Perovskite oxide catalyst for oxygen evolution reactions

Abstract

A catalyst for an oxygen evolution reaction has a higher and longer-life catalytic activity than that of the conventional and expensive noble metal oxide catalysts, such as RuO.sub.2 and IrO.sub.2. An A-site ordered perovskite oxide catalyst (such as CaCu.sub.3Fe.sub.4O.sub.12 and CaMn.sub.3Mn.sub.4O.sub.12 etc.) as an oxygen evolution reaction catalyst is excellent in cost effectiveness. The catalyst has a high catalytic activity compared with a noble metal oxide catalyst, and a long repetition use life since it is extremely stable also under the oxidative reaction conditions. Use of the catalyst is expected to the important energy conversion reactions such as a charge reaction of a metal-air battery, an anode oxygen evolution reaction in the case of a direct water decomposition reaction by sunlight, etc.

Claims

1. A catalyst composition comprising: a catalyst comprising an A-site ordered perovskite oxides. represented by the chemical formula (1): AA'.sub.3B.sub.4O.sub.12, wherein A represents at least one metallic element selected from the group consisting of Na, K, Ca, Sr, Ba, Ag, Pb, Bi, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, A represents at least one transition metal element selected from the group consisting of Cu, Mn, Fe, Co and Pd, and forms a covalent bond, and B represents at least one metallic element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ru, Rh, Re, 1r, Pt, Al, Ga, Ge, Sn and Sb; and a carrier.

2. The catalyst composition according to claim 1, wherein an ionic radius of the A-site metal ion is larger than an ionic radius of the A-site metal ion in the A-site ordered perovskite by 0.37 or more.

3. The catalyst composition according to claim 1, wherein the A-site ordered perovskite oxide is the A-site ordered perovskite oxide represented by the chemical formula (2): A.sup.ICu.sub.3Fe.sub.4O.sub.12, wherein A.sup.I represents at least one metallic element selected from the group consisting of Ca, Sr, Y, La and Ce, and this Cu has a covalent bond.

4. The catalyst composition according to claim 1, wherein the A-site ordered perovskite oxide is the A-site ordered perovskite oxide represented by the chemical formula (3): CaCu.sub.3B.sup.I.sub.4O.sub.12, wherein Cu has a covalent bond and B.sup.I is at least one transition metal element selected from the group consisting of Ti, Mn, Fe and Ru.

5. The catalyst composition according to claim 1, wherein the A-site ordered perovskite oxide is the A-site ordered perovskite oxide which is represented by the chemical formula (4): CaCu.sub.3Fe.sub.4O.sub.12, and this Cu has a covalent bond.

6. The catalyst composition according to claim 1, wherein the A-site ordered perovskite oxide is an A-site ordered perovskite oxide represented by the chemical formula (5): A.sup.IICu.sub.3B.sup.II.sub.4O.sub.12 or the chemical formula (6): A.sup.IIMn.sub.3B.sup.II.sub.4O.sub.12, wherein A.sup.II represents at least one metallic element selected from the group consisting of Ca, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and B.sup.II represents Ti, Mn, Ru or (Fe.sub.0.5+Sb.sub.0.5).

7. The catalyst composition according to claim 6, wherein the A-site ordered perovskite oxide represented by the chemical formula (5) is CaCu.sub.3Ti.sub.4O.sub.12, CaCu.sub.3Ru.sub.4O.sub.12, CaCu.sub.3(Fe.sub.2Sb.sub.2)O.sub.12 or CaCu.sub.3(Fe.sub.2Re.sub.2)O.sub.12, or the A-site ordered perovskite oxide represented by the chemical formula (6) is CaMn.sub.3Mn.sub.4O.sub.12.

8. The catalyst composition according to claim 7 wherein the A-site ordered perovskite oxide is produced by an atmospheric pressure synthetic process.

9. The catalyst composition according to claim 1, wherein the A-site ordered perovskite oxide is produced by a high pressure synthetic process of 1 GPa -20 GPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a comparison between the result of a measurement of the OER electric current per catalyst unit surface area vs. the sweep electric potential (OER current-potential curve: Example 1) on the A-site ordered perovskite oxide catalyst (CaCu.sub.3Fe.sub.4O.sub.12: abbreviated as CCFO) to which the present invention is applied, and the OER current-potential curve of a simple perovskite oxide catalyst La.sub.0.7Sr.sub.0.3CoO.sub.3 as a comparative example (refer to patent document 1).

(2) FIG. 2 is shows a comparison between the OER electric potential and the electric current curve of the CCFO catalyst to which the present invention is applied, and the OER electric potential and the electric current curve of other catalysts. Other catalysts used are simple perovskite oxide catalysts La.sub.0.7Sr.sub.0.3CoO.sub.3 (refer to patent document 1), (Ba.sub.0.5Sr.sub.0.5)Co.sub.0.8Fe.sub.0.2O.sub.3- (abbreviated as BSCF: refer to non-paten cited references 5 and 7) of J.-I. Jung et al. and (Pr.sub.0.5Ba.sub.0.5)CoO.sub.3- (abbreviated as PBCO: refer to non-patenting cited reference 4.) of A. Grimaud et al, and a noble metal oxide catalysts RuO.sub.2 and IrO.sub.2.

(3) FIG. 3 shows a comparison of crystal structures between the A-site ordered perovskite oxide AA.sub.3B.sub.4O.sub.12 (right) to which the present invention is applied, and a simple perovskite oxide ABO.sub.3 (left).

(4) FIG. 4 shows the HRTEM image (High Resolution Transmission Electron Microscope image) and the FFT image (Fast Fourier Transform image) of immediately after synthesis, immediately after application, and after 100 times OER measurements of SrFeO.sub.3, CaFeO.sub.3, and CaCu.sub.3Fe.sub.4O.sub.12. The boundary of a crystalline region and an amorphous region is shown by the dashed line. All the FFT images are obtained in the surface about 1010 nm.sup.2 region.

(5) FIG. 5 is a powder X-ray diffraction pattern corresponding to each of the A-site ordered perovskite oxides CaCu.sub.3B.sub.4O.sub.12 (BFe, Mn, Cr, V, or Ti) to which the present invention is applied (Cu-K). It is confirmed that these A-site ordered perovskite oxides have a single phase without mixing of impurity.

