Preparation, Characterization And Catalytic Activity Of CE_0.8ZR_0.2-xY_xO_2-δ（x=0, 0.1） Mixed Oxide With Controlled Morphologies

CeO2 is one of the important materials of catalysis. Different morphologies of CeO2 can expose different facets, increase the concentration of oxygen vacancies and thus improve the oxygen storage capacity(OSC). The doped CeO2 based mixed oxide has unique physical and chemical properties due to its lattice structure distorted and easy to generate lattice defects. Therefore, it is widely used to automotive exhaust purification, CO oxidation, and water-gas shift etc.In this paper, the Ce0.8Zr0.2-xYxO2-δ(x=0, 0.1) mixed oxide with different morphologies were successfully synthesized by hydrothermal method. The obtained samples were characterized by XRD, Raman, SEM, XPS and TPR techniques. The catalytic performance of these samples for CO oxidation was investigated and the relationship between its catalytic properties and microstructure was discussed.1. The uniform dispersity of micro-rod Ce0.8Zr0.2O2-δ mixed oxide was synthesized by cetyltrimethylammonium bromide(CTAB) as the surfactant and reacted at 150 ℃ for 24 h, the dendrite structure Ce0.8Zr0.2O2-δ mixed oxide was synthesized by 180 ℃ for 24 h. However, with citrid acid(CA) as the surfactant, Uniform dispersity and surface smooth of micro-sphere Ce0.8Zr0.2O2-δ mixed oxide was synthesized by 180 ℃ for 24 h. HRTEM results showed that the micro-rod and dendrite samples preferentially exposed(220) active planes besides(111) stable planes. However, only(111) facets exposed for the microsphere sample. Raman and XPS results reflected that the micro-rod and dendrite samples possessed more oxygen vacancies and Ce3+/Ce4+ concentration. Moreover, the micro-rod and dendrite samples also had higher reducibility and activity, which is likely related to its exposed(220) active plane and possess higher Ce3+/Ce4+ and oxygen vacancies concentration.2. SEM and HRTEM results showed that the introduction of the third component Y has little effect on the morphologies. However, compared to Ce0.8Zr0.2O2-δ mixed oxide, the concentration of oxygen vacancies and Ce3+/Ce4+ in the Ce0.8Zr0.1Y0.1O2-δ mixed oxide were significantly increased, the ability of low temperature reduction was also significantly enhanced, and thus the Ce0.8Zr0.1Y0.1O2-δ mixed oxide showed better CO oxidation activity.3. With the increase of calcinations temperatures, the surface area and low temperature reduced ability of the superior catalytic performance of Ce0.8Zr0.1Y0.1O2-δ mixed oxide gradually decreased, thus lead to the CO catalytic activity decreased eventually. Yet, although after high temperature calcination, the catalytic activity of Ce0.8Zr0.1Y0.1O2-δ mixed oxide is superior to pure CeO2, because the former has better ability of low temperature reduction and higher concentration of oxygen vacancies. The results also indicated that the introduction of Zr and Y greatly enhanced the CO oxidation activity and thermal stability of CeO2.