JP2009140693A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain further output voltage improvement in a solid oxide fuel cell with an air electrode structured by a ceria compound and a perovskite oxide. <P>SOLUTION: The solid oxide fuel cell includes an electrolyte 101 consisting of a material of zirconia system, a fuel electrode 102 formed on one side of the electrolyte 101, and the air electrode 103 formed on the other side of the electrolyte 101 and containing with and structured by a cerium oxide (ceria compound: a first material) with rare earth added and a perovskite metal oxide (perovskite oxide: a second material) with praseodymium (Pr) added. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell using an air electrode comprising a perovskite-type metal oxide and a cerium oxide to which a rare earth is added.

  There is a growing interest in solid oxide fuel cells using zirconia-based oxygen ion conductors, which are excellent electrolyte materials. In particular, from the viewpoint of effective use of energy, solid fuel cells have essentially high energy conversion efficiency because they are not restricted by Carnot efficiency, and have excellent features such as good environmental conservation. have.

  The solid oxide fuel cell initially had a high operating temperature of 900 to 1000 ° C., and all members were made of ceramic. For this reason, it was not easy to reduce the manufacturing cost of the cell stack. Here, if the operating temperature can be lowered to 800 ° C. or less, a heat-resistant alloy material can be used for the interconnector, and the manufacturing cost can be reduced. However, as the operating temperature decreases, the electrochemical resistance at the air electrode, that is, the overvoltage, suddenly increases and the output voltage decreases.

In order to solve the problem of the air electrode due to such a decrease in operating temperature, La _1-X Sr _X Fe _1-Y Ni _Y O ₃ (LSFC: X = 0.1 to 0.3, Y = 0.1 ~0.6, X + Y <0.7) , La 1-X Sr X CoO 3 (X = 0.1~0.5), LaNi 1-X Fe X O 3 (LNF: X = 0.3~0 There is a technique using a perovskite-type metal oxide (perovskite oxide) having high electrode activity (electrochemical reaction performance) such as .8). These materials are perovskite oxides containing La and Sr at the A site and Ni, Co, and Fe at the B site. Some A sites contain La and Ca. These materials are suitable for an air electrode for low temperature operation.

However, since the air electrode is manufactured by firing in contact with an electrolyte containing zirconia, an insulator such as La ₂ Zr ₂ O ₇ is generated in a portion in contact with the electrolyte, and this product is This is one of the causes of deteriorating characteristics in the air electrode. In order to prevent this problem, a ceria layer made of cerium oxide (ceria compound) to which rare earth is added, such as Ce _0.9 Gd _0.1 O ₂ and Ce _0.9 Sm _0.2 O ₂ , is provided between the air electrode and the electrolyte. A method of breaking the contact between the pole-side perovskite oxide and the electrolyte-side zirconia has been studied (Non-Patent Document 1). The ceria layer thus provided has high oxygen ion conductivity, and a reaction that generates an insulator with the perovskite oxide is less likely to occur.

Further, in order to further improve the low temperature characteristics of a solid oxide fuel cell using an air electrode composed of the above-described materials, a method of providing a mixture of perovskite oxide particles and a ceria compound in the vicinity of an electrolyte is known. (See Non-Patent Document 2). By forming the air electrode in a state where the perovskite oxide powder (powder) and the fine powder of the ceria compound are mixed, the active area of the electrode generated at the joint between the electrolyte and the air electrode is increased. Interfacial resistance can be reduced. The ceria compound is suitable as a material to be mixed with the air electrode because the reaction deterioration with the Co-based and Fe-based air electrode materials described above hardly occurs. In the air electrode made of this mixture, the perovskite oxide particles are arranged to be covered with ceria compound particles, and the direct contact between the zirconia-based material portion constituting the electrolyte and the perovskite oxide material is suppressed, Production of reaction products with harmful zirconia such as La ₂ Zr ₂ O ₇ is suppressed.

