JP2007066805A - Gas diffusion layer, gas diffusion electrode, and membrane electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas diffusion layer, a gas diffusion electrode and a membrane electrode assembly which easily and securely achieve a polyelectrolyte fuel cell which can suppress the decomposition degradation of a polyelectrolyte membrane over a long period, sufficiently prevent the degradation in the initial characteristics, and has an excellent durability even if the operation and the stopping are repeated. <P>SOLUTION: The gas diffusion layer comprises a gas diffusion layer base material which contains a water-repellent carbon layer containing a conductive carbon and a water-repellent material, and a gas diffusion layer base material supporting the water-repellent carbon layer and containing a water-repellent material. The outer edge part of the water-repellent carbon layer is made to be 10 to 100 μm higher than the center part of the water-repellent carbon layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas diffusion layer, a gas diffusion electrode, and a membrane electrode assembly used in a polymer electrolyte fuel cell.

  Since fuel cells (FC) have high power generation efficiency and a low environmental load, they are expected to spread in the future as distributed energy systems. In particular, polymer electrolyte fuel cells using a polymer electrolyte having cation (hydrogen ion) conductivity have high output density, low operating temperature, and can be miniaturized. It is expected to be used in mobile units, distributed power generation systems, and home cogeneration systems.

  A conventional polymer electrolyte fuel cell generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. Here, FIG. 9 is a schematic cross-sectional view showing an example of the basic configuration of a membrane-electrode assembly (MEA) mounted on a conventional polymer electrolyte fuel cell. FIG. 10 is a schematic cross-sectional view showing an example of the basic configuration of a unit cell mounted on a polymer electrolyte fuel cell on which the membrane electrode assembly 100 shown in FIG. 9 is mounted.

  As shown in FIG. 9, in the membrane catalyst layer assembly 100, an electrode catalyst (for example, a platinum-based metal catalyst) is supported on carbon powder on both surfaces of a polymer electrolyte membrane 101 that selectively transports hydrogen ions. A catalyst layer 102 containing the obtained catalyst-supporting carbon and a polymer electrolyte having hydrogen ion conductivity is formed. As the polymer electrolyte membrane 101, a polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (trade name) manufactured by DuPont, USA) is generally used.

The membrane electrode assembly 100 includes a gas diffusion layer base material 104 such as carbon paper subjected to water repellent treatment and a water repellent carbon layer 105 on the outer surface of the catalyst layer 102, and has both air permeability and electronic conductivity. A gas diffusion layer 103 is provided. The combination of the catalyst layer 102 and the gas diffusion layer 103 constitutes an electrode (anode or cathode).
Furthermore, the unit cell, which is the basic configuration of the polymer electrolyte fuel cell, includes a membrane electrode assembly 100, a gasket 106, and a pair of separators 107, as shown in FIG. The gasket 106 is disposed around the electrode with the polymer electrolyte membrane 101 interposed therebetween in order to prevent leakage and mixing of the supplied fuel gas and oxidant gas to the outside. The gasket 106 is integrated with the electrode and the polymer electrolyte membrane 101 in advance. A combination of the polymer electrolyte membrane 101, the pair of electrodes (catalyst layer 102 and gas diffusion layer 103) and the gasket 106 may be referred to as a membrane electrode assembly.

  A pair of separators 107 for mechanically fixing the membrane electrode assembly 100 is disposed outside the membrane electrode assembly 100. A reaction gas (fuel gas or oxidant gas) is supplied to the electrode of the separator 107 in contact with the membrane electrode assembly 100, and an electrode reaction product and a gas containing an unreacted reaction gas are supplied from the reaction field to the outside of the electrode. A gas flow path 107a for carrying away is formed. Although the gas flow path 107a can be provided separately from the separator 107, a method of forming a gas flow path 107a by providing a groove on the surface of the separator 107 as shown in FIG. Further, on the side of the separator 107 opposite to the membrane electrode assembly 100, a groove is formed by cutting to form a cooling water flow path 107b.

Thus, the membrane electrode assembly 100 is fixed by the pair of separators 107, the fuel gas is supplied to the gas flow path 107a of one separator 107, and the oxidant gas is supplied to the gas flow path 107a of the other separator 107. Thus, an electromotive force of about 0.7 to 0.8 V can be generated with one single battery when a practical current density of several tens to several hundred mA / cm ² is applied. However, when a polymer electrolyte fuel cell is normally used as a power source, a voltage of several to several hundred volts is required. In practice, the required number of cells are connected in series and stacked. Use as

  In order to supply the reaction gas to the gas flow path 107a, the piping for supplying the reaction gas is branched into a number corresponding to the number of separators 107 to be used, and the branch destinations are directly connected to the gas flow path 107a on the separator 107. Manifolds that are members to be connected to are required. In particular, a manifold of the type that is directly connected to the separator 107 from an external pipe that supplies reaction gas is called an external manifold. On the other hand, there is a so-called internal manifold having a simpler structure. The internal manifold is constituted by a through hole provided in the separator 107 in which the gas flow path 107a is formed. The inlet / outlet of the gas flow path 107a is communicated with this hole, and the reaction gas is directly passed from the through hole to the gas flow path 107a. Can be supplied.

  Here, the catalyst layer 102 mainly has four functions. The first function is a function of supplying the reaction gas supplied from the gas diffusion layer 103 to the reaction site of the catalyst layer 102, and the second function is hydrogen ions or generation necessary for the reaction on the electrode catalyst. It is a function to conduct the generated hydrogen ions. The third function is a function of conducting electrons necessary for the reaction or the generated electrons, and the fourth function is a function of accelerating the electrode reaction by high catalyst performance and its wide reaction area. That is, the catalyst layer 112 needs high reaction gas permeability, hydrogen ion conductivity, electron conductivity, and catalyst performance.

  In general, as the catalyst layer 102, a catalyst layer having a porous structure and a gas channel is formed using a fine carbon powder or a pore-forming material having a developed structure structure in order to have gas permeability. Yes. In order to provide hydrogen ion permeability, a polymer electrolyte is dispersed in the vicinity of the electrode catalyst in the catalyst layer 102 to form a hydrogen ion network. Further, in order to provide electron conductivity, an electron channel is formed by using an electron conductive material such as carbon fine powder or carbon fiber as an electrode catalyst carrier. In order to improve the catalyst performance, a catalyst body in which a very fine particle electrode catalyst having a particle size of several nm is supported on a fine carbon powder is highly dispersed in the catalyst layer 102. ing.

  Next, the gas diffusion layer 103 mainly has the following three functions. The first function is a function of diffusing the reaction gas in order to uniformly supply the reaction gas from the gas flow path 107a of the separator 107 located outside the gas diffusion layer 103 to the electrode catalyst in the catalyst layer 102. The second function is a function for quickly discharging water generated by the reaction in the catalyst layer 102 to the gas flow path 107a. The third function is a function of conducting electrons necessary for the reaction or generated electrons. In other words, the gas diffusion layer 103 is required to have high reactive gas permeability, moisture exhaustability, and electronic conductivity.

