JP5144023B2 - Membrane-electrode assembly - Google Patents

Description

  The present invention relates to a membrane-electrode assembly constituting a solid polymer fuel cell and the like.

The polymer electrolyte fuel cell is configured as a unit in which a cell in which an anode electrode and a cathode electrode are disposed on both sides of a solid polymer electrolyte membrane and both sides are sandwiched between separators.
The electrode includes an electrode base material that promotes gas diffusion and collects current, and a catalyst layer that actually becomes an electrochemical reaction field. Specifically, in the anode electrode, the fuel gas reacts in the catalyst layer to generate protons and electrons, the electrons are conducted to the electrode base material and sent to the external circuit, and the protons are passed through the electrode electrolyte to the solid polymer electrolyte membrane. Conducted to. On the other hand, in the cathode electrode, the oxidizing gas in the catalyst layer, protons conducted from the solid polymer electrolyte membrane, and electrons conducted from the electrode substrate through an external circuit react to generate water.

  Examples of the electrolyte in the polymer solid electrolyte membrane and electrode used in the polymer electrolyte fuel cell as described above include perfluoro electrolytes represented by Nafion (registered trademark, manufactured by DuPont) and various hydrocarbon electrolytes. (Non-perfluoro-based electrolytes) are known, but these all require water in the electrolyte in order to exhibit proton conductivity. On the other hand, it is known that solid polymer fuel cells have higher power generation efficiency as the operating temperature increases.

  When the operating conditions are in a highly humid state, proton conductivity is improved. However, water generated during power generation stays in the porous electrode, or the electrolyte having a proton acid group swells and the pores are easily blocked, and a flooding phenomenon in which the reactive gas cannot reach the catalyst occurs. As a result, there arise problems that the reaction efficiency is lowered and sufficient output cannot be obtained. On the other hand, if the operating condition is a low humidity state, the flooding phenomenon does not occur, but water in the electrolyte necessary for proton conductivity is insufficient, which causes a decrease in the output of the fuel cell. Fuel cells are expected to be used as power sources for automobiles and as distributed power generators. However, fuel gas humidifiers are simplified and non-humidified, and power is generated for a long time even at higher temperatures (100 ° C or higher). It was desired that the output could be maintained.

  In addition, the applicant of the present invention is a method of providing a gradient in the ion exchange capacity (protonic acid group concentration) of the polymer electrolyte used for the anode electrode catalyst layer and the cathode electrode catalyst layer, that is, ion exchange of the ion exchange resin used for the anode electrode catalyst layer. An attempt was made to increase the capacity by 0.05 meq / g or more compared to the ion exchange capacity of the ion exchange resin used for the cathode electrode catalyst layer, but it was still necessary to make improvements.

  That is, an object of the present invention is to provide a fuel cell having a combination of an anode electrode catalyst layer and a cathode electrode catalyst layer capable of maintaining an appropriate wet state in a long-term power generation operation and excellent in maintaining an output voltage for a long time. It is in providing the membrane-electrode assembly obtained.

  The present inventors have intensively studied in view of the above problems in the prior art. As a result, by paying attention to the weight of F atoms contained in the polymer constituting the polymer electrolyte constituting the anode electrode catalyst layer and the cathode electrode catalyst layer, the amount of such F is in a specific relationship, It has been found that the joined body can be maintained in an appropriate wet state to improve the power generation characteristics and the power generation durability under high temperature and low humidity conditions.

That is, the configuration of the membrane-electrode assembly according to the present invention is as follows.
[1] An electrode-membrane assembly comprising a polymer electrolyte membrane, an anode electrode catalyst layer containing at least catalyst particles and a polymer electrolyte on both sides thereof, and a cathode electrode catalyst layer containing at least catalyst particles and a polymer electrolyte. Any one of the polymer electrolytes used for the anode electrode catalyst layer and the cathode electrode catalyst layer has a high fluorine content defined by the ratio of the total weight of fluorine atoms contained in the polymer electrolyte of less than 0 to 40% by weight. A membrane-electrode assembly, which is a molecular electrolyte and the other is a polymer electrolyte having a fluorine content of 40% by weight or more.

  By setting it as such a structure, the membrane-electrode assembly which can hold | maintain a suitable wet state and was excellent in the output maintenance on the high temperature low humidity conditions for a long time is obtained. Although the reason for this is not clear, the polymer electrolyte in the electrode catalyst layer having a fluorine content of 0 to less than 40% by weight is water-retaining, and the polymer electrolyte in the electrode catalyst layer having a fluorine content of 40% by weight or more As a role to play, it is drainage, and by using this combination, moderate water can be retained inside the membrane-electrode assembly, and it should be performed in a form suitable for long-term power generation operation under high temperature and low humidity conditions. I think you can.

  When a polymer electrolyte having a fluorine content of 0 to less than 40% by weight is used on the anode side and a polymer electrolyte having a fluorine content of 40% by weight or more is used on the cathode side, the polymer electrolyte having a fluorine content of less than 0 to 40% by weight is Proton ions generated in step (b) have water retention so that the ion can be optimally and stably diffused to the cathode through the polymer electrolyte membrane, and the polymer electrolyte having a fluorine content of 40% by weight or more has diffused to the cathode. Thus, it is possible to obtain a membrane-electrode assembly having drainage so that water generated by the side oxidation reaction is optimally and stably discharged out of the system and no flooding occurs.

Conversely, when a polymer electrolyte having a fluorine content of 40% by weight or more is used on the anode side and a polymer electrolyte having a fluorine content of 0 to less than 40% by weight is used on the cathode side, the polymer electrolyte having a fluorine content of 40% by weight or more is It has a drainage property so that water diffused back to the anode side from the cathode side without disturbing diffusion of proton ions generated on the cathode side to the cathode side can be optimally and stably discharged out of the system, and a fluorine content of 0 to 40 A polymer electrolyte of less than% by weight can provide a membrane-electrode assembly having water retention capacity that can optimally and stably retain water necessary for the oxidation reaction occurring on the cathode side.
[2] The membrane-electrode assembly according to [1], wherein the difference in fluorine content of the polymer electrolyte used for the anode electrode catalyst layer and the cathode electrode catalyst layer is 20% by weight or more.
[3] The polymer electrolyte having a fluorine content of 0 to less than 40% by weight used for either the anode electrode catalyst layer or the cathode electrode catalyst layer is a protonic acid group-containing aromatic polymer [1] or [ 2] Membrane-electrode assembly.
[4] The membrane-electrode assembly according to [3], wherein the protonic acid group-containing aromatic polymer is a sulfonic acid group-containing polyarylene having a structure represented by the following general formula (1).

[In the formula (1), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, —
(CF ₂ ) _i — (i represents an integer of 1 to 10) or —C (CF ₃ ) ₂ —, Z is independently a direct bond, — (CH ₂ ) _j — (j is 1 to Represents an integer of 10.), —C (CH ₃ ) ₂ —, —O— or —S—, and Ar represents —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF _{2) p} SO ₃ H _(p represents an aromatic group having a substituent represented by indicating.) an integer of 1 to 12, m represents an integer of 0, n is an integer of 0 K represents an integer of 1 to 4.

A and D are each independently a direct bond, —CO—, —SO ₂ —, —SO—, —CON
H—, —COO—, — (CF ₂ ) _i — (i represents an integer of 1 to 10), — (CH ₂ ) _j — (j represents an integer of 1 to 10), —CR ′. _2- (R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, —O— or —S—, and B is independently An oxygen atom or a sulfur atom, and R ^{1 to} R ¹⁶
Each independently represents a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group partially or wholly halogenated, an allyl group, an aryl group, a nitro group or a nitrile group, and s and t are each 0 to 4 represents an integer, and r represents 0 or an integer of 1 or more. ]
Z represents a direct bond or at least one structure selected from the group consisting of —O— and —S—, and Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO. −, − (CF ₂ ) _l −
(L is an integer of 1 to 10), and represents at least one structure selected from the group consisting of —C (CF ₃ ) ₂ —, and R ²⁰ represents a nitrogen-containing heterocyclic group. q represents an integer of 1 to 5, and p represents an integer of 0 to 4.

x, y, z represents a molar ratio when x + y + z = 100 mol%. ]
[5] The polymer electrolyte having a fluorine content of 40% by weight or more,
At least one perfluoroolefin selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, perfluoroalkoxy vinyl ether as a monomer;
_{CF 2 = CF- (OCF 2 CFX} ) m -O q - (CF 2) n -A ( wherein m = 0~3, n = 0~12, q = 0 or 1, X = F or CF _3, A = a sulfonic acid group, a carboxylic acid group, a phosphonic acid group or a phosphoric acid group) and a film of [1] to [4], which is a copolymer with at least one of the fluorovinyl compounds shown below An electrode assembly.
CF ₂ = CFO (CF ₂ ) _1-8 A
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _1-8 A
CF ₂ = CF (CF ₂ ) _0-8 A
CF ₂ = CF (OCF ₂ CF (CF ₃ )) _1-5 O (CF ₂ ) ₂ A
[6] A polymer electrolyte having a fluorine content of 0 to less than 40% by weight is contained in the anode side electrode catalyst,
The membrane-electrode assembly according to any one of [1] to [5], wherein a polymer electrolyte having a fluorine content of 40% by weight or more is contained in the cathode side electrode catalyst.
[7] The membrane-electrode assembly according to [1] to [6], wherein the polymer electrolyte having a fluorine content of less than 0 to 40% by weight contains a water repellent.
[8] The water repellent is
(A) a fluorine-containing copolymer having a structural unit derived from (meth) acrylate containing a polyfluoroalkyl group, and
(B) Fluorine-containing compound having a structural unit represented by the following general formula (2) derived from a fluorine-containing olefin monomer and a structural unit represented by the following general formula (3) derived from a vinyl ether monomer. [7] The membrane-electrode assembly according to [7], comprising at least one selected from the group consisting of copolymers.

[In Formula (2), X ¹ is a fluorine atom, a fluoroalkyl group or a group represented by —OW ¹ (W ¹
Represents an alkyl group or a fluoroalkyl group. ). ]

[In the formula (3), X ² represents a hydrogen atom or a methyl group, and X ³ represents a group represented by — (CH ₂ ) _h OW ² (W ² represents an alkyl group, a hydroxyalkyl group, a glycidyl group or a fluoroalkyl group. H represents an integer of 0 to 2), a group represented by -OCOW ³ (W ³ represents an alkyl group, a hydroxyalkyl group or a glycidyl group), a carboxyl group or an alkoxycarbonyl group. . ]

  The membrane-electrode assembly of the present invention is suitable for long-term power generation operation under high temperature conditions by making the polymer electrolyte used for the anode electrode catalyst layer different from the polymer electrolyte used for the cathode electrode catalyst layer. Water retention, drainage and water repellency can be maintained. Therefore, if the membrane-electrode assembly of the present invention is used, a fuel cell exhibiting excellent power generation characteristics can be obtained.

