Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary.
Langmuir. 2010 Nov 2;26(21):16312-24. doi: 10.1021/la1014913.
Gold based model systems exhibiting the structural versatility of nanoparticle ensembles and being accessible for surface spectroscopic investigations are expected to provide new information about the adsorption of carbon monoxide, a key process influencing the CO oxidation activity of this noble metal in nanoparticulate form. Accordingly, in the present work the interaction of CO is studied with an ion bombardment modified Au(111) surface by means of a combination of photoelectron spectroscopy (XPS and UPS), sum frequency generation vibrational spectroscopy (SFG), and scanning tunneling microscopy (STM). While no adsorption was found on intact Au(111), data collected on the ion bombarded surface at cryogenic temperatures indicated the presence of stable CO adsorbates below 190 K. A quantitative evaluation of the C 1s XPS spectra and the surface morphology explored by STM revealed that the step edge sites created by ion bombardment are responsible for CO adsorption. The identification of the CO binding sites was confirmed by density functional theory (DFT) calculations. Annealing experiments up to room temperature showed that at temperatures above 190 K unstable adsorbates are formed on the surface under dynamic exposure conditions that disappeared immediately when gaseous CO was removed from the system. Spectroscopic data as well as STM records revealed that prolonged CO exposure at higher pressures of up to 1 mbar around room temperature facilitates massive atomic movements on the roughened surface, leading to its strong reordering toward the structure of the intact Au(111) surface, accompanied by the loss of the CO binding capacity.
基于金的模型系统展示了纳米粒子集合的结构多样性，并且可以进行表面光谱研究，预计将提供有关一氧化碳吸附的新信息，一氧化碳的吸附是影响该贵金属在纳米颗粒形式下 CO 氧化活性的关键过程。因此，在本工作中，通过光电发射光谱（XPS 和 UPS）、和频产生振动光谱（SFG）以及扫描隧道显微镜（STM）的组合，研究了 CO 与离子轰击修饰的 Au(111)表面的相互作用。虽然在完整的 Au(111)表面上没有发现吸附，但在低温下收集的离子轰击表面上的数据表明，在 190 K 以下存在稳定的 CO 吸附物。对 C 1s XPS 光谱和 STM 探测的表面形貌的定量评估表明，离子轰击产生的台阶边缘位点是 CO 吸附的原因。CO 结合位点的鉴定通过密度泛函理论（DFT）计算得到了证实。直至室温的退火实验表明，在高于 190 K 的温度下，在动态暴露条件下在表面上形成了不稳定的吸附物，当从系统中除去气态 CO 时，这些吸附物立即消失。光谱数据以及 STM 记录表明，在室温下高达 1 mbar 的较高压力下长时间暴露于 CO 会促进粗糙表面上的大量原子运动，导致其强烈地重新排列到完整的 Au(111)表面结构，同时失去 CO 的结合能力。
