Catalyst layer-equipped electrolyte membrane, method for producing catalyst layer-equipped electrolyte membrane, laminate, membrane electrode assembly, and water electrolysis device

Abstract

[Solution] Provided are: a catalyst layer-equipped electrolyte membrane comprising an electrolyte membrane and a catalyst layer disposed on the electrolyte membrane, the catalyst layer containing a resin and catalyst particles, some of the catalyst particles forming secondary particles having a major axis of 100 μm or longer, and the abundance rate of secondary particles having a major axis of 100 μm or longer on the surface of the catalyst layer being 0.01 particles / cm2 to 2.0 particles / cm2; and application therefor.

Description

Electrolyte membrane with catalyst layer, method for manufacturing an electrolyte membrane with catalyst layer, laminate, membrane electrode assembly, and water electrolysis apparatus

[0001] This disclosure relates to an electrolyte membrane with a catalyst layer, a method for manufacturing an electrolyte membrane with a catalyst layer, a laminate, a membrane electrode assembly, and a water electrolysis apparatus.

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

[0003] For example, Japanese Patent Publication No. 2023-132339 describes a water electrolytic catalyst comprising iridium oxide powder, wherein the iridium oxide powder includes amorphous iridium oxide powder, and the average particle size of the iridium oxide powder is 0.01 μm or more and 30 μm or less, and an electrode film for water electrolysis obtained by mixing this water electrolytic catalyst with an ionomer.

[0004] Japanese Patent Publication No. 2021-89803 describes a fuel cell catalyst layer containing a carbon carrier on which Pt particles are supported and Ir oxide particles, wherein the ratio of the average primary crystallite diameter of the Ir oxide particles to the average primary crystallite diameter of the Pt particles is 20.0 or more.

[0005] In electrolyte membranes with a catalyst layer, it is sometimes necessary to suppress localized overheating in order to increase productivity.

[0006] One embodiment of this disclosure aims to solve, in view of the above circumstances, and provides a catalyst-layered electrolyte membrane, laminate, membrane electrode assembly, and water electrolysis device in which the state of aggregates of catalyst particles on the surface is controlled. Another embodiment of this disclosure aims to solve, and provides a method for manufacturing a catalyst-layered electrolyte membrane that can be manufactured with high precision while suppressing localized overheating during the manufacturing process.

[0007] This disclosure includes the following aspects: <1> an electrolyte membrane and a catalyst layer disposed on the electrolyte membrane, wherein the catalyst layer comprises a resin and catalyst particles, a portion of which the catalyst particles form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm ２ ~2.0 pieces / cm ２<1> The electrolyte membrane with a catalyst layer. <2> The electrolyte membrane with a catalyst layer according to <1>, wherein the catalyst layer comprises a first catalyst layer and a second catalyst layer, and the first catalyst layer, the electrolyte membrane, and the second catalyst layer are provided in this order, the catalyst in the first catalyst layer comprises iridium, and the catalyst in the second catalyst layer comprises platinum. <3> The electrolyte membrane with a catalyst layer according to <1> or <2>, wherein the catalyst layer has an average thickness T of 0.1 μm to 50 μm and a maximum thickness of 3T or less. <4> A method for producing an electrolyte membrane with a catalyst layer, comprising the step of forming a catalyst layer on an electrolyte membrane, the step of forming a catalyst layer comprising the step of applying a catalyst layer forming composition containing a resin and catalyst particles, and the step of drying the catalyst layer forming composition, wherein the average thickness T of the catalyst layer after drying is 0.1 μm to 50 μm and the maximum thickness is 3T or less. <5> The method for manufacturing an electrolyte membrane with a catalyst layer according to <4>, wherein the coating thickness of the catalyst layer forming composition is 1 μm to 500 μm. <6> The method for manufacturing an electrolyte membrane with a catalyst layer according to <4> or <5>, wherein the steps of coating the catalyst layer forming composition and drying the catalyst layer forming composition are performed on a substrate with an inclination of 0° to 5° with respect to the horizontal direction. <7> The method for manufacturing an electrolyte membrane with a catalyst layer according to any one of <4> to <6>, wherein the step of coating the catalyst layer forming composition is performed in an atmosphere with a dew point of 20°C or lower. <8> The method for manufacturing an electrolyte membrane with a catalyst layer according to any one of <4> to <7>, wherein the step of coating the catalyst layer forming composition is performed by a screen printing method. <9> A method for manufacturing an electrolyte membrane with a catalyst layer according to any one of <4> to <8>, comprising the steps of forming a catalyst layer, applying a catalyst layer forming composition containing a resin and catalyst particles onto a temporary support, drying the catalyst layer forming composition to produce a transfer substrate having a catalyst layer, arranging the transfer substrate on the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact, and performing thermocompression bonding between the electrolyte membrane and the transfer substrate, and peeling off the temporary support. <10> A method for manufacturing an electrolyte membrane with a catalyst layer according to any one of <4> to <8>, comprising a temporary support and a catalyst layer disposed on the temporary support, wherein the catalyst layer contains a resin and catalyst particles, some of the catalyst particles form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm２ ~2.0 pieces / cm ２ A laminate. <11> A membrane electrode assembly comprising an electrolyte membrane with a catalyst layer as described in any one of <1> to <3>. <12> A water electrolysis apparatus comprising the membrane electrode assembly described in <11>.