Hereinafter, the membrane-electrode assembly according to the present invention will be described in detail.
The membrane-electrode assembly of the present invention comprises a polymer electrolyte membrane, and anode-side electrode catalyst layers and cathode-side electrode catalyst layers containing catalyst particles and polymer electrolyte, which are formed on both surfaces of the membrane.

  In the present invention, one of the polymer electrolytes constituting the anode side electrode catalyst layer and the cathode side electrode catalyst layer is a polymer electrolyte having a fluorine content of 0 to less than 40% by weight, and the other is a fluorine content of 40% by weight or more. As a polymer electrolyte.

  Thus, by using polymer electrolytes having different structures for the anode-side polymer electrolyte and the cathode-side electrolyte, the wet state of the membrane-electrode assembly can be maintained appropriately, and power generation characteristics and long-term power generation operation can be maintained. Power generation durability performance is improved.

  Among these, a membrane-electrode assembly using a polymer electrolyte having a fluorine content of 0 to less than 40% by weight on the anode side and a polymer electrolyte having a fluorine content of 40% by weight or more on the cathode side is capable of long-term power generation under high temperature and low humidity conditions. It is preferable in terms of output maintenance. Although the detailed reason is unknown, when a low-humidity hydrogen-containing fuel gas is supplied under high-temperature conditions, the polymer electrolyte having a fluorine content of 0 to less than 40% by weight is used as the anode-side electrolyte. It is thought that it is easier to retain water than a polymer electrolyte of wt% or more, and to suppress a decrease in output due to drying.

The difference in fluorine content of the polymer electrolyte between the anode-side and cathode-side electrode catalyst layers is desirably 20% by weight or more, preferably 30% by weight or more.
[Electrocatalyst layer]
The electrode catalyst layer constituting the membrane-electrode assembly of the present invention is composed of catalyst particles and a polymer electrolyte.
<Catalyst particles>
The catalyst particles consist of a catalyst supported on carbon or a metal oxide carrier, or a single catalyst.

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

The catalyst forms catalyst particles, either alone or supported on a carrier.
As the carrier for supporting the catalyst, carbon black such as oil furnace black, channel black, lamp black, thermal black and acetylene black is preferably used in view of the electron conductivity and the specific surface area. Further, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin, and the like may be used.

  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 form of these carbons, in addition to particles, fibers can also be used. The amount of the catalyst supported on the carbon is not particularly limited as long as it can effectively exhibit the catalytic activity, but the supported amount is 0.1 to 9.0 g- Metal / g-carbon, preferably in the range of 0.25 to 2.4 g-metal / g-carbon.

In addition to carbon, the carrier may be a metal oxide such as titania, zinc oxide, silica, ceria, alumina, alumina spinel, magnesia, zirconia, and the like.
<Ion exchange resin with a fluorine content of 0 to less than 40% by weight>
The ion exchange resin having a fluorine content of 0 to less than 40% by weight used in the electrode paste composition has an aromatic main chain skeleton used in engineer plastics and the like from the viewpoint of improving heat resistance and mechanical strength. Protonic acid group-containing aromatic polymers can be suitably used.

  The protonic acid group in the protonic acid group-containing aromatic polymer is preferably an ionic group such as a sulfonic acid group, a carboxylic acid group, a phosphonic acid group or a phosphoric acid group, and contains at least one or more of these. Is used. Among these, a sulfonic acid group is most preferable because it is excellent in proton conduction efficiency in the fuel cell.

  The main chain skeleton in the protonic acid group-containing aromatic polymer includes polyether ether ketone, polyether sulfone, polyimide, polybenzo having a skeleton formed by covalently bonding aromatic rings excellent in heat resistance and mechanical strength. Those containing at least one selected from the group consisting of oxazole and polyarylene are used. Among these, those having a polyarylene main chain skeleton excellent in heat resistance, mechanical strength, and oxidation stability in the fuel cell are preferable.

  As the sulfonic acid group-containing polyarylene, preferably, a polymer segment (A) having a sulfonic acid group, a polymer segment (B) not having an ion conductive component, and a segment having a nitrogen-containing heterocyclic group (C) ) Are covalently bonded block copolymers, and particularly preferably a structural unit represented by the following general formula (A) (hereinafter also referred to as “structural unit (A)” or “sulfonic acid unit”). And a structural unit represented by the following general formula (B) (hereinafter also referred to as “structural unit (B)” or “hydrophobic unit”), and a structural unit represented by the following general formula (C) (hereinafter referred to as “structural unit (B)”). , Which is also referred to as “structural unit (C)” or “basic unit”), and a polyarylene having a sulfonic acid group represented by the following general formula (D).

  (Sulfonic acid unit)

... (A)
In the above formula (A), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—.
_{, - (CF 2) i -} (i is an integer from 1 to 10.) Or -C (CF _{3) 2} - shows a. Of these, —CO— and —SO ₂ — are preferable.

Z independently represents a direct bond, — (CH ₂ ) _j — (j represents an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O— or —S—. Among these, a direct bond and —O— are preferable.

Ar is —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p is 1 to
An integer of 12 is shown. The aromatic group which has a substituent represented by this is shown. Examples of the aromatic group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and the like. In these, a phenyl group and a naphthyl group are preferable. Ar represents —SO ₃ H;
It is necessary to have at least one substituent represented by —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H, and two in the case of a naphthyl group It is preferable to have the above.

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 preferred structure of the structural unit (A), in the above formula (A),
(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 substituents;
(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 structures.

  (Hydrophobic unit)

In the above formula (B), A and D are each independently a direct bond, —CO—, —SO ₂ —, —
SO—, —CONH—, —COO—, — (CF ₂ ) _i — (i represents an integer of 1 to 10), — (CH ₂ ) _j — (j represents an integer of 1 to 10) , -CR _'2 -, showing cyclohexylidene group, a fluorenylidene group, -O- or -S-. Among these, a direct bond, —CO—, —SO ₂ —, —CR ′ ₂ —, a cyclohexylidene group, a fluorenylidene group, and —O— are preferable. R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group. For example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, A propyl group, an octyl group, a decyl group, an octadecyl group, a phenyl group, a trifluoromethyl group, etc. are mentioned.

B independently represents an oxygen atom or a sulfur atom, preferably an oxygen atom.
R ^{1 to} R ¹⁶ each independently represent a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group, an allyl group, an aryl group, a nitro group or a nitrile group, which is partially or wholly halogenated.

Examples of the alkyl group in R ^{1 to} R ¹⁶ 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. Examples of the aryl group include a phenyl group and a pentafluorophenyl group.

s and t each represent an integer of 0 to 4. r shows 0 or an integer greater than or equal to 1, and an upper limit is 100 normally, Preferably it is 1-80.
As a preferred structure of the structural unit (B), in the above formula (B),
(1) s = 1, t = 1, A is —CR ′ ₂ —, a cyclohexylidene group or a fluorenylidene group, B is an oxygen atom, and D is —CO— or —SO ₂ —. , R ^{1 to} R ¹⁶ are hydrogen atoms or fluorine atoms,
(2) A structure in which s = 1, t = 0, B is an oxygen atom, D is —CO— or —SO ₂ —, and R ^{1 to} R ¹⁶ are hydrogen atoms or fluorine atoms,
(3) s = 0, t = 1, A is —CR ′ ₂ —, a cyclohexylidene group or a fluorenylidene group, B is an oxygen atom, and R ^{1 to} R ¹⁶ are a hydrogen atom, a fluorine atom or Examples thereof include a structure that is a nitrile group.
(Basic unit)

In the formula, Z represents a direct bond or at least one structure selected from the group consisting of —O— and —S—, and Y represents —CO—, —SO ₂ —, —SO—, —CONH—. _{, -COO -, - (CF 2} ) l - (l is an integer of 1 to _{10), - C (CF 3)} 2 - represents at least one structure selected from the group consisting of, R ²⁰ is A nitrogen-containing heterocyclic group is shown. q represents an integer of 1 to 5, and p represents an integer of 0 to 4.

  The nitrogen-containing heterocyclic group is not particularly limited, but pyrrole, thiazole, isothiazole, oxazole, isoxazole, pyridine, imidazole, imidazoline, pyrazole, 1,3,5-triazine, pyrimidine, pyritazine, pyrazine, Derived from a compound selected from the group consisting of nitrogen-containing heterocyclic compounds consisting of indole, quinoline, isoquinoline, bryne, benzimidazole, benzoxazole, benzthiazole, tetrazole, tetrazine, triazole, carbazole, acridine, quinoxaline, quinazoline and their derivatives Or at least one kind of group which may be used in combination.

  (Polymer structure)

In the above formula (D), A, B, D, Y, Z, Ar, k, m, n, r, s, t and R ^{1 to} R ¹⁶ are represented by the above formulas (A), (B) and (C ) And x, y, and z represent molar ratios when x + y + z = 100 mol%.

    The structural units (B) and (C) are optional components, and the remainder excluding (A) in the polymer corresponds to the amount of the structural units (B) and (C). Moreover, (B) and (C) may not be included. When this structural unit (B) is included, it is easy to adjust the molecular weight, the content of each repeating unit, the ion exchange amount, and the like, while suppressing swelling and elution in hot water, , A thermally and chemically stable polymer can be obtained. By including the structural unit (C), the stability of the sulfonic acid group under high temperature conditions is improved by the action of the nitrogen-containing heterocyclic group, and as a result, the heat resistance is improved. Since the nitrogen atom of the nitrogen-containing heterocyclic aromatic compound has basicity, it forms an ionic interaction with the sulfonic acid group. This enhances the stability of the sulfonic acid group and suppresses the elimination of the sulfonic acid group under high temperature conditions. Similarly, the cross-linking reaction between polymer molecules derived from sulfonic acid groups can be suppressed under high temperature conditions. The nitrogen-containing heterocyclic aromatic compound is a compound having an adequately strong basicity that can exhibit these effects without impairing proton conductivity.

  The above-mentioned ion exchange capacity can be adjusted by changing the type, usage ratio, and combination of the structural unit (A), the structural unit (B), and the structural unit (C). Therefore, it can be adjusted by changing the charge amount ratio and type of the precursor (monomer / oligomer) for deriving the structural units (A) to (C) during the polymerization. If the ion exchange capacity of the polymer electrolyte having a fluorine content of less than 0 to 40% by weight is too low, proton conductivity in the fuel cell cannot be expressed and sufficient output cannot be obtained. On the other hand, if it is too high, the hot water generated in the fuel cell will clog the pores due to dissolution and swelling, thereby preventing the reactive gas from reaching the catalyst and reducing the power generation output. Preferably, it is 0.5 to 3.0 meq / g, more preferably 0.8 to 2.8 meq / g.

In the formula (D), the ratio of the repeating structural unit represented by the formula (C) to the repeating structural unit represented by the formula (A), that is, the unit of [] _x , that is, the unit of [] _z. (z / x) is 0.001 mol% to 50 mol%, preferably 0.1 mol% to 3 mol
It is 0 mol%, More preferably, it is 1 mol%-25 mol%.

The molecular weight of the polymer 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).
(Method for producing sulfonated polyarylene)
For the production of a polymer having a sulfonic acid group, for example, the following three methods, Method A, Method B and Method C, can be used.

