Atomic-Structural Synergy for Catalytic CO Oxidation over Palladium鈥揘ickel Nanoalloys
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- 作者：Shiyao Shan ; Valeri Petkov ; Lefu Yang ; Jin Luo ; Pharrah Joseph ; Dina Mayzel ; Binay Prasai ; Lingyan Wang ; Mark Engelhard ; Chuan-Jian Zhong
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：May 14, 2014
- 年：2014
- 卷：136
- 期：19
- 页码：7140-7151
- 全文大小：642K
- 年卷期：v.136,no.19(May 14, 2014)
- ISSN：1520-5126
文摘
Alloying palladium (Pd) with other transition metals at the nanoscale has become an important pathway for preparation of low-cost, highly active and stable catalysts. However, the lack of understanding of how the alloying phase state, chemical composition and atomic-scale structure of the alloys at the nanoscale influence their catalytic activity impedes the rational design of Pd-nanoalloy catalysts. This work addresses this challenge by a novel approach to investigating the catalytic oxidation of carbon monoxide (CO) over palladium鈥搉ickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable maximal catalytic activity at Pd:Ni ratio of 50:50. Key to understanding the structural-catalytic synergy is the use of high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis to probe the atomic structure of PdNi nanoalloys under controlled thermochemical treatments and CO reaction conditions. Three-dimensional (3D) models of the atomic structure of the nanoalloy particles were generated by reverse Monte Carlo simulations (RMC) guided by the experimental HE-XRD/PDF data. Structural details of the PdNi nanoalloys were extracted from the respective 3D models and compared with the measured catalytic properties. The comparison revealed a strong correlation between the phase state, chemical composition and atomic-scale structure of PdNi nanoalloys and their catalytic activity for CO oxidation. This correlation is further substantiated by analyzing the first atomic neighbor distances and coordination numbers inside the nanoalloy particles and at their surfaces. These findings have provided new insights into the structural synergy of nanoalloy catalysts by controlling the phase state, composition and atomic structure, complementing findings of traditional density functional theory studies.