Patent Application
20120315571
The present invention relates to a fuel cell used as a power supply for driving a mobile object such as a mobile electronic device or a car, a dispersed power generation system, a domestic cogeneration system, or the like, and more particularly to a method for producing a catalyst-coated membrane provided in the fuel cell.
A fuel cell (such as a polymer electrolyte type fuel cell) allows a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air to electrochemically react with each other, such that electric power, heat, and water are produced at the same time.
In general, a fuel cell includes stacking a plurality of cells, pressurizing and fastening them with a fastening member such as a bolt or a band. The one cell is configured such that a membrane-electrode assembly (hereinafter, referred to as the MEA) is sandwiched by one paired plate-like conductive separators.
The MEA includes a polymer electrolyte membrane and one paired electrode layers arranged on both surfaces of the polymer electrolyte membrane. One of the paired electrode layers is an anode electrode, and the other is a cathode electrode. Each of the one paired electrode layers includes a catalyst layer containing, as its main component, carbon powder bearing a metal catalyst, and a porous and conductive gas diffusion layer arranged on the catalyst layer. Here, an assembly of the polymer electrolyte membrane and the catalyst layer is referred to as a catalyst-coated membrane (CCM). When the fuel gas comes in contact with the anode electrode, and the oxidant gas comes in contact with the cathode electrode, the electrochemical reaction is generated, whereby electric power, heat, and water are generated.
Next, a description will be given of one example of a conventional method for producing the catalyst-coated membrane (refer to Patent Document 1: Japanese Unexamined Patent Publication No. 2002-289207, for example), with reference to
First, as shown in
As described above, the technique to produce the catalyst-coated membrane by directly printing or applying the catalyst ink on the polymer electrolyte membrane 101 attracts attention as an ideal method for producing the catalyst-coated membrane because interface resistance between the polymer electrolyte membrane 101 and the catalyst layers 104a and 104b can be extremely reduced.
In general, the polymer electrolyte membrane 101 is a member which is extremely thin (such as 20 μm to 50 μm thick), and is likely to be deformed even with little moisture. Therefore, in the case where the catalyst ink is directly printed or applied onto the polymer electrolyte membrane 101, a solvent contained in the catalyst ink penetrates into the polymer electrolyte membrane 101, and force is exerted to swell from an inner side toward an outer side in the polymer electrolyte membrane 101 as shown by arrows in
However, the above production method has an issue that water in the polymer electrolyte membrane 101 is dried when the catalyst ink is dried to form the catalyst layer 104a. In this case, force is exerted to shrink from the outer side to the inner side in the polymer electrolyte membrane 101 as shown by arrows in
Therefore, it is an object of the present invention to improve the above issue, and to provide a method for producing a catalyst-coated membrane in which a polymer electrolyte membrane is prevented from being curled when catalyst ink is dried to form a catalyst layer.
In order to attain the above object, the present invention is configured as will be described below.
The present invention provides a method for producing a catalyst-coated membrane provided in a fuel cell, the method including:
a film attaching step of preparing a membrane-shape retaining film-assembly produced so that a shape retaining film having a width longer than that of a polymer electrolyte membrane is attached on one surface of the electrolyte membrane so as to protrude from both sides of the electrolyte membrane in a width direction, and
a catalyst layer forming step of forming a catalyst layer by applying catalyst ink onto an other surface of the electrolyte membrane having the attached shape retaining film, and drying the electrolyte membrane.
According to the method for producing the catalyst-coated membrane according to the present invention, the membrane-shape retaining film-assembly is prepared such that the shape retaining film is attached on the one surface of the polymer electrolyte membrane so as to protrude from both sides of the polymer electrolyte membrane in the width direction, and the catalyst layer is formed on the other surface of the polymer electrolyte membrane, so that the polymer electrolyte membrane can be prevented from being curled. Thus, a conveyance trouble and an appearance defect can be prevented from being generated. As a result, the catalyst-coated membrane can be produced by the roll-to-roll type production device, so that production efficiency of the catalyst-coated membrane can be improved.
