JP2008311180A - Membrane electrode assembly, its manufacturing method, and fuel cell using the membrane electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of producing high reaction gas and achieving oxidized gas penetration power and a moisture control function. <P>SOLUTION: In a membrane electrode assembly in which an electrode catalyst layer with a bulk density of 14-20 mg/cm<SP>3</SP>holding a polymer electrolyte membrane and catalyst and including carbon powder and a polymer electrolyte, and a porous electrode base material where ≥80% of a pore volume exists in a range of 1 to 100 micrometers of pore diameters and a peak of the pore diameters exists in a range of 10 to 50 micrometers are laminated in sequence, the bulk density of the electrode catalyst layer can be achieved by performing elimination of a solvent of the polymer electrolyte solution while being left under existence of gas of the solvent of the polymer electrolyte solution. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a membrane electrode assembly used for a polymer electrolyte fuel cell, a manufacturing method thereof, a fuel cell using the membrane electrode assembly, 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). Further, a gas diffusion electrode having a catalyst layer mainly composed of carbon powder supporting a noble metal catalyst and a porous electrode base material having gas diffusibility is provided on both sides of the polymer electrolyte membrane with the catalyst layer side inside. It is the structure joined to.

  Such a joined body composed of a polymer electrolyte membrane and at least one, preferably two, gas diffusion electrodes is called a membrane electrode assembly (MEA: MEMBRANE ELECTRODE ASSEMBLY). Also, a gas flow path for supplying fuel gas or oxidizing gas to both sides of the MEA in which two gas diffusion electrodes are joined to both surfaces of the polymer electrolyte membrane, and for discharging generated gas and excess gas The separator which formed is installed.

  Electrode reactions in the catalyst layers of the anode and cathode of the polymer electrolyte fuel cell proceed at a three-phase interface where each reaction gas, electrode catalyst, and electrolyte simultaneously exist. Therefore, in a polymer electrolyte fuel cell, a metal catalyst-supporting carbon fine particle having a large specific surface area (for example, a platinum supported on a carbon black carrier) coated with the same or different ion electrolyte as that of a conventional polymer electrolyte membrane is used as an electrode. The three-phase interface is increased by using it as a constituent material of the catalyst layer and making the three-phase interface in the electrode catalyst layer three-dimensional. In the electrode catalyst layer formed as described above, voids composed of fine pores formed between the secondary particles or the tertiary particles of the carbon fine particles as the constituent material are three-dimensionally formed. The void functions as a diffusion flow path for each reaction gas supplied to the three-phase interface.

  In order for the reaction in the fuel cell to proceed smoothly, the gas diffusion electrode composed of the electrode catalyst layer and the porous electrode base material needs to have the following functions. The first function is to supply the fuel gas or the oxidizing gas uniformly to the noble metal catalyst in the electrode catalyst layer from the gas flow path formed in the separator disposed outside the porous electrode substrate. The second function is to discharge water produced by the reaction in the electrode catalyst layer through the porous electrode substrate. The third function is to conduct electrons necessary for the reaction in the electrode catalyst layer or generated electrons to the separator through the porous electrode substrate.

  Therefore, the gas diffusion electrode is required to have high reactive gas and oxidant gas permeability, water dischargeability, and electronic conductivity.

  In addition, the polymer electrolyte membrane used in a general solid polymer fuel cell exhibits proton conductivity in a water-containing state, so that not only the generated water drainage but also the polymer electrolyte membrane in the gas diffusion electrode. The contradictory function of water retention is required. In the case where the gas permeability of the porous electrode base material constituting the gas diffusion electrode is increased and the drainage capacity of the generated water is increased, the proton conduction resistance increases and the power generation performance decreases as the polymer electrolyte membrane dries. To do. On the contrary, in the case where the gas permeability of the porous electrode substrate is lowered and the water retention capacity of the polymer electrolyte membrane is increased, the power generation performance is improved by flooding in which the diffusion of the reaction gas and the oxidizing gas is hindered due to poor drainage of the generated water descend.

