JP2000090944A - Manufacture of catalyst layer-electrolyte film joint body and solid polymer electrolyte fuel cell using the joint body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell having high reliability while restricting the increase in the resistance due to extension of an electrolyte film by pinching a substrate-electrolyte film layered structure laminated on one surface or both surfaces of a solid polymer electrolyte film in the wet condition so that a catalyst surface of the substrate formed with the catalyst layer in the surface thereof contacts with the solid polymer electrolyte film, and heating them for pressure-contact. SOLUTION: A catalyst layer forming substrate 7 is laminated on both surfaces of an electrolyte film 1 in the wet condition so that the catalyst layer 2 is directed to the electrolyte film 1, and the electrolyte 1 is coated with a film 3 for restricting the lowering of the moisture content from both sides of the layered structure. Unnecessary moisture existing between the electrolyte film 1 and the catalyst layer 2, between the catalyst layer 2 and the film 3, and between the electrolyte film 1 and the film 3 is eliminated so as to tightly fit these laminated material. The layers structure is placed on a flat plate 4, and the water is scraped by a rubber scraper. The layered structure, of which moisture is eliminated, is set in a pressing jig 6, and heated for pressure-contact so as to transfer the catalyst layer 2 on the catalyst layer forming substrate 7 to the electrolyte film 1, and thereafter, the film 3 and the catalyst layer forming substrate 7 are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a catalyst layer-electrolyte membrane assembly and a solid polymer electrolyte fuel cell using the same.

[0002]

2. Description of the Related Art In a fuel cell, for example, oxygen is used as a cathode gas at one of gas diffusion electrodes arranged on both sides of an electrolyte.
This is a device for supplying electric power by supplying, for example, hydrogen as an anode gas to the other and electrochemically reacting it. In a solid polymer electrolyte fuel cell, the electrolyte is a polymer membrane,
For example, a membrane exhibiting proton conductivity in a water-containing state, such as a perfluorosulfonic acid resin membrane, which is a kind of ion exchange resin membrane, is used.

[0003] A gas diffusion electrode-electrolyte membrane assembly is formed by bonding anode and cathode gas diffusion electrodes to both surfaces of the electrolyte membrane. The gas diffusion electrode is composed of a gas diffusion layer and a catalyst layer.Each of the anode and cathode catalyst layers includes platinum group metal particles or carbon particles carrying these particles as a catalyst. It is made of porous carbon paper.

A unit cell as a basic unit includes a gas diffusion electrode.
The electrolyte membrane assembly is sandwiched between a pair of gas-impermeable separators having a gas supply channel, and a plurality of such cells are stacked to form a solid polymer electrolyte fuel cell.

In a solid polymer electrolyte fuel cell, hydrogen is supplied to the anode and oxygen is supplied to the cathode, and the following electrochemical reaction proceeds.

[0006] The ^{_{anode: 2H 2 → 4H + + 4e}} - ^{_{cathode: O 2 + 4H + + 4e}} - → 2H 2 O gas diffusion electrode - electrolyte membrane assembly is made mainly in two ways: .

[0007] First, an ink-like or paste-like catalyst mixture containing a catalyst is applied to the surface of an electrolyte membrane by a method such as a sedimentation method, a printing method, or a spray method to form a catalyst layer on the electrolyte film. After that, this and the gas diffusion layer are integrally joined by a method such as heating and pressure welding.

[0008] Second, a catalyst mixture containing a catalyst in the form of an ink or paste is applied to the surface of the gas diffusion layer by a method such as a sedimentation method, a printing method, or a spray method to form a catalyst layer on the gas diffusion layer. After that, this and the electrolyte membrane are integrally joined by a method such as heating and pressure welding. As the gas diffusion layer, for example, carbon paper having water repellency is used.

However, since the electrolyte membrane has a property of swelling when absorbing an organic solvent such as water or alcohol, and shrinking when dried, the dimensions of the electrolyte membrane change when the water content changes.

For this purpose, in the first method of directly applying an ink-like or paste-like catalyst mixture containing an organic solvent such as water or alcohol to the electrolyte membrane, the electrolyte membrane is deformed to form a uniform catalyst layer. It is difficult to do.

