Catalyst layer of fuel cell and fuel cell

Abstract

To provide a catalyst layer for a fuel cell, achieving both high conductivity and excellent drainage.SOLUTION: A catalyst layer in the present disclosure is interposed between a gas diffusion layer and an electrolyte membrane of a fuel cell. The catalyst layer includes a first catalyst layer adjacent to the gas diffusion layer and a second catalyst layer adjacent to the electrolyte membrane. The first catalyst layer and the second catalyst layer each include a first conductive material, a second conductive material having a mode diameter smaller than that of the first conductive material, and a catalyst supported on at least one of the first conductive material and the second conductive material. The first catalyst layer has a smaller ratio of weight of the second conductive material relative to the total weight of the first conductive material and the second conductive material than the second catalyst layer. The catalyst layer of the present disclosure is preferably used for a catalyst layer of an electrode on a side where water is generated during power generation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a catalyst layer of a fuel cell and a fuel cell.

Background Art

[0002] Patent Document 1 discloses a technique capable of more efficiently discharging the moisture in the catalyst layer and suppressing flooding of the fuel cell. This fuel cell includes an electrolyte membrane, a catalyst layer formed on the surface of the electrolyte membrane, and a gas diffusion layer formed on the surface of the catalyst layer opposite to the electrolyte membrane.

[0003] This catalyst layer includes an ionomer having proton conductivity, a catalyst carrier at least partially covered with the ionomer, and pores in the catalyst layer that extend from the gas diffusion layer toward the electrolyte membrane. The cross-sectional area of the pores in the direction in which the electrolyte membrane, the catalyst layer, and the gas diffusion layer are laminated is larger on the gas diffusion layer side than on the electrolyte membrane side of the catalyst layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure provides a catalyst layer of a fuel cell having high-efficiency power generation performance by achieving both high conductivity and excellent drainage performance.

Means for Solving the Problems

[0006] The catalyst layer in the present disclosure is a catalyst layer interposed between the gas diffusion layer and the electrolyte membrane of a fuel cell, and this catalyst layer has a first catalyst layer adjacent to the gas diffusion layer and a second catalyst layer adjacent to the electrolyte membrane.

[0007] The first catalyst layer and the second catalyst layer each include a first conductive material, a second conductive material having a smaller mode diameter compared to the first conductive material, and a catalyst supported on at least one of the first conductive material and the second conductive material.

[0008] Furthermore, the first catalyst layer is characterized by having a smaller proportion of the weight of the second conductive material relative to the total weight of the first and second conductive materials compared to the second catalyst layer. [Effects of the Invention]

[0009] The catalyst layer in this disclosure can improve the drainage of the catalyst layer while suppressing the decrease in electrical conductivity due to a reduction in the contact area between conductive materials. Therefore, using the catalyst layer in this disclosure in a fuel cell can improve the power generation performance of the fuel cell. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram showing the general cross-sectional configuration of a fuel cell cell in Embodiment 1. [Figure 2] A schematic diagram showing the general configuration of the cross-section of the catalyst layer in Embodiment 1. [Figure 3] A schematic diagram illustrating the capillary pressure acting on water within a void where the void diameter increases as the direction of movement increases. [Figure 4] Schematic diagram to explain a close-packed sphere structure. [Figure 5] Schematic diagram illustrating the positional relationship between the mesoporous material and the ionomer in the catalyst layer in Embodiment 1. [Modes for carrying out the invention]

[0011] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived of this disclosure, fuel cells were attracting attention as a key device necessary for realizing a decarbonized society because they generate electricity by reacting hydrogen and oxygen and produce only water during the power generation process.

[0012] In order to improve the power generation efficiency of a fuel cell, it is necessary to efficiently discharge the water generated during the power generation reaction so that the reaction gases, oxygen and hydrogen, can reach the catalyst sites without being inhibited.

[0013] As a measure to promote the discharge of the generated water, by utilizing the property that the water in the gaps is pushed out from the smaller-diameter side to the larger-diameter side by capillary pressure, a configuration is adopted to promote drainage from the catalyst layer with a smaller gap diameter toward the gas diffusion layer and the separator with a larger gap diameter.

