JP7091278B2 - Electrode material for solid oxide fuel cell, anode electrode for solid oxide fuel cell using it, and solid oxide fuel cell using it - Google Patents

Description

The present invention relates to an electrode material for a solid oxide fuel cell, an anode electrode for a solid oxide fuel cell using the same, and a solid oxide fuel cell using the same.

As the anode electrode of the conventional solid oxide fuel cell, a cermet of metal Ni and an oxygen ion (O ^2- ) conductor (for example, yttria-stabilized zirconia (YSZ)) has been used. However, in the anode electrode made of cermets of Ni and YSZ, the operating temperature of the solid oxide fuel cell is high, so that Ni aggregates during the operation of the solid oxide fuel cell, and the solid oxide fuel cell. There was a problem that the power generation performance of the fuel cell was deteriorated.

Therefore, in order to solve such a problem, Tadazaki et al. (Non-Patent Document 1) stated that as an oxygen ion conductor that replaces YSZ in the anode electrode, it is excellent not only in oxygen ion conductivity but also in electron conductivity. In addition, Ca was added to Gd ₂ Ti ₂ O ₇ and Y ₂ Ti ₂ O ₇ having a pyrochlor structure (Gd _0.9 Ca _0.1 ) ₂ Ti ₂ O ₇ (GCT) and (Y _0.9 Ca). _0.1 ) ₂ Ti ₂ O ₇ (YCT) has been proposed.

Further, in Japanese Patent Application Laid-Open No. 2008-91264 (Patent Document 1), an oxygen absorber made of a pyrochlor type Ce ₂ Zr ₂ O ₇ is supported as an electrode for a fuel cell using a pyrochlor type ceria-zirconia composite oxide. Disclosed is a fuel cell cathode electrode having a catalyst layer composed of a catalyst-supported conductor and a polymer electrolyte. However, the pyrochlore _- type Ce ₂ Zr ₂ O7 used here does not have sufficiently high heat resistance and is not suitable as an electrode material for a solid oxide fuel cell that operates at a high temperature.

Japanese Unexamined Patent Publication No. 2008-91264

Sasouzaki et al., Proceedings of the Annual Meeting of the Petroleum Society / Autumn Meeting, 2014, p. 89

The present invention has been made in view of the above-mentioned problems of the prior art, and is an anode electrode for a solid oxide fuel cell having excellent thermal stability and a solid oxide having excellent durability at high temperatures during power generation. It is an object of the present invention to provide a type fuel cell and an electrode material for obtaining the anode electrode.

As a result of diligent research to achieve the above object, the present inventors have obtained a specific ratio of Ce, and the pyrochlore-type ceria-zirconia-lanthana whose superlattice structure is sufficiently maintained even when exposed to high temperatures. It was found that an anode electrode for a solid oxide fuel cell having excellent thermal stability can be obtained by adding an electrode material made of a composite oxide to the anode electrode material, and further, power generation is performed by using this anode electrode. We have found that a solid oxide fuel cell having excellent durability at medium high temperatures can be obtained, and have completed the present invention.

That is, the electrode material for a solid oxide fuel cell of the present invention has a chemical composition of Ce _x Zr ₂ La _(2-x) O ₇ (x = 0.2 to 0.6) and has a super lattice structure. It is characterized by being composed of a pyrochlore-type composite oxide.

In such an electrode material for a solid oxide fuel cell of the present invention, the pyrochlore-type composite oxide is heated in the air at 1400 ° C. for 5 hours and then X-rays obtained by X-ray diffraction measurement using CuKα. The condition that the intensity ratio {I (14/29) value} of the diffraction line of 2θ = 14.5 ° and the diffraction line of 2θ = 29 ° obtained from the diffraction pattern is as follows:
I (14/29) value ≧ 0.02
It is preferable that the particle size satisfies the above conditions, and the average particle size of the pyrochlore-type composite oxide is preferably 1 μm or less.

The anode electrode for a solid oxide fuel cell of the present invention is characterized by containing the electrode material for a solid oxide fuel cell of the present invention, and the solid oxide fuel cell of the present invention is characterized by containing the electrode material for the solid oxide fuel cell of the present invention. It is characterized by including the anode electrode of the present invention.

Although it is not always clear why the anode electrode for a solid oxide fuel cell of the present invention has excellent thermal stability, that is, the electrode characteristics are maintained even at high temperatures during power generation, the present inventors. Infers as follows. That is, in the solid oxide fuel cell, the oxygen ions (O ^-2- ) that have moved from the solid electrolyte layer during power generation dissipate the oxygen ion conductor (for example, yttrium stabilized zirconia (YSZ)) in the anode electrode. It moves and reacts with hydrogen (H ₂ ) introduced into the anode electrode to produce water (H ₂ O). In the conventional anode electrode for solid oxide fuel cells, it is presumed that this water oxidizes the active material (for example, metallic Ni) under high temperature during power generation, so that the active material is deactivated and the electrode characteristics deteriorate. Will be done.

On the other hand, also in the solid oxide fuel cell of the present invention, as shown in FIG. 1, oxygen ions ( ^O2- ) that have moved from the solid electrolyte layer 11 are oxygen ion conductors 12a (for example, for example) in the anode electrode 12. Ittium-stabilized zirconia (YSZ)) is transferred and reacts with hydrogen (H ₂ ) introduced into the anode electrode 12 to generate water (H ₂ O). The anode electrode 12 for a solid oxide fuel cell of the present invention contains an electrode material composed of a pyrochlore-type ceria-zirconia-lanthana composite oxide containing Ce in a specific ratio and having a super lattice structure. This pyrochlore-type ceria-zirconia-lanthana composite oxide has a sufficiently maintained superlattice structure even at high temperatures during power generation and has high oxygen occlusion performance. Therefore, as shown in FIG. 2, during power generation. Oxygen in the water molecule ( _H2O ) generated in is stored in the oxygen occlusion site 21 of the pyrochlore-type ceria-zirconia-lanthana composite oxide. As a result, in the anode electrode for a solid oxide fuel cell of the present invention, oxidation of the active material (for example, metallic Ni) by water is unlikely to occur even at a high temperature during power generation, and the active material is not deactivated. .. Further, since the stored oxygen is reduced by hydrogen existing in the power generation atmosphere, oxygen defects (oxygen storage sites) 21 are generated in the pyrochlore-type ceria-zirconia-lanthana composite oxide, and again in the water molecule. It becomes possible to occlude oxygen. It is presumed that the anode electrode for a solid oxide fuel cell of the present invention maintains the electrode characteristics even at a high temperature during power generation by such a mechanism.

