JP2006216382A - Manufacturing method of membrane-catalyst layer assembly and manufacturing method of membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a membrane-catalyst layer assembly capable of reducing a time required for manufacturing it and of suppressing damage of a polymer electrolyte membrane; and to provide a membrane-electrode assembly using it. <P>SOLUTION: This manufacturing method of a membrane-catalyst layer assembly comprises: a step for forming a first catalyst layer 2C1 on at least either of principal surfaces of the polymer electrolyte membrane 1 by spraying catalyst layer-forming ink thereto; and a step for forming a second catalyst layer 2C2 on the first catalyst layer 2C1 by transcription. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a membrane-catalyst layer assembly and a method for producing a membrane-electrode assembly using the same.

  In a conventional polymer electrolyte fuel cell, a membrane-electrode assembly (MEA) (hereinafter abbreviated as MEA) is formed, for example, in a state of adhering to both main surfaces of the polymer electrolyte membrane. The gas diffusion layer is formed on the outer surface of the catalyst layer. In addition, a structure in which catalyst layers are formed on both main surfaces of the polymer electrolyte membrane is generally called a membrane-catalyst layer assembly (for example, a structure excluding the gas diffusion layer in the MEA). The membrane-catalyst layer assembly is generally produced by spraying, applying, filtering and transferring the catalyst layer forming ink onto the surface of the polymer electrolyte membrane (for example, paragraph [0046] in Patent Document 5). Thru [0050]).

Further, in the formation of this catalyst layer, a polymer electrolyte fuel cell having a multilayer structure of the catalyst layer has been proposed in order to improve the performance of the polymer electrolyte fuel cell (for example, Patent Documents 1 to 4). 4). In this case, as a method of forming a catalyst layer having a multilayer structure, a method of applying the catalyst layer forming ink a plurality of times is disclosed. Furthermore, it is disclosed that the thickness of each catalyst layer should be adjusted based on the function of each catalyst layer (see, for example, paragraphs 2 to [0052] of Patent Document 2).
JP 2001-338654 A Japanese Patent Laid-Open No. 2002-8679 JP 2002-8678 A JP 2002-15743 A JP 2002-110202 A

  On the other hand, the method for forming a catalyst layer on a polymer electrolyte membrane, that is, the method for producing a membrane-catalyst layer assembly, is considered to be a coating method from the viewpoint of simplicity of operation. However, the study has not been sufficiently conducted from the viewpoint of improving the required time and yield in manufacturing (for example, see paragraph [0048] of Patent Document 5). In other words, the manufacturing method of the membrane-catalyst layer assembly does not sufficiently take into account the time required for manufacturing, damage to the polymer electrolyte membrane accompanying the manufacturing method, and defective formation of the catalyst layer. There is room.

  Accordingly, the present invention has been made to solve the above-described problems, and can reduce the time required for production and can suppress damage to the polymer electrolyte membrane. It aims at providing the manufacturing method of a layered assembly, and the manufacturing method of a membrane-electrode assembly using the same.

  As a result of intensive studies to achieve the above object, the present inventors have made a method for forming a catalyst layer by spraying a catalyst layer forming ink on the main surface of a polymer electrolyte membrane (hereinafter referred to as a spray method). Compared with other methods such as a method of forming a catalyst layer by transferring a pre-formed catalyst layer onto the main surface of the polymer electrolyte membrane (hereinafter referred to as a transfer method), a doctor blade method, etc. It has been found that the internal electrical resistance of the electrolyte fuel cell is reduced. Although the details of obtaining this result have not been clearly elucidated, the present inventors have suppressed the swelling of the polymer electrolyte membrane by evaporating a suitable amount of the solvent in the ink during spraying. In addition to improving the adhesion of the catalyst layer to the polymer electrolyte membrane, the reduced proton conduction resistance at the interface between the polymer electrolyte membrane and the catalyst layer contributes to the reduction of internal electrical resistance. I guess. However, the spray method has a small amount of catalyst layer formation per hour, and it takes a considerable time to stack the catalyst-forming ink to a predetermined thickness.

  On the other hand, the transfer method is, for example, a process in which a catalyst layer is placed on a polymer electrolyte membrane and hot-pressed. Therefore, compared with other methods such as a spray method and a doctor blade method, the transfer method can be performed in a shorter time. Since a catalyst layer can be formed on the molecular electrolyte membrane, it is effective from the viewpoint of mass production. However, according to the study of the present inventor, it has been found that high adhesion between the polymer electrolyte membrane and the catalyst layer as in the spray method cannot be obtained, and the insulation property of the polymer electrolyte membrane is lowered. . Although the details of obtaining this result are not clearly elucidated, the present inventors presume that the polymer electrolyte membrane is slightly damaged during transfer.

  Based on these examination results, in order to solve the above-mentioned problems, the method for producing a membrane-catalyst layer assembly of the present invention comprises spraying catalyst layer forming ink on at least one main surface of the polymer electrolyte membrane. Forming a first catalyst layer, and forming a second catalyst layer on the first catalyst layer by transfer (claim 1). With such a configuration (manufacturing procedure), it is possible to suppress damage to the polymer electrolyte membrane by the step of spraying the catalyst layer forming ink to form the first catalyst layer, and the first catalyst. The time required for production can be shortened by the step of forming the second catalyst layer by transfer on the layer. That is, the present invention sufficiently reduces the disadvantages of conventional membrane-catalyst layer assembly production methods such as the transfer method, spray method, and doctor blade method, and is particularly advantageous for mass production of membrane-catalyst layer assemblies. is there.

