Construction of hierarchically porous biomass carbon using iodine as pore-making agent for energy storage

High specific surface area, hierarchical porosity, high conductivity and heteroatoms doping have been considered as the dominating factors of high-performance carbon-based supercapacitors. Inspired by the blue phenomenon of combination of starch and iodine, iodine is employed firstly as pore-making agent to create micropores for the starch-derived carbon in this study. Based on this mechanism, the hierarchically porous carbon is synthesized through simple solvent heating and high-temperature (1000 °C) carbonization, which achieves high specific surface area of 2989 m2 g−1 (an increase of 39.7% compared to that without iodine) and low electrical resistivity of 0.21 Ω·cm. The assembled symmetric supercapacitors, combined with dual redox-active electrolyte (Bi3+ and Br−), deliver the specific capacitance of 1216 F g−1, energy density of 65.4 Wh kg−1, as well as power density of 787.3 W kg−1 at 2 A g−1. In brief, the abundant biomass resource starch is exploited as carbon source, and the iodine sublimation reaction is conducted to provide more micropores to develop high-performance electrodes of supercapacitors.