Catalyst layer and method for manufacturing the same, membrane-electrode assembly and method for manufacturing the same

Abstract

A catalyst layer is provided that improves the performance and durability of a membrane-electrode assembly. According to one aspect of the present invention, a catalyst layer is provided that has a flexural modulus of 50 to 400 MPa and a flexural strength of 0.3 to 10 MPa.

Description

[Technical Field]

[0001] The present invention relates to a membrane-electrode assembly having a catalyst layer that satisfies mechanical properties and a method for manufacturing the same, and more particularly to a membrane-electrode assembly having a catalyst layer that satisfies specific mechanical properties and a method for manufacturing the same. [Background technology]

[0002] Recently, environmental pollution caused by the excessive use of fossil fuels and rising oil prices have led to growing interest in fuel cells, which are energy-efficient and produce fewer pollutants. Fuel cells do not convert the chemical energy of raw materials into mechanical energy, but rather convert it directly into electrical energy using an electrochemical conversion method. However, fuel cells operate on the opposite principle to water electrolysis. While water electrolysis uses external electricity to split water into hydrogen and oxygen, fuel cells generate electricity through an electrochemical reaction between hydrogen and oxygen. This can be expressed as chemical reaction equations (1) and (2).

[0003] Formula (1)

[0004] Anode electrode: H2→2H + +2e -

[0005] The reaction at the anode is an oxidation reaction, and the oxidation of hydrogen occurs easily with a platinum catalyst. The anode catalyst in a low-temperature fuel cell must oxidize hydrogen, and in an actual system, the fuel may contain CO, S, or NH3 rather than pure hydrogen. Of these, CO is the main toxic substance in low-temperature fuel cells and is easily adsorbed by the platinum catalyst. Carbon monoxide adsorbed on the platinum catalyst attaches to the catalyst's active sites, reducing the reaction area with hydrogen and weakening the catalyst. To reduce the damage caused by carbon monoxide, CO must be oxidized to CO2.

[0006] Formula (2)

[0007] Cathode electrode: 1 / 2O2+2H + +2e- →H2O

[0008] The reaction at the cathode is a reduction reaction, which travels through the electrolyte to the anode, where it combines with the hydrogen oxidized at the anode to produce water. Cathode has been widely studied due to the excellence of platinum-based catalysts, which are the most effective at reducing oxygen. To compensate for the low reactivity caused by low-temperature operation, the amount of metal added for the oxygen catalyst is high. This type of fuel cell also uses air as the cathode gas, but the partial pressure of oxygen is lower than that of pure oxygen, which reduces the activity of the reaction. The porosity of the cathode layer can be optimized by adding pore-forming materials.

[0009] Fuel cells come in a variety of types, depending on the fuel and material used, including polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs), and molten carbonate fuel cells (MCFCs). A fuel cell power generation system consists of a fuel reformer, which converts common hydrogen-containing fuels (LPG, LNG, methane, coal gas, methanol, etc.) into the hydrogen-rich gas required by the fuel cell; a stack, which uses the hydrogen from the fuel reformer and oxygen from the air to generate direct current (DC), water, and heat as a by-product; and an inverter, which converts the DC power output from the fuel cell into AC power. The most important part of the stack is the membrane electrode assembly (MEA). The membrane electrode assembly (MEA) is a film-shaped assembly that converts the chemical reaction between oxygen and hydrogen into electrical energy. Hydrogen and oxygen supplied to the fuel cell release electrons at the anode and cathode, respectively, to become ions, and the released electrons escape to the outside to generate electric current. This reaction occurs in the membrane electrode assembly. The membrane-electrode assembly is composed of an electrolyte membrane, an anode, and a cathode.

[0010] Meanwhile, the catalyst layer that constitutes a polymer electrolyte fuel cell is manufactured by forming a catalyst layer using a catalyst slurry in which catalyst particles and a polymer electrolyte (binder) are mixed in a solvent, and then drying the catalyst layer. Traditionally, after manufacturing a catalyst layer or a membrane-electrode assembly, only mechanical properties such as Young's modulus or tensile strength have been measured and used as reference data. Factors that affect the mechanical strength of a catalyst layer or a membrane-electrode assembly include the type and content of materials used, and the manufacturing method. If the mechanical strength of a catalyst layer or a membrane-electrode assembly is not at an appropriate level, the following problems may occur.

[0011] 1) The rate of deformation due to dry-wet cycles is much greater for the polymer electrolyte membrane than for the catalyst layer, so the dry-wet cycles caused by fuel cell operation result in deformation of the polymer electrolyte membrane, which in turn induces deformation of the catalyst layer, such as cracking and peeling.

[0012] 2) When the water in the catalyst layer freezes under low-temperature conditions, the volume expansion caused by the phase change of the water induces deformation of the catalyst layer. As a result, the deformed catalyst layer becomes isolated from the fuel cell reaction system, reducing the amount of catalyst that can contribute to power generation and significantly reducing the power generation function.

