Membrane electrode assembly manufacturing process
Methods and compositions for making fuel cell components are described. In one embodiment, the method comprises providing a substrate, and forming or adhering an electrode on the substrate, wherein the forming includes depositing an aqueous mixture comprising water, a water-insoluble component, a catalyst, and an ionomer. The water-insoluble component comprises a water-insoluble alcohol, a water-insoluble carboxylic acid, or a combination thereof. The use of such water-insoluble components results in a stable liquid medium with reduced reticulation upon drying, reduced dissolution of the substrate, and reduced penetration of the pores of the substrate.
1. An aqueous mixture composition for forming a fuel cell electrode, the composition comprising:
a) Water;
b) a water-insoluble component comprising a C 5 -C 10 carboxylic acid;
c) a catalyst; and
d) an ionomer, wherein the water is present in an amount greater than 35 wt. % based on a total weight of the ionomer and a liquid portion of the aqueous mixture, and wherein the water-insoluble component is present in an amount from 1 wt. % to 20 wt. %, based on the total weight of the ionomer and liquid portion of the aqueous mixture.
2. The composition of claim 1 , wherein the catalyst comprises a noble metal, a transition metal, or an alloy thereof.
3. The composition of claim 1 , wherein the catalyst is a supported catalyst.
4. The composition of claim 3 , wherein the supported catalyst comprises carbon.
5. The composition of claim 1 wherein the catalyst is present in the aqueous mixture in an amount less than 90 wt. %.
6. The composition of claim 1 , wherein the water-insoluble component further comprises a C 5 -C 10 alcohol.
7. The composition of claim 1 wherein the ionomer is perfluorosulfonic acid.
8. The composition of claim 1 , wherein the ionomer is present in the aqueous mixture in an amount less than 50 wt. %.
9. The composition of claim 1 , wherein the composition further comprises a water-soluble compound.
10. The composition of claim 9 , wherein the water-soluble compound is present in the aqueous mixture in an amount less than 50 wt. %.
11. The composition of claim 9 , wherein the water-soluble compound is a water-soluble alcohol.
12. The composition of claim 11 , wherein the water-soluble alcohol comprises isopropanol, tert-butanol, or a glycol ether.
13. The composition of claim 12 , wherein the water-soluble compound comprises the glycol ether, and the glycol ether comprises dipropylene glycol (DPG) or propylene glycol methyl ether (PGME).