Boosting Membrane Hydration for High Current Densities in Membrane Electrode Assembly CO₂ Electrolysis

Area of Science:

• Electrochemistry
• Chemical Engineering
• Materials Science

Background:

• Carbon dioxide (CO2) electrolysis is crucial for sustainable chemical production.
• Efficiency losses in CO2 electrolyzers are primarily caused by mass and ionic transport limitations within the membrane electrode assembly (MEA).

Purpose of the Study:

• To enhance CO2 electrolysis efficiency by increasing cation exchange membrane (CEM) hydration.
• To investigate the impact of humidifying the CO2 reactant stream on MEA performance.

Main Methods:

• Utilized a membrane electrode assembly (MEA) electrolyzer cell featuring a CEM.
• Introduced humidified CO2 reactant streams to the electrolyzer.
• Developed a semiempirical CEM water uptake model to analyze performance changes.

Main Results:

• Achieved a high current density of 755 mA/cm2 with humidified CO2.
• Reduced ohmic losses by fourfold at 575 mA/cm2 through full humidification.
• Observed an 11% increase in membrane water uptake and ionic conductivity.

Conclusions:

• Humidifying the CO2 reactant stream effectively increases CEM hydration and ionic conductivity.
• This strategy significantly reduces ohmic losses, overcoming critical bottlenecks in CO2 electrolysis.
• The findings enable more efficient and commercially viable CO2 electrolyzer technology.