This study reports favorable reaction mechanisms of SO2 oxidation by molecular O-2 over Si-doped graphene by means of DFT calculations. The SO2 oxidation reaction proceeds through the following elementary steps (a) SO2 + O-2 -> O-ads and (b) O-ads + SO2 -> SO3. It is found that the first and second steps are fulfilled via the Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms, with an activation energy of 4.7 and 9.5 kcal/mol, respectively. Results show that the low-cost Si-doped graphene can be used as an efficient catalyst for SO2 oxidation at room temperature. (C) 2016 Elsevier B.V. All rights reserved.