JP2003059507A - Electrolyte film and electrode junction for fuel cell, its manufacturing method and polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte film and electrode junction for a fuel cell with excellent proton conductivity, a polymer electrolyte fuel cell of high efficiency using the same, and a method of manufacturing the above electrolyte film and electrode junction with ease and in stable quality. SOLUTION: A polymer electrolyte film including carbon particles supporting metal contained on both sides of a surface layer, an electrolyte film and electrode junction equipped with a pair of gas-diffusion layers arranged on its both sides, and a fuel call using the same are provided. The electrolyte film is formed by applying dispersion liquid of polymer electrolyte with at least two kinds of metal-supporting carbon particles of hydrophilicity or with different specific weights dispersed on a support, having the particles in the dispersion liquid applied above precipitated and floated according to their hydrophilicity or specific weights, and then, by volatilizing solvent in the dispersion liquid in that state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte membrane-electrode assembly for use in a polymer electrolyte fuel cell, and a method for producing the same.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell converts chemical energy into electric energy and heat by electrochemically reacting a fuel gas such as hydrogen and an oxidant gas containing oxygen such as air at electrodes. It is what makes me. An example of the electrolyte membrane-electrode assembly of the polymer electrolyte fuel cell will be described with reference to FIG. An anode side catalyst layer 32 and a cathode side catalyst layer 33 are arranged in close contact with each of both side surfaces of the polymer electrolyte membrane 31 that selectively transports protons. The catalyst layers 32 and 33 are layers in which carbon particles carrying a platinum-based metal catalyst as a main component are mixed with a proton conductive polymer electrolyte. These catalyst layers 3
2 and 33, an anode-side gas diffusion layer 34 and a cathode-side gas diffusion layer 35, which have gas permeability and electronic conductivity, are arranged in close contact with each other, whereby an electrolyte membrane is formed.
The electrode assembly 36 is configured. Usually, for the gas diffusion layer, a conductive material having air permeability, which is water repellent treated such as carbon paper or carbon cloth, is used.

In the battery using the electrolyte membrane-electrode assembly 36, the fuel gas or the oxidant gas is used as the gas diffusion layer 34.
Alternatively, the gas is supplied from a gas passage provided in a separator plate disposed outside 35, passes through the gas diffusion layer 34 or 35, and reaches the catalyst layer 32 or 33. In order to prevent these fuel gas and oxidant gas from leaking out and mixing with each other, a gas sealing material and a gasket are arranged around the gas diffusion layers 34 and 35 with the polymer electrolyte membrane interposed therebetween. There is.

In order to extract electric power from the polymer electrolyte fuel cell, protons must move in the polymer electrolyte membrane. Protons moving in the polymer electrolyte membrane are generated by the reaction of the following formula (1) in the anode side catalyst layer.

H ₂ → 2H ⁺ + 2e ⁻ (1)

In the cathode-side catalyst layer, water is produced by the reaction of the protons transferred from the anode and oxygen with the following equation (2).

1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)

As the polymer electrolyte, a perfluorocarbon sulfonic acid having a main chain of --CF _2- , and a side chain having a sulfonic acid group (--SO ₃ H) as a terminal functional group introduced thereinto, for example, Nafion (Dupont) is used. Company), Flem
Ion (manufactured by Asahi Glass Co., Ltd.) and Aciplex (manufactured by Asahi Kasei Co., Ltd.) are generally used. In these polymer electrolytes, the conductive paths formed by aggregating sulfonic acid groups and spreading in a three-dimensional network function as proton conductive channels.

There are two main methods for producing the conventional electrolyte membrane-electrode assembly. The first manufacturing method is a method in which a catalyst layer is first formed on the surface of a polymer electrolyte membrane and a gas diffusion layer is bonded to the catalyst layer. An example of this method will be described with reference to the process chart of FIG. First, a catalyst paste containing carbon particles carrying a metal catalyst and a polymer electrolyte is applied on a support 45 made of a film such as polypropylene, polyethylene terephthalate or polytetrafluoroethylene, and dried to form a catalyst layer 42 or 43. Form.
Each of the catalyst layers 42 and 43 thus formed on the support body 45 is transferred to both sides of the polymer electrolyte membrane 41 formed in advance by hot pressing or heat roll as shown in FIG. 6A. .

