JPH08236123A - Fuel cell electrode and manufacture thereof - Google Patents

Abstract

PURPOSE: To uniformly disperse a raw material of a catalyst layer to enhance the sheet forming capability, and surly form a three-dimensional reaction site in the catalyst layer to improve the electrode characteristics by adding a viscosity increasing agent or the viscosity increasing agent and a nonionic surfactant to a raw material mixed solution when the catalyst layer is formed. CONSTITUTION: A fuel cell electrode is prepared by forming a catalyst layer containing catalyst particles, a polytetrafluoroethylene family polymer, and a polymer electrolyte on a gas diffusion layer. The catalyst layer is formed in such a way that a viscosity increasing agent or the viscosity increasing agent and a nonionic surfactant are mixed to a mixed solution of the catalyst particles and polytetrafluoroethylene family polymer dispersion, the mixture is heat-treated, then coated with the polymer electrolyte. As the viscosity increasing agent, carboxymethylcellulose, methylcellulose, casein, polyvinyl alcohol, ammonium polyacrylate, and starch are listed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene polymer and a polymer electrolyte, and a method for producing the same.

[0002]

2. Description of the Related Art A fuel cell, for example, a solid polymer electrolyte type fuel cell is characterized in that an ionic conductor, that is, an electrolyte is a solid and a polymer. An ion-exchange resin membrane is used for this, and both the negative electrode and the positive electrode are arranged with the electrolyte membrane sandwiched between them. For example, by supplying hydrogen to the negative electrode side and oxygen or air to the positive electrode side, an electrochemical reaction To generate electricity.

For both the negative electrode and the positive electrode in contact with the solid polymer electrolyte membrane, there is a type in which platinum, palladium or other catalyst is added and used in the electrode in order to accelerate the reaction. Although various methods have been proposed so far for manufacturing a type of electrode, for example, in US Pat. No. 3,134,697, catalyst particles are mixed with an ion exchange resin to form an electrode sheet, which is used as a solid polymer electrolyte. It is manufactured by thermocompression bonding to the ion-exchange resin membrane.

Further belonging to this system are US Pat. Nos. 3,297,484 and 3,432,355. In both of these techniques, catalyst particles such as platinum black and palladium black are mixed with polytetrafluoroethylene to form an electrode. A sheet is described, and a method of thermocompression-bonding this to an ion-exchange resin membrane is described. In these techniques, mixing polytetrafluoroethylene with catalyst particles in such a manner means that the catalyst layer is formed in the electrode sheet. It is for binding and binding the catalyst components to be formed.

However, if the solid polymer electrolyte membrane and the electrode sheet are simply joined together by thermocompression bonding or the like as described above, the reaction site (reaction region) is limited to the two-dimensional interface between the electrolyte and the electrode. The active area is small. Therefore, as one of the methods to improve this, a styrene-divinylbenzenesulfonic acid resin membrane as a solid polymer electrolyte, carbon powder carrying a catalytic metal, styrene-divinylsulfonic acid resin powder and polystyrene binder By joining the electron-ion mixed conductor layer made of a mixture, the number of contacts between the electrode material and the solid electrolyte membrane material is increased,
It has been proposed to make the reaction site three-dimensional.

For example, "Electrochemistry" 53, No. 10
(1985), P. 812 to 817, in the fuel cell using the styrene-divinylbenzene-based ion exchange resin membrane as the electrolyte as described above, even if the electron-ion mixed conductor layer is provided, the current density that can be taken out is low. Having pointed out that there is such a problem, an attempt to use a perfluorocarbon sulfonic acid resin membrane instead of this to make the reaction site three-dimensional and increase the working area is introduced. According to this, NAF, which is a kind of perfluorocarbon sulfonic acid resin membrane, is used as the solid polymer electrolyte membrane.
An ION-117 membrane (manufactured by Du Pont, trade name) is used, and a platinum electrode is bonded to one surface of this NAFION membrane by an electroless plating method (penetration method) to form a hydrogen electrode (anode). The oxygen electrode constituting the counter electrode, that is, the cathode side electrode, is generally manufactured by the following steps.

First, platinum black powder or carbon powder carrying 10% platinum (hereinafter referred to as "platinum-supporting carbon powder") was used as a catalyst powder, and Amberlite IR-120B (T-3) [styrene- Divinylbenzenesulfonic acid resin, Na type, powder with a particle size of 30 μm,
Organo, trade name] or NAFION-117
[Perfluorocarbon sulfonic acid resin (H type), 5% solution in a mixed solvent of aliphatic alcohol and water, Aldri
ch Chemical, trade name] are mixed in various mixing ratios.

