JP7278468B1 - Electrolytic cell and cell stack device - Google Patents

Abstract

An electrolytic cell and a cell stack device capable of stabilizing performance are provided. An electrolytic cell (10) includes a support substrate (4), a first element portion (5a), and a second element portion (5b). A first channel 43 through which water vapor and carbon dioxide flow is formed inside the support substrate 4 . The second element portion 5 b is arranged downstream of the first element portion 5 a in the flow direction of H 2 O and CO 2 flowing through the first flow path 43 . The hydrogen electrode active portion 62 of each of the first element portion 5a and the second element portion 5b contains an oxygen ion conductive material and nickel. The grain size of nickel contained in the hydrogen electrode active portion 62 of the first element portion 5a is larger than the grain size of nickel contained in the hydrogen electrode active portion 62 of the second element portion 5b. [Selection drawing] Fig. 5

Description

The present invention relates to electrolytic cells and cell stack devices.

Technology for synthesizing hydrogen (H 2 ) and carbon monoxide (CO) by co-electrolyzing water vapor (H ₂ O) and carbon dioxide (CO ₂ ) using an electrolytic cell consisting _of ceramic electrodes and electrolytes. It has been known.

For example, the electrolytic cell described in Patent Literature 1 has an element portion and a support substrate that supports the element portion. Flow paths through which CO ₂ and H ₂ O flow are formed inside the support substrate. The element part has a hydrogen electrode arranged on a support substrate, an oxygen electrode, and an electrolyte arranged between the hydrogen electrode and the oxygen electrode. The hydrogen electrode can be composed of an oxygen ion conductive material and nickel (Ni).

Japanese Patent No. 6110246

However, during the operation of the electrolytic cell, in the region of the hydrogen electrode where the partial pressure of water vapor is high, Ni bonds with each other due to surface tension and coarsens (agglomerates), resulting in a decrease in the activity of the hydrogen electrode. performance is degraded. Therefore, there is a demand for stabilizing the performance of electrolytic cells.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic cell and a cell stack device capable of stabilizing performance.

An electrolytic cell according to a first aspect of the present invention includes a support substrate, a first element section, and a second element section. A first channel through which water vapor and carbon dioxide flow is formed inside the support substrate. The first element section is supported by the support substrate. The second element section is supported by the support substrate and arranged downstream of the first element section in the flow direction of water vapor and carbon dioxide flowing in the first channel. Each of the first element portion and the second element portion has an oxygen electrode, a hydrogen electrode active portion arranged between the oxygen electrode and the supporting substrate, and an electrolyte arranged between the oxygen electrode and the hydrogen electrode active portion. . The hydrogen electrode active portion of each of the first element portion and the second element portion contains an oxygen ion conductive material and nickel. The grain size of nickel contained in the hydrogen electrode active portion of the first element portion is larger than the grain size of nickel contained in the hydrogen electrode active portion of the second element portion.

An electrolytic cell according to a second aspect of the present invention includes a support substrate, a first element section, and a second element section. A first channel through which water vapor flows is formed inside the support substrate. The first element section is supported by the support substrate. The second element section is supported by the support substrate and arranged downstream of the first element section in the direction in which the water vapor flowing through the first channel flows. Each of the first element portion and the second element portion has an oxygen electrode, a hydrogen electrode active portion arranged between the oxygen electrode and the supporting substrate, and an electrolyte arranged between the oxygen electrode and the hydrogen electrode active portion. . The hydrogen electrode active portion of each of the first element portion and the second element portion contains an oxygen ion conductive material and nickel. The grain size of nickel contained in the hydrogen electrode active portion of the first element portion is larger than the grain size of nickel contained in the hydrogen electrode active portion of the second element portion.

An electrolytic cell according to a third aspect of the present invention relates to the first or second aspect, wherein each of the first element portion and the second element portion is arranged between the support substrate and the hydrogen electrode active portion. Each of the hydrogen electrode current collectors of the first element part and the second element part contains nickel, and the particle size of the nickel contained in the hydrogen electrode current collector of the first element part is , larger than the grain size of nickel contained in the current collecting portion of the hydrogen electrode of the second element portion.

An electrolytic cell according to a fourth aspect of the present invention includes a support substrate, a first channel formed in the support substrate through which water vapor and carbon dioxide flow, and an element portion supported by the support substrate. The element part has an oxygen electrode active part, a hydrogen electrode active part arranged between the oxygen electrode active part and the support substrate, and an electrolyte arranged between the oxygen electrode active part and the hydrogen electrode active part. The hydrogen electrode active portion includes a first portion and a second portion connected downstream of the first portion in the flow direction of water vapor and carbon dioxide flowing in the first channel. The first portion and the second portion each contain an oxygen ion conductive material and nickel. The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion.

An electrolytic cell according to a fifth aspect of the present invention includes a support substrate, a first channel formed in the support substrate through which water vapor flows, and an element portion supported by the support substrate. The element part has an oxygen electrode active part, a hydrogen electrode active part arranged between the oxygen electrode active part and the support substrate, and an electrolyte arranged between the oxygen electrode active part and the hydrogen electrode active part. The hydrogen electrode active portion includes a first portion and a second portion connected downstream of the first portion in the flow direction of water vapor flowing in the first channel. The first portion and the second portion each contain an oxygen ion conductive material and nickel. The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion.

An electrolytic cell according to a sixth aspect of the present invention includes an electrolyte, an oxygen electrode active portion arranged on the first main surface side of the electrolyte, and a hydrogen electrode active portion arranged on the second main surface side of the electrolyte. Prepare. The hydrogen electrode active portion includes a first portion and a second portion connected downstream of the first portion in the flow direction of water vapor and carbon dioxide flowing in the flow path on the second main surface side of the electrolyte. The first portion and the second portion each contain an oxygen ion conductive material and nickel. The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion.

An electrolytic cell according to a seventh aspect of the present invention includes an electrolyte, an oxygen electrode active portion arranged on the first main surface side of the electrolyte, and a hydrogen electrode active portion arranged on the second main surface side of the electrolyte. Prepare. The hydrogen electrode active portion includes a first portion and a second portion connected downstream of the first portion in the flow direction of water vapor flowing in the flow path on the second main surface side of the electrolyte. The first portion and the second portion each contain an oxygen ion conductive material and nickel. The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion.

An electrolytic cell according to an eighth aspect of the present invention relates to any one of the fourth to seventh aspects, wherein the hydrogen electrode active portion has a first overlapping portion in which the first portion and the second portion overlap. .

An electrolytic cell according to a ninth aspect of the present invention relates to any one of the fourth to eighth aspects, and includes a hydrogen electrode current collecting portion disposed on the hydrogen electrode active portion, the hydrogen electrode current collecting portion comprising: A third portion and a fourth portion connected downstream of the third portion in the flow direction, the third portion and the fourth portion each containing nickel, and the grain size of the nickel contained in the third portion is larger than the grain size of nickel contained in the fourth portion.

An electrolytic cell according to a tenth aspect of the present invention relates to the ninth aspect, wherein the hydrogen electrode current collecting portion has a second overlapping portion in which the third portion and the fourth portion are overlapped.

A cell stack device according to an eleventh aspect of the present invention comprises a manifold having a supply chamber and a recovery chamber, the first to fifth aspects supported by the manifold, and the fourth or fifth aspect. and an electrolytic cell according to any one of the eighth to tenth aspects cited above. The support substrate has a second channel communicating with the first channel at the tip. The first channel communicates with the supply chamber. The second channel communicates with the recovery chamber.

ADVANTAGE OF THE INVENTION According to this invention, the electrolytic cell and cell stack apparatus which can stabilize a performance can be provided.

FIG. 2 is a perspective view of a cell stack device; Sectional drawing of a manifold. A plan view of the manifold. Sectional drawing of a cell stack apparatus. Fig. 2 is a plan view of an electrolytic cell attached to a manifold; Sectional drawing of an electrolytic cell. FIG. 4 is a cross-sectional view of the electrolytic cell at its proximal end; Sectional drawing of the electrolysis cell in a front-end|tip part. The top view of the electrolytic cell which concerns on the modification c. AA sectional view of FIG. The top view of the electrolytic cell which concerns on the modification d.

Hereinafter, an electrolytic cell according to this embodiment will be described with reference to the drawings. In addition, this embodiment demonstrates using a solid oxide electrolysis cell (SOEC) as an example of an electrolysis cell. FIG. 1 is a perspective view showing a cell stack device, and FIG. 2 is a sectional view of a manifold. FIG. 3 is a plan view of the manifold. 1 to 3, description of some electrolytic cells is omitted.

[Cell stack device]
As shown in FIG. 1 , the cell stack device 100 includes a manifold 2 and multiple electrolytic cells 10 .

[Manifold]
As shown in FIG. 2, manifold 2 is configured to distribute gas to each of a plurality of electrolysis cells 10 . Manifold 2 is also configured to collect gas produced by electrolysis cell 10 . The manifold 2 has a supply chamber 21 and a collection chamber 22 . Water vapor (H ₂ O), carbon dioxide (CO ₂ ), and the like are supplied to the supply chamber 21 . Hydrogen (H ₂ ) may be further supplied to the supply chamber 21 . The recovery chamber 22 recovers H ₂ and carbon monoxide (CO) produced in each electrolytic cell 10 .

