Electrochemical reaction single cell and electrochemical reaction cell stack

Abstract

To achieve an improvement in durability of an electrochemical reaction single cell.SOLUTION: An electrochemical reaction single cell includes an electrolyte layer, an air electrode and a fuel electrode containing a reforming catalyst. The electrochemical reaction single cell includes: a reaction part where the electrolyte layer, the air electrode and the fuel electrode overlap in a first direction; and a non-reaction part that is not included in the reaction part and that includes a first part that is a part of the fuel electrode and located on one side of the reaction part in a second direction crossing the first direction, and a second part that is a part of the fuel electrode and located on the other side of the reaction part in the second direction. In a cross section parallel to the first direction, a first length from a first position that is a boundary with the reaction part in the first part and in contact with the electrolyte layer to a second position that is furthest from the first position in the first part is shorter than a second length which from a third position that is a boundary with the reaction part in the second part and in contact with the electrolyte layer to a fourth position that is furthest from the third position in the second part.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The technology disclosed herein relates to electrochemical reaction units and electrochemical reaction cell stacks. [Background technology]

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs") are known as one type of fuel cell that generates electricity by utilizing an electrochemical reaction between hydrogen and oxygen. A single fuel cell (hereinafter simply referred to as a "single cell"), which is a constituent unit of an SOFC, comprises an electrolyte layer, an air electrode arranged on one side of the electrolyte layer in a predetermined direction (hereinafter referred to as the "first direction"), and a fuel electrode arranged on the other side of the electrolyte layer in the first direction.

[0003] Conventionally, a fuel cell unit has been disclosed that includes an electrolyte layer, an air electrode, and an anode with a reforming catalyst, and has a power generation section in which the electrolyte layer, the air electrode, and the anode overlap in a first direction, and a non-power generation section that is not included in the power generation section. The reforming catalyst functions as a catalyst for producing hydrogen-rich fuel gas using gas such as hydrocarbon (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-156004 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, the reforming catalyst contained in the anode catalyzes the hydrogen generation reaction (e.g., CH4+H2O→CO+3H2) using gas such as hydrocarbon as the raw material. On the other hand, the reforming catalyst also catalyzes the carbon deposition reaction (e.g., CH4→C+2H2) under certain conditions, and the carbon generated by this reaction can cause the anode to expand, resulting in cracks. The carbon deposition reaction is more likely to proceed the lower the amount of water vapor contained in the gas supplied to the anode, and also the lower the temperature. In general, the non-power generation part of the anode has a lower temperature than the power generation part, so it is particularly prone to cracks depending on the amount of water vapor in the gas contained in the anode. The occurrence of cracks in the non-power generation part of the anode could reduce the durability of the unit cell.

[0006] Such issues are also common to single electrolysis cells that contain carbon compounds as reactive gases, such as solid oxide electrolysis cells (hereinafter referred to as "SOECs") that utilize electrolysis reactions to produce ethanol or ethylene using carbon dioxide as a raw material. In this specification, single fuel cell cells and single electrolysis cells are collectively referred to as single electrochemical reaction cells, and fuel cell stacks and electrolysis cell stacks are collectively referred to as electrochemical reaction cell stacks. Furthermore, such issues are not limited to SOFCs and SOECs, but are also common to other types of electrochemical reaction cell stacks.

[0007] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0008] The technology disclosed in this specification can be realized, for example, in the following forms.

[0009] (1) The electrochemical reaction unit cell disclosed in this specification includes an electrolyte layer, an air electrode disposed on one side of the electrolyte layer in a first direction, and an anode disposed on the other side of the electrolyte layer in the first direction, the anode containing a reforming catalyst. The electrochemical reaction unit cell has a reaction section and a non-reaction section. The reaction section is formed by overlapping the electrolyte layer, the air electrode, and the anode in the first direction. The non-reaction section is a non-reaction section not included in the reaction section, and includes a first section that is a part of the anode and is located on one side of the reaction section in a second direction intersecting the first direction, and a second section that is a part of the anode and is located on the other side of the reaction section in the second direction. In a cross section parallel to the first direction, a first length, which is the length from a first position that is a boundary between the reaction portion in the first portion and contacts the electrolyte layer, to a second position in the first portion that is the furthest from the first position, is shorter than a second length, which is the length from a third position that is a boundary between the reaction portion in the second portion and contacts the electrolyte layer, to a fourth position in the second portion that is the furthest from the third position.

[0010] According to the present electrochemical reaction unit cell, for example, when applied to an electrochemical reaction cell stack in which a gas flow passage facing the fuel electrode is formed and gas flows in a second direction, the first portion can be arranged on the side of the second direction where the H2O content is relatively low during operation. This makes it possible to reduce the number of places in the non-reaction part of the fuel electrode where H2O is not easily supplied, suppress the occurrence of cracks due to carbon deposition in the non-reaction part of the fuel electrode, and improve the durability of the electrochemical reaction unit cell.

[0011] (2) In the electrochemical reaction unit cell, the first length may be 7 mm or less. According to this configuration, since the first length is 7 mm or less, when applied to an electrochemical reaction cell stack, it is possible to reduce the number of locations in the non-reaction portion of the fuel electrode to which H2O is difficult to be supplied, suppress the occurrence of cracks due to carbon deposition in the non-reaction portion of the fuel electrode, and more effectively improve the durability of the electrochemical reaction unit cell.

[0012] (3) In the above electrochemical reaction unit cell, the content of the reforming catalyst in the first portion may be 40 vol% or less. With this configuration, since the content of the reforming catalyst in the first portion is 40 vol% or less, it is possible to suppress a carbon deposition reaction in the non-reaction portion of the fuel electrode, and the occurrence of cracks due to carbon deposition in the non-reaction portion of the fuel electrode can be suppressed, and the durability of the electrochemical reaction unit cell can be more effectively improved.

