JP2009038014A - Fuel cell and manufacturing method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell maintaining high and continuous output power generation. <P>SOLUTION: The fuel cell includes cathodes 13, 14, anodes 11, 12, and an electrolyte membrane 15 pinched by the cathodes 13, 14 and the anodes 11, 12. The cathodes 13, 14 include a cathode catalyst layer 13 arranged in opposition to one face of the electrolyte membrane 15, and a cathode gas diffusion layer 14 arranged in opposition to the cathode catalyst layer 13. The anodes 11, 12 include an anode catalyst layer 11 arranged in opposition to the other face of the electrolyte membrane 15, and an anode gas diffusion layer 13 arranged in opposition to the anode catalyst layer 11. At least either the cathode gas diffusion layer 14 or the anode gas diffusion layer 13 has a predetermined hydrophobicity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell and a fuel cell manufacturing method, and more particularly to a liquid fuel direct supply type fuel cell and a manufacturing method thereof.

  2. Description of the Related Art In recent years, electronic devices have been reduced in size, performance, and portability due to advances in electronic technology. In portable electronic devices, there is an increasing demand for higher energy density of batteries used. For this reason, a battery having a large capacity while being lightweight and small is required, and a lithium ion battery or the like has been developed.

  However, the operation time of portable electronic devices tends to increase further, and in the lithium ion battery, the improvement in energy density is reaching the limit from the viewpoint of material and structure, and it is becoming impossible to meet further demands.

  In view of the above situation, small fuel cells are attracting attention instead of lithium ion batteries. In particular, a direct methanol fuel cell (DMFC) that uses methanol as a fuel has less difficulty in handling hydrogen gas or a device that reforms organic fuel into hydrogen gas compared to a fuel cell that uses hydrogen gas. Therefore, it is excellent in miniaturization.

  DMFC oxidizes and decomposes methanol at the fuel electrode to produce carbon dioxide, protons, and electrons, while oxygen is obtained from the air at the air electrode, protons that are supplied by obtaining an electrolyte membrane from the fuel electrode, and fuel Water is generated by electrons supplied from the poles through an external circuit, and power is supplied by electrons passing through the external circuit.

  Since the DMFC generates electricity with the above-described configuration, a pump for supplying methanol and a blower for feeding air are provided as supplementary notes, and a DMFC having a complicated form as a system has been developed. Therefore, it has been difficult to reduce the size of the fuel cell.

Instead of supplying methanol with a pump, a methanol storage chamber is provided in the vicinity of the power generation element, and methanol is supplied through the gas-liquid separation membrane provided between the methanol storage chamber and the power generation element, thereby reducing the size. It was advanced. For intake of air, a compact DMFC has been proposed by directly installing an air inlet in a power generation element instead of a blower (see Patent Document 1).
JP 2004-164903 A

  However, in the small DMFC as described above, since the mechanism is simplified, water generated by power generation stays inside the power generation element, and air intake into the cathode catalyst layer becomes insufficient. When power is generated, there is a problem that the output decreases.

  The present invention has been made in view of the above problems, and takes air into the cathode catalyst layer by discharging water generated inside the power generation element to the outside of the power generation element without stagnation. An object of the present invention is to provide a fuel cell and a fuel cell manufacturing method capable of maintaining continuous and high-output power generation.

  The fuel cell according to the first aspect of the present invention includes a cathode, an anode, and an electrolyte membrane sandwiched between the cathode and the anode, and the cathode is disposed to face one surface of the electrolyte membrane. A cathode gas diffusion layer disposed opposite to the cathode catalyst layer, the anode comprising an anode catalyst layer disposed opposite to the other surface of the electrolyte membrane; and the anode An anode gas diffusion layer disposed opposite to the catalyst layer, and at least one of the cathode gas diffusion layer and the anode gas diffusion layer has a predetermined hydrophobicity.

  A method of manufacturing a fuel cell according to a second aspect of the present invention includes a step of forming a cathode, a step of forming an anode, and a step of forming an electrolyte membrane sandwiched between the cathode and the anode, The step of forming a cathode includes a step of forming a cathode gas diffusion layer and a step of forming a cathode catalyst layer, and the step of forming the cathode gas diffusion layer includes a step in which the cathode gas diffusion layer has a predetermined hydrophobicity. A step of performing a hydrophobic treatment so as to have

  Further, another fuel cell manufacturing method of the present invention includes a step of forming a cathode, a step of forming an anode, and a step of forming an electrolyte membrane sandwiched between the cathode and the anode, The step of forming an anode includes a step of forming an anode gas diffusion layer and a step of forming an anode catalyst layer, and the step of forming the anode gas diffusion layer is such that the anode gas diffusion layer has a predetermined hydrophobicity. A step of performing a hydrophobic treatment so as to have

  According to the present invention, the water generated inside the power generation element is discharged to the outside of the power generation element without stagnation, so that air can be taken into the cathode catalyst layer, and continuous high power generation is maintained. A fuel cell and a method for manufacturing the fuel cell can be provided.

