Method for producing catalyst layer-coated ion-exchange membrane

Abstract

This method for producing a catalyst layer-coated ion-exchange membrane comprises: a step A for obtaining a laminate having an ion-exchange membrane and a polygonal catalyst dispersion layer, by disposing a catalyst dispersion layer on a least one surface of the ion-exchange membrane, wherein the catalyst dispersion layer is formed by molding, into a prescribed shape, a catalyst dispersion that contains a catalyst and an ionomer resin and has a viscosity of 1-500 Pa·s at 25°C; and a step B for pressing the laminate that has been heated to a temperature of 100-200°C.

Description

Method for manufacturing ion exchange membrane with catalyst layer

[0001] The present disclosure relates to a method for producing a catalyst-layered ion exchange membrane.

[0002] In recent years, the use of hydrogen has been attracting attention from the viewpoint of utilizing renewable energy, etc. One method for producing hydrogen is solid polymer water electrolysis. In solid polymer water electrolysis, a catalyst-coated membrane (CCM) has recently been used as a component constituting a water electrolysis device. The catalyst-coated membrane (CCM) has an electrode catalyst layer containing a water electrolysis catalyst and a solid electrolyte (e.g., an ion-exchange membrane) formed on both sides of a solid polymer electrode membrane (PEM).

[0003] The catalyst layer for water electrolysis that the CCM has is, for example, a catalyst for H (hydrogen) generation, Pt / C (platinum supported carbon), O ２ IrO as an (oxygen) generating catalyst ２ A commonly known catalyst layer is formed by dispersing each of these catalysts in an ionomer resin, and then dispersing the resulting catalyst ink in water or a lower alcohol, applying the resulting catalyst ink to a release material, drying the material, and then thermally transferring the layer formed by the catalyst ink onto an ion exchange membrane.

[0004] Regarding the production of catalyst ink, Japanese Patent Laid-Open No. 2021-150174 discloses a process of dispersing catalyst-supported particles in a solvent using a jet mill to produce a catalyst dispersion, and a process of shearing a mixture of the catalyst dispersion and an ionomer to produce a catalyst ink for fuel cells. Furthermore, Japanese Patent No. 6310741 discloses a coating method in which a coating liquid is intermittently applied in a predetermined manner with the objective of obtaining a uniform coating shape, using a catalyst ink as the coating liquid.

[0005] In a catalyst-layered ion exchange membrane used in a solid polymer water electrolysis device, it is considered to be an important factor from the viewpoint of highly efficient hydrogen production that a catalyst layer with excellent shape stability is disposed at a predetermined position on the ion exchange membrane.

[0006] However, it is difficult to obtain a catalyst layer with excellent shape stability using a method in which a catalyst ink is wet-coated and dried, and then a catalyst layer is formed on an ion-exchange membrane by thermal transfer. Furthermore, while there is a demand for a polygonal catalyst layer shape from the viewpoint of the piping layout in a water electrolysis apparatus, forming a polygonal catalyst layer can result in edge defects. Edge defects in the catalyst layer significantly impair the efficiency of hydrogen production.

[0007] The present disclosure has been made in view of the above circumstances, and an object of one embodiment of the present disclosure is to provide a method for producing an ion exchange membrane with a catalyst layer, which is capable of forming a catalyst layer with excellent dimensional stability.

[0008] The present disclosure includes the following aspects.

[0009] <1> A method for producing an ion exchange membrane with a catalyst layer, comprising: Step A: disposing, on at least one surface of an ion exchange membrane, a catalyst dispersion formed into a predetermined shape from a catalyst dispersion containing a catalyst and an ionomer resin and having a viscosity of 1 Pa·s to 500 Pa·s at 25°C, to obtain a laminate having the ion exchange membrane and the catalyst dispersion layer; and Step B: pressing the laminate heated to a temperature of 100°C to 200°C. <2> The method for producing the ion exchange membrane with a catalyst layer according to <1>, wherein the catalyst dispersion contains an alcohol. <3> The method for producing the ion exchange membrane with a catalyst layer according to <2>, wherein the alcohol is at least one selected from ethanol and 2-propanol. <4> The method for producing an ion exchange membrane with a catalyst layer according to any one of <1> to <3>, wherein the catalyst contains aggregates having a secondary particle size of 10 μm or less. <5> The method for producing an ion exchange membrane with a catalyst layer according to any one of <1> to <4>, wherein in step A, the catalyst dispersion layer is formed on both sides of the ion exchange membrane to obtain the laminate. <6> The method for producing an ion exchange membrane with a catalyst layer according to any one of <1> to <5>, wherein in step A, a catalyst dispersion layer formed by molding the catalyst dispersion into a predetermined shape is disposed on one side of a substrate X to obtain a transfer material X having the substrate X and the catalyst dispersion layer, and then the catalyst dispersion layer of the transfer material X is superimposed on at least one side of the ion exchange membrane to obtain the laminate. <7> The method for producing an ion exchange membrane with a catalyst layer according to <6>, wherein in step A, the catalyst dispersion layer of the transfer material X is preheated to a temperature of 70°C to 180°C, and then the catalyst dispersion layer is superimposed on at least one side of the ion exchange membrane to obtain the laminate.

[0010] According to one embodiment of the present disclosure, there is provided a method for producing an ion exchange membrane with a catalyst layer, which is capable of forming a catalyst layer with excellent dimensional stability.

[0011] Fig. 1 is a schematic diagram illustrating an example of carrying out a series of steps including step A and step B, which include forming a catalyst dispersion layer on at least one side of an ion exchange membrane using a transfer substrate X. Fig. 2 is a schematic diagram showing an image inspection device for evaluating the dimensional stability of a catalyst layer. Fig. 3 is a photograph taken from above of the entire decagonal catalyst layer formed in Example 1. Fig. 4 is a photograph illustrating a portion with a disordered edge in the evaluation of dimensional stability.

