JP3446254B2 - Fuel cell and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to fuel cells, and more particularly to
The present invention relates to a polymer electrolyte fuel cell using a polymer ion exchange membrane as an electrolyte.

[0002]

2. Description of the Related Art As an electrolyte, for example, a polymer ion exchange membrane such as a perfluorocarbon sulfonic acid polymer provided under the trade name of Nafion (registered trademark) by DuPont is used, and a fuel is provided on both sides of the electrolyte. A so-called polymer electrolyte fuel cell is known in which a cell reaction is obtained by arranging an electrode and an air electrode and supplying hydrogen and oxygen to the fuel electrode and the oxidation electrode, respectively.

This polymer electrolyte fuel cell can be reduced in size and weight, and since the electrolyte is solid, there is no danger of loss, and therefore, the electric fuel cell operated in place of or in combination with the gasoline engine is operated. It has been attracting attention as a motor power source suitable for in-vehicle use.

A constitutional example of a conventional polymer electrolyte fuel cell is
As shown in FIG. 1 of JP-A-3-295176, gas diffusion electrodes 2A and 2B serving as a fuel electrode and an oxidation electrode are arranged on both sides of the solid polymer electrolyte membrane 1 to form a gas serving as a fuel electrode. Hydrogen is supplied to the diffusion electrode 2A via the gas separator 5, and oxygen is supplied to the gas diffusion electrode 2B serving as an oxidizing electrode via the gas separator 6.

The separator is made of a conductive thin plate (for example, made of metal), and functions as a partition plate for preventing mixing of oxygen and hydrogen supplied to the adjacent air electrode and fuel electrode when fuel cells are stacked. do. In addition, the separator electrically connects the air electrode and the fuel electrode which are adjacent to each other, thereby electrically connecting the stacked fuel cells in series.

Each of the gas diffusion electrodes 2A and 2B is formed by joining the reaction films 3A and 3B on the solid polymer electrolyte membrane 1 side and the gas diffusion films 4A and 4B on the gas supply side.

The gas diffusion films 4A and 4B need to play the role of supplying the gases (hydrogen and oxygen) supplied through the gas separators 5 and 6 to the reaction films 3A and 3B while evenly diffusing them. It is required that the solid polymer electrolyte membrane 1 is not corroded by the sulfonic acid group (—SO ₃ H) contained in the solid polymer electrolyte membrane 1 and that it has electrical conductivity, and a carbon sheet is generally used to satisfy these requirements. ing.

The reaction films 3A and 3B are gas diffusion films 4A and 4A.
A gas (hydrogen, oxygen) supplied through B obtains a battery reaction at the interface with the solid polymer electrolyte membrane 1, and is, for example, polytetrafluoroethylene (PT).
A sintered mixture of a water repellent material such as FE) and catalyst particles such as platinum (Pt) or platinum-supporting carbon is used.

[0009]

However, a carbon sheet used as a gas diffusion film in a conventional fuel cell electrode generally has a high resistance value.

The gas permeability of the carbon sheet is only about 850 ml · mm / hr · cm ² · mmAq, which is the catalog value of the gas supply capacity of a commercially available product of carbon paper.

Therefore, in order to improve the power generation efficiency, it is desired to use a material having a smaller resistance and a higher gas permeability than the carbon sheet for the gas diffusion film of the electrode.

[0012]

In order to solve the above-mentioned problems, the present inventor replaced the conventional carbon sheet with a porous metal material such as nickel (Ni) foam and the like as a gas diffusion film or gas supply layer of the electrode. Recalled to be used as. As a result of the test, it was found that the electrode using the porous metal material as the gas diffusion film has a much smaller specific resistance value than the electrode using the conventional carbon sheet as the gas diffusion film. It was also confirmed that the gas supply ability was better than that of the carbon sheet.

However, in view of the fact that metals such as nickel have poor corrosion resistance to sulfonic acid groups in the electrolyte, are easily corroded when they come into contact with the electrolyte, and are eluted into the electrolyte to directly participate in the battery reaction. To prevent
Recalling that a layer made of a corrosion resistant material, especially carbon, is interposed between the reaction film and the catalyst layer, Japanese Patent Application No.
He has filed an application for 27362.

