JP2007200762A - Membrane electrode assembly for polymer electrolyte fuel cell and method for producing the same - Google Patents

Abstract

A membrane electrode assembly for a polymer electrolyte fuel cell that has a high initial voltage and can maintain a high voltage for a long period of time in a wide range of current densities, and a method for easily manufacturing the membrane electrode assembly. To do.
A least one of the catalyst layer 11 includes an electrode catalyst, fibrous carbon and ion exchange resin, the electrode catalyst has an average lattice spacing d ₀₀₂ of [002] face be 0.350~0.390nm And an electrode catalyst in which platinum or a platinum alloy is supported on a carbon support having a specific surface area of 250 to 1500 m ² / g, and fibrous carbon has a fiber diameter of 1 to 500 nm and a fiber length of 100 μm or less. Membrane electrode which is fibrous carbon which is present and has no metal supported, and the ratio of electrode catalyst to fibrous carbon (electrode catalyst / fibrous carbon) is 7/3 to 1/9 (mass ratio) The joined body 10.
[Selection] Figure 1

Description

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

A fuel cell using hydrogen and oxygen has attracted attention as a power generation system that hardly has an adverse effect on the environment because the reaction product of an electrode reaction is only water in principle. In particular, polymer electrolyte fuel cells using proton-conductive ion exchange membranes as electrolyte membranes are promising as in-vehicle power supplies because of their low operating temperature, high output density, and miniaturization. ing.
Although the polymer electrolyte fuel cell has a feature that the operating temperature is low (50 to 120 ° C.), it has a problem that it is difficult to effectively use the exhaust heat for auxiliary power. In order to compensate for this problem, the polymer electrolyte fuel cell is required to have high utilization rates of hydrogen and oxygen, that is, high energy efficiency and high power density.

In order to meet this requirement, an electrode catalyst in which catalyst metal fine particles such as platinum and platinum alloys are supported in a highly dispersed manner on a carrier carbon having a large specific surface area is used as an electrode catalyst to be included in the catalyst layer of a polymer electrolyte fuel cell. It has been. By using the electrode catalyst, the reaction area at the electrode is expanded and high output can be achieved.
However, the polymer electrolyte fuel cell using the electrode catalyst has a problem that the voltage decreases as it is operated for a long period of time for the following reason.

That is, in the operation of fuel cells for automobiles, households, cogeneration, etc., the cathode potential under normal power generation is 0.6 V or more. Further, when the fuel cell is started and stopped, a small amount of air is mixed into the anode side, and as a result, the cathode potential becomes 1.2 V or more. When the cathode potential is 0.6 V or higher, the oxidation reaction shown in the following formula occurs, and the carrier carbon is oxidatively corroded.
C + H ₂ O → CO + 2H ⁺ + 2e ⁻ : 0.52 V,
C + 2H ₂ O → CO ₂ + 4H ⁺ + 4e ⁻ : 0.21V.

On the other hand, in the anode, when the supply of hydrogen is insufficient, a predetermined current density is maintained, so that an electrolysis reaction of water and an oxidation reaction of the carbon support may occur instead of the oxidation reaction of hydrogen. is there.
As described above, when the oxidation reaction of the carbon carrier proceeds and the carbon carrier undergoes oxidative corrosion (gasification), the supported catalyst metal fine particles are released and aggregated in the ion exchange resin of the catalyst layer. As a result, the power generation characteristics of the catalyst layer deteriorate. As a result, the voltage of the polymer electrolyte fuel cell is lowered. The problem becomes significant when trying to maintain a high current density.

The following electrode catalysts have been proposed as electrode catalysts in which the oxidation of the carbon support is suppressed.
(1) An electrode catalyst using a carbon support in which the degree of graphitization of carbon is increased by treatment at a high temperature of 2000 ° C. or higher and oxidation resistance is improved.
(2) An electrode catalyst in which a pore-forming agent is mixed with an electrode catalyst using a carbon support having a high degree of graphitization (Patent Document 1).
(3) An electrode catalyst in which electrode catalysts having different utilization rates of the catalyst are mixed and the sacrificial corrosion effect is utilized (Patent Document 2).

