JP2007035350A - Manufacturing method of fuel cell electrode, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a fuel cell electrode reducing permeation of catalyst layer into a diffusion layer, restraining generation of crack in the catalyst layer. <P>SOLUTION: The fuel cell electrode is manufactured through a diffusion layer preparing process S1 preparing the diffusion layer 1 having fluid permeation property and conductivity, a middle layer forming process S2 forming a middle layer 2 on one face of the diffusion layer 1, and a catalyst layer forming process S3 forming the catalyst layer 3 on the middle layer 2 by a transcription method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a fuel cell electrode and a fuel cell.

  The fuel cell is expected as a power generation device that can reduce the environmental load. In particular, polymer electrolyte fuel cells that use polymer electrolyte membranes as electrolytes are expected to be used as in-vehicle fuel cells for automobiles, stationary fuel cells for home and business use, and portable fuel cells for personal computers. Yes.

  FIG. 3 is an explanatory sectional view schematically illustrating a single cell structure of a polymer electrolyte fuel cell. The polymer electrolyte membrane 11 is sandwiched between the fuel electrode 12 and the oxidant electrode 13 and joined to produce the membrane electrode assembly 10. Both the fuel electrode 12 and the oxidant electrode 13 are fuel cell electrodes. The fuel electrode 12 is composed of a fuel electrode catalyst layer 12a and a fuel electrode diffusion layer 12b, and the oxidant electrode 13 is composed of an oxidant electrode catalyst layer 13a and an oxidant electrode diffusion layer 13b. A membrane cell assembly 10 is sandwiched between separators 14 and 15 to constitute a single cell of a fuel cell. The separators 14 and 15 are conductive members having a fuel channel 14a and an oxidant channel 15a, respectively.

  Fuel is supplied to the fuel flow path 14a from the inlet 14b and discharged from the outlet 14c. Oxidant is supplied to the oxidant channel 15a from the inlet 15b and discharged from the outlet 15c. Hydrogen, hydrogen-containing gas, methanol or the like is used as the fuel. An oxygen-containing gas such as air is used as the oxidizing agent. Here, an example using hydrogen as a fuel and air as an oxidant will be described.

The hydrogen supplied to the fuel flow path 14a passes through the fuel electrode diffusion layer 12b, which is also a current collector, and reaches the fuel electrode catalyst layer 12a, and the following electrode reaction occurs.

Proton H ⁺ generated at the fuel electrode 12 moves through the polymer electrolyte membrane 11 toward the oxidant electrode 13 together with water molecules. At the same time, the electrons e ⁻ generated in the fuel electrode 12 pass through the fuel electrode catalyst layer 12a and the fuel electrode diffusion layer 12b and move to the oxidant electrode 13 through an external circuit (not shown).

On the other hand, in the oxidant electrode 13, the air passes through the oxidant electrode diffusion layer 13b, which is also a current collector, and reaches the oxidant electrode catalyst layer 13a, and oxygen in the air moves through the external circuit. The electrons are collected and reduced by the following reaction, and combined with proton H ⁺ that has moved from the fuel electrode 12 through the polymer electrolyte membrane 11 to become water.

  Since the polymer electrolyte membrane 11 needs to move protons or the like, ion conductivity is required. At the same time, if the fuel and oxidant permeate as they are, the power generation performance is lowered, so that shielding against them is required.

  As a method of manufacturing the membrane electrode assembly 10, a fuel electrode catalyst layer 12a is formed on one surface of the polymer electrolyte membrane 11, and an oxidant electrode catalyst layer 13a is formed on the other surface by a transfer method (decal method). A method is known in which a fuel electrode diffusion layer 12b is joined to the electrode catalyst layer 12a, and an oxidant electrode diffusion layer 13b is joined to the oxidant electrode catalyst layer 13a. In this case, the transfer method is a method in which a catalyst layer is formed on one side of a film-like sheet member and transferred to one side of the polymer electrolyte membrane.

  The catalyst layer is formed by molding and drying a paste containing catalyst-carrying conductive particles carrying a catalyst on conductive particles and an electrolyte. The transfer is performed by bringing one surface of the polymer electrolyte membrane into contact with the catalyst layer, pressing between the other surface of the sheet member and the other surface of the polymer electrolyte membrane, pressurizing and hot pressing, and then peeling the sheet member. Thus, a joined body of the polymer electrolyte membrane and the catalyst layer is formed.

