Reduced-graphene oxide/polypyrrole nanofiber (RGO/PPy-Nf) nanocomposite has been prepared as the electrodematerial of the supercapacitor. This nanocomposite was prepared via a facile two-step process, including exfoliation and reduction of graphene oxide by microwave irradiation (MRGO) and in situ polymerization pyrrole onto it. The morphological, structural, and porosity characterizations of this nanocomposite were shown the proper formation of RGO/PPy-Nf composite with a mesoporous structure. The high specific capacitance of 277 F g−1 was obtained for the RGO/PPy-Nf nanocomposite at a constant current density of 1 A g−1 in a 1M H2SO4solution electrolyte. This nanocomposite revealed the highest energy density of 38.5 Wh kg−1 with a corresponding power density of 500 W kg−1 , and the capacitive retention of 95% after 1000 cycles. In evaluating the samples by electrochemical impedance spectroscopy, the values of capacitor response time revealed that the dominant mechanism in pristine PPy and MRGO is faradaic reactions and electrical double-layer capacitance (EDLC), respectively, and both mechanisms play a role in the RGO/PPy-Nf nanocomposite. Also, the relaxation time investigation revealed this nanocomposite exhibit an ideal capacitive behavior at very low frequency.

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