JP2003051320A - Membrane-electrode junction for solid polymer type fuel cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer type fuel cell having an excellent power generation characteristic and excellent durability by providing a mass-producible membrane-electrode junction having a thin electrolyte membrane and/or a catalyst layer having a uniform thickness, and is low resistance and high tear strength and easy to handle. SOLUTION: In this manufacturing method for the membrane-electrode junction used for arranging and integrating a cathode and an anode comprising electrodes having catalyst layers on/with both surfaces of a solid polymer electrolyte membrane, a cation exchange membrane and/or the catalyst layer is formed by using a dispersion liquid prepared by dispersing an ion exchanger polymer comprising a fluorine-containing polymer having a sulfonic acid group and a fibril-like fluorocarbon polymer in a dispersion medium.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a membrane / electrode assembly for a polymer electrolyte fuel cell, a method for producing the same, and a polymer electrolyte fuel cell including the membrane / electrode assembly.

[0002]

2. Description of the Related Art A hydrogen / oxygen fuel cell has been attracting attention as a power generation system that has a reaction product of only water in principle and has almost no adverse effect on the global environment. The polymer electrolyte fuel cell was once installed in a spacecraft under the Gemini and biosatellite projects, but the cell power density at that time was low. Later, higher performance alkaline fuel cells were developed, and alkaline fuel cells have been adopted for space use up to the present space shuttle.

However, polymer electrolyte fuel cells have been receiving attention again due to technological progress in recent years. The reasons are as follows. (1) A highly conductive membrane has been developed as a solid polymer electrolyte. (2) By supporting the catalyst used in the gas diffusion electrode layer on carbon and coating it with an ion exchange resin, high activity can be obtained.

In order to further improve the performance, it is considered that the electrical resistance is reduced by increasing the concentration of sulfonic acid groups and reducing the thickness of the solid polymer electrolyte membrane. However, a significant increase in the concentration of sulfonic acid groups reduces the mechanical strength and tear strength of the electrolyte membrane, causes dimensional changes during handling, and causes the electrolyte membrane to creep easily during long-term operation, resulting in reduced durability. Problems such as occur. On the other hand, the reduction in thickness causes problems such as reduction in mechanical strength and tear strength of the electrolyte membrane, and further deterioration in workability and handleability when the membrane is bonded to a gas diffusion electrode.

Further, in order to improve the performance, it has been attempted to increase the platinum loading rate to make the catalyst layer thin.
The catalyst portion in the catalyst layer is brittle, and the ion-exchange resin contained in the catalyst layer is usually formed using a coating liquid, so mechanical properties such as compression creep and elastic modulus are not sufficient, and durability is improved. Problems are likely to occur.

[0006]

As a method for solving the above problems, polytetrafluoroethylene (hereinafter referred to as PT
It is called FE. ) A method of impregnating a porous ion exchange polymer having a sulfonic acid group into a porous membrane has been proposed (Japanese Patent Publication No. 5-75835). However, although the thickness can be reduced, the electrical resistance of the porous PTFE is high. There was a problem that it did not fall sufficiently. Further, in this method, since the interface between the PTFE porous membrane and the ion exchange polymer is not completely adhered, when used as an electrolyte membrane of a polymer electrolyte fuel cell, hydrogen gas leaks due to poor adhesion after long-term use. However, there is a problem that the battery performance increases and the battery performance decreases.

As a method for solving the problem that the electric resistance of the reinforced membrane is high, a cation exchange membrane reinforced with a fibril-like, woven cloth-like or non-woven cloth-like perfluorocarbon polymer has been proposed (Japanese Patent Laid-Open No. Hei 6) 231779). This membrane had low resistance, and the fuel cell produced using this membrane had relatively good power generation characteristics, but the thickness was 100 to 100 at most.
Since the thickness was 200 μm, and the thickness was not sufficiently thin and the thickness was uneven, the power generation characteristics and mass productivity were insufficient. Further, the adhesion between the perfluorocarbon polymer and the fluorinated ion exchanger polymer having a sulfonic acid group was not sufficient, and the hydrogen gas permeability was relatively high, so the output when the fuel cell was constructed was insufficient. .

