JP2008218341A - Forming method for electrode layer and manufacturing method for film electrode structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method for an electrode layer capable of restraining flooding and improving its performance as an electrode layer, and a manufacturing method for a film electrode structure having the electrode layer manufactured by the manufacturing method. <P>SOLUTION: In the forming method for the electrode layer having a catalyst-carrying carrier for making a conductive carrier carry a catalyst and a proton conductive polymer, the forming method for the electrode layer having the catalyst-carrying carrier, the proton conductive carrier comprises a first process for producing a composition by mixing pure water, a second process for adding a water-repellent solvent into the composition produced in the first process and producing an ink-like composition by mixing the composition and a water-repellent solvent, and a third process for forming a layer by applying the ink-like composition produced in the second process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an electrode layer provided in a fuel cell, and a method for manufacturing a membrane electrode structure including an electrode layer manufactured by the manufacturing method.

  A fuel cell has a membrane electrode structure (hereinafter referred to as “MEA”) including an electrolyte layer (hereinafter referred to as “electrolyte membrane”) and electrodes (anode and cathode) respectively disposed on both sides of the electrolyte membrane. The electrical energy generated by the electrochemical reaction is taken out to the outside through current collectors arranged on both sides of the MEA. Among fuel cells, a polymer electrolyte fuel cell (hereinafter, also referred to as “PEFC”) used in a home cogeneration system or an automobile can be operated in a low temperature region. In addition, PEFC has attracted attention as a power source and portable power source for electric vehicles because it exhibits high energy conversion efficiency, has a short start-up time, and is compact and lightweight.

  A single cell of PEFC includes an electrolyte membrane, an anode and a cathode provided with at least a catalyst layer, and has a theoretical electromotive force of 1.23V. During operation of the PEFC, a hydrogen-containing gas (hereinafter referred to as “hydrogen”) is supplied to the anode, and an oxygen-containing gas (hereinafter referred to as “air”) is supplied to the cathode. The hydrogen supplied to the anode reacts under the action of a catalyst metal (hereinafter referred to as “catalyst”) contained in the catalyst layer (hereinafter referred to as “anode catalyst layer”) of the anode, whereby protons and electrons are reacted. The protons generated from hydrogen pass through the anode catalyst layer and the electrolyte membrane and reach the cathode catalyst layer (hereinafter referred to as “cathode catalyst layer”). On the other hand, electrons reach the cathode catalyst layer through an external circuit, and through such a process, electric energy can be extracted. Then, protons and electrons that reach the cathode catalyst layer react with oxygen contained in the air supplied to the cathode catalyst layer under the action of the catalyst contained in the cathode catalyst layer, thereby generating water. Is done.

  The water generated during the operation of the PEFC can be discharged out of the single cell together with hydrogen or air (hereinafter sometimes referred to as “reactive gas”) supplied to the single cell. However, when more water is generated than can be discharged, water accumulates in the electrodes and the like, and the water is immersed (hereinafter sometimes referred to as “flooding”). When flooding occurs, the diffusion of the reaction gas in the electrode or the like is hindered, resulting in a decrease in power generation performance. Therefore, in order to improve the power generation performance of PEFC, it is important to suppress flooding in electrodes and the like.

  On the other hand, as described above, reactions in the anode catalyst layer and the cathode catalyst layer (hereinafter, these may be simply referred to as “catalyst layer” or “electrode layer”) occur under the action of the catalyst. Therefore, in order to improve the performance of the electrode layer by facilitating the reaction, it is important to make the function of the catalyst easy to express. To make the function of the catalyst easy to express, the reaction gas and It is important to increase the surface area of the catalyst that forms the interface.

  Several techniques aimed at improving the power generation performance of PEFC have been disclosed so far. For example, Patent Document 1 relates to an electrode ink for a solid polymer electrolyte fuel cell, comprising a catalyst-supporting conductive carbon powder to which a polymer electrolyte is attached, a polymer electrolyte, and a dispersion medium. Technology is disclosed. The electrode ink is composed of a catalyst-carrying conductive carbon powder to which a polymer electrolyte is attached, a polymer electrolyte, and water, so that the solid content and viscosity can be easily controlled, the ink state is stable, ignition, etc. The electrode ink can be provided without any danger.

  Patent Document 2 discloses a technology relating to a fuel cell unit, a method for manufacturing the same, and a fuel cell employing the fuel cell unit.

