JP4949009B2 - Membrane-electrode structure for polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a membrane-electrode structure for a polymer electrolyte fuel cell.

  The electrolyte is usually used in a (water) solution. However, in recent years, there is an increasing tendency to replace this with a solid system. The first reason is, for example, the ease of processing when applied to electric / electronic materials, and the second reason is the shift to light, thin, small and power saving.

  Conventionally, as proton-conductive materials, both inorganic materials and organic materials are known. Examples of inorganic substances include uranyl phosphate, which is a hydrated compound, but these inorganic compounds do not have sufficient contact at the interface, and there are many problems in forming a conductive layer on a substrate or electrode.

  On the other hand, as organic substances, polymers belonging to so-called cation exchange resins, for example, sulfonated products of vinyl polymers such as polystyrene sulfonic acid, perfluoroalkyl sulfonic acid polymers represented by Nafion (trade name, manufactured by DuPont), perfluoro Examples thereof include organic polymers such as alkylcarboxylic acid polymers and polymers obtained by introducing sulfonic acid groups or phosphoric acid groups into heat-resistant polymers such as polybenzimidazole and polyetheretherketone (for example, see Non-Patent Documents 1 to 3). ).

  However, sulfonated vinyl polymers such as polystyrene sulfonic acid have a problem of poor chemical stability (durability). Perfluorosulfonic acid electrolyte membranes are difficult to manufacture and are very expensive. For this reason, it is difficult to apply to general uses such as automobiles and household fuel cells, and it can be applied only to limited applications. In addition, since perfluorosulfonic acid electrolyte membranes have a large amount of fluorine atoms in the molecule, there are significant environmental problems in waste disposal after use. A polymer produced by introducing a sulfonic acid group or a phosphoric acid group into a heat-resistant polymer such as polybenzimidazole or polyetheretherketone also has a problem that it is inferior in hot water resistance and durability.

  On the other hand, a sulfonated aromatic polymer can be produced industrially at a low cost, and is known as a proton conductive material having excellent hot water resistance and durability. Usually, sulfonated aromatic polymers are produced by preparing a polymer by polymerizing aromatic compounds and reacting the polymer with a sulfonating agent to introduce sulfonic acid groups into the polymer.

  However, in the conventional method, a large amount of a sulfonating agent such as concentrated sulfuric acid, fuming sulfuric acid and chlorosulfuric acid is used when introducing sulfonic acid. There is a problem that the burden of waste liquid treatment during collection is large. Further, the conventional method has a problem that it is not easy to control the amount and introduction position of the sulfonic acid group introduced into the polymer.

  In addition, generally used fluorocarbon-based membranes (Dupont Nafion (trade name) and similar products) are expensive, and performance deteriorates when the temperature exceeds 80 ° C. For this reason, in the case of a fuel cell vehicle, a complicated and huge cooling device is required.

  In contrast, a membrane made of a sulfonated aromatic polymer is suitable as an alternative because it can be used at a higher temperature than a fluorocarbon conductive membrane. However, since the hydrocarbon-based conductive membrane inherently has low proton conductivity, it is inferior in output characteristics particularly at low humidity. Furthermore, many of the hydrocarbon-based conductive membranes swell greatly due to water absorption under power generation conditions, eventually leading to mechanical breakdown and early deterioration of fuel cell performance.

  Many attempts have been made to improve the performance of solid polymer electrolytes used as proton conducting membranes. For example, blending a proton conducting polymer and an inert component improves the mechanical and chemical stability of the membrane, but usually reduces the proton conductivity of the membrane. Alternatively, it is also known that a rigid hydrophobic unit having resistance to excessive swelling is introduced into the polymer electrolyte structure, and that high proton conductivity is obtained by a strong acidic ionic group.

［上記式中、Ｒ_１〜Ｒ_８は、水素、アリール、オキシアリール、チオアリール、スルホンアリール、カルボニルアリール、オキシアリーロキシアリール、ヒドロキシ、またはイオン解離性基を示す。］ For example, Patent Document 1 has a hydrophobic main chain that is at least partially functionalized with at least one pendant ion group selected from the group consisting of a sulfonyl group, a phosphoryl group, and a carboxyl group (m-phenylene). ) A solid polymer electrolyte comprising a copolymer is disclosed. Specifically, a solid polymer electrolyte represented by the following general formula is disclosed.

[Wherein R _{1 to} R ₈ represent hydrogen, aryl, oxyaryl, thioaryl, sulfonearyl, carbonylaryl, oxyaryloxyaryl, hydroxy, or an ion dissociable group. ]

According to Patent Document 1, it is proposed that a functional polymer having a sulfonic acid in a meta (phenylene) unit exhibits high proton conductivity. However, the above polymer is obtained by post-sulfonating a hydrophobic polymer precursor, and post-sulfonation is difficult to control and is not environmentally preferable. Further, the action of a highly active sulfonating agent may cause a deterioration reaction of the polymer and a decrease in mechanical properties.
International Publication No. 97/11099 Pamphlet Polymer Preprints, Japan, Vol. 42, no. 7, pp. 2490-2492 (1993) Polymer Preprints, Japan, Vol. 43, no. 3, pp. 735-736 (1994) Polymer Preprints, Japan, Vol. 42, no. 3, p. 730 (1993)

  Therefore, the object of the present invention is to improve the properties of the solid polymer electrolyte used as the proton conductive membrane without adversely affecting the environment, thereby improving the solid polymer type excellent in proton conductivity particularly in a low humidity environment. The object is to provide a membrane-electrode structure for a fuel cell.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it has been found that according to the membrane-electrode structure for a polymer electrolyte fuel cell using a polyarylene containing a specific repeating structural unit as a proton conducting membrane, the above problems can be solved, and the present invention is completed. It came. More specifically, the present invention provides the following.

［式（１’）中、Ｗは、水素原子、芳香族基、または−Ｂ−（ＳＯ_３Ｈ）_ｍ（ここで、Ｂは直接結合または芳香族基を示し、ｍは０〜２の整数である）で表される基を示す。Ａは直接結合または芳香族基を示し、ｋは１〜３の整数である。Ａが直接結合の場合、前記プロトン伝導膜は、下記式（１’ａ）または（１’ｂ）で表される。

［式（１’ａ）及び（１’ｂ）中のＷ、Ａ、ｋは前記式（１’）と同じである。］］ (1) In a membrane-electrode structure for a polymer electrolyte fuel cell in which an anode electrode is provided on one side of a proton conducting membrane and a cathode electrode is provided on the other side, the proton conducting membrane is represented by the following formula (1 ′). A membrane-electrode structure for a polymer electrolyte fuel cell comprising a repeating structural unit represented.

