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WO2010047125A1 - Material for use in formation of electrode layer for fuel cell, membrane electrode assembly for fuel cell, fuel cell, process for producing material for use in formation of electrode layer for fuel cell, and process for producing electrode layer for fuel cell - Google Patents

Material for use in formation of electrode layer for fuel cell, membrane electrode assembly for fuel cell, fuel cell, process for producing material for use in formation of electrode layer for fuel cell, and process for producing electrode layer for fuel cell Download PDF

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Publication number
WO2010047125A1
WO2010047125A1 PCT/JP2009/005590 JP2009005590W WO2010047125A1 WO 2010047125 A1 WO2010047125 A1 WO 2010047125A1 JP 2009005590 W JP2009005590 W JP 2009005590W WO 2010047125 A1 WO2010047125 A1 WO 2010047125A1
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Prior art keywords
electrode layer
fuel cell
catalyst
primary particles
particles
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PCT/JP2009/005590
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French (fr)
Japanese (ja)
Inventor
小川直也
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電源開発株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8825—Methods for deposition of the catalytic active composition
    • H01M4/886—Powder spraying, e.g. wet or dry powder spraying, plasma spraying
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a fuel cell electrode layer forming material suitable for a polymer electrolyte fuel cell, a fuel cell membrane electrode assembly, a fuel cell, a method for producing a fuel cell electrode layer forming material, and a fuel cell electrode layer. It relates to the manufacturing method. Specifically, the double layer structure of the electrode layer particles is intended to improve the cell characteristics by increasing the substantial surface area of the electrode layer and improving the ionic conductivity by securing the gas diffusion passage and the discharge passage of the generated water. is there.
  • This application claims priority based on Japanese Patent Application No. 2008-273095 filed in Japan on October 23, 2008, the contents of which are incorporated herein by reference.
  • FIG. 6 shows an example of a membrane electrode assembly (MEA) forming a reaction part of a polymer electrolyte fuel cell.
  • MEA membrane electrode assembly
  • On one surface of the polymer electrolyte membrane 101 for example, an anode electrode layer 102 having a thickness of about 20 ⁇ m is formed.
  • On the other surface of the polymer electrolyte membrane 101 for example, a cathode electrode layer 103 having a thickness of about 20 ⁇ m is formed.
  • the membrane electrode assembly 100 is formed by integrating the polymer electrolyte membrane 101, the anode electrode layer 102, and the cathode electrode layer 103.
  • a diffusion layer such as carbon paper is provided on the surfaces of the anode electrode layer 102 and the cathode electrode layer 103.
  • the polymer electrolyte membrane 101 for example, a film made of a perfluorosulfonic acid polymer having a thickness of about 30 to 70 ⁇ m is used.
  • a liquid in which a catalyst is dispersed hereinafter referred to as catalyst ink
  • carbon paper serving as a diffusion layer and dried.
  • catalyst-supported particles in which catalyst particles made of platinum particles having a particle diameter of about 2 to 5 nm are supported on a conductive catalyst body such as carbon particles having a particle diameter of about 30 nm are used.
  • a material dispersed in a polymer electrolyte solution made of an ion conductive polymer, isopropanol, water or the like is used.
  • the membrane electrode assembly 100 is formed by bonding the carbon paper on which the anode electrode layer 102 and the cathode electrode layer 103 are formed on both surfaces of the polymer electrolyte membrane 101. There is also a production method in which catalyst ink is applied to both surfaces of the polymer electrolyte membrane 101 to form electrode layers 102 and 103, and then a diffusion layer is joined to the membrane electrode assembly 101.
  • a method of applying the catalyst ink to the diffusion layer or the polymer electrolyte membrane (hereinafter referred to as a target)
  • a method of spraying the catalyst ink toward the target using an air spray device has been conventionally employed.
  • the method using the conventional air spray device there is a concern that the catalyst-carrying particles in the formed electrode layer are easily dispersed unevenly.
  • the electrode layer formed by the conventional ultrasonic spray device is an electrode having a structure in which the catalyst-supported particles grow together and the grown particle groups are combined, like the electrode layer formed by the conventional air spray device. Only a layer was obtained.
  • the electrode layer constituting the membrane electrode assembly is excellent in ion conductivity while ensuring gas permeability (diffusibility).
  • an electrode layer formed by a conventional ultrasonic spray device In this case, the catalyst-supported particles grow together and the voids of the grown particles are not sufficiently formed, so there is a problem in gas permeability. At the same time, the number of catalysts that do not contribute to the reaction increases due to agglomeration, which causes a decrease in performance.
  • the present invention has been made in order to solve the above-described problems, increases the substantial surface area involved in the catalytic reaction, facilitates intrusion and diffusion of fuel and oxidant, and provides ion conduction.
  • An object of the present invention is to provide a fuel cell electrode layer forming material, a fuel cell membrane electrode assembly, and a fuel cell capable of forming a fuel cell electrode layer that is excellent in performance.
  • the present invention provides a fuel cell electrode layer forming material, a fuel cell membrane electrode assembly, a fuel cell, a method for producing a fuel cell electrode layer forming material, and a fuel cell A method for producing an electrode layer is provided. That is, the material for forming the electrode layer for a fuel cell according to the present invention is primary particles including at least catalyst-carrying particles in which a catalyst is carried on a carrier and a first ion-conductive polymer, and a liquid substance is removed. It includes at least substantially spherical primary particles in a dry state.
  • the average particle diameter of the primary particles may be 5 ⁇ m or more and less than 100 ⁇ m.
  • the primary particles and the second ion conductive polymer may be dispersed in a solvent.
  • the membrane electrode assembly for a fuel cell comprises catalyst-carrying particles formed on at least one surface of an electrolyte membrane carrying an electrolyte and carrying a catalyst on the carrier, and a first ion conductive polymer.
  • the electrode layer includes at least secondary particles obtained by agglomerating a plurality of substantially spherical primary particles in a dry state from which a liquid material is removed, which are at least primary particles, which are aggregated with a second ion conductive polymer.
  • the average particle diameter of the primary particles is preferably 5 ⁇ m or more and less than 100 ⁇ m, and the maximum side of the secondary particles is preferably 10 ⁇ m or more and 1000 ⁇ m or less.
  • At least one of the electrode layers is a primary particle containing at least a catalyst-carrying particle in which a catalyst is carried on a carrier and a first ion-conductive polymer, and a dry material from which a liquid material has been removed
  • the electrode layer includes at least secondary particles obtained by agglomerating a large number of substantially spherical primary particles in a state with a second ion conductive polymer.
  • the average particle diameter of the primary particles is preferably 5 ⁇ m or more and less than 100 ⁇ m, and the maximum side of the secondary particles is preferably 10 ⁇ m or more and 1000 ⁇ m or less.
  • the method for producing a material for forming an electrode layer for a fuel cell according to the present invention includes a first solution containing at least catalyst-carrying particles in which a catalyst is supported, a first ion-conductive polymer, and a first solvent. Is sprayed in the atmosphere to volatilize the solvent, and a spraying step for obtaining dried substantially spherical primary particles is provided.
  • the spraying step is preferably performed by spraying the first solution using an ultrasonic spray device.
  • the method for producing an electrode layer for a fuel cell comprises a first solution containing at least catalyst-carrying particles having a catalyst supported on a carrier, a first ion-conductive polymer, and a first solvent in the atmosphere. Spraying to vaporize the solvent to obtain dried substantially spherical primary particles, and a second solution containing at least the primary particles, the second ion-conductive polymer, and the second solvent.
  • the electrode layer containing at least secondary particles obtained by aggregating a number of the primary particles with the second ion conductive polymer by spraying on at least one surface of the target including the electrolyte membrane or the diffusion layer is provided on at least one surface of the target.
  • an electrode layer for a fuel cell According to the material for forming an electrode layer for a fuel cell, a membrane electrode assembly for a fuel cell, and a fuel cell according to the present invention, sufficient gas permeability is provided, and the catalyst efficiency is increased by increasing the exposed surface area of the catalyst.
  • An electrode layer for a fuel cell with improved conductivity and improved electron conductivity due to the binding of primary particles can be easily formed at low cost with few steps.
  • primary particles are formed by a spraying process, and therefore a catalyst that prevents aggregation of primary particles and does not contribute to the reaction. Can be reduced.
  • an electrode layer composed of secondary particles by forming an electrode layer composed of secondary particles using the primary particles, a large number of primary particles are aggregated via an ion conductive polymer, that is, a large number of primary particles are second ion conductive. It is possible to form an electrode layer made of a substantially spherical or amorphous aggregate covered with a conductive polymer.
  • Such an electrode layer has sufficient gas permeability from the pores present in the primary particles (raw material particles), the sponge-like gaps between the primary particles in the secondary particles, and the large gaps between the secondary particles.
  • the catalyst efficiency is increased by increasing the exposed surface area.
  • the proton conductivity is improved and the electron conductivity is improved due to the binding between the primary particles. Therefore, it is possible to form an electrode layer for a fuel cell that allows easy penetration and diffusion of fuel and oxidant and is excellent in ion conductivity.
  • FIG. 1 is an exploded perspective view showing an example of a fuel cell provided with an electrode layer for a fuel cell according to the present invention.
  • the fuel cell 1 uses, for example, methanol as a fuel, and includes a unit cell 2 for generating power as shown in FIG.
  • the fuel cell 1 is configured by sandwiching the unit cell 2 with a separator 4.
  • Such a fuel cell 1 may be composed of a single unit cell 2, but normally, in order to obtain a sufficient output, the unit cells 2 are stacked and used as one package. This package corresponds to the stack 3 in the figure.
  • the unit cell 2 is composed of a membrane electrode assembly (MEA) 9 and a separator 4 sandwiching the membrane electrode assembly 9.
  • the membrane electrode assembly 9 includes a polymer electrolyte membrane 5, an anode electrode layer 6 formed on one surface of the polymer electrolyte membrane 5, and a cathode electrode layer 7 formed on the other surface of the polymer electrolyte membrane 5. It is integrated. Furthermore, a diffusion layer (not shown) made of carbon paper or the like is provided on the surfaces of the anode electrode layer 6 and the cathode electrode layer 7.
  • the separator 4 is formed with a fuel supply groove 11 for supplying fuel to the anode electrode layer 6 and an air supply groove 14 for supplying air to the cathode electrode layer 7.
  • fuel gas is supplied to the anode electrode layer 6 via the fuel supply groove 11, and air is supplied to the cathode electrode layer 7 via the air supply groove 14.
