JP2003082488A - Membrane electrode assembly and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane electrode which does not impair electrochemical characteristics even in a hot water environment or a high-temperature humidified environment by reinforcing a solid polymer electrolyte membrane to prevent the membrane from being damaged in a manufacturing process. Provided is a joined body and a manufacturing method thereof. SOLUTION: In a membrane electrode assembly for an electrochemical device in which catalyst electrode layers 3 and 4 are bonded to both main surfaces of a central portion of an electrolyte membrane 1, an outer peripheral surface portion of an electrolyte membrane to which no catalyst electrode layer is bonded is provided. A reinforcing layer 2 formed by melting and solidifying a resin is provided in a frame shape. In the method for manufacturing a membrane / electrode assembly, the reinforcing layer 2 may be formed by applying a resin solution to the outer peripheral surface of the electrolyte membrane 1. After being applied in a shape, it may be formed by drying, or the reinforcing layer 2 may be formed by applying a resin powder to the electrolyte membrane 1.
The resin powder layer is formed by melting and solidifying the resin powder layer by heating under pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane electrode assembly for an electrochemical device in which a catalyst electrode layer is joined to both main surfaces of a central portion of a solid polymer electrolyte membrane and a method for producing the same.

[0002]

Solid polymer electrolyte membranes are membranes for electrochemical devices such as fuel cells, water electrolyzers, salt electrolyzers, hydrochloric acid electrolyzers, ozone water production devices, oxygen or hydrogen separators, and various gas sensors. It is widely used as an electrode assembly, and a typical example thereof is a perfluorocarbon sulfonic acid film. Products include Nafion (trade name of DuPont, USA), Aciplex (trade name of Asahi Kasei Corporation), Fulem
ion (a product name of Asahi Glass Co., Ltd.) and the like.

Regarding the above-mentioned membrane electrode assembly for an electrochemical device, the most suitable water electrolysis device to which the present invention is applied will be described below as a typical example.

A water electrolysis apparatus separates an anode side and a cathode side by using a solid polymer electrolyte membrane as a diaphragm, and electrolyzes while supplying pure water or water containing ions to the anode side, and oxygen is discharged from the anode side. The gas is configured to generate hydrogen gas from the cathode side, and various proposals have been made regarding the system configuration, stack structure, operating method, etc. (for example, Japanese Utility Model Laid-Open No. 2-51263 or Actual Kaihei 3
-74670 full-text specification, JP-A-7-252682
Japanese Unexamined Patent Publication No. Hei 8-311676, Japanese Unexamined Patent Publication No. 2000
-54175 gazette etc.).

The full-text specification of the above-mentioned Japanese Utility Model Publication No. 3-74670 discloses a schematic structure of a water electrolysis cell, which is shown in FIG. The water electrolysis cell shown in FIG. 3 includes a membrane electrode assembly in which catalyst electrodes 20 and 21 are joined to both main surfaces of a solid polymer electrolyte membrane 24, and porous current collectors 18 and 19 provided on both sides thereof. And the terminal plates 22 and 23 for energization provided on both sides thereof, and the anode chamber 13 and the cathode chamber 14 partitioned by the solid polymer electrolyte membrane 24 form a water electrolysis cell.

In the above structure, by supplying water from the feed water inlet 15 to the anode chamber 13 and applying a DC voltage between the terminal plates 22 and 23, electrolysis of the water occurs and the anode chamber 1
3, oxygen gas is generated, and simultaneously generated hydrogen ions H ⁺ pass through the solid polymer electrolyte membrane 24 toward the cathode chamber 14, and hydrogen ions H ⁺ acquire electrons from the cathode to generate hydrogen gas H ₂
Occurs. The hydrogen gas and water are discharged from the port indicated by part number 16, and the oxygen gas and water are discharged from the port indicated by part number 17. The operating temperature of the water electrolysis cell is 60 to 90 ° C, usually 80 ° C.