In the second method in which a catalyst layer is formed on the surface of the gas diffusion electrode in advance, since carbon paper or the like is a porous material having rough irregularities on the surface, the thickness of the catalyst layer formed on this surface is reduced. And it is difficult to control the amount of application with high accuracy.

Therefore, a catalyst mixture in the form of an ink or paste is applied to a catalyst layer-forming substrate by a method such as a precipitation method, a printing method, or a spray method to form a uniform catalyst layer. A transfer method has been devised in which a catalyst layer is transferred to an electrolyte membrane by heating and pressing the catalyst layer, and the catalyst layer and the electrolyte membrane are integrally joined. According to this method, the control of the coating amount is relatively easy, and a relatively uniform and thin catalyst layer can be formed on the electrolyte membrane.

[0013]

In the transfer method, a dry or water-containing electrolyte membrane can be used. The electrolyte membrane has the property of expanding when water is taken in and the water content increases. Here, the water content of the electrolyte membrane is defined as the ratio of the weight of water contained in the electrolyte to the dry weight of the electrolyte membrane.

When the electrolyte membrane in a dry state is used, if the water content of the electrolyte membrane of the catalyst layer-electrolyte membrane assembly increases, the bonded catalyst layer is extended. When the catalyst layer is extended, the distance between the carbon particles supporting the catalyst constituting the catalyst layer becomes coarse, so that the contact between the carbon particles is reduced and the electric resistance of the catalyst layer is increased.

Therefore, before and after the joining of the catalyst layers, it is preferable that there is no extension of the catalyst layer due to the extension of the electrolyte membrane. For the formation of the catalyst layer-electrolyte membrane assembly, it is necessary to use an electrolyte membrane that is more hydrated than dry. It is preferable to use them.

On the other hand, when a water-containing electrolyte membrane is used, the water content of the electrolyte membrane rapidly decreases due to heating when the catalyst layer is transferred to the electrolyte membrane. The electrolyte membrane is deformed. The deformation of the electrolyte membrane is remarkable in the peripheral portion of the bonded catalyst layer.

In general, in a fuel cell in which a gas diffusion electrode-electrolyte membrane assembly is sandwiched between a pair of separators having processed channels, an O-ring or gasket is provided between the separator and the peripheral portion of the electrolyte membrane. The airtightness is maintained by applying an appropriate amount of pressure, and a structure for preventing leakage of the reaction gas to the outside of the battery is adopted. Therefore, the deformation of the electrolyte membrane in the peripheral portion of the joined catalyst layer causes a decrease in the airtightness of the fuel cell, and thus causes a problem that the reliability of the fuel cell is reduced.

[0018]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a catalyst layer-electrolyte membrane assembly for transferring a catalyst layer formed on a catalyst layer forming substrate to an electrolyte membrane, using a hydrous electrolyte membrane. This suppresses the increase in the resistance of the catalyst layer due to the expansion of the electrolyte membrane before and after the bonding of the catalyst layer, and the vicinity of the bonded catalyst layer due to heating, which causes a decrease in airtightness when a fuel cell is configured. A method for producing a catalyst layer-electrolyte membrane assembly having a low resistance overvoltage by suppressing deformation of an electrolyte membrane in a portion, and providing a solid polymer electrolyte fuel cell having high reliability and excellent characteristics. Is to do.

According to the present invention, a catalyst layer is first formed on a catalyst layer-forming substrate, cut into a desired size, and then placed on one or both sides of a hydrated electrolyte membrane so that the catalyst layer surface is in contact with the electrolyte membrane. Deploy. Further, a laminate for heating and pressing is produced by completely covering the electrolyte membrane from both sides with a film larger than the electrolyte membrane. The film is for suppressing a decrease in the water content of the electrolyte membrane.

After removing excess water present between the electrolyte membrane and the catalyst layer-forming substrate-catalyst layer and the film of the laminated body for heating and press-bonding and bringing them into close contact with each other, it is placed in a press jig and heated. By pressing, the catalyst layer on the catalyst layer forming substrate is transferred to the electrolyte membrane. Thereafter, the film and the catalyst layer-forming substrate are removed to obtain a desired catalyst layer-electrolyte membrane assembly.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for producing a catalyst layer-electrolyte membrane assembly according to the present invention will be specifically described with reference to the schematic diagram shown in FIG. In FIG. 1, 1 is an electrolyte membrane, 2 is a catalyst layer, 3
Is a film, 4 is a flat plate, 5 is a rubber spatula, 6 is a press jig, 7 is a catalyst layer forming base, and 8 is a catalyst layer-electrolyte membrane assembly. Transfer of the catalyst layer to the electrolyte membrane consists of four steps.

