JP3888145B2 - Manufacturing method of fuel cell electrode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a solid polymer electrolyte fuel cell electrode in which a plurality of different types of catalyst layers are coated.
[0002]
[Prior art]
A solid polymer electrolyte fuel cell is a membrane-electrode assembly (MEA) comprising an electrolyte membrane made of an ion exchange membrane, an anode placed on one surface of the electrolyte membrane, and a cathode placed on the other surface of the electrolyte membrane. Electrode Assembly) and a plurality of separators that form a fluid flow path for supplying fuel gas (hydrogen) and oxidizing gas (oxygen, usually air) to the anode and cathode to form a cell laminate, Terminals (electrode plates), insulators, and end plates are arranged at both ends of the cell stacking direction, the cell stacking body is tightened in the cell stacking direction, and a fastening member (for example, a tension plate) extending in the cell stacking direction outside the cell stacking body It consists of a fixed stack. The anode and cathode have a catalyst layer. A diffusion layer is provided between the catalyst layer and the separator.
In a solid polymer electrolyte fuel cell, a reaction for converting hydrogen into hydrogen ions and electrons is performed on the anode side, the hydrogen ions move through the electrolyte membrane to the cathode side, and oxygen, hydrogen ions and electrons (adjacent to the cathode side). The electrons produced at the anode of the MEA come through the separator, or the electrons produced at the anode of the cell at one end of the cell stack come through an external circuit).
Anode side: H ₂ → 2H ⁺ + 2e ⁻
Cathode side: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O
As the electrolyte membrane, one having a thickness of about 10 to 100 μm is usually used.
Each of the catalyst layers has a thickness of about 1 to 10 μm and is applied and formed on both sides of the electrolyte membrane or on one side of the diffusion layer (made of carbon paper or carbon cloth).
Conventionally, electrode (anode, cathode) material is applied to the electrolyte membrane by a wet coating method in which printing, roller coating, spraying, or the like is applied directly, and a catalyst layer previously applied to a polytetrafluoroethylene sheet or the like is thermally transferred ( There is a method of removing the sheet by attaching it to the electrolyte membrane by hot pressing. As a special coating method, Japanese Patent Application Laid-Open No. 3-295168 discloses a method of attaching an electrode material of a fuel cell to the entire surface of an electrolyte membrane by static electricity.
[0003]
[Problems to be solved by the invention]
The method disclosed in Japanese Patent Laid-Open No. 3-295168 can eliminate problems such as attack of the electrolyte membrane of the solvent in conventional wet coating, cracking of the electrode due to swelling / shrinkage, etc., but the following problems are present. there were.
In other words, in an electrode having a predetermined shape pattern, it is possible to make an electrode in which the composition and concentration of electrode constituents are changed three-dimensionally (in at least one direction of the electrode thickness direction and the in-plane direction orthogonal to the electrode thickness direction) Can not.
An object of the present invention is to provide a fuel cell electrode in which the composition and concentration of electrode constituents in an electrode having an arbitrary predetermined shape are changed three-dimensionally (in at least one direction of the electrode thickness direction and the in-plane direction orthogonal thereto) It is in providing the manufacturing method of.
[0004]
[Means for Solving the Problems]
The present invention for achieving the above object is as follows.
(1) The photosensitive drum is charged and irradiated with light, and the irradiated portion is neutralized according to the intensity of the light, and the electrode material is attached to the charged portion with static electricity according to the intensity of the charge, and this is transferred to the film. Is a method of manufacturing a fuel cell electrode in which the electrode structure is changed three-dimensionally by varying the type of electrode material each time and controlling the coating layer thickness each time. portion and the coating density was varied in the electrode plane direction, the portion corresponding to the gas passage of the separator and a high concentration of catalyst components than the portion pressed by the separator ribs, corresponding to the lower stream portion of the gas flow channel of the separator in method for manufacturing a fuel cell electrode and a high concentration of catalyst components than the portion corresponding to the upper stream portion of the gas passage of the separator.
(2) The electrode material is composed of carbon particles, a catalyst noble metal supported on the carbon particles, and an electrolyte binder mixed with the carbon particles and the catalyst noble metal before the carbon particles and the catalyst noble metal are transferred to the film. The type of the electrode material is made different by changing at least one of the types of these components, the mixing ratio, the mixing method, and the particle size of each component. Electrode manufacturing method.
