JP2020136214A - Manufacturing method of membrane electrode assembly for polymer electrolyte fuel cell - Google Patents

Abstract

To provide a manufacturing method of a membrane electrode assembly for a polymer electrolyte fuel cell, which can obtain a high output voltage in a wide range of current density.SOLUTION: In a manufacturing method of a membrane electrode assembly 1 including a first electrode 10 having a first catalyst layer 12 and a first gas diffusion layer 14, a second electrode 20 having a second catalyst layer 22 and a second gas diffusion layer 24, and an electrolyte membrane 30, the first gas diffusion layer 14, a first intermediate having a first catalyst layer 12 formed by annealing after coating on the surface of the electrolyte membrane 30, and a second intermediate having a second catalyst layer 22 formed by coating on the surface of the second gas diffusion layer 24 are bonded such that the first catalyst layer 12 is located between the first gas diffusion layer 14 and the electrolyte membrane 30, and the second catalyst layer 22 is located between the second gas diffusion layer 24 and the electrolyte membrane 30.SELECTED DRAWING: Figure 1

Description

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

A polymer electrolyte fuel cell is a conductive separator in which a gas flow path is formed by forming a membrane electrode assembly in which electrodes (cathode (air electrode) and anode (fuel electrode)) are arranged on both sides of a polymer electrolyte membrane. It is composed of multiple stacks via. The electrode is composed of a catalyst layer in contact with the solid polymer electrolyte membrane and a porous gas diffusion layer arranged outside the catalyst layer. The gas diffusion layer plays a role of diffusing air or fuel into the electrode and a role of draining water generated in the electrode.

The following methods are known as a method for producing a membrane electrode assembly.
(1) A coating liquid containing an electrode catalyst is applied to the surface of a gas diffusion layer to form a catalyst layer to form an electrode, which is hot-pressed with a solid polymer electrolyte membrane sandwiched between the two electrodes. Method of joining (Patent Document 1).
(2) A coating liquid containing a catalyst is applied onto the base film to form a first catalyst layer, and a coating liquid containing an ion exchange resin is applied onto the first catalyst layer. A solid polymer electrolyte film is formed, and a coating liquid containing a catalyst is applied onto the solid polymer electrolyte film to form a second catalyst layer, and a first catalyst formed on the base film. A method in which the base film is peeled off from a laminate containing a layer, a solid polymer electrolyte membrane, and a second catalyst layer, and the laminate is hot-pressed and bonded while being sandwiched between two gas diffusion layers. (Patent Document 2).

However, in the membrane electrode assembly obtained by the method (1), since the catalyst layers of both poles are formed by coating directly on the surface of the gas diffusion layer, a part of the catalyst layer is formed on the gas diffusion layer of both poles. Invades and blocks a part of the voids in the gas diffusion layer. As a result, the gas diffusibility of the gas diffusion layer is lowered, so that there is a problem that the output voltage of the polymer electrolyte fuel cell becomes insufficient in the high current density region.

In the membrane electrode assembly obtained by the method (2), since the solid polymer electrolyte membrane is formed directly on the surface of the first catalyst layer by coating, an ion exchange resin is formed on the first catalyst layer. Part of this invades and closes many of the voids in the first catalyst layer. As a result, the gas diffusibility of the first catalyst layer is lowered, so that there is a problem that the output voltage of the polymer electrolyte fuel cell using the membrane electrode assembly becomes insufficient in the high current density region.

Japanese Unexamined Patent Publication No. 04-162365 International Publication No. 02/005371

The present invention provides a method capable of producing a membrane electrode assembly for a polymer electrolyte fuel cell, which can obtain a high output voltage in a wide range of current densities.

The method for producing a membrane electrode junction for a polymer electrolyte fuel cell of the present invention comprises a first electrode having a first catalyst layer and a first gas diffusion layer, and a second catalyst layer and a second gas diffusion. In a method for producing a membrane electrode junction for a polymer electrolyte fuel cell, which comprises a second electrode having a layer and an electrolyte membrane interposed between the first electrode and the second electrode, a base material is used. After applying a coating liquid containing an ion exchange resin on top, an electrolyte film is formed by annealing at 100 to 250 ° C., and an electrode catalyst and the formula (A) described later are used on the surface of the obtained electrolyte film. A first intermediate composed of an electrolyte membrane and a first catalyst layer by forming the first catalyst layer by applying a coating liquid containing an ion exchange resin containing the represented unit. The second gas diffusion layer is coated with a coating liquid containing an electrode catalyst and an ion exchange resin containing a unit represented by the formula (A) described later on the surface of the second gas diffusion layer. A second intermediate composed of the second gas diffusion layer and the second catalyst layer is produced by forming the first gas diffusion layer and the electrolyte membrane between the first gas diffusion layer and the electrolyte membrane. The first gas diffusion layer, the first intermediate, and the above so that the second gas diffusion layer is located and the second catalyst layer is located between the second gas diffusion layer and the electrolyte membrane. It is characterized by joining with a second intermediate.

The bonding of the first gas diffusion layer, the first intermediate, and the second intermediate is preferably performed by a hot press.

It is preferable that the base material is peeled off after joining the first intermediate and the first gas diffusion layer, and then the second intermediate is joined to the electrolyte membrane.

The first gas diffusion layer is a coating containing a carbon fiber having a fiber diameter of 50 to 200 nm and a fiber length of 1 to 50 μm and a fluororesin on the surface of the gas diffusible base material and the gas diffusible base material. It has a carbon layer formed by applying a working liquid, and joins the first intermediate body and the second intermediate body so that the carbon layer and the first catalyst layer are in contact with each other. Is preferable.

The second gas diffusion layer is a coating containing a carbon fiber having a fiber diameter of 50 to 200 nm and a fiber length of 1 to 50 μm and a fluorine-containing resin on the surface of the gas diffusible base material and the gas diffusible base material. It has a carbon layer formed by applying a working liquid, and the second catalyst layer is placed on the surface of the second gas diffusion layer so that the carbon layer and the second catalyst layer are in contact with each other. It is preferable to form it.

The first intermediate is a peeling base material, the electrolyte membrane formed by applying a coating liquid containing an ion exchange resin on the surface of the peeling base material, and an electrode catalyst and an electrode catalyst on the surface of the electrolyte membrane. It has the first catalyst layer formed by coating with a coating liquid containing an ion exchange resin, and the first gas diffusion layer and the first intermediate are joined to form a laminated body. After peeling the release base material from the laminate, it is preferable to join the laminate and the second intermediate.

According to the method for producing a membrane electrode assembly for a polymer electrolyte fuel cell of the present invention, a membrane electrode assembly for a polymer electrolyte fuel cell can be produced, which can obtain a high output voltage in a wide range of current densities.