[0008] According to one embodiment of the present disclosure, a catalyst-layered electrolyte membrane, a laminate, a membrane electrode assembly, and a water electrolysis device are provided in which the state of aggregates of catalyst particles on the surface is controlled. Furthermore, according to another embodiment of the present disclosure, a method for manufacturing a catalyst-layered electrolyte membrane is provided that can be manufactured with high precision while suppressing localized overheating during the manufacturing process.

[0009] In this disclosure, numerical ranges indicated using "~" mean ranges that include the numbers before and after "~" as the minimum and maximum values, respectively. In this disclosure, the term "process" is included not only in the sense of an independent process, but also in the sense of a process that is not clearly distinguishable from other processes, as long as the intended purpose of that process is achieved. In numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the value shown in the example. In this disclosure, two or more preferred forms or combinations of embodiments are considered more preferred forms or embodiments.

[0010] [Electrolyte membrane with catalyst layer] The electrolyte membrane with a catalyst layer according to this disclosure comprises an electrolyte membrane and a catalyst layer disposed on the electrolyte membrane, wherein the catalyst layer contains a resin and catalyst particles, some of which form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm ２ ~2.0 pieces / cm ２ That is the case.

[0011] The inventors of this invention found that, since catalyst particles contained in the catalyst layer tend to aggregate and form aggregates, controlling the overall size and proportion of aggregated particles can suppress the phenomenon of localized overheating during the manufacturing process. In particular, if the major axis of the secondary particles is less than 100 μm, the effect on overheating is small, but if the major axis of the secondary particles is 100 μm or more, localized overheating is likely to occur, and the proportion of secondary particles with a major axis of 100 μm or more is 0.01 particles / cm². ２ ~2.0 pieces / cm ２ By controlling the temperature within a certain range, it is possible to suppress localized overheating during the manufacturing process. This reduces the impact of unexpected and unwanted heat during manufacturing, allowing for stable and accurate manufacturing.

[0012] Japanese Patent Publication No. 2023-132339 and Japanese Patent Publication No. 2021-89803 only describe the use of catalyst particles with small particle sizes, and do not mention any focus on suppressing aggregation of catalyst particles.

[0013] (Electrolyte membranes) Examples of electrolyte membranes include fluorine-based electrolyte membranes and hydrocarbon-based electrolyte membranes. Specifically, examples of electrolyte membranes include perfluorocarbon sulfonic acid polymers represented by 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, sulfonated polysulfones, sulfonated polybenzimidazoles, sulfonated polystyrene, sulfonated polyoxetanes, sulfonated polyimides, sulfonated polyphenylene sulfide, sulfonated polyphenylene oxide, and sulfonated polyphenylene membranes.

[0014] The thickness of the electrolyte membrane is preferably 30 μm to 250 μm, and more preferably 50 μm to 200 μm. The thickness of the electrolyte membrane is measured by the method described in JIS K 7130:1999.

[0015] (Catalyst layer) The catalyst layer includes a resin and catalyst particles.

[0016] A catalyst particle means that the catalyst exists in a particulate form, and the catalyst particles include primary particles and secondary particles. The catalyst particles in the catalyst layer may include primary particles and secondary particles, and in a part of the catalyst particles, they exist in the state of secondary particles in which a plurality of primary particles are aggregated. The secondary particles in the catalyst layer in the present disclosure include those that are aggregates with a major axis of 100 μm or more.

[0017] In the electrolyte membrane with a catalyst layer according to the present disclosure, the state of secondary particles having a major axis of 100 μm or more (hereinafter also referred to as "coarse particles") among the secondary particles present in the catalyst layer is controlled. That is, the presence ratio of coarse particles on the surface of the catalyst layer is 0.01 particles / cm ２ to 2.0 particles / cm ２ is.

[0018] When the presence ratio of the coarse particles is 2.0 particles / cm ２ or less, local overheating during the manufacturing process can be suppressed. Specifically, when the presence ratio of the coarse particles is 2.0 particles / cm ２ or less, the secondary particles (coarse particles) tend to exist on the surface of the catalyst layer in a highly uniform state, the separation of the resin and the secondary particles in the catalyst layer is suppressed, and local overheating during the manufacturing process can be suppressed. Further, when the presence ratio of the coarse particles is 2.0 particles / cm ２ or less, the charge concentration on the coarse particles is suppressed, and the generation of pores in the electrolyte membrane caused by the coarse particles is suppressed. Thereby, the peeling between the electrolyte membrane and the catalyst layer is suppressed. Furthermore, when the presence ratio of the coarse particles is 2.0 particles / cm ２ or less, the concentration of internal stress is suppressed, and the peeling between the electrolyte membrane and the catalyst layer is suppressed. On the other hand, when the presence ratio of the coarse particles is 0.01 particles / cm ２ or more, the coating rate of the resin on the catalyst particles does not become too high, and the electrolysis efficiency is maintained.

