JP2010153145A - Anode electrode for direct-methanol fuel cells, and membrane-electrode complex and fuel cell using the same - Google Patents

Anode electrode for direct-methanol fuel cells, and membrane-electrode complex and fuel cell using the same Download PDF

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JP2010153145A
JP2010153145A JP2008328714A JP2008328714A JP2010153145A JP 2010153145 A JP2010153145 A JP 2010153145A JP 2008328714 A JP2008328714 A JP 2008328714A JP 2008328714 A JP2008328714 A JP 2008328714A JP 2010153145 A JP2010153145 A JP 2010153145A
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anode
fuel cell
layer
direct methanol
methanol fuel
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JP2008328714A
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Yoshihiko Nakano
Atsushi Tamura
Takeshi Ume
義彦 中野
武 梅
淳 田村
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Toshiba Corp
株式会社東芝
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1009Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
    • H01M8/1011Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/86Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88Processes of manufacture
    • H01M4/8803Supports for the deposition of the catalytic active composition
    • H01M4/8807Gas diffusion layers
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/02Details
    • H01M8/0202Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023Porous and characterised by the material
    • H01M8/0241Composites
    • H01M8/0243Composites in the form of mixtures
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/02Details
    • H01M8/0202Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023Porous and characterised by the material
    • H01M8/0241Composites
    • H01M8/0245Composites in the form of layered or coated products
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/86Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90Selection of catalytic material
    • H01M4/92Metals of platinum group
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/50Fuel cells
    • Y02E60/52Fuel cells characterised by type or design
    • Y02E60/521Proton Exchange Membrane Fuel Cells [PEMFC]
    • Y02E60/522Direct Alcohol Fuel Cells [DAFC]
    • Y02E60/523Direct Methanol Fuel Cells [DMFC]

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anode capable of obtaining a high-output direct-methanol fuel cell, as water produced in a cathode is diffused at the anode to deeply influence stability in the fuel cell depending on thickness in an anode layer and a cathode layer and quantity of nafion. <P>SOLUTION: The anode includes an anode catalyst layer 11, a first fuel-diffusion layer 12 formed on the anode catalyst layer, and a hydrophilic conductive layer 13 formed on the first fuel-diffusion layer and comprising a coating film containing a conductive particle and a hydrophilic polymer molecule. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an anode electrode for a direct methanol fuel cell, a membrane electrode composite using the anode electrode, and a fuel cell.

  In a direct methanol fuel cell (DMFC) using methanol as a fuel, methanol is oxidatively decomposed at the fuel electrode to generate carbon dioxide, protons and electrons. On the other hand, in the air electrode, water is generated by oxygen obtained from air, protons supplied from the fuel electrode through the electrolyte membrane, and electrons supplied from the fuel electrode through an external circuit. Electric power is supplied by electrons passing through the external circuit.

  In order to advance power generation with such a configuration, the DMFC is equipped with a pump for supplying methanol and a blower for supplying air as auxiliary devices. As a result, the system becomes complicated, and it is difficult to reduce the size of the DMFC having such a structure.

  A small DMFC (passive DMFC) was constructed as follows. First, the fuel pump was made smaller by increasing the concentration of the fuel used. For intake of air, an air inlet directly attached to the power generation element was installed without using a blower. Due to the use of high concentration fuel, methanol crossover is large. Therefore, it is difficult for this passive DMFC to obtain a high output as compared with a normal active DMFC in which a low concentration fuel is used.

  In such a passive DMFC, water produced at the cathode diffuses into the anode and is used as a fuel. The amount of diffusion water greatly depends on the balance of anode catalyst layer thickness, cathode catalyst layer thickness, nafion amount, and the like. When the amount of the anode catalyst is reduced, it is difficult to increase the stability of the power generation state of the conventional fuel cell.

Therefore, an anode diffusion comprising a conductive porous body, a hydrophilic polymer layer impregnated on one side of the conductive porous body, and a hydrophobic polymer layer impregnated on the other side of the conductive porous body It has been proposed to increase the output by using layers (see, for example, Patent Document 1).
JP 2008-186799 A

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an anode from which a high-power direct methanol fuel cell can be obtained.

An anode according to one embodiment of the present invention includes an anode catalyst layer,
A first fuel diffusion layer provided on the anode catalyst layer;
And a hydrophilic conductive layer formed on the first fuel diffusion layer and made of a coating film containing conductive particles and a hydrophilic polymer.

  A membrane electrode assembly according to one embodiment of the present invention includes the above-described anode, cathode, and a polymer electrolyte membrane disposed between the anode and the cathode.

  A direct methanol fuel cell according to one embodiment of the present invention includes the above-described membrane electrode assembly and is supplied with liquid fuel.

  ADVANTAGE OF THE INVENTION According to this invention, the anode from which a high output fuel cell is obtained is provided.

  Hereinafter, an embodiment will be described with reference to the drawings.

  As shown in FIG. 1, in a direct methanol fuel cell 10 according to an embodiment, a fuel electrode (anode) 32, an air electrode (cathode) 33, and a polymer electrolyte membrane 15 sandwiched between them are provided. A membrane electrode assembly (MEA) 18 is used as an electromotive unit. The polymer electrolyte membrane 15 has proton (hydrogen ion) conductivity.

  In the fuel electrode 32, the fuel electrode (anode) catalyst layer 11 is provided in contact with the polymer electrolyte membrane 15, and the first fuel diffusion layer 12 and the hydrophilic conductive layer 13 are sequentially disposed thereon. In the illustrated example, the second fuel diffusion layer 14 is provided on the hydrophilic conductive layer 13, but the second fuel diffusion layer is not always essential. On the other hand, in the air electrode 33, an air electrode (cathode) catalyst layer 16 is provided in contact with the polymer electrolyte membrane 15, and an air electrode gas (cathode) diffusion layer 17 is disposed thereon.

