JP2009211953A - Electrode base, electrode, membrane electrode assembly, fuel cell, and manufacturing method of electrode base material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode base material of a fuel cell to enable stable output. <P>SOLUTION: The electrode base material 100 constitutes a part of an electrode installed on a surface of an electrolyte membrane for the fuel cell, and has a low water repellent fiber 102 made of a metal fiber or a carbon fiber, and a high water repellent fiber 104 made of the metal fiber or the carbon fiber higher in water repellency than the low water repellent fiber 102. Thus, when used for the electrode of the fuel cell, in the case formed water is generated by a reaction during power generation, since the formed water becomes easy to gather at surroundings of the low water repellent fiber 102, and the formed water becomes difficult to stay at the surroundings of the high water repellent fiber 104, it is suppressed that a flow passage of a gas exhausted or consumed during power generation is blocked. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrode substrate used for an electrode of a fuel cell.

  In recent years, fuel cells that have high energy conversion efficiency and do not generate harmful substances due to power generation reactions have attracted attention. As one of such fuel cells, a polymer electrolyte fuel cell that operates at a low temperature of 100 ° C. or lower is known.

  A polymer electrolyte fuel cell has a basic structure in which a polymer electrolyte membrane, which is an electrolyte membrane, is disposed between a fuel electrode (anode) and an air electrode (cathode), and a fuel gas containing hydrogen in the fuel electrode, air It is an apparatus that supplies an oxidant gas containing oxygen to the electrode and generates power by the following electrochemical reaction.

The fuel _{^{electrode: H 2 → 2H + + 2e}} - ···· (1)
^{_{Cathode: 1 / 2O 2 + 2H +}} + 2e - → H 2 O ···· (2)
The anode and cathode each have a structure in which a catalyst layer and a gas diffusion layer are laminated. The catalyst layers of the electrodes are arranged opposite to each other with the solid polymer film interposed therebetween, thereby constituting a fuel cell. The catalyst layer is a layer formed by binding a catalyst or carbon particles supporting the catalyst with an ion exchange resin. The gas diffusion layer becomes a passage for the oxidant gas and the fuel gas.

  At the anode, hydrogen contained in the supplied fuel is decomposed into hydrogen ions and electrons as shown in the above formula (1). Among these, hydrogen ions move inside the solid polymer electrolyte membrane toward the air electrode, and electrons move to the air electrode through an external circuit. On the other hand, in the cathode, oxygen contained in the oxidant gas supplied to the cathode reacts with hydrogen ions and electrons that have moved from the fuel electrode, and water is generated as shown in the above formula (2).

  As a general electrode base material used in an anode or a cathode, a carbon woven fabric or carbon paper subjected to a water repellent treatment with PTFE can be used. However, in such an electrode base material, the diffusion path of oxidant gas and fuel gas and the discharge path of generated water generated at the cathode are not considered at all. Therefore, the allowable range of operating conditions of fuel cells using such electrode base materials tends to be narrow, and the robustness against fluctuations in output and humidification temperature is low, so problems such as flooding and drying of the electrolyte membrane May occur.

In view of this, a gas diffusion electrode has been devised that uses a mixed woven fabric or mixed non-woven fabric of metal fibers and organic fibers and has different hydrophilicity between the metal fibers and the organic fibers (see Patent Document 1).
JP-A-6-267555

  However, even with the gas diffusion electrode described in Patent Document 1, it cannot be said that the robustness with respect to fluctuations in output and humidification temperature is still sufficient, and further improvement is required.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an electrode base material for a fuel cell that enables stable output.

  In order to solve the above problems, an electrode substrate according to an aspect of the present invention is an electrode substrate that constitutes a part of an electrode provided on the surface of an electrolyte membrane for a fuel cell, and is made of metal fiber or carbon fiber. And a second fiber made of metal fiber or carbon fiber having higher water repellency than the first fiber.

