Data mining method, electrolytic apparatus, electrolytic method, oxygen evolution catalyst, and hydrogen evolution catalyst

Abstract

This invention provides an electrolytic method using metal oxides that are inexpensive and have excellent catalytic performance. [Solution] The electrolytic apparatus 200 of the present invention comprises a first electrode 201, a first catalyst layer 203 provided on the first electrode 201, a second electrode 202, a second catalyst layer 204 provided on the second electrode 202, a membrane 206 disposed between the first electrode 201 and the second electrode 202, a solution 205 containing water and an electrolyte surrounding the first electrode 201, the first catalyst layer 203, the second electrode 202, the second catalyst layer 204, and the membrane 206, a container 207 for containing the solution 205, and a power supply 209 connected between the first electrode 201 and the second electrode 202 by wiring 208, wherein the first catalyst layer 203 and the second catalyst layer 204 contain RbSbWO6 molecules.

Description

[Technical Field]

[0001] The present invention relates to a data mining method, an electrolytic apparatus, an electrolytic method, an oxygen evolution catalyst, and a hydrogen evolution catalyst. [Background technology]

[0002] Apparatus for electrolyzing compounds such as oxygen, chlorine, and hydrogen in an electrolyte-containing solution is known. By generating a potential difference between two electrodes in contact with the solution, compounds in the solution can be electrolyzed, producing molecules such as oxygen and chlorine from the positive electrode and hydrogen from the negative electrode. From the viewpoint of chemical stability, platinum compounds and ruthenium dioxide are generally used as catalysts for the positive or negative electrode (Patent Document 1, etc.), but a challenge is to reduce the operating cost of the electrolytic apparatus using electrolytic reactions with these catalysts. There is a need for inexpensive catalysts with catalytic performance equivalent to that of platinum compounds.

[0003] Data mining using computational materials databases is a common method for searching for unknown metal oxides. This data mining method can search for metal oxides with a predetermined catalytic performance. However, the results expected from data mining may not match experimental results. If the data mining method does not take into account the surface state of the metal oxide, it may incorrectly identify the metal oxide. There is a need for a data mining method that can search for metal oxides with a predetermined catalytic performance with high accuracy. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2018 / 194008 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] This invention has been made in view of the above circumstances, and aims to provide an electrolytic apparatus, an electrolytic method, a catalyst layer (oxygen evolution catalyst and hydrogen evolution catalyst) used in electrolysis, and a data mining method that enables the search for such a metal oxide from among multiple materials, using an inexpensive metal oxide with excellent catalytic performance. [Means for solving the problem]

[0006] To solve the above problems, the present invention employs the following means.

[0007] (1) An oxygen evolution catalyst according to one aspect of the present invention contains an RbSbWO6 molecule.

[0008] (2) A hydrogen generation catalyst according to one aspect of the present invention contains an RbSbWO6 molecule.

[0009] (3) An electrolytic apparatus according to one aspect of the present invention comprises a first electrode, a first catalyst layer provided on the first electrode, a second electrode, a second catalyst layer provided on the second electrode, a membrane disposed between the first electrode and the second electrode, a solution containing water and an electrolyte surrounding the first electrode, the first catalyst layer, the second electrode, the second catalyst layer, and the membrane, a container for containing the solution, and a power supply connected by wiring between the first electrode and the second electrode, wherein the first catalyst layer and the second catalyst layer contain RbSbWO6 molecules.

[0010] (4) An electrolytic method according to one aspect of the present invention comprises the steps of preparing a solution containing water and an electrolyte, and generating a potential difference between two electrodes in contact with the solution, wherein a catalyst layer containing RbSbWO6 molecules is provided on the surfaces of the two electrodes.