  Hereinafter, a fuel cell according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a cross section of a direct methanol fuel cell 10 according to an embodiment of the present invention.

  As shown in FIG. 1, the fuel cell 10 includes an anode composed of an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode composed of a cathode catalyst layer 13 and a cathode gas diffusion layer 14, an anode catalyst layer 11 and a cathode catalyst layer. A membrane electrode assembly (MEA: Membrane Electrode Assembly) 16 composed of a proton (hydrogen ion) conductive electrolyte membrane 15 sandwiched therebetween is provided as an electromotive unit.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 13 include platinum group elements such as single metals such as Pt, Ru, Rh, Ir, Os, and Pd, alloys containing platinum group elements, and the like. Can be mentioned.

  Specifically, it is preferable to use Pt—Ru or Pt—Mo having strong resistance to methanol or carbon monoxide as the anode catalyst layer 11 and platinum or Pt—Ni as the cathode catalyst layer 13. However, it is not limited to these. Further, a supported catalyst using a conductive support such as a carbon material or an unsupported catalyst may be used.

  Examples of the proton conductive material that constitutes the electrolyte membrane 15 include fluorinated resins having a sulfonic acid group, such as perfluorosulfonic acid polymer (Nafion (trade name, manufactured by DuPont), Flemion (trade name, Asahi Glass Co., Ltd.)), sulfonic acid group-containing hydrocarbon resins, and inorganic substances such as tungstic acid and phosphotungstic acid, but are not limited thereto.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 serves to uniformly supply fuel to the anode catalyst layer 11 and also serves as a current collector for the anode catalyst layer 11. On the other hand, the cathode gas diffusion layer 14 stacked on the cathode catalyst layer 13 serves to uniformly supply the oxidant to the cathode catalyst layer 13 and also serves as a current collector for the cathode catalyst layer 13.

  The anode gas diffusion layer 12 and the cathode gas diffusion layer 14 are made of a known conductive material made of a porous material so that gas can pass therethrough. Further, at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 is configured to have a predetermined hydrophobicity. Since at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 has a predetermined hydrophobicity, the water generated at the cathode is discharged to the outside of the fuel cell 10 without being liquefied, and the cathode catalyst layer 13 You can take in air. As a result, in the fuel cell 10 according to the present embodiment, the reduction reaction in the cathode catalyst layer 13 is promoted, and it is possible to maintain continuous and high power generation.

  Here, the predetermined hydrophobicity of the cathode gas diffusion layer 14 or the predetermined hydrophobicity of the anode gas diffusion layer 12 is specifically the hydrophobicity of the cathode gas diffusion layer 14 or the hydrophobicity of the anode gas diffusion layer 12. When the contact angle θ is expressed by a water droplet, the contact angle θ is hydrophobic with a contact angle θ of 100 degrees or more and 130 degrees or less. The variation in the contact angle θ is caused by measuring at a plurality of cathode gas diffusion layers 14 and measuring at a plurality of positions of the cathode gas diffusion layers 14.

  By setting the hydrophobicity of at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 in the range of the contact angle θ as described above, the amount of air taken into the cathode catalyst layer 13 becomes sufficient, and the cathode The reduction reaction in the catalyst layer 13 is promoted.

  Here, the contact angle θ of water droplets with respect to at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 is such that the droplets and the cathode gas diffusion layer 14 are in contact as shown in FIG. 2D. This is the angle formed by the tangent to the surface curve of the droplet at the point P and the surface of the cathode gas diffusion layer 14.

  This contact angle θ is measured as follows. The measuring device used was a contact angle meter (DropMaster 100), a solid-liquid interface analyzer (DropMaster 500), and a measurement / analysis integrated system software (FAMAS: 2004/7) manufactured by Kyowa Interface Science Co., Ltd.

  First, as shown in FIG. 2A, pure water droplets DR are formed with a microsyringe M (Teflon (registered trademark) coated needle 28G (φ0.1 mm)). In the case of the fuel cell according to the present embodiment, the droplet DR is about 0.5 microliter.

  Next, as shown in FIG. 2B, the bottom of the droplet DR is attached to the measurement object CP (carbon paper). Then, when the microsyringe M is separated from the measurement target CP, the water droplet DR adheres to the surface of the measurement target CP as shown in FIG. 2C. In this state, after 3000 ms, the height h of the water droplet DR and the radius r of the water droplet DR are measured.

