JP3535455B2 - Electrolyte membrane-electrode assembly for polymer electrolyte fuel cells - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to the electrolyte membrane of a polymer electrolyte fuel cell - electrode assembly, in particular, comprises an electrolyte membrane and an air electrode and the fuel electrode sandwich the electrolyte membrane, the electrolyte <br / > The membrane has a first polymer ion exchange component, and the air electrode and the fuel electrode respectively have a second polymer ion exchange component .
And a catalyst particle, and the first polymer ion exchange component
And an electrolyte membrane-electrode assembly for a polymer electrolyte fuel cell, which enables recovery of the catalyst particles .

[0002]

2. Description of the Related Art Conventionally, a fluororesin ion exchanger has been used as a polymer ion exchange component in this type of assembly.

[0003]

Since the fluororesin ion exchanger is generally insoluble in a solvent, it is practically impossible to recover and reuse it, which is uneconomical.

Further, in the case of recovering the catalyst particles contained in the air electrode and the fuel electrode, for example, carbon black particles carrying a plurality of Pt (platinum) particles, when recovering the air electrode and the fuel electrode, Since the electrolyte membrane is generally integrated by hot pressing, the assembly is burned, but there is also a problem that the recovery by burning is poor in workability.

[0005]

The present invention makes it possible to recover and reuse an electrolyte membrane by using a specific polymer ion exchange component, and to use catalyst particles contained in an air electrode and a fuel. It is an object of the present invention to provide the above-mentioned assembly which can be easily recovered.

According to the present invention to achieve the above object,
An electrolyte membrane, and a its sandwich the electrolyte membrane air electrode and the fuel electrode, the electrolyte membrane of the first polymeric ion exchange component
And the air electrode and the fuel electrode respectively have a second polymer ion exchange component and catalyst particles,
Enables recovery of child ion exchange components and the catalyst particles
And solid polymer electrolyte fuel cell electrolyte membrane - electrode assembly der
The second polymer ion exchange component is the catalyst particles.
The electrolyte membrane-electrode assembly was immersed in a solvent to collect the particles.
High content of fluorine-free aromatic hydrocarbons that dissolves when pickled
The first polymer ion exchange, which is composed of a child ion exchange component.
The replacement component was removed from the solvent to recover it.
A fluorine-free solution that dissolves undissolved substances when immersed in a solvent.
Provided is an electrolyte membrane-electrode assembly for a polymer electrolyte fuel cell, which comprises an aromatic hydrocarbon-based polymer ion exchange component .

When the assembly is dipped in a solvent, the aromatic hydrocarbon-based polymer ion exchange components on the air electrode and the fuel electrode on the outer side are dissolved, whereby the catalyst particles are recovered. After that, if the undissolved substance is taken out from the solvent, it is a portion corresponding to the electrolyte membrane, so that the electrolyte membrane is recovered. An electrolyte membrane can be obtained by using this as a membrane molding material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 1, a cell 1 which constitutes a polymer electrolyte fuel cell comprises an electrolyte membrane 2, an air electrode 3 and a fuel electrode 4 which are in close contact with both sides of the electrolyte membrane 2, and electrodes 3 and 4 thereof. The diffusion layers 5 and 6 are in close contact with each other, and the separators 7 and 8 are in close contact with the diffusion layers 5 and 6. In the embodiment, the electrolyte membrane-electrode assembly 9 includes
Not only the electrolyte membrane 2, the air electrode 3 and the fuel electrode 4, but also both diffusion layers 5 and 6 are included.

The electrolyte membrane 2 is composed of an aromatic hydrocarbon polymer ion exchange component. Each of the air electrode 3 and the fuel electrode 4 is composed of a plurality of catalyst particles in which a plurality of Pt particles are carried on the surface of carbon black particles, and an aromatic hydrocarbon-based polymer ion exchange component which is the same as or different from the above.

Each of the diffusion layers 5 and 6 is made of porous carbon paper, carbon plate or the like, and each of the separators 7 and 8 is made of graphitized carbon so as to have the same form, and is a separator on the side of the air electrode 3. Grooves 1 in 7
0 is supplied with air, and hydrogen is supplied with a plurality of grooves 11 existing in the separator 8 on the fuel electrode 4 side and intersecting the grooves 10.