[0011] (5) In the electrolysis method described in (4) above, it is preferable that the pH of the electrolyte around the catalyst layer and the potential of the first electrode, which has a higher potential than the other two electrodes, are adjusted so that they fall within the region between the first line segment and the second line segment in the Pourbet diagram, wherein the first line segment is a line segment connecting a point where the pH is 0 and the potential is 1.23V and a point where the pH is 14 and the potential is 0.404V, and the second line segment is a line segment connecting a point where the pH is 0 and the potential is 2V and a point where the pH is 14 and the potential is 1.174V.

[0012] (6) In the electrolysis method described in (4) above, it is preferable that the pH of the electrolyte around the catalyst layer and the potential of the second electrode, which has a lower potential than the other two electrodes, are adjusted so that they fall within the region between the first line segment and the second line segment in the Pourbet diagram, wherein the first line segment is a line segment connecting a point where the pH is 0 and the potential is 0V and a point where the pH is 14 and the potential is -0.826V, and the second line segment is a line segment connecting a point where the pH is 0 and the potential is -0.8V and a point where the pH is 14 and the potential is -1.626V.

[0013] (7) In the electrolysis method described in (4) above, the pH around the catalyst layer may be set to 1.3 or higher and 12.6 or lower.

[0014] (8) A data mining method according to one aspect of the present invention is a data mining method for searching for metal oxides as catalysts for oxygen evolution reactions and hydrogen evolution reactions, comprising: a first step of selecting a predetermined metal oxide from metal oxides recorded in a database; and from the metal oxide selected in the first step, E hull A second step of selecting a metal oxide that satisfies the condition that E becomes 0, and from the metal oxide selected in the second step, Form A third step involves selecting a metal oxide that satisfies the condition for minimizing the Gibbs free energy, and for each of the metal oxides selected in the third step, the Gibbs free energy being 0.5eVatom -1 The method comprises a fourth step of creating a Pourbet diagram that defines the stable region as the pH and potential range below, and a fifth step of selecting a metal oxide that is stable in a predetermined reaction as an electrode catalyst by referring to the Pourbet diagram created in the fourth step.

[0015] (9) In the data mining method according to (8) above, a combination of the metal oxide selected in the third step and the Pourbaix diagram created in the fourth step is recorded in a predetermined recording device, and the selection of the metal oxide to be the electrode catalyst may be performed by searching the recording of the recording device.

[0016] (10) In the data mining method according to any one of (8) or (9) above, the method may further include a step of selecting, from the metal oxides selected in the third step, those containing a predetermined number of metal elements.

[0017] (11) In the data mining method according to any one of (8) to (10) above, the metal oxide may be selected by examining the surface state in consideration of the surface coverage rate and the difference in pores of the surface structure.

[0018] (12) In the data mining method according to (11) above, the surface structure may be considered by applying microkinetic modeling. [Advantages of the Invention]

[0019] According to the present invention, it is possible to provide an electrolysis device, an electrolysis method, a catalyst layer (oxygen generation catalyst and hydrogen generation catalyst) used for electrolysis using a metal oxide that is inexpensive and has excellent catalyst performance, and a data mining method that enables searching for the metal oxide from among a plurality of materials. In the data mining of the present invention, by considering the surface state of the metal oxide, it is possible to prevent the metal oxide from being mis-identified. [Brief Description of the Drawings]

[0020] [Figure 1] It is a configuration diagram of an electrolysis device used for the electrolysis method according to the first embodiment of the present invention. [Figure 2] It is a configuration diagram of an electrolysis device used for the electrolysis method according to the second embodiment of the present invention. [Figure 3] This is a process flow of a data mining method according to one embodiment of the present invention. [Figure 4] This graph shows the number of metal oxides selected in each step of the example. [Figure 5] This graph categorizes the metal oxides after the third process according to the number of metal elements they contain. [Figure 6] (a) to (c) are diagrams classifying the reactions in which each metal element exhibits thermodynamic stability in solutions with pH values ​​of 0, 7, and 14. [Figure 7] This graph shows the results of X-ray diffraction measurements performed on RbSbWO6 synthesized in the example. [Figure 8] This graph shows the results of measuring the time evolution of the active state of RbSbWO6 in acidic and alkaline solutions. [Figure 9] This graph shows the measured current-voltage characteristics obtained when electrolyzing water using RbSbWO6 in an acidic solution. [Figure 10] This graph shows the measured current-voltage characteristics obtained when electrolyzing water using RbSbWO6 in an alkaline solution. [Figure 11] This is a Pourbet diagram showing the surface state of the catalyst layer specified. [Figure 12] This is a Pourbet diagram showing the surface state of the catalyst layer during the hydrogen evolution reaction. [Modes for carrying out the invention]

