Electrodes, membrane electrode assemblies, electrochemical cells, stacks, electrolytic devices

Abstract

The embodiment provides an electrode with excellent durability. [Solution] The electrode of the embodiment comprises a substrate containing metal fibers or metal particles and having a first surface and a second surface located opposite to the first surface, and a catalyst layer provided on the first surface side of the substrate where the fibers or metal particles of the substrate are located. The average fiber diameter of the metal fibers and the average primary diameter of the metal particles are D, the direction from the first surface of the substrate toward the second surface of the substrate is defined as the thickness direction of the substrate, and the catalyst layer is provided at a depth of 3 × D or more and 10 × D or less from the first surface.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to electrodes, membrane electrode assemblies, electrochemical cells, stacks, and electrolytic devices. [Background technology]

[0002] In recent years, electrochemical cells have been actively researched. Among electrochemical cells, polymer electrolyte membrane electrolysis cells (PEMECs) are expected to be used for hydrogen production in large-scale energy storage systems. To ensure sufficient durability and electrolytic properties, platinum (Pt) nanoparticle catalysts are generally used for the cathode of PEMECs, and precious metal catalysts such as iridium (Ir) nanoparticle catalysts are generally used for the anode. Methods for obtaining hydrogen from ammonia are also being investigated. In addition, they can be used as anodes in electrolytic devices that electrolyze carbon dioxide to produce organic substances such as methanol and ethylene, as well as carbon monoxide. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-167620 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The embodiment provides a highly durable electrode. [Means for solving the problem]

[0005] The electrode of the embodiment comprises a substrate containing metal fibers or metal particles and having a first surface and a second surface located opposite to the first surface, and a catalyst layer provided on the first surface side of the substrate where the fibers or metal particles are located. The average fiber diameter of the metal fibers and the average primary diameter of the metal particles are D, the direction from the first surface of the substrate toward the second surface of the substrate is defined as the thickness direction of the substrate, and the catalyst layer is provided at a depth of 3 × D or more and 10 × D or less from the first surface. [Brief explanation of the drawing]

[0006] [Figure 1] A schematic diagram of the electrode in the embodiment. [Figure 2] A schematic cross-sectional view of the catalyst layer of the embodiment. [Figure 3] A partial schematic diagram of the electrode in the embodiment. [Figure 4] A partial schematic diagram of the electrode in the embodiment. [Figure 5] A partial schematic diagram of the electrode in the embodiment. [Figure 6] A partial schematic diagram of the electrode in the embodiment. [Figure 7] A partial schematic diagram of the electrode in the embodiment. [Figure 8] A partial schematic diagram of the electrode in the embodiment. [Figure 9] A partial schematic diagram of the electrode in the embodiment. [Figure 10] A partial schematic diagram of the electrode in the embodiment. [Figure 11] Analysis spot for the embodiment. [Figure 12] A schematic diagram of the film electrode assembly according to the embodiment. [Figure 13] A partial schematic diagram of the film electrode assembly of the embodiment. [Figure 14] Schematic diagram of an electrochemical cell according to an embodiment. [Figure 15] A schematic diagram of the stack in the embodiment. [Figure 16] Conceptual diagram of an electrolytic apparatus according to an embodiment. [Figure 17] Table of examples. [Figure 18] Table of examples. [Modes for carrying out the invention]

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are given to the same members, etc., and the description of the members, etc. that have been described once will be omitted as appropriate.

[0008] The physical property values in the specification are values at a temperature of 25 [°C] and a pressure of 1 [atom]. The thickness of each member is the average value of the distance in the stacking direction.

[0009] (First Embodiment) The first embodiment relates to an electrode. FIG. 1 shows a schematic cross-sectional view of the electrode 100 of the embodiment. The electrode 100 has a base material 1 and a catalyst layer 2. The catalyst layer 2 is provided on the base material 1.

[0010] In the embodiment, the catalyst layer 2 is used as an electrolysis catalyst. The electrolysis reaction is, for example, to generate hydrogen from water or ammonia or to generate ammonia from nitrogen. The electrolysis reaction is, for example, to generate carbon monoxide from carbon dioxide. The catalyst layer 2 is used as a catalyst in these reactions.

[0011] The electrode 100 of the first embodiment can be used, for example, as an anode for water electrolysis. If the catalyst layer 2 further contains a catalyst for a fuel cell, the electrode 100 of the embodiment can also be used as an oxygen electrode for a fuel cell. The electrode 100 of the embodiment can also be used as an anode for electrolytic production of ammonia. The electrode of the embodiment can be used as an anode for an electrolytic device for ammonia synthesis. In the following description of the first embodiment and other embodiments, water electrolysis will be used as an example, but the electrode 100 of the embodiment can also be used as an anode for a membrane electrode assembly used in electrolysis for ammonia synthesis, where, for example, ultrapure water or an electrolyte is supplied to the anode, the water is decomposed at the anode to produce protons and oxygen, the protons that have been generated pass through the electrolyte membrane, and nitrogen supplied to the cathode combines with the protons and electrons to produce ammonia. The electrode 100 of the embodiment can also be used as a cathode to electrolyze ammonia and produce hydrogen. The electrode of the embodiment can be used as a cathode for a hydrogen generator. In the following description of the first embodiment and other embodiments, water electrolysis will be used as an example. However, the electrode 100 of this embodiment can be used as the cathode of a membrane electrode assembly used in electrolysis for ammonia decomposition, for example, in which ammonia is supplied to the cathode, the ammonia is decomposed at the cathode to produce protons and nitrogen, the generated protons pass through the electrolyte membrane, and at the anode the protons and electrons combine to produce hydrogen.

[0012] As the base material 1, it is preferable to use a porous material with high conductivity. The base material 1 is a porous component that allows gases and liquids to pass through.

[0013] The base material 1 contains metal fibers 1A or metal particles 1B. Preferably, the base material 1 contains valve metal metal fibers 1A or metal particles 1B.

[0014] The base material 1 containing metal fibers 1A is preferably a cloth containing metal fibers 1A. The metal fibers 1A are preferably laminated in the thickness direction C of the base material 1. The cloth containing metal fibers 1A is preferably a mesh of metal fibers 1A or a nonwoven fabric of metal fibers 1A.

[0015] The substrate 1 containing the metal particles 1B is preferably a sintered body in which the metal particles 1B are aggregated. The metal particles 1B are preferably laminated in the thickness direction C of the substrate 1.

[0016] The metal fiber 1A preferably contains one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, nickel, platinum, tungsten, bismuth, and antimony, more preferably contains titanium which is stable under electrolytic conditions, and more preferably is titanium.

[0017] The fiber diameter of metal fiber 1A is preferably 1 [μm] or more and 500 [μm] or less, and more preferably 1 [μm] or more and 100 [μm] or less, considering reactivity and power supply properties. The average fiber diameter of metal fiber 1A is preferably 1 [μm] or more and 500 [μm] or less, and more preferably 1 [μm] or more and 100 [μm] or less, considering reactivity and power supply properties. If the fiber is thicker than this, the surface irregularities of the catalyst become large, reducing the contact interface with the film and the area of ​​the contact interface with the catalyst, which is undesirable. Also, since a thinner film is preferable because it has lower cell resistance, a thicker fiber is undesirable as it can cause electrical short circuits such as piercing the film. On the other hand, if the fiber is too thin, water or electrolyte will fill the voids, reducing gas diffusion, which is undesirable.

