Electrochemical reaction module and method for manufacturing the electrochemical reaction module

Abstract

To inhibit the scattering of Mn contained in a specific member into a fuel chamber, the specific member constituting a gas passage where gas supplied to a fuel electrode flows.SOLUTION: An electrochemical reaction module includes an electrochemical reaction device including an electrochemical reaction single cell that includes an electrolyte layer containing a solid oxide, and an air electrode and a fuel electrode facing each other with the electrolyte layer sandwiched therebetween, a specific gas passage where gas supplied to a fuel electrode flows being formed in the electrochemical reaction module. An oxide film is formed on at least part of a surface of a specific member that defines the specific gas passage and that is a Mn-containing member, the oxide film facing the specific gas passage and including a specific compound that is a compound of Mn and a specific element of at least one element selected from among Si, Al, Ti and S.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The technology disclosed herein relates to an electrochemical reaction module and a method for manufacturing an electrochemical reaction module. [Background technology]

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs") are known as one type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen. SOFCs are used, for example, in the form of a fuel cell module that includes a fuel cell stack and other devices (see, for example, Patent Document 1). The other devices are, for example, a combustor and a reformer for generating gas (fuel gas) to be supplied to the fuel cell stack.

[0003] A fuel cell stack is a structure comprising multiple power generation units. Each power generation unit has a fuel cell unit cell (hereinafter simply referred to as a "unit cell") including an electrolyte layer and an air electrode and a fuel electrode facing each other across the electrolyte layer. The fuel cell module also has a gas flow path (hereinafter referred to as a "specific gas flow path") through which gas supplied to the fuel electrode flows. Gas introduced into the fuel cell stack via the specific gas flow path and the other devices described above is supplied to the fuel electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-091683 A Summary of the Invention [Problem to be solved by the invention]

[0005] A material containing Mn (manganese) is sometimes used as a material for constituting (defining) a specific gas flow path (for example, a fuel electrode-side gas supply flow path connecting a reformer and a fuel cell stack), which is a gas flow path through which gas supplied to the fuel electrode flows. In such a configuration in which the specific gas flow path contains Mn, the Mn contained in the specific gas flow path flows through the gas flow path together with the gas and is eventually dispersed into the fuel chamber, which increases the Mn vapor pressure in the fuel chamber, which is the space facing the fuel electrode, and may eventually cause cracks in the electrolyte layer, adversely affecting the performance of the single cell (and thus the fuel cell stack).

[0006] These issues are also common to electrolysis modules that include an electrolysis cell stack, which is a type of electrolysis cell (hereinafter referred to as "SOEC") that generates hydrogen using the electrolysis reaction of water. An electrolysis cell stack is a structure that includes an electrolysis block, which is a structure in which a plurality of electrolysis cell units, each of which has an electrolysis unit cell, are arranged in a predetermined direction. In this specification, a fuel cell unit cell and an electrolysis unit cell are collectively referred to as an electrochemical reaction unit cell, a fuel cell power generation unit and an electrolysis cell unit are collectively referred to as an electrochemical reaction unit cell, a fuel cell stack and an electrolysis cell stack are collectively referred to as an electrochemical reaction cell stack, and a fuel cell module and an electrolysis module are collectively referred to as an electrochemical reaction module. These issues are not limited to SOFCs and SOECs, but are also common to other types of electrochemical reaction cell stacks and electrochemical reaction modules that include such 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 module disclosed in this specification comprises an electrochemical reaction device having an electrochemical reaction unit cell including an electrolyte layer containing a solid oxide, and an air electrode and an anode facing each other with the electrolyte layer sandwiched therebetween, and in which a specific gas flow path is formed through which a gas supplied to the anode flows. In this electrochemical reaction module, an oxide coating film is formed on at least a portion of the surface of a specific component that defines the specific gas flow path and is a component containing Mn, facing the specific gas flow path and containing a specific compound that is a compound of Mn and a specific element that is at least one element selected from Si, Al, Ti, and S.

[0010] As described above, in the present electrochemical reaction module, an oxide coating is formed on at least a portion of the surface of the specific component that defines the specific gas flow path and contains Mn. The oxide coating faces the specific gas flow path and contains a specific compound, which is a compound of Mn and at least one specific element selected from Si, Al, Ti, and S. Therefore, in the present electrochemical reaction module, even though the specific component that defines the specific gas flow path contains Mn, the Mn contained in the specific component is prevented from scattering into the gas. This is because the Mn becomes a specific compound (a compound of Mn and the specific element), making it less likely to scatter into the gas. Therefore, with the present electrochemical reaction module, it is possible to suppress an increase in Mn vapor pressure in the fuel chamber compared to the above-mentioned conventional technology, thereby improving the performance of the electrochemical reaction unit cell.

[0011] (2) In the electrochemical reaction module, the oxide film may be configured such that MnO is not identified by X-ray diffraction. In this electrochemical reaction module, Mn contained in the specific component is less likely to scatter into the gas than in a configuration in which MnO is identified by X-ray diffraction. Therefore, this electrochemical reaction module can more effectively suppress an increase in Mn vapor pressure in the fuel chamber, thereby improving the performance of the electrochemical reaction unit cell.

[0012] (3) In the above electrochemical reaction module, the specific member may contain Cr. In this electrochemical reaction module, Cr2O3 is formed on the surface of the specific member. Therefore, a compound of Mn and a specific element formed on the surface of the specific member serves as a nucleus to form a compound of Mn and Cr (such as (Cr, Mn)3O4) with a low Mn vapor pressure, thereby further suppressing Mn from scattering into the fuel chamber. Therefore, this electrochemical reaction module can more effectively suppress an increase in Mn vapor pressure in the fuel chamber, thereby improving the performance of the electrochemical reaction unit cell.

[0013] (4) In the electrochemical reaction module, the specific element may be Si, and the specific compound may be Mn2SiO4 or a compound in which at least one of the Mn and Si contained in Mn2SiO4 is partially substituted with another element. Because Si has particularly good reactivity with Mn, this electrochemical reaction module can more effectively suppress an increase in Mn vapor pressure in the fuel chamber compared to a configuration containing only a specific element other than Si (e.g., Ti, Al, S), thereby improving the performance of the electrochemical reaction unit cell.

[0014] (5) In the electrochemical reaction module, the electrochemical reaction unit cell is a fuel cell unit cell, and the electrochemical reaction module is equipped with a reformer having a space formed therein that communicates with the specific gas flow path, the reformer reforming the gas supplied to the electrochemical reaction device, and an oxide coating containing the specific compound may be formed on at least a portion of the surface of the specific member containing Mn that defines the portion of the specific gas flow path between the reformer and the electrochemical reaction device.

[0015] The reformer requires high temperatures (e.g., 500 to 700°C) for reforming. Therefore, the gas passing through the high-temperature reformer and flowing through the portion of the specific gas flow path between the reformer and the electrochemical reaction device becomes hot. Furthermore, the higher the gas temperature, the more likely Mn is to be dispersed into the gas from the specific surface of the specific component. Therefore, in a conventional configuration in which (all of) the Mn contained in the specific surface of the specific component, which is the portion of the specific gas flow path connecting the reformer and the electrochemical reaction device, is present in a state other than as a specific compound, Mn is particularly likely to be dispersed into the gas from the specific surface of the specific component.

[0016] In this electrochemical reaction module, in a configuration in which Mn is particularly susceptible to scattering in the gas, the oxide coating containing the specific compound is formed on the specific surface of the specific component, which defines the specific gas flow path and contains Mn, as described above, and this is particularly preferable because it prevents the Mn contained in the specific component from scattering in the gas.