[0014] However, it has become clear that since the gap diameter distribution in the catalyst layer is approximately constant, the generated water accumulates in the catalyst layer, inhibiting gas diffusion and becoming one of the factors causing a decrease in power generation performance.

[0015] In order to further improve the power generation performance, it is necessary to further improve the drainage property in the catalyst layer, and an idea was obtained to give a distribution in which the gap diameter increases from the electrolyte membrane side toward the gas diffusion layer side in the catalyst layer.

[0016] However, when a single catalyst-supported material is laminated and the gap diameter is controlled by the density of the lamination, the inventors found that the contact area between the catalyst-supported materials decreases in the region with a large gap diameter, resulting in a decrease in conductivity, and it is difficult to achieve both excellent drainage and high conductivity. In order to solve this problem, the inventors have come to form the subject matter of the present disclosure.

[0017] Therefore, the present disclosure provides a catalyst layer and a fuel cell that improve the power generation efficiency in a fuel cell by achieving both excellent drainage and high conductivity.

[0018] 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. This is to avoid making the following description overly redundant and to facilitate the understanding of those skilled in the art.

[0019] The attached 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.

[0020] (Embodiment 1) Hereinafter, Embodiment 1 will be described with reference to FIGS. 1 to 5.

[0021] [1-1. Configuration] (Fuel cell) FIG. 1 shows a configuration example of a fuel cell which is a basic unit of a fuel cell. The fuel cell 7 shown in FIG. 1 is a solid polymer electrolyte fuel cell that generates electricity by reacting hydrogen supplied to the anode and oxygen supplied to the cathode.

[0022] As shown in FIG. 1, the fuel cell 7 has an electrolyte membrane-electrode assembly 6 between an anode separator 5a and a cathode separator 5c.

[0023] The anode separator 5a has a flow path on the surface contacting the anode 2a of the electrolyte membrane-electrode assembly 6 for flowing hydrogen supplied to the fuel cell 7 to the anode 2a of the electrolyte membrane-electrode assembly 6. [[ID=2,7]]

[0024] The cathode separator 5c has a flow path on the surface contacting the cathode 2c of the electrolyte membrane-electrode assembly 6 for flowing oxygen supplied to the fuel cell 7 to the cathode 2c of the electrolyte membrane-electrode assembly 6.

[0025] When the fuel cell 7 has a stack structure, the adjacent anode separator 5a and cathode separator 5c electrically connect the adjacent cells.

[0026] The electrolyte membrane-electrode assembly 6 includes an electrolyte membrane 1, an anode (fuel electrode) 2a including an anode catalyst layer 3a and an anode gas diffusion layer 4a, and a cathode (air electrode) 2c including a cathode catalyst layer 3c and a cathode gas diffusion layer 4c, and is configured to sandwich both sides of the electrolyte membrane 1 between the anode 2a and the cathode 2c.

[0027] (electrolyte membrane) The electrolyte membrane 1 facilitates ion conduction between the anode 2a and the cathode 2c, and therefore needs to possess both ionic conductivity and gas barrier properties. In this embodiment, a perfluorosulfonic acid resin membrane was used as the electrolyte membrane 1. This perfluorosulfonic acid resin membrane is preferred because it has high hydrogen ion conductivity and remains stable even under the power generation environment of a fuel cell.

[0028] (Gas diffusion layer) The anode gas diffusion layer 4a and the cathode gas diffusion layer 4c are layers that possess current collection properties, gas permeability, and water repellency. The anode gas diffusion layer 4a and the cathode gas diffusion layer 4c may also consist of two layers: a substrate and a coating layer.

[0029] The substrate can be any material that has excellent conductivity and permeability to gases and liquids. In this embodiment, carbon paper was used as the substrate.

[0030] The coating layer is interposed between the substrate and the catalyst layer (anode catalyst layer 3a or cathode catalyst layer 3c) to reduce contact resistance and improve liquid permeability (drainage). In this embodiment, the coating layer was formed mainly from a conductive material such as carbon black and a water-repellent resin such as polytetrafluoroethylene (PTFE).

