From biological waste to honeycomb-like porous carbon for high energy density supercapacitor

We develop a facile and sustainable method for the synthesis of three-dimensional (3D) interconnected honeycomb-like porous carbon (HPC) derived from sunflowers stem. The optimized sample has large specific surface area with 3D interconnected honeycomb-like porous structure and high oxygen content. Due to their synergistic effect, the HPC-2 material shows a high specific capacitance of 349 F g(-1) at 1 A g(-1), good rate capability (247 F g(-1) at 50A g(-1)) and excellent cycling stability (retaining 98.6% after 10000 cycles) in 6M KOH aqueous electrolyte. Moreover, the HPC-2//HPC-2/MnO2 asymmetric supercapacitor shows a high energy density of 58.8Wh kg(-1) and good electrochemical stability (83.1% of initial capacitance retention after 10000 cycles). Therefore, these unique properties enable the material to become a promising high-performance electrode material for supercapacitors.