High capacitive property for supercapacitor using Fe 3+ /Fe 2+ redox couple additive electrolyte

H 2 SO 4 + Fe 3+ /Fe 2+ electrolyte was selected as redox active electrolyte and PANI with nanoflower morphology was used as porous active material electrode, symmetric PANI supercapacitor (SC) has been assembled and the enhanced behaviors of H 2 SO 4 + Fe 3+ /Fe 2+ redox active electrolyte on the capacitance, energy density, and the cycling stability of PANI SC were systematically investigated. In the present work, the specific capacitance of symmetric PANI SC is heightened to 1062 F g −1 in 1 M H 2 SO 4 + 0.8 M Fe 3+ /Fe 2+ redox active electrolyte at an applied current density of 2 A g −1 , which is three times as high as that in 1 M H 2 SO 4 electrolyte. Moreover, the PANI nanoflower symmetric SC exhibits an improved energy density as high as 22.1 Wh kg −1 at a power density of 774.0 W kg −1 , and delivers the capacitance retention of 93% after 10000 charge-discharge cycles. The H 2 SO 4 + Fe 3+ /Fe 2+ redox active electrolyte can also enhance the capacitive performance of RGO double layer SC. These encouraging results suggest that H 2 SO 4 + Fe 3+ /Fe 2+ redox active electrolyte can be used as a prospective measure for improving the electrochemical performance of SCs for large-scale energy storage.