JP2009181738A - Manufacturing method of porous carbon electrode base material, and membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a porous carbon electrode base material, a membrane-electrode assembly using the same, capable of alleviating damage to a polymer electrolyte membrane used for a solid polymer fuel cell, with high gas permeability maintained. <P>SOLUTION: In the manufacturing method of the porous carbon electrode base material, at least one of the surfaces of a carbon sheet having carbon staple fiber bound with carbon with a bulk density of 0.27 g/cm<SP>3</SP>or less is brushed with a goat hair brush. The porous carbon electrode base material thus obtained is arranged in the membrane-electrode assembly with the brushed face put inward. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a porous carbon electrode substrate suitably used for a polymer electrolyte fuel cell and a membrane-electrode assembly.

  A polymer electrolyte fuel cell is characterized by using a proton-conducting polymer electrolyte membrane, and is an apparatus for obtaining an electromotive force by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as oxygen. . The polymer electrolyte fuel cell can be used as a self-power generation device or a power generation device for a moving body such as an automobile.

  Such a polymer electrolyte fuel cell has a polymer electrolyte membrane that selectively conducts hydrogen ions (protons). In addition, a gas diffusion electrode having a catalyst layer mainly composed of carbon powder supporting a noble metal catalyst and a porous carbon electrode substrate was bonded to both surfaces of the polymer electrolyte membrane with the catalyst layer side inside. It has a structure.

  Such a joined body composed of a polymer electrolyte membrane and two gas diffusion electrodes is called a membrane-electrode assembly (MEA). In addition, separators are provided on both outer sides of the MEA so as to supply a fuel gas or an oxidizing gas and to form a gas flow path for the purpose of discharging generated gas and excess gas.

  The porous carbon electrode substrate mainly has the following three functions. The first function is to supply the fuel gas or the oxidizing gas uniformly to the noble metal catalyst in the catalyst layer from the gas flow path formed in the separator disposed outside the porous carbon electrode substrate. The second function is to discharge water generated by the reaction in the catalyst layer. The third function is to conduct electrons necessary for the reaction in the catalyst layer or generated electrons to the separator.

  Therefore, the porous carbon electrode base material is required to have reactive gas and oxidizing gas permeability, water dischargeability, and electronic conductivity. Furthermore, in order to improve the power generation performance of the polymer electrolyte fuel cell and promote cost reduction, it is necessary to operate in a high power density region, and the porous carbon electrode base material has a low bulk density and is high. It is required to have gas permeability. Further, in a general solid polymer fuel cell, the porous carbon electrode base material is bonded to both sides of the polymer electrolyte membrane by pressure when the MEA is manufactured, and is sandwiched between two separators and fastened. It is necessary to reduce damage to the polymer electrolyte membrane that causes cross-leakage of reaction gas due to the carbon material in the porous carbon electrode base material penetrating into the polymer electrolyte membrane, and micro shorts between the anode and cathode. It has been.

The most common technique for reducing cross-leakage of reactive gases and micro-shorts between the anode and cathode electrodes, and reducing damage to the polymer electrolyte membrane, is a dense material made of fluororesin or carbon black. A technique of applying a layer onto a porous carbon electrode substrate is used. As another method, Patent Document 1 includes a porous sheet-like support made of a synthetic resin, and a coating layer made of conductive carbon particles and a thermoplastic resin that covers the sheet-like support. A gas diffusion layer for a fuel cell is disclosed. Patent Document 2 discloses a membrane-electrode assembly comprising a polymer electrolyte membrane, a catalyst layer provided on the surface of the polymer electrolyte membrane, and a diffusion layer provided on the surface of the catalyst layer. In the polymer electrolyte fuel cell provided, the catalyst layer has a fibrous conductive material, and the content of the conductive material in the vicinity of the end region of the diffusion layer in the thickness direction of the catalyst layer is A solid polymer fuel cell is disclosed in which the content of the conductive material in a region in the vicinity of the end of the polymer electrolyte membrane is greater than that of the polymer electrolyte membrane. Patent Document 3 discloses that part or all of the fiber fluff on at least one surface of the carbon cloth is cut or broken with a shaver.
JP 2004-152744 A JP 2005-228601 A JP 2007-149613 A

