Preparation of Nafion/poly(vinyl alcohol) electro-spun fiber composite membranes for direct methanol fuel cells

In this work, we prepared crosslinked poly(vinyl alcohol) (PVA) nano-fiber thin film by electro-spinning from a PVA aqueous solution and then treating the electro-spun fiber film with glutaraldehyde vapor to start crosslinking reaction. The crosslinked PVA nano-fiber thin film is impregnated in a Nafion solution to prepare Nafion/PVA-fiber composite membranes. We show that the optimum PVA content of Nafion/PVA-fiber membrane is ∼10 wt%, which is higher than the 5 wt% PVA content of Nafion/PVA blend membrane reported by DeLuca and Elabd. The introduction of 10 wt% crosslinked PVA nano-fiber in a Nafion membrane allows us to reduce the thickness of the Nafion/PVA-fiber membrane (thickness ∼50 μm) to less than 1/3 of that of Nafion-117 membrane (thickness ∼175 μm) and DeLuca and Elabdʹs Nafion/5 wt% PVA blend membrane (thickness ∼181 μm) without causing large increment of methanol crossover across the membrane. However, the smaller thickness of Nafion/PVA-fiber membrane causes it to have lower proton resistance than Nafion-117 and Nafion/PVA blend membranes. We show that the Nafion/PVA-fiber membrane consisting of 10 wt% crosslinked PVA nano-fiber has a better DMFC performance than Nafion-117 and Nafion/5 wt% PVA blend membranes.