JP2014067539A - Method of producing membrane electrode assembly for fuel cell and solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress cracking or wrinkling of the catalyst layer in a membrane electrode assembly due to swelling of an electrolyte membrane in the membrane electrode assembly, when producing the membrane electrode assembly of a solid polymer fuel cell.SOLUTION: When forming a catalyst layer in a membrane electrode assembly on an electrolyte membrane 1 by repeating a step for applying a catalyst ink onto an electrolyte membrane 1, and a step for thermally drying the catalyst ink applied onto the electrolyte membrane 1 a plurality of times, a catalyst ink having a swelling ratio of 30% or less in the coating surface direction of each solvent with respect to the electrolyte membrane 1 is used as a catalyst ink 2 being applied onto the electrolyte membrane 1 for the first time. After applying the catalyst ink onto the electrolyte membrane 1, the catalyst ink thus applied is thermally dried thus forming the catalyst layer on the electrolyte membrane 1.

Description

  The present invention relates to a technique for manufacturing a membrane electrode assembly used in a polymer electrolyte fuel cell.

A fuel cell is a power generation system that converts a chemical energy of a fuel into electric energy and extracts it by electrochemically reacting a fuel such as hydrogen with an oxidant such as air. This power generation method is expected to be a new energy because of its advantages such as high power generation efficiency, excellent quietness, and low emissions of NOx and SOx that cause air pollution and CO _{2 that} causes global warming. ing.
Examples of the application of this fuel cell include a long-time power supply for portable electric devices, a stationary generation hot water supply machine for cogeneration, a fuel cell vehicle, and the like, which have various uses and scales.

The types of fuel cells are classified into solid polymer type, phosphoric acid type, molten carbonate type, solid oxide type, alkaline type, etc. depending on the electrolyte used. Is also different.
The one using a cation exchange membrane as an electrolyte is called a polymer electrolyte fuel cell, and can operate at a relatively low temperature among fuel cells, and the internal resistance can be reduced by reducing the thickness of the electrolyte membrane. Therefore, high output and compactness are possible, and it is considered promising for use as a vehicle-mounted source or a household stationary power source.

  A polymer electrolyte fuel cell is a fuel in which a pair of electrode catalyst layers are arranged on both sides of an electrolyte membrane called a membrane electrode assembly (MEA), and hydrogen is contained in one of the electrodes. The battery is sandwiched between a pair of separator plates in which a gas flow path for supplying gas and supplying an oxidant gas containing oxygen to the other electrode is formed. A battery sandwiched between the pair of separator plates is called a single battery cell.

  A polymer electrolyte fuel cell is used by stacking a plurality of unit cells for the purpose of increasing power density and making the entire fuel cell compact. The number of sheets to be stacked varies depending on the required electric power. For portable power sources of general portable electric devices, several to about 10 sheets, for stationary electric and hot water supply machines for cogeneration, about 60 to 90 sheets, and for automobile applications, 250 to About 400 sheets. In order to increase the output, it is necessary to increase the number of stacks, and the cost of the unit cell greatly affects the cost of the entire fuel cell. From the viewpoint of process cost, a membrane electrode assembly structure with a small number of parts and easy assembly is desired.

In recent years, when manufacturing a membrane electrode assembly, a method of forming a catalyst layer by directly applying a catalyst ink to an electrolyte membrane has been attempted. It has attracted attention as an ideal method because it does not require any auxiliary material and can reduce the process cost, and since the adhesion between the electrolyte membrane and the catalyst layer is high, the performance is improved.
However, there is a problem that the electrolyte membrane swells as soon as it comes into contact with the solvent of the catalyst ink. The solvent in the catalyst ink applied on the electrolyte membrane diffuses into the electrolyte membrane, and the electrolyte membrane becomes swollen. In the drying step after the coating step, the solvent in the catalyst ink evaporates and a catalyst layer is formed. At this time, the catalyst layer dries and shrinks as the solvent diffused in the electrolyte membrane evaporates. As a result, soot is generated in the electrolyte membrane, and accordingly, soot and cracks are generated in the catalyst layer formed on the electrolyte membrane.