It is a schematic sectional drawing which shows an example of the membrane electrode assembly for a polymer electrolyte fuel cell. It is schematic cross-sectional view which shows one step of the manufacturing method of the membrane electrode assembly for a polymer electrolyte fuel cell of this invention. It is schematic cross-sectional view which shows one step of the manufacturing method of the membrane electrode assembly for a polymer electrolyte fuel cell of this invention. It is the schematic sectional drawing which shows another example of the membrane electrode assembly for a polymer electrolyte fuel cell. It is schematic cross-sectional view which shows one step of the manufacturing method of the membrane electrode assembly for a polymer electrolyte fuel cell of this invention. It is schematic cross-sectional view which shows one step of the manufacturing method of the membrane electrode assembly for a polymer electrolyte fuel cell of this invention. It is a schematic sectional drawing which shows an example of a solid polymer fuel cell. It is a figure which showed the state which the electrolyte membrane is deformed when the electrolyte membrane and the catalyst layer are peeled off during operation of a solid polymer fuel cell. It is a figure which showed the apparatus for measuring the 90 ° peel strength between an electrolyte membrane and a catalyst layer in an Example of this invention.

The meanings of the terms in the present invention are as follows.
The "unit" in a polymer means an atomic group derived from one molecule of the monomer formed by polymerizing the monomer. The unit may be an atomic group directly formed by the polymerization reaction, or may be an atomic group obtained by processing a polymer obtained by the polymerization reaction and converting a part of the atomic group into another structure. .. The content (mol%) of each unit with respect to all the units contained in the polymer is determined by analyzing the polymer by nuclear magnetic resonance spectral method.
In the present specification, the compound represented by the formula (1) is referred to as compound (1). Compounds represented by other formulas are also described in the same manner.
Further, the unit represented by the formula (A) is referred to as a unit (A). Units expressed by other formulas are also described in the same manner.
"Sulfonic acid type functional group" means a sulfonic acid group (-SO ₃ H) or a sulfonic acid base (-SO ₃ M ² ; where M ² is an alkali metal or a quaternary ammonium cation). To do.
The "precursor group" means a group that can be converted into a sulfonic acid type group by hydrolysis treatment, acidification treatment, or other treatment such as salt exchange with a metal cation.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing an example of a membrane electrode assembly for a polymer electrolyte fuel cell (hereinafter, referred to as a membrane electrode assembly). The membrane electrode assembly 1 has a first electrode 10 having a first catalyst layer 12 and a first gas diffusion layer 14, and a second electrode having a second catalyst layer 22 and a second gas diffusion layer 24. An electrolyte membrane 30 interposed between the 20 and the first electrode 10 and the second electrode 20 in contact with the first catalyst layer 12 and the second catalyst layer 22 is provided.

(Catalyst layer)
The first catalyst layer 12 and the second catalyst layer 22 (hereinafter, collectively referred to as a catalyst layer) are layers containing an electrode catalyst and an ion exchange resin containing the unit (A).

Examples of the electrode catalyst include a catalyst in which platinum, a platinum alloy, a core-shell catalyst or a carbon alloy is supported on the carrier, and a supported catalyst in which platinum or a platinum alloy is supported is preferable.
Examples of the carrier include a carbon carrier and a metal oxide carrier, and a carbon carrier is preferable.
The metal oxide carrier is at least one selected from the group consisting of rare earth elements, alkaline earth metals, transition metals (preferably niobium, zirconium, molybdenum, tantalum, tungsten), bismuth, tin, antimony and indium. Oxides of metal elements can be mentioned, and it is preferable to include oxides of tin from the viewpoint of more excellent power generation efficiency of fuel cells.
Examples of the carbon carrier include activated carbon and carbon black.
The specific surface area of the carbon carrier is preferably 100 m ² / g or more. The specific surface area of the carbon carrier is measured by adsorbing nitrogen on the carbon surface with a BET specific surface area device.

Platinum alloys include platinum group metals other than platinum (lutenium, rhodium, palladium, osmium, iridium), gold, silver, chromium, iron, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, etc. An alloy of platinum with one or more metals selected from the group consisting of and tin is preferred. The platinum alloy may contain a metal alloyed with platinum and an intermetallic compound of platinum.
As the platinum alloy for the anode, an alloy containing platinum and ruthenium is preferable from the viewpoint that the activity of the electrode catalyst is stable even when a gas containing carbon monoxide is supplied.
The amount of platinum or platinum alloy supported is preferably 10 to 70% by mass based on the electrode catalyst (100% by mass).

The ion exchange capacity of the ion exchange resin is preferably 0.5 to 2.0 mm equivalent / gram dry resin, and 0.8 to 1.5 mm equivalent / gram dry resin is particularly preferable from the viewpoint of conductivity and gas permeability. preferable.

The ion exchange resin contained in the catalyst layer contains a unit A and is a kind of fluorine-containing ion exchange resin. The unit A is a unit represented by the formula (A).

In the formula (A), R ^{f1 is} a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.
R ^f2 and R ^f3 are each independently a perfluoroalkylene group which may contain an oxygen atom between a single bond or a carbon atom and a carbon atom. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.
r and m are independently 0 or 1, respectively.
M is a hydrogen atom, alkali metal or quaternary ammonium cation.

The unit A is preferably a unit (A-1). In formula (A-1), R ^f1 , R ^f2 and M are synonymous with R ^f1 , R ^f2 and M in formula (A), respectively.

Specific examples of the unit (A-1) include the following.

The ion exchange resin containing the unit (A) is obtained by converting the precursor group of the compound (a) having the precursor group of the sulfonic acid type functional group into the sulfonic acid type functional.

Wherein ^{(a), R f1, R} f2, R f3, r and m each have the same meanings as ^{R f1, R f2, R f3} , r and m of formula (A).
A is a group that can be converted into a sulfonic acid type functional group (precursor group of the sulfonic acid type functional group). The group that can be converted into a sulfonic acid type functional group is preferably a functional group that can be converted into a sulfonic acid type functional group by hydrolysis. Specific examples of the group that can be converted into a sulfonic acid type functional group include -SO ₂ F, -SO ₂ Cl, and -SO ₂ Br.

The compound (a) is preferably the compound (a-1). Wherein ^{(a-1), R f1} , R f2 and A are as defined ^{R f1, R f2} and A in the formula (a).

Specific examples of the compound (a-1) include the following.

The ion exchange resin contained in the catalyst layer preferably contains a unit other than the unit (A). Specific examples of such units include units based on fluorine-containing olefins.
Examples of the fluorine-containing olefin include fluoroolefins having one or more fluorine atoms in the molecule and having 2 to 3 carbon atoms. Specific examples of the fluoroolefin include tetrafluoroethylene (hereinafter, also referred to as “TFE”), chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene, and TFE is preferable.
As the fluorine-containing olefin, one type may be used alone, or two or more types may be used in combination.

The content of the unit A is preferably 15 to 55% by mass, particularly preferably 20 to 33% by mass, based on all the units of the ion exchange resin contained in the catalyst layer.
When the ion exchange resin contained in the catalyst layer contains units based on the fluorine-containing olefin, the content of the units based on the fluorine-containing olefin is 30 to 85% by mass with respect to all the units of the ion exchange resin contained in the catalyst layer. Is preferable, and 50 to 80% by mass is particularly preferable.

The ratio of the electrode catalyst to the fluorine-containing ion exchange resin (electrode catalyst / ion exchange resin) is preferably 4/6 to 9.5 / 0.5 (mass ratio) from the viewpoint of electrode conductivity and water repellency. 6/4 to 8/2 is particularly preferable.
The amount of platinum contained in the catalyst layer is preferably 0.01 to 0.5 mg / cm ² and 0.05 to 0.35 mg / cm ² from the viewpoint of the optimum thickness for efficiently performing the electrode reaction described later. More preferred.