Step 1 is a laminating step, and its cross section is shown in FIG.
Shown in After laminating the catalyst layer forming substrate 7 on which the catalyst layer 2 has been formed in a direction in which the catalyst layer 2 faces the electrolyte membrane 1, A film 3, for example, a polytetrafluoroethylene-hexafluoropropylene copolymer film (trade name, Daikin Industries, Neoflon 50 μm thick) for suppressing a decrease in water content larger than the electrolyte membrane from both sides of the laminate. Are laminated so as to cover.

FIG. 2 schematically shows a state in which this laminate is viewed from above. In FIG. 2, symbols 1 to 3 indicate the same as those in FIG. As shown in FIG. 2, the catalyst layer 2 and the electrolyte membrane 1
And the size of the film 3, the catalyst layer 2 is the smallest and the film 3 is the largest.

In the description with reference to FIG. 2, the catalyst layer 2, the electrolyte membrane 1
And the film 3 is rectangular, but if the catalyst layer 2 is laminated without protruding from the electrolyte membrane 1 and the electrolyte membrane 1 is laminated without protruding from the film 3, their shapes are limited to rectangular. However, the shape may be any shape such as a circle and a polygon.

Film 3 for suppressing a decrease in water content
As, besides the above-mentioned fluorine-based polymer film,
The film has substantially no water permeability and is at least 180
Organic or inorganic films such as other polymer films or metal foils can be used as long as they are stable at a temperature of ° C.

As a method for forming the catalyst layer 2 on the catalyst layer forming substrate 7, a conventionally known method such as a sedimentation method, a printing method or a spray method can be used. Can be arbitrarily selected. Catalyst layer forming substrate 7
As for the material, a polymer, an inorganic substance, or a metal can be used as long as the material is a sheet or plate capable of forming a catalyst layer by the above-described method.

In order to facilitate the transfer of the catalyst layer 2 formed on the catalyst layer-forming substrate 7 to the electrolyte membrane 1 by heating and pressure welding, it is preferable to use a catalyst layer-forming substrate having excellent releasability.
For example, a fluorine-based polymer sheet or the like can be used. Further, in order to improve the heat conductivity and the adhesiveness of the film 3 for suppressing a decrease in the water content at the time of heating and pressing, the catalyst layer forming substrate 7 preferably has a thin sheet-like thickness. However, a tetrafluoroethylene hexafluoropropylene copolymer sheet having a thickness of 0.025 mm, an aluminum foil or a copper foil having a thickness of 0.015 mm can be used.

Step 2 is a step of removing excess moisture, and a cross section is shown in FIG. 1-b. In the laminate of step 1, excess water present between the electrolyte membrane 1 and the catalyst layer 2, between the catalyst layer 2 and the film 3, or between the electrolyte membrane 1 and the film 3 is removed,
These laminates are brought into close contact.

In this step, for example, the above-mentioned laminate is placed on a flat plate 4 such as a glass plate, and excess water can be removed by using a rubber spatula 5 such as a squeegee blade. In addition to this, any method may be used as long as excess water can be removed and a laminate can be adhered by using a method of applying a roll or a method of passing a slit having a fixed width.

Step 3 is a heating and pressing step, and its cross section is shown in FIG.
-C. After the laminate from which excess water has been removed is placed on the press jig 6, the catalyst layer 2 on the catalyst layer forming substrate 7 is transferred to the electrolyte membrane 1 by heating and pressing under predetermined conditions.

The press surface of the press jig 6 is slightly larger than the catalyst layer 2 to be transferred, and the shape of the catalyst layer 2 and the shape of the press surface are preferably similar, and the entire surface of the catalyst layer contacts the press surface. Install as follows. It is preferable that the pressed surface does not hit the electrolyte membrane 1 around the catalyst layer 2, but the pressed surface may be sufficiently larger than the catalyst layer 2 and hit the electrolyte membrane 1.