As a method for solving this problem, a method has been proposed in which an electrolyte membrane is placed on a heat-adsorbing plate and backside heating is performed to apply a catalyst ink and simultaneously dry and remove the solvent (Patent Documents 1 and 2). reference).
For example, in Patent Document 1, ethanol is used as a solvent in a catalyst ink for the purpose of improving volatility, and an electrolyte membrane to which the catalyst ink is applied is placed on an adsorption plate heated to 60 ° C. Techniques for manufacturing membrane electrode assemblies are described.
Further, Patent Document 2 uses a mixed system of ethanol and water as a solvent in the catalyst ink, and the coating process is performed at a temperature at which the saturated vapor pressure of the solvent component having the highest volatility in the catalyst ink is 80 KPa or more. A technique for manufacturing a membrane electrode assembly for a fuel cell by specifying an ambient temperature is described.

JP 2003-100314 A JP 2006-344517 A

However, in the technique described in Patent Document 1, even if the evaporation of the solvent is promoted, the solvent diffuses into the electrolyte membrane before the evaporation is completed, and thus the swelling of the electrolyte membrane cannot be sufficiently suppressed. .
In addition, the technique described in Patent Document 2 has a problem that the atmosphere in the coating process is limited and cannot be applied to various coating environments.

  The present invention has been made in consideration of the above problems, and when producing a membrane electrode assembly of a polymer electrolyte fuel cell, the electrolyte membrane of the membrane electrode assembly swells, so that wrinkles and cracks are formed in the membrane electrode. It aims at providing the manufacturing method of the membrane electrode assembly for polymer electrolyte fuel cells which can suppress generating in the catalyst layer of a conjugate | zygote. Another object of the present invention is to provide a polymer electrolyte fuel cell including a membrane electrode assembly produced by the above production method.

  In order to solve the above-mentioned problems, the invention of claim 1 includes a step of applying a catalyst ink containing at least a polymer material and a plurality of kinds of solvents on an electrolyte membrane, and a catalyst applied on the electrolyte membrane. A method of manufacturing a fuel cell membrane electrode assembly by alternately repeating a step of heating and drying the ink a plurality of times, wherein the catalyst ink is applied to the electrolyte membrane for the first time. A catalyst ink having a swelling rate of 30% or less in the direction of the coating surface of the solvent is applied on the electrolyte membrane.

The invention of claim 2 is characterized in that, when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink in which one kind of the solvent is water is applied on the electrolyte membrane.
The invention of claim 3 is characterized in that, when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink in which one kind of the solvent is an alcohol solvent is applied on the electrolyte membrane. .

The invention of claim 4 is characterized in that the alcohol solvent is a divalent alcohol.
According to a fifth aspect of the present invention, when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink having a ratio of the water to the alcohol solvent of 1.0 to 2.0 is applied on the electrolyte membrane. It is characterized by applying.
The invention according to claim 6 is characterized in that when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink having a solid content ratio of 10 to 15% with respect to the solvent is applied on the electrolyte membrane. And

According to the seventh aspect of the present invention, when the catalyst ink is applied onto the electrolyte membrane for the second time or later, the catalyst ink is evaporated so that the plurality of solvents evaporate at a temperature lower than the heating and drying temperature of the catalyst ink. It is characterized by being coated on
The invention according to claim 8 is characterized in that when the catalyst ink is applied on the electrolyte membrane for the second time or later, the catalyst ink in which one kind of the solvent is water is applied on the electrolyte membrane. .

In the invention of claim 9, when the catalyst ink is applied on the electrolyte membrane for the second time and thereafter, the catalyst ink having a solid content ratio of 8 to 10% with respect to the solvent is applied on the electrolyte membrane. Features.
The invention of claim 10 is characterized by comprising a membrane electrode assembly manufactured by the manufacturing method according to any one of claims 1 to 9.

According to the present invention, the step of applying the catalyst ink on the electrolyte membrane and the step of heating and drying the catalyst ink applied on the electrolyte membrane are alternately repeated a plurality of times, thereby applying on the electrolyte membrane. The amount of the catalyst ink applied per time can be reduced, and the amount of solvent that touches the electrolyte membrane is also reduced, so that swelling of the electrolyte membrane is suppressed.
In addition, when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink having a swelling rate of 30% or less in the direction of the coating surface of the solvent with respect to the electrolyte membrane is applied on the electrolyte membrane. The diffusion of the solvent to the electrolyte membrane is suppressed, whereby the electrolyte membrane of the membrane / electrode assembly swells and soot and cracks can be prevented from occurring in the catalyst layer of the membrane / electrode assembly.

