Catalyst layer for membrane electrode assembly, membrane electrode assembly, and method for manufacturing catalyst layer

Abstract

To improve the efficiency of the electrochemical reaction in a catalyst layer.SOLUTION: A catalyst layer 109 according to the present disclosure includes a support particle 11, a catalyst particle 12 supported on the support particle 11, a conductive fiber 13 arranged so as to be in contact with the support particle 11, a first resin layer 15a containing a first resin material having proton conductivity and covering at least a portion of the surface of the conductive fiber 13, and a second resin layer 15b containing a second resin material having lower hydrophilicity than the first resin material and covering at least a portion of the outer surface of the first resin layer 15a.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a catalyst layer for a membrane electrode assembly, a membrane electrode assembly, and a method for manufacturing the catalyst layer.

Background Art

[0002] In an electrochemical device such as a fuel cell, a membrane electrode assembly having an anode, an electrolyte membrane, and a cathode is used. The anode and cathode of the membrane electrode assembly each have a catalyst layer. In the catalyst layer, carbon particles carrying catalyst particles or the like are used as an electrode catalyst. In the catalyst layer, the electrode catalyst is covered with a polymer electrolyte having ion conductivity.

[0003] Patent Document 1 describes an electrode catalyst layer for a polymer electrolyte fuel cell. The electrode catalyst layer includes a catalyst, carbon particles, a polymer electrolyte, and a fibrous substance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the prior art, it has been desired to improve the efficiency of an electrochemical reaction by achieving both proton conductivity and drainage in the catalyst layer.

Means for Solving the Problems

[0006] The present disclosure is carrier particles, catalyst particles supported on the carrier particles, conductive fibers arranged so as to be in contact with the carrier particles, A first resin layer containing a first resin material having proton conductivity and covering at least a part of the surface of the conductive fiber, A second resin layer containing a second resin material having lower hydrophilicity than the first resin material and covering at least a part of the outer surface of the first resin layer, A catalyst layer for a membrane electrode assembly is provided.

[0007] In another aspect, the present disclosure A catalyst layer for a membrane electrode assembly, Carrier particles, Catalyst particles supported on the carrier particles, Conductive fibers arranged in contact with the carrier particles, A resin material attached to the conductive fibers, Comprising The resin material includes a first resin material having proton conductivity and a second resin material having lower hydrophilicity than the first resin material, When the alternating current impedance measurement of the membrane electrode assembly including the catalyst layer is performed under the conditions of a temperature of 50 ° C and a relative humidity of 100%, the proton conduction resistance of the catalyst layer measured is 250 mΩ / cm 2 Or less, A catalyst layer for a membrane electrode assembly is provided.

[0008] In yet another aspect, the present disclosure Mixing carrier particles carrying catalyst particles, conductive fibers, a first resin material having proton conductivity, and a solvent to prepare a preliminary solution, Dispersing a second resin material having lower hydrophilicity than the first resin material in the preliminary solution to prepare a catalyst ink, Applying the catalyst ink to a substrate to form a catalyst layer, A method for manufacturing a catalyst layer for a membrane electrode assembly is provided.

Advantages of the Invention

[0009] According to the technology of the present disclosure, it is possible to achieve both proton conductivity and drainage in the catalyst layer and improve the efficiency of the electrochemical reaction.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0011] (Findings etc. underlying the present disclosure) When the inventors of the present invention arrived at the idea of the present disclosure, a catalyst layer containing fibrous substances such as carbon nanofibers was known (Patent Document 1). The fibrous substance was considered to promote the formation of pores and improve drainage and gas diffusibility. However, a polymer electrolyte having a sulfonic acid group has been used in the conventional catalyst layer, and it has a characteristic of high hydrophilicity. Therefore, water generated during operation and water generated from the humidified gas tend to stay in the pores of the catalyst layer. When water stays in the pores, the diffusion of gas is inhibited. As a result, the performance of the electrochemical device deteriorates. This phenomenon is often called flooding.

[0012] Under such circumstances, the inventors of the present invention studied the configuration of a catalyst layer capable of achieving both proton conductivity and drainage. As a result of intensive studies, the catalyst layer of the present disclosure was completed.