[0018] The metal particles 1B preferably contain one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, nickel, platinum, tungsten, bismuth, and antimony, more preferably contain titanium, and even more preferably be titanium.

[0019] The primary particle size (diameter) of metal particles 1B is preferably 1 [μm] or more and 500 [μm] or less, and more preferably 1 [μm] or more and 100 [μm] or less, considering reactivity and power supply properties. The average primary particle size (average diameter) of metal particles 1B is preferably 1 [μm] or more and 500 [μm] or less, and more preferably 1 [μm] or more and 100 [μm] or less, considering reactivity and power supply properties. If it is larger than this, the surface irregularities of the catalyst become large, reducing the contact interface with the film and the area of ​​the contact interface with the catalyst, which is undesirable. Also, since a thinner film is preferable because it has lower cell resistance, a larger size is undesirable as it can cause electrical short circuits such as piercing the film. On the other hand, if it is too small, water or electrolyte fills the voids, reducing gas diffusion, which is undesirable.

[0020] The porosity of the substrate 1 is suitable if it is between 30% and 70%, and more preferably between 40% and 60%, considering the movement of materials. If the porosity of the substrate 1 is low, the catalyst layer 2 tends to form too deep, preventing it from contributing to the electrolytic reaction. Also, water and electrolyte can fill the voids, reducing gas diffusion, which is undesirable. Conversely, if the porosity of the substrate 1 is high, the catalyst layer 2 tends to form in thin areas on the surface of the substrate 1. This also leads to poor electrical conductivity, reducing reaction efficiency, which is undesirable. Furthermore, it becomes difficult to maintain the physical structure of the substrate 1, making it prone to cracking, which is undesirable because it lacks structural stability during transport, manufacturing, and as a product.

[0021] The base material 1 has a first surface A and a second surface B located opposite to the first surface A. The first surface A and the second surface B are the main surfaces of the base material 1. The first surface A and the second surface B of the base material 1 are flat or substantially flat surfaces.

[0022] The direction from the first surface A of the base material 1 to the second surface B of the base material 1 is defined as the thickness direction C of the base material 1. If the first surface A and / or the second surface B are non-flat surfaces, the length of the line segment connecting the average surface of the first surface A to the average surface of the second surface B is defined as the thickness of the base material 1. Also, if the first surface A and / or the second surface B are non-flat surfaces, the direction in which the line segment connecting the average surface of the first surface A to the average surface of the second surface B extends is defined as the thickness direction C.

[0023] A catalyst layer 2 is provided on the first surface A side of the substrate 1. The catalyst layer 2 is provided on the surface of the metal fibers 1A or metal particles 1B of the substrate 1. Preferably, the catalyst layer 2 is provided directly on the surface of the metal fibers 1A or metal particles 1B of the substrate 1.

[0024] The catalyst layer 2 preferably contains one or more elements selected from the group consisting of Ir, Ru, Pt, Pd, Ni, Co, Mn, Fe, Cu, V, Au, Cr, Sr, Y, Ag, Sn, W, Zn, Nb, Ta, Zr, Ti, Mo, and Hf. The catalyst layer 2 preferably contains an oxide containing one or more elements selected from the group consisting of Ir, Ru, Pt, Pd, Ni, Co, Mn, Fe, Cu, V, Au, Cr, Sr, Y, Ag, Sn, W, Zn, Nb, Ta, Zr, Ti, Mo, and Hf.

[0025] The catalyst layer 2 preferably contains one or more noble metals selected from the group consisting of Ir, Ru, Pt, and Pd. The catalyst layer 2 preferably contains one or more elements selected from the group consisting of Ni, Co, Mn, and Fe, and more preferably contains Ni.

[0026] The catalyst layer 2 is preferably a porous material. The porosity of the catalyst layer 2 is preferably 10% to 90%, and more preferably 30% to 70%. If it is lower than this, water or electrolyte will fill the voids, reducing gas diffusion, which is undesirable. If it is higher, electrical conductivity will deteriorate, reducing the efficiency of the reaction, which is undesirable. Furthermore, it will be difficult to maintain the physical structure of the substrate 1, making it prone to cracking and delamination, resulting in a lack of structural stability during transport, manufacturing, and as a product, which is undesirable.

[0027] The amount of precious metal in catalyst layer 2 is 0.01 [mg / cm³]. 2 ] or more 1.0[mg / cm 2 Preferably less than or equal to 0.05 [mg / cm³]. 2 ] or more 0.5[mg / cm 2The following applies. This sum of masses can be measured by ICP-MS. It is preferable to use as little as possible without significantly hindering the reaction in order to reduce the amount of expensive precious metals.

[0028] The thickness of the catalyst layer 2 is preferably 0.1 [μm] or more and 10 [μm] or less, and more preferably 0.5 [μm] or more and 5 [μm] or less.

[0029] The thickness of the catalyst layer 2 is preferably 0.00002% to 10% of the thickness of the substrate 1, and more preferably 0.0005% to 0.5%.

[0030] The catalyst layer 2 preferably has a structure in which sheet layers 2A and gap layers 2B are alternately stacked. The stacked structure of the catalyst layer 2 is shown in the schematic cross-sectional view of the catalyst layer 2 in Figure 2. The sheet layers 2A and gap layers 2B are stacked in substantially parallel order. The gap layers 2B are mostly hollow, but in some parts, sheet layers 2A protrude and connect to them. The sheet layers 2A are connected by columnar bodies 2C present in the gap layers 2B, and the stacked structure is maintained.

[0031] Sheet layer 2A is a layer in which unsupported catalysts, such as metal oxides, are arranged in a sheet-like aggregate. There are some voids within sheet layer 2A. Sheet layer 2A is a dense layer containing a large amount of catalyst.

[0032] The gap layer 2B is a region sandwiched between the sheet layers 2A and contains catalyst particles, which are unsupported metal oxide particles. Unlike the sheet layers 2A, the gap layer 2B does not have a regular structure of catalyst. The gap layer 2B is a region with a low catalyst density.

[0033] The average thickness of each layer of sheet layer 2A is preferably 6 nm or more and 50 nm or less. The average thickness of each layer of gap layer 2B is preferably 6 nm or more and 50 nm or less. The average thickness of each layer of sheet layer 2A is preferably greater than the average thickness of each layer of gap layer 2B.

[0034] Referring to the schematic diagrams of the electrode 100 shown in Figures 3 to 10, the position where the catalyst layer 2 is provided on the substrate 1 will be explained. As in this embodiment, the provision of the catalyst layer 2 improves the durability and electrolytic characteristics of the electrode 100.

[0035] When the average fiber diameter of the metal fiber 1A and the average primary diameter of the metal particles 1B are D, the catalyst layer 2 of the electrode 100 in this embodiment is provided at a depth of 3 × D from the first surface A (first starting point) to a depth of 10 × D from the position E (first endpoint) to the position F (second endpoint).

[0036] The schematic diagram in Figure 3 shows the depths H at 1XD, G at 2XD, E at 3XD, and F at 10XD of an electrode 100 using a substrate 1 containing metal fibers 1A. The metal fibers 1A partially overlap. The schematic diagram in Figure 3 shows the range from the first surface A (first starting point) to position E (first endpoint) at a depth of 3×D and the range from the first surface A (first starting point) to position F (second endpoint) at a depth of 10×D.

