The effect of the MEA preparation procedure on both ethanol crossover and DEFC performance
In the present work, the changes of Nafion((R))-115 membrane porosity in the presence of ethanol aqueous solutions of different concentrations were determined by weighing vacuum-dried and ethanol solution-equilibrated membranes. It was found that membrane porosity increases as ethanol concentration increases. Membrane electrode assemblies (MEAs) have been prepared by following both the conventional and the decal transfer method. The ethanol crossover through these two MEAs was electrochemically quantified by a voltammetric method. A 10h stability test of direct ethanol fuel cell (DEFC) at a current density of 50 mA cm(-2) was carried out. It was found that the electrode preparation procedure has an obvious effect on ethanol crossover and direct ethanol fuel cell's performance and stability. The single DEFC test results showed that about 15 and 34% of the original peak power density was lost after 10h of life test for the MEAs prepared by the decal transfer method and the conventional method, respectively. Electrochemical impedance spectrum (EIS) results of the MEAs showed that, in the case of the membrane electrode assembly prepared by the following decal transfer method, the internal cell resistance was almost the same, 0.236 Ohm cm(2) before the life test and 0.239 Ohm cm(2) after 10h of life test, while the respective values for the membrane electrode assembly by the conventional method are 0.289 and 0.435 Ohm cm(2). It is supposed that the improved cell performance with MEA by the decal transfer method could be resorted to both a better contact between the catalyst layer and the electrolyte membrane and higher catalyst utilization. Furthermore, based on the experimental results, the increased internal cell resistance and the degraded single DEFC performance could be attributed to the delamination of the catalyst layer from the electrolyte membrane. (C) 2004 Elsevier B.V. All rights reserved.