Turning Waste Honeysuckle Vine into High-Performance Supercapacitor Electrodes via Optimized KOH Activation

In the context of the global dual-carbon strategy, developing sustainable and high-performance electrode materials for supercapacitors is of great significance. In this work, a facile two-step method was employed to convert honeysuckle vine, an agricultural byproduct, into hierarchically porous activated carbon (HVAC) via precarbonization and KOH activation. By systematically regulating KOH/HVC mass ratio and the activation temperature, we elucidated the reaction mechanism of KOH etching. At elevated temperatures, KOH reacts with the carbon framework to generate K 2 CO 3 and metallic K, whose continuous volatilization and migration create an interconnected pore network. The optimized sample, HVAC-6-800, exhibits a high specific surface area of 3489.04 m 2 g –1, a well-developed porous structure, and oxygen doping. The HVAC-6-800 electrode delivers a high specific capacitance of 338.7 F g –1 at 1 A g –1, excellent rate capability (68% retention at 20 A g –1 ), and outstanding cycling stability (94% retention after 5000 cycles). Symmetric supercapacitors assembled with HVAC-6-800 electrodes in 6 M KOH and [BMIM]BF 4 electrolytes achieve energy densities of 16.85 Wh kg –1 (150 W kg –1 ) and 49.0 Wh kg –1 (377 W kg –1 ), respectively, along with superior cycling performance (97% capacitance retention after 8000 cycles in KOH). This work demonstrates that honeysuckle vine-derived porous carbon is a promising, sustainable, and high-performance electrode material for supercapacitors.