Electrolytic cell and electrolytic device

Abstract

To provide an electrolytic cell and an electrolytic device which are capable of reducing the temperature at the end portions of the electrolytic cell.SOLUTION: An electrolytic cell includes laminated three or more elements, which include an electrolyte isolating two electrodes. A plurality of the elements are electrically connected in series. When the number of the elements is divided equally into three parts, and the elements are divided into a central portion and two end portions on both sides of the central portion in the lamination direction, an average of the area of the elements in at least one of the two end portions is greater than an average of the area of the elements in the central portion.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electrolytic cell and an electrolytic device in which element parts containing an electrolyte separating two electrodes are stacked. [Background technology]

[0002] An electrolytic cell (cell stack) in which element parts (single cells) containing an electrolyte that separates two electrodes are stacked has a gas passageway along the stacking direction of the element parts, and gas is supplied to the passageway from a tube connected to the end of the passageway in the stacking direction (Patent Document 1). In the electrolytic cell, gas that has passed through the passageway from the tube and reached the element part is electrolyzed in the element part to which a voltage is applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-73494 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for a technique for reducing the temperature at the ends of the electrolytic cell in order to reduce the thermal degradation of the seal material that prevents gas leakage between the ends of the passages and the tubes.

[0005] The present invention has been made to meet this demand, and has an object to provide an electrolytic cell and an electrolytic apparatus capable of reducing the temperature at the ends of the electrolytic cell. [Means for solving the problem]

[0006] A first aspect for achieving this object is an electrolytic cell in which three or more element parts each containing an electrolyte separating two electrodes are stacked, and the multiple element parts are electrically connected in series, and when the number of element parts is divided into thirds and the element parts are partitioned into a central part and two end parts located on either side of the central part in the stacking direction, the average area of ​​the element parts at least at one of the two end parts is larger than the average area of ​​the element parts in the central part.

[0007] In a second embodiment, in the first embodiment, the average area of ​​the element portion at the two ends is greater than the average area of ​​the element portion at the center.

[0008] A third aspect is the first or second aspect, wherein the average area of ​​the element portion in the central portion is 40% or more of the average area of ​​the element portion in the end portion.

[0009] In a fourth aspect, in any one of the first to third aspects, the average area of ​​the element portion in the central portion is 97% or less of the average area of ​​the element portion in the end portion.

[0010] A fifth aspect comprises an electrolytic cell according to any one of the first to fourth aspects, a power source that passes a current through a circuit connected to the electrodes, and an adjustment unit that adjusts the output of the power source, wherein the adjustment unit sets an average voltage of the central portion to a voltage higher than the thermal neutral point where heat absorption and heat generation are balanced in the electrolytic cell set to a predetermined temperature, and sets an average voltage of at least one end portion to a voltage lower than the thermal neutral point. Effect of the Invention

[0011] According to the present invention, when the number of element units included in the electrolytic cell is divided into three equal parts, a central unit, and two end units located on both sides of the central unit in the stacking direction, the average area of ​​the element units at the end units is larger than the average area of ​​the element units at the central unit. Since the element units are connected in series, the same current flows through the end units and the central unit, and the current density of the element units at the end units can be made smaller than the current density of the element units at the central unit. Since the Joule heat at the end units of the electrolytic cell can be made smaller than the Joule heat at the central unit, the temperature at the end units can be reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of an electrolysis cell in one embodiment. [Diagram 2] FIG. 2 is an exploded view of the electrolysis cell. [Diagram 3] 1 is a graph showing the current-voltage characteristics and heat generation characteristics of an electrolysis cell. [Figure 4] FIG. 2(a) is a schematic diagram of an electrolytic cell, and FIG. 2(b) is a schematic diagram of an electrolytic cell in a modified example. [Diagram 5] FIG. 1 is a block diagram of an electrolysis device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a perspective view of an electrolytic cell 10 in one embodiment. The electrolytic cell 10 is a flat-plate solid oxide electrolytic cell.

