Gas diffusion electrode substrate and method for producing gas diffusion electrode substrate
The purpose of the present invention is to provide: a method for producing a gas diffusion electrode base which enables the achievement of a gas diffusion electrode base that has a microporous layer with small surface roughness and is not susceptible to damaging an electrolyte membrane; and a gas diffusion electrode base that has a microporous layer with small surface roughness and is not susceptible to damaging an electrolyte membrane. For the purpose of achieving the above-described purpose, the present invention has the configuration described below. Namely, a specific gas diffusion electrode base which has a carbon sheet and a microporous layer, and wherein the carbon sheet is porous and the DBP oil absorption of a carbon powder contained in the microporous layer is 70-155 ml/100 g.
1. A method for producing a gas diffusion electrode substrate including a carbon sheet and a microporous layer, wherein
the carbon sheet is porous,
the method comprises an application step of applying a coating liquid for forming the microporous layer (hereinafter, described as an MPL coating liquid) onto at least one surface of the carbon sheet by a slit die coater (hereinafter, described as an MPL application step),
the slit die coater has a lip-tip length of 0.10 to 10.00 mm, and
the MPL coating liquid contains a carbon powder having a DBP oil absorption of 70 to 155 ml/100 g and an ash content of less than 0.10% by mass, and contains a dispersion medium.
2. The method for producing a gas diffusion electrode substrate according to claim 1 , wherein the MPL coating liquid has a viscosity of 1.0 to 20.0 Pa·s at a shear rate of 17 s −1 .
3. The method for producing a gas diffusion electrode substrate according to claim 1 , wherein
after the application of the MPL coating liquid in the MPL application step, the MPL coating liquid-applied carbon sheet is retained horizontally for 1 second or more and 5 minutes or less, and
subsequently, the carbon sheet is dried and sintered.
4. The method for producing a gas diffusion electrode substrate according to claim 1 , comprising water as the dispersion medium.
5. The method for producing a gas diffusion electrode substrate according to claim 1 , wherein all carbon powder(s) contained in 100% by mass of the MPL coating liquid is 10 to 50% by mass.
6. The method for producing a gas diffusion electrode substrate according to claim 1 , wherein
one surface of the carbon sheet has a covering rate of 70 to 90%, the other surface has a covering rate lower than the covering rate of the one surface by 5 to 20 points, and
the MPL coating liquid is applied onto the one surface of the carbon sheet in the MPL application step.