Proton Conducting Membranes for Fuel Cell Applications

Proton conducting membranes lie at the heart of polymer electrolyte membrane fuel cells (PEMFCs), enabling selective proton transport from anode to cathode while blocking electrons and fuel crossover. Commercial perfluorosulfonic acid membranes have set performance benchmarks, yet they face limitations in cost, operating temperature and environmental impact. Research is therefore advancing a diverse array of hydrocarbon polymers, heterocycle‐based materials and composite systems. Key challenges include sustaining high proton conductivity under low humidity or elevated temperatures, mechanical and chemical stability in oxidative environments, and minimising gas crossover. Innovations in membrane architecture—such as three‐dimensional cross‐linking, incorporation of inorganic or paramagnetic fillers, fibre templating and alignment techniques—have demonstrated enhanced proton channel continuity, improved water retention and acid anchoring. Such developments promise to extend operational windows beyond 120 °C, reduce reliance on precious‐metal catalysts, and facilitate integration with reforming or electrolysis units in hydrogen economies worldwide.

Research from Nature Portfolio

Recent studies have unveiled gel‐state polybenzimidazole membranes featuring double cross‐linked, three‐dimensional layered networks. In these materials, phosphate bridges and branched PBI chains anchor phosphoric acid dopant, curtail dehydration and migration at temperatures above 200 °C and maintain proton conductivities approaching 0.35 S cm⁻¹. These membranes deliver record power densities over 1.2 W cm⁻² at 220 °C with minimal voltage decay over hundreds of hours. In a complementary approach, orientation of proton channels has been achieved by applying strong magnetic fields during membrane casting. By embedding a paramagnetic, proton‐conducting complex into the polymer matrix, through‐plane alignment of continuous channels is realized, boosting conductivity and fuel cell performance while suppressing acid leaching. Such alignment strategies also confer radical‐scavenging benefits, further enhancing operational durability under dynamic load cycles.

Proton Conducting Membranes for Fuel Cell Applications publication trend

The graph below shows the total number of articles in proton conducting membranes for fuel cell applications across all publications each year (not limited to Nature Index journals).

Technical terms

Polymer electrolyte membrane (PEM): A solid ionomer film that conducts protons but is impermeable to electrons and reactant gases in a fuel cell.

Perfluorosulfonic acid (PFSA): A class of fluorinated polymers bearing sulfonic acid groups, noted for high proton conductivity and chemical stability (e.g., Nafion).

Polybenzimidazole (PBI): A class of heterocyclic polymers doped with phosphoric acid to achieve proton conduction at high temperatures without reliance on water.

Cross-linking: Chemical linkage between polymer chains that enhances mechanical strength, dimensional stability and retention of acid or water.

Proton conductivity: A measure of a membrane’s ability to transport H⁺ ions, typically reported in siemens per centimetre (S cm⁻¹).

References

1. Double cross-linked 3D layered PBI proton exchange membranes for stable fuel cell performance above 200 °C. Nature Communications (2024).
2. Magnetic field alignment of stable proton-conducting channels in an electrolyte membrane. Nature Communications (2019).
3. 74 µm PEEK‐Reinforced Sulfonated Poly(phenylene sulfone)‐Membrane for Stable Water Electrolysis with Lower Gas Crossover and Lower Resistance than Nafion N115. Advanced Energy Materials (2023).
4. On the evolution of sulfonated polyphenylenes as proton exchange membranes for fuel cells. Materials Advances (2021).