JP 2004-139899 A JP 2003-272640 A

  However, in the technique disclosed in Patent Document 1, since the dispersion medium is substantially only water, the number of pores provided in the electrode layer manufactured using the electrode ink according to Patent Document 1 is small, There was a problem that flooding was likely to occur. Further, in the technique disclosed in Patent Document 2, since a polar organic solvent is used when producing the catalyst layer forming composition, the catalyst aggregates due to heat generated when the catalyst layer forming composition is produced. Cheap. Therefore, the catalyst layer provided in the fuel cell unit manufactured by the technique according to Patent Document 2 has a problem that the surface area of the catalyst is easily reduced and the performance as the electrode layer is easily lowered.

  Therefore, the present invention provides an electrode layer manufacturing method capable of suppressing flooding and improving performance, and a membrane electrode structure including an electrode layer manufactured by the manufacturing method It is an object to provide a method for manufacturing a body.

In order to solve the above problems, the present invention takes the following means. That is,
A first aspect of the present invention is a method for producing an electrode layer comprising a catalyst-carrying carrier in which a catalyst is carried on a conductive carrier and a proton-conductive polymer, the catalyst-carrying carrier, the proton-conductive polymer, A first step of preparing a composition by mixing pure water, adding a water-repellent solvent to the composition prepared by the first step, and mixing the composition and the water-repellent solvent to form an ink A method for producing an electrode layer, comprising: a second step of producing a composition; and a third step of forming a layer by applying the ink-like composition produced in the second step. is there.

  Here, as the “conductive carrier”, a carbon compound typified by silicon carbide or the like can be used in addition to a carbon material typified by carbon black, carbon nanotube, carbon nanohorn or the like. Furthermore, the “catalyst” means a substance that functions as a catalyst for an electrochemical reaction occurring in the electrode layer of PEFC. Specific examples of the catalyst are selected from the group consisting of Pt, Co, Ru, Ir, Au, Ag, Cu, Ni, Fe, Cr, Mn, V, Ti, Mo, Pd, Rh, and W. Examples thereof include a Pt alloy having one or more metals and Pt. Furthermore, the “proton conductive polymer” means a polymer capable of conducting protons generated under the action of the catalyst. Specific examples of the proton conductive polymer include a fluorine-based polymer having at least one of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton. Furthermore, specific examples of the “water-repellent solvent” that can be used in the present invention include fluorine-based solvents. Furthermore, “pure water” means water that does not substantially contain impurities, and water that contains inevitable impurities can also be used as the pure water of the present invention. Furthermore, the object (material to be applied) to which the ink-like composition is applied in the third step of the present invention is not particularly limited as long as the electrode layer can be formed. Specific examples of the material to be coated include an electrolyte membrane and a transfer sheet made of a fluororesin, and in the case where a gas diffusion layer is provided in a fuel cell including an electrode layer manufactured according to the present invention, the gas diffusion layer, etc. Can be mentioned.

  In the first aspect of the present invention, the water-repellent solvent is preferably a solvent that volatilizes more easily than pure water.

  In the first aspect of the present invention, where the water-repellent solvent is more volatile than pure water, the volatile solvent is preferably a fluorine-based solvent.

  Here, as the “fluorine-based solvent” usable in the present invention, in addition to hydrofluoroether, perfluoroheptane, hexafluorobenzene, perfluoromethylcyclohexane, etc., perfluoroalkane and perfluoroaromatic are used. A solvent having a boiling point of 100 ° C. or lower can be exemplified.

  In the first aspect of the present invention (including modifications), the composition and the volatile solvent are preferably mixed in the second step by an ultrasonic vibration method.

  According to a second aspect of the present invention, there is provided a membrane electrode structure including an electrolyte membrane, a first electrode layer formed on one surface of the electrolyte membrane, and a second electrode layer formed on the other surface of the electrolyte membrane. A method for producing a membrane electrode structure, wherein the first electrode layer and / or the second electrode layer is produced by the method for producing an electrode layer according to the first aspect of the present invention. It is.

