Electrode, membrane electrode assembly, electrochemical cell, stack, and electrolysis device

Abstract

An electrode according to an embodiment is provided with a base material and a catalyst layer that is provided on the base material and is formed by alternately laminating sheet layers and gap layers. The gap layer contains a first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb.

Description

[0001] References to related applications

[0002] This application is based on Japanese Patent Application 2024-148309 (filed on August 30, 2024), which enjoys priority. This application incorporates the entire contents of that application by reference. Technical Field

[0003] This invention relates to electrodes, membrane electrode assemblies, electrochemical cells, fuel cells, and electrolysis devices. Background Technology

[0004] In recent years, electrochemical cells have been actively studied. Among electrochemical cells, solid polymeric water electrolyzers (PEMECs) are expected to be utilized for hydrogen generation in large-scale energy storage systems. To ensure sufficient durability and electrolysis performance, platinum (Pt) nanoparticle catalysts are generally used for the cathode of PEMECs, while noble metal catalysts such as iridium (Ir) nanoparticle catalysts are generally used for the anode. In addition, methods for obtaining hydrogen from ammonia have also been studied. Furthermore, it can also be used as the anode in electrolysis devices that electrolyze carbon dioxide to produce organic compounds such as methanol and ethylene, or carbon monoxide. Summary of the Invention

[0005] The implementation methods involve electrodes, membrane electrode assemblies, electrochemical cells, stacks, and electrolysis devices.

[0006] The electrode of the embodiment includes a substrate and a catalyst layer, wherein the catalyst layer is disposed on the substrate and is formed by alternating layers of sheet material and interstitial layers. The interstitial layer comprises a first oxide, wherein the first oxide contains one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb.

[0007] Based on the above configuration, an electrode with excellent properties and durability can be obtained. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the electrodes in the embodiment.

[0009] Figure 2 This is a partial schematic cross-sectional view of the electrode in the embodiment.

[0010] Figure 3 This is a partial schematic cross-sectional view of the electrode in the embodiment.

[0011] Figure 4 This is the analysis point for the implementation method.

[0012] Figure 5 This is a schematic diagram of the membrane electrode assembly according to the embodiment.

[0013] Figure 6 This is a schematic diagram of the electrochemical cell used in the implementation method.

[0014] Figure 7 This is a schematic diagram of the fuel cell stack used in the implementation method.

[0015] Figure 8 This is a conceptual diagram of the electrolysis apparatus for an implementation method.

[0016] Figure 9 This is a table of an example.

[0017] Explanation of symbols

[0018] 1: Substrate

[0019] 2: Catalyst layer

[0020] 2A: Sheet layer

[0021] 2B: Interstitial layer

[0022] 2C: columnar body

[0023] 11: Electrode 1

[0024] 11A: First catalyst layer

[0025] 11B: First substrate

[0026] 12: Second electrode

[0027] 12A: Second catalyst layer

[0028] 12B: Second substrate

[0029] 13: Electrolyte membrane

[0030] 21: Washer

[0031] 22: Washer

[0032] 23: Diaphragm

[0033] 24: Diaphragm

[0034] 31: Fastening plate

[0035] 32: Fastening plate

[0036] 41: Power supply

[0037] 42: Gas-liquid separation device

[0038] 43: Mixing tank

[0039] 44: Ion exchange water production equipment

[0040] 46: Pump

[0041] 47: Check valve

[0042] 48: Gas-liquid separation device

[0043] 49: Hydrogen refining unit

[0044] 50: Valve

[0045] 100: Electrode

[0046] 200: Membrane electrode assembly

[0047] 300: Electrochemical Cell

[0048] 400: Fuel cell stack

[0049] 500: Electrolysis apparatus Detailed Implementation

[0050] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0051] It should be noted that in the following description, the same symbol will be used to mark the same component, and the description of components that have been described before should be omitted.

[0052] The physical property values ​​in the instruction manual are those at a temperature of 25°C and a pressure of 1 atm. The thickness of each component is the average of the distances in the stacking direction.

[0053] The thickness and structure of the components described in the specification can be obtained, for example, from images of the cross-section obtained using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a high-angle Annular DarkField Scanning Transmission Electron Microscope (HAADF-STEM). Furthermore, the boundaries of the components described in the specification can be determined from images obtained by a scanning electron microscope or a transmission electron microscope, from measurements taken by a scanning electron microscope with an energy-dispersive X-ray spectroscopy (SEM-EDS) or a transmission electron microscope with an energy-dispersive X-ray spectroscopy (TEM-EDX), or from secondary ion mass analysis. Furthermore, the composition of the components described in the specification can be determined using methods such as secondary ion mass analysis, inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy with energy-dispersive X-ray spectrometry (EDX-SMS), or transmission electron microscopy with EDH-SMS. Additionally, the crystallinity of the components described in the specification can be evaluated using images obtained through X-ray diffraction (XRD), electron backscatter diffraction (EBSD), or high-angle annular dark-field scanning transmission electron microscopy, scanning electron microscopy, or transmission electron microscopy. The materials contained in the components described in the specification (crystal defects, bonding states, etc.) can be evaluated using high-angle annular dark-field scanning transmission electron microscopy, photoluminescence (PL), or X-ray photoelectron spectrophotometry (XPS). These analytical methods are examples and do not negate the specific analytical methods described in the specification.

[0054] (First Embodiment)

[0055] The first embodiment relates to an electrode. Figure 1 The figure shows a schematic cross-sectional view of the electrode 100 according to an embodiment. The electrode 100 has a substrate 1 and a catalyst layer 2. The catalyst layer 2 is disposed on the substrate 1.

[0056] In this embodiment, catalyst layer 2 is used as a catalyst for electrolysis. Electrolysis reactions include, for example, the production of hydrogen or nitrogen from water or ammonia. Electrolysis reactions include, for example, the production of carbon monoxide from carbon dioxide. Catalyst layer 2 is used as a catalyst in these reactions.