  In general, as shown in FIG. 9, the gas diffusion layer 103 is formed of a water-repellent material and conductive carbon provided on the surface of the gas diffusion layer base material 104 and the surface of the gas diffusion layer base material 104 in contact with the catalyst layer 102. And a water repellent carbon layer 105 composed of The gas diffusion layer base material 104 has a porous structure made of carbon fine powder, pore former, carbon paper or carbon cloth having a developed structure structure in order to give gas permeability. A conductive substrate is used. Further, in order to provide drainage, water repellent polymer such as fluororesin is dispersed in the gas diffusion layer base material 104, and in addition, carbon is provided in order to provide electron conductivity. The gas diffusion layer substrate 104 is also composed of an electron conductive material such as fiber, metal fiber, or carbon fine powder.

  Here, various studies for improving the performance of the membrane electrode assembly as described above have been conducted for the practical application of the polymer electrolyte fuel cell. For example, Patent Documents 1 and 2 intend to enhance the mechanical strength and heat resistance of the polymer electrolyte membrane itself in order to suppress degradation of the portion of the polymer electrolyte membrane located in the periphery of the electrode. Technology has been proposed. Specifically, a method of reinforcing a portion of the polymer electrolyte membrane located in the periphery of the electrode with a fiber material, or a method of constituting only the above portion with an ion exchange resin having a low water content in order to suppress swelling and shrinkage Has been proposed.

As for the catalyst layer, for example, Patent Documents 3 and 4 propose a structure of the catalyst layer intended to suppress deterioration of a portion located in the periphery of the electrode in the polymer electrolyte membrane. Specifically, a structure in which the outer periphery of the cathode and the anode formed with the polymer electrolyte membrane interposed therebetween is not polymerized, or a structure in which a refractory layer is provided on the outer periphery of the catalyst layer from the viewpoint of promoting heat dissipation has been proposed.
Japanese Patent Laid-Open No. 08-185872 JP 2000-223136 A Japanese Patent Laid-Open No. 10-172587 Japanese Unexamined Patent Publication No. 07-201346

  However, the prior art as described above has been proposed with the intention of improving the mechanical strength and heat resistance of the polymer electrolyte membrane. In the case of assuming that the fuel cell is operated for a long time. It has not been sufficiently studied to improve the durability and life characteristics of the gas diffusion layer, the gas diffusion electrode, the membrane electrode assembly, and the fuel cell.

  Specifically, the deterioration of the membrane electrode assembly when it is assumed that the fuel cell is operated over a long period of time only by reinforcing the durability of the polymer electrolyte membrane based on the techniques described in Patent Documents 1 and 2 above. However, there is still room for improvement from the viewpoint of realizing a membrane electrode assembly with a long life and high efficiency. In addition, deterioration suppression of the polymer electrolyte membrane based on the techniques described in Patent Documents 3 and 4 is not sufficient, and there is still room for improvement from the viewpoint of realizing a long-life and high-efficiency membrane electrode assembly. . That is, the fuel cells described in Patent Documents 1 to 4 still have room for improvement from the viewpoint of durability and life characteristics.

  The present invention has been made in view of the above viewpoints, and even if the operation and stop of the polymer electrolyte fuel cell are repeated, the degradation of the polymer electrolyte membrane can be suppressed over a long period of time, and the initial characteristics are lowered. An object of the present invention is to provide a gas diffusion layer, a gas diffusion electrode and a membrane electrode assembly capable of easily and reliably realizing a polymer electrolyte fuel cell having excellent durability that can sufficiently prevent the above. In addition, the present invention uses the gas diffusion electrode, gas diffusion layer, and membrane electrode assembly of the present invention, can sufficiently prevent deterioration of initial characteristics, and exhibits sufficient battery performance over a long period of time. It is an object of the present invention to provide a polymer electrolyte fuel cell having

As a result of intensive studies to achieve the above object, the present inventors have studied the possibility that the gas diffusion layer located on the outer periphery of the catalyst layer has a great influence on the durability of the polymer electrolyte membrane. The inventors have found that the durability of the membrane electrode assembly can be improved by devising the configuration of the gas diffusion layer to the following configuration, and the present invention has been achieved.
That is, the present invention
A gas diffusion layer that is used in a gas diffusion electrode including a catalyst layer including an electrode catalyst and serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer substrate and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer has an outer edge portion that is located outside the outer peripheral portion of the catalyst layer with respect to the central portion where the catalyst layer is to be disposed, and the outer edge portion is 10 to 100 μm higher. Formed so as to cover at least a part of the side surface;
A gas diffusion layer is provided.

  By using the gas diffusion layer of the present invention as at least one gas diffusion electrode of a polymer electrolyte fuel cell, the polymer electrolyte membrane can be decomposed over a long period of time even when the polymer electrolyte fuel cell is repeatedly operated and stopped. It is possible to configure a gas diffusion layer that can easily and reliably realize a polymer electrolyte fuel cell having excellent durability that can suppress deterioration and sufficiently prevent deterioration of initial characteristics.

Here, in the present invention, a clear mechanism for elucidating that the above-described effects of the present invention can be obtained by forming the above-described gas diffusion layer on at least one gas diffusion electrode of the polymer electrolyte fuel cell. However, the present inventors speculate as follows.
That is, it has been reported that the deterioration of the membrane electrode assembly proceeds mainly in the polymer electrolyte membrane. Specifically, it has been reported that the degradation of the portion located in the periphery of the electrode in the polymer electrolyte membrane is large (for example, S. Grot, Abstract p860, Fuel Cell Seminar Nov. 2003). The deterioration of the polymer electrolyte membrane at the above site is presumed to be caused by the gas diffusion layer in direct contact with the polymer electrolyte membrane without passing through the catalyst layer in the periphery of the electrode. More specifically, the unevenness, fluff and fraying due to the density of the base material constituting the gas diffusion layer are considered to break the polymer electrolyte membrane through the water-repellent carbon layer.

  The inventors have determined the thickness of the outer edge of the water-repellent carbon layer that is in direct contact with the polymer electrolyte membrane and is located outside the outer peripheral portion of the catalyst layer and inside the seal portion of the polymer electrolyte membrane. It is considered that by increasing the height of the carbon layer by 10 to 100 μm, the unevenness, fluff and fraying of the gas diffusion layer substrate, which is the cause of deterioration, can be alleviated and deterioration of the polymer electrolyte membrane can be suppressed. It came to be completed.

  When the thickness at the center of the water-repellent carbon layer takes a large value as in the outer edge, it becomes difficult to effectively discharge the generated water, which induces vibration and reduction of the output voltage. Causes flooding. As described above, a membrane electrode assembly that can simultaneously realize excellent life characteristics, that is, high durability and high efficiency, by constructing a structure in which the thickness of the water-repellent carbon layer is increased at the outer edge of the gas diffusion layer. Can be obtained.

