Membrane electrode assembly for polymer electrolyte membrane water electrolysis and water electrolyzer

Abstract

Provided are a membrane electrode assembly for polymer electrolyte membrane water electrolysis and a water electrolyzer with which a low electrolysis voltage can be achieved and decomposition of the fluorinated polymer contained can be suppressed. A membrane electrode assembly for polymer electrolyte membrane water electrolysis, which comprises: a polymer electrolyte membrane comprising a fluorinated polymer having ion exchange groups, a cathode catalyst layer comprising a fluorinated polymer having ion exchange groups, provided on one side of the polymer electrolyte membrane, and an anode catalyst layer provided on the other side of the polymer electrolyte membrane, wherein when the membrane electrode assembly for polymer electrolyte membrane water electrolysis is observed from the normal direction of the surface, cerium ions are contained in a region overlapping the cathode catalyst layer, and the relation of the formula (X) is satisfied: ( A Ce × 3 ) / A IEG ⁢ _ ⁢ C ≤ 0.9 formula ⁢ ( X ) wherein A Ce is the amount of substance (mol) of cerium ions contained in the above region, and A IEG_c is the amount of substance (mol) of the ion exchange groups of the fluorinated polymer contained in the cathode catalyst layer.

What is claimed is: 
     
         1 . A membrane electrode assembly for polymer electrolyte membrane water electrolysis, which comprises:
 a polymer electrolyte membrane comprising a fluorinated polymer having ion exchange groups,   a cathode catalyst layer comprising a fluorinated polymer having ion exchange groups, provided on one side of the polymer electrolyte membrane, and   an anode catalyst layer provided on the other side of the polymer electrolyte membrane,   wherein when the membrane electrode assembly for polymer electrolyte membrane water electrolysis is observed from the normal direction of the surface, cerium ions are contained in a region overlapping the cathode catalyst layer, and   the relation of the formula (X) is satisfied:   
       
         
           
             
               
                 
                   
                     
                       
                         ( 
                         
                           
                             A 
                             Ce 
                           
                           × 
                           3 
                         
                         ) 
                       
                       / 
                       
                         A 
                         
                           IEG 
                           ⁢ 
                           _ 
                           ⁢ 
                           C 
                         
                       
                     
                     ≤ 
                     0.9 
                   
                 
                 
                   
                     formula 
                     ⁢ 
                         
                     
                       ( 
                       X 
                       ) 
                     
                   
                 
               
             
           
         
         wherein A Ce  is the amount of substance (mol) of cerium ions contained in the above region, and A IEG_C  is the amount of substance (mol) of the ion exchange groups of the fluorinated polymer contained in the cathode catalyst layer. 
       
     
     
         2 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the fluorinated polymer contained in the polymer electrolyte membrane has an ion exchange capacity of 1.10 meq/g dry resin or more. 
     
     
         3 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the content of the fluorinated polymer contained in the polymer electrolyte membrane is from 80 to 100 mass % to the total mass of the polymer in the polymer electrolyte membrane. 
     
     
         4 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the cerium ions are contained in the polymer electrolyte membrane. 
     
     
         5 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the cerium ions are contained in the cathode catalyst layer. 
     
     
         6 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the ion exchange groups of the fluorinated polymer contained in the polymer electrolyte membrane are sulfonic acid functional groups. 
     
     
         7 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the fluorinated polymer contained in the polymer electrolyte membrane comprises at least one species of units selected from the group consisting of units represented by the formula (1-3) and units represented by the formula (1-4): 
       
         
           
           
               
               
           
         
         in the formula (1-3) and the formula (1-4), R f1  is a perfluoroalkylene group which may have an oxygen atom between carbon atoms, R f2  is a single bond or a perfluoroalkylene group which may have an oxygen atom between carbon atoms, R f3  is a single bond or a perfluoroalkylene group which may have an oxygen atom between carbon atoms, r is 0 or 1, m is 0 or 1, and M is a hydrogen atom, an alkali metal or a quaternary ammonium cation. 
       
     
     
         8 . The membrane electrode assembly for polymer electrolyte membrane water electrolysis according to  claim 1 , wherein the polymer electrolyte membrane further comprises a reinforcing material. 
     
     
         9 . A water electrolyzer comprising the membrane electrode assembly for polymer electrolyte membrane water electrolysis as defined in  claim 1 , a power supply member connecting the cathode catalyst layer side and the anode catalyst layer side of the membrane electrode assembly for polymer electrolyte membrane water electrolysis, and a water supply member to supply water to the anode catalyst layer side.