JP2003077479A - Polymer electrolyte type fuel cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell that has an excellent battery property by using a catalyst layer having excellent hydrogen ion conductivity. SOLUTION: This is a polymer electrolyte type fuel cell which comprises a hydrogen ion conductive polymer electrolyte membrane, an anode and a cathode that pinch the above membrane, an anode side separator that has a gas passage for supplying a fuel gas to the anode, and a cathode side separator that has a gas passage for supplying an oxidizer gas to the cathode, and the above anode and cathode are made of a catalyst layer that makes contact with the above membrane respectively and a gas diffusion layer, and at least one of the catalyst layers of the above anode and cathode contains a polymer dispersed agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell, and more particularly to a catalyst layer for its electrode and a method for producing the same.

[0002]

2. Description of the Related Art First, a general structure of a conventional polymer electrolyte fuel cell will be described. A fuel cell using a polymer electrolyte electrochemically reacts a fuel gas containing hydrogen with an oxidant gas containing oxygen such as air to simultaneously generate electric power and heat.

FIG. 1 is a schematic sectional view of a part of a polymer electrolyte fuel cell unit cell. As shown in FIG. 1, catalyst layers 12 are arranged on both sides of a polymer electrolyte membrane 11 that selectively transports hydrogen ions. As the polymer electrolyte membrane 11, perfluorocarbon sulfonic acid (for example, Nafion membrane manufactured by Du Pont, USA) is generally used. The catalyst layer 12 is a mixture of carbon powder carrying a platinum-based metal catalyst and a hydrogen ion conductive polymer electrolyte.

On the outer surface of the catalyst layer 12, a gas diffusion layer 13 having both air permeability and electron conductivity is further arranged.
As the gas diffusion layer 13, for example, carbon paper subjected to water repellent treatment is used. The catalyst layer 12 and the gas diffusion layer 13 form an electrode 14. A gas sealant and a gasket are arranged around the electrode 14 with the polymer electrolyte membrane sandwiched therebetween so that the supplied fuel gas and oxidant gas do not leak to the outside and the two kinds of gas do not mix with each other. . The polymer electrolyte membrane, the electrodes, and the gas sealing material and the gasket are preassembled and integrated as an MEA (electrolyte membrane electrode assembly) 15.

As shown in FIG. 2, a conductive separator 21 for mechanically fixing the MEA 15 is arranged outside the MEA 15. FIG. 2 is a schematic cross-sectional view for explaining the structure of the unit cell 23 of the polymer electrolyte fuel cell. On the surface of the separator 21 facing the MEA 15,
A gas flow path 22 is formed for supplying a reaction gas to the electrodes and carrying away the generated gas and surplus gas generated at the electrodes.
The gas flow paths 22 are formed on both surfaces of the separator 21 so that the MEA 15 and the separator 21 can be repeatedly and alternately arranged. The gas flow path may be provided separately from the separator, but it is common to provide a groove on the surface of the separator to form the gas flow path. In this manner, the MEA 15 is fixed by the conductive separator 21, the fuel gas is supplied to the gas passage on the anode side, and the oxidant gas is supplied to the gas passage on the cathode side. An electromotive force of about 8 V can be generated.

Usually, when a fuel cell is used as a power source, a voltage of several volts to several hundreds of volts is required.
In practice, the required number of unit cells 23 are connected in series. By repeatedly arranging the separator and the MEA as shown in FIG. 2 alternately, it is possible to connect a plurality of unit cells in series.

In order to supply gas to the gas flow path, the gas supply pipe is branched into the number of separators to be used,
A piping jig that directly connects the branching point to the gas passage of the separator is required. A jig for directly connecting the gas supply pipe as described above to the gas passage of the separator is called an external manifold. Further, by providing a through hole in the separator having the gas flow path and connecting the inlet and outlet of the gas flow path to this hole, the gas can be directly supplied to the gas flow path from the through hole. Such a structure is called an internal manifold.

Next, the gas diffusion layer and the catalyst layer forming the electrode of the fuel cell will be described. The gas diffusion layer mainly has the following three functions. The first is the function of diffusing a reaction gas for uniformly supplying the reaction gas to the catalyst in the catalyst layer from the gas flow path on the surface of the separator that is in contact with the gas diffusion layer. The second is the function of promptly discharging the water generated by the reaction in the catalyst layer to the gas flow path. The third is a function of conducting electrons necessary for the reaction or generated electrons.
That is, the gas diffusion layer needs to have excellent reaction gas permeability, water vapor permeability, and electron conductivity.

