Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany.
Beilstein J Nanotechnol. 2013;4:111-28. doi: 10.3762/bjnano.4.13. Epub 2013 Feb 19.
The catalytic properties of nanostructured Au and their physical origin were investigated by using the low-temperature CO oxidation as a test reaction. In order to distinguish between structural effects (structure-activity correlations) and bimetallic/bifunctional effects, unsupported nanoporous gold (NPG) samples prepared from different Au alloys (AuAg, AuCu) by selective leaching of a less noble metal (Ag, Cu) were employed, whose structure (surface area, ligament size) as well as their residual amount of the second metal were systematically varied by applying different potentials for dealloying. The structural and chemical properties before and after 1000 min reaction were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic behavior was evaluated by kinetic measurements in a conventional microreactor and by dynamic measurements in a temporal analysis of products (TAP) reactor. The data reveal a clear influence of the surface contents of residual Ag and Cu species on both O2 activation and catalytic activity, while correlations between activity and structural parameters such as surface area or ligament/crystallite size are less evident. Consequences for the mechanistic understanding and the role of the nanostructure in these NPG catalysts are discussed.
采用低温 CO 氧化反应作为探针反应，研究了纳米结构 Au 的催化性能及其物理起源。为了区分结构效应（结构-活性关系）和双金属/双功能效应，使用了通过选择性浸出较不活泼金属（Ag、Cu）从不同 Au 合金（AuAg、AuCu）制备的无载体纳米多孔金（NPG）样品，其结构（表面积、连接体尺寸）以及通过施加不同的脱合金电势来系统地改变其第二金属的残余量。通过扫描电子显微镜（SEM）、X 射线衍射（XRD）和 X 射线光电子能谱（XPS）对反应前 1000 分钟和后的结构和化学性质进行了表征。通过在传统微反应器中的动力学测量和在产物时间分析（TAP）反应器中的动态测量来评估催化行为。数据表明，残余 Ag 和 Cu 物种的表面含量对 O2 活化和催化活性都有明显的影响，而活性与表面积或连接体/微晶尺寸等结构参数之间的相关性则不明显。讨论了这些 NPG 催化剂中纳米结构的机制理解和作用的影响。
