Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland.
J Chem Phys. 2009 Dec 28;131(24):244702. doi: 10.1063/1.3271910.
In this paper we use density functional theory corrected for on-site Coulomb interactions (DFT+U) to study the adsorption of CO at La-doped ceria (111) and (110) surfaces. Doping of ceria with La is known to enhance oxidation of CO to CO(2) and this study investigates the atomic level details of this reaction. With La(3+) doping, an [La(3+)-O(-)] defect state with an oxygen hole is formed at both surfaces. The formation energy of an oxygen vacancy is reduced and vacancy formation results in the appearance of Ce(3+), instead of hole compensation. On the doped surfaces weak and strong adsorption of CO is found. In the former, the molecule remains intact. In the latter, the final adsorption species depends strongly on the surface and whether oxygen vacancies are present or not. On (111) a CO(2)-like species forms, while on the (110) surface, mono- or bidentate carbonates are present. La-doping of ceria surfaces shows enhanced reactivity over the undoped surfaces and we discuss the origin of the enhanced reactivity and the nature of the surface species upon CO adsorption.
在本文中，我们使用考虑局域库仑相互作用的密度泛函理论（DFT+U）来研究 CO 在 La 掺杂氧化铈（111）和（110）表面上的吸附。已知 CeO2 中掺杂 La 可以增强 CO 氧化为 CO2，本研究探讨了该反应的原子水平细节。La(3+) 掺杂在两个表面上形成了一个带有氧空位的 [La(3+)-O(-)] 缺陷态。氧空位的形成能降低，空位形成导致 Ce(3+) 的出现，而不是空穴补偿。在掺杂表面上，CO 表现出弱吸附和强吸附。在前者中，分子保持完整。在后者中，最终的吸附物种强烈依赖于表面和是否存在氧空位。在（111）表面上形成类似 CO2 的物种，而在（110）表面上，则存在单齿或双齿碳酸盐。CeO2 表面的 La 掺杂表现出比未掺杂表面更高的反应活性，我们讨论了增强反应性的起源以及 CO 吸附时表面物种的性质。
