Method for manufacturing catalyst coating films

Abstract

The present invention provides a method for producing a catalyst-coated ion-conductive film for use in electrochemical devices such as fuel cells or electrolytic devices. The method includes providing an electrolyte membrane having a first surface and a second surface, the first surface being located opposite the second surface. A first catalyst ink is deposited on the first surface of the electrolyte membrane to form a first wet catalyst layer, which is then dried to form a first catalyst layer on the first surface of the electrolyte membrane. The first catalyst ink comprises a first ion-conducting polymer, a first electrolytic catalyst, and a first dispersant. Next, a second catalyst ink is deposited on the second surface of the electrolyte membrane to form a second wet catalyst layer, which is then dried to form a second catalyst layer. The second catalyst ink comprises a second ion-conducting polymer, a second electrolytic catalyst, and a second dispersant. Before depositing the second catalyst ink onto the second surface of the electrolyte film, the first catalyst layer is exposed to a temperature A of 130°C or higher, and the second catalyst layer is exposed to a temperature B lower than temperature A.

Description

Technical Field

[0001] The present invention relates to a method for producing a catalyst coated membrane for an electrochemical device such as a fuel cell or an electrolyzer. The present invention also relates to related catalyst coated membranes.

Background Art

[0002] The electrolysis of water to produce high purity hydrogen and oxygen can be carried out in both alkaline and acidic electrolyte systems. These electrolyzers using an electrolyte membrane which is a solid proton conductive polymer membrane or a proton exchange membrane (PEM) are known as proton exchange membrane water electrolysers (PEMWE). An electrolytic cell utilizing a solid anion conductive polymer membrane or an anion exchange membrane (AEM) is known as an anion exchange membrane water electrolyser (AEMWE).

[0003] Electrolyte membranes such as PEM and AEM (also known as ion conductive membranes) are also used in fuel cells. In a proton exchange membrane fuel cell (PEMFC), the membrane is proton conductive, and protons generated at the anode are transported through the membrane to the cathode where they combine with oxygen to form water.

[0004] A catalyst coated membrane (CCM) can be used in an electrochemical device such as an electrolyzer and a fuel cell. Such a CCM includes an electrolyte membrane such as a PEM or an AEM, and an anode catalyst layer and / or a cathode catalyst layer are applied to the surface of the membrane, and the anode catalyst layer and the cathode catalyst layer are applied to the surfaces on the opposite sides of the membrane.

[0005] In water electrolysis applications, hydrogen evolution reaction (HER) catalysts, such as platinum-containing HER catalysts like platinum on a carbon support, are used in the cathode catalyst layer. Oxygen evolution reaction (OER) catalysts are used in the anode catalyst layer of the electrolysis device. In PEMWE applications, suitable OER catalysts include iridium or iridium oxide, or oxides containing both iridium and ruthenium. In AEMWE applications, non-platinum group metal OER catalysts, such as alloys and oxides of nickel, cobalt, iron, and copper, can also be used.

[0006] In fuel cell applications, an oxygen reduction reaction (ORR) catalyst is used in the cathode catalyst layer, and a hydrogen oxidation reaction (HOR) catalyst is used in the anode catalyst layer. In PEMFC applications, suitable cathode and anode catalyst materials include platinum group metals or alloys of platinum group metals with one or more other metals, such as platinum or alloys of platinum with one or more other metals.

[0007] A CCM may be incorporated into a membrane electrode assembly (MEA) that essentially consists of five layers. The central layer is an electrolyte membrane. On either side of the electrolyte membrane are electrocatalyst layers containing electrocatalysts designed for specific electrolytic reactions. Finally, adjacent to each electrocatalyst layer, depending on the final MEA application and stack configuration, there are gas diffusion layers or porous transport layers. Such layers allow reactants to reach the electrocatalyst layers and products to detach.

[0008] Membrane electrode assemblies can be constructed by many known methods. A common method involves depositing one or both of the electrocatalytic layers onto a decal transfer substrate and transferring the electrocatalytic layers to both sides of an ion-conducting membrane. Subsequently, a gas diffusion layer is applied to the electrocatalytic layer. Alternatively, the electrocatalytic layer can be applied to a gas diffusion layer to form a gas diffusion electrode, which is then combined with the ion-conducting membrane. Membrane electrode assemblies can be prepared by a combination of these methods, for example, by applying one electrocatalytic layer to an ion-conducting membrane to form a catalyst-coated ion-conducting membrane and applying the other electrocatalytic layer as a gas diffusion electrode. Conventionally, the electrocatalytic layers are coated using an electrocatalytic ink containing an electrocatalytic material, an ion-conducting polymer, a solvent / dispersant and / or diluent, and any desired agents to be included in the electrocatalytic layer.