[0013] Hereinafter, embodiments will be described in detail with reference to the drawings. However, a more detailed description may be omitted as necessary. For example, a detailed description of well-known matters or a redundant description of substantially the same configuration may be omitted.

[0014] 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 described in the claims.

[0015] (Embodiment 1) Hereinafter, Embodiment 1 will be described with reference to FIGS. 1 to 4.

[0016] [1-1. Configuration] FIG. 1 is a schematic cross-sectional view of a fuel cell 101 in Embodiment 1. The fuel cell 101 includes a membrane electrode assembly 113, an anode separator 106, and a cathode separator 111. The membrane electrode assembly 113 is disposed between the anode separator 106 and the cathode separator 111. The fuel cell 101 is, for example, a polymer electrolyte fuel cell.

[0017] The membrane electrode assembly 113 can also be used in other electrochemical devices such as a hydrogen purification device for purifying hydrogen.

[0018] The membrane electrode assembly 113 has an anode 103, an electrolyte membrane 102, and a cathode 108. The anode 103 is joined to one surface of the electrolyte membrane 102. The cathode 108 is joined to the other surface of the electrolyte membrane 102.

[0019] The electrolyte membrane 102 is disposed between the anode 103 and the cathode 108. The electrolyte membrane 102 is made of a polymer material having proton conductivity. The electrolyte membrane 102 is, for example, a membrane made of a perfluorocarbon sulfonic acid-based polymer material having a sulfonic acid group or a hydrocarbon-based polymer material.

[0020] The anode 103 has an anode catalyst layer 104 and an anode gas diffusion layer 105. The anode catalyst layer 104 is disposed between the electrolyte membrane 102 and the anode gas diffusion layer 105. The cathode 108 has a cathode catalyst layer 109 and a cathode gas diffusion layer 110. The cathode catalyst layer 109 is disposed between the electrolyte membrane 102 and the cathode gas diffusion layer 110.

[0021] The anode catalyst layer 104 has a function of promoting an electrochemical reaction that dissociates hydrogen molecules into protons. The anode catalyst layer 104 has an electrode catalyst and a polymer electrolyte. The anode catalyst layer 104 may have carbon particles supporting catalyst particles and a polymer electrolyte.

[0022] The anode gas diffusion layer 105 has a function of supplying a hydrogen-containing gas to the anode catalyst layer 104 and a function of receiving electrons from the anode catalyst layer 104. The anode gas diffusion layer 105 is composed of a material having gas permeability and conductivity. The anode gas diffusion layer 105 mainly has, for example, a porous body having conductivity. Examples of the porous body include a carbon fiber aggregate such as carbon paper.

[0023] The cathode catalyst layer 109 has a function of promoting an electrochemical reaction that generates water from protons and oxygen. The detailed structure of the cathode catalyst layer 109 will be described later.

[0024] The cathode gas diffusion layer 110 has a function of supplying an oxidant gas to the cathode catalyst layer 109 and a function of delivering electrons to the cathode catalyst layer 109. The cathode gas diffusion layer 110 is composed of a material having gas permeability and conductivity. The cathode gas diffusion layer 110 mainly includes, for example, a porous body having conductivity. Examples of the porous body include a carbon fiber aggregate such as carbon paper.

[0025] The anode separator 106 is provided with an anode gas flow path 107 which is a flow path for anode gas. The cathode separator 111 is provided with a cathode gas flow path 112 which is a flow path for cathode gas. The anode separator 106 and the cathode separator 111 are each made of a conductive material such as carbon or metal. A corrosion-resistant coating such as resin or plating may be provided to prevent corrosion.

[0026] Figure 2 is a partially enlarged cross-sectional view of the cathode catalyst layer 109. The cathode catalyst layer 109 includes an electrode catalyst 10, a conductive fiber 13, and a resin material 15. The electrode catalyst 10, the conductive fiber 13, and the resin material 15 are in contact with each other. Pores 14 exist between the electrode catalyst 10 and the electrode catalyst 10, between the electrode catalyst 10 and the conductive fiber 13, and / or between the conductive fiber 13 and the conductive fiber 13. The resin material 15 is sometimes called an ionomer.

