In order to determine the reaction intermediates involved in the electrochemical reduction of nitrogen, a spectroscopic method suited to examinations of the surface of an electrode must be tested. Using sum-frequency generation vibrational spectroscopy, which is specific to interfaces, the NH vibrational modes of adsorbed ammonia are investigated. The gas/solid interface and the liquid/solid interface are probed to investigate the adsorbed molecules on the surface of a gold substrate. We were able to detect the adsorbed NH3 at gas/solid interface at approximately 3300 cm-1 wavenumber and in the liquid/solid interface at approximately 3200 cm-1, and the resulting spectra was fit based on a Lorentzian line shape equation. Further analysis of the peak position can support different modes of adsorption. The development of this methodology can be used to conduct in-situ SFG tests of electrochemical reactions of nitrogen compounds.

SFG spectroscopy study of the NH vibrational modes at gas/solid and solid/liquid interfaces

ACS Fall 2021

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