[In Formula (1 ′), W represents a hydrogen atom, an aromatic group, or —B— (SO ₃ H) _m (where B represents a direct bond or an aromatic group, and m represents an integer of 0 to 2). Is a group represented by: A represents a direct bond or an aromatic group, and k is an integer of 1 to 3. When A is a direct bond, the proton conductive membrane is represented by the following formula (1′a) or (1′b).

[W, A, and k in Formulas (1′a) and (1′b) are the same as those in Formula (1 ′). ]]

［式（１’ｃ）中のＷ、Ａ、ｋは前記式（１’）と同じである。］ (2) The proton conducting membrane is represented by the formula (1′b) or the following formula (1′c), and when A is a direct bond, the proton conducting membrane is represented by the formula (1′b). The membrane-electrode structure for a polymer electrolyte fuel cell according to (1).

[W, A, and k in Formula (1′c) are the same as in Formula (1 ′). ]

  (3) The solid polymer type according to (1) or (2), wherein A and B in the formula (1 ′) are each independently a phenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, or a phenanthrenyl group. A membrane-electrode structure for a fuel cell.

  (4) A and B in the formula (1 ′) are combined to form a condensed ring structure composed of naphthalenyl, anthracenyl, phenanthrenyl, or a benzo derivative thereof (1) to (3) A membrane-electrode structure for a polymer electrolyte fuel cell as described above.

［上記式（Ａ’）中、Ａ及びＤは、それぞれ独立して、直接結合、または、−ＣＯ−、−ＳＯ−、−ＳＯ_２−、−ＣＯＮＨ−、−ＣＯＯ−、−（ＣＦ_２）_ｐ−（ｐは１〜１０の整数である）、−（ＣＨ_２）_ｐ−（ｐは１〜１０の整数である）、−ＣＲ’_２−（Ｒ’は脂肪族炭化水素基、芳香族炭化水素基、またはハロゲン化炭化水素基である）、シクロヘキシリデン基、フルオレニリデン基、−Ｏ−、及び−Ｓ−よりなる群から選ばれる２価の基である。Ｂは、酸素原子または硫黄原子であり、Ｒ^１からＲ^１６は、同一でも異なっていてもよく、水素原子、フッ素原子、アルキル基、部分的または完全にハロゲン置換されたハロゲン化アルキル基、アリール基、アリル基、ニトロ基、及びニトリル基よりなる郡から選ばれる少なくとも１種の原子または基である。ｓ及びｔはそれぞれ独立して０〜４の整数であり、ｒは０または正の整数である。］ (5) 0.5 to 100 mol% of the repeating structural unit represented by the formula (1 ′) and more than 0 mol% of the repeating structural unit represented by the following formula (A ′) The membrane-electrode structure for a polymer electrolyte fuel cell according to any one of (1) to (4), containing 5 mol% or less.

[In the above formula (A ′), A and D are each independently a direct bond, or —CO—, —SO—, —SO ₂ —, —CONH—, —COO—, — (CF ₂ ). _p - (p is an integer of 1 to _{10), - (CH 2) p} - (p is an integer of 1 to _{10), - CR '2 - (} R' is an aliphatic hydrocarbon group, an aromatic A divalent group selected from the group consisting of a hydrocarbon group or a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, -O-, and -S-. B is an oxygen atom or a sulfur atom, and R ¹ to R ¹⁶ may be the same or different, and are a hydrogen atom, a fluorine atom, an alkyl group, a partially or completely halogen-substituted halogenated alkyl group, an aryl It is at least one atom or group selected from the group consisting of a group, an allyl group, a nitro group, and a nitrile group. s and t are each independently an integer of 0 to 4, and r is 0 or a positive integer. ]

  According to the present invention, by using polyarylene having a specific structural unit, proton conductivity is improved particularly in a low humidity environment, and the membrane for a polymer electrolyte fuel cell having excellent power generation performance under a wide range of humidification conditions An electrode structure is obtained.

Hereinafter, embodiments of the present invention will be described in detail.
<Aromatic sulfonic acid ester derivative>
An aromatic sulfonic acid ester derivative that induces polyarylene used as a proton conducting membrane of a membrane-electrode structure for a polymer electrolyte fuel cell according to the present invention is represented by the following general formula (1).

In the above formula (1), X and Y may be the same or different and each represents an atom or group selected from the group consisting of a halogen atom excluding a fluorine atom, —OSO ₂ CH ₃ , and —OSO ₂ CF _3. . A represents a direct bond or an aromatic group, and k is an integer of 1 to 3. When the group represented by A is an aromatic group, this aromatic group is a divalent aromatic hydrocarbon group, and is not particularly limited, but includes a phenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, and A phenanthracenyl group may be mentioned. Of these, a phenyl group and a naphthyl group are preferred. With such a group, it is easy to obtain a high molecular weight polymer, and the solubility of the resulting polymer is excellent. When A is a direct bond, Y is other than the ortho position with respect to -A- (SO ₃ R ^a ) _k . Ra represents ^a hydrocarbon group having 1 to 20 carbon atoms. W represents a hydrogen atom, an aromatic group, or —B— (SO ₃ R ^b ) _m (where B represents a direct bond or an aromatic group, R ^b represents a hydrocarbon group having 1 to 20 carbon atoms, and m represents Which is an integer of 0 to 2), particularly —B— (SO ₃ R ^b ) _m .

In the above formula (1), R ^a and R ^b may be the same or different and represent a hydrocarbon group having 1 to 20 carbon atoms, preferably a hydrocarbon group having 4 to 20 carbon atoms. Specifically, tert-butyl group, iso-butyl group, n-butyl group, sec-butyl group, neopentyl group, cyclopentyl group, hexyl group, cyclohexyl group, cyclopentylmethyl group, cyclohexylmethyl group, adamantylmethyl group, adamantylmethyl group 2-ethylhexyl group, bicyclo [2.2.1] heptyl group, bicyclo [2.2.1] heptylmethyl group, tetrahydrofurfuryl group, 2-methylbutyl group, 3,3-dimethyl-2,4-dioxolane Examples thereof include a linear hydrocarbon group such as a methyl group, a branched hydrocarbon group, an alicyclic hydrocarbon group, or a hydrocarbon group having a 5-membered heterocyclic ring. Among these, n-butyl group, neopentyl group, tetrahydrofurfuryl group, cyclopentylmethyl group, cyclopentyl group, cyclohexyl group, cyclohexylmethyl group, adamantylmethyl group, and bicyclo [2,2,1] heptylmethyl group are preferable, Neopentyl groups are most preferred.

