Atomic-Structural Synergy for Catalytic CO Oxidation over Palladium-Nickel Nanoalloys
Atomic-Structural Synergy for Catalytic CO Oxidation over Palladium-Nickel Nanoalloys
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DOI：
10.1021/ja5026744
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发表时间：
2014-05-14
影响因子：
15
通讯作者：
Zhong, Chuan-Jian
中科院分区：
文献类型：
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作者：
Shan, Shiyao;Petkov, Valeri;Zhong, Chuan-Jian
钯与其他过渡金属在纳米尺度上合金化是制备低成本、高活性、高稳定性催化剂的重要途径。然而，缺乏了解的合金相状态，化学组成和纳米合金的原子尺度结构如何影响其催化活性，阻碍了钯纳米合金催化剂的合理设计。这项工作解决了这一挑战，通过一种新的方法来研究一氧化碳（CO）在钯镍（PdNi）纳米合金上的催化氧化，该合金具有明确的组成，其在Pd：Ni比为50：50时具有显着的最大催化活性。理解结构-催化协同作用的关键是使用高能同步加速器X射线衍射耦合原子对分布函数（HE-XRD/PDF）分析来探测受控热化学处理和CO反应条件下PdNi纳米合金的原子结构。纳米合金颗粒的原子结构的三维（3D）模型是由实验HE-XRD/PDF数据指导的反向蒙特卡罗模拟（RMC）生成的。从相应的3D模型中提取PdNi纳米合金的结构细节，并与测得的催化性能进行比较。结果表明，PdNi纳米合金的相态、化学组成和原子尺度结构与其催化CO氧化活性之间存在着很强的相关性。通过分析纳米合金颗粒内部和表面的第一原子近邻距离和配位数，进一步证实了这种相关性。这些发现通过控制相态、组成和原子结构，为纳米合金催化剂的结构协同作用提供了新的见解，补充了传统密度泛函理论研究的结果。
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 nickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable maximal catalytic activity at Pd:Ni ratio of similar to 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.