[0037] The schematic diagram in Figure 4 shows the depths H at 1XD, G at 2XD, E at 3XD, and F at 10XD of an electrode 100 using a substrate 1 containing metal particles 1B. The metal particles 1B are partially in direct contact. The schematic diagram in Figure 4 shows the range from the first surface A (first starting point) to a depth of 3×D at position E (first endpoint) and from the first surface A (first starting point) to a depth of 10×D at position F (second endpoint) of the substrate 1 containing metal particles 1B.

[0038] It is preferable that the catalyst layer 2 is also provided on surfaces of the substrate 1 that are not facing the opposite direction to the thickness direction C.

[0039] The region from the first surface A (first starting point) of the substrate 1 to position H (third endpoint) at a depth of 1 × D in the thickness direction C of the substrate 1 is defined as the first region a. The region from position H (second starting point) at a depth of 1 × D in the thickness direction C of the substrate 1 to position G (fourth endpoint) at a depth of 2 × D in the thickness direction C of the substrate 1 is defined as the second region b. In this case, it is preferable that the average thickness of the catalyst layer 2 in the first region a is greater than the average thickness of the catalyst layer 2 in the second region b. This is because the reaction mainly takes place near the film side of the catalyst layer, so it is better to have more catalyst closer to the first surface. In the depth direction, the reaction proceeds almost entirely up to the fourth endpoint, so the contribution of catalyst at deeper locations to the reaction is small.

[0040] The average thickness of the catalyst layer 2 in the second region b is preferably 0.01 times or more and 0.5 times or less than the average thickness of the catalyst layer 2 in the first region a, more preferably 0.05 times or more and 0.4 times or less, and even more preferably 0.1 times or more and 0.3 times or less.

[0041] The region from the first surface A (first starting point) of the substrate 1 to position E (fifth ending point) at a depth of 3 × D in the thickness direction C of the substrate 1 is defined as the third region c. The region from position E (third starting point) at a depth of 3 × D in the thickness direction C of the substrate 1 to position F at a depth of 10 × D in the thickness direction C of the substrate 1 is defined as the fourth region d. In this case, it is preferable that the average thickness of the catalyst layer 2 in the third region c is greater than the average thickness of the catalyst layer 2 in the fourth region d.

[0042] The average thickness of the catalyst layer 2 in the fourth region d is preferably 0.001 times or more and 0.2 times or less than the average thickness of the catalyst layer 2 in the third region c, more preferably 0.001 times or more and 0.1 times or less, and even more preferably 0.001 times or more and 0.08 times or less.

[0043] The area of ​​the metal fibers 1A in the portion where the catalyst layer 2 is provided is preferably the same as or larger than the area of ​​the first surface A (= [vertical length of the first surface A] × [horizontal length of the first surface A]), more preferably 100% to 150% of the area of ​​the first surface A, and even more preferably 100% to 110%.

[0044] The area of ​​the metal particles 1B in the portion where the catalyst layer 2 is provided is preferably the same as or larger than the area of ​​the first surface A (= [vertical length of the first surface A] × [horizontal length of the first surface A]), more preferably 100% to 150% of the area of ​​the first surface A, and even more preferably 100% to 110%.

[0045] As shown in the schematic partial diagram of electrode 100 in Figure 5, it is preferable that the catalyst layer 2 is also provided on the surface of the metal fibers 1A on the side along the thickness direction C. The catalyst layer 2 is also provided on the surface of the metal fibers 1A in the portion of the substrate 1 that is not covered by the metal fibers 1A in the thickness direction C, with the catalyst layer 2 facing away from the thickness direction C. By providing the catalyst layer 2 not only on the surface of the metal fibers 1A in the portion of the substrate 1 that is not covered by the metal fibers 1A in the thickness direction C, with the catalyst layer 2 facing away from the thickness direction C, but also on the surface of the metal fibers 1A on the side along the thickness direction C, the area over which the catalyst layer 2 is provided is increased, contributing to improved catalyst utilization efficiency.

[0046] The surface of the metal fiber 1A along the thickness direction C is the surface of the metal fiber 1A within the range of 45° to 135° and 225° to 315° from the thickness direction C of the base material 1, centered on the center of the circumscribed circle of the cross-section of the metal fiber 1A along the length direction. Preferably, the catalyst layer 2 is also provided on the surface of the metal fiber 1A within the range of 45° to 135° and 225° to 315° from the thickness direction C of the base material 1, centered on the center of the circumscribed circle of the cross-section of the metal fiber 1A. The catalyst layer 2 is also provided on the surface (first surface A side) of the metal particles 1B within the range of greater than 135° and less than 225° from the thickness direction C of the base material 1, centered on the center of the circumscribed circle of the cross-section of the metal fiber 1A.

[0047] The catalyst layer 2 provided on the surface of the metal fiber 1A along the thickness direction C is preferably 30 wt% to 90 wt%, more preferably 40 wt% to 85 wt%, and even more preferably 50 wt% to 80 wt% of the total catalyst layer 2.

[0048] Preferably, the catalyst layer 2 provided on the metal fiber 1A side along the thickness direction C also has a structure in which sheet layers 2A and gap layers 2B are alternately stacked.

[0049] As shown in the schematic partial diagram of electrode 100 in Figure 6, it is preferable that the catalyst layer 2 is also provided on the surface of the metal particles 1B on the side along the thickness direction C. The catalyst layer 2 is also provided on the surface of the metal fibers 1A in the portion of the substrate 1 where the metal particles 1B are not covered by the metal particles 1B in the thickness direction C, with the catalyst layer 2 facing away from the thickness direction C. By providing the catalyst layer 2 not only on the surface of the metal particles 1B in the portion of the substrate 1 where the metal particles 1B are not covered by the metal particles 1B in the thickness direction C, with the catalyst layer 2 facing away from the thickness direction C, but also on the surface of the metal particles 1B on the side along the thickness direction C, the area over which the catalyst layer 2 is provided is increased, contributing to improved catalyst utilization efficiency. The cross-section of the metal particles 1B may correspond to a cross-section perpendicular to the direction along the length direction of the metal fibers 1A.

[0050] The surface of the metal particle 1B along the thickness direction C is the surface of the metal particle 1B within the range of 45[°] to 135[°] and 225[°] to 315[°] from the thickness direction C of the base material 1, centered on the center of the circumscribed circle (dashed line) of the cross-section of the metal particle 1B. It is preferable that the catalyst layer 2 is also provided on the surface of the metal particle 1B within the range of 45[°] to 135[°] and 225[°] to 315[°] from the thickness direction C of the base material 1, centered on the center of the circumscribed circle of the cross-section of the metal particle 1B. The catalyst layer 2 is also provided on the surface of the metal particle 1B (first surface A side) within the range of greater than 135[°] and less than 225[°] from the thickness direction C of the base material 1, centered on the center of the circumscribed circle of the cross-section of the metal particle 1B.

[0051] The catalyst layer 2 provided on the surface of the metal particles 1B along the thickness direction C is preferably 30 [wt%] to 90 [wt%] of the total catalyst layer 2, more preferably 40 [wt%] to 85 [wt%], and even more preferably 50 [wt%] to 80 [wt%].

[0052] Preferably, the catalyst layer 2 provided on the surface of the metal particles 1B along the thickness direction C also has a structure in which sheet layers 2A and gap layers 2B are alternately stacked.

