Xu Tao, Schwarz Matthias, Werner Kristin, Mohr Susanne, Amende Max, Libuda Jörg
Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany), Fax.
Erlangen Catalysis Resource Center and Interdisciplinary Center Interface Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany.
Chemistry. 2016 Apr 4;22(15):5384-96. doi: 10.1002/chem.201504810. Epub 2016 Mar 2.
We have performed a model study to explore the influence of surface structure on the anchoring of organic molecules on oxide materials. Specifically, we have investigated the adsorption of phthalic acid (PA) on three different, well-ordered, and atomically defined cobalt oxide surfaces, namely 1) Co3O4(111), 2) CoO(111), and 3) CoO(100) on Ir(100). PA was deposited by physical vapor deposition (PVD). The formation of the PA films and interfacial reactions were monitored in situ during growth by isothermal time-resolved IR reflection absorption spectroscopy (TR-IRAS) under ultrahigh vacuum (UHV) conditions. We observed a pronounced structure dependence on the three surfaces with three distinctively different binding geometries and characteristic differences depending on the temperature and coverage. 1) PA initially binds to Co3O4(111) through the formation of a chelating bis-carboxylate with the molecular plane oriented perpendicularly to the surface. Similar species were observed both at low temperature (130 K) and at room temperature (300 K). With increasing exposure, chelating mono-carboxylates became more abundant and partially replaced the bis-carboxylate. 2) PA binds to CoO(100) in the form of a bridging bis-carboxylate for low coverage. Upon prolonged deposition of PA at low temperature, the bis-carboxylates were converted into mono-carboxylate species. In contrast, the bis-carboxylate layer was very stable at 300 K. 3) For CoO(111) we observed a temperature-dependent change in the adsorption mechanism. Although PA binds as a mono-carboxylate in a bridging bidentate fashion at low temperature (130 K), a strongly distorted bis-carboxylate was formed at 300 K, possibly as a result of temperature-dependent restructuring of the surface. The results show that the adsorption geometry of PA depends on the atomic structure of the oxide surface. The structure dependence can be rationalized by the different arrangements of cobalt ions at the three surfaces.
我们进行了一项模型研究，以探讨表面结构对有机分子在氧化物材料上锚定的影响。具体而言，我们研究了邻苯二甲酸（PA）在三种不同的、有序的且原子级明确的氧化钴表面上的吸附情况，即1）Co3O4(111)，2）CoO(111)，以及3）Ir(100)上的CoO(100)。PA通过物理气相沉积（PVD）进行沉积。在超高真空（UHV）条件下，通过等温时间分辨红外反射吸收光谱（TR-IRAS）在生长过程中原位监测PA膜的形成和界面反应。我们观察到在这三种表面上存在明显的结构依赖性，具有三种截然不同的结合几何结构以及取决于温度和覆盖度的特征差异。1）PA最初通过形成螯合双羧酸盐与Co3O4(111)结合，分子平面垂直于表面取向。在低温（130 K）和室温（300 K）下均观察到类似的物种。随着暴露量增加，螯合单羧酸盐变得更加丰富，并部分取代了双羧酸盐。2）对于低覆盖度，PA以桥连双羧酸盐的形式与CoO(100)结合。在低温下长时间沉积PA后，双羧酸盐转化为单羧酸盐物种。相比之下，双羧酸盐层在300 K时非常稳定。3）对于CoO(111)，我们观察到吸附机制随温度变化。尽管PA在低温（130 K）下以桥连双齿方式作为单羧酸盐结合，但在300 K时形成了严重扭曲的双羧酸盐，这可能是表面温度依赖性重构的结果。结果表明，PA的吸附几何结构取决于氧化物表面的原子结构。这种结构依赖性可以通过三种表面上钴离子的不同排列来合理化。
