Electrolyte film laminate and method for producing electrolyte film laminate

Abstract

Provided is an electrolyte film laminate including: an electrolyte film; and a catalyst layer provided on a part of each of one surface and the other surface of the electrolyte film. The flatness A of the surface of the catalyst layer is higher than the flatness B of the surfaces of the electrolyte film where the catalyst layer is not arranged. Also provided are applications thereof.

Description

Electrolyte membrane laminate and method for manufacturing the electrolyte membrane laminate

[0001] The present disclosure relates to an electrolyte membrane laminate and a method for manufacturing an electrolyte membrane laminate.

[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 ionomer resin) formed on both sides of a solid polymer electron membrane (PEM), which is an ion exchange membrane.

[0003] For example, Japanese Patent Application Laid-Open No. 2015-220185 describes a method for manufacturing a membrane electrode assembly having an electrolyte membrane and a catalyst layer by applying a catalyst layer-forming ink containing a catalyst component to the electrolyte membrane, the method comprising the steps of: a placing step of placing the electrolyte membrane on a placing surface of a suction stage provided in a decompression chamber; a suction step of fixing the electrolyte membrane placed on the placing surface by suction from the surface opposite to the placing surface; a coating step of applying the catalyst layer-forming ink to the surface of the electrolyte membrane fixed to the placing surface; and a drying step of drying the catalyst layer-forming ink applied to the electrolyte membrane by suctioning and reducing the pressure inside a decompression chamber while the electrolyte membrane is fixed to the placing surface.

[0004] Japanese Patent Laid-Open Publication No. 2023-88529 describes a method for manufacturing a membrane electrode assembly, the method including: an adsorption device provided with a flat adsorption surface; and a transport path for transporting a plurality of the adsorption devices in a predetermined direction; a sheet-fed loader process for adsorbing and holding an electrolyte membrane on the adsorption surface of each of the plurality of adsorption devices transported on the transport path; a sheet-fed coating process for coating one of the surfaces of the adsorption-held electrolyte membrane of each of the plurality of adsorption devices transported on the transport path from the loader process with a catalyst layer ink; a drying process for heating and drying the plurality of adsorption devices transported on the transport path from the coating process and on which the electrolyte membrane coated with the catalyst layer ink is adsorbed and held; and an unloader process for releasing the adsorption of the electrolyte membrane on which the catalyst layer ink has dried and an electrode catalyst layer has been formed from the adsorption device and transporting it to a storage location.

[0005] When a catalyst layer is formed by applying a catalyst layer composition onto an electrolyte membrane, the electrolyte membrane is prone to deformation due to absorption of the solvent in the catalyst layer composition, and distortion may occur in the resulting catalyst layer-coated membrane (electrolyte membrane laminate).

[0006] The problem to be solved by one embodiment of the present disclosure has been made in view of the above circumstances, and is to provide an electrolyte membrane laminate having a catalyst layer with higher flatness than conventional ones, and a method for manufacturing the same.

[0007] The present disclosure includes the following aspects: <1> An electrolyte membrane laminate including an electrolyte membrane and catalyst layers disposed on a portion of each of one and other surfaces of the electrolyte membrane, wherein a flatness A of the surface of the catalyst layers is higher than a flatness B of a surface of the electrolyte membrane on which the catalyst layers are not disposed. <2> The electrolyte membrane laminate according to <1>, wherein the difference between the flatness A and the flatness B is 1 mm or more. <3> A method for manufacturing an electrolyte membrane laminate, comprising the steps of: adsorbing the second surface of the electrolyte membrane to a first adsorption table, placing a first frame on the first surface of the electrolyte membrane, supplying a first coating liquid containing a catalyst into the first frame, drying the supplied first coating liquid to form a first catalyst layer on the first surface, and removing the first frame after drying, adsorbing the first surface of the electrolyte membrane to a second adsorption table and then releasing the adsorption by the first adsorption table, placing a second frame on the second surface of the electrolyte membrane, supplying a second coating liquid containing a catalyst into the second frame, and drying the supplied second coating liquid to form a second catalyst layer on the second surface of the electrolyte membrane. <4> A method for manufacturing an electrolyte membrane laminate according to <3>, wherein the first adsorption table adsorbs at least a region of the second surface of the electrolyte membrane that corresponds to the opening of the first frame placed on the first surface of the electrolyte membrane. <5> The method for manufacturing an electrolyte membrane laminate according to <3> or <4>, wherein at least a region having a first catalyst layer on a first surface of the electrolyte membrane is adsorbed onto the second adsorption platform. <6> The method for manufacturing an electrolyte membrane laminate according to any one of <3> to <5>, wherein in the step of installing the first frame, the first frame is installed at a position where the shortest distance between the first frame and the first adsorption platform is equal to or greater than the thickness of the electrolyte membrane, and in the step of installing the second frame, the second frame is installed at a position where the shortest distance between the second frame and the second adsorption platform is equal to or greater than the thickness of the electrolyte membrane. <7> The method for manufacturing an electrolyte membrane laminate according to any one of <3> to <6>, wherein at least a surface of the first frame that comes into contact with the first coating liquid is water-repellent treated, and at least a surface of the second frame that comes into contact with the second coating liquid is water-repellent treated.

