JP2009004207A - Gas diffusion layer and manufacturing method therefor, and fuel cell, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas diffusion layer capable of improving a water draining property; its manufacturing method; a fuel cell provided with the gas diffusion layer, and to provide its manufacturing method. <P>SOLUTION: This gas diffusion layer 1 includes a diffusion layer base material 2 containing a carbon material, and a water-repellent layer 3 formed on a surface of the diffusion layer base material 2, wherein a carbon material and a water-repellent resin are included in the water-repellent layer 3, and a hot-water treatment is applied to the diffusion layer base material 2 and the water-repellent layer 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas diffusion layer and a manufacturing method thereof, and a fuel cell including the gas diffusion layer and a manufacturing method thereof.

  A fuel cell may be referred to as a membrane electrode structure (hereinafter referred to as “MEA”) including an electrolyte layer (hereinafter referred to as “electrolyte membrane”) and electrodes (anode and cathode) respectively disposed on both sides of the electrolyte membrane. )), And an electric energy generated by the electrochemical reaction is taken out to the outside through current collectors arranged on both sides of the MEA. Among fuel cells, polymer electrolyte fuel cells (hereinafter sometimes referred to as “PEFC”) used in household cogeneration systems and automobiles have the feature that they can be operated in a low temperature range. Yes. This PEFC has been attracting attention as a power source and portable power source for electric vehicles because of its high energy conversion efficiency, short start-up time, and small and light system.

  A single cell of PEFC includes an MEA and a pair of current collectors that sandwich the MEA, and the MEA contains a proton conductive polymer that exhibits proton conductivity by being kept in a water-containing state. . During operation of the PEFC, a hydrogen-containing gas (hereinafter referred to as “hydrogen”) is supplied to the anode, and an oxygen-containing gas (hereinafter referred to as “air”) is supplied to the cathode. The hydrogen supplied to the anode is separated into protons and electrons under the action of the catalyst contained in the catalyst layer of the anode (hereinafter also referred to as “anode catalyst layer”). It reaches the cathode catalyst layer (hereinafter also referred to as “cathode catalyst layer”) through the layer and the electrolyte membrane. On the other hand, electrons reach the cathode catalyst layer through an external circuit, and through such a process, electric energy can be extracted. Then, the protons and electrons that have reached the cathode catalyst layer react with oxygen supplied to the cathode catalyst layer, thereby generating water.

  In order to extract electric energy with PEFC, hydrogen is required to be supplied to the anode catalyst layer and oxygen is required to be supplied to the cathode catalyst layer. In order to improve the power generation performance of PEFC, hydrogen is required to be supplied to the anode catalyst layer. In addition to being supplied uniformly, oxygen must be supplied uniformly to the cathode catalyst layer. From this point of view, the PEFC single cell has a gas diffusion layer having electron conductivity and gas permeability between the anode catalyst layer and the current collector and / or between the cathode catalyst layer and the current collector. Is disposed.

  On the other hand, when the PEFC is operated in a high load state (high current density region), a large amount of water is generated in the single cell. The water (steam) generated in the single cell is condensed by contact with a heat exchange member (for example, a separator or a cooling pipe) that is cooled for the purpose of suppressing an excessive temperature rise of the single cell. It becomes droplet water, which can flow into the MEA. When the MEA enters a water-immersion state (flooding) due to the inflow of droplet water, the diffusion of the reaction gas is hindered and the performance of the PEFC is deteriorated. Therefore, the gas diffusion layer disposed outside the MEA is required to have the property of reducing the inflow of water (water repellency) in addition to the above performance. As described above, various properties are required for the gas diffusion layer provided in the PEFC, and it is possible to improve the performance of the PEFC by controlling the performance of the gas diffusion layer.

  As a technique related to a gas diffusion layer, for example, in Patent Document 1, a gas diffusion layer having a water repellent layer on a gas diffusion base material, and a gas diffusion layer having a water permeation path in at least a part of the water repellent layer. Is disclosed, and a water permeation path comprising hydrophilically treated carbon particles is disclosed. According to the gas diffusion layer, it is possible to improve drainage.

JP 2006-179317 A

  The electrolyte membrane provided in a single cell of PEFC exhibits proton conduction performance under water-containing conditions. Therefore, during operation of PEFC, humidified hydrogen and air (hereinafter, these may be collectively referred to as “reactive gas”) .) Is supplied to a single cell, and there is a lot of water in the single cell. In such a state, when the gas diffusion layer disclosed in Patent Document 1 is used, there is a problem that water tends to stay in the water permeation path composed of the carbon particles subjected to hydrophilic treatment, and the drainage performance of the gas diffusion layer is likely to deteriorate. It was. Moreover, in order to make the gas diffusion layer disclosed in Patent Document 1 into a form that can improve drainage, it is necessary to make both ends of the water permeation path open to the front and back surfaces of the gas diffusion layer. However, there is also a problem that it is difficult to control the direction of the water permeation path during the production of the gas diffusion layer.

  Then, this invention makes it a subject to provide the gas diffusion layer which can improve drainage, its manufacturing method, a fuel cell provided with the said gas diffusion layer, and its manufacturing method.

In order to solve the above problems, the present invention takes the following means. That is,
1st this invention has the diffusion layer base material containing a carbon material, and the water repellent layer formed in the surface of this diffusion layer base material, and a carbon material and water-repellent resin are in a water repellent layer. A gas diffusion layer containing the diffusion layer base material and the water-repellent layer, which has been subjected to hot water treatment.

