JP2007335142A - Nickel-ceria fuel electrode material for solid oxide fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nickel-ceria fuel electrode material for a solid oxide fuel battery good in gas permeability, excellent in electrochemical reactivity and conductivity and excellent in durability, especially redox resistance and to provide a high-performance fuel electrode and a fuel cell using the fuel electrode material, and a fuel battery including the fuel cell. <P>SOLUTION: The nickel-ceria fuel electrode material for the solid oxide fuel battery comprises a mixture of a coarse ceria particle group, a nickelic particle group and a fine ceria particle group and is characterized in that average particle sizes of the respective particle groups satisfies a relationship of the coarse ceria particle group > the nickelic particle group > the fine ceria particle group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nickel-ceria-based fuel electrode material for a solid oxide fuel cell, a fuel electrode and a fuel cell using the same, and a fuel cell including the fuel cell.

  In recent years, fuel cells have attracted attention as a source of clean energy, and their use has been rapidly studied for improvement and practical application mainly from household power generation to commercial power generation, and further to power generation for automobiles.

  By the way, as an electrode material for a solid oxide fuel cell, a porous cermet in which ceramic particles are mixed with conductive metal particles is used. This is because thermal stress is generated due to the difference in coefficient of thermal expansion between the metal particles, which are the main conductive components, and the solid electrolyte or other members, which induces internal strain, which destroys or damages the fuel cell. This is to prevent this.

  However, when this type of material is exposed to a high temperature of 800 to 1000 ° C., which is a typical operating temperature of a solid oxide fuel cell, for a long time, the aggregation and sintering of nickel particles having electronic conductivity gradually occur. As it progresses, the electrochemical reactivity and conductivity decrease, and the power generation performance decreases over time, and various methods have been proposed as a solution.

For example, Patent Document 1 discloses a Ni / CeO ₂ cermet in which nickel metal is supported on ceria in order to suppress a decrease in output due to carbon deposition that occurs when a fuel modified from light hydrocarbons is used. Document 2 describes a cermet in which nickel metal is supported on ceria-zirconia, ceria-yttria stabilized zirconia, or the like. Patent Document 3 discloses a large-sized ceria particle and a small-diameter particle on the surface of a porous nickel skeleton having a network structure as a fuel electrode of a small-sized high-power solid oxide fuel cell. What ceria particles are deposited is disclosed.

By the way, in Non-Patent Document 1, nickel oxide, which is a fuel electrode material, is reduced to metal nickel by being reduced by hydrogen, city gas, or the like as a fuel. It is described that a change in the fuel electrode structure causes a drop in performance or destruction of the fuel cell. On the other hand, according to Non-Patent Document 2, the ceria-based oxide solid solution is supposed to expand in a reducing atmosphere.
JP-A-4-121964 Japanese Unexamined Patent Publication No. 7-6768 JP 2005-166640 A Misuzu Yokoyama et al., Abstracts of 13th SOFC Research Presentation, 48, 2004 Yasuda Isa et al., 5th SOFC Research Presentation Abstracts, page 107, 1996

  As described above, conventionally, a nickel-ceria-based fuel electrode material for a solid oxide fuel cell has been known, but it is not particularly satisfactory in terms of durability. For example, the power generation durability disclosed in Patent Documents 1 and 2 is at most 200 hours, and cannot be said to satisfy the long-term durability that is practical.

  Further, since nickel oxide is reduced to metallic nickel in a reducing atmosphere on the fuel electrode side of the solid oxide fuel cell, its volume shrinks, while ceria expands. Therefore, it is considered that by using a nickel-ceria-based material as the fuel electrode material, volume change in the fuel electrode due to power generation and operation stop of the fuel cell is suppressed, and the redox resistance of the fuel cell is improved. However, the conventional fuel electrode material for nickel-ceria-based solid oxide fuel cells does not take this redox resistance into consideration, and the durability is not sufficient. For example, in the nickel-ceria-based solid oxide fuel cell fuel electrode material of Patent Document 3, although the ceria particle size is also taken into consideration, since these are supported on porous nickel, the ceria particles It is thought that the change in volume due to the oxidation-reduction reaction of nickel oxide cannot be suppressed by ceria because the particle size of nickel oxide is excessively large relative to the diameter.

  Therefore, the problem to be solved by the present invention is a nickel-ceria-based solid oxide fuel cell having excellent gas permeability, excellent electrochemical reactivity and conductivity, and durability, particularly excellent redox resistance. It is to provide an anode material. Another object of the present invention is to provide a high-performance fuel electrode and fuel cell using the fuel electrode material, and a fuel cell including the fuel cell.

  The inventors of the present invention have made extensive studies to solve the above-mentioned problems. As a result, the fuel electrode material is composed of nickel oxide particles and large and small ceria particles, and the average particle size of each particle is appropriately defined. Thus, the present invention has been completed by finding that the above-mentioned problems can be solved.