  According to this aspect, when generated water is generated by a reaction during power generation, the generated water is easily collected around the first fiber having a lower water repellency than the second fiber. Since the generated water is less likely to stay around the second fiber, the passage of the gas discharged or consumed during power generation is prevented from being blocked. For this reason, a region through which gas passes is ensured even at high output when the amount of generated water increases, and a decrease in output due to flooding is suppressed. In addition, at the time of low output when the generated water is low, drying of the electrolyte membrane is suppressed by the generated water remaining around the first fiber. As a result, a stable fuel cell can be realized in a wide output range. In the same way, output reduction due to flooding during high humidification is suppressed, and membrane drying during low humidification is suppressed, realizing a fuel cell that enables stable output over a wide range of humidification temperatures. can do.

  Both the first fiber and the second fiber are carbon fibers, and the degree of graphitization of the second fiber is higher than the degree of graphitization of the first fiber. This makes it possible to provide a difference in water repellency between the first fiber and the second fiber without performing a water repellent treatment with a water repellent material such as a fluororesin, thereby reducing the resistance of the electrode substrate. It becomes possible to make it. Further, since both the first fiber and the second fiber are carbon fibers, it is easy to reduce the electric resistance as compared with the case where the organic resin is mixed.

  The metal fiber may contain at least one of stainless steel, periodic table 4A group element, periodic table 5A group element, periodic table 6A group element, periodic table 8 group element, and periodic table 1B group element.

  You may have the area | region where the 1st fiber is unevenly distributed, and the area | region where the 2nd fiber is unevenly distributed. Thereby, the area | region where the 1st fiber is unevenly distributed functions as a water retention area | region, and the area | region where the 2nd fiber is unevenly distributed can function as a gas diffusion area | region.

  Another embodiment of the present invention is also an electrode substrate. This electrode base material is an electrode base material that constitutes a part of an electrode provided on the surface of an electrolyte membrane for a fuel cell. The electrode base material has a first fiber made of metal fiber or carbon fiber, and is more repellent than the first fiber. Second fibers made of resin fibers having a high aqueous property. It has a region where the first fibers are unevenly distributed and a region where the second fibers are unevenly distributed.

  According to this aspect, when generated water is generated by a reaction during power generation, the generated water is easily collected around the first fiber having a lower water repellency than the second fiber. Since the generated water is less likely to stay around the second fiber, the passage of the gas discharged or consumed during power generation is prevented from being blocked. For this reason, a region through which gas passes is ensured even at high output when the amount of generated water increases, and a decrease in output due to flooding is suppressed. In addition, at the time of low output when the generated water is low, drying of the electrolyte membrane is suppressed by the generated water remaining around the first fiber. As a result, a fuel cell capable of stable output can be realized.

  A space surrounded by the first fibers may be formed in a region where the first fibers are unevenly distributed. A space surrounded by the second fibers may be formed in a region where the second fibers are unevenly distributed. As a result, the space surrounded by the first fiber functions as a discharge part and a storage part of the generated water, and the space surrounded by the second fiber is generated in the power generation or consumed gas. It can function as a passing part.

  The first fiber and the second fiber may be bonded without being woven. A woven fabric in which the first fibers and the second fibers are woven may be used.

  A state in which a plurality of first fibers and second fibers are alternately arranged in parallel in a state aligned in a predetermined direction, and the first fibers and second fibers are aligned in a direction intersecting the predetermined direction The plurality of regions may be alternately arranged in parallel. Thereby, the space surrounded by the first fiber and the space surrounded by the second fiber can be easily formed at a desired location.

  Yet another embodiment of the present invention is an electrode. This electrode includes the above-described electrode base material and a catalyst layer.

  Yet another embodiment of the present invention is a membrane electrode assembly. This membrane electrode assembly includes an electrolyte membrane and the above-described electrode provided on the surface of the electrolyte membrane.

  Yet another embodiment of the present invention is a fuel cell. This fuel cell incorporates the membrane electrode assembly described above.

