Porous electrode material for SOEC / SOFC and method for manufacturing the same

Abstract

To provide an electrode material for use in the cathode of an SOEC or the anode of an SOFC, which has excellent electrode reaction efficiency (for example, reduction reaction efficiency in the cathode of an SOEC).SOLUTION: A porous electrode material for SOEC / SOFC, includes a porous ionic conductor, in the porous ionic conductor, after heating in air at a temperature in the range of 1000 to 1500°C for 5 hours, the pore volume of pores has a diameter of 1 μm or less is 0.03 cm3 / g or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a porous electrode material for solid oxide electrolytic cells (SOECs) / solid oxide fuel cells (SOFCs) and a method for producing the same. [Background technology]

[0002] Solid oxide electrolytic cells (SOECs) are water electrolysis devices that use a solid electrolyte. By supplying carbon dioxide or water vapor to the cathode (hydrogen electrode) and passing an electric current between the electrodes, carbon monoxide and hydrogen are produced. Solid oxide fuel cells (SOFCs), on the other hand, are fuel cells that use a solid electrolyte. While their structure is the same as SOECs, the electrode reaction is reversed. That is, by supplying fuel such as hydrogen, carbon monoxide, or hydrocarbons to the anode (fuel electrode) and oxygen to the cathode (oxygen electrode), the electrode reaction proceeds and carbon dioxide and water are produced. Common electrode materials used for the cathodes of SOECs and the anodes of SOFCs include nickel-yttria stabilized zirconia (Ni-YSZ cermet), nickel-scandia stabilized zirconia (Ni-ScSZ cermet), and nickel-samaria doped ceria (Ni-SDC).

[0003] Furthermore, Japanese Patent Publication No. 2015-201428 (Patent Document 1) describes a solid oxide fuel cell comprising an inner first electrode containing Ni and / or NiO and an oxide (excluding oxides containing the element Zr) that acts as a fuel electrode, and an inner second electrode containing Ni and NiO and a cerium-containing oxide that acts as a fuel electrode catalyst layer. In addition, Patent Document 1 describes an inner first electrode containing Ni and / or NiO and Y2O3, and a cerium-containing oxide doped with yttrium (Y) (YDC) as the cerium-containing oxide.

[0004] Furthermore, Japanese Patent Publication No. 2013-143189 (Patent Document 1) describes an electrode-forming material used to form a porous electrode, comprising an electrode material having electronic conductivity and / or ionic conductivity, and a pore-forming material consisting of plant powder containing glutinous rice starch. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-201428 [Patent Document 2] Japanese Patent Publication No. 2013-143189 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the electrode reaction efficiency (for example, the reduction reaction efficiency in the cathode of an SOEC) was not always sufficient in the electrode materials used in the cathodes of conventional SOECs and the anodes of SOFCs.

[0007] The present invention has been made in view of the problems of the prior art described above, and aims to provide an electrode material used in the cathode of an SOEC or the anode of an SOFC, which has excellent electrode reaction efficiency (for example, reduction reaction efficiency in the cathode of an SOEC), and a method for manufacturing the same. [Means for solving the problem]

[0008] As a result of intensive research to achieve the above object, the present inventors mixed an aqueous salt-containing solution containing a yttrium salt, a cerium salt, and a zirconium salt, an alkaline aqueous solution containing a dispersant, and a thermosetting resin precursor to prepare a slurry containing the thermosetting resin precursor. The thermosetting resin precursor in the slurry containing the thermosetting resin precursor was converted into a thermosetting resin to prepare a slurry containing the thermosetting resin. The slurry containing the thermosetting resin was dried to prepare a solid component containing the thermosetting resin. The thermosetting resin in the solid component was carbonized to prepare a solid component containing carbide. By firing the solid component containing carbide in an air atmosphere, it was found that a porous ion conductor having a large pore volume with a pore diameter of 1 μm or less, a yttrium-added ceria-zirconia solid solution, was obtained. Furthermore, it was found that an electrode material containing this yttrium-added ceria-zirconia solid solution is excellent in electrode reaction efficiency (for example, reduction reaction efficiency at the cathode of SOEC). Thus, the present invention has been completed.

[0009] That is, the present invention provides the following aspects.

[0010] [1] A porous electrode material for SOEC / SOFC, containing a porous ion conductor, The porous ion conductor is a solid solution containing at least yttrium, cerium, and zirconium, The solid solution containing at least yttrium, cerium, and zirconium has the following compositional formula (1): Y x Ce y Zr 1-x-y O 2-δ (1) (In formula (1), x and y each satisfy 0 < x < 0.2 and 0 < y < 0.2, and δ is a value that maintains electrical neutrality.) It is a yttrium-added ceria-zirconia solid solution represented by The porous ion conductor is having a pore volume of 0.03 cm 3 / g or more with a pore diameter of 1 μm or less, a fired product of and being for SOEC / SOFC.

[0011] [2] The porous electrode material for SOEC / SOFC according to [1], wherein the porous ion conductor has an oxygen storage capacity.

