Electrode and solid oxide cell

Abstract

The porous electrode (1) of the present invention is composed of a mixture containing solid electrolyte particles (11) composed of a proton-conducting oxide and catalyst particles (12) composed of an electron-conducting oxide or metal and having electrode catalytic activity. The electrode (1) satisfies at least one of requirement A and requirement B. Requirement A: minute projections (13) are present on the surface of the catalyst particles (12), the minute projections (13) containing at least one of the element group constituting the catalyst particles (12) or a part thereof and the element group constituting the solid electrolyte particles (11) or a part thereof; requirement B: a thin film layer (14) is present at least one of the interface between the solid electrolyte particles (11) and the catalyst particles (12) and the interface between the solid electrolyte particles (11) and the solid electrolyte layer (20), the thin film layer (14) containing at least one of the element group forming the catalyst particles (12) or a part thereof and the element group forming the solid electrolyte particles (1) or a part thereof.

Description

Technical Field

[0001] This disclosure relates to electrodes and solid oxide single cells. Background Technology

[0002] Previously, solid oxide cells (SOECs) using solid oxides as electrolytes were known. Specifically, SOECs include solid oxide electrolysis cells (hereinafter sometimes called SOECs) and solid oxide fuel cell cells (hereinafter sometimes called SOFCs). SOECs can synthesize hydrogen or hydrocarbons, thus being useful for realizing a carbon cycle society. Furthermore, while SOECs also depend on the materials used, they can also function as SOFCs with the same structure.

[0003] As a technology related to solid oxide single cells, for example, Patent Document 1 discloses an electrochemical single cell that can be used as both a solid oxide fuel cell and a single cell for steam electrolysis. This single cell has an oxygen electrode, a proton-conductive solid electrolyte layer, and a hydrogen electrode, with the proton-conductive solid electrolyte layer sandwiched between the oxygen and hydrogen electrodes. The oxygen electrode comprises a perovskite-type metal oxide and a proton-conductive solid electrolyte, wherein the perovskite-type metal oxide contains Ba at site A and Co at site B. Furthermore, in the embodiments of this document, an A / cm² output of approximately 0.5 A / cm² is described at a single cell operating temperature of 600°C and a voltage of 1.3 V. 2 The output.

[0004] Furthermore, for example, Patent Document 2 discloses a proton-ceramic reversible single cell comprising a steam electrolysis single cell and a fuel cell. This single cell sequentially comprises an air electrode, an air electrode interface functional layer, a proton-conducting ceramic layer, and a fuel electrode. The air electrode interface functional layer comprises a specific metal oxide and / or its hydrate having a perovskite structure. Additionally, this document describes forming the air electrode interface functional layer at the interface between the proton-conducting ceramic layer and the air electrode using a pulsed laser deposition method. Existing technical documents Patent documents

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-135987 [Patent Document 2] Japanese Patent Application Publication No. 2023-146930 Summary of the Invention

[0006] The following problems exist in the existing technology. Specifically, solid oxide single-cell batteries generally tend to have lower output as the cell operating temperature decreases. At a low operating temperature of 500°C for any of the aforementioned single-cell batteries, sufficient initial output cannot be obtained; furthermore, achieving high Faraday efficiency is difficult.

[0007] This disclosure was made in view of this problem, and its object is to provide an electrode that can achieve high initial output and high Faradaic efficiency even at relatively low single-cell operating temperatures when used in a solid oxide single cell, and a solid oxide single cell using the electrode.

[0008] One aspect of this disclosure is an electrode. It is a porous electrode used in solid oxide single cells with a solid electrolyte layer exhibiting proton conductivity. It consists of a mixture comprising at least solid electrolyte particles formed from oxides exhibiting proton conductivity and catalyst particles formed from oxides or metals exhibiting electronic conductivity and possessing electrode catalytic activity. At least one of the following requirements A and B must be met. Requirement A: The surface of the catalyst particles has minute protrusions, the minute protrusions containing at least one of the element group or a portion thereof that forms the catalyst particles, and the element group or a portion thereof that forms the solid electrolyte particles. Requirement B: At least one of the interface between the solid electrolyte particles and the catalyst particles and the interface between the solid electrolyte particles and the solid electrolyte layer has a thin film layer, the thin film layer comprising at least one of the element group or a portion thereof forming the catalyst particles and the element group or a portion thereof forming the solid electrolyte particles.

[0009] Another aspect of this disclosure is a solid oxide single cell. It has a solid electrolyte layer that exhibits proton conductivity and an electrode in contact with the solid electrolyte layer.

[0010] The electrode described above has the aforementioned configuration. Therefore, the region containing reaction sites within the electrode is expanded, and chemical reactivity is enhanced. Consequently, when used in solid oxide single-cell batteries, this electrode achieves high initial output and high Faradaic efficiency even at relatively low single-cell operating temperatures.

[0011] The aforementioned solid oxide single cell has the above-described configuration. Therefore, the aforementioned solid oxide single cell can achieve high initial output and high Faraday efficiency even at relatively low single-cell operating temperatures. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view schematically showing an example of the structure of the electrode in the embodiment. Figure 2 This is a cross-sectional view schematically illustrating other construction examples of the electrodes involved in the embodiment. Figure 3 This is a cross-sectional view schematically showing an embodiment of a solid oxide single cell having electrodes of the embodiment. Figure 4 This is a scanning electron microscope (SEM) image showing the microstructure (electrode surface) of the electrode representing sample 2 obtained in the experimental example. Figure 5 It is a SEM image (compared to) the microstructure (electrode surface) of the electrode representing sample 2 obtained in the experimental example. Figure 4 (High magnification) chart. Figure 6 This is a graph showing the scanning transmission electron microscope (STEM)-energy dispersive X-ray analysis (EDS) image of the electrode of sample 2 obtained in the experimental example. Figure 7 This is a diagram showing the STEM-EDS image of the electrode of sample 6 obtained in the experimental example. Figure 8 This indicates the electrode of sample 6 obtained in the experimental example and... Figure 7 Images of different STEM-EDS images. Figure 9 This indicates the electrode of sample 6 obtained in the experimental example and... Figure 7 and Figure 8 Images of STEM-EDS from different perspectives. Figure 10 This is a diagram showing the measurement of the maximum outer diameter of the tiny protrusions in the SEM image of the electrode (electrode surface) of sample 2 used in the experimental example. Figure 11 This is an explanatory diagram schematically illustrating the method for measuring the current density of a solid oxide single cell fabricated in the experimental example. Detailed Implementation

[0013] The following describes an electrode and a solid oxide single cell according to one embodiment of the present disclosure, but the present disclosure is not limited to the examples of the following embodiments.