Therefore, the present invention has a uniform thickness and a low resistance, a low hydrogen gas permeability, a small dimensional change due to heat and humidification, a high anisotropy, a high tear strength and an excellent handling property. Provided is a method for producing an electrolyte membrane and / or catalyst layer for a polymer electrolyte fuel cell that can be mass-produced, and a solid polymer having excellent power generation characteristics and durability by including the obtained electrolyte membrane and / or catalyst layer. An object is to provide a type fuel cell.

[0009]

The present invention provides a solid polymer in which a cathode and an anode each having an electrode having a catalyst layer containing a catalyst are arranged and integrated on both sides of a solid polymer electrolyte membrane composed of a cation exchange membrane. In the method for producing a membrane / electrode assembly for a fuel cell, the cation exchange membrane comprises an ion exchange polymer composed of a fluoropolymer having a sulfonic acid group and a fibril-like fluorocarbon polymer dispersed in a dispersion medium. Provided is a method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell, which is characterized in that the dispersion is used to form a membrane.

Further, the present invention provides a solid polymer electrolyte fuel cell in which a cathode and an anode each having an electrode having a catalyst layer containing a catalyst are arranged on both sides of a solid polymer electrolyte membrane each composed of a cation exchange membrane. In the method for producing a membrane / electrode assembly for an electrode, the cathode catalyst layer and / or the anode catalyst layer comprises an ion-exchange polymer made of a fluoropolymer having a sulfonic acid group and a fibril-like fluorocarbon polymer. Provided is a method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell, which is formed by using a liquid obtained by mixing a dispersion liquid dispersed in a dispersion medium and a catalyst.

Furthermore, the present invention provides a solid polymer electrolyte fuel cell in which a cathode and an anode each having an electrode having a catalyst layer containing a catalyst are arranged and integrated on both sides of a solid polymer electrolyte membrane which is a cation exchange membrane. In the membrane / electrode assembly for use in the cathode, the catalyst layer of the cathode and / or the catalyst layer of the anode contains an ion-exchange polymer made of a fluoropolymer having a sulfonic acid group, a fibril-like fluorocarbon polymer and a catalyst. A membrane / electrode assembly for a polymer electrolyte fuel cell, which is characterized by being included, and a solid high to which the membrane / electrode assembly is provided, to which a gas containing oxygen and a gas containing hydrogen are supplied to the cathode and the anode, respectively. A molecular fuel cell is provided.

An ion exchange membrane formed by a dispersion liquid (hereinafter referred to as the present dispersion liquid) in which an ion exchange polymer and a fibrillar fluorocarbon polymer according to the present invention are dispersed in a dispersion medium is in the in-plane direction of the membrane. A reinforcing material (hereinafter referred to as the present reinforcing material) uniformly composed of a fibrillar fluorocarbon polymer is included. Normally, when a film containing the reinforcing material is produced by extrusion molding, the fibrils are strongly oriented in the MD direction (the direction of extrusion when forming the film), resulting in strength in the MD direction and the TD direction (direction perpendicular to the MD direction). Anisotropy of different values occurs. With the ion exchange membrane obtained using this dispersion, such anisotropy can be reduced, and the anisotropy can be substantially eliminated, and the mechanical strength such as tear strength and tensile strength of the membrane can be improved. It can be improved without directionality.

Therefore, the membrane-electrode assembly provided with this membrane as an electrolyte membrane is excellent in handleability, and the dimensional change due to heat and humidification can be extremely isotropically reduced. As a result, it is possible to easily manufacture a membrane-electrode assembly including a thin cation exchange membrane, which was difficult with the conventional technique.

Furthermore, the film produced using this dispersion is M
Since the mechanical strength is high without anisotropy in the D and TD directions,
The durability of the membrane / electrode assembly including the membrane is excellent.
In the polymer electrolyte fuel cell, the gas supplied to the anode and the cathode is usually an ion exchanger polymer (hereinafter referred to as a catalyst layer resin) contained in the catalyst layer and saturated steam for ensuring the proton conductivity of the membrane. It is often humidified to near pressure. However, when the current density and water vapor concentration in the membrane / electrode assembly were simulated, the current density distribution, temperature distribution, and water vapor pressure distribution were not uniform on all sides of the membrane / electrode assembly, and Heat is generated and the catalyst layer resin in the membrane or catalyst layer is partially dried,
It has been found that there is a high probability of non-uniform, localized shrinkage or swelling. In such a case, if the reinforcing material is uniformly dispersed in the film, mechanical deformation or crack due to local shrinkage or swelling is less likely to occur, and for example, a film / electrode provided with a film having a thickness of 30 μm or less. It is considered that even a bonded body has excellent durability.

