JP2008146976A - Proton exchange membrane for high concentration direct methanol fuel cell, and fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton exchange membrane for a high concentration direct methanol fuel cell. <P>SOLUTION: This is the proton exchange membrane for the high concentration direct methanol fuel cell containing aromatic hydrocarbon based polymer for the direct methanol fuel cell in which methanol-water solution of 20 wt.% concentration or more is used as a fuel. The aromatic hydrocarbon based polymer is a polymer having softening initiation temperatures of 80 to 180°C and having a repeating unit expressed by (formula 1), and an area swelling rate against the methanol water solution of 40°C and 30 wt.% at 40°C ranges from 0.5 to 30%. In the formula, X is -S(=O)<SB>2</SB>-group or -C(=O)-group, Y is H or a monovalent cation, Z<SP>1</SP>is either one of O or S atom, Z<SP>2</SP>is any one of O atom, -C(CH<SB>3</SB>)<SB>2</SB>-group, -C(CF<SB>3</SB>)<SB>2</SB>-group. -(CH<SB>3</SB>)<SB>q</SB>-group, or a cyclohexyl group, and q and n1 express respectively an integer of one or more. However, in the case n1 is 2 or more, Z<SP>2</SP>expresses O atom. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention particularly relates to a proton exchange membrane for a direct methanol fuel cell using a high-concentration aqueous methanol solution as a fuel.

  A direct methanol fuel cell is a polymer electrolyte fuel cell that generates electricity using methanol as a fuel, and is expected to be used as a portable power source such as a notebook personal computer, a PDA, and a mobile phone. The structure of the direct methanol fuel cell is mainly composed of a structure called a membrane electrode assembly (MEA) in which a pair of electrodes are joined to both sides of a proton exchange membrane. A methanol aqueous solution is applied to one electrode, A fuel cell can be operated by supplying an oxidizing gas such as air to the other electrode. The higher the methanol concentration is, the higher the energy density is, and it is possible to operate for a long time and miniaturize the fuel tank, which is excellent as a portable power source. However, if methanol is used at a high concentration, methanol easily permeates the proton exchange membrane. As a side reaction occurs, there is a problem that sufficient power generation performance cannot be obtained.

  The proton exchange membrane used for MEA must have proton conductivity as a cation exchange membrane and be sufficiently stable chemically, thermally, electrochemically and mechanically. For this reason, perfluorocarbon sulfonic acid membranes have been mainly used as those that can be used over a long period of time. However, perfluorocarbon sulfonic acid membranes have remarkable methanol permeation, and there is a problem that the power generation performance is reduced by methanol crossover.

For this reason, proton exchange membranes that are less prone to methanol crossover have been developed, and polymer proton exchange membranes in which sulfonic acid groups are introduced into hydrocarbon polymers have been widely studied (for example, Patent Document 1). However, it cannot be said that the methanol permeation inhibiting property is sufficient, and there are still problems to be solved such as a problem that the electrode is easily peeled off.
Membranes that further inhibit methanol permeation have also been developed by impregnating or cross-linking proton exchange resins with porous materials. This type of proton exchange membrane is more permeable to methanol than hydrocarbon proton exchange membranes. However, it is difficult to operate as a direct methanol fuel cell because the membrane is fragile and the bonding property with the electrode is poor.
Thus, in the case of a hydrocarbon proton exchange membrane, or a composite membrane or a crosslinked membrane using a hydrocarbon proton exchange membrane, the problem to be solved is how to improve the bondability with the electrode while improving the performance. It is.

Journal of Membrane Science 185 (2001) p. 29-39 Proceedings of the 47th Battery Symposium (2006), pages 154-157

It is formed by copolymerizing a component containing a cationic functional group such as a sulfonic acid group that contributes to the expression of proton conductivity in the polymer skeleton and a hydrophobic component made of, for example, an aromatic skeleton that does not contribute to proton conductivity. In the proton exchange membrane, when the proportion of the proton conductive component is increased, the proton conductivity increases, but in correlation therewith, the methanol crossover also increases. On the other hand, if the proportion of the proton conductive component is reduced, methanol crossover can be suppressed, but the proton conductivity also decreases. That is, since the channel through which protons can move and the channel through which methanol can move are basically hydrophilic sites, there is a positive correlation between them. Therefore, in order to reduce the permeation of methanol, it is basically necessary to suppress the swelling with respect to the aqueous methanol solution.
Therefore, the present invention is particularly excellent in swelling resistance against methanol aqueous solution and has excellent bondability with an electrode even when a high concentration (20% by mass or more) aqueous methanol solution is used as a fuel. However, the present invention intends to provide a proton exchange membrane for a direct methanol fuel cell that operates well.

  As a result of intensive studies, the inventors of the present invention have used a proton exchange membrane having a specific structure of an aromatic hydrocarbon proton exchange polymer having an area swelling ratio with respect to a specific aqueous methanol solution and a softening start temperature of the polymer. The present inventors have found that a direct methanol fuel cell that can use a high-concentration methanol aqueous solution as a fuel can be provided, and the present invention employs the following configuration. That is,

(1) A proton exchange membrane containing an aromatic hydrocarbon polymer for a direct methanol fuel cell using a methanol aqueous solution having a concentration of 20% by mass or more as a fuel, wherein the aromatic hydrocarbon polymer is 80 to 180 ° C. The polymer has a softening start temperature in the range and a repeating unit represented by the following (formula 1), and the area swelling ratio of the proton exchange membrane with respect to a 40 ° C., 30% by mass methanol aqueous solution is 0.5-30. % Proton exchange membrane for high-concentration direct methanol fuel cells, characterized by being in the range of%.