Further, by directly applying the catalyst ink on the electrolyte membrane, the electrolyte membrane and the catalyst layer formed on the surface thereof have excellent adhesion. Therefore, a decrease in battery performance due to poor adhesion is prevented.
In addition, since the catalyst ink applied after the second time is formed on the catalyst layer applied and dried at the first time, it does not directly touch the electrolyte membrane. Swelling of the electrolyte membrane due to the solvent in the catalyst ink applied after the second time is suppressed.

  In addition, when applying the catalyst ink on the electrolyte membrane for the second time or later, the drying step is performed by applying the catalyst ink on which the plural types of solvents evaporate at a temperature lower than the heating drying temperature of the catalyst ink. The removal of the solvent smoothly proceeds, the catalyst layer becomes porous, and the gas diffusibility is improved. Accordingly, a decrease in battery performance due to poor gas diffusibility is prevented.

It is sectional drawing which shows an example of the membrane electrode assembly used for a polymer electrolyte fuel cell. It is a figure which shows an example in the case of forming a catalyst layer on the electrolyte membrane shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a membrane electrode assembly used in a polymer electrolyte fuel cell. A membrane electrode assembly 8 shown in FIG. 1 has an electrolyte membrane 1, and catalyst layers 21 and 22 are formed on both surfaces (upper surface and lower surface in the figure) of the electrolyte membrane 1.
The membrane electrode assembly 8 has a catalyst layer 31, and the catalyst layer 31 is formed on the catalyst layer 21. Further, the membrane electrode assembly 8 has gasket layers 41 and 42, and these gasket layers 41 and 42 are formed on both surfaces of the electrolyte membrane 1 so as to surround the catalyst layers 21, 22 and 31.

FIG. 2 is a diagram showing an example in which a catalyst layer is formed on the electrolyte membrane shown in FIG. 1. When the catalyst layers 21 and 31 are formed on the electrolyte membrane 1, first, the mask 5 is a gasket layer. A frame-like masked gasket layer 6 integrated with 4 is formed on the electrolyte membrane 1.
Next, after applying the first catalyst ink 2 on the electrolyte membrane 1 from the opening 7 formed in the central portion of the gasket layer 6 with mask, the catalyst ink 2 applied on the electrolyte membrane 1 is heated. Then, the catalyst layer 21 is formed on the electrolyte membrane 1 by drying. Then, after applying the catalyst ink 3 for the second time on the electrolyte membrane 1 from the opening 7 of the gasket layer 6 with the mask, the catalyst ink 3 applied on the electrolyte membrane 1 is heated and dried. A catalyst layer 31 is formed on the catalyst layer 21.

Even when the catalyst layer 22 is formed on the electrolyte membrane 1, the catalyst layer 22 is formed on the electrolyte membrane 1 by using the same method as described above.
When the catalyst inks 2 and 3 are applied on the electrolyte membrane 1, the catalyst inks 2 and 3 may be applied on the electrolyte membrane 1 by using, for example, a spray method, a gravure printing method, a brush coating method, a die coating method, or the like. Although possible, it is not limited to these methods.

When the catalyst inks 2 and 3 applied on the electrolyte membrane 1 are dried by heating, in this embodiment, the initial stage of heating the electrolyte membrane 1 simultaneously with the application of the catalyst inks 2 and 3 from one side of the electrolyte membrane 1 is performed. Drying is performed. Further, the main drying after the initial drying is performed by heat drying as in the case of the initial drying, but the direction of heating is not limited to one side of the electrolyte membrane 1.
As the electrolyte membrane 1 to which the catalyst inks 2 and 3 are applied, those used for the polymer electrolyte fuel cell can be used, and examples thereof include a fluorine-based electrolyte membrane and a hydrocarbon electrolyte membrane.

