Electrode, electrolysis cell, and carbon dioxide reduction device

Abstract

The electrode has a catalyst layer and a gas diffusion layer. The catalyst layer is formed by a skeleton and pores. The skeleton is formed from a metal. The gas diffusion layer covers the catalyst layer. The gas diffusion layer is formed from a porous material. The gas diffusion layer has a first surface and a second surface. The first surface faces the skeleton. The second surface is opposite from the first surface. The contact angle of ultrapure water dripped onto the second surface is 115-140°. Part of the gas diffusion layer is inside the pores.

Description

Electrodes, electrolytic cells, and carbon dioxide reduction devices

[0001] This disclosure relates to electrodes, electrolytic cells, and carbon dioxide reduction devices. This application claims priority under Japanese Patent Application No. 2024-202611, filed on November 20, 2024. All provisions contained in said Japanese Patent Application are incorporated herein by reference.

[0002] In recent years, efforts have been made to promote the use of renewable energy and hydrogen in order to achieve carbon neutrality. However, carbon dioxide (CO2) ２ ) emissions will never be zero. Therefore, in order to achieve carbon neutrality, CO ２ Technology for collecting CO ２ The development of technologies that utilize this is needed.

[0003] Japanese Patent Publication No. 2013-544957 (Patent Document 1) contains CO ２ An apparatus for electrochemically reducing CO2 to formate or formic acid is described. The apparatus comprises an electrochemical reactor, an anode, a porous cathode, and a diffuser adjacent to the cathode. The cathode separates the cathodelime compartment from the gas compartment. The cathodelime is introduced into the cathodelime compartment and CO2 is introduced into the gas compartment. ２ A gas is introduced, and a DC voltage is applied between the anode and cathode. This results in CO ２ At least a portion of it is converted to formate.

[0004] Special Publication No. 2013-544957

[0005] The electrode according to this disclosure comprises a catalyst layer and a gas diffusion layer. The catalyst layer is formed of a framework and pores. The framework is made of metal. The gas diffusion layer covers the catalyst layer. The gas diffusion layer is made of a porous material. The gas diffusion layer has a first surface and a second surface. The first surface faces the framework. The second surface is opposite the first surface. The contact angle of ultrapure water dropped onto the second surface is 115° to 140°. A portion of the gas diffusion layer penetrates into the pores.

[0006] Figure 1 is a schematic cross-sectional view showing the configuration of the electrode according to this embodiment. Figure 2 is an enlarged schematic plan view showing the configuration of the catalyst layer. Figure 3 is an enlarged schematic cross-sectional view showing the configuration of the catalyst layer. Figure 4 is an enlarged schematic cross-sectional view showing region IV in Figure 1. Figure 5 is a schematic diagram showing the configuration of the carbon dioxide reduction device according to this embodiment. Figure 6 is a schematic diagram showing the operation of the carbon dioxide reduction device according to this embodiment. Figure 7 is a scanning electron microscope image showing a cross-section of the electrode according to the example.

[0007] According to the apparatus described in Patent Document 1, due to the porous nature of both the cathode and the diffuser, the cathode liquid (electrolyte) may leak to the outside of the diffuser through the cathode and the diffuser (gas diffusion layer).

[0008] This disclosure has been made in view of the above-mentioned problems, and its purpose is to provide an electrode, an electrolytic cell, and a carbon dioxide reduction device capable of preventing leakage of electrolyte from a gas diffusion layer.

[0009] According to this disclosure, it is possible to provide electrodes, electrolytic cells, and carbon dioxide reduction devices that can prevent leakage of electrolyte from a gas diffusion layer.

[0010] First, embodiments of the present disclosure will be listed and described. (1) The electrode according to the present disclosure comprises a catalyst layer and a gas diffusion layer. The catalyst layer is formed of a skeleton and pores. The skeleton is made of metal. The gas diffusion layer covers the catalyst layer. The gas diffusion layer is made of a porous material. The gas diffusion layer has a first surface and a second surface. The first surface faces the skeleton. The second surface is opposite the first surface. The contact angle of ultrapure water dropped onto the second surface is 115° or more and 140° or less. A portion of the gas diffusion layer extends into the pores. This prevents leakage of electrolyte from the gas diffusion layer.

[0011] (2) In the electrode according to (1) above, the gas diffusion layer may have a first part and a second part. The first part may extend into the interior of the pores. The second part may be connected to the first part. The second part may face the framework. The maximum thickness of the first part may be greater than the maximum thickness of the second part. This makes it possible to more reliably prevent leakage of the electrolyte from the gas diffusion layer.

[0012] (3) In the electrode according to (2) above, the maximum thickness of the first portion may be 1.3 times or more and 4 times or less the maximum thickness of the second portion. By having the maximum thickness of the first portion be 1.3 times or more the maximum thickness of the second portion, leakage of the electrolyte from the gas diffusion layer can be prevented more reliably.

[0013] (4) In the case of the electrode according to (2) or (3) above, the maximum thickness of the first portion may be 7 μm or more and 30 μm or less. By having a maximum thickness of 7 μm or more for the first portion, leakage of the electrolyte from the gas diffusion layer can be prevented more reliably.

[0014] (5) In the case of an electrode according to any of (2) to (4) above, in a cross section parallel to the thickness direction of the gas diffusion layer, the width of the second portion in the direction perpendicular to the thickness direction of the gas diffusion layer may be 1 to 4 times the width of the first portion in the direction perpendicular to the thickness direction of the gas diffusion layer. This allows for sufficient supply of electrolyte to the interface between the catalyst layer and the gas diffusion layer, and for a sufficient increase in the contact area between the catalyst layer and the gas diffusion layer.

[0015] (6) In the case of the electrode according to any of (1) to (5) above, the surface of the catalyst layer may contain at least one of copper, tin, and zinc. This allows CO ２ This can improve the reaction efficiency of reduction reactions.

[0016] (7) In the case of an electrode according to any of (1) to (6) above, the gas diffusion layer may be formed of an insulating material. This prevents unintended reactions from occurring in the gas diffusion layer.

[0017] (8) In the electrode according to (7) above, the gas diffusion layer may be mainly composed of polytetrafluoroethylene. This makes it possible to more reliably prevent the electrolyte from leaking to the outside of the gas diffusion layer through the gas diffusion layer.

[0018] (9) In the case of an electrode according to any of (1) to (8) above, the peel strength between the catalyst layer and the gas diffusion layer may be 0.02 N / cm or more and 0.2 N / cm or less. By having a peel strength of 0.02 N / cm or more between the catalyst layer and the gas diffusion layer, it is possible to prevent the catalyst layer and the gas diffusion layer from peeling off.

