The ternary MnFe2O4/graphene/polyaniline hybrid composite as negative electrode for supercapacitors

The ternary MnFe2O4/graphene/polyaniline (PANI) composite was successfully prepared for the negative electrode in hybrid supercapacitors. The MnFe2O4 particles are synthesized by polymer assisted solution combustion method without any high temperature calcinations. Similarly, the flexible graphene and PANI are prepared by eco-friendly hydrothermal and in situ polymerization method, respectively. The presence of possible functional groups and the existence of individual constituents in the composite were identified through Fourier transform infra-red spectra (FT-IR) and Raman spectra. Transmission electron microscope (TEM) image reveals that the MnFe2O4 particles are dispersed on the flexible graphene sheet and are wrapped by PANI. The ternary composite electrode delivered a specific capacitance of 241 F g(-1) at 0.5 mA cm(-2), which was 7.5 times higher than MnFe(2)0O(4). The calculated b-value elucidates that the charge storage mechanism in the ternary system is based on the capacitive behavior rather than intercalation. The increase in ratio between capacitive and intercalation current with respect to scan rate corroborates that the pseudocapacitive charge storage mechanism is dominant. Further, the fabricated hybrid supercapacitor provides the maximum specific capacitance and energy density of 48.5 F g(-1) at 0.5 mA cm(-2) and 17 Wh kg(-1), respectively. In addition, the hybrid supercapacitor exhibits excellent cyclic stability of up to 5000 successive cycles. (C) 2014 Elsevier B.V. All rights reserved.