According to the present invention, an anode electrode for a solid oxide fuel cell having excellent thermal stability, a solid oxide fuel cell having excellent durability at high temperatures during power generation, and the anode electrode can be obtained. It becomes possible to obtain an electrode material for a solid oxide fuel cell.

It is a schematic diagram which shows the reaction mechanism in the anode electrode for a solid oxide fuel cell of this invention. It is a schematic diagram which shows the occlusion mechanism of oxygen in a water molecule ( _H2O ) in the anode electrode for a solid oxide type fuel cell of this invention. It is a schematic diagram which shows the single cell for a fuel cell produced in an Example and a comparative example. It is a graph which shows the relationship between the content rate of Ce in a ceria-zirconia-Lantana (CZL) composite oxide, and the durability time of a single cell for a fuel cell.

Hereinafter, the present invention will be described in detail according to the preferred embodiment thereof.

[Electrode material]
First, the electrode material for a solid oxide fuel cell of the present invention will be described. The electrode material of the present invention is an electrode material used for a solid oxide fuel cell, and has a chemical composition of Cex Zr ₂ La (2- _{x )} O ₇ (x = 0.2 to 0.6). , It is composed of a pyrochlor type composite oxide having a super lattice structure.

(Pyrochlore type composite oxide)
The composite oxide constituting the electrode material of the present invention is a pyrochlore-type composite oxide containing cerium (Ce), zirconium (Zr) and lanthanum (La) and having a superlattice structure. Hereinafter, the composite oxide containing cerium (Ce), zirconium (Zr), and lanthanum (La) is referred to as "CZL composite oxide", and the pyrochlore-type CZL composite oxide having a superlattice structure is referred to as "pyrochlore-type CZL". It is called "composite oxide". Since such a pyrochlor-type CZL composite oxide has a superlattice structure and exhibits high oxygen absorption / release ability, the reaction between oxygen ions (O ^2- ) and hydrogen (H ₂ ) during power generation at the anode electrode. Oxygen in the water molecule generated by water can be stored to suppress the oxidation of the active material (for example, metallic Ni) in the anode electrode by water. In addition, since the stored oxygen is reduced by hydrogen existing in the power generation atmosphere, oxygen defects (oxygen storage sites) are generated in the pyrochlore type CZL composite oxide, and oxygen in the water molecules is stored again. Is possible. The anode electrode for a solid oxide fuel cell of the present invention exhibits excellent durability by such a mechanism.

The superlattice structure (regular phase) of the pyrochlor type CZL composite oxide, that is, the crystal phase having a ordered structure formed by cerium ions and zirconium ions, is obtained by X-ray diffraction measurement using CuKα. A crystal arrangement structure (φ'phase (the same phase as the κ phase) type) in which the 2θ angles of the line diffraction pattern have peaks at positions of 14.5 °, 28 °, 37 °, 44.5 ° and 51 °, respectively. Regular array phase: a superlattice structure that occurs in the fluorite structure). Therefore, the formation of the superlattice structure (regular phase) of the pyrochlore-type CZL composite oxide is formed in the pyrochlore phase having the superlattice structure in the X-ray diffraction pattern of the CZL composite oxide obtained by the X-ray diffraction measurement using CuKα. It can be confirmed by recognizing the existence of the derived peak (the peak at which the 2θ angle of the X-ray diffraction pattern using CuKα appears at 14.0 ° to 16.0 °).

The chemical composition of the pyrochlore-type CZL composite oxide used in the present invention is Ce _x Zr ₂ La _(2-x) O ₇ (x = 0.2 to 0.6). When x is 0.2 to 0.6, that is, the content of Ce is 5 to 15 at% with respect to the total amount of Ce, Zr and La, the pyrochlor type CZL composite oxide is exposed to high temperature. However, since the super lattice structure is sufficiently maintained and it has a high oxygen absorption / release capacity, it can occlude oxygen in the generated water molecules even at high temperatures during power generation, and the anode electrode with water can be used. Oxidation of the active material inside can be suppressed. In addition, since the stored oxygen is reduced by hydrogen existing in the power generation atmosphere, oxygen defects (oxygen storage sites) are generated in the pyrochlore type CZL composite oxide, and oxygen in the water molecules is stored again. Is possible. The anode electrode for a solid oxide fuel cell of the present invention exhibits excellent thermal stability by such a mechanism. On the other hand, when x is less than 0.2, that is, when the Ce content is less than 5 at%, the CZL composite oxide does not exhibit sufficient oxygen absorption / release ability, and sufficiently oxygen in the water molecule generated during power generation is sufficient. Since it cannot be stored and the oxidation of the active material in the anode electrode by water cannot be sufficiently suppressed, it becomes difficult to form an anode electrode having excellent durability. On the other hand, when x exceeds 0.6, that is, when the Ce content exceeds 15 at%, the CZL composite oxide does not sufficiently maintain its superlattice structure when exposed to high temperatures, and has an oxygen absorption / release capacity. Also declines. As a result, at high temperatures during power generation, oxygen in the generated water molecules cannot be sufficiently occluded, and oxidation of the active material in the anode electrode by water cannot be sufficiently suppressed, so that thermal stability is not sufficient. It becomes difficult to form an excellent anode electrode. Further, from the viewpoint of improving the thermal stability of the anode electrode, it is preferable that x is 0.4 to 0.6, that is, the Ce content is 10 to 15 at%.

Further, in the pyrochlor type CZL composite oxide used in the present invention, 2θ = 14. obtained from an X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα after heating at 1400 ° C. for 5 hours in the atmosphere. The condition that the intensity ratio {I (14/29) value} between the 5 ° diffraction line and the 2θ = 29 ° diffraction line is as follows:
I (14/29) value ≧ 0.02
It is preferable to satisfy. The pyrochlore-type CZL composite oxide having the I (14/29) value satisfying the above conditions has a superlattice structure sufficiently maintained even when exposed to a high temperature and has a high oxygen absorption / release capacity, so that it can generate power. Even at a high temperature inside, oxygen in the generated water molecules can be occluded and oxidation of the active material in the anode electrode by water can be suppressed. In addition, since the stored oxygen is reduced by hydrogen existing in the power generation atmosphere, oxygen defects (oxygen storage sites) are generated in the pyrochlore type CZL composite oxide, and oxygen in the water molecules is stored again. Is possible. The anode electrode for a solid oxide fuel cell of the present invention exhibits excellent thermal stability by such a mechanism. On the other hand, when the CZL composite oxide having an I (14/29) value of less than the lower limit is exposed to a high temperature, the superlattice structure is not sufficiently maintained and the oxygen absorption / release capacity is also lowered. As a result, at high temperatures during power generation, oxygen in the generated water molecules cannot be sufficiently occluded, and oxidation of the active material in the anode electrode by water cannot be sufficiently suppressed, so that thermal stability is not sufficient. It tends to be difficult to form an excellent anode electrode. The upper limit of the I (14/29) value is not particularly limited, but I (14/29) of the pyrochlore phase (Ce ₂ Zr ₂ O ₇ ) calculated from the PDF card (PDF 2: 01-075-2694). ) It is preferably 0.05 or less from the viewpoint that the value becomes the upper limit.

