Eggshell as a biotemplate for the synthesis of layered porous carbon by co-pyrolysis with eucalyptus leaves

Based on its substantial specific surface area (SSA), quick ion transport path, and excellent pore structure, biomass carbon is a common ingredient in energy storage materials. In this study, hierarchical porous carbon was fabricated by the hard template method, using eucalyptus leaves (EL) as raw material, eggshells (ES) obtained from biomass waste act as a green biotemplating agent, and through co-pyrolysis technology to acquire high-value biomass carbon materials. A large SSA with a hierarchical porous structure displayed a honeycomb appearance obtained by adding eggshells in appropriate proportions. The ELES0.25 electrodes demonstrated a specific capacitance (Cs) of 310 F g−1 (0.5 A g−1) and 232 F g−1 (20 A g−1) in a three-electrode system, which displayed a capacitance retention of 74.8% with an outstanding electrochemical stability. The assembled ELES0.25//ELES0.25 symmetric supercapacitor displays a desirable energy density of 7.35 Wh kg−1 at a power density of 65 W kg−1 and preserves a capacitance retention of 97.38% after a charge/discharge cycle for 10,000 times. This research on ES acts as the biological template for assisted pyrolysis synthesis of porous carbon and proposes a novel approach for the clean and effective use of biomass waste.