［式中、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ¹はＯ又はＳ原子のいずれかを、Ｚ^２は、Ｏ原子、Ｓ原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−（ＣＨ_２）ｑ−基、シクロヘキシル基のいずれかを表し、ｑ、ｎ１は１以上の整数を表す。但しｎ１が２以上の場合、Ｚ^２はＯ原子を表す。］
（２）下記（式２）で表される繰り返し単位を芳香族炭化水素系ポリマー中にさらに有する（１）に記載の高濃度ダイレクトメタノール型燃料電池用プロトン交換膜。

[Wherein X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents any one of an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a — (CH ₂ ) q— group, and a cyclohexyl group, and q and n1 are Represents an integer of 1 or more. Provided that when n1 is 2 or more, ^{Z 2} represents O atom. ]
(2) The proton exchange membrane for a high concentration direct methanol fuel cell according to (1), wherein the aromatic hydrocarbon polymer further has a repeating unit represented by the following (formula 2).

［式中、Ｚ^３はＯ又はＳ原子のいずれかを、Ｚ^４は、Ｏ原子、Ｓ原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−（ＣＨ_２）ｑ−基、シクロヘキシル基のいずれかを表し、ｑ、ｎ１は１以上の整数を表す。但しｎ２が２以上の場合、Ｚ^４はＯ原子を表す。］
（３）下記（式３）で表される繰り返し単位を芳香族炭化水素系ポリマー中にさらに有する（２）に記載の高濃度ダイレクトメタノール型燃料電池用プロトン交換膜。

[Wherein Z ³ represents either O or S atom, Z ⁴ represents O atom, S atom, —C (CH ₃ ) ₂ — group, —C (CF ₃ ) ₂ — group, — (CH ₂ ) Represents either a q-group or a cyclohexyl group, and q and n1 represent an integer of 1 or more. However, when n2 is 2 or more, Z ⁴ represents an O atom. ]
(3) The proton exchange membrane for high-concentration direct methanol fuel cells according to (2), wherein the aromatic hydrocarbon polymer further has a repeating unit represented by the following (formula 3).

［式中、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ^５はＯ又はＳ原子のいずれかを表す。］

[Wherein, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. ]

(4) A fuel cell using the proton exchange membrane for a high concentration direct methanol fuel cell according to any one of (1) to (3).

  The proton exchange membrane for a direct methanol fuel cell according to the present invention includes an aromatic hydrocarbon polymer having a specific polyarylene ether structure as a part of a polymer skeleton, and having a sulfonic acid group in the polymer, and is aromatic. Since a polymer whose softening temperature of the hydrocarbon polymer is in a specific range is used, the resulting proton exchange membrane is excellent in swelling resistance against a high-concentration aqueous methanol solution and has excellent bonding properties with an electrode. It is suitable as a proton exchange membrane of a fuel cell used as a fuel.

  The proton exchange membrane in the present invention includes an aromatic hydrocarbon polymer having at least a polyarylene ether structure as a part of a polymer skeleton, and also having a sulfonic acid group in the polymer. The softening start temperature of the aromatic hydrocarbon polymer is in the range of 80 to 180 ° C., and the area swelling ratio of the ion exchange membrane with respect to 40 ° C. and a 30% by mass methanol aqueous solution is in the range of 0.5 to 30%. is important.

In the present invention, the area swelling ratio with respect to a methanol aqueous solution of 40 ° C. and 30% by mass indicates the equilibrium swelling degree of the proton exchange membrane with respect to a methanol aqueous solution of 40 ° C. and 30% by mass, and the membrane thickness is in the range of 20 to 200 μm. After immersing a dry film (area: As) having a size of 5 × 5 cm in an aqueous methanol solution of 30% by mass at 40 ° C. for 2 hours, the area (Aw) of the film was measured, and the following formula was obtained: It is required to use.
Area swelling rate (%) = (Aw−As) / As × 100 (%)

  There is a correlation between area swellability and methanol permeability, and a membrane having a lower swellability with respect to an aqueous methanol solution is more effective in that the crossover of methanol can be kept low. In this respect, the proton exchange membrane for a direct methanol fuel cell using a methanol aqueous solution having a concentration of 20% by mass or more as a fuel has an area swelling ratio of 0.5 to 30% with respect to methanol at 40 ° C. and 30% by mass. It is necessary to be. When the area swelling ratio is smaller than 0.5%, even in the proton exchange membrane having improved bonding properties with the electrode of the present invention, bonding with the electrode tends to be difficult. On the other hand, when it exceeds 30%, the methanol permeation inhibiting property is insufficient, and when power is generated using a high-concentration aqueous methanol solution, the performance tends to deteriorate. In particular, the area swelling rate is particularly preferably in the range of 1 to 15%.

  Even in an aromatic hydrocarbon polymer having a conventional polyarylene ether structure, if the area swelling rate can be kept low, methanol permeation can be kept low, but there is a problem that the bonding property with the electrode is deteriorated. is there. However, in the proton exchange membrane including the polyarylene ether structure having an area swelling rate of the present invention and the aromatic hydrocarbon polymer containing a sulfonic acid group, the softening start temperature of the aromatic hydrocarbon polymer is 80 to 180 ° C. When it is within the range, the bonding property with the electrode is good. When the softening start temperature of the aromatic hydrocarbon polymer is less than 80 ° C., the deformation of the ion exchange membrane becomes large and there is a tendency to short-circuit. When the softening start temperature of the aromatic hydrocarbon polymer exceeds 180 ° C., the bondability with the electrode tends to be insufficient. The softening onset temperature is optimally in the range of 90-160 ° C.

