Preparation Of Graphene-based Conducting Polymer Nanocomposite Materials And Their Applications In Electroanalysis And Supercapacitors

In this thesis,graphene-based conducting polymer nanocomposite materials with synergistic enhancement effects are synthesized by electrochemical or chemical methods due to the high specific surface area,high electrical conductivity,excellent thermal stability of graphene and the high electrochemical activity of conducting polymers.The morphology,composition,and structure of the obtained nanocomposite materials were characterized by using scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Fourier transform infrared spectroscopy（FTIR）,ultraviolet-visible spectroscopy（UV-vis）,X-ray photoelectron spectroscopy（XPS）,X-ray single crystal diffraction spectroscopy（XRD）and other technologies,and they were used for electrochemical sensors and supercapacitors to study the electrochemical performances.Conducting polymers were electrochemically synthesized on graphene oxide sheets,and the resulting nanocomposite materials can be used for high-sensitivity detection of ascorbic acid（AA）and dopamine（DA）.The ternary composite materials of graphene,conductive polymers and metal oxides（metal hydroxides）were prepared by chemical methods,and their electrochemical properties were studied when they were used as supercapacitor electrode materials.The electrochemical sensor based on graphene oxide-based conductive polymer nanocomposites has high sensitivity,good selectivity and stable performance.The mentioned graphene-based ternary composite nanomaterials can be used as electrochemical capacitor electrode materials having high specific capacitance values,rapid charge and discharge,and long cycle life.The main research contents of the thesis are listed as follows:1.poly（aniline-co-thionine）（P（ANI-co-THI））was prepared using cyclic voltammetry on the surface of graphene oxide（GO）to obtain graphene oxide/poly（aniline-co-thionine）（GO/P（ANI-co-THI））nanocomposite material modified electrodes.The obtained modified electrodes were used as sensitive current-type electrochemical sensors of ascorbic acid（AA）and dopamine（DA）.The morphology and structure of the nanocomposite materials were characterized by SEM,TEM,FTIR and UV-vis spectroscopies.AA and DA were detected in a 0.2 mol/L PBS solution of p H=7.0 using differential pulse voltammetry（DPV）.The GO/P（ANI-co-THI）nanocomposite modified electrode shows good detection activity for DA and AA.When the GO/P（ANI-co-THI）modified glassy carbon electrode was used for the detection of AA and DA,the oxidation peak current was significantly higher than that of graphene oxide modified electrode（GO/GCE）.GO/P（ANI-co-THI）modified electrode can simultaneously detect AA and DA,and the detection results are satisfactory.The oxidation peak currents of GO/P（ANI-co-THI）modified electrodes for AA and DA are 2.9 and 2.6 times than those of GO/GCE,respectively.In the concentration range from 0.002 to 0.5 mmol/L,the response to DA is linear and the detection limit is 2μmol/L.In the concentration range from 0.5 to 5 mmol/L,the response to AA was linear and the detection limit is 242μmol/L.In addition,the electrochemical sensor based on GO/P（ANI-co-THI）also exhibits high selectivity,good reproducibility and stability,wide detection range,and low detection line.2.First,the graphene oxide/polythionine composite material（GO/PTHI）was prepared by chemical in-situ polymerization.Then,nickel nitrate hexahydrate（Ni（NO₃）₂?6H₂O）was added.Controlling the mass ratio of GO/PTHI and Ni（NO₃）₂?6H₂O,the ternary nanocomposite r GO/PTHI/Ni（OH）₂was obtained through hydrothermal reaction.The surface morphology,structure and composition of the resultant ternary composites were characterized by SEM,TEM,XPS,XRD,and energy dispersive spectroscopy（EDS）.The cyclic voltammetry（CV）,galvanostatic charge-discharge（GCD）,and electrochemical impedance spectroscopy（EIS）measurements were used to study the electrochemical performance of the ternary nanocomposites used as supercapacitor electrode materials.The results show that r GO/PTHI/Ni（OH）₂-30 obtained with the mass ratio of GO/PTHI and Ni（NO₃）₂?6H₂O of 1:30 has good electrochemical performance.At a current density of 1 A/g,its specific capacity is as high as 3057 F/g;at 5 A/g,over 1000 charge/discharge cycles,its high specific capacity is still maintained.This result proves that r GO/PTHI/Ni（OH）₂-30 ternary nanocomposites have ultra-high specific capacitance performance and good structural stability.3.The three-dimensional gel-like graphene oxide-based manganese dioxide（r GO@MnO₂）nanomaterials were obtained by hydrothermal method,and then the thionine monomer was added to prepare the r GO@MnO₂/PTHI ternary nanocomposite materials by a chemical method.By controlling the different mass ratios of PTHI and r GO@MnO₂,the r GO@MnO₂/PTHI-X（mass ratios（X）:0.2,0.5,1,and 2）ternary nanocomposite materials with different mass ratios were prepared.The surface morphology,structure and composition of the prepared electrode materials were characterized by SEM,TEM,XRD,XPS and EDS.Then CV,GCD,and EIS were used to characterize the electrochemical performance of ternary nanocomposite materials for supercapacitors.The results show that r GO@MnO₂/PTHI ternary nanocomposites exhibit excellent electrochemical performances.The r GO@MnO₂/PTHI-0.5 ternary nanocomposite material shows a specific capacitance of 964.67 F/g at 1 A/g and has a capacitance retention rate of91.2%after 1000 charge/discharge cycles at 2 A/g.Therefore,This result proves that r GO@MnO₂/PTHI-0.5 ternary composite material has excellent specific capacitance performance and good cycle stability.