R ^a and R ^b in the above formula (1) are derived from the first alcohol used when synthesizing the aromatic sulfonate derivative. The β-carbon of the primary alcohol is preferably a tertiary or quaternary carbon atom. In this case, the carbon atom has excellent stability in the polymerization step, and does not inhibit the polymerization or induce a crosslinking reaction by the sulfonic acid generated by deesterification. A preferred embodiment is one in which R ^a and R ^b are derived from a primary alcohol having a quaternary β-carbon atom.

  As described above, A and B in the above formula (1) each independently represent a direct bond or an aromatic group, preferably a phenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, or a phenanthrenyl group. is there. Furthermore, it is preferable that A and B are combined to form a condensed ring structure composed of naphthalenyl, anthracenyl, phenanthrenyl, or a benzo derivative thereof.

Y is preferably meta or para to X. When a solid polymer electrolyte is prepared using an aromatic sulfonic acid ester derivative having a substituent at this position (that is, other than the ortho position), a polymer having a high molecular weight can be easily obtained and contains such a solid polymer electrolyte. The proton conducting membrane exhibits excellent mechanical strength. Specific examples of the aromatic sulfonic acid ester derivative include the following novel polymerizable compounds.

X and Y in the above formulas are as described above. Further, R is ^{R a,} represents a hydrocarbon group having 1 to 20 carbon atoms.

The aromatic sulfonic acid ester derivative used in the present invention can be synthesized by a conventionally known method. For example, it can be synthesized by transesterifying a sulfone chloride compound having a desired skeleton. Moreover, it is compoundable by the method disclosed by Unexamined-Japanese-Patent No. 2004-137444. Specifically, as shown in the chemical reaction formula below, the compound can be synthesized through (I) sulfonation, (II) sulfonic acid chloride formation, and (III) sulfonic acid esterification.

(I) Sulfonation For example, after 2,5-dichlorobiphenyl is dropped and reacted with sulfuric acid, caustic soda is added, and if necessary, washed with water and dried to obtain a finely powdered sodium sulfonate salt.

(II) Sulfonic Acid Chloride The above sodium sulfonate is dissolved or suspended in a solvent (sulfolane / acetonitrile mixed solvent), heated to 70 ° C., and phosphoryl chloride is reacted. After the reaction, the reaction product is diluted with a large excess of cold water, extracted with a solvent, dehydrated with magnesium sulfate, and then the solvent is removed to obtain a purified product. If chlorosulfonic acid is used, it can be converted to sulfonated chloride at once.

(III) Sulfonic acid esterification The above sulfonic acid chloride is dropped and reacted in a mixed solution in which equal amount or more (usually 1 to 3 moles) of i-butyl alcohol and pyridine are cooled with respect to the sulfonic acid chloride. . The reaction is limited to ~ 20 ° C. The reaction time is about 10 minutes to 5 hours depending on the reaction scale. The reaction mixture is treated with dilute hydrochloric acid, washed with water, and the desired product is extracted with ethyl acetate. The extract is concentrated and separated, and then recrystallized with methanol to obtain the aromatic sulfonic acid ester derivative used in the present invention.

［上記式（１’）中、Ｗ、Ａ、ｋは、上記式（１）と同様である。］ <Polyarylene>
The polyarylene used as the proton conducting membrane of the membrane-electrode structure for a polymer electrolyte fuel cell according to the present invention is a polyarylene composed of repeating structural units derived from an aromatic compound, and is represented by the following formula (1 ′) It has the repeating structural unit represented by these.

[W, A, k in the above formula (1 ′) are the same as in the above formula (1). ]

［式（１’ａ）及び（１’ｂ）中のＷ、Ａ、ｋは上記式（１’）と同じである。］ When A in the formula (1 ′) is a direct bond, the polyarylene is represented by the following formula (1′a) or (1′b).

[W, A, and k in Formulas (1′a) and (1′b) are the same as those in Formula (1 ′) above. ]

［式（１’ｃ）中のＷ、Ａ、ｋは上記式（１’）と同じである。］ The polyarylene is represented by the above formula (1′b) or the following formula (1′c), and when A is a direct bond, it is preferably represented by the above formula (1′b).

[W, A, and k in Formula (1′c) are the same as in Formula (1 ′) above. ]

The polyarylene used in the present invention preferably contains a repeating structural unit represented by the following formula (A ′) together with a repeating structural unit represented by the above formula (1 ′). When such a polymer component is contained, the strength and chemical resistance of the electrolyte can be improved.

In the above formula (A ′), A and D are each independently a direct bond, or —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) _p. - (p is an integer of 1 to _{10), - (CH 2) p} - (p is an integer of 1 to _{10), - CR '2 - (} R' is an aliphatic hydrocarbon group, an aromatic hydrocarbon A divalent group selected from the group consisting of a hydrogen group or a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, -O-, and -S-. Here, specific examples of the structure represented by —CR ′ ₂ — include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, propyl group, octyl group, decyl group. Group, octadecyl group, phenyl group, trifluoromethyl group and the like. Among these, a direct bond, —CO—, —SO ₂ —, —CR ′ ₂ — (R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a halogenated hydrocarbon group), cyclohexylidene Group, fluorenylidene group, and -O- are preferred.

B is an oxygen atom or a sulfur atom, preferably an oxygen atom. R ^{1 to} R ¹⁶ may be the same as or different from each other, and are a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group partially or wholly halogenated, an allyl group, an aryl group, a nitro group, and a nitrile. At least one atom or group selected from the group consisting of groups is shown. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, a hexyl group, a cyclohexyl group, and an octyl group. Examples of the halogenated alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. Examples of the allyl group include a propenyl group, and examples of the aryl group include a phenyl group and a pentafluorophenyl group.

s and t each independently represent an integer of 0 to 4. r represents 0 or an integer of 1 or more, and the upper limit is usually 100. Preferred r is 1-80. Preferred combinations of the values of s and t and the structures of A, B, D and R ^{1 to} R ¹⁶ include (i) s = 1 and t = 1, and A is —CR ′ ₂ — (R ′ Represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a halogenated hydrocarbon group), a cyclohexylidene group, or a fluorenylidene group, B is an oxygen atom, D is -CO-, or -SO _2- , a structure in which R ^{1 to} R ¹⁶ are a hydrogen atom or a fluorine atom, (ii) s = 1, t = 0, B is an oxygen atom, D is —CO—, or —SO ₂ A structure in which R ^{1 to} R ¹⁶ are a hydrogen atom or a fluorine atom, (iii) s = 0, t = 1, A is —CR ′ ₂ — (R ′ is an aliphatic hydrocarbon group, aromatic Group hydrocarbon group or halogenated hydrocarbon group), cyclohexylidene group, A fluorenylidene group, B is an oxygen atom, R ¹ to R ¹⁶ is a hydrogen atom, a fluorine atom or a structure like a nitrile group.