[0019] From the above viewpoints, the presence ratio of the coarse particles on the surface of the catalyst layer is preferably 0.03 particles / cm ２ to 1.0 particles / cm ２ , and more preferably 0.05 particles / cm ２ to 0.5 particles / cm ２It is preferable that it be so.

[0020] In this disclosure, the proportion of coarse particles on the surface of the catalyst layer is calculated by the following method. First, light is shone onto the surface of the catalyst layer using a light-reflecting detector. The in-plane distribution of reflected light is binarized to detect areas with high brightness. Areas where catalyst particles are aggregated have increased scattered light and higher brightness. From the image obtained by binarization, secondary particles with a major axis of 100 μm or more are identified. The major axis refers to the length of the longest part of the aggregated particles. ２ In any region, the number of secondary particles with a major axis of 100 μm or more is measured. Based on the measured number, the proportion of coarse particles is calculated.

[0021] The lighting will be diffuse illumination, and the camera will be a CCD camera (resolution 30 μm).

[0022] By measuring using a light-reflecting detector, the surface state of the catalyst layer can be confirmed.

[0023] The average particle diameter of the catalyst particles (i.e., the average primary particle diameter) is preferably 1 μm to 10 μm. The average primary particle diameter is a value measured by a particle size distribution analyzer.

[0024] Examples of catalysts include metals such as platinum, gold, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, as well as alloys thereof. From the viewpoint of catalytic activity and durability, the catalyst preferably contains platinum or iridium.

[0025] The catalyst may be supported on a carbon material. Examples of carbon materials include carbon black, activated carbon, coke, natural graphite, and artificial graphite. Specifically, examples include Ketjenblack, Vulcan black, acetylene black, carbon fibers, single-wall carbon nanotubes, multi-wall carbon nanotubes, graphitized Ketjenblack, graphitized Vulcan black, and graphitized acetylene black.

[0026] The resin is preferably a polymer having a proton-donating group. Examples of the resin include perfluorocarbon sulfonic acid polymers typified by Nafion (registered trademark), poly(meth)acrylates having a phosphate group in the side chain, sulfonated polyether ether ketone, sulfonated polyether ketone, sulfonated polyether sulfone, sulfonated polysulfone, sulfonated polybenzimidazole and other heat-resistant aromatic polymers; sulfonated polystyrene, sulfonated polyoxetane, sulfonated polyimide, sulfonated polyphenylene sulfide, sulfonated polyphenylene oxide, and sulfonated polyphenylene.

[0027] The catalyst layer is disposed on the electrolyte membrane. There may be only one catalyst layer disposed on the electrolyte membrane, or two or more catalyst layers. Further, the catalyst layer may be disposed only on one surface of the electrolyte membrane, or the catalyst layer may be disposed on both surfaces of the electrolyte membrane. When the catalyst layer is disposed on both surfaces of the electrolyte membrane, the catalyst layer disposed on one surface may be only one or two or more.

[0028] In the electrolyte membrane with a catalyst layer according to the present disclosure, it is preferable that the catalyst layer is disposed on both surfaces of the electrolyte membrane. That is, the electrolyte membrane with a catalyst layer according to the present disclosure preferably includes a first catalyst layer, an electrolyte membrane, and a second catalyst layer in this order.

[0029] For example, when the first catalyst layer is a negative electrode layer, the reaction in the negative electrode layer is as follows. 2H ２ O → 4H ＋ + O ２ + 4e － The oxygen generation reaction becomes a highly acidic condition (that is, low pH). Since the oxygen generation reaction in the negative electrode layer proceeds under corrosive conditions (that is, low pH, significant overvoltage), the negative electrode layer preferably contains noble metals such as ruthenium and iridium, and oxides thereof. On the other hand, when the second catalyst layer is a positive electrode layer, the reaction in the positive electrode layer is as follows. 4H++4e － → 2H ２Platinum is preferably used as the catalyst in the positive electrode layer, and platinum supported on carbon (platinum-supported carbon) is generally used in the research of fuel cells. From the above, it is preferable that the catalyst in the first catalyst layer contains iridium, and the catalyst in the second catalyst layer contains platinum.

[0030] The amount of catalyst contained in each catalyst layer can be controlled, for example, by the thickness of the catalyst layer.

[0031] The average thickness T of the catalyst layer is not particularly limited, but from the viewpoint of ensuring the supported amount of the catalyst, it is preferably 0.1 μm to 50 μm, and more preferably 0.5 μm to 40 μm.

[0032] Also, the maximum thickness of the catalyst layer is preferably 3T or less. That is, in the catalyst layer, it is preferable that there is no portion thicker than three times the average thickness T.

[0033] The fact that the maximum thickness of the catalyst layer is 3T or less indicates that the proportion of coarse particles in the catalyst layer is reduced, and indicates that local overheating during the manufacturing process is more suppressed.

[0034] The average thickness T of the catalyst layer is measured by the method described in JIS K 7130:1999.