(Method A)
For example, similarly to the method described in JP-A-2004-137444, a monomer represented by the following general formula (A ′), a monomer represented by the following general formula (B ′), and the following general formula (C ′) To produce a polymer having a sulfonic acid ester group, deesterifying the sulfonic acid ester group, and converting the sulfonic acid ester group into a sulfonic acid group. it can.

Monomer (A ')

In the formula (A ′), X represents an atom or group selected from a chlorine atom, a bromine atom and —OSO ₂ Rb (where Rb represents an alkyl group, a fluorine-substituted alkyl group or an aryl group).
Y, Z, Ar, m, n, and k are the same as those in formula (A), and R represents an alkyl group having 4 to 12 carbon atoms.

  Specific examples of the compound represented by the general formula (A ′) include a compound represented by the following general formula, JP-A Nos. 2004-137444, 2004-345997, and 2004-346163. Mention may be made of the sulfonic acid esters described in the publication.

In the compound represented by the general formula (A ′), the sulfonate structure is usually bonded to the meta position of the aromatic ring.
Monomer (B ')

R ′ and R ″ represent an atom or group selected from a chlorine atom, a bromine atom and —OSO ₂ Rb (where Rb represents an alkyl group, a fluorine-substituted alkyl group or an aryl group).
R ^{1 to} R ¹⁶ , A, B, D, s, t, and r are the same as those in the general formula (B).

As specific examples of the monomer (B ′), when r in the general formula (B ′) is 0, for example, 4,4′-dichlorobenzophenone, 4,4′-dichlorobenzanilide, 2,2-bis (4-
Chlorophenyl) difluoromethane, 2,2-bis (4-chlorophenyl) -1,1,1,3,3,3-hexafluoropropane, 4-chlorobenzoic acid-4-chlorophenyl ester, bis (4-chlorophenyl) sulfoxide Bis (4-chlorophenyl) sulfone, 2,6
-Dichlorobenzonitrile. In these compounds, a compound in which a chlorine atom is replaced with a bromine atom or an iodine atom is exemplified.

  Further, when r in the general formula (B ′) is 1, the following compounds and compounds described in JP-A-2003-113136 can be exemplified.

  When r in the general formula (B ′) is r ≧ 2, for example, compounds having the following structures can be given.

Monomer (C ')

X represents an atom or group selected from a chlorine atom or a bromine atom, and -OSO ₂ Rb (wherein Rb represents an alkyl group, a fluorine-substituted alkyl group or an aryl group).
Y, Z, R ²⁰ , p and q are the same as in the general formula (C).

  Specific examples of the monomer (C) include the following compounds.

Furthermore, compounds in which a chlorine atom is replaced with a bromine atom, and isomers having different bonding positions of chlorine and bromine atoms can be exemplified. In addition, a compound in which a —CO— bond is replaced with a —SO ₂ — bond can be exemplified. These compounds may be used alone or in combination of two or more.

  Examples of the method for synthesizing the monomer (C ′) include a method in which a compound represented by the following general formula (4) and a nitrogen-containing heterocyclic compound are subjected to a nucleophilic substitution reaction.

In the formula, X, Y, p and q are the same as those defined in the general formula (C ′).
X ′ represents a halogen atom. A fluorine atom or a chlorine atom is preferable, and a fluorine atom is more preferable.

Specific examples of the compound represented by the general formula (4) include 2,4-dichloro-4′-fluorobenzophenone, 2,5-dichloro-4′-fluorobenzophenone, and 2,6-dichloro-4′-fluoro. Benzophenone, 2,4-dichloro-2'-fluorobenzophenone, 2,5-dichloro-2'-fluorobenzophenone, 2,6-dichloro-2'-fluorobenzophenone, 2,4-dichlorophenyl-4'-fluorophenylsulfone , 2, 5
-Dichlorophenyl-4'-fluorophenylsulfone, 2,6-dichlorophenyl-4'-fluorophenylsulfone, 2,4-dichlorophenyl-2'-fluorophenylsulfone, 2,4-dichlorophenyl-2'-fluorophenylsulfone, 2, , 4-Dichlorophenyl-2'-fluorophenylsulfone.
Of these compounds, 2,5-dichloro-4'-fluorobenzophenone is preferred.

The nitrogen-containing heterocyclic compound has active hydrogen, and this active hydrogen is subjected to a substitution reaction with the group represented by X ′ of the compound represented by the general formula (4).
Examples of the nitrogen-containing heterocyclic compound having active hydrogen include pyrrole, thiazole, isothiazole, oxazole, isoxazole, pyridine, imidazole, imidazoline, pyrazole, 1,3,5-triazine, pyrimidine, pyritazine, pyrazine, indole, quinoline, Isoquinoline, bromine, benzimidazole, benzoxazole, benzthiazole, tetrazole, tetrazine, triazole, carbazole, acridine, quinoxaline, quinazoline, 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, 3-hydroxyquinoline, 8-hydroxy Quinoline, 2-hydroxypyrimidine, 2-mercaptopyridine, 3-mercaptopyridine, 4-mercaptopyridine, 2-mercaptopyrimidine, 2-me , And the like mercapto benzthiazole.

Of these compounds, pyrrole, imidazole, indole, carbazole, benzoxazole, and benzimidazole are preferable.
The reaction between the compound represented by the general formula (4) and the nitrogen-containing heterocyclic compound having active hydrogen is preferably performed in an organic solvent. A polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, sulfolane, diphenylsulfone, dimethylsulfoxide is used. In order to accelerate the reaction, alkali metal, alkali metal hydride, alkali metal hydroxide, alkali metal carbonate, or the like is used. The ratio of the compound represented by the general formula (2) to the nitrogen-containing heterocyclic compound having active hydrogen is such that the nitrogen-containing heterocyclic compound having equimolar or active hydrogen is added in excess. Specifically, the nitrogen-containing heterocyclic compound having active hydrogen is preferably used in an amount of 1 to 3 times mol, particularly 1 to 1.5 times mol of the compound represented by the general formula (4).

The reaction temperature is 0 ° C to 300 ° C, preferably 10 ° C to 200 ° C. The reaction time is 15 minutes to 100 hours, preferably 1 hour to 24 hours.
The product is preferably used after being purified by a method such as recrystallization.
Polymerization In order to obtain the polymer, the monomer (A ′), the monomer (C ′) and, if necessary, the monomer (B ′) are first copolymerized to obtain a precursor.

This copolymerization is carried out in the presence of a catalyst. The catalyst used at this time is a catalyst system containing a transition metal compound, and this catalyst system is (1) a transition metal salt and a ligand. Compound(
Hereinafter, it is referred to as “ligand component”. ), Or transition metal complexes with ligands coordinated (including copper salts)
As well as (2) a reducing agent as an essential component, and in order to further increase the polymerization rate, a “salt” may be added.

  As specific examples of these catalyst components, the use ratio of each component, reaction solvent, concentration, temperature, time, and other polymerization conditions, the compounds and conditions described in JP-A No. 2001-342241 can be employed.

For example, as the transition metal salt, nickel chloride, nickel bromide and the like are preferably used, and as the compound serving as a ligand, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, Tri-p-tolylphosphine, tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, 2,2'-bipyridine and the like are preferably used. Furthermore, nickel chloride bis (triphenylphosphine) and nickel chloride (2,2′bipyridine) are preferably used as the transition metal (salt) in which the ligand is coordinated in advance. Examples of the reducing agent include iron, zinc, manganese, aluminum, magnesium, sodium, and calcium, and zinc, magnesium, and manganese are preferable. As the “salt”, sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferable. A polymerization solvent may be used for the reaction, and specifically, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, 1-methyl-2-pyrrolidone and the like are preferably used.
The proportion of each component used in the catalyst system is usually from 0.0001 to 10 mol, preferably from 0.0001 to 10 mol, based on 1 mol of the total amount of monomers of the transition metal salt or the transition metal (salt) coordinated with the ligand. 01-0.5 mol. If it exists in this range, it can polymerize with high catalyst activity and high molecular weight. When “salt” is used in the catalyst system, the amount used is generally 0.001 to 100 mol, preferably 0.01 to 1 mol, per 1 mol of the total amount of monomers. Within such a range, the effect of increasing the polymerization rate is sufficient. The total concentration of monomers in the polymerization solvent is usually 1 to 90% by weight, preferably 5 to 40% by weight. Moreover, the polymerization temperature at the time of superposing | polymerizing a polymer is 0-200 degreeC normally, Preferably it is 50-100 degreeC. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 40 hours.

Next, the obtained polymer is hydrolyzed to convert the sulfonic acid ester group (—SO ₃ R) in the structural unit into a sulfonic acid group (—SO ₃ H).
Hydrolysis includes (1) a method in which the polymer having a sulfonic acid ester group is added to an excess amount of water or alcohol containing a small amount of hydrochloric acid, and the mixture is stirred for 5 minutes or longer. A method in which a polymer having an acid ester group is reacted at a temperature of about 80 to 120 ° C. for about 5 to 10 hours, (3) 1 to 3 mol per mol of the sulfonic acid ester group (—SO ₃ R) in the polymer After the polymer having a sulfonic acid ester group is reacted at a temperature of about 80 to 150 ° C. for about 3 to 10 hours in a solution containing double moles of lithium bromide, such as N-methylpyrrolidone, hydrochloric acid is added. It can be performed by the method of doing.

(Method B)
For example, similar to the method described in JP-A-2001-342241, the above general formula (A ′)
And a monomer having no sulfonic acid group or sulfonic acid ester group, the monomer (B ′) and the monomer (C ′) are copolymerized, and the polymer is sulfonated. It can also be synthesized by sulfonation using an agent.

  As specific examples of the monomer having no sulfonic acid group or sulfonic acid ester group that can be a structural unit represented by the above general formula (A) that can be used in Method B, JP-A-2001-342241, Mention may be made of the dihalides described in JP-A-2002-29389.

(Method C)
In the general formula (A), when Ar is an aromatic group having a substituent represented by —O (CH ₂ ) _h SO ₃ H or —O (CF ₂ ) _h SO ₃ H, for example, Similarly to the method described in Japanese Patent Application Laid-Open No. 2005-606254, a precursor monomer that can be a structural unit represented by the general formula (A), and a monomer that can be a structural unit represented by the general formula (B), Alternatively, it can be synthesized by a method in which an oligomer and a monomer as a structural unit represented by the above general formula (C) are copolymerized, and then an alkylsulfonic acid or a fluorine-substituted alkylsulfonic acid is introduced.

Specific examples of precursor monomers that can be used in (Method C) and can be structural units represented by the above general formula (A) include dihalides described in JP-A-2005-36125. Can be mentioned. Specifically, 2,5-dichloro-4′-hydroxybenzophenone, 2,4-dichloro-4′-hydroxybenzophenone, 2,6-dichloro-4′-hydroxybenzophenone, 2,5-dichloro-2 ′, Examples thereof include 4′-dihydroxybenzophenone and 2,4-dichloro-2 ′, 4′-dihydroxybenzophenone. Moreover, the compound which protected the hydroxyl group of these compounds by the tetrahydropyranyl group etc. can be mention | raise | lifted. Further, those in which a hydroxyl group is replaced with a thiol group and those in which a chlorine atom is replaced with a bromine atom or an iodine atom can also be mentioned.

