Composition and structure of nanoporous Au dealloyed from AuAg and AuCu

AuAg 和 AuCu 脱合金纳米孔 Au 的成分和结构

• 批准号: 269856009
• 负责人: Professor Dr. Andreas Rosenauer
• 金额: --
• 依托单位: Institut für Festkörperphysik (IFP)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/269856009?language=en
• 关键词: Composition; structure; nanoporous; Au; dealloyed

One of the main results in the first period of sub-project “Composition and structure of mono and bimetallic nanoporous foams” of the research unit FOR2213 was the observation of Ag rich clusters within npAu dealloyed from AuAg. This until then unexpected finding gave rise to a variety of questions concerning the understanding of their formation, their occurrence for small residual Ag concentrations and the composition of their surface. It is believed that Ag clusters are a possible reason for the low reproducibility of the catalytic behavior of npAu. Therefore, a part of the present project contributes to a systematic investigation of the aforementioned effects and the development of preparation routes producing a homogenous composition distribution for production of reproducible catalysts.Lattice strain relative to a reference region was measured extensively in npAu ligaments in the first period. It was found that the lattice in partially cylindrical ligaments is contracted along its axis and expanded in radial direction matching theoretical predictions by continuum mechanics. In the second period, we are aiming for a consolidated understanding of strain by quantitative matching of measured absolute strain with strain computed using energy relaxation with empirical potentials based on geometrical models derived from HAADF-STEM measurements. In the second period the portfolio of systems will be extended twofold: First, the role of the less noble element will be further investigated by replacing Ag by Cu in the starting alloys. The distribution of the less noble element is expected to play an important role, since the material system is exhibiting various ordered crystal phases for temperatures below 380°C that impose regions with different compositions. It is also expected that strain effects are significantly larger, since the lattice mismatch between Cu(Ag) and Au is 11.5% (~0%). Second, porous nanoparticles shall bridge the gap between nanoparticles representing smallest length scales of only few nm and npAu foams with ligament sizes of several tens of nanometers. In both cases the composition distribution, strain state and morphology will strongly depend on dealloying parameters such as potential, current and duration and might also change during catalysis. In order to achieve an in-depth understanding of catalytic properties, the characterization of composition, strain and morphology of the nanoporous materials at various stages of its life cycle is an indispensable prerequisite.

FOR2213研究单位的子项目“单金属和双金属纳米多孔泡沫的组成和结构”第一阶段的主要成果之一是观察到从AuAg脱合金的npAu内富银团簇。这一意想不到的发现引发了一系列问题，涉及如何理解它们的形成、它们在少量残留银浓度下的出现以及它们表面的组成。人们认为Ag簇是npAu催化行为重现性低的一个可能原因。因此，本项目的一部分有助于系统研究上述效应，并开发制备路线，产生均匀的成分分布，以生产可重复的催化剂。在第一阶段，对 npAu 韧带相对于参考区域的晶格应变进行了广泛测量。研究发现，部分圆柱形韧带中的晶格沿其轴线收缩并沿径向膨胀，这与连续介质力学的理论预测相匹配。在第二阶段，我们的目标是通过将测量的绝对应变与使用基于 HAADF-STEM 测量得出的几何模型的经验势的能量弛豫计算得到的应变进行定量匹配，来加深对应变的理解。在第二阶段，系统组合将扩大两倍：首先，将通过在起始合金中用铜代替银来进一步研究次贵金属的作用。次贵金属的分布预计将发挥重要作用，因为材料系统在低于 380°C 的温度下表现出各种有序的晶相，从而形成具有不同成分的区域。由于 Cu(Ag) 和 Au 之间的晶格失配为 11.5% (~0%)，因此预计应变效应会显着增大。其次，多孔纳米颗粒将弥合代表最小长度尺度（仅几纳米）的纳米颗粒与韧带尺寸为几十纳米的npAu泡沫之间的差距。在这两种情况下，成分分布、应变状态和形态将强烈依赖于脱合金参数，例如电势、电流和持续时间，并且也可能在催化过程中发生变化。为了深入了解催化性能，纳米多孔材料在其生命周期各个阶段的组成、应变和形貌的表征是不可或缺的先决条件。