[0053] As shown in the partially schematic diagram of the electrode 100 in Figure 7, it is preferable that the catalyst layer 2 is also provided on the surface of the metal fibers 1A in a direction that faces the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1.

[0054] The surface of the metal fiber 1A facing the second surface B of the substrate 1 rather than the direction perpendicular to the thickness direction C of the substrate 1 is the back surface of the metal fiber 1A (the surface of the metal fiber 1A in the area where the polarized light PL irradiated in the thickness direction C is in the shadow of the electrode 100 (substrate 1)). It is preferable that the catalyst layer 2 is also provided on the surface of the metal fiber 1A in the area where the polarized light PL irradiated in the thickness direction C is in the shadow of the electrode 100 (substrate 1) (area enclosed by dashed lines).

[0055] The catalyst layer 2, which is also provided on the surface of the metal fibers 1A that are oriented in a direction facing the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1, preferably comprises 1 [wt%] to 50 [wt%] of the total catalyst layer 2, more preferably 2 [wt%] to 40 [wt%], and even more preferably 5 [wt%] to 30 [wt%].

[0056] As shown in the partially schematic diagram of the electrode 100 in Figure 8, it is preferable that the catalyst layer 2 is also provided on the surface of the metal particles 1B in a direction that faces the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1. The cross-section of the metal particles 1B may correspond to a cross-section perpendicular to the direction along the length direction of the metal fibers 1A.

[0057] It is preferable that the catalyst layer 2, which is also provided on the surface of the metal fibers 1A that are oriented in a direction facing the second surface B of the base material 1 rather than in a direction perpendicular to the thickness direction C of the base material 1, also has a structure in which sheet layers 2A and gap layers 2B are alternately laminated.

[0058] The surface of the metal particles 1B facing towards the second surface B of the substrate 1 rather than in the direction perpendicular to the thickness direction C of the substrate 1 is the back surface of the metal particles 1B (the surface of the metal particles 1B in the area where the polarized light PL irradiated in the thickness direction C is in the shadow of the electrode 100 (substrate 1)). It is preferable that the catalyst layer 2 is also provided on the surface of the metal particles 1B in the area where the polarized light PL irradiated in the thickness direction C is in the shadow of the electrode 100 (substrate 1) (area enclosed by dashed lines).

[0059] The catalyst layer 2, which is also provided on the surface of the metal particles 1B that are oriented in a direction facing the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1, preferably comprises 1 [wt%] to 50 [wt%] of the total catalyst layer 2, more preferably 2 [wt%] to 45 [wt%], and even more preferably 5 [wt%] to 40 [wt%].

[0060] It is preferable that the catalyst layer 2, which is also provided on the surface of the metal particles 1B facing the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1, also has a structure in which sheet layers 2A and gap layers 2B are alternately stacked.

[0061] As shown in the schematic partial diagram of electrode 100 in Figure 9, it is preferable that electrode 100 includes a catalyst layer 2 provided on the surface of the metal fiber 1A in a direction facing the second surface B side of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1 (generally the area enclosed by the dashed line) and a catalyst layer 2 facing the thickness direction C of the substrate 1 (the area enclosed by the dashed line).

[0062] The total amount of catalyst layer 2 provided on the surface of the metal fiber 1A in a direction facing the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1, and the catalyst layer 2 facing the thickness direction C of the substrate 1, is preferably 3 [wt%] or more and 30 [wt%] or less of the total amount of catalyst layer 2, more preferably 4 [wt%] or more and 25 [wt%] or less, and even more preferably 5 [wt%] or more and 20 [wt%] or less.

[0063] It is preferable that both the catalyst layer 2 provided on the surface of the metal fiber 1A in a direction facing the second surface B of the base material 1 rather than in a direction perpendicular to the thickness direction C of the base material 1, and the catalyst layer 2 facing the thickness direction C of the base material 1, have a structure in which sheet layers 2A and gap layers 2B are alternately laminated.

[0064] As shown in the schematic partial diagram of the electrode 100 in Figure 10, it is preferable that the electrode 100 includes a catalyst layer 2 provided on the surface of the metal particles 1B in a direction facing the second surface B of the substrate 1 rather than in a direction perpendicular to the thickness direction C of the substrate 1 (generally the area enclosed by the dashed line) and a catalyst layer 2 facing the thickness direction C of the substrate 1 (the area enclosed by the dashed line). Note that the cross-section of the metal particles 1B may correspond to a cross-section perpendicular to the direction along the length direction of the metal fibers 1A.

[0065] The total amount of catalyst layer 2 provided on the surface of metal particles 1B facing the second surface B of the substrate 1 rather than the direction perpendicular to the thickness direction C of the substrate 1, and the catalyst layer 2 facing the thickness direction C of the substrate 1, is preferably 3 [wt%] or more and 40 [wt%] or less of the total catalyst layer 2, more preferably 4 [wt%] or more and 35 [wt%] or less, and even more preferably 5 [wt%] or more and 30 [wt%] or less.

[0066] It is preferable that both the catalyst layer 2 provided on the surface of the metal particles 1B facing the second surface B of the substrate 1 rather than the direction perpendicular to the thickness direction C of the substrate 1, and the catalyst layer 2 facing the thickness direction C of the substrate 1, have a structure in which sheet layers 2A and gap layers 2B are alternately laminated.

[0067] The area where the catalyst layer 2 is provided and its ratio can be determined by observing the cross-sections of multiple analysis spots. As shown in Figure 11, if the length D1 and width D2 (D1≧D2) of the electrode 100 are given by imaginary lines drawn at a distance of D3 (=D1 / 10) inward from two opposing sides in the width direction of the electrode 100, and imaginary lines drawn at a distance of D4 (=D2 / 10) inward from two opposing sides in the length direction of the electrode 100, and further imaginary lines parallel to the width direction passing through the center of the electrode 100, and imaginary lines parallel to the length direction passing through the center of the electrode 100, the region centered on the nine intersection points of these imaginary lines is defined as analysis spots A1 to A9. Each spot is square in shape and at least 1 mm in diameter. 2 It has the region shown. The cross-section observed by SEM is perpendicular to the plane in Figure 10 and parallel to the width direction. The thickness of each gap layer 2B for analysis spots A1 to A9 is determined at 50 nm intervals in the width direction of the SEM image. The ratio of catalyst layer 2 present in specific locations is the average value for each spot. The ratio of catalyst layer 2 present in specific locations can be determined from the volume and ratio of catalyst layer 2. In addition, the composition of substrate 1 and catalyst layer 2 is determined by analysis using SEM-EDX.

[0068] Next, an example of a method for fabricating electrode 100 is shown. Sheet layer precursors, which are substantially precursors of sheet layer 2A, and gap layer precursors, which are substantially precursors of gap layer 2B, are alternately sputtered onto substrate 1. When forming the sheet layer precursors and gap layer precursors, sputtering is also performed from an angle inclined with respect to the thickness direction C of substrate 1 (including both sputtering in the thickness direction C of substrate 1 and sputtering from an angle inclined with respect to the thickness direction of substrate 1), so that the catalyst layer 2 can be formed not only on the part exposed on the opposite side of the thickness direction C of substrate 1. At this time, the sheet layer precursors and gap layer precursors are formed in an oxidizing atmosphere. The laminate in which the sheet layer precursors and gap layer precursors are alternately stacked is treated with a solution in which the precursor of gap layer 2B is selectively dissolved. The solution used for dissolution is, for example, sulfuric acid. After the solution treatment, the electrode 100 is optionally obtained by heat treatment in an oxidizing atmosphere.

