Tailoring hierarchically porous structure of biomass-derived carbon for high-performance supercapacitors

Biowaste-derived hierarchical porous carbon materials and understanding their structure-property relationship have a significant impact on the development of low-cost and high-performance supercapacitors. Herein, we report the effective one-step construction of large specific surface area and hierarchical porous carbon materials (CPC) using waste corncobs as raw material and investigated the relationship between intrinsic pore characteristics and specific capacitance. The textural properties such as surface area and pore characteristics, are controlled by modulating the various activating agent, carbonization temperature and time. The as-prepared porous carbon material (particularly CPC-3) at activation temperature of 700 °C obtained via potassium permanganate modulation with optimal specific surface area and volume of pores 1612.86 m2 g−1 and 2.25 cm3 g−1, which exhibited the ultra-high capacitance of 691.05 F g−1 at a current density of 0.5 A g−1 with good rate capability. In addition, the electrode exhibits excellent capacitance retention of 109.7 % over 10000 charge-discharge cycles at a current density of 10 A g−1. Furthermore, the assembled symmetric supercapacitor using CPC-3 and PVA-KOH gel electrolyte delivered a high energy/power density of 16.47 Wh kg−1/15360 W kg−1, respectively. The as-prepared quasi-solid-state device also shows superior applicability and outstanding cycling stability over a wide temperature range of −25 to +60 °C. This work provides a fundamental understanding of the structure-property relationship of the biomass-derived hierarchical porous carbon and allows for the development of supercapacitors in harsh temperature conditions.