  In the present invention, the increase in the thickness of the water-repellent carbon layer at the outer edge of the water-repellent carbon layer relative to the central portion of the water-repellent carbon layer is preferably 10 to 100 μm. If the increase in thickness is less than 10 μm, the unevenness, fluff and fraying of the gas diffusion layer substrate cannot be alleviated, and the effect of suppressing deterioration of the polymer electrolyte membrane becomes insufficient. In addition, if the increase in thickness exceeds 100 μm, the center of the gas diffusion layer and the catalyst layer are not sufficiently bonded even when the battery is fastened, flooding occurs, and stable battery output cannot be obtained. .

The present invention also provides:
A gas diffusion layer that is used in a gas diffusion electrode including a catalyst layer including an electrode catalyst and serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer substrate and comprising conductive carbon and a water repellent material;
Has a configuration including
The water-repellent carbon layer is a water-repellent material that constitutes an outer edge portion that is positioned outside the outer peripheral portion of the catalyst layer with respect to the mass per unit area of the water-repellent material constituting the central portion where the catalyst layer is to be disposed. That the mass per unit area of the water material is 5 to 40% higher,
A gas diffusion layer is also provided.

  The inventors of the present invention have made the mass per unit area of the water repellent material constituting the water repellent carbon layer 5 to 40% higher at the outer edge of the water repellent carbon layer than the center of the water repellent carbon layer. The present inventors have completed the present invention, considering that the unevenness, fluff and fraying of the gas diffusion layer base material, which is a cause of deterioration, can be alleviated and deterioration of the polymer electrolyte membrane can be suppressed.

  In the present invention, the increase in the mass per unit area of the water-repellent material at the outer edge of the water-repellent carbon layer relative to the central portion of the water-repellent carbon layer is desirably 5 to 40%. If the increase in mass per unit area of the water-repellent material is less than 5%, the unevenness, fluff and fraying of the gas diffusion layer substrate cannot be alleviated, and the effect of suppressing deterioration of the polymer electrolyte membrane becomes insufficient. Further, if the increase in the mass per unit area of the water repellent material is more than 40%, the fastening pressure is concentrated on the outer edge of the gas diffusion layer when fastening the battery, leading to the damage of the polymer electrolyte membrane. there is a possibility.

The present invention also provides:
A gas diffusion layer that is used in a gas diffusion electrode including a catalyst layer including an electrode catalyst and serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer substrate and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer is divided into a central portion where the catalyst layer is to be disposed and an outer edge portion which is located outside the central portion and where the catalyst layer is not disposed,
The outer edge contains a polymer electrolyte,
A gas diffusion layer is also provided.

By including a polymer electrolyte in the outer edge of the water-repellent carbon layer, the present inventors can alleviate unevenness, fluff and fraying of the gas diffusion layer base material that are the cause of deterioration, and can suppress deterioration of the polymer electrolyte membrane. The present invention has been completed.
In the center of the water-repellent carbon layer, when the polymer electrolyte is contained in the same manner as the outer edge of the water-repellent carbon layer, the porosity is reduced in the layer at the center of the water-repellent carbon layer, and the generated water is effectively discharged. May decrease and cause a flooding phenomenon.

Furthermore, the present invention provides
A gas diffusion layer that is used in a gas diffusion electrode including a catalyst layer including an electrode catalyst and serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer substrate and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer is divided into a central portion where the catalyst layer is to be disposed and an outer edge portion which is located outside the central portion and where the catalyst layer is not disposed,
A layer containing a polymer electrolyte and conductive carbon is further disposed on the outer edge so as to cover at least part of the side surface of the catalyst layer,
A gas diffusion layer is also provided.

The inventors of the present invention have formed a layer containing a polymer electrolyte and conductive carbon on the water-repellent carbon layer at the outer edge of the water-repellent carbon layer, thereby forming irregularities on the gas diffusion layer base material that is a cause of deterioration. Thus, the present inventors have completed the present invention, considering that fluff and fraying can be alleviated and deterioration of the polymer electrolyte membrane can be suppressed.
In the center of the water-repellent carbon layer, as in the outer edge of the water-repellent carbon layer, when a layer containing a polymer electrolyte and conductive carbon is formed on the water-repellent carbon layer, the center of the water-repellent carbon layer In some layers, flooding due to inhibition of gas diffusibility may occur, and stable battery output may not be obtained.

The gas diffusion layer of the present invention described above can be used as a gas diffusion electrode by disposing a catalyst layer on the water-repellent carbon layer of the gas diffusion layer.
That is, the present invention provides a gas diffusion electrode comprising the gas diffusion layer of the present invention and a catalyst layer formed on a water-repellent carbon layer of the gas diffusion layer.
Since the gas diffusion electrode of the present invention includes the gas diffusion layer described above, the deterioration of the polymer electrolyte membrane in the membrane electrode assembly is suppressed, and the operation and stop of the polymer electrolyte fuel cell are repeated. However, the deterioration of the initial characteristics can be sufficiently prevented over a long period of time, and excellent life characteristics can be realized.

Furthermore, the present invention also provides a membrane electrode assembly including the gas diffusion electrode described above.
Since the membrane electrode assembly of the present invention includes the gas diffusion electrode described above, deterioration of the polymer electrolyte in the membrane electrode assembly is suppressed, and the operation and stop of the polymer electrolyte fuel cell are repeated. However, the deterioration of the initial characteristics can be sufficiently prevented over a long period of time, and excellent life characteristics can be realized.

  According to the present invention, it is possible to suppress damage and decomposition of the polymer electrolyte membrane over a long period of time even when the operation and stop of the polymer electrolyte fuel cell are repeated, and it is possible to sufficiently prevent deterioration of the initial characteristics. It is possible to provide a gas diffusion layer, a gas diffusion electrode, and a membrane electrode assembly including the gas diffusion layer that can surely realize a polymer electrolyte fuel cell having high durability. Also provided is a polymer electrolyte fuel cell having excellent durability that can sufficiently prevent deterioration in initial characteristics and exhibits sufficiently stable battery performance over a long period of time using the membrane electrode assembly of the present invention. can do.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description may be abbreviate | omitted.

[First embodiment]
FIG. 1 is a schematic cross-sectional view showing an example of a basic configuration of a membrane-electrode assembly 10 (MEA: Membrane-electrode assembly) constituting a unit cell mounted in a preferred embodiment of a polymer electrolyte fuel cell of the present invention. FIG. FIG. 2 is a schematic cross-sectional view showing an example of a basic configuration of a unit cell mounted on a polymer electrolyte fuel cell on which the membrane electrode assembly 10 shown in FIG. 1 is mounted.

  As shown in FIG. 1, the membrane electrode assembly 10 of the present embodiment has an electrode catalyst (for example, a platinum-based metal catalyst) supported on carbon powder on both surfaces of a polymer electrolyte membrane 11 that selectively transports hydrogen ions. The catalyst layer 12 containing the catalyst-supported carbon obtained by the above and a polymer electrolyte having hydrogen ion conductivity is formed. The polymer electrolyte membrane 11 is not particularly limited, and a polymer electrolyte membrane mounted on a normal solid polymer fuel cell can be used. For example, a polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (trade name) manufactured by DuPont, USA, Aciplex (trade name) manufactured by Asahi Kasei Co., Ltd., GSII manufactured by Japan Gore-Tex Co., Ltd., etc.) Can be used. In addition, the thickness of the polymer electrolyte membrane 11 will not be specifically limited if it is in the range which can acquire the effect of this invention.