  Since the contact angle θ is equal to twice the angle θ1 (= arctan (r / h)) shown in FIG. 2D, the following equation (A) is used from the height h and radius r of the measured water droplet DR. The value of the contact angle θ is calculated.

θ = 2 arctan (r / h) Expression (A)
The contact angle θ calculated as described above indicates that the larger the value, the higher the hydrophobicity of the measurement target CP, and the smaller the value, the lower the hydrophobicity of the measurement target CP.

  An anode conductive layer 17 is stacked on the anode gas diffusion layer 12, and a cathode conductive layer 18 is stacked on the cathode gas diffusion layer 14. The anode conductive layer 17 and the cathode conductive layer 18 are composed of a porous layer such as a mesh made of a conductive metal material such as gold. The anode conductive layer 17 and the cathode conductive layer 18 are configured so that fuel and oxidant do not leak from their peripheral edges.

  Between the anode conductive layer 17 and the electrolyte membrane 15, an anode sealing material 19 having a rectangular frame shape is disposed. The anode sealing material 19 is disposed so as to surround the anode catalyst layer 11 and the anode gas diffusion layer 12.

  On the other hand, a cathode sealing material 20 having a rectangular frame shape is disposed between the cathode conductive layer 18 and the electrolyte membrane 15. The cathode sealing material 20 is disposed so as to surround the cathode catalyst layer 13 and the cathode gas diffusion layer 14.

  The anode sealing material 19 and the cathode sealing material 20 are made of, for example, a rubber O-ring, and prevent fuel leakage and oxidant leakage from the membrane electrode assembly 16. The shapes of the anode sealing material 19 and the cathode sealing material 20 are not limited to a rectangular frame shape, and are appropriately configured to correspond to the outer edge shape of the fuel cell 10.

  As shown in FIG. 1, a gas-liquid separation membrane 22 is disposed so as to cover an opening of a liquid fuel storage chamber 21 that stores liquid fuel F. On the gas-liquid separation membrane 22, a frame 23 (here, a rectangular frame) configured in a shape corresponding to the outer edge shape of the fuel cell 10 is disposed.

  On the frame 23, the membrane electrode assembly 16 including the anode conductive layer 17 and the cathode conductive layer 18 is disposed. The membrane electrode assembly 16 is laminated so that the anode conductive layer 17 is on the frame 23 side. Here, the frame 23 is made of an electrically insulating material, and is specifically formed of a thermoplastic polyester resin such as polyethylene terephthalate (PET).

  The liquid fuel F stored in the liquid fuel storage chamber 21 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.

  The vaporized component of the liquid fuel F means vaporized methanol when liquid methanol is used as the liquid fuel F, and the vaporized component of methanol when an aqueous methanol solution is used as the liquid fuel F. It means an air-fuel mixture consisting of water vaporization components.

  A vaporized fuel storage chamber 24, which is a space surrounded by the gas-liquid separation film 22, the fuel electrode conductive layer 17, and the frame 23, temporarily stores the vaporized component of the liquid fuel F that has permeated through the gas-liquid separation film 22, Furthermore, it functions as a space for making the fuel concentration distribution in the vaporized component uniform.

  The gas-liquid separation membrane 22 described above separates the vaporized component of the liquid fuel F and the liquid fuel F, and allows the vaporized component to permeate the anode catalyst layer 11 side. The gas-liquid separation membrane 22 is formed in a sheet shape with a material that is inert to the liquid fuel F and does not dissolve, and specifically, silicone rubber, low-density polyethylene (LDPE) thin film, polyvinyl chloride (PVC) thin film. , Polyethylene terephthalate (PET) thin film, fluororesin (for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), etc.), etc. The gas-liquid separation membrane 22 is configured so that fuel or the like does not leak from the periphery.

  In order to further promote the effect of the present invention, the moisture retaining layer 26 is disposed on the air electrode conductive layer 18 via a frame 25 (here, a rectangular frame) configured in a shape corresponding to the outer edge shape of the fuel cell 10. Are stacked. On the moisturizing layer 26, a surface cover layer 27 in which a plurality of air inlets 28 for taking in air as an oxidant is formed is laminated. The surface cover layer 27 functions as a surface layer.

  Since the surface cover layer 27 also plays a role of pressurizing the laminated body including the membrane electrode assembly 16 and improving its adhesion, it is made of a metal such as SUS304, for example. Similarly to the frame 23 described above, the frame 25 is made of an electrically insulating material. Specifically, the frame 25 is made of, for example, a thermoplastic polyester resin such as polyethylene terephthalate (PET).