In the present invention, it is preferable that the content ratio of the hydrogen ion conductive polymer electrolyte is higher in the first catalyst layer than in the second catalyst layer. Here, in the present invention, the “content ratio of the hydrogen ion conductive polymer electrolyte in the catalyst layer” refers to [(total mass W _{P of the} hydrogen ion conductive polymer electrolyte contained in the catalyst layer) / (the catalyst Total mass of layer W _L )]. By adopting such a configuration, the density of reaction sites can be increased in the vicinity of the polymer electrolyte membrane, and the drainage can be increased as the distance from the polymer electrolyte membrane increases, so the performance of the polymer electrolyte fuel cell can be improved. Can be improved.

  In the present invention, it is preferable that the thickness of the first catalyst layer is 1 μm or more and 6 μm or less. With this configuration, it is possible to more reliably suppress defective formation of the catalyst layer. Thus, if the thickness of the 1st catalyst layer is 1 micrometer or more, the insulation of a polymer film can be ensured more reliably at the time of transcription. Further, when the thickness of the first catalyst layer is 6 μm or less, the tendency that the transfer substrate can be more easily peeled during transfer increases. Moreover, in this case, the time for producing the first catalyst layer can be more reliably shortened, which is advantageous for mass production.

  Furthermore, in the present invention, it is preferable that the thickness of the first catalyst layer is not less than 1/10 and not more than 1/3 of the entire thickness of the second catalyst layer. With this configuration, it is possible to more reliably suppress defective formation of the catalyst layer. At this time, if the thickness of the first catalyst layer is approximately one-tenth or more of the total thickness of the second catalyst layer, the insulating property of the polymer film can be more reliably ensured during transfer. Further, when the ratio is 1/3 or less, a tendency that the transfer substrate can be easily peeled at the time of transfer increases. In this case, the entire catalyst layer does not become thick, and the gas diffusibility can be ensured more reliably.

In the present invention, in the step of forming the first catalyst layer, two or more catalyst layer forming inks may be sequentially sprayed to form a first catalyst layer composed of a plurality of layers. . With such a configuration, various properties such as “content ratio of hydrogen ion conductive polymer electrolyte” of the catalyst layer forming ink can be adjusted, and the properties of the first catalyst layer can be adjusted more finely. Can do. Here, the “content ratio of the hydrogen ion conductive polymer electrolyte” of the catalyst layer forming ink is [(total mass W _{P of the} hydrogen ion conductive polymer electrolyte contained in the catalyst forming ink) / (the catalyst formation). The total ink mass W _I )].

  Furthermore, in the present invention, in the step of forming the first catalyst layer composed of a plurality of layers by sequentially spraying two or more types of inks for forming the catalyst layer, the content ratio of the hydrogen ion conductive polymer electrolyte is lower in the lower layer. It should be high (claim 6).

  Here, in the present invention, the “lower layer” in the case of forming the first catalyst layer composed of a plurality of layers by sequentially spraying two or more types of catalyst layer forming inks means that the first catalyst layer has two types. The layer on the side close to the polymer electrolyte membrane is assumed on the assumption that the above catalyst layer forming ink is formed by spraying sequentially.

In addition, the state that “the lower the content of the hydrogen ion conductive polymer electrolyte is higher in the lower layer” is based on the premise that the first catalyst layer is formed by sequentially spraying two or more types of catalyst layer forming inks. The catalyst layer forming ink used on the side closer to the polymer electrolyte membrane of the catalyst layer where the hydrogen ion conductive polymer electrolyte content ratio (W _P / W _I ) of the catalyst forming ink is farther from the polymer electrolyte membrane The state is finally smaller than the catalyst layer forming ink used in the above. That is, when the formed first catalyst layer is viewed as a whole, the mass ratio (W _P / W _I ) is generally reduced from the side closer to the polymer electrolyte membrane to the side farther from the polymer electrolyte membrane. For example, the mass ratio (W _P / W _I ) is monotonically decreasing from the side closer to the polymer electrolyte membrane to the side farther from the polymer electrolyte membrane. When three or more types of catalyst-forming inks are used, the catalyst-forming ink used between the lowermost layer and the uppermost layer has a mass ratio (W _P / W) of any of the catalyst-forming inks used before and after. a _I) and the mass ratio of the same value (W _P / W _I) may be. Furthermore, although the catalyst layer forming ink used on the side closer to the polymer electrolyte membrane as a whole is smaller than the catalyst layer forming ink used on the side far from the polymer electrolyte membrane, In some catalyst-forming inks, the mass ratio (W _P / W _I ) of the catalyst-forming ink used on the upper layer side may be larger than the mass ratio (W _P / W _I ) of the catalyst-forming ink used on the lower layer side. May be. However, from the viewpoint of gas diffusibility or drainage, the catalyst-forming ink should be used so that the mass ratio (W _P / W _I ) decreases from the lowermost layer to the uppermost layer, or the lowermost layer and the uppermost layer It is more preferable that the catalyst forming ink used during the period is the same mass ratio (W _P / W _I ) as the mass ratio (W _P / W _I ) of any of the catalyst forming inks used before and after. . With this configuration, the density of reaction sites can be increased in the vicinity of the polymer electrolyte membrane in the first catalyst layer, and the gas diffusibility or drainage can be increased as the distance from the polymer electrolyte membrane increases. The performance of the molecular electrolyte fuel cell can be improved.