  Yet another embodiment of the present invention is a method for producing an electrode substrate. This method is a method of manufacturing an electrode base material that constitutes a part of an electrode provided on the surface of an electrolyte membrane for a fuel cell, and includes a first fiber made of metal fiber or carbon fiber, and a first fiber. A first step of preparing a second fiber made of a metal fiber or carbon fiber having high water repellency, and a region where the first fiber is unevenly distributed and a region where the second fiber is unevenly distributed are formed. A bonding step of bonding the plurality of fibers and the second fibers so that a plurality of the fibers and the second fibers are alternately arranged.

  According to this aspect, the region surrounded by the first fibers and the region surrounded by the second fibers can be easily formed at a desired location.

  According to the present invention, a fuel cell capable of stable output can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. Moreover, the structure described below is an illustration and does not limit the scope of the present invention at all.

(Fuel cell)
FIG. 1 is a perspective view schematically showing the structure of the fuel cell 10 according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line AA of FIG. The fuel cell 10 includes a flat membrane electrode assembly 50, and a separator 34 and a separator 36 are provided on both sides of the membrane electrode assembly 50. Although only one membrane electrode assembly 50 is shown in this example, the fuel cell 10 may be configured by stacking a plurality of membrane electrode assemblies 50 via the separator 34 or the separator 36.

  The membrane electrode assembly 50 includes a solid polymer electrolyte membrane 20, an anode 22, and a cathode 24. The anode 22 has a laminate composed of a catalyst layer 26 and a gas diffusion layer 28. On the other hand, the cathode 24 has a laminate composed of a catalyst layer 30 and a gas diffusion layer 32. The catalyst layer 26 of the anode 22 and the catalyst layer 30 of the cathode 24 are provided to face each other with the solid polymer electrolyte membrane 20 interposed therebetween.

  A gas flow path 38 is provided in the separator 34 provided on the anode 22 side. Fuel gas is distributed to a gas flow path 38 from a fuel supply manifold (not shown), and the fuel gas is supplied to the membrane electrode assembly 50 through the gas flow path 38. Similarly, a gas flow path 40 is provided in the separator 36 provided on the cathode 24 side.

  The oxidant gas is distributed to the gas flow path 40 from the oxidant supply manifold (not shown), and the oxidant gas is supplied to the membrane electrode assembly 50 through the gas flow path 40. Specifically, during operation of the fuel cell 10, fuel gas, for example, hydrogen gas, flows from the upper side to the lower side along the surface of the gas diffusion layer 28 in the gas flow path 38, thereby supplying the fuel gas to the anode 22. Is done.

  On the other hand, during operation of the fuel cell 10, an oxidant gas, for example, air flows through the gas flow path 40 from the upper side to the lower side along the surface of the gas diffusion layer 32, whereby the oxidant gas is supplied to the cathode 24. The Thereby, a reaction occurs in the membrane electrode assembly 50. When hydrogen gas is supplied to the catalyst layer 26 via the gas diffusion layer 28, hydrogen in the gas becomes protons, and these protons move through the solid polymer electrolyte membrane 20 to the cathode 24 side. At this time, the emitted electrons move to the external circuit and flow into the cathode 24 from the external circuit. On the other hand, when air is supplied to the catalyst layer 30 through the gas diffusion layer 32, oxygen is combined with protons to become water. As a result, electrons flow from the anode 22 toward the cathode 24 in the external circuit, and power can be taken out.

  The solid polymer electrolyte membrane 20 exhibits good ion conductivity in a wet state, and functions as an ion exchange membrane that moves protons between the anode 22 and the cathode 24. The solid polymer electrolyte membrane 20 is formed of a solid polymer material such as a fluorine-containing polymer or a non-fluorine polymer. A fluorocarbon polymer or the like can be used. Examples of the sulfonic acid type perfluorocarbon polymer include Nafion (manufactured by DuPont: registered trademark) 112. Examples of non-fluorine polymers include sulfonated aromatic polyetheretherketone and polysulfone.