  Moreover, as a polymer electrolyte which comprises the polymer electrolyte membrane 11, what has a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a sulfonimide group as a cation exchange group is mentioned preferably. From the viewpoint of hydrogen ion conductivity, those having a sulfonic acid group are particularly preferred. The polymer electrolyte having a sulfonic acid group preferably has an ion exchange capacity of 0.5 to 1.5 meq / g dry resin. When the ion exchange capacity of the polymer electrolyte is 0.5 meq / g dry resin or more, the resistance value of the obtained catalyst layer is preferably not increased during power generation, and the ion exchange capacity is 1.5 meq / g dry resin or less. It is preferable because the water content of the obtained catalyst layer does not increase, the catalyst layer does not easily swell, and the pores are not clogged. The ion exchange capacity is particularly preferably 0.8 to 1.2 meq / g dry resin.

As the polymer _{electrolyte, CF 2 = CF- (OCF 2} CFX) m -O p - (CF 2) a perfluorovinyl compound represented by _n -SO ₃ H (m is an integer of 0 to 3 , N represents an integer of 1 to 12, p represents 0 or 1, X represents a fluorine atom or a trifluoromethyl group), and tetrafluoroethylene represented by CF ₂ = CF ₂ A perfluorocarbon copolymer containing a polymerization unit based on The fluorocarbon polymer may contain, for example, an etheric oxygen atom.

Preferable examples of the perfluorovinyl compound include compounds represented by the following formulas (1) to (3). However, in the following formula, q is an integer of 1 to 8, r is an integer of 1 to 8, and t is an integer of 1 to 3.
_{CF 2 = CFO (CF 2)} q -SO 3 H ··· (1)
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) r -SO 3 H ··· (2)
_{CF 2 = CF (OCF 2 CF} (CF 3)) t O (CF 2) 2 -SO 3 ··· (3)

The polymer electrolyte membrane may be composed of one or more types of polymer electrolytes, but may contain a reinforcing body (filler) inside. However, the arrangement state (for example, the degree of density or regularity) of the reinforcing body in the polymer electrolyte membrane is not particularly limited.
The material constituting such a reinforcing body is not particularly limited, and examples thereof include polytetrafluoroethylene, polyfluoroalkoxyethylene, and polyphenyl sulfide. The shape of the reinforcing body is not particularly limited, and examples thereof include a porous reinforcing body and fibril, fibrous and spherical reinforcing body particles.

  The membrane electrode assembly 10 includes a gas diffusion layer base material 14 such as carbon paper subjected to water repellent treatment and a water repellent carbon layer 15 on the outer surface of the catalyst layer 12, and has both air permeability and electronic conductivity. A gas diffusion layer 13 is provided. An electrode (anode or cathode) is configured by a combination of the catalyst layer 12 and the gas diffusion layer 13 that serves as a support for the catalyst layer 12.

  The carbon powder (conductive carbon particles) that is a carrier in the catalyst layer 12 is preferably a carbon material having conductive pores, such as carbon black, activated carbon, carbon fiber, and carbon tube. be able to. Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Activated carbon can be obtained by carbonizing and activating materials containing various carbon atoms.

The specific surface area of the carbon powder is preferably 50 to 1500 m ² / g. When the specific surface area is 50 m ² / g or more, it is preferable because the loading ratio of the electrode catalyst is easily improved and the output characteristics of the cathode catalyst layer and the anode catalyst layer do not deteriorate, and the specific surface area is 1500 m ² / g or less. It is preferable because the pores are not too fine and the coating with the polymer electrolyte becomes easier and the output characteristics of the catalyst layer do not deteriorate. The specific surface area is particularly preferably 200 to 900 m ² / g.

As an electrode catalyst used for the catalyst layer 12, it is preferable to use platinum or a platinum alloy. Platinum alloys include platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, iridium), iron, titanium, gold, silver, chromium, manganese, molybdenum, tungsten, aluminum, silicon, rhenium, zinc, and tin. An alloy of at least one metal selected from the group consisting of platinum and platinum is preferable. The platinum alloy may contain an intermetallic compound of platinum and the metal.
Furthermore, an electrode catalyst mixture obtained by mixing an electrode catalyst made of platinum and an electrode catalyst made of a platinum alloy may be used, or the same electrode catalyst may be used on the anode side and the cathode side, or different electrode catalysts may be used. .

The primary particle diameter of the electrode catalyst is preferably 1 to 20 nm in order to make the catalyst layer 12 highly active, and in particular, it is possible to ensure a large surface area in order to increase the reaction activity. From the viewpoint, it is preferably 2 to 10 nm.
The catalyst loading rate of the catalyst-carrying carbon (ratio of the mass of the supported electrode catalyst to the total mass of the catalyst-carrying carbon) may be 20 to 80% by mass, and particularly preferably 40 to 60% by mass. . Within this range, high battery output can be obtained. As described above, when the catalyst loading is 20% by mass or more, sufficient battery output can be obtained more reliably, and when it is 80% by mass or less, the electrode catalyst particles are supported on the carbon powder with good dispersibility. And the effective catalyst area can be further increased.

As the polymer electrolyte having hydrogen ion conductivity contained in the catalyst layer 12 and attached to the catalyst-supporting carbon, a polymer electrolyte constituting the polymer electrolyte membrane 11 may be used. The polymer electrolyte constituting the catalyst layer 12 and the polymer electrolyte membrane 11 may be the same type or different types. For example, commercially available products such as Nafion (trade name) manufactured by DuPont, USA, Flemion (trade name) manufactured by Asahi Glass Co., Ltd., and Aciplex (trade name) manufactured by Asahi Kasei Co., Ltd. may be used. The specific surface area of the carbon powder is preferably 50 to 1500 m ² / g. When the specific surface area is 50 m ² / g or more, it is preferable because it is easy to improve the loading ratio of the electrode catalyst and the output characteristics of the catalyst layer 12 do not deteriorate, and when the specific surface area is 1500 m ² / g or less, it is fine. Since the pores are not too fine, the coating with the polymer electrolyte is easier, and the output characteristics of the catalyst layer 12 are not likely to deteriorate. The specific surface area is particularly preferably 200 to 900 m ² / g.

The polymer electrolyte is preferably added in proportion to the mass of the catalyst-carrying carbon constituting the catalyst layer 12 in order to cover the catalyst-carrying carbon particles and secure a three-dimensional hydrogen ion conduction path.
Specifically, the mass of the polymer electrolyte constituting the catalyst layer 12 is desirably 0.2 to 2.0 times the mass of the catalyst-supporting carbon. Within this range, high battery output can be obtained. As described above, if the mass of the polymer electrolyte is 0.2 times or more, sufficient hydrogen ion conductivity can be ensured, and if it is 2.0 times or less, flooding can be avoided, resulting in higher battery output. Can be realized.