[0057] The electrode 100 of the first embodiment can be used, for example, as the anode of water electrolysis. If the catalyst layer 2 further includes a catalyst for a fuel cell, the electrode 100 of the embodiment can also be used as the oxygen electrode of a fuel cell. The electrode 100 of the embodiment can also be used as the anode for electrolysis to generate ammonia. The electrode of the embodiment can be used as the anode of an electrolysis apparatus for ammonia synthesis. Hereinafter, in the first embodiment and other embodiments, water electrolysis will be used as an example, but in addition to water electrolysis, the electrode 100 of the embodiment can be used, for example, as the anode of a membrane electrode assembly used in electrolysis for ammonia synthesis: ultrapure water or electrolyte is supplied to the anode, water is decomposed at the anode to generate protons and oxygen, and the generated protons pass through the electrolyte membrane, and nitrogen supplied to the cathode combines with protons and electrons to generate ammonia. The electrode 100 of the embodiment can also be used as the cathode for electrolysis of ammonia to generate hydrogen. The electrode of the embodiment can be used as the cathode of a hydrogen generation apparatus. Hereinafter, in the first embodiment and other embodiments, water electrolysis will be used as an example for explanation. However, in addition to water electrolysis, the electrode 100 of the embodiment can be used as the cathode of a membrane electrode assembly used in electrolysis for ammonia decomposition, for example: ammonia is supplied to the cathode, ammonia is decomposed at the cathode to generate protons and nitrogen, the generated protons pass through the electrolyte membrane, and at the anode, the protons combine with electrons to generate hydrogen.

[0058] The substrate 1 is preferably made of a porous material with high electrical conductivity. The substrate 1 is a porous component that allows gas and liquid to pass through.

[0059] Substrate 1 comprises metal fibers or metal particles. Substrate 1 preferably comprises metal fibers or metal particles of valve metal. The metal fibers and metal particles may also be plated.

[0060] The substrate 1 containing metal fibers is preferably a fabric containing metal fibers. The fabric containing metal fibers is preferably a web of metal fibers or a nonwoven fabric of metal fibers.

[0061] The substrate 1 containing metal particles is preferably a sintered body formed by the agglomeration of metal particles. The metal particles are preferably stacked along the thickness direction of the substrate 1.

[0062] The metal fiber preferably contains one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth and antimony, more preferably titanium, and even more preferably titanium.

[0063] The fiber diameter of the metal fiber is preferably 1 μm or more and 500 μm or less, and more preferably 1 μm or more and 100 μm or less, taking into account reactivity and charge-donating properties. The average fiber diameter of the metal fiber is preferably 1 μm or more and 500 μm or less, and more preferably 1 μm or more and 100 μm or less, taking into account reactivity and charge-donating properties.

[0064] The metal particles preferably include one or more metals selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb, more preferably including Ti, and even more preferably Ti.

[0065] The primary particle size (diameter) of the metal particles is preferably 1 μm or more and 500 μm or less, and more preferably 1 μm or more and 100 μm or less, taking into account reactivity and charge-donating properties. The average primary particle size (average diameter) of the metal particles is preferably 1 μm or more and 500 μm or less, and more preferably 1 μm or more and 100 μm or less, taking into account reactivity and charge-donating properties.

[0066] The substrate 1 is a conductive porous body. Considering the movement of matter, the porosity of the substrate 1 is preferably 20% or more and 95% or less, more preferably 40% or more and 90% or less.

[0067] The substrate 1 has a first surface A and a second surface B located on the opposite side of the first surface A. The first surface A and the second surface B are the main surfaces of the substrate 1. The first surface A and the second surface B of the substrate 1 are flat or substantially flat surfaces. The catalyst layer 2 is disposed on the first surface A side of the substrate 1.

[0068] 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, Mo, Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb. Catalyst layer 2 preferably contains oxides 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, Mo, Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb.

[0069] Catalyst layer 2 preferably contains an oxide of one or more noble metals selected from the group consisting of Ir, Ru, Pt and Pd.

[0070] The catalyst layer 2 is preferably a porous material. The porosity of the catalyst layer 2 is preferably 10 vol% or more and 90 vol% or less, more preferably 30 vol% or more and 70 vol% or less.

[0071] The amount of noble metal in catalyst layer 2 is preferably 0.01 mg / cm³. 2 ] and above 1.0 [mg / cm 2 ] or less, more preferably 0.03 [mg / cm] 2 ] and above and 0.5 [mg / cm 2 Below, it is even more preferred to be 0.04 mg / cm³. 2 Above and 0.1 mg / cm³ 2 The following is a summary of the mass values. The total mass can be determined by ICP-MS.

[0072] The thickness of the catalyst layer 2 is preferably 0.1 μm or more and 2 μm or less, more preferably 0.5 μm or more and 1 μm or less.

[0073] The catalyst layer 2 preferably has a structure in which sheet layers 2A and interstitial layers 2B are alternately stacked. The stacked structure of the catalyst layer 2 disposed on the substrate 1 is shown in [illustration]. Figure 2 and Figure 3 The diagram shows a partial cross-sectional view of the electrodes. Sheet layer 2A and spacer layer 2B are stacked in a generally parallel arrangement. Spacer layer 2B is mostly void, but in a portion, it is connected by the protrusion of sheet layer 2A. Sheet layer 2A is connected by columnar bodies 2C present in spacer layer 2B, maintaining the stacked structure. Figure 2 Schematic diagram and Figure 3 The difference in the schematic diagram is that the layer existing on the substrate 1 side is a sheet layer 2A ( Figure 2 ), or gap layer 2B ( Figure 3 ).

[0074] The structure formed by alternating layers of sheet 2A and spacer 2B can also be determined, for example, by the density of the layers in a cross-sectional SEM image of catalyst layer 2.

[0075] Sheet layer 2A is a layer composed of sheet-like aggregates of unsupported catalyst particles, such as metal oxides. Some voids also exist within sheet layer 2A. Sheet layer 2A is a dense layer containing many catalyst particles.

[0076] Interstitial layer 2B is the region sandwiched between sheet layers 2A, containing unsupported metal oxide particles, i.e., catalyst particles. Unlike sheet layers 2A, interstitial layer 2B does not have the regular structure of catalyst particles. Interstitial layer 2B is a region with low catalyst particle density. Columnar bodies 2C exist in interstitial layer 2B. In columnar bodies 2C present in interstitial layer 2B, unsupported particles, such as metal oxides, extend along the stacking direction of sheet layers 2A and interstitial layer 2B, connecting sheet layers 2A.