[0069] The angle inclined with respect to the thickness direction C of the substrate 1 when forming the sheet layer precursor and gap layer precursor preferably includes an angle inclined between 1° and 179° with respect to the surface direction of the substrate 1, more preferably includes an angle inclined between 5° and 120°, and even more preferably includes an angle inclined between 10° and 90° or / and an angle inclined between 90° and 170°. Furthermore, it is even more preferable to include an angle inclined between 10° and less than 90° or / and an angle inclined greater than 90° and 170° or less. Since sputtering from a very shallow angle (e.g., 1°) results in poor catalyst sputtering efficiency, a deeper angle of inclination is preferable. Considering the need to sputter evenly at all of the above angles, film formation would involve moving the target or substrate, making it difficult to sputter by igniting voltage on the target only at specific angles. Therefore, it is preferable to sputter from angles that include shallow angles. On the other hand, if sputtering is performed only at an angle nearly perpendicular to the surface of the substrate 1 (90°), catalyst will not be formed on the sides or back of the fibers or metal particles. Therefore, it is desirable that the sputtering angle includes fewer 90° angles relative to the surface direction of the substrate 1, and includes angles other than 90°.

[0070] In this embodiment, the electrode 100 has a catalyst layer 2 provided over a wide area of ​​the surface of the substrate 1. As an electrolytic electrode, the electrode 100 of this embodiment has high durability and high electrolytic characteristics.

[0071] (Second Embodiment) The second embodiment relates to a membrane electrode assembly (MEA). Figure 12 shows a schematic diagram of the membrane electrode assembly 200 of the embodiment. The membrane electrode assembly 200 has a first electrode 11, a second electrode 12, and an electrolyte membrane 13. Preferably, the first electrode 11 is an anode electrode and the second electrode 12 is a cathode electrode. Preferably, the electrode 100 of the first embodiment is used for the first electrode 11 or the second electrode 12. Preferably, the membrane electrode assembly 200 of the embodiment is used in an electrochemical cell or stack that performs hydrogen generation or oxygen generation.

[0072] The first electrode 11 has a first substrate 11B and a first catalyst layer 11A. The first catalyst layer 11A is provided on the first substrate 11B. Preferably, the first catalyst layer 11A is in direct contact with the electrolyte membrane 13. When electrode 100 is used as the first electrode 11, the first catalyst layer 11A is catalyst layer 2, and the first substrate 11B is substrate 1.

[0073] The second electrode 12 has a second substrate 12B and a second catalyst layer 12A. The second catalyst layer 12A is provided on the second substrate 12B. The second catalyst layer 12A is provided on the electrolyte membrane 13 side. It is preferable that the second catalyst layer 12A is in direct contact with the electrolyte membrane 13.

[0074] As the second base material 12B, it is preferable to use a porous material with high conductivity. The second base material 12B is a porous member that allows gases and liquids to pass through. The second base material 12B is, for example, carbon paper or a metal mesh. As the metal mesh, a porous base material of valve metal is preferred. As the porous base material of valve metal, a porous base material containing one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony is preferred, or a porous base material containing one metal selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony is preferred. The second base material 12B has a carbon layer (MPL layer) containing carbon fine particles and a water-repellent resin (fluororesin such as PTFE or Nafion). The carbon layer is provided, for example, between the carbon paper and the second catalyst layer 12A.

[0075] The second catalyst layer 12A has a catalyst metal. The second catalyst layer 12A preferably consists of catalyst metal particles with the catalyst metal not supported on a carrier. The second catalyst layer 12A is preferably a porous catalyst layer. The catalyst metal is not particularly limited, but for example, it includes one or more selected from the group consisting of Pt, Rh, Os, Ir, Pd, and Au. It is preferable to include one or more selected from the group consisting of such catalyst materials. The catalyst metal is preferably a metal, an alloy, or a metal oxide. The second catalyst layer 12A preferably has, for example, a plurality of catalyst units in which sheet-like catalyst layers and gap layers are alternately laminated.

[0076] The metal amount per unit area of the second catalyst layer 12A is preferably 0.02 [mg / cm 2 or more and 1.0 [mg / cm 2 or less, more preferably 0.05 [mg / cm 2 or more and 0.5 [mg / cm 2 or less. The sum of this mass can be measured by ICP-MS.

[0077] The porosity of the second catalyst layer 12A is preferably 10 [%] or more and 90 [%] or less, more preferably 30 [%] or more and 70 [%] or less.

[0078] The electrolyte membrane 13 is preferably a proton conductive membrane. As the electrolyte membrane 13, a fluorine-based polymer or an aromatic hydrocarbon-based polymer having one or more selected from the group consisting of a sulfonic acid group, a sulfonimide group, and a sulfate group is preferable. As the electrolyte membrane 13, a fluorine-based polymer having a sulfonic acid group is preferable. As the fluorine-based polymer having a sulfonic acid group, for example, Nafion (trademark, manufactured by DuPont), Flemion (trademark, manufactured by Asahi Kasei), Selemion (trademark, manufactured by Asahi Kasei), Aquivion (trademark; Solvay Specialty Polymers), or Aciplex (trademark, manufactured by Asahi Glass) can be used. Note that instead of the proton conductive membrane, an anion exchange membrane, a porous membrane, or the like can be used as various conductive membranes in some cases.

[0079] The thickness of the electrolyte membrane 13 can be appropriately determined considering the membrane's permeability characteristics and durability. From the viewpoint of strength, solubility, and MEA output characteristics, the thickness of the electrolyte membrane 13 is preferably 20 [μm] to 500 [μm], more preferably 50 [μm] to 300 [μm], and even more preferably 80 [μm] to 200 [μm].

[0080] The membrane electrode assembly 200 preferably does not contain an ionomer. It is preferable that the membrane electrode assembly 200 does not contain an ionomer, for example, coated on the electrode-side surface.

[0081] The electrolyte membrane 13 preferably includes a noble metal region on the first electrode 11 side. The noble metal region contains noble metal particles. The noble metal region is preferably located on the surface of the electrolyte membrane 13. The noble metal region is preferably composed of a single region, but may be composed of multiple separate regions.

[0082] The precious metal particles are preferably one or more precious metal particles selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles may also include alloy particles containing one or more precious metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles are preferably one precious metal particle selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. Pt particles are preferred for the precious metal particles. Re particles are preferred for the precious metal particles. Rh particles are preferred for the precious metal particles. Ir particles are preferred for the precious metal particles. Pd particles are preferred for the precious metal particles. Ru particles are preferred for the precious metal particles.

[0083] The precious metal particles generate on the cathode side and oxidize the hydrogen passing through the electrolyte membrane 13. The precious metal particles can suppress hydrogen leakage. Because the precious metal particles are present on the anode side, they are less likely to oxidize the hydrogen emitted from the cathode side. The region where the precious metal particles are present may also exist in the electrolyte membrane 13 on the second electrode 12 (cathode) side.

[0084] The average circumscribed diameter of the precious metal particles is preferably 0.5 nm or more and 50 nm or less, more preferably 1 nm or more and 10 nm or less, and even more preferably 1 nm or more and 5 nm or less.

