JP5283826B2 - Membrane electrode assembly and polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a membrane electrode assembly for a polymer electrolyte fuel cell, a method for producing the membrane electrode assembly, and a polymer electrolyte fuel cell. In particular, the present invention relates to a membrane electrode assembly in which power generation efficiency is improved by improving a contact state between constituent members.

  A fuel cell is an electrochemical oxidation of a fuel composed of a reducing agent such as hydrogen, methanol, or reformed hydrogen from fossil fuels using an oxidant such as oxygen or air, thereby converting the chemical energy of the fuel into electricity. It is converted into energy and extracted.

  Among these, the polymer electrolyte fuel cell has the first advantage that the operation temperature is low, and the second advantage that the internal resistance can be reduced by thinning the electrolyte part, so that the current can be taken out with high efficiency. It is suitable for reducing the battery size.

  The membrane electrode assembly used in this polymer electrolyte fuel cell has a structure in which an anode (fuel electrode) and a cathode (air electrode) are joined with a solid polymer electrolyte membrane interposed therebetween. The polymer electrolyte fuel cell is formed into a cell by stacking the membrane electrode assembly with a separator interposed therebetween.

  Usually, the anode or cathode and the solid polymer electrolyte membrane are joined via a catalyst-carrying conductive material made of a mixture of a catalyst and conductive carbon, and a diffusion layer that allows gas or liquid to permeate non-linearly. The fuel supplied to the anode side passes through the pores in the diffusion layer, reaches the catalyst, releases electrons by the catalyst, and becomes hydrogen ions. Hydrogen ions pass through the solid polymer electrolyte membrane and reach the cathode side, and react with oxygen supplied to the diffusion layer on the cathode side and electrons flowing from the external circuit to generate water. Electrons emitted from the fuel pass through the catalyst in the electrode and the conductive carbon on which the catalyst is supported, are led from the anode to the external circuit, and flow from the external circuit to the cathode. As a result, in the external circuit, electrons flow from the anode to the cathode and electric power is taken out.

  At this time, if the solid polymer electrolyte membrane and the electrode (anode and cathode) are insufficiently bonded, the movement of hydrogen ions is inhibited at the interface between the electrode and the polymer electrolyte membrane. As a result, the internal resistance of the whole membrane electrode assembly increases. Further, the joining interface between the solid polymer electrolyte and the electrode is also a three-phase interface where a catalytic reaction occurs. The larger the area of this three-phase interface, the more hydrogen ions are generated. That is, the joining state of the polymer electrolyte membrane and the electrode in the membrane electrode assembly greatly affects the characteristics of the polymer electrolyte fuel cell.

  As a conventional method for producing a membrane electrode assembly, a method is described in which a solid polymer electrolyte membrane and a gas diffusion electrode are joined by hot pressing with the solid polymer electrolyte membrane sandwiched between gas diffusion electrodes (patent) Reference 1).

In addition, as another method for producing a membrane electrode assembly, a method for applying and drying a catalyst layer forming paste to an electrolyte membrane obtained by filling a porous membrane mainly composed of polyimide with an electrolyte component is described. (See Patent Document 2).
JP-A-8-106915 Japanese Patent Laid-Open No. 2004-247152

  However, the membrane electrode assembly according to the conventional manufacturing method still has insufficient bonding at the interface between the electrolyte membrane and the diffusion layer and three-dimensional interface at the three-phase interface. This means an increase in the internal resistance of the battery and a decrease in the utilization rate of the catalyst. Therefore, sufficient output characteristics of the polymer electrolyte fuel cell have not been obtained from the membrane electrode assembly according to the conventional manufacturing method.

  Even when hot pressing is performed with the electrolyte membrane sandwiched between the diffusion layers, the electrolyte membrane is also applied when the catalyst layer forming paste is applied to the electrolyte membrane obtained by filling the porous membrane with the electrolyte component and dried. The junction interface between the diffusion layer and the diffusion layer is almost flat. In other words, the adhesive strength at the interface is not sufficient in a power generation environment, and the interface may peel off. Therefore, it is necessary to improve the bonding strength between the electrolyte membrane and the diffusion layer.