Then, the support 45 is attached to the catalyst layers 42 and 4.
After peeling from 3, the electrolyte membrane with a catalyst layer as shown in FIG. 6B is formed. In addition to the above transfer method, the polymer electrolyte membrane 4
The catalyst layers 42 and 43 can be formed by applying a catalyst paste to the front and back sides of 1 by printing, spraying, etc. and drying. Gas diffusion layers 47 and 48 made of carbon paper are attached on the catalyst layers 42 and 43, respectively, to prepare an electrolyte membrane-electrode assembly as shown in FIG. 6C.

In the second conventional manufacturing method, the catalyst layers 42 and 43 previously formed on the gas diffusion layers 47 and 48 are superposed on both sides of the preformed polymer electrolyte membrane 41, and hot pressed. Alternatively, it is a method for producing an electrolyte membrane-electrode assembly having the same structure as in FIG. 6C by hot pressing with a hot roll. Above catalyst layer 4
2 or 43 is formed by a method in which a catalyst paste is applied onto the gas diffusion layer 47 or 48 by a printing method, a spray method or the like and then dried.

However, in the above-mentioned conventional method for manufacturing an electrolyte membrane-electrode assembly in which a catalyst layer is bonded onto a preformed polymer electrolyte membrane, the polymer electrolyte membrane itself has a discontinuous portion of a proton conductive channel. In addition to the above, a discontinuous surface is formed at the interface between the proton conductive channel in the polymer electrolyte membrane and the proton conductive channel in the catalyst layer.
There is a problem that the proton conductivity of the electrode assembly is lowered.

FIG. 7 shows an electrolyte membrane according to a conventional manufacturing method.
FIG. 3 is an enlarged schematic view of the vicinity of the joint between the polymer electrolyte membrane of the electrode assembly and the anode-side catalyst layer. Polymer electrolyte membrane 67
Is known to have a structure in which a proton conductive channel 62 is stretched in a network shape in a polytetrafluoroethylene resin portion 61. In order for the polymer electrolyte membrane 67 to operate properly as a proton-conducting solid electrolyte, the surface of the polymer electrolyte membrane 67 on the anode side is connected to the surface of the cathode side by a continuous proton-conducting channel 62. There is a need.

When the polymer electrolyte membrane 67 is formed by a conventional manufacturing method, for example, a casting method, as the solvent in the polymer electrolyte dispersion liquid coated on the support is volatilized, the solubility parameter and the surface energy are increased. Both low polytetrafluoroethylene resin portion 61 and solubility parameter,
A sulfonic acid group portion having high surface energy is phase-separated, and a network of the proton conductive channel 62 is formed. However, when the surface of the coating film of the polymer electrolyte dispersion is in contact with air having a low surface energy, the free energy of exposing the polytetrafluoroethylene resin portion 61 to the air is lower than that of the sulfonic acid group portion. The ethylene resin portion 61 preferentially covers the surface. As a result, the proton conductive channel 62 is blocked by the surface layer of the polymer electrolyte membrane 67, and the proton conductive channel 62 that should penetrate between the anode side surface and the cathode side surface of the polymer electrolyte membrane 67 becomes discontinuous. It will be easier.

The catalyst layer 68 is composed of a polymer electrolyte having a proton conductive channel 64 formed in a polytetrafluoroethylene resin portion 63 and carbon particles 66 carrying a metal 65. When the catalyst layer 68 and the polymer electrolyte membrane 67 are bonded by a conventional method, it is very difficult to bond them in such a positional relationship that both proton conductive channels 62 and 64 are in communication with each other. . Therefore, the proton conductive channel is likely to be discontinuous at the interface between the polymer electrolyte membrane 67 and the catalyst layer 68, and the protons generated in the catalyst layer 68 smoothly flow into the proton conductive channel 62 of the polymer electrolyte membrane 67. I can't.