That is, the anode material for the nickel-ceria-based solid oxide fuel cell of the present invention is
It consists of a mixture of coarse ceria particles, nickel oxide particles, and fine ceria particles,
The average particle diameter of each particle group satisfies the relationship of coarse ceria particle group> nickel oxide particle group> fine ceria particle group.

  In the fuel electrode material, the content ratio of each particle group is preferably a coarse ceria particle group: 15 to 50% by mass, a nickel oxide particle group: 40 to 70% by mass, and a fine ceria particle group: 5 to 30% by mass. . Nickel oxide is a necessary component for conductivity in the fuel electrode, but if it is excessively large, volume change due to repetition of oxidation reaction and reduction reaction becomes large, so the content ratio is preferably in the above range. On the other hand, the coarse ceria particles relieve the volume change of the fuel electrode due to nickel oxide, and the fine ceria particles combine with the nickel compound to increase the strength of the fuel electrode itself, resulting in improved durability. In addition, since the ceria particles exhibit an excellent oxygen absorption capacity, there is an effect of improving gas permeability. These effects are satisfactorily exhibited in the content ratio range.

  The average particle size of each particle is preferably 2 to 50 μm for the coarse ceria particle group, 0.5 to 5 μm for the nickel oxide particle group, and 0.1 to 3 μm for the fine ceria particle group. In the examples described later, it has been demonstrated that a fuel electrode composed of each particle group having an average particle diameter in such a range exhibits excellent gas permeability and durability.

As the coarse ceria particle group and / or fine ceria particle group,
Ceria doped with yttrium, samarium or gadolinium;
Ceria-zirconia composite particles having a ceria content of 51% by mass or more; and ceria doped with yttrium, samarium, or gadolinium, the content of which is 51% by mass or more, and zirconia and / or alumina; Mixed particles of
One or more selected from the group consisting of: The effect of the fuel electrode containing such ceria particles has been demonstrated in the examples described later.

  The fuel electrode for a solid oxide fuel cell according to the present invention is a fuel electrode formed on one side of a solid electrolyte in a solid oxide fuel cell, and the fuel electrode is formed of the fuel electrode material. The solid oxide fuel cell of the present invention is a solid oxide fuel cell in which a fuel electrode is formed on one side of a solid electrolyte and an air electrode is formed on the other side, The fuel electrode is formed of the above fuel electrode material.

  Furthermore, the solid oxide fuel cell of the present invention includes the solid oxide fuel cell.

  The fuel electrode material for the nickel-ceria-based solid oxide fuel cell of the present invention has good gas permeability, electrochemical reactivity and conductivity, and further excellent durability. A fuel electrode for a solid oxide fuel cell that does not cause damage or destruction due to thermal stress with other members can be manufactured. Since the fuel electrode material of the present invention is particularly excellent in redox resistance, it is suitable as a fuel electrode material for a solid oxide fuel cell that is repeatedly operated and stopped. Therefore, the present invention is extremely useful industrially as a solid oxide fuel cell that is closer to practical use.

The fuel electrode material for nickel-ceria based solid oxide fuel cell of the present invention is:
It consists of a mixture of coarse ceria particles, nickel oxide particles, and fine ceria particles,
The average particle diameter of each particle group satisfies the relationship of coarse ceria particle group> nickel oxide particle group> fine ceria particle group.

  As the ceria particles used in the present invention, in addition to particles consisting only of ceria and doped ceria, composite particles or mixed particles mainly containing ceria, that is, the proportion of ceria in the particles being 51% by mass or more are used. be able to. For example, ceria; ceria doped with yttrium, samarium, or gadolinium; ceria-zirconia composite particles having a ceria content of 51% by mass or more; those doped with yttrium, samarium, or gadolinium, the content of which is The mixed particle | grains of the ceria which is 51 mass% or more, and a zirconia and / or an alumina can be mentioned, You may select and use 1 type from these, or after mixing 2 or more types. The doping amount is not particularly limited, but is preferably in the range of 5 to 40 atomic%, more preferably 10 to 30 atomic% with respect to cerium. Here, the “composite particle” is a mixture of ceria particles or a solution of cerium salt and a solution of zirconium salt or the like, and then drying or calcining a compound generated by hydrolysis or coprecipitation. It is obtained and is not simply a mixture of particles. “Mixed particles” refers to particles obtained by mixing ceria particles doped with yttrium or the like, zirconia particles and / or aluminum particles.

  In the present invention, coarse particles and fine particles are used as the ceria particle group. The hard-sintered coarse ceria particles form a strong structural skeleton, which can increase the structural strength of the fuel electrode and suppress sintering that occurs when exposed to high temperatures for long periods of time. be able to. Furthermore, the expansion and contraction due to the change between nickel oxide and metallic nickel due to repeated oxidation and reduction reactions are alleviated, and the redox resistance of the fuel electrode is enhanced. On the other hand, the fine ceria particle group has a role of improving the durability of the fuel electrode by being dispersed between coarse ceria particles and nickel oxide particles and increasing the strength of the fuel electrode itself. In addition, since ceria particles have a good oxygen absorption capacity, when metallic nickel is rapidly exposed to an oxidizing atmosphere, the ceria particles in the vicinity absorb oxygen, so that metallic nickel becomes nickel oxide and rapidly. It also has the effect of suppressing the occurrence of cracks and the like due to volume expansion.

