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

Abstract

To provide a catalyst layer for electrochemical devices suitable for suppressing reduction of efficiency of an electrochemical device such as a fuel cell.SOLUTION: A catalyst layer 100 for electrochemical devices comprises a first layer 10, which is positioned on the side of a first principal surface 101, and a second layer 20 which is positioned on the side of a second principal surface 102. The first layer 10 includes a plurality of first conductive columnar bodies 11 extending in a thickness direction T of the catalyst layer 100 and first catalyst particles 12 carried by the plurality of first conductive columnar bodies 11. The second layer 20 includes a plurality of second conductive columnar bodies 13 extending in a direction other than the thickness direction T and second catalyst particles 14 carried by the plurality of second conductive columnar bodies 13.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

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

[0002] Patent Document 1 describes a method for manufacturing a membrane electrode assembly for a fuel cell, in which a catalytic electrode is transferred to at least one surface of an electrolyte membrane. The catalytic electrode includes a plurality of carbon nanotubes grown perpendicular to the surface of a substrate and a catalytic metal supported on the carbon nanotubes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5417038 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, it is desirable to suppress the decrease in efficiency of electrochemical devices such as fuel cells.

[0005] An object of the present disclosure is to provide a catalyst layer for an electrochemical device, a membrane electrode assembly, and an electrochemical device that are suitable for suppressing a decrease in the efficiency of an electrochemical device such as a fuel cell. [Means for solving the problem]

[0006] The catalyst layer for an electrochemical device according to the present disclosure comprises: A catalyst layer comprising a first layer located on a first main surface side and a second layer located on a second main surface side, the first layer includes a plurality of first conductive columns extending in a thickness direction of the catalyst layer and first catalyst particles supported on the plurality of first conductive columns; The second layer includes a plurality of second conductive columns extending in a direction other than the thickness direction, and second catalyst particles supported on the plurality of second conductive columns.

[0007] In another aspect, the membrane electrode assembly of the present disclosure comprises: an anode; a cathode; an electrolyte membrane disposed between the anode and the cathode; Equipped with at least one selected from the group consisting of the anode and the cathode includes the catalyst layer for an electrochemical device according to the present disclosure; In the at least one selected from the group consisting of the anode and the cathode, the second main surface of the catalyst layer for an electrochemical device is in contact with the electrolyte membrane.

[0008] In yet another aspect, the electrochemical device of the present disclosure comprises: The device includes the membrane electrode assembly of the present disclosure. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to suppress a decrease in the efficiency of an electrochemical device such as a fuel cell. [Brief explanation of the drawings]

[0010] [Figure 1A] Schematic cross-sectional view of a catalyst layer in the first embodiment. [Figure 1B] Enlarged view of part of Figure 1A [Figure 2] Schematic cross-sectional view of a catalyst layer in Modification 1 [Figure 3] Schematic cross-sectional view of a catalyst layer in Modification 2 [Figure 4] Schematic cross-sectional view of a catalyst layer in Modification 3 [Figure 5A] Schematic cross-sectional view of a membrane electrode assembly in embodiment 2. [Figure 5B] Enlarged view of part of Figure 5A [Figure 6]Schematic cross-sectional view of an electrochemical device according to a second embodiment.

[0011] (Findings that formed the basis of this disclosure) To improve the efficiency of fuel cells, the development of technologies for promoting electrochemical reactions in the cathode catalyst layer has been investigated. To promote the electrochemical reactions in the cathode catalyst layer, it is necessary to smoothly supply reactants such as oxygen to the cathode catalyst layer, smoothly discharge water, which is a product, from the cathode catalyst layer, and increase the reaction sites in the cathode catalyst layer. To address these issues, a catalyst layer has been proposed in which conductive columns such as carbon nanotubes carrying catalyst particles are aligned in a direction substantially perpendicular to the surface of the electrolyte membrane. A membrane electrode assembly including such a catalyst layer is manufactured, for example, by transferring a catalyst layer including a plurality of conductive columns grown substantially perpendicular to the surface of a substrate onto the electrolyte membrane (see, for example, Patent Document 1).

[0012] When a catalyst layer including a plurality of conductive pillars grown perpendicularly to the surface of a substrate is transferred onto an electrolyte membrane, the ends of the conductive pillars may pierce the electrolyte membrane. When the ends of the conductive pillars pierce the electrolyte membrane, defects such as pinholes and tears may occur in the electrolyte membrane. Such electrolyte membrane defects can cause cross-leakage, short-circuiting between the cathode and anode, and other problems in electrochemical devices such as fuel cells, thereby reducing the efficiency of the electrochemical device.

[0013] Under these circumstances, the inventors focused on the structure of the catalyst layer and came up with the subject matter of the present disclosure in order to prevent the ends of the conductive pillars from piercing the electrolyte membrane when they are transferred to the electrolyte membrane.

[0014] The present disclosure provides a catalyst layer for an electrochemical device, a membrane electrode assembly, and an electrochemical device that are suitable for suppressing a decrease in the efficiency of an electrochemical device such as a fuel cell.

[0015] Hereinafter, embodiments will be described in detail with reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

[0016] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0017] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to FIGS. 1A to 2. FIG.