[0014] The electrolysis cell 10 includes a rectangular reaction unit 11 formed by stacking a plurality (three or more) of reaction units 11 in the thickness direction, and rectangular end plates 12, 13 that sandwich the reaction unit 11 in the thickness direction. Bolts 14 are disposed at the four corners of the periphery of the electrolysis cell 10, penetrating the reaction unit 11 and the end plates 12, 13 in the thickness direction. The reaction unit 11 and the end plates 12, 13 are fastened together by the bolts 14.

[0015] The four spaces that penetrate the periphery of the electrolytic cell 10 in the thickness direction function as a passage 15 through which gas enters from outside the electrolytic cell 10 to a fuel chamber 29 (described later) of the reaction unit 11, a passage 16 through which gas exits from the fuel chamber 29 to the outside of the electrolytic cell 10, a passage 17 through which gas enters from outside the electrolytic cell 10 to an air chamber 31 (described later) of the reaction unit 11, and a passage 18 through which gas exits from the air chamber 31 to the outside of the electrolytic cell 10.

[0016] Fig. 2 is an exploded view of the electrolysis cell 10 taken along line II-II in Fig. 1, passing through the passages 15 and 16. Fig. 2 is a cross-sectional view taken along line II-II, in which components constituting one reaction unit 11 are separated in the thickness direction. In Fig. 2, the thickness of each part is exaggerated. The reaction unit 11 includes, in order in the thickness direction, an interconnector 19, an anode frame 20, a cell 21 with a separator, and an cathode frame 22.

[0017] The separator-equipped cell 21 includes an element portion 23 and a separator 27 disposed in an electrolyte 24 of the element portion 23. The interconnector 19, the fuel electrode frame 20, the separator 27 and the air electrode frame 22 have holes (passages 15-18) penetrating therethrough.

[0018] The element section 23 includes an electrolyte 24, and an anode 25 and an cathode 26 isolated by the electrolyte 24. The material of the electrolyte 24 is a solid oxide, and examples thereof include stabilized zirconia, a ceria-based solid solution, and a solid solution of alumina and one or more selected from stabilized zirconia and a ceria-based solid solution. Examples of stabilizers for stabilized zirconia include CaO, MgO, Y2O3, Sc2O3, and Yb2O3. Examples of elements dissolved in ceria in the ceria-based solid solution include Gd, Sm, and Y.

[0019] Examples of the material of the fuel electrode 25 include a material containing a catalyst containing Ni and zirconia with Y as a solid solution, and a material containing a catalyst containing Ni and ceria with Gd as a solid solution. Examples of the catalyst include Ni, Ni-based alloys, and cermets that are composites (sintered bodies) of NiO and oxides (solid electrolytes).

[0020] The material of the cathode 26 is a perovskite oxide called La1-X Sr X MnO 3-δ ,La 1-X Sr X Chief of Staff 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ Examples are given below.

[0021] The separator 27 is a rectangular frame-shaped member having an opening larger than the air electrode 26. The material of the separator 27 is, for example, stainless steel. The separator 27 is airtightly joined to the electrolyte 24 by brazing material or the like, avoiding the air electrode 26.

[0022] The interconnectors 19 are conductive rectangular plate-like members arranged on both sides in the thickness direction of the element section 23. The interconnectors 19 electrically connect the reaction units 11 adjacent to each other in the thickness direction. An example of the material of the interconnectors 19 is stainless steel.

[0023] The fuel electrode frame 20 is a rectangular frame-shaped member disposed between the interconnector 19 and the separator 27. An example of the material for the fuel electrode frame 20 is stainless steel. The fuel electrode frame 20 surrounds the element portion 23 and a current collector 28 provided in the center of the interconnector 19.

[0024] The current collector 28 electrically connects the fuel electrode 25 and the interconnector 19. An example of the material of the current collector 28 is a gas permeable porous body made of a metal such as Ni. A fuel chamber 29 surrounded by the interconnector 19 and the separator-equipped cell 21 is provided inside the fuel electrode frame 20.

