Poly(vinyl alcohol)-based polymer electrolyte membranes for direct methanol fuel cells

We have prepared polymer electrolyte membranes (PEMs) from poly(vinyl alcohol) (PVA) and modified PVA polyanion containing 2 or 4 mol% of 2-methyl-1-propanesulfonic acid (AMPS) groups as a copolymer. The PEMs of various AMPS content and cross-linking conditions were prepared to determine the effect of AMPS content and cross-linking conditions on PEM properties. Proton conductivity and permeability of methanol through the PEMs increased with increasing AMPS content, CAMPS, and with decreasing cross-linker concentration, CGA, because of the increase in the water content. The permeability coefficient of methanol through the PEM prepared under the conditions of CAMPS = 2.7 mol% and CGA = 0.35 vol% was about 30 times lower than that of Nafion®117 under the same measurement conditions. The proton permselectivity of the PEM, which is defined as the ratio of the proton conductivity to the permeability coefficient of methanol, gave a maximum value of 66 × 103 S cm−3 s. The value is about three times higher than that of Nafion®117.