When Flooding Is Not Catastrophic-Woven Gas Diffusion Electrodes Enable Stable CO₂ Electrolysis

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Electrochemical CO2 reduction offers a pathway to convert renewable electricity into valuable chemicals and fuels.
• Gas diffusion electrodes (GDEs) are crucial for efficient CO2 mass transfer but are prone to flooding under hydrostatic pressure, hindering scalability.
• Understanding flooding effects is vital for optimizing GDE performance in CO2 electrolyzers.

Purpose of the Study:

• To investigate the impact of flooding on CO2 reduction performance using various gas diffusion layer materials.
• To evaluate the tolerance of different GDE microstructures to varying pressures and flow regimes.
• To identify GDE materials suitable for large-scale CO2 electrolysis.

Main Methods:

• Tested six commercial gas diffusion layer materials (carbon cloth and carbon paper) coated with silver (Ag) catalyst.
• Exposed GDEs to differential pressures simulating gas breakthrough, flow-by, and liquid breakthrough regimes.
• Measured CO2 reduction performance, focusing on Faradaic efficiency for CO (FECO) at current densities up to 200 mA cm-2.

Main Results:

• Most carbon papers showed reduced FECO due to electrowetting-induced flooding at high current densities.
• Carbon cloth GDEs maintained high CO2 reduction performance despite electrolyte flooding, attributed to their bimodal pore structure.
• Carbon cloth GDEs sustained an average FECO of 69% at 200 mA cm-2 even under continuous liquid breakthrough at 100 cm height pressure.

Conclusions:

• The bimodal pore structure of carbon cloth GDEs effectively mitigates flooding issues in CO2 electrolysis.
• Carbon cloth GDEs demonstrate robustness and high efficiency across a wide range of operating conditions, making them suitable for scale-up.
• This finding advances the development of practical CO2 electrolyzers for sustainable chemical and fuel production.