[0008] According to one embodiment of the present disclosure, an electrolyte membrane stack having a catalyst layer with a higher degree of flatness than conventional ones and a method for manufacturing the same are provided.

[0009] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. 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. In the 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 the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described 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. In the present disclosure, a combination of two or more preferred embodiments or aspects is a more preferred embodiment or aspect.

[0010] [Electrolyte Membrane Stack] The electrolyte membrane stack according to the present disclosure includes an electrolyte membrane and a catalyst layer disposed on a portion of each of one and the other surfaces of the electrolyte membrane, and the flatness A of the surface of the catalyst layer is higher than the flatness B of the surface of the electrolyte membrane on which the catalyst layer is not disposed.

[0011] When a catalyst layer is formed by applying a composition for a catalyst layer onto an electrolyte membrane, the electrolyte membrane is prone to deformation due to absorption of the solvent in the composition for a catalyst layer. In contrast, in the electrolyte membrane laminate according to the present disclosure, the surface flatness of the portion of the electrolyte membrane where the catalyst layer is disposed is higher than the surface flatness of the electrolyte membrane where the catalyst layer is not disposed, resulting in an electrolyte membrane laminate having a catalyst layer with higher flatness than conventional ones.

[0012] There is no need to increase the flatness of the surface of the electrolyte membrane where the catalyst layer is not disposed, and by focusing on increasing the flatness of the laminated portion where the catalyst layer is disposed, an electrolyte membrane laminate having a catalyst layer with a higher flatness than conventional ones has been obtained.

[0013] In contrast, Japanese Patent Application Laid-Open No. 2015-220185 and Japanese Patent Application Laid-Open No. 2023-88529 do not include any description focusing on flatness.

[0014] <Electrolyte Membrane> Examples of the electrolyte membrane include a fluorine-based electrolyte membrane and a hydrocarbon-based electrolyte membrane. Specific examples of the electrolyte membrane include perfluorocarbon sulfonic acid polymers such as Nafion (registered trademark), poly(meth)acrylates having phosphate groups in their side chains, heat-resistant aromatic polymers such as sulfonated polyether ether ketones, sulfonated polyether ketones, sulfonated polyether sulfones, sulfonated polysulfones, and sulfonated polybenzimidazoles, sulfonated polystyrenes, sulfonated polyoxetanes, sulfonated polyimides, sulfonated polyphenylene sulfides, sulfonated polyphenylene oxides, and sulfonated polyphenylene membranes.

[0015] The thickness of the electrolyte membrane is preferably 50 μm to 250 μm, and more preferably 100 μm to 200 μm. The thickness of the electrolyte membrane is measured using a laser displacement meter, such as a "Multicolor Laser Coaxial Displacement Meter" manufactured by Keyence Corporation.

[0016] <Catalyst Layer> The catalyst layer contains a catalyst. The catalyst layer may contain components other than the catalyst. The catalyst layer preferably contains a catalyst and a binder.

[0017] Examples of the catalyst include metals such as platinum, gold, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, and alloys thereof. From the viewpoints of catalytic activity and durability, the catalyst preferably contains platinum or iridium.

