Facet-Dependent Photocatalytic\nCO<sub>2</sub> Reduction\non TiO<sub>2</sub> Crystals in the Presence of SO<sub>2</sub>: Role\nof Surface Hydroxyl

Photocatalytic CO<sub>2</sub> reduction to solar energy\nmakes great\nsense to mitigate the greenhouse effect caused by CO<sub>2</sub>,\nand great efforts have been made to promote CO<sub>2</sub> conversion\nefficiency. However, the effect of impurities in the photoreduction\nof CO<sub>2</sub> has received relatively little attention. Here,\nthe different CO<sub>2</sub> photoreduction behaviors of TiO<sub>2</sub> exposed (101) facet (TiO<sub>2</sub>-101) and (001) facet (TiO<sub>2</sub>-001) with an SO<sub>2</sub> impurity were investigated. On\nTiO<sub>2</sub>-101, SO<sub>2</sub> accelerates the deactivation of\nthe catalyst for CO<sub>2</sub> photoreduction activity, since SO<sub>2</sub> mainly binds to the OH<sub>b</sub> site of TiO<sub>2</sub>-101. This site is highly susceptible to the transfer of photogenerated\nholes, resulting in the rapid generation of SO<sub>4</sub><sup>2–</sup>, which occupies the active site and poisons the catalyst. For TiO<sub>2</sub>-001, SO<sub>2</sub> has relatively little negative effect\non stability, as SO<sub>2</sub> mainly binds to the weak binding site\n(OH<sub>t</sub>) of TiO<sub>2</sub>-001, preventing it from being\noxidized to SO<sub>4</sub><sup>2–</sup>, which alleviates catalyst\ndeactivation and ensures the continuity of CO<sub>2</sub> reduction.\nThis paper provides further insights into the role of SO<sub>2</sub> in CO<sub>2</sub> photoreduction over distinct TiO<sub>2</sub> facets\nand reveals the importance of facet engineering in the photocatalytic\nreduction of CO<sub>2</sub> from industrial flue gas.