Catalyst layer for fuel cell, and fuel cell
The preset disclosure provides a catalyst layer that has a small contact resistance with a gas diffusion layer and excellent gas diffusion properties. The catalyst layer for a fuel cell has a uniform thickness and includes fibrous conductive members and catalyst particles. The fibrous conductive members are inclined relative to a surface direction of the catalyst layer, and a lengthwise direction of the fibrous conductive members, on average, matches a first direction.
1. A method for producing a catalyst layer for a fuel cell comprising:
preparing a catalyst ink;
applying the catalyst ink onto a surface of an electrolyte membrane, and drying the catalyst ink to form the catalyst layer, or,
applying the catalyst ink to a transfer substrate sheet, then drying the ink to form the catalyst layer, and transferring the catalyst layer onto a surface of an electrolyte membrane,
the catalyst ink comprising:
fibrous conductive members;
a proton conductive resin; and
catalyst particles, wherein:
the fibrous conductive members are inclined relative to a surface direction of the catalyst layer,
a length L f of the fibrous conductive members and a thickness T of the catalyst layer satisfy the following relational expression: L f /T≤3, and
a lengthwise direction of the fibrous conductive members, on average, matches a first direction.
2. The method for producing a catalyst layer for a fuel cell in accordance with claim 1 , wherein, when the catalyst layer is viewed from a direction perpendicular to the surface direction, an average angle formed by a reference line that extends in the first direction and the lengthwise direction of the fibrous conductive members is 30° or less.
3. A method for producing a fuel cell comprising:
preparing a membrane electrode assembly; and
preparing a first separator and a second separator that sandwich the membrane electrode assembly,
wherein the membrane electrode assembly includes: an electrolyte membrane; and a first electrode and a second electrode that sandwich the electrolyte membrane in a stack direction,
the first electrode includes a first catalyst layer and a first gas diffusion layer in this order from the electrolyte membrane side, and
the first catalyst layer is the catalyst layer produced in accordance with claim 1 .
4. The method for producing a fuel cell in accordance with claim 3 , wherein:
the first separator has a first gas flow path, and when viewed from the stack direction of the membrane electrode assembly, the first direction matches an average flow path direction of the first gas flow path.
5. The method for producing a fuel cell in accordance with claim 4 , wherein:
the first gas flow path includes a plurality of first linear portions that are oriented in the first direction, and
a proportion of a total length of the plurality of first linear portions relative to a total length of the first gas flow path is 80% or more and 100% or less.
6. The method for producing a fuel cell in accordance with claim 5 ,
wherein, in the first catalyst layer, the fibrous conductive members are unidirectionally inclined such that first gas diffusion layer-side end portions of the fibrous conductive members are located on a downstream side of the average flow path direction of the first gas flow path relative to electrolyte membrane-side end portions of the fibrous conductive members.
7. The method for producing a catalyst layer for a fuel cell in accordance with claim 1 , comprising applying the catalyst ink onto a surface of an electrolyte membrane, and drying the catalyst ink to form the catalyst layer.