CO₂ selective adsorption over O₂ on N−doped activated carbon: Experiment and quantum chemistry study

Utilizing flue gas as feedstock for CO₂ electro−reduction systems is a promising technology to address problems caused by excessive CO₂ emissions. However, the O₂ contained in the flue gas has a significant adverse effect on the CO₂ reduction. Herein, a facile strategy was proposed to suppress the influence of O₂ by constructing a CO₂−enriched region. N−doping was demonstrated to be an efficient way to enhance CO₂ adsorption selectivity over O₂ on activated carbon. The N−doped activated carbon achieved 3.7 times increase in CO₂ adsorption selectivity over O₂ than that before modification under simulated flue gas atmosphere (75 %N₂ + 15 %CO₂ + 10 %O₂). The distinction in adsorption mechanism between CO₂ and O₂ was revealed by quantum chemistry study. The increased polarity of the carbon materials favored CO₂ adsorption and had less impact on O₂ adsorption. The electrostatic interaction between CO₂ and carbon material was demonstrated to be enhanced after the introduction of pyridinic N and pyrrolic N, which led to an improvement in the CO₂ adsorption capacity. The dispersion interaction, which fully regulated O₂ adsorption, was weakened due to the deviation of the O₂ adsorption position. This study provided a reference for the subsequent development of CO₂ selective adsorption materials.