JP2010232043A - Method for manufacturing gas diffusion layer or gas diffusion electrode for polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a gas diffusion layer and a method for manufacturing a gas diffusion electrode for a polymer electrolyte fuel cell for manufacturing the polymer electrolyte fuel cell having high performance without obstructing supply of fuel and an oxidant to a catalyst layer and exhaust of excess moisture by preventing penetration of a microporous layer and the catalyst layer into a conductive porous substrate. <P>SOLUTION: The method for manufacturing the gas diffusion layer for the polymer electrolyte fuel cell includes the steps of: (A) impregnating a penetration preventing agent in a molten state into a conductive porous substrate; (B) forming a microporous layer by applying a paste composition for forming the microporous layer to the conductive porous substrate into which a penetration preventing agent is impregnated and drying; and (C) removing the penetration preventing agent impregnated into the conductive porous substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a gas diffusion layer or gas diffusion electrode for a polymer electrolyte fuel cell.

  A fuel cell is an electrochemical system in which electrodes are arranged on both sides of an electrolyte membrane and generates electricity by an electrochemical reaction between hydrogen and oxygen, and only water is generated during power generation. Thus, unlike conventional internal combustion engines, fuel cells do not generate environmental load gases such as carbon dioxide, and therefore are expected to become popular as next-generation clean energy systems. Among them, the polymer electrolyte fuel cell, in particular, has a low operating temperature, low electrolyte resistance, and uses a highly active catalyst, so it can obtain high output even in a small size, such as a home cogeneration system. As soon as practical use is expected.

  This polymer electrolyte fuel cell has a structure in which a solid polymer electrolyte membrane having proton conductivity is used, a catalyst layer is arranged on both sides of the electrolyte membrane, and a gas diffusion layer is arranged on the outside thereof. Yes. And it has the structure which has arrange | positioned the gasket so that the circumference | surroundings of the electrode which consists of a catalyst layer and a gas diffusion layer may be enclosed, and also this was pinched | interposed with the separator.

  Normally, in a polymer electrolyte fuel cell, drying is prevented by humidifying and supplying a fuel or an oxidant in order to keep proton conductivity of the polymer electrolyte membrane high. On the other hand, when excessive moisture is supplied, a phenomenon called flooding occurs in which water is condensed in the catalyst layer and the gas diffusion layer to block the pores. As a result, the movement of the fuel and the oxidant within the electrode is hindered, and there is a possibility that a problem occurs in the power generation of the fuel cell. Therefore, in order to prevent flooding, it is important that the gas diffusion layer and the catalyst layer have water repellency.

  Generally, a conductive porous substrate such as carbon paper or carbon cloth is used for the gas diffusion layer, and surface treatment is performed with polytetrafluoroethylene (PTFE) or the like in order to impart water repellency thereto. .

  For example, as described in the Examples of Patent Document 1, after immersing the conductive porous substrate in a dispersion of PTFE, firing is performed at a high temperature of about 350 ° C. to remove the dispersion medium, the dispersant, and the like. By doing so, a water repellent treatment is performed.

  As described above, a conductive porous substrate is used for the gas diffusion layer, but an intermediate layer may be provided between the conductive porous substrate and the catalyst layer. This is called an underlayer, MPL (micro porous layer), etc., and a catalyst layer having a uniform thickness is formed on the gas diffusion layer, gas supply to the catalyst layer is made uniform, etc. It is a functional layer with the role of As with the gas diffusion layer, it is desirable that the microporous layer has water repellency in order to prevent flooding. For example, the microporous layer is composed of carbon particles and PTFE. In the case where the microporous layer is provided, the conductive porous substrate is called a gas diffusion substrate, and the one in which the microporous layer is formed on the gas diffusion substrate is called a gas diffusion layer.

  The microporous layer is formed, for example, by applying and drying a paste composition made of carbon particles, PTFE, a dispersant, and the like on the conductive porous substrate. However, when the paste composition is applied, a part of the paste composition penetrates into the pores of the conductive porous substrate. If this amount of soaking is large, the pores of the conductive porous substrate will be blocked, and the supply of fuel or oxidant necessary for the reaction to the catalyst layer will be hindered, or excessive water discharge will be hindered. Therefore, sufficient power generation performance as a fuel cell cannot be obtained. In addition, if the amount of the soaked paste composition is not uniform, distribution occurs in the electrode due to the supply of fuel or oxidant necessary for the reaction and excessive water discharge, and the power generation performance of the fuel cell decreases.

  In order to prevent the microporous layer forming paste composition from penetrating into the conductive porous substrate as described above, as a conventional method, the water repellent treatment of the conductive porous substrate as described above is used. Is done. However, the effect of suppressing the penetration of the paste composition obtained by increasing the water repellency of the conductive porous substrate was insufficient.