［上記式（Ｉ）中、Ｗ、Ａ、Ｒ^ａ、ｋ、Ｄ、Ｂ、Ｒ^１〜Ｒ^１６、ｓ、ｔ、ｒは、上記と同様である。］ Examples of such polyarylene include a copolymer represented by the following formula (I).

[W, A, R ^a , k, D, B, R ^{1 to} R ¹⁶ , s, t, and r in the above formula (I) are the same as above. ]

  In the copolymer, the repeating structural unit represented by the above formula (1 ′) (that is, the y unit) is 0.5 mol% or more and less than 100 mol%, and the repeating structure represented by the above formula (A ′). It is preferable to contain a unit (that is, a unit of x) in a ratio of more than 0 mol% and not more than 99.5 mol%. More preferably, the repeating structural unit represented by the formula (1 ′) is 10 mol% to 99.999 mol%, and the repeating structural unit represented by the formula (A ′) is 0.001 to 90 mol%. It is desirable to contain it in a proportion.

［上記式（ＩＩ）中、Ｗ、Ａ、ｋ、Ｄ、Ｂ、Ｒ^１〜Ｒ^１６、ｓ、ｔ、ｒは上記と同様である。］ Polyarylene used in the present invention, as represented by the following formula (II), SO ₃ part of R ^a or all may be a hydrolyzed to sulfonic acid.

[W, A, k, D, B, R ^{1 to} R ¹⁶ , s, t, and r in the above formula (II) are the same as above. ]

<Method for producing polyarylene>
For production of the polyarylene used in the present invention, for example, Method A shown below can be used.

[Method A]
For example, in the method described in JP-A No. 2004-137444, a monomer having a sulfonate group that can be a repeating structural unit represented by the above formula (1 ′) (that is, an aromatic sulfonic acid of the above formula (1) The polyarylene having a sulfonate group can be synthesized by copolymerizing an ester derivative) and a monomer or oligomer that can be a repeating structural unit represented by the above formula (A ′). Also, polyarylene having a sulfonic acid group can be synthesized by deesterifying the sulfonic acid ester group to convert the sulfonic acid ester group into a sulfonic acid group.

[Method B]
For example, in the method described in JP-A No. 2001-342241, a monomer having a skeleton represented by the above formula (1 ′) and having no sulfonic acid group or sulfonic acid ester group, and the above formula (A ′) It is also possible to synthesize by copolymerizing a monomer or oligomer that can be a structural unit represented by the formula (I) and sulfonating the copolymer using a sulfonating agent.

Specific examples of the monomer or oligomer that can be the structural unit represented by the above formula (A ′) are as follows.
[When r = 0]
For example, 4,4′-dichlorobenzophenone, 4,4′-dichlorobenzanilide, 2,2-bis (4-chlorophenyl) difluoromethane, 2,2-bis (4-chlorophenyl) -1,1,1,3 , 3,3-hexafluoropropane, 4-chlorobenzoic acid-4-chlorophenyl ester, bis (4-chlorophenyl) sulfoxide, bis (4-chlorophenyl) sulfone, and 2,6-dichlorobenzonitrile. Moreover, the compound etc. with which the chlorine atom in these compounds was substituted by the bromine atom or the iodine atom are mentioned.

[When r = 1]
For example, the compounds described in JP2003-113136A can be mentioned.

[When r ≧ 2]
For example, JP 2004-137444 A, JP 2004-244517 A, JP 2004-346146 A, JP 2005-112985 A, Japanese Patent Application 2003-348524, Japanese Patent Application 2004-211739, and Japanese Patent Application 2004. The compounds described in -211740.

  In order to obtain polyarylene used in the present invention, first, a monomer that can be a structural unit represented by the above formula (1 ′), and a monomer or oligomer that can be a structural unit represented by the above formula (A ′) To obtain a precursor polyarylene. This copolymerization is carried out in the presence of a catalyst, and the catalyst used here is a catalyst system containing a transition metal compound. The catalyst system includes a transition metal salt and a compound that becomes a ligand (hereinafter referred to as “ligand component”), a transition metal complex in which a ligand is coordinated (including a copper salt), and a reducing agent. And an essential component, and a salt added to increase the polymerization rate.

  Specific examples of these catalyst components, the use ratio of each component, the reaction solvent, concentration, temperature, time, and other polymerization conditions include the polymerization conditions described in JP-A-2001-342241.

The polyarylene having a sulfonic acid group used in the present invention can be obtained by converting the precursor polyarylene to a polyarylene having a sulfonic acid group. Examples of this method include the following three methods.
(Method A) A method of deesterifying a polyarylene having a sulfonic acid ester group as a precursor by the method described in JP-A-2004-137444.
(Method B) A method of sulfonating a precursor polyarylene by the method described in JP-A-2001-342241.
(Method C) A method of introducing an alkylsulfonic acid group into the precursor polyarylene by the method described in JP-A-2005-60625.

  The ion exchange capacity of the polyarylene having a sulfonic acid group produced by the method as described above is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, more preferably 0.8. ~ 2.8 meq / g. If it is less than 0.3 meq / g, the proton conductivity is low and the power generation performance is low. On the other hand, if it exceeds 5 meq / g, the water resistance may be significantly lowered.

  The amount of the aromatic sulfonic acid derivative used to derive the polyarylene having the sulfonic acid group is changed by changing the amount, type, and combination of the monomers, or the amount of the polyarylene forming the repeating structural unit. It can be adjusted by changing the type and combination.

  The molecular weight of the polyarylene having a sulfonic acid group thus obtained is 10,000 to 1,000,000, preferably 20,000 to 800,000 in terms of polystyrene-reduced mass average molecular weight by gel permeation chromatography (GPC). is there.

  The polyarylene having the sulfonic acid group can also be obtained by introducing the aromatic sulfonic acid ester derivative into the polyarylene and then hydrolyzing the corresponding sulfonic acid ester to form a sulfonic acid group.