[0005]
In the fuel cell electrode manufacturing method of (1) and (2) above, the electrode material type is varied at each time, and the coating layer thickness is controlled at each time, so the electrode structure (composition / density, film thickness, etc.) It can be arbitrarily controlled three-dimensionally (in the electrode thickness direction and the in-plane direction perpendicular thereto).
When this method is applied to color copying (color copying), each type of electrode material corresponds to the color of the color copying, and each coating layer thickness corresponds to the darkness of the color applied at that time.
The type of the electrode material can be changed by changing at least one of the mixing ratio of the components, the mixing method , and the particle size of each component.
This method is a dry method because of the adhesion and transfer of electrode material to the surface of the photosensitive drum due to static electricity, and there is no attack of the electrolyte membrane of the solvent in conventional wet coating, and no cracking of the electrode due to swelling / shrinkage. .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Below, the manufacturing method of the fuel cell electrode of this invention is demonstrated with reference to FIGS.
A fuel cell having an electrode manufactured by the method for manufacturing a fuel cell electrode of the present invention is a solid polymer electrolyte fuel cell 10. The fuel cell 10 of the present invention is mounted on, for example, a fuel cell vehicle. However, it may be used other than an automobile.
[0007]
As shown in FIGS. 1 and 2, the solid polymer electrolyte fuel cell 10 includes an electrolyte membrane 11 made of an ion exchange membrane, an anode 14 disposed on one surface of the electrolyte membrane 11, and the other surface of the electrolyte membrane 11. A membrane-electrode assembly (MEA) composed of the cathode 17 and a fuel gas flow path 27 for supplying fuel gas (hydrogen) and oxidizing gas (oxygen, usually air) to the anode and cathode A plurality of separators 18 forming the oxidizing gas flow path 28 are stacked to form a stacked body of cells 19, and terminals 20 (electrode plates), insulators 21, and end plates 22 are arranged at both ends of the cell stacked body in the cell stacking direction. The cell stack is clamped in the cell stacking direction, and is fixed by a fastening member (tension plate 24) extending in the cell stacking direction outside the cell stack and the bolt 25. Stack 23. The anode 14 and the cathode 17 have catalyst layers 12 and 15. Diffusion layers 13 and 16 are provided between the catalyst layers 12 and 15 and the separator 18. The separator 18 is also formed with a refrigerant channel 26 through which a refrigerant (usually cooling water) for cooling the cells flows.
[0008]
The electrodes 14 and 18 formed of the catalyst layers 12 and 15 are formed on both sides of the electrolyte membrane 11 or formed on one side of the diffusion layers 13 and 16. The electrode forming material is obtained by supporting a catalytic noble metal (for example, Pt) on carbon powder. The electrode forming material of carbon powder and catalytic noble metal has conductivity but is non-magnetic. It differs from the toner of a copier in that it is non-magnetic. As the electrode forming material, a material mixed with a binder (electrolyte) powder may be used. The electrolyte membrane is nonmagnetic and nonconductive.
[0009]
As shown in FIGS. 3 and 4, the apparatus for carrying out the method for producing a fuel cell electrode of the present invention has a plurality of electrode material transfer portions installed in order in the film feeding direction.
Each electrode material transfer unit projects a photosensitive drum 30, a charging roller 31 for charging the surface of the photosensitive drum 30 with static electricity, and a predetermined pattern (on the predetermined pattern portion) on the surface of the photosensitive drum by projecting on the photosensitive drum 30. A light projecting device 32 for neutralizing a portion other than the electrode layer (where the electrode layer is formed) (the portion where the laser beam is projected is neutralized), and a photosensitive drum from a container 33 containing the electrode material powders 12P and 15P. A film made of the electrolyte 11 or the diffusion layers 13 and 16 is passed between the material supply roller 34 for supplying the electrode material powders 12P and 15P to the surface 30 and the photosensitive drum 30, which is the film 11 (or 13, 16). Hereinafter, the film 11 is referred to as another drum 30A or a roller 30B that is in pressure contact with the photosensitive drum 30, and the downstream side of the film 11 in the feed direction from the position of the photosensitive drum 30. A fixing roller 35 which is provided, consists of.
