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.

研究单元的第一个阶段“单声道和双金属纳米孔泡沫的组成和结构”的主要结果之一是，FOR2213的观察到了与Auag的NPAU内的富农业簇的观察。直到那时，意外发现引起了有关其形成的理解，对小残留Ag浓度的发生以及表面组成的各种问题。据认为，Ag簇是NPAU催化行为可重复性低的可能原因。因此，本项目的一部分有助于对优先效应的系统投资和制备途径的开发，该途径在第一个时期内在NPAU韧带中广泛测量了相对于参考区域的可重复性催化剂的同质组成分布。已经发现，部分圆柱韧带中的晶格沿其轴收缩，并沿径向方向扩展，通过持续力学匹配理论预测。在第二阶段，我们的目标是通过基于基于HAADF-STEM测量的几何模型，使用能量弛豫的经验势与经验势计算出的能量弛豫的菌株对应变进行综合理解。在第二阶段，系统的投资组合将被扩展双重：首先，通过替换Cu在起始合金中替换Ag，将进一步研究较不贵的元素的作用。由于材料系统暴露在380°C以下的温度下，材料系统暴露了各种有序的晶体相，因此预计较小元素的分布将发挥重要作用。还可以预期应变效应明显更大，因为Cu（Ag）和Au之间的晶格不匹配为11.5％（〜0％）。其次，多孔纳米颗粒应弥合纳米颗粒之间的缝隙，该纳米颗粒只有几个纳米的韧带大小的最小长度尺度和NPAU泡沫的最小尺度。在这两种情况下，组成分布，应变状态和形态都将在很大程度上取决于处理参数，例如电势，当前和持续时间，并且在催化过程中也可能发生变化。为了深入了解催化特性，在其生命周期的各个阶段，纳米多孔材料的组成，应变和形态的表征是必不可少的先决条件。