Method for manufacturing catalyst coating film

Abstract

A method of making a catalyst coated ion conducting membrane for use in an electrochemical device, such as a fuel cell or an electrolytic cell, is provided. The method includes providing an electrolyte membrane having a first face and a second face, the first face disposed opposite the second face. A first catalyst ink is deposited onto the first side of the electrolyte membrane to form a first wet catalyst layer, and then dried to form a first catalyst layer on the first surface of the electrolyte membrane. The first catalyst ink comprises a first ionically conductive polymer; a first electrocatalyst; and a first dispersant. Subsequently, a second catalyst ink is deposited onto a second face of the electrolyte membrane to form a second wet catalyst layer and dried to form a second catalyst layer. The second catalyst ink comprises a second ionically conductive polymer; a second electrocatalyst; and a second dispersant. Before depositing the second catalyst ink onto the second side of the electrolyte membrane, the first catalyst layer is subjected to a temperature A of 130 DEG C or more, and the second catalyst layer is subjected to a temperature B lower than the 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 the associated catalyst-coated membrane. Background Art

[0002] The electrolysis of water can be performed in both alkaline and acidic electrolyte systems to produce high-purity hydrogen and oxygen. Electrolyzers that employ an electrolyte membrane (i.e., a solid proton-conducting polymer membrane or proton exchange membrane (PEM)) are referred to as proton exchange membrane water electrolyzers (PEMWE). Electrolyzers that utilize a solid anion-conducting polymer membrane or anion exchange membrane (AEM) are referred to as anion exchange membrane water electrolyzers (AEMWE).

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

[0004] Catalyst coated membranes (CCMs) can be used in electrochemical devices such as electrolyzers and fuel cell units. Such CCMs comprise an electrolyte membrane such as a PEM or AEM, with an anode catalyst layer and / or a cathode catalyst layer applied to one side of the membrane and the anode and cathode catalyst layers applied to the opposite side of the membrane.

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

[0006] For 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. For 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] The CCM can be incorporated into a membrane electrode assembly (MEA), which essentially consists of five layers. The central layer is the electrolyte membrane. On either side of the electrolyte membrane are electrocatalyst layers, which contain electrocatalysts designed for specific electrolysis reactions. Finally, adjacent to each electrocatalyst layer is a gas diffusion layer or porous transport layer, depending on the final MEA application and stack configuration. These layers allow reactants to reach the electrocatalyst layers and products to leave.

[0008] The membrane electrode assembly can be constructed by a variety of known methods. One common method involves depositing one or both of the electrocatalyst layers on a decal transfer substrate and transferring the electrocatalyst layers to either side of the ion-conducting membrane. Subsequently, a gas diffusion layer is applied to the electrocatalyst layer. Alternatively, the electrocatalyst layer can be applied to the gas diffusion layer to form a gas diffusion electrode, which is then combined with the ion-conducting membrane. The membrane electrode assembly can be prepared by combining these methods, for example, applying one electrocatalyst layer to the ion-conducting membrane to form a catalyst-coated ion-conducting membrane, and applying another electrocatalyst layer as a gas diffusion electrode. The electrocatalyst layer is applied using an electrocatalyst ink that typically contains an electrocatalyst material, an ion-conducting polymer, a solvent / dispersant and / or diluent, and any reagents desired to be included in the electrocatalyst layer.

[0009] To achieve net zero targets, demand for hydrogen-based carbon reduction solutions is expected to continue to grow rapidly. To meet this demand, the production of key components such as CCMs needs to be rapidly increased. This has significant benefits in minimizing the use of key raw materials (such as platinum group metal catalysts, such as iridium-based catalyst materials, and ion-conducting polymers), reducing waste, and promoting recycling.