[0031] (catalyst layer) The anode catalyst layer 3a and the cathode catalyst layer 3c are layers that promote the electrochemical reaction between the anode 2a and the cathode 2c.

[0032] The catalyst layers of the anode catalyst layer 3a and the cathode catalyst layer 3c each include a conductive material, a catalyst supported on the conductive material, and an ionomer (hydrogen ion conductive resin) that covers at least a portion of the conductive material.

[0033] As shown in Figure 2, the cathode catalyst layer 3c has a first catalyst layer 11a adjacent to the cathode gas diffusion layer 4c and a second catalyst layer 11b adjacent to the electrolyte membrane 1.

[0034] The first catalyst layer 11a and the second catalyst layer 11b each consist of the first conductive material 10a and, It consists of a second conductive material 10b having a smaller mode diameter compared to the first conductive material 10a, a catalyst 12 supported on at least one of the first conductive material 10a and the second conductive material 10b, and an ionomer 13 covering at least a portion of the first conductive material 10a and the second conductive material 10b.

[0035] Furthermore, the first catalyst layer 11a has a smaller ratio X of the weight of the second conductive material 10b to the total weight of the first conductive material 10a and the second conductive material 10b compared to the second catalyst layer 11b.

[0036] In this embodiment, in order to suppress the decrease in conductivity due to a decrease in the contact area between conductive materials, the ratio X in the first catalyst layer 11a was 0.05, and in order to improve gas diffusion by reducing the thickness of the cathode catalyst layer 3c, the ratio X in the second catalyst layer 11b was 0.3.

[0037] (Conductive materials) In this embodiment, a mesoporous carbon with a mode diameter of approximately 500 nm was used as the first conductive material 10a, and carbon black with a mode diameter of 50 nm was used as the second conductive material 10b. In this embodiment, the mode diameter of the second conductive material 10b was 10% of the mode diameter of the first conductive material 10a.

[0038] (catalyst) As shown in Figure 2, the catalyst 12 is supported on at least the first conductive material 10a of the first conductive material 10a and the second conductive material 10b. In this embodiment, a platinum-containing alloy was used as the catalyst 12. The mode diameter of the catalyst 12 was 5 nm.

[0039] (Ionoma) As shown in Figure 2, ionomer 13 is composed of hydrogen ions (H + ) is a conductive polymer that coats at least a portion of the first conductive material 10a and the second conductive material 10b. In this embodiment, a perfluorosulfonic acid polymer with high hydrogen ion conductivity and stable presence even under the power generation environment of a fuel cell was used as the ionomer 13.

[0040] (Mesoporous material) In this embodiment, the first conductive material 10a is the mesoporous material 14 shown in Figure 5, and the mesoporous material 14 is mesoporous carbon. Before supporting the catalyst 12, the mode diameter of the mesopores 15 of this mesoporous material 14 is 10 nm, and the pore volume of the mesopores 15 is 2.0 cm³. 3 The value was / g. Furthermore, the mode diameter of mesoporous material 14 was 500 nm.

[0041] [1-2. Operation] Based on Figure 1, the operation method and function of the fuel cell cell 7 will be explained. The temperature of the fuel cell cell 7 is set (maintained) at 60°C, hydrogen with a dew point of 60°C is supplied to the flow path of the anode separator 5a at a flow rate of 100 cc / min, and air with a dew point of 60°C is supplied to the cathode separator 5c at a flow rate of 300 cc / min, causing a current of 10 A to flow through the external circuit connecting the anode 2a and cathode 2c.

[0042] Next, we will explain the movement of substances and electrochemical reactions within the electrochemical device during operation. Hydrogen supplied to the channel of the anode separator 5a passes through the anode gas diffusion layer 4a and reaches the catalyst in the anode catalyst layer 3a.

