This study reports the adsorption and favorable reaction mechanism of SO3 reduction by CO molecule over Si- or Al-doped graphene using DFT calculations. The adsorption energy of the most stable configuration of SO3 is calculated to be about -103 and -124 kcal/mol over the Si- and Al-doped graphene, respectively. The SO3 reduction over these surfaces proceeds through the following elementary steps (a) SO3 -> SO2 + O-ads and (b) O-ads + CO -> CO2. The estimated activation energy (E-act) for the dissociation of SO3 over the Si-doped graphene is about 9 kcal/mol smaller than that on the Al-doped graphene. (C) 2016 Elsevier B.V. All rights reserved.