  Furthermore, in Patent Document 2, a method of suppressing penetration of a paste composition into a conductive porous substrate by dissolving a disappearing substance in a solvent and filling the pores of the conductive porous substrate. Has been proposed. However, the filling method involves immersing the solution in which the disappearing substance is dissolved or spraying it by coating, and the distribution of the disappearing substance in the pores of the conductive porous substrate is uneven. Met. For this reason, the technique of Patent Document 2 cannot sufficiently suppress the penetration of the microporous layer forming paste composition into the pores of the conductive porous substrate.

Japanese Patent Laid-Open No. 2005-19298 JP-A-2005-38695

  The present invention prevents the components constituting the microporous layer and the catalyst layer from penetrating into the conductive porous substrate, thereby inhibiting the supply of fuel and oxidant to the catalyst layer, the discharge of excess moisture, etc. It is an object of the present invention to provide a gas diffusion layer for a polymer electrolyte fuel cell and a method for producing a gas diffusion electrode, which can produce a high-performance polymer electrolyte fuel cell without performing the above.

  As a result of intensive studies to solve the above problems, the present inventors filled the conductive porous base material with an infiltration agent in a molten state, and then formed a microporous layer or a catalyst layer. It has been found that a desired gas diffusion layer and gas diffusion electrode that solve the above-mentioned problems can be obtained by removing the penetration inhibitor. The present invention has been completed based on such findings.

  That is, the present invention relates to the following gas diffusion layer and gas diffusion electrode manufacturing method, gas diffusion layer, gas diffusion electrode, membrane-electrode assembly, and polymer electrolyte fuel cell.

Item 1. (A) A step of filling a conductive porous substrate with a permeation preventive agent in a molten state,
(B) Applying and drying a microporous layer forming paste composition on a conductive porous substrate filled with an infiltration inhibitor, and forming a microporous layer; and (C) a conductive porous substrate. A method for producing a gas diffusion layer for a polymer electrolyte fuel cell, comprising a step of removing an infiltration agent filled in the solid polymer fuel cell.

  Item 2. Item 2. The method for producing a gas diffusion layer according to Item 1, wherein the penetration inhibitor has a melting point of 0 to 30 ° C and a boiling point of 50 to 120 ° C.

  Item 3. Item 3. The method for producing a gas diffusion layer according to Item 1 or 2, wherein the step (A) is a step of immersing the conductive porous substrate in a liquid film of the infiltration agent in a melted state.

  Item 4. Item 4. The method for producing a gas diffusion layer according to Item 3, wherein the thickness of the liquid film of the penetration inhibitor is 40 to 80% of the thickness of the conductive porous substrate.

  Item 5. Item 5. A gas diffusion layer for a polymer electrolyte fuel cell obtained by the method for producing a gas diffusion layer according to any one of Items 1 to 4.

  Item 6. Item 6. A gas diffusion electrode for a polymer electrolyte fuel cell, wherein a catalyst layer is formed on the microporous layer of the gas diffusion layer according to Item 5.

Item 7. (A) filling a conductive porous substrate with a soaking agent in a molten state;
(B) a step of applying and drying the catalyst layer forming paste composition on the conductive porous substrate filled with the infiltration inhibitor and forming a catalyst layer; and (c) filling the conductive porous substrate. A method for producing a gas diffusion electrode for a polymer electrolyte fuel cell, comprising a step of removing the permeation inhibitor.

  Item 8. Item 8. The method for producing a gas diffusion electrode for a polymer electrolyte fuel cell according to Item 7, wherein the infiltration agent has a melting point of 0 to 30 ° C and a boiling point of 50 to 120 ° C.

  Item 9. Item 9. The gas diffusion electrode for a polymer electrolyte fuel cell according to Item 7 or 8, wherein the step (a) is a step of immersing the conductive porous substrate in a liquid film of the infiltration agent in a melted state. Production method.

  Item 10. Item 10. The method for producing a gas diffusion electrode for a polymer electrolyte fuel cell according to Item 9, wherein the liquid film of the infiltration agent is 40 to 80% of the thickness of the conductive porous substrate.

  Item 11. Item 11. A gas diffusion electrode for a polymer electrolyte fuel cell obtained by the method for producing a gas diffusion electrode according to any one of Items 7 to 10.

  Item 12. The gas diffusion layer of Item 5 is laminated so that the catalyst layer and the microporous layer are in contact with one side or both sides of the catalyst layer-electrolyte membrane laminate in which the catalyst layer is formed on one side or both sides of the electrolyte membrane. A membrane-electrode assembly for a polymer electrolyte fuel cell.

