JP2015162309A - Method for manufacturing film electrode assembly, film electrode assembly, and solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a film electrode assembly which enables the improvement of the diffusibility of reactive gas, and the water retention characteristic without interfering with the removal of water resulting from an electrode reaction or the like, and which includes an electrode catalyst layer showing a high power generating property even under a low humidification condition.SOLUTION: A film electrode assembly includes: a pair of electrode catalyst layers, and a polymer electrolytic film held between the pair of electrode catalyst layers. The pair of electrode catalyst layers each include a polymer electrolyte, and particles supporting a catalyst material. At least one of the pair of electrode catalyst layers is divided in at least two, namely a first electrode catalyst part, and a second electrode catalyst part adjacent thereto in a direction of the plane of the polymer electrolytic film. As to the value of the volume of pores of 1.0 μm or less in diameter, as an equivalent based on a cylinder approximation on the pores, which is determined by a mercury press-in method on the electrode catalyst layer thus divided, the value of the second electrode catalyst part provided on the side of gas outlet is larger than the value of the first electrode catalyst part provided on the side of gas inlet; the difference therebetween is 0.1-1.0 mL/g.

Description

  The present invention relates to a membrane electrode assembly used for a polymer electrolyte fuel cell and a method for producing the same.

  A fuel cell is a power generation system that generates electricity simultaneously with heat by causing a hydrogen gas-containing fuel gas and an oxygen-containing oxidant gas to undergo reverse reaction of water electrolysis at an electrode including a catalyst. This power generation system has features such as high efficiency, low environmental load, and low noise compared with the conventional power generation method, and is attracting attention as a clean energy source in the future. There are several types depending on the type of ionic conductor used, and those using proton conducting polymer membranes are called polymer polymer fuel cells (PEFC).

  Among fuel cells, polymer electrolyte fuel cells can be used near room temperature, so they are considered promising for use in in-vehicle power sources and household stationary power sources. In recent years, various research and development have been conducted. Yes. A polymer electrolyte fuel cell is a fuel in which a pair of electrode catalyst layers are arranged on both sides of a polymer electrolyte membrane called a membrane electrode assembly (MEA), and hydrogen is contained in one of the electrodes. The battery is sandwiched between a separator plate having a gas flow path for supplying gas and a separator plate having a gas flow path for supplying an oxidant gas containing oxygen to the other electrode. Here, the electrode for supplying the fuel gas is called a fuel electrode, and the electrode for supplying the oxidant is called an air electrode. These electrodes are composed of an electrode catalyst layer formed by laminating carbon particles carrying a catalyst material such as a platinum-based noble metal and a polymer electrolyte, and a gas diffusion layer having both gas permeability and electron conductivity.

  Here, with respect to the electrode catalyst layer, efforts have been made to increase gas diffusibility in order to improve the output density of the fuel cell. The pores in the electrode catalyst layer are located in front of the separator plate through the gas diffusion layer and serve as a passage for transporting a plurality of substances. The fuel electrode not only smoothly supplies the fuel gas to the three-phase interface, which is the oxidation-reduction reaction field, but also functions to supply water for smoothly conducting the generated protons in the polymer electrolyte membrane. . The air electrode functions to smoothly remove water generated by the electrode reaction along with the supply of the oxidant gas. In order to prevent a so-called “flooding” phenomenon in which the power generation reaction stops due to hindering mass transport, methods for improving drainage have been used so far (for example, Patent Document 1, Patent Document 2, Patent Reference 3 and Patent Document 4).

  Issues for the practical application of polymer electrolyte fuel cells include improvement of output density and durability, but the biggest issue is cost reduction (cost reduction). One way to reduce the cost is to reduce the number of humidifiers. Perfluorosulfonic acid membranes and hydrocarbon membranes are widely used as the polymer electrolyte membrane located at the center of the membrane electrode assembly, but in order to obtain excellent proton conductivity, it is close to a saturated water vapor pressure atmosphere. Moisture management is required, and at present, moisture is supplied from the outside by a humidifier. Therefore, in order to reduce power consumption and simplify the system, polymer electrolyte membranes that exhibit sufficient proton conductivity even under low humidification conditions that do not require a humidifier are being developed. .

  However, the electrode catalyst layer with improved drainage properties needs to improve the water retention by optimizing the electrode catalyst layer structure because the polymer electrolyte dries up under low humidification conditions. In order to improve the water retention of the fuel cell under low humidification conditions, a method of sandwiching a humidity adjusting film between the electrode catalyst layer and the gas diffusion layer has been devised. For example, Patent Document 5 discloses a method in which a humidity adjustment film composed of conductive carbonaceous powder and polytetrafluoroethylene exhibits a humidity adjustment function and prevents dry-up. Patent Document 6 discloses a method of providing grooves on the surface of the catalyst electrode layer in contact with the polymer electrolyte membrane. A method for suppressing a decrease in power generation performance under low humidification conditions by forming a groove having a width of 0.1 to 0.3 mm is disclosed.

JP 2006-120506 A JP 2006-332041 A JP 2007-87651 A JP 2007-80726 A JP 2006-252948 A JP 2007-141588 A

However, the membrane electrode assemblies described in these patent documents have a problem that they do not have satisfactory power generation performance. In addition, the manufacturing method is complicated and the cost is high.
In order to solve the above problems, in the present invention, the diffusibility of the reaction gas is increased, the water retention is increased without hindering the removal of water generated by the electrode reaction, and the high power generation characteristics are exhibited even under low humidification conditions. It aims at providing the manufacturing method of a membrane electrode assembly provided with an electrode catalyst layer, and the membrane electrode assembly.

  The manufacturing method of the membrane electrode assembly which concerns on 1 aspect of this invention is a manufacturing method of the membrane electrode assembly which pinched | interposed the polymer electrolyte membrane by a pair of electrode catalyst layer. The step of forming at least one electrode catalyst layer of the pair of electrode catalyst layers is performed by applying the first catalyst ink to the first region in the planar direction of the polymer electrolyte membrane and drying it. A step of forming an electrode catalyst portion, and applying a second catalyst ink to a second region adjacent to the first region in the planar direction of the polymer electrolyte membrane and drying the first electrode catalyst portion. Forming a second electrode catalyst portion adjacent to the first electrode catalyst portion. At this time, the pore volume of the second electrode catalyst part is made larger than the pore volume of the first electrode catalyst part. The drying rate of the first catalyst ink in the step of forming the first electrode catalyst portion is higher than the drying rate of the second catalyst ink in the step of forming the second electrode catalyst portion.

