10th U6+ Consortium of African Universities International Conference

Herein, the impact of incorporating a redox-active electrolyte into the pristine electrolyte on the specific capacitance of a sludge-based activated carbon (SAC) electrode was investigated, with a focus on the electrolyte concentration. KOH-activated carbon (SACK) was prepared from wastewater sludge via activation followed by carbonization. The SACK was characterized in terms of its structure and morphology, which were determined using XRD, SEM-EDX, BET, and FTIR. Using 6 M KOH as the pristine electrolyte and mixtures of 6 M KOH with varying concentrations (0.05 M, 0.1 M, and 0.15 M) of potassium ferrocyanide (K4Fe(CN)6), the electrochemical characteristics of the electrode created using SACK were examined in a three-electrode setup. Cyclic voltammetry (CV) suggests the coexistence of an Electric Double Layer Capacitance (EDLC) and pseudocapacitive contribution arising from a Faradaic redox process. The specific capacitance from galvanostatic charge–discharge analysis (Csp, GCD) at 0.5 A g-1 is 65.0, 88.4, 116.3, and 71.7 F g-1 for 6 M KOH, 6 M KOH + 0.05 M K4Fe(CN)6, 6 M KOH + 0.1 M K4Fe(CN)6, and 6 M KOH + 0.15 M K4Fe(CN)6, respectively. Specifically, the addition of 0.1 M K4Fe(CN)6 to 6 M KOH exhibits the best performance, with a 78% enhancement compared to the base electrolyte (6 M KOH). The enhancement is attributed to the combined contributions of the carbon electrode's electric double-layer and pseudocapacitive behaviour, brought about by the redox reaction of [Fe(CN)6]4-/[Fe(CN)6]3-.This work highlights the potential of redox-active electrolytes at a particular threshold concentration as a simple and effective strategy to improve the specific capacitance of carbon-based electrodes for supercapacitors.