Department of Chemistry, University of Nebraska-Lincoln , Lincoln, Nebraska 68588, United States.
J Am Chem Soc. 2014 Nov 12;136(45):15857-60. doi: 10.1021/ja508666a. Epub 2014 Oct 29.
We show Born-Oppenheimer molecular dynamics (BOMD) simulation evidence of the generation of oxygen vacancies at the golden cage Au16 and TiO2 (110) interface for CO oxidation. Unlike the conventional Langmuir-Hinshelwood (L-H) mechanism, the CO molecule adsorbed at the perimeter Au sites of Au16 tends to attack a nearby lattice oxygen atom on the TiO2 (110) surface rather than the neighboring co-adsorbed molecular O2. Our large-scale BOMD simulation provides, to our knowledge, the first real-time demonstration of feasibility of the Mars-van Krevelen (M-vK) mechanism as evidenced by the generation of oxygen vacancies on the TiO2 surface in the course of the CO oxidation. Furthermore, a comparative study of the CO oxidation at the golden cage Au18 and TiO2 interface suggests that the L-H mechanism is more favorable than the M-vK mechanism due to higher structural robustness of the Au18 cage. It appears that the selection of either M-vK or L-H mechanism for the CO oxidation is dependent on the structural fluxionality of the Au cage clusters on the TiO2 support.
我们展示了金笼 Au16 和 TiO2（110）界面上 CO 氧化产生氧空位的玻恩-奥本海默分子动力学（BOMD）模拟证据。与传统的 Langmuir-Hinshelwood（L-H）机制不同，吸附在 Au16 周边 Au 位的 CO 分子倾向于攻击 TiO2（110）表面上附近的晶格氧原子，而不是相邻共吸附的分子 O2。我们的大规模 BOMD 模拟提供了，据我们所知，第一个实时证明 Mars-van Krevelen（M-vK）机制可行性的例子，这是通过在 CO 氧化过程中 TiO2 表面上产生氧空位来证明的。此外，对 Au18 和 TiO2 界面上 CO 氧化的比较研究表明，由于 Au18 笼的结构稳定性更高，L-H 机制比 M-vK 机制更有利。似乎 CO 氧化中选择 M-vK 或 L-H 机制取决于 TiO2 载体上 Au 笼簇的结构流变性。