When the catalyst inks 2 and 3 are applied on the electrolyte membrane 1, the catalyst ink 2 applied for the first time on the electrolyte membrane 1 includes at least a polymer material and a plurality of types of solvents. It is preferable to use a catalyst ink in which the swelling ratio of each solvent in the direction of the coated surface, that is, the average of the swelling ratio in the direction of the coated surface and the direction perpendicular to the coated surface is 30% or less.
Here, the swelling rate in the coating surface direction refers to the average value of the swelling rate in the coating direction X and the swelling rate in the direction Y perpendicular to the coating direction. The swelling rate is measured by immersing the electrolyte membrane 1 in a solvent for 5 minutes, measuring the dimensions of the electrolyte membrane 1 before and after the immersion, and calculating the dimensional elongation rate.

The lower the swelling rate in the coated surface direction, the more the solvent is diffused into the electrolyte membrane. Therefore, a solvent having a small swelling rate in the coated surface direction is desirable.
Further, as the catalyst ink 2 applied for the first time on the electrolyte membrane 1, one of a plurality of solvents contained in the catalyst ink is water and the other is a divalent alcohol catalyst ink. Is preferably used.

Examples of the divalent alcohol include ethylene glycol, propylene glycol, triethylene glycol, and 2-methyl 1,3-pentadiol.
Furthermore, it is preferable that the solid content ratio of the catalyst ink 2 used at the time of the 1st application | coating is 10-15 mass%. As the solid content ratio is higher, the solvent component contained in the catalyst ink is reduced and the diffusion of the solvent into the electrolyte membrane is suppressed. Therefore, it is desirable to use a catalyst ink having a high solid content ratio. However, since the application of the catalyst ink 2 to the electrolyte membrane 1 becomes difficult when the solid content ratio of the catalyst ink is high, the solid content ratio with respect to the solvent is preferably 10 to 15% by mass.

  As the catalyst ink 3 used in the second and subsequent coatings, it is preferable to use a catalyst ink that contains at least a polymer material and a plurality of solvents, and each solvent evaporates at a temperature lower than the heating drying temperature of the catalyst ink. . The heating and drying temperature of the catalyst ink is preferably 150 ° C. or less in consideration of the softening point of the polymer material contained in the catalyst ink and the drying unevenness of the catalyst layer formed on the electrolyte membrane, and the boiling point of each solvent Is desirably 100 ° C. or lower.

  In the second and subsequent coatings, the catalyst ink 3 is formed on the first catalyst layer 21 and does not directly touch the electrolyte membrane 1. Therefore, the swelling ratio of each solvent contained in the catalyst ink 3 used for the second and subsequent coatings with respect to the electrolyte membrane 1 is not particularly defined. When the swelling rate of each solvent contained in the catalyst ink 3 with respect to the electrolyte membrane 1 is 70% or less, it can be suitably used.

  Moreover, it is desirable that at least one of the solvents contained in the catalyst ink 3 used at the second and subsequent coatings is water. Furthermore, the solid content ratio of the catalyst ink 3 used in the second and subsequent coatings is desirably 8 to 10% by mass. When the solid content ratio is extremely high, the dispersion of the catalyst and the polymer material in the catalyst ink is inhibited. When the solid content ratio is extremely low, the catalyst in which the solvent in the catalyst ink is formed by the first application. It passes through the pores of the layer and reaches the electrolyte membrane, leading to swelling of the electrolyte membrane. The solid content ratio of the catalyst ink 3 is preferably 8 to 10% by mass with good dispersion of the catalyst and the polymer material in the catalyst ink.

  Examples of the catalyst contained in the catalyst inks 2 and 3 include fine particles of platinum or an alloy of platinum and other metals (for example, Ru, Rh, Mo, Cr, Co, Fe, etc.) (the average particle diameter is preferably 10 nm or less). ) Can be used. Conductive carbon fine particles such as carbon black (average particle diameter: about 20 to 100 nm) can be used. As the polymer material contained in the catalyst inks 2 and 3, a polymer solution such as a perfluorosulfonic acid resin solution can be used.

  Examples of the material of the gasket layer 4 used when applying the catalyst inks 2 and 3 on the electrolyte membrane 1 include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and polyimide (PI). It may also contain polymers such as other hard polymeric materials that are sufficiently thin, sufficiently strong and fully compatible with the fuel cell environment.

