Cooperative redox-active additives of anthraquinone-2,7-disulphonate and K4Fe(CN)6 for enhanced performance of active carbon-based capacitors

Abstract

Two redox additives of anthraquinone-2,7-disulphonate (AQDS) and K4Fe(CN)6 are introduced into the neutral medium of KNO3 for enhanced performance of active carbon-based (AC) capacitor. The Faradaic redox reactions of AQ/H2AQ and Fe(CN)63−/Fe(CN)64− are diffusion-controlled and occurred on the negative electrode and the positive electrode respectively and simultaneously, resulting in the enhancement of specific capacitance, power density and energy density of 240 F g−1, 527 W kg−1 and 26.3 Wh kg−1, respectively at a current density of 1.0 A g−1 for a symmetric AC capacitor in the electrolyte of 1 M KNO3-0.017 M K4Fe(CN)6-0.017 M AQDS. These values are much higher than those in the controls of either 1 M KNO3-0.017 M K4Fe(CN)6 or 1 M KNO3-0.017 M AQDS with only one pair of redox additives. These results demonstrate the cooperative K4Fe(CN)6 and AQDS for enhanced performance of AC capacitor, and thus provide an alternative approach for efficient capacitors.