Synthesis And Supercapacitive Performance Of Novel Carbon Based Conducting Polymer Nanocomposite For Supercapacitor

Since supercapacitor has quite high power density,long-time cycling longevity and effective charging-discharging process,it has become one of the most focused energy storage devices,which can relieve the energy problem caused by the shortage of fuel energy.Among all the components of supercapacitor,electrode material is the key point,since its morphology,conductivity and specific surface area all play an important role on the integral capacitive properties of the supercapacitor,such as the specific capacitance,rate capability and stability.Therefore,the core content of the research of supercapacitor is exploring the electrode materials with high performance.Among most of the electrode materials applied to supercapacitor,carbon based nanomaterials are regarded as the most potential electrode materials due to their excellent electrochemical properties,low cost and environmentally-friendly trait.The work in this paper began with the study of sole conducting polymer,and then used conducting polymer and carbon nanomaterials to form their nanocomposite followed by adjusting the bonding way between these two kinds of materials to improve the capacitive characteristics of these materials.The specific works are showed below.(1)In this experiment,Fe3O4 porous nanospheres with different size(Fe3O4-8h,Fe3O4-12h and Fe3O4-16h)were obtained by hydrothermal method,and then they were used as template and the source of evocator(Fe3+)for the polymerization of pyrrole monomers,synthesizing corresponding PPy porous nanospheres with different sizes(PPy-8h,PPy-12h and PPy-16h).Morphology structure and supercapacitive performance of these materials were characterized and studied,respectively.Meanwhile,we also explored the effects of polypyrrole(PPy)size on its capacitive characteristics.Results from these testing indicated that the prepared PPy-8h,PPy-12h and PPy-16h inherited the structure of corresponding Fe3O4-8h,Fe3O4-12h and Fe3O4-16h completely,with diameter of 180 nm,200 nm and 230 nm respectively.In symmetric two-electrode system,PPy-12h showed the most excellent capacitive performance(specific capacitance of 220 F g-1 at 1 A g-1,and stability of 81%after 5000 cycles).(2)Fe3O4 nanoparticles were embedded into graphene layers and surface by calcination,and then were used as template and the source of evocator(Fe3+)for the in-situ polymerization of pyrrole monomers mentioned in(1),obtaining the composite of graphene and polypyrrole(r-GO-PPy).In comparison,uncontrolled polymerization was also employed to obtain different composite of graphene and polypyrrole(r-GO/PPy).The morphology structure and supercapacitive performance of these materials were investigated.The results manifested that the PPy nanoparticles in r-GO-PPy dispersed uniformly on the surface and layers of graphene,and this structure impeded the agglomeration of graphene effectively as well as offered effective passway for the migration of electrons and ions.As far as that of r-GO-PPy,PPy covered on the surface of graphene,so that two kinds of materials were stacked together seriously.In symmetric two-electrode system,r-GO-PPy presented more excellent electrochemical performance compared with r-GO/PPy,showing specific capacitance of 284 F g-1 at 1 A g-1 and stability of 86.7%after 5000 cycles.(3)Diazotization was used to obtain aniline-functionalized graphene oxide(a-GO),and then polymerization was followed to form poly(o-phenylenediamine)(PoPD)layers on the surface of a-GO.Subsequently,we utilized the solubility of PoPD in aqueous solution,rinsing out these PoPD that connected with graphene oxide through physical bond and leaving the section that connected with the aniline group grafted on graphene oxide.After reduction,stereoregular PoPD-graphene nanocomposite(r-GO-a-PoPD)connected by only chemical bond was obtained.The morphology structure and supercapacitive performance of r-GO-a-PoPD were studied.It showed a large specific surface area of 520 m g-1.Meanwhile,results from these testing manifested that PoPD generated on the surface of graphene was in the form of single chain,which can forbid the agglomeration of graphene effectively.When the current density is 1 A g-1,r-GO-a-PoPD showed quite high capacitance of 381 F g-1.Additionally,after 5000 cycles of charging-discharging,its capacitance still retained 90%of the initial value.The excellent capacitive performance was derived from single-stranded like poly PoPD onto graphene.They connected only through chemical bond,and because of the special structure,surface of graphene and PoPD could be exposed as much as possible.In this way,it realized the maximum utilization of electric double-layer capacitance and pseudo-capacitance.