  The polymer electrolyte membrane 15 is made of a proton conductive material, and for example, a resin having a sulfonic acid group can be used. Specifically, fluororesin such as perfluorosulfonic acid polymer (Nafion (trade name, manufactured by DuPont), Flemion (trade name, manufactured by Asahi Glass), etc.), hydrocarbon-based resin having sulfonic acid group, tungsten Examples thereof include inorganic substances such as acid and phosphotungstic acid, but are not limited thereto.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 16 include platinum group elements such as Pt, Ru, Rh, Ir, Os, and Pd. Such a platinum group element can be used as a single metal. Alternatively, an alloy containing a platinum group element may be used as a catalyst. Specifically, for the anode catalyst layer 11, Pt—Ru, Pt—Mo or the like having strong resistance to methanol or carbon monoxide is preferably used. The cathode catalyst layer 13 is preferably made of platinum or Pt—Ni, but is not limited thereto. Furthermore, a supported catalyst using a conductive support such as a carbon material or an unsupported catalyst may be used.

In order to exert the effect as a catalyst layer, it is desirable that the catalyst is supported on the anode catalyst layer 11 and the cathode catalyst layer 16 in an amount of at least about 0.1 mg / cm 2 . However, when an excessive catalyst is loaded, the diffusion resistance of fuel and air may increase. It is desirable that the amount of the catalyst supported on the anode catalyst layer 11 and the cathode catalyst layer 16 be limited to about 4 g / cm 2 .

  The first fuel diffusion layer 12 laminated on the anode catalyst layer 11 serves to supply fuel to the anode catalyst layer 11 uniformly. The first fuel diffusion layer 12 can be formed using any porous material having conductivity. It is also required that an anode catalyst layer can be formed on the first fuel diffusion layer 12 by coating or sputtering. Specific examples of materials that can be used for the first fuel diffusion layer 12 include, but are not limited to, porous carbon materials such as carbon paper and carbon cloth.

  Carbon paper, carbon cloth, and the like may be subjected to water repellent treatment with a fluororesin. The first fuel diffusion layer 12 can have a microporous layer made of carbon nanofibers (CNF), carbon nanotubes (CNT) or nanocarbon particles on the anode catalyst layer 11 side.

  The hydrophilic conductive layer 13 laminated on the first fuel diffusion layer 12 has an action of adjusting the amount of methanol supplied from the fuel tank 27. Further, the hydrophilic conductive layer 13 has a role of controlling the diffusion of water generated at the cathode into the anode catalyst layer 11 and the first fuel diffusion layer 12 and adjusts the balance of water between the anode and the cathode. It has a function.

  With these functions, methanol, water (water vapor), and the like at the anode are stably supplied, so that stable output can be obtained and deterioration of the anode due to excessive supply of methanol can be suppressed. Since the hydrophilic conductive layer 13 is exposed to high-concentration methanol, the hydrophilic conductive layer 13 is required to be hardly soluble in methanol. On the other hand, in order to further improve the balance at the anode of water, it is preferable that the hydrophilic conductive layer 13 is water retentive against moisture.

  The hydrophilic conductive layer 13 is composed of a coating film containing conductive particles and a hydrophilic polymer. The content of the hydrophilic polymer in the hydrophilic conductive layer can be appropriately determined according to the molecular weight and the like. The molecular weight of the hydrophilic polymer can be controlled by, for example, the degree of polymerization. For example, when polyvinyl alcohol having a degree of polymerization of about 4500 is used as the hydrophilic polymer, a desired effect can be obtained if it is contained at about 1 wt%. The degree of polymerization of the hydrophilic polymer can be determined, for example, by the solution viscosity method.

  The degree of polymerization of the hydrophilic polymer is desirably about 500 to 10,000. If it is too small, the film-forming ability will be small, and it will be difficult to form hydrophilic conductivity. On the other hand, when the molecular weight is too large, the solubility in a solvent is greatly reduced. In addition to this, there is a risk that the viscosity becomes too large and it becomes difficult to adjust the slurry for the hydrophilic conductive layer.

  The hydrophilic polymer preferably occupies 1 to 30 wt% of the weight of the hydrophilic conductive layer 13. When the hydrophilic polymer is less than 1 wt%, the coating property is deteriorated. On the other hand, if it exceeds 30 wt%, the resistance will increase and the performance will deteriorate. The hydrophilic polymer is more preferably 5 to 20 wt% of the weight of the hydrophilic conductive layer.

  As the hydrophilic polymer, any material having a hydrophilic group (polar group) and insoluble in methanol can be used. Specific examples include polyvinyl alcohol (PVA) and methyl cellulose, but are not limited thereto. In addition, after forming the hydrophilic conductive layer 13, the resistance to water and methanol can be improved by chemical crosslinking using heat treatment or a part of the polar group.

Examples of the conductive particles include carbon, graphite, carbon nanotube, and carbon nanofiber. Furthermore, conductive nitrides such as TiN, conductive oxides such as WO 2 , and conductive sulfides such as W 2 S can be used as the conductive particles, but are not limited thereto.

  The average particle diameter of the conductive particles can be appropriately selected according to the specific surface area, the amount of oil absorption, etc., but is desirably about 0.01 to 10 μm. The average particle diameter can be usually determined by a laser diffraction scattering method.

  The concentration of the conductive particles in the hydrophilic conductive layer 13 is preferably about 50 to 99 wt%. When there are too few electroconductive particles, sufficient electroconductivity cannot be ensured. On the other hand, when the conductive particles are excessively contained, film formation may be difficult.

  The thickness of the hydrophilic conductive layer 13 is preferably in the range of 10 to 100 μm. When the thickness of the hydrophilic conductive layer 13 is less than 10 μm, a sufficient effect cannot be exhibited. On the other hand, if it exceeds 100 μm, the diffusion of methanol as a fuel is greatly suppressed, and a sufficient current density cannot be obtained.

  A metal oxide may be contained in the hydrophilic conductive layer 13. Water retention improves by containing a metal oxide. Examples of the metal oxide include, but are not limited to, silicon oxide, titanium oxide, zirconia oxide, and tin oxide.

  If such a metal oxide is contained in the hydrophilic conductive layer in an amount of about 5 wt%, an effect can be obtained. Since the remarkable effect is not exhibited when it is contained excessively, it is desirable that the upper limit of the content be limited to about 30 wt%.

  The second fuel diffusion layer 14 laminated on the hydrophilic conductive layer 13 can be formed using any porous material having conductivity. By providing the second fuel diffusion layer 14, the uniformity of fuel diffusion is improved. Specific examples of materials that can be used for the second fuel diffusion layer 14 include, but are not limited to, porous carbon materials such as carbon paper and carbon cloth.