[0085] Figure 13 shows a partial cross-sectional view of the membrane electrode assembly 200. Figure 13 illustrates a configuration in which electrode 100 is used as the first electrode 11. Some of the catalyst layer 2 does not need to be in direct contact with the electrolyte membrane 13. Since the catalyst layer 2 that is not in direct contact with the electrolyte membrane 13 is located in a relatively shallow region from the first surface A of the substrate 1, the catalyst layer 2 that is not in direct contact with the electrolyte membrane 13 also contributes to the electrolytic reaction due to the presence of water diffused in the substrate 1.

[0086] The catalyst layer 2 that is not in direct contact with the electrolyte membrane 13 preferably comprises 3 wt% to 50 wt% of the total catalyst layer 2, more preferably 5 wt% to 40 wt%, and even more preferably 5 wt% to 30 wt%.

[0087] By using the highly durable and characteristic electrode 100 as the anode of the membrane electrode assembly 200, long-term operation with high activity becomes possible.

[0088] (Third embodiment) The third embodiment relates to an electrochemical cell. Figure 14 shows a cross-sectional view of the electrochemical cell 300 of the second embodiment. The electrochemical cell 300 will be described below using water electrolysis as an example, but hydrogen can also be generated by decomposing ammonia or other substances in addition to water.

[0089] As shown in Figure 14, the electrochemical cell 300 of Embodiment 2 includes a first electrode (anode) 11, a second electrode (card) 12, an electrolyte membrane 13, a gasket 21, a gasket 22, a separator 23, and a separator 24. The sealing material for the first electrode 11 may be used as gasket 21. The sealing material for the second electrode 12 may be used as gasket 22.

[0090] It is preferable to use a membrane electrode assembly 200 in which a first electrode (anode) 11, a second electrode (card) 12, and an electrolyte membrane 13 are joined together. The anode power supply may be provided separately from the separator 23. The cathode power supply may be provided separately from the separator 24.

[0091] In the electrochemical cell 300 shown in Figure 14, a power supply (not shown) is connected to separators 23 and 24, and a reaction occurs at the first electrode 11 and the second electrode 12. For example, water is supplied to the first electrode 11, where the water is decomposed into protons, oxygen, and electrons. The electrode support and power supply are porous materials, and these porous materials function as flow channels. The generated water and unreacted water are discharged, and the protons and electrons are used in the cathode reaction. In the cathode reaction, protons and electrons react to produce hydrogen. Either or both of the generated hydrogen and oxygen can be used as fuel for a fuel cell, for example.

[0092] (Fourth Embodiment) The fourth embodiment relates to a stack. Figure 15 is a schematic cross-sectional view showing a stack 400 of the fourth embodiment. The stack 400 of the third embodiment shown in Figure 15 consists of multiple MEA200s or electrochemical cells 300s connected in series. Clamping plates 31 and 32 are attached to both ends of the MEAs or electrochemical cells.

[0093] Since the amount of hydrogen produced by an electrochemical cell 300 consisting of a single MEA200 is small, a large amount of hydrogen can be obtained by configuring a stack 400 consisting of multiple MEA200s or multiple electrochemical cells 300s connected in series.

[0094] (Fifth embodiment) The fifth embodiment relates to an electrolytic apparatus. Figure 16 shows a conceptual diagram of the electrolytic apparatus of the fifth embodiment. The electrolytic apparatus 500 uses an electrochemical cell 300 or a stack 400. The electrolytic apparatus in Figure 16 is for water electrolysis. An electrolytic apparatus for water electrolysis will be described. For example, when generating hydrogen from ammonia, it is preferable to use a different configuration apparatus using electrode 100. The electrodes of the embodiment can also be used in electrolytic apparatuses that electrolyze carbon dioxide to produce organic substances such as methanol and ethylene, or carbon monoxide.

[0095] As shown in Figure 16, a stack 400 is formed by stacking single cells for water electrolysis in series. A power supply 41 is attached to the stack 400, and a voltage is applied between the anode and cathode. A gas-liquid separator 42 and a mixing tank 43 are connected to the anode side of the stack 400 to separate the generated gas from unreacted water. Water is supplied to the mixing tank 43 by a pump 46 from an ion-exchange water production device 44, and then mixed in the mixing tank 43 through a check valve 47 from the gas-liquid separator 42 before being circulated to the anode. The oxygen generated at the anode passes through the gas-liquid separator 42 to obtain oxygen gas. On the cathode side, a hydrogen purification device 49 is connected in conjunction with the gas-liquid separator 48 to obtain high-purity hydrogen. Impurities are discharged through a path with a valve 50 connected to the hydrogen purification device 49. To stably control the operating temperature, the stack and mixing tank can be heated, and the current density during thermal decomposition can be controlled.

[0096] The present invention will be described more specifically below based on examples, but the present invention is not limited to the following examples.

[0097] (Example A) (Example A-1) A nonwoven titanium metal fiber fabric with a porosity of 60% and a thickness of 200 [μm] is used as the substrate, and a catalyst layer is formed on the substrate. The catalyst layer has a structure in which 40 sheet layers and 40 gap layers are alternately stacked. Sheet layer precursors containing Ir oxide and gap layer precursors containing Ni oxide are alternately formed by sputtering in an oxidizing atmosphere, with the angle changing in the direction within the range of 1 [°] to 179 [°] with respect to the surface direction of the substrate. The loading density of the precious metal is 0.1 [mg / cm³]. 2 This is done. Then, the majority of the gap layer precursor is selectively dissolved with sulfuric acid to obtain the electrode of the embodiment. The obtained electrode is used as the anode.

[0098] An electrode is obtained by using carbon paper as a substrate and forming a porous catalyst layer containing Pt on the substrate. The obtained electrode is used as a cathode. The loading density of the precious metal is 1 [mg / cm³]. 2 ]

[0099] A Nafion membrane is sandwiched between the obtained anode and cathode as an electrolyte membrane and pressed together to obtain a membrane electrode assembly. The obtained membrane electrode assembly is placed between two channel separators, and the membrane electrode assembly sealed with a gasket is fixed to obtain an electrochemical cell. For the obtained electrochemical cell, the measurement temperature is 80 [°C] and the current density is 2 [A / cm²]. 2 The water electrolysis operation will be performed for 5000 hours to evaluate durability and cell voltage.

[0100] (Examples A-2 to A-7, Comparative Examples A-1 to A-7) An anode is prepared in the same manner as in Example A-1 using a substrate with the porosity shown in the table in Figure 17. In the comparative examples where X is written in the sputtering gradient column in the table in Figure 17, the sheet layer precursor and gap layer precursor are formed by fixing the direction at 90° with respect to the surface direction of the substrate 1. An electrochemical cell is prepared in the same manner as in Example A-1, and the cell voltage is evaluated 30 hours and 5000 hours after the start of water electrolysis operation. A table in Figure 17 summarizes the comparative examples of porosity, sputtering gradient, and cell voltage 30 hours and 5000 hours after the start of water electrolysis operation.