(Method C) A method of introducing an alkyl sulfonic acid group into a precursor polymer (having no sulfonic acid group) by the method described in JP-A-2005-60625. For example, it can be introduced by reacting the hydroxyl group of the precursor polymer with propane sultone, butane sultone, or the like.
<Polymer electrolyte with fluorine content of 40% by weight or more>
The polymer electrolyte having a fluorine content of 40% by weight or more used in the present invention is not particularly limited, but one having the following structure is used.

  A sulfonic acid group, a carboxylic acid group, or a phosphonic acid group, which is an ionic group having a proton content of 40% by weight or more and a fluorine content in a proportion of fluorine atom weight contained in the total weight in the polymer electrolyte And those containing phosphate groups are used. Among these, perfluoroalkyl type sulfone resins having a sulfonic acid group having excellent chemical stability and excellent proton conductivity are preferably used.

Examples of the polymer used in the polymer electrolyte include at least one perfluoroolefin such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroalkoxy vinyl ether, and CF ₂ ═CF— (OCF ₂ CFX _{) m -O q - (CF 2} ) n -A ( wherein m = 0~3, n = 0~12, q = 0 or 1, X = F or CF _3, A = a sulfonic acid group, a carboxylic acid group , A phosphonic acid group or a phosphoric acid group) and the following fluorovinyl compound CF ₂ ═CFO (CF ₂ ) _1-8 A
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _1-8 A
CF ₂ = CF (CF ₂ ) _0-8 A
CF ₂ = CF (OCF ₂ CF (CF ₃ )) _1-5 O (CF ₂ ) ₂ A
A perfluoroalkyl sulfonic acid resin characterized by being a copolymer with at least one of them.

  If the ion exchange capacity of the polymer electrolyte having a fluorine content of 40% by weight or more is too low, proton conductivity in the fuel cell cannot be expressed and sufficient output cannot be obtained. On the other hand, if it is too high, the hot water generated in the fuel cell will clog the pores due to dissolution and swelling, thereby preventing the reactive gas from reaching the catalyst and reducing the power generation output. Preferably, it is 0.5 to 3.0 meq / g, more preferably 0.8 to 2.8 meq / g.

Although it does not specifically limit as a perfluoroalkyl-type sulfonic acid resin, Nafion (R) (DuPont), Flemion (R) (Asahi Glass), Aciplex (R) (
Asahi Kasei) and the like are preferable.

The ion exchange resin having a fluorine content of 0 to less than 40% by weight may contain a water repellent in the electrode catalyst layer.
<Water repellent>
The water repellent used in the electrode catalyst layer of the present invention is
(A) a fluorine-containing copolymer having a structural unit derived from (meth) acrylate containing a polyfluoroalkyl group (hereinafter referred to as “fluorine-containing copolymer (a)”), and
(B) A structural unit represented by the following general formula (5) derived from a fluorine-containing olefin monomer (hereinafter also referred to as “structural unit (5)”), and a general formula ( 6) selected from the group consisting of a fluorine-containing copolymer (hereinafter referred to as “fluorine-containing copolymer (b)”) having the structural unit (hereinafter also referred to as “structural unit (6)”). Contains at least one.

In formula (5), X ¹ is a fluorine atom, a fluoroalkyl group or a group represented by —OW ¹ (W ¹
Represents an alkyl group or a fluoroalkyl group. ).

In Formula (6), X ² represents a hydrogen atom or a methyl group, and X ³ represents a group represented by — (CH ₂ ) _h OW ² (W ² represents an alkyl group, a hydroxyalkyl group, a glycidyl group, or a fluoroalkyl group. H represents an integer of 0 to 2), a group represented by -OCOW ³ (W ³ represents an alkyl group, a hydroxyalkyl group or a glycidyl group), a carboxyl group or an alkoxycarbonyl group.
“(Meth) acrylate” includes both “acrylate” and “methacrylate”.
Hereinafter, the fluorine-containing copolymers (a) and (b) will be described more specifically.

<Fluorine-containing copolymer (a)>
The fluorine-containing copolymer (a) is a polyfluoroalkyl group (hereinafter referred to as “R ^f group”).
Having a structural unit derived from (meth) acrylate.

Here, the R ^f group refers to a group in which two or more hydrogen atoms of an alkyl group are substituted with fluorine atoms. 1-20 are preferable and, as for carbon number of ^Rf group, 4-16 are especially preferable. The R ^f group may have either a linear structure or a branched structure, and in the case of a branched structure, it is preferable that the branched portion is present at the terminal portion of the R ^f group. A part of carbon atoms of the R ^f group may be substituted with an etheric oxygen atom or a thioetheric sulfur atom. Further, the R ^f group may contain a halogen atom other than a fluorine atom (for example, a chlorine atom).

The R ^f group is preferably a perfluoroalkyl group in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms from the viewpoint of easy water repellency imparting to the electrode catalyst layer.
As the R ^f group-containing (meth) acrylate used for producing the fluorine-containing copolymer (a), a compound represented by the following general formula (7) is preferable.
CH ₂ = C (R) COO-QR ^f (7)
In formula (7), R represents a hydrogen atom or a methyl group. Q represents a divalent organic group, preferably an alkylene group and a divalent organic group containing an alkylene group, and more preferably an alkylene group. Specifically, —CH ₂ CH ₂ —, —CH (CH ₃ ) CH ₂ —, —CH ₂ CH ₂ N (CH ₃ ) CO—, —CH ₂ CH ₂ N (CH ₃ ) SO ₂ —, — CH (CH ₂ Cl) CH ₂ OCH ₂ CH ₂ N (CH ₃ ) SO ₂ — and the like are preferable.

As described above, R ^f is preferably a perfluoroalkyl group, and particularly a linear structure of perfluoroalkyl group represented by C _n F _{2n + 1} — (wherein n represents an integer of 4 to 16, preferably 6 to 12). A fluoroalkyl group is preferred.

As the R ^f group-containing (meth) acrylate represented by the above formula (7), for example,
CH ₂ = CRCOOCH ₂ CH ₂ R ^f ,
CH ₂ = CRCOOCH (CH ₃ ) CH ₂ R ^f ,
CH ₂ = CRCOOCH ₂ CH ₂ N (CH ₃ ) COR ^f ,
CH ₂ = CRCOOCH ₂ CH ₂ N (C ₂ H ₅ ) COR ^f ,
CH ₂ = CRCOOCH ₂ CH ₂ N (C ₃ H ₇ ) COR ^f ,
_{CH 2 = CRCOOCH 2 CH 2 N} (CH 3) SO 2 R f,
_{CH 2 = CRCOOCH 2 CH 2 N} (C 2 H 5) SO 2 R f,
_{CH 2 = CRCOOCH 2 CH 2 N} (C 3 H 7) SO 2 R f,
_{CH 2 = CRCOOCH (CH 2 Cl} ) CH 2 OCH 2 CH 2 N (CH 3) SO 2 R f
However, the present invention is not limited to these.

The R ^f group-containing (meth) acrylate may be used alone or in combination of two or more. Moreover, you may use together 2 or more types of compounds from which carbon number of ^Rf group differs.
The fluorine-containing copolymer (a), for the purpose of, for example, adjusting the fluorine content in the polymer, R ^f
It is preferable to contain a polymerization unit derived from a monomer other than the group-containing (meth) acrylate (hereinafter referred to as “other monomer”).

  As said other monomer, the monomer which has a radically polymerizable unsaturated bond is preferable. Specifically, vinyl chloride, stearyl (meth) acrylate, ethylene, vinyl acetate, vinyl fluoride, halogenated vinyl styrene, α-methyl styrene, p-methyl styrene, (meth) acrylic acid, alkyl (meth) acrylate Esters, polyoxyalkylene (meth) acrylates, (meth) acrylamides, diacetone (meth) acrylamides, N-methylol (meth) acrylamides, vinyl alkyl ethers, halogenated alkyl vinyl ethers, vinyl alkyl ketones, butadiene, isoprene, chloroprene, glycidyl ( (Meth) acrylate, aziridinyl (meth) acrylate, benzyl (meth) acrylate, 2-isocyanatoethyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl ( Data) acrylate, maleic anhydride, having a polysiloxane (meth) acrylate, etc. N- vinyl carbazole. Among these, vinyl chloride and stearyl (meth) acrylate are particularly preferable (from the viewpoint of improving water repellency).

The polymer unit derived from the R ^f group-containing (meth) acrylate in the fluorine-containing copolymer (a) is contained in the range of 25 to 100% by weight, preferably 30 to 85% by weight of the polymer (a). It is desirable. When the content of the polymerization unit derived from the R ^f group-containing (meth) acrylate is within the above range, the electrode catalyst layer is excellent in the balance of water repellency and water retention, and good in both low humidity and high humidity conditions. Power generation performance can be obtained.

The fluorine-containing copolymer (a) is produced using the R ^f group-containing (meth) acrylate and, if necessary, other monomers, appropriately employing known or well-known polymerization methods and conditions. Can do.

  Examples of the polymerization method include a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and a solution polymerization. Moreover, in addition to radical polymerization reaction, it can also manufacture by polymerization reactions, such as a radiation polymerization reaction and a photopolymerization reaction. In particular, an emulsion polymerization method using a radical polymerization reaction is preferable.

  In the case of applying the emulsion polymerization method, a method in which a monomer, a surfactant and the like are emulsified in the presence of water and then polymerized by stirring is preferably employed. Further, a method in which a monomer, a surfactant, water and the like are preliminarily emulsified using an emulsifier such as a homogenizer and then polymerized with stirring is preferably employed.

  As the polymerization initiator, various polymerization initiators such as organic acid peroxides, azo compounds and persulfates are preferable. In addition, as the surfactant, various anionic, cationic, amphoteric or nonionic surfactants can be used.

  The number average molecular weight (Mn) of the fluorine-containing copolymer (a) used in the present invention is preferably 1,000 to 100,000, particularly preferably 10,000 to 100,000. If the Mn of the fluorinated copolymer (a) is lower than the above range, it becomes difficult to impart water repellency to the electrode catalyst layer, and it tends to be difficult to obtain good power generation performance under high humidity conditions. On the other hand, when the Mn of the fluorinated copolymer (a) exceeds the above range, the viscosity of the electrode paste is remarkably increased and it tends to be difficult to produce an electrode catalyst layer.

<Fluorine-containing copolymer (b)>
The fluorine-containing copolymer (b) includes the structural unit (5) and the structural unit (6), preferably a structural unit derived from a monomer containing a hydroxyl group (hereinafter referred to as “hydroxyl group-containing structural unit”). Further).

Examples of the fluoroalkyl group in X ¹ in the structural unit (5) include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluorohexyl group, and a perfluorocyclohexyl group. A C1-C6 fluoroalkyl group is mentioned. Examples of the alkyl group for W ¹ include a methyl group,
C1-C6 alkyl groups, such as an ethyl group, a propyl group, a butyl group, a hexyl group, a cyclohexyl group, etc. are mentioned. Examples of the fluoroalkyl group in W ¹ include the same fluoroalkyl groups as in X ¹ .

