JP2013084427A - Method for manufacturing membrane-catalyst layer assembly and method for manufacturing membrane electrode assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a membrane-catalyst layer assembly, by which occurrences of wrinkles and deflections of a polymer electrolyte membrane as a whole can be suppressed furthermore and deterioration in durability thereof can be also suppressed.SOLUTION: A method for manufacturing a membrane-catalyst layer assembly for a fuel cell includes the steps of: coating a first catalyst-containing ink 3a on one surface of a polymer electrolyte membrane 1 having the other surface on which a first base material 2a is formed and then drying the ink to form a first catalyst layer 3a; peeling off the first base material 2a from the other surface of the polymer electrolyte membrane 1; and coating a second catalyst-containing ink on the polymer electrolyte membrane 1 exposed by peeling off the first base material 2a and then drying the ink to form a second catalyst layer. The method includes, prior to the step of peeling off the first base material, a step of swelling the polymer electrolyte membrane in the thickness direction thereof while the first base material is formed.

Description

  The present invention relates to a fuel cell used as a driving source for a mobile body such as an automobile, a distributed power generation system, a household cogeneration system, and the like, and in particular, a method for manufacturing a membrane-catalyst layer assembly provided in the fuel cell and The present invention relates to a method for producing a membrane electrode assembly.

  BACKGROUND ART A fuel cell (for example, a polymer electrolyte fuel cell) is an apparatus that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. It is.

  A fuel cell is generally configured by stacking a plurality of cells and pressurizing them with a fastening member such as a bolt. One cell is configured by sandwiching a membrane-electrode assembly (MEA) between a pair of plate-like conductive separators.

  The membrane / electrode assembly is composed of a polymer electrolyte membrane and a pair of electrode layers disposed on both sides of the polymer electrolyte membrane. One of the pair of electrode layers is an anode electrode, and the other is a cathode electrode. The pair of electrode layers is composed of a catalyst layer mainly composed of carbon powder carrying a metal catalyst and a porous and conductive gas diffusion layer disposed on the catalyst layer. Here, the assembly of the polymer electrolyte membrane and the catalyst layer is referred to as a membrane-catalyst layer assembly (CCM). When the fuel gas comes into contact with the anode electrode and the oxidant gas comes into contact with the cathode electrode, an electrochemical reaction occurs, and electric power and heat are generated.

  In order to improve the performance of the fuel cell, it is considered effective to optimize the manufacturing method of the membrane electrode assembly. In particular, the process of forming the catalyst layer on the polymer electrolyte membrane is considered to have a great influence on the performance and durability of the fuel cell.

  As a method of forming a catalyst layer on a polymer electrolyte membrane, for example, a method of directly applying a catalyst-containing ink to a polymer electrolyte membrane is known. This method is attracting attention as an ideal method for producing a membrane-catalyst layer assembly because the interface resistance between the polymer electrolyte membrane and the catalyst layer can be made extremely low.

  However, since the catalyst-containing ink used in the above method usually contains a large amount of solvent, the solvent permeates into the polymer electrolyte membrane, the polymer electrolyte membrane expands, and the polymer electrolyte membrane is wrinkled or bent. There is a problem that occurs. When wrinkles and deflection occur, the dimensions of the polymer electrolyte membrane change, making it difficult to handle in the subsequent process. In addition, a fuel cell manufactured using a polymer electrolyte membrane in which wrinkles or deflection has occurred tends to cause problems such as voltage concentration on the wrinkled or bent portion and damage to the polymer electrolyte membrane. Low durability.

  As a method of suppressing wrinkles and deflection of the polymer electrolyte membrane, for example, there is a method disclosed in Patent Document 1 (Japanese Patent Publication No. 2006-507623). Patent Document 1 discloses a method of applying a catalyst-containing ink in a state where a base material is attached to a polymer electrolyte membrane. Hereinafter, the method of patent document 1 is demonstrated using FIG. 9A-FIG. 9F.

  First, as shown in FIG. 9A, a first substrate 102a is formed on one surface of a polymer electrolyte membrane 101. Next, as shown in FIG. 9B, the first catalyst-containing ink is applied to the other surface of the polymer electrolyte membrane 101 and then dried to form the first catalyst layer 103a. Next, as shown in FIG. 9C, the second base material 102b is formed on the first catalyst layer 103a. Next, as shown in FIG. 9D, the first base material 102a formed on one surface of the polymer electrolyte membrane 101 is peeled off. Next, as shown in FIG. 9E, the second catalyst-containing ink is applied to one surface of the polymer electrolyte membrane 101 and then dried to form the second catalyst layer 103b.

  According to the method of Patent Document 1, the first base material 102a is previously formed on one surface of the polymer electrolyte membrane 101, and the first catalyst-containing ink is applied in a state where the polymer electrolyte membrane 101 is fixed. Therefore, wrinkles and deflection of the polymer electrolyte membrane 101 can be suppressed. In addition, since the second base material 102b is formed in advance on the other surface of the polymer electrolyte membrane 101 and the second catalyst-containing ink is applied in a state where the polymer electrolyte membrane 101 is fixed, the polymer electrolyte membrane 101 wrinkles and deflection can be suppressed.

  Moreover, as another method for suppressing wrinkles and deflection of the polymer electrolyte membrane, for example, there is a method disclosed in Patent Document 2 (Japanese Patent Publication No. 2006-310237). Patent Document 2 discloses a method of applying a catalyst-containing ink in a state where a swelling liquid is infiltrated into a polymer electrolyte membrane and the outer peripheral portion of the polymer electrolyte membrane is fixed with a work.

  According to the method of Patent Literature 2, it is possible to prevent the solvent of the catalyst-containing ink from penetrating into the polymer electrolyte membrane by infiltrating the swelling liquid into the polymer electrolyte membrane in advance. Wrinkles and deflection of the electrolyte membrane can be suppressed.

