JPH1167224A - Membrane-electrode bonding body for solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of a fluorine-contained material, and satisfy high proton conductivity and long durability at high temperature at the same time by using sulfonated polyaryl ether sulfone having the specified structure in an ion-exchange membrane and a catalyst layer. SOLUTION: Sulfonated polyaryl ether sulfone represented by the formula is contained in an ion-exchange membrane and/or a catalyst layer of a membrane-electrode bonding body. In the formula (a) is an integer of 1-4, (p) is an integer of 1-5, (n) is an integer of 2-1,000, X represents H or a mono to tetra relent metal, Ar represents an aromatic residue. The catalyst layer is made of a catalyst covered with sulfonated polyarl ether sulfone, and the ion-exchange membrane is preferably a fluorine-contained polymer having a sulfone group. The equipment weight of the sulfonated polyaryl ether sulfone is preferably 150-2,000 g/eq. The sulfonated polyaryl ether sulfone is obtained by reacting polyaryl ether sulfone with a well-known sulfonating agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power generation system having a high power generation efficiency.
The present invention relates to a membrane-electrode assembly used for a polymer electrolyte fuel cell having features such as low pollution and low noise.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell is a fuel cell characterized in that the electrolyte is solid and a polymer ion exchange membrane is used. As shown in FIG. 1, the basic structure of such a polymer electrolyte fuel cell includes the ion-exchange membrane 1 and a pair of gas diffusion electrodes 2 bonded to both surfaces thereof.
The catalyst layer is carried on at least the ion exchange membrane 1 side of each of the gas diffusion electrodes 2 and 3. As shown in FIG. 2, which corresponds to an enlarged view of the portion A in FIG. 1, the catalyst layer comprises a catalyst comprising platinum-supported carbon and a binder polymer covering the catalyst, and has a porous structure. It is. The one obtained by integrating the ion exchange membrane, the gas diffusion electrode, and the catalyst layer is called a membrane-electrode assembly.

[0003] A fuel (eg, hydrogen) is supplied to the gas diffusion electrode 2 and an oxidant (eg, oxygen or air) is supplied to the gas diffusion electrode 3, and an external load circuit is connected between the gas diffusion electrodes 2, 3. Thereby, it operates as a fuel cell. The site where the polymer electrolyte material is used in the membrane-electrode assembly of the polymer electrolyte fuel cell is the binder polymer of the ion exchange membrane and the catalyst layer. Here, the binder polymer is used to increase the three-phase interface of the electrolyte, the catalyst, and the reaction gas in the catalyst layer by coating the surface of the platinum catalyst, and at the same time, to increase the proton conductivity. The binder polymer is also called a “joining material” in terms of its function. It is known that the binder polymer of the catalyst layer greatly affects the performance of the fuel cell (JP-A-6-333574).

Conventionally, a perfluorocarbon sulfonic acid represented by the following chemical formula (3) has been used as such a solid polymer electrolyte material. As a commercially available ion exchange membrane having the structure of the chemical formula (3), “Nafion (registered trademark)” manufactured by DuPont, USA is known. As a bonding material for the catalyst layer, a “Nafion solution” (for example, a 5% by weight solution) manufactured by Aldrich Corporation of the United States, which is a polymer solution containing an ion-exchange resin constituting the “Nafion”, is mainly used.

[0005]

Embedded image

(Where m is an integer of 0 to 3, y is an integer of 1 to 5, and x / y is 1 to 15.) The ionic conductivity of the fluorocarbon sulfonic acid membrane is 5 × 10 ^-2 at 25 ° C. ~ 1 ×
About 10 ⁻¹ S · cm ⁻¹ and generally 10 to 200 μm in thickness
The resistance per unit area is 0.05
About 0.4Ω. The performance required for the polymer electrolyte material used in the fuel cell includes the following items. Proton conductivity at room temperature is 10 ⁻² S · cm ⁻¹ or more. The temperature change of the proton conductivity from room temperature to around 100 ° C. is small. Long-term stability.

At present, the above-mentioned fluorocarbon sulfonic acid ion-exchange membrane is used as a polymer electrolyte which satisfies these required performances to some extent. However, fluorocarbon sulfonic acid-based ion exchange membranes are manufactured from special fluorine-based vinyl ether monomers through multiple steps, consume a large amount of energy in their manufacture, and have a large impact on fuel cells, especially in the automotive applications, in reducing the environmental burden. For the purpose, it is not necessarily a suitable material, and there is a need for a polymer electrolyte that consumes less total energy in its production. Materials containing fluorine are expected to have an adverse effect on the environment and incinerators when considering disposal, such as landfills and incineration. From this point of view, it is desired to reduce the amount of materials containing fluorine. .

[0008] As an alternative material to fluorocarbon sulfonic acid, an ethylene-tetrafluoroethylene copolymer film is reacted with α, β, β-trifluorostyrene and then sulfonated (Proc. Intern)
national FuelCell Conferen
ce. , 417, 1992) and a membrane obtained by grafting styrene to polytetrafluoroethylene and performing sulfonation (J. Appl. Polym. Sci., 37, 281).
7, 1989).