The present dispersion can also be used for forming a catalyst layer by mixing catalyst powder. That is, by using a liquid obtained by mixing the main dispersion liquid and the catalyst powder, it is possible to form a membrane / electrode assembly including a catalyst layer containing a reinforcing material (main reinforcing material) made of a fibril-like fluorocarbon polymer. By including this reinforcing material in the catalyst layer resin, the tensile elastic modulus of the catalyst layer resin is improved and the mechanical properties of the catalyst layer resin are improved, so the durability of the membrane / electrode assembly during power generation is improved. .

In the present invention, examples of the fibril-like fluorocarbon polymer include copolymers containing 95 or more mol% of polymer units based on PTFE and tetrafluoroethylene. In the case of a copolymer, it must be a fibrillizable copolymer, preferably a copolymer of tetrafluoroethylene and a fluorine-containing monomer, and containing 99% or more of polymer units based on tetrafluoroethylene. Is preferred. Specifically, PTFE, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-perfluoro (2,2
-Dimethyl-1,3-dioxole) copolymers, tetrafluoroethylene-perfluoro (butenyl vinyl ether) copolymers and other tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymers, and the like, but especially PTFE Is preferred.

The fibrillar fluorocarbon polymer is
It is preferable that 0.5 to 15 mass% of the total solid content of the present dispersion is contained. If it is less than 0.5% by mass, the reinforcing effect is not sufficiently exhibited, and if it is more than 15% by mass, the resistance tends to increase. When the fibrillar fluorocarbon polymer is 2 to 10% by mass based on the total solid content, the resistance does not increase and the reinforcing effect is sufficiently expressed, and the viscosity of the dispersion is not too high, and the electrolyte membrane or It is particularly preferable because the catalyst layer can be easily formed. The content of the fibrillar fluorocarbon polymer referred to here is the content of all the fibrillated or fibrillizable fluorocarbon polymers, the polymer contained without fibrillation and the fibrillated It also includes the amount of polymer present. That is, for example, when PTFE is used as the polymer, it indicates the content of PTFE in the total mass of the solid content.

As the fluorine-containing polymer having a sulfonic acid group in the present invention, well-known polymers are widely adopted, but the general formula CF ₂ ═CF (OCF ₂ CFX) _m —O _p — (C
F ₂ ) _n SO ₃ H (wherein X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, and n is 0 to
It is an integer of 12, p is 0 or 1, and when n = 0, p = 0. A copolymer containing a polymer unit based on a perfluorovinyl compound represented by the formula (1) and a polymer unit based on a perfluoroolefin or a perfluoroalkyl vinyl ether is preferable. Specific examples of the perfluorovinyl compound include compounds represented by any one of formulas 1 to 4. However, in Formulas 1 to 4, q is 1
Is an integer of -9, r is an integer of 1-8, s is 0-
Is an integer of 8 and z is 2 or 3.

[0019]

[Chemical 1]

A polymer containing polymerized units based on a perfluorovinyl compound having a sulfonic acid group is usually -SO ₂
It is polymerized using a perfluorovinyl compound having an F group. The perfluorovinyl compound having a —SO ₂ F group can be homopolymerized, but since it has low radical polymerization reactivity, it is usually used by copolymerizing with a comonomer such as perfluoroolefin or perfluoro (alkyl vinyl ether). To be Examples of the perfluoroolefin serving as a comonomer include tetrafluoroethylene, hexafluoropropylene and the like, and usually tetrafluoroethylene is preferably used.

As perfluoro (alkyl vinyl ether) as a comonomer, CF ₂ ═CF— (OCF ₂ C
The compound represented by FY) _t —O—R ^f is preferable. However, in the formula, Y is a fluorine atom or a trifluoromethyl group, t is an integer of 0 to 3, R ^f is a linear or branched perfluoroalkyl group represented by C _u F _{2u + 1.} (1 ≦
u ≦ 12). _{CF 2 = CF- (OCF 2 CFY} ) t
Preferred examples of the compound represented by —O—R ^f include the compounds represented by any one of formulas 5 to 7. However, in the formulas 5 to 7, v is an integer of 1 to 8 and w is 1 to
Is an integer of 8 and x is an integer of 1 to 3.