The manifold 2 has a manifold body portion 23 and a partition plate 24 . The manifold main body 23 has a space inside. The manifold body portion 23 has a rectangular parallelepiped shape.

The partition plate 24 airtightly partitions the space of the manifold main body 23 into the supply chamber 21 and the recovery chamber 22 . Specifically, the partition plate 24 extends in the longitudinal direction of the manifold body portion 23 .

A supply port 211 is formed in the bottom surface of the supply chamber 21 . A discharge port 221 is formed on the bottom surface of the recovery chamber 22 . Note that the supply port 211 and the discharge port 221 may be formed on the side surface or the top surface instead of the bottom surface.

The supply port 211 is arranged, for example, closer to the first end 201 than the center C of the manifold 2 in the arrangement direction (z-axis direction) of the electrolytic cells 10 . On the other hand, the outlet 221 is arranged, for example, on the second end 202 side of the center C of the manifold 2 in the arrangement direction (z-axis direction) of the electrolytic cells 10 .

As shown in FIG. 3 , a plurality of through holes 232 are formed in the top plate portion 231 of the manifold body portion 23 . The through holes 232 are arranged at intervals in the longitudinal direction (z-axis direction) of the manifold main body 23 . Each through hole 232 extends in the width direction (y-axis direction) of the manifold body portion 23 . Each through hole 232 communicates with the supply chamber 21 and the recovery chamber 22 . Each through hole 232 may be divided into a portion communicating with the supply chamber 21 and a portion communicating with the recovery chamber 22 .

[Electrolytic cell]
FIG. 4 is a cross-sectional view of the cell stack device. Also, FIG. 5 is a plan view of the electrolytic cell 10 attached to the manifold. As shown in FIGS. 4 and 5, electrolysis cells 10 extend from manifold 2 in a first direction. In addition, in this embodiment, the electrolytic cell 10 extends upward from the manifold 2 .

The electrolytic cell 10 has a proximal end 101 and a distal end 102 . Electrolytic cell 10 is attached to manifold 2 at proximal end 101 . That is, the manifold 2 supports the base end portion 101 of each electrolytic cell 10 . On the other hand, the tip portion 102 of the electrolytic cell 10 is not fixed to a manifold or the like. That is, the tip portion 102 of the electrolytic cell 10 is a free end. In this embodiment, the base end portion 101 of the electrolytic cell 10 means the lower end portion, and the distal end portion 102 of the electrolytic cell 10 means the upper end portion.

As shown in FIG. 1, each electrolytic cell 10 is arranged so that the main surfaces thereof face each other. Each electrolysis cell 10 is arranged along the longitudinal direction (z-axis direction) of the manifold 2 at intervals. That is, the arrangement direction of the electrolytic cells 10 is along the longitudinal direction of the manifold 2 .

As shown in FIGS. 4 and 5, the electrolytic cell 10 has a support substrate 4 and a plurality of element portions 5. As shown in FIGS. Moreover, the electrolytic cell 10 further has a communication member 3 .

[Supporting substrate]
A support substrate 4 extends upward from the manifold 2 . The support substrate 4 is plate-shaped. Specifically, the support substrate 4 has a rectangular shape in plan view (viewed in the z-axis direction). The support substrate 4 has a longitudinal direction (x-axis direction) and a width direction (y-axis direction). In this embodiment, the vertical direction (x-axis direction) in FIGS. 4 and 5 is the longitudinal direction of the support substrate 4, and the horizontal direction (y-axis direction) in FIGS. 4 and 5 is the width direction of the support substrate 4. .

The support substrate 4 has a proximal end portion 41 and a distal end portion 42 . The base end portion 41 and the tip end portion 42 are both end portions of the support substrate 4 in the longitudinal direction (x-axis direction). In this embodiment, the base end portion 41 of the support substrate 4 means the lower end portion, and the distal end portion 42 of the support substrate 4 means the upper end portion.

A base end portion 41 of the support substrate 4 is attached to the manifold 2 . For example, the base end portion 41 of the support substrate 4 is attached to the top plate portion 231 of the manifold 2 with a bonding material 400 or the like. Specifically, the base end portion 41 of the support substrate 4 is inserted into a through hole 232 formed in the top plate portion 231 . Note that the base end portion 41 of the support substrate 4 does not have to be inserted into the through hole 232 . That is, the support substrate 4 may be placed on the top plate portion 231 so that the through holes 232 are covered by the first end surfaces 411 of the support substrate 4 .

A plurality of first channels 43 and one second channel 44 are formed in the support substrate 4 . The number of the first flow paths 43 and the number of the second flow paths 44 can be changed as appropriate.

The first and second channels 43 and 44 extend in the first direction inside the support substrate 4 . The first direction means the direction in which the first and second flow paths 43 and 44 extend. In this embodiment, the first and second channels 43 and 44 extend in the longitudinal direction of the support substrate 4 . Also, a direction intersecting with the first direction is referred to as a "second direction". Note that in the present embodiment, the second direction is orthogonal to the first direction. The second direction extends along the width direction (y-axis direction) of the support substrate 4 .

The first and second channels 43 and 44 penetrate through the support substrate 4 . Each first flow path 43 is spaced apart from each other in the second direction. Also, each of the second flow paths 44 is spaced apart from the first flow paths 43 in the second direction. That is, each of the first flow paths 43 and the second flow paths 44 are spaced apart from each other in the second direction. In addition, it is preferable that the interval between the first channel 43 and the second channel 44 is larger than the interval between the first channels 43 .

The first channel 43 communicates with the supply chamber 21 at its base end 431 . Therefore, H ₂ O, CO ₂ and the like are supplied from the supply chamber 21 to the first flow path 43 . That is, H ₂ O and CO ₂ flow along the first direction from the base end portion 431 of the first channel 43 toward the tip end portion 432 .

The second flow path 44 communicates with the first flow path 43 at its distal end portion 442 . That is, the tip portion 432 of the first channel 43 and the tip portion 442 of the second channel 44 communicate with each other. Specifically, the distal end portion 432 of the first flow path 43 and the distal end portion 442 of the second flow path 44 communicate with each other via a communication flow path 30 which will be described later. Also, the second flow path 44 communicates with the recovery chamber 22 at its base end portion 441 .

H _{2 ,} CO, and the like generated by the electrolytic cell 10 flow from the distal end portion 442 toward the proximal end portion 441 in the second flow path 44 . H _{2 ,} CO, etc. flowing in the second flow path 44 along the first direction are discharged from the base end portion 441 of the second flow path 44 to the recovery chamber 22 .

The support substrate 4 is made of a porous material that does not have electronic conductivity. The support substrate 4 can be made of, for example, yttria (Y ₂ O ₃ ), magnesium oxide (MgO), magnesia alumina spinel (MgAl ₂ O ₄ ), or a composite of these. The porosity of the support substrate 4 is, for example, approximately 20 to 60%. This porosity is measured, for example, by the Archimedes method.

The support substrate 4 is covered with a dense layer 48 . The dense layer 48 is configured to prevent the gas diffused into the support substrate 4 from the first channel 43 and the second channel 44 from being discharged to the outside. In this embodiment, the dense layer 48 covers a portion of the surface of the support substrate 4 where the element portion 5 is not formed. In this embodiment, the dense layer 48 can be made of a material used for the electrolyte 7, which will be described later, crystallized glass, or the like. The dense layer 48 is denser than the support substrate 4 . For example, the dense layer 48 has a porosity of about 0 to 7%.

6 and 7 show cut surfaces obtained by cutting the electrolytic cell 10 along a plane perpendicular to the second direction. 6 and 7 are cross sections of the electrolytic cell 10 cut along the first flow path 43. FIG.

As shown in FIG. 6 , the support substrate 4 has a first principal surface 45 , a second principal surface 46 , a plurality of recesses 49 and a plurality of crosspieces 50 . The recesses 49 are spaced apart from each other in the first direction. The recess 49 extends in the second direction. In addition, in the present embodiment, the concave portion 49 is not formed in a portion that overlaps with the second flow path 44 in a plan view (viewed in the z-axis direction).

The crosspiece 50 is arranged between the pair of recesses 49 . That is, the portion between the pair of concave portions 49 becomes the crosspiece portion 50 . The crosspiece 50 extends in the second direction. The recesses 49 and the crosspieces 50 are alternately arranged in the first direction.

[Communication member]
As shown in FIG. 4 , the electrolytic cell 10 has a communication channel 30 that communicates the first channel 43 and the second channel 44 . The communicating channel 30 is formed in the communicating member 3 attached to the support substrate 4 . The communication member 3 is preferably formed integrally with the support substrate 4 .

The communication member 3 is porous, for example. Further, the communicating member 3 has a dense layer 31 forming its outer surface. The dense layer 31 is formed denser than the main body of the communicating member 3 . For example, the dense layer 31 has a porosity of about 0 to 7%. The dense layer 31 can be made of the same material as the communicating member 3, the material used for the electrolyte 7, crystallized glass, or the like.