As a conventional general technique, a porous substrate such as carbon paper and carbon cloth is used for the gas diffusion layer in order to secure good gas permeability. Also, in order to ensure good water vapor permeability,
For example, a water-repellent polymer typified by a fluororesin is dispersed in the gas diffusion layer. Further, in order to secure good electron conductivity, the gas diffusion layer is made of electron conductive material such as carbon fiber, metal fiber and carbon powder.

Next, the catalyst layer mainly has the following four functions. The first is the function of supplying the reaction gas such as the fuel gas or the oxidant gas supplied from the gas diffusion layer to the reaction site of the catalyst layer. The second is a function of rapidly transmitting the hydrogen ions necessary for the reaction on the catalyst or the generated hydrogen ions to the electrolyte membrane. The third is a function of conducting electrons necessary for the reaction or generated electrons. The fourth is the function of promoting the electrode reaction. That is, the catalyst layer needs to have excellent reaction gas permeability, hydrogen ion conductivity, electron conductivity and catalytic performance, and a wide reaction area.

As a conventional general technique, in order to secure good gas permeability, the catalyst layer is formed by using carbon powder or a pore-forming material that constitutes a porous chain-like aggregate. Has a porous structure. Further, in order to secure good hydrogen ion conductivity, a polymer electrolyte is dispersed near the catalyst in the catalyst layer to form a hydrogen ion conductive network. Further, in order to secure good electron conductivity, the catalyst carrier is made of an electron conductive material such as carbon powder or carbon fiber. Further, in order to ensure good catalytic performance, a metal catalyst with high reaction activity represented by platinum having a particle size of several n is used.
It has been carried out that carbon particles are supported on the carbon powder as very fine particles and highly dispersed in the catalyst layer.

However, it is very difficult to disperse the polymer electrolyte in the vicinity of the catalyst in the catalyst layer to form a good hydrogen ion conduction network. Generally, the carbon powder used for the catalyst layer has a specific surface area of several tens to several thousands m.
^When it is ² / g, primary particles of several tens of nm are combined to form a chain-like aggregate. The catalyst is supported in the pores of several nm to several 100 nm formed inside the chain-shaped aggregate. Therefore, it is difficult to uniformly disperse the polymer electrolyte having a particle size of several 100 nm in the vicinity of the catalyst.
Therefore, it is difficult to secure a sufficient effective reaction area of the catalyst.

There is also a problem that it is difficult to form a hydrogen ion conductive network due to the binding of the polymer electrolytes, and sufficient hydrogen ion conductivity cannot be ensured.

Since the carbon powder used for the catalyst layer forms a chain-like aggregate, the catalyst ink prepared by mixing the carbon powder carrying the catalyst, the polymer electrolyte, and the dispersion medium such as water and alcohol. Then, carbon powder or the like is very likely to aggregate. Therefore, in the usual stirring and dispersion methods using a stirrer, an ultrasonic bath, etc., the particles in the catalyst ink show a particle size distribution having a median diameter of several tens of μm. Therefore,
When the catalyst ink is applied to the electrolyte membrane, the gas diffusion layer, the substrate sheet, or the like, an aggregate layer of powder having a particle size of several tens of μm is formed as the catalyst layer, which is thinner than several tens μm
There is a problem that it is difficult to obtain a dense and smooth catalyst layer.

In the gas diffusion layer, various surfactants are used in order to obtain a good dispersed state of the water repellent polymer material. A typical example thereof is JP-A-11-335886.
Japanese Patent Laid-Open No. 11-269689, Japanese Patent Laid-Open No. 11-269689
No. 050290, Japanese Patent Application Laid-Open No. 10-092439, and Japanese Patent Application Laid-Open No. 6-116774. These publications disclose the use of alkylphenol octylphenol ethoxylate (trade name: Triton X-100) as a dispersant for the water-repellent polymer material. However, the techniques disclosed in these publications are not disclosures of techniques relating to dispersion of the polymer electrolyte and carbon powder in the catalyst layer of the present invention.