[0010] There remains a need for further improvement and development of methods for producing catalyst-coated ion-conducting membranes, in particular methods that enable large-scale manufacturing while optimizing the use and recycling of key raw materials. Summary of the Invention

[0011] According to a first aspect of the present invention, there is provided a method for manufacturing a catalyst coated membrane, the method comprising:

[0012] providing an electrolyte membrane having a first side and a second side, wherein the first side is disposed opposite to the second side;

[0013] depositing a first catalyst ink onto the first side of the electrolyte membrane to form a first wet catalyst layer; the first catalyst ink comprising a first ion-conducting polymer, a first electrocatalyst, and a first dispersant; and drying the first wet catalyst layer to form a first wet catalyst layer on the electrolyte membrane;

[0014] forming a first catalyst layer on the first surface of the electrolyte membrane; and

[0015] Depositing a second catalyst ink onto a second side of the electrolyte membrane (opposite the first catalyst layer) to form a second wet catalyst layer, the second catalyst ink comprising a second ion-conducting polymer, a second electrocatalyst, and a second dispersant; and drying the second wet catalyst layer.

[0016] drying to form a second catalyst layer;

[0017] wherein, before depositing the second catalyst ink onto the second side of the electrolyte membrane, the first catalyst layer is subjected to temperature A and the temperature A is 130°C or above; and wherein the second catalyst layer is subjected to temperature B and the second temperature B is lower than the temperature A.

[0018] This method can be described as a direct-to-membrane (DTM) manufacturing method, which differs from conventional decal methods in that the catalyst ink is applied directly to the electrolyte (ion-conducting) membrane rather than to a decal transfer substrate or gas diffusion layer.

[0019] Compared to decaling, the DTM method offers many advantages. For example, it may require fewer steps, improving efficiency. Avoiding hot pressing can result in higher-quality CCMs. For example, the CCM layers can be more uniform (consistent thickness). Hot pressing uses high temperatures and pressures, which can cause deformation.

[0020] While some DTM processes are known, they haven't been widely adopted because the electrolyte membrane can become dimensionally unstable when exposed to water or organic solvents. Catalyst inks use water or organic solvents to disperse the electrocatalyst, which can cause the membrane to swell and create defects in the layer. While these issues can be mitigated at small scales (e.g., in the lab), they are more challenging in real-world applications.

[0021] Park et al. (Journal of Power Sources, 479, 2020, 228819, ISSN 0378-7753) describe roll-to-roll production of catalyst-coated membranes for low-temperature electrolyzers. First, IrO2 ink is roll-to-roll (R2R) coated directly onto the membrane (80°C to 100°C), and then a Pt / C electrocatalyst layer is applied by spraying. Subjecting the first catalyst layer to temperatures of 130°C or above is not disclosed.

[0022] The method of the present invention allows both sides of the electrolyte membrane to be directly coated with catalyst ink. After the first layer has been subjected to temperature A, the second catalyst layer is applied to the electrolyte membrane. Without being bound by theory, the inventors believe that using temperature A changes the structure of the first catalyst layer. This structural change provides beneficial effects for subsequent processing and the resulting CCM. Using temperature A, which is higher than temperature B, improves the cell performance of the resulting CCM.

[0023] The invention also relates to a CCM obtained or obtainable by the process of the invention and its use in electrochemical devices such as fuel cell units and electrolysers. DETAILED DESCRIPTION

[0024] The method of the present invention requires subjecting the first catalyst layer to a temperature A prior to depositing the second catalyst ink. In this manner, the second catalyst ink is deposited onto the second side of the electrolyte membrane opposite the first catalyst layer.

[0025] Temperature A

[0026] Temperature A is 130° C. or higher. Temperature A may 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.

[0027] In one embodiment, temperature A is from 135°C to 175°C, such as from 140°C to 170°C, as demonstrated in the Examples.