[0025] The air electrode frame 22 is a rectangular frame-shaped member disposed between the interconnector 19 and the separator 27. The material of the air electrode frame 22 is, for example, an insulator such as mica. The air electrode frame 22 surrounds a current collector 30 provided in the center of the interconnector 19. The current collector 30 electrically connects the air electrode 26 and the interconnector 19. In this embodiment, the current collector 30 is formed integrally with the interconnector 19, but this is not limited to this. It is of course possible for the current collector 30 to be a separate member from the interconnector 19.

[0026] An air chamber 31 surrounded by the interconnector 19 and the separator-equipped cell 21 is provided inside the air electrode frame 22. The separator 27 separates the fuel chamber 29 from the air chamber 31, preventing mixing of the fuel gas in the fuel chamber 29 with the oxidizer gas (oxygen, air, etc.) in the air chamber 31. Examples of the fuel gas include water vapor, carbon dioxide, and a mixture thereof.

[0027] Returning to FIG. 1, the electrolysis cell 10 includes a terminal plate 32 arranged between the end plate 12 and the reaction unit 11, and a terminal plate 33 arranged between the end plate 13 and the reaction unit 11. The reaction units 11 are electrically connected in series between the terminal plates 32, 33. The terminal plate 32 is connected to the air electrode 26, and the terminal plate 33 is connected to the fuel electrode 25. The protruding portions of the terminal plates 32, 33 function as terminals. The terminal plate 33 has holes (passages 15-18) penetrating it.

[0028] Insulating plates 34, 35 are respectively disposed between the end plate 12 and the terminal plate 32, and between the end plate 13 and the terminal plate 33. A hole (passage 15-18) penetrates the insulating plate 35, and the insulating plate 34 closes the end of the passage 15-18.

[0029] Joints 36 and 37 are arranged on the end plate 13. Joint 36 is a tube connected to passage 15, and joint 37 is a tube connected to passage 18. Joints (not shown) are also connected to passages 16 and 17. Pipes through which gas flows are connected to all of the joints. The fuel gas that enters passage 15 from joint 36 passes through a fuel chamber 29 (see FIG. 2) provided in each reaction unit 11, passes through passage 16, and leaves the electrolysis cell 10 from a joint (not shown). The oxidant gas that enters passage 17 from a joint (not shown) passes through an air chamber 31 provided in each reaction unit 11, passes through passage 18, and leaves the electrolysis cell 10 from joint 37.

[0030] When the positive electrode of a power supply (not shown) is connected to the terminal plate 32 and the negative electrode of the power supply is connected to the terminal plate 33, electrons begin to flow toward the fuel electrode 25 of the element unit 23. The fuel gas that has entered the fuel chamber 29 is reduced at the fuel electrode 25. Since electrons are lost at the air electrode 26 of the element unit 23, oxide ions that have moved to the air electrode 26 via the electrolyte 24 are oxidized at the air electrode 26. As a result, energy carriers such as hydrogen and hydrocarbons are synthesized in the electrolysis cell 10.

[0031] 3 is a graph showing the current-voltage characteristics and heat generation characteristics of the electrolysis cell 10. Since the electrolysis of water vapor, carbon dioxide, and the like contained in the fuel gas is an endothermic reaction, the temperature of the element unit 23 (the temperature of the exhaust gas flowing through the passage 18) decreases with an increase in current density compared to the temperature at the open circuit voltage of the element unit 23 when the current starts to flow (the average voltage of the element unit 23 when the current density is 0). When the current density increases further, the temperature of the element unit 23 begins to rise due to Joule heat, and reaches a thermal neutral point N where the heat absorption and heat generation are balanced.

[0032] At the thermal neutral point N, the electrolytic cell 10 neither generates nor absorbs heat, but when the current density of the element unit 23 becomes lower than the current density of the element unit 23 at the thermal neutral point N, heat absorption becomes predominant in the electrolytic cell 10, and the temperature decreases. When the current density of the element unit 23 becomes higher than the current density of the element unit 23 at the thermal neutral point N, heat generation becomes predominant in the electrolytic cell 10, and the temperature increases.

