JP2008277282A - Membrane-electrode assembly for direct methanol fuel cell and direct methanol fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane-electrode assembly having high methanol utilization factor and capable of operating with high concentration methanol aqueous solution; and to provide a direct methanol fuel cell using the membrane-electrode assembly. <P>SOLUTION: The membrane-electrode assembly for the direct methanol fuel cell is equipped with an aromatic ion exchange resin membrane; a catalyst layer including at least catalyst-supported carbon and an ion exchange resin electrolyte; and a gas diffusion layer. The aromatic ion exchange resin membrane is composed of a polyarylene polymer including a structural unit represented by formula (5) and sulfonic acid unit. In the formula, T is a specific phenylene group; A is a direct bond, -CO-, -SO-, -CONH-, -COO-, or the like; B is an O atom or a S atom. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a membrane-electrode assembly and a direct methanol fuel cell using the membrane-electrode assembly.

  In recent years, a shortage of battery capacity has become a problem with increasing power consumption of portable devices. In order to solve this problem, fuel cells and lithium ion batteries have been actively researched as large-capacity power sources.

  Direct methanol fuel cells are particularly compact because they do not require a reformer for reforming fuel cells or high-pressure hydrogen tanks for hydrogen fuel fuel cells, and the volume energy density of methanol, the fuel, is high. Is easy and suitable for portable power supply. In particular, since it is theoretically possible to downsize more than a lithium ion battery, application to a power source for portable devices is being actively studied.

  Perfluoroalkylsulfonic acid polymers are used as proton conducting membranes in direct methanol fuel cells. However, although perfluoroalkylsulfonic acid polymers have high proton conductivity, methanol permeability is high, and methanol permeates from the anode to the cathode, resulting in a decrease in output, fuel loss, and water to several percent. There was a problem that the volumetric energy density of the fuel was lowered due to the fact that it had to be diluted with the above. In addition, an expensive noble metal catalyst such as platinum is used for the electrode catalyst of the fuel cell, but the noble metal catalyst in the electrode is also used for the combustion of the permeated methanol, so the amount of noble metal more than that required for the original power generation is exceeded. There was a problem that it was necessary to use a catalyst for the cathode.

In addition, the present applicant has disclosed in Japanese Patent Laid-Open No. 2003-331868 (Patent Document 1) and Japanese Patent Laid-Open No. 2004-149056 (Patent Document 2) a direct methanol type containing a sulfonated polyarylene having a specific structural formula. Proposed electrolyte membranes for fuel cells.
JP2003-331868 Japanese Patent Laid-Open No. 2004-149056

An object of the present invention is to provide a membrane-electrode assembly that has a high methanol utilization rate and can operate with a high-concentration aqueous methanol solution, and a direct methanol fuel cell using the membrane-electrode assembly.

The present inventors have intensively studied in view of the above problems in the prior art. As a result, by using a membrane-electrode assembly using an aromatic ion exchange resin with low methanol permeability as a proton conducting membrane, it is possible to generate power even with a high concentration of aqueous methanol solution, and use about several percent aqueous methanol solution. In this case, it was found that the amount of noble metal such as platinum used in the cathode can be reduced without impairing the power generation performance.

The configuration of the present invention is as follows.
[1] A membrane-electrode assembly for a direct methanol fuel cell comprising an aromatic ion exchange resin membrane, a catalyst layer containing at least a catalyst-supporting carbon and an ion exchange resin electrolyte, and a gas diffusion layer, the aromatic system The ion exchange resin membrane has a structural unit represented by the following formula (5) and the following formula (6):
A membrane-electrode assembly for a direct methanol fuel cell, comprising a polyarylene polymer characterized in that it comprises a structural unit represented by:

[In formula (5), T is represented by the following formula (2) and includes at least a structure represented by the following formula (3).

A and C are independently a direct bond, or —CO—, —SO ₂ , —SO—, —CONH—, —C
_{OO -, - (CF 2)} l - (l is an integer of 1 to _{10), - (CH 2) l} - (l is an integer of 1 to _{10), - CR '2 - (} R' is An aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, -O-, -S-, and at least one structure selected from the group consisting of ,
B is independently an oxygen atom or a sulfur atom,
D represents a 2,2-propylidene group or a 1,1-cyclohexylidene group represented by the following formula (4).

R ^{1 to} R ¹⁶ may be the same as or different from each other, and may be a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group in which some or all are halogenated, an allyl group, an aryl group, a nitro group. , Represents at least one atom or group selected from the group consisting of nitrile groups.

R ¹⁷ and R ¹⁸ may be the same or different except for a hydrogen atom, and each represents a hydrogen atom, a methyl group, an isopropyl group, an isobutyl group, a t-butyl group, or a cyclohexyl group.
s and t represent an integer of 0 to 4, and r represents an integer of 1 or more. ].

[In the formula (6), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (
CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), at least one structure selected from the group consisting of —C (F ₃ ) —
Z is a direct bond or at least one selected from the group consisting of — (CH ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O—, and —S—. Show the structure of the species,
Ar represents an aromatic group having a substituent represented by —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H.

p shows the integer of 1-12, m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4. ].
[2] The membrane-electrode assembly for a direct methanol fuel cell according to [1], wherein the coating amount of the platinum catalyst contained in the catalyst layer on the anode side is 0.7 mg / cm ² or more and 8.0 mg / cm ² or less.
[3] The membrane-electrode assembly for a direct methanol fuel cell according to [1] or [2], wherein the thickness of the catalyst layer on the cathode side is 5 to 100 μm.
[4] The membrane-electrode assembly for a direct methanol fuel cell according to [1] to [3], wherein the thickness of the catalyst layer on the anode side is 5 to 100 μm.
[5] In the membrane-electrode assembly for a direct methanol fuel cell, the gas diffusion layer on at least one side of the aromatic ion exchange resin membrane is composed of a porous substrate, and the porous substrate and the catalyst layer The membrane-electrode assembly for a direct methanol fuel cell according to [1] to [4], comprising a microporous layer comprising a water repellent and carbon powder in between.
[6] In the membrane-electrode assembly for a direct methanol fuel cell, the gas diffusion layer on at least one side of the aromatic ion exchange resin membrane is composed of a water repellent-coated porous base material, The membrane-electrode assembly for a direct methanol fuel cell according to [1] to [5], comprising a microporous layer made of a water repellent and carbon powder between the catalyst layer and the catalyst layer.
[7] The direct methanol fuel according to [6], wherein the gas diffusion layer on the cathode side of the aromatic ion exchange resin membrane is composed of a water repellent-coated porous base material in the membrane-electrode assembly for a direct methanol fuel cell. Battery membrane-electrode assembly.
[8] The membrane-electrode assembly for a direct methanol fuel cell according to [1] to [7], wherein the gas permeability of the gas diffusion layer on the anode side is 800 g / m ² / h to 3000 g / m ² / h.
[9] The membrane-electrode assembly for a direct methanol fuel cell according to [1] to [8], wherein the gas diffusion layer on the cathode side has a moisture permeability of 500 g / m ² / h to 2500 g / m ² / h.
[10] At least one electricity generating unit including at least one membrane-electrode assembly and separators located on both sides thereof;
A fuel supply unit for supplying fuel to the electricity generation unit;
And a direct methanol fuel cell including an oxidant supply unit for supplying an oxidant to the electricity generation unit,
A direct methanol fuel cell, wherein the membrane-electrode assembly is one of [1] to [9].

According to the present invention, a laminate comprising a catalyst layer containing a catalyst-supporting carbon and an ion exchange resin, a porous substrate coated with carbon and a water repellent, and a microporous layer made of the water repellent and carbon powder is added to the fragrance. In membrane-electrode assemblies and direct methanol fuel cells on both sides of an aromatic ion-exchange resin membrane, it is possible to generate power even with a high concentration aqueous methanol solution by suppressing methanol permeation by the aromatic ion-exchange resin. When an aqueous methanol solution is used, the amount of platinum at the cathode can be reduced in terms of power generation performance, and a membrane-electrode assembly and a direct methanol fuel cell can be provided.

Hereinafter, the membrane-electrode assembly and the direct methanol fuel cell according to the present invention will be described in detail.
The membrane-electrode assembly according to the present invention includes an aromatic ion exchange resin membrane, a catalyst layer containing at least catalyst-supporting carbon and an ion exchange resin electrolyte, and a gas diffusion layer for a direct methanol fuel cell membrane-electrode assembly. Is the body.

[Aromatic ion exchange resin membrane]
The aromatic ion exchange resin membrane is a structural unit (hydrophobic unit) represented by the following general formula (5):
And a polyarylene polymer having a sulfonic acid group containing a structural unit (sulfonic acid unit) represented by the following general formula (6). The weight average molecular weight in terms of polystyrene measured by gel permeation chromatography of the polymer (hereinafter simply referred to as “weight average molecular weight”) is 10,000 to 1,000,000, preferably 20,000 to 800,000.
<Hydrophobic unit>
The hydrophobic unit (hereinafter also referred to as “unit (A)”) is represented by the following formula (5).

[In formula (5), T is represented by the following formula (2) and includes at least a structure represented by the following formula (3).

A and C are independently a direct bond or -CO-, -SO _2- , -SO-, -CONH-,-
COO—, — (CF ₂ ) ₁ — (l is an integer of 1 to 10), — (CH ₂ ) ₁ — (l is an integer of 1 to 10), —CR ′ ₂ — (R ′ is An aliphatic hydrocarbon group, an aromatic hydrocarbon group, and 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), a cyclohexylidene group , A fluorenylidene group, and -O- are preferable.

B is independently an oxygen atom or a sulfur atom, preferably an oxygen atom.
X is a halogen atom, preferably a chlorine atom.
D represents a 2,2-propylidene group or a 1,1-cyclohexylidene group represented by the following formula (4).

R ^{1 to} R ¹⁶ may be the same as or different from each other, and may be a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group in which some or all are halogenated, an allyl group, an aryl group, a nitro group. , Represents at least one atom or group selected from the group consisting of nitrile groups.

  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.

R ¹⁷ and R ¹⁸ may be the same as or different from each other, and each represents a hydrogen atom, a methyl group, an isopropyl group, an isobutyl group, a t-butyl group, or a cyclohexyl group. However, the case of mutual hydrogen atoms is excluded.

s and t represent an integer of 0 to 4. r shows the integer of 1-100, Preferably it is 1-80.
As a structure which is a preferable combination of the values of s and t and A, B, D and R ^{1 to} R ¹⁸ , s =
1, t = 1, A is —CO— or —SO ₂ —, B is an oxygen atom, D is —CR ′ ₂ — (R ′ is an aliphatic hydrocarbon group, aromatic hydrocarbon A cyclohexylidene group or a fluorenylidene group, R ^{1 to} R ¹⁶ are a hydrogen atom or a fluorine atom, R ¹⁷ and R ¹⁸ are a hydrogen atom, a methyl group, or t-butyl. And a structure that is a group, a cyclohexyl group, or a phenyl group.

