The Super Capacitor In The Preparation Of Graphene/polymer Composites And Their Performance

Graphene, a2D sheet of sp2-bonded carbon atoms arranged in a honeycomb lattice, has attracted increasing attention since it was firstly isolated from3D graphite by mechanical exfoliation. Due to its extraordinary thermal, mechanical, and electrical properties, graphene is usually considered as a competitive candidate for next-generation electronic applications such as electronic and energy storage devices, field-effect transistors, sensors, catalysts, etc. Supercapacitors based on graphene materials have been investigated compactly in recent years. However, the pure graphene electrode seemed not to exhibit the desired capacitance because of inevitable aggregation of graphene sheets. To alleviate this embarrassing disagreement, logical building of graphene/polymer composites was proposed and exerted positive effects in practice, and newly-prepared graphite oxide by improved Hummers method was also proposed. The dissertation is mainly focused on:1. Graphene oxide with rich functional groups (IGO) was prepared by improved Hummers method. Fourier transform infrared spectroscopy (FT-IR), Raman spectrometer, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that improved graphene oxide (IGO) was easier to disperse in water and possessed more oxygen-containing groups than graphene oxide synthesized by traditional Hummers method (HGO), which was advantageous to the following preparation.2. Ethylene glycol reduced graphene oxide/polypyrrole (EG-RGO/PPy) composite was prepared by in-situ polymerization. As water-insoluble graphene that is hard to disperse uniformly in aqueous pyrrole solution, IGO was used as reactive precursor and directly involved in preparation of graphene oxide/Polypyrrole (GO/PPy) composite which was then reduced by ethylene glycol. Diverse types of general characterization and electrochemical measurements were valued and manifested that the specific capacitance of EG-RGO/PPy was as high as420F·g-1at a current density of0.5A·g-1in1mol·L-1H2SO4electrolytes.3. Carboxyl-functionalized graphene oxide/polyaniline (CFGO/PANI) composite was prepared by in-situ polymerization. IGO possessed the maximum quantities of hydroxyl and epoxy groups bound on the basal planes in addition to partial carboxyl groups located at the edges. To make the best use of the basal oxygenated groups to create orderly constructed composites, CFGO/PANI was prepared by an esterification reaction followed by the introduced oxalic acid (HOOC-COOH) interacting with-OH groups to realize carboxylation of GO sheets. CFGO/PANI was characterized by SEM, TEM (transmission electron microscopy), FT-IR, XRD, TGA and Raman spectrometer, and measured by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and capacitance retaining performance with charge/discharge cycling which indicated that the specific capacitance of CFGO/PANI was as high as541F·g-1at a current density of0.3A·g-1in1mol·L-1H2SO4electrolytes; the retaining rate of capacitance of CFGO/PANI was91%after200circles.