Chemical Imaging of Metal Surfaces at the Solid-Liquid Interface: Effects of Grain Structure on Electrocatalytic Reactions

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With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) and the Chemical Measurement and Imaging (CMI) Programs in the Division of Chemistry, Professor Steven Baldelli from the University of Houston is using highly sensitive surface techniques to understand how molecules react on polycrystalline electrodes. Chemical reactivity of analytes adsorbed to an electrode depends on the underlying crystallinity of a surface as well as its adjacent grains. Studying these effects require the use of methods that reveal surface crystallography, depend on the electrode surface electronic state and symmetry, and impact local vibrational information about the adsorbed molecules. By controlling the system electrochemically, Professor Baldelli and his students will map surface chemistry and link it to underlying crystallography to develop a physical understanding of how crystalline domains influence heterogeneous catalysis. Graduate, undergraduate, and high school students will be mentored and collaborate through this research. Students will develop skills related to instrument building, data analysis, and spectral and microscopy image interpretation.This project uses in situ sum frequency generation vibrational spectroscopy/microscopy (SFG) to probe molecules adsorbed to an electrode while second harmonic generation microscopy (SHG) assists in the determination of the electronic state and symmetry of the electrode. Because SHG anisotropy is related to surface crystallography, the combination of these techniques results in the generation of correlated maps of surface chemistry and underlying crystallography. Surface reactivity is then interrogated using cyclic voltammetry with sub-micron resolution under reaction conditions. In so doing, impacts of adjacent grains in a polycrystalline surface are evaluated. Broader impacts of this work have the potential to advance surface sensitive spectroscopy and microscopy tools that could advance the chemical and physical understanding of how the electrode influences heterogeneous electrocatalysis.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.