  When a membrane / electrode assembly is manufactured by this method, there is a possibility that the conductive fibers constituting the diffusion layers 12b and 13b may pierce the polymer electrolyte membrane 11, and the polymer electrolyte membrane 11 may be damaged. . In addition, the fuel electrode and the oxidant electrode may be electrically short-circuited by the piercing of the conductive fiber. Patent Document 1 describes a polymer electrolyte fuel cell in which an insulating layer is formed on the surface of a protrusion of a diffusion layer in a method for producing a membrane electrode assembly by transferring a catalyst layer to a polymer electrolyte membrane. Yes. In the fuel cell of Patent Document 1, electrical short-circuiting can be reduced, but the proton conduction path in the polymer electrolyte membrane is hindered and performance degradation is unavoidable.

  As another manufacturing method of the membrane electrode assembly 10, the fuel electrode catalyst layer 12a is formed on the diffusion layer 12b for the fuel electrode by a coating method to manufacture the fuel electrode 12, and the diffusion layer 13b for the oxidant electrode is formed. A method is known in which, after forming the oxidant electrode 13 by forming the oxidant electrode catalyst layer 13a by a coating method, the fuel electrode 12 is joined to one surface of the polymer electrolyte membrane 11, and the oxidant electrode 13 is joined to the other surface. ing. Even with this method, as long as it is applied in liquid form, the protruding portion remains due to soaking, and the piercing of the conductive fiber into the polymer electrolyte membrane 11 cannot be completely prevented. The coating method in this case is a method in which a liquid material containing a catalyst is directly applied to one side of the diffusion layer and then dried, and includes a coating screen printing, a doctor blade method, a spray coating method, a dipping method, and the like.

  In any method, there is a problem that the liquid containing the catalyst soaks into the diffusion layer. As a result, there is a problem that the amount of permeation changes due to the minute surface shape and porosity variation of the diffusion layer, and a catalyst layer having a uniform thickness cannot be obtained. Further, there is a problem that the catalyst utilization rate (ratio of the catalyst contributing to the electrode reaction with respect to all the catalysts in the catalyst layer) is lowered, and the power generation performance of the fuel cell is lowered. Furthermore, since the diffusion performance of the diffusion layer is also hindered, there is a problem that the supply of fuel and oxidant is hindered and the power generation performance of the fuel cell is lowered.

As a method for preventing the penetration of the catalyst into the diffusion layer, Patent Document 2 describes a polymer electrolyte fuel cell electrode in which an intermediate layer is provided between the catalyst layer and the gas diffusion layer. Specifically, it is described that after an intermediate layer is formed by a coating method, a catalyst layer is formed on the intermediate layer by a coating method, or the catalyst layer is formed a plurality of times by a coating method. It is described that it is desirable to reduce the porosity of the intermediate layer and the underlying catalyst layer in order to prevent the catalyst layer from penetrating.
JP-A-2004-71324 (Claim 1 etc.) JP-A-9-245801 (Claims 1 and 7, paragraphs [0011], [0019], [0025], [0029], etc.) However, even in Patent Document 2, the catalyst layer applied on the upper side is an intermediate layer or a base layer. There remains a problem of soaking into the catalyst layer to some extent. For this reason, it is required to reduce the porosity of the intermediate layer and the underlying catalyst layer. When the porosity is reduced, the supply of fuel and oxidant to the catalyst layer is hindered, and there is a problem that the power generation performance of the fuel cell is lowered. In addition, since a plurality of layers are formed by a coating method, there is a high possibility that cracks will occur in the catalyst layer due to drying shrinkage during drying after coating the second and subsequent catalyst layers. The effect is greater as the catalyst layer is thicker. As a result, there arises a problem that the power generation performance of the fuel cell is lowered.

  The present invention solves the above-described problems, and provides a fuel cell electrode manufacturing method and a fuel cell excellent in power generation performance that can reduce the penetration of the catalyst layer into the diffusion layer and suppress the crack generation of the catalyst layer. .

  In order to solve the above technical problem, in the invention of claim 1, a diffusion layer preparation step for preparing a diffusion layer having fluid permeability and electrical conductivity, and an intermediate for forming an intermediate layer on one surface of the diffusion layer A fuel cell electrode manufacturing method is provided, wherein a layer forming step and a catalyst layer forming step of forming a catalyst layer on the intermediate layer by a transfer method are provided.

  According to a second aspect of the present invention, in the method for producing a fuel cell electrode according to the first aspect, the intermediate layer is a layer formed by a coating method.

  According to a third aspect of the present invention, the intermediate layer is any one of an electrolyte layer, a conductive particle layer, and a catalyst layer. The method for producing a fuel cell electrode according to the second aspect is provided.