[0018] [1-1.Configuration] FIG. 1A is a schematic cross-sectional view of a catalyst layer 100 for an electrochemical device according to a first embodiment. The catalyst layer 100 has a first main surface 101 and a second main surface 102 opposite the first main surface 101. In this specification, the term "main surface" refers to the surface of the catalyst layer 100 having the largest area. The direction from the first main surface 101 to the second main surface 102 is defined as the thickness direction T of the catalyst layer 100. FIG. 1A is a cross-sectional view of the catalyst layer 100 parallel to the thickness direction T. The catalyst layer 100 includes a first layer 10 located on the first main surface 101 side and a second layer 20 located on the second main surface 102 side. The first layer 10 includes a plurality of first conductive columns 11 extending in the thickness direction T and first catalyst particles 12 supported by the plurality of first conductive columns 11. The second layer 20 includes a plurality of second conductive columns 13 extending in a direction other than the thickness direction T, and second catalyst particles 14 supported on the plurality of second conductive columns 13.

[0019] In the catalyst layer 100, the second conductive columns 13 extend in a direction other than the thickness direction T in the second layer 20 located on the second main surface 102 side. This prevents the ends of the second conductive columns 13 from piercing the electrolyte membrane when the catalyst layer 100 is transferred to the electrolyte membrane so that the second main surface 102 faces the electrolyte membrane. This prevents defects such as pinholes and tears from occurring in the electrolyte membrane, making cross leaks and short circuits between the cathode and anode less likely to occur in electrochemical devices. Therefore, the catalyst layer 100 is suitable for preventing a decrease in the efficiency of electrochemical devices.

[0020] As shown in FIG. 1A, in the catalyst layer 100, the first main surface 101 is formed by a plurality of first conductive columns 11, and the second main surface 102 is formed by a plurality of second conductive columns 13.

[0021] In the catalyst layer 100, the first layer 10 and the second layer 20 are in electrical contact. Such a structure makes it easier to achieve the above-mentioned effect. That is, when the catalyst layer 100 is transferred onto the electrolyte membrane so that the second main surface 102 faces the electrolyte membrane, it is easier to prevent the ends of the multiple second conductive columns 13 from piercing the electrolyte membrane.

[0022] As shown in Figure 1A, the first layer 10 and the second layer 20 may be continuous, i.e., there may be no other layers between the first layer 10 and the second layer 20.

[0023] The second conductive columns 13 in the second layer 20 may be continuous or discontinuous with the first conductive columns 11 in the first layer 10. The second conductive columns 13 may include a portion that is continuous with the first conductive columns 11 and a portion that is discontinuous with the first conductive columns 11.

[0024] 1A, in a cross section of the catalyst layer 100 parallel to the thickness direction T, the smallest angle between the thickness direction T and the outer surface 11s of the end 11e of each first conductive columnar member 11 is defined as angle α1, within a range of 0° to 90°. In this specification, "multiple first conductive columns 11 extending in the thickness direction T" means that the angle α1 satisfies 0°≦α1<45°. In this specification, the surface of each first conductive columnar member 11 extending in the longitudinal direction is defined as the outer surface 11s of the first conductive columnar member 11, and the surfaces located at both ends of the first conductive columnar member 11 are defined as the end faces 11d of the first conductive columnar member 11.

[0025] The angle α1 can be determined, for example, by the following method. First, a sample is prepared by exposing a cross section of the catalyst layer 100 parallel to the thickness direction T. A cross-sectional image of the sample is obtained using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). In the obtained cross-sectional image, the smallest angle between the thickness direction T and the outer surface 11s of the end 11e of an arbitrary number (e.g., 100) of first conductive columns 11 is measured within the range of 0° to 90°. The average of the measured values ​​can be regarded as the angle α1.

[0026] The angle α1 may satisfy the relationship 0°≦α1≦30°, 0°≦α1≦20°, or 0°≦α1≦10°.

[0027] The multiple first conductive columns 11 may be oriented in a direction perpendicular to the first main surface 101. In this specification, "perpendicular" means that the angle α1 satisfies 0°≦α1≦10°. That is, the angle α1 may satisfy 0°≦α1≦10°.

[0028] As described above, in the second layer 20, the multiple second conductive columns 13 extend in a direction other than the thickness direction T. In this specification, "the multiple second conductive columns 13 extend in a direction other than the thickness direction T" includes, for example, the multiple second conductive columns 13 extending in random directions in the second layer 20.

[0029] In the example shown in FIG. 1A , the second conductive columns 13 extend in random directions in the second layer 20. In this specification, "the second conductive columns 13 extend in random directions" means that the second conductive columns 13 do not have a specific orientation and each of the second conductive columns 13 extends irregularly in various directions. This structure can reduce the number of ends of the second conductive columns 13 exposed to the second main surface 102. Therefore, when the catalyst layer 100 is transferred to the electrolyte membrane so that the electrolyte membrane faces the second main surface 102, the ends of the second conductive columns 13 are more likely to pierce the electrolyte membrane.