The I (14/29) value in the present invention is obtained from an X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα after heating the CZL composite oxide to be measured in the air at 1400 ° C. for 5 hours. It is the intensity ratio of the obtained diffraction line of 2θ = 14.5 ° and the diffraction line of 2θ = 29 °. Here, the diffraction line of 2θ = 14.5 ° belongs to the (111) plane of the ordered phase (κ phase), and the diffraction line of 2θ = 29 ° belongs to the (222) plane of the ordered phase. Since the diffraction line and the diffraction line belonging to the cubic phase (111) plane of the ceria-zirconia solid solution (CZ solid solution) overlap, the I (14/29) value, which is the intensity ratio of both diffraction lines, is calculated. It is defined as an index showing the superlattice structure (regular phase) maintenance rate (presence rate). When determining the diffraction line intensity, the average diffraction line intensity of 2θ = 10 ° to 12 ° is subtracted from the value of each diffraction line intensity as a background value. Further, the completely ordered phase includes a κ phase (Ce ₂ Zr ₂ O ₈ ) completely filled with oxygen and a pyrochlor phase (Ce ₂ Zr ₂ O ₇ ) completely depleted of oxygen, and each PDF is used. The I (14/29) value of the κ phase calculated from the card (PDF 2: 01-070-4048 for the κ phase, PDF 2: 01-075-2694 for the pyrochlor phase) is 0.04, and the I (14/29) of the pyrochlor phase. ) The value is 0.05.

As the method of the X-ray diffraction measurement, an X-ray diffractometer X-ray diffractometer (“RINT-Ultima” manufactured by Rigaku Co., Ltd.) is used, and CuKα ray is used as an X-ray source at 40 KV, 40 mA, 2θ = 5 ° /. A method of measuring under the condition of minutes can be adopted. Further, the "peak" in the X-ray diffraction pattern means that the height from the baseline to the peak top is 30 cps or more.

Further, as the average particle size of the pyrochlor type CZL composite oxide used in the present invention, a cermet is formed with an active material (metal Ni or the like) or an oxygen ion conductor (yttrium-stabilized zirconia (YSZ) or the like) described later. From the viewpoint of easy operation, 1 μm or less is preferable. The lower limit of the average particle size of the pyrochlore-type CZL composite oxide is not particularly limited, but is preferably 0.1 μm or more from the viewpoint of ensuring heat resistance. The average particle size of such a pyrochlor-type CZL composite oxide is determined by commercially available image analysis software (for example, "A" manufactured by Asahi Kasei Engineering Co., Ltd., based on an SEM image (2000 times) obtained by observation with a transmission electron microscope. It can be obtained by using "Image-kun").

As a method for preparing the pyrochlore-type CZL composite oxide used in the present invention, for example, the atomic ratio is Ce / Zr / La = x / 2 / 2-x (x = 0.2 to 0.6, A method of subjecting the lanthana-containing cerium-zirconia solid solution, which is preferably 0.4 to 0.6), to a reduction treatment at a temperature of 1300 to 1500 ° C. for 1 to 10 hours and then to an oxidation treatment can be mentioned.

The lanthana-containing cerium-zirconia solid solution has an atomic ratio of Ce / Zr / La = x / 2 / 2-x (x = 0.2 to 0.6, preferably 0.4 to 0.6). Although not particularly limited, in the pyrochlore-type CZL composite oxide, a solid solution in which cerium and zirconia are mixed at the atomic level is preferable from the viewpoint of sufficiently forming a superlattice structure.

Such a lantana-containing ceria-zirconia solid solution can be prepared, for example, by a coprecipitation method. Specifically, the atomic ratio of the obtained lanterna-containing cerium-zirconia solid solution is Ce / Zr / La = x / 2 / 2-x (x = 0.2 to 0.6, preferably 0.4 to 0.6). ) In an aqueous solution containing a salt of cerium (eg, cerium nitrate), a salt of zirconium (eg, zirconium nitrate) and a salt of lanthanum (eg, lanthanum nitrate), a co-deposit in the presence of ammonia. The lantana-containing cerium-zirconia solid solution can be obtained by producing the above-mentioned cerium and drying the obtained co-precipitate and then calcining it.

In the method for preparing the pyrochlore-type CZL composite oxide, first, the lanthana-containing ceria-zirconia solid solution having the atomic ratio is charged with a temperature of 1300 to 1500 ° C. (preferably 1400 to 1500 ° C.) for 1 to 10 hours (preferably 1400 to 1500 ° C.). Preferably, the reduction treatment (1 to 5 hours) is performed. This makes it possible to obtain a pyrochlore-type CZL composite oxide having excellent thermal stability. When the reduction treatment temperature is less than the above lower limit, the thermal stability of the superlattice structure becomes low, and the obtained pyrochlore-type CZL composite oxide does not sufficiently maintain the superlattice structure when exposed to high temperatures, and oxygen. The absorption and release capacity also decreases. As a result, at high temperatures during power generation, oxygen in the generated water molecules cannot be sufficiently occluded, and oxidation of the active material in the anode electrode by water cannot be sufficiently suppressed, so that thermal stability is not sufficient. It becomes difficult to form an excellent anode electrode. On the other hand, when the reduction treatment temperature exceeds the upper limit, the balance between the energy (for example, electric power) required for the reduction treatment and the performance improvement deteriorates. Further, when the reduction treatment time is less than the above lower limit, the obtained CZL composite oxide does not sufficiently form a superlattice structure and does not exhibit sufficient oxygen absorption / release ability. As a result, oxygen in the water molecules generated during power generation cannot be sufficiently occluded, and oxidation of the active material in the anode electrode by water cannot be sufficiently suppressed, so that the anode electrode has excellent durability. Becomes difficult to form. On the other hand, when the reduction treatment time exceeds the upper limit, the balance between the energy (for example, electric power) required for the reduction treatment and the performance improvement deteriorates.