[0033] Returning to FIG. 1, a sealant (not shown) is disposed between all joints, including the joints 36 and 37, and the pipe through which the gas flows, to prevent gas leakage. The electrolytic cell 10 is used in a state in which the element unit 23 (see FIG. 2) is at an operating temperature (for example, about 700° C.), and in order to reduce deterioration of the sealant due to heat, it is desirable that the temperature in the vicinity of the joints 36 and 37 is low. In addition, in order to reduce deterioration due to heat of the connection between the electric circuit that applies voltage to the element unit 23 and the terminal plates 32 and 33, it is desirable that the temperature of the terminal plates 32 and 33 is also low. Since the joints 36 and 37 and the terminal plates 32 and 33 are disposed at the ends of the element unit 23 of the electrolytic cell 10 in the stacking direction, the temperatures of the joints 36 and 37 and the terminal plates 32 and 33 can be reduced by reducing the temperature of the ends of the electrolytic cell 10.

[0034] FIG. 4(a) is a schematic diagram of the electrolytic cell 10 in which the element portion 23 built into the reaction unit 11 (see FIG. 2) of the electrolytic cell 10 is represented by lines (the same applies to FIG. 4(b) and FIG. 5). The length of the lines in the diagram indicates the size of the area of ​​the element portion 23. The area of ​​the element portion 23 refers to the area of ​​the portion where the electrolyte 24 (see FIG. 2), the fuel electrode 25, and the air electrode 26 overlap. The area of ​​the element portion 23 can be changed, for example, by changing the area of ​​the fuel electrode 25 or the air electrode 26. The positions of the lines in the diagram indicate the positions of the stacked element portions 23. In FIG. 4(a), the electrolytic cell 10 in which eight element portions 23 are stacked is illustrated as a set of eight lines.

[0035] The central portion 40 is a portion located at the center in the stacking direction when the number of element portions 23 included in the electrolytic cell 10 is divided into thirds and the element portions 23 are divided into three portions. The end portions 41 and 42 are portions located on both sides of the central portion 40 in the stacking direction when the number of element portions 23 included in the electrolytic cell 10 is divided into thirds and the element portions 23 are divided into three portions. In this embodiment, the end portion 41 is located near the end plate 12 (see FIG. 1 ), and the end portion 42 is located near the end plate 13.

[0036] The method of dividing the number of element portions 23 into thirds and dividing the central portion 40 and the end portions 41, 42 differs depending on whether the number of element portions 23 is a multiple of 3 or not. When the number of element portions 23 is a multiple of 3, the number of element portions 23 included in the central portion 40, the number of element portions 23 included in the end portions 41, and the number of element portions 23 included in the end portions 42 are equal.

[0037] When the number of element portions 23 is not a multiple of three, the number of element portions 23 is divided by three to find the quotient and remainder, and then the remainder is allocated to the central portion 40 or the ends 41 and 42 so that the number of element portions 23 included in the end portion 41 is equal to the number of element portions 23 included in the end portion 42. The reason why the number of element portions 23 included in the end portion 41 is equal to the number of element portions 23 included in the end portion 42 is to fairly evaluate the areas of the element portions 23 included in the ends 41 and 42.

[0038] For example, when the remainder when the number of element portions 23 is divided by 3 is 1, the number of element portions 23 included in end portion 41 and the number of element portions 23 included in end portion 42 are each set as the quotient, and the number of element portions 23 included in central portion 40 is set as the quotient plus the remainder, 1. When the remainder when the number of element portions 23 is divided by 3 is 2, the number of element portions 23 included in central portion 40 is set as the quotient, and the number of element portions 23 included in end portion 41 and the number of element portions 23 included in end portion 42 are each set as the quotient plus 1.

[0039] 4(a) has eight element portions 23, so when eight is divided by three the quotient is two with a remainder of two. Therefore, the number of element portions 23 included in the central portion 40 is two, and the numbers of element portions 23 included in the end portions 41 and 42 are each three. The first three element portions 23 from the ends in the stacking direction are included in the end portions 41 and 42, and the two element portions 23 on the inside of the end portions 41 and 42 in the stacking direction are included in the central portion 40.