A. Mai, et al., "Ferrite-based perovskites as cathode materials for anode-suported solid oxide fuel cells Part II influence of the CGO circulating", Solid State Ionics 177, pp.2103-2107, 2006. Y. Matsuzaki, et al., "Electrochemical properties of reduced-temperature SOFCs with mixed ionic-electronic conductors in electrodes and / or referrings", Solid State Ionics 152-153, pp.463-468, 2002. Hiroaki Tagawa, Solid oxide fuel cell and global environment, Agne Jofusha Co., Ltd., 1st edition, 1st edition, 1998.

  As described above, by forming the air electrode from the ceria compound and the perovskite oxide, the problem of the air electrode due to a decrease in operating temperature, such as a decrease in output voltage due to an increase in electrochemical resistance in the air electrode, is solved. However, further improvement of the output voltage at the air electrode has been required.

  The present invention has been made to solve the above problems, and in a solid oxide fuel cell in which an air electrode is composed of a ceria compound and a perovskite oxide, the output voltage can be further improved. It aims to be obtained.

  The solid oxide fuel cell according to the present invention is a solid oxide fuel cell including a fuel electrode, an electrolyte, and an air electrode. The air electrode includes a first material made of cerium oxide to which a rare earth is added, and praseodymium. And a second material made of a perovskite-type metal oxide to which is added.

  In the above solid oxide fuel cell, if the air electrode is composed of a sintered body of a mixed powder in which the first powder made of the first material and the second powder made of the second material are mixed. Good.

  In the solid oxide fuel cell, the air electrode may be disposed on the electrolyte side and include a region made of the first material and the second material.

  The solid oxide fuel cell may include an intermediate layer that is disposed between the electrolyte and the air electrode and is made of cerium oxide to which a rare earth is added.

  The solid oxide fuel cell may include a current collecting layer that is disposed on the opposite side of the air electrode from the electrolyte and is made of a perovskite metal oxide.

In the solid oxide fuel cell, the second material is (Sm _1-x Pr _x ) _1-z Sr _z CoO ₃ (0.04 ≦ x ≦ 0.5, 0 ≦ z ≦ 0.6). , La _1-x Pr _x Ni _1-y Fe _y O ₃ (0.04 ≦ x ≦ 1.0, 0.3 ≦ y ≦ 0.8), and (La _1-x Pr _x ) _1-z Sr Any of _z Fe _1-y Co _y O ₃ (0.04 ≦ x ≦ 1.0, 0.1 ≦ y ≦ 0.4, 0, 1 ≦ z ≦ 0.5) may be used.

  As described above, according to the present invention, the air electrode includes the first material made of cerium oxide to which rare earth is added and the second material made of perovskite metal oxide to which praseodymium is added. Therefore, in the solid oxide fuel cell in which the air electrode is composed of the ceria compound and the perovskite oxide, an excellent effect of further improving the output voltage can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a configuration example of a solid oxide fuel cell according to Embodiment 1 of the present invention. This solid oxide fuel cell includes an electrolyte 101 made of a zirconia-based material and a fuel electrode 102 formed on one surface of the electrolyte 101. In addition, the solid oxide fuel cell of the present embodiment is formed on the other side of the electrolyte 101, and a perovskite to which cerium oxide (ceria compound: first material) to which rare earth is added and praseodymium (Pr) is added. And an air electrode 103 including a metal oxide of a type (perovskite oxide: second material).

  For example, the air electrode 103 is a mixture of a powder having a predetermined particle size (first powder) made of a ceria compound and a powder (second powder) having a predetermined particle size made of a perovskite oxide to which Pr is added. What is necessary is just to be comprised from the sintered compact of the mixed powder made. In the air electrode 103, the ceria compound particles in contact with the perovskite oxide particles to which Pr is added and the perovskite oxide to which Pr is added without being in contact with the particles of the perovskite oxide to which Pr is added And ceria compound particles which are present apart from the particles.

The electrolyte 101 may be, for example, scandium oxide (Sc ₂ O ₃ ) and aluminum oxide (Al ₂ O ₃ ) stabilized ZrO ₂ (SASZ), yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), Samaria. What is necessary is just to be comprised from the sintered compact of the powder of zirconia materials, such as stabilized zirconia (SSZ). In the fuel electrode 102, for example, nickel metal is mixed with an oxide material constituting the electrolyte 101 such as nickel-yttria stabilized zirconia cermet (Ni-YSZ), nickel-scandia stabilized zirconia (Ni-ScSZ). It is only necessary to be composed of a sintered body of a powder of a metal-oxide mixture (cermet) having electron conductivity.

