JP2005174565A - POLYMER ELECTROLYTE MEMBRANE, MEMBRANE / ELECTRODE ASSEMBLY, METHOD FOR PRODUCING THE SAME, AND FUEL CELL USING THE SAME - Google Patents

Abstract

【Task】
The object of the present invention is to improve the adhesion between the polymer electrolyte membrane and the electrode layer, and to improve the efficiency of the fuel cell. An object of the present invention is to provide a membrane / electrode assembly comprising an electrode layer formed on a polymer electrolyte membrane, a production method thereof, and a fuel cell.
[Solution]
The present invention relates to a polymer electrolyte membrane having a microhole group formed by plastic working on one side or both sides of a portion where an electrode layer of a polymer electrolyte membrane for a fuel cell is formed, and a method for producing the polymer electrolyte membrane . The present invention is in a membrane / electrode assembly in which minute hole groups formed in a polymer electrolyte membrane are filled with an electrode material and a method for producing the membrane / electrode assembly. The present invention is directed to a fuel cell membrane / electrode assembly and a method for producing the membrane / electrode assembly, which has a group of minute holes formed by composition processing on one side or both sides of an electrode layer.
[Selection] Figure 2

Description

  The present invention relates to a novel electrolyte membrane for a fuel cell, a membrane / electrode assembly, a production method thereof, and a fuel cell.

  In recent years, fuel cells using polymer electrolyte membranes have been remarkably improved in performance due to the development of electrolyte membranes and catalyst technology, and are attracting attention as a low-pollution automobile power source and a high-efficiency power generation method. A fuel cell using a polymer electrolyte membrane has a structure in which an electrode layer having an oxidation / reduction catalyst is formed on the surface of the electrolyte membrane. In this case, it is known that when unevenness is formed on the surface of the polymer electrolyte membrane to increase the surface area, the adhesion between the polymer electrolyte membrane and the electrode layer is improved and the efficiency of the electrochemical reaction is improved. As a method for forming the unevenness, a method of applying unevenness to the film surface by a chemical or mechanical polishing method disclosed in Patent Document 1, a mixture of a solid electrolyte material and a pyrolysis material disclosed in Patent Document 2 There are known a method of firing a molded body to form irregularities on the surface, a method of pressure bonding a metal foil having irregularities on the surface disclosed in Patent Document 3, and dissolving and removing the metal foil.

JP-A-9-320616 Japanese Patent Laid-Open No. 9-277226 JP 2003-68328 A

  However, in any of the patent documents, it is difficult to control the surface unevenness, and it is difficult to form the unevenness uniformly on the film surface. Furthermore, in any of the patent documents, the shape of the unevenness was only a mountain-valley shape, the unevenness was larger, and the surface area could not be further increased. In addition, there is a problem that the pyrolysis material and the metal foil component cannot be completely removed even in the removing step, which adversely affects the performance of the fuel cell.

  The object of the present invention is to improve the adhesion between the polymer electrolyte membrane and the electrode layer, and to improve the efficiency of the fuel cell. An object of the present invention is to provide a membrane / electrode assembly comprising an electrode layer formed on a polymer electrolyte membrane, a production method thereof, and a fuel cell.

  The first step of the present invention uses a micro mold (precision mold) in which convex portions (hereinafter referred to as pillars) having a specific planar shape are formed on one side or both sides of a polymer electrolyte membrane. Pressing against a plastic polymer electrolyte membrane and forming a pattern according to the type of pillar group. The electrolyte membrane for fuel cells has a microhole group formed by plastic working.

  The microhole group is formed in accordance with a predetermined planar shape, is columnar, and preferably has a diameter of 0.1 μm to 500 μm, a depth of 1 μm or more, and 50% or less of the thickness of the polymer electrolyte. .