[0009] Demand for hydrogen-based solutions to reduce carbon emissions is expected to continue to grow rapidly in line with net-zero targets. To meet this demand, a rapid increase in the production of key components such as CCMs is required. Minimizing the use of key raw materials (such as platinum group metal catalysts, e.g., iridium-based catalyst materials, and ion-conducting polymers), reducing waste, and promoting recycling offer significant advantages.

[0010] There is a need to further enhance and develop methods for manufacturing catalyst-coated ion-conductive films, particularly methods that enable large-scale production while optimizing the use and recycling of key raw materials. [Overview of the project]

[0011] In a first aspect of the present invention, a method for producing a catalyst coating film is provided, the method being: To provide an electrolyte membrane having a first surface and a second surface, wherein the first surface is located on the opposite side of the second surface, The method involves depositing a first catalyst ink on a first surface of an electrolyte membrane to form a first wet catalyst layer, and the first catalyst ink comprises a first ion-conducting polymer, a first electrolytic catalyst, and a first dispersant, and drying the first wet catalyst layer to form a first catalyst layer on the first surface of the electrolyte membrane. The method includes depositing a second catalyst ink, comprising a second ion-conducting polymer, a second electrolytic catalyst, and a second dispersant, onto a second surface of an electrolyte membrane (opposite to the first catalyst layer) to form a second wet catalyst layer, and drying the second wet catalyst layer to form a second catalyst layer. Before depositing the second catalyst ink onto the second surface of the electrolyte film, the first catalyst layer is exposed to temperature A, which is 130°C or higher, and the second catalyst layer is exposed to temperature B, which is lower than temperature A.

[0012] The method can be described as a direct-to-membrane (DTM) manufacturing method, which differs from conventional decal methods. The DTM method requires the catalytic ink to be applied directly to an electrolyte (ion-conducting) membrane, rather than to a decal transfer substrate or gas diffusion layer.

[0013] The DTM method can offer many advantages over the decal method. For example, it requires fewer steps and is more efficient. Avoiding hot pressing can result in higher quality CCM. For instance, the CCM may have a more uniform (consistent thickness) layer. Hot pressing uses high temperatures and pressures that can cause deformation.

[0014] While several DTM processes are known, they are not widely adopted because electrolyte membranes can become dimensionally unstable when exposed to water / organic solvents. Catalyst inks use water / organic solvents to disperse electrolytic catalysts, which can cause the membrane to swell and create defects in the layer. Such problems can be mitigated on a small scale (e.g., laboratory scale), but prove more challenging in real-world situations.

[0015] Park et al. (Journal of Power Sources, 479, 2020, 228819, ISSN 0378-7753) describe a roll-to-roll fabrication of a catalyst coating film for a cryogenic electrolytic cell. First, an IrO2 ink was directly coated onto the film roll-to-roll (R2R) (80-100°C), and then a Pt / C electrolytic catalyst layer was applied by spray coating. Exposure of the first catalyst layer to temperatures above 130°C is not disclosed.

[0016] The method of the present invention allows for the direct coating of both sides of an electrolyte membrane with a catalyst ink. The second catalyst layer is applied to the electrolyte membrane after the first layer has been exposed to temperature A. While not bound by theory, the inventors believe that the use of temperature A alters the structure of the first catalyst layer. This structural alteration provides advantages to subsequent processing and the resulting CCM. By using temperature A, which is higher than temperature B, the battery performance of the resulting CCM is improved.

[0017] The present invention also relates to CCMs obtained or obtainable by the methods of the present invention, as well as their use in electrochemical devices such as fuel cells and electrolytic cells.

[0018] (Detailed explanation) The method of the present invention requires exposing the first catalyst layer to temperature A before depositing the second catalyst ink. In this way, the second catalyst ink is deposited on the second surface of the electrolyte membrane opposite to the first catalyst layer.

[0019] Temperature A Temperature A is 130°C or higher. Temperature A may also be 135°C or higher, 140°C or higher, 145°C or higher, 150°C or higher, 155°C or higher, 160°C or higher, or 165°C or higher, and / or Temperature A may be 220°C or lower, 210°C or lower, 200°C or lower, 190°C or lower, 180°C or lower, or 170°C or lower.