[0013] 3) In order to improve the strength of the catalyst layer, the amount of ionomer contained in the catalyst layer can be increased, but this can lead to a decrease in power generation performance due to a decrease in drainage and gas diffusion.

[0014] Therefore, there is a current demand for improvements that can improve the driving efficiency of fuel cells while maintaining the mechanical properties of the catalyst layer and increasing durability. Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has been made to solve the above-mentioned problems, and aims to provide a membrane-electrode assembly having improved performance and durability, which is provided with a catalyst layer that satisfies specific mechanical properties, by measuring the mechanical properties of the catalyst layer or membrane-electrode assembly to predict its performance and durability, and a method for manufacturing the same. [Means for solving the problem]

[0016] To achieve the above object, according to a first aspect of the present invention, there is provided a catalyst layer having a flexural modulus of 50 to 400 MPa and a flexural strength of 0.3 to 10 MPa, where the flexural strength is the maximum force applied to a catalyst layer sample until permanent deformation occurs, measured using an Instron 5966 instrument.

[0017] According to a second aspect of the present invention, in the first aspect, the catalyst layer may be a free-standing catalyst layer.

[0018] According to a third aspect of the present invention, in the second aspect, the freestanding catalyst layer may have a Young's modulus of 150 to 500 MPa.

[0019] According to a fourth aspect of the present invention, in the second or third aspect, the freestanding catalyst layer may have a tensile strength of 1 to 30 MPa.

[0020] According to a fifth aspect of the present invention, in any one of the second to fourth aspects, the freestanding catalyst layer may have an indentation hardness of 0.05 to 3.0 MPa.

[0021] According to a sixth aspect of the present invention, in any one of the second to fifth aspects, the density of the freestanding catalyst layer is 0.1 to 2.0 g / cm 3 may be.

[0022] According to a seventh aspect of the present invention, in any one of the second to sixth aspects, the freestanding catalyst layer may include a sub-catalyst layer and an interfacial bonding layer (IBL) disposed on at least one surface of the sub-catalyst layer.

[0023] According to an eighth aspect of the present invention, in the seventh aspect, the thickness of the interface adhesive layer may be 0.1 to 1.5 μm.

[0024] According to a ninth aspect of the present invention, there can be provided a method for manufacturing a catalyst layer, including: a first step of preparing an electrode slurry containing a catalyst and an ionomer; a second step of coating the electrode slurry on a substrate and drying it to form a sub-catalyst layer; a third step of coating one side of the sub-catalyst layer with an ionomer solution and drying it to form an interfacial adhesion layer; and a fourth step of immersing the result of the third step in water and leaving it to stand to separate the catalyst layer from the substrate.

[0025] According to a tenth aspect of the present invention, there can be provided a membrane-electrode assembly comprising the catalyst layer according to any one of the first to eighth aspects, wherein the membrane-electrode assembly has a flexural modulus of 450 to 1,000 MPa and a flexural strength of 12 to 80 MPa.

[0026] According to an eleventh aspect of the present invention, in the tenth aspect, the membrane-electrode assembly may have a Young's modulus of 650 to 1,600 MPa.

[0027] According to a twelfth aspect of the present invention, in the tenth or eleventh aspect, the membrane-electrode assembly may have a tensile strength of 35 to 90 MPa.

[0028] According to a thirteenth aspect of the present invention, in any one of the tenth to twelfth aspects, the membrane-electrode assembly may have an indentation hardness of 2.0 to 9.0 MPa.

[0029] According to a fourteenth aspect of the present invention, there can be provided a method for producing a membrane-electrode assembly, the method including a step of joining the catalyst layer according to any one of the first to eighth aspects to an electrolyte membrane.

[0030] According to a fifteenth aspect of the present invention, in any one of the tenth to thirteenth aspects, the electrolyte membrane and the interface adhesive layer can be in contact with each other. [Effects of the Invention]

[0031] As described above, the present invention provides a membrane-electrode assembly that satisfies specific mechanical properties and includes a catalyst layer that satisfies the mechanical properties, thereby making it possible to improve the mechanical properties of the membrane-electrode assembly.

[0032] Furthermore, the present invention has the effect of providing new parameters for a membrane-electrode assembly including a catalyst layer that satisfies mechanical properties and a free-standing catalyst layer.

[0033] In addition, the characterization of mechanical properties allows the development and utilization of catalyst layers with satisfactory mechanical properties and membrane-electrode assemblies having the same.

