JP2000353529A - Forming method for carbon thin film to high polymer film and manufacture of solid high polymer fuel cell using method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for positively forming a carbon thin film on a water repellent sheet and accurately transferring this carbon thin film to a high polymer film, and a solid high polymer fuel cell manufactured by using method thereof. SOLUTION: In this forming method of a carbon thin film to a high polymer film performed by forming the carbon thin film 20 on a blank sheet 2 superior in water repellency and then transferring this carbon thin film 20 to the high polymer film 43, the transfer of the carbon thin film 20 to the high polymer film 43 is performed by pressing the carbon thin film 20 against the high polymer film 43 in a state wherein the blank sheet 2 and the high polymer film 43 are heated at different temperatures, for example, a state wherein a heating temperature of the high polymer film 43 is lower than a glass-transition temperature of the high polymer film 43, and a heating temperature of the blank sheet 2 is higher than the glass-transition temperature of the high polymer film 43 and lower than a melting point of the blank sheet 2, and then peeling the blank sheet 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a carbon thin film on a polymer film and a method for manufacturing a polymer electrolyte fuel cell using the method to form a catalyst layer on a solid polymer film.

[0002]

2. Description of the Related Art In a fuel cell, hydrogen as a negative electrode active material is brought into contact with a catalyst such as platinum (platinum) to dissociate it into electrons and protons, and then this proton is reacted with oxygen as a positive electrode active material to produce water. Is obtained based on the reaction mechanism. That is, in the fuel cell, an electromotive force is generated by the movement of the electrons released from the hydrogen gas.

[0003] A fuel cell that generates an electromotive force based on such a principle also has a positive electrode, a negative electrode, and an electrolyte, similar to a general cell. Depending on the type of the electrolyte, an alkaline type, a solid polymer type, Phosphoric acid type, molten carbonate type and solid oxide type can be roughly classified. For example, a solid polymer fuel cell has a configuration in which an ion exchange membrane as a solid polymer is interposed between a positive electrode and a negative electrode with a catalyst layer provided on both surfaces thereof. Each catalyst layer is formed as a porous layer by catalyst particles in which a catalyst such as platinum is supported on carbon particles.

[0004] Such a catalyst layer is desired to be formed as thin as possible for the purpose of reducing the thickness of the fuel cell and the amount of catalyst used, or for facilitating the passage of gas. Therefore, a method has been proposed in which, after the ink is applied onto a water-repellent sheet, the solvent component of the ink is removed to form a carbon thin film, and the carbon thin film is transferred onto an ion exchange membrane to form a catalyst layer. In this method, ink is first applied onto a water-repellent sheet and dried to form a film. Since the liquid cannot be applied to the water-repellent sheet with a large thickness, it is possible to eventually form a thin carbon film on the water-repellent sheet. In addition, since the solvent component of the ink is blown off on the water-repellent sheet, there is an advantage that the ion exchange membrane is not poisoned by the solvent component of the ink. The carbon thin film thus formed is heated and pressed by being sandwiched between a pair of press dies, each of which is heated to about 160 ° C., in a state where the carbon thin film and the ion exchange membrane are in contact with each other. It is transferred onto an ion exchange membrane. That is, since the catalyst layer corresponding to the thickness of the carbon thin film formed on the water-repellent sheet is transferred onto the ion exchange membrane, a catalyst layer having a small thickness can be formed on the ion exchange membrane.

[0005]

However, it is not always easy to form a carbon thin film on a water-repellent sheet as a method of forming the above-mentioned catalyst layer. Even if the carbon thin film is formed well, It is difficult to properly transfer this to an ion exchange membrane.

First, since the water-repellent sheet naturally has poor wettability, it is difficult to apply ink with a certain planar spread, and it is not easy to form a carbon thin film as desired. Absent. Second, there is a problem that the carbon thin film is not securely adhered to the ion exchange membrane. This may be due to the presence of moisture in the ion exchange membrane during transfer, the presence of impurities in the carbon thin film, or the magnitude of pressure applied to the water repellent sheet or ion exchange membrane during transfer. The inventor tried transfer while removing these causes as much as possible, but did not reach a fundamental solution.

The present invention has been conceived in view of the above circumstances, and provides a method for forming a carbon thin film on a water-repellent sheet without fail and transferring the carbon thin film to a polymer film with high accuracy. It is an object of the present invention to provide a method for producing a polymer electrolyte fuel cell using the method.