[0021] Hereinafter, an electrolysis method and a data mining method according to embodiments of the present invention will be described in detail with reference to the drawings. Note that, for the sake of clarity, the drawings used in the following description may show enlarged versions of key features, and the dimensional ratios of each component may not be the same as those in reality. Furthermore, the materials, dimensions, etc., exemplified in the following description are merely examples, and the present invention is not limited to these; it can be implemented with appropriate modifications without altering its essence.

[0022] <First Embodiment> [Electrolyzer] Figure 1 is a schematic diagram showing the configuration of an electrolytic apparatus 200 used in the electrolytic method according to the first embodiment of the present invention. The electrolytic apparatus 200 mainly consists of two electrodes (first electrode 201, second electrode 202), catalyst layers provided on each electrode (first catalyst layer 203, second catalyst layer 204), a solution 205 surrounding the two electrodes and catalyst layers, a membrane (separator) 206 placed between the two electrodes, a container 207 housing them, and a power supply 209 connected between the two electrodes by wiring 208.

[0023] The first electrode 201 and the second electrode 202 are composed of a chemically stable and conductive material (such as platinum or ruthenium dioxide). The solution 205 contains an oxidizing agent (a substance to be electrolyzed) and an electrolyte (electrolyte solution) in a predetermined ratio. The electrolyte is a chemically stable substance through which substances produced by electrolysis (in this embodiment, oxygen molecules O2 and hydrogen molecules H2) can easily propagate. It is preferable that the solution 205 is provided not only between the first electrode 201 and the second electrode 202, but also around the entire circumference of the first electrode 201 and the entire circumference of the second electrode 202. The membrane 206 has a mesh structure with a size that prevents the produced oxygen molecules O2 and hydrogen molecules H2 from passing through.

[0024] The first catalyst layer (catalyst layer, oxygen evolution catalyst) 203 formed on the surface of the first electrode 201, and the second catalyst layer (catalyst layer, hydrogen evolution catalyst) 204 formed on the surface of the second electrode 202, both contain RbSbWO6 molecules as an essential material. The first catalyst layer 203 and the second catalyst layer 204 may contain only RbSbWO6 molecules, or they may contain RbSbWO6 as a main component, preferably 10% or more, for example, 90%. The thickness of the first catalyst layer 203 is not particularly limited.

[0025] The formation of the first catalyst layer 203 containing RbSbWO6 molecules is not particularly limited, but can be carried out in the same procedure as the first catalyst layer 103 in the first embodiment.

[0026] [Electrolysis method] The electrolysis method of this embodiment is a method for generating oxygen and hydrogen, and mainly comprises the following first and second steps.

[0027] (first step) A solution is prepared containing the substance to be electrolyzed and an electrolyte in a predetermined ratio. The substance to be electrolyzed is not particularly limited, but for example, compounds of oxygen and hydrogen such as water (H2O) can be used. Here, the case using water is given as an example.

[0028] (Second process) The prepared solution is placed in a designated container, and two electrodes (first electrode 201, second electrode 202) are brought into contact with this solution. A potential difference is generated between the first electrode 201 and the second electrode 202. This potential difference can be generated by applying a voltage between the first electrode 201 (positive electrode) and the second electrode 202 (negative electrode). In this case, the first electrode 201 will have a relatively higher potential, and the second electrode 202 will have a relatively lower potential. The surfaces of the first electrode 201 and the second electrode 202 are provided with a first catalyst layer 203 and a second catalyst layer 204, respectively, containing RbSbWO6 molecules.