(6) FIG. 6 shows the cell constructed by the tungsten carbide (WC) super hard anvil of the high pressure synthesizer unit (Kawai type high pressure synthesizer unit, for example) used by the present invention. MgO octahedron is a hydraulic medium. The sample part containing oxide powders of raw materials is put in this cell, and the cell is pressurized to about 1-20 GPa, heated at 700-1000 C., and kept for tens of minutes.

(7) FIG. 7 shows a rotating ring disk electrode used by the present invention.

(8) FIG. 8 shows a mechanism of OER measurement using a rotating ring disk electrode used by the present invention.

(9) FIG. 9 shows the result of measuring the OER electric current with respect to the sweep electric potential per catalyst unit mass of the A-site ordered perovskite oxide catalyst (CaCu.sub.3Fe.sub.4O.sub.12 (abbreviated as CCFO)) to which the present invention is applied (OER current-potential curve) (Example 1). The results of measuring the current-potential curves for RuO.sub.2 and IrO.sub.2 as conventional catalysts are also shown as comparative examples.

(10) FIG. 10 shows the result of measuring the OER electric current with respect to the sweep electric potential per catalyst unit surface area of the A-site ordered perovskite oxide catalyst (CaCu.sub.3Fe.sub.4O.sub.12 (abbreviated as CCFO)) to which the present invention is applied (OER current-potential curve) (Example 1). The results of the measuring the current-potential curve of RuO.sub.2 and IrO.sub.2 which are conventional catalysts are also shown as comparative examples.

(11) FIG. 11 shows the results of measuring the OER electric current with respect to the sweep electric potential per unit mass of the A-site ordered perovskite oxide catalysts ACu.sub.3Fe.sub.4O.sub.12 (abbreviated as ACFO; A=Ca, Sr, Y, La or Ce) to which the present invention is applied (OER current-potential curve).

(12) FIG. 12 shows the result of measuring the OER electric current with respect to the sweep electric potential per unit surface area of the A-site ordered perovskite oxide catalysts ACu.sub.3Fe.sub.4O.sub.12 (abbreviated as ACFO; A=Ca, Sr, Y, La or Ce) to which the present invention is applied (OER current-potential curve).

(13) FIG. 13 shows a comparison of durability in the case of repetition uses between the A-site ordered perovskite oxide catalyst CaCu.sub.3Fe.sub.4O.sub.12(CCFO) to which the present invention is applied and a simple perovskite oxide CaFeO.sub.3 catalyst, and also shows current-potential curves in the case of repetition uses (up to 100th time).

(14) FIG. 14 shows a comparison of durability in the case of repetition uses between the A-site ordered perovskite oxide catalyst CaCu.sub.3Fe.sub.4O.sub.12(CCFO) to which the present invention is applied and a simple perovskite oxide CaFeO.sub.3 catalyst, and also shows changes of the OER current density in the case of repeated-uses (up to 100th time).

(15) FIG. 15 shows enlarged views of rising parts of the OER current-potential curves by the A-site ordered perovskite oxide catalysts CaCu.sub.3B.sub.4O.sub.12 (BTi, Mn, Fe, or Ru) to which the present invention is applied.

(16) FIG. 16 shows the OER current-potential curves of the A-site ordered perovskite oxide catalysts AMn.sub.3Mn.sub.4O.sub.12 (A=La or Ca) to which the present invention is applied. As a comparative example, the OER current-potential curves of usual type perovskite oxide catalysts AMnO.sub.3 (wherein, A is the same as above) are also shown together. The notation of LaMn.sub.7O.sub.12 is synonymous with the A-site ordered perovskite oxide LaMn.sub.3Mn.sub.4O.sub.12. Similarly, the notation of CaMn.sub.7O.sub.12 is synonymous with the A-site ordered perovskite oxide CaMn.sub.3Mn.sub.4O.sub.12 (it is the same hereafter).

(17) FIG. 17 shows a powder X-ray diffraction pattern (Cu-K) of the A-site ordered perovskite oxide catalyst CaMn.sub.3Mn.sub.4O.sub.12 (it is of the same meaning with CaMn.sub.7O.sub.12) to which the present invention is applied. Here, 950 C. is a synthesizing temperature of the oxide catalyst.

(18) FIG. 18 shows a powder X-ray diffraction pattern (Cu-K) of the A-site ordered perovskite oxide catalyst LaMn.sub.3Mn.sub.4O.sub.12 (it is of the same meaning with LaMn.sub.7O.sub.12) to which the present invention is applied. Round marks represent the impurity peaks of LaMnO.sub.3 origin in the figure. Here, 6.5 GPa-900 C. is a synthesizing pressure-temperature of the oxide catalyst.

(19) FIG. 19 shows a durability at repeated-uses of the OER catalyst performance (OER current-potential curve) of the A-site ordered perovskite oxide catalyst CaMn.sub.3Mn.sub.4O.sub.12 in which the present invention is applied (Example 6).

(20) FIG. 20 shows a durability at repeated-uses of the OER catalyst performance (OER current-potential curve) of a simple perovskite oxide catalyst CaMnO.sub.3 as a comparative example.

(21) FIG. 21 shows a durability at repeated-uses of the OER catalyst performance (OER current-potential curve) of the A-site ordered perovskite oxide catalyst LaMn.sub.7O.sub.12 (this being of the same meaning with LaMn.sub.3Mn.sub.4O.sub.12) in which the present invention is applied (Example 7).

(22) FIG. 22 shows a durability at repeated-uses of the OER catalyst performance (OER current-potential curve) of the simple perovskite oxide LaMnO.sub.3 catalyst as a comparative example.

(23) FIG. 23 shows a comparison between the OER current-potential-curve of the A-site ordered perovskite oxide catalyst CaCu.sub.3Fe.sub.4O.sub.12 (abbreviated as CCFO) to which the present invention is applied (Example 1) and the OER current-potential-curves of simple perovskite oxide catalysts of comparative examples. Two kinds of simple perovskite oxide catalysts shown here: (Ba.sub.0.5Sr.sub.0.5) Co.sub.0.5Fe.sub.0.2O.sub.3- (abbreviated as BSCF: Refer to non-patent cited-references 5 and 7) of J.-I. Jung et al., and (Pr.sub.0.5Ba.sub.0.5)CoO.sub.3- (abbreviated as PBCO: Refer to non-patent cited-reference 4) of A. Grimaud et al. are said to have the highest activity for the OER in the perovskite oxide catalysts reported as an academic paper until now.