JP-T-2006-507623 JP 2006-310237 A

  However, in the method of Patent Document 1, although the wrinkles and deflection of the entire polymer electrolyte membrane 101 can be suppressed when the first catalyst layer 103a is formed, the polymer electrolyte membrane is formed when the second catalyst layer 103b is formed. 101 Wrinkles and deflection of the whole cannot be suppressed. This is considered to be due to the following reason.

  That is, when the first catalyst layer 103 a is formed, the first base material 102 a is directly formed on the entire one surface of the polymer electrolyte membrane 101. For this reason, the 1st base material 102a can suppress a wrinkle and a deflection of the polymer electrolyte membrane 101 whole. On the other hand, when the second catalyst layer 103b is formed, the second base material 102b is directly formed only on a part of the other surface of the polymer electrolyte membrane 101, and the other surface of the polymer electrolyte membrane 101 is formed. Other portions are indirectly formed through the first catalyst layer 103a. Since the first catalyst layer 103a is a porous layer having irregularities, the second base material 102b and the first catalyst layer 103a are not bonded. For this reason, since the part which contacts the 1st catalyst layer 103a of the polymer electrolyte membrane 101 is not fixed by the 2nd base material 102b, wrinkles and a deflection | deviation generate | occur | produce. Therefore, the method of Patent Document 1 still has room for improvement from the viewpoint of suppressing wrinkles and deflection of the entire polymer electrolyte membrane.

  Moreover, in the method of patent document 2, the polymer electrolyte membrane is swollen not only in the thickness direction but also in the surface direction by previously infiltrating the polymer electrolyte membrane with a swelling liquid. If the catalyst-containing ink is applied to the polymer electrolyte membrane in a swollen state in the surface direction and then dried, tension may be generated in the surface direction to damage the polymer electrolyte membrane, which may reduce durability.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, and to produce a membrane-catalyst layer assembly that can further suppress wrinkles and deflections of the entire polymer electrolyte membrane and suppress a decrease in durability. The object is to provide a method and a method for producing a membrane electrode assembly.

In order to achieve the above object, the present invention is configured as follows.
According to the present invention, there is provided a method for producing a membrane-catalyst layer assembly for a fuel cell, wherein the first catalyst-containing ink is applied to the other surface of the polymer electrolyte membrane having the first substrate formed on one surface. Forming a first catalyst layer by applying and then drying;
Peeling the first substrate from one surface of the polymer electrolyte membrane;
Forming a second catalyst layer by applying a second catalyst-containing ink onto the polymer electrolyte membrane exposed by peeling off the first substrate and then drying;
A method for producing a membrane-catalyst layer assembly for a fuel cell, comprising:
A method for producing a membrane-catalyst layer assembly comprising a step of swelling the polymer electrolyte membrane in a thickness direction in a state where the first substrate is formed before the step of peeling the first substrate. provide.

  According to the method for producing a membrane-catalyst layer assembly according to the present invention, it is possible to further suppress wrinkles and deflection of the entire polymer electrolyte membrane and to suppress the decrease in durability.

It is sectional drawing which shows typically the manufacturing method of the membrane-catalyst layer assembly concerning embodiment of this invention. It is sectional drawing which shows the process of following FIG. 1A. It is sectional drawing which shows the process of following FIG. 1B. FIG. 1C is a cross-sectional view showing a step following FIG. 1C. FIG. 1D is a cross-sectional view showing a step that follows FIG. 1D. It is sectional drawing which shows the process of following FIG. 1E. It is sectional drawing which shows the modification of the process shown to FIG. 1B. It is sectional drawing which shows the modification of the process shown to FIG. 1C. It is a photograph which shows the state which irradiated the white light from the downward direction with respect to the membrane-catalyst layer assembly manufactured by setting the temperature of a roll to 130 degreeC. It is a photograph which shows the state which irradiated the white light from the downward direction with respect to the membrane-catalyst layer assembly manufactured by setting the temperature of a roll to 125 degreeC. It is sectional drawing which shows typically the manufacturing method of the membrane electrode assembly concerning embodiment of this invention. It is sectional drawing which shows the process of following FIG. 4A. FIG. 4B is a cross-sectional view showing a step that follows FIG. 4B. It is sectional drawing which shows the modification of the process shown to FIG. 1D. It is sectional drawing which shows the modification of the process shown to FIG. 1E. It is sectional drawing which shows the modification of the process shown to FIG. 1F, FIG. 4A, and FIG. 4B. It is sectional drawing which shows typically the basic composition of a fuel cell provided with the membrane electrode assembly concerning embodiment of this invention, and is a figure which shows the example by which the gas flow path was provided in the separator. FIG. 7 is an exploded perspective view showing a basic configuration of a fuel cell stack in which a plurality of the fuel cells of FIG. 6 are connected. It is sectional drawing which shows typically the basic composition of a fuel cell provided with the membrane electrode assembly concerning embodiment of this invention, and is a figure which shows the example by which the gas flow path was provided in the gas diffusion layer. It is sectional drawing which shows typically the manufacturing method of the conventional membrane-catalyst layer assembly. It is sectional drawing which shows the process of following FIG. 9A. It is sectional drawing which shows the process of following FIG. 9B. It is sectional drawing which shows the process of following FIG. 9C. It is sectional drawing which shows the process of following FIG. 9D.

  The inventors of the present invention have obtained the following knowledge as a result of intensive studies in order to solve the problems of the prior art.