[0014] 3 nickel is supported on the solid solution containing at least yttrium, cerium, and zirconium, 1 or 2 the porous electrode material for SOEC / SOFC according to any one of

[0015] 4 the pore volume of pores with a pore diameter of 1 μm or less is 0.04 cm 3 / g or more, the porous electrode material for SOEC / SOFC according to any one of [1] to 3

[0016] 5 A first step of mixing an aqueous salt solution containing a yttrium salt, a cerium salt, and a zirconium salt, an alkaline aqueous solution containing a dispersant, and a thermosetting resin precursor to obtain a thermosetting resin precursor-containing slurry having a pH of 6.0 or more; A second step of converting the thermosetting resin precursor in the thermosetting resin precursor-containing slurry into a thermosetting resin to obtain a thermosetting resin-containing slurry; A third step of drying the thermosetting resin-containing slurry to obtain a solid component containing the thermosetting resin; A fourth step of carbonizing the thermosetting resin in the solid component to obtain a carbide-containing solid component; firing the carbide-containing solid component in an air atmosphere to contain a solid solution containing at least yttrium, cerium, and zirconium, 1 to 4 A fifth step of obtaining the porous electrode material according to any one of A method for producing a porous electrode material for SOEC / SOFC, including

[0017] 6 In the first step, the aqueous salt solution and the alkaline aqueous solution are mixed under a high shear force to prepare a slurry, and then the thermosetting resin precursor is mixed with the slurry to obtain the thermosetting resin precursor-containing slurry, 5 ​​​​A method for producing porous electrode material for SOEC / SOFC as described in [ ].

[0018] [ 7 In the first step, the salt-containing aqueous solution, the alkaline aqueous solution, and the thermosetting resin precursor are mixed under high shear force to obtain the thermosetting resin precursor-containing slurry, 5 A method for producing porous electrode material for SOEC / SOFC as described in [ ].

[0019] [ 8 In the first step, the high shear force is such that the shear rate is 100,000 sec. -1 Under the above high shear force, 6 ] or [ 7 A method for producing porous electrode material for SOEC / SOFC as described in [ ].

[0020] [ 9 In the second step, the thermosetting resin precursor is converted into the thermosetting resin by adjusting the pH of the slurry containing the thermosetting resin precursor to less than 6.0, thereby obtaining the slurry containing the thermosetting resin. 5 ]~[ 8 A method for producing a porous electrode material for SOEC / SOFC as described in any one of the following items.

[0021] [ 10 In the fifth step, the carbide-containing solid component is reduced and fired in an inert atmosphere, and then fired in an air atmosphere to obtain a porous electrode material containing a solid solution containing at least yttrium, cerium, and zirconium. 5 ]~[ 9 A method for producing a porous electrode material for SOEC / SOFC as described in any one of the following items.

[0022] Although the reason why the porous electrode material of the present invention exhibits excellent electrode reaction efficiency is not entirely clear, the inventors speculate as follows: As shown in Figures 1A and 1B, the yttrium-doped ceria-zirconia solid solution (YCZ solid solution) (Figure 1A), used as a porous ion conductor in the present invention, has a larger pore volume of pores with a diameter of 1 μm or less inside the secondary particles compared to a conventional YCZ solid solution (Figure 1B). Therefore, the diffusivity of the reaction substrate into the YCZ solid solution (for example, carbon dioxide or water vapor in the cathode of SOEC, or hydrogen, carbon monoxide, or hydrocarbons in the anode of SOFC) is improved, and as a result, the electrode reaction efficiency is improved. [Effects of the Invention]

[0023] According to the present invention, it is possible to obtain an electrode material used in the cathode of an SOEC or the anode of an SOFC that exhibits excellent electrode reaction efficiency (for example, reduction reaction efficiency in the cathode of an SOEC). [Brief explanation of the drawing]

[0024]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0025] Hereinafter, the present invention will be described in detail according to its preferred embodiments.

[0026] 〔Porous electrode material for SOEC / SOFC〕 First, the porous electrode material for SOEC / SOFC of the present invention will be described. The porous electrode material for SOEC / SOFC of the present invention contains a porous ion conductor, and as the porous ion conductor, those having oxygen storage ability are preferable, and a solid solution containing at least yttrium, cerium, and zirconium is more preferable. The following composition formula (1): Y x Ce y Zr 1-x-y O 2-δ (1) (In formula (1), x and y each satisfy 0 < x < 0.2 and 0 < y < 0.2, and δ is a value that maintains electrical neutrality.) The yttrium-added ceria-zirconia solid solution (YCZ) represented by is particularly preferable. By using a porous ion conductor having oxygen storage ability, oxygen generated in the electrode reaction is stored in the porous ion conductor, so that deterioration due to oxidation of the electrode material is suppressed. The "value that maintains electrical neutrality" means that the total valence of Y x and Ce y and Zr 1-x-y is equal to the total valence of O 2-δ , and the following formula: 3×x + 4×y + 4×(1 - x - y) = 2×(2 - δ) δ that satisfies.

[0027] When ceria-zirconia solid solution (CZ) without yttrium (i.e., x=0 in the above composition formula (1)) is used as an electrode material for SOEC / SOFC, oxide ion conductivity is insufficient, and electrode characteristics deteriorate. Furthermore, when yttrium-added zirconia (YZ) without ceria (i.e., y=0 in the above composition formula (1)) is used as an electrode material for SOEC / SOFC, oxidation of Ni during the electrode reaction cannot be suppressed, and electrode deterioration progresses.