  According to a fourth aspect of the present invention, there is provided the fuel cell electrode manufacturing method according to the first aspect, wherein the intermediate layer is an electrolyte layer formed by a transfer method.

  According to a fifth aspect of the present invention, there is provided a fuel cell characterized in that an electrode for a fuel cell manufactured by the manufacturing method according to any one of the first to fourth aspects is provided.

  According to the invention of claim 1, since the intermediate layer is formed on the diffusion layer and the catalyst layer is formed thereon by the transfer method, the penetration of the catalyst layer into the diffusion layer can be reduced and the catalyst layer There is an effect of suppressing the occurrence of cracks.

  According to the invention of claim 2, since the intermediate layer is formed by the coating method, there is an effect that the contact resistance of the diffusion layer and the intermediate layer can be reduced. In addition, by intentionally densifying (filling in) the pores on the catalyst layer side of the diffusion layer, there is an effect that it is possible to control the diffusibility of the fluid such as gas and the water discharge property.

  According to the invention of claim 3, since any one of the electrolyte layer, the conductive particle layer, and the catalyst layer is used as the intermediate layer formed by the coating method, in the case of the electrolyte layer, the contact resistance with the catalyst layer ( In the case of a conductive particle layer, the electrical resistance can be reduced, and in the case of a catalyst layer, the intermediate layer also has a catalytic function, so the amount of catalyst layer supported can be increased without cracking. There is an effect.

  According to the invention of claim 4, since the electrolyte layer is formed by the transfer method as the intermediate layer, there is an effect that the change in the pores of the diffusion layer due to the intermediate layer can be reduced.

  According to the invention of claim 5, since the fuel cell electrode in which the penetration of the catalyst layer into the diffusion layer is reduced and the crack generation of the catalyst layer is suppressed is used, the power generation performance of the fuel cell can be improved. There is.

  The present inventor considered that if the catalyst layer is formed on the diffusion layer by the transfer method, the catalyst can be prevented from seeping into the diffusion layer and cracking of the catalyst layer can be prevented. However, it was difficult to transfer the catalyst layer to the porous diffusion layer. Even if it is possible, the contact area between the catalyst layer and the diffusion layer is not sufficient, the electric resistance is increased, and the power generation performance of the fuel cell is lowered.

  The inventor has intensively studied to arrive at the present invention. In other words, if an intermediate layer is formed on the diffusion layer and then the catalyst layer is formed on the intermediate layer by the transfer method, the catalyst layer can be transferred, and the catalyst can penetrate into the diffusion layer, and the catalyst layer can crack. Also found that it can be reduced.

  FIG. 1 is a flow chart for explaining the manufacturing process of the fuel cell electrode of the present invention. First, a diffusion layer is prepared (step S1: diffusion layer preparation step). The diffusion layer needs to have fluid permeability (fluid diffusibility) to allow fuel or oxidant to permeate therethrough. Further, since the diffusion layer needs to conduct electrons, it needs electrical conductivity. For this reason, a porous body of a conductive material (conductive fiber, conductive particle, etc.) is used. In general, the diffusion layer is required to have corrosion resistance against a fuel, an oxidant, or an electrode reaction. Therefore, carbon materials such as carbon fibers and carbon particles are often used as the conductive material. Among them, carbon fiber is frequently used. In the diffusion layer preparation step, a diffusion layer having a shape necessary for the fuel cell may be purchased or may be prepared by punching a large sheet made of a material forming the diffusion layer into a necessary shape. Further, the diffusion layer may be subjected to a treatment such as a water repellent treatment. This treatment may be performed before or after the diffusion layer punching process.

  The porosity of the diffusion layer used in the present invention is preferably 10 to 80%. Furthermore, 20 to 60% and 30 to 50% are desirable. If the porosity is too small, the permeability of the fluid (fuel or oxidant) may be insufficient. If the porosity is too large, the unevenness of the diffusion layer surface is large, and even if an intermediate layer is provided, the transfer of the catalyst layer may be affected. In addition to these, when the intermediate layer is formed by a coating method, if the porosity is too small, the contact between the intermediate layer and the diffusion layer may be small, and if the porosity is too large, the intermediate layer may be soaked too much.