However, the electrode catalyst (1) has a problem that the specific surface area is reduced by high-temperature treatment, so that the dispersibility of the catalyst metal fine particles on the carbon support is deteriorated, and as a result, the power generation characteristics of the catalyst layer are deteriorated.
The catalyst layer using the electrode catalyst of (2) or (3) does not necessarily have high initial power generation characteristics, and has a problem that a complicated operation is required for forming the electrode (catalyst layer).

In addition, in order to improve the power generation characteristic of a catalyst layer, it is described in patent document 3 that a vapor growth carbon fiber is mixed with a catalyst layer. However, the reason why the vapor-grown carbon fiber is mixed is to control the wetting by water in the catalyst layer, and as a result, to improve the power generation characteristics of the catalyst layer, and to suppress the oxidation of the carbon support. Absent. Therefore, the ratio (electrode catalyst / fibrous carbon) of the conductive powder (corresponding to the electrode catalyst) and the vapor growth carbon fiber (corresponding to the fibrous carbon) is 9.99 / 0.01. -7/3 (mass ratio).
JP 2005-26174 A JP 2005-190712 A Japanese Patent No. 3606083

  An object of the present invention is to provide a membrane electrode assembly for a polymer electrolyte fuel cell that has a high initial voltage and can maintain a high voltage for a long period of time in a wide range of current densities, and the membrane electrode assembly can be easily produced. It is to provide a method.

A membrane electrode assembly for a polymer electrolyte fuel cell of the present invention includes an anode having a catalyst layer and a gas diffusion layer, a cathode having a catalyst layer and a gas diffusion layer, and an electrolyte membrane interposed between the anode and the cathode. And at least one catalyst layer of the anode and the cathode contains an electrode catalyst, fibrous carbon, and an ion exchange resin, and the electrode catalyst has an average lattice spacing d _{002 of} [002] plane of 0.350. Platinum or a platinum alloy is supported on a carbon carrier having a specific surface area of 250 to 1500 m ² / g, and the fibrous carbon has a fiber diameter of 1 to 500 nm and a fiber length. Is 100 μm or less, no metal is supported, and the ratio of the electrode catalyst to the fibrous carbon in the catalyst layer (electrode catalyst / fibrous carbon) is 7/3 to 1 / Characterized in that it is a (mass ratio).
The fiber carbon preferably has a fiber diameter of 1 to 150 nm.

The method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to the present invention includes an anode having a catalyst layer and a gas diffusion layer, a cathode having a catalyst layer and a gas diffusion layer, and an anode and a cathode. In the method for producing a membrane electrode assembly for a polymer electrolyte fuel cell comprising an electrolyte membrane, at least one catalyst layer is formed by coating the following coating liquid on a substrate. .
(Coating fluid)
Electrocatalyst is a coating liquid containing a fibrous carbon and ion exchange resins, wherein the electrode catalyst is 0.350~0.390nm average lattice spacing d ₀₀₂ of [002] plane, and a specific surface area of 250 Platinum or a platinum alloy is supported on a carbon carrier of ˜1500 m ² / g, the fibrous carbon has a fiber diameter of 1 to 500 nm, a fiber length of 100 μm or less, and a metal is supported. The coating liquid whose ratio (electrode catalyst / fibrous carbon) of the electrode catalyst and the fibrous carbon in the catalyst layer is 7/3 to 1/9 (mass ratio).

The membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention has a high initial voltage and can maintain a high voltage for a long period of time in a wide range of current densities.
According to the method for producing a membrane electrode assembly for a polymer electrolyte fuel cell of the present invention, a membrane for a polymer electrolyte fuel cell that has a high initial voltage and can maintain a high voltage for a long period of time in a wide range of current densities. An electrode assembly can be easily manufactured.

  In the present specification, a compound represented by the formula (1) is referred to as a compound (1). The same applies to compounds represented by other formulas.