(24) FIG. 24 shows a comparison between the OER potential-current-curve of the CCFO catalyst to which the present invention is applied and the OER potential-current-curves of BSCF, PBCO, RuO.sub.2, and IrO.sub.2.

EMBODIMENT FOR CARRYING OUT INVENTION

(25) Hereinafter, although the embodiments for carrying out the present invention are explained in detail, the scope of the present invention is not limited to these embodiments.

(26) <A-Site Ordered Perovskite Oxide Used as a Catalyst by the Present Invention>

(27) The details of the A-site ordered perovskite oxide used as a catalyst by the present invention are described as follows.

(28) The A-site ordered perovskite oxide used by the present invention has a simple perovskite structure. That is, the A-site ordered perovskite oxide is an oxide in which A-sites are organized so that a metallic element A occupies one fourth of A sites of the chemical formula ABO.sub.4 in the left figure of FIG. 3 and a transition metal element A occupies the residual three fourths (Chemical formula (1): AA.sub.3B.sub.4O.sub.12 in the right figure of FIG. 3). Ain the chemical formula (1) represents at least one metal element selected from the group consisting of Na, K, Ca, Sr, Ba, Ag, Pb, Bi, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, A represents at least one transition metal element selected from the group consisting of Cu, Mn, Fe, Co and Pd, and forms a covalent bond, and B represents at least one metallic element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ru, Rh, Re, Ir, Pt, Al, Ga, Ge, Sn and Sb. Here, it is one of the features as mentioned above that Cu of the A site metal has overlap of an electron orbital, i.e., a covalent bond, in addition to an ionic bond with O. Although the ionic bond reacts with OH etc. and is easily made amorphous since its stability is low. However, since the covalent bond tends to be difficult to become amorphous, it is considered that Cu in this case can act as a stable active site. As a result, since the covalent bond of Cu has a structure spreading around freely within the crystal structure, it becomes extremely stable, and the active site is maintained firmly. It is considered that there also exists a synergistic effect that movement of a charge becomes smooth by an all-around covalent bond network in three dimensions, and an electrochemical reaction becomes fast for its reason.

(29) In the chemical formula (1), the CuFe family A-site ordered perovskite oxide represented by the chemical formula (2): A.sup.ICu.sub.3Fe.sub.4O.sub.12 (wherein A.sup.I represents at least one metallic element selected from the group consisting of Ca, Sr, Y, La and Ce) is preferably used in terms of oxygen-evolution catalyst efficiency. As mentioned above, in A.sup.ICu.sub.3Fe.sub.4O.sub.12, Cu also acts as an active site in addition to Fe, therefore, there are more active sites than CaFeO.sub.3, and the movement of the charge is also rapid. Accordingly, A.sup.ICu.sub.3Fe.sub.4O.sub.12 is considered to exhibit a more efficient catalytic action, and is preferably used in terms of cost effectiveness also because it does not contain a rare metal such as Pt and Ir.

(30) In the chemical formula (1), the A-site ordered perovskite oxide represented by the chemical formula (3): CaCu.sub.3B.sup.I.sub.4O.sub.12 (wherein, Cu has a covalent bond and B.sup.I represents at least one transition metal element selected from the group consisting of Ti, Mn, Fe and Ru.) has many active sites as mentioned above because of the covalent bond property of Cu, and the movement of a charge is also rapid. Accordingly, it is preferably used in terms of oxygen evolution catalyst efficiency. It is preferably used in terms of cost effectiveness also at the point which does not contain a rare metal such as Pt and Ir.

(31) In the chemical formula (1) or (2), the A-site ordered perovskite oxide represented by the chemical formula (4): CaCu.sub.3Fe.sub.4O.sub.12 has a covalent bonding Cu and many active sites as mentioned above because of the covalent bond property of Cu. In addition, the movement of a charge is also rapid. Accordingly, it is preferably used in terms of an oxygen evolution catalyst efficiency. It is preferably used in terms of cost effectiveness also at the point that it does not contain a rare metal such as Pt and Ir.

(32) In the chemical formula (1), the A-site ordered perovskite oxide represented by the chemical formula (5): A.sup.IICu.sub.3B.sup.II.sub.4O.sub.12, or the chemical formula (6): A.sup.IIMn.sub.3B.sup.II.sub.4O.sub.12 (wherein, A.sup.II represents at least one metallic element selected from the group consisting of Ca, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and B represents Ti, Mn, Ru, or (Fe.sub.0.5+Sb.sub.0.5)) is preferably used in that it has a high oxygen evolution catalytic efficiency uniformly. It is preferably used in terms of cost effectiveness also at the point that it does not contain a rare metal, such as Pt and Ir.

(33) In the chemical formula (5), at least one A-site ordered perovskite oxide selected from the group consisting of CaCu.sub.3Mn.sub.4O.sub.12, CaCu.sub.3Ti.sub.4O.sub.12, CaCu.sub.3Ru.sub.4O.sub.12, CaCu.sub.3(Fe.sub.2Sb.sub.2)O.sub.12 and CaCu.sub.3(Fe.sub.2Re.sub.2)O.sub.12, or in the chemical formula (6), the A-site ordered perovskite oxide of CaMn.sub.3Mn.sub.4O.sub.12 (it is of the same meaning with CaMn.sub.7O.sub.12) is preferably used in that it has a high oxygen evolution catalyst efficiency uniformly. It is preferably used in terms of cost effectiveness also at the point that it does not contain a rare metal, such as Pt and Ir.

(34) In the above-mentioned A-site ordered perovskite used by the present invention, the ionic radius of the A-site metal ion is characterized by being larger than the ionic radius of A site metal ion 0.37 or more. In the A-site ordered perovskite oxide CaCu.sub.3Fe.sub.4O.sub.12 used in the present invention, for example, the ionic radius of Ca.sup.2+ of the A site is 1.34 , and that of Cu.sup.2+ of the A site is 0.57 . Since the ionic radius of Cu is small, if the A site and the A site take an irregular sequence, distortion will be generated and it will not be stabilized. However, it is stabilized by being regularly arranged. Also from this, in the perovskite of the ordered type, the A-site metal and the A site metal take alternately regular arrangement, therefore they are considered to become stable chemically. In the A-site ordered perovskite, as shown in the right figure of FIG. 3, the position of O atom has shifted from the position of O of a regular perovskite by distortion of a lattice. Thereby, near ones and remote ones are mutually produced for the spatial relationship of OH.sup. which are produced during an electrolysis at O. The development of O.sub.2 is considered to be fast by these near ones.

