Predictive Design and Scalable Synthesis of New Multimetallic Nanoparticles with Enhanced Surface Reactivity

University Of Texas At Austin, Austin TX

Investigators

Abstract

This a collaborative synthetic and computational research program between the groups of Profs. Simon M. Humphrey and Graeme Henkelman at the University of Texas at Austin, which focuses on the preparation and studies of new nano-catalyst materials. Catalysts reduce the total energy used in large-scale chemical processes, including the synthesis of fuels, polymers and textiles, drugs, and the remediation of environmental pollutants. Catalysts also reduce the amount of waste by-products that are generated. The majority of catalysts currently in use are based on precious metals, which are unfortunately also both scarce and expensive. Therefore, it is critically important to find ways to prepare modern catalysts that can operate using less total metal, whilst maintaining their catalytic performance. With support from the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, this project directly addresses these issues by studying the synthesis and properties of metallic nanoparticle catalysts that comprise only a few thousand atoms per entity; nanoparticles are attractive compared with bulk metals because they exhibit superior reactivity, as well as having very large surface areas compared to their volumes. The project also studies the use of scalable and environmentally-sustainable synthesis methods, such as microwave heating, to prepare new nanoparticle catalysts comprised of previously unstudied mixtures of precious metals. The fundamental properties of these new catalysts are assessed using experimental and theoretical (computational) methods, in order to understand how composition relates to performance improvements in real chemical reactions. The ultimate aim is to apply experimental and computational expertise to predict new catalyst compositions that should have optimal properties for given industrial processes. The project is also significantly enhanced through integration with an innovative new undergraduate educational program, called the Austin-International Framework in which undergraduates travel overseas to collaborate with world-renown research group. This highly collaborative synthetic and computational research program between the groups of Profs. Simon M. Humphrey and Graeme Henkelman at the University of Texas at Austin focuses on the synthesis and studies of new noble metal nanoparticle catalysts with unusual compositions. The major objectives of this research activity are to make direct connections between the structure and function of novel metallic nanoparticles that are comprised of unusual binary and ternary combinations of precious metals. There are significant intellectual challenges to achieve this goal. First, determining the atomic structure of supported multicomponent metal nanoparticles is difficult. A combination of electron microscopy, total X-ray scattering to generate pair distribution function data, extended X-ray fine structure spectroscopy, and temperature programmed desorption/reaction will be used to experimentally quantify structural parameters. This data will be used to inform realistic theoretical models at the atomic scale. Second, structural information with atomic detail is also critical to building theoretical models of active site, reactivity descriptors, and predictions of selectivity. It is also important to have feedback in terms of predictions from theory that can be tested experimentally, so that the models can be validated and calibrated. The ultimate goal of this work is to be able to rationally predict optimal structures and compositions of new catalysts that should have desired reactivity for specific applications. Meanwhile, differences between predictions and experimentally observed reactivity are equally valuable for improving the computational methods developed in this work. The project is also significantly enhanced through integration with an innovative new undergraduate educational program, called the Austin-International Framework (AIF). The AIF is an innovative and modern-thinking program that provides a fully immersive, scholarship-supported international exchange experience to UT Austin undergraduates. It provides students the unique opportunity to broaden their horizons by witnessing first-hand the global nature of science. The students involved in this program receive course credit for their research experiences and scholarships are provided to cover their basic cost-of-living expenses while doing research overseas. 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.