JP5637652B2 - ELECTROCHEMICAL CELL AND ITS MANUFACTURING METHOD AND OPERATION METHOD - Google Patents

Description

  The present invention relates to an electrochemical cell that causes an electrochemical reaction such as a reaction for electrolyzing water vapor and a battery reaction for discharging water vapor, and an operation method thereof.

  One new energy is hydrogen. As a field of utilization of hydrogen, a fuel cell that converts chemical energy into electric energy by electrochemically reacting hydrogen and oxygen has attracted attention. Fuel cells have high energy use efficiency and are being developed as large-scale distributed power sources, household power sources, and mobile power sources.

  Fuel cells are classified into a solid polymer type, a phosphoric acid type, a molten carbonate type, a solid oxide type, and the like depending on the temperature range and the type of material and fuel used. Among these, a solid oxide fuel cell (SOFC) that uses a solid oxide electrolyte to obtain electric energy through an electrochemical reaction has attracted attention in terms of efficiency and the like.

  Further, hydrogen can be produced by electrolysis of water. Among such hydrogen production methods, in the high temperature steam electrolysis method in which electrolysis is performed in a steam state at a high temperature, the operation principle is a reverse reaction of SOFC. For this reason, the electrolysis cell using the electrolyte of a solid oxide can be used for the electrolysis by a high temperature steam electrolysis method similarly to SOFC.

  A fuel cell or an electrolysis cell is generally composed of an electrolyte and an electrode, and is called an electrochemical cell. The solid oxide electrolyte is characterized by having oxygen ion conductivity, and generally a dense molded body of stabilized zirconia is used. Examples of the stabilized zirconia include yttria stabilized zirconia (YSZ) and scandia stabilized zirconia (ScYZ). Further, as the electrolyte material, a perovskite oxide or a ceria-based solid solution having better oxygen ion conductivity than stabilized zirconia may be used. As the ceria-based solid solution, ceria (SDC) to which samaria is added, ceria (GDC) to which gadolinia is added, or the like is used.

Taking the SOFC as an example, the electrode is divided into an air electrode and a fuel electrode. At the air electrode, oxygen in the air takes in electrons (e ⁻ ), oxygen ions are generated by an electrochemical reaction, and move to the electrolyte. At the fuel electrode, H ₂ that is the fuel gas and oxygen ions that have moved through the electrolyte react electrochemically to generate H ₂ O and electrons (e ⁻ ).

  In general, a perovskite oxide or an oxide in which some of these sites are substituted is used for the air electrode. Examples of such oxides include LaSrMn oxide (LSM), LaSrCo oxide (LSC), LaSrCoFe oxide (LSCF), and LaSrFe oxide (LSF). Moreover, a mixture with solid oxide used for electrolytes, such as LSM-YSZ, LSM-ScSZ, LSC-SDC, LSC-GDC, may be used for an air electrode, for example.

  Generally, a mixed sintered body (cermet) of a metal and a solid oxide is used for the fuel electrode. Examples of such cermets include Ni—YSZ (yttria stabilized zirconia) and Ni—ScSZ (scandia stabilized zirconia). In some cases, a single metal such as Ni, Co, Fe, Ni—Fe, Ni—Mg, or Pt, or a mixture or alloy of these metals may be used for the fuel electrode.

In the fuel electrode, generally, a metal component such as Ni serves as a catalyst component, and the reaction is promoted. In order to improve the characteristics, it is necessary to increase the reaction area of a catalyst component such as Ni. The reaction area of the catalyst component can be increased by increasing the amount of the catalyst component such as Ni or by highly dispersing the catalyst component. Patent Document 1 describes a method of increasing the specific surface area by reducing the particle diameter of a catalyst component such as Ni.
Japanese Patent No. 3363985

In the fuel electrode, generally, a metal component such as Ni serves as a catalyst component, and the reaction is promoted. However, a catalyst component such as Ni is likely to agglomerate at a temperature as high as the operating temperature of SOFC .