Next, polytetrafluoroethylene was added to each mixture obtained above in the form of an aqueous suspension and mixed and kneaded. The kneaded product was rolled by roll rolling to form a sheet, which was vacuum dried, This electrode sheet is hot pressed against a NAFION film as a solid polymer electrolyte at a temperature of 100 ° C. and a pressure of 210 kg / cm ² . And there, NA as a solid polymer electrolyte
By mixing the ion exchange resin as described above into the oxygen electrode integrally bonded to the FION membrane, the electrode reaction site can be made three-dimensional and the polarization characteristics can be remarkably improved. It has been pointed out that the effect of the incorporation of the above is great when platinum-supporting carbon powder is used as an electrode catalyst.

In the above technique, all of the electrode sheets are manufactured by forming a kneaded material of the electrode material into a sheet by a method such as rolling. As a method of manufacturing the electrode sheet, the electrode sheet is used as a base material. Another mode is also used in which a porous paper or sheet is separately used and the catalyst particles are supported on the porous paper or sheet. In this case, for example, carbon paper having a predetermined porosity and thickness is used as the paper or sheet, and a polytetrafluoroethylene-based dispersion is impregnated into the paper, and then heat treatment is performed to obtain water repellency. The catalyst layer and other components of the electrode layer are adhered and carried on the water repellent carbon paper, and JP-A-4-162365 is one example.

This technique is characterized in that a mixture of platinum black catalyst-supported carbon black particles and non-catalyst-supported carbon black particles is used as the fine powder for forming the sheet-like catalyst layer, and both of these particles are used. The sheet here is coated with an ion exchange resin as a polymer electrolyte, and the sheet here uses water-repellent carbon paper as its base material, and a mixed solution containing the coated catalyst particles and polytetrafluoroethylene is filtered and dried. After that, this is sprinkled on the water-repellent carbon paper, and the paper is attached by pressing under heating.

In the polymer electrolyte fuel cell incorporating the electrode having the catalyst layer containing the catalyst particles, the polymer electrolyte and polytetrafluoroethylene in this manner, the catalyst particles coexist with the polymer electrolyte and the gas phase, By securing more of these three-phase interfaces, the battery performance can be improved, but polytetrafluoroethylene not only plays the role of a binder for the catalyst particles, but is itself water repellent and gas-repellent. The effect of securing the phase is also achieved (that is, during the operation of the cell, for example, the catalyst layer is prevented from being wet by water generated by the reaction of fuel hydrogen and oxygen, and the gas space is secured).

[0012] By the way, polytetrafluoroethylene can be improved in its crystallinity and can be present more uniformly among the catalyst particles by "heat-treating" it because of its unique property. Regarding this polytetrafluoroethylene, a derivative having further improved properties is also known. However, if polytetrafluoroethylene cannot be effectively heat-treated, the water repellency due to this cannot be sufficiently exerted, and therefore it is necessary to increase the mixing amount of polytetrafluoroethylene. If the amount is increased, the resistance of the electrode is increased, and in order to obtain a stable polytetrafluoroethylene dispersion, a surfactant such as a fluoroalkyl compound is usually added. There is also a problem that a large amount is mixed in the electrode.

Not only that, but when a mixed solution of catalyst particles, a polytetrafluoroethylene polymer and a polymer electrolyte is formed as a catalyst layer by a coating method, it is necessary to evaporate the solvent until an appropriate viscosity is obtained. However, in adjusting the viscosity of the solution only by the amount of the solvent, that is, the concentration of the catalyst layer raw material, there is a drawback that the raw material components cannot be uniformly dispersed,
For this reason, it has been difficult to make the catalyst layer constituting the electrode uniform.

[0014]

Therefore, in the present invention, regarding a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte, a raw material mixture liquid for forming the catalyst layer is used. By separately adding a thickener or a thickener and a nonionic surfactant, the catalyst particles, which are the raw material of the catalyst layer, the polytetrafluoroethylene-based polymer and the polyelectrolyte are uniformly dispersed. The electrode and the electrode capable of increasing the moldability into a sheet to more surely form the three-dimensional reaction site in the catalyst layer and maintaining the electrode characteristics and the battery characteristics using the electrode for a long time. It is intended to provide a manufacturing method.

[0015]

First, the present invention relates to a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte,
The catalyst layer is a catalyst layer formed by mixing a thickening agent in a mixed liquid of catalyst particles and a dispersion of a polytetrafluoroethylene-based polymer, heat-treating the mixture, and then coating with a polymer electrolyte. To provide an electrode for a fuel cell.

