Catalyst layer for electrochemical devices, film electrode assembly, and electrochemical device

Abstract

This invention provides a catalyst layer for electrochemical devices that exhibits excellent proton transport properties and is suitable for improving power generation efficiency. [Solution] The catalyst layer 100 of the present disclosure includes a porous conductive material 11 having a first main surface 101 and a second main surface 102 and pores 11p, catalyst particles 12 disposed inside the pores 11p, a first ionomer 31 and a second ionomer 32. The swelling rate R of the first ionomer 31 is greater than the swelling rate R of the second ionomer 32. The portion including the first main surface 101 and located on the side of the first main surface 101 is defined as the first portion 101p, and the portion including the second main surface 102 and located on the side of the second main surface 102 is defined as the second portion 102p. The proportion of the mass of the first ionomer 31 contained in the first portion 101p is greater than the proportion of the mass of the second ionomer 32, and the proportion of the mass of the second ionomer 32 contained in the second portion 102p is greater than the proportion of the mass of the first ionomer 31.

Description

[Technical Field]

[0001] This disclosure relates to a catalyst layer for an electrochemical device, a film electrode assembly, and an electrochemical device. [Background technology]

[0002] Patent Document 1 describes an electrode catalyst layer comprising catalyst supports coated with a polymer electrolyte (ionomer) having selective hydrogen ion permeability, wherein the amount of polymer electrolyte coating the catalyst supports is varied along the stacking direction of the catalyst supports, thereby increasing the voids between catalyst supports on the electrode side compared to the solid polymer electrolyte membrane side. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-88008 [Overview of the project] [Problems that the invention aims to solve]

[0004] The purpose of this disclosure is to provide a catalyst layer for electrochemical devices that exhibits excellent proton transport properties and is suitable for improving power generation efficiency. [Means for solving the problem]

[0005] The catalyst layer for electrochemical devices in this disclosure is A catalyst layer having a first main surface and a second main surface, The material comprises a porous conductive material having pores, catalyst particles disposed inside the pores of the conductive material, a first ionomer, and a second ionomer. The swelling rate of the first ionomer in water is greater than the swelling rate of the second ionomer in water. When the portion including the first main surface and located on the side of the first main surface is defined as the first portion, and the portion including the second main surface and located on the side of the second main surface is defined as the second portion, The ratio of the mass of the first ionomer contained in the first portion to the total mass of the resin components contained in the first portion is greater than the ratio of the mass of the second ionomer contained in the first portion to the total mass of the resin components contained in the first portion. The ratio of the mass of the second ionomer contained in the second portion to the total mass of the resin components contained in the second portion is greater than the ratio of the mass of the first ionomer contained in the second portion to the total mass of the resin components contained in the second portion.

[0006] In another aspect, the film electrode junction in this disclosure is A-scatter, Cathode and, An electrolyte membrane disposed between the anode and the cathode, Equipped with, The cathode includes the catalyst layer for the electrochemical device described herein.

[0007] In another respect, the electrochemical devices in this disclosure are The present invention comprises the film electrode assembly described above. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a catalyst layer for electrochemical devices that has excellent proton transport properties and is suitable for improving power generation efficiency. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic cross-sectional view showing an example of a catalyst layer in Embodiment 1. [Figure 2A] A schematic cross-sectional view showing an example of a conductive material supporting catalyst particles and a first ionomer that may be included in the first portion of the catalyst layer. [Figure 2B]Schematic cross-sectional view showing an example of a conductive material supporting catalyst particles and a second ionomer that may be included in a second portion of the catalyst layer [Figure 3] Flowchart showing an example of a method for manufacturing a catalyst layer in Embodiment 1 [Figure 4A] Schematic cross-sectional view of a membrane electrode assembly in Embodiment 2 [Figure 4B] Partial enlarged view of FIG. 4A [Figure 5] Schematic cross-sectional view of an electrochemical device in Embodiment 2

Mode for Carrying Out the Invention

[0010] (Findings and the like on which the present disclosure is based) For the purpose of improving the power generation efficiency of electrochemical devices such as fuel cells, the development of technologies for promoting the electrochemical reaction of the cathode catalyst layer has been studied. In order to promote the electrochemical reaction of the cathode catalyst layer, it is considered as one of the problems that reactants such as oxygen and protons (H + ) smoothly move inside the cathode catalyst layer and reach the catalyst. In order to solve such problems, for example, a catalyst layer in which the amount of the ionomer present on the electrolyte membrane side is made larger than the amount of the ionomer present on the gas diffusion layer side has been proposed (for example, Patent Document 1). In the catalyst layer described in Patent Document 1, in order to suppress the poisoning and deterioration of the catalyst by the ionomer, the catalyst particles are supported inside the pores of the porous conductive material as the catalyst carrier.

[0011] Under such circumstances, the inventors have obtained the finding that if the amount of the ionomer present on the electrolyte membrane side is made larger than the amount of the ionomer present on the gas diffusion layer side, the following problems occur. On the electrolyte membrane side, the pores of the conductive material are likely to be blocked by the ionomer, and the transport of protons to the catalyst present inside the pores is suppressed. When the transport of protons to the catalyst is suppressed, the utilization rate of the catalyst decreases, so the reaction overvoltage of the catalyst layer increases. On the other hand, on the gas diffusion layer side, since the amount of the ionomer is smaller than that on the electrolyte membrane side, it is difficult to improve the proton transport property. Therefore, the catalyst layer described in Patent Document 1 has room for reconsideration from the viewpoint of improving the proton transport property.

[0012] Therefore, the inventors focused on the swelling ratio of the ionomer in water. An ionomer with a small swelling ratio in water is less likely to block the pores of the conductive material and is less likely to inhibit the transport of protons to the catalyst present inside the pores. On the other hand, an ionomer with a large swelling ratio in water can increase the volume occupied in the catalyst layer, so the proton transport property can be improved. Based on these findings, the inventors have come to constitute the subject matter of the present disclosure.

[0013] The present disclosure provides a catalyst layer for an electrochemical device that is excellent in proton transport property and suitable for improving power generation efficiency.

[0014] Hereinafter, embodiments will be described in detail with reference to the drawings. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters or duplicate descriptions of substantially the same configurations may be omitted. This is to avoid making the following description overly redundant and to facilitate the understanding of those skilled in the art.

[0015] The accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0016] (Embodiment 1) Embodiment 1 will be described below with reference to Figures 1 to 2B.