Accordingly, an object of the present invention is to realize a dispersed state of a catalyst component of a fuel electrode of an electrochemical cell.

In order to achieve the above-mentioned object, the present invention provides an electrochemical cell comprising NiAl ₂ O containing cermet comprising a solid oxide having oxygen ion conductivity and a first catalyst component and Ni being the second catalyst component. ₄ is sandwiched between a fuel electrode formed by mixing and physically bonding by spinel represented by ₄ , an air electrode having oxygen ion conductivity and electronic conductivity, and the air electrode and the fuel electrode. It provided so as to have an electrolyte containing a solid oxide having oxygen ion conductivity, and, by holding a predetermined time the fuel electrode in a reducing atmosphere, on the surface of the spinel first pre Symbol Ni, which is the catalyst component of No. 2, is highly dispersed and precipitated with a size of several nanometers to several tens of nanometers. The mixing ratio of the cermet and the spinel is such that the spinel ratio exceeds 0 wt% and is within 10 wt%. Arco The features.

The present invention also provides a method for producing an electrochemical cell, tables in NiAl ₂ O ₄ containing a solid oxide having oxygen ion conductivity and a cermet and a second catalyst component comprising a first catalyst component Ni And a step of forming a fuel electrode formed by mixing and being physically combined by firing, a step of forming an air electrode having oxygen ion conductivity and electronic conductivity, the air electrode and the fuel A step of forming an electrolyte containing a solid oxide having oxygen ion conductivity provided so as to be sandwiched between electrodes, and a reduction step of holding the fuel electrode in a reducing atmosphere for a predetermined time, On the surface of the spinel, Ni as the second catalyst component is highly dispersed and precipitated with a size of several nanometers to several tens of nanometers, and the mixing ratio of the cermet and the spinel is the ratio of the spinel. Is 0wt% Beyond wherein the and is within 10 wt%.

Further, the present invention includes a spinel represented by NiAl ₂ O ₄ containing a solid oxide having oxygen ion conductivity and a cermet and a second catalyst component comprising a first catalyst component Ni is mixed calcined A solid electrode having oxygen ion conductivity provided to be sandwiched between the air electrode and the fuel electrode, a fuel electrode physically coupled by the air electrode, an air electrode having ion conductivity and electronic conductivity In an operation method of an electrochemical cell comprising an electrolyte containing an oxide, a reduction step of holding the fuel electrode in a reducing atmosphere for a predetermined time, and a step of causing an electrochemical reaction after the reduction step. On the surface of the spinel, Ni as the second catalyst component is highly dispersed and precipitated with a size of several nanometers to several tens of nanometers, and the mixing ratio of the cermet and the spinel is: Spinel Discount There is characterized in that within exceeded and 10 wt% of 0 wt%.

According to the present invention, a dispersed state of the catalyst component of the fuel electrode of the electrochemical cell can be realized .

  An embodiment of a solid oxide fuel cell according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 2 is a cross-sectional view of a single cell in the first embodiment of the solid oxide fuel cell according to the present invention.

  A single cell 10 of a solid oxide fuel cell includes an electrolyte 11, a fuel electrode 12, and an air electrode 13. The electrolyte 11 supports the fuel electrode 12 and the air electrode 13 so as to be sandwiched between them. The electrolyte 11 is a solid oxide having oxygen ion conductivity. Both the fuel electrode 12 and the air electrode 13 have oxygen ion conductivity and electronic conductivity. Note that any one of the fuel electrode 12 and the air electrode 13 may be used as a support. The solid oxide fuel cell is formed, for example, so as to obtain a higher electromotive force than that of a single cell 10 by electrically connecting a plurality of single cells 10 in series.

The electrolyte 11 is formed of a material having oxygen ion conductivity such as stabilized zirconia. Stabilized zirconia is, for example, Y ₂ O ₃ , Sc ₂ O ₃ , Yb ₂ O ₃ , Gd ₂ O ₃ , Nd ₂ O ₃ , CaO, MgO or the like added to zirconia (ZrO ₂ ) as a stabilizer. It is.

