Boron- and nitrogen-doped graphene quantum dots with enhanced supercapacitance

Graphene quantum dots (GQDs) with their very large specific surface area and numerous edges can offer promising novel features as metal-free and inexpensive electrodes of supercapacitors. Here, we investigated the effect of boron and nitrogen doping in GQDs on their electrochemical energy storage properties. The GQDs as well as B-GQDs and N-GQDs were synthesized by a facile hydrothermal method and characterized by X-ray diffractometry, UV-Vis absorption spectrophotometry, transmission electron microscopy, and energy-dispersive X-ray mapping techniques. Electrochemical properties of the nanoparticles were investigated in a three-electrode setup using cyclic voltammetry and galvanostatic charge/discharge techniques in KOH electrolyte. The N-GQDs electrode showed the highest specific capacitance of 283 F/g at 1 A/g as compared to the GQDs and B-GQDs electrodes. The N-GQDs electrode exhibited the specific energy and specific power of 6.2 Wh/Kg and 108 W/Kg, respectively. The N-GQDs electrode showed also better cycling stability (80% capacity retention) than the GQDs and B-GQDs electrodes.