[0017] [1-1. Structure] Figure 1 is a schematic cross-sectional view showing an example of a catalyst layer 100 for an electrochemical device in Embodiment 1. The catalyst layer 100 has a first main surface 101 and a second main surface 102 opposite to the first main surface 101. The first main surface 101 is the surface that should be positioned on the gas diffusion layer side in the electrochemical device. The second main surface 102 is the surface that should be positioned on the electrolyte membrane side in the electrochemical device. In this specification, "main surface" means the surface of a plate-like member such as the catalyst layer 100 that has the largest area. The direction from the first main surface 101 to the second main surface 102 is defined as the thickness direction T100 of the catalyst layer 100. Figure 1 is a cross-sectional view of the catalyst layer 100 parallel to the thickness direction T100.

[0018] The catalyst layer 100 includes a porous conductive material 11 having pores 11p, catalyst particles 12 disposed inside the pores 11p of the conductive material 11, a first ionomer 31, and a second ionomer 32. The swelling rate R of the first ionomer 31 in water is greater than the swelling rate R of the second ionomer 32 in water. In this embodiment, the swelling rate R of the ionsomers in water is a value obtained by the calculation method described below.

[0019] <Method for calculating the swelling coefficient R of ionomers in water> The volume of the dry ionomer after vacuum drying at 80°C for 120 minutes is measured. The measured value is the volume V1 (cm³) of the dry ionomer. 3 ) is considered as the volume. The volume of the ionomer in its hydrated state is measured after immersion in 80°C water for 16 hours. The measured value is considered as the volume of the ionomer in its hydrated state V2 (cm³). 3 ) is considered to be the swelling coefficient R of the ionomer in water is calculated by the following formula (1). Swelling rate R(%)=(V2 / V1)×100...(1)

[0020] As shown in Figure 1, in the catalyst layer 100, the portion including the first main surface 101 and located on the side of the first main surface 101 is defined as the first portion 101p. The portion including the second main surface 102 and located on the side of the second main surface 102 is defined as the second portion 102p. The mass of the first portion 101p and the mass of the second portion 102p may be the same. In this case, in the catalyst layer 100, the ratio C1 (wt%) of the mass of the first ionomer 31 contained in the first portion 101p to the total mass of the resin components contained in the first portion 101p is greater than the ratio C2 (wt%) of the mass of the second ionomer 32 contained in the first portion 101p to the total mass of the resin components contained in the first portion 101p. The ratio C4 (wt%) of the mass of the second ionomer 32 contained in the second portion 102p to the total mass of the resin components contained in the second portion 102p is greater than the ratio C3 (wt%) of the mass of the first ionomer 31 contained in the second portion 102p to the total mass of the resin components contained in the second portion 102p. However, in this embodiment, "total mass of the resin components contained in the first portion 101p" means the sum of the mass of the first ionomer 31 and the mass of the second ionomer 32 contained in the first portion 101p. "Total mass of the resin components contained in the second portion 102p" means the sum of the mass of the first ionomer 31 and the mass of the second ionomer 32 contained in the second portion 102p.

[0021] The catalyst layer 100 in this embodiment can improve proton transport. The second portion 102p contains more of the second ionomer 32, which has a smaller swelling rate R than the first ionomer 31. Therefore, on the electrolyte membrane side, the pores 11p of the conductive material 11 are less likely to be blocked by the first ionomer 31 or the second ionomer 32. This promotes the transport of protons to the catalyst particles 12 present inside the pores 11p of the conductive material 11. On the other hand, the first portion 101p contains more of the first ionomer 31, which has a larger swelling rate R than the second ionomer 32. Therefore, on the gas diffusion layer side, the volume of the first ionomer 31 can be increased, thereby improving proton transport. As a result, a catalyst layer 100 with excellent proton transport properties and suitable for improving power generation efficiency can be realized.

[0022] The mass ratio C1 (wt%) of the first ionomer 31 and the mass ratio C2 (wt%) of the second ionomer 32 contained in the first portion 101p are determined, for example, by fluorine-19 nuclear magnetic resonance (FNC) using a nuclear magnetic resonance spectrometer. 19 This can be determined by 1F-NMR measurement. As shown in the example in Figure 1, the first portion 101p (e.g., 50 mg) is scraped off from the catalyst layer 100 (e.g., 100 mg), and the resulting sample is dissolved in a non-deuterated solvent (NPA, 1-propanol) and water (H2O). 19 The F-NMR measurement is performed under conditions of a resonance frequency of 375 MHz and a measurement temperature of 23°C. From the obtained NMR spectrum, the integral values ​​of the peaks originating from the first ionomer 31 and the integral values ​​of the peaks originating from the second ionomer 32 are identified. Using the identified integral values, the mass percentage C1 (wt%) of the first ionomer 31 and the mass percentage C2 (wt%) of the second ionomer 32 contained in the first portion 101p can be determined. The mass percentage C4 (wt%) of the second ionomer 32 and the mass percentage C3 (wt%) of the first ionomer 31 contained in the second portion 102p can be determined in the same manner. The masses of the first portion 101p and the second portion 102p may be the same.

[0023] The ratio of C2 to C1 (C2 / C1) may be 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, and even 0.5 or less. The lower limit of the ratio of C2 to C1 may be 0 (zero) or 0.05.

[0024] The ratio of C3 to C4 (C3 / C4) may be 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, and even 0.5 or less. The lower limit of the ratio of C3 to C4 may be 0 (zero) or 0.05.

[0025] The swelling rate R of the first ionomer 31 in water may be greater than 180%. The first ionomer 31 whose swelling rate R satisfies the above numerical range is likely to increase the volume of the ionomer. The upper limit of the swelling rate R of the first ionomer 31 may be 210%, 205%, or even 200%. The lower limit of the swelling rate R of the first ionomer 31 may be 185% or 190%.

[0026] The swelling rate R of the second ionomer 32 with respect to water may be 180% or less. The second ionomer 32 whose swelling rate R satisfies the above numerical range is less likely to clog the pores 11p of the conductive material 11. The lower limit of the swelling rate R of the second ionomer 32 may be 130%, 135%, or even 140%. The upper limit of the swelling rate R of the second ionomer 32 may be 175%, 170%, or even 165%.

[0027] From another perspective, the amount U1 of the first ionomer 31 utilized in the pores of the first portion 101p of the catalyst layer 100 may be smaller than the amount U2 of the second ionomer 32 utilized in the pores of the second portion 102p of the catalyst layer 100. In this embodiment, the amount U of the ionomer utilized in the pores of a predetermined portion is a value obtained by the calculation method described below.