  In the first invention and the invention shown below (hereinafter referred to as “the present invention”), the “diffusion layer substrate containing a carbon material” means, in other words, carbon as a substance constituting the diffusion layer substrate. Is contained. Specific examples of the diffusion layer substrate that can be used in the present invention include carbon paper and carbon cloth. Furthermore, in the present invention, the form of the “water-repellent layer” is not particularly limited as long as it is a layer having water repellency, electron conductivity, and gas permeability. In the present invention, specific examples of the “carbon material” contained in the water-repellent layer (or the composition to constitute the water-repellent layer) include vapor grown carbon fiber (VGCF), carbon black, carbon nanotube, and carbon nanohorn. Etc. Specific examples of the “water-repellent resin” contained in the water-repellent layer (or the composition to constitute the water-repellent layer) include polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer Combined resin (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene-ethylene copolymer resin (ETFE), chlorotrifluoroethylene resin (PCTFE), fluorovinylidene resin (PVDF) Etc. Furthermore, in the present invention, “hot water treatment” means that the diffusion layer base material and the water repellent layer are immersed in hot water, or hot water is applied to the diffusion layer base material and the water repellent layer, etc. It means a treatment in which hot water is brought into contact with the water repellent layer. In the present invention, “hot water” means hot water at a temperature at which the degree of water repellency of a structure having a diffusion layer substrate and a water repellent layer can be reduced (the apparent contact angle is reduced). In the present invention, the temperature of hot water may be 40 ° C. or higher and 80 ° C. or lower. The time for contacting with hot water is not particularly limited as long as it can reduce the degree of water repellency of the structure (reducing the apparent contact angle), but it is 1 hour or more and 20 hours or less. It is preferable.

  In the first aspect of the present invention, the water repellent resin preferably contains a polytetrafluoroethylene resin.

  2nd this invention is a method of manufacturing a gas diffusion layer provided with the diffusion layer base material containing a carbon material, and the water-repellent layer formed in the surface of this diffusion layer base material, Comprising: A water repellent layer forming step of forming a water repellent layer on the surface of the diffusion layer base material by applying a composition containing a carbon material and a water repellent resin to the surface of the material; A method for producing a gas diffusion layer, comprising: a hydrothermal treatment step of treating a structure produced by a layer formation step with hot water.

  In the second aspect of the present invention, the water repellent resin preferably contains a polytetrafluoroethylene resin.

  A third aspect of the present invention includes a membrane electrode structure and a gas diffusion layer disposed on at least one of the membrane electrode structures, and the gas diffusion layer includes the first aspect of the present invention (including modifications). And a gas diffusion layer according to claim 1).

  In the present invention, the “membrane electrode structure” means a solid polymer membrane containing a proton conducting polymer, and a catalyst layer (anode catalyst layer) formed on one surface and the other surface of the solid polymer membrane, respectively. And a cathode catalyst layer). Furthermore, in the present invention, the “gas diffusion layer disposed on at least one of the membrane electrode structures” means that the fuel cell of the present invention has the above-mentioned outside of the anode catalyst layer and / or outside of the cathode catalyst layer. It means that the gas diffusion layer according to the first aspect of the present invention is provided. The fuel cell of the present invention is not limited to a mode in which only the gas diffusion layer according to the first aspect of the present invention is provided as the gas diffusion layer, and for example, the first diffusion layer is disposed outside the cathode catalyst layer. The gas diffusion layer according to the present invention may be provided, and a conventional gas diffusion layer may be provided outside the anode catalyst layer.

  4th this invention is a method of manufacturing a fuel cell provided with a membrane electrode structure and the gas diffusion layer arrange | positioned in at least one of this membrane electrode structure, Comprising: The said gas diffusion layer is carbon A diffusion layer base material containing a material and a water repellent layer formed on the surface of the diffusion layer base material, and a composition containing a carbon material and a water repellent resin on the surface of the diffusion layer base material By applying, a structure manufacturing step for forming a structure by forming a water repellent layer on the surface of the diffusion layer base material, and by treating the structure manufactured by the structure manufacturing step with hot water, The gas diffusion layer is formed on at least one of a gas diffusion layer production step for producing a diffusion layer, a membrane electrode structure production step for producing a membrane electrode structure, and a membrane electrode structure produced by the membrane electrode structure production step. A disposing step of disposing a gas diffusion layer produced by the producing step; Characterized in that it comprises a a method for manufacturing a fuel cell.

  According to the first aspect of the present invention, since the hydrothermal treatment is performed on the diffusion layer base material and the water repellent layer containing the carbon material, the water repellency of the carbon material contained in the diffusion layer base material and the water repellent layer is provided. As a result, the degree of water repellency of the gas diffusion layer can be reduced. When the degree of water repellency of the gas diffusion layer is reduced, compared to before the degree of water repellency is reduced, the water vapor and the water in the droplets easily enter the gas diffusion layer. A water-repellent gas diffusion layer having an increased contact area with water can be obtained. Since the gas diffusion layer of this form can come into contact with a lot of water vapor and water of droplets, it is possible to improve drainage. Therefore, according to 1st this invention, the gas diffusion layer which can improve drainage can be provided.