  In addition, as is well known, each of these layers produces a slurry of powder or mixed powder, and forms a slurry film (layer) by molding by a doctor blade method or application by a screen printing method, This can be produced by firing at 1000 to 1200 ° C.

  According to the solid oxide fuel cell of the present embodiment configured as described above, in the air electrode 103, mixed conduction in which electron (hole) conductivity is improved and ion conductivity and electron (hole) conductivity is improved. A body region is formed, and the characteristics are improved to improve the output voltage. In addition, fuel gas containing hydrogen obtained by reforming hydrocarbon gas such as city gas is supplied to the fuel electrode 102, and air containing oxygen as oxidant gas is supplied to the air electrode 103, A power generation operation is performed.

  Here, the addition of Pr will be described. When Pr is added to the perovskite oxide constituting the air electrode 103 (solid solution), Pr enters the so-called A site in the perovskite oxide, and a part of the A site is replaced with Pr atoms. Will be. As described above, a part of Pr added to the perovskite oxide is simultaneously diffused and dissolved in the ceria compound that exists in the air electrode 103 and is in contact with the perovskite oxide. In the ceria compound that is solid-solved by partly diffusing Pr in this manner, the hole conductivity is greatly improved. Note that solid solution indicates a state of being dissolved in a solid state, and indicates that the added element enters the crystal of the base substance while maintaining the crystal structure of the base substance.

  On the other hand, in the ceria compound not in contact with the perovskite oxide to which Pr is added, Pr does not diffuse and dissolve as described above. Therefore, in the air electrode 103, the ceria compound at a portion away from the perovskite oxide maintains an ideal composition as a material as an electrolyte, and the ion conductivity does not decrease due to the addition of Pr.

  Thus, in the air electrode 103, in the region where the perovskite oxide exists, the hole conductivity of the ceria compound adjacent thereto is greatly improved.

By the way, the electrochemical reaction in the air electrode includes a ceria compound that is an ionic conductor constituting an electrolyte, a perovskite oxide that is an electron conductor (hole conductor), and air (oxidation) that is supplied to the air electrode. It occurs in the region (three-phase interface) where the three phases are in contact with the agent gas. When oxygen gas (O ₂ ) in the air supplied to the air electrode touches the perovskite oxide that can have electron conductivity and receives electrons, it becomes oxygen ions (O ²⁻ ), and these oxygen ions (oxidation) The product ions) conduct through the ceria compound, which is an ionic conductor constituting the electrolyte. Therefore, basically, an electrochemical reaction in the air electrode occurs at the interface between the air electrode and the fuel electrode.

  On the other hand, according to the present embodiment, even in the ceria compound constituting the air electrode, the portion in contact with the perovskite oxide becomes a mixed conductor having hole conductivity. For this reason, even in the ceria compound in which Pr is diffused in the air electrode, the oxygen gas that has come into contact with it receives electrons to become oxygen ions, and conducts this ceria compound to reach the electrolyte. Thus, according to the solid oxide fuel cell of the present embodiment, the reaction field (three-phase interface) of the electrochemical reaction in the air electrode is from the interface between the air electrode and the fuel electrode to the air electrode side. Will also spread. For example, the three-phase interface expands on the air electrode 103 side so that oxygen (oxygen ions) ionized in the ceria compound having hole conductivity due to Pr can reach the electrolyte.

  As a result, in this embodiment, the ceria compound in the vicinity of the perovskite oxide of the air electrode 103 also has a three-phase interface without lowering the ionic conductivity and electron conductivity (hole conductivity) in the air electrode 103. Therefore, it is considered that the characteristics are improved and the output voltage is further improved. In the above description, Pr is added to the perovskite oxide throughout the air electrode 103. However, the present invention is not limited to this. In a predetermined region (layer) on the electrolyte 101 side of the air electrode 103, Pr is added to the perovskite oxide, and in a region farther from the electrolyte 101 side than this region, Pr is added to the perovskite oxide. Even if it is not done, the same effect as described above can be obtained.