[0028] <Method for calculating the amount of ionomer utilized in the pores U> The amount of ionomer utilized within its pores U can be determined based on a membrane electrode assembly (MEA) fabricated using the ionomer in question. For example, the amount of first ionomer 31 utilized within its pores U1 in the first portion 101p can be determined as follows. First, a catalyst layer containing a conductive material 11 with catalyst particles 12 arranged inside pores 11p and the first ionomer 31 is fabricated based on the manufacturing method of the catalyst layer 100 described later, and this catalyst layer is used as the cathode catalyst layer to fabricate an MEA. The fabricated MEA is designated as the first sample. Under high humidity conditions of 100% RH relative humidity, the electrical double layer capacitance Cdl1 formed at the interface between the conductive material 11 and the first ionomer 31 in the first sample is measured. Next, under low humidity conditions of 20% RH relative humidity, the electrical double layer capacitance Cdl2 formed at the interface between the conductive material 11 and the first ionomer 31 in the first sample is measured. The value calculated by the following equation (2-1) can be considered as the amount of pore utilization U1 of the first ionomer 31 in the first portion 101p. Similarly, the amount of pore utilization U2 of the second ionomer 32 in the second portion 102p can be determined as follows. First, a catalyst layer containing a conductive material 11 with catalyst particles 12 arranged inside the pores 11p and a second ionomer 32 is prepared, and this catalyst layer is used as a cathode catalyst layer to prepare an MEA. The prepared MEA is designated as the second sample. Under high humidity conditions of 100% RH relative humidity, the electrical double layer capacitance Cdl3 formed at the interface between the conductive material 11 and the second ionomer 32 in the second sample is measured. Next, under low humidity conditions of 20% RH relative humidity, the electrical double layer capacitance Cdl4 formed at the interface between the conductive material 11 and the second ionomer 32 in the second sample is measured. The value calculated by the following formula (2-2) can be considered as the amount U2 of the second ionomer 32 utilized in the pores of the second portion 102p. Pore ​​utilization U1(F / g) = Cdl1 - Cdl2 ... (2-1) Pore ​​utilization U2(F / g) = Cdl3 - Cdl4 ... (2-2)

[0029] Under high humidity conditions, there is a large amount of water present in the catalyst layer 100, so the amount of water penetrating into the pores 11p of the conductive material 11 increases. Under low humidity conditions, there is a small amount of water present in the catalyst layer 100, so the amount of water penetrating into the pores 11p of the conductive material 11 decreases. Therefore, the amount of ionomer utilized in the pores U, which is calculated as the difference between the electrical double layer capacitance Cdl under high humidity conditions and the electrical double layer capacitance Cdl under low humidity conditions, can serve as an indicator of how much of the catalyst particles 12 placed inside the pores 11p of the conductive material 11 were utilized under high humidity conditions. According to the inventors' studies, the smaller the amount of ionomer utilized in the pores U, the larger the expansion coefficient R of the ionomer with respect to water tends to be.

[0030] When measuring the electrical double-layer capacitance Cdl by electrochemical impedance spectroscopy, for example, the HZ-7000 electrochemical measurement system manufactured by Hokuto Denko Co., Ltd. can be used as the measuring device. The measurement conditions shown in Table 1 can be adopted.

[0031] [Table 1]

[0032] The amount U1 of the first ionomer 31 available in the pores of the first portion 101p may be 60 F / g or less. The upper limit of the amount U1 available in the pores may be 55 F / g or 50 F / g. The lower limit of the amount U1 available in the pores may be 15 F / g or 20 F / g.

[0033] The amount of the second ionomer 32 available in the pores U2 in the second portion 102p may be 55 F / g or more. The lower limit of the amount pores U2 may be 60 F / g or more, or it may be more than 60 F / g. The upper limit of the amount of the amount of the amount of the amount of the amount of the amount of the amount of the amount of the amount of the amount of the amount of the second ionomer 32 in the pores may be 55 F / g or more.

[0034] In this embodiment, the catalyst layer 100 comprises a first layer 100a including a first portion 101p and a second layer 100b including a second portion 102p. The catalyst layer 100 having such a configuration is excellent in proton transport and is suitable for improving power generation efficiency.

[0035] In the catalyst layer 100, the first layer 100a and the second layer 100b are in electrical contact. A catalyst layer 100 having such a configuration is suitable because it has excellent proton transport properties and improves power generation efficiency.

[0036] In the example shown in Figure 1, the first layer 100a and the second layer 100b are continuous in the thickness direction T100. Thus, the first layer 100a and the second layer 100b may be continuous. In other words, there does not need to be any other layer between the first layer 100a and the second layer 100b.

[0037] The thickness of the first layer 100a may be equal to the thickness of the second layer 100b. With this configuration, it is easier to realize a catalyst layer 100 with an excellent balance between the amount of the first ionomer 31 and the amount of the second ionomer 32. As a result, it is easier to improve the proton transport performance of the catalyst layer 100.

[0038] The thickness of the first layer 100a is, for example, in the range of 5 μm to 15 μm. With this configuration, it is easy to improve the proton transport performance of the catalyst layer 100.

[0039] The thickness of the second layer 100b is, for example, in the range of 5 μm to 15 μm. With this configuration, it is easy to improve the proton transport performance of the catalyst layer 100.

[0040] The thickness of the catalyst layer 100 is, for example, in the range of 10 μm to 30 μm. The lower limit of the thickness of the catalyst layer 100 may be 12 μm or 15 μm. The upper limit of the thickness of the catalyst layer 100 may be 28 μm or 25 μm.

[0041] The thickness of the first layer 100a can be determined, for example, by the following method. First, a sample is prepared in which a cross-section of the catalyst layer 100 parallel to the thickness direction T100 is exposed. Multiple (e.g., 10) cross-sectional SEM images of the sample are obtained using a scanning electron microscope (SEM). The thickness of the first layer 100a is measured for each of the obtained SEM images. In this embodiment, the boundary between the first layer 100a and the second layer 100b can be recognized by using an SEM. The average of the measured values ​​is considered to be the thickness of the first layer 100a. The thickness of the second layer 100b can be determined in the same manner. The thickness of the catalyst layer 100 can be determined as the average of the values ​​measured for each of the obtained cross-sectional SEM images.

