Nanoporous carbons derived from poplar catkins for high performance supercapacitors with a redox active electrolyte of p-phenylenediamine

Abstract Nanoporous carbons (NPCs) have been successfully prepared from poplar catkins (PCs) as a sustainable and renewable carbon source by a facile carbonization and subsequent KOH activation procedure. The KOH-activated NPCs at 800 °C (NPC800) exhibits a hierarchical porous structure containing macroporous frameworks and microporous textures, with a high specific surface area of 1251.5 m 2  g −1 and a large pore volume up to 0.85 cm 3  g −1 . In addition, a novel redox-active electrolyte through introducing a redox-mediator ( p -phenylenediamine, PPD) into KOH electrolytes was used to improve the electrochemical performance of the NPCs-based supercapacitors. The NPC800 exhibits a high specific capacitance of 557 F g -1  at 0.1 A g −1 , a good rate capability of 254 F g -1  at 10 A g −1 and excellent cycle stability with 77.4% capacitance retention after 500 cycles at 1 A g −1 . With a favorable capacitive performance, the waste biomass PCs could be a new source of carbonaceous materials for high performance and low-cost supercapacitors.