Fe3+/Fe2+ redox electrolyte for high-performance polyaniline/SnO2 supercapacitors

The Fe3+/Fe2+ redox electrolyte for use in polyaniline/tin oxide (PANI/SnO2) supercapacitors was reported. The influences of redox electrolyte based on different Fe3+/Fe2+ ion pair concentrations in 1 mol/L H2SO4 solution on the pseudocapacitive behaviors of PANI/SnO2 supercapacitor were investigated. The electrochemical properties of the supercapacitor were studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. It is found that the performance of the supercapacitor is the best when the Fe3+/Fe2+ concentration is 0.4 mol/L and its initial specific capacitance is 1172 F/g at an applied current density of 1 A/g. The long-term cycling experiment shows good stability with the retention of initial capacitance values of 88% after 2000 galvanostatic cycles. The experimental results testify that using Fe3+/Fe2+ redox electrolyte has a good prospect for improving the performances of energy-storage devices.