The Effect on In-Cell Measurements from Water and Methanol Transport in Direct Methanol Proton Exchange Membrane Fuel Cells

Abstract

This submission relates to direct methanol fuel cells (DMFCs) and to a method for the determination, simultaneously, of in-cell methanol crossover and water diffusion coefficients. Preliminary experimental results are presented describing an extension of the electrochemical methanol crossover technique in a fuel cell. A purge gas flow rate dependence is shown to arise in the methanol crossover current when that cathode purge gas is not humidified and it is suggested that this flow rate dependence drives water flux across the cell. At limiting flow, conditions prevail that allow the determination of trans-membrane water diffusion coefficient. This offers the possibility of deriving this important water transport parameter from a simple and near ubiquitously used electrochemical method. Beyond this, our experiments have suggested that the use of zero-flow purge for methanol permeation current measurement gives rapid and reliable results.