JP2007227009A - Porous carbon electrode substrate and fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous carbon electrode substrate in which demonstration of moisture control function in a fuel cell is facilitated and uniformity of moisture control function on a surface can be improved, and a fuel cell equipped with the same. <P>SOLUTION: A porous carbon electrode substrate is used in which a water repellent is applied to one or more sheets of the conductive porous substrate made of the same carbon material, and at least two sheets of the conductive porous substrates made of the carbon material which have different amounts of water repellent are laminated in order of the amount of water repellent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a porous carbon electrode substrate used for a polymer electrolyte fuel cell, a fuel cell using the same, and the like.

  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 needs to have high reactive gas and oxidizing gas permeability, water dischargeability, and electronic conductivity. In addition, polymer electrolyte membranes used in general polymer electrolyte fuel cells exhibit proton conductivity in a water-containing state, so that the porous carbon electrode substrate is not only a drainage of produced water, but also a polymer. The contradictory function of water retention of the electrolyte membrane is required. In the case where the gas permeability of the porous carbon electrode base material is increased and the drainage capacity of the generated water is increased, the proton conduction resistance is increased by the drying of the polymer electrolyte membrane, and the power generation performance is decreased. On the other hand, in the case where the gas permeability of the porous carbon electrode substrate is lowered and the water retention capacity of the polymer electrolyte membrane is increased, power generation performance is achieved by flooding in which the diffusion of reaction gas and oxidizing gas is hindered due to poor drainage of generated water Decreases.

For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-109604) discloses a technique for suppressing flooding and a decrease in gas diffusibility resulting therefrom, and a catalyst layer comprising a carbon powder supporting a catalyst and a polymer electrolyte, A gas diffusion electrode comprising a porous substrate made of a carbon material and supporting the catalyst layer, and a water repellent applied to the porous substrate, wherein the water repellent in the porous substrate A fuel cell gas diffusion electrode is disclosed in which the amount continuously changes from the side in contact with the catalyst layer toward the other side.
JP 2003-109604 A

  The porous carbon electrode base material used in the polymer electrolyte fuel cell requires a moisture management function inside the polymer electrolyte fuel cell such as drainage of generated water and water retention of the polymer electrolyte membrane. In order to develop this moisture management function, water repellents such as fluororesins and methods of dispersing oxides such as silica in porous carbon electrode base materials have been used. Water repellents such as these fluororesins Since oxides such as silica and silica are often insulators, there is a problem in that the conductivity decreases when oxides such as fluororesin and silica are dispersed in the porous carbon electrode substrate. There is a limit on the amount.

  In addition, for the manifestation of this moisture management function, the generated water exists in a liquid state on the side in contact with the polymer electrolyte membrane, but in the porous carbon electrode base material, diffusion of fuel gas or oxidizing gas Since a path must be secured, it is necessary to move the surplus generated water as water vapor that is in a gaseous state rather than a liquid state through the porous carbon electrode substrate. Therefore, it is necessary to develop different moisture management functions on the side of the porous carbon electrode substrate that contacts the catalyst layer and the side of the porous carbon electrode substrate that contacts the separator.

  In addition, in order to express the moisture management function, the amount of adhesion of water repellent and the like is continuously controlled in the thickness direction in the porous carbon electrode substrate, and the amount of adhesion is accurately controlled. It is difficult to make the performance of the polymer electrolyte fuel cell uniform within the electrode area.

  The present invention solves the above-mentioned problems of the prior art, facilitates the expression of the moisture management function inside the fuel cell of the porous carbon electrode substrate, and improves the uniformity of the moisture management function in the plane. It is an object of the present invention to provide a porous carbon electrode substrate that can be made high and a fuel cell using the same.

  The above-mentioned problem is that two identical porous carbon electrode substrates that are one of the main components of the present invention are laminated, and the amount of water repellent applied to the laminated porous carbon electrode substrates is different. Solved by a porous carbon electrode substrate.

  That is, the present invention provides a conductive porous substrate made of the above carbon material in which a water repellent is applied to one or more of the conductive porous substrates made of the same carbon material and the amount of the water repellent is different. It is related with the porous carbon electrode base material characterized by laminating | stacking at least 2 of these in order of the amount of water-repellent agents.

  According to the present invention, one or more conductive porous substrates made of the same carbon material are provided with a water repellent, and the conductive porous groups made of the carbon material differ in the amount of the water repellent. By laminating at least two of the materials in the order of the amount of water repellent, the amount of water repellent varies stepwise as a porous carbon electrode substrate, and the amount of water repellent of each conductive porous substrate to be laminated Therefore, it is possible to increase the uniformity of the moisture management function in the plane by combining them.