  Next, an intermediate layer is formed on one surface of the diffusion layer (step S2: intermediate layer forming step). There are no particular limitations on the method and type (components, etc.) for forming the intermediate layer. However, as a method for forming the intermediate layer, a coating method or a transfer method is desirable. In the coating method, a paste is prepared by dissolving or dispersing each component in a liquid that is also a solvent for the electrolyte, and this paste is applied to one side of the diffusion layer by a doctor blade or the like and then dried. Examples of the solvent include water, lower alcohols (methanol, ethanol, normal propanol, isopropanol, isobutanol) and aprotic solvents (dimethyl sulfoxide, dimethylformamide). In the transfer method, a paste is prepared by dissolving or dispersing each component in a liquid that is also an electrolyte solvent, and this paste is formed into a film such as a sheet made of ethylene / tetrafluoroethylene copolymer resin (hereinafter also referred to as ETFE sheet). The sheet member is coated and dried in a layer form with a doctor blade or the like, and then bonded to the transfer side surface of the diffusion layer, and then the ETFE sheet is peeled off. The thickness of the intermediate layer is preferably 0.5 to 1.0 μm in a dry state. Furthermore, 1-7 micrometers and 2-5 micrometers are desirable.

  If the intermediate layer is formed by a coating method, the contact resistance of the diffusion layer and the intermediate layer can be reduced, and the pores on the catalyst layer side of the diffusion layer are intentionally made dense (filled), so that the fluid such as gas can be removed. Can control diffusivity and water discharge. Examples of the intermediate layer include an electrolyte layer, a conductive particle layer, and a catalyst layer in the case of a coating method, and an electrolyte layer in the case of a transfer method. In the case of the electrolyte layer, the contact resistance (ion conduction resistance) with the catalyst layer can be reduced. In the case of a conductive particle layer, electric resistance can be reduced. In the case of the catalyst layer, since the intermediate layer also has a catalytic function, the supported amount of the catalyst layer can be increased without causing cracks. If the electrolyte layer is formed as the intermediate layer by a transfer method, changes in the pores of the diffusion layer due to the intermediate layer can be reduced.

  The electrolyte layer is a layer containing an electrolyte such as an ion exchange resin as a main component, and the electrolyte content can be 50% or more, 70% or more, 80% or more, 90% or more, 100% in terms of dry weight. . The conductive particle layer is a layer mainly composed of conductive particles, in which conductive particles such as carbon particles are mixed with an electrolyte, conductive particles such as carbon particles, and polytetrafluoroethylene (hereinafter also referred to as PTFE). For example, a mixture of a water-repellent material such as an electrolyte and an electrolyte. The catalyst layer is a layer containing a catalyst and can be exemplified by a mixture of catalyst-carrying conductive particles carrying a catalyst on conductive particles, a water repellent material such as PTFE, and an electrolyte. Examples of the catalyst include noble metal catalysts such as platinum and an alloy of platinum and ruthenium, but are not limited thereto. In the case of a catalyst that is not a noble metal catalyst, particles formed by the catalyst itself without being supported on catalyst carrier particles such as conductive particles may be used as they are.

  The same electrolyte may be used as the electrolyte used for the electrolyte layer, the conductive particle layer, and the catalyst layer, or different electrolytes may be used. If the same electrolyte is used, there is no problem even if they are mixed with each other through the interface. Examples of the electrolyte include Nafion manufactured by DuPont, Aciplex manufactured by Asahi Kasei Co., Ltd., and Flemion manufactured by Asahi Glass Co., Ltd.

  Next, a catalyst layer is formed by a transfer method on the intermediate layer formed by the intermediate layer forming step (step S3: catalyst layer forming step). The transfer method and the catalyst layer are the same method and the same as those described for the intermediate layer. The transfer conditions for the catalyst layer are not particularly limited, but the pressure is preferably 3 to 20 MPa, more preferably 5 to 15 MPa, and 8 to 12 MPa. As temperature, 100-180 degreeC is preferable and 110-160 degreeC and 120-150 degreeC are more preferable. The time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 10 minutes, and 1 to 3 minutes. By forming the catalyst layer on the intermediate layer by a transfer method, the penetration of the catalyst layer into the diffusion layer can be prevented. Moreover, a catalyst layer can be formed without crack generation.

  The fuel cell electrode of at least one of the fuel electrode and the oxidant electrode is manufactured by this manufacturing method. The membrane electrode assembly is manufactured by hot pressing the polymer electrolyte membrane between the fuel electrode and the oxidant electrode so that the catalyst layers of the produced fuel electrode and oxidant electrode are in contact with the polymer electrolyte membrane. A fuel cell is manufactured by arranging separators on both surfaces of the membrane electrode assembly.