  As the coarse ceria particle group, those having an average particle diameter in the range of 2 μm or more and 50 μm or less are preferably used. If it is 2 μm or more, the skeleton of the fuel electrode can be sufficiently formed, and not only satisfactory gaps are formed between the particles and satisfactory air permeability is obtained, but sintering proceeds under high temperature use conditions. This makes it difficult to reduce the porosity. In addition, if the particle size becomes excessively large, the strength can be lowered, but if it is 50 μm or less, the strength can be sufficiently secured, and it is necessary to add excessively fine ceria particles for joining coarse ceria particles. In addition, the electronic conductivity by the nickel oxide particles can be maintained. In view of the above, the average particle size of the more preferable coarse ceria particle group is 3 μm or more and 30 μm or less, more preferably 3 μm or more and 20 μm or less.

  In the present invention, in addition to the average particle diameter of the coarse ceria particle group described above, the fuel electrode layer is homogenized by suppressing the amount of extremely coarse particles mixed as much as possible, and more preferably 90% by volume. The diameter is preferably 5 μm or more and 80 μm or less, more preferably 7 μm or more and 70 μm or less, and still more preferably 9 μm or more and 50 μm or less.

  On the other hand, as the fine ceria particle group, those having an average particle size in the range of 0.1 μm to 3 μm are preferably used. If it is 0.1 μm or more, it can sufficiently contribute to improving the strength of the fuel electrode, and if it is 3 μm or less, it can be sufficiently dispersed between the coarse ceria particles, so that coarse ceria particles and nickel oxide particles are joined. It can contribute to the improvement of the strength of the fuel electrode. In consideration of the above, the average particle size of the more preferable fine ceria particle group is 0.2 μm or more and 2 μm or less, and more preferably 0.3 μm or more and 1 μm or less.

  In order to homogenize the fuel electrode layer even in the fine ceria particle group, the 90% by volume diameter is more preferably 0.1 μm or more and 3 μm or less, more preferably 0.2 μm or more and 2 μm or less, and further preferably 0.3 μm. The thickness is preferably 1 μm or less.

The average particle diameter (50 volume% diameter) of each particle group in the present invention is 0.2 mass% of metalin as a dispersant in distilled water using a laser diffraction particle size distribution analyzer “LA-920” manufactured by Horiba. An aqueous solution to which sodium acid is added is used as a dispersion medium, and 0.01 to 0.5% by mass of each particle is added to about 100 cm ^{3 of the} dispersion medium. is there. Moreover, 90 volume% diameter means the particle size of the position of 90 volume% in the particle size distribution of each sample particle measured by the same method.

  When operating as a fuel cell, the nickel oxide particle group is reduced by being exposed to a fuel gas such as hydrogen, and changes to a metal nickel particle group that forms a conductive path. At this time, since the particle size shrinks by about 10 to 20%, the average particle size is 0.5 to 5 μm in consideration of the change to the nickel particles in the relationship with the fine ceria particle group used together. It is better to adjust so that it is within the range.

  Incidentally, if the average particle diameter of the nickel oxide particles is 0.5 μm or more, sintering does not proceed excessively even when exposed to a high temperature for a long time, and sufficient electron conductivity can be secured. . On the other hand, if it is 5 μm or less, a contact point with the coarse ceria particles can be secured, and sufficient electronic conductivity can be easily obtained. Considering this, the average particle size of the nickel oxide particle group is more preferably 0.7 μm or more and 3 μm or less, and further preferably 1 μm or more and 3 μm or less.

  Similarly to the case of the coarse ceria particle group, the nickel oxide particle group also preferably has a 90 volume% diameter of 1 μm or more in order to minimize the mixing amount of extremely coarse particles and to make the fuel electrode uniform. 15 μm or less, more preferably 2 μm or more and 10 μm or less, still more preferably 2 μm or more and 8 μm or less.

  The fuel electrode material of the present invention is composed of a mixture of coarse ceria particles, nickel oxide particles, and fine ceria particles, and the relationship between the average particle diameters of these particles is specified. The nickel oxide particle group is dispersed in the electrode to form a conduction path between electricity and ions. In addition, by defining the relationship between the average particle sizes, the contact points between the three types of particle groups are increased, and as a result, the coarse ceria particle groups are firmly bonded.

  As a result, the fuel electrode formed from the uniform mixture of the above three types of particle groups exhibits excellent electrochemical characteristics, and a structural skeleton is formed by the coarse-sintered coarse ceria particle groups. By increasing the structural strength of the fuel electrode and, by extension, the formation of such a strong structural skeleton, it is possible to suppress the sintering that tends to occur when exposed to high temperatures for a long period of time, thereby maintaining an appropriate porosity. Long lasting electrochemical properties. In addition, since the fine ceria particles are interposed between the coarse ceria particles and sintered and bonded, the coarse ceria particle skeleton is strengthened, so that the pores required on the fuel electrode side as the fuel electrode are blocked. In addition, excellent gas permeability can be maintained for a long time.