  The inventors of the present invention prepare a polymer electrolyte membrane in which a substrate is not formed and a polymer electrolyte membrane in which a substrate is formed, and change the environment from a temperature of 23 ° C. and a humidity of 53% to a temperature. The dimensional change rate when the temperature was changed to 80 ° C. and humidity 90% was examined. As a result, the dimension of the polymer electrolyte membrane on which the base material is not formed increases by 16% in both the surface direction and the thickness direction, and the dimension of the polymer electrolyte membrane on which the base material is formed does not change in the surface direction. It was found that only 46% increase in the thickness direction.

  From the above results, the inventors of the present invention maintain the shape of the polymer electrolyte membrane in the surface direction when the polymer electrolyte membrane is swollen by humidification or the like in a state where the substrate is formed. For this reason, it has been found that the polymer electrolyte membrane swells mainly in the thickness direction and can suppress damage in the polymer electrolyte membrane by suppressing the tension in the surface direction. Further, the inventors of the present invention, when a catalyst-containing ink is applied to a polymer electrolyte membrane swollen in the thickness direction, the catalyst-containing ink solvent is prevented from penetrating into the polymer electrolyte membrane, and the polymer electrolyte It was found that wrinkles and deflection of the entire membrane can be suppressed. Based on these findings, the inventors of the present invention have reached the following present invention.

According to the first aspect of the present invention, the first catalyst layer is formed by applying the first catalyst-containing ink to the other surface of the polymer electrolyte membrane having the first substrate formed on one surface and then drying. And a process of
Peeling the first substrate from one surface of the polymer electrolyte membrane;
Forming a second catalyst layer by applying a second catalyst-containing ink onto the polymer electrolyte membrane exposed by peeling off the first substrate and then drying;
A method for producing a membrane-catalyst layer assembly for a fuel cell, comprising:
A method for producing a membrane-catalyst layer assembly comprising a step of swelling the polymer electrolyte membrane in a thickness direction in a state where the first substrate is formed before the step of peeling the first substrate. provide.

  According to the second aspect of the present invention, the membrane-catalyst layer bonding according to the first aspect, wherein the step of swelling the polymer electrolyte membrane in the thickness direction includes humidifying the polymer electrolyte membrane. A method for manufacturing a body is provided.

  According to the third aspect of the present invention, the humidification is performed in a state where the first catalyst layer is formed on the other surface of the polymer electrolyte membrane, and the membrane-catalyst layer assembly according to the second aspect. A manufacturing method is provided.

  According to the 4th aspect of this invention, the said humidification is performed by arrange | positioning the said polymer electrolyte membrane in a constant temperature and humidity chamber, The manufacturing method of the membrane-catalyst layer assembly as described in a 2nd or 3rd aspect. I will provide a.

  According to the fifth aspect of the present invention, in the step of swelling the polymer electrolyte membrane in the thickness direction, the first catalyst-containing ink is applied to the other surface of the polymer electrolyte membrane and then semi-dried. A method for producing a membrane-catalyst layer assembly according to the first aspect is provided.

  According to the sixth aspect of the present invention, the polymer on which the first catalyst layer is formed after the step of swelling the polymer electrolyte membrane in the thickness direction and before the step of peeling off the first substrate. The manufacturing method of the membrane-catalyst layer assembly as described in any one of the 1st-5th aspect including the process of forming a 2nd base material in the other surface of an electrolyte membrane is provided.

According to a seventh aspect of the present invention, there is provided a method for producing a membrane / electrode assembly including the method for producing a membrane-catalyst layer assembly according to any one of the first to fifth aspects,
After the step of swelling the polymer electrolyte membrane in the thickness direction and before the step of peeling off the first substrate, the other surface of the polymer electrolyte membrane on which the first catalyst layer is formed, The manufacturing method of a membrane electrode assembly including the process of forming a gas diffusion layer in contact with 1 catalyst layer is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all of the following drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

<Embodiment>
A method for producing a membrane-catalyst layer assembly according to an embodiment of the present invention will be described. 1A to 1F are cross-sectional views schematically showing a method for producing a membrane-catalyst layer assembly according to this embodiment.

  First, as shown to FIG. 1A, the 1st base material 2a is formed in one surface of the polymer electrolyte membrane 1 (1st base material formation process).

  Next, as shown in FIG. 1B, the first catalyst-containing ink is applied to the other surface of the polymer electrolyte membrane 1 and then dried to form the first catalyst layer 3a (first catalyst layer forming step).

  Next, as shown in FIG. 1C, the polymer electrolyte membrane 1 on which the first catalyst layer 3a is formed is placed in a constant temperature and humidity chamber 4, and the polymer electrolyte membrane 1 is humidified (humidification step). At this time, since the shape of the polymer electrolyte membrane 1 in the surface direction is held by the first base material 2a, the polymer electrolyte membrane 1 is suppressed from swelling in the surface direction and is mainly swollen in the thickness direction. For example, the polymer electrolyte membrane 1 swells until the thickness is about 20 μm to 40 μm. In addition, the constant temperature and humidity tank 4 is a tank which has the area | region controlled by fixed humidity and fixed temperature. The constant temperature and humidity chamber 4 may have a function of spraying a solvent such as water vapor or alcohol.

  Next, as shown in FIG. 1D, a second substrate 2b is formed on the other surface of the polymer electrolyte membrane 1 so as to cover the first catalyst layer 3a (second substrate forming step).

  Next, as shown in FIG. 1E, the first substrate 2a is peeled from the polymer electrolyte membrane 1 on which the second substrate 2b is formed (first substrate peeling step).

  Next, as shown in FIG. 1F, the second catalyst-containing ink is applied on the polymer electrolyte membrane 1 exposed by peeling off the first substrate 2a, and then dried to form the second catalyst layer 3b (the first catalyst layer 3b). 2 catalyst layer formation process).

  By performing each of the above steps, the membrane-catalyst layer assembly according to the present embodiment can be manufactured.

