Porous electrode substrate, method for producing the same, membrane electrode assembly, and polymer electrolyte fuel cell
View Patent ↗Provided is a porous electrode substrate having high mechanical strength, good handling properties, high thickness precision, little undulation, and adequate gas permeability and conductivity. Also provided is a method for producing a porous electrode substrate at low costs. A porous electrode substrate is produced by joining short carbon fibers (A) via mesh-like of carbon fibers (B) having an average diameter of 4 μm or smaller. Further provided are a membrane-electrode assembly and a polymer electrolyte fuel cell that use this porous electrode membrane. A porous electrode substrate is obtained by subjecting a precursor sheet, in which short carbon fibers (A) and short carbon fiber precursors (b) having an average diameter of 5 μm or smaller have been dispersed, to carbonization treatment after optional hot press forming and optional oxidization treatment.
1. A porous electrode substrate comprising short carbon fibers which are not directly bonded, but joined via mesh carbon fibers having an average diameter of 4 μm or smaller,
wherein the mesh carbon fibers are derived from short carbon fiber precursors obtained by cutting long carbon fiber precursors.
2. A membrane electrode assembly comprising a porous electrode substrate according to claim 1 .
3. A polymer electrolyte fuel cell comprising a membrane electrode assembly according to claim 2 .
4. The porous electrode substrate of claim 1 , wherein the porous electrode substrate has a shape of a sheet or a spiral.
5. The porous electrode substrate of claim 4 , wherein the porous electrode substrate has a shape of a sheet.
6. The porous electrode substrate of claim 5 , wherein a basis weight of the porous electrode substrate is from 15 to 100 g/m 2 .
7. The porous electrode substrate of claim 1 , wherein a thickness of the porous electrode substrate is from 50 to 300 μm.
8. The porous electrode substrate of claim 1 , wherein a gas permeability is 500 ml/hr/cm 2 /mmAq or higher.
9. The porous electrode substrate of claim 1 , wherein an electric resistance in a thickness direction is 50 mΩ·cm 2 or lower.
10. The porous electrode substrate of claim 1 , wherein the short carbon fibers are dispersed planarly.
11. The porous electrode substrate of claim 1 , wherein the short carbon fibers have a linear shape.
12. The porous electrode substrate of claim 1 , wherein the short carbon fibers comprise carbon fibers obtained by a method comprising cutting carbon fibers into a suitable length.
13. The porous electrode substrate of claim 12 , wherein the carbon fibers are at least one selected from the group consisting of a polyacrylonitrile-based carbon fiber, a pitch-based carbon fiber and a rayon-based carbon fiber.
14. The porous electrode substrate of claim 12 , wherein the length of the short carbon fibers is from 2 to 12 mm.
15. The porous electrode of claim 12 , wherein the carbon fiber is a polyacrylonitrile-based carbon fiber.
16. The porous electrode substrate of claim 1 , wherein a diameter of the short carbon fiber is from 3 to 9 μm.
17. The porous electrode substrate of claim 1 , wherein a diameter of the short carbon fiber is from 4 to 8 μm.
18. The porous electrode of claim 1 , wherein a shape of the mesh carbon fibers is linear.
19. The porous electrode substrate of claim 1 , wherein the mesh carbon fibers are in a bent state or a curved state at a joining portion with the short carbon fibers.
20. The porous electrode substrate of claim 1 , wherein based on 100% by mass of the porous electrode substrate, the mesh carbon fibers are from 25% to 60% by mass.