Unique κ-Ce₂Zr₂O₈ Superstructure Promoting the NO Adsorption-Selective Catalytic Reduction (AdSCR) Performance of the...

Selective catalytic reduction of NO by NH₃ (NH₃-SCR) for diesel emission control at low temperatures is still a great challenge due to the limit of the urea injection threshold and inferior SCR activity of state-of-the-art catalyst systems below 200 °C. Fabricating bifunctional catalysts with both low temperature NO adsorption-storage capacity and medium-high temperature NO reduction activity is an effective strategy to solve the issues mentioned above but is rarely investigated. Herein, the WO₃/Ce_0.68Zr_0.32O (W/CZ) catalyst containing the κ-Ce₂Zr₂O₈ pyrochlore structure was successfully developed by a simple H₂ reduction method, not only showing superior NO adsorption-storage ability below 180 °C but also exhibiting excellent NH₃-SCR activity above 180 °C. The presence of the pyrochlore structure effectively increased the oxygen vacancies on the κ-Ce₂Zr₂O₈-containing W/CZ catalyst with enhanced redox property, which significantly promoted the NO adsorption-storage as active nitrate species below 180 °C. Upon NH₃ introduction above 180 °C, the κ-Ce₂Zr₂O₈-containing W/CZ catalyst showed greatly improved NO reduction performance, suggesting that the pyrochlore structure played a vital role in improving the NO adsorption-selective catalytic reduction (AdSCR) performance. This work provides a new perspective for designing bifunctional CeZrO-based catalysts to efficiently control the NO emissions from diesel engines during the cold-start process.