  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 fuel cell using a porous carbon electrode substrate proposed in the present invention.

  As shown in FIG. 1, the polymer electrolyte fuel cell according to this embodiment includes a cathode-side catalyst layer 2 made of an oxidizing gas catalyst on one side of a polymer electrolyte membrane 1 having proton conductivity, and the other side. Comprises an anode side catalyst layer 3 made of a catalyst for fuel gas, and a cathode side porous carbon electrode base material 4 made of short carbon fibers 4 and an anode side porous carbon electrode base material 5 made of carbon short fibers outside each catalyst layer. Is provided. Further, the cathode in which the cathode-side gas flow path 13 is formed so as to sandwich the membrane-electrode assembly 6 composed of the polymer electrolyte membrane 1, the catalyst layers 2 and 3, and the porous carbon electrode base materials 4 and 5. A side separator 7 and an anode side separator 8 having an anode side gas flow path 14 are provided.

  Each separator is provided with an oxidizing gas introduction part 9 and a discharge part 10, and a fuel gas introduction part 11 and a discharge part 12. The fuel gas is introduced from the introduction part 11 and supplied to the catalyst layer 3 through the porous carbon electrode substrate 5 from the gas flow path 14 formed in the anode side separator 8 and dissociated into protons and electrons. The electrons are conducted from the catalyst layer 3 to the separator 8 through the porous carbon electrode substrate 5 and supplied to an external load. Protons are conducted through the polymer electrolyte membrane 1 and move to the cathode. On the other hand, the oxidizing gas is introduced from the introduction part 9 and supplied to the catalyst layer 2 through the porous carbon electrode substrate 4 from the gas flow path 13 formed in the cathode side separator 7 and is conducted through the polymer electrolyte membrane 1. It combines with the protons that have been generated to produce water. In this way, a desired electromotive force can be taken out.

  FIG. 2 is a schematic cross-sectional view showing an example of a porous carbon electrode substrate proposed in the present invention. The porous carbon electrode substrate according to the present invention includes a water repellent agent applied to one or more conductive porous substrates made of the same carbon material, and the amount of the water repellent agent is different from the carbon material. By stacking at least two conductive porous substrates, different moisture management functions are exhibited on the side in contact with the catalyst layer and the side in contact with the separator. As shown in FIG. 2 (a), two conductive porous substrates with different amounts of water repellent are laminated, as shown in FIG. 2 (b), three sheets of conductive with different amounts of water repellent. As shown in FIG. 2 (c), two conductive porous substrates having the same amount of water repellent and conductive porous substrates having a different amount of water repellent as shown in FIG. (In FIG. 2 (c), two conductive porous substrates with a small amount of water repellent agent and one conductive porous substrate with a large amount of water repellent agent are used, but this may be reversed.) The thing laminated | stacked etc. are mentioned. When three or more conductive porous substrates having different amounts of water repellent are used, they are combined so that the amount of water repellent increases or decreases sequentially from one surface to the other.

  As the conductive porous base material made of the carbon material according to the present invention, in the polymer electrolyte fuel cell, the inside is an acidic atmosphere, and therefore a carbon porous material having acid resistance is more preferable. The carbon porous material is preferably a carbon porous film, a woven fabric formed by aggregating a plurality of carbon fibers, or a paper body formed by aggregating a plurality of carbon short fibers, and has a high surface smoothness and electrical contact. A papermaking body formed by aggregating a plurality of short carbon fibers that is good in that the short circuit due to the piercing of the polymer electrolyte membrane is reduced is more preferable.

  Any carbon short fiber constituting the paper body can be used, but from polyacrylonitrile (hereinafter abbreviated as PAN) carbon fiber, pitch carbon fiber, rayon carbon fiber, phenolic carbon fiber. It is preferable to include one or more selected carbon fibers, and it is more preferable to include PAN-based carbon fibers.

  The average diameter of the short carbon fibers is preferably about 3 to 30 μm, more preferably 4 to 20 μm, and even more preferably 4 to 8 μm for imparting surface smoothness and conductivity. It is also preferable to use two or more types of short carbon fibers having different average diameters in order to achieve both surface smoothness and conductivity.

  The length of the short carbon fibers is preferably 3 mm or more and 12 mm or less, and more preferably 4 mm or more and 9 mm or less in order to improve the dispersibility during papermaking and the mechanical strength. 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.