  Carbon paper, carbon cloth, and the like may be subjected to water repellent treatment with a fluororesin. The second fuel diffusion layer 14 can have a microporous layer made of CNF, CNT and nanocarbon particles on the side opposite to the hydrophilic conductive layer 13.

  The thickness of the second fuel diffusion layer 14 can be appropriately determined according to the amount of catalyst, the composition and thickness of the first fuel diffusion layer and the hydrophilic conductive layer, and the like. However, if the thickness is excessively large, the amount of fuel diffusion may be reduced.

  The cathode diffusion layer 17 laminated on the cathode catalyst layer 16 serves to uniformly supply the oxidant to the cathode catalyst layer 16 and also serves as a current collector for the cathode. The cathode diffusion layer 17 can be formed using any porous material having conductivity. It is also required that a cathode catalyst layer can be formed on the cathode diffusion layer 17 by coating or sputtering.

  Specific examples of materials that can be used for the cathode diffusion layer 17 include, but are not limited to, porous carbon materials such as carbon paper and carbon cloth. Carbon paper, carbon cloth, and the like may be subjected to water repellent treatment with a fluororesin. The cathode diffusion layer 17 can have a microporous layer made of CNF, CNT, or nanocarbon particles on the cathode catalyst layer 16 side.

  An anode current collector 19 is laminated on the second fuel diffusion layer 14, and a cathode current collector 20 is laminated on the cathode diffusion layer 17. The anode current collector 19 and the cathode current collector 20 can be composed of a porous layer such as a hole or a mesh made of a conductive metal material such as gold.

  A rubber O-ring 21 is disposed between the polymer electrolyte membrane 15 and the anode current collector 19, and a rubber O-ring 22 is disposed between the polymer electrolyte membrane 15 and the cathode current collector 20. Is placed. Such an O-ring prevents fuel leakage and oxidant leakage from the membrane electrode assembly 18.

  A hydrophobic porous film 23 is laminated on the anode current collector 19, and a laminated body including the cathode current collector 20 is sandwiched between frames 24 and 25. The frames 24 and 25 can have a shape corresponding to the outer edge shape of the fuel cell 10, and can be a rectangular frame, for example.

  The frames 24 and 25 can be formed of, for example, a thermoplastic polyester resin such as polyethylene terephthalate (PET). The anode-side frame 24 is connected via a gas-liquid separation membrane 26 to a liquid fuel tank 27 that functions as a fuel supply unit. The gas-liquid separation membrane 26 functions as a vapor phase fuel permeable membrane that allows only the vaporized component of the liquid fuel to permeate and does not allow the liquid fuel to permeate.

  An opening (not shown) is provided for deriving a vaporized component of the fuel in the liquid fuel tank 27, and a gas-liquid separation membrane 26 is disposed so as to close the opening. The gas-liquid separation film 26 has an action of separating the vaporized component of the fuel and the liquid fuel and further vaporizing the liquid fuel. The gas-liquid separation membrane 26 can be made of, for example, a material such as silicone rubber.

  A permeation adjustment membrane (not shown) can be provided on the gas-liquid separation membrane 26 on the liquid fuel tank 27 side. The permeation amount adjusting membrane adjusts the permeation amount of the vaporized component of the fuel in addition to separating the gas and liquid in the same manner as the gas-liquid separation membrane 26. The permeation amount of the vaporized component by the permeation amount adjusting film can be adjusted by changing the aperture ratio of the permeation amount adjusting film. For the permeation amount adjusting film, for example, a material such as polyethylene terephthalate is used. By providing the permeation amount adjusting membrane, it is possible to perform gas-liquid separation of the fuel and to adjust the supply amount of the vaporized component of the fuel supplied to the anode catalyst layer 11 side.

  The liquid fuel stored in the liquid fuel tank 27 is a methanol aqueous solution having a concentration exceeding 50 mol% or pure methanol. The purity of pure methanol is preferably 95% by weight or more and 100% by weight or less. By using such high-concentration liquid fuel, the fuel tank can be miniaturized.

  The vaporized component of liquid fuel means vaporized methanol when liquid methanol is used as the liquid fuel, and when the methanol aqueous solution is used as liquid fuel, the vaporized component of methanol and the vaporized component of water Means an air-fuel mixture consisting of

  The porous membrane 23 has hydrophobicity and prevents water from entering the channel of the channel plate from the second fuel diffusion layer 14 side via the porous membrane 23. On the other hand, the fuel supply from the flow path is expanded by the porous membrane 23 so as to be supplied uniformly to the second fuel diffusion layer 14. The porous film 23 can be formed using, for example, polytetrafluoroethylene (PTFE), a water-repellent treated silicone sheet, or the like.

  Since it is disposed between the anode current collector 19 and the flow path plate, the porous membrane 23 further has the following effects. For example, the osmotic pressure phenomenon promotes a phenomenon in which water generated in the cathode catalyst layer 16 moves to the anode catalyst layer 11 through the electrolyte membrane 15. Water that has moved can be prevented from entering the anode current collector 19 and the gas-liquid separation membrane 26 side below the anode current collector 19.

  As a result, it is possible to proceed without hindering the vaporization of the fuel in the liquid fuel tank 27. In addition, by holding water between the anode catalyst layer 11 and the porous membrane 23, it is possible to replenish water in the anode catalyst layer 11. For example, pure methanol is used as the liquid fuel. Since water is not supplied from the liquid fuel tank 27, the porous membrane 23 is particularly effective. In addition, the movement of water from the cathode catalyst layer 16 side to the anode catalyst layer 11 side due to the osmotic pressure phenomenon changes the number and size of the air inlets 30 of the surface layer 29 installed on the moisturizing layer 28, thereby opening the area. It can be controlled by adjusting etc.

  The moisturizing layer 28 can be made of, for example, a material such as a polyethylene porous film. The maximum pore diameter is preferably about 20 to 50 μm. If the maximum pore diameter is less than 20 μm, air permeability may be reduced. On the other hand, when the maximum pore diameter is larger than 50 μm, moisture evaporation becomes excessive. In some cases, the fuel cell 10 may be configured without using the moisturizing layer 28. In this case, it is preferable to install the surface layer 29 on the cathode-side frame 25 to adjust the amount of water stored in the cathode catalyst layer 16 and the amount of water transpiration. 10 may be configured.

