Method for preparing a catalyst layer

Abstract

The present invention provides a method for preparing a catalyst layer for a fuel cell or electrolytic cell. This method includes (i) providing a donor substrate having opposing first and second surfaces, and providing a catalyst ink disposed as a layer on the second surface, wherein the catalyst ink comprises an electrolytic catalyst, an ion-conducting polymer, and a solvent; (ii) providing an acceptor substrate, wherein the second surface of the donor substrate faces the acceptor substrate; and (iii) irradiating the catalyst ink with laser radiation of a wavelength absorbed by the catalyst ink to transfer the catalyst ink from the donor substrate to the acceptor substrate.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a catalyst layer for electrochemical devices such as fuel cells or water electrolytic cells. The present invention also relates to a method for producing a catalyst-coated ion-conducting film for electrochemical devices, and to related catalyst layers and catalyst-coated ion-conducting films produced by such a method. [Background technology]

[0002] Electrolysis of water to produce high-purity hydrogen and oxygen can be carried out using both alkaline and acidic electrolyte systems. Electrolytic cells using solid proton-conducting polymer membranes or proton exchange membranes (PEM) are known as proton exchange membrane water electrolyzers (PEMWE). Electrolytic cells utilizing solid anion-conducting polymer membranes or anion exchange membranes (AEM) are known as anion exchange membrane water electrolyzers (AEMWE).

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

[0004] Catalyst-coated (ion-conducting) membranes (CCMs) can be used in electrochemical devices such as electrolytic cells and fuel cells. Such CCMs include an ion-conducting 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] 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] Such cathode and anode catalyst layers used in fuel cells and electrolytic cells incorporating ion-conducting membranes contain an ion-conducting polymer in addition to the electrolytic catalyst. The ion-conducting polymer acts as a binder and transport medium, playing a crucial role in the performance of the catalyst layer. Therefore, the reproducible formation of high-performance catalyst layers incorporating such polymers is a critical challenge in the manufacturing of fuel cell and electrolytic cell components.

[0008] 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 catalyst layers containing catalysts designed for specific electrolytic reactions. Finally, adjacent to each catalyst layer, depending on the final MEA application and stack configuration, are gas diffusion layers or porous transport layers. Such layers allow reactants to reach the electrocatalyst layers and products to detach.

[0009] Membrane electrode assemblies can be constructed by many known methods. A common method involves depositing one or both catalyst layers onto a decal transfer substrate and transferring the catalyst layers to both sides of an ion-conducting film. Subsequently, a gas diffusion layer (or porous transport layer) is applied to the electrocatalyst layer. Alternatively, the catalyst layer can be applied to the gas diffusion layer (or porous transport layer) to form a gas diffusion electrode (or porous transport electrode), which is then combined with the ion-conducting film. As a further alternative, the catalyst layer can be directly coated onto either side of the ion-conducting film. Membrane electrode assemblies can be prepared by a combination of these methods, for example, by applying one catalyst layer to an ion-conducting film to form a catalyst-coated ion-conducting film and applying the other catalyst layer as a gas diffusion electrode.

[0010] Catalyst layers are conventionally deposited using catalyst inks containing an electrocatalyst, an ion-conducting polymer, a solvent / dispersant and / or diluent, and any desired agents or additives within the electrocatalyst layer. Known printing techniques such as slot die printing, spray coating, screen printing, inkjet printing, and gravure printing require the catalyst ink to have strict physical properties (e.g., rheology) to produce an acceptable catalyst layer. Such catalyst inks typically contain volatile organic compounds, such as short-chain alcohols, as a solvent or as part of a solvent mixture, which can pose undesirable safety risks during the manufacturing process. It is desirable to develop deposition techniques that enable the production of catalyst layers using catalyst inks with a wider range of physical properties (e.g., rheological properties).

[0011] 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. Methods for manufacturing catalyst-coated ion-conducting films, particularly those that optimize the use and recycling of key raw materials and enable large-scale production while minimizing waste, need to be further enhanced and developed. In particular, increasing the production throughput of key components such as CCMs while maintaining performance is desirable. [Overview of the project]

[0012] The present invention aims to address at least some of the problems, desires, and needs outlined above. The inventors have surprisingly found that catalyst inks containing ion-conducting polymers and electrolytic catalysts can be advantageously transferred using laser irradiation to produce fuel cell and electrolytic cell catalyst layers with good layer quality. In particular, the present invention provides a method for preparing catalyst layers at a faster throughput than known methods, while at least maintaining performance. The method of the present invention is also suitable for using inks with a wide range of physical (e.g., rheological) properties. For example, inks with high solids content can be used in this method, which reduces the number of passes required to deposit the catalyst layer, thereby further improving the production speed. Furthermore, inks with low VOC content (e.g., ≤10 wt% organic solvent content) are suitable for use in this method, which improves the safety of the production process.

