JP6286932B2 - Catalyst layer manufacturing apparatus and catalyst layer manufacturing method - Google Patents

Description

The present invention relates to the production how the manufacturing apparatus and the catalyst layer of the catalyst layer of the polymer electrolyte fuel cell membrane electrode assembly.

  A fuel cell is a power generation system that produces electricity by reverse reaction of water electrolysis using hydrogen and oxygen as fuel. This has features such as high efficiency, low environmental load and low noise compared with the conventional power generation method, and is attracting attention as a clean energy source in the future. In particular, polymer electrolyte fuel cells that can be used near room temperature are expected to be used for in-vehicle power sources and household stationary power sources, and in recent years, various research and development have been conducted.

  In general, a polymer electrolyte fuel cell is configured by stacking a large number of single cells. A single cell has a structure in which a membrane / electrode assembly joined by sandwiching a polymer electrolyte membrane between two electrodes, an oxidation electrode and a reduction electrode, is sandwiched by a separator having a gas flow path. The challenge for the practical application of fuel cells is to find a low-cost and efficient membrane / electrode assembly manufacturing technology as well as improving battery performance and infrastructure.

As a method of forming a membrane / electrode assembly for a polymer electrolyte fuel cell, a method is known in which a catalyst layer sheet provided with a catalyst layer on a base film is thermocompression bonded to a polymer electrolyte membrane, and the catalyst layer is transferred. ing. The catalyst layer sheet is produced by applying a catalyst ink comprising a catalyst, a carrier, a polymer electrolyte, a solvent, etc. to a base film and drying it.
In the catalyst layer of the catalyst layer sheet, a catalyst carrier and a polymer electrolyte aggregate generated in the production process may be mixed as foreign matters or bubbles may be mixed. In addition, depending on the conditions at the time of forming the catalyst layer, the thickness of the catalyst layer changes in the plane, and particularly the end portion may become too thick.

When a catalyst layer that has foreign matter attached or has a large in-plane thickness is thermocompression bonded to the polymer electrolyte membrane, the polymer electrolyte membrane may be damaged, resulting in a pinhole in the membrane / electrode assembly. There is a possibility that a part of the polymer electrolyte membrane is thinned or the adhesion between the polymer electrolyte membrane and the catalyst layer is lowered.
Pinholes generated in the membrane / electrode assembly cause deterioration in battery performance and durability. In addition, there is a concern that the defective rate in manufacturing increases, leading to an increase in cost.

As a method for preventing problems caused by pinholes, for example, as described in Patent Document 1, pinholes generated in a polymer electrolyte membrane or a membrane / electrode assembly are filled with a material that solidifies after drying, such as silica sol. There is a way to repair.
In addition, as another method for preventing defects due to pinholes, for example, as described in Patent Document 2, first, foreign matters on the catalyst layer sheet are first removed, and then the defects formed there are almost the same components as the catalyst ink. There is a method of repairing by filling with correction ink.

JP 2004-214089 A JP 2013-020753 A

However, the method described in Patent Document 1 is a method of filling the pinhole portion with a material other than the polymer electrolyte after the pinhole of the polymer electrolyte membrane or the membrane / electrode assembly is generated. For this reason, even if the method described in Patent Document 1 is used, the polymer electrolyte membrane is once perforated, which may cause a problem in battery performance and durability.
Further, the method described in Patent Document 2 is a method for correcting defects in the catalyst layer sheet. However, the steps of removing defective portions, applying correction ink, and drying correction ink are increased, resulting in complicated manufacturing equipment. There is a problem of cost increase.

  The present invention has been made in order to solve the above-mentioned problems, and has a catalyst layer having no protrusion that damages the polymer electrolyte membrane, and a membrane / electrode assembly that prevents deterioration of battery characteristics and durability. Is provided at low cost and with high efficiency.

In order to solve the above-described problems, an apparatus for producing a catalyst layer constituting a membrane / electrode assembly for a polymer electrolyte fuel cell according to an aspect of the present invention includes at least a catalyst and a polymer on one surface of a substrate. A catalyst layer forming means for forming the catalyst layer including an electrolyte; and the same layer as the normal portion by removing a protruding portion protruding from a flat normal portion of the catalyst layer formed by the catalyst layer forming means. And a removing means for making a thickness.
The catalyst layer manufacturing apparatus may further include cooling means for cooling the catalyst layer reaching the removing means.