  The fuel cell 10 having the above-described configuration operates with the following reaction.

  First, the liquid fuel (for example, aqueous methanol solution) in the liquid fuel tank 27 is vaporized, and the vaporized mixture of methanol and water vapor forms the gas-liquid separation membrane 26, the porous membrane 23, and the anode current collector 19. pass. Further, it is diffused in the second fuel diffusion layer 14 and supplied to the anode catalyst layer 11 through the hydrophilic conductive layer 13 and the first fuel diffusion layer 12. The air-fuel mixture supplied to the anode catalyst layer 11 causes an internal reforming reaction of methanol represented by the following reaction formula (1).

CH 3 OH + H 2 O → CO 2 + 6H + + 6e Formula (1)
Note that when pure methanol is used as the liquid fuel, water vapor is not supplied from the liquid fuel tank 27. For this reason, it is water generated in the cathode catalyst layer 16, water in the electrolyte membrane 15, etc. that are involved in the internal reforming reaction represented by the above reaction formula (1). Alternatively, the internal reforming reaction is generated by another reaction mechanism that does not require water, regardless of the internal reforming reaction of the reaction formula (1).

Protons (H + ) generated by the internal reforming reaction are conducted through the electrolyte membrane 15 and reach the cathode catalyst layer 16. The air taken in from the air inlet 30 of the surface layer 29 diffuses through the moisturizing layer 28, the cathode current collector 20, and the cathode diffusion layer 17 and is supplied to the cathode catalyst layer 16. The air supplied to the cathode catalyst layer 16 reacts with protons as represented by the following reaction formula (2). By this reaction, water is generated and a power generation reaction occurs.

(3/2) O 2 + 6H + + 6e → 3H 2 O Formula (2)
The water generated in the cathode catalyst layer 16 by such reaction diffuses in the cathode diffusion layer 17 and reaches the moisture retention layer 28. A part of the water is evaporated from the air inlet 30 of the surface layer 29 provided on the moisturizing layer 28, and the remaining water is prevented from being evaporated by the surface layer 29. In particular, when the reaction of the above reaction formula (2) proceeds, the amount of water whose transpiration is inhibited by the surface layer 29 increases, and the amount of water stored in the cathode catalyst layer 16 increases.

  In this case, as the reaction represented by the reaction formula (2) proceeds, the water storage amount of the cathode catalyst layer 16 becomes larger than the water storage amount of the anode catalyst layer 11. As a result, the phenomenon that the water generated in the cathode catalyst layer 16 moves to the anode catalyst layer 11 through the electrolyte membrane 15 by the osmotic pressure phenomenon is promoted.

  Therefore, as compared with the case where the supply of moisture to the anode catalyst layer 11 depends only on the vapor vaporized from the liquid fuel tank 27, the supply of moisture is promoted, and the internal reforming reaction of methanol in the above-described formula (1) is promoted. Can be made. As a result, the output density can be increased and the high output density can be maintained over a long period of time.

  Further, even when a methanol aqueous solution having a methanol concentration exceeding 50 mol% or pure methanol is used as the liquid fuel, water that has moved from the cathode catalyst layer 16 to the anode catalyst layer 11 should be used for the internal reforming reaction. Therefore, water can be stably supplied to the anode catalyst layer 11. Thereby, the reaction resistance of the internal reforming reaction of methanol can be further reduced, and the long-term output characteristics and the load current characteristics are further improved. Furthermore, the liquid fuel tank 27 can be downsized.

  Thus, according to the direct methanol fuel cell 10 of one embodiment, the fuel cell 10 is configured by laminating the porous membrane 23 so that the porous membrane 23 is on the anode catalyst layer 11 side. Thus, methanol can be released to the anode catalyst layer 11 side. As a result, the influence of the change in the amount of vaporization of methanol in the liquid fuel tank 27 can be mitigated, and methanol having a predetermined concentration can be uniformly supplied to the anode catalyst layer 11.

  In the embodiment described above, a direct methanol fuel cell using a methanol aqueous solution or pure methanol as the liquid fuel has been described. However, the liquid fuel is not limited thereto. For example, the present invention can also be applied to a liquid fuel direct supply type fuel cell using ethyl alcohol, isopropyl alcohol, butanol, dimethyl ether, or the like, or an aqueous solution thereof.

  Specific examples of the present invention are shown below.

Example 1
First, about 75 g of zirconia balls were weighed and accommodated in a polyethylene pot. To this, 2.0 g of platinum-supporting carbon (TEC10EPTM70 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and 2.0 g of water were added. Furthermore, 3.0 g of 1-propanol and 2.5 g of Nafion solution DE2020 (trade name: manufactured by DuPont) were added and mixed by a ball mill to prepare a slurry for the cathode catalyst layer.

The obtained slurry was applied to carbon paper (carbon paper GPH-090 manufactured by Toray Industries, Inc.) to which water repellent treatment was performed by adding 14 wt% PTFE. This was dried at room temperature to produce an air electrode. The amount of catalyst PtRu is about 2.0 mg / cm 2 .

  Further, 2.0 g of platinum-ruthenium-supported carbon (TEC61E54DM manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), 3.0 g of water, and 15.0 g of Nafion solution DE2020 (trade name: manufactured by DuPont) were mixed with a ball mill to obtain an anode catalyst layer. A slurry was prepared.

The obtained slurry was applied to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) treated with water repellent treatment by adding 14 wt% PTFE. After drying this at room temperature, it was cut into 12 cm 2 to produce a fuel electrode. The water-repellent treated carbon paper acts as a diffusion layer (first fuel diffusion layer). The amount of catalyst PtRu was about 1.7 mg / cm 2 .

  2.0 g of graphite particles (TIMREX KS-6 manufactured by Timcal) as conductive particles and 10 g of 5% PVA aqueous solution as a hydrophilic polymer were placed in a polyethylene pot. The average particle diameter of the graphite particles is about 6 μm, and the polymerization degree of PVA is 2000. This was dispersed for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation) to prepare a slurry for a hydrophilic conductive layer.

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.6 mm. This was dried at room temperature, and 12 cm 2 was cut to prepare a diffusion layer with a hydrophilic conductive layer (sample 1).

  In the diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (second fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a PVA layer containing graphite particles, and the thickness thereof was 45 μm.