[0019] (10) In the case of an electrode according to any of (1) to (9) above, the framework may have an internal space. In a cross section parallel to the thickness direction of the gas diffusion layer, the width of the internal space in the direction perpendicular to the thickness direction of the gas diffusion layer may be greater than the length of the internal space in the thickness direction of the gas diffusion layer. This increases the contact area between the catalyst layer and the gas diffusion layer.

[0020] (11) In the case of an electrode according to any of (1) to (10) above, the skeleton may have a third surface and a fourth surface. The third surface may face the gas diffusion layer. The fourth surface may be opposite the third surface. The third surface may have an uneven surface. The fourth surface may have a flat surface. This increases the contact area between the third surface and the gas diffusion layer.

[0021] (12) In the case of an electrode according to any of (1) to (11) above, the average diameter of the pores, when viewed parallel to the thickness direction of the gas diffusion layer and in the direction from the catalyst layer toward the gas diffusion layer, may be 20 μm or more and 70 μm or less. This allows for sufficient supply of electrolyte to the interface between the catalyst layer and the gas diffusion layer, and for a sufficient increase in the contact area between the catalyst layer and the gas diffusion layer.

[0022] (13) In the case of an electrode according to any of (1) to (12) above, the Gurley seconds of the gas diffusion layer may be 15 seconds or more and 600 seconds or less. By having a Gurley seconds of 600 seconds or less for the gas diffusion layer to be CO ２ It allows sufficient gas permeability.

[0023] (14) According to the electrode according to any one of (1) to (13) above, the maximum thickness of the catalyst layer may be 50 μm or more and 300 μm or less.

[0024] (15) According to the electrode according to any one of (1) to (14) above, the catalyst layer may have a three-dimensional network structure.

[0025] (16) The electrolytic cell according to the present disclosure has a container, an ion exchange membrane, a cathode, and an anode. The ion exchange membrane partitions the inside of the container into a first space and a second space. The cathode is disposed inside the first space. The anode is disposed inside the second space. The cathode is the electrode according to any one of (1) to (15) above. Thereby, leakage of the electrolytic solution from the gas diffusion layer of the cathode can be prevented.

[0026] (17) The carbon dioxide reduction device according to the present disclosure has the electrolytic cell according to (16) above, a gas supply device, a power source, a recovery device, and a circulation device. The gas supply device supplies a gas containing carbon dioxide to the cathode. The power source applies a DC voltage between the cathode and the anode. The recovery device recovers the product generated by the reaction of the gas at the cathode. The circulation device circulates the electrolytic solution accommodated inside the container. Thereby, leakage of the electrolytic solution from the gas diffusion layer of the cathode can be prevented.

[0027] Hereinafter, embodiments of the present disclosure (also referred to as the present embodiment) will be described based on the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0028] (Electrode) First, the configuration of the electrode 10 according to the present embodiment will be described. FIG. 1 is a schematic cross-sectional view showing the configuration of the electrode 10 according to the present embodiment. As shown in FIG. 1, the electrode 10 has a catalyst layer 1 and a gas diffusion layer 2. The catalyst layer 1 and the gas diffusion layer 2 are joined. Specifically, the catalyst layer 1 and the gas diffusion layer 2 are joined by pressure bonding. The electrode 10 is a gas diffusion electrode.

[0029] The outer shape of the catalyst layer 1 is sheet-like. The catalyst layer 1 is formed of a metal porous body. The catalyst layer 1 is configured such that gas and liquid can flow along the thickness direction of the catalyst layer 1. The catalyst layer 1 has a third surface 11 and a fourth surface 12. The third surface 11 faces the gas diffusion layer 2. The fourth surface 12 is opposite to the third surface 11.

[0030] The outer shape of the gas diffusion layer 2 is sheet-like. The gas diffusion layer 2 is configured such that gas can flow along the thickness direction of the gas diffusion layer 2. The gas diffusion layer 2 is formed of a hydrophobic porous material. The gas diffusion layer 2 is formed of an insulating material. Specifically, the gas diffusion layer 2 is formed of, for example, a resin material. More specifically, the gas diffusion layer 2 mainly contains, for example, polytetrafluoroethylene. Here, the main component refers to a component having a content of 50% by mass or more.

[0031] The gas diffusion layer 2 has a first surface 21 and a second surface 22. The first surface 21 faces the catalyst layer 1. The first surface 21 is in contact with the third surface 11. The second surface 22 is opposite to the first surface 21.

[0032] The direction from the catalyst layer 1 toward the gas diffusion layer 2 is defined as the first direction 101. The first direction 101 is parallel to each of the thickness direction of the catalyst layer 1 and the thickness direction of the gas diffusion layer 2. The maximum thickness (the fourth thickness T4) of the electrode 10 in the first direction 101 is, for example, 0.09 mm or more and 0.3 mm or less.

[0033] FIG. 2 is an enlarged plan schematic view showing the configuration of the catalyst layer 1. In FIG. 2, the configuration of the catalyst layer 1 as viewed in the first direction 101 is shown. As shown in FIG. 2, the catalyst layer 1 has a skeleton 16. The skeleton 16 forms a three-dimensional network structure. In other words, the catalyst layer 1 has a three-dimensional network structure. The skeleton 16 is formed of a metal. Details of the material of the skeleton 16 will be described later.

[0034] Figure 3 is a schematic cross-sectional view showing the internal structure of the catalyst layer 1 according to this embodiment. As shown in Figure 3, the framework 16 is provided with an internal space 18. The framework 16 has, for example, a main portion 31 and a coating layer 32. The main portion 31 is formed of a metal such as copper (Cu) and nickel (Ni).

[0035] The coating layer 32 covers at least a portion of the main portion 31. In other words, the coating layer 32 forms at least a portion of the surface of the framework 16. The coating layer 32 may cover the entire main portion 31.

[0036] The coating layer 32 is, for example, a plating layer. The coating layer 32 is formed of a metal. The coating layer 32 is formed of, for example, at least one of copper (Cu), tin (Sn), and zinc (Zn). In other words, the surface of the catalyst layer 1 contains at least one of copper, tin, and zinc. Note that the framework 16 does not have a coating layer 32. In this case, the surface of the catalyst layer 1 is formed by the main part 31.