  The “electrolyte membrane” is not particularly limited as long as it is a solid polymer membrane containing a proton conducting polymer. Specific examples of the proton conductive polymer contained in the electrolyte membrane include a fluorine-based polymer having at least one of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton, and a polyolefin. Examples thereof include hydrocarbon-based polymers having a hydrocarbon as a skeleton. Specific examples of the electrolyte membrane containing the fluorine polymer include Nafion (“Nafion” is a registered trademark of DuPont, USA) and Flemion (“Flemion” is a registered trademark of Asahi Glass Co., Ltd.). . On the other hand, as a specific example of the electrolyte membrane containing the hydrocarbon-based polymer, there can be mentioned Selemion and the like (“Selemion” is a registered trademark of Asahi Glass Co., Ltd.).

  According to the first aspect of the present invention, an electrode layer is formed by applying an ink-like composition prepared by mixing a catalyst-supporting carrier, a proton conductive polymer, pure water, and a water-repellent solvent. Is done. Since the ink-like composition contains pure water and a water-repellent solvent, the ink-like composition produced by mixing them contains a hydrophobic portion of the proton conductive polymer having the water-repellent property. It contains a proton-conductive polymer with a micelle structure that faces the solvent and has the hydrophilic portion of the proton-conductive polymer toward the pure water. According to the first aspect of the present invention, an electrode layer having a large number of pores can be formed by applying an ink-like composition containing the proton conductive polymer of this form to form an electrode layer. By actively increasing the number of pores, it is possible to manufacture an electrode layer having a form with improved porosity. Thus, when a large number of pores are provided in the electrode layer, the generated water can be discharged through the pores, so that flooding can be suppressed. Furthermore, since the reaction gas can be diffused through the pores, the performance as an electrode layer can be improved. Therefore, according to the first aspect of the present invention, it is possible to provide an electrode layer manufacturing method capable of suppressing flooding and improving performance.

  In the first aspect of the present invention, when the water-repellent solvent is more volatile than pure water, an electrode layer having a large number of pores can be easily produced.

  In the first aspect of the present invention, an electrode layer having a large number of pores can be easily produced by using a readily available fluorine-based solvent as a solvent that is more volatile than pure water.

  Further, in the first aspect of the present invention, the second step in which the composition and the water-repellent solvent are mixed by an ultrasonic vibration method is provided, so that the ink-like composition before being applied in the third step is volatilized. In order to reduce the amount of the water-repellent solvent, the composition contained in the container provided with the lid and the water-repellent solvent can be easily mixed. By reducing the amount of water-repellent solvent that volatilizes from the ink-like composition before being applied in the third step, the number of pores is positively increased to produce an electrode layer with improved porosity. Therefore, an electrode layer with improved porosity can be manufactured more easily by adopting such a configuration.

  According to the second aspect of the present invention, it is possible to manufacture a membrane electrode structure (MEA) provided with an electrode layer manufactured by the method for manufacturing an electrode layer according to the first aspect of the present invention. Therefore, according to the second aspect of the present invention, it is possible to provide a method for manufacturing a membrane electrode structure capable of suppressing flooding and improving performance.

  Hereinafter, the manufacturing method of the electrode layer of the present invention and the manufacturing method of the membrane electrode structure (MEA) of the present invention will be specifically described with reference to the drawings.

1. Electrode Layer Manufacturing Method FIG. 1 is a flowchart schematically showing the steps of an electrode layer manufacturing method of the present invention. FIG. 2 is a conceptual view showing a simplified form of the second step provided in the method for producing an electrode layer of the present invention. FIG. 2 (a) shows the state immediately after adding the water-repellent solvent in the second step, and FIG. 2 (b) shows the state after mixing the composition and the water-repellent solvent in the second step. Each is shown schematically. FIG. 3 is a conceptual diagram schematically showing an example of the third step provided in the method for producing an electrode layer of the present invention. FIG. 4 is a conceptual diagram showing an enlarged partial cross-section of the electrode layer manufactured by the electrode layer manufacturing method of the present invention. FIG. 5 is a diagram schematically showing a conventional electrode layer manufacturing process. FIG. 6 is a conceptual diagram showing an enlarged partial cross-section of an electrode layer manufactured by a conventional electrode layer manufacturing method. Hereafter, the manufacturing method of the electrode layer of this invention is demonstrated, referring FIGS.

  As shown in FIG. 1, the electrode layer manufacturing method of the present invention (hereinafter referred to as “the electrode manufacturing method of the present invention”) includes a first step (step S11), a second step (step S12), And a third step (step S13).