[0030] As long as they extend in a direction other than the thickness direction T, the structure of the plurality of second conductive columns 13 in the second layer 20 is not limited to the example shown in FIG. 1A.

[0031] Fig. 2 is a schematic cross-sectional view of a catalyst layer 110 in Modification 1. The catalyst layer 110 shown in Fig. 2 has the same structure as the catalyst layer 100 shown in Fig. 1A, except for the structure of the second layer 20. In Modification 1, elements common to the above-described catalyst layer 100 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0032] As shown in FIG. 2 , in a cross section of the catalyst layer 110 parallel to the thickness direction T, the smallest angle between the thickness direction T and the outer surface 13s of the end 13e of each second conductive columnar member 13, within a range of 0° to 90°, is defined as angle α2. In this specification, "multiple second conductive columns 13 extending in a direction other than the thickness direction T" includes, for example, the case where angle α2 satisfies 45°≦α2≦90°. When angle α2 satisfies 45°≦α2≦90°, the number of the ends of the second conductive columns 13 exposed on the second main surface 102 may be reduced. In this specification, the surface of each second conductive columnar member 13 extending in the longitudinal direction is defined as the outer surface 13s of the second conductive columnar member 13.

[0033] The angle α2 can be determined, for example, by the following method. First, a sample is prepared by exposing a cross section of the catalyst layer 110 parallel to the thickness direction T. A cross-sectional image of the sample is obtained using a TEM or SEM. In the obtained cross-sectional image, the smallest angle between the thickness direction T and the outer surface 13s of the end 13e of an arbitrary number (e.g., 100) of second conductive columns 13 is measured within the range of 0° to 90°. The average of the measured values ​​can be regarded as the angle α2.

[0034] The angle α2 may satisfy the relationship 60°≦α2≦90°, 70°≦α2≦90°, or 80°≦α2≦90°.

[0035] The second conductive columns 13 may be oriented in a direction parallel to the second main surface 102. In this specification, "parallel" means that the angle α2 satisfies 80°≦α2≦90°. That is, the angle α2 may satisfy 80°≦α2≦90°.

[0036] Fig. 3 is a schematic cross-sectional view of a catalyst layer 120 in Modification 2. The catalyst layer 120 shown in Fig. 3 has the same structure as the catalyst layer 110 shown in Fig. 2, except for the structure of the second layer 20. In Modification 2, elements common to the above-described catalyst layer 100 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0037] 3, the second conductive columns 13 may include second conductive columns 13 whose angle α2 satisfies 45°≦α2≦90° and whose inclination directions are different from each other. This structure can also reduce the number of ends of the second conductive columns 13 exposed on the second main surface 102.

[0038] In the first layer 10, the multiple first conductive columns 11 may extend in the thickness direction T while being finely curled. In other words, in the first layer 10, the multiple first conductive columns 11 may extend in the thickness direction T and have a corrugated shape. In the second layer 20, the multiple second conductive columns 13 may extend in a direction other than the thickness direction T while being finely curled. In other words, in the second layer 20, the multiple second conductive columns 13 may extend in a direction other than the thickness direction T and have a corrugated shape.

[0039] The degree of crimp of the second conductive columns 13 in the second layer 20 may be greater than the degree of crimp of the first conductive columns 11 in the first layer 10. Such a structure can reduce the number of ends of the second conductive columns 13 exposed to the second main surface 102. Therefore, when the catalyst layer 100 is transferred to the electrolyte membrane so that the second main surface 102 faces the electrolyte membrane, the ends of the second conductive columns 13 are more likely to pierce the electrolyte membrane. The fact that the degree of crimp of the second conductive columns 13 in the second layer 20 is greater than the degree of crimp of the first conductive columns 11 in the first layer 10 can be confirmed, for example, by observing a cross-sectional image obtained using a TEM or SEM.

[0040] The degree of entanglement of the second conductive columns 13 in the second layer 20 may be greater than the degree of entanglement of the first conductive columns 11 in the first layer 10. In this specification, the term "the degree of entanglement of the second conductive columns 13 in the second layer 20 is greater than the degree of entanglement of the first conductive columns 11 in the first layer 10" means that the number of contact points between the second conductive columns 13 in the second layer 20 is greater than the number of contact points between the first conductive columns 11 in the first layer 10. This structure can reduce the number of end portions of the second conductive columns 13 exposed on the second main surface 102. Therefore, when the catalyst layer 100 is transferred to the electrolyte membrane so that the second main surface 102 faces the electrolyte membrane, the end portions of the second conductive columns 13 are more likely to pierce the electrolyte membrane. The fact that the degree of entanglement of the multiple second conductive columns 13 in the second layer 20 is greater than the degree of entanglement of the multiple first conductive columns 11 in the first layer 10 can be confirmed, for example, by observing a cross-sectional image obtained using a TEM or SEM.

[0041] The ratio of the thickness of the second layer 20 to the thickness of the catalyst layer 100 may be 10% or less. With such a structure, the ratio of the thickness of the first layer 10 is large, so that an increase in the oxygen diffusion resistance in the catalyst layer 100 can be suppressed.