[0012] The method for producing a catalyst-coated ion-exchange membrane according to the present disclosure will be described below. However, the method for producing a catalyst-coated ion-exchange membrane according to the present disclosure is not limited to the following embodiments and can be modified as appropriate within the scope of the present disclosure.

[0013] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​described before and after "to" as the lower and upper limits. In numerical ranges described in stages in the present disclosure, the upper limit value described in a certain numerical range may be replaced with the upper limit value of another numerical range described in stages, and the lower limit value described in a certain numerical range may be replaced with the lower limit value of another numerical range described in stages. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0014] In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect. In the present specification, the amount of each component in the composition means the total amount of the corresponding multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition.

[0015] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0016] In the present disclosure, "mass %" and "wt %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. In the present disclosure, "total solid content" refers to the total mass of the components excluding the solvent from the entire composition of the composition. The "solid content" may be solid or liquid at 25°C.

[0017] The method for producing an ion exchange membrane with a catalyst layer according to the present disclosure includes step A (hereinafter also simply referred to as "step A") of arranging, on at least one surface of an ion exchange membrane, a catalyst dispersion formed into a predetermined shape from a catalyst dispersion (hereinafter also referred to as "specific catalyst dispersion") that contains a catalyst and an ionomer resin and has a viscosity of 1 Pa·s to 500 Pa·s at 25°C, to obtain a laminate having the ion exchange membrane and the catalyst dispersion layer, and step B (hereinafter also simply referred to as "step B") of pressing the laminate heated to a temperature of 100°C to 200°C.

[0018] In addition to step A and step B, the method for producing a catalyst-layered ion exchange membrane according to the present disclosure may include other steps as necessary.

[0019] According to the method for producing a catalyst-coated ion-exchange membrane of the present disclosure, it is possible to obtain a catalyst-coated ion-exchange membrane having a catalyst layer with excellent dimensional stability. The reason for this is not clear, but is presumed to be as follows.

[0020] In the method for producing a catalyst-coated ion exchange membrane according to the present disclosure, a specific catalyst dispersion having a viscosity of 1 Pa·s to 500 Pa·s is used in step A, thereby enabling the production of a laminate having a catalyst dispersion layer of a predetermined shape at a predetermined position on the ion exchange membrane with good precision. That is, because the viscosity of the specific catalyst dispersion is high, at 1 Pa·s to 500 Pa·s, the resulting catalyst dispersion layer exhibits excellent edge shape stability in plan and cross-sectional views and has a desired thickness. Furthermore, because the viscosity of the specific catalyst dispersion is 1 Pa·s to 500 Pa·s, the load during drying of the catalyst dispersion layer is significantly reduced, thereby effectively suppressing deformation during the formation of the multiple catalyst dispersion layer on the ion exchange membrane and / or substrate X. Furthermore, in step B, the laminate is heated to a temperature of 100°C to 200°C during pressing. By pressing the heated laminate, dissolution of the ionomer resin can be controlled, effectively suppressing thermal deformation of the resulting catalyst layer. It is believed that this makes it possible to obtain a catalyst layer-attached ion exchange membrane having a catalyst layer with excellent dimensional stability.

[0021] On the other hand, Japanese Patent Application Laid-Open No. 2021-150174 and Japanese Patent No. 6310741 do not describe matters corresponding to steps A and B of the catalyst layer-attached ion exchange membrane according to the present disclosure.

[0022] Furthermore, catalysts for water electrolysis contain valuable rare metals such as platinum, but the method for producing a catalyst-coated ion exchange membrane according to the present disclosure has the advantage of not causing loss of rare metals because it is possible to use only the amount of specific catalyst dispersion necessary for forming the catalyst layer.

[0023] Furthermore, the method for producing a catalyst-coated ion exchange membrane according to the present disclosure has the advantage of not requiring a drying step. The drying process is a very energy-intensive process, and it is well known that it accounts for the majority of the heat costs in production. In other words, the drying process is a process that emits a large amount of carbon dioxide. In the first place, technology for efficiently extracting hydrogen has the perspective of reducing carbon dioxide and is a technology that can also contribute to the realization of carbon neutrality. For this reason, it is desirable that the method for achieving highly efficient hydrogen production itself can also suppress carbon dioxide emissions. The method for producing a catalyst-coated ion exchange membrane according to the present disclosure can also meet this demand.

[0024] Hereinafter, each step of the method for producing a catalyst-coated ion exchange membrane according to the present disclosure will be described.

[0025] [Step A] Step A is a step of arranging a catalyst dispersion layer, which is obtained by molding a catalyst dispersion (specific catalyst dispersion) containing a catalyst and an ionomer resin and having a viscosity of 1 Pa·s to 500 Pa·s at 25°C into a predetermined shape, on at least one surface of an ion exchange membrane to obtain a laminate having an ion exchange membrane and a catalyst dispersion layer.

[0026] In step A, a catalyst dispersion layer formed by molding a specific catalyst dispersion into a predetermined shape is disposed on at least one surface of the ion exchange membrane. The predetermined shape can be the shape of the catalyst layer desired when the catalyst-layered ion exchange membrane is incorporated into a water electrolysis device. The shape may be a circle or a polygon in plan view, and is preferably a convex polygon. Examples of the convex polygon include a quadrangle, pentagon, hexagon, heptagon, octagon, nonagon, decagon, decagon, decagon, decagon, and decagon. Some or all of the corners of the convex polygon may have a curve (in other words, a "radius").

