Novel Redox Active Molecule Naphthol Green B Combined with Biomass Porous Carbon for High-Performance Supercapacitors

The energy density of biomass-derived porous carbon can be enhanced by the introduction of redox active molecules. Finding efficient materials for pseudocapacitive charge storage has become a grand challenge. Herein, using cyclic voltammetry, naphthol green B (NGB) for the first time is used as an organic redox active material in combination with biomass-based porous carbon (DS-2), which is produced from dandelion stems by precarbonization and KOH activation. The results demonstrate that DS-2/NGB50-5 exhibits a specific capacitance of 700 F g–1 at 1 A g–1 in 1 M H2SO4, which is almost 2.5 times greater than that of DS-2 (the specific capacitance of 249 F g–1). Even at 20 A g–1, 86% of the original capacitance is retained, indicating an excellent rate performance. The high specific capacitance mainly depends on the reversible reaction of −N═O groups of NGB molecules and H+ in the electrolyte at the charge and discharge durations. The symmetric capacitor based on DS-2/NGB50-5 delivers a high energy density of 36.6 Wh kg–1 at a power density of 650 W kg–1 and shows good cycling stability (capacitance retention of 78.4% after 10,000 cycles). This work has successfully developed a kind of redox active molecule with efficient energy storage, which opens a new avenue for the design of high-performance supercapacitors.