That is, according to the invention of the prior application, the fuel electrode and the oxidizing electrode are each provided with a gas supply layer made of a porous metal material on the gas supply side, and a catalyst layer for reacting the supplied gas with a cell. A fuel cell is provided in contact with a solid electrolyte, and a contact-resistant layer made of a material having corrosion resistance to a strongly acidic component in the electrolyte is interposed between the gas supply layer and the catalyst layer.

According to this prior invention, the disadvantages of the conventional fuel cell can be eliminated, but improvements have been made for the purpose of further reducing the resistance value and the present invention has been completed.

That is, the present invention is a fuel cell comprising an electrolyte and a fuel electrode and an oxidizing electrode on both sides of the electrolyte, wherein at least one of the fuel electrode and the oxidizing electrode is a porous metal capable of supplying gas. A gas supply layer made of a material, a catalyst layer provided in contact with the electrolyte for cell reaction of gas supplied from the gas supply layer, and carbon provided between the gas supply layer and the catalyst layer With a corrosion resistant layer,
The carbon corrosion-resistant layer is joined to the gas supply layer in an anchored and entangled state.

Further, a conductive separator can be diffusion-bonded to the non-catalyst layer side of the gas supply layer.

The fuel cell having such a structure comprises an electrolyte,
A catalyst layer provided in contact with both sides of the electrolyte and a contact-resistant layer made of a contact-resistant material for an electrolyte component provided outside the catalyst layer are integrally bonded to create an electrode structure, On the other hand, a gas supply layer made of a porous metal material capable of gas supply and a conductive separator are joined to create a polar chamber structure, and the touch-resistant layer in the electrode structure and the gas in the polar chamber structure. It is manufactured by joining the supply layer to each other so that the anticorrosion layer and the gas supply layer are anchored and entangled.

[0019]

The gas supply layer made of a porous metal material has a small resistance value and a good gas supply ability, and serves to enhance power generation efficiency.

The anticorrosion layer interposed between the gas supply layer and the catalyst layer has a corrosion resistance against a strongly acidic component in the electrolyte, particularly a sulfonic acid group when a solid polymer electrolyte such as Nafion is used. It is formed of the material shown, for example, a carbon sheet, and prevents the porous metal material of the gas supply layer from being corroded by the strongly acidic component.

Since the gas supply layer and the touch-resistant layer are pressed against each other in an anchored and entangled state due to the porosity of the former and the elasticity of the latter, the contact area between them is increased. Further, the pressure contact reduces the thickness of the gas supply layer and the touch-resistant layer, so that the entire electrode is formed thin. These greatly reduce the resistance value of the electrodes.

[0022]

EXAMPLE FIG. 1 schematically shows a constitutional example of a fuel cell according to the present invention, in which a fuel electrode 11 and an oxidizing electrode 15 are laminated on both sides of a solid polymer electrolyte 10. Although Nafion is generally used as the ion exchange resin forming the solid polymer electrolyte 10, for example, PSSA-PVA (polystyrene sulfonic acid-polyvinyl alcohol copolymer) or PSSA-EVOH (polystyrene sulfonic acid-).
It is also possible to use (ethylene vinyl alcohol copolymer) or the like.

Hydrogen gas as a fuel is supplied to the fuel electrode 11, and air containing oxygen as an oxidant is supplied to the oxidizing electrode 15. As is well known, in the fuel electrode 11, H
The reaction of ₂ → 2H ⁺ + 2e ⁻ is 1 at the oxidation electrode 15.
A reaction of / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O is obtained, and hydrogen ions move from the fuel electrode 11 through the solid polymer electrolyte 10 to the oxidizing electrode 15, while the electrons move toward the fuel electrode side separator 19. Flow toward the oxidation electrode side separator 20 to obtain electric power.

The fuel electrode 11 has a gas supply layer 12 made of a porous metal material on the side to which hydrogen gas is supplied, a contact-resistant carbon layer 13 on the inside, and a catalyst layer 14 on the side in contact with the solid polymer electrolyte 10. To have.

The gas supply layer 12 is made of a porous metal material, for example, a commercially available nickel foam sheet (thickness: 80).
(0 to 1000 μm) is water-repellent-treated by immersing it in a 7.5 wt% PTFE aqueous solution for about 2 minutes and then drying it in an inert gas atmosphere.

As the carbon layer 13, a commercially available carbon sheet can be used. Generally, the carbon particles in the carbon sheet are surface-coated with a water repellent material such as PTFE.