  The aromatic hydrocarbon polymer used for producing the proton exchange membrane of the present invention includes a polymer containing at least a polyarylene ether structure having a repeating unit represented by the above (formula 1) and a sulfonic acid group. Preferably it is 50 mass% or more, More preferably, it contains 70 mass% or more. By including the polyarylene ether structure of (Formula 1), the area swelling rate when a proton exchange membrane is formed tends to be kept low, and the bonding property with the electrode is improved.

  As a method of introducing a sulfonic acid group into a polymer, for example, a suitable sulfonating agent is reacted with a polymer having a polyarylene ether skeleton having a basic skeleton obtained by removing the sulfonic acid group from the structure of (Formula 1). Can be obtained. Examples of such a sulfonating agent include those using concentrated sulfuric acid or fuming sulfuric acid, which have been reported as an example of introducing a sulfonic acid group into an aromatic ring-containing polymer (for example, Solid State Ionics, 106, P.A. 219 (1998)), those using chlorosulfuric acid (for example, J. Polym. Sci., Polym. Chem., 22, P. 295 (1984)), those using anhydrous sulfuric acid complex (for example, J. Polym Sci., Polym.Chem., 22, P.721 (1984), J. Polym.Sci., Polym.Chem., 23, P.1231 (1985)) and the like are effective. It can carry out by selecting reaction conditions according to each polymer using these reagents. Moreover, it is also possible to use the sulfonating agent described in Japanese Patent No. 2884189.

  In addition, the aromatic hydrocarbon polymer having a sulfonic acid group represented by (Formula 1) may be synthesized using a monomer containing a sulfonic acid group or a derivative thereof as at least one of monomers used for polymerization. it can. For example, polysulfone, polyethersulfone, polyetherketone, etc. synthesized from aromatic dihalide and aromatic diol are synthesized by using sulfonic acid group-containing aromatic dihalide or sulfonic acid group-containing aromatic diol as at least one monomer. I can do it. At this time, it is preferable to use a sulfonic acid group-containing dihalide rather than a sulfonic acid group-containing diol because the degree of polymerization tends to increase and the thermal stability of the obtained polymer increases.

  In the case of including a polyimide skeleton synthesized from an aromatic diamine and an aromatic tetracarboxylic dianhydride, a sulfonic acid group-containing polyimide skeleton is introduced into at least one of the aromatic diamines using a sulfonic acid group-containing diamine. I can do it. In the case of polybenzoxazole synthesized from aromatic diamine diol and aromatic dicarboxylic acid, and polybenzthiazole synthesized from aromatic diamine dithiol and aromatic dicarboxylic acid, at least one kind of aromatic dicarboxylic acid has a sulfonic acid group. A sulfonic acid group-containing polybenzoxazole or polybenzthiazole skeleton can be introduced by using the contained dicarboxylic acid.

  In the present invention, an aromatic hydrocarbon polymer for forming a proton exchange membrane containing a polyarylene ether structure and a sulfonic acid group, particularly, a polymer containing a skeleton represented by the following (formula 1) in the molecule has an area swelling. It is preferable for controlling the property and the softening start temperature.

［式１中、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ¹はＯ又はＳ原子のいずれかを、Ｚ^２は、Ｏ原子、Ｓ原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−（ＣＨ_２）ｑ−基、シクロヘキシル基のいずれかを表し、ｑ、ｎ１は１以上の整数を表す。但しｎ１が２以上の場合、Ｚ^２はＯ原子を表す。］

[In Formula 1, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents any one of an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a — (CH ₂ ) q— group, and a cyclohexyl group, q, n 1 Represents an integer of 1 or more. Provided that when n1 is 2 or more, ^{Z 2} represents O atom. ]

  Furthermore, by further containing the structure represented by the following (formula 2), the area swelling rate is suppressed by the electronic action of the cyano group, which is more preferable.

［式中、Ｚ^３はＯ又はＳ原子のいずれかを、Ｚ^４は、Ｏ原子、Ｓ原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−（ＣＨ_２）ｑ−基、シクロヘキシル基のいずれかを表し、ｑ、ｎ１は１以上の整数を表す。但しｎ２が２以上の場合、Ｚ^４はＯ原子を表す。］

[Wherein Z ³ represents either O or S atom, Z ⁴ represents O atom, S atom, —C (CH ₃ ) ₂ — group, —C (CF ₃ ) ₂ — group, — (CH ₂ ) Represents either a q-group or a cyclohexyl group, and q and n1 represent an integer of 1 or more. However, when n2 is 2 or more, Z ⁴ represents an O atom. ]

  The polyarylene ether-based polymer containing a sulfonic acid group may contain structural units other than those represented by the above (Formula 1) and (Formula 2). At this time, it is preferable that the structural units other than those represented by the above (Formula 1) or (Formula 2) are 70% by mass or less. By setting it to 70% by mass or less, a proton exchange membrane utilizing the characteristics of the polymer can be obtained. Particularly preferably, it is 50% by mass or less.

  The aromatic hydrocarbon polymer for forming the proton exchange membrane of the present invention preferably has a sulfonic acid group content in the range of 0.3 to 1.9 meq / g. When it is less than 0.3 meq / g, even when the softening start temperature is within the range of the present invention, the bondability with the electrode when producing MEA is poor, and the internal resistance when a direct methanol fuel cell is obtained. Will increase. On the other hand, when it is larger than 1.9 meq / g, the area swelling rate tends to be too large, and it cannot be stably operated. The sulfonic acid group content can be calculated from the polymer composition. More preferably, it is 0.6-1.7 meq / g.

