Durable fuel cell membrane electrode assembly with combined additives

Abstract

A fuel cell membrane electrode assembly is provided comprising a polymer electrolyte membrane comprising a first polymer electrolyte and at least one manganese compound; and one or more electrode layers comprising a catalyst and at least one cerium compound. The membrane electrode assembly demonstrates an unexpected combination of durability and performance.

1 - 18 . (canceled) 
     
     
         19 . A catalyst coated membrane comprising:
 a) a polymer electrolyte membrane comprising a first polymer electrolyte and at least one manganese cation, wherein the distribution of manganese cations across the thickness of the polymer electrolyte membrane is uniform, and wherein the distribution of manganese cations throughout the polymer electrolyte membrane is uniform; and   b) at least one electrode layer comprising a catalyst and at least one of CeO 2  or Ce 2 O 3 , wherein a total amount of the at least one of CeO 2  or CE 2 O 3  is between 0.01 and 5 percent by weight relative to the weight of catalyst present.   
     
     
         20 . The catalyst coated membrane according to  claim 19 , wherein the first polymer electrolyte comprises bound anionic functional groups, wherein at least a portion of said anionic functional groups are in acid form and at least a portion of said anionic functional groups are neutralized by manganese cations. 
     
     
         21 . The catalyst coated membrane according to  claim 20 , wherein the amount of manganese cations present is between 0.001 and 0.5 charge equivalents based on the molar amount of anionic functional groups present in the first polymer electrolyte. 
     
     
         22 . The catalyst coated membrane according to  claim 20 , wherein the amount of manganese cations present is between 0.01 and 0.1 charge equivalents based on the molar amount of anionic functional groups present in the first polymer electrolyte. 
     
     
         23 . The catalyst coated membrane according to  claim 20 , wherein said manganese cations are Mn 2+  cations. 
     
     
         24 . The catalyst coated membrane according to  claim 19 , wherein the first polymer electrolyte is highly fluorinated. 
     
     
         25 . The catalyst coated membrane according to  claim 19 , wherein the first polymer electrolyte is perfluorinated. 
     
     
         26 . The catalyst coated membrane according to  claim 19 , wherein the one or more electrode layers additionally comprise a second polymer electrolyte. 
     
     
         27 . The catalyst coated membrane according to  claim 24 , wherein the second polymer electrolyte is highly fluorinated. 
     
     
         28 . The catalyst coated membrane according to  claim 24 , wherein the second polymer electrolyte is perfluorinated. 
     
     
         29 . The catalyst coated membrane according to  claim 19 , wherein said first polymer electrolyte has an equivalent weight of 900 or less. 
     
     
         30 . The catalyst coated membrane according to  claim 19 , wherein said first polymer electrolyte comprises pendent groups according to the formula:
   —O—CF 2 —CF 2 —CF 2 —CF 2 —SO 3 H.
   
     
     
         31 . The catalyst coated membrane according to  claim 19 , additionally comprising a porous support. 
     
     
         32 . The catalyst coated membrane according to  claim 19  which contains at least 50% less manganese in the electrode layer(s) than in the polymer electrolyte membrane and at least 50% less cerium in the polymer electrolyte membrane than in the electrode layer(s). 
     
     
         33 . The catalyst coated membrane according to  claim 19 , wherein a total amount of the at least one of CeO 2  or Ce 2 O 3  is between 0.1 and 2 percent by weight relative to the weight of catalyst present. 
     
     
         34 . The catalyst coated membrane according to  claim 19 , wherein a total amount of the at least one of CeO 2  or Ce 2 O 3  is between 0.2 and 1.3 percent by weight relative to the weight of catalyst present.