[0040] In the electrolysis cell 10, the average area of ​​the element portions 23 at at least one of the end portions 41, 42 is larger than the average area of ​​the element portions 23 in the central portion 40. The area of ​​the element portions 23 at the end portion 41 of the electrolysis cell 10 gradually decreases toward the central portion 40, and the area of ​​the element portions 23 at the end portion 42 also gradually decreases toward the central portion 40. The areas of the element portions 23 in the central portion 40 are equal to each other. In this embodiment, the average area of ​​the element portions 23 at both the end portions 41, 42 is larger than the average area of ​​the element portions 23 in the central portion 40.

[0041] It is preferable that the average area of ​​the element portion 23 in the central portion 40 is 40% or more of the average area of ​​the element portion 23 in at least one of the end portions 41, 42, because this can prevent the current density of the element portion 23 in the central portion 40 from becoming excessive and reduce deterioration of the element portion 23 in the central portion 40. Furthermore, it is preferable that the average area of ​​the element portion 23 in the central portion 40 is 97% or less of the average area of ​​the element portion 23 in at least one of the end portions 41, 42, because this can differentiate between heat generation of the element portion 23 in the central portion 40 and heat generation of the element portion 23 in at least one of the end portions 41, 42.

[0042] Fig. 4(b) is a schematic diagram of an electrolytic cell 43 in a modified example. In Fig. 4(b), the electrolytic cell 43 in which six element portions 23 are stacked is illustrated as a set of six line segments. Since the number of element portions 23 is a multiple of three, the number of element portions 23 included in the central portion 40, the end portion 41, and the end portion 42 is two.

[0043] In the electrolytic cell 43, the average area of ​​the element portions 23 at at least one of the ends 41, 42 is larger than the average area of ​​the element portions 23 at the central portion 40. The area of ​​the element portions 23 at the end 41 of the electrolytic cell 43 is larger closer to the central portion 40, and the area of ​​the element portions 23 at the end 42 is also larger closer to the central portion 40. The areas of the element portions 23 at the central portion 40 are equal to each other. In this embodiment, the average area of ​​the element portions 23 at both the end portions 41, 42 is larger than the average area of ​​the element portions 23 at the central portion 40.

[0044] Returning to FIG. 4(a), the following description will be given. Since the element parts 23 of the electrolysis cell 10 are electrically connected in series, the same current flows through the element parts 23. Since the average area of ​​the element parts 23 at the ends 41, 42 is larger than the average area of ​​the element parts 23 at the center 40, the current density of the element parts 23 at the ends 41, 42 is lower than the current density of the element parts 23 at the center 40. As a result, the temperature of the ends 41, 42 is lower than the temperature of the center 40 due to a balance between heat absorption and heat generation, so that the temperature of the joints 36, 37 (see FIG. 1) arranged near the end 42 can be lowered. Furthermore, the temperature of the terminal plates 32, 33 arranged near the end 41, 42 can be lowered. Therefore, the deterioration due to heat of the seal materials provided at the joints 36, 37 and the connection parts provided at the terminal plates 32, 33 (neither of which is shown) can be reduced.

[0045] 5 is a block diagram of an electrolysis apparatus 50. The electrolysis apparatus 50 includes an electrolysis cell 10, a power supply 51 that supplies current to the element section 23 of the electrolysis cell 10, and an adjustment section 53 that adjusts the output of the power supply 51. An ammeter 52 that measures the current flowing through the circuit is disposed in a circuit connected to the power supply 51. The power supply 51 outputs a unipolar pulsating current, pulse, or direct current to the circuit.

[0046] The electrolysis device 50 is equipped with a thermometer 54 that detects the temperature of the electrolytic cell 10. The thermometer 54 is disposed at the joint 37 (see FIG. 1 ) of the electrolytic cell 10, and detects the temperature of the exhaust gas flowing through the passage 18 as a representative value of the temperature of the electrolytic cell 10. However, this is not limited to this, and it is of course possible to dispose the thermometer 54 at a location other than the joint 37 and detect a representative value of the temperature of the electrolytic cell 10.