On the other hand, JP-A-8-236123, JP-A-9-180727, and JP-A-10-28.
4086 discloses the use of surfactants in the catalyst layer. In these publications, a method of mixing a surfactant with a raw material of a catalyst layer to form a catalyst layer and then impregnating the obtained catalyst layer with a polymer electrolyte, or impregnating a catalyst layer previously formed with the surfactant. After that, a method of further impregnating or coating with a polyelectrolyte is disclosed. In this case, the surfactant has a role of making it easier for the polymer electrolyte to soak into the catalyst layer.

However, in these methods, since the polymer electrolyte is not present in the catalyst layer when the surfactant is used, the dispersion state of both the carbon powder and the polymer electrolyte is simultaneously controlled by the surfactant. Can not. Therefore, it is impossible to prevent the carbon powder from aggregating in the catalyst layer and disperse the polymer electrolyte at the same time to form a good hydrogen ion conductive network, and it is not possible to obtain a dense and smooth catalyst layer.

Further, for example, when a surfactant having a molecular weight of 300 to 600 disclosed in Japanese Patent Laid-Open No. 10-284086 is added to a catalyst ink, foaming becomes severe during preparation of the catalyst ink and a good catalyst ink cannot be prepared. . For this reason, there is a problem that a stable catalyst layer cannot be formed.

As an effective dispersion method of the catalyst ink, JP-A 2000-164224 discloses a method using a ball mill or a homogenizer. When the catalyst ink is dispersed using these methods, the particle diameter of the carbon powder carrying the catalyst in the catalyst ink is about several μm.

However, when the homogenizer is used, there is a problem that the foaming is severe even without the use of a surfactant, and the bubbles are mixed into the catalyst ink and a defoaming step is required. Further, when a ball mill is used, it is basically a batch-type construction method, and there is a problem that a process for removing the balls is added and the process cost increases.

[0021]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by using a catalyst layer having excellent hydrogen ion conductivity to provide a polymer electrolyte fuel cell having excellent cell characteristics. The purpose is to provide. The present invention also provides a catalyst layer in which a carbon powder carrying a catalyst and a polymer electrolyte in a well-dispersed state are obtained, and a low-cost polymer in which variations in coating amount and coating defects in the manufacturing process are reduced. An object is to provide a method for manufacturing an electrolyte fuel cell.

[0022]

The fuel cell of the present invention comprises a hydrogen ion conductive polymer electrolyte membrane, an anode and a cathode sandwiching the membrane, an anode side separator having a gas flow path for supplying a fuel gas to the anode, And a cathode-side separator having a gas flow path for supplying an oxidant gas to the cathode, wherein the anode and the cathode each include a catalyst layer in contact with the membrane and a gas diffusion layer, and at least the anode and the cathode. One catalyst layer is
It is characterized by containing a polymer dispersant. The polymer dispersant preferably comprises at least one selected from the group consisting of carboxylic acid, carboxylic acid salt and amine.

The method for producing a polymer electrolyte fuel cell of the present invention comprises a step (1) of preparing a catalyst ink comprising a polymer dispersant, carbon powder carrying a catalyst, a polymer electrolyte and a solvent, and the above ink. A step of forming a catalyst layer by coating on the gas diffusion layer or the hydrogen ion conductive polymer electrolyte membrane, or after coating on the base material sheet and transferring to the hydrogen ion conductive polymer electrolyte membrane ( 2), Here, the step (1) is preferably a step of preparing a catalyst ink by dispersing the polymer dispersant, the carbon powder supporting the catalyst and the polymer electrolyte in a solvent using a bead mill dispersing device. Furthermore, the diameter of beads provided in the bead mill dispersion device is 0.05 to 2.0 m.
It is preferably m.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION A polymer dispersant will be described with reference to "Pigment Dispersion Technology" (published by Technical Information Institute). The polymer dispersant is broadly included in the category of surfactants, and usually has a molecular weight of several thousand or more and is composed of a hydrophilic group and a hydrophobic group, and has both the function of the surfactant and the characteristics of the polymer. It is defined as an amphipathic polymer.

Surfactants that do not correspond to polymer dispersants include
Since the molecular weight is as small as 200 or more and less than 2000, foaming easily occurs. In addition, since the effect due to its own steric hindrance is small, when the surfactant is mixed in the catalyst ink, there are drawbacks such as suppressing the aggregation of carbon powder in the catalyst ink and the effect of dispersing the polymer electrolyte is small. is there.