  The moisturizing layer 26 impregnates part of the water generated in the cathode catalyst layer 13 to suppress the transpiration of water, and uniformly introduces an oxidant into the anode gas diffusion layer 14, thereby providing a cathode catalyst. It also has a function as an auxiliary diffusion layer that promotes uniform diffusion of the oxidizing agent into the layer 13.

  Next, the operation of the fuel cell 10 described above will be described. The liquid fuel F (for example, aqueous methanol solution) in the liquid fuel storage chamber 21 is vaporized, and the vaporized mixture of methanol and water vapor passes through the gas-liquid separation membrane 22 and is temporarily stored in the vaporized fuel storage chamber 24, and the concentration Distribution is made uniform. The air-fuel mixture once stored in the vaporized fuel storage chamber 24 passes through the anode conductive layer 17, is further diffused in the anode gas diffusion layer 12, and is supplied to the anode catalyst layer 11.

  Here, in the fuel cell 10 according to the embodiment, the porosity of the anode gas diffusion layer 12 is set to be larger than the porosity of the cathode gas diffusion layer 14, and a predetermined amount of vaporized mixture is passed through the anode gas diffusion layer 12. Thus, the anode catalyst layer 11 can be supplied efficiently. The air-fuel mixture supplied to the anode catalyst layer 11 causes an internal reforming reaction of methanol represented by the following formula (1).

CH3OH + H2O → CO2 + 6H ++ 6e ⁻ (1)
In addition, when pure methanol is used as the liquid fuel F, since water vapor is not supplied from the liquid fuel storage chamber 21, water generated in the cathode catalyst layer 13, water in the electrolyte membrane 15 and the like are methanol and the above. The internal reforming reaction of the formula (1) is generated, or the internal reforming reaction is generated by another reaction mechanism that does not require water, regardless of the internal reforming reaction of the formula (1).

Protons (H ⁺ ) generated by the internal reforming reaction are conducted through the electrolyte membrane 15 and reach the cathode catalyst layer 13.

  Air taken in from the air inlet 28 of the surface cover layer 27 diffuses through the moisture retention layer 26, the cathode conductive layer 18, and the cathode gas diffusion layer 14 and is supplied to the cathode catalyst layer 13. The air supplied to the cathode catalyst layer 13 undergoes a reaction represented by the following formula (2). By this reaction, water is generated and a power generation reaction occurs.

(3/2) O2 + 6H ++ 6e ⁻ → 3H2O Formula (2)
A part of the water generated in the cathode catalyst layer 13 by this reaction is stored in the cathode gas diffusion layer 14, and the remaining water reaches the moisture retention layer 26 via the cathode gas diffusion layer 14. In the fuel cell 10 according to this embodiment, since the cathode gas diffusion layer 14 has a predetermined hydrophobicity, water generated at the cathode is released to the moisture retention layer 26 without being liquefied. A part of the water reaching the moisture retaining layer 26 is evaporated from the air inlet 28 of the surface cover layer 27 provided on the moisture retaining layer 26, and the remaining water is temporarily stored in the moisture retaining layer 26.

  Furthermore, when the reaction of Formula (2) proceeds, the amount of generated water increases, and the amount of water stored in the cathode gas diffusion layer 14 and the cathode catalyst layer 13 increases. In this case, as the reaction of Formula (2) proceeds, the water storage amount in the cathode gas diffusion layer 14 and the cathode catalyst layer 13 becomes larger than the water storage amount in the anode catalyst layer 11.

  As a result, the phenomenon that the water generated in the cathode catalyst layer 13 moves to the anode catalyst layer 11 through the electrolyte membrane 15 is promoted by the osmotic pressure phenomenon. Therefore, compared with the case where the supply of moisture to the anode catalyst layer 11 is dependent only on the water vapor evaporated from the liquid fuel storage chamber 21, the supply of moisture is promoted, and the internal reforming reaction of methanol in the above-described equation (1) is performed. Can be promoted.

  Even when a methanol aqueous solution having a methanol concentration exceeding 50 mol% or pure methanol is used as the liquid fuel F, water that has moved from the cathode catalyst layer 13 to the anode catalyst layer 11 may be used for the internal reforming reaction. As a result, 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 load current characteristics can be further improved. Further, the liquid fuel storage chamber 21 can be downsized.

  In the above-described embodiment, 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 to these. For example, ethanol fuel such as ethanol aqueous solution or pure ethanol, propanol fuel such as propanol aqueous solution or pure propanol, glycol fuel such as glycol aqueous solution or pure glycol, dimethyl ether, formic acid, or other liquid fuel may be used. In any case, liquid fuel corresponding to the fuel cell is accommodated.

