Understanding heterogeneous catalysis at the molecular level is one of the grand challenges facing the development of efficient fuel cells, batteries, and solar-to-fuel technologies. This talk will demonstrate that catalytic intermediates at surfaces, which most generally result from charge localization to a surface site, can also be identified by well-defined molecular modes. Furthermore, it will show how to utilize these molecular, surface localized modes to detect the intermediates’ dynamic interaction with molecules in the electrolyte. By ultrafast mid-infrared spectroscopy and theory of the n-SrTiO3/aqueous interface upon pulsed UV excitation of the photo-catalytic water oxidation reaction, the Oxyl radical (Ti-O●) is detected by a sub-surface vibration of the O in the plane right below it. Such a radical, because it lacks a new bond when Ti-OH transforms into Ti-O● and occurs at a surface, has otherwise eluded direct spectroscopic detection. By an analysis of its vibrational lineshape, we observe that the sub-surface vibration couples to water librations, which means that the spectroscopy is sensitive to local H-bond making and breaking events generated by the Oxyl radical.

Observing molecular vibrations of catalytic intermediates at electrode surfaces

253rd National Meeting (2017)

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