These and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which:
After a great deal of consideration by the inventors of the present invention in order to improve the issue of the conventional technique, the following knowledge has been obtained.
According to the conventional production method, the width of the polymer electrolyte membrane and the width of the shape retaining film are set to the same dimension in view of costs and the like. Meanwhile, when the width of the shape retaining film is set to be longer than the width of the polymer electrolyte membrane, and the shape retaining film is attached so as to protrude from both sides of the polymer electrolyte membrane in a width direction, the knowledge that the polymer electrolyte membrane is considerably prevented from being curled is obtained. This is considered to be because the part of the shape retaining film protruding from both sides of the polymer electrolyte membrane in the width direction functions as a weight, and force is applied to the direction opposite to the direction in which the polymer electrolyte membrane is curled. Based on this knowledge, the inventors of the present invention have reached the following present invention.
According to a first aspect of the present invention, there is provided a method for producing a catalyst-coated membrane provided in a fuel cell, the method comprising:
preparing a membrane-shape retaining film-assembly produced so that a shape retaining film having a width longer than that of a polymer electrolyte membrane is attached on one surface of the electrolyte membrane so as to protrude from both sides of the electrolyte membrane in a width direction; and
forming a catalyst layer by applying catalyst ink onto an other surface of the electrolyte membrane having the attached shape retaining film, and drying the electrolyte membrane.
According to a second aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to the first aspect, wherein
an amount of the shape retaining film protruding in the width direction of the electrolyte membrane is 5 mm or more.
According to a third aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to the first or second aspect, further comprising:
attaching a second shape retaining film having a width longer than that of the electrolyte membrane, on the other surface of the electrolyte membrane having the catalyst layer so as to protrude from both sides of the electrolyte membrane in the width direction;
peeling off the shape retaining film from the electrolyte membrane having the attached second shape retaining film; and
forming a second catalyst layer by applying second catalyst ink on the electrolyte membrane exposed after the shape retaining film has been peeled off, and drying the electrolyte membrane.
According to a fourth aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to the third aspect, wherein
an amount of the second shape retaining film protruding in the width direction of the electrolyte membrane is 5 mm or more.
According to a fifth aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to the third or fourth aspect, wherein
the amount of the second shape retaining film protruding in the width directions of the electrolyte membrane is 50 mm or less.
According to a sixth aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to any one of third to fifth aspects, wherein
the amount of the second shape retaining film protruding in the width direction of the electrolyte membrane is 30 mm or less.
According to a seventh aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to any one of the third to sixth aspects, further comprising:
attaching a third shape retaining film having a width longer than that of the electrolyte membrane, on the one surface of the electrolyte membrane having the second catalyst layer so as to protrude from both sides of the electrolyte membrane in the width direction.
According to an eighth aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to the seventh aspect, wherein
an amount of the third shape retaining film protruding in the width direction of the electrolyte membrane is 50 mm or less.
According to a ninth aspect of the present invention, there is provided the method for producing a catalyst-coated membrane according to the seventh or eighth aspect, wherein the amount of the third shape retaining film protruding in the width direction of the electrolyte membrane is 30 mm or less.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Referring to
A polymer film 10 is wound around the supply roll 11. In this embodiment, the polymer film 10 refers to polymer films 10a to 10f each having a structure shown in any one of
As shown in
In addition, in a case where a second catalyst layer 4b is to be formed on the second surface (one surface) of the polymer electrolyte membrane 1 as shown in
The polymer electrolyte membrane 1 may include conventionally used various kinds of polymer electrolyte membranes formed of fluorine series or hydrocarbon series. For example, the polymer electrolyte membrane 1 may include a polymer electrolyte membrane formed of perfluorocarbonsulfonate (such as Nafion (registered trademark) made by DuPont Company, USA, Flemion (registered trademark) made by Asahi Glass Company, Limited, or Aciplex (registered trademark) made by ASAHI KASEI CORPORATION). In general, the polymer electrolyte membrane 1 is a member which is extremely thin and likely to be deformed even with little moisture. Therefore, the first, second, or third shape retaining film 2, 3, or 5 is attached on the first or second surface of the polymer electrolyte membrane 1. In addition, similar to the first and second shape retaining films 2 and 3, a third shape retaining film 5 also has a width longer than that of the polymer electrolyte membrane 1 in the direction perpendicular to the conveyance direction X, and is attached on the polymer electrolyte membrane 1 so as to protrude from both sides of the polymer electrolyte membrane 1 in the width direction. Hereinafter, a part of the third shape retaining film 5 protruding from both sides of the polymer electrolyte membrane 1 in the width direction is referred to as a lug part 5a. The lug part 5a is continuously formed in a longitudinal direction of the third shape retaining film 5.