Examples of the alkoxycarbonyl group for X ³ in the structural unit (6) include a methoxycarbonyl group and an ethoxycarbonyl group. Examples of the fluoroalkyl group for W ² in the structural unit (6) include the same fluoroalkyl groups for X ¹ in the structural unit (5). The alkyl group in W ² and W ³ in the structural unit (6) in, for example, mentioned a methyl group, an ethyl group, a propyl group, a hexyl group, a cyclohexyl group, an alkyl group having 1 to 12 carbon atoms such as lauryl group It is done. Examples of the hydroxyalkyl group in W ² and W ³ include 2-hydroxyethyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 3-hydroxybutyl group, and 5-hydroxypentyl. Group, 6-hydroxyhexyl group and the like.

Examples of the fluorine-containing olefin monomer that can be the structural unit (5) include compounds having at least one polymerizable unsaturated double bond group and at least one fluorine atom. Specifically, fluoroolefins such as tetrafluoroethylene, hexafluoropropylene and 3,3,3-trifluoropropylene;
Alkyl perfluorovinyl ethers or fluoroalkyl perfluorovinyl ethers represented by the general formula CF ₂ ═CF—O—W ¹ (W ¹ is as defined above);
Perfluoro (alkyl vinyl ether) s such as perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), perfluoro (butyl vinyl ether), perfluoro (isobutyl vinyl ether); perfluoro (propoxypropyl vinyl ether) Perfluoro (alkoxyalkyl vinyl ethers) such as

  The said fluorine-containing olefin type monomer may be used individually by 1 type, or may use 2 or more types together. Among the fluorine-containing olefin monomers, hexafluoropropylene, perfluoroalkyl perfluorovinyl ether and perfluoro (alkoxyalkyl vinyl ether) are preferable, and it is more preferable to use these in combination.

  Content of the structural unit (5) in the said fluorine-containing copolymer (b) is 20-70 mol%, Preferably it is 25-60 mol%, More preferably, it is 30-55 mol%. If the content of the structural unit (5) is lower than the above range, the electrode catalyst layer tends to have poor drainage properties, and thus good power generation performance may not be obtained under high humidity conditions. On the other hand, when the above range is exceeded, the solubility of the obtained fluorinated copolymer (b) in an organic solvent is remarkably lowered, and it may be difficult to produce a uniform electrode paste composition.

As a vinyl ether monomer that can be the structural unit (6), for example,
Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, n-dodecyl vinyl ether, 2-ethylhexyl Alkyl vinyl ethers or cycloalkyl vinyl ethers such as vinyl ether and cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl stearate, etc .; methyl (meta ) Acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, (Meth) acrylic acid esters such as butyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2- (n-propoxy) ethyl (meth) acrylate; (meth) acrylic Examples thereof include carboxyl group-containing compounds such as acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid.

  Content of the structural unit (6) in the said fluorine-containing copolymer (b) is 5-70 mol%, Preferably it is 10-60 mol%, More preferably, it is 20-50 mol%. When the content of the structural unit (6) is lower than the above range, the water retention in the electrode tends to be inferior, and thus good power generation performance may not be obtained under low humidity conditions. On the other hand, if the above range is exceeded, the drainage of the electrode catalyst layer tends to be inferior, and thus good power generation performance may not be obtained under high humidity conditions.

  Examples of the monomer containing a hydroxyl group that can be a hydroxyl group-containing structural unit include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 5 Hydroxyl group-containing vinyl ethers such as hydroxypentyl vinyl ether and 6-hydroxyhexyl vinyl ether; hydroxyl group-containing allyl ethers such as 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether and glycerol monoallyl ether; allyl alcohol; ) Acrylic acid ester and the like. These compounds may be used alone or in combination of two or more.

  In the said fluorine-containing copolymer (b), content of a hydroxyl-containing structural unit is 5-70 mol%, Preferably it is 10-60 mol%, More preferably, it is 20-50 mol%. When the content of the hydroxyl group-containing structural unit is lower than the above range, the water retention in the electrode tends to be inferior, and thus good power generation performance may not be obtained under low humidity conditions. On the other hand, if the above range is exceeded, the drainage of the electrode catalyst layer tends to be inferior, and thus good power generation performance may not be obtained under high humidity conditions.

  In the production of the fluorine-containing copolymer (b), when the monomer containing the hydroxyl group is used, from the viewpoint of increasing the yield in the polymerization reaction, the vinyl ether monomers are alkyl vinyl ethers, cycloalkyl vinyl ethers. It is preferable to use carboxylic acid vinyl esters or carboxyl group-containing compounds. In particular, from the viewpoint of increasing the fluorine content copolymerized in the fluorine-containing copolymer (B), for example, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, vinyl acetate, vinyl propionate, vinyl butyrate, pivalin. Low molecular weight monomers such as vinyl acid are preferred.

  The fluorine-containing copolymer (b) has a fluorine content of 30 to 70% by weight, preferably 40 to 60% by weight. If the fluorine content is lower than the above range, the water repellency of the electrode catalyst layer may be reduced, and good power generation performance may not be obtained under high humidity conditions. On the other hand, if the fluorine content exceeds the above range, the electrode catalyst layer The water retention is reduced, and good power generation performance may not be obtained under low humidity conditions. In addition, the said fluorine content measures the weight of a fluorine atom by the Alizari complexone method.

  Mn of the fluorine-containing copolymer (b) is a value in terms of polystyrene measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent, and is 5,000 to 500,000, preferably 10,000. To 300,000, more preferably 10,000 to 100,000. If Mn is smaller than the above range, the water repellency of the electrode catalyst layer is lowered, and good power generation performance may not be obtained under high humidity conditions, whereas if it exceeds the above range, the viscosity of the electrode paste composition is increased, The production of the electrode catalyst layer may be difficult.

  The polymerization mode for producing the fluorine-containing copolymer (b) may be any of emulsion, suspension, bulk or solution polymerization in the presence of a radical polymerization initiator, and may be batch, semi-continuous or continuous. The operation can be selected as appropriate. As the radical polymerization initiator, azo group-containing polysiloxane can be used, but other radical initiators can also be used in combination.

Examples of other radical polymerization initiators that can be used in combination include:
Diacyl peroxides such as acetyl peroxide and benzoyl peroxide;
Ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; hydroperoxides such as hydrogen peroxide, tert-butyl hydroperoxide and cumene hydroperoxide; di-tert-butyl peroxide, dicumyl peroxide, di Dialkyl peroxides such as lauroyl peroxide; peroxy esters such as tert-butyl peroxyacetate and tert-butyl peroxypivalate; azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile; Persulfates such as ammonium sulfate, sodium persulfate, potassium persulfate; perfluoroethyl iodide, perfluoropropyl iodide, perfluorobutyl iodide, (Perful (Robutyl) ethyl iodide, perfluorohexyl iodide, 2- (perfluorohexyl) ethyl iodide, perfluoroheptyl iodide, perfluorooctyl iodide, 2- (perfluorooctyl) ethyl iodide, perfluorodecyl iodide Dide, 2- (perfluorodecyl) ethyl iodide, heptafluoro-2-iodopropane, perfluoro-3-methylbutyl iodide, perfluoro-5-methylhexyl iodide, 2- (perfluoro-5-methyl Hexyl) ethyl iodide, perfluoro-7-methyloctyl iodide, 2- (perfluoro-7-methyloctyl) ethyl iodide, perfluoro-9-methyldecyl iodide, 2- (perfluoro-9 Methyldecyl) ethyl iodide, 2,2,3,3-tetrafluoropropyl iodide, 1H, H, 5H-octafluoropentyl iodide, 1H, 1H, 7H-dodecafluoroheptyl iodide, tetrafluoro-1,2 -An iodine-containing fluorine compound such as diiodoethane, octafluoro-1,4-diiodobutane, dodecafluoro-1,6-diiodohexane, and the like can be given.

  In addition, the radical polymerization initiator may be used in combination with an inorganic reducing agent such as sodium hydrogen sulfite and sodium pyrosulfite, and an organic reducing agent such as cobalt naphthenate and dimethylaniline as necessary.

The production of the fluorinated copolymer (b) is preferably carried out in a solvent system using a solvent. Examples of the solvent include esters such as ethyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, and cellosolve; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; cyclic ethers such as tetrahydrofuran and dioxane; N Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; aromatic hydrocarbons such as toluene and xylene, etc., and alcohols and aliphatic hydrocarbons may be mixed as necessary. Can also be used.
<Dispersant>
You may add a dispersing agent to an electrode catalyst layer further as needed. This dispersant is added in order to enhance the dispersibility of each component when forming the electrode catalyst layer.

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 alkyl amine 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 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 used for forming the electrode catalyst layer, the storage stability and fluidity are excellent, and the productivity during coating is improved.
<Carbon fiber>
The electrode catalyst layer used in the present invention may further contain carbon fibers 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 carbon fiber is included, the pore volume in the electrode catalyst layer increases, so that the diffusibility of fuel gas and oxygen gas is improved, and flooding due to the generated water can be improved, and the power generation performance is improved. .

The carbon fiber may be contained in one or both of the anode-side and cathode-side electrode catalyst layers.
The electrode catalyst layer constituting the electrode-membrane assembly of the present invention contains the above catalyst particles in an amount of 20 to 90% by weight, preferably 40 to 85% by weight, and 5% of the above polymer electrolyte (copolymer). It is contained in a range of ˜60% by weight, preferably 10 to 50% by weight. When the electrode catalyst phase contains a water repellent, the water repellent is contained in an amount of 0 to 20% by weight, preferably 1 to 10% by weight. The dispersant used as necessary is contained in the range of 0 to 10% by weight, preferably 0 to 3% by weight, and the carbon fiber used as necessary is 0 to 20% by weight, preferably It is desirable to contain in the range of 1 to 10% by weight (note that the total of these is 100% by weight).

  When the content of the catalyst particles is lower than the above range, the electrode reaction rate may be reduced. When the content exceeds the above range, the proton conductivity efficiency may be reduced, and power generation performance may be reduced in the electrode catalyst layer. There is a tendency that a sufficient pore volume cannot be secured. If the content of the polymer electrolyte is lower than the above range, the proton conductivity tends to decrease, and the electrode may not be formed because it cannot function as a binder. The pore volume inside tends to decrease. When the content of the water repellent is within the above range, the wet state in the catalyst layer can be appropriately maintained, and the power generation output is improved.

  When the content of the dispersant is within the above range, an electrode paste having excellent storage stability can be obtained, and an electrode catalyst layer in which each component is uniformly dispersed can be formed. When the carbon fiber is within the above range, the pore volume is appropriately secured, the drainage is good, and the power generation output is improved.