  Moreover, in this invention, you may further have the step of forming one or more 3rd catalyst layers on the said 2nd catalyst layer (Claim 7). Here, in the present invention, as the “third catalyst layer”, for example, a catalyst layer containing at least a catalyst (such as Pt) -supporting carbon (conductive carbon), a hydrogen ion conductive polymer electrolyte, and a catalyst (such as Pt) ) Catalyst layer containing at least supported carbon (conductive carbon), water repellent material and catalyst (such as Pt) Catalyst layer containing at least supported carbon (conductive carbon), water repellent material, hydrogen ion conductive polymer electrolyte and catalyst ( Pt and the like) and a catalyst layer containing at least supported carbon (conductive carbon). Furthermore, in the present invention, the “third catalyst layer” includes a layer made of a water repellent material and conductive carbon (carbon not supporting a catalyst). With such a configuration, the electrode reaction area of the catalyst layer of the membrane-catalyst layer assembly can be adjusted, and various properties such as gas diffusibility, water repellency, and electron conductivity can be adjusted. The properties of the catalyst layer can be adjusted. In particular, when a layer composed of a water repellent material and conductive carbon (carbon not supporting a catalyst) is disposed as the third layer, the adhesion between the gas diffusion layer and the second catalyst layer is improved, and the gas diffusion It is possible to prevent damage to the second catalyst layer and / or the polymer electrolyte membrane behind it due to the surface roughness (existence of irregularities) of the layer. In this case, since no electrode reaction product water is generated because no catalyst is contained, gas diffusibility (particularly, gas diffusibility of the second catalyst layer) can be improved. Moreover, as the above-mentioned water repellent material, a substance having high chemical stability is preferable, for example, polytetrafluoroethylene (PTFE) or tetrafluoroethylene / hexafluoropropylene copolymer (FEP).

  Furthermore, in this invention, when it further has the step of forming one or more 3rd catalyst layers on the said 2nd catalyst layer, the content rate of a hydrogen ion conductive polymer electrolyte is so high that it is a lower layer. (Claim 8).

Here, in the present invention, the “lower layer” in the case of further comprising the step of forming one or more third catalyst layers on the second catalyst layer means that three or more catalyst layers are formed. Is the catalyst layer on the side close to the polymer electrolyte membrane. In addition, “the lower layer has a higher hydrogen ion conductive polymer electrolyte content” state means that three or more catalyst layers are formed, and the hydrogen ion conductive polymer of the formed catalyst layer. The catalyst content rate (W _P / W _L ) near the polymer electrolyte membrane is finally smaller than the catalyst layer far from the polymer electrolyte membrane, and the membrane-catalyst layer junction When viewed as a whole catalyst layer, the mass ratio (W _P / W _L ) of each catalyst layer is generally reduced from the side closer to the polymer electrolyte membrane to the side farther from the polymer electrolyte membrane. For example, the mass ratio (W _P / W _L ) may be monotonically decreasing from the side closer to the polymer electrolyte membrane to the side farther from the polymer electrolyte membrane. For example, the mass ratio (W _P / W _L ) of some adjacent catalyst layers may be in the same value. Furthermore, when comparing the mass ratio (W _P / W _L ) between some adjacent catalyst layers, the mass ratio (W _P / W _L ) of the upper catalyst layer is equal to the mass ratio of the lower catalyst layer (W _P / W _L ). It may be larger than (W _P / W _L ). However, from the viewpoint of gas diffusibility or drainage, the mass ratio (W _P / W _L ) decreases monotonically from the bottom layer to the top layer, or is disposed between the bottom layer and the top layer Among the layers, it is preferable that the mass ratio (W _P / W _L ) between some adjacent layers has the same value. With this configuration, the density of reaction sites in the vicinity of the polymer electrolyte membrane can be increased, and the gas diffusibility or drainage can be increased as the distance from the polymer electrolyte membrane increases. Can be improved. The performance of the gas-diffusible membrane-electrode assembly can also be adjusted by “forming one or more third catalyst layers on the second catalyst layer”.

  Further, the method for producing a membrane-electrode assembly of the present invention is provided above the second catalyst layer of the membrane-catalyst layer assembly produced by the method for producing a membrane-catalyst layer assembly according to claim 1. A gas diffusion layer is disposed (claim 9).

  Here, “disposing the gas diffusion layer above the second catalyst layer of the membrane-catalyst layer assembly” means that when the above-described third catalyst layer is not formed, the gas diffusion layer is the second catalyst layer. It arrange | positions in the state closely_contact | adhered on the catalyst layer. In the case of forming the third catalyst layer, the third catalyst layer is disposed between the second catalyst layer and the gas diffusion layer. In other words, this indicates that the gas diffusion layer is disposed in close contact with the third catalyst layer. Here, “arrange” means a case where adhesion is performed by heat treatment or the like, and a case where adhesion is performed by placing and pressing without adhesion.

  In order to produce a membrane-electrode assembly using the membrane-catalyst layer assembly produced by the above-described method for producing a membrane-catalyst layer assembly of the present invention, The time required for manufacturing the membrane-electrode assembly can be shortened, and damage to the polymer electrolyte membrane can be suppressed.

  As described above, the method for producing a membrane-catalyst layer assembly of the present invention and the method for producing a membrane-electrode assembly using the same can reduce the time required for production, and the polymer electrolyte membrane. There is an effect that damage can be suppressed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a partially exploded perspective view showing the structure of a main part of a polymer electrolyte fuel cell produced by a preferred embodiment of a method for producing a membrane-catalyst layer assembly and a method for producing a membrane-electrode assembly of the present invention. FIG.

