Polymerization of polypyrrole nanospheres on carbon nanotubes with PMo12-xWx as oxidant and redox dopant for supercapacitor

Polypyrrole (PPy) nanospheres are successfully assembled on the surface of multiwalled carbon nanotubes (MWNTs) with the aid of PMo12-xWx (mixture of phosphomolybdic acid andphosphotungstic acid with molar ratio of 3:1) as both oxidant and the redox dopant. The resulting multi-walled carbon nanotubes (MWNTs)/PPy nanocomposites (MPNs) exhibited a well-defined core-shell structure, leading to the fast and efficient transmission/transfer of both electrolyte ions and electrons. An intrinsic increase in electrochemical performance of the nanocomposites has been achieved by the combination of the double-layer and the Faradaic capacitance originated from both PPy and PMo12-xWx. In a typical three-electrode system, MPN10 (the mass ratio of MWNT: pyrrole is 10:90) can provide the highest specific capacitance of 570F/g. Moreover, in a typical two-electrode symmetric system with MPN10 as electrodes and polyvinyl alcohol (PVA)-H2SO4 gel as electrolyte, the super capacitor device exhibited a specific and areal capacitance of 93F/g and 466 mF/cm(2), respectively and showed an outstanding cycling stability after 10000 cycles.