Ion exchange assembly for an electrochemical cell
View Patent ↗This invention provides a solid polymer ion exchange membrane/electrode assembly, or an electrode/solid polymer ion exchange membrane/electrode assembly, for an electrochemical cell, which consists of planar layers of materials intimately joined together to form a unitary structure. The layers are joined together by solid polymer ion exchange resin present in at least one of each pair of adjacent layers. The unitary assembly can be used in an electrochemical cell such as a battery, electrolytic reactor, or fuel cell.
1. A unitary assembly for an electrochemical cell comprising:
an electrode having at least one electrically conductive material and a membrane support comprising polytetrafluoroethylene, said support being impregnated with a polymer ion exchange resin and having a surface, and
a layer of ionomer joined to the electrode at said surface having a polymer ion exchange resin.
2. A unitary assembly according to claim 1 , in which the polytetrafluoroethylene of the electrode is expanded polytetrafluoroethylene.
3. A unitary assembly according to claim 1 , in which said layer of ionomer comprises a polytetrafluoroethylene support.
4. A unitary assembly according to claim 3 , in which said polytetrafluoroethylene support comprises:
a composite nonporous solid polymer ion exchange membrane having first and second planar surfaces, said ion exchange membrane comprising at least one preformed membrane-support film of porous expanded polytetrafluoroethylene having a plurality of micropores, and
a solid polymer ion exchange resin essentially completely filling the micropores of the membrane support film.
5. A unitary assembly according to claim 3 in which said polytetrafluoroethylene support of said layer of ionomer is preformed.
6. A unitary assembly according to claim 3 , in which said polytetrafluoroethylene support of said layer of ionomer has a thickness of 1 to 100 micrometers.
7. A unitary assembly according to claim 3 , in which said polytetrafluoroethylene support of said layer of ionomer has a pore volume of 60 to 98 percent.
8. A unitary assembly according to claim 3 , in which said polytetrafluoroethylene support of said layer of ionomer has a thickness of 1 to 100 micrometers and a pore volume of 60 to 98 percent.
9. A unitary assembly according to claim 3 , in which said porous polytetrafluoroethylene support of said layer of ionomer is made nonporous by said solid polymer ion exchange resin.
10. A unitary assembly according to claim 1 , in which said layer of ionomer comprises a porous expanded polytetrafluoroethylene support.
11. A unitary assembly according to claim 1 in which the polytetrafluoroethylene of the electrode is preformed.
12. A unitary assembly according to claim 1 , in which the polytetrafluoroethylene of the electrode is a particle-filled expanded polytetrafluoroethylene film.
13. A unitary assembly according to claim 1 , in which said electrically conductive material comprises a catalyst.
14. A unitary assembly according to claim 13 , wherein said catalyst is selected from the group consisting of lead dioxide, platinum and platinum alloys, and mixtures thereof.
15. A unitary assembly according to claim 14 in which said platinum and platinum alloys catalysts are supported on carbon black.
16. A unitary assembly according to claim 13 , in which said membrane support comprises a polytetrafluoroethylene membrane impregnated with a liquid dispersion of noncatalytic electrically-conductive particles and a liquid composition containing a precursor of said catalyst and said polymer ion exchange resin.
17. A unitary assembly according to claim 13 , in which said catalyst precursor is bonded to exchange groups of said polymer ion exchange resin.
18. A unitary assembly according to claim 13 , in which said noncatalytic electrically-conductive particles comprise carbon black.
19. A unitary assembly according to claim 13 , in which said catalyst precursor comprises a platinum-ammine complex solution.
20. A unitary assembly according to claim 13 , in which said catalyst is contained in the polytetrafluoroethylene of the electrode.
21. A unitary assembly according to claim 1 , in which the electrode and said layer of ionomer are adhesively joined by said polymer ion exchange resin.