  As shown in FIG. 1, a polymer electrolyte fuel cell 100 is configured by stacking cells 10.

  Although not shown, a current collector plate, an insulating plate, and an end plate are attached to the outermost layers at both ends of the cell 10, and the cell 10 has a fastening bolt (not shown) and a nut inserted through the bolt hole 11 from both ends. It is constructed by fastening with.

  The cell 10 is configured by sandwiching an MEA-gasket assembly (hereinafter abbreviated as MEA assembly) 7 between a pair of an anode separator 9A and a cathode separator (both are collectively referred to as a separator) 9C. The separator is made of a conductive material and constitutes a part of the cathode side or anode side electrode.

  The MEA assembly 7 is configured by sandwiching a polymer electrolyte membrane extending around the peripheral edge of the MEA 5 between a pair of fluororubber gaskets 6. Therefore, the MEA 5 is exposed on both surfaces of the central opening of the gasket 6.

  In the peripheral portions of the separators 9A and 9C and the MEA assembly 7, a reducing agent gas manifold holes 12, 22, 32 and an oxidizing agent gas are formed to form a pair of manifolds through which the reducing agent gas and the oxidizing agent gas circulate. Manifold holes 13, 23, 33 are formed. In addition, water manifold holes 14, 24, and 34 that form a pair of manifolds through which water flows are also drilled.

  A groove-like reducing agent gas passage 21 is formed on the inner main surface of the anode separator 9A so as to connect the pair of reducing agent gas manifold holes 22 and 22 together.

  On the inner main surface of the cathode separator 9C, a groove-like oxidant gas flow path 31 is formed so as to connect the pair of oxidant gas manifold holes 33, 33.

  Further, in the same manner as the reducing agent gas passage 21 or the oxidizing gas passage 31, grooves are formed on the outer main surface, that is, the rear surface of the separators 9A and 9C so as to connect the pair of water manifold holes 24 and 34. A water channel (not shown) is formed. As a result, when the cell 10 is stacked, these manifold holes are stacked to form a pair of manifolds of oxidant gas, reductant gas, and water. The flow paths of the oxidant gas, the reductant gas, and the water are branched from one manifold, that is, from the supply side manifold to the flow paths 21 and 31 formed in the separator and a water flow path (not shown). , Each of the other manifolds, ie, the discharge side manifold. The oxidant gas and the reductant gas are exposed to the MEA 5 exposed at the center of the MEA assembly 7 in the reductant gas flow path 21 or the oxidant gas flow path 31, respectively, and cause an electrochemical reaction. Further, since water flows between the back surfaces of the separators 9A and 9C, that is, between the adjacent cells 10, the polymer electrolyte fuel cell is maintained at a predetermined temperature suitable for the electrochemical reaction by the heat transfer capability of water. Can do.

Here, FIG. 2A is a side view of the MEA, and FIG. 2B is a plan view of the MEA.
The MEA 5 is mainly composed of a polymer electrolyte membrane 1 made of an ion exchange membrane that selectively permeates hydrogen ions and a carbon powder carrying a platinum group metal catalyst formed so as to sandwich the polymer electrolyte membrane 1. A pair of anode-side catalyst layer 2A and cathode-side catalyst layer 2C, and a pair of anode-side gas diffusion layer 4A and cathode-side gas diffusion layer 4C disposed on the outer surfaces of the pair of catalyst layers 2A, 2C are provided. It is configured. The gas diffusion layers 4A and 4C are configured to have both air permeability and electronic conductivity. For example, it has a porous structure.
The cathode side catalyst layer 2C, the cathode side gas diffusion layer 4C and the cathode separator 9C constitute the cathode.

  Further, the anode side catalyst layer 2A, the anode side gas diffusion layer 4A and the anode separator 9A constitute an anode.

  Next, the operation of the polymer electrolyte fuel cell 100 configured as described above will be described. An oxidant gas is branched and supplied to each cell 10 via the oxidant flow path 30. In each cell 10, oxidant gas is supplied to the cathode. Here, the cathode side gas diffusion layer 4C is exposed. Similarly, hydrogen or a reducing agent gas containing hydrogen is supplied to the anode. Here, the anode side gas diffusion layer 4 </ b> A is exposed via the reducing agent channel 40. The oxidant gas passes through the cathode side gas diffusion layer 4C and reaches the cathode side catalyst layer 2C. Similarly, the reducing agent gas also passes through the anode side gas diffusion layer 4A and reaches the anode side catalyst layer 2A.

  Here, the cathode-side catalyst layer 2C and the anode-side catalyst layer 2A are electrically connected via the cathode separator 9C, the anode separator 9A, a current collector (not shown), and an external electric circuit (not shown). When the circuit is configured, hydrogen is ionized in the anode catalyst layer 2A. Hydrogen ions permeate the polymer electrolyte membrane 1 and combine with oxygen ions in the cathode side catalyst layer 2C to generate water. Further, electrons generated in the anode side catalyst layer 2A due to hydrogen ionization flow through an external electric circuit (not shown) via the anode side gas diffusion layer 4A to generate an electric output.

  Here, a method for forming the catalyst layers 2A and 2C on the polymer electrolyte membrane 1, that is, a method for producing the membrane-catalyst layer assembly 3 (a preferred embodiment of the method for producing the membrane-catalyst layer assembly of the present invention). Will be described. Here, for the sake of convenience, the manufacturing process of the cathode side catalyst layer 2C is shown and described. The anode side catalyst layer 2A is also formed in the same manner as the cathode side catalyst layer 2C, but the description thereof is omitted here.