The temperature of the heating and pressing is preferably 100 ° C. or less, more preferably 50 ° C. to 90 ° C., so that water in the electrolyte membrane does not rapidly evaporate. Any temperature may be used as long as the catalyst layer can be transferred to the electrolyte membrane. Further, the pressure of this heating pressure welding is determined in consideration of the heating temperature and is 25 kg / cm ^2.
The pressure is preferably from 500 kg / cm ² to 500 kg / cm ^2, but any pressure can be used as long as the catalyst layer on the catalyst layer-forming substrate can be transferred to the electrolyte membrane.

Step 4 is a step of removing the substrate on which the catalyst layer is formed, and its cross section is shown in FIG. 1-d. The film 3 and the catalyst layer forming substrate 7 are removed from the laminate in which the catalyst layer 2 has been transferred to the electrolyte membrane 1 by heating and pressing. The catalyst layer-forming substrate 7 can be easily peeled off. However, when a metal foil is used as the catalyst layer-forming substrate 7, the catalyst layer-forming substrate can be removed by dissolving it in an acid or the like. The catalyst layer-electrolyte membrane assembly thus produced is stored in purified water.

The water-containing electrolyte membrane used for producing the catalyst layer-electrolyte membrane assembly of the present invention can be used after it has been subjected to a pretreatment for protonation. For example, in this pretreatment, a commercially available electrolyte membrane (for example, a Nafion membrane or the like) is washed several times with purified water, then subjected to boiling treatment with 3% hydrogen peroxide for about 1 hour for degreasing, and several times with purified water. After the washing, the counter ion of the electrolyte membrane is exchanged for protons by performing boiling treatment with 0.5 M diluted sulfuric acid for about 1 hour, and further washed several times with purified water.

The proton conductivity of the electrolyte membrane increases as the water content increases. Conversely, when the water content decreases, the proton conductivity decreases, and when the water content becomes zero, the electrolyte does not exhibit proton conductivity. It is possible to further increase the water content by setting the boiling conditions in the pretreatment to high temperature and high pressure, but it is difficult to maintain a high water content at normal temperature.

The water content of the electrolyte membrane pretreated under the above-mentioned conditions and stored in purified water at room temperature is about 35 wt%, which is almost the maximum of the water content at room temperature. Therefore, to keep the proton conductivity of the electrolyte membrane high,
It is desired to produce an electrolyte membrane-catalyst layer assembly without performing a pretreatment and reducing the water content of the electrolyte membrane stored in purified water.

The electrolyte membrane for forming the electrolyte membrane-catalyst layer assembly may be one which is taken out of the purified water that has been subjected to pretreatment and stored, and the surface of which has stored water. After forming a laminate on which a film for suppressing a decrease in the water content is formed from both sides of the electrolyte membrane having a high moisture content, excess water present on the surface of the electrolyte membrane or the like is drawn out and the laminate is adhered to the laminate. .

The electrolyte membrane used in the present invention is not limited to those having the above-mentioned water content pretreated by the above-mentioned method. May be applied to the electrolyte membrane. Also,
As the electrolyte membrane, any membrane can be used as long as it is a polymer membrane that exhibits proton conductivity in a water-containing state, such as perfluorosulfonic acid, perfluorocarboxylic acid, and stilvinylbenzenesulfonic acid.

The fuel cell gas diffusion electrode-electrolyte membrane assembly is produced, for example, as follows. The catalyst layer-electrolyte membrane assembly is taken out from the stored purified water, water-repellent carbon paper is laminated as a gas diffusion layer while water is present on the surface, and water is impregnated from both sides so as to cover the electrolyte membrane. The laminate is configured to be covered with a film for suppressing a reduction in the rate. This laminate is placed in a press jig and heated and pressed to join the gas diffusion layer to the catalyst layer. By arranging the film, it is possible to suppress a decrease in the water content at the time of heating and pressing.

[0040]

EXAMPLES Examples of the method for producing a catalyst layer-electrolyte membrane assembly of the present invention will be described.

