In present work, we demonstrate a simple but effective redox additive of pyrocatechol violet ( abbr . PCV) to largely promote the capacitive performances especially when carried out in three different kinds of electrolytes (H 2 SO 4 , Na 2 SO 4 and KOH), mostly due to its fast electron and proton transfer occurring in the electrode/electrolyte interface. It reveals that the PCV dosage incorporated into electrolyte plays a crucial role in the determination of capacitive performance. When conducted in a two-electrode system, incorporating 0.06 mol L −1 PCV into 1 mol L −1 H 2 SO 4 can achieve large capacitance up to 200 F g −1 , which is almost 2.06 times than the one without the addition of PCV; besides, the corresponding energy density is of 28 Wh kg −1 (also increasing 2 times). What’s more, PCV has been extended as the redox additive in other electrolytes such as Na 2 SO 4 and KOH, and remarkable promotion in capacitance and energy density also occur, well evincing the high efficiency and universal applicability of PCV for the large promotion of supercapacitors’ performances due to its prominent electrochemical reversibility and high solubility.
