Polymerization of redox-active alizarin in biomass porous carbon with enhanced cycling stability for supercapacitor

Redox-active organic molecules have optimistic application prospects in energy storage due to their high theoretical capacitance, designable electrochemical activity and environmental friendliness. However, low conductivity and solubility in electrolyte severely hinder their redox activity. Here, alizarin molecules containing carbonyl and phenolic hydroxyl are encapsulated in biomass-derived porous carbon, and stable alizarin polymers are further grown on porous carbon substrate by electrochemical polymerization. Porous carbon as conductive network can improve electron transport properties, and provide suitable accommodation environment for confinement and polymerization of alizarin. The electrochemical polymerization strategy on carbon substrate allows alizarin to be connected by rigid C-O-C bond, which inhibits the dissolution of organic monomers while maintaining redox activity. The optimized polyalizarin/porous carbon composite (PAZ/PC-0.5) exhibits superior charge storage performance, with a specific capacitance of 355.8 F g- 1 at 1 A g- 1 and 220.8 F g- 1 at high current density of 30 A g- 1 . Moreover, PAZ/PC electrode has more durable long-term charge-discharge stability (capacitance retention is 98 % after 10,000 charge and discharge cycles). The assembled symmetrical super- capacitor exhibits excellent energy-power characteristics (21.4 Wh kg- 1 at 700 W kg- 1 ) and durable cycle stability. This work sheds light on the design of stable organic electrode towards high-performance supercapacitor.