WO2023095406A1 - Alkaline water electrolysis method, and anode for alkaline water electrolysis - Google Patents

Alkaline water electrolysis method, and anode for alkaline water electrolysis Download PDF

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WO2023095406A1
WO2023095406A1 PCT/JP2022/032238 JP2022032238W WO2023095406A1 WO 2023095406 A1 WO2023095406 A1 WO 2023095406A1 JP 2022032238 W JP2022032238 W JP 2022032238W WO 2023095406 A1 WO2023095406 A1 WO 2023095406A1
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hmh
electrolysis
alkaline water
anode
catalyst
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Japanese (ja)
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重徳 光島
義之 黒田
郁男 永島
達也 谷口
雄太 佐々木
善則 錦
昭博 加藤
アワルディン ジャエナル
贇 包
貴章 中井
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デノラ・ペルメレック株式会社
国立大学法人横浜国立大学
川崎重工業株式会社
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Priority to JP2023563521A priority Critical patent/JPWO2023095406A1/ja
Publication of WO2023095406A1 publication Critical patent/WO2023095406A1/en

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    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
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    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the present invention relates to an alkaline water electrolysis method and an anode for alkaline water electrolysis. Specifically, a large amount of the catalyst can be added to at least the anode chamber constituting the electrolytic cell by a simple means of supplying, as needed, an electrolytic solution in which a catalyst having a unique structure exhibiting good dispersibility is dispersed. It is possible to form the catalyst in a short time and maintain the catalytic activity of the oxygen generating anode for a long period of time.
  • the present invention relates to a technology that makes it possible to perform more stable alkaline water electrolysis over a long period of time without deteriorating the electrolysis performance.
  • Hydrogen is a secondary energy that is suitable for storage and transportation and has a small environmental impact, so there is growing interest in hydrogen energy systems that use hydrogen as an energy carrier.
  • hydrogen is mainly produced by steam reforming of fossil fuels.
  • water electrolysis from renewable energies such as solar power and wind power has become important among the basic technologies. Water electrolysis is low cost and suitable for large-scale production, and is a promising technology for hydrogen production.
  • alkaline water electrolysis in which a high-concentration alkaline aqueous solution is used as an electrolyte.
  • solid polymer type water electrolysis in which a solid polymer membrane (SPE) is used as an electrolyte.
  • SPE solid polymer membrane
  • a high-concentration alkaline aqueous solution increases in conductivity as the temperature rises, but also in corrosiveness. For this reason, the upper limit of the operating temperature of alkaline water electrolysis is suppressed to about 80 to 90°C.
  • the electrolysis cell voltage is reduced to the current density. It is improved to 2V or less at 0.6 Acm ⁇ 2 .
  • Non-Patent Documents 1 and 2 As anodes for alkaline water electrolysis, nickel-based materials that are stable in highly concentrated aqueous alkaline solutions are used. In alkaline water electrolysis using a stable power source, nickel-based anodes have been used for decades or more.
  • Non-Patent Documents 1 and 2 When renewable energy is used as a power source, there are many cases where severe conditions such as severe start-up and stoppages and load fluctuations occur, and deterioration of the performance of nickel-based anodes is a problem (Non-Patent Document 3).
  • the current generated by the battery reaction leaks through the piping that connects the cells.
  • a countermeasure for preventing such current leakage for example, there is a method of continuing to flow a very small current when the device is stopped.
  • special power supply control is required, and oxygen and hydrogen are always generated, which requires an excessive amount of time and effort in terms of operation management.
  • the oxygen generating anode catalyst (anode catalyst) used in alkaline water electrolysis includes platinum group metals, platinum group metal oxides, valve metal oxides, iron group oxides, lanthanide group metal oxides, and the like.
  • Other anode catalysts include nickel-based alloy systems such as Ni—Co, Ni—Fe; nickel with increased surface area; spinel-based Co 3 O 4 , NiCo 2 O 4 , perovskite-based LaCoO 3 , LaNiO; Conductive oxides (ceramic materials) such as 3 ; noble metal oxides; and oxides composed of lanthanide group metals and noble metals are also known (Non-Patent Document 3).
  • anode for alkaline water electrolysis in which a lithium-containing nickel oxide catalyst layer containing lithium and nickel at a predetermined molar ratio is formed on the surface of a nickel substrate (Patent Document 1);
  • An anode for alkaline water electrolysis is proposed in which a catalyst layer containing ruthenium oxide is formed on the surface of a nickel substrate (Patent Document 2).
  • the present inventors have already proposed an oxygen generating anode with an unprecedented structure as a technique for solving the problems of the conventional techniques proposed above.
  • a catalyst layer comprising hybrid cobalt hydroxide nanosheets (Co-ns), which is a composite of a metal hydroxide and an organic substance, is placed on the surface of a conductive substrate whose surface is made of nickel or a nickel-based alloy.
  • An anode for oxygen evolution is proposed.
