JP2002280020A - Membrane electrode joint body for fuel cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane electrode joint body for a fuel cell controllably, uniformly attaching a catalyst layer to a polymer electrolyte membrane to provide high performance, and provide the method of manufacturing for the membrane electrode joint body and the fuel cell using the membrane electrode joint body. SOLUTION: In the method of manufacturing for the membrane electrode joint body for the fuel cell in which the catalyst layer is attached to a hydrogen ion conductive polymer electrolyte membrane by heat-bonding, the surface of a jig pressing the catalyst layer has a flatness of 0.010 mm or less, and the flatness of a base film forming the catalyst layer is 0.005 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a portable power supply,
The present invention relates to a fuel cell using a solid polymer electrolyte used for electric vehicles and home cogeneration systems, and more particularly to a method for producing a membrane / electrode assembly as a constituent element and a fuel cell using the same.

[0002]

2. Description of the Related Art A fuel cell using a solid polymer electrolyte is
This is a power generation device that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen with a fuel gas containing oxygen such as air. The structure is such that a catalyst reaction layer mainly composed of carbon powder carrying a platinum-based metal catalyst is formed on both sides of a polymer electrolyte membrane that selectively transports hydrogen ions. At present, perfluorosulfonic acid is generally used as a polymer electrolyte. next,
On the outer surface of the catalytic reaction layer, a gas diffusion layer having both fuel gas permeability and electron conductivity is formed. Generally, carbon paper or carbon cloth is used for the gas diffusion layer. The above-described catalyst reaction layer alone, or a combination of the catalyst reaction layer and the gas diffusion layer is referred to as an electrode.

[0003] Next, in order to prevent leakage of supplied fuel gas and to prevent mixing of two types of fuel gas, a gas seal material or a gasket is disposed so as to sandwich the polymer electrolyte membrane around the electrode. This gas seal material or gasket is integrated with the electrode and polymer electrolyte membrane in advance and assembled to form a membrane electrode assembly (Me
mbrane-Electrode-Assembly (MEA).

Outside the MEA, a separator having conductivity and airtightness for mechanically fixing the MEA and electrically connecting adjacent MEAs in series with each other is arranged. In the part of the separator that comes into contact with the MEA, a gas flow path for supplying a reaction gas to the electrode surface and carrying away generated gas and surplus gas is formed. Although the gas flow path can be provided separately from the separator, a method of providing a groove on the surface of the separator to form a gas flow path is general. A structure in which the MEA is fixed by the pair of separators is referred to as a unit cell as a basic unit.

[0005] A plurality of the unit cells are connected in series, and a manifold, which is a piping jig for supplying fuel gas, is arranged to constitute a fuel cell.

In a solid polymer electrolyte fuel cell, a so-called three-phase interface formed by pores serving as reaction gas supply channels, hydrogen ion conductive solid polymer electrolyte, and an electrode material that is an electronic conductor. Is one of the important factors influencing the discharge performance of the battery.

Conventionally, in order to increase the three-phase interface,
Attempts have been made to form a catalyst layer in which an electrode material and a solid polymer electrolyte are mixed and dispersed, and to apply the catalyst layer to the interface between the polymer electrolyte membrane and the porous electrode.

[0008] The method of applying the catalyst layer to the interface between the polymer electrolyte membrane and the porous electrode is as follows. A catalyst paint is formed on the porous electrode or the polymer electrolyte membrane by a printing method or a spray method, and is then hot-pressed. A method of integrating a molecular electrolyte membrane and an electrode.

Alternatively, a catalyst layer is formed on a base film made of polytetrafluoroethylene (hereinafter, PTFE), polyethylene terephthalate (hereinafter, PET), polypropylene (hereinafter, PP), or the like, and the catalyst is applied to the polymer electrolyte membrane. There is a method in which a layer is applied by heating and pressing, and a polymer electrolyte membrane provided with a catalyst layer and a porous electrode are integrated by hot pressing.

A method of forming a catalyst layer on a base film and applying it to a polymer electrolyte membrane by thermocompression bonding is generally called a transfer method.