[0013] (4) Another electrochemical reaction single cell disclosed in the present specification includes an electrolyte layer, an air electrode disposed on one side of the electrolyte layer in a first direction, and an anode disposed on the other side of the electrolyte layer in the first direction, the anode containing a reforming catalyst. The electrochemical reaction single cell has a reaction section and a non-reaction section. The reaction section is formed by overlapping the electrolyte layer, the air electrode, and the anode in the first direction. The non-reaction section is a non-reaction section not included in the reaction section, and includes a first section that is a part of the anode and is located on one side of the reaction section in a second direction intersecting the first direction, and a second section that is a part of the anode and is located on the other side of the reaction section in the second direction. When viewed in the first direction, the center of the reaction section in the second direction is shifted from the center of the anode in the second direction to the one side of the second direction.

[0014] According to the present electrochemical reaction unit cell, for example, when applied to an electrochemical reaction cell stack in which a gas flow passage facing the fuel electrode is formed and gas flows in a second direction, the center of the reaction unit can be shifted to the side of the second direction where the H2O content is relatively low during operation. This makes it possible to reduce the number of places in the non-reaction unit of the fuel electrode where H2O is not easily supplied, suppress the occurrence of cracks due to carbon deposition in the non-reaction unit of the fuel electrode, and improve the durability of the electrochemical reaction unit cell.

[0015] (5) The electrochemical reaction cell stack disclosed in the present specification comprises a plurality of electrochemical reaction units arranged in the first direction, at least one of the plurality of electrochemical reaction units has the electrochemical reaction unit cell described in any one of (1) to (4) above, and includes a first manifold that exchanges gas with a gas flow passage facing the fuel electrode, and a second manifold that exchanges gas with the gas flow passage facing the fuel electrode, through which gas having a lower H2O content than gas passing through the first manifold passes during operation. The second manifold communicates with the gas flow passage on the one side in the second direction.

[0016] According to this electrochemical reaction cell stack, a first manifold and a second manifold are formed to exchange gas with the gas flow path facing the fuel electrode, and the second manifold, which is the side with a relatively low H2O content during operation, is connected to the gas flow path facing the fuel electrode on the same side as the first part of the electrochemical reaction unit cell. Therefore, it is possible to reduce the areas in the non-reaction part of the fuel electrode where H2O is not easily supplied, suppress the occurrence of cracks due to carbon deposition in the non-reaction part of the fuel electrode, and improve the durability of the electrochemical reaction cell stack.

[0017] The technology disclosed in this specification can be realized in various forms, such as an electrochemical reaction unit cell, an electrochemical reaction cell stack having a plurality of electrochemical reaction units each having an electrochemical reaction unit cell, a manufacturing method thereof, etc. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 10 according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 10 taken along the line II-II in FIG. [Diagram 3] FIG. 2 is an explanatory diagram showing an XZ cross-sectional configuration of the fuel cell stack 10 taken along the line III-III in FIG. 1. [Figure 4]FIG. 4 is an explanatory diagram showing a YZ cross-sectional configuration of the fuel cell stack 10 taken along the line IV-IV in FIG. [Diagram 5] FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent generating units 100U at the same position as the cross-section shown in FIG. 2. [Figure 6] FIG. 4 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 100U at the same position as the cross-section shown in FIG. [Figure 7] FIG. 1 is a perspective view showing a schematic configuration of a single cell 110. [Figure 8] FIG. 8 is an explanatory diagram showing the XZ cross-sectional configuration of a single cell 110 taken along the line VIII-VIII in FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A. Embodiment: A-1. Configuration of fuel cell stack 10: FIG. 1 is a perspective view showing the external configuration of the fuel cell stack 10 in this embodiment, FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 10 at the position II-II in FIG. 1, FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 10 at the position III-III in FIG. 1, and FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 10 at the position IV-IV in FIG. 1. Each figure shows mutually orthogonal XYZ axes for specifying directions. In this specification, for convenience, the Z axis direction is called the up-down direction, the Z axis positive direction is called the up direction, the Z axis negative direction is called the down direction, the X axis direction is called the left-right direction, the X axis positive direction is called the right direction, and the X axis negative direction is called the left direction, but the fuel cell stack 10 may actually be installed in a direction different from these directions. The fuel cell stack 10 is an example of an electrochemical reaction cell stack in the claims. The up-down direction is an example of a first direction in the claims. The left-right direction is an example of a second direction in the claims.

[0020] (Overall configuration of fuel cell stack 10) 1 to 4, the fuel cell stack 10 includes a power generation block 100, an end separator 230, a first plate 232, a second plate 260, a first terminal plate 240, a second terminal plate 250, an insulating section 220, a first end plate 210, a second end plate 270, and four gas passage members 280. The first end plate 210, the insulating section 220, the end separator 230, the first terminal plate 240, the power generation block 100, the second terminal plate 250, the second plate 260, and the second end plate 270 have rectangular outer shapes of approximately the same size, and are arranged overlapping in this order in a predetermined arrangement direction (vertical direction).

[0021] As shown in Figures 1 and 4, the fuel cell stack 10 has bolt holes BH near each of the four corners, penetrating from the first end plate 210 to the second end plate 270. A bolt B is inserted into each bolt hole BH. A nut N is screwed onto both ends of each bolt B. These bolts B and nuts N fasten the members from the first end plate 210 to the second end plate 270 together. As shown in Figures 2 to 4, the first plate 232 is supported by the end separator 230, and the four gas passage members 280 are connected to the second end plate 270.

[0022] As shown in Figs. 2 to 4, the power generation block 100 is made up of a plurality of power generation units 100U (seven in this embodiment) arranged side by side in a predetermined arrangement direction (vertical direction).

[0023] (First end plate 210) The first end plate 210 is a member formed by pressing (bending) a single plate-shaped member, and is formed of a conductive material such as stainless steel. As shown in Figs. 1 to 4, the first end plate 210 includes a rectangular frame-shaped flat portion 211 having a through hole 212 near the center, and an outer convex portion 213 and an inner convex portion 214 that protrude from the flat portion 211 in the opposite direction to the insulating portion 220 (upward in Fig. 2). The flat portion 211 has holes that form the bolt holes BH described above. The outer convex portion 213 protrudes from the outer periphery of the flat portion 211. The outer convex portion 213 is formed around the entire circumference of the outer periphery of the flat portion 211. The inner convex portion 214 protrudes from the inner periphery of the flat portion 211. The inner convex portion 214 is formed around the entire circumference of the inner periphery of the flat portion 211.