The electrolyte membrane-electrode assembly manufactured by the conventional manufacturing method has many problems in that the number of manufacturing steps is long and the manufacturing time is long, in addition to the problem that the proton conductivity is lowered.

[0017]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and has a high proton conductivity electrolyte membrane-electrode assembly for a fuel cell and a high-performance polymer electrolyte fuel cell using the same. The purpose is to provide. Another object of the present invention is to provide a method capable of easily producing such an electrolyte membrane-electrode assembly.

[0018]

The electrolyte membrane-electrode assembly for a fuel cell of the present invention comprises a polymer electrolyte membrane having carbon particles supporting a metal contained in both surface layers, and a polymer electrolyte membrane comprising: It is provided with a pair of gas diffusion layers arranged on both sides.

The first method for producing an electrolyte membrane-electrode assembly for a fuel cell according to the present invention is a polymer electrolyte aqueous dispersion in which at least two kinds of carbon particles carrying a metal and having different hydrophilicities are dispersed. The step of coating on, the coated support is left to stand, the carbon particles of the hydrophilicity in the applied dispersion are allowed to settle in the lower layer portion of the dispersion, and the carbon of the hydrophilicity is weakened. The particles are floated on the upper layer of the dispersion, and thus the carbon particles having stronger hydrophilicity are placed on the lower layer of the dispersion.
The method comprises the steps of unevenly distributing the less hydrophilic carbon particles in the upper layer of the dispersion, and volatilizing the solvent contained in the dispersion to form a polymer electrolyte membrane containing carbon particles. It is characterized by

A second method for producing an electrolyte membrane-electrode assembly for a fuel cell according to the present invention is a polymer electrolyte dispersion liquid in which at least two kinds of carbon particles carrying a metal and having different specific gravities are dispersed on a support. The step of applying, the coated support is left to stand, the carbon particles having a higher specific gravity are allowed to settle in the lower layer of the applied dispersion, and the carbon particles having a lower specific gravity are applied to the upper layer of the dispersion. The method is characterized by including a step of floating and a step of volatilizing a solvent contained in the dispersion to form a polymer electrolyte membrane containing carbon particles.

The third method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is a step of applying a polymer electrolyte dispersion liquid in which carbon particles supporting a metal are dispersed on a support, The step of allowing the support to stand and allowing the carbon particles in the applied dispersion to float on the upper layer or settle to the lower layer, volatilize the solvent contained in the dispersion, and carbon particles on the support. A step of forming a polymer electrolyte membrane that includes unevenly distributed in the upper layer portion or the lower layer portion, and two sheets of the polymer electrolyte membrane formed on the support, the surface on the side where the carbon particles are unevenly distributed. It is characterized in that it has a step of joining to the outside.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In a polymer electrolyte membrane in an electrolyte membrane-electrode assembly of the present invention, carbon particles (catalyst-supporting particles) carrying a metal are unevenly distributed on both surface layers, and the uneven distribution layer is used as a catalyst layer. It works. This polymer electrolyte membrane does not have discontinuities in the proton conductive channel of the polymer electrolyte layer itself, and also has a proton conductive channel in the polymer electrolyte layer and a proton conductive channel of the polymer electrolyte in the catalyst layer. There is no discontinuous surface at the interface. Therefore, by using such a polymer electrolyte membrane, it is possible to provide an electrolyte membrane-electrode assembly having excellent proton conductivity.

Further, in the method for producing an electrolyte membrane-electrode assembly of the present invention, a polymer electrolyte dispersion liquid in which catalyst-supporting particles are dispersed is applied onto a support, and this is left to stand to carry the catalyst in the dispersion liquid. According to the strength of hydrophilicity or the magnitude of specific gravity of the particles, the particles are floated on the upper layer of the dispersion and / or settled in the lower layer, and then the solvent in the dispersion is volatilized and removed. A polymer electrolyte membrane of the present invention having an electrolyte layer and a catalyst layer is formed. With this, since the catalyst layer combined with the electrolyte layer can be formed at the same time as the formation of the polymer electrolyte membrane, an electrolyte membrane-electrode assembly having high proton conductivity can be easily manufactured.