1.1. 1st process (process S11)
Step S11 is a step of preparing a composition by mixing a catalyst-supporting carrier, a proton conductive polymer, and pure water. That is, platinum-supporting carbon 3, 3,... Is used as a catalyst-supporting carrier having a catalyst (platinum 2, 2,...) Supported on a conductive carrier (carbon 1, 1,...), And Nafion 4 is used as a proton-conducting polymer. In this case, the steps of preparing the composition 5 by putting platinum-supported carbon 3, 3,..., Nafion 4 and pure water as a main solvent into a container (for example, a beaker 7) and stirring them. Step S11.

1.2. Second step (Step S12)
Step S12 is a step of preparing an ink-like composition by mixing the composition prepared in step S11 and a water-repellent solvent. For example, when a fluorine-based solvent (for example, hydrofluoroether) 6 that is more volatile than pure water is used as the water-repellent solvent, the container 7 used in step S11 is further added with fluorine as a sub-solvent. The step of preparing the ink-like composition 8 by adding the system solvent 6 and mixing the composition 5 prepared in step S11 and the added fluorine-based solvent 6 is step S12.

  When the fluorine-based solvent 6 is added to the composition 5 prepared in step S11, the fluorine-based solvent 6 added in step S12 repels pure water contained in the composition 5 prepared in step S11. Therefore, as shown in FIG. 2A, when the fluorine-based solvent 6 is added to the container 7 containing the composition 5 prepared in step S11, the fluorine-based solvent immediately after being added to the composition 5 is added. The solvent 6 does not mix with the composition 5, for example, a form in which a lump of the fluorine-based solvent 6 exists in the composition 5.

  In step S12 provided in the electrode manufacturing method of the present invention, after adding the fluorine-based solvent 6, the composition 5 and the fluorine-based solvent 6 are mixed. When the composition 5 in the container 7 and the fluorine-based solvent 6 are mixed by, for example, an ultrasonic vibration method in a state where the container 7 is covered, as shown in FIG. The system solvent 6, 6,... Is dispersed in the composition 5. In this manner, when the ink-like composition 8 is produced by dispersing the minute fluorine-based solvents 6, 6,... In the composition 5, it is contained in the ink-like composition 8. The hydrophobic part of Nafion 4 is directed toward the fluorine-based solvent 6, 6,..., And the hydrophilic part of the Nafion 4 is directed toward the pure water contained in the ink-like composition 8 to become Nafion 4 having a micelle structure. Therefore, according to step S12 provided in the electrode manufacturing method of the present invention, an ink-like composition 8 containing minute fluorine-based solvents 6, 6,... And micelle-structured Nafion 4 can be produced. .

1.3. Third step (step S13)
Step S13 is a step of forming an electrode layer (catalyst layer) by applying the ink-like composition produced in step S12. The object (the material to be coated) to which the ink-like composition is applied in step S13 is not particularly limited. However, when the material to be coated is an electrolyte film, for example, the object is prepared in step S12. By applying the ink-like composition to the electrolyte membrane by a spray coating method, an electrode layer can be formed on the surface of the electrolyte membrane.

  As shown in FIG. 3, when the ink-like composition 8 produced in the step S12 is applied to the electrolyte membrane 9 by a spray coating method, the fluorine-based solvents 6, 6,. Is more volatile than the pure water contained in the ink-like composition 8, so that the fluorine-based solvents 6, 6, ... are volatilized before the pure water. When the fluorine-based solvents 6, 6,... Are volatilized, pores (hereinafter referred to as “pores”) are formed at locations where the fluorine-based solvents 6, 6,. Therefore, when the ink-like composition 8 applied to the electrolyte membrane 9 is dried, the electrode layer 10 having a form in which the porosity is improved by actively increasing the space occupied by the pores 11, 11,... (See FIGS. 3 and 4).

  In contrast, as shown in FIG. 5, an ink-like composition is prepared by mixing a catalyst-supporting carrier (for example, platinum-supporting carbon), a proton conductive polymer, alcohol, and pure water, and the ink-like composition. When an electrode layer (catalyst layer) is formed by coating, oxygen and alcohol react with each other on platinum during mixing in producing the ink-like composition, and heat is locally generated. When heat is generated locally, platinum supported on carbon aggregates and the specific surface area of platinum decreases. Therefore, when an electrode layer is formed using an ink-like composition produced by a conventional method, there is a problem that an electrode layer with low performance is formed because platinum contained in the electrode layer has a small specific surface area.