[0024] (insulating part 220) Insulating section 220 is a rectangular frame-shaped member having a through hole near the center, and is formed of, for example, an insulating material. Insulating section 220 is sandwiched between first end plate 210 and end separator 230 as shown in Fig. 2, so that insulation between first end plate 210 and end separator 230 is ensured.

[0025] (Terminal separator 230) As shown in FIGS. 2 to 4, end separator 230 is a rectangular frame-like member having a through hole 231 near the center, and is made of, for example, metal.

[0026] (First Plate 232) The first plate 232 is a rectangular flat member and is made of a conductive material such as stainless steel. As shown in Figures 2 to 4, the first plate 232 is joined to the periphery of the through hole 231 in the end separator 230 by, for example, welding. The end separator 230 and the first plate 232 separate the power generation block 100 from the external space of the fuel cell stack 10.

[0027] The first plate 232 is connected to an interconnector 190 (described below) provided in a power generating unit 100U arranged at one end (the upper end in Figure 2) of the multiple power generating units 100U that make up the power generating block 100, via a connecting member having the same structure as the anode current collecting member 144 (described below), thereby electrically connecting the power generating unit 100U and the first plate 232.

[0028] (First terminal plate 240) The first terminal plate 240 is a rectangular frame-shaped member having a through hole 241 near the center, and is made of a conductive material such as ferritic stainless steel that forms an alumina oxide film on its surface. The first terminal plate 240 is electrically connected to the power generating unit 100U arranged at one end (the upper end in FIG. 2) of the multiple power generating units 100U that make up the power generating block 100, via the first plate 232 and the end separator 230. One end (the right end in FIG. 2) of the first terminal plate 240 protrudes laterally from the power generating block 100, and this protruding portion functions as a positive output terminal for the fuel cell stack 10.

[0029] (2nd terminal plate 250) The second terminal plate 250 is a rectangular plate-like member, and is made of a conductive material such as ferritic stainless steel that forms an alumina oxide coating on its surface. The second terminal plate 250 is electrically connected to the power generating unit 100U arranged at the other end (the lower end in FIG. 2) of the multiple power generating units 100U that make up the power generating block 100. One end (the right end in FIG. 2) of the second terminal plate 250 protrudes laterally from the power generating block 100, and this protruding portion functions as a negative output terminal for the fuel cell stack 10.

[0030] (Second plate 260) The second plate 260 is a rectangular flat member and is made of, for example, an insulating material. The peripheral portion of the second plate 260 is sandwiched between the second terminal plate 250 and the second end plate 270, thereby ensuring insulation between the second terminal plate 250 and the second end plate 270.

[0031] (Second end plate 270) The second end plate 270 is a member formed by pressing (bending) a single plate-shaped member, and is formed of a conductive material such as stainless steel. The second end plate 270 includes a rectangular frame-shaped flat portion 271 having a through hole 272 near the center, and an outer convex portion 273 and an inner convex portion 274 that protrude from the flat portion 271 in the opposite direction to the second terminal plate 250 (downward in FIG. 2). The flat portion 271 has holes that form the bolt holes BH described above. The outer convex portion 273 protrudes from the outer periphery of the flat portion 271. The outer convex portion 273 is formed around the entire circumference of the outer periphery of the flat portion 271. The inner convex portion 274 protrudes from the inner periphery of the flat portion 271. The inner convex portion 274 is formed around the entire circumference of the inner periphery of the flat portion 271.

[0032] (Manifolds 311, 312, 321, 322) 1, 2, and 3, the fuel cell stack 10 has four holes penetrating from the power generation block 100 to the second end plate 270. The four holes are an oxidant gas supply manifold 311, an oxidant gas discharge manifold 312, a fuel gas supply manifold 321, and a fuel gas discharge manifold 322. The fuel gas discharge manifold 322 is an example of a first manifold in the claims. The fuel gas supply manifold 321 is an example of a second manifold in the claims.

[0033] 2, the oxidant gas supply manifold 311 is a gas flow path that supplies the oxidant gas OG introduced from outside the fuel cell stack 10 to an air chamber 313 (described later) of each power generating unit 100U. The oxidant gas discharge manifold 312 is a gas flow path that discharges the oxidant off-gas OOG discharged from the air chamber 313 of each power generating unit 100U to the outside of the fuel cell stack 10. For example, air is used as the oxidant gas OG. The oxidant gas supply manifold 311 and the oxidant gas discharge manifold 312 are disposed on opposite sides of each other with the air chamber 313 in between.

[0034] As shown in Fig. 3, the fuel gas supply manifold 321 is a gas flow path that supplies the fuel gas FG introduced from outside the fuel cell stack 10 to a fuel chamber 323 (described later) of each power generating unit 100U. The fuel gas discharge manifold 322 is a gas flow path that discharges the fuel off-gas FOG discharged from the fuel chamber 323 of each power generating unit 100U to the outside of the fuel cell stack 10. As the fuel gas FG, for example, a hydrogen-rich gas obtained by reforming city gas is used. The fuel gas supply manifold 321 and the fuel gas discharge manifold 322 are arranged on opposite sides of the fuel chamber 323.

[0035] (Gas passage member 280) As shown in Figs. 1 to 3, each of the four gas passage members 280 includes a main body portion 281 and a flange portion 282. The main body portion 281 is formed with a gas through hole 283 that penetrates in the vertical direction. The flange portion 282 is provided so as to protrude outward from the other end (the lower end in Fig. 2) of the main body portion 281. The flange portion 282 has a plurality of bolt holes 284. A bolt (not shown) for connecting the fuel cell stack 10 to an external device is inserted into each bolt hole 284. One end (the upper end in Figs. 2 and 3) of the main body portion 281 included in each of the four gas passage members 280 is joined to the second end plate 270 by, for example, welding, and the gas through holes 283 are connected to the manifolds 311, 312, 321, and 322, respectively. A gas pipe for supplying or discharging gas is connected to each of the main body portions 281 (not shown).