Further, in order to increase the radical resistance of the ion exchange resin, it is preferable to add 1 to 20 mol% of the radical quencher with respect to the amount of the sulfonic acid group, and it is particularly preferable to add 3 to 15 mol%. As the radical quencher, a compound of cerium or manganese, an organic ammonium salt, or a cerium cation or a manganese cation is preferable.

The thickness of the catalyst layer is preferably 20 μm or less, more preferably 1 to 15 μm, from the viewpoint of facilitating gas diffusion in the catalyst layer and improving the characteristics of the polymer electrolyte fuel cell. Further, the thickness of the catalyst layer is preferably uniform. If the thickness of the catalyst layer is reduced, the amount of electrode catalyst present per unit area may decrease and the reaction activity may decrease. In this case, platinum or a platinum alloy is supported as an electrode catalyst with a high loading rate. If a catalyst is used, the reaction activity of the electrode can be maintained high without insufficient amount of the electrode catalyst even if it is thin.

(Gas diffusion layer)
The first gas diffusion layer 14 and the second gas diffusion layer 24 (hereinafter, collectively referred to as a gas diffusion layer) are layers having a gas diffusible base material.
The gas diffusible base material is a porous base material having conductivity. Examples of the gas diffusible base material include carbon cloth, carbon paper, carbon felt and the like.
The gas diffusible base material may be either water-repellent or hydrophilic, but is preferably water-repellent, and is preferably water-repellent treated with polytetrafluoroethylene or a mixture of polytetrafluoroethylene and carbon black.
The thickness of the gas diffusion layer is preferably 100 to 400 μm, more preferably 140 to 350 μm.

(Electrolyte membrane)
The electrolyte membrane 30 is made of an ion exchange resin membrane.
Examples of the ion exchange resin constituting the electrolyte membrane include a fluorine-containing ion exchange resin and a non-fluorine-based ion exchange resin, and a fluorine-containing ion exchange resin is preferable from the viewpoint of durability.
As the fluorine-containing ion exchange resin, a perfluorocarbon polymer having a sulfonic acid group (may contain an etheric oxygen atom) is preferable, and a unit based on TFE and a unit based on perfluorovinyl ether having a sulfonic acid group are preferable. A copolymer containing and is particularly preferable. Normally such copolymers, after copolymerizing a perfluorovinyl ether having precursor groups of sulfonic acid groups, such as TFE and -SO 2 _F groups, hydrolysis, obtained by acid form.

The compound (1) is preferable as the perfluorovinyl ether having a precursor group of a sulfonic acid group.
CF ₂ = CF (OCF ₂ CFX) _m −O _p − (CF ₂ ) _n −SO ₂ F (1).
However, m is an integer of 0 to 3, n is an integer of 1 to 12, p is 0 or 1, and X is F or CF ₃ .

As the compound (1), the compounds (1-1) to (1-3) are preferable.
CF ₂ = CFO (CF ₂ ) _q SO ₂ F (1-1),
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _r SO ₂ F (1-2),
CF ₂ = CF (OCF ₂ CF (CF ₃ )) _t O (CF ₂ ) _s SO ₂ F (1-3).
However, q, r, and s are integers of 1 to 8, and t is an integer of 1 to 3.

As the fluorine-containing ion exchange resin, it is also preferable to use an ion exchange resin similar to the ion exchange resin of the catalyst layer.

Specific examples of the non-fluorinated ion exchange resin include sulfonated polyarylene, sulfonated polybenzoxazole, sulfonated polybenzothiazole, sulfonated polybenzoimidazole, sulfonated polysulfone, sulfonated polyether sulfone, and sulfonated polyether ether. Sulfone, sulfonated polyphenylene sulfone, sulfonated polyphenylene oxide, sulfonated polyphenylene sulfoxide, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyether ketone, sulfonated polyether ether ketone, sulfonated polyether ketone ketone, sulfonated Sulfone can be mentioned.

The thickness of the electrolyte membrane 30 is preferably 50 μm or less, more preferably 3 to 40 μm, and particularly preferably 5 to 30 μm. By setting the thickness of the electrolyte membrane 30 to 50 μm or less, the electrolyte membrane 30 tends to be in a dry state, and deterioration of the characteristics of the polymer electrolyte fuel cell can be suppressed. By setting the thickness of the electrolyte membrane 30 to 3 μm or more, a short circuit does not occur.

(Manufacturing method of membrane electrode assembly)
The method for producing a film electrode junction of the present invention is a first gas diffusion layer, and a first gas diffusion layer, and a coating liquid containing an electrode catalyst and an ion exchange resin are applied to the surface of the electrolyte membrane and the electrolyte membrane. It was formed by applying a coating liquid containing an electrode catalyst and an ion exchange resin on the surfaces of the first intermediate having one catalyst layer, the second gas diffusion layer and the second gas diffusion layer. The first catalyst layer is located between the first gas diffusion layer and the electrolyte membrane, and the second intermediate having the second catalyst layer is located between the second gas diffusion layer and the electrolyte membrane. This is a method of joining so that the second catalyst layer is located in the water. Then, in the step of producing the first intermediate, an electrolyte membrane was formed by applying a coating liquid containing an ion exchange resin on the substrate and then annealing at 100 to 250 ° C. to obtain the obtained. The first catalyst layer is formed on the surface of the electrolyte membrane.

Specific examples of the method for manufacturing the membrane electrode assembly 1 of the first embodiment include the following methods.
(I) A method in which a first gas diffusion layer and a first intermediate are joined to form a laminated body, and then the laminated body and a second intermediate are joined.
(II) A method of simultaneously joining the first gas diffusion layer, the first intermediate, and the second intermediate.

(Method of (I))
Examples of the method (I) include a method having the following steps (I-1) to (I-5).
(I-1) A step of preparing the first gas diffusion layer 14 as shown in FIG.
(I-2) A step of producing a first intermediate 50 having a release base material 52, an electrolyte membrane 30, and a first catalyst layer 12, as shown in FIG. 2.
(I-3) A step of producing a second intermediate 60 (that is, a second electrode 20) having a second gas diffusion layer 24 and a second catalyst layer 22, as shown in FIG.
(I-4) As shown in FIG. 2, the first gas diffusion layer 14 and the first gas diffusion layer 14 and the first gas diffusion layer 14 are located so that the first catalyst layer 12 is located between the first gas diffusion layer 14 and the electrolyte membrane 30. A step of joining the intermediate body 50 to form a laminated body 70.
(I-5) As shown in FIG. 3, after the peeling base material 52 is peeled from the laminate 70, the second catalyst layer 22 is located between the second gas diffusion layer 24 and the electrolyte membrane 30. A step of joining the laminated body 70 and the second intermediate body 60 to form a membrane electrode assembly 1.

