Preparation and Characterization of CeO2-based Oxygen Storage Materials

Four types of CeO2-based oxide storage materials were prepared by co-precipitation, and their physicochemical properties were characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption (BET), H2-temperature-programmed reduction (H2-TPR), oxygen pulsing technique, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XRD patterns reveal that only characteristic peaks of CeO2 are observed in the CeO2 and CeO2-Al2O3 (CA), while CeO2-ZrO2 (CZ) and CeO2-ZrO2-Al2O3 (CZA) show Ce0.75Zr0.25O2 phases. XPS studies show that 4+ and 3+ oxidation states of cerium coexist on the surface of CZ, CA and CZA. However, almost no 3+ oxidation state is detected in pure CeO2. The best textural properties, higher oxygen storage capacity (OSC) and excellent thermal stability are obtained for CZA. In addition, in order to compare the differences among the four samples, a new insight is proposed that Al3+ might be inserted into the inter-space of the fluorite structure or highly dispersed in the solid solution. CZA solid solution may consist of interstitial solid solution and substitutional solid solution, which can be verified by the presence of two oxide species or two types of oxygen channels in CA and CZA. However, the evidence is not detailed enough to support this argument, so further investigation is necessary.

Duke Scholars

Author Li Lan Molecular Genetics and Microbiology