Electroactive Anthraquinone-Grafted Reduced Graphene Oxide as a Versatile Electrode for Affordable Supercapacitors and Lithium-Ion Batteries

Hybrid electrodes that reconcile diffusion and surface-controlled redox are essential for high-power and durable storage. Herein, we engineer reduced graphene oxide (rGO) by covalently grafting anthraquinone (AQ) motifs to create dual-function materials that operate efficiently in supercapacitors and lithium-ion batteries (LIBs). Two precursors─2-aminoanthraquinone (AAQ) and 2-(bis(4-aminophenyl)amino)anthracene-9,10-dione (APAAD)─were coupled to graphene oxide and chemically reduced to yield AQ-rGO and APAD-rGO. FT-IR and X-ray photoelectron spectroscopy confirm amide linkages, while powder X-ray diffraction shows enlarged interlayer spacings of 0.930 (AQ-rGO) and 1.280 nm (APAD-rGO). Electrochemical analyses reveal pseudocapacitive behavior with medium-dependent kinetics. In aqueous supercapacitors, cyclic-voltammetry b-values of 0.553 (AQ-rGO) and 0.526 (APAD-rGO) indicate diffusion-influenced charge storage. In LIB system, the b-value increases to 0.85 and 0.82, respectively, with capacitive fractions of ∼77% and ∼69% at 0.5–1.0 mV s–1, reflecting accelerated surface redox and shortened ion paths. Temperature-dependent impedance spectroscopy gives activation energies of 32.7 kJ mol–1 (AQ-rGO) and 26.7 kJ mol–1 (APAD-rGO), consistent with galvanostatic intermittent titration analysis, showing higher Li+ diffusivity in APAD-rGO. Furthermore, the electrochemical performance mirrors these kinetics. As a supercapacitor, the anthraquinone-grafted rGO demonstrates a specific capacitance of 60 F g–1 up to 70 cycles under a scan rate of 5 mV s–1. As a LIB cathode, APAD-rGO delivers 129.7 mA h g–1 at 50 mA g–1, maintains a rate capability from 100 to 2000 mA g–1, and sustains 1000-cycle durability with excellent stability. This cathode outperforms the rGO cathode with 45 mA h g–1 under a 50 mA g–1 current density. As anodes, AQ-rGO and APAD-rGO, respectively, provide initial capacities of 403 and 340 mA h g–1, stabilize at 345 and 283 mA h g–1 after 100 cycles, and operate up to 2000 mA g–1 with progressive activation. Overall, quinone grafting activates dense redox sites, tunes transport length scales, and bridges capacitive and diffusion storage in carbon frameworks.