Preparation Of Shape-controlled Graphene-based Nanocomposites And Their Application In Supercapacitors

In this thesis, different supercapacitor active electrode materials were synthesized, including graphene-metal oxide composites and graphene-conductive polymer composites nanomaterials. In addition, the morphology of the samples was observed by scanning electron microscopy(SEM). Meanwhile, the structure of products were characterized by Fourier transform infrared spectroscopy(FT-IR), X-ray photoelectron spectroscopy(XPS), X-ray powder diffraction(XRD), UV-visible(UV-Vis) absorption spectroscopy, and so on. Furthermore, the electrochemical properties of these materials were also studied. The main research contents are as follows:1. Graphene-MnO2 nanocomposites with different morphologies were obtained by a facile self-assembly method. The formation mechanism of graphene-MnO2 composites with different shapes of MnO2 is discussed in detail. Nanostructured MnO2 with different morphologies was distributed on the surface of graphene uniformly. The prepared graphene-MnO2 composites could be used as electrode materials for supercapacitors. The graphene-MnO2(flowerlike nanospheres) composite(405 F·g-1) exhibited better capacitive performance than that of the graphene-MnO2(nanowires) composite(318 F·g-1) at a current density of 1.0 A·g-1. The synergistic effect of graphene and MnO2 endowed the composite with high electrochemical capacitance. Moreover, the graphene-MnO2(flowerlike nanospheres) composite showed a fast charge-discharge process and high cyclic stability.2. Graphene-polyaniline(PANI) nanocomposites with different morphologies were successfully fabricated by an effective one-step hydrothermal method. The morphologies of PANI could be controlled from nanowires to nanocones by adjusting the amount of aniline with the assistance of an ultrasonication process. By taking the advantages of the high conductivity of graphene and the pseudocapacitance of PANI, graphene-PANI composites were used as an example for the application to the supercapacitor electrode materials. The cyclic voltammograms(CV) and galvanostatic charge-discharge measurements demonstrate that the graphene-PANI shows excellent electrochemical properties. The graphene-PANI nanowire composite(724.6 F·g-1) exhibited higher specific capacitance than that of the graphene-PANI nanocone composite(602.5 F·g-1) at a current density of 1.0 A·g-1. Furthermore, the graphene-PANI nanowire composite exhibited outstanding capacitive performance with a high specific capacitance of 957.1 F·g-1 at 2 mV·s-1 and a high cycle reversibility of 90% after charge-discharge 1000 cycles. The improved electrochemical properties of the graphene-PANI nanocomposites suggest their promising applications to high-performance supercapacitors.