[0037] Figure 4 is an enlarged schematic cross-sectional view showing region IV of Figure 1. Figure 4 shows a cross-section parallel to the thickness direction of the gas diffusion layer 2. As shown in Figure 4, in cross-sectional view, the framework 16 is stacked along the first direction 101. The framework 16 forms the third surface 11 and the fourth surface 12 of the catalyst layer 1 (see Figure 1), respectively. In other words, the framework 16 has a third surface 11 and a fourth surface 12.

[0038] The third surface 11 is the surface of the skeleton 16 that is visible when the skeleton 16 is viewed in the direction opposite to the first direction 101. In other words, the third surface 11 is the surface of the skeleton 16 that is exposed when the catalyst layer 1 is viewed in the direction opposite to the first direction 101.

[0039] The third surface 11 has an uneven surface. The third surface 11 may be formed by an uneven surface, for example. In other words, in a cross-sectional view, the third surface 11 may be formed by a curve, for example. The third surface 11 may have a flat portion. In other words, in a cross-sectional view, a part of the third surface 11 may be straight.

[0040] The fourth surface 12 is a surface of the skeleton 16 that is visible when the skeleton 16 is viewed in the first direction 101. In other words, the fourth surface 12 is a surface of the skeleton 16 that is exposed when the skeleton 16 is viewed in the first direction 101.

[0041] The fourth surface 12 has a flat portion 14 and a recess 15. In cross-sectional view, the flat portion 14 is linear. In cross-sectional view, the flat portion 14 extends along a second direction 102. The second direction 102 is perpendicular to the thickness direction of the gas diffusion layer 2 in cross-sectional view. The second direction 102 is perpendicular to the first direction 101.

[0042] There may be multiple flat sections 14 in a cross-sectional view. In a cross-sectional view, each of the multiple flat sections 14 is parallel to the others. In a cross-sectional view, each of the multiple flat sections 14 may lie on the same straight line.

[0043] In cross-sectional view, the recess 15 is curved. The recess 15 is recessed in the first direction 101 relative to the flat portion 14. From another point of view, the recess 15 is located in the first direction 101 relative to the flat portion 14. A protrusion (not shown) may be provided in the recess 15. The area of ​​the recess 15 on the fourth surface 12 is smaller than the area of ​​the uneven portion on the third surface 11.

[0044] The framework 16 forms the pores 19. From another perspective, the catalyst layer 1 (see Figure 1) is formed by the framework 16 and the pores 19. The pores 19 penetrate the third surface 11 and the fourth surface 12. The pores 19 are configured to allow the flow of gas and liquid.

[0045] The average diameter of the pores 19 when viewed in the first direction 101 is between 20 μm and 70 μm. The average diameter of the pores 19 can be measured using, for example, a Keyence VHX series digital microscope. Specifically, light is shone onto the electrode 10 in the direction opposite to the first direction 101. The light transmitted through the electrode 10 is observed. Using the automatic detection function of the digital microscope, the outer edge of the portion of the pores 19 that penetrates the catalyst layer 1 along the first direction 101 (penetration portion) is identified. When viewed in the first direction 101, the maximum distance between two points on the outer edge of the penetration portion is calculated as the maximum diameter of the penetration portion. The average value of the maximum diameter of the penetration portion is taken as the average value of the diameter of the pores 19 when viewed in the first direction 101. The lens magnification is, for example, 50x.

[0046] The average diameter of the pores 19 when viewed in the first direction 101 may be 25 μm or more, or 30 μm or more. The average diameter of the pores 19 may be 65 μm or less, or 60 μm or less.

[0047] As shown in Figure 4, the gas diffusion layer 2 covers the catalyst layer 1. The first surface 21 faces the framework 16. Specifically, the first surface 21 and the third surface 11 face each other. The gas diffusion layer 2 is in contact with the third surface 11 of the framework 16. Although not shown in Figure 4, the gas diffusion layer 2 has numerous minute pores.

[0048] The gas diffusion layer 2 has a first portion 26 and a second portion 27. The first portion 26 is the part of the gas diffusion layer 2 that penetrates into the pores 19 of the catalyst layer 1. In other words, a part of the gas diffusion layer 2 penetrates into the pores 19. The first portion 26 is exposed from the framework 16 when viewed in the first direction 101. From another point of view, the first portion 26 is located within the portion (penetration) of the pores 19 that penetrates the catalyst layer 1 along the first direction 101. The first portion 26 is convex in the direction opposite to the first direction 101.

[0049] The second part 27 is connected to the first part 26. In a cross-sectional view, the first part 26 and the second part 27 are arranged alternately along the second direction 102. The second part 27 faces the skeleton 16. Specifically, the second part 27 faces the third surface 11 of the skeleton 16.

[0050] The second portion 27 is the portion of the gas diffusion layer 2 located in the first direction 101 relative to the framework 16. From another perspective, when viewed in the first direction 101, the second portion 27 is covered by the framework 16. The second portion 27 is in contact with the third surface 11 of the framework 16. A gap is provided between the second portion 27 and the framework 16. In the first direction 101, the distance between the second portion 27 and the flat portion 14 of the fourth surface 12 is longer than the distance between the first portion 26 and the flat portion 14.

[0051] The maximum thickness of the first portion 26 is defined as the first thickness T1. The first thickness T1 is the maximum distance in the first direction 101 between the first surface 21 and the second surface 22 formed by the first portion 26. The maximum thickness of the second portion 27 is defined as the second thickness T2. The second thickness T2 is the maximum distance in the first direction 101 between the first surface 21 and the second surface 22 formed by the second portion 27.

[0052] The first thickness T1 is thicker than the second thickness T2. The first thickness T1 is, for example, 1.3 times or more and 4 times or less than the second thickness T2. The first thickness T1 may be, for example, 1.5 times or more and 2 times or more the second thickness T2. The first thickness T1 may be, for example, 3.8 times or less and 3.5 times or less.

[0053] The first thickness T1 is, for example, 7 μm or more and 30 μm or less. The first thickness T1 may be, for example, 10 μm or more, or 13 μm or more. The first thickness T1 may be 27 μm or less, or 25 μm or less.

[0054] In a cross-sectional view, the width of the first portion 26 in the second direction 102 is defined as the first width W1. If there are multiple first portions 26 in the cross-sectional view, the first width W1 is defined as the sum of the widths of each of the multiple first portions 26 in the cross-sectional view. In a cross-sectional view, the width of the second portion 27 in the second direction 102 is defined as the second width W2. If there are multiple second portions 27 in the cross-sectional view, the second width W2 is defined as the sum of the widths of each of the multiple second portions 27 in the cross-sectional view.

