Atomistic insight into the properties of nanoporous gold using single crystalline model surfaces

NpAu催化剂的合理设计需要对反应机理及其对表征体系的不同参数的依赖，如氧化反应中催化剂表面存在低配位、第二金属组分的浓度或氧相的存在等。在这个项目中，我们的目标是研究模型表面，通过测量表面反应的微观动力学(使用质谱仪分析气相)和反应条件下存在的表面物种(原位红外光谱)作为这些参数的函数，深入了解低配位位置、第二金属成分或其他反应伙伴(如水)的存在对体系催化性能的影响。通过与理论子项目SP7(Klüner)和SP8(Moskaleva)以及气相催化项目SP1(Bäumer)的密切合作，我们旨在获得观察到的反应性的全面原子图。在这个项目中，甲醇和丙烯的部分氧化将被阐明为原型反应，以测试上述参数的影响。酯(甲醇)和环氧丙烷(丙烯)的形成通过复杂的机理进行，其特点是各种平行反应路径，这使得选择性成为一个主要问题。在这种情况下，特别重要的是等温地研究反应，使用确定的排泄物浓度来解决选择性问题。因此，我们使用分子束能够提供可控制的排泄物流量来撞击给定温度的样品。Au(111)和Au(332)表面将作为模型来阐明低配位对体系反应活性的影响。在第二步中，这些表面将被银和铜修饰。将特别关注水的作用，先前的实验表明水能够显著改变金表面的反应性。为了能够在模型体系的反应性与NP-Au的反应性之间进行直接比较，计划在超高真空系统上建立一个高压室，这将允许表征该系统在大气压下的反应性。这种超高真空装置的扩展还将能够在超高真空条件下研究NP-Au样品，这将允许直接比较两个系统的反应性。

The rational design of npAu catalysts requires an atomistic understanding of the reaction mechanisms as well as their dependence on different parameters characterizing the system such as the presence of low coordinated sites, the concentration of a second metal component or the presence of an oxygen phase on the surface of the catalyst during oxidation reactions. Within this project we aim at investigating model surfaces to gain insight into the impact of low coordinated sites, the second metal component or the presence of additional reactions partners such as water on the catalytic properties of the system by measuring the micro kinetics of the surface reactions (analyzing the gas phase using mass spectrometry) and the surface species present under reaction conditions (in-situ IR spectroscopy) as a function of these parameters. Through the tight cooperation with the theoretical subprojects SP7 (Klüner) and SP8 (Moskaleva) as well as the gas phase catalysis project SP1 (Bäumer) we aim at a comprehensive atomistic picture of the observed reactivity. Within this project the partial oxidation of methanol and propene will be elucidated as prototypical reactions to test for the impact of the abovementioned parameters. The formation of the ester (methanol) and propylene oxide (propene) proceed via complex mechanisms characterized by a variety of parallel reactions paths, which renders selectivity a major issue. In such a case it is of particular importance to investigate the reaction isothermally using a defined concentration of educts to address the question of selectivity. Therefore, we employ molecular beams capable to provide a controllable flux of educts to impinge on the sample of a given temperature. Au(111) and Au(332) surface will be used as models to elucidate the impact of low coordinated sites on the reactivity of the systems. In a second step these surfaces will be modified by Ag and Cu. A particular focus will be on the role of water, which was shown in previous experiments to be able to significantly alter the reactivity of Au surfaces.To enable the direct comparison between the reactivity of the model system with that of np-Au it is planned to set up a high pressure cell attached to the ultrahigh vacuum system, which will allow to characterize the reactivity of the system at atmospheric pressure. This extension of the UHV apparatus will also enable to study np-Au samples under UHV conditions, which will allow compare the reactivity of both systems directly.