[0020] In one embodiment, temperature A is 135 to 175°C, for example, 140 to 170°C, as demonstrated in the example.

[0021] Wet catalyst layer The method includes depositing a first catalyst ink on a first surface of an electrolyte membrane to form a first wet catalyst layer. The catalyst ink can be deposited on the electrolyte membrane as a single continuous strip so as to extend substantially along the length of the membrane (i.e., in the mechanical direction), for example. The catalyst ink can be deposited as a plurality of parallel continuous strips in the mechanical direction, each continuous strip preferably extending substantially along the length of the ion-conducting membrane. Alternatively, the catalyst formulation can be deposited as a plurality of spaced-apart (i.e., discontinuous) patches, each patch spaced apart in the mechanical direction. Each continuous strip or patch can extend partially or completely across the width of the membrane (i.e., in the transverse direction). The wet catalyst layer can extend partially or completely across the width of the membrane (i.e., in the transverse direction).

[0022] The first catalyst ink can be deposited using a slot die coating process, knife coating, bar coating, inkjet printing, gravure printing, curtain coating, screen printing, or spray coating process.

[0023] Preferably, the first catalyst ink is deposited by a slot die. The slot die coating process allows the wet catalyst layer to be formed with a consistent thickness in a single pass. In contrast, spray coating requires multiple coats to achieve the desired thickness and results in greater thickness variation.

[0024] The first wet catalyst layer can be obtained by depositing a single layer. Alternatively, the first wet catalyst layer may be obtained by depositing two or more sublayers, that is, by constructing the wet layer before drying.

[0025] Preferably, the first wet catalyst layer is obtained by depositing a single layer in order to reduce the number of steps required to fabricate the CCM. The method of the present invention can enable a thicker catalyst layer to be deposited in a single pass while maintaining an acceptable low level of cracking defects. The first wet catalyst layer may have a thickness of at least 50 μm, at least 70 μm, or at least 100 μm, and / or the first wet catalyst layer may have a thickness of 150 μm or less, 120 μm or less, or 90 μm or less, for example, 50-90 μm. The wet layer thickness can be measured directly. However, it may be more practical to determine the wet layer thickness from the dry layer thickness and the solid content of the catalyst ink.

[0026] Dry The first wet catalyst layer can be dried using a drying oven or furnace (e.g., heated by hot air impingement and / or infrared rays), and / or the first catalyst layer can be exposed to temperature A.

[0027] Preferably, the drying oven or furnace is in the form of a drying tunnel, i.e., having two separate openings (an inlet and an outlet), allowing an object to be transported into one opening and out again through the tunnel. This enables the process to be operated continuously rather than as a batch process.

[0028] The wet catalyst layer can be rapidly dried by transporting it through the drying tunnel, for example, at a speed of at least 2 m / min (2 meters per minute), at least 5 m / min, or at least 10 m / min, and / or at a speed of 20 m / min or less or 15 m / min or less.

[0029] The first catalyst layer may be exposed to temperature A by transporting it through the drying tunnel. Using the drying tunnel, it can be ensured that substantially all of the dispersant from the catalyst ink is removed in a single heating step.

[0030] Preferably, a single drying tunnel is used to dry the first wet catalyst layer, and then the first (dried) catalyst layer is exposed to temperature A. In this way, the first wet catalyst layer can be dried and the first catalyst layer can be exposed to temperature A by passing through the drying tunnel in a single pass. The drying tunnel may include two or more zones having different temperatures. For example, one zone may have a temperature lower than A, and another zone may have a temperature higher than A. In this way, one zone may be useful for drying the wet catalyst layer, and another zone may be used for annealing the resulting dry catalyst layer. Preferably, a single drying tunnel is used to dry the first wet catalyst layer, and then the first (dried) catalyst layer is exposed to temperature A, where A is 135 to 175°C, as shown in the examples.

[0031] electrolyte membrane Providing an electrolyte membrane may include unwinding the electrolyte membrane from a supply roller. The electrolyte membrane may be provided as part of a laminated substrate, and providing an electrolyte membrane may include unwinding the laminated substrate from a supply roller, the laminated substrate including the electrolyte membrane and a first support film located on a second surface of the electrolyte membrane.