(I-1) Step:
As the first gas diffusion layer 14, a gas diffusing base material such as carbon paper, carbon cloth, or carbon felt can be used as it is. If necessary, the gas diffusible substrate may be treated with a water-repellent treatment using a solution or dispersion containing a water-repellent fluororesin. When the water repellent treatment is performed, it is possible to prevent water or the like generated in the cathode catalyst layer from blocking the pores formed in the gas diffusion layer and suppressing the diffusion of the gas. At this time, it is more preferable to treat the surface of the gas diffusion layer with a dispersion liquid containing a water-repellent fluororesin and a conductive carbon such as carbon black in terms of the conductivity of the membrane electrode assembly. Examples of the water-repellent fluororesin include polytetrafluoroethylene and the like. The surface-treated side of the gas diffusion layer is arranged on the catalyst layer side. The thickness of the gas diffusion layer is usually preferably 50 to 400 μm.

(I-2) Step:
The first intermediate 50 forms an electrolyte membrane 30 by applying a coating liquid containing an ion exchange resin (hereinafter referred to as a coating liquid for an electrolyte membrane) on the surface of the release base material 52, and is annealed. After that, the first catalyst layer 12 is formed by applying a coating liquid containing an electrode catalyst and an ion exchange resin (hereinafter, referred to as a coating liquid for the first catalyst layer) on the surface of the electrolyte membrane 30. And is made.

Examples of the release base material 52 include a resin film.
Examples of the material of the resin film include the following resins.
Non-fluorinated resins such as polyethylene terephthalate, polyethylene, polypropylene and polyimide.
Fluororesin such as polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer, and polyvinylidene fluoride.
The non-fluorinated resin film is preferably surface-treated with a release agent.

The coating solution for an electrolyte membrane is prepared by dissolving or dispersing an ion exchange resin in a solvent.
The coating liquid for the first catalyst layer is prepared by dispersing the electrode catalyst in a solvent and dissolving or dispersing the ion exchange resin in the solvent.

When the ion exchange resin is a fluorine-containing ion exchange resin, the solvent is preferably an alcohol or a fluorine-containing solvent.
Examples of alcohols include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and the like. In order to increase the solubility of the ion exchange resin, a mixed solvent of alcohols and water may be used.

Examples of the fluorine-containing solvent include the following.
Hydrofluorocarbons: 2H-perfluoropropane, 1H, 4H-perfluorobutane, 2H, 3H-perfluoropentane, 3H, 4H-perfluoro (2-methylpentane), 2H, 5H-perfluorohexane, 3H-perfluoro (2-Methylpentane) etc.
Fluorocarbons: perfluoro (1,2-dimethylcyclobutane), perfluorooctane, perfluoroheptane, perfluorohexane and the like.
Hydrochlorofluorocarbons: 1,1-dichloro-1-fluoroethane, 1,1,1-trifluoro-2,2-dichloroethane, 3,3-dichloro-1,1,1,2,2-pentafluoropropane, 1,3-Dichloro-1,1,2,2,3-pentafluoropropane and the like.
Fluoroether: 1H, 4H, 4H-perfluoro (3-oxapentane), 3-methoxy-1,1,1,2,3,3-hexafluoropropane and the like.
Fluorotelomer alcohol: 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, etc. ..

When the ion exchange resin is a non-fluorine ion exchange resin, the solvent used is N, N-dimethylformamide, dimethyl sulfoxide, methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, 1,1,2-. Examples thereof include trichloroethane, trichlorethylene and tetrachloroethylene.
In the case of an electrolyte membrane made of a fluorine-containing ion exchange resin, examples of the solvent include alcohol and a fluorine-containing solvent, and ethanol, n-propanol and isopropanol are preferable.

The solid content concentration of the coating solution for the electrolyte membrane is preferably 5 to 30% by mass, more preferably 20 to 30% by mass.
The solid content concentration of the coating liquid for the first catalyst layer is preferably 4 to 15% by mass, more preferably 8 to 12% by mass.
By setting the solid content concentration of the coating liquid in the above range, the coating liquid has an appropriate viscosity, the coating can be uniformly applied, and the formed coating film is not cracked.

Further, the coating liquid for the first catalyst layer preferably contains 5 to 100% of the total mass of the solvent, and more preferably 30 to 100%, which has an action of dissolving the ion exchange resin. With this configuration, when the coating liquid for the first catalyst layer is applied onto the electrolyte membrane, a part of the surface of the electrolyte membrane is dissolved by the solvent and bound to the electrolyte in the catalyst layer. As a result, the bonding strength between the electrolyte membrane and the catalyst layer becomes sufficiently high.

Water is generated during operation of the polymer electrolyte fuel cell, but normally, the catalyst layer hardly changes its dimension in the plane direction due to the water content during the operation of the fuel cell, whereas the electrolyte membrane is accompanied by the water content. It is easy to change the dimensions. However, when the catalyst layer is brought into close contact with the surface of the electrolyte membrane with sufficient binding strength, the catalyst layer that hardly causes a dimensional change changes in the plane direction (the surface in contact with the catalyst layer) due to the water content of the electrolyte membrane. Is suppressed, and the dimensional change of the electrolyte membrane is less likely to occur. On the other hand, when the bonding strength between the electrolyte membrane and the catalyst layer is low, the electrolyte membrane and the catalyst layer are peeled off and the electrolyte membrane is significantly deformed when the membrane electrode assembly is exposed during fuel cell operation. Problems arise. When the coating liquid for the first catalyst layer is applied onto the electrolyte membrane as described above to form the first catalyst layer, high binding strength is obtained, and the electrolyte membrane and the catalyst layer do not peel off. Deformation of the electrolyte membrane is unlikely to occur.
It has been confirmed that deformation of the electrolyte membrane hardly occurs if at least one side of the electrolyte membrane is sufficiently bonded to the catalyst layer, and both sides of the electrolyte membrane do not have to be strongly bonded to the catalyst layer. ..

Examples of the coating method include a batch coating method and a continuous coating method.
Examples of the batch coating method include a bar coater method, a spin coater method, and a screen printing method.
Examples of the continuous coating method include a post-weighing method and a pre-weighing method. The post-measurement method is a method in which an excess coating liquid is applied and then the coating liquid is removed so as to have a predetermined thickness. The pre-measurement method is a method of applying an amount of a coating liquid required to obtain a predetermined thickness.

Examples of the post-measurement method include an air doctor coater method, a blade coater method, a rod coater method, a knife coater method, a squeeze coater method, an impregnation coater method, and a comma coater method.
Examples of the pre-measurement method include a die coater method, a reverse roll coater method, a transfer coater method, a gravure coater method, a kiss roll coater method, a cast coater method, a spray coater method, a curtain coater method, a calendar coater method, and an extrusion coater method. Be done.
As the coating method, the screen printing method or the die coater method is preferable from the viewpoint of forming a uniform electrolyte film 30 or the first catalyst layer 12, and the die coater method is more preferable from the viewpoint of production efficiency.

