Sum frequency generation vibrational spectroscopy at solid-gas interfaces: CO adsorption on Pd model catalysts at ambient pressure
Sum frequency generation vibrational spectroscopy at solid-gas interfaces: CO adsorption on Pd model catalysts at ambient pressure
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DOI：
10.1016/s0039-6028(01)01907-0
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发表时间：
2002-04-10
期刊：
影响因子：
1.9
通讯作者：
Freund, HJ
中科院分区：
文献类型：
--
作者：
Rupprechter, G;Unterhalt, H;Freund, HJ
通过振动和频发生光谱法在10（-8）至1000 mbar和100至400 K范围内研究了一氧化碳在Pd（111）和Al 2 O3/NiAl（110）负载的Pd纳米颗粒上的吸附。在高真空（近似10（-7）mbar，95 K）和高压（例如大于或等于1 mbar，190 K）下在Pd（111）上观察到相同的CO饱和结构，没有压力诱导的表面重排的迹象。特别注意在高压下可能发生的实验伪影，可能被误解为“高压效应”。CO在富含缺陷的Pd（111）上的振动光谱显示出一个额外的峰，该峰源自CO与缺陷（台阶或边缘）位点的结合。负载型Pd纳米颗粒上的CO吸附质结构与Pd（111）不同，但更类似于阶梯状Pd（111）。在低压（10（-7）mbar CO）下，吸附物结构强烈依赖于I d形态，揭示了负载纳米颗粒和单晶表面的吸附性质的具体差异。在高压（例如200毫巴CO）下，这些差异甚至更明显。在Pd（111）上的突出的高覆盖度CO结构不能在Pd颗粒上建立。然而，尽管在结构上的差异，以及刻面和粗糙的I'd纳米粒子几乎相同的吸附位点occupations在这两种情况下观察到在200毫巴CO。Pd/Al 2 O3/NiAl（110）的催化活性的初步测试乙烯加氢在I巴显示了显着的活性和稳定性的模型系统的催化性能类似浸渍催化剂。(C)2002 Elsevier Science B. V.保留所有权利。
Carbon monoxide adsorption on Pd(111) and Pd nanoparticles supported by Al2O3/NiAl(110) was examined by vibrational sum frequency generation spectroscopy from 10(-8) to 1000 mbar, and from 100 to 400 K. Identical CO saturation structures were observed on Pd(111) under ultrahigh vacuum (similar to10(-7) mbar, 95 K) and at high pressure (e.g. greater than or equal to 1 mbar, 190 K) with no indications of pressure-induced surface rearrangements. Special attention was paid to experimental artifacts that may occur under elevated pressure and may be misinterpreted as "high pressure effects". Vibrational spectra of CO on defect-rich Pd(111) exhibited an additional peak that originated from CO bound to defect (step or edge) sites. The CO adsorbate structure on supported Pd nanoparticles was different from Pd(111) but more similar to stepped Pd(111). At low pressure (10(-7) mbar CO) the adsorbate structure depended strongly on the I'd morphology revealing specific differences in the adsorption properties of supported nanoparticles and single crystal surfaces. At high pressure (e.g. 200 mbar CO) these differences were even more pronounced. Prominent high coverage CO structures on Pd(111) could not be established on Pd particles. However, in spite of structural differences between well faceted and rough I'd nanoparticles nearly identical adsorption site occupancies were observed in both cases at 200 mbar CO. Initial tests of the catalytic activity of Pd/Al2O3/NiAl(110) for ethylene hydrogenation at I bar revealed a remarkable activity and stability of the model system with catalytic properties similar to impregnated catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.