The Study Of Controllable Synthesis And Electrochemical Performance Of Conducting Polymer And Its Carbon-based Composites

Due to their high power density and long cycling stability, supercapacitors are promising energy conversion and storage devices. Developing novel electrode materials is the key to improve the performance of supercapacitors. So far, conducting polymer, porous carbon, graphene and their composites have been widely used as electrode materials for supercapacitors. In this dissertation, the preparation, structures,properties, formation mechanism, and application in supercapacitors of conducting polymer and their derivatives have been investigated.（1） Organic acid buffer solutions have been used to control the morphologies and structures of the oxidation products of aniline. The results showed that polyaniline（PANI） can only be formed at a p H value lower than 2.6, and they can be used as electrode materials for supercapacitors. When the p H was higher than 3.2, the molecular weight of products mainly was 364 or 289. The oligoaniline can assemble into a variety of hierarchical structures and showed a lower redox current and well hydrophobic.（2） PANI-grafted reduced graphene oxide（PANi-g-r GO） composites have been synthesized via a diazotization of polyaniline in the medium of concentrated sulfuric acid of GO. It was confirmed that PANI chains can be grafted onto the surface of r GO by covalent linkages. The PANi-g-r GO composites exhibited specific capacitance of300 F g^-1 at 0.2 A g^-1 and still achieved 208 F g^-1 at a current density of 5.0 A g^-1,implying that they had relatively good rate capability. After 1000 cycles, the decay of capacitance was no more than 10%.（3） Ammonium persulfate（APS） was first used as the oxidant to prepare monodispersed polypyrrole（PPy） nanospheres within formic acid buffer solution of F108. Dynamic light scattering（DLS） results showed that pyrrole dissolved in formic acid buffer solution of F108 was conducive to the formation of monodispersed micelles. At a lower reaction temperature, APS slowly oxidized the monomer dissolved in the micelles, resulting in the formationof PPy nanospheres. The as-prepared PPy nanospheres can be easily dispersed in water, ethanol and DMF.（4） Hierarchical porous carbon nanospheres（HPCNS） have been prepared via carbonized the PPy nanospheres and further activated it by KOH. HPCNS/PANI composites have been synthesized via in situ polymerization of aniline at the surfaceof HPCNS. These results showed that the specific surface area（SSA） of the HPCNS was up to 2817 m2 g^-1. The application of the HPCNS in supercapacitors based on 1 M H2SO4 solution showed a specific capacitance as high as 320 F g^-1at 0.2 A g^-1, and the retention ratio was 100% after 1000 times charge-discharge cycles at the current density of 5.0 A g^-1. As for the HPCNS/PANI, high specific capacitances of 584 F g^-1at a current density of 0.2 A g^-1 and 407 F g^-1 at 5.0 A g^-1 were achieved, and the capacitance at 5.0 A g^-1 can be maintained 85% of the initial specific capacitances after 1000 cycles.（5） The preparation and formation mechanism of GO@PPy nanosheets have been investigated in different systems. The results confirmed that PPy can be grafted onto GO with an amide band when GO-Fe Cl3 complex were used as both the template and the oxidant. The as-prepared GO/PPy nanosheets had a higher SSA and good conductivity than those samples synthesized in other systems. The GO/PPy synthesized with GO-Fe Cl3 showed a maximum specific capacitance of 398 F g^-1 at a discharge current density of 0.2 A g^-1, while other GO/PPy electrodes delivered specific capacitances lower than 297 F g^-1.（6） High-performance nitrogen-doped graphene/porous carbons（NPGCs） have been synthesized via one step chemical activation of graphene oxide/polypyrrole（GO/PPy） composites by KOH. It was found that the NPGCs obtained by activating GO/PPy with 3.5 time’s mass of KOH at 650 o C exhibited an outstanding electrochemical property. The highest specific capacitance of 405 F g^-1 can be achieved at a current density of 0.2 A g^-1, and above 96% of the original capacitance can be retained after 1000 cycles at a current density of 10 A g^-1.