Ultrahigh‐Surface Area Hierarchically Porous Carbon Derived From Sweet Potato Extraction Residue‐Syrup for High Performance Supercapacitor

Abstract Converting biomass waste into value‐added products is desirable and a major goal for the circular economy. Herein, the agricultural waste and sweet potato extraction residues (SPR) were converted into hierarchially porous carbons (HPCs) by a facile method using KOH as the activation agent. The as‐obtained SPR‐HPCs exhibited a well developed pore structure and very high specific surface area (SSA). By controlling the fabrication conditions including the dosage of KOH and activation temperature, the optimized SPR‐HPC‐3.5–800 had an ultrahigh SSA of 3206 m2 g−1 with high pore volume of 2.132 cm3 g−1. When used as electrode materials, the electrochemical studies demonstrated that the SPR‐HPC‐3.5–800 based electrode achieved high specific capacitance of 320 F g−1 at a current density of 0.5 A g−1 and the symmetrical supercapacitor in 6 M KOH achieved energy density of 6.8 Wh kg−1 at 249 W kg−1. Furthermore, high electrochemical stability was achieved for the SPR‐HPCs. This study provides a good example of the production of value‐added products from biowastes.