As a technique for controlling the pore diameter, pore distribution, and porosity of the catalyst layer, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-110202) discloses a technique between an anode and a cathode and between the anode and the cathode. And the anode and the cathode are formed of a gas diffusion porous electrode substrate, the gas diffusion porous electrode substrate, and the polymer electrolyte membrane. A polymer electrolyte fuel cell comprising a catalyst disposed between and an electrode catalyst layer containing an ion exchange resin, wherein at least one of the anode and the cathode has a total pore volume. A solid polymer fuel cell is disclosed, wherein the ratio of the pore volume of 10 to 30 μm pore diameter to 20 to 60% is 20-60%. Patent Document 2 (Japanese Patent Laid-Open No. 2005-310714) discloses pores as a fuel electrode (anode) side diffusion layer (referred to as a liquid fuel diffusion layer) in a polymer electrolyte fuel cell using a liquid fuel such as methanol. The ratio of the pore diameter in the range of 20 to 65%, the diameter in the range of 50 to 800 nm is 30% or more of the total pore volume of the liquid fuel diffusion layer, and the pore diameter is in the range of 100 to 800 nm. The fuel diffusion layer includes a fibrous supported catalyst and a particulate catalyst, and the fibrous supported catalyst is supported on the carbon nanofiber having a herringbone or platelet structure and the carbon nanofiber. The particulate supported catalyst contains carbon black particles, the carbon black particles, and the carbon black particles. An anode electrode for liquid fueled solid polymer fuel cell, wherein is disclosed that contains a supported catalyst particles.
JP 2002-110202 A JP 2005-310714 A

  The gas diffusion electrode has a water management function inside the polymer electrolyte fuel cell, such as drainage of generated water in the polymer electrolyte fuel cell and water retention of the polymer electrolyte membrane to reduce proton conduction resistance, and A high reactive gas and oxidizing gas permeability is required. In order to improve the moisture management function, gas permeability, and fuel cell performance, it is effective to optimize the bulk density, pore diameter, and pore distribution of the gas diffusion electrode. That is, it is necessary to optimize the bulk density, pore diameter and pore distribution of the catalyst layer constituting the gas diffusion electrode and the bulk density, pore diameter and pore distribution of the porous electrode substrate.

  Patent Documents 1 and 2 control the porosity, pore diameter, and pore distribution only in the electrode catalyst layer, and pass through the reaction gas and oxidizing gas as a gas diffusion electrode in combination with a porous electrode substrate. It is not enough in terms of improving performance and water discharge.

  The present invention solves the above-mentioned problems of the prior art, and a gas diffusion electrode comprising a porous electrode base material and an electrode catalyst layer has a high reactive gas and oxidizing gas permeability and moisture management function inside the fuel cell. An object of the present invention is to provide a fuel cell to be developed.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have reached the present invention. That is, the present invention
A membrane electrode assembly comprising a polymer electrolyte membrane, an electrode catalyst layer containing a carbon powder supporting a catalyst and a polymer electrolyte, and a porous electrode substrate, which are laminated in this order,
The electrode catalyst layer has a bulk density of 14 to 20 mg / cm ³ ,
The porous electrode substrate is a porous electrode substrate in which 80% or more of the pore volume is present in the pore diameter range of 1 to 100 μm and the pore diameter peak is in the range of 10 to 50 μm. About.

  In order to achieve the bulk density of the electrode catalyst layer, the present invention forms a film comprising a composition comprising a carbon powder carrying a catalyst and a polymer electrolyte solution on an arbitrary substrate, and the polymer electrolyte When removing the solvent of the solution, it is performed by leaving it in the presence of a solvent gas of the polymer electrolyte solution, and the obtained electrode catalyst layer is transferred to the polymer electrolyte membrane, and further, the porous electrode The present invention relates to a method for producing a membrane electrode assembly by laminating a base material so as to overlap the electrode catalyst layer.

  According to the present invention, an electrode catalyst layer having a high bulk density can be obtained by drying the electrode catalyst layer in an atmosphere of isopropyl alcohol or the like regardless of whether it is an anode or a cathode. By using the combined membrane electrode assembly, the balance between water retention and drainage is excellent, and the power generation characteristics of the polymer electrolyte fuel cell can be improved.

  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 polymer electrolyte fuel cell using a membrane electrode assembly having a combination of an electrode catalyst layer and a porous electrode base material proposed in the present invention. In the following example, a structure in which a gas diffusion electrode comprising an electrode catalyst layer and a porous electrode substrate is provided on both sides of a polymer electrolyte membrane will be described. The minimum unit of the membrane electrode assembly in the present invention is a polymer electrolyte. In this structure, a gas diffusion electrode is provided on either one of the films.

  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 electrode base material 4 made of short carbon fibers 4 and an anode side porous electrode base material 5 are provided outside each catalyst layer. ing. Furthermore, a cathode side separator in which a cathode side gas flow path 13 is formed so as to sandwich a membrane electrode assembly 6 composed of the polymer electrolyte membrane 1, the catalyst layers 2 and 3, and the porous electrode base materials 4 and 5, An anode side separator 8 in which an anode side gas flow path 14 is formed is provided.