The method of the reduction treatment is not particularly limited as long as it is a method capable of heat-treating the lanthana-containing ceria-zirconia solid solution under a predetermined temperature condition in a reducing atmosphere, and (i) the above-mentioned in a vacuum heating furnace. After installing a lanthana-containing ceria-zirconia solid solution and drawing a vacuum, a reducing gas is flowed into the furnace to make the atmosphere inside the furnace a reducing atmosphere, and heating is performed at a predetermined temperature to perform reduction treatment (ii). ) Using a graphite furnace, the lanthana-containing ceria-zirconia solid solution is placed in the furnace, evacuated, and then heated at a predetermined temperature to reduce the CO, HC, etc. generated from the furnace body, heated fuel, etc. A method of reducing the atmosphere in the furnace with gas as a reducing atmosphere, (iii) CO generated from activated carbon or the like by installing the lanthana-containing ceria-zirconia solid solution in a crucible filled with activated carbon and heating it at a predetermined temperature. And a method of performing a reduction treatment using a reducing gas such as HC or HC to make the atmosphere in the crucible a reducing atmosphere.

_The reducing gas used to achieve such a reducing atmosphere is not particularly limited, and examples thereof include reducing gases such as CO, HC, H2, and other hydrocarbon gases. Further, among such reducing gases, carbon (C) is not contained from the viewpoint of preventing the formation of compound products such as zirconium carbide (ZrC) when the reduction treatment is carried out at a higher temperature. The one is preferable. When such a reducing gas containing no carbon (C) is used, reduction treatment at a higher temperature close to the melting point of zirconium or the like is possible, so that the thermal stability of the superlattice structure can be further improved. Is possible.

In the method for preparing a pyrochlore-type CZL composite oxide, an oxidation treatment is further performed after such a reduction treatment. As a result, oxygen lost during the reduction treatment is supplemented, and the stability as a pyrochlore-type CZL composite oxide is improved. The method of such an oxidation treatment is not particularly limited, and for example, a method of heat-treating the pyrochlore-type CZL composite oxide after the reduction treatment in an oxidizing atmosphere (for example, in the atmosphere) can be preferably adopted. .. The oxidation treatment temperature is not particularly limited, but is preferably about 300 to 700 ° C. (more preferably about 400 to 600 ° C.). Further, the oxidation treatment time is not particularly limited, but is preferably about 3 to 7 hours (more preferably about 4 to 6 hours).

Further, in the method for preparing the pyrochlore-type CZL composite oxide, it is preferable to pulverize the pyrochlore-type CZL composite oxide after the reduction treatment and / or the oxidation treatment. The method of the pulverization treatment is not particularly limited, and examples thereof include a wet pulverization method, a dry pulverization method, and a freeze pulverization method.

(Electrode material for solid oxide fuel cell)
The electrode material for a solid oxide fuel cell of the present invention is made of a pyrochlore-type CZL composite oxide having the above-mentioned chemical composition and a superlattice structure. Since such a pyrochlor-type CZL composite oxide has a sufficiently maintained superlattice structure even when exposed to high temperatures and has a high oxygen absorption / release capacity, an electrode made of this pyrochlor-type CZL composite oxide is formed. By adding the material to the anode electrode, oxygen in the generated water molecules can be stored even at a high temperature during power generation, and oxidation of the active material in the anode electrode by water can be suppressed. In addition, since the stored oxygen is reduced by hydrogen existing in the power generation atmosphere, oxygen defects (oxygen storage sites) are generated in the pyrochlore type CZL composite oxide, and oxygen in the water molecules is stored again. Is possible. The anode electrode for a solid oxide fuel cell of the present invention exhibits excellent thermal stability by such a mechanism.

[Anode electrode]
Next, the anode electrode for a solid oxide fuel cell of the present invention will be described. The anode electrode of the present invention is an anode electrode used in a solid oxide fuel cell, and is derived from the electrode material of the present invention, that is, a pyrochlorite type CZL composite oxide having the chemical composition and a super lattice structure. It contains an electrode material.

The content of the electrode material composed of the pyrochroma-type CZL composite oxide in the anode electrode of the present invention is not particularly limited as long as it does not impair the effect of the present invention, but it may be under high temperature during power generation. Oxidation in the generated water molecules can be stored to suppress the oxidation of the active material in the anode electrode by water, and the stored oxygen is reduced by the hydrogen present in the power generation atmosphere to form a pyrochlor type CZL. From the viewpoint that oxygen defects (oxygen storage sites) are generated in the composite oxide, oxygen in water molecules can be stored again, and an anode electrode having excellent thermal stability can be formed. 5% by mass or more is preferable with respect to the entire anode electrode, 10% by mass or more is more preferable, 15% by mass or more is particularly preferable, and from the viewpoint of ensuring the structural stability of the anode electrode, with respect to the entire anode electrode. 30% by mass or less is preferable, 25% by mass or less is more preferable, and 20% by mass or less is particularly preferable.

Further, the anode electrode of the present invention usually contains an active material and an oxygen ion conductor in addition to the electrode material made of the pyrochloro-type CZL composite oxide. As such an active material and an oxygen ion conductor, an active material and an oxygen ion conductor used for an anode electrode of a conventional solid oxide fuel cell can be used.

For example, examples of the active material include Ni, Fe, Co, precious metals (Pt, Pd, etc.), Cu, Zn, Cr, Ti, Al, W, Mo, and alloys thereof. These active substances may be used alone or in combination of two or more. Among these active materials, Ni, Fe, Co, and noble metals (Pt, Pd, etc.) are preferable, and Ni is more preferable, from the viewpoint of excellent electrical conductivity and catalytic activity.

Further, as the oxygen ion conductor, zirconia; zirconia doped with at least one element of Y, Sc, Sm, Gd and La; ceria; Y, Sm, Gd, La, Nd, Yb, Ca and Examples thereof include ceria doped with at least one element of Ho. These oxygen ion conductors may be used alone or in combination of two or more. Among these oxygen ion conductors, zirconia-based oxides such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) are preferable from the viewpoint of excellent strength and thermal stability. Yttria-stabilized zirconia (YSZ) is more preferred from the viewpoint of excellent conductivity.

Further, as a combination of these active materials and an oxygen ion conductor, the electric conductivity, catalytic activity, heat resistance and oxygen ion conductivity of the anode electrode are increased, and the power generation characteristics of the fuel cell are improved. A combination in which the active material is Ni and the oxygen ion conductor is Itria stabilized zirconia (YSZ); the active material is Fe and the oxygen ion conductor is Ittoria stabilized zirconia (YSZ); the active material is Co. The combination in which the oxygen ion conductor is itria-stabilized zirconia (YSZ) is preferable, the combination in which the active material is Ni and the oxygen ion conductor is ittoria-stabilized zirconia (YSZ) is more preferable.

