Systems, methods, and devices for cation-associating fuel cell components
Improved membrane electrode assemblies, cation-associating components thereof, and methods of making and treating the same are provided. Membrane electrode assemblies may include an ionomer having a first pKa value, and a water-insoluble net polymer having a weakly-acidic functional group, wherein the weakly-acidic functional group has a second pKa value greater than the first pKa value.
1. A membrane electrode assembly, comprising:
a proton exchange membrane disposed between an anode catalyst layer and a cathode catalyst layer; and
a cation-associating layer comprising a water-insoluble net polymer,
wherein the water-insoluble net polymer comprises a weakly-acidic functional group configured to preferentially associate with contaminant cations,
wherein the proton exchange membrane comprises a first ionomer,
wherein the weakly-acidic functional group comprises phosphonic acid, and
wherein the cation-associating layer is disposed in at least one of a portion of the cathode catalyst layer, a portion of a cathode microporous layer, or between the cathode catalyst layer and the cathode microporous layer.
2. The membrane electrode assembly of claim 1 , wherein the first ionomer comprises perfluorinated sulfonic acid.
3. The membrane electrode assembly of claim 1 , wherein the water-insoluble net polymer comprises fluoropolymeric phosphonic acid.
4. The membrane electrode assembly of claim 1 , wherein the cation-associating layer comprises at least one of a pure cation-associating layer, a blended cation-associating layer, a copolymer, or a terpolymer.
5. The membrane electrode assembly of claim 1 , further comprising a radical scavenger configured to preferentially associate with the weakly-acidic moiety.
6. The membrane electrode assembly of claim 5 , wherein the radical scavenger comprises at least one of a lanthanide metal or a transition metal having more than one oxidation state.
7. The membrane electrode assembly of claim 6 , wherein the radical scavenger comprises cerium.
8. The membrane electrode assembly of claim 3 , wherein a first portion of cation-associating net layer comprises the first ionomer, and wherein a second portion of the net layer comprises the water-insoluble net polymer.
9. The membrane electrode assembly of claim 8 , wherein a distribution of the first ionomer and the water-insoluble net polymer in the cation-associating layer is substantially even.
10. The membrane electrode assembly of claim 8 , wherein a distribution of the first ionomer and the water-insoluble cation-associating polymer in the net layer comprises an in-plane gradient.
11. The membrane electrode assembly of claim 8 , wherein a distribution of the first ionomer and the water-insoluble net polymer in the cation-associating layer comprises a through-plane gradient.
12. The membrane electrode assembly of claim 1 , wherein the weakly-acidic functional group is bound to a backbone of the water-insoluble net polymer.
13. The membrane electrode assembly of claim 1 , wherein the weakly-acidic functional group is bound to a side-chain of the water-insoluble net polymer.