Method for making catalysts for fuel cell oxygen electrodes

Abstract

A method for making a catalyst having catalytically active material supported on a carrier matrix. The catalytically active material may be a mixed-valence, nanoclustered oxide(s), an organometallic material or a combination thereof. In one method, a metal salt solution is combined with a metal complexing agent to form a metal complex. The metal complex is then combined with a suspension that includes a carrier matrix and the system is subjected to ultrasonic agitation. A base is then added to induce a controlled crystallization of a catalytic nanocluster metal material onto the carrier matrix. The supported catalytic material is particularly useful for catalyzing oxygen reduction in a fuel cell, such as an alkaline fuel cell.

1 . A method for making a catalytic material comprising the steps of: 
 providing a first metal complex, said first metal complex including a first metal and a first complexing agent;    combining said first metal complex with a suspension, said suspension including a carrier matrix suspended in a solvent;    adding an agent to said combination of said first metal complex and said suspension, said agent inducing a breakdown of said first metal complex, said breakdown causing said first metal to precipitate onto said carrier matrix.    
     
     
         2 . The method of  claim 1 , wherein said precipitate of said first metal is in the form of a nanoclustered metal oxide.  
     
     
         3 . The method of  claim 2 , wherein said nanoclustered metal oxide includes said first metal in two or more oxidation states.  
     
     
         4 . The method of  claim 3 , wherein said first metal is present in three or more oxidation states.  
     
     
         5 . The method of  claim 1 , wherein said first metal is Co or Mn.  
     
     
         6 . The method of  claim 1 , wherein said first complexing agent comprises nitrogen.  
     
     
         7 . The method of  claim 1 , wherein said agent is a base.  
     
     
         8 . The method of  claim 7 , wherein said base is a hydroxide.  
     
     
         9 . The method of  claim 1 , further comprising the step of agitating said combination of said first metal complex and said suspension.  
     
     
         10 . The method of  claim 1 , further comprising the steps of: 
 dissolving a metal salt to form a metal salt solution;    adding said complexing agent to said metal salt solution, said complexing agent combining with said metal to form said first metal complex.    
     
     
         11 . The method of  claim 1 , further comprising the steps of: 
 dissolving a metal salt to form a metal salt solution;    adding said complexing agent to said suspension;    combining said metal salt solution with said suspension containing said complexing agent, said combining step forming said first metal complex.    
     
     
         12 . The method of  claim 1 , further comprising the step of combining a second metal complex with said combination of said first metal complex and said suspension, said second metal complex including a second metal and a second complexing agent, wherein said adding agent step further induces a breakdown of said second metal complex, said breakdown causing said second metal to precipitate on said carrier matrix.  
     
     
         13 . The method of  claim 12 , wherein said precipitate of said first metal and said precipitate of second metal are layered on said carrier matrix.  
     
     
         14 . The method of  claim 12 , wherein said precipitate of said first metal and said precipitate of said second metal are in the form of nanoclustered metal oxides.  
     
     
         15 . The method of  claim 1 , further comprising the step of combining an organometallic with said combination of said first metal complex and said suspension, said organometallic forming a layer on said carrier matrix.  
     
     
         16 . The method of  claim 15 , wherein said organometallic layer is formed over said precipitate of said first metal.  
     
     
         17 . The method of  claim 15 , wherein said organometallic is combined with said combination of said first metal complex and said suspension after the addition of said agent.  
     
     
         18 . The method of  claim 15 , wherein said organometallic comprises a macrocycle.  
     
     
         19 . The method of  claim 1 , wherein said carrier matrix comprises carbon.