The Impact of Incorporating Reduced Graphene Oxide Quantum Dots into KOH Electrolyte on the Electrochemical Performance of Supercapacitors Using Sugarcane Bagasse Active Electrodes

This study used reduced graphene oxide quantum dots (rGO-QDs) to enhance the ionic conduction and specific capacitance of the sugarcane bagasse carbon active electrode in a supercapacitor. The rGO-QDs solution was mixed with the KOH electrolyte at 0.5, 1.0, 3.0, and 5.0% by weight (rGO-QDs-<i>X</i>%/6M-KOH). The sugarcane bagasse-activated carbon (SAC) was prepared from sugarcane bagasse (SB) waste through activation by annealing in an argon atmosphere and ground in a high-speed three-dimensional (3-D) ball mill (AC3D-SAC). The rGO-QDs were synthesized and verified by high-resolution transmission electron microscopy (HRTEM), which showed that the size of the rGO-QDs was less than 10 nm. Raman spectroscopy displayed peaks of the D-band and G-band. The rGO-QDs-3%/6M-KOH electrolyte exhibited the highest ionic conductivity, 26 mS/cm. The AC3D-SAC active carbon had a specific surface area of 915.57 m²/g. The active electrodes made with AC3D-SAC and rGO-QDs-3%/6M-KOH for the half-cell electrode showed the highest specific capacitance of 176.83 F/g at 0.5 A/g. The working electrode symmetric supercapacitor coin cell device, using the rGO-QDs-3%/6M-KOH electrolyte, achieved a maximum specific capacitance of 54.53 F/g at 0.5 A/g. These results were twice as high as those with the KOH electrolyte alone. The efficiency retention of the coin cell dropped to 90% after 5000 cycles. The supercapacitor demonstrated impressive electrochemical performance with high ionic conduction and capacitance, thanks to the rGO-QDs/6M-KOH electrolyte and the large surface area of the AC3D-SAC active carbon. The findings confirmed that adding rGO-QDs to the KOH electrolyte improved the electrochemical performance of the symmetric supercapacitor device.