Permselectivity and microstructure of anion exchange membranes

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Anion exchange membranes (AEMs) are crucial in electrochemical applications.
• Understanding their microheterogeneous structure is key to optimizing performance.
• Previous models often simplified membrane internal structures.

Purpose of the Study:

• To validate the two-phase model (gel and interstitial phases) for AMV and AMX anion exchange membranes.
• To investigate the influence of these phases on membrane properties and permselectivity.
• To analyze ion transport mechanisms within the membrane structure.

Main Methods:

• Determination of water content and ion exchange capacity.
• Conductivity measurements to validate the two-phase model.
• Chronopotentiometry to assess surface homogeneity.
• Analysis of KCl sorption to confirm partition equilibrium.

Main Results:

• The two-phase model was validated for AMV and AMX membranes.
• Chronopotentiometry confirmed overall surface homogeneity.
• Co-ions were found predominantly in the interstitial phase, not affecting counter-ion transport in the gel phase.
• Partition equilibrium of KCl between the interstitial phase and external solution was confirmed.

Conclusions:

• The two-phase model effectively represents the microheterogeneous structure of AEMs.
• The distinct phases significantly influence membrane permselectivity and ion transport.
• Partition equilibrium is a critical factor in understanding ion distribution within AEMs.