[0022]

[Chemical 2]

Further, in addition to perfluoroolefin and perfluoro (alkyl vinyl ether), a fluorine-containing monomer such as perfluoro (3-oxahepta-1,6-diene) has a --SO ₂ F group as a comonomer. It may be copolymerized with.

In the present invention, the concentration of the sulfonic acid group in the fluoropolymer having a sulfonic acid group constituting the electrolyte membrane and / or the catalyst layer resin, that is, the ion exchange capacity is 0.5 to 2.0 mm. Equivalent / g dry resin, especially 0.
It is preferably 7 to 1.6 meq / g dry resin. When the ion exchange capacity is lower than this range, the resulting electrolyte membrane and / or catalyst layer resin has a large resistance,
On the other hand, when it is high, the mechanical strength of the electrolyte membrane and / or the resin of the catalyst layer becomes insufficient.

The dispersion medium of the present dispersion liquid is not particularly limited, but examples thereof include the following. Methyl alcohol, ethyl alcohol, n-propyl alcohol, n
-Monohydric alcohols such as butyl alcohol and isopropyl alcohol. Polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin. 2,2,2-
Trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 2,2,3,3-tetrafluoro-1-propanol, 2,2,3,4,4,4
-Hexafluoro-1-butanol, 2,2,3,3,
4,4,4-heptafluoro-1-butanol, 1,
Fluorine-containing alcohols such as 1,1,3,3,3-hexafluoro-2-propanol.

Perfluoro oxygen-containing or nitrogen-containing compounds such as perfluorotributylamine and perfluoro-2-n-butyltetrahydrofuran, chlorofluorocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane , 3,3-dichloro-1,1,1,2,2-
Pentafluoropropane, 1,3-dichloro-1,1,
In addition to hydrochlorofluorocarbons such as 2,2,3-pentafluoropropane, polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and water can be used. These dispersion media may be used alone or in combination of two or more.

The concentration of the dispersion is preferably 0.3 to 30% by mass of the ion exchanger polymer based on the total mass of the solution. If it is less than 0.3% by mass, it takes time to volatilize the solvent, or high temperature heating is required to reduce the time, and if heated at a high temperature, ion clusters in the ion exchange resin become irreversibly small, Proton conductivity is reduced. When it exceeds 30% by mass, the viscosity of the present dispersion becomes high and the coatability at the time of forming the electrolyte membrane or the catalyst layer becomes poor. Further, when a catalyst is prepared by dispersing the catalyst in the present dispersion liquid, the thickness of the coating film of the catalyst layer resin that coats the catalyst may be increased and the battery performance may be deteriorated. It is particularly preferable that the concentration is 5 to 25% by mass.

In the present invention, the catalyst contained in the catalyst layer is platinum or a platinum alloy having a specific surface area of 50 to 2000 m.
A supported catalyst supported on a carbon material such as carbon black or activated carbon of about ² / g is preferable. As the platinum alloy, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium), gold, silver, chromium, iron,
Titanium, manganese, cobalt, nickel, molybdenum,
An alloy of platinum and one or more metals selected from the group consisting of tungsten, aluminum, silicon, zinc and tin can be preferably used. The catalyst contained in the cathode and the catalyst contained in the anode may be the same or different.

The thickness of the catalyst layer and the electrolyte membrane in the present invention is not particularly limited, but the thickness of the electrolyte membrane is 80 μm or less,
In particular, it is preferably 70 μm or less, more preferably 50 μm or less. When the thickness of the electrolyte membrane exceeds 80 μm, the concentration gradient of the amount of water vapor becomes small in the electrolyte membrane sandwiched between the anode and the cathode, and the electrolyte membrane tends to be in a dry state. Drop,
In addition, the membrane resistance itself increases, and the characteristics of the battery may deteriorate. From the above viewpoint, it is preferable that the electrolyte membrane is thinner, but if it is too thin, a short circuit occurs, or the hydrogen gas permeation amount increases and the open circuit voltage decreases, so it is more preferably 5 to 70 μm, further 10 to 50 μm. preferable.

