Ternary and Quaternary Metallic Nanoalloys: Highly Tunable Catalysts for Sustainable Chemistry

University Of Texas At Austin, Austin TX

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Profs. Simon M. Humphrey and Graeme Henkelman at the University of Texas at Austin are leading a collaborative research program involving the synthesis, catalytic and computational studies of new nanoparticle-based catalyst materials. The targeted catalysts are based on unstudied (and, in some cases, previously inaccessible) compositions of metallic elements, such that cooperative properties provide access to catalysts with new types of reactivity, and advanced chemical selectivity. Metal-based catalysts are widely utilized in large-scale conversions of simple chemical feedstocks to provide value-added products that are crucial to produce drugs, polymers, textiles, detergents, and many other materials required by modern society. Catalysts also reduce the production of waste by-products, which is environmentally important. This project will specifically aim to discover and study new catalyst materials that contain combinations of three or four different metallic species, whose specific catalyst compositions that have been predicted by computational chemistry to be capable of achieving advanced reactivity in the conversion of (a) bioethanol into hydrogen, and (b) to use the generated hydrogen in reaction with carbon dioxide to produce methanol. Bioethanol is an increasingly widely available liquid fuel, produced in the USA by natural (biological) fermentation of waste biomass, corn, grain etc. Meanwhile, biological processes do not provide easy access to methanol, which is required as a key chemical feedstock but must be prepared by traditional chemical processes that utilize fossil fuels, resulting in negative environmental impacts. The overarching aim of this project is to design new catalysts that can directly convert bioethanol into hydrogen and methanol. The performance of newly prepared catalysts is assessed using tandem experimental and computational methods. This work therefore provides a deeper fundamental understanding of how catalyst composition relates to reactivity enhancements, for future industrial implementation. With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Profs. Simon M. Humphrey and Graeme Henkelman at the University of Texas at Austin are leading an experimental-computational research program that targets the formation of new ternary and quaternary metallic nanoalloys for selective conversion of bioethanol into hydrogen and methanol. The collaborative research team utilizes computation approaches to predict specific combinations of noble and earth-abundant transition metals, which may not be accessible in bulk but are stable on the nanoscale. Synergistic effects in the nanoalloys are predicted to enable catalytic reactivity that is highly tunable towards two specific reactions: (a) reforming of bio-ethanol with water to yield hydrogen and carbon dioxide; (b) subsequent conversion of the hydrogen and carbon dioxide to generate selectively methanol. Bioethanol is an increasingly available and viable chemical feedstock, but the synthesis of methanol is still almost entirely dependent on traditional, energy-intensive pathways and produce by-products of environmental concern. Esoteric synthetic methods will be exploited to determine routes toward previously unstudied metallic alloys, enabling detailed model studies to elucidate important relationships between catalyst composition and structure and resulting reaction selectivity. The catalysts will feature new combinations of noble metals (Rh, Ir, Pd, Pt, Au) alloyed with earth-abundant transition metals (Co, Ni, Cu). The overarching goal is to obtain commercially viable catalysts for future production of methanol from bioethanol, at scale. To achieve this aim, the team utilizes model reaction studies conducted in water, under industrially realistic reaction conditions. By leveraging fundamental experimental results in combination with a palette of spectroscopic techniques, further computational studies provide realistic theoretical models at the atomic scale, which predict necessary catalyst refinements to further improve reaction activity and selectivity. 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.