When this hydrophobic unit is included, a hydrophobic portion can be imparted to the polymer. Moreover, since it has a condensed aromatic ring, methanol resistance can be imparted to the polymer.
Such hydrophobic units are derived from the following aromatic compounds.

  The aromatic compound according to the present invention is represented by the following formula (1), and is hereinafter also referred to as “compound (1)”.

In formula (1), T, s, t, r, A, B, and R _{1 to} R ⁸ are the same as in formula (5).
X is a halogen atom, preferably a chlorine atom.
Compound (1) can be synthesized, for example, by the method shown below.

First, in order to convert the bisphenol compound into an alkali metal salt of bisphenol, lithium in a polar solvent having a high dielectric constant such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, sulfolane, diphenylsulfone, and dimethylsulfoxide is used. An alkali metal such as sodium or potassium, or an alkali metal compound such as an alkali metal hydride, an alkali metal hydroxide, or an alkali metal carbonate is added. Usually, an alkali metal or the like is reacted in excess with respect to the hydroxyl group of bisphenol, and usually 1.1 to 2 times equivalent is used. Preferably, 1.2 to 1.5 times equivalent is used.

Here, bisphenol is at least 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-di-t-butyl-4-hydroxyphenyl) propane, 2-bis (3-phenyl-4-hydroxyphenyl) propane, 1,1
-Bis (3,5-dimethyl-4-hydroxyphenyl) cyclohexane, 1,1-bis (3-di-t-butyl-4-hydroxyphenyl) cyclohexane, 1,1-bis (3-cyclohexyl-4-hydroxy) Phenyl) cyclohexane and 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis (4-hydroxyphenyl) ketone, 2 , 2-bis (4-hydroxyphenyl) sulfone, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-
Phenylphenyl) fluorene, 9,9-bis (4-hydroxy-3,5-diphenylphenyl) fluorene, 4,4'-bis (4-hydroxyphenyl) diphenylmethane, 4,4'-bis (4-hydroxy-3) -Phenylphenyl) diphenylmethane, 4,4'-bis (4-hydroxy3,5-diphenylphenyl) diphenylmethane, hydroquinone, resorcinol, 2-phenylhydroquinone and the like may be used.

In this case, an aromatic dihalide compound activated with an electron-withdrawing group in the presence of a solvent azeotropic with water such as benzene, toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, and phenetole. (Active aromatic divalide compound), for example, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-chlorofluorobenzophenone, bis (4-chlorophenyl) sulfone, bis (4-fluorophenyl) Sulfone, 4-fluorophenyl-4′-chlorophenylsulfone, bis (3-nitro-4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, hexafluorobenzene,
Decafluorobiphenyl, 2,5-difluorobenzophenone, 1,3-bis (4-chlorobenzoyl) benzene and the like are reacted.

  The active aromatic dihalide compound is preferably a fluorine compound if importance is attached to the reactivity here, but if importance is attached to the aromatic coupling reactivity, which is the next step, aromatic nucleophilic substitution so that the terminal is a chlorine atom. Chlorine compounds are preferred because the reaction needs to be assembled. The active aromatic dihalide is 2 to 4 times mol, preferably 2.2 to 2.8 times mol, of bisphenol. These may be previously converted to alkali metal salts of bisphenol before the aromatic nucleophilic substitution reaction. Most preferred as the active aromatic dihalide is a chlorofluoro compound having halogen atoms with different reactivities one by one. In this case, the fluorine atom preferentially undergoes a nucleophilic substitution reaction with phenoxide. It is convenient to obtain a modified terminal chloro form.

The reaction temperature is 60 ° C to 300 ° C, preferably 80 ° C to 250 ° C. The reaction time ranges from 15 minutes to 100 hours, preferably from 1 hour to 24 hours.
Specific examples of such compound (1) include compounds represented by the following formulas.

  In the following formula, a and b indicate the composition ratio of each unit.

<Sulphonic acid unit>
The copolymer according to the present invention includes a structural unit represented by the following formula (6) together with the structural unit represented by the formula (5) (sulfonic acid unit, hereinafter also referred to as “unit (6)”). Is desirable.

In Formula (6), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (
CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10) and at least one structure selected from the group consisting of —C (CF ₃ ) ₂ —. Of these, —CO— and —SO ₂ — are preferable.

Z is a direct bond, at least one selected from the group consisting of — (CH ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O—, and —S—. The structure of is shown. Among these, a direct bond and -O- are preferable.

Ar is an aromatic group having a substituent represented by —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p represents an integer of 1 to 12). Indicates.
Examples of the aromatic group include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group. Of these, a phenyl group and a naphthyl group are preferable. -SO ₃ H,
It is necessary that at least one substituent represented by —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p represents an integer of 1 to 12) is substituted. In the case of a naphthyl group, two or more are preferably substituted.

m is an integer of 0 to 10, preferably 0 to 2, n is an integer of 0 to 10, preferably 0 to 2, and k is an integer of 1 to 4.
As a structure which is a preferable combination of the values of m and n and Y, Z and Ar,
(1) a structure in which m = 0, n = 0, Y is —CO—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(2) a structure in which m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(3) a structure in which m = 1, n = 1, k = 1, Y is —CO—, Z is —O—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(4) A structure in which m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a naphthyl group having two —SO ₃ H as a substituent;
(5) m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a phenyl group having —O (CH ₂ ) ₄ SO ₃ H as a substituent. Examples include the structure.

<Polymer structure>
The polyarylene polymer having a sulfonic acid group used in the present invention is represented by the following formula (7). Hereinafter, the polyarylene polymer having a sulfonic acid group is also referred to as “copolymer (7)”.

In the formula (7), A, B, D, Y, Z, Ar, k, m, n, r, s, t, and R ^{1 to} R ⁸ are respectively A in the above formulas (5) and (6). , B, D, T, Y, Z, Ar, k, m, n, r, s, t, and R ^{1 to} R ⁸ . x and y are molar ratios when x + y = 100 mol%, x represents the molar ratio of units (6), and y represents the molar ratio of units (5).

  The value of x in the copolymer (7) according to the present invention is 0.5 to 99.999 mol%, preferably 10 to 99.999 mol%, and the value of y is 99.5 to 0.001 mol%. , Preferably it is 90-0.001 mol%.

<Method for producing polyarylene polymer having sulfonic acid group (copolymer (7))>
For the production of the copolymer (7), for example, the following three methods, Method I, Method II and Method III, can be used.

  (Method I) For example, by the method described in JP-A No. 2004-137444, a monomer or oligomer that can be a unit (5) and a monomer having a sulfonate group that can be a unit (6) are copolymerized to form a sulfonate ester. It can be synthesized by producing a polyarylene having a group, deesterifying the sulfonate group, and converting the sulfonate group to a sulfonate group.

  (Method II) For example, in the method described in JP-A No. 2001-342241, the monomer or oligomer that can be the unit (5) and the skeleton represented by the unit (6) have a sulfonic acid group and a sulfonic acid ester group. It is also possible to synthesize the copolymer by copolymerizing with a monomer that does not, and sulfonating the copolymer using a sulfonating agent.

(Method III) In the formula (6), when Ar is an aromatic group having a substituent represented by —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H, For example, JP-A-2005-060
The monomer or oligomer that can become the unit (5) and the precursor monomer that can become the unit (6) are copolymerized by the method described in 625, and then an alkylsulfonic acid or a fluorine-substituted alkylsulfonic acid is introduced. It can also be synthesized by the method.

  Specific examples of the monomer having a sulfonic acid ester group that can be used as a unit (6) that can be used in (Method I) are JP-A Nos. 2004-137444, 2004-345997, and 2004-. Examples thereof include sulfonic acid esters described in Japanese Patent No. 346163.

  As specific examples of the monomer having no sulfonic acid group or sulfonic acid ester group that can be used as the unit (6) that can be used in (Method II), JP-A Nos. 2001-342241 and 2002-293889 are disclosed. Mention may be made of the dihalides described in the publication.

Specific examples of the precursor monomer that can be used in (Method III) and can be the unit (6) include dihalides described in JP-A-2005-36125.

  In order to obtain the copolymer (7), it is first necessary to copolymerize the monomer or oligomer that can be the unit (5) and the monomer that can be the unit (6) to obtain a precursor polyarylene. is there. This copolymerization is carried out in the presence of a catalyst, and the catalyst used in this case is a catalyst system containing a transition metal compound. This catalyst system is (1) a transition metal salt and a ligand. A compound (hereinafter referred to as “ligand component”), or a transition metal complex (including a copper salt) coordinated with a ligand, and (2) a catalyst having a reducing agent as an essential component, Further, a “salt” may be added thereto in order to increase the polymerization rate.

  Specific examples of these catalyst components, the use ratio of each component, the polymerization conditions such as the reaction solvent, concentration, temperature, time, etc. include the compounds described in JP-A No. 2001-342241.

  The copolymer (7) can be obtained by converting the precursor polyarylene into a polyarylene polymer having a sulfonic acid group. As this method, there are the following three methods.

A method of deesterifying a polyarylene polymer having a sulfonate group of a precursor by a method described in JP-A-2004-137444.
A method of sulfonating a precursor polyarylene copolymer by the method described in JP-A-2001-342241.

A method of introducing an alkylsulfonic acid group into the precursor polyarylene polymer by the method described in JP-A-2005-060625.
The ion exchange capacity of the copolymer (7) produced by the above method is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, more preferably 0.8 to 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 ion exchange capacity can be adjusted, for example, by changing the type, use ratio, and combination of the monomer or oligomer that can be the unit (5) and the precursor monomer that can be the unit (6).

  The molecular weight of the copolymer (7) thus obtained is 10,000 to 1,000,000, preferably 20,000 to 800,000 in terms of polystyrene-equivalent weight average molecular weight by gel permeation chromatography (GPC).

