Porous electrode substrate, method for producing the same, precursor sheet, membrane electrode assembly, and polymer electrolyte fuel cell

摘要

The provision of a porous electrode substrate that has large sheet strength, low production costs, high handling properties, high thickness precision and surface smoothness, and sufficient gas permeability and electrical conductivity. A porous electrode substrate including a three-dimensional entangled structure including short carbon fibers (A) dispersed in a three-dimensional structure, joined together via three-dimensional mesh-like carbon fibers (B). A method for producing a porous electrode substrate, including a step (1) of producing a precursor sheet including short carbon fibers (A), and short carbon fiber precursors (b) and/or fibrillar carbon fiber precursors (b′) dispersed in a two-dimensional plane; a step (2) of subjecting the precursor sheet to entanglement treatment; and a step (3) of subjecting this sheet to carbonization treatment at 1000° C. or higher. It is preferable to include a step (4) of subjecting the sheet to hot press forming at lower than 200° C. between step (2) and step 3), and to further include a step (5) of subjecting the sheet after hot press forming to oxidation treatment at 200° C. or higher and lower than 300° C. between step (4) and step (3).

主权项

1. A porous electrode substrate having a three-dimensional entangled structure, the porous electrode substrate comprises short carbon fibers (A) having a length of from 2 to 12 mm dispersed in the three-dimensional structure which are joined together via three-dimensional mesh-like carbon fibers (B), wherein the porous electrode substrate is produced by the method comprising:
(1) producing a precursor sheet X-1 comprising (i) short carbon fibers (A) having a length of from 2 to 12 mm and (ii) at least one fiber selected from the group consisting of short carbon fiber precursors (b) having a length of from 2 to 20 mm and fibrillar carbon fiber precursors (b′) dispersed in a two-dimensional plane; (2) subjecting the precursor sheet X-1 obtained in (1) to entanglement treatment, thereby three-dimensionally orienting the short carbon fibers (A) and providing a three-dimensional entangled porous electrode substrate precursor sheet X-2; and (3) subjecting the three-dimensional entangled porous electrode substrate precursor sheet X-2 to carbonization treatment at a temperature of 1000° C. or higher, thereby producing the porous electrode substrate, wherein the entanglement treatment is carried out by at least one method selected from the group consisting of a needle punching method, a water jet punching method, and a stream jet punching method.