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

在这个由化学系设计材料革新和设计我们的未来(DMREF)计划资助的项目中，德克萨斯大学的Graeme Henkelman和Richard Crooks教授、Yeshiva大学的Anatoly Frenkel教授和匹兹堡大学的Judith Yang教授将实验和计算方法结合起来，旨在发现有毒气体一氧化碳电化学氧化的最佳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(仅包含数百个原子)，这些颗粒部分覆盖着一层名为树枝状大分子的分子保护层，以防止金属颗粒聚集。目前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。正在进行计算研究，以预测新的催化剂结构，然后准备和分析这些结构；实验研究的结果被用于改进计算方法。项目参与者参与了教育和外展活动，让本科生直接参与项目的各个方面，包括让德克萨斯大学奥斯汀分校的一些学生有机会在布鲁克海文国家实验室和匹兹堡大学度过长达一周的时间。该研究小组正在对各种金属组合的整个纳米颗粒结构进行密度泛函理论(DFT)计算-一种金属吸附一氧化碳，另一种金属解离吸附氧气。可用反应机理的密度泛函计算，加上动力学建模和与催化剂结构和组成的预期变化的关联，确定了将在后续screening-synthesis-characterization-evaluation循环中使用的机理和反应性描述符。用原位和扫描电子显微镜(TEM/STEM)和扩展X射线吸收精细结构(EXAFS)对其进行了表征。正在开发将密度泛函计算与透射电子显微镜和EXAFS数据相结合的方法，以改进在原子尺度上确定纳米粒子结构的方法。从科学/技术的角度来看，这项研究正在推进树枝状大分子辅助催化剂合成的方法，使人们更清楚地了解所产生的颗粒的性质及其催化活性。这项研究正在将以前关于双金属粒子的工作扩展到金属-金属氧化物系统，并相应地扩展了计算和表征工作。在本研究过程中开发的合成、表征和建模工具广泛适用于各种反应和催化剂配方，这些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.