Tailoring the Electronic Structure of Single Ag Atoms in Ag/WO3 for Efficient NO Reduction by CO in the Presence of O2

Developing efficient catalysts for the selective catalytic reduction of NO x by CO (CO-SCR) is the key challenge for commercializing this technology. Ag-based catalysts with relatively low costs are promising but widely believed to be not efficient enough for this reaction. Here, we demonstrate that atomically dispersed Ag supported on ordered mesoporous WO 3 (m-WO 3 ) can serve as a highly active catalyst for CO-SCR under O 2 -containing conditions. By altering the amount of the Ag precursor, the local environment of the Ag atom coordinated with the O atom can be tailored. Furthermore, at 250 °C and an O 2 /CO ratio of 2.5:1, 0.3Ag/m-WO 3 (0.3 wt % Ag) with six-coordinated Ag–O exhibited much better catalytic performance than 5 Ag/m-WO 3 (5 wt % Ag) with two-coordinated Ag–O (e.g., 0.43 vs 0.02 mol NO g Ag –1 h –1 in the reaction rate) and previously reported Ag-based catalysts in the literature. The theoretical calculations confirm that the six-coordinated Ag atoms in 0.3Ag/m-WO 3 possess a more positive oxidation state and a higher d-band center than the two-coordinated Ag atoms in 5Ag/m-WO 3, promoting its bonding strength with co-adsorption of the critical intermediates of N 2 O* and CO*. This work provides a feasible route for regulating the local environment of a Ag single atomic catalyst to enhance its catalytic property for CO-SCR.