The catalyst layer formed by the transfer method is difficult to cause the penetration of the paint into the porous electrode by the printing method or the spray method, and the destruction or deformation of the polymer electrolyte membrane due to the solvent in the paint. A method that can control and uniform the film pressure. In addition, by using a coater such as a multi-coater to form the catalyst layer on the base film, it is an effective method for mass production from the possibility of reducing the yield by continuous coating of the catalyst layer and effective use of the catalyst paint. Attention has been paid.

[0012]

However, in the method for producing a membrane electrode assembly by a transfer method, it is necessary to perform mass transfer such that a catalyst layer previously formed on a base film is newly applied to the polymer electrolyte membrane. When the transfer of the catalyst layer to the polymer electrolyte membrane by transfer is in an insufficient state below the required electrode area or the position of the upper and lower catalyst layers is shifted,
Damage to the polymer electrolyte membrane due to electrical load and pinholes may occur. In addition, if the surface of the catalyst layer applied to the polymer electrolyte membrane that contacts the porous electrode by transfer has irregularities, voids are generated between the catalyst layer and the porous electrode, resulting in a decrease in contact resistance and flooding during battery operation. It may cause performance degradation.

[0013] The present invention provides a membrane electrode assembly for a fuel cell, in which the application of a catalyst layer to a polymer electrolyte membrane is formed with good controllability or uniformity and exhibits higher performance, a method for producing the same, and a fuel using the same. It is intended to provide a battery.

[0014]

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for producing a polymer electrolyte, wherein a catalyst layer formed on a base film is applied to a polymer electrolyte by thermocompression bonding.
The jig for pressing the catalyst layer has a flatness in contact with the base film of 0 to 0.010 mm or less.

It is characterized in that a hot press is used as an apparatus for heating and pressing the catalyst layer to the polymer electrolyte membrane.

Further, one dimension of the pressing jig is 10% or more in length and width with respect to the dimension of the other jig.

When a hot roller machine is used as the heating and pressing device, for example, it is effective that the flatness of the contact surface of the pressure roller with the catalyst layer is 0.010 mm or less.

It is effective that the substrate film on which the catalyst layer is formed has a flatness of 0.005 mm or less.

The controllability, by optimizing the flatness and dimensions of the pressing jig for applying the catalyst layer to the polymer electrolyte membrane by thermocompression bonding and the flatness of the base film forming the catalyst layer, A catalyst layer with excellent uniformity can be applied to a polymer electrolyte, and a membrane electrode assembly exhibiting higher performance, a method for producing the same, and a fuel cell using the same can be provided.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

[0021]

EXAMPLES Example 1 Specific surface area was 800 m ² / g, D
Platinum was supported on Ketjen Black EC (furnace black manufactured by Ketjen Black International) with a BP oil absorption of 360 mL / 100 g at a weight ratio of 50%. 35 g of water and 59 g of an alcohol dispersion of a hydrogen ion conductive polymer electrolyte (trade name: 9% FFS, manufactured by Asahi Glass Co., Ltd.) were weighed and dispersed using an ultrasonic stirrer, and 10 g of the catalyst powder was dispersed. Created. The catalyst layer ink was applied to a coating machine using a comma coater M200L (manufactured by Hirano Tecseed Co., Ltd.) and a 50 μm-thick polypropylene film (manufactured by Toray Industries, trade name: Torayfan 50-2)
500) and dried to form a catalyst layer. The amount of platinum catalyst in the obtained catalyst layer was adjusted to 0.3 mg / cm ² .

The polymer electrolyte membrane is Nafion 112
(Manufactured by Du-Pont, film thickness 50 μm) was used.

FIG. 1 is a schematic diagram of applying a catalyst layer on a substrate film to a polymer electrolyte membrane by hot pressing using a hot press machine. FIG. 2 is a cross-sectional view between AA ′.

As shown in FIG. 1, a polymer electrolyte membrane 3 is sandwiched between base films 2 on which a catalyst layer 1 is formed, and a pressing jig 4
A, and a pressing force of 50 kgf / cm ² at a temperature of 130 ° C. is applied by hot presses 5A and 5B equipped with a pressing jig 4B having a dimension 2 mm larger in length and width than the pressing jig 4A.
The catalyst layer 1 was applied to the polymer electrolyte membrane 3 from the base film 2. By making one dimension of the pressing jig larger than the electrode area and the other 2 mm longer and shorter than the other, the position of the catalyst layer applied to both sides of the polymer electrolyte membrane can be adjusted in the area where pressure is applied, that is, the dimension is increased by the electrode area. It is specified by the pressure jig 4A, and the controllability of accurate positioning of both catalyst layers can be improved.