Since the polyarylene polymer has a structural unit containing a specific condensed aromatic ring, it has hydrophobicity and has high methanol resistance. Therefore, sulfonic acid groups can be introduced at a high concentration. In the polyarylene polymer having a sulfonic acid group used in the present invention, the linking group forming the main chain skeleton contains at least one meta bond or ortho bond, and the sulfonic acid group By controlling the glass transition point of the polyarylene polymer having a group within the range of 60 ° C. to 190 ° C., the intended high performance membrane-electrode assembly for direct methanol fuel cell and fuel cell can be obtained. .
(About glass transition point)
The glass transition point of the polymer obtained by the above method is measured by a dynamic viscoelasticity measuring device in a film state). The glass transition point is preferably in the range of 60 ° C to 190 ° C, more preferably 80 ° C to 170 ° C. By controlling this temperature within the above range, the bonding temperature with the electrode can be reduced. Furthermore, the bonding treatment at a low temperature can suppress the chemical change (desorption, dehydration reaction) of the sulfonic acid at the time of bonding, and a high output can be obtained in the power generation evaluation. This time, by providing the above chemical structure in the polymer, the glass transition point of the conductive film can be controlled within the target region.
Production of Ion Exchange Resin Membrane In the present invention, the polyarylene polymer having a sulfonic acid group is dissolved in a solvent to form a solution, which is then cast on a substrate to form a film. An ion-exchange resin membrane can be produced by molding into a shape. Here, the substrate is not particularly limited as long as it is a substrate used in an ordinary solution casting method. For example, a substrate made of plastic, metal, or the like is used, and preferably a heat treatment such as a polyethylene terephthalate (PET) film. A substrate made of a plastic resin is used.

  Examples of the solvent for dissolving the polyarylene polymer having a sulfonic acid group include N-methyl-2-pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, dimethyl sulfoxide, and dimethylurea. And aprotic polar solvents such as dimethylimidazolidinone, and N-methyl-2-pyrrolidone (hereinafter also referred to as “NMP”) is particularly preferable from the viewpoint of solubility and solution viscosity. The aprotic polar solvent can be used alone or in combination of two or more.

As a solvent for casting the polyarylene polymer having a sulfonic acid group, a mixture of the above aprotic polar solvent which is a good solvent and an alcohol which is a poor solvent can also be used. Examples of alcohols that are poor solvents include methanol, ethanol, propyl alcohol, iso-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like. preferable. The alcohol combined with the aprotic polar solvent can be used alone or in combination of two or more.

  When a mixture of an aprotic polar solvent and an alcohol is used as the solvent, the aprotic polar solvent is 95 to 25% by weight, preferably 90 to 25% by weight, and the alcohol is 5 to 75% by weight, preferably 10 to 75% by weight (however, the total is 100% by weight). When the amount of alcohol is within the above range, the effect of lowering the solution viscosity is excellent.

  The polymer concentration of the solution in which the polyarylene polymer having a sulfonic acid group is dissolved depends on the molecular weight of the polyarylene polymer having a sulfonic acid group, but is usually 5 to 40% by weight, preferably 7 to 25%. % By weight. If it is less than 5% by weight, it is difficult to form a thick film, and pinholes are easily generated. On the other hand, if it exceeds 40% by weight, the solution viscosity is so high that it is difficult to form a film, and surface smoothness may be lacking.

The solution viscosity is usually from 2,000 to 100,000 mPa · s, preferably 3,000, although it depends on the molecular weight of the polyarylene polymer having a sulfonic acid group and the polymer concentration.
˜50,000 mPa · s. If it is less than 2,000 mPa · s, the retention of the solution during film formation is poor, and it may flow from the substrate. On the other hand, if it 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.

  After film formation as described above, when the obtained undried film is immersed in water, the organic solvent in the undried film can be replaced with water, and the amount of residual solvent in the resulting ion exchange resin film is reduced. can do.

  In addition, after film formation, before immersing an undried film in water, you may predry an undried film. The preliminary drying is performed by holding the undried film at a temperature of usually 50 to 150 ° C. for 0.1 to 10 hours.

  When immersing an undried film in water, it may be a batch method in which a single wafer is immersed in water, or a laminated film in a state where it is usually formed on a substrate film (for example, PET), or A continuous method may be used in which the film separated from the substrate is immersed in water and wound.

In the case of the batch method, the formation of wrinkles on the surface of the film that has been treated by a method such as placing the treated film in a frame is advantageous.
When the undried film is immersed in water, the contact ratio of water is 10 parts by weight or more, preferably 30 parts by weight or more with respect to 1 part by weight of the undried film. In order to minimize the residual solvent amount of the obtained ion exchange resin membrane, it is preferable to maintain a contact ratio as large as possible. It is also effective to reduce the amount of residual solvent in the resulting ion-exchange resin 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. It is. In order to suppress the in-plane distribution of the amount of organic solvent remaining in the ion exchange resin membrane, it is effective 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 in the range of 5 to 80 ° C. The higher the temperature, the faster the replacement rate between the organic solvent and water, but the greater the amount of water absorbed by the film, so there is a concern that the surface state of the ion exchange resin membrane obtained after drying will be rough. Usually, a temperature range of 10 to 60 ° C. is convenient because of the replacement speed and ease of handling.

The immersion time is usually in the range of 10 minutes to 240 hours, although depending on the initial residual solvent amount, contact ratio, and treatment temperature. Preferably, it is in the range of 30 minutes to 100 hours.
When the undried film is immersed in water and dried as described above, an ion exchange resin membrane having a reduced amount of residual solvent is obtained. The residual solvent amount of the ion exchange resin membrane thus obtained is usually 5%. % By weight or less.

  Further, depending on the dipping conditions, the amount of residual solvent in the obtained ion exchange resin membrane can be 1% by weight or less. As such conditions, for example, the contact ratio between the undried film and water is 50 parts by weight or more with respect to 1 part by weight of the undried film. There is a method of setting the time to 10 minutes to 10 hours.

  After immersing the undried film in water as described above, the film is dried at 30-100 ° C, preferably 50-80 ° C, for 10-180 minutes, preferably 15-60 minutes, and then at 50-150 ° C. The ion exchange resin membrane can be obtained by vacuum drying under reduced pressure of 500 mmHg to 0.1 mmHg for 0.5 to 24 hours.

The ion exchange resin membrane used in the present invention has a dry film thickness of usually 10 to 100 μm, preferably 20 to 80 μm.
Further, in the present invention, the above sulfonated polyarylene polymer is formed into a film by the above-described method without hydrolysis, and then hydrolyzed by the same method as described above. An ion exchange resin membrane made of a polyarylene polymer having a sulfonic acid group can also be produced.

  The ion exchange resin membrane may contain an anti-aging agent, preferably a hindered phenol compound having a molecular weight of 500 or more, and by containing an anti-aging agent, the durability as an ion exchange resin membrane is further improved. Can do.

As a hindered phenol compound having a molecular weight of 500 or more that can be used in the present invention, triethylene glycol-bis [3- (3-tert-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: IRGANOX 259), 2,4-bis- (n- Octylthio) -6- (4-hydroxy-3,5-di-
t-Butylanilino) -3,5-triazine (trade name: IRGANOX 565), pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1010 ) 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1035), octadecyl-3- (3,5-di-) (t-butyl-4-hydroxyphenyl) propionate) (trade name: IRGANOX 1076), N, N-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (IRGAONOX 1098), 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 (quotient Name: IRGANOX 3114), 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8 , 10-tetraoxaspiro [5.5] undecane (trade name: Sumilizer GA-80).

  In the present invention, the hindered phenol compound having a molecular weight of 500 or more is preferably used in an amount of 0.01 to 10 parts by weight with respect to 100 parts by weight of the polyarylene polymer having a sulfonic acid group.

[Membrane-electrode assembly]
The membrane-electrode assembly of the present invention comprises the above-described aromatic ion exchange resin membrane, a catalyst layer containing at least catalyst-supporting carbon and an ion exchange resin electrolyte, and a gas diffusion layer.
(Catalyst layer)
The catalyst layer constituting the membrane-electrode assembly contains at least carbon carrying a catalyst and an ion exchange resin electrolyte.
(1) Carbon carrying a catalyst The catalyst used in the present invention contains platinum as an essential component. Further, in addition to platinum, noble metals such as palladium, gold, ruthenium and iridium may be included. Further, the noble metal catalyst may be one containing two or more elements such as an alloy or a mixture.

  The carbon supporting the catalyst is preferably carbon black such as oil furnace black, channel black, lamp black, thermal black, and acetylene black from the viewpoint of electron conductivity and specific surface area.

  Examples of the oil furnace black include “Vulcan XC-72”, “Vulcan P”, “Black Pearls 880”, “Black Pearls 1100”, “Black Pearls 1300”, “Black Pearls 2000”, and “Regal 400” manufactured by Cabot Corporation. “Ketjen Black EC” manufactured by Lion Corporation, “# 3150, # 3250” manufactured by Mitsubishi Chemical Corporation, and the like. Examples of the acetylene black include “DENKA BLACK” manufactured by Denki Kagaku Kogyo.

  Further, as the carbon, artificial graphite or carbon obtained from an organic compound such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin, or the like may be used.

As the form of the carbon material, not only particles but also fibers can be used.
The amount of the catalyst supported on the carbon is not particularly limited as long as the catalyst activity can be effectively exhibited, but the catalyst content in the catalyst-supported carbon is 60 to 100% by weight. Is preferable, and it is more preferable that it is 80 to 95 weight%. When the catalyst content is larger than the above range, the number of catalysts that are not used effectively increases, resulting in an inefficient electrode. Further, when the catalyst content is smaller than the above, a sufficient amount of catalyst cannot be obtained, so that the battery performance is lowered. As the form of these carbons, in addition to particles, fibers can also be used. Further, the amount of the catalyst supported on the carbon is not particularly limited as long as the amount of the catalyst can be effectively exhibited. Preferably, 60 to 90% by weight is more preferable, and 65 to 90% by weight is particularly preferable. Further, the catalyst loading of the catalyst layer on the anode side is preferably 50 to 90% by weight, more preferably 70 to 90% by weight, and particularly preferably 75 to 90% by weight.

Here, the catalyst loading rate is defined by the following equation.
Catalyst loading rate = catalyst weight supported on the catalyst layer ÷ (catalyst weight supported on the catalyst layer + catalyst weight supported on carbon)
(2) Ion exchange resin electrolyte The ion exchange resin electrolyte functions as a binder component for binding the carbon carrying the catalyst, and efficiently supplies ions generated by the reaction on the catalyst to the ion conductive membrane at the fuel electrode. In addition, the air electrode efficiently supplies ions supplied from the ion conductive membrane to the catalyst.

The ion exchange resin for the catalyst layer used in the present invention is preferably a polymer having a proton exchange group in order to improve proton conductivity in the catalyst layer. Proton exchange groups contained in such polymers include sulfonic acid groups, carboxylic acid groups, and phosphoric acid groups, but are not particularly limited. A polymer having such a proton exchange group is also selected without any particular limitation, and a polymer having a proton exchange group composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain, or a sulfonated polyarylene. Etc. are preferably used. Further, it may be a polymer containing the above-described fluorine atom having a proton exchange group, another polymer obtained from ethylene or styrene, a copolymer or a blend thereof.

