Microstructure evolution and impact of mechanics for catalysis

在非均相催化下，材料表面的过程取决于表面的状态，包括局部化学成分、缺陷的密度（如台阶边或结）以及稳定吸附物质（如氧）的存在。化学成分是一个特别重要的问题，因为先前关于合金腐蚀制备纳米孔金的催化工作强调了腐蚀过程中牺牲元素Ag的残余含量对催化的影响。在正在进行的第一个资助期，该项目的两个主要目标中的第一个是合成和表征纳米多孔金属样品，其中探索成分，吸附物覆盖范围和结构尺寸的变化。这些样品将提供给所有实验子项目（SPs），用于研究催化活性（SP1-SP4）和表征表面组成（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的协议制备样品，作为既定样品质量的基准。SP3的研究重点将转移到研究脱合金和退火（调整韧带尺寸的关键步骤）过程中的微观结构演变以及催化过程中的操作。这项调查将以原子计算机模拟研究为基础，以便考虑诸如时间-温度分布和地表化学环境等环境变量。为此，我们将使用我们团队中已经建立的动态蒙特卡罗计算机代码。模拟将使用DFT中的材料参数（SP7, SP8, SP8(new)），并将与x射线光电子能谱（SP4）和透射电子显微镜（SP6）的表面组成实验研究相匹配。最近的理论和实验表明弹性应变在多相催化中起着决定性的作用。无纳米孔的金属具有固有的张力。探索和理解纳米多孔金催化性能的相关力学是该项目的第二个主要目标。晶格应变在实验中被量化为所有正在研究的样品质量，部分是与SP6合作。平面电极的参考测量探讨了平面电极表面快速循环应变过程中调制的电催化反应速率。这些观察将与催化或电催化活性（SP1-SP4）和原子尺度结构（SP6）的实验研究联系起来，并将与提供吸附焓（SP7）和表面组成谱（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).