[0043] In the anode catalyst layer 3a, the hydrogen shown in (Chemical Formula 1) is converted into hydrogen ions (H + ) and dissociates into electrons An oxidation reaction occurs, and hydrogen ions (H) are formed. + The ions pass through the anode catalyst layer 3a (ionomer), conduct through the electrolyte membrane 1, and reach the catalyst 12 in the cathode catalyst layer 3c.

[0044] [ka]

[0045] Electrons dissociated in the anode catalyst layer 3a pass through the anode catalyst layer 3a, the anode gas diffusion layer 4a, and the anode separator 5a, then through the electric wire and electronic load device, and finally through the cathode separator 5c, the cathode gas diffusion layer 4c, and the cathode catalyst layer 3c, to reach the catalyst 12 in the cathode catalyst layer 3c.

[0046] Oxygen in the air supplied to the flow path of the cathode separator 5c passes through the cathode gas diffusion layer 4c and reaches the catalyst 12 in the cathode catalyst layer 3c. In the cathode catalyst layer 3c, hydrogen ions (H) as shown in (Chemical Formula 2) are present. + A reduction reaction occurs in which oxygen (O) and electrons combine to produce water.

[0047] [ka]

[0048] In order to improve the power generation performance of the fuel cell cell 7, it is necessary for the raw materials, hydrogen and oxygen, to efficiently reach the anode catalyst layer 3a and cathode catalyst layer 3c, respectively. However, since the water generated during the power generation reaction inhibits gas diffusion in the cathode catalyst layer 3c, it is necessary for the water to be efficiently discharged from the cathode catalyst layer 3c through the cathode gas diffusion layer 4c into the flow path of the cathode separator 5c.

[0049] As shown in Figure 2, the cathode catalyst layer 3c has a smaller mode diameter of the pore on the electrolyte membrane 1 side than on the cathode gas diffusion layer 4c side. The magnitude of the capillary pressure acting at the gas-liquid interface of water accumulated in the pore follows the Young-Laplace equation shown in (Equation 1) and is proportional to the reciprocal of the pore diameter.

[0050] As a result, as shown in Figure 3, the capillary pressure P1 on the surface with a small gap diameter is greater than the capillary pressure P2 on the surface with a large gap diameter. This causes the water accumulated in the gaps in the cathode catalyst layer 3c to be pushed out from the electrolyte membrane 1 side towards the cathode gas diffusion layer 4c side, thus improving drainage. Furthermore, increasing the contact area between conductive materials improves conductivity.

[0051]

number

[0052] As shown in Figure 4, when spheres a of radius r are packed tightly in a hexagonal arrangement, connecting the centers of four adjacent spheres a forms a regular tetrahedron with side length 2r. The distance between the centroid of the regular tetrahedron and its vertices is calculated to be approximately 1.22r, and therefore, when spheres a of radius r are packed tightly in a hexagonal arrangement... The maximum radius of a sphere that can be placed in the gap between four adjacent spheres a is approximately 0.22r.

[0053] Therefore, if the mode diameter of the second conductive material 10b is 22% or less of the mode diameter of the first conductive material 10a, the second conductive material 10b can be placed in the gaps created between the hexagonally close-packed first conductive material 10a, and the mode diameter of the gaps becomes smaller.

[0054] When the mode diameter of the gaps within the cathode catalyst layer 3c decreases, the difference in mode diameter between the cathode catalyst layer 3c and the cathode gas diffusion layer 4c increases. This increases the force of capillary pressure that expels water from the cathode catalyst layer 3c to the cathode gas diffusion layer 4c, thereby improving drainage. Additionally, the contact area between the conductive materials increases, improving the conductivity of the cathode catalyst layer 3c.

[0055] If the first conductive material 10a is a mesoporous material 14 having mesopores 15 inside, and the catalyst 12 is supported within the mesopores 15, then contact between the ionomer 13 and the catalyst 12 within the mesopores 15 can be suppressed.

[0056] Since the mode diameter of the shortest side of the ionomer 13 is 50 nm or more, if the catalyst 12 is supported in a mesopore 15 with a smaller diameter than that, the ionomer 13 cannot enter the mesopore 15, and contact is suppressed. It is known that catalytic activity decreases when the catalyst 12 and the ionomer 13 come into contact, but this decrease in activity can be suppressed by suppressing contact.

