Preconditioning treatment to enhance redox tolerance of solid oxide fuel cells

Abstract

A high temperature, redox tolerant fuel cell anode electrode and method of fabrication in which the anode electrode is pre-conditioned by application of an initial controlled redox cycle to the electrode whereby an initial re-oxidation of the anode electrode is carried out at temperatures less than or equal to about 650° C.

1 . A method for preconditioning a solid oxide fuel cell anode electrode comprising the steps of: 
 subjecting a sintered said anode electrode to an initial redox cycle in which re-oxidation is carried out at a temperature less than or equal to about 650° C.    
   
   
       2 . A method in accordance with  claim 1 , wherein said sintered anode electrode comprises a metal oxide and zirconia.  
   
   
       3 . A method in accordance with  claim 2 , wherein said zirconia is stabilized with yttria.  
   
   
       4 . A method in accordance with  claim 2 , wherein said metal oxide is NiO.  
   
   
       5 . A method in accordance with  claim 1 , wherein said redox cycle is carried out to at least a 100% redox depth.  
   
   
       6 . A method in accordance with  claim 1 , wherein said temperature is in a range of about 400° C. to about 650° C.  
   
   
       7 . A method of fabricating a solid oxide fuel cell anode electrode comprising the steps of: 
 forming a mixture of metal oxide particles and YSZ particles into a green anode structure;    sintering said green anode structure, forming a sintered anode structure;    contacting said sintered anode structure with a reducing agent at a reducing temperature in a range of about 600° C. to about 1000° C., forming a reduced anode structure having a first microstructure;    contacting said reduced anode structure with an oxidizing agent at an oxidizing temperature in a range of about400° C. to about 650° C., forming an oxidized anode structure; and    contacting said oxidized anode structure with said reducing agent at said reducing temperature, forming said reduced anode structure with a second microstructure.    
   
   
       8 . A method in accordance with  claim 7 , wherein said metal oxide is NiO.  
   
   
       9 . A method in accordance with  claim 7 , wherein said second microstructure is redox tolerant.  
   
   
       10 . In a solid oxide fuel cell having a metal-cermet anode electrode, a method for enhancing redox tolerance of said solid oxide fuel cell comprising the steps of: 
 contacting said metal-cermet anode electrode with an oxidizing agent at a temperature in a range of about 400° C. to about 650° C., forming an oxidized anode electrode; and    contacting said oxidized anode electrode with a reducing agent at a reducing temperature in a range of about 600° C. to about 1000° C., forming a preconditioned metal-cermet anode electrode.    
   
   
       11 . A method in accordance with  claim 10 , wherein said oxidizing agent is provided in an amount sufficient to provide at least a 100% redox depth.  
   
   
       12 . A method in accordance with  claim 10 , wherein said metal-cermet comprises Ni and YSZ.  
   
   
       13 . In a solid oxide fuel cell having an anode electrode, a cathode electrode and a solid electrolyte disposed between said anode electrode and said cathode electrode, the improvement comprising: 
 said anode electrode preconditioned by an initial re-oxidation at a temperature less than or equal to about 650° C.    
   
   
       14 . A solid oxide fuel cell in accordance with  claim 13 , wherein said anode electrode comprises Ni and YSZ.  
   
   
       15 . A solid oxide fuel cell in accordance with  claim 13 , wherein said anode electrode is preconditioned to at least a 100% redox depth.  
   
   
       16 . A solid oxide fuel cell in accordance with  claim 13 , wherein said temperature of said initial re-oxidation is in a range of about 400° C. to about 650° C.  
   
   
       17 . A solid oxide fuel cell in accordance with  claim 13 , wherein said anode electrode is preconditioned in-situ.  
   
   
       18 . A solid oxide fuel cell in accordance with  claim 13 , wherein said anode electrode is preconditioned prior to assembly into said solid oxide fuel cell.  
   
   
       19 . A solid oxide fuel cell anode electrode comprising: 
 a porous metal-YSZ structure having a microstructure produced by initially re-oxidizing said structure at a temperature less than or equal to about 650° C.    
   
   
       20 . A solid oxide fuel cell anode electrode in accordance with  claim 19 , wherein said metal is Ni.  
   
   
       21 . A solid oxide fuel cell anode electrode in accordance with  claim 19 , wherein said temperature of said initial re-oxidizing is in a range of about 400° C. to about 650° C.