  Item 13. A membrane-electrode assembly for a polymer electrolyte fuel cell, wherein the gas diffusion electrode according to Item 6 or 11 is laminated on one surface or both surfaces of the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact with each other.

  Item 14. Item 14. A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to Item 12 or 13.

1. Gas diffusion layer The method for producing a gas diffusion layer for a polymer electrolyte fuel cell of the present invention comprises:
(A) A step of filling a conductive porous substrate with a permeation preventive agent in a molten state,
(B) Applying and drying a microporous layer forming paste composition on a conductive porous substrate filled with an infiltration inhibitor, and forming a microporous layer; and (C) a conductive porous substrate. The step of removing the permeation preventive agent filled in is provided.

<Process (A)>
In the step (A), the conductive porous base material is filled with a soaking agent in a melted state.

  The conductive porous substrate is not particularly limited, and a substrate that can permeate the fuel or the oxidant and has electronic conductivity is used. In general, a metal material, a carbon material, or the like is selected as the material, but carbon paper, carbon cloth, carbon felt, carbon nonwoven fabric, or the like made of carbon fiber is preferably used from the viewpoint of durability, price, and the like.

  The thickness of the conductive porous substrate is not particularly limited, and may be in a range generally adopted as a gas diffusion layer of a polymer electrolyte fuel cell. Specifically, it is about 50-1000 micrometers normally, Preferably it is about 100-400 micrometers.

  In the present invention, the permeation preventive agent is filled in the conductive porous substrate in a molten state. As in Patent Document 2, when the penetration inhibitor is dissolved in a solvent and filled, the distribution of the penetration inhibitor in the pores of the conductive porous substrate becomes non-uniform. In this invention, it can distribute uniformly in the pore of an electroconductive porous base material by filling in the state which melt | dissolved the permeation preventive agent without using a solvent etc. Thereby, it can prevent that the microporous layer formed at a process (B) permeates into an electroconductive porous base material.

  Although this penetration prevention agent is based also on the temperature conditions at the time of performing process (A)-(C), melting | fusing point is about 0-30 degreeC, Preferably it is about 5-26 degreeC, and a boiling point is 50-120 degreeC. A degree, preferably about 59-85 ° C. is preferred. When the melting point of the soaking inhibitor is within the above range, since the soaking inhibitor is solid at room temperature, the microporous layer forming paste composition can be applied at room temperature in step (B). Further, when the boiling point of the soaking inhibitor is within the above range, the soaking inhibitor can be removed at the same time when the microporous layer forming paste composition is applied and then dried.

  In addition, in the removal step of the step (C), a soaking agent that does not damage the microporous layer, specifically, a material that does not induce decomposition, corrosion, or the like by contacting the microporous layer is preferable. In addition, in the removal process utilizing phenomena such as combustion and evaporation, attention should be paid to the selection of substances or the setting of removal conditions so as not to physically destroy the microporous layer due to rapid volume expansion.

  Examples of the permeation preventive agent satisfying the above conditions include t-butyl alcohol (melting point: 25 ° C., boiling point: 83 ° C.), benzene (melting point: 6 ° C., boiling point: 80 ° C.), and the like. A low melting point material or a low softening point material such as polyethylene glycol (molecular weight of about 600, softening point: about 20 ° C., boiling point: about 250 ° C.) can also be used. Among these, t-butyl alcohol can also be used as a dispersion medium for the microporous layer forming paste composition, so when the microporous layer forming paste composition is dried, the permeation preventive agent is simultaneously removed. This is preferable.

  There is no particular limitation on the method of filling the conductive porous substrate with the melted infiltration agent. For example, as shown in FIG. 1, the infiltration agent in the molten state of the conductive porous substrate is used. Examples include a method of immersing in a liquid film.

  When adopting a method of immersing the conductive porous substrate in a liquid film of the infiltration agent in a melted state, for example, the following method may be used to fill the infiltration agent into the conductive porous substrate. it can.

  First, in a container (bat, petri dish, etc.) having a flat bottom and a side wall high enough to prevent liquid from leaking, a soaked infiltration agent is placed in the container, and the liquid film has a desired thickness. Adjust so that At this time, the thickness of the liquid film is preferably about 40 to 80%, more preferably about 50 to 75% of the thickness of the conductive porous substrate. By setting the thickness of the liquid film within this range, the penetration inhibitor can be more uniformly distributed in the pores of the conductive porous substrate. As a result, peeling and dropping of the microporous layer can be prevented, and gas supply and moisture discharge are made uniform, and excellent battery characteristics can be obtained.

  Next, the conductive porous base material is immersed in the soaked infiltration agent in a melted state, and is cooled while being held horizontally to solidify the infiltration agent. The method for cooling the container may be a commonly used method. For example, the container may be placed in a cold storage box, or the container may be cooled using a cooling stage, a cooling agent, or the like.