[0013] In a first aspect of the present invention, a method for preparing a catalyst layer for a fuel cell or electrolytic cell, A step of providing a donor substrate having opposing first and second surfaces, and providing a catalyst ink disposed as a layer on the second surface, wherein the catalyst ink comprises an electrolytic electrode catalyst, an ion-conducting polymer, and a solvent. A step of providing an acceptor substrate, wherein the second surface of the donor substrate faces the acceptor substrate, A method is provided that includes irradiating a catalyst ink with laser radiation having a wavelength absorbed by the catalyst ink to transfer the catalyst ink from a donor substrate to an acceptor substrate.

[0014] Preferably, the fuel cell or electrolytic cell is a proton exchange membrane fuel cell or a proton exchange membrane electrolytic cell.

[0015] This method can further include a step of drying the catalyst ink on the acceptor substrate to remove substantially all of the solvent.

[0016] In a further aspect, a catalyst layer obtained by the method of the first aspect is provided.

[0017] In a further aspect, a catalyst-coated ion-conductive membrane including the catalyst layer obtained by the method of the first aspect is provided.

Brief Description of the Drawings

[0018] [Figure 1] A plot showing voltage versus current density for a membrane electrode assembly including a catalyst layer manufactured using the method of the present invention and a comparative membrane electrode assembly manufactured using a known method. [Figure 2] A temperature sweep at 2.5 A / cm2 of the same membrane electrode assembly as that illustrated in FIG. 1 for the data. [Figure 3] A plot showing voltage versus current density for a membrane assembly including a catalyst layer manufactured using the method of the present invention. [Figure 4] A photograph of a catalyst layer manufactured using the method of the present invention.

Modes for Carrying Out the Invention

[0019] The following describes preferred and / or optional features of the present invention. Any aspect of the present invention can be combined with any other aspect of the present invention unless otherwise required by context. Any preferred or optional feature of any aspect can be combined with any aspect of the present invention, individually or in combination, unless otherwise required by context.

[0020] The present invention provides a method for preparing catalyst layers for electrochemical devices such as fuel cells or electrolytic cells. This method can optionally be used to prepare anode catalyst layers and / or cathode catalyst layers. This method includes using a laser-induced forward transfer (LIFT) process. The method of the present invention can be carried out, for example, using the apparatus described in International Publication No. 2019 / 145300.

[0021] This method includes the step of providing a donor substrate having opposing first and second surfaces. The donor substrate is preferably transparent to laser radiation; that is, the donor substrate absorbs laser radiation to a substantially negligible degree. The donor substrate is an ink carrier, for example, a circulating ribbon. A layer of catalyst ink is provided as a layer on the donor substrate. The catalyst ink can be applied to the donor substrate using an ink unit. Preferably, the catalyst ink is applied as a layer to uniformly cover the donor substrate substantially over its second surface. The layer of catalyst ink on the second surface can have a thickness of 100 μm or less, preferably 75 μm or less, preferably 50 μm or less, more preferably 30 μm or less, and most preferably 25 μm or less. The layer of catalyst ink placed on the second surface of the donor substrate can have a thickness of 10 μm or more, 15 μm or more, and 20 μm or more. The thickness of the catalyst ink layer placed on the second surface of the donor substrate may be in a range including any combination of the aforementioned ranges, for example, in the range of about 10 μm to 100 μm, preferably about 15 μm to 75 μm, and preferably about 20 μm to 50 μm.

[0022] The method further includes the step of providing an acceptor substrate, wherein the second surface of the donor substrate faces the acceptor substrate. The second surface of the donor substrate and the acceptor substrate are typically separated by a gap. The gap may be about 2 mm or less, 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. The acceptor substrate may be a porous substrate. For example, the acceptor substrate may be an ion-conducting membrane, such as a polymer electrolyte membrane, a porous reinforcing material, a gas diffusion layer, a porous transport layer, or a porous carrier sheet. The ion-conducting membrane may be a partially fluorinated or fully fluorinated sulfonic acid polymer membrane, such as Nafion® (EIDuPont de Nemours and Co.), Aciplex® (Asahi Kasei), Aquivion® (Solvay Speciality Polymers), or Flemion® (Asahi Glass Co.). The ion-conducting film may be based on a hydrocarbon-based ion-conducting film, such as those available from FuMA-Tech GmbH as products in the fumapem® P, E, or K series, or from JSR Corporation, Toyobo Corporation, and other companies, or based on sulfonated hydrocarbons. In other embodiments, the acceptor substrate may be a non-porous substrate. For example, the acceptor substrate may be a non-porous carrier sheet, such as a non-porous decal transfer substrate. In some embodiments, the acceptor substrate is a hydrocarbon-based ion-conducting film, and the catalyst ink comprises a partially fluorinated or fully fluorinated sulfonic acid polymer.

