Unique κ-Ce2Zr2O8 Superstructure Promoting the NOx Adsorption-Selective Catalytic Reduction (AdSCR) Performance of the WO3/CeZrOx Catalyst

Selective catalytic reduction of NOx 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 degrees C. Fabricating bifunctional catalysts with both low temperature NOx adsorption-storage capacity and medium-high temperature NOx reduction activity is an effective strategy to solve the issues mentioned above but is rarely investigated. Herein, the WO3/Ce0.68Zr0.32Ox (W/CZ) catalyst containing the kappa-Ce2Zr2O8 pyrochlore structure was successfully developed by a simple H-2 reduction method, not only showing superior NOx adsorption-storage ability below 180 degrees C but also exhibiting excellent NH3-SCR activity above 180 degrees C. The presence of the pyrochlore structure effectively increased the oxygen vacancies on the kappa-Ce2Zr2O8-containing W/CZ catalyst with enhanced redox property, which significantly promoted the NOx adsorption-storage as active nitrate species below 180 degrees C. Upon NH3 introduction above 180 degrees C, the kappa-Ce2Zr2O8-containing W/CZ catalyst showed greatly improved NOx reduction performance, suggesting that the pyrochlore structure played a vital role in improving the NOx adsorption-selective catalytic reduction (AdSCR) performance. This work provides a new perspective for designing bifunctional CeZrOx-based catalysts to efficiently control the NOx emissions from diesel engines during the cold-start process.

Automated summary

A W/CZ catalyst with a pyrochlore structure was successfully developed, showing excellent NOx adsorption-storage ability below 180°C and superior NH3-SCR activity above 180°C. The pyrochlore structure increased oxygen vacancies and enhanced redox property, significantly promoting NOx adsorption-storage at low temperature and improving NH3-SCR performance.