Heating dictates the scalability of CO₂ electrolyzer types

Area of Science:

• Electrochemistry
• Chemical Engineering
• Renewable Energy

Background:

• Electrochemical CO2 reduction converts renewable energy to valuable hydrocarbons for hard-to-abate sectors.
• Lab-scale progress is significant, but industrial scale-up faces challenges, particularly thermal management.
• Non-isothermal effects at larger scales can severely impact efficiency.

Purpose of the Study:

• To model non-isothermal behavior in membrane electrode assembly (MEA) CO2 electrolyzers beyond 1D.
• To compare the performance of liquid anolyte-fed (exchange MEA) and fully gas-fed (full MEA) configurations at scale.
• To identify optimal operating temperatures for CO2 reduction.

Main Methods:

• Developed a 2D model for two types of MEA CO2 electrolyzers: exchange MEA and full MEA.
• Simulated non-isothermal behavior and its impact on electrochemical performance.
• Analyzed thermal gradients, membrane dehydration, and Ohmic losses.

Main Results:

• Full MEA configurations show poor performance at larger scales due to severe heating, membrane dehydration, and Ohmic losses.
• Exchange MEA configurations effectively prevent large thermal gradients, maintaining constant current density and indicating suitability for scale-up.
• An optimal operating temperature range of 60-70 °C was identified, balancing kinetics, conductivity, pH, and CO2 solubility.

Conclusions:

• Exchange MEA designs are well-suited for scaling up electrochemical CO2 reduction.
• Effective thermal management is crucial for efficient, large-scale CO2 conversion.
• Optimizing operating temperature enhances overall system performance.