Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
Phys Chem Chem Phys. 2012 Apr 28;14(16):5769-77. doi: 10.1039/c2cp00061j. Epub 2012 Mar 20.
In this paper, we investigated the primary reduction and oxygen replenishing processes over Mn substitutionally doped CeO(2)(111) surfaces by density functional theory with the on-site Coulomb correction (DFT + U). The results indicated that Mn doping could make the surface much more reducible and the adsorbed O(2) could be effectively activated to form superoxo (O(2)(-)) and/or peroxo species (O(2)(2-)). The Mn doping induced the Mn 3d-O 2p gap state instead of Ce 4f acting as an electrons acceptor and donor during the first oxygen vacancy formation and O(2) replenishing, which helped to lower the formation energy of the first and second oxygen vacancies to -0.46 eV and 1.40 eV, respectively. In contrast, the formation energy of a single oxygen vacancy in the pure ceria surface was 2.08 eV and only peroxo species were identified as the O(2) molecule adsorbed. Our work provides a theoretical and electronic insight into the catalytic redox processes of Mn doped ceria surfaces, which may help to understand the enhanced catalytic performances of MnO(x)-CeO(2) oxides, as reported in previous experimental works.
本文通过含局域库仑修正的密度泛函理论（DFT + U）研究了 Mn 取代掺杂 CeO(2)(111)表面的初步还原和氧补充过程。结果表明，Mn 掺杂可以使表面更具还原性，吸附的 O(2) 可以被有效激活，形成超氧（O(2)(-)) 和/或过氧物种（O(2)(2-))。Mn 掺杂诱导了 Mn 3d-O 2p 间隙态而不是 Ce 4f 在第一个氧空位形成和 O(2)补充过程中充当电子受体和供体，这有助于降低第一个和第二个氧空位的形成能分别降至-0.46 eV 和 1.40 eV。相比之下，纯氧化铈表面上单个氧空位的形成能为 2.08 eV，仅鉴定出过氧物种作为吸附的 O(2)分子。我们的工作为 Mn 掺杂氧化铈表面的催化氧化还原过程提供了理论和电子见解，这可能有助于理解先前实验工作中报道的 MnO(x)-CeO(2)氧化物增强的催化性能。