  The membrane electrode assembly according to one embodiment of the present invention is a membrane electrode assembly in which a polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers. At least one of the pair of electrode catalyst layers includes a first electrode catalyst portion and a second electrode catalyst portion adjacent to the first electrode catalyst portion in the planar direction of the polymer electrolyte membrane. It is divided into at least two.

  According to one aspect of the present invention, at least one electrode catalyst layer of the pair of electrode catalyst layers is disposed adjacent to the first electrode catalyst portion and the first electrode catalyst portion in the planar direction of the denatured membrane. It is divided into at least two of two electrode catalyst parts. Thereby, the pore volume having a diameter of 1.0 μm or less in terms of the cylindrical approximation of the pores determined by the mercury intrusion method can be set to a different value between the first electrode catalyst part and the second electrode catalyst part. it can. For example, the pore volume of the second electrode catalyst part provided on the gas outlet side can be made larger than the pore volume of the first electrode catalyst part provided on the gas inlet side. This makes it easy to efficiently and economically produce a membrane electrode assembly with an electrode catalyst layer that enhances water retention without hindering the removal of water produced by electrode reactions and exhibits high power generation characteristics even under low humidification conditions. can do.

It is a cross-sectional schematic diagram of the membrane electrode assembly which concerns on embodiment of this invention. 1 is an exploded cross-sectional view of a polymer electrolyte fuel cell according to an embodiment of the present invention.

<Embodiment>
Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited to embodiment described below, Even if there is a change of the range which does not deviate from the summary of this invention, it is included in this invention.
[Membrane electrode assembly]
First, the membrane electrode assembly 11 according to the present embodiment will be described.

  FIG. 1 is a schematic cross-sectional view showing a membrane electrode assembly 11 according to this embodiment. As shown in FIG. 1, the membrane / electrode assembly 11 includes a polymer electrolyte membrane 1, an electrode catalyst layer 2, and an electrode catalyst layer 3. The electrode catalyst layer 2 and the electrode catalyst layer 3 sandwich the polymer electrolyte membrane 1. At least one of the electrode catalyst layers 2 and 3 includes catalyst material-carrying particles and a polymer electrolyte. Further, each of the electrode catalyst layers 2 and 3 is divided into two in the plane direction of the polymer electrolyte membrane 1. More specifically, the electrode catalyst layer 2 is divided into a first electrode catalyst part 2a located on the gas inlet side and a second electrode catalyst part 2b located on the gas outlet side. The first electrode catalyst part 2a and the second electrode catalyst part 2b are adjacent to each other. Similarly, the electrode catalyst layer 3 is divided into a first electrode catalyst portion 3a located on the gas inlet side and a second electrode catalyst portion 3b located on the gas outlet side. The first electrode catalyst part 3a and the third electrode catalyst part 3b are adjacent to each other.

  In the membrane electrode assembly 11, the value of the pore volume having a diameter of 1.0 μm or less in terms of the cylindrical approximation of the pores determined by the mercury intrusion method is the first electrode catalyst part 2a or 3a provided on the gas inlet side. Rather, the second electrode catalyst portion 2b or 3b provided on the gas outlet side is larger. In other words, the value of the pore volume of the second electrode catalyst part 2b or 3b on the downstream side of the gas is larger than the value of the pore volume of the first electrode catalyst part 2a or 3a on the upstream side of the gas. ing.

  In the membrane electrode assembly 11, the first electrode catalyst part 2a or 3a provided on the gas inlet side is made denser than the second electrode catalyst part 2b or 3b provided on the gas outlet side. Water retention is enhanced by the first electrode catalyst part 2a or 3a provided on the gas inlet side, and water removal is promoted by the second electrode catalyst part 2b or 3b provided on the gas outlet side. Thus, the membrane electrode assembly 11 has both the drainage of water generated by the electrode reaction and water retention under low humidification conditions.

  In the membrane / electrode assembly 11, unlike in the case where the conventional humidity adjusting film is applied or the formation of grooves on the surfaces of the electrode catalyst layers 2 and 3 is used to reduce the humidity, the power generation characteristics are reduced due to the increase in interface resistance. I can't. From this, the solid polymer fuel cell provided with the membrane electrode assembly 11 is remarkably high in power generation characteristics even under low humidification conditions, compared with the solid polymer fuel cell provided with the conventional membrane electrode assembly. There is an effect.

  For the pore volume with a diameter of 1.0 μm or less in terms of the cylindrical approximation of the pores determined by the mercury intrusion method, the value of the pore volume of the second electrode catalyst part 2b or 3b and the first electrode catalyst part 2a Or it is preferable that the difference with the value of the pore volume of 3a is 0.1 mL / g or more and 1.0 mL / g or less. When the difference between the pore volume value of the second electrode catalyst portion 2b or 3b and the pore volume value of the first electrode catalyst portion 2a or 3a is less than 0.1 mL / g, It may be difficult to achieve both the drainage of water produced by the electrode reaction and water retention under low humidification conditions. Even if the difference between the pore volume value of the second electrode catalyst portion 2b or 3b and the pore volume value of the first electrode catalyst portion 2a or 3a exceeds 1.0 mL / g. It may be difficult to achieve both the drainage of water produced by the electrode reaction and water retention under low humidification conditions.

  In the membrane electrode assembly 11, the number of divisions of the electrode catalyst layers 2 and 3 is not limited to two. The number of divisions of the electrode catalyst layers 2 and 3 may be three or more. When the number of divisions of the electrode catalyst layers 2 and 3 is 3 or more, the pore volume having a diameter of 1.0 μm or less in terms of the cylindrical approximation of the pores obtained by the mercury intrusion method of the electrode catalyst layers 2 and 3 Change in steps. In other words, even in the case of a membrane electrode assembly in which the number of divisions of the electrode catalyst layer is 3 or more, the value of the pore volume in the downstream portion of the gas is larger than the value of the pore volume in the upstream portion of the gas. Change so that is larger.

