Nonconductive Metal Oxide Gas Diffusion Layer for Mitigating Electrowetting during CO₂ Electrolysis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Gas diffusion electrodes (GDEs) are crucial for electrochemical CO2 reduction (ECO2R) at high current densities.
• Conventional carbon-based gas diffusion layers (GDLs) in GDEs are prone to electrolyte flooding due to electrowetting, limiting performance.
• Electrowetting is linked to the electrical conductivity of carbon supports, hindering CO2 electrolysis.

Purpose of the Study:

• To investigate the impact of electrical conductivity in GDLs on electrowetting and ECO2R performance.
• To develop alternative GDL materials that mitigate flooding issues in GDEs for enhanced CO2 electrolysis.
• To explore the potential of nonconductive GDLs for stable and efficient electrochemical CO2 reduction.

Main Methods:

• Constructed a GDE utilizing a copper (Cu) mesh substrate with a nonconductive microporous GDL composed of alumina and polytetrafluoroethylene (PTFE).
• Compared the performance of the alumina-based GDL GDE with a conventional Vulcan carbon-based GDL GDE under electrochemical CO2 reduction conditions.
• Utilized in situ microscopy to observe electrode flooding during electrolysis.

Main Results:

• The alumina-based GDL GDE demonstrated stable operation at -200 mA cm-2 with 70% selectivity for ECO2R, including significant C2+ product formation.
• Severe flooding and rapid loss of activity were observed with the conventional carbon-based GDL GDE.
• In situ microscopy confirmed the absence of flooding with the nonconductive alumina GDL.

Conclusions:

• A nonconductive alumina-based GDL effectively prevents electrowetting-induced flooding in GDEs for electrochemical CO2 reduction.
• Replacing conductive carbon supports with nonconductive materials offers a promising strategy to enhance ECO2R stability and performance.
• This work provides a new perspective on GDL material design for advanced CO2 electrolysis applications.