The surface of the release base material 52 is coated with an electrolyte film coating solution and then dried to form the electrolyte film 30. The drying temperature is preferably 70 to 170 ° C. After drying or at the same time as drying, the electrolyte membrane 30 is annealed. The annealing temperature is 100 to 250 ° C, preferably 130 to 220 ° C. The optimum temperature for annealing differs depending on the polymer constituting the film, and it is preferable to anneal at a temperature higher than the glass transition temperature (Tg) of the polymer and at a temperature of (Tg + 100) ° C. or lower. By forming the catalyst layer on the membrane annealed in the above temperature range, a high-power membrane electrode assembly can be obtained. The reason for this is not always clear, but by annealing the membrane, the water content in the membrane is adjusted, and by forming a catalyst layer on the membrane in a stable state by annealing, the adhesion between the membrane and the catalyst layer It is considered that a high-power membrane electrode assembly can be obtained.
The annealing time is preferably 5 minutes to 3 hours, and particularly preferably 10 minutes to 1 hour, from the viewpoint of more exerting the above-mentioned effects and improving productivity.
Further, if the membrane electrode assembly is used for a long time, the output decreases due to the deterioration of the membrane. Since it is considered that this is due to the formation of peroxide, it is also preferable to add an inhibitor that suppresses the formation of peroxide to the film. This inhibitor is preferably contained in the coating liquid for the electrolyte membrane.
Next, the surface of the electrolyte membrane 30 is coated with the coating liquid for the first catalyst layer and then dried to form the first catalyst layer 12. The drying temperature is preferably 70 to 150 ° C.

(I-3) Step:
The second intermediate 60 is coated with a coating liquid containing an electrode catalyst and an ion exchange resin (hereinafter, referred to as a coating liquid for a second catalyst layer) on the surface of the second gas diffusion layer 24. The second catalyst layer 22 is formed and produced.

The coating liquid for the second catalyst layer is prepared by dispersing the electrode catalyst in a solvent and dissolving or dispersing the ion exchange resin in the solvent.
Examples of the solvent include the same solvents as those used in the coating liquid for the first catalyst layer.
The solid content concentration of the coating liquid for the second catalyst layer is preferably in the same range as the solid content concentration of the coating liquid for the first catalyst layer.
Examples of the coating method include the same method as in step (I-2).
The surface of the second gas diffusion layer 24 is coated with the coating liquid for the second catalyst layer and then dried to form the second catalyst layer 22. The drying temperature is preferably 70 to 170 ° C.

Steps (I-4) to (I-5):
Examples of the joining method include a hot press method, a hot roll press, and ultrasonic fusion, and the hot press method is preferable from the viewpoint of in-plane uniformity.
The temperature of the press plate in the press machine is preferably 100 to 165 ° C, more preferably 110 to 155 ° C.
The press pressure is preferably 0.5 to 2.0 MPa.

(Method of (II))
Examples of the method (II) include a method having the following steps (II-1) to (II-5).
(II-1) A step of preparing the first gas diffusion layer 14 as shown in FIG.
(II-2) A step of producing a first intermediate 50 having a release base material 52, an electrolyte membrane 30, and a first catalyst layer 12, as shown in FIG. 2.
(II-3) A step of producing a second intermediate 60 (that is, a second electrode 20) having a second gas diffusion layer 24 and a second catalyst layer 22, as shown in FIG.
(II-4) A step of peeling the peeling base material 52 from the first intermediate 50.
(II-5) The first catalyst layer 12 is located between the first gas diffusion layer 14 and the electrolyte membrane 30, and the second catalyst is located between the second gas diffusion layer 24 and the electrolyte membrane 30. A step of simultaneously joining the first gas diffusion layer 14, the first intermediate body 50, and the second intermediate body 60 so that the layer 22 is located to form a membrane electrode assembly 1.

The steps (II-1) to (II-3) may be performed in the same manner as the steps (I-1) to (I-3).
The joining method and conditions in the step (II-5) may be the same methods and conditions as in the steps (I-4) to (I-5).

In the membrane electrode assembly 1 manufactured in the first embodiment, the second electrode 20 may be a cathode or an anode, but the second electrode 20 is an anode for the following reasons. Is preferable.
In a polymer electrolyte fuel cell, a gas containing hydrogen (fuel) is usually supplied to the anode and a gas (air) containing oxygen is supplied to the cathode. Since a part of the coating liquid for the second catalyst layer permeates the second gas diffusion layer 24 in the step (I-3) or (II-3) of the second electrode 20, the second gas diffusion A part of the layer 24 is easily blocked. Therefore, when the second electrode 20 is used as the cathode, oxygen having a lower transmittance than hydrogen must pass through the second gas diffusion layer 24, and the gas diffusibility tends to decrease. On the other hand, if the second electrode 20 is used as the anode, hydrogen is relatively easily permeated even in the closed portion, so that the gas diffusibility is unlikely to decrease. That is, the gas diffusion layer of the cathode needs to be kept porous, and the gas diffusion layer of the anode does not have to be as porous as the cathode. Therefore, if the second electrode 20 is used as the anode, the porosity of the cathode is maintained. A high-performance solid-polymer fuel cell can be obtained.

[Second Embodiment]
FIG. 4 is a schematic cross-sectional view showing a membrane electrode assembly 1 in which the gas diffusion layer has a carbon layer 84 on the surface of the gas diffusion base material 82. A part of the carbon layer 84 may penetrate into the voids of the gas diffusing base material 82. The gas diffusible base material 82 may be water-repellent treated with a fluororesin or a coating liquid containing conductive carbon particles and the fluororesin, and a carbon layer 84 may be formed.
The configuration other than the carbon layer and the preferred embodiment in the second embodiment are the same as those in the first embodiment.

(Carbon layer)
The carbon layer 84 is a layer containing carbon fibers and a fluororesin.
As the fluororesin, a fluoroion-containing ion exchange resin is preferable from the viewpoint of carbon fiber dispersibility, and the same ion exchange resin as the catalyst layer is particularly preferable from the viewpoint of adhesion at the interface with the catalyst layer.

As the carbon fiber, carbon nanofiber is preferable from the viewpoint of being fine and having electron conductivity. Examples of carbon nanofibers include vapor-grown carbon fibers, carbon nanotubes (single wall, double wall, multi-wall, cup laminated type, etc.) and the like.

The fiber diameter of the carbon fiber is 50 to 200 nm, and the fiber length is 1 to 50 μm. By using the carbon fiber, at the interface between the carbon layer 84 and the catalyst layer, the electron conductive substance (platinum or platinum alloy, and carbon carrier) contained in the catalyst layer is entangled, and the electron conductive substance is point-contacted. Since a new conductive path is developed in addition to the conductive path, the electron conductivity of the catalyst layer is improved. In addition, the carbon fibers are likely to be entangled with each other to form voids when the coating liquid containing the carbon fibers is applied, and the voids function as gas channels. In a polymer electrolyte fuel cell, water (water vapor) is generated in the catalyst layer on the cathode side, and the water is discharged to the outside of the system through a gas diffusion layer arranged adjacent to the catalyst layer. By providing the carbon layer 84 mainly composed of carbon fibers between the catalyst layer and the gas diffusion layer, water quickly moves from the catalyst layer to the carbon layer 84 by capillarity, and the polymer electrolyte fuel cell operation The problem of flooding of time is solved.

