Copper-modified ceria catalysts, (CuO)x /Ce0.9 Cu0.1 O2 nanospheres, for low-temperature CO oxidation were fabricated simply by using the hydrothermal synthesis of Cu-doped CeO2 (Ce0.9 Cu0.1 O2 ) nanospheres followed by deposition of CuO over Ce0.9 Cu0.1 O2 . The X-ray diffraction and electron spectroscopy characterizations demonstrated that the as-prepared nanospheres were composed of cubic CeO2 and monoclinic CuO with a typical diameter of around 70 nm. Moreover, the X-ray photoelectron spectroscopy (XPS) analysis illustrated the coexistence of Ce4+ /Ce3+ and Cu2+ /Cu+ redox couples in (CuO)x /Ce0.9 Cu0.1 O2 and H2 temperature-programmed reduction (TPR) measurements indicated the excellent reduction behavior of the catalyst. The Raman spectra illustrated the oxygen vacancy in (CuO)0.3 /Ce0.9 Cu0.1 O2 , and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrated the stable existence of Cu+ species during CO oxidation. The (CuO)x /Ce0.9 Cu0.1 O2 nanospheres showed excellent catalytic activity toward CO oxidation in normal feed gas (volume ratio of CO/O2 /N2 =1:10:89) at ambient temperature. Catalytic tests revealed that the proportion of CuO in the final product has a strong influence on the resultant catalytic activities. The (CuO)x /Ce0.9 Cu0.1 O2 nanospheres hold great application potential as new catalysts for CO oxidation.
Keywords: CO oxidation; catalytic activity; copper; surface defects; synergistic effects.
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