As the electrolyte membrane, a fixed electrolyte membrane Nafion 112 manufactured by DuPont was prepared. An air electrode was disposed on one side of the electrolyte membrane, and a fuel electrode and a diffusion layer with a hydrophilic conductive layer were disposed on the other side. The diffusion layer with a hydrophilic conductive layer was disposed with the hydrophilic conductive layer in contact with the fuel electrode. This was pressed under the conditions of 120 ° C. and 30 kgf / cm 2 to produce a membrane electrode assembly (MEA). The electrode areas of the air electrode and the fuel electrode were both 12 cm 2 .

  Subsequently, this MEA was sandwiched between gold foils having a plurality of openings for taking in air and vaporized methanol, thereby forming an anode current collector and a cathode current collector.

  A laminate in which the MEA, the anode current collector, the cathode current collector, and the porous film were laminated was sandwiched between two resin frames. A rubber O-ring was sandwiched between the MEA air electrode side and one frame, and between the MEA fuel electrode side and the other frame, respectively.

  The frame on the fuel electrode side was fixed to the liquid fuel tank with a screw through a gas-liquid separation membrane. A silicone sheet was used as the gas-liquid separation membrane. On the other hand, a moisturizing layer was formed by disposing a porous plate on the air agent side frame. On this moisturizing layer, a stainless steel plate (SUS304) with a thickness of 2 mm formed with air inlets (4 mm diameter, 64 holes) for air intake is arranged to form a surface layer, and by screwing Fixed.

As described above, a direct methanol fuel cell (DMFC) having a configuration as shown in FIG. 1 was produced. The DMFC liquid fuel tank thus obtained was injected with 5 ml of pure methanol as the liquid fuel. Under the conditions of a temperature of 25 ° C. and a relative humidity of 50%, the maximum output value was measured from the current value and the voltage value. As a result, the maximum output value was 30.5 mW / cm 2 .

(Example 2)
Graphite particles (TIMREX KS-6 manufactured by Timcal) 4.0 g as conductive particles, 10.0 g of 5% PVA (PVA polymerization degree 2000) aqueous solution as a conductive polymer, 5.5 g of water, and metal oxide 0.5 g of silica (300CF manufactured by Nippon Aerosil Co., Ltd.) was placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.5 mm. This was dried at room temperature, and 12 cm 2 was cut to prepare a diffusion layer with a hydrophilic conductive layer (sample 2).

  In the diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (second fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a layer of PVA containing graphite particles and silica, and the thickness thereof was 45 μm.

An MEA was constructed in the same manner as in Example 1 except that the thus obtained diffusion layer with a hydrophilic conductive layer was used, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 24.2 mW / cm 2 .

(Example 3)
A diffusion layer with a hydrophilic conductive layer was produced in the same manner as in Example 2 except that PTFE added to the carbon paper was changed to 25 wt%. An MEA was constructed in the same manner as in Example 1 except that the obtained diffusion layer with a hydrophilic conductive layer was used, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. The maximum value of output was 24.5 mW / cm 2 .

Example 4
A diffusion layer with a hydrophilic conductive layer was produced in the same manner as in Example 2 except that the PTFE added to the carbon paper was changed to 35 wt%. An MEA was constructed in the same manner as in Example 1 except that the obtained diffusion layer with a hydrophilic conductive layer was used, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. The maximum output value was 25.6 mW / cm 2 .

(Example 5)
Platinum ruthenium-supported carbon (TEC61E54DM manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) 2.0 g, water 3.0 g, and Nafion solution DE2020 (trade name: manufactured by DuPont) 5.0 g are mixed in a ball mill to prepare a slurry for the anode catalyst layer. Prepared.

The obtained slurry was applied to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) treated with water repellent treatment by adding 14 wt% PTFE. After drying this at room temperature, it was cut into 12 cm 2 to produce a fuel electrode. The amount of catalyst PtRu was about 1.7 mg / cm 2 .

An MEA was constructed in the same manner as in Example 1 except that the obtained anode was used, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. The maximum value of output was 21.1 mW / cm 2 .

(Example 6)
First, about 75 g of zirconia balls were weighed and accommodated in a polyethylene pot. To this, 2.0 g of platinum-supporting carbon (TEC10EPTM70 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and 2.0 g of water were added. Furthermore, 3.0 g of 1-propanol and 2.5 g of Nafion solution DE2020 (trade name: manufactured by DuPont) were added and mixed by a ball mill to prepare a slurry for the cathode catalyst layer.

The obtained slurry was applied to carbon paper (carbon paper GPH-090 manufactured by Toray Industries, Inc.) treated with water repellent treatment by adding 14 wt% PTFE. This was dried at room temperature to produce an air electrode. The amount of catalyst PtRu was about 2.0 mg / cm 2 .

  Graphite particles as conductive particles (TIMREX KS-6 manufactured by Timcal) 4.0 g, 5% PVA (PVA polymerization degree 2000) aqueous solution 10 g as conductive polymer, and silica as metal oxide (manufactured by Nippon Aerosil Co., Ltd.) (300CF) 0.5 g was placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

  The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.6 mm. This was dried at room temperature to prepare a carbon paper with a hydrophilic conductive layer. In this diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (first fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a PVA layer containing graphite particles, and the thickness was 47 μm.

  Next, 2.0 g of platinum-ruthenium-supported carbon (TEC61E54DM manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), 3.0 g of water, and 15.0 g of Nafion solution DE2020 (trade name: manufactured by DuPont) are mixed with a ball mill for the anode catalyst layer. A slurry was prepared.

This slurry was applied to the surface of the carbon paper with a hydrophilic conductive layer opposite to the conductive catalyst layer, dried at room temperature, and then cut into 12 cm 2 to prepare a fuel electrode. The water-repellent treated carbon paper acts as a diffusion layer (first fuel diffusion layer). The amount of catalyst PtRu was about 1.7 mg / cm 2 .

As the electrolyte membrane, a fixed electrolyte membrane Nafion 112 manufactured by DuPont was prepared. An air electrode was disposed on one side of the electrolyte membrane, and a fuel electrode and a diffusion layer with a hydrophilic conductive layer were disposed on the other side. The diffusion layer with a hydrophilic conductive layer was disposed with the hydrophilic conductive layer in contact with the fuel electrode. This was pressed under the conditions of 120 ° C. and 30 kgf / cm 2 to produce a membrane electrode assembly (MEA). The electrode areas of the air electrode and the fuel electrode were both 12 cm 2 .