[0017] (6) The method for manufacturing the electrochemical reaction module may include a preparation step of preparing a first material, the first material being a material for a component that defines the specific gas flow path and contains Mn, and a second material being a material that contains the specific element, and a firing step of arranging the first material and the second material in the same space in a firing furnace and firing the first material and the second material to form the oxide film on a specific surface of the first material that is at least a portion of the surface that defines the specific gas flow path, and to heat-treat the surface of the first material other than the specific surface. This manufacturing method allows the electrochemical reaction module to be manufactured more efficiently than a manufacturing method in which the step of forming the oxide film on the specific surface of the first material and the step of heat-treating the surface of the first material other than the specific surface are performed separately.

[0018] (7) In the method for manufacturing the electrochemical reaction module, the firing step may be configured to be a step of firing in an air atmosphere. According to this manufacturing method, the electrochemical reaction module can be manufactured efficiently.

[0019] (8) In the method for manufacturing the electrochemical reaction module, the firing step may be configured to be a step of firing in an inert atmosphere or an atmosphere containing hydrogen. According to this manufacturing method, the electrochemical reaction module can be manufactured efficiently.

[0020] The technology disclosed in this specification can be realized in various forms, for example, in the form of an electrochemical reaction module and a manufacturing method thereof. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a fuel cell module 10 according to a first embodiment. [Figure 2] FIG. 2 is a perspective view showing the external configuration of the fuel cell stack 100 shown in FIG. 1. [Figure 3] FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along the line III-III in FIG. 2. [Figure 4] 4 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along the line IV-IV in FIG. 2. [Figure 5] FIG. 3 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 at the position VV in FIG. 2. [Figure 6] FIG. 4 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 3. [Figure 7] FIG. 5 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 4. [Figure 8] 2 is an explanatory diagram showing an enlarged XY cross-sectional configuration of a portion (portion X in FIG. 1) of the fuel cell module 10. FIG. [Figure 9] 4 is a flowchart showing a method for manufacturing the fuel cell module 10 in the first embodiment. [Figure 10] 7. FIG. 8 is an explanatory diagram showing an enlarged XZ cross-sectional configuration of a part (corresponding to a part of FIG. 6 or FIG. 7) of a fuel cell stack 100A provided in a fuel cell module 10A according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] A. First embodiment: A-1. Configuration of fuel cell module 10: FIG. 1 is an explanatory diagram schematically showing the configuration of a fuel cell module 10 in a first embodiment. The fuel cell module 10 includes a fuel cell stack 100 and other devices (such as a reformer / heater 330, which will be described later). Below, the configuration of the fuel cell stack 100 will be described first, and then the configurations of the other devices that make up the fuel cell module 10 will be described. Note that the fuel cell module 10 is an example of an electrochemical reaction module in the claims, and the fuel cell stack 100 is an example of an electrochemical reaction device in the claims.

[0023] A-2. Configuration of fuel cell stack 100: FIG. 2 is a perspective view showing the external configuration of the fuel cell stack 100 shown in FIG. 1. FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along line III-III in FIG. 2. FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 taken along line IV-IV in FIG. 2. FIG. 5 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 taken along line VV in FIG. 2. Each figure shows mutually orthogonal X, Y, and Z axes for specifying directions (the same applies to FIG. 6 and subsequent figures). For convenience, the positive Z-axis direction will be referred to as the upward direction and the negative Z-axis direction will be referred to as the downward direction in this specification; however, the fuel cell stack 100 may actually be installed in an orientation different from these orientations. Note that the installation orientation of the fuel cell stack 100 may be changed without changing the installation orientation of the fuel cell module 10 or the installation orientation of devices other than the fuel cell stack 100 (for example, the arrangement direction of the power generation units 102 will be referred to as the Y-axis direction).

[0024] As shown in FIGS. 2 to 5, the fuel cell stack 100 includes a plurality of (seven in this embodiment) fuel cell power generation units (hereinafter simply referred to as "power generation units") 102 stacked in a predetermined arrangement direction (vertical direction (Z-axis direction) in this embodiment), a bottom separator 189, and a pair of end plates 104, 106. The seven power generation units 102 are arranged side by side in the predetermined arrangement direction (vertical direction in this embodiment). One of the pair of end plates 104, 106 (hereinafter referred to as the "upper end plate 104") is located above an assembly made up of a power generation block 103 consisting of the seven power generation units 102 and the bottom separator 189, and the other of the pair of end plates 104, 106 (hereinafter referred to as the "lower end plate 106") is located below the bottom separator 189, which is located below the power generation block 103. The pair of end plates 104, 106 are arranged to sandwich from above and below the power generation block 103 and the lower-end separator 189. The above-mentioned arrangement direction (vertical direction) corresponds to the first direction in the claims.

[0025] Holes that penetrate each layer in the vertical direction are formed near the four corners of the outer periphery around the Z-axis of each layer (upper end plate 104, each power generating unit 102, lower end separator 189) that make up the fuel cell stack 100, and holes (screw holes) are formed in the upper surface of the lower end plate 106 near the four corners of the outer periphery around the Z-axis. Corresponding holes formed in these layers communicate with each other in the vertical direction to form bolt holes 109 that extend in the vertical direction. In the following description, the holes formed in each layer of the fuel cell stack 100 to form the bolt holes 109 may also be referred to as bolt holes 109.

[0026] A bolt 22 is inserted into each bolt hole 109. The lower end of each bolt 22 is threaded into a threaded hole formed in the lower end plate 106, and a nut 24 is fitted onto the upper end of each bolt 22. The lower surface of the nut 24 abuts against the upper surface of the end plate 104 via an insulating sheet 26. The bolts 22 and nuts 24 configured in this manner fasten the layers of the fuel cell stack 100 together. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a pressed ceramic powder sheet, a glass sheet, a glass ceramic composite, or the like.

[0027] 2 to 4, four holes that vertically penetrate each layer are formed in the peripheral portion around the Z axis direction of each layer (each power generating unit 102, lower end separator 189, lower end plate 106) that make up the fuel cell stack 100, and corresponding holes formed in each layer are vertically connected to each other to form communication holes 108 that extend vertically from the uppermost power generating unit 102 to the lower end plate 106. In the following description, the holes formed in each layer of the fuel cell stack 100 to form the communication holes 108 may also be referred to as communication holes 108.

[0028] 2 and 3, one communication hole 108 located near one side (the side on the positive X-axis side of two sides parallel to the Y-axis) that constitutes the outer periphery of the fuel cell stack 100 around the Z-axis functions as an air electrode-side supply manifold 161, which is a gas flow path through which oxidant gas OG is introduced from outside the fuel cell stack 100 and supplied to an air chamber 166 (described later) of each power generation unit 102, and one communication hole 108 located near the opposite side (the side on the negative X-axis side of two sides parallel to the Y-axis) functions as an air electrode-side discharge manifold 162, which is a gas flow path through which oxidant off-gas OOG, which is gas discharged from the air chamber 166 of each power generation unit 102, is discharged to the outside of the fuel cell stack 100. Air, for example, is used as the oxidant gas OG.

[0029] 2 and 4, among the sides constituting the outer periphery of the fuel cell stack 100 around the Z axis, another communication hole 108 located near the side closest to the communication hole 108 functioning as the air electrode-side supply manifold 161 described above functions as the anode-side supply manifold 171, which is a gas flow path through which fuel gas FG is introduced from outside the fuel cell stack 100 and supplied to a fuel chamber 176 (described later) of each power generating unit 102, and another communication hole 108 located near the side closest to the communication hole 108 functioning as the air electrode-side discharge manifold 162 described above functions as the anode-side discharge manifold 172, which is a gas flow path through which fuel off-gas FOG, which is gas discharged from the fuel chamber 176 of each power generating unit 102, is discharged to the outside of the fuel cell stack 100. For example, hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG.

