增加的反向结合解释了纳米粒子上CO激活的阶段边缘反应性和粒子大小效应
Lucas Foppa1, Christophe Copéret1, Aleix Comas-Vives1
1Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir Prelog Weg 1-5, CH-8093 Zürich, Switzerland.
Journal of the American Chemical Society
|December 20, 2016
概括
小金属纳米颗粒 (NP) 对一氧化碳 (CO) 吸附和激活的反应性比较低. 这种令人惊的效果源于阶段边缘的化学结合的微妙差异,影响了CO裂变.
科学领域:
- 表面科学
- 材料化学
- 计算化学
背景情况:
- 一氧化碳 (CO) 是化学过程中的关键分子,其对金属纳米粒子 (NP) 的反应性受到粒子大小的显著影响.
- 较小的NP,尽管具有更多的阶段边缘原子,但与较大的NP相比,其反应性出乎意料地较低.
研究的目的:
- 在 (Ru) 纳米粒子上研究CO吸附和激活的颗粒大小依赖反应性.
- 阐明小和大NP之间观察到的反应性差异的分子水平起源.
主要方法:
- 使用明确的Ru纳米粒子模型 (1-2nm) 的第一原理计算.
- 晶体轨道汉密尔顿群 (COHP) 分析以研究分子轨道相互作用.
- 在阶段边缘位置分析CO协调 (η1和η2).
主要成果:
- 在小型和大型NP上,由于微妙的结合变化,阶段边缘位点 (B5,B6) 呈现大小依赖的反应性.
- CO 协调模式 (平面 η1 和形 η2) 影响了电子回捐和 CO 结合.
- 在较大的NP上,由于在η2模式下更广泛的Ru-O相互作用,使过渡状态稳定,因此CO裂变更容易.
结论:
- 小NP的反应性降低归因于在η2吸附模式下较弱的Ru-O相互作用,破坏了CO裂变过渡状态.
- 提供了分子层面的粒子大小对金属NP反应性的理解.
- 这些发现与对纳米颗粒的二氧化碳吸附和激活的实验观测一致.
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