As such an ion exchange resin electrolyte, a known one can be used without particular limitation, and for example, those disclosed in Nafion (Du Pont, registered trademark), Japanese Patent Application Laid-Open No. 2007-26820 can be used without any particular limitation. Moreover, you may use the ion exchange resin used with the above-mentioned aromatic ion exchange resin membrane.
Catalyst layer composition In the present invention, the use ratio of the catalyst particles is 1 to 20% by weight, preferably 3 to 10% by weight, and the use ratio of the ion exchange resin is 1% by weight. % To 30% by weight, preferably 1% to 15% by weight, and the proportion of the resin having no ion exchange group used as necessary is 1% to 95% by weight, preferably 30%. The use ratio of the dispersant used as necessary is 0% by weight to 10% by weight, preferably 0% by weight to 2% by weight, and is used as necessary. The carbon fiber used is used in a weight ratio of 0% to 20% by weight, preferably 1% to 10% by weight.

If the catalyst layer formed on the substrate is on the cathode side, the amount of platinum catalyst contained in the catalyst layer (also referred to as the amount of platinum catalyst applied in the catalyst layer) is 0.7 mg / cm ^{2 to} 6.0 mg. is preferably / cm ^2, more preferably from ^{1.0mg / cm 2 ~4.0mg / cm 2} , and preferably the thickness of the catalyst layer is 5 m to 100 m, more preferably at 20μm~80μm And particularly preferably 30 μm to 80 μm. If the anode, a platinum catalyst content in the catalyst layer is preferably from ^{0.7mg / cm 2 ~8.0mg / cm 2} , more preferably 1.0mg / cm ² ~5.0mg / cm ² and the thickness of the catalyst layer is preferably 5 μm to 150 μm, more preferably 20 μm to 100 μm, and particularly preferably 30 μm to 80 μm.

  If the amount of platinum catalyst contained in the catalyst layer is less than the above range, the protonation reaction amount of methanol, which is a fuel, on both the cathode side and the anode side is reduced, and the power generation performance is lowered. If the amount of platinum catalyst contained in the catalyst layer is more than the above range, the amount of platinum catalyst that is not used in the reaction increases. On the anode side, the permeability of the methanol aqueous solution as the fuel, and the dioxide produced by the anode catalyst are increased. If the cathode is on the cathode side, the carbon permeability is lowered, and the air (oxygen) permeability and drainage properties are lowered, and the power generation performance may be lowered.

Such a catalyst layer can be produced using the catalyst paste shown below.
The catalyst paste ion exchange resin and the catalyst-supporting carbon are those described above.

When producing a normal paste, the following components are used as necessary.
(3) Dispersant A dispersant may be further added to the catalyst paste composition used in the present invention, if necessary. Examples of such a dispersant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

Examples of the anionic surfactant include oleic acid / N-methyltaurine, potassium oleate / diethanolamine salt, alkyl ether sulfate / triethanolamine salt, polyoxyethylene alkyl ether sulfate / triethanolamine salt, special modified polyether Amine salt of ester acid, amine salt of higher fatty acid derivative, amine salt of special modified polyester acid, amine salt of high molecular weight polyether ester acid, amine salt of special modified phosphoric ester, high molecular weight polyester acid amide amine salt, special fatty acid derivative Amidoamine salts, alkylamine salts of higher fatty acids, amidoamine salts of high molecular weight polycarboxylic acids, sodium laurate, sodium stearate, sodium oleate sodium lauryl sulfate, sodium cetyl Sulfate sodium salt, stearyl sulfate sodium salt, oleyl sulfate sodium salt, lauryl ether sulfate, sodium alkylbenzene sulfonate, oil-soluble alkylbenzene sulfonate, α-olefin sulfonate, higher alcohol phosphate monoester disodium Salt, higher alcohol phosphoric acid diester disodium salt, zinc dialkyldithiophosphate and the like.

Examples of the cationic surfactant include benzyldimethyl {2- [2- (P-1
, 1,3,3-tetramethylbutylphenoxy) ethoxy] ethyl} ammonium chloride, octadecylamine acetate, tetradecylamine acetate, octadecyltrimethylammonium chloride, tallow trimethylammonium chloride, dodecyltrimethylammonium chloride, coconut trimethylammonium chloride Hexadecyltrimethylammonium chloride, behenyltrimethylammonium chloride, coconut dimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride, dioleyldimethylammonium chloride, 1-hydroxyethyl-2-tallow imidazoline quaternary salt, 2-Heptadecenyl-hydroxyethyl Imidazoline, stearamide ethyl diethylamine acetate, stearamide ethyl diethylamine hydrochloride, triethanolamine monostearate formate, alkyl pyridium salt, higher alkylamine ethylene oxide adduct, polyacrylamide amine salt, modified polyacrylamide amine salt, par And fluoroalkyl quaternary ammonium iodide.

Examples of the amphoteric surfactant include dimethyl coconut betaine, dimethyl lauryl betaine, sodium laurylaminoethylglycine, sodium laurylaminopropionate, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, amide betaine, imidazolinium betaine, lecithin, 3 -[Ω-fluoroaccanoyl-N-ethylamino] -1-propanesulfonic acid sodium, N- [3- (perfluorooctanesulfonamido) propyl] -N, N-dimethyl-N-carboxymethyleneammonium betaine, etc. Can be mentioned.

  Examples of the nonionic surfactant include coconut fatty acid diethanolamide (1: 2 type), coconut fatty acid diethanolamide (1: 1 type), bovine fatty acid diethanolamide (1: 2 type), and bovine fatty acid diethanolamide (1). : 1 type), oleic acid diethanolamide (1: 1 type), hydroxyethyl lauryl amine, polyethylene glycol lauryl amine, polyethylene glycol palm amine, polyethylene glycol stearyl amine, polyethylene glycol beef tallow amine, polyethylene glycol beef tallow propylene diamine, polyethylene glycol di Oleylamine, dimethyllaurylamine oxide, dimethylstearylamine oxide, dihydroxyethyllaurylamine oxide, perfluoroalkylamine oxide, poly Vinylpyrrolidone, higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, fatty acid ester of glycerin, fatty acid ester of pentaerythritol, fatty acid ester of sorbit, fatty acid ester of sorbitan And fatty acid esters of sugar.

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, the storage stability and fluidity are excellent, and the productivity during coating is improved.
(4) Carbon fiber Carbon fiber may be further added to the electrode paste composition used in the present invention as necessary. As such carbon fibers, rayon-based carbon fibers, PAN-based carbon fibers, lignin pover-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, and the like can be used. Among these, vapor-grown carbon fibers Is preferred.

When such carbon fibers are further added to the catalyst paste composition, the pore volume in the catalyst layer is increased, so that the diffusibility of fuel gas and oxygen gas is improved, and flooding due to generated water can be improved. , Power generation performance is improved.
(5) Water If necessary, water may be further added to the catalyst paste composition used in the present invention. By adding water, there is an effect of reducing heat generation when preparing the catalyst paste composition.
(6) Resin not having ion exchange group In the electrode paste composition used in the present invention, a resin having no ion exchange group may be used as necessary. Although it will not specifically limit if it melt | dissolves or disperse | distributes in the said organic solvent, It is preferable that it is resin with high water repellency. For example, a fluorine-containing copolymer, a silane coupling agent, a silicone resin, a wax, polyphosphazene and the like can be mentioned, and a fluorine-containing copolymer is preferable.

The fluorine-containing copolymer is not particularly limited as long as it is dissolved or dispersed in the organic solvent. For example, a vinylidene fluoride copolymer or a perfluorocarbon polymer having an aliphatic ring structure in the molecule is used. And a copolymer of a fluorine-containing olefin and a hydrocarbon-based olefin, and a copolymer of a fluorine-containing acrylate and an acrylate or / and methacrylate. Use of these resins having no ion exchange group is preferable because the wet state in the catalyst layer can be appropriately maintained.
(7) Organic solvent As the solvent used in the present invention, ethanol, n-propyl alcohol, 2-propanol, 2-methyl-2-propanol, 2-butanol, n-butyl alcohol, 2-methyl-1-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2 -Dimethyl 1-propanol, cyclohexanol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 1- Methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol 1-octanol, 2-octanol, 2-ethyl-1-hexanol, dioxane, butyl ether, phenyl ether, isopentyl ether, 1,2-dimethoxyethane, diethoxyethane, bis (2-methoxyethyl) ether, bis ( 2-ethoxyethyl) ether, cineol, benzyl ethyl ether, anisole, phenetole, acetal, methyl ethyl ketone, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone, 2-hexanone, 4-methyl-2-pentanone, 2-heptanone 2,4-dimethyl-3-pentanone, 2-octanone, γ-butyrolactone, n-butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, 3-methoxybutyl acetate, methyl butyrate, Ethyl acetate, methyl lactate, ethyl lactate, butyl lactate, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2- Propanol, dimethyl sulfoxide, N-methylformamide,
N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, tetramethylurea, toluene, xylene, heptane, octane and other hydrocarbon organic solvents, ethylene glycol, Examples thereof include polyhydric alcohol organic solvents such as propylene glycol and glycerol. These may be used in combination of one or more. Preferably, the boiling point is 75 to 250 ° C., and from —O—, —OH, —CO—, —SO—, —SO ₂ —, —COO—, —CONR— (where R is a hydrogen atom or a hydrocarbon group). And an organic solvent having at least one group. Within these ranges, the fluidity and coating properties of the catalyst paste are excellent.
In the catalyst paste composition paste, the catalyst-supporting carbon is used in a weight ratio of 1% by weight to 20% by weight, preferably 3% by weight to 10% by weight, and the electrolyte is used in a weight ratio of 1% by weight. -30% by weight, preferably 1% by weight to 15% by weight, and the proportion of the organic solvent having a boiling point of 100 ° C to 200 ° C is 1% by weight to 90% by weight, preferably 1% by weight to 50%. The use ratio of the water-soluble organic solvent having a boiling point of less than 100 ° C. is 1% by weight to 95% by weight, preferably 30% by weight to 80% by weight. The use ratio of the agent is 0% by weight to 10% by weight, preferably 0% by weight to 2% by weight, and the required use ratio of the carbon fiber is 0% by weight to 20% by weight. % By weight, preferably 1% to 10% by weight , Proportion of water used, if necessary 0 wt% to 70 wt% by weight, preferably, 5 wt% to 30 wt%.

  When the ratio of the carbon black on which the hydrogen reduction catalyst is supported is less than the above range, the electrode reaction rate decreases. On the other hand, if it is larger than the above range, the viscosity of the electrode paste increases and uneven coating occurs during coating.

  When the use ratio of the electrolyte is less than the above range, the proton conductivity decreases. Furthermore, it cannot play the role of a binder, and an electrode cannot be formed. Moreover, when larger than the said range, the pore volume in an electrode will reduce.

When the proportion of the organic solvent having a boiling point of 100 ° C. to 200 ° C. is within the above range, the pore volume in the electrode increases.
When the use ratio of the water-soluble organic solvent having a boiling point of less than 100 ° C. is within the above range, the coating property during electrode formation is excellent. When the use ratio of the dispersant is within the above range, an electrode paste having excellent storage stability can be obtained.