  In addition, the present invention can be applied to an active fuel cell, and also to a semi-passive fuel cell using a pump or the like for a part of fuel supply, etc. The same operation effect as the case where there was was obtained.

  Next, in the fuel cell 10 in which the contact angle θ of the cathode gas diffusion layer 14 with water droplets is set in the range of 100 degrees to 130 degrees, excellent output characteristics can be obtained as follows. Examples will be described.

(First embodiment)
The fuel cell 10 according to the present embodiment was produced as follows. That is, after immersing carbon paper (TGP-H-120 manufactured by Toray Industries, Inc.) in a PTFE solution prepared to 10% by mass, the carbon paper was dried and fired to prepare the cathode gas diffusion layer 14.

  A platinum-supported graphite particle and a Nafion solution (DEPON DE 2020) were mixed with a dissolver to prepare a slurry. The slurry was applied to one surface of the carbon paper which is the cathode gas diffusion layer 14, and then dried to form the cathode catalyst layer 13 to produce a cathode.

  Next, platinum ruthenium graphite particles and a Nafion solution (DE2020 manufactured by DuPont) were mixed with a dissolver to prepare a slurry. The slurry was applied to one surface of the carbon paper that was the anode gas diffusion layer 12 and then dried to form an anode catalyst layer 11 to produce an anode.

  A solid electrolyte membrane (Nafion 112 manufactured by DuPont) (hereinafter referred to as an electrolyte membrane) is used as the electrolyte membrane 15, and a cathode with the cathode catalyst layer 13 facing one of the electrolyte membranes 15 and an anode with the anode catalyst layer 11 facing the other are disposed. And it joined by hot press, and the membrane electrode assembly 16 (henceforth, MEA) was produced.

  Water was dropped on the cathode gas diffusion layer 14 of the MEA 16 to measure the contact angle θ. As a result of the measurement, the contact angle θ was 110 degrees or more and 120 degrees or less. Each of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 of the MEA 16 is provided with a gold foil having a plurality of holes for taking in air or taking in vaporized methanol, thereby forming the cathode conductive layer 13 and the anode conductive layer 11. .

  A resin frame having a plurality of holes for taking in air or taking in vaporized methanol was disposed in the laminate of the MEA 16, the cathode gas diffusion layer 14, and the anode gas diffusion layer 12. Further, rubber O-rings 19 and 20 were sandwiched and sealed between the cathode side of the MEA 16 and one frame, and between the anode side of the MEA 16 and the other frame, respectively.

  The anode-side frame 23 was fixed to the liquid fuel storage chamber 21 with screws through the gas-liquid separation membrane 22. A silicon sheet having a thickness of 0.2 mm was used for the gas-liquid separation membrane 22.

  On the other hand, a porous plate was disposed on the cathode-side frame 25 to form a moisture retention layer 26. On this moisturizing layer 26, a surface cover layer 27 is formed by disposing a stainless steel plate (SUS304) having a thickness of 2 mm on which air inlets for intake of air (diameter 4 mm, number 64) are formed, It was fixed to the frame 25 by screwing.

10 ml of pure methanol was injected into the liquid fuel storage chamber 21 of the fuel cell 10 formed as described above, and the maximum output value was measured from the current value and the voltage value in an environment of a temperature of 25 ° C. and a relative humidity of 50%. . As a result of the measurement, the maximum output value of the fuel cell 10 was 25 mW / cm ² .

(Second embodiment)
Another fuel cell 10 according to the present embodiment was produced as follows. That is, after immersing carbon paper (TGP-H-120 manufactured by Toray Industries, Inc.) in a PTFE solution prepared to 10% by mass, the carbon paper was dried and fired to prepare the anode gas diffusion layer 12.

  Platinum ruthenium graphite particles and Nafion solution (DE2020 manufactured by DuPont) were mixed with a dissolver to prepare a slurry. The slurry was applied to one surface of the carbon paper which is the anode gas diffusion layer 12 and then dried to form an anode catalyst layer 11 to produce an anode.

  Next, the platinum-supported graphite particles and Nafion solution (DuPont DE2020) were mixed with a dissolver to prepare a slurry. The slurry was applied to one surface of carbon paper as the cathode gas diffusion layer 14 and then dried to form the cathode catalyst layer 13 to produce a cathode.

  A solid electrolyte membrane (Nafion 112 manufactured by DuPont) (hereinafter referred to as an electrolyte membrane) is used as the electrolyte membrane 15, and a cathode with the cathode catalyst layer 13 facing one of the electrolyte membranes 15 and an anode with the anode catalyst layer 11 facing the other are disposed. And it joined by hot press, and the membrane electrode assembly 16 (henceforth, MEA) was produced.