[0030] As shown in FIGS. 3 and 4, the fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body 28 and a hollow cylindrical branch portion 29 branching off from the side surface of the main body 28. The holes in the branch portion 29 are in communication with the holes in the main body 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. As shown in FIG. 3, the hole in the main body 28 of the gas passage member 27 arranged at the position of the air electrode-side supply manifold 161 is in communication with the air electrode-side supply manifold 161, and the hole in the main body 28 of the gas passage member 27 arranged at the position of the air electrode-side discharge manifold 162 is in communication with the air electrode-side discharge manifold 162. 4, the holes in main body 28 of gas passage member 27 arranged at the position of fuel electrode-side supply manifold 171 communicate with fuel electrode-side supply manifold 171, and the holes in main body 28 of gas passage member 27 arranged at the position of fuel electrode-side exhaust manifold 172 communicate with fuel electrode-side exhaust manifold 172. An insulating sheet 26 is interposed between each gas passage member 27 and the surface of lower end plate 106.

[0031] (Configuration of end plates 104 and 106) As shown in FIGS. 3 to 5 , the pair of end plates 104, 106 are flat, plate-shaped members with a substantially rectangular outer shape as viewed in the Z-axis direction, and are made of a conductive material such as stainless steel. Holes 32, 34 are formed near the centers of the pair of end plates 104, 106, respectively, penetrating in the Z-axis direction. As viewed in the Z-axis direction, the inner circumferential lines of the holes 32, 34 formed in each of the pair of end plates 104, 106 encompass each of the unit cells 110, which will be described later. Therefore, the compressive force in the Z-axis direction generated by fastening the bolts 22 and nuts 24 acts primarily on the periphery of each power generating unit 102 (the portion outer than each of the unit cells 110, which will be described later). In this embodiment, the upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

[0032] (Configuration of the lower separator 189) 3 to 5, the lower-end separator 189 is a flat member having a substantially rectangular outer shape when viewed in the Z-axis direction, and is made of, for example, metal. The peripheral edge of the lower-end separator 189 is sandwiched between the power generation block 103 and the lower end plate 106, and is joined to the lower end plate 106 by welding, for example, and is electrically connected to the lower end plate 106.

[0033] (Configuration of power generation unit 102) Figure 6 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in Figure 3, and Figure 7 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in Figure 4.

[0034] 6 and 7, the power generating unit 102 includes a fuel cell unit (hereinafter referred to as a "unit cell") 110, a unit cell separator 120, a pair of interconnectors 190 constituting the uppermost and lowermost layers of the power generating unit 102, an interconnector separator 191, an air electrode side frame 130, an anode side frame 140, and an anode side current collecting portion 144. Holes constituting the communication holes 108 that function as the manifolds 161, 162, 171, and 172, and holes constituting the bolt holes 109 are formed in the peripheral portions around the Z axis direction of the unit cell separator 120, the air electrode side frame 130, the anode side frame 140, and the interconnector separator 191.

[0035] The unit cell 110 is a fuel cell unit including an electrolyte layer 112, an air electrode 114 and an anode 116 that face each other in the Z-axis direction with the electrolyte layer 112 sandwiched therebetween, and a reaction prevention layer 118 that 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, and reaction prevention layer 118) that make up the unit cell 110. The unit cell 110 is an example of an electrochemical reaction unit cell as defined in the claims.

[0036] The electrolyte layer 112 is a substantially rectangular, flat-plate member when viewed in the Z-axis direction, and is configured to contain a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). That is, the unit cell 110 of this embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte. The air electrode 114 is a substantially rectangular, flat-plate member that is smaller than the electrolyte layer 112 when viewed in the Z-axis direction, and is configured to contain, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The fuel electrode 116 is a substantially rectangular, flat-plate member that is substantially the same size as the electrolyte layer 112 when viewed in the Z-axis direction, and is formed of, for example, Ni (nickel), a cermet made of Ni and ceramic particles, a Ni-based alloy, or the like. The reaction prevention layer 118 is a substantially rectangular, flat-plate member that is substantially the same size as the air electrode 114 when viewed in the Z-axis direction, and is configured to contain, for example, GDC (gadolinium-doped ceria) and YSZ. The reaction prevention layer 118 has the function of preventing elements (e.g., Sr) diffused from the air electrode 114 from reacting with elements (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO3).

[0037] The single cell separator 120 is a frame-like member formed with a substantially rectangular through-hole 121 penetrating vertically near the center, and is made of, for example, metal. The portion of the single cell separator 120 surrounding the through-hole 121 (hereinafter referred to as the "through-hole surrounding portion") faces the upper surface of the peripheral portion of the single cell 110 (electrolyte layer 112). The single cell separator 120 is joined (connected) to the single cell 110 (electrolyte layer 112) by a joint portion 124 formed with a brazing material (e.g., Ag brazing) placed in the facing portion. The single cell separator 120 defines an air chamber 166 facing the air electrode 114 and a fuel chamber 176 facing the fuel electrode 116, thereby suppressing gas leakage (cross-leakage) from one electrode side to the other electrode side at the peripheral portion of the single cell 110.

[0038] A glass seal portion 125 containing glass is disposed near the through-hole 121 in the unit cell separator 120. The glass seal portion 125 is located on the air chamber 166 side of the joint portion 124, and is formed so as to be in contact with both the surface of the unit cell separator 120 around the through-hole and the surface of the unit cell 110 (electrolyte layer 112 in this embodiment). The glass seal portion 125 effectively prevents gas leakage (cross leakage) from one electrode side to the other electrode side at the periphery of the unit cell 110.

[0039] The interconnector 190 is a conductive member having a flat plate portion 150 in the shape of a substantially rectangular plate and a plurality of substantially columnar air electrode-side current collecting portions 134 protruding from the flat plate portion 150 toward the air electrode 114, and is made of a metal containing Mn and Cr (e.g., ferritic stainless steel). In this embodiment, a conductive coating layer 194 made of, for example, a spinel-type oxide is formed on the surface of the interconnector 190 (the surface facing the air chamber 166). Hereinafter, the interconnector 190 covered with the coating layer 194 will be simply referred to as the interconnector 190. In each power generation unit 102, the upper interconnector 190 is disposed on the upper side of the single cell 110 across the air chamber 166 (on the opposite side of the electrolyte layer 112 in the Z-axis direction with respect to the air electrode 114). The upper interconnector 190 (of each air electrode-side current collecting portion 134) is bonded to the air electrode 114 of the unit cell 110 via a conductive bonding material 196 made of, for example, a spinel-type oxide, and is thereby electrically connected to the air electrode 114 of the unit cell 110. In each power generating unit 102, the lower interconnector 190 is disposed below the unit cell 110 with the fuel chamber 176 interposed therebetween, and is electrically connected to the anode 116 of the unit cell 110 via an anode-side current collecting portion 144, which will be described later. The interconnector 190 ensures electrical conduction between the power generating units 102 and also suppresses mixing of reactant gases between the power generating units 102. In this embodiment, when two power generating units 102 are disposed adjacent to each other, one interconnector 190 is shared by the two adjacent power generating units 102. That is, the upper interconnector 190 of a certain power generating unit 102 is the same material as the lower interconnector 190 of another power generating unit 102 adjacent to the upper side of that power generating unit 102. Also, because the fuel cell stack 100 is provided with a lower-end separator 189, the power generating unit 102 located at the bottom of the fuel cell stack 100 does not have a lower interconnector 190 (see Figures 3 to 5).

