engleski

Ceria-zirconia solid solutions as possible constituents for Three-way catalysts towards CO oxidation

Ceria is a well-known material used as catalyst for different oxidation reactions due to the presence of oxygen vacancies owing to switchable oxidation states. However, the stability of ceria is low at elevated temperatures which is why it is doped with zirconia as a catalyst support. In this research CexZr1−xO2 solid solutions and dry impregnated and calcined CeO2 on ZrO2 particles were prepared in order to explore catalytic activity for the CO oxidation. The as-prepared compounds were characterized by the X-ray diffraction (XRD) followed by the Rietveld refinement, Raman spectroscopy (Raman), and X- ray photoelectron spectroscopy (XPS). The distinct morphology of CeO2 on ZrO2 particles is responsible for the high specific activity in the gas-phase oxidation. The complete oxygen storage capacity (OSCc) at 430 °C is shown to be linearly correlated to the CO oxidation activity at 430 °C as a function of the Ce concentration x. Thus, it is compatible with the expected Mars–van-Krevelen mechanism. The CeO2 on ZrO2 catalyst calcined at 600 °C is chemically even more stable than the one calcined at 900 °C, where a solid solution of ZrO2 and CeO2 is formed at the solid interface. The improved stability of the CeO2 layer calcined at 600 °C is traced to its sharp interface formed with the ZrO2 support. This kind of active and stable layer morphology of CeO2 supported on ZrO2 could be beneficial for other catalytic oxidation reactions as well.

ceria ; ceria-zirconia ; CO oxidation

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