Examples of the present invention and comparative examples will be described below. In addition, the Example mentioned later is one Example of this invention, and this invention is not limited only to this Example.
A platinum supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum supported amount of 50% by mass and Nafion (registered trademark, manufactured by DuPont), which is a 20% by mass polymer electrolyte solution, were mixed at a mixing ratio of 1: 1 (swelling rate: 5.0%, boiling point: 100.0 ° C.) and ethylene glycol (swelling rate: 14.5%, boiling point: 197.9 ° C.) mixed solvent. The solid content ratio at this time was set to 14% by mass. Subsequently, dispersion treatment was performed with a planetary ball mill to prepare a catalyst ink to be used for the first application.

  A platinum supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum supported amount of 50% by mass and Nafion (registered trademark, manufactured by DuPont), which is a 20% by mass polymer electrolyte solution, were mixed at a mixing ratio of 1: 1: 1 water, 1-propanol (swelling rate: 62.5%, boiling point: 97.2 ° C), 2-propanol (swelling rate: 42.5%, boiling point: 82.4 ° C) mixed in a mixed solvent . The solid content ratio at this time was set to 8% by mass. Subsequently, a dispersion treatment was performed with a planetary ball mill to prepare a catalyst ink to be used for the second and subsequent coatings.

A center portion of a two-layer film in which a polyethylene terephthalate film with a weak adhesive layer was bonded to the gasket layer was punched out to produce a frame-shaped two-layer mask. The opening size of the mask is 50 mm square. Subsequently, the produced frame-shaped mask was bonded to the electrolyte membrane. As the electrolyte membrane, Nafion212 (manufactured by DuPont) was used.
An electrolyte membrane in which a frame-like mask was bonded onto the adsorption plate was fixed. The temperature of the adsorption plate at this time was set to 60 ° C. for the purpose of suppressing the diffusion of the solvent in the catalyst ink into the electrolyte membrane and facilitating the removal of the solvent.

The adjusted catalyst ink applied for the first time was applied onto the electrolyte membrane by the blade method. The blade gap was adjusted so that the platinum loading at this time was 0.1 mg / cm ^2, and the first coating step was performed. Subsequently, the temperature on the adsorption plate was raised to 120 ° C., and the first drying step was performed.
The adjusted catalyst ink applied after the second time was applied on the catalyst layer formed first time by the blade method. The blade gap was adjusted so that the platinum loading at this time was 0.1 mg / cm ^2, and the second coating step was performed. Subsequently, the temperature on the adsorption plate was raised to 120 ° C., and a second drying step was performed.

The application and drying were repeated using the catalyst ink applied for the second time and thereafter, and the third and fourth application steps and the drying step, in which the total amount of platinum supported on the catalyst layer was 0.4 mg / cm ² , were performed.
Finally, the polyethylene terephthalate film with a weak adhesive layer was peeled off from the gasket layer to form a membrane electrode assembly in which the cathode catalyst layer was formed on one side of the electrolyte membrane and the gasket layer was disposed on the periphery of the catalyst layer.

The membrane electrode assembly with the prepared catalyst layer formed on one side is turned upside down, the anode catalyst layer is formed in the same way on the surface opposite to the cathode catalyst layer formation surface, and the catalyst layer is formed on both surfaces of the electrolyte membrane Thus, a membrane / electrode assembly in which a gasket was disposed on the periphery of the catalyst layer was obtained. The coating step and the drying step were performed only once so that the amount of platinum supported was 0.1 mg / cm ² equivalent to the anode catalyst layer.
When the electrolyte membrane and the catalyst layer of the produced membrane / electrode assembly were observed, no flaws or cracks were observed.

[Comparative Example 1]
A platinum supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum supported amount of 50% by mass and Nafion (registered trademark, manufactured by DuPont), which is a 20% by mass polymer electrolyte solution, were mixed at a mixing ratio of 1: 1: 1 water, 1-propanol (swelling rate: 62.5%, boiling point: 97.2 ° C), 2-propanol (swelling rate: 42.5%, boiling point: 82.4 ° C) mixed in a mixed solvent . The solid content ratio at this time was set to 8% by mass. Subsequently, a dispersion treatment was performed with a planetary ball mill to prepare a catalyst ink.

Using the prepared catalyst ink, the cathode catalyst layer was applied four times and the anode catalyst layer was applied once and dried in the same manner as in Example 1 to prepare a membrane electrode assembly.
When the cathode catalyst layer was observed after the first coating step / drying step, a large number of soot and cracks were observed in the electrolyte membrane. It was also observed that the size and number of wrinkles and cracks increased as the number of coating and drying steps increased.