However, the technique of applying a dense layer on the porous carbon electrode substrate has a problem that the physical properties such as gas permeability of the porous carbon electrode substrate change by forming the dense layer. There are limitations on the composition, structure, and thickness of the dense layer. In the method described in Patent Document 1, in order to reduce the damage of the polymer electrolyte membrane causing the cross leak of the reaction gas and the micro short circuit between the anode and the cathode, the synthesis is performed without using the porous carbon electrode substrate. Since the gas diffusion electrode is formed of a coating layer made of conductive carbon particles and a thermoplastic resin in the form of a porous sheet made of resin, it becomes difficult to obtain sufficient gas diffusibility and electrical conductivity. Further, in the method described in Patent Document 2, since a small amount of fibrous material is contained in the catalyst layer in the region in contact with the polymer electrolyte membrane, the reaction gas cross-leakage and between the anode and cathode both electrodes. It is difficult to sufficiently reduce the damage of the polymer electrolyte membrane that causes a micro short circuit.
Further, in the method described in Patent Document 3, it is possible to remove the fluff of the carbon cloth in a state where no load is applied, but the porous carbon electrode base material is deformed due to the load when incorporated in the fuel cell. It is difficult to remove sufficient fluff in the state. Further, in the sheet-like porous carbon electrode base material having a papermaking structure, the short carbon fibers are oriented in a substantially two-dimensional plane, and therefore the fibers that are fluffy compared to the carbon carbon porous carbon electrode base material. However, it is difficult to sufficiently reduce the damage of the polymer electrolyte membrane that causes cross-leakage of the reaction gas and micro short-circuit between the anode and cathode electrodes by the method described in Patent Document 3.

  In order to reduce damage to the polymer electrolyte membrane, it is possible to increase the mechanical strength of the polymer electrolyte membrane or increase the film thickness, but in general increase the mechanical strength. The proton conduction resistance increases by increasing the film thickness, and the power generation performance decreases when used in a polymer electrolyte fuel cell. Therefore, the mechanical strength of the polymer electrolyte membrane used in the polymer electrolyte fuel cell is reduced. There is a limit to film thickness.

  The present invention relates to a method for producing a porous carbon electrode substrate and a membrane-electrode assembly capable of reducing damage to a polymer electrolyte membrane used in a polymer electrolyte fuel cell while maintaining high gas permeability. The purpose is to provide.

The present invention is as follows.
(1) A method for producing a porous carbon electrode substrate, in which at least one surface of a carbon sheet having a bulk density of 0.27 g / cm ³ or less obtained by binding short staple fibers with carbon is printed with a goat hair brush. (2) Provided on the outer sides of the polymer electrolyte membrane, the cathode-side catalyst layer and the anode-side catalyst layer provided on both surfaces of the polymer-electrolyte membrane, and the cathode-side catalyst layer and the anode-side catalyst layer, respectively. A membrane-electrode assembly having an anode-side porous carbon electrode substrate and a cathode-side porous carbon electrode substrate, wherein at least one of the anode-side porous carbon electrode substrate and the cathode-side porous carbon electrode substrate On the other hand, there is a membrane-electrode assembly in which the porous carbon electrode substrate of (1) is arranged with the surface printed with a brush facing inward.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and membrane-electrode of the porous carbon electrode base material which can reduce the damage to the polymer electrolyte membrane used for a polymer electrolyte fuel cell, maintaining high gas permeability A joined body can be provided.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a membrane-electrode assembly and a polymer electrolyte fuel cell using a porous carbon electrode substrate according to the present invention. As shown in FIG. 1, the membrane-electrode assembly and the polymer electrolyte fuel cell according to this embodiment include a cathode side made of an oxidizing gas catalyst on one surface of a polymer electrolyte membrane 1 having proton conductivity. The catalyst layer 2 is provided with an anode side catalyst layer 3 made of a catalyst for fuel gas on the other side, and the cathode side porous carbon electrode substrate 4 and the anode side are provided outside the catalyst layers 2 and 3, respectively. A porous carbon electrode substrate 5 is provided. Here, the portion composed of the polymer electrolyte membrane 1, the catalyst layers 2 and 3, and the porous carbon electrode base materials 4 and 5 is the membrane-electrode assembly 6. Furthermore, a cathode-side separator 7 in which a cathode-side gas flow path 13 is formed and an anode-side separator 8 in which an anode-side gas flow path 14 is formed are provided so as to sandwich the membrane-electrode assembly 6. Each separator 7, 8 is provided with an oxidizing gas introducing part 9 and an oxidizing gas discharging part 10, and a fuel gas introducing part 11 and a fuel gas discharging part 12.