[0036] (Overall configuration of 100U generating unit) Fig. 5 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 100U at the same position as the cross-section shown in Fig. 2. Fig. 6 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 100U at the same position as the cross-section shown in Fig. 3. As shown in Figs. 5 and 6, the power generating unit 100U includes a single cell 110, a single cell separator 120, an air electrode frame 130, an anode frame 140, an anode current collecting member 144, two interconnectors 190, and two IC separators 180. One IC separator 180, the air electrode frame 130, the single cell separator 120, the anode frame 140, and the other IC separator 180 are arranged in this order in a stacked manner. The single cell 110 is supported by a single cell separator 120, the interconnector 190 is supported by an IC separator 180, and the anode current collecting member 144 is disposed between the single cell 110 and the interconnector 190. The power generation unit 100U is an example of an electrochemical reaction unit in the claims. The single cell 110 is an example of an electrochemical reaction single cell in the claims.

[0037] 5 and 6, the IC separator 180 and the interconnector 190 are shared by two adjacent power generating units 100U. However, as shown in FIG. 2, the power generating unit 100U located at the other end (the lower end in FIG. 2) of the multiple power generating units 100U does not have the IC separator 180 and interconnector 190 adjacent to the fuel electrode frame 140, and the second terminal plate 250 overlaps the fuel electrode frame 140.

[0038] (single cell 110) The unit cell 110 includes an electrolyte layer 112, an air electrode 114, an anode 116, and a reaction prevention layer 118. As shown in Fig. 5 and Fig. 6, the air electrode 114 is disposed on one side (upper side) of the electrolyte layer 112 in the vertical direction, the anode 116 is disposed on the other side (lower side) of the electrolyte layer 112 in the vertical direction, and the reaction prevention layer 118 is disposed between the electrolyte layer 112 and the air electrode 114. The unit cell 110 of this embodiment is an anode-supported unit cell in which the anode 116 supports the other layers (electrolyte layer 112, air electrode 114, reaction prevention layer 118) constituting the unit cell 110.

[0039] The electrolyte layer 112 is a rectangular flat member having one surface (upper surface in Figs. 5 and 6) on which the air electrode 114 is disposed, and another surface (lower surface in Figs. 5 and 6) on which the fuel electrode 116 is disposed and parallel to the first surface. The electrolyte layer 112 is a layer containing a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). The air electrode 114 is a layer having a rectangular shape smaller than the electrolyte layer 112, and contains, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The fuel electrode 116 is a layer having a rectangular shape of approximately the same size as the electrolyte layer 112, and contains, for example, Ni (nickel), Ru (ruthenium), Rh (rhodium), or the like, as a reforming catalyst, and a solid oxide (e.g., YSZ). The reaction prevention layer 118 is a layer having a rectangular outer shape and approximately the same size as the air electrode 114, and contains, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has a function of suppressing the generation of a highly resistive substance (for example, SrZrO3) caused by an element (for example, Zr) diffused from the air electrode 114 reacting with an element (for example, Zr) contained in the electrolyte layer 112. The configuration of the single cell 110 will be described in detail later.

[0040] (Separator for single cell 120) As shown in Figures 5 and 6, the single cell separator 120 is a rectangular frame-like member having a substantially rectangular through-hole 121 near the center, and is made of, for example, metal. The peripheral portion of the through-hole 121 in the single cell separator 120 is joined to the peripheral portion of one surface of the electrolyte layer 112 (the surface on which the air electrode 114 is disposed: the upper surface in Figures 5 and 6) by a joint 124. The joint 124 is made of, for example, a brazing material (Ag brazing).

[0041] (Air electrode frame 130) 5 and 6, the air electrode frame 130 is a rectangular frame-like member having a substantially rectangular through-hole 131 near the center, and is made of, for example, mica. As shown in Fig. 5, the air electrode frame 130 has an oxidant gas supply communication channel 132 that connects the oxidant gas supply manifold 311 and the air chamber 313, and an oxidant gas discharge communication channel 133 that connects the air chamber 313 and the oxidant gas discharge manifold 312.

[0042] (fuel electrode frame 140) 5 and 6, the fuel electrode frame 140 is a rectangular frame-like member having a substantially rectangular through-hole 141 near the center, and is made of, for example, metal. As shown in Fig. 6, the fuel electrode frame 140 has a fuel gas supply communication channel 142 that connects the fuel gas supply manifold 321 and the fuel chamber 323, and a fuel gas discharge communication channel 143 that connects the fuel chamber 323 and the fuel gas discharge manifold 322.

[0043] (IC separator 180) As shown in FIGS. 5 and 6, IC separator 180 is a rectangular frame-like member having a through hole 181 near the center, and is made of, for example, metal.

[0044] (Interconnector 190 and anode current collecting member 144) 5 and 6, the interconnector 190 includes a rectangular flat plate portion 191, a plurality of plate-shaped air electrode current collectors 192 protruding from one surface of the flat plate portion 191 toward the air electrode 114, and a coating layer 193. The flat plate portion 191 and the air electrode current collector 192 are conductive and made of a metal (e.g., ferritic stainless steel). The coating layer 193 is conductive and is disposed so as to cover the surface of the air electrode current collector 192 and the surface of the flat plate portion 191 on which the air electrode current collector 192 is disposed. The flat plate portion 191 is joined to the periphery of the through hole 181 in the IC separator 180 by, for example, welding.

[0045] The anode current collecting member 144 is a member that connects the interconnector 190 and the anode 116, and is formed of a conductive material such as nickel, a nickel alloy, or stainless steel. As shown in Figures 5 and 6, the anode current collecting member 144 includes an interconnector facing portion 146, an electrode facing portion 145 parallel to the interconnector facing portion 146, and a connecting portion 147 that connects the electrode facing portion 145 and the interconnector facing portion 146, and has a U-shape overall. The electrode facing portion 145 is in contact with the anode 116, and the interconnector facing portion 146 is in contact with a flat portion 191 of the interconnector 190.

[0046] As described above, the interconnector 190 is shared by two adjacent power generating units 100U. More specifically, as shown in Fig. 5 and Fig. 6, the air electrode current collecting portion 192 is joined to the air electrode 114 of the unit cell 110 provided in one of the two adjacent power generating units 100U via a conductive bonding material 196 made of, for example, a spinel-type oxide, and is thus electrically connected to the air electrode 114. The flat plate portion 191 is electrically connected to the anode 116 of the unit cell 110 provided in the other of the two adjacent power generating units 100U via an anode current collecting member 144. This ensures electrical continuity between the two adjacent power generating units 100U.