  By the way, as a perovskite oxide used for an air electrode of a solid oxide fuel cell, the case where the A site is La is common, and in this case, the best electron conductivity (hole conductivity) is realized, In many cases, chemical stability can be realized. Therefore, the case where the composition is such that all the A sites of the perovskite oxide constituting the air electrode 103 are replaced with Pr atoms is not good. In the air electrode 103, Pr is added to such an extent that the hole conductivity of the ceria compound in contact with the perovskite oxide is expressed within a range in which the characteristics of the original air electrode (ceria compound) are not significantly deteriorated. It is good to have. If Pr is added at 3 at% to the perovskite oxide, Pr can diffuse into the ceria compound in contact with the perovskite oxide to improve hole conductivity. From the above viewpoint, the amount of Pr added is: A maximum of 80 at% is better.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically showing a configuration example of the solid oxide fuel cell according to Embodiment 2 of the present invention. This solid oxide fuel cell includes an electrolyte 101, a fuel electrode 102 formed on one surface of the electrolyte 101, and an air electrode 103 formed on the other side of the electrolyte 101. These configurations have been described above. The same as in the first embodiment.

  In addition to the above-described configuration, the solid oxide fuel cell according to the present embodiment includes a current collecting layer 201 that is disposed on the opposite side of the air electrode 103 from the electrolyte 101 and is made of a perovskite metal oxide. It is a thing. In this case, the electrolyte 101 is arranged on one side of the air electrode 103, and the current collecting layer 201 is arranged on the other side of the air electrode 103, and the air electrode 103 is sandwiched between the electrolyte 101 and the current collecting layer 201. Become.

  As is well known, in a solid oxide fuel cell, a plurality of single cells composed of an electrolyte 101, a fuel electrode 102, and an air electrode 103 are stacked through an interconnector to generate a practical voltage. It is configured to take out. In order to obtain a good electrical connection between the fuel electrode 102 and the air electrode 103 and each interconnector in the case of such a stacked structure, a current collector made of, for example, a platinum mesh or the like. Should be used.

  In the present embodiment, since the current collecting layer 201 made of perovskite oxide, which is an electron conductor (hole conductor), is provided on the air electrode 103 side, it is connected to the air electrode 103. A better electrical connection with the interconnector can be obtained. It can be considered that the entire air electrode 103 including the current collecting layer 201 functions as an air electrode.

[Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing a configuration example of the solid oxide fuel cell according to Embodiment 3 of the present invention. The solid oxide fuel cell includes an electrolyte 101, a fuel electrode 102 formed on one surface of the electrolyte 101, an air electrode 103 formed on the other side of the electrolyte 101, and an air electrode 103 on the opposite side of the electrolyte 101. And a current collecting layer 201 made of a perovskite metal oxide. These are the same as those of the solid oxide fuel cell of Embodiment 2 described above.

In the present embodiment, in addition to the above-described configuration, an intermediate layer 301 is provided that is disposed between the electrolyte 101 and the air electrode 103 and is made of cerium oxide to which rare earth is added. For example, the intermediate layer 301 may be made of a sintered body of GDC (Ce _0.9 Gd _0.1 O) powder. By providing the intermediate layer 301 in this manner, the zirconia constituting the electrolyte 101 and the perovskite oxide constituting the air electrode 103 can be more efficiently separated, and a solid oxide fuel cell (air The interfacial resistance in the electrode / electrolyte can be further suppressed.

  Next, the characteristic measurement result in the single cell of the actually produced solid oxide fuel cell will be described below.

[Measuring method]
First, measurement will be described. As will be described later, in each of the fabricated sample cells, the interfacial resistance, which is an index of electrode performance, is measured by an AC impedance method. At the time of measurement, it is performed under the condition of an open circuit voltage, a minute AC signal is applied between the air electrode and the fuel electrode, and a minute electric potential change between the air electrode and the reference electrode (fuel electrode) is measured. The impedance is obtained from the result. In the measurement, humidified hydrogen gas at room temperature (about 23 ° C.) was supplied as fuel gas to the fuel electrode, and oxygen was supplied to the air electrode. Moreover, as an open electromotive force, the value of 1.13V or more is obtained at 800 degreeC.