(35) The form, size, etc. of the A-site ordered perovskite oxide catalyst are not limited in particular. They should just be suitably set up corresponding to the target parts etc. From viewpoints of the processing simplicity of parts, etc., particulates are desirable. When the above-mentioned perovskite type oxide is particulates, about 1-1000 m of mean particle diameter are desirable. What is necessary is just to adopt a well-known method as the measuring method of the mean particle diameter. For example, a transmission electron microscope method (abbreviated as TEM), a scanning electron microscope method (abbreviated as SEM), etc. are mentioned.

(36) A crystal structure of the A-site ordered perovskite oxide catalyst can be confirmed by an X-ray diffraction method (abbreviated as XRD), Mossbauer spectroscopy, etc., for example.

(37) <Production Method of the A-Site Ordered Perovskite Oxide>

(38) The A-site ordered perovskite oxide catalyst (chemical formula (1): AA.sub.3B.sub.4O.sub.12) can usually be produced by carrying out heat treatment (calcination) under high temperature and high pressure (a high-pressure solid-phase-synthesis method) after mixing oxides of A, oxides of A, and oxides of B, for example. On the other hand, specific A-site ordered perovskite oxide, such as CaCu.sub.3Ti.sub.4O.sub.12, CaCu.sub.3Ru.sub.4O.sub.12, CaCu.sub.3(Fe.sub.2Sb.sub.2)O.sub.12, and CaMn.sub.3Mn.sub.4O.sub.12, can be also produced by an ordinary pressure synthetic process.

(39) Since the solid-phase-synthesis method is a chemical reaction between solids, a rate of reaction becomes markedly slow compared with a liquid phase process etc. It is because diffusion of oxide powder particles serves as a rate-determining step. In order to conquer this problem, it is required to make size of particles as small as possible using a ball mill etc.

(40) The blending ratio of the oxide of A, the oxide of A, and the oxide of B is not limited, in particular, and for example, what is necessary is just to set up suitably so that the A-site ordered perovskite oxide shown by the chemical formula (1) (AA.sub.3B.sub.4O.sub.12) may be obtained. For example, when the A-site ordered perovskite oxide of CaCu.sub.3Fe.sub.4O.sub.12 is produced, the perovskite type oxide catalyst used by the present invention is suitably obtained by using CaO, CuO, and Fe.sub.2O.sub.3 in a ratio of 1:3:2 by a molar ratio.

(41) The above-mentioned heat treatment can be performed in accordance with a well-known method. For example, after filling up a platinum capsule with the mixture of the oxide of A, the oxide of A, and the oxide of B, the obtained capsule is pressurized and heated using high-pressure synthesis equipment, when high pressure is required. However, in the case of the oxide in which ordinary pressure synthesis is possible (refer to the above), a pressure device is not required although there are few examples. As a well-known pressure device, the DIA type high-pressure generation system which is a multi-anvil equipment which can generate a high-pressure up to about 10 GPa is exemplified. The Kawai type equipment is further exemplified in which the high-pressure development of 25-50 GPa is possible by pressurizing successively through putting in a second more step of an anvil. The pressures during heat-treating the mixture of each oxide shown in FIG. 6 are 0.1-50 GPa, preferably 0.5-40 GPa, more preferably 1-20 GPa, for example, 10-18 GPa. About 700 C. or more of the heat treatment temperature is desirable, and about 1000-1200 C. is more desirable. The A-site ordered perovskite oxide catalyst used by the present invention is suitably obtained by especially carrying out at the pressure of about 10 or more GPa (for example, 15 GPa), and the temperature of 1000 C. or more (for example, 1200 C.).

(42) Heat treatment time may be suitably adjusted corresponding to heat treatment conditions, such as heat treatment temperature, so that raw materials may fully react, and it is usually for about several minutes to 120 minutes, preferably for 10 minutes to 60 minutes, for example, for 20 minutes to 40 minutes.

(43) The above-mentioned mixture may contain well-known additives in advance of the above-mentioned heat treatment. As well-known additives, oxidizing agents, such as KClO.sub.4, are mentioned, for example.

(44) On the other hand, methods for avoiding diffusion problems of solid powder include a citric acid complex polymerizing method. A precursor which is a multiple oxide is synthesized in the state of a homogeneous reaction by this citric acid complex polymerizing method, and the precursor powder which has enabled mixing in atomic levels is obtained. This method is a method of producing the target A-site ordered perovskite oxide catalyst by carrying out a high-pressure high-temperature treatment of the powder.

(45) More specifically, at first, a metal salt is dissolved and a metal hydroxy carboxylic acid complex is made to form in the solution of glycol (ethylene glycol, propylene glycol, etc.) which contains hydroxy carboxylic acid, such as citric acid, excessively. This solution is heated at a temperature of about 120-150 C., an esterification reaction is generated continuously, and a polyester polymer gel is obtained. Since metal ions are distributed uniformly in this gel, the segregation level of metallic elements is suppressed low. High grade multiple oxide precursors can be obtained by carrying out the pyrolysis of this at about 400 C. (refer to non-patent document 8). By calcining multiple oxide precursors at a high-pressure high-temperature condition, the A-site ordered perovskite oxide catalyst can be obtained. During calcination, a pressure is usually 1-20 GPa, and calcination temperature is usually 600-1,000 C., preferably 700-900 C., for example, 850 C.

(46) In addition, the A-site ordered perovskite type oxides which can be synthesized in ordinary pressure conditions by the application of this citric acid complex polymerizing method as above-mentioned are not many, and CaCu.sub.3Ti.sub.4O.sub.12, CaCu.sub.3Ru.sub.4O.sub.12, CaCu.sub.3(Fe.sub.2Sb.sub.2)O.sub.12 and CaMn.sub.3Mn.sub.4O.sub.12 are exemplified.

(47) <Air Electrode Catalyst Layer>

(48) In the present invention, the A-site ordered perovskite oxide is used for an oxygen generating electrode layer of a battery as a catalyst. The air electrode catalyst layer is a layer which contains an air electrode catalyst and an electrolyte for the air electrode preferably. The air electrode catalyst layer may contain a binding material further if needed.