[0042] In the catalyst layer 100, the ratio C5 (wt%) of the mass of the first ionomer 31 contained in the first layer 100a to the total mass of the resin components contained in the first layer 100a may be greater than the ratio C6 (wt%) of the mass of the second ionomer 32 contained in the first layer 100a to the total mass of the resin components contained in the first layer 100a, and the ratio C8 (wt%) of the mass of the second ionomer 32 contained in the second layer 100b to the total mass of the resin components contained in the second layer 100b may be greater than the ratio C7 (wt%) of the mass of the first ionomer 31 contained in the second layer 100b to the total mass of the resin components contained in the second layer 100b. However, in this embodiment, "total mass of the resin components contained in the first layer 100a" means the sum of the mass of the first ionomer 31 and the mass of the second ionomer 32 contained in the first layer 100a. "Total mass of resin components contained in the second layer 100b" means the sum of the mass of the first ionomer 31 and the mass of the second ionomer 32 contained in the second layer 100b.

[0043] The mass ratios C5 (wt%) of the first ionomer 31 and C6 (wt%) of the second ionomer 32 contained in the first layer 100a, and the mass ratios C8 (wt%) of the second ionomer 32 and C7 (wt%) of the first ionomer 31 contained in the second layer 100b can be determined by the same method as described above for the mass ratios C1 (wt%) of the first ionomer 31 and C2 (wt%) of the second ionomer 32 contained in the first portion 101p.

[0044] The ratio of C6 to C5 (C6 / C5) may be 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, and even 0.5 or less. The lower limit of the ratio of C6 to C5 may be 0 (zero) or 0.05.

[0045] The ratio of C7 to C8 (C7 / C8) may be 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, and even 0.5 or less. The lower limit of the ratio of C7 to C8 may be 0 (zero) or 0.05.

[0046] Figure 2A is a schematic cross-sectional view showing an example of a conductive material 11 supporting catalyst particles 12 and a first ionomer 31 that may be included in the first portion 101p of the catalyst layer 100. Figure 2B is a schematic cross-sectional view showing an example of a conductive material 11 supporting catalyst particles 12 and a second ionomer 32 that may be included in the second portion 102p of the catalyst layer 100. An electrochemical reaction is promoted on the surface of the catalyst particles 12.

[0047] As shown in Figures 2A and 2B, in this embodiment, the conductive material 11 is a conductive porous material having pores 11p. The pores 11p open to the surface of the conductive material 11. In other words, the surface of the conductive material 11 has irregularities. The pores 11p may be interconnected or independent.

[0048] As shown in Figures 2A and 2B, in this embodiment, the catalyst particles 12 are arranged inside the pores 11p of the conductive material 11. Protons (H) are released to the catalyst particles 12 arranged inside the pores 11p via the first ionomer 31 or the second ionomer 32 attached to the surface of the conductive material 11. + ) can be reached. The swelling rate R of the second ionomer 32 is smaller than the swelling rate R of the first ionomer 31. Therefore, in the second portion 102p including the second main surface 102, the pores 11p of the conductive material 11 are less likely to be blocked by the ionomer. This promotes the transport of protons to the catalyst particles 12 present inside the pores 11p of the conductive material 11. As a result, the utilization rate of the catalyst particles 12 supported on the conductive material 11 can be improved.

[0049] The conductive material 11 may be porous conductive particles such as carbon particles. Typically, the conductive material 11 is mesoporous carbon particles. When the conductive material 11 is mesoporous carbon particles, its average particle size is, for example, 0.6 μm to 2.0 μm.

[0050] Examples of carbon particles include furnace black and acetylene black particles. The conductive material 11 may contain at least one selected from the group consisting of furnace black, acetylene black, and thermal black. Furnace black includes those using petroleum-based hydrocarbons or coal-based hydrocarbons as raw materials, and gas furnace black using natural gas as a raw material.

[0051] The catalyst particles 12 are not particularly limited as long as they are metal particles that have a reducing effect on oxygen-containing gases. From the viewpoint of improving the catalytic activity and heat resistance of the catalyst layer 100, the material of the catalyst particles 12 may be particles containing noble metals such as platinum and platinum alloys. Examples of platinum alloys include alloys of platinum and at least one selected from the group consisting of cobalt, nickel, ruthenium, and palladium. The catalyst particles 12 may also contain at least one selected from the group consisting of platinum, palladium, iridium, ruthenium, and rhodium.

[0052] The platinum content in the catalyst particles 12 may be 30 atomic% or more and 90 atomic% or less, and the content of other metals (e.g., cobalt) may be 10 atomic% or more and 70 atomic% or less.

[0053] The average particle diameter of the catalyst particles 12 is not particularly limited. From the viewpoint of catalyst utilization rate and durability, it is desirable that the average particle diameter of the catalyst particles 12 be between 1 nm and 30 nm. The average particle diameter can be calculated, for example, from a cross-sectional image of the catalyst layer 100 obtained using TEM or SEM. In the cross-sectional image, the equivalent diameter of any number (e.g., 10) of catalyst particles 12 is measured. The average of the equivalent diameters can be considered as the average particle diameter.

[0054] As shown in Figure 2A, the first ionomer 31 may be attached to the surface of the conductive material 11. As shown in Figure 2B, the second ionomer 32 may be attached to the surface of the conductive material 11. The first ionomer 31 may be present so as to cover the pores 11p of the conductive material 11. The second ionomer 32 may be present so as to cover the pores 11p of the conductive material 11.

[0055] As described above, in this embodiment, the swelling rate R of the first ionomer 31 in water is greater than the swelling rate R of the second ionomer 32 in water. The swelling rate of an ionomer in water can be adjusted by controlling the number of functional groups, the type of functional groups, the spacing of the side chains, the length of the main chain, the rigidity of the main chain, etc. For example, the more functional groups that have a high affinity for water there are, the greater the swelling rate of the ionomer in water tends to be. The narrower the spacing of the side chains, the easier it is for the molecular structure to incorporate water, so the swelling rate of the ionomer in water tends to be greater. The less rigid the main chain is, the more flexible the molecular structure is, and the easier it is for the molecular structure to incorporate water, so the swelling rate of the ionomer in water tends to be greater.

[0056] As the first ionomer 31 and the second ionomer 32, polymer electrolytes having ionic conductivity such as protons can be used. The first ionomer 31 and the second ionomer 32 link the catalyst particles 12 and the conductive material 11 in a state that allows for ionic conduction. As the first ionomer 31 and the second ionomer 32, for example, perfluorocarbon sulfonic acid-based polymer materials having sulfonic acid groups, hydrocarbon-based polymer materials, etc., can be used. Perfluorosulfonic acid resins may also be used as the first ionomer 31 and the second ionomer 32. Perfluorosulfonic acid resins exhibit excellent proton conductivity and remain stable even under the power generation environment of electrochemical devices. The first ionomer 31 and the second ionomer 32 typically contain perfluorocarbon sulfonic acid-based polymer electrolytes having sulfonic acid groups.