[0034] Furthermore, there is an effect that the mechanical properties of the catalyst layer or membrane-electrode assembly can be measured to predict and utilize the performance and durability. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 shows the size of a dog-bone shaped test piece of CCM in Experimental Example 1 of the present invention. [Figure 2A]FIG. 2A is an image of the free-standing catalyst layers of Experimental Examples 2 and 3 of the present invention before the Young's modulus and tensile strength were measured. [Figure 2B] FIG. 2B is an image of the free-standing catalyst layers of Experimental Examples 2 and 3 of the present invention after measuring Young's modulus and tensile strength. [Figure 3A] FIG. 3A is an image of the membrane-electrode assemblies of Experimental Examples 2 and 3 of the present invention before the Young's modulus and tensile strength were measured. [Figure 3B] FIG. 3B is an image of the membrane-electrode assemblies of Experimental Examples 2 and 3 of the present invention after Young's modulus and tensile strength were measured. DETAILED DESCRIPTION OF THE INVENTION

[0036] In the drawings shown below, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of description. The embodiments described below are merely examples, and various modifications are possible from such embodiments. Hereinafter, terms are used only to distinguish one component from another. Unless otherwise clearly indicated in the context, singular expressions include plural expressions. Furthermore, when a part "comprises" a certain component, this does not mean to exclude other components, but means that it can further include other components, unless otherwise specified.

[0037] As used herein, a "freestanding catalyst layer" can refer to a catalyst layer that can exist in an independently standing form without a separate support or substrate.

[0038] The catalyst layer satisfying the mechanical properties of the present invention can be prepared using an electrode slurry satisfying specific mechanical properties. The electrode slurry of the present invention can be prepared in various ways by mixing the catalyst and the ionomer in a specific ratio.

[0039] The membrane-electrode assembly according to the present invention includes a catalyst layer that satisfies mechanical properties, and has a flexural modulus of 450 to 1,000 MPa and a flexural strength of 12 to 80 MPa.

[0040] The flexural modulus is a mechanical property that evaluates the stiffness or bending resistance of a membrane-electrode assembly. It can be evaluated when a load is applied perpendicular to a long material. For example, the flexural modulus of a membrane-electrode assembly is calculated by measuring the slope of the linear portion of the stress-strain curve (SS curve), where the stress is divided by the corresponding deformation. Ideally, the flexural modulus of a membrane-electrode assembly is equal to the Young's modulus. However, in practice, the higher the flexural modulus, the more difficult it is to bend. Conversely, the lower the flexural modulus, the more easily the membrane-electrode assembly bends under applied force. The flexural modulus can be measured, for example, using an Instron 5966 instrument in compression mode, by repeatedly applying a load (10 N) approximately 20 times using a puncture test probe and holder. Alternatively, it can be measured using a Nanoindenter instrument by measuring the deformation rate using the indentation method at a loading rate of 5.0 mN / min. The flexural modulus of the membrane-electrode assembly of the present invention may be 450 to 1,000 MPa, specifically 500 to 850 MPa, and more specifically 600 to 700 MPa. If the flexural modulus is less than 450 MPa, the elasticity of the membrane-electrode assembly may decrease, resulting in reduced mechanical durability. If the flexural modulus exceeds 1,000 MPa, the elasticity of the membrane-electrode assembly may become excessively high, resulting in a relatively high ionomer content, which may make the membrane-electrode assembly sensitive to moisture and reduce processability. Additionally, the flexural modulus corresponds to the mechanical durability of the membrane-electrode assembly, and membrane-electrode assemblies having a flexural modulus within the range proposed in the present invention exhibit higher mechanical durability than membrane-electrode assemblies having a flexural modulus less than 450 MPa.

[0041] Flexural strength can be defined as the normal stress generated in a membrane-electrode assembly by bending the membrane-electrode assembly in a bending test. The flexural strength can be determined, for example, by measuring the maximum force applied to a sample until permanent deformation occurs using an Instron 5966 instrument. It can be expressed as the average value of at least 10 repeated measurements. The flexural strength of the membrane-electrode assembly of the present invention may be 12 to 80 MPa, specifically 13 to 50 MPa, and more specifically 15 to 20 MPa. If the flexural strength is less than 12 MPa, the mechanical properties of the membrane-electrode assembly may be reduced, making it susceptible to deformation even with a small external force and making it difficult to process. If the flexural strength exceeds 80 MPa, the flexibility of the membrane-electrode assembly may be reduced, resulting in reduced processability during subsequent attachment of a subgasket and a gas diffusion layer (GDL).

[0042] On the other hand, the Young's modulus of the membrane-electrode assembly of the present invention may be 650 to 1,600 MPa.

[0043] Young's modulus is a coefficient that represents the relative change in length of an elastic membrane-electrode assembly with respect to stress. For example, it can be determined by stretching a test specimen at a stretch speed of 50 mm / min using an Instron 5966 instrument and measuring the slope in the 0.25 to 1% strain range. It can be expressed as the average value of at least 10 repeated measurements. The Young's modulus of the membrane-electrode assembly of the present invention may be 650 to 1,600 MPa, specifically 800 to 1,300 MPa, and more specifically 900 to 1,000 MPa. If the Young's modulus of the membrane-electrode assembly is less than 650 MPa, the membrane-electrode assembly may be prone to tearing and deformation even with a small external force, making it difficult to process. If the Young's modulus is more than 1,600 MPa, the membrane-electrode assembly may be too elastic, resulting in poor processability during subsequent attachment of a subgasket and gas diffusion layer (GDL).