(49) The air electrode catalyst for metal air batteries regarding the present invention excels the conventional air electrode catalyst in oxidation resistance, and even if exposed under a severe oxidizing atmosphere, it has such a feature as being hard to receive deterioration. From a viewpoint that an electrode reaction is performed more smoothly, the air electrode catalyst is desirable to be supported on a conductive material. What is necessary is just to have conductivity as a conductive material used for an air electrode catalyst layer, and it is not limited especially. For example, a carbon material, a perovskite type conductive material, a porous conductive polymer, a metal porous body, etc. can be mentioned. A carbon material may have porous structure and may not have porous structure. As a carbon material which has porous structure, meso-porous carbon etc. can specifically be mentioned. On the other hand, as a carbon material which does not have porous structure, graphite, acetylene black, a carbon nanotube, a carbon fiber, etc. can specifically be mentioned.

(50) <Rotating Ring Disk Catalyst Electrode>

(51) In the present invention, the production method of the catalyst electrode for rotating ring disks used for measurement of the catalyst electrode characteristics is not limited, in particular. As an example, an illustrative procedure is shown below.

(52) That is, a catalyst ink is produced by mixing and agitating an A-site ordered perovskite oxide powder as an oxygen generating catalyst, acetylene black as a conductive material, Nafion dispersion liquid being ion-exchanged with a K.sup.+ ion as a fixed binder which does not prevent movement to the catalyst surface of dissolved oxygen, and tetrahydrofuran as a dispersion medium. After carrying out ultrasonic stirring of the obtained catalyst ink, it is dropped on the glassy carbon disk of a disk part, and after that, at a room temperature, it is dried in vacuum overnight, and the catalyst electrode for measurement is obtained (refer to FIGS. 7 and 8.).

(53) The Nafion dispersing element which is ion-exchanged with 3.33 wt % of K.sup.+ ion is specifically prepared by mixing 5 wt % of a proton type Nafion dispersing element and a 0.1 M-KOH aqueous solution in volume ratio of 2:1. The catalyst ink of the A-site ordered perovskite oxide is prepared by mixing 50 mg of oxides concerned, 10 mg of acetylene black (AB), and 0.3 ml of 3.33 wt % K.sup.+ ion exchanged Nafion dispersing body. By adding tetrahydrofuran, the volume of the ink is adjusted to 10 ml. After the rotating ring disk electrode consisting of a glassy carbon disk of 0.4 cm in diameter and a Pt ring of outside diameter of 0.7 cm and 0.5 cm in inside diameter is ground by an alumina slurry of 0.05 m, this rotating ring disk electrode is used as a working electrode. The catalyst ink of 6.4 -liter is dropped and developed on the glassy carbon (GC) electrode portion (0.20.2cm.sup.2). The catalyst layer on glassy carbon has the following composition after vacuum dried at a room temperature overnight: 0.25 mg-oxide cm.sup.2-disk, 0.05 mg-AB cm.sup.2-disk, and 0.005 mg-Nafion cm.sup.2-disk.

(54) <Measurement of the Electrochemical Characteristic of the OER Catalyst>

(55) The electrochemical characteristic of the OER catalyst is measured in the following procedures using the catalyst electrode obtained above. The glassy carbon electrode supporting the catalyst is dipped in the electrolyte (for example, a KOH solution) saturated with oxygen, sweep is carried out up to predetermined electric potential (for example, to 0.3-0.9 V vs. Hg/HgO) using the rotating ring disk device equipped with a bipotentiostat with a predetermined electric potential sweep rate (for example, 10 mV/sec), then, the sweep is carried out up to initial electric potential with the same electric potential sweep rate (to 0.9-0.3 V vs. Hg/HgO), and the current density (OER current-potential curve) during the period is measured (refer to FIG. 1.). The measurement is carried out by using Pt wire electrode as a counter electrode, and the Hg/HgO electrode filled with a 0.10 M-KOH aqueous solution as a reference electrode. The relation of 0 V vs. Hg/HgO=+0.926 V vs. RHE exists between the electric potential of a Hg/HgO electrode basis and the electric potential of a reversible hydrogen electrode (RHE: Reversible Hydrogen Electrode) basis, and this relationship always holds whenever the pH values of an electrolyte and the internal liquid of the Hg/HgO electrode are the same. All measurements are performed at a room temperature under a saturated oxygen, and the measurements are carried out by fixing the reversible electrode potential of an O.sub.2/H.sub.2O redox couple to 0.304 V vs. Hg/HgO (1.23 V vs. RHE). For the catalyst characterization of the perovskite oxide to the OER reaction, the electric potential of the glassy carbon portion modified with the catalyst is controlled by 0.3 to 0.9 V vs. Hg/HgO (1.23 to 1.83 V vs. RHE) at the electric potential sweep rate of 10 mVs.sup.1. In the following working examples, all the OER electric current are shown as a relative electric current value per presumed surface area of the perovskite oxide catalyst, and electric potential rectifies iR drops by the resistance component of the electrolyte (it is decided by the alternating-current-impedance method that the iR drops will be about 43 ohms), and is shown as the electric potential (E-iR/V vs. RHE) of the RHE basis. In addition, it may be displayed as relative electric current values per oxide catalyst weight for comparison.

(56) The OER reaction on the disk in an alkaline aqueous solution proceeds along the following reaction formula (7): 4OH.sup.->O.sub.2+2H.sub.2O+4e.sup. (7) (refer to FIG. 8.).

(57) <Evaluation Index of OER Catalyst Performance>

(58) An evaluation index of catalyst performance will be explained below using a current-potential curve obtained by sweeping of an electric potential. For promoting OER of the above (7) on a catalyst surface, it is necessary to apply a voltage for the energy accompanying oxygen generation. This voltage is kept constant by the pH of a solution. On the other hand, it is necessary to apply excessively the voltage for the activation energy of the oxygen evolution reaction further. This is called overvoltage, and the OER catalyst performance will be excellent when the overvoltage is low (that is, when rising of the electric current is at a low electric potential). In addition, the OER catalyst performance will be excellent, when rising of the electric current is steep (that is, when increase in the electric current value to predetermined electric potential (electric current gradient) is high). Therefore, in the current-potential curve, both overvoltage value and gradient of a current-potential curve become an evaluation index of the OER catalyst performance.