<Solid polymer electrolyte>
The solid polymer electrolyte used for the preparation of the proton conducting membrane of the membrane-electrode structure for a polymer electrolyte fuel cell according to the present invention contains the above polyarylene. The solid polymer electrolyte used in the present invention may contain an antioxidant such as a phenolic hydroxyl group-containing compound, an amine compound, an organic phosphorus compound, or an organic sulfur compound as long as proton conductivity is not impaired. The solid polymer electrolyte used in the present invention can be used in various shapes such as a granular shape, a fiber shape, and a membrane shape depending on the application, but when used directly in a solid polymer fuel cell, The shape is preferably a membrane (proton conducting membrane).

<Proton conducting membrane>
The proton conducting membrane included in the membrane-electrode structure for a polymer electrolyte fuel cell according to the present invention is formed by dissolving the solid polymer electrolyte in a solvent to form a solution, and then casting on the substrate. Or can be produced by casting. The base material used here is not particularly limited, and can be selected from base materials used in ordinary solvent casting methods. Examples of the substrate include a plastic substrate and a metal substrate. A substrate made of a thermoplastic resin such as a polyethylene terephthalate (PET) film is preferably used.

  In the production of the proton conductive membrane, an inorganic acid such as sulfuric acid and phosphoric acid, an organic acid containing a carboxylic acid, an appropriate amount of water, and the like can be used in combination with the polyarylene.

  Solvents for dissolving the polyarylene include N-methyl-2-pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, dimethyl sulfoxide, dimethylurea, and dimethylimidazolidinone (DMI). And aprotic polar solvents such as In particular, N-methyl-2-pyrrolidone is preferable from the viewpoint of solubility and solution viscosity. These aprotic polar solvents may be used alone or in combination of two or more.

  The solvent may be a mixture of the above aprotic polar solvent and alcohol. Examples of the alcohol include methanol, ethanol, propyl alcohol, isopropyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. In particular, methanol is preferable in that an appropriate low solution viscosity can be obtained over a wide copolymer composition. These alcohols may be used alone or in combination of two or more.

  The mixed solvent contains an aprotic polar solvent in an amount of 25 to 95% by mass, preferably 25 to 90% by mass, and an alcohol in an amount of 5 to 75% by mass, preferably 10 to 75% by mass. . By containing alcohol at this ratio, an appropriate low solution viscosity can be obtained.

  The concentration of polyarylene in the solution (that is, the polymer concentration) is usually 5 to 40% by mass, preferably 7 to 25% by mass, although it depends on the molecular weight of the polyarylene. When the polymer concentration is less than 5% by mass, it is difficult to produce a thick film, and pinholes are easily generated. On the other hand, if the polymer concentration exceeds 40% by mass, the solution viscosity is too high, making it difficult to produce a film, and the surface smoothness of the resulting film may be reduced.

  The solution viscosity is usually 2,000 to 100,000 mPa · s, preferably 3,000 to 50,000 mPa · s, although it depends on the molecular weight and polymer concentration of polyarylene. When the solution viscosity is less than 2,000 mPa · s, the solution stays poorly and may flow from the substrate during film formation. On the other hand, when the solution viscosity exceeds 100,000 mPa · s, the viscosity is too high to be extruded from the die, and it may be difficult to form a film by the casting method.

  By immersing the undried film obtained as described above in water, the organic solvent in the undried film is replaced with water, and the amount of residual solvent in the resulting proton conducting membrane can be reduced. In addition, you may predry an undried film before immersing an undried film in water. The preliminary drying is performed by holding the undried film at a temperature of 50 to 150 ° C. for 0.1 to 10 hours.

  When the undried film is immersed in water, for example, a batch method in which each sheet is immersed in water is employed. Alternatively, a continuous system in which the laminated film is immersed in water in a state where the film is formed on a substrate film such as a PET film, or a film separated from the substrate is immersed in water and wound is adopted. In the case of the batch method, a method of fitting the treated film to the frame is preferable in that wrinkle formation on the surface of the treated film is suppressed.

  When immersing an undried film in water, it is preferable that water has a contact ratio of 10 parts by mass or more, preferably 30 parts by mass or more with respect to 1 part by mass of the undried film. In order to minimize the amount of residual solvent in the resulting proton conducting membrane, it is preferable to maintain a contact ratio as large as possible. In addition, it is effective in reducing the amount of residual solvent in the resulting proton conducting membrane by changing the water used for immersion or allowing it to overflow so that the organic solvent concentration in the water is always kept below a certain level. is there. In order to suppress the in-plane distribution of the amount of the organic solvent remaining in the proton conductive membrane, it is preferable to homogenize the concentration of the organic solvent in water by stirring or the like.

  The temperature of water when the undried film is immersed in water is preferably 5 to 80 ° C. The higher the water temperature, the faster the replacement rate of the organic solvent and water, but the greater the amount of water absorbed by the film, so the surface of the proton conducting membrane obtained after drying may become rough. Considering the replacement speed and ease of handling, a temperature range of 10 to 60 ° C. is more preferable. The immersion time varies depending on the initial residual solvent amount, contact ratio, and water temperature, but is usually in the range of 10 minutes to 240 hours, preferably 30 minutes to 100 hours.

  Thus, when an undried film is immersed in water and then dried, a proton conductive membrane with a reduced amount of residual solvent is obtained, and the residual solvent amount in the proton conductive membrane is usually 5% by mass or less. Also, for example, the contact ratio between the undried film and water is 50 parts by mass or more of water with respect to 1 part by mass of the undried film, the temperature of the water when dipping is 10 to 60 ° C., and the dipping time is 10 minutes By setting it to 10 hours, the residual solvent amount of the proton conductive membrane obtained can be made 1 mass% or less.

  As described above, after the undried film is immersed in water, the film is dried at 30 to 100 ° C., preferably 50 to 80 ° C., for 10 to 180 minutes, preferably 15 to 60 minutes. Subsequently, the film is dried at 50 to 150 ° C. under a reduced pressure of 0.5 to 24 hours, preferably 500 to 0.1 mmHg to obtain the proton conducting membrane of the present invention. The proton conductive membrane thus obtained has a dry film thickness of usually 10 to 100 μm, preferably 20 to 80 μm.