[0027] The thickness of the catalyst dispersion layer of the laminate can be, for example, 0.5 μm to 50 μm. The area of ​​the catalyst dispersion layer of the laminate is not limited to its size and can be determined depending on the shape of the catalyst dispersion layer, its position on the ion exchange membrane, etc. The area of ​​the catalyst dispersion layer of the laminate can be, for example, 2 cm in plan view. ２ ~100,000 cm ２ It can be said that:

[0028] The ion exchange membrane is not particularly limited as long as it has proton conductivity and can be used in a solid polymer water electrolysis device. Examples of resins constituting the ion exchange membrane include perfluorosulfonic acid polymers and hydrocarbon polymers, with perfluorosulfonic acid polymers being preferred.

[0029] The ion exchange membrane may be in the form of a sheet or a strip, but from the viewpoint of productivity, a strip is preferred.

[0030] In step A, a laminate having an ion exchange membrane and a catalyst dispersion layer may be obtained by forming a specific catalyst dispersion into a predetermined shape directly on at least one side of the ion exchange membrane to form a catalyst dispersion layer.

[0031] In step A, from the viewpoint of productivity, a preferred mode for obtaining a laminate having an ion exchange membrane and a catalyst dispersion layer is to place a catalyst dispersion formed into a predetermined shape on one side of a substrate X to obtain a transfer material X having the substrate X and a catalyst dispersion layer, and then superimpose at least one side of the ion exchange membrane and the catalyst dispersion layer of the transfer material X to obtain a laminate.

[0032] Examples of methods for forming a catalyst dispersion layer on an ion exchange membrane or on a substrate X include a method of filling a polygonal mold with a specific catalyst dispersion, a printing method such as screen printing, inkjet printing, spray printing, a dispenser, a die coater, and the like. In one embodiment, it is preferable to use screen printing. By using screen printing, it is possible to form the formed specific dispersion layer into a better shape without damaging the edge portions.

[0033] When forming the catalyst dispersion layer, it is preferable to apply the specific catalyst dispersion in a predetermined shape onto the ion exchange membrane or onto the substrate X, and then dry it. As the drying means, for example, a general drying means such as hot air drying using an oven or the like, or drying using electromagnetic waves such as microwaves, can be used. The drying temperature may be set depending on the components, such as the solvent, contained in the specific catalyst dispersion. The drying temperature can be, for example, 30°C to 300°C. A realistic drying time is, for example, in the range of 1 second to 1 hour.

[0034] A mode (hereinafter referred to as "mode X") in which a catalyst dispersion layer formed by molding a specific catalyst dispersion into a predetermined shape is placed on one side of a substrate X to obtain a transfer material X having the substrate X and the catalyst dispersion layer, and then the catalyst dispersion layer of the transfer material X is superimposed on at least one side of an ion exchange membrane to obtain a laminate will be described. Mode X is a mode in which the laminate is obtained using a so-called transfer method.

[0035] The substrate X may be in the form of a sheet or a strip, but from the viewpoint of productivity, a strip is preferred.

[0036] The substrate X may be, for example, a fluororesin such as polytetrafluoroethylene (PTFE), or a film substrate such as polyethylene terephthalate (PET) or polypropylene (PP). The substrate X functions as a release agent.

[0037] A laminate obtained by superposing at least one surface of the ion exchange membrane and the catalyst dispersion layer of the transfer material X can be obtained, for example, by bringing at least one surface of the ion exchange membrane and the catalyst dispersion layer of the transfer material X into contact with each other and then applying pressure.

[0038] The pressing means may be a roll press, a flat press, etc. The pressure applied may be, for example, 0.1 MPa to 100 MPa.

[0039] In step A, it is preferable to form a catalyst dispersion layer on both sides of the ion exchange membrane to obtain a laminate. The catalyst dispersion layer may be formed on one side of the ion exchange membrane and then on the other side, or may be formed on both sides of the ion exchange membrane simultaneously.

[0040] When forming catalyst dispersions on both surfaces of the ion exchange membrane and disposing catalyst dispersion layers on them, it is preferable that the two catalyst dispersion layers facing each other via the ion exchange membrane have the same shape and that these two catalyst dispersion layers are disposed in positions where their outer peripheries overlap without misalignment to form a laminate via the ion exchange membrane. By performing step A, catalyst dispersion layers can be formed with high precision at desired positions on both surfaces of the ion exchange membrane.

[0041] (Specific Catalyst Dispersion) The specific catalyst dispersion used in step A contains a catalyst and an ionomer resin, and has a viscosity at 25°C of 1 Pa·s to 500 Pa·s.

[0042] <Viscosity> The viscosity of the specific catalyst dispersion is 1 Pa·s to 500 Pa·s, preferably 0.5 Pa·s to 700 Pa·s, and more preferably 0.3 Pa·s to 800 Pa·s at 25° C. When the viscosity of the specific catalyst dispersion is within the above range, the specific catalyst dispersion can be easily formed into a convex polygonal shape, and the productivity of the catalyst layer-equipped ion exchange membrane is further improved.

[0043] The viscosity of the specific catalyst dispersion can be adjusted by the types and amounts of components contained in the specific catalyst dispersion, such as the catalyst and ionomer resin.

[0044] The viscosity of the specific catalyst dispersion can be measured by a Brookfield viscometer.

[0045] <Catalyst> The specific catalyst dispersion contains a catalyst. The catalyst is not particularly limited as long as it is a catalyst used in a catalyst layer in solid polymer water electrolysis.

[0046] Suitable catalysts include simple noble metals such as platinum, iridium, ruthenium, rhodium, and palladium, alloys of platinum with manganese, iron, cobalt, nickel, copper, zinc, and the like, and ternary alloys of platinum, ruthenium, and manganese, iron, cobalt, nickel, copper, zinc, and the like. The catalyst may also be an oxide containing any of the above metals (for example, iridium oxide).

[0047] The catalyst may be supported on conductive particles. Suitable conductive particles include carbon particles such as oil furnace black, gas furnace black, acetylene black, thermal black, graphite, carbon nanotubes, and graphene, and metal oxide particles such as tin oxide. Examples of catalysts supported on conductive particles include platinum supported on carbon particles (hereinafter also referred to as platinum-supported carbon).