The thickness of the catalyst layer is 20 μm from the viewpoint of facilitating gas diffusion in the catalyst layer and improving battery characteristics.
m or less, more preferably uniform,
It is preferably smooth. According to the production method of the present invention, even a catalyst layer having a thickness of 20 μm or less can be formed with a uniform thickness. If the thickness of the catalyst layer is reduced, the amount of catalyst present per unit area may decrease and the reaction activity may decrease, but in this case, a supported catalyst in which platinum or a platinum alloy is supported at a high loading rate as a catalyst is used. If used, the reaction activity of the electrode can be kept high without depleting the amount of catalyst even if it is thin. From the above viewpoint, the thickness of the catalyst layer is more preferably 1
Is about 15 μm.

The method for producing the present dispersion is not particularly limited, but the following method may be mentioned, for example. A mixture of a fluorine-containing polymer having a —SO ₂ F group and a powder of a fibrillatable fluorocarbon polymer is biaxially extruded to obtain pellets. When it is desired to further fibrillate the fluorocarbon polymer, the pellets may be extruded and formed into a film. Then, the obtained pellet or film is subjected to hydrolysis and acid type treatment to convert the —SO ₂ F group into a sulfonic acid group (—SO ₃ H group) and disperse this in a dispersion medium to obtain the present dispersion liquid. can get. Before the pellets or film are dispersed in the dispersion medium, it is preferable to grind into powder having a particle size of about 1 to 500 μm with a grinder such as a freeze grinder because the powder can be easily dispersed.

Here, the fluorocarbon polymer which can be fibrillated at the time of kneading with a twin-screw extruder (and at the time of extrusion forming into a film) is subjected to a shearing force to be fibrillated. The presence of the fibrillar fluorocarbon polymer in the present dispersion can be confirmed by, for example, removing the dispersion medium from the present dispersion and observing it with a scanning electron microscope (SEM). Specifically, it can be confirmed by the following method.

The thickness of this dispersion when dried is approximately uniform to about 3
A cast film is formed by dropping it on a petri dish so as to have a thickness of 0 μm and holding it in an oven at 60 ° C. for 3 hours.
After the cast film is peeled from the petri dish, the surface is subjected to plasma etching treatment and observed by SEM at a magnification of 5,000 to 10,000 times. In the case of this dispersion prepared by the above method, it can be confirmed that the fibrillated fluorocarbon polymer has a short fiber shape.

The electrode in the membrane-electrode assembly of the present invention is
Both the cathode and anode may consist of only the catalyst layer, but a conductive porous body such as carbon cloth or carbon paper is placed as a gas diffusion layer on the outside of the membrane / electrode assembly to make the gas uniform in the catalyst layer. You may make it play the role of diffusing in and the role of a collector. The gas diffusion layer may be arranged not only on the outside of the catalyst layer but also by hot pressing, for example, to be joined to the catalyst layer.

In the polymer electrolyte fuel cell of the present invention, for example, a separator having a groove serving as a gas flow path is provided outside the membrane / electrode assembly, and oxygen such as air is provided on the cathode side of the separator. A gas containing hydrogen is caused to flow, and a gas containing hydrogen is supplied to the anode side to generate electricity. A plurality of membrane / electrode assemblies may be laminated via a separator to form a stack.

The method for producing a membrane / electrode assembly using this dispersion is not particularly limited. For example, a catalyst layer-forming coating liquid in which a catalyst and a catalyst layer resin are dispersed is applied to a separately prepared base material. Then, two dispersions were applied to form the ion-exchange membrane to form the ion-exchange membrane, and the ion-exchange membranes were faced to each other so that they face each other.
It is possible to obtain a membrane / electrode assembly in which a membrane formed by laminating a plurality of ion exchange membranes is used as an electrolyte membrane. In addition, three base materials were prepared, and the coating liquid for forming the catalyst layer for the anode, the coating liquid for forming the catalyst layer for the cathode, and the main dispersion were coated one by one to prepare the anode catalyst layer and the cathode. After forming the catalyst layer and the ion exchange membrane and peeling the ion exchange membrane from the substrate,
It can also be obtained by hot pressing with the ion exchange membrane sandwiched between the anode catalyst layer and the cathode catalyst layer facing each other.