  Water was dropped on the anode gas diffusion layer 12 of the MEA 16 to measure the contact angle θ. As a result of the measurement, the contact angle θ was 110 degrees or more and 120 degrees or less. Each of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 of the MEA 16 is provided with a gold foil having a plurality of holes for taking in air or taking in vaporized methanol, thereby forming the cathode conductive layer 13 and the anode conductive layer 11. .

  A resin frame having a plurality of holes for taking in air or taking in vaporized methanol was disposed in the laminate of the MEA 16, the cathode gas diffusion layer 14, and the anode gas diffusion layer 12. Further, rubber O-rings 19 and 20 were sandwiched and sealed between the cathode side of the MEA 16 and one frame, and between the anode side of the MEA 16 and the other frame, respectively.

  The anode-side frame 23 was fixed to the liquid fuel storage chamber 21 with screws through the gas-liquid separation membrane 22. A silicon sheet having a thickness of 0.2 mm was used for the gas-liquid separation membrane 22.

  On the other hand, a porous plate was disposed on the cathode-side frame 25 to form a moisture retention layer 26. On this moisturizing layer 26, a surface cover layer 27 is formed by disposing a stainless steel plate (SUS304) having a thickness of 2 mm on which air inlets for intake of air (diameter 4 mm, number 64) are formed, It was fixed to the frame 25 by screwing.

10 ml of pure methanol was injected into the liquid fuel storage chamber 21 of the fuel cell 10 formed as described above, and the maximum output value was measured from the current value and the voltage value in an environment of a temperature of 25 ° C. and a relative humidity of 50%. . As a result of the measurement, the maximum output value of the fuel cell 10 was 25 mW / cm ² .

(Third embodiment)
Another fuel cell 10 according to the present embodiment was produced as follows. That is, after carbon paper (TGP-H-120 manufactured by Toray Industries, Inc.) was immersed in a PTFE solution prepared to 10% by mass, the carbon paper was dried and fired, and the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 were obtained. Was made.

  A platinum-supported graphite particle and a Nafion solution (DEPON DE 2020) were mixed with a dissolver to prepare a slurry. The slurry was applied to one surface of the carbon paper which is the cathode gas diffusion layer 14, and then dried to form the cathode catalyst layer 13 to produce a cathode.

  Next, platinum ruthenium graphite particles and a Nafion solution (DE2020 manufactured by DuPont) were mixed with a dissolver to prepare a slurry. The slurry was applied to one surface of the carbon paper that was the anode gas diffusion layer 12 and then dried to form an anode catalyst layer 11 to produce an anode.

  A solid electrolyte membrane (Nafion 112 manufactured by DuPont) (hereinafter referred to as an electrolyte membrane) is used as the electrolyte membrane 15, and a cathode with the cathode catalyst layer 13 facing one of the electrolyte membranes 15 and an anode with the anode catalyst layer 11 facing the other are disposed. And it joined by hot press, and the membrane electrode assembly 16 (henceforth, MEA) was produced.

  Water was dropped onto the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 of the MEA 16 to measure the contact angle θ. As a result of the measurement, the contact angle θ was 110 degrees or more and 120 degrees or less. Each of the cathode gas diffusion layer 14 and the anode gas diffusion layer 12 of the MEA 16 is provided with a gold foil having a plurality of holes for taking in air or taking in vaporized methanol, thereby forming the cathode conductive layer 13 and the anode conductive layer 11. .

  A resin frame having a plurality of holes for taking in air or taking in vaporized methanol was disposed in the laminate of the MEA 16, the cathode gas diffusion layer 14, and the anode gas diffusion layer 12. Further, rubber O-rings 19 and 20 were sandwiched and sealed between the cathode side of the MEA 16 and one frame, and between the anode side of the MEA 16 and the other frame, respectively.

  The anode-side frame 23 was fixed to the liquid fuel storage chamber 21 with screws through the gas-liquid separation membrane 22. A silicon sheet having a thickness of 0.2 mm was used for the gas-liquid separation membrane 22.

  On the other hand, a porous plate was disposed on the cathode-side frame 25 to form a moisture retention layer 26. On this moisturizing layer 26, a surface cover layer 27 is formed by disposing a stainless steel plate (SUS304) having a thickness of 2 mm on which air inlets for intake of air (diameter 4 mm, number 64) are formed, It was fixed to the frame 25 by screwing.

10 ml of pure methanol was injected into the liquid fuel storage chamber 21 of the fuel cell 10 formed as described above, and the maximum output value was measured from the current value and the voltage value in an environment of a temperature of 25 ° C. and a relative humidity of 50%. . As a result of the measurement, the maximum output value of the fuel cell 10 was 25 mW / cm ² .