[0014] In addition, the lower and upper limits of the numerical ranges shown below include the values ​​recorded in the experimental examples and can be combined arbitrarily.

[0015] (electrode) use Figure 1 , Figure 2 The electrodes of the embodiment will be described. For example... Figure 1 , Figure 2 As illustrated, electrode 1 in this embodiment is an electrode for the solid oxide single cell 2 described later (electrode for solid oxide single cell). It will be noted that the solid oxide single cell 2 has a solid electrolyte layer 20 exhibiting proton conductivity, details of which will be described later.

[0016] In this embodiment, such as Figure 1 , Figure 2 As illustrated, electrode 1 can be formed in contact with the solid electrolyte layer 20. Figure 1 , Figure 2 The diagram illustrates an example where an electrode 1 is formed on one surface of a layered (e.g., plate-like, film-like, etc.) solid electrolyte layer 20. Depending on the shape of the solid electrolyte layer 20, the electrode 1 can be formed entirely on one surface of the solid electrolyte layer 20, or it can be formed on a portion of one surface of the solid electrolyte layer 20. Furthermore, the electrode 1 can be formed on either one surface or the other surface of the solid electrolyte layer 20, or both. Figure 1 , Figure 2 The image shows an example where an electrode 1 is formed on one surface of a solid electrolyte layer 20. It should be noted that a laminate having a solid electrolyte layer 20 and an electrode 1 stacked on at least one surface of the solid electrolyte layer 20 can also be referred to as an electrolyte layer / electrode junction.

[0017] like Figure 1 , Figure 2 As illustrated, electrode 1 is composed of a mixture comprising at least solid electrolyte particles 11 and catalyst particles 12.

[0018] The solid electrolyte particles 11 are formed from oxides exhibiting proton conductivity. Examples of oxides exhibiting proton conductivity in the solid electrolyte particles 11 include: oxides formed by replacing a portion of Zr in BaZrO3 with at least one selected from Ce, Y, Yb, and Tb; oxides formed by replacing a portion of Zr in SrZrO3 or CaZrO3 with at least one selected from Ce, Y, and Yb; and oxides formed by replacing a portion of Zr in LaPO4, LaP3O9, or La7P3O9. 18 Oxides formed by substituting a portion of La with at least one of Sr and Ca. These may use only one or more of these oxides. Oxides exhibiting proton conductivity are preferably composite oxides containing at least Ba, Zr, and Ce. It should be noted that oxides exhibiting proton conductivity may have indefinite proportions.

[0019] The catalyst particles 12 are formed from oxides or metals exhibiting electronic conductivity and possess electrode catalytic activity. Specifically, the catalyst particles 12 can be formed from oxides exhibiting electronic conductivity and possess electrode catalytic activity, or they can be formed from metals exhibiting electronic conductivity and possess electrode catalytic activity. Alternatively, the catalyst particles 12 can also be a mixture of particles of oxides exhibiting electronic conductivity and particles of metals exhibiting electronic conductivity, thus possessing electrode catalytic activity. Specifically, when the solid oxide single cell 2 is operated, for example, as a proton-conductive SOEC described later, the catalyst particles 12 can possess water vapor dissociation catalytic activity that promotes the dissociation of water vapor in the flowing gas as an electrode catalytic activity. Furthermore, when the solid oxide single cell 2 is operated, for example, as a proton-conductive SOFC described later, the catalyst particles 12 can possess oxygen dissociation catalytic activity that promotes the dissociation of oxygen in the flowing gas as an electrode catalytic activity. Thus, the catalyst particles 12 can possess at least one of the aforementioned electrode catalytic activities depending on the operating mode of the solid oxide single cell 2.

[0020] Examples of oxides used in catalyst particles 12 include: composite oxides containing Pr and Ba, and at least one selected from Sr, Co, and Fe; lanthanum-strontium-cobalt composite oxides; lanthanum-strontium-cobalt-iron composite oxides; lanthanum-strontium-manganese composite oxides; cerium-manganese-iron composite oxides; lanthanum-nickel composite oxides; praseodymium-nickel composite oxides; barium-strontium-cobalt-iron composite oxides; strontium-molybdenum-iron composite oxides; and oxides obtained by substituting a portion of the elements in these composite oxides with at least one element selected from vanadium, copper, and zinc. Only one element may be used, or two or more may be used in combination. The oxide used in catalyst particles 12 is preferably a composite oxide containing at least Pr and Ba. It should be noted that the oxide used in catalyst particles 12 may have an indefinite ratio. Additionally, examples of metals used in catalyst particles 12 include Ru, Rh, Pd, Ir, Pt, and Au. Only one element may be used, or two or more may be used in combination. The metal used in catalyst particles 12 is preferably a metal containing at least Pr and Ba.

[0021] In electrode 1, from the viewpoint of ensuring sufficient proton conduction performance, the average particle size of the solid electrolyte particles 11 can be larger than the average particle size of the catalyst particles 12. The average particle size of the specified particles is the arithmetic mean of the particle sizes (maximum outer diameters) of any 40 specified particles measured in the surface SEM image obtained by observing the surface of electrode 1 using a scanning electron microscope (SEM).

[0022] From the viewpoint of ensuring sufficient proton conductivity, the average particle size of the solid electrolyte particles 11 is preferably 100 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more. From the viewpoint of easily improving single-cell output by increasing the contact points with the catalyst particles 12, the average particle size of the solid electrolyte particles 11 is preferably 900 nm or less, more preferably 800 nm or less, and even more preferably 700 nm or less. On the other hand, from the viewpoint of suppressing particle aggregation during single-cell operation and ensuring reliable and continuous output, the average particle size of the catalyst particles 12 is preferably 50 nm or more, more preferably 75 nm or more, and even more preferably 100 nm or more. From the viewpoint of easily improving single-cell output by increasing the surface area of ​​the catalyst particles 12 that facilitates the reaction, the average particle size of the catalyst particles 12 is preferably 350 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less.

[0023] In electrode 1, from the viewpoint of ensuring sufficient proton conduction pathways between solid electrolyte particles 11 and sufficient electron conduction pathways between catalyst particles 12, the mass ratio of solid electrolyte particles 11 to catalyst particles 12 (solid electrolyte particles 11 / catalyst particles 12) is preferably 80 / 20 to 20 / 80, more preferably 70 / 30 to 30 / 70, and even more preferably 60 / 40 to 40 / 60.