  • carbon dioxide, ionized hydrogen (hydrogen ions) and electrons are generated from methanol and water as fuel gas (CH 3 OH + H 2 O ⁇ CO 2 + 6H + + 6e ⁇ ). This is called an anodic reaction.
  • FIG. 2 is an enlarged cross-sectional view showing an example of the fuel cell electrode layer of the present invention and a material for forming the electrode layer.
  • FIG. 2 a is a cross-sectional view showing a forming material for forming a fuel cell electrode layer.
  • the material for forming the fuel cell electrode layer is composed of primary particles 23 which are fine particles.
  • Each of the primary particles 23 is composed of, for example, an aggregate in which the catalyst support particles 27 in which the catalyst 25 is supported on the support 26 are infinitely aggregated by the first ion conductive polymer 24.
  • the catalyst-carrying particles may be in any form as long as the catalyst is carried on the carrier.
  • support as used herein means, for example, a support in which a catalyst is dispersed and supported on a support, a support in which a catalyst layer is formed around the support, or a support and a catalyst stacked in layers.
  • the catalyst may be supported on the support in any form.
  • the carrier is coated with a catalyst thin film. It is done.
  • the catalyst 25 may be, for example, a catalyst metal such as platinum, palladium, iridium having an average particle diameter of about 1 to 5 nm. Moreover, catalysts other than metals can also be used.
  • the carrier 26 may be conductive particles typified by carbon powder having an average particle size of about 10 to 80 nm, for example.
  • the first ion conductive polymer 24 may be, for example, an ionomer resin.
  • the primary particles 23 may be formed in a spherical shape or a shape close to this (substantially spherical shape). Further, the primary particles 23 are in a dry state from which a liquid material such as a solvent used for forming the primary particles 23 is removed. Furthermore, the average particle diameter of the primary particle 23 should just be formed in the range whose average particle diameter is 5 micrometers or more and less than 100 micrometers, for example. In addition, the manufacturing method of the primary particle 23 having such a configuration will be described in detail later.
  • FIG. 2B is a cross-sectional view showing another example of the forming material for forming the fuel cell electrode layer.
  • a forming material for forming the fuel cell electrode layer is composed of a solution 29 in which the primary particles 23 and the second ion conductive polymer 22 described above are dispersed in a solvent 28.
  • the solution 29 contains a catalyst ink that is a material for forming a fuel cell electrode layer.
  • the second ion conductive polymer 22 may be the same as the first ion conductive polymer 24, for example, an ionomer resin.
  • the solvent 28 should just be a liquid mixture of organic solvents, such as isopropanol, and water, for example.
  • the electrode layer By spraying or applying the solution 29, which is a material for forming the electrode layer for a fuel cell, toward the polymer electrolyte membrane or the diffusion layer that constitutes the cell of the fuel cell,
  • the electrode layer can be easily formed.
  • the membrane electrode assembly (MEA) 9 includes an anode electrode layer (fuel cell electrode layer) 6 and a cathode electrode layer (fuel cell electrode layer) 7 formed on one surface and the other surface of the polymer electrolyte membrane 5, respectively. It is configured.
  • the anode electrode layer (fuel cell electrode layer) 6 and the cathode electrode layer (fuel cell electrode layer) 7 have a thickness of about 10 to 100 ⁇ m, for example, and innumerable secondary particles 21 are subjected to second ion conduction. It is comprised from the aggregate
  • the secondary particles 21 are aggregated in a state close to point contact with each other, and are porous with a high porosity like a sponge.
  • the secondary particles 21 may be, for example, irregular particles having a maximum side of 10 ⁇ m or more and less than 1000 ⁇ m. Such secondary particles 21 are composed of aggregates of the primary particles 23 having the above-described configuration. The primary particles 23 are aggregated in a state close to point contact with each other, and are porous with a high porosity like a sponge. These primary particles 23 are bonded together by a second ion conductive polymer 22 to form secondary particles 21.
  • the second ion conductive polymer 22 may be, for example, an ionomer resin.
  • a membrane electrode assembly (MEA) 9 including an anode electrode layer (fuel cell electrode layer) 6 and a cathode electrode layer (fuel cell electrode layer) 7 having the above-described configuration a fuel cell, for example, a solid If a molecular fuel cell is formed, a fuel cell capable of generating power efficiently can be realized.
  • the anode electrode layer (fuel cell electrode layer) 6 and the cathode electrode layer (fuel cell electrode layer) 7 are secondary particles in which a large number of primary particles 23 in which a large number of catalyst-carrying particles 27 are aggregated are aggregated in a cluster shape.
  • the particles 21 and forming the secondary particles 21 in a sponge-like porous shape By forming the particles 21 and forming the secondary particles 21 in a sponge-like porous shape, an electrode layer that facilitates intrusion and diffusion of fuel and oxidant and has excellent ion conductivity is formed. . As a result, the power generation efficiency is increased and a high-performance fuel cell can be realized.
  • an electrode layer for a fuel cell of the present invention by using the material for forming an electrode layer for a fuel cell of the present invention, an electrode layer that facilitates the penetration and diffusion of the fuel and the oxidant as described above and has excellent ion conductivity can be obtained with a small number of steps. It can be formed easily and at low cost.
  • the formation of the electrode layer includes the concept of injecting, injecting, applying, and dropping a solution to form particles, and the solution is applied to an object (object to be sprayed). It shows that it is applied and spread in layers.
  • the target indicates a polymer electrolyte membrane or diffusion layer constituting a fuel cell, that is, a layer on which an anode electrode layer or a cathode electrode layer is formed.
  • FIG. 3 is a schematic view showing a method for producing an electrode layer for a fuel cell according to the present invention.
  • an electrode layer When forming an anode electrode layer or a cathode electrode layer (hereinafter simply referred to as an electrode layer), first, primary particles are first formed as shown in FIG.
  • the catalyst-supporting particles 31 in which the catalyst is supported on the support, the first ion conductive polymer 32, and the first solvent 38 are mixed to obtain the first solution (catalyst ink) 34.
  • the catalyst-carrying particles 31 may be, for example, those obtained by carrying a catalytic metal such as platinum, palladium, iridium or the like having an average particle size of about 1 to 5 nm on a support made of carbon powder having an average particle size of about 10 to 80 nm. That's fine.
  • the catalyst-carrying particles 31 may be a catalyst made of an inorganic substance or an organic substance in addition to the metal.
  • the first ion conductive polymer 32 may be, for example, an ionomer resin.
  • the 1st solvent 38 should just be a liquid mixture of organic solvents, such as isopropanol, and water, for example.
  • this 1st solution 34 is sprayed toward flat plates, such as the collection tray 42, for example using the ultrasonic spray apparatus 41 (spraying process).
  • primary particles (raw material particles) 33 in which countless catalyst-supporting particles 31 are aggregated via the first ion conductive polymer 32 are formed on the recovery tray 42.
  • liquid material such as the first solvent 38 contained in the first solution 34 is volatilized by the drying means 36 until the sprayed mist-like first solution 34 reaches the collection tray 42.
  • the drying unit 36 include a method of increasing the interval T between the spray port of the ultrasonic spray device 41 and the collection tray 42 to promote volatilization of the first solvent 38.
  • a method of promoting volatilization of the first solvent 38 using a heater 36a such as an infrared lamp is also preferable.
  • the primary particles 33 thus obtained are, for example, substantially spherical aggregates in which the catalyst-carrying particles 31 are aggregated innumerably via the first ion conductive polymer 32, and the average particle diameter is 5 ⁇ m or more and less than 100 ⁇ m. It is formed in the range. Porous pores of about 0.1 to 0.5 ⁇ m are formed inside. Further, the drying means 36 volatilizes the liquid material such as the first solvent 38 to make it dry.
  • the ultrasonic spray device 41 applies ultrasonic vibration of, for example, about 20 to 100 kHz from the ultrasonic oscillator to the first solution 34 to make the first solution 34 a mist made of fine particles.
  • the ultrasonic output of the ultrasonic spray device 41 may be about 3 to 10 W, for example.
  • a method of spraying using an ultrasonic spray device is preferable because fine particles are obtained and the residence time in the atmosphere is long and easy to dry.
  • any device can be used as long as the first solution 34 can be made into fine particles, such as an ordinary air spray device, and is not limited.
  • the dried substantially spherical primary particles (raw material particles) 33 obtained by the spraying step, the second ion conductive polymer 51, and the second solvent 52 are mixed.
  • a second solution (solvent ink) 37 is obtained.
  • the second ion conductive polymer 51 may be the same as the first ion conductive polymer 32, for example, an ionomer resin.
  • the second solvent 52 may be a mixed liquid of an organic solvent such as isopropanol and water.
  • an electrode layer is formed on the target 55, that is, the polymer electrolyte membrane or the diffusion layer constituting the fuel cell (electrode layer forming step).
  • secondary particles 57 formed by aggregating innumerable primary particles (raw material particles) 33 via the second ion conductive polymer 51 are formed on the target 55 on the target 55, and the electrode layer 59 and become.
  • the electrode layer 59 may be formed by coating with a die coater or the like.
  • the obtained secondary particles 57 include, for example, a large number of primary particles (raw material particles) 33 gathered through the second ion conductive polymer 51, that is, a large number of primary particles (raw material particles) 33 are first particles.
  • a substantially spherical or amorphous aggregate covered with the second ion conductive polymer 51 is formed.
  • Such secondary particles 57 are formed, for example, in a range having a maximum side of 10 ⁇ m or more and 1000 ⁇ m.
  • the secondary particles 57 are formed in a large number of layers, and an electrode layer 59, that is, an anode electrode layer and a cathode electrode layer are formed.
  • an electrode layer 59 has sufficient gas permeability from the pores present in the primary particles (raw material particles) 33 and the sponge-like gaps between the primary particles 33 when the primary particles 33 are aggregated.
  • the catalyst efficiency is increased by increasing the exposed surface area.
  • the proton conductivity is improved and the electron conductivity due to the binding of the primary particles 33 is improved. Therefore, it is possible to form an electrode layer 59 for a fuel cell that allows easy penetration and diffusion of fuel and oxidant and is excellent in ion conductivity.
  • FIG. 4A, FIG. 4C, and FIG. 4E are examples of the present invention in which primary particles (raw material particles) are formed in the spraying process and an electrode layer composed of secondary particles is formed using the primary particles as described above. It is a microscope picture which shows the mode of the electrode layer in. Moreover, FIG. 4B, FIG. 4D, and FIG. 4F are the microscope pictures which show the mode of the electrode layer formed in one step (one process) using the air spray apparatus as a comparative example. 4A and 4B were taken at 200 times, FIGS. 4C and 4D were taken at 500 times, and FIGS. 4E and 4F were taken at 1000 times, respectively.