[0010]
The electrode material transfer unit including the photosensitive drum 30, the charging roller 31, the material supply roller 34, and another drum 30A or roller 30B that is in pressure contact with the photosensitive drum 30, and the fixing unit including the fixing roller 31 are not included. It is disposed in the active gas atmosphere 36. The inert gas is, for example, nitrogen. Arrangement in the inert gas atmosphere 36 is performed in a heated atmosphere (for example, when the fixing roller 35 is heated, it is heated to 50 to 150 ° C.), thereby eliminating the possibility of ignition of the carbon powder. This is to ensure complete safety.
[0011]
When the electrode material powders 12P and 15P are coated with a binder (the binder is made of an electrolyte) or are not mixed with binder particles, the apparatus for carrying out the method for producing a fuel cell electrode of the present invention uses a fixing roller 35. You may further have the binder supply apparatus 37 provided in the feed direction downstream of the film | membrane 11, and the drying part 40 provided in the downstream. The binder supply device 37 constitutes a binder application unit. When the electrode material powders 12P and 15P are covered with a binder or mixed with binder particles, the binder supply device 37 and the drying unit 40 may not be provided. The drying unit 40 has a temperature from room temperature to 150 ° C., and dries the binder.
[0012]
The fuel cell electrode manufacturing method of the present invention includes a step of holding the electrode material powders 12P and 15P on the photosensitive drum 30 by static electricity, and transferring the electrode material powder on the photosensitive drum 30 (photosensitive member). The target film (including a case where the film is the electrolyte film 11 hereinafter) including the case where the film is once transferred from the drum 30 to the intermediate medium film and then transferred from the intermediate medium film to the target film. May be transferred), and the transferred electrode material powders 12P and 15P having a predetermined pattern may be fixed to the film 11.
[0013]
In the step of holding the electrode material powder on the photosensitive drum 30 with static electricity, the charging roller 31 is brought into contact with the photosensitive drum 30 to charge the surface of the photosensitive drum 30 with static electricity, and the surface of the photosensitive drum 30 is A pattern is applied to the surface of the photosensitive drum 30 by supplying a laser beam to the photosensitive drum 30 and supplying the electrode material powders 12P and 15P to the photosensitive drum 30 (a pattern opposite to the pattern of the discharging portion). The electrode material powders 12P and 15P are held by the static electricity at the charged portions according to the strength of charging. In the case of a copying machine, the powder is held on the drum by magnetic force. In the present invention, the electrode material powders 12P and 15P are held on the photosensitive drum 30 by static electricity. Next, the electrostatically held electrode material powders 12P and 15P are transferred to the film 11.
By performing this transfer once at a plurality of electrode material transfer sites, an electrode that has been applied a plurality of times is formed when all of the electrode material transfer sites have passed.
[0014]
FIG. 5 shows an example of the predetermined pattern. In FIG. 5, the in-plane configuration of the catalyst layer includes a portion corresponding to the gas flow paths 27 and 28 (portion indicated by “black”) and a portion corresponding to the separator rib (portion indicated by “red”). It shows what has changed. The portions corresponding to the gas flow paths 27 and 28 are preferably pressed by the separator ribs, so that the gas flows sufficiently to cause a power generation reaction. Since the gas flow is insufficient at the pressed portion, it is desirable to reduce the amount of expensive catalyst components by reducing the amount of catalyst components. This condition can be easily satisfied by changing the pattern to which the laser light is applied and the intensity of the light (the rib-corresponding portion increases the laser light amount and the gas flow passage-corresponding portion makes the laser light amount zero or weaker). It is possible to achieve both optimum output and cost reduction.
[0015]
In the step of fixing the electrode material powders 12P, 15P having a predetermined pattern transferred to the film 11 to the film 11, fixing is performed with a predetermined pressure and a predetermined heat. The pressure is 4 MPa or more, about 10 times the pressure of a copying machine, and the temperature is preferably 50 to 150 ° C. This is because the film 11 is damaged by the temperature when the temperature is 150 ° C. or higher, and the heating effect is small when the temperature is 50 ° C. or lower. About 80-120 degreeC is preferable.