[0040] The interconnector separator 191 is a frame-like member having a substantially rectangular through-hole 181 formed near the center and penetrating in the vertical direction, and is made of, for example, metal. A portion of the interconnector separator 191 surrounding the through-hole 181 (hereinafter referred to as the "through-hole surrounding portion") is joined to the upper surface of the peripheral portion of the interconnector 190, for example by welding. Of a pair of interconnector separators 191 included in a certain power generating unit 102, the upper interconnector separator 191 separates the air chamber 166 of that power generating unit 102 from the fuel chamber 176 of another power generating unit 102 adjacent to the power generating unit 102 on the upper side. Furthermore, of a pair of interconnector separators 191 included in a certain power generating unit 102, the lower interconnector separator 191 separates the fuel chamber 176 of that power generating unit 102 from the air chamber 166 of another power generating unit 102 adjacent to the power generating unit 102 on the lower side. In this way, the interconnector separator 191 prevents gas leakage between the power generating units 102 at the periphery of the power generating units 102. The interconnector separator 191 joined to the upper interconnector 190 of the power generating unit 102 located at the uppermost position in the fuel cell stack 100 is electrically connected to the upper end plate 104.

[0041] The air electrode side frame 130 is a frame-shaped member with a substantially rectangular hole 131 formed near the center that penetrates in the vertical direction, and is made of an insulator such as mica. The hole 131 in the air electrode side frame 130 forms an air chamber 166 that faces the air electrode 114. The air electrode side frame 130 is in contact with the upper surface of the peripheral portion of the single cell separator 120 and the lower surface of the peripheral portion of the upper interconnector separator 191, and functions as a sealing member that ensures gas sealing between the two (i.e., gas sealing of the air chamber 166). The air electrode side frame 130 also provides electrical insulation between a pair of interconnector separators 191 included in the power generation unit 102 (i.e., between a pair of interconnectors 190). The air electrode side frame 130 is formed with an air electrode side supply communication flow path 132 that connects the air electrode side supply manifold 161 and the air chamber 166, and an air electrode side discharge communication flow path 133 that connects the air chamber 166 and the air electrode side discharge manifold 162.

[0042] The fuel electrode side frame 140 is a frame-like member having a substantially rectangular hole 141 formed near the center that penetrates in the vertical direction, and is made of, for example, metal. The hole 141 in the fuel electrode side frame 140 forms a fuel chamber 176 that faces the fuel electrode 116. The fuel electrode side frame 140 is in contact with the lower surface of the peripheral portion of the unit cell separator 120 and the upper surface of the peripheral portion of the lower interconnector separator 191. The fuel electrode side frame 140 is formed with a fuel electrode side supply communicating channel 142 that connects the fuel electrode side supply manifold 171 and the fuel chamber 176, and a fuel electrode side discharge communicating channel 143 that connects the fuel chamber 176 and the fuel electrode side discharge manifold 172.

[0043] The anode side current collecting portion 144 is disposed within the fuel chamber 176. The anode side current collecting portion 144 includes an interconnector facing portion 146, an electrode facing portion 145, and a connecting portion 147 connecting the electrode facing portion 145 and the interconnector facing portion 146, and is formed of, for example, nickel, a nickel alloy, stainless steel, or the like. The electrode facing portion 145 is in contact with the lower surface of the anode 116, and the interconnector facing portion 146 is in contact with the upper surface of the interconnector 190. However, as described above, the power generating unit 102 located at the bottom of the fuel cell stack 100 does not include a lower interconnector 190, and therefore the interconnector facing portion 146 of the anode side current collecting portion 144 of that power generating unit 102 is in contact with the lower-end separator 189. The anode side current collecting portion 144 has such a configuration, and thus electrically connects the anode 116 and the interconnector 190 (or the lower-end separator 189). A spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 of the fuel electrode side current collecting portion 144 and the interconnector facing portion 146. This allows the fuel electrode side current collecting portion 144 to follow deformation of the power generating unit 102 due to temperature cycles and reactant gas pressure fluctuations, and good electrical connection between the fuel electrode 116 and the interconnector 190 (or the lower-end separator 189) via the fuel electrode side current collecting portion 144 is maintained.

[0044] A-3. Configuration of devices other than the fuel cell stack 100 in the fuel cell module 10: Next, the configuration of devices other than the fuel cell stack 100 in the fuel cell module 10 will be described. As shown in FIG. 1, the fuel cell module 10 includes an auxiliary device 300 including an evaporator 310 and a reformer / heater 330, and various flow paths connecting each device. Each device (fuel cell stack 100, auxiliary device 300) is housed in an insulated space 351 surrounded by a heat insulating material 350. For convenience, the heat insulating material 350 is depicted in FIG. 1 as having a simple rectangular shape that surrounds all of the devices. In reality, however, it surrounds all of the devices and also surrounds each device. In FIG. 1, the flow of gases (including raw fuel gas RFG, fuel gas FG, and fuel off-gas FOG) on the fuel electrode side is indicated by a dashed line, the flow of gases (including oxidant gas OG and oxidant off-gas OOG) on the air electrode side is indicated by a solid line, the flow of exhaust gas EG is indicated by a dashed line, and the flow of water is indicated by a two-dot chain line.

[0045] The evaporator 310 is a box-shaped member with an internal space and is made of, for example, metal. The evaporator 310 is a device for evaporating water WA to generate steam. A pure water inlet flow path 251 for introducing the water WA is connected to the evaporator 310. The pure water inlet flow path 251 is mainly composed of piping, and an ion exchange resin (not shown), a purified water tank / float (not shown), and a flow control mechanism (not shown) are provided on the pure water inlet flow path 251. The water WA supplied from a water supply source (not shown) to the pure water inlet flow path 251 is subjected to removal of calcium ions and the like by the ion exchange resin, purified and stored in the purified water tank / float, and introduced as pure water into the evaporator 310 at a flow rate controlled by the flow control mechanism.

[0046] A raw fuel gas introduction passage 261 for introducing the raw fuel gas RFG is also connected to the evaporator 310. The raw fuel gas introduction passage 261 is mainly composed of piping, and a flow rate control mechanism (not shown) and a hydrodesulfurizer (not shown) are provided on the raw fuel gas introduction passage 261. The raw fuel gas RFG supplied from a gas source to the raw fuel gas introduction passage 261 has sulfur components removed in the hydrodesulfurizer, and is then introduced into the evaporator 310 at a flow rate controlled by the flow rate control mechanism.

[0047] Also connected to the evaporator 310 are an exhaust gas relay passage 226 for sending the exhaust gas EG from a housing 335 (described later) of the reformer / heater 330 to the evaporator 310, a mixed gas passage 228 for sending the mixed gas from the evaporator 310 to a reformer 331 (described later) of the reformer / heater 330, and an exhaust gas discharge passage (not shown) for discharging the exhaust gas EG from the evaporator 310. These passages are mainly composed of piping.

[0048] The reformer / heater 330 includes a reformer 331, a combustor 333, and a housing 335. The housing 335 is a sealed container made of, for example, metal, and houses the reformer 331 and the combustor 333. The housing 335 has a double-wall structure including an inner wall 336 and an outer wall 337. Heat transfer fins 339 are arranged in an air flow path 338 formed between the inner wall 336 and the outer wall 337. Note that part of the heat transfer fins 339 is not shown in FIG. 1 . An air introduction flow path 271 for introducing an oxidant gas OG (air) is connected to the housing 335. The air introduction flow path 271 is mainly composed of piping, and a flow rate control mechanism (not shown) is provided on the air introduction flow path 271. The oxidant gas OG supplied to the air introduction flow path 271 is introduced into the air flow path 338 of the housing 335 at a flow rate controlled by the flow rate control mechanism. In addition, the housing 335 is connected to an air electrode side gas supply passage 61 for sending out an oxidant gas OG toward an air electrode side supply manifold 161 (described later) of the fuel cell stack 100. The air electrode side gas supply passage 61 is mainly composed of piping.