[0044] The tensile strength of the membrane-electrode assembly of the present invention may be 35 to 90 MPa.

[0045] Tensile strength refers to the maximum stress that a membrane-electrode assembly can withstand before it breaks due to a tensile load. For example, the tensile strength can be calculated by the maximum tensile load (W max) divided by the original cross-sectional area (A0) of the test piece. Tensile strength can be broadly divided into tensile strength at the yield point and tensile strength at the break point, with the yield point representing the maximum force a material can withstand, and the break point representing the force at which the material breaks. The tensile strength of the membrane-electrode assembly of the present invention refers to the tensile strength at the break point of the test piece. The tensile strength can be determined by preparing a test piece of the membrane-electrode assembly, stretching it at a stretch speed of 50 mm / min using a tensile strength tester, for example, an Instron 5966, and measuring the maximum stress value. The tensile strength of the membrane-electrode assembly of the present invention may be 35 to 90 MPa, specifically 45 to 80 MPa, and more specifically 60 to 70 MPa. If the tensile strength is less than 35 MPa, the membrane-electrode assembly will be too flexible and easily broken or deformed even with a small external force, resulting in reduced mechanical properties. If the tensile strength exceeds 90 MPa, the membrane-electrode assembly will be too stiff, resulting in reduced processability when attaching the subgasket and gas diffusion layer (GDL) later.

[0046] The indentation hardness of the membrane-electrode assembly of the present invention may be 2.0 to 9.0 MPa.

[0047] Indentation hardness is a measure of strength measured by an indentation method. While there are various methods for measuring hardness, the indentation hardness method currently widely used around the world is the one used to measure hardness. This involves pressing a test specimen with an indenter (such as a steel ball or diamond prism) into the specimen, and measuring the size of the indentation. The value obtained by this method is called the indentation hardness. Indentation hardness can be measured, for example, using a nanoindenter to measure the maximum force required for permanent deformation of the surface. It can be expressed as the average value of 10 or more repeated measurements. The indentation hardness of the membrane-electrode assembly of the present invention may be 2.0 to 9.0 MPa, specifically 2.5 to 7.0 MPa, and more specifically 3.0 to 5.0 MPa. If the indentation hardness is less than 2.0 MPa, the membrane-electrode assembly may be too flexible, resulting in a weak catalyst layer structure and reduced mechanical properties. If the indentation hardness exceeds 9.0 MPa, the membrane-electrode assembly may become too brittle, and the hard catalyst layer surface may make it difficult to attach and balance the subgasket and gas diffusion layer (GDL).

[0048] In addition, the catalyst layer of the present invention may include an interfacial bonding layer (IBL).

[0049] Such an interfacial adhesive layer enables the membrane-electrode assembly to have low hydrogen permeability without reducing proton conductivity, improves the adhesion at the interface between the catalyst layer and the electrolyte membrane, and thereby improves the durability of the membrane-electrode assembly, thereby improving the performance and durability of the membrane-electrode assembly under high temperature / low humidity conditions.

[0050] In this case, the thickness of the interfacial adhesive layer may be 0.1 to 1.5 μm. If the thickness of the interfacial adhesive layer is less than the above range, the catalyst layer and the membrane-electrode assembly including the same may not satisfy the mechanical properties that the present invention aims to achieve, and durability may be reduced. If the thickness of the interfacial adhesive layer is more than the above range, the elasticity of the catalyst layer and the membrane-electrode assembly including the same may be excessively high or flexibility may be reduced, resulting in reduced processability. Also, the ion transport path may be lengthened, resulting in reduced performance.

[0051] The membrane-electrode assembly according to the present invention can be manufactured by bonding a catalyst layer having satisfactory mechanical properties to an electrolyte membrane, which may be, but is not limited to, a fluorine-based reinforced membrane commonly used in fuel cells.

[0052] On the other hand, the freestanding catalyst layer according to the present invention has a flexural modulus of 50 to 400 MPa and a flexural strength of 0.3 to 10 MPa.

[0053] The free-standing catalyst layer can be prepared by coating a catalyst layer satisfying the above-mentioned mechanical properties on a substrate such as glass, drying it, and then separating it.

[0054] The flexural modulus of the freestanding catalyst layer may be 50 to 400 MPa, specifically 150 to 300 MPa, and more specifically 190 to 240 MPa. If the flexural modulus is less than 50 MPa, the elasticity of the catalyst layer may decrease, whereas if the flexural modulus exceeds 400 MPa, the elasticity of the catalyst layer may become too large, resulting in a decrease in the bond strength with the electrolyte membrane and other deterioration in processability.