The ratio of the carbon fiber to the fluororesin (carbon fiber / fluororesin) is preferably 1 / 0.1 / 1/5 (mass ratio), more preferably 1 / 0.2 to 1/1. Within this range, the dispersibility of the carbon fibers, the adhesion between the carbon layer 84 and the gas diffusing base material 82, the gas diffusibility of the carbon layer 84 and the drainage property are improved.
The thickness of the carbon layer 84 is preferably 2 to 20 μm. Within this range, the adhesion between the carbon layer 84 and the gas diffusing base material 82 becomes good, the contact resistance between the gas diffusion layer and the catalyst layer can be sufficiently reduced, and the membrane electrode assembly is made thin. it can.

(Manufacturing method of membrane electrode assembly)
Specific examples of the method for manufacturing the membrane electrode assembly 1 of the second embodiment include the following methods.
(I) A method in which a first gas diffusion layer and a first intermediate are joined to form a laminated body, and then the laminated body and a second intermediate are joined.
(Ii) A method of simultaneously joining the first gas diffusion layer, the first intermediate, and the second intermediate.

(Method in (i))
Examples of the method (i) include a method having the following steps (i-1) to (i-5).
(I-1) A step of preparing a first gas diffusion layer 14 in which a (first) carbon layer 84 is formed on the surface of a gas diffusion base material 82 as shown in FIG.
(I-2) A step of preparing a first intermediate 50 having a release base material 52, an electrolyte membrane 30, and a first catalyst layer 12, as shown in FIG.
(I-3) As shown in FIG. 6, on the second gas diffusion layer 24 and the (second) carbon layer 84 in which the (second) carbon layer 84 is formed on the surface of the gas diffusion base material 82. A step of producing a second intermediate 60 (ie, a second electrode 20) having a second catalyst layer 22 in contact with it.
(I-4) As shown in FIG. 5, the first catalyst layer 12 is located between the first gas diffusion layer 14 and the electrolyte membrane 30, and the (first) carbon layer 84 and the first A step of joining the first gas diffusion layer 14 and the first intermediate 50 so as to be in contact with the catalyst layer 12 to form a laminated body 70.
(I-5) As shown in FIG. 6, after the peeling base material 52 is peeled from the laminate 70, the second catalyst layer 22 is located between the second gas diffusion layer 24 and the electrolyte membrane 30. A step of joining the laminated body 70 and the second intermediate body 60 to form a membrane electrode assembly 1.

(I-1) Step:
The first gas diffusion layer 14 is a coating liquid (hereinafter, carbon) containing carbon fibers having a fiber diameter of 50 to 200 nm and a fiber length of 1 to 50 μm and a fluororesin on the surface of the gas diffusible base material 82. The (first) carbon layer 84 is formed and produced by applying (referred to as a layer coating liquid).

The coating liquid for a carbon layer is prepared by dispersing carbon fibers in a solvent and dissolving or dispersing a fluororesin in the solvent.
When the fluororesin is a fluoroion-containing exchange resin, the above-mentioned alcohols or fluorine-containing solvent are preferable as the solvent.
The solid content concentration of the coating liquid for the carbon layer is preferably 5 to 20% by mass, more preferably 8 to 15% by mass.
By setting the solid content concentration of the coating liquid in the above range, the coating liquid has an appropriate viscosity, the coating can be uniformly applied, and the formed coating film is not cracked.

Examples of the coating method include the batch coating method and the continuous coating method described above, and the screen printing method or the die coater method is preferable from the viewpoint of forming a uniform (first) carbon layer 84, and from the viewpoint of production efficiency. , The die coater method is more preferable.
The surface of the gas diffusible base material 82 is coated with a coating liquid for a carbon layer and then dried to form a (first) carbon layer 84. The drying temperature is preferably 80 to 150 ° C.

(I-2) Step:
The production of the first intermediate 50 may be carried out in the same manner as in the step (I-2) in the first embodiment.

(I-3) Step:
The second gas diffusion layer 24 may be produced in the same manner as in step (i-1).
The second catalyst layer 22 is formed on the surface of the second gas diffusion layer 24 so that the (second) carbon layer 84 and the second catalyst layer 22 are in contact with each other.
The formation of the second catalyst layer 22 may be performed in the same manner as in the step (I-3) of the first embodiment.

Steps (i-4) to (i-5) The joining methods and conditions in the steps (i-4) to (i-5) are the same as the steps (I-4) to (I-5) in the first embodiment. The same method and conditions may be used.

(Method of (ii))
Examples of the method (ii) include a method having the following steps (ii-1) to (ii-5).
(Ii-1) A step of preparing a first gas diffusion layer 14 in which a (first) carbon layer 84 is formed on the surface of a gas diffusion base material 82 as shown in FIG.
(Ii-2) A step of producing a first intermediate 50 having a release base material 52, an electrolyte membrane 30, and a first catalyst layer 12, as shown in FIG.
(Ii-3) As shown in FIG. 6, on the second gas diffusion layer 24 and the (second) carbon layer 84 in which the (second) carbon layer 84 is formed on the surface of the gas diffusion base material 82. A step of producing a second intermediate 60 (ie, a second electrode 20) having a second catalyst layer 22 in contact with it.
(Ii-4) A step of peeling the peeling base material 52 from the first intermediate 50.
(Ii-5) The first catalyst layer 12 is located between the first gas diffusion layer 14 and the electrolyte membrane 30, and the (first) carbon layer 84 and the first catalyst layer 12 are in contact with each other. And the first gas diffusion layer 14, the first intermediate 50, and the second intermediate 60 so that the second catalyst layer 22 is located between the second gas diffusion layer 24 and the electrolyte membrane 30. At the same time to form a membrane electrode assembly 1.

The steps (ii-1) to (ii-3) may be performed in the same manner as the steps (i-1) to (i-3).
The joining method and conditions in the step (ii-5) may be the same methods and conditions as in the steps (i-4) to (i-5).

In the membrane electrode assembly 1 manufactured in the second embodiment, since the carbon layer 84 exists between the gas diffusing base material 82 and the catalyst layer, the voids of the gas diffusing base material 82 are unlikely to be closed. Therefore, the decrease in the output voltage of the polymer electrolyte fuel cell in all regions can be suppressed. Further, when the carbon layer 84 is present, the second gas diffusion layer can be prevented from being blocked, so that a high-performance membrane electrode assembly can be obtained even if the second gas diffusion layer side is used as the cathode or the anode. Is.

As shown in the cross-sectional view of FIG. 7, by arranging the separator 90 in which the groove 100 serving as the gas flow path is formed on both sides of the membrane electrode assembly manufactured in the first or second embodiment. , A solid polymer fuel cell is obtained. Examples of the separator 90 include a separator made of various conductive materials such as a metal separator, a carbon separator, and a separator made of a material obtained by mixing graphite and a resin.
In the polymer electrolyte fuel cell, power generation is performed by supplying a gas containing oxygen to the cathode and a gas containing hydrogen to the anode. Further, the membrane electrode assembly of the present invention can also be applied to a methanol fuel cell that generates electricity by supplying methanol to the anode.

