Catalytic Chemistry with Shape-Tuned Nanoparticles

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In this project funded by the Chemical Catalysis Program of the Chemistry Division, Beatriz Roldan Cuenya of the University of Central Florida (UCF) will synthesize metal nanoparticles (NPs) with uniform sizes (1-3 nm), shapes, and structures and investigate the correlation between their geometrical shape and catalytic properties. Target material systems will include gold, platinum, and palladium NPs supported on titanium dioxide, strontium titanate, aluminum oxide, and zirconium dioxide. Reactions of environmental and economic importance such as carbon monoxide oxidation and the water-gas-shift reaction over gold and platinum NPs and nitrous oxide (NOx) reduction over palladium NPs will be investigated. Understanding the relationship between the structure and function of catalysts requires detailed information about their three-dimensional atomic configurations as well as possible chemical changes occurring under reaction conditions. To address the complexity of real-world catalysts, a synergistic approach taking advantage of a variety of experimental methods will be undertaken. These methods include in-situ X-ray absorption spectroscopy, atomically-resolved scanning and environmental transmission electron microscopy, scanning tunneling and atomic force microscopy, X-ray photoelectron spectroscopy and diffuse reflectance Fourier transform infrared spectroscopy. Tailoring the chemical reactivity of nanomaterials at the atomic level is one of the most important challenges in catalysis research. To achieve this elusive goal, fundamental understanding of the geometric and electronic structure of these complex systems must be obtained. Numerous studies have been devoted to understanding the properties that affect the catalytic performance of metal nanoparticles such as their size, interaction with the support, and oxidation state. The role played by the nanoparticle shape on catalytic performance is, however, less understood. Complicating the analysis is the fact that the former parameters cannot be considered independently, since the NP size as well as the support will have an impact on the most stable NP shapes. In addition, the dynamic nature of the NP catalysts and their response to the environment must be taken into consideration, since the working state of a NP catalyst might not be the state in which the catalyst was prepared, but rather a structural and/or chemical isomer that adapted to the particular reaction conditions. The selected model reactions have broad applications in the fields of energy generation and environmental remediation, as for example NOx reduction in turbines and automotive catalytic processes. This project will support the research efforts of doctoral students and K-12 students at UCF, which will also be trained at the user facilities of Brookhaven National Laboratory and Argonne National Laboratory. Furthermore, the principal investigator will bring concepts related to the field of nanoscience closer to the general public via her involvement with the Orlando Science Center, including the organization of an annual poster exhibit entitled "Art in Science, Science in Art".