  FIG. 2 is an explanatory sectional view schematically showing the fuel cell electrode of the present invention. This figure shows only the vicinity of the surface in an enlarged manner. An intermediate layer 2 is formed on the diffusion layer 1, and a catalyst layer 3 is formed thereon. Here, the intermediate layer 2 and the catalyst layer 3 are each shown as an example of only one layer, but each may have a multilayer structure, and there may be different layers in the middle of the multilayer structure (for example, in the middle of a plurality of catalyst layers). Structure in which an electrolyte layer is formed).

  Since the diffusion layer 1 is a porous body, it is uneven when the surface is viewed microscopically. The intermediate layer 2 is in a state of entering the recess (pore portion). When the intermediate layer 2 is formed by a coating method, the intermediate layer 2 enters the concave portion of the diffusion layer 1 by soaking. When the intermediate layer 2 is formed by the transfer method, the intermediate layer 2 enters the concave portion of the diffusion layer 1 during transfer due to the flexibility of the intermediate layer 2. Since a part of the intermediate layer 2 penetrates into the diffusion layer 1, it is possible to secure an adhesive force that does not peel even if the intermediate layer or the catalyst layer swells and shrinks. When the intermediate layer 2 is formed by the transfer method, the intrusion into the diffusion layer 1 can be minimized (the state in which the intermediate layer 2 does not substantially penetrate into the diffusion layer 1). Can be formed without soaking. Since the penetration of the catalyst layer 3 is eliminated, it is possible to prevent a decrease in water repellency near the interface between the diffusion layer 1 and the catalyst layer 3. Moreover, the diffusibility fall of the diffusion layer 1 by penetration can be prevented, and the power generation performance in a high current density region can be improved. Furthermore, the water repellency of the diffusion layer can be prevented from being lowered, and the durability can be improved. In addition, the catalyst layer can be formed only in necessary portions without masking. If there is no catalyst permeation, an improvement in catalyst utilization can be expected.

When the intermediate layer is formed by a coating method, it is preferable to control the coating amount. The coating amount is preferably such that the material of the intermediate layer does not soak into the diffusion layer and the unevenness on the surface of the diffusion layer is sufficiently relaxed. The amount of coating for that purpose depends on the type of diffusion layer (material, porosity, etc.), the material of the intermediate layer, and the nature of the paste for the intermediate layer (viscosity, etc.). It is preferable that it is 0.05-5.0 mg / cm < ² >. More preferably 0.1-3.0 mg ^/ cm 2, may is 0.15~1.5mg / cm ^2. (
Further, since the concave portion is filled with the intermediate layer 2, the concave and convex portions are in a relaxed state. For this reason, the contact area between the diffusion layer 1 including the intermediate layer 2 and the catalyst layer 3 is increased. As a result, the transfer of the catalyst layer 3 onto the diffusion layer 1 becomes possible. If the intermediate layer 2 is an electrolyte layer, a conductive particle layer containing an electrolyte, or a catalyst layer containing an electrolyte, and a catalyst layer containing an electrolyte is used as the catalyst layer 3, the transfer of the catalyst layer 3 is easy due to adhesion between the electrolytes. become. Furthermore, since the catalyst layer 3 is formed on the intermediate layer 2 by the transfer method, the catalyst layer 3 can be formed with a relatively uniform thickness. For this purpose, it is desirable that the conductive particle layer as the catalyst layer 3 and the catalyst layer contain 30% or more of electrolyte in terms of solid content. More preferably, the electrolyte is contained in an amount of 40% or more and 50% or more in terms of solid content.

  In FIG. 2, a part of the diffusion layer 1 (projection 1 a) protrudes from the surface of the intermediate layer 2. Even when the intermediate layer 2 is formed of a non-conductive material such as an electrolyte layer that does not contain a conductive substance, the protruding portion 1a of the diffusion layer 1 and the catalyst layer 3 are in contact with each other, so that the contact resistance between the diffusion layer 1 and the catalyst layer 3 is Can be reduced. When a conductive layer such as a conductive particle layer or a catalyst layer is used as the intermediate layer 2, the contact resistance between the diffusion layer 1 and the intermediate layer 2 can be reduced, and the contact between the diffusion layer 1 and the catalyst layer 3 can be reduced. There is an advantage that the resistance can be reduced. In this case, the surface of the intermediate layer 2 may completely cover the diffusion layer 1.

