Synitiesis And Electrochemical Properties Of Graphene And Graphene-based Composites

With the discovery of graphene to its application, the researchers found that it hasnot been shown in practice that graphene has many excellent properties in theory.Andcomposite materials not only own the basic properties of nanomaterials, but alsoexhibit composite synergistic multifunctional effects. In this paper, according to thelarger specific surface area and good capability of electronic transmission of graphene,grapheme-based nanocomposites were prepared by using solvothermal method and itselectrochemical properties was studied. The main results are as follows：(1) Reduced graphene oxide (RGO) nanosheets with high quality were prepared byusing reducing agent from graphene oxide through hydrothermal method. The RGOnanosheets were characterized by SEM, XRD and FT-IR, and then used to modify theglassy carbon electrode(GCE). The electrochemical behavior of guaiacol on theunmodified GCE and RGO nanosheets modified GCE was compared. The RGOnanosheets have been proven to remarkably enhance electrochemical catalysis ofguaiacol. The current value of oxidation peak for guaiacol was markedly improvedafter the glassy carbon electrode modified by RGO nanosheets. As a result, a novelelectrochemical method with high sensitivity and rapid response was developed forthe detection of guaiacol. After30s accumulation, the linear range was from5×10-7to5×10-4mol/L with a linear coefficient of0.998, and the detection limitation forguaiacol was2×10-7mol/L. Finally, it was used to determine guaiacol in bamboojuice, and the recovery was over the range between98.9%and105.8%.(2) Uniform reduced graphene oxide-wrapped WO3nanowire nanocomposite(WO3/RGO nanowire) was prepared by a facile approach of one-stepsolvothermal method. The obtained composite, WO3/RGO nanowire, wascharacterized by FT-IR, XRD and SEM, and then used to modify the glassy carbonelectrode(GCE). The electrochemical behavior of honokiol on the unmodified GCE,WO3nanowire modified GCE and WO3/RGO nanowire modified GCE was compared. WO3/RGO nanowire composite has been proven to remarkably enhanceelectrochemical catalysis of honokiol. The current value of oxidation peak forhonokiol was markedly improved after the glassy carbon electrode modified by WO3/RGO nanowire. After2-min under open circuit, the linear range was from1.0×10-8to2.0×10-5mol/L, and the detection limitation for honokiol was as low as8×10-9mol/L. This analysis method has high recovery ratio of honokiol up to103%.(3) Fe2O3/reduced graphene oxide (RGO) nanocomposite was prepared byhydrothermal process from Fe(OH)3/graphene oxide (GO) which were assembledelectrostatically by mixing a negatively charged GO sheets aqueous solution with apositively charged Fe(OH)3aqueous dispersion at room temperature. The obtainedproducts was characterized by XRD, SEM, FT-IR and TGA, and then used to modifythe glassy carbon electrode(GCE). The electrochemical behavior of rutin on theunmodified GCE, RGO modified GCE, Fe2O3modified GCE and Fe2O3/RGOmodified GCE was compared. Fe2O3/RGO composite has been proven to remarkablyenhance electrochemical catalysis of rutin. As a result, the Fe2O3/RGO modified GCEwith high sensitivity and rapid response was used for the detection of rutin. After90sunder open circuit, the linear range was from1.5×10-8to1.8×10-5mol/L, and thedetection limitation for rutin was as low as9.8×10-9mol/L. This analysis method hashigh recovery ratio of rutin up to99.5%.(4) CoS2/reduced graphene oxide (CoS2/RGO) composites were obtained by usingNa2S2O3as reducing agent and the source of sulfur also through one-pot hydrothermalmethod. The products were characterized by XRD, SEM, FT-IR, TGA andelectrochemical tests. The supercapacitor performance of RGO, CoS2and CoS2/RGOelectrode was compared. The results of electrochemical tests show the specificcapacitance of CoS2/RGO composites was higher than that the signle RGO and CoS2materials. After1000cycles, its specific capacitance was97.28%than that of theinitial value. It demonstated that CoS2/RGO composites has good cycle performance.(5) One-step hydrothermal method was used for preparing CoOOH/MnO2/FGS fromthermally exfoliated graphene oxide as carrier. Several characterizations such as SEM,XRD, FT-IR and TGA were employed to investigate the product, and it was proved to be a composite nanomaterial composed of graphene-based CoOOH/MnO2nanoparticles. The SEM images show the nanoparticles were dispersed on thegraphene sheets. The supercapacitor performance of CoOOH/MnO2nanoparticles,RGO and CoOOH/MnO2/FGS nanocomposites were compared. When FGS content ofCoOOH/MnO2/FGS nanocomposites is65%, the maximum capacitance is as high as509.00F/g. After1000cycles, its specific capacitance was84.45%than that of the thesignle CoOOH/MnO2nanoparticles. It is obvious that CoOOH/MnO2/FGSnanocomposites exhibits excellent supercapacitive behaviors.