Catalysts are the unsung heroes of chemistry: Widely used in industry, they speed up chemical reactions by making the reactions much more efficient. Many important reactions related to global issues, such as climate change and carbon-neutral fuel production, take place on the surfaces of metal catalysts. Today we know very little about how these reactions proceed. My research is aimed at understanding the fundamental physics that occur during chemical reactions on the catalytic surfaces. We study these systems using lasers to obtain a better understanding of heterogeneous catalysis and to use this knowledge to selectively and efficiently drive chemical reactions. Students in my group work with their peers on a project, with each student leading a specific aspect of the project.

Photocatalysts that use the visible light to mediate solar-to-chemical transformations are necessary for the development of green methods for chemical synthesis. Plasmonic nanoparticles are a promising class of green photocatalysts for a range of important chemical reactions due to their large surface area, high number of low-coordinated sites, high absorption cross-sections, and efficient electron-hole pair generation. Plasmons are a collective oscillation of the electron gas in the metal catalysts and can lead to highly energetic (hot) electrons. One of the biggest challenges in creating plasmonic nanoparticle photocatalysts, however, is the ability to tune the chemical environment for specific reactions as most plasmonic nanoparticles are composed of either gold, silver, or copper. My research involves designing highly selective and active plasmonic photocatalysts through modifying the chemical environment using d-band transition metal shells on the plasmonic gold nanoparticles (M-AuNP), and probing these reactions using surface-enhanced Raman spectroscopy (SERS). SERS is a powerful surface sensitive spectroscopic technique that uses the inelastic scattering of light to provide information about bond energies for the reactants, intermediates, and products involved during chemical reactions. Reactions of interest include carbon monoxide (CO) oxidation, CO hydrogenation (Fischer-Tropsch process), hydrocarbon formation, and water formation.

X-ray free-electron laser (XFEL) sources are a powerful tool to probe the element- and chemical-dependent dynamics of chemical reactions. We probe the time evolution of the electronic structure of photochemical reactions on metal catalysts using femtosecond x-rays from XFELs, revealing detailed information about the dynamics of the electronic structure. Each experiment generates 10s of terabytes of data, which must be parsed, analyzed, and stitched together using Python to generate the time-dependent electronic structure maps. Once completed, these electronic structure maps are coupled with theoretical calculations to reveal detailed reaction dynamics. Reactions of interest include carbon monoxide (CO) formation, CO oxidation, CO hydrogenation (Fischer-Tropsch process), and water-gas-shift.