[0016]
A step of applying a liquid binder 38 on the fixed electrode material powder after the step of fixing the transferred electrode material powder 12P, 15P made of carbon particles and catalyst noble metal to the film 11 by the fixing roller 35. And you may provide the process of drying the apply | coated liquid binder. The liquid binder 38 may be applied by a roller 39 or by spray application. The reason why these steps are provided is to make the fixing of the electrode material powders 12P and 15P to the film 11 more complete.
[0017]
However, in the step of holding the electrode material powders 12P and 15P with a predetermined pattern on the photosensitive drum 30 by static electricity, the electrode material powders 12P and 15P made of carbon and a catalyst noble metal are preliminarily coated with a binder, or carbon, When a powder binder is mixed in advance with the electrode material powders 12P and 15P made of catalyst noble metal, the electrode material powders 12P and 15P made of carbon, catalyst noble metal and binder are sufficiently fixed to the film 11 in the fixing step. The liquid binder 38 coating step and the drying step may not be provided.
[0018]
In the method of the present invention, as shown in FIGS. 6 to 8, when the electrodes 14 and 17 are formed by performing the transfer of the electrode materials 12P and 15P to the film 11 a plurality of times to form the electrodes 14P, The type of 15P is varied and the coating layer thickness is controlled each time to control the electrode structure three-dimensionally.
When the production of the fuel cell electrode is adapted to color copying, the type of electrode material at each time corresponds to the color of color copying, and the thickness of the coating layer at each time corresponds to the darkness of the color applied at that time.
[0019]
The electrode materials 12P and 15P are mixed with the carbon particles and the catalytic noble metal supported on the carbon particles, and before or after the carbon particles and the catalytic noble metal are transferred to the film. A binder is included as a component, and the type of the electrode material is made different by changing at least one of the type, mixing ratio, mixing mode, and particle size of each component. More specifically, change the carbon particle diameter or shape, or change the type of noble metal supported on the carbon particles (platinum, ruthenium, or a mixture of multiple types of noble metals, or a mixture with different mixing ratios, etc.). Or whether to change the content ratio of carbon, noble metal and electrolyte, or to change the way the electrolyte is mixed (whether the noble metal-supported carbon particles are coated with the electrolyte, or the electrolyte particles are mixed with the noble metal-supported carbon particles) , Etc.), the type of the electrode material can be changed.
[0020]
There are four colors for color copying: blue, red (magenta), yellow, and black. However, in the case of an electrode material, the number of colors need not be limited to four. Then, as many electrode material accommodation devices 33 as the number of types of electrode materials are installed in the film feeding direction, and each type of electrode material is separately placed in the electrode material accommodation device 33 and sent. Various electrode materials are sequentially applied to the film 11.
[0021]
FIGS. 7 and 8 show examples of cross-sectional structures of the electrodes 14 and 17 when four types of electrode materials (four colors in color copying) are applied on the electrolyte membrane 11. In the example of FIG. 7, the first catalyst layer is applied with the first type of electrode material (for example, the color is “black” in color copying) on the electrolyte membrane plane with a light and shade in the in-plane direction. The second catalyst layer is made of an electrode material of the second type (for example, “yellow” in color copying) having a different thickness in the in-plane direction on the first catalyst layer plane (in color copying, Apply over and over again. The third catalyst layer is made of a third type of electrode material (for example, “red” in color copying) having a different thickness in the in-plane direction on the second catalyst layer plane (in color copying, Apply over and over again. The fourth catalyst layer has a fourth type of electrode material (for example, “blue” in color copy), with the thickness being varied in the in-plane direction on the third catalyst layer plane (in color copy, Apply shades and shades. As a result, electrodes 14 and 17 having the cross-sectional structure shown in FIG. 8 are formed. In this case, it is desirable that the thickness of the electrode composed of a plurality of layers is constant in order to make the contact pressure uniform.
[0022]
For example, the hydrogen concentration decreases along the fuel gas flow path from the hydrogen inlet to the hydrogen outlet, and the oxygen concentration also decreases along the oxidizing gas flow path from the air inlet to the air outlet. In the case of performing uniformly, the catalyst metal ratio of the anode 14 is increased on the hydrogen outlet side compared to the hydrogen inlet side, and the catalyst metal ratio of the cathode 17 is increased on the air outlet side compared to the air inlet side. It is.
