Dissociation of O2 and its reactivity on O/S doped graphene

Abstract

It is routinely believed that the oxidation of SO₂ to SO₃ dominates the removal rate of SO₂ on carbon-based catalysts. Recently, both experiment and theoretical calculations evidence that SO₂ is readily oxidized by epoxy groups on graphene oxides at room temperature. Based on this fact, we hypothesize in this study that the real rate-determining step for SO₂ catalytic oxidation under O₂ atmosphere could be the dissociation of molecular O₂, which further forms oxygen functional groups on the graphene surface. Density functional theory corrected with dispersion was employed to investigate the dissociation of O₂ on O or S doped graphene and then its reactivity for SO₂ oxidation. The results showed that O/S doping greatly promotes the dissociation, which leads to the formation of epoxy and/or carbonyl groups on the graphene surface. However, a high oxidation barrier for the oxidation of SO₂ by the carbonyl group was found, which implies that the carbonyl group is of low reactivity. Therefore, dopant screening or the design of doped structures should be carefully considered to avoid the formation of carbonyl during O₂ dissociation.