Example 1 First, a method for forming a catalyst layer will be described. That is, commercially available Nafion solution 5
30% platinum in 13.2ml wt% (Aldrich)
1.5 g of a carbon catalyst loaded with wt% was added, heated to 60 ° C. with stirring, and concentrated to prepare an ink-like mixture whose viscosity was adjusted. This catalyst mixture was applied to the surface of an aluminum foil as a catalyst layer forming substrate by screen printing using a 300 mesh, and then dried to form a catalyst layer. This was cut into 5 cm x 5 cm to prepare a catalyst layer-catalyst layer forming substrate. The catalyst layer obtained here has a thickness of about 1
0 μm, and the weight of the platinum catalyst is about 0.1 mg / cm ²
Met.

Next, the pretreatment of the electrolyte membrane will be described. As the electrolyte membrane, a commercially available Nafion 115 (registered trademark of DuPont), which is a perfluorosulfonic acid resin membrane, was used. After washing the Nafion 115 membrane three times with purified water,
After boiling for 1 hour in 3% hydrogen peroxide solution, it was washed three times with purified water. Further, after boiled with 0.5 M diluted sulfuric acid for 1 hour in order to make the counter ion of the Nafion membrane into a proton type,
Washed three times with purified water. After performing such pre-processing,
The Nafion 115 membrane was stored in purified water at room temperature until use.

Next, transfer of the catalyst layer to the electrolyte membrane will be described. The previously prepared catalyst layer-catalyst layer forming substrate was
It was arranged at a predetermined position on both sides of the electrolyte membrane subjected to the pretreatment described above. At this time, the positions of the catalyst layers on both sides were matched via the electrolyte membrane. Then, a film for suppressing a decrease in the water content was disposed so as to cover from both sides to form a laminate.

As the film, a 50 μm-thick tetrafluoroethylene-hexafluoropropylene copolymer film (manufactured by Daikin Industries, Ltd., trade name: Neoflon film) was used. The water content of the electrolyte membrane at this time is about 35
wt%. Place this stack on a flat glass slope,
Using a squeegee blade, excess water in the laminate was drawn out and removed to bring the laminate into close contact.

This laminate was placed on a press jig and placed
After transferring the catalyst layer to the electrolyte membrane by heating and pressing under the conditions of kg / cm ² , 90 ° C. and 90 seconds, the film and the catalyst layer-forming substrate were peeled off to produce a catalyst layer-electrolyte membrane assembly.
This was designated as catalyst layer-electrolyte membrane assembly A of the present invention.

Next, a method for producing the gas diffusion electrode-electrolyte membrane assembly will be described. The gas diffusion electrode-electrolyte membrane assembly is obtained by joining a gas diffusion layer to the catalyst layer portion of the catalyst layer-electrolyte membrane assembly. As the gas diffusion layer, a carbon paper having a thickness of 0.2 mm was impregnated with a dispersion polytetrafluoroethylene solution and then fired to give water repellency. This carbon paper having water repellency is cut into a size of 5 cm × 5 cm, and placed on the catalyst layers on both sides of the previously prepared catalyst layer-electrolyte membrane assembly A to further suppress a decrease in water content. The film was laminated on both sides so as to cover it from both sides, and placed in a press jig, and heated and pressed under the conditions of 120 kg / cm ² , 90 ° C., and 5 minutes to join the gas diffusion layer to the catalyst layer. The film was peeled off, and a gas diffusion electrode-electrolyte membrane assembly A produced using the catalyst layer-electrolyte membrane assembly A of the present invention was produced.

The gas diffusion electrode-electrolyte membrane assembly A was sandwiched between a pair of metal separators in which gas channels were processed, to form a solid polymer electrolyte fuel cell A.

Gas Diffusion Electrode Made Using Film
The electrolyte membrane around the gas diffusion electrode of the electrolyte membrane assembly,
The change in shape was less than when no film was used.
For this reason, when a fuel cell is constructed by sandwiching the gas diffusion electrode-electrolyte membrane assembly between separators, the airtightness between the electrolyte membrane and the separator in the peripheral portion of the assembly is improved, and a higher gas pressure is applied. No more leaks. On the other hand, a gas diffusion electrode made without using a film
The shape of the electrolyte membrane around the gas diffusion electrode of the electrolyte membrane assembly greatly changed, resulting in a decrease in the airtightness of the fuel cell.