However, the latter example has insufficient durability, and the former example has the same durability as the fluorocarbon sulfonic acid system, but it is not easy to obtain a monomer. Further, an ion exchange membrane in which a sulfonic acid group is introduced into a copolymer of α, β, β-trifluorostyrene and m-trifluoromethyl-α, β, β-trifluorostyrene (Japanese Patent Application Laid-Open No. Hei 8-512358) ) Has been announced. This ion exchange membrane is called a ballad membrane, and its performance is close to that of a fluorocarbon sulfonic acid system, but it requires multiple steps for synthesis of a monomer and is not easily available industrially.

Also, a heat-resistant wholly aromatic polymer, PE
EK (short for polyetheretherketone)
93114) or a material obtained by sulfonating PPBP (abbreviation of polyphenoxybenzophenone) (fuel and combustion,
63 (10) p. 14 (1996)). However, the sulfonated PEEs shown in the patent
The performance of K as a fuel cell is extremely low. This is thought to be due to the low proton conductivity of the sulfonated PEEK. Regarding the sulfonated PPBP, an example applied to an ion exchange membrane of a fuel cell has not been published yet. However, although high durability is expected, the published proton conductivity is 10 ⁻³ to 10 ^−2. And the conductivity is lower than that of fluorocarbon sulfonic acid by one digit or more, which is not satisfactory. Further, PPBP is not industrially produced and cannot be used in large quantities as a fuel cell material for automobiles.

German Patent DE 44 37 492 shows a sulfonated polyetherketone-based ion-exchange membrane coated on its surface with a finely dispersed catalytically active metal.
Although the performance as a fuel cell is not clear, practical performance cannot be expected due to the low proton conductivity of sulfonated PEEK. Further, an example of water electrolysis using a partially sulfonated polyaryl ether sulfone as an ion exchange membrane has been reported. (Journal of M
embrane Science, 83 p. 211
(1993)) (Group Conf. Ser.
Publ. , 3 (1993)) However, since sulfonylation of an aromatic ring is an equilibrium reaction, it has been shown that sulfonic acid groups are unstable and elimination occurs at a high temperature near 100 ° C, resulting in insufficient durability.

[0012]

DISCLOSURE OF THE INVENTION The present invention requires a large amount of energy for production, is costly, reduces the amount of fluorine-based material which has a problem of disposal, and has a high proton conductivity and high temperature. An object of the present invention is to provide a membrane-electrode assembly for a polymer electrolyte fuel cell having a polymer electrolyte material that simultaneously satisfies the long-term durability of the present invention.

[0013]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, surprisingly, the sulfonated polyarylethersulfone having a specific structure has a similar structure to the fluorocarbon sulfonic acid type. It has high proton conductivity and stable proton conductivity against temperature change, and at the same time, the sulfonic acid group is hardly eliminated even at high temperature and for a long time. Was found to improve the water resistance and the durability, and completed the membrane-electrode assembly of the present invention.

That is, the present invention relates to [1] a membrane-electrode assembly for a polymer electrolyte fuel cell comprising an ion exchange membrane, a catalyst layer bonded to the ion exchange membrane, and a gas diffusion electrode. A membrane-electrode assembly for a polymer electrolyte fuel cell, wherein the membrane and / or the catalyst layer has a sulfonated polyarylethersulfone represented by the chemical formula (1).

[0015]

Embedded image

(A is an integer of 1 to 4; p is an integer of 1 to 5; n is an integer of 2 to 1000. X represents H or a monovalent to tetravalent metal. Ar is [2] The membrane-electrode junction for a polymer electrolyte fuel cell according to the above [1], wherein the catalyst layer is composed of a catalyst coated with a sulfonated polyaryl ether sulfone. [3] The membrane-electrode assembly for a solid polymer fuel cell according to the above [1] or [2], wherein the ion exchange membrane is a fluoropolymer having a sulfonic acid group; [4] a sulfonated polyarylether sulfone Has an equivalent weight of 150-20
The membrane-electrode assembly for a polymer electrolyte fuel cell according to the above [1], [2] or [3], which is a sulfonated polyaryl ether sulfone of 00 g / eq; [5] sulfonation represented by the chemical formula (1) X 1 of the polyaryl ether sulfone
% To 95% is a monovalent to tetravalent metal [1],
[2], [3] or the membrane for polymer electrolyte fuel cells of [4]-
The electrode assembly, [6] the solid polymer fuel according to the above [1], [2], [3], [4] or [5], wherein the sulfonated polyaryl ether sulfone has a structure represented by the chemical formula (2). Membrane-electrode assembly for batteries,

[0017]

Embedded image

(C and d are each an integer of 0 to 4 and neither c nor d is 0. n is an integer of 2 to 1000. X is H or a monovalent to tetravalent metal. Represents.). Hereinafter, the present invention will be described in detail. In the sulfonated polyaryl ether sulfone represented by the chemical formula (1) in the present invention, Ar is a wholly aromatic residue. Preferably a wholly aromatic residue having 6 to 30 carbon atoms is
More preferably, it is a wholly aromatic residue having 6 to 18 carbon atoms.
For example, p-phenylene group, m-phenylene group, o-phenylene group, biphenylene group, naphthylene group, 2-phenyl-1,4-phenylene group, 2,6-diphenyl-1,
4-phenylene group and the like.

