JP2014072016A - Membrane electrode assembly, polymer fuel cell, and method for manufacturing membrane electrode assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane electrode assembly having no gap between a catalyst layer and a gasket member and excellent in durability.SOLUTION: Catalyst layers 2 and 3 are formed on both sides of a polymer electrolyte membrane 1, respectively. A filler is filled in spaces 21 and 22 between gasket members 13 and 14 and the catalyst layers 2 and 3 around which the gasket members 13 and 14 are arranged, respectively. The filler is formed of the same material as the catalyst layers 2 and 3, or a gas sealing material. The gasket members 13 and 14 are formed of a film.

Description

  The present invention relates to a membrane electrode assembly, a polymer fuel cell using the same, and a method for producing the membrane electrode assembly.

In recent years, fuel cells have attracted attention as effective solutions for environmental problems and energy problems. A fuel cell is one that oxidizes a fuel such as hydrogen using an oxidant such as oxygen and converts chemical energy associated therewith into electrical energy.
Fuel cells are classified into alkaline, phosphoric acid, polymer, molten carbonate, solid oxide, etc., depending on the type of electrolyte. Among these, polymer fuel cells (PEFC) are expected to be applied as portable power sources, household power sources, and in-vehicle power sources because of their low-temperature operation and high output density, which can be reduced in size and weight. ing.

A polymer fuel cell (PEFC) has a structure in which a polymer electrolyte membrane, which is an electrolyte membrane, is sandwiched between a fuel electrode (anode) and an air electrode (cathode), a fuel gas containing hydrogen on the fuel electrode side, By supplying an oxidant gas containing oxygen to the air electrode side, the following electrochemical reaction occurs to generate electricity.
Anode: H ₂ → 2H ⁺ + 2e ⁻ (1)
^{_{Cathode: 1 / 2O 2 + 2H +}} + 2e - → H 2 O ...... (2)

  The anode and cathode each have a laminated structure of a catalyst layer and a gas diffusion layer. The fuel gas supplied to the catalyst layer on the anode side becomes protons and electrons by the electrode catalyst (reaction 1). Protons move to the cathode through the polymer electrolyte in the catalyst layer on the anode side. The electrons travel through the external circuit to the cathode. In the catalyst layer on the cathode side, protons, electrons, and oxidant gas supplied from the outside react to generate water (reaction 2). In this way, power can be generated by electrons passing through an external circuit.

  Conventionally, a membrane electrode assembly, which is a structure in which a catalyst layer to be an air electrode (cathode) side electrode is formed on one surface of a polymer electrolyte membrane and a catalyst layer to be a fuel electrode (anode) side electrode is formed on the other surface As a production method, a catalyst layer slurry comprising a catalyst-supported carbon particle, a polymer electrolyte and a solvent is produced, and the catalyst layer slurry is directly applied to a polymer electrolyte membrane. A method is known in which a base material or a gas diffusion layer is applied and then thermocompression bonded to a polymer electrolyte membrane.

Among these methods, the method of producing a membrane electrode assembly by directly applying the slurry for the catalyst layer to the polymer electrolyte membrane has good adhesion at the interface between the polymer electrolyte membrane and the catalyst layer, and improves power generation performance and durability. An excellent membrane electrode assembly can be produced.
However, when the slurry for the catalyst layer is directly applied to the polymer electrolyte membrane, the polymer electrolyte membrane is swollen by the solvent of the slurry for the catalyst layer during coating, and contracts during drying. Therefore, the catalyst layer cannot be formed in a desired shape.

In order to solve such a problem, in the invention of Patent Document 1, a masking member having a hole hollowed into a target shape is disposed on the electrolyte membrane, and the slurry for the catalyst layer is directly applied to the polymer electrolyte membrane. A method has been proposed.
By using the above method, the catalyst layer can be roughly formed into the desired shape, and a gas barrier sheet (gasket member) is laminated as a masking member to easily manufacture a membrane electrode assembly with a gasket member. can do.

JP 2005-63780 A

However, in the method of Patent Document 1, a gap is generated between the gasket member and the catalyst layer due to swelling / shrinkage of the electrolyte membrane and drying shrinkage of the coating film in the coating process of the catalyst layer slurry. Therefore, the polymer electrolyte membrane is exposed in the gap. It is known that the exposure of the polymer electrolyte membrane accelerates the deterioration of the membrane electrode assembly and lowers the durability.
An object of the present invention is to form a catalyst layer in a desired shape in a membrane electrode assembly in which a catalyst layer is disposed opposite to both surfaces of a polymer electrolyte membrane, and a gasket member is disposed around the catalyst layer. And a membrane electrode assembly excellent in durability with no gap between the catalyst layer and the gasket member, a polymer fuel cell using the membrane electrode assembly, and a method for producing the membrane electrode assembly Is to provide.

