Synthesis And Electrochemical Properties Of Graphene And Poly(azure A) Composites

In recent years,due to their unique structure and electronic characteristics,graphene and conductive polymers have been investigated widely.In this thesis,graphene/conductive polymer composites were prepared for electrochemical sensors and supercapacitors.The excellent properties of graphene are fully utilized,such as the high conductivity,high specific surface area and excellent cycle stability.Based on reduced graphene oxide,chemical and electrochemical methods are used to prepare multi-component composites with conductive polymers and metal sulfides,which is applied to simultaneously detect ascorbic acid,dopamine and uric acid and to study the electrochemical performance of supercapacitors.The main experimental content is listed as follows:1.Simultaneous electrochemical determination of ascorbic acid,dopamine and uric acid based on electrochemically reduced graphene oxide/poly?azure A?complex modified electrodeSynthesis of electrochemically reduced graphene oxide/poly?azure A??ERGO/PAA?composites via a two-step electrochemical method.ERGO was first prepared by cyclic voltammetry?CV?to reduce graphene oxide?GO?on the surface of the glassy carbon electrode?GCE?at a negative potential,while azure A was polymerized on the surface of ERGO to obtain ERGO/PAA composites.Scanning electron microscopy?SEM?,Ultraviolet-visible absorption spectroscopy?UV-Vis?,Fourier transform infrared spectroscopy?FTIR?,and X-ray photoelectron spectroscopy?XPS?were applied to characterize the morphology,structure,and composition of the obtained composite materials,which confirmed the successful electrochemical reduction of GO and the successful preparation of ERGO/PAA composites.In addition,the electrochemical activity test confirmed that the conductivity of the composite was remarkably improved compared with pure PAA or ERGO film modified electrode.ERGO/PAA composite modified electrode can simultaneously detect ascorbic acid?AA?,dopamine?DA?and uric acid?UA?.The experimental results show that the prepared composite modified electrode has high sensitivity,low detection limit and good stability for the detection of the three substances.For AA,DA and UA,the ERGO/PAA composite electrode exhibits a wide detection range(0.8?1200,0.25?600,and 0.6?960?mol·L^-1)and has a very low detection limit of 0.271,0.054 and 0.116?mol·L^-1.In addition,the ERGO/PAA modified electrode has high reproducibility and selectivity and can also be applicable to the detection of target molecules in actual samples.2.Preparation and electrochemical performance of nitrogen-doped graphene/poly?azure A?compositesNitrogen-doped graphene?NG?was obtained in an autoclave by mixing the GO dispersion with the same amount of ammonia,urea,and ethylenediamine respectively by a hydrothermal solvent method.Nitrogen-doped graphene/poly?azure A??NG/PAA?composite materials were prepared via in-situ polymerization of azure A and NG in an acidic solution.SEM,transmission electron microscopy?TEM?,FTIR,Raman spectroscopy,XPS and X-ray diffraction spectroscopy?XRD?measurements were carried out to characterize the morphology,structure,and composition of the resulting composites.The electrochemical performances of the NG and NG/PAA composite were analyzed through CV,galvanostatic charge/discharge?GCD?and electrochemical impedance spectroscopy?EIS?tests.Compared with pure poly?azure A?and urea-nitrogen-doped graphene,urea-nitrogen-doped graphene/poly?azure A?composite materials have better energy storage performance.The as-prepared composite materials exhibit high specific capacitance(408.4F·g^-1 at a current density of 1 A·g^-1)and excellent cycle stability?95.2%maintenance of specific capacitance after 1000 charging/discharging cycles?.The outstanding electrochemical performance of the composites is attributed to the good synergy between the NG and PAA.3.Preparation of cobalt sulfide@electrochemically reduced graphene oxide/poly?azure A?ternary composite for supercapacitorsCobalt sulfide@electrochemically reduced graphene oxide/poly?azure A??Co S@ERGO/PAA?ternary composite materials were prepared by electrochemical deposition-polymerization method.First,cyclic voltammetry and potentiostatic deposition were used to sequentially load Co S and ERGO on the surface of nickel foam,and then Co S@ERGO was used as a carrier to polymerize azure A monomer onto the surface of Co S@ERGO.Finally,three-dimensional Co S@ERGO/PAA-X?X=3,4,5,and 6 min?composites were prepared with different polymerization times.The morphology,composition,and structure of 3D composites were characterized by SEM,TEM,FTIR,XRD and XPS.In addition,CV,GCD and EIS tests were used to explore the electrochemical performance of the composites.The results show that Co S@ERGO/PAA-5composites exhibit better electrochemical performance than the other comparable composite materials,display an excellent performance with high specific capacitance of 3394.7 F·g^-1 at a current density of 1 A·g^-1 and the capability can reach to 2244 F·g^-1 even at 50 A·g^-1.Furthermore,the cycle retention rate was 86.5%after 2000 cycles,indicating an outstanding cycling stability.The superior electrochemical properties and network structure of three-dimensional composite materials make them have stupendous application potential in the field of new energy storage.