[0029] From the viewpoint of chemical stability, it is preferable to adjust the pH of the solution 205 surrounding the first catalyst layer 203 and the potential of the first electrode 201 so that they fall within the region between the first line segment and the second line segment in the Pourbet diagram. In this case, it is preferable that the first line segment is the line segment connecting the point where the pH is 0 and the potential is 1.23V and the point where the pH is 14 and the potential is 0.404V, and the second line segment is the line segment connecting the point where the pH is 0 and the potential is 2V and the point where the pH is 14 and the potential is 1.174V.

[0030] Furthermore, from the same viewpoint, it is preferable to adjust the pH of the solution 205 surrounding the second catalyst layer 204 and the potential of the second electrode 202 so that they fall within the region between the first line segment and the second line segment in the Pourbet diagram. In this case, it is preferable that the first line segment is the line segment connecting the point where the pH is 0 and the potential is 0V and the point where the pH is 14 and the potential is -0.826V, and the second line segment is the line segment connecting the point where the pH is 0 and the potential is -0.8V and the point where the pH is 14 and the potential is -1.626V.

[0031] The potential difference between the first electrode 201 and the second electrode 202 causes the oxidizing agent (in this case, an oxygen compound) in the solution 205 to be electrolyzed into oxygen atoms and other atoms. The oxygen atoms are attracted to the higher potential of the first electrode 201, while the hydrogen atoms are attracted to the lower potential of the second electrode 202.

[0032] In the first catalyst layer 203, oxygen atoms attracted to the first electrode 201 undergo an oxygen evolution reaction (OER) in which they combine in pairs, thereby generating oxygen molecules. Hydrogen atoms attracted to the second electrode 202 undergo a hydrogen evolution reaction (HER) in which they combine in pairs, thereby generating hydrogen molecules. Each of the generated molecules can be recovered, for example, by recovery devices 210 and 211 connected to a container.

[0033] As described above, according to the electrolysis method of this embodiment, the first electrode 201 that generates oxygen molecules O2 is equipped with a first catalyst layer 203 containing RbSbWO6 molecules, and the second electrode 202 that generates hydrogen molecules H2 is equipped with a second catalyst layer 204 containing RbSbWO6 molecules. RbSbWO6 can be synthesized at a lower cost than platinum compounds and has catalytic performance equivalent to that of platinum compounds. Both the oxygen evolution reaction that occurs at the first electrode 201 and the hydrogen evolution reaction that occurs at the second electrode 202 can generate a large current by interposing RbSbWO6 molecules. Furthermore, since RbSbWO6 molecules are composed of chemically stable elements, they can maintain their catalytic performance over a long period of time, and as a result, a large current can be generated.

[0034] <Second Embodiment> [Electrolyzer] Figure 2 is a schematic diagram showing the configuration of an electrolytic apparatus 250 used in the electrolysis method according to the second embodiment of the present invention. This embodiment differs from the first embodiment only in that it uses chlorine compounds and hydrogen compounds as the substances to be electrolyzed. The components of the electrolytic apparatus 250 are the same as those of the electrolytic apparatus 200 in the first embodiment.

[0035] In this embodiment, solution 205 contains a chlorine compound, water, and an electrolyte. The electrolyte is chemically stable and readily transmits substances produced by electrolysis (in this embodiment, chlorine molecules Cl2 and hydrogen molecules H2). The membrane 206 has a mesh structure of a size that prevents the generated chlorine molecules Cl2 and hydrogen molecules H2 from passing through.

[0036] [Electrolysis method] The electrolysis method of this embodiment is a method for generating chlorine and mainly comprises the following first and second steps.

[0037] (first step) A solution is prepared containing an oxidizing agent (a substance to be electrolyzed) and an electrolyte in a predetermined ratio. The oxidizing agent is not particularly limited, but for example, chlorine compounds such as sodium chloride (NaCl) can be used.