[0027] The electrode catalyst 10 has a particle shape. The particles of the electrode catalyst 10 have carrier particles 11 and a plurality of catalyst particles 12. The plurality of catalyst particles 12 are supported on the carrier particles 11.

[0028] The carrier particles 11 have conductivity. The carrier particles 11 are, for example, solid or porous carbon particles. Examples of the solid carbon particles include carbon black particles such as ketjen black and acetylene black. In the case of solid carbon particles, the catalyst particles 12 are supported on the surface thereof. Examples of the porous carbon particles include mesoporous carbon particles. In the case of porous carbon particles, the catalyst particles 12 are disposed inside the pores (mesopores). By disposing the catalyst particles 12 inside the pores of the mesoporous carbon particles, poisoning of the catalyst particles 12 by the resin material 15 can be suppressed.

[0029] When the carrier particles 11 are solid carbon particles, their average particle diameter is, for example, from 20 nm to 40 nm. When the carrier particles 11 are mesoporous carbon particles, their average particle diameter is, for example, from 0.6 μm to 2.0 μm.

[0030] The average particle diameter of the carrier particles 11 is the average value of the diameters of a plurality (for example, 20 or more) of the carrier particles 11. The diameter of the carrier particles 11 can be measured using a scanning electron microscope or a transmission electron microscope (SEM or TEM). In the SEM image or TEM image of the carrier particles 11, the area of the carrier particles 11 is obtained by image processing. The diameter of a circle having an area equal to the obtained area can be regarded as the diameter of the carrier particles 11.

[0031] When the carrier particles 11 include mesoporous carbon particles, the technology of the present disclosure is particularly effective. Mesoporous carbon particles tend to have larger dimensions compared to solid carbon particles. Therefore, when mesoporous carbon particles are used as the carrier particles 11, the thickness of the cathode catalyst layer 109 tends to increase. When the thickness of the cathode catalyst layer 109 increases, the gas diffusivity in the cathode catalyst layer 109 decreases. The decrease in gas diffusivity due to the use of mesoporous carbon particles can be compensated for by the technology of the present disclosure.

[0032] The catalyst particles 12 can be particles containing a noble metal such as platinum or a platinum alloy. Examples of the platinum alloy include an alloy of platinum and at least one selected from the group consisting of cobalt, nickel, ruthenium, and palladium.

[0033] The catalyst particles 12 may be nanoparticles. The catalyst particles 12 have, for example, an average particle diameter of 1 nm or more and 30 nm or less.

[0034] The average particle diameter of the catalyst particles 12 is the average value of the diameters of a plurality (for example, 100 or more) of the catalyst particles 12. The diameter of the catalyst particles 12 can be measured using a transmission electron microscope. In the TEM image of the electrode catalyst 10, the area of the catalyst particles 12 is determined by image processing. The diameter of a circle having an area equal to the determined area can be regarded as the diameter of the catalyst particles 12.

[0035] The conductive fibers 13 promote the formation of pores 14 and enhance the drainage and gas diffusivity in the cathode catalyst layer 109. In the cathode catalyst layer 109, the conductive fibers 13 are arranged in contact with the carrier particles 11 of the electrode catalyst 10. The particles of the electrode catalyst 10 are connected to each other by the conductive fibers 13. Thereby, the electron conduction in the cathode catalyst layer 109 is promoted. A resin material 15 adheres to the conductive fibers 13. The proton conduction in the cathode catalyst layer 109 is promoted by the conductive fibers 13 to which the resin material 15 adheres.

[0036] The conductive fiber 13 is, for example, a carbon fiber. Examples of the carbon fiber include carbon nanotubes, carbon nanofibers, and vapor-grown carbon fibers.

[0037] The average length of the conductive fiber 13 is, for example, 2 μm or more and 10 μm or less. The average fiber diameter of the conductive fiber 13 is, for example, 0.15 nm or more and 0.30 nm or less.

