Pyrolysis Regulation of Agarose into Hierarchical Porous Carbon for Supercapacitor Applications

Fundamental understanding of the biomass pyrolysis process on a molecular level provides important guidelines for designing advanced porous carbon materials. In this study, the effects of KOH and K2CO3activators on the thermal decomposition of agarose were elucidated using TG-FTIR-GCMS coupling techniques. The results demonstrate that the presence of KOH/K2CO3shifts the pyrolysis gaseous products from organic fragments to CO2and H2O, thereby preserving more C-C bonds in the solid phase and facilitating the subsequent aromatization process. Furthermore, compared to using KOH as the sole activator, the K2CO3/KOH co-activation strategy suppresses the violent evolution of CO2within the 300–400 °C range, thereby alleviating the structural shock to the material skeleton and ensuring its integrity. Therefore, the HPC-KCO prepared via a synergistic KOH/K2CO3co-activation and one-step carbonization process exhibits a high specific surface area of 1670 m2g−1and successfully retains its interconnected hierarchical porous framework. Benefiting from its well-developed porous structure, HPC-KCO exhibits an impressive specific capacitance of 370 F g−1when employed in zinc-ion capacitors. Furthermore, the assembled symmetric supercapacitor demonstrates robust stability over a wide temperature range from −60 to 100 °C, delivering a remarkable capacitance of 121 F g−1even at −60 °C. This work offers a new insight for synthesizing porous structures of biomass-derived carbon.