  • the electrode layer formed by the manufacturing method of the present invention has more fine voids and promotes the porous structure than the electrode layer of the comparative example. .
  • the electrode layer formed by the manufacturing method of the present invention can easily penetrate and diffuse the fuel and oxidant.
  • the electrode layer formed by the production method of the present invention is connected to each other in a network form, although there are many fine voids. As a result, the electrode layer formed by the production method of the present invention is also excellent in ion conductivity.
  • the electrode layer of the comparative example slit-like thin cracks can be seen, but it can be seen that there are few voids as a whole compared to the examples of the present invention, and the surface area is small because of no increase in porosity. Therefore, in the electrode layer of the comparative example, it seems that intrusion and diffusion of fuel and oxidant are inferior. From the above, the effect of the method for producing a fuel cell electrode layer according to the present invention was confirmed.
  • FIG. 5 shows a graph obtained by measuring the relationship between the voltage value and the current density for the membrane electrode assembly (MEA) according to the present invention and the membrane electrode assembly of the comparative example.
  • the membrane electrode assembly (MEA) of the present invention as described in the above-described embodiment, is a two-stage formation in which, after producing primary particles, an electrode layer including secondary particles is formed using the primary particles. It is manufactured.
  • the membrane electrode assembly of the comparative example is manufactured by one-step formation in which an electrode layer is formed on a target using a solution in which catalyst-carrying particles and an ion conductive polymer are dispersed in a solvent.
  • the membrane electrode assembly (MEA) of the present invention has a higher voltage value with respect to the current density than the membrane electrode assembly of the comparative example. As a result, it was confirmed that the membrane electrode assembly (MEA) of the present invention can obtain excellent power generation characteristics when used as a fuel cell.
  • an electrode layer for a fuel cell According to the material for forming an electrode layer for a fuel cell, a membrane electrode assembly for a fuel cell, and a fuel cell according to the present invention, sufficient gas permeability is provided, and the catalyst efficiency is increased by increasing the exposed surface area of the catalyst.
  • An electrode layer for a fuel cell with improved conductivity and improved electron conductivity due to the binding of primary particles can be easily formed at low cost with few steps.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Fuel Cell (AREA)
  • Inert Electrodes (AREA)

Abstract

A material for use in the formation of an electrode layer for a fuel cell, which comprises at least approximately spherical primary particles, wherein each of the primary particles comprises at least a catalyst-supported particle comprising a carrier and a catalyst supported on the carrier and a first ion-conductive polymer and has been dried by removing any liquid material therefrom.

Description

燃料電池用電極層の形成材料、燃料電池用膜電極接合体、燃料電池、燃料電池用電極層の形成材料の製造方法、燃料電池用電極層の製造方法FORMING MATERIAL FOR FUEL CELL ELECTRODE LAYER, MEMBRANE ELECTRODE ASSEMBLY FOR FUEL CELL, FUEL CELL, METHOD FOR PRODUCING FORMING MATERIAL FOR ELECTRODE LAYER FOR CELL CELL,
　本発明は、固体高分子形燃料電池に好適な燃料電池用電極層の形成材料、燃料電池用膜電極接合体、燃料電池、燃料電池用電極層の形成材料の製造方法、燃料電池用電極層の製造方法に関する。詳しくは、電極層粒子の二重構造によって、ガス拡散通路や生成水の排出路の確保による電極層の実質的な表面積の増加やイオン伝導性を向上させ、セル特性の向上を図ったものである。
　本願は、２００８年１０月２３日に、日本に出願された特願２００８－２７３０９５号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a fuel cell electrode layer forming material suitable for a polymer electrolyte fuel cell, a fuel cell membrane electrode assembly, a fuel cell, a method for producing a fuel cell electrode layer forming material, and a fuel cell electrode layer. It relates to the manufacturing method. Specifically, the double layer structure of the electrode layer particles is intended to improve the cell characteristics by increasing the substantial surface area of the electrode layer and improving the ionic conductivity by securing the gas diffusion passage and the discharge passage of the generated water. is there.
This application claims priority based on Japanese Patent Application No. 2008-273095 filed in Japan on October 23, 2008, the contents of which are incorporated herein by reference.
　図６は、固体高分子形燃料電池の反応部をなす膜電極接合体（ＭＥＡ）の一例を示すものである。
　高分子電解質膜１０１の一面には、例えば厚さ２０μｍ程度のアノード電極層１０２が形成される。また、高分子電解質膜１０１の他面には、例えば、厚さ２０μｍ程度のカソード電極層１０３が形成される。膜電極接合体１００は、これら高分子電解質膜１０１，アノード電極層１０２，カソード電極層１０３が一体化されてなる。更に、アノード電極層１０２およびカソード電極層１０３の表面には、カーボンペーパーなどの拡散層（図示せず）が設けられているのが好ましい。 FIG. 6 shows an example of a membrane electrode assembly (MEA) forming a reaction part of a polymer electrolyte fuel cell.
On one surface of the polymer electrolyte membrane 101, for example, an anode electrode layer 102 having a thickness of about 20 μm is formed. On the other surface of the polymer electrolyte membrane 101, for example, a cathode electrode layer 103 having a thickness of about 20 μm is formed. The membrane electrode assembly 100 is formed by integrating the polymer electrolyte membrane 101, the anode electrode layer 102, and the cathode electrode layer 103. Furthermore, it is preferable that a diffusion layer (not shown) such as carbon paper is provided on the surfaces of the anode electrode layer 102 and the cathode electrode layer 103.
　高分子電解質膜１０１には、例えば、厚さ３０～７０μｍ程度のパーフルオロスルホン酸系ポリマーなどからなるフィルムが用いられる。アノード電極層１０２およびカソード電極層１０３には、例えば、触媒を分散させた液体（以下、触媒インクと称する）を拡散層となるカーボンペーパーに塗布し、乾燥したものが用いられる。 As the polymer electrolyte membrane 101, for example, a film made of a perfluorosulfonic acid polymer having a thickness of about 30 to 70 μm is used. For the anode electrode layer 102 and the cathode electrode layer 103, for example, a liquid in which a catalyst is dispersed (hereinafter referred to as catalyst ink) is applied to carbon paper serving as a diffusion layer and dried.
　触媒インクとしては、例えば粒径２～５ｎｍ程度の白金微粒子などからなる触媒粒子を、粒径３０ｎｍ程度のカーボン粒子など導電性の触媒体に担持させた触媒担持粒子を用い、この触媒担持粒子をイオン伝導性ポリマー、イソプロパノール、水などからなる高分子電解質溶液に分散させたものが用いられる。 As the catalyst ink, for example, catalyst-supported particles in which catalyst particles made of platinum particles having a particle diameter of about 2 to 5 nm are supported on a conductive catalyst body such as carbon particles having a particle diameter of about 30 nm are used. A material dispersed in a polymer electrolyte solution made of an ion conductive polymer, isopropanol, water or the like is used.
　これらアノード電極層１０２、カソード電極層１０３が形成されたカーボンペーパーを高分子電解質膜１０１の両面に接合して、膜電極接合体１００が形成される。なお、触媒インクを高分子電解質膜１０１の両面にそれぞれ塗布して電極層１０２、１０３を形成したのち、これに拡散層を接合して膜電極接合体１０１とする製法もある。 The membrane electrode assembly 100 is formed by bonding the carbon paper on which the anode electrode layer 102 and the cathode electrode layer 103 are formed on both surfaces of the polymer electrolyte membrane 101. There is also a production method in which catalyst ink is applied to both surfaces of the polymer electrolyte membrane 101 to form electrode layers 102 and 103, and then a diffusion layer is joined to the membrane electrode assembly 101.
　拡散層または高分子電解質膜（以下、これらをターゲットと称する）へ触媒インクを塗布する方法として、従来、エアスプレー装置を用いて、触媒インクをターゲットに向けて噴霧する方法が採用されていた。しかし、従来のエアスプレー装置を用いる方法では、形成した電極層における触媒担持粒子が不均一に分散しやすいという懸念があった。 As a method of applying the catalyst ink to the diffusion layer or the polymer electrolyte membrane (hereinafter referred to as a target), a method of spraying the catalyst ink toward the target using an air spray device has been conventionally employed. However, in the method using the conventional air spray device, there is a concern that the catalyst-carrying particles in the formed electrode layer are easily dispersed unevenly.
　こうした従来のエアスプレー装置を用いて電極層を形成する際の課題を解決する方法として、例えば、超音波スプレー装置による塗布方法が提案されている（特許文献１、２参照）。超音波スプレー装置を用いた塗布方法では、得られた電極層における触媒担持粒子の分散を均一にできるというメリットがあるとされる。 As a method for solving the problems in forming an electrode layer using such a conventional air spray device, for example, a coating method using an ultrasonic spray device has been proposed (see Patent Documents 1 and 2). The coating method using an ultrasonic spray device is said to have an advantage that the catalyst-supported particles can be uniformly dispersed in the obtained electrode layer.
特開２００６－２１０２００号公報JP 2006-210200 A 特開２００６－２３６８８１号公報JP 2006-236881 A
　しかしながら、従来の超音波スプレー装置によって形成した電極層は、従来のエアスプレー装置によって形成した電極層と同様に、触媒担持粒子どうしが合体して成長し、成長した粒子群が結合した構造の電極層が得られるに過ぎなかった。 However, the electrode layer formed by the conventional ultrasonic spray device is an electrode having a structure in which the catalyst-supported particles grow together and the grown particle groups are combined, like the electrode layer formed by the conventional air spray device. Only a layer was obtained.
　即ち、膜電極接合体を構成する電極層は、ガスの透過性（拡散性）を確保しつつ、イオン伝導性にも優れているものが好ましいが、従来の超音波スプレー装置によって形成した電極層では、触媒担持粒子どうしが合体して成長し、成長した粒子群の空隙が充分に形成されないため、ガスの透過性に課題があった。また、同時に凝集により反応に寄与しない触媒が増加して性能を低下させる原因となっていた。 That is, it is preferable that the electrode layer constituting the membrane electrode assembly is excellent in ion conductivity while ensuring gas permeability (diffusibility). However, an electrode layer formed by a conventional ultrasonic spray device. In this case, the catalyst-supported particles grow together and the voids of the grown particles are not sufficiently formed, so there is a problem in gas permeability. At the same time, the number of catalysts that do not contribute to the reaction increases due to agglomeration, which causes a decrease in performance.