The present invention also provides catalyst particles on the gas diffusion layer,
A fuel cell electrode having a catalyst layer containing a polytetrafluoroethylene-based polymer and a polymer electrolyte, wherein the catalyst layer comprises a thickener in a mixed liquid of catalyst particles and a polytetrafluoroethylene-based polymer. There is provided a fuel cell electrode comprising a catalyst layer obtained by mixing a nonionic surfactant, heat-treating it, and then coating it with a polymer electrolyte.

The present invention also provides a method for producing an electrode for a fuel cell having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte, wherein the catalyst layer comprises the catalyst particles and the polytetrafluoroethylene-based polymer. After mixing the thickener to the mixture with the dispersion of
The present invention provides a method for producing an electrode for a fuel cell, which is characterized by forming by heat treatment and then coating with a polymer electrolyte.

The present invention also provides a method for producing a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte on a gas diffusion layer, wherein the catalyst layer is (1) a catalyst. A thickener is mixed in a mixed solution of particles and a dispersion of polytetrafluoroethylene-based polymer, and (2) the film thickness is controlled on the gas diffusion layer by a feeder equipped with one or more blades for controlling the film thickness. A method for producing an electrode for a fuel cell, which is characterized by being formed by applying (3) and then coating with a polymer electrolyte after applying the electrode (hereinafter, referred to as an electrode production method of this type by a blade). Coating method).

[0019]

There are various types of fuel cells, such as phosphoric acid type, alkaline type, and solid polymer type. The electrode of the present invention and the method for producing the same are applicable to any of these electrodes for fuel cells. be able to. Further, as the catalyst particles in the present invention, platinum black powder, platinum alloy powder, palladium black powder, carbon powder supporting platinum or palladium, and other catalysts applicable for electrodes of fuel cells can be used. As the above-mentioned polymer electrolyte, various ion exchange resins and the like can be used, but preferably, a fluororesin type ion exchange membrane having excellent heat resistance at high temperature, for example, a perfluoro-bonsulfonic acid type resin such as NAFION 110 type is used. use.

The thickener used in the present invention is not particularly limited as long as it can impart viscosity and tackiness to the catalyst particles at the time of forming the catalyst layer (provided, for example, Na ion such as sodium polyacrylate). Etc., except those containing components that remain in the catalyst layer and hinder electrode characteristics and battery performance), examples of which are preferably carboxymethyl cellulose, methyl cellulose, casein, polyvinyl alcohol, ammonium polyacrylate, starch, etc. Can be mentioned.

Further, in the present invention, the catalyst raw material components are uniformly dispersed by mixing a nonionic surfactant in addition to the above thickener, and the fuel cell using the electrode obtained through this The performance of can be further improved. This nonionic surfactant (nonionic su
The rfactant is not particularly limited as long as it is a nonionic type such as polyethylene glycol alkyl ether, polyethylene glycol fatty acid ester, sorbitan fatty acid ester, and fatty acid monoglyceride, but the temperature is about 360 ° C. in relation to the heat treatment after the slurry application. It is desirable that it decomposes at the following heat treatment temperatures. Further, these are not limited to one kind, and two or more kinds of nonionic surfactants may be used in combination.

The viscosity of the slurry containing the above-mentioned thickener is sufficient if it has such viscosity that it does not flow and diffuse to the peripheral edge after coating on a suitable surface and can be controlled to a desired film thickness. However, it is preferably about 2000 to 20000 cp (centipoise). And this point is the same as in the case of adding a nonionic surfactant in addition to the thickener. In the present invention, after coating the slurry to a predetermined thickness, the coating surface is impregnated with an electrolyte. As the electrolyte, various ion exchange resins and the like can be used, but preferably, a fluororesin ion exchange membrane having excellent heat resistance at high temperature, for example, a perfluoro-bonsulfonic acid resin such as NAFION110 is used. Among the fuel cells, for example, in the case of a solid polymer type, when using a NAFION-based perfluorocarbon sulfonic acid type resin film as the solid polymer electrolyte membrane, it is preferable to use the same type of perfluorocarbon sulfonic acid resin. .

A solid polymer type fuel cell electrode is usually applied as an electrode sheet. As a method of forming the sheet, (1) the catalyst constituent material is directly attached to, for example, a solid polymer electrolyte membrane as a battery body, and (2) the catalyst constituent material is kneaded into a sheet by rolling or the like. [In addition, the electrode sheet obtained in these (1) and (2) becomes an electrode which also serves as a diffusion layer and a catalyst layer by itself], (3) Various kinds of catalyst constituent materials as a gas diffusion layer The present invention is carried out in any of these aspects (1) to (3), though it is carried out in various aspects such as adhering onto a porous paper or sheet made of a material, preferably carbon paper or water repellent carbon paper. Is something that can be done. Hereinafter, among the aspects (1) to (3),
Although the description will focus on the case of adopting the aspect of (3), it can be similarly implemented in any of the aspects.

