Graphene-quantum-dots-induced MnO2 with needle-like nanostructure grown on carbonized wood as advanced electrode for supercapacitors

Abstract

Hydrothermal and electrochemical deposition methods have been employed to fabricate porous wood carbon (PWC)/pseudocapacitive hybrid materials for use as free-standing supercapacitor electrodes. However, their cycling stability is poor because of the inherent storage mechanism of pseudocapacitive materials, and their specific capacitance requires further improvement. In this study, PWC was directly produced as a conductive matrix by pyrolyzing natural balsa wood, and then manganese dioxide (MnO2) and graphene quantum dots (GQDs) were deposited to fabricate a PWC/MnO2/GQDs electrode by a hydrothermal method. GQDs significantly boosts the ions transport, and protects MnO2 from falling off both the external surface and inside the channel of PWC. Compared with a PWC/MnO2 electrode, the unique needle-like nanostructures formed by adding GQDs resulted in a better electrochemical performance for a supercapacitor electrode, including a moderate areal specific capacitance (2712 mF cm−2 at a current density of 1.0 mA cm−2), good rate capability, and excellent cycling stability (95.3% retention after 2000 cycles). This indicated that GQDs-decorated composites will promote the development of high-performance energy storage devices.