Moreover, the said catalyst layer manufacturing apparatus is good also as providing the cleaning means which cleans the surface of the said catalyst layer from which the said protrusion part was removed.
The catalyst layer manufacturing apparatus may further include transport means for sequentially performing the formation of the catalyst layer and the removal of the protruding portion while transporting the base material.
In addition, a membrane / electrode assembly for a polymer electrolyte fuel cell according to an aspect of the present invention includes a catalyst layer produced by the production apparatus.

The method for producing a catalyst layer constituting the membrane / electrode assembly for a polymer electrolyte fuel cell according to one aspect of the present invention includes the catalyst comprising at least a catalyst and a polymer electrolyte on one surface of the substrate. A catalyst layer forming step of forming a layer, and a removing step of removing a protruding portion protruding from a flat normal portion to have the same film thickness as the normal portion among the catalyst layer formed in the catalyst layer forming step It is characterized by providing.
Further, in the removing step of the method for producing the catalyst layer, the protrusion may be removed while cooling the catalyst layer.

In the removal step of the catalyst layer manufacturing method, the surface of the catalyst layer from which the protrusions have been removed may be cleaned.
Moreover, the manufacturing method of the said catalyst layer is good also as performing the said catalyst layer formation process and the said removal process sequentially, conveying the said base material.
In addition, a membrane / electrode assembly for a polymer electrolyte fuel cell according to one aspect of the present invention includes the catalyst layer produced by the above production method.

According to the present invention, the catalyst carrier in the catalyst layer of the catalyst layer sheet, the aggregated foreign matter of the polymer electrolyte, the bubbles, and the damage to the polymer electrolyte membrane due to the protruding portion of the catalyst layer due to the catalyst layer forming conditions are not caused. Transfer of the catalyst layer to the polymer electrolyte membrane can be performed. For this reason, if it is this invention, the membrane-electrode assembly which prevented the fall of the battery characteristic and durability can be provided.
In addition, according to the present invention, it is not necessary to correct a defect generated in the catalyst layer sheet using a correction ink or the like, so that it is not necessary to add a correction process. For this reason, if it is this invention, since the complexity of manufacturing equipment is not required, a membrane electrode assembly can be provided at low cost and high efficiency.

Further, when the cooling means is provided, it is possible to prevent the polymer electrolyte in the removed aggregated foreign matter from being softened by heat and reattaching to the catalyst layer.
Moreover, when the cleaning means is provided, it is possible to prevent the removed aggregated foreign matter from remaining on the catalyst layer and reattaching to the catalyst layer.
Moreover, when the conveyance means for performing each process sequentially while conveying a base material is provided, a membrane electrode assembly can be provided at low cost and high efficiency.

1 is a schematic cross-sectional view of a membrane / electrode assembly according to an embodiment of the present invention. It is a schematic cross section of the membrane electrode assembly which concerns on a prior art. It is explanatory drawing of the catalyst layer manufacturing apparatus which concerns on one Embodiment of this invention. It is explanatory drawing of the catalyst layer formation process which concerns on one Embodiment of this invention. It is explanatory drawing of the removal process which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail. Note that this embodiment is an example of the present invention and does not limit the present invention.
First, a membrane / electrode assembly according to an embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view of a membrane / electrode assembly 1 according to an embodiment of the present invention. The membrane / electrode assembly 1 has an anode-side and cathode-side catalyst layer 12 disposed and bonded with a polymer electrolyte membrane 11 interposed therebetween. The catalyst layer 12 includes at least a polymer electrolyte, a catalyst, and a carrier.

  2A and 2B are schematic cross-sectional views of the membrane / electrode assembly 2 according to the related art. Similar to the membrane / electrode assembly 1 according to one embodiment of the present invention, the membrane / electrode assembly 2 includes an anode-side and cathode-side catalyst layer 12 sandwiched between and joined to the polymer electrolyte membrane 11. It is what. However, in the membrane / electrode assembly 2, the protruding portion 13 protrudes on the side of the catalyst layer 12 in contact with the polymer electrolyte membrane 11, so that the polymer electrolyte membrane 11 is damaged by being sunk into the polymer electrolyte membrane 11. Yes.

Of the polymer electrolyte membrane 11 used in the membrane / electrode assembly for a solid polymer fuel cell of the present embodiment, the polymer electrolyte in the catalyst layer 12 may have any proton conductivity, such as fluorine. Polymer electrolytes, hydrocarbon polymer electrolytes, and the like.
In this case, as the fluorine-based polymer electrolyte, for example, Nafion (registered trademark) manufactured by DuPont, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., Aciplex (registered trademark) manufactured by Asahi Kasei Co., Ltd., Gore Select (manufactured by Gore) Registered trademark) or the like.