[0035] [Method for manufacturing an electrolyte membrane with a catalyst layer] The method for manufacturing an electrolyte membrane with a catalyst layer according to the present disclosure includes a step of forming a catalyst layer on an electrolyte membrane. The step of forming a catalyst layer includes a step of applying a catalyst layer forming composition containing a resin and catalyst particles (hereinafter, also referred to as the "coating step"), and a step of drying the catalyst layer forming composition (hereinafter, also referred to as the "drying step"). After drying, the average thickness T of the catalyst layer is set to 0.1 μm to 50 μm, and the maximum thickness is set to 3T or less.

[0036] In the method for manufacturing an electrolyte membrane with a catalyst layer according to the present disclosure, by setting the average thickness T of the catalyst layer after drying to 0.1 μm to 50 μm and the maximum thickness to 3T or less, the proportion of coarse particles in the catalyst layer can be reduced.

[0037] Furthermore, in the method for manufacturing an electrolyte membrane with a catalyst layer according to this disclosure, by setting the average thickness T of the catalyst layer after drying to 0.1 μm to 50 μm and the maximum thickness to 3 T or less, catalyst particles are uniformly distributed within the catalyst layer, and localized overheating is suppressed.

[0038] Methods to ensure the maximum thickness of the catalyst layer after drying is 3T or less include using a substrate with an inclination of 0° to 5° relative to the horizontal direction in the coating and drying processes, and using coating equipment such as applicators and squeegees extensively. For example, in areas where thickness fluctuations are likely to occur, such as the start and end of coating, a method can be used to control the layer thickness uniformly by passing the material through a clearance multiple times. Depending on the shape of the temporary support, methods can also be used to hold the surrounding area with a frame to prevent liquid from accumulating at the edges. In addition, regulating plates may be installed at the start and end of coating.

[0039] (Coating Process) In the coating process, a catalyst layer-forming composition containing a resin and catalyst particles is applied. As will be described later, the catalyst layer-forming composition may be applied to an electrolyte membrane or to a temporary support. That is, the object to which the catalyst layer-forming composition is applied may be an electrolyte membrane or a temporary support.

[0040] The catalyst layer formation composition comprises a resin and catalyst particles. Details of the resin and catalyst particles are as described above.

[0041] From the viewpoint of ease of application, the catalyst layer-forming composition preferably contains a solvent. Examples of solvents include water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol.

[0042] The catalyst layer forming composition may be a solution or a dispersion.

[0043] In order to achieve an average thickness T of the catalyst layer after drying of 0.1 μm to 50 μm, it is preferable to apply the catalyst layer-forming composition to a thickness of 1 μm to 500 μm, and more preferably to a thickness of 1.5 μm to 30 μm.

[0044] "Coating thickness" refers to the thickness of the catalyst layer-forming composition film before drying, which is formed by coating the catalyst layer-forming composition.

[0045] The coating process is preferably carried out in an atmosphere with a dew point of 20°C or lower. The dew point is measured using a dew point meter. By carrying out the coating process in an atmosphere with a dew point of 20°C or lower, aggregation of catalyst particles due to moisture absorption can be suppressed, and the proportion of coarse particles in the catalyst layer can be further reduced.

[0046] The coating process may be carried out in a dry room under an atmosphere with a dew point of -40°C or higher.

[0047] The application method is not particularly limited, and known application methods can be used.

[0048] Examples of coating devices include bar coaters, screen printers, doctor blades, reverse coaters, die coaters, spray coaters, gravure coaters, and comma coaters. Among these, the coating process is preferably carried out by screen printing. In screen printing, the catalyst layer-forming composition is usually applied to the object to be coated via a mesh plate. As the catalyst layer-forming composition passes through the mesh plate, the slightly aggregated catalyst particles in the catalyst layer-forming composition can be dispersed, and the proportion of coarse particles in the catalyst layer can be further reduced.

[0049] Furthermore, before applying the catalyst layer-forming composition to the object to be coated, the catalyst layer-forming composition may be passed through a filter, and then applied by a coating method other than screen printing.

[0050] (drying process)

[0051] The method for drying the catalyst layer-forming composition is not particularly limited, and known drying methods can be used. The drying temperature is, for example, 25°C to 130°C. The drying time is, for example, 1 minute to 1 hour.

[0052] To ensure that the maximum thickness of the catalyst layer after drying is 3T or less, it is preferable that the coating process and the drying process be performed on a substrate with an inclination of 0° to 5° with respect to the horizontal direction. For example, an object to be coated is placed on a substrate with an inclination of 0° to 5° with respect to the horizontal direction, and the catalyst layer forming composition is applied to the object to be coated.

[0053] By performing the coating and drying processes on a substrate with an inclination of 0° to 5° relative to the horizontal, liquid accumulation at the edges of the object being coated due to the flow of the catalyst layer forming composition is less likely to occur. As a result, the maximum thickness of the catalyst layer after drying can be 3T or less.

[0054] The following describes in detail the step of forming a catalyst layer on an electrolyte membrane in the method for manufacturing an electrolyte membrane with a catalyst layer according to this disclosure.