[0008]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems, the present invention takes the following technical means.

That is, the method for forming a carbon thin film on a polymer film provided by the first aspect of the present invention comprises: forming a carbon thin film on a blank sheet having excellent water repellency; A method of forming a carbon thin film on a polymer film by transferring, wherein the transfer of the carbon thin film to the polymer film is performed by heating the blank sheet and the polymer film to different temperatures. After pressing on the molecular membrane,
It is characterized in that it is performed by peeling a blank sheet from a polymer film.

Conventionally, a carbon thin film has been transferred from a blank sheet to a polymer film while a polymer film or a blank sheet is sandwiched between a pair of press dies heated to the same temperature. That is, the carbon thin film was transferred while the blank sheet and the polymer film were heated to the same temperature. However, the temperature at which the carbon thin film can be appropriately peeled off from the blank sheet and the temperature at which the carbon thin film is properly bonded to the polymer film are not necessarily the same, but rather, these temperatures are It is hard to imagine that they are on the same level. Therefore, the present inventor has paid attention to this point, and has arrived at the present invention in which the heating temperature of the blank sheet and the polymer film at the time of transfer is intentionally set to different temperatures.

That is, in the present invention, for example, the heating temperature of the blank sheet is set within a temperature range in which the carbon thin film can be appropriately peeled from the blank sheet, while the heating temperature of the polymer film is set to the carbon thin film. Can be set within a temperature range suitable for bonding. When the blank sheet or polymer film is heated to such a temperature, the carbon thin film is appropriately peeled from the blank sheet, and the carbon thin film is appropriately bonded to the polymer film. The carbon thin film can be reliably and reproducibly transferred from the sheet to the polymer film.

As described above, a thinner film can be formed on a blank sheet having excellent water repellency, as compared with a case where a carbon thin film is formed directly on a polymer film. . Therefore, in the method of forming a carbon thin film on a blank sheet first and then transferring the carbon thin film to a polymer film, a thinner film is formed as compared with a case where a carbon thin film is formed directly on a polymer film. Can be.

The heating temperature of the polymer film at the time of transfer of the carbon thin film, that is, the temperature range in which the carbon thin film is appropriately bonded includes, for example, a temperature lower than the glass transition temperature of the polymer film. That is, when the polymer film is heated to a temperature higher than the glass transition temperature, the polymer film becomes in a rubbery state, and it becomes difficult to transfer the carbon thin film. On the other hand, it is preferable that the surface of the polymer film is softened (rubberized) to some extent in order to enhance the adhesiveness to the transferred carbon thin film, so that the polymer film is heated to a temperature close to the glass transition temperature. It is preferable to transfer the carbon thin film in this state.

The heating temperature of the blank sheet, that is, the temperature at which the carbon thin film can be appropriately peeled, is, for example, a temperature higher than the glass transition temperature of the polymer film and lower than the melting point of the sheet. This is because at a temperature lower than the glass transition temperature of the polymer film, the bond between the carbon thin film and the blank sheet cannot be cut sufficiently, while at a temperature higher than the melting point of the blank sheet, the blank sheet melts. This is because the carbon thin film sticks to the blank sheet and the blank sheet cannot be peeled off properly.

Examples of the blank sheet include those made of fluororesin such as polytetrafluoroethylene and polychlorotrifluoroethylene, and examples of the polymer film include those made of perfluorosulfonic acid polymer. In this case, the heating temperature of the blank sheet during transfer is about 150 to 200 ° C., and the heating temperature of the polymer film is 80 to 130 ° C.

More specifically, the transfer of the carbon thin film to the polymer film is performed, for example, by placing a carbon thin film between a press mold heated to 150 to 200 ° C. and a press mold heated to 80 to 130 ° C. Is carried out by sandwiching the blank sheet and the polymer film on which is formed. At this time, the pressure applied to the blank sheet or the polymer film is, for example, 5
0 to 100 MPa, and its transfer time (heating time)
Is, for example, 30 to 300 seconds.

Here, the carbon thin film is formed on the blank sheet by, for example, treating the surface of the blank sheet by corona discharge or plasma discharge, applying an ink containing carbon to the treated surface, and drying or firing the ink. It is done by things.

When the surface of the blank sheet is treated by corona discharge or plasma discharge, the wettability of the sheet surface is improved, so that a uniform and thin carbon thin film is formed on the blank sheet surface with a certain planar spread. be able to.

