Yee Nelson, Chottiner Gary S, Scherson Daniel A
Departments of Chemistry and Physics, Case Western Reserve University, Cleveland, OH 44106, USA.
J Phys Chem B. 2005 Mar 31;109(12):5707-12. doi: 10.1021/jp044641i.
The vibrational spectra of CO adsorbed on Ru-modified Pt(100) surfaces prepared by chemical vapor deposition (condensation of Ru(3)(CO)(12) at 105 K followed by X-ray irradiation and thermal decomposition at 650 K in ultrahigh vacuum, UHV) was investigated by time-resolved infrared reflection absorption spectroscopy (IRAS) in UHV. Spectra were recorded while Ru/Pt(100) bimetallic surfaces (theta(Ru) = 0.24 and 0.52 by X-ray photoelectron spectroscopy, XPS) were dosed with gas-phase CO. Analysis of the data revealed that for a wide range of calibrated CO exposures, the linear CO-stretching region displays two features: a higher energy peak (2085-2100 cm(-1)), attributed to CO adsorbed on pristine Pt(100) sites, and a lower energy peak (2066-2092 cm(-1)), ascribed to adsorption of CO on sites on the surface induced by the presence of Ru. Similar experiments were performed on bimetallic specimens annealed repeatedly in UHV to 650 K to promote partial Ru dissolution into the lattice and thus render surfaces gradually enriched in Pt. For all surfaces and CO exposures examined, the total integrated area under the two CO spectral features remained fairly constant and equal in value to the corresponding areas found for bare Pt(100). If it is assumed that a fixed exposure leads to a fixed coverage on both bare and Ru-modified Pt(100)surfaces, and the thermal treatment leads to an exchange of Ru by Pt sites without altering significantly the total number of metal sites on the surface, the absorption cross sections for both of these peaks are virtually the same.
通过超高真空（UHV）中的时间分辨红外反射吸收光谱（IRAS）研究了化学气相沉积制备的Ru修饰的Pt(100)表面（105 K下Ru(3)(CO)(12)冷凝，随后进行X射线辐照并在650 K下超高真空中热分解）上吸附的CO的振动光谱。在向Ru/Pt(100)双金属表面（通过X射线光电子能谱（XPS）测得θ(Ru)=0.24和0.52）通入气相CO时记录光谱。数据分析表明，在广泛的校准CO暴露范围内，线性CO伸缩区域显示出两个特征：一个较高能量的峰（2085 - 2100 cm(-1)），归因于吸附在原始Pt(100)位点上的CO；一个较低能量的峰（2066 - 2092 cm(-1)），归因于Ru的存在诱导的表面位点上CO的吸附。对在超高真空中反复退火至650 K以促进部分Ru溶解到晶格中从而使表面逐渐富含Pt的双金属试样进行了类似实验。对于所有检查的表面和CO暴露情况，两个CO光谱特征下的总积分面积保持相当恒定，并且与裸Pt(100)相应区域的值相等。如果假设固定暴露导致裸Pt(100)和Ru修饰的Pt(100)表面上的覆盖度固定，并且热处理导致Ru被Pt位点交换而不会显著改变表面上金属位点的总数，则这两个峰的吸收截面实际上是相同的。
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