[0055] -First Embodiment (Transfer Method)- In the first embodiment of the method for manufacturing an electrolyte membrane with a catalyst layer according to the present disclosure, the step of forming the catalyst layer preferably includes: applying a catalyst layer forming composition containing a resin and catalyst particles onto a temporary support (hereinafter also referred to as "coating step A"), drying the catalyst layer forming composition to produce a transfer substrate having a catalyst layer (hereinafter also referred to as "drying step A"), arranging the transfer substrate on the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact, and performing thermocompression bonding between the electrolyte membrane and the transfer substrate (hereinafter also referred to as "thermocompression bonding step"), and peeling off the temporary support to produce an electrolyte membrane with a catalyst layer (hereinafter also referred to as "temporary support peeling step").

[0056] (Coating process A) The temporary support is not particularly limited as long as it is a substrate that can hold the catalyst layer and can be peeled off after the thermocompression bonding process.

[0057] Examples of temporary supports include polymer films such as polyimide, polyethylene terephthalate, polycarboxylic acid aramid, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyetherimide, polyacrylate, and polyethylene naphthalate. Alternatively, the temporary support may be a fluororesin film such as ethylene tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroperfluoroalkyl vinyl ether copolymer, or polytetrafluoroethylene (PTFE).

[0058] The thickness of the temporary support is not particularly limited, but is preferably 250 μm or less, and more preferably 50 μm or less. The lower limit of the thickness is, for example, 30 μm.

[0059] The thickness of the temporary support is measured by the method described in JIS K 7130:1999.

[0060] Details of the method for applying the catalyst layer-forming composition are as described in the section on the application process above.

[0061] (Drying Step A) In drying step A, the catalyst layer-forming composition is dried to produce a transfer substrate having a catalyst layer. Details of the method for drying the catalyst layer-forming composition are as described in the drying step section above.

[0062] The transfer substrate comprises a temporary support and a catalyst layer disposed on the temporary support. In the transfer substrate, the catalyst layer contains a resin and catalyst particles, some of which form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm². ２ ~2.0 pieces / cm ２ It is preferable that this be the case.

[0063] (Thermocompression bonding process) In the thermocompression bonding process, a transfer substrate is placed on the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact, and thermocompression bonding is performed between the electrolyte membrane and the transfer substrate.

[0064] The thermocompression bonding process can be carried out using a known thermocompression bonding apparatus, for example, by pressing a heating element against the material or by sandwiching it between heating elements. Examples of heating elements include a heating plate, a heating block, and a heating roll. Alternatively, a laminator equipped with a pair of heating rolls may be used, and the material may be passed between the pair of rolls to perform the thermocompression bonding.

[0065] The temperature for heat sealing is preferably 80°C to 200°C, and more preferably 130°C to 180°C. The pressure for heat sealing is preferably 0.1 MPa to 5.0 MPa, and more preferably 0.5 MPa to 3.0 MPa.

[0066] (Temporary support removal process) The method for removing the temporary support is not particularly limited and can be carried out by a method that is generally known.

[0067] When manufacturing an electrolyte membrane with a catalyst layer using a transfer method, quality control during the manufacturing process can be performed by measuring the proportion of coarse particles on the surface of the catalyst layer in the transfer substrate.

[0068] The first embodiment of the method for manufacturing an electrolyte membrane laminate according to this disclosure may include other steps besides the steps described above.

[0069] A step of heating the transfer substrate and electrolyte membrane may be included before the thermocompression bonding process. Heating the transfer substrate and electrolyte membrane softens the catalyst layer contained in the transfer substrate, improving adhesion to the electrolyte membrane. The means of heating the transfer substrate and electrolyte membrane are not particularly limited, and known heating methods can be used. The heating temperature of the transfer substrate is, for example, 50°C to 200°C. The heating temperature of the electrolyte membrane is, for example, 50°C to 150°C.

[0070] Alternatively, two transfer substrates may be prepared, and the transfer substrates may be placed on each side of the electrolyte membrane, and the electrolyte membrane and the transfer substrates may be heat-compressed. For example, the first transfer substrate comprises a first temporary support and a first catalyst layer (containing iridium as a catalyst) placed on the first temporary support. The second transfer substrate comprises a second temporary support and a second catalyst layer (containing platinum as a catalyst) placed on the second temporary support.

[0071] In the first embodiment of the method for manufacturing an electrolyte membrane with a catalyst layer according to the present disclosure, in drying step A, the average thickness T of the catalyst layer after drying is set to 0.1 μm to 50 μm, and the maximum thickness is set to 3T or less, thereby reducing the proportion of coarse particles in the catalyst layer. As a result, charge concentration on coarse particles is suppressed, and the generation of pores in the electrolyte membrane caused by coarse particles is suppressed.

[0072] -Second Embodiment (Coating Method)- In the second embodiment of the method for manufacturing an electrolyte membrane with a catalyst layer according to the present disclosure, the step of forming the catalyst layer preferably includes a step of coating an electrolyte membrane with a catalyst layer-forming composition containing a resin and catalyst particles (hereinafter also referred to as "coating step B") and a step of drying the catalyst layer-forming composition to produce an electrolyte membrane with a catalyst layer (hereinafter also referred to as "drying step B").