  When a catalyst layer is used as the intermediate layer 2, a part of the intermediate layer 2 penetrates into the concave portion of the diffusion layer 1, and this alone reduces the catalyst utilization rate. However, since the catalyst layer 3 is formed on the intermediate layer 2 by the transfer method, the portion of the intermediate layer 2 also ensures contact with the polymer electrolyte membrane by the catalyst layer 3 and functions as a catalyst. Compared with the catalyst utilization rate can be improved.

  After the formation of the catalyst layer, the fuel cell electrode may be immersed in ion-exchanged water and kept at 127 ° C. and 0.175 MPa in an autoclave apparatus and autoclaved for 1 hour. Thereby, impurities can be removed more effectively than room temperature or boiling treatment with ion-exchanged water. In washing with an organic solvent, a part of the electrolyte may be eluted, but there is no fear of it. The autoclave treatment may be performed after the intermediate layer is formed or after the membrane electrode assembly is formed. The present invention can also be applied to a membrane / catalyst layer assembly formed by transferring a catalyst layer to a polymer electrolyte membrane. The conditions for the autoclave treatment can be selected optimally for the constituent components of the diffusion layer, intermediate layer, catalyst layer, polymer electrolyte membrane, and the like.

  Examples of the present invention will be described below.

  Carbon paper TGH-H-60 (manufactured by Toray Industries, Inc.) was used as the base material of the diffusion layer. Carbon paper (Vulcan XC-72R) and polytetrafluoroethylene dispersion (Polyflon D1: manufactured by Daikin Industries, Ltd.) are mixed and dispersed in carbon paper, impregnated, dried, baked at 380 ° C. for 1 hour, and repellent. A water-treated diffusion layer was prepared.

  Platinum-supported carbon TEC10E70TPM (Tanaka Kikinzoku Co., Ltd .: platinum support rate 67 wt%) 10 g, polymer electrolyte solution SS-1100 / 05 (Asahi Kasei Co., Ltd .: polymer electrolyte content 5 wt%) 82.5 g, ion exchange 34 g of water was dispersed in a sand mill for 1 hour to prepare a catalyst paste. The electrolyte / carbon ratio of this catalyst paste is 1.25. Here, the electrolyte / carbon ratio is the weight ratio of the electrolyte solid to the carbon in the catalyst paste or catalyst layer. Platinum-supporting carbon is catalyst-supporting conductive particles using platinum as a catalyst and carbon particles as conductive particles.

The obtained catalyst paste was applied and dried on a diffusion layer treated with water repellency by a doctor blade so as to have a catalyst supporting weight of 0.2 mg / cm ^2, and a first catalyst layer was formed on the diffusion layer. The entire diffusion layer was punched out to an area of 59 cm ² .

Next, the above catalyst paste was applied and dried with a doctor blade onto a 50 μm thick ETFE sheet, which is a film-like sheet member, and the second catalyst layer (dry film thickness 5 μm, platinum carrying weight 0. 32 mg / cm ² ) was formed. This was punched out to an area of 59 cm ² , the second catalyst layer was brought into contact with the first catalyst layer formed on the diffusion layer, and hot-pressed at 150 ° C. and 10 MPa for 1 minute with a hot press apparatus. Thereafter, the ETFE sheet was peeled off to transfer the second catalyst layer onto the first catalyst layer to produce a fuel cell electrode. The transfer rate of the second catalyst layer was 100%. The transfer rate is the ratio of the area of the layer not remaining on the ETFE sheet to the area of the layer before transfer. That is, the ratio of the area of the transferred layer among the layers on the ETFE sheet before transfer. Further, no crack was observed in the second catalyst layer. The total catalyst supporting weight of the first catalyst layer and the second catalyst layer is 0.52 mg / cm ² .

The polymer electrolyte solution SS-1100 / 05 alone was applied and dried with a doctor blade on the water-repellent diffusion layer produced in the same manner as in Example 1, and the electrolyte layer (dry film thickness 2 μm, electrolyte carrying weight 0.18 mg). / Cm ² ), and the entire diffusion layer was punched into an area of 59 cm ² . Next, the same catalyst paste as in Example 1 was applied and dried on an ETFE sheet with a doctor blade to form a catalyst layer (dry film thickness 7 μm, catalyst supporting weight 0.65 mg / cm ² ) on the ETFE sheet. This was punched out to an area of 59 cm ² , the catalyst layer was brought into contact with the electrolyte layer formed on the diffusion layer, and hot-pressed at 150 ° C., 10 MPa for 1 minute, sandwiched between hot-press devices. Then, the catalyst layer was transferred onto the electrolyte layer by peeling off the ETFE sheet, and a fuel cell electrode was produced. The transfer rate of the catalyst layer was 100%, and no crack was observed in the catalyst layer.