[0048] The catalyst preferably contains aggregates having an average secondary particle diameter of 20 μm or less, and more preferably 10 μm or less. By using a catalyst with a secondary particle diameter of 20 μm or less (preferably 10 μm or less), it becomes easier to control the viscosity of the specific catalyst dispersion to 1 Pa·s to 500 Pa·s, and the shape of the catalyst becomes uniform, contributing to improved performance of the catalyst-layered ion exchange membrane. The lower limit of the average secondary particle diameter is preferably, for example, 0.01 μm.

[0049] The agglomerates can be obtained, for example, by crushing a solid material made of the catalyst using a crushing means such as a ball mill, a jet mill, or a homogenizer.

[0050] The average secondary particle diameter is measured using a particle size distribution analyzer. A laser diffraction / scattering particle size distribution analyzer (product name: LA-960, manufactured by Horiba, Ltd.) can be used as the particle size distribution analyzer. Specifically, the catalyst dispersion to be measured is diluted in a measurement solvent to prepare a sample liquid, and the particle size distribution in the sample liquid is measured using the particle size distribution analyzer to measure the secondary particle diameter of the aggregates. The measurement is performed three times, and the arithmetic average of the obtained measured values ​​is calculated and rounded to one decimal place to obtain the average secondary particle diameter.

[0051] The catalyst content in the specific catalyst dispersion is preferably 1% by mass to 90% by mass, more preferably 5% by mass to 70% by mass, and even more preferably 7% by mass to 50% by mass, relative to the total amount of the specific catalyst dispersion.

[0052] <Ionomer Resin> The specific catalyst dispersion contains an ionomer resin. The ionomer resin preferably has proton conductivity.

[0053] Examples of ionomer resins include perfluorosulfonic acid-based polymers and hydrocarbon-based polymers.

[0054] The specific catalyst dispersion may contain only one type of ionomer resin, or may contain two or more types of ionomer resins.

[0055] Commercially available ionomer resins may be used, such as Nafion (registered trademark, manufactured by Chemours), Aquivion (registered trademark, manufactured by Solvay), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), and Fumion F (registered trademark, manufactured by FuMA-Tech).

[0056] When the ionomer resin is contained in the specific catalyst dispersion, from the viewpoint of uniformly dispersing the ionomer resin in the specific catalyst dispersion, it is also preferable to use the ionomer resin solid by crushing and pulverizing it using a crushing means. Examples of the crushing means include a mill, a ball mill, a jet mill, a homogenizer, etc. Uniform dispersion of the ionomer resin in the specific catalyst dispersion contributes to improving the performance of the catalyst-layered ion exchange membrane.

[0057] In addition, when a solution containing an ionomer resin is obtained and used, it is also preferable to dry the solution containing the ionomer resin to solidify it, and then crush the solidified product into fine particles.

[0058] The content of the ionomer resin in the specific catalyst dispersion is preferably 0.5% by mass to 50% by mass, more preferably 1% by mass to 30% by mass, and even more preferably 2% by mass to 20% by mass, relative to the total amount of the specific catalyst dispersion.

[0059] <Solvent> The specific catalyst dispersion may contain a solvent as long as the viscosity at 25°C is 1 Pa·s to 500 Pa·s. The solvent can function as a dispersion medium for the catalyst in the specific catalyst dispersion. Examples of the solvent include solvents having a hydroxyl group, and the solvent having a hydroxyl group is preferably at least one selected from water and alcohol.

[0060] When the specific catalyst dispersion contains a solvent, the content of the solvent in the specific catalyst dispersion is preferably 85 mass% or less, more preferably more than 0 mass% and 65 mass% or less, and even more preferably 0.1 mass% to 25 mass%, relative to the total amount of the specific catalyst dispersion.

[0061] <<Alcohol>> The specific catalyst dispersion preferably contains an alcohol. That is, in one aspect, the specific catalyst dispersion preferably contains a catalyst, an ionomer resin, and an alcohol as a solvent, and has a viscosity at 25°C of 1 Pa s to 500 Pa s.

[0062] When the specific catalyst dispersion contains alcohol, the dispersibility of the catalyst in the catalyst dispersion and the adhesion between the catalysts and / or between the catalyst and the ion exchange membrane or the substrate X are improved, thereby resulting in a catalyst layer with excellent dimensional stability.

[0063] When the specific catalyst dispersion contains alcohol, the specific catalyst dispersion can contain alcohol in a range that allows the viscosity at 25° C. to be adjusted to 1 Pa·s to 500 Pa·s.

[0064] The alcohol includes a monohydric alcohol, and for example, at least one selected from the group consisting of methanol, ethanol, 2-propanol (also referred to as isopropanol), 1-propanol, and butanol is preferable, and from the viewpoint of dispersibility of the ionomer resin, at least one selected from ethanol and 2-propanol is more preferable.

[0065] The specific catalyst dispersion may not contain a solvent, that is, the content of the solvent relative to the total amount of the specific catalyst dispersion may be 0 mass %.

[0066] <Other Components> The specific catalyst dispersion may contain other components. Specifically, additives such as a dispersant for controlling the dispersibility of the catalyst, a viscosity modifier for adjusting the viscosity of the dispersion and / or the sedimentation of the catalyst, a surfactant for controlling the surface tension, an antioxidant for preventing oxidation of the catalyst and / or ionomer, a curing agent for controlling the thermal curing of the resin, and a slipping material for controlling the transport and lamination of the film may be optionally added.

[0067] Step A can be carried out, for example, as follows.

[0068] <Preparation of specific catalyst dispersion> The specific catalyst dispersion can be prepared by mixing the catalyst, the ionomer resin, a solvent if desired, and any other components.