[Element part]
As shown in FIG. 5, a plurality of element units 5 are arranged on the support substrate 4 . In addition, in this embodiment, a plurality of element portions 5 are supported on both surfaces of the support substrate 4 . The number of the plurality of element portions 5 formed on each of the first main surface 45 and the second main surface 46 is not particularly limited, and may be two or more. The number of element portions 5 formed on the first main surface 45 and the number of element portions 5 formed on the second main surface 46 may be the same or different. Further, the element section 5 may be supported by only one of the first main surface 45 and the second main surface 46 of the support substrate 4 . In the following description, attention will be paid to the plurality of element portions 5 arranged on the first main surface 45 of the support substrate 4 .

The plurality of element units 5 are arranged in the first direction. That is, the electrolytic cell 10 according to the present embodiment is a so-called horizontal-striped electrolytic cell. The plurality of element units 5 are electrically connected in series with each other by an interconnector 9 (see FIG. 6).

As shown in FIG. 5, the plurality of element portions 5 includes one first element portion 5a and three second element portions 5b. The first element portion 5a is arranged upstream of the three second element portions 5b in the flow direction of H ₂ O and CO ₂ flowing in the first flow path 43 (hereinafter abbreviated as the “flow direction”). be done. The first element portion 5 a is closest to the manifold 2 among the plurality of element portions 5 . Each of the three second element portions 5b is arranged downstream of the first element portion 5a in the flow direction. The three second element portions 5b are arranged in order in the flow direction. In addition, in this embodiment, the distribution direction is the same as the first direction.

The element portion 5 extends in the second direction. In the present embodiment, the element portion 5 overlaps the first flow path 43 but does not overlap the second flow path 44 in plan view (z-axis direction view). That is, the first channel 43 is arranged so as to overlap with the element portion 5 in plan view, and the second channel 44 is arranged so as not to overlap with the element portion 5 in plan view. In addition, planar view means viewing along the thickness direction of the electrolytic cell 10 .

The support substrate 4 can be divided into a first region R1 and a second region R2. The first region R1 is a region that overlaps with the supply chamber 21 when viewed in the first direction (viewed in the x-axis direction). The second region R2 is a region that overlaps with the recovery chamber 22 when viewed in the first direction (viewed in the x-axis direction).

The element section 5 is arranged in the first region R1 of the support substrate 4 and not arranged in the second region R2. The first flow path 43 is formed within the first region R1 of the support substrate 4, and the second flow path 44 is formed within the second region R2 of the support substrate 4. As shown in FIG.

As shown in FIGS. 6 and 7, each element section 5 has a hydrogen electrode 6 (cathode), an electrolyte 7, and an oxygen electrode 8 (anode). A hydrogen electrode 6, an electrolyte 7, and an oxygen electrode 8 are arranged in this order from the support substrate 4 side. Each element section 5 further has a reaction prevention film 11 . The basic configuration of the first element portion 5a shown in FIG. 7 is the same as the basic configuration of the second element portion 5b shown in FIG. are doing.

[Hydrogen electrode]
A hydrogen electrode 6 is arranged between the support substrate 4 and the electrolyte 7 . The hydrogen electrode 6 produces H ₂ , CO, and O ²⁻ from CO ₂ and H ₂ O according to the electrochemical reaction of co-electrolysis shown in the following formula (1).

・Hydrogen electrode 6: CO ₂ +H ₂ O+ 4e ⁻ →CO+H ₂ +2O ²⁻ (1)

The hydrogen electrode 6 is made of a porous material having electronic conductivity. The hydrogen electrode 6 is a fired body. The hydrogen electrode 6 has a hydrogen electrode collector portion 61 and a hydrogen electrode active portion 62 . Each hydrogen electrode 6 is arranged on the support substrate 4 . Each hydrogen electrode 6 is spaced apart from each other in the first direction (x-axis direction).

[Hydrogen electrode current collector]
The hydrogen electrode collector 61 is arranged on the support substrate 4 . The hydrogen electrode collector 61 is arranged between the support substrate 4 and the oxygen electrode 8 . More specifically, the hydrogen electrode current collecting portion 61 is arranged between the support substrate 4 and the hydrogen electrode active portion 62 .

In this embodiment, the hydrogen electrode collector 61 is arranged inside the recess 49 . A recess 49 is formed in the support substrate 4 . Specifically, the hydrogen electrode current collector 61 fills the recess 49 and has the same shape as the recess 49 .

A main surface 611 of the hydrogen electrode current collecting portion 61 is substantially flush with the first main surface 45 of the support substrate 4 . That is, the first main surface 45 of the support substrate 4 and the main surface 611 of each hydrogen electrode current collector 61 constitute one surface. Note that the main surface 611 of the hydrogen electrode current collecting portion 61 does not have to be completely on the same plane as the first main surface 45 of the support substrate 4 . There may be a step of about 20 μm or less.

The hydrogen electrode collector 61 has electronic conductivity. The hydrogen electrode current collector 61 preferably has higher electron conductivity than the hydrogen electrode active portion 62 . The hydrogen electrode collector 61 may or may not have oxygen ion conductivity.

The hydrogen electrode collector 61 according to this embodiment contains nickel (Ni). Ni functions as an electronically conductive material. Ni contained in the hydrogen electrode current collecting portion 61 basically exists in the state of metallic Ni, but part of it may exist in the state of nickel oxide (NiO).

The hydrogen electrode collector 61 may contain an oxygen ion conductive material. Oxygen ion conductive materials include yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), scandia-stabilized zirconia (ScSZ), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), and among these A mixed material or the like in which two or more materials are combined can be used. The thickness of the hydrogen electrode current collecting portion 61 and the depth of the concave portion 49 are, for example, about 50 to 500 μm.

The hydrogen electrode current collecting portion 61 can be formed by firing a molded body containing NiO. The compact may optionally contain at least one of an oxygen ion conductive material and a non-oxygen ion conductive material. In the compact of the hydrogen electrode current collector 61, the NiO content can be, for example, 55 wt % or more and 85 wt % or less. In the molded body of the hydrogen electrode current collector 61, the total content of the oxygen ion conductive material and the non-oxygen ion conductive material can be, for example, 15 wt % or more and 45 wt % or less.

[Hydrogen electrode active part]
The hydrogen electrode active portion 62 is arranged on the hydrogen electrode collector portion 61 . The hydrogen electrode active portion 62 is arranged between the oxygen electrode 8 and the support substrate 4 . More specifically, the hydrogen electrode active portion 62 is arranged between the hydrogen electrode current collecting portion 61 and the electrolyte 7 .

In this embodiment, the hydrogen electrode active portion 62 is arranged on the principal surface 611 of the hydrogen electrode current collector 61 . Therefore, the hydrogen electrode active portion 62 protrudes from the concave portion 49 . That is, the hydrogen electrode active portion 62 is not embedded in the hydrogen electrode collector portion 61 . The edge of the hydrogen electrode active portion 62 is formed inside the edge of the hydrogen electrode collector portion 61 on the main surface 611 . Specifically, the hydrogen electrode active portion 62 has a smaller area in plan view (z-axis direction view) than the hydrogen electrode collector portion 61 . The hydrogen electrode active portion 62 is accommodated within the main surface 611 of the hydrogen electrode current collecting portion 61 .

The hydrogen electrode active portion 62 has oxygen ion conductivity and electron conductivity. The hydrogen electrode active portion 62 preferably has higher oxygen ion conductivity than the hydrogen electrode collector portion 61 . The hydrogen electrode active portion 62 is responsible for the electrochemical reaction shown in formula (1) above.

The hydrogen electrode active portion 62 contains Ni and an oxygen ion conductive material. Ni functions as an electronically conductive material and as an electrode catalyst. Ni contained in the hydrogen electrode active portion 62 basically exists in the state of metallic Ni, but part of it may exist in the state of NiO. As the oxygen ion conductive material, YSZ, _Y2O3 , CSZ, ScSZ, _GDC , SDC, a mixed material in which two or more of these are combined, and the like can be used.

The hydrogen electrode active portion 62 may be thinner than the hydrogen electrode collector portion 61 . The thickness of the hydrogen electrode active portion 62 is, for example, about 5 to 30 μm.

The hydrogen electrode active portion 62 can be formed by firing a compact containing NiO and an oxygen ion conductive material. In the compact of the hydrogen electrode active portion 62, the NiO content can be, for example, 50 wt % or more and 70 wt % or less. The content of the oxygen ion conductive material in the molded body of the hydrogen electrode active portion 62 can be, for example, 30 wt % or more and 50 wt % or less.

[Particle size of Ni in the hydrogen electrode active part 62]
The grain size of Ni contained in the hydrogen electrode active portion 62 of the first element portion 5a (see FIGS. 5 and 7) is larger than the grain size of Ni.

That is, the Ni contained in the hydrogen electrode active portion 62 of the first element portion 5a located on the upstream side is relatively coarse, and the Ni contained in the hydrogen electrode active portion 62 of the second element portion 5b located on the downstream side is relatively coarse. Ni is relatively fine-grained.