  In such a polymer electrolyte fuel cell, the fuel gas is introduced from the fuel gas introduction part 11 and from the anode side gas flow path 14 formed in the anode side separator 8 through the anode side porous carbon electrode substrate 5. Is supplied to the anode catalyst layer 3 and dissociated into protons and electrons. The electrons are conducted from the anode side catalyst layer 3 to the anode side separator 8 through the anode side porous carbon electrode base material 5 and supplied to an external load. Protons are conducted through the polymer electrolyte membrane 1 and move to the cathode side. On the other hand, the oxidizing gas is introduced from the oxidizing gas introduction part 9 and supplied to the cathode side catalyst layer 2 through the cathode side porous carbon electrode substrate 4 from the cathode side gas flow path 13 formed in the cathode side separator 7. In combination with protons conducted through the polymer electrolyte membrane 1, water is generated. In this way, a desired electromotive force can be taken out.

  As the polymer electrolyte membrane 1, it is preferable to use a polymer into which proton dissociable groups such as —OH group, —OSO 3 H group, —COOH group, —SO 3 H group and the like are introduced. Is more preferable from the viewpoints of chemical stability and proton conductivity.

  Examples of the catalyst constituting the cathode side catalyst layer 2 and the anode side catalyst layer 3 include platinum, platinum alloy, palladium, magnesium, vanadium, etc., but platinum or platinum alloy is preferably used. The catalyst preferably constitutes each catalyst layer in a state of being supported on a carrier such as carbon powder.

  As the cathode-side separator 7 and the anode-side separator 8, the same separators as in the past can be used.

  The porous carbon electrode substrate according to the present invention is used for at least one of the anode side porous carbon electrode substrate and the cathode side porous carbon electrode substrate. Here, the porous carbon electrode substrate according to the present invention is manufactured by printing at least one surface of a carbon sheet having a bulk density of 0.27 g / cm 3 or less obtained by binding carbon short fibers with carbon with a brush. The Then, as at least one of the anode side porous carbon electrode substrate and the cathode side porous carbon electrode substrate, the porous carbon electrode substrate according to the present invention is arranged with the surface printed with a brush facing inward. . The porous carbon electrode base material according to the present invention is disposed on both the anode side porous carbon electrode base material and the cathode side porous carbon electrode base material with the surface printed with a brush facing inward. preferable. When the porous carbon electrode substrate according to the present invention is used for one of the anode-side porous carbon electrode substrate and the cathode-side porous carbon electrode substrate, the same porous carbon electrode substrate as that used in the past is used for the other. You can also.

  The porous carbon electrode substrate according to the present invention can be obtained by printing at least one surface of a carbon sheet having a bulk density of 0.27 g / cm 3 or less obtained by binding carbon short fibers with carbon with a goat hair brush. .

  The carbon sheet is preferably a paper body made up of a plurality of short carbon fibers having high surface smoothness, good electrical contact, and high mechanical strength.

  The short carbon fiber can be used regardless of the raw material, but one or more selected from polyacrylonitrile (hereinafter abbreviated as PAN) carbon fiber, pitch carbon fiber, rayon carbon fiber, and phenolic carbon fiber. It is preferable that the carbon fiber is included, and it is more preferable that the PAN-based carbon fiber is included.

  The average diameter of the short carbon fibers is preferably about 3 to 30 μm, more preferably 4 to 20 μm, and still more preferably 4 to 8 μm. Within this range, surface smoothness and high conductivity can be imparted.

  The length of the short carbon fiber is preferably 2 to 12 mm, and more preferably 3 to 9 mm. Within this range, dispersibility and mechanical strength during papermaking can be enhanced.

  As a carbon material for binding the short carbon fibers to each other, a carbon material obtained by carbonizing a resin by heating can be used. The resin used for this purpose can be appropriately selected from known resins that can bind the carbon fibers of the porous carbon electrode substrate at the stage of carbonization. From the viewpoint of easily remaining as a conductive substance after carbonization, a phenol resin, an epoxy resin, a furan resin, pitch, and the like are preferable, and a phenol resin having a high carbonization rate upon carbonization by heating is particularly preferable.

