Application of ionic liquids in CO2 capture and electrochemical reduction: A review

As a new type of green solvent with non-volatility, high thermal stability, high conductivity and various adjustable properties, ionic liquid (IL) has been widely used in the capture and electrochemical reduction of carbon dioxide (CO2). To date, many studies have been made to investigate CO2 capture by using different types of ILs and CO2 electrochemical reduction (CO2ER) with ILs as either electrolyte or other catalytic active components. Some structure–activity relationships between the structure and adsorption or catalytic properties of ILs have been found. Herein, the absorption performances and mechanisms of conventional ILs, amino-functionalized ILs, non-amino functionalized ILs and supported ILs for CO2 capture, as well as the performances and action mechanisms of ILs as the electrolyte, electrolyte additive, and/or electrode modifier in the process of CO2ER are summarized. Many researches indicate that the unique interaction between the anion or cation of IL and CO2 has a significant contribution to promote the absorption and conversion of CO2. However, the ILs used for CO2 capture and electrochemical reduction should be further explored. Especially, a more in-depth investigation of the adsorption and catalytic mechanisms with the help of quantum chemical calculation, molecular simulation, and in situ characterization techniques is necessary. It is expected to design and develop more efficient ILs used for CO2 capture and conversion on a large scale.