SO2 oxidation with H2O on low surface coverage Pt(111): A density functional theory investigation

• SO 2 oxidation with H 2 O follows an Eley-Rideal instead of a Langmuir-Hinshelwood mechanism to form H 2 SO 4 and H 2 on Pt(111). • SO 2 and H 2 O coadsorption leads to less reactive intermediates. • Without solvent effects, HSO 3 and H 2 SO 3 are readily formed intermediates on Pt(111). Despite recent advances towards understanding SO 2 oxidation to H 2 SO 4 and H 2 on Pt, uncertainties regarding the reaction mechanism and intermediates exist. In this paper, SO 2 oxidation with H 2 O on Pt(111) was modelled with density functional theory. On low surface coverages, SO 2 oxidation to H 2 SO 4 and H 2 followed an Eley-Rideal instead of a Langmuir-Hinshelwood mechanism. Eley-Rideal oxidation was favoured more when H 2 O was adsorbed instead of SO 2 , and in both the Eley-Rideal and Langmuir-Hinshelwood mechanisms, H 2 SO 4 and H 2 formation were significantly influenced by reaction intermediates and their adsorption geometries. More energy was consumed by SO 2 oxidation to H 2 SO 4 and H 2 upon reactant coadsorption, with molecular and dissociated sulphurous acid readily formed as oxidation intermediate.