  Furthermore, the ink-like composition produced in the step shown in FIG. 5 does not contain a water-repellent solvent. Therefore, when an electrode layer is formed using the ink-like composition, an electrode layer 12 having a low porosity is formed (see FIG. 6). Since the electrode layer 12 having a low porosity is difficult to discharge water generated during operation of the fuel cell, when the electrode layer 12 is operated in a state where a large amount of water is generated (high current density state), the electrode layer 12 is immersed in water. And flooding is likely to occur. When flooding occurs, the supplied reaction gas is less likely to diffuse into the electrode layer 12, so that the reaction gas reaching the catalysts 2, 2,. Performance decreases. Therefore, the electrode layer 12 manufactured by the conventional method has a problem that the performance is likely to deteriorate.

  However, as described above, an organic solvent such as alcohol is not used in steps S11 to S13 included in the electrode manufacturing method of the present invention. Therefore, it is possible to suppress local heat that may be generated during the production of the ink-like composition 8, and as a result, aggregation of the catalyst (platinum 2, 2,...) Is suppressed and platinum 2, 2,. The reduction in the specific surface area can be suppressed. In addition, as described above, in the electrode manufacturing method of the present invention, since the water-repellent solvent (fluorine-based solvent 6) is added in step S12, the space occupied by the pores 11, 11,. It is possible to form the electrode layer 10 having the shape formed. The electrode layer 10 in a form in which the porosity is improved by actively increasing the space occupied by the pores 11, 11,... Can easily discharge water generated during operation of the fuel cell, Furthermore, since the supplied reaction gas can be easily diffused into the electrode layer 10, the frequency of occurrence of electrochemical reactions can be improved. Therefore, according to the electrode layer 10 manufactured by the electrode manufacturing method of the present invention, flooding can be suppressed and the performance can be improved.

  In the above description regarding the electrode manufacturing method of the present invention, an ink-like composition is prepared by mixing the composition 5 and a fluorine-based solvent (water-repellent solvent 6) by an ultrasonic vibration method while the container 7 is covered. Although the 2nd process of the form which produces 8 was illustrated, the 2nd process with which the electrode manufacturing method of the present invention is provided is not limited to the form. However, by suppressing the evaporation of the water-repellent solvent added in the second step and increasing the amount of the water-repellent solvent evaporated from the ink-like composition applied in the third step, the porosity is further improved. From the viewpoint of enabling the formation of the electrode layer, it is preferable to include a second step in which the composition and the water-repellent solvent are mixed while the container is covered.

  Further, in the above description regarding the electrode manufacturing method of the present invention, the form in which platinum-supported carbon 3, 3,... Is used as the catalyst-supporting carrier is exemplified, but the electrode manufacturing method of the present invention is not limited to this form. . In the electrode manufacturing method of the present invention, a catalyst-supporting carrier that can be provided in the PEFC catalyst layer (electrode layer) can be appropriately used.

  Moreover, in the said description regarding the electrode manufacturing method of this invention, although the form using Nafion4 as a proton conductive polymer was illustrated, the electrode manufacturing method of this invention is not limited to the said form. In the electrode manufacturing method of the present invention, a proton conductive polymer that can be provided in the catalyst layer (electrode layer) of PEFC can be used as appropriate.

  Moreover, in the said description regarding the electrode manufacturing method of this invention, although the 3rd process of the form in which the electrode layer 10 is formed by apply | coating the ink-like composition 8 to the electrolyte membrane 9 was illustrated, the electrode manufacturing of this invention The third step provided in the method is not limited to this form. The object (material to be coated) to which the ink-like composition prepared in the second step is applied is not particularly limited as long as the electrode layer can be formed by applying the ink-like composition. For example, in addition to a fluororesin transfer sheet, when a gas diffusion layer is provided in a fuel cell including an electrode layer manufactured according to the present invention, the gas diffusion layer may be used.

  In addition, in the above description regarding the electrode manufacturing method of the present invention, the third step of forming the electrode layer 10 by applying the ink-like composition 8 by the spray coating method is exemplified, but the electrode manufacturing of the present invention is illustrated. The third step provided in the method is not limited to this form. Examples of other methods that can be used when applying the ink-like composition in the third step include a screen printing method and a doctor blade method.

