Synthesis and Structural Characterization of Eu2O3 Doped CeO2: Influence of Oxygen Defects on CO Oxidation

Abstract

In this study, nanosized Ce0.9Eu0.1O2−δ (CE 91) and Ce0.8Eu0.2O2−δ (CE 82) solid solutions were prepared by a modified co-precipitation method, followed by calcination at 773 and 1,073 K. Structural properties of the prepared materials were thoroughly investigated by different characterization techniques, namely, X-ray powder diffraction (XRD), Brunauer–Emmett–Teller surface area, high resolution transmission electron microscopy, Raman spectroscopy, UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), and X-ray photoelectron spectroscopy (XPS). The catalytic activity for CO oxidation was assessed and compared with the well-established CeO2–ZrO2 (CZ) catalyst. As confirmed by powder XRD, the synthesized materials maintain the F-type crystalline structure characteristic of ceria (CeO2). The interaction of CeO2 with Eu3+ dopant promoted the formation of oxygen vacancies as revealed by Raman results. UV–Vis DRS and XPS data suggest that Ce exists in both 3+ and 4+ oxidation states and Eu in the 3+ state. Results of catalytic CO oxidation indicate that Eu doped ceria exhibits a better performance than Zr doped ceria irrespective of the calcination temperature. This may be due to the increased number of oxygen defects and the easily reducible nature of the material, which results from the substitution of Ce4+ species with Eu3+ ions.