[0057] The second ionomer 32 has, for example, a cyclic structure. The second ionomer 32 may have a cyclic structure in at least one selected from the group consisting of the main chain and side chains. The second ionomer 32 having a cyclic structure in at least one selected from the group consisting of the main chain and side chains is permeable to gases such as oxygen, so for example, the gas diffusivity of the second layer 100b can be improved. The cyclic structure may be a 5-membered ring structure or a 6-membered ring structure. Whether or not the ionomer has a cyclic structure is determined by the fluorine-19 nuclear magnetic resonance (FCR) test described above. 19 This can be determined by using a combination of 1F-NMR (fluorescent-fluorescent) measurement and infrared absorption spectroscopy (IR).

[0058] The second ionomer 32 may be a high oxygen permeability ionomer (HOPI). In this specification, a high oxygen permeability ionomer is an ionomer whose oxygen permeability is improved by having a sterically hindrance cyclic structure in the main chain. High oxygen permeability ionomers can exhibit excellent oxygen permeability.

[0059] The second ionomer 32 may have a cyclic structure in its main chain. The second ionomer 32 having a cyclic structure in its main chain is more permeable to gases such as oxygen. As a result, for example, the gas diffusivity of the second layer 100b can be further improved.

[0060] The second ionomer 32 may have annular structures in both the main chain and the side chains. The second ionomer 32 having annular structures in both the main chain and the side chains is more permeable to gases such as oxygen. As a result, for example, the gas diffusivity of the second layer 100b can be further improved.

[0061] The second ionomer 32 may also be represented by the following formula (3), which includes multiple types of repeating units.

[0062] [ka]

[0063] In equation (3) above, m and n represent numbers greater than 0, independently of each other.

[0064] The first ionomer 31, for example, does not have a cyclic structure. Ionomers without a cyclic structure tend to penetrate the pores of conductive materials more easily than ionomers with a cyclic structure, although they have lower gas permeability. Therefore, if the first ionomer 31 does not have a cyclic structure, for example, it is easier to improve the proton conductivity to the catalyst particles 12 placed inside the pores 11p in the first layer 100a.

[0065] The first ionomer 31 may have a linear structure in its main chain and side chains. The first ionomer 31 having a linear structure in its main chain and side chains readily penetrates the pores 11p of the conductive material 11. As a result, the proton conductivity to the catalyst particles 12 placed inside the pores 11p can be improved.

[0066] The first ionomer 31 may also be represented by the following formula (4), which includes multiple types of repeating units.

[0067] [ka]

[0068] In equation (4) above, x and y represent numbers greater than 0, independently of each other.

[0069] Formula (4) above may also be a random copolymer.

[0070] The first ionomer 31 may have a molecular structure in which 2 to 20 hydrophobic parts and 2 to 10 hydrophilic parts are randomly bonded together.

[0071] The second ionomer 32 does not have to have a ring structure. As a second ionomer 32 that does not have a ring structure, the ones listed above for the first ionomer 31 can be used.

[0072] The first ionomer 31 may have a ring structure. As the first ionomer 31 having a ring structure, those listed above for the second ionomer 32 can be used.

[0073] Although not shown in the diagram, the catalyst layer 100 may further comprise a fibrous conductive material. A first ionomer 31 or a second ionomer 32 may be attached to the surface of the fibrous conductive material. With such a configuration, for example, in the first layer 100a, the first ionomer 31 attached to the surface of the conductive material 11 and the first ionomer 31 attached to the surface of the fibrous conductive material are more likely to bond. For example, in the second layer 100b, the second ionomer 32 attached to the surface of the conductive material 11 and the second ionomer 32 attached to the surface of the fibrous conductive material are more likely to bond. Therefore, the proton conductivity in the catalyst layer 100 can be further improved.

[0074] Next, the manufacturing method for the catalyst layer 100 described above will be explained.

[0075] Figure 3 is a flowchart showing an example of a method for manufacturing the catalyst layer 100. As shown in Figure 3, the method for manufacturing the catalyst layer 100 includes, for example, steps S1 to S7. Step S1 is a step of preparing a first solution by dispersing a conductive material 11 having catalyst particles 12 arranged inside pores 11p and a first ionomer 31 in a first solvent. Step S2 is a step of preparing a second solution by dispersing a conductive material 11 having catalyst particles 12 arranged inside pores 11p and a second ionomer 32 in a second solvent. Step S3 is a step of coating the first solution onto a gas diffusion layer to form a first coating film. Step S4 is a step of removing the first solvent from the first coating film to produce a first layer 100a. Step S5 is a step of coating the second solution onto an electrolyte membrane to form a second coating film. Step S6 is a step of removing the second solvent from the second coating film to produce a second layer 100b. Step S7 is a step of joining the first layer 100a and the second layer 100b. The swelling rate R of the first ionomer 31 with respect to water is greater than the swelling rate R of the second ionomer 32 with respect to water. According to this manufacturing method, the first layer 100a containing the first ionomer 31 with a large swelling rate R can be placed on the gas diffusion layer side, and the second layer 100b containing the second ionomer 32 with a small swelling rate R can be placed on the electrolyte membrane side. As a result, a catalyst layer 100 with excellent proton transport properties and suitable for improving power generation efficiency can be manufactured.

[0076] The manufacturing method may include, before step S1, arranging catalyst particles 12 inside the pores 11p of the conductive material 11 (step S0).

[0077] In step S0, the method for arranging the catalyst particles 12 inside the pores 11p of the conductive material 11 is not particularly limited. For example, after dispersing the conductive material 11 in a solvent, a metal precursor solution such as a platinum precursor is added, stirred to prepare a mixed solution, and the resulting mixed solution is filtered and dried. This allows the catalyst particles 12 to be arranged inside the pores 11p of the conductive material 11.

[0078] Step S0 may include producing a conductive material 11 having pores 11p. For example, a porous conductive material 11 can be produced by heat-treating the raw material composite, then washing it with dilute sulfuric acid and drying it.

[0079] In step S1, the conductive material 11, in which catalyst particles 12 are arranged inside the pores 11p, and the first ionomer 31 are dispersed in a first solvent to prepare the first solution. For example, an aqueous ethanol solution can be used as the first solvent.