  Carbonization of the carbon material can be performed by firing at 1500 to 2200 ° C. in an inert gas.

In order to give the porous carbon electrode base material high gas permeability, the bulk density of the carbon sheet is preferably 0.27 g / cm ³ or less. 0.18 to 0.27 g / cm ³ is more preferable, and 0.20 to 0.26 g / cm ³ is more preferable.
Within this range, it is preferable in that it has sufficient mechanical strength while maintaining high gas permeability.

  The porous carbon electrode substrate is pressed at a pressure of about 0.2 MPa to 3.0 MPa when it is incorporated into a polymer electrolyte membrane and a catalyst layer, or hot press for bonding to a fuel cell. At this time, short carbon fibers that fall off the porous carbon electrode base material and carbon binding carbon short fibers cause damage to the polymer electrolyte membrane. Therefore, carbon short fibers and carbon short fibers that fall off the porous carbon electrode substrate are removed by printing with a goat hair brush before the porous carbon electrode substrate is pressurized. As a result, damage to the polymer electrolyte membrane can be reduced. In a membrane-electrode assembly or a polymer electrolyte fuel cell, the porous carbon electrode substrate according to the present invention is arranged with the surface printed with a goat hair facing inward, When the electrode assembly is assembled, damage to the polymer electrolyte membrane due to the carbon short fibers and the carbon binding the carbon short fibers due to pressurization during production of the solid polymer fuel cell or during power generation can be reduced.

  The brush is preferably made of a material that is softer than the carbon material constituting the porous carbon electrode substrate, and goat hair is particularly preferable.

  As a printing method, it is preferable to print the same portion 5 to 35 times with a brush, and particularly preferably 10 to 30 times. Within this range, the leakage current is significantly reduced.

  In a polymer electrolyte fuel cell, water as an electrode reaction product and water penetrating a polymer electrolyte membrane are generated on the cathode side. Further, humidified fuel is supplied on the anode side to suppress drying of the polymer electrolyte membrane. Therefore, the porous carbon electrode substrate according to the present invention can also contain a water-repellent polymer as a water-repellent agent in order to ensure gas permeability in a humidified gas atmosphere. As the water-repellent polymer, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether, which is chemically stable and has high water repellency. It is preferable to use a fluororesin such as a copolymer (PFA).

  As a method for introducing the water-repellent polymer into the porous carbon electrode substrate, a dip method in which the porous carbon electrode substrate is immersed in a dispersion in which fine particles of the water-repellent polymer are dispersed, or spraying the dispersion A spray method or the like is preferable.

[Example 1]
As carbon short fibers, 100 parts by mass of PAN-based carbon short fibers having an average diameter of 7 μm cut to a length of 3 mm and polyvinyl alcohol (PVA) fibers having a length of 3 mm (trade name: VBP105-1, manufactured by Kuraray Co., Ltd.) 11 After mass parts were dispersed in water and continuously formed on a wire mesh, they were dried to obtain carbon fiber paper.
100 parts by mass of this carbon fiber paper is impregnated with a methanol solution of a phenol resin (trade name: Phenolite J-325, manufactured by Dainippon Ink and Chemicals), and the methanol is sufficiently dried at room temperature, so that the nonvolatile content of the phenol resin 84 mass parts of phenol resin impregnated carbon fiber paper was obtained.
Two sheets of this phenol resin-impregnated carbon fiber paper were stacked and roll-pressed at a linear force of 8 × 10 ⁴ N / m at a temperature of 250 ° C. to cure the phenol resin. Then, it carbonized continuously in a 1900 degreeC furnace in nitrogen gas atmosphere, and obtained the carbon sheet which consists of a papermaking body of the carbon short fiber whose bulk density is 0.26 g / cm < ³ >.
One surface of this carbon sheet is covered with a goat hair brush (a cosmetic cheek brush with a diameter of 1.8 cm and a length of 3.8 cm, product name: slide cheek brush, manufactured by Kiyoshi Shinda Co., Ltd.). Reprinting was performed to obtain a porous carbon electrode substrate. The obtained porous carbon electrode substrate had a low leakage current of 9.9 mA / cm @ 2 and exhibited good characteristics.

[Example 2]
A porous carbon electrode substrate was obtained in the same manner as in Example 1 except that printing was performed 20 times. The obtained porous carbon electrode substrate showed a good characteristic with a low leakage current of 8.7 mA / cm @ 2.