The aromatic hydrocarbon-based polymer ion-exchange component has the characteristics that it is fluorine-free and soluble in solvents. This type of polymer ion exchange component is shown in Table 1.
Various ion exchangers listed in 1 above are used.

[0012]

[Table 1]

Various polar solvents listed in Table 2 are used as the solvent.

[0014]

[Table 2]

Aromatic hydrocarbon type polymer ion exchange component constituting the electrolyte membrane 2, that is, the first polymer ion exchange component.
Min, aromatic hydrocarbon-based polymer ion-exchange components of the air electrode 3 and the fuel electrode 4, i.e. the second polymeric ion exchange Ingredient
The solubility of the second polymer ion-exchange component in the solvent is preferably higher than that of the first polymer ion-exchange component. The reason is that the air electrode 3 and the fuel electrode 4 are
Since the second polymer ion-exchange component is present in the vicinity of the position where the catalytic reaction occurs, the second polymer ion-exchange component is severely thermally deteriorated. Therefore, the second polymer ion-exchange component is collected and discarded before the electrolyte membrane 2. Thereby, the purity of the first polymer ion-exchange component of the electrolyte membrane 2 can be increased.

This difference in solubility is achieved by providing a difference in the average molecular weight of both the high molecular weight ion exchange components when the first and second high molecular weight ion exchange components are the same or of the same type. That is, the one having a lower average molecular weight is more easily dissolved than the one having a higher average molecular weight. For example, in consideration of durability, assuming that the first and second polymer ion-exchange components have an average molecular weight of 5000 or more, the average molecular weight of the first polymer ion-exchange component is A, and When the average molecular weight of the high molecular weight ion exchange component of 2 is B, the ratio B / A of both average molecular weights is preferably 0.1 ≦ B / A <1.0. However, when the ratio B / A becomes B / A <0.1, the durability of the air electrode 3 and the fuel electrode 4 deteriorates, and their thickness retaining ability greatly decreases, so that there is a secular change in power generation performance and the like. It will be noticeable. On the other hand, when B / A ≧ 1.0, the recovery rate of the first polymer ion-exchange component forming the electrolyte membrane 2 decreases.

As the first and second polymer ion exchange components, it is also possible to use two types of compounds having different solubilities in solvents and having different chemical compositions.

A specific example will be described below. I. Production of Electrolyte Membrane-Electrode Assembly Carbon Black Particles (Brand Name: Ketjen Black E
Pt particles were supported on C) to prepare catalyst particles. The content of Pt particles in the catalyst particles is 50 wt%. [Example-I] As an aromatic hydrocarbon-based polymer ion-exchange component, it is Example 1 (PEEK) in Table 1 and has an average molecular weight of 5
50,000 first polymer ion exchange components and a second polymer ion exchange component having an average molecular weight of 45,000 were prepared. In this case, the ratio B / A of the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component is B / A = 0.9.

An electrolyte membrane 2 having a thickness of 50 μm was formed using the first polymer ion exchange component. The second polymer ion-exchange component was dissolved in NMP shown in Table 2 under reflux. The content of the second polymer ion-exchange component in this solution was 6 wt.
%.

In the second polymer ion-exchange component-containing solution,
Second polymer ion exchange component: catalyst particles = 3 by weight ratio.
The catalyst particles are mixed so as to be 5, and then the catalyst particles are dispersed by using a ball mill, and the air electrode 3 and the fuel electrode 4 are mixed.
A slurry for use was prepared. This slurry has a Pt content of 0.5 mg
/ Cm ^{2 on} both sides of the electrolyte membrane 2 respectively, and after drying, apply a water repellent porous carbon plate for the diffusion layers 5 and 6 to each of the coated layers.
Hot pressing was performed under the conditions of 0 ° C., 1.5 MPa, and 1 minute to obtain an electrolyte membrane-electrode assembly 9. This is Example (1). [Example-II] The same as Example-I, except that the aromatic hydrocarbon-based polymer ion-exchange component is Example 1 (PEEK) in Table 1,
A first polymer ion exchange component having an average molecular weight of 50,000 and a second polymer ion exchange component having an average molecular weight of 45,000 were prepared. In this case, the ratio B / A of the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component is B / A = 0.9.