  FIG. 3A to FIG. 3D are diagrams schematically showing a manufacturing process of the cathode catalyst layer of the membrane-catalyst layer assembly.

Here, the polymer electrolyte membrane 1 preferably includes a membrane having an ion exchange function of selectively permeating hydrogen ions. Further, as such a membrane, a polymer electrolyte membrane having a structure in which —CF ₂ — is a main chain skeleton and a sulfonic acid group is introduced at the end of a side chain is preferably exemplified. As a membrane having such a structure, for example, a perfluorocarbon sulfonic acid membrane {for example, Nafion 112 (registered trademark) manufactured by DUPONT} is preferably exemplified.

  Further, the catalyst layer forming ink is prepared as follows. The electrode catalyst powder mixed with the catalyst-forming ink for the cathode side catalyst layer 2C, for example, carries 25 wt% of platinum particles having an average particle diameter of about 3 nm on Ketjen Black EC (manufactured by AKZO Chemie). Use catalyst powder. Examples of the electrode catalyst powder mixed with the catalyst-forming ink for the anode side catalyst layer 2A include, for example, ketjen black EC (manufactured by AKZO Chemie, trade name), platinum-ruthenium alloy particles having an average particle diameter of about 3 nm. A catalyst powder supporting 25 wt% (for example, Pt: Ru = 1: 1 by mass ratio) is used. These electrode catalyst powders are dispersed in isopropanol, and then an ethyl alcohol dispersion (for example, trade name “Flemion FSS-1” manufactured by Asahi Glass Co., Ltd.) of a hydrogen ion conductive polymer electrolyte (for example, perfluorocarbon sulfonic acid powder). ).

  Next, as shown in FIG. 3A, the catalyst layer forming ink is spray-coated by the spray device 200 to form the first catalyst layer 2 </ b> C <b> 1 on the main surface of the polymer electrolyte membrane 1. Although not shown, when spray coating is performed, the polymer electrolyte membrane 5A is covered with a mask having an opening having a shape corresponding to the planar shape of the first catalyst layer 2C1, and the catalyst layer is formed except for the required portion. It is protected from ink sticking. As a result, the sprayed catalyst layer forming ink has better adhesion to the surface of the polymer electrolyte membrane 1 as compared with the transfer and doctor blade methods, so the polymer electrolyte membrane 1 and the first catalyst layer 2C1 The proton transfer interface performance can be improved.

  On the other hand, as shown in FIG. 3B, the catalyst-forming ink is applied onto the transfer substrate P to form the second catalyst layer 2C2. The second catalyst layer 2C2 is formed in the same planar shape as the first catalyst layer 2C1. As the transfer substrate P, a PP sheet or a PTEF sheet can be suitably used. In addition, the components do not elute into the catalyst layer due to adhesion of the catalyst layer or hot pressing, and the peelability after transfer is good. Materials can be used.

  Next, as shown in FIG. 3 (c), the second catalyst layer 2C2 is overlaid on the first catalyst layer 2C1, and hot pressing (for example, pressure 1 MPa, temperature 140 ° C., time 30 minutes) Thus, the cathode side catalyst layer 2C is formed.

  Then, as shown in FIG. 3D, the transfer substrate P is peeled off, and the second catalyst layer 2C2 is transferred onto the first catalyst layer 2C1. Thereby, the catalyst layer 2C in which the first catalyst layer 2C1 and the second catalyst layer 2C2 are joined is formed.

  As described above, the time required for the step of forming the second catalyst layer 2C2 by transferring it to the first catalyst layer 2C1 is shorter than the time required for the step of forming the entire catalyst layer 2C by spray coating. Since time is sufficient, the time for manufacturing the membrane-catalyst layer assembly 3 can be shortened.

  The properties of the ink for forming the catalyst layer of the cathode-side first catalyst layer 2C1 and the cathode-side second catalyst layer 2C2 may not be the same. For example, the catalyst layer forming ink may be prepared so that the content ratio of the hydrogen ion conductive polymer electrolyte in the cathode-side first catalyst layer 2C1 is higher than that in the cathode-side second catalyst layer 2C2. That is, the catalyst layer forming ink in which the mixing ratio of the alcohol dispersion of the hydrogen ion conductive polymer electrolyte is increased as compared with the catalyst layer forming ink used for forming the cathode side second catalyst layer 2C2. It may be used for forming the layer 2C1. As a result, the density of the reaction sites of the cathode-side first catalyst layer 2C1 can be increased, and the drainage of the cathode-side second catalyst layer 2C2 can be increased (see Patent Document 2). The performance of the battery 100 is improved.

  Moreover, since no reaction water is generated on the anode side due to electrochemical reaction, the drainage performance is not required to be as high as that on the cathode side. Therefore, on the anode side, the properties of the catalyst layer forming ink of the anode side first catalyst layer 2A1 and the anode side second catalyst layer 2A2 may remain the same.

  Next, a method for manufacturing MEA 5 (a preferred embodiment of a method for manufacturing a membrane-electrode assembly of the present invention) will be described.

  The MEA 5 of the present invention is manufactured using the membrane-catalyst layer assembly 3 described above. That is, as shown in FIG. 2A, the MEA 5 is manufactured by forming the gas diffusion layers 4A and 4C on the catalyst layers 2A and 2C.