(1) One aspect of the present invention is a polymer electrolyte membrane, a catalyst layer formed on each side of the polymer electrolyte membrane, a gasket member disposed around the catalyst layer, and the catalyst layer And a filler filled in a space between the gasket member and the membrane electrode assembly.
(2) In this case, the filler may be formed of the same material as the catalyst layer, or may be a gas seal material.

(3) Furthermore, the gasket member may be a film.
(4) According to another aspect of the present invention, the membrane electrode assembly, a gas diffusion layer provided on each of the catalyst layers, and a gas diffusion layer provided on each of the gas diffusion layers are provided. A gas flow path is formed on the surface on the layer side, a cooling water flow path is formed on the surface on the opposite side, and a separator made of an electrically conductive and gas impermeable material is provided. This is a molecular fuel cell.

  (5) Another embodiment of the present invention is a structure in which a catalyst layer is formed on both sides of a polymer electrolyte membrane, and a gasket member is disposed around the catalyst layer. A first step performed by directly applying a slurry for a catalyst layer on a molecular electrolyte membrane; and a second step of filling a gap between the catalyst layer and the gasket member with a filler after the completion of the first step; And a method for producing a membrane electrode assembly.

(6) In this case, the second step may be filled with the filler by applying ink to a gap between the catalyst layer and the gasket member.
(7) In the second step, the slurry for the catalyst layer or the gas seal material may be used as the ink.
(8) Further, in the first step, a film may be used as the gasket member.

According to one aspect of the present invention of (1), (4), (6), and (5), there is no gap between the catalyst layer and the gasket member, and the membrane electrode assembly and polymer fuel cell having excellent durability Can be provided.
(2) According to one aspect of the present invention of (7), it is possible to provide a membrane electrode assembly that prevents the polymer electrolyte membrane from being exposed and is further excellent in durability.
(3) According to one aspect of the present invention of (8), it is possible to provide a membrane electrode assembly excellent in compressive deformation.

It is a longitudinal cross-sectional view of the membrane electrode assembly which is one Embodiment of this invention. 1 is an exploded perspective view of a polymer fuel cell according to an embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described in detail. The present invention is not limited to the embodiments described below, and modifications such as design changes can be added based on the knowledge of those skilled in the art, and such modifications are added. The embodiments are also included in the scope of the present invention.

[Structure of membrane electrode assembly]
The structure of the membrane electrode assembly according to this embodiment will be described.
FIG. 1 is a longitudinal sectional view of a membrane electrode assembly 12 of the present embodiment. In this membrane electrode assembly 12, a catalyst layer 2 serving as an air electrode (cathode) side electrode is laminated on one surface of the polymer electrolyte membrane 1, and a catalyst layer 3 serving as a fuel electrode (anode) side electrode on the other surface. Are stacked. Gasket members 13 and 14 are disposed around the catalyst layers 2 and 3, respectively. The gap 21 between the catalyst layer 2 and the gasket member 13 and the gap 22 between the catalyst layer 3 and the gasket member 14 are filled with a filler, respectively.

[Polymer fuel cell structure]
Next, the structure of a polymer fuel cell using the membrane electrode assembly 12 will be described.
FIG. 2 is an exploded perspective view of the unit cell 11 of the polymer fuel cell according to the present embodiment. In the polymer fuel cell (single cell) 11, the catalyst layer 2 serving as the air electrode side electrode of the membrane electrode assembly 12 and the catalyst layer 3 serving as the fuel electrode side electrode (the catalyst layer 3 is a polymer in FIG. 2). The gas diffusion layer 4 on the air electrode side and the gas diffusion layer 5 on the fuel electrode side are disposed opposite to the electrolyte membrane 1. Thereby, the air electrode 6 and the fuel electrode 7 are comprised, respectively. The gas diffusion layer 4 on the air electrode side and the gas diffusion layer 5 on the fuel electrode side are provided with a gas flow path 8 for reaction gas distribution, and a cooling water flow path 9 for cooling water distribution is provided on the opposing main surface. A single cell 11 of a polymer fuel cell is configured by being sandwiched by a pair of separators 10 made of a highly conductive and gas-impermeable material. Then, an oxidant such as air or oxygen is supplied to the air electrode 6, and a fuel gas containing hydrogen or an organic fuel is supplied to the fuel electrode 7 to generate electricity.

