Optimizing composition of K4Fe(CN)6-based redox-active electrolyte as a key factor for improving electrochemical performance of rice-husk-derived activated carbon in supercapacitor electrode

Currently, the use of redox-active additives is an effective way to enhance the electrochemical performance of supercapacitors. Despite a lot of publications in the literature, the choice of redox-active electrolyte composition is still unclear. This work focuses on the study of the correlation between the K 4 Fe(CN) 6 fraction (0–0.05 M) in 1 M Na 2 SO 4 and electrochemical characteristics of rice-husk-derived activated carbon (AC). The effect of electrolyte composition was clarified by cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The increase in the K 4 Fe(CN) 6 fraction in the electrolyte significantly improved the specific capacitance of AC from 59 up to 288 F/g at a current density of 1 A/g. Nevertheless, despite the fact that the concentrated 0.05 M K 4 Fe(CN) 6 –1 M Na 2 SO 4 electrolyte provided excellent capacitance, it led to a high self-discharge and charge transfer resistance, not beneficial for electrochemical applications.