[0069] The specific catalyst dispersion can be prepared, for example, by mixing the catalyst, a dispersion solution of the ionomer resin, and a solvent (preferably alcohol) using any stirring means. As the stirring means, for example, a homogenizer (e.g., a rotary homogenizer) can be used. The stirring speed may be, for example, 100 rpm to 10,000 rpm (revolutions per minute, the same applies hereinafter). The prepared specific catalyst dispersion may be filled into any container and used. The solid content concentration of the specific catalyst dispersion is preferably 5% by mass to 30% by mass.

[0070] In step A, the catalyst dispersion layer of the transfer material X may be preheated (i.e., preheated) to a temperature of 70°C to 180°C, and then the catalyst dispersion layer may be superposed on at least one surface of the ion exchange membrane to obtain a laminate.

[0071] The preheating may also serve as heating of the laminate in step B.

[0072] Prior to step B, in step A, the catalyst dispersion layer of the transfer material X is preheated, whereby the ionomer resin contained in the catalyst dispersion layer is dissolved, and when pressing is carried out in step B, the adhesion between the ion exchange membrane and the catalyst layer is further improved, which is preferable.

[0073] Heating means used for the preheating include a heater, microwaves, and the like.

[0074] [Step B] In step B, the laminate heated to a temperature of 100° C. to 200° C. is pressed. By pressing, the ion exchange membrane and the catalyst dispersion layer are thermally fused and bonded together, thereby forming a catalyst layer on at least one side of the ion exchange membrane, thereby obtaining an ion exchange membrane with a catalyst layer.

[0075] In step B, the laminate needs to be heated to a temperature of 100°C to 200°C when pressing begins. In one embodiment, the temperature of the laminate is preferably 120°C to 130°C. The heating temperature in step B is preferably the melting point of the ionomer resin or a temperature near the melting point. The temperature near the melting point is, for example, in the range of the melting point ±20°C.

[0076] In step B, the temperature of the laminate means the surface temperature of the catalyst dispersion layer of the laminate. A thermocouple can be used to measure the temperature.

[0077] The laminate can be adjusted to a temperature of 100° C. to 200° C., for example, by the following embodiment (1) or (2).

[0078] Aspect (1): The laminate obtained in step A is heated to 100°C to 200°C. The laminate may be a laminate in an aspect in which a specific catalyst dispersion is molded into a predetermined shape directly on at least one surface of an ion exchange membrane to form a catalyst dispersion layer. The laminate may also be a laminate obtained by arranging a catalyst dispersion layer formed by molding a specific catalyst dispersion into a predetermined shape on one surface of a substrate X to obtain a transfer material X having the substrate X and the catalyst dispersion layer, and then superposing the catalyst dispersion layer of the transfer material X on at least one surface of the ion exchange membrane.

[0079] Aspect (2): In step A, the catalyst dispersion layer of transfer material X is preheated to a temperature of 70°C to 180°C, and then a laminate is used, obtained by superposing the catalyst dispersion layer on at least one surface of an ion exchange membrane. In this aspect, if the temperature of the laminate is less than 100°C, the laminate can be heated to 100°C to 200°C and then pressed. In this aspect, if the temperature of the laminate exceeds 100°C, the laminate can be pressed as is.

[0080] Furthermore, when the temperature of the laminate heated to 100°C to 200°C drops to below 100°C, it may be heated again to 100°C to 200°C.

[0081] In step B, the pressure applied when pressing the laminate can be set appropriately. From the viewpoint of adhesion between the ion exchange membrane and the catalyst layer, the pressure is preferably 1 MPa to 20 MPa, more preferably 1 MPa to 10 MPa. As a pressing means, a roll press, a flat press, or the like can be used. The pressing time is preferably 0.1 minutes to 20 minutes, more preferably 0.5 minutes to 10 minutes. When a roll press is used, the feed speed can be about 0.5 m / min to 5 m / min.

[0082] In the method for producing an ion exchange membrane with a catalyst layer according to the present disclosure, when a transfer material X is used, step B preferably further includes a step of peeling off the substrate X after the pressing.

[0083] In the step of peeling off the substrate X, the substrate X is peeled off from the pressed laminate. As the peeling means, a peeling bar, a suction roll, a vacuum chuck, or the like can be used.

[0084] FIG. 1 is a schematic diagram for explaining an example of carrying out a series of steps including step A and step B using a transfer substrate X.

[0085] As shown in FIG. 1, in this example, first, a transfer material X1 and a transfer material X2 are prepared by using a screen printing method to form a specific catalyst dispersion layer.

[0086] Specifically, the screen printing plate 16 is placed on top of the substrate Xa or substrate Xb placed on the support 10. In this example, the support 10 and the substrate Xa and substrate Xb are placed on a heating pallet 14. The heating pallet 14 is a heating means for performing preheating.

[0087] Next, in the production of the transfer material X1, the specific catalyst dispersion 20A filled in the dispenser 18A is applied to the inside of the mold frame of the screen printing plate 16. In this example, the specific catalyst dispersion 20A contains iridium (O ２The specific catalyst dispersion 20B is a slurry containing platinum (H catalyst), an ionomer resin, and alcohol. In the production of the transfer material X2, the specific catalyst dispersion 20B filled in the dispenser 18B is applied to the inside of the frame of the screen printing plate 16. In this example, the specific catalyst dispersion 20B contains platinum (H catalyst), an ionomer resin, and alcohol. ２ The slurry contains a catalyst, an ionomer resin, and an alcohol.

[0088] The specific catalyst dispersion 20A or 20B applied to the inside of the frame of the screen printing plate 16 is preferably leveled using a leveling means such as a squeegee 22.

