Unexpected Redox Role of WO ₃ in V ₂ O ₅ ‐WO ₃ /TiO ₂ Catalysts for Selective Reduction of NO by Forming V–W Dinuclear Sites

Promoters can greatly improve the activity of catalysts; however, the mechanism by which they interact with the primary catalyst to enhance catalytic activity is not always clear. It has been widely demonstrated that WO₃ in V₂O₅-WO₃/TiO₂ catalysts acts as a promoter to enhance the surface acidity and regulate the dispersion of active V₂O₅ species, while it is believed that the redox process takes place entirely at the V sites in the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). Here, by combining in situ spectroscopic measurements and density functional theory (DFT) calculations, we validate that the WO₃ directly participates in the oxidative activation of NH₃, and hence explicitly exerts a redox effect in NH₃-SCR by forming V-W dinuclear sites with V₂O₅. This study sheds new light on a long-standing puzzle regarding the role of WO₃ as a promoter and hence advances the understanding of the working principle of V₂O₅-WO₃/TiO₂ catalysts.