CAREER: Engineering the Reactivity of Single Atom Electrocatalysts Beyond their Active Site

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Electricity generation from renewable sources, such as wind and sunlight, is becoming increasingly cheap and available. To meet our nation’s decarbonization goals, however, technologies are needed that can leverage this renewable electricity to produce useful chemicals and fuels with low carbon dioxide (CO2) emissions. Electrochemical processes are poised to address this critical need. For example, the electrochemical splitting of water can produce green hydrogen, while the oxidation of green hydrogen can yield carbon free energy on demand. But the viability of these processes depends on the performance and cost of catalytic materials needed for the electrochemical reactions. These catalysts are typically composed of rare and expensive metals such as platinum, palladium, and iridium. One strategy to improve the performance of these materials is to disperse the metal as individual atoms on a high surface area support. These “single-atom” catalysts (SACs) provide maximum metal usage efficiency and display unique catalytic properties. But key fundamental questions remain about how these catalysts carry out electrocatalytic reactions and what their true structure is under operating conditions. The project seeks to develop a fundamental understanding of electrochemical catalysis over SACs, and use this understanding to design new materials with improved performance and precious metal usage efficiency. The research will be integrated with educational efforts aimed at engaging students from underrepresented groups, particularly LatinX students, and exciting them about the role of catalysis in sustainability. Currently, single-atom electrocatalysts suffer from a lack of uniformity in their active site structures. To address that issue, the project will utilize atomic layer deposition (ALD) to synthesize catalysts with highly uniform catalytic active sites deposited on precisely synthesized metal oxide nanocrystalline supports. A combination of site-specific and in situ spectroscopies will be used to understand the atomic structure of the active sites and how their structure may evolve under reaction conditions. Having identified the nature of these active sites, links will be made between their structure and catalytic behavior. These structure-property relationships will be leveraged to design catalysts with optimal activity, systematically tuning the bonding of the metal site to the oxide support. This continuous tuning will be enabled by electrochemical ion insertion into the metal oxide support. In addition to understanding how the catalytic sites respond to changes in bonding to their support, the project will further demonstrate how their properties can be controlled by changing the electrochemical medium in which they operate. The insights developed in these studies will be used to design catalysts for selective electrochemical oxidation reactions using glycerol, a major byproduct of biodiesel, as a representative substrate.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.