  The catalyst layer 26 constituting the anode 22 is composed of an ion exchange resin and carbon particles carrying a catalyst, that is, catalyst-carrying carbon particles. The ion exchange resin has a role of transmitting protons between the carbon particles carrying the catalyst and the solid polymer electrolyte membrane 20 connected to each other. The ion exchange resin may be formed of the same polymer material as the solid polymer electrolyte membrane 20. Examples of the supported catalyst include metals such as platinum, ruthenium, rhodium and palladium, or alloys of these metals. Examples of the carbon particles supporting the catalyst include acetylene black, ketjen black, furnace black, carbon nanotube, and carbon nano-onion.

  The gas diffusion layer 28 constituting the anode 22 has an anode gas diffusion base material and a microporous layer applied to the anode gas diffusion base material. The anode gas diffusion base material is preferably composed of a porous body having electron conductivity, and for example, metal fibers, carbon paper, carbon woven fabric or nonwoven fabric can be used.

  The microporous layer applied to the anode gas diffusion base material is a paste-like kneaded product obtained by kneading a conductive powder and a water repellent. For example, carbon black can be used as the conductive powder. As the water repellent, a fluorine resin such as tetrafluoroethylene resin (PTFE) can be used. The water repellent agent preferably has binding properties. Here, the binding property refers to a property that can be made sticky (state) by joining things that are less sticky or those that tend to break apart. Since the water repellent has binding properties, a paste can be obtained by kneading the conductive powder and the water repellent.

  The gas diffusion layer 32 constituting the cathode 24 has a cathode gas diffusion base material and a microporous layer applied to the cathode gas diffusion base material. The cathode gas diffusion base material is preferably composed of a porous body having electron conductivity. For example, metal fibers, carbon paper, carbon woven fabric or nonwoven fabric can be used.

  The microporous layer applied to the cathode gas diffusion substrate is a paste-like kneaded product obtained by kneading a conductive powder and a water repellent. For example, carbon black can be used as the conductive powder. Further, as the water repellent, a fluorine resin such as tetrafluoroethylene resin can be used. The water repellent agent preferably has binding properties. Since the water repellent has binding properties, a paste can be obtained by kneading the conductive powder and the water repellent.

  The catalyst layer 30 constituting the cathode 24 is composed of an ion exchange resin and carbon particles carrying a catalyst, that is, catalyst-carrying carbon particles. The ion exchange resin has a role of transmitting protons between the carbon particles carrying the catalyst and the solid polymer electrolyte membrane 20 connected to each other. The ion exchange resin may be formed of the same polymer material as the solid polymer electrolyte membrane 20. Examples of the supported catalyst include metals such as platinum, palladium, iridium, and ruthenium, or alloys of these metals. Examples of the carbon particles supporting the catalyst include acetylene black, ketjen black, furnace black, carbon nanotube, and carbon nano-onion.

(Electrode substrate)
Next, the structure of the anode gas diffusion base material and cathode gas diffusion base material which are electrode base materials is demonstrated. The electrode base material according to the present embodiment is formed in a state where a space through which gas or water easily passes is surrounded by fibers by intersecting two types of fibers having different water repellency.

  FIG. 3 is a top view of the main part of the electrode substrate according to the embodiment. Hereinafter, a cathode gas diffusion base material (hereinafter referred to as “electrode base material”) used for the gas diffusion layer 32 constituting the cathode 24 will be described as an example. Since an almost similar configuration can be adopted for the anode gas diffusion base material, differences from the cathode gas diffusion base material will be mainly described, and the others will be omitted as appropriate.

  As shown in FIG. 3, the electrode substrate 100 includes a low water-repellent fiber 102 having a relatively low water repellency and a high water-repellent fiber 104 having a relatively high water repellency. By using such an electrode substrate 100 as an electrode of a fuel cell, when generated water is generated due to a reaction during power generation, generated water is generated around the low water-repellent fiber 102 having a lower water repellency than the high water-repellent fiber 104. And the generated water is less likely to stay around the highly water-repellent fiber 104, so that the flow path of gas discharged or consumed during power generation is suppressed. For this reason, a region through which gas passes is ensured even at high output when the amount of generated water increases, and a decrease in output due to flooding is suppressed. In addition, at the time of low output when the generated water is low, drying of the electrolyte membrane is suppressed by the generated water remaining around the low water-repellent fiber 102. As a result, a fuel cell capable of stable output can be realized.

