Ionic liquids have recently been suggested to suppress the hydrogen evolution reaction (HER), as well as increase selectivity and activity for CO2 reduction to high value chemicals and fuels. To learn more about the origin of this effect, we have studied the influence of the ionic liquid 1-ethyl-3-methylimidazolium chloride ([EMIM] Cl) on HER on Ag, Cu and Fe electrodes in acidic and basic media. In the absence of CO2, HER is suppressed on all three electrodes in acidic media; no such suppression is observed in basic media. Furthermore, we used 1H NMR spectroscopy to identify compounds that are formed as the [EMIM] Cl breaks down at both the working and counter electrodes under electrochemical reaction conditions.