▎ 摘　　要

In this article, charcoal is used as a new raw material for the synthesis of high yield graphene quantum dots (GQDs). The synthesized GQDs were characterized using various characterization techniques. The supercapacitive properties of the GQDs were investigated using electrochemical measurements. The electrode made using GQDs shows a specific capacitance (SC) of 257 F g(-1)at a current density of 3 A g(-1)with a better cyclic stability and a capacitance retention of 96% after 3000 cycles. A flexible symmetric supercapacitor (SSC) device, using GQDs as the active material, was built using a simple fabrication method. The fabricated device delivers an energy density of 17.36 W h kg(-1)and a power density of 191.7 W kg(-1)with excellent durability and 91% capacitance retention after 1000 cycles. This study does not only explain the experimental observations but also provides insightful direction to develop a method for the synthesis and engineering of GQDs, which could be useful for making flexible energy-oriented devices.