  According to the method for manufacturing a membrane-catalyst layer assembly according to the present embodiment, the polymer electrolyte membrane 1 is humidified in a state where the first base material 2a is formed. Therefore, the polymer electrolyte membrane 1 is mainly used. It can be swollen in the thickness direction. Thereby, it can suppress that tension | tensile_strength generate | occur | produces in the surface direction with respect to the polymer electrolyte membrane 1, can suppress the damage of the polymer electrolyte membrane 1, and can suppress the fall of durability. In addition, since the polymer electrolyte membrane 1 is swollen in the thickness direction in advance before the formation of the second catalyst layer 3b, the solvent of the second catalyst-containing ink is prevented from penetrating into the polymer electrolyte membrane 1. can do. Thereby, wrinkles and deflection of the entire polymer electrolyte membrane 1 can be suppressed.

  In the above description, as described with reference to FIG. 1C, the polymer electrolyte membrane 1 is humidified in a state where the first catalyst layer 3a is formed. However, the present invention is not limited to this. For example, as shown in FIGS. 2A and 2B, the polymer electrolyte membrane 1 on which the first substrate 2a is formed is placed in a constant temperature and humidity chamber 4 and humidified, and then the other surface of the polymer electrolyte membrane 1 is provided. Alternatively, the first catalyst-containing ink may be applied to form the first catalyst layer 3a. It should be noted that the polymer electrolyte membrane 1 is humidified with the first catalyst layer 3a formed, rather than the polymer electrolyte membrane 1 is humidified with the first catalyst layer 3a not formed. The effect of suppressing wrinkles and deflection of the entire membrane 1 is high.

  In the above description, the constant temperature and humidity chamber 4 is used to swell the polymer electrolyte membrane 1, but the present invention is not limited to this. For example, the polymer electrolyte membrane 1 may be swollen by infiltrating the polymer electrolyte membrane 1 with the solvent of the first catalyst-containing ink. Alternatively, the polymer electrolyte membrane 1 may be swollen using a conventionally known humidification technique such as spraying steam directly on the polymer electrolyte membrane 1. From the viewpoint of manufacturing control accuracy, it is preferable to swell the polymer electrolyte membrane 1 using the constant temperature and humidity chamber 4.

  If the first catalyst layer forming step is performed after swelling the polymer electrolyte membrane 1, the polymer electrolyte membrane 1 is also dried when the first catalyst-containing ink is dried. The swelling state of the polymer electrolyte membrane 1 may be lost. Therefore, in the first catalyst layer forming step, semi-drying is performed so that the first catalyst-containing ink is not completely dried, and in the second catalyst layer forming step, the first catalyst-containing ink is fully dried. It is preferable. Also by such a method, when the second catalyst-containing ink is applied, the polymer electrolyte membrane 1 is swollen in the thickness direction, so that the solvent of the second catalyst-containing ink permeates the polymer electrolyte membrane 1. Can be suppressed. Thereby, wrinkles and deflection of the entire polymer electrolyte membrane 1 can be suppressed.

  Moreover, a 2nd base material formation process can be performed by pinching the laminated body arrange | positioned as shown to FIG. 1D with two rolls, and applying a pressure to the said laminated body with the said two rolls, for example. . In this case, if the temperature of the roll is too high, the water in the polymer electrolyte membrane 1 evaporates due to the heat of the roll, and the moisture content of the polymer electrolyte membrane 1 decreases. Wrinkles and deflection of the entire polymer electrolyte membrane 1 are more likely to occur as the moisture content of the polymer electrolyte membrane 1 becomes lower. For this reason, from the viewpoint of maintaining the water content of the polymer electrolyte membrane 1 as high as possible, the temperature of the roll is preferably 130 ° C. or less, and more preferably 125 ° C. or less. Moreover, when the temperature of a roll is too low, it will become difficult to fully adhere | attach the polymer electrolyte membrane 1 and a 2nd base material. In this case, the second base material cannot hold the shape of the polymer electrolyte membrane 1 in the surface direction, and as a result, the polymer electrolyte membrane 1 may be wrinkled or bent. From this viewpoint, the temperature of the roll is preferably 100 ° C. or higher, and more preferably 110 ° C. or higher.

  In addition, after manufacturing the laminated body shown to FIG. 1D by setting the temperature of a roll to 130 degreeC, when the 1st base material 2a was peeled and the moisture content of the polymer electrolyte membrane 1 was measured, the said moisture content is It was 2.8%. The non-defective product ratio of the membrane-catalyst layer assembly produced using the polymer electrolyte membrane 1 was 18%. On the other hand, after the roll temperature was set to 125 ° C. and the laminate shown in FIG. 1D was manufactured, the first substrate 2a was peeled off and the moisture content of the polymer electrolyte membrane 1 was measured. The rate was 3.6%. The non-defective product ratio of the membrane-catalyst layer assembly produced using the polymer electrolyte membrane 1 was 47%. The moisture content is defined as the ratio of the difference in weight of the polymer electrolyte membrane before and after being put into a dryer controlled at 80 ° C. for 5 minutes to the weight of the electrolyte membrane after drying.

  FIG. 3A is a photograph showing a state in which white light is irradiated from below on a membrane-catalyst layer assembly produced by setting the roll temperature to 130 ° C. FIG. 3B is a photograph showing a state in which white light is irradiated from below on the membrane-catalyst layer assembly produced by setting the roll temperature to 125 ° C. When wrinkles are generated in the polymer electrolyte membrane, cracks are generated in the catalyst layer and white light is transmitted. Therefore, the white portions in FIG. 3A and FIG. 3B indicate portions where wrinkles are generated in the polymer electrolyte membrane. From FIG. 3A and FIG. 3B, it can be seen that the wrinkles of the polymer electrolyte membrane are clearly reduced when the roll temperature is set to 125 ° C. than when the roll temperature is set to 130 ° C.