<Membrane electrode assembly>
FIG. 1 is a schematic cross-sectional view showing an example of a membrane electrode assembly for a polymer electrolyte fuel cell of the present invention (hereinafter referred to as a membrane electrode assembly). The membrane electrode assembly 10 is in contact with the catalyst layer 11 between the anode 13 having the catalyst layer 11 and the gas diffusion layer 12, the cathode 14 having the catalyst layer 11 and the gas diffusion layer 12, and the anode 13 and the cathode 14. And an electrolyte membrane 15 interposed therebetween.

(Catalyst layer)
At least one of the catalyst layers 11 is a specific catalyst layer including a specific electrode catalyst, a specific fibrous carbon, and an ion exchange resin, and the electrode catalyst and the fibrous carbon are in a specific ratio. The specific catalyst layer is preferably at least the catalyst layer 11 of the cathode 14, and particularly preferably the catalyst layer 11 of the anode 13 and the cathode 14.

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

Examples of the ion exchange resin include a fluorine-containing polymer and a hydrocarbon-based polymer, and a fluorine-containing polymer is preferable from the viewpoint of durability.
The fluoropolymer is preferably a perfluorocarbon polymer (which may contain an etheric oxygen atom), and is a copolymer containing units based on tetrafluoroethylene and units based on perfluorovinyl ether having a sulfonic acid group. Polymers are particularly preferred.

As the perfluorovinyl ether having a sulfonic acid group, the compound (1) is preferable.
_{CF 2 = CF (OCF 2 CFX} ) m -O p - (CF 2) n -SO 3 H ··· (1).
However, m is an integer of 0 to 3, n is an integer from 1 to 12, p is 0 or 1, X is F or CF _3.

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

  In the case of a perfluorocarbon polymer having a sulfonic acid group, the polymer terminal may be fluorinated by fluorination after polymerization. When the polymer terminal is fluorinated, the durability against hydrogen peroxide and peroxide radicals is further improved, so that the durability is improved.

  Hydrocarbon polymers include sulfonated polyarylene, sulfonated polybenzoxazole, sulfonated polybenzothiazole, sulfonated polybenzimidazole, sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, and sulfonated. Examples include 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, and sulfonated polyimide. It is done.

  The electrode catalyst is an electrode catalyst in which platinum or a platinum alloy is supported on a carbon support. The supported amount of platinum or platinum alloy is preferably 10 to 70% by mass in the electrode catalyst (100% by mass).

Carbon support, [002] is the average lattice spacing d ₀₀₂ is 0.350~0.390nm the surface, and a specific surface area of 250~1500m ² / g, a high carbon support of amorphous. From the viewpoint that a high voltage can be maintained, a carbon support having a d ₀₀₂ of 0.355 to 0.380 nm and a specific surface area of 400 to 850 m ² / g is preferable. By setting d ₀₀₂ to 0.350 nm or more and the specific surface area to 250 m ² / g or more, platinum or a platinum alloy can be supported at a high supporting rate, and the initial performance is improved. The d ₀₀₂ is less 0.390 nm, and by a 1500 m ² / g or less specific surface area, the development of micropores is suppressed, can be effectively utilized platinum or a platinum alloy.

The d ₀₀₂ of the carbon support can be measured using a powder X-ray diffractometer. The electrode catalyst powder is set as a sample, and the d ₀₀₂ of the carbon support is calculated from the diffraction pattern. The specific surface area of the carbon support can be measured by nitrogen adsorption on the carbon surface using a BET specific surface area apparatus.

  The ratio of the electrode catalyst to the ion-containing 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. / 4 to 8/2 is particularly preferable.

  Fibrous carbon is fibrous carbon having a fiber diameter of 1 to 500 nm, a fiber length of 100 μm or less, and no metal supported thereon. Even after the carbon support of the electrode catalyst is oxidatively corroded, fibrous carbon having a fiber diameter of 1 to 350 nm and a fiber length of 50 μm or less is preferable from the viewpoint of easy contact with platinum or a platinum alloy. By making the fiber diameter 500 nm or less, contact with platinum or a platinum alloy is easy. By setting the fiber length to 100 μm or less, damage to the electrolyte membrane can be suppressed without significantly protruding from the catalyst layer (usually about 5 to 30 μm in thickness).

