANI/GQDs composite electrode and GO-doped EMITFSI ionic liquid. Doping with GO, the ion conductivity of EMITFSI would increase significantly because strong Coulombic force between GO and EMITFSI hindered the motion of molecule and GO as a 3D network acted like an ion “highway” throughout the gel electrolyte. When 4 wt% of GO was added to the EMITFSI, the gel point was reached. The best specific capacitance of 151.06 F/g at 1 A/g was also obtained. Cycle number test of charge-discharge indicated that the supercapacitor with Go-doped gel electrolyte had better durability than that with aqueous electrolyte.
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