Microstructure evolution and impact of mechanics for catalysis

在多相催化中，材料表面的过程取决于表面局部化学成分的状态，缺陷的密度，如台阶边或扭结，以及是否存在稳定的吸附物种，如氧。化学成分是一个特别重要的问题，因为以前关于合金腐蚀制备的纳米多孔金的催化作用的工作强调了腐蚀过程中牺牲元素银的残余含量对催化的影响。在正在进行的第一个资助期，该项目的两个最高目标中的第一个是合成和表征纳米多孔金属样品，其中探索了组成、吸附覆盖率和结构尺寸的变化。这些样品正被提供给所有实验子项目(SPS)，用于研究催化活性(SP1-SP4)以及表征表面组成(SP4)和结构(SP6)。在要求的第二个资助期内，我们建议继续通过既定方案制备样品，作为既定样品质量的基准。SP3的研究重点将转向研究脱合金化和退火过程中的组织演变(这是调整界面尺寸的关键步骤)以及催化过程中的操作过程。这项调查将基于原子计算机模拟研究，以考虑环境变量，如时间-温度分布和表面的化学环境。为此，我们将使用我们团队中已经建立的动力学蒙特卡罗计算机代码。模拟将使用DFT的材料参数(SP7，SP8，SP8(新))，并将与X射线光电子能谱(SP4)的表面组成和透射电子显微镜(SP6)的溶质分布的实验研究相匹配。最近的理论和实验表明，弹性应变对多相催化具有决定性作用。不含钠的金属天生就是应变的。探索和理解纳米多孔金的催化性能与力学的相关性是该项目的第二个最高目标。晶格应变正在对所有研究中的样品质量进行实验量化，部分是与SP6合作进行的。平面电极上的参考测量探索了平面电极表面快速循环应变期间调制的电催化反应速率。这些观察结果将与催化或电催化活性的实验研究(在SP1-SP4中)和原子级结构的实验研究(在SP6中)相联系，并将与提供吸附热(SP7)和表面组成分布(SP8)数据的理论项目密切反馈。

Processes at materials surfaces in heterogeneous catalysis depend on the state of the surface through local chemical composition, density of defects such as step edges or kinks, and the presence of stable adsorbed species such as oxygen. Chemical composition is a particularly important issue, since previous work on the catalysis of nanoporous gold made by alloy corrosion has emphasized the impact of the re-sidual content of the sacrificial element in the corrosion process, Ag, for catalysis. The first of the two superordinate aims of this project in the ongoing first funding period is to synthesize and characterize nanoporous metal samples in which variations in composition, adsorbate coverage, and structure size are explored. These samples are being supplied to all experimental subprojects (SPs) for studies of catalytic activity (SP1–SP4) and for characterization of surface composition (SP4) and structure (SP6). In the requested second funding period we propose to continue preparing samples via the established protocols as benchmarks for the established sample quality. The research focus in SP3 will shift to investi-gating the microstructure evolution during dealloying and during annealing (a key step for tuning the lig-ament size) as well as in operando during catalysis. This investigation will be based on atomistic computer simulation studies, conducted so as to account for the environmental variables such as time-temperature profiles and the chemical environment at the surface. To this end we shall use a Kinetic Monte Carlo computer code that is already established in our team. The simulation will use materials parameters from DFT (SP7, SP8, SP8(new)) and will be matched to experimental studies of surface composition by x-ray photoelectron spectroscopy (SP4) and of solute distribution by transmission electron microscopy (SP6).Recent theory and experiment advertise a decisive role of elastic strain for heterogeneous catalysis. Na-noporous metals are inherently strained. Exploring and understanding the relevance of mechanics for the catalytic performance of nanoporous gold is the second superordinate aim of this project. The lattice strain is being experimentally quantified for all sample qualities under study, partly in cooperation with SP6. Reference measurements on planar electrodes explore modulated electrocatalytic reaction rates during fast cyclic straining of planar electrode surfaces. The observations will be connected to the exper-imental studies of catalytic or electro-catalytic activity (in SP1–SP4) and of atomic-scale structure (in SP6), and they will be conducted in close feedback with the theory projects supplying in data for adsorption enthalpies (SP7) and surface composition profiles (SP8).