Comparison of Methanol Crossover among Four Types of Nafion Membranes

The crossover behavior of methanol through Nafion 112, 117, 1035, and 1135 membranes using cyclic voltammetry (CV) was studied at 25°C and the results compared. The multiple CV technique was used to study the electrochemical characteristics of the crossed methanol during this crossover. Meanwhile, a method established in our laboratory was introduced to determine the concentrations of methanol crossover. The use of various types of Nafion membranes resulted in significant differences in the anodic current responses of the CV curves under similar experimental conditions. The concentration of crossed methanol decreases with time for all four types of Nafion membrane. The mathematical expression of the variation of the methanol crossover changes with the initial methanol concentrationt and the thickness of the membrane. The type of the expression depends on the membrane thickness and the initial methanol concentration. By contrast, the concentration of crossed methanol decreases with an increase in the thickness of the Nafion membrane. It was observed that, for membranes of the same thickness, the crossed methanol increases with a decrease in the equivalent weight of the membrane.