[0028] Furthermore, if x in the composition formula (1) exceeds the upper limit, the toughness of YCZ decreases, and the strength of the electrode decreases. Also, if y exceeds the upper limit, the lattice expansion of YCZ during the reduction reaction increases, and the durability of the electrode decreases.

[0029] Furthermore, in the porous ionic conductor, the pore volume of pores with a diameter of 1 μm or less (hereinafter also simply referred to as "pore volume of pores with a diameter of 1 μm or less") after heating in air at a temperature in the range of 1000 to 1500°C for 5 hours is 0.03 cm³. 3 It is necessary that the amount be 1 / g or more. The pore volume of pores with a diameter of 1 μm or less is the total pore volume of pores with a diameter of 1 μm or less, calculated based on the pore distribution of the porous ion conductor obtained by the mercury intrusion method using a mercury porosimeter.

[0030] When the pore volume of a pore with a diameter of 1 μm or less falls below the lower limit, the diffusivity of reaction substrates into the secondary particles of the porous ionic conductor (for example, carbon dioxide or water vapor in the cathode of an SOEC, or hydrogen, carbon monoxide, or hydrocarbons in the anode of an SOFC) decreases, and the electrode reaction efficiency (for example, the reduction reaction efficiency in the cathode of an SOEC or the oxidation reaction efficiency in the anode of an SOFC) decreases. Furthermore, from the viewpoint of improving the diffusivity of reaction substrates into the secondary particles of the porous ionic conductor and improving the electrode reaction efficiency, the pore volume of a pore with a diameter of 1 μm or less is 0.04 cm³. 3 Preferably 0.05 cm or more per gram. 3 More preferably 0.07 cm² or more, and 0.07 cm² or more. 3 More preferably 0.09 cm or more,3 A value of 1 / g or more is particularly preferred. While there is no particular upper limit on the pore volume of pores with a diameter of 1 μm or less, from the viewpoint of structural stability when forming electrodes, 1.0 cm is preferable. 3 Preferably less than / g, and 0.7cm 3 It is more preferable that the value be less than or equal to / g. Furthermore, the lower limit of the pore diameter is greater than or equal to the detection limit of the pore diameter that can be measured by a mercury porosimeter (for example, 0.001 μm or more).

[0031] In the porous electrode material for SOEC / SOFC of the present invention, it is preferable that nickel is supported in the solid solution containing at least yttrium, cerium, and zirconium. The catalytic action of the nickel supported in the solid solution promotes the reduction reaction in the cathode of the SOEC and the oxidation reaction in the anode of the SOFC, thereby improving the electrode reaction efficiency. Furthermore, supporting nickel in the solid solution tends to suppress the deterioration of the SOEC cathode due to the oxidation of nickel. The reason why the deterioration of the SOEC cathode due to the oxidation of nickel is suppressed is not entirely clear, but the inventors speculate as follows. That is, for example, in a conventional SOEC cathode in which nickel (Ni) is supported on a support such as yttria-stabilized zirconia (YSZ cermet), as shown in Figure 2A, oxygen generated by the reduction reaction of water vapor oxidizes the surface of Ni, so the catalytic activity of Ni decreases and the SOEC cathode deteriorates. On the other hand, when Ni supported in a solid solution containing at least yttrium, cerium, and zirconium, such as YCZ, is supported on a support such as YSZ cermet, as shown in Figure 2B, the oxygen generated by the reduction reaction of water vapor is stored in the oxygen vacancies in the solid solution such as YCZ, so it is presumed that oxidation of the Ni surface is suppressed and deterioration of the SOEC cathode is suppressed.

[0032] The amount of nickel supported is preferably 5 to 70% by mass, and more preferably 10 to 60% by mass, relative to the total amount of the solid solution containing at least yttrium, cerium, and zirconium and nickel oxide, in terms of nickel oxide. If the amount of nickel supported falls below the lower limit, the effect of supporting nickel may not be fully realized, while if the amount of nickel supported exceeds the upper limit, the performance tends to saturate.

[0033] [Method for manufacturing porous electrode materials for SOEC / SOFC] Next, the method for manufacturing the porous electrode material for SOEC / SOFC of the present invention will be described. The method for manufacturing the porous electrode material for SOEC / SOFC of the present invention is as follows: A first step involves mixing a salt-containing aqueous solution containing yttrium salt, cerium salt, and zirconium salt, an alkaline aqueous solution containing a dispersant, and a thermosetting resin precursor to obtain a thermosetting resin precursor-containing slurry with a pH of 6.0 or higher. A second step is to convert the thermosetting resin precursor in the aforementioned thermosetting resin precursor-containing slurry into a thermosetting resin to obtain a thermosetting resin-containing slurry. A third step involves drying the thermosetting resin-containing slurry to obtain a solid component containing the thermosetting resin, A fourth step involves carbonizing the thermosetting resin in the solid component to obtain a carbide-containing solid component, A fifth step involves firing the carbide-containing solid component in an atmospheric environment to obtain a porous electrode material consisting of a solid solution containing at least yttrium, cerium, and zirconium. This method includes [something].

[0034] <First step> In the first step, a salt-containing aqueous solution containing yttrium salt, cerium salt, and zirconium salt is mixed with an alkaline aqueous solution containing a dispersant and a thermosetting resin precursor. This yields a slurry containing a thermosetting resin precursor with a pH of 6.0 or higher.

