Model thin films of Ce(III)‐based mixed oxides
Model thin films of Ce(III)‐based mixed oxides
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DOI：
10.1002/sia.5458
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发表时间：
2014-10
影响因子：
1.7
通讯作者：
T. Skála;V. Matolín
中科院分区：
文献类型：
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作者：
T. Skála;V. Matolín
众所周知，铈氧化物催化剂上的Ce（III）位点在许多反应中都很活跃。为了研究二氧化铈与三种易氧化元素（铝、硅和钨）的相互作用，并制备Ce（III）电子结构的多组分材料，我们采用了两种相反的方法：我们将(i) Al、Si或W分层沉积到CeO2（111）上，（ii） CeO2沉积到Al（111）、Si（111）或W（110）上。我们发现，在所有的情况下，相互作用都很强，并导致形成CeAlO3， Ce4.67Si3O13和Ce6WO12的混合氧化物。这些元素以Ce(III), Al(III), Si（IV）和W（VI）氧化态存在，并且薄膜的最大厚度受到限制，因为较厚的覆盖层阻止了元素从衬底扩散。超过这个极限，沉积的铝、硅或钨在其纯元素形式生长之前就在表面形成了氧化态较低的氧化物，而在相反的体系中，来自Al、Si和W衬底的扩散不足导致CeO2在混合氧化物膜上生长。我们表明，这种方法允许制备各种厚度的模型薄膜和精细可调的Ce（IV）贡献和位置（低于或高于混合氧化物）。版权所有©2014 John Wiley & Sons， Ltd。
Ce(III) sites on cerium oxide‐based catalysts are known to be active in many reactions. In order to study the interaction of cerium dioxide with three easily oxidizable elements, aluminum, silicon, and tungsten, and to prepare multicomponent materials of the Ce(III) electronic structure, we followed two inverse approaches: we step‐wisely deposited (i) Al, Si, or W onto CeO2(111) and (ii) CeO2 onto Al(111), Si(111), or W(110). We found out that the interaction in all cases was very strong and lead to a formation of mixed oxides of CeAlO3, Ce4.67Si3O13, and Ce6WO12 composition determined by quantitative XPS. The elements were present in Ce(III), Al(III), Si(IV), and W(VI) oxidation states, and the maximum thickness of the films was limited as thicker overlayers prevent the diffusion of the element from the substrate. Above this limit, the deposited aluminum, silicon, or tungsten formed oxides of consequently lower oxidation states on the surface before their purely elemental form was growing, while in the inverse systems, the insufficient diffusion from the Al, Si, and W substrates caused the growth of CeO2 on top of the mixed oxide films. We show that this method permits to prepare model thin films of various thickness and finely tunable Ce(IV) contribution and position (below or above the mixed oxide). Copyright © 2014 John Wiley & Sons, Ltd.