[Production of cell]
Next, taking a solid oxide fuel cell (comparative sample cell: # 1-1-0) as a comparative sample as an example, production of a single cell will be described. First, well known Sc ₂ O ₃ obtained by firing molded into a sheet by a doctor blade method, Al ₂ O ₃ doped zirconia _{(0.89ZrO 2 -0.10Sc 2 O 3 -0.01Al} 2 O 3: SASZ An electrolyte substrate is prepared. The electrolyte substrate is formed to a thickness of 0.2 mm. Next, a mixed powder obtained by mixing 8 mol% Y ₂ O ₃ added zirconia powder (40 wt%) with an average particle diameter of about 0.3 μm and NiO powder (60 wt%) with an average particle diameter of 0.8 μm. A slurry is prepared, and this slurry is applied to one surface of the above-described electrolyte substrate by a well-known screen printing method (see Non-Patent Document 3) to form a fuel electrode coating film. In addition, a current collector made of platinum mesh is disposed on the fuel electrode coating film, and these are fired in air under a heat treatment condition of 1400 ° C. for 4 hours. A fuel electrode having a thickness of 60 μm is formed.

Next, LaNi _0.6 Fe _0.4 O ₃ (LFN) powder (50 wt%) having an average particle diameter of 0.1 μm, and Ce _0.9 Gd _0.1 O ₂ (GDC) powder (50 wt%) having an average particle diameter of 0.1 μm, A slurry of mixed powder is prepared, and this slurry is applied to the other surface of the electrolyte substrate by the screen printing method to form an air electrode coating film. LFN is a perovskite oxide and GDC is a ceria compound. Next, the electrolyte substrate on which the air electrode coating film is formed is baked under heat treatment conditions of 1000 ° C. for 2 hours to form a state in which an air electrode having a thickness of 4 μm made of a sintered body of the mixed powder is formed.

Next, a slurry of LaNi _0.6 Fe _0.4 O ₃ (LFN) powder having an average particle size of 1.0 μm is prepared, and this slurry is applied on the air electrode by the screen printing method to form a current collecting layer coating film. It is assumed that it is formed. Thereafter, the electrolyte substrate on which the current collector layer coating film is formed is fired under heat treatment conditions of 1150 ° C. for 2 hours, and a current collector having a thickness of 40 μm made of a sintered body of LFN powder is formed on the air electrode. A layer is formed. As shown in the perspective view of FIG. 4, the unit cell formed in this way is an air electrode 402 formed in a disk having a diameter of 10 mm on an electrolyte substrate 401 formed in a square plate shape with a side of 30 mm. Has been placed. In FIG. 4, the fuel electrode disposed below the electrolyte substrate 401 is omitted from illustration. In addition, this single cell includes the reference electrode 403 made of platinum around the electrolyte substrate 401, and performs the above-described measurement in a state where it is connected thereto.

[Example 1]
Next, as Example 1, the production of solid oxide fuel cells (sample cells: # 1-1-1 to # 1-1-6) to be samples will be described. This sample cell uses a perovskite oxide powder in which Pr is added to LFN used for the air electrode of the above-described comparative sample cell, and a part of La constituting LFN is replaced with Pr. It is produced in the same manner as the cell. When the above-described measurement is performed on these sample cells, as shown in Table 1 below, the interface resistance is low and good compared to the comparative sample cell (# 1-1-0). The result is obtained.

Further, when LSFC is used instead of LFN, the following occurs. First, La _0.8 Sr _0.2 Fe _0.8 Co _0.2 O ₃ (LSFC) was used instead of LFN used for the air electrode of the above-described comparative sample cell, and the mixing ratio (% by weight) between this and GDC was changed to LSFC. : GDC = 3: 2 and the air electrode is produced as described above. In addition, in the LSFC, a sample cell (# 1-2-1 to # 1-2-6) is prepared using a perovskite oxide powder in which Pr is added and a part of La constituting the LSFC is replaced with Pr. ). As a comparative sample cell (# 1-2-0) for these, LSFC to which Pr is not added is used. When the above-described measurement was performed in these sample cells, as shown in Table 1 below, any sample (# 1-2-1 to # 1) was compared with the comparative sample cell (# 1-2-0). -2-6) Even in the cell, good results have been obtained with low interface resistance.