  As the shape of the minute hole group, it is preferable that the equivalent diameter of the tip end part is equal to or smaller than the equivalent diameter of the bottom face part of the columnar hole group. In the present invention, the equivalent diameter of the columnar microhole is an equivalent diameter at an intermediate position of the hole. The term equivalent diameter is used because the cross section of the hole is not necessarily circular but may be an ellipse, a polygon, an asymmetric shape, and the like.

  The second step is to directly form an electrode layer on the polymer electrolyte membrane provided with the microhole group in the first step by a spray method, an ink jet method or the like. By dropping the electrode material on the polymer electrolyte membrane with fine droplets, the electrode material is spread to the inside of the microhole group. The electrode layer and the polymer electrolyte membrane formed in this way have an increased contact area due to the geometrical shape having the irregularities. In addition, since the polymer electrolyte membrane expands by absorbing moisture present in the use environment, the adhesion between the electrode layer and the polymer electrolyte membrane is improved. As described above, the contact resistance between the electrode layer and the polymer electrolyte membrane can be reduced. In addition, since the outermost surface of the electrode layer is formed with irregularities on the surface in accordance with the shape of the microhole group formed in the polymer electrode layer, the activity of the electrode layer is improved by increasing the contact area with the reactive species. .

Further, as a third step, in order to control the unevenness of the electrode layer and increase the reaction active surface area, after forming the electrode layer on the polymer electrolyte membrane, a micro mold (precision mold) having micro protrusions is formed. A microhole group may be formed in the electrode layer. By doing so, the reactive surface area is further increased, and the reactive species can easily diffuse to the deep part of the electrode layer (on the polymer electrolyte membrane side), thereby preventing performance degradation due to diffusion rate limiting of the reactive species at high loads. It becomes. The micro-formation type microprojection group is formed according to a predetermined plane shape, has a columnar shape, has a diameter of 0.1 μm to 500 μm, a height of 1 μm or more, and a maximum thickness of the electrode layer + high It is preferable to be 50% or less of the molecular electrolyte film thickness.

  The present invention also provides a method for producing an electrolyte membrane for a fuel cell, wherein a microhole group is formed on one side or both sides of a polymer electrolyte membrane by plastic working, and an electrolyte membrane for a fuel cell in which the microhole group is formed The present invention resides in a method for producing a membrane / electrode assembly for a fuel cell obtained by applying a catalyst layer thereon.

  Furthermore, the present invention is characterized in that a microhole group is formed in the polymer electrolyte membrane by pressing a mold having convex portions of a predetermined plane pattern on one side or both sides of the polymer electrolyte membrane. It is in the manufacturing method of the membrane for fuel cells. The diameter of the hole is preferably 500 μm or less. In the present invention, the electrode material is directly applied onto the polymer electrolyte membrane by a spray method or an ink jet method so that the electrode layer reaches the deepest part of the recess on one side or both sides of the fuel cell electrolyte membrane thus produced. It is the formation method of the electrode layer dropped by a drop. According to the present invention, a microhole group is formed in the electrode layer by pressing a mold having convex portions of a predetermined plane pattern on one or both sides of the electrode layer formed on the electrolyte membrane for a fuel cell. It is in the manufacturing method of the membrane electrode assembly for fuel cells characterized.

  The present invention relates to a polymer electrolyte membrane, equal or different kinds of catalyst layers formed on a support on both surfaces of the electrolyte membrane, and diffusion layers formed in contact with the catalyst layers. And the anode electrode formed in contact with one of the diffusion layers and the cathode electrode formed in contact with the other diffusion layer, wherein the polymer electrolyte membrane has microhole groups on its surface. Is formed by plastic working, and the catalyst is supported on the carrier in the microhole group.

  It is preferable that the carrier is made of a carbon material and the diffusion layer is a carbon sheet.

