Synergistic effect of novel redox additives of p-nitroaniline and dimethylglyoxime for highly improving the supercapacitor performances

In present work, we demonstrate a simple but effective strategy for high-performance supercapacitors by adding the p-nitroaniline (PNA) into an alkaline electrolyte of KOH. PNA possesses a unique molecular structure with the functional groups of –NH2 and –NO2. Besides, both the product of nitro-reduction (–NH2) and intrinsic –NH2 on the benzene ring can lead to the occurrence of Faradaic redox reactions accompanied by the electron/proton transfer in the mixed electrolytes, whose pseudocapacitance can greatly enhance the total capacitance. Furthermore, another effective additive of the dimethylglyoxime (DMG) has been incorporated into carbon materials for further improving the performances of supercapacitors with a PNA + KOH electrolyte. As for the DMG + PNA + KOH system, a galvanostatic capacitance up to 386.1 F g−1 of the DMG-0.15–PNA-0.15 sample at 3 A g−1, which is nearly two times higher than that of the PNA-0.15 sample (183.6 F g−1) in the PNA + KOH system and nearly three-fold capacitance of the carbon-blank (132.3 F g−1) in the KOH system at the same current density. Furthermore, the specific capacitance still can reach up to 260.0 F g−1 even at 40 A g−1 with a 67.4% capacitance retention ratio. Besides, the DMG-0.15–PNA-0.15 sample exhibits an exceptional capacitance retention of 113% after 5000 charge/discharge cycles by virtue of the potential activated process, which clearly reveals the excellent cycling stability. These remarkable enhancements are ascribed to the synergistic effects of novel additives of PNA and DMG.