[0080] For example, by introducing a conductive material 11 in which catalyst particles 12 are arranged inside the pores 11p into a first solvent, a first catalyst solution can be obtained. Then, by adding the first ionomer 31 to the first catalyst solution and stirring, a first solution can be obtained.

[0081] In step S2, the conductive material 11, in which catalyst particles 12 are arranged inside the pores 11p, and the second ionomer 32 are dispersed in a second solvent to prepare a second solution. For example, an aqueous ethanol solution can be used as the second solvent.

[0082] For example, a second catalyst solution can be obtained by introducing a conductive material 11 in which catalyst particles 12 are arranged inside the pores 11p into a second solvent, and then adding a second ionomer 32 to the second catalyst solution and stirring to obtain a second solution.

[0083] In step S3, the first solution is applied to the gas diffusion layer to form the first coating film. This allows for the easy formation of the first layer 100a on the gas diffusion layer.

[0084] In step S4, the first solvent is removed from the first coating film to produce the first layer 100a. The method for removing the solvent from the coating film is not particularly limited. For example, the solvent may be removed from the coating film by air drying or by heating. After step S4, the first layer 100a is formed on the gas diffusion layer.

[0085] In step S5, the second solution is applied to the electrolyte membrane to form a second coating film. This allows for the easy formation of a second layer 100b on the electrolyte membrane.

[0086] In step S6, the second solvent is removed from the second coated film to create the second layer 100b. After step S6, the second layer 100b is formed on the electrolyte film.

[0087] In step S7, the first layer 100a and the second layer 100b are joined together. This gives rise to the catalyst layer 100.

[0088] However, the method for manufacturing the catalyst layer 100 is not limited to the example described above. The method for manufacturing the catalyst layer 100 may, for example, include steps ST3 to ST6 instead of steps S3 to S7 described above. Step ST3 is a step of applying the second solution to the electrolyte membrane to form a second coating film. Step ST4 is a step of removing the second solvent from the second coating film to produce a second layer 100b. Step ST5 is a step of applying the first solution to the second layer 100b to form a first coating film. Step ST6 is a step of removing the first solvent from the first coating film to produce a first layer 100a. By such a manufacturing method, a catalyst layer 100 can be manufactured in which the first layer 100a, which is to be placed on the gas diffusion layer side, contains a first ionomer 31 with a large swelling rate R, and the second layer 100b, which is to be placed on the electrolyte membrane side, contains a second ionomer 32 with a small swelling rate R.

[0089] [1-2. Operation] The operation and function of the catalyst layer 100 configured as described above will be explained in the electrochemical device 300 of Embodiment 2, which will be described later.

[0090] (Embodiment 2) Embodiment 2 will be described below with reference to Figures 4A to 5.

[0091] [2-1. Structure] Figure 4A is a schematic cross-sectional view of the membrane electrode assembly 200 in Embodiment 2. Figure 4B is a partially enlarged view of part IIIB in Figure 4A. Figure 5 is a schematic cross-sectional view of the electrochemical device 300 in Embodiment 2. The electrochemical device 300 comprises the membrane electrode assembly 200, an anode separator 301, and a cathode separator 302. The membrane electrode assembly 200 is positioned between the anode separator 301 and the cathode separator 302.

[0092] In this embodiment, the electrochemical device 300 may be used in a fuel cell. In this way, a fuel cell with high power generation performance and high efficiency can be obtained.

[0093] In the example shown in Figure 5, the electrochemical device 300 is a polymer electrolyte fuel cell (PEFC) that generates electricity by receiving hydrogen-containing gas G1 as the anode gas and oxygen-containing gas G3 as the cathode gas. In addition to being a fuel cell, the electrochemical device 300 may also be used as other electrochemical devices such as a hydrogen purification device for purifying hydrogen or a water electrolysis device for electrolyzing water.

[0094] As shown in Figure 4A, the membrane electrode assembly 200 has an anode 202, an electrolyte membrane 201, and a cathode 203. The electrolyte membrane 201 is positioned between the anode 202 and the cathode 203. The anode 202 is bonded to one side of the electrolyte membrane 201. The cathode 203 is bonded to the other side of the electrolyte membrane 201.

[0095] Anode 202 has an anode catalyst layer 204 and an anode gas diffusion layer 205. The anode catalyst layer 204 is positioned between the electrolyte membrane 201 and the anode gas diffusion layer 205. Cathode 203 has a cathode catalyst layer 206 and a cathode gas diffusion layer 207. The cathode catalyst layer 206 is positioned between the electrolyte membrane 201 and the cathode gas diffusion layer 207.

[0096] The electrolyte membrane 201 facilitates proton conduction between the anode catalyst layer 204 and the cathode catalyst layer 206. The electrolyte membrane 201 is made of a polymer material having proton conductivity and gas barrier properties. Typically, the electrolyte membrane 201 is a perfluorocarbon sulfonic acid-based or hydrocarbon-based polymer electrolyte membrane having sulfonic acid groups. The electrolyte membrane 201 may also be a perfluorosulfonic acid-based polymer electrolyte membrane. Perfluorosulfonic acid-based polymer electrolyte membranes exhibit excellent proton conductivity and remain stable even under the power generation environment of the electrochemical device 300.

[0097] The electrolyte membrane 201 has a surface in contact with the anode catalyst layer 204 and a surface in contact with the cathode catalyst layer 206. These surfaces are flat. When the surface of the electrolyte membrane 201 is flat, drainage on the surface of the electrolyte membrane 201 is good. "Flat surface" means a surface that has not been processed to create irregularities.

[0098] The anode catalyst layer 204 has the function of promoting an electrochemical reaction that dissociates hydrogen into protons. The anode catalyst layer 204 includes a conductive material and catalyst particles supported on the conductive material. The anode catalyst layer 204 may further include an ionomer.

[0099] The membrane electrode assembly 200 may include the catalyst layer 100 described in Embodiment 1 as the anode catalyst layer 204.

[0100] The anode gas diffusion layer 205 has the function of supplying hydrogen-containing gas G1 to the anode catalyst layer 204 and receiving electrons from the anode catalyst layer 204. The anode gas diffusion layer 205 is composed of a material that is gas permeable, water-repellent, and conductive. The anode gas diffusion layer 205 has, for example, a conductive porous material as its main material. Examples of porous materials include carbon fiber aggregates such as carbon paper.

[0101] The cathode catalyst layer 206 has the function of promoting an electrochemical reaction that produces water from protons and oxygen. The cathode catalyst layer 206 includes a conductive material and catalyst particles supported on the conductive material. The cathode catalyst layer 206 further includes an ionomer.