On the other hand, the polymeric dispersant has a large molecular weight of, for example, 2000 to 200,000, and therefore foaming hardly occurs. Further, since the effect of the steric hindrance of itself is great, when the polymer dispersant is mixed in the catalyst ink, the effect of suppressing the aggregation of carbon powder in the catalyst ink and dispersing the polymer electrolyte is great.

Since the polymer dispersant has many adsorption sites, the dispersed particles can be stabilized. Therefore, by including the polymer dispersant in the catalyst layer, the polymer electrolyte and the carbon powder carrying the catalyst can be uniformly dispersed, and a sufficient effective reaction area of the catalyst can be secured.

Since the dispersed particles of the carbon powder carrying the polymer electrolyte and the catalyst are stably present as described above, the stability of the catalyst ink containing them becomes high. Therefore, in manufacturing processes such as coating and printing of the catalyst ink, clogging of the catalyst ink in the pipes and pumps and changes in the concentration of the catalyst ink during storage can be suppressed. Furthermore, variations in coating amount and coating defects during coating are reduced, and adhesion with the polymer electrolyte membrane and the gas diffusion layer is improved.

Examples of the polymer dispersant include the following. As the polymer dispersant comprising a carboxylic acid or a carboxylic acid salt, a styrene-maleic anhydride copolymer,
Examples thereof include an olefin-maleic anhydride copolymer, sodium polyacrylate, a partial hydrolyzate of polyacrylamide, an acrylamide-sodium acrylate copolymer, and sodium alginate.

Examples of the polymeric dispersant composed of amines include polyethyleneimine, polyvinylimidazoline, aminoacrylmethacrylate-acrylamide copolymer, polyacrylamide, polyacrylamide-Mannich modified product, chitosan and the like. Further, polyvinyl alcohol, formaldehyde condensate of naphthalene sulfonate, copolymer of polyoxyethylene ether ester, starch and the like can be used as the polymer dispersant.

Commercially available polymeric dispersants include Disp.
erbyk191 (manufactured by Big Chemie), Disparon DA-703-50 (manufactured by Kusumoto Kasei Co., Ltd.), Polity N
-100K (manufactured by Lion Corporation), Dimor N (manufactured by Kao Corporation) and the like.

Ketjen black, acetylene black or the like is used as the carbon powder carrying the catalyst. Examples of commercially available products include Vulcan XC-72 (manufactured by Cabot).

For the polymer electrolyte membrane and the polymer electrolyte used for the catalyst layer, perfluorocarbon sulfonic acid ionomer or the like is used. Examples of commercially available products include Flemion film and Flemion solution (manufactured by Asahi Glass Co., Ltd.).

By using a bead mill dispersing device for the dispersion treatment of the catalyst ink, the particle diameter of the particles in the catalyst ink can be reduced to the submicron level, and the dispersion treatment can be continuously performed. Also in terms of the process, it is not necessary to separate the beads to be used, which enables cost reduction.

As a bead mill dispersion device used for the dispersion treatment of the catalyst ink, Dispermat SL-C12Z
(Produced by Getzmann Co., Ltd. of Germany) may be used, but any other device may be used as long as it is a bead mill dispersing device. Further, the material of the beads used in the bead mill dispersion device and the like may be those applicable to the present invention.

According to the present invention, the median diameter of the particles in the prepared catalyst ink can be controlled within the range of 0.1 to 1.0 μm, and a thin, dense and smooth catalyst layer can be obtained. Regarding the method for forming the catalyst layer, the catalyst ink may be coated on the gas diffusion layer or on the polymer electrolyte membrane, or after coating on the base material sheet, transfer to the polymer electrolyte membrane. Good.

[0037]

EXAMPLES The present invention will be specifically described below based on examples. Example 1 (i) Preparation of Gas Diffusion Layer Aqueous dispersion of acetylene black (Denka Black, particle size 35 nm, manufactured by Denki Kagaku Kogyo KK), which is carbon powder, and polytetrafluoroethylene (PTFE) (Daikin) A water-repellent ink containing 20% by weight of PTFE and 80% by weight of acetylene black as dry weight was prepared by mixing with D1) manufactured by Kogyo Co., Ltd. This water-repellent ink is spray-coated on carbon paper (TGPH060H, manufactured by Toray Industries, Inc.), which is the base material of the gas diffusion layer, and after impregnation, heat-treated at 300 ° C. using a hot-air dryer to diffuse gas. Layers were obtained.

