Graphene/oligoaniline based supercapacitors: Towards conducting polymer materials with high rate charge storage

Abstract

Carbon-based supercapacitors exhibit great rate capability, power density and cycle life, but suffer from relatively low energy density. Polyaniline provides high specific capacitance, but lacks cycling stability. By combining carbon-based materials with tetraaniline, an oligomer of polyaniline, a hybrid composite is formed that demonstrates improved supercapacitor performance relative to either material alone. In this study, the reduced graphene oxide-oligoaniline composites have been synthesized by a one-step hydrothermal process without the need for adding any oxidizing or reducing agents. FTIR, Raman spectroscopy, XPS, and MALDI-TOF mass spectroscopy indicate the successful reduction of GO to rGO and the formation of aniline oligomers. Unlike most polyaniline nanostructures for which charge storage kinetics are limited by slow diffusion-controlled reactions, the majority of oligoaniline in this composite is exposed to the electrolyte and stores charge through fast surface-controlled reactions. The unique microstructure of the rGO-oligoaniline composites facilitates transport of ions and electrons, leading to greater utilization of the active materials, high specific capacitance of 640 F/g at 0.2 mA/cm2 (corresponding to 707 C/g specific capacity), great rate capability and good cycle stability (91% retention after 2000 cycles).