[0102] In this embodiment, the cathode 203 includes the catalyst layer 100 described in Embodiment 1. That is, the membrane electrode assembly 200 includes the catalyst layer 100 described in Embodiment 1 as the cathode catalyst layer 206. Therefore, the cathode catalyst layer 206 includes a first ionomer 31 and a second ionomer 32 having a smaller swelling rate R in water than the first ionomer 31. Figure 4B shows an example where the membrane electrode assembly 200 includes the catalyst layer 100 as the cathode catalyst layer 206. As shown in Figure 4B, the first main surface 101 of the cathode catalyst layer 206 is in contact with the cathode gas diffusion layer 207. The second main surface 102 of the cathode catalyst layer 206 is in contact with the electrolyte membrane 201. With this configuration, protons necessary for the power generation reaction can be smoothly transported in the cathode catalyst layer 206. As a result, the electrochemical reaction of the cathode catalyst layer 206 can be promoted. This makes it possible to improve the power generation efficiency of the electrochemical device 300 using the membrane electrode assembly 200.

[0103] The cathode gas diffusion layer 207 has the function of supplying oxygen-containing gas to the cathode catalyst layer 206 and transferring electrons to the cathode catalyst layer 206. The cathode gas diffusion layer 207 is composed of a material that is gas permeable, water-repellent, and conductive. The cathode gas diffusion layer 207 mainly consists of a conductive porous material, for example. Examples of porous materials include carbon fiber aggregates such as carbon paper.

[0104] The anode catalyst layer 204 may have the same structure as the cathode catalyst layer 206, or it may have a different structure.

[0105] As shown in Figure 5, the anode separator 301 has an anode gas inlet 303, an anode gas outlet 304, and an anode gas channel 301g. The anode gas channel 301g is a groove-shaped gas channel that guides hydrogen-containing gas G1 to the anode 202. The anode gas inlet 303 is provided at the upstream end of the anode gas channel 301g. The anode gas outlet 304 is provided at the downstream end of the anode gas channel 301g. Hydrogen-containing gas G1 is introduced into the anode gas channel 301g from the outside through the anode gas inlet 303. Unreacted hydrogen-containing gas G2 is discharged to the outside from the anode gas channel 301g through the anode gas outlet 304. The direction of anode gas flow in the anode separator 301 is parallel to the main surface of the anode separator 301.

[0106] The cathode separator 302 has a cathode gas inlet 305, a cathode gas outlet 306, and a cathode gas flow path 302g. The cathode gas flow path 302g is a groove-shaped gas flow path that guides oxygen-containing gas G3 to the cathode 203. The cathode gas inlet 305 is provided at the upstream end of the cathode gas flow path 302g. The cathode gas outlet 306 is provided at the downstream end of the cathode gas flow path 302g. Oxygen-containing gas G3 is introduced into the cathode gas flow path 302g from the outside through the cathode gas inlet 305. Unreacted oxygen-containing gas G4 is discharged from the cathode gas flow path 302g to the outside through the cathode gas outlet 306. The direction of cathode gas flow in the cathode separator 302 is parallel to the main surface of the cathode separator 302.

[0107] The shapes of the anode gas channel 301g and the cathode gas channel 302g are not particularly limited. The anode gas channel 301g and the cathode gas channel 302g may each have a serpentine shape. A serpentine shape is the shape of a channel in which one or more channels meander within a plane. If the anode gas channel 301g and the cathode gas channel 302g have the above shapes, gas can be supplied to the entire catalyst layers 204 and 206 at a constant flow rate. This makes it easier for the gas to reach all of the catalyst particles.

[0108] The anode separator 301 and the cathode separator 302 are made of a conductive material. The anode separator 301 and the cathode separator 302 may each be made of a conductive material such as carbon or metal. In order to prevent corrosion, the anode separator 301 and the cathode separator 302 may be provided with a corrosion-resistant coating such as resin or plating.

[0109] [2-2. Operation] Regarding the electrochemical device 300 configured as described above, its operation and action will be described below using FIG. 5.

[0110] A hydrogen-containing gas G1 is supplied from the anode gas inlet 303 to the anode gas flow path 301g of the anode separator 301. The hydrogen-containing gas G1 is a humidified gas containing hydrogen. The humidified gas containing hydrogen may be, for example, humidified hydrogen gas. Thereby, the hydrogen-containing gas G1 is supplied to the anode catalyst layer 204 through the anode gas diffusion layer 205. An oxygen-containing gas G3 is supplied from the cathode gas inlet 305 to the cathode gas flow path 302g of the cathode separator 302. The oxygen-containing gas G3 is a humidified gas containing oxygen. The humidified gas containing oxygen may be, for example, humidified air. Thereby, the oxygen-containing gas G3 is supplied to the cathode catalyst layer 206 through the cathode gas diffusion layer 207. It becomes possible to draw a current between the anode catalyst layer 204 supplied with the hydrogen-containing gas G1 and the cathode catalyst layer 206 supplied with the oxygen-containing gas G3.

[0111] In the anode catalyst layer 204 supplied with the hydrogen-containing gas G1, hydrogen (H2) becomes a proton (H + ) and an electron (e -An oxidation reaction occurs in which the protons dissociate into protons and electrons. The protons move through the electrolyte membrane 201 to the cathode catalyst layer 206. The electrons dissociated in the anode catalyst layer 204 move from the anode 202 to the cathode 203 through the external circuit 401 equipped with a load 402, and reach the cathode catalyst layer 206. In the cathode catalyst layer 206, a reduction reaction occurs in which water (H2O) is produced by an electrochemical reaction of protons, oxygen (O2), and electrons, as shown in the following equation (II). The protons used in this reduction reaction are those that dissociated in the oxidation reaction in the anode catalyst layer 204 shown in the following equation (I), and moved through the electrolyte membrane 201 to the cathode catalyst layer 206.

[0112] H2→2H + +2e - (I) 4H + +O2+4e - →2H2O (II)

[0113] In the electrochemical device 300, protons necessary for the power generation reaction can be smoothly transported in the cathode catalyst layer 206. As a result, the electrochemical reaction in the cathode catalyst layer 206 can be accelerated.

[0114] (Other embodiments) As described above, Embodiments 1 and 2 have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited thereto and can be applied to embodiments that have been modified, added to, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in the above embodiments and modifications.