  The proton conductive membrane used in the present invention may contain an antiaging agent, preferably a hindered phenol compound having a molecular weight of 500 or more. By containing an anti-aging agent, the durability of the proton conducting membrane can be further improved. As such a hindered phenol compound having a molecular weight of 500 or more, specifically, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 245), 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX259), 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -3,5-triazine (trade name: IRGANOX565), pentaerythrityl-tetrakis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate] (trade name: IRGANOX 1010), 2,2-thio-diethylenebis [3 (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1035), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) (trade name) : IRGANOX1076), N, N-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (trade name: IRGANOX1098), 1,3,5-trimethyl-2,4 6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (trade name: IRGANOX 1330), tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate ( Product name: IRGANOX 3114) and 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methyl) ) Propionyloxy] -1,1-dimethylethyl] -2,4,8,10-spiro [5.5] undecane (trade name: Sumilizer GA-80), and the like. These hindered phenol compounds are preferably used in an amount of 0.01 to 10 parts by mass with respect to 100 parts by mass of polyarylene.

  The proton conductive membrane used in the present invention exhibits excellent hot water resistance, solvent resistance, heat resistance, oxidation resistance, toughness, electrode adhesion, and workability while maintaining high proton conductivity. For this reason, fuel cells for household power supplies, fuel cell vehicles, fuel cells for mobile phones, fuel cells for personal computers, fuel cells for mobile terminals, fuel cells for digital cameras, portable CDs, fuel cells for MD players, and fuel for headphone stereos It is suitably used for applications such as batteries, fuel cells for pet robots, fuel cells for electric assist bicycles, fuel cells for electric scooters, and direct methanol fuel cells. In particular, it can be suitably used as a proton conducting membrane of a membrane-electrode structure for a polymer electrolyte fuel cell.

<Electrode>
The electrode of the membrane-electrode structure for a polymer electrolyte fuel cell according to the present invention comprises a catalyst metal particle or an electrode catalyst in which the catalyst metal particle is supported on a conductive support, and an electrode electrolyte. Other components such as carbon fiber, a dispersant, a water repellent may be included.

  The catalyst metal particles are not particularly limited as long as they have catalytic activity, but metal black made of noble metal fine particles such as platinum black can be used. The conductive carrier for supporting the catalyst metal particles is not particularly limited as long as it has conductivity and appropriate corrosion resistance, but has a sufficient specific surface area for highly dispersing the catalyst metal particles and sufficient electron conduction. Therefore, it is desirable to use carbon (carbon) as a main component. The catalyst carrier that constitutes the electrode not only supports the catalyst metal particles, but also must function as a current collector for taking out electrons to the external circuit or taking them in from the external circuit. When the electric resistance of the catalyst carrier is high, the internal resistance of the battery is increased, and as a result, the performance of the battery is lowered. For this reason, the electronic conductivity of the catalyst carrier contained in the electrode must be sufficiently high. That is, it can be used as long as it has sufficient electronic conductivity as an electrode catalyst carrier, and preferably a carbon material with fine pores is used. As the carbon material having developed pores, carbon black, activated carbon or the like can be preferably used. Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Activated carbon is obtained by carbonizing and activating materials containing various carbon atoms. It is also possible to include metal oxides, metal carbides, metal nitrides and polymer compounds having electronic conductivity. In addition, the main component said here means containing 60% or more of carbonaceous matter.

  Further, platinum or a platinum alloy is used as the catalytic metal particles supported on the conductive carrier. However, when a platinum alloy is used, stability and activity as an electrode catalyst can be further imparted. Platinum alloys include platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, iridium), cobalt, iron, titanium, gold, silver, chromium, manganese, molybdenum, tungsten, aluminum, silicon, rhenium, zinc, Further, an alloy of platinum and one or more selected from the group consisting of tin and platinum is preferable, and the platinum alloy may contain an intermetallic compound of a metal alloyed with platinum.

  The supported rate of platinum or platinum alloy (ratio of the mass of platinum or platinum alloy to the total mass of the supported catalyst) is preferably 20 to 80% by mass, particularly preferably 30 to 55% by mass. Within this range, high output can be obtained. If the loading rate is less than 20% by mass, sufficient output may not be obtained. If the loading rate exceeds 80% by mass, platinum or platinum alloy particles may not be supported on the carbon material serving as a carrier with good dispersibility.

  The primary particle diameter of platinum or platinum alloy is preferably 1 to 20 nm in order to obtain a highly active gas diffusion electrode. In particular, a large surface area of platinum or platinum alloy can be secured in terms of reaction activity. It is preferably ˜5 nm.

As the electrode electrolyte, an ion conductive polymer electrolyte (ion conductive binder) having a sulfonic acid group is suitably used. Usually, the supported catalyst is covered with the electrolyte, and protons (H ⁺ ) move through a path where the electrolyte is connected.

  As the ion conductive polymer electrolyte having a sulfonic acid group, a perfluorocarbon polymer represented by Nafion (registered trademark), Flemion (registered trademark), and Aciplex (registered trademark) is particularly preferably used. In addition to perfluorocarbon polymers, sulfonated products of vinyl monomers such as polystyrene sulfonic acid, polymers having sulfonic acid groups or phosphoric acid groups introduced into heat-resistant polymers such as polybenzimidazole and polyether ether ketone, Alternatively, an ion conductive polymer electrolyte mainly composed of an aromatic hydrocarbon compound such as a sulfonated polyarylene described in the present specification may be used.

  Moreover, it is preferable to contain the said ion conductive binder in the ratio of 0.1-3.0 by mass ratio with respect to catalyst particles, and it is preferable to contain especially in the ratio of 0.3-2.0. When the ion conductive binder ratio is less than 0.1, protons cannot be transmitted to the electrolyte membrane, and there is a fear that sufficient output cannot be obtained. When the ion conductive binder ratio exceeds 3.0, the ion conductive binder is not sufficient. May completely cover the catalyst particles, the gas cannot reach platinum, and there is a possibility that sufficient output cannot be obtained.

  As carbon fibers that can be added as necessary, rayon-based carbon fibers, PAN-based carbon fibers, lignin poval-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, and the like can be used. Then, vapor growth carbon fiber is preferable. When carbon fiber is included, the pore volume in the electrode catalyst layer increases, so that the diffusibility of fuel gas and oxygen gas is improved, and flooding due to the generated water can be improved, and the power generation performance is improved. . The carbon fiber may be contained in one or both of the anode-side and cathode-side electrode catalyst layers.

  Examples of the dispersant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. The said dispersing agent may be used individually by 1 type, or may be used in combination of 2 or more type. Among these, a surfactant having a basic group is preferable, an anionic or cationic surfactant is more preferable, and a surfactant having a molecular weight of 5,000 to 30,000 is more preferable. When the above dispersant is added to the electrode paste composition used for forming the electrode catalyst layer, the storage stability and fluidity are excellent, and the productivity during coating is improved.