[Comparative Example 2]
A platinum supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum supported amount of 50% by mass and Nafion (registered trademark, manufactured by DuPont), which is a 20% by mass polymer electrolyte solution, were mixed at a mixing ratio of 1: 1 (swelling rate: 5.0%, boiling point: 100.0 ° C.) and ethylene glycol (swelling rate: 14.5%, boiling point: 197.9 ° C.) mixed solvent. The solid content ratio at this time was set to 14% by mass. Subsequently, the dispersion treatment was performed with a planetary ball mill, and the catalyst ink applied for the first time was prepared.

The coating process was performed by the same blade method as in Example 1 using the prepared catalyst ink. In the coating process, the cathode catalyst layer is formed so that the platinum loading amount becomes 0.4 mg / cm ² by one coating, and the anode catalyst layer so that the platinum loading amount becomes 0.1 mg / cm ² by one coating. To form a membrane electrode assembly.
When the electrolyte membrane and the catalyst layer of the produced membrane / electrode assembly were observed, a large number of soot and cracks were observed in the cathode catalyst layer.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a polymer electrolyte fuel cell, particularly a polymer electrolyte fuel cell single cell or stack in a fuel cell automobile, a household fuel cell, and the like.

DESCRIPTION OF SYMBOLS 1 ... Electrolyte membrane 2 ... The catalyst ink used at the time of the 1st application | coating 3 ... The catalyst ink used at the time of the 2nd and subsequent application | coating 4 ... Gasket layer 5 ... Mask 6 ... Gasket layer with a mask 7 ... Opening part 8 ... Membrane electrode assembly 21 ... Cathode catalyst layer after first application 22 ... Anode catalyst layer after first application 31 ... Cathode catalyst layer after second application 41 ... Cathode gasket layer 42 ... Anode gasket layer

Claims (10)

  A fuel is produced by alternately repeating a step of applying a catalyst ink containing at least a polymer material and a plurality of types of solvents on the electrolyte membrane and a step of heating and drying the catalyst ink applied on the electrolyte membrane a plurality of times. A method for producing a membrane electrode assembly for a battery, wherein when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst has a swelling rate of 30% or less in the direction of the coating surface of the solvent with respect to the electrolyte membrane. A method for producing a membrane electrode assembly for a fuel cell, comprising applying ink onto the electrolyte membrane.   2. The fuel cell according to claim 1, wherein when the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink in which one kind of the solvent is water is applied on the electrolyte membrane. Of manufacturing membrane electrode assembly for use.   3. When the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink in which one kind of the solvent is an alcohol solvent is applied on the electrolyte membrane. Of manufacturing a fuel cell membrane electrode assembly.   The method for producing a membrane electrode assembly for a fuel cell according to claim 3, wherein the alcohol solvent is a divalent alcohol.   When the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink having a ratio of the water to the alcohol solvent of 1.0 to 2.0 is applied on the electrolyte membrane. The manufacturing method of the membrane electrode assembly for fuel cells of Claim 3 or 4.   6. When the catalyst ink is applied on the electrolyte membrane for the first time, the catalyst ink having a solid content ratio of 10 to 15% with respect to the solvent is applied on the electrolyte membrane. The manufacturing method of the membrane electrode assembly for fuel cells as described in any one of these.   When the catalyst ink is applied on the electrolyte membrane for the second time or later, the catalyst ink in which the plurality of solvents evaporate at a temperature lower than the heating and drying temperature of the catalyst ink is applied on the electrolyte membrane. The manufacturing method of the membrane electrode assembly for fuel cells as described in any one of Claims 1-6 characterized by the above-mentioned.   8. The catalyst ink according to claim 1, wherein when the catalyst ink is applied on the electrolyte membrane for the second time or later, the catalyst ink in which one kind of the solvent is water is applied on the electrolyte membrane. A process for producing a membrane electrode assembly for a fuel cell according to claim 1.   The catalyst ink having a solid content ratio of 8 to 10% with respect to the solvent is applied on the electrolyte membrane when the catalyst ink is applied on the electrolyte membrane for the second time or later. The method for producing a membrane electrode assembly for a fuel cell according to claim 8.   A polymer electrolyte fuel cell comprising the membrane electrode assembly produced by the production method according to claim 1.

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