[0035] Examples of the yttrium salt include yttrium nitrate, yttrium chloride, yttrium sulfate, and yttrium acetate. Examples of the cerium salt include cerium ammonium nitrate, cerium nitrate, cerium chloride, cerium sulfate, and cerium acetate. Examples of the zirconium salt include zirconium nitrate, zirconyl oxynitrate, zirconium chloride, zirconium sulfate, and zirconium acetate.

[0036] The salt-containing aqueous solution can be prepared by dissolving the yttrium salt, the cerium salt, and the zirconium salt in water. In the salt-containing aqueous solution, the ratio of the yttrium salt, the cerium salt, and the zirconium salt is adjusted as appropriate so that the yttrium (Y), cerium (Ce), and zirconium (Zr) in the YCZ satisfy the composition formula (1).

[0037] Examples of the dispersant include alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, and ethylenediamine; and ammonium salts of carboxylic acids such as ammonium polyacrylate (molecular weight 2000-6000).

[0038] In the method for producing a porous electrode material for SOEC / SOFC of the present invention, the aqueous solution containing the dispersant must be alkaline. The alkalinity of the aqueous solution containing the dispersant causes all of the yttrium (Y) to precipitate, allowing it to be uniformly dissolved in the solid solution containing at least yttrium, cerium, and zirconium. On the other hand, if the aqueous solution containing the dispersant is acidic, precipitation of yttrium (Y) does not occur, resulting in only a portion being incorporated into the solid solution, which leads to segregation of yttrium oxide.

[0039] An alkaline aqueous solution containing the aforementioned dispersant (dispersant-containing alkaline aqueous solution) can be prepared by dissolving the dispersant in water. If the resulting aqueous solution is alkaline, it can be used as is. On the other hand, if the resulting aqueous solution is acidic, a basic compound is added to adjust it to alkalinity. Examples of the basic compound include aqueous ammonia, ammonium carbonate, sodium hydroxide, potassium hydroxide, and sodium carbonate. It is also possible to adjust the solution to alkalinity by increasing the amount of the alkanolamine-based dispersant added.

[0040] Examples of the thermosetting resin precursors include urea resin precursors (a mixture of urea and formaldehyde), melamine resin precursors (melamine and formaldehyde, or commercially available methylolmelamine), and other resin precursors that react with formaldehyde to form methylol groups.

[0041] In the method for producing a porous electrode material for SOEC / SOFC of the present invention, there are no particular limitations on the method for mixing the salt-containing aqueous solution, the dispersant-containing alkaline aqueous solution, and the thermosetting resin precursor, as long as a slurry (thermosetting resin precursor-containing slurry) containing the solid solution containing at least yttrium, cerium, and zirconium and the thermosetting resin precursor is obtained. For example, a method in which the salt-containing aqueous solution and the dispersant-containing alkaline aqueous solution are mixed to prepare a slurry containing the solid solution containing at least yttrium, cerium, and zirconium, and then the thermosetting resin precursor is mixed into this slurry (first method); a method in which the salt-containing aqueous solution and the dispersant and the thermosetting resin precursor are mixed into an alkaline aqueous solution (second method). Of these methods, the first method is more preferred from the viewpoint of increasing the pore volume of the resulting solid solution with a pore diameter of 1 μm or less.

[0042] When mixing the salt-containing aqueous solution with the dispersant-containing alkaline aqueous solution, or when mixing the salt-containing aqueous solution with the dispersant and the thermosetting resin precursor, the mixing is performed under high shear force (preferably with a shear rate of 10,000 sec). -1 In summary, a more preferable shear rate is 15,000 sec. -1 It is preferable to carry out the process under the above-mentioned high shear force. This results in the solid solution containing at least yttrium, cerium, and zirconium being atomized into fine particles, and an electrode material with excellent electrode reaction efficiency is obtained. As an example of a method for mixing under high shear force, one can use the "apparatus for producing ultrafine particles and porous material precursors" described in Japanese Patent No. 6658564.

[0043] In the slurry containing a thermosetting resin precursor obtained in this manner, the content ratio of the solid solution containing at least yttrium, cerium, and zirconium to the thermosetting resin precursor is preferably 1:4 to 1:10 by mass, more preferably 1:5 to 1:8, and particularly preferably 1:6 to 1:7. If the proportion of the thermosetting resin precursor falls below the lower limit, the predetermined pore volume tends to become insufficient. On the other hand, if the proportion of the thermosetting resin precursor exceeds the upper limit, production efficiency decreases, and resin components are wasted, which is undesirable from the viewpoint of carbon neutrality. The mixing ratio of the salt-containing aqueous solution, the dispersant-containing alkaline aqueous solution, and the thermosetting resin precursor, as well as the mixing ratio of the salt-containing aqueous solution and the alkaline aqueous solution containing the dispersant and the thermosetting resin precursor, are appropriately adjusted so that the content ratio of the solid solution to the thermosetting resin precursor falls within the above range.

