Preparation and Specific Capacitance Properties of Sulfur, Nitrogen Co-Doped Graphene Quantum Dots

Sulfur, nitrogen co-doped graphene quantum dots (S, N-GQDs) with high crystallinity were obtained by a top-down strategy. The as-prepared S, N-GQDs were investigated and the results indicate that S, N-GQDs exhibit a transverse dimension about 20 nm and a topographic height of 1-2 layers graphene. The incorporation of S, N can effectively reduce the layers of GQDs and strip the graphene sheets. Moreover, the S, N-GQDs reveal an absorption band located at 405 nm and exhibit an adjustable fluorescence characteristic in the excitation-visible range. Meanwhile, the S, N-GQDs shows a high specific capacitance of 362.60 F g^-1 at a fixed scan rate of 5 mV s ^-1. This high performance is ascribed to the additional high pseudocapacitance provided by the doped S, N and the doping state acting as a trap state to enhance the charge storage capacity. The high specific capacitance advantages of S, N-GQDs illustrate their potential prospects in the capacitors.