In the first and second manufacturing methods of the present invention,
The anode side catalyst layer and the cathode side catalyst layer can be simultaneously formed as a continuous layer via the electrolyte layer.
Further, in the third production method of the present invention, two sheets of the polymer electrolyte membrane in which the electrolyte layer and one of the catalyst layers are formed as a continuous layer are bonded to each other, and the anode side catalyst layer and the cathode are provided on both sides of the electrolyte layer. A side catalyst layer can be formed.

In the present invention, platinum, gold, palladium, rubidium, iridium, ruthenium and the like can be used as the metal supported on the catalyst supporting particles. Among them, a metal containing at least one selected from the group consisting of platinum, gold and ruthenium is preferable, and a metal containing at least platinum is more preferable. Further, the smaller the average particle size of the metal, the larger the surface area per unit weight effective for the reaction, and therefore the amount of the metal used can be reduced. Therefore, the metal preferably has an average particle diameter of 10 nm or less, particularly 5 nm or less.

FIG. 3 schematically shows an enlarged cross section of the vicinity of the joint between the electrolyte layer of the polymer electrolyte membrane and the anode side catalyst layer in the electrolyte membrane-electrode assembly of the present invention. Catalyst layer 7
In FIG. 8, carbon particles 76 supporting a metal 75 are densely dispersed in a polymer electrolyte in which a proton conductive channel 74 is formed in a polytetrafluoroethylene resin portion 73. A proton conducting channel 72 is formed in the polytetrafluoroethylene resin portion 71 of the electrolyte layer 77. The catalyst layer 78 and the electrolyte layer 77 are surface-bonded without a boundary surface. (In FIG. 3, for convenience, the boundary surface is indicated by a broken line.)

Since the electrolyte layer 77 does not come into contact with air in the process of forming the polymer electrolyte membrane, the proton conductive channel 72 in the electrolyte layer 77 is not blocked. Further, the proton-conducting channel 72 in the electrolyte layer 77 is continuously formed with the proton-conducting channel 74 in the catalyst layer 78, and the discontinuity of the proton-conducting channel is formed at the boundary surface between the electrolyte layer 77 and the catalyst layer 78. There are no faces. Therefore, in the electrolyte membrane-electrode assembly using this polymer electrolyte membrane, the protons generated in the anode side catalyst layer can smoothly move to the cathode side catalyst layer.

In the first production method of the present invention, an aqueous dispersion of a polymer electrolyte in which at least two kinds of catalyst-supporting particles having different hydrophilicities are dispersed is applied on a support, and then the applied dispersion is applied. The catalyst-supporting particles having a stronger hydrophilicity in the dispersion are allowed to settle, and the catalyst-supporting particles having a weaker hydrophilicity are floated. Then, the solvent in this dispersion is volatilized and removed to form an electrolyte layer in the intermediate layer, and a polymer in which a first catalyst layer and a second catalyst layer are formed as continuous layers on both sides of the electrolyte layer. An electrolyte membrane is prepared.

In the first production method of the present invention, in order to obtain catalyst-supporting particles having different hydrophilicities, it is preferable to selectively use hydrophobic carbon particles and hydrophilic carbon particles as raw materials. In addition, as a method of making the catalyst-supporting particles hydrophilic, it is preferable to oxidize hydrogen groups or alkyl groups on the surface of the carbon particles to convert the hydrophilic groups into carboxyl groups or hydroxyl groups. Examples of the treatment method include a method of heating the catalyst-supported particles in nitric acid at 100 ° C. for about 2 hours,
There is a method of heating in steam at 300 ° C. for several hours.
On the other hand, as a hydrophobic method for weakening the hydrophilicity of the catalyst-supporting particles, for example, a method of heating in an inert gas or hydrogen gas at 600 ° C. for 2 hours may be adopted.

Further, the solvent used in the aqueous dispersion in which the polymer electrolyte is dissolved or dispersed is preferably water or a mixed solvent in which water occupies the majority. A solvent containing a large amount of a solvent having a surface energy smaller than that of water, such as ethanol, is not preferable because it easily precipitates even the catalyst-supporting particles having weak hydrophilicity.