When the use ratio of the carbon fiber is less than the above range, the effect of increasing the pore volume in the electrode is low. Moreover, when larger than the said range, an electrode reaction rate will fall. If the ratio of water used is within the above range, the risk of heat generation and ignition during electrode paste preparation can be reduced.
Preparation of catalyst paste composition The catalyst paste composition can be prepared , for example, by mixing the above-mentioned components at a predetermined ratio and kneading by a conventionally known method. The order of mixing the components is not particularly limited. For example, all the components are mixed and stirred for a certain period of time, or components other than the dispersant are mixed and stirred for a certain period of time, and then the dispersant is added as necessary. It is preferable to add and to stir for a certain time. Moreover, you may adjust the quantity of an organic solvent as needed, and may adjust the viscosity of a composition.
Formation of Catalyst Layer The catalyst layer of the membrane-electrode assembly according to the present invention is formed by directly applying the electrode paste composition onto an ion exchange resin film and drying it, or by forming the electrode paste composition into a porous layer. It can form by apply | coating on the microporous layer surface of the porous base material in which the porous base material or the microporous layer was formed, and drying.

Examples of the electrode paste composition coating method include brush coating, brush coating, bar coater coating, knife coater coating, doctor blade method, screen printing, and spray coating.
Removal of the solvent of the coating film formed on the substrate is performed by drying at a temperature of 30 ° C. to 200 ° C., preferably 40 ° C. to 180 ° C., for a time of 1 minute to 250 minutes, preferably 5 minutes to 120 minutes. Can do.

[Gas diffusion layer]
The gas diffusion layer is composed of a porous substrate. The gas diffusion layer on at least one side of the aromatic ion exchange resin membrane preferably includes a microporous layer made of a water repellent and carbon powder between the porous substrate and the catalyst layer. In particular, it is preferable to provide a microporous layer made of a water repellent and carbon powder. More preferably, the gas diffusion layer on at least one side of the aromatic ion exchange resin membrane is provided with a water repellent-coated porous substrate, and a fine particle comprising a water repellent and carbon powder between the porous substrate and the catalyst layer. Providing a porous layer.

More preferably, in the membrane-electrode assembly, the gas diffusion layer on the cathode side of the aromatic ion exchange resin membrane comprises a water repellent-coated porous substrate, and the repellent property between the porous substrate and the catalyst layer. And providing a microporous layer comprising a liquid medicine and carbon powder.

  When the gas diffusion layer is provided with a microporous layer made of a water repellent and carbon powder between the porous substrate and the catalyst layer, the contact area of the catalyst layer and the gas diffusion layer is improved, and the interface resistance is preferably reduced. Furthermore, when the catalyst layer and the gas diffusion layer are joined by pressing, the introduction of a microporous layer having excellent smoothness suppresses damage to the catalyst layer, and the catalyst layer is coated with a catalyst paste on the gas diffusion layer. Is preferable because it can suppress a decrease in the catalyst utilization rate of the catalyst layer due to the penetration of the catalyst paste into the porous substrate. In addition, in order to improve power generation performance, it is important for the catalyst layer on the cathode side to have a good balance between drainage and water retention necessary for proton conduction. By providing a microporous layer in the cathode gas diffusion layer, It is particularly preferable to form a microporous layer in the cathode gas diffusion layer because the balance between drainage and water retention can be adjusted.

  When the gas diffusion layer is provided with a water repellent-coated porous base material, the permeability of the methanol aqueous solution as fuel is improved on the anode side, and the drainage is improved and power generation performance is improved on the cathode side. This is preferable.

Further, the film according to the present invention - In the electrode assembly, it is preferable that the moisture permeability of the anode side gas diffusion layer is ^{800g / m 2 / h ~3000g /} m 2 / h, more preferably, 1000 g / m ² / h to 3000 g / m ² / h. Moisture permeability of the gas diffusion layer on the cathode side is 500 g / m ² / h to 25
Is preferably 00g / m ² / h, more preferably from ^{800g / m 2 / h ~ 2500g} / m 2 / h. The moisture permeability is a value when measured in an environment of 23 ° C. by the potassium acetate method of the apparatus, material, and form of FIG.

The moisture permeability of the gas diffusion layer can be adjusted by the pore diameter and porosity of the porous substrate, the amount of water repellent coating on the porous substrate, the composition of the microporous layer, and the coating amount.
If the moisture permeability on the anode side is less than the above range, the supply of methanol aqueous solution as fuel and the discharge of carbon dioxide generated in the anode catalyst layer are not sufficiently performed, so that the power generation performance is lowered. On the other hand, if the above range is exceeded, the supply of methanol aqueous solution as fuel will be excessive, the methanol aqueous solution will not be able to react, the amount of methanol crossover that will reach the cathode catalyst layer will increase, and the power generation performance will be reduced There are things to do.

  If the moisture permeability on the cathode side is less than the above range, the supply of air (oxygen) and the discharge of water are not performed sufficiently, and the power generation performance is reduced. On the other hand, if the above range is exceeded, moisture may not be sufficiently retained in the cathode catalyst layer, proton conductivity may be reduced, and power generation performance may be reduced.

Below, the porous base material which is a structural member of a gas diffusion layer, and a microporous layer are demonstrated in detail.
Porous substrate
(1) Porous base material As the porous base material used in the present invention, a porous base material generally used in fuel cells, for example, a porous conductive sheet mainly composed of a conductive substance, is particularly limited. It can be used without being done.

  Examples of the conductive substance include a fired body from polyacrylonitrile, a fired body from pitch, carbon materials such as graphite and expanded graphite, stainless steel, molybdenum, and titanium. Although the form of the said conductive substance is not specifically limited, such as fibrous form or particle form, Preferably it is a fibrous conductive inorganic substance (inorganic conductive fiber), Most preferably, it is a carbon fiber.

  As a porous conductive sheet using inorganic conductive fibers, either a woven fabric or a non-woven fabric structure can be used. As the woven fabric, plain weaving, oblique weaving, satin weaving, crest weaving, binding weaving and the like can be used without any particular limitation. Moreover, as a nonwoven fabric, what was manufactured by methods, such as a papermaking method, a needle punch method, a spun bond method, a water jet punch method, a melt blow method, can be used without being specifically limited. The porous conductive sheet using inorganic conductive fibers may be a knitted fabric.

In particular, when carbon fiber is used as such a fabric, a plain fabric using flame-resistant spun yarn is carbonized or graphitized, and the flame-resistant yarn is carbonized after being processed into a nonwoven fabric by a needle punch method or a water jet punch method. Or a graphitized nonwoven fabric, a flame-resistant yarn, a mat nonwoven fabric by a paper making method using carbonized yarn or graphitized yarn, and the like are preferable. For example, Toray carbon papers “TGP series” and “SO series”, carbon cloth made by E-TEK, carbon paper made by SGL, and carbon felt are preferably used.
(2) Water repellent coated porous substrate The water repellent coated porous substrate used in the present invention is a dispersion in which the water repellent is dispersed in water or a water repellent dissolved in an organic solvent. Using a liquid, it can be produced by coating a water repellent with a method described later and drying and thermally decomposing components other than the water repellent (such as a solvent and a dispersant). As the water repellent coating method, a dip coating method, a screen printing method, a spray coating method or a coating method using a doctor blade, a gravure coating method, a silk screen method, a painting method, etc. are used depending on the viscosity of the composition. It is not limited to this. Among these, the dip coating method is preferable. In the case of the dip coating method, the water repellent coating amount can be adjusted by the dispersion or the concentration of the water repellent solution.

The water repellent coating amount on the porous substrate is preferably such that the weight ratio of the water repellent to the water repellent coated porous substrate is 1 wt% to 50 wt%. Preferably, it is 2 wt% to 30 wt%, more preferably 2 wt% to 20 wt%.

  It is preferable that the amount of the water repellent coating on the porous substrate is within the above range because the aqueous methanol solution and the drainage are good and the power generation characteristics are improved. Further, when the microporous layer forming paste is applied to the water repellent coated porous substrate, the pore blocking of the porous substrate due to the penetration of the microporous layer forming paste into the porous substrate is suppressed. Since a diffusion path for an aqueous solution, water, and gas can be secured, power generation characteristics are improved, which is preferable.

Examples of the water repellent used for the water repellent coating on the porous substrate in the present invention include polytetrafluoroethylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, silane coupling agent, and silicone resin. , Wax, polyphosphazene, perfluorocarbon polymer having an aliphatic ring structure in the molecule, copolymer of fluorine-containing olefin and hydrocarbon olefin, copolymer of fluorine-containing acrylate and acrylate or / and methacrylate, poly Vinylidene fluoride, polychlorotrifluoroethylene, polyhexafluoropropylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tet Fluoroethylene - ethylene copolymer, polyvinylidene fluoride - hexafluoropropene like, or using these copolymers. Of these, polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymers are preferred from the standpoint of water repellency and ease of handling in use.

The water repellent is preferably used in a state dissolved in an organic solvent or in a state dispersed in water for ease of handling in use.
[Microporous layer]
The microporous layer is made of a water repellent and carbon powder. In the microporous layer composition, the carbon powder and the water repellent agent are preferably present in a weight ratio of 30 to 90:70 to 10, and more preferably in a weight ratio of 40 to 60:60 to 40. When the content of the carbon powder is less than 30% by weight, it is difficult to form micropores in the microporous layer, and the reactants are not easily diffused. When the content of the carbon powder exceeds 90% by weight, the carbon powder may fall off, which is not preferable.

The coating amount of the microporous layer used in the present invention is preferably from ^{0.5mg / cm 2 ~15mg / cm 2} , and still more preferably present ^{0.5mg / cm 2 ~10mg / cm 2} . If the coating amount is less than the above range, the microporous layer is not sufficiently smooth due to the influence of the porous substrate, and the effect of forming the microporous layer cannot be obtained. On the other hand, when the coating amount exceeds the above range, the permeability of the methanol aqueous solution as the fuel and the discharge of carbon dioxide produced by the anode catalyst are lowered on the anode side, and air (oxygen) is produced on the cathode side. ) Permeability and drainage, and power generation performance may be reduced.

Such a microporous layer is formed using the following paste for forming a microporous layer.
Hereinafter, the microporous layer forming paste used in the present invention will be described in detail.
(1) Carbon powder The carbon powder used in the present invention does not carry a catalyst. For example, carbon powder, carbon fiber, fullerene, carbon nanotube, carbon nanofiber, and the surface are covered with a carbon film. And silicon carbide whiskers. These may be used alone or in combination of two or more.

  The carbon powder is preferably carbon black such as oil furnace black, channel black, lamp black, thermal black, and acetylene black from the viewpoint of electron conductivity and specific surface area.