2. Manufacturing Method of Membrane Electrode Structure FIG. 7 is a flowchart schematically showing manufacturing steps of the membrane electrode structure of the present invention. FIG. 8 is a cross-sectional view schematically showing the form of MEA manufactured by the method for manufacturing a membrane electrode structure of the present invention. 7 and 8, the same reference numerals as those used in FIGS. 1 to 4 are used for those having the same configuration as the substances shown in FIGS. 1 to 4, and description thereof is omitted as appropriate. Hereinafter, the manufacturing method of the membrane electrode structure of the present invention will be described with reference to FIGS. 1 to 4, 7, and 8.

  As shown in FIG. 7, the method for manufacturing a membrane electrode structure of the present invention (hereinafter referred to as “MEA manufacturing method of the present invention”) includes a first step (step S71) and a second step (step S72). ) And the third step (step S73), and the third step includes step S31 and step S32. Since step S71 and step S72 included in the MEA manufacturing method of the present invention are the same steps as step S11 and step S12 included in the electrode manufacturing method of the present invention, here, step S31 included in step S73. And process S32 is explained.

  Step S31 is a step of applying the ink-like composition 8 produced in step S72 to form the first electrode layer 10 on one surface of the electrolyte membrane 9, and step S32 is an ink form produced in step S72. In this step, the composition 8 is applied to form the second electrode layer 10 ′ on the other surface of the electrolyte membrane 9. That is, in the MEA manufacturing method of the present invention, for example, the ink-like composition 8 is applied to one surface of the electrolyte membrane 9 by the spray coating method in step S31 to form the first electrode layer 10, and the electrolyte in step S32. The ink-like composition 8 is applied to the other surface of the film 9 by a spray coating method to form the second electrode layer 10 ′. Through this process, according to the MEA manufacturing method of the present invention, the MEA 13 including the electrolyte membrane 9, the first electrode layer 10, and the second electrode layer 10 ′ can be manufactured (see FIG. 8). .

  The first electrode layer 10 and the second electrode layer 10 ′ formed by applying the ink-like composition 8 have a space ratio occupied by the pores 11, 11,... Rather than the electrode layer 12 manufactured by the conventional method. Is big. Therefore, when operating the PEFC including the MEA 13 manufactured by the MEA manufacturing method of the present invention, water is supplied through the numerous pores 11, 11,... Provided in the first electrode layer 10 and the second electrode layer 10 ′. Since it can discharge | emit, according to MEA13, flooding can be suppressed. Further, since many reaction gases can be diffused to the catalysts 2, 2,... Through the numerous pores 11, 11,... Provided in the first electrode layer 10 and the second electrode layer 10 ′, the MEA 13 According to the above, the frequency of occurrence of the electrochemical reaction can be increased, and as a result, the power generation performance of the MEA 13 can be improved. Therefore, according to the MEA manufacturing method of the present invention, it is possible to manufacture the MEA 13 that can suppress flooding and improve performance.

  In the above description regarding the MEA manufacturing method of the present invention, the mode in which the first electrode layer 10 and the second electrode layer 10 ′ are formed by applying the ink-like composition 8 to the electrolyte membrane 9 by spray coating is illustrated. However, the MEA manufacturing method of the present invention is not limited to this mode. In addition to the spray coating method, the first electrode layer and the second electrode layer can be formed by applying the ink-like composition to the electrolyte membrane by a screen printing method, a doctor blade method, or the like.

  In the above description regarding the MEA manufacturing method of the present invention, the first electrode layer 10 and the second electrode layer 10 ′ are formed on the electrolyte membrane 9 by directly applying the ink-like composition 8 to the electrolyte membrane 9. However, the MEA manufacturing method of the present invention is not limited to this mode. When a gas diffusion layer is provided in a fuel cell including an MEA manufactured by the MEA manufacturing method of the present invention, an electrode composition is applied to the surface of the gas diffusion layer by applying an ink-like composition to the surface of the gas diffusion layer. Forming a first electrode layer and a second electrode layer on one side and the other side of the electrolyte membrane by forming a layer and then thermocompression bonding the gas diffusion layer with the electrode layer and the electrolyte membrane. Is also possible. In addition, an electrode layer is formed on the surface of the transfer sheet by applying the ink-like composition to a transfer sheet made of fluororesin, and the electrode layer formed on the surface of the transfer sheet is It is also possible to form an electrode layer on one surface and the other surface of the electrolyte membrane by transferring to the other surface and the other surface.