[0028] Wet catalyst layer

[0029] The method includes depositing a first catalyst ink onto a first face of the electrolyte membrane to form a first wet catalyst layer. The catalyst ink can be deposited as a single continuous strip on the electrolyte membrane along the length of the electrolyte membrane (i.e., in the longitudinal direction), for example, so as to extend substantially completely along the length of the membrane. The catalyst ink can be deposited in the longitudinal direction as a plurality of parallel continuous strips, each continuous strip suitably extending substantially completely along the length of the ion-conducting membrane. Alternatively, the catalyst formulation can be deposited as a plurality of spaced-apart (i.e., discontinuous) blocks, wherein each block is spaced apart in the longitudinal direction. Each continuous strip or block may extend partially or completely across the width of the membrane (i.e., in the transverse direction). The wet catalyst layer may extend partially or completely across the width of the membrane (i.e., in the transverse direction).

[0030] The first catalyst ink may be deposited using a slot die coating process, knife coating, rod coating, ink jet printing, gravure printing, curtain coating, screen printing, or a spray coating process.

[0031] Preferably, the first catalyst ink is deposited by slot die. The slot die coating process allows the wet catalyst layer to be formed in a single pass with consistent thickness. In contrast, spray coating requires multiple coats to achieve the desired thickness and can result in greater thickness fluctuations.

[0032] The first wet catalyst layer may be obtained by depositing a single layer. Alternatively, the first wet catalyst layer may be obtained by depositing two or more sub-layers, ie by building up the wet layer before drying.

[0033] Preferably, the first wet catalyst layer is obtained by depositing a single layer to reduce the number of steps required to prepare the CCM. The method of the present invention can make it possible to deposit a thicker catalyst layer in a single pass while maintaining an acceptably low level of cracking defects. The thickness of the first wet catalyst layer can be at least 50 μm, at least 70 μm or at least 100 μm; and / or the thickness of the first wet catalyst layer can be 150 μm or less, 120 μm or less or 90 μm or less, for example 50 μm to 90 μm. The wet layer thickness can be measured directly. However, it may be more practical to determine the wet layer thickness based on the solids content of the catalyst ink and the dry layer thickness.

[0034] dry

[0035] The first wet catalyst layer may be dried and / or subjected to temperature A using a drying oven or a heating furnace (eg, by hot air impingement and / or infrared heating).

[0036] Preferably, the drying box or heating oven is in the form of a drying tunnel, i.e. has two separate openings (inlet and outlet) so that the objects can be transported in one opening, through the tunnel and out again. This makes it possible to operate the process continuously rather than as a batch process.

[0037] The wet catalyst layer can be rapidly dried by conveying it through a drying tunnel, for example, at a rate of at least 2 m / min (2 meters / minute), at least 5 m / min, or at least 10 m / min; and / or at a rate of 20 m / min or less or 15 m / min or less.

[0038] The first catalyst layer may be subjected to temperature A by conveying it through a drying tunnel. A drying tunnel may be employed to ensure that substantially all of the dispersant in the catalyst ink is removed in a single heating step.

[0039] Preferably, a single drying channel is used to dry the first wet catalyst layer, and then the first (dried) catalyst layer is subjected to temperature A. In this way, the first wet catalyst layer can be dried and the first catalyst layer can be subjected to temperature A by a single pass through the drying channel. The drying channel may include two or more regions with different temperatures. For example, the temperature of one region may be lower than temperature A, while the temperature of another region may be equal to or higher than A. In this way, one region can be used to dry the wet catalyst layer, and another region can be used to anneal the resulting dried catalyst layer. Preferably, a single drying channel is used to dry the first wet catalyst layer, and then the first (dried) catalyst layer is subjected to temperature A, wherein A is 135°C to 175°C, as shown in the embodiment.

[0040] electrolyte membrane

[0041] Providing the electrolyte membrane may include unwinding the electrolyte membrane from a supply roll. The electrolyte membrane may be provided as part of a laminated substrate material, and providing the electrolyte membrane may include unwinding the laminated substrate material from a supply roll, the laminated substrate material comprising the electrolyte membrane and a first carrier film positioned on a second side of the electrolyte membrane.