The fiber diameter and fiber length of the fibrous carbon can be measured by observation with an optical microscope, SEM (scanning electron microscope), TEM (transmission electron microscope) or the like.
As the fibrous carbon, fine fibrous carbon having electron conductivity is preferable, and vapor-grown carbon fibers, carbon nanotubes (single wall, double wall, multi-wall, cup laminated type, etc.) and the like can be mentioned.

  The ratio of the electrode catalyst to the fibrous carbon (electrode catalyst / fibrous carbon) is 7/3 to 1/9 (mass ratio), and more preferably 6.5 / 3.5 to 1.5 / 8.5. Preferably, 6/4 to 2/8 is more preferable because the electrode reaction can be performed efficiently and good power generation characteristics can be maintained even after the carbon support of the electrode catalyst has undergone some oxidative corrosion. By setting the ratio of fibrous carbon to 3 or more out of the total 10 of the electrode catalyst and fibrous carbon, contact with platinum or a platinum alloy is obtained even after the carbon support of the electrode catalyst is oxidatively corroded. Cheap. By setting the ratio of fibrous carbon to 9 or less in the total 10 of the electrode catalyst and fibrous carbon, the ratio of the electrode catalyst becomes sufficient, and the decrease in the initial voltage can be suppressed.

  Fibrous carbon tends to be entangled with each other in the catalyst layer to form pores. Since the pores function as a gas channel, the effect of eliminating the flooding problem at the time of operation of the fuel cell particularly under a high current density can be expected.

(Gas diffusion layer)
Examples of the gas diffusion layer 12 include carbon cloth, carbon paper, and carbon felt.
The gas diffusion layer is preferably water repellent treated with polytetrafluoroethylene or the like.

(Electrolyte membrane)
Examples of the electrolyte membrane 15 include an ion exchange resin membrane.
Examples of the ion exchange resin include those similar to the ion exchange resin of the catalyst layer.

<Method for producing membrane electrode assembly>
The manufacturing method of the membrane electrode assembly of the present invention is a method characterized in that the above-mentioned specific catalyst layer is formed by applying a coating liquid described later on a substrate.
As the substrate, a polymer film, an electrolyte membrane, or a gas diffusion layer is used.
Examples of the polymer film include film sheets made of polypropylene, polyethylene terephthalate, ethylene / tetrafluoroethylene copolymer, polytetrafluoroethylene, and the like.

When a polymer film is used as the substrate, the catalyst layer formed on the substrate is transferred to the surface of the electrolyte membrane (or gas diffusion layer) by hot pressing or the like, and then the polymer film is peeled off to form the catalyst layer and the gas diffusion layer. (Membrane electrode assembly) can be obtained by pasting together (or electrolyte membrane).
When an electrolyte membrane is used as a substrate, a membrane electrode assembly is obtained by bonding a catalyst layer formed on the electrolyte membrane and a gas diffusion layer.
When a gas diffusion layer is used as a substrate, a membrane electrode assembly is obtained by bonding a catalyst layer formed on the gas diffusion layer and an electrolyte membrane.

  In addition, a coating liquid is applied on the polymer film to form a catalyst layer on the anode (or cathode) side, and an electrolyte membrane is formed on the catalyst layer by applying a polymer solution for forming an electrolyte membrane. Then, a coating solution is applied on the electrolyte membrane to form a cathode (or anode) side catalyst layer to obtain a membrane catalyst layer assembly, and then a gas diffusion layer is formed on both sides of the membrane catalyst layer assembly. A membrane electrode assembly is obtained by pasting.

The coating liquid is a coating liquid containing a specific electrode catalyst, a specific fibrous carbon, and an ion exchange resin, wherein the electrode catalyst and the fibrous carbon are in a specific ratio.
The coating liquid is prepared by dispersing a specific electrode catalyst, a specific fibrous carbon, and an ion exchange resin in a solvent.