Next, the membrane-electrode assembly proposed in the present invention will be described with reference to FIG.
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. It is more preferable to use an acid film from the viewpoint of chemical stability and proton conductivity.

  Examples of the catalyst include platinum, a platinum alloy, palladium, magnesium, vanadium, etc., but it is preferable to use platinum or a platinum alloy.

  In the polymer electrolyte fuel cell, water as an electrode reaction product and water penetrating the polymer electrolyte membrane are generated on the cathode side. On the anode side, humidified fuel is supplied to suppress drying of the polymer electrolyte membrane. From such points, the porous carbon electrode substrate according to the present invention includes a water-repellent polymer as a water-repellent agent in at least one conductive porous substrate in order to ensure gas permeability. Water-repellent polymers include chemically stable and highly water-repellent polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether. It is preferable to use a fluororesin such as a polymer (PFA).

  As a method for introducing a water-repellent polymer into the porous carbon electrode substrate, a dip method in which the porous substrate is immersed in a dispersion solution in which fine particles of the water-repellent polymer are dispersed, or a spray method in which the dispersion solution is sprayed However, a dipping method with a high uniformity of the introduction amount in the in-plane direction and the thickness direction is preferable.

  In addition, in order to evenly express different moisture management functions in the surface of the porous carbon electrode substrate on the surface side in contact with the catalyst layer of the porous carbon electrode substrate and on the surface side in contact with the separator, It is preferable to stack two or more porous carbon electrode substrates having the same physical properties but different amounts of molecules.

The amount of water-repellent polymer introduced is defined as follows.
Introduction amount of water-repellent polymer = mass per unit area of introduced water-repellent polymer / mass per unit area of porous substrate

  The amount of the water-repellent polymer introduced is preferably 0 to 50% by mass for manifesting the moisture management function of the porous carbon electrode substrate, and more preferably 0 to 40% by mass from the viewpoint of gas permeability and electrical resistance. .

  Moreover, it is preferable that the difference in the introduction amount of the water-repellent polymer between two or more superposed conductive porous substrates is 5% by mass or more. When the amount is less than 5% by mass, the difference in moisture management function is not clear, and a substantially uniform moisture management function appears in the thickness direction. Therefore, at least one conductive porous porous substrate contains 5% by mass or more of the water-repellent polymer.

  The porous carbon electrode substrate of the present invention has a water repellent so that the amount of water-repellent polymer introduced decreases toward the catalyst layer and polymer electrolyte membrane side mainly composed of carbon powder carrying a catalyst. It is preferable to arrange two or more conductive porous substrates having different amounts. Also, conductive porous substrates with different amounts of water repellent so that the amount of water repellent polymer introduced increases toward the catalyst layer and the polymer electrolyte membrane side mainly composed of carbon powder carrying the catalyst. It is also preferable to arrange two or more of them. Thereby, the water retention of the polymer electrolyte membrane is improved and flooding due to the generated water is suppressed.

  When a porous carbon electrode substrate is manufactured by laminating different conductive porous substrates, the thickness of each conductive porous substrate may be combined in any way as long as a desired moisture management function can be obtained. However, it is preferable to use the same thickness or to thicken the base material having a smaller amount of the water repellent introduced.

[Example 1]
30% by mass of PAN-based carbon short fibers cut to 3 mm length and 4 μm in average diameter and 70% by mass of PAN-based carbon short fibers cut to 3 mm in length and average diameter of 7 μm are dispersed in water The paper was continuously made on a wire mesh, and 28% by mass of polyvinyl alcohol (PVA) (trade name: VBP105-1, manufactured by Kuraray Co., Ltd.) was adhered as a binder, followed by drying to obtain carbon fiber paper.

  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. A phenol resin-impregnated carbon fiber paper adhered by mass% was obtained.

Two sheets of this carbon fiber paper impregnated with phenol resin are stacked and roll pressed by applying a pressure of 1.0 MPa at a temperature of 250 ° C. to cure the phenol resin, and in an inert gas (nitrogen) atmosphere at 1900 ° C. Carbonization was continuously performed to obtain a conductive porous substrate (thickness 115 μm, thickness direction gas permeability 420 ml / cm ² · hr · Pa) made of a short carbon fiber paper body.