The membrane electrode assembly comprising the catalyst electrodes 20 and 21 and the solid polymer electrolyte membrane 24 has substantially the same structure in electrochemical devices other than the water electrolysis device. Manufactured by various procedures. Figure 2
2A and 2B are schematic diagrams for explaining the outline of the manufacturing procedure of the membrane electrode assembly, in which FIG. 2A shows a state before joining and FIG. 2B shows a state after joining.

As shown in FIG. 2 (a), after the electrolyte membrane 1 is sandwiched by the PTFE sheet 5 having the catalyst electrode layer (anode) 3 and the catalyst electrode layer (cathode) 4, it is assembled in a joining jig. By heating and pressurizing, the catalyst electrode layer and the electrolyte membrane are bonded. Here, the heating temperature and the pressure are, for example, 180
° C and 20 MPa. After joining as described above, it is removed from the joining jig and the PTFE sheet 5 is peeled off.
A membrane electrode assembly having catalyst electrode layers formed on both surfaces of the electrolyte membrane shown in (b) is obtained.

The perfluorocarbon sulfonic acid membrane as a solid polymer electrolyte membrane used in this membrane electrode assembly has good electrochemical performance, but has a problem that it is easily damaged due to its small thickness.

For example, when a plurality of membrane electrode assemblies shown in FIG. 2 (b) are used to form a stack together with a current collector, the assembly is usually assembled by inserting a sealing material surrounding the catalyst electrode layer in a frame shape. To be As described above, when the mechanical strength of the electrolyte membrane is low, the electrolyte membrane may be damaged especially in the vicinity of the sealing material due to the pressure difference between the oxygen gas and the hydrogen gas and the mechanical stress.

As a method of reinforcing this solid polymer electrolyte membrane, conventionally, a method of inserting a woven fabric made of a fluoropolymer such as PTFE into the membrane, a method of filling the PTFE fibrillated fiber, and a frame shape around the electrode are used. There is known a method of heat-sealing the resin film (see JP-A-5-234606), a method of attaching a frame-shaped resin sheet with an adhesive to the peripheral portion of the electrode (see JP-A-10-154521). ing.

[0012]

However, the conventional methods for reinforcing a solid polymer electrolyte membrane described above have the following problems.

First, in the case of a method of inserting a woven cloth such as PTFE into the electrolyte membrane, slight unevenness due to the woven cloth is generated on the surface of the electrolyte membrane, so that the catalyst electrode layers cannot be evenly bonded and the electrical contact resistance is reduced. There is a problem that it becomes higher and the electrochemical characteristics deteriorate.

Further, in the case of the method of filling the PTFE fibrillated fiber in the electrolyte membrane, the ionic conductivity is lowered, so that the cell voltage is increased and similarly the electrochemical characteristics are lowered.

Further, when a frame-shaped resin film is heat-sealed around the electrodes, particularly when applied to a water electrolysis device,
Since the electrolyte membrane is exposed to a hot water environment of 60 to 90 ° C., the catalyst electrode portion is wrinkled due to the swelling (about 10%) of the electrolyte membrane due to the difference in elongation between the electrolyte membrane and the frame-shaped resin membrane. Occurs, and electrochemical characteristics such as electrolytic characteristics deteriorate.

Furthermore, in the case of a method of attaching a frame-shaped resin sheet with an adhesive to the periphery of the electrode, even if the elongation is adjusted to some extent in terms of material, the direction of extension of the solid polymer electrolyte membrane and the resin sheet Since a portion different from the extending direction occurs, it is impossible to solve the problem that wrinkles occur and the electrolytic characteristics are deteriorated.

Further, not only the water electrolysis device but also an electrochemical device such as a polymer electrolyte fuel cell which is not exposed to a hot water environment is under a high temperature humidification environment of about 60 to 90 ° C., and therefore there is a difference in degree. However, there is a problem similar to the above.

The present invention has been made to solve the above problems, and an object of the present invention is to reinforce a solid polymer electrolyte membrane to prevent the membrane from being damaged in the manufacturing process and to provide a hot water environment. Another object of the present invention is to provide a membrane / electrode assembly and a method for producing the same, which does not impair the electrochemical characteristics even under a high temperature and humid environment.

