JP5117834B2 - Solid oxide fuel cell - Google Patents

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 is added with a first material composed of a perovskite metal oxide and praseodymium. look containing a second material consisting of cerium oxide, the second _{material, Ce 1-xy R x Pr} y O 2 (R = Gd, Sm, Y; 0 ≦ y ≦ 0.3; 0.02 ≦ x ≦ 0.3; 0.07 ≦ x + y ≦ 0.30) is obtained by the der so that.

  In the solid oxide fuel cell, the air electrode is configured by mixing the first material and the second material. In this case, the air electrode should just be comprised from the sintered compact of the mixed powder with which the 1st powder which consists of 1st materials, and the 2nd powder which consists of 2nd materials.

  In the solid oxide fuel cell, the air electrode is disposed on the electrolyte side, the first layer made of the second material, and the second layer disposed in contact with the first layer. With. In this case, the second layer of the air electrode is composed of the first material and the second material. The second layer of the air electrode is composed of cerium oxide to which a rare earth element other than the first material and praseodymium is added. The first layer is composed of a sintered body of second powder made of the second material. .

  The solid oxide fuel cell includes an intermediate layer made of cerium oxide to which a rare earth other than praseodymium is added and disposed between the electrolyte and the air electrode.

  The solid oxide fuel cell includes a current collecting layer that is disposed on the opposite side of the air electrode from the electrolyte and is made of a first material.

In the solid oxide fuel cell , the first material is La _1-x R _x MO ₃ (R = Sr, Ca; 0 ≦ x ≦ 0.6; M is at least Fe, Co, and Ni. One) and LaNi _1-y Fe _y O ₃ (0.3 ≦ y ≦ 0.8).

As described above, according to the present invention, the air electrode, viewed contains a first material containing the perovskite-type metal oxide, and a second material consisting of cerium oxide, praseodymium is added, the second material Is Ce _1-xy R _x Pr _y O ₂ (R = Gd, Sm, Y; 0 ≦ y ≦ 0.3; 0.02 ≦ x ≦ 0.3; 0.07 ≦ x + y ≦ 0.30) Oh so it was so that, in the solid oxide fuel cell more air electrode ceria compound and perovskite oxide is formed, an excellent effect that as a further improvement in the output voltage can be obtained is 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. Further, the solid oxide fuel cell of the present embodiment is formed on the other side of the electrolyte 101, and is a cerium oxide to which a perovskite-type metal oxide (perovskite oxide: first material) and praseodymium (Pr) are added. And an air electrode 103 including a material (ceria compound: second material). The air electrode 103 may be configured by mixing a ceria compound to which a perovskite oxide and praseodymium are added.

For example, the air electrode 103 is a mixture of a powder having a predetermined particle size (first powder) made of perovskite oxide and a powder having a predetermined particle size (second powder) made of a ceria compound to which Pr is added. What is necessary is just to be comprised from the sintered compact of the mixed powder made. As the perovskite oxide, LaNiFeO ₃ (LNF), LaSrFeNiO ₃ (LSFC), LaCoO ₃ (LC), SmSrCoO ₃ (SSC), or the like can be used. Further, as the ceria compound, CeGdO ₂ , CeSmO ₂ , CeYO _{2 and the} like can be used.

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). The fuel electrode 102 is made of, for example, nickel-yttria stabilized zirconia cermet (Ni-YSZ), nickel-scandia stabilized zirconia (Ni-ScSZ), and the like, in which metal nickel is mixed with an oxide material constituting the electrolyte 101. 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. First, the cerium elements in ceria compounds take the mixed-valence of Ce ⁴⁺ and Ce ³⁺ is in a reducing atmosphere, the Ce ⁴⁺ in an atmosphere containing air. For this reason, the ceria compound has low electron conductivity in the atmosphere, and can be regarded as an oxygen ion conductor in the air electrode to which air is supplied. On the other hand, it is known that Pr added to the ceria compound in the atmosphere generates holes and causes the ceria compound to exhibit hole conductivity. As a result, the ceria compound to which Pr is added has both oxygen ion conductivity and hole conductivity.

