JP2000208151A - Gas diffusion electrode and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the output by providing a catalytic layer having the structure containing a fine porous assembly consisting of a catalyst and an electrolyte B in the pores of a porous electrolyte having three-dimensionally communicating pores. SOLUTION: A fine porous assembly 3 consisting of a catalyst and an electrolyte B is included in pores of a porous electrode A2 having three-dimensionally communicating pores. A first gas diffusion layer 4 is bonded to a first catalyst layer 1 to form a first gas diffusion electrode 5. The catalyst consists of a so-called platinum support carbon catalyst having platinum supported as catalyst on a carbon carrier. As the catalyst, fine powder of a platinum group metal or alloy thereof, for example, platinum black powder is also usable. The electrolyte B covering the catalyst has the function of an adhesive, and forms a so- called three-phase interface where electrochemical reaction progresses. Since the film of the electrolyte B forms the route for proton movement to the reaction site, it desirably has high proton conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst layer for a gas diffusion electrode of a solid polymer electrolyte fuel cell and a method for producing the same.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is an electrochemical device that supplies electric power, for example, hydrogen as an anode, and oxygen, for example, as an oxidant to an anode and electrochemically reacts them to produce electric power. The anode and the cathode are gas diffusion electrodes, and the anode is joined to one surface of the electrolyte membrane and the cathode is joined to the other surface to form a gas diffusion electrode.
Construct an electrolyte membrane assembly. The gas diffusion electrode is composed of a gas diffusion layer and a catalyst layer, and the catalyst layers of the anode and the cathode are provided with metal particles of platinum group metals or carbon particles carrying these particles as a catalyst, and the gas diffusion layer is water repellent. For example, a porous carbon paper having the following is used. This gas diffusion electrode-electrolyte membrane assembly is sandwiched between a pair of gas-impermeable separators in which gas supply channels are formed to form a unit cell as a basic unit. A plurality of such unit cells are stacked to form a solid polymer electrolyte fuel cell. When the solid polymer electrolyte fuel cell is operated, the following electrochemical reaction proceeds. Anode: 2H ₂ → 4H ⁺ + 4e ⁻ Cathode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O The electrochemical reaction of the cathode and anode of a solid polymer electrolyte fuel cell having a solid polymer electrolyte membrane is based on the cathode and the anode. It proceeds at the interface between the catalyst contained in the anode and the electrolyte. Therefore, in order to increase the output of these fuel cells, it is required to increase the contact area at the interface between the catalyst and the solid polymer electrolyte membrane. For this purpose, a method has been devised in which irregularities are provided on the surface of the electrolyte membrane to increase the contact area with the electrode containing the catalyst, particularly the catalyst layer. One of them is
This is a method of increasing the surface area of the solid polymer electrolyte membrane to increase the contact interface with the electrode. For example, Japanese Patent Application Laid-Open No. 3-158
No. 486, a method using a roll having irregularities, Japanese Patent Laid-Open No. 4-169069, a method using sputtering,
Japanese Patent Application Laid-Open No. 4-220957 proposes a method using plasma etching, and Japanese Patent Application Laid-Open No. 6-279600 proposes providing a surface of a solid polymer electrolyte membrane with irregularities by a method in which a cloth is embedded and then peeled off. Or,
There is a method in which holes are provided in the surface of the solid polymer electrolyte membrane to increase the contact area between the electrolyte membrane and the catalyst layer. For example, Japanese Patent Application Laid-Open No. Sho 58-7432 discloses a method in which a dispersion medium dissolving an electrolyte is crystallized into small droplets and then removed.
No. 146926 proposes a method of removing particles after embedding them, or Japanese Patent Application Laid-Open No. 5-194664 discloses a method of mixing and removing low molecular weight organic materials. Another method is to increase the contact interface between the electrolyte and the catalyst by adhering a platinum group metal to the surface of the electrolyte membrane. For example, Japanese Patent Publication No. 59-42078 and Japanese Patent Publication No.
No. 43830 proposes a method of performing electroless plating on the surface of an electrolyte. Further, there is a method of increasing the contact interface between the catalyst and the electrolyte by adding an electrolyte to the catalyst layer.
For example, Japanese Patent Publication No. 2-7398 describes a method for preparing an electrode from a mixture of a catalyst and an electrolyte solution and a fluororesin such as PTFE, and Japanese Patent Publication No. 2-7399 describes a method for preparing an electrode from a catalyst coated with an electrolyte and a fluororesin such as PTFE. A way to do that has been proposed. Also, in USP 5211984,
A method for producing an electrode from a mixture of a medium and a solution of an electrolyte has been proposed.