Example 3
A porous carbon electrode substrate was obtained in the same manner as in Example 1 except that printing was performed 30 times. The obtained porous carbon electrode base material had a low leakage current of 10.1 mA / cm ² and exhibited good characteristics.

Example 4
As carbon short fibers, 25 parts of PAN-based carbon short fibers having an average diameter of 7 μm cut to a length of 3 mm and polyvinyl alcohol (PVA) fibers having a length of 3 mm (trade name: VBP105-1, manufactured by Kuraray Co., Ltd.) are 25. Mass parts are dispersed in water and manually using a standard square sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd., trade name: No. 2555 standard square sheet machine) according to JIS P-8209 method. Papermaking was performed and dried to obtain a carbon fiber paper.
100 parts by mass of this carbon fiber paper is impregnated with a methanol solution of a phenol resin (trade name: Phenolite J-325, manufactured by Dainippon Ink Chemical Co., Ltd.), and the methanol is sufficiently dried at room temperature. Of carbon fiber paper impregnated with 100 parts by mass of phenol resin was obtained.
Two sheets of this phenol resin-impregnated carbon fiber paper were stacked and heated and pressurized for 3 minutes at 180 ° C. and 3 MPa in a batch press apparatus to cure the phenol resin. Then, the carbon sheet which consists of a papermaking body of the carbon short fiber whose bulk density is 0.25g / cm < ³ > by performing carbonization processing in a nitrogen gas atmosphere at the furnace internal temperature of 2000 degreeC in a batch carbonization furnace for 1 hour. Got.
One surface of this carbon sheet was printed ten times with a goat hair brush to obtain a porous carbon electrode substrate. The obtained porous carbon electrode base material had a low leakage current of 11.3 mA / cm ² and exhibited good characteristics.

Example 5
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the bulk density was 0.23 g / cm ³ . The obtained porous carbon electrode substrate showed a good characteristic with a low leak current of 11.4 mA / cm ² .

Example 6
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the bulk density was 0.22 g / cm ³ . The obtained porous carbon electrode base material showed a good characteristic with a low leakage current of 10.4 mA / cm ² .

Example 7
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the bulk density was 0.20 g / cm ³ . The obtained porous carbon electrode base material had a low leakage current of 11.3 mA / cm ² and exhibited good characteristics.

[Comparative Example 1]
A porous carbon electrode substrate was obtained in the same manner as in Example 1 except that the brush was not printed. The obtained porous carbon electrode base material had a leakage current of 12.7 mA / cm ² , which was higher than that of Example 1.

[Comparative Example 2]
While attaching a wool brush (a cosmetic brush with a diameter of 2.5 cm and a length of 5 cm) around the suction port, using a suction device that is fixed so that the suction port is almost covered with the brush. A porous carbon electrode substrate was obtained in the same manner as in Example 1 except that the same portion was printed 10 times with a woolen brush. The suction power of this suction device was 260 W, and the suction time was 10 seconds. The obtained porous carbon electrode base material had a leakage current of 12.8 mA / cm 2 and a higher leakage current than that of Example 1.

[Comparative Example 3]
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the brush was not printed. The obtained porous carbon electrode base material had a leakage current of 12.0 mA / cm ² and showed a higher leakage current than that of Example 4.

[Comparative Example 4]
A porous carbon electrode base material was obtained in the same manner as in Example 4 except that the bulk density was 0.23 g / cm ³ and it was not printed with a brush. The obtained porous carbon electrode base material had a leakage current of 13.7 mA / cm ² and a higher leakage current than that of Example 5.

[Comparative Example 5]
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the bulk density was 0.22 g / cm ³ and the brush was not printed. The obtained porous carbon electrode base material had a leak current of 14.0 mA / cm ² , which was higher than that of Example 6.

[Comparative Example 6]
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the bulk density was 0.20 g / cm ³ and the brush was not printed. The obtained porous carbon electrode base material had a leak current of 14.3 mA / cm ² , which was higher than that of Example 7.

Example 8
A porous carbon electrode substrate was obtained in the same manner as in Example 4 except that the bulk density was 0.27 g / cm ³ . The obtained porous carbon electrode base material had a leakage current of 9.3 mA / cm @ 2, indicating a low leakage current.