As described above, since the Ni contained in the hydrogen electrode active portion 62 of the first element portion 5a, in which the water vapor partial pressure tends to increase during the operation of the electrolytic cell 10, is coarse, the Ni is bonded to each other by surface tension. Coarseness (aggregation) can be suppressed. Therefore, it is possible to prevent the performance of the electrolytic cell 10 from fluctuating (decreasing) due to the decrease in the activity of the hydrogen electrode active portion 62 during the operation of the electrolytic cell 10 .

In addition, since the Ni contained in the hydrogen electrode active portion 62 of the second element portion 5b is less likely to increase the water vapor partial pressure during the operation of the electrolytic cell 10, the electrode activity of the hydrogen electrode active portion 62 is increased, and the electrolytic cell 10 overall performance can be maintained.

As described above, by relatively increasing the particle size of Ni contained in the upstream hydrogen electrode active portion 62, the initial performance of the electrolytic cell 10 can be ensured while suppressing performance degradation over time.

The grain size of Ni contained in the hydrogen electrode active portion 62 of the first element portion 5a can be, for example, 0.3 μm or more and 4.0 μm or less. The grain size of Ni contained in the hydrogen electrode active portion 62 of the first element portion 5a is preferably 0.3 μm or more and 2.0 μm or less. The grain size of Ni contained in the hydrogen electrode active portion 62 of the second element portion 5b can be, for example, 0.3 μm or more and 3.0 μm or less. The grain size of Ni contained in the hydrogen electrode active portion 62 of the second element portion 5b is preferably 0.3 μm or more and 2.0 μm or less.

By observing the cross section of the hydrogen electrode 6 with an SEM (electron microscope), the interface between the hydrogen electrode current collecting portion 61 and the hydrogen electrode active portion 62 can be identified.

The grain size of Ni contained in the hydrogen electrode active portion 62 is measured by the following method.

First, the cross section of the hydrogen electrode active portion 62 is subjected to precision mechanical polishing, and then subjected to ion milling processing using IM4000 manufactured by Hitachi High-Technologies Corporation.

Next, using an FE-SEM (Field Emission Scanning Electron Microscope) using an in-lens secondary electron detector, an oxygen ion conductive material and Ni particles are observed. An enlarged SEM image of the cross section of the hydrogen electrode active portion 62 is acquired at a magnification (for example, 5000 to 30000 times).

Next, by classifying the brightness of the SEM image into 256 gradations, the difference in brightness between the oxygen ion conductive material, Ni, and pores is tri-valued. For example, the oxygen ion conductive material can be displayed in light gray, Ni in dark gray, and pores in black.

Next, the SEM image is analyzed using image analysis software HALCON manufactured by MVTec (Germany) to obtain an analysis image in which the Ni particles are highlighted. Then, the average circle equivalent diameter of 50 Ni particles randomly selected from the analysis image is taken as the Ni particle size. The average equivalent circle diameter of the Ni particles is the arithmetic mean value of the equivalent circle diameters of the respective Ni particles. The equivalent circle diameter of the Ni particles is the diameter of a circle having the same area as the Ni particles.

[Particle size of Ni in the hydrogen electrode current collector 61]
The particle size of Ni contained in the hydrogen electrode current collecting portion 61 of the first element portion 5a (see FIGS. 5 and 7) is It is preferably larger than the grain size of the contained Ni.

That is, the Ni contained in the hydrogen electrode current collecting portion 61 of the first element portion 5a located on the upstream side is preferably relatively coarse, and the Ni contained in the hydrogen electrode current collecting portion 61 of the second element portion 5b located on the downstream side is preferably relatively coarse. Ni contained in the portion 61 is preferably relatively fine particles.

As described above, since the Ni contained in the hydrogen electrode current collecting portion 61 of the first element portion 5a tends to increase the water vapor partial pressure during operation of the electrolytic cell 10, the Ni particles are coarse grains, and the Ni particles are bonded to each other by surface tension. coarsening can be suppressed. Therefore, it is possible to suppress the decrease in the conductivity of the hydrogen electrode current collecting portion 61 during the operation of the electrolytic cell 10 , thereby further suppressing the fluctuation (decrease) of the performance of the electrolytic cell 10 .

In addition, since the Ni contained in the hydrogen electrode current collector 61 of the second element portion 5b is less likely to increase the water vapor partial pressure during operation of the electrolytic cell 10, the conductivity of the hydrogen electrode current collector 61 is increased. The performance of the electrolytic cell 10 as a whole can be maintained.

As described above, by relatively increasing the particle size of Ni contained in the upstream hydrogen electrode current collector 61, it is possible to further suppress deterioration in performance over time while ensuring the initial performance of the electrolytic cell 10. can.

The grain size of Ni contained in the hydrogen electrode current collecting portion 61 of the first element portion 5a can be, for example, 0.5 μm or more and 5.0 μm or less. The grain size of Ni contained in the hydrogen electrode current collecting portion 61 of the first element portion 5a is preferably 0.5 μm or more and 3.0 μm or less. The grain size of Ni contained in the hydrogen electrode current collecting portion 61 of the second element portion 5b can be, for example, 0.5 μm or more and 4.0 μm or less. The grain size of Ni contained in the hydrogen electrode current collecting portion 61 of the second element portion 5b is preferably 0.5 μm or more and 2.0 μm or less.

The grain size of Ni contained in the hydrogen electrode current collecting portion 61 is measured by the same method as the grain size of Ni contained in the above-described hydrogen electrode active portion 62 .

[Electrolytes]
An electrolyte 7 is arranged between the hydrogen electrode 6 and the oxygen electrode 8 . More specifically, the electrolyte 7 is arranged between the hydrogen electrode active portion 62 and the oxygen electrode 8 .

The electrolyte 7 has oxygen ion conductivity. The electrolyte 7 transfers O ²⁻ produced at the hydrogen electrode 6 to the oxygen electrode 8 . The electrolyte 7 is arranged so as to cover the hydrogen electrode 6 . Specifically, the electrolyte 7 extends in the first direction from one interconnector 9 to another interconnector 9 . That is, the electrolytes 7 and the interconnectors 9 are alternately arranged in the first direction.

The electrolyte 7 is denser than the support substrate 4 . For example, the electrolyte 7 has a porosity of about 0 to 7%. The electrolyte 7 is a sintered body composed of a dense material that has ionic conductivity but no electronic conductivity. The electrolyte 7 can be composed of, for example, YSZ or LSGM (lanthanum gallate). The thickness of the electrolyte 7 is, for example, approximately 3 to 50 μm.

[Reaction prevention film]
The anti-reaction film 11 is a sintered body made of a dense material. The reaction prevention film 11 has substantially the same shape as the hydrogen electrode active portion 62 in plan view, and is arranged so as to overlap the hydrogen electrode active portion 62 . The reaction prevention film 11 is arranged at a position corresponding to the hydrogen electrode active portion 62 with the electrolyte 7 interposed therebetween. In the reaction prevention film 11, a phenomenon occurs in which YSZ in the electrolyte 7 reacts with Sr in the oxygen electrode active portion 81 to form a reaction layer having a large electric resistance at the interface between the electrolyte 7 and the oxygen electrode active portion 81. is provided to suppress The reaction prevention film 11 can be composed of, for example, GDC=(Ce, Gd)O ₂ (gadolinium-doped ceria). The thickness of the reaction prevention film 11 is, for example, about 3 to 50 μm.

[Oxygen electrode]
The oxygen electrode 8 generates O ² from O 2− transmitted from the hydrogen electrode 6 via the electrolyte 7 according to the chemical reaction shown _in the following formula (2).

・Oxygen electrode 8: 2O ²⁻ → O ₂ +4e ⁻ (2)

The oxygen electrode 8 is made of a porous material having electronic conductivity. The oxygen electrode 8 is a fired body. The oxygen electrode 8 is arranged so as to sandwich the electrolyte 7 in cooperation with the hydrogen electrode 6 . The oxygen electrode 8 has an oxygen electrode active portion 81 and an oxygen electrode current collecting portion 82 .

[Oxygen active part]
The oxygen electrode active portion 81 is arranged on the reaction prevention film 11 . The oxygen electrode active portion 81 has oxygen ion conductivity and electronic conductivity. The oxygen electrode active portion 81 preferably has a higher oxygen ion conductivity than the oxygen electrode current collecting portion 82 .

The oxygen electrode active portion 81 is made of a porous material. The oxygen electrode active portion 81 is a sintered body. The oxygen electrode active portion 81 is composed of, for example, LSCF=(La, Sr)(Co, Fe) O ₃ (lanthanum strontium cobalt ferrite), LSF=(La, Sr) FeO ₃ (lanthanum strontium ferrite), LNF=La(Ni , Fe)O ₃ (lanthanum nickel ferrite), LSC=(La,Sr)CoO ₃ (lanthanum strontium cobaltite), or SSC=(Sm,Sr)CoO ₃ (samarium strontium cobaltite), and those with GDC, etc. It can be composed of a composite with an oxygen ion-conducting material. Further, the oxygen electrode active portion 81 may be composed of two layers, a first layer (inner layer) made of LSCF and a second layer (outer layer) made of LSC. The thickness of the oxygen electrode active portion 81 is, for example, 10 to 100 μm.