[0018] The catalyst may be supported on a carbon material, such as carbon black, activated carbon, coke, natural graphite, and artificial graphite, and specific examples thereof include Ketjen black, Vulcan black, acetylene black, carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphitized Ketjen black, graphitized Vulcan black, and graphitized acetylene black.

[0019] The binder is preferably a polymer having a proton-donating group. Examples of the binder include perfluorocarbon sulfonic acid polymers such as Nafion (registered trademark), poly(meth)acrylates having phosphoric acid groups in their side chains, heat-resistant aromatic polymers such as sulfonated polyether ether ketones, sulfonated polyether ketones, sulfonated polyether sulfones, sulfonated polysulfones, and sulfonated polybenzimidazoles; sulfonated polystyrenes, sulfonated polyoxetanes, sulfonated polyimides, sulfonated polyphenylene sulfides, sulfonated polyphenylene oxides, and sulfonated polyphenylenes.

[0020] The catalyst layer is disposed on a portion of each of the surfaces of one side and the other side of the electrolyte membrane. The position of the catalyst layer on the electrolyte membrane in a plan view is not particularly limited, but the catalyst layer is preferably disposed in the center of the electrolyte membrane. Specifically, the catalyst layer is preferably not disposed on the peripheral edge portion in the circumferential direction of the electrolyte membrane, but is disposed in the central portion equidistant from the two peripheral edges of the electrolyte membrane that are on the same line.

[0021] The shape of the catalyst layer is not particularly limited and may be circular, rectangular, or polygonal in plan view. The size of the catalyst layer is adjusted appropriately to be smaller than the size of the electrolyte membrane in plan view.

[0022] In the electrolyte membrane laminate according to the present disclosure, the flatness A of the surface of the catalyst layer is higher than the flatness B of the surface of the electrolyte membrane on which the catalyst layer is not disposed. The flatness A being higher than the flatness B means that the height a indicating the flatness A and the height b indicating the flatness B, which are calculated as follows, satisfy the relationship of height a<height b.

[0023] The flatness A is measured by the following method. A portion of the electrolyte membrane laminate in which one catalyst layer, the electrolyte membrane, and the other catalyst layer are stacked in this order is cut out. The size of the cut sample is 30 mm × 30 mm. The cut sample is placed on a glass plate, and the lift from the glass plate is measured using a laser displacement meter (product name "Multicolor Laser Coaxial Displacement Meter" manufactured by Keyence Corporation). The flatness A is expressed as the height of the lift, with a lower height indicating a higher flatness. Note that if a sample measuring 30 mm × 30 mm cannot be cut out, the size of the sample is set to the maximum area that can be cut out, and multiple samples of the same area are prepared and the flatness is evaluated relatively. Furthermore, when the electrolyte membrane laminate is manufactured using the electrolyte membrane laminate manufacturing method described below, the surface of the catalyst layer is photographed with a CCD camera, and the installation positions of the first and second frames on the electrolyte membrane (specifically, the areas of the openings of the first and second frames) can be confirmed by observing the captured image. When cutting out the sample, portions of the catalyst layer corresponding to the regions of the openings of the first frame and the second frame are cut out.

[0024] The flatness B is measured by the following method. An electrolyte membrane on which no catalyst layer is disposed is cut out from the electrolyte membrane laminate. The size of the cut sample is 30 mm x 30 mm. The cut sample is placed on a glass plate, and the lift-up from the glass plate is measured using a laser displacement meter (product name "Multicolor Laser Coaxial Displacement Meter", manufactured by Keyence Corporation). The flatness B is expressed by the height of the lift-up, with a lower height indicating a higher flatness.

[0025] The height a indicating the flatness A is preferably 3 mm or less, more preferably 1 mm or less. The height b indicating the flatness B is preferably more than 2 mm, more preferably 4 mm or more.

[0026] The difference between the flatness A and the flatness B is preferably 1 mm or more, and more preferably 3 mm or more.

