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

Abstract

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.