  The gas diffusion layers 4A and 4C are made of a porous body having a large number of fine pores. As a result, when the gas enters the hole, the gas diffuses and easily reaches the catalyst layers 2A and 2C. In the present embodiment, water-repellent carbon paper (trade name (TGP-H-090) manufactured by TORAY, thickness: 270 μm) is used. The water repellent treatment is performed, for example, by immersing the carbon paper in an aqueous dispersion of polytetrafluoroethylene (PTFE) and then performing a drying treatment. Further, instead of carbon paper, carbon cloth or carbon felt made of carbon fiber, carbon powder, organic binder or the like may be used as the gas diffusion layer. Then, the carbon paper is hot-pressed (for example, pressure 0.5 MPa, temperature 135 ° C., time 5 minutes) so as to be bonded onto the catalyst layers 2A and 2C to form gas diffusion layers 4A and 4C. . As a result, the time required for forming the catalyst layers 2A and 2C on the polymer electrolyte membrane 1 can be shortened, so that the time for manufacturing the MEA 5 can be shortened.

  As described above, the present invention can suppress damage to the polymer electrolyte membrane by the step of spraying the catalyst layer forming ink to form the first catalyst layer, and transfer the first catalyst layer onto the first catalyst layer. The time required for production can be shortened by the step of forming the second catalyst layer. That is, the present invention sufficiently reduces the disadvantages of conventional membrane-catalyst layer assembly production methods such as the transfer method, spray method, and doctor blade method, and is particularly advantageous for mass production of membrane-catalyst layer assemblies. is there.

As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment. For example, in the step of forming the first catalyst layer 2C1, two or more types of catalyst layer forming inks may be sequentially sprayed to form the first catalyst layer 2C1 composed of a plurality of layers. With this configuration, various properties such as “content ratio of hydrogen ion conductive polymer electrolyte” of the catalyst layer forming ink can be adjusted, and the properties of the first catalyst layer can be adjusted more finely. it can. Here, the “content ratio of the hydrogen ion conductive polymer electrolyte” of the catalyst layer forming ink is [(total mass W _{P of the} hydrogen ion conductive polymer electrolyte contained in the catalyst forming ink) / (the catalyst formation). The total ink mass W _I )].

In the step of forming the first catalyst layer 2C1 composed of a plurality of layers by sequentially spraying two or more types of catalyst layer forming inks, the lower the layer, the higher the content ratio of the hydrogen ion conductive polymer electrolyte is. Here, the “lower layer” refers to a layer on the side close to the polymer electrolyte membrane 1 on the assumption that the first catalyst layer 2C1 is formed by sequentially spraying two or more types of catalyst layer forming inks. . In addition, the state where “the lower the hydrogen ion conductive polymer electrolyte content ratio is higher in the lower layer” means that the hydrogen ion conductive polymer electrolyte content ratio (W _P / W _I ) of the catalyst forming ink is higher in the catalyst layer. The state in which the catalyst layer forming ink used on the side closer to the molecular electrolyte membrane 1 is finally smaller than the catalyst layer forming ink used on the side far from the polymer electrolyte membrane 1 is shown. That is, when the formed first catalyst layer 2C1 is viewed as a whole, the mass ratio (W _P / W _I ) is generally reduced from the side closer to the polymer electrolyte membrane 1 to the side farther from it. . For example, the mass ratio (W _P / W _I ) is monotonously decreasing from the side closer to the polymer electrolyte membrane 1 to the side farther from it. When three or more types of catalyst-forming inks are used, the catalyst-forming ink used between the lowermost layer and the uppermost layer has a mass ratio (W _P / W) of any of the catalyst-forming inks used before and after. a _I) and the mass ratio of the same value (W _P / W _I) may be. Furthermore, although the catalyst layer forming ink used on the side closer to the polymer electrolyte membrane 1 as a whole is finally smaller than the catalyst layer forming ink used on the side far from the polymer electrolyte membrane 1, In some catalyst forming inks, the mass ratio (W _P / W _I ) of the catalyst forming ink used on the upper layer side is larger than the mass ratio (W _P / W _I ) of the catalyst forming ink used on the lower layer side There may be. However, from the viewpoint of gas diffusibility or drainage, the catalyst-forming ink should be used so that the mass ratio (W _P / W _I ) decreases from the lowermost layer to the uppermost layer, or the lowermost layer and the uppermost layer It is more preferable that the catalyst forming ink used during the period is the same mass ratio (W _P / W _I ) as the mass ratio (W _P / W _I ) of any of the catalyst forming inks used before and after. . With this configuration, in the same manner as described above, in the first catalyst layer 2C1, the density of reaction sites is increased in the vicinity of the polymer electrolyte membrane 1, and gas diffusibility or drainage is increased as the distance from the polymer electrolyte membrane 1 increases. Therefore, the performance of the polymer electrolyte fuel cell 100 can be improved.