  In the catalyst layer 12 of the present embodiment, it is sufficient that the polymer electrolyte is partially attached to the surface of the catalyst-carrying carbon particles, that is, it covers only at least a part of the catalyst-carrying carbon particles. However, it is not always necessary to cover the entire catalyst-supporting carbon particles. Of course, the polymer electrolyte may cover the entire surface of the catalyst-supporting carbon particles.

  The catalyst layer 12 can be formed using a plurality of inks for forming a catalyst layer prepared to have a component composition capable of realizing the configuration of the catalyst layer 12. The dispersion medium used to prepare the ink for forming the catalyst layer may be a polymer electrolyte that can be dissolved or dispersible (part of the polymer electrolyte is dissolved and the other part is dispersed without being dissolved) It is preferable to use a liquid containing an alcohol. The dispersion medium preferably contains at least one of water, methanol, ethanol, propanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol. These water and alcohol may be used alone or in combination of two or more. The alcohol is particularly preferably a straight chain having one OH group in the molecule, and ethanol is particularly preferable. This alcohol includes those having an ether bond such as ethylene glycol monomethyl ether.

  Further, the composition of the ink for forming the catalyst layer may be appropriately adjusted according to the configuration of the catalyst layer 12, but the solid content concentration is preferably 0.1 to 20% by mass. When the solid content concentration is 0.1% by mass or more, a catalyst layer having a predetermined thickness can be formed without spraying or coating many times in preparing the catalyst layer by spraying or coating the ink for forming the catalyst layer. The production efficiency is not lowered. Moreover, when the solid content concentration is 20% by mass or less, the viscosity of the mixed solution does not become too high, and the resulting catalyst layer is not likely to be non-uniform. The solid content concentration is particularly preferably 1 to 10% by mass.

  The ink for forming the catalyst layer can be prepared based on a conventionally known method. Specifically, a method using a stirrer such as a homogenizer or a homomixer, a method using high-speed rotation such as using a high-speed rotating jet flow method, or a high-pressure emulsifying apparatus or the like is used to push the dispersion from a narrow part. The method of giving a shearing force to a dispersion liquid by taking out is mentioned.

  When the catalyst layer 12 is formed using the catalyst layer forming ink, any of the indirect coating method for indirectly forming the polymer electrolyte membrane 11 is adopted even if the direct coating method is directly formed on the polymer electrolyte membrane 11. It is also possible to do. Examples of the coating method include a screen printing method, a die coating method, a spray method, and an ink jet method. As an indirect coating method, for example, after forming the catalyst layer 12 on the support made of polypropylene or polyethylene terephthalate by the above method, it is formed on the polymer electrolyte membrane 11 or the previously formed catalyst layer 12 by thermal transfer. The method of doing is mentioned.

  Next, as the gas diffusion layer base material 14 constituting the gas diffusion layer 13, carbon fine powder having a developed structure structure, a pore former, carbon paper, carbon cloth, or the like is used in order to provide gas permeability. A conductive substrate having a porous structure produced in the above manner can be used. In order to provide drainage, a water repellent polymer typified by a fluororesin may be dispersed in the gas diffusion layer base material 14. In order to give electron conductivity, the gas diffusion layer base material 14 may be made of an electron conductive material such as carbon fiber, metal fiber, or carbon fine powder.

Further, the gas diffusion layer 13 of the present embodiment has a water repellent carbon layer 15 composed of a water repellent material (polymer) and conductive carbon powder on the surface of the gas diffusion layer base material 14 that contacts the catalyst layer 12. It is provided and configured. The same gas diffusion layer or different gas diffusion layers may be used on the cathode side and the anode side.
The water repellent carbon layer 15 can be formed by preparing a water repellent carbon layer ink containing a water repellent material (polymer), a conductive carbon powder, and a dispersion medium, and applying and drying the ink.

  Examples of the water repellent material include polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene / ethylene. A fluororesin such as a copolymer (ETFE) can be used.

  As the carbon powder, for example, carbon black, activated carbon, carbon fiber, carbon tube and the like can be used. Examples of carbon black include channel black, furnace black, thermal black, and acetylene black.

  As the dispersion medium, the same one as in the case of the ink for forming the catalyst layer described above can be used. Further, the composition of the water repellent carbon layer ink may be appropriately adjusted within a range not impairing the effects of the present invention.

  Furthermore, the unit cell, which is the basic configuration of the polymer electrolyte fuel cell according to the present embodiment, includes a membrane electrode assembly 10, a gasket 16, and a pair of separators 17, as shown in FIG. The gasket 16 is disposed around the electrode with the polymer electrolyte membrane 11 interposed therebetween in order to prevent leakage and mixing of the supplied fuel gas and oxidant gas to the outside. The gasket 16 is integrated with the electrode and the polymer electrolyte membrane 11 in advance. A combination of the polymer electrolyte membrane 11, the pair of electrodes (catalyst layer 12 and gas diffusion layer 13), and the gasket 16 may be referred to as a membrane electrode assembly.

  A pair of separators 17 for mechanically fixing the membrane electrode assembly 10 is disposed outside the membrane electrode assembly 10. A reaction gas (fuel gas or oxidant gas) is supplied to the electrode at a portion of the separator 17 that contacts the membrane electrode assembly 10, and an electrode reaction product and a gas containing an unreacted reaction gas are supplied from the reaction field to the outside of the electrode. A gas flow path 17a for carrying away is formed. In the present embodiment, as shown in FIG. 2, a groove is provided on the surface of the separator 17 to form a gas flow path 17a. The separator 17 has a configuration in which a groove is provided by cutting on the side opposite to the membrane electrode assembly 10 to form a cooling water channel 17b.

Thus, the membrane electrode assembly 10 is fixed by the pair of separators 17, the fuel gas is supplied to the gas flow path 17 a of one separator 17, and the oxidant gas is supplied to the gas flow path 17 a of the other separator 17. Thus, an electromotive force of about 0.7 to 0.8 V can be generated with one single battery when a practical current density of several tens to several hundred mA / cm ² is applied. When a polymer electrolyte fuel cell is used as a power source, a required number of cells can be connected in series and used as a stack (not shown).

  In order to supply the reaction gas to the gas flow path 17a, the piping for supplying the reaction gas is branched into a number corresponding to the number of separators 17 to be used, and the branch destinations are directly connected to the gas flow path 17a on the separator 17. However, in this embodiment, either an external manifold or an internal manifold can be used.

Here, FIG. 3 shows an enlarged view of a portion indicated by P in FIG. FIG. 4 shows a schematic cross-sectional view of the gas diffusion layer 13 in the present embodiment.
In the present embodiment, as shown in FIG. 3, the area of the main surface of the water repellent carbon layer 15 on the side in contact with the gas diffusion layer base material 14 and the water repellent carbon layer 15 of the gas diffusion layer base material 14. The area of the main surface of the catalyst layer 12 is smaller than the area of the main surface of the water repellent carbon layer 15 and the main surface of the gas diffusion layer base material 14.