[0055] The bending strength of the freestanding catalyst layer of the present invention may be 0.3 to 10 MPa, specifically 1 to 5 MPa, or more specifically 2 to 3 MPa. If the bending strength is less than 0.3 MPa, the mechanical properties will be reduced and the layer will be easily bent, whereas if the bending strength exceeds 10 MPa, the flexibility of the catalyst layer will be reduced, which may result in reduced processability, such as a reduced adhesive strength with the electrolyte membrane.

[0056] The Young's modulus of the freestanding catalyst layer may be 150 to 500 MPa, specifically 200 to 400 MPa, or more specifically 300 to 320 MPa. If the Young's modulus is less than 150 MPa, the elasticity of the catalyst layer may decrease, making it prone to breakage and possibly even breaking. If the Young's modulus exceeds 500 MPa, the elasticity of the catalyst layer may become too great, resulting in reduced processability, such as a decrease in the bonding strength with the electrolyte membrane.

[0057] The tensile strength of the freestanding catalyst layer of the present invention may be 1 to 30 MPa, specifically 1 to 10 MPa, and more specifically 2 to 5 MPa. If the tensile strength is less than 1 MPa, the catalyst layer may be excessively flexible and have reduced mechanical properties, whereas if the tensile strength exceeds 30 MPa, the catalyst layer may be excessively hard and have reduced processability, such as a reduced adhesive strength with the electrolyte membrane.

[0058] Furthermore, the indentation hardness of the freestanding catalyst layer of the present invention may be 0.05 to 3.0 MPa, specifically 0.1 to 3.0 MPa, and more specifically 1.0 to 3.0 MPa. If the indentation hardness is less than 0.05 MPa, the catalyst layer may be excessively flexible and have poor mechanical properties, whereas if the indentation hardness exceeds 3.0 MPa, the catalyst layer may become too brittle, and the hard catalyst layer surface may result in poor adhesion to the electrolyte membrane, and difficulty in adhering the subgasket and gas diffusion layer and achieving a balance between these.

[0059] The density of the free-standing catalyst layer of the present invention is 0.1 to 2.0 g / cm3 may be.

[0060] The density of the free-standing catalyst layer is, for example, 25 cm 2 The weight of the catalyst layer is determined by measuring the weight after coating the area with the catalyst layer and the weight after removing the catalyst layer with tape, and the volume is calculated from the average thickness of the catalyst layer using an SEM to obtain the density, which can be expressed as the average value of 10 or more repeated measurements. The density of the freestanding catalyst layer of the present invention is 0.1 to 2.0 g / cm 3 Specifically, it is 0.5 to 1.5 g / cm 3 More specifically, it may be 0.9 to 1.0 g / cm 3 The density of the free-standing catalyst layer may be 0.1 g / cm 3 If it is less than 2.0 g / cm, the catalyst layer may be too flexible and the volume may increase, resulting in poor mechanical properties. 3 If the content is too high, the structure of the catalyst layer becomes dense, which may hinder the transfer of materials and reduce performance.

[0061] Meanwhile, the freestanding catalyst layer of the present invention can be prepared by coating an electrode slurry onto a substrate having releasability. Once peeled off from the substrate, the freestanding catalyst layer is in a freestanding state, eliminating the need for a support material to support the material. Here, "freestanding" refers to the ability to exist independently in a standing form without the need for an additional support material or substrate. For example, the freestanding catalyst layer may have a film shape.

[0062] The free-standing catalyst layer in this state has excellent flexibility, can exist independently, and is easy to handle. In order to form the free-standing catalyst layer of the present invention, the substrate preferably has releasability so that the film can be easily peeled off after being formed on the substrate.

[0063] That is, according to yet another embodiment of the present invention, the method for manufacturing the free-standing catalyst layer includes a first step of preparing an electrode slurry containing a catalyst and an ionomer, a second step of coating the electrode slurry on a substrate to form an electrode slurry coating layer, and a third step of drying the electrode slurry coating layer and then immersing the dried electrode slurry coating layer in water at room temperature and leaving it to stand to separate the free-standing catalyst layer from the substrate. Furthermore, the separated catalyst layer can be further dried on another substrate.

[0064] For example, a free-standing catalyst layer can be produced by applying an electrode slurry to a substrate and then heat-treating the substrate to form a film. The heat treatment can be carried out at a temperature between 60°C and 200°C, specifically between 80°C and 180°C. If the heat treatment is carried out at a temperature lower than this range, the structural stability of the film may be reduced, making it difficult to produce a free-standing catalyst layer.

[0065] The method for producing a membrane-electrode assembly of the present invention includes a first step of preparing an electrode slurry containing a catalyst and an ionomer; a second step of coating the electrode slurry on a substrate to form an electrode slurry coating layer; a third step of drying the electrode slurry coating layer to form a catalyst layer that satisfies mechanical properties; and a fourth step of bonding the catalyst layer that satisfies the mechanical properties to an electrolyte membrane.