[0042] As shown in FIG. 1A, in a cross section of the catalyst layer 100 parallel to the thickness direction T, a line passing through the end faces 11d of the surface profiles of the multiple first conductive columns 12 and perpendicular to the thickness direction T of the catalyst layer 100 is defined as a reference line Ld. The reference line Ld is a line corresponding to the first main surface 101. FIG. 1B is a partial enlarged view of region IB in FIG. 1A. As shown in FIG. 1B, in a cross section of the catalyst layer 100 parallel to the thickness direction T, a line passing through point 13p, which defines the maximum height of the surface profiles of the multiple second conductive columns 13, and perpendicular to the thickness direction T of the catalyst layer 100 is defined as a reference line Lp. In a cross section of the catalyst layer 100 parallel to the thickness direction T, a line passing through point 13q, which defines the minimum height of the surface profiles of the multiple second conductive columns 13, and perpendicular to the thickness direction T of the catalyst layer 100 is defined as a reference line Lq. The reference line Lq is a line corresponding to the second main surface 102. In this specification, the thickness of the second layer 20 means the length in the thickness direction T from the reference line Lp to the reference line Lq. The thickness of the first layer 10 means the length in the thickness direction T from the reference line Ld to the reference line Lp. The thickness of the catalyst layer 100 means the length in the thickness direction T from the reference line Ld to the reference line Lq.

[0043] The thickness of the second layer 20 can be measured, for example, by the following method. Using the same method as above, multiple (e.g., 10) cross-sectional images of the catalyst layer 100 are obtained. The thickness of the second layer 20 is measured for each of the multiple cross-sectional images obtained. The average of the measured values ​​is considered to be the thickness of the second layer 20. The thickness of the other layers can be determined in a similar manner.

[0044] The upper limit of the ratio of the thickness of the second layer 20 to the thickness of the catalyst layer 100 may be 20% or less, or may be 10% or less. The lower limit of the ratio of the thickness of the second layer 20 to the thickness of the catalyst layer 100 is, for example, 0.05% or more. The lower limit of the ratio of the thickness of the second layer 20 to the thickness of the catalyst layer 100 may be 0.1% or more, or may be 0.5% or more.

[0045] The ratio of the volume of the second conductive columns 13 to the volume of the second layer 20 may be larger than the ratio of the volume of the first conductive columns 11 to the volume of the first layer 10. Such a structure can reduce the number of ends of the second conductive columns 13 exposed to the second main surface 102. Therefore, when the catalyst layer 100 is transferred to the electrolyte membrane so that the second main surface 102 faces the electrolyte membrane, the ends of the second conductive columns 13 are more likely to pierce the electrolyte membrane. The fact that the ratio of the volume of the second conductive columns 13 to the volume of the second layer 20 is larger than the ratio of the volume of the first conductive columns 11 to the volume of the first layer 10 can be confirmed, for example, by observing a cross-sectional image obtained using a TEM or SEM.

[0046] There is no particular limitation on the arrangement of the ends 11e of the first conductive columns 11 on the first main surface 101. On the first main surface 101, the ends 11e of the first conductive columns 11 may be arranged at equal intervals or at uneven intervals.

[0047] Examples of the configuration in which the ends 11e of the multiple first conductive columns 11 are arranged at equal intervals on the first main surface 101 include a configuration in which the ends 11e are arranged at the lattice points of a square lattice, with one side of the square lattice being parallel to one side of the catalyst layer 100, and a configuration in which the ends 11e are arranged at the lattice points and the center point of the square lattice, with one side of the square lattice being parallel to one side of the catalyst layer 100.

[0048] The first conductive columns 11 are spaced apart from each other by 1 cm on the first main surface 101. 2 10 per 9 The number density of the first conductive columns 11 may be equal to or greater than 1. With such a structure, high integration of the first conductive columns 11 can be achieved.

[0049] The first conductive columns 11 are spaced apart from each other by 1 cm on the first main surface 101. 2 10 per 10 The number density may be 10 or more.11 The number density may be greater than or equal to 1000.

[0050] The upper limit of the number density of the plurality of first conductive columns 11 can be set appropriately depending on, for example, the diameter of the first conductive columns 11. For example, when the diameter of the first conductive columns 11 is 10 nm, the plurality of first conductive columns 11 are arranged at an area of ​​1 cm on the first main surface 101. 2 10 per 12 The number density may be less than one.

[0051] The longitudinal dimension of the first conductive columnar body 11 may be, for example, 1 μm or more and 100 μm or less. The lateral dimension of the first conductive columnar body 11, which is perpendicular to the longitudinal direction, may be, for example, 10 nm or more and 200 nm or less. The longitudinal dimension of the first conductive columnar body 11 corresponds to the thickness of the first layer 10. When the first conductive columnar body 11 has a cylindrical or columnar shape like a carbon nanotube, the lateral dimension of the first conductive columnar body 11 corresponds to the diameter of the first conductive columnar body 11.

[0052] The longitudinal and lateral dimensions of the first conductive pillars 11 can be determined, for example, by the following method. A cross-sectional image of the catalyst layer 100 is obtained by the same method as above. The longitudinal dimensions of an arbitrary number (e.g., 100) of first conductive pillars 11 in the obtained cross-sectional image are measured. The average of the measured values ​​is regarded as the longitudinal dimension of the first conductive pillars 11. The lateral dimension of the first conductive pillars 11 can be determined in a similar manner.