[0019]

In order to solve the above-mentioned problems, the present invention provides a membrane electrode assembly for an electrochemical device in which a catalyst electrode layer is joined to both central surfaces of a solid polymer electrolyte membrane. In the invention, a reinforcing layer formed by melting and solidifying a resin is provided in a frame shape on the outer peripheral surface portion of the solid polymer electrolyte membrane to which the catalyst electrode layer is not joined (the invention of claim 1).

According to the above, since the solid polymer electrolyte membrane has the reinforcing layer, it is possible to prevent damage during the manufacturing process of the membrane electrode assembly. In addition, since the reinforcing layer formed by melting and solidifying the resin is isotropic with respect to elongation, the problem of wrinkles occurring in the membrane electrode assembly is eliminated and stabilized in a hot water environment or a high temperature humidified environment. The electrochemical characteristics can be maintained.

The subject matter of the invention of claim 1 is as follows:
A water electrolysis device in which the solid polymer electrolyte membrane is exposed to a hot water environment is optimal. That is, in the membrane electrode assembly according to claim 1, the electrochemical device is a water electrolysis device (the invention of claim 2).

As a method for producing the membrane electrode assembly, the inventions of claims 3 to 6 below are preferable. That is, in the method for producing a membrane electrode assembly according to claim 1 or 2, the reinforcing layer is formed by applying a resin solution to the outer peripheral surface of the solid polymer electrolyte membrane in a frame shape and then drying the resin solution. (Invention of Claim 3).

Further, in the manufacturing method according to claim 3, the resin solution is an electrolyte solution for the solid polymer electrolyte membrane (invention of claim 4). According to the invention of claim 4, since the elongation rates of the electrolyte membrane and the frame-shaped resin membrane are equal to each other, it is most suitable from the viewpoint of followability to swelling.

Further, as a manufacturing method different from the inventions of claims 3 to 4, the invention of claim 5 is preferable from the viewpoint of improving dimensional accuracy. That is, in the method for producing a membrane electrode assembly according to claim 1 or 2, the reinforcing layer is formed by dispersing resin powder in a frame shape on the outer peripheral surface of the solid polymer electrolyte membrane, and adding the resin powder layer. It is formed by melting and solidifying by pressure heating.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG. 1A and 1B show the state before joining, FIG. 1B shows the state after joining the catalyst electrode layers, and FIG. 1C shows the state after forming the reinforcing layer. Members having the same functions as those shown are given the same reference numerals and detailed description thereof will be omitted.

1 is different from FIG. 2 in that, in FIG. 1, the resin is melted and solidified in a frame shape on the outer peripheral surface of the solid polymer electrolyte membrane 1 where the catalyst electrode layers 3 and 4 are not joined. The point is that the formed reinforcing layer 2 is provided.

[0027]

[Examples] Examples relating to the manufacturing method of the embodiment shown in FIG. 1 in which a resin solution is applied and examples in which resin powder is melted and solidified by heating under pressure are described below.

Example 1 A commercially available electrolyte solution (a solution of perfluorocarbon sulfonic acid) was added onto the electrolyte membrane around the outer periphery of the catalyst layer where the catalyst was not joined in the membrane electrode assembly used in the electrochemical device. Double concentrated solution (concentration 10
%, Water: ethanol = 1: 1), and the mixture was dried at room temperature. After drying, the solution was similarly applied to the opposite surface and dried at room temperature. The coating and drying were repeated three times to reinforce the outer peripheral surface portion to form a frame-shaped reinforcing layer. In the sample of the membrane electrode assembly according to the conventional method of FIG. 2 without reinforcement, damage was detected in the peripheral portion of the electrolyte membrane, but in the sample of the reinforced membrane electrode assembly, no damage was detected.

The reinforced membrane electrode assembly and the non-reinforced membrane electrode assembly according to the conventional method shown in FIG.
After being immersed in warm water of 0 ° C. for 15 minutes to swell the electrolyte membrane, the initial electrolytic characteristics were comparatively measured just in case. According to the result, the cell voltage is 1.537 V, the current efficiency is 99%, the energy efficiency is 95.
It was 2%, and it was confirmed that the provision of the reinforcing layer did not affect the initial characteristics.

