Carbon nanosheets-based supercapacitors: Design of dual redox additives of 1, 4-dihydroxyanthraquinone and hydroquinone for improved performance

Abstract

Abstract Using thiocarbanilide and Mg(OH) 2 powders as carbon precursor and template, respectively, novel 2D carbon nanosheets with large area have been produced. Next, based on the cooperative effect, 1, 4-dihydroxyanthraquinone (DQ) and hydroquinone (HQ) regarded as efficient dual redox additives have been incorporated into the electrode carbon material and H 2 SO 4 electrolyte, respectively, to largely elevate the capacitive performance of supercapacitors. More importantly, the cooperative effect results from the redox processes of DQ and HQ consecutively occurring in the electrode carbon material and aqueous H 2 SO 4 electrolyte, respectively. Besides, the molar ratio of DQ and HQ exerts a crucial role in the determination of the electrochemical behaviors and eventually the optimum condition is the mass ratio of 1:1 concerning the DQ and porous carbon within solid electrode while retaining the HQ concentration as 20 mmol L −1 in 1 mol L −1 H 2 SO 4 electrolyte. As a result, the maximum specific capacitance is achieved of 239 F g −1 at 3 A g −1 , and furthermore the maximum energy density up to 21.1 Wh kg −1 is almost 3.5 times larger than that of the one without introducing any redox additive.