Graphene covalently functionalized with 2,6-diaminoanthraquinone (DQ) as a high performance electrode material for supercapacitors

Abstract

2,6-Diaminoanthraquinone (DQ) molecules were covalently modified onto the surface of graphene (GO) via a nucleophilic displacement reaction between the epoxy groups on the surface of GO and the –NH₂ groups of DQ molecules in the presence of ammonia to form a composite material (labeled as DQ–RGO). The rapid reversible faradaic reactions of DQ molecules are realized by means of the good conductivity of graphene. Therefore, the DQ–RGO composite material can combine the Faraday pseudocapacitance of DQ with the double-layer capacitance of graphene, thus displaying outstanding electrochemical performance in acidic electrolyte solution, including a high specific capacitance (332 F g⁻¹ at 1 A g⁻¹), excellent rate capability (the capacitance retention rate is 72.9% at 50 A g⁻¹) and good cycling stability (maintaining 81.8% of the initial capacitance after 5000 cycles). Meanwhile, a thionine-functionalized graphene hydrogel (Th–GH) was also prepared via a non-covalent strategy. Finally, the DQ–RGO composite acted as the negative electrode and Th–GH acted as the positive electrode to construct an asymmetric supercapacitor (ASC). The ASC exhibited an energy density of 14.2 W h kg⁻¹ along with a power density of 0.763 kW kg⁻¹ and long cycling durability (maintaining 80% of the initial capacitance after 8000 cycles at 5 A g⁻¹). More importantly, two such devices in series successfully illuminated 16 red light-emitting diodes (LEDs), demonstrating its outstanding energy storage performance. This work can provide ideas for the construction of green, all-carbon and excellent electrochemical performance devices.