Influence of the preparation method on the catalytic activity of Co/Zr1−xCexO2 for NO oxidation

• The preparation method affected the dispersion of cobalt in the Ce–Zr systems.
• Co/Zr1−xCexO2 catalysts prepared by citrate complexation showed high catalytic activity.
• The surface concentration of Ce3+ was favorable to high catalytic performance.
• The addition of large amount of Zr had a negative effect on catalytic activity.

A series of cobalt supported on Zr1−xCexO2 catalysts were synthesized by citrate complexation method (CC-series) and impregnation method (IM-series) and their catalytic performance of the NO oxidation to NO2 were tested. CC-series exhibited higher catalytic activity than IM-series. These prepared samples were characterized by various techniques such as XRD, Raman spectroscopy, BET, TEM, H2-TPR, UV–vis DRS and XPS. CC-series was found to possess easier reducibility, lower crystallite size and higher relative amount of Ce3+ compared with IM-series, which in turn led to their higher catalytic activity. The effect of Ce/Zr ratio on the catalytic activity of samples was also investigated. The results showed that adding large amount of Zr into Co/CeO2 system had a negative effect on the activity because of the corresponding decreasing of the surface Ce3+ concentration which was related with the production of oxygen vacancy.

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