  In the present invention, the polymer electrolyte membrane is a general term for a polymer film having a polymer having a group having ion exchange ability or a substance having an ion exchange ability contained in the polymer film. It is roughly divided into a cation exchange membrane and an anion exchange membrane. There are also membranes in which both exchange membranes are joined. Examples of the cation exchange membrane include an ion exchange membrane having a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group in a polymer chain in the membrane, and sulfuric acid, sulfonic acids, phosphoric acids, carboxylic acids and solid acids in the polymer membrane. And those containing acidic substances such as fine particles.

  Examples of the anion exchange membrane include a polymer molecule having a basic group such as an amino group, quaternary ammonium hydroxide, and guanidine group, and a membrane in which a solid base is dispersed in the membrane. In addition, there are those in which the acid or base portion in the film is made into a salt, and those in which the salt is impregnated.

  As the most typical ion exchange membrane for fuel cells, polyperfluorosulfonic acid is formed into a film, for example, manufactured by DuPont, USA; trade name Nafion, Asahi Glass Co., Ltd .: trade name Flemion, Asahi Kasei Kogyo Co., Ltd. : Product name Aciplex or aromatic hydrocarbon polymer electrolyte membrane or the like.

  When the polymer electrolyte membrane having a roughened surface produced according to the present invention is used in a fuel cell, the reaction efficiency is improved, and as a result, the performance such as battery output is improved. The reason is considered to be that extremely large irregularities can be formed on the surface of the film, and the surface area of the film is greatly increased. As a result, ions generated by an electrochemical reaction on the film surface can be efficiently dissolved.

  The polymer electrolyte membrane of the present invention includes a film and a sheet.

  The film or substrate provided with the group of micro holes of the present invention is a thermoplastic polymer electrolyte using a micro mold (precision mold) in which convex portions (hereinafter referred to as pillars) having a specific planar shape are formed. Press against the film to form a pattern according to the type of pillar group. The depth of the concave portion formed in the polymer electrolyte membrane can be adjusted by the height of the forming convex portion, and the position and area of the concave portion formed on the surface of the polymer electrolyte membrane can be adjusted by the position and bottom area of the convex portion. .

  In the microhole group, it is desirable that the equivalent diameter of the tip portion is equal to the equivalent diameter of the bottom surface portion, or the equivalent diameter of the bottom surface portion is slightly larger than the equivalent diameter of the tip portion. The position and the bottom area of the recess on the polymer electrolyte membrane can be arbitrarily adjusted by the position and the bottom area of the protrusion formed in the micro-forming mold. Since the microhole assembly of the present invention can have a structure in which microholes are densely packed, individual microholes can be made difficult to collapse.

In the present invention, the electrode layer comprises a catalyst metal and an electrolyte. The electrode layer may contain a water repellent material typified by polytetrafluoroethylene. Examples of the catalyst include platinum and ruthenium, rhodium, rhenium, palladium, gold, rhodium, palladium, iridium, osmium, rhenium, gold, silver, nickel, cobalt, yttrium and other supports and alloys. The catalyst may be used in a state of being supported on a carbon material typified by carbon black or carbon nanotube. Most typical examples include TEC61E54 and TEC10E50E manufactured by Tanaka Kikinzoku Co., Ltd. The electrolyte can be selected from the materials of the polymer electrolyte membrane. The electrolyte is used in a state dissolved in a solvent suitable for each selected polymer electrolyte material. The membrane material of the polymer electrolyte membrane and the electrolyte mixed in the electrode layer need not be the same material.

