Study On N-doping Graphene Foam And PANI-F/GNA Composites

Supercapacitors have attracted considerable attention in recent years attributed totheir high power density, high rate capability and long cycle life, however, relativelylow energy density have limited their practical applications. AS a star in the fields ofscience and technology, graphene become the hotspot of the electrode materials,owingto the unique structure and excellent mechanical, electrical and thermal properties;Nevertheless, rGO prone to agglomeration and stacking during the preparationprocess of the materials, resulting in reduced capacity supercapacitors. In order toimprove the capacitance of graphene-based ECs, many methods have been reported,including the introduction of fillers, dopants to graphene and Construction ofmulti-level structure. These methods would prevent the restacking of graphene sheetsas well as increase the entire capacitance due to the additional redox-active functionalgroups. Up to now, several methods have been employed to synthesizeNitrogen-doping graphene. For example, Chemical vapor deposition in the presenceof nitrogen containing precursors, arc discharge of graphite electrodes in aH2/pyridine or H2/NH3atmosphere, electrothermal reaction and thermal annealing.However, these processes suffer from rigorous conditions and sophisticatedequipments, and sometimes together with low product yield and high cost. Thus, it isof great importance for green controllable building electrode materials with highercapacitance without sacrificing excellent cycling stability.Based on the above discussion, in this study, N-doped graphene foam have beenprepared through a one-step hydrothermal reaction by using o-phenylenediamine,m-phenylenediamine and p-phenylenediamine as reductive dopant, and discuss theeffect of experiment conditions on electrochemical performance of N-dopinggraphene. Moreover, with a variety of characterization methods discuss the formingmachine-made of N-doping type and content. In the end, a polyaniline fibers/reducedgraphene oxide composite was synthesized using self-assembled of PANI-F and GOfollowed by hydrothermal reaction. The details are as follows:(1) Discuss the influence factor on electrochemical performance of N-dopinggraphene by one step hydrothermal method. N-doped graphene foam have beenprepared through a one-step hydrothermal reaction by using o-phenylenediamine,m-phenylenediamine and p-phenylenediamine as reductive dopant, respectively. Discuss the effect of feed ratio, hydrothermal temperature and hydrothermal time onelectrochemical performance of N-doping graphene foam, the results showed asfollows: the HOGO has the best electrochemical performance under the experimentalconditions of hydrothermal temperature:180℃, hydrothermal time:7h, feed ratio:1, ahigh specific capacitance of645F/g and500F/g was obtained at current density of1A/g and50A/g, respectively, as well as a high capacitance retention of97.6%measured charge-discharged after1000cycle at current density of20A/g; the HPGO5has the best electrochemical performance under the experimental conditions ofhydrothermal temperature:120℃, hydrothermal time:12h, feed ratio:5; a highspecific capacitance of467F/g and285F/g was obtained at current density of1A/gand50A/g, respectively, as well as a high capacitance retention of91%measuredcharge-discharged after1000cycle at current density of20A/g; the HMGO10has thebest electrochemical performance under the experimental conditions of hydrothermaltemperature:150℃, hydrothermal time:12h, feed ratio:10; a high specificcapacitance of365.7F/g and128F/g was obtained at current density of1A/g and50A/g, respectively, as well as a high capacitance retention of83%measuredcharge-discharged after1000cycle at current density of20A/g.(2) Discuss the forming machine-made of N-doping type and structuralcharacterization of graphene foam. The morphology and structure of graphene foamwere characterized by SEM, TEM, Raman, XRD and XPS. Discuss the formingmachine-made of N-doping of three Kinds of reductive dopant, the results showed asfollows: o-phenylenediamine was beneficial to the for formation of Quaternary-N;m-phenylenediamine was beneficial to the for formation of Pyridinic-N;p-phenylenediamine was beneficial to the for formation of Pyrrolic-N.(3) Synthesis of high electrochemical performance of PANI-F/GNs composites. Apolyaniline fibers (PANI-F)/reduced graphene oxide (rGO) composite wassynthesized using self-assembled of PANI-F and GO followed by hydrothermalreaction. The morphology and structure of samples were characterized by scanningelectron microscopy (SEM), Fourier transform infrared spectrometer(FT-IR)and X-raydiffraction (XRD), Electrochemical properties were characterized by cyclicvoltammetry (CV), galvanostatic charge/discharge(GCD) and Electrochemicalimpedance spectrum(EIS). It turned out that the rGO was homogeneously coated onsurfaces of PANI-F, and a high specific capacitance of517F/g (based on PAGO10composite) was obtained at a current density of1A/g compared to378F/g for PANI-F.Most of all, a high specific capacitance of356F/g was obtained at a current density of 10A/g compared to107F/g for PANI-F.