[0038] The average length of the conductive fiber 13 can be measured, for example, by the following method. The cathode catalyst layer 109 is dispersed in a solvent such as a water-ethanol mixture to prepare a dispersion, and the dispersion is thinly applied onto a substrate such as a glass plate to form a coating film. After drying the coating film, the coating film is observed in one or a plurality of fields of view using SEM or TEM. The lengths of a plurality of conductive fibers 13 are measured from the SEM image or TEM image. For example, the average value of 20 or more measured values counted from the longer ones can be regarded as the average length of the conductive fiber 13. The average fiber diameter can also be obtained by the same method. The average length of the conductive fiber 13 may be measured by direct observation of the cathode catalyst layer 109 using an electron microscope.

[0039] In the present embodiment, the conductive fiber 13 can be a material that does not carry the catalyst particles 12. According to such a configuration, it is possible to avoid the poisoning of the catalyst particles 12 by the resin material 15. However, the catalyst particles 12 that have fallen off from the electrode catalyst 10 may adhere to the conductive fiber 13. That is, "the conductive fiber 13 does not carry the catalyst particles 12" means that no treatment for causing the conductive fiber 13 to carry the catalyst particles 12 has been performed.

[0040] The resin material 15 contains an electrolyte having proton conductivity and connects the electrode catalysts 10 in a state where proton conduction is possible between them. The resin material 15 adheres to each of the carrier particles 11 and the conductive fibers 13. Only a part of the surface of the carrier particles 11 may be covered by the resin material 15, or the entire surface of the carrier particles 11 may be covered by the resin material 15. Only a part of the surface of the conductive fibers 13 may be covered by the resin material 15, or the entire surface of the conductive fibers 13 may be covered by the resin material 15.

[0041] In the present embodiment, the resin material 15 includes a first resin material having proton conductivity and a second resin material having lower hydrophilicity than the first resin material. When the alternating current impedance of the membrane electrode assembly 113 including the cathode catalyst layer 109 is measured under the conditions of a temperature of 50°C and a relative humidity of 100%, the proton conduction resistance measured is 250 mΩ / cm 2 or less. According to such a configuration, it is possible to achieve both proton conductivity and drainage in the cathode catalyst layer 109. As a result, flooding can be suppressed and the efficiency of the electrochemical reaction in the cathode catalyst layer 109 can be improved, and thus the efficiency of the fuel cell 101 can be improved.

[0042] According to the findings of the present inventors, when cathode catalyst layers are produced with various compositions, the proton conduction resistance capable of exhibiting desired performance is all 220 mΩ / cm 2 or less. Therefore, it can be said that the fuel cell can exhibit desired performance when the proton conduction resistance is 250 mΩ / cm 2 or less.

[0043] The lower limit value of the proton conduction resistance is not particularly limited. The proton conduction resistance may be 100 mΩ / cm 2 or more.

[0044] The proton conduction resistance is measured for the entire anode catalyst layer 104 and cathode catalyst layer 109. The proton conduction resistance can be measured by the following method. A fuel cell 101 including a single membrane electrode assembly 113 to be measured is prepared. Hydrogen gas with a relative humidity of 100% is supplied to the anode 103 at an appropriate flow rate. Nitrogen gas with a relative humidity of 100% is supplied to the cathode 108 at an appropriate flow rate. The ambient temperature is adjusted so that the temperatures of the anode 103 and cathode 108 are 50°C. The flow rates of the hydrogen gas and nitrogen gas are adjusted so that variations in the moisture content and gas leakage rate within the membrane electrode assembly 113 are sufficiently suppressed. After stabilizing the atmosphere around the anode 103 and cathode 108, an impedance analyzer is connected to the power output terminals, and AC impedance measurement is performed. The measurement is performed, for example, under conditions of a set voltage of 0.2 V, an amplitude of 0.01 V, and a frequency range of 0.1 Hz to 10 kHz. This gives a complex impedance plot.

[0045] FIG. 5 is a diagram illustrating a method for calculating the proton conduction resistance from a complex impedance plot obtained by AC impedance measurement. In the complex impedance plot, a line A is drawn to extrapolate the linear portion on the high frequency side onto the real axis. The value at the intersection of line A and the real axis is taken as the proton conduction resistance R of the electrolyte membrane. pem Next, draw line B to extrapolate the linear portion on the low frequency side to the real axis. Identify the value R on the real axis corresponding to the intersection C of lines A and B. The value R and the proton conduction resistance R of the electrolyte membrane are calculated. pem Difference with (RR pem The overall proton conduction resistance R of the anode catalyst layer 104 and the cathode catalyst layer 109 is calculated. cl is (RR pem )=R cl It can be calculated using the formula / 3.