[Oxygen electrode current collector]
The oxygen electrode current collecting portion 82 is arranged on the oxygen electrode active portion 81 . The oxygen electrode current collecting portion 82 extends from the oxygen electrode active portion 81 toward the adjacent element portion 5 . The oxygen electrode current collecting portion 82 is electrically connected to the hydrogen electrode current collecting portion 61 of the adjacent element portion 5 via the interconnector 9 . The hydrogen electrode current collecting portion 61 and the oxygen electrode current collecting portion 82 extend in opposite directions from the reaction region in the first direction. The reaction region is a region where the hydrogen electrode active portion 62 , the electrolyte 7 , and the oxygen electrode active portion 81 overlap when viewed from above (in the z-axis direction) of the electrolytic cell 10 .

The oxygen electrode current collector 82 is made of a porous material having electronic conductivity. The oxygen electrode current collector 82 is a fired body. The oxygen electrode current collecting portion 82 preferably has higher electron conductivity than the oxygen electrode active portion 81 . The oxygen electrode current collector 82 may or may not have oxygen ion conductivity.

The oxygen electrode collector 82 can be made of, for example, LSCF, LSC, Ag (silver), Ag--Pd (silver-palladium alloy), or the like. The thickness of the oxygen electrode current collecting portion 82 is, for example, about 50 to 500 μm.

[Interconnector]
The interconnector 9 is configured to electrically connect the element portions 5 adjacent to each other in the first direction. The interconnector 9 electrically connects the hydrogen electrode 6 of one of the adjacent element portions 5 and the oxygen electrode 8 of the other element portion 5 . Specifically, the interconnector 9 electrically connects the hydrogen electrode current collecting portion 61 of one element portion 5 of the adjacent element portions 5 and the oxygen electrode current collecting portion 82 of the other element portion 5 . .

In this manner, each element section 5 is connected in series from the base end section 101 to the tip section 102 of the electrolytic cell 10 on each of the first and second main surfaces 45 and 46 by the interconnector 9 .

The interconnector 9 is arranged on the main surface 611 of the hydrogen electrode current collector 61 . The interconnector 9 is spaced apart from the hydrogen electrode active portion 62 in the first direction.

The interconnector 9 is made of a dense material having electronic conductivity. The interconnector 9 is a sintered body. The interconnector 9 is denser than the support substrate 4 . For example, the interconnector 9 has a porosity of about 0 to 7%. The interconnector 9 can be made of, for example, LaCrO ₃ (lanthanum chromite) or (Sr, La)TiO ₃ (strontium titanate). The thickness of the interconnector 9 is, for example, 10-100 μm.

As shown in FIG. 7, the interconnector 9 arranged on the most proximal side in each electrolytic cell 10 includes the element portion 5 arranged on the first main surface 45 and the element portion arranged on the second main surface 46. 5 are electrically connected.

The oxygen electrode current collecting portion 82 of the element portion 5 arranged on the most proximal side of the second main surface 46 extends from the second main surface 46 to the first main surface 45 via the side surface of the support substrate 4 . That is, the oxygen electrode current collecting portion 82 of the element portion 5 arranged on the most proximal side extends annularly. The interconnector 9 arranged on the most proximal side on the first main surface 45 includes an oxygen electrode current collector 82 extending from the second main surface 46 to the first main surface 45 and It is electrically connected to the hydrogen electrode current collecting portion 61 of the element portion 5 arranged on the end side.

Thus, the plurality of element portions 5 connected in series on the first main surface 45 and the plurality of element portions 5 connected in series on the second main surface 46 are connected by the interconnector 9 to the proximal end of the electrolytic cell 10. They are connected in series in the section 101 .

[Current collector]
As shown in FIG. 8, the cell stack device 100 further has a collector member 12 . The collector members 12 are arranged between adjacent electrolytic cells 10 . The collector members 12 electrically connect adjacent electrolytic cells 10 to each other. The current collecting member 12 joins the tip portions 102 of the adjacent electrolytic cells 10 . For example, the current collecting member 12 is arranged on the tip side of the element portion 5 arranged on the most tip side among the plurality of element portions 5 arranged on both main surfaces of the support substrate 4 . The current collecting member 12 electrically connects the element portions 5 of the adjacent electrolytic cells 10 arranged on the most tip side.

The current collecting member 12 is bonded to the oxygen electrode current collecting portion 82 extending from the element portion 5 via the conductive bonding material 103 . Well-known conductive ceramics or the like can be used as the conductive bonding material 103 . For example, the conductive bonding material 103 is composed of at least one selected from (Mn, Co) ₃ O ₄ , (La, Sr) MnO ₃ , (La, Sr) (Co, Fe) O ₃ and the like. can be done.

[how to use]
In the cell stack device 100 configured as described above, H ₂ O and CO ₂ are supplied to the supply chamber 21 of the manifold 2 while supplying power between the electrodes. Then, the H ₂ O and CO ₂ flowing in the first flow path 43 are co-electrolyzed in the element section 5 to generate H ₂ and CO. The H ₂ and CO thus produced flow through the second flow path 44 and are recovered in the recovery chamber 22 .

[Modification]
Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the gist of the present invention.

(a) In the above embodiment, the electrolytic cell 10 has one first element portion 5a and three second element portions 5b, but the present invention is not limited to this. As long as the electrolytic cell 10 has one first element portion 5a and one second element portion 5b arranged downstream of the first element portion 5a, the first element portion 5a and the second The number and arrangement of the element portions 5b can be changed as appropriate. For example, a plurality of first element portions 5a may be arranged, or only one second element portion 5b may be arranged.

(b) In the above embodiment, the gas generated by the electrolytic cell 10 is collected in the manifold 2, but this is not the only option. For example, the communication member 3 of the electrolytic cell 10 may be omitted, and gas may be recovered from the first flow path 43 opening at the tip portion 102 of the electrolytic cell 10 .

(c) In the above embodiment, the electrolysis cell 10 is a so-called horizontal-stripe electrolysis cell, but it may be a so-called vertical-stripe electrolysis cell. As shown in FIG. 9 , the vertically-striped electrolytic cell 20 has one element portion 5 c arranged on one main surface 45 of the support substrate 4 .

10 is a cross-sectional view taken along line AA of FIG. 9. FIG. As shown in FIG. 10, the element portion 5c includes an oxygen electrode 8, a hydrogen electrode 6a arranged between the oxygen electrode 8 and the support substrate 4, and an electrolyte 7 arranged between the oxygen electrode 8 and the hydrogen electrode 6a. and The hydrogen electrode 6 a includes a hydrogen electrode active portion 65 and a hydrogen electrode current collecting portion 66 . The structure of the element portion 5c other than the hydrogen electrode 6a is as described in the above embodiment.

The hydrogen electrode active portion 65 includes a first portion 65a and a second portion 65b connected downstream of the first portion 65a in the flow direction of H ₂ O and CO ₂ flowing in the first flow path 43 . Each of the first portion 65a and the second portion 65b contains an oxygen ion conductive material and Ni.

The grain size of Ni contained in the first portion 65a is larger than the grain size of Ni contained in the second portion 65b. In this way, since the Ni contained in the first portion 65a, in which the water vapor partial pressure tends to increase during the operation of the electrolytic cell 10, is coarse, it is possible to suppress the Ni from becoming coarse, so that the performance of the electrolytic cell 20 can be suppressed from fluctuating (decreasing). In addition, since the Ni contained in the second portion 65b, in which the water vapor partial pressure is unlikely to increase during the operation of the electrolytic cell 20, is fine, the electrode activity of the hydrogen electrode active portion 65 is increased, and the performance of the electrolytic cell 20 as a whole is maintained. can do. Therefore, deterioration of performance over time can be suppressed while ensuring the initial performance of the electrolytic cell 10 .

The grain size of Ni contained in the first portion 65a can be, for example, 0.3 μm or more and 4.0 μm or less. The grain size of Ni contained in the first portion 65a is preferably 0.3 μm or more and 2.0 μm or less. The grain size of Ni contained in the second portion 65b can be, for example, 0.3 μm or more and 3.0 μm or less. The grain size of Ni contained in the second portion 65b is preferably 0.3 μm or more and 2.0 μm or less.

As shown in FIG. 10, the hydrogen electrode active portion 65 has an overlapping portion 65x where the downstream end of the first portion 65a and the upstream end of the second portion 65b overlap in the second direction. Thereby, the connectivity between the first portion 65a and the second portion 65b can be improved compared to the case where the end surfaces of the first portion 65a and the second portion 65b are connected.

The ratio of the area of each of the first and second portions 65a and 65b to the total area of the hydrogen electrode active portion 65 in plan view of the main surface on the electrolyte side of the hydrogen electrode active portion 65 is determined to ensure initial performance and prevent performance deterioration. It can be appropriately set depending on which of suppression and suppression is emphasized. Similarly, the ratio of the areas of the first and second portions 65a and 65b to the total area of the hydrogen electrode active portion 65 in plan view of the main surface of the hydrogen electrode current collecting portion side of the hydrogen electrode active portion 65 also affects the initial performance. It can be set as appropriate depending on which of securing and suppressing performance deterioration is emphasized.

