Operando Transmission Electron Microscopy - A New Tool for Catalysis Research

原位环境透射电子显微镜（TEM）是研究高比表面积多相催化剂在反应气体条件下的结构和组成的一种重要手段。然而，在多相催化研究中，我们希望将催化剂中发生的结构和化学变化与反应产物的同时测量相关联，或所谓的操作数方法。原子分辨率分析与气相催化产物的同时检测相结合尚未在电子显微镜内得到证实。亚利桑那州立大学的研究员Peter Crozier愿意用一些创造性的思维和设备以及方法设计来应对这一挑战。这一建议的主要目标是发展原子分辨率的操作透射电子显微镜（TEM），并将这种方法应用于高表面积多相催化剂的基本问题。为了实现这一目标，将开发样品制备方法，其显著增加电子显微镜的反应池中的催化剂的体积，使得产生更大量的产物气体。还将开发基于电子能量损失谱和质谱的产品气体定量检测方法。气体分析与电子能量损失光谱是特别适合于拟议的operando目标，因为它是兼容的原子分辨率成像。操作技术将被用来研究纳米粒子在催化过程中发生的变化，为一些重要的能源相关的反应。在中温CO氧化将在各种负载型金属和负载型氧化物催化剂上进行研究。通过在显微镜反应池中同时检测气体产物，可以确定催化开始时纳米颗粒中发生的独特结构和行为变化。此外，亦会就甲烷部分氧化反应进行实验，以探讨在高温条件下的操作能力。这一提议是变革性的，因为操作TEM的成功开发将为催化研究人员提供一种强大的新原子分辨率工具，用于关联高表面积材料的结构和催化作用。一种用于检测单个纳米颗粒表面上的气体吸附物和中间体的方法也将使用高空间分辨率电子能量损失谱法开发。即使在这一领域取得部分成功，也将为纳米颗粒上的气体-表面相互作用提供全新的见解。操作显微镜技术将广泛应用于催化领域的许多问题，并允许在高表面积材料上探索结构-性能关系。这项工作的长期目标是开发高空间分辨率的原位技术，使动态纳米结构材料的变化与催化性能相关。该研究计划将培养研究生和本科生，以促进和了解能源相关的非均相催化剂，纳米材料合成方法和先进的原位纳米表征的发展。PI教授一门关于能源生产和储存的纳米材料的课程，并将广泛利用这项研究来教授催化纳米颗粒的基本功能。能源和催化纳米材料的教育模块将开发和有针对性地使用亚利桑那州立大学最佳方案的中学生和亚利桑那州立大学科学是有趣的方案，目标是K-12。这两个推广方案都专门针对女性和少数民族学生，鼓励他们考虑从事科学和工程职业。

ABSTRACTIn situ environmental transmission electron microscopy has been employed for many years to investigate the structure and composition of high surface area heterogeneous catalysts under reactive gas conditions. However in heterogeneous catalysis research, we want to correlate the structural and chemical changes taking place in a catalyst with simultaneous measurement of reaction products, or so-called operand methods. The combination of atomic resolution analysis coupled with simultaneous detection of gas phase catalysis products has not yet been demonstrated within the electron microscope. Investigator Peter Crozier of Arizona State University is willing to tackle this challenge with some creative thought and equipment and methodology design.The main goal of this proposal is to develop atomic resolution operando transmission electron microscopy (TEM) and apply this approach to fundamental problems in high surface area heterogeneous catalysts. To accomplish this goal, sample preparation methods will be developed that substantially increase the volume of catalyst in the reaction cell of the electron microscope so that larger quantities of product gas are generated. Quantitative methods for detecting product gases based on electron energy-loss spectroscopy and mass spectrometry will also be developed. Gas analysis with electron energy-loss spectroscopy is particularly well suited to the proposed operando goal because it is compatible with atomic resolution imaging. The operando technique will be employed to investigate the changes taking place on nanoparticles during catalysis for a number of important energy related reactions. CO oxidation at intermediate temperatures will be studied on a variety of supported metal and supported oxide catalysts. With simultaneous detection of gas products in the microscope reaction cell, it will be possible to determine the unique structural and behavioral changes that take place in the nanoparticles at the onset of catalysis. Experiments will also be performed on reactions relevant to partial oxidation of methane to explore the operando capability under high temperature conditions. This proposal is transformative because successful development of operando TEM will provide researchers in catalysis with a powerful new atomic resolution tool for correlating structure and catalysis on high surface area materials. An approach for detecting gas adsorbates and intermediates on the surfaces of individual nanoparticles will also be developed using high spatial resolution electron energy-loss spectroscopy. Even partial success in this area would provide completely new insights into gas-surface interactions on nanoparticles. The technique of operando microscopy will have wide application to many problems in catalysis and allow structure-property relations to be explored on high surface area materials. A long-term goal of this work is to develop high spatial resolution in situ techniques that allow dynamic nanostructural materials changes to be correlated with catalytic properties. This research program will train graduate and undergraduate students to contribute and learn about the developments in energy-related heterogeneous catalysts, methods of nanomaterials synthesis and advanced in situ nanocharacterization. The PI teaches a course on nanomaterials for energy production and storage and will draw extensively on this research to teach fundamental functionalities in catalytic nanoparticles. Educational modules on energy and catalytic nanomaterials will be developed and targeted using ASUs Best Program for middle school students and ASUs Science is Fun program which targets K-12. Both outreach programs specifically target female and minority student to encourage them to consider careers in science and engineering.