FIG. 1 shows an example of a manufacturing process according to the first manufacturing method of the present invention. First, an aqueous dispersion 11 of a polymer electrolyte prepared by putting two types of catalyst-supporting particles having different hydrophilicities and a polymer electrolyte in a solvent and mixing and stirring the mixture is shown in FIG.
As shown in (a), it is applied on the support 15. This is left to stand, and the catalyst-supporting particles 13 having weak hydrophilicity as shown in FIG.
The catalyst-supporting particles 12 having strong hydrophilicity are allowed to settle in the lower layer portion of the dispersion liquid 11 coated with. The support in this state is left at room temperature to volatilize the solvent in the applied dispersion liquid 11 and further dry the polymer electrolyte membrane 16
To form. The support 15 is peeled off from the polymer electrolyte membrane 16 to produce the polymer electrolyte membrane 16 as shown in FIG. On one surface layer of the polymer electrolyte membrane 16 is formed a catalyst layer in which the weakly hydrophilic catalyst-supporting particles 13 are concentrated and unevenly distributed, and on the other surface layer, the highly hydrophilic catalyst-supporting particles 12 are formed. A catalyst layer that is densely and unevenly distributed is formed.

In this case, the catalyst-supporting particles 1 in the dispersion 11
Since the sedimentation or floating of 2 or 13 is insufficient, there is no problem even if a small amount of catalyst-supporting particles 12 or 13 is present in the electrolyte layer of the intermediate layer of the polymer electrolyte membrane 16. This is because the metal 14 present in the electrolyte layer has an action of generating water by the reaction of the fuel gas and the oxidant gas that have cross-leaked from the anode side and the cathode side, and causes the polymer electrolyte membrane 16 to be self-humidified. This is because it is effective, and it is possible to prevent a decrease in proton conductivity during low-humidity operation. Gas diffusion layers 17 and 18 made of carbon paper or the like are arranged on the outer sides of the respective catalyst layers of the polymer electrolyte membrane 16, and the gasket 1 is provided on the peripheral portions thereof.
9 is arranged by pressure bonding with a hot press to integrate them, and an electrolyte membrane-electrode assembly with a gasket as shown in FIG. 1D is produced.

In the second production method of the present invention, a polymer electrolyte dispersion liquid in which at least two kinds of catalyst-supporting particles having different specific gravities are dispersed is coated on a support, and then the coated support is left standing. The catalyst-supporting particles having a higher specific gravity in the applied dispersion are allowed to settle, and the catalyst-supporting particles having a lower specific gravity are floated. Then, the solvent in this dispersion is volatilized and removed to form an electrolyte layer in the intermediate layer, and a polymer in which a first catalyst layer and a second catalyst layer are formed as continuous layers on both sides of the electrolyte layer. An electrolyte membrane is prepared. In this case, a small amount of catalyst-supporting particles may be present in the electrolyte layer for the same reason as in the case of the first manufacturing method. By using this polymer electrolyte membrane, an electrolyte membrane-electrode assembly with a gasket can be produced in the same manner as in the first production method.

The catalyst-supporting particles having different specific gravities in the second production method of the present invention can be prepared by a method of changing the amount of metal supported (% by weight), a method of using raw material carbon particles having different specific gravities, or the like. Further, the solvent of the polymer electrolyte dispersion liquid may be appropriately selected as long as it can prepare a dispersion liquid of the polymer electrolyte having a specific gravity intermediate between the specific gravities of the catalyst-supporting particles having different specific gravities.

In the third production method of the present invention, the polymer electrolyte dispersion liquid in which the catalyst-supporting particles are dispersed is applied onto the support, and then the applied support is allowed to stand, and the polymer is dispersed in the applied dispersion liquid. The catalyst-supported particles are floated on the upper layer or settled on the lower layer. Then, the solvent in this dispersion is volatilized to prepare a polymer electrolyte membrane having a catalyst layer formed on one surface side. Then, the electrolyte layers of the two produced polymer electrolyte membranes are bonded to each other to produce an integrated polymer electrolyte membrane having catalyst layers on both sides.

