Acidic CO₂ Electrolysis With Near-Ideal Selectivity and Carbon Efficiency Enabled by Overcoming Its Inherent...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Acidic electrolytes offer a promising route for carbon dioxide electroreduction (CO2R), avoiding issues seen in alkaline or neutral media.
• High alkali cation concentrations (≥3 M) are typically needed for CO2 activation and to suppress water reduction, but this leads to carbonate formation and low single-pass carbon efficiency (SPCE).
• A trade-off exists between increasing cation concentration for higher Faradaic efficiency (FE) and maintaining SPCE in CO2R.

Purpose of the Study:

• To overcome the trade-off between FE and SPCE in acidic CO2R.
• To develop a novel strategy for efficient CO2 activation and reduction in dilute acidic electrolytes.
• To demonstrate a practical method for enhancing both carbon and electron efficiency in CO2 electrolysis.

Main Methods:

• Theoretical and experimental analysis of cation concentration effects on CO2R.
• Development of a polyimide-modification strategy utilizing amino groups to create a local alkaline microenvironment.
• Proof-of-concept experiment using polyimide-modified SnO2 nanoparticles as a CO2R catalyst.

Main Results:

• The polyimide modification effectively captures protons, establishing a localized alkaline environment at the electrode surface.
• Modified SnO2 nanoparticles achieved near-ideal SPCE (95.7%) and high FE (96% towards HCOOH) simultaneously.
• These results were obtained in a dilute acidic electrolyte (pH 1.36) with low potassium ion concentration (0.1 M).

Conclusions:

• The polyimide-modification strategy successfully overcomes the inherent trade-off in acidic CO2R.
• This approach enables highly efficient CO2 conversion to products like formic acid using dilute electrolytes.
• The findings are expected to accelerate the development of efficient and practical acidic CO2 electrolysis systems.