Structuring graphene quantum dots anchored CuO for high-performance hybrid supercapacitors

Pseudocapacitive materials with multiple oxidation/reduction modes can deliver an improved specific capacity and energy density owing to their reversible Faradic redox reactions. Also, ingeniously integrating a conductive carbon material and a pseudocapacitive transition metal to develop reactive compounds with a high conductivity is a plausible solution to make up for the deficiencies of individual oxides and hydroxides. In this study, we rationally design graphene quantum dots decorated CuO nanoframework (GQDs/CuO) for high-performance supercapacitors. Specifically, the Cu-MOF template as the precursor with a confined porosity and skeleton as well as Cu2+ as the central atoms is converted into CuO by in-situ growth and annealing. Afterward, the negatively charged GQDs can adsorb and uniformly anchor on the CuO surface via electrostatic and coordination interactions by a subsequent hydrothermal treatment. The deposited GQDs with carboxyl functional groups not only increase the surface area for electrochemical reactions but also modulate the conductivity and reduce interfacial resistance by allowing effective paths for electron transportation, leading to better redox reaction kinetics. As a supercapacitor cathode material, the integrated GQDs/CuO electrode affords a high specific capacitance of 729 F g-1 at a current density of 1 A g-1 and good-rate capability together with an improved cyclic performance (82.2% retention after 3000 cycles). Moreover, the asfabricated asymmetric supercapacitor (ASC) with a large output voltage window of 1.5 V realizes an energy density of 32.2 W h kg-1 at power density of 748.9 W kg-1 with an enhanced cyclability over 8000 cycles, benefiting from the enriched electrochemical active sites and intimated connection between Cu species and doped GQDs. Thus, the adopted strategy may demonstrate an effective opportunity to explore high-performance electrode materials for energy harvesting. (c) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The study successfully designed a graphene quantum dots-decorated copper oxide nanoframework as an electrode material for high-performance supercapacitors, showing excellent specific capacitance and cyclic performance. The assembled asymmetric supercapacitor exhibited high energy density and large power density, with significantly improved cyclic performance.