[0032] After the first catalyst layer is applied, the substrate may be rewound onto a recovery roller. Thus, the method may further include rewounding an electrolyte membrane onto a recovery roller, the electrolyte membrane being positioned between the first catalyst layer and the first support film.

[0033] The electrolyte membrane contains an ion-conducting polymer. Preferably, the ion-conducting polymer is a proton-conducting polymer. Preferred ion-conducting polymers are partially or fully fluorinated sulfonic acid polymers, such as perfluorosulfonic acid polymers. For example, the ion-conducting polymer may be based on perfluorosulfonic acid materials such as Nafion® (Chemours Company), Aquivion® (Solvay Specialty Polymers), Flemion® (Asahi Glass Group), and Aciplex® (Asahi Kasei Chemicals Corp.). Alternatively, the ion-conducting material may be based on sulfonated hydrocarbon polymers, such as those available from FuMA-Tech GmbH as fumapem® P, E, or K series products, or those available from JSR Corporation, Toyobo, and other companies.

[0034] The electrolyte membrane may include reinforcing components, such as planar reinforcing components. Preferably, the reinforcing components are porous (i.e., contain pores). The reinforcing components can impart mechanical strength to the ion-conducting membrane. The reinforcing components may include porous reinforcing materials, such as expanded polytetrafluoroethylene (ePTFE) materials, or nanofiber networks, such as networks containing polybenzimidazole (PBI) fibers or glass fibers.

[0035] Typically, in methods for producing catalyst coating films, the electrolyte membrane is an elongated strip.

[0036] The electrolyte membrane may be optionally provided on the support film such that the surface on which the first catalyst ink is deposited faces away from the support film. The support film may provide support and dimensional stability during the step of forming the first catalyst layer, and may provide support and strength during any subsequent storage and / or transport, if not immediately removed. The material forming the support film must provide the necessary support, withstand the process conditions involved in the production of the first catalyst layer, be easily removed without damage, and allow the application of the second catalyst layer. Examples of suitable materials for use include fluoropolymers, e.g., polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymer (PFA), fluorinated ethylene propylene (FEP - copolymer of hexafluoropropylene and tetrafluoroethylene), and polyolefins, e.g., biaxially oriented polypropylene (BOPP).

[0037] Second wet catalyst layer The second ink is deposited on the second surface of the electrolyte membrane to form a second catalyst layer. The second catalyst layer can be obtained by a roll-to-roll (R2R) process.

[0038] The electrolyte membrane may be supported on a roller during deposition. The roller may be a suction (vacuum) roller and / or a heated roller, preferably a heated suction roller. The electrolyte membrane has a first catalyst layer and is fragile, and the suction roller provides stability during the deposition of the second catalyst ink. The heated roller dries the second catalyst ink.

[0039] In one embodiment, depositing the second catalyst ink includes: a) unwinding an elongated porous substrate from a porous substrate supply roller toward the outer surface of a suction roller; b) supporting the porous substrate by suction on the outer surface of the suction roller; c) unwinding an electrolyte membrane from an electrolyte membrane supply roller toward the surface of the porous substrate held toward the outer surface of the suction roller; d) supporting the electrolyte membrane by suction on the outer surface of the porous substrate; e) applying the second catalyst ink to the second surface of the electrolyte membrane; f) peeling the electrolyte membrane coated with the second electrolytic catalyst layer ink from the surface of the porous substrate and winding it onto an electrolyte membrane recovery roller; and g) peeling the porous substrate from the surface of the suction roller.

[0040] Temperature B The second catalyst layer is exposed to temperature B, which is lower than temperature A. Thus, temperature A is the highest temperature experienced by the first catalyst layer.

[0041] Temperature B may be at least 40°C, at least 50°C, at least 60°C, at least 70°C, at least 80°C, or at least 90°C lower than temperature A. Temperature B may be 30°C or higher, 40°C or higher, or 50°C or higher, and / or Temperature B may be 100°C or lower, 90°C or lower, 80°C or lower, 70°C or lower, or 60°C or lower. The second catalyst layer may be exposed to temperature B by a heated roller (e.g., a heated suction roller).

[0042] First catalyst ink and second catalyst ink The first catalytic ink and / or the second catalytic ink comprises an electrolytic catalyst, an ion-conducting polymer (e.g., PFSA), and a dispersant. Preferably, the dispersant comprises water and / or an organic solvent, such as ethanol, propanol (n-propanol / isopropanol), or a mixture thereof.

