Porous electrode substrate, method for manufacturing same, precursor sheet, membrane electrode assembly, and polymer electrolyte fuel cell
View Patent ↗According to the present invention, a porous electrode substrate with greater sheet strength, lower production cost, and excellent gas permeability and conductivity as well as its manufacturing method are provided. Also provided are a precursor sheet for forming such a substrate, and a membrane electrode assembly and a polymer electrolyte fuel cell containing such a substrate. The method for manufacturing such a porous electrode substrate includes the following steps [1]˜[3]: [1] a step for manufacturing a sheet material in which short carbon fibers (A) are dispersed; [2] a step for manufacturing a precursor sheet by adding a water-soluble phenolic resin and/or water-dispersible phenolic resin to the sheet material; and [3] a step for carbonizing the precursor sheet at a temperature of 1000° C. or higher. The present invention also relates to a porous electrode substrate obtained by such a manufacturing method as well as a precursor sheet to be used for manufacturing the substrate, a membrane electrode assembly and a polymer electrolyte fuel cell.
1. A method for manufacturing a porous electrode substrate for a polymer electrolyte fuel cell, the method comprising:
manufacturing a sheet material in which short carbon fibers (A) are dispersed without using a binder;
continuously entangling the sheet material;
adding a water-soluble phenolic resin and a water-dispersible phenolic resin to the entangled sheet material, thereby forming a precursor sheet; and
carbonizing the precursor sheet at a temperature of 1000 C or higher.
2. The method according to claim 1 , further comprising:
drying the sheet material between the manufacturing and the adding.
3. The method according to claim 1 , further comprising:
drying the sheet material between the manufacturing and the entangling, the entangling and the adding, or both.
4. The method according to claim 1 ,
wherein the manufacturing is manufacturing a sheet material in which short carbon fibers (A) along with carbon fiber precursor short fibers (b1), fibrillar fibers (b2), or both are dispersed.
5. The method according to claim 1 , further comprising:
hot pressing the precursor sheet at a temperature of from 100° C. to 250° C. between the adding and the carbonizing.
6. The method according to claim 5 , further comprising:
drying the precursor sheet between the adding and the hot pressing.
7. The method according to claim 1 ,
wherein the sheet material obtained during the manufacturing comprises a water-soluble binder, and
an amount of the water-soluble binder in the sheet material is 10 g/m 2 or less.
8. The method according to claim 1 , wherein the adding is adding the water-soluble phenolic resin and water-dispersible phenolic resin to the sheet material by spraying, dripping, or flowing.
9. A porous electrode substrate manufactured by the method according to claim 1 .