[0044] The pH of the thermosetting resin precursor-containing slurry obtained in this way is usually 6.0 or higher, preferably 6.2 or higher, more preferably 6.4 or higher, and usually 8.0 or lower, preferably 7.5 or lower, more preferably 7.0 or lower. Furthermore, when preparing a thermosetting resin precursor-containing slurry by the first method described above, the pH of the slurry containing the solid solution obtained by mixing the salt-containing aqueous solution and the dispersant-containing alkaline aqueous solution is adjusted to preferably 9.0 or higher, more preferably 9.5 or higher, in order to form the solid solution. There is no particular upper limit on the pH of the slurry containing the solid solution, but a pH of 10 or lower is preferred. Then, by mixing the thermosetting resin precursor with the slurry containing the solid solution at such a pH, a thermosetting resin precursor-containing slurry with a pH within the above range is obtained.

[0045] <Second step> In the second step, the thermosetting resin precursor in the slurry containing the thermosetting resin precursor obtained in the first step is converted into a thermosetting resin. This yields a slurry containing a thermosetting resin.

[0046] There are no particular limitations on the method for converting the thermosetting resin precursor into a thermosetting resin, but for example, one method is to adjust the pH of the slurry containing the thermosetting resin precursor to less than 6.0, preferably 5.8 or less, and more preferably 5.5 or less. One method for adjusting the pH of the slurry containing the thermosetting resin precursor to the above range is to add an acid to the slurry containing the thermosetting resin precursor. Examples of the acid include organic carboxylic acids such as maleic acid, citric acid, malic acid, and acetic acid.

[0047] <Third step> In the third step, the thermosetting resin-containing slurry obtained in the second step is dried. This yields a solid component containing the thermosetting resin.

[0048] The drying conditions for the thermosetting resin-containing slurry are not particularly limited as long as they can remove water from the slurry. For example, the drying temperature is preferably 110 to 180°C, more preferably 140 to 160°C, and the drying time is preferably 7 to 15 hours, more preferably 10 to 12 hours.

[0049] <Fourth step> In the fourth step, the thermosetting resin in the solid component obtained in the third step is carbonized. This yields a carbide-containing solid component.

[0050] There are no particular restrictions on the heating conditions for carbonizing the thermosetting resin, but for example, the heating temperature is preferably 200 to 350°C, more preferably 280 to 320°C, and the heating time is preferably 1 to 5 hours, more preferably 2 to 4 hours.

[0051] <The fifth step> In the fifth step, the carbide-containing solid component obtained in the fourth step is calcined in an atmospheric environment. This yields a porous electrode material containing a solid solution comprising at least yttrium, cerium, and zirconium, with a pore volume having a pore diameter of 1 μm or less within a predetermined range.

[0052] There are no particular restrictions on the firing conditions for the carbide-containing solid component, but for example, the firing temperature is preferably 1250 to 1400°C, more preferably 1300 to 1350°C, and the firing time is preferably 3 to 10 hours, more preferably 4 to 6 hours.

[0053] Furthermore, in the fifth step, it is preferable to reduce and calcine the carbide-containing solid component in an inert atmosphere, and then calcine it in an air atmosphere. This increases the pore volume of the resulting solid solution, where the pore diameter is 1 μm or less. Reduced calcination in an inert atmosphere suppresses excessive sintering between the oxide fine particles of the solid solution while maintaining the carbon content, and promotes the growth of necks between the oxide fine particles. This allows for increased oxygen ion conductivity of the solid solution while maintaining a porous state.

[0054] There are no particular restrictions on the inert atmosphere, but examples include an argon gas atmosphere, a nitrogen gas atmosphere, and a helium gas atmosphere. There are no particular restrictions on the reduction firing conditions, but for example, the reduction firing temperature is preferably 800 to 1000°C, more preferably 850 to 950°C, and the reduction firing time is preferably 3 to 10 hours, more preferably 4 to 6 hours. If the reduction firing temperature is below the lower limit, the formation of the neck tends to be insufficient, on the other hand, if the reduction firing temperature exceeds the upper limit, carbon (carbides) derived from the thermosetting resin and zirconia in the solid solution may form carbides (ZrC), which may destroy the porous structure. [Examples]

[0055] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0056] (Example 1) <Preparation of aqueous solution A-1> 10.34 g of yttrium nitrate hexahydrate (Y(NO3)3·6H2O, manufactured by Kanto Chemical Co., Ltd.), 10.96 g of cerium ammonium nitrate (Ce(NH4)2(NO3)6, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 104.74 g of zirconium oxynitrate aqueous solution (Zr(NO3)2, 18% by mass aqueous solution, "Zircozol" manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.) were mixed, and deionized water was added to prepare a total volume of 400 ml of aqueous solution A-1. The pH of this aqueous solution A-1 was 1.29.

[0057] <Preparation of aqueous solution B-1> 57.04 g of 2-aminoethanol (monoethanolamine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 253.16 g of ammonium polyacrylate ("Aron A30SL," manufactured by Toagosei Co., Ltd.) were added to deionized water to prepare a total volume of 400 ml of aqueous solution B-1. The pH of this aqueous solution B-1 was 10.3.