  The membrane-electrode structure in the present invention may consist of only the anode catalyst layer, the proton conducting membrane, and the cathode catalyst layer. However, both the anode and cathode are electrically conductive such as carbon paper or carbon cloth outside the catalyst layer. More preferably, a gas diffusion layer made of a porous porous substrate is disposed. Since the gas diffusion layer also functions as a current collector, in this specification, when the gas diffusion layer is provided, the gas diffusion layer and the catalyst layer are collectively referred to as an electrode.

  In the polymer electrolyte fuel cell having the membrane-electrode structure of the present invention, a gas containing oxygen is supplied to the cathode, and a gas containing hydrogen is supplied to the anode. Specifically, for example, a separator in which a groove to be a gas flow path is formed is disposed outside both electrodes of the membrane-electrode structure, and the gas is flowed through the gas flow path to thereby form the membrane-electrode structure. Supply fuel gas.

  As a method for producing the membrane-electrode structure of the present invention, a method in which a catalyst layer is directly formed on an ion exchange membrane and sandwiched between gas diffusion layers as necessary, on a base material to be a gas diffusion layer such as carbon paper A method of forming a catalyst layer and bonding it to an ion exchange membrane, a method of forming a catalyst layer on a flat plate and transferring it to the ion exchange membrane, then peeling the flat plate and further sandwiching it with a gas diffusion layer if necessary Various methods can be employed.

  As a method for forming the catalyst layer, a dispersion obtained by dispersing a supported catalyst and a perfluorocarbon polymer having a sulfonic acid group in a dispersion medium (if necessary, a water repellent, a pore former, a thickener, A known method of adding a diluting solvent or the like to the ion exchange membrane, gas diffusion layer, or flat plate can be employed.

  Examples of the method for forming the electrode paste composition include brush coating, brush coating, bar coater coating, knife coater coating, doctor blade method, screen printing, and spray coating.

  When the catalyst layer is not directly formed on the ion exchange membrane, the catalyst layer and the ion exchange membrane are preferably joined by a hot press method, an adhesion method (see JP-A-7-220741) or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples at all. In the examples, the molecular weight, ion exchange capacity, proton conductivity, and power generation characteristics were evaluated as follows.

<Measurement of molecular weight>
For the polymer having no sulfonic acid group, tetrahydrofuran (THF) was used as an eluent as a solvent, and the weight average molecular weight in terms of polystyrene was determined by GPC. For the polymer having a sulfonic acid group, a mixed solution of 7.83 g of lithium bromide, 3.3 ml of phosphoric acid, and 2 L of N-methyl-2-pyrrolidone (NMP) was used as an eluent, and polystyrene was obtained by GPC. The converted weight average molecular weight was determined.

<Measurement of ion exchange capacity>
The obtained aromatic sulfonimide-containing polyarylene was washed with distilled water until the water was neutralized, sufficiently washed with water except for the remaining free acid, and then dried. Thereafter, a predetermined amount is weighed and dissolved in a THF / water mixed solvent, titrated with a standard solution of NaOH using phenolphthalein as an indicator, and an equivalent amount of sulfonic acid groups (ion exchange capacity) from the neutralization point. (Meq / g) was determined.

<Measurement of proton conductivity>
For AC resistance, a proton conductive membrane sample is formed into a strip shape having a width of 5 mm, a platinum wire (φ = 0.5 mm) is pressed against the surface of the membrane sample, the membrane sample is held in a constant temperature and humidity apparatus, and platinum It was obtained from AC impedance measurement between lines. The impedance at AC 10 kHz was measured in an environment of 85 ° C., relative humidity 90% and 50%. As a resistance measuring device, a Solartron SI1260 impedance analyzer was used, and as a constant temperature and humidity device, a small environmental tester SH-241 manufactured by Espec was used. Five platinum wires were pressed at intervals of 5 mm, the distance between the wires was changed from 5 mm to 20 mm, and the AC resistance was measured. From the distance between lines and the gradient of resistance, the specific resistance of the membrane was calculated according to the following formula (1), the alternating current impedance was calculated from the reciprocal of the specific resistance, and the proton conductivity was determined from this impedance.

<Evaluation of power generation characteristics>
Using the membrane-electrode structure of the present invention, power generation at a temperature of 85 ° C., fuel electrode / oxygen electrode relative humidity of 100% / 100% and 50% / 50%, and current density of 1 A / cm ² The power generation performance was evaluated according to the conditions. Pure hydrogen was supplied to the fuel electrode side, and air was supplied to the oxygen electrode side.

<Example 1>
(1) Preparation of neopentyl 3,5-dichlorobenzenesulfonate Neopentyl 3,5-dichlorobenzenesulfonate was prepared according to the following chemical reaction formula.

Specifically, 3,5-dichlorobenzenesulfonyl chloride (114.65 g, 467 mmol) was added to a pyridine (300 mL) solution of neopentyl alcohol (45.30 g, 514 mmol) over 15 minutes while stirring little by little. did. During this time, the reaction temperature was kept at 18-20 ° C. The reaction mixture was stirred for an additional 30 minutes with cooling before ice-cold 10% HCl (1600 mL) was added. Insoluble components in water were extracted with 700 mL ethyl acetate, washed twice with 1N HCl (700 mL each), washed twice with 5% NaHCO ₃ (700 mL each) and dried over MgSO ₄ . The solvent was removed using a rotary dryer and the residue was recrystallized from 500 mL methanol. As a result, pure (more than 99% purity by 1H NMR) neopentyl 3,5-dichlorobenzenesulfonate was obtained as glossy colorless crystals. The yield was 105.98 g, and the yield was 76%. Moreover, melting | fusing point of the obtained crystal | crystallization was 62.5-63.5 degreeC.

(2) Synthesis of polyarylene having neopentylsulfonic acid ester as a protecting group Compound (9.66 g, 32.50 mmol) of the above (1), 2-chlorobenzonitrile-terminated poly (ether nitrile) oligomer (Mn = 8200, 7.27 g, 0.89 mmol), Ni (PPh ₃ ) ₂ Cl ₂ (0.66 g, 1.00 mmol), PPh ₃ (3.50 g, 13.35 mmol), NaI (0.15 g, 1.00 mmol), To a mixture of Zn powder (5.46 g, 83.46 mmol), dry DMAc (35 mL) was added under a stream of dry nitrogen. The reaction mixture was mechanically stirred at 80 ° C. for 3 hours. The resulting high viscosity suspension was diluted with DMAc (100 mL) and filtered using a celite pad to remove excess Zn. The resulting clear solution was coagulated in 6 volumes of methanol. As a result, a grayish powdery polymer was obtained in an amount of 14.8 g. Some amount of DMAc was trapped in the polymer. As a result of measuring the molecular weight by GPC, the number average molecular weight in terms of polystyrene was 28,000, and the mass average molecular weight was 57,700.