[0003]

As described above, in the method using a roll, the method using sputtering, the method using plasma etching, or the method using cloth,
There are problems in that the process of providing the unevenness is complicated and the productivity is poor, and that the formed unevenness is rough and insufficient to increase the contact area at the interface with the electrode. The method of forming pores by removing the crystallized dispersion medium, embedded particles or mixed low molecular organic materials,
It is difficult to completely remove the dispersion medium, particles or low molecular organic materials, and these residues hinder the contact between the electrolyte membrane and the electrode and cause a decrease in electrode activity. Alternatively, these residues hinder ionic conduction between the electrolyte membrane and the electrode. In addition, the electrolyte is deteriorated by the heating or solvent treatment performed in the step of removing them, and the ionic conductivity is reduced. For the above reasons, there is a problem that the performance of a fuel cell using this electrolyte membrane is reduced. The platinum group metal formed on the surface of the electrolyte membrane by a method such as electroless plating has a small surface area and a low activity as a catalyst, and the improvement of the catalyst activity by this method is insufficient. In general, in a fuel cell in which oxygen reacts with hydrogen, a large activation overvoltage of the oxygen reduction reaction is one of the causes of a decrease in voltage at a high current density. Therefore, a catalyst such as a platinum group metal is applied to the cathode to reduce the activation overvoltage. Increasing the surface area of the catalyst by increasing the catalyst in the catalyst layer is effective in reducing the activation overvoltage, but increasing the catalyst leads to an increase in the thickness of the catalyst layer. In this case, especially at a high current density, the effect of the proton conductivity of the catalyst layer becomes large. For example, Electrochem. Soc. , V
ol. 140 , 3513 (1993) states that since the proton conductivity of a catalyst layer made of a mixture of a catalyst and an electrolyte is low, the proton transfer resistance of the catalyst layer is large, and the battery voltage decreases at a high current density. The portion of the catalyst layer where the effect of the voltage drop due to the proton transfer resistance is small indicates that the portion is near the electrolyte membrane. Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to improve the proton conductivity of the catalyst layer and to provide a catalyst layer having a small voltage drop due to resistance of proton transfer. An object of the present invention is to provide a high-output fuel cell by these improvements.

[0004]

