Study On The Controllable Synthesis Of Polypyrrole And Porous Carbon

Supercapacitor is a new kind of energy device, which has attracted widespread attention around the world due to its high power density, rate capability and fast charge and discharge characteristic. The electrode materials(including carbon, transition metal oxides and conducting polymer materials) have been regarded as the key factor to affect the performance of supercapacitor. Among these electrode materials, conductive polypyrrole(PPy) has arised further research as its simple synthesis, environmental stability and high conductivity. Recently, PPy materials with micro/nano structure have gradually become the dominant development direction, because these materials own the properties of themselves and micro/nano size characteristics. However, the reports of two-dimensional(2D) PPy micro/nano structure are relatively rare. Among carbon materials, porous carbon materials(including actived carbon, carbon aerogel and so on) have become the most commonly used supercapacitor electrode materials because of its high specific surface area, excellent physical and chemical stability and low cost. The main factors influencing the electrochemical properties of porous carbon materials include specific surface area, pore size distribution, pore length, surface properties, electrical conductivity and microstructure. Presently, how to coordinate the above affecting factors to prepare the porous carbon electrode materials with high electrochemical performance has become an important part of the study of the current supercapacitor.Based on the above discussion, this paper mainly studied on the controllable synthesis of 2D micro/nano PPy and porous carbon materials with high electrochemical performance through controlling the micro morphology, improving the surface properties and improving the conductivity of the porous carbon materials. The main research contents and results are summarized as follows:(1) 2D micro/nano structure of PPy was prepared by soft template method using cationic surfactant cetyl trimethyl ammonium bromide(CTAB) and pyrrole monomer to form micelle, with propionic acid(PA) as the doping agent and ammonium persulfate(APS) as oxidant. The morphology, structure and electrochemical properties have been characterized by SEM, TEM, AFM, FT-TR, XRD, TG, DLS, CV and EIS. The influence of CTAB concentration on the the synthesis of micro/nano structure morphology of PPy was also discussed. Results show that when the concentration of CTAB, PA and pyrrole were 0.017 M, 3.1 M and 0.0 28 M, the most regular morphology of PPy is prepared. This structure was formed by PPy nanoparticals with diameter of about 60 nm paking to rectangular “sheets”. This doping state PPy with amorphous structure has excellent thermal stability and electrochemical activity.(2) Activated spherical carbon was prepared using petal-spherical polyaniline(PANI) as precursor through carbonization and activation with KOH. The morphology, structure and surface chemical composition were analyzed by SEM, TEM, Raman, XRD, N2 adsorption-desorption and XPS. The influence of carbonization temperature, activation temperature and the dosage of KOH on the electrochemical performance of activated carbon was also investigated. The activated carbon prepared at the carbonization temperature of 750 ℃, activation temperature 850 ℃ and mass ratio of KOH/carbonized sample 4:1 has a small diameter about 2 μm, large specific surface area(2496.6 m2/g) and optimized porous distribution. It exhibited a high specific capacitance up to 247 F/g at 0.5 A/g and 182 F/g even at a high current density of 20 A/g, which indicated it possesses good rate capability. Moreover, 102% of the initial specific capacitance was retained after 1000 cycles at a high current density of 10 A/g.(3) Nitrogen-doped porous carbon/MWCNT materials was prepared by directly carbonized metal-organic coordination polymer/MWCNT(MOCP/MWCNT). While MOCP was formed by the complexation reation of 4, 4’-Bipyridine(BPD) and Fe Cl3. The morphology, structure and surface chemical compositi on were analyzed by SEM, TEM, XRD, Raman, N2 adsorption-desorption and XPS. The influence of feed ratio and carbonization temperature on the electrochemical performance of nitrogen-doped porous carbon/MWCNT was also investigated. The nitrogen-doped porous carbon/MWCNT prepared with mass ratio of MWCNT/BPD 1:15, molar ratio of BPD/Fe Cl3 1:1 and carbonization temperature 650 ℃ has proper three-dimensional multi-level pore stucture, large specific surface area(1023 m2/g) and high nitrogen content(10.71 at.%). It exhibited a high specific capacitance up to 295.2 F/g at 0.5 A/g and 186 F/g even at a high current density of 20 A/g, which ind icated it possesses good rate capability. Almost no sacrifice of specific capacitance after 2000 cycles at a high current density of 10 A/g.