Catalytic Selectivity Control in Electrochemical Systems using Self-Assembled Monolayers

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A major limitation of many chemical processes for synthesis of fuels and chemicals is the formation of unwanted byproducts. Catalysts are often used to direct chemical reactions towards desirable products. Combining electrochemistry with catalysis (i.e., electrocatalysis) opens the door not only to improved process selectivity, but also to improved energy efficiency and reduced environmental impact via sustainable and/or renewable energy from power sources such as wind and solar energy, and biomass. The study investigates modifications to electrocatalyst composition by surface coatings known as organic self-assembled monolayers (SAMS). The SAMS can be used in conjunction with electrocatalysts to convert renewable materials such as biomass to higher-value fuels and chemicals. The project will include training of postdoctoral researchers, graduate students, and community college instructors and students. Faculty and students on the project will prepare online instructional materials on electrochemistry that will be broadly disseminated.This project will develop new tools for selectivity control that employ an applied voltage to manipulate the structure of the catalyst, and thus its catalytic properties. Although “passive” SAMs have been used previously to improve catalyst performance, here the focus will be on the use of “active” SAMs that change their structure in response to the electric charge on the surface. Catalysts will be modified with ligands that undergo reversible coupling reactions or form bonds to the surface as a result of changes in electric potential. Such SAM-modified catalysts will then be evaluated for reactions where selectivity is a major challenge, using applied voltage as a new control for enhancing performance. The project will advance knowledge of how the organic near-surface environment can be designed to control selectivity on electrocatalysts and identify methods to design switchable surfaces that can hypothetically turn particular catalyst functions “on” or “off” using an electrical signal. To develop catalysts with electrically responsive coatings, the project will focus on the deposition of organothiolate SAMs on late transition metal surfaces such as Pd, Pt, and Au, and on SAM structures that have been shown to undergo potential-dependent changes in oxidation state, shape, and/or chemical bonding. The objectives of the project are to (i) conduct initial investigations of the use of SAM-modified catalysts under electrochemical conditions for a reaction system that has been thoroughly investigated in thermal catalysis to identify how the electrochemical environment affects the SAM; (ii) develop new methods to control cross-linking and surface density in SAMs that will provide fundamental information on design rules for potential-responsive systems; and (iii) modify catalysts with electroactive SAMs that enable potential-driven switching of catalyst performance.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.