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 electrolyte .

On the other hand, according to the present embodiment, the ceria compound to which Pr constituting the air electrode is added becomes a mixed conductor having hole conductivity as well as ion conductivity. For this reason, even in the ceria compound to which Pr is added 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. As described above, according to the solid oxide fuel cell of the present embodiment, the reaction field (three-phase interface) of the electrochemical reaction at the air electrode is also transferred from the interface between the air electrode and the electrolyte to the air electrode side. Will 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.

  The amount of Pr added to the ceria compound is desirably in a range in which hole conductivity is expressed in the ceria compound and the original characteristics of the air electrode using the ceria compound are not deteriorated. If 1 at% of Pr is added to the ceria compound, the above-described effect of improving the characteristics can be obtained. On the other hand, since the solid solubility limit of Pr with respect to the ceria compound is about 30 at%, the amount of Pr added with respect to the ceria compound may be set to 1 to 30 at%.

  By the way, the ceria compound is usually obtained by adding rare earth elements such as Gd, Sm, and Y to cerium oxide. The amount of these rare earth elements added to the ceria compound generally used is 8-30 at%. It is considered as a range. Therefore, it suffices that Pr is added to the ceria compound so that the total amount with rare earth elements such as Gd, Sm, and Y is about 8 to 30 at%. Further, when the additive amount of Pr is increased by replacing an additive of an original ceria compound such as Gd, the conductivity of oxygen ions is somewhat decreased. From this point of view, in the region (layer) closer to the electrolyte 101 in the air electrode 103, the amount of Pr added to the ceria compound should be reduced, and the region farther from the electrolyte 101 should have a larger amount of Pr added to the ceria compound. .

[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. In the present embodiment, the air electrode 103 is disposed on the electrolyte 101 side, and is disposed in contact with the buffer layer 103a (first layer) 103a made of a ceria compound to which Pr is added, and the buffer layer 103a. And an electrode layer (second layer) 103b.

  The electrode layer 103b only needs to be made of at least a perovskite oxide (first material). The electrode layer 103b may be made of a perovskite oxide and a ceria compound. The electrode layer 103b may be made of a ceria compound (second material) to which perovskite oxide and Pr are added. In the first embodiment described above, an example in which the entire air electrode 103 is composed of a perovskite oxide (first material) and a ceria compound (second material) to which Pr is added has been described. In the second embodiment, the buffer layer 103a composed of a ceria compound to which Pr is added is provided at least on the electrolyte 101 side. For example, it may be a sintered body of powder of each material. In any case, the air electrode 103 includes a ceria compound to which perovskite oxide and Pr are added.

According to the solid oxide fuel cell of the present embodiment, since the buffer layer 103a including the ceria compound to which Pr is added is disposed on the electrolyte 101 side of the air electrode 103, as described above, A mixed conductor is formed, and the three-phase interface extends from the interface between the air electrode 103 and the electrolyte 101 to the air electrode 103 (buffer layer 103a) side. As a result, also in the solid oxide fuel cell of the present embodiment, in the air electrode 103 (buffer layer 103a), the electron (hole) conductivity is improved and the ion conductivity and the electron (hole) conductivity are improved. As a result, a mixed conductor region is formed, and the characteristics are improved and the output voltage is improved.

  The solid oxide fuel cell according to the present embodiment includes a current collecting layer 202 made of a perovskite metal oxide and disposed on the opposite side of the air electrode 103 from the electrolyte 101 in addition to the above-described configuration. . In this case, the electrolyte 101 is arranged on one side of the air electrode 103, and the current collecting layer 202 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 202. 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 202 made of perovskite oxide, which is an electron conductor (hole conductor), is provided on the air electrode 103 side, the air electrode 103 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 202 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. 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. The air electrode 103 includes a buffer layer 103a and an electrode layer 103b. The solid oxide fuel cell includes a current collecting layer 201. 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 composed of cerium oxide to which a rare earth other than Pr is added. is there. For example, the intermediate layer 301 may be composed of a sintered body of powder of _{GDC (Ce 0.8 Gd 0.2 O)} . 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. In addition, it can also be considered that the entire air electrode 103 including the intermediate layer 301 functions as an air electrode.