[0055] The second width W2 is, for example, 1 to 4 times the first width W1. The second width W2 may be 1.2 times or more the first width W1, or 1.5 times or more the first width W1. The second width W2 may be 3.8 times or less the first width W1, or 3.5 times or less the first width W1.

[0056] As shown in Figure 4, a plurality of internal spaces 18 are provided in cross-sectional view. In cross-sectional view, each of the plurality of internal spaces 18 is separated from each other by the framework 16. Each of the plurality of internal spaces 18 may also be separated from each other by the main part 31 of the framework 16.

[0057] Each of the multiple internal spaces 18 is separated from the pores 19 by, for example, the framework 16. Each of the multiple internal spaces 18 may also be connected to the outside of the framework 16. From another point of view, the framework 16 may be provided with gaps (not shown) that connect to the internal spaces 18.

[0058] In a cross-sectional view, the internal space 18 extends along the second direction 102. In a cross-sectional view, the width of the internal space 18 in the second direction 102 (third width W3) is greater than the length L of the internal space 18 in the thickness direction of the gas diffusion layer 2. The third width W3 is, for example, 1.3 times or more and 10 times or less of the length L.

[0059] The maximum thickness (third thickness T3) of the catalyst layer 1 is 50 μm or more and 300 μm or less. The third thickness T3 is the maximum distance between the third surface 11 and the fourth surface 12 in the first direction 101. The third thickness T3 may be, for example, 65 μm or more, or 80 μm or more. The third thickness T3 may be, for example, 280 μm or less, or 260 μm or less. The third thickness T3 may be thicker than the first thickness T1.

[0060] Each of the above-mentioned first thickness T1, second thickness T2, third thickness T3, first width W1, second width W2, and third width W3 can be measured by creating a cross-section by cutting the electrode 10 and observing the cross-section using a scanning electron microscope. Specifically, the electrode 10, cut to approximately 1 cm x 1 cm, is embedded in epoxy resin while fixed perpendicular to the processing surface, and the processing surface is polished with a polishing machine to create a cross-section. As a scanning electron microscope, for example, the "Miniscope TM3030Plus" (trademark) scanning electron microscope manufactured by Hitachi High-Tech Corporation can be used.

[0061] The contact angle of ultrapure water dropped onto the second surface 22 is used as an indicator of the hydrophobicity of the gas diffusion layer 2. The contact angle of ultrapure water dropped onto the second surface 22 is between 115° and 140°. The contact angle of ultrapure water dropped onto the second surface 22 may be, for example, 117° or higher, or 119° or higher. The contact angle of ultrapure water dropped onto the second surface 22 may be, for example, 138° or lower, or 135° or lower. The contact angle can be measured using the "CONTACT ANGLE METER CA-D" (trademark) manufactured by Kyowa Interface Science Co., Ltd., in accordance with the static drop method of JIS (Japanese Industrial Standards) R 3257:1999. The electrical resistivity of ultrapure water is, for example, between 15 MΩ·cm and 18.2 MΩ·cm.

[0062] The Gurley seconds of the gas diffusion layer 2 are between 15 seconds and 600 seconds. The Gurley seconds are an indicator of how easily gases pass through the membrane. The Gurley seconds may be, for example, 20 seconds or more, or 25 seconds or more. The Gurley seconds may be, for example, 400 seconds or less, or 200 seconds or less.

[0063] The Gurley seconds are measured by the following method. First, the catalyst layer 1 is peeled off from the gas diffusion layer 2. The Gurley seconds of the gas diffusion layer 2 are measured using a Wangyan permeability tester in accordance with JIS P 8117:2009. Specifically, 100 ml of air is permeated at a differential pressure of 1.22 kPa with respect to a membrane effective area of 6.42 cm ２ and the time required for permeation is measured. The measured time is defined as the Gurley seconds of the gas diffusion layer 2.

[0064] The peel strength between the catalyst layer 1 and the gas diffusion layer 2 is 0.02 N / cm or more and 0.2 N / cm or less. The peel strength between the catalyst layer 1 and the gas diffusion layer 2 may be, for example, 0.05 N / cm or more, or may be 0.1 N / cm or more. The peel strength between the catalyst layer 1 and the gas diffusion layer 2 may be, for example, 0.18 N / cm or less, or may be 0.15 N / cm or less.

[0065] For the measurement of the peel strength, for example, a tabletop tester "EZtest EZ-LX" (trademark) manufactured by Shimadzu Corporation can be used. The peel strength is measured by a 180-degree peel test. Specifically, first, the electrode 10 is cut into a size of 20 mm × 50 mm. A portion 30 mm from one end in the longitudinal direction of the cut electrode 10 is peeled off.

[0066] With the peeled portion of the gas diffusion layer 2 bent at 180°, the end of the peeled gas diffusion layer 2 is attached to the upper chuck of the measuring device. Next, the end of the peeled catalyst layer 1 is attached to the lower chuck of the measuring device. Using the upper chuck and the lower chuck, the tensile strength is measured by pulling the gas diffusion layer 2 and the catalyst layer 1 upward and downward, respectively. The pulling speed is 10 mm / min. The average value of the tensile strength between a displacement of 5 mm or more and 10 mm or less is defined as the peel strength.

[0067] <Method for manufacturing electrode> Next, a method for manufacturing the electrode 10 will be described.

[0068] The electrode 10 is manufactured using rolling processing. First, a catalyst layer material and a gas diffusion layer material are prepared. The catalyst layer material forms the catalyst layer 1. The gas diffusion layer material forms the gas diffusion layer 2.

[0069] The catalyst layer material has, for example, a three-dimensional network structure. The surface of the catalyst layer material contains at least one of copper, tin, and zinc. As the catalyst layer material, for example, tin-plated copper cellmet (trademark) is prepared. The thickness of the cellmet is, for example, 1 mm. The number of cells in the cellmet is, for example, 47 cells / inch. The weight of tin plating in the cellmet per unit area is, for example, 180 g / m². ２ It is said that the weight of copper in a cellmet per unit area is, for example, 180 g / m². ２ It is said that...

[0070] The gas diffusion layer material is formed from a hydrophobic porous material. For example, Poreflon (trademark) manufactured by Sumitomo Electric Industries is prepared as the gas diffusion layer material. The Poreflon model number is, for example, FP-500-100. The pore size of Poreflon is, for example, 5 μm. The thickness of Poreflon is, for example, 100 μm.