When both the ion exchange membrane and the catalyst layer contain a fibrillar fluorocarbon polymer, the dispersion liquid obtained by mixing the main dispersion liquid and the catalyst can be used as the coating liquid for forming the catalyst layer in each of the above-mentioned methods. Good. When an ion exchange membrane is not produced using the dispersion, (1) a method of applying a catalyst layer-forming coating liquid containing the dispersion on both sides of the ion exchange membrane, (2) a gas diffusion layer A method of forming two sheets by applying a coating liquid for forming a catalyst layer containing the main dispersion liquid to the above and hot pressing them with an ion exchange membrane interposed therebetween, (3) applying the main dispersion liquid to a separately prepared substrate. A method of transferring two catalyst layers to an ion exchange membrane by hot pressing with an ion exchange membrane sandwiched between two prepared catalyst layer-forming coating solutions Various known methods can be adopted.

[0038]

EXAMPLES [Example 1 (Example)] Tetrafluoroethylene
Based polymerized units and CF₂= CF-OCF₂CF (C
F ₃) O (CF₂)₂SO₂Consisting of polymerized units based on F
Copolymer powder (ion exchange capacity 1.1 meq / g
Dry resin, hereinafter referred to as copolymer A. ) 9730g and P
TFE powder (trade name: Fluon CD-1, manufactured by Asahi Glass Co., Ltd.)
270g is mixed and pelletized by biaxial extrusion molding
What was done (9500 g) was obtained. Freeze this pellet
After crushing with a crusher, 30% of the total mass of the solution
15% by weight of the total solution of potassium sulfoxide and potassium hydroxide
Hydrolyze in an aqueous solution containing um to give 1 mol / L hydrochloric acid
Immerse at room temperature for 16 hours-SO₂The F group is in the acid form (sulfo
Acid group), washed with water and dried.

This was dispersed in ethanol, the dispersoid concentration was 10% of the total mass of the dispersion, and the fibril-like fluorocarbon polymer (2.7% of the total solute) and perfluorocarbon containing sulfonic acid groups. A fibrillar fluorocarbon polymer-containing ion-exchanger polymer dispersion (hereinafter referred to as dispersion a) containing a polymer was obtained.

Polymerized units based on tetrafluoroethylene
And CF₂= CF-OCF₂CF (CF ₃) O (CF₂)₂S
O₃Copolymer consisting of polymerized units based on H and platinum ruthe
Supporting a nickel alloy (platinum: ruthenium in a molar ratio of 4: 6)
Carbon (carbon: alloy is 1: 1 by mass ratio) and 5:
9 in a mass ratio of 9 and solids dissolved or dispersed in ethanol.
Dispersion liquid for forming anode catalyst layer having a concentration of 10 mass%
And

Further, the above-mentioned copolymer and platinum-supporting carbon (platinum: carbon in a mass ratio of 1: 1) are contained in a mass ratio of 1: 2, and a solid content concentration of ethanol is 13.7.
The dispersion liquid of mass% was used as the dispersion liquid for forming the cathode catalyst layer.

A dispersion liquid for forming an anode catalyst layer was formed to a thickness of 50.
The amount of platinum ruthenium deposited on one surface of a substrate made of a polypropylene (hereinafter referred to as PP) film having a thickness of 0.5 μm is 0.5.
The anode catalyst layer was formed by coating by a die coating method so as to be 0 mg / cm ² and drying. Similarly, the cathode catalyst layer-forming dispersion liquid was applied to one surface of a base material made of a PP film having a thickness of 50 μm, which was different from the above PP film, by a die coating method so that the amount of platinum deposited was 0.40 mg / cm ^2. Then, the cathode catalyst layer was formed by drying.

Next, the dispersion a is applied onto a PP film other than the above-mentioned PP film by a die coating method, and dried in an oven at 80 ° C. for 10 minutes to obtain a thickness containing a reinforcing material composed of a fibril-like fluorocarbon polymer. An ion exchange membrane having a thickness of 30 μm was formed.

The PP film having the cathode catalyst layer obtained above on one surface and the P film having the anode catalyst layer formed thereon
The P film was made to face with the surface on which the catalyst layer was formed facing inward, and the above ion exchange membrane from which the PP film had been peeled off was sandwiched between them as an electrolyte membrane to perform hot pressing. Hot press conditions are 130 ℃,
The pressure was set to 3 MPa for 4 minutes, and after hot pressing, the catalyst layer was transferred to the membrane by peeling the PP film from the catalyst layer for both the cathode and the anode, to obtain a membrane / electrode assembly including the catalyst layer and the ion exchange membrane.

