Electrochemical CO₂ Reduction on a Bi-Sn Eutectic Alloy in Acidic Media for Formic Acid Production

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Electrochemical CO2 reduction (eCO2R) is a sustainable carbon utilization pathway.
• Neutral/alkaline media limit eCO2R by forming (bi)carbonate, complicating product recovery and long-term operation.

Purpose of the Study:

• To investigate acidic conditions for direct formic acid production via eCO2R.
• To develop and evaluate a Bi-Sn gas-diffusion electrode (GDE) for enhanced performance and stability.

Main Methods:

• Operated eCO2R in a pH 3 electrolyte using a eutectic Bi-Sn GDE.
• Characterized electrode performance via Faradaic efficiency (FE) and current density.
• Utilized density functional theory (DFT) to understand reaction mechanisms.
• Assessed GDE stability over 100 hours of continuous operation.

Main Results:

• Achieved 81.3% FE for formic acid at -100 mA cm-2 in pH 3 electrolyte.
• Formic acid remained the dominant product up to -400 mA cm-2.
• Identified a synergistic Bi-Sn interfacial effect suppressing hydrogen evolution and promoting formic acid formation.
• Demonstrated stable performance with <10% FE loss over 100 h continuous operation.

Conclusions:

• Acidic eCO2R is a viable strategy for high-purity formic acid production.
• Interfacial alloy engineering of GDEs can significantly advance CO2 electrolysis.
• This approach supports scalable, renewable energy-powered chemical manufacturing.