[0071] Next, the catalyst layer material and the gas diffusion layer material are rolled. Specifically, for example, the catalyst layer material and the gas diffusion layer material are rolled under the condition that the roll press spacing is 0.3 mm. Next, for example, the catalyst layer material and the gas diffusion layer material are rolled under the condition that the roll press spacing is 0.1 mm. In the rolling process, for example, with the protective sheet of Poreflon attached to the Poreflon, the Cellmet and Poreflon are rolled. The electrode 10 is manufactured by the above process.

[0072] (Carbon dioxide reduction device and electrolytic cell) Next, the configuration of the carbon dioxide reduction device 200 and the electrolytic cell 100 according to this embodiment will be described.

[0073] Figure 5 is a schematic diagram showing the configuration of the carbon dioxide reduction device 200 according to this embodiment. As shown in Figure 5, the carbon dioxide reduction device 200 mainly comprises an electrolytic cell 100 and a power supply 51.

[0074] The electrolytic cell 100 includes a container 43, an ion exchange membrane 42, a cathode 40, and an anode 41. A space is provided inside the container 43. The ion exchange membrane 42 is located inside the container 43. The ion exchange membrane 42 divides the inside of the container 43 into a first space 91 and a second space 92. For example, Nafion™ is used as the ion exchange membrane 42.

[0075] The cathode 40 is located inside the first space 91. The cathode 40 is the electrode 10 (see Figure 1) according to the above embodiment. In other words, the cathode 40 has a catalyst layer 1 and a gas diffusion layer 2. The cathode 40 divides the first space 91 into a cathode section 97 and a gas section 96, for example. The second space 92 and the cathode section 97 are each portions in which the electrolyte 99 is contained.

[0076] The catalyst layer 1 of the cathode 40 faces the cathode portion 97. From another perspective, the catalyst layer 1 faces the ion exchange membrane 42. The gas diffusion layer 2 of the cathode 40 faces the gas portion 96. The anode 41 is located inside the second space 92. The anode 41 is formed of, for example, platinum.

[0077] The power supply 51 is electrically connected to the catalyst layer 1 of the cathode 40 and the anode 41, respectively. The power supply 51 applies a DC voltage between the cathode 40 and the anode 41. The power supply 51 is located outside the container 43.

[0078] The carbon dioxide reduction device 200 includes a gas cylinder 54, a gas supply device 55, and a gas circulation device 56. The gas cylinder 54 stores gas containing carbon dioxide. The gas supply device 55 supplies gas containing carbon dioxide from the gas cylinder 54 to the cathode 40. Specifically, the gas supply device 55 supplies gas containing carbon dioxide to the gas section 96 of the container 43. Hereinafter, the gas containing carbon dioxide will also be referred to as the supply gas.

[0079] The gas circulation device 56 is connected to the gas supply device 55 and the gas section 96 of the container 43. The gas circulation device 56 returns the gas discharged from the gas section 96 of the container 43 to the gas supply device 55.

[0080] The carbon dioxide reduction device 200 includes a first recovery device 52, a first circulation device 57, a second recovery device 53, and a second circulation device 58. The first recovery device 52 recovers the products generated by the reaction of the supply gas in the cathode 40. Specifically, the first recovery device 52 separates the products from the electrolyte 99. The products are valuable substances such as carbon monoxide and formic acid. The first circulation device 57 circulates the electrolyte 99 contained inside the container 43. Specifically, the first circulation device 57 returns the electrolyte 99 from which the products have been separated back to the cathode portion 97 of the container 43. The first recovery device 52 and the first circulation device 57 may be configured as a single device.

[0081] The second recovery device 53 recovers the gas (generated gas) produced by the reaction of the supply gas at the anode 41. Specifically, the second recovery device 53 separates the generated gas from the electrolyte 99. The second circulation device 58 circulates the electrolyte 99 contained inside the container 43. Specifically, the second circulation device 58 returns the electrolyte 99 from which the generated gas has been separated back into the second space 92 of the container 43. The second recovery device 53 and the second circulation device 58 may be configured as a single device.

[0082] Next, the operation of the electrode 10, electrolytic cell 100, and carbon dioxide reduction device 200 according to this embodiment will be described.

[0083] Figure 6 is a schematic diagram illustrating the reduction reaction of carbon dioxide using electrode 10. As shown in Figure 6, electrolyte 99 is contained in the cathode portion 97 of container 43. As a result, the electrolyte 99 reaches the first surface 21 of the gas diffusion layer 2 through the catalyst layer 1. Specifically, the electrolyte 99 is supplied to the gap (see Figure 4) between the fourth surface 12 of the framework 16 and the second portion 27 of the gas diffusion layer 2. A DC voltage is applied between electrode 10 and anode 41 (see Figure 5) by power supply 51 (see Figure 5).

[0084] Next, CO2 enters the gas section 96 of container 43. ２ Gas is supplied. CO ２ The gas flows into the gas diffusion layer 2 along arrow A. CO ２The gas diffuses into the gas diffusion layer 2. As a result, CO is released inside the electrode 10. ２ A three-phase interface is formed where the gas, electrolyte 99 (liquid), and catalyst layer 1 (solid) are in contact. An electrolytic reaction occurs at the three-phase interface. Specifically, CO ２ Products are generated by the reaction between the gas and the electrolyte 99.

[0085] Next, the effects of the electrode 10, electrolytic cell 100, and carbon dioxide reduction device 200 according to this embodiment will be described.

[0086] Typically, CO2 is produced using a gas diffusion electrode as shown in Figure 6. ２ When a reduction reaction is carried out, due to the porous nature of both the catalyst layer 1 and the gas diffusion layer 2, the electrolyte 99 may seep into the gas diffusion layer 2. In this case, solid matter may precipitate inside the gas diffusion layer 2 due to vaporization of the electrolyte 99 within the gas diffusion layer 2. The electrolyte 99 may leak out to the outside of the gas diffusion layer 2 via this solid matter. CO2 may be released by the electrolyte 99 leaking from the gas diffusion layer 2. ２ The gas is blocked. Therefore, CO ２ The gas may not be able to reach electrode 10. This can cause CO ２ The gas reduction reaction stops. From another perspective, the electrode 10 has low durability if electrolyte 99 leaks from the gas diffusion layer 2.