In addition, as the hydrocarbon polymer electrolyte, for example, sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, sulfonated polyphenylene and the like can be used.
In particular, a Nafion (registered trademark) material manufactured by DuPont can be suitably used as the polymer electrolyte membrane.

  As described above, various polymer electrolytes in the catalyst layer 12 in the polymer electrolyte membrane 11 in the present embodiment can be used. The interface resistance between the polymer electrolyte membrane 11 and the catalyst layer 12, humidity, and the like. In consideration of the rate of dimensional change in the catalyst layer 12 and the polymer electrolyte membrane 11 at the time of change, it is preferable that the polymer electrolyte in the catalyst layer 12 and the polymer electrolyte membrane 11 to be used are the same component. .

Examples of the catalyst in the present embodiment include platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and the like. These metals and their alloys, oxides, double oxides, carbides, and the like can be used.
Further, the carrier supporting these catalysts used in the present embodiment may be any fine powder that has conductivity and is not affected by the catalyst. For example, carbon black, graphite, graphite, activated carbon, carbon nanotubes, Fullerene or the like can be preferably used. The catalyst carrier used in the present embodiment may not be carbon as long as it has conductivity and is not affected by the catalyst.

  3-5 is explanatory drawing which shows an example of the manufacturing apparatus and manufacturing process of the catalyst layer 12 based on this embodiment. In the apparatus for producing the catalyst layer 12 constituting the membrane / electrode assembly 1 for a polymer electrolyte fuel cell according to this embodiment, as shown in FIG. 3, first, a catalyst, a carrier, a polymer electrolyte, a solvent, etc. The catalyst ink 14 contained is applied to the base material 21 by the catalyst layer forming means 22, and then passed through a catalyst layer forming process in which the applied catalyst ink 14 is dried by the drying means 23. A catalyst layer sheet on which a catalyst layer 12 including at least a catalyst and a polymer electrolyte is formed is obtained. When using a roll-to-roll system that sequentially passes through each process while transporting the base material 21, the base material 21 wound around the roll is unwound and transported by the base material unwinding means 28.

  In the catalyst layer sheet obtained by the catalyst layer forming step, there may be a protruding portion 13 protruding from a normal portion of the catalyst layer 12 (that is, a flat portion having a preset film thickness) (see FIG. 4). ). The protruding portion 13 is, for example, a catalyst carrier or a polymer electrolyte agglomerated in the catalyst layer forming step, a catalyst layer 12 generated by bubbles inside the catalyst layer 12 or between the base material 21 and the catalyst layer 12. Or a thick film portion at an end portion caused by the application condition of the catalyst ink 14.

The solvent used as a dispersion medium for the catalyst ink 14 in the present embodiment is any solvent that does not erode the catalyst particles and the polymer electrolyte and can dissolve or disperse the polymer electrolyte in a highly fluid state. There is no particular limitation. The solvent may contain water that is compatible with the polymer electrolyte. The amount of water added is not particularly limited as long as the polymer electrolyte is not separated to cause white turbidity or gelation.
In addition, it is desirable that at least a volatile liquid organic solvent is contained, but those using lower alcohol as the solvent have a high risk of ignition, and when using such a solvent, it is preferable to use a mixed solvent with water. preferable.

As the catalyst layer forming means for applying the catalyst ink 14 to the substrate 21 in the present embodiment, various known methods such as die coating, roll coating, curtain coating, spray coating, squeegee, spin coating can be used. is there.
Further, as a drying means for drying the applied catalyst ink 14, for example, a warm air oven, IR drying, reduced pressure drying, or the like can be used.

  Examples of the base material 21 used in the present embodiment include an ethylene tetrafluoroethylene copolymer (ETFE), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and a tetrafluoroperfluoroalkyl vinyl ether copolymer ( A fluororesin excellent in transferability such as PFA) or polytetrafluoroethylene (PTFE) can be used. In addition, for example, polymer films such as polyimide, polyethylene terephthalate, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, polyethylene naphthalate may be used. it can. Moreover, you may use what processed the release layer etc. to these base materials.

  The catalyst layer sheet that has undergone the catalyst layer forming step is then observed by the observation means 24 for the presence of the protrusions 13 on the surface of the catalyst layer 12 (see FIG. 5). In this observation step, when it is recognized that the protruding portion 13 is present, the protruding portion 13 is removed in the next removing step. In the removing step, the protruding portion 13 protruding from the normal portion of the catalyst layer 12 of the catalyst layer sheet obtained in the catalyst layer forming step is removed by the removing means 25. At this time, fine fragments of the removed catalyst layer are generated. By operating the cleaning means 26 simultaneously with the removal, it is possible to prevent scattering and contamination of the surroundings.