As a specific example of the above chemical formula (1), a polymer having the following structure in the repeating unit can be preferably used. Among them, a polymer having the structure represented by the chemical formula (2) in the repeating unit is preferable.

[0020]

Embedded image

(A is an integer of 1 to 4, preferably 1
And is an integer of 2 and particularly preferably 1. c and d are each an integer of 0 to 4 and neither c nor d is 0. Preferably c = d = 1 and c = 0, d = 1
It is. X is H or a monovalent to tetravalent metal. ) Documents described in the prior art (Journal of Me)
mbrane Science, 83, 211 pages, 1993 and Group Conf. Ser.
Publ. , Sulfonated polyarylether sulfone 3,1993), the polyarylethersulfone before sulfonation, -Ph-SO ₂ -Ph-O-
The structure obtained by sulfonating this is inevitably a SO ₃ group with a phenylene group sandwiched between an SO ₂ group and an ether group.
You will have H. On the other hand, the sulfonated polyarylether sulfone of the membrane-electrode assembly of the present invention has a structure before sulfonation of -Ph-SO ₂ -Ph
—O—Ar—O—, and when it is sulfonated, an SO ₃ H group is bonded to an aromatic residue sandwiched between ether groups due to its electron donating property. As a result, an aromatic residue sandwiched between two ether groups has a SO ₃ H group,
It is presumed that, due to the electron donating property of the ether group, the chemical stability against the desulfonation reaction of the SO ₃ H group was high, and the durability was increased.

The method for producing the sulfonated polyaryl ether sulfone used in the present invention can be obtained by reacting the polyaryl ether sulfone having the above structure with a known sulfonating agent. More specifically, sulfonation can be carried out using a sulfonating agent such as sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, SO ₃ and triethyl phosphate in a solvent such as methylene chloride or chloroform. Some non-sulfonated polyaryl ether sulfones of the above structural formula are commercially available,
There is no particular problem if these commercially available polymers are used as raw materials.

Also, sulfonated monomers such as 4,
The above sulfonated polymer can also be obtained by polycondensation of a sulfonated product of 4'-biphenol and dichlorodiphenyl sulfone. The above-mentioned sulfonated repeating unit may be present in a part of the molecular chain, and such a polymer may be obtained in the form of a block copolymer or a random copolymer by using a non-sulfonated monomer and a sulfonated monomer. Can also.

A block copolymer can also be obtained by using a polyaryl ether sulfone which has been previously crystallized with a solvent in sulfonation. In the sulfonated polyarylethersulfone obtained by the above method, X is H in the structure represented by the chemical formula (1). By converting X of this polymer from a monovalent to a tetravalent metal, a polymer in which at least a part of X is a metal can be obtained. A polymer in which all of X are H undergoes dimensional change due to swelling due to moisture absorption, and when this material is used for a long time as an ion exchange membrane of a fuel cell,
Problems such as peeling from the catalyst layer and bending of the film itself may occur, and eventually the film may break. Therefore, it is preferable that a part of X is a metal. By introducing a metal, the water resistance of the polymer is improved, and a polymer that satisfies the required durability can be obtained. This is because the polymer has a partially cross-linked structure, reduces water absorption, and swells. It is presumed that the problem of dimensional change caused by this can be solved to a considerable extent.

As the monovalent metal, an alkali metal such as Na, K, or Rb can be used. As the divalent metal, in addition to an alkaline earth metal such as Mg, Ca, or Ba, Zn,
Cu or the like can also be used. As the trivalent metal, A
1, Ga, In, Y, La, rare earth metals, etc.
As the valence metal, Ti, Zr, Hf, or the like can be used. Among them, Ba, which is a divalent metal, Al, Ga, In, Y, La, which is a trivalent metal, and a rare earth metal are preferable, and Ba, La, and a rare earth metal are more preferable.

The substitution amount of the metal is preferably 1% to 95%, more preferably 2% to 95% of the total X in the chemical formula (1).
60%. If the substitution amount is less than 1%, the dimensional change due to moisture absorption may be large depending on the substitution amount of the sulfonic acid group. If the substitution amount is more than 95%, the proton conductivity decreases, and the battery performance decreases. The metal is introduced by dissolving the H-form sulfonated polyarylethersulfone in a soluble solvent or suspending the H-type sulfonated polyarylethersulfone in an insoluble solvent, adding a salt solution of the metal thereto, and stirring and mixing for a predetermined time. It depends. Solvents include water, methanol,
Ethanol, tetrahydrofuran, diethyl ether,
N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like can be suitably used. The metal salt is not particularly limited, but for example, an hydroxide salt, an acetate salt, an acetylacetonate salt, an alkoxy salt such as an isopropoxy salt, or the like can be used. Upon addition, it is preferable to dissolve in a solvent. The metal-substituted polymer may be filtered and washed if it becomes insoluble after the addition of the metal salt, or it may be simply washed with an insoluble solvent after distilling off the solvent if dissolved. Can be separated and purified. In order to further strengthen the bond with the metal, the obtained metal-added polymer may be heat-treated at a temperature of 60 ° C to 200 ° C for several hours.

