Electrochemical conversion of CO₂ in non‐conventional electrolytes: Recent achievements and future challenges

Abstract

Electrochemical reduction of CO2 in traditional aqueous electrolytes suffers from low faradaic efficiency towards desired products which can be traced back to low CO2 solubility and strong competition from the hydrogen evolution reaction. The use of non‐conventional electrolytes aims to mitigate these issues. This review will give a focused overview summarizing some of the most recent contributions on the electrochemical conversion of CO2 in organic solvents, ionic liquids, solid electrolytes, and brines. We summarize the findings in terms of activity, selectivity, and durability for each of the systems. In addition, it provides an outlook about the role of water, cations, and anions in the reaction. We also highlight the challenges of the electrochemical reduction of CO2 in each of the electrolytes. All the studies referred to in this review contribute meaningfully to reaching the technical targets for CO2 electrolyzers in non‐conventional electrolytes.

In Situ Spectroscopic Characterization of an Intermediate of CO2 Electroreduction on a Au Electrode in Room-Temperature Ionic Liquids

“…Indeed, near 100% efficiency was reported for neat and diluted RTILs. , In addition, the issue of high overpotentials was also improved by the use of RTIL electrolytes. The decrease of overpotential of CO 2 reduction in RTILs was first reported by Rosen et al through the experiment using 1-ethyl-3-methyl-imidazolium tetrafluoroborate [C 2 mim]­[BF 4 ] and later reported for various RTILs. − …”

Advanced Catalyst Design and Reactor Configuration Upgrade in Electrochemical Carbon Dioxide Conversion

“…However, it is not practical because of its high cost and high viscosity. [250][251][252][253] An estimation shows that in aqueous electrolytes, the CO 2 RR-specific reaction current is limited to 100 mA cm −2 , basically dictated by the slow CO 2 mass transport rate. [254] Obviously, this is insufficient to reach industrial demand.…”

Review on CO2 Management: From CO2 Sources, Capture, and Conversion to Future Perspectives of Gas-Phase Electrochemical Conversion and Utilization

“…To prevent the interaction of doped material with electrode, a layer of doped CeO 2 is usually added between the electrode and electrolyte . In such systems, the perovskite materials are usually utilized as cathode catalyst for CO 2 conversion, mainly producing CO. , The total solid-state electrochemical cells are called solid oxide electrolysis cells (SOECs), which may be combined with other CO 2 conversion systems, such as Fischer–Tropsch synthesis in the presence of H 2 , to obtain more reduced products, such as CH 4 . − Molten inorganic electrolytes, such as phosphate or carbonate salts, which can be melted at modest temperatures (usually 350–600 °C), have also been proposed for CO 2 electroreduction, as they have offered higher selectivity than aqueous electrolytes. − Even though they can be operated at lower temperatures than SOECs, they have not been developed as well as other methods because of difficulty in controlling phase transfer of electrolyte from the solid to molten state.…”