Non-covalently functionalizing a graphene framework by anthraquinone for high-rate electrochemical energy storage

Abstract

Anthraquinone (AQ) molecules with electrochemically reversible redox couples (anthraquinone/anthracenol) have been selected to functionalize a graphene framework (GF) through non-covalent modification. The π–π stacking interactions between components induce a favorable molecular orientation so that the aromatic ring of AQ is parallel to the sp² network of GF. In this case, the fast Faradaic reactions between anthraquinone and anthracenol generate additional pseudocapacitance for enhancing the supercapacitive performance of GF. In the three-electrode configuration, AQ-functionalized GF (AQ/GF) shows a high capacitance value (396 F g⁻¹ at 1 A g⁻¹, two times higher than bare GF), ultrahigh rate capability (64% capacitance retention at 100 A g⁻¹) and long cycle life (97% retention after 2000 cycles). For further practical application, a novel asymmetric supercapacitor with high energy and power densities has been assembled by using AQ/GF as negative electrode and GF as positive electrode in H₂SO₄ aqueous electrolyte. Maximum energy (13.2 Wh kg⁻¹) and power (9175.3 W kg⁻¹) densities have been obtained for the GF//AQ/GF device.