[Comparative Example] The electrolyte membrane (Nafion 115) pretreated in Example 1 was sandwiched between several filter papers and paper towels, and the pressure was reduced under pressure. The pressure was reduced at 80 ° C. overnight (about 16 hours). ) Vacuum drying was performed to prepare an electrolyte membrane having a water content of zero. The same catalyst layer as that prepared in Example 1 was disposed on both sides of the electrolyte membrane having a water content of zero, and had a thickness of 50%.
A laminate in which a μm tetrafluoroethylene-hexafluoropropylene copolymer film was disposed so as to cover from both sides was formed. This laminate is placed on a press jig and
After transferring the catalyst layer to the electrolyte membrane by heating and pressing under the conditions of kg / cm ² , 90 ° C. and 90 seconds, the film and the catalyst layer-forming substrate are peeled off, and a catalyst layer-electrolyte membrane assembly is produced. The electrolyte membrane was immersed in water to return to a water-containing state. This was designated as catalyst layer-electrolyte membrane assembly B.

As in Example 1, water-repellent carbon paper as a gas diffusion layer was disposed on both surfaces of the catalyst layer-electrolyte membrane assembly B, and the film was laminated so as to cover both sides, and the resultant was applied to a press jig. 120 kg / c
The gas diffusion layer was joined to the catalyst layer by heating and pressing under conditions of m ² , 90 ° C., and 5 minutes. Peel off the film, catalyst layer-
A gas diffusion electrode-electrolyte membrane assembly B produced using the electrolyte membrane assembly B was produced.

The polymer electrolyte fuel cell B was constituted by sandwiching the gas diffusion electrode-electrolyte membrane assembly B between a pair of metal separators having gas channels formed therein.

The solid polymer electrolyte fuel cell A manufactured in Example 1 and the solid polymer electrolyte fuel cell B manufactured in Comparative Example were operated under the same conditions. That is, pure hydrogen was used as the fuel gas, and the fuel gas was humidified by a bubbler humidifier set at 60 ° C., and then supplied to the battery at a flow rate at which the utilization factor became 70%. After humidifying with a bubbler humidifier set to 60 ° C. using pure oxygen as the oxidizing gas, the gas was supplied to the battery at a flow rate at which the utilization factor became 50%. The reaction gases were each supplied at atmospheric pressure. Coolant at 65 ° C. was circulated through the battery to keep the battery temperature constant.

FIG. 3 shows the current-voltage characteristics of the solid polymer electrolyte fuel cells A and B. 3, reference numeral 11 denotes a current-voltage characteristic of the solid polymer electrolyte fuel cell A, and reference numeral 12 denotes a current-voltage characteristic of the solid polymer electrolyte fuel cell B.

As is evident from FIG. 3, the solid polymer electrolyte fuel cell A according to the present invention, which uses a hydrated electrolyte membrane when producing a catalyst layer-electrolyte membrane assembly, uses a dry electrolyte membrane. Compared to the solid polymer electrolyte fuel cell B of the comparative example used, the voltage drop due to the increase in the current density was small, indicating excellent characteristics.

An internal resistance meter (TSURUGAMODEL)
When the internal resistance of these solid polymer electrolyte fuel cells at an open circuit voltage was measured using 3562), the solid polymer electrolyte fuel cell A showed a value of 9.6 mΩ, while the solid polymer electrolyte fuel cell A showed a value of 9.6 mΩ. Type fuel cell B showed a value of 17.2 mΩ. This means that the solid polymer electrolyte fuel cell B
Has a higher internal resistance than that of the solid polymer electrolyte fuel cell A. Therefore, it is considered that the characteristics of the former decrease due to an increase in the resistance overvoltage. The water content of the electrolyte membrane was measured for the catalyst layer-electrolyte membrane assembly B immersed in purified water to return to a water-containing state, and the water content was 31 wt.
%Met. This value was smaller than the water content of 35 wt% after the pretreatment, and it was shown that once the electrolyte membrane was dried, the water content was not sufficiently restored only by immersing it in purified water.

From these facts, when a catalyst layer-electrolyte membrane assembly is produced, it is better to use a hydrated electrolyte membrane.
A solid polymer electrolyte fuel cell having a low resistance overvoltage and a high output density can be manufactured.