[0024] Electrode 1 is formed as a porous material. Specifically, as follows: Figure 1 , Figure 2 As illustrated, electrode 1 has a plurality of pores 10a. That is, electrode 1 contains a plurality of pores 10a in a mixture comprising solid electrolyte particles 11 and catalyst particles 12. The plurality of pores 10a are formed by gaps formed between the particles constituting electrode 1.

[0025] In the mixture, multiple solid electrolyte particles 11 can exist in a continuous state. Specifically, examples of the continuous state of multiple solid electrolyte particles 11 include a state in which the solid electrolyte particles 11 are continuously in contact with each other (interconnected), a state in which the solid electrolyte particles 11 are stacked, and combinations thereof. It should be noted that, in the mixture, as long as the proton conduction path of the solid electrolyte particles 11 can perform proton conduction without interruption, there may be locations in the mixture where the solid electrolyte particles 11 exist in a discontinuous state due to reasons unavoidable in manufacturing. Similarly, in the mixture, multiple catalyst particles 12 can exist in a continuous state. Specifically, examples of the continuous state of multiple catalyst particles 12 include a state in which the catalyst particles 12 are continuously in contact with each other (interconnected), a state in which the catalyst particles 12 are stacked, and combinations thereof. It should be noted that, in the mixture, as long as the electronic conduction path caused by the electronic conductivity of the catalyst particles 12 can perform electrode function without interruption, there may be locations in the mixture where the catalyst particles 12 exist in a discontinuous state due to reasons unavoidable in manufacturing.

[0026] Electrode 1 satisfies at least one of the following requirements A and B. Requirement A: The catalyst particle 12 has a small protrusion 13 on its surface, the small protrusion 13 containing at least one of the element group or a portion thereof that forms the catalyst particle 12 and the element group or a portion thereof that forms the solid electrolyte particle 11. Requirement B: At least one of the interfaces between the solid electrolyte particles 11 and the catalyst particles 12 and the interfaces between the solid electrolyte particles 11 and the solid electrolyte layer 20, there is a thin film layer 14 comprising at least one of the group of elements forming the catalyst particles 12 or a portion thereof and the group of elements forming the solid electrolyte particles 11 or a portion thereof. The following provides a more detailed explanation of requirement A and requirement B.

[0027] like Figure 1 , Figure 2As illustrated, requirement A is that the catalyst particles 12 have minute protrusions 13 on their surface. A minute protrusion 13 is a tiny protrusion that appears on the surface of the catalyst particles 12. The minute protrusions 13 can be, for example, particle-shaped. The minute protrusions 13 can be abundantly distributed on the surface of the catalyst particles 12. It should be noted that the minute protrusions 13 can exist on all surfaces of the catalyst particles 12 contained in the mixture, or only on a portion of the surface of the catalyst particles 12 contained in the mixture. Furthermore, due to unavoidable manufacturing reasons, sometimes the minute protrusions 13 are not present on a portion of the surface of the catalyst particles 12. However, requirement A does not preclude the presence of minute protrusions 13 on the surface of the solid electrolyte particles 11 due to unavoidable manufacturing reasons.

[0028] On the other hand, such as Figure 1 , Figure 2 As illustrated, requirement B is that at least one of the interfaces between the solid electrolyte particles 11 and the catalyst particles 12, and between the solid electrolyte particles 11 and the solid electrolyte layer 20, has a thin film layer 14. It should be noted that in... Figure 1 , Figure 2 The illustration shows an example where a thin film layer 14 is present at the interface between solid electrolyte particles 11 and catalyst particles 12; however, an example where a thin film layer 14 is present at the interface between solid electrolyte particles 11 and solid electrolyte layer 20 is not shown. Furthermore, the thin film layer 14 may exist in all or part of the aforementioned interface.

[0029] Furthermore, the micro protrusions 13 mentioned in requirement A and the thin film layer 14 mentioned in requirement B each contain at least one of the element group forming the catalyst particles 12 or a portion thereof, and the element group forming the solid electrolyte particles 11 or a portion thereof. That is, the micro protrusions 13 and the thin film layer 14 may contain all of the element group forming the catalyst particles 12, or a portion thereof, or all of the element group forming the solid electrolyte particles 11, or a portion thereof, or both of the element group forming the catalyst particles 12 and the solid electrolyte particles 11, or both of the element group forming the catalyst particles 12 and the solid electrolyte particles 11, or both of the element group forming the catalyst particles 12 and the solid electrolyte particles 11.

[0030] Specifically, from the viewpoint of achieving improved electrode catalytic activity at lower single-cell operating temperatures, the micro protrusions 13 and the thin film layer 14 may contain at least one of Pr, Ba, and Ce.

[0031] From the viewpoints of greatly enhancing the chemical reactivity brought about by the micro protrusions 13 and achieving stable operation during long-term operation by suppressing the reaction with the solid electrolyte particles 11, electrode 1 preferably satisfies condition A or satisfies both condition A and condition B.

[0032] Electrode 1 satisfying condition A can be manufactured, for example, as follows. A brief explanation follows. At least an unfired sheet for forming a solid electrolyte layer containing the solid electrolyte material constituting the solid electrolyte layer 20, an unfired paste for forming an electrode containing solid electrolyte particle material constituting electrode 1, catalyst particle material, and a pore-forming agent are prepared. Next, the sheet for forming the solid electrolyte layer is fired in an oxidizing atmosphere to obtain a sintered body. Then, the electrode-forming paste is coated onto one surface of the sintered body, forming a state where the coating surface is covered with solid electrolyte particle material. The coating surface is then fired in an oxidizing atmosphere. Furthermore, the solid electrolyte particle material covering the surface after firing can simply be brushed off. Thus, electrode 1 satisfying condition A can be manufactured. A detailed example is shown in the experimental examples.

[0033] On the other hand, electrode 1 that satisfies condition B can be manufactured, for example, as follows. A brief explanation follows. At least the following are prepared: an unfired sheet for forming a solid electrolyte layer containing the solid electrolyte material constituting the solid electrolyte layer 20; solid electrolyte particle material constituting electrode 1; catalyst particle material; a pore-forming agent; and an unfired paste for forming electrodes, consisting of particle material formed from oxides containing one or more elements constituting the solid electrolyte particle material and the catalyst particle material. Next, the sheet for forming the solid electrolyte layer is fired in an oxidizing atmosphere in the atmosphere to obtain a sintered body. Then, the electrode-forming paste is coated onto one surface of the sintered body, forming a state where the coating surface is covered with solid electrolyte particle material. The coating surface is then fired in an oxidizing atmosphere in the atmosphere with the coating surface closed to the atmosphere. Furthermore, the solid electrolyte particle material covered after firing can simply be brushed off. Thus, electrode 1 that satisfies condition B can be manufactured. A detailed example is shown in the experimental examples.