  In the first aspect of the present invention, when the water-repellent resin contained in the water-repellent layer is a polytetrafluoroethylene resin, a gas diffusion layer capable of improving drainage can be easily obtained.

  According to the second aspect of the present invention, since the hot water treatment step of treating the structure including the diffusion layer substrate containing the carbon material and the water repellent layer with hot water is provided, the gas having a reduced degree of water repellency. A diffusion layer can be manufactured. By reducing the degree of water repellency, it becomes possible to increase the drainage by increasing the contact area with water. Therefore, according to the second aspect of the present invention, the gas that can improve the drainage The manufacturing method of a gas diffusion layer which can manufacture a diffusion layer can be provided.

  In the second aspect of the present invention, a gas diffusion layer capable of producing a gas diffusion layer capable of easily improving drainage by making the water-repellent resin contained in the water-repellent layer a polytetrafluoroethylene resin. Can be provided.

  The fuel cell according to the third aspect of the present invention includes the gas diffusion layer according to the first aspect of the present invention. Therefore, according to the third aspect of the present invention, a fuel cell capable of improving drainage can be provided.

  In the method of manufacturing a fuel cell according to the fourth aspect of the present invention, a gas diffusion layer manufacturing step of manufacturing a gas diffusion layer by treating a structure including a diffusion layer substrate containing a carbon material and a water repellent layer with hot water. And a fuel cell including the gas diffusion layer manufactured in the gas diffusion layer manufacturing process is manufactured. Since the gas diffusion layer with improved drainage can be produced by treating the structure with hot water, according to the fourth aspect of the present invention, a fuel cell capable of improving drainage can be manufactured. A fuel cell manufacturing method can be provided.

1. Gas Diffusion Layer FIG. 1 is a cross-sectional view schematically showing an embodiment of the gas diffusion layer of the present invention. Hereinafter, the gas diffusion layer of the present invention will be specifically described with reference to FIG.

  As shown in FIG. 1, the gas diffusion layer 1 of the present invention includes a diffusion layer substrate 2 and a water-repellent layer 3 formed on the surface of the diffusion layer substrate 2 (hereinafter, subjected to hydrothermal treatment). The diffusion layer base material 2 and the water repellent layer 3 before the treatment are referred to as “diffusion layer base material 2 ′” and “water repellent layer 3 ′”). The diffusion layer substrate 2 contains a carbon material and is made of, for example, carbon paper. The water repellent layer 3 contains a carbon material (for example, VGCF) and a water repellent resin (for example, polytetrafluoroethylene resin). The diffusion layer substrate 2 and the water repellent layer 3 are subjected to a hot water treatment (for example, a treatment immersed in hot water at 60 ° C. for 10 hours).

  By performing the hot water treatment, the surface free energy of the carbon material exposed to the hot water or water vapor generated from the hot water can be increased, so that the water repellency of the diffusion layer base material 2 ′ and the water repellent layer 3 ′ can be increased. The gas diffusion layer 1 with a reduced water repellency can be obtained. When the degree of water repellency is thus reduced, the contact area of water or water vapor with the gas diffusion layer 1 that is water repellant can be increased. When the contact area with water or water vapor is increased, a large amount of water or water vapor can be brought into contact with the water-repellent gas diffusion layer 1, so that gas diffusion can be achieved by supplying gas to the gas diffusion layer 1 separately. A large amount of water in contact with the surface of the layer 1 can be discharged (the drainage performance can be improved). Therefore, according to this invention, the gas diffusion layer 1 which can improve drainage can be provided.

  In addition, from the viewpoint of increasing the contact area of the gas diffusion layer with water or water vapor, the diffusion layer substrate and the water repellent layer containing a carbon material having a low water repellency (high hydrophilicity). It is also conceivable to form a gas diffusion layer of the form consisting of However, such a gas diffusion layer has insufficient water repellency, and thus cannot improve drainage. Therefore, in the present invention, after producing a structure having sufficient water repellency, the structure is subjected to hot water treatment to reduce the degree of water repellency of the structure, thereby ensuring drainage while ensuring the required water repellency. It is set as the gas diffusion layer 1 which can improve property.

2. 2. Method for Producing Gas Diffusion Layer FIG. 2 is a flowchart schematically showing steps provided in the method for producing a gas diffusion layer of the present invention. FIG. 3 is a conceptual diagram showing an example of a water repellent layer forming step. Hereinafter, a method for producing the gas diffusion layer 1 by the method for producing a gas diffusion layer of the present invention will be specifically described with reference to FIGS. 1 to 3.

  As shown in FIG. 2, the method for producing a gas diffusion layer of the present invention includes a water repellent layer forming step (step S11) and a hydrothermal treatment step (step S12), and through steps S11 and S12, The gas diffusion layer 1 is manufactured.

2.1. Water repellent layer forming step (step S11)
In step S11, a composition containing a carbon material (for example, VGCF) and a water-repellent resin (for example, polytetrafluoroethylene resin) is applied to the surface of the diffusion layer substrate 2 ′, and the water-repellent resin is dissolved. For this purpose, the solvent contained in the composition is volatilized to form a water repellent layer 3 ′ on the surface of the diffusion layer substrate 2 ′, and the structure including the diffusion layer substrate 2 ′ and the water repellent layer 3 ′ This is a process for producing the body 4 (see FIG. 3). In step S11, the method for applying the composition to the surface of the diffusion layer substrate 2 ′ is not particularly limited. In step S11, for example, the composition in a fluid state can be applied to the surface of the diffusion layer substrate 2 ′ by a method such as spray coating, brush coating, or screen printing. FIG. 3 shows how the water-repellent layer 3 ′ is formed on the surface of the diffusion layer substrate 2 ′ by spray coating.

