Developing efficient catalysts for the selective catalytic reduction of NOx 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 WO3 (mWO3) can serve as a highly active catalyst for CO-SCR under O2-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 degrees C and an O2/CO ratio of 2.5:1, 0.3Ag/m-WO3 (0.3 wt % Ag) with six-coordinated Ag-O exhibited much better catalytic performance than 5 Ag/m-WO3 (5 wt % Ag) with two coordinated Ag-O (e.g., 0.43 vs 0.02 molNO gAg -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-WO3 possess a more positive oxidation state and a higher d-band center than the two-coordinated Ag atoms in 5Ag/m-WO3, promoting its bonding strength with co adsorption of the critical intermediates of N2O* 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.

Selective catalytic reduction of NOx by CO (CO-SCR) to both N2 and CO2 is a promising way to simultaneously remove two harmful gases, CO and NOx, in automobile and factory exhaust gases. The development of efficient catalysts is the key challenge for the technology to be commercialized. The low-cost Cu-based catalysts have shown promising performance in CO-SCR, but there are some technical problems that obstruct their practical implementation, such as high reduction temperature and low O2, H2O, and SO2 resistance. This paper provides a comprehensive overview and insights into CO-SCR under O2-containing conditions over the Cu-based catalysts, including catalytic performances of non-supported, supported mono-metallic, supported bimetallic, and supported multi-metallic Cu-based catalysts. In addition, the effects of O2 concentration, reaction temperature, H2O, and SO2 on the catalytic performance are discussed. Furthermore, the reaction mechanism of CO-SCR on Cu-based catalysts is briefly summarized. Lastly, challenges and perspectives with respect to this reaction are discussed. We hope this work can provide theoretical guidance for the rational design of efficient Cu-based catalysts in the CO-SCR reaction for commercial applications.

Generating different types of defects in heterogeneous catalysts for synergetic promotion of the reactivity and selectivity in catalytic reactions is highly challenging due to the lack of effective theoretical guidance. Herein, we demonstrate a facile strategy to introduce two types of defects into the CuO-ZnO model catalyst, namely oxygen vacancies (OVs) induced by H-2 partial reduction and localized amorphous regions (LARs) generated via the ball milling process. Using industrially important Rochow-MUller reaction as a representative, we found OVs predominantly improved the target product selectivity of dimethyldichlorosilane, while LARs significantly increased the conversion of reactant Si. The CuO-ZnO catalyst with optimized OVs and LARs contents achieved the best catalytic property. Theoretical calculation further revealed that LARs promote the generation of the Cu3Si active phase, and OVs impact the electronic structure of the Cu3Si active phase. This work provides a new understanding of the roles of different catalyst defects and a feasible way of engineering the catalyst structure for better catalytic performances.