The content of the active material in the anode electrode of the present invention is not particularly limited as long as the effect of the present invention is not impaired, but the reaction at the anode electrode proceeds sufficiently and the fuel cell having excellent power generation characteristics can be obtained. From the viewpoint of being obtained, 30% by mass or more is preferable, 50% by mass or more is more preferable, 60% by mass or more is particularly preferable, and from the viewpoint of suppressing the volume shrinkage of the anode electrode, the volume shrinkage of the anode electrode is preferably suppressed. It is preferably 80% by mass or less, more preferably 70% by mass or less, based on the entire electrode material.

The content of the oxygen ion conductor in the anode electrode of the present invention is not particularly limited as long as the effect of the present invention is not impaired, but an anode electrode having excellent oxygen ion conductivity can be obtained and power generation is performed. From the viewpoint of obtaining a fuel cell having excellent characteristics, 10% by mass or more is preferable, 20% by mass or more is more preferable, and 20% by mass or more is more preferable with respect to the entire electrode material, and from the viewpoint of suppressing deterioration of the power generation characteristics of the fuel cell. 70% by mass or less is preferable, 55% by mass or less is more preferable, and 40% by mass or less is particularly preferable with respect to the entire electrode material.

The average particle size of the active material is preferably 1 μm or less from the viewpoint of improving the power generation characteristics of the fuel cell. Further, the lower limit of the average particle size of the active material is not particularly limited.

The average particle size of the oxygen ion conductor is preferably 1 μm or less from the viewpoint of maintaining the oxygen ion conductivity of the anode electrode. Further, the lower limit of the average particle size of the oxygen ion conductor is not particularly limited.

The average particle size of such an active material and the oxygen ion conductor is defined as the particle size (diameter) d50 when the cumulative frequency is 50% in the volume-based cumulative frequency distribution measured by the laser diffraction / scattering method. Can be asked.

The average thickness of the anode electrode of the present invention is preferably 100 μm or more, more preferably 200 μm or more, particularly preferably 300 μm or more, and hydrogen introduced in the anode electrode from the viewpoint of ensuring the strength of the anode electrode. From the viewpoint of improving the diffusivity of the above, 800 μm or less is preferable, 700 μm or less is more preferable, and 600 μm or less is particularly preferable.

The anode electrode of the present invention may be dense, but is preferably porous from the viewpoint of diffusivity of hydrogen introduced into the anode electrode in a solid oxide fuel cell. The pore ratio of such a porous anode electrode is preferably 20% or more, more preferably 22% or more, particularly preferably 25% or more, and particularly preferably 25% or more, from the viewpoint of the diffusivity of hydrogen in the anode electrode. From the viewpoint of ensuring strength and electrical conductivity, and the reactivity of hydrogen and oxygen ions in the anode electrode, 60% or less is preferable, 58% or less is more preferable, and 55% or less is particularly preferable.

Further, the anode electrode of the present invention may be composed of one layer or two or more layers. Examples of the anode electrode composed of two or more layers include an anode electrode having a diffusion layer and an active layer. The diffusion layer is a layer for diffusing hydrogen introduced into the anode electrode into the anode electrode, and the active layer is a layer containing an active point of reaction between hydrogen and oxygen ions, and has electrode activity. It is a layer.

The average thickness of the diffusion layer is preferably 100 μm or more, more preferably 200 μm or more, particularly preferably 300 μm or more, and diffusion of introduced hydrogen in the anode electrode from the viewpoint of ensuring the strength as a support. From the viewpoint of improving the properties, 800 μm or less is preferable, 700 μm or less is more preferable, and 600 μm or less is particularly preferable.

The average thickness of the active layer is preferably 10 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, and particularly preferably introduced at the anode electrode, from the viewpoint of increasing the active site of the reaction between hydrogen and oxygen ions. From the viewpoint of improving the diffusivity of the hydrogen produced, 80 μm or less is preferable, 50 μm or less is more preferable, and 40 μm or less is particularly preferable.

The diffusion layer and the active layer may be dense, but are preferably porous from the viewpoint of improving the diffusivity of hydrogen in the anode electrode. The porosity of the porous diffusion layer is preferably 40% or more, more preferably 45% or more, particularly preferably 50% or more, and the strength of the diffusion layer, from the viewpoint of improving the diffusivity of hydrogen in the diffusion layer. From the viewpoint of ensuring electrical conductivity, 60% or less is preferable, 58% or less is more preferable, and 55% or less is particularly preferable. Further, the porosity of the porous active layer is preferably 20% or more, more preferably 22% or more, from the viewpoint of improving the diffusivity of hydrogen in the active layer and improving the discharge of the generated water. 25% or more is particularly preferable, and 40% or less is preferable, 35% or less is more preferable, and 30% or less is particularly preferable, from the viewpoint of ensuring the reactivity between hydrogen and oxygen ions in the active layer.

As a method for producing such an anode electrode of the present invention, for example, first, it is composed of the active material, the oxygen ion conductor, and a pyrochlorite type CZL composite oxide having the chemical composition and a superlattice structure. An anode electrode forming slurry containing the electrode material of the present invention and further containing a pore-forming agent (for example, carbon) and a binder is prepared, and the anode electrode forming slurry is used to form an anode electrode. A sheet for forming an anode electrode is prepared, and then the sheet for forming an anode electrode is used alone or together with a sheet for forming another layer described later at 900 to 1500 ° C. (preferably 950 to 1450 ° C.) in an air atmosphere. Examples thereof include a method of firing at a temperature for 1 to 10 hours (preferably 2 to 5 hours). When the firing temperature is less than the lower limit, the densification of the anode electrode tends not to proceed sufficiently, while when the firing temperature exceeds the upper limit, the constituent material of the anode electrode tends to be thermally decomposed. Further, when the firing time is less than the lower limit, the densification of the anode electrode tends not to proceed sufficiently, while when the firing time exceeds the upper limit, the processing cost tends not to be commensurate with the effect of firing.

[Solid oxide fuel cell]
Next, the solid oxide fuel cell of the present invention will be described. The solid oxide fuel cell of the present invention includes the anode electrode of the present invention, that is, an anode electrode containing an electrode material made of a pyrochlorite type CZL composite oxide having the chemical composition and a super lattice structure. Is. More specifically, it comprises an anode electrode containing the active material, the oxygen ion conductor, and an electrode material made of a pyrochlore-type CZL composite oxide having the chemical composition and a superlattice structure. ..

Further, in the solid oxide fuel cell of the present invention, the anode electrode of the present invention, the solid electrolyte layer, and the cathode electrode are usually laminated in this order, and further, if necessary, the solid electrolyte layer is laminated. An anti-reaction layer may be arranged between the cathode electrode and the cathode electrode.