[0046] FIG. 3 is a partially enlarged view of FIG. 2. As shown in FIG. 3, the resin material 15 forms a plurality (two) of layers 15a and 15b on the surface of the conductive fiber 13. The plurality of layers 15a and 15b include a first resin layer 15a and a second resin layer 15b. The first resin layer 15a is a layer containing a first resin material having proton conductivity and covers at least a part of the surface of the conductive fiber 13. All of the surface of the conductive fiber 13 may be covered by the first resin layer 15a. The second resin layer 15b is a layer containing a second resin material having lower hydrophilicity than the first resin material contained in the first resin layer 15a. The second resin layer 15b covers at least a part of the outer surface of the first resin layer 15a. All of the outer surface of the first resin layer 15a may be covered by the second resin layer 15b.

[0047] According to the above configuration, proton conductivity is imparted to the conductive fiber 13 by the first resin layer 15a, and drainage property is imparted to the conductive fiber 13 by the second resin layer 15b. Therefore, the drainage property of the pores 14 can be enhanced while maintaining proton conductivity. That is, it is possible to achieve both proton conductivity and drainage property in the cathode catalyst layer 109. As a result, flooding can be suppressed and the efficiency of the electrochemical reaction in the cathode catalyst layer 109 can be improved, and thus the efficiency of the fuel cell 101 can be improved.

[0048] The first resin layer 15a may be a proton conduction layer responsible for proton conduction, and the first resin layer 15a may be a layer made of the first resin material. That is, the first resin layer 15a may contain only the first resin material except for inevitable impurities.

[0049] The first resin material may contain a polymer electrolyte or may be the polymer electrolyte itself. According to such a configuration, high proton conductivity can be imparted to the conductive fiber 13.

[0050] Examples of the first resin material include polymer materials having proton-conductive groups such as sulfonic acid groups, phosphoric acid groups, and carboxy groups. Specifically, examples of the first resin material include perfluorocarbon sulfonic acid-based polymer materials and hydrocarbon-based polymer materials.

[0051] Examples of the polymer material having a sulfonic acid group include the polymer material represented by the following formula (1). In formula (1), m and x each independently represent a positive integer.

[0052]

Chemical formula

[0053] The second resin layer 15b can be a hydrophobic layer for enhancing the drainage property of the pores 14. The second resin layer 15b may be a layer made of a second resin material. That is, the second resin layer 15b may contain only the second resin material except for inevitable impurities.

[0054] The second resin material may include a polymer material having no proton-conductive functional group, or may be such a polymer material itself. According to such a configuration, the pores 14 can have high hydrophobicity. Therefore, the drainage property of the cathode catalyst layer 109 can be further enhanced. Here, the proton-conductive functional group means a sulfonic acid group, a phosphoric acid group, a carboxy group, an amino group, or the like.

[0055] Examples of the second resin material include fluororesins. The fluororesin desirably has no proton-conductive functional group. Specifically, examples of the second resin material include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and the like. One or a mixture of two or more selected from these can be used as the second resin material.

[0056] In this embodiment, the degree of hydrophilicity and hydrophobicity of the resin material can be determined by the equivalent weight (EW) of the resin material. The equivalent weight is a value indicating the amount of ion exchange groups in the resin material, and represents the number of grams of the resin material in a dry state containing 1 mole of proton conductive groups (unit: g / mol). The larger the equivalent weight, the lower the hydrophilicity of the resin material. The smaller the equivalent weight, the higher the hydrophilicity of the resin material. The equivalent weight can be 1 specified by 1H-NMR measurement. The fact that the first resin material and the second resin material are included in the cathode catalyst layer 109 can be 1 examined by 1H-NMR measurement.

[0057] The equivalent weight of the first resin material may be smaller than the equivalent weight of the second resin material. According to such a configuration, according to such a configuration, high hydrophobicity can be imparted to the pores 14 while maintaining proton conductivity. Therefore, the drainage property of the cathode catalyst layer 109 can be further enhanced.