  In the above description regarding the MEA manufacturing method of the present invention, the MEA 13 including the first electrode layer 10 and the second electrode layer 10 ′ formed by the electrode manufacturing method of the present invention is illustrated. The manufacturing method of MEA is not limited to this form. In addition to the above embodiment, only one of the first electrode layer and the second electrode layer is formed by the electrode manufacturing method of the present invention, and the other electrode layer not formed by the electrode manufacturing method of the present invention is formed by a conventional method. It is also possible. However, from the viewpoint of producing a high-performance MEA by suppressing flooding and improving the diffusibility of the reaction gas, the first electrode layer and the second electrode layer are formed by the electrode production method of the present invention. It is preferable.

  Moreover, the electrolyte membrane in which the electrode layer is formed on the surface by the MEA manufacturing method of the present invention is not particularly limited as long as it is a solid polymer membrane containing a proton conductive polymer. Specific examples of the proton conductive polymer contained in the electrolyte membrane include a fluorine-based polymer having at least one of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton, and a polyolefin. Examples thereof include hydrocarbon-based polymers having a hydrocarbon as a skeleton.

1. Production of single cell 1.1. Example 2 [g] of a catalyst-supported carrier prepared by loading 50 parts by mass of a conductive carrier (carbon black) with 50 parts by mass of a catalyst (platinum), and the 2 [g] catalyst-supported carrier was measured. In a container. Then, 20 [ml] pure water was added to the container, and centrifugal stirring was performed for 5 minutes. Next, an electrolyte solution in which Nafion is dispersed in pure water so that the ratio X / Y of the mass X of Nafion and the mass Y of carbon contained in the catalyst-carrying support in the container is 0.8. After adding to the said container and stirring for 6 hours with a stirrer, the composition was produced by stirring for 15 minutes with a bead mill (200 rpm). Thereafter, 50 [μl] of hydrofluoroether was added to the container containing the composition, and the mixture was stirred using an ultrasonic homogenizer to prepare an ink-like composition according to the example.
Then, the second electrode layer is applied to the other surface of the electrolyte membrane having the first electrode layer formed on one surface by applying the ink-like composition according to the example by a spray coating method. The MEA according to the example was formed. And a gas diffusion layer is arrange | positioned to one side and the other side of MEA concerning an Example, respectively, and a laminated body is produced, and a carbon separator is each arrange | positioned to the one side and the other side of the said laminated body. Thereby, the single cell concerning an Example was produced.

1.2. Comparative Example 2 [g] of a catalyst-supported carrier prepared by loading 50 parts by mass of a conductive carrier (carbon black) with 50 parts by mass of a catalyst (platinum) was weighed. In a container. Thereafter, 10 [ml] pure water was added to the container, and centrifugal stirring was performed for 5 minutes. Next, an electrolyte solution in which Nafion is dispersed in pure water so that the ratio X / Y of the mass X of Nafion and the mass Y of carbon contained in the catalyst-carrying support in the container is 0.8. In addition to the said container, 10 [ml] ethanol was further added to the said container. And after stirring for 6 hours with a stirrer, it stirred for 15 minutes with the bead mill (200 rpm), and the ink-like composition concerning a comparative example was produced.
Then, the second electrode layer is applied to the other surface by applying the ink-like composition according to the comparative example to the other surface of the electrolyte membrane having the first electrode layer formed on one surface by a spray coating method. The MEA according to the comparative example was formed. And a gas diffusion layer is arrange | positioned to one side and the other side of MEA concerning a comparative example, respectively, and a laminated body is produced, and a carbon separator is each arrange | positioned to the one side and the other side of the said laminated body. Thereby, the single cell concerning a comparative example was produced.

2. Single Cell Performance Evaluation Test The single cell according to the example manufactured through the above steps and the single cell according to the comparative example are kept at 80 ° C., respectively, and hydrogen (80 [° C.]) is supplied to the first electrode layer provided in each single cell. In addition, by supplying air (80 [° C.], relative humidity 100%) to the second electrode layer, each single cell was operated and performance was evaluated. The result of the single cell concerning an Example and the result of the single cell concerning a comparative example are shown collectively in FIG. The vertical axis in FIG. 9 is the cell voltage [V], and the horizontal axis is the current density [A / cm ² ].