As the material for the solid electrolyte layer, zirconia-based oxides such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) are preferable from the viewpoint of excellent strength and thermal stability, and have oxygen ion conductivity. Yttria-stabilized zirconia (YSZ) is more preferred from the standpoint of excellence. The average thickness of the solid electrolyte is preferably 3 to 20 μm, more preferably 4 to 15 μm, and particularly preferably 5 to 10 μm from the viewpoint of reducing ohmic resistance.

Materials for cathode electrodes include La _x Sr _1-x CoO ₃ oxides, La _x Sr _1-x Coy Fe _{1-y O 3} oxides, and Sm _x Sr _1-x CoO ₃ oxides (these are). In the chemical formula of, a transition metal perovskite type oxide such as 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) can be mentioned. These cathode electrode materials may be used alone or in combination of two or more. The average thickness of the cathode electrode is preferably 10 μm or more, more preferably 15 μm or more, particularly preferably 20 μm or more, and cracks due to the difference in coefficient of linear thermal expansion from other layers, from the viewpoint of improving current collection. From the viewpoint of suppressing the occurrence, 100 μm or less is preferable, 80 μm or less is more preferable, and 60 μm or less is particularly preferable.

Examples of the anti-reaction layer material include CeO ₂ ; CeO ₂ doped with at least one element of Gd, Sm, Y, La, Nd, Yb, Ca and Ho. These anti-reaction layer materials may be used alone or in combination of two or more. The average thickness of the reaction prevention layer is preferably 1 to 20 μm, more preferably 2 to 10 μm, from the viewpoint of reducing ohmic resistance and suppressing element diffusion from the cathode electrode.

Such an anode electrode of the present invention, a solid electrolyte layer, and a cathode electrode are laminated in this order, and a reaction prevention layer is further arranged between the solid electrolyte layer and the cathode electrode as needed. The solid oxide fuel cell of the present invention can be manufactured, for example, by the following method. That is, first, as in the case of the anode electrode, a solid electrolyte layer forming slurry, a reaction prevention layer forming slurry, and a cathode electrode forming slurry are prepared, and these slurrys are used to form a solid electrolyte layer forming sheet. A sheet for forming an anti-reaction layer and a sheet for forming a cathode electrode are prepared. Next, the anode electrode forming sheet, the solid electrolyte layer forming sheet, the reaction prevention layer forming sheet, and the cathode electrode forming sheet are laminated in this order (crimped if necessary) to prepare an unfired body. The solid oxide fuel cell of the present invention is formed by firing an unfired body in an atmospheric atmosphere at a temperature of 900 to 1500 ° C. (preferably 950 to 1450 ° C.) for 1 to 10 hours (preferably 2 to 5 hours). A single cell of a fuel cell can be obtained.

The solid oxide fuel cell of the present invention can also be manufactured by the following method. That is, first, as in the case of the anode electrode, a slurry for forming a solid electrolyte layer and a slurry for forming an anti-reaction layer are prepared. As for the cathode electrode, a paste for forming the cathode electrode is prepared. Next, using the slurry, a sheet for forming a solid electrolyte layer and a sheet for forming an anti-reaction layer are produced. Next, the sheet for forming the anode electrode, the sheet for forming the solid electrolyte layer, and the sheet for forming the reaction prevention layer are laminated in this order (crimped if necessary) to prepare an unfired body, and the unfired body is used as an air atmosphere. Bake at a temperature of 900 to 1500 ° C. (preferably 950 to 1450 ° C.) for 1 to 10 hours (preferably 2 to 5 hours). Then, a cathode electrode paste is applied onto the obtained fired body to form a cathode electrode paste layer, which is subjected to an air atmosphere and a temperature of 900 to 1500 ° C. (preferably 950 to 1450 ° C.). By firing for 1 to 10 hours (preferably 2 to 5 hours), a cathode electrode is formed, and a single cell of the solid oxide fuel cell of the present invention can be obtained.

Further, the solid oxide fuel cell of the present invention can also be manufactured by the following method. That is, first, a paste for forming a solid electrolyte layer, a paste for forming an anti-reaction layer, and a paste for forming a cathode electrode are prepared. Next, a paste for forming a solid electrolyte layer is applied onto the sheet for forming an anode electrode to form a paste layer for forming a solid electrolyte layer, which is heated at 900 to 1500 ° C. (preferably 950 to 1450) under an air atmosphere. A solid electrolyte layer is formed by firing at a temperature of (° C.) for 1 to 10 hours (preferably 2 to 5 hours). Then, a paste for forming an anti-reaction layer is applied onto the solid electrolyte layer to form a paste layer for forming an anti-reaction layer, which is heated at 900 to 1500 ° C. (preferably 950 to 1450 ° C.) under an air atmosphere. The reaction-preventing layer is formed by firing at a temperature of 1 to 10 hours (preferably 2 to 5 hours). Further, a cathode electrode forming paste layer is applied onto the reaction prevention layer to form a cathode electrode forming paste layer, which is subjected to an atmospheric atmosphere and a temperature of 900 to 1500 ° C. (preferably 950 to 1450 ° C.). The cathode electrode is formed by firing for 1 to 10 hours (preferably 2 to 5 hours), and a single cell of the solid oxide fuel cell of the present invention can be obtained.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1)
61.4 g of a cerium nitrate aqueous solution having a concentration of 28% by mass in terms of CeO ₂ , 278.4 g of a zirconium nitrate aqueous solution having a concentration of 18% by mass in terms of ZrO ₂ , and lanthanum nitrate hexahydrate 130. Mix with an aqueous solution in which 0 g is dissolved, add the obtained mixed solution to an aqueous solution diluted with 100 g of 25% ammonia water with 900 ml of pure water, and stir at 300 rpm for 10 minutes using a homogenizer to form a co-precipitate. I let you. The aqueous solution containing the coprecipitate was divided into three beakers having a capacity of 1 L and heated at 150 ° C. for 7 hours in an air atmosphere using a degreasing furnace to evaporate the water and dry the coprecipitate. This coprecipitate was further calcined at 400 ° C. for 5 hours to obtain a lantana-containing ceria-zirconia solid solution.

After filling 20 g of this lanthanum-containing ceria-zirconia solid solution into a graphite crucible and placing it in a small vacuum pressure sintering furnace (“FVPS-R-150” manufactured by Fuji Dempa Kogyo Co., Ltd.), the inside of the furnace is replaced with an argon atmosphere. It was heated to 1000 ° C. with a temperature rise time of 1 hour, further heated to 1500 ° C. (reduction treatment temperature) with a temperature rise time of 3 hours, and held for 5 hours. Then, the mixture was cooled to 1000 ° C. with a cooling time of 4 hours, and further cooled to room temperature by natural cooling to obtain a reduction-treated product.

