Role of Small Pd Ensembles in Boosting CO Oxidation in AuPd Alloys

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• 作者：Hyung Chul Ham ; J. Adam Stephens ; Gyeong S. Hwang ; Jonghee Han ; Suk Woo Nam ; Tae Hoon Lim
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2012
• 出版时间：March 1, 2012
• 年：2012
• 卷：3
• 期：5
• 页码：566-570
• 全文大小：285K
• 年卷期：v.3,no.5(March 1, 2012)
• ISSN：1948-7185

文摘

We present a theoretical explanation on how PdAu alloy catalysts can enhance the oxidation of CO molecules based on density functional theory calculations of CO adsorption and oxidation on AuPd/Pd(111) surfaces. Our study suggests that the enhanced activity is largely attributed to the possible existence of 鈥減artially-poisoned鈥?Pd ensembles that accommodate fewer CO molecules than Pd atoms. Whereas the oxidation of preadsorbed CO is likely governed by O₂ trapping, our study shows that small Pd ensembles such as dimers and compact trimers tend to provide more active sites than larger ensembles; CO adsorbed on a Pd monomer is found to react hardly with O₂ to form CO₂. In addition, we find the tendency of CO-induced Pd agglomeration, which may in turn facilitate CO oxidation by creating more dimers and compact trimers as compared with the adsorbate-free surface where monomers are likely prevailing.

Keywords:

palladium鈭抔old alloys; surface ensembles; CO oxidation