Electrochemical impedance model-assisted optimization of biomass hierarchical porous carbon electrodes for supercapacitors†

The development of cost-effective and straightforward methodologies for the fabrication of high-performance electrode materials represents a crucial advancement in the application and evolution of supercapacitors (SCs). Hierarchical porous carbon materials have been considered a type of promising material for SCs owing to their high specific surface area and excellent electronic conductivity. Herein, the synthesis of structurally controllable porous carbons from pomelo peel through carbonization, the template method and activation treatment is reported. In this work, an impedance model was used to evaluate the charge storage capacity and ion transmission rate of porous electrodes of SCs. Biochar materials were prepared using CaCO₃ and KOH as the template and activator, respectively, and the effects of different template and activator contents on the specific surface area, pore volume, morphology and electrochemical properties of the prepared biochar materials were investigated. The as-prepared biochar, designated as 800-PAC-750-1:1, possessed a hierarchically porous framework with a relatively high specific surface area of 2384 m² g⁻¹ and a specific capacitance of 240.3 F g⁻¹ at a current density of 0.5 A g⁻¹. The 800-PAC-750-1:1 electrode also exhibited excellent cycling stability with 87.5% capacitance retention after 10 000 cycles.