  Therefore, as shown in FIGS. 3 and 4, the catalyst layer is in contact with the water repellent carbon layer central portion 15 b in contact with the catalyst layer 12 (that is, the central portion of the water repellent carbon layer 15 where the catalyst layer 12 is to be disposed) 15 b. An outer edge of the water repellent carbon layer (that is, an outer edge of the water repellent carbon layer 15 that is positioned outside the outer periphery of the catalyst layer 12) 15 a is formed outside the outer periphery of 12. That is, the water repellent carbon layer outer edge portion 15a is formed on the portion indicated by the arrow Q in FIG. 3 (the portion outside the outer peripheral portion of the catalyst layer 12 and the portion where the gasket 16 seals the polymer electrolyte membrane 11). Exists.

  In the water repellent carbon layer 15 of the present embodiment, the water repellent carbon layer outer edge portion 15 a located outside the outer peripheral portion of the catalyst layer 12 and inside the seal portion of the polymer electrolyte membrane 11 is water repellent. The thickness of the water-repellent carbon layer 15 is 10 to 100 μm higher than the carbon layer center portion 15b. That is, the difference ΔX between the thickness of the water repellent carbon layer outer edge portion 15a and the thickness of the water repellent carbon layer center portion 15b is 10 to 100 μm. As described above, by thickening the water-repellent carbon layer 15 in the periphery of the polymer electrolyte membrane 11 where the progress of deterioration is fast, it is possible to obtain the unevenness, fluff and frayed film of the gas diffusion layer base material 14 which is presumed to be a deterioration factor. It is thought that direct contact of the slag can be suppressed.

  If the increase in thickness at the outer edge 15a of the water-repellent carbon layer is less than 10 μm, the unevenness, fluff and fraying of the gas diffusion layer base material 14 cannot be alleviated, and the deterioration suppressing effect of the polymer electrolyte membrane 11 becomes insufficient. . Further, if the increase in thickness exceeds 100 μm, even when the battery is fastened, the water repellent carbon layer central portion 15b and the catalyst layer 12 are not sufficiently bonded, resulting in flooding and stable battery output. I can't.

  The structure of the water-repellent carbon layer 15 of this embodiment may be formed at the time of producing the water-repellent carbon layer, and after the substantially flat water-repellent carbon layer is produced, the thickness of the outer edge of the water-repellent carbon layer is increased. You may increase and form. For example, when the water repellent carbon layer is formed, a mask corresponding to the increase in the thickness of the water repellent carbon layer outer edge portion 15a is disposed at the water repellent carbon layer central portion 15b, so that the water repellent carbon layer outer edge portion is formed. What is necessary is just to increase the application quantity in 15a.

  According to the present embodiment, the thickness of the outer edge of the water-repellent carbon layer that is in direct contact with the polymer electrolyte membrane and outside the outer peripheral portion of the catalyst layer and inside the seal portion of the polymer electrolyte membrane is determined by the above repellent properties. By making the central portion of the water carbon layer 10 to 100 μm higher, the unevenness, fluff and fraying of the gas diffusion layer base material, which is the cause of deterioration, can be alleviated, and deterioration of the polymer electrolyte membrane can be suppressed. Therefore, according to this embodiment, even if the polymer electrolyte fuel cell is repeatedly operated and stopped, the polymer electrolyte membrane can be prevented from being damaged and decomposed over a long period of time, and the initial characteristics can be sufficiently prevented from being deteriorated. It is possible to provide a gas diffusion layer, a gas diffusion electrode, and a membrane electrode assembly including the gas diffusion layer that can surely realize a polymer electrolyte fuel cell having excellent durability. Further, it is possible to provide a polymer electrolyte fuel cell having excellent durability, which can sufficiently prevent deterioration of initial characteristics, exhibits sufficiently stable battery performance over a long period of time, using the membrane electrode assembly described above. it can.

[Second Embodiment]
Next, a second embodiment of the polymer electrolyte fuel cell of the present invention will be described. The membrane electrode assembly constituting the unit cell mounted on the fuel cell (not shown) of the second embodiment is different from the gas diffusion layer in the membrane electrode assembly 10 of the first embodiment shown in FIG. The configuration other than the gas diffusion layer is the same as that of the membrane electrode assembly 10 of the first embodiment.
Hereinafter, the gas diffusion layer provided in the membrane electrode assembly of the second embodiment will be described. FIG. 5 is a schematic cross-sectional view of the gas diffusion layer 23 provided in the membrane electrode assembly of the second embodiment.

  In the present embodiment, as shown in FIG. 5, the water-repellent carbon layer 25 per unit area of the water-repellent material constituting the central portion (water-repellent carbon layer central portion 25 b) where the catalyst layer 12 is to be disposed. The mass per unit area of the water-repellent material constituting the outer edge portion (water-repellent carbon layer outer edge portion 25a) located outside the outer peripheral portion of the catalyst layer 12 is 5 to 40% higher than the mass. It is characterized by being formed. In this way, the unevenness of the gas diffusion layer base material 24, which is assumed to be a cause of deterioration, is increased by increasing the water-repellent material constituting the water-repellent carbon layer 25 in the peripheral portion of the polymer electrolyte membrane 11 where the progress of deterioration is fast. It is thought that direct contact of fluff and fraying with the polymer electrolyte membrane 11 can be suppressed.

  When the increase in the mass per unit area of the water repellent material at the outer edge 25a of the water repellent carbon layer is lower than 5%, the unevenness, fluff and fraying of the gas diffusion layer base material 25 cannot be alleviated, and the polymer electrolyte membrane 11 Insufficient deterioration suppression effect. Further, if the increase in the water repellent material exceeds 40%, even when the battery is fastened, the gas diffusion layer central portion 25b and the catalyst layer 12 are not sufficiently bonded, and flooding occurs, thereby obtaining a stable battery output. I can't.

  In the present embodiment, the water repellent carbon layer outer edge portion 25a is required to have a mass per unit area of the water repellent material 5 to 40% higher than the water repellent carbon layer central portion 25b, and in the thickness direction. The ratio of the water-repellent material in may be changed. For example, as shown in FIG. 6, after the water-repellent carbon layer is uniformly applied to the gas diffusion layer base material 24 as in the prior art, the ratio of the material of the water-repellent carbon layer 24 is high only on the outer edge 25a of the water-repellent carbon layer. The layers may be applied in layers. FIG. 6 is a schematic cross-sectional view of a modified example of the gas diffusion layer 23 provided in the membrane electrode assembly of the present embodiment.

  The water repellent carbon layer 25 in this embodiment is prepared by preparing water repellent carbon layer inks having different compositions at the water repellent carbon layer outer edge portion 25a and the water repellent carbon central portion 25b, respectively, and using the ink. It can be formed by the same method as the form.

