High-Performance Supercapacitor of Graphene Quantum Dots with Uniform Sizes

Abstract

Graphene quantum dots (GQDs) with uniform sizes of less than 5 nm are synthesized by a novel top-down strategy. Nitric acid as a strong oxidant can be used to cut graphene oxide via sonication and hydrothermal processes. Moreover, purified GQDs are obtained from removing oxygen-containing functional groups in a heat treatment process. Both nanoscale size and edge effect of GQDs improve their abundant active sites and restrain the restack of graphene nanosheets. Meanwhile, their electrochemical performance demonstrates the properties of the GQDs for practical application in energy storage. The GQD electrode material shows an ideal electric double-layer capacitance behavior such as a high specific capacitance of 296.7 F g, a satisfactory energy density of 41.2 W h kg at 1 A g, a low internal resistance, a small relaxation time, and an excellent cycling stability. The results illustrate excellent electrochemical activity, high conductivity, and enhanced ion transport rate on the surface of electrolyte and electrode. The advantages of GQDs confirm their unique characteristics for potential applications in the field of electrode materials for supercapacitors.

The Research Development of Quantum Dots in Electrochemical Energy Storage

“…The fabricated 2.3 V aqueous ECs exhibited an energy density of 118 W h kg −1 at the power density of 923 W kg −1 with excellent rate performance. Zhang et al synthesized purified GQDs from removing oxygen‐containing functional groups in a heat treatment process. The GQDs showed an energy density of 41.2 W h kg −1 at 1 A g −1 using galvanostatic charge–discharge method through a two‐electrode cell in 2.0 m KOH applied for EDLCs.…”

“…And, whenever QDs are used in an electrochemical device, the electrochemical signature of the QD based electrode must be shown. These excellent properties guarantee remarkable applications of QDs in a variety of fields, such as biomolecular analysis, sensors, organic photovoltaic devices, fluorescence, photochemical reagents, solar cells, light‐emitting diodes, and catalysis . Taking all of the above into consideration, it is hardly surprising that QDs have recently gained widespread applications in the areas of batteries and ECs ( Scheme ).…”

In‐situ formation and intercalation of carbon dots induced high‐yield 1T‐molybdenum disulfide as electrode materials

“…The galvanostatic charge‐discharge (GCD) curve exhibits a nearly symmetrical triangle, indicating fast current‐voltage response in the electron‐transfer process . According to mass capacitance equation in Supporting Information, the specific mass capacitance C m of S0, S1, S2, S3, and S4 hybrids at 0.5 A/g is 203, 243, 274, 301, and 380 F/g (Figure A), respectively.…”

Application of sonication in improving the Cu(II) adsorptivity and recycling performanc of activated carbon fibers

“…Sonication-assisted propagating in liquid has the function of accelerating liquids' mechanical motion and cavitation effect. The cavitation effect can produce local high temperature, local high pressure, strong shock wave and high speed micro-jet, which provides a high-energy reaction environment for the progress physicochemical reaction progress of graphite-like microcrystalline carbon and amorphous carbon [21,22]. Hence, pore-forming and pore wall destruction functions exist in the reactivation process intensely and concurrently.…”