[0053] The first conductive columnar body 11 and the second conductive columnar body 13 are made of a conductive material such as carbon. For example, a conductive long material such as a carbon nanotube or a carbon fiber can be used as the first conductive columnar body 11 and the second conductive columnar body 13. The first conductive columnar body 11 and the second conductive columnar body 13 may be made of the same carbon nanotube. The carbon nanotube may have a single-layer structure or a multi-layer structure.

[0054] From the viewpoint of improving catalytic activity and heat resistance, the first catalyst particles 12 and the second catalyst particles 14 may be particles containing a precious metal such as platinum or a platinum alloy. Examples of platinum alloys include alloys of platinum with at least one selected from the group consisting of cobalt, nickel, ruthenium, and palladium. The first catalyst particles 12 and the second catalyst particles 14 may each contain at least one precious metal selected from the group consisting of platinum, palladium, iridium, ruthenium, and rhodium. The first catalyst particles 12 and the second catalyst particles 14 may be the same catalyst particles.

[0055] The average particle diameter of the first catalyst particles 12 and the second catalyst particles 14 is not particularly limited. From the viewpoint of catalyst utilization rate and durability, the average particle diameter of the first catalyst particles 12 and the second catalyst particles 14 may be 1 nm or more and 30 nm or less. The average particle diameter is calculated, for example, from a TEM image of the first catalyst particles 12. In the TEM image, the equivalent diameter of an arbitrary number (for example, 10) of first catalyst particles 12 is measured. The average of the measured equivalent diameters can be considered as the average particle diameter of the first catalyst particles 12. The equivalent diameter means the diameter of a circle having the same area. The average particle diameter of the second catalyst particles 14 can be calculated in a similar manner.

[0056] The catalyst layer 100 in the first embodiment may further include a coating layer containing an electrolyte resin and coating at least a portion of the surface of each of the second conductive columns 13. The electrolyte resin is an electrolyte having proton conductivity. The coating layer can connect the second catalyst particles 14 and the second conductive columns 13 in a proton-conductive state. Therefore, when the catalyst layer 100 includes a coating layer made of an electrolyte resin, an increase in the proton diffusion resistance can be suppressed.

[0057] The electrolyte resin contained in the coating layer may be a polymer electrolyte having ion conductivity. The electrolyte resin contained in the coating layer may be a perfluorocarbon sulfonic acid-based polymer material having sulfonic acid groups, a hydrocarbon-based polymer material, or the like. The electrolyte resin contained in the coating layer may be a perfluorosulfonic acid resin. Perfluorosulfonic acid resins exhibit excellent proton conductivity. The electrolyte resin contained in the coating layer typically includes a perfluorocarbon sulfonic acid-based polymer electrolyte having sulfonic acid groups.

[0058] The electrolyte resin contained in the coating layer is also called an ionomer.

[0059] Hereinafter, an example of a catalyst layer further including a coating layer containing an electrolyte resin will be described as Modification 3. In Modification 3, elements common to the above-described catalyst layer 100 will be denoted by the same reference numerals and detailed description will be omitted.

[0060] 4 is a schematic cross-sectional view of a catalyst layer 130 in Modification 3. The catalyst layer 130 further includes a coating layer 15 that contains an electrolyte resin and coats at least a portion of the surface of each of the second conductive columns 13.

[0061] According to the catalyst layer 110 of Modification 3, the provision of the coating layer 15 can further reduce the number of ends of the second conductive columns 13 exposed on the second main surface 102. Therefore, when the catalyst layer 110 is transferred to the electrolyte membrane so that the electrolyte membrane faces the second main surface 102, the ends of the multiple second conductive columns 13 are further prevented from piercing the electrolyte membrane.

[0062] Although not shown in the figure, the coating layer 15 may further cover at least a part of the surface of each of the plurality of first conductive columns 11. In this case, the thickness of the coating layer 15 may decrease from the second main surface 102 side of the first conductive columnar body 11 toward the first main surface 101 side.

[0063] The catalyst layers 100 to 130 described above can be manufactured, for example, by the following method. The following method is an example in which the first conductive columnar body 11 and the second conductive columnar body 13 are carbon nanotubes.

[0064] First, metal particles are supported on a substrate on which a metal thin film has been formed, and then carbon nanotubes are grown on the substrate using a thermal CVD method, a plasma CVD method, or the like. In the early stages of growth, the carbon nanotubes grow in directions other than the thickness direction T while entangling with each other. By controlling the arrangement of the metal particles, the growth rate of the carbon nanotubes, and the like, a second layer 20 can be formed in the early stages of growth. After the second layer 20 is formed, the carbon nanotubes grow in the thickness direction T while lifting up the second layer 20. In this way, the first layer 10 is formed.

[0065] Next, catalyst particles are supported on the carbon nanotubes on the substrate. The method for supporting the catalyst particles on the carbon nanotubes is not particularly limited. For example, either a wet method or a dry method may be used.