[0077] The average thickness of the first layer of the sheet layer 2A is preferably 10 nm or more and 200 nm or less, more preferably 10 nm or more and 100 nm or less, and even more preferably 10 nm or more and 50 nm or less.

[0078] The porosity of the sheet layer 2A is preferably 20 vol% or more and 80 vol% or less, more preferably 30 vol% or more and 70 vol% or less, and even more preferably 40 vol% or more and 60 vol% or less.

[0079] The average thickness of the first layer of the interstitial layer 2B is preferably 10 nm or more and 200 nm or less, more preferably 10 nm or more and 100 nm or less, and even more preferably 10 nm or more and 50 nm or less.

[0080] When the average thickness of the first layer of the gap layer 2B is set to d1, the thickness of the first layer of the sheet layer 2A is preferably 0.5 times or more and 10 times or less than d1, more preferably 1 time or more and 5 times or less, and even more preferably 2 times or more and 4 times or less.

[0081] When the porosity of the gap layer 2B is set to d2, the porosity of the sheet layer 2A is preferably 0.5 times or more and 5 times or less than d2, more preferably 1 times or more and 4 times or less, and even more preferably 2 times or more and 3 times or less.

[0082] The interstitial layer 2B preferably comprises an oxide (oxide of the first element) containing one or more elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb. The first oxide containing one or more elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb is preferably an oxide containing one or more elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb. The oxide containing one or more elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb is an oxide that is difficult to dissolve during the dissolution treatment during the formation of the interstitial layer 2B.

[0083] The interstitial layer 2B preferably comprises an oxide (oxide of the second element) containing one or more elements selected from the group consisting of Ni, Co, Mn, and Fe. The second oxide containing one or more elements selected from the group consisting of Ni, Co, Mn, and Fe is preferably an oxide selected from the group consisting of Ni, Co, Mn, and Fe. The second oxide containing one or more elements selected from the group consisting of Ni, Co, Mn, and Fe is an oxide that is easily soluble during the dissolution treatment during the formation of the interstitial layer 2B.

[0084] The interstitial layer 2B preferably comprises a first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb, and further comprises a second oxide containing one or more second elements selected from the group consisting of Ni, Co, Mn and Fe.

[0085] By including a first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb in the interstitial layer 2B, the increase in diffusion overvoltage is less even with extended electrolysis operating time, i.e., the overall structural stability of the catalyst layer 2 is improved. Improved overall structural stability of the catalyst layer 2 can suppress its degradation. Even with reduced amounts of noble metal catalyst during electrode fabrication, a low cell voltage can be maintained in the catalyst layer 2B containing a first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb.

[0086] The appropriate ratios shown below are those used when manufacturing electrode 100.

[0087] The total mass of the first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb contained in the interstitial layer 2B is preferably 20% or more and 80% or less of the total mass of the interstitial layer 2B, more preferably 20% or more and 70% or less, and even more preferably 30% or more and 60% or less.

[0088] The total mass of the first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb in the interstitial layer 2B containing the first oxide is preferably 20% or more and 80% or less of the mass of the interstitial layer 2B containing the first oxide, more preferably 30% or more and 70% or less, and even more preferably 40% or more and 60% or less.

[0089] For example, when the initial cell voltage of the catalyst layer 2B, which does not contain a first oxide of one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb, but has a large amount of Ir, is set to 100, the cell voltage of the catalyst layer 2B, which contains a first oxide of one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb, and has a small amount of Ir, is greater than 100. However, during long-term operation, the cell voltage of a catalyst layer 2 containing a first oxide of one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb, and with a low amount of Ir, in the interstitial layer 2B, is lower than that of a catalyst layer 2 containing no first oxide of one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb, but with a high amount of Ir. Therefore, the electrode 100 of the embodiment has a low amount of noble metal (for example, the amount of noble metal in the catalyst layer 2 is 0.01 mg / cm³). 2 Above and 0.1 mg / cm³ 2 The effect of improving durability becomes significant under the following conditions.

[0090] For example, by reducing the thickness of the sheet layer 2A and reducing the number of repeated layers of the sheet layer 2A and the interstitial layer 2B, the amount of precious metals such as Ir in the catalyst layer 2 can be reduced.

[0091] The total mass of the first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb contained in the sheet layer 2A is preferably 0% or more and 80% or less, more preferably 20% or more and 70% or less, and even more preferably 30% or more and 60% or less.

[0092] The first element contained in the first oxide is preferably one or more selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb, more preferably one or more selected from the group consisting of Ti, Ta, Nb, Hf, Zr, Zn, W and Sb, and even more preferably one or more selected from the group consisting of Ti, Ta, Nb, Hf, Zr and W.

[0093] The first oxide containing the first element is preferably less in the sheet layer 2A and more in the interstitial layer 2B. If the sheet layer 2A contains a large amount of the first oxide containing the first element, the catalytic activity of the catalyst layer 2 will decrease. Compared with the catalyst layer 2 containing the first oxide containing the first element throughout, it is preferable to selectively (concentratedly) contain the first oxide containing the first element in the interstitial layer 2B.

[0094] The total mass of the second oxide containing one or more second elements selected from the group consisting of Ni, Co, Mn and Fe contained in the sheet layer 2A is preferably 20% or more and 80% or less, more preferably 30% or more and 70% or less, and even more preferably 40% or more and 60% or less.

[0095] The second element contained in the second oxide is preferably one or more selected from the group consisting of Ni, Co, Mn and Fe, more preferably one or more selected from the group consisting of Ni and Co, and even more preferably Ni.

[0096] The second oxide containing the second element is preferably less in the sheet layer 2A and more in the interstitial layer 2B. If the sheet layer 2A contains a large amount of the second oxide containing the second element, the catalytic activity of the catalyst layer 2 will decrease. Compared with the catalyst layer 2 containing the second oxide containing the second element throughout, it is preferable to selectively (concentratedly) contain the second oxide containing the second element in the interstitial layer 2B.