The catalyst layer 14 is formed by mixing carbon with a catalyst with an ion exchange resin, which is a component of the solid polymer electrolyte 10, and integrally molding this mixture into a sheet by a method such as pressing or screen printing. .

Platinum is suitable as the catalyst, but even when a raw material hydrocarbon gas such as methanol is supplied to the fuel electrode 11 in a hydrogen-rich state by a reformer,
Some carbon monoxide gas cannot be avoided.
Therefore, in order to prevent the poisoning of platinum by carbon monoxide gas contained in the supplied hydrogen gas, it is preferable to use an alloy of platinum and ruthenium (Ru) or platinum and tin (Sn) as a catalyst. preferable.

Generally, the gas supply layer 12 is 500 to 800 μm.
It is formed to a thickness of m. Carbon layer 13 and catalyst layer 14
The thickness of the former is generally about 100 to 150 μm, and the latter is about 40 to 50 μm. However, use the thinnest possible one without impairing the action of each, and increasing the contact area between the layers makes it possible to increase the entire electrode. It is advantageous in reducing the resistance value as.

From this viewpoint, the gas supply layer 12 and the carbon layer 13 utilize the former porosity and the latter elasticity,
It is pressed against the ship as it is entangled as an anchor. As a result, the thickness of the fuel electrode 11 is reduced.

The structure and manufacturing method of the oxidizing electrode 15 are also the fuel electrode 1.
1 has a gas supply layer 16 made of a porous metal material on the side to which the air gas is supplied, a carbon layer 17 on the inside, and a catalyst layer 18 on the side in contact with the solid polymer electrolyte 10. Therefore, the gas supply layer 16 and the carbon layer 17 are pressed and contacted in an anchored and entangled state.

However, when it is applied together with the reformer,
In the catalyst layer 18 of the oxidizing electrode 15 to which air is supplied,
Since the problem of poisoning by carbon monoxide, which has been considered in the catalyst layer 14 of the fuel electrode 11, does not occur, platinum is used alone as the catalyst.

On the outside of the gas supply layer 12 of the fuel electrode 11 and the gas supply layer 16 of the oxidizing electrode 15, a gas separator for evenly diffusing the supplied gas can be provided. In this case, a gas supply layer is bonded to one side of the gas separator to form a polar chamber structure, and two polar chamber structures are formed in the electrode structure in which the anti-contact carbon layer and the catalyst layer are formed on both sides of the solid electrolyte. 10-20kg / c from both sides
The fuel cell of the present invention can be obtained by collectively pressurizing with a cold press of about m ² .

The manufacturing process of this fuel cell will be described below. 1. Assembling process of electrode structure: A carbon sheet, which has been subjected to water repellent treatment by PTFE or the like, has carbon powder carrying Pt or Pt / Ru catalyst on one surface thereof, and Nafion used as a solid electrolyte.
And the like, and a paste component prepared by mixing a thickener such as water, alcohol, or glycerin with screen printing, and then applying the thickener in the paste component in N ₂ gas at 80 ° C. or at a low level. Dry off in vacuum. In this way, the reaction layer (catalyst layer) is formed on one side of the carbon sheet.

This carbon sheet + two reaction layers are prepared, with the reaction layers inside, the solid electrolyte (ion exchange membrane)
Placed on both sides of the hot press (130 ° C., applied load 150 kg / cm ² or less, 20 sec to 3 mi)
Joined according to n).

Thus, the electrode structure 34 in which the fuel electrode 32 and the oxidizing electrode 33 are formed on both sides of the solid electrolyte 31.
Is obtained (FIG. 2). 32a and 33a are reaction layers, 3
2b and 33b are anticorrosion carbon layers. 2. Assembling process of polar chamber structure A porous metal material such as foamed Ni (for example, "Celmet (trademark)" manufactured by Sumitomo Electric Industries) or mesh SUS (for example, "Naslon (trademark)" manufactured by Nippon Seisen) is used. After immersing this in PTFE diffusion,
Water-repellent treatment is performed by drying and melting in N ₂ gas at 350 ° C.

A water-repellent porous metal material is
l, Cu or dense (= gas permeability is almost 0)
A separator material made of carbon or the like is bonded to one surface, and a sealing agent made of a thermosetting resin adhesive or the like is injected into the pressure contact portion in order to maintain gas tightness.