(Ii) Formation of catalyst layer Ketjen Black (Ketjen Black manufactured by Ketjen Black International Co., Ltd.) which is carbon powder.
50 parts by weight of Pt was carried on 100 parts by weight of EC and particle size of 30 nm.

The obtained Pt-supported carbon powder and a perfluorocarbon sulfonic acid ionomer (US Ald
Rich 5% by weight Nafion dispersion), isopropyl alcohol as a solvent, and Disperbyk 191 (manufactured by Big Chemie) consisting of an amine as a polymer dispersant were mixed at a weight ratio of 150: 10: 10: 10. To prepare a catalyst ink A.

The dispersion treatment of the prepared catalyst ink A was carried out by a bead mill dispersion device (Disperm manufactured by Getzmann, Germany).
at SL-C12Z) was used. The beads have a diameter of 0.
A 5 mm one was used. The particle size distribution of this catalyst ink A was measured with a Microtrac HRAX-100 particle size analyzer (manufactured by Nikkiso Co., Ltd.). Median diameter at this time (D5
The value of 0) was 0.3 μm. This catalyst ink A is spray-coated on the diffusion layer to form a catalyst layer, which is joined to both sides of a polymer electrolyte membrane (Nafion 112 membrane manufactured by Du Pont, USA) which is slightly larger than the catalyst layer, and is shown in FIG. The structure MEA-A was prepared.

Comparative Example 1 Instead of the polymer dispersant, a surfactant having a molecular weight of 646 which does not correspond to the polymer dispersant (manufactured by ACROS ORGANICS, Triton X-
MEA-B was produced in the same manner as in Example 1 except that 100) was used. The particle size distribution of the catalyst ink B at this time was measured in the same manner as in Example 1. Median diameter (D5
0) was 1.5 μm.

Comparative Example 2 MEA-C was prepared in the same manner as in Example 1 except that the polymer dispersant was not added. The particle size distribution of the catalyst ink C at this time was measured in the same manner as in Example 1. The median diameter (D50) was 4.2 μm.

Example 2 Next, the M prepared in Example 1 was used.
A rubber gasket plate was bonded to the outer peripheral portion of the EA-A polymer electrolyte membrane. Manifold holes for cooling water, fuel gas, and oxidant gas flow paths were formed on the gasket plate.

Then, a conductive separator made of a graphite plate impregnated with a phenol resin was prepared. This conductive separator has outer dimensions of 20 cm × 32 cm × 1.3 mm and a depth of 0.5 mm of fuel gas or oxidant gas,
And a flow path for cooling water. Using two of these conductive separators, a separator having an oxidant gas flow channel formed on the cathode side of MEA-A and a separator having a fuel gas flow channel formed on the anode side were stacked to obtain a single cell.
A unit cell using MEA-A manufactured by the above method was set as a battery A.

Comparative Example 3 Battery B was prepared in the same manner as in Example 2 except that MEA-B produced in Comparative Example 1 was used as the MEA.
Was produced.

Comparative Example 4 A battery C was prepared in the same manner as in Example 2 except that the MEA-C produced in Comparative Example 2 was used as the MEA.
Was produced.

Pure hydrogen gas was supplied to the anodes of the batteries A, B, and C, and air was supplied to the cathode, and a discharge test was performed on each battery. The cell temperature during the test was 75 ° C., the fuel gas utilization rate (Uf) was 70%, and the air utilization rate (Uo) was 40%. The gas humidification was performed by passing the fuel gas through a bubbler at 70 ° C and the air at 50 ° C.

Battery A of the example of the present invention and battery B of the comparative example
And the result of having investigated the current-voltage characteristic of the battery C is shown in FIG. In addition, the results of examining the life characteristics of these batteries are shown in FIG.
Shown in. In the figure, Battery A of the present invention exhibits excellent discharge characteristics and life characteristics as compared with Battery B in which a surfactant not corresponding to the polymer dispersant is added and Battery C in which the polymer dispersant is not added.