An example of a manufacturing process according to the third manufacturing method of the present invention is shown in FIG. First, the catalyst-supported particles and the polymer electrolyte are put in a solvent, and the polymer electrolyte dispersion liquid 21 prepared by mixing and stirring is applied onto the support 25 as shown in FIG. The coated support is allowed to stand for a while to allow the catalyst-supporting particles 22 to settle as shown in FIG. 2 (b). In this case, the catalyst-supporting particles 22 include the polymer electrolyte dispersion 21.
What has a larger specific gravity may be used. When an aqueous dispersion is used as the polymer electrolyte dispersion, catalyst-supporting particles having strong hydrophilicity may be used. When attempting to float the catalyst-supporting particles, use catalyst-supporting particles having a smaller specific gravity than the polymer electrolyte dispersion, or use an aqueous dispersion in which the catalyst-supporting particles having weak hydrophilicity are dispersed. Good.

Next, the dispersion liquid 21 in which the catalyst-supporting particles 22 are settled is dried to volatilize the solvent, and a polymer electrolyte having a layer (catalyst layer) in which the catalyst-supporting particles 22 are dense as shown in FIG. 2C. The film 26 is formed on the support 25. further,
The two support bodies 25 on which the polymer electrolyte membrane 26 is formed are
After each support side is faced outward, they are superposed by pressure bonding with a heat roller or the like to be integrated, and then each support 25
Peel off. As a result, the composite polymer electrolyte membrane 27 having the catalyst layer formed continuously with the electrolyte layer as shown in FIG. 2D is provided on both sides. This composite polymer electrolyte membrane 2
One of the catalyst layers 7 serves as an anode catalyst layer, and the other catalyst layer serves as a cathode catalyst layer. Gas diffusion layer 2
2, 8, and gasket 30 attached,
An electrolyte membrane-electrode assembly with a gasket as in (e) is prepared.

[0038]

EXAMPLES Next, the method for producing the electrolyte membrane-electrode assembly for a fuel cell of the present invention will be described in detail with reference to examples.

Example 1 An electrolyte membrane-electrode assembly was produced by the manufacturing process shown in FIG. First, the catalyst-supporting particles 12 having strong hydrophilicity have an average diameter of 30 nm in which 50 wt% of platinum powder having an average diameter of 2 nm as the supporting metal 14 is supported.
20 g of fuming nitric acid (manufactured by Kanto Chemical Co., Inc.) was added to 2.0 g of carbon particles (Ketjen Black EC manufactured by Ketjen International), heated with stirring at 100 ° C. for 2 hours with a stirrer, and then distilled water was sufficient. Washed to
Prepared by drying. Further, the catalyst-supporting particles 1 having weak hydrophilicity
3 was prepared by heating 2.0 g of carbon particles carrying 50% by weight of platinum powder and having an average diameter of 30 nm in hydrogen gas at 600 ° C. for 2 hours as in the above.

The polymer electrolyte dispersion is water: ethanol =
20 m of liquid in which a polymer electrolyte (Flemion manufactured by Asahi Glass Co., Ltd.) was dispersed in a mixture liquid of 80:20 at a concentration of 7% by weight.
The above-mentioned two types of catalyst-supporting particles 12 having different hydrophilicities
Add 0.15g each of 13 and 13, and add 30 with an ultrasonic stirrer.
It was prepared by stirring for 1 minute. The aqueous dispersion of this polymer electrolyte was placed in a petri dish having a diameter of 15 cm to serve as the support 15 to form a layer of the coating dispersion 11 on the bottom surface thereof, and the mixture was allowed to stand overnight at room temperature and then dried at 130 ° C. for 30 minutes. did. In this way, the polymer electrolyte membrane 16 having a film thickness of 25 μm, in which the catalyst layers were provided on both sides of the electrolyte layer, was produced.

