| Abstract
| - Direct methanol fuel cells (DMFCs) are promising portable power sources. However, their performancediminishes significantly because of high methanol crossover (flux) in the polymer electrolyte membrane (e.g.,Nafion 117) at the desired stoichiometric methanol feed concentration. In this study, the diffusion and sorptionof methanol and water in Nafion 117 were measured using time-resolved Fourier transform infrared−attenuatedtotal reflectance (FTIR-ATR) spectroscopy. This technique is unique because of its ability to measuremulticomponent diffusion and sorption within a polymer on a molecular level in real time as function ofconcentration. Both the effective mutual diffusion coefficients and concentrations of methanol and water inNafion 117 were determined with time-resolved FTIR-ATR spectroscopy as a function of methanol solutionconcentration. The methanol flux, calculated from FTIR-ATR, matched that determined from a conventionaltechnique (permeation cell) and increased by almost 3 orders of magnitude over the methanol solutionconcentration range studied (0.1−16 M). Furthermore, the data obtained in this study reveal that the maincontribution to the increase in methanol flux is due to methanol sorption in the membrane.
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