[0043] Preferably, the ion-conducting polymer is a proton-conducting polymer. Preferably, the ion-conducting polymer contains sulfonic acid groups. Preferably, the ion-conducting polymer is a perfluorinated sulfonic acid (PFSA) ionomer, a partially fluorinated sulfonic acid ionomer, a non-fluorinated hydrocarbon sulfonic acid ionomer, or a mixture thereof. It may be even more preferable that the ion-conducting polymer is a perfluorinated sulfonic acid ionomer or a partially fluorinated sulfonic acid ionomer. It may be particularly preferable that the ion-conducting polymer is a perfluorinated sulfonic acid ionomer. The catalyst ink may contain a blend of ion-conducting polymers, such as a blend of perfluorinated sulfonic acid ionomers.

[0044] First electrolytic catalyst and second electrolytic catalyst Typically, the first electrocatalyst differs from the second electrocatalyst because it is used to catalyze a different reaction. Nevertheless, each of the first and second electrocatalysts optionally includes metal particles supported on a conductive carrier. That is, each of the first and second electrocatalysts may be unsupported metal particles (e.g., finely divided unsupported metal powder) or a supported electrocatalyst in which metal particles (e.g., nanoparticles) are dispersed on a conductive carrier such as a conductive particulate carbon carrier. The metal particles of the electrocatalyst are preferably, (i) Platinum group metals (i.e., platinum, palladium, rhodium, ruthenium, iridium, and osmium), (ii) Gold or silver, (iii) base metals, or (iv) Alloys or mixtures containing one or more of these metals or oxides. Selected from.

[0045] Preferably, the metal in the metal particles of the electrocatalyst is a platinum group metal or an alloy of platinum group metals. The most preferred electrocatalyst metal is platinum, which can be alloyed with other noble or base metals. The base metal is tin or a transition metal, which is not a noble metal. The noble metal is a platinum group metal (platinum, palladium, rhodium, ruthenium, iridium, or osmium), silver, or gold. Preferred base metals are copper, cobalt, nickel, zinc, iron, titanium, molybdenum, vanadium, manganese, niobium, tantalum, chromium, and tin.

[0046] When the electrolytic catalyst is a supported catalyst, the amount of metal particles supported on the conductive support material is preferably in the range of 10 to 90% by weight or 20 to 80% by weight, for example, 30% to 75% by weight, preferably 40% to 60% by weight, and most preferably 45% to 55% by weight, based on the weight of the electrolytic catalyst. The amount of metal particles supported can be determined using inductively coupled plasma mass spectrometry (ICPMS).

[0047] Preferably, the electrocatalyst comprises a conductive carrier and metal particles supported on the conductive carrier. The term “supported” will be readily understood by those skilled in the art. For example, the term “supported” will be understood to include metal particles of the electrocatalyst that are dispersed on (and / or within the pores of) the carrier material and are bonded to or immobilized on the carrier material by physical or chemical bonds. For example, the catalyst may be bonded to or immobilized on the carrier material by ionic or covalent bonds, or by nonspecific interactions such as van der Waals forces.

[0048] The conductive carrier may be a conductive carbon carrier material. Preferably, the conductive carbon carrier material may be carbon powder, for example, carbon black or graphitized carbon black, for example, commercially available carbon black (Cabot Corp. (Vulcan® XC72R) or Akzo Nobel (Ketjen® Black Series)). Another suitable carbon carrier material is acetylene black (for example, Chevron Phillips (Shawinigan Black®) or available from Denka). The conductive carbon carrier can be prepared by the method disclosed in International Publication No. 2013 / 045894. Alternatively, the conductive carrier may be a metal oxide or mixed oxide, in particular a conductive mixed oxide such as niobia-doped titania, phosphorus-doped tin oxide and mixed platinum-based metal oxide or mixed metal oxide (disclosed in International Publication No. 2012 / 080726), a carbide (e.g., tungsten carbide, molybdenum carbide or titanium carbide, preferably tungsten carbide or titanium carbide), or a nitride, in particular a conductive nitride (e.g., titanium nitride or titanium aluminum nitride).

[0049] Preferably, the first electrolytic catalyst contains platinum (such as platinum on a carbon support), and the second electrolytic catalyst contains platinum (such as platinum on a carbon support). The second catalyst ink contains an iridium-containing catalyst (iridium oxide IrO x It is preferable to further include an oxygen evolution catalyst such as iridium metal oxide (e.g., iridium ruthenium oxide or iridium tantalum oxide). This combination of electrolytic catalysts may be useful when using CCM in a fuel cell.