  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: # 1-0-0) 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%) with an average particle size of 0.1 μm, Ce _0.7 Gd _0.3 O ₂ (GDC) powder (50 wt%) with an average particle size of 0.2 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. Finally, a Pt mesh current collector is placed on the current collecting layer and fired under heat treatment conditions of 1000 ° C. for 2 hours.

  As shown in the perspective view of FIG. 4, the single cell formed in this way is formed on a disk 10 mm in diameter 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, sample solid oxide fuel cells (sample cells: # 1-1-1 to # 1-1-5, # 1-2-1 to # 1-2-4, The creation of # 1-3-1 to # 1-3-3 and # 1-4-1 to # 1-4-3) will be described. This sample cell uses ceria compound powder in which Pr is added to GDC used for the air electrode of the above-described comparative sample cell, and a part of Gd constituting GDC is replaced with Pr. Prepare in the same way.

In addition, comparative sample cells (# 1-2-0, # 1-3-0, # 1-4-0) with different amounts of Gd added (composition ratio) in GDC were also produced, and the comparative sample cells (# 1- 0-0) and sample cells (# 1-1-1 to # 1-1-5), and compare sample cells (# 1-2-0) and sample cells (# 1-2-1 to # 1- 2-4), the comparison sample cell (# 1-3-0) and the sample cell (# 1-3-1 to # 1-3-3) are compared, and the comparison sample cell (# 1-4- 0) and the sample cell (# 1-4-1 to # 1-4-3) are compared. In the comparison sample cell (# 1-0-0) and sample cell (# 1-1-1 to # 1-1-5), the total number of rare earth elements to be added is 0.3, and the comparison sample cell (# 1 -2-0) and sample cells (# 1-2-1 to # 1-2-4), the total number of rare earth elements to be added is 0.2, and comparative sample cells (# 1-3-0) and In the sample cells (# 1-3-1 to # 1-3-3), the total number of rare earth elements to be added is 0.1, and the comparative sample cell (# 1-4-0) and sample cell (# 1- In 4-1 to # 1-4-3), the total amount of rare earth elements to be added is 0.08.

  When the above-described measurements were performed on these sample cells, as shown in Table 1 below, comparative sample cells (# 1-0-0, # 1-2-0, # 1-3-0, # 1-4 -0), any sample cell (# 1-1-1 to # 1-1-5, # 1-2-1 to # 1-2-4, # 1-3-1 to # 1 -3-3, # 1-4-1 to # 1-4-3) also show good results 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, the air electrode of the above-described comparative sample cell is arranged on the electrolyte side and is made of a ceria compound to which Pr is added, and is placed in contact with the buffer layer and Pr is added. And an electrode layer containing a ceria compound. In Example 2, GDC is used as the ceria compound. In addition, as a comparative sample cell (# 2-1-0) for these, a buffer layer is composed of GDC (Pe _0.8 Gd _0.2 O ₂ ) to which no Pr is added, and the ceria compound contained in the electrode layer Is GDC to which Pr is not added (Ce _0.7 Gd _0.3 O ₂ ).

  In Example 2, GDC or ceria compound powder to which Pr is added is used, and the buffer layer coating layer is formed on the other surface of the electrolyte substrate by screen printing, and this is heat treated at 1200 ° C. Baking is performed under conditions to form a buffer layer having a thickness of 4 μm. Thereafter, an electrode layer coating layer is applied and formed on the buffer layer in the same manner as described above, and this is baked to form an electrode layer. The buffer layer and the electrode layer form an air electrode.

  When the above-described measurement is performed in these sample cells, as shown in Table 2 below, any sample cell (# 2-1-1 to ##) is compared with the comparative sample cell (# 2-1-0). Also in 2-1-6), good results have been obtained with low interface resistance.