The present inventor, when producing a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte, is a mixture of catalyst particles and a dispersion of polytetrafluoroethylene-based polymer. Was freeze-dried and then heat-treated to separately develop and apply for a technique capable of significantly increasing the effect of the polytetrafluoroethylene-based polymer (Japanese Patent Application No. 6-339777). In the present invention, in addition to the addition of the above-mentioned thickener or the addition of the thickener and the nonionic surfactant, the freeze-drying and the subsequent heat treatment operation are used in combination to uniformly disperse the raw material of the catalyst layer. Moreover, by increasing the formability of the sheet, the formation of the three-dimensional reaction site can be made more reliable.

After the freeze-drying and the subsequent heat treatment, the catalyst particles are further freeze-pulverized to evenly distribute the catalyst layer-constituting powder to an appropriate particle size and increase the reaction points (three-dimensional reaction sites). However, in addition to the addition and mixing of the above-mentioned thickener, or in addition to the addition and mixing of the thickener and the nonionic surfactant, by using these methods together, a polytetrafluoroethylene-based polymer can be obtained. The heat treatment can be more effectively performed and the action can be enhanced.

As a preferred method of the above combination in the present invention, its outline and the following modes (A) to (C) can be adopted. Here, the symbol + means addition or mixing, the symbol → means to move to the next step, and these aspects are the same also in the case of mixing a nonionic surfactant in addition to the thickener. . (A) Dispersion of catalyst particles + polytetrafluoroethylene-based polymer → freeze-drying → heat treatment → thickener → heat treatment → coating with an electrolyte membrane. (B) Dispersion of catalyst particles + polytetrafluoroethylene-based polymer → freeze-drying → heat treatment → freeze-grinding →
+ Thickener → heat treatment → coating with electrolyte membrane. (C) Dispersion of catalyst particles + polytetrafluoroethylene-based polymer → lyophilization → + thickener → heat treatment →
Coating with electrolyte membrane.

As described above, the present invention can take various aspects. First, in the case of the above (A), the catalyst layer is (1) a mixed solution of catalyst particles and a dispersion of a polytetrafluoroethylene-based polymer is freeze-dried and then heat treated, and (2) a thickener is then added. After being mixed and heat-treated, (3) it is formed by coating with a polymer electrolyte. In the case of (B), (1) first, a mixed liquid of catalyst particles and a dispersion of a polytetrafluoroethylene-based polymer is freeze-dried, (2) a thickener is then added and blended, and then heat treated. Then, (3) it is formed by coating with a polymer electrolyte. Further, in the aspect of (C), (1) first, the catalyst particles and a dispersion of a polytetrafluoroethylene-based polymer are mixed,
(2) Next, after adding and blending a thickener, heat treatment is performed,
(3) It is formed by coating with a polymer electrolyte.

As described above, the heat treatment for the polytetrafluoroethylene-based polymer is for improving the crystallinity of the polytetrafluoroethylene-based polymer and for making the polytetrafluoroethylene-based polymer more evenly present among the catalyst particles. Typically, the heat treatment is performed at about 360 ° C., but the heat treatment in the present invention can be similarly performed in any of the above-described modes. Here, in the present specification, “polytetrafluoroethylene-based polymer” is meant to include not only polytetrafluoroethylene (PTFE) itself but also tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and other derivatives thereof. In addition, not only polytetrafluoroethylene itself but also tetrafluoroethylene-hexafluoropropylene copolymer and other derivatives thereof are referred to in the present invention. It is possible to obtain the same operational effect as in the case of polytetrafluoroethylene itself.

Here, as an example of the above-mentioned modes, (A)
More specifically, the case (including the aspect of part (B)) will be described. (1) First, for example, tetrafluoroethylene-hexafluoropropylene co-polymer is added to carbon paper having a porosity of 75% and a thickness of 0.4 mm. Polymer (FE
P) After impregnation with the dispersion, heat treatment is performed,
A water repellent carbon paper in which the tetrafluoroethylene-hexafluoropropylene copolymer accounts for 10 to 40% by weight is obtained. FIG. 1B schematically shows the water repellent carbon paper, which serves as the diffusion layer 2 in the electrode.