[0058] The first resin material may include, for example, a polymer material having an equivalent weight of 500 g / mol or more and 1100 g / mol or less. According to such a configuration, high proton conductivity can be imparted to the conductive fibers 13.

[0059] The second resin material may include, for example, a polymer material having an equivalent weight of 1200 g / mol or more and 2000 g / mol or less. According to such a configuration, high hydrophobicity can be imparted to the pores 14. Therefore, the drainage property of the cathode catalyst layer 109 can be further enhanced.

[0060] The contact angle θ2 of the thin film made of the second resin material with respect to water may be 20 degrees or more larger than the contact angle θ1 of the thin film made of the first resin material with respect to water. According to such a configuration, proton conductivity and drainage can be imparted to the conductive fiber 13. The upper limit of the difference (θ2 - θ1) between the contact angle θ2 and the contact angle θ1 is not particularly limited, and is, for example, 120 degrees. The contact angle (static contact angle) can be measured according to the provisions of Japanese Industrial Standard (JIS) R3257:1999.

[0061] In the present embodiment, the ratio of the total mass of the first resin material and the second resin material to the total mass of the carrier particles 11 and the conductive fiber 13 is, for example, in the range of 0.80 or more and 1.50 or less. According to such a configuration, the resin material 15 can be uniformly adhered to the surface of the conductive fiber 13. Therefore, the proton conduction path is less likely to be interrupted inside the cathode catalyst layer 109. As a result, a cathode catalyst layer 109 having high proton conductivity can be obtained.

[0062] The average length of the conductive fiber 13 may be larger than the average particle diameter of the carrier particles 11. According to such a configuration, pores 14 are likely to be formed between the particles of the electrode catalyst 10 connected by the conductive fiber 13.

[0063] In the cathode catalyst layer 109, the ratio of the mass of the conductive fiber 13 to the total mass of the carrier particles 11, the catalyst particles 12, and the conductive fiber is, for example, in the range of 0.20 or more and 0.50 or less. According to such a configuration, the proton conductivity and drainage in the cathode catalyst layer 109 can be improved. Note that the conductive fiber 13 can be separated from the electrode catalyst 10 by centrifugation.

[0064] FIG. 4 is a process diagram showing a method for manufacturing the cathode catalyst layer 109.

[0065] In step S1, a carrier particle 11 supporting catalyst particles 12, a conductive fiber 13, a first resin material having proton conductivity, and a solvent are mixed to prepare a preliminary solution. The carrier particle 11 supporting the catalyst particles 12 can be produced by a known method (Patent Document 2). Examples of the solvent include water, ethanol, and mixtures thereof. By uniformly dispersing the carrier particle 11 supporting the catalyst particles 12, the conductive fiber 13, and the first resin material in the solvent, a preliminary solution is obtained. In the preliminary solution, the first resin material adheres to the surface of the conductive fiber 13 to form a first resin layer 15a.

[0066] In step S2, a second resin material is dispersed in the preliminary solution to prepare a catalyst ink. The second resin material can be uniformly dispersed in the catalyst ink.

[0067] In step S3, the catalyst ink is applied to a substrate to form a catalyst layer. The substrate is an electrolyte membrane 102, a cathode gas diffusion layer 110, or a transfer film. An example of the catalyst layer is a cathode catalyst layer 109. When the catalyst ink is applied to the substrate and the solvent is removed from the coating film by heating or the like, the second resin material adheres to the outer surface of the first resin layer 15a. Thereby, a second resin layer 15b is formed. According to the manufacturing method of the present embodiment, a catalyst layer having the structure described with reference to FIGS. 2 and 3 can be efficiently manufactured.

[0068] Before moving to step S2, the preliminary solution may be held for a predetermined time. The predetermined time is, for example, from 1 hour to 10 hours. Thereby, the first resin material can be sufficiently adsorbed on the surface of the conductive fiber 13. Holding the preliminary solution may be to let the preliminary solution stand still.

[0069] [1-2. Operation] Regarding the fuel cell 101 configured as described above, its operation and action will be described below with reference to FIG. 1.