[0023] This method further includes the step of irradiating a catalyst ink (on a donor substrate) with laser radiation to transfer the catalyst ink from the donor substrate to an acceptor substrate. Preferably, the catalyst ink is irradiated with pulses of laser radiation. The laser radiation is directed through a first surface of the donor substrate so that it can strike the catalyst ink, preferably at or near the interface between the catalyst ink and a second surface of the donor substrate. The catalyst ink absorbs the laser radiation. For example, an electrocatalyst can absorb the laser radiation. In embodiments where the electrocatalyst includes metal-containing particles supported on a conductive carrier, the conductive carrier can absorb the laser radiation. The laser radiation heats the catalyst ink in a targeted local area, causing a portion of the catalyst ink in that local area to evaporate. Such a process can induce the ejection of droplets of catalyst ink from the donor substrate to the acceptor substrate. That is, droplets of catalyst ink are precisely transferred from the second surface of the donor substrate to the acceptor substrate.

[0024] This method may further include a step of drying the catalyst ink on the acceptor substrate to remove substantially all of the solvent. Such a drying step may include heating the acceptor substrate to a temperature of at least 80°C, preferably at least 90°C, and more preferably at least 100°C.

[0025] This process (including optionally a drying step) can be repeated as needed to prepare a catalyst layer having a desired thickness and / or a desired electrolytic catalyst filling amount. The catalyst layer may have a substantially uniform thickness. The catalyst layer may have a (dry) thickness of at least 1 μm, at least 2 μm, or at least 3 μm. The catalyst layer may have a (dry) thickness of 50 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. The catalyst layer may have a (dry) thickness in a range including any combination of the aforementioned lower and upper limits. In some embodiments, the catalyst layer may have a substantially non-uniform thickness or may be deposited in a predetermined pattern. In such cases, the catalyst layer may include at least one first region having a first thickness and at least one second region having a second thickness, which differs from the first and second thicknesses. In some embodiments, the catalyst layer may include at least one region having a first thickness and at least one region having no thickness (i.e., a region where the catalyst ink was not transferred). The first thickness may be at least 1 μm, at least 2 μm, or at least 3 μm. The first thickness may be 50 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. The second thickness may be ≥0 μm, at least 1 μm, at least 2 μm, or at least 3 μm. The second thickness may be 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, or 5 μm or less. The first and second thicknesses may each be within a range that includes any combination of the aforementioned lower and upper limits.

[0026] This process (including an optional drying step) can be repeated as needed to prepare a catalyst layer having a desired catalyst load. The catalyst layer may have a substantially uniform catalyst load. The catalyst layer has a load of 0.03 mg / cm³. 2 ~4.0 mg / cm³ 2 The catalyst packing amount can be in the range of . In the case of the anode catalyst layer of a fuel cell, the electrolytic catalyst packing amount is 0.03 mg / cm³. 2 ~0.2 mg / cm³ 2It can be within the range of. In the case of the anode catalyst layer for an electrolytic cell, the filling amount of the electrolytic catalyst is 0.4 mg / cm 2 ~4.0 mg / cm 2 It can be within the range of. In the case of the cathode catalyst layer for a fuel cell, the filling amount of the electrolytic catalyst is 0.05 mg / cm 2 ~1.0 mg / cm 2 It can be within the range of. In the case of the cathode catalyst layer for an electrolytic cell, the filling amount of the electrolytic catalyst is 0.05 mg / cm 2 ~1.0 mg / cm 2 It can be within the range of. In some embodiments, the catalyst layer can have a substantially non-uniform catalyst layer filling amount (e.g., as a gradient in the catalyst layer), or can be deposited in a predetermined pattern (e.g., a continuous track having a serpentine path). In such a case, the catalyst layer can include at least one first region having a first catalyst layer filling amount and at least one second region having a second catalyst layer filling amount, and the first catalyst layer filling amount and the second catalyst layer filling amount are different. In some embodiments, the catalyst layer can include at least one region having a first catalyst layer filling amount and at least one region having a zero catalyst layer filling amount (i.e., a region where the catalyst ink was not transferred). The first catalyst layer filling amount can be within the range of 0.03 mg / cm 2 ~4.0 mg / cm 2 The second thickness can be within the range of ≧0 mg / cm 2 ~<4.0 mg / cm 2 It can be within the range of.

[0027] The catalyst ink suitable for the method of the present invention is used in the production of catalyst layers for electrochemical devices such as fuel cells and electrolytic cells. Typically, such inks include an electrolytic catalyst for the desired anode or cathode reaction, an ion-conductive polymer, a solvent, and optionally other desired additives, such as, but not limited to, radical scavengers, recombination catalysts, battery reversal resistance additives, conductive additives, and / or fibrous materials as known in the art.