(2) On the other hand, catalyst particles supporting 25 to 50% platinum or an alloy containing platinum and polytetrafluoroethylene dispersion are adjusted so that polytetrafluoroethylene is about 5 to 40% by weight in the total amount of the catalyst. Mix with a colloid mill. In this respect, for example, when the catalyst layer is formed on the water-repellent carbon paper by the filtration method, about 5
It is necessary to add a larger amount in the range of ˜50% by weight, but by combining with the freeze-drying method, the above-mentioned about 5-4
The same or higher effect can be obtained with a small addition amount of 0% by weight.

(3) Next, the mixed solution is added to about -80 to-
Cool to about 50 ° C. and freeze to maximize the surface area. This is freeze-dried to a vacuum degree of about 0.1 torr to sublimate the solvent to obtain a powder.
(4) Subsequently, for example, at a temperature of 280 ° C. for 10 hours, 360
Heat treatment is performed in a nitrogen stream at 5 ° C. for 5 hours. As described above, this treatment is performed in order to improve the crystallinity of the polytetrafluoroethylene-based polymer and to make it more evenly present among the catalyst particles. (5) In the above aspect B, freeze pulverization is further carried out, but this makes it possible to obtain catalyst particles having a uniform particle size. In this case, the method of freeze-grinding may be, for example, frozen in liquid nitrogen and ground with dry ice.

(6) Next, a thickener is added to make a slurry, and the viscosity, fluidity and the like are adjusted, and then the slurry itself is adjusted to 0.05.
A film having a thickness of about 0.2 mm is formed, or (7) the suspension is formed on a water repellent carbon paper by a doctor blade method or the like to have a thickness of about 0.05 mm to 0.2 mm. This formed film is heat-treated in a nitrogen stream at a temperature of 280 ° C. for 10 hours and at 360 ° C. for about 5 hours. (8) When the molded film is obtained in (6), the molded film is placed on water-repellent carbon paper and, if necessary, pressure-molded, for example, at a temperature of 280 ° C. for 10 hours at 360 ° C.
For 5 hours in a nitrogen stream. (9), (7)
Alternatively, in (8), the surface of the catalyst layer formed on the water repellent carbon paper is impregnated with an alcohol solution of a solid polymer electrolyte or the like, and then the solvent is removed by evaporation in a vacuum at a temperature of 80 ° C., for example. FIG. 1 (c) schematically shows an electrode sheet obtained by the above steps (1) to (9). (10) A battery (solid polymer electrolyte membrane-electrode assembly) is obtained by sandwiching and pressing, for example, a solid polymer electrolyte membrane between the two electrodes thus produced.

Here, the material for making the carbon paper water repellent is not particularly limited, but in view of using a polytetrafluoroethylene-based polymer as a binder (also a water repellent) in the present invention, It is preferable to use the same type of material. The material of the same system includes not only polytetrafluoroethylene but also tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and other derivatives thereof. The solvent used here is water,
Alcohol, a mixed solvent of both, and the like do not have to be particularly different from those conventionally used, and the quantitative ratios of various components are the same as above.

<< Aspect of Electrode Production by Blade Coating Method >> FIG. 3 shows a method of forming a slurry in which a thickener is mixed with a mixed solution of catalyst particles and a dispersion of a polytetrafluoroethylene-based polymer in the present invention. It is a schematic diagram for demonstrating the blade system which can be applied especially advantageously in the film-forming of the slurry which added and mixed the nonionic surfactant with the thickener. In FIG. 3, 4 is a rotating roller, and 5 is a gas diffusion layer. A slurry feeder 6 includes a front blade (front blade) 7 and a rear blade (front blade) 8. Further, 9 is a catalyst layer to be formed, and S is a slurry. During this operation, the slurry S is supplied to the feeder 6 and the thickness of the catalyst layer 9 to be applied is adjusted to the front blade 7 and the rear blade 8.
The rotating roller 4 is rotated as shown by the arrow in FIG. As a result, the catalyst layer 9 having a predetermined thickness is formed on the diffusion layer 5. In place of the movement by the rotating roller 4, the diffusion layer 5 may be fixed by an appropriate supporting member and the feeder 6, the front blade 7 and the rear blade 8 may be moved relatively.