Examples of the solvent include water, acetone, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, alcohols such as ethylene glycol, pentafluoroethanol, heptafluorobutanol, or a mixed solvent thereof. Can be mentioned.
In the coating liquid, increase the drainage of the water generated by the electrode reaction, maintain the shape stability of the catalyst layer itself, improve coating unevenness during coating, improve coating stability, etc. For the purpose, a water repellent, a pore former, a thickener, a diluting solvent and the like may be added as necessary.

The coating liquid may be subjected to a dispersion treatment as necessary in order to improve the coating stability. Examples of the dispersion treatment include ball mill grinding, homogenizer grinding, planetary mill grinding, and ultrasonic grinding.
Examples of the coating method include a method using an applicator, a bar coater, a die coater, etc .; a screen printing method, a gravure printing method, and the like.
After coating a coating liquid on a base material, it is dried to form a catalyst layer. As for the drying temperature of a coating film, 60-100 degreeC is preferable.

A polymer electrolyte fuel cell can be obtained by disposing separators in which grooves serving as gas flow paths are formed on both surfaces of the membrane electrode assembly thus manufactured. Examples of the separator include a separator made of various conductive materials such as a metal separator, a carbon separator, and a separator made of a material in which graphite and a resin are mixed.
In the polymer electrolyte fuel cell, power is generated by supplying a gas containing oxygen to the cathode and a gas containing hydrogen to the anode. The membrane electrode assembly of the present invention can also be applied to a methanol fuel cell that generates power by supplying methanol to the anode.

  In the membrane electrode assembly of the present invention described above, at least one of the two catalyst layers includes a specific electrode catalyst, a specific fibrous carbon, and an ion exchange resin, and the electrode catalyst and the fiber. Since the carbon is a specific catalyst layer having a specific ratio, it has a high initial voltage and can maintain a high voltage for a long time in a wide range of current densities.

  That is, even if the oxidation reaction of the carbon carrier proceeds under high potential conditions at the cathode and gasifies, and platinum or platinum alloy is released into the ion exchange resin, Since the contact with the fibrous carbon having a carbon dioxide is taken, an electrode reaction is possible and a high voltage can be maintained for a long time. In addition, since fibrous carbon usually has a high degree of graphitization, it is very excellent in oxidation corrosion resistance.

  Also in the anode, when the supply of hydrogen is insufficient, a predetermined current density is maintained, so that an oxidation reaction of the carrier carbon may occur instead of the oxidation reaction of hydrogen. In the present invention, the same effect as the above-described cathode can be obtained by mixing fibrous carbon in the catalyst layer of the anode as in the cathode.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Examples 1, 3, 4, and 6 are examples, and examples 2, 5, and 7 are comparative examples.

[Example 1]
Formation of catalyst layer (1):
A catalyst (trade name: TEC36E52, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which a platinum-cobalt alloy (platinum / cobalt = 46/5 (mass ratio)) is supported on a carbon support (d ₀₀₂ 0.377 nm, specific surface area 800 m ² / g). 10 g of platinum / cobalt alloy supported amount) was added to 75.1 g of distilled water and stirred well. Further, 26.0 g of ethanol was added and stirred well. To this, copolymer (A) (trade name: Flemion, manufactured by Asahi Glass Co., Ltd., ion exchange capacity 1.1 meq / g dry resin, units based on tetrafluoroethylene and CF ₂ = CFOCF (CF ₃ ) O (CF ₂ ) A liquid having a solid content concentration of 9% by mass in which a copolymer composed of units based on ₂ SO ₃ H is dispersed in ethanol (hereinafter referred to as an ethanol dispersion of copolymer (A)). 0 g was added and further mixed and pulverized using an ultrasonic dispersion device to prepare a dispersion (a).

17.0 g of ethanol and 47.3 g of distilled water were added to 7.0 g of vapor grown carbon fiber (trade name: VGCF-H, manufactured by Showa Denko KK, fiber diameter: about 150 nm, fiber length: 10 to 20 μm) and stirred well. . To this was added 38.9 g of an ethanol dispersion of copolymer (A), stirred well, and further mixed and pulverized using an ultrasonic dispersion device to prepare dispersion (b).
The dispersion liquid (a) 10.0g and the dispersion liquid (b) 10.0g were mixed and stirred, and the coating liquid (1) was prepared.

