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.

在研究单位FOR 2213的子项目“单纳米多孔泡沫和双纳米多孔泡沫的组成和结构”的第一阶段的主要成果之一是在从AuAg脱合金的npAu中观察到富Ag团簇。直到那时，这一意想不到的发现引起了各种各样的问题，关于它们的形成，它们的发生小残留银浓度和它们的表面组成的理解。据信，Ag簇是npAu的催化行为的低再现性的可能原因。因此，本项目的一部分，有助于上述影响的系统调查和制备路线的发展，生产可再生的catalysts.Lattice应变相对于一个参考区域的均匀组合物分布广泛测量在npAu韧带在第一阶段。结果发现，在部分圆柱形韧带的晶格是收缩沿着其轴向和径向扩展匹配的连续介质力学的理论预测。在第二阶段，我们的目标是通过测量的绝对应变与使用能量弛豫与基于HAADF-STEM测量得出的几何模型的经验势计算的应变的定量匹配来巩固对应变的理解。在第二阶段，系统的组合将扩展到两个方面：首先，通过在起始合金中用Cu取代Ag，将进一步研究较不贵重的元素的作用。预计较低贵元素的分布将发挥重要作用，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，从而形成具有不同组成的区域。还预期应变效应显著更大，因为Cu（Ag）和Au之间的晶格失配为11.5%（~0%）。第二，多孔纳米颗粒将桥接代表仅几纳米的最小长度尺度的纳米颗粒与具有几十纳米的韧带尺寸的npAu泡沫之间的差距。在这两种情况下的组成分布，应变状态和形态将强烈依赖于脱合金参数，如电位，电流和持续时间，也可能在催化过程中发生变化。为了实现对催化性能的深入理解，表征纳米多孔材料在其生命周期的各个阶段的组成、应变和形态是必不可少的先决条件。