CAREER: Spectrokinetic Studies for Understanding Metal-Support Interactions in Catalytic Oxidation of Ethanol

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Ethanol is a major commodity chemical produced from biorenewable sources that is primarily used in transportation fuel. The project will focus on improved catalysts for expanding the ethanol market by converting the ethanol to value-added derivatives such as acetic acid. Specifically, the project will study the interactions between gold nanoparticles and metal oxide catalyst supports to gain fundamental understanding that will be used to design more active and selective catalysts for acetic acid production. The fundamental knowledge gained in this project will contribute to the long-term sustainability of U.S. bioethanol plants. Mechanistic insights will also provide better general understanding of metal-support interactions involving noble metals in applications such as automotive exhaust oxidation catalysis. The research is integrated with an educational plan that provides training and leadership opportunities to a diverse group of undergraduate and graduate students through research and community engagement.The project addresses the effects of charge transfer processes in heterogeneous catalysis. The limited number of experimental tools to assess in situ charge transfer rates and their kinetic relevance for surface catalyzed reactions has been a major obstacle for advancing the understanding of metal-support interactions. Three enabling spectroscopic techniques have been developed to facilitate 1) in situ evaluation of adsorbed oxygen on gold catalysts (Gold-Surface Plasmon Resonance-UV-visible spectroscopy, i.e. Au-SPR-UV-vis), 2) identify surface reaction intermediates (Modulation Excitation-Phase Sensitive Detection-Diffuse Reflectance Infrared Fourier Transform Spectroscopy, i.e. ME-PSD-DRIFTS), and charge transfer between metal and support (Modulation Excitation-Phase Sensitive Detection-UV-visible spectroscopy, i.e. ME-PSD-UV-vis). This project will systematically examine electronic and structural metal-support effects by studying a variety of catalysts while isolating gold particle size, support nature, and catalyst synthesis method. It is hypothesized that supports with n-type semiconducting properties facilitate charge transfer from and to the gold nanoparticle periphery, thereby promoting active species that oxidize ethanol to acetic acid. Overall, the combination of Au-SPR-UV-vis, ME-PSD-FTIR, ME-PSD-UV-vis, spectrokinetics, and reaction kinetics will provide a comprehensive mechanistic view of gas phase ethanol oxidation to describe the observed activity and selectivity trends. The new knowledge and techniques will assist in the design of next-generation gold oxidation catalysts. They will also be transferable to other oxidation reactions, thus expanding their applicability to a wide range of surface catalyzed reactions. The research and educational programs will produce a trained cadre of diverse students to enter the workforce in STEM disciplines. A new outreach after-school science initiative, EMPower (Energy, Matter, & Power) club, will also provide undergraduate students with leadership opportunities while serving as role models and mentors for elementary school children from underrepresented groups and low-income backgrounds. The initiative will serve as a catalyst to spark children's curiosity through hands-on activities to let them appreciate science with fun activities and inspire them to pursue education in STEM fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.