Single Pd Atom Embedded in CeO2(111) for NO Reduction with CO: A First-Principles Study

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• 作者：Wu-Chen Ding ; Xiang-Kui Gu ; Hai-Yan Su ; Wei-Xue Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 12, 2014
• 年：2014
• 卷：118
• 期：23
• 页码：12216-12223
• 全文大小：441K
• 年卷期：v.118,no.23(June 12, 2014)
• ISSN：1932-7455

文摘

Environmental and economic constraints necessitate further improvement of the activity and selectivity of dispersed Pd, Rh, and Pt metals for use in NO_x reduction. We present here a density functional theory plus U study of NO reduction with CO catalyzed by a single Pd₁ atom embedded in CeO₂(111) (noted as Pd₁/CeO₂(111)). The complete catalytic cycle for NO + CO 鈫?CO₂ + 1/2N₂, including competitive adsorption of reactants, generation of the oxygen vacancy by CO, formation of N₂O₂* intermediates, scission of N鈥揙 bonds, and formation of N₂, is mapped out. The calculations indicate that Pd₁/CeO₂(111) is active and selective toward N₂, in agreement with available experimental literature. The key intermediate N₂O₂* toward N₂ is identified, and the rate-limiting step is the first deoxygenation step of N₂O₂* with a barrier of 1.43 eV. The Pd₁鈥揙_V pair embedded in CeO₂(111) is proposed to be the active site, responsible not only for the formation of N₂O₂* by the reaction of two NO molecules but also for the subsequent two deoxygenation steps to make N₂. Detailed electronic structure analysis indicates that the formation of the Pd₁鈥揙_V pair and the synergetic effect between Pd 4d electron and reducibility of CeO₂ are responsible for the catalytic activity of single Pd atom embedded in ceria.