[0038] (Second process) The prepared solution is placed in a designated container, and two electrodes (first electrode 201, second electrode 202) are brought into contact with this solution to generate a potential difference between the first electrode 201 and the second electrode 202. Relatively, the first electrode 201 will be at a higher potential, and the second electrode 202 will be at a lower potential. The surface of the first electrode 201, which is at the higher potential, is provided with a first catalyst layer 203 containing RbSbWO6 molecules.

[0039] Furthermore, from the viewpoint of chemical stability, it is preferable to adjust the pH of the solution 205 surrounding the first catalyst layer 203 and the potential of the first electrode 201 so that they fall within the region between the first line segment and the second line segment in the Pourbet diagram. In this case, it is preferable that the first line segment is the line segment connecting the point where the pH is 0 and the potential is 1.36V and the point where the pH is 14 and the potential is 0.534V, and that the second line segment is the line segment connecting the point where the pH is 0 and the potential is 2.16V and the point where the pH is 14 and the potential is 1.334V.

[0040] Furthermore, from the same viewpoint, it is preferable to adjust the pH of the solution 205 surrounding the second catalyst layer 204 and the potential of the second electrode 202 so that they fall within the region between the first line segment and the second line segment in the Pourbet diagram. In this case, it is preferable that the first line segment is the line segment connecting the point where the pH is 0 and the potential is 0V and the point where the pH is 14 and the potential is -0.826V, and the second line segment is the line segment connecting the point where the pH is 0 and the potential is -0.8V and the point where the pH is 14 and the potential is -1.626V.

[0041] The potential difference between the first electrode 201 and the second electrode 202 causes the chlorine compounds in solution 205 to be electrolyzed into chlorine atoms and other atoms, and the water in solution 205 to be electrolyzed into hydrogen atoms and oxygen atoms. The chlorine atoms are attracted to the first electrode 201, which has a higher potential. The hydrogen atoms are attracted to the second electrode 202, which has a lower potential.

[0042] In the first catalyst layer 203, chlorine atoms attracted to the first electrode 201 undergo a chlorine evolution reaction (CER) in which they combine in pairs, thereby generating chlorine molecules. Hydrogen atoms attracted to the second electrode 202 also undergo a hydrogen evolution reaction (HER) in which they combine in pairs, thereby generating hydrogen molecules. Each of the generated molecules can be recovered, for example, by recovery devices 210 and 211 connected to a container.

[0043] As described above, the electrolysis method of this embodiment includes a first catalyst layer 203 containing RbSbWO6 molecules in the first electrode 201 that generates chlorine molecules Cl2, and a second catalyst layer 204 containing RbSbWO6 molecules in the second electrode 202 that generates hydrogen molecules H2. RbSbWO6 can be synthesized at a lower cost than platinum compounds and has catalytic performance equivalent to that of platinum compounds. The chlorine generation reaction occurring in the first electrode 201 can generate a large current by interposing RbSbWO6 molecules. Furthermore, since RbSbWO6 molecules are composed of chemically stable elements, they can maintain their catalytic performance over a long period of time, and as a result, a large current can be generated.

[0044] (Data mining methods) Figure 3 shows a process flow of a data mining method according to one embodiment of the present invention. The data mining method of this embodiment is a method for searching for (searching for) metal oxide electrode catalysts, and mainly comprises the following steps.

[0045] (first step) From the metal oxides recorded in the database, a predetermined metal oxide is selected, and other metal oxides are excluded. Examples of metal oxides to be selected include metal oxides that can be obtained at low cost, or metal oxides that do not contain radioactive elements, halogen elements, elements that are gaseous at room temperature and pressure, organic elements, etc.

[0046] (Second process) From the metal oxide selected in the first step, the Energy above hull (E) is used as an indicator of relative thermodynamic stability. hull Select the metal oxides that satisfy the condition that ) becomes 0, and exclude the other metal oxides. hull This can be determined by first-principles calculations, and metal oxides with lower values ​​are more stable and easier to produce.