The application control includes a reaction gas flow path pattern, a design concentration of the reaction gas along the flow path, a temperature, a humidity, a design current density in the cell surface, types of various electrode materials put in each electrode material storage device 33, Are input to a computer to calculate the intensity value of the light to be projected by the light projecting device 32, send the output value to the light projecting device 32, and perform light projection scanning in the in-coating surface direction. This can be done easily by controlling the intensity of the light projection.
[0023]
Next, the operation of the above-described method of the present invention will be described.
First, the entire surface of the photosensitive drum 30 is charged, and when laser light is projected, pattern exposure is performed on a portion where the electrode material is not applied to remove the charge, and only the portion charged with static electricity is the electrode material powder 12P. Since 15P is deposited and transferred to a film made of the electrolyte 11 or the diffusion layers 13 and 16, the electrodes 14 and 17 having an arbitrary shape can be controlled by controlling the exposure pattern and the strength of each part of the exposure pattern. Electrodes 14 and 17 with different concentrations and the like can be made at each site in the shape.
[0024]
In other words, the electrodes 14 and 17 having an arbitrary shape are obtained for pattern exposure, and the electrode density (light and shade in terms of copying) can be changed within the shape. For example, the portion corresponding to the groove (gas flow path) of the separator is formed with a high concentration of electrode material powder, and the portion of the separator rib (portion that is not the gas flow path) pressed through the diffusion layer is made of electrode material powder. It can be formed at a low concentration, and the amount of expensive catalyst noble metal applied can be reduced. In addition, since the concentration of the gas becomes lower as it goes downstream, the application concentration of the electrode material powder can be changed in accordance with the concentration, which can contribute to uniform power generation along the flow path. Conventionally, the pattern and density cannot be changed in such a cell plane, but in the present invention, it can be easily changed in the same manner as copying.
[0025]
Further, since the electrode material powders 12P and 15P are electrostatically attached to the surface of the photosensitive drum 30 and transferred (transfer to the film 11), the present invention is a dry method, and the electrolyte membrane of the solvent in the conventional wet coating The problem of electrode cracking due to attack and swelling / shrinkage is eliminated.
[0026]
Next, the method shown in each embodiment of FIGS. 3 and 4 will be described.
In the embodiment of FIG. 3, electrode material powders 12 </ b> P and 15 </ b> P are applied to both surfaces of the film 11 to form catalyst layers 12 and 15.
The membrane 11 is sent from top to bottom.
The electrode material transfer process and the fixing process are executed a plurality of times in the film feed direction. The illustrated example shows a case where the process is executed a plurality of times (in the example of FIG. 3, the case is shown twice, but is not limited to two times). The first electrode material transfer unit, its fixing unit, the second time An electrode material transfer portion and its fixing portion are provided in this order in the film feed direction, and coating and fixing are executed.
In addition, since the electrode material powders 12P and 15P in the electrode material powder container 33 are not coated with a binder or are not mixed with binder particles, a binder coating step and a binder drying step are performed after the final fixing step. Is provided. The binder is applied by, for example, roll coating.
In the method of FIG. 3, different types of electrode materials 12P (15p) are put in the electrode material powder container 33, and the application pattern shape, concentration, and layer thickness of each layer are changed in each electrode material transfer portion. be able to. Thereby, the coating pattern shape in the cell in-plane direction, the concentration, the composition, the layer thickness in the thickness direction, the composition, and the like can be changed, and the structure of the electrodes 14 and 17 can be changed in three dimensions. .
[0027]
In the embodiment of FIG. 4, a plurality of electrode material transfer portions are provided on one side of the film 11 (or 13, 16) in the film feeding direction, and the number of times is two (in the illustrated example, the number is two, but is not limited to two). ), Electrode material powders 12P and 15P are applied, and after application of all layers, the applied electrode material is fixed to the film 11 (or 13, 16) by the fixing unit 35, and the electrodes 14 and 17 are formed.
The membrane 11 (or 13, 16) is sent horizontally.
Since the electrode material powders 12P and 15P in the electrode material powder container 33 are not coated with binder or binder particles are not mixed, a binder coating step and a binder drying step are provided after the fixing step. .