  Examples of the oil furnace black include “Vulcan XC-72”, “Vulcan P”, “Black Pearls 880”, “Black Pearls 1100”, “Black Pearls 1300”, “Black Pearls 2000”, and “Regal 400” manufactured by Cabot Corporation. “Ketjen Black EC” manufactured by Lion Corporation, “# 3150, # 3250” manufactured by Mitsubishi Chemical Corporation, and the like. Examples of the acetylene black include “DENKA BLACK” manufactured by Denki Kagaku Kogyo.

As the carbon fiber, rayon-based carbon fiber, PAN-based carbon fiber, lignin pover-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, and the like can be used. Among these, vapor-grown carbon fiber is preferable.
(2) Water repellent agent The water repellent agent may be contained in the microporous layer forming paste. Examples of the water repellent include polytetrafluoroethylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, silane coupling agent, silicone resin, wax, polyphosphazene, and a polymer having an aliphatic ring structure in the molecule. Fluorocarbon polymer, copolymer of fluorine-containing olefin and hydrocarbon olefin, copolymer of fluorine-containing acrylate and acrylate or / and methacrylate, polyvinylidene fluoride, polychlorotrifluoroethylene, polyhexafluoropropylene, tetra Fluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, polyfluorinated Vinylidene - hexafluoropropane, or it can be used those copolymers. Of these, polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymers are preferred from the standpoint of water repellency and ease of handling in use.

The water repellent is preferably used in a state dissolved in an organic solvent or in a state dispersed in water for ease of handling in use.
(3) Dispersant If necessary, a dispersant may be further added to the microporous layer forming paste used in the present invention. Examples of such a dispersant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  Examples of the anionic surfactant include oleic acid / N-methyltaurine, potassium oleate / diethanolamine salt, alkyl ether sulfate / triethanolamine salt, polyoxyethylene alkyl ether sulfate / triethanolamine salt, special modified polyether Amine salt of ester acid, amine salt of higher fatty acid derivative, amine salt of special modified polyester acid, amine salt of high molecular weight polyether ester acid, amine salt of special modified phosphoric acid ester, high molecular weight polyester acid amide amine salt, special fatty acid derivative Amidoamine salt, alkylamine salt of higher fatty acid, amidoamine salt of high molecular weight polycarboxylic acid, sodium laurate, sodium stearate, sodium oleyl sulfate sodium salt, cetyl Sulfate sodium salt, stearyl sulfate sodium salt, oleyl sulfate sodium salt, lauryl ether sulfate ester, sodium alkylbenzene sulfonate, oil-soluble alkylbenzene sulfonate, α-olefin sulfonate, higher alcohol phosphate monoester disodium Salt, higher alcohol phosphoric acid diester disodium salt, zinc dialkyldithiophosphate and the like.

Examples of the cationic surfactant include benzyldimethyl {2- [2- (P-1
, 1,3,3-tetramethylbutylphenoxy) ethoxy] ethyl} ammonium chloride, octadecylamine acetate, tetradecylamine acetate, octadecyltrimethylammonium chloride, tallow trimethylammonium chloride, dodecyltrimethylammonium chloride, coconut trimethylammonium chloride Hexadecyltrimethylammonium chloride, behenyltrimethylammonium chloride, coconut dimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride, dioleyldimethylammonium chloride, 1-hydroxyethyl-2-tallow imidazoline quaternary salt, 2-Heptadecenyl-hydroxyethyl Imidazoline, stearamide ethyl diethylamine acetate, stearamide ethyl diethylamine hydrochloride, triethanolamine monostearate formate, alkyl pyridium salt, higher alkylamine ethylene oxide adduct, polyacrylamide amine salt, modified polyacrylamide amine salt, par And fluoroalkyl quaternary ammonium iodide.

Examples of the amphoteric surfactant include dimethyl coconut betaine, dimethyl lauryl betaine, sodium laurylaminoethylglycine, sodium laurylaminopropionate, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, amide betaine, imidazolinium betaine, lecithin, 3 -[Ω-fluoroaccanoyl-N-ethylamino] -1-propanesulfonic acid sodium, N- [3- (perfluorooctanesulfonamido) propyl] -N, N-dimethyl-N-carboxymethyleneammonium betaine, etc. Can be mentioned.

  Examples of the nonionic surfactant include coconut fatty acid diethanolamide (1: 2 type), coconut fatty acid diethanolamide (1: 1 type), bovine fatty acid diethanolamide (1: 2 type), and bovine fatty acid diethanolamide (1). : 1 type), oleic acid diethanolamide (1: 1 type), hydroxyethyl lauryl amine, polyethylene glycol lauryl amine, polyethylene glycol palm amine, polyethylene glycol stearyl amine, polyethylene glycol beef tallow amine, polyethylene glycol beef tallow propylene diamine, polyethylene glycol di Oleylamine, dimethyllaurylamine oxide, dimethylstearylamine oxide, dihydroxyethyllaurylamine oxide, perfluoroalkylamine oxide, poly Vinylpyrrolidone, higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, fatty acid ester of glycerin, fatty acid ester of pentaerythritol, fatty acid ester of sorbit, fatty acid ester of sorbitan And fatty acid esters of sugar.

The said dispersing agent may be used individually by 1 type, or may be used in combination of 2 or more type.
Of these, alkylphenol ethylene oxide adducts are preferred. When the above dispersant is added to the microporous layer forming paste, the storage stability and fluidity are excellent, and the productivity during coating is improved.
(4) Solvent The solvent for the microporous layer forming paste used in the present invention is not particularly limited, but water, methanol, ethanol, n-propyl alcohol, 2-propanol, 2-methyl-2-propanol, 2-butanol. Alcohols such as isobutyl alcohol; ethers such as furan, tetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and γ-butyrolactone; dimethyl sulfoxide, N-methylformamide, N, N-dimethylformamide,
N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolodon and the like can be mentioned.

The said solvent may be used individually by 1 type, or may be used in combination of 2 or more type.
In the present invention, the carbon powder in the paste is used in a weight ratio of 0.3 wt% to 50 wt%, preferably 1.0 wt% to 30 wt%. The use ratio of the agent is 0.05 to 40% by weight, preferably 1.0 to 15% by weight, and the use ratio of the solvent is 50 to 97% by weight, Preferably, it is 60% to 90% by weight, and the proportion of the dispersant used as necessary is 0% to 45% by weight, preferably 0% to 20% by weight.

When the use ratio of the carbon powder is less than the above range, it is difficult to form micropores in the microporous layer, and the reactant is not easily diffused. If it is larger than the above range, the carbon powder may fall off.

  If the ratio of the water repellent used is less than the above range, the carbon powder may fall off, which is not preferable. In addition, the water repellency becomes insufficient, the diffusibility of methanol water and water may decrease, and the power generation characteristics may decrease, and if it is larger than the above range, it is difficult to form micropores in the microporous layer. The diffusion of objects may not be easy.

When the use ratio of the solvent is within the above range, the coating property at the time of forming the microporous layer is excellent.
When the proportion of the dispersant used is in the above range, a microporous layer-forming paste having excellent fluidity and storage stability can be obtained.
Preparation of microporous layer forming paste composition The microporous layer forming paste composition used in the present invention is prepared , for example, by mixing the above-mentioned components at a predetermined ratio and kneading them by a conventionally known method. Can do. The order of mixing the components is not particularly limited. For example, all the components are mixed and stirred for a certain period of time, or components other than the dispersant are mixed and stirred for a certain period of time, and then the dispersant is added as necessary. It is preferable to add and to stir for a certain time. Moreover, you may adjust the quantity of an organic solvent as needed, and may adjust the viscosity of a composition.
Formation of the microporous layer The microporous layer used in the present invention can be formed by directly applying the paste on a water repellent coated porous substrate or catalyst layer and then drying it. Alternatively, the microporous layer forming paste may be applied on another transfer base material and then dried to form a microporous layer, which may be transferred onto the water repellent-coated porous base material or the catalyst layer by hot pressing. Moreover, you may form by laminating | stacking the said microporous layer in several times.

Examples of the microporous layer forming paste coating method include brush coating, brush coating, bar coater coating, knife coater coating, doctor blade method, screen printing, and spray coating.
Removal of the solvent of the coating film formed on the substrate is performed by drying at a temperature of 30 ° C. to 200 ° C., preferably 40 ° C. to 180 ° C., for a time of 1 minute to 250 minutes, preferably 5 minutes to 120 minutes. Can do. Furthermore, the dispersant used as necessary can be removed by immersing in a solvent and extracting the dispersant as necessary. The solvent is selected from solvents that dissolve only the dispersant without dissolving the water repellent, and examples thereof include alcohols such as methanol, ethanol, 1-propanol, and 2-propanol. Further, the dispersant can be thermally decomposed and removed at a temperature lower than the decomposition and alteration temperature of the water repellent. The thermal decomposition is performed at a temperature of 200 ° C. to 400 ° C., preferably 250 ° C. to 380 ° C., for a time of 30 seconds to 250 minutes, preferably 10 minutes to 180 minutes. As the transfer substrate, a polytetrafluoroethylene (PTFE) sheet or a glass plate or a metal plate whose surface is treated with a release agent can be used.

The hot pressing conditions are as follows: temperature 30 ° C. to 200 ° C., preferably 40 ° C. to 180 ° C., pressure 5 to 300 kg / cm ² , preferably 10 to 180 kg / cm ² , time 30 seconds to 60 minutes, preferably 1 minute to 30 For minutes. Within the above range, the water repellent-coated porous substrate or the catalyst layer and the microporous layer have good bonding properties.
[Formation of membrane-electrode assembly]
The membrane-electrode assembly according to the present invention is a method of joining the ion exchange resin membrane on which the catalyst layer is formed and a porous substrate by hot pressing or the like, and a porous substrate on which the catalyst layer is formed and ion exchange. The resin membrane is manufactured by a method of joining by hot pressing or the like so that the catalyst layer side is in contact with the ion exchange resin membrane.

The conditions of the hot press are as follows: temperature is 50 ° C. to 200 ° C., preferably 100 ° C. to 180 ° C., pressure is 5 to 200 kg / cm ² , preferably 10 to 100 kg / cm ² , and time is 10 seconds to 60 minutes, preferably 1 to 30 minutes. By performing hot pressing under conditions within the above range, the bondability between the electrode layer and the film is improved.
[Direct methanol fuel cell]
The direct methanol fuel cell of the present invention includes at least one electricity generating unit including at least one membrane-electrode assembly and separators located on both sides thereof; a fuel supply unit that supplies fuel to the electricity generating unit; and A direct methanol fuel cell including an oxidant supply unit that supplies an oxidant to the electricity generation unit, wherein the membrane-electrode assembly is as described above.

  As the separator used in the battery of the present invention, those used in ordinary fuel cells can be used. Specifically, carbon type or metal type can be used.