[0097] The total mass of the first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb contained in the sheet layer 2A is preferably 10 wt% or more and 90 wt% or less, more preferably 20 wt% or more and 80 wt% or less, and even more preferably 30 wt% or less, of the total mass of the first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb contained in the interstitial layer 2B. The total mass of the second oxide containing one or more second elements selected from the group consisting of Ni, Co, Mn and Fe contained in the sheet layer 2A is preferably 10% or more and 90% or less, more preferably 20% or more and 80% or less, and even more preferably 30% or more and 70% or less, of the total mass of the second oxide containing one or more second elements selected from the group consisting of Ni, Co, Mn and Fe contained in the interstitial layer 2B.

[0098] The total mass of the first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi and Sb contained in the interstitial layer 2B is preferably 20% or more and 80% or less, more preferably 30% or more and 70% or less, and even more preferably 40% or more and 60% or less.

[0099] From the perspective of balancing high catalytic activity and improved structural stability of catalyst layer 2, the ratio of the total amount of first oxides containing the first element to the total amount of second oxides containing the second element in interstitial layer 2B preferably satisfies the above-mentioned relationship. If the ratio of first oxides of the first element in interstitial layer 2B is relatively high, the porosity of interstitial layer 2B increases. If the ratio of second oxides of the second element in interstitial layer 2B is relatively high, the porosity of interstitial layer 2B decreases.

[0100] The first oxide containing the first element and the second oxide containing the second element can be different oxides, or they can exist in the catalyst layer 2 as a composite oxide of the first oxide and the second oxide, or they can exist in the catalyst layer 2 as a first oxide containing the first element, a second oxide containing the second element, and a composite oxide of the first oxide and the second oxide. The ratio of oxides in the specification also takes into account the ratio of composite oxides.

[0101] The catalyst layer 2 comprises two or more interstitial layers 2B. Preferably, the interstitial layers 2B, which consist of one or more layers, contain a first oxide of the first element. When the number of interstitial layers 2B without the first oxide is set to n, the number of interstitial layers 2B containing the first oxide of the first element is preferably 1×n (1 times n) or more and 10×n (10 times n) or less, more preferably 3×n (3 times n) or more and 7×n (7 times n) or less, and even more preferably 4×n (4 times n) or more and 6×n (6 times n) or less.

[0102] The total mass of the oxides (third oxides) of noble metals (third elements) selected from the group consisting of Ir, Ru, Pt and Pd contained in the interstitial layer 2B is preferably 10 [wt%] or more and 80 [wt%] or less, more preferably 20 [wt%] or more and 70 [wt%] or less, and even more preferably 30 [wt%] or more and 60 [wt%] or less.

[0103] The third oxide of the third element is preferably less in the interstitial layer 2B and more in the sheet layer 2A. It is preferable to selectively include the third oxide of the third element in the sheet layer 2A, rather than including it throughout the catalyst layer 2.

[0104] The determination of the sheet layer 2A and interstitial layer 2B of catalyst layer 2, as well as the distribution of the first oxide, the second oxide, and the third oxide, can be obtained by observing cross-sections at multiple analytical points. For example... Figure 4 As shown, with the length D1 and width D2 of electrode 100 set to (D1≥D2), imaginary lines are drawn at distances D3 (=D1 / 10) inward from each of the two opposite sides in the width direction of electrode 100, and imaginary lines are drawn at distances D4 (=D2 / 10) inward from each of the two opposite sides in the length direction of electrode 100. Then, imaginary lines parallel to the width direction and passing through the center of electrode 100 are drawn, and imaginary lines parallel to the length direction and passing through the center of electrode 100 are drawn. The region centered at the intersection point 9 of these imaginary lines is designated as analysis points A1~A9. Each point is square and has a diameter of at least 10 μm. 2 The area is defined as [ ]. The image obtained by observing each point can also be a mosaic image created by combining multiple raster images (mosaic). Furthermore, the observation section using SEM-EDX or TEM-EDX is relative to [ ]. Figure 1The plane is perpendicular to the width direction. The thickness of the interstitial layer 2B at analysis points A1–A9 is determined at 50 nm intervals along the width direction of the SEM or TEM image. The ratio of catalyst layer 2 located in a specific location is set as the average value at each point. The ratio of catalyst layer 2 located in a specific location is determined from the volume and ratio of catalyst layer 2.

[0105] Next, an example of a method for fabricating electrode 100 is shown. A sheet layer precursor, which is essentially a precursor of sheet layer 2A, and an interstitial layer precursor, which is essentially a precursor of interstitial layer 2B, are alternately sputtered onto a substrate 1. The target used in forming the sheet layer precursor contains a third element. The target used in forming the interstitial layer precursor contains a first element and a second element. The sheet layer precursor and the interstitial layer precursor are formed in an oxidizing atmosphere. The laminate formed by alternating layers of the sheet layer precursor and the interstitial layer precursor is treated with a solution containing a second oxide of the second element of the interstitial layer precursor, which can be selectively dissolved. The dissolving solution is, for example, sulfuric acid, hydrochloric acid, or nitric acid. After solution treatment, the electrode 100 is obtained by arbitrary heating treatment in an oxidizing atmosphere.

[0106] In the electrode 100 of the embodiment, the structural stability of the catalyst layer 2 is improved. The electrode 100 of the embodiment, as an electrode for electrolysis, possesses high durability and excellent electrolysis characteristics.

[0107] (Second Implementation)

[0108] The second embodiment relates to a membrane electrode assembly (MEA). Figure 5 The diagram shows a schematic of the membrane electrode assembly 200 according to an embodiment. The membrane electrode assembly 200 has a first electrode 11, a second electrode 12, and an electrolyte membrane (diaphragm) 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 either the first electrode 11 or the second electrode 12. The membrane electrode assembly 200 of the embodiment is preferably used in an electrochemical cell or stack for hydrogen or oxygen generation.

[0109] The first electrode 11 has a first substrate 11B and a first catalyst layer 11A. The first catalyst layer 11A is disposed on the first substrate 11B. The first catalyst layer 11A is preferably in direct contact with the electrolyte membrane 13. When the 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.