  The present invention improves strength and high power generation by improving the bonding state between members constituting the membrane electrode assembly and reducing internal resistance, and by increasing the reaction area by making the three-phase interface three-dimensional. An object of the present invention is to provide a membrane electrode assembly having good characteristics, a method for producing the membrane electrode assembly, and a polymer electrolyte fuel cell.

The first of the present invention is a membrane electrode assembly comprising a solid polymer electrolyte membrane and a diffusion layer bonded on both sides thereof, the solid polymer electrolyte membrane comprising a porous polymer membrane and the porous A proton conductive group provided in the pores of the polymer membrane and a catalyst-carrying conductive material embedded in pores at least near the surface of both surfaces of the porous polymer membrane, The porous polymer contains conductive carbon having an average particle diameter of 5 nm to 1000 nm on which a metal catalyst having a particle diameter of 1 nm to 10 nm is supported, and the embedding depth per one side of the catalyst-supporting conductive material is It is a membrane electrode assembly characterized by being 6.7% or more and 20% or less with respect to the thickness of the membrane. Here, “inside the hole in the vicinity of the surface” means a part of the inside of the hole communicating with the opening on the surface of the porous polymer film, and “in the vicinity” is associated with a specific distance. It is not a thing.

  The proton conductive group and the porous polymer membrane are preferably chemically bonded. The chemical bond refers to any of an ionic bond, a covalent bond, a coordination bond, a metal bond, and a hydrogen bond.

The proton conductive group is preferably a sulfonic acid group and / or a phosphoric acid group.
The thickness of the porous polymer film is preferably 15 μm or more and 150 μm or less.
The embedding depth of the catalyst-carrying conductive material is preferably 1% or more and less than 50% with respect to the thickness of the porous polymer film.

The average diameter of the pores observed on the surface of the porous polymer film is preferably 0.1 μm or more and 10 μm or less.
The porous polymer membrane is preferably insoluble in water.

  The porous polymer film is preferably a film made of any one of a polyimide polymer, a polytetrafluoroethylene polymer, a polyamide polymer, a polyimide-amide polymer film, and a polyolefin polymer.

A second aspect of the present invention is a polymer electrolyte fuel cell comprising the membrane electrode assembly and an electrode for taking out the current generated in the membrane electrode assembly to the outside.

  According to the present invention, it is possible to provide a membrane electrode assembly and a polymer electrolyte fuel cell having good strength and high output power generation characteristics.

Hereinafter, modes for carrying out the present invention will be described.
[Features of Membrane Electrode Assembly and Polymer Electrolyte Fuel Cell in the Present Invention]
A general configuration of a solid polymer fuel cell obtained by the present invention is schematically shown in FIG. 101 is a porous polymer membrane, 102 is a catalyst-carrying conductive material, 103 is a diffusion layer, 2 is an anode, 3 is a cathode, and 4 is a solid polymer electrolyte membrane. Although not shown, proton conductive groups are provided in the pores of the porous polymer membrane 101.

In the present invention, the assembly comprising the porous polymer membrane 101, the proton conductive group (not shown), the catalyst-carrying conductive material 102, and the diffusion layer 103 is referred to as the membrane electrode assembly 1.
Hereinafter, the description of the present invention will be made with reference to FIG. 1, but the configurations and shapes of the membrane electrode assembly and the polymer electrolyte fuel cell of the present invention are not limited to those shown in FIG.

  The material of the porous polymer film 101 in the present invention is selected from polymer materials that are insoluble in water. Specifically, various types such as polyimide (for example, Upilex manufactured by Ube Industries), polytetrafluoroethylene (for example, porous PTFE film manufactured by Nitto Denko), polyamide, polyimide-amide, polyolefin, etc. Resin material can be used. When methanol is selected as the fuel for the membrane electrode assembly of the present invention, the porous polymer membrane 101 is a material that is insoluble in methanol and water, and is substantially free of methanol and water. Select from materials that do not swell. Of the above materials, the polyimide-based material is most excellent in terms of insolubility in methanol and water, physical strength, and chemical stability. The polyimide polymer is polyimide or its derivative. The same applies to other polymers.

