Understanding the Influence of [EMIM]CI on the Suppression of the Hydrogen Evolution Reaction on Transition Metal Electrodes

We have studied the influence of low concentrations (0.1 M) of the ionic liquid 1-ethyl-3methylimidazolium chloride ([EMIM]Cl) on suppressing the hydrogen evolution reaction (HER) using polycrystalline Ag, Cu, and Fe electrodes in aqueous acidic and basic media. HER suppression is generally desired when aiming to catalyze other reactions of interests, e.g., CO2 electro-reduction. Cyclic voltammetry and chronoamperometry measurements were performed at potentials between 0.2 and 0.8 V versus the reversible hydrogen electrode was suppressed by 75% at 0.5 V versus RHE. In contrast to the effect of [EMIM] Cl in an acidic electrolyte, no HER suppression was observed in basic media. Using 'El nuclear magnetic resonance spectroscopy on the electrolyte before and after electrolysis, it was determined that [EMIM]Cl breaks down at both the working and counter electrodes under reaction conditions under both acidic and basic conditions. These results underscore the challenges in employing ionic liquids for electrochemical reactions such as CO2 reduction.(RHE) to investigate HER activity in a simulated CO2 electrolysis environment without the CO2. In an acidic electrolyte, a decrease in HER activity