FIG. 3 is a schematic diagram showing the flatness of the pressing jig. The flatness is obtained by placing a jig on a horizontal platen, measuring the unevenness of the jig surface with a dial gauge, and indicating the difference between the highest value and the lowest value of the obtained values (JIS-B0021).

Using a pressing machine made by Shinto Metal Industry Co., Ltd. as the hot press machine, the size of the pressing jig was set to 90 mm × 2 electrode area.
The catalyst layer formed on the base film was applied to the polymer electrolyte membrane by heating and thickening, using 00 mm, the other having a size of 95 mm × 205 mm, and a flatness of contact surface with the catalyst layer of 0.010 mm. This was used as a membrane electrode assembly.

Example 2 FIG. 4 is a schematic diagram of applying a catalyst layer on a substrate film to a polymer electrolyte membrane by heating and pressing using a hot roller machine. The dimensions of the catalyst layer formed on the base film were adjusted to an electrode area of 90 mm x 200 mm.
The other is cut to 95 mm × 205 mm, and the polymer electrolyte membrane 13 is interposed therebetween, so that the contact flatness with the catalyst layer is 0.0
With the rollers 6A and 6B which are 10 mm, the temperature is 130 ° C.,
A pressure of 5 MPa was applied, and the catalyst layer formed on the substrate film was applied to the polymer electrolyte membrane by heating and adhesion. This was used as a membrane electrode assembly.

Example 3 A membrane electrode assembly was produced in the same manner as in Example 1, except that polypropylene having a flatness of 0.005 mm was used as a base film for forming a catalyst layer.

Example 4 A membrane electrode assembly was produced in the same manner as in Example 2, except that polypropylene having a flatness of 0.005 mm was used as the base film for forming the catalyst layer.

(Comparative Example 1) A catalyst layer formed on a base film by a hot press using a pressing jig having a flatness of 0.015 mm in the same manner as in Example 1 was used to form a polymer electrolyte membrane. The film was applied by heat thick deposition.

(Comparative Example 2) A catalyst layer formed on a substrate film by a hot roller machine in the same manner as in Example 1 using a pressing jig having a flatness of 0.020 mm and a polymer electrolyte membrane The film was applied by heat thick deposition.

(Preparation of Battery) A mixture of 150 g of carbon particles (trade name: Denka Black, manufactured by Denki Kagaku Kogyo) and 36 g of a dispersion of polytetrafluoroethylene (trade name: Lubron LDW-40, manufactured by Daikin) was mixed. The obtained water-repellent layer ink was applied to carbon paper (manufactured by Toray, trade name: TGP-H).
-060) and baked at 350 ° C to produce a gas diffusion layer having a water-repellent layer. A gas diffusion layer and a gasket are provided to the membrane electrode assemblies manufactured in Examples 1, 2, 3, and 4 and Comparative Examples 1 and 2, and a conductive separator, a current collector, a heater, and an end plate are sandwiched in this order and fastened. 15kgf / c pressure with rod
m ² and a cell was produced.

(Evaluation Test) Pure hydrogen gas was supplied to the fuel electrode and air was supplied to the air electrode of each of the above cells.
5 ° C., fuel gas utilization rate (Uf) is 75%, air utilization rate (Uo) is 40%, and gas humidification is performed through a bubbler so that the dew point is 70 ° C. for fuel gas and 65 ° C. for air. Supplied. A battery discharge test was performed under the above conditions.

