Ethanol/water mixture permeation through a Nafion® based membrane electrode assembly

In the present work, the permeation behavior of ethanol/water mixtures through a Nafion®-115 based membrane electrode assembly (MEA) has been investigated. The crossover measurements were carried out in a single fuel cell test apparatus. Ethanol aqueous solutions at different concentrations were supplied to the anode compartment while high-purity dry helium was fed to the cathode in order to sweep off the permeated water and ethanol. The quantitative analysis of water and ethanol from the cathode effluent has been carried out on-line by a GC under the following operation conditions: Tcell = 30–90 °C, ethanol aqueous solution concentration Cethanol = 0–12.0 mol L−1, helium flow rate at the cathode FHe in the range of 80–1500 mL min−1 and liquid solution flow rate to the anode Fl = 0.2 mL min−1.It was found that the water crossover rate is almost one order of magnitude higher than ethanol's. It was also found that the ethanol crossover rate depends on ethanol concentration and presents a volcano behavior, with the peak value at ethanol concentration of 8.0 mol L−1. This could be attributed to the different swelling behavior of the Nafion® membrane in the presence of various ethanol aqueous solutions. A similar behavior was also observed in the case of water with the peak value at 2.0 mol L−1 which could be attributed to thermodynamical reasons.