  Each separator 7, 8 is provided with an oxidizing gas introducing part 9 and a discharging part 10, and a fuel gas introducing part 11 and a discharging part 12. The fuel gas is introduced from the introduction part 11 and supplied to the catalyst layer 3 through the porous electrode substrate 5 from the gas flow path 14 formed in the separator 8 and dissociated into protons and electrons. Electrons are conducted from the catalyst layer 3 to the separator 8 through the porous 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 electrode substrate 4 from the gas flow path 13 formed in the separator 7, and protons conducted in the polymer electrolyte membrane 1. Combine to produce water. In this way, a desired electromotive force can be taken out.

  As the porous electrode substrates 4 and 5 according to the present invention, it is preferable to use a carbon porous material having conductivity and gas permeability, or a metal porous material such as gold or stainless steel. In the polymer electrolyte fuel cell, since the inside is an acidic atmosphere, 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 can be used as the paper body, but it is selected from polyacrylonitrile (hereinafter abbreviated as PAN) carbon fiber, pitch carbon fiber, rayon carbon fiber, and phenolic carbon fiber. It is preferable to include one or more 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 fiber is preferably 2 mm or more and 12 mm or less, and more preferably 3 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 capable of binding the carbon fibers of the porous 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 6 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.

  Further, when forming the electrode catalyst layer, the bulk density, pore diameter and pore distribution are the concentration, viscosity, dispersity of the solution comprising the carbon powder supporting the catalyst and the polymer electrolyte, or the drying speed at the time of layer formation, It can be controlled by a dry atmosphere or the like. In particular, it is preferable to control the drying speed and the drying atmosphere during layer formation. Furthermore, examples of the catalyst layer forming method include a screen printing method and a doctor blade method, but are not limited thereto.

In order to form an electrode catalyst layer having a bulk density proposed by the present invention, a composition comprising a carbon powder carrying a catalyst and a polymer electrolyte solution is formed on an arbitrary substrate, and the polymer electrolyte is formed. When removing the solvent of the solution, it is performed by leaving it in the presence of a solvent gas of the polymer electrolyte solution, the obtained electrode catalyst layer is transferred to the polymer electrolyte membrane, and the porous electrode substrate It is preferable to manufacture a membrane electrode assembly by laminating a material so as to overlap the electrode catalyst layer.
As the polymer electrolyte solution, a solution obtained by dissolving or dispersing a solid polymer such as Nafion (registered trademark) in a mixed solvent of water and a lower alcohol is used, and among these, in the presence of a gas of a solvent of the lower alcohol. The electrode catalyst layer having a high bulk density can be obtained by mild evaporation of the lower alcohol.

  The concentration of the solvent in the gas atmosphere is not particularly limited, but is preferably in an equilibrium state.

  The standing time is required to dry the electrode catalyst layer sufficiently in the presence of a lower alcohol gas, and is preferably 1 hour or longer.

  There is no particular limitation on the base material on which the composition comprising the carbon powder carrying the catalyst and the polymer electrolyte solution is formed, but a resin film excellent in the peelability of the electrode catalyst layer after drying, such as PTFE, etc. Of these, a fluororesin film is preferred.

  Further, in order to transfer the obtained electrode catalyst layer to the polymer electrolyte membrane, it is preferable to transfer the electrode catalyst layer under a pressing condition such as a hot press method.

  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, a humidified gas is supplied to suppress drying of the polymer electrolyte membrane. From such a point, the porous electrode substrate according to the present invention preferably contains a water-repellent polymer 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 electrode substrate, a dip method in which the porous electrode 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.

The amount of water-repellent polymer introduced is defined as follows.
Introduction amount of the water-repellent polymer = weight per unit area of the introduced water-repellent polymer / weight per unit area of the gas diffusion electrode substrate The amount of the water-repellent polymer introduced is the water content of the porous electrode substrate In order to develop the management function, 0 to 50 wt% is preferable, and 0 to 40 wt% is more preferable from the viewpoint of gas permeability and electric resistance.

[Example 1]
(1) Electrocatalyst paste preparation 2.5 g of P6.5-supported carbon powder (manufactured by Tanaka Kikinzoku Co., Ltd.) 2.5 g and pure water 5.0 g, 5 mass% Nafion solution (manufactured by Aldrich) 22.5 g were mixed and stirred. The electrode catalyst paste was obtained.

