Pseudocapacitive anthraquinone modified with reduced graphene oxide for flexible symmetric all-solid-state supercapacitors

Pseudocapacitive materials with high capacitance are promising for enabling high energy density supercapacitors (SCs). Herein, 1, 4, 5, 8 tetrahydroxy anthraquinone (THAQ) with rich carbonyl groups is explored as a novel redox-active electrode material for SCs. THAQ is uniformly anchored on conductive reduced graphene oxide (rGO) sheets by π-π aromatic interactions and a robust, flexible THAQ/graphene composite electrode on filter paper is prepared by a vacuum-filtration method. The filter paper scaffold guarantees the high mechanical strength, meanwhile the conductive graphene sheets serve as an electronic transport medium for THAQ to ensure its remarkable pseudocapacitance. The THAQ/rGO composite achieves a specific capacitance 259 F g⁻¹ at 1 A g⁻¹ and a capacitance retention of 97.9% after 10,000 cycles at 20 A g⁻¹. Moreover, the flexible electrode exhibits a sharp decrease in the charge transfer resistance (R_ct = 2.3 Ω for the THAQ:rGO ratio of 1:1) in comparison with that of pure THAQ (R_ct = 1063 Ω) and a high areal capacitance of 122.7 mF cm⁻² at a current density of 0.1 mA cm⁻², as well as a long cycle life (81.8% after 2000 cycles at 1 mA cm⁻²), providing a good solution to solve the low electronic conductivity issue currently plagued in quinone-based electrode materials.