  In addition, in order to reduce an area swelling rate, it exists in the more preferable tendency to bridge | crosslink a polymer or to contain a filler or a porous material. Due to the swelling-inhibiting effect of the cross-linking / filler / porous material, a proton exchange membrane with further suppressed methanol permeation can be obtained.

  Furthermore, a proton exchange membrane having a repeating unit represented by the following (formula 3) in the molecule of the aromatic hydrocarbon polymer is preferable because the area swelling rate is suppressed and the toughness is high.

［式３中、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ^５はＯ又はＳ原子のいずれかを表す。］

[In Formula 3, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. . ]

The sulfonic acid group-containing polyarylene ether-based polymer having the repeating units of (Formula 1) and (Formula 2) includes an aromatic nucleophilic compound containing compounds represented by the following (Formula 4) and (Formula 5) as monomers. It can polymerize by a substitution reaction.
Specific examples of the compound represented by the formula (4) include 3,3′-disulfo-4,4′-dichlorodiphenylsulfone, 3,3′-disulfo-4,4′-difluorodiphenylsulfone, 3,3 Examples include '-disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl ketone, and those whose sulfonic acid group is converted to a salt with a monovalent cationic species. It is done. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto.
Examples of the compound represented by (Formula 5) include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2,4-difluorobenzonitrile, and the like. .

（ただし、Ｘは−Ｓ（＝Ｏ）_２基または−Ｃ（＝Ｏ）基、Ｙは１価のカチオン種、Ｚ^６は塩素またはフッ素を示す。）

(Where X represents a —S (═O) ₂ group or —C (═O) group, Y represents a monovalent cation species, and Z ⁶ represents chlorine or fluorine.)

  In the present invention, the above 2,6-dichlorobenzonitrile and 2,4-dichlorobenzonitrile are in an isomer relationship, and any of them is used for good proton conductivity, heat resistance, workability and dimensional stability. Can be achieved. The reason is considered that both monomers are excellent in reactivity and that the structure of the whole molecule is made harder by constituting a small repeating unit.

  In the above-described aromatic nucleophilic substitution reaction, various activated difluoroaromatic compounds and dichloroaromatic compounds can be used as monomers together with the compounds represented by the above (formula 4) and (formula 5). Examples of these compounds include 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorodiphenyl sulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, decafluorobiphenyl, and the like. However, other aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like that are active in aromatic nucleophilic substitution can also be used.

  The structural unit represented by the above (Formula 1) to (Formula 2) is an aromatic nucleophilic compound using a diol or dithiol as a monomer together with the compound represented by the above (Formula 4) or (Formula 5). It can be obtained by carrying out a substitution reaction. Examples of such diol or dithiol monomers include 4,4′-biphenol, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy). Phenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, terminal hydroxyl group-containing polyphenylene ether oligomer, 4,4 '-Thiobisbenzenethiol, 1,4-benzenedithiol, 1,3-benzenedithiol, 4,4'-biphenyldithiol, 1,4-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,2-bis (4 -Hydroxy-3,5-dimethylphenyl) propane, bis (4 Hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, bis (4-hydroxyphenyl) diphenylmethane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, hydroquinone, resorcin, bis (4-hydroxyphenyl) ) Ketone, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, bis (4-hydroxyphenyl) ether, bis (4 -Hydroxyphenyl Sulfide, bis (4-hydroxyphenoxy) -1,4-benzene, bis (4-hydroxyphenoxy) -1,3-benzene, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol 1,4-bis (hydroxyphenyl) butane, 1,1-bis (hydroxyphenyl) methane, 1,2-bis (hydroxyphenyl) ethane, 1,3-bis (hydroxyphenyl) propane, 1,5-bis (Hydroxyphenyl) heptane, 1,6-bis (hydroxyphenyl) hexane, 1,1-bis (4-hydroxyphenyl) cyclohexane, and the like. In addition to these, polyarylene ether type by aromatic nucleophilic substitution reaction Various aromatic diols that can be used for polymerization of the compound can also be used.

  In addition, these aromatic diols are bonded to substituents such as alkyl groups having 1 to 30 carbon atoms, aromatic substituents such as phenyl groups, halogens, cyano groups, sulfonic acid groups and their salt compounds. You may do it. A substituent such as a halogen, a cyano group, or a sulfonic acid group may be bonded to an alkyl group or an aromatic substituent. The kind of substituent is not particularly limited, and is preferably 0 to 2 per aromatic ring. These diols or dithiol compounds can be used alone or in combination.

  When a polyarylene ether-based polymer containing a sulfonic acid group is polymerized by an aromatic nucleophilic substitution reaction, an activated difluoroaromatic compound and / or a dichloroaromatic compound including the compounds represented by the above (formula 4) and (formula 5) A polymer can be obtained by reacting a compound with a diol or dithiols in the presence of a basic compound. The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 230 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed.

  The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more. Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like, and those that can convert an aromatic diol into an active phenoxide structure may be used. It can use without being limited to. In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used.

  When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the polymer concentration obtained is 5 to 40% by mass. When the amount is less than 5% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, when it is more than 40% by mass, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration.

  The polyarylene ether-based polymer containing a sulfonic acid group of the present invention preferably has a polymer log viscosity of 0.1 or more. When the logarithmic viscosity is less than 0.1, the membrane tends to become brittle when formed as a proton exchange membrane. The reduced specific viscosity is more preferably 0.3 or more. On the other hand, if the reduced specific viscosity exceeds 5, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

  If necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, a dispersant, a polymerization inhibitor, Various additives such as radical inhibitors, precious metals for controlling the properties of the proton exchange membrane, inorganic compounds, inorganic-organic hybrid compounds, ionic liquids, and the like may be included. Further, a plurality of items may be mixed as much as possible.