　本発明は、上述したような課題を解決するためになされたものであり、触媒反応に関与する実質的な表面積を大きくし、燃料、酸化剤の侵入、拡散が容易であり、かつ、イオン伝導性にも優れる燃料電池用電極層を形成することができる燃料電池用電極層の形成材料、燃料電池用膜電極接合体、燃料電池を提供することを目的とする。 The present invention has been made in order to solve the above-described problems, increases the substantial surface area involved in the catalytic reaction, facilitates intrusion and diffusion of fuel and oxidant, and provides ion conduction. An object of the present invention is to provide a fuel cell electrode layer forming material, a fuel cell membrane electrode assembly, and a fuel cell capable of forming a fuel cell electrode layer that is excellent in performance.
　上記課題を解決するために、本発明は次のような燃料電池用電極層の形成材料、燃料電池用膜電極接合体、燃料電池、燃料電池用電極層の形成材料の製造方法、燃料電池用電極層の製造方法を提供する。
　すなわち、本発明の燃料電池用電極層の形成材料は、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーとを少なくとも含む一次粒子であって、液状物を除去した乾燥状態にある略球形の一次粒子を少なくとも含む。 In order to solve the above problems, the present invention provides a fuel cell electrode layer forming material, a fuel cell membrane electrode assembly, a fuel cell, a method for producing a fuel cell electrode layer forming material, and a fuel cell A method for producing an electrode layer is provided.
That is, the material for forming the electrode layer for a fuel cell according to the present invention is primary particles including at least catalyst-carrying particles in which a catalyst is carried on a carrier and a first ion-conductive polymer, and a liquid substance is removed. It includes at least substantially spherical primary particles in a dry state.
　前記一次粒子の平均粒径は、５μｍ以上１００μｍ未満であればよい。 The average particle diameter of the primary particles may be 5 μm or more and less than 100 μm.
　前記一次粒子と、第二のイオン伝導性ポリマーとを溶剤に分散させたものであってもよい。 The primary particles and the second ion conductive polymer may be dispersed in a solvent.
　本発明の燃料電池用膜電極接合体は、電解質を担持させた電解質膜の少なくとも一方の面に形成され、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーとを少なくとも含む一次粒子であって、液状物を除去した乾燥状態にある略球形の一次粒子を、第二のイオン伝導性ポリマーによって多数凝集させた二次粒子を少なくとも含む電極層を有する。 The membrane electrode assembly for a fuel cell according to the present invention comprises catalyst-carrying particles formed on at least one surface of an electrolyte membrane carrying an electrolyte and carrying a catalyst on the carrier, and a first ion conductive polymer. The electrode layer includes at least secondary particles obtained by agglomerating a plurality of substantially spherical primary particles in a dry state from which a liquid material is removed, which are at least primary particles, which are aggregated with a second ion conductive polymer.
　前記一次粒子の平均粒径は、５μｍ以上１００μｍ未満であり、前記二次粒子の最大辺は、１０μｍ以上１０００μｍ以下であることが好ましい。 The average particle diameter of the primary particles is preferably 5 μm or more and less than 100 μm, and the maximum side of the secondary particles is preferably 10 μm or more and 1000 μm or less.
　本発明の燃料電池は、電極層の少なくとも一方が、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーとを少なくとも含む一次粒子であって、液状物を除去した乾燥状態にある略球形の一次粒子を、第二のイオン伝導性ポリマーによって多数凝集させた二次粒子を少なくとも含む電極層を有する。 In the fuel cell of the present invention, at least one of the electrode layers is a primary particle containing at least a catalyst-carrying particle in which a catalyst is carried on a carrier and a first ion-conductive polymer, and a dry material from which a liquid material has been removed The electrode layer includes at least secondary particles obtained by agglomerating a large number of substantially spherical primary particles in a state with a second ion conductive polymer.
　前記一次粒子の平均粒径は、５μｍ以上１００μｍ未満であり、前記二次粒子の最大辺は、１０μｍ以上１０００μｍ以下であることが好ましい。 The average particle diameter of the primary particles is preferably 5 μm or more and less than 100 μm, and the maximum side of the secondary particles is preferably 10 μm or more and 1000 μm or less.
　本発明の燃料電池用電極層の形成材料の製造方法は、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーと、第一の溶剤とを少なくとも含んだ第一溶液を大気中に噴霧して、溶剤を揮発させ、乾燥した略球状の一次粒子を得る噴霧工程を備える。 The method for producing a material for forming an electrode layer for a fuel cell according to the present invention includes a first solution containing at least catalyst-carrying particles in which a catalyst is supported, a first ion-conductive polymer, and a first solvent. Is sprayed in the atmosphere to volatilize the solvent, and a spraying step for obtaining dried substantially spherical primary particles is provided.
　前記噴霧工程は、超音波スプレー装置を用いて前記第一溶液を噴霧するのが好ましい。 The spraying step is preferably performed by spraying the first solution using an ultrasonic spray device.
　本発明の燃料電池用電極層の製造方法は、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーと、第一の溶剤とを少なくとも含んだ第一溶液を大気中に噴霧して、溶剤を揮発させ、乾燥した略球状の一次粒子を得る噴霧工程と、前記一次粒子と、第二のイオン伝導性ポリマーと、第二の溶剤とを少なくとも含んだ第二溶液を、電解質膜または拡散層を含むターゲットの少なくとも一面に噴霧することで、前記一次粒子を前記第二のイオン伝導性ポリマーによって多数凝集させた二次粒子を少なくとも含む電極層を前記ターゲットの少なくとも一面に形成する電極層形成工程と、を少なくとも含む。 The method for producing an electrode layer for a fuel cell according to the present invention comprises a first solution containing at least catalyst-carrying particles having a catalyst supported on a carrier, a first ion-conductive polymer, and a first solvent in the atmosphere. Spraying to vaporize the solvent to obtain dried substantially spherical primary particles, and a second solution containing at least the primary particles, the second ion-conductive polymer, and the second solvent. The electrode layer containing at least secondary particles obtained by aggregating a number of the primary particles with the second ion conductive polymer by spraying on at least one surface of the target including the electrolyte membrane or the diffusion layer is provided on at least one surface of the target. An electrode layer forming step to be formed.
　本発明の燃料電池用電極層の形成材料、燃料電池用膜電極接合体、燃料電池によれば、充分なガス透過性を備え、触媒の露出表面積の増加による触媒効率が高められ、かつ、プロトン導電性の向上と、一次粒子どうしの結着による電子伝導性が向上した燃料電池用の電極層を、少ない工程で容易に、かつ低コストに形成できる。 According to the material for forming an electrode layer for a fuel cell, a membrane electrode assembly for a fuel cell, and a fuel cell according to the present invention, sufficient gas permeability is provided, and the catalyst efficiency is increased by increasing the exposed surface area of the catalyst. An electrode layer for a fuel cell with improved conductivity and improved electron conductivity due to the binding of primary particles can be easily formed at low cost with few steps.
　本発明の燃料電池用電極層の形成材料の製造方法、燃料電池用電極層の製造方法によれば、噴霧工程によって一次粒子を形成するので、一次粒子どうしの凝集を防止し反応に寄与しない触媒を低減することができる。また、この一次粒子を用いて二次粒子からなる電極層を形成することにより、多数の一次粒子がイオン伝導性ポリマーを介して無数に集合した、即ち、多数の一次粒子が第二のイオン伝導性ポリマーによって覆われた略球状、ないし不定形な集合体からなる電極層を形成することができる。こうした電極層は、一次粒子（原料粒子）に存在する細孔と、二次粒子内の一次粒子どうしのスポンジ状の隙間と二次粒子間の大きな隙間から、充分なガス透過性を備え、触媒の露出表面積の増加による触媒効率が高められる。 According to the method for producing a material for forming an electrode layer for a fuel cell and a method for producing an electrode layer for a fuel cell according to the present invention, primary particles are formed by a spraying process, and therefore a catalyst that prevents aggregation of primary particles and does not contribute to the reaction. Can be reduced. In addition, by forming an electrode layer composed of secondary particles using the primary particles, a large number of primary particles are aggregated via an ion conductive polymer, that is, a large number of primary particles are second ion conductive. It is possible to form an electrode layer made of a substantially spherical or amorphous aggregate covered with a conductive polymer. Such an electrode layer has sufficient gas permeability from the pores present in the primary particles (raw material particles), the sponge-like gaps between the primary particles in the secondary particles, and the large gaps between the secondary particles. The catalyst efficiency is increased by increasing the exposed surface area.
　しかも、二次粒子のイオン伝導性ポリマーによる被覆で、プロトン導電性の向上と、一次粒子どうしの結着による電子伝導性が向上する。よって、燃料、酸化剤の侵入、拡散が容易であり、かつ、イオン伝導性にも優れた燃料電池用の電極層を形成することが可能になる。 In addition, by covering the secondary particles with the ion conductive polymer, the proton conductivity is improved and the electron conductivity is improved due to the binding between the primary particles. Therefore, it is possible to form an electrode layer for a fuel cell that allows easy penetration and diffusion of fuel and oxidant and is excellent in ion conductivity.
本発明の燃料電池用電極層を備えた燃料電池の一例を示す分解斜視図である。It is a disassembled perspective view which shows an example of the fuel cell provided with the electrode layer for fuel cells of this invention. 本発明の燃料電池用電極層、およびその形成材料の一例を示す拡大断面図である。It is an expanded sectional view which shows an example of the electrode layer for fuel cells of this invention, and its formation material. 本発明の燃料電池用電極層の製造方法の一例を示す断面図である。It is sectional drawing which shows an example of the manufacturing method of the electrode layer for fuel cells of this invention. 本発明の実施例を示す顕微鏡写真である。It is a microscope picture which shows the Example of this invention. 比較例を示す顕微鏡写真である。It is a microscope picture which shows a comparative example. 本発明の実施例を示す顕微鏡写真である。It is a microscope picture which shows the Example of this invention. 比較例を示す顕微鏡写真である。It is a microscope picture which shows a comparative example. 本発明の実施例を示す顕微鏡写真である。It is a microscope picture which shows the Example of this invention. 比較例を示す顕微鏡写真である。It is a microscope picture which shows a comparative example. 本発明による膜電極接合体（ＭＥＡ）と、比較例の膜電極接合体について、電圧値と電流密度との関係を測定したグラフである。It is the graph which measured the relationship between a voltage value and a current density about the membrane electrode assembly (MEA) by this invention, and the membrane electrode assembly of a comparative example. 従来技術の燃料電池用電極層の一例を示す断面図である。It is sectional drawing which shows an example of the electrode layer for fuel cells of a prior art.