<Process (B)>
Next, in the step (B), the microporous layer forming paste composition is applied and dried on the conductive porous base material filled with the soaking-in preventing agent to form a microporous layer.

  As the microporous layer forming paste composition, for example, a paste containing conductive carbon particles and a dispersion medium is used. The microporous layer forming paste composition may contain a water repellent, a dispersant and the like.

  As the conductive carbon particles, for example, particulate or powdery carbon materials such as acetylene black, furnace black, activated carbon and the like are preferably used. Carbon fibers, carbon nanotubes, carbon nanofibers and the like may also be used.

  As the dispersion medium, a known or commercially available solvent can be used. In general, water and alcohols such as ethanol are preferably used.

  As the dispersant, a so-called surfactant is preferably used. For example, a known or commercially available aqueous dispersant can be used. For example, polyoxyethylene alkylene alkyl ether, polyethylene glycol alkyl ether, polyoxyethylene fatty acid ester, acidic group-containing structure-modified polyacrylate and the like can be mentioned. Although it is more preferable that it has the characteristic which can be easily removed by extraction, thermal decomposition, etc., it is not specifically limited. This dispersant is used for uniformly dispersing conductive carbon particles, a water repellent, and the like in a dispersion medium.

  The water repellent is added to increase the water repellency of the microporous layer for the purpose of suppressing flooding due to moisture retention. Generally, polytetrafluoroethylene (PTFE), carbon fluoride, fluoride pitch, or the like is used.

  The ratio of each component contained in the paste composition for forming a microporous layer is not limited and can be appropriately selected within a wide range. Specifically, about 3 to 20 parts by weight (preferably about 4 to 19 parts by weight) of the dispersion medium and about 0.05 to 3 parts by weight of the dispersant (preferably about 0.1 to 3 parts by weight) with respect to 1 part by weight of the conductive carbon particles. 07 to 2 parts by weight) and a water repellent of about 0.05 to 20 parts by weight (preferably about 0.1 to 10 parts by weight).

  The method for applying the microporous layer forming paste composition may be a generally used technique, and is not particularly limited. Examples thereof include screen printing, die coating, bar coating, blade coating, and spray coating. It is done.

  Moreover, the method of drying after apply | coating the paste composition for microporous layer formation should just be performed by a general method, and is not specifically limited. Drying conditions may be performed, for example, in the air or under reduced pressure. Further, the temperature may be raised or it may be normal temperature.

  If the boiling point of the dispersion medium to be used is about the same as the boiling point of the soaking inhibitor, the drying treatment can be performed at a temperature equal to or higher than the boiling point of the soaking inhibitor to form a microporous layer and prevent the soaking agent. Removal can be done simultaneously. In this case, the step (C) described later is not necessary.

  The thickness of the microporous layer formed in this way is not limited, but generally about 10 to 100 μm is preferable.

<Process (C)>
Furthermore, in the step (C), the permeation preventive agent filled in the conductive porous substrate is removed. As described above, when the drying treatment in the step (B) is performed at a temperature equal to or higher than the boiling point of the soaking agent, this step (C) is unnecessary.

  Removal of the soaking agent from the conductive porous substrate is performed, for example, by heating. Specifically, it may be heated to a temperature higher than the melting point of the anti-soaking agent and the molten anti-soaking agent may be removed by washing with a solvent, or slowly heated to a temperature higher than the boiling point of the anti-soaking agent. Alternatively, the penetration inhibitor may be removed by evaporation.

  Care must be taken not to damage the microporous layer when the melted penetration inhibitor is washed away. In addition, when evaporating the soaking preventive agent, it is necessary to take care that the microporous layer is not damaged by sudden boiling of the soaking preventive agent when heated rapidly.

<Others>
Thus, after obtaining the gas diffusion layer of this invention, you may perform a baking process about 300 degreeC for the heat processing of the water repellent used for formation of a microporous layer. This is to disperse and remove the dispersant such as the surfactant and to once melt the water repellent such as PTFE to coat the surface of the conductive carbon particles.

2. Gas diffusion electrode < Gas diffusion electrode with MPL>
The gas diffusion electrode for a polymer electrolyte fuel cell according to the first aspect of the present invention has a catalyst layer formed on the microporous layer of the gas diffusion layer of the present invention described above.

  The catalyst layer is not particularly limited as long as it is generally used for a polymer electrolyte fuel cell. Generally, (1) catalyst-carrying carbon particles (carbon particles carrying a catalyst) and ( 2) A material containing a hydrogen ion conductive electrolyte is used.