Further, the polymer electrolyte contained in the catalyst layer 12 and the projecting portion 13 is softened due to heat at the time of removal, and the shape is changed, and fine fragments of the removed catalyst layer are prevented from reattaching to the catalyst layer 12. For the purpose, it is preferable that the cooling means 27 is provided. By this removal step, a catalyst layer sheet can be obtained in which no portion protruding from the normal portion of the catalyst layer 12 is present on the surface.
As the removing means 25 in the present embodiment, for example, a polishing machine or a laser whose polishing head rotates or reciprocates can be used.

Further, as the cleaning means 26 in the present embodiment, for example, a nozzle provided with a fan that sucks air and collects dust, a nozzle that jets air, a slightly adhesive roller, and the like can be used. In particular, when a nozzle having a fan that sucks air and collects dust is used, it is possible to collect fragments of the protruding portion 13 without contacting the catalyst layer 12 and the cleaning means 26, which is preferable.
Moreover, as the cooling means 27 in this embodiment, a cooling mechanism can be provided in the stage which installs the base material 21, and the removal means 25, or a catalyst layer sheet can be put in a cooling atmosphere.

  After each of the anode catalyst layer sheet and the cathode catalyst layer sheet is formed by the above-described steps, the polymer electrolyte membrane 11 is composed of the anode catalyst layer sheet and the cathode catalyst layer sheet so that the substrate surfaces face each other. The laminated body that has been aligned is heated and pressurized. Thus, the polymer electrolyte membrane 11 is joined to the anode catalyst layer and the cathode catalyst layer. Finally, by peeling off the base material 21, a membrane / electrode assembly 1 as shown in FIG. 1 is obtained.

The pressure applied to the electrode catalyst layers (the anode catalyst layer and the cathode catalyst layer) in the joining step affects the battery performance of the membrane / electrode assembly 1. For this reason, in order to obtain the membrane / electrode assembly 1 with good battery performance, the pressure applied to the laminate is preferably in the range of 0.5 MPa to 20 MPa, more preferably in the range of 2 MPa to 15 MPa. It is. When the pressure exceeds 20 MPa, the catalyst layer 12 is excessively compressed, and when the pressure is less than 0.5 MPa, the bondability between the catalyst layer 12 and the polymer electrolyte membrane 11 is lowered, and the battery performance is lowered.
Further, the temperature at the time of bonding is set near the glass transition point of the polymer electrolyte in the catalyst layer 12, so that the bonding property at the interface between the polymer electrolyte membrane 11 and the catalyst layer 12 is improved, and the interface resistance can be suppressed. Effective in terms and desirable.

[Example]
A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), a mixed solvent of water and ethanol, and a polymer electrolyte (Nafion: registered trademark of DuPont) are mixed and dispersed with a planetary ball mill. A catalyst ink was prepared. And the adjusted catalyst ink was apply | coated to the surface of the PTFE film in the rectangle using the slit die coater. Subsequently, the PTFE film coated with the catalyst ink was put in a warm air oven at 80 degrees and dried to prepare a cathode side catalyst layer sheet. Moreover, the anode side catalyst layer sheet was produced by the same method.

Next, the surfaces of the cathode side catalyst layer and the anode side catalyst layer were observed using a non-contact type surface shape measuring device (Wyco NT8000 three-dimensional surface roughness meter VM-0156 manufactured by Veeco). A portion protruding from the surface of the average catalyst layer was removed using a small grinder, and at the same time, debris removed by a small suction machine was sucked.
Then, the anode catalyst layer and the cathode catalyst layer are arranged so as to face both surfaces of the polymer electrolyte membrane (Nafion 212: registered trademark, manufactured by Dupont), and the PTFE film is peeled after hot pressing the laminate. Thus, the membrane / electrode assembly of the example was obtained.

[Comparative example]
A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), a mixed solvent of water and ethanol, and a polymer electrolyte (Nafion: registered trademark of DuPont) are mixed and dispersed with a planetary ball mill. A catalyst ink was prepared. And the adjusted catalyst ink was apply | coated to the surface of the PTFE film in the rectangle using the slit die coater. Subsequently, the PTFE film coated with the catalyst ink was put in a warm air oven at 80 degrees and dried to prepare a cathode side catalyst layer sheet. Moreover, the anode side catalyst layer sheet was produced by the same method.

