DMREF: Collaborative Research: Toolkit to Characterize and Design Bi-functional Nanoparticle Catalysts

在这个项目中，由化学部门设计材料以革新和工程我们的未来（DMREF）项目资助，德克萨斯大学的Graeme Henkelman和Richard Crooks教授，叶史瓦大学的Anatoly Frenkel教授，和匹兹堡大学的Judith Yang教授正在结合实验和计算方法，旨在为有毒气体一氧化碳的电化学氧化发现最佳的双功能催化剂配方和结构。这项研究的一个关键要素是使用极小的催化剂颗粒（只含有几百个原子），这些催化剂颗粒部分被一层称为树突分子的保护层所覆盖，这种保护层可以防止金属颗粒聚结。人们正在研制各种催化剂，并对它们的结构和催化活性进行了分析。计算研究正在进行，以预测新的催化剂结构，然后制备和分析；利用实验研究结果对计算方法进行了改进。这种结合的方法代表了一种新的工具，用于发现和开发具有改进性能的新催化材料。项目参与者参与教育和推广活动，让本科生直接参与项目的各个方面，包括为德克萨斯大学奥斯汀分校的一些学生提供在布鲁克海文国家实验室和匹兹堡大学度过长达一周的机会。研究小组正在对不同金属组合的整个纳米粒子结构进行密度泛函理论（DFT）计算——一种是吸附一氧化碳的，另一种是离解吸附氧的。可用反应机制的DFT计算，以及动力学建模和与催化剂结构和组成的预期变化的相关性，确定了将在随后的筛选-合成-表征-评估周期中使用的机制和反应性描述符。通过原位和扫描透射电子显微镜（TEM/STEM）以及扩展x射线吸收精细结构（EXAFS）进行表征。人们正在开发将DFT计算与TEM和EXAFS数据相结合的方法，以改进原子尺度上纳米颗粒结构的测定。从科学/技术的角度来看，该研究正在推进树状大分子辅助催化剂合成的方法，更清楚地了解所产生的颗粒的性质及其催化活性。该研究将先前的双金属颗粒研究扩展到金属-金属氧化物系统，并相应扩展了计算和表征工作。在本研究过程中开发的合成、表征和建模工具具有广泛的适用性，适用于广泛的反应和催化剂配方，并且软件工具将免费分发给催化科学界。

In this project, funded by the Designing Materials to Revolutionize and Engineer our Future (DMREF) Program of the Chemistry Division, Professors Graeme Henkelman and Richard Crooks at the University of Texas, Professor Anatoly Frenkel at Yeshiva University, and Professor Judith Yang of the University of Pittsburgh are combining experimental and computational methods aimed at discovering optimal bi-functional catalyst formulations and structures for the electrochemical oxidation of the poisonous gas, carbon monoxide. A key element of the research is the use of extremely small catalyst particles (containing only several hundred atoms) that are partially coated with a protective layer of molecules called dendrimers that keep the metal particles from coalescing. A variety of catalysts are being made, and their structures and catalytic activities are being analyzed. Computational studies are being performed to predict new catalyst structures that are then prepared and analyzed; the results from the experimental studies are used to refine the computational methods. The combined approach represents a new toolkit for the discovery and development of new catalytic materials having improved performance.The project participants are involved in educational and outreach activities to engage undergraduate students directly in various aspects of the project including an opportunity for some of the University of Texas - Austin students to spend up to a week at Brookhaven National Laboratory and the University of Pittsburgh. The research team is conducting density functional theory (DFT) calculations of the entire nanoparticle structure for various combinations of metals - one which adsorbs carbon monoxide and one which adsorbs oxygen dissociatively. The DFT calculations of available reaction mechanisms, together with kinetic modeling and correlations to expected variations in catalyst structures and compositions, identify mechanisms and reactivity descriptors that will be used in subsequent screening-synthesis-characterization-evaluation cycles. Characterizations are being conducted by both in situ and scanning transmission electron microscopy (TEM/STEM) and extended X-ray absorption fine structure (EXAFS). Methods are being developed for combining the DFT calculations with the TEM and EXAFS data to improve the determination of nanoparticle structures at the atomic scale. From a scientific/technical standpoint, the study is advancing the dendrimer-aided approach to catalyst synthesis, with a clearer understanding of the nature of the particles that are produced and their catalytic activity. The study is extending previous work on bi-metallic particles to metal-metal oxide systems, with corresponding extension of computational and characterization efforts. The synthesis, characterization, and modeling tools developed during the course of this study have broad applicability to a wide range of reactions and catalyst formulations, and the software tools will be freely distributed to the catalysis science community.