[0087] In the electrode 10 according to this embodiment, the catalyst layer 1 is formed by a framework 16 and pores 19. The gas diffusion layer 2 is formed of a porous material. The contact angle of ultrapure water dropped onto the second surface 22 of the gas diffusion layer 2 is 115° or more. In this way, the hydrophobicity of the gas diffusion layer 2 is sufficiently improved. Therefore, it is possible to prevent the electrolyte 99 from seeping into the interior of the gas diffusion layer 2. In addition, a part of the gas diffusion layer 2 is embedded inside the pores 19. As a result, the thickness of the gas diffusion layer 2 located near the pores 19, which are the flow path for the electrolyte 99, is increased. Therefore, leakage of the electrolyte 99 from the gas diffusion layer 2 can be prevented. By preventing leakage of the electrolyte 99, the durability of the electrode 10 can be improved.

[0088] Because a portion of the gas diffusion layer 2 penetrates into the interior of the pores 19, the contact area between the catalyst layer 1 and the gas diffusion layer 2 can be increased. This allows CO ２ The area of ​​the three-phase interface where the gas, electrolyte 99, and catalyst layer 1 are in contact can be increased. Therefore, CO ２ This can improve the reaction efficiency of reduction reactions.

[0089] According to the electrode 10 of this embodiment, the gas diffusion layer 2 has a first portion 26 and a second portion 27. The first portion 26 extends into the interior of the pore portion 19. The second portion 27 faces the framework 16. The maximum thickness of the first portion 26 (first thickness T1) is greater than the maximum thickness of the second portion 27 (second thickness T2). Therefore, it is possible to more reliably prevent the electrolyte 99 flowing through the pore portion 19 toward the gas diffusion layer 2 from leaking to the outside of the gas diffusion layer 2.

[0090] According to the electrode 10 of this embodiment, in a cross-sectional view, the width of the second portion 27 (second width W2) in the direction perpendicular to the thickness direction of the gas diffusion layer 2 is 1 to 4 times the width of the first portion 26 (first width W1) in the direction perpendicular to the thickness direction of the gas diffusion layer 2. By having the second width W2 be 1 or more times the first width W1, the size of the pores 19 of the catalyst layer 1 is sufficiently increased. This allows sufficient electrolyte 99 to be supplied to the interface between the catalyst layer 1 and the gas diffusion layer 2. By having the second width W2 be 4 times or less of the first width W1, the contact area between the catalyst layer 1 and the gas diffusion layer 2 can be sufficiently increased. Therefore, CO ２ This can improve the reaction efficiency of reduction reactions.

[0091] According to the electrode 10 of this embodiment, the surface of the catalyst layer 1 contains at least one of copper, tin, and zinc. Therefore, each of copper, tin, and zinc is CO ２ It functions as a catalyst in the reduction reaction of CO. ２ This can improve the reaction efficiency of reduction reactions.

[0092] In the electrode 10 according to this embodiment, the gas diffusion layer 2 is formed of an insulating material. Therefore, the current applied to the electrode 10 does not flow through the gas diffusion layer 2. This prevents unintended reactions from occurring in the gas diffusion layer 2.

[0093] According to the electrode 10 of this embodiment, the gas diffusion layer 2 is mainly composed of polytetrafluoroethylene. This allows the hydrophobicity of the gas diffusion layer 2 to be sufficiently improved. Therefore, leakage of the electrolyte 99 to the outside of the gas diffusion layer 2 through the gas diffusion layer 2 can be prevented more reliably.

[0094] According to the electrode 10 of this embodiment, the peel strength between the catalyst layer 1 and the gas diffusion layer 2 is 0.02 N / cm or more. This prevents the catalyst layer 1 and the gas diffusion layer 2 from peeling off.

[0095] In the electrode 10 according to this embodiment, an internal space 18 is provided in the framework 16. In a cross-sectional view, the width of the internal space 18 (third width W3) in the direction perpendicular to the thickness direction of the gas diffusion layer 2 is longer than the length L of the internal space 18 in the thickness direction of the gas diffusion layer 2. In this way, the framework 16 is deformed to expand along the direction perpendicular to the thickness direction of the gas diffusion layer 2. This increases the contact area between the catalyst layer 1 and the gas diffusion layer 2.

[0096] According to the electrode 10 of this embodiment, the skeleton 16 has a third surface 11 facing the gas diffusion layer 2 and a fourth surface 12 opposite to the third surface 11. The third surface 11 has an uneven surface. This increases the contact area between the third surface 11 and the gas diffusion layer 2.

[0097] According to the electrode 10 of this embodiment, the average diameter of the pores 19, when viewed parallel to the thickness direction of the gas diffusion layer 2 and in the direction from the catalyst layer 1 toward the gas diffusion layer 2, is 20 μm or more and 70 μm or less. The average diameter of the pores 19 being 20 μm or more allows for sufficient supply of electrolyte 99 to the interface between the catalyst layer 1 and the gas diffusion layer 2. The average diameter of the pores 19 being 70 μm or less allows for a sufficient increase in the contact area between the catalyst layer 1 and the gas diffusion layer 2.

[0098] According to the electrode 10 of this embodiment, the Gurley seconds of the gas diffusion layer 2 are 600 seconds or less. Therefore, the gas diffusion layer 2 is CO ２ It allows sufficient gas permeation. Therefore, CO ２ This can improve the reaction efficiency of reduction reactions.

[0099] The electrolytic cell 100 according to this embodiment has a cathode 40. The cathode 40 is the electrode 10 according to this embodiment. Therefore, leakage of the electrolyte 99 from the gas diffusion layer 2 can be prevented.

[0100] The carbon dioxide reduction device 200 according to this embodiment has an electrolytic cell 100 according to this embodiment. Therefore, leakage of the electrolyte 99 from the gas diffusion layer 2 can be prevented.

[0101] (Sample Preparation) First, electrodes 10 for samples 1 to 11 were prepared. Samples 1 to 9 are examples. Samples 10 and 11 are comparative examples.

[0102]

[0103] Table 1 shows the composition of the catalyst layer material and gas diffusion layer material used in the preparation of each sample. In samples 1 through 6, 10, and 11, Sn-plated Cu cellmet was used as the catalyst layer material. From another perspective, the main part 31 of the catalyst layer 1 was formed of Cu. The coating layer 32 of the catalyst layer 1 was formed of Sn. The cellmet part number was #6. The thickness of the cellmet was 1 mm. In the cellmet, the weight of Cu per unit area was 180 g / m². ２ In Cellmet, the weight of Sn plating per unit area was 180 g / m². ２ That was the case.