[0057] If the first conductive material 10a or the second conductive material 10b is a carbon-based material, the drainage of the cathode catalyst layer 3c is improved. Carbon materials are highly hydrophobic among conductive materials and can improve the drainage of the cathode catalyst layer 3c.

[0058] [1-3. Effects, etc.] As described above, in this embodiment, the cathode catalyst layer 3c has a first catalyst layer 11a adjacent to the cathode gas diffusion layer 4c and a second catalyst layer 11b adjacent to the electrolyte membrane 1.

[0059] The first catalyst layer 11a and the second catalyst layer 11b each include a first conductive material 10a, a second conductive material 10b having a smaller mode diameter compared to the first conductive material 10a, and a catalyst 12 supported on at least one of the first conductive material 10a and the second conductive material 10b.

[0060] Furthermore, the first catalyst layer 11a is characterized in that the ratio of the weight of the second conductive material 10b to the total weight of the first conductive material 10a and the second conductive material 10b is smaller than that of the second catalyst layer 11b.

[0061] As a result, in the cathode catalyst layer 3c, the second catalyst layer 11b adjacent to the electrolyte membrane 1 has a smaller gap mode diameter between conductive materials than the first catalyst layer 11a adjacent to the cathode gas diffusion layer 4c. This improves drainage because the water generated in the cathode catalyst layer 3c during power generation is subjected to a force that pushes it from the electrolyte membrane 1 side towards the cathode gas diffusion layer 4c side due to capillary pressure.

[0062] Furthermore, by increasing the contact area between conductive materials, conductivity can be improved. This allows for the creation of a highly efficient catalyst layer.

[0063] Furthermore, as in this embodiment, the cathode catalyst layer 3c is the motor of the second conductive material 10b. The mode diameter may be 22% or less of the mode diameter of the first conductive material 10a.

[0064] With this configuration, the second conductive material 10b can be placed in the gap between the first conductive material 10a. By reducing the gap between the conductive materials in the cathode catalyst layer 3c, the difference in mode diameter between the cathode catalyst layer 3c and the cathode gas diffusion layer 4c becomes larger, thus improving drainage. As a result, a highly efficient catalyst layer can be obtained.

[0065] Furthermore, as in this embodiment, the first conductive material 10a of the cathode catalyst layer 3c may be a mesoporous material in which at least a portion is coated with an ionomer 13, has mesopores 15 with a mode diameter of 1 to 50 nm inside, and supports the catalyst 12 within the mesopores 15.

[0066] With this configuration, contact between the ionomer 13, which has a mode diameter of several tens of nanometers, and the catalyst 12 supported in the mesopores is suppressed, thereby preventing a decrease in catalytic activity due to contact and enabling the production of a highly efficient catalyst layer.

[0067] Furthermore, as in this embodiment, the second conductive material 10b of the cathode catalyst layer 3c may be a carbon material.

[0068] With this configuration, carbon-based materials, among conductive materials, possess high hydrophobicity, which can further improve the drainage of the cathode catalyst layer 3c and allow for the creation of a highly efficient cathode catalyst layer 3c.

[0069] Alternatively, as in this embodiment, the fuel cell cell 7 may be constructed using the cathode catalyst layer 3c of this embodiment.

[0070] With this configuration, the drainage and conductivity of the cathode catalyst layer 3c are improved compared to conventional cathode catalyst layers, thereby improving the power generation performance of the fuel cell cell 7.

[0071] (Other embodiments) As described above, Embodiment 1 was explained as an example of the technology disclosed in this question. However, the technology in this disclosure is not limited to this and can be applied to embodiments that have been modified, replaced, or added. Furthermore, it is possible to create new embodiments by combining the components described in Embodiment 1 above.

[0072] Therefore, other embodiments are illustrated below.