[0027] [Method for manufacturing an electrolyte membrane laminate] A method for manufacturing an electrolyte membrane laminate according to the present disclosure includes a step of adsorbing the second surface of the electrolyte membrane onto a first adsorption table (hereinafter also referred to as a "first adsorption step"), a step of placing a first frame on the first surface of the electrolyte membrane (hereinafter also referred to as a "first frame placement step"), a step of supplying a first coating liquid containing a catalyst into the first frame (hereinafter also referred to as a "first coating liquid supply step"), a step of drying the supplied first coating liquid to form a first catalyst layer on the first surface (hereinafter also referred to as a "first drying step"), and a step of removing the first frame after drying (hereinafter also referred to as a "first frame removal step"). the step of adsorbing the first surface of the electrolyte membrane to the second adsorption platform and then releasing the adsorption by the first adsorption platform (hereinafter also referred to as the "second adsorption step" and the "first adsorption releasing step"); the step of placing a second frame on the second surface of the electrolyte membrane (hereinafter also referred to as the "second frame placing step"); the step of supplying a second coating liquid containing a catalyst into the second frame (hereinafter also referred to as the "second coating liquid supplying step"); and the step of drying the supplied second coating liquid to form a second catalyst layer on the second surface of the electrolyte membrane (hereinafter also referred to as the "second drying step").

[0028] <First Adsorption Step> The method for manufacturing an electrolyte membrane stack according to the present disclosure includes a step of adsorbing the second surface of the electrolyte membrane onto a first adsorption table.

[0029] In the first frame installation step, it is preferable to place the electrolyte membrane on the first adsorbent in advance. Even if the electrolyte membrane is placed on the first adsorbent in the first frame installation step, it is preferable to place the first frame on the first surface of the electrolyte membrane and then adsorb the second surface of the electrolyte membrane by the first adsorption platform.

[0030] For example, a number of through holes are formed in one surface of the first suction stand, and an air suction device is connected to each of the through holes via a tube. When air is sucked through each of the through holes by the air suction device, the electrolyte membrane is adsorbed and held on the other surface of the first suction stand.

[0031] It is preferable that the first adsorption platform adsorbs at least a region of the second surface of the electrolyte membrane that corresponds to the opening of a first frame placed on the first surface of the electrolyte membrane. A first coating liquid containing a catalyst, which will be described later, is supplied to the opening of the first frame, and therefore a first catalyst layer is formed in the region of the opening of the first frame. In other words, adsorbing at least a region of the second surface of the electrolyte membrane that corresponds to the opening of the first frame placed on the first surface means adsorbing at least a region where the first catalyst layer is to be formed. By adsorbing at least the region where the first catalyst layer is to be formed, deformation of the portion of the electrolyte membrane where the first catalyst layer is disposed can be suppressed.

[0032] From the viewpoint of further suppressing deformation in the portion of the electrolyte membrane where the first catalyst layer is disposed, it is preferable that the first adsorption platform adsorbs an area on the second surface of the electrolyte membrane that corresponds to the opening of the first frame body placed on the first surface and an area that is 0.1 mm to 5 mm away from the periphery of the opening of the first frame body.

[0033] <First Frame Installation Step> The method for manufacturing an electrolyte membrane stack according to the present disclosure includes the step of installing a first frame on the first surface of the electrolyte membrane.

[0034] The preferred embodiments of the electrolyte membrane are as described above.

[0035] In the method for manufacturing an electrolyte membrane laminate according to the present disclosure, catalyst layers are provided on both sides of an electrolyte membrane, and one of the two sides of the electrolyte membrane is designated as a first side and the other is designated as a second side. The first side and the second side are selected as appropriate.

[0036] The position where the first frame is disposed on the first surface of the electrolyte membrane in a plan view is not particularly limited, but the first frame is usually disposed in the center of the electrolyte membrane.

[0037] Furthermore, to prevent the electrolyte membrane from being deformed by placing the first frame on the first surface of the electrolyte membrane, the first frame is preferably placed at a position where the shortest distance between the first frame and the first suction mount is equal to or greater than the thickness of the electrolyte membrane. From the viewpoint of preventing the first coating liquid from flowing into the gap between the first frame and the electrolyte membrane, the shortest distance between the first frame and the first suction mount is preferably equal to or greater than the thickness of the electrolyte membrane but equal to or less than 0.1 mm larger than the thickness of the electrolyte membrane.

