Hydrophilic layer on flowfield for water management in PEM fuel cell
View Patent ↗A fluid distribution element is provided for a fuel cell having a major surface facing a membrane electrode assembly (MEA) and one or more flow channels for transporting gas and liquid to and from the MEA. One or more regions of the major surface are overlaid with a super-hydrophilic corrosion-resistant layer comprising a fluoropolymer. Methods of making such a fluid distribution element are also provided.
1. A fluid distribution element for a fuel cell comprising:
an impermeable element having a major surface facing a membrane electrode assembly (MEA), wherein one or more regions of the major surface are overlaid with a super-hydrophilic corrosion-resistant layer comprising a super-hydrophilic fluoropolymer, wherein said layer has a porosity of greater than 40% and wherein the layer is surface-modified by plasma activation of a fluoropolymer to produce the super-hydrophilic fluoropolymer on its surface in a substitution of a portion of the original fluorine atoms with groups selected from hydroxyl groups, alkoxy groups, nitrogen-containing groups, carbonyl groups, and mixtures thereof.
2. The element of claim 1 , wherein said major surface defines one or more flow channels for transporting gas and liquid to and from the MEA and said one or more regions are overlaid with said super-hydrophilic corrosion-resistant layer corresponding to said flow channels.
3. The element of claim 2 , wherein said major surface is patterned with a plurality of grooves and lands and said one or more flow channels correspond to said grooves, wherein one or more of said lands are overlaid with an electrically conductive corrosion-resistant coating.
4. The element of claim 1 , wherein said super-hydrophilic corrosion-resistant layer has a static contact angle of less than or equal to about 20°.
5. The element of claim 1 , wherein said fluoropolymer comprises polytetrafluoroethylene (PTFE).
6. The element of claim 5 , wherein said PTFE is surface-modified by plasma activation with oxygen to replace fluorine atoms with oxygen atoms.
7. The element of claim 6 , wherein said super-hydrophilic fluoropolymer comprises surface-modified PTFE wherein the surface modification comprises covalently bonded groups selected from the group consisting of hydroxyl groups, carbonyl groups, nitrogen-containing groups, and combinations thereof.
8. The element of claim 7 , wherein the covalently bonded groups selected from the group consisting of hydroxyl groups, carbonyl groups, and combinations thereof.
9. The element of claim 1 , wherein said layer has pores with an average pore of between about 0.05 to about 5 μm.