  In addition, although the preferable temperature of the roll was demonstrated above, when not using a roll in a 2nd base material formation process, what is necessary is just to consider that the temperature of the 2nd base material 2b corresponds to the temperature of a roll. Even in this case, a similar result can be obtained.

  Next, the manufacturing method of the membrane electrode assembly concerning embodiment of this invention is demonstrated. 4A to 4C are cross-sectional views schematically showing a method for manufacturing a membrane electrode assembly according to the present embodiment.

  First, as described with reference to FIGS. 1A to 1F, a membrane-catalyst layer assembly with the second substrate 2b is manufactured.

  Next, as shown in FIG. 4A, the first gas diffusion layer 5a is formed on the second catalyst layer 3b (first gas diffusion layer forming step). Thereby, the electrode layer of either an anode electrode or a cathode electrode is formed with the 2nd catalyst layer 3b and the 1st gas diffusion layer 5a.

  Next, as shown in FIG. 4B, the second substrate 2b is peeled from the other surface of the polymer electrolyte membrane 1 (second substrate peeling step).

  Next, as shown in FIG. 4C, a second gas diffusion layer 5b is formed on the adhesive layer 4 exposed by peeling off the second substrate 2b (second gas diffusion layer forming step). As a result, the first electrode layer 3a, the adhesive layer 4, and the second gas diffusion layer 5b form the other electrode layer of the anode electrode or the cathode electrode.

  By performing the above steps, the membrane electrode assembly according to the present embodiment can be manufactured.

  In the above description, as described with reference to FIGS. 1D to 1F and 4A, the second base material 2b is formed on the other surface of the polymer electrolyte membrane 1 so as to cover the first catalyst layer 3a. The present invention is not limited to this. For example, as shown in FIG. 5A, instead of the second substrate 2b, a second gas diffusion layer 5b is formed on the other surface of the polymer electrolyte membrane 1 so as to cover the first catalyst layer 3a, and the second You may make it hold | maintain the shape of the surface direction of the polymer electrolyte membrane 1 by the gas diffusion layer 5b. In this case, as shown in FIG. 5B, the first substrate 2a is peeled from one surface of the polymer electrolyte membrane 1, and the first substrate 2a is peeled and exposed as shown in FIG. 5C. The second catalyst layer 3b is formed on the first electrode, and the first gas diffusion layer 5a is formed on one surface of the polymer electrolyte membrane 1 so as to cover the second catalyst layer 3b as shown in FIG. The membrane electrode assembly according to the embodiment can be manufactured. According to this manufacturing method, the process related to the second base material 2b can be omitted, so that the manufacturing time can be shortened.

  Next, the shape, material, etc. of each member constituting the membrane electrode assembly will be described.

  The polymer electrolyte membrane 1 is preferably a polymer membrane having hydrogen ion conductivity. The polymer electrolyte membrane 1 is not particularly limited. For example, a fluorine-based polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (registered trademark) manufactured by DuPont, USA, manufactured by Asahi Kasei Corporation) Aciplex (registered trademark), Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., GSII (trade name) manufactured by Japan Gore-Tex Co., Ltd.) and various hydrocarbon electrolyte membranes can be used. The material of the polymer electrolyte membrane 1 may be any material that selectively moves hydrogen ions. The polymer electrolyte membrane 1 may be reinforced with a core material or the like in order to ensure mechanical strength and dimensional stability.

  Moreover, the film thickness of the polymer electrolyte membrane 1 is not particularly limited, but is, for example, 20 to 50 μm. Some polymer electrolyte membranes having a thickness of 20 to 50 μm are commercially available while being bonded to a substrate. In the case of using the polymer electrolyte membrane in a state where this base material is bonded, the first base material forming step described with reference to FIG. 1A can be omitted.

  Moreover, the ion exchange capacity of the polymer electrolyte membrane 1 is not particularly limited, but is, for example, 0.5 to 2.0 milliequivalent / g membrane dry weight. In order to enhance the ion conductivity and improve the battery characteristics, the ion exchange capacity of the polymer electrolyte membrane is preferably 1.1 milliequivalent / g membrane dry weight or more. However, it should be noted that when the ion exchange capacity of the polymer electrolyte membrane is increased, the moisture content is improved, the amount of change in the wet and dry dimensions is increased, and wrinkles and deflection are likely to occur.

  Further, as shown in FIG. 4C, the polymer electrolyte membrane 1 is larger in size than the catalyst layers 3a and 3b and the gas diffusion layers 5a and 5b, and is provided so that the peripheral edge protrudes from them. The catalyst layers 3a and 3b may be the same size or larger than the gas diffusion layers 5a and 5b. However, as explained with reference to FIG. 5A, when the shape of the polymer electrolyte membrane 1 in the plane direction is held in the gas diffusion layer 5b, the polymer electrolyte membrane 1 and the gas diffusion layer 5b are joined, The catalyst layer 3a needs to be smaller in size than the gas diffusion layer 5b.

  The catalyst layers 3a and 3b can be formed, for example, by applying a catalyst-containing ink on the surface of the polymer electrolyte membrane 1 and then drying it. Examples of the method for applying the catalyst-containing ink include spray coating, die coating, doctor blade coating, roll coater coating, cast coater, curtain coater, electrostatic coating, screen printing, and gravure printing. And printing methods such as letterpress printing and planographic printing. In addition, as a drying method of the catalyst-containing ink, a known drying technique such as a method of heating a stage or the like on which the polymer electrolyte membrane 1 is disposed, a method of disposing in a dryer, or a method of heating and drying using far infrared rays is used. Can be applied. From the viewpoint of maintaining the water content of the polymer electrolyte membrane 1 as high as possible, it is preferable to dry the catalyst-containing ink so that the temperature in the vicinity of the applied catalyst-containing ink is 100 ° C. or lower.