  The coating liquid (1) was coated on a polypropylene substrate film with a die coater and then dried in an oven at 80 ° C. for 10 minutes to form a catalyst layer (1). Included in the catalyst layer (1) by measuring the mass of only the base film before forming the catalyst layer (1) and the mass of the catalyst layer and base film after forming the catalyst layer (1) The amount of platinum per unit area calculated was 0.2 mg / cm 2. The ratio of the electrode catalyst and fibrous carbon contained in the catalyst layer (1) (electrode catalyst / fibrous carbon) was 4.8 / 5.2 (mass ratio).

Formation of catalyst layer (2):
10.0 g of a catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., platinum supported amount 50 mass%) in which platinum is supported on a carbon support (d ₀₀₂ 0.377 nm, specific surface area 800 m ² / g) Added to 5 g and stirred well. Further, 22.5 g of ethanol was added and stirred well. To this, 50.0 g of an ethanol dispersion of copolymer (A) was added, and further mixed and pulverized using an ultrasonic dispersion device to prepare a coating liquid (2).

The coating liquid (2) was coated on a polypropylene substrate film with a die coater, and then dried in an oven at 80 ° C. for 10 minutes to form a catalyst layer (2). Included in the catalyst layer (2) by measuring the mass of only the base film before forming the catalyst layer (2) and the mass of the catalyst layer and base film after forming the catalyst layer (2) The amount of platinum per unit area calculated was 0.2 mg / cm ² .

Manufacture of membrane electrode assembly:
As an electrolyte membrane, an ion exchange membrane (trade name: Flemion, manufactured by Asahi Glass Co., Ltd., ion exchange capacity 1.1 milliequivalent / g dry resin) made of a perfluorocarbon polymer having a sulfonic acid group was prepared.
The catalyst layer (1) formed on the base film is disposed on one surface of the electrolyte membrane as a cathode-side catalyst layer, and the catalyst layer (on the base film formed on the other surface of the electrolyte membrane ( 2) was arranged as a catalyst layer on the anode side. The laminated body is pressed by a hot press method, the catalyst layer is transferred to the electrolyte membrane, the base film is peeled off, and a membrane / catalyst layer assembly comprising an electrolyte membrane and a catalyst layer, the electrode area of which is 25 cm ² is obtained. Obtained.

The membrane / catalyst layer assembly was sandwiched between two gas diffusion layers made of carbon cloth having a thickness of 350 μm to obtain a membrane / electrode assembly. The membrane electrode assembly is assembled in a power generation cell, hydrogen (utilization rate 70%) / air (utilization rate 40%) is supplied at normal pressure, and the cell temperature is 80 ° C., and the current density is 0.2 A / cm. Initial cell voltages at ² and 1.0 A / cm ² were measured. However, hydrogen having a dew point of 80 ° C. was supplied to the anode side, and air having a dew point of 80 ° C. was supplied to the cathode side. The results are shown in Table 1.

Next, at a cell temperature of 95 ° C., hydrogen with a dew point of 90 ° C. is supplied to the anode side, air with a dew point of 90 ° C. is supplied to the cathode side, a potentiostat is connected from the outside, and the cathode side potential is 1.2V. The sample was operated for 100 hours to conduct an oxidative corrosion test. After the oxidative corrosion test, hydrogen having a dew point of 80 ° C. was supplied to the anode side at a cell temperature of 80 ° C., and air having a dew point of 80 ° C. was supplied to the cathode side, and current densities were 0.2 A / cm ² and 1.0 A / cm. The cell voltage at ² was measured. The results are shown in Table 2.

[Example 2 (comparative example)]
A membrane / catalyst layer assembly having an electrode area of 25 cm ² was prepared in the same manner as in Example 1 except that the catalyst layer (2) was used as the catalyst layer on the anode side and the cathode side. An electrode assembly was produced. With respect to the membrane / electrode assembly, the initial cell voltage was measured under the same conditions as in Example 1. The results are shown in Table 1. Moreover, the oxidation corrosion test was implemented on the same conditions as Example 1, and the cell voltage of the oxidation corrosion test was measured. The results are shown in Table 2.