  Two pieces of the conductive porous base material are impregnated in PTFE dispersion (trade name: PTFE dispersion, manufactured by Mitsui-DuPont Fluorochemical Co., Ltd.) having a concentration different from 10% by mass and 30% by mass, respectively. And then heat treated at 360 ° C. for 1 hour. Accordingly, the conductive porous substrate A containing 13% by mass of the water-repellent polymer compound and the conductive porous material containing 39% by mass of the water-repellent polymer compound with respect to each conductive porous substrate. A base material B was obtained. The amount of the introduced water-repellent polymer changed in the thickness direction by using one each of the conductive porous substrates A and B (thickness of 115 μm each) into which the water-repellent polymer compound was introduced and overlapping them. A porous carbon electrode substrate for a fuel cell was obtained.

  Table 1 shows the results of the introduction amount of the water-repellent polymer and the thickness after introduction of each porous substrate.

[Example 2]
Except for changing the PTEF dispersion concentration to 0% by mass and 20% by mass, in the same manner as in Example 1, the conductive porous substrate C into which the water-repellent polymer compound was not introduced (repels the porous substrate). A conductive porous substrate D in which 26% by mass of a water-repellent polymer was introduced with respect to the porous substrate was obtained. A porous carbon electrode substrate for a fuel cell in which the amount of introduced water-repellent polymer was changed in the thickness direction by using each of the obtained conductive porous substrates C and D one by one and overlapping them. Obtained. Further, the physical property values were measured as in Example 1. The measurement results are shown in Table 1.

[Comparative Example 1]
Four sheets of carbon fiber paper impregnated with phenol resin are stacked and roll pressed by applying a pressure of 1.0 MPa at a temperature of 250 ° C. to cure the phenol resin and continuously at 1900 ° C. in an inert gas (nitrogen) atmosphere. A carbonized conductive porous substrate (thickness 200 μm, thickness direction gas permeability 130 ml / cm ² · hr · Pa) was used in the same manner as in Example 1 except that the PTEF dispersion concentration was 20% by mass. Thus, a conductive porous substrate E into which 26% by mass of a water-repellent polymer was introduced with respect to the conductive porous substrate was obtained. Using this conductive porous substrate E alone, a porous carbon electrode substrate for a fuel cell was obtained in which the amount of water-repellent polymer introduced did not change in the thickness direction. Further, the physical property values were measured as in Example 1. The measurement results are shown in Table 1.

[Comparative Example 2]
Two conductive porous substrates D obtained in Example 2 were laminated to obtain a porous carbon electrode substrate for a fuel cell in which the amount of introduced water-repellent polymer did not change in the thickness direction.

[Comparative Example 3]
A conductive porous substrate F into which 13% by mass of a water repellent polymer was introduced was obtained in the same manner as in Comparative Example 1 except that the PTEF dispersion concentration was 10% by mass. Using only this conductive porous substrate F, a porous carbon electrode substrate for a fuel cell was obtained in which the amount of water-repellent polymer introduced did not change in the thickness direction. Further, the physical property values were measured as in Example 1. The measurement results are shown in Table 1.

[Comparative Example 4]
Two conductive porous substrates A obtained in Example 1 were laminated to obtain a porous carbon electrode substrate for a fuel cell in which the amount of introduced water-repellent polymer did not change in the thickness direction.

The characteristic evaluation of the porous carbon electrode substrate was performed as follows.
[Water repellent amount]
The amount of water repellent was calculated using the following formula.
Water repellent amount (% by mass) = mass per unit area of the introduced water-repellent polymer / mass per unit area of the porous substrate

[Thickness]
The thickness was measured using a dial thickness gauge 7321 (trade name, manufactured by Mitutoyo Corporation). Note that the size of the probe at this time was 10 mm in diameter and the measurement pressure was 1.5 kPa.

[Thickness direction gas permeability]
Based on JIS-P8117, a Gurley type densometer was used, and the time required for 200 mm ³ gas to pass through was measured and calculated.

Example 3
(1) Production of MEA Two sets of porous carbon electrode substrates of Example 1 were prepared for the cathode and the anode. Perfluorosulfonic acid-based polymer electrolyte in which a catalyst layer (catalyst layer area 25 cm ² , Pt attached amount 0.3 mg / cm ² ) made of catalyst-supported carbon (catalyst: Pt, catalyst support amount 50% by mass) is formed on both sides Membranes (thickness 30 μm) were sandwiched with the conductive porous substrate A side of the two sets of porous carbon electrode substrates as the inside, and these were joined to obtain MEA.

(2) Evaluation of MEA Fuel Cell Characteristics The MEA produced in (1) was sandwiched between two carbon separators having a bellows-like gas flow path to form a solid polymer fuel cell (single cell).

