CAREER: Growth, Properties and Reactivity of Oxygen Phases on Noble Metal Catalysts: Bridging the Pressure Gap with Gas-Phase Oxygen Atoms

氧化物负载的贵金属在商业氧化过程中被广泛用作催化剂，通常在常压下运行。不幸的是，在这种压力下，这些催化剂上存在的许多氧相在原子水平上很难被理解，这在很大程度上是因为在控制良好的超高真空(UHV)条件下产生这些相是困难的。这项职业研究计划的主要目标是促进对贵金属(Pd，Pt，Rh)模型催化剂在有效模拟高压氧化环境下制备的氧相的生长、性质和反应活性的基本了解。在本项目中，将通过在超高真空中生长薄的氧化物薄膜，然后将催化金属沉积到薄膜上来制备模型催化剂。然后，将使用低能原子氧束来提高氧在贵金属上的化学吸附速度，以便在超高真空环境中制备和研究在商业相关压力下重要的氧相。用几种表面分析方法研究了表面氧相的发展和性质，用分子束方法研究了CO和其他简单分子在氧改性催化剂上的反应。在这些实验中使用原子氧束提供了在各种条件下在很难在特高压下氧化的金属上产生高覆盖率氧相的机会。此外，原位制备模型催化剂为以可控的方式改变氧化物负载的金属纳米团簇的尺寸和形态特征提供了手段。这项研究有望为理解特定的催化剂性质和氧化条件如何控制表面氧相的生长和性质提供新的见解，而表面氧相的生长和性质对现实世界的催化非常重要。除了为本科生和研究生提供高质量的技术培训外，这一职业计划的教育部分将涉及到教学模块的开发、评估和评估，这些模块可以整合到高中化学课程中，以传达当前表面科学的技术应用。这些单元的目标是增强高中化学学生的教育经验，改善学生对科学和工程的态度，最终目标是吸引更多的学生投身科学和工程职业。每个模块将聚焦于一个标准的高中化学主题，并提供与该主题直接相关的应用程序。因此，这些模块将支持现有的化学课程，同时也向学生介绍令人兴奋的技术应用。这些模块将在当地一所高中进行测试，并评估它们对学生知识、态度和行为的影响。

Oxide-supported noble metals are widely used as catalysts in commercial oxidation processes, typically operating at atmospheric pressure. Unfortunately, many of the oxygen phases that exist on these catalysts at this pressure are poorly understood at the atomic level due in large part to difficulties in generating such phases under well-controlled ultrahigh vacuum (UHV) conditions. The main objective of this CAREER research plan is to advance the fundamental understanding of the growth, properties and reactivity of oxygen phases prepared on model noble-metal (Pd, Pt, Rh) catalysts under conditions that effectively simulate a high-pressure oxidizing environment. In this project, model catalysts will be prepared by growing thin oxide films in UHV and then vapor depositing the catalytic metals onto the films. A low energy atomic oxygen beam will then be used to enhance the rate of oxygen chemisorption on the noble metals so that the oxygen phases important at commercially relevant pressures can be prepared and investigated in the UHV environment. Several surface analytical methods will be used to investigate the development and properties of the surface oxygen phases, and molecular beam methods will be employed to investigate the reactions of CO and other simple molecules on the oxygen-modified catalysts. The use of an atomic oxygen beam in these experiments affords an opportunity to generate high-coverage phases of oxygen over a wide range of conditions on metals that are difficult to oxidize in UHV. Moreover, preparing model catalysts in situ provides a means for varying the sizes and morphological characteristics of the oxide-supported metal nanoclusters in a controllable way. This research is expected to provide new insights for understanding how specific catalyst properties and oxidizing conditions govern the growth and properties of the surface oxygen phases that are important to real-world catalysis. In addition to providing high quality technical training to undergraduate and graduate students, the educational component of this CAREER plan will involve the development, evaluation and assessment, and dissemination of instructional modules that can be integrated into high school chemistry courses to convey current technological applications of surface science. The objectives of the modules are to enhance the educational experiences of high school chemistry students and to improve student attitudes toward science and engineering, with the ultimate goal of attracting more students to careers in science and engineering. Each module will focus on a standard high school chemistry topic and will present an application that relates directly to the topic. As such, the modules will support the existing chemistry curriculum while also introducing students to exciting technological applications. The modules will be tested at a local high school and their impact on student knowledge, attitudes and behavior assessed.