The membrane-electrode assembly of the present invention is characterized in that the ion-exchange membrane and / or the catalyst layer has a sulfonated polyarylethersulfone represented by the chemical formula (1). However, the ion exchange membrane may contain another polymer having a sulfonic acid group or a polymer having no sulfonic acid group within a range not less than about 10 ^-2 . Other polymers include, for example, fluorocarbon sulfonic acid-based polymers of Formula (3) and sulfonated PEEK, and non-sulfonated polymers include polytetrafluoroethylene,
Wholly aromatic polymers such as polyethersulfone, PE
EK or the like can be used.

More specifically, there is provided a membrane-electrode assembly in which a fluorocarbon sulfonic acid-based polymer represented by the chemical formula (3) is used as the ion exchange membrane and the binder polymer of the catalyst layer is the sulfonated polyaryl ether sulfone shown in the present invention. preferable. The amount of sulfonic acid groups of the sulfonated polyarylethersulfone of the present invention is defined by the equivalent weight, ie, the dry weight of the sulfonated polymer per equivalent of ion exchange group. This equivalent weight can be experimentally determined by dissolving the dried sulfonated polymer in a solvent such as alcohol, which dissolves uniformly in water, and titrating with an alkali. The equivalent weight of the sulfonated polymer of the present invention is preferably from 150 to 2000 g / eq, and more preferably from 200 to 950 g / eq. When the equivalent weight is lower than 150 g / eq, the water swelling property becomes large and the water becomes soluble, so that it cannot be used as a membrane-electrode assembly for a fuel cell. 2000g
If it is higher than / eq, sufficient proton conductivity cannot be obtained.

As a method for obtaining an ion-exchange membrane used for a membrane-electrode assembly from the sulfonated polymer obtained by the above method, a method in which the polymer is dissolved in a solvent and cast, or a method in which the polymer is cast and immersed in a poor solvent. A known molding method such as a method, hot press molding, roll molding, or extrusion molding can be used. The film thickness is from 10 μm to 3
A thickness of 00 μm is preferred.

Further, the above sulfonated polymer is adhered to the surface of a conductive material (carbon particles or the like) on which a catalyst of a gas diffusion electrode is supported, and is used as a binder polymer. The catalyst layer may be formed by mixing a raw material powder (particles composed of conductive material particles and a catalyst) forming a catalyst layer in a powder state and a binder or the like added as necessary, and molding this. Then, the catalyst layer of the gas diffusion electrode formed in advance may be impregnated with the solution of the sulfonated polymer.

When the sulfonated polymer is used as a binder polymer as a solution, the solvent may be a single solvent of a lower alcohol such as methanol, ethanol, 1-propanol, 2-propanol, butanol, or two kinds selected from these. The above mixed solvents can be used. Further, a mixed solvent of water and the above solvent can also be used. Since the concentration of the sulfonated polymer solution is preferably made of a catalyst coated with a sulfonated polyarylethersulfone, the catalyst layer is suitable for the catalyst surface when impregnated on the catalyst layer side of the gas diffusion electrode. The concentration at which a suitable coating is easily formed is preferable, and
20% by weight is preferred. If the concentration is too high, the coating formed on the catalyst surface is too thick to prevent gas diffusion into the catalyst, or the catalyst surface cannot be uniformly coated with the sulfonated polymer and the catalyst utilization is reduced. As a result, the output of the fuel cell may decrease.

On the other hand, if the concentration is too low, the viscosity of the sulfonated polymer solution is too low, so that the bonding between the ion exchange membrane and the gas diffusion electrode is incomplete, or if the solution reaches deep inside the gas diffusion electrode. In some cases, the water may penetrate and reach the hydrophobic layer inside from the catalyst layer of the gas diffusion electrode, thereby inhibiting the appropriate hydrophobicity of the hydrophobic layer. As a method of impregnating the catalyst layer of the gas diffusion electrode with such a binder polymer solution, as the simplest method, for example, the solution is applied to the surface of the gas diffusion electrode on the catalyst layer side using a brush, A method in which a required amount of the solution is dropped on the surface of the gas diffusion electrode on the catalyst layer side and the solution is spread with a spatula or the like can be used.

The coating amount of the binder polymer depends on the fuel
It is an important factor that has a significant effect on battery performance.
The amount of coating depends on the amount of catalyst metal (such as platinum) supported in the catalyst used.
The optimal amount can be selected depending on the amount. Catalyst gold
Although it depends on the amount of metal supported,
The weight of the on-exchange resin is 0.1 to 10 mg / cm after drying. ^Two
It is preferable to apply so that

The binder polymer solution applied to the catalyst-side surface of the gas diffusion electrode penetrates into the inside of the catalyst layer of the gas diffusion electrode, and the conductive material particles (such as carbon particles) carrying the catalyst (such as platinum). After the solvent is dried, the binder polymer component remains as a thin film on the surface of the conductive material particles. Note that the binder polymer may be present only in a part of the catalyst layer, but is preferably present in the entire catalyst layer. In addition, when the binder polymer is provided in a state of being in contact with the ion exchange membrane when the ion exchange membrane and the gas diffusion electrode constituting the membrane-electrode assembly are joined, the binder polymer acts as a bonding material and performs ion exchange. The bonding strength between the membrane and the gas diffusion electrode can be increased.