  The catalyst-carrying carbon particles are those in which a catalyst is carried on carbon particles, and known or commercially available ones can be used.

  The carbon particles constituting the catalyst-supporting carbon particles are not particularly limited, and examples thereof include carbon black such as channel black, furnace black, thermal black, acetylene black, and lamp black, graphite, activated carbon, carbon fiber, and carbon nanotube. .

  The catalyst supported on the carbon particles is not particularly limited as long as it causes a cell reaction in the fuel electrode or air electrode of the fuel cell. For example, platinum, a platinum alloy, a platinum compound, etc. are mentioned. Examples of the platinum alloy include an alloy of platinum and at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, iron, cobalt, and the like.

  The hydrogen ion conductive electrolyte is not limited, and a known or commercially available one can be used. Examples thereof include perfluorosulfonic acid-based fluorine ion exchange resins, particularly perfluorocarbon sulfonic acid-based polymers (PFS-based polymers) in which C—H bonds of hydrocarbon-based ion exchange membranes are substituted with fluorine. Specific examples of such a hydrogen ion conductive polymer electrolyte include, for example, “Nafion” (registered trademark) manufactured by DuPont, “Flemion” (registered trademark) manufactured by Asahi Glass Co., Ltd., and manufactured by Asahi Kasei Corporation. “Aciplex” (registered trademark), “Gore Select” (registered trademark) manufactured by Gore, and the like.

  The content ratio of the catalyst-supporting carbon particles and the hydrogen ion conductive electrolyte membrane may be about 0.1 to 5 parts by weight, preferably about 0.2 to 4 parts by weight, with respect to 1 part by weight of the former. .

  The catalyst layer may contain a known additive such as carbon fiber, for example, vapor grown carbon fiber (VGCF), carbon nanotube, or carbon nanowire, if necessary.

  The thickness of the catalyst layer is not limited and may be in a range generally adopted as a catalyst layer of a polymer electrolyte fuel cell. For example, it may be about 5 to 120 μm, preferably about 10 to 50 μm, more preferably about 15 to 30 μm.

  Examples of a method for forming such a catalyst layer include a method of applying and drying a paste composition for forming a catalyst layer on a microporous layer of a gas diffusion layer.

  Examples of the paste composition for forming a catalyst layer include those obtained by mixing (1) catalyst-carrying carbon particles, (2) a hydrogen ion conductive electrolyte, and (3) a viscosity adjusting solvent.

  As the catalyst-supporting carbon particles and the hydrogen ion conductive electrolyte, those described above can be used.

  Examples of the solvent include various alcohols, various ethers, various dialkyl sulfoxides, water, or a mixture thereof. Examples of the alcohol include monohydric alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, isobutanol, and t-butanol, propylene glycol, ethylene glycol, diethylene glycol, Examples include polyhydric alcohols such as glycerin.

  The proportions of the components (1) to (3) contained in the catalyst layer forming paste composition are not limited and can be appropriately selected within a wide range.

  For example, the component (2) is 0.1 to 5 parts by weight (preferably 0.15 to 3 parts by weight) and the component (3) is 5 to 50 parts by weight with respect to 1 part by weight of the catalyst-supported carbon particles of (1). About 10 parts by weight (preferably 10 to 25 parts by weight) should be contained, with the remainder being water. The ratio of water is usually from 10 to 10 times the weight of the catalyst-supporting carbon particles.

  The catalyst layer forming paste composition is produced by mixing the components (1) to (3). The order of mixing the components (1) to (3) is not particularly limited. For example, the paste composition for forming a catalyst layer can be prepared by mixing the component (1), the component (2), and the component (3) sequentially or simultaneously to disperse the catalyst-supporting carbon particles.

  There is no restriction | limiting in particular as an application | coating method and drying conditions, It can carry out similarly to the time of forming the above-mentioned microporous layer.

  As another method for forming a catalyst layer, a catalyst layer is formed on a microporous layer of a gas diffusion layer using a catalyst layer transfer film in which a paste composition for forming a catalyst layer is formed on a transfer substrate. Examples of the method include a transfer method.

  The transfer substrate is not particularly limited. For example, polyimide, polyethylene terephthalate, polyparabanic acid aramid, polyamide (nylon, etc.), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, polyethylene Examples thereof include polymer films such as naphthalate and polypropylene. In addition, ethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), etc. It is also possible to use a heat-resistant fluororesin. Further, the base material may be paper such as art paper, coated paper, light coated paper, and other non-coated paper such as notebook paper and copy paper, in addition to the polymer film. Among these, an inexpensive and easily available polymer film is preferable, and polyethylene terephthalate or the like is more preferable.

  The thickness of the transfer substrate is usually about 5 to 100 μm, preferably about 10 to 60 μm, from the viewpoint of handleability and economy.