[0110] The second electrode 12 has a second substrate 12B and a second catalyst layer 12A. The second catalyst layer 12A is disposed on the second substrate 12B. The second catalyst layer 12A is disposed on the electrolyte membrane 13 side. Preferably, the second catalyst layer 12A is in direct contact with the electrolyte membrane 13.

[0111] The second substrate 12B is preferably made of a porous material with high electrical conductivity. The second substrate 12B is a porous component that allows gas and liquid to pass through. The second substrate 12B is, for example, carbon paper or a metal mesh. As a metal mesh, a porous substrate of valve metal is preferred. As a porous substrate of valve metal, a porous substrate comprising one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony, or a porous substrate comprising one metal selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony, is preferred. The second substrate 12B has a carbon layer (MPL layer) comprising carbon microparticles and a water-resistant resin (PTFE, Nafion, or other fluoropolymers). The carbon layer is, for example, disposed between the carbon paper and the second catalyst layer 12A.

[0112] The second catalyst layer (cathode catalyst layer) 12A has a catalyst metal. The second catalyst layer 12A is preferably composed of catalyst metal particles, and the catalyst metal is 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, alloy, or metal oxide. The second catalyst layer 12A preferably has, for example, multiple catalyst units formed by alternating layers of sheet-like catalyst layers and interstitial layers.

[0113] The amount of noble metal per unit area of ​​the second catalyst layer 12A is preferably 0.02 mg / cm². 2 ] and above 1.0 [mg / cm 2 ] or less, more preferably 0.05 [mg / cm³] 2 ] and above and 0.5 [mg / cm 2 The following is a summary of the mass values. The total mass can be determined by ICP-MS.

[0114] The amount of noble metal (noble metal is one or more elements selected from the group consisting of Ir, Ru, Pt and Pd) per unit area of ​​the first catalyst layer 11A of the anode [mg / cm²] 2 The preferred amount of noble metal (one or more elements selected from the group consisting of Ir, Ru, Pt, and Pd) per unit area of ​​the second catalyst layer 12A of the cathode is [mg / cm²]. 2The content of the precious metal is 5% or more and 35% or less, more preferably 7% or more and 30% or less, and even more preferably 7% or more and 20% or less. By using the electrode 100 of the first embodiment on the anode, high activity and durability are achieved with relatively little precious metal compared to the cathode.

[0115] The porosity of the second catalyst layer 12A is preferably 10 vol% or more and 90 vol% or less, more preferably 30 vol% or more and 70 vol% or less.

[0116] The electrolyte membrane 13 is preferably a proton-conducting membrane. The electrolyte membrane 13 is preferably composed of one or more fluorinated polymers or aromatic hydrocarbon polymers selected from the group consisting of sulfonic acid groups, sulfonylimide groups, and sulfate groups. The electrolyte membrane 13 is preferably a fluorinated polymer having sulfonic acid groups. Examples of fluorinated polymers having sulfonic acid groups include Nafion (manufactured by DuPont), FLEMION (manufactured by Asahi Kasei Corporation), SELEMION (manufactured by Asahi Kasei Corporation), aquivion (manufactured by Solvay Specialty Polymers), or Aciplex (manufactured by Asahi Glass Co., Ltd.). It should be noted that, instead of a proton-conducting membrane, various conductive membranes such as anion exchange membranes and porous membranes can sometimes be used.

[0117] The thickness of the electrolyte membrane 13 can be appropriately determined by taking into account the membrane's permeation characteristics, durability, and other properties. From the viewpoint of strength, solvent resistance, and MEA output characteristics, the thickness of the electrolyte membrane 13 is preferably 20 μm or more and 500 μm or less, more preferably 50 μm or more and 300 μm or less, and even more preferably 80 μm or more and 200 μm or less.

[0118] The electrolyte membrane 13 preferably includes a noble metal region on the side of the first electrode 11. The noble metal region contains noble metal particles. The noble metal region is preferably present on the surface of the electrolyte membrane 13. The noble metal region is preferably composed of a single region, but it may also be composed of multiple separate regions.

[0119] The precious metal particles are preferably particles of one or more precious metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles may also include particles containing alloys selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles are preferably particles of one precious metal selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. Pt particles are preferred. Re particles are preferred. Rh particles are preferred. Ir particles are preferred. Pd particles are preferred. Ru particles are preferred.

[0120] The noble metal particles oxidize the hydrogen generated on the cathode side and passing through the electrolyte membrane 13. The noble metal particles suppress hydrogen leakage. Because the noble metal particles are present on the anode side, they do not readily oxidize the hydrogen discharged from the cathode side. The region containing the noble metal particles may also exist within the electrolyte membrane 13 on the second electrode 12 (cathode) side.

[0121] The average circumscribed circle diameter of the noble 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.

[0122] By using the durable and high-performance electrode 100 as the anode of the membrane electrode assembly 200, it is possible to operate with high activity for a long time.

[0123] (Third Implementation)

[0124] The third embodiment relates to an electrochemical cell. Figure 6 A schematic cross-sectional view of the electrochemical cell 300 according to the third embodiment is shown. The electrochemical cell 300 will be described below using water electrolysis as an example, but hydrogen can also be produced by decomposing ammonia or other substances besides water.

[0125] like Figure 6 The electrochemical cell 300 of Embodiment 3 shown has a first electrode (anode) 11, a second electrode (cathode) 12, an electrolyte membrane 13, gaskets 21 and 22, a diaphragm 23, and a diaphragm 24. The sealing material of the first electrode 11 can also be used as gasket 21. The sealing material of the second electrode 12 can also be used as gasket 22.

[0126] Preferably, a membrane electrode assembly 200 is formed by joining a first electrode (anode) 11, a second electrode (cathode) 12, and an electrolyte membrane 13. Alternatively, the anode feeder can be provided separately from the diaphragm 23. The cathode feeder can also be provided separately from the diaphragm 24.

[0127] Figure 6 In the electrochemical cell 300, a power source (not shown) is connected to membranes 23 and 24, where reactions occur at the first electrode 11 and the second electrode 12. For the first electrode 11, for example, water is supplied, and at the first electrode 11, water is decomposed into protons, oxygen, and electrons. The electrode support and charge supply are porous materials that function as flow path plates. The generated water and unreacted water are discharged, and the protons and electrons are utilized in the cathode reaction. The cathode reaction is a reaction of protons and electrons to produce hydrogen. Either or both of the generated hydrogen and oxygen can be used, for example, as fuel for a fuel cell.