  In the region shown in FIG. 3 of the electrode substrate 100, two low water-repellent fibers 102 and two highly water-repellent fibers 104 are alternately arranged in parallel in the lateral direction. Two highly water-repellent fibers 104 are alternately arranged in parallel in a state where they are aligned in the vertical direction.

  Thereby, a region R1 where the low water-repellent fibers 102 are unevenly distributed and a region R2 where the high water-repellent fibers 104 are unevenly formed are formed.

  In addition, in the region R1 where the low water-repellent fibers 102 are unevenly distributed, a space S1 surrounded by the low water-repellent fibers 102 is formed, and in the region R2 where the high water-repellent fibers 104 are unevenly distributed, A space S <b> 2 surrounded by 104 is formed. As a result, the space S1 surrounded by the low water-repellent fiber 102 functions as a discharge part or a storage part of the generated water, and the space S2 surrounded by the high water-repellent fiber 104 generates gas or consumption generated in power generation. It can be made to function as a gas passage part.

  In addition, by appropriately adjusting a region in which a plurality of low water-repellent fibers 102 and high water-repellent fibers 104 are juxtaposed, the space S1 surrounded by the low water-repellent fibers 102 and the periphery are surrounded by the high water-repellent fibers 104. The space S2 thus formed can be easily formed in a desired location of the electrode substrate 100 at a desired ratio.

  In addition, the ratio of the highly water-repellent fiber 104 to the whole electrode base material has the good range of 5-95%. When the ratio of the highly water-repellent fibers 104 is higher than this range, the generated water is difficult to be discharged, and the output is likely to decrease due to flooding. Further, when the ratio of the highly water-repellent fibers 104 is lower than this range, the flow path of gas discharged or consumed during power generation is likely to be blocked. The ratio of the highly water-repellent fiber 104 to the entire electrode substrate is preferably 15 to 85%, more preferably 30 to 70%.

  In addition, the ratio of the total area of the space S2 to the sum of the total area of the space S1 functioning as the generated water discharge part and the storage part and the total area of the space S2 functioning as the gas passage part is 20 to 95%. The range is good. When the ratio of the total area of the space S2 is higher than this range, the generated water is difficult to be discharged, and the output is likely to decrease due to flooding. Further, if the ratio of the total area of the space S2 is lower than this range, the flow path of gas discharged or consumed during power generation is likely to be blocked. The ratio of the total area of the space S2 is preferably 30 to 90%, more preferably 40 to 85%.

  Hereinafter, a specific combination of the low water-repellent fiber 102 and the high water-repellent fiber 104 is exemplified, and a method for manufacturing the electrode base material is also described.

[Example 1]
In the electrode substrate according to this example, carbon fiber having a low graphitization degree is used as the low water-repellent fiber 102, and graphite carbon fiber having a high graphitization degree is used as the high water-repellent fiber 104, as shown in FIG. In addition, a plurality of low water-repellent fibers 102 and a plurality of highly water-repellent fibers 104 are woven so as to be alternately arranged in parallel in the longitudinal direction and the transverse direction. This makes it possible to provide a difference in water repellency between the low water repellant fiber 102 and the high water repellant fiber 104 without performing water repellency treatment with a water repellent material such as fluororesin. Can be reduced. Moreover, since both the low water-repellent fiber 102 and the high water-repellent fiber 104 are carbon fibers, it is easy to reduce the electric resistance as compared with the case where an organic resin is mixed. The diameter of each fiber is preferably about 0.1 μm to 10 μm. Each fiber may be a bundle of a plurality of fibers.