  Subsequently, this MEA was sandwiched between gold foils having a plurality of openings for taking in air and vaporized methanol, thereby forming an anode current collector and a cathode current collector.

  A laminate in which the MEA, the anode current collector, the cathode current collector, and the porous film were laminated was sandwiched between two resin frames. A rubber O-ring was sandwiched between the MEA air electrode side and one frame, and between the MEA fuel electrode side and the other frame, respectively.

  The frame on the fuel electrode side was fixed to the liquid fuel tank with a screw through a gas-liquid separation membrane. A silicone sheet was used as the gas-liquid separation membrane. On the other hand, a moisturizing layer was formed by disposing a porous plate on the air agent side frame. On this moisturizing layer, a stainless steel plate (SUS304) with a thickness of 2 mm formed with air inlets (4 mm diameter, 64 holes) for air intake is arranged to form a surface layer, and by screwing Fixed.

As described above, a direct methanol fuel cell (DMFC) having a configuration as shown in FIG. 1 was produced. The DMFC liquid fuel tank thus obtained was injected with 5 ml of pure methanol as the liquid fuel. Under the conditions of a temperature of 25 ° C. and a relative humidity of 50%, the maximum output value was measured from the current value and the voltage value. As a result, the maximum output value was 24.1 mW / cm 2 .

(Example 7)
An MEA was constructed in the same manner as in Example 6 except that carbon paper without water repellent treatment (carbon paper GPH-060 manufactured by Toray Industries, Inc.) was used as the first fuel diffusion layer, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.7 mW / cm 2 .

(Example 8)
An MEA was constructed in the same manner as in Example 2 except that the hydrophilic conductive layer was disposed on the anode current collector side, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.5 mW / cm 2 .

Example 9
An MEA was constructed in the same manner as in Example 4 except that a diffusion layer with a hydrophilic conductive layer was disposed on the anode current collector side, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.4 mW / cm 2 .

(Example 10)
An MEA was constructed to prepare a DMFC in the same manner as in Example 5 except that the hydrophilic conductive layer of the diffusion layer with a hydrophilic conductive layer was disposed on the anode current collector side. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output was 20.8 mW / cm 2 .

(Example 11)
An MEA was constructed to prepare a DMFC in the same manner as in Example 1 except that the conductive particles used in the hydrophilic conductive layer were changed to carbon particles (Printex 25 manufactured by Degussa). With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.8 mW / cm 2 .

Example 12
A MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that the carbon paper with a hydrophilic conductive layer (Sample 2) was heat-treated at 150 ° C. for 10 minutes. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.2 mW / cm 2 .

  The hydrophilic conductive layer of Sample 2 is gradually dissolved in boiling water and peeled off. By performing the heat treatment as described above, dissolution and dropping off were not observed even in boiling water for 1 hour, and water resistance was improved.

(Example 13)
An MEA was constructed in the same manner as in Example 2 except that the metal oxide particles used in the hydrophilic conductive layer were changed to titanium oxide (Super Titania F6 manufactured by Showa Denko KK), and a DMFC was prepared. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.9 mW / cm 2 .

(Example 14)
Platinum ruthenium-supported carbon (TEC61E54DM manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) 2.0 g, 5 wt% WO 3 -supported TiO 2 0.4 g, water 3.0 g, 1-methoxy-2-propanol 6.0 g, and Nafion solution DE2020 (trade name) : DuPont) 5.0 g was mixed with a ball mill to prepare a slurry for the anode catalyst layer.

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.5 mm. After drying this at room temperature, it was cut into 12 cm 2 to produce a fuel electrode. The amount of catalyst PtRu was about 1.7 mg / cm 2 .

An MEA was constructed in the same manner as in Example 5 except that this fuel electrode was used, and a DMFC was produced. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 19.9 mW / cm 2 .

(Example 15)
2.0 g of graphite particles (TIMREX KS-6 manufactured by Timcal) as conductive particles, 10 g of 5% PVA (PVA polymerization degree 2000) aqueous solution as a conductive polymer, 10 wt% ammonium metatungstate (Nippon Inorganic Chemical Industries, Ltd.) AMT-72) 1.0 g of an aqueous solution and 0.5 g of silica as a metal oxide (300CF manufactured by Nippon Aerosil Co., Ltd.) were placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.6 mm. This was dried at room temperature, and 12 cm 2 was cut to prepare a diffusion layer with a hydrophilic conductive layer (sample 15). Further, it was obtained by heating at 150 ° C. for 10 minutes.

  In the diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (second fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a PVA layer containing graphite particles, and the thickness thereof was 42 μm. This hydrophilic conductive layer was not dissolved or slipped in boiling water.

A MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that the diffusion layer with a hydrophilic conductive layer prepared here was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 23.5 mW / cm 2 .

(Example 16)
1.98 g of graphite particles (TIMREX KS-6 manufactured by Timcal) as conductive particles, 1.0 g of 5% PVA (PVA: degree of polymerization 4500, manufactured by Kuraray Co.) as a hydrophilic polymer, and ion-exchanged water 5 0.0 g was placed in a polyethylene pot. The average particle size of the graphite particles is about 6 μm. This was dispersed for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation) to prepare a slurry for a hydrophilic conductive layer.

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.6 mm. This was dried at room temperature and cut to 12 cm 2 to prepare a diffusion layer with a hydrophilic conductive layer.

An MEA was constructed to prepare a DMFC in the same manner as in Example 1 except that the obtained diffusion layer with a hydrophilic conductive layer was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 21.5 mW / cm 2 .

(Example 17)
2.0 g of graphite particles (TIMREX KS-6 manufactured by Timcal) as conductive particles, 10.0 g of 5% PVA (PVA polymerization degree 2000) aqueous solution as a conductive polymer, and silica as a metal oxide (Nippon Aerosil) 0.5 g of 300CF) was accommodated in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.5 mm. This was dried at room temperature, and 12 cm 2 was cut to prepare a diffusion layer with a hydrophilic conductive layer.