[0104] In Sample 7, a Sn-plated Ni cellmet was used. From another perspective, the main part 31 of the catalyst layer 1 was formed of Ni. The coating layer 32 of the catalyst layer 1 was formed of Sn. The cellmet part number was #8. The thickness of the cellmet was 1.2 mm. In the cellmet, the weight of Ni per unit area was 315 g / m². ２In Cellmet, the weight of Sn plating per unit area was 180 g / m². ２ That was the case.

[0105] In Sample 8, Cu cellmet was used. From another perspective, the main part 31 of the catalyst layer 1 was formed of Cu, and the catalyst layer 1 did not have a coating layer 32. The cellmet part number was #6. The thickness of the cellmet was 1 mm. In the cellmet, the weight of Cu per unit area was 180 g / m². ２ That was the case.

[0106] In Sample 9, a SnZn plated Cu cellmet was used. From another perspective, the main part 31 of the catalyst layer 1 was formed of Cu. The coating layer 32 of the catalyst layer 1 was formed of Sn and Zn. The part number of the SnZn plated Cu cellmet was #6. The thickness of the cellmet was 1 mm. In the cellmet, the weight of Cu per unit area was 180 g / m². ２ In Cellmet, the weight of SnZn plating per unit area was 180 g / m². ２ That was the case.

[0107] The samples (Samples 1 to 9) for the examples were prepared in accordance with the manufacturing method of the electrode 10 described above. In the preparation of Samples 1 to 9, Poaflon manufactured by Sumitomo Electric Industries was prepared as the gas diffusion layer material. From another point of view, in Samples 1 to 9, the material of the gas diffusion layer 2 was PTFE.

[0108] In samples 1, 5 through 9, the thickness of the gas diffusion layer material was 100 μm. In samples 2 through 4, the thickness of the gas diffusion layer material was 100 μm. In samples 1, 2, 5 through 9, the pore size of the gas diffusion layer material was 5 μm. In sample 3, the pore size of the gas diffusion layer material was 0.22 μm. In sample 4, the pore size of the gas diffusion layer material was 0.1 μm.

[0109] In Sample 10, hydrophilic Poreflon manufactured by Sumitomo Electric Industries was used as the gas diffusion layer material. From another perspective, in Sample 10, the material of the gas diffusion layer 2 was PTFE, and the gas diffusion layer 2 was hydrophilic. In Sample 10, the thickness of the gas diffusion layer material was 100 μm. The pore size of the gas diffusion layer material was 5 μm.

[0110] In Sample 11, carbon paper was used as the gas diffusion layer material. Specifically, MFA-K manufactured by Mitsubishi Chemical Corporation was used. The thickness of the gas diffusion layer material was 200 μm.

[0111]

[0112]

[0113] In all samples, the shape of each part of the electrode 10, such as the thickness of the electrode 10 (fourth thickness T4), was measured. As shown in Table 2, in all samples, the thickness of the electrode 10 was between 0.1 mm and 0.2 mm. In samples 5 and 6, the thickness of the electrode 10 was thicker compared to the other samples because the roll press spacing was wider.

[0114] The maximum thickness (third thickness T3) of the catalyst layer 1 was 74 μm or more and 165 μm or less. The maximum thickness (first thickness T1) of the first portion 26 of the gas diffusion layer 2 was 28 μm or more and 70 μm or less. The maximum thickness (second thickness T2) of the second portion 27 of the gas diffusion layer 2 was 7 μm or more and 45 μm or less. In the sample according to the example, the first thickness T1 was 1.9 times or more and 4.0 times the second thickness T2. In sample 11, the first thickness T1 was 1.6 times the second thickness T2.

[0115] In all samples, the width of the first section 26 (first width W1) was between 130 μm and 230 μm. The width of the second section 27 (second width W2) was between 300 μm and 400 μm. The second width W2 was between 1.3 and 3.1 times the width of the first width W1.

[0116] As shown in Table 3, the peel strength between the catalyst layer 1 and the gas diffusion layer 2 was 0.11 N / cm in all samples. In samples 1, 3 to 11, the Gurley seconds of the gas diffusion layer 2 were between 16.8 seconds and 252 seconds. In sample 2, the Gurley seconds of the gas diffusion layer 2 were 9 seconds. In measuring the Gurley seconds of the gas diffusion layer 2, the time required to pass 1000 mL of air through was measured, and the time required to pass 100 mL of air through was calculated by dividing the measured time by 10.

[0117] In the sample according to the example, the contact angle of the ultrapure water dropped onto the second surface 22 was 120°. In sample 10, the contact angle could not be measured because the ultrapure water dropped onto the second surface 22 spread out due to the gas diffusion layer 2 being formed of a hydrophilic material. In sample 11, the contact angle of the ultrapure water dropped onto the second surface 22 was 110°.

[0118] (Test Method) Electrolytic tests were performed on all samples. Specifically, the electrode 10 of the sample was attached to the carbon dioxide reduction device 200 described above. The area of ​​the fourth surface 12 and the second surface 22 of the electrode 10 was 1.76 cm². ２ The electrolyte 99 was potassium hydroxide solution. The concentration of the potassium hydroxide solution was 1 mol / L (1 M KOH). Nafion™ was used as the ion exchange membrane 42. The anode 41 was made of platinum. A silver-silver chloride electrode was used as the reference electrode. CO2 was supplied to the container 43. ２ The gas flow rate was set to 15 mL / min.

[0119] Electrolysis was performed at a constant potential. The applied potential was -2.1V vs Ag / AgCl. The electrolysis test was conducted continuously for 240 hours. At the end of the electrolysis test, the presence or absence of leakage of electrolyte 99 from the gas diffusion layer 2 and the durability of the electrode 10 were confirmed. In the test of the electrode 10's durability, the current density between the cathode 40 and the anode 41 was measured. The durability of the electrode 10 was tested by observing the change in current density during the electrolysis test.

[0120] Table 3 shows the evaluation results for all samples. In the "Durability Test Results" column in Table 3, "A" indicates that the current density was measurable from the start to the end of the electrolytic test. "B" indicates that the current density became unmeasurable during the electrolytic test.

[0121] As shown in Tables 1 to 3, the current density was measurable from the start to the end of the electrolytic test in the samples with a contact angle of 120° (Samples 1 to 9). Specifically, in Samples 1 to 9, no leakage of the electrolyte 99 occurred, so the current density was measurable from the start to the end of the electrolytic test. On the other hand, in Sample 10, where the gas diffusion layer 2 is formed of a hydrophilic porous material, and in Sample 11, where the contact angle is 110°, the current density became unmeasurable during the electrolytic test. Specifically, in Samples 10 and 11, leakage of the electrolyte 99 occurred, making it impossible to measure the current density.

