Sulfonated polyvinylidene fluoride and functional copolymer based blend proton exchange membrane for fuel cell application and studies on methanol crossover

Abstract

Copolymers of poly(methyl methacrylate)-co-poly (2-acrylamido-2-methyl-1-propane sulfonic acid (PMMA-co-PAMPS) have been prepared via radical polymerization with different MMA to AMPS mol ratio and blended with polyvinylidene fluoride (PVDF) and sulfonated PVDF (S-PVDF) in a different weight ratio to prepare proton exchange membranes (PEMs) by simple solution casting method for fuel cells application (PEMFCs). Five different PEMs have been prepared from only PMMA-co-PAMPS, blending PMMA-co-PAMPS with PVDF, and also by blending PMMA-co-PAMPS with S-PVDF to get the suitable membrane for PEMFCs application. We have also studied the effect of PVDF and S-PVDF in the blend membranes on the water uptake, mechanical stability, thermal stability, proton conductivity (Km), and methanol permeability (PM) properties. PEMs prepared by blending with S-PVDF exhibited high Km and low PM value. PEM-5 membrane prepared by blending S-PVDF with PMMA-co-PAMPS (30:70 w/w) exhibited Km at room temperature 5.7 × 10−2 S/cm, PM value 5.24 × 10−7 cm2/s and maximum power density 477 mW/cm2. This PM value is much lower than that of the Nafion® 117 membrane (22 × 10−7 cm2/s). This low PM, high Km and high selectivity make the S-PVDF blend membranes a good candidate in PEMFCs or direct methanol fuel cells (DMFCs) application.