  The porosity in the present invention represents a state in which a large number of fine pores exist in the material of the polymer film. It is preferable that these holes are not independent, but are connected in a suitable manner so as to form a passage through which gas or liquid can pass from one side of the membrane to the other side. However, if gas or liquid can pass without resistance, it causes fuel crossover and leads to performance degradation. Therefore, it is preferable that these holes are connected non-linearly and the substantial permeation distance is increased. The degree of permeation can be controlled by the thickness of the porous polymer film 101, the size of the pores, and the like.

  The film thickness and pore size of the porous polymer membrane 101 are selected from the material, the strength of the target membrane / electrode assembly, the characteristics of the target polymer electrolyte fuel cell, etc., and are not particularly limited. However, a suitable film thickness considered from the use of a general polymer electrolyte fuel cell is 15 μm or more and 150 μm or less, preferably 30 μm or more and 100 μm or less. If the thickness of the porous polymer membrane 101 is less than 15 μm, the strength at the time of assembling the membrane electrode assembly or use as a solid polymer fuel cell is difficult. Since it becomes too long, power generation efficiency decreases.

  The average diameter of the pores observed on the surface of the porous polymer film 101 is 0.1 μm or more and 10 μm or less, preferably 0.1 μm or more and 5 μm or less. If the average diameter of the pores observed on the surface of the porous polymer membrane 101 is smaller than 0.1 μm, the number of places where proton conductive groups can exist becomes too small, so the power generation efficiency decreases. There is a possibility that the amount of crossover increases and a reverse reaction occurs on the cathode side.

  In the present invention, proton conductive groups are provided in the pores of the porous polymer membrane 101. The proton conductive group needs to be physically or chemically adsorbed to the porous polymer film 101 with a strength that does not flow out during the power generation reaction. It is more preferable that the proton conductive group and the porous polymer film 101 are chemically bonded. The proton conductive group and the porous polymer film 101 may be directly chemically bonded, or the compound having the proton conductive group at the terminal and the porous polymer film 101 may be chemically bonded.

  The proton conductive group in the present invention refers to a functional group having proton conductivity, for example, sulfonic acid group, sulfinic acid group, carboxylic acid group, phosphonic acid group, phosphoric acid group, phosphinic acid group, boronic acid group. Groups. Among these, it is more preferable that the proton conductive group contained in the membrane electrode assembly 1 of the present invention is a sulfonic acid group and / or a phosphoric acid group. Since both sulfonic acid groups and phosphoric acid groups have a high degree of acid dissociation, the effect of improving proton transport efficiency is high.

In the present invention, part or all of the catalyst-carrying conductive material 102 is embedded in the holes near the surfaces of both surfaces of the porous polymer film 101. The amount and depth of embedding are not particularly limited, but a more preferable embedding depth per side is 1% or more and less than 50% with respect to the thickness of the porous polymer film 101. When embedded on both surfaces, the total embedded depth on both surfaces is preferably 2% or more and less than 100% with respect to the thickness of the porous polymer film 101.

The term “embedding depth” in the present invention represents a depth measured from the surface of the porous polymer film 101 of the catalyst-carrying conductive material 102 present without interruption from the surface of the porous polymer film 101. If the embedding depth is less than 1% with respect to the thickness of the porous polymer film 101, the effect of improving the joining state between the members and the three-dimensional interface at the three-phase interface, which are the gist of the present invention, cannot be expected. On the other hand, if the embedding depth is 50% or more with respect to the thickness of the porous polymer film 101, there is a possibility that the catalyst-carrying conductive material 102 will come into contact with each other during both-side embedding, and electric leakage will occur. In this case, the portion that does not contribute to power generation increases too much.

  The constituent components of the catalyst-carrying conductive material 102 in the present invention are not particularly limited, but preferably contain conductive carbon and an electrode catalyst as in the case of a general membrane electrode assembly. For example, the catalyst-carrying conductive material on the anode side is formed of conductive carbon carrying a metal catalyst made of at least platinum. Instead of platinum, a platinum group metal such as rhodium, ruthenium, iridium, palladium, and osmium may be used, or an alloy of platinum and the above metal may be used. In particular, when methanol is used as the fuel, it is preferable to use an alloy of platinum and ruthenium.