[0049] The reformer 331 is a box-shaped member with an internal space, and is made of, for example, metal. The reformer 331 is a device for reforming (steam reforming) raw fuel gas RFG to generate fuel gas FG. A catalyst for promoting the reforming reaction is disposed within the reformer 331. As described above, the reformer 331 is connected to the mixed gas flow path 228 for sending mixed gas from the evaporator 310 to the reformer 331. The reformer 331 is also connected to the fuel electrode side gas supply flow path 71 for sending fuel gas FG toward the fuel electrode side supply manifold 171 (described below) of the fuel cell stack 100. The fuel electrode side gas supply flow path 71 is mainly composed of piping.

[0050] The combustor 333 is a box-shaped member with an internal space and is made of, for example, metal. The combustor 333 is a device for combusting the oxidant off-gas OOG and the fuel off-gas FOG. A catalyst for promoting the combustion of the oxidant off-gas OOG and the fuel off-gas FOG may be disposed inside the combustor 333. The combustor 333 is connected to an air electrode-side gas discharge flow path 240 through which the oxidant off-gas OOG is discharged from the air electrode-side discharge manifold 162 of the fuel cell stack 100, and an anode-side gas discharge flow path 230 through which the fuel off-gas FOG is discharged from the anode-side discharge manifold 172 of the fuel cell stack 100. These flow paths are mainly composed of piping.

[0051] A-4. Operation of fuel cell module 10: Next, the operation of the fuel cell module 10 will be described. As shown in FIG. 1, the oxidant gas OG flows through the air inlet passage 271 and is introduced into the air passage 338 formed in the housing 335 of the reformer / heater 330. The oxidant gas OG introduced into the air passage 338 flows through the air passage 338 while being heated by the combustion heat (exhaust gas EG) generated by the combustor 333, and is supplied to the air electrode-side supply manifold 161 of the fuel cell stack 100 via the air electrode-side gas supply passage 61. As shown in FIGS. 3 and 5, the oxidant gas OG supplied to the air electrode-side supply manifold 161 is supplied from the air electrode-side supply manifold 161 to the air chamber 166 via the air electrode-side supply communication passage 132 of each power generation unit 102. 1, when raw fuel gas RFG is supplied to evaporator 310 via raw fuel gas introduction passage 261 and water WA is supplied to evaporator 310 via pure water introduction passage 251, the evaporator 310 uses the heat of exhaust gas EG introduced via exhaust gas relay passage 226 to evaporate the water WA, generating steam, which is then mixed with raw fuel gas RFG. The raw fuel gas RFG mixed with the steam is introduced from evaporator 310 via mixed gas passage 228 to reformer 331, where it is steam reformed, generating hydrogen-rich fuel gas FG. The generated fuel gas FG is supplied to fuel electrode-side supply manifold 171 of fuel cell stack 100 via fuel electrode-side gas supply passage 71. As shown in Figures 4 and 6, fuel gas FG supplied to the fuel electrode side supply manifold 171 is supplied from the fuel electrode side supply manifold 171 to the fuel chamber 176 via the fuel electrode side supply communication channel 142 of each power generation unit 102.

[0052] When an oxidant gas OG is supplied to the air chamber 166 of each power generating unit 102 and a fuel gas FG is supplied to the fuel chamber 176, power is generated in the unit cells 110 of each power generating unit 102 through an electrochemical reaction between the oxygen contained in the oxidant gas OG and the hydrogen contained in the fuel gas FG. This power generation reaction is exothermic. In each power generating unit 102, the air electrode 114 of the unit cell 110 is electrically connected to one interconnector 190 via the air electrode-side current collector 134, and the anode 116 is electrically connected to the other interconnector 190 via the anode-side current collector 144. The multiple power generating units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, electrical energy generated in each power generating unit 102 is extracted from the end plates 104, 106, which function as output terminals of the fuel cell stack 100. Note that SOFCs generate power at relatively high temperatures (e.g., 700°C to 1000°C).

[0053] As shown in FIGS. 1, 3, and 6, the oxidant off-gas OOG discharged from the air chamber 166 of each power generating unit 102 through the air electrode-side exhaust communication channel 133 to the air electrode-side exhaust manifold 162 is introduced into the combustor 333 through the air electrode-side gas exhaust channel 240. As shown in FIGS. 1, 4, and 7, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generating unit 102 through the anode-side exhaust communication channel 143 to the anode-side exhaust manifold 172 is introduced into the combustor 333 through the anode-side gas exhaust channel 230. The oxidant off-gas OOG and fuel off-gas FOG introduced into the combustor 333 are mixed and combusted in the combustor 333, and then discharged as exhaust gas EG to the evaporator 310 through the exhaust gas relay channel 226. The heat generated in the combustor 333 promotes the reforming reaction in the reformer 331 and heats the fuel cell stack 100.

[0054] A-5. Detailed configuration of the fuel electrode side gas supply channel 71 and its surroundings: As described above, the fuel electrode-side gas supply channel 71 is a channel for sending out fuel gas FG from the reformer 331 toward the fuel electrode-side supply manifold 171 of the fuel cell stack 100 (see FIG. 1), and is mainly composed of piping, as shown in FIG. 8. Hereinafter, the member that constitutes (defines) the fuel electrode-side gas supply channel 71 will be referred to as a specific piping member 71P. The specific piping member 71P is an example of a specific member in the claims.

[0055] Fig. 8 is an explanatory diagram showing an enlarged XY cross-sectional configuration of a portion (X portion in Fig. 1) of the fuel cell module 10. Fig. 8 shows the XY cross-sectional configuration of a specific piping member 71P that constitutes (defines) the fuel electrode-side gas supply flow path 71. Note that Fig. 8 shows only a portion of the specific piping member 71P, and the illustration of other portions is omitted.

[0056] It can be said that a series of gas flow paths (hereinafter referred to as the "specific gas flow path") 400, which is made up of the raw fuel gas introduction flow path 261 formed in the fuel cell module 10, the mixed gas flow path 228, the fuel electrode-side gas supply flow path 71, the flow paths through which the fuel gas FG passes within the fuel cell stack 100 (fuel electrode-side supply manifold 171, fuel chamber 176, etc.), and the flow paths within each device (reformer 331, etc.) provided between these flow paths, is a gas flow path through which the gas supplied to the fuel electrode 116 flows. In this case, it can be said that the fuel electrode-side gas supply flow path 71 is a part of the specific gas flow path 400, and also a portion of the specific gas flow path 400 that connects the reformer 331 and the fuel cell stack 100.

[0057] 8, the specific piping member 71P is a cylindrical member having a gas flow path formed therein. The specific piping member 71P is made of a member (for example, a metal) containing Mn (manganese) and Cr (chromium).

[0058] An oxide coating OC1 containing a compound of Mn and Si (silicon) is formed on at least a portion (hereinafter referred to as the "specific surface") 71S of the surface of the specific piping member 71P (the surface defining the flow path through which the gas flowing to the anode 116 passes). Si corresponds to at least one element (hereinafter referred to as the "specific element") selected from Si, Al (aluminum), Ti (titanium), and S (sulfur). The compound of Mn and Si is Mn2SiO4 (manganese silicate) or a compound in which at least one of the Mn and Si contained in Mn2SiO4 is partially substituted with another element. Si is an example of a specific element in the claims, and a compound of Mn and Si is an example of a specific compound in the claims.

[0059] In the oxide coating film OC1 of this embodiment, X-ray diffraction identifies compounds in which at least one of Mn and Si contained in MnSiO4 or MnSiO4 is partially substituted with another element, but does not identify MnO. The measurement conditions for this X-ray diffraction are as follows: a tube voltage of 40 kV, a tube current of 20 mA, and a wavelength of CuKα (1.541862 Å). The phrase "MnO is not identified" refers to the observation of two or more peaks attributed to MnO within the measurement range of 10° to 80° (the same applies hereinafter).