[0034] From the viewpoints of achieving greater improvements in electrode catalytic activity at low single-cell operating temperatures, increased initial output at low single-cell operating temperatures, and improved Faraday efficiency, the aforementioned micro-protrusions 13 and thin film layer 14 preferably contain at least one material selected from Pr, Ba, and Ce. Such a configuration, for example, as described above, is more easily achieved by coating an electrode forming paste onto one surface of the sintered body, forming a state where the coating surface is not exposed to the atmosphere, and by performing sintering in a moderately oxidizing atmosphere.

[0035] From the viewpoint of suppressing the aggregation of the micro-protrusions 13 during single-cell operation, thus facilitating reliable and continuous output, the outer diameter of the micro-protrusions 13 is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. From the viewpoint of easily improving single-cell output by increasing the surface area conducive to the reaction, the outer diameter of the micro-protrusions 13 is preferably 90 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less. On the other hand, from the viewpoint of easily obtaining sufficient single-cell output by suppressing the interdiffusion of solid electrolyte particles and catalyst particles, the film thickness of the thin film layer 14 is preferably 3 nm or more, more preferably 5 nm or more, even more preferably 8 nm or more, and even more preferably 10 nm or more. From the viewpoint of easily obtaining sufficient single-cell output by reducing the proton conduction rate limit in the thin film layer 14, the film thickness of the thin film layer 14 is preferably 90 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, and even more preferably 20 nm or less.

[0036] The outer diameter of the micro protrusion 13 is the arithmetic mean of the maximum outer diameters of any 40 micro protrusions measured in a surface SEM image obtained by observing the surface of the electrode 1 using SEM. On the other hand, the film thickness of the thin film layer 14 is the arithmetic mean of the film thickness measurements of any 10 thin film layers obtained in a cross-sectional STEM image obtained by observing a cross-section along the thickness direction of the electrode 1 using a scanning transmission electron microscope (STEM).

[0037] From the perspective of easily improving high initial output and / or high Faraday efficiency at low single-cell operating temperatures, such as Figure 2 As illustrated, the mixture constituting electrode 1 may further comprise an aggregate 10 having solid electrolyte microparticles 11a and catalyst microparticles 12a. The aggregate 10, by aggregating at least solid electrolyte microparticles 11a and catalyst microparticles 12a, can, as a whole, take on a particle-like shape. Such an aggregate 10 can exist in large quantities dispersed within the mixture constituting electrode 1.

[0038] In the aggregate 10, the solid electrolyte microparticles 11a are tiny particles derived from solid electrolyte particles 11. The solid electrolyte microparticles 11a have an extremely small particle size compared to solid electrolyte particles 11. "Derived from solid electrolyte particles 11" means that the solid electrolyte microparticles 11a are particles generated (precipitated) during the manufacture of the electrode 1, at least due to the presence of solid electrolyte particles 11. On the other hand, the catalyst microparticles 12a are tiny particles derived from catalyst particles 12. The catalyst microparticles 12a have an extremely small particle size compared to catalyst particles 12. "Derived from catalyst particles 12" means that the catalyst microparticles 12a are particles generated (precipitated) during the manufacture of the electrode 1, at least due to the presence of catalyst particles 12.

[0039] From the viewpoint of suppressing agglomeration during single-cell operation and thus facilitating reliable and continuous output, the average particle size of the microparticles forming the aggregate 10 is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. From the viewpoint of easily improving single-cell output by increasing the surface area conducive to the reaction, the average particle size of the microparticles forming the aggregate 10 is preferably 250 nm or less, more preferably 230 nm or less, even more preferably 200 nm or less, and even more preferably 150 nm or less.

[0040] It should be noted that the microparticles forming aggregate 10 are used in the sense of including the aforementioned solid electrolyte microparticles 11a and catalyst microparticles 12a. The average particle size of the microparticles forming aggregate 10 is the arithmetic mean of the particle sizes (maximum outer diameters) of any 10 microparticles measured in the cross-sectional STEM image obtained by observing a cross-section along the thickness direction of electrode 1.

[0041] The electrode 1, which includes the assembly 10, can be generated, for example, in the manufacturing methods of the electrode 1 that satisfies condition A and the electrode 1 that satisfies condition B, when the solid electrolyte particle material and the catalyst particle material used in the manufacturing are mixed, for example, the manufacturing of the electrode 1 is based on mixing and crushing using a method that applies sufficient crushing energy, such as a planetary ball mill.

[0042] Here, as a comparison with electrode 1 of this embodiment, although not shown, we consider the electrode of Comparative Embodiment 1, which is composed only of catalyst particles 12 with electrode catalytic activity, formed from oxides or metals exhibiting proton conductivity, and does not contain solid electrolyte particles 11 formed from oxides exhibiting proton conductivity. In the electrode of Comparative Embodiment 1, for example, the reaction site for the dissociation reaction of H2O is only formed at the interface with the solid electrolyte layer 20, so the amount of reaction sites is insufficient. Therefore, when used in a solid oxide type single cell 2, the initial output and Faradaic efficiency are low at low single cell operating temperatures. Next, as a comparison with electrode 1 of this embodiment, although not shown, we consider the electrode of Comparative Embodiment 2, which is composed of a mixture of solid electrolyte particles 11 formed from oxides exhibiting proton conductivity and catalyst particles 12 formed from oxides exhibiting electron conductivity and exhibiting electrode catalytic activity. However, the electrode of Comparative Embodiment 2 does not satisfy the above-mentioned requirements A and B. Compared to the electrode in Comparative Method 1, the insufficient proton conductivity of the catalyst particles 12 in Comparative Method 2 is enhanced by the solid electrolyte particles 11, which are formed from oxides exhibiting proton conductivity. Therefore, the region where the reaction site exists is expanded into the electrode interior. However, simply combining the solid electrolyte particles 11 with the catalyst particles 12 is insufficient to adequately improve the initial output and Faraday efficiency at low single-cell operating temperatures due to inadequate chemical reactions.

[0043] In contrast, the electrode 1 of this embodiment has the above-described configuration. That is, the electrode 1 of this embodiment is not only composed of a mixture comprising at least solid electrolyte particles 11 formed from oxides exhibiting proton conductivity and catalyst particles 12 formed from oxides or metals exhibiting electron conductivity and possessing electrode catalytic activity, but also has specific micro-protrusions 13 on the surface of the catalyst particles 12 (element A), and / or has specific thin film layers 14 (element B) at least one of the interfaces between the solid electrolyte particles 11 and the catalyst particles 12, and between the solid electrolyte particles 11 and the solid electrolyte layer 20. Therefore, the region containing reaction sites inside the electrode 1 of this embodiment is expanded, and chemical reactivity is improved. Therefore, when used in a solid oxide single cell 2, the electrode 1 of this embodiment can achieve high initial output and high Faradaic efficiency even at relatively low single-cell operating temperatures.