  Further, the electrolyte 11 may be formed of a perovskite oxide. Examples of the perovskite oxide include LaSrGaMg oxide, LaSrGaMgCo oxide, LaSrGaMgCoFe oxide, and the like.

The electrolyte 11 may be formed of a ceria-based electrolyte solid solution. As the ceria-based electrolyte solid solution, Sm ₂ O ₃ added to ceria (CeO ₂ ) (SDC), Gd ₂ O ₃ added to ceria (GDC), Y ₂ O ₃ added to ceria ( YDC), La ₂ O ₃ added to ceria (LDC), CaO added to ceria (CDC), and the like can be used. Note that substances other than these may be used for the electrolyte 11.

  The air electrode 13 is formed of, for example, a material having oxygen ion conductivity and electronic conductivity. Examples of such a material include LaSrMn oxide (LSM), LaSrCo oxide (LSC), LaSrCoFe oxide (LSCF), LaSrFe oxide (LSF), LaSrMnCo oxide (LSMC), LaSrMnCr oxide (LSMC). LaCoMn oxide (LCM), LaSrCu oxide (LSC), LaSrFeNi oxide (LSFN), LaNiFe oxide (LNF), LaBaCo oxide (LBC), LaNiCo oxide (LNC), LaSrAlFe oxide (LSAF), LaSrCoNiCu oxide (LSCNC), LaSrFeNiCu oxide (LSFNC), LaNi oxide (LN), GdSrCo oxide (GSC), GdSrMn oxide (GSM), PrCaMn oxide (PCaM), PrSrMn (PSM), PrBaCo oxide (PBC), SmSrCo oxide (SSC), NdSmCo oxide (NSC), BiSrCaCu oxide (BSCC), BaLaFeCo oxide (BLFC), BaSrFeCo oxide (BSFC), YSrFeCo oxide (YLFC), YCuCoFe oxide (YCCF), YBaCu oxide (YBC), and the like.

  The air electrode 13 may be a mixture with a material having oxygen ion conductivity that can also be used for the electrolyte 11. For example, the air electrode 13 can be formed of LSM-YSZ, LSCF-SDC, LSCF-GDC, LSCF-YDC, LSCF-LDC, LSCF-CDC, LSM-ScSZ, LSM-SDC, LSM-GDC, or the like. Further, for example, a catalyst component such as Pt, Ru, Au, Ag, or Pd may be added thereto.

  FIG. 1 is a schematic diagram of a fuel electrode in the present embodiment.

  The fuel electrode 12 is a mixture of the cermet 14 and the spinel 15. The cermet 14 used for the fuel electrode 12 is a composite material of a solid oxide having oxygen ion conductivity and a metal having a catalytic action. The fuel electrode 12 also has electronic conductivity because the cermet 14 contains a metal, for example. In FIG. 1, the particle sizes of all cermets 14 and spinels 15 are expressed in the same manner, but in practice, the particle sizes of cermets 14 and spinels 15 may all be different.

As the solid oxide having oxygen ion conductivity constituting the cermet 14, for example, stabilized zirconia is used. Examples of the stabilized zirconia include stabilized zirconia in which Y ₂ O ₃ , Sc ₂ O ₃ , Yb ₂ O ₃ , Gd ₂ O ₃ , Nd ₂ O ₃ , CaO, MgO or the like is added as a stabilizer. .

  Further, a perovskite oxide may be used as a solid oxide having oxygen ion conductivity that constitutes the cermet 14. Examples of the perovskite oxide include LaSrGaMg oxide, LaSrGaMgCo oxide, LaSrGaMgCoFe oxide, and the like.

A ceria (CeO ₂ ) -based electrolyte solid solution may be used as a solid oxide having oxygen ion conductivity constituting the cermet 14. Examples of the ceria-based electrolyte solid solution include Sm ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , La ₂ O _{3 and the} like. You may use electrolytes other than these.

