Promotion of Ceria Catalysts by Precious Metals: Changes in Nature of the Interaction under Reducing and Oxidizing Conditions

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• 作者：Nadia Acerbi ; Stan Golunski ; Shik Chi Tsang ; Helen Daly ; Chris Hardacre ; Richard Smith ; Paul Collier
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：June 28, 2012
• 年：2012
• 卷：116
• 期：25
• 页码：13569-13583
• 全文大小：699K
• 年卷期：v.116,no.25(June 28, 2012)
• ISSN：1932-7455

文摘

By depositing ceria over supported precious metal (PM) catalysts and characterizing them with in situ diffuse reflectance UV (DR UV) and in situ Raman spectroscopy, we have been able to prove a direct correlation between a decrease in ceria band gap and the work function of the metal under reducing conditions. The PM鈥揷eria interaction results in changes on the ceria side of the metal鈥揷eria interface, such that the degree of oxygen vacancy formation on the ceria surface also correlates with the precious metal work function. Nevertheless, conclusive evidence for a purely electronic interaction could not be provided by X-ray photoelectron spectroscopy (XPS) analysis. On the contrary, the results highlight the complexity of the PM鈥揷eria interaction by supporting a spillover mechanism resulting from the electronic interaction under reducing conditions. Under oxidizing conditions, another effect has been observed, namely, a structural modification of ceria induced by the presence of PM cations. In particular, we have been able to demonstrate by in situ Raman spectroscopy that, depending on the PM ionic radius, it is possible to create PM鈥揷eria solid solutions. We observed that this structural modification prevails under an oxidizing atmosphere, whereas electronic and chemical interactions take place under reducing conditions.