(Example 2) 5 mg / cm ^{2 of} low-density polyethylene powder was placed on the electrolyte membrane in the outer peripheral portion of the catalyst layer where the catalyst was not joined in the membrane electrode assembly used in the electrochemical device.
Then, only the outer peripheral portion was pressurized and heated at 0.5 MPa and 100 ° C. to reinforce the outer peripheral surface portion. No damage was detected in the reinforced membrane electrode assembly sample.

Further, regarding the reinforced membrane electrode assembly and the membrane electrode assembly according to the conventional method of FIG. 2 without reinforcement, 8
After being immersed in warm water of 0 ° C. for 15 minutes to swell the electrolyte membrane, the initial electrolytic characteristics were comparatively measured just in case. According to the result, the cell voltage is 1.535 V, the current efficiency is 99%, the energy efficiency is 95.
It was 4%, and it was confirmed that the provision of the reinforcing layer did not affect the initial characteristics.

[0032]

EFFECTS OF THE INVENTION According to the present invention, as described above, in the membrane electrode assembly for an electrochemical device in which the catalyst electrode layers are joined to both central surfaces of the solid polymer electrolyte membrane, the catalyst electrode layers are The outer peripheral surface of the unbonded solid polymer electrolyte membrane is frame-shaped, and a reinforcing layer formed by melting and solidifying a resin is provided, and in the method for manufacturing the membrane electrode assembly, the reinforcing layer is used. Is to be formed by applying a resin solution to the outer peripheral surface of the solid polymer electrolyte membrane in a frame shape and then drying it, or the reinforcing layer is formed of resin powder as the solid polymer electrolyte membrane. Since it was sprayed in a frame shape on the outer peripheral surface of the, and was formed by melting and solidifying this resin powder layer by pressurizing and heating, the film was prevented from being damaged in the manufacturing process, and even in a hot water environment or a high temperature and humid environment, The one that impairs the electrochemical characteristics No membrane electrode assembly can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the outline of the manufacturing procedure of a membrane electrode assembly of the present invention.

FIG. 2 is a schematic diagram illustrating an outline of a conventional procedure for manufacturing a membrane electrode assembly.

FIG. 3 is a schematic configuration diagram of a water electrolysis cell.

[Explanation of symbols]

1: electrolyte membrane, 2: reinforcing layer, 3: catalyst electrode layer (anode),
4: Catalyst electrode layer (cathode), 5: PTFE sheet.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4K011 CA06 DA01                 4K021 AA01 BA02 DB43                 5H026 AA06 CX05

Claims (5)

[Claims] 1. A membrane electrode assembly for an electrochemical device, comprising a catalyst electrode layer bonded to both main surfaces of a central portion of a solid polymer electrolyte membrane, wherein the solid polymer electrolyte membrane is not bonded to the catalyst electrode layer. A membrane-electrode assembly, comprising a frame-like reinforcing layer provided on the outer peripheral surface of the resin, the reinforcing layer being formed by melting and solidifying a resin. 2. The membrane electrode assembly according to claim 1, wherein the electrochemical device is a water electrolysis device. 3. The method of manufacturing a membrane electrode assembly according to claim 1, wherein the reinforcing layer is formed by applying a resin solution to the outer peripheral surface of the solid polymer electrolyte membrane in a frame shape.
A method of manufacturing a membrane electrode assembly, which comprises drying and forming. 4. The method for manufacturing a membrane electrode assembly according to claim 3, wherein the resin solution is an electrolyte solution for the solid polymer electrolyte membrane. 5. The method for manufacturing a membrane electrode assembly according to claim 1, wherein the reinforcing layer sprays resin powder on the outer peripheral surface of the solid polymer electrolyte membrane in a frame shape to form a resin powder. A method for producing a membrane electrode assembly, which comprises melting and solidifying a layer by heating under pressure.