The thickness of the ion exchange membrane used in the fuel cell is, for example, 10 to 300 μm. If the ion exchange membrane is thinner than 10 μm, the strength at the time of film formation cannot be maintained, and if it is thicker than 300 μm, the resistance of the ion exchange membrane increases and the output characteristics during operation of the fuel cell deteriorate. The preferred thickness of the ion exchange membrane is about 50 to 100 μm. The ion exchange membrane used in the current proton exchange membrane fuel cell is mainly a uniform membrane of perfluorosulfonic acid, "Nafion (registered trademark)" manufactured by DuPont in the United States,
"Aciplex-S (registered trademark)" manufactured by Asahi Kasei Kogyo Co., Ltd. and "Flemion (registered trademark)" manufactured by Asahi Glass Co., Ltd.

The catalyst layer is made of a conductive material carrying fine particles of a catalyst metal, and may contain a water repellent or a binder as necessary. Further, a layer composed of a conductive material not carrying a catalyst and a water repellent or a binder contained as necessary may be formed outside the catalyst layer.
The catalyst metal used in the catalyst layer may be any metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen, for example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, Examples include iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. Further, nitrogen-containing chromium, nitrogen-containing iron, nitrogen-containing cobalt and the like can also be used. Among such catalysts, especially platinum is often used.

The particle size of the metal serving as the catalyst is usually 10 to 3
00 °. The smaller the particle size, the higher the catalytic performance. However, if the particle size is less than 10 °, it is difficult to produce the catalyst. The preferred catalyst metal particle size is 15-100 °. The supported amount of the catalyst is, for example, 0.01 to 10 mg in a state where the electrode is formed.
/ Cm ² . The amount of supported catalyst is 0.01 mg / cm ²
If it is less than 10, the performance of the catalyst will not be exhibited, and the performance will be saturated even if it exceeds 10 mg / cm ² . A more preferred value of the amount of the supported catalyst is 0.1 to 5.0 mg / cm ² .

As the conductive material, any material may be used as long as it is an electronic conductive material, and examples thereof include various metals and carbon materials. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, and graphite. These may be used alone or in combination. As the water repellent, for example, fluorinated carbon or the like is used.

As the binder, various resins are used, and a fluorine-containing resin having water repellency is preferable. And
Among the fluororesins, those having excellent heat resistance and oxidation resistance are more preferable, for example, polytetrafluoroethylene,
Examples thereof include a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer and a tetrafluoroethylene-hexafluoropropylene copolymer.

As a method for producing a gas diffusion electrode having a catalyst layer bonded thereto using the above-mentioned materials, a metal particle serving as a catalyst is supported on a powdered conductive material, and then a binder polymer and a binder ( A water repellent may be separately added if necessary.), Or a porous body may be formed by using a conductive material and a binder (and a separate water repellent if necessary). After that, metal particles serving as a catalyst may be supported on this, followed by impregnation with a binder polymer.

As a commercially available gas diffusion electrode, US-E-T
There is an EK gas diffusion electrode, which is often used. This is an electrode having both gas permeability and hydrophobicity in which platinum fine particles are uniformly supported on carbon as an electrode catalyst and mixed with a polytetrafluoroethylene resin (binder). The bonding between the ion exchange membrane and the gas diffusion electrode is performed using a device capable of applying pressure and heating. Generally, it is performed by, for example, a hot press machine, a roll press machine, or the like. The pressing temperature at that time may be any temperature as long as it is equal to or higher than the glass transition temperature of the ion exchange membrane used as the electrolyte, and is generally 120 ° C. to 250 ° C. The pressing pressure depends on the hardness of the gas diffusion electrode to be used, but is usually 5 to 20.
It is 0 kg / cm ² .

Incidentally, it is common practice to insert a spacer thinner than the thickness of the electrode during hot pressing, since it is possible to prevent the number of holes in the gas diffusion electrode from being reduced. Further, it is preferable to perform hot pressing in a state where the ion exchange membrane is wet in the coexistence of water, a solvent, and the like, because the water content in the ion exchange membrane increases, and the output performance is improved. As a method for bonding the ion exchange membrane and the gas diffusion electrode, as described above, a method in which a binder polymer solution is applied to the surface of the gas diffusion electrode on the catalyst layer side and then the surface is bonded to the ion exchange membrane. preferable.

The fuel cell is obtained by inserting a joined body comprising such an ion exchange membrane and a gas diffusion electrode between a pair of current collectors and a pair of graphite gas separators having gas flow grooves formed therein. It is assembled and operates by supplying hydrogen gas as a fuel to one gas diffusion electrode and a gas (oxygen or air) containing oxygen to the other gas diffusion electrode.

Operating the fuel cell at a high temperature is as follows:
It is desirable because the catalytic activity of the electrode is increased and the electrode overvoltage is reduced. However, since the ion exchange membrane serving as the electrolyte does not function without moisture, it must be operated at a temperature at which moisture can be controlled. A preferable range of the operating temperature of the fuel cell is 30 to 15
0 ° C.