[0050] Preferably, the first electrocatalyst contains platinum (such as platinum on a carbon support), and the second electrocatalyst contains iridium (such as iridium oxide (IrOx)), or iridium metal oxide (e.g., iridium ruthenium oxide or iridium tantalum oxide), or the first electrocatalyst contains iridium (such as iridium oxide (IrOx)), or iridium metal oxide (e.g., iridium ruthenium oxide or iridium tantalum oxide), and the second electrocatalyst contains platinum (such as platinum on a carbon support). This combination of electrocatalysts may be useful when using CCM in a water electrolysis apparatus. [Brief explanation of the drawing]

[0051] Herein, embodiments of the present invention will be described merely as examples with reference to the attached drawings. [Figure 1] This is a flowchart illustrating an exemplary method for manufacturing a catalyst coating film. [Figure 2] This is a schematic diagram of a CCM manufactured according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing an intermediate in the method of the present invention. [Figure 4] This is a schematic diagram showing an intermediate in the method of the present invention. [Figure 5] This is a plot of current density against temperature difference (temperature A - temperature B). [Modes for carrying out the invention]

[0052] Figure 1 shows a flow diagram of an exemplary method for manufacturing the CCM 100 shown in Figure 2. Referring to Figure 2, a schematic cross-section of a catalyst-coated ion-conductive film (CCM) 100 manufactured according to an embodiment of the present invention is shown. The CCM 100 includes an electrolyte membrane 110 having a first surface 120 and a second surface 130 opposite to it. A first catalyst layer 140 is located on the first surface 120, a second catalyst layer 150 is located on the second surface 130, and the electrolyte membrane 110 is located between the first catalyst layer 140 and the second catalyst layer 150.

[0053] Referring to Figure 3, this method includes providing an electrolyte membrane 110 having a first surface 120 and a second surface 130 on both sides of the electrolyte membrane. The electrolyte membrane may be elongated and may be unwound from a supply roller. Providing the electrolyte membrane 110 may also include unwinding a laminated substrate 160 from a supply roller, the substrate 160 comprising the electrolyte membrane 110 and a first support film 170 positioned on the second surface 130 of the electrolyte membrane.

[0054] The first catalyst ink is preferably deposited directly onto the first surface 120 of the electrolyte membrane 110 by a slot die to form a first wet catalyst layer 180, as shown in Figure 3A. The slot die allows the wet catalyst layer 180 with a uniform thickness (thk-L1-wet) to be formed in a single pass. Spray coating requires multiple passes to achieve a similar thickness. The thickness of the first wet catalyst layer (thk-L1-wet) can be measured in a direction perpendicular to the first surface 120 of the membrane.

[0055] The first wet catalyst layer 180 is dried, as shown in Figure 3B, to form a catalyst layer 140 with a thickness (thk-L1-dry). It will be understood that the dry thickness is smaller than the wet thickness due to the evaporation of the dispersant. Figure 3B shows an intermediate 190 comprising an electrolyte membrane 110 having the first catalyst layer 140 on a first surface 120 and a support film 170 on the opposite second surface 130. The intermediate 190 may be distinguishable from those made according to conventional methods. In particular, the intermediate does not suffer from defects associated with hot pressing, such as in the decal method. Thus, a good interface exists between the membrane 110 and the first catalyst layer 140.

[0056] If present, the support film 170 needs to be removed to allow an additional catalyst layer to be applied to the second surface 130. The electrolyte membrane may be inverted so that the exposed second surface 130 faces upward, as shown in Figure 4A. The second catalyst ink may be deposited directly onto the second surface 130, preferably by a slot die, to form a second wet catalyst layer 200, as shown in Figure 4B. The second wet catalyst layer 200 has a thickness (thk-L2-wet) measured perpendicular to the membrane. The second wet catalyst layer 200 can be dried to form a second catalyst layer 150, thereby forming the CCM 100 shown in Figure 2. [Examples]

[0057] Preparation of cathode catalyst ink (first catalyst ink) The cathode electrolytic catalyst was prepared using a method following the general procedure for preparing carbon-supported platinum catalysts described in International Publication No. 2013 / 045894.