3. Results From FIG. 9, in the low current density region, the performance of the single cell according to the example and the performance of the single cell according to the comparative example are equivalent, but in the high current density region, the single cell according to the example is a comparative example. As a result, the difference in performance became more remarkable as the current density increased. Here, in the operation in the high current density region, a lot of water is generated in the second electrode layer. The single cell according to the example includes the second electrode layer formed by the electrode manufacturing method of the present invention, and includes the MEA manufactured by the MEA manufacturing method of the present invention. Therefore, flooding is suppressed by discharging water through a large number of pores, and furthermore, air can be diffused to the catalyst through the pores, resulting in a decrease in power generation performance in a high current density region. It is thought that it was suppressed. On the other hand, since the single cell according to the comparative example was provided with the second electrode layer formed by the conventional electrode manufacturing method, flooding could not be suppressed, and air diffused into the second electrode layer could not be suppressed. As a result of the reduction in the amount, it is considered that the decrease in power generation performance in the high current density region becomes remarkable.
From the above, it is possible to suppress flooding and improve performance by using an electrode layer manufactured by the electrode manufacturing method of the present invention and an MEA manufactured by the MEA manufacturing method of the present invention. become.

It is a flowchart which shows the process of the electrode manufacturing method of this invention roughly. It is a conceptual diagram which simplifies and shows the form of the 2nd process with which the electrode manufacturing method of this invention is equipped. FIG. 2A schematically shows a state immediately after adding a water-repellent solvent in the second step. FIG. 2B schematically shows a state after the composition and the water-repellent solvent are mixed in the second step. It is a conceptual diagram which shows the example of a 3rd process with which the electrode manufacturing method of this invention is equipped. It is sectional drawing which shows the example of the form of the electrode layer manufactured by the electrode manufacturing method of this invention. It is a figure which shows the manufacturing process of the conventional electrode layer roughly. It is sectional drawing which shows the example of a form of the electrode layer manufactured by the conventional method. It is a flowchart which shows the process of the manufacturing method of MEA of this invention. It is sectional drawing which shows the example of form of MEA manufactured by the manufacturing method of MEA of this invention. It is a figure which shows the result of the performance evaluation test of a single cell.

Explanation of symbols

1 ... Carbon (conductive carrier)
2 ... Platinum (catalyst)
3 ... Platinum-supported carbon (catalyst-supported carrier)
4. Nafion (proton conductive polymer)
5 ... Composition 6 ... Fluorine-based solvent (water repellent solvent)
DESCRIPTION OF SYMBOLS 7 ... Beaker 8 ... Ink-like composition 9 ... Electrolyte membrane 10 ... Electrode layer (1st electrode layer)
10 '... electrode layer (second electrode layer)
DESCRIPTION OF SYMBOLS 11 ... Pore 12 ... Electrode layer 13 ... MEA (membrane electrode structure)

Claims (5)

A method for producing an electrode layer comprising a catalyst-carrying carrier in which a catalyst is carried on a conductive carrier, and a proton-conducting polymer,
A first step of preparing a composition by mixing the catalyst-supporting carrier, the proton conductive polymer, and pure water;
A second step of adding a water-repellent solvent to the composition prepared in the first step, and mixing the composition and the water-repellent solvent to prepare an ink-like composition;
A third step of forming a layer by applying the ink-like composition produced in the second step;
A method for producing an electrode layer, comprising: The method for producing an electrode layer according to claim 1, wherein the water-repellent solvent is a solvent that is more volatile than the pure water. The method for producing an electrode layer according to claim 2, wherein the volatile solvent is a fluorine-based solvent. The method for producing an electrode layer according to any one of claims 1 to 3, wherein in the second step, the composition and the volatile solvent are mixed by an ultrasonic vibration method. . A method of manufacturing a membrane electrode structure comprising: an electrolyte membrane; a first electrode layer formed on one surface of the electrolyte membrane; and a second electrode layer formed on the other surface of the electrolyte membrane. And
The said 1st electrode layer and / or the said 2nd electrode layer are manufactured by the manufacturing method of the electrode layer of any one of Claims 1-4, The manufacturing method of the membrane electrode structure characterized by the above-mentioned. .

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