(2) Production method of porous electrode substrate 30% by mass of PAN-based carbon short fibers having an average diameter of 4 μm cut to a length of 3 mm and 70 mass of PAN-based carbon short fibers having an average diameter of 7 μm cut to a length of 3 mm % Carbon short fiber 66% by mass, vinylon fiber (trade name: Vinylon, manufactured by Unitika Ltd.) 20% by mass and polyvinyl alcohol (PVA) (trade name: VBP105-1, manufactured by Kuraray Co., Ltd.) 14% by mass % Was dispersed in water, continuously made on a wire mesh, and dried to obtain a 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 and Chemicals), 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. Continuously carbonized to obtain a porous electrode substrate made of a short carbon fiber papermaking body. The obtained porous electrode substrate had a thickness of 115 μm and a bulk density of 0.31 g / cm ³ . Further, when the porosity, pore size distribution and pore size peak were determined with a mercury porosimeter, the porosity was 0.81, the pore size distribution was in the range of 1 to 100 μm, and the pore size peak was in the range of 10 to 50 μm. Existed. However, the pore size distribution being in the range of 1 to 100 μm means that the pore volume of the porous electrode substrate is 80% or more in the range of the pore diameter of 1 to 100 μm.

(3) Giving water repellency to the porous electrode base material The porous electrode base material is cut out to 5.4 cm × 5.4 cm, and 20 wt% PTFE dispersion (trade name: PTFE dispersion, manufactured by Mitsui-Dupont Fluorochemical Co., Ltd.) ), Dried and then heat treated at 360 ° C. for 1 hour. As a result, a water-repellent polymer compound was contained.

(4) Production of membrane electrode assembly (MEA) Nafion (trade name: Nafion112, manufactured by DuPont) was used as a polymer electrolyte membrane. After applying the electrode catalyst paste prepared in (1) above onto a PTFE sheet by a doctor blade method so as to be 5 cm × 5 cm, both the anode side and the cathode side are dried in an isopropyl alcohol atmosphere, and the electrode catalyst layer is formed. Obtained. The amount of Pt in the produced electrode catalyst layer was 0.12 mg / cm ² . The bulk density was calculated from the thickness and weight of the obtained catalyst layer. The results are shown in Table 1.

  The produced electrode catalyst layer was sandwiched between both surfaces of the polymer electrolyte membrane, a 5 MPa load was applied, and hot pressing was performed at 135 ° C. for 8 minutes, and then the PTFE sheet was peeled off. An MEA was obtained by using a gas diffusion electrode with the electrode substrate interposed therebetween.

[Example 2]
The dry atmosphere of the electrode catalyst layer was evaluated in the same manner as in Example 1 except that the anode was in the air and the cathode was in an isopropyl alcohol atmosphere. The results are shown in Table 1.

Example 3
The dry atmosphere of the electrode catalyst layer was evaluated in the same manner as in Example 1 except that the anode was in an isopropyl alcohol atmosphere and the cathode was in the air. The results are shown in Table 1.

[Comparative Example 1]
Evaluation was performed in the same manner as in Example 1 except that the drying atmosphere of the electrode catalyst layer was performed in the air for both the anode and the cathode. The results are shown in Table 1.

Example 4
(3) Evaluation of fuel cell characteristics The MEA produced in Example 1 was sandwiched between two carbon separators having a bellows-like gas flow path to form a polymer electrolyte 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.
When the humidification temperature was 80 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel cell was 0.555 V, and the internal resistance of the cell was 3.01 mΩ.
Further, when the humidification temperature was 60 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel cell was 0.482 V, and the internal resistance of the cell was 6.62 mΩ, which showed good characteristics.

Example 5
A single cell was formed in the same manner as in Example 4 except that the MEA produced in Example 2 was used, and was similarly evaluated.
When the humidification temperature was 80 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel cell was 0.555 V, and the internal resistance of the cell was 3.16 mΩ.
Further, when the humidification temperature was 60 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel battery cell was 0.477 V, and the internal resistance of the cell was 7.46 mΩ, which showed good characteristics.

Example 6
A single cell was formed in the same manner as in Example 4 except that the MEA produced in Example 3 was used, and was similarly evaluated.
When the humidification temperature was 80 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel cell was 0.536 V, and the internal resistance of the cell was 3.07 mΩ.
Further, when the humidification temperature was 60 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel battery cell was 0.462 V, and the internal resistance of the cell was 6.77 mΩ, which showed good characteristics.