[0058] A well-dispersed cathode catalyst ink was prepared by conventional means using an ionomer dispersion containing perfluorinated sulfonic acid (PFSA) ionomer, a Pt / C electrolytic catalyst, and a dispersant (a mixture of water and alcohol).

[0059] Preparation of anode catalyst ink (second catalyst ink) The anode electrolytic catalyst was prepared using a method following the general procedure for preparing carbon-supported platinum catalysts described in WO2013 / 045894. A well-dispersed anode catalyst ink was prepared by conventional means using an ionomer dispersion containing perfluorinated sulfonic acid (PFSA) ionomer, a Pt / C electrolytic catalyst, optionally an iridium-containing OER catalyst, and a dispersant (a mixture of water and alcohol).

[0060] First catalyst layer A cathode catalyst ink was deposited onto the first surface of an elongated electrolyte membrane using a slot die coating process to form a first wet catalyst layer. The coated electrolyte membrane was passed through a drying tunnel in a single pass, thereby drying the first wet catalyst layer and exposing the first catalyst layer to temperature A.

[0061] Second catalyst layer The anode catalyst ink was deposited onto a second surface of the electrolyte membrane using a roll-to-roll process. The second catalyst ink was deposited onto a suction roller heated by a slot die, which dried the second catalyst layer and exposed it to temperature B (50°C).

[0062] Decals For comparison, a cathode catalyst layer was prepared using a decal transfer method as follows: Catalyst ink was deposited onto a decal transfer substrate (e.g., a skived PTFE sheet) using a slot die coating process, and the dispersant was removed by drying. The cathode catalyst layer was transferred to the first surface of the electrolyte membrane using a decal process, and heat and pressure were applied to transfer the cathode catalyst layer from the decal transfer substrate to the ion-conducting membrane, thereby forming the cathode catalyst layer.

[0063] An anode catalyst layer was prepared using a decal transfer method as follows: An anode catalyst ink was deposited onto a decal transfer substrate (e.g., a skived PTFE sheet) using a slot die coating process. The anode ink layer was dried to remove the dispersant. The anode catalyst layer was transferred from the decal transfer substrate to the second surface of the electrolyte membrane using a decal process. Heat and pressure were applied to transfer the anode catalyst layer from the decal transfer substrate to the ion-conducting membrane.

[0064] Preparation of membrane electrode assemblies (MEAs) The catalyst coating film (CCM) was prepared by first preparing a cathode catalyst layer on a first surface of an ion-conducting film, and then preparing an anode catalyst layer on a second surface of the same ion-conducting film, using the method described above.

[0065] The sealing components were applied to the peripheral regions of each face of the CCM. The sealing components are nonionic conductive.

[0066] A complete membrane electrode assembly was formed by applying a gas diffusion layer to each surface of the CCM. The gas diffusion layer used was carbon fiber paper having a hydrophobic microporous layer containing carbon and PTFE applied to the surface in contact with the catalyst-coated ion-conductive membrane.

[0067] MEA Performance Test The temperature sweep was performed by fixing the dew point of hydrogen and air at 50°C at the battery inlet and controlling the battery temperature at different points between approximately 40°C and 90°C. The battery voltage (V) was set to 1.2 A / cm². 2 The current density was measured.

[0068] [Table 1]

[0069] In the DTM example of the present invention, drying the cathode catalyst ink layer at a higher temperature improved battery performance under relatively colder / weaker conditions (e.g., 40°C). However, performance was maintained even under relatively hotter / drier conditions. Overall, MEA4 (temperature A=160°C, temperature B=50°C) showed improved battery performance under all tested temperature / relative humidity conditions compared to MEA1 (i.e., a comparative example prepared by the decal transfer process).

[0070] Further MEAs were prepared to investigate the effects of temperatures A and B on current density. As shown in Figure 5, good current density was obtained for the MEA produced according to the method of the present invention. Increasing the difference between temperature A (first catalyst layer) and temperature B (second catalyst layer) leads to an increase in current density.