[Example 3]
A membrane-catalyst layer assembly having an electrode area of 25 cm ² was prepared in the same manner as in Example 1 except that the catalyst layer (1) was used as the anode-side and cathode-side catalyst layers. An electrode assembly was produced. With respect to the membrane / electrode assembly, the initial cell voltage was measured under the same conditions as in Example 1. The results are shown in Table 1. Moreover, the oxidation corrosion test was implemented on the same conditions as Example 1, and the cell voltage of the oxidation corrosion test was measured. The results are shown in Table 2.

[Example 4]
10 g of the dispersion (a) and 4.5 g of the dispersion (b) were mixed and stirred to prepare a coating liquid (3).
The coating liquid (3) was coated on a polypropylene base film with a die coater, and then dried in an oven at 80 ° C. for 10 minutes to form a catalyst layer (3). Included in the catalyst layer (3) by measuring the mass of the base film only before forming the catalyst layer (3) and the mass of the catalyst layer and base film after forming the catalyst layer (3) The amount of platinum per unit area calculated was 0.2 mg / cm ² . The ratio (electrode catalyst / fibrous carbon) of the electrode catalyst and fibrous carbon contained in the catalyst layer (3) was 6.5 / 3.5 (mass ratio).

A membrane / catalyst layer assembly having an electrode area of 25 cm ² was prepared in the same manner as in Example 1 except that the catalyst layer (3) was used as the anode-side and cathode-side catalyst layers. An electrode assembly was produced. With respect to the membrane / electrode assembly, the initial cell voltage was measured under the same conditions as in Example 1. The results are shown in Table 1. Moreover, the oxidation corrosion test was implemented on the same conditions as Example 1, and the cell voltage of the oxidation corrosion test was measured. The results are shown in Table 2.

[Example 5 (comparative example)]
10 g of the dispersion liquid (a) and 2.3 g of the dispersion liquid (b) were mixed and stirred to prepare a coating liquid (4).
The coating liquid (4) was coated on a polypropylene base film with a die coater, and then dried in an oven at 80 ° C. for 10 minutes to form a catalyst layer (4). Included in the catalyst layer (4) by measuring the mass of only the base film before forming the catalyst layer (4) and the mass of the catalyst layer and base film after forming the catalyst layer (4) The amount of platinum per unit area calculated was 0.2 mg / cm ² . The ratio (electrode catalyst / fibrous carbon) of the electrode catalyst and fibrous carbon contained in the catalyst layer (4) was 8/2 (mass ratio).

A membrane / catalyst layer assembly having an electrode area of 25 cm ² was prepared in the same manner as in Example 1, except that the catalyst layer (4) was used as the catalyst layer on the anode side and the cathode side. An electrode assembly was produced. With respect to the membrane / electrode assembly, the initial cell voltage was measured under the same conditions as in Example 1. The results are shown in Table 1. Moreover, the oxidation corrosion test was implemented on the same conditions as Example 1, and the cell voltage of the oxidation corrosion test was measured. The results are shown in Table 2.

[Example 6]
5 g of the dispersion (a) and 24.9 g of the dispersion (b) were mixed and stirred to prepare a coating liquid (5).
The coating liquid (5) was coated on a polypropylene substrate film with a die coater, and then dried in an oven at 80 ° C. for 10 minutes to form a catalyst layer (5). Included in the catalyst layer (5) by measuring the mass of only the base film before forming the catalyst layer (5) and the mass of the catalyst layer and base film after forming the catalyst layer (5) The amount of platinum per unit area calculated was 0.2 mg / cm ² . The ratio of the electrode catalyst and fibrous carbon contained in the catalyst layer (5) (electrode catalyst / fibrous carbon) was 1.5 / 8.5 (mass ratio).

A membrane / catalyst layer assembly having an electrode area of 25 cm ² was prepared in the same manner as in Example 1 except that the catalyst layer (5) was used as the catalyst layer on the anode side and the cathode side. An electrode assembly was produced. With respect to the membrane / electrode assembly, the initial cell voltage was measured under the same conditions as in Example 1. The results are shown in Table 1. Moreover, the oxidation corrosion test was implemented on the same conditions as Example 1, and the cell voltage of the oxidation corrosion test was measured. The results are shown in Table 2.

