Optimized preparation of core–shell composites based on polypyrrole doped with carbon nanotubes for high performance electrochemical capacitors

Abstract

Polypyrrole/carbon nanotubes (PPy/CNTs) core–shell composite electrodes have been prepared by facile electrochemical co-deposition. A detailed study regarding the effects of different preparation conditions including electrodeposition mode, parameter, current collector, and carboxylation degree of CNTs on the supercapacitive performances of PPy/CNTs electrodes is carried out. Electrochemical tests suggest a significant effect of current collector on supercapacitive properties of the obtained PPy/CNTs electrodes. Graphite foil as the current collector with low resistance shows remarkably superior capacitive performances relative to FTO conducting glass and ITO conductive plastic. SEM characterizations show galvanostatically deposited PPy/CNTs have a favorable three-dimensional porous nano-network microstructure, while potentiostatically deposited PPy/CNTs present a compact two-dimensional morphology. Furthermore, the CNTs with higher carboxylation degree introduce more PPy, thereby resulting in better electrochemical performances. The optimized PPy/CNTs composite electrodes show a high specific capacitance of 185.3 mF cm−2 at 0.5 mA cm−2, superior rate capability, and outstanding cycling stability (retaining 88.5% of initial capacitance for 10,000 cycles). These results provide a useful orientation to optimize the electrochemical properties of PPy/CNTs core–shell composites applied as electrode material for high performance supercapacitors.