  The polymer shown above can be made into a proton exchange membrane by any method such as extrusion, rolling or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. Examples of the solvent include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and hexamethylphosphonamide, alcohols such as methanol and ethanol, An appropriate one can be selected from ethers, ketones or a mixed solvent of water with them, but is not limited thereto. A plurality of these solvents may be used as a mixture within a possible range. The compound concentration in the solution is preferably in the range of 0.1 to 50% by mass. If the compound concentration in the solution is less than 0.1% by mass, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by mass, the workability tends to deteriorate.

A method of obtaining a molded body from a solution can be performed using a conventionally known method. The most preferable method for forming the proton exchange membrane is casting from a solution, and the proton exchange membrane can be obtained by removing the solvent from the cast solution as described above.
The solvent is preferably removed by drying from the viewpoint of the uniformity of the proton exchange membrane. Moreover, in order to avoid decomposition | disassembly and alteration of a compound or a solvent, it can also dry at the lowest temperature possible under reduced pressure. Further, when the viscosity of the solution is high, when the substrate or the solution is heated and cast at a high temperature, the viscosity of the solution is lowered and the casting can be easily performed.

  The thickness of the solution at the time of casting is not particularly limited, but is preferably 10 to 2500 μm. More preferably, it is 50-1500 micrometers. If the thickness of the solution is thinner than 10 μm, the form as a proton exchange membrane tends to be not maintained, and if it is thicker than 2500 μm, a non-uniform proton exchange membrane tends to be easily formed.

  As a method for controlling the cast thickness of the solution, a known method can be used. For example, the thickness can be controlled with the amount and concentration of the solution with a constant thickness using an applicator, a doctor blade, or the like, and with a cast area constant using a glass petri dish or the like. The cast solution can obtain a more uniform film by adjusting the solvent removal rate. For example, in the case of heating, there is a method in which the first stage is performed at a low temperature and the temperature is raised later. In addition, when immersed in a non-solvent such as water, the coagulation rate of the compound can be adjusted by leaving the solution in air or an inert gas for an appropriate time.

  The proton exchange membrane of the present invention can have any thickness depending on the purpose, but is preferably as thin as possible from the viewpoint of proton conductivity. Specifically, it is preferably 3 to 200 μm, and more preferably 5 to 150 μm. If the thickness of the proton exchange membrane is less than 3 μm, handling of the proton exchange membrane becomes difficult and a short circuit or the like tends to occur when a fuel cell is produced. If the thickness is greater than 200 μm, the proton exchange membrane becomes too strong and handling becomes difficult. There is a tendency. In the present invention, although described as a proton exchange membrane, processing in a hollow fiber shape is also a preferred form, and a known formulation can be used for processing.

When the proton exchange membrane finally obtained is used, the ionic functional group in the membrane may contain a part of the metal salt, but it is converted to the acid type by appropriate acid treatment. The shape is preferred. At this time, the proton conductivity of the proton exchange membrane is preferably 1.0 × 10 ⁻³ S / cm or more. When the proton conductivity of 1.0 × ¹⁰ -3 S / cm or higher, tend to better output is obtained in the fuel cell using the proton exchange membrane, less than ^1.0x10 -3 S / cm In this case, the output of the fuel cell tends to decrease.

In order to prevent methanol crossover, the methanol permeation rate is preferably in the range of 0.1 to 1.8 mmol / m ² / s, and more preferably 1.5 mmol / m ² / s. Small is desirable.

  In the present invention, the method for joining the electrode and the proton exchange membrane is not particularly limited, and a known method such as a hot press method can be used. Generally, MEAs can be obtained by bonding electrodes to both sides of a proton exchange membrane. The configuration of the electrode for the fuel cell is not particularly limited and can be appropriately selected. The method of joining the electrode and the proton exchange membrane by hot pressing is a technique of joining by applying heat, pressure, and temperature in a state where the electrode and the proton exchange membrane are laminated, and is a widely used known technique. is there.

  In the proton exchange membrane, electrodes are bonded to both sides of the membrane, and the electrode is generally in the form of two or more layers including a gas diffusion layer and a catalyst layer, and the catalyst layer is on the proton exchange membrane. It is usually formed and a gas diffusion layer is arranged outside thereof. Here, the type of the catalyst, the type of the gas diffusion layer used for the electrode, the bonding method, and the like are not particularly limited, and a known one can be used, and a combination of known techniques can also be used.

  The catalyst used for the electrode can be appropriately selected from the viewpoint of acid resistance and catalytic activity, but platinum group metals and alloys and oxides thereof are particularly preferable. For example, platinum or a platinum-based alloy for the cathode and platinum or a platinum-based alloy or an alloy of platinum and ruthenium for the anode are suitable for high-efficiency power generation. Multiple types of catalysts may be used and may be distributed. The porosity in the electrode is not particularly limited. The type and amount of proton conductive resin mixed with the catalyst in the catalyst layer is not particularly limited. In addition, a technique for controlling the gas diffusibility of the gas diffusion layer and the catalyst layer, such as impregnation with a hydrophobic compound typified by a fluorine-based binder, can be suitably used.