　以下、本発明に係る燃料電池用電極層の製造方法、および燃料電池用電極層の一実施形態を、図面に基づいて説明する。なお、本発明はこのような実施形態に限定されるものではない。また、以下の説明で用いる図面は、本発明の特徴をわかりやすくするために、便宜上、要部となる部分を拡大して示している場合があり、各構成要素の寸法比率などが実際と同じであるとは限らない。 Hereinafter, an embodiment of a method for producing a fuel cell electrode layer and a fuel cell electrode layer according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to such an embodiment. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.
　図１は、本発明に係る燃料電池用電極層を備えた燃料電池の一例を示す分解斜視図である。
　この燃料電池１は、例えばメタノールを燃料とするものであり、図１に示すように、発電を行うための単位セル２を備えている。そして、燃料電池１はこの単位セル２がセパレータ４により挟持されて構成されている。こうした燃料電池１は、単位セル２が１個から構成されるものであってもよいが、通常、充分な出力を得るために、単位セル２を重ねてそれらが一つのパッケージとして使用される。このパッケージは、図中のスタック３に相当する。 FIG. 1 is an exploded perspective view showing an example of a fuel cell provided with an electrode layer for a fuel cell according to the present invention.
The fuel cell 1 uses, for example, methanol as a fuel, and includes a unit cell 2 for generating power as shown in FIG. The fuel cell 1 is configured by sandwiching the unit cell 2 with a separator 4. Such a fuel cell 1 may be composed of a single unit cell 2, but normally, in order to obtain a sufficient output, the unit cells 2 are stacked and used as one package. This package corresponds to the stack 3 in the figure.
　単位セル２は、膜電極接合体（ＭＥＡ）９と、この膜電極接合体９を挟持するセパレータ４とから構成される。膜電極接合体９は、高分子電解質膜５と、この高分子電解質膜５の一面に形成されたアノード電極層６と、高分子電解質膜５の他面に形成されたカソード電極層７とが一体化されてなる。更に、アノード電極層６およびカソード電極層７の表面には、カーボンペーパー等からなる拡散層（図示せず）が設けられる。 The unit cell 2 is composed of a membrane electrode assembly (MEA) 9 and a separator 4 sandwiching the membrane electrode assembly 9. The membrane electrode assembly 9 includes a polymer electrolyte membrane 5, an anode electrode layer 6 formed on one surface of the polymer electrolyte membrane 5, and a cathode electrode layer 7 formed on the other surface of the polymer electrolyte membrane 5. It is integrated. Furthermore, a diffusion layer (not shown) made of carbon paper or the like is provided on the surfaces of the anode electrode layer 6 and the cathode electrode layer 7.
　セパレータ４には、アノード電極層６に燃料を供給するための燃料供給溝１１や、カソード電極層７に空気が供給するための空気供給溝１４が形成されている。 The separator 4 is formed with a fuel supply groove 11 for supplying fuel to the anode electrode layer 6 and an air supply groove 14 for supplying air to the cathode electrode layer 7.
　以上のような構成の燃料電池１の運転時には、アノード電極層６に燃料供給溝１１を介して燃料ガスを供給するとともに、カソード電極層７に空気供給溝１４を介して空気を供給する。すると、アノード電極層６において、燃料ガスであるメタノールと水から二酸化炭素とイオン化された水素（水素イオン）と電子とが生成される（ＣＨ３ＯＨ＋Ｈ２Ｏ　→　ＣＯ２＋６Ｈ＋＋６ｅ－）。これをアノード反応という。 During operation of the fuel cell 1 configured as described above, fuel gas is supplied to the anode electrode layer 6 via the fuel supply groove 11, and air is supplied to the cathode electrode layer 7 via the air supply groove 14. Then, in the anode electrode layer 6, carbon dioxide, ionized hydrogen (hydrogen ions) and electrons are generated from methanol and water as fuel gas (CH 3 OH + H 2 O → CO 2 + 6H + + 6e − ). This is called an anodic reaction.
　これら生成物質のうち、電子は、外部回路を通ってカソード電極層７に電流として流れる。水素イオンは、高分子電解質膜５を通ってカソード電極層７に移動する。また、二酸化炭素は排出される。そして、空気供給溝１４を介して供給された空気中の酸素が、カソード電極層７の全体に送られる。 Among these generated substances, electrons flow as current through the cathode electrode layer 7 through an external circuit. Hydrogen ions move to the cathode electrode layer 7 through the polymer electrolyte membrane 5. Carbon dioxide is also emitted. Then, oxygen in the air supplied through the air supply groove 14 is sent to the entire cathode electrode layer 7.
　そして、カソード電極層７において、これら酸素と水素イオンと電子とが反応して水が生成される（Ｏ２＋４Ｈ＋＋４ｅ－　→　２Ｈ２Ｏ）。これをカソード反応という。ここで生じた水は、アノード側電極部６に向けて環流されることにより、燃料ガスの反応に使用されるとともに、アノード電極層６、カソード電極層７および高分子電解質膜５を保湿する。このようにして、外部回路に流れた電子により生じた電流を直流電流として利用することができる。 In the cathode electrode layer 7, these oxygen, hydrogen ions, and electrons react to generate water (O 2 + 4H + + 4e − → 2H 2 O). This is called a cathodic reaction. The water generated here is circulated toward the anode-side electrode portion 6 to be used for the reaction of the fuel gas, and to keep the anode electrode layer 6, the cathode electrode layer 7 and the polymer electrolyte membrane 5 moisturized. In this way, the current generated by the electrons flowing in the external circuit can be used as a direct current.
　図２は、本発明の燃料電池用電極層、およびその形成材料の一例を示す拡大断面図である。図２のａは、燃料電池用電極層を形成する形成材料を示す断面図である。燃料電池用電極層の形成材料は、微細な粒子である一次粒子２３から構成される。個々の一次粒子２３は、例えば、触媒２５を担持体２６に担持させた触媒担持粒子２７が、第一のイオン伝導性ポリマー２４によって無数に凝集した集合体から構成されている。 FIG. 2 is an enlarged cross-sectional view showing an example of the fuel cell electrode layer of the present invention and a material for forming the electrode layer. FIG. 2 a is a cross-sectional view showing a forming material for forming a fuel cell electrode layer. The material for forming the fuel cell electrode layer is composed of primary particles 23 which are fine particles. Each of the primary particles 23 is composed of, for example, an aggregate in which the catalyst support particles 27 in which the catalyst 25 is supported on the support 26 are infinitely aggregated by the first ion conductive polymer 24.
　なお、触媒担持粒子は、担持体に触媒が担持された形態であれば、どのようなものであってもよい。ここで言う担持とは、例えば、担持体に触媒を分散して担持させたもの、担持体の周囲に触媒の層を形成して担持させたもの、担持体と触媒とを層状に重ねて担持させたものなどが挙げられ、触媒が担持体に対してどのような形態で担持されていても良い。本実施形態のような、微粒子状の触媒２５を担持体２６に担持させた触媒担持粒子２７以外で、好ましい触媒担持粒子の形態としては、例えば、担持体を触媒の薄膜でコーティングしたものが挙げられる。 The catalyst-carrying particles may be in any form as long as the catalyst is carried on the carrier. The term “support” as used herein means, for example, a support in which a catalyst is dispersed and supported on a support, a support in which a catalyst layer is formed around the support, or a support and a catalyst stacked in layers. The catalyst may be supported on the support in any form. As a preferred form of the catalyst-carrying particles other than the catalyst-carrying particles 27 in which the particulate catalyst 25 is carried on the carrier 26 as in the present embodiment, for example, the carrier is coated with a catalyst thin film. It is done.
　触媒２５は、例えば、平均粒径が１～５ｎｍ程度の白金、パラジウム、イリジウムなどの触媒金属であればよい。また、金属以外の触媒も用いることができる。また、担持体２６は、例えば、平均粒径が１０～８０ｎｍ程度のカーボンパウダーに代表される導電性粒子であればよい。第一のイオン伝導性ポリマー２４は、例えば、アイオノマー樹脂であればよい。 The catalyst 25 may be, for example, a catalyst metal such as platinum, palladium, iridium having an average particle diameter of about 1 to 5 nm. Moreover, catalysts other than metals can also be used. The carrier 26 may be conductive particles typified by carbon powder having an average particle size of about 10 to 80 nm, for example. The first ion conductive polymer 24 may be, for example, an ionomer resin.
　一次粒子２３は、球形ないしこれに近い形状（略球形）に形成されればよい。また、一次粒子２３は、この一次粒子２３を形成する際に使われる溶剤などの液状物を除去した乾燥状態にされる。更に、一次粒子２３の平均粒径は、例えば、平均粒径が５μｍ以上１００μｍ未満の範囲に形成されていればよい。なお、このような構成の一次粒子２３の製造方法は、後ほど詳述する。 The primary particles 23 may be formed in a spherical shape or a shape close to this (substantially spherical shape). Further, the primary particles 23 are in a dry state from which a liquid material such as a solvent used for forming the primary particles 23 is removed. Furthermore, the average particle diameter of the primary particle 23 should just be formed in the range whose average particle diameter is 5 micrometers or more and less than 100 micrometers, for example. In addition, the manufacturing method of the primary particle 23 having such a configuration will be described in detail later.
　図２のｂは、燃料電池用電極層を形成する形成材料の他の一例を示す断面図である。
　この燃料電池用電極層を形成する形成材料は、上述した一次粒子２３と、第二のイオン伝導性ポリマー２２とを溶剤２８に分散させた溶液２９からなる。溶液２９は、燃料電池用電極層の形成材料である触媒インクを含む。 FIG. 2B is a cross-sectional view showing another example of the forming material for forming the fuel cell electrode layer.
A forming material for forming the fuel cell electrode layer is composed of a solution 29 in which the primary particles 23 and the second ion conductive polymer 22 described above are dispersed in a solvent 28. The solution 29 contains a catalyst ink that is a material for forming a fuel cell electrode layer.
　第二のイオン伝導性ポリマー２２は、第一のイオン伝導性ポリマー２４と同様のもの、例えば、アイオノマー樹脂であればよい。また、溶剤２８は、例えば、イソプロパノールなどの有機溶媒と水との混合液であればよい。 The second ion conductive polymer 22 may be the same as the first ion conductive polymer 24, for example, an ionomer resin. Moreover, the solvent 28 should just be a liquid mixture of organic solvents, such as isopropanol, and water, for example.