[Example 2]
Next, as Example 2, the production of solid oxide fuel cells (sample cells: # 2-1-1 to # 2-1-6) to be samples will be described. In this sample cell, an air electrode is prepared using Ce _0.8 Sm _0.2 O ₂ instead of the GDC described above, and the air electrode is prepared with a mixing ratio (% by weight) of this to the perovskite oxide being 1: 1. ing. In addition, an intermediate layer made of GDC is provided between the air electrode and the electrolyte. In the production of the intermediate layer, a slurry of GDC powder having an average particle size of 0.1 μm is applied to the electrolyte substrate by a screen printing method to form an intermediate layer application layer, which is fired under heat treatment conditions of 1200 ° C. for 2 hours. Then, an intermediate layer made of a sintered body of GDC powder is formed, and thereafter, an air electrode is formed as described above. As a comparative sample cell (# 2-1-0) for these, LNF not added with Pr is used. When the measurement described above was performed in these sample cells (# 2-1-1 to # 2-1-6), as shown in Table 2 below, it was compared with the comparative sample cell (# 2-1-0). In any sample cell, good results were obtained with low interface resistance.

  Also, instead of the above-mentioned sample cells (# 2-1-1 to # 2-1-6), sample cells (# 2-2-1 to # 2-2-6) using LSFC are also produced. To do. As a comparative sample cell (# 2-2-0) for these, LSFC to which Pr is not added is used. When the measurement described above was performed in these sample cells (# 2-2-1 to # 2-2-6), as shown in Table 2 below, it was compared with the comparative sample cell (# 2-2-0). In any sample cell, good results were obtained with low interface resistance.

[Example 3]
Next, Example 3 will be described. Here, as comparative sample cells (# 3-0-1 to # 3-0-5), the composition of LNF in the comparative sample cell (# 2-1-0) is LaNi _0.7 Fe _0.3 O ₃ , LaNi _0.6 Fe. It is made by changing to _0.4 O ₃ , LaNi _0.5 Fe _0.5 O ₃ , LaNi _0.4 Fe _0.6 O ₃ , and LaNi _0.2 Fe _0.8 O ₃ . In addition, sample cells (# 3-1-1 to # 3-1-5) in which La in the comparative sample cells (# 3-0-1 to # 3-0-5) is partially replaced with Pr atoms are used. Make it. When the above-described measurement is performed in these, as shown in Table 3 below, the interfacial resistance is low and good results are obtained in any of the sample cells as compared with the comparative sample cells.

[Example 4]
Next, Example 4 will be described. This is a comparison sample cell (# 4-0-1 to # 4-0-6) and sample cell (# 4-1-1 to # 4-1) using LSFC instead of the LNF in Example 3 described above. -6). In Example 4, GDC is mixed in the air electrode instead of SDC, and the comparison sample cells (# 4-0-1 to # 4-0-6) and sample cells (# 4-1-1 to Make # 4-1-6). When the above-described measurements are performed in these samples, as shown in Table 4 below, the interfacial resistance is low and good results are obtained in any of the sample cells as compared with the comparative sample cells.

[Example 5]
Next, Example 5 will be described. This is a comparative sample cell (# 5-0-1 to # 5-0-3) and Sm _0.5 Sr _0.5 CoO ₃ (SSC) using LaSrCoO ₃ (LSC) instead of the LSFC in Example 4 described above. Sample cells (# 5-1-1 to # 5-1-4) in which a part of La of LSC was replaced with Pr atoms were prepared. ) And a part of SSC Sm is replaced with Pr atoms (# 5-1-4). In addition, sample cells (# 5-2-1 to # 5-2-4) in which part of La of LSC is replaced with Pr atoms to change the composition of Sr (including Sr composition 0) are produced. . When the above-described measurements are performed, as shown in Table 5 below, the interface resistance is low and the characteristics are improved in each of the corresponding sample cells as compared with the comparative sample cell.