The gas diffusion electrode for a fuel cell according to the present invention includes a catalyst layer and a gas diffusion layer, and the catalyst layer has three-dimensional communication having high proton conductivity and a large surface area. Then, a porous electrolyte A having pores is formed, and then the pores of the porous electrolyte A contain a microporous aggregate composed of the catalyst and the electrolyte B. The porous electrolyte A having pores with three-dimensional communication is manufactured by a method in which ionic conductivity does not decrease due to contamination or deterioration of impurities. The first invention is
In a gas diffusion electrode including a catalyst layer and a gas diffusion layer,
The structure of the catalyst layer is characterized in that the porous electrolyte A having three-dimensionally communicating pores is provided with a microporous aggregate composed of a catalyst and an electrolyte B in the pores. The second invention is
This is a method for producing a gas diffusion electrode in which a microporous aggregate composed of a catalyst and an electrolyte B is contained in pores of a porous electrolyte A having pores having three-dimensional communication. A third invention is a solid polymer electrolyte fuel cell including the gas diffusion electrode.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows an example of a manufacturing process of a gas diffusion electrode according to the present invention. This manufacturing process can be divided into five stages. In the first step, a porous electrolyte A having three-dimensionally communicating pores is formed. In the second step, a catalyst dispersion in which a catalyst such as a platinum-supported carbon catalyst is dispersed in a solution containing the electrolyte B is prepared. In the third step, the catalyst dispersion is contained in the pores of the porous electrolyte A having three-dimensionally communicating pores. In the fourth step, the catalyst dispersion is filled into the pores of the porous electrolyte A having three-dimensionally communicating pores by a method such as applying pressure, and the catalyst and the electrolyte B are filled in the pores. A catalyst layer provided with the sexual aggregate is formed. In the fifth step, a gas diffusion electrode is produced by bonding carbon paper having water repellency as a gas diffusion layer to the catalyst layer. In the catalyst layer of the present invention, the porous electrolyte A having pores having three-dimensional communication has a function of improving proton conductivity, and the microporous aggregate composed of the catalyst and the electrolyte B contained in the pores is used. The electrolyte B has a function of forming a so-called three-phase interface. In the catalyst layer of the present invention, a porous electrolyte A having three-dimensionally communicating pores having high proton conductivity and a portion provided with a catalyst contained in the pores and a microporous aggregate composed of the electrolyte B are included. Many contacts are formed. In the porous electrolyte A having the above-mentioned three-dimensionally communicating pores, pores which are three-dimensionally communicated in the thickness direction and the plane direction of the electrolyte exhibiting proton conductivity are formed. A skeletal structure is formed and communicates three-dimensionally in the thickness direction and the plane direction. Since the porous electrolyte A having the three-dimensionally connected pores has three-dimensionally formed fine pores,
Its surface area is extremely large. In the catalyst layer of the present invention,
The microporous aggregate comprising the catalyst and the electrolyte B provided in the pores of the porous electrolyte A having three-dimensionally communicating pores contains, for example, water-repellent particles such as PTFE and conductive particles such as carbon or metal. What is essential is that at least the catalyst and the microporous aggregate composed of the electrolyte B are provided in the pores. As the catalyst, platinum group metals, alloys or oxides thereof, or particles of platinum group metals, alloys or oxides thereof supported on conductive carriers such as carbon can be used. Next, a method for producing the catalyst layer of the present invention will be specifically described. In the first step, a porous electrolyte A having three-dimensionally communicating pores
Is prepared by applying a solution of an electrolyte dissolved in a solvent containing alcohols to at least one of the electrolyte membranes and then immersing the solution in an organic solvent having a polar group other than an alcoholic hydroxyl group. The solution obtained by dissolving the electrolyte in a solvent containing alcohol used at this time is a solution obtained by dissolving a perfluorosulfonic acid resin in a mixed solvent of water and alcohol.
For example, a 5 wt% Nafion solution (Aldrich, USA) which is a commercially available solution of perfluorosulfonic acid resin can be used. The electrolyte solution can be adjusted to an arbitrary concentration by a method such as dilution or concentration. That is, there are a method of adding alcohol or water or a mixture thereof to an electrolyte solution to dilute the solution, and a method of heating and removing a part of the solvent of the electrolyte solution to concentrate the solution. In this case, as the alcohol, methanol having 4 or less carbon atoms, ethanol, 1-propanol,
2-propanol, 1-butanol or 2-butanol can be used. Organic solvents having a polar group other than an alcoholic hydroxyl group include organic solvents having 1 to 7 carbon atoms in the carbon chain having an alkoxycarbonyl group in the molecule, for example, propyl formate, butyl formate, isobutyl formate,
Ethyl acetate, propyl acetate, isopropyl acetate, allyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, butyl acrylate, isobutyl acrylate, methyl butyrate , Methyl isobutyrate, ethyl butyrate, ethyl isobutyrate, methyl methacrylate, propyl butyrate, isopropyl isobutyrate, 2-ethoxyethyl acetate, 2- (2ethoxyethoxy) ethyl acetate, etc., alone or in a mixture, or an ether bond in the molecule An organic solvent having 3 to 5 carbon atoms in the carbon chain having