　このような、燃料電池用電極層の形成材料である溶液２９を、燃料電池のセルを構成する高分子電解質膜や拡散層に向けて噴霧、ないし塗布することによって、次に説明する燃料電池用電極層を容易に形成することができる。 By spraying or applying the solution 29, which is a material for forming the electrode layer for a fuel cell, toward the polymer electrolyte membrane or the diffusion layer that constitutes the cell of the fuel cell, The electrode layer can be easily formed.
　図２のｃは、本発明の燃料電池用電極層を備えた膜電極接合体（ＭＥＡ）を示す拡大断面図である。膜電極接合体（ＭＥＡ）９は、高分子電解質膜５の一面および他面にそれぞれ形成したアノード電極層（燃料電池用電極層）６、およびカソード電極層（燃料電池用電極層）７とから構成されている。 2c is an enlarged cross-sectional view showing a membrane electrode assembly (MEA) provided with the electrode layer for a fuel cell of the present invention. The membrane electrode assembly (MEA) 9 includes an anode electrode layer (fuel cell electrode layer) 6 and a cathode electrode layer (fuel cell electrode layer) 7 formed on one surface and the other surface of the polymer electrolyte membrane 5, respectively. It is configured.
　アノード電極層（燃料電池用電極層）６、およびカソード電極層（燃料電池用電極層）７は、例えば、厚さ１０～１００μｍ程度のもので、無数の二次粒子２１が第二のイオン伝導性ポリマー２２で包まれるように集合した集合体から構成されている。二次粒子２１は、相互に点接触に近い状態で集合しており、スポンジ状に空隙率が高い多孔質となっている。 The anode electrode layer (fuel cell electrode layer) 6 and the cathode electrode layer (fuel cell electrode layer) 7 have a thickness of about 10 to 100 μm, for example, and innumerable secondary particles 21 are subjected to second ion conduction. It is comprised from the aggregate | assembly assembled so that it might be wrapped with the property polymer 22. The secondary particles 21 are aggregated in a state close to point contact with each other, and are porous with a high porosity like a sponge.
　二次粒子２１は、例えば、最大辺が１０μｍ以上１０００μｍ未満の不定形の粒子でもよい。このような二次粒子２１は、前述した構成の一次粒子２３が集合した集合体から構成されている。この一次粒子２３どうしも、互いに点接触に近い状態で集合しており、スポンジ状に空隙率が高い多孔質となっている。これら一次粒子２３どうしは、第二のイオン伝導性ポリマー２２により結合され、二次粒子２１を構成している。第二のイオン伝導性ポリマー２２は、例えば、アイオノマー樹脂などであればよい。 The secondary particles 21 may be, for example, irregular particles having a maximum side of 10 μm or more and less than 1000 μm. Such secondary particles 21 are composed of aggregates of the primary particles 23 having the above-described configuration. The primary particles 23 are aggregated in a state close to point contact with each other, and are porous with a high porosity like a sponge. These primary particles 23 are bonded together by a second ion conductive polymer 22 to form secondary particles 21. The second ion conductive polymer 22 may be, for example, an ionomer resin.
　以上のような構成のアノード電極層（燃料電池用電極層）６、カソード電極層（燃料電池用電極層）７を備えた膜電極接合体（ＭＥＡ）９を用いて燃料電池、例えば、固体高分子形燃料電池を形成すれば、効率よく発電が可能な燃料電池が実現できる。即ち、アノード電極層（燃料電池用電極層）６、カソード電極層（燃料電池用電極層）７は、触媒担持粒子２７が無数に集合した一次粒子２３を、さらにクラスター状に集合させて二次粒子２１を形成し、この二次粒子２１をスポンジ状に多孔質に形成することによって、燃料、酸化剤の侵入、拡散が容易であり、かつ、イオン伝導性に優れた電極層が形成される。これによって、発電効率が高められ、高性能な燃料電池を実現することが可能になる。 Using a membrane electrode assembly (MEA) 9 including an anode electrode layer (fuel cell electrode layer) 6 and a cathode electrode layer (fuel cell electrode layer) 7 having the above-described configuration, a fuel cell, for example, a solid If a molecular fuel cell is formed, a fuel cell capable of generating power efficiently can be realized. In other words, the anode electrode layer (fuel cell electrode layer) 6 and the cathode electrode layer (fuel cell electrode layer) 7 are secondary particles in which a large number of primary particles 23 in which a large number of catalyst-carrying particles 27 are aggregated are aggregated in a cluster shape. By forming the particles 21 and forming the secondary particles 21 in a sponge-like porous shape, an electrode layer that facilitates intrusion and diffusion of fuel and oxidant and has excellent ion conductivity is formed. . As a result, the power generation efficiency is increased and a high-performance fuel cell can be realized.
　また、本発明の燃料電池用電極層の形成材料を用いれば、上述したような、燃料、酸化剤の侵入、拡散が容易であり、かつ、イオン伝導性に優れた電極層を、少ない工程で容易に、かつ低コストに形成することが可能になる。 Further, by using the material for forming an electrode layer for a fuel cell of the present invention, an electrode layer that facilitates the penetration and diffusion of the fuel and the oxidant as described above and has excellent ion conductivity can be obtained with a small number of steps. It can be formed easily and at low cost.
　次に、上述したような構成の燃料電池用電極層の形成材料の製造方法、燃料電池用電極層の製造方法について説明する。なお、以下の製造方法の説明において、電極層の形成とは、粒子を形成するために、溶液を噴射、射出、塗布、滴下する概念を含み、対象物（被噴霧物）に対して溶液が層状に塗布、展着されることを示すものである。また、ターゲットとは、燃料電池のセルを構成する高分子電解質膜や拡散層、即ち、アノード電極層やカソード電極層が形成される層を示すものである。 Next, a method for manufacturing a material for forming a fuel cell electrode layer configured as described above and a method for manufacturing a fuel cell electrode layer will be described. In the following description of the manufacturing method, the formation of the electrode layer includes the concept of injecting, injecting, applying, and dropping a solution to form particles, and the solution is applied to an object (object to be sprayed). It shows that it is applied and spread in layers. The target indicates a polymer electrolyte membrane or diffusion layer constituting a fuel cell, that is, a layer on which an anode electrode layer or a cathode electrode layer is formed.
　図３は、本発明の燃料電池用電極層の製造方法を示した概略図である。アノード電極層やカソード電極層（以下、単に電極層という）を形成する際には、図３のｄに示すように、まず、最初に一次粒子を形成する。例えば、触媒を担持体に担持させた触媒担持粒子３１と、第一のイオン伝導性ポリマー３２と、第一の溶剤３８とを混合し、第一溶液（触媒インク）３４を得る。 FIG. 3 is a schematic view showing a method for producing an electrode layer for a fuel cell according to the present invention. When forming an anode electrode layer or a cathode electrode layer (hereinafter simply referred to as an electrode layer), first, primary particles are first formed as shown in FIG. For example, the catalyst-supporting particles 31 in which the catalyst is supported on the support, the first ion conductive polymer 32, and the first solvent 38 are mixed to obtain the first solution (catalyst ink) 34.
　触媒担持粒子３１は、例えば、平均粒径が１～５ｎｍ程度の白金、パラジウム、イリジウムなどの触媒金属を、平均粒径が１０～８０ｎｍ程度のカーボンパウダーからなる担持体に担持させたものであればよい。なお、触媒担持粒子３１は、金属以外にも、無機物や有機物からなる触媒であってもよい。また、第一のイオン伝導性ポリマー３２は、例えば、アイオノマー樹脂であればよい。更に、第一の溶剤３８は、例えば、イソプロパノールなどの有機溶媒と水との混合液であればよい。 The catalyst-carrying particles 31 may be, for example, those obtained by carrying a catalytic metal such as platinum, palladium, iridium or the like having an average particle size of about 1 to 5 nm on a support made of carbon powder having an average particle size of about 10 to 80 nm. That's fine. The catalyst-carrying particles 31 may be a catalyst made of an inorganic substance or an organic substance in addition to the metal. The first ion conductive polymer 32 may be, for example, an ionomer resin. Furthermore, the 1st solvent 38 should just be a liquid mixture of organic solvents, such as isopropanol, and water, for example.
　そして、この第一溶液３４を、例えば、超音波スプレー装置４１を用いて、回収トレイ４２などの平板に向けて噴霧する（噴霧工程）。これによって、回収トレイ４２には、無数の触媒担持粒子３１が第一のイオン伝導性ポリマー３２を介して凝集した一次粒子（原料粒子）３３が形成される。 And this 1st solution 34 is sprayed toward flat plates, such as the collection tray 42, for example using the ultrasonic spray apparatus 41 (spraying process). As a result, primary particles (raw material particles) 33 in which countless catalyst-supporting particles 31 are aggregated via the first ion conductive polymer 32 are formed on the recovery tray 42.
　この時、噴霧したミスト状の第一溶液３４が回収トレイ４２に到達するまでに、乾燥手段３６によって、第一溶液３４に含まれる第一の溶剤３８などの液状物を揮発させる。乾燥手段３６としては、例えば、超音波スプレー装置４１の噴射口と回収トレイ４２との間隔Ｔを長く取り、第一の溶剤３８の揮発を促進させる方法が挙げられる。また、赤外線ランプなどヒーター３６ａを用いて、第一の溶剤３８の揮発を促進させる方法も好ましい。 At this time, liquid material such as the first solvent 38 contained in the first solution 34 is volatilized by the drying means 36 until the sprayed mist-like first solution 34 reaches the collection tray 42. Examples of the drying unit 36 include a method of increasing the interval T between the spray port of the ultrasonic spray device 41 and the collection tray 42 to promote volatilization of the first solvent 38. A method of promoting volatilization of the first solvent 38 using a heater 36a such as an infrared lamp is also preferable.
　このようにして得られた一次粒子３３は、例えば、触媒担持粒子３１が第一のイオン伝導性ポリマー３２を介して無数に集合した略球状の集合体であり、平均粒径が５μｍ以上１００μｍ未満の範囲に形成されている。そして、内部に０．１～０．５μｍ程度のポーラスな細孔が形成されている。また、乾燥手段３６によって、第一の溶剤３８などの液状物が揮発し、乾燥状態とされる。 The primary particles 33 thus obtained are, for example, substantially spherical aggregates in which the catalyst-carrying particles 31 are aggregated innumerably via the first ion conductive polymer 32, and the average particle diameter is 5 μm or more and less than 100 μm. It is formed in the range. Porous pores of about 0.1 to 0.5 μm are formed inside. Further, the drying means 36 volatilizes the liquid material such as the first solvent 38 to make it dry.