[0058] <Preparation of Slurry C-1> The aqueous solution A-1 and the aqueous solution B-1 were mixed using the "apparatus for producing ultrafine particles and porous material precursors" described in Japanese Patent No. 6658564, with a rotor rotation speed of 8000 rpm, a liquid delivery speed of 5 ml / min, and a shearing speed of 15000 sec. -1 Slurry C-1 was prepared by mixing under the specified conditions. The SA (Shear-Agitation) reactor used in the manufacturing apparatus was an outer nozzle type SA reactor of the type shown in Figures 5A and 5B of the aforementioned patent publication. During mixing, nozzles 15A and flow path 16A were not used, while nozzles 15B and 15C and flow paths 16B and 16C were used. The pH of the obtained slurry C-1 was 9.72.

[0059] <Preparation of Slurry D-1> 52.74 g of urea (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to water to prepare a total volume of 250 ml of urea aqueous solution. Additionally, 128.30 g of formaldehyde (36-38% aqueous solution, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to deionized water to prepare a total volume of 250 ml of formaldehyde aqueous solution. The urea aqueous solution and the formaldehyde aqueous solution were each added dropwise to slurry C-1 at a flow rate of 10 ml / min using a cassette tube pump and mixed to prepare slurry D-1 containing a urea resin precursor. The pH of slurry D-1 was 6.52.

[0060] <Preparation of Slurry E-1> 29.05 g of maleic anhydride was added to deionized water and stirred using a magnetic stirrer to prepare a total volume of 200 ml of maleic acid aqueous solution. The pH of this maleic acid aqueous solution was 1.59. The maleic acid aqueous solution was added dropwise to slurry D-1 at a flow rate of 10 ml / min using a cassette tube pump and mixed to convert the urea resin precursor into urea resin, thereby preparing slurry E-1 containing the urea resin. The pH of slurry E-1 was 5.45.

[0061] <Drying> First, the slurry E-1 was stirred overnight using a magnetic stirrer, then divided into two 1L glass beakers and placed in a hot air dryer, where it was dried at 150°C for 12 hours.

[0062] <Carbonization> Next, the obtained solid component was heated at 300°C for 4 hours using a hot air dryer to carbonize the urea resin.

[0063] <Firing> Next, the carbonized solid components were transferred from a glass beaker to a carbon container and placed in a small vacuum pressurized sintering furnace (FVPS-R-150, manufactured by Fuji Denpa Kogyo Co., Ltd.). Under an argon gas atmosphere, they were reduced and fired at 900°C for 5 hours. The solid components after reduced firing were transferred from the carbon container to an alumina crucible and placed in a Kanthal Super electric furnace (NE-3550G, manufactured by Motoyama Co., Ltd.). Under an atmospheric atmosphere, the temperature was raised to 1340°C at a heating rate of 134°C / h, and then held at this temperature for 5 hours to obtain a Y-added CeO2-ZrO2 solid solution powder (YCZ powder). The atomic ratio of this YCZ powder is Y / Ce / Zr = 13.5 / 10.0 / 76.5.

[0064] (Example 2) <Preparation of aqueous solution B-2> 57.04 g of 2-aminoethanol (monoethanolamine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 253.16 g of ammonium polyacrylate ("Aron A30SL," manufactured by Toagosei Co., Ltd.), 52.74 g of urea (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 128.30 g of formaldehyde (36-38% aqueous solution, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to deionized water to prepare a total volume of 400 ml of aqueous solution B-2. The pH of this aqueous solution B-2 was 8.96.

[0065] <Preparation of Slurry D-2> Aqueous solutions A-1 and B-2, prepared in the same manner as in Example 1, were subjected to a process using the "Apparatus for Manufacturing Ultrafine Particles and Porous Precursors" described in Japanese Patent No. 6658564, with a rotor rotation speed of 8000 rpm, a liquid delivery speed of 5 ml / min, and a shearing speed of 15000 sec. -1Slurry D-2 containing a urea resin precursor was prepared by mixing under the specified conditions. The SA (Shear-Agitation) reactor used in the manufacturing apparatus was an outer nozzle type SA reactor of the type shown in Figures 5A and 5B of the aforementioned patent publication. During mixing, nozzles 15A and flow path 16A were not used, while nozzles 15B and 15C and flow paths 16B and 16C were used. The pH of the obtained slurry D-2 was 7.12.

[0066] <Preparation of Slurry E-2> An aqueous maleic acid solution prepared in the same manner as in Example 1 was added dropwise to slurry D-2 at a flow rate of 10 ml / min using a cassette tube pump and mixed to convert the urea resin precursor into urea resin, thereby preparing slurry E-2 containing the urea resin. The pH of slurry E-2 was 5.75.

[0067] <Drying, carbonization, and firing> A Y-added CeO2-ZrO2 solid solution powder (YCZ powder) was obtained in the same manner as in Example 1, except that slurry E-2 was used instead of slurry E-1. The atomic ratio of this YCZ powder is Y / Ce / Zr = 13.5 / 10.0 / 76.5.

[0068] (Example 3) <Firing> The carbonized solid components prepared in the same manner as in Example 1 were transferred from a glass beaker to an alumina crucible and placed in a Kanthal Super electric furnace (Motoyama Corporation, "NE-3550G"). Under an atmospheric environment, the temperature was raised to 1340°C at a heating rate of 134°C / h, and then held at this temperature for 5 hours to obtain Y-added CeO2-ZrO2 solid solution powder (YCZ powder). The atomic ratio of this YCZ powder is Y / Ce / Zr = 13.5 / 10.0 / 76.5.

