Pore development by tuning gasification severity and chemical activating agents: Using dual CO2/N2 adsorption model

This study investigates the influence of activation strategy on pore development in biochar derived from Eucalyptus globulus , with a particular focus on accurately identifying ultramicroporous structures using a dual CO 2 /N 2 adsorption approach combined with a 2D non-local density functional theory (2D-NLDFT) model. Activated biochar produced via CO 2 and H 2 O/CO 2 gasification (700, 800, 900 °C) at various reaction times was compared with chemically activated biochars prepared using KOH, ZnCl 2 , and H 3 PO 4 under controlled temperatures (700 and 800 °C) and activation severities. The results demonstrate that activation method and burn-off extent strongly govern pore evolution pathways. CO 2 gasification predominantly enhances microporosity through ultramicropore formation and widening into supermicropores, while steam-containing gasification promotes pore coalescence and significant mesopore development at high conversion. Chemical activation yields highly microporous carbons across all agents, with KOH producing the highest surface areas and ultramicropore volumes, ZnCl 2 favoring supermicropore formation, and H 3 PO 4 preserving narrowly distributed ultramicroporosity. The dual CO 2 /N 2 adsorption model proves to be essential for accurately capturing these effects, particularly in the ultramicropore regime inaccessible to conventional single-gas methods. The findings provide mechanistic insight into how activation chemistry and operational parameters can be tuned to design biochars with tailored pore architectures for applications in gas adsorption, catalysis, and electrochemical energy storage.