Proton conducting membrane, method for producing the same, and fuel cell using the same

Abstract

The present invention provides relates to a crosslinkable, proton-conducting membrane having a crosslinked structure, excellent in heat resistance, durability, dimensional stability and fuel barrier characteristics, and showing excellent proton conductivity at high temperature, characterized by comprising (a) an organic/inorganic hybrid structure (A) covalently bonded to 2 or more silicon-oxygen crosslinks and, at the same time, having a carbon atom, and (b) an acid containing structure (B) having an acid group, covalently bonded to a silicon-oxygen crosslink and having an acidic group; and provides a fuel cell using the same membrane. The present invention also provides a method for producing the proton-conducting membrane, comprising steps of preparing a mixture containing an organic/inorganic hybrid, crosslinkable compound (C) and compound (D), the former having 2 or more crosslinkable silyl groups and carbon atoms each being bonded to the silyl group via the covalent bond and the latter having a crosslinkable silyl group and acid group, as the first step; forming the above mixture into a film as the second step; and hydrolyzing/condensing or only condensing the hydrolyzable silyl group contained in the mixture formed into the film to form a crosslinked structure as the third step.

1 . A method for producing a proton conducting membrane, comprising steps of preparing a mixture containing an organic/inorganic hybrid, crosslinkable compound (C) and compound (D), the former having 2 or more crosslinkable silyl groups and carbon atoms each being bonded to the silyl group via the covalent bond and the latter having a crosslinkable silyl group and acid group, as the first step; forming the above mixture into a film as the second step; and hydrolyzing/condensing or only condensing the hydrolyzable silyl group contained in the mixture formed into the film to form a crosslinked structure as the third step.  
   
   
       2 . A method for producing a proton conducting membrane, comprising steps of preparing a mixture containing an organic/inorganic hybrid, crosslinkable compound (C) and compound (E), the former having 2 or more crosslinkable silyl groups and carbon atoms each being bonded to the silyl group via the covalent bond and the latter having a crosslinkable silyl group and mercapto group, as the first step; forming the above mixture into a film as the second step; hydrolyzing and condensing the hydrolyzable silyl group contained in the mixture formed into the film to form a crosslinked structure as the third step; and oxidation of the mercapto group in the crosslinked structure obtained in the third step into sulfonic acid as the fourth step.  
   
   
       3 . A method for producing a proton conducting membrane, comprising steps of preparing a mixture containing an organic/inorganic hybrid, crosslinkable compound (C) and compound (F), the former having 2 or more crosslinkable silyl groups and carbon atoms each being bonded to the silyl group via the covalent bond and the latter having a crosslinkable silyl group and polysulfide group, as the first step; forming the above mixture into a film as the second step; hydrolyzing and condensing the hydrolyzable silyl group contained in the mixture formed into the film to form a crosslinked structure as the third step; and oxidation of the polysulfide group in the crosslinked structure obtained in the third step into sulfonic acid as the fourth step.  
   
   
       4 . A method for producing a proton conducting membrane, comprising steps of preparing a mixture containing an organic/inorganic hybrid, crosslinkable compound (C) and compound (H), the former having 2 or more crosslinkable silyl groups and carbon atoms each being bonded to the silyl group via the covalent bond and the latter having a crosslinkable silyl group and halogen group, as the first step; forming the above mixture into a film as the second step; hydrolyzing and condensing the hydrolyzable silyl group contained in the mixture formed into the film to form a crosslinked structure as the third step; and substitution of the halogen group in the crosslinked structure obtained in the third step with sulfonic acid group as the fourth step.  
   
   
       5 . The method according to one of  claims 1  to  4  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) is represented by the general formula (7):  
     
       
         
         
             
             
         
       
     
     (wherein, R 1  is a carbon-containing group of 1 to 50 carbon atoms; R 2  is methyl, ethyl, propyl or phenyl group; R 5  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; and “n” is 0, 1 or 2).  
   
   
       6 . The method according to  claim 5  for producing the proton conducting membrane, wherein R 1  in the general formula (7) is a hydrocarbon group.  
   
   
       7 . The method according to  claim 6  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) is represented by the general formula (8):  
     
       
         
         
             
             
         
       
     
     (wherein, R 2  is methyl, ethyl, propyl or phenyl group; R 5  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; “m” is an integer of 1 to 30; and “n” is 0, 1 or 2).  
   