Example 2 The electrolyte membrane (Nafion 115) subjected to the pretreatment in Example 1 was placed in a container whose relative humidity was controlled for 2 days to produce electrolyte membranes having various water contents. The water content of the prepared electrolyte membrane was 3
They are 1 wt%, 28 wt%, 25 wt%, 23 wt% and 20 wt%. The same catalyst layer as that prepared in Example 1 was arranged on both sides of the electrolyte membrane having each moisture content, and a laminate was arranged so as to cover from both sides a film for suppressing a decrease in moisture content.

This laminate was placed on a press jig and placed
After transferring the catalyst layer to the electrolyte membrane by heating and pressing under the conditions of kg / cm ² , 90 ° C. and 90 seconds, the film and the catalyst layer-forming substrate are peeled off to form a catalyst layer-electrolyte membrane assembly, and purified water To return the electrolyte membrane to a water-containing state.

A catalyst layer-electrolyte membrane assembly C, 28 of the present invention was prepared using an electrolyte membrane having a water content of 31 wt%.
The catalyst layer-electrolyte membrane assembly D of the present invention was prepared using a wt% electrolyte membrane, and the catalyst layer-electrolyte membrane assembly E of the present invention was prepared using a 25 wt% electrolyte membrane.
A catalyst layer-electrolyte membrane assembly F of the present invention was prepared using a 3 wt% electrolyte membrane. A catalyst layer-electrolyte membrane assembly G of the present invention was prepared using a 20 wt% electrolyte membrane.

As in Example 1, carbon paper having water repellency as a gas diffusion layer was disposed on both surfaces of the catalyst layer-electrolyte membrane assemblies C, D, E, F and G of the present invention. And placed on a press jig so as to cover from both sides, at 120 kg / cm ² , 90 ° C., 5
The gas diffusion layer was joined to the catalyst layer by heating and pressing under the conditions of minutes. The film was peeled off to produce gas diffusion electrode-electrolyte membrane assemblies C, D, E, F and G of the present invention. These gas diffusion electrode-electrolyte membrane assemblies C, D,
The solid polymer electrolyte fuel cells C, D, E, F and G are respectively sandwiched between a pair of metal separators each having a gas channel processed in each of E, F and G, and are the same as those in Example 1. Operated under conditions.

FIG. 4 shows the solid polymer electrolyte fuel cells A, B, C, and C produced in Example 1, Example 2, and Comparative Example.
FIG. 4 shows the relationship between the terminal voltage of D, E, F, and G at a current density of 500 mA / cm ² and the water content of the electrolyte membrane used when producing the catalyst layer-electrolyte membrane assembly.

The terminal voltage at a current density of 500 mA / cm ² is the highest for a solid polymer electrolyte fuel cell A prepared using an electrolyte membrane having a water content of 35 wt%, and decreases as the water content of the electrolyte membrane decreases. Decrease gradually, 20wt%
At lower moisture contents, a significant decrease was observed.

An internal resistance meter (TSURUGA MODEL)
3562), the current density of these solid polymer electrolyte fuel cells A, C, D, E, F, G and B was 50
When the internal resistance at 0 mA / cm ² was measured, it was 9.8 mΩ, 9.8 mΩ, 10.0 mΩ, and 11.5 mΩ, respectively.
The values of Ω, 11.9 mΩ, 13.8 mΩ, and 17.5 mΩ indicated that the internal resistance increased as the water content at the time of transferring the catalyst layer decreased.

FIG. 5 shows the relationship between the relative size of the electrolyte membrane and the water content when the length of one side of the electrolyte membrane is 1 when the water content is 35 wt% when a square electrolyte membrane is used. When the water content becomes 28 wt%, the length of one side of the electrolyte membrane becomes about 3
%, 23 wt% about 5%, 20 wt% about 9%, 0%
In the case of wt%, it shrinks by as much as 16%.
When it was returned to the vicinity of t%, it was expanded by the contracted ratio.

That is, when the catalyst layer is transferred to the contracted electrolyte membrane, when the water content of the electrolyte membrane is increased and the electrolyte membrane is extended, the catalyst layer is extended accordingly. It is conceivable that the contact between the carbon particles holding the catalyst constituting the catalyst layer becomes poor due to expansion and contraction due to the change in the water content of the electrolyte membrane, which adversely affects the electron and proton conductivity of the catalyst layer.