  A paste-like kneaded material obtained by kneading the above-described conductive powder and water repellent as a microporous layer is applied to the electrode substrate thus prepared, and then dried and heat-treated. Next, a catalyst slurry is applied on the electrode substrate on which the microporous layer is formed. Hereinafter, a method for producing and applying a catalyst slurry, and a method for producing an electrode and a membrane electrode assembly will be described.

<Cathode catalyst slurry preparation>
Platinum-supported carbon (TEC10E50E, Tanaka Kikinzoku Kogyo Co., Ltd.) was used as the cathode catalyst, and Nafion (registered trademark) DE2020CS solution (20%, Ew = 1050, manufactured by DuPont) was used as the ion exchange resin. 10 mL of ultrapure water was added to 5 g of platinum-supporting carbon and stirred, and then 15 mL of ethanol was added. The catalyst dispersion solution was subjected to ultrasonic stirring and dispersion for 1 hour using an ultrasonic stirrer. A predetermined Nafion solution was diluted with an equal amount of ultrapure water, stirred with a glass rod for 3 minutes, and then subjected to ultrasonic dispersion for 1 hour using an ultrasonic cleaner to obtain an aqueous Nafion solution. Thereafter, an aqueous Nafion solution was slowly dropped into the catalyst dispersion. During the dropping, stirring was continuously performed using an ultrasonic stirrer. After completion of the Nafion solution dropping, 10 g (1: 1 by weight) of a mixed solution of 1-propanol and 1-butanol was dropped, and the resulting solution was used as a catalyst slurry. During mixing, the water temperature was all adjusted to about 60 ° C., and ethanol was evaporated and removed.

<Cathode fabrication>
The catalyst slurry produced by the above method was applied onto the fine pore layer by screen printing (150 mesh), dried at 80 ° C. for 3 hours and heat treated at 180 ° C. for 45 minutes to form a catalyst layer.

<Anode catalyst slurry preparation>
The anode catalyst slurry preparation method is the same as the cathode catalyst slurry preparation method except that platinum ruthenium-supported carbon (TEC61E54) is used as the catalyst.

<Anode fabrication>
The catalyst slurry prepared by the above method is applied to a gas diffusion layer with a pore layer prepared by Vulcan XC72 by screen printing (150 mesh), dried at 80 ° C. for 3 hours, and heat treated at 130 ° C. for 45 minutes. And a catalyst layer was formed.

<Preparation of membrane electrode assembly>
Hot pressing is performed with the solid polymer electrolyte membrane sandwiched between the anode and cathode produced by the above method. Aciplex (registered trademark) (SF7201x, Asahi Kasei Chemicals) was used as the solid polymer electrolyte membrane. A membrane electrode assembly was produced by hot pressing the anode, the solid polymer electrolyte membrane, and the cathode under the bonding conditions of 170 ° C. and 200 seconds. The solid polymer electrolyte membrane had a thickness of 50 μm, the cathode catalyst layer had a thickness of 20 μm, and the anode catalyst layer had a thickness of 20 μm. Further, a fuel cell is fabricated by incorporating this membrane electrode assembly.

[Example 2]
In the electrode base material according to the present embodiment, a stainless steel fiber whose surface is hydrophilized as the low water repellent fiber 102 and a stainless steel fiber whose surface is not hydrophilized as the high water repellent fiber 104 are used. . As the hydrophilization treatment, for example, a method in which the surface of the fiber is subjected to plasma treatment, laser treatment, or corona treatment, or a method in which inorganic nanoparticles are mixed into the fiber can be applied. The electrode, membrane electrode assembly, and fuel cell fabrication method using this electrode substrate is the same as in Example 1.