[0042] After the first catalyst layer has been applied, the matrix material may be rewound onto a collection roll.Thus, the method may further comprise rewinding the electrolyte membrane onto a collection roll, the electrolyte membrane being arranged between the first catalyst layer and the first carrier film.

[0043] The electrolyte membrane comprises an ion-conducting polymer. The ion-conducting polymer is suitably a proton-conducting polymer. Preferred ion-conducting polymers are partially or fully fluorinated sulfonic acid polymers, such as perfluorinated sulfonic acid polymers. For example, the ion-conducting polymer may be based on a perfluorinated sulfonic acid material, such as (Chemours Company), (Solvay Specialty Polymers)、 (AsahiGlass Group) and (Asahi Kasei Chemicals Corp.). Alternatively, the ion-conducting material may be based on a sulfonated hydrocarbon polymer, such as that available from FuMA-Tech GmbH ( P, E or K series products), sulfonated hydrocarbon polymers from JSR Corporation, Toyobo Corporation, etc.

[0044] The electrolyte membrane may include a reinforcing component, such as a planar reinforcing component. Preferably, the reinforcing component is porous (i.e., has holes). The reinforcing component can impart mechanical strength to the ion-conducting membrane. The reinforcing component can include a porous reinforcing material such as expanded polytetrafluoroethylene (ePTFE) material, or a nanofiber network such as a network comprising polybenzimidazole (PBI) fibers or glass fibers.

[0045] Typically in the process of making catalyst coated membranes, the electrolyte membrane is in the form of an elongated strip.

[0046] The electrolyte membrane may optionally be disposed on a support film so that the face on which the first catalyst ink is deposited faces away from the support film. The support film provides support and dimensional stability during the step of forming the first catalyst layer and, if it is not immediately removed, provides support and strength during any subsequent storage and / or transport. The material from which the support film is made should provide the required support, be able to withstand the process conditions involved in producing the first catalyst layer, and be capable of being easily removed without damage so that the second catalyst layer can be applied. Examples of materials suitable for use include fluoropolymers such as polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymers (PFA), fluorinated ethylene propylene (FEP - a copolymer of hexafluoropropylene and tetrafluoroethylene) and polyolefins such as biaxially oriented polypropylene (BOPP).

[0047] Second wet catalyst layer

[0048] The second ink is deposited onto the second side of the electrolyte membrane to form a second catalyst layer. The second catalyst layer can be obtained by a roll-to-roll (R2R) process.

[0049] During deposition, the electrolyte membrane can be supported on a roller. This roller can be an adsorption (vacuum) roller and / or a heated roller; preferably, a heated adsorption roller. The electrolyte membrane has a first catalyst layer thereon and is fragile; the adsorption roller provides stability during deposition of the second catalyst ink. The heated roller dries the second catalyst ink.

[0050] In one embodiment, depositing the second catalyst ink includes: a) unwinding the elongated porous base material from the porous base material supply roller toward the peripheral surface of the adsorption roller; b) adsorbing and supporting the porous base material on the outer surface of the adsorption roller; c) unwinding the electrolyte membrane from the electrolyte membrane supply roller toward the surface of the porous base material held on the peripheral surface of the adsorption roller; d) adsorbing and supporting the electrolyte membrane on the outer surface of the porous base material; e) applying the second catalyst ink to the second side of the electrolyte membrane; f) separating the electrolyte membrane to which the second electrocatalyst layer ink is applied from the surface of the porous base material and winding the electrolyte membrane onto the electrolyte membrane collection roller; and g) separating the porous base material from the surface of the adsorption roller.

[0051] Temperature B

[0052] The second catalyst layer is subjected to temperature B, and temperature B is lower than temperature A. In this way, temperature A is the highest temperature experienced by the first catalyst layer.

[0053] 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 60°C or lower. The second catalyst layer may be subjected to temperature B using a heated roller (e.g., a heated adsorption roller).

