Descriptors for Electrochemical CO₂ Reduction in Imidazolium-Based Electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Electrochemical CO2 reduction (CO2R) offers a pathway for carbon cycle closure and renewable energy storage.
• Syngas production via electrocatalysis is energy-efficient and industrially relevant.
• Ionic liquids (ILs) are explored as electrolytes to optimize CO2R selectivity.

Purpose of the Study:

• To rationalize the competition between hydrogen evolution (HER) and CO2R on silver catalysts in imidazolium-based electrolytes using density functional theory (DFT).
• To develop a DFT-based analytical model to predict CO2R selectivity.
• To establish guidelines for designing improved IL electrolytes for CO2R.

Main Methods:

• Density Functional Theory (DFT) calculations to analyze reaction mechanisms and energetics.
• Development of a DFT-based analytical model incorporating electrolyte properties.
• Investigation of imidazolium-based ILs with varying anions, focusing on cation/carbene species and Lewis basicity.

Main Results:

• The electrolyte anion's Lewis basicity influences the concentration of catalytically active IL cation species versus hindering carbene species.
• Weak Lewis base anions (e.g., fluorinated) favor the abundance of active IL cations, promoting CO2R.
• High CO partial current densities and electrochemically active surface area were observed with specific IL electrolytes.

Conclusions:

• The study provides descriptors to predict HER and CO2R selectivity on silver in IL electrolytes.
• The findings enable rational design of ILs for enhanced CO2R performance.
• This work contributes to advancing efficient carbon capture and utilization technologies.