[0045]

Embodiments of the present invention will be described below in detail. Method for measuring equivalent weight: 100 mg of sulfonated polymer was placed in 20 ml of methanol and stirred at room temperature. 60 ml of a 1 / 100N NaOH aqueous solution was added to this solution and stirred at room temperature overnight. Back titration was performed using a 1 / 100N aqueous HCl solution to determine the equivalent weight of the sulfonated polymer. -Water resistance measurement method: metal-containing sulfonated poly (1,4-
Biphenylene ether ether sulfone (100 mg) was placed in 4 ml of water, kept at 80 ° C. for 96 hours, and the weight of the insoluble polymer was measured. -Proton conductivity: metal-containing sulfonated poly (1,4-
Biphenylene ether ether sulfone) 5 wt% DM
The solution F was used to prepare a 30 μm cast film.
Proton conductivity was measured in the temperature range from 30C to 80C.

[0046]

Example 1 1,4-biphenylene ether ethers
Lehon [(-C₆H_Four-4-SO_TwoC₆H_Four-4-OC₆H_Four-4-C₆H_Four-4-O-)_n ]
(D1.29, Tg208 ° C) 4.0 g (Aldrich
Was dissolved at 60 ° C. in 100 ml of chloroform.
To this solution was added 1.165 g of chlorosulfonic acid in 1,1,
The solution dissolved in 50 ml of 2,2-tetrachloroethane
Added over 10 minutes. The reaction was stirred at 60 ° C. for 4 hours.
Was. The precipitated polymer was filtered and chloroform 150m
l. 250 m of methanol is added to the obtained polymer.
1 was added and dissolved at 60 ° C. Vacuum the solution at 60 ° C to dryness
Dried. The obtained polymer is suspended in 250 ml of water,
The insoluble polymer was filtered. Pentaacid for water-insoluble polymer
It was dried at 100 ° C. under reduced pressure on phosphorus chloride. 3.60g of po
A rimmer was obtained. This polymer is insoluble in water,
Was soluble in water.¹HNMR and ¹³Analysis of CNMR
To SO_ThreeBiphenylene group in which H group is sandwiched between ether groups
Confirm that the structure is substituted on the phenylene ring of
Was. The equivalent weight was 512 g / eq.

As an electrode, a gas diffusion electrode manufactured by E-TEK (catalyst carrying amount 0.38 mg / cm ² , size: 2 cm ×
2 cm) as a set of two sheets, and the above sulfonated poly (1,4
-Biphenylene ether ether sulfone) was dissolved in methanol, and a 5 wt% solution was applied with a brush.
Dry at 80 ° C. for 1 hour. At this time, application was performed such that the weight of the sulfonated polymer present on the catalyst-supporting surface after drying was 0.6 mg / cm ² . This gas diffusion electrode is arranged on both sides of an ion exchange membrane of Aciplex-S (equivalent weight: 1000 g / eq) manufactured by Asahi Kasei Corporation, and has an opening of 2 cm × 2 cm from the outside, and has a thickness of 2 cm × 2 cm. Two gaskets made of a polytellorafluoroethylene resin having a thickness of 0.2 mm were sandwiched from both sides so that each gas diffusion electrode fits into the opening of each gasket.
In addition, the surface of the gas diffusion electrode opposite to the ion exchange membrane is covered with a 0.05 mm thick “Kapton (registered trademark)” film manufactured by Dupont Toray Co., Ltd. Avoid evaporation. Such a combined product was placed in a press device, pressed at 145 ° C. and 60 kg / cm ² for 90 seconds, and then taken out of the press device. The fuel cell was assembled by inserting the membrane-electrode assembly thus formed between a pair of current collectors and a pair of graphite gas separators in which gas flow grooves were formed.

The fuel cell was connected to an external load, and on the one hand, 1 atm hydrogen gas saturated with 70 ° C. steam and 1 atm oxygen gas saturated with 70 ° C. steam on the other side.
The fuel cell body was maintained at 70 ° C. while supplying the gas from each gas inlet, and the change in output voltage was measured by changing the current density while changing the external load. As a result 700m
The battery voltage at a current density of A / cm ² was 550 mV. 700m current density after 500 hours operation under these conditions
The battery voltage at A / cm ² was 538 mV, and the voltage drop was 2.2%. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0049]

EXAMPLE 2 1,4-phenylene ether sulfone _{[(-C 6 H 4 -4-} SO 2 -C 6 H 4 -4-OC 6 H 4 -4-O-) n] (Tg19
The same reaction and post-treatment as in Example 1 were carried out using 4.0 g (2 ° C.) (Aldrich) and 1.44 g of chlorosulfonic acid. 4.08 g of a light brown polymer was obtained. This polymer was insoluble in water and soluble in methanol.

From the analysis of ¹ HNMR and ¹³ CNMR, it was found that SO
It was confirmed that the structure was such that the ₃ H group was substituted on the phenylene ring interposed between the ether groups. Equivalent weight is 458g
/ Eq. Example 1 except that the obtained sulfonated 1,4-phenylene ether ether sulfone was used.
The fuel cell was assembled in the same manner as described above. It was operated under the same conditions as in Example 1. As a result, 700 mA / cm ²
The battery voltage at the current density of was 535 mV. A current density of 700 mA / cm ² after operating for 500 hours under these conditions
Battery voltage is 524 mV and the voltage drop is 2.1%
Met. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0051]

Example 3 In Example 1, 2.3 chlorosulfonic acid was used.
The same reaction was conducted except that 3 g was used. The precipitated polymer was filtered and washed with 150 ml of chloroform. 250 ml of methanol was added to the obtained polymer and dissolved at 60 ° C. The solution was dried at 60 ° C. under reduced pressure. The polymer was further dried at 100 ° C. under reduced pressure over phosphorus pentoxide.
5.57 g of polymer were obtained. This polymer is
It was soluble in water and methanol. ¹ H NMR and ¹³ CN
From MR analysis, it was confirmed that the structure was such that one SO ₃ H group was substituted on each phenylene ring of a biphenylene group sandwiched between ether groups. The equivalent weight was 273 g / eq.

