▎ 摘　　要

NOVELTY - Preparing graphene quantum dots with uniform size involves using graphite powder, sodium nitrate, potassium permanganate and concentrated sulfuric acid as raw materials, and obtain graphene oxide powder by hummers method. The ultrasonic pretreatment is carried out by dispersing 25-100mg graphene oxide in 50ml concentrated nitric acid solution and performing ultrasonic treatment for 2-6 hours to obtain orange-yellow dispersion liquid. The dispersion liquid is transferred to a stainless steel autoclave lined with polytetrafluoroethylene for sealing, and reacts for 8-24 hours at 80-180 degrees C for carrying out hydrothermal treatment in the environment of concentrated nitric acid with concentration of 68 wt.%, then cooling to room temperature, and the solution is centrifuged at 8000 revolutions/minute (r/min) for 10 minutes to remove the upper liquid, and the obtained light yellow slurry is placed in a petri dish and naturally dried in a ventilated place. USE - Method for preparing graphene quantum dots with uniform size used as electrode materials of electric double layer supercapacitors (claimed), and as electrode material of energy storage devices. ADVANTAGE - The method has simple process and mild conditions, and the prepared graphene quantum dots has good purity, small particle size and uniform size distribution, excellent conductivity, high specific capacity, excellent rate performance, fast ion adsorption, transmission rate and long cycle life, and has good application potential in the field of energy storage devices. DETAILED DESCRIPTION - Preparing graphene quantum dots with uniform size involves using graphite powder, sodium nitrate, potassium permanganate and concentrated sulfuric acid as raw materials, and obtain graphene oxide powder by hummers method. The ultrasonic pretreatment is carried out by dispersing 25-100mg graphene oxide in 50ml concentrated nitric acid solution and performing ultrasonic treatment for 2-6 hours to obtain orange-yellow dispersion liquid. The dispersion liquid is transferred to a stainless steel autoclave lined with polytetrafluoroethylene for sealing, and reacts for 8-24 hours at 80-180 degrees C for carrying out hydrothermal treatment in the environment of concentrated nitric acid with concentration of 68 wt.%, then cooling to room temperature, and the solution is centrifuged at 8000 revolutions/minute (r/min) for 10 minutes to remove the upper liquid, and the obtained light yellow slurry is placed in a petri dish and naturally dried in a ventilated place. The sample is placed in a tube furnace for high temperature calcination under argon atmosphere, and bright black products are collected to obtain graphene quantum dots with uniform size distribution. The number of graphene quantum dots prepared is 1-3, and the average size is 1-3 nm. The prepared graphene quantum dot material has electric double layer capacitance behavior.