  The electrode layer is formed on the polymer electrolyte membrane of the present invention by directly applying the electrode layer onto the electrolyte membrane using a spray method or an ink jet method. By controlling the viscosity (solvent amount) of the solution containing the catalyst and electrolyte, the coating amount, and the temperature of the electrolyte membrane, it is possible to spread the electrode forming material to the deep part of the minute recesses formed on the polymer electrolyte membrane. Become. The electrode layer and the polymer electrolyte membrane formed in this way have an increased contact area due to the geometrical shape having the irregularities. In addition, since the polymer electrolyte membrane expands by absorbing moisture present in the use environment, the adhesion between the electrode layer and the polymer electrolyte membrane is improved. As described above, the contact resistance between the electrode layer and the polymer electrolyte membrane can be reduced. In addition, since the outermost surface of the electrode layer is formed with irregularities on the surface in accordance with the shape of the microhole group formed in the polymer electrode layer, the activity of the electrode layer is improved by increasing the contact area with the reactive species. . Further, after the electrode layer is formed on the polymer electrolyte membrane, the micro hole group may be formed in the electrode layer using a micro mold (precision mold) having a micro projection group. By doing so, the reactive surface area is further increased, and the reactive species can easily diffuse to the deep part of the electrode layer (on the polymer electrolyte membrane side), thereby preventing performance degradation due to diffusion rate limiting of the reactive species at high loads. It becomes.

  According to the present invention, the surface unevenness capable of improving the efficiency of the fuel cell is large, the polymer electrolyte membrane having a large three-dimensional surface area is excellent, and the polymer electrolyte membrane has excellent adhesion, and the surface area is large. It is possible to provide a membrane / electrode assembly comprising an electrode layer, a manufacturing method thereof, and a fuel cell. Further, since a micro-forming mold is used for manufacturing a columnar micro-hole group, a simple manufacturing technique by press molding is used. It can be formed.

  The best mode for carrying out the present invention will be described below. In addition, this invention is not limited to the Example shown below.

In this example, Nafion 115 (thickness: about 125 μm) manufactured by DuPont, USA was used as the polymer electrolyte membrane. One side on the Nafion 115 is pressed onto a 3 cm square center of the Nafion 115 cut into a 6 cm square, a micro-forming mold in which cones with a diameter of 20 μm and a height of 30 μm are formed in an XY plane at intervals of 50 μm. A microhole group was formed in Next, a microhole group was formed on the other side by the same method. Thus, an electrode layer was formed on the polymer electrolyte membrane in which the microhole group was formed. Regarding the anode electrode, TEC61E54 manufactured by Tanaka Kikinzoku Co., Ltd. was used as the catalyst. This TEC61E54 and Aldrich Nafion 5% solution were mixed at a solid content ratio of 10:10 to obtain an anode electrode solution. This anolyte solution was applied using a spray to a 3 cm square portion where a microhole group was formed on Nafion 115 heated to 80 ° C. using a hot plate so that the amount of platinum was 1 mg / cm ² . . Next, a cathode electrode was formed on the surface opposite to the surface on which the anode electrode was formed. TEC10E50E manufactured by Tanaka Kikinzoku Co., Ltd. was used as the cathode electrode catalyst. This TEC10E50E and Alfrich Nafion 5% solution were mixed at a solid content ratio of 10:10 to obtain a cathode electrode solution. This catholyte solution was applied using a spray to a 3 cm square portion where a microhole group was formed on Nafion 115 heated to 80 ° C. using a hot plate so that the amount of platinum was 1 mg / cm ² . . After forming the anode and cathode in this manner, this was heated and pressed for 2 minutes under the conditions of 120 ° C. and a pressure of 50 kg / cm ² to produce a membrane-electrode assembly for a fuel cell. FIG. 1 is a schematic cross-sectional view of a membrane / electrode assembly produced in this example. In this embodiment, the microhole group is formed on both the anode side and the cathode side of the polymer electrolyte membrane. However, the hole group may be formed only on either the anode side or the cathode side. In addition, although the same micro-forming mold was used for both the anode and cathode electrodes, micro-hole groups with the same shape were formed. May be. Further, the diameter, depth, and interval of the holes can be arbitrarily set, and adjacent holes do not need to have the same diameter and depth.