2.2. Hot water treatment process (process S12)
Step S12 is a step of manufacturing the gas diffusion layer 1 by performing hot water treatment on the structure 4 produced in the step S11. The temperature of the hot water used in step S12 is a temperature at which the surface free energy of the carbon material contained in the diffusion layer substrate 2 ′ and the water repellent layer 3 ′ can be increased to reduce the degree of water repellency of the structure 4. If it is, it will not specifically limit. However, from the viewpoint of increasing the surface free energy of the carbon material within an appropriate time, it is preferably 40 ° C. or higher. On the other hand, from the viewpoint of controlling the degree of change in the surface free energy of the carbon material so that the degree of water repellency can be easily controlled, the temperature is preferably 80 ° C. or lower.

  On the other hand, the time for the hot water treatment is not particularly limited as long as it can increase the surface free energy of the carbon material contained in the diffusion layer base material 2 ′ and the water repellent layer 3 ′. It can change suitably according to the temperature of hot water. The hot water treatment time in step S12 can be, for example, 1 hour or more and 20 hours or less.

  In step S12, the form of the hot water treatment applied to the structure 4 is particularly limited as long as hot water can be brought into contact with the diffusion layer base material 2 ′ and the water repellent layer 3 ′ provided in the structure 4. It is not something. However, from the viewpoint of easily and surely bringing the hot water into contact with the diffusion layer base material 2 ′ and the water repellent layer 3 ′, the hot water contained in a predetermined container is given a predetermined time (for example, 1 It is preferable that the structure 4 is immersed for a period of time to 20 hours.

3. Fuel Cell FIG. 4 is a cross-sectional view schematically showing an example of a single cell provided in the fuel cell of the present invention. 4, components having the same configuration as in FIG. 1 are denoted by the same reference numerals as those used in FIG. 1, and description thereof is omitted as appropriate. Hereinafter, the fuel cell of the present invention will be specifically described with reference to FIGS. 1 and 4.

  As shown in FIG. 4, the single cell 10 includes an electrolyte membrane 5, an anode catalyst layer 6 formed on one surface of the electrolyte membrane 5, and a cathode catalyst layer formed on the surface opposite to the anode catalyst layer 6. 7 and gas diffusion layers 1 and 1 disposed on one side and the other side of the MEA 8 (hereinafter referred to as “gas diffusion layer 1 disposed on the anode catalyst layer 6 side”). The gas diffusion layer 1 disposed on the cathode catalyst layer 7 side is sometimes referred to as “gas diffusion layer 1b”), and disposed outside the gas diffusion layer 1a and the gas diffusion layer 1b. The separators 9 and 9 (hereinafter, the separator 9 disposed on the gas diffusion layer 1a side is sometimes referred to as "separator 9a", and the separator 9 disposed on the gas diffusion layer 1b side is sometimes referred to as "separator 9b". And). The gas diffusion layer 1a is disposed in such a manner that the water repellent layer 3 and the anode catalyst layer 6 are in contact with each other, and the diffusion layer substrate 2 and the separator 9a are in contact with each other. The cathode catalyst layer 7 is in contact with the diffusion layer base material 2 and the separator 9b in contact with each other. The separator 9a is provided with grooves 9x, 9x,... On the surface on the gas diffusion layer 1a side, and the separator 9b is provided with grooves 9y, 9y,.

  The electrolyte membrane 5 is a solid polymer membrane containing a proton conducting polymer that exhibits proton conduction performance when kept in a water-containing state in a temperature environment of about 80 ° C. On the other hand, the anode catalyst layer 6 and the cathode catalyst layer 7 are composed of metal particles (for example, Pt or the like; hereinafter simply referred to as “catalyst”) that function as a catalyst for causing an electrochemical reaction when the single cell 10 is operated. And a proton conductive polymer. On the other hand, the separator 9a and the separator 9b are made of a material (for example, a metal or a carbon material) having gas impermeability, electronic conductivity, heat resistance, and the like.

  During operation of the single cell 10, hydrogen is supplied through the grooves 9x, 9x,... Of the separator 9a, and air is supplied through the grooves 9y, 9y,. Cooled by the refrigerant flowing through the refrigerant flow path (not shown). By being supplied through the grooves 9x, 9x,..., The hydrogen that has passed through the gas diffusion layer 1a and reached the anode catalyst layer 6 becomes protons and electrons under the action of the catalyst contained in the anode catalyst layer 6. To separate. Protons generated in the anode catalyst layer 6 reach the cathode catalyst layer 7 through the proton conductive polymer contained in the anode catalyst layer 6, the electrolyte membrane 5, and the cathode catalyst layer 7. The generated protons reach the cathode catalyst layer 7 via the external circuit and the gas diffusion layer 1b. .. Are supplied through the grooves 9y, 9y,..., Oxygen contained in the air that has passed through the gas diffusion layer 1b and reached the cathode catalyst layer 7, and from the anode catalyst layer 6 to the cathode catalyst layer 7 The protons and electrons that have moved to react with each other under the action of the catalyst contained in the cathode catalyst layer 7, whereby water is generated in the cathode catalyst layer 7. It should be noted that hydrogen that was not used in the reaction in the anode catalyst layer 6 is discharged and recovered outside the single cell 10 through the grooves 9x, 9x,... And is not used in the reaction in the cathode catalyst layer 7. The air is discharged out of the unit cell 10 through the grooves 9y, 9y,.