The obtained reduction-treated product was heated in the air at 500 ° C. for 5 hours to obtain a ceria-zirconia-lantana (CZL) composite oxide. This CZL composite oxide is pulverized and sieved using a pulverizer so that the particle size is 75 μm or less, and cerium having an atomic ratio (Ce / Zr / La) = 12.5 / 50 / 37.5. A zirconia-lanthana (CZL) composite oxide powder (chemical composition: Ce _0.5 Zr ₂ La _1.5 O ₇ , Ce content: 12.5 at%) was obtained.

(Comparative Example 1)
Zirconia-lanthanum (ZL) with an atomic ratio (Zr / La) = 50/50 in the same manner as in Example 1 except that the amount of lanthanum nitrate hexahydrate was changed to 173.2 g without using an aqueous solution of cerium nitrate. A composite oxide powder (chemical composition: Zr ₂ La ₂ O ₇ , Ce content: 0 at%) was obtained.

(Comparative Example 2)
The atomic ratio was the same as in Example 1 except that the amount of cerium nitrate aqueous solution having a concentration of 28% by mass in terms of CeO ₂ was changed to 122.8 g and the amount of lanthanum nitrate hexahydrate was changed to 86.6 g. Ce / Zr / La) = 25/50/25 ceria-zirconia-lanthanum (CZL) composite oxide powder (chemical composition: Ce ₁ Zr ₂ La ₁ O ₇ , Ce content: 25 at%) was obtained.

<Heat resistance test>
Each composite oxide powder obtained in Examples and Comparative Examples was heated in the air at 1400 ° C. for 5 hours.

<X-ray diffraction measurement>
For each composite oxide powder before and after the heat resistance test, X-rays were used under the conditions of 40 kV, 40 mA, 2θ = 5 ° / min using CuKα as an X-ray source using an X-ray diffractometer (“RINT-Ultima” manufactured by Rigaku Co., Ltd.). Diffraction measurement was performed. From the obtained X-ray diffraction pattern, the intensity ratio {I (14/29) value} of the diffraction line of 2θ = 14.5 ° and the diffraction line of 2θ = 29 ° was obtained. The results are shown in Table 1.

<Measurement of average particle size and particle size distribution>
Each composite oxide powder obtained in Examples and Comparative Examples was observed using a scanning electron microscope (“S-5500” manufactured by Hitachi High-Technologies Corporation). Based on the obtained SEM image (2000 times), the average particle size and particle size distribution of the composite oxide powder were obtained using image analysis software (“A image-kun” manufactured by Asahi Kasei Engineering Co., Ltd.). These results are shown in Table 1.

<Measurement of oxygen absorption / release amount (OSC)>
A reducing gas (H ₂ (4% by volume) + N 2 (H 2 (4% by volume)) + N ₂ ("TGA-50" manufactured by Shimadzu Corporation) was used on 15 mg of the composite oxide powder after the heat resistance test at a temperature of 700 ° C. The remaining)) was circulated for 5 minutes (flow rate 100 ml / min), then switched to an oxidizing gas (O ₂ (5% by volume) + N ₂ (remaining)) and circulated for 5 minutes (flow rate 100 ml / min). This series of operations was repeated a total of three times, and the amount of mass loss during the third reduction gas flow was measured to determine the oxygen absorption / release amount (OSC). The results are shown in Table 1.

<Manufacturing of single cell for fuel cell>
(Preparation of sheet for forming diffusion layer of anode electrode)
65 parts by mass of NiO powder (average particle size: 1.0 μm) and 35 parts by mass of yttria-stabilized zirconia (YSZ) powder (average particle size: 0.8 μm) containing ₈ mol% Y2O3 _, and examples or Using a ball mill, 10 parts by mass of the composite oxide powder obtained in the comparative example, carbon powder (pore-forming agent), polyvinyl butyral (binder), and a mixed solvent containing isoamyl acetate, 2-butanol and ethanol were used. The mixture was mixed to prepare a slurry for forming a diffusion layer of an anode electrode. The average particle size of the NiO powder and the YSZ powder is the particle size (diameter) d50 when the cumulative frequency is 50% in the volume-based cumulative frequency distribution measured by the laser diffraction / scattering method (hereinafter, the same applies). ).

The obtained diffusion layer forming slurry is coated in a layer on a resin sheet using a doctor blade, dried in the air at 80 ° C. for 2 hours, and then the resin sheet is peeled off to diffuse the anode electrode. A layer-forming sheet (average thickness: 500 μm) was obtained. The average thickness of the sheet is a value obtained by measuring the thickness of the sheet at 10 randomly selected measurement points with a scanning electron microscope and averaging them (hereinafter, the same applies).

(Preparation of sheet for forming active layer of anode electrode)
65 parts by mass of the NiO powder, 35 parts by mass of the YSZ powder, 10 parts by mass of the composite oxide powder obtained in Examples or Comparative Examples, the carbon powder (pore-forming agent), and polyvinyl butyral (binder). , Isoamyl acetate and a mixed solvent containing 1-butanol were mixed using a ball mill to prepare a slurry for forming an active layer of an anode electrode. A sheet for forming an active layer of an anode electrode was produced by the same method as the sheet for forming a diffusion layer except that this slurry for forming an active layer was used instead of the slurry for forming a diffusion layer.

(Preparation of sheet for forming solid electrolyte layer)
The YSZ powder, polyvinyl butyral (binder), and a mixed solvent containing isoamyl acetate, 2-butanol, and ethanol were mixed using a ball mill to prepare a slurry for forming a solid electrolyte layer. A solid electrolyte layer forming sheet was produced by the same method as the diffusion layer forming sheet except that the solid electrolyte layer forming slurry was used instead of the diffusion layer forming slurry.

(Preparation of anti-reaction layer forming sheet)
Using a ball mill, a 10 mol% Gd-doped CeO ₂ (GDC) powder (average particle size: 0.8 μm), polyvinyl butyral (binder), and a mixed solvent containing isoamyl acetate, 2-butanol, and ethanol are used. To prepare a slurry for forming an anti-reaction layer. A reaction-preventing layer-forming sheet was produced by the same method as the diffusion layer-forming sheet except that the reaction-preventing layer-forming slurry was used in place of the diffusion layer-forming slurry.

(Preparation of paste for forming cathode electrode)
La _0.6 Sr _0.4 CoO ₃ (LSC) powder (average particle size: 0.6 μm), the carbon powder (pore-forming agent), ethyl cellulose (binder), and terpineol (solvent) using a ball mill. And mixed to prepare a paste for forming a cathode electrode.