[0069] (Comparative Example 1) A mixture of 49.1 g of cerium nitrate solution at a concentration equivalent to 28% by mass in terms of CeO2, 418.2 g of zirconium nitrate aqueous solution at a concentration equivalent to 18% by mass in terms of ZrO2, 99.8 g of 30% hydrogen peroxide solution, and yttrium nitrate aqueous solution (41.4 g of yttrium nitrate dissolved in 50 ml of pure water) was prepared. The resulting mixture was added to diluted ammonia water (145.9 g of 25% ammonia water diluted in 400 ml of pure water) while stirring with a propeller stirrer, and then stirred at 1000 rpm for 10 minutes using a homogenizer to generate a precipitate. The solution containing this precipitate was divided into three 1 L beakers and placed in a degreasing furnace. After drying in the air at 150°C for 7 hours, it was calcined at 400°C for 5 hours. The calcined powder was placed in a Kanthal Super electric furnace (NE-3550G, manufactured by Motoyama Co., Ltd.), heated to 1340°C at a heating rate of 134°C / h under an atmospheric environment, and then held at this temperature for 5 hours to obtain Y-added CeO2-ZrO2 solid solution powder (YCZ powder). The atomic ratio of this YCZ powder is Y / Ce / Zr = 13.5 / 10.0 / 76.5.

[0070] [Pore distribution measurement] The pore distribution of the obtained YCZ powder was measured using a mercury porosimeter (Anton Paar "PoreMaster 60GT") by the mercury intrusion method. The results are shown in Figure 3. In addition, the pore volume of pores with a diameter of 1 μm or less was determined based on the obtained pore distribution. The results are shown in Table 1.

[0071] [Catalyst preparation] The obtained YCZ powder was impregnated with nickel(II) nitrate so that the NiO load was 10% by mass, then evaporated to dryness, and the resulting dry material was calcined in air at 400°C for 3 hours to prepare a powder in which NiO was supported on the YCZ (NiO-supported YCZ powder). Furthermore, this NiO-supported YCZ powder was heated in air at 1340°C for 5 hours to obtain a catalyst powder. 3 g of this catalyst powder and 1 g of γ-alumina powder were mixed in a mortar, and 1000 kgf / cm² was added to the resulting mixed powder. 2 After applying cold isostatic pressing (CIP) for 1 minute at a pressure (molding pressure) of 98 MPa, the material was pulverized into pellets with a diameter of 0.5 to 1 mm to obtain catalyst powder for evaluating hydrogen generation capacity.

[0072] Furthermore, the obtained YCZ powder was heated in air at 1340°C for 5 hours to obtain a heat-treated YCZ powder. This heat-treated YCZ powder was then impregnated with a dinitrodiammineplatin(II) acid solution, evaporated to dryness, and the resulting dry material was calcined at 300°C for 3 hours to obtain a catalyst powder for measuring oxygen release amount (Pt load: 1% by mass) in which platinum (Pt) was supported on the YCZ powder.

[0073] [Hydrogen generation capacity evaluation test] One g of the catalyst powder prepared as described above for evaluating hydrogen production capacity was packed into a reaction tube and set in a fixed-bed flow type catalytic reaction evaluation apparatus (CATA-5000-SP7, manufactured by Best Measuring Instruments Co., Ltd.). While flowing O2 (5%)-containing gas (remaining: N2) at a gas flow rate of 5 L / min, the catalyst bed was heated from room temperature to 700°C over 14 minutes (Step 1), and then held at 700°C for 10 minutes (Step 2). Next, while maintaining the catalyst bed at 700°C, N2 was flowed at a gas flow rate of 5 L / min for 5 minutes. After circulating the gas (Step 3), a gas containing 1% H2 (the remainder being N2) was circulated for 10 minutes (Step 4), followed by another 10 minutes of N2 circulation (Step 5). Then, a gas containing 20% ​​water vapor (the remainder being N2) was circulated for 20 minutes (Step 6). Subsequently, the catalyst bed was maintained at 700°C for 1 minute while circulating N2 at a gas flow rate of 5 L / min (Step 7), and then allowed to cool to room temperature (Step 8). The amount of H2 produced in Step 6 was measured. The results are shown in Figure 4 and Table 1.

[0074] <Oxygen release measurement> 15 mg of the catalyst powder for measuring oxygen release, prepared as described above, was placed in a thermogravimetric analyzer (Shimadzu Corporation, "TGA-50"). At a temperature of 700°C, reducing gas (H2 (5 vol%) + N2 (remainder)) and oxidizing gas (O2 (5 vol%) + N2 (remainder)) were alternately passed through the catalyst powder at a gas flow rate of 100 ml / min, switching every 5 minutes. The increase or decrease in the mass of the catalyst powder during this period was measured. The amount of mass loss of the catalyst powder during the third pass of reducing gas was determined and defined as the oxygen release amount. The results are shown in Figure 5 and Table 1.

[0075] [Table 1]

[0076] As shown in Table 1, catalysts using YCZ powder prepared by heating a solid component consisting of a mixture of YCZ powder and a resin component to carbonize the resin component (Examples 1-3) showed a larger pore volume of pores with a diameter of 1 μm or less compared to catalysts using YCZ powder prepared by coprecipitation (Comparative Example 1).