[0066] Here, the substrate may be a release film or a glass plate, but is not limited to these, and any substrate having release properties can be used without limitation.

[0067] In a method for manufacturing a membrane-electrode assembly according to the present invention, for example, a catalyst and an ionomer are mixed in a specific composition ratio to prepare an electrode slurry, and the electrode slurry is then coated on a release film and dried to form a catalyst layer with satisfactory mechanical properties. An ionomer solution is then spray-coated onto the catalyst layer to manufacture an electrode including an interfacial bonding layer (IBL). The electrode including the IBL thus prepared can be transferred to or bonded to an electrolyte membrane using an isostatic decal laminator to manufacture a catalyst-coated membrane (CCM) or a membrane-electrode assembly (MEA). The electrolyte membrane may be a fluorine-based reinforced membrane commonly used in the field of fuel cells.

[0068] In the catalyst layer according to the present invention, which satisfies the mechanical properties, the type of catalyst support, the type and amount of metal catalyst supported, the type and content of ionomer, additives, solid content, catalyst layer structure, etc. can be appropriately adjusted according to the required mechanical properties.

[0069] The catalyst support may be selected from the group consisting of silica, alumina, zirconia and titania, but is not limited thereto.

[0070] The ionomer is preferably one or a mixture of two selected from a fluorine-based ionomer and a hydrocarbon-based ionomer, and the fluorine-based ionomer may be one or more selected from Nafion, Flemion, and Aciplex. The hydrocarbon ionomer may be selected from homo copolymers, alternating copolymers, random copolymers, block copolymers, multiblock copolymers, graft copolymers, and mixtures thereof, containing one or more hydrocarbons selected from the group consisting of sulfonated imides, sulfonated aryl ether sulfones, sulfonated ether ether ketones, sulfonated benzimidazoles, sulfonated sulfones, sulfonated styrenes, sulfonated phosphazenes, sulfonated ether ether sulfones, sulfonated ether sulfones, sulfonated ether benzimidazoles, sulfonated arylene ether ketones, sulfonated ether ketones, sulfonated imidazoles, sulfonated ether ketone ketones, aryl ether benzimidazoles, and combinations thereof.

[0071] The catalyst may be any that can be used as a catalyst for hydrogen oxidation reactions and oxygen reduction reactions, and preferably a platinum-based metal is used. Examples of the platinum-based metal include platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloys (wherein M is palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au), zinc (Zn), and tin (Sn). The catalyst metal may include any one or more selected from the group consisting of molybdenum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh), and a combination thereof, and more preferably, a combination of two or more metals selected from the group of platinum-based catalyst metals may be used, but is not limited thereto, and any platinum-based catalyst metal that can be used in this technical field may be used without limitation.

[0072] Example 1: Catalyst layer configuration and production of membrane-electrode assembly

[0073] Electrode slurry production

[0074] Cathode electrode slurry with an I / C ratio of 1.1 was produced using a 50% Pt-Co / C catalyst from TANAKA and a PFSA ionomer from 3M. Anode electrode slurry with an I / C ratio of 1.0 (I / C=1.0) was produced using a 50% Pt-Ru / C catalyst particle from TANAKA and a PFSA ionomer from 3M.

[0075] Sub-catalyst layer formation step

[0076] The prepared electrode slurry was applied to a release film with a cathode loading of 0.4 mg / cm. 2 Anode loading: 0.1 mg / cm 2After coating with each of these, the coating was dried at 90°C for 180 minutes to prepare a sub-catalyst layer.

[0077] Step of forming an interface bonding layer and step of manufacturing a catalyst layer

[0078] A PFSA ionomer solution (total solids content: 5 wt%, equivalent weight: 3-10) was sprayed onto one side of each of the prepared sub-catalyst layers and then dried at 120°C for 1 minute to form an interfacial bonding layer (IBL) with a thickness of 0.1-1.5 μm (average thickness: 0.6 μm). As a result, a catalyst layer consisting of a sub-catalyst layer and an interfacial bonding layer was prepared.

[0079] Membrane-electrode assembly manufacturing steps

[0080] The interface bonding layer of the prepared catalyst layer was placed in contact with the electrolyte membrane, and then the membrane-electrode assembly was fabricated by bonding it to the electrolyte membrane using an isostatic decal laminator. The electrolyte membrane was a fluorine-based reinforced membrane impregnated with a PFSA ionomer solution on a porous support (PTFE support, porosity 70%, thickness 5 μm).

[0081] (Example 2) Catalyst layer configuration and production of membrane-electrode assembly (different catalyst types)

[0082] A membrane-electrode assembly was produced in the same manner as in Example 1, except that a 50% Pt / C catalyst manufactured by TANAKA was used in producing the cathode slurry.

[0083] (Example 3) Catalyst layer configuration and production of membrane-electrode assembly (different types of ionomer)

[0084] A membrane-electrode assembly was produced in the same manner as in Example 1, except that Nafion PFSA ionomer from Chemours was used in producing the cathode slurry.