[Production method of membrane electrode assembly]
Next, a method for manufacturing the membrane electrode assembly 12 will be described.
In the method for manufacturing the membrane electrode assembly 12, the membrane electrode assembly 12 is manufactured through the following first and second steps.
(1) 1st process The catalyst layer 2 used as an air electrode (cathode) side electrode is laminated | stacked on one surface of the polymer electrolyte membrane 1, and the catalyst layer 3 used as a fuel electrode (anode) side electrode is laminated | stacked on the other surface. Thus, a structure in which gasket members 13 and 14 are arranged around the catalyst layers 2 and 3 is manufactured.

This production may be performed by forming the catalyst layers 2 and 3 on the polymer electrolyte membrane 1 and then bonding the gasket members 13 and 14 to each other. Alternatively, the gasket members 13 and 14 are bonded to the polymer electrolyte membrane 1. Then, the catalyst layers 2 and 3 may be formed.
In order to form the catalyst layers 2 and 3 on the polymer electrolyte membrane 1, the catalyst layers 2 and 3 are formed by directly applying the catalyst layer slurry to the polymer electrolyte membrane 1.

(2) Second Step After the completion of the first step, the gaps 21 and 22 between the catalyst layers 2 and 3 and the gasket members 13 and 14 are filled with a filler. The filling material is formed by applying ink to the gaps 21 and 22.
Specifically, the formation of the catalyst layers 2 and 3 on the polymer electrolyte membrane 1 by applying ink in the first step is, for example, used to form the catalyst layers 2 and 3 on the polymer electrolyte membrane 1. The same catalyst layer slurry can be applied and dried.

The method for drying the catalyst layer slurry is not particularly limited, but warm air drying, IR (infrared) drying, reduced pressure drying, and the like are preferable.
Here, in the application of the slurry for the catalyst layer to the polymer electrolyte membrane 1 with the gasket members 13 and 14 having the conventional openings, the polymer electrolyte membrane is exposed due to drying shrinkage of the slurry for the catalyst layer. A large residual stress is generated in the membrane electrode assembly 12 thus formed.
In this embodiment, since only the gaps 21 and 22 between the catalyst layers 2 and 3 and the gasket members 13 and 14 are applied with ink, the drying shrinkage of the slurry for the catalyst layer is small and the polymer electrolyte membrane 1 is prevented from being exposed. Can do. Moreover, the residual stress of the manufactured membrane electrode assembly 12 can be reduced.

  The ink application method used in the present embodiment includes a doctor blade coating method, a dipping coating method, a slit coating method, a die coating method, a spray method, a screen printing method, a flexographic printing method, an offset printing method, a dispenser printing method, and an inkjet printing method. And a coating method such as a gravure printing method. Considering that the ink is applied to the gaps 21 and 22, a dispenser printing method and an ink jet printing method that can apply ink to a predetermined position are preferable.

In this embodiment, it is desirable that the ink is the catalyst layer slurry or the gas sealant described above. When the catalyst layer slurry is used, the catalyst layers 2 and 3 can be formed in the same shape as the openings of the gasket members 13 and 14, and the effective area of the catalyst layers 2 and 3 can be increased. Further, when the gas seal material is used, the exposed portion of the polymer electrolyte membrane 1 is gas-sealed, and the supply gas can be prevented from reaching the polymer electrolyte membrane 1 directly. Thereby, deterioration of the polymer electrolyte membrane 1 can be suppressed.
In the first step, the catalyst layer slurry includes an electrolyte, catalyst particles, and a solvent. The catalyst layer slurry is applied to the gaps 21 and 22 between the catalyst layers 2 and 3 and the gasket members 13 and 14. Furthermore, the gap between the catalyst layers 2 and 3 and the gasket members 13 and 14 can be filled with the same material as that of the catalyst layers 2 and 3 by passing through a drying process as necessary.

Hereinafter, the membrane electrode assembly, the structure of the polymer fuel cell, and various materials used in the method for manufacturing the membrane electrode assembly will be described in detail.
The electrolyte used in the present embodiment is not particularly limited as long as it has ionic conductivity. However, considering the adhesion between the catalyst layers 2 and 3 and the polymer electrolyte membrane 1, a material having the same quality as the polymer electrolyte membrane 1 is selected. It is preferable to do. For example, Nafion (manufactured by DuPont, registered trademark) is used as the fluorine-based resin, and engineering plastics or copolymers obtained by introducing sulfonic acid groups into the copolymer are exemplified.