For example, dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tripropylene glycol monomethyl ether, tetrahydrofuran, etc. alone or in a mixture, or an organic compound having a carbon chain having a carbonyl group in the molecule having 4 to 8 carbon atoms. Solvents, for example, methyl butyl ketone, methyl isobutyl ketone, methyl hexyl ketone,
Dipropyl ketone or the like alone or as a mixture, or an organic solvent having 1 to 5 carbon atoms in the carbon chain having an amino group in the molecule, for example, isopropylamine, isobutylamine, tert-butylamine, isopentylamine, diethylamine, etc. Or a mixture, or an organic solvent having 1 to 6 carbon atoms in the carbon chain having a carboxyl group in the molecule, such as propionic acid, valeric acid, caproic acid, heptanoic acid, etc., alone or in combination, or a combination thereof. Can be used. However,
The organic solvent having a polar group other than the alcoholic hydroxyl group used for forming the porous electrolyte A having three-dimensionally connected pores is preferably an organic solvent having an alkoxycarbonyl group. In the second step, the catalyst dispersion is prepared by dispersing the catalyst in a dispersion medium, adding an electrolyte solution thereto, and mixing well. Carbon supporting a platinum group metal as a catalyst,
Platinum group metals, their oxides, or mixtures thereof can be used. As the dispersion medium, alcohols having 4 or less such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol or 2-butanol having 4 or less carbon atoms, water or a mixture thereof can be used. The electrolyte solution is obtained by dissolving a perfluorosulfonic acid resin in a mixed solvent of water and alcohol, for example, a commercially available solution of perfluorosulfonic acid resin.
A wt% Nafion solution (Aldrich, USA) can be used. In the third step, the catalyst dispersion prepared in the second step is contained in the porous electrolyte A having the three-dimensionally communicating pores in the porous electrolyte A having the three-dimensionally communicating pores. In this step, for example, a coating method such as spraying, a doctor blade method, a screen printing method, or a conventionally known method such as a precipitation method or an impregnation method can be used. In the fourth step, the catalyst dispersion is applied to the porous electrolyte A having three-dimensionally communicating pores by, for example, pressing the porous electrolyte A having three-dimensionally communicating pores provided with the catalyst dispersion. To form a catalyst layer comprising a catalyst and a microporous aggregate made of electrolyte B. The compression can be applied, for example, by a method such as a flat press or a roll press. In the fifth step, the gas diffusion layer is joined to the catalyst layer by heating and pressure welding to produce the gas diffusion electrode of the present invention. As the gas diffusion layer, for example, a sheet-like material in which water-repellent carbon paper or carbon powder is formed using a water-repellent fluorine-based resin such as PTFE as a binder can be used. As an example of the present invention, FIG. 1 shows a schematic diagram of a cross section of a gas diffusion electrode electrolyte membrane assembly having the gas diffusion electrode of the present invention on one surface of an electrolyte membrane. In FIG. 1, 1 is the first
The catalyst layer 2 is a porous electrolyte A having three-dimensionally communicating pores, and the microporous assembly 3 is composed of a catalyst and an electrolyte B. The microporous aggregate 3 composed of the catalyst and the electrolyte B is contained in the pores of the porous electrolyte A having three-dimensionally communicating pores. Reference numeral 4 denotes a first gas diffusion layer, and reference numeral 5 denotes a first gas diffusion electrode. The first gas diffusion electrode 5 has the first catalyst layer 1
This is the gas diffusion electrode 5 of the present invention to which the gas diffusion layer 4 is joined. Reference numeral 6 denotes an electrolyte membrane C of the fuel cell, the first gas diffusion electrode 5 of the present invention on one side, and the second gas diffusion electrode 9 on the other side.
Is provided. The second gas diffusion electrode 9 is formed by joining the second gas diffusion layer 8 to the second catalyst layer 7. The second catalyst layer 7 is made of, for example, a catalyst dispersion composed of a catalyst and an electrolyte, and the second gas diffusion layer 8 is made of, for example, the same material as the first gas diffusion layer 4. A fuel cell having a first gas diffusion electrode 5 or a second gas diffusion electrode 9 on both sides of an electrolyte membrane C, or a first gas diffusion electrode 5 on one side of the electrolyte membrane and a second gas diffusion electrode 5 on the other side. The one provided with the gas diffusion electrode 9 is the gas diffusion electrode electrolyte membrane assembly 10. As the electrolyte membrane C of the fuel cell, a membrane having proton conductivity is used. For example, a Nafion 115 membrane (manufactured by DuPont, USA) which is a commercially available perfluorosulfonic acid resin membrane can be used. Nafion is a registered trademark of DuPont. FIG. 3 is an enlarged schematic diagram of a microporous aggregate including the catalyst and the electrolyte B contained in the pores of the porous electrolyte A having three-dimensionally communicating pores. In FIG. 3, 1
1 is a carbon carrier, 12 is a catalyst, and 13 is an electrolyte covering the catalyst. For example, carbon black or the like is used for the carbon carrier 11, and the catalyst 12 is a particle such as a simple substance of a platinum group metal such as platinum or an alloy thereof.
A catalyst in which platinum is supported on a carbon carrier as a catalyst is a so-called platinum-supported carbon catalyst. As the catalyst, fine powder of a platinum group metal or an alloy thereof, for example, platinum black powder or the like can be used. The electrolyte 13 covering the catalyst is formed in a film form on the surface of the catalyst and in the vicinity thereof, has a function of a binder, and forms a so-called three-phase interface in which an electrochemical reaction proceeds. The coating of the electrolyte 13 covering the catalyst preferably has high proton conductivity because it forms a path for proton transfer to the reaction site.