[0038] The shortest distance between the first frame and the first suction stand specifically means the distance between the bottom surface of the first frame and the top surface of the first suction stand.

[0039] The first frame includes, for example, an opening and a frame surrounding the opening. The opening is usually located at the center of the first frame.

[0040] The shape of the opening is not particularly limited and may be circular or rectangular. The size of the opening is appropriately adjusted according to the desired size of the first catalyst layer. Since the first coating liquid containing the catalyst described below is supplied to the opening of the first frame, the shape and size of the first catalyst layer formed by drying the coating liquid will be the same as the shape and size of the opening. However, the shape and size of the first catalyst layer do not completely match the shape and size of the opening of the first frame.

[0041] The outer peripheral shape of the frame is not particularly limited, and may be circular, rectangular, or polygonal.

[0042] The material of the first frame placed on the first surface of the electrolyte membrane is not particularly limited, and examples include a metal mask (a mask made of stainless steel, aluminum, etc.), a resin mask (a mask made of PET, Teflon (registered trademark), silicone rubber, etc.), and a mesh frame.

[0043] When a first coating fluid (described later) is supplied into the first frame, the first coating fluid tends to be attracted toward the first frame at the contact point between the first coating fluid and the first frame (specifically, the inner peripheral surface of the frame of the first frame), which tends to increase the thickness of the first catalyst layer at the contact point between the first coating fluid and the first frame.

[0044] It is preferable that at least the surface of the first frame that comes into contact with the first coating liquid is treated to be water-repellent. If the surface of the first frame is treated to be water-repellent, the thickness of the supplied first coating liquid will be uniform, and as a result, the thickness of the first catalyst layer will be uniform.

[0045] The surface that is treated to be water-repellent may be only the surface of the first frame that comes into contact with the first coating liquid, i.e., the inner surface of the frame portion, but from the viewpoint of ease of manufacturing and availability of the first frame, it is preferable that it be the entire surface of the first frame.

[0046] <First Coating Liquid Supplying Step> The method for manufacturing an electrolyte membrane laminate according to the present disclosure includes a step of supplying a first coating liquid containing a catalyst into the first frame.

[0047] The first coating liquid contains a catalyst. The first coating liquid may contain components other than the catalyst. The first coating liquid preferably contains a catalyst, a binder, and a solvent. That is, the first catalyst layer preferably contains a catalyst and a binder.

[0048] Preferred embodiments of the catalyst and binder are as described above.

[0049] Examples of solvents include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, and tert-butanol.

[0050] The first coating liquid is preferably supplied to the inside of the first frame, specifically, to the opening of the first frame.

[0051] The method for supplying the first coating liquid is not particularly limited, and can be carried out by a commonly known method.

[0052] From the viewpoint of suppressing excess liquid, it is preferable that the first coating liquid be supplied using a leveling member such as a squeegee.

[0053] The first coating liquid is preferably supplied to the opening of the first frame while the first frame is brought close to the electrolyte membrane, but a portion of the first coating liquid may be supplied between the frame of the first frame and the electrolyte membrane. In this case, the first catalyst layer is formed to be larger than the opening of the first frame.

[0054] <First Drying Step> The method for producing an electrolyte membrane laminate according to the present disclosure includes a step of drying the supplied first coating liquid to form a first catalyst layer on the first surface.

[0055] The method for drying the supplied first coating liquid is not particularly limited, and a drying method using a known drying means can be used. Examples of the drying means include an oven, a hot air blower, an infrared (IR) heater, etc. The first coating liquid may be dried from above the first coating liquid, from below the first adsorption table, or both.

[0056] The drying temperature is, for example, 70° C. to 120° C. The drying time is, for example, 1 minute to 1 hour.

[0057] The thickness of the first catalyst layer to be formed is not particularly limited, but from the viewpoint of ensuring the amount of catalyst necessary for water decomposition, it is preferably 1 μm to 100 μm, and more preferably 2 μm to 20 μm.

[0058] The thickness of the first catalyst layer is measured using a laser displacement meter, and as the laser displacement meter, for example, a "Multicolor Laser Coaxial Displacement Meter" manufactured by Keyence Corporation is used.

