Ionic Liquids-Promoted Electrocatalytic Reduction of Carbon Dioxide

Abstract

The excessive consumption of global fossil fuels leads to the rapid increase of CO2 content in the atmosphere, causing serious consequences, such as global warming, which have attracted extensive attention from the international community. As a kind of abundant and inexpensive carbon resource, CO2 can be converted into high-utilization chemicals and fuels, and its resource utilization is of great significance to environmental protection and energy security. Among the many CO2 conversion technologies, electrochemical CO2 reduction (ECR) is considered to be one of the most promising methods, and it is a research hotspot in the world at present. In recent years, ionic liquids (ILs) have provided opportunities for the electroreduction of CO2 due to their unique physical and chemical properties. ILs have attracted more and more attention in the electrochemical reduction of CO2 due to their advantages of reducing reaction overpotential, inhibiting the hydrogen evolution reaction (HER), and improving product selectivity. In this paper, the research progress in recent years of ILs in electrocatalytic CO2 reduction is reviewed from three aspects: adsorption of CO2 by ILs, ILs-based electrolyte, and modification and preparation of electrodes in ILs. At the end of this paper, some issues and challenges to which more attention needs to be paid in future research were discussed as well.

Ionic Liquids and Deep Eutectic Solvents for CO2 Conversion Technologies—A Review

“…Bohlen et al [46] performed the electrodeposition of indium from 1:2 M choline based DES (ChCl:EG-1:2), employed them as an electrocatalyst for the electrochemical reduction of CO 2 to formate. As per the Cui et al [15] review, this was the first publication which reported on the preparation of CO 2 reduction catalysts by electrodeposition in DESs. Extending this method by tailoring the DES electrolyte properties and the electrodeposition conditions, it is possible to develop other metals with different sizes, shapes and structures and faces.…”

“…Ionic liquids have recently attracted a lot of interest as electrolytes because of their high CO 2 adsorption capacity, solubility, selectivity to CO 2 over other gases (such as N 2 , O 2 , CH 4 ), and low energy consumption. They are a very diverse and efficient family of promoters in the electrochemical reduction of CO 2 , with the ability to improve reaction characteristics by changing their interaction and exhibiting high electrochemically stable windows (4-5 V), high ionic conductivities, and low vapour pressures [10,15]. Also, it has been observed that ILs can lower the energy barrier of reactions by building complexes with the intermediates generated during the reaction [28].…”

“…CO 2 utilization via electrochemical route has been, and is a hot topic, with ILs, gaining increased attention. There are a lot of reviews published in the electrochemical reduction of CO 2 using ILs [10,15] and the electrosynthesis of organic compounds using CO 2 [8,9]. However, reviews on the combination of CO 2 reduction and transformation employing ILs and deep eutectic solvents (DESs) are very scarce.…”

Efficient Electroreduction of CO2 to CO on Porous ZnO Nanosheets with Hydroxyl Groups in Ionic Liquid‐based Electrolytes

“…The electrolyte is the medium for electrochemical reduction of CO 2 , which also has a great influence on the interactions among the electrocatalysts, CO 2 and its intermediates [1f,8] . Compared with aqueous electrolytes (e. g., 0.5 M KHCO 3 ), [9] ionic liquid (IL) has higher CO 2 capture ability, stronger ionic conductivity, and wider potential windows, which is considered as a promising electrolyte for CO 2 electroreduction [1d,10] . The special microenvironment of IL is conducive to dissolving and activating CO 2 molecules, and reducing the reaction energy barrier of CO 2 anion radicals’ formation [1d,10c] .…”

“…Compared with aqueous electrolytes (e. g., 0.5 M KHCO 3 ), [9] ionic liquid (IL) has higher CO 2 capture ability, stronger ionic conductivity, and wider potential windows, which is considered as a promising electrolyte for CO 2 electroreduction [1d,10] . The special microenvironment of IL is conducive to dissolving and activating CO 2 molecules, and reducing the reaction energy barrier of CO 2 anion radicals’ formation [1d,10c] . Meanwhile, it also can coordinate with the catalysts to regulate the catalytic performance of CO 2 electroreduction [11]…”