Organic Non-Nucleophilic Electrolyte Resists Carbonation during Selective CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Catalysis
• Green Chemistry

Background:

• Spontaneous carbonation of electrolytes in CO2 electrolyzers reduces efficiency.
• Aprotic solvents with low water content and non-nucleophilic acids are proposed to mitigate carbonation.

Purpose of the Study:

• To investigate if an aprotic electrolyte design can achieve high CO2 reduction selectivity and low carbonation.
• To demonstrate a new electrolyte strategy for efficient CO2 electroreduction.

Main Methods:

• Electrochemical CO2 reduction using a polycrystalline Au catalyst.
• Dimethyl sulfoxide as the solvent with acetic acid/acetate as the proton donor.
• Nuclear Magnetic Resonance (NMR) spectroscopy for electrolyte analysis.

Main Results:

• Over 90% faradaic efficiency for CO2 to CO reduction was achieved.
• Low millimolar bicarbonate concentrations were observed, indicating minimal carbonation.
• High proton activity and stability were maintained in the aprotic electrolyte, even with added water.

Conclusions:

• Electrolyte carbonation can be attenuated and decoupled from efficient CO2 reduction.
• Aprotic solvents offer a viable strategy for designing advanced CO2 electrolyzer electrolytes.
• This work provides new principles for low-temperature CO2 electroreduction systems.