Directly observing active surface intermediates and interfacial solvation structure represents a major challenge for bridging surface science to electrocatalysis. Toward this goal, we utilized plasmon-enhanced vibrational sum frequency generation spectroscopy to measure reaction intermediates and interfacial solvation structure at a gold/electrolyte interface during electrochemical carbon dioxide reduction (CO2R). Specifically, selectivity and activity of CO2R are sensitive functions of the electrolyte cation. By measuring the vibrational Stark shift of in-situ generated CO on Au in the presence of alkali cations, we quantify the total electric field present during turnover and deconvolute this field into contributions from 1) the electrochemical Stern layer and 2) the Onsager, or solvation-induced, reaction field. The magnitude of the Onsager field is shown to be on the same order as the Stern layer field (∼10 MV/cm) but follows an opposite trend with cation, increasing from Li+&lt; Na+&lt; K+&lt; Rb+≈Cs+. Contrary to theoretical reports, CO2R kinetics are not correlated with the Stern field but instead are controlled by the strength of the Onsager reaction field These findings show that both the Onsager reaction field and interfacial solvation structure must be explicitly considered for accurate modeling of CO2R reaction kinetics.

Probing interfacial solvation structure and electric fields during CO2 reduction electrocatalysis on gold

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.