[0089] Next, after removing the screen printing plate 16, the specific catalyst dispersion 20A arranged on one side of the substrate Xa and the specific catalyst dispersion 20B arranged on one side of the substrate Xb are each dried in a drying furnace 24, to obtain a transfer material X1 having the substrate Xa and the specific catalyst dispersion layer 26A, and a transfer material X2 having the substrate Xb and the specific catalyst dispersion layer 26B.

[0090] Next, in this example, one surface of the ion exchange membrane 28 is superimposed on the specific catalyst dispersion layer 26B of the transfer material X2 to form a laminate 30, and then the specific catalyst dispersion layer 26B of the transfer material X2 and the specific catalyst dispersion layer 26A of the transfer material X1 are aligned so that they face each other in a position where their outer peripheries overlap without any misalignment, with the ion exchange membrane 28 interposed therebetween. While Fig. 1 shows an example in which the formed transfer material X1 is inverted to position the specific catalyst dispersion layer 26A and the specific catalyst dispersion layer 26B facing each other, the alignment method is not limited to the above.

[0091] Next, the laminate 30 and the transfer material X1 are heated to a temperature of 100° C. to 200° C. and pressed in the direction of arrow A (ie, hot pressing).

[0092] After pressing, the substrates Xa and Xb are peeled off to obtain a catalyst-layered ion exchange membrane 34 having an iridium catalyst layer 32A and a platinum catalyst layer 32B on both sides of the ion exchange membrane 28.

[0093] In this example, both transfer material X1 and transfer material X2 are used during pressing, but one of transfer material X1 and transfer material X2 may be heat-pressed first, and then the other may be heat-pressed.

[0094] In the method for producing a catalyst-layered ion exchange membrane according to the present disclosure, after performing step A and step B, step A and step B may be further repeated. By repeating step A and step B, the thickness of the catalyst layer can be adjusted to any desired thickness. When step A and step B are repeated, specifically, step A may be performed by arranging a catalyst dispersion in a polygonal shape on a catalyst layer formed on at least one surface of the ion exchange membrane to form a polygonal catalyst dispersion layer, and then step B may be performed.

[0095] [Other Steps] In addition to Step A and Step B, the method for producing a catalyst-coated ion exchange membrane according to the present disclosure may include other steps.

[0096] The method for producing an ion exchange membrane with a catalyst layer according to the present disclosure will be explained in more detail below with reference to examples. However, the method for producing an ion exchange membrane with a catalyst layer according to the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the method. Unless otherwise specified, "%" is based on mass.

[0097] Example 1 [Step A] = Preparation of Platinum Catalyst Sheet = (Preparation of Platinum Catalyst Dispersion 1) 7.2 g of platinum-supported carbon, 21.4 g of 20% Nafion dispersion solution (ionomer resin dispersion solution, DE2020CS type manufactured by Fujifilm Wako Chemical Co., Ltd.), and 47.6 g of 2-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for electronics industry use) as a dispersion solvent were prepared, weighed in a glove box, and placed in a vial to form a turbid mixture. The turbid mixture removed from the glove box was stirred at 2000 rpm with a rotary homogenizer to obtain a platinum catalyst-containing solution 1. The solids concentration of the prepared platinum catalyst-containing solution 1 was 15%, and the viscosity at 25 ° C. was 1500 CP (1.5 Pa s). The average secondary particle size of the catalyst (aggregate) was measured for the obtained platinum catalyst-containing liquid 1 using a particle size analyzer (Partica LA-9600V2) manufactured by Horiba, Ltd. The average secondary particle size was 3 μm. The solvent was evaporated from the prepared platinum catalyst-containing liquid 1 using an evaporator, and the solids concentration was increased to 90% and the viscosity at 25 ° C. to 10,000 CP (10 Pa s), thereby obtaining platinum catalyst dispersion 1 (specific catalyst dispersion).

[0098] (Preparation of Platinum Catalyst Sheet) A PET sheet (thickness: 50 μm, 150 mm square) was prepared as the substrate X. A screen printing machine was used to form the specific catalyst dispersion layer. A PTFE sheet was placed on the screen printing machine, and the platinum catalyst dispersion 1 was applied to the frame of the screen printing plate in the form of a decagon (area: approximately 100 cm) with a thickness of 20 μm. ２ ) to form a specific catalyst dispersion layer, thereby obtaining a platinum catalyst sheet 1 (transfer material X) having a platinum catalyst dispersion layer.

[0099] The platinum catalyst sheet was placed on a hot press (160°C, manufactured by Toyo Seiki Seisakusho, product name: mini test press-10) and left to stand for 1 minute, and then aligned and brought into contact with a 125 μm thick, 150 mm square ion exchange membrane (manufactured by Chemours, Nafion N115), to obtain a laminate in which the ion exchange membrane and the surface of the platinum catalyst sheet having the specific catalyst dispersion layer were superimposed.

[0100] [Step B] Next, a 500 μm thick elastic sheet was further stacked on the above laminate, and the resultant was pressed in a hot press at 1.5 MPa for 5 minutes. The temperature of the laminate at the start of pressing was 140° C. As a result, a platinum catalyst layer was formed on one side of the ion exchange membrane. After releasing the press, the laminate was cooled, and the elastic sheet and the PTFE sheet were peeled off. As a result, the catalyst-layered ion exchange membrane of Example 1, which had a platinum catalyst layer on one side of the ion exchange membrane, was obtained.

[0101] Example 2 A catalyst-layered ion exchange membrane of Example 2 having a platinum catalyst layer on one side of the ion exchange membrane was obtained in the same manner as in Example 1, except that platinum catalyst dispersion 2 prepared as described below was used to prepare platinum catalyst sheet 2 instead of platinum catalyst dispersion 1 in Example 1.