　噴霧工程における超音波スプレー装置４１は、第一溶液３４に対して、超音波発振子から例えば２０～１００ｋＨｚ程度の超音波振動を与え、第一溶液３４を微細な粒子からなる霧状物とする。超音波スプレー装置４１の超音波出力は、例えば３～１０Ｗ程度であればよい。 In the spraying process, the ultrasonic spray device 41 applies ultrasonic vibration of, for example, about 20 to 100 kHz from the ultrasonic oscillator to the first solution 34 to make the first solution 34 a mist made of fine particles. . The ultrasonic output of the ultrasonic spray device 41 may be about 3 to 10 W, for example.
　なお、こうした噴霧工程で一次粒子（原料粒子）３３を形成する際には、超音波スプレー装置を用いて噴霧する方法が微細な粒子が得られ大気中に滞留する時間が長く乾燥しやすいため好ましいが、通常のエアースプレー装置など、第一溶液３４を微細な粒子にできるものであれば、どのような装置を用いても良く、限定されるものではない。 When forming the primary particles (raw material particles) 33 in such a spraying process, a method of spraying using an ultrasonic spray device is preferable because fine particles are obtained and the residence time in the atmosphere is long and easy to dry. However, any device can be used as long as the first solution 34 can be made into fine particles, such as an ordinary air spray device, and is not limited.
　次に、図３のｅに示すように、噴霧工程によって得た、乾燥した略球形の一次粒子（原料粒子）３３と、第二のイオン伝導性ポリマー５１と、第二の溶剤５２とを混合し、第二溶液（溶媒インク）３７を得る。第二のイオン伝導性ポリマー５１は、第一のイオン伝導性ポリマー３２と同様のもの、例えば、アイオノマー樹脂であればよい。また、第二の溶剤５２も、第一の溶剤３８と同様に、例えば、イソプロパノールなどの有機溶媒と水との混合液であればよい。 Next, as shown in e of FIG. 3, the dried substantially spherical primary particles (raw material particles) 33 obtained by the spraying step, the second ion conductive polymer 51, and the second solvent 52 are mixed. As a result, a second solution (solvent ink) 37 is obtained. The second ion conductive polymer 51 may be the same as the first ion conductive polymer 32, for example, an ionomer resin. Similarly to the first solvent 38, the second solvent 52 may be a mixed liquid of an organic solvent such as isopropanol and water.
　そして、この第二溶液３７を用いて、ターゲット５５、即ち、燃料電池のセルを構成する高分子電解質膜や拡散層に電極層を形成する（電極層形成工程）。これによって、ターゲット５５には、無数の一次粒子（原料粒子）３３が第二のイオン伝導性ポリマー５１を介して凝集してなる二次粒子５７が、ターゲット５５上で形成され、電極層５９となる。 Then, using the second solution 37, an electrode layer is formed on the target 55, that is, the polymer electrolyte membrane or the diffusion layer constituting the fuel cell (electrode layer forming step). As a result, secondary particles 57 formed by aggregating innumerable primary particles (raw material particles) 33 via the second ion conductive polymer 51 are formed on the target 55 on the target 55, and the electrode layer 59 and Become.
　なお、電極層５９の形成方法としては、例えば、例えば、エアースプレー装置４５を用いて、第二溶液３７を噴霧させ、ターゲット５５の一面に付着させる方法が挙げられる。
　他にも、例えば、ダイコーターなどによる塗布によって電極層５９を形成してもよい。 In addition, as a formation method of the electrode layer 59, the method of spraying the 2nd solution 37 using the air spray apparatus 45, for example, and making it adhere to the one surface of the target 55 is mentioned, for example.
In addition, for example, the electrode layer 59 may be formed by coating with a die coater or the like.
　得られた二次粒子５７は、例えば、多数の一次粒子（原料粒子）３３が第二のイオン伝導性ポリマー５１を介して無数に集合した、即ち、多数の一次粒子（原料粒子）３３が第二のイオン伝導性ポリマー５１によって覆われた略球状、ないし不定形な集合体を成す。
　こうした二次粒子５７は、例えば、最大辺が１０μｍ以上１０００μｍの範囲に形成されている。 The obtained secondary particles 57 include, for example, a large number of primary particles (raw material particles) 33 gathered through the second ion conductive polymer 51, that is, a large number of primary particles (raw material particles) 33 are first particles. A substantially spherical or amorphous aggregate covered with the second ion conductive polymer 51 is formed.
Such secondary particles 57 are formed, for example, in a range having a maximum side of 10 μm or more and 1000 μm.
　そして、この二次粒子５７が多数層状に形成され、電極層５９、即ち、アノード電極層やカソード電極層が形成される。こうした電極層５９は、一次粒子（原料粒子）３３に存在する細孔と、一次粒子３３が凝集した際の一次粒子３３どうしのスポンジ状の隙間とから、充分なガス透過性を備え、触媒の露出表面積の増加による触媒効率が高められる。 The secondary particles 57 are formed in a large number of layers, and an electrode layer 59, that is, an anode electrode layer and a cathode electrode layer are formed. Such an electrode layer 59 has sufficient gas permeability from the pores present in the primary particles (raw material particles) 33 and the sponge-like gaps between the primary particles 33 when the primary particles 33 are aggregated. The catalyst efficiency is increased by increasing the exposed surface area.
　しかも、二次粒子５７のイオン伝導性ポリマーの被覆によって、プロトン導電性の向上と、一次粒子３３どうしの結着による電子伝導性が向上している。よって、燃料、酸化剤の侵入、拡散が容易であり、かつ、イオン伝導性にも優れた燃料電池用の電極層５９を形成することが可能になる。 In addition, by covering the secondary particles 57 with the ion conductive polymer, the proton conductivity is improved and the electron conductivity due to the binding of the primary particles 33 is improved. Therefore, it is possible to form an electrode layer 59 for a fuel cell that allows easy penetration and diffusion of fuel and oxidant and is excellent in ion conductivity.
　図４Ａ、図４Ｃ及び図４Ｅは、上述したように、噴霧工程で一次粒子（原料粒子）を形成し、この一次粒子を用いて二次粒子からなる電極層を形成した、本発明の実施例における電極層の様子を示す顕微鏡写真である。また、図４Ｂ、図４Ｄ及び図４Ｆは、比較例として、エアースプレー装置を用いて一段階（一工程）で形成した電極層の様子を示す顕微鏡写真である。倍率は、それぞれ図４Ａ及び図４Ｂが２００倍、図４Ｃ及び図４Ｄが５００倍、図４Ｅ及び図４Ｆが１０００倍で撮影を行った。 FIG. 4A, FIG. 4C, and FIG. 4E are examples of the present invention in which primary particles (raw material particles) are formed in the spraying process and an electrode layer composed of secondary particles is formed using the primary particles as described above. It is a microscope picture which shows the mode of the electrode layer in. Moreover, FIG. 4B, FIG. 4D, and FIG. 4F are the microscope pictures which show the mode of the electrode layer formed in one step (one process) using the air spray apparatus as a comparative example. 4A and 4B were taken at 200 times, FIGS. 4C and 4D were taken at 500 times, and FIGS. 4E and 4F were taken at 1000 times, respectively.
　図４Ａ～図４Ｆに示す顕微鏡写真によれば、本発明の製造方法によって形成した電極層は、比較例の電極層と比較して、細かい空隙が多く多孔質化が促進されていることがわかる。この結果、本発明の製造方法によって形成した電極層は、燃料、酸化剤の侵入、拡散が容易となる。また、本発明の製造方法によって形成した電極層は、細かい空隙が多いにもかかわらず、粒子相互は網目状に繋がっていることがわかる。この結果、本発明の製造方法によって形成した電極層は、イオン伝導性にも優れる。一方、比較例の電極層では、スリット状の細いヒビが見られるが、本発明の実施例と比較して全体的に空隙が少なく、多孔質化が進んでおらず表面積も小さいことがわかる。よって、比較例の電極層では、燃料、酸化剤の侵入、拡散が劣ると思われる。
　以上により、本発明による燃料電池用電極層の製造方法の効果が確認された。 According to the micrographs shown in FIGS. 4A to 4F, it can be seen that the electrode layer formed by the manufacturing method of the present invention has more fine voids and promotes the porous structure than the electrode layer of the comparative example. . As a result, the electrode layer formed by the manufacturing method of the present invention can easily penetrate and diffuse the fuel and oxidant. In addition, it can be seen that the electrode layer formed by the production method of the present invention is connected to each other in a network form, although there are many fine voids. As a result, the electrode layer formed by the production method of the present invention is also excellent in ion conductivity. On the other hand, in the electrode layer of the comparative example, slit-like thin cracks can be seen, but it can be seen that there are few voids as a whole compared to the examples of the present invention, and the surface area is small because of no increase in porosity. Therefore, in the electrode layer of the comparative example, it seems that intrusion and diffusion of fuel and oxidant are inferior.
From the above, the effect of the method for producing a fuel cell electrode layer according to the present invention was confirmed.
　次に、本発明による膜電極接合体（ＭＥＡ）と、比較例の膜電極接合体について、電圧値と電流密度との関係を測定したグラフを図５に示す。本発明の膜電極接合体（ＭＥＡ）は、上述した実施形態に記載した通り、一次粒子を製造した後、この一次粒子を用いて二次粒子を備える電極層を形成した、二段階の形成によって製造したものである。一方、比較例の膜電極接合体は、溶剤に触媒担持粒子とイオン伝導性ポリマーとを分散させた溶液を用いて、ターゲットに電極層を形成した、一段階の形成によって製造したものである。 Next, FIG. 5 shows a graph obtained by measuring the relationship between the voltage value and the current density for the membrane electrode assembly (MEA) according to the present invention and the membrane electrode assembly of the comparative example. The membrane electrode assembly (MEA) of the present invention, as described in the above-described embodiment, is a two-stage formation in which, after producing primary particles, an electrode layer including secondary particles is formed using the primary particles. It is manufactured. On the other hand, the membrane electrode assembly of the comparative example is manufactured by one-step formation in which an electrode layer is formed on a target using a solution in which catalyst-carrying particles and an ion conductive polymer are dispersed in a solvent.