[0044] The electrode 1 in this embodiment can be suitable for use as, for example, a solid oxide single cell 2, preferably an air electrode (oxygen electrode) in an SOEC. The use of electrode 1 will be described in detail in the following description of the solid oxide single cell 2.

[0045] (Solid oxide type single cell) use Figure 3The solid oxide type single cell 2 of the embodiment will be described. For example... Figure 3 As illustrated, the solid oxide single cell 2 of this embodiment has a solid electrolyte layer 20 exhibiting proton conductivity and an electrode 1 of the above embodiment connected to the solid electrolyte layer 20. It should be noted that the solid oxide single cell 2 having a solid electrolyte layer 20 exhibiting proton conductivity can be called a proton-conductive solid oxide single cell. Specifically, examples of proton-conductive solid oxide single cells include proton-conductive SOEC and proton-conductive SOFC.

[0046] Specifically, such as Figure 3 As illustrated, the solid oxide single cell 2 includes a solid electrolyte layer 20 exhibiting proton conductivity, a first electrode 21, and a second electrode 22 paired with the first electrode 21. The first electrode 21 is disposed on one side of the solid electrolyte layer 20. The second electrode 22 is disposed on the opposite side of the solid electrolyte layer 20. The solid electrolyte layer 20, the first electrode 21, and the second electrode 22 can all be formed in a layered manner. The first electrode 21 can function as a fuel electrode (hydrogen electrode), and the second electrode 22 can function as an air electrode (oxygen electrode). In the solid oxide single cell 2, the first electrode 21, the solid electrolyte layer 20, and the second electrode 22 are stacked sequentially and bonded to each other. Furthermore, in... Figure 3 The image shows an example where the shape of the second electrode 22 is smaller than that of the solid electrolyte layer 20.

[0047] In addition, such as Figure 3 As illustrated, the solid oxide single cell 2 can have a planar single cell structure, although not shown, it can also have a cylindrical single cell structure. Furthermore, the solid oxide single cell 2 can be configured such that the first electrode 21 also functions as a support, although not shown, the solid electrolyte layer 20 also functions as a support, although not shown, the second electrode 22 also functions as a support, although not shown, the first electrode 21 or the second electrode 22 can be supported by other supports such as metal components.

[0048] Examples of proton-conducting solid electrolyte materials that can constitute the solid electrolyte layer 20 include the aforementioned proton-conducting oxides. To ensure airtightness, the solid electrolyte layer 20 is typically formed as a dense material. The thickness of the solid electrolyte layer 20 can be several μm or more but less than several hundred μm, for example, more than 1 μm but less than 500 μm.

[0049] The second electrode 22 is composed of the electrode 1 described in the above embodiment. The thickness of the second electrode 22 can be, for example, set to be 5 μm or more and 20 μm or less.

[0050] The first electrode 21 can have the same configuration as the second electrode 22, or it can be made of other electrode materials. Examples of other electrode materials include metals such as Ni, Pt, Ir, Fe, and Cu; oxides of the aforementioned metals that can become the aforementioned metals when exposed to a reducing atmosphere (e.g., NiO relative to metallic Ni); and mixtures of solid electrolyte materials such as oxides exhibiting electron conductivity and electrode catalytic activity, as well as oxides exhibiting proton conductivity. The thickness of the first electrode 21 can be, for example, 20 μm or more and 800 μm or less.

[0051] The solid oxide single cell 2 of this embodiment has the above-described configuration. Therefore, the solid oxide single cell 2 of this embodiment can achieve high initial output and high Faraday efficiency even at relatively low single cell operating temperatures.

[0052] In the case of the aforementioned solid oxide single cell 2, for example, a proton-conducting SOEC, an electrochemical reaction occurs by supplying a gas containing, for example, H2O (water vapor) to the second electrode 22 (air electrode) and supplying electricity to the single cell. H2O is electrolyzed at the second electrode 22 (air electrode), and H2 is obtained at the first electrode 21 (fuel electrode). That is, in this case, at the second electrode 22, which is the air electrode side (oxygen electrode side), water vapor dissociates to form oxygen and protons. The protons are conducted to the fuel electrode side (hydrogen electrode side) via the solid electrolyte layer 20, where they are released as hydrogen. In this case, from the viewpoint of sufficiently increasing the reaction rate, the single cell operating temperature of the solid oxide single cell 2 can be, for example, 300°C or higher, preferably 400°C or higher, and more preferably 450°C or higher. Furthermore, the single cell operating temperature of the solid oxide single cell 2 can also be set to 1000°C or lower, for example, but from the viewpoint of practicality and fully obtaining the effects of this disclosure, it is preferable to set it to below 600°C. More preferably, the temperature can be set to 550°C or below. That is, the solid oxide type single cell 2 tends to have a lower output as the single cell operating temperature increases, so it can also operate at a single cell operating temperature of 600°C or above. However, since the electrode 1 of the above embodiment is used as the second electrode 22, even at a single cell operating temperature lower than 600°C, a higher initial output than before can be obtained. In addition, the solid oxide type single cell 2 can be heated to the optimal temperature by a single cell heating source such as an electric furnace or a heater. Furthermore, the solid oxide type single cell 2 can not only perform water (water vapor) electrolysis, but also supply H2O to the air electrode side and CO2 to the fuel electrode side to obtain co-electrolysis of hydrogen and CO.

[0053] Thus, the solid oxide single cell 2 can at least be used as a solid oxide electrolytic cell (SOEC). In recent years, surplus electricity has been used to synthesize hydrogen and hydrocarbons from water vapor or carbon dioxide. In particular, renewable energy sources, such as solar power, which is expected to have a wider range of applications in the future, exhibit large fluctuations in power generation per unit of long-term operation each year. Therefore, a technology is desired that synthesizes hydrogen and hydrocarbons during periods of high power generation and utilizes them during periods of low power generation. The solid oxide single cell 2 can at least be used as an SOEC, thus enabling the efficient synthesis of hydrogen or hydrocarbons. Furthermore, as described above, the electrode 1 of the solid oxide single cell 2 exhibits excellent mechanical strength and long-term durability, thus contributing to the widespread adoption of SOEC.

[0054] In addition to being used as an SOEC, the solid oxide single cell 2 can also be used as a solid oxide fuel cell (SOFC). In this case, a load is connected to the solid oxide single cell 2, H2 is supplied to the first electrode 21, and O2 or air is supplied to the second electrode 22, thereby generating electricity through an electrochemical reaction.

