| Abstract
| - Catalytic oxidation of CO over CexHf1-xO2 (CH; 8:2 mole ratio) and CexZr1-xO2 (CZ; 1:1 mole ratio)nanocomposite oxides reveals that the former combination exhibits more conversion at much lower temperaturethan the latter. Thermal and textural stability of both the combinations, obtained by a coprecipitation methodand calcined at 773 and 1073 K, were examined by X-ray diffraction, Raman spectroscopy, and CO-temperatureprogrammed reduction techniques. The XRD results disclose formation of a stable Ce0.8Hf0.2O2 cubic phasein the case of the CH sample, whereas CZ suffers phase segregation from Ce0.75Zr0.25O2 to Ce0.6Zr0.4O2 at1073 K. Oxygen storage capacity (OSC) and CO-TPR measurements reveal a high OSC and low-temperaturereducibility for the CH sample due to the defective fluorite structure generated upon incorporation of smallerHf4+ cations (0.78 Å ionic radius), in comparison to Zr4+ (0.84 Å), into the ceria cubic lattice. The observedhigh activity of Ce0.8Hf0.2O2 was proven to be due to the generation of lattice defects, formation of moreoxygen vacancies, and easy reducibility.
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