Next, the specific procedure of this coating method will be described in the following (a) to (e). (A) For example, a thickening agent (for example, polyvinyl alcohol) is mixed with a liquid obtained by mixing 50% platinum-supported carbon catalyst particles and PTFE at a weight ratio of 4: 3, and prepared so that the viscosity becomes, for example, about 8000 cp. (In the case of this blade method, the viscosity is 2000 to 2000.
If it is about 0 cp, it can be effectively applied).
(B) The feeder 6 is set on the water repellent carbon paper 5, and the slurry liquid prepared in (a) is put in the portion of the slurry S. While adjusting the gap between the front blade 7 and the rear blade 8 with respect to the paper 5, the paper is moved to apply the slurry liquid. (C) Next, in a nitrogen stream, for example, at a temperature of 3
Heat treatment is performed at 60 ° C. to decompose and remove the thickener. (D) The coated surface is impregnated with an electrolyte solution, and the solution is removed by vacuum drying or the like to form an electrode. These points are the same when a nonionic surfactant is added in addition to the thickener.
(E) For example, a solid polymer electrolyte membrane is sandwiched between the produced electrodes and pressed to obtain a battery.

[0036]

EXAMPLES Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples. Of these, Examples 2 and 3 are examples when the blade coating method is applied.

Example 1 Porosity 75%, Thickness 0.4
mm carbon paper on NEOFLON [tetrafluoroethylene-hexafluoropropylene copolymer (FE
P), manufactured by Daikin Industries, Ltd., and then heat-treated to obtain a water-repellent carbon paper in which neoflon accounts for about 20% by weight of the entire paper. On the other hand, platinum catalyst powder is added to carbon particles in an amount of 50
Dispersion of polyflon (polytetrafluoroethylene, a registered trademark of Daikin Industries, Ltd.) in 3% of the total amount of the catalyst layer-constituting material with respect to the catalyst particles supported by weight%.
It was added to 0% by weight and mixed intimately with a colloid mill. This solution was cooled to about -80 ° C and frozen so that the surface area was as large as possible. In the freeze dryer, the vacuum degree was raised to 0.1 torr to sublimate the solvent to obtain a dry powder.

Subsequently, the temperature was 280 ° C. for 10 hours, and 36
Heat treatment was performed at 0 ° C. for 5 hours in a nitrogen stream. Then, a viscous aqueous solution of methyl cellulose was added to the heat-treated powder as a thickener and mixed by stirring (addition amount = 5% by weight) to prepare a viscosity of about 8000 cp. An area of 100 cm ² and a thickness of 0.1 was formed on the water-repellent carbon paper prepared above by a doctor blade method.
It was formed into a mm film. This serves as a catalyst layer in the electrode [see reference numeral 1 in FIG. 1]. The heat treatment was performed on the formed film obtained in any one of steps 1 to 3 at a temperature of 280 ° C. for 10 hours and at a temperature of 360 ° C. for 5 hours in a nitrogen stream. After impregnating the alcohol layer solution of the solid polymer electrolyte into the catalyst layer formed in step (1), the solvent was removed in vacuum at a temperature of 80 ° C.

Using the two electrode sheets prepared in the above steps, a NAFION-117 membrane (perfluorocarbon sulfonic acid resin membrane, Du Pont) as a solid polymer electrolyte membrane is provided between both electrodes on the hydrogen side and the oxygen side. Manufactured by
Sandwiching the product name), temperature 140 ℃, pressure 100kgf / c
After pressing under a pressure of m ² for 60 seconds, this was assembled in a fuel cell frame and set, and a conducting wire, a gas pipe and the like were connected to construct a solid polymer type fuel cell for a test sample.

On the other hand, the fuel cell of Comparative Example was tested in the same manner as in Example 1 except that methylcellulose was not added (after applying the freeze-drying method, heat treatment was performed without adding methylcellulose). Done and said NAFI
A battery was prepared in the same manner as above using the two obtained electrode sheets (coated with an alcohol solution of ON-117). FIG. 2 shows the relationship between the current density and the cell voltage measured for both the test electrodes of these examples and comparative examples.

As a cell operating condition, hydrogen was used as a fuel and was supplied to the anode side, while oxygen was supplied to the cathode side. The supply amount of both gases is 2.
0 l / min, oxygen 0.5 l / min, and supply pressure were both 2.0 atm. Further, hydrogen was humidified at 75 ° C. and oxygen was humidified at 25 ° C., and the battery was operated while maintaining the temperature at 60 ° C. There is a correlation between cell voltage and current density,
As the current density increases, the cell voltage relatively decreases, and the high cell voltage means that the catalyst utilization rate is high. However, as shown in FIG. 2, the cell voltage is higher than that of the comparative test battery. , The test battery according to the present invention has a current density of 0.
It can be seen that a high cell voltage is exhibited in a region of 1 A / cm ² or less, the electrode characteristics are excellent, and a high catalyst utilization rate is obtained.