  Further, in the membrane electrode assembly 11, only one of the electrode catalyst layers 2 or 3 of the electrode catalyst layers 2 and 3 formed on both surfaces of the polymer electrolyte membrane 1 is divided into portions having different pore volumes. May be. When only one electrode catalyst layer 2 or 3 is divided into different pore volumes, the electrode catalyst layer divided into different pore volumes may be arranged on the air electrode (cathode) side where water is generated by the electrode reaction. preferable. However, it is more preferable that the electrode catalyst layers divided into different pore volumes are formed on both surfaces of the polymer electrolyte membrane 1 from the viewpoint of water retention of the polymer electrolyte under low humidification conditions.

[Solid polymer fuel cell]
Next, the polymer electrolyte fuel cell 12 according to this embodiment will be described.
FIG. 2 is an exploded cross-sectional view of the polymer electrolyte fuel cell 12 according to the present embodiment. The polymer electrolyte fuel cell 12 includes a gas diffusion layer 4 on the air electrode 6 side and a gas diffusion layer 5 on the fuel electrode 7 side disposed so as to face the electrode catalyst layers 2 and 3 of the membrane electrode assembly 11. Is provided. The electrode catalyst layer 2 and the gas diffusion layer 4 form an air electrode (cathode) 6. The electrode catalyst layer 3 and the gas diffusion layer 5 form a fuel electrode (anode) 7. Further, outside the gas diffusion layer 4 on the air electrode 6 side and the gas diffusion layer 5 on the fuel electrode 7 side, a pair of separators 10 made of a conductive and impermeable material are disposed. Each of the pair of separators 10 is provided with a gas flow path 8 for gas distribution on a surface facing the gas diffusion layer 4 or 5. Further, a cooling water passage 9 for circulating cooling water is provided on the surface opposite to the gas diffusion layer 4 or 5. For example, hydrogen gas is supplied as a fuel gas from the gas flow path 8 of the separator 10 on the fuel electrode 7 side. On the other hand, a gas containing oxygen, for example, is supplied as an oxidant gas from the gas flow path 8 of the separator 10 on the air electrode 6 side. An electromotive force can be generated between the fuel electrode 7 and the air electrode 6 by causing an electrode reaction between the fuel gas hydrogen and oxygen gas in the presence of a catalyst.

  In the polymer electrolyte fuel cell 12, the polymer electrolyte membrane 1, the electrode catalyst layers 2 and 3, and the gas diffusion layers 4 and 5 are sandwiched by a set of separators 10. The polymer electrolyte fuel cell 12 is a single cell fuel cell, but a plurality of cells may be stacked via the separator 10 to form a polymer electrolyte fuel cell.

[Production method of membrane electrode assembly]
Next, a manufacturing method of the membrane electrode assembly 11 according to this embodiment will be described.
In the manufacturing method of the membrane electrode assembly 11 according to the present embodiment, the following first to third steps are included.
(First Step) A step of forming first electrode catalyst portions 2a and 3a by applying a catalyst ink in which a catalyst-supported particle and a polymer electrolyte are dispersed in a solvent and drying it (second step) Step) Step of forming second electrode catalyst portions 2b and 3b by applying a catalyst ink in which particles carrying a catalyst and a polymer electrolyte are dispersed in a solvent and drying the catalyst ink (Third Step) Step) Forming the first electrode catalyst portions 2a and 3a and the second electrode catalyst portions 2b and 3b on at least one surface of both surfaces of the polymer electrolyte membrane

  In the step of forming the first electrode catalyst portions 2a and 3a and the second electrode catalyst portions 2b and 3b, the electrode catalyst portions having different pore volumes can be formed by changing the drying speed of the catalyst ink. it can. These electrode catalyst parts are formed by applying a catalyst ink in which catalyst-supported particles and polymer electrolyte are dispersed in a solvent to form a coating film, and then removing the solvent in the coating film. Is done. At this time, when the drying speed of the catalyst ink is increased, the pore volume of the electrode catalyst portion to be formed can be reduced as compared with the case where the drying speed is decreased. Further, when the drying speed of the catalyst ink is reduced, the pore volume of the electrode catalyst portion to be formed can be increased as compared with the case where the drying speed is increased.

  That is, in the method of manufacturing the membrane electrode assembly 11, the drying temperature of the catalyst ink in the step of forming the first electrode catalyst portions 2a and 3a (first step) is set to the second electrode catalyst portions 2b and 3b. The temperature is higher than the drying temperature of the catalyst ink in the step (second step). By raising the drying temperature of the catalyst ink, the drying speed of the catalyst ink is increased, and the pore volume of the electrode catalyst portion to be formed can be reduced. In addition, by lowering the drying temperature of the catalyst ink, the drying speed of the catalyst ink is reduced, and the pore volume of the electrode catalyst portion to be formed can be increased.

  Moreover, it is preferable that the difference of the drying temperature in the process of forming the 1st electrode catalyst parts 2a and 3a and the drying temperature in the process of forming the 2nd electrode catalyst parts 2b and 3b is 40 degreeC or more. If the difference between the drying temperature in the step of forming the first electrode catalyst portions 2a and 3a and the drying temperature in the step of forming the second electrode catalyst portions 2b and 3b is less than 40 ° C., the first electrode to be formed The difference in pore volume between the electrode catalyst parts 2a and 3a and the second electrode catalyst parts 2b and 3b is reduced, and both the drainage of the water produced by the electrode reaction and the water retention under low humidification conditions can be achieved. It can be difficult.

The difference between the value of the pore volume of 1.0 μm or less in diameter in the first electrode catalyst parts 2a and 3a and the value of the pore volume of 1.0 μm or less in diameter in the second electrode catalyst parts 2b and 3b is mercury. It is preferably 0.1 mL / g or more and 1.0 mL / g or less as a conversion value by cylindrical approximation of pores obtained by a press-fitting method. When the difference between the pore volume values of the second electrode catalyst portions 2b and 3b and the pore volume values of the first electrode catalyst portions 2a and 3a is less than 0.1 mL / g, It may be difficult to achieve both the drainage of the generated water and the water retention under low humidification conditions. Moreover, even when the difference in pore volume exceeds 1.0 mL / g, it may be difficult to achieve both the drainage of water generated by the electrode reaction and the water retention under low humidification conditions. .
Further, the catalyst ink used when forming the first electrode catalyst portions 2a and 3a and the catalyst ink used when forming the second electrode catalyst portions 2b and 3b may be the same. May be different.