[0073] (Coating Process B) Details of the electrolyte membrane are as described above. Details of the method for coating the catalyst layer formation composition are as described in the coating process section above.

[0074] (Drying Step B) In drying step B, the catalyst layer-forming composition is dried. Details of the method for drying the catalyst layer-forming composition are as described in the drying step section above.

[0075] In a second embodiment of the method for manufacturing an electrolyte membrane with a catalyst layer according to the present disclosure, in drying step B, the average thickness T of the catalyst layer after drying is set to 0.1 μm to 50 μm, and the maximum thickness is set to 3T or less, thereby reducing the proportion of coarse particles in the catalyst layer. As a result, internal stress concentration is suppressed, and delamination between the electrolyte membrane and the catalyst layer is suppressed.

[0076] [Laminate] The laminate according to this disclosure comprises a temporary support and a catalyst layer disposed on the temporary support, wherein the catalyst layer includes a resin and catalyst particles, some of which form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm ２ ~2.0 pieces / cm ２ That is the case.

[0077] The laminate according to this disclosure is useful as a transfer substrate in the first embodiment of the method for manufacturing the catalyst layer-attached electrolyte membrane described above.

[0078] In the laminate according to this disclosure, by having the proportion of coarse particles on the surface of the catalyst layer within the above range, localized overheating during the manufacturing process can be suppressed. Furthermore, by having the proportion of coarse particles within the above range, charge concentration on the coarse particles is suppressed, and the generation of pores in the electrolyte membrane caused by the coarse particles is suppressed.

[0079] [Membrane Electrode Assembly] The membrane electrode assembly according to this disclosure includes an electrolyte membrane with a catalyst layer according to this disclosure. Specifically, the electrolyte membrane with a catalyst layer according to this disclosure preferably comprises an anode catalyst layer, an electrolyte membrane, and a cathode catalyst layer in this order, and the membrane electrode assembly according to this disclosure preferably comprises an anode gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode gas diffusion layer.

[0080] Examples of gas diffusion layers include porous carbon materials and porous metal materials. Examples of porous carbon materials include carbon paper, carbon cloth, carbon mesh, and nonwoven carbon fabric. Examples of porous metal materials include metal mesh, foamed metal, metal fabric, sintered metal, and nonwoven metal fabric. Examples of metals include titanium, aluminum, nickel, nickel-chromium alloys, copper and its alloys, silver, aluminum alloys, zinc alloys, lead alloys, titanium, niobium, tantalum, iron, stainless steel, gold, and platinum.

[0081] The membrane electrode assembly according to this disclosure includes an electrolyte membrane with a catalyst layer according to this disclosure, and therefore offers excellent productivity.

[0082] [Water electrolysis apparatus] The water electrolysis apparatus according to this disclosure includes a membrane electrode assembly according to this disclosure. In particular, the water electrolysis apparatus according to this disclosure is preferably a solid polymer type water electrolysis apparatus.

[0083] The present disclosure will be further explained below with reference to examples. The materials, amounts used, proportions, and details of each process shown in the following examples may be modified as appropriate, as long as they do not deviate from the spirit of this disclosure. Therefore, the scope of this disclosure is not limited to the specific examples shown below. Note that "parts" are all based on mass.

[0084] [Example 1] <Preparation of the composition for forming the first catalyst layer> 3.96 g of iridium oxide (manufactured by Furuya Metals Co., Ltd.), 2.58 g of a 1:1 mixture of isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as dispersion solvents, and 4.5 g of 20% by mass Nafion® dispersion solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed in a nitrogen-purged glove box and placed in a vial (solid content concentration 44% by mass, approximately 10% by volume). The turbidity removed from the glove box was stirred in a rotary homogenizer at 2000 rpm (revolutions per minute) for 30 minutes to obtain a dispersion, which was used as the composition for forming the first catalyst layer.

[0085] <Preparation of Composition for Forming the Second Catalyst Layer> 6.17 g of platinum-supported carbon (manufactured by Tanaka Kikinzoku Co., Ltd.), 37.95 g of a 1:1 mixture of isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as dispersion solvents, and 18.35 g of 20% by mass Nafion® dispersion solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed in a nitrogen-purged glove box and placed into vials (solid content concentration 16% by mass, approximately 7% by volume). The turbidity removed from the glove box was stirred in a rotary homogenizer at 2000 rpm for 30 minutes to obtain a dispersion, which was used as the composition for forming the second catalyst layer.

[0086] <Filtration of the first and second catalyst layer forming compositions> A filter with a mesh diameter of 200 μm was set at the tip of a syringe, and the first and second catalyst layer forming compositions were respectively pumped through the filter for filtration. Particles larger than 200 μm were removed by filtration.

