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Abstract Electrochemical CO₂reduction (CO₂RR) on copper (Cu) shows promise for higher‐value products beyond CO. However, challenges such as the limited CO₂solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion‐CO₂adducts and a hydrogen bond donor (HBD) upon CO₂absorption to modulate CO₂RR on Cu in a non‐aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface‐enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum‐mechanical/molecular mechanics (IC‐QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO₂availability, reduced overpotential, and suppressed HER where C₄products are obtained. This study deepens the understanding of electrolyte effects in CO₂RR and the role of IL ions towards electrocatalytic microenvironment design.