[0047] (Third step) From the metal oxide selected in the second step, the formation energy E FormSelect a metal oxide that satisfies the condition of minimizing and exclude all other metal oxides. After the third step, there may be a further step of selecting from the metal oxides selected in the third step those containing a predetermined number of metal elements.

[0048] (Fourth step) For each metal oxide selected in the third step, the Gibbs free energy is 0.5 eV·atom. -1 Create a Pourbet diagram that defines the stable region as the following pH and potential range.

[0049] (Fifth step) Referencing the Pourbet diagram created in the fourth step, select a metal oxide that is stable in the oxygen evolution reaction and the hydrogen evolution reaction as the electrode catalyst. For example, when using an acidic solution as the electrolyte, select a metal oxide that is stable in the potential range corresponding to the pH range of the acidic solution in the Pourbet diagram. Similarly, when using an alkaline solution as the electrolyte, select a metal oxide that is stable in the potential range corresponding to the pH range of the alkaline solution in the Pourbet diagram.

[0050] The combination of the metal oxide selected in the third step and the Pourbet diagram created in the fourth step may be recorded in a predetermined recording device, and the selection of a new metal oxide to be used as an electrode catalyst may be performed by searching the records in this recording device. This recording device may also be an online search engine that enables searching in a network environment connected to the internet.

[0051] In the data mining method described above, metal oxides may be selected by examining their surface state, taking into account differences in surface coverage and pores in the surface structure. In this case, the surface structure may be considered by applying microkinetic modeling.

[0052] The data mining method described above allows for the exploration of not only commonly known monometallic oxides (compounds of one metal element and oxygen) but also multimetallic oxides (compounds of multiple metal elements and oxygen). Examples of monometallic oxides to be explored include Sb2O and W2O3. Examples of multimetallic oxides to be explored include Hg(SbO3)2, Cd(SbO3)2, Zn(SbO3)2, Mn(SbO3)2, Ni(SbO3)2, Co(SbO3)2, Fe(SbO3)2, Sc2(MoO4)3, Fe2(MoO4)3, GaSbO4, BiSbO4, CsSbWO6, RbSbWO6, Ge3Sb2O9, MgCr2O4, Sb2WO6, TiSnO3, RbSbWO6, and Li4CrFe3O8.

[0053] As monometallic oxides, metal oxides containing Sb (such as Sb2O) are excellent as electrode catalysts for oxygen evolution and oxygen reduction reactions. Furthermore, since W has the second highest stability after Sb, as a multimetallic oxide, metal oxides containing both Sb and W (such as Sb2WO6) are excellent as electrode catalysts that promote oxygen evolution and oxygen reduction reactions.

[0054] As described above, the data mining method of this embodiment makes it possible to easily and accurately search for metal oxides that function as electrode catalysts in a given reaction. In the fourth step, for each metal oxide, the Gibbs free energy is 0.5 eVatom -1 The following pH and potential ranges are identified. This allows for the highly accurate identification of metal oxides that possess thermodynamic stability and are suitable for a given reaction. [Examples]

[0055] The effects of the present invention will be made clearer by the following examples. However, the present invention is not limited to the following examples and can be modified as appropriate without altering its essence.

[0056] (Data mining) The data mining method of the embodiment described above was applied to the metal oxides recorded in the database. Figure 4 is a graph showing the number of metal oxides selected after the first, second, and third steps. By performing up to the third step, the number of candidate metal oxides to be selected has been narrowed down to 1159.

[0057] Figure 5 is a graph that categorizes the 1159 selected metal oxides according to the number of constituent metal elements. Among the 1159 selected metal oxides, those containing two metal elements and those containing three metal elements are particularly numerous.