(First comparative example)
The structure of the fuel cell used in the first comparative example is that carbon paper (TGP-H-120 manufactured by Toray Industries, Inc.) is immersed in a PTFE solution prepared to 5% by mass, and then the carbon paper is dried and fired. Except for using the produced cathode gas diffusion layer, the configuration is the same as that of the fuel cell according to the above-described embodiment.

Water was dropped on the gas diffusion layer of the MEA cathode to measure the contact angle. As a result of the measurement, the contact angle θ was 90 degrees or more and 100 degrees or less. The measurement method and measurement conditions of the maximum output value are the same as the measurement method and measurement conditions in the fuel cell according to the example. As a result of the measurement, the maximum value of the output of the fuel cell according to the first comparative example was 20 mW / cm ² .

  The maximum output value of the fuel cell according to the first comparative example is lower than that of the fuel cell according to the example because the cathode gas diffusion layer of the fuel cell according to the comparative example has insufficient hydrophobicity and is generated at the cathode. This is thought to be because the collected water stays in the gas diffusion layer of the cathode and cannot take in air.

(Second comparative example)
The structure of the fuel cell used in the first comparative example was that carbon paper (TGP-H-120 manufactured by Toray Industries, Inc.) was immersed in a PTFE solution prepared to 15% by mass, and then the carbon paper was dried and fired. Except for using the produced cathode gas diffusion layer, the configuration is the same as that of the fuel cell of the first embodiment.

Water was dropped on the MEA cathode gas diffusion layer to measure the contact angle. As a result of the measurement, the contact angle θ was 130 degrees or more and 140 degrees or less. The measurement method and measurement conditions of the maximum value of the output of the fuel cell according to the second comparative example are the same as the measurement method and measurement conditions in the fuel cell according to the example. As a result of the measurement, the maximum value of the output of the fuel cell according to the second comparative example was 15 mW / cm ² .

  In the fuel cell according to the second comparative example, the maximum output value is lower than that of the fuel cell according to the example because the hole of the cathode gas diffusion layer is clogged with PTFE. This is probably because the flow rate of the air to be taken in has become smaller.

  On the other hand, the maximum output value in the above-described example of the fuel cell according to the present embodiment is high because the cathode gas diffusion layer is sufficiently hydrophobic in the fuel cell according to the example, and the water generated at the cathode is high. This is considered to be because the gas is released without being liquefied and the flow rate for taking in air is secured.

  As described above, the maximum output value of the fuel cell according to the example was higher than the maximum output value of the fuel cell according to the first comparative example and the second comparative example. That is, it was found that excellent output characteristics can be obtained in the fuel cell according to the present embodiment.

  That is, according to the fuel cell according to the present embodiment, air can be taken into the cathode catalyst layer by discharging water generated inside the power generation element to the outside of the power generation element without stagnation, and continuously. A fuel cell capable of maintaining high power generation can be provided.

  In addition, in said Example, although the mass concentration of the PTFE solution in which carbon paper (TGP-H-120 by Toray Industries, Inc.) is immersed was 10%, if it can acquire the effect of this invention, it is. The concentration of the PTFE solution may be changed as appropriate.

  Furthermore, in the above embodiment, in order to adjust the hydrophobicity of at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer, carbon paper was immersed in PTFE solutions having different mass concentrations. For example, the hydrophobicity of at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer may be adjusted by adjusting the time during which the carbon paper is immersed in the PTFE solution. The hydrophobicity of at least one of the cathode gas diffusion layer 14 and the anode gas diffusion layer can be adjusted by impregnation by spraying or coating.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In the above embodiment, the passive DMFC has been described as an example. However, the structure of the fuel cell is not limited as long as the structure uses not only the passive type but also water generated by the reaction on the anode side. Absent.

  Further, the configuration of the fuel cell 10 is not limited to the above-described configuration. For example, a hydrophobic porous film may be provided between the anode conductive layer 17 and the frame 23. By providing this porous film, it is possible to prevent water from entering from the anode gas diffusion layer 12 side to the vaporized fuel storage chamber 24 side via the porous film.

  As a result, a decrease in fuel concentration that occurs on the liquid fuel storage chamber 21 side from the anode gas diffusion layer 12 can be suppressed, and fuel having a predetermined concentration can be supplied to the anode catalyst layer 11. Specific examples of the material for the porous film include polytetrafluoroethylene (PTFE) and a water-repellent treated silicone sheet.

  Further, a permeation amount adjusting membrane for adjusting the permeation amount of the vaporized component of the fuel is provided on the liquid fuel storage chamber 21 side of the gas-liquid separation membrane 22 and has the same gas-liquid separation function as the gas-liquid separation membrane 22 May be. The adjustment of the permeation amount of the vaporized component by the permeation amount adjusting film is performed by adjusting the diameter of the opening provided in the permeation amount adjusting film.