Embodiment 1 An example of a method for manufacturing a gas diffusion electrode according to the present invention will be specifically described. The manufacturing method can be divided into, for example, five steps as shown in FIG. First step: A method of forming a porous electrolyte A having three-dimensionally connected pores on one surface of an electrolyte membrane. First, a commercially available 5 wt% Nafion solution was placed in a sample bottle and heated to 60 ° C. while stirring to concentrate the solution to 16 wt%. Next, the commercially available Nafion 115 membrane is washed three times with purified water, then boiled with 3% hydrogen peroxide solution for 1 hour as a degreasing treatment, washed several times with purified water, and further subjected to 0.1% as a protonation treatment. The mixture was boiled with 5 M sulfuric acid for 1 hour, washed several times with purified water, and stored in purified water. Subsequently, the Nafion 115 was subjected to an ethanol treatment for immersing it in ethanol for 10 minutes to swell sufficiently. Nafion 11 treated with proton and ethanol
After removing the five membranes from the ethanol and wiping off excess ethanol present on the surface of the swollen Nafion 115 membrane using a filter paper, spray the Nafion 115 solution by spraying a 16 wt% Nafion solution before the Nafion 115 membrane is dried. A coating layer of a Nafion solution was formed on one surface of the film. The coating amount of this Nafion solution was about 3 mg / cm ^{2 on} one side. The Nafion 115 film on which the Nafion solution coating layer was formed was immersed in butyl acetate for 10 minutes, then taken out, and the butyl acetate was dried at room temperature.
A porous electrolyte A having three-dimensionally connected pores was formed on the surface of the Nafion 115 membrane. The porous electrolyte A portion having the three-dimensionally connected pores has a diameter of 3.5 cm and a thickness of about 6 cm.
μm. Second step: A method for preparing a catalyst dispersion. To 1.5 g of a carbon catalyst supporting 30 wt% of platinum, 5 g
wt% Nafion solution (Aldrich, USA) 13
ml was gradually added with stirring, and the mixture was further stirred for 30 minutes. The mixture was further heated to 60 ° C. with stirring, and concentrated until the solid content of Nafion became 15 wt% with respect to the dispersion medium to prepare a catalyst dispersion. Third step: a method of providing a catalyst dispersion in the pores of the porous electrolyte A having three-dimensionally communicating pores. The Nafion 115 membrane formed with the porous electrolyte A having three-dimensionally connected pores on the surface prepared in the first step is formed on a flat plate made of glass or the like, and the surface on which the porous electrolyte A having three-dimensionally connected holes is formed. Was arranged on the upper surface. 15 gaps
Using a doctor blade adjusted to μm, the catalyst dispersion prepared in the second step was applied to the porous electrolyte A having three-dimensionally communicating pores. Next, the catalyst dispersion applied to the porous electrolyte A having three-dimensionally communicating pores is left in a circular shape having a diameter of 3 cm, and other unnecessary catalyst dispersions are removed. Was formed. On the other hand, a release-paper-catalyst-dispersed-coated body having a catalyst layer formed on release paper was prepared by the following method. That is, 13 ml of a 5 wt% Nafion solution (manufactured by Aldrich, USA) was gradually added to 1.5 g of a carbon catalyst carrying 30 wt% of platinum while stirring, and the mixture was further stirred for 30 minutes. Further, the mixture was heated to 60 ° C. with stirring, and concentrated until the weight of the solid content of Nafion with respect to the dispersion medium became 18% by weight to prepare a catalyst dispersion. The catalyst dispersion was applied to a tetrafluoroethylene-hexafluoropropylene copolymer sheet as release paper by screen coating to prepare a release paper catalyst dispersion coated body, which was cut into a circular shape having a diameter of 3 cm. Fourth step: filling the inside of the pores with the catalyst dispersion to prepare a catalyst layer having a catalyst and a microporous aggregate composed of the electrolyte B in the pores of the porous electrolyte A having three-dimensionally communicating pores how to. The electrolyte membrane catalyst dispersion applied product and the release paper catalyst dispersion applied product produced in the third step were laminated and placed in a press.
At this time, the release-paper-catalyst dispersion-applied body was laminated such that the application surface faced the electrolyte membrane and the application surface was in agreement with the electrolyte membrane via the electrolyte membrane. In this state, 2
Pressure was applied by heating and pressing at 50 kg / cm ² at 135 ° C. for 5 minutes. Then, the catalyst layer was transferred from the release paper to the electrolyte membrane on the surface on which the release-catalyst layer dispersion applied body was laminated. On the surface of the electrolyte membrane catalyst dispersion coated body, the catalyst dispersion applied to the pores of the porous electrolyte A having three-dimensionally communicating pores is filled by heating and pressing, and the inside of the pores is filled with the catalyst and the electrolyte B. And a catalyst layer comprising the microporous aggregate. Thus, on one surface of the Nafion 115 membrane, the porous electrolyte A having the three-dimensionally connected pores of the present invention is provided.
And a catalyst layer comprising a catalyst and a microporous aggregate comprising electrolyte B in the pores thereof, and a catalyst layer / electrolyte membrane assembly comprising a catalyst layer comprising a catalyst dispersion on the other surface of the Nafion 115 membrane. This catalyst layer electrolyte membrane assembly was designated as catalyst layer electrolyte membrane assembly X of the present invention. Fifth step: joining of gas diffusion layers. A water-repellent carbon paper cut to a diameter of 3 cm as a gas diffusion layer is arranged on both sides of the catalyst layer / electrolyte membrane assembly X, and heated and pressed (120 kg / cm ² , 135 ° C., 5 ° C.).
Minutes) to form a gas diffusion electrode / electrolyte membrane assembly X. Carbon paper having a thickness of 0.2 mm was used. This carbon paper was impregnated with a dispersion of polytetrafluoroethylene, dried, and then fired at 400 ° C. to impart water repellency. The gas diffusion electrode / electrolyte membrane assembly X is sandwiched between metal separators having gas supply passages formed thereon, and the cathode side is arranged so as to be the catalyst layer of the present invention, whereby a solid polymer electrolyte fuel cell X is formed. did.