For applying the ink to the blank sheet, for example, a method such as screen printing, spin coating, roll coating, or potting is employed, and particularly, screen printing is suitably employed.

As the ink, a colloidal solution in which carbon powder (carbon black) is suspended in an organic solvent such as glycerin is preferably used. In addition, when transferring to the polymer film, the carbon thin film is suitably adhered to the polymer film, and in order to make the proton enter the membrane better, a single amount of the polymer constituting the polymer film is contained in the ink. It is preferable to mix a polymer or a polymer.

Another method for forming a carbon thin film on a blank sheet is as follows.
There is a method in which the ink is applied in a state where a vibration of 0 kHz is applied, and the ink is dried or baked. Preferably,
The ink is applied to the blank sheet one drop at a time, and the drying of the ink is performed each time one drop of the ink is applied.

When the blank sheet is subjected to vibration, particularly ultrasonic vibration, the wettability of the blank sheet surface is improved. For this reason, even in the method of applying the ink while applying the vibration, a uniform and thin carbon thin film can be formed on the surface of the blank sheet. In addition, in the method of drying the ink every time one ink is applied, the carbon thin film is formed in a thickness corresponding to the diameter of the ink droplet without applying the ink in the thickness direction of the sheet more than necessary. Can be.

According to a second aspect of the present invention, there is provided a structure in which catalyst layers are provided on both surfaces of a solid polymer film as an electrolyte, and the solid polymer film is interposed between a pair of electrodes. Wherein the catalyst layer is formed by the method of forming a carbon thin film according to the first aspect of the present invention using a catalyst and an ink having carbon. A method for manufacturing a polymer electrolyte fuel cell is provided.

As described above, when the method for forming a carbon thin film described in the first aspect of the present invention is employed, the method is compared with the case where a carbon thin film (catalyst layer) is formed directly on a solid polymer film. Thus, a catalyst layer having a smaller thickness can be formed. As a result, not only can the thickness of the entire polymer electrolyte fuel cell be reduced, but also the amount of catalyst used can be reduced.

In the fuel cell having the above structure, hydrogen gas as a negative electrode active material is dissociated into hydrogen ions and electrons in one catalyst layer (negative electrode catalyst layer). And the electrons are taken out of the fuel cell via one electrode. In the positive electrode catalyst layer, oxygen gas as a positive electrode active material reacts with electrons supplied from outside the fuel cell and hydrogen ions moving through the solid polymer membrane to generate water. Then, the water generated in the positive electrode catalyst layer usually moves to the electrode side, but if the thickness of the catalyst layer is set small, the back diffusion of water into the solid polymer membrane can be appropriately promoted. . That is, as in the polymer electrolyte fuel cell provided by the production method of the present invention, if the thickness of the catalyst layer is reduced, water generated in the positive electrode catalyst layer is back-diffused into the ion exchange membrane to perform ion exchange. The membrane can be suitably wetted. In addition, if water generated in the positive electrode catalyst layer can be used, it is possible to appropriately avoid a situation in which water accumulates in the gas flow path, particularly the oxygen gas flow path, and obstructs gas flow.

As the solid polymer membrane, one which selectively allows hydrogen ions to pass therethrough, specifically, a polystyrene-based cation exchange membrane, for example, a perfluorosulfonic acid polymer is suitably used. This polymer exhibits proton conductivity when wet with water, and protons (hydrogen ions) generated by dissociation of hydrogen gas in the negative electrode catalyst layer permeate in a hydrated state and move to the positive electrode catalyst layer. It has been made like that. For this reason, it is significant that the water generated in the positive electrode catalyst layer can be back-diffused to wet the solid polymer film. The thickness of the solid polymer film is set to, for example, about 0.13 to 0.25 mm.

Further, the ink used in the production method according to this aspect needs to contain a catalyst in addition to the carbon powder. This catalyst may be, for example, previously supported on carbon powder or another carrier, or may be coexisted in the ink without being supported on carbon powder or the like (solid powder or ionic state). . The catalyst forming the negative electrode catalyst layer includes, for example, platinum, gold, nickel, tungsten carbide, and the like, and the catalyst forming the positive electrode catalyst layer includes, for example, platinum, gold, silver, rhodium, and the like.