  For the cermet 14 of the fuel electrode 12, the same solid oxide as the electrolyte 11 may be used, or a different solid oxide may be used. When the same solid oxide as the electrolyte 11 is used for the cermet 14 of the fuel electrode 12, there is an advantage that physical properties such as a thermal expansion coefficient of the fuel electrode 12 are close to those of the electrolyte 11.

  The metal having a catalytic action mixed with the cermet 14 is, for example, Ni. Therefore, the cermet used for the fuel electrode 12 is, for example, Ni—YSZ, Ni—ScSZ, Ni—SDC, Ni—GDC, Ni—YDC, or the like. In addition, for example, metals such as Fe, Co, Cu, Mg, Al, Pt, Ru, Au, or alloys thereof may be added to these.

The spinel 15 used for the fuel electrode 12 is an equiaxed crystal oxide and is represented by the general formula AB ₂ O ₄ . Here, A represents a catalyst component, B represents an unspecified element, and O represents oxygen. Co, Cu, Fe ²⁺ , Ge, Mg, Mn ²⁺ , Ni, Ti, Zn, and the like are coordinated at the site (atomic position) represented by A, and Al is represented at the site represented by B. , Cr ³⁺ , Fe ²⁺ , Fe ³⁺ , Mg, Mn ³⁺ , Ti, V ³⁺ , and the like are coordinated. In addition, each component as described above may be used alone at the A site, or a part thereof may be replaced with another component. The same applies to the B site, and each of the above components may be used alone or a part thereof may be substituted with another component.

  When power generation is performed using an SOFC in which such single cells 10 are stacked, a hydrocarbon such as methane is supplied to the fuel electrode 12 and air containing oxygen is supplied to the air electrode 13. The hydrocarbons supplied to the fuel electrode 12 cause a reforming reaction using Ni or the like in the fuel electrode 12 as a reforming catalyst. Hydrogen is generated by internal reforming at the fuel electrode 12 and used for the cell reaction.

  In both the fuel electrode 12 and the air electrode 13, the amount of gas used for the reaction increases when hydrocarbons or oxygen enters inside as much as possible. For this reason, it is preferable that the fuel electrode 12 and the air electrode 13 are porous bodies.

  When the cermet is manufactured, since the materials are mixed and then sintered, at least a part of the metal component having the catalytic action of the cermet used for the fuel electrode 12 is oxidized. If oxidized, the component having catalytic action does not perform its function. Therefore, it is necessary to reduce the oxidized component.

  During the operation of the SOFC, hydrogen is generated inside the fuel electrode 12, so that a reducing atmosphere is created. Further, the fuel electrode 12 becomes high temperature during the operation of the SOFC. For this reason, many of the catalyst components constituting the cermet used in the fuel electrode 12 that have been oxidized at the time of manufacture are reduced to exhibit their functions.

Further, reduction processing may be performed on the fuel electrode 12 before the operation of the SOFC. For example, while supplying a gas containing H ₂ to the fuel electrode 12, the fuel electrode 12 is reduced for 10 minutes by holding at 1000 ° C. for 10 minutes. In this case, it is preferable that the oxidizing gas does not coexist in the atmosphere. If the temperature of the fuel electrode 12 during the reduction treatment is 700 ° C. or lower, the rate of the reduction reaction is slow and not practical. Moreover, the maximum operating temperature of SOFC is about 1000 ° C., and it is better not to exceed this temperature during the reduction process. For this reason, the reduction temperature is desirably in the range of 700 ° C to 1000 ° C.

By subjecting the fuel electrode 12 to a reduction treatment, the A-site substance of the equiaxed oxide that can be expressed by AB ₂ O ₄ is about several nanometers to several tens of nanometers on the surface of the equiaxed oxide. Precipitate in size.

FIG. 3 is a photomicrograph showing the state of Ni dispersion in a state where an electrode formed of NiAl ₂ O ₄ is subjected to a reduction treatment.

