CAREER:Fundamental Studies of the Roles and Interactions of Disparate Metals in p-d Alloy Catalysts

双金属催化剂长期以来一直受到科学的关注，因为存在着通过改变组成和创建独特的局部系综(活性中心)来调整催化剂性能的有趣可能性。Norskov和他的同事通过分析d带过渡金属的行为，对我们对催化的理解做出了很大贡献。Norskov等人已经证明，过渡金属及其合金的简单关系同样适用，并且表层金属原子的平均d带填充(S)是吸附强度的预测因子。然而，有一些相当重要的催化剂体系(例如，用于催化重整的PtSn催化剂)，其中d带过渡金属与非过渡金属(在价带的p轨道上有一些占位的金属)合金化，而将d带中心作为通用预测指标的简单图景似乎是不够的。因此，这一建议将通过理论和实验相结合的方法，试图建立简单的规则来描述p-d合金(与d-带金属合金化的p-电子金属)的吸附行为，其方式类似于Norskov等人先前建立的d-带过渡金属合金的吸附行为。这项工作的重要性是将已建立的描述d-过渡金属合金的关联式扩展到一类新的催化剂：包括d-带过渡金属(例如铂)的合金和涉及主族金属(例如锡或锌)的合金。这项工作将在实验和理论之间的合作努力中进行，利用多种技术。将合成各种p-d合金催化剂，并用EXAFS、原位XPS和STEM-EELS对其进行广泛的表征。在对催化剂进行表征后，将使用传统的微反应器在实际操作条件下对催化剂进行测试，以努力将材料的组成和结构与其对两个相当重要的反应的反应性(和选择性)联系起来：水煤气变换和丙烷脱氢。密度泛函理论研究将考察这些材料的电子结构及其在反应条件下的稳定性。最后，理论将被用来提高我们对机理的理解，从而帮助我们设计新的催化剂。更广泛的影响这项研究具有非常一般性的性质，因此最终可能导致？经验法则？在催化剂设计中，作为诺尔斯科夫？S开创性的工作，对于d带理论，本工作希望加以补充和效仿。多名合作研究人员将在这个项目上与学生合作，每个人都有独特的研究视角(部分是作为他们所属机构的产品)。因此，学生将获得在工业(BP的Jeff Miller博士)、政府(Argonne国家实验室的Jeremy Kropf博士)和学术机构(芝加哥伊利诺伊大学的Robert Klie和John Regalbuto教授；普渡大学的Fabio Ribeiro教授)的研究方面的欣赏。PI打算大量使用Argonne国家实验室的高级光子源(APS)(用于EXAFS)和劳伦斯·伯克利实验室的高级光源(ALS)(用于高压XPS)的一般用户设施，这将使学生接触到各种各样的研究环境和一些协同技术。这项工作包括实际的例子，说明了本科生水平的化学热力学和反应动力学的用处，这些可以被纳入到由PI教授的现有课程中。这些催化剂的测试反应涉及传统的碳氢催化和氢气生产，这一反应对我们未来的能源具有越来越重要的潜在意义。这些例子将被整合在适当的背景下？S系为化学工程一年级学生开设的新入门课程。最后，它希望通过与伊利诺伊州数学和科学学院的互动，将这项研究进一步扩展到高中水平。

0747646MeyerBimetallic catalysts have long been of scientific interest due to the intriguing possibilities that exist with regard to tuning the properties of the catalyst by varying the composition and creating unique local ensembles (active sites). Norskov and coworkers have greatly contributed to our understanding of catalysis through an analysis of the behavior of d-band transition metals. Norskov et al have shown that simple relationships hold equally for transition metals and their alloys and that the average d-band filling of the metal atoms in surface layer(s) acts a predictor of adsorption strength. However, there are a few catalyst systems of considerable importance (e. g. PtSn catalysts for catalytic reforming) where a d-band transition metal is alloyed with a non-transition metal (a metal with some occupancy in p-orbitals in the valence band) and the simple picture of examining the d-band center as a universal predictor seems insufficient. Therefore, this proposal through a combined theoretical/experimental approach will attempt to develop simple rules which could describe the adsorption behavior of p-d alloys (p-electron metals alloyed with d-band metals) in a similar way as has been previously established by Norskov et al for d-band transition metal alloys. Intellectual Merit The importance of this work is to extend established correlations which describe d-transition metal alloys to a new class of catalysts: alloys involving a d-band transition metal (e.g Pt) and one involving a main group metal (e.g. Sn or Zn). The work will be performed in a collaborative effort between experiment and theory utilizing multiple techniques. A variety of p-d alloy catalysts will be synthesized, and extensively characterized using EXAFS, in situ-XPS, and STEM-EELS. Following their characterization the catalyst will be tested under realistic operating conditions using a traditional microreactor in an effort to link the composition and structure of our materials to their reactivity (and selectivity) for two reactions of considerable importance: water gas shift and propane dehydrogenation. Density Functional Theory studies will examine the electronic structure of these materials and their stability under reaction conditions. Finally theory will be called upon to improve our understanding of the mechanism and thereby aid our design of new catalysts. Broader Impact This study is of a very general nature and as such may ultimately lead toward ?rules of thumb? in catalyst design as Norskov?s seminal work regarding d-band theory which this work hopes to augment and emulate. Multiple collaborative investigators will work together with the students on this project, each with a unique research perspective (partially as a product of the institutions with which they are affiliated). Therefore the student will gain an appreciation of research at industrial (Dr. Jeff Miller of BP), governmental (Dr. Jeremy Kropf of Argonne National Laboratory) and academic institutions (Professor Robert Klie and John Regalbuto of the University of Illinois at Chicago; Prof. Fabio Ribeiro of Purdue University). The PI intends to make considerable use general user facilities at the Advanced Photon Source (APS) at Argonne National Lab (for EXAFS) and the Advanced Light Source (ALS) at Lawrence Berkeley Labs (for high pressure XPS) which will expose the students to a large variety of research environments as well as a number of synergistic techniques. This work involves practical examples which illustrate the usefulness of undergraduate level chemical thermodynamics and reaction kinetics which can be incorporated into existing courses taught by the PI. The test reactions of interest for these catalysts involve both traditional hydrocarbon catalysis and hydrogen production, a reaction of increasing potential importance to our energy future. These examples will be integrated in the appropriate context to the department?s new introductory course for first year students in chemical engineering. Finally, it is hoped to extend this even further to high school level through interaction with the Illinois Math and Science Academy.