Preparation And Electrochemical Research Of Graphene/Conducting Polymer Nanocomposites

Graphene as a new type of carbon material has excellent features, such as greatspecific surface area, good electrical property, thermal stability and porosity. So it hasa good prospect of application in the field of new energy materials, sensors, catalystsand energy storage. Graphene has more advantages in electronic conduction rate,specific surface area and so on compared with conventional carbon materials, such asactivated carbon. The macroscopic preparation of graphene is one of the core issues ofthe material basic research and industrial application. At present, the effective way forpreparing macroscopic graphene is called chemical oxidation stripping graphite.However, the specific surface area of graphene is greatly decreased due to theagglomeration of graphene.Controllable synthesis of chemical reduced graphene oxide （RGO）/conductivepolymer composite and its electrochemical performance as electrode materials forsupercapacitor were systematically researched in the paper. Poly-p-phenylene diamineand polyaniline were grafted to graphene by amidation, respectively. Graphene/carbonnanotube grafting poly-p-phenylene diamine was also prepared for supercapacitorelectrode material. Some new results in the preparation of high oxidation degree of GOand RGO/conductive polymer composite were obtained. The specific contents are asfollows:1. High oxidation degree of graphene （GO） with size concentrated in20⁷0nmwas prepared using modified Hummers method. With the advantage of a lot ofoxygen-containing functional groups such us hydroxyl group, epoxy group andcarboxyl group in the GO surface, a new high-performance electrochemical capacitorelectrode material, reduced graphene oxide/poly-p-phenylene diamine （RGO/PPD）composite, was prepared by covalent bond grafting PPD to GO using amidation andremoving the unreacted oxygen-containing functional groups by further reduction. Thegraphene was uniformly covered and embedded by spherical nano-PPD when it wasusded as skeleton, and the RGO/PPD composite with regular morphology was obtainedby changing the quality ratio. A variety of characterization methods and data analysisshowed that RGO combined with PPD mainly through the amide bond, which enhancesthe electrochemical stability of the composite material to some extent. Moreover, thecorrelation between specific capacity and proportion of RGO in RGO/PPD composite was discussed. The initial specific capacity reaches the maximum value when the massratio of GO to PD is5:1, the capacity of the composite is up to347F g^-1under thecurrent density of1A g^-1, which is much higher than the pure component of RGO144and PPD66F g^-1. The capacitance value retained90.1%of the initial value under10Ag^-1current density through1000cycles of charge and discharge, showing excellentlong-term stability of the electricity storage performance.2. Polyaniline （PANI） is a conductive polymer with ideal high specificcapacitance, but the poor cycle stability of PANI limits its industrial application. PANIcovalently modified RGO/PANI （1:50） composite was prepared through amidation.The infrared spectroscopy of the amide group-specific C=O and C-N bond stretchingvibration peaks in RGO-PANI showed that PANI was grafted to graphene by amidobond. SEM and TEM of RGO/PANI clearly indicated that PANI uniformly covered onthe graphene sheet layers. Electrochemical tests showed that the composite has aspecific capacitance of211F g^-1after doped by HCl. The introduction of graphene didnot reduce the capacitance value of PANI, but greatly improved the cycle stability ofPANI.3. RGO/CNT/PPD ternary composite was prepared by p-phenylene diamine,oxidized graphite and carbon nanotubes. The preparation steps are as follows: firstly,GO/CNT was prepared by cooxidation. Secondly, p-phenylene diamine was grafted tothe GO/CNT by amidation. Thirdly, the remaining p-phenylene diamine waspolymerized with ammonium persulfate. Finally, sodium borohydride was added toremove the unreacted oxygen-containing functional group. Supercapacitor electrodematerial was prepared using the intercalation of PPD and the double layer capacitanceof RGO and CNT. The experiment results showed that the dispersion of the compositeis significantly improved compared to pure RGO and CNT. The morphology andcapacitive performance of the composite was also investigated. SEM showed that theaverage size of spherical PPD nanoparticles is50nm and PPD uniformly covered thesurface of the carbon material. The electrochemical performance studies show ed thatthe composite has the specific capacity of263F g^-1under the current density of1A g^-1,which is better than that of the individual component due to the synergistic effect andinterfacial effect.