Then, the gas diffusion layer 17 on the anode side, the gas diffusion layer 18 on the cathode side and the gasket 19 are attached to the polymer electrolyte membrane 16 by hot pressing at 135 ° C., and an electrolyte membrane with a gasket as shown in FIG. 1D is attached. -The electrode assembly was prepared. In the gas diffusion layers 17 and 18, after immersing carbon paper (manufactured by Toray Co., Ltd.) in an aqueous fluororesin dispersion liquid (ND-1 manufactured by Daikin Industries, Ltd.), 30
What was baked at 0 ° C. was used.

Comparative Example 1 20 ml of a polymer electrolyte ethanol dispersion (Flemion manufactured by Asahi Glass Co., Ltd., concentration 7% by weight) was placed in a Petri dish, allowed to stand overnight at room temperature, and then dried at 130 ° C. for 30 minutes. To form a polymer electrolyte membrane having a thickness of 20 μm. Both sides of the polymer electrolyte membrane peeled from the petri dish were sandwiched between two supports on which a catalyst layer had been previously formed, and the catalyst layers were transferred to both sides of the polymer electrolyte membrane by applying pressure with a heat roller. . An electrolyte membrane-electrode assembly with a gasket was produced in the same manner as in Example 1 by using the electrolyte membrane with a catalyst layer produced by peeling this support from the catalyst layer.

The support on which the catalyst layer has been previously formed is a catalyst layer formed by coating the catalyst paste on a polypropylene film support having a thickness of 50 μm with a bar coater and drying at room temperature. The catalyst paste has an average diameter of 30 nm carrying 50% by weight of platinum having an average diameter of 2 nm.
15 cc of distilled water was added to 5.0 g of carbon particles (Ketjen Black EC manufactured by Ketjen International),
In addition to this, a polyelectrolyte ethanol dispersion (Asahi Glass Co., Ltd.)
25.0 g of Flemion (concentration 9% by weight) made by a stirrer while applying ultrasonic vibration.
It was prepared by stirring for an hour.

Then, using the electrolyte membrane-electrode assembly with a gasket prepared in Example 1 and Comparative Example 1, unit cells of a polymer electrolyte fuel cell were prepared and their operating characteristics were evaluated. FIG. 8 shows the configuration of a unit cell using the electrolyte membrane-electrode assembly with a gasket of FIG. 1 produced in Example 1. In FIG. 8, separator plates 84 and 85 having an anode side gas flow channel 80 and a cathode side gas flow channel 81 are arranged outside the gas diffusion layers 17 and 18 on both sides of the electrolyte membrane-electrode assembly with a gasket. ing. Cooling water flow paths 82 and 83 are provided outside the separator plates 84 and 85, respectively. A unit cell using the electrolyte membrane-electrode assembly with a gasket of Comparative Example 1 was also constructed according to the above. Maintaining the battery temperature of these cells at 75 ° C, hydrogen gas heated and humidified to have a dew point of 70 ° C on the anode side, and air heated and humidified to have a dew point of 30 ° C on the cathode side. Were supplied respectively.

These unit cells were operated under the conditions of hydrogen utilization rate of 70% and air utilization rate of 40%, and the relationship between discharge current and operating voltage was examined. The results are shown in FIG. The vertical axis represents the battery voltage (V) of the unit cell, and the horizontal axis represents the discharge current (mA / cm ² ) per unit area of the electrolyte membrane-electrode assembly. As shown in FIG. 4, the unit cell of Example 1 in which the electrolyte layer and the catalyst layer were simultaneously formed was higher than the unit cell of Comparative Example 1 in which the catalyst layer was bonded to the preformed polymer electrolyte membrane. Output was obtained.

Using the unit cells of Example 1 and Comparative Example 1 described above, a battery stack in which 100 cells were laminated was prepared. At this time, a stainless steel collector plate,
Both ends of the battery stack were sandwiched between an insulating plate and a single plate, and fixed with a tightening rod. The tightening pressure was 15 kgf / cm ² per area of the separator plate. The operating characteristics of each of the battery stacks thus manufactured were evaluated in the same manner as in the case of the unit cell. As a result, similar to the case of the unit cell, the battery stack of Example 1 obtained higher output than the battery stack of Comparative Example 1.