[0054] First and second catalyst inks

[0055] The first catalyst ink and / or the second catalyst ink comprises an electrocatalyst, an ionically conductive polymer (eg, PFSA) and a dispersant. Suitably, the dispersant comprises water and / or an organic solvent such as ethanol, propanol (n-propanol / isopropanol) or a mixture thereof.

[0056] Suitably, the ion-conducting polymer is a proton-conducting polymer. Preferably, the ion-conducting polymer comprises sulfonic acid groups. The ion-conducting polymer is preferably 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 further be preferred that the ion-conducting polymer is a perfluorinated sulfonic acid ionomer or a partially fluorinated sulfonic acid ionomer. It may be particularly preferred that the ion-conducting polymer is a perfluorinated sulfonic acid ionomer. The catalyst ink may comprise a blend of ion-conducting polymers, such as a blend of perfluorinated sulfonic acid ionomers.

[0057] First and second electrocatalysts

[0058] Typically, the first electrocatalyst is different from the second electrocatalyst because they are used to catalyze different reactions. Nevertheless, the first electrocatalyst and the second electrocatalyst each comprise metal particles optionally supported on a conductive support. That is, the first electrocatalyst and the second electrocatalyst each can be unsupported metal particles (e.g., finely divided unsupported metal powder) or can be a supported electrocatalyst in which the metal particles (e.g., nanoparticles) are dispersed on a conductive support such as a conductive particulate carbon support. The metal particles of the electrocatalyst are suitably selected from:

[0059] (i) platinum group metals (i.e., platinum, palladium, rhodium, ruthenium, iridium and osmium),

[0060] (ii) gold or silver,

[0061] (iii) base metals, or

[0062] (iv) Alloys or mixtures comprising one or more of these metals or their oxides.

[0063] Preferably, the metal in the metal particles of the electrocatalyst is a platinum group metal or an alloy of a platinum group metal. The most preferred electrocatalyst metal is platinum, which can be alloyed with other precious metals or base metals. The base metal is tin or a transition metal that is not a precious metal. The precious 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.

[0064] If the electrocatalyst is a supported catalyst, the loading of the metal particles on the conductive support material is suitably in the range of 10 wt % to 90 wt % or 20 wt % to 80 wt %, such as 30 wt % to 75 wt %, preferably 40 wt % to 60 wt %, most preferably 45 wt % to 55 wt %, based on the weight of the electrocatalyst. The loading of the metal particles can be determined using inductively coupled plasma mass spectrometry (ICPMS).

[0065] Preferably, the electrocatalyst comprises a conductive support and metal particles supported on the conductive support. The term "supported" will be readily understood by a skilled artisan. For example, it will be understood that the term "supported" includes metal particles of the electrocatalyst that are dispersed on a support material (and / or in the pores of a support material) and are bound or fixed to the support material by physical or chemical bonds. For example, the catalyst may be bound or fixed to the support material by ionic or covalent bonds, or non-specific interactions such as van der Waals forces.

[0066] The conductive support may be a conductive carbon support material. Suitably, the conductive carbon support material is a carbon powder which may be, for example, carbon black or graphitized carbon black, such as commercially available carbon black (such as available from Cabot Corp. XC72R) or Akzo Nobel( Another suitable carbon support material is acetylene black (available, for example, from ChevronPhillips (Shawinigan ) or those of Denka). The conductive carbon support can be prepared by the method disclosed in WO2013 / 045894. Alternatively, the conductive support can be a metal oxide or mixed oxide (particularly a conductive mixed oxide, such as niobium-doped titanium dioxide, phosphorus-doped tin oxide and mixed platinum group metal oxides or mixed metal oxides (as disclosed in WO2012 / 080726), a carbide (for example, tungsten carbide, molybdenum carbide or titanium carbide, suitably tungsten carbide or titanium carbide), a nitride (particularly a conductive nitride (for example, titanium nitride or titanium aluminum nitride)).