[0070] A hydrogen-containing gas is supplied to the anode gas flow path 107. An oxidant gas is supplied to the cathode gas flow path 112. The oxidant gas is typically air. At the anode 103, in the electrochemical reaction represented by the following formula (1), hydrogen (H2) is separated into protons (H + ) and electrons (e - ). The protons conduct through the electrolyte membrane 102 and move from the anode 103 toward the cathode 108. The electrons move from the anode 103 toward the cathode 108 through the external circuit. At the cathode 108, in the electrochemical reaction represented by the following formula (2), water (H2O) is generated by the electrochemical reaction of protons, oxygen (O2), and electrons.

[0071] H2 → 2H + + 2e - (1) 4H + + O2 + 2e - → 2H2O (2)

[0072] [1 - 3. Supplementary Note] With the description of the above embodiments, the following technologies are disclosed.

[0073] (Technology 1) Carrier particles, Catalyst particles supported on the carrier particles, Conductive fibers arranged to contact the carrier particles, A first resin layer containing a first resin material having proton conductivity and covering at least a part of the surface of the conductive fibers, A second resin layer containing a second resin material having lower hydrophilicity than the first resin material and covering at least a part of the outer surface of the first resin layer, A catalyst layer for a membrane electrode assembly, comprising:

[0074] (Technology 2) A catalyst layer for a membrane electrode assembly, comprising: Carrier particles, Catalyst particles supported on the carrier particles, Conductive fibers arranged to contact the carrier particles, The resin material adhered to the conductive fiber, comprising, The resin material includes a first resin material having proton conductivity and a second resin material having lower hydrophilicity than the first resin material. When the alternating current impedance of the membrane electrode assembly including the catalyst layer is measured under the conditions of a temperature of 50 °C and a relative humidity of 100%, the proton conduction resistance of the catalyst layer measured is 250 mΩ / cm 2 or less. A catalyst layer for a membrane electrode assembly.

[0075] According to Technologies 1 and 2, it is possible to improve the efficiency of the electrochemical reaction by achieving both proton conductivity and drainage in the catalyst layer.

[0076] (Technology 3) The catalyst layer for a membrane electrode assembly according to Technology 1 or 2, wherein the first resin material contains a polymer electrolyte. According to such a configuration, high proton conductivity can be imparted to the conductive fiber.

[0077] (Technology 4) The catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 3, wherein the second resin material contains a polymer material having no proton-conductive functional group. According to such a configuration, the pores can have high hydrophobicity.

[0078] (Technology 5) The catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 4, wherein the equivalent mass of the first resin material is smaller than the equivalent mass of the second resin material. According to such a configuration, high hydrophobicity can be imparted to the pores while maintaining proton conductivity.

[0079] (Technology 6) The catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 5, wherein the second resin material contains a polymer material having an equivalent mass of 1200 g / mol or more and 2000 g / mol or less. According to such a configuration, high hydrophobicity can be imparted to the pores.

[0080] (Technology 7) The contact angle of the thin film made of the second resin material with respect to water is 20 degrees or more larger than the contact angle of the thin film made of the first resin material with respect to water, the catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 6. According to such a configuration, proton conductivity and drainage can be imparted to the conductive fibers.

[0081] (Technology 8) The ratio of the total mass of the first resin material and the second resin material to the total mass of the carrier particles and the conductive fibers is in the range of 0.80 or more and 1.50 or less, the catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 7. According to such a configuration, the resin material 15 can be uniformly adhered to the surface of the conductive fibers.

[0082] (Technology 9) The average length of the conductive fibers is larger than the average particle diameter of the carrier particles, the catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 8. According to such a configuration, pores are likely to be formed between the particles of the electrode catalyst connected by the conductive fibers.

[0083] (Technology 10) The ratio of the mass of the conductive fibers to the total mass of the carrier particles, the catalyst particles and the conductive fibers is in the range of 0.20 or more and 0.50 or less, the catalyst layer for a membrane electrode assembly according to any one of Technologies 1 to 9. According to such a configuration, the proton conductivity and drainage in the catalyst layer can be improved.