Claims

1. A method for manufacturing a catalyst coating film, To provide an electrolyte membrane having a first surface and a second surface, wherein the first surface is located on the opposite side of the second surface, The method involves depositing a first catalyst ink on the first surface of the electrolyte membrane to form a first wet catalyst layer, wherein the first catalyst ink comprises a first ion-conducting polymer, a first electrolytic catalyst, and a first dispersant, and the first wet catalyst layer is dried to form a first catalyst layer on the first surface of the electrolyte membrane. The method includes depositing a second catalyst ink containing a second ion-conducting polymer, a second electrolytic catalyst, and a second dispersant onto the second surface of the electrolyte membrane to form a second wet catalyst layer, and drying the second wet catalyst layer to form a second catalyst layer. A method wherein, before depositing the second catalyst ink onto the second surface of the electrolyte film, the first catalyst layer is exposed to a temperature A, which is 130°C or higher, and the second catalyst layer is exposed to a temperature B, which is lower than the temperature A.

2. The method according to claim 1, wherein the temperature B is at least 40°C lower than the temperature A, preferably at least 50°C, at least 60°C, at least 70°C, at least 80°C, or at least 90°C lower than the temperature A.

3. (i) The method according to claim 1 or 2, wherein the temperature A is 130 to 220°C and / or (ii) the temperature B is 30 to 100°C.

4. The method according to any one of claims 1 to 3, wherein the temperature A is 135 to 175°C.

5. The method according to any one of claims 1 to 4, wherein the exposure of the first catalyst layer to the temperature A includes transporting it through a drying tunnel.

6. The method according to claim 5, wherein a single pass through the drying tunnel is used for both drying the first wet catalyst layer to form the first catalyst layer and exposing the first catalyst layer to temperature A.

7. The method according to any one of claims 1 to 6, wherein providing the electrolyte membrane includes unwinding the electrolyte membrane from a supply roller.

8. The method according to claim 7, wherein providing the electrolyte membrane comprises unwinding a laminated substrate from the supply roller, the laminated substrate comprising the electrolyte membrane and a first support film positioned on the second surface of the electrolyte membrane.

9. The method according to claim 8, further comprising unwinding the electrolyte membrane onto a recovery roller, wherein the electrolyte membrane is positioned between the first catalyst layer and the first support film.

10. The method according to any one of claims 1 to 9, wherein the first ink is deposited on the first surface of the electrolyte membrane by a roll-to-roll process.

11. The method according to any one of claims 1 to 10, wherein the first ink is deposited on the first surface of the electrolyte membrane by slot die deposition.

12. The method according to any one of claims 1 to 11, wherein the first wet catalyst layer is obtained by depositing a single layer.

13. The method according to any one of claims 1 to 11, wherein the first wet catalyst layer is obtained by depositing two or more sublayers.

14. The method according to claim 13, wherein the first wet catalyst layer is obtained by spray coating.

15. The method according to any one of claims 1 to 14, wherein the second catalyst ink is deposited on the second surface of the electrolyte membrane by a slot die.

16. The method according to any one of claims 1 to 15, wherein the second catalyst ink is deposited on the second surface of the electrolyte membrane by a roll-to-roll process.

17. The method according to claim 16, wherein the electrolyte membrane is supported on a heated roller during the deposition of the second catalyst ink.

18. The method according to any one of claims 1 to 17, wherein the electrolyte membrane is supported on a suction roller during the deposition of the second catalyst ink.

19. The method according to claim 17 and / or 18, wherein the electrolyte membrane is supported on a suction roller that is heated during the deposition of the second ink.

20. (i) The first electrolytic catalyst includes a platinum electrolytic catalyst such as a carbon-supported platinum electrolytic catalyst, and / or (ii) The first ion-conducting polymer comprises a perfluorinated sulfonic acid (PFSA) ionomer and / or (iii) The second electrolytic catalyst includes a platinum electrolytic catalyst such as a carbon-supported platinum electrolytic catalyst and / or (iv) The method according to any one of claims 1 to 19, wherein the second ion-conducting polymer comprises a perfluorinated sulfonic acid (PFSA) ionomer.

21. (i) The first catalyst layer includes a platinum electrocatalyst such as a carbon-supported platinum electrocatalyst, and (ii) the second catalyst layer includes a platinum electrocatalyst such as a carbon-supported platinum electrocatalyst and iridium oxide (IrO ｘ The method according to any one of claims 1 to 20, comprising an iridium-containing catalyst such as iridium or an oxygen-evolving catalyst such as iridium metal oxide.

22. A catalyst coating film that can be obtained by the method described in any one of claims 1 to 21.

23. A membrane electrode assembly for a fuel cell or electrolytic cell, comprising the catalyst coating film described in claim 22.

24. An electrochemical device comprising a catalyst coating film according to claim 22 or a film electrode assembly according to claim 23.

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