Investigation On Synthesis And Characterization Of Graphene And Graphene-based Composite And Their Supercapacitive Properties

Graphene had been successfully produced in 2004. This type of new material has been paying great attention due to its unique physical, chemical, and mechanics properties. In this thesis, graphene were synthesized by the chemical reduction and thermal exfoliation of graphite oxide, respectively. In addition, graphene oxide/amorphous carbon, FGS300/FDU15, FGS300/RuO₂·xH₂O composites are prepared by the blending and self-assembly method. The obtained samples were characterized by XRD, SEM, TEM, N2 adsorption-desorption analysis and so on. These samples were also investigated the performance of their supercapacitor behaviors as the electrode material. Finally, FGS300/Ni composite was prepared by the deposition approach and its magnetic properties is tested.Graphene was prepared by the reduction of graphite oxide with hydrazine. The sample has good performance of supercapacitor behaviors. The result of N2 adsorption-desorption analysis shows that the prepared sample has lower BET surface area, which is mainly due to large amounts of reunion between the graphite layers and cause to reconstitute the bulk graphite structure. Functionalized graphene sheets are prepared by thermal exfoliation of graphite oxide at different temperature. The prepared samples by low temperature thermal exfoliation of graphite oxide have good supercapacitve performances due to a lot of functional groups on the surface of the samples. The specific capacitance values of samples with further high temperature heat treatment are significantly lower than those of the samples with low temperature thermal exfoliation. However, the samples with further high temperature heat treatment have fine supercapacitive performances at high scan rates and current densities because of their good conductive behaviors. The graphene oxide/amorphous carbon composite got higher BET surface area compared with the two kinds of monomers itselves. FGS300/FDU15 composite has good performance of supercapacitor behaviors and capacitance retention at high scan rates and current densities. This is mainly due to the composite with relatively uniform pore size distribution and it is conductive to the transmission of the electrolyte. The results of electrochemical tests show as follows: FGS300/RuO₂·xH₂O composite with 5wt% RuO₂·xH₂O got the best electrochemical utilization reached 50% (1040F/g). With the increase of the mass of the RuO₂·xH₂O, the composite specific capacitance values don't increase obviously. That's because the RuO₂·xH₂O has not a good conductive property and large amounts of reunion on the surface of FGS300 occurred, which it geatly decreased the active area of the RuO₂·xH₂O. Finally, FGS300/Ni composite is prepared. The XRD test indicates that Ni nanoparticles with good degree of crystallinity is the cubic phase. A simple magnetic test showed that FGS300/Ni composite had good magnetic properties.