[0047] However, as described above, the power generating unit 100U located at the other end (the lower end in FIG. 2) of the multiple power generating units 100U does not have an interconnector 190 on the anode 116 side. The anode 116 included in this power generating unit 100U is connected to the second terminal plate 250 via the anode current collecting member 144.

[0048] A spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the anode current collecting member 144 follows the deformation of the power generating unit 100U caused by temperature cycles and reactant gas pressure fluctuations, and the electrical connection between the anode 116 and the interconnector 190 (or second terminal plate 250) via the anode current collecting member 144 is maintained well.

[0049] (Air chamber 313 and fuel chamber 323) 5 and 6, the space partitioned by the single cell separator 120, the single cell 110, the air electrode frame 130, the IC separator 180, and the interconnector 190 faces the air electrode 114 and serves as an air chamber 313 through which the oxidant gas OG flows. The air electrode frame 130 partitions the air chamber 313 from the outside space all around, and seals the gap between the single cell separator 120 and the IC separator 180, preventing gas from leaking from the air chamber 313 to the outside space.

[0050] The space partitioned by the single cell separator 120, the single cell 110, the fuel electrode frame 140, the IC separator 180, and the interconnector 190 faces the fuel electrode 116 and serves as a fuel chamber 323 through which the fuel gas FG flows. The fuel electrode frame 140 partitions the entire periphery of the fuel chamber 323 from the outside space, and seals the gap between the single cell separator 120 and the IC separator 180, thereby preventing gas from leaking from the fuel chamber 323 to the outside space. The fuel chamber 323 is an example of a gas flow path in the claims.

[0051] The single cell separator 120 separates the air chamber 313 and the fuel chamber 323, and suppresses gas leakage (cross leakage) from the air electrode 114 side to the fuel electrode 116 side or from the fuel electrode 116 side to the air electrode 114 side around the single cell 110. In addition, the IC separator 180 and the interconnector 190 suppress gas leakage between adjacent power generating units 100U.

[0052] A-2. Operation of fuel cell stack 10: As shown in FIGS. 2 and 5, the oxidizing gas OG is supplied to the oxidizing gas supply manifold 311 via a gas piping (not shown) and a gas passage member 280, and is supplied to the air chamber 313 via the oxidizing gas supply communicating passage 132.

[0053] As shown in FIGS. 3 and 6, the fuel gas FG is supplied to a fuel gas supply manifold 321 via a gas piping (not shown) and a gas passage member 280, and is supplied to the fuel chamber 323 via a fuel gas supply communication passage 142.

[0054] When the oxidant gas OG is supplied to the air chamber 313 of each power generating unit 100U and the fuel gas FG is supplied to the fuel chamber 323, power is generated in the single cell 110 by an electrochemical reaction between the oxidant gas OG and the fuel gas FG. This power generating reaction is an exothermic reaction. As described above, the interconnector 190 is shared by two adjacent power generating units 100U, and the interconnector 190 ensures electrical continuity between the two adjacent power generating units 100U. That is, the multiple power generating units 100U included in the fuel cell stack 10 are electrically connected in series. In addition, the second terminal plate 250 is electrically connected to the power generating unit 100U located at the other end (lower end of FIG. 2) of the multiple power generating units 100U, and the first terminal plate 240 is electrically connected to the power generating unit 100U located at one end (upper end of FIG. 2). As a result, electrical energy generated in each power generating unit 100U is taken out from the terminal plates 240, 250 that function as output terminals of the fuel cell stack 10. Since SOFCs generate electricity at relatively high temperatures (e.g., 700°C to 1000°C), after startup, the fuel cell stack 10 may be heated by a heater (not shown) until the heat generated by power generation can maintain the high temperature.

[0055] 2 and 5, the oxidant off-gas OOG discharged from the air chamber 313 of each power generating unit 100U to the oxidant gas discharge manifold 312 via the oxidant gas discharge communication passage 133 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281. Also, as shown in Figures 3 and 6, the fuel off-gas FOG discharged from the fuel chamber 323 of each power generating unit 100U to the fuel gas discharge manifold 322 via the fuel gas discharge communication passage 143 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281.

[0056] A-3. Detailed configuration of single cell 110: Fig. 7 is a perspective view showing a schematic configuration of the unit cell 110. Fig. 8 is an explanatory diagram showing an XZ cross-sectional configuration of the unit cell 110 at the position of VIII-VIII in Fig. 7. As shown in Figs. 5 to 8, the unit cell 110 has a power generation section PG and a non-power generation section NPG. The power generation section PG is an example of a reaction section in the claims. The non-power generation section NPG is an example of a non-reaction section in the claims.

[0057] The power generation section PG is a section where the electrolyte layer 112, the air electrode 114, and the fuel electrode 116 overlap in the vertical direction. The non-power generation section NPG is a section of the unit cell 110 that is not included in the power generation section PG, and surrounds the power generation section PG when viewed in the vertical direction. The non-power generation section NPG includes a first section FN1 that is a part of the fuel electrode 116 and is located on one side (right side) of the power generation section PG in the horizontal direction, and a second section FN2 that is a part of the fuel electrode 116 and is located on the other side (left side) of the power generation section PG in the horizontal direction. Due to this configuration, the power generation section PG can be said to be a section of the unit cell 110 where the power generation reaction is relatively likely to occur, and conversely, the non-power generation section NPG can be said to be a section of the unit cell 110 where the power generation reaction is relatively unlikely to occur.

[0058] In the vertical view, the center of the power generation unit PG in the horizontal direction is shifted to one side (right side) in the horizontal direction from the center of the fuel electrode 116 in the horizontal direction. Specifically, as shown in FIG. 8, in a cross section (XZ cross section) parallel to the vertical direction, a first length L1, which is a length from a first position P1 at the boundary between the power generation unit PG in the first portion FN1 and the electrolyte layer 112, to a second position P2 in the first portion FN1 that is the furthest from the first position P1, is shorter than a second length L2, which is a length from a third position P3 at the boundary between the power generation unit PG in the second portion FN2 and the electrolyte layer 112, to a fourth position P4 in the second portion FN2 that is the furthest from the third position P3. In this case, the first length L1 is 7 mm or less. The content of the reforming catalyst in the first portion FN1 is 40 vol% or less. In the unit cell 110 of this embodiment, the second position P2 is located on the outer edge OE1 in the left-right direction of the first portion FN1, and the fourth position P4 is located on the outer edge OE2 in the left-right direction of the second portion FN2.