  In the catalyst-containing ink, for example, a polymer electrolyte having the same components as the polymer electrolyte membrane 1 in addition to the catalyst is dispersed or dissolved in a solvent, and a small amount of an additive such as a surfactant or a water repellent is added as necessary. Can be prepared. The catalyst layers 3a and 3b formed by drying the catalyst-containing ink contain a catalyst and a polymer electrolyte.

  The catalyst is for smoothly carrying out an electrode reaction, and carries a noble metal catalyst on the surface of carbon fine particles. Normally, carbon fine particles having an alloy catalyst such as Pt (platinum) or PtRu (platinum-ruthenium) supported on the surface are used for the catalyst on the anode side. Further, carbon fine particles having an alloy catalyst such as Pt or PtCo supported on the surface are used as the cathode side catalyst.

  The polymer electrolyte is added between the catalyst fine particles and between the polymer electrolyte membrane 1 and the catalyst fine particles so as to perform the electrode reaction more smoothly. A liquid in which a polymer electrolyte is previously dispersed or dissolved in a predetermined solvent is already on the market.

  As the solvent for the catalyst-containing ink, a solvent having a relatively low boiling point or low molecular weight, such as water (preferably ion-exchanged water or pure water), ethanol, n-propanol, isopropyl alcohol, n-butanol, 2-butanol, It is possible to use at least one selected from the group consisting of primary to tertiary alcohols such as tert-butanol, derivatives thereof, and organic solvents such as ether type, ester type and fluorine type. The solvent needs to have sufficient solubility so that the polymer electrolyte does not precipitate and the dispersed state does not decrease. Moreover, in order to form a catalyst layer efficiently in a short time, it is necessary to select a solvent having an appropriate boiling point and vapor pressure. When the boiling point of the solvent is low and the vapor pressure is high, the solvent dries too quickly and it becomes difficult to continuously print and apply the catalyst-containing ink. Moreover, when the boiling point of the solvent is high and the vapor pressure is low, it takes a long time to dry the coating film.

The amount of the noble metal (or alloy) adhering to the carbon fine particles is not particularly limited, but usually needs to be controlled to about 0.1 to 0.6 mg / cm ² . If the printing method or the coating method is used, the amount of noble metal (or alloy) attached to the carbon fine particles can be easily managed. In addition, by controlling the particle size of the catalyst in the catalyst-containing ink, the amount of catalyst added, the solvent composition, etc., and adjusting the viscosity of the catalyst-containing ink, it is possible to control and manage the adhesion amount with higher accuracy. it can.

  The base materials 2a and 2b are shape holding films for holding the shape of the polymer electrolyte membrane 1 in the surface direction (stabilizing dimensions). The base materials 2a and 2b are preferably those whose shapes do not change even when humidified. As the base materials 2a and 2b, for example, polyethylene terephthalate, polypropylene, polyetherimide, polyimide, polyamide, polycarbonate, polyacetal, fluororesin, rubber-like elastic body, and the like having a heat resistance that does not undergo thermal deformation during lamination processing It can be used without any particular limitation.

  Although the film thickness of the base materials 2a and 2b is not specifically limited, For example, it is 50-500 micrometers. When the thicknesses of the base materials 2a and 2b are thinner than 50 μm, the mechanical strength is lowered, so that the ability to maintain the shape of the polymer electrolyte membrane 1 is insufficient. On the other hand, when the film thickness of the base materials 2a and 2b is thicker than 500 μm, it is difficult to wind the base material when a roll-to-roll manufacturing apparatus is employed. From these viewpoints, the thickness of the base materials 2a and 2b is preferably 100 to 300 μm.

  In addition, when the adhesiveness and peelability of the base material 2a, 2b and the polymer electrolyte membrane 1 are not sufficient, the surface of the base material 2a, 2b may be subjected to surface treatment such as corona treatment or plasma treatment. Moreover, you may provide the guide hole for positioning or roll conveyance for raising the positional accuracy of printing or an application | coating site | part as needed in the base materials 2a and 2b. In addition, it is preferable to use the substrates 2a and 2b having relatively excellent thermal and chemical stability. Thereby, since it can suppress that base material 2a, 2b is damaged at the time of manufacture of a membrane-catalyst layer assembly, it becomes possible to reuse base material 2a, 2b. Moreover, the base material 2a and the base material 2b may be comprised with the same material, or may be comprised with another material.

  The gas diffusion layers 5a and 5b are configured by, for example, a so-called baseless gas diffusion layer configured without using carbon fiber as a base material. As an example of the base material-less gas diffusion layer, there is a gas diffusion layer composed of a porous member mainly composed of conductive particles and a polymer resin. Here, the “porous member mainly composed of conductive particles and polymer resin” means a structure (so-called self-supporting structure) that is supported only by conductive particles and polymer resin without using carbon fiber as a base material. It means a porous member having a support structure. When producing a porous member with conductive particles and a polymer resin, for example, a surfactant and a dispersion solvent are used. In this case, during the production process, the surfactant and the dispersion solvent are removed by firing, but they may not be sufficiently removed and may remain in the porous member. Therefore, as long as the “porous member mainly composed of conductive particles and polymer resin” has a self-supporting structure in which carbon fiber is not used as a base material, the surfactant and the dispersion remaining in this manner are dispersed. It means that a solvent may be included in the porous member. In addition, if the self-supporting structure does not use carbon fibers as a base material, it means that other materials (for example, carbon fibers of short fibers) may be included in the porous member.