Thereafter, an electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example-I, except that the hot press temperature was set to 200 ° C. This is the embodiment (2)
And [Example-III] As an aromatic hydrocarbon-based polymer ion-exchange component, it is Example 2 (PES) in Table 1 and has an average molecular weight of 5
50,000 first polymer ion exchange components and a second polymer ion exchange component having an average molecular weight of 45,000 were prepared. In this case, the ratio B / A of the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component is B / A = 0.9.

Thereafter, an electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example-I except that the hot press temperature was set to 190 ° C. This is the embodiment (3)
And [Example-IV] As an aromatic hydrocarbon-based polymer ion-exchange component, it is Example 3 (PSF) in Table 1 and has an average molecular weight of 5
50,000 first polymer ion exchange components and a second polymer ion exchange component having an average molecular weight of 25,000 were prepared. In this case, the ratio B / A of the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component is B / A = 0.5.

Thereafter, an electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example-I, except that the hot press temperature was set at 170 ° C. This is the embodiment (4)
And [Example-V] The first aromatic polymer-based polymer ion-exchange component is the same as in Example-IV, which is Example 3 (PSF) in Table 1 and has an average molecular weight of 50,000. Then, a second polymer ion exchange component having an average molecular weight of 12,500 was prepared. In this case, the ratio B / A of the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component is B / A = 0.25.

Thereafter, an electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example-I, except that the hot pressing temperature was set to 170 ° C. as in Example-IV. This is Example (5). [Example-VI] As an aromatic hydrocarbon-based polymer ion-exchange component, Example- I
Similarly, in Example 1 (PEEK) of Table 1, a first polymer ion exchange component having an average molecular weight of 50,000 and a second polymer ion exchange component having an average molecular weight of 5,000 were prepared. . In this case, the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component
The ratio B / A with B / A is 0.1. Thereafter, as in Example IV, the electrolyte membrane was prepared in the same manner as in Example I except that the hot press temperature was set at 170 ° C.
The electrode assembly 9 was obtained. This is Example (6). [Example-VII] As an aromatic hydrocarbon-based polymer ion-exchange component, Example-I
Similarly, in Example 1 (PEEK) of Table 1, a first polymer ion exchange component having an average molecular weight of 50,000 and a second polymer ion exchange component having an average molecular weight of 2,500 were prepared. . In this case, the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component
The ratio B / A with B / A = 0.05.

Thereafter, as in Example-IV, an electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example-I, except that the hot press temperature was set at 170 ° C. This is designated as Comparative Example (1). [Example-VIII] As the aromatic hydrocarbon-based polymer ion exchange component, the same as Example-I, which is Example 1 (PEEK) in Table 1 and has an average molecular weight of 50,000. Then, a second polymer ion exchange component having an average molecular weight of 75,000 was prepared. In this case, the ratio B / A of the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component is B / A = 1.5.

Thereafter, an electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example-I, except that the hot pressing temperature was set to 170 ° C. as in Example-IV. This will be referred to as Comparative Example (2). II. DMAc (boiling point: 165.5 ° C.) in Table 2 is shown in Example (1) for recovering the first polymer ion-exchange component constituting the electrolyte membrane
Second, the DMAc is heated to 165 ° C., and the air electrode 3 and the fuel electrode 4 are thereby formed.
The high molecular weight ion exchange component was dissolved. The electrolyte membrane 2 and the diffusion layers 5 and 6 were taken out from the DMAc, and the DMAc was subjected to a pressure filtration treatment to separate the mixture of the catalyst particles and the second polymer ion exchange component from the DMAc. The mixture was burned to recover catalyst particles.

On the other hand, the electrolyte membrane 2 was dipped in a new DMAc, and then the DMAc was heated to 165 ° C., whereby the electrolyte membrane 2 and thus the first polymer ion exchange component was completely dissolved. This solution was continuously kept at a temperature rising state and concentrated until the balance became 50 vol% or less.
Acetone was added to the concentrated solution to precipitate the first polymer ion-exchange component, and then filtration was performed to recover the first polymer ion-exchange component.

The same operation as described above was carried out for Examples (2) to (6) and Comparative Examples (1) and (2) to recover the catalyst particles and the first polymer ion-exchange component therein.

Then, with the initial weight of the first polymer ion-exchange component as D and the weight of the first polymer ion-exchange component after recovery as E, a recovery rate F = (E / D) × 100 (%) was calculated.