[0058] Figures 6(a) to (c) are graphs comparing the thermodynamic stability of metal elements in various reactions (nitrogen reduction reaction (NRR), hydrogen evolution reaction (HER), chlorine evolution reaction (CER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR)) in aqueous solutions with pH values ​​of 0, 7, and 14, respectively. Regardless of the state of the aqueous solution, Sb exhibits the best stability in OER and ORR.

[0059] These results indicate that, as a single-component metal oxide, metal oxides containing Sb (Sb2O) are excellent as electrocatalysts for oxygen evolution reactions. Furthermore, since the stability of W is the second highest after the stability of Sb, it can be seen that, as a multi-component metal oxide, metal oxides containing both Sb and W are excellent as electrocatalysts.

[0060] (RbSbWO6's evaluation) Of the metal oxides explored, RbSbWO6 was synthesized, and X-ray diffraction (XRD) measurements were performed on it. Figure 7 shows a graph of the measurement results. The position of the diffraction peak of the synthesized RbSbWO6 almost coincides with the position of the diffraction peak of standard RbSbWO6. From this result, it can be seen that the synthesized RbSbWO6 has a similar crystal structure to standard RbSbWO6.

[0061] (Evaluation of the active state) In 0.5 M H2SO4 solution and 0.1 M KOH solution respectively, electrolysis of water was carried out, and the time variation of the active states of the oxygen evolution reaction and hydrogen evolution reaction using RbSbWO6 as a catalyst was measured. Figure 8 is a graph showing the results. It can be seen that both the active states of the oxygen evolution reaction and hydrogen evolution reaction are maintained for a long time, and the reaction in acidic H2SO4 solution shows a higher active state compared to the reaction in alkaline KOH solution.

[0062] (Evaluation of stability) In 0.5 M H2SO4 solution and 1 M KOH solution respectively, OER and HER using RbSbWO6 as a catalyst were carried out. The catalyst was mixed with a conductive additive (carbon black, Vulcan XC - 72R) at a mass ratio of 4:1 and supported on a glassy carbon electrode (0.2 cm 2 ) at 0.5 mg·cm -2 (based on metal oxide). For HER, pre - cycling was carried out at 50 mV s RHE between 0.1~ - 0.6 V -1 . For OER, pre - cycling was carried out at 50 mV s RHE between 1~1.6 V -1 . Then, an LSV curve was obtained at a rotation speed of 1600 rpm at 5 mV s -1 .

[0063] Figures 9 and 10 are graphs showing the measurement results of HER performance and OER performance obtained in 0.5 M H2SO4 electrolyte and 0.1 M KOH electrolyte respectively. It can be seen that RbSbWO6 shows higher stability in terms of catalyst performance promoting current characteristics when used in acidic H2SO4 solution than when used in alkaline KOH solution.

[0064] (Analysis of Surface State) For electrolysis using a catalyst layer containing RbSbWO6 molecules, Pourbet diagrams were created and the surface structures A and B of the catalyst layer were analyzed. Figures 11 and 12 are Pourbet diagrams showing the surface state of the catalyst layer during the oxygen evolution reaction and the hydrogen evolution reaction, respectively. Surface structure A contains 4 Rb sites, 2 W sites, and 4 O sites. Surface structure B contains 4 Sb sites, 2 W sites, and 14 O sites.

[0065] From Figure 11, we can see the following: 1.23~2.0V SHE At the OER potential, surface structure A either maintains its original state or is affected by 1 / 6 ML of O * , or 2 / 6ML O * It is covered by [something]. In contrast, the voltage ranges from -0.8 to 0V. SHE At the HER potential, surface structure A is 1 / 6 ML of H * , 3 / 6ML H * , 4 / 6ML H * , or covered with 3 / 6ML of 0v.