[0067] Suitably, the first electrocatalyst comprises platinum (such as platinum on a carbon support) and the second electrocatalyst comprises platinum (such as platinum on a carbon support). It may be preferred that the second catalyst ink additionally comprises an oxygen evolution catalyst, such as an iridium-containing catalyst (such as iridium oxide (IrO x ) or iridium metal oxide (e.g., iridium ruthenium oxide or iridium tantalum oxide). This combination of electrocatalysts may be useful when a CCM is employed in a fuel cell unit.

[0068] Suitably, the first electrocatalyst comprises platinum (such as platinum on a carbon support) and the second electrocatalyst comprises iridium (such as iridium oxide (IrOx) or an iridium metal oxide (e.g., iridium ruthenium oxide or iridium tantalum oxide); or the first electrocatalyst comprises iridium (such as iridium oxide (IrOx) or an iridium metal oxide (e.g., iridium ruthenium oxide or iridium tantalum oxide) and the second electrocatalyst comprises platinum (such as platinum on a carbon support). Such combinations of electrocatalysts may be useful when employing a CCM in a water electrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0070] Figure 1 is a flow chart of an exemplary method of making a catalyst coated membrane;

[0071] Figure 2 is a schematic diagram of a CCM made according to one embodiment of the present invention.

[0072] 3 and 4 are schematic diagrams illustrating intermediates in the process of the present invention.

[0073] Figure 5 This is a graph showing the relationship between current density and temperature difference (temperature A - temperature B).

[0074] Figure 1 Shows the manufacturing Figure 2 Flowchart of an exemplary method of CCM 100 is shown. Figure 2, a schematic diagram of a cross-section of a catalyst-coated ion-conducting membrane (CCM) 100 produced according to one embodiment of the present invention is shown. CCM 100 includes an electrolyte membrane 110 having a first face 120 and an opposing second face 130. A first catalyst layer 140 is disposed on first face 120, while a second catalyst layer 150 is disposed on second face 130, such that electrolyte membrane 110 is located between first catalyst layer 140 and second catalyst layer 150.

[0075] 3 , the method includes providing an electrolyte membrane 110 having a first side 120 and a second side 130 on opposite sides of the electrolyte membrane. The electrolyte membrane can be elongated and unwound from a supply roll. Providing the electrolyte membrane 110 can include unwinding a laminated substrate material 160 from a supply roll, the substrate material 160 comprising the electrolyte membrane 110 and a first carrier film 170 positioned on the second side 130 of the electrolyte membrane.

[0076] The first catalyst ink is preferably deposited directly onto the first side 120 of the electrolyte membrane 110 using a slot die to form a first wet catalyst layer 180, such as Figure 3A As shown. The slot die allows a single pass to form a uniform thickness (thk-L1-wet) of the wet catalyst layer 180. Multiple spraying passes would be required to achieve a similar thickness. The first wet catalyst layer thickness (thk-L1-wet) can be measured perpendicular to the first side 120 of the membrane.

[0077] The first wet catalyst layer 180 is dried to form a catalyst layer 140 having a thickness (thk-L1-dry), such as Figure 3B It will be appreciated that the dry thickness is less than the wet thickness due to evaporation of the dispersant. Figure 3B An intermediate body 190 is shown, comprising an electrolyte membrane 110 having a first catalyst layer 140 on a first side 120 and a support film 170 on an opposing second side 130. Intermediate body 190 can be distinguished from those produced according to conventional methods. In particular, intermediate body 190 does not exhibit defects associated with hot pressing, such as those found in decaling methods. Thus, a good interface exists between membrane 110 and first catalyst layer 140.

[0078] If a carrier film 170 is present, it needs to be removed so that an additional catalyst layer can be applied to the second side 130. The electrolyte membrane can be inverted so that the exposed second side 130 can face upwards, as shown in FIG. Figure 4A The second catalyst ink may be deposited directly onto the second face 130 using a slot die to form a second wet catalyst layer 200, as shown. Figure 4BThe second wet catalyst layer 200 has a thickness (thk-L2-wet) measured in a direction perpendicular to the membrane. The second wet catalyst layer 200 may be dried to form the second catalyst layer 150, thereby forming Figure 2 CCM 100 is shown.