The membrane / electrode assembly obtained above was cut out so that the effective electrode area was 25 cm ^2, and incorporated into a cell for measuring battery performance. Hydrogen gas was supplied to the anode and air was supplied to the cathode, and the cell temperature was set to 80. A power generation test was conducted at ° C. The initial output voltage at a current density of 0.2 A / cm ² and the output voltage after continuous operation for 1000 hours were measured. The results are shown in Table 1.

Example 2 (Example) The amount of the copolymer A powder used for pelletizing was changed to 9600 g, and PT
A dispersion liquid (hereinafter referred to as dispersion liquid b) was obtained in the same manner as in Example 1 except that the amount of FE powder was changed to 400 g. A membrane / electrode assembly was obtained in the same manner as in Example 1 except that an ion exchange membrane was prepared using this dispersion liquid b instead of the dispersion liquid a. The obtained membrane-electrode assembly was incorporated into a cell for measuring battery performance in the same manner as in Example 1 and tested in the same manner as in Example 1. The results are shown in Table 1.

Example 3 (Example) The amount of the copolymer A powder used for pelletization was changed to 9300 g, and PT
A dispersion liquid was obtained in the same manner as in Example 1 except that the amount of FE powder was changed to 700 g. A membrane / electrode assembly was obtained in the same manner as in Example 1 except that an ion exchange membrane was prepared using this dispersion instead of the dispersion a. The obtained membrane-electrode assembly was used in Example 1
It was incorporated into a cell for measuring battery performance in the same manner as above and tested in the same manner as in Example 1. The results are shown in Table 1.

Example 4 (Example) Used in Dispersion a in Example 1 such that the total amount of the fibrillar fluorocarbon polymer and the ion-exchanger polymer and the platinum-carrying carbon were in a mass ratio of 1: 2. The same platinum-carrying carbon as described above was dispersed to obtain a dispersion liquid having ethanol as a solvent and having a solid content concentration of 13.7% by mass. A membrane / electrode assembly was obtained in the same manner as in Example 1 except that this was used as a dispersion liquid for forming a cathode catalyst layer to form a cathode catalyst layer. The membrane / electrode assembly obtained above was incorporated into a cell for measuring battery performance in the same manner as in Example 1, and the same test as in Example 1 was conducted. The results are shown in Table 1.

[Example 5 (Comparative Example)] The anode catalyst layer-forming dispersion liquid used in Example 1 was coated on one side of a 50-μm-thick PP film substrate with platinum ruthenium adhesion of 0.50 m.
The anode catalyst layer was formed by coating by a die coating method so as to be g / cm ² and drying. Similarly, using a cathode catalyst dispersion liquid, a cathode catalyst layer was formed by a die coating method so that the platinum deposition amount was 0.40 mg / cm ^{2 on} one surface of a base material made of a PP film having a thickness of 50 μm different from the above PP film. Was coated and dried to form a cathode catalyst layer.

The two sheets obtained as described above are made to face each other with the surface on which the catalyst layer is formed facing inward, and an ion exchange membrane made of a sulfonic acid type perfluorocarbon polymer as a solid polymer electrolyte membrane is provided therebetween ( Product name: Flemion HR, manufactured by Asahi Glass Co., Ltd., ion exchange capacity: 1.1 meq / g dry resin, dry film thickness 30 μm) were sandwiched and hot pressed. The conditions of hot pressing are 130 ° C. and 3 MPa for 4 minutes, and after hot pressing, the catalyst layer is transferred to the membrane by peeling the base material sheet from the catalyst layer for both the cathode and the anode, and the membrane / electrode composed of the catalyst layer and the membrane. A joined body was obtained.

The obtained membrane-electrode assembly was incorporated into a cell for measuring battery performance in the same manner as in Example 1 and tested in the same manner as in Example 1. The results are shown in Table 1.

[0052]

[Table 1]

[0053]

EFFECTS OF THE INVENTION According to the present invention, a membrane / electrode assembly including an electrolyte membrane and / or a catalyst layer having a uniformly thin thickness, a low resistance and a high tear strength can be obtained. The polymer electrolyte fuel cell including the body has excellent power generation characteristics and durability. Furthermore, the manufacturing method of the present invention,
Suitable for mass production.