[0085] (Example 4) Catalyst layer configuration and production of membrane-electrode assembly (different I / C ratios)

[0086] A membrane-electrode assembly was produced in the same manner as in Example 1, except that a composition with I / C=0.95 was used in producing the cathode slurry.

[0087] (Example 5) Catalyst layer configuration and production of membrane-electrode assembly (different loading amounts)

[0088] After preparing the cathode electrode slurry, the prepared electrode slurry was applied to a release film with a cathode loading of 0.3 mg / cm. 2 A membrane-electrode assembly was manufactured in the same manner as in Example 1, except that the electrode was manufactured by coating with the cellulose acetate solution and then drying it.

[0089] (Example 6) Catalyst layer configuration and production of membrane-electrode assembly (different joining method)

[0090] A membrane-electrode assembly was manufactured in the same manner as in Example 1, except that the electrode containing the IBL was joined to the electrolyte membrane using a hydraulic hot and cold press.

[0091] (Example 1-1) Production of a free-standing catalyst layer

[0092] The cathode electrode slurry prepared in Example 1 was coated on a glass plate and then dried. An ionomer solution was applied to the dried electrode to prepare an IBL with a thickness of 0.1 to 1.5 μm (average thickness: 0.6 μm). The prepared electrode was immersed in water at room temperature and then left to stand, after which it was separated. The separated electrode was then dried on another glass plate to prepare a free-standing catalyst layer.

[0093] (Comparative Example 1) Catalyst Layer Configuration and Membrane-Electrode Assembly Production (Difference in IBL Thickness)

[0094] A membrane-electrode assembly was manufactured in the same manner as in Example 1, except that an ionomer solution was applied to the manufactured electrode by spraying to prepare an IBL having an average thickness of 0.06 μm.

[0095] (Comparative Example 1-1) Production of free-standing catalyst layer (IBL thickness difference)

[0096] The cathode electrode slurry prepared in Example 1 was coated on a glass plate and then dried. An ionomer solution was applied to the dried electrode to prepare an IBL with an average thickness of 0.06 μm. The prepared electrode was immersed in water at room temperature and then left to stand, after which it was separated. The separated electrode was then dried on another glass plate to prepare a free-standing catalyst layer.

[0097] (Comparative Example 2) Catalyst Layer Configuration and Production of Membrane-Electrode Assembly

[0098] A membrane-electrode assembly was fabricated in the same manner as in Example 1, except for the step of spraying an ionomer solution onto the electrode to fabricate an interfacial bonding layer (IBL).

[0099] (Comparative Example 2-1) Production of a Free-standing Catalyst Layer

[0100] The cathode electrode slurry prepared in Example 1 was coated on a glass plate and dried. A free-standing catalyst layer was prepared in the same manner as in Example 1, except for the process of preparing an IBL by applying an ionomer solution to the dried electrode.

[0101] (Experimental Example 1) Preparation of Young's modulus and tensile strength test specimens

[0102] The free-standing catalyst layer was cut into a 5 × 50 mm specimen, and a membrane-electrode assembly was prepared in the dog bone shape shown in Figure 1.

[0103] (Experimental Example 2) Measurement of Young's modulus

[0104] Using Instron 5966 equipment, the specimen was stretched at a stretch speed of 50 mm / min and the slope of the 0.25 to 1% strain range was measured. The average value of 10 or more repeated measurements was calculated, and the measurement results are shown in Table 1.

[0105] [Table 1]

[0106] (Experimental Example 3) Measurement of Tensile Strength

[0107] Using Instron 5966 equipment, the specimen was stretched at a stretch speed of 50 mm / min and the maximum stress value was measured. The average value of 10 or more repeated measurements was calculated, and the measurement results are shown in Table 2.

[0108] For reference, Fig. 2A is an image of the free-standing catalyst layers of Experimental Examples 2 and 3 of the present invention before Young's modulus and tensile strength measurement, Fig. 2B is an image of the free-standing catalyst layers of Experimental Examples 2 and 3 of the present invention after Young's modulus and tensile strength measurement, Fig. 3A is an image of the membrane-electrode assemblies of Experimental Examples 2 and 3 of the present invention before Young's modulus and tensile strength measurement, and Fig. 3B is an image of the membrane-electrode assemblies of Experimental Examples 2 and 3 of the present invention after Young's modulus and tensile strength measurement.

[0109] [Table 2]

[0110] (Experimental Example 4) Preparation of Flexural Modulus & Flexural Strength Test Pieces

[0111] The free-standing catalyst layer and the membrane-electrode assembly were cut into 50 x 50 mm test pieces to prepare test pieces.

[0112] (Experimental Example 5) Measurement of Flexural Modulus

[0113] First, an Instron 5966 instrument was used in compression mode. A load (10 N) was repeatedly applied (20 times) using a puncture test probe and holder. Second, a Nanoindenter instrument was used to measure the deformation rate using the indentation method at a loading rate of 5.0 mN / min. The results are shown in Table 3.

