Gas diffusion electrode substrate and method for producing gas diffusion electrode substrate

Abstract

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 gas diffusion electrode substrate comprising a carbon sheet and a microporous layer, wherein
 the carbon sheet is porous,   a carbon powder included in the microporous layer has a DBP oil absorption of 70 to 155 ml/100 g,   the microporous layer has an infiltration index (L/W) of 1.10 to 8.00, the infiltration index being calculated from an areal weight (W) of the microporous layer and a thickness (L) of the microporous layer (L), and   the microporous layer has a thickness (L) of 10 to 100 μm.   
     
     
         2 . The gas diffusion electrode substrate according to  claim 1 , wherein the microporous layer has a surface roughness of 3.0 to 7.0 μm. 
     
     
         3 . The gas diffusion electrode substrate according to  claim 1 , having a variety in thickness of 10.0 μm or less. 
     
     
         4 . A gas diffusion electrode substrate comprising a carbon sheet and a microporous layer, wherein
 the carbon sheet is porous,   a carbon powder included in the microporous layer has a DBP oil absorption of 70 to 155 ml/100 g, and   the microporous layer has a surface roughness of 3.0 to 7.0 μm.   
     
     
         5 . A gas diffusion electrode substrate comprising a carbon sheet and a microporous layer, wherein
 the carbon sheet is porous,   a carbon powder included in the microporous layer has a DBP oil absorption of 70 to 155 ml/100 g, and   the gas diffusion electrode substrate has a variety in thickness of 10.0 μm or less.   
     
     
         6 . The gas diffusion electrode substrate according to  claim 1 , wherein the microporous layer includes as a carbon powder a linear carbon having an aspect ratio of 30 to 5000. 
     
     
         7 . The gas diffusion electrode substrate according to  claim 1 , wherein a size (peak size) of a pore having a pore size in the range of 0.03 to 1.00 μm and a maximum volume is in the range of 0.10 to 1.00 μm. 
     
     
         8 . The 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 microporous layer is on a side of the one surface of the carbon sheet.   
     
     
         9 . 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.   
     
     
         10 . The method for producing a gas diffusion electrode substrate according to  claim 9 , wherein the MPL coating liquid has a viscosity of 1.0 to 20.0 Pa·s at a shear rate of 17 s −1 . 
     
     
         11 . The method for producing a gas diffusion electrode substrate according to  claim 9 , 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.   
     
     
         12 . The method for producing a gas diffusion electrode substrate according to  claim 9 , comprising water as the dispersion medium. 
     
     
         13 . The method for producing a gas diffusion electrode substrate according to  claim 9 , wherein all carbon powder(s) contained in 100% by mass of the MPL coating liquid is 10 to 50% by mass. 
     
     
         14 . The method for producing a gas diffusion electrode substrate according to  claim 9 , 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.   
     
     
         15 . A fuel cell comprising the gas diffusion electrode substrate according to  claim 1  or a gas diffusion electrode substrate obtained by the method according to any of  claims 9  to  14 .