EXAMPLES

(59) The present invention is explained specifically by the following examples. However, the scope of the present invention is not limited to these examples.

Example 1 of Catalyst Preparation

Preparation of A-Site Ordered Perovskite Oxide Catalyst CaCu3Fe4O12

(60) (1) Preparation of a Precursor by the Citric Acid Complex Polymerizing Method:

(61) First, a precursor mixed oxide of CaCu.sub.3Fe.sub.4O.sub.12 was prepared in the following procedures by the citric acid complex polymerizing method. That is, each raw material is prepared so as the molar ratio is set to CaCO.sub.3:Cu(NO.sub.3).sub.23H.sub.2O:Fe(NO.sub.3).sub.3. 9 H.sub.2O:Citric acid=1:3:4:40. An evaporating dish was set on a magnet stirrer having a hot plate, a magnet for stirring was put in, and 5 ml of distilled water was added. Subsequently, 0.775 g CaCO.sub.3 (from Wako Pure Chem Co.) was added, and mixing-stirring was started. 2 ml of nitric acid was added thereto to dissolve CaCO.sub.3, then 0.561 g Cu(NO.sub.3).sub.2.3H.sub.2O (from Wako Pure Chem Co.), 1.25 g Fe(NO.sub.3).sub.3.9H.sub.2O (from Wako Pure Chem Co.) and 5.95 g of anhydrous citric acid (from Wako Pure Chem Co.) were added, and stirring was continued, then, they were heated a little for dissolving all. Subsequently, 2 ml of ethylene glycol was added, and the mixture was heated to such an extent that it did not boil. The temperature of the solution was checked with an infrared thermometer (AD-5611A). When the temperature of the solution becomes near 90 C., brown NO.sub.2 will be emitted. Since the viscosity of the solution begins to rise gradually after discharge of NO.sub.2 finishes, the magnet is taken out, and heating is continued until the solution is dried up. After drying-up, high temperature treatment for 1 hour was performed by an electric furnace at 400 C., and the organic substance contained in a polymer complex was decomposed and removed to some extent, then, the precursor was obtained. This precursor was mixed by an agate mortar, and it was put into an alumina crucible, and, after high temperature treatment for 12 hours at 675 C., the precursor 0.3 g from which the organic substances etc. were removed completely was obtained.

(62) (2) Manufacture of the A-Site Ordered Perovskite Oxide Catalyst by the High-Pressure Synthetic Process

(63) Next, the A-site ordered perovskite oxide catalyst was produced as follows from the precursor produced above using the Kawai type high-pressure synthesis device. In the cell (MgO octahedron (one side is 10 mm) is a pressure-transmitting-medium body) constructed by the tungsten carbide (WC) super hard metal anvil shown in FIG. 6, a sample section was filled up with the precursor oxide powder 0.0285 g obtained above (1) and KClO.sub.4 0.0040 g (from Wako Pure Chem Co.), and the state was maintained for 30 minutes at 15 GPa and 1000 C. Subsequently, it was quenched to near room temperature in several seconds by intercepting a heating power (quenching). Then, over about 12 hours, the pressure was lowered gradually and it was returned to ordinary pressure. The product (A-site ordered perovskite oxide) in high pressure can be frozen as a metastable phase by this quench operation. By carrying out the powder X-ray diffraction measurement (Ultima IV by Rigaku Inc.: with Cu-K ray irradiation) of the obtained product, it was confirmed that the product was CaCu.sub.3Fe.sub.4O.sub.12 of the A-site ordered perovskite oxide structure (refer to FIG. 5.). The specific surface area computed based on the particle size distribution from the scanning electron microscope (SEM) image of this thing was 0.32 m.sup.2g.sup.1, and the specific surface area measured by the BET adsorption process was 0.45 m.sup.2g.sup.1.

Example 2 of Catalyst Preparation

Preparation of A-Site Ordered Perovskite Oxide Catalyst CaCu3Mn4O12

(64) (1) Preparation of the A-Site Ordered Perovskite Oxide Catalyst by High-Pressure Synthetic Process

(65) The A-site ordered perovskite oxide was produced according to the example 1 (2) of catalyst preparation by using the Kawai type high-pressure synthesis device after CaO, CuO, and MnO.sub.2 (both from Wako Pure Chem Co.) were mixed so that they become a molar ratio of 1:3:4. Synthetic conditions were for 30 minutes at 12 GPa and 1000 C. According to the powder X-ray diffraction of the obtained product, it was confirmed that the product was CaCu.sub.3Mn.sub.4O.sub.12 of the A-site ordered perovskite oxide structure (refer to FIG. 5.). The specific surface area computed based on the particle size distribution from the scanning electron microscope (SEM) image of this product was 0.42 m.sup.2g.sup.1.

Example 3 of Catalyst Preparation

Preparation of A-Site Ordered Perovskite Oxide Catalysts CaCu3B4O12 (BTi or Ru)

(66) (1) Preparation of the A-Site Ordered Perovskite Oxide Catalyst by an Ordinary-Pressure Synthetic Process

(67) CaCO.sub.3, CuO, and BO.sub.2 (BTi or Ru) (both from Wako Pure Chem Co.) were mixed so that it becomes a molar ratio of 1:3:4, and the A-site ordered perovskite oxide catalyst was produced by an ordinary pressure and high-temperature synthesis method. Synthetic conditions were for 15 hours in air and at 1000 C. According to the powder X-ray diffraction (XRD) of the obtained products, it was confirmed that the products were CaCu.sub.3Ti.sub.4O.sub.12 and CaCu.sub.3Ru.sub.4O.sub.12 of the A-site ordered perovskite oxide structure, respectively (the XRD profile of BTi was shown in FIG. 5.). The specific surface areas computed based on the particle size distribution from the scanning electron microscope (SEM) image of these products were 0.24 m.sup.2g.sup.1 (BTi) and 0.12 m.sup.2g.sup.1 (BRu), respectively.

Example 4 of Catalyst Preparation

Preparation of the A-Site Ordered Perovskite Oxide Catalyst CaMn7O12

(68) (1) Preparation of the Precursor by the Citric Acid Complex Polymerizing Method

(69) According to the citric acid complex polymerizing method of the example 1 (1) of catalyst preparation, a precursor oxide was obtained from a mixture of CaCO.sub.3: Mn(NO.sub.3).sub.2: citric acid=1:7:40 (molar ratio).