(3) Synthesis of polyarylene having a sulfonic acid group A mixture of the crude polymer (14.8 g) of (2) above and anhydrous lithium bromide (5.65 g, 65 mmol, 2 times excess with respect to SO ₃ ), Dissolved in DMAc (100 mL). When the obtained transparent yellow solution was heated to 135 ° C. and stirred for 30 minutes, a gel was obtained. The reaction product was held at the above temperature for an additional hour and stirred vigorously with 10 volumes of acetone until a uniform suspension was formed. Filter using a nylon mesh to separate the solids. The separated solid was washed with acetone and dried, and then stirred with 1 liter of 2N hydrochloric acid for 1 hour. The polymer was separated by filtration and acid-treated again. By repeating washing with deionized water, all remaining acid was removed (pH increase) and the solid residue was dried at 90 ° C. until constant weight. As a result, acid-state polyarylene was obtained as a cream-colored powder. The yield was 9.12 g, and the yield was 74%. Moreover, the number average molecular weight of polystyrene conversion by GPC measurement was 39,500, and the mass average molecular weight was 85,700.

  A 10% by mass N-methylpyrrolidone (NMP) solution of the obtained polyarylene was cast on a glass plate to form a proton conductive membrane having a thickness of 50 μm.

(4) Production of membrane-electrode structure Platinum particles were supported on carbon black (furnace black) having an average diameter of 50 nm at a mass ratio of carbon black: platinum = 1: 1 to produce catalyst particles. Next, in a perfluoroalkylenesulfonic acid polymer compound (DuPont Nafion (registered trademark)) solution as an ion conductive binder, the above catalyst particles are added at a mass ratio of ion conductive binder: catalyst particles = 8: 5. A catalyst paste was prepared by uniformly dispersing. The catalyst paste was applied to both sides of the proton conducting membrane obtained in this example with a bar coater so that the platinum content was 0.5 mg / cm ² and dried to dry the electrode coating membrane (Catalyst Coated Membrane). CCM was obtained. Drying was performed at 100 ° C. for 15 minutes and then at 140 ° C. for 10 minutes. Carbon black and polytetrafluoroethylene (PTFE) particles are mixed at a mass ratio of carbon black: PTFE particles = 4: 6, and a slurry in which the resulting mixture is uniformly dispersed in ethylene glycol is mixed on one side of carbon paper. The base layer was coated and dried to prepare two gas diffusion layers composed of the base layer and carbon paper.

  The CCM was sandwiched between the gas diffusion layer and the base layer side, and hot pressing was performed to obtain a membrane-electrode structure. Hot pressing was performed at 160 ° C. and 3 MPa for 5 minutes. Further, the membrane-electrode structure obtained in this example can constitute a solid polymer fuel cell by further laminating a separator that also serves as a gas passage on the gas diffusion layer.

<Comparative Example 1>
A membrane-electrode structure was obtained in the same manner as in Example 1 except that Nafion 112 (registered trademark) manufactured by DuPont was used as the proton conductive membrane.

<Evaluation>
Table 1 shows the results of evaluating the membrane-electrode structures obtained in the above Examples and Comparative Examples.

As shown in Table 1, according to this example, by using polyarylene having a specific structural unit, proton conductivity was improved particularly in a low humidity environment, and power generation performance was excellent under a wide range of humidification conditions. A membrane-electrode structure is obtained.

Claims (4)

In a membrane-electrode structure for a polymer electrolyte fuel cell in which an anode electrode is provided on one side of a proton conducting membrane and a cathode electrode is provided on the other side,
The proton conductive membrane is seen containing a repeating structural unit represented by the following formula (1'b) or the following formula (1'c),
If the following A is a direct bond, the proton conducting membrane, the repeating structural units including a solid polymer electrolyte fuel cell membrane which is represented by the following formula (1'b) - electrode assembly.

[In Formula (1′b) and Formula (1′c) , W represents a hydrogen atom, an aromatic group, or —B— (SO ₃ H) _m (wherein B represents a direct bond or an aromatic group) , M is an integer of 0 to 2). A represents a direct bond or an aromatic group, and k is an integer of 1 to 3. ] W in the formula (1′b) and the formula (1′c) is —B— (SO ₃ H) _m ,
Formula (1'b) and A and B in the formula (1'c) are each independently a phenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, or claim 1 wherein the solid high phenanthrenyl group, Membrane-electrode structure for molecular fuel cell. W in the formula (1′b) and the formula (1′c) is —B— (SO ₃ H) _m ,
In the formula (1′b) and the formula (1′c), each of A and B in the formula is bonded to form a common aromatic group, whereby naphthalenyl, anthracenyl, phenanthrenyl, or these polymer electrolyte fuel cell membrane of claim 1 wherein forming a condensed ring structure composed of benzo derivatives - electrode assembly. The repeating structural unit represented by the formula (1′b) or the formula (1′c) is 0.5 mol% or more and less than 100 mol%, and the repeating structural unit represented by the following formula (A ′) is 0. The membrane-electrode structure for a polymer electrolyte fuel cell according to any one of claims 1 to 3 , comprising more than mol% and not more than 99.5 mol%.

[In the above formula (A ′), A and D are each independently a direct bond, or —CO—, —SO—, —SO ₂ —, —CONH—, —COO—, — (CF ₂ ). _p - (p is an integer of 1 to _{10), - (CH 2) p} - (p is an integer of 1 to _{10), - CR '2 - (} R' is an aliphatic hydrocarbon group, an aromatic A divalent group selected from the group consisting of a hydrocarbon group or a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, -O-, and -S-. B is an oxygen atom or a sulfur atom, and R ¹ to R ¹⁶ may be the same or different, and are a hydrogen atom, a fluorine atom, an alkyl group, a partially or completely halogen-substituted halogenated alkyl group, an aryl It is at least one atom or group selected from the group consisting of a group, an allyl group, a nitro group, and a nitrile group. s and t are each independently an integer of 0 to 4, and r is 0 or a positive integer. ]