Ionic Liquids as Interfacial Media for Metal-Free Electrochemical CO ₂ Reduction in Water

The electrochemical carbon dioxide reduction reaction (CO2RR) in water offers a sustainable pathway to mitigate carbon emissions while generating value-added chemicals. Most conventional CO2RR systems rely heavily on metal-based catalysts. Beyond traditional metal-based catalyst design, attention has increasingly shifted to understanding how the electrochemical microenvironment and the electrode–electrolyte interface influence CO2RR. Ionic liquids (ILs), widely regarded as green solvents, have previously been employed as electrolytes or cocatalysts in metal-catalyzed systems. Yet, the ability of ILs to facilitate CO2RR at metal-free interfaces in aqueous media remains underexplored. Here, we demonstrate that ILs polarize CO2 and facilitate CO2 electrochemical response at a glassy carbon interface under aqueous conditions, while simultaneously functioning as electrolytes. Spectroscopic, electrochemical, and computational analyses reveal that ILs interact with CO2, thereby increasing its dipole moment. This interaction suggests a favorable environment for CO2 polarization that correlates with the observed electrochemical response. The response efficiency depends on the chemical identity of the ILs, highlighting the tunability of this IL-based system. These findings redefine the functional role of ILs in CO2RR, establishing IL-induced molecular polarization as a potential strategy for promoting the reactivity of otherwise inert molecules. More broadly, this work introduces IL-driven dipole modulation as a general approach for enabling reactivity of nonpolar small molecules, with implications for sustainable chemical synthesis.