[0066] Next, if necessary, the carbon nanotubes of the second layer 20 on the substrate are coated with a material containing an electrolyte resin to form the coating layer 15. There are no particular limitations on the method for coating the carbon nanotubes of the second layer 20 with the material containing an electrolyte resin. For example, the carbon nanotubes of the second layer 20 may be impregnated with a solution containing a precursor of the electrolyte resin, dried, and then polymerized by irradiation with radiation such as ultraviolet light or by heating.

[0067] Finally, the carbon nanotubes on the substrate are placed so that the electrolyte membrane and second layer 20 are in contact with each other, and the carbon nanotubes are transferred to the electrolyte membrane by hot pressing. After transfer, the substrate is peeled off from the carbon nanotubes. This results in a catalyst layer arranged so that the second main surface 102 of the catalyst layer is in contact with the electrolyte membrane.

[0068] (Embodiment 2) Hereinafter, the second embodiment will be described with reference to FIGS. 5A to 6. FIG.

[0069] [2-1.Configuration] Fig. 5A is a schematic cross-sectional view of a membrane electrode assembly 200 in embodiment 2. Fig. 5B is a partial enlarged view of region IIIB in Fig. 5A. Fig. 6 is a schematic cross-sectional view of an electrochemical device 300 in embodiment 2. The electrochemical device 300 includes the membrane electrode assembly 200, an anode separator 301, a cathode separator 302, and a power source 307. The membrane electrode assembly 200 is disposed between the anode separator 301 and the cathode separator 302.

[0070] The electrochemical device 300 may be used in a fuel cell, thereby providing a highly efficient fuel cell with high power generation performance.

[0071] 6, the electrochemical device 300 is a polymer electrolyte fuel cell (PEFC) that generates electricity by receiving a supply of a hydrogen-containing gas G1 as an anode gas and an oxygen-containing gas G3 as a cathode gas. The electrochemical device 300 may be used as other electrochemical devices, such as a hydrogen purification device that purifies hydrogen or a water electrolysis device that electrolyzes water, in addition to a fuel cell.

[0072] 5A, the membrane electrode assembly 200 has an anode 202, an electrolyte membrane 201, and a cathode 203. The electrolyte membrane 201 is disposed between the anode 202 and the cathode 203. The anode 202 is bonded to one surface of the electrolyte membrane 201. The cathode 203 is bonded to the other surface of the electrolyte membrane 201.

[0073] The anode 202 has an anode catalyst layer 204 and an anode gas diffusion layer 205. The anode catalyst layer 204 is disposed between the electrolyte membrane 201 and the anode gas diffusion layer 205. The cathode 203 has a cathode catalyst layer 206 and a cathode gas diffusion layer 207. The cathode catalyst layer 206 is disposed between the electrolyte membrane 201 and the cathode gas diffusion layer 207.

[0074] The electrolyte membrane 201 conducts protons between the anode catalyst layer 204 and the cathode catalyst layer 206. The electrolyte membrane 201 is made of a polymer material that has 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. A perfluorosulfonic acid-based polymer electrolyte membrane exhibits excellent proton conductivity and is stable even in the power generation environment of the electrochemical device 300.

[0075] 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. A flat surface of the electrolyte membrane 201 allows for good drainage on the surface of the electrolyte membrane 201. The "flat surface" means a surface that has not been processed to provide irregularities.

[0076] The anode catalyst layer 204 has the function of promoting the 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 include a coating layer made of an electrolyte resin that covers at least a portion of the surface of the conductive material.

[0077] The membrane electrode assembly 200 may include, as the anode catalyst layer 204, any one of the catalyst layers 100 to 130 described in the first embodiment.

[0078] The anode gas diffusion layer 205 has a function of supplying the hydrogen-containing gas G1 to the anode catalyst layer 204 and a function of receiving electrons from the anode catalyst layer 204. The anode gas diffusion layer 205 is made of a material that is gas permeable, water repellent, and conductive. The anode gas diffusion layer 205 has, as its main material, for example, a conductive porous body. An example of the porous body is a carbon fiber aggregate such as carbon paper.

[0079] 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 may include a coating layer made of an electrolyte resin that covers at least a portion of the surface of the conductive material.

[0080] In this embodiment, the cathode 203 includes any one of the catalyst layers 100 to 130 described in the first embodiment. That is, the membrane electrode assembly 200 includes any one of the catalyst layers 100 to 130 described in the first embodiment as the cathode catalyst layer 206. FIG. 5B shows an example in which the membrane electrode assembly 200 includes the catalyst layer 100 as the cathode catalyst layer 206. As shown in FIG. 5B, the second main surface 102 of the cathode catalyst layer 206 is in contact with the electrolyte membrane 201. This configuration prevents the ends of the multiple second conductive columns 13 from piercing the electrolyte membrane 201 when the catalyst layer 100 is transferred to the electrolyte membrane 201 so that the second main surface 102 faces the electrolyte membrane 201. Therefore, pinholes, tears, etc., occurring in the electrolyte membrane 201 and quality defects such as cross leakage and short circuits between the cathode and anode are suppressed, and a decrease in the efficiency of the electrochemical device 300 is suppressed.