[0128] (Fourth implementation)

[0129] The fourth embodiment relates to a fuel cell stack. Figure 7 This is a schematic cross-sectional view showing the fuel cell stack 400 of the fourth embodiment. Figure 7 The fuel cell stack 400 shown in the third embodiment is formed by connecting multiple MEAs 200 or electrochemical cells 300 in series. Fastening plates 31 and 32 are installed at both ends of the MEAs or electrochemical cells.

[0130] Since the amount of hydrogen produced in an electrochemical cell 300 containing a single MEA200 is small, a large amount of hydrogen can be obtained by constructing a stack 400 consisting of multiple MEA200s or multiple electrochemical cells 300 connected in series.

[0131] (Fifth Embodiment)

[0132] The fifth embodiment relates to an electrolysis apparatus. Figure 8 A conceptual diagram of the electrolysis apparatus according to the fifth embodiment is shown. For the electrolysis apparatus 500, an electrochemical cell 300 or a fuel cell stack 400 is used. Figure 8 The electrolysis apparatus is used for water electrolysis. An electrolysis apparatus for water electrolysis will be described. For example, in the case of producing hydrogen from ammonia, an apparatus with other configurations using electrode 100 is preferred. Furthermore, the electrode of the embodiment can also be used in an electrolysis apparatus for electrolyzing carbon dioxide to produce organic compounds such as methanol or ethylene, or carbon monoxide.

[0133] like Figure 8 As shown, a fuel cell stack 400 is used, which consists of single cells for water electrolysis stacked in series. A power supply 41 is installed in the fuel cell stack 400 to apply voltage between the anode and cathode. On the anode side of the fuel cell stack 400, the generated gas is connected to a gas-liquid separator 42 and a mixing tank 43 to separate unreacted water. For the mixing tank 43, a pump 46 supplies liquid from an ion-exchange water production unit 44, which mixes the liquid in the mixing tank 43 via a check valve 47 and then circulates it to the anode. Oxygen generated at the anode is obtained by passing it through the gas-liquid separator 42. On the cathode side, a hydrogen refining unit 49 is continuously connected to the gas-liquid separator 48 to obtain high-purity hydrogen. Impurities are discharged through a path with a valve 50 connected to the hydrogen refining unit 49. To stably control the operating temperature, the heating of the fuel cell stack and mixing tank, and the current density during thermal decomposition, can be controlled.

[0134] The present invention will now be described in more detail based on embodiments, but the present invention is not limited to the following embodiments.

[0135] (Example 1)

[0136] A catalyst layer is formed on a nonwoven fabric containing titanium metal fibers as the substrate. The catalyst layer has a structure consisting of 40 alternating layers of sheet material and interstitial layers. A sheet material precursor containing Ir oxide and an interstitial layer precursor containing Ni oxide and Ta oxide are alternately formed by sputtering in an oxidizing atmosphere. The loading density of the noble metal is set to 0.05 mg / cm³. 2 Subsequently, sulfuric acid was used to selectively dissolve most of the interstitial layer precursor to obtain the electrode of the embodiment. The obtained electrode was used as the anode.

[0137] An electrode was obtained by forming a porous catalyst layer containing Pt on carbon paper as a substrate. The resulting electrode was used as the cathode. The loading density of the noble metal was set to 0.4 mg / cm³. 2 ].

[0138] A membrane electrode assembly was obtained by sandwiching a Nafion membrane as an electrolyte membrane between the obtained anode and cathode and pressing them together. The obtained membrane electrode assembly was then placed between two flow-path diaphragms and fixed with a gasket to obtain an electrochemical cell. For the obtained electrochemical cell, the temperature was measured at 80 °C and the current density at 2 A / cm². 2 The system underwent 48 hours of water electrolysis operation to evaluate durability and cell voltage.

[0139] The cell voltage was evaluated after 100 hours, 200 hours, 300 hours, 400 hours, 500 hours, and 600 hours from the start of operation. The difference between the rate of increase of the cell voltage of Example 1 (the rate of increase of the cell voltage after each time period from the start of operation) and the rate of increase of the cell voltage of Comparative Example 1 (the rate of increase of the cell voltage of Comparative Example 1 - the rate of increase of the cell voltage of Example 1) ([rate of increase of the cell voltage of Comparative Example 1] - [rate of increase of the cell voltage of Example 1]) was 0% or more and less than 0.5%, rated as A; 0.5% or more and less than 1.0%, rated as B; 1.0% or more and less than 1.5%, rated as C; 1.5% or more and less than 2.0%, rated as D; 2.0% or more and less than 2.5%, rated as E; and 2.5% or more and less than 3.0%, rated as F.

[0140] (Comparative Example 1)

[0141] As an interstitial layer precursor, it does not contain Ta oxide but forms Ni oxide. Otherwise, the anode is fabricated in the same manner as in Example 1, and the fabricated anode is used to fabricate an electrochemical cell. The cell voltage is measured using the fabricated electrochemical cell under the same conditions as in Example 1.

[0142] Regarding the rate of rise of the cell voltage in Example 1, where the comparison object is set as Comparative Example 1, it is summarized in Figure 9 The table shows that the rate of rise of the cell voltage in Example 1 is less than that in Comparative Example 1. Figure 9 As shown in the table, the rate of increase of the cell voltage in the comparative example increased over time, while the rate of increase in Example 1 remained relatively unchanged over time. Therefore, it was found that the difference between the rate of increase of the cell voltage in Example 1 and the rate of increase of the cell voltage in Comparative Example 1 increased over time. Furthermore, if the diffusion overvoltage of Example 1 and Comparative Example 1 was also evaluated, the increase in diffusion overvoltage of Example 1 was less than that of Comparative Example 1. Diffusion overvoltage can evaluate the structural collapse of the catalyst layer, and the diffusion overvoltage also indicates that the electrode of Example 1 has high durability.