  Further, a release layer may be laminated on the transfer substrate. Examples of the release layer include those composed of known waxes and plastic films coated with known fluororesins.

  The pressure level at the time of transfer is usually about 0.5 to 20 MPa, preferably about 1 to 10 MPa, more preferably about 1 to 5 MPa in order to avoid transfer failure. In addition, it is preferable to heat the pressure surface during the pressurization in order to avoid transfer defects. The heating temperature is usually about 30 to 200 ° C., preferably about 135 to 150 ° C., in order to avoid breakage or modification of the electrolyte membrane.

  In the present invention, the step of forming the catalyst layer on the microporous layer may be performed after the step (C) of removing the permeation preventive agent or may be performed before the step (C). When the catalyst contained in the catalyst layer has some reactivity with the soaking agent (for example, when it ignites), it is desirable to remove the soaking agent before forming the catalyst layer.

<Gas diffusion electrode without MPL>
The gas diffusion electrode for a polymer electrolyte fuel cell according to the second aspect of the present invention comprises:
(A) filling a conductive porous substrate with a soaking agent in a molten state;
(B) a step of applying and drying the catalyst layer forming paste composition on the conductive porous substrate filled with the infiltration inhibitor and forming a catalyst layer; and (c) filling the conductive porous substrate. A step of removing the permeation preventive agent.

  Steps (a) to (c) are different from steps (A) to (C) in forming the gas diffusion layer, using a paste composition for forming a catalyst layer, not a paste composition for forming a microporous layer. Only the formation of the catalyst layer is different, and all other conditions are the same.

  Moreover, what was demonstrated in said gas diffusion electrode with MPL can be used for the paste composition for catalyst layer formation. In addition, when the catalyst contained in a catalyst layer has a certain reactivity with respect to a permeation preventive agent, it is desirable to cope with not reacting. For example, when firing, it is preferable to apply and dry the paste in a container sealed in an inert atmosphere such as nitrogen gas or argon gas. It is also an effective measure to suppress ignition by cooling.

3. Membrane-electrode assembly <When gas diffusion layer is laminated on catalyst layer-electrolyte membrane laminate>
The membrane-electrode assembly for a polymer electrolyte fuel cell according to the first aspect of the present invention is provided on one side or both sides of a catalyst layer-electrolyte membrane laminate in which a catalyst layer is formed on one side or both sides of an electrolyte membrane. The gas diffusion layer of the invention is laminated so that the catalyst layer and the microporous layer are in contact with each other. For example, it can be produced by disposing a gas diffusion layer on one side or both sides of the catalyst layer-electrolyte membrane laminate so that the catalyst layer and the microporous layer face each other. Note that the catalyst layer-electrolyte membrane laminate and the gas diffusion layer may or may not be joined by hot pressing.

  The catalyst layer can be as described above.

  The electrolyte membrane is not limited as long as it is hydrogen ion conductive, and a known or commercially available membrane can be used. Specific examples of the electrolyte membrane include, for example, “Nafion” (registered trademark) membrane manufactured by DuPont, “Flemion” (registered trademark) membrane manufactured by Asahi Glass Co., Ltd., and “Aciplex” (registered trademark) manufactured by Asahi Kasei Corporation. ) Membrane, “Gore Select” (registered trademark) membrane manufactured by Gore, and the like.

  The thickness of the electrolyte membrane is usually about 10 to 500 μm, preferably about 15 to 300 μm, more preferably about 20 to 150 μm.

  Further, the method, conditions, and the like for producing the catalyst layer-electrolyte membrane laminate are the production of the gas diffusion electrode according to the first aspect of the present invention except that an electrolyte membrane is used instead of the conductive porous substrate. It can be similar to the method.

  The pressure level at the time of hot pressing is usually about 0.5 to 20 MPa, preferably about 1 to 10 MPa. Moreover, the heating temperature in this case may be about 30-200 degreeC normally.

<When gas diffusion electrode is laminated on electrolyte membrane>
In the membrane-electrode assembly for a polymer electrolyte fuel cell according to the second aspect of the present invention, the gas diffusion electrode of the present invention is laminated on one surface or both surfaces of the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact with each other. Become. For example, the gas diffusion electrode can be arranged on one side or both sides of the electrolyte membrane so that the electrolyte membrane and the catalyst layer face each other and hot-pressed.

  As the electrolyte membrane and the gas diffusion electrode, those described above can be used.

  The pressure level at the time of hot pressing is usually about 0.5 to 20 MPa, preferably about 1 to 10 MPa. Moreover, the heating temperature in this case may be about 30-200 degreeC normally.