[0079] Example

[0080] Preparation of cathode catalyst ink (first catalyst ink)

[0081] The cathode electrocatalyst was prepared using a method according to the general method for preparing carbon-supported platinum catalysts described in WO 2013 / 045894.

[0082] Well-dispersed cathode catalyst ink was prepared by conventional methods using an ionomer dispersion containing perfluorinated sulfonic acid (PFSA) ionomer, Pt / C electrocatalyst, and a dispersant (a mixture of water and alcohol).

[0083] Preparation of anode catalyst ink (second catalyst ink)

[0084] The anode electrocatalyst was prepared using a method according to the general method for preparing carbon-supported platinum catalysts described in WO2013 / 045894. A well-dispersed anode catalyst ink was prepared by conventional methods using an ionomer dispersion containing a perfluorinated sulfonic acid (PFSA) ionomer, a Pt / C electrocatalyst, an optional iridium-containing OER catalyst, and a dispersant (a mixture of water and alcohol).

[0085] First catalyst layer

[0086] The cathode catalyst ink is deposited onto the first side of the elongated electrolyte membrane using a slot die coating process to form a first wet catalyst layer. The coated electrolyte membrane is passed through a drying channel in a single pass; thereby drying the first wet catalyst layer and subjecting the first catalyst layer to temperature A.

[0087] Second catalyst layer

[0088] The anode catalyst ink was deposited onto the second side of the electrolyte membrane using a roll-to-roll process. The second catalyst ink was deposited onto a heated adsorption roll using a slot die; thereby drying the second catalyst layer and subjecting the second catalyst layer to temperature B (50° C.).

[0089] applique

[0090] For comparison, a cathode catalyst layer was prepared using the following decal transfer method. The catalyst ink was deposited onto a decal transfer substrate (e.g., a cut PTFE sheet) using a slot die coating process and dried to remove the dispersant. The cathode catalyst layer was transferred to the first side of the electrolyte membrane using a decal process, wherein heat and pressure were applied to transfer the cathode catalyst layer from the decal transfer substrate to the ion-conducting membrane to form the cathode catalyst layer.

[0091] An anode catalyst layer is prepared using the following decal transfer method. A slot die coating process is used to deposit an anode catalyst ink onto a decal transfer substrate (e.g., a cut PTFE sheet). The anode ink layer is dried to remove the dispersant. The anode catalyst layer is transferred from the decal transfer substrate to the second side of the electrolyte membrane using a decal process. Heat and pressure are applied to transfer the anode catalyst layer from the decal transfer substrate to the ion-conducting membrane.

[0092] Membrane electrode assembly (MEA) preparation

[0093] A catalyst coated membrane (CCM) was prepared by first preparing a cathode catalyst layer on a first side of an ion conducting membrane and subsequently preparing an anode catalyst layer on a second side of the (same) ion conducting membrane using the method described above.

[0094] A sealing component is applied to the peripheral area of ​​each face of the CCM. The sealing component is a non-ionically conductive component.

[0095] A gas diffusion layer is applied to each face of the CCM to form a complete membrane electrode assembly. The gas diffusion layer used is a carbon fiber paper having a hydrophobic microporous layer comprising carbon and PTFE applied to the face in contact with the catalyst coated ion conducting membrane.

[0096] MEA performance test

[0097] The temperature sweep analysis was performed by fixing the dew point of hydrogen and air at the cell inlet at a temperature of 50°C and controlling the cell temperature at different points between about 40°C and 90°C. 2 The current density is used to measure the battery cell voltage (V).