  In this example, a micro-hole group was formed in the electrode layer by pressing a micro-forming mold against the electrode surface of the membrane-electrode assembly prepared in Example 1. A micro-forming mold in which a cone having a diameter of 10 μm and a height of 30 μm is formed in an XY plane at an interval of 50 μm is pressed against the portion where the anode electrode layer of the membrane-electrode assembly produced in Example 1 is formed, Microhole groups were formed on one side of the anode electrode layer. Next, a micro-forming mold in which a cone having a diameter of 50 μm and a height of 40 μm is formed in an XY plane is pressed against the portion where the cathode electrode layer is formed, and a group of micro holes is formed on one side of the cathode electrode layer. Formed. FIG. 2 is a schematic cross-sectional view of the membrane-electrode assembly produced in this example. In this embodiment, the micro hole group is formed on both the anode side and the cathode side of the electrode layer, but the hole group may be formed only on either the anode side or the cathode side. In addition, although the same micro-forming mold was used for both the anode and cathode electrodes, micro-hole groups with the same shape were formed, but micro-hole groups with different shapes were formed using different micro-forming molds for the anode and cathode electrodes. May be. Further, the diameter, depth, and interval of the holes can be arbitrarily set, and adjacent holes do not have to have the same diameter and depth.

[Comparative Example 1]
Made by DuPont, USA: Nafion 115 (film thickness: about 125 μm) was used. An electrode layer was formed as it was in the center 3 cm square area of Nafion 115 cut out to 6 cm square. Regarding the anode electrode, TEC61E54 manufactured by Tanaka Kikinzoku Co., Ltd. was used as the catalyst. This TEC61E54 and Aldrich Nafion 5% solution were mixed at a solid content ratio of 10:10 to obtain an anode electrode solution. This anolyte solution was applied using a spray to a 3 cm square portion where a microhole group was formed on Nafion 115 heated to 80 ° C. using a hot plate so that the amount of platinum was 1 mg / cm ² . . Next, a cathode electrode was formed on the surface opposite to the surface on which the anode electrode was formed. TEC10E50E manufactured by Tanaka Kikinzoku Co., Ltd. was used as the cathode electrode catalyst. This TEC10E50E and Alfrich Nafion 5% solution were mixed at a solid content ratio of 10:10 to obtain a cathode electrode solution. This catholyte solution was applied using a spray to a 3 cm square portion where a microhole group was formed on Nafion 115 heated to 80 ° C. using a hot plate so that the amount of platinum was 1 mg / cm ² . . After forming the anode and cathode in this manner, this was heated and pressed for 2 minutes under the conditions of 120 ° C. and a pressure of 50 kg / cm ² to produce a membrane-electrode assembly for a fuel cell.

  The membrane / electrode assembly produced in Example 1, Example 2 and Comparative Example 1 was incorporated into a cell for fuel cell evaluation to evaluate the performance. The performance evaluation conditions were as shown below. A 3 wt% aqueous methanol solution was supplied to the anode side using 5 ml / min. Air was supplied to the cathode electrode side at 200 ml / min. The temperature was room temperature. The voltage at that time was measured while changing the current using a potentiostat, and a current density-voltage curve was created from the result. As a result, it was confirmed that the membrane / electrode assembly produced in Example 1 and Example 2 had higher performance than Comparative Example 1. In particular, Example 2 showed the highest performance.

FIG. 2 is a schematic cross-sectional view of the membrane / electrode assembly produced in Example 1. FIG. 3 is a schematic cross-sectional view of a membrane / electrode assembly produced in Example 2. The current density-potential curve of Example 1, Example 2, and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Polymer electrolyte membrane, 102 ... Anode electrode layer, 103 ... Cathode electrode layer.