4). Polymer electrolyte fuel cell The polymer electrolyte fuel cell of the present invention can be obtained by providing a known or commercially available separator to the membrane-electrode assembly of the present invention.

  According to the present invention, the penetration of the microporous layer-forming paste composition and the catalyst layer-forming paste composition into the conductive porous substrate is prevented, the supply of fuel and oxidant to the catalyst layer, and excess moisture. Thus, it is possible to obtain a gas diffusion layer and a gas diffusion electrode that can suppress a decrease in cell potential without hindering the discharge of gas. Thereby, a polymer electrolyte fuel cell excellent in power generation performance can be obtained.

In the present invention, as an example of a method for filling a conductive porous substrate with a melted infiltration agent, a method of immersing the conductive porous substrate in a melted infiltration liquid film is shown. FIG. It is a graph which shows the current-voltage characteristic of the polymer electrolyte fuel cell produced using the gas diffusion layer of Examples 1-4 and the comparative example 1. FIG.

  The present invention will be described more specifically with reference to the following examples and comparative examples. Needless to say, the present invention is not limited to the following examples.

Example 1
The paste composition for forming a microporous layer is composed of 3 parts by weight of carbon black (manufactured by CABOT, VULCAN XC-72), 1.66 parts by weight of polytetrafluoroethylene (PTFE) dispersion (manufactured by ALDRICH, 60 wt%) and pure It was prepared by mixing and dispersing 35.3 parts by weight of water.

  In an environment where the temperature is about 26 ° C., t-butyl alcohol (manufactured by Nacalai Tesque Co., Ltd., special grade) is poured into a stainless steel vat, and carbon paper (manufactured by Toray Industries, Inc., TGP-H-090, thickness 280 μm). Soaked. With the bat kept horizontal, the amount of liquid was adjusted so that the thickness of the liquid film was 200 μm (the thickness of the liquid film of the infiltration agent was about 71.4% of the thickness of the conductive porous substrate. ). While maintaining this state, the bat was moved to a cool box and cooled for 10 minutes.

  It was visually confirmed that the t-butyl alcohol in the bat had solidified, and the bat was taken out. The prepared paste composition for forming a microporous layer was quickly applied onto carbon paper filled with t-butyl alcohol in a vat in an environment at room temperature of 24 ° C. The vat was transferred into a drying oven maintained at 90 ° C., and dried for 20 minutes while maintaining the level to remove the soaking agent. Furthermore, it baked at 350 degreeC for 1 hour.

Example 2
A gas diffusion layer of Example 2 was prepared in the same manner as in Example 1 except that the amount of liquid was adjusted so that the thickness of the liquid film of t-butyl alcohol was about 140 μm (solution of the soaking inhibitor). The thickness of the membrane is about 50.0% of the thickness of the conductive porous substrate).

Example 3
A gas diffusion layer of Example 3 was prepared in the same manner as in Example 1 except that benzene was used as an anti-soaking agent instead of t-butyl alcohol (the thickness of the anti-soaking liquid film was About 71.4% of the thickness of the conductive porous substrate).

Example 4
The paste composition for forming a microporous layer was the same as in Example 1.

  In an environment where the temperature is about 26 ° C., polyethylene glycol 600 (manufactured by Kishida Chemical Co., Ltd., grade 1) is poured into a stainless steel vat, and carbon paper (manufactured by Toray Industries, Inc., TGP-H-090, thickness 280 μm). Soaked. With the bat kept horizontal, the amount of liquid was adjusted so that the thickness of the liquid film was 200 μm (the thickness of the liquid film of the infiltration agent was about 71.4% of the thickness of the conductive porous substrate. ). While maintaining this state, the bat was moved to a cool box and cooled for 10 minutes.

  It was visually confirmed that the polyethylene glycol in the bat had solidified, and the bat was taken out. The prepared paste composition for forming a microporous layer was quickly applied onto carbon paper filled with polyethylene glycol in a vat in an environment at room temperature of 24 ° C. The vat was transferred into a drying oven maintained at 90 ° C. and dried for 20 minutes while maintaining the level. Thereafter, ethanol was poured into a stainless steel vat, and the conductive porous substrate on which the microporous layer was formed was immersed in a state heated to about 40 ° C. to dissolve and remove polyethylene glycol. Subsequently, it was dried in a drying oven maintained at 90 ° C. for 10 minutes, and finally baked at 350 ° C. for 1 hour to completely remove polyethylene glycol.

Comparative Example 1
A gas diffusion layer of Comparative Example 1 was prepared with reference to Patent Document 2.