[Example 7 (comparative example)]
2 g of dispersion liquid (a) and 24.2 g of dispersion liquid (b) were mixed and stirred to prepare a coating liquid (6).
The coating liquid (6) was coated on a polypropylene base film with a die coater, and then dried for 10 minutes in an oven at 80 ° C. to form a catalyst layer (6). Included in the catalyst layer (6) by measuring the mass of only the base film before forming the catalyst layer (6) and the mass of the catalyst layer and base film after forming the catalyst layer (6) The amount of platinum per unit area calculated was 0.2 mg / cm ² . The ratio of the electrode catalyst and fibrous carbon contained in the catalyst layer (6) (electrode catalyst / fibrous carbon) was 0.7 / 9.3 (mass ratio).

A membrane / catalyst layer assembly having an electrode area of 25 cm ² was prepared in the same manner as in Example 1 except that the catalyst layer (6) was used as the catalyst layer on the anode side and the cathode side. An electrode assembly was produced. With respect to the membrane / electrode assembly, the initial cell voltage was measured under the same conditions as in Example 1. The results are shown in Table 1. Moreover, the oxidation corrosion test was implemented on the same conditions as Example 1, and the cell voltage of the oxidation corrosion test was measured. The results are shown in Table 2.

  It can be seen that when the membrane / electrode assembly of the present invention is used, a high voltage is obtained even in a high current density region, and good power generation characteristics are maintained even after the oxidation corrosion test.

  The membrane / electrode assembly of the present invention has a high initial voltage in a wide range of current densities and can maintain a high voltage for a long period of time. It is.

It is a schematic sectional drawing which shows an example of the membrane electrode assembly for polymer electrolyte fuel cells of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Membrane electrode assembly 11 Catalyst layer 12 Gas diffusion layer 13 Anode 14 Cathode 15 Electrolyte membrane

Claims (3)

An anode having a catalyst layer and a gas diffusion layer;
A cathode having a catalyst layer and a gas diffusion layer;
An electrolyte membrane interposed between the anode and the cathode,
The catalyst layer of at least one of the anode and the cathode contains an electrode catalyst, fibrous carbon, and an ion exchange resin;
The electrode catalyst, average lattice spacing d ₀₀₂ of [002] face is 0.350～0.390Nm, and a specific surface area carbon carrier is 250~1500m ² / g, platinum or a platinum alloy supported And
The fibrous carbon has a fiber diameter of 1 to 500 nm, a fiber length of 100 μm or less, and no metal is supported,
Membrane / electrode joining for polymer electrolyte fuel cells, wherein the ratio of the electrode catalyst to the fibrous carbon (electrode catalyst / fibrous carbon) in the catalyst layer is 7/3 to 1/9 (mass ratio) body.   The membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the fibrous carbon has a fiber diameter of 1 to 150 nm. Manufacture of a membrane electrode assembly for a polymer electrolyte fuel cell comprising an anode having a catalyst layer and a gas diffusion layer, a cathode having a catalyst layer and a gas diffusion layer, and an electrolyte membrane interposed between the anode and the cathode In the method
A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell, wherein at least one of the catalyst layers is formed by coating the following coating liquid on a substrate.
(Coating fluid)
It is a coating liquid containing an electrode catalyst, fibrous carbon and an ion exchange resin,
In the electrode catalyst, platinum or a platinum alloy is supported on a carbon support having an average lattice spacing d _{002 of} [002] plane of 0.350 to 0.390 nm and a specific surface area of 250 to 1500 m ² / g. And
The fibrous carbon has a fiber diameter of 1 to 500 nm, a fiber length of 100 μm or less, and no metal is supported,
The coating liquid whose ratio (electrode catalyst / fibrous carbon) of the electrode catalyst and the fibrous carbon in the catalyst layer is 7/3 to 1/9 (mass ratio).

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