Bifunctional Ionic Deep Eutectic Electrolytes for CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Green Chemistry

Background:

• Carbon dioxide (CO2) is a low-cost monomer for carboxylation reactions.
• Sustainable activation of CO2 via electroreduction (ECO2R) requires stable electrolyte media.
• Ionic deep eutectic electrolytes offer potential for enhanced electrochemical processes.

Purpose of the Study:

• To synthesize and characterize a novel diethyl ammonium chloride-diethanolamine (DEACl-DEA) ionic deep eutectic electrolyte.
• To evaluate the performance of DEACl-DEA in the electroreduction of CO2.
• To investigate the mechanism promoting ECO2R using bifunctional CO2 sorption.

Main Methods:

• Synthesis and characterization of DEACl-DEA electrolyte.
• Electrochemical evaluation of CO2 electroreduction using cyclic voltammetry and chronoamperometry.
• Analysis of CO2 capture capacity and electrolyte stability.
• Electrochemical impedance spectroscopy (EIS) and COSMO-RS modeling.

Main Results:

• DEACl-DEA exhibits a deep eutectic point of -69.78 °C and a cathodic stability limit of -1.7 V vs. Ag/AgCl.
• The DEACl-DEA (1:3) electrolyte achieved 94% faradaic efficiency for CO2 electroreduction to CO2•− at -1.5 V vs. Ag/AgCl.
• The electrolyte demonstrated a high ambient CO2 capture capacity of 52.71 mol/L.
• EIS and COSMO-RS analyses confirmed bifunctional CO2 sorption enhances ECO2R, evidenced by reduced electrochemical double layer capacitance (EDCL) due to CO2-electrolyte interactions.

Conclusions:

• The synthesized DEACl-DEA (1:3) electrolyte effectively promotes sustainable CO2 electroreduction.
• Bifunctional CO2 sorption and a high cathodic limit are crucial for efficient ECO2R electrolytes.
• This study establishes a new criterion for designing electrolytes for CO2 electroreduction.