  In order to effectively exhibit such characteristics, it is important that the average particle diameter of each particle group satisfies the relationship of “coarse ceria particle group> nickel oxide particle group> fine particle ceria particle group”.

  Further, the content of each of the above particles is in the range of 15 to 50% by mass of the coarse ceria particle group, 40 to 70% by mass of the nickel oxide particle group, and 5 to 30% by mass of the fine ceria particle group. Well, more preferable content is 20% by mass or more and 35% by mass or less for the coarse ceria particle group, 45% by mass or more and 65% by mass or less for the nickel oxide particle group, 10% by mass or more for the fine ceria particle group, 25 It is the range of the mass% or less.

  If the content of coarse ceria particles is 15% by mass or more, skeleton formation is sufficient and not only the strength of the fuel electrode can be sufficiently secured, but also a decrease in porosity over time can be sufficiently suppressed, and gas permeation can be achieved. Sex can be secured. On the other hand, if the coarse particles are added excessively, the strength may be lowered, but if it is 50% by mass or less, the skeleton strength can be sufficiently secured. Further, if the content of the nickel oxide particle group is 40% by mass or more, sufficient electronic conductivity can be secured, and if it is 70% by mass or less, excessive sintering of nickel particles during operation of the fuel cell can be suppressed. . If the content of the fine ceria particle group is 5% by mass or more, coarse ceria particles and the like can be sufficiently joined, which can contribute to the improvement of the strength of the fuel electrode. Progress of excessive sintering of particles at high temperature can be suppressed, and the deterioration of porosity with time is less likely to occur.

  When a fuel electrode is manufactured using a fuel electrode material using the above three kinds of particle groups, the coarse ceria particle group is 15 to 50% by mass, the nickel oxide particle group is 40 to 70% by mass, and the fine particles What is necessary is just to weigh each raw material particle so that a ceria particle group may be in the range of 5 to 30% by mass (total, 100% by mass) and uniformly mix with a mill or the like. It is particularly preferable that a predetermined amount of coarse ceria particles and nickel oxide particles are first mixed, and nickel oxide particles are uniformly attached to the surface of the coarse ceria particles, and then a predetermined amount of fine ceria particles is added thereto. It is a method of mixing uniformly.

  The type of the mixing apparatus used in this case is not particularly limited, but a preferable mixing apparatus used by the present inventors is, for example, a multi-purpose mixer manufactured by Mitsui Mining Co., Ltd. After adding nickel oxide particles to the surface of the coarse ceria particles by rotation and adding the fine ceria particles to this, if the method of mixing by rotating the rotary blade of the apparatus at low speed is adopted, It is confirmed that the particles can be mixed evenly and uniformly.

  The mixed material thus obtained is mixed with a binder such as ethyl cellulose, polyethylene glycol or polyvinyl butyral resin; a solvent such as ethanol, toluene, α-terpineol or carbitol; a plasticizer such as glycerin, glycol or dibutyl phthalate; A paste for a fuel electrode can be obtained by using a three-roll mill, a planetary mill, or the like together with a dispersant, an antifoaming agent, a surfactant, and the like, which are blended as necessary.

  The binder is not particularly limited as long as it is easily pyrolyzed and has a fluidity suitable for printing and coating by dissolving in a solvent, and a conventionally known organic binder can be appropriately selected and used. . Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetal resins. And vinyl formal resins, vinyl alcohol resins, waxes, celluloses such as ethyl cellulose, and the like.

  Among these, 10 carbon atoms such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc. from the viewpoint of film formation of the fuel electrode layer and thermal decomposability during baking. Alkyl acrylates having the following alkyl groups; and alkyls having 20 or less carbon atoms such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, etc. Alkyl methacrylates having hydroxy groups; hydroxyethyl acrylate, hydroxypropyl acrylate Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having a hydroxyalkyl group such as hydroxyethyl methacrylate and hydroxypropyl methacrylate; aminoalkyl acrylates or aminoalkyl methacrylates such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; acrylic acid and methacrylic acid; A number average molecular weight of 20,000 to 200,000 obtained by polymerizing or copolymerizing at least one selected from carboxyl group-containing monomers such as maleic acid and maleic acid half ester such as monoisopropylmalate, More preferably, 50,000 to 100,000 (meth) acrylate copolymer is recommended.

  As the solvent, those having low volatility at normal temperature are preferable in order to reduce the viscosity change during printing. For example, terpineol, dibutyl carbitol, butyl carbitol acetate, 2,2,4-trimethyl-1,3-pentanediol High-boiling solvents such as monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, and oleyl alcohol are used alone or in combination of two or more thereof, or acetone, A low-boiling organic solvent such as methyl ethyl ketone, methanol, ethanol, isopropanol, butanols, denatured alcohol, ethyl acetate, toluene, xylene is mixed and used.