   
       8 . The method according to  claim 7  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) is represented by the general formula (9):  
     
       
         
         
             
             
         
       
     
     (wherein, R 5  is OCH 3  or OC 2 H 5  group; and “n” is 0, 1 or 2).  
   
   
       9 . The method according to  claim 5  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) is represented by the general formula (10):  
     
       
         
         
             
             
         
       
     
     (wherein, R 11 , R 12 , R 13  and R 14  are each methyl, ethyl, propyl or phenyl group, which may be the same or different; R 5  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; “m” is an integer of 1 to 30; and “n” is 0, 1 or 2).  
   
   
       10 . The method according to  claim 9  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) is represented by the general formula (11):  
     
       
         
         
             
             
         
       
     
     (wherein, R 5  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; “m” is an integer of 1 to 30; and “n” is 0, 1 or 2).  
   
   
       11 . The method according to  claim 1  for producing the proton conducting membrane, wherein said acid containing compound (D) is represented by the general formula (12):  
     
       
         
         
             
             
         
       
     
     (wherein, R 3  is a molecular chain group having at least one acid group; R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; “m” is 0, 1 or 2).  
   
   
       12 . The method according to  claim 11  for producing the proton conducting membrane, wherein said acid containing compound (D) is sulfonic acid group.  
   
   
       13 . The method according to  claim 12  for producing the proton conducting membrane, wherein said acid containing compound (D) is represented by the general formula (13):  
     
       
         
         
             
             
         
       
     
     (wherein, R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; X is hydrogen, an alkali metal, alkyl group or ammonium group; “m” is 0, 1 or 2; and “n” is an integer of 1 to 20).  
   
   
       14 . The method according to  claim 13  for producing the proton conducting membrane, wherein “n” in the general formula (13) is 3.  
   
   
       15 . The method according to  claim 1  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) and acid containing compound (D) are incorporated in a mixing ratio of 9:1 to 1:9 by weight.  
   
   
       16 . The method according to  claim 2  for producing the proton conducting membrane, wherein said compound (E) having mercapto group is represented by the general formula (14):  
     
       
         
         
             
             
         
       
     
     (wherein, R 7  is a molecular chain group having at least one mercapto group; R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; and “m” is 0, 1 or 2).  
   
   
       17 . The method according to  claim 16  for producing the proton conducting membrane, wherein said compound (E) having mercapto group is represented by the general formula (15):  
     
       
         
         
             
             
         
       
     
     (wherein, R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; “m” is 0, 1 or 2; and “n” is an integer of 1 to 20).  
   
   
       18 . The method according to  claim 2  for producing the proton conducting membrane, wherein said compound (E) having mercapto group is represented by the general formula (16):  
     
       
         
         
             
             
         
       
     
     (wherein, R 6  is H, or CH 3 , C 2 H 5 , C 3 H 7  or C 6 H 5  group; R 4  is CH 3 , C 2 H 5 , C 3 H 7 , C 6 H 5 , OH, OCH 3 , OC 2 H 5 , OC 6 H 5  group, or O—Si bond; “m” is an integer of 1 to 20; and “n” is an integer of 3 to 500).  
   
   
       19 . The method according to  claim 18  for producing the proton conducting membrane, wherein R 4 , “m” and “n” in the general formula (16) are OCH 3  group, 3 and an integer of 3 to 100, respectively.  
   
   
       20 . The method according to  claim 18  for producing the proton conducting membrane, wherein R 4 , “m” and “n” in the general formula (16) are CH 3  group, 3 and an integer of 3 to 300, respectively.  
   
   
       21 . The method according to  claim 2  for producing the proton conducting membrane, wherein said compound (E) having mercapto group is represented by the general formula (17):  
     
       
         
         
             
             
         
       
     
     (wherein, R 6  is H, or CH 3 , C 2 H 5 , C 3 H 7  or C 6 H 5  group; R 4  is CH 3 , C 2 H 5 , C 3 H 7 , C 6 H 5 , OH, OCH 3 , OC 2 H 5  or OC 6 H 5  group, R 11  is a substitute of 6 carbon atoms or less; “m” is an integer of 1 to 20; “n” is an integer of 3 to 500; and “n+x” is an integer of 500 or less, where the unit containing mercapto group and that containing R 11  may be present in a block or random form).  
   