The first, second, or third shape retaining film 2, 3, or 5 may be formed of polyethylene terephthalate, polypropylene, polyetherimide, polyimide, or fluorine resin, for example. It is sufficient that the first, second, or third shape retaining film 2, 3, or 5 is to be a film having heat resistance so as not to be thermally deformed at the time of lamination.
The polymer film 10 drawn from the supply roll 11 is suspended by the backup roll 13, and is wound up by the wind-up roll 18. The wind-up roll 18 has a motor (not shown), and is continuously rotated by driving force of the motor to continuously wind up the polymer film 10. According to this embodiment, as will be described below, the first catalyst layer 4a (or second catalyst layer 4b) is formed on the first surface (or the second surface) of the polymer electrolyte membrane 1 during a time from when the polymer film 10 is drawn from the supply roll 11 till when it is wound up by the wind-up roll 18, so that the catalyst-coated membrane can be mass-produced.
When the polymer film 10c shown in
For example, the backup roll 13 is a columnar member having a diameter of 300 mm. In addition, since the first shape retaining film 2 or second shape retaining film 3 is attached on the polymer electrolyte membrane 1, the backup roll 13 does not necessarily have a suction function.
The die 14 is arranged so as to be opposed to the backup roll 13 through the polymer film 10. The die 14 is connected to a supply pump P. The die 14 is configured to be able to discharge (apply) catalyst ink of which the catalyst layer is formed, from the supply pump P to a contact part between the polymer film 10 and the backup roll 13.
The catalyst ink is produced by mixing carbon fine particles bearing platinum series metal catalyst, with a solvent. For example, the metal catalyst may include platinum, ruthenium, rhodium, and iridium. The carbon powder may include carbon black, ketjen black, and acetylene black. The solvent may include water, and organic solvents of alcohol series such as ethanol, n-propanol, or n-butanol, ether series, ester series, and fluorine series. The first and second catalyst layers 4a and 4b each containing, as its main component, carbon powder bearing the metal catalyst can be formed by drying the solvent of the platinum series metal catalyst ink.
The drying device 15 is arranged on a downstream side of the conveyance direction X with respect to the backup roll 13 so as to surround the polymer film 10. The drying device 15 is adapted to dry the catalyst ink applied from the die 14 onto the first surface (or the second surface) of the polymer electrolyte membrane 1 by heating the polymer electrolyte membrane 1 from both of the first surface and the second surface of the polymer electrolyte membrane 1. Through the drying process by the drying device 15, the solvent of the catalyst ink is completely dried, and the first catalyst layer 4a (or the second catalyst layer 4b) is formed. The drying device 15 may include a convection type hot air drying device, for example.
The shape retaining film supplying device 16 is arranged on the downstream side of the conveyance direction X with respect to the drying device 15. After the polymer film 10b shown in
The attaching device 17 is arranged on the downstream side of the conveyance direction X with respect to the shape retaining film supplying device 16. The attaching device 17 is configured to be able to attach the first, second, or the third shape retaining film 2, 3, or 5 on the first surface or the second surface of the polymer electrolyte membrane 1 so as to ensure predetermined bonding strength. More specifically, the attaching device 17 includes one paired columnar attachment rolls 17a and 17b. Each of the attachment rolls 17a and 17b is a columnar member having a diameter of 200 mm, for example. The attachment rolls 17a and 17b are configured to be able to come close to each other and apply predetermined pressure and heat to the polymer film 10 when the polymer film 10 is supplied therebetween.