  As a dispersant, in order to improve the dispersion of the oxide powder, polyalcohol esters such as glycerin and sorbitan, polyether (polyol) and amines, polymer electrolytes such as polyacrylic acid and ammonium polyacrylate, Organic acids such as citric acid and tartaric acid, copolymers of isobutylene or styrene and maleic anhydride and ammonium salts and amine salts thereof, copolymers of butadiene and maleic anhydride and ammonium salts thereof are particularly used. Preferred is sorbitan triol. As the plasticizer, polyethylene glycol derivatives and phthalate esters are preferable, and dibutyl phthalate and dioctyl phthalate are particularly preferable.

  The fuel electrode paste is prepared by kneading the oxide powder with a solvent and a binder with a ball mill or the like by a known method, but at this time, if necessary, a bonding aid, an antifoaming agent, a leveling improver, A rheology modifier or the like may be added.

  The leveling improver mainly has an action of suppressing the generation of pinholes in the fuel electrode layer, and exhibits the same effect as a so-called lubricant. For example, a hydrocarbon-based polyethylene wax, a urethane-modified polymer Examples include ether, alcohol-based polyglycerol, polyhydric alcohol, fatty acid-based higher fatty acid, oxyacid, and the like, but particularly preferable are fatty acid-based compounds such as stearic acid and hydroxystearic acid.

  Then, a binder or a solvent is added to the above-described oxide powder, and the mixture is kneaded and mixed uniformly with a cracking machine, a ball mill, a three-roll mill or the like to obtain a paste. When the fuel electrode is formed by coating or dipping, the B-type viscometer should be adjusted to 1 to 50 mPa · s, more preferably 2 to 20 mPa · s. The preferred slurry viscosity when forming the fuel electrode by screen printing is 50,000 to 2,000,000 mPa · s, more preferably 80,000 to 1,000,000 mPa · s, more preferably, by Brookfields viscometer. The range is from 100,000 to 500,000 mPa · s.

  After adjusting the viscosity, for example, it is coated on a solid electrolyte with a bar coater, spin coater, dipping device or the like, or formed into a thin film by a screen printing method or the like, and then a temperature of 40 to 150 ° C., for example, 50 ° C., 80 ° C., The fuel electrode layer is formed by heating and drying at a constant temperature such as 120 ° C. or sequentially successively.

  The thickness of the fuel electrode layer is suitably about 10 to 300 μm, preferably 15 to 100 μm, particularly preferably 20 to 50 μm.

Examples of the oxide for forming the solid electrolyte film include zirconia, alkaline earth metal oxides such as MgO, CaO, SrO, and BaO, Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , and Nd ₂ O. ₃ , rare earth metal oxides such as Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Zirconia ceramics containing one or more of Sc ₂ O ₃ , Bi ₂ O ₃ , In ₂ O _3, etc .; alkaline earth metals such as MgO, CaO, ScO, BaO in CeO ₂ or Bi ₂ O _{3 oxides, Y 2 O 3, La 2} O 3, CeO 2, Pr 2 O 3, Nd 2 O 3, Sm 2 O 3, Eu 2 O 3, Gd 2 O 3, Tb 2 O 3, Dy 2 O 3 , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O _{3 and} other rare earth metal oxides, Sc ₂ O ₃ , In ₂ O ₃ , PbO , WO ₃ , MoO ₃ , V ₂ O ₅ , Nb ₂ O _5, or other ceria-based or bismuth-based ceramics, and AZrO ₃ having a perovskite structure (A: alkali such as Sr) Earth elements) doped with In, Ga, etc .; LaGaO ₃ with alkaline earth metal oxides such as MgO, CaO, SrO, BaO, Y ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , rare earth metal oxides, and Sc Transition metal oxides such as ₂ O ₃ , TiO ₂ , V ₂ O ₅ , Cr ₂ O ₃ , Mn ₂ O ₃ , Fe ₂ O ₃ , Co ₃ O ₄ , NiO, CuO, ZnO, Nb ₂ O ₅ , WO _{3 things, Al 2 O 3, SiO 2} , in 2 O 3, Sb 2 O 3, Bi 2 O 3 , etc. Type metal oxide such as doped or dispersion strengthened gallate-based ceramics, such as indium-based ceramics such as Ba ₂ In ₂ O ₅ having a brownmillerite structure is exemplified. During these ceramics, there is further comprising _{SiO 2, Al 2 O 3,} GeO 2, SnO 2, Sb 2 O 3, PbO, Ta 2 O 5, Nb 2 O 5 or the like as another oxide Also good.

  Among these, particularly preferred are solid electrolytes made of zirconia oxide stabilized with one or more of Y, Ce, Sm, Pr, and Sc, and these solid electrolytes are made of a group consisting of alumina, titania and silica. A compound containing at least one selected from 0.1 to 2% by mass is also recommended.