　図５に示すグラフによれば、本発明の膜電極接合体（ＭＥＡ）は、比較例の膜電極接合体よりも電流密度に対する電圧値が高いことが分かる。この結果、本発明の膜電極接合体（ＭＥＡ）は、燃料電池として用いたときに優れた発電特性を得られることが確認された。 According to the graph shown in FIG. 5, it can be seen that the membrane electrode assembly (MEA) of the present invention has a higher voltage value with respect to the current density than the membrane electrode assembly of the comparative example. As a result, it was confirmed that the membrane electrode assembly (MEA) of the present invention can obtain excellent power generation characteristics when used as a fuel cell.
　本発明の燃料電池用電極層の形成材料、燃料電池用膜電極接合体、燃料電池によれば、充分なガス透過性を備え、触媒の露出表面積の増加による触媒効率が高められ、かつ、プロトン導電性の向上と、一次粒子どうしの結着による電子伝導性が向上した燃料電池用の電極層を、少ない工程で容易に、かつ低コストに形成できる。 According to the material for forming an electrode layer for a fuel cell, a membrane electrode assembly for a fuel cell, and a fuel cell according to the present invention, sufficient gas permeability is provided, and the catalyst efficiency is increased by increasing the exposed surface area of the catalyst. An electrode layer for a fuel cell with improved conductivity and improved electron conductivity due to the binding of primary particles can be easily formed at low cost with few steps.
　１　　燃料電池
　２　　単位セル
　３　　スタック
　４　　セパレータ
　５　　高分子電解質膜
　６　　アノード電極層
　７　　カソード電極層
　９　　膜電極接合体
　１１　　燃料供給溝
　１４　　空気供給溝
　２１　　二次粒子
　２２　　第二のイオン伝導性ポリマー
　２３　　一次粒子
　２４　　第一のイオン伝導性ポリマー
　２５　　触媒
　２６　　担持体
　２７　　触媒担持粒子
　２８　　溶剤
　２９　　溶液
　３１　　触媒担持粒子
　３２　　第一のイオン伝導性ポリマー
　３３　　一次粒子（原料粒子）
　３４　　第一溶液（触媒インク）
　３６　　乾燥手段
　３６ａ　　ヒーター
　３７　　第二溶液（触媒インク）
　３８　　第一の溶剤
　４１　　超音波スプレー装置
　４２　　回収トレイ
　４５　　エアースプレー装置
　５１　　第二のイオン伝導性ポリマー
　５２　　第二の溶剤
　５５　　ターゲット
　５７　　二次粒子
　５９　　電極層
　１００　　膜電極接合体
　１０１　　高分子電解質膜
　１０２　　アノード電極層
　１０３　　カソード電極層
　ａ　　燃料電池用電極層を形成する形成材料を示す断面図
　ｂ　　燃料電池用電極層を形成する形成材料の他の一例を示す断面図
　ｃ　　本発明の燃料電池用電極層を備えた膜電極接合体（ＭＥＡ）を示す拡大断面図
　ｄ　　一次粒子を形成する噴霧工程
　ｅ　　電極層形成工程
　Ｔ　　超音波スプレー装置４１の噴射口と回収トレイ４２との間隔 DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Unit cell 3 Stack 4 Separator 5 Polymer electrolyte membrane 6 Anode electrode layer 7 Cathode electrode layer 9 Membrane electrode assembly 11 Fuel supply groove 14 Air supply groove 21 Secondary particle 22 Second ion conductive polymer 23 Primary Particle 24 First ion conductive polymer 25 Catalyst 26 Support 27 Catalyst support particle 28 Solvent 29 Solution 31 Catalyst support particle 32 First ion conductive polymer 33 Primary particle (raw material particle)
34 First solution (catalyst ink)
36 Drying means 36a Heater 37 Second solution (catalyst ink)
38 First Solvent 41 Ultrasonic Spray Device 42 Recovery Tray 45 Air Spray Device 51 Second Ion Conductive Polymer 52 Second Solvent 55 Target 57 Secondary Particle 59 Electrode Layer 100 Membrane Electrode Assembly 101 Polymer Electrolyte Membrane 102 Anode electrode layer 103 Cathode electrode layer a Cross-sectional view showing a forming material for forming a fuel cell electrode layer b Cross-sectional view showing another example of a forming material for forming a fuel cell electrode layer c Fuel cell electrode layer of the present invention FIG. 4 is an enlarged cross-sectional view showing a membrane electrode assembly (MEA) provided with d. Spraying step for forming primary particles e. Electrode layer forming step T. Spacing between injection port of ultrasonic spray device 41 and collection tray 42

Claims (11)

  1. 　触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーとを少なくとも含む一次粒子であって、液状物を除去した乾燥状態にある、略球形の一次粒子を少なくとも含む燃料電池用電極層の形成材料。 A fuel cell comprising at least substantially spherical primary particles, which are primary particles including at least a catalyst-carrying particle having a catalyst supported on a carrier and a first ion-conductive polymer, in a dry state from which a liquid is removed. Material for forming electrode layers.
  2. 　前記一次粒子の平均粒径は、５μｍ以上１００μｍ未満である請求項１記載の燃料電池用電極層の形成材料。 The material for forming a fuel cell electrode layer according to claim 1, wherein the average particle diameter of the primary particles is 5 µm or more and less than 100 µm.
  3. 　前記一次粒子と、第二のイオン伝導性ポリマーとを溶剤に分散させる請求項１または請求項２記載の燃料電池用電極層の形成材料。 The material for forming an electrode layer for a fuel cell according to claim 1 or 2, wherein the primary particles and the second ion conductive polymer are dispersed in a solvent.
  4. 　電解質膜の少なくとも一方の面に形成され、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーとを少なくとも含む一次粒子であって、液状物を除去した乾燥状態にある略球形の一次粒子を、第二のイオン伝導性ポリマーによって多数凝集させた二次粒子を少なくとも含む電極層を有する燃料電池用膜電極接合体。 Primary particles formed on at least one surface of the electrolyte membrane and containing at least a catalyst-carrying particle having a catalyst supported on a carrier and a first ion-conducting polymer, in a dry state from which a liquid material has been removed A membrane electrode assembly for a fuel cell having an electrode layer containing at least secondary particles obtained by aggregating a number of substantially spherical primary particles with a second ion conductive polymer.
  5. 　前記一次粒子の平均粒径は、５μｍ以上１００μｍ未満であり、前記二次粒子の最大辺は、１０μｍ以上１０００μｍ以下である請求項４記載の燃料電池用膜電極接合体。 The membrane electrode assembly for a fuel cell according to claim 4, wherein the average particle diameter of the primary particles is 5 µm or more and less than 100 µm, and the maximum side of the secondary particles is 10 µm or more and 1000 µm or less.
  6. 　電極層の少なくとも一方が、触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーとを少なくとも含む一次粒子であって、液状物を除去した乾燥状態にある略球形の一次粒子を、第二のイオン伝導性ポリマーによって多数凝集させた二次粒子を少なくとも含む電極層を有する燃料電池。 At least one of the electrode layers is a primary particle including at least a catalyst-carrying particle having a catalyst supported on a carrier and a first ion-conductive polymer, and a substantially spherical primary in a dry state from which a liquid is removed A fuel cell having an electrode layer including at least secondary particles obtained by aggregating a large number of particles with a second ion conductive polymer.
  7. 　前記一次粒子の平均粒径は、５μｍ以上１００μｍ未満であり、前記二次粒子の最大辺は、１０μｍ以上１０００μｍ以下である請求項６記載の燃料電池。 The fuel cell according to claim 6, wherein the average particle diameter of the primary particles is 5 µm or more and less than 100 µm, and the maximum side of the secondary particles is 10 µm or more and 1000 µm or less.
  8. 　触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーと、第一の溶剤とを少なくとも含んだ第一溶液を大気中に噴霧して、溶剤を揮発させ、乾燥した略球状の一次粒子を得る噴霧工程を少なくとも含む燃料電池用電極層の形成材料の製造方法。 A first solution containing at least a catalyst-carrying particle having a catalyst supported on a carrier, a first ion-conducting polymer, and a first solvent is sprayed into the atmosphere to volatilize the solvent and then dry. A method for producing a material for forming an electrode layer for a fuel cell, comprising at least a spraying step for obtaining spherical primary particles.
  9. 　前記噴霧工程は、超音波スプレー装置を用いて前記第一溶液を噴霧する工程を少なくとも含む請求項８記載の燃料電池用電極層の形成材料の製造方法。 The method for producing a fuel cell electrode layer forming material according to claim 8, wherein the spraying step includes at least a step of spraying the first solution using an ultrasonic spray device.
  10. 　触媒を担持体に担持させた触媒担持粒子と、第一のイオン伝導性ポリマーと、第一の溶剤とを少なくとも含んだ第一溶液を大気中に噴霧して、溶剤を揮発させ、乾燥した略球状の一次粒子を得る噴霧工程と、
    　前記一次粒子と、第二のイオン伝導性ポリマーと、第二の溶剤とを少なくとも含んだ第二溶液を、電解質膜または拡散層を含むターゲットの少なくとも一面に噴霧することで、前記一次粒子を前記第二のイオン伝導性ポリマーによって多数凝集させた二次粒子を少なくとも含む電極層を前記ターゲットの少なくとも一面に形成する電極層形成工程と、
    を少なくとも含む燃料電池用電極層の製造方法。     A first solution containing at least a catalyst-carrying particle having a catalyst supported on a carrier, a first ion-conducting polymer, and a first solvent is sprayed into the atmosphere to volatilize the solvent and then dry. A spraying step to obtain spherical primary particles;
    By spraying the second solution containing at least the primary particles, the second ion-conductive polymer, and the second solvent onto at least one surface of the target including the electrolyte membrane or the diffusion layer, the primary particles are An electrode layer forming step of forming an electrode layer including at least secondary particles agglomerated by a second ion conductive polymer on at least one surface of the target;
    The manufacturing method of the electrode layer for fuel cells which contains at least.
  11. 　前記噴霧工程は、超音波スプレー装置を用いて前記第一溶液を噴霧する工程を少なくとも含む請求項１０記載の燃料電池用電極層の製造方法。 The method for producing an electrode layer for a fuel cell according to claim 10, wherein the spraying step includes at least a step of spraying the first solution using an ultrasonic spray device.
PCT/JP2009/005590 2008-10-23 2009-10-23 Material for use in formation of electrode layer for fuel cell, membrane electrode assembly for fuel cell, fuel cell, process for producing material for use in formation of electrode layer for fuel cell, and process for producing electrode layer for fuel cell WO2010047125A1 (en)

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