Taming the Complexity of High Entropy Alloy for Catalysis using Multinary Intermetallics

在化学系化学催化项目的支持下，宾夕法尼亚州立大学的Robert Rioux和Michael Janik将研究用于选择性加氢催化的多元合金的反应性。由许多金属成分制成的催化剂，被称为“高熵合金”，可能会为提高性能提供新的途径。然而，由于当许多金属混合在一起时形成大量的结构，所以理解多金属的相互作用是复杂的。这个合作研究小组将致力于使用一种结构定义的合金(称为金属间化合物)来识别和量化催化剂中与多达五种不同金属的这些复杂相互作用，以降低结构复杂性。这些合金将含有三到五种不同的金属，使研究小组能够通过在合金结构中系统地加入更多的金属来探索这些复杂的金属相互作用。利用实验和计算相结合的方法，该团队旨在了解组成不同的金属间化合物对烯烃和烯烃选择加氢的催化行为的起源(S)。通过这个项目，Rioux博士和Janik博士将帮助培养下一代催化科学家，以解决化学催化剂设计和优化中的基础和应用问题。作为这一项目的一部分，本科生将大量参与研究，利用宾夕法尼亚州立大学既定的招生计划。γ-黄铜金属间化合物结构提供了其原子成分在四个对称不对等位置上的明确和可控的分布。固相合成过程中精确的化学计量控制使M8-11Zn44-41系统的制备成为可能，该系统可以分布M(Pd，Ni)原子，这些原子要么被所有的锌近邻隔离，要么以小的M3团簇分布。宾夕法尼亚州立大学的Rioux和Janik将准备、表征和检查通过替换一定数量的铂、Ir、铜和/或Au原子而产生的三元、四元和五元γ-黄铜系统的反应性。对组成复杂性的控制引入旨在通过组合的、多方面的实验和计算研究来发展高熵材料的定量催化科学。H2-D2交换和乙烯加氢对三聚体中心的组成高度敏感，而1，3-丁二烯的选择性加氢将探测三聚体活性中心组成的选择性。对观察到的催化活性-选择性的解释将有助于对γ-黄铜金属间组织、晶体结构的严格表征，以及表征γ-黄铜HEI上存在的三聚体位置的方法。基于密度泛函和团簇展开计算的计算工作将把稳定的整体和表面三聚体组件定义为多元γ-黄铜金属间化合物组成的函数。基本反应能量学的DFT计算将为微动力学模型提供信息，以比较速率，假设由于锌宿主中的站点隔离，分布一组站点组成的表面的速率将是单个站点的速率的简单总和。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Catalysis program in the Division of Chemistry, Robert Rioux and Michael Janik of the Pennsylvania State University will examine the reactivity of multinary alloys for selective hydrogenation catalysis. Catalysts made with many metal constituents, referred to as “high entropy alloys,” may offer new avenues for improved performance. However, understanding the multi-metal interactions is complex due to the large number of structures that form when mixing many metals together. This collaborative research team will pursue an effort to identify and quantify these complex interactions in catalysts with up to five different metals using a structurally defined alloy, called an intermetallic, to reduce the structural complexity. These alloys will contain from three to five different metals allowing the team to probe these complex metal interactions by systematically incorporating more metals into the alloy structure. Using a combined experimental and computational approach, the team aims to understand the origin(s) of the catalytic behavior of compositionally-diverse intermetallics for selective hydrogenation of alkynes and alkenes. Through this project, Drs. Rioux and Janik will help to train the next generation of catalytic scientists to solve fundamental and applied problems in chemical catalyst design and optimization. There will a significant participation of undergraduates in research as part of this projecting, leveraging established recruitment programs at Pennsylvania State University.The γ-brass intermetallic structure offers well-defined and controllable distribution of its atomic constituents among four symmetry inequivalent sites. Precise stoichiometric control during solid-state synthesis enables preparation of M8-11Zn44-41 systems that distribute M (Pd, Ni) atoms either isolated by all Zn nearest neighbors or in small M3 clusters. Rioux and Janik of the Pennsylvania State University will prepare, characterize, and examine the reactivity of ternary, quaternary, and quinary γ-brass systems generated by substituting some number of Pt, Ir, Cu, and/or Au atoms. Controlled introduction of compositional complexity is designed to enable the development of a quantitative catalysis science of high entropy materials through a combined, multi-faceted experimental and computational study. H2-D2 exchange and ethylene hydrogenation are highly sensitive to the composition of the trimer sites, while selective hydrogenation of 1,3-butadiene will probe selectivity on the trimer active site composition. Interpretation of the observed catalytic activity-selectivity will be aided by rigorous characterization of γ-brass intermetallic microstructure, crystal structure, and methods to characterize the trimer sites present on γ-brass HEIs. Computational efforts based on DFT- and cluster-expansion calculations will define stable bulk and surface trimer assemblies as a function of multinary γ-brass intermetallic composition. DFT calculations of elementary reaction energetics will inform microkinetic models to compare rates, with the hypothesis that rates on surfaces distributing an array of site compositions will be a simple sum of rates on individual sites due to site isolation in the Zn host.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.