Effect of mechanical compaction and nitrogen doping treatment on ultramicropore structure of biomass-based porous carbon and the mechanism of CO2 capture

In the preparation of biomass-derived porous carbon, targeting the enhancement of ultramicropore volume and understanding the effects of nitrogen doping on ultramicroporous structure are crucial for improving CO2 capture. Here, we prepared porous carbon using mechanical compaction and urea-assisted KOH activation of tobacco stem-derived hydrochar. The results showed that mechanical compaction increased the ultramicropore volume with little impact on oxygen content, leading to an increase in CO2 adsorption capacity, with a maximum adsorption capacity of 5.6mmol g(-1) at 25 degrees C and 1 bar. In contrast, nitrogen doping negatively affected the ultramicropore structure and oxygen functionalities, resulting in a decrease in CO2 adsorption capacity. Furthermore, experimental and molecular simulation studies revealed that ultramicropore smaller than 0.5 nm predominantly determine the CO2 adsorption capacity at 0.15 bar and CO2/N-2 selectivity. These findings provide theoretical and practical support for the development of efficient carbon-based CO2 adsorbents.