Moreover, as a member which comprises a fuel cell, it is possible to use a well-known thing without a restriction | limiting in particular. The battery of the present invention can be used as a single cell or as a stack in which a plurality of single cells are connected in series. As a stacking method, a known method can be used. Specifically, planar stacking in which single cells are arranged in a planar manner, and bipolar stacking in which single cells are stacked via separators each having a fuel or oxidant flow path formed on the back surface of the separator can be used. .
[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.
[Synthesis Example 1]
Synthesis of hydrophobic unit To a 1 L three-necked flask equipped with a stirrer, thermometer, Dean-stark tube, nitrogen inlet tube, and condenser tube, 4,91 ′ (433 mmol) of 4,4′-difluorobenzophenone, 4-chloro-4 ′ -Weighed 15.64 g (67 mmol) of fluorobenzophenone, 75.28 g (265 mmol) of 2,2-bis (3-phenyl-4-hydroxyphenyl) propane, and 44.23 g (320 mmol) of potassium carbonate. After nitrogen substitution, 313 mL of N, N-dimethylacetamide (DMAc) and 125 mL of toluene were added and stirred. The reaction solution was heated to reflux at 150 ° C. in an oil bath. Water produced by the reaction was trapped in a Dean-stark tube. After 3 hours, when almost no water was observed, toluene was removed from the Dean-stark tube out of the system. The reaction temperature was gradually raised to 165 ° C. and stirring was continued for 3 hours. Then, 7.82 g (33 mmol) of 4-chloro-4′B-fluorobenzophenone was added, and the reaction was further continued for 5 hours.

The reaction solution was allowed to cool and then poured into 2 L of methanol to precipitate the product. The precipitated product was filtered and dried to obtain 92.2 g of the desired product. The number average molecular weight (Mn) measured by GPC was 4,400.

Synthesis of copolymer (7) In a 1 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introducing tube, 18.29 g (45.5 mmol) of neopentyl 3- (2,5-dichlorobenzoyl) benzenesulfonate, the above composition 19.96 g of 4,400 (Mn) hydrophobic units obtained by unit synthesis (
4.50 mmol), bis (triphenylphosphine) nickel dichloride 1.64 g (2.50 mmol), sodium iodide 0.225 g (1.50 mmol), triphenylphosphine 5.25 g (20.0 mmol), zinc 7.84 g (120 mmol) was weighed and replaced with dry nitrogen. DMAc126mL was added here, and stirring was continued for 3 hours, keeping reaction temperature at 80 degreeC, Then, DMAc126mL was added and diluted, and the insoluble matter was filtered.

  The obtained solution was put into a 2 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, heated and stirred at 115 ° C., and 11.9 g (126.8 mmol) of lithium bromide was added. After stirring for 7 hours, the product was precipitated by pouring into 5 L of acetone. Subsequently, it was washed with 1N hydrochloric acid and pure water in this order and dried to obtain 27.0 g of the intended sulfonated polymer (1). The weight average molecular weight (Mw) of the obtained polymer was 71,000. It was confirmed that the obtained polymer was a sulfonated polymer represented by the formula (II).

[Production Example 1]
A 21 wt% N-methylpyrrolidone (NMP) / methanol solution (3/1 weight ratio) of the sulfonated polymer (1) obtained in Synthesis Example 1 was cast on a glass plate to form a film having a thickness of 30 μm. Ion exchange resin membrane (A) was obtained. The ion exchange capacity was 1.48 (meq / g), and the glass transition temperature was 161 ° C.

[Synthesis Example 2]
Synthesis of hydrophobic unit In a 1 L three-necked flask equipped with a stirrer, thermometer, Dean-stark tube, nitrogen introduction tube, and cooling tube, 51.34 g (235 mmol) of 4,4′-difluorobenzophenone, 4-chloro-4 ′ -13.8 g (59 mmol) of fluorobenzophenone, 45.17 g (159 mmol) of 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 9,9-bis (4-hydroxy-3-phenylphenyl) Weighed 53.43 g (106 mmol) of fluorene and 43.9 g (318 mmol) of potassium carbonate. After nitrogen substitution, 313 mL of N, N-dimethylacetamide (DMAc) and 125 mL of toluene were added and stirred. The reaction solution was heated to reflux at 150 ° C. in an oil bath. Water produced by the reaction was trapped in a Dean-stark tube. After 3 hours, when almost no water was observed, toluene was removed from the Dean-stark tube out of the system. The reaction temperature was gradually raised to 165 ° C. and stirring was continued for 3 hours. Then, 6.90 g (29 mmol) of 4-chloro-4′-fluorobenzophenone was added, and the reaction was further continued for 5 hours.

  The reaction solution was allowed to cool and then poured into 2 L of methanol to precipitate the product. The precipitated product was filtered and dried to obtain 118 g of the desired product. The number average molecular weight (Mn) measured by GPC was 4,400.

Synthesis of copolymer (7) In a 1 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introducing tube, 18.29 g (45.5 mmol) of neopentyl 3- (2,5-dichlorobenzoyl) benzenesulfonate, the above composition 19.96 g (4.50 mmol) of a hydrophobic unit of 4,400 (Mn) obtained by synthesis of the unit, 1.64 g (2.50 mmol) of bis (triphenylphosphine) nickel dichloride, 0.225 g of sodium iodide ( 1.50 mmol), 5.25 g (20.0 mmol) of triphenylphosphine, and 7.84 g (120 mmol) of zinc were weighed and substituted with dry nitrogen. DMAc126mL was added here, and stirring was continued for 3 hours, keeping reaction temperature at 80 degreeC, Then, DMAc126mL was added and diluted, and the insoluble matter was filtered.

  The obtained solution was put into a 2 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, heated and stirred at 115 ° C., and 11.9 g (126.8 mmol) of lithium bromide was added. After stirring for 7 hours, the product was precipitated by pouring into 5 L of acetone. Subsequently, it was washed with 1N hydrochloric acid and pure water in this order and dried to obtain 28.1 g of the target sulfonated polymer (2). The weight average molecular weight (Mw) of the obtained polymer was 82,000. It was confirmed that the obtained polymer was a sulfonated polymer represented by the formula (IV).

[Production Example 2]
A 21 wt% N-methylpyrrolidone (NMP) / methanol solution (3/1 weight ratio) of the sulfonated polymer (2) obtained in Synthesis Example 2 was cast on a glass plate to form a film having a thickness of 30 μm. Ion exchange resin membrane (B) was obtained. The ion exchange capacity was 1.45 (meq / g), and the glass transition temperature was 164 ° C.
[Example 1]
(Preparation of water repellent coated porous substrate)
Carbon paper (trade name: TGPH-060, manufactured by Toray Industries, Inc.) as a porous substrate is cut into a size of 5 cm × 5 cm, and this is placed in 30 mL of 1.2 wt% polytetrafluoroethylene resin fine particle dispersed aqueous solution for 5 minutes. After being immersed, it was dried in a 75 ° C. drying oven for 15 minutes. This substrate was baked in an electric furnace at 370 ° C. for 1 hour to produce a water repellent coated porous substrate for anode and cathode. The water repellent coating amount at this time was 2% by weight in terms of the weight ratio of the water repellent to the water repellent coated porous substrate. The moisture permeability of this water repellent coated porous substrate was measured. The results are shown in Table 1 below.
(Preparation of catalyst paste composition)
Commercially available 81% platinum / ruthenium catalyst-supported carbon (trade name: TEC81E81, Tanaka Kikinzoku Co., Ltd.) 1.2 g, a small amount of distilled water 1.4 g, DuPont 20% Nafion (registered trademark) solution 4.2 g, and isopropanol 5.0 g was mixed, and this mixture was stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch Co.) until uniform to prepare an anode catalyst paste. In the same manner, instead of platinum / ruthenium catalyst supporting carbon, 70% platinum catalyst supporting carbon (trade name: TEC10E70TPM, manufactured by Tanaka Kikinzoku Co., Ltd.) was used, and 70% platinum catalyst supporting carbon (trade name: TEC10E70TPM, Tanaka). 2.0 g of a precious metal company), 2.4 g of a small amount of distilled water, 5.2 g of a 20% Nafion (registered trademark) solution made by DuPont, and 10.2 g of isopropanol were mixed to prepare a catalyst paste for a cathode.
(Production of electrodes)
The anode catalyst paste was uniformly applied to the water repellent coated porous substrate using an applicator so that the amount of platinum deposited was 3.0 mg / cm ² , and then dried in a 75 ° C. drying oven. The electrode for anode was produced by drying for 30 minutes. Using a similar technique, the cathode catalyst paste was uniformly applied to the water repellent coated porous substrate using an applicator so that the amount of platinum deposited was 1.2 mg / cm ^2. The electrode for a cathode was produced by drying for 30 minutes in a drying oven at 0 ° C. The results of measuring the amount of catalyst and the thickness of the catalyst layer are shown in Table 1 below.
(Preparation of membrane-electrode assembly)
The ion exchange resin membrane (A) produced in Production Example 1 is sandwiched between the two types of electrodes so that the catalyst layer is in contact with the membrane, and heated at 160 ° C., 60 kgf / cm ² for 15 minutes using a hot press machine. MEA was produced by pressure heating. This MEA was incorporated into an evaluation fuel cell manufactured by Electrochem to produce a fuel cell. This fuel cell was evaluated for current-voltage characteristics by the following method.

A 1 mol / L aqueous methanol solution was supplied at a flow rate of 1.6 mL / min. Was supplied to the anode, air was supplied to the cathode at a flow rate of 285 mL / min, and the effective voltage and methanol utilization efficiency at the time of power generation were measured at a battery temperature of 70 ° C. and a current density of 200 mA / cm ² . Table 1 shows the results.
Shown in
[Example 2]
(Preparation of water repellent coated porous substrate)
In the same manner as in Example 1, a water repellent coated porous substrate was produced.
(Formation of microporous layer)
Carbon particles (trade name: Ketjen Black EC, manufactured by Lion Corporation) 2.4 g, 60 wt% polytetrafluoroethylene resin fine particle dispersion aqueous solution 6.2 g, distilled water 104.9 g, dispersant (trade name: TRITONX-100, Sigma-Aldrich) 10.3 g was mixed, and this mixture was stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch) until uniform, and the anode microporous layer forming paste was obtained. Prepared. After applying this paste uniformly using an applicator so that the weight of the microporous layer is 1.0 mg / cm ² , 7
The substrate was dried in a drying oven at 5 ° C. for 30 minutes to prepare a water repellent coated porous substrate with a microporous layer for the anode.