  As described above, when the single cell 10 is operated, protons and electrons move, and thus heat is generated due to resistance during the movement. The proton conducting polymer contained in the MEA 8 exhibits proton conducting performance by being kept in a water-containing state in a temperature environment such as about 80 ° C., for example. In order to improve the performance of the single cell 10, It is necessary to prevent an excessive temperature rise of the cell 10. From such a viewpoint, the separator 9a and the separator 9b are cooled by the refrigerant flowing in the refrigerant flow path (not shown). Therefore, when the water (water vapor) generated in the cathode catalyst layer 7 by the reaction comes into contact with the cooled separator 9b and / or the separator 9a, it is condensed and becomes droplet water.

  In the single cell 10, the gas diffusion layer 1a disposed between the separator 9a and the MEA 8 and the gas diffusion layer 1b disposed between the separator 9b and the MEA 8 are made of carbon paper having gas permeability. Due to the construction, water droplets can pass through. When the water in the droplets that has passed through the gas diffusion layer 1b and / or the gas diffusion layer 1a reaches the MEA 8, and the MEA 8 is immersed in water, the diffusion of the reaction gas to the anode catalyst layer 6 and the cathode catalyst layer 7 is inhibited. Therefore, the performance of the single cell 10 is reduced. Therefore, in order to prevent the performance degradation of the single cell 10, the gas diffusion layer 1b and the gas diffusion layer 1a are required to have drainage.

  As described above, the gas diffusion layer 1b and the gas diffusion layer 1a include the diffusion layer base material 2 and the water repellent layer 3 that have been subjected to hydrothermal treatment. The diffusion layer substrate 2 and the water repellent layer 3 contain a carbon material whose water repellency is reduced by being subjected to hot water treatment. Since the water-repellent gas diffusion layer 1b and the gas diffusion layer 1a having a reduced degree of water repellency have a form in which the contact area with water is increased, the gas diffusion layer 1b and the gas diffusion layer 1a have a large amount of water. Can contact with. Here, the gas diffusion layer 1a side surface of the separator 9a is provided with grooves 9x, 9x,. 9y,... Are provided. Therefore, in the single cell 10, a large amount of water that has contacted the surface of the gas diffusion layer 1a can be discharged out of the single cell 10 together with the hydrogen flowing through the grooves 9x, 9x,. A large amount of water in contact with the surface can be discharged out of the single cell 10 together with the air flowing through the grooves 9y, 9y,. Therefore, according to the single cell 10 provided with the gas diffusion layer 1a of the present invention and the gas diffusion layer 1b of the present invention, drainage can be improved. Therefore, according to the fuel cell of the present invention including the single cell 10, drainage can be improved and performance can be improved.

4). Fuel Cell Manufacturing Method FIG. 5 is a flowchart schematically showing steps provided in the fuel cell manufacturing method of the present invention. Hereinafter, a method for manufacturing a fuel cell including the single cell 10 by the method for manufacturing a fuel cell of the present invention will be described in detail with reference to FIGS. 4 and 5.

  As shown in FIG. 5, the fuel cell manufacturing method of the present invention includes a structure manufacturing step (step S21), a gas diffusion layer manufacturing step (step S22), a membrane electrode structure manufacturing step (step S23), The fuel cell including the single cell 10 is manufactured through the steps S21 to S25 including the disposing step (step S24) and the stacking step (step S25).

4.1. Structure manufacturing process (process S21)
Step S21 is a step of forming the structure 4 including the diffusion layer substrate 2 ′ and the water repellent layer 3 ′ by forming the water repellent layer 3 ′ on the surface of the diffusion layer substrate 2 ′. Step S21 can have the same form as step S11.

4.2. Gas diffusion layer manufacturing process (process S22)
Step S22 is a step of manufacturing the gas diffusion layer 1 by performing hot water treatment on the structure 4 manufactured in the above step S21. Step S22 can have the same form as step S12.

4.3. Membrane electrode structure manufacturing step (step S23)
In step S23, the anode catalyst layer 6 is formed on one surface of the electrolyte membrane 5, and the cathode catalyst layer 7 is formed on the surface opposite to the surface on which the anode catalyst layer 6 is to be formed. In this step, an MEA 8 including the membrane 5, the anode catalyst layer 6, and the cathode catalyst layer 7 is manufactured. The step S23 is not particularly limited as long as the MEA 8 can be manufactured. As a specific example of the method of forming the anode catalyst layer 6 in the step S23, a fluid composition containing a catalyst and a proton conductive polymer (hereinafter referred to as “catalyst ink”) is spray-coated, brush-coated, The form which forms the anode catalyst layer 6 on the surface of the electrolyte membrane 5 by apply | coating to the surface of the electrolyte membrane 5 by methods, such as screen printing, and volatilizing the solvent contained in catalyst ink can be mentioned. In step S23, the cathode catalyst layer 7 can be formed by the same method as the anode catalyst layer 6.