In the method of FIG. 4, different types of electrode materials 12P (15p) are placed in the electrode material powder container 33, and the application pattern shape, concentration, and layer thickness of each layer are changed in each electrode material transfer portion. be able to. Thereby, the coating pattern shape in the cell in-plane direction, the concentration, the composition, the layer thickness in the thickness direction, the composition, and the like can be changed, and the structure of the electrodes 14 and 17 can be changed in three dimensions. .
[0028]
【The invention's effect】
According to the fuel cell electrode manufacturing method of claims 1 and 2 , since the type of the electrode material is varied at each time and the coating layer thickness is controlled at each time, the electrode structure (composition / density, film thickness, etc.) It can be arbitrarily controlled in three dimensions (in the electrode thickness direction and the in-plane direction perpendicular thereto). In addition, this method is a dry method because of the adhesion and transfer of the electrode material to the surface of the photosensitive drum due to static electricity. Attack of the electrolyte membrane of the solvent in conventional wet coating, electrode cracking due to swelling / shrinkage There is no.
According to the fuel cell electrode manufacturing method of claim 2 , the type of the electrode material can be changed by changing at least one of the mixing ratio of the components, the mixing method , and the particle size of each component. .
[Brief description of the drawings]
FIG. 1 is an overall front view of a fuel cell having an electrode manufactured by a method of manufacturing a fuel cell electrode according to the present invention.
FIG. 2 is an enlarged cross-sectional view of the cell of FIG.
FIG. 3 is a side view of an apparatus for carrying out a method of manufacturing a fuel cell electrode according to an embodiment of the present invention.
FIG. 4 is a side view of an apparatus for carrying out a method of manufacturing a fuel cell electrode according to another embodiment of the present invention.
FIG. 5 is a plan view showing a coating pattern of a fuel cell electrode manufactured by the method for manufacturing a fuel cell electrode of the present invention.
FIG. 6 is a plan view showing the distribution of gas pressure and concentration along the flow path of the fuel cell electrode manufactured by the method for manufacturing a fuel cell electrode of the present invention.
FIG. 7 is a plan view of each coating layer showing changes in concentration (corresponding to color) in the coating surface after each coating in the method for producing a fuel cell electrode of the present invention.
8 is a cross-sectional view in the thickness direction of an electrode showing a plurality of coating layers of FIG.
[Explanation of symbols]
10 (solid polymer electrolyte type) fuel cell 11 electrolyte membrane 12 catalyst layer 12P electrode material powder (for anode)
13 Diffusion layer 14 Electrode (Anode, Fuel electrode)
15 Catalyst layer 15P Electrode material powder (for cathode)
16 Diffusion layer 17 Electrode (cathode, air electrode)
18 Separator 19 Cell 20 Terminal 21 Insulator 22 End plate 23 Stack 24 Tension plate 25 Bolt 30 Photosensitive drum 30A Opposing drum 30B Opposing roller 31 Charging roller 32 Projecting device (laser beam projecting means)
33 Electrode material container 34 Electrode material powder supply roller 35 Fixing roller 36 Inert gas atmosphere 37 Binder application unit 38 Binder 39 Binder application roller 40 Drying section

Claims (2)

The photosensitive drum is charged and irradiated with light, and the irradiated portion is neutralized according to the intensity of the light, and the electrode material is attached to the charged portion with static electricity according to the intensity of the charge, and this is transferred to the film multiple times. This is a method of manufacturing a fuel cell electrode in which the electrode structure is changed three-dimensionally by controlling the coating layer thickness at each time by varying the type of electrode material each time. is varied in the electrode plane direction, the catalyst components and higher density than the portion to be pressed by the separator ribs at the portion corresponding to the gas passage of the separator, the separator is the portion corresponding to the lower stream portion of the gas flow channel of the separator method for manufacturing a fuel cell electrode and a high concentration of catalyst components than the portion corresponding to the upper stream portion of the gas flow path.   The electrode material includes carbon particles, a catalyst noble metal supported on the carbon particles, and an electrolyte binder mixed with the carbon particles and the catalyst noble metal before the carbon particles and the catalyst noble metal are transferred to the film. 2. The fuel cell electrode manufacturing method according to claim 1, wherein the type of the electrode material is made different by changing at least one of the type, mixing ratio, mixing method, and particle size of each component. Method.

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