Institute of Chemistry, Humboldt-Universität zu Berlin , Unter den Linden 6, 10099 Berlin, Germany.
J Am Chem Soc. 2013 Dec 26;135(51):19222-8. doi: 10.1021/ja408772p. Epub 2013 Dec 10.
Ultrathin Fe-doped silicate films were prepared on a Ru(0001) surface and, as a function of the Fe/Si ratio, structurally characterized by low-energy electron diffraction, X-ray photoelectron spectroscopy, infrared reflection-absorption spectroscopy, and scanning tunneling microscopy. Density functional theory (DFT) was used to identify the atomic structure. The results show that uniform substitution of Si by Fe in the silicate bilayer frame is thermodynamically unfavorable: the film segregates into a pure silicate and an Fe-silicate phase. The DFT calculations reveal that the Fe-silicate film with an Fe/Si = 1:1 ratio consists of a monolayer of [SiO4] tetrahedra on top of an iron oxide monolayer. As such, it closely resembles the structure of the clay mineral nontronite, a representative of the Fe-rich smectites. Furthermore, the DFT calculations predict formation of bridging Fe-O-Ru bonds between the Fe-silicate film and the Ru substrate accompanied by charge transfer from the metal substrate to the film, so that iron is in the oxidation state +III as in nontronite.
在 Ru(0001) 表面上制备了超薄的 Fe 掺杂硅酸盐薄膜，并通过低能电子衍射、X 射线光电子能谱、红外反射吸收光谱和扫描隧道显微镜对其作为 Fe/Si 比的函数进行了结构表征。使用密度泛函理论 (DFT) 来确定原子结构。结果表明，硅在硅酸盐双层框架中被均匀取代 Fe 在热力学上是不利的：薄膜会分离成纯硅酸盐和 Fe-硅酸盐相。DFT 计算表明，具有 Fe/Si = 1:1 比的 Fe-硅酸盐薄膜由顶部的氧化亚铁单层上的[SiO4]四面体单层组成。因此，它非常类似于富铁蒙脱石层状硅酸盐粘土矿物蒙脱石的结构。此外，DFT 计算预测在 Fe-硅酸盐薄膜和 Ru 基底之间形成桥接的 Fe-O-Ru 键，同时金属基底向薄膜转移电荷，使得铁处于 +III 氧化态，如蒙脱石中一样。