(Manufacturing of single cell for fuel cell)
First, the diffusion layer forming sheet, the active layer forming sheet, the solid electrolyte layer forming sheet, and the reaction prevention layer forming sheet are laminated in this order, and these sheets are pressed under hydrostatic pressure. By the (WIP) molding method, crimping was performed under the conditions of a temperature of 80 ° C., a pressing force of 50 MPa, and a pressurizing time of 10 minutes. Then, the obtained crimped body was subjected to degreasing treatment.

This crimped body is fired at 1350 ° C. for 2 hours in an air atmosphere to obtain a sintered body in which an anode electrode layer composed of a diffusion layer and an active layer, a solid electrolyte layer, and a reaction prevention layer are laminated in this order. rice field. Next, the cathode electrode forming paste is uniformly coated on the surface of the reaction prevention layer of the sintered body in a layered manner by a screen printing method, and then fired at 1000 ° C. for 2 hours in an air atmosphere to form a cathode electrode layer. As shown in FIG. 3, the anode electrode layer 31 composed of the diffusion layer 31a (average thickness: 300 μm) and the active layer 31b (average thickness: 20 μm) and the solid electrolyte layer 32 (average thickness: 10 μm) are formed. ), The reaction prevention layer 33 (average thickness: 10 μm), and the cathode electrode layer 34 (average thickness: 60 μm) were laminated in this order to prepare a single cell (button type cell) for a fuel cell. The average thickness of each layer was determined by observing the cross section of a single cell with a scanning electron microscope and measuring the thickness of each layer at 10 randomly selected measurement points in the obtained SEM image. It is a value obtained on average.

<Power generation durability test of single cell for fuel cell>
First, the anode electrode layer of the single cell was reduced at 800 ° C. in a hydrogen gas atmosphere. Next, 3% humidified hydrogen was introduced into the anode electrode layer and air was introduced into the cathode electrode layer to continuously introduce this single cell at a temperature of 700 ° C. so that the current density was 1.5 A / cm ² . A power generation test was performed to determine the change in potential over time. Based on the obtained results, the time until the potential dropped to 0.5 V was determined, and this was plotted as the endurance time with respect to the content of Ce in the added composite oxide. The results are shown in FIG.

As shown in Table 1, the CZL composite oxide containing 12.5 at% of Ce prepared in Example 1 had an I (14/29) value of 0.02 or more even after the heat resistance test. It was confirmed that it is a pyrochlore-type CZL composite oxide that maintains its superlattice structure even when exposed to high temperatures. Furthermore, it was confirmed that this pyrochlore-type CZL composite oxide has a high oxygen absorption / release ability. Further, as shown in FIG. 4, a single cell for a fuel cell provided with an anode electrode to which an electrode material made of a pyrochlore-type CZL composite oxide having a Ce content of 12.5 at% is added is excellent in thermal stability. It turned out to be.

On the other hand, as shown in Table 1, the Ce-free ZL composite oxide prepared in Comparative Example 1 had an I (14/29) value of 0.02 or more even after the heat resistance test, so that the temperature was high. It was confirmed that it is a pyrochlore-type ZL composite oxide whose superlattice structure is maintained even when exposed. However, it was found that this pyrochlore-type ZL composite oxide does not exhibit oxygen absorption / release ability. Further, as shown in FIG. 4, the fuel cell single cell provided with the anode electrode to which the electrode material made of the pyrochlor-type ZL composite oxide containing no Ce is added has a Pyrochlor-type CZL having a Ce content of 12.5 at%. It was found that the thermal stability was inferior to that of the fuel cell single cell (Example 1) provided with the anode electrode to which the electrode material made of the composite oxide was added.

Further, as shown in Table 1, the CZL composite oxide containing 25.0 at% of Ce prepared in Comparative Example 2 had an I (14/29) value of less than 0.02 after the heat resistance test. Therefore, it was confirmed that it is a pyrochlore-type CZL composite oxide whose superlattice structure is difficult to maintain when exposed to high temperatures. Furthermore, it was found that this pyrochlore-type CZL composite oxide is also inferior in oxygen absorption / release ability to the pyrochlore-type CZL composite oxide having a Ce content of 12.5 at%. Further, as shown in FIG. 4, a single cell for a fuel cell provided with an anode electrode to which an electrode material made of a pyrochlor type CZL composite oxide having a Ce content of 25.0 at% is added has a Ce content of 12. It was found that the thermal stability was inferior to that of a single cell for a fuel cell (Example 1) provided with an anode electrode to which an electrode material composed of 5 at% pyrochlore-type CZL composite oxide was added.

From the above results, by adding an electrode material made of a pyrochlorite type CZL composite oxide, which contains Ce in a specific ratio and maintains a super lattice structure even when exposed to high temperatures, to the anode electrode, the thermal stability is improved. It was confirmed that an excellent anode electrode for a solid oxide fuel cell was obtained, and by using this anode electrode, a solid oxide fuel cell having excellent durability under high temperature during power generation could be obtained.

As described above, according to the present invention, it is possible to obtain an anode electrode for a solid oxide fuel cell having excellent thermal stability. Therefore, since the solid oxide fuel cell of the present invention is provided with such an anode electrode for a solid oxide fuel cell having excellent thermal stability, it can be used as a stationary or vehicle-mounted solid oxide fuel cell or the like. It is useful.

11: Solid electrolyte layer 12: Anode electrode 12a: Oxygen ion conductor 21: Oxygen storage site 31: Anode electrode layer 31a: Diffusion layer 31b: Active layer 32: Solid electrolyte layer 33: Reaction prevention layer 34: Cathode electrode layer

Claims (5)

A solid oxide type having a chemical composition of Ce _x Zr ₂ La _(2-x) O ₇ (x = 0.2 to 0.6) and composed of a pyrochlore-type composite oxide having a superlattice structure. Electrode material for fuel cells. 2θ = 14.5 ° diffraction line and 2θ = 29 obtained from the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα after heating the pyrochlor type composite oxide at 1400 ° C. for 5 hours in the atmosphere. The condition that the intensity ratio {I (14/29) value} with the diffraction line of ° is as follows:
I (14/29) value ≧ 0.02
The electrode material for a solid oxide fuel cell according to claim 1, wherein the electrode material satisfies the above conditions. The electrode material for a solid oxide fuel cell according to claim 1 or 2, wherein the pyrochlore-type composite oxide has an average particle size of 1 μm or less. An anode electrode for a solid oxide fuel cell, which comprises the electrode material according to any one of claims 1 to 3. A solid oxide fuel cell comprising the anode electrode according to claim 4.

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