Enhanced Electrochemical Performance Of Aqueous Supercapacitors Through Optimized Redox-Active Materials

Abstract

Aqueous super capacitors are gaining prominence in energy storage due to their high power density, fast charge/discharge cycles, low environmental impact, and cost-effectiveness. Despite these benefits, they suffer from relatively low energy density compared to batteries. One of the emerging strategies to improve energy storage performance is the introduction of redox-active species in electrolytes. In this study, p-phenylenediamine (PPD), an organic redox-active molecule, is incorporated into 1 M KOH aqueous electrolyte and used with high-surface-area carbon bead electrodes. The influence of PPD concentration (0, 0.05, 0.10, 0.20 M) on electrochemical performance is evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Surface morphology is characterized via atomic force microscopy (AFM) and scanning electron microscopy (SEM). Optimized system (0.10 M PPD) has a given capacitance (518 F/g) of 94% capacitance retention at 5000 cycles and low equivalent series resistance of 1.3 Ω. These results validate the role of redox mediation by PPD in making the storage of energy much better, hence its potential in the future development of aqueous super capacitor systems of the next generation.