Probing Defect Sites on CeO2 Nanocrystals with Well-Defined Surface Planes by Raman Spectroscopy and O2 Adsorption
Probing Defect Sites on CeO2 Nanocrystals with Well-Defined Surface Planes by Raman Spectroscopy and O2 Adsorption
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DOI：
10.1021/la101723w
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发表时间：
2010-11-02
期刊：
影响因子：
3.9
通讯作者：
Overbury, Steven H.
中科院分区：
文献类型：
--
作者：
Wu, Zili;Li, Meijun;Overbury, Steven H.
缺陷位在CeO_2催化中起着至关重要的作用。在本研究中，我们合成了具有明确表面积的CeO_2纳米晶，并将其用于缺陷位的拉曼光谱和O-2吸附研究。利用CeO2纳米棒({110}+{100})、纳米立方体({100})和纳米八面体({111})分析了不同表面缺陷的数量和质量。在氧化表面上，纳米棒具有最丰富的本征缺陷位，其次是纳米立方体和纳米八面体。当被还原时，诱导的缺陷位在纳米棒上比在纳米立方体上更聚集，尽管在两个表面上产生了相似数量的这样的缺陷位(基于表面积)。由于最小的还原能力，在纳米八面体上可以产生很少的缺陷位。这些差异可以通过纳米CeO_2晶体表面的结晶学终止来解释。这些纳米晶上不同的缺陷位置导致了不同的表面氧物种的吸附。CeO_2纳米晶表面存在不同聚集度的单电子缺陷位上的超氧化物和两电子缺陷位上的过氧化产物，而且这些氧物种的稳定性和反应活性也与表面有关，这对CeO_2催化氧化反应具有重要意义。
Defect sites play an essential role in ceria catalysis. In this study, ceria nanocrystals with well-defined surface planes have been synthesized and utilized for studying defect sites with both Raman spectroscopy and O-2 adsorption. Ceria nanorods ({110} + {100}), nanocubcs ({100}), and nano-octahedra ({111}) are employed to analyze the quantity and quality of defect sites on different ceria surfaces. On oxidized surfaces, nanorods have the most abundant intrinsic defect sites, followed by nanocubcs and nano-octahedra. When reduced, the induced defect sites are more clustered on nanorods than on nanocubes, although similar amounts (based on surface area) of such defect sites are produced on the two surfaces. Very few defect sites can be generated on the nano-octahedra due to the least reducibility. These differences can be rationalized by the crystallographic surface terminations of the ceria nanocrystals. The different defect sites on these nanocrystals lead to the adsorption of different surface dioxygen species. Superoxide on one-electron defect sites and peroxide on two-electron defect sites with different clustering degree are identified on the ceria nanocrystals depending on their morphology, Furthermore, the stability and reactivity of these oxygen species are also found to be surface-dependent, which is of significance for ceria-catalyzed oxidation reactions.