[0081] Although not shown, when the cathode catalyst layer 206 further includes a coating layer 15 made of an electrolyte resin, the electrolyte membrane 201 and the plurality of second conductive columns 13 may be bonded together by the coating layer 15.

[0082] The cathode gas diffusion layer 207 has the function of supplying an oxygen-containing gas to the cathode catalyst layer 206 and the function of transferring electrons to the cathode catalyst layer 206. The cathode gas diffusion layer 207 is made of a gas-permeable, water-repellent, and conductive material. The cathode gas diffusion layer 207 has, as its main material, for example, a conductive porous body. An example of the porous body is a carbon fiber aggregate such as carbon paper.

[0083] The anode catalyst layer 204 may have the same structure as the cathode catalyst layer 206, or may have a different structure.

[0084] As shown in Fig. 6, the anode separator 301 has an anode gas inlet 303, an anode gas outlet 304, and an anode gas flow channel 301g. The anode gas flow channel 301g is a groove-shaped gas flow channel that guides a hydrogen-containing gas G1 to the anode 202. The anode gas inlet 303 is provided at the upstream end of the anode gas flow channel 301g. The anode gas outlet 304 is provided at the downstream end of the anode gas flow channel 301g. The hydrogen-containing gas G1 is introduced into the anode gas flow channel 301g from the outside through the anode gas inlet 303. Unreacted hydrogen-containing gas G2 is discharged from the anode gas flow channel 301g to the outside through the anode gas outlet 304.

[0085] The cathode separator 302 has a cathode gas inlet 305, a cathode gas outlet 306, and a cathode gas flow channel 302g. The cathode gas flow channel 302g is a groove-shaped gas flow channel that guides an oxygen-containing gas G3 to the cathode 203. The cathode gas inlet 305 is provided at the upstream end of the cathode gas flow channel 302g. The cathode gas outlet 306 is provided at the downstream end of the cathode gas flow channel 302g. The oxygen-containing gas G3 is introduced into the cathode gas flow channel 302g from the outside through the cathode gas inlet 305. The unreacted oxygen-containing gas G4 is discharged from the cathode gas flow channel 302g to the outside through the cathode gas outlet 306.

[0086] The shapes of the anode gas flow channel 301g and the cathode gas flow channel 302g are not particularly limited. The anode gas flow channel 301g and the cathode gas flow channel 302g may each have a serpentine shape. A serpentine shape is a shape of a flow channel in which one or more flow channels meander within a plane. When the anode gas flow channel 301g and the cathode gas flow channel 302g have the above-mentioned shapes, gas can be supplied to the entire catalyst layers 204, 206 at a constant flow rate. This makes it easier for the gas to reach all of the catalyst particles.

[0087] 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. To prevent corrosion, the anode separator 301 and the cathode separator 302 may be provided with a corrosion-resistant coating such as a resin or plating.

[0088] [2-2. Operation] The operation and function of the electrochemical device 300 configured as above will be described below with reference to FIG.

[0089] A hydrogen-containing gas G1 is supplied from the anode gas inlet 303 to the anode gas flow channel 301g of the anode separator 301. The hydrogen-containing gas G1 is humidified hydrogen gas. As a result, the hydrogen-containing gas G1 is supplied to the anode catalyst layer 204 via the anode gas diffusion layer 205. An oxygen-containing gas G3 is supplied from the cathode gas inlet 305 to the cathode gas flow channel 302g of the cathode separator 302. The oxygen-containing gas G3 is humidified air. As a result, the oxygen-containing gas G3 is supplied to the cathode catalyst layer 206 via the cathode gas diffusion layer 207. A current is applied by a power source 307 between the anode catalyst layer 204 to which the hydrogen-containing gas G1 has been supplied and the cathode catalyst layer 206 to which the oxygen-containing gas G3 has been supplied.

[0090] In the anode catalyst layer 204 to which the hydrogen-containing gas G1 is supplied, hydrogen (H2) is converted into protons (H + ) and electrons (e -) occurs. The protons pass through the electrolyte membrane 201 and move to the cathode catalyst layer 206. The electrons dissociated in the anode catalyst layer 204 move from the anode 202 toward the cathode 203 through an external circuit (not shown) 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 expressed by the following formula (II). The protons used in this reduction reaction are protons that are dissociated by the oxidation reaction in the anode catalyst layer 204 shown in the following formula (I), pass through the electrolyte membrane 201, and move to the cathode catalyst layer 206.

[0091] H2→2H + +2e - (I) 4H + +O2+2e - →2H2O (II)

[0092] (Other embodiments) As described above, Embodiments 1 and 2 have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these and can be applied to embodiments with modifications, additions, omissions, etc. Furthermore, it is also possible to combine the components described in the above embodiments and modifications to create new embodiments.

[0093] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0094] (Addendum) The above description of the embodiments discloses the following techniques.

[0095] (Technology 1) A catalyst layer comprising a first layer located on a first main surface side and a second layer located on a second main surface side, the first layer includes a plurality of first conductive columns extending in a thickness direction of the catalyst layer and first catalyst particles supported on the plurality of first conductive columns; the second layer includes a plurality of second conductive columns extending in a direction other than the thickness direction, and second catalyst particles supported on the plurality of second conductive columns. Catalyst layers for electrochemical devices.