[0143] (Example 2)

[0144] Compared to Example 1, the ratio of Ta oxide in the interstitial layer precursor was increased. Otherwise, the process was the same as in Example 1, and the anode was used to fabricate the electrochemical cell. The cell voltage was measured using the fabricated electrochemical cell under the same conditions as in Example 1. The rate of increase in cell voltage of Comparative Example 1 (which served as a comparison object for Example 2) was compared with the rate of increase in cell voltage of Example 2 to evaluate the rate of increase in cell voltage of Example 2.

[0145] (Example 3)

[0146] Compared to Example 1, the ratio of Ta oxide in the interstitial layer precursor was reduced. Otherwise, the process was the same as in Example 1, and the electrochemical cell was fabricated using the fabricated anode. The cell voltage was measured using the fabricated electrochemical cell under the same conditions as in Example 1. The rate of increase in cell voltage of Comparative Example 1 (which served as a comparison object for Example 3) was compared with the rate of increase in cell voltage of Example 3 to evaluate the rate of increase in cell voltage of Example 3.

[0147] Similar to Example 1, the difference between the rate of increase of cell voltage in Examples 2 and 3 and the rate of increase of cell voltage in Comparative Example 1 increases over time. Although Example 3, which has relatively less Ta oxide in the interstitial layer, has a larger rate of increase of cell voltage, Example 3 also effectively suppresses the increase of cell voltage compared to Comparative Example 1. In terms of examples, although Ta oxide is used, the case where a first oxide of a first element other than Ta is used is also more difficult to dissolve than an oxide of a second element, so the first oxide remains in the interstitial layer. Therefore, examples that use Ta oxide but a first oxide of a first element other than Ta also have a low rate of increase of cell voltage and high durability, similar to Example 1.

[0148] In the instruction manual, some elements are represented only by element symbols.

[0149] The technical solutions for the implementation methods are described below.

[0150] Technical Solution 1

[0151] An electrode comprising a substrate and a catalyst layer,

[0152] The catalyst layer is disposed on the aforementioned substrate and is composed of alternating layers of sheet material and interstitial layers.

[0153] The aforementioned interstitial layer comprises a first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb.

[0154] Technical Solution 2

[0155] According to the electrode of technical solution 1, the interstitial layer comprises a second oxide containing one or more second elements selected from the group consisting of Ni, Co, Mn and Fe.

[0156] Technical Solution 3

[0157] According to the electrode of technical solution 1 or 2, the total mass of the first oxide contained in the interstitial layer is more than 20 [wt%] and less than 80 [wt%] of the total mass of the interstitial layer.

[0158] Technical Solution 4

[0159] According to the electrode described in any one of technical solutions 1 to 3, the total mass of the first oxide contained in the interstitial layer is 20% or more and 80% or less of the mass of the interstitial layer containing the first oxide.

[0160] Technical Solution 5

[0161] According to the electrode described in any one of technical solutions 1 to 4, the total mass of the first oxide contained in the sheet layer is 0% or more and 80% or less of the total mass of the first oxide contained in the gap layer.

[0162] Technical Solution 6

[0163] According to the electrode described in any one of technical solutions 1 to 5, the first element contained in the first oxide is selected from one or more elements selected from the group consisting of Ti, Ta, Nb, Hf, Zr and W.

[0164] Technical Solution 7

[0165] According to the electrode of technical solution 2, the total mass of the second oxide contained in the sheet layer is 20% or more and 80% or less of the total mass of the second oxide contained in the gap layer.

[0166] Technical Solution 8

[0167] According to the electrode described in any one of technical solutions 1 to 7, when the number of the interstitial layers is set to n, the number of the interstitial layers containing the first oxide is 1×n or more and 10×n or less.

[0168] Technical Solution 9

[0169] According to the electrode described in any one of technical solutions 1 to 8, the average thickness of one layer of the aforementioned sheet material is 10 nm or more and 200 nm or less.

[0170] The average thickness of the first layer of the aforementioned interstitial layer is 10 nm or more and 200 nm or less.

[0171] Technical Solution 10

[0172] According to the electrode described in any one of technical solutions 1 to 9, the thickness of the catalyst layer is 0.1 μm or more and 2 μm or less.

[0173] Technical Solution 11

[0174] The electrode according to technical solution 2 or 7, wherein a composite oxide as a first oxide and a second oxide exists in the catalyst layer.

[0175] Technical Solution 12

[0176] According to the electrode described in any one of technical solutions 1 to 11, the total mass of the first oxide contained in the sheet layer is 10% or more and 90% or less of the total mass of the first oxide contained in the gap layer.

[0177] Technical Solution 13

[0178] According to the electrode described in technical solutions 2, 7 or 11, the total mass of the first oxide contained in the interstitial layer is 20% or more and 80% or less of the total mass of the second oxide contained in the interstitial layer 2B.

[0179] Technical Solution 14

[0180] According to the electrode described in any one of technical solutions 1 to 13, the total mass of the first oxide contained in the interstitial layer is 20% to 80% of the total mass of the interstitial layer.

[0181] The total mass of the first oxide contained in the interstitial layer, which contains the first oxide, is 20% or more and 80% or less of the mass of the interstitial layer containing the first oxide.

[0182] The total mass of the first oxide contained in the sheet layer is 0% or more and 80% or less of the total mass of the first oxide contained in the gap layer.

[0183] Technical Solution 15

[0184] According to the electrode described in technical solutions 2, 7, 11 or 13, the total mass of the second oxide contained in the sheet layer is 20% or more and 80% or less of the total mass of the second oxide contained in the interstitial layer.

[0185] The total mass of the first oxide contained in the aforementioned sheet layer is 10% or more and 90% or less of the total mass of the first oxide contained in the aforementioned gap layer.

[0186] The total mass of the first oxide contained in the interstitial layer is 20% or more and 80% or less of the total mass of the second oxide contained in the interstitial layer.

[0187] Technical Solution 16

[0188] A membrane electrode assembly comprising:

[0189] The anode of the electrode described in any of technical solutions 1 to 10,

[0190] The cathode containing the cathode catalyst layer, and

[0191] The electrolyte membrane that is in direct contact with the electrodes mentioned above.