About this single cell, the fuel cell characteristic evaluation was performed by measuring a current density-voltage characteristic. Hydrogen gas was used as the fuel gas, and air was used as the oxidizing gas. 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 80 ° C., respectively. When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.624 V, and the internal resistance of the cell was 1.9 mΩ, showing good characteristics.

Example 4
When producing MEA, it carried out similarly to Example 3 except having pinched the polymer electrolyte membrane in which the catalyst layer was formed by making the electroconductive porous base material B side of the porous carbon electrode base material of Example 1 into the inner side. A single cell was assembled and evaluated.

When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.623 V, and the internal resistance of the cell was 2.0 mΩ, which showed good characteristics.

[Comparative Example 5]
A single cell was assembled and evaluated in the same manner as in Example 3 except that the porous carbon electrode substrate of Comparative Example 1 was used instead of the porous carbon electrode substrate of Example 1.
When the current density was 0.6 A / cm ² , flooding occurred and power generation was not possible.

[Comparative Example 6]
A single cell was assembled and evaluated in the same manner as in Example 3 except that the porous carbon electrode substrate of Comparative Example 2 was used instead of the porous carbon electrode substrate of Example 1.

When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.490 V, the internal resistance of the cell was 1.9 mΩ, and the characteristics were lower than those of Examples 3 and 4.

Example 5
The porous carbon electrode substrate of Example 2 is used instead of the porous carbon electrode substrate of Example 1, and the polymer electrolyte membrane with the catalyst layer formed is sandwiched with the conductive porous substrate C side inside. A single cell was assembled and evaluated in the same manner as in Example 3 except that the MEA was manufactured.

When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.625 V, the internal resistance of the cell was 1.9 mΩ, and good characteristics were exhibited.

Example 6
Example 5 is the same as Example 5 except that the porous carbon electrode substrate of Example 2 was used, and the polymer electrolyte membrane on which the catalyst layer was formed was sandwiched with the conductive porous substrate D side as the inside. A single cell was assembled and evaluated in the same manner.

When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.658 V, and the internal resistance of the cell was 1.9 mΩ, which showed good characteristics.

[Comparative Example 7]
A single cell was assembled and evaluated in the same manner as in Example 3 except that the porous carbon electrode substrate of Comparative Example 3 was used instead of the porous carbon electrode substrate of Example 1.

When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.532 V, the internal resistance of the cell was 1.8 mΩ, and the characteristics were lower than those of Examples 5 and 6.

[Comparative Example 8]
A single cell was assembled and evaluated in the same manner as in Example 3 except that the porous carbon electrode substrate of Comparative Example 4 was used instead of the porous carbon electrode substrate of Example 1.

When the current density was 0.6 A / cm ² , the cell voltage of the fuel cell was 0.504 V, the internal resistance of the cell was 1.9 mΩ, and the characteristics were lower than those of Examples 5 and 6.

It is a typical sectional view showing one form of a polymer electrolyte fuel cell of the present invention. It is a schematic sectional drawing which shows one form of the porous carbon electrode base material of this 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 (6)

  At least two of the conductive porous substrates made of the carbon material, each having a water repellent agent applied to one or more of the conductive porous substrates made of the same carbon material and having different amounts of the water repellent agent. A porous carbon electrode base material, which is laminated in order of the amount of water repellent.   The difference in the amount of the water repellent applied to each of the laminated porous carbon substrates in each of the at least two porous carbon substrates is 5% by mass or more, respectively. Porous carbon electrode substrate.   A membrane-electrode assembly obtained by bonding the porous carbon electrode substrate according to claim 1 or 2 to both surfaces of a polymer electrolyte membrane through a catalyst layer mainly composed of carbon powder carrying a catalyst, A membrane-electrode assembly in which the conductive porous substrate side having the smaller amount of water repellent of the porous carbon electrode substrate is bonded to the polymer electrolyte membrane via the catalyst layer.   A membrane-electrode assembly obtained by bonding the porous carbon electrode substrate according to claim 1 or 2 to both surfaces of a polymer electrolyte membrane through a catalyst layer mainly composed of carbon powder carrying a catalyst, A membrane-electrode assembly in which the conductive porous substrate side of the porous carbon electrode substrate having the larger amount of water repellent is bonded to the polymer electrolyte membrane via the catalyst layer.   A polymer electrolyte fuel cell using the porous carbon electrode substrate according to claim 1 or 2. A polymer electrolyte fuel cell using the membrane-electrode assembly according to claim 3 or 4.

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