Next, a description will be given of a method for producing the catalyst-coated membrane according to this embodiment.
First, the polymer film (membrane-shape retaining film-assembly) 10a shown in
Then, the polymer film 10a shown in
Then, the motor (not shown) of the wind-up roll 18 is driven, and the polymer film 10a is continuously fed from the supply roll 11 to the wind-up roll 18.
Then, the catalyst ink is discharged from the supply pump P through the die 14 to the polymer film 10a positioned on the backup roll 13 by the above feeding action. Thus, the catalyst ink is applied onto the first surface (other surface) of the polymer electrolyte membrane 1.
Then, the polymer film 10a having the applied catalyst ink is fed into the drying device 15 by the above feeding action, and is heated by the drying device 15. Thus, the polymer electrolyte membrane 1 is heated from both sides of the first surface and second surface of the polymer electrolyte membrane 1, so that the catalyst ink is dried and the first catalyst layer 4a is formed as shown in
Then, on the first surface of the polymer film 10b shown in
Then, the attachment rolls 17a and 17b apply the pressure and heat to the unconnected polymer film 10c which has been fed between the attachment rolls 17a and 17b of the attaching device 17 by the above feeding action. The polymer electrolyte membrane 1 and the second shape retaining film 3 are connected by this pressure and heat (second film attaching step).
Then, the polymer film 10c shown in
Then, the polymer film 10c shown in
Then, the motor (not shown) of the wind-up roll 18 is driven to continuously feed the polymer film 10c from the supply roll 11 to the wind-up roll 18.
Then, the first shape retaining film 2 is peeled from the polymer film 10c which has been fed to the lower side of the peeling device 12 by the above feeding action, whereby the polymer film 10d is formed as shown in
Then, the catalyst ink is discharged from the supply pump P through the die 14, to the polymer film 10d positioned on the backup roll 13 by the above feeding action. Thus, the catalyst ink is applied to the second surface of the polymer electrolyte membrane 1. In addition, at this time, the catalyst ink (second catalyst ink) applied to the second surface of the polymer electrolyte membrane 1 may be the same as the catalyst ink (first catalyst ink) applied to the first surface of the polymer electrolyte membrane 1 or may be different from that.
Then, the polymer film 10d having the applied catalyst ink and fed into the drying device 15 by the above feeding action is heated by the drying device 15. Thus, the polymer electrolyte membrane 1 is heated from both sides of the first surface and the second surface of the polymer electrolyte membrane 1, and the catalyst ink is dried, whereby the second catalyst layer 4b is formed as shown in
Then, on the second surface of the polymer film 10e shown in
Then, the attachment rolls 17a and 17b apply pressure and heat to the unconnected polymer film 10f which has been fed between the attachment rolls 17a and 17b of the attaching device 17 by the above feeding action. The polymer electrolyte membrane 1 and the third shape retaining film 5 are connected by the pressure and heat (third film attaching step).
Then, the polymer film 10f shown in
According to the method for producing the catalyst-coated membrane according to this embodiment, since the first shape retaining film 2 is formed so as to have the lug part 2a, the lug part 2a functions as the weight, so that the polymer electrolyte membrane 1 can be prevented from being curled. Thus, a conveyance trouble such as a jam of the polymer film 10b or 10e between the attachment rolls 17a and 17b, and an appearance defect of the polymer film 10c or 10f can be prevented from being generated. As a result, the catalyst-coated membrane can be produced by the roll-to-roll type production device, so that production efficiency of the catalyst-coated membrane can be improved.
Next, a description will be given of a result of a review of a curl height of the polymer electrolyte membrane and bonding strength between the polymer electrolyte membrane and the shape retaining film which are provided by the method for producing the catalyst-coated membrane according to this embodiment.
Table 1 below shows curl heights of the polymer films 10b formed while the widths of the lug parts 2a of the first shape retaining films 2 are changed, and data about the bonding strength of the polymer film 10c in which the second shape retaining film 3 is attached on the polymer film 10b.