[0055] It should be noted that the above descriptions of electrodes and solid oxide single cells can be referenced as needed. In addition, the components described in each description can be used individually or in any combination as needed.

[0056] (Experimental Example) [Electrodes of the sample, fabrication of solid oxide single cells] <Sample 1> NiO powder (average particle size: 0.7 μm), BaZr 0.4 Ce 0.4 Y 0.1 Yb 0.1 O 3-σ A slurry is prepared by mixing NiO powder (average particle size: 0.5 μm), carbon (pore-forming agent), polyvinyl butyral (organic material), isoamyl acetate, 2-butanol, and ethanol (mixed solvent) using a ball mill. The mass ratio of NiO powder to BZCYYb powder is 60:40. It should be noted that the average particle size mentioned above refers to the particle size (diameter) d50 at which the cumulative frequency distribution of the volume reference determined by laser diffraction / scattering shows 50% (the same applies below). The slurry is applied in layers onto a plastic substrate using a doctor blade and dried to prepare an unburned sheet for forming a fuel electrode (green sheet for fuel electrode formation).

[0057] BZCYYb powder (average particle size: 0.5 μm), polyvinyl butyral (organic material), isoamyl acetate, 2-butanol, and ethanol (mixed solvent) were mixed in a ball mill to prepare a slurry. The slurry was then coated in layers onto a plastic substrate using a doctor blade and allowed to dry, thereby preparing an unfired sheet for forming a solid electrolyte layer (green sheet for forming a solid electrolyte layer).

[0058] BZCYYb powder (average particle size: 0.5 μm), PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+σ (Hereinafter sometimes referred to as PBSCF) powder (average particle size: 0.2 μm), ethyl cellulose (organic material), and terpineol (solvent) were mixed in a single-shaft ball mill for 24 hours to prepare an unburned air electrode forming paste. The mass ratio of BZCYYb powder to PBSCF powder was 70:30.

[0059] Next, fuel electrode forming sheets and solid electrolyte layer forming sheets are sequentially stacked, pressed together using CIP molding, and then cut into coin shapes with a diameter of 16 mm. After degreasing, a laminate is fabricated. The resulting laminate is then fired at 1450°C for 2 hours in atmosphere to obtain a sintered body.

[0060] Next, an air electrode forming paste was applied to the surface of the solid electrolyte layer on the side opposite to the fuel electrode of the obtained sintered body using screen printing. Then, BZCYYb powder (average particle size: 0.5 μm) was applied to the coating surface. The coating was then fired at 900°C for 2 hours with atmospheric gas introduced, ensuring the coating surface was not exposed to the atmosphere. It should be noted that in this experimental example, the purpose of applying BZCYYb powder to the coating surface was to cover the periphery of the air electrode during firing with Ba vapor, promoting the formation of small protrusions. After firing, the applied BZCYYb powder was removed. Through these operations, a solid oxide single cell of sample 1, having the electrode (air electrode) of sample 1, was fabricated.

[0061] <Sample 2> In the preparation of sample 1, when preparing the paste for forming the air electrode, the mass ratio of BZCYYb powder to PBSCF powder was set to 50:50. Otherwise, a solid oxide single cell of sample 2 with the electrode of sample 2 was prepared in the same manner.

[0062] <Sample 3> In the preparation of sample 1, when preparing the paste for forming the air electrode, the mass ratio of BZCYYb powder to PBSCF powder was set to 30:70. Otherwise, a solid oxide single cell of sample 3 with the electrode of sample 3 was prepared in the same manner.

[0063] <Sample 4> In the preparation of sample 1, when preparing the paste for air electrode formation, Pr2BaO was further added to BZCYYb powder and PBSCF powder. 4-σ (Hereinafter sometimes referred to as PBO) powder (average particle size: 0.2 μm), with the mass ratio of BZCYYb powder, PBSCF powder and PBO powder set to 49.5:50:0.5, the powders were mixed using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours). In addition, a solid oxide single cell of sample 4 with the electrode of sample 4 was prepared in the same manner.

[0064] <Sample 5> In the preparation of Sample 1, when preparing the paste for forming the air electrode, PBO powder (average particle size: 0.2 μm) was further added to BZCYYb powder and PBSCF powder. The mass ratio of BZCYYb powder, PBSCF powder and PBO powder was set to 48:50:2. The powders were mixed using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours). In addition, a solid oxide single cell of Sample 5 with the electrode of Sample 5 was prepared in the same manner.

[0065] <Sample 6> In the preparation of Sample 1, when preparing the paste for forming the air electrode, PBO powder (average particle size: 0.2 μm) was further added to BZCYYb powder and PBSCF powder. The mass ratio of BZCYYb powder, PBSCF powder and PBO powder was set to 45:50:5. The powders were mixed using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours). In addition, a solid oxide single cell of Sample 6 with the electrode of Sample 6 was prepared in the same manner.

[0066] <Sample 7> In the preparation of Sample 1, when preparing the paste for forming the air electrode, PBO powder (average particle size: 0.2 μm) was further added to BZCYYb powder and PBSCF powder. The mass ratio of BZCYYb powder, PBSCF powder and PBO powder was set to 40:50:10. The powders were mixed using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours). In addition, a solid oxide single cell of Sample 7 with the electrode of Sample 7 was prepared in the same manner.

[0067] <Sample 8> In the preparation of Sample 1, when preparing the paste for forming the air electrode, PBO powder (average particle size: 0.2 μm) was further added to BZCYYb powder and PBSCF powder, so that the mass ratio of BZCYYb powder, PBSCF powder and PBO powder was 25:50:25. The powders were mixed using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours). In addition, a solid oxide single cell of Sample 8 with the electrode of Sample 8 was prepared in the same manner.

[0068] <Sample 9> In the preparation of Sample 1, when preparing the paste for forming the air electrode, PBO powder (average particle size: 0.2 μm) was further added to BZCYYb powder and PBSCF powder. The mass ratio of BZCYYb powder, PBSCF powder and PBO powder was set to 50:25:25. The powders were mixed using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours). In addition, a solid oxide single cell of Sample 9 with the electrode of Sample 9 was prepared in the same manner.

[0069] <Sample 10> In the preparation of sample 1, in the preparation of the paste for forming the air electrode, in addition to using BZCYYb powder and adding La... 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-σ In addition to this point, further adding PBO powder (average particle size: 0.2 μm), setting the mass ratio of BZCYYb powder to PBSCF powder to PBO powder to 45:50:5, and mixing the powders using a planetary ball mill (Fritsch PULVERISETTE 7, 400 rpm, 24 hours), a solid oxide single cell with the electrode of sample 10 was also prepared.

