Proton-Exchange Membranes with Stabilized Conductivity

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Proton-exchange membranes (PEMs) are vital for fuel cells and water electrolyzers.
• Dehydration under low humidity significantly degrades PEM performance.
• Current reviews often lack mechanistic analysis of proton conductivity stabilization.

Purpose of the Study:

• To systematically review and evaluate methods for enhancing moisture-independent proton conductivity in PEMs.
• To analyze the mechanisms behind proton conductivity stabilization under dehydration.
• To assess the prospects of various strategies for PEMs operating under harsh conditions.

Main Methods:

• Literature review and systematic analysis of experimental results.
• Categorization of strategies into hybrid composites, ionomer structure control, and novel polymers.
• Evaluation of factors influencing conductivity: microstructure, sulfonic group concentration, and hydration.
• Assessment of water retention and thermal resistance for dry condition stability.

Main Results:

• Hybrid composites, ionomer pre-treatments, and new polymers are key strategies.
• Hydrophilic additives forming stable hydrates enable proton transport at high temperatures (up to 120 °C, 50% RH).
• Sulfonated aromatic polymers and PBI-based membranes show promise but face durability challenges.
• Nafion-based composites currently offer a superior balance of conductivity, stability, and processability.

Conclusions:

• Stabilizing proton conductivity under low humidity is achievable through water retention mechanisms.
• Oriented channels, MOFs, and graphene-based materials are promising future research directions.
• Long-term performance and additive degradation remain critical research gaps for PEM development.