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.