The data in Table 1 is provided under the condition that the width of each of the lug parts 2a and 2a of the first shape retaining film 2, and the width of each of the lug parts 3a and 3a of the second shape retaining film 3 are all set to the same dimension within a range of 0 to 51 mm.
In addition, the data of “curl height” in Table 1 is data of a curl height of the polymer film 10b which corresponds to a curl height of the polymer electrolyte membrane 1. In a section of “curl decision” in Table 1, a cross means that the conveyance trouble due to the curl height is generated. A circle means that the conveyance trouble due to the curl height is not likely to be generated. A double circle means that the conveyance trouble due to the curl height is hardly generated.
In addition, “bonding strength ratio” in Table 1 means a ratio of the bonding strength of the polymer film 10c in which the width of the lug part 3a is changed, with respect to the bonding strength of the polymer film 10c in which the width of the lug part 3a is set to 50 mm. Here, the “bonding strength of the polymer film 10c” means the bonding strength between the polymer electrolyte membrane 1 and the second shape retaining film 3. In a section of “bonding decision” in Table 1, a cross means that the bonding strength is not established as a product. A circle means that the bonding strength can be established as a product, but it is lower than the conventional case. A double circuit means that the bonding strength is higher than the conventional case.
In addition, “total decision” in Table 1 means a determination whether or not the polymer film 10c having the lug parts 2a and 3a shown in Table 1 is preferably used as the catalyst-coated membrane. In the section of the “total decision”, a cross means that it is not preferable to be used as the catalyst-coated membrane. A circle means that a failure such as the conveyance trouble is not generated even when used as the catalyst-coated membrane, and it is preferable to be used as the catalyst-coated membrane although the curl is generated or the bonding strength decreases a little. A double circle means that it is preferable to be used as the catalyst-coated membrane.
In addition, here, as the polymer electrolyte membrane 1, a fluorine series polymer electrolyte membrane is used. The width of the polymer electrolyte membrane 1 is set to 300 mm.
In addition, as each of the first and second shape retaining films 2 and 3, a polyethylene terephthalate film having a thickness of 75 μm which has been subjected to a surface treatment on its one surface is used. When the second shape retaining film 3 is attached on the polymer electrolyte membrane 1, the applied pressure by the attaching device 17 is set to 0.1 to 1.0 Mpa, and the heating temperature by the attaching device 17 is set to 80 to 150° C. The width of the first shape retaining film 2 is provided by adding the widths of the lug parts 2a to the width of the polymer electrolyte membrane 1. For example, when the width of the lug part 2a is 50 mm, the width of the first shape retaining film 2 is set to 400 mm. The width of the second shape retaining film 3 is set to the same dimension as the width of the first shape retaining film 2.
In addition, in each of a case where the first catalyst layer 4a is formed and a case where the second catalyst layer 4b is formed, a conveyance speed of the polymer film 10 is set to 0.5 m/min. In addition, the heating temperature by the drying device 15 is set to 60° C., and the heating time by the drying device 15 is set to 5 minutes.
In addition, as the catalyst ink to form the first catalyst layer 4a used herein, the catalyst ink is produced by adding 10 g of ion-exchange water to 5 g of carbon black, then adding 10 g of ethanol solution, and mixing them with an ultrasonic vibration applied thereto. As for the carbon black used herein, it has an average grain diameter of 50 to 60 nm and bears 50% by weight of platinum having an average grain diameter of 3 nm. As for the ethanol solution used herein, it contains 91% by weight of perfluorocarbonsulfonate.
In addition, as for the catalyst ink to form the second catalyst layer 4b used herein, the catalyst ink is produced by adding 15 g of ion-exchange water to 5 g of carbon black, then adding 10 g of ethanol solution, and mixing them with an ultrasonic vibration applied thereto. As for the carbon black used herein, it has an average grain diameter of 50 to 60 nm and bears 50% by weight of an alloy of platinum and ruthenium having an average grain diameter of 2 to 3 nm. As for the ethanol solution used herein, it contains 91% by weight of perfluorocarbonsulfonate.