  In the diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (second fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a PVA layer containing graphite particles and silica, and its thickness was 41 μm.

An MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that the obtained diffusion layer with a hydrophilic conductive layer was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 22.1 mW / cm 2 .

(Example 18)
Graphite particles as conductive particles, TIMCAL TIMREX KS-6 (4.0 g), conductive polymer as 5% PVA (PVA polymerization degree 2000) aqueous solution (15.0 g), and metal oxide as silica (Nippon Aerosil Co., Ltd.) 0.25 g (manufactured 300CF) was placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

An MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that a slurry having this composition was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output was 20.5 mW / cm 2 .

(Example 19)
Graphite particles as conductive particles, TIMEX KS, TIMREX KS-6 (4.0 g), conductive polymer as 5% PVA (PVA polymerization degree 2000) aqueous solution (5.0 g), and metal oxide as silica (Nippon Aerosil Co., Ltd.) 0.75 g (manufactured 300CF) was placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

An MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that a slurry having this composition was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output value was 21.5 mW / cm 2 (Example 20)
Graphite particles as conductive particles, TIMCAL TIMREX KS-6) 4.0 g, conductive polymer as 5% PVA (PVA polymerization degree 2000) aqueous solution 10.0 g, water 5.0 g, cross-linking material (Matsumoto Trading Co., Ltd.) 0.5 g of organotics TC-315 aqueous solution) and 0.5 g of silica as a metal oxide (300CF manufactured by Nippon Aerosil Co., Ltd.) were placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.6 mm. This was dried at room temperature and cut to 12 cm 2 to prepare a diffusion layer with a hydrophilic conductive layer.

  In the diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (second fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a PVA layer containing graphite particles, and the thickness thereof was 42 μm. This hydrophilic conductive layer was not dissolved or slipped in boiling water.

An MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that the obtained diffusion layer with a hydrophilic conductive layer was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output was 22.4 mW / cm 2 .

(Example 21)
The carbon paper with hydrophilic conductivity prepared in Example 2 was immersed in a solution obtained by adding 0.5 g of sulfuric acid to 100 g of 5% aqueous glutaraldehyde solution, and dried by heating to crosslink PVA. By this treatment, dissolution in boiling water was not observed.

An MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that the obtained diffusion layer with a crosslinked hydrophilic conductive layer was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output was 21.8 mW / cm 2 .

(Example 22)
Graphite particles as conductive particles, TIMCAL TIMREX KS-6) 4.0 g, conductive polymer as 5% methylcellulose (methylation degree 47%) aqueous solution 10.0 g, crosslinker (Matsumoto Trading Co., Organotix TC) -315 aqueous solution) and 0.5 g of silica as a metal oxide (300CF manufactured by Nippon Aerosil Co., Ltd.) were placed in a polyethylene pot. A slurry for a hydrophilic conductive layer was prepared by dispersing for about 30 minutes with a defoaming machine (Nerimataro (trademark): manufactured by Sinky Corporation).

The obtained slurry was applied with an applicator to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. At this time, the gap of the applicator was 0.6 mm. This was dried at 70 ° C., and 12 cm 2 was cut to prepare a diffusion layer with a hydrophilic conductive layer.

  In the diffusion layer with a hydrophilic conductive layer, the water-repellent carbon paper acts as a diffusion layer (second fuel diffusion layer). On the other hand, the hydrophilic conductive layer was composed of a PVA layer containing graphite particles, and the thickness thereof was 42 μm. This hydrophilic conductive layer was not dissolved or slipped in boiling water.

An MEA was constructed and a DMFC was prepared in the same manner as in Example 2 except that the obtained diffusion layer with a hydrophilic conductive layer was used. With respect to the obtained DMFC, the maximum output value was measured under the same conditions as in Example 1. As a result, the maximum output was 22.4 mW / cm 2 .

(Comparative Example 1)
First, about 75 g of zirconia balls were weighed and accommodated in a polyethylene pot. To this, 2.0 g of platinum-supporting carbon (TEC10EPTM70 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and 2.0 g of water were added. Furthermore, 3.0 g of 1-propanol and 2.5 g of Nafion solution DE2020 (trade name: manufactured by DuPont) were added and mixed by a ball mill to prepare a slurry for the cathode catalyst layer.

  The obtained slurry was applied to carbon paper (carbon paper GPH-090 manufactured by Toray Industries, Inc.) to which water repellent treatment was performed by adding 14 wt% PTFE. This was dried at room temperature to produce an air electrode.

  Further, platinum ruthenium-supported carbon (TEC61E54DM manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) 2.0, water 3.0 g, and Nafion solution DE2020 (trade name: manufactured by DuPont) 15.0 g were mixed with a ball mill to form an anode catalyst layer. A slurry was prepared.

The obtained slurry was applied to carbon paper (carbon paper GPH-120 manufactured by Toray Industries, Inc.) to which 14 wt% PTFE was added and subjected to water repellent treatment. After drying this at room temperature, it was cut into 12 cm 2 to produce a fuel electrode. The amount of catalyst PtRu was about 1.7 mg / cm 2 .

As the electrolyte membrane, a fixed electrolyte membrane Nafion 112 manufactured by DuPont was prepared. This electrolyte membrane was sandwiched between an air electrode and a fuel electrode. This was pressed under the conditions of 120 ° C. and 30 kgf / cm 2 to produce a membrane electrode assembly (MEA). The electrode areas of the air electrode and the fuel electrode were both 12 cm 2 .

A DMFC was prepared in the same manner as in Example 1 except that the obtained MEA was used, and the maximum output value was evaluated. As a result, the maximum output value was 18.2 mW / cm 2 .

(Comparative Example 2)
An MEA was produced in the same manner as in Example 1 except that the diffusion layer with a hydrophilic conductive layer was changed to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) which was water-repellent treated by adding 14 wt% PTFE. A DMFC was prepared in the same manner as in Example 1 except that the obtained MEA was used, and the maximum output value was evaluated. The maximum output value was 17.8 mW / cm 2 .

(Comparative Example 3)
An MEA was produced in the same manner as in Example 5 except that the diffusion layer with a hydrophilic conductive layer was changed to carbon paper (carbon paper GPH-060 manufactured by Toray Industries, Inc.) that was subjected to water repellent treatment by adding 14 wt% PTFE. A DMFC was prepared in the same manner as in Example 1 except that the obtained MEA was used, and the maximum output value was evaluated. The maximum value of output was 10.7 mW / cm 2 .