1.0 g of the obtained sulfonated poly (1,4-biphenylene ether ether sulfone) was dissolved in 20 ml of methanol, and a solution of 20 mg of magnesium acetate tetrahydrate dissolved in 4 ml of methanol was added to the solution. And stirred at room temperature overnight. The methanol was distilled off from the solution under reduced pressure, washed with 5 ml of chloroform and dried to obtain 0.97
g of Mg-containing polymer were obtained. The polymer is removed under reduced pressure for 1
Heat treatment was performed at 00 ° C. for 4 hours. As a result of the water resistance test, the insoluble polymer weight was 78 mg, and the proton conductivity was 0.5 × 1.
It was from 0 ⁻¹ Scm ⁻¹ to 1 × 10 ⁻¹ Scm ⁻¹ .

The Mg-containing sulfonated poly (1,1) obtained above
4-biphenylene ether ether sulfone) in DMF
The resulting solution was used to obtain a 50 μm cast film. A membrane-electrode assembly was prepared in the same manner as in Example 1 except that this was used as an ion exchange membrane, and a fuel cell was assembled. It was operated under the same conditions as in Example 1. As a result 70
The battery voltage at a current density of 0 mA / cm ² was 540 mV. Current density 70 after 500 hours of operation under these conditions
The battery voltage at 0 mA / cm ² was 527 mV, and the voltage drop was 2.4%. This fuel cell is 1000
Even after continuous operation for a long time, stable operation was possible.

[0054]

Example 4 The same operation as in Example 3 was carried out except that the amount of magnesium acetate tetrahydrate was changed to 79 mg. Results of the water resistance test, insoluble polymer weight 96 mg, proton conductivity was ^{0.3 × 10 -1 Scm -1 ~0.9 ×} 10 -1 Scm -1. A membrane-electrode assembly was prepared in the same manner as in Example 3 except that the metal-containing sulfonated poly (1,4-biphenylene ether ether sulfone) was used, and a fuel cell was assembled. As a result of the measurement, the battery voltage at a current density of 700 mA / cm ² was 530 mV. 5 under these conditions
After operating for 00 hours, the battery voltage at a current density of 700 mA / cm ² was 522 mV, and the voltage drop was 1.6%. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0055]

Example 5 The same operation as in Example 3 was carried out except that the amount of magnesium acetate tetrahydrate was changed to 196 mg. As a result of the water resistance test, the weight of the insoluble polymer was 98 mg, and the proton conductivity was 0.1 × 10 ⁻¹ Scm ^{−1 to} 0.5 × 10 ⁻¹ Scm ^−1.
Met. A membrane-electrode assembly was prepared in the same manner as in Example 3 except that the metal-containing sulfonated poly (1,4-biphenylene ether ether sulfone) was used, and a fuel cell was assembled. As a result of the measurement, the battery voltage at a current density of 700 mA / cm ² was 524 mV. After operating under these conditions for 500 hours, the battery voltage at a current density of 700 mA / cm ² was 518 mV, and the voltage drop was 1.1%. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0056]

Example 6 The same operation was carried out except that 50 mg of aluminum triisopropoxide was used instead of magnesium acetate tetrahydrate of Example 3. As a result of the water resistance test, the insoluble polymer weight was 98 mg, and the proton conductivity was 0.3 × 10
It was ^{-1 Scm -1 ~0.9 × 10 -1 Scm} -1. A membrane-electrode assembly was prepared in the same manner as in Example 3 except that the metal-containing sulfonated poly (1,4-biphenylene ether ether sulfone) was used, and a fuel cell was assembled. As a result of the measurement, the battery voltage at a current density of 700 mA / cm ² was 532 mV. After 500 hours of operation under these conditions, the battery voltage at a current density of 700 mA / cm ² was 5
It was 24 mV and the voltage drop was 1.5%. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0057]

Example 7 The same operation was carried out except that 300 mg of lanthanum acetate hydrate was used instead of magnesium acetate tetrahydrate of Example 3. 0.98 g of the La-containing polymer was obtained.
This polymer was heated at 150 ° C. for 4 hours under reduced pressure.
Insoluble polymer weight 99mg, proton conductivity 0.4
× 10 ⁻¹ Scm ⁻¹ to 1 × 10 ⁻¹ Scm ⁻¹ . A membrane-electrode assembly was prepared in the same manner as in Example 3 except that the metal-containing sulfonated poly (1,4-biphenylene ether ether sulfone) was used, and a fuel cell was assembled. As a result of the measurement, the battery voltage at a current density of 700 mA / cm ² was 540 mV. After 500 hours of operation under these conditions, the battery voltage at a current density of 700 mA / cm ² was 5
It was 35 mV and the voltage drop was 0.9%. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0058]