  As particles used for the catalyst constituting the catalyst layers 2 and 3 used in the present embodiment, platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt, nickel Further, metals such as manganese, vanadium, molybdenum, gallium, and aluminum, alloys thereof, oxides, double oxides, and the like can be used. Of these, platinum and platinum alloys are preferred. Moreover, since the activity of a catalyst will fall when the particle size of these catalyst particles is too large, and the stability of a catalyst will fall when too small, 0.5-20 nm is preferable. More preferably, 1-5 nm is good.

  The catalyst particles may be used alone or preferably, supported on a conductive carrier. Generally, carbon particles are used as the conductive carrier. Any carbon particles can be used as long as they are in the form of fine particles, have conductivity and are not affected by the catalyst, but carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, and fullerene are used. it can. If the particle size of the carbon particles is too small, it becomes difficult to form an electron conduction path. If the particle size is too large, the electrode catalyst layer becomes thick and the resistance increases, resulting in a decrease in output characteristics. preferable. More preferably, 10-100 nm is good.

  The solvent for the catalyst layer slurry used in the present embodiment is not particularly limited, but a solvent capable of dispersing or dissolving the electrolyte is preferable. Commonly used solvents include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol and other alcohols, acetone, methyl ethyl ketone, methyl propyl ketone , Ketones such as methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, pentanone, heptanone, cyclohexanone, methylcyclohexanone, acetonyl acetone, diethyl ketone, dipropyl ketone, diisobutyl ketone, tetrahydrofuran, tetrahydropyran, dioxane, diethylene glycol Ethers such as dimethyl ether, anisole, methoxytoluene, diethyl ether, dipropyl ether, dibutyl ether, isopropyl Amines such as amine, butylamine, isobutylamine, cyclohexylamine, diethylamine, aniline, propyl formate, isobutyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, propionic acid Esters such as methyl, ethyl propionate, butyl propionate and the like, acetic acid, propionic acid, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and the like may be used. The glycol and glycol ether solvents include ethylene glycol, diethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diacetone alcohol, 1-methoxy-2-propanol, and 1-ethoxy-2. -Propanol etc. are mentioned.

  The gas sealing material is not particularly limited as long as it can be applied. Generally, rubbers such as silicone rubber, ethylene-propylene-diene rubber, nitrile butadiene rubber, silicone elastomers, thermoplastic elastomers, thermosetting elastomers, UV curable resins and the like can be mentioned. These materials may be used alone, or are dissolved in the solvent for the catalyst layer slurry described above to prepare ink and applied to the gaps 21 and 22 between the catalyst layers 2 and 3 and the gasket members 13 and 14. . Furthermore, the gaps 21 and 22 between the catalyst layers 2 and 3 and the gasket members 13 and 14 can be filled with a gas sealing material by passing through a drying process and a curing process as necessary.

The gasket member can be formed by coating molding, in-mold molding, film lamination, or the like, and film lamination is particularly preferable.
The gasket members 13 and 14 may be made of a film. The membrane electrode assembly 12 is laminated and used in a state where a compressive force is applied. Moreover, since there exists suitable thickness in the membrane electrode assembly 12, it is preferable that the gasket members 13 and 14 are excellent in thickness uniformity and compressive deformation. Since the gasket members 13 and 14 made of a film are uniform in thickness, they are suitable as the gasket members 13 and 14 and are preferably made of a material excellent in compressive deformation. Here, “excellent in compressive deformation” means that the amount of deformation of the material when a pressure is applied is small.

The gasket members 13 and 14 made of a film are provided with an adhesive layer or an adhesive layer on at least one surface of the film, and may have a release layer on the other surface. The adhesive layer is provided between the film and the polymer electrolyte, and improves the gas sealability at the interface. The release layer facilitates the removal of the ink applied to the gasket member surface.
Examples of the film include materials having excellent compressive deformation properties such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, polypropylene, polyethylene, and polyimide. These may be used alone or in combination.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Production of slurry for catalyst layer]
Put platinum-supported carbon (TEC10E50E, manufactured by Tanaka Kikinzoku Co., Ltd.) into a container, add water, mix, add 2-propanol and electrolyte (Nafion (registered trademark) dispersion, manufactured by Wako Pure Chemical Industries, Ltd.) and stir. Thus, a slurry for the catalyst layer was obtained.
[Production of polymer electrolyte membrane with gasket member]
An opening (size 50 mm × 50 mm) was formed in the gasket member (PET film with adhesive layer), and then bonded to both surfaces of the polymer electrolyte membrane 1 (Nafion 211CS, manufactured by DuPont).

