Amine-enriched Graphene Quantum Dots for High-pseudocapacitance Supercapacitors

The applications of carbon-based supercapacitors have been limited by their low energy storage density owing to their limited active storage sites. To overcome this limitation, amine-enriched porous carbon electrodes have been fabricated by the electrostatic fusion of amine-functionalized single-crystalline graphene quantum dots (GQDs) within conductive, vertically ordered TiO2 nanotube arrays as the collectors. The carbon films deliver ultrahigh specific capacitance (400-595 F g(-1)) even beyond the theoretical upper limit of single-layer graphene by inducing a high concentration of active amine moieties at edge. Symmetrical GQD supercapacitors in H2SO4 electrolyte offer energy density up to 21.8 Wh kg(-1) and retain 90% of the initial capacitance after 10000 cyclic voltammetry tests. The results show that amine-enriched GQDs can function as a new kind of highly active, solution-processable, and low-cost pseudocapacitive materials applicable to high-performance supercapacitors. (C) 2016 Elsevier Ltd. All rights reserved.