Other features and advantages of the present invention will become more apparent from the detailed description given below.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an overall perspective view of a fuel cell stack in which polymer electrolyte fuel cells are assembled in series, FIG. 2 is an exploded perspective view of the polymer electrolyte fuel cell, and FIG. FIG. 4 and FIG. 5 are cross-sectional views of the polymer electrolyte fuel cell taken along a diagonal line of the plate and enlarged views of main parts thereof. FIGS. 4 and 5 illustrate a method of forming a catalyst layer on an ion exchange membrane. FIG.

As shown in FIG. 1, the fuel cell stack 4 has a plurality of polymer electrolyte fuel cells 40 which share one plate between adjacent fuel cells 40 and are arranged in series. One end plate 4A and the other end plate 4B side communicate with each other through four communication holes 4a to 4d.

Each of the solid polymer fuel cells 40 includes a first plate 41 and a second plate 42 as shown in FIGS. 2 and 3, and a solid polymer interposed between the plates 41 and 42. Ion exchange membrane 43 as a membrane and this ion exchange membrane
A negative electrode current collector 44 or a positive electrode current collector 45 interposed between 43 and the first plate 41 or the second plate 42 is disposed so as to surround the negative electrode current collector 44 or the positive electrode current collector 45. And a first gasket 47 or a second gasket 48.

Each of the plates 41 and 42 is entirely made of metal or alloy,
For example, it is formed of a conductor such as carbon, titanium, or stainless steel, and has first to fourth through holes 41a to 41d, 42a to
42d is provided. A plurality of individual grooves 41e, 42e extending in the left-right direction in FIG. 2 are formed on the surfaces 41A, 42A of the plates 41, 42 so as to be arranged in the vertical direction. Are connected by first common grooves 41f and 42f extending in the vertical direction, and the other ends are connected by second common grooves 41g and 42g. The first common groove portions 41f and 42f are
Diagonally arranged first and second through holes 41a, 41b, 42
a and 42b communicate with the first through holes 41a and 42a, and the second common grooves 41g and 42g are connected to the second through holes 41b and 42b.
Is in communication with The other surfaces 41B and 42B of the respective plates 41 and 42 are not clearly shown in the drawing, but one surface 41A, 42A
An individual groove and a common groove similar to those on the side are formed, and each common groove is formed in the third through-hole 41c, 42c or the fourth through-hole.
It communicates with the through holes 41d and 42d. That is, each plate
A flow path for oxygen gas as a positive electrode active material is formed on one surface 41A, 42A side of 41, 42, and a flow path for hydrogen gas as a negative electrode active material is formed on the other surface 41B, 42B side. One plate 41, 42 is shared between the matching fuel cells 40.

In a state where each fuel cell 40 constitutes the stack 4, the first through holes 41a and 42a of the first and second plates 41 and 42 are located coaxially.
The first and second plates 41 and 42 are arranged such that the fourth through holes 41b to 41d and 42b to 42d are also coaxially located.

The ion exchange membrane 43 has through holes 43a to 43d formed at the four corners corresponding to the first and second plates 41 and 42, and the negative electrode catalyst layer 43 is formed on one surface and the other surface.
A and the cathode catalyst layer 43B are formed respectively.

The ion exchange membrane 43 has proton conductivity and selectively allows hydrogen ions to pass therethrough. As the ion exchange membrane 43, for example, a perfluorosulfonic acid polymer, which is a polystyrene cation exchange membrane, is used. This polymer exhibits conductivity when wetted with water, and hydrates hydrogen ions. Pass by.

The anode catalyst layer 43A is, for example, a porous layer composed of catalyst particles having platinum supported on the surface of carbon particles, and is capable of passing hydrogen molecules and hydrogen ions. In the anode catalyst layer 43A, the supplied hydrogen gas is dissociated into hydrogen ions and electrons. On the other hand, the cathode catalyst part
43B is, for example, a porous layer composed of catalyst particles in which platinum and rhodium coexist and are supported on the surface of carbon particles so that oxygen molecules can pass therethrough. In the positive electrode catalyst layer 43B, hydrogen ions react with oxygen and electrons to generate water.

As shown in FIG. 4, the anode catalyst layer 43A and the cathode catalyst layer 43B having the above-described structures are formed by a carbon thin film forming step of forming the carbon thin film 20 on the blank sheet 2, as shown in FIG. Then, a step of transferring the carbon thin film to the ion exchange membrane 43 is formed.

In the carbon thin film forming step, the wettability of the blank sheet 2 is improved by performing corona discharge or plasma discharge on the blank sheet 2 (FIG. 4).
(A)), an ink containing a carbon powder and a catalyst is applied on a blank sheet, and this is dried (FIG. 4 (b)).

