Synergistic enhancement of CO2 adsorption performance of porous biochar by N/O heteroatoms and pore structure: Experiment and DFT simulation

Surface modification of porous biochar is a key strategy for enhancing CO 2 adsorption performance. Herein, HNO 3 solution impregnation, along with concurrent pore structure modulation via KOH chemical activation, was used to functionalize pine nut shell-derived biochar. The influence of HNO 3 concentration on heteroatom doping and pore configuration was also systematically investigated. Combining experimental characterization with density functional theory calculations, the dual contributions of pore structure and heteroatom-induced interactions to the enhanced CO 2 uptake in modified biochars were decoupled. The optimized functionalized porous biochar exhibited N and O doping levels of 1.67   at.% and 11.1   at.%, respectively, a specific surface area of 1498 m 2 g −1 , and an ultra-micropore (<0.7   nm) volume of 0.40 cm 3 g −1 . This material achieved a CO 2 adsorption capacity of 4.82   mmol   g −1 at 25 °C and 1   bar. Notably, the ultra-micropore filling rate exceeded 80% at 0 °C and 1   bar. Therefore, the developed synergistic regulation strategy facilitates concurrent optimization of heteroatom functionality and pore structure. This strategy yields superior CO 2 capture performance under ambient conditions (25 °C, 1   bar), and provides insights for advancing carbon capture technologies.