Synthesis And Properties Of Co²⁺Doped Polyaniline And Its Nanocomposites

Supercapacitors are new-green energy storage devices,which combines the advantages of high power density of traditional capacitors and high energy density of secondary batteries.It is well know that electrode material is the key factor to influence the performance of supercapacitors.Among conductive polymers,polyaniline has been a promising candidate for electrode material due to the features of low-cost,easy synthesis,high conductivity,desirable chemical stability and the optimized morphological structure by the adjustment of dopant or doping level.In this paper,H+,Co2+ codoped polyaniline,H+,Fe3+ codoped Polyaniline and H+,Zn2+ codoped Polyaniline,marked as PHCo,PHFe and PHZn,were synthesized via chemical oxidation polymerization.PHCo was selected and optimized by various process parameters.Then on this basis,Co2+ doped PANI/CNTs nanocomposite and Co2+ doped PANI/graphite felt hierarchical composite were successfully prepared by chemical oxidation polymerization and ultrasonic polymerization,respectively.The main results are as follows:(1)H+,transition metal ion codoped polyanilines as PHCo,PHFe and PHZn were synthesized by chemical oxidation polymerization,and their structures,morphologies and electrochemical properties were studied.The results showed that the transition metal ions could promote polyaniline to generate antennae with porous structure as well as improve the thermal stability.PHCo exhibited better overall electrochemical properties compared to PHFe and PHZn.The specific capacitance of 354 F/g was obtained at a current density of 0.2 A/g and it maintained 81.9%after 1000 cycles.(2)PHCo was optimized by process parameters,such as:the molar ratio of Co2+/An,the kinds of doping acid and the volume ratio of water/ethanol during the chemical oxidation polymerization.The effects of these parameters on the structures,morphologies and electrochemical properties of products were studied.It was found that PHCo had long cilia with improved specific capacitance of 374 F/g at a current density of 0.2 A/g,which remained 85.2%after 1000 cycles when the molar ratio of Co2+/An was 2:1,HCl as doping acid and the volume ratio of water/ethanol was 1:1.(3)Co2+ doped PANI/CNTs nanocomposites marked as PCi and PC2 were synthesized by Co2+ doped PANI with functionalized CNTs of CNTs-COOH and CNTs-NH2,respectively.The nanocomposites were produced by chemical oxidation polymerization and then the structures,morphologies and electrochemical properties were studied.The specific capacitance of PC2 was up to 487.8 F/g at a current density of 0.2 A/g,meanwhile,the retention of the capacitance after 1000 cycles was 86.6%.(4)Co2+ doped PANI/graphite felt hierarchical composite was constructed by ultrasonic polymerization.This composite had a loose porous structure with graphite felt acted as supporting frame,and then the structure,morphology and electrochemical properties were studied.According to the results,the morphology of the composite could be controlled by adjusting the molar ratio of An/Co2+ and the An concentration.With the polymerization conditions of the molar ratio of An/Co2+ was 1:3,An concentration was 0.02 M and the ultrasonic power was 120 W,the specific capacitance of Co2+ doped PANI/graphite felt could reach up to 562 F/g at a current density of 0.2 A/g and showed 92.9%capacitance retention after 1000 cycles.