  Furthermore, you may further have the step of forming one or more 3rd catalyst layers (not shown) on the 2nd catalyst layer 2C2 by transcription | transfer, spraying, or application | coating. Here, examples of the “third catalyst layer” include a catalyst layer containing at least a catalyst (such as Pt) -supporting carbon (conductive carbon), a hydrogen ion conductive polymer electrolyte, and a catalyst (such as Pt) -supporting carbon (conductive). Catalyst layer containing at least a conductive carbon), a water repellent material and a catalyst layer containing a catalyst (such as Pt) supported carbon (conductive carbon), a water repellent material, a hydrogen ion conductive polymer electrolyte, and a catalyst (such as Pt) supported carbon Examples thereof include a catalyst layer containing at least (conductive carbon). Furthermore, the “third catalyst layer” may be a layer composed of a water repellent material and conductive carbon (carbon not supporting a catalyst). With such a configuration, the electrode reaction area of the catalyst layer of the membrane-catalyst layer assembly can be adjusted, and various properties such as gas diffusibility, water repellency, and electron conductivity can be adjusted. The properties of the catalyst layer can be adjusted. In particular, when a layer composed of a water repellent material and conductive carbon (carbon not supporting a catalyst) is disposed as the third layer, the adhesion between the gas diffusion layer and the second catalyst layer is improved, and the gas diffusion It is possible to prevent damage to the second catalyst layer 2C2 and / or the polymer electrolyte membrane 1 in the back thereof due to the surface roughness (existence of irregularities) of the layer. In this case, since no electrode reaction product water is generated because no catalyst is contained, gas diffusibility (particularly, gas diffusibility of the second catalyst layer) can be improved. Moreover, as the above-mentioned water repellent material, a substance having high chemical stability is preferable, for example, polytetrafluoroethylene (PTFE) or tetrafluoroethylene / hexafluoropropylene copolymer (FEP).

And when it further has the step of forming one or more 3rd catalyst layers on the 2nd catalyst layer 2C2, it is good that the content rate of a hydrogen ion conductive polymer electrolyte is so high that it is a lower layer. Here, the “lower layer” in the case of further including the step of forming one or more third catalyst layers on the second catalyst layer 2C2 is based on the premise that three or more catalyst layers are formed. The catalyst layer on the side close to the polymer electrolyte membrane 1 is said. In addition, “the lower layer has a higher hydrogen ion conductive polymer electrolyte content” state means that three or more catalyst layers are formed, and the hydrogen ion conductive polymer of the formed catalyst layer. The catalyst content ratio (W _P / W _L ) of the electrolyte is finally smaller in the catalyst layer closer to the polymer electrolyte membrane 1 than in the catalyst layer farther from the polymer electrolyte membrane 1, and the membrane-catalyst When viewed as the entire catalyst layer of the layered assembly 3, the mass ratio (W _P / W _L ) of each catalyst layer is schematically reduced from the side closer to the polymer electrolyte membrane 1 to the side farther from it. For example, the mass ratio (W _P / W _L ) may be monotonically decreasing from the side closer to the polymer electrolyte membrane 1 to the side farther from it. For example, the mass ratio (W _P / W _L ) of some adjacent catalyst layers may be in the same value. Furthermore, when comparing the mass ratio (W _P / W _L ) between some adjacent catalyst layers, the mass ratio (W _P / W _L ) of the upper catalyst layer is equal to the mass ratio of the lower catalyst layer (W _P / W _L ). It may be larger than (W _P / W _L ). However, from the viewpoint of gas diffusibility or drainage, the mass ratio (W _P / W _L ) decreases monotonically from the bottom layer to the top layer, or is disposed between the bottom layer and the top layer Among the layers, it is preferable that the mass ratio (W _P / W _L ) between some adjacent layers has the same value. With this configuration, the density of reaction sites in the vicinity of the polymer electrolyte membrane 1 can be increased, and the gas diffusibility or drainage can be increased as the distance from the polymer electrolyte membrane 1 increases, so that the polymer electrolyte fuel cell 100 performance can be improved. Moreover, the performance of the gas diffusible membrane-electrode assembly 5 can be adjusted by “forming one or more third catalyst layers on the second catalyst layer”.

  Hereinafter, although the Example is given and the manufacturing method of the membrane-electrode assembly of this invention is demonstrated in more detail, this invention is not limited to these Examples at all.

  The membrane-catalyst layer assembly 3 in which the thickness t1 + t2 of the catalyst layer 2C is 20 μm is used in Examples S1 to S7 using the thickness t1 of the first catalyst layer 2C1 and the thickness t2 of the second catalyst layer 2C2 as parameters. Manufactured. Further, as Comparative Example T1, a membrane-catalyst assembly formed only by the transfer method, that is, by forming only the second catalyst layer 2C2 without forming the first catalyst layer 2C1 was manufactured.

  Then, performance tests were conducted using 10 samples each of Examples S1 to S7 and Comparative Example T1.

  FIG. 4 is a table showing the performance test results of the membrane-catalyst layer assembly of this example. In the table, the evaluation item N is that when the transfer substrate P was peeled from the catalyst layer 2C, a part of the catalyst layer 2C was adhered to the transfer substrate P, resulting in defective production due to incomplete peeling. It is a number indicating the number of times, that is, the difficulty of peeling off the transfer substrate P. The evaluation item E is a voltage of 0.2 V passing through the membrane-catalyst layer assembly measured by the chronoamperometric method (CA method) for the membrane-catalyst layer assembly 3 extracted from each example. Is a numerical value indicating the current value per unit area 10 minutes after application of, that is, the cross-leakage current per unit area of the membrane-catalyst layer assembly 3 that increases in accordance with the degree of damage of the polymer electrolyte membrane. is there.

  As shown in the table, Examples S1 to S5 of the membrane-catalyst layer assembly 3 having a thickness ratio t1 / (t1 + t2) of 1/10 or more and 1/3 or less are difficult to peel off the transfer substrate P. The occurrence frequency of defects was low, and in the cross-leakage current E, there was almost no decrease in insulation, which proved more suitable as a method for manufacturing the membrane-catalyst layer assembly 3. Alternatively, it was found that the thickness t1 of the first catalyst layer 2C1 is more preferably 1 μm or more and 6 μm or less as a method for producing a membrane-catalyst layer assembly.