[Formation of electrode catalyst layer]
The electrode catalyst layer (anode side and cathode side) is formed using, for example, an electrode paste composition in which the above components are dispersed. Specifically, it contains carbon carrying the catalyst, a polymer electrolyte, and an organic solvent, and optionally contains a water repellent, a dispersant, carbon fiber, water, and the like.
<Organic solvent>
Examples of the organic solvent used in the electrode paste composition include 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-methylcyclo Hexanol, 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, dairy Methyl acid, ethyl butyrate, 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 (NMP), tetramethylurea, toluene And hydrocarbon organic solvents such as xylene, heptane and octane, and polyhydric alcohol organic solvents such as ethylene glycol, propylene glycol and glycerol.

The organic solvent may be used alone or in combination of two or more, but preferably contains a water-soluble aprotic dipolar organic solvent from the viewpoint of solubility of the ion exchange resin. More preferably, it is desirable to contain 10% or more of a water-soluble aprotic dipolar organic solvent.

Examples of the water-soluble aprotic dipolar organic solvent include dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, tetramethylurea, 1,3-dimethyl-2-imidazolide. Non-, γ-butyrolactone and the like can be mentioned.
<Water>
You may add water to the said electrode paste composition further as needed. By adding water, there is an effect of reducing heat generation when preparing the catalyst paste composition.
<Composition>
In the electrode paste composition, the composition of the catalyst particles, the ion exchange resin, the water repellent, the dispersant and the carbon fiber is blended in such an amount as to form the above composition when the electrode catalyst layer is formed. The amount of the organic solvent used in preparing the electrode catalyst paste composition is 5 to 95% by weight, preferably 15 to 90% by weight, when the paste composition is 100% by weight. Yes, the amount of water used as necessary is 0 to 70% by weight, preferably 2 to 30% by weight.

When the amount of the organic solvent used is within the above range, the composition becomes a paste and is suitable for handling. When the amount of water used is within the above range, heat generation during preparation of the catalyst paste can be efficiently reduced.
<Preparation method>
The electrode paste composition can be prepared, for example, by mixing the above components at a predetermined ratio and kneading them 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 method>
The electrode catalyst layer constituting the electrode-membrane assembly of the present invention may be formed by applying the electrode paste composition onto an electrode substrate, a transfer substrate or a polymer electrolyte membrane described later and drying. it can.

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

  As the electrode substrate, an electrode substrate generally used for a fuel cell, for example, a porous conductive sheet mainly composed of a conductive substance can be used without particular limitation. As the transfer substrate, a polytetrafluoroethylene (PTFE) sheet, a glass plate or a metal plate whose surface is treated with a release agent, and the like can be used.

  Examples of the conductive material 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 the porous conductive sheet using inorganic conductive fibers, any structure of woven fabric and non-woven fabric 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 fibers are used as such a fabric, a woven fabric obtained by carbonizing or graphitizing a plain fabric using a flame-resistant spun yarn, and processing the nonwoven fabric by a needle punch method, a water jet punch method, or the like, Carbonized or graphitized nonwoven fabrics, flame-resistant yarns, mat nonwoven fabrics made by paper making using carbonized yarns or graphitized yarns, and the like are preferable. For example, Toray carbon paper TGP series, SO series, E-TEK carbon cloth, etc. are preferably used.

It is also preferable to add conductive particles such as carbon black or conductive fibers such as carbon fibers as an auxiliary agent to the porous conductive sheet in order to improve conductivity.
The thickness of the coating film applied as described above (that is, the thickness of the electrode catalyst layer) is not particularly limited, but the metal supported as a catalyst is 0.05 to 4.0 mg / cm per application unit area. ² , preferably in the range of 0.1 to 2.0 mg / cm ² in the electrocatalyst layer. Within this range, sufficiently high catalytic activity is exhibited and protons can be efficiently extracted.

  The removal of the solvent after the application of the electrode paste composition is performed at a drying temperature of 20 to 180 ° C., preferably 50 to 160 ° C., and a drying time of 5 to 180 minutes, preferably 30 to 120 minutes. Moreover, it can also remove by water immersion as needed. As water immersion conditions, the water immersion temperature is 5 to 120 ° C., preferably 15 to 95 ° C., and the water immersion time is 1 minute to 72 hours, preferably 5 minutes to 48 hours.

The pore volume of the electrode catalyst layer thus obtained is 0.1 to 3.0 mL / g- (electrode catalyst layer), preferably 0.2 to 2.0 mL / g- (electrode catalyst layer). . When the pore volume exceeds the above range, the mechanical properties tend to be lowered, and the electron conduction and proton conduction paths are cut, and the power generation performance may be lowered. On the other hand, if the pore volume is lower than the above range, the water discharge performance is poor and the power generation performance may be lowered.
[Polymer electrolyte membrane]
The polymer electrolyte membrane constituting the membrane-electrode assembly of the present invention is not particularly limited, and a known polymer electrolyte membrane can be used. It is preferable to use an electrolyte. More preferably, as described above, a protonic acid group-containing aromatic polymer is preferable, and still more preferable is a sulfonated polyarylene having a structure as described above. The ion exchange capacity of the ion exchange resin is 0.3 to 5.0 meq / g, preferably 0.5 to 4.0 meq / g.

  The polymer electrolyte of either the anode electrode catalyst layer or the cathode electrode catalyst layer has a high fluorine content defined by the proportion of the total weight of fluorine atoms contained in the polymer electrolyte being less than 0 to 40% by weight. A molecular electrolyte is used, and on the other hand, a protonic acid group-containing aromatic polymer having a fluorine content of 40% by weight or more is used. At this time, the difference in fluorine content of the polymer electrolyte used for the anode electrode catalyst layer and the cathode electrode catalyst layer is preferably 20 wt% or more, more preferably 30 wt% or more. With such a difference, the effect of the present invention becomes more apparent, and high water retention, drainage, and water repellency can be maintained even during long-term power generation operation under high temperature conditions. In the present invention, it is desirable that a polymer electrolyte having a fluorine content of 0 to less than 40% by weight is contained in the anode side electrode catalyst, and a polymer electrolyte having a fluorine content of 40% by weight or more is contained in the cathode side electrode catalyst. With this configuration, the generated water moves smoothly from the anode side to the cathode side, and the diffusibility of the cathode gas and the discharge of the generated water are promoted. Therefore, the concentration overvoltage is reduced and the high voltage is increased. It can be taken out.

  For the polymer electrolyte membrane using the sulfonated polyarylene, for example, a composition containing an organic solvent similar to that exemplified as the organic solvent used in the electrode paste composition is prepared, and this composition is applied to the substrate. It can be produced by a casting method in which the film is cast into a film shape. In addition to the polymer electrolyte and the organic solvent, the composition may contain an inorganic acid such as sulfuric acid and phosphoric acid, an organic acid containing a carboxylic acid, an appropriate amount of water, and the like.

  The polymer concentration in the composition is usually 5 to 40% by weight, preferably 7 to 25% by weight, although it depends on the molecular weight of the polymer electrolyte. If the polymer concentration is lower than the above range, it is difficult to increase the film thickness, and pinholes tend to be easily generated. On the other hand, if the polymer concentration exceeds the above range, the solution viscosity is too high to form a film, and the surface smoothness is reduced. May lack sexuality.

The solution viscosity of the above composition depends on the molecular weight of the copolymer and the polymer concentration.
000 to 100,000 mPa · s, preferably 3,000 to 50,000 mPa · s. If the solution viscosity is lower than the above range, the retention of the solution during processing is poor and may flow from the substrate.On the other hand, if it exceeds the above range, the viscosity is too high to be extruded from the die, Film formation by the casting method may be difficult.

  The above composition is prepared by, for example, mixing the above-described components at a predetermined ratio and mixing them using a conventionally known method, for example, a mixer such as a wafer blower, a homogenizer, a disperser, a paint conditioner, or a ball mill. Can do.

  The substrate is not particularly limited as long as it is a substrate used in a usual solution casting method. For example, a substrate made of plastic or metal is used, and preferably a thermoplastic resin such as a polyethylene terephthalate (PET) film. A substrate is used. Moreover, the said electrode catalyst layer can also be used as a base | substrate.

After film formation by the above casting method, a polymer electrolyte membrane can be obtained by drying at a temperature of 30 to 160 ° C., preferably 50 to 150 ° C. for 3 to 180 minutes, preferably 5 to 120 minutes. The dry film thickness is usually 10 to 100 μm, preferably 20 to 80 μm. If the solvent remains in the membrane after drying, the solvent may be removed by water extraction as necessary. In addition to the polymer electrolyte, the polymer electrolyte membrane may contain an inorganic acid such as sulfuric acid and phosphoric acid, an organic acid containing a carboxylic acid, an appropriate amount of water, and the like.
[Method for producing membrane-electrode assembly]
The membrane-electrode assembly according to the present invention can be produced by forming the electrode catalyst layer on both surfaces of the polymer electrolyte membrane.

  As a method of forming the electrode catalyst layer on both surfaces of the polymer electrolyte membrane, for example, a method of forming the electrode paste composition by directly applying the electrode paste composition on the polymer electrolyte membrane and drying the electrode paste composition, An electrode having an electrode catalyst layer is prepared by coating on an electrode substrate and drying, and the obtained electrode and the polymer electrolyte membrane are hot pressed so that the electrode catalyst layer side is in contact with the polymer electrolyte membrane. And a method of applying the electrode paste composition onto another base material (transfer base material) to form an electrode catalyst layer and then transferring it onto the polymer electrolyte membrane or the electrode base material. It is done.

The conditions of the hot press are as follows: the temperature is 30 ° C. to 200 ° C., preferably 40 ° C. to 180 ° C., the pressure is 5 to 300 kg / cm ² , preferably 10 to 180 kg / cm ² , and the time is 30 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.

Moreover, when joining gas diffusion layers, such as carbon paper, on the said electrode catalyst layer, an electrode catalyst layer and a gas diffusion layer can be joined by the hot press conditions similar to the above. [Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. The ion exchange capacity and molecular weight were measured as follows.
1. Ion exchange capacity A polymer electrolyte membrane and a membrane composed of polymer electrolyte components constituting each electrode catalyst layer are prepared, and a predetermined amount is weighed and phenolphthalein dissolved in a tetrahydrofuran (THF) / water mixed solvent is used as an indicator. Titration was performed using a standard solution of NaOH, and the ion exchange capacity was determined from the neutralization point.
2. Molecular weight The molecular weight of polyarylene having no sulfonic acid group was determined by GPC using polystyrene (THF) as a solvent and the molecular weight in terms of polystyrene. The molecular weight of the polyarylene having a sulfonic acid group was determined by GPC using polystyrene as a molecular weight using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added.
"Synthesis of sulfonated polyarylene"
A synthesis example of a sulfonated polyarylene having a fluorine content of 0 to 40% by weight and preferably used as a sulfonic acid group-containing aromatic polymer according to the present invention will be described. The present invention is not particularly limited to the following synthesis examples, but when these sulfonated polyarylenes are used as a polymer electrolyte in an electrode or a polymer electrolyte membrane, a fuel cell exhibiting good power generation characteristics is obtained. Can do.
[Synthesis Example 1] (1) Synthesis of hydrophobic unit 48.8 g (284 mmol) of 2,6-dichlorobenzonitrile was added to a 1 L three-necked flask equipped with a stirrer, thermometer, Dean-Stark tube, nitrogen introduction tube, and cooling tube. ), 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane (89.5 g, 266 mmol) and potassium carbonate (47.8 g, 346 mmol). After nitrogen substitution, 346 mL of sulfolane and 173 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 200 ° C. and stirring was continued for 3 hours. Then, 9.2 g (53 mmol) of 2,6-dichlorobenzonitrile was added, and the reaction was further continued for 5 hours.