  Using the DMFCs of Examples 1 and 2 and Comparative Examples 1 and 2, a long-term deterioration test was performed by the following method. The fuel tank part of the passive DMFC evaluation device was made thin so that the amount of accumulated fuel was reduced as much as possible. As a system for supplying the used fuel (methanol) with a pump (several tens of μL), the pump was controlled to be turned on and off at the cathode temperature (about 55 ° C.). With this method, intermittent power generation was performed at a constant voltage. One cycle of intermittent operation was performed with an operation time of 4 hours and a downtime of 5 hours, and the deterioration of the output after 500 hours was examined.

  In Examples 1 and 2, they were about 78% and 75% of the initial output after 500 hours. On the other hand, it was as low as 50% in Comparative Example 1 and 35% in Comparative Example 2, and the effect of suppressing output deterioration by the hydrophilic conductive layer was confirmed.

  As shown in the above results, it is confirmed that the output of a direct methanol fuel cell is improved by using an anode provided with a hydrophilic conductive layer made of a coating film containing conductive particles and a hydrophilic polymer. It was done.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a cross-sectional view of a passive fuel cell according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Passive type fuel cell; 11 ... Anode catalyst layer; 12 ... First fuel diffusion layer 13 ... Hydrophilic conductive layer; 14 ... Second fuel diffusion layer; 32 ... Anode 15 ... Polymer electrolyte membrane; 17 ... Cathode diffusion layer 33 ... Cathode; 18 ... Membrane electrode assembly (MEA); 19 ... Anode current collector 20 ... Cathode current collector; 21 ... O-ring; 22 ... O-ring; Membrane 24 ... Anode frame; 25 ... Cathode frame; 26 ... Gas-liquid separation membrane 27 ... Fuel tank; 28 ... Moisturizing layer; 29 ... Surface layer;

Claims (20)

  1. An anode catalyst layer;
    A first fuel diffusion layer provided on the anode catalyst layer;
    An anode for a direct methanol fuel cell, comprising a hydrophilic conductive layer formed on the first fuel diffusion layer and comprising a coating film containing conductive particles and a hydrophilic polymer.
  2.   The anode for direct methanol fuel cells according to claim 1, further comprising a second fuel diffusion layer on the hydrophilic conductive layer.
  3.   The anode for a direct methanol fuel cell according to claim 1 or 2, wherein the content of the hydrophilic polymer is 1 wt% or more and 30 wt% or less of the hydrophilic conductive layer.
  4.   The anode for a direct methanol fuel cell according to any one of claims 1 to 3, wherein the hydrophilic conductive layer has a thickness of 1 µm to 100 µm.
  5.   5. The conductive particles according to claim 1, wherein the conductive particles are selected from the group consisting of carbon, graphite, carbon nanotubes, carbon nanofibers, conductive nitrides, conductive oxides, and conductive sulfides. The anode for a direct methanol fuel cell according to any one of the above.
  6.   6. The anode for a direct methanol fuel cell according to claim 1, wherein an average particle diameter of the conductive particles is 0.01 μm or more and 10 μm or less.
  7.   The anode for a direct methanol fuel cell according to any one of claims 1 to 6, wherein the conductive particles are contained in the hydrophilic conductive layer in an amount of 50 wt% or more and 99 wt% or less.
  8.   The direct methanol fuel cell according to any one of claims 1 to 7, wherein the hydrophilic polymer is selected from the group consisting of polyvinyl alcohol, polyalcohol copolymer, methylcellulose, and cellulose derivatives. For anode.
  9.   The anode for a direct methanol fuel cell according to any one of claims 1 to 8, wherein the degree of polymerization of the hydrophilic polymer is 500 or more and 10,000 or less.
  10.   The anode for a direct methanol fuel cell according to any one of claims 1 to 9, wherein the hydrophilic conductive layer further contains metal oxide particles.
  11.   11. The anode for a direct methanol fuel cell according to claim 10, wherein the metal oxide particles include at least one selected from the group consisting of silicon oxide, titanium oxide, zirconia oxide, and tin oxide.
  12.   The anode for a direct methanol fuel cell according to claim 10 or 11, wherein the metal oxide particles are contained in an amount of 1 wt% to 30 wt%.
  13.   13. The anode for a direct methanol fuel cell according to claim 10, wherein an average particle size of the metal oxide particles is 0.001 μm or more and 1 μm or less.
  14. The anode catalyst layer, 0.1 mg / cm 2 or more 4 mg / cm 2 or less of one anode for direct methanol fuel cell according to one of claims 1 to 13, characterized in that it comprises a catalyst.
  15.   The direct methanol fuel cell anode according to claim 14, wherein the catalyst contains a platinum group element.
  16.   The anode for a direct methanol fuel cell according to any one of claims 1 to 15, wherein the thickness of the first fuel diffusion layer is not less than 50 µm and not more than 600 µm.
  17.   17. The anode for a direct methanol fuel cell according to claim 2, wherein the thickness of the second fuel diffusion layer is 50 μm or more and 600 μm or less.
  18. The anode according to any one of claims 1 to 17,
    A membrane electrode assembly comprising: a cathode; and a polymer electrolyte membrane disposed between the anode and the cathode.
  19.   A direct methanol fuel cell comprising the membrane electrode assembly according to claim 18 and supplied with liquid fuel.
  20.   The direct methanol fuel cell according to claim 19, wherein the liquid fuel is a methanol aqueous solution having a concentration exceeding 50 mol% or liquid methanol.
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JP4293831B2 (en) * 2003-05-16 2009-07-08 三洋電機株式会社 Fuel cell
JP2006108031A (en) * 2004-10-08 2006-04-20 Nissan Motor Co Ltd Mea for fuel cell and fuel cell using it
US20090087711A1 (en) * 2005-12-16 2009-04-02 Kabushiki Kaisha Equos Research Fuel cell electrode, fuel cell, and fuel cell stack
JP2008186799A (en) * 2007-01-31 2008-08-14 Toshiba Corp Fuel cell

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JP2013200972A (en) * 2012-03-23 2013-10-03 Fujikura Ltd Direct methanol fuel cell

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