As is clear from the measurement result of the median diameter, the ink A contains a polymer dispersant,
The carbon powder supporting the polymer electrolyte and the catalyst was sufficiently dispersed without uneven distribution. Therefore, it is considered that the decrease in water content of the polymer electrolyte and the decrease in water repellency of the carbon powder were suppressed, and good hydrogen ion conductivity, gas diffusibility, and water vapor permeability were secured for a long time. It was

Further, in Battery A, the carbon powder carrying the polymer electrolyte and the catalyst was sufficiently dispersed in the catalyst ink, so that the effective reaction area of the catalyst was sufficiently secured, and the polymer electrolyte ionomers were appropriately dispersed. The bonding made it possible to form a homogeneous hydrogen ion conduction network. Therefore, the hydrogen ion conductivity was sufficiently secured, and the initial characteristics were also improved.

Example 3 Ketjen Black which is a carbon powder (manufactured by Ketjen Black International,
Ketjen Black EC, particle size 30 nm) 10
40 parts by weight of Pt and 20 parts by weight of Ru were carried on 0 part by weight, and heat treatment was carried out. Thus, a carbon powder carrying an alloyed Pt-Ru catalyst was produced.

MEA-A2 was prepared in the same manner as in Example 1 except that the Pt-Ru catalyst was used instead of the Pt catalyst. Then, a battery A2 was produced in the same manner as in Example 2 except that MEA-A2 was used as the MEA. ME
The particle size distribution of the catalyst ink A2 prepared at the time of preparation of A-A2 was measured by the same method as in Example 1. Catalyst ink A2
Had a median diameter (D50) of 0.2 μm.

Comparative Example 5 MEA-B2 was prepared in the same manner as in Example 3 except that the same surfactant as in Comparative Example 1 was added instead of the polymer dispersant. Then, a battery B2 was produced in the same manner as in Example 2 except that MEA-B2 was used as the MEA. The catalyst ink B2 prepared at the time of preparing MEA-B2 was measured for particle size distribution in the same manner as in Example 1. Median diameter of catalyst ink B2 (D50)
Was 3.8 μm.

Comparative Example 6 MEA-C2 was prepared in the same manner as in Example 3 except that the polymer dispersant was not added.
Then, a battery C2 was produced in the same manner as in Example 2 except that MEA-C2 was used as the MEA. MEA-C2
The particle size distribution of the catalyst ink C2 prepared at the time of manufacture was measured by the same method as in Example 1. The median diameter (D50) of the catalyst ink C2 was 9.0 μm.

Assuming reformed gas, supply to the anode
50ppm CO in fuel gas, CO ₂H containing 20%₂Ba
Example 2 and Comparative Example 3, except that lance gas was introduced.
Current of batteries A2, B2, and C2 under the same conditions as in 4
The voltage characteristics were investigated. The result is shown in FIG. Polymer dispersion
The battery A2 of Example 3 containing the agent showed excellent battery characteristics.
did.

From the measurement result of the median diameter, it is found that the particles in the catalyst ink by adding the polymer dispersant are better when using the carbon powder supporting the Pt-Ru alloy catalyst than when using the carbon powder supporting the Pt catalyst. It has been clarified that it is effective in improving the dispersibility of. Further, even when a reformed gas was assumed, excellent battery characteristics were shown.

Example 4 Example 1 was the same as Example 1 except that a homogenizer (Ultra Turrax Disperser manufactured by IKA Japan Co., Ltd.) was used instead of the bead mill dispersing device for the dispersion treatment of the catalyst ink. Catalyst ink A3 was prepared in the same manner.

Comparative Example 7 A catalyst ink B3 was prepared in the same manner as in Example 4 except that the same surfactant as in Comparative Example 1 was added instead of the polymer dispersant. The catalyst ink B3 using the same surfactant as in Comparative Example 1 had a large amount of foaming, and it was difficult to highly disperse the catalyst ink. on the other hand,
The catalyst ink A3 containing the polymer dispersant of Example 1 had less foaming than the catalyst ink B3, but the median diameter (D50) after dispersion was 1.0 μm. Therefore,
The homogenizer could not disperse the particles in the catalyst ink to a high degree as much as the beads mill disperser, and could not reduce the particle size to the submicron level.

