Hydrophobic Onium Salt Addition to Fuel Cell Electrode Inks for Improved Manufacturability

1 . An ink composition for forming a fuel cell layer, the ink composition comprising:

a solvent system;

an ion-conducting polymer dispersed within the solvent system;

a supported catalyst dispersed within the solvent system; and

an onium compound having a hydrophobic hydrocarbon moiety, the onium compound being substantially soluble in the solvent system.

2 . The ink composition of claim 1 wherein the hydrophobic hydrocarbon moiety is selected from the group consisting of C 5 -C 30 alkyl, C 5 -C 30 alkenyl, and C 6 -C 30 aryl.

3 . The ink composition of claim 1 having an average particle size less than about 1.5 microns.

4 . The ink composition of claim 1 wherein the onium compound is selected from the group consisting of ammonium cations, phosphonium cations, and combinations thereof.

5 . The ink composition of claim 1 wherein the onium compound is formed from oleylamine.

6 . The ink composition of claim 1 wherein the onium compound includes primary ammonium cations.

7 . The ink composition of claim 1 wherein the onium compound is present in an amount such that 5 mole % to 100 mole % of protogenic groups in the ion-conducting polymer are neutralized.

8 . The ink composition of claim 1 wherein the onium compound is present in an amount such that 10 mole % to 50 mole % of protogenic groups in the ion-conducting polymer are neutralized.

9 . The ink composition of claim 1 wherein the catalyst and its support are each present in an amount of 1 to 10 weight percent of the total weight of the ink composition.

10 . The ink composition of claim 1 wherein the ion conducting polymer is present in an amount of 1 to 20 weight percent of the total weight of the ink composition.

11 . The ink composition of claim 1 wherein the ion conducting polymer comprises a PFSA polymer.

12 . An ink composition for forming a fuel cell layer, the ink composition comprising:

a solvent system;

an ion-conducting polymer dispersed within the solvent system;

a supported catalyst dispersed within the solvent system; and

a primary ammonium compound including a hydrophobic hydrocarbon moiety selected from the group consisting of C 5 -C 30 alkyl, C 5 -C 30 alkenyl, and C 6 -C 30 aryl.

13 . The ink composition of claim 12 wherein the ammonium compound is present in an amount of 0.02 to 5 weight percent of the total weight the composition.

14 . The ink composition of claim 12 wherein the ammonium compound is present in an amount of 0.1 to 2 weight percent of the total weight of the ink composition.

15 . The ink composition of claim 12 wherein the catalyst and its support are each present in an amount of 3 to 5 weight percent of the total weight of the ink composition.

16 . The ink composition of claim 12 wherein the ion conducting polymer is present in an amount of 3 to 10 weight percent of the total weight of the ink composition.

17 . The composition of claim 12 wherein the ion conducting polymer comprises a PFSA polymer.

18 . A method for making a catalyst layer for a fuel cell, the method comprising:

combining a first liquid composition with an onium compound to form a second liquid composition, the first liquid composition including a solvent system, a supported catalyst, and an ion-conducting polymer, the onium compound including a hydrophobic hydrocarbon moiety; and

forming the catalyst layer from the second liquid composition.

19 . The method of claim 18 wherein the hydrophobic hydrocarbon moiety is selected from the group consisting of C 5 -C 30 alkyl, C 5 -C 30 alkenyl, and C 6 -C 30 aryl.

20 . The method of claim 19 wherein the onium compound is selected from the group consisting of primary ammonium cations, primary phosphonium cations, and combinations thereof.

21 . The method of claim 19 wherein the onium compound comprises a primary ammonium cation.