As shown in FIG. 10 , the hydrogen electrode collector 66 is arranged between the hydrogen electrode active portion 65 and the support substrate 4 .

The hydrogen electrode current collector 66 includes a third portion 66a and a fourth portion 66b connected to the downstream side of the third portion 66a in the flow direction of H ₂ O and CO ₂ flowing in the first channel 43. . Each of the third portion 66a and the fourth portion 66b contains Ni. Each of the third portion 66a and the fourth portion 66b may contain an oxygen ion conductive material.

The grain size of Ni contained in the third portion 66a is larger than the grain size of Ni contained in the fourth portion 66b. In this way, since the Ni contained in the third portion 66a, in which the water vapor partial pressure tends to increase during operation of the electrolytic cell 20, is coarse, it is possible to suppress the Ni from becoming coarse, so that the performance of the electrolytic cell 20 can be further suppressed from fluctuating (decreasing). In addition, since the Ni contained in the fourth portion 66b, in which the water vapor partial pressure is unlikely to increase during the operation of the electrolytic cell 20, is fine, the conductivity of the hydrogen electrode current collecting portion 66 is increased, and the performance of the electrolytic cell 20 as a whole is improved. can be maintained. Therefore, the deterioration of performance over time can be further suppressed while ensuring the initial performance of the electrolytic cell 10 .

The grain size of Ni contained in the third portion 66a can be, for example, 0.5 μm or more and 5.0 μm or less. The grain size of Ni contained in the third portion 66a is preferably 0.5 μm or more and 3.0 μm or less. The grain size of Ni contained in the fourth portion 66b can be, for example, 0.5 μm or more and 4.0 μm or less. The grain size of Ni contained in the fourth portion 66b is preferably 0.5 μm or more and 2.0 μm or less.

As shown in FIG. 10, the hydrogen electrode collector 66 has an overlapping portion 66x where the downstream end of the third portion 66a and the upstream end of the fourth portion 66b overlap in the second direction. Thereby, the connectivity between the third portion 66a and the fourth portion 66b can be improved compared to the case where the end faces of the third portion 66a and the fourth portion 66b are connected.

The ratio of the area of each of the third and fourth portions 66a and 66b to the total area of the hydrogen electrode current collecting portion 66 in a plan view of the main surface of the hydrogen electrode current collecting portion 66 on the side of the active portion of the hydrogen electrode is the initial performance. It can be set as appropriate depending on which of securing and suppressing performance deterioration is emphasized. Similarly, the ratio of the area of each of the third and fourth portions 66a and 66b to the total area of the hydrogen electrode current collecting portion 66 in plan view of the supporting substrate side main surface of the hydrogen electrode current collecting portion 66 also ensures the initial performance. It can be appropriately set depending on which of the performance degradation and the suppression of performance deterioration is emphasized.

(d) In the above embodiment, the electrolysis cell 10 is a so-called horizontal-stripe electrolysis cell, but it may be a so-called flat-plate electrolysis cell. As shown in FIG. 11, the plate-type electrolytic cell 30 includes an electrolyte 7, an oxygen electrode 8 arranged on the first main surface 71 side of the electrolyte 7, and an oxygen electrode 8 arranged on the second main surface 72 side of the electrolyte 7. and a hydrogen electrode 6b. The hydrogen electrode 6b includes a hydrogen electrode active portion 67 and a hydrogen electrode current collecting portion 68 . The electrolytic cell 30 is arranged between an interconnector electrically connected to the oxygen electrode 8 and an interconnector electrically connected to the hydrogen electrode 6b. The electrolyte 7 is bonded to the separator via a dense insulating bonding material. A flow path L2 through which H ₂ O and CO ₂ flow is formed on the 72 side.

As shown in FIG. 11, the hydrogen electrode active portion 67 is connected to a first portion 67a and a second portion connected downstream of the first portion 67a in the flow direction of H ₂ O and CO ₂ flowing in the second flow path L2. 2 parts 67b. Each of the first portion 67a and the second portion 67b contains an oxygen ion conductive material and Ni.

The grain size of Ni contained in the first portion 67a is larger than the grain size of Ni contained in the second portion 67b. In this way, since the Ni contained in the first portion 67a, in which the water vapor partial pressure tends to increase during the operation of the electrolytic cell 10, is coarse, it is possible to suppress the Ni from being coarsened. can be suppressed from fluctuating (decreasing). In addition, since the Ni contained in the second portion 67b, in which the water vapor partial pressure is unlikely to increase during the operation of the electrolytic cell 30, is fine particles, the electrode activity of the hydrogen electrode active portion 67 is enhanced, and the performance of the electrolytic cell 30 as a whole is maintained. can do. Therefore, deterioration of performance over time can be suppressed while ensuring the initial performance of the electrolytic cell 10 .

The grain size of Ni contained in the first portion 67a can be, for example, 0.3 μm or more and 4.0 μm or less. The grain size of Ni contained in the first portion 67a is preferably 0.3 μm or more and 2.0 μm or less. The grain size of Ni contained in the second portion 67b can be, for example, 0.3 μm or more and 3.0 μm or less. The grain size of Ni contained in the second portion 67b is preferably 0.3 μm or more and 2.0 μm or less.

As shown in FIG. 11, the hydrogen electrode active portion 67 has an overlapping portion 67x where the downstream end of the first portion 67a and the upstream end of the second portion 67b overlap in the second direction. Thereby, the connectivity between the first portion 67a and the second portion 67b can be improved compared to the case where the end surfaces of the first portion 67a and the second portion 67b are connected.

The ratio of the area of each of the first and second portions 67a and 67b to the total area of the hydrogen electrode active portion 67 in plan view of the main surface on the electrolyte side of the hydrogen electrode active portion 67 is determined to ensure initial performance and prevent performance deterioration. It can be appropriately set depending on which of suppression and suppression is emphasized. Similarly, the ratio of the areas of the first and second portions 67a and 67b to the total area of the hydrogen electrode active portion 67 in plan view of the main surface of the hydrogen electrode current collecting portion side of the hydrogen electrode active portion 67 also affects the initial performance. It can be set as appropriate depending on which of securing and suppressing performance deterioration is emphasized.

As shown in FIG. 11 , the hydrogen electrode collector 68 is arranged on the hydrogen electrode active portion 67 .

The hydrogen electrode current collector 68 includes a third portion 68a and a fourth portion 68b connected downstream of the third portion 68a in the flow direction of H ₂ O and CO ₂ flowing in the second flow path L2. . Each of the third portion 68a and the fourth portion 68b contains Ni. Each of the third portion 68a and the fourth portion 68b may contain an oxygen ion conductive material.

The grain size of Ni contained in the third portion 68a is larger than the grain size of Ni contained in the fourth portion 68b. In this way, since the Ni contained in the third portion 68a, in which the water vapor partial pressure tends to increase during operation of the electrolytic cell 30, is coarse, it is possible to suppress the Ni from becoming coarse, so the performance of the electrolytic cell 30 can be further suppressed from fluctuating (decreasing). In addition, since the Ni contained in the fourth portion 68b, in which the water vapor partial pressure is unlikely to increase during the operation of the electrolytic cell 30, is fine, the conductivity of the hydrogen electrode current collecting portion 68 is increased, and the performance of the electrolytic cell 30 as a whole is improved. can be maintained. Therefore, the deterioration of performance over time can be further suppressed while ensuring the initial performance of the electrolytic cell 10 .

The grain size of Ni contained in the third portion 68a can be, for example, 0.5 μm or more and 5.0 μm or less. The grain size of Ni contained in the third portion 68a is preferably 0.5 μm or more and 3.0 μm or less. The grain size of Ni contained in the fourth portion 68b can be, for example, 0.5 μm or more and 4.0 μm or less. The grain size of Ni contained in the fourth portion 68b is preferably 0.5 μm or more and 2.0 μm or less.

As shown in FIG. 11, the hydrogen electrode collector 68 has an overlapping portion 68x where the downstream end of the third portion 68a and the upstream end of the fourth portion 68b overlap in the second direction. Thereby, the connectivity between the third portion 68a and the fourth portion 68b can be improved as compared with the case where the end surfaces of the third portion 68a and the fourth portion 68b are connected to each other.

The ratio of the area of each of the third and fourth portions 68a and 68b to the total area of the hydrogen electrode current collecting portion 68 in plan view of the main surface of the hydrogen electrode current collecting portion 68 on the side of the active portion of the hydrogen electrode is the initial performance. It can be set as appropriate depending on which of securing and suppressing performance deterioration is emphasized. Similarly, the ratio of the area of each of the third and fourth portions 68a and 68b to the total area of the hydrogen electrode current collecting portion 68 in plan view of the main surface of the hydrogen electrode current collecting portion 68 opposite to the hydrogen electrode active portion is , can be appropriately set depending on which of securing initial performance and suppressing performance deterioration is emphasized.