The metal catalyst is preferably supported on the surface of conductive carbon. The average particle diameter of the supported metal catalyst particles is 1 nm to 10 nm, preferably 2 nm to 6 nm. When the particle diameter of the metal catalyst is less than 1 nm, the activity becomes too high with the catalyst particles alone, making handling difficult. Conversely, if the particle diameter of the metal catalyst exceeds 10 nm, the surface area of the catalyst may decrease and the activity may decrease.

The conductive carbon can be selected from carbon black, carbon fiber, graphite, carbon nanotube, and the like. The average particle size of the conductive carbon particles is preferably 5 nm or more and 1000 nm or less, and more preferably 10 nm or more and 100 nm or less. In order to support the metal catalyst, the specific surface area is preferably large to some extent, and is preferably 50 m ² / g or more and 3000 m ² / g or less, more preferably 100 m ² / g or more and 2000 m ² / g or less.

The catalyst-carrying conductive material on the cathode side is also formed by the same electrode catalyst.
The diffusion layer 103 is a constituent member for uniformly introducing the fuel and the oxidant gas into the electrode catalyst layer with high efficiency, and for transferring the electrons in contact with the electrode. In general, a conductive porous film is preferable, and carbon paper, carbon cloth, a composite sheet of carbon and polytetrafluoroethylene, and the like can be used. The surface and / or the inside of the diffusion layer 103 may be coated with a fluorine-based paint and subjected to a water repellent treatment.

  The thickness of the diffusion layer 103 is preferably 0.1 μm or more and 500 μm or less. When the thickness of the diffusion layer 103 is less than 0.1 μm, gas diffusibility and water repellency are insufficient. Conversely, if the thickness of the diffusion layer 103 is greater than 500 μm, the electrical resistance of the diffusion layer 103 increases and ohmic loss increases, which is not preferable. A more preferable thickness of the diffusion layer 103 is 1 μm or more and 300 μm or less.

  The anode 2 and the cathode 3 are electrodes for taking out the current generated in the membrane electrode assembly 1 to the outside, and are preferably made of a conductive material. Each of the anode 2 and the cathode 3 may also serve as a flow path plate for supplying fuel and oxidant gas to the diffusion layer 103. That is, the anode 2 and the cathode 3 do not need to be flat plates, and may have a shape patterned in the current extraction portion and the flow channel.

  The polymer electrolyte fuel cell of the present invention can be obtained by using the membrane electrode assembly of the present invention. FIG. 1 shows an example of the minimum configuration of the polymer electrolyte fuel cell of the present invention, but the actual shape is arbitrary, and a plurality of membrane electrode assemblies may be combined in series or in parallel. good.

[Method for Producing Membrane / Electrode Assembly in the Present Invention]
In the method for producing a membrane / electrode assembly in the present invention, at least a step of bringing a functional compound comprising a sulfonic acid group-containing compound and / or a phosphoric acid group-containing compound into contact with the pores on both surfaces of the porous polymer membrane (hereinafter referred to as a Contact step), a step of chemically bonding the porous polymer film and the functional compound by electron beam irradiation (hereinafter referred to as a bonding step), and surplus functional compounds in the vicinity of both surfaces of the porous polymer membrane. Is removed by cleaning (hereinafter referred to as a cleaning step), a step of applying a catalyst-carrying conductive material precursor paste in the vicinity of both surfaces of the porous polymer film (hereinafter referred to as an application step), and diffusion to the surface of the paste And a step of drying the paste after applying the layer (hereinafter, a sticking drying step).

  In the contacting step, the method for bringing the porous polymer membrane into contact with the functional compound is not particularly limited. For example, the porous polymer film may be simply immersed in a liquid made of a functional compound. In order to further increase the contact efficiency, ultrasonic vibration may be applied as necessary, or a vacuum filtration or pressure filtration technique may be used in combination.

  The type of the sulfonic acid group-containing compound and phosphoric acid group-containing compound constituting the functional compound is not particularly limited, but in order to increase the power generation efficiency of the membrane electrode assembly, the ratio of the sulfonic acid group and phosphoric acid group in the compound It is preferable to use a larger one. For example, the molecular weight per functional group is preferably 500 or less.