[Example 3]
In the electrode base material according to this example, one of the low water-repellent fiber 102 and the high water-repellent fiber 104 is a carbon fiber, and the other is a metal fiber. As the hydrophilization treatment of the metal fiber, for example, a method in which the fiber surface is subjected to plasma treatment, laser treatment, or corona treatment, or a method in which inorganic nanoparticles are mixed into the fiber can be applied. In addition, as the water repellency treatment of the metal fiber, for example, a method of modifying the surface of the fiber with a fluorine treatment, a silane coupling agent, or an ion beam, or a method of mixing fluorine fine particles into the fiber can be applied. On the other hand, as a hydrophilic treatment of carbon fibers, a method of lowering the degree of graphitization can be applied in addition to the aforementioned hydrophilic treatment of metal fibers. Further, as the water repellency treatment of the carbon fiber, a method of increasing the degree of graphitization can be applied in addition to the above-described water repellency treatment of the metal fiber. By appropriately selecting each of these treatments, a carbon fiber can be used for one of the low water-repellent fiber 102 and the high water-repellent fiber 104, and a metal fiber can be used for the other. The electrode, membrane electrode assembly, and fuel cell fabrication method using this electrode substrate is the same as in Example 1.

[Example 4]
In the electrode base material according to this example, carbon fibers are used as the low water-repellent fibers 102, and PTFE fibers are used as the high water-repellent fibers 104. The electrode, membrane electrode assembly, and fuel cell fabrication method using this electrode substrate is the same as in Example 1.

[Example 5]
The electrode base material according to the present embodiment uses stainless steel fibers as the low water-repellent fibers 102 and PTFE fibers as the high water-repellent fibers 104. The electrode, membrane electrode assembly, and fuel cell fabrication method using this electrode substrate is the same as in Example 1.

[Example 6]
In the electrode base material according to this example, carbon fiber is used as the low water-repellent fiber 102 and PTFE fiber is used as the high water-repellent fiber 104, but the method for producing the electrode base material is different from that of Example 1. FIG. 4 is a diagram schematically showing a method for producing an electrode base material in Example 6.

  In this example, first, a woven fabric 110 in which low-water-repellent fibers 102 made of carbon fibers are woven in a mesh shape and a woven fabric 120 in which high-water-repellent fibers 104 made of PTFE fibers are woven in a mesh shape are separately produced. To do. And the woven fabric 110 and the woven fabric 120 are bonded together, and the electrode base material 200 is produced. In the pasting, for example, a portion where each fiber intersects may be bonded with an adhesive, or may be bonded to each other by melting the surface layer of the fiber. At this time, a plurality of low water-repellent fibers 102 and a plurality of high water-repellent fibers 104 are bonded so as to be alternately arranged.

  Thereby, a region R1 where the low water-repellent fibers 102 are unevenly distributed and a region R2 where the high water-repellent fibers 104 are unevenly formed are formed. In the method of this embodiment, in the woven fabric 110 and the woven fabric 120, the region R1 in which the low water-repellent fibers 102 are unevenly distributed and the region R2 in which the high water-repellent fibers 104 are unevenly formed are formed in desired locations. Thus, the region R1 surrounded by the low water-repellent fibers 102 and the region R2 surrounded by the high water-repellent fibers 104 can be easily formed at desired locations on the electrode substrate.

  In Example 6, the woven fabrics are bonded to each other and the electrode base material is bonded, but an electrode base material in which the woven fabrics are woven may be used. Alternatively, instead of the woven fabric as shown in FIG. 4, an electrode base material in which nonwoven fabrics are bonded together may be used. It should be noted that the woven region or the bonded region may be the entire electrode substrate or a part thereof. Further, the woven or pasted regions are not necessarily formed regularly, and may be unevenly distributed as appropriate.

  Moreover, it is also possible to use metal fibers other than stainless steel fiber in each of the above-described embodiments. For example, periodic table 4A group element, periodic table 5A group element, periodic table 6A group element, periodic table group 8 element, period It may be an alloy or a mixture made of at least one metal of Table 1B group elements, or a combination thereof. Further, as the resin fiber, for example, a material having high water repellency such as PFA, FEP, ETFE or the like can be used.

  Further, according to Examples 3 to 5, it becomes possible to provide a difference in water repellency without using a water repellent material, which contributes to a reduction in man-hours and a reduction in production variations due to the elimination of the water repellent treatment process using the water repellent material. To do.