[0059] <First Frame Removal Step> The method for producing an electrolyte membrane laminate according to the present disclosure includes a step of removing the first frame after the first drying step.

[0060] By removing the first frame while maintaining the adsorption by the first adsorption platform, the electrolyte membrane on which the first catalyst layer is formed is held without deformation. In particular, by using the first adsorption platform to adsorb at least the region of the second surface of the electrolyte membrane that corresponds to the opening of the first frame placed on the first surface, deformation of the portion of the electrolyte membrane where the first catalyst layer is located can be suppressed.

[0061] <Second adsorption process, first adsorption release process> The manufacturing method of the electrolyte membrane stack according to the present disclosure includes a process of adsorbing the first surface side of the electrolyte membrane to the second adsorption stand and then releasing the adsorption by the first adsorption stand (hereinafter also referred to as the "second adsorption process" and the "first adsorption release process").

[0062] By adsorbing the first surface side of the electrolyte membrane to the second adsorption table before releasing the adsorption by the first adsorption table, the electrolyte membrane on which the first catalyst layer is formed is held without deformation.

[0063] For example, a number of through holes are formed on one surface of the second suction stand, and an air suction device is connected to each of the through holes via a tube. The air suction device sucks air through each of the through holes, thereby suctioning and holding the electrolyte membrane on the other surface of the second suction stand.

[0064] It is preferable that at least the region having the first catalytic layer on the first surface of the electrolyte membrane is adsorbed onto the second adsorption platform. In the second frame installation step described below, it is preferable that the first catalytic layer and the second catalytic layer are formed symmetrically with respect to the electrolyte membrane. When the first catalytic layer and the second catalytic layer are formed symmetrically with respect to the electrolyte membrane, adsorbing at least the region having the first catalytic layer means adsorbing at least the region where the second catalytic layer is formed. By adsorbing at least the region where the second catalytic layer is formed, deformation of the portion of the electrolyte membrane where the first catalytic layer and the second catalytic layer are arranged can be suppressed.

[0065] To further suppress deformation of the portion of the electrolyte membrane where the first and second catalytic layers are disposed, the second adsorption platform preferably adheres to the region where the first catalytic layer is formed and a region 0.1 mm to 5 mm outward from the outer periphery of the first catalytic layer. As described above, the shape and size of the first catalytic layer do not completely match the shape and size of the opening of the first frame. The installation position of the first frame on the electrolyte membrane (specifically, the region of the opening of the first frame) can be confirmed from an image of the first catalytic layer photographed with a CCD camera. Therefore, strictly speaking, the second adsorption platform preferably adheres to at least the region of the first surface of the electrolyte membrane that corresponds to the opening of the first frame placed on the first surface of the electrolyte membrane.

[0066] As a method for releasing the suction by the first suction table, for example, there is a method for stopping the suction of air by the air suction device.

[0067] <Second Frame Installation Step> The method for manufacturing an electrolyte membrane stack according to the present disclosure includes the step of installing a second frame on the second surface of the electrolyte membrane.

[0068] The preferred aspects of the second frame are the same as the preferred aspects of the first frame, and the preferred aspects of the second frame installation step are the same as the preferred aspects of the first frame installation step.

[0069] When placing the second frame on the second surface of the electrolyte membrane, it is preferable, from the viewpoint of workability, to invert the electrolyte membrane after the second adsorption step and the first adsorption releasing step. Specifically, it is preferable that the electrolyte membrane be placed so that its first surface faces vertically upward in the first frame placing step, first adsorption step, first coating liquid supply step, first drying step, first frame removing step, second adsorption step, and first adsorption releasing step, and that the electrolyte membrane be placed so that its second surface faces vertically upward in the second frame placing step.

[0070] <Second Coating Fluid Supplying Step> The method for producing an electrolyte membrane laminate according to the present disclosure includes a step of supplying a second coating fluid containing a catalyst.

[0071] The preferred embodiments of the second coating liquid are the same as those of the first coating liquid.

[0072] The components contained in the first coating liquid and the second coating liquid may be the same or different. From the viewpoint of improving the rate of water electrolysis, it is preferable that one of the first coating liquid and the second coating liquid contains iridium and the other contains platinum.