[0073] In Embodiment 1, a perfluorosulfonic acid resin membrane was described as an example of the electrolyte membrane 1. The electrolyte membrane 1 facilitates ion (hydrogen ion) conduction between the anode 2a and the cathode 2c, and only needs to possess both hydrogen ion conductivity and gas barrier properties. Therefore, the electrolyte membrane 1 is not limited to a perfluorosulfonic acid resin membrane.

[0074] Examples of electrolyte membrane 1 include ion-exchangeable fluororesin membranes or ion-exchangeable hydrocarbon resin membranes. The ion exchange capacity of the ion-exchange resin is preferably 0.9 to 2.0 milliequivalents / g dry resin.

[0075] A ion exchange capacity of 0.9 milliequivalents / g dry resin or higher is preferable because it makes it easier to obtain high hydrogen ion conductivity, and a ion exchange capacity of 2.0 milliequivalents / g dry resin or lower is preferable because it suppresses swelling of the resin due to water content and reduces dimensional changes of the electrolyte membrane 1.

[0076] Furthermore, the thickness of the electrolyte membrane 1 is preferably 5 μm or more and 50 μm or less. A thickness of 5 μm or more provides high gas barrier properties, while a thickness of 50 μm or less provides high hydrogen ion conductivity.

[0077] In Embodiment 1, as an example of the anode gas diffusion layer 4a and cathode gas diffusion layer 4c, the structure includes two layers: a substrate and a coating layer, and carbon paper was used as the substrate. The substrate can be any material that has excellent conductivity and permeability to gases and liquids. Therefore, the substrate is not limited to carbon paper.

[0078] Examples of substrate materials other than carbon paper include porous materials such as carbon fiber cloth and carbon fiber felt.

[0079] In Embodiment 1, the ratio X of the weight of the second conductive material 10b to the total weight of the first conductive material 10a and the second conductive material 10b was 0.05 in the first catalyst layer 11a and 0.3 in the second catalyst layer 11b. The same effect is obtained when the ratio X in the first catalyst layer 11a is 0.01 or more and the ratio X in the second catalyst layer 11b is 0.9 or less.

[0080] In Embodiment 1, mesoporous carbon was used as the first conductive material 10a and carbon black was used as the second conductive material 10b, but the invention is not limited to these.

[0081] Examples of materials for the first conductive material 10a and the second conductive material 10b include carbon-based materials such as Ketjenblack (registered trademark), acetylene black, and Vulcan (registered trademark), metallic materials such as Au and Ni, metal oxide materials such as titanium, tin, niobium, tantalum, zirconium, aluminum, and silicon, and composite materials thereof.

[0082] When a mesoporous material is used as the first conductive material 10a, the mesoporous material has a mode diameter of 1 to 50 nm and a pore volume of 1.0 to 3.0 cm³ before the catalyst 12 is supported on it. 3 / g is also acceptable.

[0083] The pore volume of mesopore 15 is 1.0 cm³. 3If the amount is 3.0 cm or more, a large amount of catalyst 12 can be supported inside the mesoporous material. 3 If the value is less than / g, the structural strength of the mesoporous material increases.

[0084] Furthermore, the mesoporous material may be configured such that its mode diameter is 200 to 1000 nm. If the mode diameter is 200 nm or greater, the region in which the ionomer 13 penetrates the mesopore 15 becomes smaller relative to the pore volume of the mesopore 15, thus reducing the proportion of the catalyst 12 that is affected by poisoning from the ionomer 13.

[0085] Therefore, it is thought that catalytic activity can be improved by setting the mode diameter to 200 nm or more. Also, if the mode diameter is 1000 nm or less, the reaction gas is more easily supplied to the catalyst supported inside the mesoporous material.

[0086] In Embodiment 1, a platinum-containing alloy was used as an example of catalyst 12. Catalyst 12 is not particularly limited as long as it has catalytic activity for hydrogen gas or oxygen gas.