Thus, the polar chamber structure 37 in which the gas supply layer 35 made of a porous metal material is integrated with the separator 36 is obtained (FIG. 3). 38 is the injected sealing agent. 3. Assembling process of single cell On both sides of the electrode structure 34 of FIG. 2, the polar chamber structure 3 of FIG.
7, 37 'are arranged with the gas supply layers 35, 35' inside, and 10 kg / c from the outside of the separators 36, 36 '.
A batch pressure treatment is applied with an applied load of about m ^2, and while maintaining this state, the sealing agent 38, 3 in the atmosphere of about 80 ° C.
Dry cure 8 '. Further, the sealing agent 39, 39 'is injected into the exposed inner surface of the separator 36, 36', and similarly dried and cured in the atmosphere at about 80 ° C.
A single cell 30 having a structure as shown in FIG. 4. Cell stacking step The separator (3 of the single cell 30 obtained as described above
6, 36 ') is bonded to the same gas supply layer on the outer surface, and the same electrode structure is sandwiched between the previously prepared same polar chamber structure and pressure is applied from both sides in the same manner. A laminated body of 2 cells or 3 cells can be obtained.

By repeating this stacking step, a stack of cells of an arbitrary number can be obtained. FIG. 6 shows a laminated body 40 for four cells.

[0040]

EFFECTS OF THE INVENTION According to the present invention, a fuel cell having an improved gas supply capability and a significantly reduced resistance, and having excellent power generation efficiency is provided.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration example of a fuel cell according to the present invention.

FIG. 2 is a diagram schematically showing an electrode structure constituting a fuel cell of the present invention.

FIG. 3 is a diagram schematically showing a polar chamber structure that constitutes the fuel cell of the present invention.

4 is a diagram schematically showing a configuration of a single cell in which two electrode chamber structures shown in FIG. 3 are collectively pressure-treated with the electrode structure shown in FIG. 2 interposed therebetween.

FIG. 5 is an exploded perspective view showing a configuration of a single cell similar to that in FIG.

6 is a diagram schematically showing a laminated body formed by laminating the unit cells of FIG.

[Explanation of symbols]

10 Solid polymer electrolyte 11 Fuel pole 12 Gas supply layer 13 Carbon layer (touch resistant layer) 14 Catalyst layer 15 Oxidation pole 16 Gas supply layer 17 Carbon layer (touch resistant layer) 18 Catalyst layer 19, 20 separator 30 single cells 31 Solid electrolyte 32 fuel pole 33 Oxidation pole 34 Electrode structure 35 gas supply layer 36 separator 37 Polar Chamber Structure 40 cell stack

Claims (5)

(57) [Claims] 1. A fuel cell comprising an electrolyte and a fuel electrode and an oxidizing electrode arranged on both sides of the electrolyte, wherein at least one of the fuel electrode and the oxidizing electrode is a gas made of a porous metal material capable of supplying gas. A supply layer, a catalyst layer provided in contact with the electrolyte for cell reaction of the gas supplied from the gas supply layer, and a carbo provided between the gas supply layer and the catalyst layer.
And a carbon corrosion resistant layer, the carbon corrosion resistant layer being anchored and entangled with the gas supply layer.
A fuel cell characterized by being joined together in a fixed state . 2. A fuel cell comprising an electrolyte and a fuel electrode and an oxidizing electrode disposed on both sides of the electrolyte, wherein at least one of the fuel electrode and the oxidizing electrode is a gas made of a porous metal material capable of supplying gas. A supply layer, a catalyst layer provided in contact with the electrolyte for cell reaction of gas supplied from the gas supply layer, and a conductive separator diffusion-bonded to the non-catalyst layer side of the gas supply layer, Carbo provided between the gas supply layer and the catalyst layer
And a carbon corrosion resistant layer, the carbon corrosion resistant layer being anchored and entangled with the gas supply layer.
A fuel cell characterized by being joined together in a fixed state . 3. The fuel cell according to claim 1, wherein the porous metal material of the gas supply layer is made of nickel foam. 4. The fuel cell according to claim 1, wherein the corrosion resistant layer is made of a carbon sheet . 5. The fuel cell according to claim 1, wherein the catalyst layer contains the same component as the strongly acidic component contained in the electrolyte.