  In the technique of joining the electrode to the proton exchange membrane, it is important to prevent a large resistance from being generated at the interface between the two. It is also important to prevent this from occurring. As a method for producing this joined body, a technique that has been conventionally known as a known technique of an electrode-membrane joining method in a fuel cell, for example, a method in which a proton exchange membrane is sandwiched between electrodes and then pressed and bonded is effectively used. It is done. As the electrode, an electrode obtained by applying a catalyst on a gas diffusion layer or an electrode obtained by applying a catalyst in a film shape such as Teflon (registered trademark) is used. In the latter case, a method of overlapping with a separately prepared gas diffusion layer is common. Furthermore, a method in which the catalyst ink is deposited on the film by spraying or ink jetting and then superposed on the gas diffusion layer is preferably used.

  The proton exchange membrane for a direct methanol fuel cell according to the present invention is not only excellent in swelling resistance with respect to a methanol aqueous solution having a high concentration of 20% by mass or more, but also excellent in bondability with an electrode. Can maintain a good state for a long time. When the methanol concentration is low, the energy density is low, and it becomes a problem that the battery becomes large. Therefore, as in the present invention, the concentration of the aqueous methanol solution is preferably higher than 20% by mass, More preferably, it is 30 mass% or more. In addition, it is not preferable that the concentration of the aqueous methanol solution exceeds 60% by mass because the methanol oxidation reaction does not occur smoothly.

  In addition, the type of separator used in the fuel cell, the flow rate / supply method / flow path structure of the oxidizing gas represented by air, the operating method, operating conditions, temperature distribution, fuel cell control method, etc. It is not limited. However, depending on the method of supplying the direct methanol fuel cell, the concentration of the aqueous methanol solution supplied to the fuel tank is higher than 20% by mass. However, by providing a dilution mechanism in the apparatus, the concentration of the aqueous methanol solution supplied to the MEA is , 20% by mass can be supplied in a diluted form. However, in the direct methanol fuel cell of the present invention, a methanol aqueous solution having a concentration of 20% by mass can be directly supplied to the MEA, which simplifies the system and contributes to the realization of high energy density and miniaturization of the fuel cell. Can do.

Examples of the present invention are shown below, but the present invention is not limited to these Examples.
The evaluation methods and measurement methods used in the present invention are as follows.
<Proton exchange membrane thickness>
The thickness of the proton exchange membrane was determined by measuring a combination of PEACOCK DIGITAL GAUGE MODEL-10S and DIGITAL COUNTER. For a sample obtained by cutting a proton exchange membrane that has been allowed to stand for 24 hours or more in a measurement chamber in which the room temperature is 20 ° C. and the humidity is controlled to 50 ± 5 RH% for 20 × 5 cm, the thickness is measured at 20 locations. The average value was taken as the film thickness.

<Ion exchange capacity (acid type)>
As the ion exchange capacity (IEC), the amount of acid type functional groups present in the ion exchange membrane was measured. First, as a sample preparation, a sample piece (5 × 5 cm) was dried in an oven at 80 ° C. under a nitrogen stream for 2 hours, further allowed to cool in a glove box filled with dry nitrogen gas for 30 minutes, and then the dry mass was measured (Ws ). Next, 200 ml of a 1 mol / L sodium chloride-ultrapure aqueous solution having a concentration of 1 mol / L and the weighed sample were placed in a 200 ml sealed glass bottle and stirred at room temperature for 24 hours while being sealed. Next, 30 ml of the solution was taken out, neutralized with a 10 mM aqueous sodium hydroxide solution (commercial standard solution), and IEC was determined from the titration (T) using the following formula.
IEC (meq / g) = 10 T / (30 Ws) × 0.2
(Unit of T: ml Unit of Ws: g)

<Area swelling rate>
The measurement of the area swelling rate of the proton exchange membrane was performed by measuring the exact area (As) of the sample in the dry state indicated by the adjustment method in the section of <ion exchange capacity (acid type)>. Next, the sample was immersed in 200 ml of 40 ° C., 30% by mass aqueous methanol solution in a sealed glass bottle with stirring for 2 hours. Thereafter, the temperature of the aqueous methanol solution was lowered to 25 ° C. by cooling the glass bottle with water. Next, the sample was taken out from the glass bottle, and the area (Aw) of the sample immediately swollen with the aqueous methanol solution was measured, and the area swelling rate was determined using the following formula.
Area swelling rate (%) = (Aw−As) / As × 100 (%)

<Proton conductivity>
The proton conductivity σ was measured as follows. Four platinum wires (diameter: 0.2 mm) were pushed in parallel with each other at 10 mm intervals on the surface of a strip-shaped film sample having a width of 10 mm on a self-made measurement probe (made of polytetrafluoroethylene), After fixing with a Teflon (registered trademark) plate from above, the sample is immersed in ultrapure water adjusted to 25 ° C. together with the probe, and the AC impedance between the platinum wires is measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. It was measured. Measured by changing the distance between the electrodes from 10 mm to 40 mm at 10 mm intervals, and canceling the contact resistance between the membrane and the platinum wire from the linear slope Dr [Ω / cm] plotting the distance between the electrodes and the measured resistance value And calculated.
σ [S / cm] = 1 / (film width × film thickness [cm] × Dr)

