Development of novel iota carrageenan-g-polyvinyl alcohol polyelectrolyte membranes for direct methanol fuel cell application

In this study, novel iota carrageenan-g-PVA polyelectrolyte membranes (PEMs) developed for application in direct methanol fuel cell (DMFC). Iota carrageenan (I-Car) was cross-linked with polyvinyl alcohol (PVA) both ionically and chemically using sulfophthalic acid (SPA) and glutaraldehyde (GA) for the first time. SPA plays a dual role which is to sulfonate the PVA and act as an ionic cross-linker. The use of iota carrageenan offers much more sulfonic acid groups, compared to the kappa carrageenan, which in addition to the sulfonic group of SPA contributes to the induction of the ion-exchange capacity and consequently the ionic conductivity of the developed membranes. Factors affecting the fabrication of the membranes such as polymers composition, cross-linking time, pH, temperature, cross-linker type, and concentration were studied. The chemical structures of the prepared membranes verified through FT-IR, TGA, and XRD techniques. Mechanical properties were investigated. Moreover, the ion-exchange capacity, water, methanol sorption, and the methanol crossover flux across the PEMs were adopted as monitors for this study. It was found that the methanol permeability and the IEC were 15% and 133% of Nafion^®117. The efficiency factor for the prepared I-Car-g-PVA membrane was one order higher than that of the Nafion 117.