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Development of Energy-Dispersed Surface XAFS Method

能量色散表面XAFS方法的发展

基本信息

批准号：
12440193
负责人：
TOSHIHIKO Yokoyama
金额：
$ 9.92万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440193/
关键词：
Dispersed XAFS Time-resolved Molccular Adsorption Surface Reaction

项目摘要

The purpose of this research project is to develop a novel surface XAFS technique using energy-dispersed soft x rays and to apply it to studies of surface reactions as a tool for real-time monitoring of the reactions. In the first year of this project, we constructed the experimental setup for the dispersed-surface-XAFS at beamline 7A in KEK-PF that belongs to Research Center for Spectrochemistry of the University of Tokyo. With this technique, the typical data acquisition time is reduced by a factor of ten compared to the conventional method, which enables us to conduct in-situ tracing of surface dynamic processes. In the second year, this measurement system has been further improved by replacing a plane mirror with a cylindrical mirror to obtain better photon focusing on the sample and by modification of the electron lens system of the spatially-resolved electron energy analyzer to get better electron focusing on the detector, which resulted in significant increases both hi signal intensity and energy resolution. Furthermore, this technique was applied to a surface reaction. The reaction studied here was CO oxidation reaction on Pt(111). Although this reaction is one of the most studied catalytic reactions, only recent STM study has provided information about the atomic-level aspect of the surface species under the reaction. The STM study seems to reveal the reaction mechanism but does not guarantee that all the surface species are clearly imaged and that the observed local area is representative of the whole surface. We have investigated this reaction with the dispersive-surface-XAFS technique in the same condition as used in the STM study and found two reaction processes with different reaction orders, one of which was not observable by STM due to fast diffusion of the reaction species. To summarize, we have successfully developed the dispersed-surface-XAFS technique as a new powerful tool for studies of surface dynamic processes.

本研究项目的目的是开发一种利用能量分散软x射线的新型表面XAFS技术，并将其应用于表面反应的研究，作为实时监测反应的工具。在项目的第一年，我们在属于东京大学光谱化学研究中心的KEK-PF的光束线7A处构建了分散表面xafs的实验装置。与传统方法相比，该技术的典型数据采集时间减少了十倍，使我们能够对地表动态过程进行原位跟踪。第二年，对该测量系统进行了进一步改进，将平面反射镜改为圆柱反射镜，以获得更好的光子对样品的聚焦；对空间分辨电子能量分析仪的电子透镜系统进行了改进，以获得更好的电子对探测器的聚焦，使得高信号强度和能量分辨率都得到了显著提高。此外，还将该技术应用于表面反应。本文研究的是CO在Pt（111）上的氧化反应。虽然该反应是研究最多的催化反应之一，但只有最近的STM研究才提供了反应下表面物质的原子水平方面的信息。STM研究似乎揭示了反应机制，但不能保证所有的表面物种都清晰成像，也不能保证观察到的局部区域代表整个表面。我们在与STM研究相同的条件下，用弥散表面- xafs技术对该反应进行了研究，发现了两个不同反应级数的反应过程，其中一个由于反应物质的快速扩散而无法被STM观察到。总之，我们已经成功地开发了分散表面- xafs技术，作为研究表面动态过程的一种新的有力工具。