Mechanistic Studies of Water鈥揋as-Shift Reaction on Transition Metals
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- 作者：Chia-Hao Lin ; Chung-Liang Chen ; Jeng-Han Wang
- 刊名：Journal of Physical Chemistry C
- 出版年：2011
- 出版时间：September 29, 2011
- 年：2011
- 卷：115
- 期：38
- 页码：18582-18588
- 全文大小：887K
- 年卷期：v.115,no.38(September 29, 2011)
- ISSN：1932-7455
文摘
A density functional theory (DFT) calculation has been carried out to investigate a water鈥揼as-shift reaction (WGSR) on a series of chemical related materials of Co, Ni, and Cu (from the 3d row); Rh, Pd, and Ag (from the 4d row); and Ir, Pt, and Au (from the 5d row). The result shows that WGSR mechanism involves the redox, carboxyl, and formate pathways, which correspond to CO* + O* 鈫?CO2(g), CO* + OH* 鈫?COOH* 鈫?CO2(g) + H*, and CO* + H* + O* 鈫?CHO* + O* 鈫?HCOO** 鈫?CO2(g) + H*, respectively. The reaction barriers in the three pathways are competitive and have a similar trend that groups 9 > 10 > 11 and 3d > 4d >5d. Thus, the bottom-right d-block metals (Cu, Pt, and Au) show better WGSR activity. The experimentally most observed formate can be attributed to its lower formation and higher dissociation barriers. Furthermore, the catalytic behavior on these active metal surfaces has been examined. The result shows that WGSR is mostly follows the redox pathway on Au(111) surface due to the negligible CO* oxidation barriers; on the other hand, all the three pathways contribute similarly in WGSR on Cu(111) and Pt(111) surfaces. Finally, the feasible steps of formyl in Fischer鈥揟ropsch synthesis (FTS), the combustion reaction, and formate pathway, CHO* 鈫?CH* + O*, CHO* 鈫?CO* + H*, and CHO* + O* 鈫?HCOO**, respectively, have also been studied. The result shows that activities of FTS and the WGSR have opposite trends on these metal surfaces.