  An ethanol solution of paradichlorobenzene (volume ratio 1: 1) was prepared in a stainless steel vat, and carbon paper (manufactured by Toray Industries, Inc., TGP-H-090, thickness 280 μm) was immersed in the stainless steel vat. . After 5 minutes, the immersed carbon paper was taken out and dried for 30 minutes in the air at room temperature. Hereinafter, the gas diffusion layer of Comparative Example 2 was formed by applying a paste composition for forming a microporous layer by the same method as in Example 1 and baking at 350 ° C. for 2 hours. In addition, it confirmed by visual observation that the para dichlorobenzene with which it filled in the electroconductive porous base material lose | disappeared through the baking at the said 350 degreeC.

Test example: Nafion (registered trademark) 112 membrane (manufactured by DuPont, film thickness: 50 μm) was used as the electrolyte membrane for PEFC power generation , and Pt / C catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, platinum loading 45.9 wt. %) And Nafion (registered trademark) solution (manufactured by DuPont, DN520) to prepare a catalyst layer-electrolyte membrane laminate (CCM) having a catalyst layer.

The catalyst load was 0.5 mg-Pt / cm ^{2 for} both electrodes. As the gas diffusion layer, untreated Toray Co., Ltd. carbon paper TGP-H-090 was used on the fuel electrode side, and the gas diffusion layers of Examples 1-2 and Comparative Examples 1-2 were used on the air electrode side. . Current-voltage characteristics were obtained from single cell evaluation at a cell temperature of 80 ° C., a fuel electrode dew point of 80 ° C., an air electrode dew point of 70 ° C., and a fuel utilization factor of Uf / Uo = 70% / 40%. The result is shown in FIG. From FIG. 2, it can be seen that Examples 1 to 4 have no significant difference in power generation performance. On the other hand, in Comparative Example 1, it can be seen that the cell potential is greatly reduced from around 600-700 mA / cm ² . Compared with Examples 1-4, the degree is remarkable, and it is suggested that power generation performance falls by flooding.

Claims (14)

(A) A step of filling a conductive porous substrate with a permeation preventive agent in a molten state,
(B) Applying and drying a microporous layer forming paste composition on a conductive porous substrate filled with an infiltration inhibitor, and forming a microporous layer; and (C) a conductive porous substrate. A method for producing a gas diffusion layer for a polymer electrolyte fuel cell, comprising a step of removing an infiltration agent filled in the solid polymer fuel cell. The manufacturing method of the gas diffusion layer of Claim 1 whose melting | fusing point of a permeation prevention agent is 0-30 degreeC, and whose boiling point is 50-120 degreeC. The method for producing a gas diffusion layer according to claim 1 or 2, wherein the step (A) is a step of immersing the conductive porous substrate in a liquid film of a permeation preventive in a molten state. The manufacturing method of the gas diffusion layer of Claim 3 whose thickness of the liquid film of a permeation preventive agent is 40 to 80% of the thickness of a conductive porous base material. A gas diffusion layer for a polymer electrolyte fuel cell obtained by the method for producing a gas diffusion layer according to any one of claims 1 to 4. A gas diffusion electrode for a polymer electrolyte fuel cell, comprising a catalyst layer formed on the microporous layer of the gas diffusion layer according to claim 5. (A) filling a conductive porous substrate with a soaking agent in a molten state;
(B) a step of applying and drying the catalyst layer forming paste composition on the conductive porous substrate filled with the infiltration inhibitor and forming a catalyst layer; and (c) filling the conductive porous substrate. A method for producing a gas diffusion electrode for a polymer electrolyte fuel cell, comprising a step of removing the permeation inhibitor. The method for producing a gas diffusion electrode for a polymer electrolyte fuel cell according to claim 7, wherein the infiltration agent has a melting point of 0 to 30 ° C and a boiling point of 50 to 120 ° C. The gas diffusion electrode for a polymer electrolyte fuel cell according to claim 7 or 8, wherein the step (a) is a step of immersing the conductive porous substrate in a liquid film of a permeation preventive in a molten state. Manufacturing method. The method for producing a gas diffusion electrode for a polymer electrolyte fuel cell according to claim 9, wherein the thickness of the liquid film of the infiltration agent is 40 to 80% of the thickness of the conductive porous substrate. A gas diffusion electrode for a polymer electrolyte fuel cell, obtained by the method for producing a gas diffusion electrode according to any one of claims 7 to 10. The gas diffusion layer according to claim 5 is laminated so that the catalyst layer and the microporous layer are in contact with one side or both sides of the catalyst layer-electrolyte membrane laminate in which the catalyst layer is formed on one side or both sides of the electrolyte membrane. A membrane-electrode assembly for a polymer electrolyte fuel cell. A membrane-electrode assembly for a polymer electrolyte fuel cell, wherein the gas diffusion electrode according to claim 6 or 11 is laminated on one or both surfaces of the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact with each other. A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 12 or 13.

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