(536j) The Effect of Alkali and Quaternary Ammonium Cations on the Electrochemical Interface Studied By in-Situ Infrared Spectroscopy

Recent computational studies have suggested that the adsorption of alkali metal cations may have significant impact on electrochemical processes, particularly those which occur at low potentials such as the hydrogen evolution (HER) and oxidation (HOR) reactions. It has also been demonstrated that the reactivity and selectivity of other important electrochemical processes such as CO₂ reduction are influenced by the presence of alkali cations in the electrolyte. In this study we employ surface-enhanced infrared absorption spectroscopy to study the adsorption of alkali and various quaternary ammonium cations using CO as a probe molecule on Pt electrodes. Linearly adsorbed CO is displaced at low electrode potentials (below the potential of zero charge) by electrostatically bound cations and forced to a bridge-bonded configuration. It is found that larger alkali cations such as K⁺ have stronger surface interactions with adsorbed CO than smaller alkali cations. Quaternary ammonium cations show the least pronounced effect.