Next, the surfaces of the cathode side catalyst layer and the anode side catalyst layer were observed using a non-contact type surface shape measuring apparatus (Wyco NT8000 three-dimensional surface roughness meter VM-0156 manufactured by Veeco), from the average catalyst layer surface. It was also confirmed that there was a protruding part.
Then, the anode catalyst layer and the cathode catalyst layer are arranged so as to face both surfaces of the polymer electrolyte membrane (Nafion 212: registered trademark, manufactured by Dupont), and the PTFE film is peeled after hot pressing the laminate. Thus, a membrane / electrode assembly of a comparative example was obtained.

The cross section of the membrane / electrode assembly of the example and the cross section at the portion where the protruding portion of the membrane / electrode assembly of the comparative example was observed were observed by SEM.
As a result, in the membrane / electrode assembly of the comparative example, there was a portion where the aggregated foreign matter of the catalyst ink protruded from the average catalyst layer surface, so that the polymer electrolyte membrane was crushed and made thinner than other portions. confirmed.
On the other hand, in the membrane / electrode assembly of Example, it was confirmed that the polymer electrolyte membrane was not thinned because there was no portion protruding from the average catalyst layer surface.

  When the membrane / electrode assembly of the present invention is used in a polymer electrolyte fuel cell, pinholes hardly occur and long-term durability is enhanced. Therefore, the present invention can be suitably used for a fuel cell using a polymer electrolyte membrane, particularly a stationary cogeneration system and a fuel cell vehicle.

DESCRIPTION OF SYMBOLS 1, 2 ... Membrane / electrode assembly 11 ... Polymer electrolyte membrane 12 ... Catalyst layer 13 ... Projection 14 ... Catalyst ink 21 ... Base material 22 ... Catalyst layer forming means 23 ... Drying means 24 ... Observation means 25 ... Removal means 26 ... cleaning means 27 ... cooling means 28 ... substrate unwinding means 29 ... catalyst layer sheet

Claims (10)

An apparatus for producing a catalyst layer constituting a membrane / electrode assembly for a polymer electrolyte fuel cell,
A catalyst layer forming means for forming the catalyst layer containing at least a catalyst and a polymer electrolyte on one surface of the substrate;
Of the catalyst layer formed by the catalyst layer forming means, a removing means that removes a protruding part protruding from a flat normal part to have the same film thickness as the normal part,
And a cooling means for cooling the catalyst layer was Tsu optimum to the removing means,
The cooling means includes at least one of a cooling mechanism provided on a stage on which the substrate is installed, a cooling mechanism provided on the removing means, and a cooling mechanism that cools the catalyst layer in a cooling atmosphere. An apparatus for producing a catalyst layer. The apparatus for producing a catalyst layer according to claim 1, further comprising observation means for observing the surface of the catalyst layer before reaching the removal means to determine the presence or absence of the protruding portion.   The apparatus for producing a catalyst layer according to claim 1, further comprising a cleaning unit that cleans the surface of the catalyst layer from which the protrusions have been removed.   4. The apparatus according to claim 1, further comprising transport means for sequentially performing the formation of the catalyst layer and the removal of the protruding portion while transporting the base material. 5. An apparatus for producing the catalyst layer as described. The apparatus for producing a catalyst layer according to any one of claims 1 to 4, wherein the removing unit removes only the protruding portion. A method for producing a catalyst layer constituting a membrane / electrode assembly for a polymer electrolyte fuel cell,
A catalyst layer forming step of forming the catalyst layer containing at least a catalyst and a polymer electrolyte on one surface of the substrate;
Of the catalyst layer formed in the catalyst layer forming step, a removal step of removing the protruding portion protruding from the flat normal portion and having the same film thickness as the normal portion ,
In the removing step, at least one of a cooling mechanism provided on a stage on which the base material is installed, a cooling mechanism provided on a removing unit that removes the protrusion, and a cooling mechanism that cools the catalyst layer in a cooling atmosphere. with, while cooling the catalyst layer, a method of producing a catalyst layer characterized that you remove the protruding portion. The method for producing a catalyst layer according to claim 6, further comprising an observation step of observing the surface of the catalyst layer and determining the presence or absence of the protruding portion before the removing step.   The method for producing a catalyst layer according to claim 6 or 7, wherein, in the removing step, the surface of the catalyst layer from which the protruding portion is removed is cleaned.   The method for producing a catalyst layer according to any one of claims 6 to 8, wherein the catalyst layer forming step and the removing step are sequentially performed while the base material is conveyed. The method for producing a catalyst layer according to any one of claims 6 to 9, wherein, in the removing step, only the protruding portion is removed.

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