Ternary Ionic-Liquid-Based Electrolyte Enables Efficient Electro-reduction of CO₂ over Bulk Metal Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Efficient electro-reduction of carbon dioxide (CO2) to valuable products like carbon monoxide (CO) is crucial for sustainable chemistry.
• Bulk metal catalysts offer an ideal but challenging route due to efficiency and selectivity issues.

Purpose of the Study:

• To develop a highly efficient system for CO2 electro-reduction to CO using bulk metal electrodes.
• To investigate the role of a novel ternary ionic-liquid electrolyte in enhancing catalytic performance and stability.

Main Methods:

• Coupling of various bulk metal electrodes with a ternary ionic-liquid electrolyte composed of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, and acetonitrile (MeCN).
• Electrochemical characterization to measure current density, Faradaic efficiency (FE) for CO, and hydrogen evolution reaction (HER) suppression.
• Analysis of electrolyte aggregation and electrochemical double-layer structure to understand performance enhancement.

Main Results:

• The ternary ionic-liquid electrolyte significantly increased current density across various bulk metal electrodes.
• High Faradaic efficiency (FE) for CO (FE_CO) approaching 100% was maintained over a wide potential range.
• Suppression of the hydrogen evolution reaction (HER) was observed, leading to improved selectivity for CO.
• Bulk metal electrodes exhibited excellent stability in the ternary electrolyte during CO2 electro-reduction.

Conclusions:

• The ternary ionic-liquid electrolyte's unique aggregation behavior and cation arrangement enhance electrode wettability and CO2 adsorption.
• Extended H+ diffusion channels within the electrochemical double layer contribute to high current density and FE_CO.
• This approach offers a promising strategy for efficient and stable electro-reduction of CO2 to CO using cost-effective bulk metal catalysts.