[0122] Based on the above, it was confirmed that the electrode 10 according to the example is capable of preventing leakage of the electrolyte 99 from the gas diffusion layer 2 compared to the electrode 10 according to the comparative example. Furthermore, it was confirmed that the electrode 10 according to the example has improved durability.

[0123] A sample according to the example was prepared in accordance with the manufacturing method of electrode 10 described above. In the manufacturing of electrode 10, a Sn-plated Cu cellmet was prepared as the catalyst layer material. The thickness of the cellmet was 1 mm. The number of cells in the cellmet was 47 cells / inch. In the cellmet, the weight of tin per unit area was 180 g / m². ２ It was determined that, in a cellmet, the weight of copper per unit area is, for example, 180 g / m². ２ It was determined that Poreflon was prepared as the gas diffusion layer material. The Poreflon model number was set to FP-100-100. The pore size of the Poreflon was set to 1 μm. The thickness of the Poreflon was set to 100 μm.

[0124] In the rolling process, Celmet and Poaflon were first rolled with a roll press spacing of 0.3 mm, and then Celmet and Poaflon were rolled again with a roll press spacing of 0.1 mm. During the rolling process, Celmet and Poaflon were rolled with the protective sheet of Poaflon attached to the Poaflon.

[0125] A scanning electron microscope image of a cross-section parallel to the thickness direction of the gas diffusion layer 2 was taken. The cross-sectional shape of the electrode 10 was confirmed using this scanning electron microscope image.

[0126] Figure 7 is a scanning electron microscope image showing a cross-section of the electrode according to the embodiment. As shown in Figure 7, a part of the gas diffusion layer 2 (first part 26) had penetrated into the interior of the pore portion 19. Thus, it has been confirmed that the electrode 10 according to this embodiment can be obtained by the manufacturing method of the electrode 10 according to this embodiment described above.

[0127] It should be understood that at least one configuration and feature described in each embodiment and example can be combined with other embodiments and examples, or modified in various ways.

[0128] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0129] 1 Catalyst layer, 2 Gas diffusion layer, 10 Electrode, 11 Third surface, 12 Fourth surface, 14 Flat section, 15 Recessed section, 16 Skeleton, 18 Internal space, 19 Pore section, 21 First surface, 22 Second surface, 26 First section, 27 Second section, 31 Main section, 32 Coating layer, 40 Cathode, 41 Anode, 42 Ion exchange membrane, 43 Container, 51 Power supply, 52 First recovery device, 53 Second recovery device, 54 Gas cylinder, 55 Gas supply device, 56 Gas circulation device, 57 First circulation device, 58 Second circulation device, 91 First space, 92 Second space, 96 Gas section, 97 Cathode section, 99 Electrolyte, 100 Electrolytic cell, 101 First direction, 102 Second direction, 200 Carbon dioxide reduction device, A Arrow, L Length, T1 First thickness, T2 Second thickness, T3; third thickness, T4; fourth thickness, W1; first width, W2; second width, W3; third width.

Claims

1. An electrode comprising: a metal skeleton; a pore portion; a catalyst layer formed by the pore portion; and a gas diffusion layer covering the catalyst layer and formed of a porous material, wherein the gas diffusion layer has a first surface facing the skeleton and a second surface opposite the first surface, the contact angle of ultrapure water dropped onto the second surface is 115° or more and 140° or less, and a portion of the gas diffusion layer penetrates into the pore portion.

2. The electrode according to claim 1, wherein the gas diffusion layer has a first portion that extends into the interior of the pore portion and a second portion that is connected to the first portion and faces the framework, and the maximum thickness of the first portion is greater than the maximum thickness of the second portion.

3. The electrode according to claim 2, wherein the maximum thickness of the first portion is 1.3 times or more and 4 times or less the maximum thickness of the second portion.

4. The electrode according to claim 2 or claim 3, wherein the maximum thickness of the first portion is 7 μm or more and 30 μm or less.

5. The electrode according to any one of claims 2 to 4, wherein, in a cross-section parallel to the thickness direction of the gas diffusion layer, the width of the second portion in a direction perpendicular to the thickness direction of the gas diffusion layer is one to four times the width of the first portion in a direction perpendicular to the thickness direction of the gas diffusion layer.

6. The electrode according to any one of claims 1 to 5, wherein the surface of the catalyst layer contains at least one of copper, tin, and zinc.

7. The electrode according to any one of claims 1 to 6, wherein the gas diffusion layer is formed of an insulating material.

8. The electrode according to claim 7, wherein the gas diffusion layer is mainly composed of polytetrafluoroethylene.

9. The electrode according to any one of claims 1 to 8, wherein the peel strength between the catalyst layer and the gas diffusion layer is 0.02 N / cm or more and 0.2 N / cm or less.

10. The electrode according to any one of claims 1 to 9, wherein the framework is provided with an internal space, and in a cross section parallel to the thickness direction of the gas diffusion layer, the width of the internal space in a direction perpendicular to the thickness direction of the gas diffusion layer is greater than the length of the internal space in the thickness direction of the gas diffusion layer.

11. The electrode according to any one of claims 1 to 10, wherein the skeleton has a third surface facing the gas diffusion layer and a fourth surface opposite the third surface, the third surface having an uneven portion and the fourth surface having a flat portion.

12. The electrode according to any one of claims 1 to 11, wherein the average diameter of the pores is 20 μm or more and 70 μm or less, when viewed parallel to the thickness direction of the gas diffusion layer and in the direction from the catalyst layer toward the gas diffusion layer.

13. The electrode according to any one of claims 1 to 12, wherein the Gurley seconds of the gas diffusion layer are 15 seconds or more and 600 seconds or less.

14. The electrode according to any one of claims 1 to 13, wherein the maximum thickness of the catalyst layer is 50 μm or more and 300 μm or less.

15. The electrode according to any one of claims 1 to 14, wherein the catalyst layer has a three-dimensional network structure.

16. An electrolytic cell comprising: a container; an ion exchange membrane that divides the inside of the container into a first space and a second space; a cathode disposed inside the first space; and an anode disposed inside the second space, wherein the cathode is the electrode described in any one of claims 1 to 15.

17. A carbon dioxide reduction apparatus comprising: an electrolytic cell according to claim 16; a gas supply device for supplying a gas containing carbon dioxide to the cathode; a power supply for applying a DC voltage between the cathode and the anode; a recovery device for recovering products generated by the reaction of the gas in the cathode; and a circulation device for circulating the electrolyte contained inside the container.

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