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Claims (11)

[Claims] 1. A membrane-electrode junction for a polymer electrolyte fuel cell, in which a cathode and an anode composed of electrodes having a catalyst layer containing a catalyst are arranged and integrated on both sides of a solid polymer electrolyte membrane composed of a cation exchange membrane. In the method for producing a body, the cation exchange membrane is a membrane using a dispersion liquid in which an ion exchange polymer composed of a fluoropolymer having a sulfonic acid group and a fibril-like fluorocarbon polymer are dispersed in a dispersion medium. A method for producing a membrane / electrode assembly for a polymer electrolyte fuel cell, which comprises: 2. A membrane / electrode junction for a polymer electrolyte fuel cell in which a cathode and an anode each having an electrode having a catalyst layer containing a catalyst are arranged and integrated on both sides of a solid polymer electrolyte membrane made of a cation exchange membrane. In the method for producing a body, in the catalyst layer of the cathode and / or the catalyst layer of the anode, an ion-exchange polymer composed of a fluoropolymer having a sulfonic acid group and a fibril-like fluorocarbon polymer are dispersed in a dispersion medium. A method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell, which comprises forming a layered structure by using a liquid obtained by mixing the dispersion liquid and the catalyst. 3. The cation exchange membrane is formed into a film by using a dispersion liquid in which an ion exchange polymer composed of a fluoropolymer having a sulfonic acid group and a fibril-like fluorocarbon polymer are dispersed in a dispersion medium. The method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell according to claim 2, which is formed. 4. The fibril-like fluorocarbon polymer is contained in the dispersion liquid in an amount of 0.5 to 15% by mass based on the total mass of the solid content of the dispersion liquid. A method for producing a membrane-electrode assembly for a polymer electrolyte fuel cell. 5. The solid polymer according to claim 1, wherein the fibril-like fluorocarbon polymer comprises a polytetrafluoroethylene or a copolymer containing 95 mol% or more of polymer units based on tetrafluoroethylene. A method for producing a membrane-electrode assembly for a molecular fuel cell. 6. The fluorinated polymer having a sulfonic acid group comprises a polymer unit based on tetrafluoroethylene and CF _{2
= CF (OCF 2 CFX) m} -O p - (CF 2) n SO 3 H in based polymer units (wherein X is a fluorine atom or a trifluoromethyl group, A is sulfonic acid group or a precursor group Yes, m is an integer of 0 to 3, n is an integer of 0 to 12, p is 0 or 1, and when n is 0, p is also 0.
Is. 6. The method for producing a membrane / electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the method is a copolymer consisting of 7. A membrane / electrode for a polymer electrolyte fuel cell in which a cathode and an anode each having an electrode having a catalyst layer containing a catalyst are arranged and integrated on both sides of a solid polymer electrolyte membrane made of a cation exchange membrane. In the joined body, the cathode catalyst layer and / or the anode catalyst layer may contain an ion exchanger polymer made of a fluorinated polymer having a sulfonic acid group, a fibril-like fluorocarbon polymer, and a catalyst. Characteristic membrane-electrode assembly for polymer electrolyte fuel cells. 8. The fibril-like fluorocarbon polymer is contained in the catalyst layer of the cathode and / or the catalyst layer of the anode in a total amount of 0.5 to 15 with the fluoropolymer having a sulfonic acid group. The membrane / electrode assembly for a polymer electrolyte fuel cell according to claim 7, wherein the membrane / electrode assembly is contained in an amount of mass%. 9. The cation exchange membrane contains an ion exchange polymer comprising a fluorinated polymer having a sulfonic acid group and a fibril-like fluorocarbon polymer.
Alternatively, the membrane / electrode assembly for a polymer electrolyte fuel cell according to item 8. 10. The solid polymer according to claim 7, wherein the fibril-like fluorocarbon polymer comprises polytetrafluoroethylene or a copolymer containing 95 mol% or more of polymer units based on tetrafluoroethylene. Membrane / electrode assembly for molecular fuel cells. 11. The film according to any one of claims 7 to 10.
A polymer electrolyte fuel cell, comprising an electrode assembly, wherein a gas containing oxygen and a gas containing hydrogen are supplied to the cathode and the anode, respectively.