[0098]

[0099] For the DTM embodiments of the present invention, drying the cathode catalyst ink layer at a higher temperature improved cell performance under relatively cooler / wetter conditions (e.g., 40°C). However, performance was also maintained under relatively warmer / drier conditions. Overall, when compared to MEA1 (i.e., a comparative example prepared by a decal transfer process), MEA4 (Temperature A = 160°C, Temperature B = 50°C) demonstrated improved cell performance under all temperature / relative humidity conditions tested.

[0100] Additional MEAs were prepared to investigate the effects of temperature A and temperature B on current density. Figure 5 As shown, the MEA produced according to the method of the present invention achieves good current density. In addition, 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 coated membrane, the method comprising: providing an electrolyte membrane having a first side and a second side, wherein the first side is disposed opposite to the second side; depositing a first catalyst ink onto the first side of the electrolyte membrane to form a first wet catalyst layer; the first catalyst ink comprising a first ion-conducting polymer, a first electrocatalyst, 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; as well as depositing a second catalyst ink onto the second side of the electrolyte membrane to form a second wet catalyst layer, the second catalyst ink comprising a second ion-conducting polymer, a second electrocatalyst, and a second dispersant; and drying the second wet catalyst layer to form a second catalyst layer; wherein, before depositing the second catalyst ink onto the second side of the electrolyte membrane, the first catalyst layer is subjected to temperature A and the temperature A is 130°C or above; and wherein the second catalyst layer is subjected to temperature B and the second temperature B 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. A method according to any one of the preceding claims, wherein (i) the temperature A is from 130°C to 220°C; and / or (ii) the temperature B is from 30°C to 100°C.

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

5. A method according to any one of the preceding claims, wherein Subjecting the first catalyst layer to the temperature A includes conveying through a drying tunnel.

6. The method according to claim 5, wherein: The first wet catalyst layer is dried to form the first catalyst layer and subjected to the temperature A using a single pass through the drying tunnel.

7. A method according to any one of the preceding claims, wherein Providing the electrolyte membrane includes unwinding the electrolyte membrane from a supply roll.

8. The method according to claim 7, wherein: Providing the electrolyte membrane includes unwinding a laminated base material from the supply roll, the laminated base material including the electrolyte membrane and a first carrier film on the second side of the electrolyte membrane. 9 . The method of claim 8 , further comprising rewinding the electrolyte membrane onto a collection roll, the electrolyte membrane being disposed between the first catalyst layer and the first support film.

10. A method according to any one of the preceding claims, wherein The first ink is deposited onto the first side of the electrolyte membrane by a roll-to-roll process.

11. A method according to any one of the preceding claims, wherein The first ink is deposited onto the first side of the electrolyte membrane by slot die deposition.

12. A method according to any one of the preceding claims, 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 sub-layers.

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

15. A method according to any one of the preceding claims, wherein The second catalyst ink is deposited onto the second side of the electrolyte membrane by slot die.

16. A method according to any one of the preceding claims, wherein The second catalyst ink is deposited onto the second side of the electrolyte membrane by a roll-to-roll process.

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

18. A method according to any one of the preceding claims, wherein During the deposition of the second catalyst ink, the electrolyte membrane is supported on an adsorption roller.

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

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

21. A method according to any one of the preceding claims, wherein (i) the first catalyst layer comprises a platinum electrocatalyst, such as a carbon-supported platinum electrocatalyst; and (ii) the second catalyst layer comprises a platinum electrocatalyst, such as a carbon-supported platinum electrocatalyst, and an oxygen evolution catalyst, such as an iridium-containing catalyst, such as iridium oxide (IrO x ) or iridium metal oxide.

22. A catalyst coated membrane obtainable by a method according to any one of the preceding claims.

23. A membrane electrode assembly for a fuel cell unit or an electrolyzer, the membrane electrode assembly comprising the catalyst coated membrane according to claim 22. 24 . An electrochemical device comprising the catalyst coated membrane according to claim 22 or the membrane electrode assembly according to claim 23 .

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