  Of these, zirconia-based solid electrolytes stabilized with 3 to 10 mol% yttria or zirconia-based solid electrolytes stabilized with 4 to 12 mol% scandia are particularly preferable. A zirconia-based solid electrolyte to which about 1 to 5% by mass of alumina, titania, silica, ceria and the like are added. The shape of the electrolyte may be any of a flat plate shape, a corrugated plate shape, a corrugated shape, a honeycomb shape, a cylindrical shape, a cylindrical flat plate shape, and the like. The thickness of the electrolyte is 50 to 500 μm, preferably 80 to 300 μm, more preferably 100 to 200 μm.

When a solid electrolyte fuel cell is produced using the fuel electrode paste, the powder mixture for the fuel electrode material is added to one side of the electrolyte membrane with a binder, a solvent, a plasticizer, and a dispersant. A film is formed by screen printing or coating using paste or slurry obtained by uniformly kneading together with the above, and baked at a temperature of 1000 to 1400 ° C., preferably 1150 to 1350 ° C., to form a fuel electrode. Next, an air electrode paste having a composition such as La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _{3 made} of a complex oxide such as La, Sr, Co, and Fe is prepared as an air electrode material. When a film is formed on the opposite surface side by screen printing or the like and baked at a temperature of, for example, 900 to 1200 ° C., preferably 1000 to 1150 ° C., a solid electrolyte fuel cell having a three-layer membrane structure is obtained.

In the present invention, the air electrode material is preferably a perovskite complex oxide or a mixture of a perovskite oxide and a solid electrolyte. Specific examples of the perovskite oxide include La _1-x Sr _x Co _1-y Fe _y O ₃ (0.2 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 0.9), Pr ₁ Preferred examples include transition metal perovskite oxides such as _-x Sr _x MnO ₃ (0.2 ≦ x ≦ 0.6) and La _1-x Sr _x MnO ₃ (0.2 ≦ x ≦ 0.6). These may be used alone or in combination of two or more in any combination.

  In the above description, the atomic ratio of oxygen in the composition formula of the perovskite oxide is represented as 3. As is apparent to those skilled in the art, for example, when the atomic ratio x (y) is not 0, oxygen vacancies are generated. In practice, therefore, the atomic ratio of oxygen often takes a value smaller than 3. However, since the number of oxygen vacancies varies depending on the type of element to be added and the manufacturing conditions, the oxygen atomic ratio is represented as 3 for convenience.

Further, as the solid electrolyte in the case of a mixture of a perovskite oxide and a solid electrolyte, specifically, yttria-stabilized zirconia containing 8 to 10 mol%, preferably 8 to 9 mol% of Y ₂ O ₃ ( YSZ) and, 9-12 mol%, preferably chosen scandia-stabilized zirconia containing Sc ₂ O ₃ of 10 to 11 mol% (ScSZ), from _{Gd 2 O 3, Y 2 O} 3, Sm 2 O 3 A ceria solid solution containing 10 to 35 mol%, preferably 15 to 30 mol%, more preferably 20 to 30 mol% of at least one oxide (hereinafter referred to as “GDC”, a ceria-based solid solution containing Gd ₂ O ₃₎ . Y ₂ O ₃ "YDC" ceria solid solution containing, as exemplified ceria solid solution containing Sm ₂ O ₃ as it is) or the like are preferable as "SDC", other that may be used are also alone, It can be used in combination of two or more kinds thereof by principal.

  Using these air electrode materials, the air electrode paste is prepared in the same manner as the above-described fuel electrode paste.

  Furthermore, since the solid electrolyte material and the air electrode material are exposed to a high temperature for a long time to cause a solid-phase reaction and an insulating material may be generated at the interface between the solid electrolyte material and the air electrode material, Is preferably provided with an intermediate layer. As the intermediate layer material for this purpose, the GDC, YDC, and SDC can be preferably used as materials that have oxygen ion conductivity and electronic conductivity and are less likely to cause a solid phase reaction with the electrolyte material or the air electrode material. Then, an intermediate layer paste using these materials may be prepared in the same manner, and formed as an intermediate layer film on the opposite electrolyte surface where the fuel electrode film is formed.

  In this case, since the air electrode is formed on the intermediate layer film, a four-layer film cell is formed.

  In the present invention, the solid electrolyte membrane, the intermediate layer, the material constituting the air electrode, the film forming method, and the like are not limited at all, and the above is only an example.

  In the above description, the case of manufacturing a flat solid electrolyte fuel cell was briefly described. However, the fuel electrode material of the present invention can be similarly applied to the manufacture of a cylindrical solid electrolyte fuel cell. Further, a fuel cell is obtained by applying the fuel electrode material of the present invention to a solid electrolyte fuel cell having a structure in which a fuel electrode, a solid electrolyte and an air electrode are formed on the surface of a porous support tube or a support plate. Of course, it is also possible to produce.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

Production Example Nickel oxide particles, coarse ceria particles and fine ceria particles described in Tables 1 and 2 below on one side of a 4ScSZ electrolyte membrane (thickness 150 μm × diameter 30 mm) made of zirconia stabilized with 4 mol% of scandia The fuel electrode was formed by pasting the fuel electrode material consisting of the above and screen printing.

