Characterisation of Fuel Cell Membranes as a Function of Drying by Means of Contact Angle Measurements

Abstract

In another paper in this volume, it is demonstrated that the electrochemical interface in MEAs, and thus the polarization performance of the resulting fuel cells, can be improved by optimising the hot‐pressing procedure in the MEA preparation. In particular, the extent of drying of the membrane during MEA preparation was shown to be critical. In the present investigation, the effect of the drying process, and thus water content, on the hydrophilicity, wetting, and surface energies of some fuel cell membranes is examined. Wetting and surface energies are well known to influence the bonding behaviour of materials. Conclusions about how membrane drying and changes in water content influence membrane bonding and the relative importance of these surface effects are drawn.

The effect of Nafion content in a graphitized carbon nanofiber-based anode for the direct methanol fuel cell

“…MEA50 is still highly hydrophobic even though Nafion is already occupying more space in the catalyst layer, while with a further increase in Nafion content (MEA70) the surface becomes less hydrophobic. The contact angles of MEA50 are in the same range as the contact angles 13 measured on commercial catalyst coated membranes for hydrogen polymer electrolyte fuel cells (144-150°) [46], while on the other hand, the contact angle on MEA70 (112°) is similar to that of a clean Nafion film hydrated at 90 °C (~110°) [47] indicating that Nafion is covering almost the whole surface of the catalyst layer. A hydrophobic nature of the catalyst layer is good for the removal of gaseous CO2 produced through the oxidation of methanol, though a highly hydrophobic surface may prevent the proper wetting of the catalyst layer and the membrane leading to a decrease in their ionic conductivities.…”

Radiation Grafted Membranes for Polymer Electrolyte Fuel Cells

“…This may be a consequence of the difference in surface energy of radiation grafted vs. perfluorinated membranes. Our studies on the wetting properties of different proton exchange membranes show that the surface energy of uncrosslinked radiation grafted membranes on the basis of FEP is similar to the values obtained for Nafion , but that the surface energy of crosslinked radiation grafted membranes is a factor of 2 lower [29,71]. This is explained with the reduced mobility of the sulfonated poly(styrene-co-divinylbenzene) segments in crosslinked membranes.…”

Effects of hydrophobicity of the cathode catalyst layer on the performance of a PEM fuel cell

“…However, after 1 h incubation of the water droplet on the CL, the surface contact angle of the normal cathode significantly decreased from 130 • to around 70 • , which was much smaller than the value of 101 • of the cathode with DSO loading of 0.5 mg/cm 2 . Nafion comprises of hydrophobic reticulated structure and percolated hydrophilic regions, which becomes hydrophobic when it is dry [20]. As a result, the normal cathode initially exhibited hydrophobic property when water droplet was just applied onto the cathode catalyst layer (Fig.…”