Claims (20)

  An electrolyte membrane for a fuel cell, comprising a group of micro holes formed by plastic working on one or both sides of a polymer electrolyte membrane.   2. The fuel membrane electrolyte membrane according to claim 1, wherein the microhole group is formed according to a predetermined planar shape.   2. The fuel cell electrolyte membrane according to claim 1, wherein the minute hole group has a columnar shape, and a fuel cell using the same.   3. The fuel cell electrolyte membrane according to claim 2, wherein the microhole group has a diameter of 0.1 μm to 500 μm, a depth of 1 μm or more, and 50% or less of the thickness of the polymer electrolyte. Fuel cell using   2. The fuel cell electrolyte membrane according to claim 1, wherein an equivalent diameter of a tip portion of the minute hole group is smaller than an equivalent diameter of a bottom surface portion of the columnar hole group, and a fuel cell using the same.   2. The fuel cell electrolyte membrane according to claim 1, wherein the microhole group has a portion that narrows from a formed base toward a tip portion, and a fuel cell using the same.   2. The fuel cell electrolyte membrane according to claim 1, comprising a thermoplastic polymer material, and a fuel cell using the same.   A method for producing an electrolyte membrane for a fuel cell, comprising forming a microhole group on one side or both sides of a polymer electrolyte membrane by plastic working.   9. The microhole group according to claim 8, wherein a molding die having a convex portion of a predetermined plane pattern is pressed on one or both surfaces of the polymer electrolyte membrane, and then the molding die is peeled off from the polymer electrolyte membrane. A method for producing an electrolyte membrane for a fuel cell, characterized by comprising:   9. The method of manufacturing an electrolyte membrane for a fuel cell according to claim 8, wherein the convex portion has a diameter of 0.1 μm to 500 μm, a depth of 1 μm or more, and 50% or less of the polymer electrolyte film thickness. .   An anode electrode and a cathode electrode comprising a polymer electrolyte membrane, an electrode layer formed of a catalyst supported on a carrier on both surfaces of the electrolyte membrane, and a diffusion layer formed in contact with each electrode layer In the fuel cell having the above structure, the polymer electrolyte membrane is formed on the polymer electrolyte membrane in a state in which a minute protrusion group is formed by plastic working on one or both surfaces of the polymer electrolyte membrane, and the electrode layer is filled in the minute hole group. An electrode layer is formed, and a fuel cell membrane / electrode assembly and a fuel cell using the same.   12. The fuel cell membrane / electrode assembly according to claim 11, wherein the electrode layer has a microhole group formed by plastic working on one side or both sides of the electrode layer, and a fuel cell using the same.   13. The fuel cell membrane / electrode assembly according to claim 12, wherein the microhole group formed in the electrode layer is formed according to a predetermined planar shape, and a fuel cell using the same.   13. The fuel cell membrane / electrode assembly according to claim 12, wherein the microhole group formed in the electrode layer has a columnar shape, and a fuel cell using the same. The microhole group formed in the electrode layer according to claim 12 has a diameter of 0.1 μm to 500 μm.
Membrane / electrode assembly for fuel cell and fuel cell using the same characterized by having a thickness of μm and depth of 1 μm or more and at most 50% or less of electrode layer thickness + polymer electrolyte film thickness .   13. The fuel cell membrane / electrode assembly according to claim 12, wherein an equivalent diameter of a tip portion of the microhole group formed in the electrode layer is smaller than an equivalent diameter of a bottom surface portion of the columnar hole group, and the same Fuel cell.   13. The fuel cell membrane / electrode assembly according to claim 12, wherein the microhole group formed in the electrode layer has a portion that narrows from the formed base toward the tip. Fuel cell.   A method for producing an electrolyte membrane for a fuel cell, comprising forming a microhole group on one side or both sides of an electrode layer of a membrane / electrode assembly for a fuel cell by plastic working.   19. The method according to claim 18, wherein a pressing die having a predetermined planar pattern is pressed on one side or both sides of the electrode layer, and then the pressing die is peeled off from the electrode layer to form a microhole group. A method for producing a membrane-electrode assembly for a fuel cell. In Claim 19, The diameter of the said convex part is 0.1 micrometer-500 micrometers, the depth is 1 micrometer or more, and it is 50% or less of the thickness of an electrode layer + polymer electrolyte film thickness at maximum. Manufacturing method of membrane-electrode assembly for fuel cell.

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