  The nickel oxide particles and coarse ceria particles are oxidized into coarse ceria particles by putting a total of 300 g in a predetermined ratio into a combined treatment tank of a multi-purpose mixer (manufactured by Mitsui Mining Co., Ltd.) and performing high-speed treatment at 10,000 rpm for 10 minutes. Composite particles in which nickel particles were dispersed were obtained.

  The fuel electrode paste is composed of 2 g of ethyl cellulose as a binder, 38 g of terpineol as a solvent, and 0.5 g of sorbitan acid ester (trade name “Ionet S-80”, manufactured by Sanyo Chemical Co., Ltd.) as a dispersant with respect to 50 g of the fuel electrode material. It was prepared by adding and milling 5 times with a 3 roll mill. Screen printing used a 100-mesh SUS wire mesh printing plate, and applied and dried to form a fuel electrode having a film thickness of 35 μm.

Next, on the opposite side, an intermediate composed of 20 mol% samarium-doped ceria (manufactured by Seimi Chemical Co., Ltd., specific surface area: 5.8 m ² / g, 50 volume% diameter: 0.8 μm, 90 volume% diameter: 2.2 μm) The layer material was pasted and screen-printed to a thickness of 8 μm using a 200-mesh SUS wire mesh printing plate. An electrolyte having an intermediate layer film coated on one side and an opposite side film is baked at 1150 ° C. for 3 hours to form a fuel electrode having a thickness of about 30 μm and an intermediate layer having a thickness of about 6 μm. did.

Further, on the formed intermediate layer, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder (manufactured by Seimi Chemical Co., Ltd., 50% by volume diameter: 1.7 μm, 90% by volume diameter: 4.1 μm) and 80% by mass The air electrode material consisting of 20% by mass of 10Sc1CeSZs powder manufactured by Daiichi Rare Element Co., Ltd. was made into a paste, and this was screen printed to form an air electrode.

  This air electrode paste was also prepared in the same manner as the fuel electrode paste, and then screen-printed using the same 100-mesh SUS wire mesh printing plate, and baked at 950 ° C. for 3 hours to a thickness of about 25 μm. A four-layer fuel cell having a diameter of 30 mm was formed.

Test Example 1 Power Generation Performance Test Using the cell of the production example, a power generation test was performed using a small single cell power generation test apparatus, and the maximum power density was measured. The fuel gas used was 3% steam humidified hydrogen at 800 ° C., and the oxidant was air. The product name “R8240” manufactured by Advantest was used as the current measuring device, and the product name “R6240” manufactured by Advantest was used as the current-voltage generator.

In addition, in order to confirm the deterioration tendency of the output density due to continuous power generation, the output voltage when the fuel utilization rate is 30% while flowing a current of 300 mA / cm ² was measured, and 200 hours, 500 hours, and 1000 hours passed from the initial stage. The subsequent deterioration rate was measured. Further, SEM images of the fuel electrode cross section after the elapse of 500 hours and 1000 hours were taken, and changes in the pore diameter of the fuel electrode were examined. The power density deterioration rate and the porosity reduction rate were determined as follows.
Output density degradation rate = [(initial output voltage−output voltage after elapse of a predetermined time) / initial output voltage] × 100 (%)

Test Example 2 Porosity Reduction Rate The location of the fuel electrode in the cross section of the four-layer structure membrane cell was observed using a scanning electron microscope (manufactured by JEOL Ltd., trade name “JSM-5410LV”) and selected at random. An SEM photograph in which a portion corresponding to 120 × 90 μm was magnified 800 times to 9.6 × 7.2 cm was taken, and the area that was black in the SEM photograph was measured as pores, and the obtained area (9. Divided by 6 × 7.2) and multiplied by 100 was taken as the porosity.
Porosity reduction rate = [(initial porosity−porosity after a predetermined time) / initial porosity] × 100 (%)

Test Example 3 Redox Resistance Test Using the cell of the production example, using 3% steam-humidified hydrogen as the fuel gas and air as the oxidant, a current utilization of 30 mA / cm ² was passed at 800 ° C., and the fuel utilization rate was 30 The cell terminal voltage at% was measured. After 168 hours from the start of the experiment, the fuel gas supply was stopped while maintaining the temperature at 800 ° C., and instead, the air was flowed for 1 hour, and then the fuel gas was flown again for 23 hours. The cell voltage drop rate after repeating the measurement was measured. In addition, the reduction rate of redox resistance was calculated | required as follows.
Reduction rate of redox resistance = [(cell voltage after 168 hours−cell voltage after predetermined redox) / cell voltage after 168 hours] × 100 (%)

