Improvement of the proton exchange membrane fuel cell performances by optimization of the hot pressing process for membrane electrode assembly
Résumé
The present study deals with PEM fuel cells, namely with the optimization of the hot pressing process for membrane electrode assembly (MEA) fabrication. Designs of experiments (DoE) have been used for evaluating the effect of hot pressing parameters (pressure, temperature, and time) on the MEA electrical performances. Full factorial 2(3) DoE showed that the most important parameter is the pressing temperature. Surface response methodology indicated a non-monotonous behavior of the MEA electrical performances with respect to the pressing temperature. The MEA electrical performances increased with the pressing temperature in the temperature range from 100 to 115 A degrees C, and decreased significantly in the temperature range from 115 to 130 A degrees C. This behavior was attributed to drastic changes of the NafionA (R) 112 membrane properties and membrane/electrode interface over this temperature range. Observations of the MEA cross-section structure by scanning electron microscopy confirmed such hypotheses. Thermo-mechanical properties of NafionA (R) as determined by dynamic scanning calorimetry allowed estimating the glass transition temperature at ca. T (g) a parts per thousand aEuro parts per thousand 117 A degrees C in the conditions of the present study. The higher H-2/air fuel cell performance of ca. 0.8 W cm(-2) was obtained with the optimized pressing temperature for MEA fabrication of ca. 115 A degrees C close to the T (g) temperature of NafionA (R) 112, whereas for higher temperature the structure of the NafionA (R) membrane and of the membrane-electrode interface is damaged.