[0059] At least one of the plurality of power generating units 100U constituting the fuel cell stack 10 has the above-mentioned single cell 110. As shown in FIG. 5 and FIG. 6, the fuel gas supply manifold 321 communicates with the fuel chamber 323 on the right side in the left-right direction (in other words, on the same side as the first portion FN1 of the fuel electrode 116). In the fuel cell stack 10, the fuel gas FG reacts with the oxidant gas OG to generate power, which generates H2O. Therefore, the fuel gas FG supplied to the fuel chamber 323 contains less H2O than the fuel off-gas FOG discharged from the fuel chamber 323. In other words, the fuel gas supply manifold 321 and the fuel gas discharge manifold 322 are manifolds that exchange gas with the fuel chamber 323, and during operation of the fuel cell stack 10, the gas that contains less H2O passes through the fuel gas supply manifold 321 than the gas that passes through the fuel gas discharge manifold 322.

[0060] A-4. Manufacturing method of fuel cell stack 10: The fuel cell stack 10 of this embodiment can be manufactured, for example, as follows.

[0061] (Formation of a laminate of the electrolyte layer 112 and the fuel electrode 116) Butyral resin, dioctyl phthalate (DOP) as a plasticizer, dispersant, and a mixed solvent of toluene and ethanol are added to the YSZ powder, and the mixture is mixed in a ball mill to prepare a slurry. The obtained slurry is thinned by a doctor blade method to obtain an electrolyte layer green sheet having a thickness of, for example, about 10 μm. NiO powder is weighed so that the Ni content in the fuel electrode 116 is 40 vol% or less, and mixed with the YSZ powder to obtain a mixed powder. Butyral resin, DOP as a plasticizer, dispersant, and a mixed solvent of toluene and ethanol are added to the mixed powder, and the mixture is mixed in a ball mill to prepare a slurry. The obtained slurry is thinned by a doctor blade method to obtain an electrolyte layer green sheet having a thickness of, for example, 270 μm. The electrolyte layer green sheet and the fuel electrode green sheet are attached and dried. Then, the mixture is fired at, for example, 1400° C. to obtain a laminate of the electrolyte layer 112 and the fuel electrode 116.

[0062] (Formation of reaction prevention layer 118) Polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to the GDC powder and mixed, and the viscosity is adjusted to prepare a paste for the reaction prevention layer. The obtained paste for the reaction prevention layer is applied to the surface of the electrolyte layer 112 in the above-mentioned laminate by, for example, screen printing, and is fired at a predetermined temperature (for example, 1200°C). As a result, the reaction prevention layer 118 is formed, and a laminate of the reaction prevention layer 118, the electrolyte layer 112, and the fuel electrode 116 is obtained.

[0063] (Formation of the air electrode 114) A mixture of a powder of a perovskite oxide (e.g., LSCF) and a powder of a sulfate (e.g., SrSO4) is prepared, and polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to the mixture, and the viscosity is adjusted to prepare a paste for an air electrode. The obtained paste for an air electrode is applied to the surface of the reaction prevention layer 118 in the laminate of the reaction prevention layer 118, the electrolyte layer 112, and the fuel electrode 116 described above, for example, by screen printing, and dried, and the laminate to which the paste for an air electrode is applied is fired at a predetermined temperature (e.g., about 1100°C). As a result, the air electrode 114 is formed, and a single cell 110 including the fuel electrode 116, the electrolyte layer 112, the reaction prevention layer 118, and the air electrode 114 is fabricated. The first length L1 and second length L2 of the single cell 110 can be adjusted by applying the air electrode paste to the surface of the reaction prevention layer 118 such that the center of the air electrode paste in the left-right direction is shifted from the center of the fuel electrode 116 in the left-right direction when viewed from the top-bottom direction.

[0064] After producing a plurality of unit cells 110 according to the above-mentioned method, assembly steps (e.g., a step of attaching other members such as unit cell separators 120 to each unit cell 110, a step of stacking the plurality of unit cells 110, a step of fastening them with bolts B, etc.) are performed. This completes the manufacture of the fuel cell stack 10.

[0065] A-5. Advantages of this embodiment: As described above, the unit cell 110 of this embodiment includes the electrolyte layer 112, the air electrode 114 arranged above the electrolyte layer 112 in the vertical direction, and the fuel electrode 116 arranged below the electrolyte layer 112 in the vertical direction, the fuel electrode 116 containing a reforming catalyst. The unit cell 110 has a power generation section PG and a non-power generation section NPG. The power generation section PG is configured such that the electrolyte layer 112, the air electrode 114, and the fuel electrode 116 overlap in the vertical direction. The non-power generation section NPG is a non-power generation section NPG that is not included in the power generation section PG, and includes a first section FN1 that is a part of the fuel electrode 116 and is located on the right side in the horizontal direction intersecting the vertical direction of the power generation section PG, and a second section FN2 that is a part of the fuel electrode 116 and is located on the left side in the horizontal direction of the power generation section PG. In a cross section parallel to the vertical direction, a first length L1, which is the length from a first position P1, which is the boundary between the first part FN1 and the power generation part PG and which contacts the electrolyte layer 112, to a second position P2 in the first part FN1 that is the farthest from the first position P1, is shorter than a second length L2, which is the length from a third position P3, which is the boundary between the second part FN2 and the power generation part PG and which contacts the electrolyte layer 112, to a fourth position P4 in the second part FN2 that is the farthest from the third position P3.

[0066] According to the unit cell 110 of this embodiment, for example, when applied to a fuel cell stack in which a gas flow passage facing the fuel electrode 116 is formed and gas flows in the left-right direction, the first portion FN1 can be arranged on the side in the left-right direction where the H2O content during operation is relatively low. This makes it possible to reduce the number of places in the non-power generation portion NPG of the fuel electrode 116 to which H2O is not easily supplied, suppresses the occurrence of cracks due to carbon deposition in the non-power generation portion NPG of the fuel electrode 116, and improves the durability of the unit cell 110.