[0087] Examples of materials for catalyst 12 include platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh), palladium (Pd), osmium (Os), tungsten (W), lead (Pb), iron (Fe), chromium (Cr), cobalt (Co), nickel (Ni), manganese (Mn), vanadium (V), molybdenum (Mo), gallium (Ga), and Examples include metals such as aluminum (Al), mixtures of these metals, and alloys. However, from the viewpoint of improving catalytic activity, toxicity to carbon monoxide, heat resistance, etc., platinum, mixtures containing platinum, or alloys are preferred.

[0088] When the catalyst 12 is made of an alloy, the composition of the alloy depends on the type of metals being alloyed, but the platinum content can be 30 to 90 atomic percent, and the content of other metals can be 10 to 70 atomic percent. The mode diameter of the catalyst 12 is not particularly limited, but from the viewpoint of improving catalyst utilization and supportability in the catalyst-supporting material, it is preferably 1 to 30 nm. When supported in the mesopores 15 of a mesoporous material, a mode diameter smaller than the mode diameter of the mesopores is preferred.

[0089] In Embodiment 1, a fuel cell cell 7 was described in which the electrolyte membrane 1 was a hydrogen ion conductive membrane and the catalyst layer of this disclosure was used as the cathode catalyst layer 3c. However, in a fuel cell cell using a hydroxide ion conductive membrane as the electrolyte membrane, it is preferable to use the catalyst layer of this disclosure as the anode catalyst layer.

[0090] In a fuel cell using a hydroxide ion conductive membrane as the electrolyte membrane, the reaction shown in (Chemical Formula 3) occurs in the anode catalyst layer to which hydrogen is supplied, and the reaction shown in (Chemical Formula 4) occurs in the cathode catalyst layer to which oxygen is supplied.

[0091] [ka]

[0092] [ka]

[0093] In fuel cell cells using a hydroxide ion conductive membrane as the electrolyte membrane, water is generated in the anode catalyst layer. Therefore, it is necessary to efficiently drain the generated water from the anode catalyst layer, and improving the drainage capacity of the anode catalyst layer is necessary for performance improvement. By using the catalyst layer of this disclosure as the anode catalyst layer, the anode catalyst layer has excellent drainage capacity and high conductivity, which can improve the performance of the fuel cell cell.

[0094] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the claims or their equivalents. [Industrial applicability]

[0095] This disclosure provides a catalyst layer with excellent drainage and high conductivity, and is applicable to catalyst layers in fuel cells. [Explanation of symbols]

[0096] 1 Electrolyte membrane 2a Anode 2c Cathode 3a Anode catalyst layer 3c Cathode Catalyst Layer 4a Anode gas diffusion layer 4c Cathode gas diffusion layer 5a Anode separator 5c Cathode Separator 6 Electrolyte membrane-electrode assembly 7 Fuel cell 10a First conductive material 10b Second conductive material 11a First catalyst layer 11b Second catalyst layer 12 Catalyst 13 Ionoma 14 Mesoporous materials 15 Mesopores

Claims

1. A catalyst layer interposed between the gas diffusion layer and the electrolyte membrane of a fuel cell, The catalyst layer comprises a first catalyst layer adjacent to the gas diffusion layer and a second catalyst layer adjacent to the electrolyte membrane. The first catalyst layer and the second catalyst layer each include a first conductive material, a second conductive material having a smaller mode diameter than the first conductive material, and a catalyst supported on at least one of the first conductive material and the second conductive material. The first catalyst layer has a smaller proportion of the weight of the second conductive material relative to the total weight of the first and second conductive materials compared to the second catalyst layer. A catalyst layer characterized in that the mode diameter of the second conductive material is 22% or less of the mode diameter of the first conductive material.

2. The invention further comprises an ionomer covering at least a portion of the first conductive material, The first conductive material is a mesoporous material having mesopores with mode diameters of 1 to 50 nm inside, The catalyst layer according to claim 1, characterized in that at least a portion of the catalyst is supported in the mesopores.

3. The catalyst layer according to claim 1 or 2, characterized in that the second conductive material is a conductive carbon material.

4. A fuel cell characterized in that the catalyst layer described in any one of claims 1 to 3 is used as the catalyst layer of the electrode on the side where water is generated during power generation.

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