[0070] <Sample 1C> In the preparation of Sample 1, when preparing the paste for forming the air electrode, the mass ratio of BZCYYb powder to PBSCF powder was set to 50:50. Instead of forming a coating surface based on the paste for forming the air electrode with BZCYYb powder (average particle size: 0.5 μm) covered, the coating surface was fired with the coating surface open to the atmosphere. In addition, a solid oxide single cell of Sample 1C with the electrode of Sample 1C was prepared in the same manner.

[0071] <Sample 2C> In the preparation of Sample 1, when preparing the paste for forming the air electrode, the mass ratio of BZCYYb powder to PBSCF powder was set to 30:70. Instead of forming a coating film based on the paste for forming the air electrode with BZCYYb powder (average particle size: 0.5 μm) covering the surface, the coating film was fired with the surface open to the atmosphere. In addition, a solid oxide single cell of Sample 2C with the electrode of Sample 2C was prepared in the same manner.

[0072] [Surface observation of the electrode (air electrode)] The surface of the electrodes in the fabricated solid oxide single cell was observed using SEM. As representative of the electrodes of samples 1 through 10, the surface SEM image of the electrode of sample 2 is shown below. Figure 4 , Figure 5 .

[0073] [Average particle size of solid electrolyte particles and catalyst particles in the electrode (air electrode)] The average particle size of the solid electrolyte particles and catalyst particles in the electrode was determined according to the above-described measurement method.

[0074] [Presence or absence of micro-protrusions in the electrode (air electrode), elemental composition of the micro-protrusions, outer diameter of the micro-protrusions, presence or absence of a thin film layer, elemental composition of the thin film layer, thickness of the thin film layer] STEM-EDS analysis was performed on the electrodes in the fabricated solid oxide single cell. The STEM-EDS image of the electrode (electrode cross-section) of sample 2 is shown below. Figure 6 The STEM-EDS image of the electrode (electrode cross-section) of sample 6 is shown below. Figure 7 The electrode (electrode cross-section) of sample 6 is compared with... Figure 7 STEM-EDS images with different fields of view are shown in Figure 8 The electrode (electrode cross-section) of sample 6 is compared with... Figure 7 and Figure 8 STEM-EDS images with different fields of view are shown in Figure 9 Additionally, the measurement of the maximum outer diameter of the minute protrusions from the SEM image of the electrode (electrode surface) of sample 2 is shown below. Figure 10It should be noted that, in Figure 10 In the diagram, a portion of the minute protrusions, identified by bright contrast, is represented by a circle. Furthermore, within this circle, as indicated by the dashed line and arrows at both ends, the measurement of the maximum outer diameter of the minute protrusion is shown. Additionally, the outer diameter of the minute protrusion and the film thickness of the thin film layer are measured according to the aforementioned method.

[0075] [Measurement of current density in solid oxide single cells] like Figure 11 As shown, a solid oxide single cell 2 is placed in an SOEC single cell characteristic measurement device 9. Additionally, in Figure 11 In this configuration, the solid oxide single cell 2 is arranged with the air electrode facing upwards. While maintaining the temperature inside the furnace 91 at 500°C, dry air (a mixture of N2: 79 vol% and O2: 21 vol%) at a flow rate of 100 cc (at ambient atmospheric pressure) / min is supplied to the air electrode side while humidifying it to a water vapor concentration of 50 vol%. That is, the gas flow rate containing water vapor is 200 cc / min. A mixture of dry gas (N2: 75 vol% and H2: 25 vol%) is supplied to the fuel electrode facing the piping 92 at a flow rate of 40 cc (at ambient atmospheric pressure). The hydrogen concentration is monitored at a frequency of 1 scan / min using a gas chromatograph G (Agilent, "GC 490") located downstream of the single cell on the piping line to the fuel electrode. After the above conditions stabilize, a voltage of 1.3 V is applied to the air electrode relative to the fuel electrode, inducing a hydrogen generation reaction based on water vapor electrolysis, and the current density is measured.

[0076] From the measured current density (mA / cm) 2 The Faraday efficiency is calculated using the following formula: Faraday efficiency = ((current density measurement) / 1000 × (air electrode area in a single cell) / 96500 / 2 × 22400 × 60) / 40 / (increase in hydrogen concentration from gas chromatography).

[0077] In this experimental example, the current density was 300 mA / cm². 2 In the above case, it is marked "B" because it has a high initial output at a single-cell operating temperature of 500°C. Additionally, the current density is 500 mA / cm². 2 The above situation, considered a preferred state with higher initial output at a single-cell operating temperature of 500°C, is designated as "A". On the other hand, a current density of less than 300 mA / cm² is preferred. 2 The case where the initial output power of a single cell is low and insufficient at an operating temperature of 500°C is marked as "C".

[0078] Furthermore, in this experimental example, when the Faraday efficiency is 0.50 or higher, it is marked as having high Faraday efficiency and is labeled "B". Additionally, when the Faraday efficiency is 0.70 or higher, it is considered a preferred state with even higher Faraday efficiency and is labeled "A". On the other hand, when the Faraday efficiency is less than 0.50, it is marked as having low Faraday efficiency and is labeled "C".

[0079] The detailed composition of the electrodes of each sample, the electrodes of each sample, and the evaluation results of the solid oxide single cell are summarized in Table 1.

[0080] [Table 1]

[0081] according to Figures 4-10 Table 1 shows the following: The electrodes of samples 1C and 2C are composed of a mixture of solid electrolyte particles and catalyst particles. The solid electrolyte particles are formed from oxides exhibiting proton conductivity, and the catalyst particles are formed from oxides exhibiting electron conductivity and possess electrode catalytic activity. However, the electrodes of samples 1C and 2C do not satisfy either requirement A or requirement B mentioned above. Specifically, the electrodes of samples 1C and 2C do not have micro-protrusions on the surface of the catalyst particles, and furthermore, they do not have a thin film layer at the interface between the solid electrolyte particles and the catalyst particles, or at the interface between the solid electrolyte particles and the solid electrolyte layer. Therefore, when used in solid oxide single cells, the electrodes of samples 1C and 2C cannot achieve high initial output and high Faradaic efficiency at a low single-cell operating temperature such as 500°C.

[0082] In contrast, the electrodes of samples 1 to 10 are composed of a mixture of solid electrolyte particles formed from oxides exhibiting proton conductivity and catalyst particles formed from oxides exhibiting electronic conductivity and having electrode catalytic activity, thereby satisfying at least one of the above-mentioned requirements A and B.

