Preparation And Electrochemical Performance Of Nitrogen-doped Graphene Based And Polyaniline Based Composites

In this paper, p-benzoquinone and p-aminophenol were adsorbed on the surface of nitrogen-doped graphene (GN) sheets by π-π interaction and p-benzoquinone nanocores were covered by polyaniline (PANI) by electrostatic interactions method and in-situ chemical oxidative polymerization. The structure and morphology of the as-prepared nanocomposites were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra and Raman spectra. In order to explore the electrochemical performance of the nanocomposites, CV, galvanostatic charge/discharge measurements and impedance spectra were tested by electrochemical workstation. The main experiments including three sections:1. A unique and convenient one-step hydrothermal process for synthesizing functionalized Nitrogen-doped graphene (FGN) via ethylenediamine, hydroquinone and graphene oxide (GO) is described. The graphene sheets of FGN provide a large surface area for hydroquinone molecules to be anchored on, which can greatly enhance the contribution of pseudocapacitance. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electrochemical workstation are used to characterize the materials. The nitrogen content exhibited in FGN can up to 9.83at% and the as-produced graphene material shows an impressive specific capacitance of 364.6 F g’1 at a scan rate of 10 mV s"1, almost triple that of GN-based one (127.5 F g’1). Furthermore, the FGN electrodes show excellent electrochemical cycle stability with 94.4% of its initial capacitance retained after 500 charge/discharge cycles at the current density of 3 A g-1.2. A simple and convenient one-step hydrothermal process for synthesizing nitrogen-doped graphene/p-aminophenol composite by using ethylenediamine, p-aminophenol and graphene oxide is described. The p-aminophenol is not only act as spacers to prevent the graphene sheets form aggregating and restacking during the hydrothermal process but also enhance the contribution of pseudocapacitance, which further improve the performance of the electrode materials. The field emission scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical workstation are used to characterize the materials. The as-produced composite material shows superior specific capacitance of 365.7 F g-1 at a scan rate of 10 mV s-1 and excellent electrochemical cycle stability.3. A Cabbage like polyaniline@hydroquinone composite microsphere was synthesized using in situ polymerization and the electrochemical performance was investigated. The core template, p-benzoquinone, is demonstrated working as an oxidizing agent for the in-situ polymerization of PANI, and to be reduced to 1,4-hydroquinone after reaction. The morphology and microstructure of samples were examined by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectra (FT-IR). The cyclic voltammetry (CV), impedance and galvanostatic charge/discharge analysis demonstrates that PANI contributes electronic conductive channels for hydroquinone and hydroquinone works as a pseudocapacitance component. The prepared PANI@hydroquinone nanocomposite exhibits brilliant electrochemical properties of a specific capacitance of 126.0 F g-1 at a scan rate of 5 mV s-1 and enhanced stability of about 85.1% of initial capacitance retained after 500 cycles scanning at a current density of 1Ag-1.