  The gas diffusion layers 5a and 5b can be manufactured by kneading, extruding, rolling, and firing a mixture containing a polymer resin and conductive particles. Specifically, carbon, which is conductive particles, a dispersion solvent, and a surfactant are introduced into a stirrer / kneader, and then kneaded, pulverized, and granulated to disperse the carbon in the dispersed solvent. Next, the fluororesin, which is a polymer resin, is further dropped into a stirrer / kneader and stirred and kneaded to disperse the carbon and the fluororesin. The obtained kneaded material is rolled to form a sheet and fired to remove the dispersion solvent and the surfactant. Thereby, the sheet-like gas diffusion layers 5a and 5b can be manufactured.

  Examples of the material of the conductive particles constituting the gas diffusion layers 5a and 5b include carbon materials such as graphite, carbon black, and activated carbon. Examples of the carbon black include acetylene black (AB), furnace black, ketjen black, vulcan, and the like. These materials may be used alone, or a plurality of materials may be used in combination. . In addition, the raw material form of the carbon material may be any shape such as powder, fiber, and granule.

  As the material of the polymer resin constituting the gas diffusion layers 5a and 5b, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), PVDF (polyvinylidene fluoride), ETFE (tetra) Fluoroethylene / ethylene copolymer), PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), and the like. Among these, PTFE is preferably used as the polymer resin material from the viewpoints of heat resistance, water repellency, and chemical resistance. Examples of the raw material form of PTFE include dispersion and powder. Among these, it is preferable from the viewpoint of workability that a dispersion is adopted as a raw material form of PTFE. The polymer resin constituting the gas diffusion layers 5a and 5b has a function as a binder for binding the conductive particles. Further, since the polymer resin has water repellency, it also has a function (water retention) for confining water in the system inside the fuel cell.

  Further, as described above, in addition to the conductive particles and the polymer resin, the gas diffusion layers 5a and 5b may contain a trace amount of a surfactant and a dispersion solvent used when the gas diffusion layer is manufactured. . Examples of the dispersion solvent include water, alcohols such as methanol and ethanol, and glycols such as ethylene glycol. Examples of the surfactant include nonionic compounds such as polyoxyethylene alkyl ethers and zwitterionic compounds such as alkylamine oxides. What is necessary is just to set suitably the quantity of the dispersion solvent used at the time of manufacture, and the quantity of surfactant according to the kind of electroconductive particle, the kind of polymer resin, those compounding ratios, etc. In general, as the amount of the dispersion solvent and the amount of the surfactant increases, the polymer resin and the conductive particles tend to be uniformly dispersed, but the fluidity increases and the sheet of the gas diffusion layer is increased. It tends to be difficult. The surfactant can be appropriately selected depending on the material of the conductive particles and the type of the dispersion solvent. Moreover, it is not necessary to use a surfactant.

  The gas diffusion layers 5a and 5b may be gas diffusion layers having the same structure on the cathode electrode side and the anode electrode side or may be gas diffusion layers having different structures. For example, a gas diffusion layer using carbon fiber as a base material may be used on either the cathode electrode side or the anode electrode side, and the base material-less gas diffusion layer may be used on either side.

  Next, a fuel cell (unit cell) including the membrane electrode assembly according to the present embodiment will be described. FIG. 6 is a cross-sectional view schematically showing the basic configuration of the fuel cell 10 including the membrane electrode assembly according to the present embodiment.

  As shown in FIG. 6, the fuel cell 10 is configured to sandwich the membrane electrode assembly between a pair of separators 30 and 40. A resin frame (also referred to as a gasket) 20 is provided on the outer peripheral portion of the membrane electrode assembly in order to improve handling properties or to seal between the polymer electrolyte membrane 1 and the separators 30 and 40. ing. The pair of separators 30 and 40 is preferably made of a material containing carbon or a material containing metal. A gas flow path 31 for fuel gas is provided on a main surface (hereinafter also referred to as an electrode surface) that contacts the second gas diffusion layer 5 b of one separator (anode separator) 30. A gas channel 41 for oxidizing gas is provided on a main surface (hereinafter also referred to as an electrode surface) of the other separator (cathode separator) 40 that contacts the first gas diffusion layer 5a. By supplying the fuel gas to the gas flow path 31 of one separator 30 and supplying the oxidant gas to the gas flow path 41 of the other separator 40, an electrochemical reaction occurs, and electric power and heat are generated. In FIG. 6, the adhesive layer 4 is illustrated as being disposed on the anode side, but the adhesive layer 4 may be disposed on the cathode side.

  When the fuel cell 10 is used as a power source, the required number of fuel cells (unit cells) 10 shown in FIG. 6 can be connected in series and used as a so-called fuel cell stack. In this case, in order to supply the reaction gas (fuel gas or oxidant gas) to the gas flow paths 31 and 41, the reaction gas is branched into a number corresponding to the number of separators 30 and 40 to be used, and the branch destinations thereof. Is required to connect the gas flow paths 31 and 41 to each other.

  FIG. 7 is an exploded perspective view showing a basic configuration of a fuel cell stack 11 in which a plurality of fuel cells 10 are connected. As shown in FIG. 7, the frame 20 and the pair of separators 30 and 40 are provided with fuel gas manifold holes 22, 32 and 42, which are a pair of through holes to which fuel gas is supplied, respectively. The frame 20 and the pair of separators 30 and 40 are provided with oxidant gas manifold holes 23, 33, and 43, which are a pair of through holes through which the oxidant gas flows. In a state where the frame 20 and the pair of separators 30 and 40 are connected as the fuel cell (unit cell) 10, the fuel gas manifold holes 22, 32 and 42 are connected to form a fuel gas manifold. Similarly, in a state where the frame 20 and the pair of separators 30 and 40 are connected as the fuel cell (unit cell) 10, the oxidant gas manifold holes 23, 33 and 43 are connected to form an oxidant gas manifold. The

  The frame body 20 and the pair of separators 30 and 40 are provided with cooling medium manifold holes 24, 34, and 44, which are two pairs of through holes, respectively, through which a cooling medium (for example, pure water or ethylene glycol) flows. Yes. In a state where the frame 20 and the pair of separators 30 and 40 are connected as the fuel cell (unit cell) 10, the cooling medium manifold holes 24, 34, and 44 are connected to form two pairs of cooling medium manifolds.