  As described above, the present invention has been described with reference to the above-described embodiments. However, the present invention is not limited to the above-described embodiments, and the configurations of the embodiments are appropriately combined or replaced. Those are also included in the present invention. Further, based on the knowledge of those skilled in the art, the order of the manufacturing method in each embodiment is appropriately changed, and various modifications such as design changes in the electrode substrate, membrane electrode assembly, and fuel cell are made to each embodiment. Embodiments to which such modifications are added can also be included in the scope of the present invention.

1 is a perspective view schematically showing the structure of a fuel cell according to a first embodiment. It is sectional drawing on the AA line of FIG. It is a top view of the principal part of the electrode base material which concerns on embodiment. It is the figure which showed typically the preparation method of the electrode base material in Example 6. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell, 20 Solid polymer electrolyte membrane, 22 Anode, 24 Cathode, 26 Catalyst layer, 28 Gas diffusion layer, 30 Catalyst layer, 32 Gas diffusion layer, 34 Separator, 36 Separator, 38 Gas flow channel, 40 Gas flow channel 50 membrane electrode assembly, 100 electrode base material, 102 low water repellency fiber, 104 high water repellency fiber, 110 woven fabric, 120 woven fabric, 200 electrode base material.

Claims (13)

An electrode base material constituting a part of an electrode provided on the surface of an electrolyte membrane for a fuel cell,
A first fiber made of metal fiber or carbon fiber;
A second fiber made of a metal fiber or carbon fiber having higher water repellency than the first fiber;
An electrode substrate characterized by comprising: The first fiber and the second fiber are both carbon fibers,
The electrode base material according to claim 1, wherein the graphitization degree of the second fiber is higher than the graphitization degree of the first fiber.   The metal fiber contains at least one of stainless steel, periodic table group 4A element, periodic table group 5A element, periodic table group 6A element, periodic table group 8 element, periodic table group 1B element. The electrode base material according to claim 1.   The electrode substrate according to any one of claims 1 to 3, comprising a region in which the first fibers are unevenly distributed and a region in which the second fibers are unevenly distributed. An electrode base material constituting a part of an electrode provided on the surface of an electrolyte membrane for a fuel cell,
A first fiber made of metal fiber or carbon fiber;
A second fiber made of a resin fiber having higher water repellency than the first fiber,
An electrode base material comprising a region where the first fibers are unevenly distributed and a region where the second fibers are unevenly distributed. In the region where the first fibers are unevenly distributed, a space surrounded by the first fibers is formed,
The electrode base material according to claim 4 or 5, wherein a space surrounded by the second fiber is formed in a region where the second fiber is unevenly distributed.   The electrode substrate according to any one of claims 1 to 6, wherein the first fibers and the second fibers are bonded without being woven.   The electrode base material according to any one of claims 1 to 6, wherein the electrode base material is a woven fabric in which the first fibers and the second fibers are woven.   A plurality of the first fibers and the second fibers are alternately arranged in parallel with each other in a predetermined direction, and the first fibers and the second fibers intersect the predetermined direction. The electrode base material according to claim 8, wherein the electrode base material has a plurality of regions alternately arranged in parallel in a direction aligned.   An electrode comprising the electrode base material according to claim 1 and a catalyst layer. An electrolyte membrane;
The electrode according to claim 10 provided on the surface of the electrolyte membrane;
A membrane electrode assembly comprising:   A fuel cell comprising the membrane electrode assembly according to claim 11 incorporated therein. A method for producing an electrode base material constituting a part of an electrode provided on the surface of an electrolyte membrane for a fuel cell,
A preparation step of preparing a first fiber made of metal fiber or carbon fiber and a second fiber made of metal fiber or carbon fiber having higher water repellency than the first fiber;
A plurality of the first fibers and the second fibers are alternately arranged so that a region where the first fibers are unevenly distributed and a region where the second fibers are unevenly formed are formed. A joining step to
The manufacturing method of the electrode base material characterized by including.

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