Nanostructured Praseodymium Oxide: Preparation, Structure, and Catalytic Properties
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- 作者：Yulia Borchert ; Patrick Sonströ ; m ; Michaela Wilhelm ; Holger Borchert ; Marcus Bä ; umer
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：February 28, 2008
- 年：2008
- 卷：112
- 期：8
- 页码：3054 - 3063
- 全文大小：247K
- 年卷期：v.112,no.8(February 28, 2008)
- ISSN：1932-7455
文摘
Nanostructured praseodymium oxides were successfully prepared via four different methods: two traditionalmethods (calcination of praseodymium nitrate and sol-gel method with propylene oxide) and two moresophisticated, modern techniques (citrate method and modified Pechini method). Powder X-ray diffractionrevealed that all synthesis methods led to praseodymium oxide PrB>6O11 with cubic fluorite-like structure. Thetemperature necessary for the formation of the crystalline oxide phase, however, was dependent on the methodand synthesis parameters. The size of the nanocrystalline domains was in the range of some 10 nm in allcases. The catalytic properties of the nanostructured oxides were studied choosing CO oxidation as a first testreaction. According to infrared spectroscopy, the surface of all samples was covered with monodentate carbonatespecies after the synthesis. After exposure to CO, two types of bidentate carbonates were observed on theoxide surface, and under the feed of both CO and O2, carbon dioxide was observed by IR spectroscopy asproduct in the gas phase at temperatures from 300 
C on. The activity with respect to CO oxidation wasfurther investigated in a catalytic test reactor. The maximum conversion of CO was reached at ~550 C, andit was ~95-96% independent of the synthesis method. At moderate temperatures (~350-500 C), the activitiesof the catalysts prepared in the present work were dependent on the synthesis method and synthesis parameters,only to a small extent, but all of them were more active than commercial Pr6O11. The differences betweenthe various samples prepared in this study can be explained by an influence of the synthesis on the oxygen ion mobility. Mechanistically, the results of our work suggest that CO oxidation occurs through theadsorption of CO as a bidentate carbonate, which is then transformed into a monodentate carbonate finallydesorbing as CO2.
C on. The activity with respect to CO oxidation wasfurther investigated in a catalytic test reactor. The maximum conversion of CO was reached at ~550 C, andit was ~95-96% independent of the synthesis method. At moderate temperatures (~350-500 C), the activitiesof the catalysts prepared in the present work were dependent on the synthesis method and synthesis parameters,only to a small extent, but all of them were more active than commercial Pr6O11. The differences betweenthe various samples prepared in this study can be explained by an influence of the synthesis on the oxygen ion mobility. Mechanistically, the results of our work suggest that CO oxidation occurs through theadsorption of CO as a bidentate carbonate, which is then transformed into a monodentate carbonate finallydesorbing as CO2.