As the blank sheet 2, the catalyst layer 43A,
From the viewpoint of forming 43B as thin as possible, those having excellent water repellency, for example, those made of fluororesin such as polytetrafluoroethylene and polychlorotrifluoroethylene are preferably used. Normally, it is difficult to form an ink layer that spreads over the entire surface of a fluororesin sheet having excellent water repellency, but as described above, the sheet is treated by corona discharge or the like to obtain a wettability. If the ink is applied after improving the quality, an ink layer having a very small thickness can be formed.

As described above, an ink containing carbon powder and a catalyst, which are formed into a colloid solution with an organic solvent such as glycerin, is used as described above. The catalyst may be supported on the carbon powder, or the catalyst may be coexisted as a solid powder or as an ion without being supported on the carbon powder. The ink may be in the form of a solution, a suspension, or a paste. Incidentally, since it is necessary to dissociate hydrogen into hydrogen ions and electrons in the anode catalyst layer 43A, examples of the catalyst used for the anode catalyst layer 43A include platinum, gold, nickel, and tungsten carbide. Tier 43
In B, since it is necessary to react oxygen with hydrogen ions and electrons, examples of the catalyst used for the positive electrode catalyst layer 43B include platinum, gold, silver, and rhodium.

The ink is applied to the blank sheet 2 by, for example, screen printing, spin coating, roll coating, or potting. In particular, screen printing is preferably employed.

Various methods can be employed for drying the ink. For example, it may be carried out by air drying for about 30 minutes to several hours, or under reduced pressure (1 to
(50 KPa). Of course, the blank sheet 2 coated with the ink may be introduced into, for example, an electric furnace to forcibly dry the ink. When the ink is dried in this way, as shown in FIG.
The liquid component of the ink evaporates, and a solid carbon thin film is formed on the blank sheet 2.

The step of transferring the carbon thin film 20 on the blank sheet 2 to the ion exchange membrane 43 is performed by a pair of press dies 3A, 3A.
B, the ion exchange membrane 43 and the blank sheet 2 are sandwiched so that the carbon thin film 20 contacts the ion exchange membrane 43,
The heating is performed by heating both the ion exchange membrane 43 and the blank sheet 2 (FIG. 5A) and then peeling the blank sheet 2 (FIG. 5B).

As the ion exchange membrane 43, the one made of a perfluorosulfonic acid polymer is suitably used as described above. In this case, the heating temperature of the ion exchange membrane 43 is lower than the glass transition temperature of the polymer. The heating temperature of the blank sheet 2 is set to about 130 ° C., and is set to about 150 to 200 ° C., which is higher than the glass transition temperature and higher than the melting point of the blank sheet 2. If the heating temperature of the ion exchange membrane 43 is set to about 130 ° C., the surface of the ion exchange membrane 43 can be softened to some extent, whereby the adhesiveness to the carbon thin film 20 can be increased. Does not soften and stick to the press die 3B or the blank sheet 2. On the other hand, if the heating temperature of the blank sheet 2 is set to about 150 to 200 ° C., the bond between the blank sheet 2 and the carbon thin film 2 is appropriately cut, and the blank sheet 2 sticks to the press die 3A or the carbon thin film 20. Without this, the carbon thin film 20 can be appropriately peeled from the blank sheet 2. Further, the carbon thin film 20 is transferred very well while the temperature is higher than that of the ion exchange membrane 43.

The negative electrode current collector 44 collects electrons dissociated from the hydrogen gas in the negative electrode catalyst layer 43A so that the electrons can be taken out of the fuel cell 40, and the hydrogen gas is supplied so that the supplied hydrogen gas reaches the negative electrode catalyst layer 43A. It must be able to pass gas. For this reason, for example, the porous body is made of a carbon-based material (carbon powder such as carbon black, graphite, carbon fiber, etc.), nickel, a nickel-chromium alloy, a nickel-cobalt alloy, silver, titanium, tantalum, an oxide semiconductor, or the like. In particular, a carbon-based material is preferably used.

The positive electrode current collector 45 receives electrons from the outside and supplies the electrons to the positive electrode catalyst portion 43B.
Further, since it is necessary to pass the oxygen gas so that the supplied oxygen gas reaches the cathode catalyst layer 43B, the oxygen gas is formed as a porous body using, for example, a carbon-based material similarly to the anode current collector 44.

