Evidence for an active oxygen species on Au/TiO2(110) model catalysts during investigation with in situ X-ray photoelectron spectroscopy
Evidence for an active oxygen species on Au/TiO2(110) model catalysts during investigation with in situ X-ray photoelectron spectroscopy
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DOI：
10.1016/j.cattod.2011.09.035
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发表时间：
2012-02
期刊：
影响因子：
5.3
通讯作者：
Karifala Dumbuya;G. Cabailh;R. Lazzari;J. Jupille;L. Ringel;M. Pistor;O. Lytken;H. Steinrück;J. M. Gottfried
中科院分区：
文献类型：
--
作者：
Karifala Dumbuya;G. Cabailh;R. Lazzari;J. Jupille;L. Ringel;M. Pistor;O. Lytken;H. Steinrück;J. M. Gottfried
采用X射线光电子能谱（XPS）和原位（高压）XPS，在300 K、O2和/或CO压力为0.1- 1 mbar的条件下，研究了氧气（O2）和一氧化碳（CO）对尺寸范围为2- 3 nm的TiO 2（110）负载的Au纳米颗粒的影响。这些实验的目的是重新审视Au 4f核心水平的变化，如文献中所报道的，最重要的是，建立依赖的核心水平的变化的知识，存在一个最大的CO氧化反应。制备了两个覆盖率对应于最大值的样品（Au覆盖率0.14-0.2 ML，粒度估计为1.2 - 2.5 nm），而第三个样品预期反应性较低（Au覆盖率0.4 ML，粒度估计为1.3 nm）。在升高的O2压力下，在所有颗粒尺寸下都演化出具有更高结合能（相对于Au（0）体信号为2.4-2.6eV）的新的Au 4f组分。它的出现归因于辐射诱导的氧的活化和金的同时氧化。活化在0.2 -2.5nm颗粒上更有效。的氧化物组分的相对强度强烈依赖于O2压力，因此，对O2的平衡覆盖。尽管在0.1mbar O2中不存在，无论暴露时间和颗粒大小如何，但在1 mbar氧气压力下，它主导了尺寸为1.2 -2.5nm的颗粒的Au 4f光谱。这种压力依赖的形成调和以前相互矛盾的XPS数据。最后，活性氧物种对CO非常活泼，如在CO和O2的1：1混合物中新的Au 4f组分的快速消失所证明的。发现该组分的演化和消耗速率取决于金覆盖率（因此，颗粒大小），并且对于较小的颗粒最高。
The influence of oxygen (O2) and carbon monoxide (CO) on Au nanoparticles supported on TiO2(110) in the size range of 2–3nm has been studied using X-ray photoelectron spectroscopy (XPS) and in situ (high pressure) XPS at 300K for O2and/or CO pressures of 0.1–1mbar. These experiments were aimed at revisiting Au 4f core level shifts as reported in the literature and most importantly, to establish the dependence of the core-level shifts on the knowledge that there exists a maximum in reactivity for CO oxidation. Two samples were prepared with a coverage corresponding to that maximum (Au coverage 0.14–0.2 ML, particle size estimated to ∼2–2.5nm) while a third sample was expected to be less reactive (Au coverage 0.4 ML, particle size estimated to ∼3.3nm). At elevated O2pressures, a new Au 4f component at higher binding energy (2.4–2.6eV relative to the Au(0) bulk signal) evolved at all particle sizes. Its appearance was attributed to a radiation-induced activation of oxygen and simultaneous oxidation of gold. The activation was much more efficient on the ∼2–2.5nm particles. The relative intensity of the oxide component depended strongly on O2pressure and, thus, on the equilibrium coverage of O2. While not present in 0.1mbar O2regardless of exposure time and particle size, it dominated the Au 4f spectrum of particles ∼2–2.5nm in size at 1mbar oxygen pressure. This pressure-dependent formation reconciles previously conflicting XPS data. Finally, the activated oxygen species were very reactive toward CO as manifested by the rapid disappearance of the new Au 4f component in a 1:1 mixture of CO and O2. The rates of evolution and consumption of this component were found to depend on gold coverage (and thus, particle size) and were highest for the smaller particles.