Further, the plate-type electrolytic cell 30 may be an electrolyte-supported cell in which the electrolyte 7 functions as a support, or a hydrogen-electrode-supported cell in which the hydrogen electrode 6b functions as a support. Alternatively, it may be a metal support type cell in which a metal substrate bonded to the hydrogen electrode 6b or the oxygen electrode 8 functions as a support. If the electrolytic cell 30 is an electrolyte-supported cell, the electrolyte 7 may be thicker than the hydrogen 6b and oxygen 8 electrodes. If the electrolytic cell 30 is a hydrogen electrode supported cell, the hydrogen electrode 6b may be thicker than the electrolyte 7 and the oxygen electrode 8.

(e) In the above embodiment, the communication channel 30 is formed in the communication member 3, but the configuration of the communication channel 30 is not limited to this. For example, the communication channel 30 may be formed inside the support substrate 4 . In this case, the cell stack device 100 does not have to include the communication member 3 . The first flow path 43 and the second flow path 44 are communicated with each other by the communication flow path 30 formed in the support substrate 4 .

(f) In the above embodiment, in the electrolytic cell 10, carbon monoxide and hydrogen are produced by supplying carbon dioxide and water vapor to the hydrogen electrode 6 and performing co-electrolysis, but water vapor is supplied to the hydrogen electrode 6. Hydrogen may be generated by electrolyzing the In this case, steam is supplied to the first channel 43 and hydrogen is recovered from the second channel 44 .

In this embodiment, by making the particle size of Ni contained in the upstream hydrogen electrode active portion larger than the particle size of Ni contained in the downstream hydrogen electrode active portion, the initial performance of the electrolytic cell is ensured and the time-dependent It was verified that it is possible to simultaneously suppress the deterioration of performance.

(Horizontal striped electrolytic cells according to Examples 1 to 7 and Comparative Examples 1 to 4)
As Examples 1 to 7 and Comparative Examples 1 to 4, horizontal striped electrolytic cells shown in FIGS. 5 to 7 were produced. In Examples 1 to 7 and Comparative Examples 1 to 4, the material composition and Ni particle size of the hydrogen electrode active portion and the hydrogen electrode current collector in the first element portion (upstream side) and the second element portion (downstream side) are different only in that they are changed as shown in Table 1. The particle size of Ni was adjusted by changing the particle size of NiO, which is the raw material powder. In this example, the particle size of Ni is the average circle equivalent diameter of the Ni particles described in the above embodiment.

In Examples 1 to 3 and 7, the grain size of Ni contained in the hydrogen electrode active portion of the first element portion was larger than the grain size of Ni contained in the hydrogen electrode active portion of the second element portion, and the grain size of Ni contained in the hydrogen electrode active portion of the second element portion was increased. The grain size of Ni contained in the hydrogen electrode current collecting portion of the element portion was the same as the grain size of Ni contained in the hydrogen electrode current collecting portion of the second element portion. In Examples 4 to 6, the particle size of Ni contained in the hydrogen electrode active portion of the first element portion was made larger than the particle size of Ni contained in the hydrogen electrode active portion of the second element portion, and the first element portion The grain size of Ni contained in the current collecting portion of the hydrogen electrode was made larger than the grain size of Ni contained in the current collecting portion of the hydrogen electrode in the second element portion.

On the other hand, in Comparative Examples 1 to 4, the grain size of Ni contained in the hydrogen electrode active portion of the first element portion was the same as the grain size of Ni contained in the hydrogen electrode active portion of the second element portion, and The grain size of Ni contained in the hydrogen electrode current collecting portion of the element portion was the same as the grain size of Ni contained in the hydrogen electrode current collecting portion of the second element portion.

(Electrolytic test)
For Examples 1 to 7 and Comparative Examples 1 to 4, after reducing NiO on the hydrogen electrode to Ni by supplying air to the oxygen electrode side while supplying hydrogen gas to the hydrogen electrode side, Electrolytic tests for hours were performed.

・Cell temperature: 750°C
・Current density: 0.5 A/cm ² (value for the area of the main surface of the hydrogen electrode)
・Supply hydrogen-containing gas to the hydrogen electrode (H ₂ O: CO ₂ : H ₂ = 28: 62: 10)
・Air is supplied to the oxygen electrode ・Electrolytic rate: 70% (value when the electrolytic rate is defined as 100% when all H ₂ O and CO ₂ are co-electrolyzed to H ₂ and CO)

Then, for Examples 1 to 7 and Comparative Examples 1 to 4, the initial voltage and the voltage after 1000 hours of continuous electrolysis were measured by measuring the voltage under constant current load. Table 1 shows the measurement results. Further, as shown in Table 1, the deterioration rate (voltage drop rate) after continuous electrolysis for 1000 hours was calculated from the following formula (3).
Degradation rate (voltage drop rate) [%] = 100 x (voltage [V] after 1000 hours - initial voltage [V]) / initial voltage [V] (3)

In Table 1, the initial performance was evaluated as "◯" when the initial voltage was less than 1.300 V, and was evaluated as "X" when the initial voltage was 1.300 V or more. In Table 1, the performance after electrolysis for 1000 hours is evaluated as "◎" if the deterioration rate is less than 2%, and is evaluated as "◯" if the deterioration rate is 2% or more and less than 10%. is 10% or more, it was evaluated as "x". Furthermore, in Table 1, as a comprehensive evaluation, if the evaluation of the initial performance is “◯” and the evaluation of the performance after 1000 hours of electrolysis is “◎”, it is evaluated as “◎”, and the evaluation of the initial performance is “◯” and 1000. If the evaluation of the performance after electrolysis for a period of time was "o", it was evaluated as "good", and if the evaluation of either the initial performance or the performance after electrolysis for 1000 hours was "poor", it was evaluated as "poor".

As shown in Table 1, in Examples 1-7, compared with Comparative Examples 1-4, both the initial performance and the performance after 1000 hours of electrolysis could be improved. Such results were obtained because the particle size of Ni contained in the hydrogen electrode active portion of the first element portion located upstream was larger than that of the hydrogen electrode active portion of the second element portion located downstream. This is because by making the particle size larger than the Ni particle size, the aggregation of Ni can be suppressed in the first element portion, and the electrode activity can be enhanced in the second element portion. From this, it was confirmed that by relatively increasing the particle size of Ni contained in the upstream active portion of the hydrogen electrode, deterioration of performance over time can be suppressed while ensuring the initial performance of the electrolytic cell.

Further, as shown in Table 1, in Examples 4 to 6, compared with Examples 1 to 3 and 7, the performance after electrolysis for 1000 hours was able to be further improved. Such results were obtained because the particle size of Ni contained in the hydrogen electrode current collecting portion of the first element portion located upstream was equal to that of the hydrogen electrode current collecting portion of the second element portion located downstream. This is because by making the grain size larger than that of Ni contained in the first element portion, the aggregation of Ni can be suppressed, and the electrode activity can be enhanced in the second element portion. For this reason, by making the particle size of Ni contained in the upstream hydrogen electrode current collector larger than the particle size of Ni contained in the downstream hydrogen electrode current collector, the initial performance of the electrolytic cell is ensured. It has been confirmed that deterioration in performance over time can be further suppressed.

(Platform electrolytic cells according to Examples 8 to 14 and Comparative Examples 5 to 8)
As Examples 8 to 14 and Comparative Examples 5 to 8, flat plate electrolytic cells shown in FIG. 11 were produced. In Examples 8 to 14 and Comparative Examples 5 to 8, the first portion (upstream side) and second portion (downstream side) of the hydrogen electrode active portion and the third portion (upstream side) and fourth portion of the hydrogen electrode current collecting portion The only difference is that the material composition and Ni grain size of each portion (downstream side) were changed as shown in Table 2. The particle size of Ni was adjusted by changing the particle size of NiO, which is the raw material powder.

In Examples 8 to 10 and 14, the grain size of Ni contained in the first portion of the hydrogen electrode active portion was made larger than the grain size of Ni contained in the second portion, and the grain size of Ni contained in the second portion of the hydrogen electrode collector portion was increased. The grain size of Ni contained in is the same as the grain size of Ni contained in the fourth portion. In Examples 11 to 13, the grain size of Ni contained in the first portion of the hydrogen electrode active portion was larger than the grain size of Ni contained in the second portion, and the grain size of Ni contained in the third portion of the hydrogen electrode current collector portion was larger. The grain size of Ni contained in the fourth portion was made larger than the grain size of Ni contained in the fourth portion.

On the other hand, in Comparative Examples 5 to 8, the grain size of Ni contained in the first portion in the hydrogen electrode active portion was the same as the grain size of Ni contained in the second portion, and the grain size of Ni contained in the second portion was the same as that in the third portion in the hydrogen electrode current collector. The grain size of Ni contained in is the same as the grain size of Ni contained in the fourth portion.

(Electrolytic test)
For Examples 8 to 14 and Comparative Examples 5 to 8, after reducing NiO on the hydrogen electrode to Ni by supplying air to the oxygen electrode side while supplying hydrogen gas to the hydrogen electrode side, Electrolytic tests for hours were performed.