The first and second gaskets 47, 48 change the sealing state between the ion exchange membrane 43 and the first or second plate 41, 42, and thus the sealing state between the adjacent plates 41, 42. It is to enhance. As the overall shape,
It has a rectangular frame shape having openings 47A and 48B having the same area as the current collector 44 (45) at the center thereof, and the first and second plates 41 and 42 are provided at the corners of the frame. Each through hole 41a
Through holes 47a to 47d, 48a corresponding to .about.41d, 42a to 42d.
~ 48d are provided.

In the fuel cell 40 having the above structure, the ion exchange membrane 43 and the members of the gaskets 47 and 48 are
Through holes 41a to 41d, 42a formed in each plate 41, 42
Each through-hole is formed corresponding to .about.42d. Therefore, as clearly shown in FIG. 3, in the state of the fuel cell 40, the through holes provided in each member are connected, and also in the state of the fuel cell stack 4, the through holes of each member are connected. Thus, first to fourth communication holes 4a to 4d communicating with the outside of the end plates 4A and 4B are formed (see FIG. 1). Of these communication holes 4a to 4d, first and second communication holes 4a, 4b located at diagonal positions
Are the individual grooves 41e, 42e or the common grooves 41f, 42f, 41g provided on one surface 41A, 42A side of each of the plates 41, 42.
The other two communication holes 4c and 4d are not clearly shown in the drawing but are provided with individual grooves or common grooves provided on the other surfaces 41B and 42B. Each is in communication.

That is, from outside the fuel cell stack 4,
When hydrogen gas is supplied from one or both of the third and fourth communication holes 4c and 4d with the other end plate 4B side as an entrance, the other surfaces 41 of all the plates 41 and 42 are provided.
Hydrogen gas is passed through the individual grooves and the common grooves on the B and 42B sides. When oxygen gas is supplied from one or both of the first and second through holes 4a and 4b, the individual grooves 41e and 42e and the common grooves 41f and 41g on the surfaces 41A and 42A of all the plates 41 and 42 are provided. , 42f, and 42g are passed with oxygen gas. The oxygen gas is usually supplied in an air state.

In each fuel cell 40, for example, a part of the hydrogen gas passing through the third communication hole 4c or the fourth communication hole 4d is transferred to the individual groove or the common groove formed on the other surface 41B of the first plate 41. The supplied hydrogen gas passes through the negative electrode current collector 44 and is dissociated into hydrogen ions and electrons in the negative electrode catalyst layer 43A (reaction formula (1) below).

[0051]

Embedded image

The electrons generated during this reaction are converted into a negative electrode current collector.
The electrons are collected at 44, and are supplied to the positive electrode current collector 45 of the adjacent fuel cell 40 that shares the first plate 41 via the first plate 41 (see FIGS. 1 and 3). On the other hand, hydrogen ions generated during the reaction in the anode catalyst layer 43A pass through the ion exchange membrane 43 in a hydrated state (the following reaction formula (2)), and move to the cathode catalyst layer 43B.

[0053]

Embedded image

The positive electrode catalyst layer 43B is further supplied with electrons from the negative electrode current collector 44 of the adjacent fuel cell 40 sharing the second plate 42, and the third communication hole 4c and the fourth communication hole 4d.
A part of the air (oxygen gas) passing through the second plate 42 is formed on one surface 42A side of the common grooves 42g and 42f, the individual grooves.
It is supplied via 42 e and the positive electrode current collector 45. In the positive electrode catalyst layer 43B to which the oxygen gas, the electrons, and the hydrogen ions have been supplied as described above, they react to generate water (the following reaction formula (3)). Some of the water generated at this time is
The cathode catalyst layer 43 </ b> B is back-diffused and supplied to the ion exchange membrane 43.

[0055]

Embedded image

In the fuel cell stack 4 described above,
The electrons collected in the negative electrode current collector 44 of one fuel cell 40 are supplied to the positive electrode current collector 45 of the adjacent fuel cell 40. Then, the electrons collected in the negative electrode current collector 44 of the fuel cell 40 located at the most downstream in the electron flow direction pass through an external circuit, and the positive electrode of the fuel cell 40 located at the most upstream in the electron flow direction is passed through the external circuit. Current collector 45
Supplied to That is, in the fuel cell stack 4, electrons flow in a certain direction as a whole, and electrons are circulated from the most downstream fuel cell 40 to the most upstream fuel cell 40 via an external circuit. I have. And
Energy is taken out and used in an external circuit.