(70) (2) Preparation of the A-Site Ordered Perovskite Oxide Catalyst by the Ordinary-Pressure Synthetic Process

(71) Using the precursor obtained above (1), the ordinary pressure synthesis was performed at 950 C. in the air for 12 hours, and the A-site ordered perovskite oxide catalyst CaMn.sub.7O.sub.12 was produced. The X-ray diffraction profile of the product is shown in FIG. 17. From this profile, it was confirmed that the product is the A-site ordered perovskite structure without an impurity phase. The specific surface area computed from the SEM image was 2.73 m.sup.2g.sup.1.

Example of catalyst preparation 5

Preparation of the A-Site Ordered Perovskite Oxide Catalyst LaMn7O12 (Henceforth, it May be Indicated as LaMn3Mn4O12 in Order to Specify that it is an A-Site Ordered.)

(72) (1) Preparation of the A-site ordered perovskite oxide catalyst by the high-pressure synthetic process La.sub.2O.sub.3 and MnO (both from Wako Pure Chem Co.) were mixed so that they become a molar ratio of 1:14, and according to the example 1 (2) of the catalyst preparation, the high-pressure synthesis was performed for 30 minutes at 6.5 GPa and 700 C. using the Kawai type high-pressure synthesis device. It was confirmed that the obtained oxide was the A-site ordered perovskite oxide catalyst LaMn.sub.7O.sub.12 although mixing of a little impurity phases (LaMnO.sub.3) was seen as a result of the powder X-ray diffraction (FIG. 18). The specific surface area computed from the SEM image was 0.48 m.sup.2g.sup.1.

Example 1

Oxygen Generation Catalyst Performance of the A-Site Ordered Perovskite Oxide Catalyst (CaCu3Fe4O12 (Abbreviated as CCFO))

(73) Using a catalyst electrode of the A-site ordered perovskite oxide obtained above, an electrochemical characteristic of the OER catalyst was measured by using a Pt wire electrode as a counter electrode, and an Hg/HgO electrode filled with a 0.10 M-KOH aqueous solution as a reference electrode. All measurements were carried out in oxygen-saturated atmosphere at room temperature by fixing a reversible electrode potential of an O.sub.2/H.sub.2O redox couple to 0.304 V vs. Hg/HgO (1.23V vs. RHE). The electric potential of a glassy carbon portion modified with the catalyst for the catalyst characterization of the A-site ordered perovskite oxide to the OER reaction was controlled by 0.3-0.9 V vs. Hg/HgO (1.23-1.83 V vs. RHE) at an electric potential sweep rate of 10 mVs.sup.1. In the following Examples, all of the OER electric current are shown on the basis of a relative electric current value per presumed surface area of the A-site ordered perovskite oxide catalyst. A relative electric current value per oxide catalyst weight may be shown supplementary. And, after rectifying iR drops by a resistance component (it has been decided by an alternating-current-impedance method to be about 43 ohms) of an electrolyte, the electric potential is shown as the electric potential (E-iR/V vs. RHE) of a RHE basis.

(74) FIG. 9 and FIG. 10 show the results (OER current-potential curve) (Example 1) of measuring the OER electric current to the sweep electric potential of the A-site ordered perovskite oxide catalyst (CaCu.sub.3Fe.sub.4O.sub.12 (abbreviated as CCFO)) to which the present invention is applied. The results of measuring the current-potential curves of RuO.sub.2 and IrO.sub.2 as the conventional catalyst are also shown as comparative examples. FIG. 9 shows the OER current-potential curve per catalyst unit mass, and FIG. 10 shows the OER current-potential curve per catalyst unit surface area. It turns out that the catalyst performance of CCFO exceeded the performances of RuO.sub.2 and IrO.sub.2 both in per catalyst unit mass and in per catalyst unit surface area.

Example 2

Oxygen-Generation Catalyst Performance of the A-Site Ordered Perovskite Oxide Catalyst ACu3Fe4O12 (A Represents Ca, Sr, Y, La, or Ce.)

(75) FIG. 11 and FIG. 12 show the measurement results of the OER electric current to the sweep electric potential of the A-site ordered perovskite oxide catalyst ACu.sub.3Fe.sub.4O.sub.12 to which the present invention is applied, wherein the oxide catalyst is abbreviated to ACFO, and A represents Ca, Sr, Y, La, or Ce. In the measurement, the catalyst layer on glassy carbon has the following composition: 0.25 mg-oxide cm.sup.2-disk, 0.05 mg-AB cm.sup.2-disk, and 0.05 mg-Nafion cm.sup.2-disk. FIG. 11 represents the OER current-potential curve per unit mass, and FIG. 12 represents the OER current-potential curve per unit surface area, respectively. When compared in per unit surface area, it turns out that there is no significant difference of the catalyst performance between ACFOs.

Example 3

Durability During Repetition Uses of the A-Site Ordered Perovskite Oxide Catalyst CaCu3Fe4O12 (CCFO)

(76) FIG. 13 and FIG. 14 show the measurement result of the durability during the repetition uses in OER of the A-site ordered perovskite oxide catalyst CaCu.sub.3Fe.sub.4O.sub.12 (CCFO) to which the present invention is applied. In this measurement, in order to remove the oxygen bubbles adhering to an electrode disk, disk rotation frequency was made into 3200 times per minute. As a comparative example, the durability measurement result during repetition uses of a simple perovskite oxide CaFeO.sub.3 catalyst is also shown together in FIG. 13 and FIG. 14. FIG. 13 represents the OER current-potential curve during repeated use (at 100th time), and FIG. 14 represents the change of the current density during repeated use (at 100th time). It turns out that CCFO of the A-site ordered perovskite oxide catalyst has high catalytic activity and durability for OER as compared with the simple perovskite oxide.

Example 4

Oxygen-Generation Catalyst Performance of the A-Site Ordered Perovskite Oxide Catalyst CaCu3B4O12 (B Represents Fe, Mn, Ru, or Ti)

(77) FIG. 15 shows the enlargement of the rising portion of the current-potential curve of OER by the A-site ordered perovskite oxide catalyst CaCu.sub.3B.sub.4O.sub.12 (B represents Fe, Mn, Ru, or Ti) to which the present invention is applied. It turns out that the overvoltage decreases in monotone and the catalyst performance is improving according to the order of Ti, Mn, Ru, and Fe of the transition metal B in the B site.