4.4. Arrangement process (process S24)
In step S24, the MEA 8 is sandwiched between the pair of gas diffusion layers 1 and 1 by disposing the gas diffusion layers 1 and 1 prepared in step S22 on both sides of the MEA 8 manufactured in step S23. It is the process of producing this 1st laminated body.

4.5. Lamination process (process S25)
Step S25 is a step of manufacturing a fuel cell including a plurality of single cells 10, 10,. In step S25, for example, a second laminate including a plurality of single cells 10, 10,... Is produced by alternately laminating the separator 9 and the first laminate produced in step S24. Then, a 3rd laminated body is formed by laminating | stacking a current collection board etc. on the both ends of the lamination direction of the single cell 10,10, ... in the said 2nd laminated body. And the fuel cell of this invention provided with the some single cell 10,10, ... can be manufactured by accommodating the said 3rd laminated body in a case member.
As described above, the fuel cell manufactured by the fuel cell manufacturing method of the present invention includes the single cells 10, 10,... Each including the gas diffusion layers 1, 1 of the present invention. Therefore, according to the fuel cell manufacturing method of the present invention, it is possible to manufacture a fuel cell capable of improving drainage.

  In the above description regarding the present invention, carbon paper is exemplified as the diffusion layer substrate 2, but the present invention is not limited to this form, and carbon cloth or the like can also be used. The diffusion layer substrate used in the present invention has an electron conductivity and gas permeability, and a property that can withstand the environment during operation of a PEFC or a direct methanol fuel cell (DMFC) equipped with a solid polymer membrane (hereinafter referred to as “resistance resistance”). As long as the constituent material contains carbon.

  Moreover, in the said description regarding this invention, although VGCF was illustrated as a carbon material which comprises the water repellent layer 3, this invention is not limited to the said form. Examples of other carbon materials that can be contained in the water-repellent layer used in the present invention include carbon black, carbon nanotube, and carbon nanohorn. Furthermore, although the polytetrafluoroethylene resin was illustrated as water-repellent resin which comprises the water-repellent layer 3 in the said description regarding this invention, this invention is not limited to the said form. Other water-repellent resins that can be contained in the water-repellent layer used in the present invention include tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA). And tetrafluoroethylene-ethylene copolymer resin (ETFE), chlorotrifluoroethylene resin (PCTFE), fluorovinylidene resin (PVDF), and the like. However, it is preferable to use a polytetrafluoroethylene resin from the viewpoint of easily producing a gas diffusion layer capable of improving drainage.

  In the fuel cell and the manufacturing method thereof according to the present invention, the form of the electrolyte membrane 5 is not particularly limited as long as it is a solid polymer membrane containing a proton conductive polymer that can be used in PEFC or DMFC. Specific examples of the proton conductive polymer contained in the electrolyte membrane 5 include fluorine-based polymers having at least one of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton, and polyolefins. Examples thereof include hydrocarbon-based polymers having a hydrocarbon skeleton. Specific examples of the electrolyte membrane 5 containing the fluorine-based polymer include Nafion (“Nafion” is a registered trademark of DuPont, USA) and Flemion (“Flemion” is a registered trademark of Asahi Glass Co., Ltd.). it can. On the other hand, as a specific example of the electrolyte membrane 5 containing the hydrocarbon polymer, there can be mentioned Selemion and the like (“Selemion” is a registered trademark of Asahi Glass Co., Ltd.).

  Further, in the fuel cell and the manufacturing method thereof according to the present invention, the catalyst contained in the anode catalyst layer 6 and the cathode catalyst layer 7 can cause the above electrochemical reaction in a temperature environment during operation of PEFC or DMFC. The metal particles are not particularly limited as long as they are metal particles having environmental resistance. Specific examples of the catalyst contained in the anode catalyst layer 6 and the cathode catalyst layer 7 include Pt, Co, Ru, Ir, Au, Ag, Cu, Ni, Fe, Cr, Mn, V, Ti, Mo, Examples thereof include a Pt alloy having one or more metals selected from the group consisting of Pd, Rh, and W and Pt. Specific examples of the proton conductive polymer contained in the anode catalyst layer 6 and the cathode catalyst layer 7 include the proton conductive polymer that can be contained in the electrolyte membrane 5.

  Further, in the fuel cell and the manufacturing method thereof according to the present invention, the form of the separator 9 is not particularly limited as long as the separator 9 is made of a material having electron conductivity and gas impermeability and having environmental resistance. . Examples of the separator 9 include carbon separators made of engineering plastics, metal separators, and the like.

  In the above description regarding the fuel cell and the manufacturing method thereof according to the present invention, the gas diffusion layers 1 and 1 are provided between the anode catalyst layer 6 and the separator 9a and between the cathode catalyst layer 7 and the separator 9a. However, the present invention is not limited to this mode, and it is sufficient that at least one of the gas diffusion layers of the present invention is provided. However, as described above, since water is generated in the cathode catalyst layer 7 during operation of the fuel cell, from the viewpoint of easily obtaining a drainage improvement effect, only the cathode side or the anode side and It is preferable that the gas diffusion layer of the present invention is provided on the cathode side.

  The present invention will be further described below with reference to examples.