[0057]

EXAMPLES Examples will be described below together with comparative examples.

[0058]

Example 1 In this embodiment, a carbon thin film was formed by applying and drying ink on one side of a blank sheet (manufactured by Nitto Denko Corporation; "Nitocron"). Transferred to an exchange membrane (Dupont; "Nafion").

The blank sheet has a corona discharge machine (TA).
Made by NTEC AS (Denmark); "Model H
V05-2 "), corona discharge generated when the voltage applied between the electrodes in the device was set to 10 KV was given in advance. As the ink, the platinum carrying amount is 3
Carbon black (particle diameter: 20 to 30 nm) on which platinum is previously supported so as to be 7.7 wt%
0.1 g was mixed with 0.667 g of Nafion solution (manufactured by DuPont; "Nafion solution 5%") and 5 g of glycerin (manufactured by Wako Pure Chemical Industries, Ltd .; "glycerin reagent") and used by stirring. . The application of the ink was performed by screen printing so that the application amount and the application area after drying were 1 g and 100 cm ² . After drying the ink at normal temperature and normal pressure for 1 hour, the ink was dried under reduced pressure (1
Pa) for another 2 hours.

The transfer of the carbon thin film is performed by holding the blank sheet and the ion exchange membrane in a heated state so that the carbon thin film contacts the ion exchange membrane between a pair of press dies, and then peeling the blank sheet. Was performed. The heating temperature of the first press die for heating the blank sheet side is 15
The temperature was 5 ° C., and the heating temperature of the second press mold for heating the ion exchange membrane side was 100 ° C. In these press dies, the blank sheet and the ion-exchange membrane were set at 70 MPa.
At a pressure of 60 seconds.

The formation of the carbon thin film on the blank sheet was attempted 10 times by the method described above, and the formation state of the carbon thin film was visually confirmed for each sample. Then, only for the sample in which the carbon thin film was successfully formed, the transfer of the carbon thin film to the ion exchange membrane was attempted, and the transfer state of the carbon thin film was visually observed. Table 1 shows the results of visually observing the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0062]

Example 2 In this example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the formation state of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was the same as Example 1 except that the temperature of the first press die was 170 ° C and the temperature of the second press die was 120 ° C. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0063]

Example 3 In this example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the formation state of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was the same as Example 1 except that the temperature of the first press mold was set to 200 ° C and the temperature of the second press mold was set to 130 ° C. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0064]

Example 4 In this example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was the same as Example 1 except that the pressing pressure between the blank sheet and the ion exchange membrane by each press mold was set to 100 MPa. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0065]

Example 5 In this example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
The procedure was the same as in Example 1 except that the pressing pressure between the blank sheet and the ion exchange membrane by each press mold was set to 50 MPa. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0066]

Example 6 In this example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
The procedure was the same as in Example 1 except that the holding time of the blank sheet and the ion exchange membrane by each press mold was set to 100 seconds. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0067]

Example 7 In this example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
The procedure was the same as in Example 1 except that the holding time of the blank sheet and the ion exchange membrane by each press mold was set to 30 seconds. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0068]

Example 8 In this example, a carbon thin film was formed in the same manner as in Example 1 except that corona discharge was not applied to the blank sheet in advance, and the formation state of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted in the same manner as in Example 1 for the sample on which the carbon thin film was successfully formed. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0069]

Comparative Example 1 In this comparative example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was carried out in the same manner as in Example 1 except that the temperature of the first press die was set to 155 ° C and the temperature of the second press die was set to 155 ° C. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0070]

Comparative Example 2 In this comparative example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was the same as Example 1 except that the temperature of the first press mold was set to 120 ° C and the temperature of the second press mold was set to 120 ° C. Table 1 shows the results of visually observing the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0071]

Comparative Example 3 In this comparative example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was the same as Example 1 except that the temperature of the first press die was 170 ° C and the temperature of the second press die was 140 ° C. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0072]

Comparative Example 4 In this comparative example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the formation state of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
Example 1 was the same as Example 1 except that the pressing pressure between the blank sheet and the ion exchange membrane by each press mold was set to 30 MPa. Table 1 shows the results of visual observation of the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0073]

Comparative Example 5 In this comparative example, a carbon thin film was formed on a blank sheet in the same manner as in Example 1, and the state of formation of the carbon thin film was visually checked. Then, the transfer of the carbon thin film to the ion exchange membrane was attempted for the sample in which the carbon thin film was successfully formed. The transfer of the carbon thin film to the ion exchange membrane
The procedure was the same as in Example 1 except that the holding time of the blank sheet and the ion exchange membrane by each press mold was 25 seconds. Table 1 shows the results of visually observing the state of formation of the carbon thin film on the blank sheet and the state of transfer of the carbon thin film to the ion exchange membrane.