[0060] The content of the specific element (Si) in the oxide coating film OC1 of this embodiment is 10 mass % or more (for example, 14 mass % in the case of Mn2SiO4). The content of the specific element (Si) in the oxide coating film OC1 can be measured by performing ICP emission spectrometry on a sample obtained by dissolving the oxide coating film OC1 (or the specific piping member 71P on which the oxide coating film OC1 is formed) using nitric acid or the like.

[0061] A-6. Manufacturing method of fuel cell module 10: 9 is a flowchart showing a method for manufacturing the fuel cell module 10 according to the first embodiment. The method for manufacturing the fuel cell module 10 is, for example, as follows.

[0062] First, a first material M1, which is the material of the specific piping member 71P, and a second material M2, which is a material containing a specific element (Si), are prepared (preparation step S11). The first material M1 is a member (e.g., a metal) containing Mn and Cr. The second material M2 is, for example, mica. Hereinafter, the portion of the surface of the first material M1 on which an oxide film OC1 containing a compound of Mn and Si (silicon) is formed is referred to as the "specific surface 71S."

[0063] Next, the first material M1 and the second material M2 are placed in the same space in a firing furnace and fired. This forms an oxide film OC1 on the specific surface 71S of the first material M1, and heat-treats the surface of the first material M1 other than the specific surface 71S. Specifically, the first material M1 and the second material M2 are placed in the same space in the firing furnace so that the second material M2 faces the specific surface 71S of the first material M1. Regarding the firing method, for example, for components that can tolerate dimensional changes due to the formation of an oxide film, firing is performed in an air atmosphere (firing temperature, for example, 1000°C). For components that cannot tolerate dimensional changes due to the formation of an oxide film (e.g., threaded joints or bolts), firing is performed in an inert atmosphere or an atmosphere containing hydrogen (firing temperature, for example, 900°C). Alternatively, the second material M2 (mica) may be mixed with water, and the resulting vapor may be bubbled with hydrogen gas and passed through the first material M1 at a predetermined temperature (e.g., about 850°C) for a predetermined time (e.g., about 10 hours), thereby adhering Si to the specific surface 71S of the first material M1. By carrying out these processes, an oxide coating OC1 containing Mn2SiO4, a compound of Mn and Si, is formed on the specific surface 71S of the first material M1.

[0064] Next, the remaining steps, such as assembling the specified piping member 71P and assembling other devices and flow paths, are carried out (S13), thereby completing the manufacture of the fuel cell module 10 configured as described above.

[0065] A-7. Advantages of the first embodiment: As described above, the fuel cell module 10 of this embodiment includes a fuel cell stack 100 having unit cells 110 each including an electrolyte layer 112 containing a solid oxide, and an air electrode 114 and an anode 116 that face each other across the electrolyte layer 112. The fuel cell module 10 is formed with a specific gas flow path 400 through which a gas supplied to the anode 116 flows. An oxide coating OC1 that faces the specific gas flow path 400 and contains a specific compound that is a compound of Mn and a specific element (Si) is formed on at least a portion of a surface (hereinafter referred to as the "specific surface") 71S of a specific piping member 71P that defines the specific gas flow path 400 and contains Mn.

[0066] As described above, in the fuel cell module 10 of this embodiment, an oxide coating OC1 that faces the specific gas flow path 400 and contains a specific compound, which is a compound of Mn and a specific element (Si), is formed on the specific surface 71S of the specific piping member 71P, which defines the specific gas flow path 400 and contains Mn. Therefore, in the fuel cell module 10 of this embodiment, even though the specific piping member 71P that defines the specific gas flow path 400 contains Mn, the Mn contained in the specific piping member 71P is prevented from scattering into the gas. This is because the Mn becomes a specific compound (a compound of Mn and the specific element (Si)), making it less likely to scatter into the gas. Therefore, with the fuel cell module 10 of this embodiment, an increase in Mn vapor pressure in the fuel chamber 176 can be suppressed compared to the conventional technology, thereby improving the performance of the unit cell 110.

[0067] In the fuel cell module 10 of this embodiment, MnO is not identified in the oxide film OC1 by X-ray diffraction. Therefore, in the fuel cell module 10 of this embodiment, Mn contained in the specific piping member 71P is less likely to scatter into the gas than in a configuration in which MnO is identified in the oxide film OC1 by X-ray diffraction. Therefore, the fuel cell module 10 of this embodiment can more effectively suppress an increase in Mn vapor pressure in the fuel chamber 176, thereby improving the performance of the unit cell 110.

[0068] In the fuel cell module 10 of this embodiment, the specific piping member 71P, which is a member containing Mn, also contains Cr. Therefore, in the fuel cell module 10 of this embodiment, Cr2O3 is formed on the surface of the specific piping member 71P. Therefore, a compound of Mn and Cr (such as (Cr, Mn)3O4) with a low Mn vapor pressure is formed using the compound of Mn and the specific element (Si) formed on the surface of the specific piping member 71P as a nucleus, which further suppresses Mn from scattering into the fuel chamber 176. Therefore, the fuel cell module 10 of this embodiment can more effectively suppress an increase in Mn vapor pressure in the fuel chamber 176, thereby improving the performance of the unit cell 110.

[0069] In the fuel cell module 10 of this embodiment, the specific element (at least one element selected from Si, Al, Ti, and S) is Si, and the specific compound (a compound of Mn and Si) is Mn2SiO4 or a compound in which at least one of the Mn and Si contained in Mn2SiO4 is partially substituted with another element. Because Si has a particularly high reactivity with Mn, the fuel cell module 10 of this embodiment can more effectively suppress an increase in Mn vapor pressure in the fuel chamber 176 compared to a configuration containing only a specific element other than Si (for example, Ti, Al, or S), thereby improving the performance of the unit cell 110.

[0070] In the fuel cell module 10 of this embodiment, the unit cell 110 is a unit fuel cell. The fuel cell module 10 includes a reformer 331 having a space communicating with a specific gas flow path 400, which reforms the gas supplied to the fuel cell stack 100. An oxide film OC1 containing a specific compound (a compound of Mn and a specific element (Si)) is formed on a portion of the specific gas flow path 400 that connects the reformer 331 and the fuel cell stack 100 (a fuel electrode-side gas supply flow path 71).

[0071] The reformer 331 requires a high temperature (for example, 500 to 700°C) for reforming. Therefore, the gas that passes through the high-temperature reformer 331 and flows through the portion of the specific gas flow path 400 between the reformer 331 and the fuel cell stack 100 becomes hot. Furthermore, the higher the gas temperature, the more likely Mn is to be dispersed into the gas from the specific surface 71S of the specific piping member 71P. Therefore, in a conventional configuration in which (all of) the Mn contained in the specific surface 71S of the specific piping member 71P, which is the portion of the specific gas flow path 400 that connects the reformer 331 and the fuel cell stack 100, is present in a state other than as a specific compound, Mn is particularly likely to be dispersed into the gas from the specific surface 71S.

[0072] In the fuel cell module 10 of this embodiment, in a configuration in which Mn is particularly susceptible to scattering in the gas, as described above, an oxide coating OC1 containing a specific compound is formed on the specific surface 71S of the specific piping member 71P, which is a member that defines the specific gas flow path 400 and contains Mn, thereby preventing the Mn contained in the specific piping member 71P from scattering in the gas, which is particularly preferable.

[0073] The manufacturing method of the fuel cell module 10 of this embodiment includes the above-described preparation step S11 and firing step S12. The preparation step S11 is a step of preparing a first material M1, which is a material for the specific piping member 71P that defines the specific gas flow path 400 and is a member containing Mn, and a second material M2, which is a material containing the specific element (Si). The firing step S12 is a step of firing the first material M1 and the second material M2 in a state where the first material M1 and the second material M2 are arranged in the same space in a firing furnace, thereby forming an oxide film OC1 on the specific surface 71S of the first material M1 and performing a heat treatment on the surface of the first material M1 other than the specific surface 71S. This manufacturing method allows the above-described fuel cell module 10 to be manufactured more efficiently than a manufacturing method in which the step of forming the oxide film OC1 on the specific surface 71S of the first material M1 and the step of performing a heat treatment on the surface of the first material M1 other than the specific surface 71S are performed separately.