1. Contact angle measurement test 1.1. Manufacture of gas diffusion layer A water repellent layer containing 20 parts by mass of VGCF and 80 parts by mass of polytetrafluoroethylene resin is formed on the surface of a diffusion layer substrate (TGP-H-060, manufactured by Toray Industries, Inc.). The structure including the diffusion layer base material and the water repellent layer was prepared by spray-coating the composition in a fluid state adjusted as described above and volatilizing the solvent contained in the composition. Thereafter, the structure was immersed in 400 ml of 60 ° C. hot water for a predetermined time and then taken out from the beaker to produce a gas diffusion layer (hereinafter referred to as the gas diffusion layer). (Referred to as “gas diffusion layer according to Example 1”). The immersion time was 15 hours, 25 hours, 45 hours, and 75 hours.
On the other hand, the gas diffusion layer concerning the comparative example 1 was manufactured by passing through the process similar to the gas diffusion layer concerning Example 1 except not performing a hot-water process.

On the other hand, in place of VGCF, Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd. “Denka Black” is a registered trademark of Denki Kagaku Kogyo Co., Ltd .; the same shall apply hereinafter) and the gas diffusion layer according to Example 1 above was used. A gas diffusion layer according to Example 2 was manufactured by the same method.
On the other hand, a gas diffusion layer according to Comparative Example 2 was manufactured by performing the same steps as those of the gas diffusion layer according to Comparative Example 1 except that Denka Black was used instead of VGCF.

1.2. Measurement of contact angle A 3 μL water droplet was allowed to stand on the surface of the gas diffusion layer produced (Example 1, Comparative Example 1, Example 2, and Comparative Example 2), and a contact angle measuring device (CA-W150, Kyowa). Θ / 2 was measured using Interface Science Co., Ltd., and the contact angle θ was calculated by doubling this. The measurement of θ / 2 was performed by the sessile drop method described in JIS R3257: 1999 “Method for testing wettability of substrate glass surface”. The relationship between the immersion time of the gas diffusion layer according to Example 1 and the gas diffusion layer according to Example 2 and the contact angle θ, and the contact angle between the gas diffusion layer according to Comparative Example 1 and the gas diffusion layer according to Comparative Example 2 The measurement result of θ is also shown in FIG. The vertical axis of FIG. 6 is the contact angle [°], and the horizontal axis is the immersion time [h].

1.3. Results From FIG. 6, the contact angle of the gas diffusion layer according to Example 1 manufactured through the hot water treatment immersed in hot water is larger than the contact angle of the gas diffusion layer according to Comparative Example 1 that has not been subjected to the hot water treatment. The contact angle of the gas diffusion layer according to Example 1 was smaller and larger than 90 [°]. Similarly, from FIG. 6, the contact angle of the gas diffusion layer according to Example 2 manufactured through the hot water treatment immersed in hot water is the contact angle of the gas diffusion layer according to Comparative Example 2 that has not been subjected to the hot water treatment. And the contact angle of the gas diffusion layer according to Example 2 was larger than 90 [°]. That is, a water-repellent gas diffusion layer with a reduced degree of water repellency could be produced by performing a hot water treatment.

2. Power generation performance evaluation test 2.1. Production of a single cell On one surface of an electrolyte membrane containing a fluorine-based polymer, a catalyst ink in a fluid state containing platinum-supported carbon in which platinum is supported on carbon particles and a fluorine-based polymer is applied, and the catalyst is applied. By volatilizing the solvent contained in the ink, an anode catalyst layer was formed on one surface of the electrolyte membrane. Furthermore, a fluidized catalyst ink containing platinum black particles and a fluorine-based polymer is applied to the surface of the electrolyte membrane opposite to the surface on which the anode catalyst layer is to be formed, and the solvent contained in the catalyst ink is volatilized. As a result, a cathode catalyst layer was formed on the other surface of the electrolyte membrane to produce an MEA. Note that the electrode areas of the anode catalyst layer and the cathode catalyst layer provided in the MEA were both 13 [cm ² ].

The gas diffusion layer according to Comparative Example 1 was disposed on the anode catalyst layer side of the MEA thus produced, and the gas diffusion layer according to Example 1 was disposed on the cathode catalyst layer side. A single cell according to Example 1 was manufactured by configuring the multilayer body according to Example 1 and disposing carbon separators having gas flow paths on both sides of the multilayer body.
On the other hand, the gas diffusion layer according to Comparative Example 1 is disposed on the anode catalyst layer side and the cathode catalyst layer side of the MEA, respectively, so that the laminate according to Comparative Example 1 is configured and both sides of the laminate are formed. The single cell concerning the comparative example 1 was produced by arrange | positioning the carbon separator provided with a gas flow path to each.

On the other hand, the gas diffusion layer according to Comparative Example 2 is disposed on the anode catalyst layer side of the MEA, and the gas diffusion layer according to Example 2 is disposed on the cathode catalyst layer side. A single cell according to Example 2 was manufactured by constituting such a laminate and disposing carbon separators each having a gas flow path on both sides of the laminate.
On the other hand, a gas diffusion layer according to Comparative Example 2 is provided on the anode catalyst layer side and the cathode catalyst layer side of the MEA, thereby forming a laminate according to Comparative Example 2, and both sides of the laminate are provided. The single cell concerning the comparative example 2 was produced by arrange | positioning each carbon separator provided with a gas flow path.

