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The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control.
| 题名： | The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control. |
| 作者： | Ozawa, M.;Loong, C.-K.; |
| 关键词： | 36 MATERIALS SCIENCE; 33 ADVANCED PROPULSION SYSTEMS ; CATALYTIC CONVERTERS; CATALYSTS; IONIC CONDUCTIVITY; NEUTRON DIFFRACTION; CRYSTAL-PHASE TRANSFORMATIONS; REDOX POTENTIAL; DOPED MATERIALS; ZIRCONIUM OXIDES; CERIUM OXIDES; LANTHANUM; NEODYMIUM; CRYSTAL DEFECTS |
| 摘要： | Rare earth (RE) modification of automotive catalysts (e.g., ZrO{sub 2}) for exhaust gas treatment results in outstanding improvement of the structural stability, catalytic functions and resistance to sintering at high temperatures. Owing to the low redox potential of nonstoichiometric CeO{sub 2}, oxygen release and intake associated with the conversion between the 3+ and 4+ oxidation states of the Ce ions in Ce-doped ZrO{sub 2} provide the oxygen storage capacity that is essentially to effective catalytic functions under dynamic air-to-fuel ratio cycling. Doping tripositive RE ions such as La and Nd in ZrO{sub 2}, on the other hand, introduces oxygen vacancies that affect the electronic and ionic conductivity. These effects, in conjunction with the nanostructure and surface reactivity of the fine powders, present a challenging problem in the development of better ZrO{sub 2}-containing three-way catalysts. We have carried out in-situ small-to-wide angle neutron diffraction at high temperatures and under controlled atmospheres to study the structural phase transitions, sintering behavior, and Ce{sup 3+}{leftrightarrow} Ce{sup 4+} redox process. We found substantial effects due to RE doping on the nature of aggregation of nanoparticles, defect formation, crystal phase transformation, and metal-support interaction in ZrO{sub 2} catalysts for automotive emission control. |
| 报告类型： | 科技报告 |
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