<Methanol permeation rate and methanol permeation coefficient>
The methanol permeation rate and methanol permeation coefficient of the proton exchange membrane were measured by the following methods. A proton exchange membrane immersed in an aqueous methanol solution with a concentration of 5 mol / liter adjusted to 25 ° C. (Methanol aqueous solution is prepared using commercially available reagent-grade methanol and ultrapure water (18 MΩ · cm)) for 24 hours. Is placed in an H-type cell, 100 ml of 5 mol / liter aqueous methanol solution is injected into one side of the cell, 100 ml of ultrapure water is injected into the other cell, and proton exchange is performed while stirring the cells on both sides at 25 ° C. The amount of methanol diffusing into the ultrapure water through the membrane was calculated by measuring with a gas chromatograph (the area of the proton exchange membrane was 2.0 cm ² ). The cell was stirred at a speed at which the methanol permeability did not change due to the influence of the stirring speed. Specifically, it was calculated using the following formula from the methanol concentration change rate [Ct] (mmol / L / s) of the cell containing ultrapure water.
Methanol permeation rate [mmol / m ² / s]
= (Ct [mmol / L / s] × 0.1 [L]) / 2 × 10 ⁻⁴ [m ² ]
Methanol permeability coefficient [μmol / m / s]
= Methanol permeation rate [mmol / m ² / s] × film thickness [m] × 1000

<Measurement of softening start temperature>
The softening start temperature of the polymer electrolyte membrane was measured as follows. A strip-shaped sample with a width of 5 mm was set on a dynamic viscoelasticity measuring apparatus (model name: Rheogel-E4000) manufactured by UBM Co., Ltd. so that the distance between chucks was 14 mm, and the sample was dried for 4 hours under a dry nitrogen stream. After that, the storage elastic modulus (E ′) and the loss elastic modulus are increased in a tensile mode at a frequency of 10 Hz, a strain of 0.7%, in a nitrogen stream, up to a measurement temperature of 25 to 250 ° C., and at a temperature rising rate of 2 ° C./min. (E ") was determined, and Tan-δ was determined from the following equation, measured at every 2 ° C measurement step.
Tan−δ = E “/ E ′
Even if the temperature rise is started, the change in Tan-δ is small, but when the temperature exceeds a certain temperature, Tan-δ rises rapidly and then a convex curve showing a peak is drawn. In this measurement, the Tan-δ rise temperature was defined as the softening start temperature, and the Tan-δ peak was defined as the glass transition temperature. Specifically, the Tan-δ rise temperature is plotted with the logarithmic scale of Tan-δ on the vertical axis and the tangent to the plateau region before the Tan-δ rise in the graph in which the temperature is plotted on the horizontal axis. The temperature at which the tangent of the straight part intersects was used.

<Power generation characteristics>
Commercially available 54% platinum / ruthenium catalyst-supporting carbon, a small amount of ultrapure water and isopropanol were added to a DuPont 20% Nafion (registered trademark) solution, and the mixture was stirred until uniform to prepare a catalyst paste. This catalyst paste is uniformly applied and dried using an applicator so that the adhesion amount of platinum is 2.1 mg / cm ² on carbon paper (TGPH-090) manufactured by Toray Industries, Inc., which has been subjected to hydrophobicity to become a gas diffusion layer. Thus, a gas diffusion layer with a catalyst layer for the anode was produced.
Further, in the same manner, a catalyst layer for a cathode is formed by forming an electrode catalyst layer on the carbon paper hydrophobized using a commercially available 40% platinum catalyst-supporting carbon instead of the platinum / ruthenium catalyst-supporting carbon. An attached gas diffusion layer was prepared (1.0 mg-platinum / cm ² ).
A proton exchange membrane was sandwiched between the two types of gas diffusion layers with a catalyst layer so that the catalyst layer was in contact with the membrane, and pressurized and heated for 3 minutes with a hot press machine to prepare an MEA. Various conditions were used for the press pressure and temperature, and the conditions under which the power generation characteristics were the best were used as the standard MEA conditions for each film.
The comparison of the power generation characteristics was the power generation performance of the MEA produced under optimized hot press conditions. The MEA was incorporated in an evaluation fuel cell manufactured by Electrochem, and the cell temperature was 60 ° C., and a 33 mass% methanol aqueous solution at 55 ° C. was supplied to the anode while supplying dry air to the cathode. The voltage when the discharge test was performed at cm ² was examined. The measurement was evaluated with a value 80 hours after the start of operation as a representative value. Moreover, the resistance of the battery measured by the current interruption method (100 μs) at a current density of 0.1 A / cm ² was measured and compared.

<Example 1>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation: S-DCDPS), 2,6-dichlorobenzonitrile (abbreviation: DCBN), 4,4′-biphenol (abbreviation: BP), 1,6-Hexanedithiol (abbreviation: HDT) and potassium carbonate were adjusted so that the molar ratio was 15: 85: 50: 50 to a total of 10 g, and 6.5 ml of dried molecular sieve 3-A was added to 200 ml. Weighed into a neck flask and flushed with nitrogen. After adding 100 ml of N-methyl-2-pyrrolidone (abbreviation: NMP) and stirring at 150 ° C. for 30 minutes, the reaction temperature is increased to 195-200 ° C. Continued. After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand.
The obtained polymer was washed in boiling water for 1 hour and then dried. It is dissolved in NMP so that the polymer concentration becomes 15%, cast on a glass plate on a hot plate using an applicator, heated at 80 ° C. for 1.0 hour, and at 150 ° C. for 0.5 hour, and then at 150 ° C. in a nitrogen atmosphere. The film was dried in an oven for 1 hour to peel the film from the glass plate.
The obtained film was immersed in pure water at room temperature for 1 day, and then immersed in a 2 mol / L sulfuric acid aqueous solution for 2 hours. Thereafter, the film was washed with pure water until the washing water became neutral, and allowed to stand in the air and dried to obtain an ion exchange membrane.
Table 1 shows the results of evaluating the obtained ion exchange membrane. Moreover, the softening start temperature calculated | required from the dynamic viscoelasticity measurement result was 110 degreeC +/- 5 degreeC (FIG. 1).