A compression durability test was conducted on Examples (1) to (6) and Comparative Examples (1) and (2) under the conditions of 150 ° C., humidity 80%, surface pressure 0.8 MPa, and 200 hours, and electrolytes The thickness holding ratio H of the membrane 2 and the thickness holding ratio J of the air electrode 3 (the fuel electrode 4 is also acceptable) are obtained, and then the ratio K of both thickness holding ratios H and J = (J / H) × 100 (% ) Was calculated.

Table 3 shows the ratio B / A of the average molecular weights A and B of the first and second polymer ion-exchange components, B / A, and the values of Examples (1) to (6) and Comparative Examples (1) and (2). The recovery rate F of the polymer ion exchange component of No. 1 and the ratio K of both thickness retention rates H and J are shown.

[0032]

[Table 3]

FIG. 2 is a graph showing the relationship between the ratio B / A of both average molecular weights, the recovery ratio F of the first polymer ion exchange component and the ratio K of both thickness retention ratios, based on Table 3. It was done.

As is clear from Table 3 and FIG. 2, in Examples (1) to (6), the recovery rate F of the first polymer ion exchange component and the ratio K of both thickness retention rates are high. This is because both average molecular weights A and B are A and B ≧ 5000 and the ratio B / A is 0.1 ≦ B / A <1.0.

In Comparative Example (1), since the average molecular weight B of the second polymer ion exchange component is B ≦ 5000, the recovery rate F of the first polymer ion exchange component is high, but the air electrode 3 Has a low compression durability and therefore the ratio K decreases.
On the other hand, in Comparative Example (2), since B / A ≧ 1.0, the first polymer ion-exchange component is more easily dissolved than the second polymer ion-exchange component. The recovery rate F of the polymer ion-exchange component is significantly reduced. III. Correlation between presence or absence of water repellent and power generation performance (1) Production of Example (7) Pt particles were carried on the first carbon black particles (trade name: Ketjen Black EC) to prepare catalyst particles for the fuel electrode 4. Prepared. The content of Pt particles in the catalyst particles is 50
wt%.

Further, Pt particles were supported on the second carbon black particles (trade name: Vulcan XC-72) to prepare catalyst particles for the air electrode 3. The content of Pt particles in this catalyst particle is 50 wt%.

As the aromatic hydrocarbon-based polymer ion-exchange component, the first polymer ion-exchange component of Example 1 (PEEK) in Table 1 having an average molecular weight of 50,000 and an average molecular weight of 45,000 were used. The second polymer ion exchange component of was prepared. In this case, the average molecular weight A of the first polymer ion exchange component and the average molecular weight B of the second polymer ion exchange component
The ratio B / A with is B / A = 0.9.

An electrolyte membrane 2 having a thickness of 50 μm was formed using the first polymer ion exchange component. The second polymer ion-exchange component was dissolved in NMP shown in Table 2 under reflux. The content of the second polymer ion-exchange component in this solution was 6 wt.
%.

In the second polymer ion-exchange component-containing solution,
Mix the catalyst particles so that the weight ratio of the second polymer ion exchange component: catalyst particles for fuel electrode 4 = 3: 5, and then use a ball mill to disperse the catalyst particles, and use for the fuel electrode 4 A slurry was prepared.

Further, the catalyst particles are mixed with the second polymer ion exchange component-containing solution so that the weight ratio of the second polymer ion exchange component: catalyst particles for air electrode 3 = 3: 5, Then, using a ball mill to disperse the catalyst particles,
A slurry for air electrode 3 was prepared. Both slurries were applied to both surfaces of the electrolyte membrane 2 so that the Pt amount was 0.5 mg / cm ^2, and after drying, the applied layers were respectively applied to the diffusion layers 5 and 5.
Apply carbon paper for 6 at 140 ℃, 1.5MPa,
Hot pressing was performed for 1 minute to obtain an electrolyte membrane-electrode assembly 9. This is Example (7).

(2) Production of Comparative Example (3) A new air electrode was prepared by adding PTFE (polytetrafluoroethylene) as a water repellent to the slurry for the air electrode 3 described in the production of Example (7). A slurry for 3 was prepared. In this case, the addition amount L of PTFE is, when M is the weight sum of the second polymer ion exchange component and the catalyst particles for the air electrode 3,
It was set to 10 wt%, that is, L = 0.1M.

An electrolyte membrane-electrode assembly 9 was obtained in the same manner as in Example (7), except that the slurry for air electrode 3 containing PTFE was used. This will be referred to as Comparative Example (3).