In the membrane electrode assembly of the present invention described above, the first catalyst formed by applying the coating liquid for the first catalyst layer to the surface of the first gas diffusion layer and the electrolyte membrane. A first intermediate having a layer and a second intermediate having a second catalyst layer formed by applying a coating liquid for a second catalyst layer to the surface of the second gas diffusion layer. Since they are bonded, they do not block the voids of the first gas diffusion layer. As a result, the decrease in gas diffusibility of the gas diffusion layer is small, and the decrease in output voltage of the polymer electrolyte fuel cell in the high current density region is suppressed.

Further, the first intermediate in which the first catalyst layer is formed by applying the coating liquid for the first catalyst layer on the surface of the electrolyte film, and the second catalyst on the surface of the second gas diffusion layer. Since the second intermediate that has formed the second catalyst layer is bonded by applying the layer coating liquid, the electrolyte film is directly applied to the surface of the first catalyst layer as in the conventional case. It does not need to be formed by coating. Therefore, a part of the ion exchange resin does not invade the first catalyst layer, and most of the voids of the first catalyst layer are not blocked. As a result, the gas diffusibility of the first catalyst layer does not decrease, and the decrease in the output voltage of the polymer electrolyte fuel cell in the high current density region can be suppressed.

Further, as described above, since the first catalyst layer is coated on the surface of the electrolyte membrane, a part of the surface of the electrolyte membrane is dissolved by the action of the solvent in the coating liquid, and the electrolyte in the catalyst layer is dissolved. It has the effect of binding, and sufficient adhesion strength between the electrolyte membrane and the catalyst layer can be obtained. As a result, the catalyst layer suppresses dimensional changes due to humidity changes during battery operation of the electrolyte membrane. In addition, it is possible to suppress a hydrogen leak in which hydrogen at the anode escapes to the cathode side due to a pressure difference.

Here, a state in which the electrolyte membrane is deformed when the electrolyte membrane and the catalyst layer are peeled off during operation of the polymer electrolyte fuel cell will be described with reference to the drawings. FIG. 8A is a partial cross-sectional view of a polymer electrolyte fuel cell in which a membrane electrode assembly is sandwiched between two separators 90. When the electrolyte membrane 30 is not sufficiently bonded to both the first catalyst layer 12 and the second catalyst layer 22, the state shown in FIG. 8B is obtained. That is, since the membrane electrode assembly of the portion pressed by the rib 101 of the separator 90 is fixed, the electrolyte membrane 30 and the catalyst layers 12 and 22 do not peel off, but are in contact with the gas flow path 100. In the portion, the electrolyte membrane 30 and the catalyst layers 12 and 22 are peeled off. Then, the water-containing electrolyte membrane 30 is greatly deformed at the portion where it is peeled off from the catalyst layers 12 and 22.

On the other hand, when the electrolyte membrane 30 and at least one of the catalyst layers 12 and 22 are sufficiently bonded, the reason is not necessarily clear, but the stable shape of the state (A) of FIG. 8 is maintained. Can be done. Neither the first catalyst layer 12 nor the second catalyst layer 22 is directly coated on the electrolyte membrane, but is coated on the gas diffusion layers 14 and 24, respectively, and later bonded to the electrolyte membrane 30 by hot pressing or the like. In such a case, the bonding strength between the electrolyte membrane 30 and the catalyst layers 12 and 22 tends to be low, and the state shown in FIG. 8 (B) tends to occur during fuel cell operation.
The bonding strength between the electrolyte membrane 30 and the catalyst layer 12 or the catalyst layer 22 can be evaluated by the method described in Examples described later, and the 90 ° peel strength measured by this method is 0.1 N / cm. In the above case, the electrolyte membrane 30 and the catalyst layer 12 (22) are less likely to be peeled off during the operation of the fuel cell, and the electrolyte membrane 30 is less likely to be deformed. The 90 ° peel strength is more preferably 0.13 N / cm or more.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In addition, Example 1 is an Example.

[Example 1]
(II-1) Step:
A first gas diffusion made of carbon paper (trade name: H2315T10AC1, manufactured by NOK) (hereinafter referred to as carbon paper (B)) whose surface is treated with a dispersion liquid containing carbon black particles and polytetrafluoroethylene. Layer 14 was prepared.

(II-2) Process:
An ultrasonic application device is provided by adding 35 g of a catalyst (platinum / cobalt = 36/4 (mass ratio)) in which 40% of a platinum-cobalt alloy is supported on a carbon carrier (specific surface area 250 m ² / g) to 226.5 g of distilled water. Was pulverized using the above, 37.5 g of ethanol was further added, and the mixture was well stirred. A copolymer obtained by copolymerizing TFE with a monomer represented by the following formula (Z), hydrolyzing and acidifying the mixture (ion exchange capacity 1.5 mm equivalent / g dry resin) ( 210 g of a dispersion liquid having a solid content concentration of 10% by mass (hereinafter referred to as an ethanol dispersion liquid of the copolymer (A)) in which the copolymer (A) is dispersed in ethanol is added. The mixture was well stirred to prepare a coating liquid (a) for the cathode catalyst layer.

On the surface of the release base material 52 made of an ETFE film, a copolymer (B) of TFE and CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ SO ₂ F is added to a mixed solvent of ethanol and water. A coating solution for an electrolyte membrane having a solid content concentration of 25% by mass dispersed in (ethanol / water = 60:40 (mass ratio)) was applied using a die coater so that the dry film thickness was 25 μm, and the temperature was 90 ° C. A laminate having an electrolyte membrane 30 formed of a cast membrane (referred to as an ion exchange membrane (C)) dried in a dryer for 10 minutes and further annealed at 140 ° C. for 30 minutes was prepared. The surface of the electrolyte membrane 30 is coated with the coating liquid (a) for the cathode catalyst layer using a die coater so that the amount of platinum is 0.2 mg / cm ^2, and dried in a dryer at 90 ° C. for 5 minutes. Then, it was further dried in a dryer at 155 ° C. for 30 minutes to prepare a first intermediate 50 in which the first catalyst layer 12 (cathode catalyst layer) was formed on the surface of the electrolyte membrane 30.

(II-3) Process:
A catalyst (trade name: TEC61E54, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., supporting platinum-ruthenium alloy) in which a platinum-ruthenium alloy (platinum / ruthenium = 31/22 (mass ratio)) is supported on a carbon carrier (specific surface area 800 m ² / g). (Amount 53% by mass.) 33 g was added to 227.5 g of distilled water, pulverized using an ultrasonic application device, and 117.5 g of ethanol was further added and stirred well. To this, 122.5 g of an ethanol dispersion liquid of the copolymer (A) was added and stirred well to prepare a coating liquid (a) for an anode catalyst layer.

The surface of the second gas diffusion layer 24 made of carbon paper (B) is coated with the coating liquid (a) for the anode catalyst layer using a die coater so that the amount of platinum is 0.2 mg / cm ² . A second catalyst layer 22 (anolyte catalyst layer) was formed on the surface of the second gas diffusion layer 24 by drying in a dryer at 90 ° C. for 5 minutes and further in a dryer at 155 ° C. for 30 minutes. A second intermediate 60 was made.

