Low-cost Synthesis And Application Research Of Graphene And Its Composite Materials

This research work is mainly composed of four sections. Including the preparation and characterization of organic anion-pillared hydrotalcites, the preparation of graphene nanosheets (GNS), the application of graphene nanosheets in supercapacitors, and the preparation and characterization of polyaniline composite doped with GNS.The organic anions of benzoate and abietate-pillared hydrotalcites were successfully intercalated into interlayer region of layered double hydroxides (LDHs) by coprecipitation method, and the MgAl-benzoate radical-LDHs and MgAl-abietate radical-LDHs were prepared. The structure and properties of samples were characterized by FT-IR, XRD, elemental analysis, SEM and TG-DSC. The results show that the organic anion intercalated into the interlayer of LDHs result in the increase of layer spacing, and the increasing degree is associated with the structure of organic anion. Although the crystallinity of these hydrotalcites were decreased, it still keeps its lamellar structure. Additionally, the protection effect of layer structure may enhance the thermal stability.At different temperatures, the MgAl-benzoate radical-LDHs and MgAl-abietate radical-LDHs were calcinated in pure argon. The calcined samples were washed with acid solution, and the graphene nanosheets (GNS) were obtained. The structure and properties of samples were characterized by XRD, elemental analysis, Raman, TEM, AFM and BET. The results show that the organic anions which intercalated in the interlayer of LDHs were graphitized under 800℃, and its specific surface area can reach 1240.7 m2 g-1 and 1318.4 m2 g-1, respectively. This method of preparation graphene nanosheets is simple, low-cost and is likely to be suitable for large scale production.In order to explore the electrical properties of the GNS, the samples were used to fabricate electrodes and symmetrical supercapacitor cells were fabricated based on two electrodes. At a current density of 100 mA g-1, the specific capacitance is calculated to be 198 F g-1 and 188.2 F g-1, which were superior to the value for LDO or activated carbon based supercapacitors. Besides, it also shows a good stability.Graphene/Polyaniline (GNS/PANI) composites was prepared via in situ polymerization. The performance of composite with different concentration of GNS were characterized by FT-IR, XRD and SEM. The characterization results show that the GNS layer is the role of connecting the PANI molecular chain and the conductive bridge in composites. The 10% GNS doping in composites shows the best morphology and crystallinity. The electrical conductivity of composites was tested by four probe method, and the result shows that the conductivity of the composites with 10% GNS is 588.20 s/m, which is significantly higher than that of PANI. The GNS/PANI composites may become promising candidates for the electrode materials.