Efficient Acidic CO₂ Electrolysis with Suppressed Crossover in a Separator-Based Membrane Electrode Assembly

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Acidic electrochemical CO2 reduction (CO2R) in flow cells faces challenges with CO2 crossover and ohmic losses due to thick catholyte layers.
• Removing catholytes leads to H2 selectivity due to excessive proton (H+) transport through cation exchange membranes (CEM).

Purpose of the Study:

• To develop a zero-gap membrane electrode assembly (MEA) that suppresses CO2 crossover and enhances C2+ production in acidic CO2R.
• To investigate the role of coupled ion transport (H+ and K+) in a novel separator for efficient CO2 electrolysis.

Main Methods:

• Fabrication of a zero-gap MEA with an electrolyte-filled hydrophilic porous separator.
• Tuning the H+ to K+ ratio and electrolyte permeance to regulate ion transport and suppress (bi)carbonate electromigration.
• Utilizing a 7,7,8,8-tetracyanoquinodimethane-modified copper oxide catalyst for CO2 reduction.

Main Results:

• Achieved significantly reduced CO2 crossover (0.19 sccm A-1).
• Attained 75% multicarbon (C2+) Faradaic efficiency and 24% energy efficiency at 3.5 V (300 mA cm-2).
• Demonstrated effective regulation of coupled H+ and K+ transport for optimized CO2R.

Conclusions:

• The developed separator-based MEA enables efficient acidic CO2 electrolysis with suppressed crossover.
• Controlling ion transport dynamics is crucial for high-performance CO2 reduction catalysts.
• This approach offers a promising pathway for efficient CO2 conversion technologies.