FIG. 3 shows the state of Ni dispersion in a state where reduction treatment is performed on an electrode using NiAl ₂ O ₄ as an equiaxed oxide that can be expressed by AB ₂ O ₄ , where Ni is NiAl ₂ O _4. On the surface of the particles, highly dispersed precipitates having a size of several nanometers to several tens of nanometers. In this case, not all Ni of NiAl ₂ O ₄ is deposited on the surface, but only a part (approximately several to 10%) is deposited on the surface. Ni deposited on the surface is involved in the reaction. Since this Ni is directly deposited from NiAl ₂ O _{4 as a} base material, no aggregation occurs even at high temperatures .

In internal reforming using hydrocarbons or the like as fuel, a fuel containing hydrocarbons or the like is directly introduced into the fuel electrode 12 and reformed at the fuel electrode 12 to generate H ₂ or CO. Electric power is generated using this H ₂ . In the fuel electrode 12 having only Ni cermet, there is a high possibility that the performance is deteriorated due to carbon deposition or the like. On the other hand, the fuel electrode 12 of the present embodiment, as possible out to play conventionally equivalent to the reforming catalyst Ni / _Al 2 _{O 3} and the supported on alumina Ni proven as a catalyst performance is NiAl ₂ O ₄ .

  4 and 5 are graphs showing the test results of the electrode characteristics in the present embodiment.

The test shown in FIG. 4 was conducted when Ni-SDC was used as the cermet, and this cermet was used for the fuel electrode 12 as a mixture with spinel represented by NiAl ₂ O ₄ . For comparison, a test result of a fuel electrode using only Ni-SDC is also shown. Here, the mixing ratio of Ni and SDC in the cermet was the same. The mixing ratio (weight ratio) of Ni and SDC in the cermet is Ni: SDC = 70: 30. The mixing ratio (weight ratio) between cermet and spinel is Ni-SDC: NiAl ₂ O ₄ = 90: 10.

Similar to the test shown in FIG. 4, the test shown in FIG. 5 was performed when a mixture of Ni-SDC and spinel represented by NiAl ₂ O ₄ was used for the fuel electrode 12. Here, the results when the mixing ratio of NiAl ₂ O ₄ is changed to 10%, 20%, and 30% are also shown. The mixing ratio (weight ratio) of Ni and SDC in the cermet is Ni: SDC = 70: 30.

  The vertical axis in FIGS. 4 and 5 represents the overvoltage resulting from the catalytic activity excluding the electrical resistance (IR). The horizontal axis in FIGS. 4 and 5 is the current density.

  As can be seen from FIG. 4, almost the same electrode characteristics were obtained. In general, characteristics of Ni cermet materials are improved by increasing the amount of Ni involved in the reaction.

  The amount of Ni contained in the Ni-SDC cermet is 70% × 90% = 63% of the weight of the entire electrode. Assuming that all the Ni in the Ni-SDC cermet is reduced, Ni corresponding to 63 wt% of the entire electrode contributes to the reaction.

Further, the amount of Ni precipitated from the spinel represented by NiAl ₂ O ₄ is several percent, and is considered to be about 10% at the maximum. That is, it is considered that Ni corresponding to 10% × 10% = 1% of the total weight of the electrode contributes to the reaction.

  Therefore, Ni contributing to the reaction of this mixed electrode is at most about 64% of the weight of the entire electrode. On the other hand, in the case of an electrode using only Ni-SDC, 70% of the total weight of the electrode should contribute to the reaction. That is, as in this embodiment, by using a mixed electrode of cermet and spinel, the equivalent characteristics can be obtained despite the small amount of Ni contributing to the reaction. It can be seen that the electrode characteristics are improved.

Further, from FIG. 4 and FIG. 5, the mixing ratio of the cermet and the spinel, the proportion of spinel, 1 0 wt% or less favorable preferable.

[Second Embodiment]
FIG. 6 is a schematic diagram of the fuel electrode in the second embodiment of the solid oxide fuel cell according to the present invention.

  The electrochemical cell of the present embodiment is different from the first embodiment in the fuel electrode 12. In the present embodiment, a high spinel region 16 is formed in the fuel electrode 12. The high spinel region 16 is a region having a higher spinel 15 content than a region where the distance from the electrolyte 11 is small.