[Details]
Hereinafter, the membrane electrode assembly 11 and the polymer electrolyte fuel cell 12 according to this embodiment will be described in more detail.
The polymer electrolyte membrane 1 only needs to have proton conductivity, and a fluorine polymer electrolyte membrane or a hydrocarbon polymer electrolyte membrane can be used. Examples of the fluoropolymer electrolyte include “NAFION (registered trademark)” manufactured by DuPont (registered trademark), “FLEION (registered trademark)” manufactured by Asahi Glass (registered trademark), and “ACIPLEX (registered trademark) manufactured by Asahi Kasei (registered trademark). Registered trademark) "and" GORE-SELECT (registered trademark) "manufactured by Gore (registered trademark) can be used. In particular, in order to increase the output voltage of the polymer electrolyte fuel cell, “NAFION (registered trademark)” manufactured by DuPont (registered trademark) is preferably used. As the hydrocarbon polymer electrolyte membrane, electrolyte membranes such as sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, and sulfonated polyphenylene can be used. In particular, as the polymer electrolyte membrane 1, a “NAFION (registered trademark)” material made by DuPont (registered trademark) can be suitably used.

The electrode catalyst layers 2 and 3 are formed on both surfaces of the polymer electrolyte membrane 1 using a catalyst ink. The catalyst ink includes at least a polymer electrolyte and a solvent.
The polymer electrolyte contained in the above-described catalyst ink may be any one having proton conductivity, and the same material as the polymer electrolyte membrane 1 can be used. For example, a fluorine-based polymer electrolyte or a hydrocarbon-based polymer electrolyte can be used. As an example of a fluorine-based polymer electrolyte, a “NAFION (registered trademark)” material manufactured by DuPont (registered trademark) or the like can be used. As the hydrocarbon polymer electrolyte, electrolytes such as sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, and sulfonated polyphenylene can be used. In particular, a “NAFION (registered trademark)” material manufactured by DuPont (registered trademark) can be suitably used as the fluorine-based polymer electrolyte. In consideration of the adhesion between the electrode catalyst layers 2 and 3 and the polymer electrolyte membrane 1, it is preferable to use the same material as that of the polymer electrolyte membrane 1.

  The catalyst substance used in the present embodiment (hereinafter sometimes referred to as catalyst particles or catalyst) includes platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt. Further, metals such as nickel, manganese, vanadium, molybdenum, gallium, and aluminum, alloys thereof, oxides, double oxides, and the like can be used. Moreover, since the activity of a catalyst will fall when the particle size of said catalyst is too large, and the stability of a catalyst will fall when it is too small, the particle size of a catalyst has preferable 0.5 nm-20 nm. More preferably, 1 nm-5 nm are good. In addition, when the catalyst particles are one or more metals selected from platinum, gold, palladium, rhodium, ruthenium, and iridium, the electrode particles are excellent in electrode reactivity, and the electrode reaction is performed efficiently and stably. be able to. When the catalyst particles are one or more metals selected from platinum, gold, palladium, rhodium, ruthenium and iridium, the polymer electrolyte fuel cell including the electrode catalyst layers 2 and 3 is high. It is preferable because it shows power generation characteristics.

  In general, carbon particles are used as the electron conductive powder supporting the catalyst material. The type of carbon particles is not particularly limited as long as it is in the form of fine particles and has conductivity and is not affected by the catalyst. For example, carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, and fullerene can be used. If the particle size of the carbon particles is too small, it becomes difficult to form an electron conduction path. On the other hand, if it is too large, the gas diffusibility of the electrode catalyst layers 2, 32, and 3 is lowered or the utilization factor of the catalyst is lowered. More preferably, 10 nm-100 nm are good.

  The solvent used as a dispersion medium for the catalyst ink is not particularly limited as long as it does not erode the catalyst substance-supporting particles and the polymer electrolyte, and can dissolve or disperse the polymer electrolyte in a highly fluid state as a fine gel. It is not something. However, it is desirable that at least a volatile organic solvent is contained. Examples of the solvent used as a dispersion medium for the catalyst ink include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, Alcohols such as pentaanol, acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, diisobutyl ketone and other ketone solvents, tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxy toluene, Ether solvents such as dibutyl ether, other dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, diacetone alcohol , It can be used polar solvents such as 1-methoxy-2-propanol. Moreover, you may use what mixed 2 or more types among the above-mentioned solvents.

  In addition, a solvent using a lower alcohol as a solvent used as a dispersion medium of the catalyst ink has a high risk of ignition. Therefore, when using a lower alcohol, it is preferable to use a mixed solvent with water. Furthermore, water (water having high affinity) that is compatible with the polymer electrolyte may be contained. The amount of water added is not particularly limited as long as the polymer electrolyte does not separate and cause white turbidity or gelation.

The solvent used as the dispersion medium for the catalyst ink forms the first catalyst ink solvent used for forming the first electrode catalyst portions 2a and 3a and the second electrode catalyst portions 2b and 3b. There is a solvent for the second catalyst ink used for this purpose, but both may be the same solvent or different solvents.
The pore volume of the electrode catalyst layers 2 and 3 depends on the composition of the catalyst ink and the dispersion conditions, and varies depending on the amount of the polymer electrolyte, the type of the dispersion solvent, the dispersion method, the dispersion time, etc., so at least one of these Preferably, the pore volume of the electrode catalyst layers 2 and 3 is controlled so as to increase from the side close to the gas diffusion layers 4 and 5 toward the polymer electrolyte membrane 1 using a combination of two or more. It is preferable to do.

