Methane Oxidation Mechanism on Pt(111): A Cluster Model DFT Study
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- 作者：George Psofogiannakis ; Alain St-Amant ; Marten Ternan
- 刊名：Journal of Physical Chemistry B
- 出版年：2006
- 出版时间：December 7, 2006
- 年：2006
- 卷：110
- 期：48
- 页码：24593 - 24605
- 全文大小：933K
- 年卷期：v.110,no.48(December 7, 2006)
- ISSN：1520-5207
文摘
The electronic energy barriers of surface reactions pertaining to the mechanism of the electrooxidation ofmethane on Pt (111) were estimated with density functional theory calculations on a 10-atom Pt cluster,using both the B3LYP and PW91 functionals. Optimizations of initial and transition states were performedfor elementary steps that involve the conversion of CH4 to adsorbed CO at the Pt/vacuum interface. As a firstapproximation we do not include electrolyte effects in our model. The reactions include the dissociativechemisorption of CH4 on Pt, dehydrogenation reactions of adsorbed intermediates (*CHx 
*CHx-1 + *Hand *CHxO *CHx-1O + *H), and oxygenation reactions of adsorbed CHx species (*CHx + *OH *CHxOH). Many pathways were investigated and it was found that the main reaction pathway is CH4 *CH3 *CH2 *CH *CHOH *CHO *CO. Frequency analysis and transition-state theory were employedto show that the methane chemisorption elementary step is rate-limiting in the above mechanism. Thisconclusion is in agreement with published experimental electrochemical studies of methane oxidation onplatinum catalysts that have shown the absence of an organic adlayer at electrode potentials that allow theoxidation of adsorbed CO. The mechanism of the electrooxidation of methane on Pt is discussed.
*CHx-1 + *Hand *CHxO *CHx-1O + *H), and oxygenation reactions of adsorbed CHx species (*CHx + *OH *CHxOH). Many pathways were investigated and it was found that the main reaction pathway is CH4 *CH3 *CH2 *CH *CHOH *CHO *CO. Frequency analysis and transition-state theory were employedto show that the methane chemisorption elementary step is rate-limiting in the above mechanism. Thisconclusion is in agreement with published experimental electrochemical studies of methane oxidation onplatinum catalysts that have shown the absence of an organic adlayer at electrode potentials that allow theoxidation of adsorbed CO. The mechanism of the electrooxidation of methane on Pt is discussed.