The results of the above Test Examples 1 to 3 are shown in Tables 1 and 2. The meanings of the abbreviations in Tables 1 and 2 are as follows.
“NiO-D”: nickel oxide powder manufactured by Shodo Chemical Co., Ltd.
“NiO”: nickel oxide powder manufactured by Seimi Chemical Co., Ltd.
“4ScSZ”: 4 mol% scandia-stabilized zirconia powder manufactured by Daiichi Rare Element Chemical Co., Ltd.
“6ScSZ”: 6 mol% scandia-stabilized zirconia powder manufactured by Daiichi Rare Elemental Chemical Co., Ltd.
“TZ-3Y-E”: 3 mol% yttria stabilized zirconia powder manufactured by Tosoh Corporation
“TZ-4YS”: 4 mol% yttria-stabilized zirconia powder manufactured by Tosoh Corporation
“TZ-8YS”: 8 mol% yttria stabilized zirconia powder manufactured by Tosoh Corporation
“SDC-30 coarse particles”: Samaria stabilized ceria coarse particles manufactured by Daiichi Rare Elemental Chemical Co., Ltd.
"SDC-20 coarse product": Samaria stabilized ceria coarse particles manufactured by Daiichi Rare Elemental Chemical Co., Ltd.
“GDC-20 calcined product”: Gadria stabilized ceria calcined product manufactured by Daiichi Rare Element Chemicals,
“YDC-20 calcined product”: Yttria stabilized ceria calcined product manufactured by Daiichi Rare Element Chemicals,
“GDC-20 0.3 μm”: Gadria-stabilized ceria particles having an average particle size of 0.3 μm manufactured by Seimi Chemical Co., Ltd.
“GDC-20 0.5 μm”: Gadria-stabilized ceria particles having an average particle size of 0.5 μm manufactured by Seimi Chemical Co., Ltd.
“SDC-20 0.3 μm”: Samarium-stabilized ceria particles having an average particle size of 0.3 μm manufactured by Seimi Chemical Co., Ltd.

  From Tables 1 and 2, it can be considered as follows.

  Experiment No. 2 in Table 2 7 and 9 are examples in which nickel oxide particles and fine ceria particles are included as materials constituting the fuel electrode, but no coarse ceria particles are included. As a result, the packing density of the particles becomes too high and excessively densified, resulting in a significant decrease in porosity. In addition, the expansion and contraction of nickel oxide due to repeated oxidation and reduction cannot be alleviated, and redox resistance is improved. It was greatly reduced. In addition, Experiment No. 8 and 10 are examples in which nickel oxide particles and coarse ceria particles are included but fine ceria particles are not included. As a result, the durability of the fuel electrode itself was not sufficient, and the power density was greatly reduced over time.

  In contrast, the experiment No. Nos. 1 to 6 are examples that satisfy the requirements of the present invention, and since the coarse ceria particle group, the nickel oxide particle group, and the fine ceria particle group are included in the fuel electrode in a well-balanced manner, the output density and porosity As can be seen from the graph, the deterioration with time is small, sufficient power generation efficiency can be maintained even during long-time operation, and all have excellent redox resistance.

6 is a schematic diagram of a small single cell power generator used in a power generation test of Example 3. FIG.

Explanation of symbols

  1: Heater, 2: Alumina outer tube, 3: Alumina inner tube, 4: Platinum lead wire, 5: Solid electrolyte sheet, 6: Air electrode, 7: Fuel electrode, 8: Sealing material

Claims (7)

It consists of a mixture of coarse ceria particles, nickel oxide particles, and fine ceria particles,
A fuel electrode material for a nickel-ceria-based solid oxide fuel cell, wherein the average particle size of each particle group satisfies a relationship of coarse ceria particle group> nickel oxide particle group> fine ceria particle group.   2. The solid according to claim 1, wherein the content ratio of each particle group is coarse ceria particle group: 15-50 mass%, nickel oxide particle group: 40-70 mass%, fine ceria particle group: 5-30 mass%. Fuel electrode material for oxide fuel cells.   The average particle size of the coarse ceria particle group is 2 to 50 µm, the average particle size of the nickel oxide particle group is 0.5 to 5 µm, and the average particle size of the fine ceria particle group is 0.1 to 3 µm. A fuel electrode material for a solid oxide fuel cell as described in 1 above. Coarse ceria particles and / or fine ceria particles are
Ceria doped with yttrium, samarium or gadolinium;
Ceria-zirconia composite particles having a ceria content of 51% by mass or more; and ceria doped with yttrium, samarium, or gadolinium, the content of which is 51% by mass or more, and zirconia and / or alumina; Mixed particles of
The fuel electrode material for a solid oxide fuel cell according to any one of claims 1 to 3, which is one or more selected from the group consisting of:   A fuel electrode formed on one side of a solid electrolyte in a solid oxide fuel cell, wherein the fuel electrode is formed of the fuel electrode material according to any one of claims 1 to 4. Fuel electrode for fuel cell.   5. A solid oxide fuel cell having a fuel electrode formed on one side of a solid electrolyte and an air electrode formed on the other side, wherein the fuel electrode is the fuel electrode according to claim 1. A solid oxide fuel cell formed of a material.   A solid oxide fuel cell comprising the solid oxide fuel cell according to claim 6.

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