・Cell temperature: 750°C
・Current density: 0.5 A/cm ₂ (value for the area of the main surface of the hydrogen electrode)
・Supply hydrogen-containing gas to the hydrogen electrode (H ₂ O: CO ₂ : H ₂ = 28: 62: 10)
・Air is supplied to the oxygen electrode ・Electrolytic rate: 70% (value when the electrolytic rate is defined as 100% when all H ₂ O and CO ₂ are co-electrolyzed to H ₂ and CO)

Then, for Examples 8 to 14 and Comparative Examples 5 to 8, the initial voltage and the voltage after 1000 hours of continuous electrolysis were measured by measuring the voltage under constant current load. Table 2 shows the measurement results. Further, as shown in Table 2, the deterioration rate (voltage drop rate) after continuous electrolysis for 1000 hours was calculated from the above formula (3).

In Table 2, the initial performance was evaluated as "◯" when the initial voltage was less than 1.300 V, and was evaluated as "X" when the initial voltage was 1.300 V or more. In Table 2, the performance after electrolysis for 1000 hours is evaluated as "◎" if the deterioration rate is less than 2%, and is evaluated as "◯" if the deterioration rate is 2% or more and less than 10%. is 10% or more, it was evaluated as "x". Furthermore, in Table 2, as a comprehensive evaluation, if the evaluation of the initial performance is “◯” and the evaluation of the performance after 1000 hours of electrolysis is “◎”, it is evaluated as “◎”, and the evaluation of the initial performance is “◯” and 1000. If the evaluation of the performance after electrolysis for a period of time was "o", it was evaluated as "good", and if the evaluation of either the initial performance or the performance after electrolysis for 1000 hours was "poor", it was evaluated as "poor".

As shown in Table 2, in Examples 8-14, compared to Comparative Examples 5-8, both the initial performance and the performance after 1000 hours of electrolysis could be improved. Such results were obtained because the grain size of Ni contained in the first portion located upstream in the active portion of the hydrogen electrode was made larger than the grain size of Ni contained in the second portion located downstream. This is because the aggregation of Ni can be suppressed in the first portion and the electrode activity can be enhanced in the second portion. From this, it was confirmed that by relatively increasing the grain size of Ni on the upstream side of the active portion of the hydrogen electrode, the deterioration of the performance over time can be suppressed while ensuring the initial performance of the electrolytic cell.

Further, as shown in Table 2, in Examples 11 to 13, compared with Examples 8 to 10 and 14, the performance after electrolysis for 1000 hours could be further improved. Such results were obtained because the particle size of Ni contained in the third portion located on the upstream side in the hydrogen electrode current collecting portion was larger than the particle size of Ni contained in the fourth portion located on the downstream side. This is because the aggregation of Ni can be suppressed in the third portion and the electrode activity can be enhanced in the fourth portion. From this, it was confirmed that by relatively increasing the grain size of Ni on the upstream side of the current collecting portion of the hydrogen electrode, the deterioration of the performance over time can be further suppressed while ensuring the initial performance of the electrolytic cell.

As described above, in Examples 8 to 14, the effect of the flat plate type electrolytic cell was confirmed, but the same effect as in Examples 8 to 14 was also obtained in the vertical striped type electrolytic cell (see FIGS. 9 and 10) having a similar basic configuration. can be obtained.

2: Manifold 21: Supply chamber 22: Recovery chamber 4: Support substrate 5: Element part 5a: First element part 5b: Second element part 6: Hydrogen electrodes 61, 65, 67: Hydrogen electrode collectors 62, 66, 68: Hydrogen electrode active part 7: Electrolyte 8: Oxygen electrode 81: Oxygen electrode active part 82: Oxygen electrode current collecting parts 10, 20, 30: Electrolytic cell 43: First channel 44: Second channel 100: Cell stack Device

Claims (11)

a support substrate in which a first channel through which water vapor and carbon dioxide flow is formed;
a first element unit supported by the support substrate;
a second element unit supported by the support substrate and arranged downstream of the first element unit in the flow direction of water vapor and carbon dioxide flowing in the first channel;
with
Each of the first element portion and the second element portion includes an oxygen electrode, a hydrogen electrode active portion arranged between the oxygen electrode and the supporting substrate, and an oxygen electrode active portion arranged between the oxygen electrode and the hydrogen electrode active portion. and an electrolyte that is
the hydrogen electrode active portion of each of the first element portion and the second element portion contains an oxygen ion conductive material and nickel;
The particle size of nickel contained in the hydrogen electrode active portion of the first element portion is larger than the particle size of nickel contained in the hydrogen electrode active portion of the second element portion,
electrolytic cell. a support substrate in which a first channel through which water vapor flows is formed;
a first element unit supported by the support substrate;
a second element unit supported by the support substrate and arranged downstream of the first element unit in a direction in which water vapor flowing in the first flow path flows;
with
Each of the first element portion and the second element portion includes an oxygen electrode, a hydrogen electrode active portion arranged between the oxygen electrode and the supporting substrate, and an oxygen electrode active portion arranged between the oxygen electrode and the hydrogen electrode active portion. and an electrolyte that is
the hydrogen electrode active portion of each of the first element portion and the second element portion contains an oxygen ion conductive material and nickel;
The particle size of nickel contained in the hydrogen electrode active portion of the first element portion is larger than the particle size of nickel contained in the hydrogen electrode active portion of the second element portion,
electrolytic cell. each of the first element portion and the second element portion has a hydrogen electrode current collecting portion disposed between the support substrate and the hydrogen electrode active portion;
the hydrogen electrode current collecting portion of each of the first element portion and the second element portion contains nickel;
The particle size of nickel contained in the hydrogen electrode current collecting portion of the first element portion is larger than the particle size of nickel contained in the hydrogen electrode current collecting portion of the second element portion,
3. Electrolysis cell according to claim 1 or 2. a support substrate;
a first channel formed in the support substrate through which water vapor and carbon dioxide flow;
an element portion supported by the support substrate;
with
The element part comprises an oxygen electrode active part, a hydrogen electrode active part arranged between the oxygen electrode active part and the support substrate, and an electrolyte arranged between the oxygen electrode active part and the hydrogen electrode active part. and
The hydrogen electrode active portion includes a first portion and a second portion connected to a downstream side of the first portion in a flow direction of water vapor and carbon dioxide flowing in the first flow path,
each of the first portion and the second portion contains an oxygen ion conductive material and nickel;
The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion,
electrolytic cell. a support substrate;
a first channel formed in the support substrate through which water vapor flows;
an element portion supported by the support substrate;
with
The element part comprises an oxygen electrode active part, a hydrogen electrode active part arranged between the oxygen electrode active part and the support substrate, and an electrolyte arranged between the oxygen electrode active part and the hydrogen electrode active part. and
The hydrogen electrode active portion includes a first portion and a second portion connected to a downstream side of the first portion in a flow direction of water vapor flowing in the first flow path,
each of the first portion and the second portion contains an oxygen ion conductive material and nickel;
The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion,
electrolytic cell. an electrolyte;
an oxygen electrode active portion disposed on the first main surface side of the electrolyte;
a hydrogen electrode active portion disposed on the second main surface side of the electrolyte;
with
The hydrogen electrode active portion includes a first portion and a second portion connected downstream of the first portion in the flow direction of water vapor and carbon dioxide flowing in the flow path on the second main surface side of the electrolyte. including
each of the first portion and the second portion contains an oxygen ion conductive material and nickel;
The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion,
electrolytic cell. an electrolyte;
an oxygen electrode active portion disposed on the first main surface side of the electrolyte;
a hydrogen electrode active portion disposed on the second main surface side of the electrolyte;
with
The hydrogen electrode active portion includes a first portion and a second portion connected downstream of the first portion in a flow direction of water vapor flowing in the flow path on the second main surface side of the electrolyte,
each of the first portion and the second portion contains an oxygen ion conductive material and nickel;
The grain size of nickel contained in the first portion is larger than the grain size of nickel contained in the second portion,
electrolytic cell. The hydrogen electrode active portion has a first overlap portion in which the first portion and the second portion overlap,
Electrolytic cell according to any one of claims 4 to 7. A hydrogen electrode current collector disposed on the hydrogen electrode active portion,
the hydrogen electrode current collector includes a third portion and a fourth portion connected downstream of the third portion in the direction of flow,
each of the third portion and the fourth portion contains nickel;
The particle size of nickel contained in the third part is larger than the particle size of nickel contained in the fourth part,
Electrolytic cell according to any one of claims 4 to 7. The hydrogen electrode current collecting portion has a second overlapping portion in which the third portion and the fourth portion overlap,
10. Electrolysis cell according to claim 9. a manifold having a supply chamber and a collection chamber;
an electrolysis cell according to any one of claims 1, 2, 4, and 5 supported by said manifold;
with
The support substrate has a second flow path communicating with the first flow path at the tip,
the first flow path communicates with the supply chamber;
the second channel communicates with the recovery chamber;
Cell stack device.

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