RUI: Quantifying Electron Donation in Metal-Support Interactions utilizing CO Adsorption Studies and Hammet Relationships for Catalyzed Organic Transformations

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Supported Au catalysts are now well established as extremely active catalysts for low temperature CO oxidation and a number of other reactions. Further advances in Au catalysis will require more detailed understanding of the important factors that govern its high catalytic activity and developing methods for tuning reaction selectivity. Many of these catalysts are comprised of Au nanoparticles dispersed on high surface area oxide carriers. The nanoparticles typically consist of tens to a few hundred atoms to maximize the number of surface atoms that are accessible to the reacting molecules. Because these particles are so small, they can be influenced by the underlying support. Further, although the support may influence the electronic properties of the nanoparticle, it is not clear how these changes affect the electronic structure of the transition state(s) for the key step(s) in the catalytic cycle. This project primarily involves developing new methods and approaches for characterizing how the underlying support changes the electronic properties of gold nanoparticles and determining how these electronic changes affect catalytic behavior. Professors Bert Chandler and Christopher Pursell at Trinity University, San Antonio, TX are teaming with Professor Robert Rioux at Pennsylvania State University to apply a known tool to aid in developing more understanding of this problem. Hammett studies have long been employed to help understand reaction mechanisms, and to evaluate charge build-up in the rate determining step. The Hammett methodology has been applied to several Au catalyzed reactions, and studies of benzyl alcohol oxidation by Au on different supports have shown significant differences, suggesting that the degree of charge building up on the organic fragment may be substantially influenced by the underlying support. These studies will be correlated with CO adsorption studies and X-ray absorption spectroscopy studies to characterize changes in the surface electronics as particle size and supports change. The aim is to provide a complete picture of how Au catalysts are affected by particle size and support effects.This RUI proposal will have a substantial impact on undergraduate education at Trinity University. Funds will be used to support several undergraduate researchers, who will be integral participants in this study. Further, initial research opportunities will be targeted to undergraduates early in their academic careers (1st and 2nd year students). This offers increased opportunities to capture students from underrepresented groups and capitalize on their interests in science, and thereby developing important human resources for our increasingly technical economy. Integrating the Trinity model that focuses on undergraduate research with a classic graduate experience at Penn State will provide a unique educational opportunity for all of the participants and will help to maximize the impact of the research performed by the undergraduates.