Redox-Active Organic Sodium Anthraquinone-2-Sulfonate (AQS) Anchored on Reduced Graphene Oxide for High-Performance Supercapacitors

Redox active organic quinones are potentially low cost, sustainable, and high-energy pseudocapacitive materials due to their fast and reversible redox reactivity. However, their electrically insulating nature prevents any practical application. Herein, for the first time, sodium anthraquinone-2-sulfonate (AQS) is examined as an organic redox-active compound and highly conductive graphene nanosheets are incorporated to enhance the electronic conductivity. The SO₃ ⁻ functional group of AQS offers excellent hydrophilicity, which promotes the molecular level binding of AQS with reduced graphene oxide (rGO) and leads to a 3D interconnected xerogel (AQS@rGO). The composite exhibits a high specific capacitance of 567.1 F g⁻¹ at 1 A g⁻¹ with a stable capacity retention of 89.1% over 10 000 cycles at 10 A g⁻¹. More importantly, the optimized composite maintains a high capacitance of 315.1 F g⁻¹ even at 30 A g⁻¹ due to the high pseudocapacitance of AQS and the capacitive contribution of rGO. First-principles calculations further elucidate that AQS offers strong adhesion to rGO sheets with the formation of a space-charge layer, which is favorable for the pseudocapacitance of AQS. This work opens a new avenue for developing high-performance supercapacitors though rational combination of redox organic molecules with highly conductive graphene.