[0115] The embodiments described above are for illustrative purposes only and may be modified, replaced, added, or omitted within the scope of the claims or equivalents.

[0116] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0117] (Technology 1) A catalyst layer having a first main surface and a second main surface, The material comprises a porous conductive material having pores, catalyst particles disposed inside the pores of the conductive material, a first ionomer, and a second ionomer. The swelling rate of the first ionomer in water is greater than the swelling rate of the second ionomer in water. When the portion including the first main surface and located on the side of the first main surface is defined as the first portion, and the portion including the second main surface and located on the side of the second main surface is defined as the second portion, The ratio of the mass of the first ionomer contained in the first portion to the total mass of the resin components contained in the first portion is greater than the ratio of the mass of the second ionomer contained in the first portion to the total mass of the resin components contained in the first portion. The ratio of the mass of the second ionomer contained in the second portion to the total mass of the resin components contained in the second portion is greater than the ratio of the mass of the first ionomer contained in the second portion to the total mass of the resin components contained in the second portion. Catalyst layer for electrochemical devices.

[0118] According to the catalyst layer for electrochemical devices of Technology 1, it is possible to realize a catalyst layer that has excellent proton transport properties and is suitable for improving power generation efficiency.

[0119] (Technology 2) A catalyst layer for an electrochemical device according to Art 1, comprising a first layer including the first portion and a second layer including the second portion. A catalyst layer having such a configuration is excellent in proton transport and is suitable for improving power generation efficiency.

[0120] (Technology 3) A catalyst layer for an electrochemical device according to Technology 2, wherein the thickness of the first layer is equal to the thickness of the second layer. With such a configuration, a catalyst layer with an excellent balance between the amount of the first ionomer and the amount of the second ionomer is easily realized. As a result, the proton transport performance of the catalyst layer is easily improved.

[0121] (Technology 4) A catalyst layer for an electrochemical device according to technology 2 or 3, wherein the first layer and the second layer are in electrical contact. A catalyst layer having such a configuration is suitable because it has excellent proton transport properties and improves power generation efficiency.

[0122] (Technology 5) A catalyst layer for an electrochemical device according to any one of the technologies 1 to 4, wherein the swelling rate of the second ionomer in water is 180% or less. The second ionomer having a swelling rate within the above numerical range is less likely to clog the pores of the conductive material.

[0123] (Technology 6) The second ionomer is a catalyst layer for an electrochemical device according to any one of the Art 1 to 5, having a cyclic structure. With such a configuration, for example, the gas diffusivity of the second layer can be improved.

[0124] (Technology 7) The catalyst layer for an electrochemical device according to any one of the techniques 1 to 6, wherein the first main surface is the surface to be positioned on the gas diffusion layer side in the electrochemical device, and the second main surface is the surface to be positioned on the electrolyte membrane side in the electrochemical device. With such a configuration, a catalyst layer with excellent proton transport properties and suitable for improving power generation efficiency can be realized.

[0125] (Technology 8) A-scatter, Cathode and, An electrolyte membrane disposed between the anode and the cathode, Equipped with, The cathode includes a catalyst layer for an electrochemical device as described in any one of the Art 1 to 6. Membrane electrode assembly.

[0126] According to the membrane electrode assembly of Technology 8, the power generation efficiency of electrochemical devices using the membrane electrode assembly can be improved.

[0127] (Technology 9) The membrane electrode assembly described in Technical 8 is provided, Electrochemical devices.

[0128] According to the electrochemical device of Technology 9, it is possible to realize an electrochemical device with high power generation performance and high efficiency. [Industrial applicability]

[0129] This disclosure is useful for electrochemical devices such as fuel cells, hydrogen purification devices, and water electrolysis devices. [Explanation of Symbols]

[0130] 100 Catalyst layer for electrochemical devices 101 First main surface 102 Second main surface Page 101, Part 1 Page 102, Part 2 100a First layer 100b Second layer 11. Conductive materials 11p pores 12 catalyst particles 31. First Ionomer 32 Second Ionomer T100 Thickness direction 200 Membrane electrode assembly 201 Electrolyte membrane 202 Anodes 203 Cathode 204 Anode catalyst layer 205 Anode gas diffusion layer 206 Cathode catalyst layer 207 Cathode gas diffusion layer 300 Electrochemical Devices 301 Anode Separator 301g Anode gas flow path 302 Cathode Separator 302g Cathode gas flow path 303 Anode gas inlet 304 Anode Gas Outlet 305 Cathode Gas Inlet 306 Cathode Gas Outlet 401 External circuit 402 load

Claims

1. A catalyst layer having a first main surface and a second main surface, The material comprises a porous conductive material having pores, catalyst particles disposed inside the pores of the conductive material, a first ionomer, and a second ionomer. The swelling rate of the first ionomer in water is greater than the swelling rate of the second ionomer in water. When the portion including the first main surface and located on the side of the first main surface is defined as the first portion, and the portion including the second main surface and located on the side of the second main surface is defined as the second portion, The ratio of the mass of the first ionomer contained in the first portion to the total mass of the resin components contained in the first portion is greater than the ratio of the mass of the second ionomer contained in the first portion to the total mass of the resin components contained in the first portion. The ratio of the mass of the second ionomer contained in the second portion to the total mass of the resin components contained in the second portion is greater than the ratio of the mass of the first ionomer contained in the second portion to the total mass of the resin components contained in the second portion. Catalyst layer for electrochemical devices.

2. A first layer comprising the first portion and a second layer comprising the second portion, A catalyst layer for an electrochemical device according to claim 1.

3. The thickness of the first layer is equal to the thickness of the second layer. A catalyst layer for an electrochemical device according to claim 2.

4. The first layer and the second layer are in electrical contact. A catalyst layer for an electrochemical device according to claim 2.

5. The swelling rate of the second ionomer in water is 180% or less. A catalyst layer for an electrochemical device according to claim 1.

6. The second ionomer has a cyclic structure, A catalyst layer for an electrochemical device according to claim 1.

7. The first main surface is the surface that should be positioned on the gas diffusion layer side in the electrochemical device, and the second main surface is the surface that should be positioned on the electrolyte membrane side in the electrochemical device. A catalyst layer for an electrochemical device according to claim 1.

8. A-scatter, Cathode and, An electrolyte membrane disposed between the anode and the cathode, Equipped with, The cathode includes a catalyst layer for an electrochemical device according to any one of claims 1 to 7. Membrane electrode assembly.

9. A membrane electrode assembly comprising the membrane electrode assembly described in claim 8, Electrochemical devices.

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