The effect of functional groups on the SO ₂ adsorption on carbon surface I: A new insight into noncovalent interaction between SO ₂ molecule and acidic oxygen-containing groups

For the aim to give a new insight into the interactions between SO ₂ molecule and carbon surface and the effect of acidic oxygen-containing groups, density functional theory and noncovalent interaction analysis in terms of reduced density gradient were employed to investigate both the intensity and type of the interactions. The results indicate that the physisorption of SO ₂ molecule mainly occurs on the basal plane of pure carbon surface due to van der Waals interactions, however, when acidic oxygen-containing groups were decorated on the carbon surface, they would facilitate SO ₂ adsorption as a result of hydrogen bonding and dipole-dipole interactions. What's more, these groups could not affect the chemisorption of SO ₂ remarkably, no matter they are near the adsorption sites or not. In addition, calculation results show that the interactions between SO ₂ and acidic oxygen-containing groups are in physisorption nature, which challenges a long-held the viewpoint of irreversible chemisorption. Acidic oxygen-containing groups could boost the effective surface area of carbon by enhancing the physisorption on edge positions.