  The frame body 20 and the pair of separators 30 and 40 are provided with four bolt holes 50 in the vicinity of each corner. A fastening bolt is inserted into each bolt hole 50, and a plurality of fuel cells 10 are fastened by connecting a nut to the fastening bolt.

  The gas flow path 31 is provided so as to connect the pair of fuel gas manifolds 32, 32. The gas flow path 41 is provided so as to connect the pair of oxidant gas manifolds 43, 43. In addition, in FIG. 7, although the gas flow paths 31 and 41 were shown as a serpentine type flow path, the flow path of another form (for example, linear type) may be sufficient.

  Moreover, although not shown in figure, the cooling medium flow path is formed in the main surface on the opposite side to the electrode surface of the separator 30, and the main surface on the opposite side to the electrode surface of the separator 40, respectively. The cooling medium flow path is formed so as to connect the two pairs of cooling medium manifold holes 34 and 44. That is, the cooling medium is configured to branch from the cooling medium manifold on the supply side to the cooling medium flow path and to flow to the cooling medium manifold on the discharge side. Thus, the fuel cell 10 is maintained at a predetermined temperature suitable for the electrochemical reaction by utilizing the heat transfer capability of the cooling medium.

  In the above description, the manifolds for the fuel gas, the oxidant gas, and the cooling water are provided in the separators 30 and 40, and the supply manifolds for the fuel gas, the oxidant gas, and the cooling water are formed when they are stacked. The so-called internal manifold type fuel cell configured as described above has been described as an example, but the present invention is not limited to this. For example, a so-called external manifold type fuel cell in which supply manifolds for fuel gas, oxidant gas, and cooling water are provided on the side surface of the fuel cell stack 11 may be used. Even in this case, the same effect can be obtained. Further, the separators 30 and 40 are formed of a porous conductive material, and cooling is performed so that the pressure of the cooling water flowing through the cooling medium flow path is higher than the pressure of the reaction gas flowing through the gas flow paths 31 and 41. A so-called internal humidification type fuel cell in which a part of water is allowed to pass through the separators 30 and 40 to the electrode surface side to wet the polymer electrolyte membrane 1 may be used.

  In the above description, the gas flow paths 31 and 41 are provided in the separators 30 and 40. However, the present invention is not limited to this. For example, as shown in FIG. 8, the gas flow path 31 may be provided in one gas diffusion layer 14 and the gas flow path 41 may be provided in the other gas diffusion layer 14. Further, the gas flow path 31 may be formed in both the separator 30 and the one gas diffusion layer 14. Further, the gas flow path 41 may be formed in both the separator 40 and the other gas diffusion layer 14.

  The method for producing a membrane-catalyst layer assembly according to the present invention can further suppress wrinkles and deflection of the entire polymer electrolyte membrane, and can also suppress a decrease in durability. This is useful as a method for producing a membrane-catalyst layer assembly provided in a fuel cell used as a drive source for a power generation system, a household cogeneration system, or the like.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2a 1st base material 2b 2nd base material 3a 1st catalyst layer 3b 2nd catalyst layer 4 Constant temperature and humidity tank 5a 1st gas diffusion layer 5b 2nd gas diffusion layer 10 Fuel cell 11 Fuel cell stack 20 Frame 30, 40 Separator 31, 41 Gas flow path

Claims (7)

Forming a first catalyst layer by applying a first catalyst-containing ink to the other surface of the polymer electrolyte membrane having the first substrate formed on one surface and then drying;
Peeling the first substrate from one surface of the polymer electrolyte membrane;
Forming a second catalyst layer by applying a second catalyst-containing ink onto the polymer electrolyte membrane exposed by peeling off the first substrate and then drying;
A method for producing a membrane-catalyst layer assembly for a fuel cell, comprising:
A method for producing a membrane-catalyst layer assembly comprising a step of swelling the polymer electrolyte membrane in a thickness direction in a state where the first substrate is formed before the step of peeling the first substrate.   The method for producing a membrane-catalyst layer assembly according to claim 1, wherein the step of swelling the polymer electrolyte membrane in the thickness direction includes humidifying the polymer electrolyte membrane.   The method for producing a membrane-catalyst layer assembly according to claim 2, wherein the humidification is performed in a state where the first catalyst layer is formed on the other surface of the polymer electrolyte membrane.   The method for producing a membrane-catalyst layer assembly according to claim 2 or 3, wherein the humidification is performed by placing the polymer electrolyte membrane in a constant temperature and humidity chamber.   The step of swelling the polymer electrolyte membrane in the thickness direction includes semi-drying after applying the first catalyst-containing ink to the other surface of the polymer electrolyte membrane. A method for producing a membrane-catalyst layer assembly.   After the step of swelling the polymer electrolyte membrane in the thickness direction and before the step of peeling the first substrate, a second group is formed on the other surface of the polymer electrolyte membrane on which the first catalyst layer is formed. The manufacturing method of the membrane-catalyst layer assembly according to any one of claims 1 to 5, comprising a step of forming a material. A method for producing a membrane electrode assembly, comprising the method for producing a membrane-catalyst layer assembly according to any one of claims 1 to 5,
After the step of swelling the polymer electrolyte membrane in the thickness direction and before the step of peeling off the first substrate, the other surface of the polymer electrolyte membrane on which the first catalyst layer is formed, The manufacturing method of a membrane electrode assembly including the process of forming a gas diffusion layer so that 1 catalyst layer may be contact | connected.