In order to disperse the catalyst material-carrying particles, the catalyst ink may contain a dispersant. Examples of the dispersant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.
Examples of the anionic surfactant include alkyl ether carboxylate, ether carboxylate, alkanoyl sarcosine, alkanoyl glutamate, acyl glutamate, oleic acid / N-methyl taurine, potassium oleate / diethanolamine salt, alkyl ether sulfate / Triethanolamine salt, polyoxyethylene alkyl ether sulfate / triethanolamine salt, amine salt of special modified polyether ester acid, amine salt of higher fatty acid derivative, amine salt of special modified polyester acid, amine of high molecular weight polyether ester acid Salts, special modified phosphate ester amine salts, high molecular weight polyester acid amido amine salts, special fatty acid derivative amido amine salts, higher fatty acid alkyl amine salts, high molecular weight polycarboxylic acid amines Doamine salts, carboxylic acid type surfactants such as sodium laurate, sodium stearate, sodium oleate, dialkylsulfosuccinate, dialkylsulfosuccinate, 1,2-bis (alkoxycarbonyl) -1-ethanesulfonate, Alkyl sulfonate, alkyl sulfonate, paraffin sulfonate, α-olefin sulfonate, linear alkyl benzene sulfonate, alkyl benzene sulfonate, polynaphthyl methane sulfonate, polynaphthyl methane sulfonate, naphthalene sulfonate-formalin condensate, alkyl naphthalene sulfonate, alkanoyl Methyl tauride, lauryl sulfate sodium salt, cetyl sulfate sodium salt, stearyl sulfate sodium salt, oleyl sulfate Ester sodium salt, lauryl ether sulfate ester salt, alkylbenzene sulfonate sodium salt, oil-soluble alkylbenzene sulfonate salt, α-olefin sulfonate surfactant, alkyl sulfate ester salt, alkyl sulfate salt, alkyl sulfate, alkyl Ether sulfate, polyoxyethylene alkyl ether sulfate, alkyl polyethoxy sulfate, polyglycol ether sulfate, alkyl polyoxyethylene sulfate, sulfated oil, highly sulfated sulfate type surfactant, phosphoric acid (mono or Di) alkyl salt, (mono or di) alkyl phosphate, (mono or di) alkyl phosphate ester salt, alkyl polyoxyethylene salt of phosphate, alkyl ether phosphate, alkyl polyethoxy Phosphate, polyoxyethylene alkyl ether, alkylphenyl phosphate polyoxyethylene salt, alkylphenyl ether phosphate, alkylphenyl polyethoxy phosphate, polyoxyethylene alkylphenyl ether phosphate, higher alcohol monophosphate Examples thereof include phosphate type surfactants such as ester disodium salt, higher alcohol phosphate diester disodium salt, and zinc dialkyldithiophosphate.

  Examples of the cationic surfactant include benzyldimethyl {2- [2- (P-1,1,3,3-tetramethylbutylphenoxy) ethoxy] ethyl} ammonium chloride, octadecylamine acetate, tetradecylamine acetic acid. Salt, octadecyltrimethylammonium chloride, tallow trimethylammonium chloride, dodecyltrimethylammonium chloride, coconut trimethylammonium chloride, hexadecyltrimethylammonium chloride, behenyltrimethylammonium chloride, coconut dimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride Chloride, dioleyldimethylammonium chloride, 1-hydroxy Chill-2-tallow imidazoline quaternary salt, 2-heptadecenyl-hydroxyethyl imidazoline, stearamide ethyl diethylamine acetate, stearamide ethyl diethylamine hydrochloride, triethanolamine monostearate formate, alkyl pyridium salt, higher alkyl Examples include amine ethylene oxide adducts, polyacrylamide amine salts, modified polyacrylamide amine salts, perfluoroalkyl quaternary ammonium iodides, and the like.

  Examples of the amphoteric surfactants include dimethyl coconut betaine, dimethyl lauryl betaine, sodium laurylaminoethylglycine, sodium laurylaminopropionate, stearyldimethylbetaine, lauryl dihydroxyethyl betaine, amide betaine, imidazolinium betaine, lecithin, 3- [Ω-fluoroalkanoyl-N-ethylamino] -1-propanesulfonic acid sodium, N- [3- (perfluorooctanesulfonamido) propyl] -N, N-dimethyl-N-carboxymethyleneammonium betaine and the like. .

  Examples of the nonionic surfactant include coconut fatty acid diethanolamide (1: 2 type), coconut fatty acid diethanolamide (1: 1 type), bovine fatty acid diethanolamide (1: 2 type), and bovine fatty acid diethanolamide (1: 1 type), oleic acid diethanolamide (1: 1 type), hydroxyethyl lauryl amine, polyethylene glycol lauryl amine, polyethylene glycol palm amine, polyethylene glycol stearyl amine, polyethylene glycol beef tallow amine, polyethylene glycol beef tallow propylene diamine, polyethylene glycol dioleyl amine , Dimethyl lauryl amine oxide, dimethyl stearyl amine oxide, dihydroxyethyl lauryl amine oxide, perfluoroalkylamine oxide, polyvinyl Loridone, higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, glycerin fatty acid ester, pentaerythritol fatty acid ester, sorbit fatty acid ester, sorbitan fatty acid ester, Examples include sugar fatty acid esters.

  Among the above surfactants, sulfonic acid type surfactants such as alkylbenzene sulfonic acid, oil-soluble alkylbenzene sulfonic acid, α-olefin sulfonic acid, sodium alkylbenzene sulfonate, oil-soluble alkylbenzene sulfonate, α-olefin sulfonate, etc. Can be suitably used as a dispersant in consideration of carbon dispersion effects, changes in catalyst performance due to the remaining dispersant, and the like.

Increasing the amount of polymer electrolyte in the catalyst ink generally decreases the pore volume. On the other hand, increasing the amount of carbon particles in the catalyst ink increases the pore volume. In addition, when a dispersant is used, the pore volume is reduced.
Further, the catalyst ink is subjected to a dispersion treatment as necessary. The viscosity of the catalyst ink and the size of the particles can be controlled by the conditions for the dispersion treatment of the catalyst ink. Distributed processing can be performed using various apparatuses. In particular, the distributed processing method is not limited. For example, as the dispersion treatment, treatment with a ball mill or roll mill, treatment with a shear mill, treatment with a wet mill, ultrasonic dispersion treatment, and the like can be given. Moreover, you may employ | adopt the homogenizer etc. which stir with centrifugal force. Further, as the dispersion time becomes longer, the aggregates of the catalyst material-carrying particles are destroyed and the pore volume becomes smaller.

