New Strategies for Creating Single and Dual Atom Catalysts on Silica Surfaces
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Catalysts allow reactions to proceed faster and to produce greater quantities of desirable products. Industrial chemistry would not be possible without the use of catalysts. However, big challenges remain regarding the sustainable use and recycling of catalysts. An optimal catalyst would consist of only one or two atoms that are prevented from grouping together and forming large bundles (aggregates). This separation of atoms can be achieved by arranging the atoms on a surface and retaining them at their specific surface sites. In this project, Professor Janet Bluemel of Texas A&M University is making use of two earlier discoveries to reach this goal. First, a well-defined one layer (monolayer) of metal complexes are placed on surfaces such as silica. The metal complexes are then modified to form single atoms that remain in place, dispersed on the surface. Similarly, two-atom assemblies are being prepared from metal complexes containing two different metal centers that are bound to the surface. Professor Bluemel''s group is exploring the catalytic activities of these single- and dual-atom catalysts, their ability to form products selectively, and their recyclability. Different analytical approaches are being used and refined to obtain better insight into the surface processes and ultimately generate more efficient catalysts with superior characteristics. The project is enhancing the fundamental knowledge about how to create well-defined, efficient, recyclable catalysts in general and is leading to more sustainable processes. This project also provides broad, in-depth training for undergraduate and graduate students in Professor Bluemel''s laboratory. In particular, the students are provided with opportunities for direct interaction with both domestic and international chemical companies, thus giving them unique and beneficial industrial experience.With funding from the Chemical Catalysis Program of the Chemistry Division, Professor Janet Bluemel of Texas A&M University is investigating dynamic processes on silica surfaces that involve supported molecular nickel, palladium, and copper complexes. The species are supported by tethering the complexes to the surface with the use of linkers. The tethered species are used as precursors to deliberately create well-defined single- and dual metal atom catalysts on surfaces such as silica. Dynamic processes do not occur only when covalently immobilized catalysts are suspended in a solvent. The Bluemel group has discovered that metal complexes adsorbed via Van der Waals interactions also display different modes of mobility on surfaces within pores, even in the absence of a solvent. At present there is a rudimentary understanding of how catalysts and their precursors diffuse in suspension or on dry surfaces. The ultimate goal of this project is to exploit the impact of specific tridentate phosphine linkers and the dry adsorption of nickelocene, which leads to well-defined monolayers, and to explore new methods for generating single- and dual atom catalysts (SACs, DACs) and well-defined nanoparticles on oxide surfaces. All approaches, which aim at stabilizing the metal particles and preventing their unrestricted growth are only feasible on surfaces. Investigating molecular immobilized and adsorbed catalyst precursors and the supported active metal catalysts generated from them, improves the understanding of their decomposition, agglomeration, and formation of metal particles. Direct insight regarding the structure and dynamics of all surface species is provided by High Resolution Transmission Electron Microscopy, dia- and paramagnetic 1H, 2H, 13C, 29Si, and 31P Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy of the dry materials and other techniques.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.