[0028] The electrocatalyst used depends on the reaction intended to be catalyzed, and its selection is within the capabilities of those skilled in the art. The electrocatalyst may preferably be a fuel cell or electrolytic tank, more preferably a cathode or anode electrocatalyst for a proton exchange membrane fuel cell or electrolytic tank. The electrocatalyst may contain catalyst particles (e.g., metal-containing particles such as a first metal, an alloy of the first metal, or oxides thereof), which are preferably dispersed on a particulate carrier material or otherwise supported. Preferably, the particulate carrier material is conductive. For example, the catalyst may be finely divided metal powder (metal black), or it may be a supported catalyst in which metal particles are dispersed on a conductive particulate carrier. The carrier material may be carbon, metal oxides, nitrides, carbides, or other conductive carriers. Preferably, the carrier material is a carbon-based carrier material. Suitable carbon-based carrier materials include those from the carbon black family, such as oil furnace black, polar conductive black, acetylene black, and graphitized versions thereof. The carbon may be commercially available carbon black (e.g., from Cabot Corp. (Vulcan® XC72R) or Akzo Nobel (Ketjen® Black Series)) or a graphitized version of these carbon blacks or other commercially available carbon blacks such as acetylene black (available from Chevron Phillips (Shawinigan Black®)) or Denka). The supporting material may also be specially designed for use in fuel cells, such as those described in International Publication No. 2013 / 045894.

[0029] Catalyst particles are preferably, (i) Platinum group metals (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.

[0030] Base metals are tin or transition metals that are not noble metals. Noble metals are platinum group metals (platinum, palladium, rhodium, ruthenium, iridium, or osmium) or gold. Preferred base metals are copper, cobalt, nickel, zinc, iron, titanium, molybdenum, vanadium, manganese, niobium, tantalum, chromium, and tin.

[0031] Typically, the electrocatalyst comprises a platinum group metal, or an alloy of a platinum group metal with a base metal, preferably a base metal, or an alloy of a platinum group metal with a preferred base metal as defined above. In particular, the electrocatalyst comprises platinum, or an alloy of platinum with a base metal, a preferred base metal as defined above, more preferably nickel or cobalt, and most preferably nickel. The atomic ratio of platinum to the alloying metal is typically in the range of 3:1 to 1:3, and includes such ratios.

[0032] When the electrolytic catalyst includes catalyst particles supported on a support, the catalyst particles (i.e., metal-containing particles) have a D of 50 nm or less, 30 nm or less, 20 nm or less, preferably 10 nm or less, more preferably 5 nm or less. 50 It may have a particle size. For example, the particle may have a diameter of at least 1 nm. 50 It has a particle size. D 50 Particle size is measured by examination using a transmission electron microscope (TEM). 50 The particle size may be within a range that includes any combination of the aforementioned upper and lower limits.

[0033] The electrocatalyst in the catalyst ink (i.e., catalyst particles and, if present, conductive carriers) is at least 0.1 μm, preferably at least 0.3 μm, preferably at least 0.5 μm, typically at least 0.75 μm. 50 The particle size (or aggregate size as needed) may be specified. The electrocatalyst in the catalyst ink has a particle size of 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less, and typically 3 μm or less. 50The particle size (or aggregate size as needed) may be present. The electrocatalyst has a particle size in the range of 0.1 μm to 20 μm, preferably 0.3 μm to 10 μm, more preferably 0.5 μm to 5 μm, and typically 0.75 μm to 3 μm. 50 It can have particle size (or aggregate size as needed). For example, the supported electrocatalyst may have a particle size of approximately 1 μm. 50 It may have particle size. 50 Particle size is measured by dynamic light scattering using a Malvern Mastersizer (trademark).

[0034] The ion-conducting polymer may be a proton-conducting polymer or an anion-conducting polymer such as a hydroxyl anion-conducting polymer. Preferably, the ion-conducting polymer is a proton-conducting polymer. Suitable examples of proton-conducting polymers include partially or fully fluorinated sulfonic acid polymers, such as perfluorosulfonic acid ionomers (e.g., Nafion® (EIDuPont de Nemours and Co.), Aciplex® (Asahi Kasei), Aquivion® (Solvay Speciality Polymers), Flemion® (Asahi Glass Co.)); or sulfonated hydrocarbon-based ionomers, such as those available from FuMA-Tech GmbH as products of the fumapem® P, E, or K series, and those available from JSR Corporation, Toyobo Corporation, and other companies. Preferably, the ionomers are perfluorosulfonic acids, particularly the Nafion® series available from Chemours, especially Nafion® 1100EW, and the Aquivion® series available from Solvay, especially Solvay® 830EW. Suitable examples of anion-conducting polymers include Tokuyama Examples include the A901 from Corporation and the Fumasep FAA from FuMA-Tech GmbH.

[0035] The catalyst ink may contain an electrocatalyst and an ion-conducting polymer in a total amount of at least 5% by weight, at least 10% by weight, at least 15% by weight, at least 16% by weight, at least 17% by weight, at least 20% by weight, or at least 25% by weight, based on the total weight of the catalyst ink. The catalyst ink may contain an electrocatalyst and an ion-conducting polymer in a total amount of less than 50% by weight, less than 40% by weight, or less than 30% by weight, based on the total weight of the catalyst ink. The total amount of the electrocatalyst and the ion-conducting polymer may be in a range including any combination of the lower and upper limits described above, for example, 5% by weight to 50% by weight.

