Porous electrode substrate and method for producing the same
View Patent ↗The present invention provides a porous electrode substrate that has low production cost, high mechanical strength, thickness precision, and surface smoothness, and sufficient gas permeability and electrical conductivity, and a method for producing the same. In the present invention, for example, a porous electrode substrate that includes short carbon fibers (A) joined together via three-dimensional mesh-like carbon fibers (B) is produced by a method including a step (1) of dispersing short carbon fibers (A), and short carbon fiber precursors (b) to be fibrillated by beating, to produce a precursor sheet; and a step (2) of subjecting the precursor sheet to carbonization treatment at a temperature of 1000° C. or higher.
1. A method for producing a porous electrode substrate, comprising:
(1) dispersing short carbon fibers (A), and short carbon fiber precursors (b), to obtain a precursor sheet; and
(2) treating the precursor sheet in a carbonization treatment at a temperature of 1000° C. or higher,
wherein the short carbon fiber precursors (b) are in the form of sea-island composite fibers, capable of fibrillation by beating, and comprise two or more different polymers.
2. The method of claim 1 , further comprising:
(3) hot press forming the precursor sheet at a temperature lower than 200° C. after dispersing the short carbon fibers (A) and the short carbon fiber precursors (b) and before treating the precursor sheet,
without impregnating the precursor sheet with a resin which is capable of carbonization before the hot press forming.
3. The method of claim 2 , further comprising:
(4) subjecting the precursor sheet to oxidation treatment at a temperature of200° C. or higher and lower than 300° C. after the hot press forming and before treating the precursor sheet.
4. A porous electrode substrate obtained by a process comprising the method of claim 1 .
5. A porous electrode substrate comprising short carbon fibers (A) that are dispersed in a two-dimensional plane and are joined together via only three-dimensional mesh-like carbon fibers (B), wherein the three-dimensional mesh-like carbon fibers (B) are derived from short carbon fiber precursors (b) which are in the form of sea-island composite fibers, capable of fibrillation by beating and comprise two or more different polymers.
6. A membrane electrode assembly comprising the porous electrode substrate of claim 4 .
7. A polymer electrolyte fuel cell comprising the membrane electrode assembly of claim 6 .
8. A membrane electrode assembly comprising the porous electrode substrate of claim 5 .
9. A polymer electrolyte fuel cell comprising the membrane electrode assembly of claim 8 .
10. The porous electrode substrate of claim 4 , as a sheet or a spiral.
11. The porous electrode substrate of claim 5 , as a sheet or a spiral.
12. The method of claim 1 , wherein the short carbon fibers (A) are polyacylonitrile-based fibers, pitch-based fibers, or rayon-based fibers, or a combination thereof.
13. The porous electrode substrate of claim 5 , wherein the short carbon fibers (A) are polyacylonitrile-based fibers, pitch-based fibers, rayon-based fibers, or a combination thereof.
14. The method of claim 1 , wherein an average length of the short carbon fibers (A) is from 2 to 12 mm and an average diameter of the short carbon fibers (A) is from 3 to 9 μm.
15. The porous electrode substrate of claim 5 , wherein an average length of the short carbon fibers (A) is from 2 to 12 mm and an average diameter of the short carbon fibers (A) is from 3 to 9 μm.
16. The porous electrode substrate of claim 5 , wherein a content of the three-dimensional mesh-like carbon fibers (B) is from 10 to 90% by mass.
17. The method of claim 1 , wherein the short carbon fiber precursors (b) comprise an acrylic polymer, a cellulosic polymer, a phenolic polymer, or a combination thereof.
18. The method of claim 1 , further comprising wet spinning to obtain the short carbon fiber precursors (b).
19. A porous electrode substrate obtained by a process comprising the method of claim 2 .
20. A porous electrode substrate obtained by a process comprising the method of claim 3 .
21. The method of claim 1 , wherein the short carbon fiber precursors (b) are fibers that have been fibrillated by mechanical beating.
22. The method of claim 1 , further comprising, before the dispersing, fibrillating the short carbon fiber precursors (b) by mechanically beating the short carbon fiber precursors (b).
23. The method of claim 2 , wherein hot press forming joins short carbon fibers by melting.