Comparative Example 1

After applying a catalyst paste similar to that of Example 1 on a water-repellent diffusion layer with a doctor blade to a catalyst loading weight of 0.59 mg / cm ² and drying, a catalyst layer was formed on the diffusion layer. Then, the entire diffusion layer was punched out to an area of 59 cm ² to produce a fuel cell electrode.

(Battery performance evaluation)
A fuel cell was produced using the fuel cell electrode produced in Examples 1 and 2 and Comparative Example 1 as an oxidant electrode, and the battery performance was evaluated.

The fuel electrode manufactured as follows was used. Platinum ruthenium-supported carbon (TEC62E58: Tanaka Kikinzoku Co., Ltd. TEC62E58: platinum support rate 27.2 wt%, ruthenium support rate 28.8 wt%) 10 g, polymer electrolyte solution (SS-1100 / 05) 110 g, ion-exchanged water 34 g Dispersion was carried out with a sand mill for 1 hour to prepare a fuel electrode catalyst paste. The obtained fuel electrode catalyst paste was applied onto a diffusion layer subjected to the same water repellent treatment as in Example 1 and dried with a doctor blade so that the platinum carrying weight was 0.22 mg / cm ^2. After preparing the catalyst layer, the entire diffusion layer was punched out to an area of 59 cm ² to prepare a fuel electrode (fuel cell electrode).

  As a polymer electrolyte membrane, Gore 30-III-B (thickness 30 μm) manufactured by Japan Gore-Tex Co., Ltd. was used. An oxidant electrode is disposed so that the catalyst layer of the oxidant electrode is in contact with one surface of the polymer electrolyte membrane, and a fuel electrode is disposed so that the catalyst layer of the fuel electrode is in contact with the other surface of the polymer electrolyte membrane, A membrane / electrode assembly was manufactured by sandwiching between the outer layers of the oxidant electrode and the fuel electrode with a hot press device and hot pressing at 100 ° C. and 4 MPa for 3 minutes.

  Separators were placed on both surfaces of the produced membrane electrode assembly, and power generation characteristics (current-voltage characteristics) were measured. Hydrogen gas was introduced into the fuel electrode at a utilization rate of 85%, and air was introduced into the oxidizer electrode at a utilization rate of 40%. The battery temperature was 77 ° C., hydrogen gas was humidified to a dew point of 57 ° C., and air was humidified to a dew point of 60 ° C.

  FIG. 4 shows the measured current-voltage characteristics. Examples 1 and 2 are superior in power generation performance to Comparative Example 3. This is presumably because the penetration of the catalyst layer into the diffusion layer was suppressed. In particular, Example 1 has the most excellent performance even though the catalyst loading weight is considerably smaller than the others. In the first and second embodiments, the present invention is applied to the oxidizer electrode, but it goes without saying that the same effect can be obtained even when applied to the fuel electrode.

  Next, an example in which the intermediate layer is formed by a transfer method is shown.

Carbon paper TGH-H-60 (manufactured by Toray Industries, Inc.) was used as the base material of the diffusion layer. Carbon paper (Vulcan XC-72R) and polytetrafluoroethylene dispersion (Polyflon D1: manufactured by Daikin Industries Co., Ltd.) mixed and dispersed in carbon paper are impregnated and dried, dried, baked at 380 ° C. for 1 hour, 59 cm ^A diffusion layer was produced by punching out to an area of ² .

A fluorine-based polymer electrolyte (perfluorosulfonic acid-based electrolyte) was used as the electrolyte. A polymer electrolyte solution SS-1100 / 05 (manufactured by Asahi Kasei Co., Ltd .: polymer electrolyte content: 5% by weight) obtained by dissolving this electrolyte in an alcohol solvent (a solvent in which water and ethanol are mixed at a weight ratio of 1: 1) %) Is applied and dried with a doctor blade onto a 50 μm thick ETFE sheet, which is a film-like sheet member (dry film thickness 2 μm, electrolyte carrying weight 0.18 mg / cm ² ), and an electrolyte layer is formed on the ETFE sheet. Formed. This was punched out to an area of 59 cm ² , the electrolyte layer was brought into contact with one surface of the diffusion layer, and hot-pressed at 150 ° C., 10 MPa for 1 minute, sandwiched between hot-press devices. Thereafter, the electrolyte layer was transferred onto the diffusion layer by peeling off the ETFE sheet. The transfer rate of the electrolyte layer was 100%.