  The sulfonic acid group-containing compound and the phosphoric acid group-containing compound constituting the functional compound are more preferably a compound having a functional group having activity for electron beam irradiation because the chemical bond in the bonding step is further strengthened. Examples of the functional group having activity in electron beam irradiation include unsaturated bonds such as double bonds and triple bonds. Among them, particularly active functional groups are methacrylic acid groups, acrylic acid groups, vinyl groups, and styrene groups.

  Examples of compounds having a sulfonic acid group and an electron beam active functional group include vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, sulfobutyl methacrylate, sulfopropyl methacrylate, 2-acrylamido-2-methylpropane sulfone. Examples include acids, sulfobenzene methacrylates and sulfobenzyl methacrylates. A monomer in which fluorine is introduced into these monomers may be used. A plurality of these monomers may be used in combination.

As the compound having a phosphate group and a functional group active on an electron beam, a (meth) acrylic acid ester derivative having a phosphate ester group in the side chain can be suitably used.
In order to strengthen the chemical bond in the bonding step, an appropriate amount of a crosslinking auxiliary material may be added to the functional compound. The cross-linking auxiliary material preferably has activity for electron beams. For example, acrylamide, acrylonitrile, N-vinylpyrrolidone and the like can be mentioned as suitable crosslinking aids.

For the purpose of adjusting the viscosity, a small amount of a suitable solvent may be added to the functional compound.
Although the amount of electron beam irradiation is not particularly limited, it is preferably set to 100 Gy or more and 10 MGy or less, particularly 5 kGy or more and 200 kGy or less. If the irradiation amount is less than 100 Gy, a chemical bond is not sufficiently formed. When the irradiation amount is larger than 10 MGy, the polymer film or the proton conductive group may be modified.

  Although the acceleration voltage of the electron beam varies depending on the thickness of the electrolyte membrane, for example, an acceleration voltage of about 50 kV to 2 MV is preferable for a film of about 15 μm to 150 μm. A plurality of electron beams having different acceleration voltages may be irradiated. Further, the acceleration voltage may be changed during the electron beam irradiation. Moreover, you may heat-process during the irradiation of an active energy ray or immediately after irradiation as needed.

  In the washing step, excess functional compounds near the surface of the polymer film are removed. By this work, the porous portion can be restored near the surface of the polymer film. The cleaning method is not particularly limited, but effective cleaning can be performed by immersing in a solvent that is soluble in the functional compound before electron beam irradiation and performing a rubbing treatment in the solvent.

  In the coating step, a catalyst paste conductive material precursor paste is applied to the surface of the polymer film. The precursor paste may contain an electrolyte material or an organic solvent in addition to the catalyst-carrying conductive material. Examples of the electrolyte material suitable for the present invention include fluoropolymers having proton conductive groups, such as Nafion (registered trademark, DuPont), sulfonic acid fluorooligomers, sulfonated polyimides, and sulfonated oligomers.

  The paste application method is not particularly limited, for example, bar coater method, spin coating method, screen printing method, air doctor coater method, blade coater method, rod coater method, knife coater method, squeeze coater method, impregnation coater method, comma coater method, Examples include a die coater method, a reverse roll coater method, a transfer roll 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.

  The amount of penetration of the paste into the porous polymer film is not particularly limited, but the penetration depth per side is more preferably 1% or more and less than 50% with respect to the thickness of the porous polymer film. The amount of penetration of the paste into the porous polymer film can be arbitrarily adjusted according to the viscosity and the coating amount of the paste.

  The coating thickness when measured from the surface of the porous polymer film of the paste is 1 mm or less, preferably 0.5 μm or more and 50 μm or less, in terms of solid content. If the thickness is less than 0.5 μm, minute pinholes, cracks, etc. are likely to occur when dried in the next step. Conversely, if the thickness is greater than 50 μm, the film resistance may increase.