[Example 6]
Next, Example 6 will be described. This is a comparative sample cell (# 6-0-1 to # 6-0-3) using a perovskite oxide in which Sr in LSFC and SSC in Example 5 is changed to Ca which is the same alkaline earth metal. ) And sample cells (# 6-1-1 to # 6-1-3, # 6-2-1 to # 6-2-3). When the above-described measurement is performed in these, as shown in Table 6 below, the interface resistance is low and the characteristics are improved in each of the corresponding sample cells as compared with the comparative sample cell.

As described above, the perovskite oxide to which Pr constituting the air electrode is added is (Sm _1−x Pr _x ) _1−z Sr _z CoO ₃ (0.04 ≦ x ≦ 0.5, 0 ≦ z ≦ 0.6), La _1-x Pr _x Ni _1-y Fe _y O ₃ (0.04 ≦ x ≦ 1.0, 0.3 ≦ y ≦ 0.8), and (La _1-x Pr _x) in _{1-z Sr z Fe 1-} y Co y O 3 either (0.04 ≦ x ≦ 1.0,0.1 ≦ y ≦ 0.4,0,1 ≦ z ≦ 0.5) I understand that it is necessary.

  In addition, the particle diameter mentioned above is an average particle diameter obtained from the measurement of the light intensity distribution pattern by the well-known laser diffraction scattering method. For example, the particle size can be measured by using a laser diffraction / scattering particle size distribution measuring device LA-910 manufactured by HORIBA, Ltd.

  As described above, in the present invention, in the air electrode composed of a perovskite oxide and a ceria compound, part of the A site of the perovskite oxide such as LNF, LSFC, and LSC is replaced with Pr atoms. Therefore, some ceria compounds constituting the air electrode can be made to have hole conductivity, so that the so-called three-phase interface can be increased, which is suitable for improving the performance of the solid oxide fuel cell. It is.

It is sectional drawing which shows typically the structural example of the solid oxide fuel cell in Embodiment 1 of this invention. It is sectional drawing which shows typically the structural example of the solid oxide fuel cell in Embodiment 2 of this invention. It is sectional drawing which shows typically the structural example of the solid oxide fuel cell in Embodiment 3 of this invention. It is a perspective view which shows the structure of a sample cell.

Explanation of symbols

  101 ... electrolyte, 102 ... fuel electrode, 103 ... air electrode.

Claims (6)

In a solid oxide fuel cell comprising a fuel electrode, an electrolyte, and an air electrode,
The air electrode is
A first material made of cerium oxide to which a rare earth is added;
And a second material made of a perovskite-type metal oxide to which praseodymium is added. The solid oxide fuel cell according to claim 1, wherein
The air electrode is
A solid oxide fuel cell comprising a sintered body of a mixed powder in which a first powder made of the first material and a second powder made of the second material are mixed. The solid oxide fuel cell according to claim 1, wherein
The air electrode is
A solid oxide fuel cell comprising a region disposed on the electrolyte side and configured of the first material and the second material. The solid oxide fuel cell according to any one of claims 1 to 3,
Disposed between the electrolyte and the air electrode;
A solid oxide fuel cell comprising an intermediate layer made of cerium oxide to which a rare earth is added. In the solid oxide fuel cell according to any one of claims 1 to 4,
A solid oxide fuel cell comprising: a current collecting layer disposed on the opposite side of the air electrode from the electrolyte and made of the perovskite metal oxide. In the solid oxide fuel cell according to any one of claims 1 to 5,
The second material is (Sm _1-x Pr _x ) _1-z Sr _z CoO ₃ (0.04 ≦ x ≦ 0.5, 0 ≦ z ≦ 0.6), La _1-x Pr _x Ni _{1− y Fe y O 3 (0.04 ≦} x ≦ 1.0,0.3 ≦ y ≦ 0.8), and _{(La 1-x Pr x)} 1-z Sr z Fe 1-y Co y O 3 ( 0.04 ≦ x ≦ 1.0, 0.1 ≦ y ≦ 0.4, 0, 1 ≦ z ≦ 0.5) .

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