  Next, platinum-supported carbon TEC10E70TPM (Inventor: T10E70TPM in the notification form, but adapted to other examples. Please check) ) 10 g, polymer electrolyte solution SS-1100 / 05 (manufactured by Asahi Kasei Corporation: polymer electrolyte content 5% by weight), and 82.5 g of ion exchanged water 34 g were dispersed in a sand mill for 1 hour to prepare a catalyst paste. The electrolyte / carbon ratio of this catalyst paste is 1.25.

The obtained catalyst paste was applied and dried with a doctor blade onto a 50 μm thick ETFE sheet, which is a film-like sheet member (dry film thickness 5 μm, platinum carrying weight 0.32 mg / cm ² ), and then onto the ETFE sheet. A catalyst layer was formed. This was punched out to an area of 59 cm ² , the catalyst layer was brought into contact with the electrolyte layer formed on the diffusion layer, and hot-pressed at 150 ° C. and 10 MPa for 1 minute with a hot press apparatus. Then, the catalyst layer was transferred onto the electrolyte layer by peeling off the ETFE sheet, and a fuel cell electrode was produced. The transfer rate of the catalyst layer was 100%, and no crack was observed in the catalyst layer.

  A catalyst paste was prepared by mixing 10 g of platinum-supported carbon TEC10E70TPM, 264 g of SS-1100 / 05, and 34 g of ion-exchanged water (the electrolyte / carbon ratio of this catalyst paste is 4.0). A fuel cell electrode was produced in the same manner as in Example 3 except that the dry film thickness of the layer was 4 μm. The transfer rate for both the electrolyte layer and the catalyst layer was 100%. Further, no crack was observed in the catalyst layer.

  A catalyst paste was prepared by mixing 10 g of platinum-supported carbon TEC10E70TPM, 132 g of SS-1100 / 05, and 34 g of ion exchange water (the electrolyte / carbon ratio of this catalyst paste is 2.0), and the catalyst. A fuel cell electrode was produced in the same manner as in Example 3 except that the dry film thickness of the layer was 3 μm. The transfer rate for both the electrolyte layer and the catalyst layer was 100%. Further, no crack was observed in the catalyst layer.

Comparative Example 2

Using the catalyst paste produced in Example 3, a catalyst layer was produced on the ETFE sheet in the same manner as in Example 3. This was punched out to an area of 59 cm ² , the catalyst layer was brought into contact with one surface of the diffusion layer prepared in the same manner as in Example 1, and hot pressed at 150 ° C., 10 MPa for 1 minute, sandwiched between hot press devices. Thereafter, the catalyst layer was transferred onto the diffusion layer by peeling off the ETFE sheet. Although it was prepared twice, the transfer rates were 50% and 39%, and neither could transfer well.

  As described above, it has been found that by forming the intermediate layer, the catalyst layer can be transferred without cracking, and the battery performance can be improved.

The flowchart figure explaining the manufacturing process of the electrode for fuel cells of this invention Explanatory sectional view schematically showing a fuel cell electrode of the present invention Cross-sectional view schematically explaining a single cell structure of a polymer electrolyte fuel cell The graph which shows the current-voltage characteristic of Example 1, 2 and the comparative example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diffusion layer 2 ... Intermediate layer 3 ... Catalyst layer 10 ... Membrane electrode assembly 11 ... Polymer electrolyte membrane 12 ... Fuel electrode 12a ... Fuel electrode catalyst layer 12b ... Fuel electrode diffusion layer 13 ... Oxidant electrode 13a ... Oxidant electrode catalyst layer 13b ... Diffusion layers for oxidant electrode 14, 15 ... Separator

Claims (5)

A diffusion layer preparation step of preparing a diffusion layer having fluid permeability and electrical conductivity, an intermediate layer formation step of forming an intermediate layer on one surface of the diffusion layer, and a catalyst layer on the intermediate layer by a transfer method The manufacturing method of the electrode for fuel cells characterized by providing the catalyst layer formation process to form. The method for producing a fuel cell electrode according to claim 1, wherein the intermediate layer is a layer formed by a coating method. The method for producing a fuel cell electrode according to claim 2, wherein the intermediate layer is any one of an electrolyte layer, a conductive particle layer, and a catalyst layer. 2. The method for producing a fuel cell electrode according to claim 1, wherein the intermediate layer is an electrolyte layer formed by a transfer method. A fuel cell comprising a fuel cell electrode manufactured by the manufacturing method according to claim 1.

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