Fluid diffusion layers for fuel cells

Abstract

Fluid diffusion layers with favorable mechanical and electrical properties are prepared for fuel cell electrodes by impregnating a porous carbonaceous web with a carbonizable polymer having pyrrolidone functionality and then carbonizing the pyrrolidone polymer. The polymer having pyrrolidone functionality is stabilized against vaporization by use of an oxidization step prior to carbonization. The fluid diffusion layers are particularly suitable for use as gas diffusion layers in solid polymer electrolyte fuel cells.

What is claimed is:  
     
         1 . A fluid diffusion layer suitable for use in a fuel cell electrode, said fluid diffusion layer comprising a porous carbonaceous web impregnated with a carbonization product of at least one polymer having pyrrolidone functionality.  
     
     
         2 . The fluid diffusion layer of  claim 1  wherein said carbonization product is carbonized polyvinylpyrrolidone.  
     
     
         3 . The fluid diffusion layer of  claim 1  wherein said fluid diffusion layer is a gas diffusion layer.  
     
     
         4 . An electrode suitable for use in a solid polymer electrolyte fuel cell, said electrode comprising the fluid diffusion layer of  claim 1  and a catalyst.  
     
     
         5 . The fluid diffusion layer of  claim 1  wherein said porous carbonaceous web is a non-woven carbon fiber mat comprising carbon fibers and a binder.  
     
     
         6 . The fluid diffusion layer of  claim 5  wherein said binder is a polymer having pyrrolidone functionality.  
     
     
         7 . The fluid diffusion layer of  claim 1  wherein said fluid diffusion layer is greater than about 50% porous.  
     
     
         8 . The fluid diffusion layer of  claim 1  additionally comprising carbon particles impregnated within said web.  
     
     
         9 . The fluid diffusion layer of  claim 8  wherein said carbon particles comprise graphite.  
     
     
         10 . The fluid diffusion layer of  claim 1  wherein said fluid diffusion layer has a Taber stiffness greater than 2 Taber units.  
     
     
         11 . The fluid diffusion layer of  claim 1  wherein said fluid diffusion layer has an electrical conductivity greater than about 1 (ohm-cm) −1 .  
     
     
         12 . The fluid diffusion layer of  claim 1  wherein said fluid diffusion layer has a Gurley air permeability of less than about 20 seconds.  
     
     
         13 . A fluid diffusion layer for use in a fuel cell electrode, the fluid diffusion layer comprising a plurality of porous carbonaceous webs impregnated with and bound together by a carbonization product of a polymer having pyrrolidone functionality.  
     
     
         14 . The fluid diffusion layer of  claim 13  wherein the carbonization product is uniformly distributed through the plurality of webs.  
     
     
         15 . The fluid diffusion layer of  claim 13  wherein the carbonization product is mostly uniformly distributed throughout the plurality of webs.  
     
     
         16 . The fluid diffusion layer of  claim 13  wherein the plurality of webs form one or more interfaces between adjacent webs, and the carbonization product is mostly disposed at the interfaces.  
     
     
         17 . The fluid diffusion layer of  claim 13  wherein the plurality of webs comprises a first web and a second web, and the first web comprises a different material than the second web.  
     
     
         18 . The fluid diffusion layer of  claim 13  wherein the plurality of webs comprises a first web and a second web, and the first web has a different structure than the second web.  
     
     
         19 . The fluid diffusion layer of  claim 1  wherein the fluid diffusion layer further comprising a non-particulate carbon filler bound to the porous carbonaceous web by the carbonization product.  
     
     
         20 . The fluid diffusion layer of  claim 19  wherein the non-particulate carbon filler comprises chopped carbon fibers.  
     
     
         21 . A fluid diffusion layer for use in a fuel cell electrode, the fluid diffusion layer comprising at least one porous carbonaceous web impregnated with a carbonization product of at least one polymer having pyrrolidone functionality, and the fluid diffusion layer defines at least one fluid distribution channel.  
     
     
         22 . The fluid diffusion layer of  claim 21  wherein the fluid diffusion layer comprises a plurality of porous carbonaceous webs impregnated with and bound together by the carbonization product.  
     
     
         23 . The fluid diffusion layer of  claim 21  additionally comprising non-particulate carbon filler bound to the web by the carbonization product.  
     
     
         24 . The fluid diffusion layer of  claim 23  wherein the non-particulate carbon filler comprises chopped carbon fibers.