The high-yield cutting conversion of porous graphene into graphene oxide quantum dots for boosting capacitive energy storage behavior

Abstract

Graphene oxide quantum dots (GOQDs) have been used in electrodes to improve the electrochemical energy storage behavior, but suffer from high cost and low yield. Here, GOQDs are prepared by high-yield cutting conversion of porous graphene (PG) with nano-sized crystal domains. The defective edges between the nano-sized graphene domains are selectively etched by a diluted acid, thus contributing to a low-loss deconstruction of the PG. As the result, the as-obtained GOQDs yield can reach up to 60 wt%, much higher than the GQDs yield derived from the decomposition of graphite. As the supercapacitor electrode additive, the simple moderate addition of GOQDs with abundant heteroatom functional groups into PG electrode can effectively alleviate the agglomeration and stacking between PG sheets, which not only improves effective specific surface area and stability of interlamellar storage of PG, but also enhances the electrical conductivity and improves the electrode wettability. Benefitting from above excellent features, the GOQDs-added PG electrode exhibits superior rate performance (120 F g−1 at 0.5 A g−1 and 102 F g−1 at 30 A g−1) and long-term cycling stability in the aqueous electrolyte. Moreover, in the organic electrolyte, it can also deliver specific capacitances of 119 and 106 F g−1 at 1 and 30 A g−1. Besides, the capacitance retention is as high as 97.3% when the temperature decreases from 25 to −40 °C, exhibiting an exceptional low temperature adaptability. The capacitive behaviors in aqueous and organic electrolyte systems of GQDs-added PG electrode are superior to the original PG electrode. This work not only provides a new high-yield and scalable synthesis method for GQDs, but also broadens its application value by employing as the electrode additive in a simple way to boosting the capacitive energy storage behavior.