Insights into the Preference of CO2 Formation from HCOOH Decomposition on Pd Surface: A Theoretical Study

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• 作者：Riguang Zhang ; Hongyan Liu ; Baojun Wang ; Lixia Ling
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：October 25, 2012
• 年：2012
• 卷：116
• 期：42
• 页码：22266-22280
• 全文大小：831K
• 年卷期：v.116,no.42(October 25, 2012)
• ISSN：1932-7455

文摘

The mechanism of HCOOH decomposition on Pd(111) surface leading to the formation of CO₂ and CO has been systematically investigated to identify the preference of CO₂ or CO as the dominant product. Here, we present the main results obtained from periodic, self-consistent density functional theory calculations. Four possible pathways of HCOOH decomposition, initiated by the activation of the O鈥揌, C鈥揌, and C鈥揙 bonds of HCOOH, as well as the activation of simultaneous C鈥揌 and C鈥揙 bonds of HCOOH, have been proposed and discussed. Then, the effects of coadsorbed H₂O and its coverage on the decomposition of HCOOH have been also considered. Our results show that CO₂ is preferentially formed as the dominant product of HCOOH decomposition on Pd(111) surface via a dual-path mechanism, which involves both the carboxyl (trans-COOH) and formate (bi-HCOO) intermediates, along with alternative bond-breaking possible steps in those intermediates. The dehydrogenation of HCOOH on Pd surface is a vital process for CO₂ formation. Further, the coadsorbed H₂O and its coverage play an important role in the decomposition of HCOOH, and the preferred catalytic pathway of CO₂ formation is qualitatively dependent on surface H₂O coverage. Therefore, our results would at the microscopic level provide insights into the mechanism, energetics, and possible reactive intermediates of HCOOH decomposition regarding the preference of CO₂ formation as the dominant product for the catalytic reactions involving HCOOH and for a direct HCOOH fuel cell on Pd system.