Proton conductive carbon material for fuel cell applications

Abstract

The present invention provides methods for the incorporation of sulfonate functional groups onto the surface of particulate carbonaceous materials and provides several surface-modified carbonaceous material compositions resulting therefrom. The composition can further comprise a conducting polymer. The composition can further comprise a metal. Devices comprising the composition can be constructed including supported electrocatalysts, membrane electrode assemblies, and fuel cells. A method for preparing the composition comprises sulfonating particulate carbonaceous material. The method can further comprise metallizing the sulfonated carbonaceous material.

What is claimed is:  
     
         1 . A device comprising 
 a sulfonated particulate carbonaceous material.    
     
     
         2 . The device of  claim 1  wherein the carbonaceous material is carbon black.  
     
     
         3 . The device of  claim 1  wherein the carbonaceous material is carbon black, graphite, nanocarbons, fullerenes, fullerenic material, finely divided carbon, or mixtures thereof.  
     
     
         4 . The device of  claim 1  wherein the sulfonated carbonaceous material comprises a plurality of sulfonate substituents of the general formula —SO 3 M surface-bonded thereto, wherein M is hydrogen or a cationic species, and wherein the surface atomic concentration of sulfur present within the surface bonded SO 3 M moieties, measured by XPS, is greater than or equal to approximately 0.25% relative to the total surface atomic concentration of the carbonaceous material.  
     
     
         5 . The device of  claim 4  wherein the surface atomic concentration of the sulfur is in the range of from about 0.25% to about 5.0%.  
     
     
         6 . The device of  claim 4  wherein the surface atomic concentration of the sulfur is in the range of from about 0.35% to about 5.0%.  
     
     
         7 . The device of  claim 4  wherein M is a cationic species of sodium, potassium, lithium, or ammonium.  
     
     
         8 . The device of  claim 1  wherein the carbonaceous material is less than about 98% of the composition.  
     
     
         9 . The device of  claim 1  wherein the carbonaceous material is about 50% to about 80% of the composition.  
     
     
         10 . The device of  claim 1  further comprising a conducting polymer.  
     
     
         11 . The device of  claim 10  wherein the conducting polymer contains hetero atoms.  
     
     
         12 . The device of  claim 10  wherein the conducting polymer is polyaniline, polypyrrole, polyfuran, polythiophene, or mixtures thereof.  
     
     
         13 . The device of  claim 10  wherein the conducting polymer is polyaniline, polypyrrole, polyfuran, polythiophene, poly(p-phenylene-oxide), poly(p-phenylene-sulfide), substituted conducting polymers, or mixtures thereof.  
     
     
         14 . The device of  claim 11  wherein the hetero atoms are N, O, and S.  
     
     
         15 . The device of  claim 11  wherein the hetero atoms are about 0.2 to about 15% of the composition according to XPS data.  
     
     
         16 . The device of  claim 10  wherein the conducting polymer is greater than about 0% and less than about 100% of the composition.  
     
     
         17 . The device of  claim 10  wherein the conducting polymer is about 2% to about 50% of the composition.  
     
     
         18 . The device of  claim 10  wherein the conducting polymer is about 20% to about 50% of the composition.  
     
     
         19 . The device of  claim 10  wherein the polymer is grafted to the particulate sulfonated carbonaceous material.  
     
     
         20 . The device of  claim 10  wherein the polymer coats the sulfonated carbonaceous material.  
     
     
         21 . The device of  claim 1  further comprising a metal.  
     
     
         22 . The device of  claim 21  wherein the metal is platinum.  
     
     
         23 . The device of  claim 21  wherein about 2% to about 80% of the composition is the metal.  
     
     
         24 . The device of  claim 21  wherein about 2% to about 60% of the composition is the metal.  
     
     
         25 . The device of  claim 21  wherein about 20% to about 40% of the composition is the metal.  
     
     
         26 . The device of  claim 21  wherein the metal is uniformly distributed on the surface of the material.  
     
     
         27 . A method for preparing a particulate carbonaceous material with enhanced electronic and protonic conductivity comprising 
 sulfonating a particulate carbonaceous material.    
     
     
         28 . The method of  claim 27  wherein the carbonaceous material is carbon black, graphite, nanocarbons, fullerenes, fullerenic material, finely divided carbon, or mixtures thereof.  
     
     
         29 . The method of  claim 27  wherein the carbonaceous material is carbon black.  
     
     
         30 . The device of  claim 1  further comprising an electrolyte membrane.  
     
     
         31 . The device of  claim 30  wherein the electrolyte membrane is Nafion®.  
     
     
         32 . A fuel cell comprising an anode, a cathode, and a proton exchange membrane (PEM).  
     
     
         33 . The fuel cell of  claim 32  wherein the PEM comprises a sulfonated particulate carbonaceous material.  
     
     
         34 . The device of  claim 1  wherein the device is a fuel cell, battery, or a capacitor.  
     
     
         35 . A method of making a fuel cell comprising 
 a) producing a sulfonated particulate carbonaceous material by a method comprising 
 i) contacting an anhydride of the generic formula (R—CO) 2 O with sulfuric acid under conditions effective to produce an organic sulfite intermediate of the generic formula R—(CO)O—SO 3 H, wherein R is an aliphatic substituent;  
 ii) contacting a carbonaceous material with the organic sulfite intermediate produced in a) under conditions effective to produce a surface-modified carbonaceous material comprising a plurality of sulfonate substituents of the general formula —SO 3 H surface-bonded thereto; and  
 iii) treating the surface-modified carbonaceous material produced in b) with a neutralizing agent under conditions effective to produce a surface-modified carbonaceous material comprising a plurality of sulfonate substituents of the general formula —SO 3 M surface-bonded thereto, wherein M is sodium, potassium, lithium, or ammonium;  
   (b) platinizing the sulfonated particulate carbonaceous material; (c) making at least one electrode comprising the platinized sulfonated particulate carbonaceous material; and (d) making a fuel cell comprising the at least one electrode.