Example 5 The influence on the median diameter of the catalyst ink after dispersion and the battery characteristics when the diameter of the beads used in the bead mill dispersion device was changed was examined. A catalyst ink was prepared in the same manner as in Example 1 except that the diameter of the beads was changed, and a battery was prepared in the same manner as in Example 2. Table 1 shows the median diameter of each catalyst ink when the bead diameter was changed from 0.03 to 3 mm, and the battery voltage at a current density of 0.2 A / cm ^{2 of} each battery produced using these catalyst inks. Show.

[0060]

[Table 1]

It was shown that when the bead diameter was in the range of 0.05 to 2.0, the median diameter was small and the battery voltage was high. It was considered that when the diameter of the beads was less than 0.05 μm, it was in an overdispersed state and the carbon particles supporting the catalyst were re-aggregated to increase the median diameter. On the other hand, when the diameter of the beads exceeded 2.0 μm, it was considered that the median diameter increased due to insufficient dispersion ability.

[0062]

As described above, according to the present invention, by using the catalyst layer having excellent hydrogen ion conductivity,
A polymer electrolyte fuel cell having excellent cell characteristics can be provided. Further, according to the present invention, a catalyst layer having a good dispersion state of the carbon powder supporting the catalyst and the polymer electrolyte can be obtained,
In addition, it is possible to provide a low-cost method for producing a polymer electrolyte fuel cell in which variations in coating amount and coating defects in the manufacturing process are reduced.

[Brief description of drawings]

FIG. 1 ME as a constituent element of a polymer electrolyte fuel cell
It is a schematic sectional drawing which shows the structure of A.

FIG. 2 is a schematic cross-sectional view showing the structure of a unit cell that is a constituent element of a polymer electrolyte fuel cell.

FIG. 3 is a first example of the present invention, a first comparative example, and a second comparative example.
3 is a graph showing current-voltage characteristics of the polymer electrolyte fuel cell of FIG.

FIG. 4 is a first example of the present invention, a first comparative example, and a second comparative example.
3 is a graph showing the life characteristics of the polymer electrolyte fuel cell of FIG.

FIG. 5 is an example 3, a comparative example 5, and a comparative example 6 of the present invention.
3 is a graph showing current-voltage characteristics of the polymer electrolyte fuel cell of FIG.

[Explanation of symbols]

11 Polymer electrolyte membrane 12 Catalyst layer 13 Gas diffusion layer 14 electrodes 15 MEA 21 Separator 22 gas flow path 23 cells

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Makoto Uchida             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Junji Morita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5H018 AA06 AS02 AS03 BB00 BB08                       BB12 HH01                 5H026 AA06 BB00 BB04 BB08 CC03                       CX05 EE17 HH01

Claims (5)

[Claims] 1. A hydrogen ion conductive polymer electrolyte membrane, an anode and a cathode sandwiching the membrane, an anode side separator having a gas flow path for supplying a fuel gas to the anode, and a gas for supplying an oxidant gas to the cathode. There is a cathode side separator having a flow path, and the anode and the cathode each include a catalyst layer in contact with the membrane and a gas diffusion layer, and at least one of the anode and the cathode has a polymer dispersant. A polymer electrolyte fuel cell comprising: 2. The polymer electrolyte fuel cell according to claim 1, wherein the polymer dispersant comprises at least one selected from the group consisting of carboxylic acid, carboxylic acid salt and amine. 3. A step (1) of preparing a catalyst ink comprising a polymer dispersant, a carbon powder carrying a catalyst, a polymer electrolyte and a solvent, and the ink on a gas diffusion layer or a hydrogen ion conductive polymer electrolyte. A polymer electrolyte fuel cell comprising a step (2) of coating on a membrane or coating on a substrate sheet and then transferring to a hydrogen ion conductive polymer electrolyte membrane to form a catalyst layer. Production method. 4. The step (1) is a step of preparing a catalyst ink by dispersing a polymer dispersant, carbon powder supporting a catalyst and a polymer electrolyte in a solvent using a bead mill dispersing device. 3. The method for producing a polymer electrolyte fuel cell according to item 3. 5. The method for producing a polymer electrolyte fuel cell according to claim 4, wherein the beads included in the bead mill dispersion device have a diameter of 0.05 to 2.00 mm.