Using a similar method, carbon particles (trade name: Vulcan XC-72, manufactured by Cabot Corporation) 5.1 g, 60 wt% polytetrafluoroethylene resin fine particle dispersion aqueous solution 8.7 g, distilled water 43.1 g, dispersant ( (Product name: TRITON-100, Sigma-Aldrich) 5.0 g is mixed, and this mixture is stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch) until uniform, for cathode A paste for forming a microporous layer was prepared. The paste was uniformly applied using an applicator so that the weight of the microporous layer was 3.0 mg / cm ^2, and then dried for 30 minutes in a drying furnace at 75 ° C. An agent-coated porous substrate was prepared. The moisture permeability of these water-repellent-coated porous substrates with microporous layers for anode and cathode was evaluated. The results are shown in Table 1 below.
(Preparation of catalyst paste composition)
A catalyst paste composition was prepared in the same manner as in Example 1.
(Production of electrodes)
Anode and cathode electrodes were prepared in the same manner as in Example 1 except that the above-described water repellent coated porous substrate with a microporous layer for anode was used instead of the water repellent coated porous substrate. did.
(Preparation of membrane-electrode assembly)
An MEA and a fuel cell were produced in the same manner as in Example 1 except that the anode and cathode electrodes were used.

[Example 3]
Except for the amount of catalyst attached on the cathode side being 2.4 mg / cm ² , the same as in Example 1,
A membrane-electrode assembly was produced.

[Example 4]
The membrane-electrode assembly described in Example 2 was evaluated in the same manner as Example 2 except that the methanol concentration in the aqueous methanol solution was changed to 5 mol / L instead of 1 mol / L.

[Example 5]
A membrane-electrode assembly in the same manner as in Example 2 except that the ion exchange resin membrane (B) obtained in Production Example 2 was used instead of the ion exchange resin membrane (A) obtained in Production Example 1. Was made.

[Comparative Example 1]
A membrane-electrode assembly was produced in the same manner as in Example 1 except for the following electrode production method.
(Production of electrodes)
The anode catalyst paste was uniformly applied to a porous substrate that was not treated with a water repellent coating using an applicator so that the amount of platinum deposited was 3.0 mg / cm ^2.
It was dried for 30 minutes in a drying oven at 0 ° C. to produce an electrode for the anode. Using a similar method, the catalyst paste for cathode was uniformly applied to a porous substrate not subjected to a water repellent coating treatment using an applicator so that the amount of platinum deposited was 1.2 mg / cm ² . Then, it was made to dry for 30 minutes in a 75 degreeC drying furnace, and the electrode for cathodes was produced. The results of measuring the thickness of the catalyst layer at this time are shown in the following table.

[Comparative Examples 2 to 4]
(Preparation of membrane-electrode assembly)
Comparative Examples 2 to 4 were the same as Examples 2 to 4 except that the ion exchange resin membrane Nafion115 (registered trademark) manufactured by DuPont was used instead of the ion exchange resin membrane obtained in each production example. MEA was produced. That is, a DuPont ion exchange resin membrane Nafion 115 (registered trademark) is sandwiched between the two types of electrodes so that the catalyst layer is in contact with the membrane, and is heated at 160 ° C., 60 kgf / cm ² for 15 minutes. By heating under pressure, ME
A was produced. This MEA was incorporated into an evaluation fuel cell manufactured by Electrochem to produce a fuel cell.

[Comparative Example 5]
An MEA was produced in the same manner as in Example 2 except that the amount of the microporous layer forming paste applied was changed to form a microporous layer as described below.
(Formation of microporous layer)
Carbon particles (trade name: Ketjen Black EC, manufactured by Lion Corporation) 2.4 g, 60 wt% polytetrafluoroethylene resin fine particle dispersion aqueous solution 6.2 g, distilled water 104.9 g, dispersant (trade name: TRITONX-100, Sigma-Aldrich) 10.3 g was mixed, and this mixture was stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch) until uniform, and the anode microporous layer forming paste was obtained. Prepared. After applying this paste uniformly using an applicator so that the weight of the microporous layer is 18.0 mg / cm ² ,
The substrate was dried in a drying furnace at 75 ° C. for 30 minutes to prepare a water repellent coated porous substrate with a microporous layer for the anode.

Using a similar method, carbon particles (trade name: Vulcan XC-72, manufactured by Cabot Corporation) 5.1 g, 60 wt% polytetrafluoroethylene resin fine particle dispersion aqueous solution 8.7 g, distilled water 43.1 g, dispersant ( (Product name: TRITON-100, Sigma-Aldrich) 5.0 g is mixed, and this mixture is stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch) until uniform, for cathode A paste for forming a microporous layer was prepared. This paste was uniformly applied using an applicator so that the weight of the microporous layer was 0.2 mg / cm ^2, and then dried for 30 minutes in a drying oven at 75 ° C. An agent-coated porous substrate was prepared. The moisture permeability of these water-repellent-coated porous substrates with microporous layers for anode and cathode was evaluated. The results are shown in Table 1 below.
[Comparative Example 6]
An MEA was produced in the same manner as in Example 2 except that the amount of the microporous layer forming paste applied was changed to form a microporous layer as described below.
(Formation of microporous layer)
Carbon particles (trade name: Ketjen Black EC, manufactured by Lion Corporation) 2.4 g, 60 wt% polytetrafluoroethylene resin fine particle dispersion aqueous solution 6.2 g, distilled water 104.9 g, dispersant (trade name: TRITONX-100, Sigma-Aldrich) 10.3 g was mixed, and this mixture was stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch) until uniform, and the anode microporous layer forming paste was obtained. Prepared. After applying this paste uniformly using an applicator so that the weight of the microporous layer is 0.1 mg / cm ² , 7
It was dried in a drying oven at 5 ° C. for 30 minutes to produce a water repellent coated porous substrate with a microporous layer for the anode.

Using a similar method, carbon particles (trade name: Vulcan XC-72, manufactured by Cabot Corporation) 5.1 g, 60 wt% polytetrafluoroethylene resin fine particle dispersion aqueous solution 8.7 g, distilled water 43.1 g, dispersant ( (Product name: TRITON-100, Sigma-Aldrich) 5.0 g is mixed, and this mixture is stirred using a planetary ball mill (trade name: P-5, manufactured by Fritsch) until uniform, for cathode A paste for forming a microporous layer was prepared. The paste was uniformly applied using an applicator so that the weight of the microporous layer was 16.0 mg / cm ^2, and then dried for 30 minutes in a drying oven at 75 ° C. An agent-coated porous substrate was prepared. The moisture permeability of these water-repellent-coated porous substrates with microporous layers for anode and cathode was evaluated. The results are shown in Table 2 below.

The schematic of the measuring apparatus used for moisture permeability measurement by this invention is shown.

Claims (10)

A membrane-electrode assembly for a direct methanol fuel cell comprising an aromatic ion exchange resin membrane, a catalyst layer containing at least a catalyst-supporting carbon and an ion exchange resin electrolyte, and a gas diffusion layer,
The aromatic ion exchange resin membrane is composed of a polyarylene polymer comprising a structural unit represented by the following formula (5) and a structural unit represented by the following formula (6): A membrane-electrode assembly for a direct methanol fuel cell, characterized by:

[In formula (5), T is represented by the following formula (2) and includes at least a structure represented by the following formula (3).

A and C are independently a direct bond, or —CO—, —SO ₂ , —SO—, —CONH—, —C
OO—, — (CF ₂ ) ₁ — (1 is an integer of 1 to 10), — (CH ₂ ) ₁ — (1 is an integer of 1 to 10), —CR ′ ₂ — (R ′ is An aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, -O-, -S-, and at least one structure selected from the group consisting of ,
B is independently an oxygen atom or a sulfur atom,
D represents a 2,2-propylidene group or a 1,1-cyclohexylidene group represented by the following formula (4).

R ^{1 to} R ¹⁶ may be the same as or different from each other, and may be a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group in which some or all are halogenated, an allyl group, an aryl group, a nitro group. , Represents at least one atom or group selected from the group consisting of nitrile groups.
R ¹⁷ and R ¹⁸ may be the same or different except for a hydrogen atom, and each represents a hydrogen atom, a methyl group, an isopropyl group, an isobutyl group, a t-butyl group, or a cyclohexyl group.
s and t represent an integer of 0 to 4, and r represents an integer of 1 or more. ].

[In the formula (6), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (
CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), at least one structure selected from the group consisting of —C (F ₃ ) —
Z is a direct bond or at least one selected from the group consisting of — (CH ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O—, and —S—. Show the structure of the species,
Ar represents an aromatic group having a substituent represented by —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H.
p shows the integer of 1-12, m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4. ]. ^2. The direct methanol fuel cell membrane-electrode junction according to claim 1, wherein a coating amount of the platinum catalyst contained in the anode-side catalyst layer is 0.7 mg / cm ² or more and 8.0 mg / cm ² or less. body.   The membrane-electrode assembly for a direct methanol fuel cell according to claim 1 or 2, wherein the cathode-side catalyst layer has a thickness of 5 to 100 µm.   The membrane-electrode assembly for a direct methanol fuel cell according to any one of claims 1 to 3, wherein the thickness of the catalyst layer on the anode side is 5 to 100 µm. In the membrane-electrode assembly for a direct methanol fuel cell, a gas diffusion layer on at least one side of an aromatic ion exchange resin membrane is composed of a porous base material, and repelling is performed between the porous base material and the catalyst layer. The membrane-electrode assembly for a direct methanol fuel cell according to any one of claims 1 to 4, further comprising a microporous layer made of liquid medicine and carbon powder. In the membrane-electrode assembly for a direct methanol fuel cell, the gas diffusion layer on at least one side of the aromatic ion exchange resin membrane is composed of a water repellent-coated porous substrate, and the porous substrate, the catalyst layer, A membrane-electrode assembly for a direct methanol fuel cell according to any one of claims 1 to 5, further comprising a microporous layer made of a water repellent and carbon powder. The gas diffusion layer on the cathode side of the aromatic ion exchange resin membrane in the membrane-electrode assembly for a direct methanol fuel cell is composed of a water repellent-coated porous base material. The membrane-electrode assembly for direct methanol fuel cells. The membrane-electrode for a direct methanol fuel cell according to any one of claims 1 to 7, wherein the gas permeability of the gas diffusion layer on the anode side is 800 g / m ² / h to 3000 g / m ² / h. Joined body. The membrane-electrode for a direct methanol fuel cell according to any one of claims 1 to 8, wherein the gas diffusion layer on the cathode side has a water vapor transmission rate of 500 g / m ² / h to 2500 g / m ² / h. Joined body. At least one electricity generator including at least one membrane-electrode assembly and separators located on both sides thereof;
A fuel supply unit for supplying fuel to the electricity generation unit;
And a direct methanol fuel cell including an oxidant supply unit for supplying an oxidant to the electricity generation unit,
A direct methanol fuel cell, wherein the membrane-electrode assembly is one according to any one of claims 1 to 9.

Images