采用溶胶-凝胶法制备了CexPr1-xO2-δ复合氧化物,用XRD和Raman光谱对复合氧化物的体相和表面结构进行了表征.结果表明,当x≥0.5时Pr离子完全进入CeO2晶格中形成单一立方相固溶体. CexPr1-xO2-δ(x>0.3)复合氧化物在465和1150cm-1附近出现具有CaF2
结构的Raman特征峰,和由氧空穴引起的不对称振动产生的570和195cm-1 Raman 谱峰.固溶体的形成使还原温度降低,提高了复合氧化物的还原性能.CO氧化活性表明氧空穴的存在对CO氧化活性有一定的对应关系;而CH4氧化活性则与还原温度和强度有关.
A series of CexPr1-xO2-δ mixed oxides were synthesized by the sol-gel method and characterized by Raman and XRD techniques. The results show that when x value is changed from 1.0 to 0.5, only a cubic
phase CeO2 appears. The samples are very well crystallized on decreasing x from 0.50 to 0.99. It can be explained to form an ordered array of O vacancies caused by the insertion of Pr atom completely
into the CeO2 crystal lattice. For CexPr1-xO2-δ samples 465cm-1 and 1150cm-1 Raman peaks are attributed to the Raman active F2g mode of CeO2. The broad peak at
about 570cm-1 in the region 0.3≤x≤ 0.99 can be linked to lattice defects resulting in oxygen vacancies. The new band at about 195cm-1 may be attributed to the asymmetric vibration that is caused
by the formation of oxygen vacancies. TPR profiles of Pr6O11 and CeO2 have two reduction peaks respectively. The reduction process of Pr6O11 is: PrO1.83→PrO1.61→PrO1.5;
For CeO2, the peak of low temperature attributed to the reduction of the surface cmoxygen of CeO2, the peak of high temperature
attributed to the reduction of bulk CeO2. The reduction peak temperature of CexPr1-xO2-δ mixed oxides is lower than that of Pr6O11 and CeO2, which indicates that the formation
of CexPr1-xO2-δ solid solutions improves the reduction-oxidation behavior. The activity of CexPr1-xO2-δ for CO oxidation indicates that the existing of the oxygen vacancies
favors CO oxidation; while the activity of CH4 oxidation is related to the temperature and the area of the reduction-oxidation peak.
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