Effect of number of cross-linkable sites on proton conducting, pore-filling membranes

Highly cross-linked membranes were prepared using a pore-filling technique for application in polymer electrolyte fuel cells (PEFCs). The electrolyte that fills the porous substrate should have a higher ion exchange capacity (IEC) than membranes prepared by a casting method. Hence, a cross-linking agent is employed to prevent the polymer electrolyte from dissolving in water. The goal of this study is to improve the chemical, mechanical, and electrochemical stability in membranes without decreasing the IEC. We evaluated the membrane characteristics using two different types of cross-linking agents—1,3,5-triacryloylhexahydro-1,3,5-triazine (C1) with three cross-linkable sites and N,N′-ethylene bisacrylamide (C2) with two cross-linkable sites. The membranes with C1 improved the chemical and electrochemical properties without a remarkable decrease in the IEC and proton conductivity compared to the membranes created with C2. Moreover, the C1 membrane also demonstrated an improvement in the electrochemical durability during the accelerated lifetime test.