It can be seen from Table 1 and
In addition, it can be seen from Table 1 and
In general, the polymer electrolyte membrane is a soft member, and the second shape retaining film is a hard member. In the case where the members having different hardness are attached to each other, air is likely to enter a space (interface) between them. Therefore, according to the conventional production method, when the second shape retaining film 103 is attached to the polymer electrolyte membrane 101, a large amount of air flows into a space 120 between them as shown in
In addition, according to the convention production method, the width of the polymer electrolyte membrane 101 is set to be the same as the width of the second shape retaining film 103. However, when the second shape retaining film 103 is attached on the polymer electrolyte membrane 101, the second shape retaining film 103 could be attached to the polymer electrolyte membrane 101 with it being shifted in a right or left direction as shown in
Meanwhile, in the case where the lug part 3a is provided in the second shape retaining film 3 as in the embodiment, as shown in
Meanwhile, as the width of the lug part 3a increases, the air in the space 20 which is originally to be pushed out becomes difficult to be moved to the outside. That is, when the polymer film 10b and the second shape retaining film 3 are pressed by the attachment rolls 17a and 17b, as shown in
In addition, the air lines 30 formed when the width of the lug part 3a is 50 mm or more deforms the second shape retaining film 3 and damages the polymer electrolyte membrane 1, so that a defect is caused such that power generation performance is lowered and the winding action of the wind-up roll 18 is hindered.
In addition, while the description has been given of the result of the review of the curl height of the polymer film 10b and the bonding strength of the polymer film 10c in the above, it has been confirmed that the same result can be obtained as for the curl height of the polymer film 10e and the bonding strength of the polymer film 10f. That is, the width of the lug part 3a of the second shape retaining film 3 is preferably 5 mm or more. Thus, the polymer electrolyte membrane 1 is considerably prevented from being curled when the second catalyst layer 4b is formed. In addition, the width of the lug part 5a of the third shape retaining film 5 is preferably 50 mm or less, and more preferably 30 mm or less. Thus, the bonding strength between the polymer electrolyte membrane 1 and the third shape retaining film 5 can be ensured above a certain level, or the bonding strength can be improved compared with the conventional case. In addition, these dimensions are preferable dimensions in common with all of the polymer electrolyte membrane 1 having the general size (such as the width of 300 mm, or width of 500 mm) at the present.
The present invention is not limited to this embodiment and can be implemented in various manners. In the above, the widths of the lug part 2a of the first shape retaining film 2, the lug part 3a of the second shape retaining film 3, and the lug part 5a of the third shape retaining film 5 are all the same, respectively, but the present invention is not limited to this. The widths of the lug part 2a, the lug part 3a, and the lug part 5a may be different, respectively.
In addition, in the above, the widths of the lug parts 2a and 2a on both sides of the first shape retaining film 2 are the same dimension, but the present invention is not limited to this. The widths of the lug parts 2a and 2a on both sides of the first shape retaining film 2 may have different dimensions. In addition, the widths of the lug parts 3a and 3a on both sides of the second shape retaining film 3, and the widths of the lug parts 5a and 5a on both sides of the third shape retaining film 5 may similarly have different dimensions, respectively.
In addition, in the above, the lug part is provided in each of the first to third shape retaining films 2, 3, and 5, but the present invention is not limited to this. The lug part only needs to be provided in the first shape retaining film 2 or the second shape retaining film 3. Thus, the curl height of the polymer electrolyte membrane 1 can be reduced compared with the conventional case.
Although the present invention has been fully described in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claim unless they depart therefrom.
The entire disclosure of Japanese Patent Application No. 2010-280293 filed on Dec. 16, 2010 including specification, drawings, and claims are incorporated herein by reference in its entirety.
According to the method for producing the membrane-electrode-assembly according to the present invention, the polymer electrolyte membrane can be prevented from being curled when the catalyst ink is dried to form the catalyst layer, so that it is useful for a method for producing a catalyst-coated membrane provided in a fuel cell used as a power supply for driving a mobile object such as a mobile electronic device or a car, a dispersed power generation system, a domestic cogeneration system, or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-280293 | Dec 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/006531 | 11/24/2011 | WO | 00 | 8/17/2012 |