   
       22 . The method according to  claim 21  for producing the proton conducting membrane, wherein R 4 , “m” and “n+x” in the general formula (17) are OCH 3  group, 3 and an integer of 50 or less, respectively.  
   
   
       23 . The method according to  claim 2  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) and compound (E) having mercapto group are incorporated in a mixing ratio of 9:1 to 1:9 by weight.  
   
   
       24 . The method according to  claim 3  for producing the proton conducting membrane, wherein said compound (F) having a polysulfide group is represented by the general formula (18):  
     
       
         
         
             
             
         
       
     
     (wherein, R 8  is a molecular chain group having at least one polysulfide group; R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; and “m” is 0, 1 or 2).  
   
   
       25 . The method according to  claim 24  for producing the proton conducting membrane, wherein said compound (F) having a polysulfide group is represented by the general formula (19):  
     
       
         
         
             
             
         
       
     
     (wherein, R 9  is a molecular chain group having at least one polysulfide group; R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; and “m” is 0, 1 or 2).  
   
   
       26 . The method according to  claim 25  for producing the proton conducting membrane, wherein said compound (F) having a polysulfide group is represented by the general formula (20):  
     
       
         
         
             
             
         
       
     
     (wherein, R 10  is a polysulfide group; R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; “m” is 0, 1 or 2; and “n” is an integer of 1 to 6).  
   
   
       27 . The method according to  claim 26  for producing the proton conducting membrane, wherein “n” in the general formula (20) is 3.  
   
   
       28 . The method according to  claim 3  for producing the proton conducting membrane, wherein said polysulfide group is tetrasulfide group (—S—S—S—S—).  
   
   
       29 . The method according to  claim 3  for producing the proton conducting membrane, wherein said polysulfide group is disulfide group (—S—S—).  
   
   
       30 . The method according to  claim 3  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) and compound (F) having a polysulfide group are incorporated in a mixing ratio of 95:5 to 10:90 by weight.  
   
   
       31 . The method according to one of  claims 1  to  4  for producing the proton conducting membrane, wherein a crosslinking agent (G) of hydrolyzable, metallic compound is used for the first step.  
   
   
       32 . The method according to  claim 31  for producing the proton conducting membrane, wherein said crosslinking agent (G) is of a compound represented by the general formula (21):  
     
       
         
         
             
             
         
       
     
     (wherein, R 6  is CH 3  or C 2 H 5  group; and “m” is an integer of 1 to 300).  
   
   
       33 . The method according to  claim 31  for producing the proton conducting membrane, wherein said crosslinking agent (G) is of a hydrolyzable, metallic compound having Ti, Zr or Al.  
   
   
       34 . The method according to  claim 4  for producing the proton conducting membrane, wherein said compound (H) having a halogen group is represented by the general formula (22):  
     
       
         
         
             
             
         
       
     
     (wherein, R 12  is a molecular chain group having at least one halogen group; R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; and “m” is 0, 1 or 2).  
   
   
       35 . The method according to  claim 34  for producing the proton conducting membrane, wherein said compound (H) having a halogen group is represented by the general formula (23):  
     
       
         
         
             
             
         
       
     
     (wherein, R 4  is methyl, ethyl, propyl or phenyl group; R 6  is Cl, or OCH 3 , OC 2 H 5 , OC 6 H 5 , OH or OCOCH 3  group; X is Cl, Br or I; “n” is an integer of 1 to 20; and “m” is 0, 1 or 2).  
   
   
       36 . The method according to  claim 4  for producing the proton conducting membrane, wherein said organic/inorganic hybrid, crosslinkable compound (C) and compound (H) having a halogen group are incorporated in a mixing ratio of 9:1 to 1:9 by weight.  
   
   
       37 . The method according to one of  claims 1  to  4  for producing the proton conducting membrane, wherein a step for aging at 100 to 300° C. is included as a post-treatment step.  
   
   
       38 . The method according to one of  claims 1  to  4  for producing the proton conducting membrane, wherein said short fibrous material (J) is incorporated in the mixture in the first step, when it is incorporated as said fibrous material (I) to be composited with the proton-conducting membrane.  
   
   
       39 . The method according to one of  claims 1  to  4  for producing the proton conducting membrane, wherein said long fibrous material (K) is loaded in the second step with the mixture obtained in the first step, when it is incorporated in the form of sheet as said fibrous material (I) to be composited with the proton-conducting membrane.