[0067] In the unit cell 110 of this embodiment, the first length L1 is 7 mm or less. According to the unit cell 110 of this embodiment, since the first length L1 is 7 mm or less, when applied to a fuel cell stack, it is possible to reduce the number of places in the non-power generation portion NPG of the anode 116 to which H2O is not easily supplied, and the occurrence of cracks due to carbon deposition in the non-power generation portion NPG of the anode 116 can be suppressed, and the durability of the unit cell 110 can be more effectively improved.

[0068] In the unit cell 110 of this embodiment, the content of the reforming catalyst in the first portion FN1 is 40 vol % or less. According to the unit cell 110 of this embodiment, since the content of the reforming catalyst in the first portion FN1 is 40 vol % or less, it is possible to suppress a carbon deposition reaction in the non-power generation portion NPG of the fuel electrode 116, and the occurrence of cracks due to carbon deposition in the non-power generation portion NPG of the fuel electrode 116 can be suppressed, and the durability of the unit cell 110 can be improved more effectively.

[0069] The unit cell 110 of this embodiment includes an electrolyte layer 112, an air electrode 114 disposed above the electrolyte layer 112 in the vertical direction, and an anode 116 disposed below the electrolyte layer 112 in the vertical direction, the anode 116 containing a reforming catalyst. The unit cell 110 includes a power generation section PG and a non-power generation section NPG. The power generation section PG is formed by stacking the electrolyte layer 112, the air electrode 114, and the anode 116 in the vertical direction. The non-power generation section NPG is a non-power generation section NPG that is not included in the power generation section PG, and includes a first section FN1 that is a part of the anode 116 and is located on the right side in the horizontal direction intersecting the vertical direction of the power generation section PG, and a second section FN2 that is a part of the anode 116 and is located on the left side in the horizontal direction of the power generation section PG. When viewed in the vertical direction, the center of the power generation section PG in the horizontal direction is shifted to the right side in the horizontal direction from the center of the anode 116 in the horizontal direction.

[0070] According to the unit cell 110 of this embodiment, for example, when applied to a fuel cell stack in which a gas flow passage facing the fuel electrode 116 is formed and gas flows in the left-right direction, the power generation part PG can be shifted in the left-right direction to the side with a relatively low H2O content during operation. This makes it possible to reduce the number of places in the non-power generation part NPG of the fuel electrode 116 to which H2O is difficult to be supplied, suppresses the occurrence of cracks due to carbon deposition in the non-power generation part NPG of the fuel electrode 116, and improves the durability of the unit cell 110.

[0071] The fuel cell stack 10 of this embodiment includes a plurality of power generating units 100U arranged vertically, at least one of the plurality of power generating units 100U having a single cell 110, and includes a fuel gas exhaust manifold 322 which exchanges gas with a fuel chamber 323 facing the fuel electrode 116, and a fuel gas supply manifold 321 which exchanges gas with the fuel chamber 323 facing the fuel electrode 116, and through which passes a gas having a lower H2O content than the gas passing through the fuel gas exhaust manifold 322 during operation. The fuel gas supply manifold 321 communicates with the fuel chamber 323 on the right side in the left-right direction.

[0072] According to the fuel cell stack 10 of this embodiment, a fuel gas exhaust manifold 322 and a fuel gas supply manifold 321 are formed to exchange gas with a fuel chamber 323 facing the fuel electrode 116, and the fuel gas supply manifold 321, which is the side having a relatively low H2O content during operation, is connected to the fuel chamber 323 facing the fuel electrode 116 on the same side as the first portion FN1 of the unit cell 110. This makes it possible to reduce the number of locations in the non-power generation portion NPG of the fuel electrode 116 to which H2O is difficult to be supplied, suppressing the occurrence of cracks due to carbon deposition in the non-power generation portion NPG of the fuel electrode 116, and improving the durability of the fuel cell stack 10.

[0073] A-6.Performance evaluation: Next, the performance evaluation of this embodiment will be described. A plurality of samples of the fuel cell stack 10 including the unit cells 110 each having a different first length L1 and second length L2 were fabricated, and the crack resistance (resistance to cracks) was evaluated using the plurality of samples. Table 1 shows the performance evaluation results.

[0074] (Evaluation of crack resistance) First, a plurality of samples of the fuel cell stack 10 were produced by the method described in "A-4. Manufacturing method of the fuel cell stack 10" above. Next, a durability test was conducted on each sample by continuously operating it at 700°C for 100 hours. In the durability test, power was generated by supplying an oxidant gas OG to the air electrode 114 and a fuel gas FG (a mixed gas of water vapor:methane=1.4:1) to the fuel electrode 116. After the durability test, the presence or absence of cracks in the first portion FN1 of the fuel electrode 116 was confirmed. The presence or absence of cracks was confirmed by observation using a SEM (scanning electron microscope).

[0075] The content of the reforming catalyst in the fuel electrode 116 is determined by the following method. A cross section of the single cell 110 parallel to the vertical direction is set, and an element mapping image (e.g., 5000x) is obtained at any position on the cross section using FIB-SEM (acceleration voltage 1.5 kV). The content (vol%) of the reforming catalyst is determined by calculating the area ratio of the corresponding element at the above position in the obtained image. In this performance evaluation, the content of the reforming catalyst in the fuel electrode 116 of each sample is set to be 40 vol%.

[0076] (Performance evaluation results) Table 1 shows the performance evaluation results. [Table 1]

[0077] Table 1 shows the first length L1, the second length L2, and the presence or absence of cracks in the first portion FN1 for each sample.

[0078] As shown in Table 1, in the sample (S1) in which the first length L1 and the second length L2 were equal, cracks occurred after the durability test, while in the samples (S2 to S4) in which the first length L1 was shorter than the second length L2, no cracks occurred after the durability test. From this result, it was confirmed that in the fuel cell stack 10 including the unit cells 110 in which the first length L1 is shorter than the second length L2, i.e., in which the center of the power generation part PG in the left-right direction is shifted to the right (the side where the fuel gas supply manifold 321 is arranged) from the center of the fuel electrode 116 in the left-right direction when viewed in the up-down direction, the occurrence of cracks due to carbon deposition in the non-power generation part NPG of the fuel electrode 116 can be suppressed.