[0074] In the manufacturing method of the fuel cell module 10 of this embodiment, the firing step S12 may be a step in which firing is performed in an air atmosphere. According to this manufacturing method, the fuel cell module 10 can be manufactured efficiently.

[0075] In the manufacturing method of the fuel cell module 10 of this embodiment, the firing step S12 may be a step of performing firing in an inert atmosphere or an atmosphere containing hydrogen. According to this manufacturing method, the fuel cell module 10 can be manufactured efficiently.

[0076] B. Second embodiment: FIG. 10 is an explanatory diagram showing an enlarged XZ cross-sectional configuration of a part (corresponding to a part of FIG. 6 or FIG. 7) of a fuel cell stack 100A provided in a fuel cell module 10A according to the second embodiment.

[0077] The configuration of the fuel cell module 10A of the second embodiment is basically the same as the configuration of the fuel cell module 10 of the first embodiment, except for the configuration of the interconnector 190A of the fuel cell stack 100A. In the following, the configuration of the fuel cell module 10A of the second embodiment that is the same as that of the fuel cell module 10 of the first embodiment described above will be denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0078] 10, an oxide coating OC2 containing a specific compound, which is a compound of Mn and a specific element (Si), is formed on at least a portion (hereinafter referred to as the "specific surface") 190S of the surface (the surface defining the fuel chamber 176, which is the flow path through which the gas flowing to the anode 116 passes) of an interconnector 190A (more specifically, the portion corresponding to the flat plate portion 150) of a fuel cell stack 100A included in a fuel cell module 10A of the second embodiment. Note that the interconnector 190A, which is the member defining the fuel chamber 176, is a member that constitutes (defines) a part of the specific gas flow path 400A, which is the gas flow path through which the gas supplied to the anode 116 passes, and corresponds to the specific member in the claims.

[0079] According to the fuel cell module 10A of this embodiment, as described above, an oxide film OC2 containing a specific compound (a compound of Mn and a specific element (Si)) is formed on the specific surface 190S of the interconnector 190A, thereby achieving the same effect as that achieved by the oxide film OC1 in the first embodiment. That is, according to the fuel cell module 10A of this embodiment, compared to the above-mentioned conventional technology, an increase in Mn vapor pressure in the fuel chamber 176 can be suppressed, thereby improving the performance of the unit cell 110.

[0080] In the oxide film OC2 of this embodiment, MnO is not identified by X-ray diffraction. Furthermore, the interconnector 190A of this embodiment is formed of a material containing Mn and Cr (e.g., ferritic stainless steel). Furthermore, the content of the specific element (Si) in the oxide film OC2 of this embodiment is 10 mass % or more (e.g., 14 mass % in the case of Mn2SiO4). The effects of these configurations are basically the same as those of the first embodiment.

[0081] In this embodiment, an oxide film OC1 containing a compound of Mn and a specific element (Si) may be formed on the specific surface 71S of the specific piping member 71P as in the first embodiment, but the oxide film OC1 may not be formed.

[0082] The manufacturing method of the fuel cell module 10A of this embodiment is basically the same, but an oxide film OC2 is formed on a specific surface 190S of the first material M1 (the material of the interconnector 190A in this embodiment), and the heat treatment performed on the surface of the first material M1 other than the specific surface 190S may be, for example, a process of baking a paste material for forming the coating layer 194 onto the surface of the interconnector 190A.

[0083] C. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the spirit thereof, for example, the following modifications are also possible.

[0084] The configuration of the fuel cell module 10 and the configuration of each part that makes up the fuel cell module 10 in the above embodiment are merely examples and can be modified in various ways. The configuration of the fuel cell stacks 100, 100A and the configuration of each part that makes up the fuel cell stacks 100, 100A in the above embodiment are also merely examples and can be modified in various ways.

[0085] In the above embodiment, oxide coatings OC1 and OC2 containing a specific compound that is a compound of Mn and a specific element (Si is at least one element selected from Si, Al, Ti, and S) are formed on the surface (specific surface 71S) of specific piping member 71P and the surface (specific surface 190S) of interconnector 190A, but a configuration may also be used in which an oxide coating containing a specific compound is formed on the surface of another member that defines specific gas flow paths 400 and 400A through which gas supplied to fuel electrode 116 flows and that contains Mn. In this configuration, the other member corresponds to the specific member in the claims, and the surface of the other member on which the oxide coating is formed (the surface that defines the flow path through which gas flowing to fuel electrode 116 passes) corresponds to the specific surface.

[0086] In the above embodiment, the specific element contained in the oxide coatings OC1 and OC2 formed on the surfaces of the members (71P and 190A) that define the specific gas flow paths 400 and 400A through which the gas supplied to the fuel electrode 116 flows is Si (Si is at least one element selected from Si, Al, Ti, and S), which is particularly preferred because Si is easily volatilized when it comes into contact with water vapor. However, instead of or in addition to Si, an element other than Si (e.g., Al, Ti, S) may be used as the specific element.

[0087] In the above embodiment, MnO is not identified in the oxide films OC1 and OC2 by X-ray diffraction, but MnO may be identified by X-ray diffraction.

[0088] In addition, in the second embodiment, an oxide film OC2 is formed on the interconnectors 190A of all power generation units 102 included in the fuel cell stack 100A, but it is not necessarily necessary that an oxide film OC2 is formed on all power generation units 102 included in the fuel cell stack 100A; it is sufficient that an oxide film OC2 is formed on at least one power generation unit 102.

[0089] The members (specific piping member 71P, interconnector 190A) that define the specific gas flow paths 400, 400A through which the gas supplied to the fuel electrode 116 flows and that contain Mn may not contain Cr.

[0090] Furthermore, in the above embodiment, the interconnector 190 includes a conductive coating layer 194, but the interconnector 190 may not include the coating layer 194. Furthermore, in the above embodiment, the unit cell 110 has a reaction prevention layer 118, but the unit cell 110 may not have a reaction prevention layer 118. Furthermore, in the above embodiment, the number of unit cells 110 (the number of power generation units 102) included in the fuel cell stack 100 is merely an example, and the number of unit cells 110 is determined appropriately depending on the output voltage required for the fuel cell stack 100, etc. Furthermore, the materials constituting each component in the above embodiment are merely examples, and each component may be made of other materials.

[0091] The interconnectors 190 and 190A may not contain Cr.

[0092] In the interconnectors 190 and 190A, each part (the flat plate part 150, the air electrode side current collecting part 134, the coating layer 194, and the oxide film OC2) may be partly or entirely made of a single member.

[0093] Although the fuel cell stack 100 of the above embodiment is a co-flow type SOFC, the technology disclosed in this specification is also applicable to counter-flow type SOFCs and cross-flow type SOFCs.

[0094] The present invention may also be applied to a configuration including a metal-supported unit cell 110, as described in JP 2018-195414 A. In this configuration, the same effects as those of the above embodiment can be obtained.

