Ionic liquids/salts for electrochemical CO₂ capture and separation

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Electrochemical CO2 capture (ECC) presents a sustainable alternative to traditional thermochemical methods, operating efficiently at constant temperatures and utilizing renewable energy.
• Ionic liquids and salts are emerging as key materials in ECC due to their low vapor pressure, high ionic conductivity, wide electrochemical windows, and tunable properties.

Purpose of the Study:

• This review critically examines the dual role of ionic liquids/salts in advancing electrochemical CO2 capture technologies.
• It explores their application as auxiliary agents and as integrated active materials for enhanced CO2 absorption.

Main Methods:

• The review synthesizes existing research on ionic liquids/salts used as solvents, electrolytes, or additives to improve redox-active carrier performance.
• It also analyzes the design of ionic materials where ionic moieties are directly integrated with redox-active cores.

Main Results:

• Ionic liquids/salts significantly enhance CO2 solubility, stabilize intermediates, prevent side reactions, and optimize energy requirements for CO2 binding.
• Integrated ionic materials, like viologens and quinone-annulated salts, demonstrate direct CO2 binding or pH modulation for capture, leading to high capacity and efficiency.

Conclusions:

• Ionic liquids/salts show great potential for high-capacity, high-efficiency, and low-energy electrochemical CO2 capture.
• Challenges include O2 sensitivity, solubility-viscosity trade-offs, and cost, but future advancements lie in computational screening, integrated capture-conversion systems, and reactor design.