[0079] Furthermore, as shown in Table 1, in the samples in which the first length L1 is shorter than the second length L2, the samples (S2 to S4) in which the first length L1 is 7 mm or less did not develop cracks after the durability test. This result confirms that in the fuel cell stack 10 including the unit cells 110 in which the first length L1 is 7 mm or less, the development of cracks due to carbon deposition in the non-power generation part NPG of the fuel electrode 116 can be suppressed.

[0080] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0081] The configurations of the fuel cell stack 10 and the unit cells 110 in the above embodiment are merely examples and can be modified in various ways. For example, the number of unit cells 110 (the number of power generation units 100U) included in the fuel cell stack 10 in the above embodiment is merely an example, and the number of unit cells 110 is appropriately determined depending on the output voltage required for the fuel cell stack 10.

[0082] The materials constituting each member in the above embodiment are merely examples, and each member may be made of other materials.

[0083] In the above embodiment, the first length L1 is 7 mm or less, but it is not necessarily required to be 7 mm or less.

[0084] In the above embodiment, the content of the reforming catalyst in the first portion FN1 is 40 vol % or less, but it is not necessarily required to be 40 vol % or less.

[0085] The fuel cell stack 10 in the above embodiment is a co-flow type SOFC, but the technology disclosed in this specification is also applicable to counter-flow type SOFCs and cross-flow type SOFCs.

[0086] In the above embodiment, the unit cell 110 is an anode-supported unit cell, but it may be another type of unit cell, such as an electrolyte-supported type or a metal-supported type.

[0087] In the above embodiment, the electrochemical reaction unit cell and the electrochemical reaction cell stack were unit cells and cell stacks used in solid oxide fuel cells (SOFCs), but the above configurations are also applicable to unit cells and cell stacks used in other types of fuel cells, such as solid polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PAFCs), and molten carbonate fuel cells (MCFCs), or unit cells and cell stacks used in solid oxide electrolysis cells (SOECs). [Explanation of symbols]

[0088] 10: Fuel cell stack 100: Power generation block 100U: Power generation unit 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Anode 118: Reaction prevention layer 120: Separator for single cell 121: Through hole 124: Joint 130: Air electrode frame 131: Through hole 132: Oxidant gas supply communication channel 133: Oxidant gas exhaust communication channel 140: Anode frame 141: Through hole 142: Fuel gas supply communication channel 143: Fuel gas exhaust communication channel 144: Anode current collecting member 145: Electrode facing portion 146: Interconnector facing portion 147: Connection portion 149: Spacer 180: IC separator 181: Through hole 190: Interconnector 191: Flat plate portion 192: Air electrode current collecting portion 193: coating layer 196: conductive bonding material 210: first end plate 220: insulating portion 230: terminal separator 231: through hole 232: first plate 240: first terminal plate 241: through hole 250: second terminal plate 260: second plate 270: second end plate 280: gas passage member 281: main body portion 282: flange portion 283: gas through hole 284: bolt hole 311: oxidizer gas supply manifold 312: oxidizer gas exhaust manifold 313: air chamber 321: fuel gas supply manifold 322: fuel gas exhaust manifold 323: fuel chamber B: bolt BH: bolt hole N: nut FG: fuel gas FOG: fuel off-gas OG: oxidizer gas OOG: oxidizer off-gas PG: power generation portion NPG: non-power generation portion FN1: first portion FN2: Second part P1: First position P2: Second position P3: Third position P4: Fourth position L1: First length L2: Second length

Claims

1. An electrolyte layer; a cathode disposed on one side of the electrolyte layer in a first direction; an anode disposed on the other side of the electrolyte layer in the first direction, the anode containing a reforming catalyst; The electrochemical reaction unit cell is a reaction section in which the electrolyte layer, the air electrode, and the fuel electrode overlap in the first direction; A non-reacting portion not included in the reaction portion, a first portion that is a part of the fuel electrode and is located on one side of the reaction portion in a second direction that intersects with the first direction; a second portion that is a part of the fuel electrode and is located on the other side of the reaction portion in the second direction; and In a cross section parallel to the first direction, a first length, which is a length from a first position, which is a boundary between the first portion and the reaction portion and is in contact with the electrolyte layer, to a second position in the first portion that is the furthest from the first position, is shorter than a second length, which is a length from a third position, which is a boundary between the second portion and the reaction portion and is in contact with the electrolyte layer, to a fourth position in the second portion that is the furthest from the third position. Electrochemical reaction unit cell.

2. 2. The electrochemical reaction unit cell according to claim 1, The first length is 7 mm or less. Electrochemical reaction unit cell.

3. 2. The electrochemical reaction unit cell according to claim 1, The content of the reforming catalyst in the first portion is 40 vol% or less. Electrochemical reaction unit cell.

4. An electrolyte layer; a cathode disposed on one side of the electrolyte layer in a first direction; an anode disposed on the other side of the electrolyte layer in the first direction, the anode containing a reforming catalyst; The electrochemical reaction unit cell is a reaction section in which the electrolyte layer, the air electrode, and the fuel electrode overlap in the first direction; A non-reacting portion not included in the reaction portion, a first portion that is a part of the fuel electrode and is located on one side of the reaction portion in a second direction that intersects with the first direction; a second portion that is a part of the fuel electrode and is located on the other side of the reaction portion in the second direction; and When viewed in the first direction, a center of the reaction portion in the second direction is shifted from a center of the fuel electrode in the second direction to the one side in the second direction. Electrochemical reaction unit cell.

5. A plurality of electrochemical reaction units are arranged in the first direction, At least one of the plurality of electrochemical reaction units has the electrochemical reaction unit cell according to any one of claims 1 to 4, a first manifold for exchanging gas with a gas flow passage facing the fuel electrode; and a second manifold for exchanging gas with the gas flow passage facing the fuel electrode, the second manifold having a higher H2 concentration than a gas passing through the first manifold during operation. ２ a second manifold through which a gas having a low O content passes; the second manifold communicates with the gas flow path on the one side in the second direction; An electrochemical reaction cell stack comprising:

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