For example, the fuel electrode 12 is formed using Ni-SDC as the cermet 14 and NiAl ₂ O ₄ as the spinel 15. The NiAl ₂ O ₄ content is reduced in the vicinity of the interface between the electrolyte 11 and the fuel electrode 12, and the NiAl ₂ O ₄ content is increased in the vicinity of the surface of the fuel electrode 12.

When power is generated by supplying methane (CH ₄ ) to the fuel electrode 12 to cause internal reforming, the CH _{4 is changed} to H ₂ and CO in the high spinel region 16 near the surface of the fuel electrode 12. Quality is promoted. In addition, carbon deposition is suppressed, and power can be generated while maintaining performance.

  In the present embodiment, the fuel electrode 12 can be divided into a region where the spinel 15 content is high and a region where the spinel 15 content is low, but the content of the spinel 15 in the fuel electrode 12 is continuously increased from the interface of the electrolyte 11. Also good.

[Third Embodiment]
FIG. 7 is a schematic view of the fuel electrode in the third embodiment of the solid oxide fuel cell according to the present invention.

  In the present embodiment, the fuel electrode 12 contains a particulate surface electronic conductor 17 whose surface is coated with a substance having electronic conductivity.

  FIG. 8 is a cross-sectional view of the surface electron conductor in the present embodiment.

  The surface electronic conductor 17 is obtained by coating the surface of a base 71 with a substance 72 having electronic conductivity. The material of the base material 71 is preferably a material having high heat resistance and stability. The substance 72 having electronic conductivity is, for example, a metal such as Ni, Fe, Co, Mg, Ti, Cu, Al, Pt, Au, Ag, Pd, and Ru. Further, as the substance 72 having electronic conductivity, a mixture or alloy thereof may be used.

  Moreover, as the base material 71, it is more preferable to use the same material as the solid oxide of the cermet 14. For example, if the cermet 14 is Ni—YSZ, YSZ may be used as the base material 71. Thereby, the affinity with the electrode active component is improved, the difference in thermal expansion coefficient can be reduced, and the mechanical deterioration and characteristic deterioration of the cell can be reduced.

  The material 72 having electronic conductivity may be, for example, a plating method, PVD method, CVD method, electrophoresis method, slurry coating method, sputtering method, plasma spray method, ion plating method, flame spray method, plasma jet torch method, EVD. The surface of the base material 71 can be coated by a method. In addition, a plurality of layers of the substance 72 having electronic conductivity may be formed on the surface of the base material 71.

  As the substance 72 having electronic conductivity, it is more preferable to use the same substance as the catalyst component of the cermet 14. For example, if the cermet 14 is Ni—YSZ, Ni may be used as the substance 72 having electronic conductivity.

  FIG. 9 is a photomicrograph of particles in which the surface of the substrate is coated with a substance having electronic conductivity.

  The surface electronic conductor 17 shown in FIG. 9 is obtained by using YSZ particles as the base material 71 and coating the surface thereof with Ag, which is a substance 72 having electronic conductivity. The surface of YSZ particles having a diameter of about 15 μm is coated with an Ag layer of about 1 μm. The fuel electrode 12 of the present embodiment contains such a surface electron conductor 17.

The spinel 15 including NiAl ₂ O ₄ generally has a high electric resistance. For this reason, for example, in the case of a mixed electrode of Ni-SDC and NiAl ₂ O ₄ , if the mixing ratio of NiAl ₂ O ₄ is too large, the electrical resistance of the electrode increases. Therefore, by mixing the substance 72 having electronic conductivity as in the present embodiment, the path of electronic conduction within the fuel electrode 12 is increased, and the electrical resistance is lowered.

[Fourth Embodiment]
FIG. 10 is a schematic diagram of the fuel electrode in the fourth embodiment of the solid oxide fuel cell according to the present invention.

  In the fuel electrode 12 of the polymer electrolyte fuel cell according to the present embodiment, a fibrous surface electronic conductor 18 is used instead of the particulate surface electronic conductor 17 (see FIG. 7) in the third embodiment. Contains. The fibrous surface electronic conductor 18 is obtained by coating the surface of an elongated base 71 with a substance 72 having electronic conductivity.