<< Embodiment 2 >> In the present embodiment 2, the blade type apparatus of the embodiment shown in FIG. 3 was used. Porosity 7
A 5% carbon paper having a thickness of 0.4 mm was impregnated with a dispersion of NEOFLON [tetrafluoroethylene-hexafluoropropylene copolymer (FEP), manufactured by Daikin Industries, Ltd., trade name] and then heat-treated to obtain NEOFLON. A water repellent carbon paper was obtained which accounted for about 20% by weight of the entire paper. On the other hand, the catalyst particles formed by supporting 50% by weight of platinum powder on the carbon particles and the dispersion of polyflon (polytetrafluoroethylene, a registered trademark of Daikin Industries, Ltd.) in a weight ratio of 4: 3.
Polyvinyl alcohol was mixed with the mixed liquid so that the viscosity was 8000 cp.

Next, the water repellent carbon paper 5 obtained in step 3 is set as shown in FIG. 3, the slurry S obtained in step 3 is supplied to the feeder 6, and the roller 4 is rotated to move the water repellent carbon paper 5. While applying the slurry liquid. Subsequently, heat treatment was performed in a nitrogen stream at a temperature of 360 ° C. for 5 hours to thermally decompose and remove the thickener. Then, the coated surface formed by is impregnated with an alcohol solution of a solid polymer electrolyte, the solvent is removed in a vacuum at a temperature of 80 ° C., and a catalyst layer having a thickness of 0.1 mm is formed on the water-repellent carbon paper. It was used as an electrode.

Using the two electrode sheets prepared in the above steps, a perfluorocarbon sulfonic acid resin membrane having a thickness of 80 μm is sandwiched as a solid polymer electrolyte membrane between both electrodes on the hydrogen electrode side and the oxygen electrode side, Temperature 140 ℃, pressure 10
After pressing for 60 seconds under a pressure of 0 kgf / cm ² , this was assembled and set in a fuel cell frame, and a conducting wire, a gas pipe and the like were connected to construct the solid polymer fuel cell for a test of Example 2. Then, a performance test was carried out. As a comparative example, the battery as in Example 1 was constructed, and this was used as a comparative test battery of Example 2.

As a cell operating condition, hydrogen was used as a fuel and was supplied to the anode side, while air (not oxygen) was supplied to the cathode side. The supply rates of both gases are 0.2 l / min of hydrogen and 0.5 l / min of air.
And the supply pressure was 2.0 atm. Further, hydrogen was humidified at a temperature of 95 ° C. and air was humidified at 80 ° C., and the temperature of the battery was kept at 80 ° C. to operate. FIG. 4 shows the result. As shown in FIG. 4, even in the test battery of the comparative example, the cell voltage gradually decreases as the current density increases, but the test battery of Example 2 exhibits excellent performance. Therefore, it is clear that it is further improved.

Example 3 In this Example 3, polyvinyl alcohol was mixed as a thickener as in Example 2, and at the same time as a nonionic surfactant, Nissan Nonion NS-204.5 (polyester) was used. 1% by weight of oxyethylene nonylphenyl ether (trade name, manufactured by NOF CORPORATION) was added, and a performance test was conducted on a test battery prepared in exactly the same manner as in Example 2 except for the above points, and the battery shown in FIG. The battery performance was almost the same as the performance.

[0047]

As described above, according to the present invention, the moldability of the catalyst layer is remarkably improved, and the heat treatment of the polytetrafluoroethylene-based polymer can be performed, so that the three-dimensional reaction site is effectively increased. Can be made. Moreover, the catalyst layer obtained by this is uniformized, and furthermore, the cracking etc. does not occur in the catalyst layer, the utilization factor of the catalyst is increased, the electrode characteristics are improved, and the performance of the battery incorporating this is significantly improved, Can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an example of a manufacturing process of an electrode catalyst layer according to the present invention.

FIG. 2 is a graph showing the relationship between the measured current density and cell voltage of each of the test batteries manufactured in Example 1 and Comparative Example.

FIG. 3 is a schematic diagram for explaining a manufacturing method of a catalyst layer by a blade coating method.

FIG. 4 is a diagram showing the relationship between the measured current density and cell voltage of each of the test batteries manufactured in Example 2 and Comparative Example.