[0073] Furthermore, the preferred aspects of the second coating liquid supplying step are the same as the preferred aspects of the first coating liquid supplying step.

[0074] The method for producing an electrolyte membrane laminate according to the present disclosure includes a step of drying the supplied second coating liquid to form a second catalyst layer on the second surface of the electrolyte membrane. A preferred aspect of the second drying step is the same as a preferred aspect of the first drying step.

[0075] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, details of each step, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. Note that "parts" are all based on mass.

[0076] [Example 1] (Preparation of first coating liquid) 2.2 g of iridium oxide (manufactured by Furuya Metal Co., Ltd.), 2.8 g of isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a dispersion solvent, and 1.0 g of 20 mass % Nafion (registered trademark) dispersion solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed in a nitrogen-substituted glove box and placed in a vial. The turbid matter removed from the glove box was stirred with a rotary homogenizer at a rotation speed of 2000 rpm (revolutions per minute) for 30 minutes to obtain a first coating liquid (catalyst liquid 1).

[0077] (Preparation of second coating liquid) 2.1 g of platinum-supported carbon (manufactured by Tanaka Kikinzoku Co., Ltd.), 8.8 g of isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a dispersion solvent, and 6.1 g of 20 mass % Nafion (registered trademark) dispersion solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed in a nitrogen-substituted glove box and placed in a vial. The turbid matter removed from the glove box was stirred with a rotary homogenizer at a rotation speed of 2000 rpm for 30 minutes to obtain a second coating liquid (catalyst liquid 2).

[0078] (Fabrication of Electrolyte Membrane Laminate) A 125 μm-thick, 50 mm square electrolyte membrane (product name "Nafion Membrane N115," manufactured by Chemours) was vacuum-attached to a first suction table (vacuum suction stage) across its entire surface. A first frame (a 50 μm-thick screen printing metal mask with a 30 mm square cutout in the center) was fixed on top of the electrolyte membrane at a distance of 125 μm from the first suction table. A first coating liquid was dropped onto the first frame, and a metal squeegee was moved parallel to the first frame at 100 mm / min to supply the first coating liquid to the cutout portion of the first frame. The first coating liquid supplied to the cutout portion was dried using a dryer, and then the first frame was removed. A 30 mm square first catalyst layer was formed in the center of one surface (first surface) of the electrolyte membrane.

[0079] While the electrolyte membrane was in contact with the first adsorption stage, a second adsorption stage (vacuum adsorption stage) was brought into contact with the first catalyst layer side of the electrolyte membrane and sucked with a vacuum. The vacuum on the first adsorption stage was turned off, and the second adsorption stage was inverted.

[0080] A second frame (a 150 μm thick screen printing metal mask with a 30 mm square cutout in the center) was fixed 128 μm away from the first adsorption platform on the electrolyte membrane adsorbed to the second adsorption platform. The installation position of the second frame was adjusted so that the cutout of the second frame matched the outline of the first catalyst layer. The second coating liquid was dropped onto the second frame, and a metal squeegee was moved parallel to the second frame at 100 mm / min to supply the second coating liquid to the cutout of the second frame. The second coating liquid supplied to the cutout was dried with a dryer, and then the second frame was removed. A 30 mm square second catalyst layer was formed on the other side (second side) of the electrolyte membrane, yielding an electrolyte membrane laminate.

[0081] [Example 2] An electrolyte membrane laminate was obtained in the same manner as in Example 1, except that the area to be adsorbed by the first adsorption stand was changed to only the area (30 mm square) corresponding to the hollow portion of the first frame, and the area to be adsorbed by the second adsorption stand was changed to only the area (30 mm square) where the first catalyst layer was formed.

[0082] Example 3 An electrolyte membrane laminate was obtained in the same manner as in Example 1, except that the first frame and the second frame were previously subjected to a water-repellent treatment.

[0083] [Example 4] An electrolyte membrane laminate was obtained in the same manner as in Example 1, except that the first frame was fixed on the electrolyte membrane at a distance of 120 μm from the first adsorption stand, and the second frame was fixed at a distance of 120 μm from the second adsorption stand.

[0084] [Comparative Example 1] A comparative electrolyte membrane laminate was obtained in the same manner as in Example 1, except that the first coating liquid was supplied to the hollow portion of the first frame and the first frame was removed before the first coating liquid was dried.

