2,6-diaminoanthraquinone anchored on functionalized biomass porous carbon boosts electrochemical stability for metal-free redox supercapacitor electrode

•The redox-active molecules are firmly anchored to amino-functionalized biomass porous carbon through hydrogen bonding, and composite electrode DAQ@FWS exhibits superior cycling stability (capacity retention of 93.1% after 10,000 cycles) compared with DAQ@WS (71.6% after 10,000 cycles).•DFT calculation indicates that adsorption energy of DAQ@FWS system (Eads=−1.66 eV) is lower than that of DAQ@WS (Eads=−0.31 eV), indicating that there is a stronger interaction between DAQ and FWS through hydrogen bonding.•The capacitance contribution from fast kinetics process of DAQ@FWS at 5 mV s−1 is 92.2%, the investigation further reveals that proton-coupled electron transfer mechanism plays a key role in charge storage behavior. The challenge of redox-active molecules for electrochemical capacitors is that they are easy to detach from the substrate during long-term charge-discharge cycles. In this work, redox-active molecule 2,6-diaminoanthraquinone (DAQ) is anchored on amino functionalized biomass porous carbon (FWS) via strong hydrogen bonding interaction. The protophilic C = O sites on the DAQ provide additional faradaic pseudocapacitance for biomass carbon-based electrode through fast redox reactions. In addition, the surface functionalization of porous carbon enhanced the interaction between the porous carbon and DAQ molecule, which inhibited the detachment of DAQ and significantly improved the electrochemical stability of the composite electrode. The optimized DAQ@FWS composite exhibits excellent specific capacitance of 424.9 F g−1 at 1 A g−1 with a stable capacity retention of 93.1% over 10,000 cycles at 10 A g−1, which is higher than unfunctionalized biomass porous carbon-based composite electrode (71.6% after 10,000 cycles). Meanwhile, DAQ@FWS composite maintains a high capacitance of 300.4 F g−1 even at 30 A g−1. Density functional theory calculations and detailed electrochemical analysis further elucidate the binding interactions of DAQ with FWS and charge storage mechanisms. Furthermore, coin-type symmetric supercapacitor based on DAQ@FWS exhibits excellent energy density (36.4 Wh kg−1 at 700.5 W kg−1), power density (7.001 kW kg−1 at 27.0 Wh kg−1) and durable cycling stability (capacitance retention is 88.3% after 10,000 cycles). Thus, amino functionalization of biomass porous carbon to anchor redox active organic quinones is promising as an effective strategy to fabricate superior performance supercapacitor electrode material. The redox-active molecule a