[0036] The catalyst ink may contain at least 5% by weight, at least 10% by weight, at least 15% by weight, at least 16% by weight, at least 17% by weight, at least 20% by weight, or at least 25% by weight of total solids (i.e., including ion-conducting polymers, electrolytic catalysts, and any other optional solid additives) based on the total weight of the catalyst ink. The catalyst ink may have less than 50% by weight, less than 40% by weight, or less than 30% by weight of total solids based on the total weight of the catalyst ink. The total solids may be in a range including any combination of the aforementioned lower and upper limits, for example, 5% by weight to 50% by weight. The method of the present invention enables the use of a wider range of inks, including inks with higher solids content, which would result in a defect layer if other known techniques such as slot die coating were used.

[0037] The solvent may have a boiling point of at least 95°C, preferably at least 100°C, and more preferably at least 110°C. The solvent may include water, an organic solvent, or a mixture of water and an organic solvent. The organic solvent is preferably miscible with water. The organic solvent is preferably a protic polar solvent, such as an alcoholic solvent. The organic solvent may be methanol, ethanol, 1-propanol or isopropanol, n-butanol, ethylene glycol, propylene glycol, dipropylene glycol, poly(ethylene glycol), poly(propylene glycol), ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or any combination thereof. Preferably, the organic solvent is ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, ethylene carbonate, propylene carbonate, or any combination thereof. Preferably, the solvent contains, based on the total weight of the solvent, at least 50% by weight of water, preferably ≥60% by weight of water, more preferably ≥70% by weight of water, more preferably ≥80% by weight of water, ≥90% by weight of water, and more preferably 95% by weight of water. More preferably, the solvent is essentially water or consists solely of water. By using a solvent that does not contain volatile organic components, the flammability of the ink can be reduced, resulting in a safer process with less chemical waste. When depositing catalytic inks onto highly hydrophobic substrates (e.g., PTFE carrier sheets, decal transfer substrates, and some fluorine-containing ion-conducting films such as films made from PFSA ionomers), organic solvents are typically added to the ink to help prevent dewetting. The method of the present invention is unexpectedly suitable for printing catalytic inks on a variety of different acceptor substrates, including hydrophobic substrates, using a solvent that is essentially water (or entirely water) while maintaining good catalytic layer properties and structure. For example, the method of the present invention makes it possible to deposit a catalyst ink, particularly an aqueous catalyst ink, containing a partially or fully fluorinated sulfonic acid ion-conducting polymer onto a fluorinated or non-fluorinated acceptor substrate, such as a hydrocarbon-based ion-conducting film, to form an acceptable catalyst layer.

[0038] The catalyst ink of the present invention can have a much wider range of acceptable rheological properties compared to catalyst inks suitable for coating technologies known in the field, such as slot die printing, spray coating, screen printing, inkjet printing, and gravure printing. For example, the catalyst ink of the present invention can withstand temperatures of 25°C and 100s. -1 When measured at a shear rate, the viscosity can be in the range of at least about 10 cP to about 1,000 cP. Furthermore, the method of the present invention does not require the ink to pass through a print head or nozzle. Therefore, the method of the present invention is not subject to the problem of clogging in the print head or nozzle, which can result in machine downtime.

[0039] If the acceptor substrate is a decal transfer substrate, the catalyst layer produced by this method can be transferred from the acceptor substrate to an ion-conducting film via a decal process (e.g., using heat and pressure) to form a catalyst-coated ion-conducting film.

[0040] When the acceptor substrate is an ion-conducting film, the product manufactured by this method is a catalyst-coated ion-conducting film; that is, it does not require a subsequent decal transfer step. The gas diffusion layer and / or porous transport layer can be applied to one or both sides of such a catalyst-coated film using methods known in the art to form a film electrode assembly.

[0041] When the acceptor substrate is a carrier sheet, the method may further include the steps of forming an ion-conductive (electrolyte) film layer on the catalyst layer (in one or more passes), and then depositing a second catalyst layer on the ion-conductive (electrolyte) film layer to form a catalyst-coated ion-conductive film. The second catalyst layer can also be deposited using the method of the present invention. The second catalyst layer is preferably different from the first catalyst layer. For example, the first and second catalyst layers typically contain different electrolytic catalysts.

[0042] When the acceptor substrate is a gas diffusion layer or a porous transport layer, the products manufactured by this method are gas diffusion electrodes or porous transport electrodes, respectively. Such gas diffusion electrodes or porous transport electrodes can be applied to the surface of an ion-conducting film using methods known in the art to form a film electrode assembly. A combination of these methods can be used to prepare an anode catalyst layer and a cathode catalyst layer. For example, the cathode catalyst layer can be prepared using the method of the present invention, and the anode catalyst layer can be prepared using the conventional technique. In other embodiments, the anode catalyst layer can be prepared using the method of the present invention, and the cathode catalyst layer can be prepared using the conventional technique. In further embodiments, both the anode catalyst layer and the cathode catalyst layer are prepared using the method of the present invention.