[0102] (Preparation of Platinum Catalyst Dispersion 2) 7.2 g of platinum-supported carbon, 21.4 g of 20% Nafion dispersion solution (DE2020CS type manufactured by Fujifilm Wako Chemical Co., Ltd.), and 47.6 g of 2-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for electronics industry use) as a dispersion solvent were prepared, weighed in a glove box, and placed in a vial. The turbid material removed from the glove box was stirred at 2000 rpm with a rotary homogenizer to obtain platinum catalyst-containing solution 2. The solids concentration of the prepared platinum catalyst-containing solution 2 was 15%. The average secondary particle size of the catalyst (aggregate) of the obtained platinum catalyst-containing solution 2 was measured using a particle size analyzer: Partica LA-9600V2 manufactured by Horiba, Ltd. The average secondary particle size was 3 μm. The solvent was evaporated from the prepared platinum catalyst-containing liquid 2 using an evaporator, and then a 5:5 solution of ethanol and water was added to increase the solids concentration to 90% and the viscosity to 10,000 CP (10 Pa s), thereby obtaining platinum catalyst dispersion 2 (specific catalyst dispersion).

[0103] Example 3 = Preparation of Platinum Catalyst Sheet = A platinum catalyst sheet 1 was prepared in the same manner as in Example 1.

[0104] =Preparation of Iridium Catalyst Sheet 1= Iridium catalyst sheet 1 (transfer material X) having a decagonal iridium catalyst dispersion layer was prepared in the same manner as in Example 1, except that platinum catalyst dispersion 1 in Example 1 was changed to iridium catalyst dispersion 1 shown below.

[0105] (Preparation of Iridium Catalyst Dispersion 1) 3.8 g of iridium oxide, 4.8 g of a 20% Nafion dispersion solution (FUJIFILM Wako Chemical Co., Ltd., DE2020CS type), and 4.6 g of 2-propanol (FUJIFILM Wako Pure Chemical Industries, Ltd., for electronics industry use) as a dispersion solvent were prepared, weighed in a glove box, and placed in a vial. The turbid matter removed from the glove box was stirred at 2000 rpm in a planetary mixer to obtain iridium catalyst-containing solution 1. The solids concentration of the prepared iridium catalyst-containing solution 1 was 36.4%. The average secondary particle size of the catalyst (aggregates) of the obtained iridium catalyst-containing solution 1 was measured using a particle size analyzer: Partica LA-9600V2 manufactured by Horiba, Ltd. The average secondary particle size was 3 μm. The solvent was evaporated from the prepared iridium catalyst-containing liquid 1 using an evaporator, and then ethanol was added to obtain an iridium catalyst dispersion 1 having a solids concentration of 90% and a viscosity of 10,000 CP (10 Pa·s).

[0106] In the same manner as in Example 1, the ion exchange membrane and platinum catalyst sheet 1 were pressed together using a hot press, and then the iridium catalyst dispersion layer of the iridium catalyst sheet 1 and the platinum catalyst layer were placed opposite each other via the ion exchange membrane on the side of the ion exchange membrane on which the platinum catalyst sheet 1 was not placed. After leaving the mixture to stand for 1 minute, an elastic sheet was placed on the iridium catalyst sheet 1, and the iridium catalyst dispersion layer was transferred onto the ion exchange membrane at the same pressure as in Example 1. The mixture was then cooled, and the elastic sheet and PTFE sheet were peeled off. As a result, a catalyst-layered ion exchange membrane of Example 3 was obtained, which had a platinum catalyst layer on one side of the ion exchange membrane and an iridium catalyst layer on the other side.

[0107] Example 4 The platinum catalyst dispersion 1 prepared in Example 1 was applied to one side of the ion exchange membrane in a 20 μm thick decagonal shape (area: 100 cm ２ ) to obtain a laminate. The obtained laminate was pressed using the same hot press apparatus and pressure conditions as in Example 1. In this way, a catalyst-layered ion exchange membrane of Example 4 was obtained, which had a platinum catalyst layer on one surface of the ion exchange membrane.

[0108] Example 5: Platinum catalyst dispersion 1 used in Example 3 was used on one side of the ion exchange membrane to form a 20 μm thick decagonal membrane (area: 100 cm ２ ) to form a first specific catalyst dispersion layer, and on the other surface, iridium catalyst dispersion 1 was applied to form a 20 μm thick decagonal (area: 100 cm) layer at a position overlapping the first specific catalyst dispersion layer. ２ ) to form a second specific catalyst dispersion layer, thereby obtaining a laminate. The obtained laminate was pressed using the same hot press apparatus and pressure conditions as in Example 3. As a result, a catalyst-layered ion exchange membrane of Example 5 was obtained, which had a platinum catalyst layer on one side of the ion exchange membrane and an iridium catalyst layer on the other side.

[0109] Comparative Example 1 A catalyst-layered ion exchange membrane of Comparative Example 1 having a platinum catalyst layer on one side of the ion exchange membrane was obtained in the same manner as in Example 1, except that platinum catalyst-containing liquid 1 was used instead of platinum catalyst dispersion 1 in Example 1.

[0110] Comparative Example 2 A catalyst-layered ion exchange membrane of Comparative Example 2 having a platinum catalyst layer on one side of the ion exchange membrane was obtained in the same manner as in Example 4, except that platinum catalyst-containing liquid 1 was used instead of platinum catalyst dispersion 1 in Example 4.

[0111] [Evaluation] The catalyst layer-attached ion exchange membranes obtained in the above examples were subjected to the following evaluation 1 (dimensional stability of catalyst layer) and evaluation 2 (amount of curl). The evaluation results are shown in Table 1.

[0112] <Evaluation 1 (Dimensional Stability of Catalyst Layer)> The dimensional stability of the catalyst layer was evaluated based on the formability of the edge portion of the catalyst layer obtained in each example.