  Further, in the case of the comparative example T1, that is, in the case of the conventional transfer method, the occurrence of a defect did not appear in the separation difficulty N of the transfer substrate P, but the insulation performance decreased in the cross leak current E. I found out. This is presumed that the pressure at the time of transfer of the second catalyst layer 2C2 affects the polymer electrolyte membrane 1, and the polymer electrolyte membrane 1 is slightly damaged.

  Further, in the case of the thickness ratio t1 / (t1 + t2) = 1/15, that is, in Example S6, the first catalyst layer 2C1 is thin, and thus there is a problem in the separation difficulty N of the transfer substrate P. However, in the cross leakage current E, it was found that the insulating property was lowered. This is because, since the first catalyst layer 2C1 is thin, the pressure during the transfer of the second catalyst layer 2C2 affects the polymer electrolyte membrane 1, and the polymer electrolyte membrane 1 is slightly damaged. Inferred.

  Further, in the case of the thickness ratio t1 / (t1 + t2) = 1/2, that is, in the case of Example S7, the first catalyst layer 2C1 is thick, so that no decrease in the insulation property appears in the cross leak current E. However, it was found that the occurrence frequency of defects was high in the separation difficulty N of the transfer substrate P. This is because since the first catalyst layer 2C1 is thick, the thickness variation becomes large, and the pressure during the transfer is not uniformly applied. When the second catalyst layer 2C2 is peeled off, the first catalyst layer 2C1 is separated from the first catalyst layer 2C1. It was inferred that the bondability with the catalyst layer 2C2 of No. 2 deteriorated and was easily peeled off.

  The method for producing a membrane-catalyst layer assembly of the present invention and the method for producing a membrane-electrode assembly using the same can reduce the time required for production and suppress damage to the polymer electrolyte membrane. It is useful as a method for producing a membrane-catalyst layer assembly and a method for producing a membrane-electrode assembly using the same.

1 is a partially exploded perspective view showing a structure of a main part of a polymer electrolyte fuel cell produced by a preferred embodiment of a method for producing a membrane-catalyst layer assembly and a method for producing a membrane-electrode assembly of the present invention. 2A is a side view of the MEA, and FIG. 2B is a plan view of the MEA. FIG. 3A to FIG. 3D are diagrams schematically showing a manufacturing process of the cathode catalyst layer of the membrane-catalyst layer assembly. It is a table | surface which shows the performance test result of the membrane-catalyst layer assembly of a present Example.

Explanation of symbols

1 polymer electrolyte membrane 2A anode side catalyst layer 2C cathode side catalyst layer 2A1 (anode side) first catalyst layer 2A2 (anode side) second catalyst layer 2C1 (cathode side) first catalyst layer 2C2 (cathode side) Second catalyst layer 3 Membrane-catalyst layer assembly 4A Anode side gas diffusion layer 4C Cathode side gas diffusion layer 5 Membrane-electrode assembly (MEA)
6 Gasket 7 MEA-Gasket Assembly 9A Anode Separator 9C Cathode Separator 10 Cell 11 Bolt Hole 12, 22, 32 Reductant Gas Manifold Hole 13, 23, 33 Oxidant Gas Manifold Hole 14, 24, 34 Water Manifold Hole 21 Reducing Agent Gas channel 31 Oxidant gas channel 100 Polymer electrolyte fuel cell 200 Spraying device S1 to S7 Examples T1 Comparative example t1 First catalyst layer thickness t2 Second catalyst layer thickness N Transfer substrate Peeling difficulty E Cross leak current P Substrate for transfer

Claims (9)

Spraying a catalyst layer forming ink on at least one main surface of the polymer electrolyte membrane to form a first catalyst layer;
Forming a second catalyst layer by transfer on the first catalyst layer. A method for producing a membrane-catalyst layer assembly.   The method for producing a membrane-catalyst layer assembly according to claim 1, wherein the first catalyst layer has a higher content ratio of the hydrogen ion conductive polymer electrolyte than the second catalyst layer.   The method for producing a membrane-catalyst layer assembly according to claim 1 or 2, wherein the thickness of the first catalyst layer is 1 µm or more and 6 µm or less.   The thickness of the said 1st catalyst layer is any one of Claims 1-3 whose thickness of the said whole 2nd catalyst layer is about 1/10 or less and 1/3 or less. A method for producing a membrane-catalyst layer assembly.   In the step of forming the first catalyst layer, two or more types of catalyst layer forming inks are sequentially sprayed to form a first catalyst layer consisting of a plurality of layers. The manufacturing method of the membrane-catalyst layer assembly of description.   The method for producing a membrane-catalyst layer assembly according to claim 5, wherein the lower the layer, the higher the content of the hydrogen ion conductive polymer electrolyte.   The method for producing a membrane-catalyst layer assembly according to any one of claims 1 to 6, further comprising a step of forming one or more third catalyst layers on the second catalyst layer.   The method for producing a membrane-catalyst layer assembly according to claim 7, wherein the lower layer has a higher content of hydrogen ion conductive polymer electrolyte. A gas diffusion layer is disposed above the second catalyst layer of the membrane-catalyst layer assembly produced by the method for producing a membrane-catalyst layer assembly according to any one of claims 1 to 6. The manufacturing method of a membrane-electrode assembly.

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