  According to this embodiment, the mass per unit area of the water-repellent material constituting the water-repellent carbon layer is increased by 5 to 40% at the outer edge of the water-repellent carbon layer with respect to the central portion of the water-repellent carbon layer. Thus, the unevenness, fluff and fraying of the gas diffusion layer base material, which is the cause of deterioration, can be alleviated, and deterioration of the polymer electrolyte membrane can be suppressed. Therefore, according to this embodiment, even if the polymer electrolyte fuel cell is repeatedly operated and stopped, the polymer electrolyte membrane can be prevented from being damaged and decomposed over a long period of time, and the initial characteristics can be sufficiently prevented from being deteriorated. It is possible to provide a gas diffusion layer, a gas diffusion electrode, and a membrane electrode assembly including the gas diffusion layer that can surely realize a polymer electrolyte fuel cell having excellent durability. Further, it is possible to provide a polymer electrolyte fuel cell having excellent durability, which can sufficiently prevent deterioration of initial characteristics, exhibits sufficiently stable battery performance over a long period of time, using the membrane electrode assembly described above. it can.

[Third embodiment]
Next, a third embodiment of the polymer electrolyte fuel cell of the present invention will be described. The membrane electrode assembly constituting the unit cell mounted on the fuel cell (not shown) of the third embodiment has a different configuration from the gas diffusion layer in the membrane electrode assembly 10 of the first embodiment shown in FIG. The configuration other than the gas diffusion layer is the same as that of the membrane electrode assembly 10 of the first embodiment.
Hereinafter, the gas diffusion layer provided in the membrane electrode assembly of the third embodiment will be described. FIG. 7 is a schematic cross-sectional view of the gas diffusion layer 33 provided in the membrane electrode assembly of the third embodiment.

  In the present embodiment, as shown in FIG. 7, the water-repellent carbon layer 35 is positioned outside the water-repellent carbon layer central portion 35b where the catalyst layer 12 is to be disposed and the water-repellent carbon layer central portion 35b. And the water repellent carbon layer outer edge 35a where the catalyst layer 12 is not disposed. The outer surface 35a of the water-repellent carbon layer contains a polymer electrolyte. More specifically, the water repellent carbon layer outer edge portion 35a of the water repellent carbon layer 35 includes a polymer electrolyte in addition to the conductive carbon and the water repellent material. The polymer electrolyte contained in the outer edge 35a of the water repellent carbon layer may be the same as or different from any of the polymer electrolytes contained in the polymer electrolyte membrane 11 and the catalyst layer 12.

Further, in the water repellent carbon layer 35 of the present embodiment, the water repellent carbon layer central portion 35b may be formed using the water repellent carbon layer ink described in the first embodiment, and the water repellent carbon layer outer edge portion 35a. Can be formed using an ink obtained by adding a polymer electrolyte to the water repellent carbon layer ink.
The polymer electrolyte constituting the outer edge 35a of the water-repellent carbon layer is desirably about 5 to 50% by weight in terms of the solid content in the ink for the water-repellent carbon layer. When the content is 5% or more, it is effective for suppressing direct contact of the unevenness, fluff and fraying of the gas diffusion layer base material 34 with the polymer electrolyte membrane 11, and is 40% or less. It is possible to keep the electron conductivity of the gas diffusion layer 33 good and ensure a sufficient battery output.

  According to the present embodiment, the polymer electrolyte is contained in the outer edge portion 35a of the water-repellent carbon layer, so that the unevenness, fluff and fraying of the gas diffusion layer base material, which is the cause of deterioration, are alleviated, and the polymer electrolyte membrane is deteriorated. Can be suppressed. Therefore, according to this embodiment, even if the polymer electrolyte fuel cell is repeatedly operated and stopped, the polymer electrolyte membrane can be prevented from being damaged and decomposed over a long period of time, and the initial characteristics can be sufficiently prevented from being deteriorated. It is possible to provide a gas diffusion layer, a gas diffusion electrode, and a membrane electrode assembly including the gas diffusion layer that can surely realize a polymer electrolyte fuel cell having excellent durability. Further, it is possible to provide a polymer electrolyte fuel cell having excellent durability, which can sufficiently prevent deterioration of initial characteristics, exhibits sufficiently stable battery performance over a long period of time, using the membrane electrode assembly described above. it can.

[Fourth embodiment]
Next, a fourth embodiment of the polymer electrolyte fuel cell of the present invention will be described. The membrane electrode assembly constituting the unit cell mounted on the fuel cell (not shown) of the fourth embodiment has a different configuration from the gas diffusion layer in the membrane electrode assembly 10 of the first embodiment shown in FIG. The configuration other than the gas diffusion layer is the same as that of the membrane electrode assembly 10 of the first embodiment.
Hereinafter, the gas diffusion layer provided in the membrane electrode assembly of the fourth embodiment will be described. FIG. 8 is a schematic cross-sectional view of the gas diffusion layer 43 provided in the membrane electrode assembly of the fourth embodiment.

  In the present embodiment, as shown in FIG. 8, the water repellent carbon layer 45 is positioned outside the water repellent carbon layer central portion 45b where the catalyst layer 12 is to be disposed and the water repellent carbon layer central portion 45b. And the water repellent carbon layer outer edge 45a where the catalyst layer 12 is not disposed. The outer edge 45a of the water-repellent carbon layer has a layer 55 containing a polymer electrolyte and carbon so as to cover at least a part of the side surface of the catalyst layer 12. By increasing the thickness of the water-repellent carbon layer 45 at the periphery of the polymer electrolyte membrane 11 where the deterioration progresses rapidly, it is possible to directly apply the unevenness, fluff and fraying film of the gas diffusion layer substrate 44, which is assumed to be a cause of deterioration. Touch can be suppressed.

  The thickness of the layer 55 containing the polymer electrolyte and carbon formed on the outer edge 45a of the water repellent carbon layer is preferably about 10 to 100 μm. When the thickness is 10 μm or more, the unevenness, fluff and fraying of the gas diffusion layer base material are sufficiently relaxed, and deterioration of the polymer electrolyte membrane 11 can be suppressed. Further, when the thickness is within 100 μm, the water repellent carbon layer central portion 45b and the catalyst layer 12 are sufficiently bound, and a stable battery output can be obtained.

The layer 55 made of the polymer electrolyte and carbon can be formed by preparing an ink containing the polymer electrolyte, carbon and a dispersion medium, and applying and drying the ink. As the dispersion medium, those described above can be used.
In the layer 55 composed of the polymer electrolyte and carbon, the polymer electrolyte may be the same as or different from any of the polymer electrolyte contained in the polymer electrolyte membrane and the catalyst layer.

The polymer electrolyte is preferably about 20 to 80% by mass in the ink. When the content is 20% by mass or more, the dispersion state of the polymer electrolyte and carbon in the ink is good, and when the content is 80% by mass or less, sufficient electronic conductivity can be secured.
In the layer composed of the polymer electrolyte and carbon, the carbon may be the same as or different from the carbon constituting the water-repellent carbon layer.