(II-4) Process:
The peeling base material 52 was peeled from the first intermediate 50.
(II-5) Step:
The first catalyst layer 12 is located between the first gas diffusion layer 14 and the electrolyte membrane 30, and the second catalyst layer 22 is located between the second gas diffusion layer 24 and the electrolyte membrane 30. As described above, the first gas diffusion layer 14, the first intermediate body 50, and the second intermediate body 60 were stacked. This was placed in a press machine preheated to 140 ° C. and heat-pressed at a press pressure of 1.5 MPa for 1 minute. The electrode area was 25 cm ² , the first electrode 10 was the cathode, and the second electrode was the second electrode. A membrane electrode assembly 1 in which the electrode 20 is an anode was obtained.

The membrane electrode assembly 1 is incorporated into a power generation cell, hydrogen (utilization rate 70%) / air (utilization rate 50%) is supplied at normal pressure, and the current density is 0.2 A / cm at a cell temperature of 65 ° C. The cell voltage at the beginning of operation was measured at ² , 0.5 A / cm ² , and 1.0 A / cm ² . However, hydrogen having a dew point of 65 ° C. was supplied to the anode side, and air having a dew point of 65 ° C. was supplied to the cathode side. The results were 0.78V, 0.68V, and 0.61V at 0.2A / cm ² , 0.5A / cm ² , and 1.0A / cm ² , respectively.
The hydrogen simulated gas (80% hydrogen, CO ₂ 20% of the mixed gas obtained by mixing CO of 20ppm the gas.) To change to measure the cell voltages at the initial stage of the operation under the same conditions. The results are shown in Table 2. The results were 0.78V, 0.67V, and 0.60V at 0.2A / cm ² , 0.5A / cm ² , and 1.0A / cm ² , respectively.

Further, by measuring the strength at which the electrolyte film 30 and the first catalyst layer 12 are peeled off or the catalyst layer itself is coagulated and broken, the binding strength (peeling strength) can be evaluated. Specifically, it is the following method.

First, a test piece having a width of 20 mm and a length of about 150 mm is prepared from the first intermediate 50. Then, as shown in FIG. 9, the surface of the electrolyte membrane 30 is attached to an aluminum plate 97 having a width of 25 mm, a length of 150 mm, and a thickness of 3 mm with a double-sided adhesive tape 96. Here, as the double-sided adhesive tape 96, a tape having an adhesive strength sufficiently higher than the peel strength between the electrolyte membrane 30 of the test piece to be measured and the first catalyst layer 12 is used. Further, a single-sided adhesive tape 95 having an adhesive strength sufficiently higher than the peel strength of the test piece to be measured is adhered to the surface of the first catalyst layer 12 by about 80 mm. Then, the single-sided adhesive tape 95 is sandwiched between a sample mounting portion of a tensile tester (not shown) at an angle of 90 ° with the test piece via a stainless steel roller 99 having a diameter of 6 mm. The integrated product of the aluminum plate 97 / double-sided tape 96 / first intermediate 50 / single-sided adhesive tape 95 is advanced in direction A through between the rollers 98, and the single-sided adhesive tape 95 is advanced in direction B so that the test piece is formed with the electrolyte membrane 30. The strength at the time of peeling from the first catalyst layer 12 is measured.

As a measurement condition, 90 ° peel strength measurement is performed at a speed of 50 mm / min. The test is performed three times for each test piece, and the peel strength is measured via a load cell and recorded on a personal computer. Then, the average value of three times is divided by the width of 20 mm of the test piece for the portion where the value is stable in the measured peel strength to obtain the 90 ° peel strength of the test piece.
When measured as described above, the peel strength is 0.13 N / cm or more.

Since the membrane electrode assembly of the present invention has a high output voltage in a wide range of current densities, it is a polymer electrolyte fuel cell used as a power source for mobile bodies such as automobiles, a distributed power generation system, a household cogeneration system, and the like. Very useful for.

1 Membrane electrode assembly 10 1st electrode 12 1st catalyst layer 14 1st gas diffusion layer 20 2nd electrode 22 2nd catalyst layer 24 2nd gas diffusion layer 30 Electrolyte film 50 1st intermediate 52 Peeling base material 60 Second intermediate 70 Laminated body 82 Gas diffusing base material 84 Carbon layer 90 Separator

Claims (5)

A first electrode having a first catalyst layer and a first gas diffusion layer, a second electrode having a second catalyst layer and a second gas diffusion layer, the first electrode and the second electrode. In a method for manufacturing a membrane electrode assembly for a polymer electrolyte fuel cell, which comprises an electrolyte membrane interposed between the electrodes.
After applying a coating liquid containing an ion exchange resin on the base material, an electrolyte membrane is formed by annealing at 100 to 250 ° C., and an electrode catalyst and the formula (A) are used on the surface of the obtained electrolyte membrane. A first intermediate composed of an electrolyte membrane and a first catalyst layer by forming the first catalyst layer by applying a coating liquid containing an ion exchange resin containing the represented unit. To make,
By forming the second catalyst layer by applying a coating liquid containing an electrode catalyst and an ion exchange resin containing a unit represented by the formula (A) on the surface of the second gas diffusion layer. A second intermediate composed of the second gas diffusion layer and the second catalyst layer was prepared.
The first catalyst layer is located between the first gas diffusion layer and the electrolyte membrane, and the second catalyst layer is located between the second gas diffusion layer and the electrolyte membrane. A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell, which comprises joining the first gas diffusion layer, the first intermediate body, and the second intermediate body as described above.
In the formula (A), R ^f1 is a perfluoroalkylene group which may contain an oxygen atom between carbon atoms, and R ^f2 and R ^f3 are independently single bonds or between carbon atoms and carbon atoms, respectively. Is a perfluoroalkylene group which may contain an oxygen atom, r and m are independently 0 or 1, respectively, and M is a hydrogen atom, an alkali metal or a quaternary ammonium cation. The membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the bonding of the first gas diffusion layer, the first intermediate, and the second intermediate is performed by a hot press. Production method. The base material according to claim 1 or 2, wherein the base material is peeled off after joining the first intermediate and the first gas diffusion layer, and then the second intermediate is joined to the electrolyte membrane. A method for manufacturing a membrane electrode assembly for a polymer electrolyte fuel cell. The first gas diffusion layer is coated on the surface of the gas diffusible base material and the gas diffusible base material containing carbon fibers having a fiber diameter of 50 to 200 nm and a fiber length of 1 to 50 μm and a fluororesin. It has a first carbon layer formed by applying a working solution and has a first carbon layer.
The solid according to any one of claims 1 to 3, wherein the first gas diffusion layer and the first intermediate are joined so that the first carbon layer and the first catalyst layer are in contact with each other. A method for manufacturing a membrane electrode assembly for a polymer electrolyte fuel cell. The second gas diffusion layer is coated on the surface of the gas diffusible base material and the gas diffusible base material containing carbon fibers having a fiber diameter of 50 to 200 nm and a fiber length of 1 to 50 μm and a fluororesin. It has a second carbon layer formed by applying a working solution and has a second carbon layer.
The method according to any one of claims 1 to 4, wherein the second catalyst layer is formed on the surface of the second gas diffusion layer so that the second carbon layer and the second catalyst layer are in contact with each other. A method for manufacturing a membrane electrode assembly for a polymer electrolyte fuel cell.