Stable proton exchange membranes and membrane electrode assemblies
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 proton exchange membrane for an electrochemical cell comprising:
an ionomer substrate, and
a catalytically active component disposed within or on a surface of the substrate, said catalytically active component comprising particles of a metal oxide,
a stabilizer comprising one or more ions containing an element from the group of aluminum, boron, tungsten, titanium, zirconium and vanadium, which stabilizer modifies the outer surface of the particles of metal oxide,
at least one metal or metal ion catalyst different from the stabilizer and selected from the group of cerium, platinum, palladium, lanthanum, yttrium, gadolinium, silver, iron, ruthenium, titanium, vanadium, and combinations thereof, which catalyst modifies the outer surface of the particles of metal oxide;
such that the catalytically active components 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 or the catalyst;
wherein the stabilizer includes boron ions.
2. The proton exchange membrane of claim 1 wherein the catalyst is from the group of cerium, platinum, lanthanum, gadolinium, iron, ruthenium, and combinations thereof.
3. The proton exchange membrane of claim 1 wherein the particles of metal oxide are selected 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.
4. The proton exchange membrane of claim 1 wherein the catalytically active components are colloidal particles having a mean particle diameter of less than 200 nanometers.
5. The proton exchange membrane of claim 4 wherein the colloidal particles contain silica.
6. The proton exchange membrane of claim 1 wherein the catalyst is from the group of cerium and ruthenium.
7. The proton exchange membrane of claim 1 wherein the catalytically active components are colloidal particles having a mean particle diameter of less than 100 nanometers, and the colloidal particles contain silica and boron ions.
8. The proton exchange membrane of claim 7 wherein the catalyst is from the group of cerium and ruthenium.
9. The proton exchange membrane of claim 7 wherein the colloidal particles have a mean particle diameter of less than 25 nanometers.
10. The proton exchange membrane of claim 1 wherein the ionomer substrate is a hydrocarbon ionomer.
11. The proton exchange membrane of claim 1 wherein the ionomer substrate is a partially fluorinated ionomer.
12. The proton exchange membrane of claim 1 wherein the ionomer substrate is a highly fluorinated ionomer.
13. The proton exchange membrane of claim 1 wherein the ionomer substrate is a perfluorinated sulfonic acid ionomer.
14. The proton exchange membrane of claim 1 wherein the ionomer substrate is a reinforced membrane.