Adsorption and Reaction of Methanol over CeOX(100) Thin Films

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• 作者：Peter M. Albrecht ; David R. Mullins
• 刊名：Langmuir
• 出版年：2013
• 出版时间：April 9, 2013
• 年：2013
• 卷：29
• 期：14
• 页码：4559-4567
• 全文大小：519K
• 年卷期：v.29,no.14(April 9, 2013)
• ISSN：1520-5827

文摘

Methanol was adsorbed on oxidized and reduced CeO_X(100) thin films to probe the active sites and reaction selectivity of these surfaces compared to those of CeO_X(111). Roughly twice as much methoxy was formed on oxidized CeO₂(100) compared to that formed on CeO₂(111). In addition to more methoxy, hydroxyl is also more stable on CeO₂(100). Unlike on CeO₂(111), however, methanol on CeO₂(100) produced CO, CO₂, and H₂ in addition to water and formaldehyde. The behavior of CeO₂(100) is related to its surface structure, which provides greater access to Ce cations and therefore more active adsorption sites and more highly undercoordinated Ce and O. The undercoordinated O may explain the enhanced dehydrogenation activity leading to CO and H₂ formation. The reduction of ceria leads to increased methanol uptake on both CeO_{2聽鈥撀?i>X}(100) and CeO_{2聽鈥撀?i>X}(111). However, although the uptake doubled on reduced CeO_{2聽鈥撀?i>X}(111) compared to the oxidized surface, it increased by only 10% on reduced CeO_{2聽鈥撀?i>X}(100) compared to that on fully oxidized CeO₂(100). Reduction of both surfaces leads to a greater production of CO and H₂. Reaction on all surfaces progresses rapidly from methoxy to products. There is no spectroscopic evidence of formyl or formate intermediates. On CeO_X(100), carbonate is detected that decomposes into CO₂ at high temperature.