[0043] Table 1 details a typical example of apparatus configuration suitable for the method of the present invention.

[0044] [Table 1] [Examples]

[0045] Example 1 A cathode catalyst ink was prepared using the following method: An aqueous dispersion of an ion-conducting polymer (Nafion® 1100 EW) was mixed with an electrolytic catalyst material (50% Pt / C prepared using a method similar to the general preparation method for carbon-supported Pt catalysts described in International Publication No. 2013 / 045894). This mixture was mechanically stirred using a stirrer until all of the catalyst was wet and dispersed in the liquid medium. The ink was then ground using an Eiger mill to form a well-dispersed ink. The solid content of the ink was approximately 25% by weight based on the total weight of the ink. The ion-conducting polymer content in the ink was 90% by weight relative to the weight of carbon. The catalyst ink was refractory at a temperature of 25°C and 100s. -1 It had a viscosity of 400 cP at a shear rate.

[0046] A cathode catalyst layer was formed using this cathode catalyst ink. The cathode catalyst ink was deposited onto a skived PTFE sheet (acceptor substrate) using a HelioSonic® printing apparatus (commercially available from HelioSonic GmbH, Germany). The catalyst ink was applied to an ink carrier (donor substrate) as a 20 μm thick wet layer, so that the catalyst ink layer faced the skived PTFE substrate. Laser pulses (70-120 W) were directed through the ink carrier and applied to the catalyst ink at specific locations. The catalyst ink was heated at these locations to evaporate a portion of it, forming a bulge. The catalyst ink was ejected as droplets and transferred from the ink carrier onto the skived PTFE substrate. This process was repeated at different locations to create a substantially uniform catalyst layer (area = 100 cm²) on the skived PTFE substrate. 2 A catalyst layer was formed. The deposited catalyst layer was heated to 100°C for 10 minutes to remove residual solvent. The catalyst layer had an average thickness of approximately 3.5 μm to 4.0 μm, as measured by FIB-SEM and the average of measurements taken from at least five different locations on the catalyst layer. The catalyst layer was 0.2 mg Pt / cm². 2 It was deposited with an apparent platinum-filling amount.

[0047] Anode catalyst ink was prepared using the following method: PFSA ion-conducting polymer (3M, 800EW) and electrolytic catalyst material (20 wt% Pt / C-HiSPEC® 3000, available from Johnson Matthey Hydrogen Technologies Limited) in a mixture of water and n-propanol. This mixture was mechanically stirred using a stirrer until all of the catalyst was wet and dispersed in the liquid medium. The ink was processed through an Eiger mill to form a well-dispersed ink.

[0048] An anode catalyst layer was formed using an anode catalyst ink. The anode catalyst ink was applied at a concentration of 0.1 mg Pt / cm³. 2The apparent platinum-filled material was coated onto a skived PTFE sheet using a slot die coating process. The coating was dried to remove the solvent and form an anode catalyst layer.

[0049] Catalyst-coated ion-conducting film (50cm) 2 The cathode and anode catalyst layers (having an effective area) were prepared by transferring them from PTFE sheets to both sides of a commercially available reinforced PFSA ion-conductive film (15 μm thick) using a decal transfer process under pressure and at a temperature of 150°C to 200°C.

[0050] A complete membrane electrode assembly was formed by applying a gas diffusion layer (Sigracet 22 BB, commercially available from SGL Carbon) to both sides of each catalyst-coated ion-conductive film. 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 film.

[0051] Example 2 The film electrode assembly was prepared in the same manner as in Example 1, except that the cathode catalyst ink was directly deposited on a commercially available reinforced PFSA ion-conductive film using a HelioSonic® printing apparatus, rather than on a skived PTFE substrate. Therefore, the subsequent decal transfer step in Example 1 was not necessary to form the cathode catalyst layer. The cathode catalyst layer was 0.3 mg Pt / cm². 2 It had an apparent platinum-filled amount. Figure 3 shows the polarization curve of the film electrode assembly fabricated in Example 2.

[0052] Example 3 A film electrode assembly was prepared in the same manner as in Example 1, except that the cathode catalyst ink was directly deposited onto a hydrocarbon sulfonate ion conductive film using a HelioSonic® printing apparatus. Therefore, the subsequent decal transfer step in Example 1 was not necessary to form the cathode catalyst layer. The cathode catalyst layer was 0.15 mg Pt / cm². 2It had an apparent platinum filling amount. The cathode catalyst layer showed good layer quality upon visual inspection.

