Promotion of Ceria Catalysts by Precious Metals: Changes in Nature of the Interaction under Reducing and Oxidizing Conditions
Promotion of Ceria Catalysts by Precious Metals: Changes in Nature of the Interaction under Reducing and Oxidizing Conditions
复制标题
DOI：
10.1021/jp212233u
复制
发表时间：
2012-06-28
影响因子：
3.7
通讯作者：
Collier, Paul
中科院分区：
文献类型：
--
作者：
Acerbi, Nadia;Golunski, Stan;Collier, Paul
通过在负载型贵金属（PM）催化剂上沉积二氧化铈并用原位漫反射UV（DR UV）和原位拉曼光谱对其进行表征，我们已经能够证明二氧化铈带隙的减小与金属在还原条件下的功函数之间的直接相关性。PM二氧化铈相互作用导致金属二氧化铈界面的二氧化铈侧的变化，使得二氧化铈表面上的氧空位形成的程度也与贵金属功函数相关。然而，X射线光电子能谱（XPS）分析不能提供纯粹的电子相互作用的确凿证据。相反，结果突出了PM氧化铈相互作用的复杂性，通过支持在还原条件下的电子相互作用产生的溢出机制。在氧化条件下，已观察到另一种效果，即，由PM阳离子的存在引起的二氧化铈的结构修饰。特别地，我们已经能够通过原位拉曼光谱证明，取决于PM离子半径，可以产生PM氧化铈固溶体。我们观察到，这种结构修饰在氧化气氛下盛行，而电子和化学相互作用发生在还原条件下。
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 ceria interaction results in changes on the ceria side of the metal ceria 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 ceria 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 ceria solid solutions. We observed that this structural modification prevails under an oxidizing atmosphere, whereas electronic and chemical interactions take place under reducing conditions.