Cross-linked comb-shaped anion exchange membranes with high base stability

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Anion exchange membranes (AEMs) are critical for electrochemical devices like fuel cells and flow batteries.
• Developing stable and conductive AEMs remains a key challenge, particularly concerning their susceptibility to hydroxide degradation.
• Quaternary ammonium functional groups are common in AEMs but can be prone to degradation.

Purpose of the Study:

• To introduce a novel one-step cross-linking strategy for quaternary ammonium-containing polymers.
• To investigate the impact of this cross-linking method on membrane properties, including swelling, conductivity, and stability.
• To evaluate the performance of the cross-linked membranes in alkaline environments.

Main Methods:

• A one-step cross-linking strategy was employed, utilizing Grubbs II-catalyzed olefin metathesis to connect quaternary ammonium centers.
• The resulting cross-linked anion exchange membranes were characterized for their swelling ratios and hydroxide conductivities.
• The stability of the cross-linked membranes against hydroxide degradation was compared to non-cross-linked analogues.

Main Results:

• The cross-linked anion exchange membranes exhibited low swelling ratios, consistently below 10%.
• Hydroxide conductivities ranged from 18 to 40 mS cm(-1), indicating good ionic transport.
• The cross-linking process significantly improved the membranes' resistance to hydroxide degradation compared to non-cross-linked membranes.

Conclusions:

• The developed one-step cross-linking strategy effectively enhances the stability and performance of anion exchange membranes.
• Grubbs II-catalyzed olefin metathesis provides a viable route for creating robust cross-linked AEMs.
• These improved AEMs show promise for applications requiring high alkaline stability and conductivity.