[Comparative Example 2]
A single cell was formed in the same manner as in Example 4 except that the MEA produced in Comparative Example 1 was used, and evaluated in the same manner.
When the humidification temperature was 80 ° C. and the current density was 0.5 A / cm ² , the cell voltage of the fuel cell was 0.542 V, and the internal resistance of the cell was 3.03 mΩ.
In addition, when the humidification temperature is 60 ° C. and the current density is 0.5 A / cm ² , the cell voltage of the fuel cell is 0.438 V, and the internal resistance of the cell is 8.17 mΩ. It was seen.

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 electrode substrate 5: Anode side porous electrode substrate 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 (9)

A membrane electrode assembly comprising a polymer electrolyte membrane, an electrode catalyst layer containing a carbon powder supporting a catalyst and a polymer electrolyte, and a porous electrode substrate, which are laminated in this order,
The electrode catalyst layer has a bulk density of 14 to 20 mg / cm ³ ,
The porous electrode substrate is a porous electrode substrate in which 80% or more of the pore volume is present in a pore diameter range of 1 to 100 μm and a pore diameter peak is present in a range of 10 to 50 μm. Membrane electrode assembly. Membrane / electrode assembly comprising an electrode catalyst layer containing a carbon powder carrying a catalyst and a polymer electrolyte on both sides of a polymer electrolyte membrane, and two porous electrode substrates laminated on both electrode catalyst layers. Because
At least one of the electrode catalyst layers has a bulk density in the range of 14 to 20 mg / cm ³ ,
The two porous electrode substrates are porous electrode substrates having a pore diameter in the range of 1 to 100 μm and 80% or more of the pore volume and a pore diameter peak in the range of 10 to 50 μm. A membrane electrode assembly characterized by the above. The membrane electrode assembly according to claim 2, wherein both of the electrode catalyst layers have a bulk density in the range of 14 to 20 mg / cm ³ .   The membrane electrode assembly according to any one of claims 1 to 3, wherein the porous electrode substrate is a carbon fiber papermaking body. A composition comprising a carbon powder carrying a catalyst and a polymer electrolyte solution is formed on an arbitrary substrate, and the solvent of the polymer electrolyte solution is removed to obtain an electrode catalyst layer. A method for producing a membrane / electrode assembly in which a porous electrode base material is laminated so as to be superimposed on the electrode catalyst layer, the electrode catalyst layer being transferred to the side surface of the polymer electrolyte membrane, And removing the solvent of the polymer electrolyte solution by leaving it in the presence of a gas of the solvent of the polymer electrolyte solution, the electrode catalyst layer having a bulk density of 14 to 20 mg / cm ³ , A porous electrode substrate in which the porous electrode substrate is present in which the pore diameter is in the range of 1 to 100 μm and 80% or more of the pore volume and the pore diameter peak is in the range of 10 to 50 μm Manufacturing method of electrode assembly. A composition comprising a carbon powder carrying a catalyst and a polymer electrolyte solution is formed on an arbitrary substrate, and the solvent of the polymer electrolyte solution is removed to obtain an electrode catalyst layer. A method for producing a membrane electrode assembly, which is transferred to both side surfaces of a membrane and further laminated with a porous electrode base material so as to overlap the electrode catalyst layer, and is transferred to both side surfaces of the polymer electrolyte membrane The electrode catalyst layer in which at least one of the layers is removed by leaving the solvent of the polymer electrolyte solution in the presence of a gas of the solvent of the polymer electrolyte solution, and has a bulk density of 14 to 20 mg / cm ^3. The porous electrode substrate is a porous electrode substrate in which 80% or more of the pore volume is present in the pore diameter range of 1 to 100 μm and the pore diameter peak is in the range of 10 to 50 μm. For manufacturing a membrane electrode assembly Both of the electrode catalyst layers transferred to both sides of the polymer electrolyte membrane are removed by leaving the solvent of the polymer electrolyte solution in the presence of a gas of the solvent of the polymer electrolyte solution, and the bulk density The method for producing a membrane / electrode assembly according to claim 6, wherein the electrode catalyst layer has a range of 14 to 20 mg / cm ³ .   The method for producing a membrane / electrode assembly according to any one of claims 5 to 7, wherein the porous electrode substrate is a carbon fiber papermaking body.   A polymer electrolyte fuel cell using the membrane electrode assembly according to any one of claims 1 to 4.

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