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

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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.