[0114] [Table 3]

[0115] (Experimental Example 6) Measurement of Flexural Strength

[0116] The maximum force applied to the sample until permanent deformation was observed was measured using an Instron 5966 instrument. The average value of 10 or more repeated measurements was calculated, and the results are shown in Table 4.

[0117] [Table 4]

[0118] (Experimental Example 7) Measurement of indentation hardness

[0119] The maximum force for permanent deformation of the surface was measured using the indentation method with a Nanoindenter device. The average value was calculated from 10 or more repeated measurements, and the results are shown in Table 5.

[0120] [Table 5]

[0121] (Experimental Example 8) Density Measurement

[0122] 25cm 2 The weight of the electrode was measured after coating the area and after removing the electrode with tape. The density was calculated from the average thickness of the catalyst layer measured using SEM and the weight per volume. The average value of more than 10 repeated measurements was calculated, and the results are shown in Table 6.

[0123] [Table 6]

[0124] (Experimental Example 9) Physical (mechanical) durability evaluation

[0125] The physical durability of each of the membrane-electrode assemblies of the Examples and Reference Examples was evaluated based on the wet-dry durability evaluation protocol of the U.S. Department of Energy (DOE). Specifically, to evaluate the physical durability of the membrane-electrode assemblies, 20,000 wet-dry cycles were performed, and then hydrogen crossover (H2 crossover) was measured. The results are shown in Table 7. The membrane-electrode assemblies of the Examples met the DOE standard (H2 crossover ≦ 15 mA / cm). 2 It demonstrated extremely stable physical durability, meeting the standard of 20,000 wet-dry cycles.

[0126] [Table 7]

[0127] Not only the method of the above-mentioned experimental example, but also other similar methods were used to confirm that the catalyst layer and membrane-electrode assembly satisfied the following parameters: Young's modulus: 150 to 500 MPa (free standing), 650 to 1600 MPa (MEA)

[0128] Tensile strength: 1~30MPa (free standing), 35~90MPa (MEA)

[0129] Flexural modulus: 50~400MPa (free standing), 450~1,000MPa (MEA)

[0130] Flexural strength: 0.3~10MPa (free standing), 12~80MPa (MEA)

[0131] Indentation hardness:0.05~3.0MPa(free standing), 2.0~9.0MPa(MEA)

[0132] Density: 0.1 to 2.0 g / cm 3

[0133] The present invention is not limited to the above-described embodiments, and can be manufactured in various different forms, and those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and not limiting.

Claims

1. A catalyst layer having a flexural modulus of 50 to 400 MPa and a flexural strength of 0.3 to 10 MPa.

2. The catalyst layer according to claim 1, wherein the catalyst layer is a free-standing catalyst layer.

3. The catalyst layer according to claim 2, wherein the freestanding catalyst layer has a Young's modulus of 150 to 500 MPa.

4. The catalyst layer according to claim 2, wherein the freestanding catalyst layer has a tensile strength of 1 to 30 MPa.

5. The catalyst layer according to claim 2, wherein the freestanding catalyst layer has an indentation hardness of 0.05 to 3.0 MPa.

6. The density of the free-standing catalyst layer is 0.1 to 2.0 g / cm ３ The catalyst layer according to claim 2, wherein

7. The free-standing catalyst layer is A sub-catalyst layer; 3. The catalyst layer of claim 2, further comprising an interfacial bonding layer (IBL) disposed on at least one surface of the sub-catalyst layer.

8. The catalyst layer according to claim 7, wherein the thickness of the interfacial adhesion layer is 0.1 to 1.5 μm.

9. A first step of preparing an electrode slurry containing a catalyst and an ionomer; a second step of coating the electrode slurry on a substrate and then drying the coating to form a sub-catalyst layer; a third step of coating an ionomer solution on one side of the sub-catalyst layer and then drying it to form an interface adhesion layer; a fourth step of immersing the resultant of the third step in water and leaving it to stand to separate the catalyst layer from the substrate.

10. A membrane-electrode assembly comprising the catalyst layer according to any one of claims 1 to 8, A membrane-electrode assembly having a flexural modulus of 450 to 1,000 MPa and a flexural strength of 12 to 80 MPa.

11. 11. The membrane-electrode assembly according to claim 10, wherein the membrane-electrode assembly has a Young's modulus of 650 to 1,600 MPa.

12. The membrane-electrode assembly according to claim 10, wherein the membrane-electrode assembly has a tensile strength of 35 to 90 MPa.

13. 11. The membrane-electrode assembly according to claim 10, wherein the indentation hardness of the membrane-electrode assembly is 2.0 to 9.0 MPa.

14. A method for producing a membrane-electrode assembly, comprising the step of joining the catalyst layer according to any one of claims 1 to 8 and an electrolyte membrane.

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