[0047] The electrolysis device 50 includes a heater (not shown) that heats the electrolytic cell 10. There are no limitations on the heater as long as it can heat the electrolytic cell 10. Examples of the heater include a heater that heats the fuel gas or oxidant gas supplied to the electrolytic cell 10 to heat the electrolytic cell 10, a heater that heats the electrolytic cell 10 by heating a heat medium (a fluid other than the fuel gas or oxidant gas) supplied to the electrolytic cell 10 to heat the electrolytic cell 10, and a heater that is disposed in a furnace that houses the electrolytic cell 10 to heat the electrolytic cell 10 from around the electrolytic cell 10.

[0048] The adjustment unit 53 includes a CPU, a ROM, a RAM, and a backup RAM (none of which are shown). The adjustment unit 53 obtains the current detected by the ammeter 52, and adjusts the output of the power source 51 so that the average temperature of the element unit 23 (the temperature of the electrolytic cell 10) becomes a temperature equivalent to the thermal neutral point N (see FIG. 3). Since the area of ​​the element unit 23 is known, the current to be passed through the electrolytic cell 10 in order to make the average temperature of the element unit 23 a temperature equivalent to the thermal neutral point N is determined in advance. The adjustment unit 53 adjusts the output of the power source 51 so that the current detected by the ammeter 52 becomes equal to the previously determined current.

[0049] Instead of the adjustment unit 53 adjusting the output of the power source 51 so that the current detected by the ammeter 52 is equal to the pre-determined current, the adjustment unit 53 may obtain the temperature detected by the thermometer 54 and adjust the output of the power source 51 so that the average temperature of the element unit 23 (the temperature of the electrolytic cell 10) becomes a temperature equivalent to the thermal neutral point N. The adjustment unit 53 may use both of these.

[0050] In the electrolytic cell 10, the average area of ​​the element portions 23 included in the end portions 41, 42 is larger than the average area of ​​the element portions 23 included in the central portion 40. Therefore, when a current flows through the electrolytic cell 10 such that the average temperature of the element portions 23 becomes a temperature corresponding to the thermal neutral point N, the average voltage of the element portions 23 included in the central portion 40 becomes higher than the voltage corresponding to the thermal neutral point N. In addition, the average voltage of the element portions 23 included in the end portions 41, 42 becomes lower than the voltage corresponding to the thermal neutral point N.

[0051] As a result, the temperature of the element portion 23 included in the central portion 40 becomes higher than the temperature corresponding to the thermal neutral point N, and the temperature of the element portion 23 included in the ends 41, 42 becomes lower than the temperature corresponding to the thermal neutral point N. This makes it possible to make the activation overvoltage of the central portion 40 lower than the activation overvoltage of the ends 41, 42. As a result, the central portion 40 can synthesize energy carriers more efficiently than the ends 41, 42 for the energy input from the power source 51 to the electrolysis cell 10. Furthermore, since the temperature of the element portion 23 included in the ends 41, 42 is lower than the temperature corresponding to the thermal neutral point N, deterioration due to heat of the sealant and the connection portion (neither of which is shown) provided near the ends 41, 42 can be reduced.

[0052] Since the electrolysis device 50 performs electrolysis near the current density of the element unit 23 corresponding to the thermal neutral point N, the temperature of the element unit 23 can be maintained even with little new energy input. Therefore, the electrolysis efficiency can be ensured. Furthermore, the durability of the element unit 23 can be improved because the temperature change of the element unit 23 can be reduced.

[0053] The present invention has been described above based on an embodiment, but the present invention is in no way limited to the above embodiment, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention without departing from the spirit of the present invention.

[0054] In the embodiments, the electrolytic cell 10 in which eight element units 23 are stacked and the electrolytic cell 43 in which six element units 23 are stacked are described, but the present invention is not necessarily limited to this. The number of stacked element units 23 is appropriately set according to the required characteristics of the electrolytic cell. However, since the number of element units 23 is divided into three equal parts to partition the element units 23 into three, the number of stacked element units 23 is three or more.

