The effect of nitrogen-containing functional groups on SO2 adsorption on carbon surface: Enhanced physical adsorption interactions

Nitrogen-containing functional groups in carbon surface have been demonstrated favorable for SO2 adsorption. While previous literature suggested the SO2 chemisorption nature due to N doping, this work highlights the enhanced physical adsorption interactions between SO2 and nitrogen-containing groups, which are elucidated by density functional theory calculations with the analyses of electrostatic potential, noncovalent interactions, and energy decomposition. The results indicate that for pristine carbon surface, SO2 physisorption mainly occurs on the basal plane due to van der Waals interactions. N doping changes the electron distribution of carbon surfaces, thus altering not only intensity but also types of involved interactions. The quaternary N atoms promote SO2 physisorption mainly by enhancing the van der Waals interactions between the basal plane and SO2 while the improvement of SO2 physisorption by pyridinic and pyrrolic N species should be ascribed to the enhanced electrostatic interactions at edge sites. These results demonstrate that N doping could boost the effective surface for SO2 adsorption by facilitating both van der Waals and electrostatic interactions.