[0101] As shown in the table in Figure 17, the single cells using the electrodes of the examples all exhibited good cell voltage after 30 hours of operation, indicating high performance. Even in the comparative example where the catalyst layer precursor was not formed by oblique sputtering, the cell voltage after 30 hours was low when the porosity was between 30% and 70%. After 5000 hours of operation, the rate of increase in cell voltage was kept low when using the electrodes of the examples. However, when using the electrodes of the comparative example, even if the cell voltage after 1 hour of operation was sufficiently low compared to the examples, the rate of increase in cell voltage or the cell voltage after 5000 hours of operation was higher than that of the examples. This demonstrates that the electrodes used in the examples all possess high durability and high electrolytic characteristics.

[0102] Furthermore, although not shown in the table in Figure 17, the anodes of the examples differ from those of the comparative examples in that, as shown in the schematic diagrams in Figures 5, 7, and 9, the catalyst layer is formed not only on the surface side of the titanium fibers but also on the sides and bottom sides of some of the titanium fibers in the region on the first surface side of the substrate.

[0103] (Example B) (Example B-1) A sintered body of titanium metal particles with a porosity of 40% and a thickness of 200 [μm] is used as the substrate, and a catalyst layer is formed on the substrate. The catalyst layer has a structure in which 40 sheet layers and 40 gap layers are alternately stacked. Sheet layer precursors containing Ir oxide and gap layer precursors containing Ni oxide are alternately formed by sputtering in an oxidizing atmosphere, with the angle changing in the direction within the range of 0 [°] to 178 [°] relative to the thickness direction of the substrate. The loading density of the precious metal is 0.05 [mg / cm³]. 2 This was done. Subsequently, the majority of the gap layer precursor was selectively dissolved with sulfuric acid to obtain the electrode of the embodiment. The obtained electrode was used as the anode.

[0104] Using the obtained electrodes, an electrochemical cell was prepared in the same manner as in Example A, and its characteristics were evaluated by performing water electrolysis.

[0105] (Examples B-2 to B-5, Comparative Examples B-1 to B-5) An anode is prepared in the same manner as in Example B-1 using a substrate with the porosity shown in the table in Figure 18. In comparative examples where X is written in the sputtering gradient column in the table in Figure 18, the sheet layer precursor and gap layer precursor are formed in a direction within the range of 0° to 178° with respect to the thickness direction of the substrate 1. An electrochemical cell is prepared in the same manner as in Example B-1, and the cell voltage is evaluated 1 hour and 5000 hours after the start of water electrolysis operation. A table in Figure 18 summarizes examples of comparative examples for porosity, sputtering gradient, and cell voltage 1 hour and 5000 hours after the start of water electrolysis operation.

[0106] As shown in the table in Figure 18, the electrochemical cells using the electrodes of the examples all exhibited good cell voltage after 1 hour of operation, indicating high performance. Even in the comparative example, where the catalyst layer precursor was not formed by oblique sputtering, the cell voltage after 1 hour was low when the porosity was between 30% and 70%. After 5000 hours of operation, the rate of increase in cell voltage was kept low when using the electrodes of the examples. However, when using the electrodes of the comparative example, even if the cell voltage after 1 hour of operation was sufficiently low compared to the examples, the rate of increase in cell voltage or the cell voltage after 5000 hours of operation was higher than that of the examples. This demonstrates that the electrodes used in all examples possess high durability and high electrolytic characteristics.

[0107] Furthermore, although not shown in the table in Figure 18, the anodes of the examples differ from those of the comparative examples in that, as shown in the schematic diagrams in Figures 6, 8, and 10, the catalyst layer is formed not only on the surface side of the titanium fibers but also on the side surfaces of some titanium fibers and on the bottom surfaces of some titanium fibers in the region on the first surface side of the substrate.

[0108] The electrode 100 of this embodiment exhibits improved durability and characteristics compared to the electrode of the comparative example when the same amount of catalyst layer 2 is formed. Therefore, since high characteristics can be maintained without increasing the amount of catalyst, the amount of target used during sputtering can be reduced, which is also preferable from an economic standpoint. It is believed that durability and high electrolytic characteristics can be achieved simultaneously because a large amount of catalyst layer 2 is present on the electrolyte membrane 13 side, and a small amount of catalyst layer 2 is present at a position slightly away from the electrolyte membrane 13.

[0109] Although the example uses water electrolysis, the electrode 100 of the embodiment also exhibits improved durability and activity when electrolysis other than water electrolysis is performed using the electrode 100.

[0110] In the specification, some elements are represented only by their element symbols.

[0111] The following is a technical proposal for an embodiment. Technical proposal 1 It contains metal fibers or metal particles and has a first surface and a second surface located on the opposite side of the first surface, and is a base material, The substrate comprises a catalyst layer provided on the first surface side of the substrate, with respect to the fibers of the substrate or the metal particles. Let D be the average fiber diameter of the metal fibers and the average primary diameter of the metal particles. The direction from the first surface of the substrate toward the second surface of the substrate is defined as the thickness direction of the substrate. The catalyst layer is provided with electrodes located at a depth of 3 × D or more and 10 × D or less from the first surface. Technical proposal 2 The average fiber diameter of the metal fibers is 1 [μm] or more and 500 [μm] or less. The electrode according to Technical Proposal 1, wherein the average primary diameter of the metal particles is 1 [μm] or more and 500 [μm] or less. Technical proposal 3 The electrode according to Technical Proposal 1 or 2, wherein the substrate is a cloth containing the metal fibers or a sintered body of the metal particles. Technical proposal 4 The aforementioned metal fiber contains titanium, The aforementioned metal particles are electrodes according to any one of the technical proposals 1 to 3, including titanium. Technical proposal 5 The region from the first surface of the substrate to a depth of 1 × D in the thickness direction of the substrate is defined as the first region. The second region is defined as the area from a depth of 1 × D in the thickness direction of the substrate from the first surface of the substrate to a position of 2 × D in the direction toward the second surface. The electrode according to any one of Technical Proposals 1 to 4, wherein the average thickness of the catalyst layer in the first region is greater than the average thickness of the catalyst layer in the second region. Technical proposal 6 The region from the first surface of the substrate to a depth of 1 × D in the thickness direction of the substrate is defined as the first region. The region from a depth of 1 × D in the thickness direction of the substrate to a depth of 2 × D in the thickness direction of the substrate, from the first surface of the substrate, is defined as the second region. The electrode according to any one of Technical Proposals 1 to 5, wherein the average thickness of the catalyst layer in the second region is 0.01 times or more and 0.5 times or less the average thickness of the catalyst layer in the first region. Technical proposal 7 The region from the first surface of the substrate to a depth of 3 × D in the thickness direction of the substrate is defined as the third region. The fourth region is defined as the area from a depth of 3 × D in the thickness direction of the substrate from the first surface of the substrate to a region of 10 × D in the thickness direction of the substrate. The electrode according to any one of Technical Proposals 1 to 6, wherein the average thickness of the catalyst layer in the fourth region is 0.001 times or more and 0.2 times or less the average thickness of the catalyst layer in the third region. Technical proposal 8 The substrate containing the metal fibers is such that the metal fibers are intertwined and the metal fibers are laminated in the thickness direction of the substrate. The electrode according to any one of Technical Proposals 1 to 7, wherein the substrate containing the metal particles is aggregated and the metal particles are laminated in the thickness direction of the substrate. Technical proposal 9 The catalyst layer is also provided on the surface of the metal fibers along the thickness direction, The electrode according to any one of Technical Proposals 1 to 8, wherein the catalyst layer is also provided on the surface of the metal particles along the thickness direction. Technical proposal 10 The catalyst layer is provided on the surface of the metal fibers facing a direction toward the second surface side of the substrate rather than a direction perpendicular to the thickness direction of the substrate, The electrode according to any one of Technical Proposals 1 to 9, wherein the catalyst layer is provided on the surface of the metal particles facing a direction toward the second surface side of the substrate rather than a direction perpendicular to the thickness direction of the substrate. Technical proposal 11 The catalyst layer is provided on the surface of the metal fibers in a direction that faces the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate, The catalyst layer provided on the surface of the metal fibers in a direction facing the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate is 3 [wt%] or more and 30 [wt%] or less of the total catalyst layer. The catalyst layer is provided on the surface of the metal particles in a direction that faces the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate, The electrode according to any one of Technical Proposals 1 to 10, wherein the catalyst layer provided on the surface of the metal particles in a direction facing the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate is 3 [wt%] or more and 40 [wt%] or less of the total catalyst layer. Technical proposal 12 The electrode according to any one of Technical Proposals 1 to 11, wherein the porosity of the substrate is 30% or more and 70% or less. Technical proposal 13 The electrode according to any one of Technical Proposals 1 to 12, wherein the porosity of the substrate is 40% or more and 60% or less. Technical proposal 14 The catalyst layer is an electrode according to any one of the technical proposals 1 to 13, having a structure in which sheet layers and gap layers are alternately stacked. Technical proposal 15 An electrode described in any one of Technical Proposals 1 to 14, An electrolyte membrane in direct contact with the electrode, and a membrane electrode assembly comprising these. Technical proposal 16 A membrane electrode assembly according to technical proposal 15, comprising the catalyst layer that does not come into contact with the membrane electrode assembly. Technical proposal 17 An electrochemical cell equipped with a membrane electrode assembly as described in Technical Proposal 15. Technical proposal 18 A stack comprising multiple electrochemical cells as described in Technical Proposal 17. Technical proposal 19 An electrolytic system equipped with the stack described in Technical Proposal 18.