  The fibrous surface electronic conductor 18 is formed by coating the surface of an elongated fibrous base material 71 made of, for example, YSZ, with a substance 72 having electronic conductivity such as Ag. The cross-sectional shape of the fibrous surface electronic conductor 18 is substantially the same as the cross-sectional shape of the particulate surface electronic conductor 18 in the third embodiment.

  Even if such a fibrous surface electronic conductor 18 is contained in the fuel electrode 12, the path of electronic conduction inside the fuel electrode 12 is increased, so that the electrical resistance is lowered. That is, as long as at least the surface is coated with a substance having electronic conductivity, it may be particulate like the third embodiment, fibrous like the present embodiment, or other Even in this shape, the electron conduction path increases and the electric resistance of the fuel electrode 12 decreases.

[Fifth Embodiment]
FIG. 11 is a schematic diagram of the fuel electrode in the fifth embodiment of the solid oxide fuel cell according to the present invention.

  In the fuel electrode 12 of the present embodiment, a material 19 having conductivity forms a current collecting layer 20 on the surface opposite to the interface with the electrolyte 11. The conductive material 19 is, for example, granular, and the current collecting layer 20 is formed so that gas can pass therethrough.

  When an electrochemical cell such as a solid oxide fuel cell is operated, a current collector is provided on the surface of each of the fuel electrode 12 and the air electrode 13 to collect current. The contact between the electrode and the current collector is very important. If the contact between the electrode and the current collector is insufficient, the resistance (current collection resistance) increases and the performance of the cell decreases.

  In the fuel electrode 12 of the present embodiment, since the current collecting layer 20 is formed of the conductive material 19 on the surface opposite to the interface with the electrolyte 11, the conductive material 19 is collected by the current collector 19. It will come into contact with the body in a wide area. For this reason, current collection resistance can be made small and the performance of the single cell 10 improves.

  Further, the current collecting layer 20 formed of the conductive material 19 on the surface opposite to the interface with the electrolyte 11 may also be provided on the air electrode 13. Thereby, the current collection resistance in the air electrode 13 can also be made small.

[Sixth Embodiment]
FIG. 12 is a perspective view of a solid oxide fuel cell according to a sixth embodiment of the present invention.

  In the unit cell 10 of the present embodiment, a conductive material 19 forms a mesh layer on the surface of the fuel electrode 12 opposite to the interface with the electrolyte 11. If such a fuel electrode 12 is used, it will contact with a collector in a wide area | region. For this reason, current collection resistance can be made small and the performance of the single cell 10 improves. Further, by using a mesh shape, the amount of the conductive material 19 used can be reduced.

[Other embodiments]
The above-described embodiments are merely examples, and the present invention is not limited to these. In each of the above-described embodiments, the solid oxide fuel cell (SOFC) has been described as an example. However, any electrochemical cell that causes an electrochemical reaction through oxygen ions passing through the electrolyte can be used. Is also applicable. For example, the present invention can also be applied to an electrolysis cell used in a high temperature steam electrolysis method in which water is electrolyzed at a high temperature to produce hydrogen. Or it is applicable also to the electrochemical cell which decomposes | disassembles oxygen dioxide. Moreover, it can also implement combining the characteristic of each embodiment.

