Supercapacitors are limited by their low energy density, which restricts their broad applications. To address this issue, this work develops novel graphene-based electrode materials covalently functionalized with commercially available industrial dyes. The AB–rGO–1 composite electrode is prepared by stably grafting a redox-active azo blue dye (AB) onto graphene oxide. This grafting occurs through the reaction between the phenolic hydroxyl groups of AB and the epoxy or carboxyl groups on graphene oxide. The extended \(\pi\) -conjugated structure and the sulfonate groups combine electric double-layer capacitance and pseudocapacitance. They also reduce graphene restacking. In addition, these features improve surface wettability and enhance ion transport kinetics. In three-electrode measurements, AB–rGO–1 achieves a high specific capacitance of 536.6 F g \(^{-1}\) . It also exhibits excellent long-term stability. The electrode retains 77.9% of its initial capacitance after 10,000 consecutive charge-discharge cycles. Benefiting from its outstanding rate capability and stable cycling performance, the flexible symmetric device delivers an energy density of 15 Wh kg \(^{-1}\) at a power density of 14.4 kW kg \(^{-1}\) . It also achieves 18.5 Wh kg \(^{-1}\) at 720 W kg \(^{-1}\) . Overall, this work highlights the advantages of covalent grafting for graphene-based electrodes. It provides a practical, scalable approach for constructing high-performance flexible energy storage systems.
