GOALI: Search for a Practical Perovskite-Based Three-Way Catalyst

摘要催化剂中具有催化活性的金属颗粒逐渐粗化是随着时间推移而失去活性的根本原因之一。对于三效汽车尾气催化剂，最近出现的一种现象，即贵金属掺杂钙钛矿型新型配方中氧化还原诱导的金属周期性再分散，已被提出作为缓解这一问题的可能方法。最近的研究表明，在这些系统中，这种现象只发生在几个纳米的距离内，这表明，实用的钙钛矿基催化剂可能会涉及超薄的钙钛矿膜或涂层。为了评估这种催化剂的可行性，GOALI奖将在密歇根大学和福特研究与创新中心的教授监督下，对模型平面和高比表面积粉末催化剂的电子显微镜和催化测量进行精心设计的组合。潘晓青和乔治·格雷厄姆，以及罗伯特·麦凯布博士。具体目标包括观察平面载体上超薄钙钛矿膜中自稳定或自再生的催化剂行为，制备钙钛矿包覆的高比表面积粉末，测量模型粉末催化系统中结构转变的动力学和详细的化学势依赖关系，通过简单的反应探测三向催化活性来表征钙钛矿基贵金属催化剂，以及最终在实际条件下评估钙钛矿基贵金属粉末催化剂的耐久性。结构-性能关系测试的一个重要方面将是明确指定负载金属颗粒或金属掺杂钙钛矿的催化活性。更广泛的意义和重要性：目前全球对铂和钯的需求中，汽车尾气催化剂占30-50%，相应的对Rh的需求更高，~80%。由于这些金属在这一应用中的利用率在历史上从未超过几个百分点，主要是由于颗粒粗化，因此实现即使是轻微的效率提高也将具有巨大的商业和科学意义。这项拟议的工作为密歇根大学的研究生和本科生提供了与福特汽车公司的催化剂研究人员及其供应商密切合作的机会，以追求这一目标，即通过开发实用的钙钛矿型三效催化剂来提高金属的利用效率。

Abstract#1159240Pan, XiaoqingGradual coarsening of the catalytically-active metal particles in a catalyst is one of the fundamental reasons for loss of activity over time. For three-way automotive exhaust-gas catalysts, a recent phenomenon, the redox-induced cyclical re-dispersion of the metal in novel precious-metal-doped-perovskite formulations has been proposed as a possible means of reducing this problem. Recent work showing that this phenomenon occurs over distances of only a few nanometers in these systems suggests that a practical perovskite-based catalyst will likely involve ultra-thin perovskite films or coatings. In an effort to assess the viability of such a catalyst, this GOALI award covers a carefully designed combination of electron microscopy and catalytic measurements on model planar and high-surface-area powder catalysts to be conducted at University of Michigan and Ford Research and Innovation Center under the supervision of Profs. Xiaoqing Pan and George Graham and of Dr. Robert McCabe, respectively. Specific objectives include the observation of self-stabilizing or self-regenerative catalyst behavior in ultra-thin perovskite films on planar supports, the production of perovskite-coated high-surface-area powders, the measurement of kinetics and detailed chemical potential dependence of structural transformations in model powder catalyst systems, the catalytic characterization of perovskite-based precious-metal catalysts using simple reactions to probe three-way catalytic activity, and ultimately the durability assessment of perovskite-based precious-metal powder catalysts under realistic conditions. An important aspect of the structure-property relationship testing will be to clearly assign catalytic activity to either supported metal particles or metal-doped perovskite.Broader Significance and Importance: Automotive exhaust-gas catalysts currently account for 30-50% of the world-wide demand for Pt and Pd, and the corresponding demand for Rh is even higher, ~80%. Since the utilization of these metals in this application has historically never exceeded a few percent by end of life, due primarily to particle coarsening, the attainment of even a modest increase in efficiency would be of tremendous significance, both commercially as well as scientifically. The proposed work affords the opportunity for graduate and undergraduate students at University of Michigan to collaborate closely with catalyst researchers at Ford Motor Company and their suppliers in the pursuit of this goal, which is to improve metal utilization efficiency through the development of a practical perovskite-based three-way catalyst.