Electrode substrate for a fuel cell, a method for preparing the same, and a membrane-electrode assembly comprising the same

Abstract

An electrode substrate for a fuel cell including a diffusion layer, a first microporous layer that embeds into the diffusion layer, with the first microporous layer having a thickness in the range of 10 to 30 μm, and a second microporous layer that forms a boundary with the diffusion layer on the surface of the first microporous layer. The electrode substrate has improved performance such as increased diffusion properties of a fuel or an oxidant, increased properties of releasing moisture, and enhanced electron conductivity.

1 . A method of preparing an electrode substrate for a fuel cell, comprising:
 mixing carbon material, a binder, and a solvent to prepare a coating composition;   coating the coating composition onto a diffusion layer; and   firing the coated diffusion layer to form a first microporous layer that embeds into the diffusion layer, the first microporous layer having a thickness in the range of 10 to 30 μm, and a second microporous layer that forms a boundary with the diffusion layer, wherein the second microporous layer is on the surface of the embedded first microporous layer.   
     
     
         2 . The method of  claim 1 , wherein the carbon material is selected from the group consisting of graphite, carbon nanotubes (CNT), fullerene (C60), activated carbon, Vulcan, ketjen black, carbon black, carbon nanohorns, and combinations thereof. 
     
     
         3 . The method of  claim 1 , wherein the binder is selected from the group consisting of poly(perfluorosulfonic acid), poly(tetrafluoroethylene), fluorinated ethylene-propylene, and combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein the coating composition comprises a solid content in the range of 20 to 40 wt %. 
     
     
         5 . The method of  claim 1 , wherein the diffusion layer is at least one material selected from the group consisting of carbon paper, carbon cloth, carbon felt, metal cloth, and combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein a thickness of the diffusion layer is in the range of 200 to 280 μm. 
     
     
         7 . The method of  claim 1 , wherein the coating composition is screen-coated. 
     
     
         8 . The method of  claim 1 , wherein the coating composition is coated on the diffusion layer at a thickness in the range of 20 to 50 μm.