The reaction solution was allowed to cool, and diluted with 100 mL of toluene. Inorganic salts insoluble in the reaction solution were filtered, and the filtrate was poured into 2 L of methanol to precipitate the product. The precipitated product was filtered and dried, then dissolved in 250 mL of tetrahydrofuran, and poured into 2 L of methanol for reprecipitation. The precipitated white powder was filtered and dried to obtain 109 g of the desired product. The number average molecular weight (Mn) measured by GPC was 9,500.
It was confirmed that the obtained compound was an oligomer represented by the formula (I).

(2) Synthesis of sulfonated polyarylene 135.2 g (337 mmol) of neopentyl 3- (2,5-dichlorobenzoyl) benzenesulfonate was added to a 1 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, (1) 48.7 g (5.1 mmol) of the hydrophobic unit of Mn 9,500 obtained in the above, 6.71 g (10.3 mmol) of bis (triphenylphosphine) nickel dichloride, 1.54 g (10.3 mmol) of sodium iodide, 35.9 g (137 mmol) of phenylphosphine and 53.7 g (821 mmol) of zinc were weighed and replaced with dry nitrogen. 430 mL of N, N-dimethylacetamide (DMAc) was added thereto, and stirring was continued for 3 hours while maintaining the reaction temperature at 80 ° C. Then, 730 mL of DMAc was added for dilution, and insoluble matters were filtered off.

  The obtained solution was put into a 2 L three-necked flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube. The mixture was heated and stirred at 115 ° C., and 44 g (506 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 then dried to obtain 122 g of the target polymer. The weight average molecular weight (Mw) of the obtained polymer was 135,000. The obtained polymer is presumed to be a sulfonated polymer represented by the formula (II). The ion exchange capacity of this polymer was 2.3 meq / g.

[Synthesis Example 2]
(1) Synthesis of basic unit
Synthesis of 2,5-dichloro-4 '-(1-imidazolyl) benzophenone

In a 2 L three-necked flask equipped with a stirrer, a thermometer, a condenser tube, and a nitrogen inlet tube, 150.7 g (0.560 mol) of 2,5-dichloro-4′-fluorobenzophenone, imidazole 114
. 4 g (1.68 mol), 100.6 g (0.728 mol) of potassium carbonate, and 840 ml of N, N′-dimethylacetamide were weighed. The reaction solution was heated at 110 ° C. for 2 hours using an oil bath in a nitrogen atmosphere. After confirming disappearance of the raw material by thin layer chromatography, the reaction solution was allowed to cool to room temperature. Thereafter, the reaction solution was gradually added to 3 L of water to coagulate the product and filtered. The product obtained by filtration was dissolved in THF (1.2 L), and toluene (4
After adding L), it was washed with brine until the aqueous layer was neutral. After the organic layer was dried with magnesium sulfate, the solvent was distilled off by an evaporator. The crude yield was 180 g. Recrystallization isolation operation was performed using a mixed solvent of 1 L of toluene heated to 80 ° C. and 20 ml of methanol to obtain 155 g of white solid (III) in a yield of 87%.
(2) Synthesis of sulfonated polyarylene 540 mL of dried N, N-dimethylacetamide (DMAc) was added to 135.0 g (336 mmol) of neopentyl 3- (2,5-dichlorobenzoyl) benzenesulfonate (Synthesis Example 1). ), 40.7 g (5.6 mmol) of the hydrophobic unit (I) synthesized with 2,5-dichloro-4 ′-(1-imidazolyl) benzophenone of the basic unit (III).
71 g (16.8 mmol), bis (triphenylphosphine) nickel dichloride 6.71 g (10.3 mmol), triphenylphosphine 35.9 g (137 mmol), sodium iodide 1.54 g (10.3 mmol), A mixture of 53.7 g (821 mmol) of zinc was added under nitrogen.

  The reaction system was heated with stirring (finally heated to 79 ° C.) and reacted for 3 hours. An increase in viscosity in the system was observed during the reaction. The polymerization reaction solution was diluted with 730 mL of DMAc, stirred for 30 minutes, and filtered using Celite as a filter aid.

A part of the filtrate was poured into methanol and solidified. The molecular weight by GPC of the copolymer comprising a sulfonic acid derivative protected with a neopentyl group is Mn = 58000, Mw = 135,3.
00.

  The filtrate was concentrated with an evaporator, 43.8 g (505 mol) of lithium bromide was added to the filtrate, and the mixture was reacted at an internal temperature of 110 ° C. for 7 hours under a nitrogen atmosphere. After the reaction, the mixture was cooled to room temperature, poured into 4 L of acetone and solidified. The coagulated product was collected by filtration, air-dried, pulverized with a mixer, and washed with 1500 mL of 1N hydrochloric acid while stirring. After filtration, the product was washed with ion-exchanged water until the pH of the washing solution reached 5 or higher, and then dried at 80 ° C. overnight to obtain 23.0 g of the target sulfonated polymer. The molecular weight of the sulfonated polymer after this deprotection was Mn = 60000 and Mw = 175000. The ion exchange capacity of this polymer was 2.4 meq / g. The obtained polyarylene having a sulfonic acid group is a compound represented by the structural formula (IV).

[Example 1]
<Preparation of electrolyte membrane>
Into a 50 ml screw tube containing a stirrer, 4.5 g of the sulfonated polyarylene (II) obtained in Synthesis Example 1 and 15.3 g of N-methyl-2-pyrrolidone and 10.2 g of methanol are taken at room temperature. Stir for 4 hours. This solution was cast on a pet film using a doctor blade, and dried at 60 ° C. for 1 hour and 120 ° C. for 1 hour using a thermostatic bath, and the solvent was distilled off. After drying, it was peeled off from the pet film to obtain a polymer electrolyte membrane having a thickness of 50 μm. In the following evaluation, power generation evaluation was performed using this film.

<Preparation of anode electrode paste>
In a 50 mL plastic bottle, 25 g of zirconia balls having a diameter of 10 mm (“YTZ balls” manufactured by Nikkato Co., Ltd.), 1.53 g of platinum-supported carbon particles (Pt: 50 wt% supported, Tanaka Kikinzoku Kogyo Co., Ltd.) 88 g, 12.47 g of n-propyl alcohol and 4.59 g of a 20.1 wt% solution of Nafion (trade name, manufactured by DuPont) were added, and the mixture was stirred for 60 minutes with a paint shaker to obtain anode electrode paste A.

<Preparation of cathode electrode paste>
Platinum-supported carbon particles (Pt: 46 wt% supported, “TEC10E50E” manufactured by Tanaka Kikinzoku Co., Ltd.) 1.51 g in a 50 mL plastic bottle containing 25 g of zirconia balls having a diameter of 10 mm (“YTZ balls” manufactured by Nikkato Co., Ltd.) , 0.88 g of distilled water, 3.23 g of N-methyl-2-pyrrolidone solution of polymer (II) of Synthesis Example 1 (solid content 15% by weight), N-methyl-
A mixture consisting of 12.47 g of 2-pyrrolidone and 0.8 g of a methyl ethyl ketone solution (solid content 15 wt%) of a fluorinated copolymer B produced using a monomer containing hexafluoropropylene and hydroxyethyl vinyl ether, Cathode electrode paste B was obtained by stirring for 60 minutes with a paint shaker.

<Manufacture of electrodes>
The surface of the polymer electrolyte membrane prepared as described above is coated with the anode electrode paste A with a doctor blade using a mask having an opening of 5 cm × 5 cm, and the surface on which the anode electrode paste A is not coated Then, the cathode electrode paste B was applied with a doctor blade using a mask having an opening of 5 cm × 5 cm. By drying this at 120 ° C. for 60 minutes, an anode electrode catalyst layer A having a platinum coating amount of 0.25 mg / cm ² and a cathode electrode catalyst layer B having a platinum coating amount of 0.5 mg / cm ² is obtained. Catalyst layer A and cathode electrode catalyst layer B were formed.

<Fabrication of fuel cell>
Carbon obtained by subjecting the electrolyte membrane in which the anode electrode catalyst layer A and the cathode electrode catalyst layer B are formed on the respective surfaces to two water repellent treatments so as to be in contact with the anode electrode catalyst layer A and the cathode electrode catalyst layer B, respectively. The membrane-electrode assembly was produced by sandwiching with paper and hot press molding under the conditions of 160 ° C. × 15 min under a pressure of 30 kg / cm ² . The obtained electrode-membrane assembly was sandwiched between two titanium current collectors, and a heater was placed on the outside thereof to produce a fuel cell for evaluation having an effective area of 25 cm ² .

[Example 2]
<Preparation of anode electrode paste>
In a 50 mL glass bottle containing 25 g of zirconia balls having a diameter of 10 mm (“YTZ ball” manufactured by Nikkato Co., Ltd.), 1.53 g of platinum-supported carbon particles (Pt: 50 wt% supported, Tanaka Kikinzoku Kogyo Co., Ltd.) .88 g, 3.23 g of N-methyl-2-pyrrolidone solution of polymer (II) of Synthesis Example 2 (solid content 15% by weight), and 12.47 g of N-methyl-2-pyrrolidone were put in, and a paint shaker was used. Anode electrode paste C was obtained by stirring for 60 minutes.

<Preparation of cathode electrode paste>
Put 50g zirconia ball ("YTZ ball" manufactured by Nikkato Co., Ltd.) 25g into a 50mL plastic bottle, 1.51g of platinum-supported carbon particles (Pt: 46% by weight, "TEC10E50E" manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), distilled 0.88 g of water, 12.47 g of n-propyl alcohol and 4.59 g of a 20.1 wt% solution of Nafion (trade name, manufactured by DuPont) were added, and the mixture was stirred for 60 minutes with a paint shaker to obtain cathode electrode paste D It was.
<Manufacture of electrodes>
An anode electrode catalyst layer C and a cathode electrode catalyst layer D were formed in the same manner as in Example 1 except that the anode electrode paste C and the cathode electrode paste D obtained as described above were used.
<Fabrication of fuel cell>
A fuel cell for evaluation was produced in the same manner as in Example 1 except that the anode electrode catalyst layer C and the cathode electrode catalyst layer D obtained as described above were used.

[Example 3]
<Preparation of anode electrode paste>
An anode electrode paste A was obtained in the same manner as in Example 1 using Nafion (trade name, manufactured by DuPont).
<Preparation of cathode electrode paste>
A cathode electrode paste E was obtained in the same manner as in Example 1 except that the sulfonated polyarylene (IV) obtained in Synthesis Example 2 was used.
<Manufacture of electrodes>
An anode electrode catalyst layer E and a cathode electrode catalyst layer F were formed in the same manner as in Example 1 except that the anode electrode paste A and the cathode electrode paste E obtained as described above were used.
<Fabrication of fuel cell>
A fuel cell for evaluation was produced in the same manner as in Example 1 except that the anode electrode catalyst layer A and the cathode electrode catalyst layer E obtained as described above were used.