[0074]

[Table 1]

[0075]

As described above, in the method for forming a carbon thin film on a polymer film according to the present invention, a carbon thin film can be reliably formed on a blank sheet. Can be transferred to a polymer film. That is, in the present invention, a carbon film having a small thickness can be formed on the polymer film. Further, the method of forming a carbon thin film on a polymer film can be suitably adopted as a method of forming a catalyst electrode of a polymer electrolyte fuel cell.

[Brief description of the drawings]

FIG. 1 is an overall perspective view illustrating an example of a fuel cell stack in which polymer electrolyte fuel cells are stacked in series.

FIG. 2 is an exploded perspective view of the polymer electrolyte fuel cell.

FIG. 3 is a cross-sectional view of a polymer electrolyte fuel cell when cut along a diagonal line of a plate constituting the fuel cell, and an enlarged view of a main part thereof.

FIG. 4 is a diagram for explaining a method of forming a catalyst layer on an ion exchange membrane.

FIG. 5 is a diagram for explaining a method of forming a catalyst layer on an ion exchange membrane.

[Explanation of symbols]

 Reference Signs List 2 blank sheet 20 carbon thin film 4 fuel cell stack 40 fuel cell 41 first plate 42 second plate 43 ion exchange membrane (polymer film) 43A negative electrode catalyst layer 43B positive electrode catalyst layer 44 positive electrode current collector 45 positive electrode current collector 47 Negative gasket 48 Positive gasket

Claims (8)

[Claims] 1. A method for forming a carbon thin film on a polymer film by forming a carbon thin film on a blank sheet having excellent water repellency, and then transferring the carbon thin film to a polymer film. The carbon thin film is transferred to the polymer film by heating the blank sheet and the polymer film to different temperatures, pressing the carbon thin film against the polymer film, and then peeling the blank sheet from the polymer film. A method for forming a carbon thin film on a polymer film. 2. The heating temperature of the polymer film during the transfer of the carbon thin film is lower than the glass transition temperature of the polymer film, and the heating temperature of the blank sheet is lower than the glass transition temperature of the polymer film. 2. The fuel cell according to claim 1, wherein the temperature is higher than the melting point of the blank sheet. 3. 3. The blank sheet is made of a fluororesin, the polymer film is made of a perfluorosulfonic acid polymer, and the heating temperature of the blank sheet during transfer is 150 to 2
00 ° C. and the heating temperature of the polymer film is 80 to 1
3. The fuel cell according to claim 2, wherein the temperature is 30 ° C. 4. The pressing of the carbon thin film on the polymer film is performed by heating and sandwiching the blank sheet and the polymer film between a pair of heated press dies under a pressure of 50 to 100 MPa for 30 to 300 seconds. The fuel cell according to any one of claims 1 to 3, wherein the fuel cell is performed. 5. The method of forming a carbon thin film on a blank sheet,
The polymer according to any one of claims 1 to 4, wherein the surface of the blank sheet is treated by corona discharge or plasma discharge, and thereafter, the treated surface is coated with an ink containing carbon powder and dried. A method for forming a carbon thin film on a film. 6. The method of forming a carbon thin film on a blank sheet,
The method of applying a carbon thin film to a polymer film according to any one of claims 1 to 4, wherein the blank sheet is applied with an ink containing carbon powder while being subjected to vibration of 1 Hz to 400 kHz, and dried. Forming method. 7. The method for forming a carbon thin film on a polymer film according to claim 6, wherein the application of the ink to the blank sheet is performed drop by drop, and the drying of the ink is performed each time a drop of the ink is applied. 8. A method for producing a polymer electrolyte fuel cell, wherein a solid polymer membrane as an electrolyte having a catalyst layer provided on both surfaces is interposed between a pair of electrodes, Is formed by the method for forming a carbon thin film according to any one of claims 1 to 7, using an ink having carbon and a catalyst, respectively.
A method for manufacturing a polymer electrolyte fuel cell.