[Example 3]
Next, as Example 3, the production of solid oxide fuel cells (sample cells: # 3-1-1 to # 3-1-6) to be samples will be described. This sample cell is an SDC instead of the GDC of the buffer layer and the electrode layer in Example 2 described above. As a comparative sample cell (# 3-1-0) for these, SDC (Ce _0.8 Sm _0.2 O ₂ ) to which Pr is not added is used for the buffer layer, and SDC (Pr is not added to the electrode layer). Ce _0.7 Sm _0.3 O ₂ ) is used.

  When the above-described measurement was performed on these sample cells, as shown in Table 3 below, any sample cell (# 3-1-1 to # 3-1) was compared with the comparative sample cell (# 3-1-0). Also in 3-1-6), good results have been obtained with low interface resistance.

[Example 4]
Next, as Example 4, the production of solid oxide fuel cells (sample cells: # 4-1-1 to # 4-1-6) to be samples will be described. This sample cell is a YDC instead of the SDC of the buffer layer and electrode layer in Example 3 described above. As a comparative sample cell (# 4-1-0) for these, YDC (Ce _0.8 Y _0.2 O ₂ ) to which Pr is not added is used for the buffer layer, and YDC (Pr is not added to the electrode layer). Ce _0.7 Y _0.3 O ₂ ) is used.

  When the above-described measurement is performed in these sample cells, as shown in Table 4 below, any sample cell (# 4-1-1 to # 4-1) is compared with the comparative sample cell (# 4-1-0). Also in 4-1-6), good results have been obtained with low interface resistance.

[Example 5]
Next, as Example 5, preparation of solid oxide fuel cells (sample cells: # 5-1-1 to # 5-1-6) to be samples will be described. In this sample cell, the electrode layer constituting the air electrode in Example 2 described above is made of perovskite oxide without containing a ceria compound. LNF is used as the perovskite oxide constituting the electrode layer. As a comparative sample cell (# 5-1-0) for these, GDC (Ce _0.7 Ge _0.3 O ₂ ) in which Pr is not added to the buffer layer is used.

  In Example 5, GDC or a ceria compound powder to which Pr was added was used, and the buffer layer coating layer was formed on the other surface of the electrolyte substrate by a screen printing method. Baking is performed under heat treatment conditions for a time to form a buffer layer having a thickness of 4 μm. Thereafter, the LNF powder is used on the buffer layer, and the electrode layer coating layer is applied and formed on the buffer layer in the same manner as described above, and this is baked under heat treatment conditions of 1150 ° C. for 2 hours. Form. The buffer layer and the electrode layer form an air electrode.

  When the above-described measurement is performed on these sample cells, as shown in Table 5 below, any sample cell (# 5-1-1 to # -5) is compared with the comparative sample cell (# 5-1-0). Also in 5-1-6), good results have been obtained with low interface resistance.

[Example 6]
Next, as Example 6, preparation of solid oxide fuel cells (sample cells: # 6-1-1 to # 6-1-5) to be samples will be described. In this sample cell, the LNF of the electrode layer in Example 2 described above is replaced with LSFC, LSC, LC, and SSC. In the electrode layer, the composition ratio of the ceria compound (GDC) is 40 wt%. As comparative sample cells (# 6-0-1 to # 6-0-5) for these, GDC (Ce _0.8 Gd _0.2 O ₂ ) to which Pr is not added is used for the buffer layer, and Pr is used for the electrode layer. GDC (Ce _0.8 Gd _0.2 O ₂ ) to which no is added is used.

  When the above-described measurement is performed in these sample cells, as shown in Table 6 below, any corresponding sample cell is compared with the comparative sample cells (# 6-0-1 to # 6-0-5). Also in (# 6-1-1 to # 6-1-5), the interface resistance is low and good results are obtained.

[Example 7]
Next, as Example 7, preparation of solid oxide fuel cells (sample cells: # 7-1-1 to # 7-1-6) to be samples will be described. In this sample cell, the LNF of the electrode layer in Example 2 described above is replaced with LSFC, LSC, LC, and SSC. In the electrode layer, the composition ratio of the ceria compound (GDC) is 40 wt%. In addition, an intermediate layer made of cerium oxide (Ce _0.8 Gd _0.2 O 2) to which a rare earth other than Pr is added is provided between the air electrode (buffer layer) and the electrolyte substrate. The thickness of the intermediate layer is 4 μm. Each layer is produced in the same manner as in Example 2.