[0053] Example 4 The cathode catalyst ink of Example 1 was deposited onto a skived PTFE sheet (acceptor substrate) using a HelioSonic® printing apparatus (commercially available from HelioSonic GmbH, Germany) under the same conditions as in Example 1. However, the catalyst ink was transferred in a non-uniform layer in a predetermined pattern. In this example, the predetermined pattern consisted of continuous tracks 401 following meandering paths separated by regions that did not contain any catalyst 402. The tracks had an average width of approximately 1 mm and were spaced at an average interval of approximately 0.5 mm. The catalyst layer contained 0.2-0.3 mg Pt / cm². 2 It consisted of a first region having an apparent platinum-filled amount and a second region in which no platinum was deposited at all. Figure 4 shows a photograph of the patterned catalyst layer.

[0054] Example 5 First, an ink containing iridium oxide (IrOx, 45% by weight) and an ion-conducting polymer (PFSA, 5% by weight) was prepared in water (11% by weight) and propane-1-ol (39% by weight). This ink was then diluted with an additional solvent to a solid content of 38% by weight to produce an electrolytic cell anode catalyst layer. This ink was deposited onto a polyimide film supported on a glass substrate (transfer substrate) using knife coating. The transfer substrate was inverted, and the ink was transferred by irradiating it with a pulsed laser (wavelength 1050-1070 nm, 30-60 kHz, 200 mW) to form a catalyst layer on a PFTE substrate. Microscopic observation showed that a layer of good quality had been formed.

[0055] Example 6 A catalyst coating film was prepared in the same manner as in Example 1, except that the cathode catalyst ink was directly deposited onto a hydrocarbon anion exchange film (as an acceptor substrate) using a HelioSonic® printing apparatus. Therefore, the subsequent decal transfer step in Example 1 was not necessary to form the cathode catalyst layer. The cathode catalyst layer had a concentration of 0.1-0.2 mg Pt / cm². 2 It had an apparent platinum-filled content. Visual inspection indicated that the transfer of the layer onto the AEM was successful.

[0056] Comparative Example 1 The cathode catalyst ink from Example 1 was deposited onto a skived PTFE sheet using a k-bar coating process to create a substantially uniform wet catalyst layer (area = 100 cm²). 2 A layer was formed. The wet catalyst layer was dried and annealed (150-200°C). The apparent platinum layer packing amount was 0.2 mg Pt / cm². 2 The k-bar coating process in Comparative Example 1 was slower than the printing process in Example 1.

[0057] The anode catalyst layer was prepared on a skived PTFE sheet using the same method as described in Example 1.

[0058] The cathode and anode catalyst layers were transferred from their respective PTFE sheets to both sides of a commercially available reinforced PFSA ion-conductive film (15 μm thick) using a decal transfer process under pressure and at a temperature of 150°C to 200°C, thereby creating a catalyst-coated ion-conductive film (50 cm²) using the same method as described in Example 1. 2 A material with an effective area of ​​the specified value was prepared.

[0059] Comparative Example 2 The cathode catalyst ink of Example 1 was deposited onto a hydrocarbon-based ion-conducting polymer film using a k-bar coating process to create a substantially uniform wet catalyst layer (area = 100 cm²). 2A wet catalyst layer was formed. The wet catalyst layer was dried and annealed (150-200°C). Upon drying, the cathode catalyst layer cracked severely, and adhesion to the hydrocarbon-based ion-conducting film substrate was insufficient. A satisfactory film electrode assembly could not be prepared.

[0060] Battery testing 50cm 2 The polarization (current vs. voltage) performance of the membrane electrode assembly was measured under fully humidified and pressurized conditions (100% RH, 100 kPag or 170 kPag inlet) in H2 / air at 80°C, using both H2 and airflow at a stoichiometric value of 2.0. To confirm any differences in the dynamic behavior of the cathode catalyst, polarization curves were also recorded at the same temperature and pressure, as well as under hydrogen stoichiometric conditions, using pure oxygen as the oxidizer on the cathode side, although the oxygen stoichiometric value used was 10.0. In all measurements, cell humidity (RH) and pressure were controlled at the anode and cathode inlets.

[0061] Temperature sweeps were measured in H2 / air (170 kPag inlet) using 2 stoichiometric rates for both H2 and air flow. The temperature sweep was performed by fixing the dew points of hydrogen and air at 53°C at the cell inlet and controlling the cell temperature at different points between approximately 40°C and 90°C. For Figure 2, the point corresponds to 2.5 A / cm². 2 It was recorded at the current density.

[0062] Results and Discussion The method for depositing the cathode catalyst layer in Example 1 was significantly faster than the k-bar coating method used in Comparative Example 1. For example, the 100 cm³ method in Example 1 2 The cathode catalyst layer in Comparative Example 1 was deposited in less than 1 second, whereas the 100 cm³ layer in Comparative Example 1 was deposited in less than 1 second. 2The cathode catalyst layer was deposited in approximately 5-10 seconds. Figure 1 shows the polarization curves of Example 1 and Comparative Example 1 using the above battery test method (at a 170 kPag inlet). Figure 2 shows the temperature sweep measured using the method described above. There was no statistically significant difference in performance between Example 1 and Comparative Example 1. Therefore, the method of the present invention can be used to manufacture catalyst layers at a significantly faster rate while maintaining performance.