EXAMPLE 2 The release paper catalyst dispersion coated body prepared in the third step of the example was coated on both sides of the Nafion 115 membrane subjected to the degreasing treatment and the protonation treatment in the same manner as in the first step of the example 1. The pieces cut to 3 cm were laminated so that the coated surfaces of the catalyst layers faced each other, and were weighed at 250 kg / cm ² and 135 kg.
The catalyst layer formed on the release paper catalyst layer dispersion coated body was transferred to a Nafion 115 membrane by heating and pressure contacting at 5 ° C. for 5 minutes, and a catalyst layer electrolyte comprising a catalyst layer composed of a catalyst dispersion on both sides of the Nafion 115 membrane A membrane assembly Y was formed. The water-repellent carbon paper produced in the fifth step of Example 1 was cut to a diameter of 3 cm and used as a gas diffusion layer. The carbon paper was disposed on both sides of the catalyst layer electrolyte membrane assembly Y, and was integrally joined by heating and pressure welding (120 kg / cm ² , 135 ° C., 5 minutes) to produce a gas diffusion electrode electrolyte membrane assembly Y. This gas diffusion electrode electrolyte membrane assembly Y
Sandwiched by a metal separator with a gas supply path formed,
A solid polymer electrolyte fuel cell Y for comparison was constructed. Pure hydrogen on the anode and air on the cathode each 2kg / c
The current-voltage characteristics of the solid polymer electrolyte fuel cell X and the solid polymer electrolyte fuel cell Y at a battery temperature of 65 ° C. were measured by supplying the battery under pressure of m ² G. At this time, the air and hydrogen were humidified using a bubbler humidifier set at 60 ° C. FIG. 4 shows current-voltage characteristics of the solid polymer electrolyte fuel cell X and the solid polymer electrolyte fuel cell Y. In FIG. 4, X is a curve showing the current-voltage characteristics of the solid polymer electrolyte fuel cell X of the present invention, and Y is a curve showing the current-voltage characteristics of the solid polymer electrolyte fuel cell Y for comparison.
Gas diffusion electrode formed by joining a gas diffusion layer to a catalyst layer comprising a porous electrolyte A having three-dimensionally communicating pores according to the present invention and a microporous aggregate comprising a catalyst and an electrolyte B in the pores Solid polymer electrolyte fuel cell X having a cathode disposed on the cathode
Showed a small output of the battery voltage at a higher current density than that of the solid polymer electrolyte fuel cell Y and a high output. This means that the use of a catalyst layer comprising a porous electrolyte A having three-dimensionally communicating pores of the present invention and a microporous aggregate comprising a catalyst and an electrolyte B in the pores at the cathode is a high solids material. This shows that it is effective for increasing the output of a molecular electrolyte fuel cell. The reason will be described with reference to FIG. The catalyst layer of the cathode of the solid polymer electrolyte fuel cell Y has the same structure as the second catalyst layer 7 of FIG. Since the proton conductivity of the second catalyst layer 7 is low, protons involved in the reaction near the gas diffusion layer have a large voltage drop due to their migration resistance. On the other hand, the catalyst layer of the solid polymer electrolyte fuel cell X has a structure as shown in the first catalyst layer 1 of FIG. In this catalyst layer, a movement path having high proton conductivity is formed in a three-dimensional network in the catalyst layer, so that the distance of proton transfer in a portion composed of the catalyst having low proton conductivity and the electrolyte is shortened, and particularly in the current density. Voltage drop due to proton transfer resistance is reduced. In other words, it is considered that the electrolyte of the present invention is a catalyst layer in which many portions where the voltage drop due to proton transfer resistance is small are formed.