Example 5

OER Catalyst Performance of the A-Site Ordered Perovskite Oxide Catalyst AMn3Mn4O12 (a Represents La or Ca in the Formula)

(78) FIG. 16 represents the OER current-potential curve of the A-site ordered perovskite oxide catalyst AMn.sub.3Mn.sub.4O.sub.12 (A represents La or Ca) to which the present invention is applied. As a comparative example, the OER current-potential curves of LaMnO.sub.3 and CaMnO.sub.3 which are simple perovskite type oxides are also shown together. In addition, in the figure, LaMn.sub.7O.sub.12 and CaMn.sub.7O.sub.12 are synonymous with the A-site ordered perovskite oxides LaMn.sub.3Mn.sub.4O.sub.12 and CaMn.sub.3Mn.sub.4O.sub.12, respectively. Rising of the OER current-potential curve of the A-site ordered perovskite oxide catalyst is steeper than that of the simple perovskite oxide catalyst in FIG. 16. Therefore, it turns out that the OER catalyst performance of the A-site ordered perovskite oxide catalyst is superior to that of the simple perovskite oxide catalyst.

Example 6

Durability During Repetition Uses of the OER Catalyst Performance of the A-Site Ordered Perovskite Oxide Catalyst CaMn3Mn4O12

(79) FIG. 19 shows the durability measurement result (OER current-potential curve) during the repetition uses in OER of the A-site ordered perovskite oxide catalyst CaMn.sub.3Mn.sub.4O.sub.12 (it is synonymous with CaMn.sub.7O.sub.12) to which the present invention is applied. As a comparative example, the durability measurement result (OER current-potential curve) during repetition uses of the simple perovskite oxide CaMnO.sub.3 catalyst is also shown altogether in FIG. 20. It turns out that the A-site ordered perovskite oxide catalyst CaMn.sub.3Mn.sub.4O.sub.12 has high OER catalytic activity and durability as compared with the simple perovskite oxide catalyst.

Example 7

Durability During Repetition Uses of the OER Catalyst Performance of the A-Site Ordered Perovskite Oxide Catalyst LaMn3Mn4O12

(80) FIG. 21 shows the measurement result of the durability during the repetition uses in OER (OER current-potential curve) of the A-site ordered perovskite oxide catalyst LaMn.sub.3Mn.sub.4O.sub.12 (it is synonymous with LaMn.sub.7O.sub.12) to which the present invention is applied. As a comparative example, the durability measurement result (OER current-potential curve) during repetition uses of the simple perovskite oxide catalyst LaMnO.sub.3 is also shown in FIG. 22. The rising of the OER current-potential curve of the A-site ordered perovskite oxide catalyst LaMn.sub.3Mn.sub.4O.sub.12 is steep, as compared with the simple perovskite oxide catalyst, and after repetition use, the steep nature is maintained. This represents that the A-site ordered perovskite oxide catalyst has an outstanding OER catalytic activity and durability as compared with the simple perovskite oxide catalyst.

Performance Comparison 1

Comparison of the OER Catalyst Performances Between the A-Site Ordered Perovskite Oxide Catalyst and the Simple Perovskite Oxide Catalyst

(81) FIG. 23 represents comparisons of the OER current-potential curve (Example 1) of the CaCu.sub.3Fe.sub.4O.sub.12 catalyst (abbreviated as CCFO) of the present invention with the OER current-potential curves of (Ba.sub.0.5Sr.sub.0.5)Co.sub.0.8Fe.sub.0.2O.sub.3- (abbreviated as BSCF) of J.-I. Jung et al. (nonpatent document 5) and (Pr.sub.0.5Ba.sub.0.5)CoO.sub.3- (abbreviated as PBCO) of A. Grimaud etc. (nonpatent document 4). Two kinds of simple perovskite oxides shown here are presumed to have the highest catalytic activity to OER in the perovskite oxide catalysts reported as academic papers until now. Accordingly, it turns out from FIG. 23 that the CCFO catalyst of the present invention has the excellent catalytic performance compared with these simple perovskite oxides known before.

Performance Comparison 2

Comparison of the OER Catalyst Performances Between the A-Site Ordered Perovskite Oxide Catalyst, the Simple Perovskite Oxide Catalyst and a Noble Metal Oxide Catalyst

(82) FIG. 24 shows comparisons of the OER electric potential and an electric current curve of the CCFO catalyst to which the present invention is applied, and the OER electric potentials and electric current curves of BSCF, PBCO, RuO.sub.2, and IrO.sub.2 catalysts. From this figure, it turns out that, in CCFO, one digit to several digits greater electric current (horizontal axis) flows at the same electric potential value (vertical axis) when compared with others, and accordingly, the oxygen evolution reaction (OER) occurs efficiently.

Performance Comparison 3

Performance Comparison with the Catalyst Shown in the Patent Document 1

(83) Comparisons of the oxygen generation catalyst performances between La.sub.0.7Sr.sub.0.3CoO.sub.3 of the patent documents 1 and CaCu.sub.3Fe.sub.4O.sub.12 of the present invention are shown in FIG. 1 and FIG. 2. The catalyst of the present invention showed far good performances.

INDUSTRIAL APPLICABILITY

(84) The A-site ordered perovskite oxide catalyst (CaCu.sub.3Fe.sub.4O.sub.12 etc.) of the present invention has high catalytic activity as a catalyst for the oxygen evolution reaction compared with the expensive noble-metal oxide catalysts such as RuO.sub.2, IrO.sub.2 etc. from the past. It is extremely stable also under oxidative catalytic reaction conditions, and it is a catalyst for oxygen evolution reaction with a long repetition use life. As a result, use for the charge reaction of the metal-air battery or the important energy conversion reaction in the direct water decomposition reaction by sunlight is expected as the oxygen evolution reaction catalyst excellent in cost effectiveness. Similarly the method for the oxygen evolution reaction using the A-site ordered perovskite oxide catalyst, and the catalyst composition containing the A-site ordered perovskite oxide, are expected for use in the practical energy conversion reaction as the oxygen evolution reaction method and the catalyst composition thereof which are more excellent in cost effectiveness compared with the oxygen generation method and the catalyst composition thereof using the noble-metal oxide catalyst from the past.