Imidazolium ionic liquid additives improve the activity and selectivity for electrochemical CO2 reduction reaction on a variety of catalyst materials. To date, there is no consensus about the mechanism by which it does so. As a first step, we determined the Pourbaix diagram for EMIM+ at the Ag(111)|water interface using density functional theory calculations. The obtained surface Pourbaix diagram shows that adsorbed EMIM+ densely covers the entire silver surface under experimental conditions; we suggest this has important implications for CO2 reduction. (Graph Presented).