[0085] The obtained electrolyte membrane laminate was evaluated for thickness distribution, defects, and flatness of the first catalyst layer and the second catalyst layer. The evaluation methods were as follows.

[0086] (Thickness Distribution) Using a multicolor laser coaxial displacement meter (manufactured by Keyence Corporation), the thickness was measured at 10,000 locations in each of the first and second catalytic layers, and the thickness distribution was calculated using the standard deviation. The evaluation criteria are as follows: A: The in-plane thickness distribution is 3% or less. B: The in-plane thickness distribution is more than 3% and 5% or less. C: The in-plane thickness distribution is more than 5%.

[0087] (Defects) The surfaces of the first catalyst layer and the second catalyst layer were visually observed, and the number of pinholes was calculated. The evaluation criteria are as follows: A: No pinholes; B: 1 to 3 pinholes; C: 4 or more pinholes.

[0088] (Flatness A) A portion (30 mm square) in which the first catalyst layer, the electrolyte membrane, and the second catalyst layer were laminated in this order was cut out. The cut-out sample was placed on a glass plate, and the lift-up from the glass plate was measured using a laser displacement meter (product name "Multicolor Laser Coaxial Displacement Meter", manufactured by Keyence Corporation).

[0089]

[0090] As can be seen from Table 1, in Examples 1 to 4, an electrolyte membrane laminate was obtained which included an electrolyte membrane and a catalyst layer disposed on a portion of each of one and the other surfaces of the electrolyte membrane, and in which the surface flatness A of the catalyst layer was higher than the surface flatness B of the electrolyte membrane on which the catalyst layer was not disposed, and which had a catalyst layer with higher flatness than conventional ones.

[0091] The disclosure of Japanese Patent Application No. 2024-033398, filed on March 5, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. An electrolyte membrane laminate comprising: an electrolyte membrane; and a catalyst layer disposed on a portion of each of one and the other surfaces of the electrolyte membrane, wherein the surface flatness A of the catalyst layer is higher than the surface flatness B of the electrolyte membrane on which the catalyst layer is not disposed.

2. The electrolyte membrane laminate according to claim 1, wherein the difference between the flatness A and the flatness B is 1 mm or more.

3. A method for manufacturing an electrolyte membrane laminate, comprising: a step of adsorbing the second surface of an electrolyte membrane onto a first adsorption platform; a step of placing a first frame on the first surface of the electrolyte membrane; a step of supplying a first coating liquid containing a catalyst into the first frame; a step of drying the supplied first coating liquid to form a first catalyst layer on the first surface; a step of removing the first frame after the drying; a step of adsorbing the first surface of the electrolyte membrane onto a second adsorption platform and then releasing the adsorption by the first adsorption platform; a step of placing a second frame on the second surface of the electrolyte membrane; a step of supplying a second coating liquid containing a catalyst into the second frame; and a step of drying the supplied second coating liquid to form a second catalyst layer on the second surface of the electrolyte membrane.

4. A method for manufacturing an electrolyte membrane stack as described in claim 3, wherein the first suction platform adsorbs at least an area on the second surface of the electrolyte membrane that corresponds to an opening of a first frame placed on the first surface of the electrolyte membrane.

5. The method for manufacturing an electrolyte membrane stack according to claim 3 or 4, wherein at least a region having a first catalyst layer on the first surface of the electrolyte membrane is adsorbed onto the second adsorption platform.

6. A method for manufacturing an electrolyte membrane stack as described in claim 3 or claim 4, wherein in the step of installing the first frame, the first frame is installed at a position where the shortest distance between the first frame and the first adsorption base is equal to or greater than the thickness of the electrolyte membrane, and in the step of installing the second frame, the second frame is installed at a position where the shortest distance between the second frame and the second adsorption base is equal to or greater than the thickness of the electrolyte membrane.

7. A method for manufacturing an electrolyte membrane laminate according to claim 3 or claim 4, wherein at least the surface of the first frame that comes into contact with the first coating liquid is treated to be water-repellent, and at least the surface of the second frame that comes into contact with the second coating liquid is treated to be water-repellent.