[0087] <Fabrication of Electrolyte Membrane with Catalyst Layer> A PTFE film (product name "Nitoflon No. 900 UL", manufactured by Nitto Denko Corporation, 50 μm thick, 50 cm x 50 cm) was prepared as a temporary support. The first temporary support was placed on a substrate with a tilt of 0° relative to the horizontal. The composition for forming the first catalyst layer was applied to a 25 cm x 25 cm area on the first temporary support using the applicator blade method. The application process was carried out in an atmosphere controlled to a temperature of 25°C and a dew point of 20°C. The clearance between the applicator and the substrate was adjusted to achieve a coating thickness of 30 μm. After drying for more than 10 seconds in the same atmosphere, it was dried in a hot air dryer at 90°C to form a first catalyst layer with an average thickness of 2.5 μm on the first temporary support. The maximum thickness of the first catalyst layer was 2.6 μm. Similarly, a second temporary support was placed on a substrate with a tilt of 0° relative to the horizontal. A composition for forming the second catalyst layer was applied to the second temporary support using the applicator blade method. The application process was carried out in an atmosphere controlled to a temperature of 25°C and a dew point of 20°C. The clearance between the applicator and the substrate was adjusted to achieve a coating thickness of 190 μm. After drying for more than 10 seconds in the same atmosphere, the material was dried in a hot air dryer at 90°C to form a second catalyst layer with an average thickness of 15 μm on the second temporary support. The maximum thickness of the second catalyst layer was 17.5 μm. This resulted in obtaining a first transfer substrate having a first temporary support and a first catalyst layer placed on the first temporary support. Furthermore, a second transfer substrate having a second temporary support and a first catalyst layer placed on the second temporary support was also obtained.

[0088] A first transfer substrate and a second transfer substrate were placed on both sides of an electrolyte membrane (product name "Nafion® N115", manufactured by Chemours, 127 μm thick, 30 cm square). The first transfer substrate was positioned so that it was in contact with the electrolyte membrane and the first catalyst layer, and the second transfer substrate was positioned so that it was in contact with the electrolyte membrane and the second catalyst layer.

[0089] The product was preheated using a heater at a temperature of 100°C for 3 minutes.

[0090] Using a roll-type press machine, the roll temperature was adjusted by induction heating, and heat-press bonding was performed at a roll temperature of 160°C and a press pressure of 1 MPa.

[0091] The first and second temporary supports were peeled off using an adhesive roll. A catalyst-layered electrolyte membrane was obtained, comprising a first catalyst layer, an electrolyte membrane, and a second catalyst layer in that order.

[0092] [Example 2] An electrolyte film with a catalyst layer was obtained in the same manner as in Example 1, except that the first and second temporary supports were placed on a substrate tilted at 5° with respect to the horizontal direction and the coating process was carried out.

[0093] [Example 3] An electrolyte membrane with a catalyst layer was obtained in the same manner as in Example 2, except that the coating thickness of the first catalyst layer forming composition was 60 μm and the coating thickness of the second catalyst layer forming composition was 400 μm.

[0094] [Example 4] An electrolyte film with a catalyst layer was obtained in the same manner as in Example 1, except that a T-die was used instead of an applicator, and the coating process was carried out with the first temporary support and the second temporary support placed on a substrate tilted at 10° with respect to the horizontal direction.

[0095] [Example 5] Without using a dispersion solvent, a first catalyst layer forming composition and a second catalyst layer forming composition were prepared using a 20% by mass Nafion® dispersion solution heated to evaporate the solvent. The obtained first catalyst layer forming composition and second catalyst layer forming composition had a solid content concentration of 50% by volume or more. The obtained first catalyst layer forming composition was applied to one surface of an electrolyte membrane (product name "Nafion® N115", manufactured by Chemours, 127 μm thick, 30 cm square) and dried. The application process was carried out in an atmosphere controlled at a temperature of 25°C and a dew point of 20°C. The application thickness was 10 μm. The obtained second catalyst layer forming composition was applied to the other surface of the electrolyte membrane and dried. The application process was carried out in an atmosphere controlled at a temperature of 25°C and a dew point of 20°C. The application thickness was 60 μm.

[0096] [Example 6] An electrolyte film with a catalyst layer was obtained in the same manner as in Example 1, except that the coating process was carried out in an atmosphere controlled to a temperature of 25°C and a dew point of 22°C.

[0097] [Example 7] An electrolyte film with a catalyst layer was obtained in the same manner as in Example 1, except that the coating process was carried out in an atmosphere controlled to a temperature of 25°C and a dew point of 15°C.

[0098] [Comparative Example 1] A catalyst layer-attached electrolyte membrane was obtained in the same manner as in Example 1, except that the dispersion time for the first catalyst layer-forming composition and the second catalyst layer-forming composition was set to 3 minutes and filtration was not performed.

[0099] In the obtained electrolyte membrane with catalyst layers, the proportion of coarse particles on the surface of the first catalyst layer and the second catalyst layer was measured.

[0100] Furthermore, the proportion of coarse particles on the surfaces of the first catalyst layer and the second catalyst layer in the first and second transfer substrates was measured. The proportion of coarse particles was similar in the first catalyst layer of the electrolyte membrane with a catalyst layer and in the first catalyst layer of the first transfer substrate. The proportion of coarse particles was also similar in the second catalyst layer of the electrolyte membrane with a catalyst layer and in the second catalyst layer of the second transfer substrate.