  If the solid content in the catalyst ink is too large, the viscosity of the catalyst ink becomes high, so that the electrode catalyst layers 2 and 3 surfaces 2 and 3 are likely to crack. On the other hand, if the solid content in the catalyst ink is too small, the film formation rate is very slow and the productivity is lowered. Therefore, the solid content in the catalyst ink is preferably 1% by mass to 50% by mass (wt%). The solid content is composed of catalyst material-supported particles and a polymer electrolyte. If the content of catalyst material-supported particles is increased in the solid content, the viscosity increases even with the same solid content. On the other hand, when the content of the catalyst substance-supporting particles is reduced in the solid content, the viscosity is lowered even with the same solid content. Therefore, the proportion of the catalyst substance-supporting particles in the solid content is preferably 10% by mass to 80% by mass. The viscosity of the catalyst ink is preferably about 0.1 cP to 500 cP (0.0001 Pa · s to 0.5 Pa · s (Pascal second)), more preferably 5 cP to 100 cP (0.005 Pa · s to 0.1 Pa).・ S) is good. Further, the viscosity can be controlled by adding a dispersing agent when the catalyst ink is dispersed.

Further, the catalyst ink may contain a pore forming agent. By removing the pore-forming agent after the electrode catalyst layers 2 and 3 are formed, pores can be formed. Examples include substances that are soluble in acids, alkalis, and water, substances that sublime such as camphor, and substances that thermally decompose. If the pore-forming agent is a substance that is soluble in warm water, it may be removed with water generated during power generation.
Examples of pore-forming agents that are soluble in acids, alkalis and water include acid-soluble inorganic salts such as calcium carbonate, barium carbonate, magnesium carbonate, magnesium sulfate and magnesium oxide, inorganic salts soluble in alkaline aqueous solutions such as alumina, silica gel and silica sol, aluminum Metals soluble in acids or alkalis such as zinc, tin, nickel and iron, water-soluble inorganic salts such as sodium chloride, potassium chloride, ammonium chloride, sodium carbonate, sodium sulfate, monosodium phosphate, polyvinyl alcohol, polyethylene glycol Water-soluble organic compounds such as Moreover, although the said pore making agent may be used individually by 1 type or in combination of 2 or more types, it is preferable to use in combination of 2 or more types.

  The catalyst ink is applied onto the substrate and dried to form the electrode catalyst layers 2 and 3. When the gas diffusion layers 4 and 5 or the transfer sheet are used as the substrate, the electrode catalyst layers 2 and 3 are bonded to both surfaces of the polymer electrolyte membrane 1. Further, the membrane / electrode assembly uses the polymer electrolyte membrane 1 as a base material, the catalyst ink is directly applied to both surfaces of the polymer electrolyte membrane 1, and the electrode catalyst layers 2 and 3 are directly applied to both surfaces of the polymer electrolyte membrane 1. It may be formed. As a coating method for coating the catalyst ink on the substrate, a doctor blade method, a dipping method, a screen printing method, a roll coating method, or the like can be employed.

  As the base material in the production of the electrode catalyst layers 2 and 3, the gas diffusion layers 4 and 5, the transfer sheet, or the polymer electrolyte membrane 1 can be used. The transfer sheet used as the substrate may be any material having good transferability. For example, ethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroper Fluorocarbon resins such as fluoroalkyl vinyl ether copolymer (PFA) and polytetrafluoroethylene (PTFE) can be used. In addition, polyimide, polyethylene terephthalate, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, polyethylene naphthalate, polymer sheets and polymer films are transferred. It can be used as a sheet. When a transfer sheet is used as the base material, the electrode catalyst layers 2 and 3 are bonded to the polymer electrolyte membrane 1 and then the transfer sheet is peeled off, and the electrode catalyst layers 2 and 3 are formed on both sides of the polymer electrolyte membrane 1. It can be set as the membrane electrode assembly 11 provided with.

  As the gas diffusion layers 4 and 5, a material having gas diffusibility and conductivity can be used. For example, porous carbon materials such as carbon cloth, carbon paper, and non-woven fabric can be used. Moreover, the gas diffusion layers 4 and 5 can also be used as a base material on which the catalyst ink is applied. When the gas diffusion layers 4 and 5 are used as the base material on which the catalyst ink is applied, the electrode diffusion layers 4 and 5 are peeled off after the electrode catalyst layers 2 and 3 are bonded to the polymer electrolyte membrane 1. There is no need.

  In the case where the gas diffusion layers 4 and 5 are used as a base material on which the catalyst ink is applied, before applying the catalyst ink to the gas diffusion layers 4 and 5, a preliminary layer is previously formed on the gas diffusion layers 4 and 5. It may be formed. The mesh layer is a layer that prevents the catalyst ink from penetrating into the gas diffusion layers 4 and 5. By forming the mesh layer, the catalyst ink is deposited on the mesh layer to form a three-phase interface even when the amount of catalyst ink applied is small. For example, the filler layer can be formed by dispersing carbon particles in a fluorine resin solution and sintering at a temperature equal to or higher than the melting point of the fluorine resin. As the fluororesin, polytetrafluoroethylene (PTFE) or the like can be used.

As the separator 10, a carbon type or a metal type can be used. The gas diffusion layers 4 and 5 and the separator 10 may be integrated. Further, when the separator 10 or the electrode catalyst layers 2 and 3 serve as the gas diffusion layers 4 and 5, the gas diffusion layers 4 and 5 may be omitted. The polymer electrolyte fuel cell 12 can be manufactured by assembling other accompanying devices such as a gas supply device and a cooling device.
Hereinafter, the method for producing an electrode catalyst layer for a polymer electrolyte fuel cell according to this embodiment will be described with reference to specific examples and comparative examples. However, this embodiment is limited by the following examples and comparative examples. Is not to be done.

<Example>
[Preparation of catalyst ink]
A platinum-carrying carbon catalyst having a platinum loading of 50% by mass and a polymer electrolyte solution having a mass of 20% by mass were mixed in a solvent and subjected to dispersion treatment with a planetary ball mill. Here, Tanaka Kikinzoku Kogyo (registered trademark “TEC10E50E”) was used as the platinum-supported carbon catalyst. Further, “NAFION (registered trademark)” manufactured by DuPont (registered trademark) was used as the polymer electrolyte solution. At this time, the dispersion time was 30 minutes to prepare a catalyst ink. The composition ratio of the starting materials of the prepared catalyst ink was 1: 1 by mass for the carbon support and the polymer electrolyte, and 1: 1 for the dispersion solvent by 1-propanol and 2-propanol by volume. . The solid content was 15% by mass.