[0066] From Figure 12, 1.23~2.0V SHE At the OER potential, surface structure B is 1 / 8ML of OH * , or 4 / 8 ml of OH * It is covered by [something]. In contrast, the voltage ranges from -0.8 to 0V. SHE In the HER potential, surface structure B is 5 / 8ML H * Covered with 11 / 8ML of 0v or 14 / 8ML of 0v. [Explanation of symbols]

[0067] 200, 250...Electrolyzer 201...first electrode 202...Second electrode 203...first catalyst layer 204...Second catalyst layer 205...solution 206...Membrane 207...container 208...Wiring 209...Power supply 210, 211... Recovery device

Claims

1. RbSbWO ６ An oxygen-evolving catalyst characterized by containing molecules.

2. RbSbWO ６ A hydrogen generation catalyst characterized by containing molecules.

3. First electrode and The first catalyst layer provided on the first electrode, The second electrode and The second catalyst layer provided on the second electrode, A membrane disposed between the first electrode and the second electrode, The first electrode, the first catalyst layer, the second electrode, the second catalyst layer, and the membrane are surrounded by a solution containing water and an electrolyte, A container for the aforementioned solution, The system comprises a power supply connected by wiring between the first electrode and the second electrode, The first catalyst layer and the second catalyst layer are RbSbWO ６ An electrolytic device characterized by containing molecules.

4. A process for preparing a solution containing water and an electrolyte, The process includes generating a potential difference between two electrodes in contact with the aforementioned solution, On the surfaces of the two electrodes, RbSbWO ６ An electrolytic method characterized by having a catalyst layer containing molecules.

5. The pH of the electrolyte surrounding the catalyst layer and the potential of the first electrode, which has a higher potential than the other two electrodes, are adjusted so that they fall within the region between the first and second line segments in the Pourbet diagram. The first line segment is a line segment connecting a point where the pH is 0 and the potential is 1.23 V, and a point where the pH is 14 and the potential is 0.404 V. The electrolysis method according to claim 4, characterized in that the second line segment is a line segment connecting a point where the pH is 0 and the potential is 2V and a point where the pH is 14 and the potential is 1.174V.

6. The pH of the electrolyte surrounding the catalyst layer and the potential of the second electrode, which has a lower potential than the other two electrodes, are adjusted so that they fall within the region between the first and second line segments in the Pourbet diagram. The first line segment is a line segment connecting a point where the pH is 0 and the potential is 0V, and a point where the pH is 14 and the potential is -0.826V. The electrolysis method according to claim 4, characterized in that the second line segment is a line segment connecting a point where the pH is 0 and the potential is -0.8V and a point where the pH is 14 and the potential is -1.626V.

7. The electrolysis method according to claim 4, characterized in that the pH around the catalyst layer is 1.3 or higher and 12.6 or lower.

8. A data mining method for searching for metal oxides as catalysts for oxygen evolution and hydrogen evolution reactions, The first step is to select a specific metal oxide from the metal oxides recorded in the database, From the metal oxide selected in the first step, E ｈｕｌｌ The second step is to select a metal oxide that satisfies the condition that becomes 0, From the metal oxide selected in the second step, E Ｆｏｒｍ A third step involves selecting a metal oxide that satisfies the condition for minimizing [the value], For each of the metal oxides selected in the third step, the Gibbs free energy is 0.5 eVatom －１ The fourth step involves creating a Pourbet diagram that defines the stable region as the following pH and potential ranges, A data mining method characterized by comprising: a fifth step of selecting a metal oxide stable in a predetermined reaction as an electrode catalyst by referring to the Pourbet diagram created in the fourth step.

9. The data mining method according to claim 8, characterized in that the combination of the metal oxide selected in the third step and the Pourbet diagram created in the fourth step is recorded in a predetermined recording device, and the selection of the metal oxide to be used as the electrode catalyst is performed by searching the records of the recording device.

10. The data mining method according to either 8 or 9, further comprising the step of selecting from the metal oxides selected in the third step those containing a predetermined number of metal elements.

11. The data mining method according to either 8 or 9, characterized in that the metal oxide is selected by examining its surface condition, taking into account differences in surface coverage and pores in the surface structure.

12. The data mining method according to claim 11, characterized in that the surface structure is considered by applying microkinetic modeling.

Images