Unique κ- Ce 2 Zr 2 O 8 Superstructure Promoting the NO x Adsorption-Selective Catalytic Reduction (AdSCR) Performance of the WO 3 /CeZrO x Catalyst.

Selective catalytic reduction of NO x by NH 3 (NH 3 -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 x adsorption-storage capacity and medium-high temperature NO x reduction activity is an effective strategy to solve the issues mentioned above but is rarely investigated. Herein, the WO 3 /Ce 0.68 Zr 0.32 O x (W/CZ) catalyst containing the κ- Ce 2 Zr 2 O 8 pyrochlore structure was successfully developed by a simple H 2 reduction method, not only showing superior NO x adsorption-storage ability below 180 °C but also exhibiting excellent NH 3 -SCR activity above 180 °C. The presence of the pyrochlore structure effectively increased the oxygen vacancies on the κ- Ce 2 Zr 2 O 8 -containing W/CZ catalyst with enhanced redox property, which significantly promoted the NO x adsorption-storage as active nitrate species below 180 °C. Upon NH 3 introduction above 180 °C, the κ- Ce 2 Zr 2 O 8 -containing W/CZ catalyst showed greatly improved NO x reduction performance, suggesting that the pyrochlore structure played a vital role in improving the NO x adsorption-selective catalytic reduction (AdSCR) performance. This work provides a new perspective for designing bifunctional CeZrO x -based catalysts to efficiently control the NO x emissions from diesel engines during the cold-start process.