1 is a schematic diagram of a fuel electrode in a first embodiment of a solid oxide fuel cell according to the present invention. It is sectional drawing of the single cell in 1st Embodiment of the solid oxide fuel cell which concerns on this invention. Is a photomicrograph showing the Ni dispersion status of a state subjected to reduction treatment electrode formed by NiAl ₂ O _4. It is a graph which shows the test result of the electrode characteristic in 1st Embodiment of the solid oxide fuel cell which concerns on this invention. It is a graph which shows the test result of the electrode characteristic in 1st Embodiment of the solid oxide fuel cell which concerns on this invention. It is a schematic diagram of the fuel electrode in 2nd Embodiment of the solid oxide fuel cell which concerns on this invention. It is a schematic diagram of the fuel electrode in 3rd Embodiment of the solid oxide fuel cell which concerns on this invention. It is sectional drawing of the surface electronic conductor in this Embodiment. It is a microscope picture of the particle | grains by which the substance which has electronic conductivity was coated on the surface of the base material. It is a schematic diagram of the fuel electrode in 4th Embodiment of the solid oxide fuel cell which concerns on this invention. It is a schematic diagram of the fuel electrode in 5th Embodiment of the solid oxide fuel cell which concerns on this invention. It is a perspective view in 6th Embodiment of the solid oxide fuel cell which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Single cell, 11 ... Electrolyte, 12 ... Fuel electrode, 13 ... Air electrode, 14 ... Cermet, 15 ... Spinel, 16 ... High spinel area | region, 17 ... Surface electron conductor, 18 ... Surface electron conductor, 71 ... Group 20, current collecting layer

Claims (6)

A cermet composed of a solid oxide having oxygen ion conductivity and a first catalyst component and a spinel represented by NiAl ₂ O ₄ containing Ni as a second catalyst component are mixed and physically bonded by firing. A fuel electrode,
An air electrode with oxygen ion conductivity and electronic conductivity;
An electrolyte containing a solid oxide having oxygen ion conductivity provided to be sandwiched between the air electrode and the fuel electrode;
Have
Wherein by a fuel electrode for a predetermined time in the reducing atmosphere, the on the surface of the spinel was highly dispersed and precipitated in the size of Ni is about several nm to several tens nm is prior Symbol second catalyst component And
The electrochemical cell according to claim 1, wherein the mixing ratio of the cermet and the spinel is such that the proportion of the spinel exceeds 0 wt% and is within 10 wt%.   The electrochemical cell according to claim 1, wherein the first catalyst component is Ni.   The fuel electrode is characterized in that the spinel content in the vicinity of the surface of the fuel electrode opposite to the interface is higher than the content of the spinel in the vicinity of the interface with the electrolyte in the fuel electrode. The electrochemical cell according to claim 1 or claim 2.   4. At least one of the fuel electrode and the air electrode contains a surface electron conductor having a base material and a material having electronic conductivity coated on the surface thereof. The electrochemical cell according to claim 1. A cermet composed of a solid oxide having oxygen ion conductivity and a first catalyst component and a spinel represented by NiAl ₂ O ₄ containing Ni as a second catalyst component are mixed and physically bonded by firing. Forming a fuel electrode comprising:
Forming an air electrode with oxygen ion conductivity and electronic conductivity;
Forming an electrolyte containing a solid oxide having oxygen ion conductivity provided to be sandwiched between the air electrode and the fuel electrode;
A reduction step of holding the fuel electrode in a reducing atmosphere for a predetermined time;
Have
On the surface of the spinel, Ni that is the second catalyst component is highly dispersed and precipitated with a size of several nanometers to several tens of nanometers,
The mixing ratio of the cermet and the spinel is such that the proportion of the spinel exceeds 0 wt% and is within 10 wt%. A cermet composed of a solid oxide having oxygen ion conductivity and a first catalyst component and a spinel represented by NiAl ₂ O ₄ containing Ni as a second catalyst component are mixed and physically bonded by firing. A fuel electrode, an air electrode having ionic conductivity and electronic conductivity, and an electrolyte containing a solid oxide having oxygen ion conductivity provided to be sandwiched between the air electrode and the fuel electrode In an operation method of an electrochemical cell comprising:
A reduction step of holding the fuel electrode in a reducing atmosphere for a predetermined time;
A step of causing an electrochemical reaction after the reduction step;
Have
On the surface of the spinel, Ni that is the second catalyst component is highly dispersed and precipitated with a size of several nanometers to several tens of nanometers,
The method of operating an electrochemical cell, wherein a mixing ratio of the cermet and the spinel is such that the proportion of the spinel exceeds 0 wt% and is within 10 wt%.