Stable proton exchange membranes and membrane electrode assemblies
View Patent ↗A proton exchange membrane and a membrane electrode assembly for an electrochemical cell such as a fuel cell are provided. A catalytically active component is disposed within the membrane electrode assembly. The catalytically active component comprises particles containing a metal oxide such as silica, metal or metalloid ions such as ions that include boron, and a catalyst. A process for increasing peroxide radical resistance in a membrane electrode is also provided that includes the introduction of the catalytically active component described into a membrane electrode assembly.
1. A membrane electrode assembly comprising:
an anode,
a cathode
an ionomer membrane disposed between said anode and cathode, and
a catalytically active component capable of decomposing hydrogen peroxide disposed within the membrane electrode assembly in a location selected from the group of within the anode, within the cathode, within the ionomer membrane, abutting the anode, abutting the cathode, abutting the ionomer membrane, and combinations thereof, said catalytically active component comprising colloidal particles, wherein the colloidal particles comprise
particles of a metal oxide,
a stabilizer, which stabilizer is one or more ions containing boron and which modifies the outer surface of the particles of metal oxide, and
at least one catalyst from the group of cerium, platinum, lanthanum, gadolinium, iron, ruthenium, and combinations thereof, which catalyst modifies the outer surface of the particles of metal oxide;
such that the colloidal particles are bi-metallic or multi-metallic surface-modified particles of metal oxide containing two or more than two different metals or metalloids on their surface, and wherein at least 10% and up to 100% of the surface sites on the particles of metal oxide are occupied by the stabilizer armor the catalyst.
2. The membrane electrode assembly of claim 1 wherein the metal oxide is from the group of alumina, silica, TiO 2 , Ti 2 O 3 , zirconium oxide, manganese dioxide, manganese oxide, Y 2 O 3 , Fe 2 O 3 , FeO, tin oxide, copper oxide, nickel oxide, tungsten oxide, germania, CeO 2 , Ce 2 O 3 , and combinations thereof.
3. The membrane electrode assembly of claim 1 wherein the colloidal particles have a mean particle diameter of less than 200 nanometers.
4. The membrane electrode assembly of claim 3 wherein the colloidal particles contain silica.
5. The membrane electrode assembly of claim 3 wherein the catalyst is from the group of cerium and ruthenium.
6. The membrane electrode assembly of claim 1 wherein the colloidal particles have a mean particle diameter of less than 100 nanometers.
7. The membrane electrode assembly of claim 6 wherein the colloidal particles contain silica and boron ions.
8. The membrane electrode assembly of claim 7 wherein the catalyst is from the group of cerium and ruthenium.
9. The membrane electrode assembly of claim 1 wherein the colloidal particles have a mean particle diameter of less than 25 nanometers.
10. The membrane electrode assembly of claim 1 wherein the ionomer is a hydrocarbon ionomer.
11. The membrane electrode assembly of claim 1 wherein the ionomer is a partially fluorinated ionomer.
12. The membrane electrode assembly of claim 1 wherein the ionomer is a highly fluorinated ionomer.
13. The membrane electrode assembly of claim 1 wherein the ionomer is a perfluorinated sulfonic acid ionomer.
14. The membrane electrode assembly of claim 3 wherein the colloidal particles are contained within the ionomer membrane.
15. The membrane electrode assembly of claim 3 wherein the ionomer membrane is a reinforced membrane.
16. The membrane electrode assembly of claim 3 wherein the colloidal particles are contained within the anode or cathode.
17. The membrane electrode assembly of claim 3 wherein the colloidal particles are present in a layer of the colloidal particles and ionomer abutting the surface of the membrane.
18. The membrane electrode assembly of claim 3 wherein membrane electrode assembly includes a gas diffusion backing layer abutting the anode and a gas diffusion backing layer abutting the cathode, and wherein the colloidal particles are present in at least one of said gas diffusion backing layers.