[Explanation of symbols]

 1 Molded Film (Catalyst Layer) 2 Gas Diffusion Layer 3 Electrode 4 Rotating Roller 5 Gas Diffusion Layer 6 Feeder for Slurry 7 Front Blade of Feeder (Front Blade) 8 Rear Blade of Feeder (Rear Blade) 9 Coating Catalyst Layer S Slurry

Claims (18)

[Claims] 1. A fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene polymer and a polymer electrolyte on a gas diffusion layer, the catalyst layer comprising the catalyst particles and the polytetrafluoroethylene polymer. After mixing the thickener in the mixture with the dispersion of, heat treatment,
An electrode for a fuel cell, which is a catalyst layer coated with a polymer electrolyte. 2. A fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte on a gas diffusion layer, the catalyst layer comprising the catalyst particles and the polytetrafluoroethylene-based polymer. An electrode for a fuel cell, which is a catalyst layer formed by mixing a thickener and a nonionic surfactant in a mixed liquid with a polymer dispersion, followed by heat treatment and then coating with a polymer electrolyte. 3. The fuel cell electrode according to claim 1, wherein the fuel cell electrode is an electrode for a polymer electrolyte fuel cell. 4. The fuel cell electrode according to claim 1, wherein the gas diffusion layer is carbon paper or water repellent carbon paper. 5. The electrode for a fuel cell according to claim 1, 2, 3 or 4, wherein the catalyst particles are carbon powder carrying platinum. 6. The fuel cell electrode according to claim 1, wherein the polymer electrolyte is a perfluorocarbon sulfonic acid-based resin. 7. The fuel cell electrode according to claim 1, wherein the thickener is carboxymethyl cellulose, methyl cellulose, casein, polyvinyl alcohol, ammonium polyacrylate or starch. 8. A method for producing a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte on a gas diffusion layer, the catalyst layer comprising the catalyst particles and polytetrafluoroethylene-based material. A method for producing a fuel cell electrode, comprising forming a mixture by adding a thickener to a mixture of a polymer dispersion, heat treatment, and then coating with a polymer electrolyte. 9. A method for producing a fuel cell electrode comprising a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte on a gas diffusion layer, wherein the catalyst layer comprises (1) catalyst particles and polytetrafluoroethylene. It is formed by freeze-drying a mixed solution of a fluoroethylene polymer dispersion, heat treatment, (2) then mixing a thickener and heat treatment, and (3) coating with a polymer electrolyte. A method for manufacturing an electrode for a fuel cell, comprising: 10. A method for producing a fuel cell electrode having a catalyst layer containing a catalyst particle, a polytetrafluoroethylene-based polymer and a polymer electrolyte on a gas diffusion layer, wherein the catalyst layer is (1) A mixed solution of a dispersion of a polytetrafluoroethylene-based polymer is freeze-dried, and (2) a thickener is then mixed, followed by heat treatment,
(3) A method for producing an electrode for a fuel cell, which is formed by coating with a polymer electrolyte. 11. A method for producing a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene-based polymer and a polymer electrolyte on a gas diffusion layer, wherein the catalyst layer is formed by (1) After freeze-drying a mixed solution of a tetrafluoroethylene-based polymer dispersion, freeze-grinding (2) mixing a thickener therewith, then heat-treating (3) then coating with an electrolyte membrane A method of manufacturing a fuel cell electrode, comprising: 12. A method for producing a fuel cell electrode having a catalyst layer containing catalyst particles, a polytetrafluoroethylene polymer and a polymer electrolyte on a gas diffusion layer, wherein the catalyst layer comprises (1) catalyst particles and polytetrafluoroethylene. A thickener was mixed with a mixed solution of fluoroethylene polymer dispersion, and (2) coated on the gas diffusion layer while controlling the film thickness by a feeder equipped with one or more blades for controlling the film thickness. After that, a method for producing an electrode for a fuel cell, which is characterized in that it is formed by heat treatment and (3) coating with a polymer electrolyte. 13. The method for producing an electrode for a fuel cell, which is a method for producing an electrode for a polymer electrolyte fuel cell.
13. The method for manufacturing a fuel cell electrode according to 9, 10, 11 or 12. 14. A nonionic surfactant is mixed in addition to the thickening agent, which is characterized in that:
14. The method for producing a fuel cell electrode according to 1, 12, or 13. 15. The gas diffusion layer is made of carbon paper or water repellent carbon paper.
15. The method for producing a fuel cell electrode according to 1, 12, 13 or 14. 16. The catalyst particles according to claim 8, wherein platinum is supported on carbon powder.
13. The method for producing a fuel cell electrode according to 13, 14 or 15. 17. The polymer electrolyte is a perfluorocarbon sulfonic acid-based resin.
17. A method for producing a fuel cell electrode according to 1, 12, 13, 14, 15 or 16. 18. The thickening agent is carboxymethyl cellulose, methyl cellulose, casein, polyvinyl alcohol, ammonium polyacrylate or starch, wherein the thickener is 8, 9, 10, 11, 12, 13, 14, 15, 15.
16. The method for producing a fuel cell electrode according to 16 or 17.