[Comparative Example 7]
A porous carbon electrode base material was obtained in the same manner as in Example 4 except that the bulk density was 0.27 g / cm ³ and it was not printed with a brush. The obtained porous carbon electrode base material had a leak current of 9.9 mA / cm 2 and showed a slightly higher leak current than that of Example 8.

  Tables 1 and 2 show the results of the measured leakage current and bulk density.

[Measurement method of leakage current]
On one side of a perfluorosulfonic acid polymer electrolyte membrane (film thickness: 30 μm), the surface treated surface of the obtained porous carbon electrode substrate (in the case of Comparative Examples 1 and 3-7, either one of them) The surface is placed in contact with each other, sandwiched between gold-plated copper plate electrodes, pressurized to 2.5 MPa, and then a digital multimeter TR6487 (manufactured by Advantest) is used to cause leakage current due to damage to the polymer electrolyte membrane. Was measured. The potential difference between the electrodes at this time was 0.6V.

Example 9
(1) Production of membrane-electrode assembly Two sets of the porous carbon electrode base material obtained in Example 1 were prepared for the cathode and the anode. A perfluorosulfonic acid polymer having a catalyst layer (catalyst layer area: 25 cm 2, Pt adhesion amount: 0.3 mg / cm 2) made of catalyst-supported carbon (catalyst: Pt, catalyst support amount: 50 mass%) on both surfaces The electrolyte membrane (film thickness: 30 μm) was sandwiched with the surfaces of the two sets of porous carbon electrode base materials printed with the brush, and these were joined to obtain a membrane-electrode assembly.
(2) Evaluation of fuel cell characteristics of membrane-electrode assembly The membrane-electrode assembly produced in (1) above was sandwiched between two carbon separators having bellows-like gas flow paths, and a polymer electrolyte fuel cell ( Single cell).
This single cell was evaluated for fuel cell characteristics by measuring current density-voltage characteristics. Hydrogen gas was used as the fuel gas, and air was used as the oxidizing gas. As measurement conditions, the cell temperature was 80 ° C., the fuel gas utilization rate was 60%, and the oxidizing gas utilization rate was 40%. Gas humidification was performed by passing fuel gas and oxidizing gas through a bubbler at 70 ° C., respectively.

  As a result, when the current density is 0.4 A / cm 2, the cell voltage of the fuel cell is 0.687 V, the open circuit voltage is as high as 0.938 V, and the cross leak between the anode and the cathode and the micro short circuit are small. It showed good characteristics.

[Comparative Example 8]
A single cell was assembled in the same manner as in Example 9 except that the porous carbon electrode substrate obtained in Comparative Example 1 was used, and the fuel cell characteristics were evaluated.

  As a result, the cell voltage of the fuel cell when the current density was 0.4 A / cm 2 was 0.687 V, but the open circuit voltage was 0.911 V, which is lower than that of Example 9, and between the anode and the cathode The cross-leakage and the micro short circuit showed the characteristic which increased from Example 9.

It is a typical sectional view showing one form of a polymer electrolyte fuel cell of the present invention.

Explanation of symbols

1: Polymer electrolyte membrane 2: Cathode side catalyst layer 3: Anode side catalyst layer 4: Cathode side porous carbon electrode base material 5: Anode side porous carbon electrode base material 6: Membrane-electrode assembly (MEA)
7: Cathode side separator 8: Anode side separator 9: Oxidizing gas introduction part 10: Oxidizing gas discharge part 11: Fuel gas introduction part 12: Fuel gas discharge part 13: Cathode side gas flow path 14: Anode side gas flow path

Claims (2)

A method for producing a porous carbon electrode base material, wherein at least one surface of a carbon sheet having a bulk density of 0.27 g / cm ³ or less obtained by binding carbon short fibers with carbon is printed with a goat hair brush.   A polymer electrolyte membrane; a cathode side catalyst layer and an anode side catalyst layer provided on both sides of the polymer electrolyte membrane; and an anode side provided on the outside of each of the cathode side catalyst layer and the anode side catalyst layer A membrane-electrode assembly having a porous carbon electrode substrate and a cathode-side porous carbon electrode substrate, wherein at least one of the anode-side porous carbon electrode substrate and the cathode-side porous carbon electrode substrate, 2. A membrane-electrode assembly in which the porous carbon electrode substrate according to claim 1 is arranged with the surface printed with a brush facing inward.

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