[0047]

According to the present invention, it is possible to provide an electrolyte membrane-electrode assembly for a fuel cell having high proton conductivity, and a high-performance polymer electrolyte fuel cell including the same. Further, the electrolyte membrane-electrode assembly can be manufactured in a short time, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for producing an electrolyte membrane-electrode assembly according to the present invention.

FIG. 2 is a process drawing showing another embodiment of the method for producing an electrolyte membrane-electrode assembly of the present invention.

FIG. 3 is a schematic cross-sectional view in the vicinity of a joint between a catalyst layer and an electrolyte layer in the electrolyte membrane-electrode assembly of the present invention.

FIG. 4 is a diagram showing operating characteristics of unit cells of Examples and Comparative Examples.

FIG. 5 is a vertical cross-sectional view of a conventional electrolyte membrane-electrode assembly.

FIG. 6 is a process drawing showing a conventional method for manufacturing an electrolyte membrane-electrode assembly.

FIG. 7 is a schematic cross-sectional view in the vicinity of a joint between a catalyst layer and an electrolyte membrane in a conventional electrolyte membrane-electrode assembly.

FIG. 8 is a vertical cross-sectional view of a unit cell according to an embodiment of the present invention.

[Explanation of symbols]

11 Polymer Electrolyte Aqueous Dispersion 12 Catalyst Support Particles 13 with High Hydrophilicity Catalyst Support Particles with Low Hydrophilicity 14, 24, 65, 75 Metals 15, 25, 45 Support 16, 26, 31, 41, 67 Polymer Electrolyte membranes 17, 18, 28, 29, 34, 35, 47, 48 Gas diffusion layers 19, 30 Gasket 21 Polymer electrolyte dispersions 22, 66, 76 Catalyst-supporting particles 27 Composite polymer electrolyte membranes 32, 33, 42 , 43, 68, 78 Catalyst layer 36 Electrolyte membrane-electrode assembly 61, 63, 71, 73 Polytetrafluoroethylene resin portion 62, 64, 72, 74 Proton conductive channel 77 Electrolyte layer 80, 81 Gas flow path 82, 83 Cooling water flow paths 84, 85 Separator plate

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Claims (5)

[Claims] 1. A polymer electrolyte membrane having carbon particles supporting a metal contained in surface layers on both sides, and a pair of gas diffusion layers arranged on both sides of the polymer electrolyte membrane. And an electrolyte membrane-electrode assembly for a fuel cell. 2. A step of applying an aqueous dispersion of a polymer electrolyte in which at least two kinds of carbon particles carrying a metal and having different hydrophilicities are dispersed on a support, and leaving the applied support standing, Hydrophilic carbon particles in the lower layer portion of the applied dispersion, a step of unevenly distributing the weaker hydrophilic carbon particles in the upper layer portion of the dispersion, respectively, and a solvent contained in the dispersion liquid The method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising the step of: volatilizing the polymer particles to form a polymer electrolyte membrane containing the carbon particles. 3. A step of applying a dispersion liquid of a polymer electrolyte in which at least two kinds of carbon particles carrying different metals and different in specific gravity are applied onto a support, and the applied support is allowed to stand to have a specific gravity of Larger carbon particles in the lower layer part of the applied dispersion, a step of unevenly distributing the carbon particles of smaller specific gravity in the upper layer part of the dispersion, and volatilizing the solvent contained in the dispersion liquid. A method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising the step of forming a polymer electrolyte membrane containing the carbon particles. 4. A step of applying a dispersion liquid of a polymer electrolyte in which carbon particles supporting a metal are dispersed on a support, the support which has been applied is allowed to stand, and the carbon particles are applied on the support. A step of unevenly distributing in the upper layer part or the lower layer part of the dispersion liquid,
Volatilizing the solvent contained in the dispersion to form a polymer electrolyte membrane containing the carbon particles on the support, and two polymer electrolyte membranes formed on the support. A method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising a step of joining with the surface on the side where the carbon particles are unevenly distributed facing outward. 5. The electrolyte membrane for a fuel cell according to claim 1.
A polymer electrolyte fuel cell having an electrode assembly.