Polymer electrolyte fuel cell, electrolyte material therefore and method for its production

Abstract

An electrolyte material for a polymer electrolyte fuel cell, which is made of a copolymer comprising repeating units based on CF 2 ═CFCF 2 OCF 2 CF 2 SO 3 H and repeating units based on tetrafluoroethylene and which has an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin). This electrolyte material has ion conductivity and durability equal to conventional electrolyte material, is easy to synthesize, has a softening point higher than electrolyte material heretofore widely used for application to fuel cells and is suitable for operation of a polymer electrolyte fuel cell at a temperature higher than the conventional material.

1 . An electrolyte material for a polymer electrolyte fuel cell, which is made of a copolymer comprising repeating units based on a monomer of the formula (1) and repeating units based on tetrafluoroethylene and which has an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin):  
         CF 2 ═CFCF 2 OCF 2 CF 2 SO 3 H  (1)  
     
     
         2 . A method for producing an electrolyte material for a polymer electrolyte fuel cell, which is made of a copolymer comprising repeating units based on a monomer of the formula (1) and repeating units based on tetrafluoroethylene and which has an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin), wherein an initiator of a perfluoro compound is used, and tetrafluoroethylene and a monomer of the formula (2) are subjected to radical copolymerization at from 60 to 100° C.:  
         CF 2 ═CFCF 2 OCF 2 CF 2 SO 3 H  (1)  CF 2 ═CFCF 2 OCF 2 CF 2 SO 2 F  (2)  
     
     
         3 . The method for producing an electrolyte material for a polymer electrolyte fuel cell according to  claim 2 , wherein the initiator of a perfluoro compound is a perfluorobenzoyl peroxide.  
     
     
         4 . The method for producing an electrolyte material for a polymer electrolyte fuel cell according to  claim 2 , wherein the polymer obtained by the copolymerization of the monomer of the formula (2) and tetrafluoroethylene, has T Q  of from 200 to 400° C. while T Q  indicates a temperature at which, when melt-extrusion of the resin is carried out using a nozzle having a length of 1 mm and an inner diameter of 1 mm under an extrusion pressure condition of 30 kg/cm 2 , the extrusion rate would be 100 mm 3 /sec., and is obtained by hydrolysis of said polymer followed by conversion to an acid-form.  
     
     
         5 . A method for producing an electrolyte material for a polymer electrolyte fuel cell, which is made of a copolymer comprising repeating units based on a monomer of the formula (1) and repeating units based on tetrafluoroethylene and which has an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin), wherein by means of a hydrocarbon type initiator, tetrafluoroethylene and a monomer of the formula (2) are subjected to radical copolymerization at a temperature of at least 20° C. and less than 50° C.:  
         CF 2 ═CFCF 2 OCF 2 CF 2 SO 3 H  (1)  CF 2 ═CFCF 2 OCF 2 CF 2 SO 2 F  (2)  
     
     
         6 . The method for producing an electrolyte material for a polymer electrolyte fuel cell according to  claim 5 , wherein the polymer obtained by the copolymerization of the monomer of the formula (2) and tetrafluoroethylene, has T Q  of from 200 to 400° C. while T Q  indicates a temperature at which, when melt-extrusion of the resin is carried out using a nozzle having a length of 1 mm and an inner diameter of 1 mm under an extrusion pressure condition of 30 kg/cm 2 , the extrusion rate would be 100 mm 3 /sec., and is obtained by hydrolysis of said polymer followed by conversion to an acid-form.  
     
     
         7 . A copolymer which comprises repeating units based on a monomer of the formula (2) and repeating units based on tetrafluoroethylene and which has T Q  of from 200 to 400° C. as an index of the molecular weight and an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin), when converted to a —SO 3 H form:  
         CF 2 ═CFCF 2 OCF 2 CF 2 SO 2 F  (2)  
     
     
         8 . A polymer electrolyte fuel cell having an anode, a cathode and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the polymer electrolyte membrane is made of a copolymer comprising repeating units based on a monomer of the formula (1) and repeating units based on tetrafluoroethylene and has an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin) and a membrane thickness of from 5 to 70 μm:  
         CF 2 ═CFCF 2 OCF 2 CF 2 SO 3 H  (1)  
     
     
         9 . A polymer electrolyte fuel cell having an anode, a cathode and a polymer electrolyte membrane disposed between the anode and the cathode, wherein at least one of the anode and the cathode has a catalyst layer which comprises a catalyst and a copolymer comprising repeating units based on a monomer of the formula (1) and repeating units based on tetrafluoroethylene and having an ion exchange capacity of from 0.9 to 1.5 (meq/g dry resin):  
         CF 2 ═CFCF 2 OCF 2 CF 2 SO 3 H (1)