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 K₂CO₃ activators on the thermal decomposition of agarose were elucidated using TG-FTIR-GCMS coupling techniques. The results demonstrate that the presence of KOH/K₂CO₃ shifts the pyrolysis gaseous products from organic fragments to CO₂ and 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 CO₂ within 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/K₂CO₃ co-activation and one-step carbonization process exhibits a high specific surface area of 1670 m² g^-1 and 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^-1 when 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^-1 even at -60 °C. This work offers a new insight for synthesizing porous structures of biomass-derived carbon.