[0113] - Evaluation method - As shown in Figure 2, an image inspection device 70 equipped with a CCD camera 72 and a light 74 was created. Using this image inspection device, the catalyst-coated ion exchange membranes obtained in each example were observed and the formability of the edge portion of the catalyst layer was evaluated. In the image inspection device 70, the ion exchange membrane 64 (catalyst-coated ion exchange membrane 60) on which the catalyst layer 62 was formed was placed on a measurement table 76, and the entire surface of the catalyst layer 62 (i.e., the entire upper surface) could be photographed using the CCD camera 72 and light 74 installed above the catalyst layer 62. The CCD camera 72 and light 74 could be moved by connecting guides 78.

[0114] The decagonal catalyst layer (area: approximately 100 mm) obtained in each of the above examples ２ ) was photographed. Figure 3 shows a photograph of the decagonal catalyst layer obtained in Example 1. For Example 3, photographs were taken of both the platinum catalyst layer and the iridium catalyst layer. Furthermore, the obtained photographed images were divided into 100 images with a 10 mm square field of view, and portions with irregular edges were extracted by image analysis. The portions with irregular edges are observed as in the photograph shown in Figure 4. Based on the results of the image analysis, the formability of the edge portion of the catalyst layer was evaluated according to the following criteria, and the results were used to evaluate the dimensional stability of the catalyst layer. A, B, C, and D are practically acceptable ranks, with A being the most excellent rank.

[0115] --Criteria-- A: The percentage of the number of captured images in which edge protrusions, etc. were observed is 1% or less. B: The percentage of the number of captured images in which edge protrusions, etc. were observed is more than 1% but not more than 3%. C: The percentage of the number of captured images in which edge protrusions, etc. were observed is more than 3% but not more than 5%. D: The percentage of the number of captured images in which edge protrusions, etc. were observed is more than 5% but not more than 10%. E: The percentage of the number of captured images in which edge protrusions, etc. were observed is more than 10%.

[0116] <Evaluation 2 (Amount of Curl)> The amount of curl (amount of lift from the measuring plate) of the catalyst layer-equipped ion exchange membrane was evaluated. This evaluation was performed on the catalyst layer-equipped ion exchange membranes obtained in the above examples, except for Example 3.

[0117] - Evaluation method - The catalyst layer-equipped ion exchange membrane to be evaluated (150 mm square) was placed on a measuring plate with the catalyst layer facing upward, and a hard ruler was placed against the measuring plate at each of the four corners to measure the amount of curl (amount of lift from the measuring plate). The greater the amount of lift, the more severely the catalyst layer-equipped ion exchange membrane is judged to curl. The obtained measured values ​​(amount of lift) were arithmetically averaged, and the value rounded to one decimal place was taken as the amount of curl, and the value was evaluated according to the following criteria. A, B, C, and D are practically acceptable ranks, with A being the best rank.

[0118] - Criteria - A: The amount of lift is 1 mm or less. B: The amount of lift is more than 1 mm and less than 3 mm. C: The amount of lift is more than 3 mm and less than 5 mm. D: The amount of lift is more than 5 mm and less than 10 mm. E: The amount of lift is more than 10 mm.

[0119]

[0120] As shown in Table 1, the ion exchange membranes with catalyst layers obtained in the examples all had excellent dimensional stability of the catalyst layers. In addition, the ion exchange membranes with catalyst layers obtained in the examples also had a small amount of curl.

[0121] (Explanation of symbols) 10 Support Xa, Xb Base material 16 Screen printing plate 14 Heating pallet 18A, 18B Dispenser 20A, 20B Specific catalyst dispersion 22 Squeegee 24 Drying furnace 26A, 26B Specific catalyst dispersion layer 28 Ion exchange membrane 30 Laminate 32B Catalyst layer (platinum catalyst layer) 32A Catalyst layer (iridium catalyst layer) 34 Ion exchange membrane with catalyst layer X1, X2 Transfer material A Press direction 70 Image inspection device 72 CCD camera 74 Lighting 78 Guide 60 Ion exchange membrane with catalyst layer 62 Catalyst layer 64 Ion exchange membrane

[0122] The disclosure of Japanese Patent Application No. 2023-193025, filed on November 13, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing an ion exchange membrane with a catalyst layer, comprising: step A of arranging a catalyst dispersion layer, which is formed into a predetermined shape on at least one surface of an ion exchange membrane, to obtain a laminate having the ion exchange membrane and the catalyst dispersion layer; and step B of pressing the laminate heated to a temperature of 100°C to 200°C.

2. The method for producing an ion exchange membrane with a catalyst layer according to claim 1, wherein the catalyst dispersion contains an alcohol.

3. The method for producing a catalyst-layered ion exchange membrane according to claim 2, wherein the alcohol is at least one selected from the group consisting of ethanol and 2-propanol.

4. The method for producing an ion exchange membrane with a catalyst layer according to claim 1 or 2, wherein the catalyst contains aggregates having an average secondary particle diameter of 10 μm or less.

5. The method for producing an ion exchange membrane with a catalyst layer according to claim 1 or 2, wherein in step A, the catalyst dispersion layer is formed on both sides of the ion exchange membrane to obtain the laminate.

6. The method for producing an ion exchange membrane with a catalyst layer according to claim 1 or 2, wherein in step A, a catalyst dispersion layer formed by molding the catalyst dispersion into a predetermined shape is disposed on one surface side of a substrate X to obtain a transfer material X having the substrate X and the catalyst dispersion layer, and then at least one surface side of the ion exchange membrane and the catalyst dispersion layer of the transfer material X are superimposed to obtain the laminate.

7. The method for producing an ion exchange membrane with a catalyst layer according to claim 6, wherein the step A includes preheating the catalyst dispersion layer of the transfer material X to a temperature of 70°C to 180°C, and then superposing the catalyst dispersion layer on at least one surface of the ion exchange membrane to obtain the laminate.