〔Base material〕
A polytetrafluoroethylene (PTFE) sheet, which is a transfer sheet, was used as a substrate.
[Method of forming electrode catalyst layers 2 and 3 on a substrate]
The catalyst ink adjusted as described above was applied onto a substrate by a doctor blade method and dried at 40 ° C. in an air atmosphere to obtain first electrode catalyst portions 2a and 3a. Similarly, the catalyst ink prepared as described above was applied onto a substrate and dried at 80 ° C. in an air atmosphere to obtain second electrode catalyst portions 2b and 3b. At this time, the amount of catalyst ink applied was adjusted so that the amount of platinum supported was 0.3 mg / cm ² . As a result of measuring the pores of each of the obtained electrode catalyst parts with a mercury porosimeter, the pore volume with a diameter of 1.0 μm or less in terms of cylinder approximation is the first electrode catalyst part 2a provided on the gas inlet side or The value of the second electrode catalyst portion 2b or 3b provided on the gas outlet side was larger than the value of 3a, and the difference was 0.16 mL / g.

[Production of membrane electrode assembly]
The base material on which the first electrode catalyst portions 2a and 3a and the second electrode catalyst portions 2b and 3b were formed was punched into a rectangular shape of 5 cm × 2.5 cm, respectively. On the polymer electrolyte membrane 1 using “NAFION (registered trademark)” manufactured by DuPont (registered trademark), the first electrode catalyst portions 2 a and 3 a are disposed on the gas inlet side, and the second electrode catalyst portions 2 b and 3 b are disposed on the polymer electrolyte membrane 1. Was placed on the gas outlet side, and 5 cm × 5 cm square electrode catalyst layers 2 and 3 were produced. The electrode catalyst layers 2 and 3 were arranged on both surfaces of the polymer electrolyte membrane 1 and hot pressed under the conditions of 130 ° C. and 6.0 × 10 ⁶ Pa to obtain a membrane electrode assembly.

<Comparative example>
[Adjustment of catalyst ink]
A catalyst ink was prepared in the same manner as in the examples.
〔Base material〕
The same substrate as in the example was used.

[Method for producing electrode catalyst layers 2 and 3]
Second electrode catalyst portions 2b and 3b were formed in the same manner as in the example.
[Production of membrane electrode assembly]
The base material on which the second electrode catalyst portions 2b and 3b are formed is punched into a 25 cm ² (5 cm × 5 cm) square, and the second electrode catalyst portions 2b and 3b are arranged so as to face both surfaces of the polymer electrolyte membrane 1. Then, hot pressing was performed under the conditions of 130 ° C. and 6.0 × 10 ⁶ Pa to obtain a membrane electrode assembly.

<Evaluation>
[Power generation characteristics]
Carbon papers used as the gas diffusion layers 4 and 5 were bonded together so as to sandwich the membrane electrode assemblies produced in Examples and Comparative Examples, and placed in a power generation evaluation cell. Using the fuel cell measurement device, the cell voltage was set to 80 ° C., and current voltage measurement was performed under the following two operating conditions. Hydrogen was used as the fuel gas and air was used as the oxidant gas, and the flow rate was controlled at a constant utilization rate. The back pressure was 100 kPa.

[Operating conditions]
1. Full humidification: anode 100% RH, cathode 100% RH
2. Low humidification: anode 40% RH, cathode 40% RH
〔Measurement result〕
The membrane / electrode assembly produced in the example shows better power generation performance under low humidification operating conditions than the membrane / electrode assembly produced in the comparative example, and the membrane / electrode assembly produced in the example is less humidified. Even under the above operating conditions, the power generation performance was at the same level as in the fully humidified operating conditions. In particular, the power generation performance in the vicinity of 0.7 V was improved, and the membrane electrode assembly produced in the example showed 1.8 times the power generation characteristics as compared with the membrane electrode assembly produced in the comparative example. From the results of the power generation characteristics of the membrane / electrode assembly produced in the example and the membrane / electrode assembly produced in the comparative example, the pore volumes of the electrode catalyst layers 2 and 3 were provided on the gas inlet side. The membrane electrode assembly in which the value of the second electrode catalyst parts 2b and 3b provided on the gas outlet side is larger than the value of the electrode catalyst parts 2a and 3a has higher water retention and power generation under low humidification operating conditions. It was confirmed that the characteristics show power generation characteristics equivalent to the operating conditions of full humidification. Moreover, the membrane electrode assembly produced in the Example under the fully humidified operating conditions showed a power generation characteristic 1.4 times that of the membrane electrode assembly produced in the comparative example. From the results of the power generation characteristics of the membrane electrode assembly produced in the example and the membrane electrode assembly produced in the comparative example, it was confirmed that the diffusibility of the reaction gas, removal of water generated by the electrode reaction, etc. were not hindered. confirmed.

<Summary>
The present embodiment relates to a membrane electrode assembly that exhibits high power generation characteristics under low humidification conditions, a method for manufacturing the membrane electrode assembly, and a polymer electrolyte fuel cell including the membrane electrode assembly.
The membrane electrode assembly according to the present embodiment is a membrane electrode assembly in which the polymer electrolyte membrane 1 is sandwiched between a pair of electrode catalyst layers 2 and 3. Here, at least one of the electrode catalyst layers 2 and / or 3 is formed on the first electrode catalyst portions 2a and / or 3a and the first electrode catalyst portions 2a and / or 3a in the planar direction of the polymer electrolyte membrane 1. It divides | segments into at least two with the adjacent 2nd electrode catalyst part 2b and / or 3b.