[0055] The size relationship of the areas of the element portions 23 at the end portions 41, 42 and at the central portion 40 described in the embodiment is merely an example. It is sufficient that the average area of ​​the element portions 23 included in the end portion 41 is set to be larger than the average area of ​​the element portions 23 included in the central portion 40, or that the average area of ​​the element portions 23 included in the end portion 42 is set to be larger than the average area of ​​the element portions 23 included in the central portion 40.

[0056] Although not explained in the embodiment, when the average area of ​​the element portions 23 at one of the ends 41, 42 is larger than the average area of ​​the element portions 23 at the central portion 40, the average area of ​​the element portions 23 at the other of the ends 41, 42 may be the same as the average area of ​​the element portions 23 at the central portion 40 or may be smaller than the average area of ​​the element portions 23 at the central portion 40.

[0057] In the embodiment, the electrolytic cells 10, 43 have a flat cell design. The flat cell design of the electrolytic cells 10, 43 may be an electrode-supported type or an electrolyte-supported type. The electrolytic cells 10, 43 may be a metal-supported type (metal-supported flat cell type) in which the electrodes and electrolyte are supported by a porous body of a metal such as an Fe-Cr-based metal.

[0058] In the embodiment, the shape of the element portion 23 is described as a rectangle, but this is not necessarily limited to this. The shape of the element portion 23 may be a circle or an ellipse, or may be a polygon other than a rectangle, such as a triangle or a pentagon.

[0059] In the embodiment, the case where the electrolyte 24 having oxide ion conductivity is used has been described, but the present invention is not necessarily limited to this. It is of course possible to use the electrolyte 24 having proton conductivity under the operating conditions of the element unit 23. Examples of substances that exhibit proton conductivity under the operating conditions of the element unit 23 include perovskite-type oxides such as SrZrO3 and BaZrO3 in which the B site is substituted with trivalent metal ions such as Y and In, pyrochlore-type oxides, and phosphates.

[0060] In the embodiment, the passages 15-18 through which the gas passes are built into the electrolytic cell 10, but this is not necessarily limited to this. It is of course possible to provide a manifold as the passages 15-18 outside the electrolytic cell by joining it to the electrolytic cell. Examples of materials for the manifold include ceramics that have high high-temperature strength.

[0061] In the embodiment, the terminal plates 32, 33 including terminals to which the power source 51 is connected are disposed in the electrolytic cell 10, but this is not necessarily limited to the above. It is of course possible to omit the terminal plates 32, 33 and the insulating plates 34, 35, electrically connect the reaction units 11 to the end plates 12, 13, and use the end plates 12, 13 as terminals of the electrolytic cell 10. [Explanation of symbols]

[0062] 10,43 Electrolysis cell 23 Element section 24 Electrolytes 25 Fuel electrode (electrode) 26 Air electrode 40 Central part 41,42 End 50 Electrolyzer 51 Power supply 53 Adjustment part

Claims

1. An electrolysis cell in which three or more element parts each including an electrolyte isolating two electrodes are stacked, and a plurality of the element parts are electrically connected in series, An electrolytic cell in which, when the number of element portions is divided into thirds and the element portions are partitioned into a central portion and two end portions located on either side of the central portion in the stacking direction, the average area of ​​the element portions in at least one of the two end portions is larger than the average area of ​​the element portions in the central portion.

2. The electrolysis cell according to claim 1 , wherein an average area of ​​the element portions at the two ends is greater than an average area of ​​the element portions at the central portion.

3. 3. The electrolysis cell according to claim 1, wherein an average area of ​​the element portions in the central portion is 40% or more of an average area of ​​the element portions in the end portions.

4. 3. The electrolytic cell according to claim 1, wherein an average area of ​​the element portions in the central portion is 97% or less of an average area of ​​the element portions in the end portions.

5. The electrolytic cell according to claim 1 or 2; A power source that applies a current to a circuit connected to the electrodes; An adjustment unit that adjusts the output of the power source, The adjustment unit adjusts the average voltage of the central portion to a voltage higher than a thermal neutral point where heat absorption and heat generation are balanced in the electrolytic cell, which is set at a predetermined temperature, and adjusts the average voltage of at least one of the ends to a voltage lower than the thermal neutral point.

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