CAS: Designing Copper-based Multi-metallic Single-atom Alloys for Cross Coupling Reactions through Combined Surface Science and Catalytic Investigations

在化学催化项目的支持下，塔夫茨大学的纳撒尼尔·伊根（Nathaniel Eagan）和查尔斯·赛克斯（Charles Sykes）正在研究一种新型催化剂的催化行为，这种催化剂含有微量的两种掺杂金属，以单原子形式存在，嵌入第三种主金属的表面。该团队将把实际催化剂的宏观尺度研究与单晶模型的原子尺度研究结合起来。这种新型催化剂是由两种不同的金属组成的，它们以单个原子的形式被隔离在第三种金属上，这种组合物被称为“三金属单原子合金”。先前对双金属单原子合金（例如两种金属）的研究表明，孤立的原子对许多重要的化学转化具有独特的效率和选择性催化作用。通过添加第三种金属，Eagan和Sykes的目标是进行更具挑战性的化学反应，例如对广泛的化学合成至关重要的碳-碳偶联反应。Eagan博士和他的学生将合成三金属单原子合金催化剂，使用广泛的分析技术表征它们的结构，并在实验室规模的化学反应器中研究它们的催化行为。Sykes博士和他的学生将合成单晶模型，并使用超高真空技术在原子水平上探测结构，并将它们与催化性能联系起来。该项目旨在为广泛的三金属单原子合金的生产和催化剂合成提供基础的新知识。该项目还将通过开发纳米科学活动和大学课程，支持将K-12和大学水平的化学和化学工程学科联系起来的努力。三金属单原子合金的设计是为了利用独特的化学性质，在单一催化表面上，不同的孤立金属原子嵌入低反应性，高选择性的铸造金属宿主中进行串联催化。这些系统平衡了复杂表面反应的不同需求，这些反应具有具有不同催化要求的基本步骤，就像许多碳-碳偶联反应一样。Eagan和Sykes将研究不同掺杂原子之间的化学中间体溢出的机制，通过这种机制，它们能够在催化循环的不同部分协同作用，并驱动比双金属单原子合金更广泛的化学反应。Sykes进行的表面科学研究将以原子分辨率提供这些材料的几何和电子结构的细节，以及基本反应步骤动力学的量化。Eagan将通过微动力学建模和使用控制良好的胶体方法合成催化剂的反应器研究，将这些研究与催化反应器的工业相关条件联系起来。了解这些材料在两种环境中的动态结构，以及它们相互影响和不相互影响的情况，是这些研究的嵌入目标。这项合作工作旨在理解和弥合表面科学和催化反应器方法之间存在的材料、压力和温度差距，从而产生新的基本见解和方法，以推进这种新型三金属单原子合金催化剂的开发。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Catalysis program in the Division of Chemistry, Nathaniel Eagan and Charles Sykes of Tufts University are studying the catalytic behavior of novel catalysts comprising trace amounts of two dopant metals present as single atoms, embedded in the surface of a third host metal. The team will combine macroscopic-scale studies of actual catalysts with atomic-scale studies of single-crystal models. The novel catalysts consist of two different metals, isolated as single atoms, on a third metal, a composition referred to as “trimetallic single-atom alloys.” Prior studies with bimetallic single-atom alloys, e.g., two metals, have shown that the isolated atoms drive uniquely efficient and selective catalysis of many important chemical transformations. By adding a third metal, Eagan and Sykes aim to perform more challenging chemistries, such as carbon-carbon coupling reactions crucial to a wide range of chemical syntheses. Dr. Eagan and his students will synthesize trimetallic single-atom alloy catalysts, characterize their structures using a wide range of analytical techniques, and examine their catalytic behaviors in laboratory-scale chemical reactors. Dr. Sykes and his students will synthesize the single-crystal models and investigate them using ultra-high vacuum techniques to probe structures at the atomistic level and correlate them with catalytic properties. This project aims to provide fundamental new knowledge from which a wide range of trimetallic single-atom alloys could be produced and implemented in catalyst syntheses. This project will also support efforts to connect the chemistry and chemical engineering disciplines at both the K-12 and university levels through the development of nanoscience activities and university courses.Trimetallic single-atom alloys are designed to leverage the unique chemistries exhibited by distinct isolated metal atoms embedded within low-reactivity, high-selectivity coinage metal hosts in tandem catalysis on a single catalytic surface. These systems balance the diverse needs of complex surface reactions which possess elementary steps with vastly differing catalytic requirements, as is the case for many carbon-carbon coupling reactions. Eagan and Sykes will investigate mechanisms by which spillover of chemical intermediates between distinct dopant atoms enables them to cooperatively act on different parts of a catalytic cycle and drive a wider range of chemistries than would be available from bimetallic single-atom alloys. Surface science studies performed by Sykes will provide details of the geometric and electronic structures of these materials with atomic resolution as well as quantification of the kinetics of elementary reaction steps. Eagan will bridge these studies to more industrially relevant conditions in catalytic reactors through microkinetic modeling and reactor studies with catalysts synthesized using well-controlled colloidal methods. Understanding the dynamic structures of these materials in the two environments, and situations in which they do and do not affect each other, are embedded targets of these studies. This collaborative work aims to understand and bridge the materials, pressure, and temperature gaps that exist between our surface science and catalytic reactor approaches thereby generating fundamental new insights and methodologies to advance the development of this novel class of trimetallic single-atom alloy catalysts.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.