Tuned polymer electrolyte membranes based on aromatic polyethers for fuel cell applications.

Area of Science:

• Polymer Science
• Electrochemistry
• Materials Science

Background:

• Poly(arylene ether sulfone)-based ionomers are crucial for polymer electrolyte membrane fuel cells (PEMFCs).
• Optimizing molecular structure is key to achieving high proton conductivity and material stability.

Purpose of the Study:

• Synthesize and optimize novel ionomers for PEMFC applications.
• Evaluate proton conductivity, chemical, mechanical, and dimensional stability.
• Compare performance against established perfluorinated membranes like Nafion.

Main Methods:

• Synthesis of poly(arylene ether sulfone)-based ionomers with sulfofluorenyl groups.
• Modification of ionomer structures, including methyl and isopropylidene tetramethylbiphenylene groups.
• Characterization of ion-exchange capacity (IEC), proton conductivity, and material properties.
• Long-term stability testing (10,000 hours) and fuel cell performance evaluation.

Main Results:

• Developed flexible, transparent membranes with IEC from 1.32 to 3.26 meq/g.
• Isopropylidene tetramethylbiphenylene moieties enhanced stability and IEC.
• Methyl-substituted membranes showed improved dimensional stability.
• Achieved proton conductivity comparable to Nafion 112 across various conditions (80-120°C, 20-93% RH).
• Highest conductivity of 0.3 S/cm at 80°C and 93% RH.
• Membranes retained properties after 10,000 hours, showing well-connected ionic clusters.
• Demonstrated superior fuel cell performance over Nafion at 90°C and 20% RH due to better water retention.

Conclusions:

• Optimized poly(arylene ether sulfone) ionomers offer a promising alternative to perfluorinated membranes for PEMFCs.
• The new membranes exhibit excellent stability and conductivity, particularly under demanding operating conditions.
• Superior performance at high temperatures and low humidity highlights their potential for advanced fuel cell applications.