[0192] Technical Solution 17

[0193] According to the membrane electrode assembly described in technical solution 16, the noble metal content per unit area of ​​the catalyst layer of the anode [mg / cm²] 2 [mg / cm³] represents the amount of noble metal per unit area of ​​the second catalyst layer at the cathode. 2 [5% to 35% of the total]

[0194] Technical Solution 18

[0195] An electrochemical cell comprising the membrane electrode assembly described in technical solution 16 or 17.

[0196] Technical Solution 19

[0197] An electric stack having multiple electrochemical cells as described in technical solution 18.

[0198] Technical Solution 20

[0199] An electrolysis apparatus comprising the electrochemical cell described in technical solution 18 or the fuel cell stack described in technical solution 19.

[0200] Several embodiments of the present invention have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. PEMEC is cited as a water electrolyzer, but the present invention is equally applicable to other electrolyzers. These novel embodiments described above can be implemented in various other ways, 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, and are also included within the scope of the invention as described in the claims and its equivalents.

Claims

1. An electrode comprising a substrate and a catalyst layer, the catalyst layer being provided on the substrate, and being formed by alternately stacking a sheet layer and a gap layer, the gap layer containing a first oxide containing one or more first elements selected from the group consisting of Ti, Al, Ta, Nb, Hf, Zr, Zn, W, Bi, and Sb.

2. The electrode of claim 1, wherein, the gap layer containing a second oxide containing one or more second elements selected from the group consisting of Ni, Co, Mn, and Fe.

3. The electrode of claim 1, wherein, the total mass of the first oxide contained in the gap layer is 20% by mass or more and 80% by mass or less of the mass of the entire gap layer.

4. The electrode of claim 1, wherein, the total mass of the first oxide contained in the gap layer containing the first oxide is 20% by mass or more and 80% by mass or less of the mass of the gap layer containing the first oxide.

5. The electrode of claim 1, wherein, the total mass of the first oxide contained in the sheet layer is 0% by mass or more and 80% by mass or less of the total mass of the first oxide contained in the gap layer.

6. The electrode of claim 1, wherein, the first elements contained in the first oxide are one or more selected from the group consisting of Ti, Ta, Nb, Hf, Zr, and W.

7. The electrode of claim 2, wherein, the total mass of the second oxide contained in the sheet layer is 20% by mass or more and 80% by mass or less of the total mass of the second oxide contained in the gap layer.

8. The electrode of claim 1, wherein, when the number of layers of the gap layer not containing the first oxide is set to n, the number of the gap layers containing the first oxide is 1 x n or more and 10 x n or less.

9. The electrode of claim 1, wherein, the average thickness of one layer of the sheet layer is 10 nm or more and 200 nm or less, the average thickness of one layer of the gap layer is 10 nm or more and 200 nm or less.

10. The electrode of claim 1, wherein, the thickness of the catalyst layer is 0.1 μm or more and 2 μm or less.

11. The electrode of claim 2, wherein, a complex oxide of the first oxide and the second oxide is present in the catalyst layer.

12. The electrode of claim 1, wherein, the total mass of the first oxide contained in the sheet layer is 10% by mass or more and 90% by mass or less of the total mass of the first oxide contained in the gap layer.

13. The electrode of claim 2, wherein, the total mass of the first oxide contained in the gap layer is 20% by mass or more and 80% by mass or less of the total mass of the second oxide contained in the gap layer.

14. The electrode of claim 1, wherein, the total mass of the first oxide contained in the gap layer is 20% by mass or more and 80% by mass or less of the mass of the entire gap layer, the total mass of the first oxide contained in the gap layer containing the first oxide is 20% by mass or more and 80% by mass or less of the mass of the gap layer containing the first oxide, the total mass of the first oxide contained in the sheet layer is 0% by mass or more and 80% by mass or less of the total mass of the first oxide contained in the gap layer.

15. The electrode of claim 2, wherein, the total mass of the second oxide contained in the sheet layer is 20% by mass or more and 80% by mass or less of the total mass of the second oxide contained in the gap layer, The total mass of the first oxide contained in the sheet layer is 10% by mass or more and 90% by mass or less of the total mass of the first oxide contained in the gap layer, The total mass of the first oxide contained in the gap layer is 20% by mass or more and 80% by mass or less of the total mass of the second oxide contained in the gap layer.

16. A membrane electrode assembly comprising: an anode of any one of claims 1 to 15, a cathode comprising a cathode catalyst layer, and an electrolyte membrane in direct contact with the anode.

17. The membrane electrode assembly of claim 16, wherein, The amount of the precious metal per unit area of the catalyst layer of the anode is 5% or more and 35% or less of the amount of the precious metal per unit area of the second catalyst layer of the cathode, in mg / cm 2 The amount of the precious metal per unit area of the catalyst layer of the anode is 5% or more and 35% or less of the amount of the precious metal per unit area of the second catalyst layer of the cathode, in mg / cm 2 The amount of the precious metal per unit area of the catalyst layer of 18. An electrochemical cell comprising the membrane electrode assembly of claim 16.

19. A stack comprising a plurality of the electrochemical cell of claim 18.

20. An electrolysis device comprising the stack of claim 19.

21. A method for producing an electrode according to any one of claims 1 to 15, comprising the steps of: preparing a first slurry containing a first oxide and a binder; preparing a second slurry containing a second oxide and a binder; and applying the first slurry and the second slurry to a substrate to form a sheet layer and a gap layer, respectively.

22. A method for producing an electrode according to any one of claims 1 to 15, comprising the steps of: preparing a first slurry containing a first oxide and a binder; preparing a second slurry containing a second oxide and a binder; and applying the first slurry and the second slurry to a substrate to form a sheet layer and a gap layer, respectively, wherein the first slurry and the second slurry are applied to the substrate in the order of the first slurry and the second slurry, or the second slurry and the first slurry.

23. A method for producing an electrode according to any one of claims 1 to 15, comprising the steps of: preparing a first slurry containing a first oxide and a binder; preparing a second slurry containing a second oxide and a binder; and applying the first slurry and the second slurry to a substrate to form a sheet layer and a gap layer, respectively, wherein the first slurry and the second slurry are applied to the

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