Ce_xTi_(1-x)O_2复合氧化物表面结构和体相结构的演变(英文)  

Evolution of surface and bulk structures of Ce_xTi_(1-x)O_2 oxide composites

作　　者：方钧[1] 石富城[1] 包蕙质 千坤[1] 姜志全[1] 黄伟新[1] 

机构地区：[1]中国科学技术大学微尺度物质科学国家实验室(筹)能量转换材料中国科学院重点实验室和化学物理系,安徽合肥230026

出　　处：《催化学报》2013年第11期2075-2083,共9页

基　　金：supported by the National Natural Science Foundation of China (11079033);National Basic Research Program of China (973 Program, 2013CB933104, 2010CB923301);Fundamental Research Funds for the Central Universities (WK2060030005)~~

摘　　要：利用X射线衍射、N2吸附等温线、X射线光电子能谱、X射线吸收谱、H2-程序升温还原、甲基橙选择化学吸附和等电点测定等方法研究了共沉淀方法制备的一系列Cex Ti1-x O2复合氧化物的结构. 成功发展了甲基橙选择化学吸附和等电点方法研究Cex Ti1-x O2复合氧化物的最外层表面结构, 并定义了"等价CeO2表面覆盖度"来描述Cex Ti1-x O2复合氧化物的最外层表面结构. Cex Ti1-x O2复合氧化物 (x ≥ 0.7)形成立方萤石相固溶体, Ce0.3Ti0.7O2表现出纯的单斜相, 而其它复合氧化物表现出混合相. CexTi1-x O2复合氧化物最外层表面结构的演变行为不同于其体相结构. Ce0.7Ti0.3O2立方萤石相固溶体最外层表面已经部分形成了单斜相Ce0.3Ti0.7O2, 随Ce含量的降低, 单斜相Ce0.3Ti0.7O2从最外层表面向体相生长. Cex Ti1-x O2复合氧化物立方萤石相固溶体和单斜相Ce0.3Ti0.7O2分别在相对较低和较高的温度表现出好的还原性能. 上述结果提供了全面和深层次的Cex Ti1-x O2复合氧化物结构信息.A series of Cex Ti1 x O2 oxide composites were synthesized using a coprecipitation method,and their structures were investigated using X-ray diffraction, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy,X-ray absorption spectroscopy,H2 temperature-programmed reduc- tion,selective chemisorption of methyl orange,and isoelectric point measurements.The selective chemisorption of methyl orange and isoelectric point measurements successfully characterized the outmost surface structures of the Cex Ti1 x O2 oxide composites,and the term 'equivalent CeO2 sur- face coverage' in a monolayer was introduced to describe the outmost surface compositions. Cex Ti1 x O2 oxide composites with x ≥ 0.7 form a cubic fluorite phase solid solution,the Ce0.3 Ti0.7 O2 oxide composite is a pure monoclinic compound,and the other oxide composites have mixed phase structures.The outmost surface structure evolves in a different way from the bulk structure.A cubic fluorite Ce0.7 Ti0.3 O2 solid solution partially undergoes cubic fluorite solid solution-to-monoclinic Ce0.3 Ti0.7 O2 phase transition on its outmost surface, and Ce0.3 Ti0.7 O2 on the outmost surface of Ce0.7 Ti0.3 O2 grows from the surface to the bulk.Cubic fluorite Cex Ti1 x O2 solid solutions exhibit good reducibilities at relatively low temperatures,whereas Ce0.3 Ti0.7 O2 exhibits good reducibility at rela- tively high temperatures.These results provide comprehensive and in-depth structural information for important Cex Ti1 x O2 oxide composites.

关 键 词：二氧化钛 氧化铈 复合氧化物 相结构 表面结构 X射线吸收谱 选择化学吸附 等电点 

分 类 号：O643.36[理学—物理化学]