Redox-active 9,10-phenanthrenequinone non-covalently modify reduced graphene oxide for high-performance asymmetric supercapacitor and zinc-ion hybrid capacitors

Redox-active organic molecules show great potential in novel renewable energy storage devices by modifying carbon-based materials in covalent or non-covalent forms due to their light-weight, rich structural diversity, good designability and abundance. Herein, we synthesized redox-active 9,10-phenanthrenequinone (PQ) molecules non-covalently modified reduced graphene oxide (RGO) nanocomposites by an improved simple one-step solvothermal method and explored their application as advanced electrode in aqueous energy storage devices. Benefiting from the rich redox-active sites brought by the anchored PQ molecules and the formation of the hierarchical porous network nanostructures with the RGO substrates that facilitates the charge transport and ion diffusion kinetics, the synthesized RGO/PQs nanocomposites exhibit significantly enhanced electrochemical energy storage performance. The optimal RGO/PQ-1.5 electrode has a high specific capacitance of 383.3 F g-1 at 0.5 A g-1 and good rate capability. And the asymmetric supercapacitor (ASC) assembled with the N-RGO negative electrode exhibits significantly better energy density than pure carbon electrode ASCs. More surprisingly, the assembled RGO/PQ-1.5//Zn zinc-ion hybrid capacitor exhibits an attractive specific capacity of 139.4 mAh g-1, a high energy density of 134.6 Wh kg-1, and an ultra-long cycling stability with 95.3 % capacity retention after 14,000 cycles, demonstrating excellent zinc-ion energy storage performance.