  This permeation amount adjusting film can be made of, for example, a material such as polyethylene terephthalate. By providing this permeation amount adjusting membrane, it is possible to adjust the supply amount of the vaporized component of the fuel supplied to the anode catalyst layer 11 side.

  Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

  For example, in the above description, the structure of the fuel cell has been described with the structure having the liquid fuel storage chamber below the membrane electrode assembly (MEA). However, the supply of fuel from the liquid fuel storage chamber to the membrane electrode assembly is not allowed to flow. It may be a structure in which roads are arranged and connected. In addition, a passive type fuel cell has been described as an example of the configuration of the fuel cell main body. However, an active type fuel cell, and a fuel of a type called a semi-passive that uses a pump or the like for part of a fuel supply, etc. The present invention can also be applied to a battery. In the semi-passive type fuel cell, the fuel supplied from the fuel storage part to the membrane electrode assembly is used for the power generation reaction, and is not circulated thereafter and returned to the fuel storage part. The semi-passive type fuel cell is different from the conventional active method because it does not circulate the fuel, and does not impair the downsizing of the device.

  In addition, the fuel cell uses a pump for supplying fuel, and is different from a pure passive system such as a conventional internal vaporization type. For this reason, the fuel cell is referred to as a semi-passive method as described above. In this semi-passive type fuel cell, a fuel cutoff valve may be arranged in place of the pump as long as fuel is supplied from the fuel storage portion to the membrane electrode assembly. In this case, the fuel cutoff valve is provided to control the supply of liquid fuel through the flow path.

Even if it is these structures, the effect similar to the above-mentioned description is acquired. The liquid fuel vapor supplied to the MEA may be all supplied as a liquid fuel vapor, but the present invention can be applied even when a part of the liquid fuel vapor is supplied in a liquid state.

The figure which shows schematically the example of 1 structure of the fuel cell which concerns on one Embodiment of this invention. The figure for demonstrating the method to measure the contact angle of the surface of the cathode gas diffusion layer of the fuel cell shown in FIG. The figure for demonstrating the method to measure the contact angle of the surface of the cathode gas diffusion layer of the fuel cell shown in FIG. The figure for demonstrating the method to measure the contact angle of the surface of the cathode gas diffusion layer of the fuel cell shown in FIG. The figure for demonstrating the method to measure the contact angle of the surface of the cathode gas diffusion layer of the fuel cell shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 ... Electrolyte membrane, 10 ... Fuel cell, 11 ... Anode catalyst layer, 12 ... Anode gas diffusion layer, 13 ... Cathode catalyst layer, 14 ... Cathode gas diffusion layer

Claims (5)

A cathode, an anode, and an electrolyte membrane sandwiched between the cathode and the anode;
The cathode includes a cathode catalyst layer disposed to face one surface of the electrolyte membrane, and a cathode gas diffusion layer disposed to face the cathode catalyst layer,
The anode has an anode catalyst layer disposed to face the other surface of the electrolyte membrane, and an anode gas diffusion layer disposed to face the anode catalyst layer,
A fuel cell in which at least one of the cathode gas diffusion layer and the anode gas diffusion layer has predetermined hydrophobicity.   The cathode gas diffusion layer has a surface formed on the surface of the cathode gas diffusion layer and the liquid droplets when the droplet made of water is placed on the surface of the cathode gas diffusion layer opposite to the surface facing the cathode catalyst layer. The fuel cell according to claim 1, wherein the contact angle with the surface has hydrophobicity that is not less than 100 degrees and not more than 130 degrees. Forming a cathode;
Forming an anode;
Forming an electrolyte membrane sandwiched between the cathode and the anode, and
The step of forming the cathode has a step of forming a cathode gas diffusion layer and a step of forming a cathode catalyst layer,
The step of forming the cathode gas diffusion layer includes a step of performing a hydrophobic treatment so that the cathode gas diffusion layer has a predetermined hydrophobicity. Forming a cathode;
Forming an anode;
Forming an electrolyte membrane sandwiched between the cathode and the anode, and
The step of forming the anode includes a step of forming an anode gas diffusion layer and a step of forming an anode catalyst layer,
The step of forming the anode gas diffusion layer includes a step of performing a hydrophobic treatment so that the anode gas diffusion layer has a predetermined hydrophobicity.   4. The method of manufacturing a fuel cell according to claim 3, wherein the step of performing the hydrophobic treatment includes a step of impregnating carbon paper with a polytetrafluoroethylene (PTFE) solution prepared to a predetermined mass percent concentration.

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