2.2. Power generation performance evaluation Hydrogen (temperature: 80 [° C.], relative humidity: 100 [%] on the anode catalyst layer side of the produced single cell (Example 1, Comparative Example 1, Example 2, and Comparative Example 2), Back pressure: 100 [kPa], flow rate: 0.272 [L / min]), and air (temperature: 80 [° C.], relative humidity: 100 [%], back pressure: 100 on the cathode catalyst layer side. [KPa], flow rate: 0.866 [L / min]) was supplied, the single cell was operated, and the power generation performance was evaluated. The result of the single cell according to Example 1 and the result of the single cell according to Comparative Example 1 are shown in FIG. 7, the result of the single cell according to Example 2 and the result of the single cell according to Comparative Example 2 are shown in FIG. Show. 7 and 8, the vertical axis represents voltage [V], and the horizontal axis represents current density [A / cm ² ].

2.3. Results As shown in FIG. 7, in the low current density region, the power generation performance of the single cell according to Example 1 and the single cell according to Comparative Example 1 was the same, but a high current density region in which a large amount of water was generated. Then, the single cell according to Example 1 had higher performance than the single cell according to Comparative Example 1. This is because the single cell according to Example 1 was provided with the gas diffusion layer according to Example 1 capable of improving drainage on the cathode catalyst layer side where water was generated. It is thought that this is because so-called flooding was suppressed as a result of being able to discharge a large amount of water outside the single cell even in the region.

  On the other hand, as shown in FIG. 8, in the low current density region, the power generation performance of the single cell according to Example 2 and the single cell according to Comparative Example 2 was the same, but a high current density at which a large amount of water was generated. In the area, the single cell according to Example 2 had higher performance than the single cell according to Comparative Example 2. This is because the single cell according to Example 2 was provided with the gas diffusion layer according to Example 2 capable of improving drainage on the cathode catalyst layer side where water was generated. It is thought that this is because so-called flooding was suppressed as a result of being able to discharge a large amount of water outside the single cell even in the region.

  As described above, according to the gas diffusion layer of the present invention, it is possible to improve drainage, and according to the fuel cell of the present invention including the gas diffusion layer, the performance can be improved particularly in a high current density region. Is possible. Furthermore, from this result, according to the present invention, there can be provided a method for producing a gas diffusion layer capable of producing a gas diffusion layer capable of improving drainage, and a fuel cell capable of improving performance. A method of manufacturing a fuel cell that can be manufactured can be provided.

2 is a cross-sectional view schematically showing an example of a form of a gas diffusion layer 1. FIG. It is a flowchart which shows roughly the process with which the manufacturing method of the gas diffusion layer of this invention is equipped. It is a conceptual diagram which shows the example of a form of a water repellent layer formation process. It is sectional drawing which shows schematically the example of the form of the single cell 10 with which the fuel cell of this invention is equipped. It is a flowchart which shows roughly the process with which the manufacturing method of the fuel cell of this invention is equipped. It is a figure which shows the relationship between immersion time and contact angle (theta). It is a figure which shows the result of a power generation performance evaluation test. It is a figure which shows the result of a power generation performance evaluation test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Gas diffusion layer 2, 2 '... Diffusion layer base material 3, 3' ... Water-repellent layer 4 ... Structure 5 ... Electrolyte membrane 6 ... Anode catalyst layer 7 ... Cathode catalyst layer 8 ... MEA (membrane electrode) Structure)
9, 9a, 9b ... separator 10 ... single cell

Claims (6)

A diffusion layer base material containing a carbon material, and a water repellent layer formed on the surface of the diffusion layer base material,
The water repellent layer contains a carbon material and a water repellent resin,
A gas diffusion layer, wherein the diffusion layer base material and the water repellent layer are subjected to hot water treatment. The gas diffusion layer according to claim 1, wherein the water-repellent resin contains a polytetrafluoroethylene resin. A method for producing a gas diffusion layer comprising a diffusion layer substrate containing a carbon material, and a water repellent layer formed on the surface of the diffusion layer substrate,
By applying a composition containing a carbon material and a water-repellent resin to the surface of the diffusion layer substrate, the water-repellent layer is formed on the surface of the diffusion layer substrate to produce a structure. An aqueous layer forming step;
A hot water treatment step of treating the structure produced by the water repellent layer forming step with hot water;
A method for producing a gas diffusion layer, comprising: The method for producing a gas diffusion layer according to claim 3, wherein the water-repellent resin contains a polytetrafluoroethylene resin. A membrane electrode structure, and a gas diffusion layer disposed on at least one of the membrane electrode structures,
The fuel cell according to claim 1, wherein the gas diffusion layer is the gas diffusion layer according to claim 1. A method of manufacturing a fuel cell comprising: a membrane electrode structure; and a gas diffusion layer disposed on at least one of the membrane electrode structures,
The gas diffusion layer has a diffusion layer base material containing a carbon material, and a water repellent layer formed on the surface of the diffusion layer base material,
A structure is produced by applying a composition containing a carbon material and a water-repellent resin to the surface of the diffusion layer base material to form the water-repellent layer on the surface of the diffusion layer base material. Body preparation process,
A gas diffusion layer preparation step of preparing a gas diffusion layer by treating the structure prepared in the structure preparation step with hot water;
Producing the membrane electrode structure, a membrane electrode structure production step;
Disposing the gas diffusion layer prepared by the gas diffusion layer preparation step on at least one of the membrane electrode structures prepared by the membrane electrode structure preparation step; and
A method for producing a fuel cell, comprising:

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