  In the method for manufacturing the membrane electrode assembly, the first catalyst ink is applied and dried to form the first electrode catalyst portions 2a and 3a, and the second catalyst ink is applied. And forming the second electrode catalyst parts 2b and 3b by drying. The coating speed of the first catalyst ink in the step of forming the first electrode catalyst portions 2a and 3a is higher than the coating speed of the second catalyst ink in the step of forming the second electrode catalyst portions 2b and 3b. large. More specifically, the drying temperature of the first catalyst ink in the step of forming the first electrode catalyst portions 2a and 3a and the drying of the second catalyst ink in the step of forming the second electrode catalyst layers 2 and 3 are described. The temperature difference is 40 ° C. or higher.

In addition, it is a conversion value by cylindrical approximation of the pores obtained by the mercury intrusion method, and the pore volume of the first electrode catalyst portions 2a and 3a having a diameter of 1.0 μm or less and the diameters of the second electrode catalyst portions 2b and 3b. The difference from the pore volume of 1.0 μm or less is 0.1 mL / g or more and 1.0 mL / g or less. In this way, the drying temperature of the catalyst ink is controlled.
The polymer electrolyte fuel cell according to the present embodiment includes the above-described membrane electrode assembly.

  According to the present embodiment, the fine volume of the first electrode catalyst portion 2a or 3a provided on the gas inlet side with respect to the pore volume of 1.0 μm or less in diameter converted by the cylindrical approximation of the pores obtained by the mercury intrusion method. Compared with the pore volume, the pore volume of the second electrode catalyst portion 2b or 3b provided on the gas outlet side is larger. Therefore, a membrane electrode assembly including an electrode catalyst layer that enhances water retention without hindering removal of water generated by the electrode reaction and exhibits high power generation characteristics even under low humidification conditions, and it can be efficiently and economically easily A manufacturing method that can be manufactured can be provided.

  The membrane electrode assembly according to the present embodiment is a membrane electrode assembly in which a polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers, and the electrode catalyst layer includes particles carrying a polymer electrolyte and a catalyst substance. Further, the electrode catalyst layer is divided into at least two in a direction perpendicular to the stacking direction, and the electrode catalyst layer has a diameter of 1.0 μm or less in terms of a cylindrical approximation of pores obtained by mercury porosimetry. The pore volume is larger in the value of the second electrode catalyst part provided on the gas outlet side than the value of the first electrode catalyst part provided on the gas inlet side, and the difference is 0.1 mL / g. It is characterized by being 1.0 mL / g or less. The first and second electrode catalyst portions can increase the water retention of the electrode catalyst layer without hindering the diffusibility of the reaction gas, the removal of water generated by the electrode reaction, and the like. Unlike the conventional application of humidity control film and the response to low humidity by forming grooves on the surface of the electrode catalyst layer, there is no decrease in power generation characteristics due to an increase in interface resistance. Compared to the provided polymer electrolyte fuel cell, the polymer electrolyte fuel cell provided with the membrane electrode assembly according to the present embodiment has a remarkable effect of exhibiting high power generation characteristics even under low humidification conditions. The above utility value is high.

  As mentioned above, although embodiment of this invention was explained in full detail, actually, it is not restricted to said embodiment, Even if there is a change of the range which does not deviate from the summary of this invention, it is included in this invention.

DESCRIPTION OF SYMBOLS 1 ... Polymer electrolyte membrane 2 ... Electrode catalyst layer 2a ... 1st electrode catalyst part 2b ... 2nd electrode catalyst part 3 ... Electrode catalyst layer 3a ... 1st electrode catalyst part 3b ... 2nd electrode catalyst part 4 ... Gas diffusion layer 5 ... Gas diffusion layer 6 ... Air electrode (cathode)
7. Fuel electrode (anode)
DESCRIPTION OF SYMBOLS 8 ... Gas flow path 9 ... Cooling water flow path 10 ... Separator 11 ... Membrane electrode assembly 12 ... Solid polymer fuel cell

Claims (8)

A method for producing a membrane electrode assembly in which a polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers,
The step of forming at least one electrode catalyst layer of the pair of electrode catalyst layers includes:
Forming a first electrode catalyst portion by applying and drying a first catalyst ink on a first region in the planar direction of the polymer electrolyte membrane; and
In the planar direction of the polymer electrolyte membrane, a second catalyst ink is applied to a second region adjacent to the first region and dried to thereby form a second electrode adjacent to the first electrode catalyst part. Forming an electrode catalyst portion;
Have
A method for producing a membrane electrode assembly, wherein the pore volume of the second electrode catalyst part is larger than the pore volume of the first electrode catalyst part.   The drying rate of the first catalyst ink in the step of forming the first electrode catalyst portion is set to be higher than the drying rate of the second catalyst ink in the step of forming the second electrode catalyst portion. The manufacturing method of the membrane electrode assembly of Claim 1 characterized by the above-mentioned.   The membrane electrode bonding according to claim 1 or 2, wherein a drying temperature in the step of forming the first electrode catalyst portion is higher than a drying temperature in the step of forming the second electrode catalyst portion. Body manufacturing method.   The difference between the drying temperature in the step of forming the first electrode catalyst portion and the drying temperature in the step of forming the second electrode catalyst portion is set to 40 ° C or more. The manufacturing method of the membrane electrode assembly as described in any one.   It is a conversion value obtained by a cylindrical approximation of the pores determined by the mercury intrusion method, and the pore volume of the first electrode catalyst portion having a diameter of 1.0 μm or less and the second electrode catalyst portion having a diameter of 1.0 μm or less. 2. The drying speed and drying temperature of the first and second catalyst inks are controlled so that the difference from the pore volume is 0.1 mL / g or more and 1.0 mL / g or less. The manufacturing method of the membrane electrode assembly as described in any one of thru | or 4. A membrane electrode assembly in which a polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers,
At least one of the pair of electrode catalyst layers includes a first electrode catalyst portion and a second electrode catalyst portion adjacent to the first electrode catalyst portion in the planar direction of the polymer electrolyte membrane. And a membrane electrode assembly, wherein the membrane electrode assembly is divided into at least two.   It is a conversion value obtained by a cylindrical approximation of the pores determined by the mercury intrusion method, and the pore volume of the first electrode catalyst portion having a diameter of 1.0 μm or less and the second electrode catalyst portion having a diameter of 1.0 μm or less. The membrane electrode assembly according to claim 6, wherein the difference from the pore volume is 0.1 mL / g or more and 1.0 mL / g or less.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 6.

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