[0084] (Technology 11) An anode, A cathode, An electrolyte membrane disposed between the anode and the cathode, Comprising, The cathode includes the catalyst layer according to any one of Technologies 1 to 10, Membrane electrode assembly.

[0085] According to Technology 11, the efficiency of the electrochemical reaction can be improved.

[0086] (Technology 12) Preparing a preliminary solution by mixing carrier particles carrying catalyst particles, conductive fibers, a first resin material having proton conductivity, and a solvent; Preparing a catalyst ink by dispersing a second resin material having lower hydrophilicity than the first resin material in the preliminary solution; Forming a catalyst layer by applying the catalyst ink to a substrate; A method for manufacturing a catalyst layer for a membrane electrode assembly, comprising:

[0087] According to the manufacturing method of the present disclosure, the catalyst layer of the present disclosure can be efficiently manufactured.

Industrial Applicability

[0088] The technology of the present disclosure is useful for electrochemical devices such as secondary batteries, fuel cells, and hydrogen purification devices.

Explanation of Reference Numerals

[0089] 10 Electrode catalyst 11 Carrier particles 12 Catalyst particles 13 Conductive fibers 14 Pores 15 Resin material 15a First resin layer 15b Second resin layer 101 Fuel cell 102 Electrolyte membrane 103 Anode 104 Anode catalyst layer 105 Anode gas diffusion layer 106 Anode separator 107 Anode gas flow channel 108 Cathode 109 Cathode catalyst layer 110 Cathode gas diffusion layer 111 Cathode separator 112 Cathode gas flow channel 113 Membrane electrode assembly

Claims

1. Support particles, Catalyst particles supported on the support particles, Conductive fibers arranged in contact with the support particles, A first resin layer containing a first resin material having proton conductivity and covering at least a part of the surface of the conductive fibers, A second resin layer containing a second resin material having lower hydrophilicity than the first resin material and covering at least a part of the outer surface of the first resin layer, A catalyst layer for a membrane electrode assembly, comprising:

2. A catalyst layer for a membrane electrode assembly, comprising: Support particles, Catalyst particles supported on the support particles, Conductive fibers arranged in contact with the support particles, A resin material attached to the conductive fibers, Comprising: The resin material includes a first resin material having proton conductivity and a second resin material having lower hydrophilicity than the first resin material, When the alternating current impedance measurement of the membrane electrode assembly including the catalyst layer is performed under the conditions of a temperature of 50° C. and a relative humidity of 100%, the proton conduction resistance of the catalyst layer measured is 250 mΩ / cm 2 is as follows A catalyst layer for a membrane electrode assembly.

3. The first resin material contains a polymer electrolyte, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

4. The second resin material contains a polymer material having no proton-conductive functional group, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

5. The equivalent mass of the first resin material is smaller than the equivalent mass of the second resin material, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

6. The second resin material includes a polymer material having an equivalent mass of 1200 g / mol or more and 2000 g / mol or less, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

7. The contact angle of the thin film made of the second resin material with respect to water is 20 degrees or more larger than the contact angle of the thin film made of the first resin material with respect to water, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

8. The ratio of the total mass of the first resin material and the second resin material to the total mass of the support particles and the conductive fibers is in the range of 0.80 or more and 1.50 or less, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

9. The average length of the conductive fibers is larger than the average particle diameter of the support particles, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

10. The ratio of the mass of the conductive fibers to the total mass of the support particles, the catalyst particles, and the conductive fibers is in the range of 0.20 or more and 0.50 or less, The catalyst layer for a membrane electrode assembly according to claim 1 or 2.

11. An anode, A cathode, An electrolyte membrane disposed between the anode and the cathode, Comprising: The cathode includes the catalyst layer according to claim 1 or 2, Membrane electrode assembly.

12. Preparing a preliminary solution by mixing carrier particles carrying catalyst particles, conductive fibers, a first resin material having proton conductivity, and a solvent; Preparing a catalyst ink by dispersing a second resin material having lower hydrophilicity than the first resin material in the preliminary solution; Forming a catalyst layer by applying the catalyst ink to a substrate; A method for manufacturing a catalyst layer for a membrane electrode assembly, comprising:

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