  In the sticking / drying step, the diffusion layer is stuck before the applied precursor paste is dried, and is dried in the air or in an inert gas atmosphere until the solvent is sufficiently evaporated at room temperature or higher.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
Example 1
(Production example of membrane electrode assembly of the present invention)
In a plastic container, vinylsulfonic acid, methacryloyloxyethyl phosphate (trade name P-1M, manufactured by Kyoeisha Chemical Co., Ltd.) and acrylonitrile were mixed in equal weights to prepare a functional compound solution. A polyimide film having a thickness of 15 μm and an average pore diameter of 0.1 μm was immersed in this solution as a porous polymer film, and the whole container was subjected to ultrasonic treatment for 5 minutes. The polyimide film taken out from the container was transferred onto a smooth SUS plate and irradiated with an electron beam having an acceleration voltage of 200 kV and a dose of 50 kGy using an electron beam irradiation apparatus (EC250 / 15 / 180L manufactured by Iwasaki Electric Co., Ltd.).

  The polyimide film after irradiation was transferred to a methanol / water mixed solution (equal volume mixing) heated to 60 ° C., and the surface was scrubbed with a sponge to remove excess functional compounds covering the surface. The washed membrane was once naturally dried.

When the surface of the washed film was observed with a scanning electron microscope, it was found that many holes having an average diameter of 0.1 μm were open near the surface.
As a precursor paste of the anode-side catalyst-carrying conductive material, 1 g of carbon (manufactured by Tanaka Kikinzoku) carrying 60 wt% Pt-Ru catalyst (Pt: Ru = 1: 1, atomic ratio) and 5 wt% Nafion solution ( A paste fully mixed with 5 g of Aldrich was prepared. As a precursor paste of the cathode-side catalyst-carrying conductive material, a paste was prepared by sufficiently mixing 1 g of carbon (manufactured by Tanaka Kikinzoku Co., Ltd.) carrying 60 wt% of Pt catalyst and 5 g of 5 wt% Nafion solution. These precursor pastes were applied to both surfaces of the cleaned polyimide film by a bar coater method so as to have a film thickness of 1 μm in terms of solid content, and carbon paper as a diffusion layer (TGP-H-30, manufactured by Toray Industries, Inc.) A thickness of 0.1 mm) was applied to the outside. This was dried under reduced pressure at 100 ° C. for 5 minutes and then at room temperature to obtain a membrane / electrode assembly of the present invention.

  When the cross section of the membrane electrode assembly was observed with a scanning electron microscope, the maximum embedding depth of the catalyst-carrying conductive material was about 3 μm on both the anode side and the cathode side. That is, the depth was 20% with respect to the thickness of the polyimide film.

Example 2
(Production example of membrane electrode assembly of the present invention)
The present invention is the same as in Example 1 except that two porous PTFE membrane filters (thickness 75 μm, average pore diameter 3 μm) are used and the acceleration voltage of electron beam irradiation is 300 kV. The membrane electrode assembly was obtained.

During the production, a large number of holes having an average diameter of 3 μm were observed on the surface of the PTFE film after the cleaning step.
When the cross section of the membrane electrode assembly was observed with a scanning electron microscope, the maximum embedding depth of the catalyst-carrying conductive material was about 10 μm on both the anode side and the cathode side. That is, the depth was 6.7% with respect to the thickness of the polyimide film.

Comparative Example 1
(Production example of membrane electrode assembly)
Acrylamide methylpropyl sulfonic acid, methylene-bis-acrylamide and 2,2′-azobis (2-amidinopropane) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.) as a reaction initiator in water at a weight ratio of 50 : A monomer aqueous solution was prepared by dissolution at a ratio of 30: 1. The same porous polyimide film as used in Example 1 was immersed in this solution, and then the porous polyimide film was taken out and sandwiched between glass plates. As it was, it was left to stand in a dryer at 50 ° C. for 12 hours to carry out heat polymerization. This was repeated three times to fill the inside of the porous polymer membrane with the polymer. Finally, the excess polymer adhering to the surface of the membrane with a weak force was removed with pure water to smooth the membrane.

  A membrane-electrode assembly for comparison was obtained by bonding the catalyst-carrying conductive material and the diffusion layer to both surfaces of the membrane by the same method as in Example 1. When the cross section of the membrane electrode assembly was observed with a scanning electron microscope, the interface between the catalyst-carrying conductive material and the polyimide film was clear, and no substantial embedding was formed.

