一个分子束研究的CO氧化在Pd集群支持:集群大小的影响
Georges Sitja1, Claude R Henry1
1CNRS, CINaM, Aix-Marseille Univsersité, F-13288 Marseille, France. georges.sitja@cnrs.fr.
(Pd) 集群对一氧化碳 (CO) 氧化的催化活性随着集群大小的增加而增加. 较小的Pd集群由于与支持的相互作用而表现出较低的活动.
科学领域:
- 不同质的催化剂.
- 表面科学是一门科学.
- 纳米材料是一种纳米材料.
背景情况:
- (Pd) 集群是各种化学反应的关键催化剂,包括CO氧化.
- 了解集群大小对催化活性的影响对于催化剂设计至关重要.
- 金属集群及其支材料之间的相互作用显著影响了催化性能.
研究的目的:
- 为了研究大小控制的Pd集群在基支持上的CO氧化活性.
- 为了确定 Pd 集群大小和稳定状态周转频率 (TOF) 之间的关系.
- 阐明支持在调节Pd集群活动中的作用.
主要方法:
- 利用分子束方法在纳米结构膜上研究Pd集群 (5-180个原子).
- 在Ni3Al(111) 基板上生长了Pd集群,形成具有狭窄尺寸分布的六角阵列.
- 测量了平稳状态的周转频率 (TOF) 作为平均集群大小的函数.
主要成果:
- 对于CO氧化的TOF通常随着Pd集群大小的增加而增加.
- 在小于大约20个原子的集群中观察到TOF的快速增加.
- 对于较大的集群,TOF增长放缓,接近于180个原子的散装Pd单晶所见的值.
结论:
- 观察到的尺寸依赖活性归因于Pd原子与支持相互作用的催化性能降低.
- 较小的Pd集群的活性较低,因为在与支架的接口处,原子的比例较高.
- 优化催化剂性能需要考虑集群大小和金属支相互作用.
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