Activated Adsorption of Ethylene on Atomic-Oxygen-Covered Ag(100) and Ag(210): Formation of an Oxametallacycle
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- 作者：Anton Kokalj ; Paola Gava ; Stefano de Gironcoli ; Stefano Baroni
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：January 31, 2008
- 年：2008
- 卷：112
- 期：4
- 页码：1019 - 1027
- 全文大小：668K
- 年卷期：v.112,no.4(January 31, 2008)
- ISSN：1932-7455
文摘
The activated adsorption of ethylene on atomic-oxygen-covered Ag(100) surface and on an open-type stepedge thereon was studied using density-functional-theory. On perfect Ag(100), such adsorption results in theformation of an oxametallacycle (OMC), with an activation energy slightly larger than 0.3 eV. We find thatthis activation energy is only weakly dependent on the coverage of on-surface oxygen (for 
1/2 ML),whereas the OMC-surface interaction is substantially reduced at high oxygen coverage. Three types of OMCshave been identified on the (100) surface, which display similar stability, and the transformation betweenthem is facile with activation energies below 0.1 eV. We find that the presence of subsurface oxygen reducesthe activation energy for OMC formation and substantially increases the OMC-surface interaction. Thereactivity of the step edge toward the OMC formation strongly depends on the local coverage of oxygen. Ourcalculations indicate that the relative stability of the OMC intermediate in ethylene epoxidation reaction isstrongly affected by the coverage and configuration of chemisorbed oxygen.
1/2 ML),whereas the OMC-surface interaction is substantially reduced at high oxygen coverage. Three types of OMCshave been identified on the (100) surface, which display similar stability, and the transformation betweenthem is facile with activation energies below 0.1 eV. We find that the presence of subsurface oxygen reducesthe activation energy for OMC formation and substantially increases the OMC-surface interaction. Thereactivity of the step edge toward the OMC formation strongly depends on the local coverage of oxygen. Ourcalculations indicate that the relative stability of the OMC intermediate in ethylene epoxidation reaction isstrongly affected by the coverage and configuration of chemisorbed oxygen.