Preparation and Study of Sulfonated Co-Polynaphthoyleneimide Proton-Exchange Membrane for a H2/Air Fuel Cell

Area of Science:

• Polymer Chemistry
• Materials Science
• Electrochemistry

Background:

• Development of advanced polymer electrolyte membranes (PEMs) is crucial for efficient fuel cell technology.
• Sulfonated aromatic polyimides offer potential for high performance and stability.

Purpose of the Study:

• To synthesize and characterize a novel sulfonated polynaphthoyleneimide polymer (co-PNIS70/30).
• To evaluate its potential as a proton exchange membrane for fuel cells.

Main Methods:

• Copolymerization of 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODAS) and 4,4'-methylenebisanthranilic acid (MDAC).
• Catalytic polyheterocyclization for high molecular weight polymer synthesis.
• Membrane casting, conductivity measurements (in- and through-plane), SFG NMR diffusometry, and membrane-electrode assembly (MEA) fabrication and testing.

Main Results:

• Synthesized co-PNIS70/30 with high molecular weight and ion-exchange capacity (2.13 meq/g).
• Achieved high in-plane (~96 mS/cm) and through-plane (~60 mS/cm) conductivities.
• Proton diffusion coefficient is lower than Nafion®, but temperature dependence of conductivity is similar.
• Optimal MEAs demonstrated a maximum output power of ~370 mW/cm² at 80 °C.

Conclusions:

• Sulfonated co-PNIS70/30 polynaphthoyleneimide membranes exhibit attractive properties for practical fuel cell applications.
• The material shows comparable performance to Nafion® with potential for further optimization.