[0095] Furthermore, while the above embodiment is directed to a fuel cell stack 100 that generates electricity by utilizing an electrochemical reaction between hydrogen contained in a fuel gas and oxygen contained in an oxidant gas, the technology disclosed in this specification is similarly applicable to an electrolysis cell stack that includes multiple electrolysis unit cells, which are constituent units of a solid oxide electrolysis cell (SOEC) that generates hydrogen by utilizing the electrolysis reaction of water. The basic configuration of an electrolysis cell stack is publicly known, as described in, for example, JP 2016-81813 A, and is roughly as follows. That is, the configuration of the electrolysis cell stack is the same as the configuration of the fuel cell stack 100 of the above-described embodiment, except that "power generation unit" is replaced with "electrolysis cell unit", "single cell" is replaced with "electrolysis single cell", "oxidant gas supply manifold" is replaced with "air discharge manifold", "oxidant gas discharge manifold" is replaced with "air supply manifold", "fuel gas supply manifold" is replaced with "hydrogen discharge manifold", "fuel gas discharge manifold" is replaced with "steam supply manifold", "oxidant gas supply communicating channel" is replaced with "air discharge communicating channel", "oxidant gas discharge communicating channel" is replaced with "air supply communicating channel", "fuel gas supply communicating channel" is replaced with "hydrogen discharge communicating channel", and "fuel gas discharge communicating channel" is replaced with "steam supply communicating channel".

[0096] During operation of the electrolysis cell stack, a voltage is applied to the electrolysis cell stack so that the air electrode 114 is positive (anode) and the fuel electrode (hydrogen electrode) 116 is negative (cathode). Steam is supplied as a raw material gas to the steam supply manifold via the gas passage member 27. The supplied steam may contain hydrogen gas. The steam supplied to the steam supply manifold is then supplied to the fuel chamber 176 from the steam supply manifold via the steam supply communication channel of each electrolysis cell unit, and is used for the water electrolysis reaction in each electrolysis unit cell. The hydrogen gas generated in the fuel chamber 176 by the water electrolysis reaction in each electrolysis unit cell is discharged, together with excess steam, via the hydrogen discharge communication channel to the hydrogen discharge manifold, and is then taken out of the electrolysis cell stack from the hydrogen discharge manifold via the gas passage member 27.

[0097] During operation of the electrolytic cell stack, air is supplied to the interior of the electrolytic cell stack as needed, for example to control the temperature of the electrolytic cell stack. In this case, air is supplied to the air supply manifold via the gas passage member 27, and then supplied from the air supply manifold to the air chamber 166 via the air supply communicating flow path of each electrolytic cell unit. The air supplied to the air chamber 166 is discharged together with oxygen generated at the air electrode 114 via the air discharge communicating flow path to the air discharge manifold, and then from the air discharge manifold to the outside of the electrolytic cell stack via the gas passage member 27.

[0098] In an electrolysis cell stack having such a configuration, by adopting the same configuration as the fuel cell stack 100 in the above embodiment, the same effects as those of the fuel cell stack 100 in the above embodiment can be achieved.

[0099] Furthermore, although the above embodiment has been described using a solid oxide fuel cell (SOFC) as an example, the technology disclosed in this specification can also be applied to other types of fuel cells (or electrolytic cells), such as a molten carbonate fuel cell (MCFC). [Explanation of symbols]

[0100] 10, 10A: fuel cell module 22: bolt 24: nut 26: insulating sheet 27: gas passage member 28: main body portion (of gas passage member) 29: branch portion (of gas passage member) 32,34: Hole 61: Air electrode side gas supply flow path 71: Anode side gas supply flow path 71P: Specific component 71S: Specific surface (of the anode side gas supply flow path) 100, 100A: Fuel cell stack 102: Power generation unit 103: Power generation block 104: Upper end plate 106: Lower end plate 108: Communication hole 109: Bolt hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Anode 118: Reaction prevention layer 120: Single cell separator 121: Through hole 124: Joint 125: Glass seal 130: Air electrode side frame 131: Hole 132: Air electrode side supply communication flow path 133: Air electrode side discharge communication flow path 134: Air electrode side current collecting part 140: Anode side frame 141: Hole 142: Anode side supply communicating flow path 143: Anode side discharge communicating flow path 144: Anode side current collecting portion 145: Electrode opposing portion (of anode side current collecting portion) 146: Interconnector opposing portion (of anode side current collecting portion) 147: Connection portion (of anode side current collecting portion) 149: Spacer (of anode side current collecting portion) 150: Flat portion (of interconnector) 161: Air electrode side supply manifold 162: Air electrode side discharge manifold 166: Air chamber 171: Anode side supply manifold 172: Anode side discharge manifold 176: Fuel chamber 180: IC separator 181: Through hole 189: Lower end separator 190, 190A: Interconnector 190S: Specific surface (of interconnector) 191: Interconnector separator 194: Coating layer 196: Conductive adhesive material 226: Exhaust gas relay flow path 228: Mixed gas flow path 230: Anode side gas exhaust flow path 240: Air electrode side gas exhaust flow path 251: Pure water inlet flow path 261: Raw fuel gas inlet flow path 271: Air inlet flow path 300: Auxiliary device 310: Evaporator 330: Reformer / heater 331: Reformer 333: Combustor 335: Housing 336: Inner wall 337: Outer wall 338: Air flow path 339: Heat transfer fin 350: Heat insulation material 351: Heat insulation space 400, 400A: Specific gas flow path EG: Exhaust gas FG: Fuel gas FOG: Fuel off-gas M1: First material M2: Second material OC1, OC2: Oxide coating OG: Oxidizer gas OOG: Oxidizer off-gas RFG: Raw fuel gas WA: Water

Claims

1. An electrochemical reaction device having an electrochemical reaction unit cell including an electrolyte layer containing a solid oxide, and an air electrode and a fuel electrode facing each other with the electrolyte layer sandwiched therebetween; An electrochemical reaction module having a specific gas flow path formed therein through which a gas supplied to the anode flows, an oxide coating film, which faces the specific gas flow path and contains a specific compound that is a compound of Mn and at least one specific element selected from Si, Al, Ti, and S, is formed on at least a part of the surface of the specific member that defines the specific gas flow path and contains Mn; Electrochemical reaction module characterized by:

2. 10. The electrochemical reaction module of claim 1, The oxide film is not identified as MnO by X-ray diffraction. Electrochemical reaction module characterized by:

3. 3. The electrochemical reaction module according to claim 1 or 2, The specific member includes Cr. An electrochemical reaction module characterized by:

4. 4. The electrochemical reaction module according to claim 1, the specific element is Si, The specific compound is Mn ２ SiO ４ , or Mn ２ SiO ４ a compound in which at least one of Mn and Si contained in An electrochemical reaction module characterized by:

5. 5. The electrochemical reaction module according to claim 1, the electrochemical reaction unit cell is a fuel cell unit cell, the electrochemical reaction module includes a reformer having a space communicating with the specific gas flow path, the reformer reforming the gas supplied to the electrochemical reaction device; an oxide film containing the specific compound is formed on at least a part of a surface of the specific component containing Mn, the specific component defining a portion of the specific gas flow path between the reformer and the electrochemical reaction device; An electrochemical reaction module characterized by:

6. A method for manufacturing the electrochemical reaction module according to any one of claims 1 to 5, comprising: a preparation step of preparing a first material that is a material of a member that defines the specific gas flow path and contains Mn, and a second material that is a material that contains the specific element; a firing step of firing the first material and the second material in a state where the first material and the second material are arranged in the same space in a firing furnace, thereby forming the oxide film on a specific surface of the first material, which is at least a part of a surface that defines the specific gas flow path, and performing a heat treatment on a portion of the surface of the first material other than the specific surface. A method for manufacturing an electrochemical reaction module, comprising:

7. 7. A method for manufacturing an electrochemical reaction module according to claim 6, comprising: The firing step is a step of firing in an air atmosphere. A method for manufacturing an electrochemical reaction module, comprising:

8. 7. A method for manufacturing an electrochemical reaction module according to claim 6, comprising: The firing step is a step of firing in an inert atmosphere or an atmosphere containing hydrogen. A method for manufacturing an electrochemical reaction module, comprising:

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