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 K2CO3 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 m2 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]BF4 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.