The membrane electrode assemblies obtained in Examples 1 and 2 and Comparative Example 1 were incorporated into an evaluation cell to form a polymer electrolyte fuel cell, and the operation was performed in a single cell.
A 5 wt% aqueous methanol solution was supplied to the anode side at 10 ml / min, and normal pressure air was supplied to the cathode side at 100 ml / min, and power generation was performed while keeping the entire cell at 80 ° C.

Table 1 shows the terminal voltages when discharged at a current density of 0.25 A / cm ² .

  In the example, since the area of the interface between the catalyst-carrying conductive material and the electrolyte membrane is large, the internal resistance of the membrane electrode assembly as a whole is reduced, and in addition, a three-phase interface is sufficiently formed. Therefore, it is considered that the output performance as a polymer electrolyte fuel cell is improved.

  Vertical and horizontal cuts were made at intervals of 2 mm in the diffusion layer portion on the anode side of the membrane electrode assemblies obtained in Examples 1 and 2 and Comparative Example 1. A cellophane tape having a width of 24 mm was applied to this surface and strongly peeled off at an angle of about 45 degrees. As a result, in the membrane / electrode assembly of Example 1, peeling was randomly observed at about 5%. In the membrane / electrode assembly of Example 2, almost no peeling was observed. On the other hand, in the membrane / electrode assembly of Comparative Example 1, peeling was observed at 50% or more.

  As described above with reference to the examples, the present invention is characterized in the structure and interface state of the members constituting the membrane electrode assembly, and is not limited to the types of raw materials or the manufacturing apparatus. .

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a membrane electrode assembly suitable for coexistence with intensity | strength and a high output power generation characteristic, the manufacturing method of a membrane electrode assembly, and a solid polymer fuel cell can be provided.

It is a cross-sectional schematic diagram which shows the general structure of the polymer electrolyte fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Membrane electrode assembly 2 Anode 3 Cathode 4 Solid polymer electrolyte membrane 101 Porous polymer membrane 102 Catalyst carrying conductive material 103 Diffusion layer

Claims (9)

A membrane electrode assembly comprising a solid polymer electrolyte membrane and a diffusion layer bonded to both sides thereof, wherein the solid polymer electrolyte membrane is in a porous polymer membrane and pores of the porous polymer membrane Proton conductive group provided and a catalyst-carrying conductive material embedded in pores at least near the surface of both surfaces of the porous polymer membrane, the catalyst-carrying conductive material having an average particle diameter of 1 nm to 10 nm Containing conductive carbon having an average particle diameter of 5 nm to 1000 nm on which the metal catalyst is supported, and the embedding depth per one side of the catalyst-supporting conductive material is relative to the thickness of the porous polymer film. 6.7% or more and 20% or less of a membrane / electrode assembly.   The membrane / electrode assembly according to claim 1, wherein the proton conductive group and the porous polymer membrane are chemically bonded.   3. The membrane electrode assembly according to claim 1, wherein the proton conductive group is a sulfonic acid group and / or a phosphoric acid group.   The membrane electrode assembly according to any one of claims 1 to 3, wherein the porous polymer membrane has a thickness of 15 µm or more and 150 µm or less.   5. The membrane electrode assembly according to claim 1, wherein the embedding depths of the catalyst-carrying conductive materials on both sides embedded in the pores in the vicinity of the surface of the porous polymer membrane are equal. .   The membrane electrode assembly according to any one of claims 1 to 5, wherein an average diameter of pores observed on the surface of the porous polymer membrane is 0.1 µm or more and 10 µm or less.   The membrane electrode assembly according to any one of claims 1 to 6, wherein the porous polymer membrane is insoluble in water.   The porous polymer film is a film made of any one of a polyimide polymer, a polytetrafluoroethylene polymer, a polyamide polymer, a polyimide-amide polymer film, and a polyolefin polymer. The membrane electrode assembly according to any one of claims 1 to 7.   9. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 1 and an electrode for taking out an electric current generated in the membrane electrode assembly to the outside.

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