FIGS. 4 and 5 show that the increase in internal resistance of a solid polymer electrolyte fuel cell using an electrolyte membrane having a relatively small range of 9% or less due to a decrease in water content was observed. The effect on the conductivity of the catalyst layer was small, but when the expansion ratio exceeded 9%, the internal resistance increased remarkably, and the effect on the conductivity of the catalyst layer was found to be large.

This means that the catalyst layer having a small resistance overvoltage is
To form an electrolyte membrane assembly, the expansion and contraction of the electrolyte membrane must be 9%.
It is necessary to keep the water content below, that is, to keep the water content at 20 wt% or more. In particular, if the expansion and contraction of the electrolyte membrane is set to 3% or less, no influence on the increase of the resistance overvoltage is observed, so that the water content of the electrolyte membrane is preferably kept at 28 wt% or more.

[0068]

According to the present invention, the contact between the electrolyte membrane and the outside air is cut off by transferring the catalyst layer to the water-containing electrolyte membrane by heating and pressing in a state where the film for suppressing the decrease in the moisture content is in close contact with the film. It is effective in maintaining a water content even when an electrolyte membrane having a relatively high water content of 35 wt% is used, and it is possible to maintain high proton conductivity of the electrolyte membrane and to have a rapid water content. The deformation of the electrolyte membrane due to the change in the temperature can be prevented.

Further, the absence of excess water between the electrolyte membrane and the catalyst layer at the time of transfer facilitates the complete transfer of the catalyst layer to the electrolyte membrane.

According to the method for producing a catalyst layer-electrolyte assembly according to the present invention, deformation of the peripheral portion of the electrolyte membrane can be suppressed, and the resulting decrease in the airtightness of the fuel cell can be prevented. Providing a solid polymer electrolyte fuel cell with high reliability and excellent characteristics by suppressing the reduction in the conductivity of electrons and protons in the catalyst layer due to the resulting catalyst layer-electrolyte membrane assembly with low resistance overvoltage can do.

[Brief description of the drawings]

FIG. 1 shows a catalyst layer using a water-containing electrolyte membrane of the present invention.
FIG. 3 is a schematic view illustrating a process for manufacturing an electrolyte membrane assembly.

FIG. 2 shows a catalyst layer using a water-containing electrolyte membrane of the present invention.
FIG. 4 is a schematic diagram showing a configuration of a laminate in a manufacturing process of an electrolyte membrane assembly.

FIG. 3 shows a catalyst layer-electrolyte membrane assembly A of Example 1 of the present invention.
The figure which shows the current-voltage characteristic of the solid polymer electrolyte type fuel cell using the catalyst layer-electrolyte membrane assembly B of the comparative example.

FIG. 4 shows the relationship between the water content of an electrolyte membrane when a catalyst layer-electrolyte membrane assembly is produced and the terminal voltage at 500 mA / cm ² of a solid polymer electrolyte fuel cell formed using the assembly. FIG.

FIG. 5 shows the dimensions of one side of an electrolyte membrane having a water content of 35 wt% as 1
The figure which showed the relationship between the relative dimension at the time of setting, and the water content of an electrolyte membrane.

[Explanation of symbols]

Reference Signs List 1 electrolyte membrane 2 catalyst layer 3 film 4 glass plate 5 rubber spatula 6 press jig 7 catalyst layer forming substrate 8 catalyst layer-electrolyte membrane assembly 11 current of solid polymer electrolyte fuel cell A of the present invention-
Voltage characteristics 12 Current of solid polymer electrolyte fuel cell B of Comparative Example-
Voltage characteristics

Claims (3)

[Claims] 1. A substrate-electrolyte in which a catalyst layer-forming substrate having a catalyst layer formed on its surface is laminated on one or both surfaces of a hydrated solid polymer electrolyte membrane such that the catalyst layer surface is in contact with the solid polymer electrolyte membrane. A method for producing a catalyst layer-electrolyte membrane assembly, wherein the membrane laminate is heated and pressed while being sandwiched between two films. 2. The solid polymer electrolyte membrane having a water content of 20 wt.
%. The method for producing a catalyst layer-electrolyte membrane assembly according to claim 1, wherein 3. A catalyst layer produced by the method according to claim 1.
A solid polymer electrolyte fuel cell comprising a gas diffusion electrode-electrolyte membrane assembly using an electrolyte membrane assembly.