[0101] <Amount of Coarse Particles> Light was irradiated onto the surface of the catalyst layer using a light-reflecting detector. The in-plane distribution of reflected light was binarized to detect areas with high brightness. From the image obtained after binarization, secondary particles with a major axis of 100 μm or larger were identified. ２ In any given region, the number of secondary particles with a major axis of 100 μm or more was measured. Based on the measured number, the proportion of coarse particles was calculated.

[0102] The following evaluations were performed using the obtained electrolyte membrane with catalyst layer.

[0103] <Uniformity> In the electrolyte membrane with a catalyst layer, the electrical resistivity of the surfaces of the first catalyst layer and the second catalyst layer was measured. Specifically, the electrical resistivity of the surfaces of the first and second catalyst layers was measured using a resistivity meter (product name "Lorestar-GXII MCP-T710", manufactured by Nitto Seikou Analytech Co., Ltd.) using the four-terminal method. Measurements were taken at 100 locations on each surface, and the average value was calculated. The percentage of locations where the electrical resistivity was 20% or more lower than the average electrical resistivity was calculated. Based on the above percentage, uniformity was evaluated. The evaluation criteria are as follows: A: 5% or less. B: 6% to 10%. C: 11% to 20%. D: 21% to 50%. E: 51% or more.

[0104]

[0105] As shown in Table 1, Examples 1 to 7 include an electrolyte membrane and a catalyst layer disposed on the electrolyte membrane. The catalyst layer contains a resin and catalyst particles, some of which form secondary particles with a major axis of 100 μm or more. The proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm². ２ ~2.0 pieces / cm ２ Therefore, it was found to have excellent uniformity. On the other hand, in Comparative Example 1, the proportion of secondary particles with a major axis of 100 μm or more was 2.0 particles / cm ２ It was extremely high, and there was a large variation in electrical resistivity.

[0106] Furthermore, the disclosure of Japanese Patent Application No. 2024-171064, filed on September 30, 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 as being incorporated by reference.

Claims

1. The apparatus comprises an electrolyte membrane and a catalyst layer disposed on the electrolyte membrane, wherein the catalyst layer contains a resin and catalyst particles, a portion of which the catalyst particles form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm². ２ ~2.0 pieces / cm ２ This is an electrolyte membrane with a catalyst layer.

2. The catalyst layer comprises a first catalyst layer and a second catalyst layer, the first catalyst layer, the electrolyte membrane, and the second catalyst layer are provided in this order, the catalyst in the first catalyst layer comprises iridium, and the catalyst in the second catalyst layer comprises platinum, as described in claim 1.

3. The catalyst layer having an average thickness T of 0.1 μm to 50 μm and a maximum thickness of 3 T or less, according to claim 1.

4. A method for manufacturing an electrolyte membrane with a catalyst layer, comprising the step of forming a catalyst layer on an electrolyte membrane, wherein the step of forming the catalyst layer comprises the step of applying a catalyst layer forming composition containing a resin and catalyst particles, and the step of drying the catalyst layer forming composition, wherein the average thickness T of the catalyst layer after drying is 0.1 μm to 50 μm, and the maximum thickness is 3T or less.

5. The method for producing an electrolyte membrane with a catalyst layer according to claim 4, wherein the coating thickness of the catalyst layer forming composition is 1 μm to 500 μm.

6. The method for manufacturing an electrolyte membrane with a catalyst layer according to claim 4 or claim 5, wherein the steps of applying the catalyst layer-forming composition and drying the catalyst layer-forming composition are performed on a substrate with an inclination of 0° to 5° with respect to the horizontal direction.

7. The method for producing an electrolyte membrane with a catalyst layer according to claim 4 or claim 5, wherein the step of applying the catalyst layer-forming composition is carried out in an atmosphere with a dew point of 20°C or lower.

8. The method for producing an electrolyte membrane with a catalyst layer according to claim 4 or claim 5, wherein the step of applying the catalyst layer-forming composition is performed by a screen printing method.

9. A method for manufacturing an electrolyte membrane with a catalyst layer according to claim 4 or 5, comprising the steps of: applying a catalyst layer forming composition containing a resin and catalyst particles onto a temporary support; drying the catalyst layer forming composition to produce a transfer substrate having a catalyst layer; arranging the transfer substrate on the electrolyte membrane so that the electrolyte membrane and the catalyst layer are in contact, and performing thermocompression bonding between the electrolyte membrane and the transfer substrate; and peeling off the temporary support.

10. The device comprises a temporary support and a catalyst layer disposed on the temporary support, wherein the catalyst layer comprises a resin and catalyst particles, a portion of which the catalyst particles form secondary particles with a major axis of 100 μm or more, and the proportion of secondary particles with a major axis of 100 μm or more on the surface of the catalyst layer is 0.01 particles / cm². ２ ~2.0 pieces / cm ２ It is a laminated structure.

11. A membrane electrode assembly comprising an electrolyte membrane with a catalyst layer according to any one of claims 1 to 3.

12. A water electrolysis apparatus comprising the membrane electrode assembly described in claim 11.

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