111) 双金属表面:在单层和覆盖层上具有独特的化学成分
Henry H Hwu1, Joseph Eng, Jingguang G Chen
1Center for Catalytic Science and Technology, Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA.
Journal of the American Chemical Society
|January 24, 2002
概括
在 (Pt) 上的单层 (Ni) 覆盖层对循环烯反应具有独特的化学反应性. 这项研究揭示了改变的结合和反应途径,增强化和抑制分解,与较厚的膜相比.
科学领域:
- 表面科学是一门学科.
- 催化剂是一种催化剂.
- 材料化学 材料化学
背景情况:
- 了解金属覆盖层的催化性能对于设计高效的催化剂至关重要.
- 过渡金属覆盖层在贵金属表面上的长轴增长允许精确控制表面结构和电子特性.
研究的目的:
- 为了比较单层Ni覆盖层在Pt(111) 上与干净的Pt(111) 和厚厚的Ni(111) 薄膜的化学反应,使用环素作为探针分子.
- 阐明环烯在这些不同表面上的吸附和反应机制.
主要方法:
- 温度编程绝吸法 (TPD) 是指温度编程绝吸法.
- 高分辨率电子能量损失光谱学 (HREELS) 是一种技术.
- 接近边缘的X射线吸收细结构 (NEXAFS) 光谱学.
主要成果:
- 环烯在单层Ni/Pt{111}上表现出独特的吸附和反应通路,与Pt{111}或厚Ni{111}相比.
- HREELS 和 NEXAFS 显示了环素在单层 Ni/Pt111 上的 pi 结合,而 Pt111 和 Ni111 上的 di-sigma 结合.
- 在单层Ni/Pt上观察到一个新的化路径在245K,在D2预曝光时,循环素产量增加了5倍,在单层Ni/Pt上观察到一个新的化路径.
- 在单层Ni上,循环烯的完整分解被显著抑制 (<2%),而厚的Ni则被抑制 (<111) (69%).
结论:
- 单层Ni/Pt111的独特化学成分归因于较弱的吸附剂-表面相互作用.
- 控制金属覆盖层厚度为操纵催化性能提供了一种方法.
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