  According to this embodiment, by forming a layer containing a polymer electrolyte and conductive carbon on the water-repellent carbon layer at the outer edge of the water-repellent carbon layer, the gas diffusion layer base material that is the cause of deterioration is formed. Unevenness, fluff and fraying can be alleviated and deterioration of the polymer electrolyte membrane can be suppressed. Therefore, according to this embodiment, even if the polymer electrolyte fuel cell is repeatedly operated and stopped, the polymer electrolyte membrane can be prevented from being damaged and decomposed over a long period of time, and the initial characteristics can be sufficiently prevented from being deteriorated. It is possible to provide a gas diffusion layer, a gas diffusion electrode, and a membrane electrode assembly including the gas diffusion layer that can surely realize a polymer electrolyte fuel cell having excellent durability. Further, it is possible to provide a polymer electrolyte fuel cell having excellent durability, which can sufficiently prevent deterioration of initial characteristics, exhibits sufficiently stable battery performance over a long period of time, using the membrane electrode assembly described above. it can.

  Whether or not the water repellent carbon layer, which is the greatest feature of the present invention as described above, is used in a gas diffusion layer, a membrane electrode assembly, and a polymer electrolyte fuel cell (unit cell) is determined by the following method. It is possible to confirm. For example, the thickness of the water repellent carbon layer can be measured by cross-sectional observation with a scanning electron microscope (SEM), and the layer structure of the outer edge of the water repellent carbon layer can be easily confirmed.

  In addition, for example, quantitative analysis of the elements constituting the water-repellent carbon layer is possible by elemental analysis such as an X-ray photoelectron spectrometer (XPS). Furthermore, the structure of the constituent material of the water-repellent carbon layer can be determined by elemental structural analysis such as a Fourier transform infrared spectrophotometer (FT-IR), a nuclear magnetic resonance apparatus (NMR), or the like.

As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment.
In the preferred embodiment of the polymer electrolyte fuel cell of the present invention described above, the polymer electrolyte fuel cell consisting of only one unit cell has been described, but the present invention is limited to this. It is not a thing. A polymer electrolyte fuel cell having a stack structure in which a plurality of unit cells are stacked is also included in the scope of the present invention.

  In the above embodiment, the cooling water flow path is provided in both the anode side and cathode side separators. However, the cooling water flow path may be provided in at least one separator. In particular, when a stack obtained by stacking a plurality of unit cells 1 is used as the polymer electrolyte fuel cell of the present invention, one cooling water channel may be provided for every two to three unit cells.

  The polymer electrolyte fuel cell of the present invention is expected to be suitably used for mobile objects such as automobiles, distributed power generation systems, and home cogeneration systems.

It is a schematic sectional drawing which shows an example of the basic composition of the membrane electrode assembly 10 (MEA: Membrane-electrode assembly) which comprises the single cell mounted in suitable one Embodiment of the polymer electrolyte fuel cell of this invention. It is a schematic sectional drawing which shows an example of the basic composition of the unit cell mounted in the polymer electrolyte fuel cell which mounts the membrane electrode assembly 10 shown in FIG. FIG. 3 is an enlarged view of a portion indicated by P in FIG. 2. It is a schematic sectional drawing of the gas diffusion layer 13 in 1st embodiment of this invention. It is a schematic sectional drawing of the gas diffusion layer 23 in 2nd embodiment of this invention. It is a schematic sectional drawing of the modification of the gas diffusion layer 23 in 2nd embodiment of this invention. It is a schematic sectional drawing of the gas diffusion layer 33 in 3rd embodiment of this invention. It is a schematic sectional drawing of the gas diffusion layer 43 in 4th embodiment of this invention. It is a schematic sectional drawing which shows an example of the basic composition of the membrane electrode assembly (MEA: Membrane-electrode assembly) mounted in the conventional polymer electrolyte fuel cell. It is a schematic sectional drawing which shows an example of the basic composition of the unit cell mounted in the polymer electrolyte fuel cell which mounts the membrane electrode assembly 100 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100 ... Membrane electrode assembly 11, 101 ... Polymer electrolyte membrane, 12, 102 ... Catalyst layer, 13, 103 ... Gas diffusion layer, 14, 24, 34, 44, 104 ... Gas diffusion layer base material, 15, 52, 35, 45, 105 ... Water repellent carbon layer, 15a, 25a, 35a, 45a ... Water repellent carbon layer outer edge, 15b, 25b, 35b, 45b ... Water repellent carbon layer central part, 16, 106 ... Gasket, 17, 107 ... Separator, 17a, 107a ... Gas flow path, 17b, 107b ... Cooling water flow path, 55 ... Layer containing polyelectrolyte and carbon

Claims (7)

It is used for a gas diffusion electrode including a catalyst layer including an electrode catalyst, and is a gas diffusion layer that serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer base material and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer has an outer edge portion that is located outside the outer peripheral portion of the catalyst layer with respect to the central portion where the catalyst layer is to be disposed, and is 10 to 100 μm higher, and the outer edge portion is Formed so as to cover at least a part of the side surface of the catalyst layer;
Gas diffusion layer characterized by It is used for a gas diffusion electrode including a catalyst layer including an electrode catalyst, and is a gas diffusion layer that serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer base material and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer is located outside the outer peripheral portion of the catalyst layer with respect to the mass per unit area of the water repellent material constituting the central portion where the catalyst layer is to be disposed. Formed so that the mass per unit area of the water repellent material constituting 5 to 40% higher,
Gas diffusion layer characterized by It is used for a gas diffusion electrode including a catalyst layer including an electrode catalyst, and is a gas diffusion layer that serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer base material and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer is divided into a central portion where the catalyst layer is to be disposed, and an outer edge portion which is located outside the central portion and where the catalyst layer is not disposed,
The outer edge portion contains a polymer electrolyte,
Gas diffusion layer characterized by It is used for a gas diffusion electrode including a catalyst layer including an electrode catalyst, and is a gas diffusion layer that serves as a support for the catalyst layer,
A gas diffusion layer substrate containing a water repellent material;
A water repellent carbon layer disposed between the catalyst layer and the gas diffusion layer base material and comprising conductive carbon and a water repellent material;
Has a configuration including
The water repellent carbon layer is divided into a central portion where the catalyst layer is to be disposed, and an outer edge portion which is located outside the central portion and where the catalyst layer is not disposed,
A layer containing a polymer electrolyte and conductive carbon is further disposed on the outer edge so as to cover at least a part of the side surface of the catalyst layer.
Gas diffusion layer characterized by The area of the main surface of the water-repellent carbon layer on the side in contact with the gas diffusion layer substrate is substantially the same as the area of the main surface of the gas diffusion layer substrate on the side in contact with the water-repellent carbon layer. ,
The gas diffusion layer according to any one of claims 1 to 4. A gas diffusion layer according to any one of claims 1 to 4,
A catalyst layer disposed in the central portion of the water-repellent carbon layer of the gas diffusion layer;
Having
A gas diffusion electrode characterized by. A membrane electrode assembly having an anode and a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode,
At least one of the anode and the cathode is the gas diffusion electrode according to claim 6;
A membrane electrode assembly characterized by the above.

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