[0112] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. Although PEMEC was given as a water electrolysis cell, the present invention can be similarly applied to other electrolysis cells. These novel embodiments described above can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0113] 1: Base material 1A: Metal fiber 1B: Metal particles 2: Catalyst layer 2A: Sheet layer 2B: Gap layer 2C: columnar body 9: Intersection 11: 1st electrode 11A: 1st catalyst layer 11B: 1st base material 12:Second electrode 12A: 2nd catalyst layer 12B: 2nd base material 13: Electrolyte membrane 21: Gasket 22: Gasket 23: Separator 24: Separator 31: Clamping plate 32: Clamping plate 41: Power supply 42: Gas-liquid separation device 43: Mixing tank 44: Ion-exchanged water production device 46: Pump 47: Check valve 48: Gas-liquid separation equipment 49: Hydrogen purification equipment 50: Valve 100: Electrode 200: Membrane electrode assembly 300: Electrochemical cell 400: Stack 500: Water electrolysis system

Claims

1. It contains metal fibers or metal particles and has a first surface and a second surface located on the opposite side of the first surface, and is a base material, The substrate comprises a catalyst layer provided on the first surface side of the substrate, with respect to the fibers of the substrate or the metal particles. Let D be the average fiber diameter of the metal fibers and the average primary diameter of the metal particles. The direction from the first surface of the substrate toward the second surface of the substrate is defined as the thickness direction of the substrate. The catalyst layer is provided with electrodes located at a depth of 3 × D or more and 10 × D or less from the first surface.

2. The average fiber diameter of the aforementioned metal fibers is 1 [μm] or more and 500 [μm] or less. The electrode according to claim 1, wherein the average primary diameter of the metal particles is 1 [μm] or more and 500 [μm] or less.

3. The electrode according to claim 1, wherein the substrate is a cloth containing the metal fibers or a sintered body of the metal particles.

4. The aforementioned metal fiber contains titanium, The electrode according to claim 1, wherein the metal particles include titanium.

5. The region from the first surface of the substrate to a depth of 1 × D in the thickness direction of the substrate is defined as the first region. The second region is defined as the area from a depth of 1 × D in the thickness direction of the substrate from the first surface of the substrate to a position of 2 × D in the direction toward the second surface. The electrode according to claim 1, wherein the average thickness of the catalyst layer in the first region is greater than the average thickness of the catalyst layer in the second region.

6. The region from the first surface of the substrate to a depth of 1 × D in the thickness direction of the substrate is defined as the first region. The region from a depth of 1 × D in the thickness direction of the substrate to a position of 2 × D in the thickness direction of the substrate, from the first surface of the substrate, is defined as the second region. The electrode according to claim 1, wherein the average thickness of the catalyst layer in the second region is 0.01 times or more and 0.5 times or less the average thickness of the catalyst layer in the first region.

7. The region from the first surface of the substrate to a depth of 3 × D in the thickness direction of the substrate is defined as the third region. The fourth region is defined as the area from a depth of 3 × D in the thickness direction of the substrate from the first surface of the substrate to a region of 10 × D in the thickness direction of the substrate. The electrode according to claim 1, wherein the average thickness of the catalyst layer in the fourth region is 0.001 times or more and 0.2 times or less the average thickness of the catalyst layer in the third region.

8. The substrate containing the metal fibers is such that the metal fibers are intertwined and the metal fibers are laminated in the thickness direction of the substrate. The electrode according to claim 1, wherein the substrate containing the metal particles is aggregated and the metal particles are laminated in the thickness direction of the substrate.

9. The catalyst layer is also provided on the surface of the metal fibers along the thickness direction, The electrode according to claim 1, wherein the catalyst layer is also provided on the surface of the metal particles along the thickness direction.

10. The catalyst layer is provided on the surface of the metal fibers facing a direction toward the second surface side of the substrate rather than a direction perpendicular to the thickness direction of the substrate, The electrode according to claim 1, wherein the catalyst layer is provided on the surface of the metal particles facing a direction toward the second surface side of the substrate rather than a direction perpendicular to the thickness direction of the substrate.

11. The catalyst layer is provided on the surface of the metal fibers in a direction that faces the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate, The catalyst layer provided on the surface of the metal fibers in a direction facing the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate is 3 [wt%] or more and 30 [wt%] or less of the total catalyst layer. The catalyst layer is provided on the surface of the metal particles in a direction that faces the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate, The electrode according to claim 1, wherein the catalyst layer provided on the surface of the metal particles in a direction facing the second surface side of the substrate rather than in a direction perpendicular to the thickness direction of the substrate is 3 [wt%] or more and 40 [wt%] or less of the total catalyst layer.

12. The electrode according to claim 1, wherein the porosity of the substrate is 30% or more and 70% or less.

13. The electrode according to claim 1, wherein the porosity of the substrate is 40% or more and 60% or less.

14. The electrode according to claim 1, wherein the catalyst layer has a structure in which sheet layers and gap layers are alternately stacked.

15. An electrode according to any one of claims 1 to 14, An electrolyte membrane in direct contact with the electrode, and a membrane electrode assembly comprising these.

16. The membrane electrode assembly according to claim 15, which includes the catalyst layer that does not come into contact with the membrane electrode assembly.

17. An electrochemical cell comprising the membrane electrode assembly described in claim 15.

18. A stack comprising a plurality of electrochemical cells as described in claim 17.

19. An electrolytic system comprising the stack described in claim 18.

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