[0063] Figure 3 shows the polarization curve for Example 2. In Example 2, the cathode layer was deposited directly onto an ion-conductive film. This method eliminates the need for a decal transfer step, further improving the speed and efficiency of production. Therefore, the method of Example 2 helps reduce the number of processing steps, which helps increase throughput.

[0064] Examples 3 and 6 demonstrate that a catalyst layer can be successfully formed on a hydrocarbon-based ion-conducting film using the method described herein. Visual inspection of the layer formed in Example 3 shows higher layer quality than that observed in Comparative Example 2 using the conventional method.

[0065] Example 4 demonstrated that a catalyst layer can be formed in a predetermined pattern that is difficult to prepare using conventional coating methods by readily using laser irradiation.

[0066] Example 5 demonstrates that an electrolytic cell anode layer incorporating an IrOx oxygen evolution catalyst can be prepared using the process described above.

Claims

1. A method for preparing a catalyst layer for a fuel cell or electrolytic cell, A step of providing a donor substrate having opposing first and second surfaces, and providing a catalyst ink disposed as a layer on the second surface, wherein the catalyst ink comprises an electrolytic catalyst, an ion-conducting polymer, and a solvent. A step of providing an acceptor substrate, wherein the second surface of the donor substrate faces the acceptor substrate, A method comprising the step of irradiating the catalyst ink with laser radiation of a wavelength absorbed by the catalyst ink to transfer the catalyst ink from the donor substrate to the acceptor substrate.

2. The method according to claim 1, further comprising the step of drying the catalyst ink on the acceptor substrate to remove substantially all of the solvent.

3. The method according to claim 1 or 2, wherein the solvent has a boiling point of at least 95°C, preferably at least 100°C, and at least 110°C.

4. The method according to claim 1 or 2, wherein the solvent comprises water, ethanol, n-propanol, isopropanol, n-butanol, methanol, ethylene glycol, propylene glycol, dipropylene glycol, poly(ethylene glycol), poly(propylene glycol), ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, or a combination thereof.

5. The method according to claim 4, wherein the solvent essentially consists of water.

6. The method according to any one of claims 1 to 5, wherein the catalyst ink comprises the electrolytic catalyst and the ion-conducting polymer in a total amount of at least 5% by weight, based on the total weight of the catalyst ink.

7. The method according to any one of claims 1 to 6, wherein the ion-conducting polymer is a partially fluorinated sulfonic acid ionomer or a fully fluorinated sulfonic acid ionomer.

8. The method according to any one of claims 1 to 6, wherein the ion-conducting polymer is a proton-conducting polymer or an anion-conducting polymer.

9. The method according to any one of claims 1 to 8, wherein the acceptor substrate includes a porous substrate.

10. The method according to any one of claims 1 to 7, wherein the acceptor substrate includes a non-porous substrate.

11. The method according to any one of claims 1 to 8, wherein the acceptor substrate includes an ion-conducting film.

12. The method according to claim 11, wherein the ion-conducting film is a hydrocarbon-based ion-conducting film.

13. The method according to any one of claims 1 to 8, wherein the acceptor substrate includes a gas diffusion layer or a porous transport layer.

14. The method according to any one of claims 1 to 10, wherein the acceptor substrate includes a decal transfer substrate.

15. The method according to any one of claims 1 to 14, wherein the layer of catalyst ink disposed on the second surface of the donor substrate has a thickness in the range of 10 μm to 100 μm.

16. The method according to any one of claims 1 to 15, wherein the catalyst layer has a substantially uniform thickness.

17. The method according to any one of claims 1 to 15, wherein the catalyst layer includes at least one region having a first thickness and at least one region having a second thickness, and the first thickness and the second thickness are different.

18. The method according to any one of claims 1 to 17, wherein the catalyst layer has a substantially uniform amount of catalyst packed in it.

19. The method according to any one of claims 1 to 17, wherein the catalyst layer has a substantially non-uniform amount of catalyst packed in it.

20. The method according to any one of claims 1 to 17, wherein the catalyst layer is deposited in a predetermined pattern.

21. The method according to any one of claims 1 to 20, wherein the electrolytic catalyst comprises metal-containing particles optionally supported on a particulate carrier material.

22. The method according to claim 21, wherein the metal-containing particles include a platinum group metal or an alloy of a platinum group metal.

23. The method according to claim 21 or 22, wherein the particulate carrier material includes a carbon-based material, a metal oxide, a nitride, a carbide, or another conductive carrier material.

24. A catalyst layer obtained using the method described in any one of claims 1 to 23.

25. A catalyst-coated ion-conducting film comprising the catalyst layer described in claim 24.

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