[0077] Furthermore, as shown in Figure 4 and Table 1, the catalysts using YCZ powder prepared by heating a solid component consisting of a mixture of YCZ powder and a resin component to carbonize the resin component (Examples 1-3) were found to produce more H2 and have superior hydrogen production ability compared to the catalyst using YCZ powder prepared by coprecipitation (Comparative Example 1).

[0078] Furthermore, as shown in Figure 5 and Table 1, the catalysts using YCZ powder prepared by heating a solid component consisting of a mixture of YCZ powder and a resin component to carbonize the resin component (Examples 1-3) showed a higher oxygen release and superior oxygen storage capacity compared to the catalyst using YCZ powder prepared by coprecipitation (Comparative Example 1).

[0079] Based on the results shown in Table 1, the amount of H2 generated was plotted against the pore volume of pores with a diameter of 1 μm or less. The results are shown in Figure 6. As shown in Figure 6, it was found that the amount of H2 generated increased as the pore volume of pores with a diameter of 1 μm or less increased. This result indicates that the increased pore volume of pores with a diameter of 1 μm or less inside the secondary particles of YCZ improved the diffusibility of water vapor into the secondary particles of YCZ, and the water vapor reduction reaction by YCZ proceeded efficiently. Therefore, it was confirmed that the electrode material of the present invention is an electrode with excellent electrode reaction efficiency because it can efficiently reduce water vapor. [Industrial applicability]

[0080] As described above, the present invention makes it possible to obtain an electrode material with excellent electrode reaction efficiency. Therefore, the porous electrode material of the present invention is useful as an electrode material used in the cathode of SOEC or the anode of SOFC.

Claims

1. It contains a porous ionic conductor, The porous ionic conductor is a solid solution containing at least yttrium, cerium, and zirconium. The solid solution containing at least yttrium, cerium, and zirconium has the following compositional formula (1): Y x Ce y Zr 1-x-y O 2-δ (1) (In equation (1), x and y satisfy 0 < x < 0.2 and 0 < y < 0.2, respectively, and δ is the value at which electrical neutrality is maintained.) It is a yttrium-added ceria-zirconia solid solution represented by, The porous ionic conductor has a pore diameter of 1 μm or less and a pore volume of 0.03 cm³. ３ It is a fired product of 1g or more. A porous electrode material for SOEC / SOFC characterized by the following.

2. The porous electrode material for SOEC / SOFC according to claim 1, characterized in that the porous ionic conductor has oxygen storage capacity.

3. The porous electrode material for SOEC / SOFC according to claim 1, characterized in that nickel is supported on the solid solution containing at least yttrium, cerium, and zirconium.

4. The pores with a diameter of 1 μm or less have a pore volume of 0.04 cm³. ３ The porous electrode material for SOEC / SOFC according to claim 1, characterized in that it is 1 g or more.

5. A first step involves mixing a salt-containing aqueous solution containing yttrium salt, cerium salt, and zirconium salt, an alkaline aqueous solution containing a dispersant, and a thermosetting resin precursor to obtain a thermosetting resin precursor-containing slurry with a pH of 6.0 or higher. A second step is to convert the thermosetting resin precursor in the aforementioned thermosetting resin precursor-containing slurry into a thermosetting resin to obtain a thermosetting resin-containing slurry. A third step involves drying the thermosetting resin-containing slurry to obtain a solid component containing the thermosetting resin, A fourth step involves carbonizing the thermosetting resin in the solid component to obtain a carbide-containing solid component, A fifth step is to calcine the carbide-containing solid component in an atmospheric environment to obtain the porous electrode material according to claim 1, which contains a solid solution comprising at least yttrium, cerium, and zirconium. A method for producing a porous electrode material for SOEC / SOFC, characterized by containing [a specific ingredient].

6. The method for producing a porous electrode material for SOEC / SOFC according to claim 5, characterized in that, in the first step, the salt-containing aqueous solution and the alkaline aqueous solution are mixed under high shear force to prepare a slurry, and then the thermosetting resin precursor is mixed into the slurry to obtain the thermosetting resin precursor-containing slurry.

7. The method for producing a porous electrode material for SOEC / SOFC according to claim 5, characterized in that, in the first step, the salt-containing aqueous solution, the alkaline aqueous solution, and the thermosetting resin precursor are mixed under high shear force to obtain the thermosetting resin precursor-containing slurry.

8. In the first step described above, the high shear force is when the shear rate is 100,000 seconds. －１ A method for producing a porous electrode material for SOEC / SOFC according to claim 6 or 7, characterized in that the process is performed under the above-mentioned high shear force.

9. The method for producing a porous electrode material for SOEC / SOFC according to claim 5, characterized in that, in the second step, the thermosetting resin precursor is converted to the thermosetting resin by adjusting the pH of the slurry containing the thermosetting resin precursor to less than 6.0 to obtain the slurry containing the thermosetting resin.

10. The method for producing a porous electrode material for SOEC / SOFC according to claim 5, characterized in that, in the fifth step, the carbide-containing solid component is reduced and calcined in an inert atmosphere, and then calcined in an air atmosphere to obtain a porous electrode material containing a solid solution comprising at least yttrium, cerium, and zirconium.

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