[0083] Specifically, in Figure 4 In the image, the relatively dark gray area represents the proton-conducting oxide BZCYYb, while the relatively light gray area represents the electron-conducting oxide PBSCF. (See image for details.) Figure 4 As shown, the electrode of sample 2 is composed of a mixture containing BZCYYb particles and PBSCF particles. Furthermore, Figure 6 It means about Figure 4 High magnification images Figure 5 A STEM-EDS image of a portion of the field of view containing numerous scattered granular portions (whitish granular portions). Here, in Figure 6In this context, focus on the granular portion seen in the center right of the area enclosed by the circle. For example... Figure 6 As shown in the elemental mappings for Co, Ba, Pr, and Ce, the granular portion is located as a whole on the surface of the Co-containing block. This Co-containing block is a PBSCF particle, and the granular portion is a small protrusion present on the surface of the PBSCF particle. Furthermore, this small protrusion contains both Ba and Ce. Based on the above results, it is confirmed that the electrode of Sample 2 has small protrusions formed on the surface of the PBSCF particles, which are catalyst particles, and these small protrusions contain at least Ba and Ce, elements found in the PBSCF particles. Furthermore, Samples 1, 3, and 10 are identical to Sample 2.

[0084] in addition, Figure 7 This represents a STEM-EDS image of the field of view including the on-particle portion in the electrode cross-section of sample 6. Here, in Figure 7 In this context, focus on the granular portion seen in the center right of the area enclosed by the circle. For example... Figure 7 As shown in the elemental mappings for Co, Ba, Pr, and Ce, the granular portion is located as a whole on the surface of the Co-containing block. This Co-containing block is a PBSCF particle, and the granular portion is a small protrusion present on the surface of the PBSCF particle. Furthermore, this small protrusion contains Pr, Ba, and Ce. Based on the above results, it is confirmed that the electrode of sample 6 has small protrusions formed on the surface of the PBSCF particles, which are catalyst particles, and these small protrusions contain at least Pr, Ba, and Ce, elements that form the PBSCF particles. Furthermore, samples 4, 5, and 7-9 are identical to sample 6.

[0085] in addition, Figure 8 This indicates that in the electrode cross-section of sample 6, regarding the portion containing the particle interface ( Figure 8 The STEM-EDS image of the field of view (the part enclosed by a circle). Figure 8 In the upper right section, a diagram showing the mapping of Ce, Ba, Co, and Pr elements is displayed. Additionally, in the lower section, from left to right, the mappings of Ce, Ba, Co, and Pr elements are shown sequentially. According to... Figure 8 It is evident that a thin film layer is formed at the interface between the solid electrolyte particles and the catalyst particles on the electrode of sample 6. Furthermore, it was confirmed that this thin film layer contains a large amount of Ba. In addition, samples 4, 5, and 7-10 are identical to sample 6.

[0086] As described above, the electrodes of samples 1 to 10 have the microstructure disclosed herein, which, when used in solid oxide single cells, enables high initial output and high Faraday efficiency at low single-cell operating temperatures such as 500°C.

[0087] in addition, Figure 9 This is for sample 6 shown. Figure 5 An image of a STEM-EDS image containing the dark gray portion of the field of view. Figure 9 The lower section shows a detailed element mapping of the quadrilateral-enclosed portion of the diagram formed by overlaying the Co, Ba, and Pr elements from the upper section. In this lower section, from left to right, the diagrams of the Co, Ba, and Pr elements are shown, along with the diagram formed by overlaying these mappings. Figure 9 It was confirmed that the portion enclosed by the aforementioned quadrilateral contained an aggregate of solid electrolyte microparticles (BZCYYb particles, which are solid electrolyte particles) and catalyst microparticles (PBSCF particles, which are catalyst particles). It is understood that such an aggregate is not a starting material, but rather a collection and mixture of particles extremely small compared to the starting material. Furthermore, samples 4, 5, and 7-10 are identical to sample 6.

[0088] According to Table 1, it was confirmed that by including the aforementioned aggregate in the mixture constituting the electrode, it is easier to improve the high initial output and / or high Faraday efficiency at low single-cell operating temperatures compared to the case where the mixture does not contain such aggregate.

[0089] This disclosure is not limited to the above-described embodiments and experimental examples, and various modifications can be made without departing from its spirit. Furthermore, the various configurations shown in the above-described embodiments and experimental examples can be arbitrarily combined.

Claims

1. An electrode (1) for use in a porous material in a solid oxide single cell (2) having a solid electrolyte layer (20) exhibiting proton conductivity, It consists of a mixture comprising at least solid electrolyte particles (11) formed of oxides exhibiting proton conductivity and catalyst particles (12) formed of oxides or metals exhibiting electronic conductivity and having electrode catalytic activity. If at least one of the following conditions A and condition B is met, Requirement A: The surface of the catalyst particles has minute protrusions (13), the minute protrusions (13) having at least one of the element group or a portion thereof that forms the catalyst particles, and the element group or a portion thereof that forms the solid electrolyte particles. Requirement B: At least one of the interface between the solid electrolyte particles and the catalyst particles and the interface between the solid electrolyte particles and the solid electrolyte layer has a thin film layer (14) comprising at least one of the element group or a portion thereof that forms the catalyst particles and the element group or a portion thereof that forms the solid electrolyte particles.

2. The electrode according to claim 1, wherein, The micro-protrusions and the thin film layer comprise at least one selected from Pr, Ba, and Ce.

3. The electrode according to claim 1, wherein, The average particle size of the solid electrolyte particles is greater than the average particle size of the catalyst particles.

4. The electrode according to claim 1, wherein, The average particle size of the solid electrolyte particles is greater than 100 nm and less than 900 nm. The average particle size of the catalyst particles is greater than 50 nm and less than 350 nm.

5. The electrode according to claim 1, wherein, The outer diameter of the micro-protrusion is greater than 10 nm and less than 90 nm. The thickness of the thin film layer is greater than 3 nm and less than 90 nm.

6. The electrode according to claim 1, wherein, The mixture comprises an aggregate (10) having solid electrolyte microparticles (11a) from the solid electrolyte particles and catalyst microparticles (12a) from the catalyst particles.

7. The electrode according to claim 6, wherein, The average particle size of the solid electrolyte microparticles and catalyst microparticles forming the aggregate is greater than 30 nm and less than 250 nm.

8. A solid oxide type single cell (2) having a solid electrolyte layer (20) exhibiting proton conductivity and an electrode (1) in contact with the solid electrolyte layer according to any one of claims 1 to 7.

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