As comparative sample cells (# 7-0-1 to # 7-0-5) for these, GDC (Ce _0.8 Gd _0.2 O ₂ ) to which Pr is not added is used for the buffer layer, and Pr is used for the electrode layer. GDC (Ce _0.8 Gd _0.2 O ₂ ) to which no is added is used.

  When the above-described measurement is performed in these sample cells, as shown in Table 7 below, any corresponding sample cell is compared with the comparative sample cells (# 7-0-1 to # 7-0-6). Also in (# 7-1-1 to # 7-1-6), the interface resistance is low and good results are obtained.

From the above examples, the ceria compound used by adding Pr is Ce _1-xy R _x Pr _y O ₂ (R = Gd, Sm, Y; 0 ≦ y ≦ 0.3; 0.02 ≦ x ≦ 0.3; 0.07 ≦ x + y ≦ 0.30). The perovskite oxide is composed of La _1-x R _x MO ₃ (R = Sr, Ca; 0 ≦ x ≦ 0.6; M is at least one of Fe, Co, and Ni) and LaNi _1-y Fe. It can be seen that any one of _y O ₃ (0.3 ≦ y ≦ 0.8) may be used.

  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 a solid oxide fuel cell including an air electrode composed of a perovskite oxide and a ceria compound, Pr is added to the ceria compound, so that the three-phase interface in the air electrode is used. This is suitable for improving the performance of a solid oxide fuel cell.

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

  DESCRIPTION OF SYMBOLS 101 ... Electrolyte, 102 ... Fuel electrode, 103 ... Air electrode, 103a ... Buffer layer (1st layer), 103b ... Electrode layer (2nd layer), 301 ... Intermediate | middle layer.

Claims (10)

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 a perovskite-type metal oxide;
And a second material consisting of cerium oxide, praseodymium is added seen including,
The second material is
_{Ce 1-xy R x Pr y} O 2 (R = Gd, Sm, Y; 0 ≦ y ≦ 0.3; 0.02 ≦ x ≦ 0.3; 0.07 ≦ x + y ≦ 0.30) Ru der A solid oxide fuel cell. The solid oxide fuel cell according to claim 1, wherein
The air electrode is configured by mixing the first material and the second material. A solid oxide fuel cell, wherein: The solid oxide fuel cell according to claim 2, 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 first layer disposed on the electrolyte side and composed of the second material;
A solid oxide fuel cell comprising: a second layer disposed in contact with the first layer. The solid oxide fuel cell according to claim 4, wherein
The second layer of the air electrode is
A solid oxide fuel cell comprising the first material and the second material. The solid oxide fuel cell according to claim 4, wherein
The second layer of the air electrode is
A solid oxide fuel cell comprising: a cerium oxide to which a rare earth element other than the first material and praseodymium is added. The solid oxide fuel cell according to any one of claims 4 to 6, wherein
The first layer is
It is comprised from the sintered compact of the 2nd powder which consists of said 2nd material. The solid oxide fuel cell characterized by the above-mentioned. The solid oxide fuel cell according to any one of claims 1 to 7,
A solid oxide fuel cell comprising: an intermediate layer made of cerium oxide disposed between the electrolyte and the air electrode to which a rare earth other than praseodymium is added. The solid oxide fuel cell according to any one of claims 1 to 8,
Disposed on the opposite side of the air electrode from the electrolyte;
A solid oxide fuel cell comprising a current collecting layer made of the first material. The solid oxide fuel cell according to any one of claims 1 to 9 ,
The first material is:
La _1-x R _x MO ₃ (R = Sr, Ca; 0 ≦ x ≦ 0.6; M is at least one of Fe, Co, and Ni) and LaNi _1-y Fe _y O ₃ (0.3 ≦ y ≦ 0.8). A solid oxide fuel cell, wherein the solid oxide fuel cell is selected.

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