Preparation And Properties Of Graphene-based Nanocomposites

Graphene, a two-dimensional carbon material, has attracted tremendous attention and researches due to its extraordinary electronic, thermal and mechanical properties. Functional materials based graphene have been proved to have potential applications in the areas of optics, electronics, sensors and power accumulators. According to many literature materials and analysis on the research achievements and in order to prepare high-quality graphene-based nanocomposites, we design and prepare some new type graphene and graphene based nanocomposites materials. Furthermore, we in depth investigate the photocatalysis and supercapacitor performance of the nanocomposites and reveal the mechanism of the enhanced performance.The main research contents of thesis are shown as follows:1. Graphite oxide as precursor was synthesized from natural graphite powder. A novel graphene-La2Ti2O7 nanocomposite was successfully synthesized using a two-step reduction process which included the high-temperature expanding process and the local photocatalysis effect of La2Ti2O7. The photocatalysis property of the nanocomposites was further investigated though the photocatalytic degradation rate of RhB dye. Compared to pure La2Ti2O7 nanosheet, the enhancement of photocalytic property of graphene-La2Ti2O7 nanocomposite was observed. The photocatalytic degradation rate of RhB by the nanocomposites achieved 80% after 30 min. We supposed that it was attributed to an excellent electronic property of graphene and large surface contact between graphene and La2Ti2O7 nanosheets. The graphene attributed to the efficient separation of electron and hole from excited La2Ti2O7 nanosheets.2. A novel three-dimensional(3D) ultrathin derived graphene(UDG) material on the nickel foam(NF) was prepared by combination of the hydrothermal method and thermal treatment. The low molecular weight phenolic resols were used as the carbon source, which is synthesized using phenol and formaldehyde as raw materials. Furthermore, the 3D NiO/UDG/NF hybrid was prepared by a chemical bath deposition of NiO on the UDG/NF scaffold. Moreover, the 3D NiO/UDG/NF hybrid was directly used as a binder-free supercapacitor electrode. Electrochemical measurements as cyclic voltammetry(CV), chronopotentiometry(CP) for charge/discharge curve and electrochemical impedance spectroscopy(EIS) were performed to investigate the supercapacitor performance of the NiO/UDG/NF electrode. Improved pseudocapacitive performance was found and the capacitance value was improved nearly 80% compared to the bare NiO/NF electrode. The mechanism was also discussed in detail.3. A novel Co3O4/flocculent graphene(FG) hybrid on commercial NF has been prepared. The unique flocculent graphene structure was prepared by combining a rapid filtering approach through NF and a template method, in which the thermally expanded graphite was used as precursor and polystyrene(PS) microspheres were used as templates. The Co3O4 nanoclusters on the FG/NF scaffold were prepared by the hydrothermal method and subsequently thermal treatment. Furthermore, the electrochemical performance of the Co3O4/FG/NF hybrid was investigated by some electrochemical measurements as CV, CP and EIS, in which the Co3O4/ FG/NF hybrid was directly used as a binder-free supercapacitor electrode. Improved pseudocapacitive performance was found and the capacitance value was improved nearly 80% compared to the bare Co3O4/NF electrode. The mechanism was also discussed in detail. The asymmetric capacitor was further designed and assembled. The electrochemical properties of the asymmetric capacitor were investigated, which made the Co3O4/FG/NF hybrid more suitable for practical applications.