[Example 4]
<Preparation of anode electrode paste>
An anode electrode paste F was obtained in the same manner as in Example 2 except that the sulfonated polyarylene (IV) obtained in Synthesis Example 2 was used.
<Preparation of cathode electrode paste>
A cathode electrode paste D was obtained in the same manner as in Example 2 except that Nafion (trade name, manufactured by DuPont) was used.
<Manufacture of electrodes>
An anode electrode catalyst layer F and a cathode electrode catalyst layer D were formed in the same manner as in Example 1 except that the anode electrode paste F and the cathode electrode paste D obtained as described above were used.
<Fabrication of fuel cell>
A fuel cell for evaluation was produced in the same manner as in Example 1 except that the anode electrode catalyst layer F and the cathode electrode catalyst layer D obtained as described above were used.

[Comparative Example 1]
<Preparation of anode electrode paste>
An anode electrode paste A was obtained in the same manner as in Example 1 except that Nafion (trade name, manufactured by DuPont) was used.
<Preparation of cathode electrode paste>
A cathode electrode paste D was obtained in the same manner as in Example 2 except that Nafion (trade name, manufactured by DuPont) was used.
<Manufacture of electrodes>
An anode electrode catalyst layer A and a cathode electrode catalyst layer D were formed in the same manner as in Example 1 except that the anode electrode paste A and the cathode electrode paste D obtained as described above were used.
<Fabrication of fuel cell>
A fuel cell for evaluation was produced in the same manner as in Example 1 except that the anode electrode catalyst layer A and the cathode electrode catalyst layer D obtained as described above were used.

[Comparative Example 2]
<Preparation of anode electrode paste>
An anode electrode paste C was obtained in the same manner as in Example 2.
<Preparation of cathode electrode paste>
Cathode electrode paste B was obtained in the same manner as Example 1.
<Manufacture of electrodes>
An anode electrode catalyst layer C and a cathode electrode catalyst layer B were formed in the same manner as in Example 1 except that the anode electrode paste C and the cathode electrode paste B obtained as described above were used.
<Fabrication of fuel cell>
A fuel cell for evaluation was produced in the same manner as in Example 1 except that the anode electrode catalyst layer C and the cathode electrode catalyst layer B obtained as described above were used.

[Comparative Example 3]
<Preparation of anode electrode paste>
An anode electrode paste F was obtained in the same manner as in Example 4.
<Preparation of cathode electrode paste>
Cathode electrode paste E was obtained in the same manner as Example 3.
<Manufacture of electrodes>
An anode electrode catalyst layer F and a cathode electrode catalyst layer E were formed in the same manner as in Example 1 except that the anode electrode paste F and the cathode electrode paste E obtained as described above were used.
<Fabrication of fuel cell>
A fuel cell for evaluation was produced in the same manner as in Example 1 except that the anode electrode catalyst layer F and the cathode electrode catalyst layer E obtained as described above were used.

[Evaluation]
It shows about the evaluation method of the fuel cell obtained in Examples 1-4 and Comparative Examples 1-3.
[Evaluation 1]
The temperature is maintained at 80 ° C., and the anode and cathode are supplied with 2 atmospheres of hydrogen and air (under a constant back pressure of 0.2 MPa) under conditions of humidity 40% RH and 80% RH, and a current density of 0.2 A. /
Terminal voltages at cm ² and 0.8 A / cm ² were measured. The results are shown in Table 1.
[Evaluation 2]
After measuring evaluation 1, the temperature of the fuel cell was kept at 120 ° C., and durability evaluation was performed under the condition of humidity 40% RH. Hydrogen and air are supplied at 2 atm (under a constant back pressure of 0.2 MPa), and the time until the terminal voltage becomes 0.3 V or less when the current density is maintained at 0.2 A / cm ² is determined. It was measured. The results are shown in Table 2.
[Evaluation 3]
After measuring evaluation 2, the voltage between terminals was measured at current densities of 0.2 A / cm ² and 0.8 A / cm ² under the same conditions as evaluation 1. The results are shown in Table 3.

As described above, a fuel cell in which an electrode using a polymer electrolyte having a fluorine content of 0 to less than 40% by weight and an electrode using a polymer electrolyte having a fluorine content of 40% by weight or more is the same polymer in both electrodes. Compared with the one using electrolyte, both high and low humidity conditions showed better power generation characteristics. In addition, when continuous durability power generation is performed in a high temperature and low humidity state, the voltage can be maintained for a long time, and the deterioration of characteristics after durability is suppressed. In particular, a membrane-electrode assembly using a polymer electrolyte having a fluorine content of 0 to less than 40% by weight on the anode side and a polymer electrolyte having a fluorine content of 40% by weight or more on the cathode side has good power generation characteristics and voltage holding. Showed sex.

Claims (8)

An electrode-membrane assembly comprising a polymer electrolyte membrane, an anode electrode catalyst layer containing at least catalyst particles and a polymer electrolyte on both sides thereof, and a cathode electrode catalyst layer containing at least catalyst particles and a polymer electrolyte,
Either one of the polymer electrolytes used for the anode electrode catalyst layer and the cathode electrode catalyst layer is a polymer having a fluorine content defined by the proportion of the total weight of fluorine atoms contained in the polymer electrolyte of less than 0 to 40% by weight. An electrolyte, and the other is a polymer electrolyte having a fluorine content of 40% by weight or more,
A membrane-electrode assembly , wherein the polymer electrolyte having a fluorine content of 0 to less than 40% by weight is a protonic acid group-containing aromatic polymer having a polyarylene main chain skeleton . An electrode-membrane assembly comprising a polymer electrolyte membrane, an anode electrode catalyst layer containing at least catalyst particles and a polymer electrolyte on both sides thereof, and a cathode electrode catalyst layer containing at least catalyst particles and a polymer electrolyte,
Either one of the polymer electrolytes used for the anode electrode catalyst layer and the cathode electrode catalyst layer is a polymer having a fluorine content defined by the proportion of the total weight of fluorine atoms contained in the polymer electrolyte of less than 0 to 40% by weight. An electrolyte, the other being a polymer electrolyte having a fluorine content of 40% by weight or more, and a polymer electrolyte having a fluorine content of 0 to less than 40% by weight contained in the cathode-side electrode catalyst layer, and having a high fluorine content of 40% by weight or more. A membrane characterized in that a polymer electrolyte containing a molecular electrolyte in an anode side electrode catalyst layer and having a fluorine content of 0 to less than 40% by weight is a protonic acid group-containing aromatic polymer having a polyarylene main chain skeleton. An electrode assembly.   The membrane-electrode assembly according to claim 1 or 2, wherein the difference in fluorine content of the polymer electrolyte used for the anode electrode catalyst layer and the cathode electrode catalyst layer is 20 wt% or more. The membrane-electrode assembly according to claim 1 or 3, wherein the protonic acid group-containing aromatic polymer is a sulfonic acid group-containing polyarylene having a structure represented by the following general formula (1). .

[In the formula (1), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) _i — (i represents an integer of 1 to 10). Or —C (CF ₃ ) ₂ —, Z is independently a direct bond, — (CH ₂ ) _j — (j represents an integer of 1 to 10), —C (CH ₃ ) ₂ —, — O— or —S— is represented, and Ar represents —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). The aromatic group which has a substituent represented by this is shown, m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4.
A and D are each independently a direct bond, —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) _i — (i represents an integer of 1 to 10. ), — (CH ₂ ) _j — (j represents an integer of 1 to 10), —CR ′ ₂ — (R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group. ), Cyclohexylidene group, fluorenylidene group, —O— or —S—, B is independently an oxygen atom or sulfur atom, and R ^{1 to} R ¹⁶ are each independently hydrogen atom, fluorine atom, alkyl Group, a halogenated alkyl group, allyl group, aryl group, nitro group or nitrile group partially or wholly halogenated, s and t each represent an integer of 0 to 4, and r is 0 or 1 or more Indicates an integer.
Z ′ represents a direct bond or at least one structure selected from the group consisting of —O— and —S—, and Y ′ represents —CO—, —SO ₂ —, —SO—, —CONH—, It represents at least one structure selected from the group consisting of —COO—, — (CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CF ₃ ) ₂ —, and R ²⁰ includes A nitrogen heterocyclic group is shown. q represents an integer of 1 to 5, and p represents an integer of 0 to 4.
x, y, z represents a molar ratio when x + y + z = 100 mol%. ] The polymer electrolyte having a fluorine content of 40% by weight or more is at least one perfluoroolefin selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroalkoxy vinyl ether as a monomer, and CF ₂ = CF— (OCF ₂ CFX) _m —O _q — (CF ₂ ) _n —A (where m = 0 to 3, n = 0 to 12, q = 0 or 1, X = F or CF ₃ , A = sulfone 5. A copolymer with at least one of the following fluorovinyl compounds represented by an acid group, a carboxylic acid group, a phosphonic acid group, or a phosphoric acid group): The membrane-electrode assembly according to claim 1.
CF ₂ = CFO (CF ₂ ) _1-8 A
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _1-8 A
CF ₂ = CF (CF ₂ ) _0-8 A
CF ₂ = CF (OCF ₂ CF (CF ₃ )) _1-5 O (CF ₂ ) ₂ A   2. A polymer electrolyte having a fluorine content of 0 to less than 40% by weight is contained in the anode side electrode catalyst, and a polymer electrolyte having a fluorine content of 40% by weight or more is contained in the cathode side electrode catalyst. 2. The membrane-electrode assembly according to 1.   The membrane-electrode assembly according to any one of claims 1 to 6, wherein the polymer electrolyte having a fluorine content of less than 0 to 40% by weight contains a water repellent. The water repellent is
(A) a fluorine-containing copolymer having a structural unit derived from (meth) acrylate containing a polyfluoroalkyl group, and
(B) Fluorine-containing compound having a structural unit represented by the following general formula (2) derived from a fluorine-containing olefin monomer and a structural unit represented by the following general formula (3) derived from a vinyl ether monomer. The membrane-electrode assembly according to claim 7, comprising at least one selected from the group consisting of copolymers.

[In Formula (2), X ¹ is a fluorine atom, a fluoroalkyl group or a group represented by —OW ¹ (W ¹
Represents an alkyl group or a fluoroalkyl group. ). ]

[In the formula (3), X ² represents a hydrogen atom or a methyl group, and X ³ represents a group represented by — (CH ₂ ) _h OW ² (W ² represents an alkyl group, a hydroxyalkyl group, a glycidyl group or a fluoroalkyl group. H represents an integer of 0 to 2), a group represented by -OCOW ³ (W ³ represents an alkyl group, a hydroxyalkyl group or a glycidyl group), a carboxyl group or an alkoxycarbonyl group. . ]