[Durability evaluation]
Gas diffusion layers 4 and 5 (SIGRACE (registered trademark) 35BC, manufactured by SGL) were disposed on both surfaces of the membrane electrode assembly 12, and OCV durability evaluation was performed using a commercially available JARI standard cell. The cell temperature was 100 ° C., and humidified hydrogen was supplied to the anode and humidified oxygen was supplied to the cathode. The humidification conditions were 25% relative humidity.

[Comparative Example 1]
The catalyst electrode slurry was applied to the polymer electrolyte membrane 1 with the gasket members 13 and 14 with a doctor blade, and dried in an oven at 80 ° C. to produce a membrane electrode assembly 12. The gap between the catalyst layers 2 and 3 and the gasket members 13 and 14 was about 50 μm.

[Example 1]
The catalyst layer slurry is applied to the gaps 21 and 22 between the catalyst layers 2 and 3 of the membrane electrode assembly 12 manufactured in Comparative Example 1 and the gasket members 13 and 14 by a dispenser printing method, and the inside of the furnace at 80 ° C. Membrane / electrode assembly 12 was manufactured by drying. In this membrane electrode assembly 12, no gap was observed between the catalyst layers 2 and 3 and the gasket members 13 and 14.

[Example 2]
A gas sealant is applied by a dispenser printing method to the gaps 21 and 22 between the catalyst layers 2 and 3 and the gasket members 13 and 14 of the membrane electrode assembly 12 manufactured in Comparative Example 1 and dried in a furnace at 100 ° C. As a result, the membrane electrode assembly 12 was manufactured. In this membrane electrode assembly 12, no gap was observed between the catalyst layers 2 and 3 and the gasket members 13 and 14.
The durability evaluation results of the membrane electrode assembly 12 (Examples 1 and 2) manufactured by the manufacturing method of this example showed about twice (30 hours) durability as compared with Comparative Example 1.
Thus, it was found that the membrane electrode assembly 12 excellent in durability can be easily produced by the production method of this example.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2 Catalyst layer 3 Catalyst layer 4 Gas diffusion layer 5 Gas diffusion layer 6 Air electrode 7 Fuel electrode 8 Gas flow path 9 Cooling water flow path 10 Separator 11 Polymer fuel cell 12 Membrane electrode assembly 13 Gasket member 14 Gasket member 21 Gap 22 Gap

Claims (8)

A polymer electrolyte membrane;
Catalyst layers respectively formed on both sides of the polymer electrolyte membrane;
A gasket member disposed around the catalyst layer;
A filler filled in a space between the catalyst layer and the gasket member;
A membrane electrode assembly comprising:   The membrane electrode assembly according to claim 1, wherein the filler is made of the same material as the catalyst layer or is a gas seal material.   The membrane electrode assembly according to claim 1 or 2, wherein the gasket member is a film. The membrane electrode assembly according to any one of claims 1 to 3,
A gas diffusion layer provided on each of the catalyst layers;
Provided on each of the gas diffusion layers, a gas flow path is formed on the surface on the gas diffusion layer side, a cooling water flow path is formed on the surface on the opposite side, has conductivity, and is gas impermeable A separator formed of a material of
A polymer fuel cell comprising: A catalyst layer is formed on both sides of the polymer electrolyte membrane, and a gasket member is arranged around the catalyst layer. The catalyst layer is formed by directly applying a catalyst layer slurry to the polymer electrolyte membrane. A first step performed by:
A second step of filling a gap between the catalyst layer and the gasket member with a filler after completion of the first step;
A method for producing a membrane electrode assembly comprising:   6. The method for manufacturing a membrane electrode assembly according to claim 5, wherein in the second step, ink is applied to a gap between the catalyst layer and the gasket member to fill the gap with the filler.   The method for producing a membrane electrode assembly according to claim 6, wherein the second step uses the catalyst layer slurry or a gas sealant as the ink.   The method for manufacturing a membrane electrode assembly according to any one of claims 5 to 7, wherein the first step uses a film as the gasket member.

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