[0006]

According to the present invention, the catalyst layer comprising the porous electrolyte A having three-dimensionally communicating pores and the microporous aggregate comprising the catalyst and the electrolyte B in the pores has protons in the catalyst layer. Since a path with high conductivity is formed, even when the current density is high, the distance of proton transfer between the catalyst and the electrolyte contained in the pores with low proton conductivity becomes shorter, and the voltage of the Reduction is suppressed. Further, even though the catalyst layer of the present invention is thick, since the resistance overvoltage due to the lack of proton conductivity is small, the activation overvoltage can be reduced by increasing the amount of catalyst in the thickness direction, so that the solid density with a high power density is high. A molecular electrolyte fuel cell can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a gas diffusion electrode / electrolyte membrane assembly according to the present invention.

FIG. 2 is a float view showing a manufacturing process of the gas diffusion electrode according to the present invention.

FIG. 3 is an enlarged schematic view of a microporous aggregate comprising a catalyst and an electrolyte B contained in pores of a porous electrolyte A having pores having three-dimensional communication.

FIG. 4 is a diagram showing current-voltage characteristics of a solid polymer electrolyte fuel cell X in which a gas diffusion electrode according to the present invention is arranged on a cathode and a solid polymer electrolyte fuel cell Y for comparison.

[Explanation of symbols]

 1 First catalyst layer 2 Porous electrolyte A having three-dimensionally communicating pores. Reference Signs List 3 Microporous aggregate composed of catalyst and electrolyte B 4 First gas diffusion layer 5 First gas diffusion electrode 6 Electrolyte membrane C for fuel cell 7 Second catalyst layer 8 Second gas diffusion layer 9 Second Gas diffusion electrode 10 Gas diffusion electrode electrolyte membrane assembly 11 Carbon carrier 12 Catalyst 13 Electrolyte covering catalyst

Claims (3)

[Claims] In a gas diffusion electrode provided with a catalyst layer and a gas diffusion layer, the structure of the catalyst layer is such that a catalyst and an electrolyte B are formed in pores of a porous electrolyte A having three-dimensionally communicating pores. A gas diffusion electrode having a structure including a porous assembly. 2. A porous electrolyte A having three-dimensionally communicating pores.
The method for producing a gas diffusion electrode according to claim 1, wherein a microporous aggregate comprising a catalyst and an electrolyte B is contained in the pores. 3. A solid polymer electrolyte fuel cell comprising the gas diffusion electrode according to claim 1.