[0096] According to the catalyst layer for electrochemical devices of Technique 1, it is possible to suppress a decrease in the efficiency of electrochemical devices such as fuel cells.

[0097] (Technology 2) The catalyst layer for electrochemical devices according to Technical Problem 1, wherein the first layer and the second layer are in electrical contact with each other. With such a structure, the above-mentioned effects can be easily obtained.

[0098] (Technology 3) The catalyst layer for an electrochemical device according to Technology 1 or 2, wherein the second conductive columns extend in random directions in the second layer. With this structure, when the catalyst layer is transferred to the electrolyte membrane so that the second main surface faces the electrolyte membrane, the ends of the second conductive columns are more effectively prevented from piercing the electrolyte membrane.

[0099] (Technology 4) The catalyst layer for an electrochemical device according to any one of techniques 1 to 3, wherein the ratio of the thickness of the second layer to the thickness of the catalyst layer is 10% or less. With this structure, an increase in oxygen diffusion resistance in the catalyst layer can be suppressed.

[0100] (Technology 5) The catalyst layer for an electrochemical device according to any one of techniques 1 to 4, wherein a ratio of the volume of the second conductive columns to the volume of the second layer is larger than a ratio of the volume of the first conductive columns to the volume of the first layer. With this structure, when the catalyst layer is transferred to the electrolyte membrane so that the second main surface faces the electrolyte membrane, the ends of the second conductive columns are more effectively prevented from piercing the electrolyte membrane.

[0101] (Technology 6) The catalyst layer for an electrochemical device according to any one of techniques 1 to 5, further comprising a coating layer containing an electrolyte resin and covering at least a part of a surface of each of the second conductive columns. With this structure, when the catalyst layer is transferred to the electrolyte membrane so that the second main surface faces the electrolyte membrane, the ends of the second conductive columns are further prevented from piercing the electrolyte membrane.

[0102] (Technology 7) an anode; a cathode; an electrolyte membrane disposed between the anode and the cathode; Equipped with at least one selected from the group consisting of the anode and the cathode includes the catalyst layer for an electrochemical device according to any one of techniques 1 to 6; the second main surface of the electrochemical device catalyst layer in at least one selected from the group consisting of the anode and the cathode is in contact with the electrolyte membrane; Membrane electrode assembly.

[0103] According to the membrane electrode assembly of Technique 7, it is possible to improve the power generation performance of an electrochemical device using the membrane electrode assembly.

[0104] (Technology 8) The membrane electrode assembly according to technique 7 is provided. Electrochemical devices.

[0105] According to the electrochemical device of Technique 8, an electrochemical device with excellent power generation performance can be realized. [Industrial Applicability]

[0106] The present disclosure is useful for electrochemical devices such as fuel cells, hydrogen purification devices, and water electrolysis devices. [Explanation of symbols]

[0107] 100,110,120,130 catalyst layer 101 first principal surface 102 Second main surface 10 First Layer 20 Second Layer 11 First conductive column 11e End 11s outer surface 11d End face 12 First catalyst particles 13 Second conductive column 14 Second catalyst particles 15 Coating layer (electrolyte resin) T thickness direction 200 Membrane electrode assembly 201 Electrolyte membrane 202 Anode 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 307 Power supply

Claims

1. A catalyst layer comprising a first layer located on a first main surface side and a second layer located on a second main surface side, the first layer includes a plurality of first conductive columns extending in a thickness direction of the catalyst layer and first catalyst particles supported on the plurality of first conductive columns; the second layer includes a plurality of second conductive columns extending in a direction other than the thickness direction, and second catalyst particles supported on the plurality of second conductive columns. Catalyst layers for electrochemical devices.

2. The first layer and the second layer are in electrical contact with each other. The catalyst layer for an electrochemical device according to claim 1 .

3. In the second layer, the plurality of second conductive columns extend in random directions. The catalyst layer for an electrochemical device according to claim 1 .

4. the ratio of the thickness of the second layer to the thickness of the catalyst layer is 10% or less; The catalyst layer for an electrochemical device according to claim 1 .

5. a ratio of the volume of the plurality of second conductive columns to the volume of the second layer is larger than a ratio of the volume of the plurality of first conductive columns to the volume of the first layer; The catalyst layer for an electrochemical device according to claim 1 .

6. a coating layer including an electrolyte resin and coating at least a portion of a surface of each of the second conductive columns; The catalyst layer for an electrochemical device according to claim 1 .

7. an anode; a cathode; an electrolyte membrane disposed between the anode and the cathode; Equipped with at least one selected from the group consisting of the anode and the cathode comprises the catalyst layer for an electrochemical device according to claim 1 ; the second main surface of the electrochemical device catalyst layer in at least one selected from the group consisting of the anode and the cathode is in contact with the electrolyte membrane; Membrane electrode assembly.

8. A fuel cell comprising the membrane electrode assembly according to claim 7 . Electrochemical devices.

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