Selectivity Change and Deactivation in Photocatalytic CO 2 Reduction Induced by SO 2

Industrial flue gas is a major source of CO 2 emissions, but the effects of its contaminants on CO 2 photoreduction remain unclear. Here, we investigated the influence of SO 2 on the photocatalytic performance of CO 2 photoreduction using Pt/TiO 2 as a model photocatalyst. SO 2 enhanced the yield of CO 2 photoreduction within 2.5 h, accompanied by a selectivity change from 100% CH 4 to predominantly CO, followed by a gradual deactivation of the catalyst. Gaseous SO 2 hindered the proton supply for CH 4 generation by suppressing H 2 O adsorption. SO 2 was oxidized into SO 4 2–, which occupied the step sites of Pt NPs and formed a new Pt–O–SO 3 species, weakening the π-electron back-bonding in the Pt(5d)-Co(2π*) bonds and thus facilitating *CO desorption. Lastly, the excessive accumulation of SO 4 2– led to catalyst poisoning. This work sheds light on the role of SO 2 during the photoreduction of CO 2 and provides a theoretical foundation for the direct photocatalytic conversion of CO 2 from industrial flue gas.