Example 8 The same operation was performed except that 65 mg of titanium isopropoxide was used instead of magnesium acetate tetrahydrate of Example 3. The insoluble polymer weight is 99 mg, and the proton conductivity is 0.4 × 10 ⁻¹ Scm ⁻¹ to 1 × 10 ⁻¹ Scm.
It was ^-1 . Except for using the metal-containing sulfonated poly (1,4-biphenylene ether ether sulfone),
A membrane-electrode assembly was prepared in the same manner as in Example 3, and a fuel cell was assembled. The measurement result was 700 mA / cm ²
At a current density of 531 mV. A current density of 700 mA / cm ² after operating for 500 hours under these conditions
Battery voltage is 520 mV and the voltage drop is 2.1%
Met. This fuel cell was able to operate stably even after continuous operation for 1000 hours.

[0059]

Comparative Example 1 Polyethersulfone [(-C₆H_Four-4-SO_TwoC₆H_Four-
4-O)_n] (D1.37) 5.00 g (Aldrich
Was dissolved in 50 ml of methylene chloride. This solution
The mixture was stirred at room temperature for one day. After 4 hours polymer crystallization
Started. Cool the suspension to 0-5 ° C with stirring
did. This suspension was stirred vigorously while 10 wt% SO
_ThreeWas added over 30 minutes.
Was. The reaction was stirred for another 2 hours. Top layer methyle chloride
The layer was removed by decantation. Precipitated poly
The product is filtered, washed with methylene chloride, and
Washed. The remaining polymer is reduced under reduced pressure over phosphorus pentoxide to 100
Dried at ° C. 5.21 g of polymer were obtained. this
The polymer was insoluble in water and soluble in methanol. Equivalent
The weight was 354 g / eq. This sulfonated poly
The ether sulfone was replaced with the sulfonated poly (1,4
-Biphenylene ether ether sulfone)
Except for using, a membrane-electrode assembly was prepared in the same manner as in Example 1.
The fuel cell was fabricated and assembled.

This fuel cell was connected to an external load, and on the one hand, 1 atm hydrogen gas saturated with 70 ° C. steam and 1 atm oxygen gas saturated with 70 ° C. steam on the other side.
The fuel cell body was maintained at 70 ° C. while supplying the gas from each gas inlet, and the change in output voltage was measured by changing the current density while changing the external load. As a result 700m
The battery voltage at a current density of A / cm ² was 560 mV. 700m current density after 500 hours operation under these conditions
The battery voltage at A / cm ² was 500 mV, and the voltage drop was 11%.

The Examples and Comparative Example 1 show that the membrane-electrode assembly of the present invention is stable for a long time. Examples 3 to
It is evident that the inclusion of a metal according to No. 8 significantly improves the water resistance, and from the results of the proton conductivity, it is clear that it can be used as an ion exchange membrane for a polymer electrolyte fuel cell.

[0062]

By using the membrane-electrode assembly of the present invention, it is possible to assemble a fuel cell having good durability represented by long-term stable operation, good proton conductivity and low generation of waste fluorine. it can.

[Brief description of the drawings]

FIG. 1 is a schematic view of a membrane-electrode assembly used for a polymer electrolyte fuel cell.

FIG. 2 is an enlarged schematic view of a portion A in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion exchange membrane 2 Gas diffusion electrode (hydrogen electrode) 3 Gas diffusion electrode (oxygen electrode) 4 Catalyst (platinum-supporting carbon) 5 Binder polymer

Claims (6)

[Claims] 1. A membrane-electrode assembly for a polymer electrolyte fuel cell comprising an ion exchange membrane, a catalyst layer joined to the ion exchange membrane and a gas diffusion electrode, wherein the ion exchange membrane and / or the catalyst A membrane-electrode assembly for a polymer electrolyte fuel cell, wherein the layer has a sulfonated polyaryl ether sulfone represented by the chemical formula (1). Embedded image (A is an integer of 1 to 4. p is an integer of 1 to 5.
n is an integer of 2 to 1000. X represents H or a monovalent to tetravalent metal. Ar represents an aromatic residue. ) 2. The membrane-electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the catalyst layer is constituted by a catalyst coated with a sulfonated polyaryl ether sulfone. 3. The membrane-electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the ion exchange membrane is a fluoropolymer having a sulfonic acid group. 4. The sulfonated polyaryl ether sulfone according to claim 1, 2 or 3, wherein the sulfonated polyaryl ether sulfone has an equivalent weight of 150 to 2000 g / eq.
Membrane-electrode assembly for a polymer electrolyte fuel cell. 5. X of the sulfonated polyaryl ether sulfone represented by the chemical formula (1) is 1% to 95% of 1
5. The membrane-electrode assembly for a polymer electrolyte fuel cell according to claim 1, which is a metal having a valence of 4 to 4. 6. The sulfonated polyaryl ether sulfone according to claim 1, wherein the sulfonated polyaryl ether sulfone has a structure represented by the chemical formula (2).
3, 4 or 5 membrane-electrode assemblies. Embedded image (C and d are each an integer of 0 to 4 and neither c nor d is 0. n is an integer of 2 to 1000.
X represents H or a monovalent to tetravalent metal. )