<Example 2>
A proton exchange membrane of Example 2 was produced according to Example 1 except that the molar ratio of S-DPPDPS, DCBN, BP, and HDT was changed to 15: 85: 75: 25. Table 1 shows the results of evaluating the obtained proton exchange membrane. Moreover, the softening start temperature calculated | required from the dynamic viscoelasticity measurement result was 168 +/- 5 degreeC.

<Example 3>
In place of BP and HDT, terminal hydroxyl group-containing phenylene ether oligomer (abbreviation: DPE) (Dainippon Ink & Co., Ltd. SPECIANOL DPE-PL, lot C106) The proton exchange of Example 3 according to Example 1 except that the average composition is n = 4.0) and S-DPPDPS, DCBN and DPE are changed to a molar ratio of 23: 77: 100. A membrane was prepared. Table 1 shows the results of evaluating the obtained proton exchange membrane. Moreover, the softening start temperature calculated | required from the dynamic viscoelasticity measurement result was 143 +/- 5 degreeC.

<Comparative Example 1>
A proton exchange membrane of Comparative Example 1 was produced by polymerizing S-DCDPS, BP, and DCBN so that the molar number of S-DCDPS, DCBN, and BP was 20: 80: 100.
Table 1 shows the results of evaluating the obtained proton exchange membrane. Although dynamic viscoelasticity was measured, the softening start temperature was not shown at a temperature of 250 ° C. or lower.

<Comparative example 2>
A proton exchange membrane of Comparative Example 2 was produced in accordance with Example 3 except that the molar ratio of S-DCDPS, DCBN, and DPE was changed to 28: 72: 100.
Table 1 shows the results of evaluating the obtained proton exchange membrane. The softening start temperature obtained from the dynamic viscoelasticity measurement result was 147 ± 5 ° C.

<Comparative Example 3>
A Nafion (registered trademark) 117 membrane manufactured by DuPont was used as a proton exchange membrane. Table 1 shows the results of the evaluation. The softening start temperature obtained from the dynamic viscoelasticity measurement result was 62 ± 5 ° C.

  From the above, the proton exchange membranes of Examples 1 to 3 of the present invention are suitable as proton exchange membranes for direct methanol fuel cells that operate with methanol having a low methanol permeability and a concentration of 20% or more as fuel. It can also be seen that the assembled fuel cell has a low cell resistance and is well bonded to the electrode.

On the other hand, the proton exchange membrane of Comparative Example 1 is a proton exchange membrane having high proton conductivity and suppressed methanol permeability. However, when incorporated in a battery and evaluated, the battery resistance is remarkably high and the battery voltage is low. there were. This is considered to be because the softening start temperature is high and the bonding with the electrode is not well performed. When similar power generation was performed using methanol at a lower temperature and a lower concentration, no particular problem was observed in battery performance. It is considered that a problem occurred at the interface between the electrode and the proton exchange membrane due to the rise in methanol concentration and power generation temperature. Therefore, it can be seen that the invention of the example can be used as a direct methanol fuel cell even under severe operating conditions.
In addition, the proton exchange membrane of Comparative Example 2 has an appropriate softening start temperature and a low resistance value when used as a battery, but has a high area swelling rate and facilitates the passage of methanol. The performance was low.
In addition, the proton exchange membrane of Comparative Example 3 had a high area swell rate as compared with Comparative Example 2 and the methanol permeation was extremely high, so that the battery performance was low.
From the above, it can be seen that the proton exchange membrane of the present invention is a proton exchange membrane suitable for a direct methanol fuel cell using a methanol aqueous solution having a concentration of 20% by mass or more as a fuel.

  The proton exchange membrane of the present invention is a proton exchange membrane suitable for a direct methanol fuel cell using a high-concentration methanol aqueous solution as a fuel, and can contribute to realization of high energy density and miniaturization of the fuel cell. .

It is the measurement example which calculated | required the softening start temperature of the proton exchange membrane in this invention from the relationship figure of Tan-delta and temperature.

Claims (4)

A proton exchange membrane containing an aromatic hydrocarbon polymer for a direct methanol fuel cell using an aqueous methanol solution having a concentration of 20% by mass or more as a fuel, wherein the aromatic hydrocarbon polymer is softened in the range of 80 to 180 ° C A polymer having a starting temperature and having a repeating unit represented by the following (formula 1), and having an area swelling ratio of 0.5 to 30% with respect to a proton exchange membrane at 40 ° C. and a 30% by mass methanol aqueous solution A proton exchange membrane for high-concentration direct methanol fuel cells, characterized in that

[Wherein X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents any one of an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a — (CH ₂ ) q— group, and a cyclohexyl group, and q and n1 are Represents an integer of 1 or more. Provided that when n1 is 2 or more, ^{Z 2} represents O atom. ] The proton exchange membrane for high-concentration direct methanol fuel cells according to claim 1, further comprising a repeating unit represented by the following (formula 2) in an aromatic hydrocarbon polymer.

[Wherein Z ³ represents either O or S atom, Z ⁴ represents O atom, S atom, —C (CH ₃ ) ₂ — group, —C (CF ₃ ) ₂ — group, — (CH ₂ ) Represents either a q-group or a cyclohexyl group, and q and n1 represent an integer of 1 or more. However, when n2 is 2 or more, Z ⁴ represents an O atom. ] The proton exchange membrane for high-concentration direct methanol fuel cells according to claim 2, further comprising a repeating unit represented by the following (formula 3) in the aromatic hydrocarbon polymer.

[Wherein, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. ]   A fuel cell using the proton exchange membrane for a high concentration direct methanol fuel cell according to claim 1.

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