(3) Using Example (7), a polymer electrolyte fuel cell was assembled to generate electricity, and the relationship between the current density and the terminal voltage was measured. The same thing was done for Comparative Example (3).

Table 4 shows the measurement results. In the table, the battery [Ex (7)] means the battery using the example (7), and the battery [ratio (3)] means the battery using the comparative example (3).
This is the same thereafter. The amount of water adsorbed at 60 ° C. was 370 cc / g for Ketjen Black EC,
Vulcan XC-72 was 72 cc / g.

[0045]

[Table 4]

FIG. 3 is a graph showing the relationship between the current density and the terminal voltage based on Table 4. As is clear from Table 4 and FIG. 3, the battery using PTFE as a water repellent [ratio (3)] is slightly superior in power generation performance to the battery without PTFE [actual (7)], The difference is so small that the terminal voltage difference at a current density of 1.0 A / cm ² is 10 mV.

In Example (7) and Comparative Example (3), the recovery rates of the electrolyte membrane 2, and thus the first polymer ion-exchange component, are almost the same, but the recovery of catalyst particles from the air electrode 3 is Comparative Example (3) is extremely difficult because it contains PTFE.

[0048]

According to the invention as set forth in claim 1, the catalyst particles contained in the air electrode and the fuel electrode and the polymer ion-exchange component of the electrolyte membrane are recovered and regenerated by the above-mentioned structure. An electrolyte membrane-electrode assembly that can be utilized can be provided.

According to the second aspect of the invention, it is possible to provide an electrolyte membrane-electrode assembly which can further improve the recovery rate of the catalyst particles and the electrolyte membrane.

[Brief description of drawings]

FIG. 1 is a schematic side view of cells constituting a polymer electrolyte fuel cell.

FIG. 2 is a graph showing a relationship between a ratio B / A of both average molecular weights, a recovery ratio F of the first polymer ion exchange component and a ratio K of both thickness retention ratios.

FIG. 3 is a graph showing the relationship between the current density and the terminal voltage of polymer electrolyte fuel cells using Example (7) and Comparative Example (3).

[Explanation of symbols]

1 ... cell 2 ... electrolyte membrane 3 ... Air electrode 4 ......... Fuel electrode

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01M 8/10 H01M 8/10 // B01D 69/12 B01D 69/12 B29K 105: 26 B29K 105: 26 (72) Inventor Saito Nobuhiro, 1-4-1, Chuo, Wako, Saitama Prefecture, Honda R & D Co., Ltd. (72) Inventor, Masaaki Nanami, 1-4-1, Chuo, Wako, Saitama, Ltd., R & D Co., Ltd. (56) References 11-288732 (JP, A) JP-A-10-45913 (JP, A) JP-A-8-171922 (JP, A) International Publication 99/029763 (WO, A1) (58) Fields investigated (Int.Cl) . ^7, DB name) H01M 8/02 H01M 8/10 H01M 8/04 B01J 38/00 301 B29B 17/02

Claims (2)

(57) [Claims] 1. An electrolyte membrane (2) and the electrolyte membrane (2)
And an air electrode (3) and the fuel electrode (4) sandwiching said <br/> electrolyte membrane (2) has a first polymeric ion exchange component,
The air electrode (3) and the fuel electrode (4) each have a second polymer ion exchange component and catalyst particles, and
It is possible to recover the polymer ion-exchange component of
An electrolyte membrane-electrode assembly for a solid polymer electrolyte fuel cell , wherein the second polymer ion exchange component is
Dissolve the electrolyte membrane-electrode assembly to recover the catalyst particles.
Fluorine-free aromatic hydrocarbons that dissolve when immersed in chemicals
The first polymer ion exchange component,
The on-exchange component is removed from the solvent to recover it.
The undissolved material is dissolved when immersed in a solvent.
An electrolyte membrane-electrode assembly for a polymer electrolyte fuel cell, which is characterized by comprising a basic aromatic hydrocarbon-based polymer ion-exchange component . Wherein said electrolyte membrane - solubility before <br/> Symbol solvent for immersing the electrode assembly, rather than high molecular ion exchange components it is of the first of said second high-molecular ion-exchange component The electrolyte membrane-electrode assembly of the polymer electrolyte fuel cell according to claim 1, which is large.