FIG. 5 shows the results of a discharge test of a unit cell using the membrane electrode assemblies of Examples 1, 3 and Comparative Example 1.
Comparing Example 1 of the present invention with Comparative Example 1, the unit cell of Example 1 showed high battery performance in a high current density region of 0.7 A / cm ² or more. In the unit cell of Comparative Example 1, the battery performance was considered to be reduced due to flooding in this region. FIG. 6 schematically shows the difference between Comparative Example 1 and Example 1. The membrane electrode assembly used in Comparative Example 1 was a gas diffusion layer 7
It is considered that since the gap 8 exists at the interface with the water, water generated by an active battery reaction in the high current density region accumulates in the gap and causes flooding. On the other hand, Example 1
The flatness of the pressure jig was 0.01
By setting the thickness to 0 mm or less, the surface of the catalyst layer in contact with the gas diffusion layer can be controlled uniformly, so that voids at the interface hardly occur. This has made it possible to avoid a decrease in battery performance due to flooding. In addition, IR of the discharge curve
Since the slope due to the loss is smaller in Example 1 than in Comparative Example 1, it can be seen that voids are hardly generated at the interface between the catalyst layer and the gas diffusion layer, and the contact resistance is reduced.

Comparing Example 1 with Example 3, Example 3 showed that the void at the interface between the catalyst layer and the gas diffusion layer was improved as compared with Example 1, and higher performance could be achieved.

FIG. 7 shows the results of a discharge test of a unit cell using the membrane electrode assemblies of Examples 2, 4 and Comparative Example 2.
As in FIG. 5, the cell performance using the membrane electrode assemblies of Examples 2 and 4 did not decrease in the high current density region of 0.7 A / cm ² or more. In the membrane electrode assemblies used in Examples 2 and 4, the catalyst layer is applied to the polymer electrolyte membrane by linear pressure using a hot roller, and thus the membrane electrodes using the hot press in Examples 1 and 3 are used. The generation of in-plane voids was further reduced as compared with the joined body. Comparing the battery performances of the first and second embodiments and the third and fourth embodiments, the second and fourth embodiments showed about 10 mV higher performance.

In the above embodiment, the dimension of the jig used to apply the catalyst layer to the polymer electrolyte membrane was 5 mm in length and width.
Although enlarged, the invention is not so limited. It was confirmed that the same effect was obtained even when a jig having one dimension of 1 mm or more was used.

[0038]

As described above, according to the present invention, the flatness and dimensions of the pressing jig for applying the catalyst layer to the polymer electrolyte membrane by thermocompression bonding, and the flatness of the base film on which the catalyst layer is formed. By optimizing the degree, a catalyst layer having excellent controllability and uniformity can be provided to the polymer electrolyte, and a membrane electrode assembly exhibiting higher performance could be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method for manufacturing a membrane electrode assembly using a hot press.

FIG. 2 is a schematic cross-sectional view illustrating a method for manufacturing a membrane / electrode assembly using a hot press.

FIG. 3 is a schematic diagram showing flatness of a pressing jig.

FIG. 4 is a schematic view showing a method for producing a membrane electrode assembly using a hot roller.

FIG. 5 is a diagram showing a discharge curve of a unit cell using the membrane / electrode assembly of Example 1, Example 3, and Comparative Example 1 of the present invention.

FIG. 6 is a schematic diagram showing a structure of a bonding surface between a catalyst layer and a gas diffusion layer according to an example of the present invention and a comparative example.

FIG. 7 is a diagram showing a discharge curve of a unit cell using the membrane electrode assemblies of Example 2, Example 4, and Comparative Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Catalyst layer 2 Base film 3 Polymer electrolyte membrane 4 Pressure jig 5 Hot press 6 Hot roller 7 Gas diffusion layer 8 Void

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Eiichi Yasumoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasushi Sugawara 1006 Kadoma, Kazuma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. 1006 Kadoma, Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F-term (reference) 5H026 AA06 BB01 BB02 BB04 CX04 HH00

Claims (1)

[Claims] Claims 1. After placing a catalyst layer formed on a base film on both sides of a hydrogen ion conductive polymer electrolyte membrane,
In the method for producing a membrane electrode assembly for a fuel cell in which the hydrogen ion conductive polymer electrolyte membrane and the catalyst layer are joined together by heating and pressurization by pressurization, the pressurization is a flatness of a contact surface with the base film. A production method of a membrane electrode assembly for a fuel cell, wherein the method is carried out through a flat pressing jig having a value of 0 to 0.010 mm.