  • an oxygen generating anode provided with a catalyst layer containing hybrid nickel hydroxide/iron nanosheets (NiFe-ns), which is a composite of a metal hydroxide and an organic substance, has excellent electrode performance. Therefore, the inventors proposed an alkaline water electrolysis method in which an electrolytic solution in which NiFe-ns is dispersed is supplied to an anode chamber and a cathode chamber that constitute an electrolytic cell, and is commonly used for electrolysis in each chamber (Patent document 4).
  • Patent Document 4 has poor dispersibility of NiFe-ns in an alkaline aqueous solution, and it is difficult to form a sufficient catalyst layer in an electrolytic cell in a short time. There was a new problem of This is an important problem to be solved because there is a concern that this point will become an obstacle in practical use.
  • excellent electrode catalyst activity can be obtained.
  • further development is required even for more effective anodes for alkaline water electrolysis using NiFe-ns as a catalyst.
  • the conventional anode for alkaline water electrolysis which is the target of these technologies, is likely to deteriorate (degrade) in electrolysis performance when powered by electric power with large output fluctuations such as renewable energy. It was difficult to say that it was still sufficient for the technical problem that it was difficult to use it stably over a long period of time. In other words, in order to fully solve the above technical problems, it is necessary to improve the electrolysis performance more quickly when the performance of the oxygen generating anode used decreases due to potential fluctuations due to sudden start-up and stoppages and potential load fluctuations. High durability that can be recovered and improved is required.
  • the anode for alkaline water electrolysis that generates oxygen is also referred to as the "oxygen generating anode”.
  • the present invention has been made in view of such conventional technology, and its problem is that even when power sources such as renewable energy with large output fluctuations are used as power sources, the electrolytic performance deteriorates.
  • the final object of the present invention is that by using the above-described excellent electrode for electrolysis, even when the power source is an electric power with large output fluctuations, the electrolysis performance is less likely to deteriorate, and the electrolysis can be performed for a long time.
  • the purpose of the present invention is to further develop the above-mentioned technology developed by the inventors and make it a technology that can be used more effectively industrially.
  • the electrolysis performance is less likely to deteriorate, and the electrolysis performance deteriorates. (i.e., the catalyst layer is self-repairing by electrolysis), excellent catalytic activity is stably maintained for a longer period, and a more durable anode for oxygen evolution is developed. is.
  • to develop a technology that can efficiently form the catalyst layer of the oxygen generating anode that provides such excellent effects over a long period of time using a more versatile material and using a simple electrolysis method. It is in.
  • the present invention provides the following alkaline water electrolysis method.
  • the expression "hmh” used in the present invention is an abbreviation for "hybrid metal hydroxide”.
  • An electrolytic cell is composed of an electrolytic solution in which a catalyst containing hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh ), which is a composite of a metal hydroxide and an organic substance, is dispersed.
  • An alkaline water electrolysis method characterized by supplying an anode chamber and a cathode chamber and using it in common for electrolysis in each chamber.
  • An electrolytic cell is composed of an electrolytic solution in which a catalyst containing hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh ), which is a composite of a metal hydroxide and an organic substance, is dispersed.
  • NixFeyCoz - hmh hybrid nickel-iron-cobalt hydroxide
  • the Ni x Fe y Co z -hmh is supplied to at least the anode chamber, and during operation, the Ni x Fe y Co z -hmh is electrolytically deposited in the electrolysis cell to constitute the anode for oxygen generation, and a catalyst layer is formed on the surface.
  • a method of electrolyzing alkaline water comprising electrolytically depositing the Ni x Fe y Co z -hmh on the surface of a conductive substrate to recover and improve electrolysis performance.
  • Preferred embodiments of the alkaline water electrolysis method described above include the following. [3] The alkaline water electrolysis method according to [1] or [2], wherein the electrolytic solution is supplied intermittently. [4]
  • the Ni x Fe y Co z -hmh is a substance having a size within the range of 1 to 200 nm, a sheet-like substance having a layered molecular structure, a needle-like substance having a tunnel structure, and The alkaline water electrolysis method according to [1] to [3], which contains at least one of particulate substances having an amorphous structure.
  • the condition for electrolytically depositing the Ni x Fe y Co z -hmh on the surface of the conductive substrate is 1.2 V to 1.8 V vs.
  • Ni x Fe y Co z -hmh As the electrolytic solution in which the Ni x Fe y Co z -hmh is dispersed, a Ni x Fe y Co z -hmh dispersion having a concentration of 5 to 100 g/L is used, and the Ni x Fe y Co z - The alkaline water electrolysis method according to any one of [1] to [5], wherein the concentration of the hmh dispersion added to the electrolytic solution is adjusted to be within the range of 0.1 to 8 mL/L.
  • Ni x Fe y Co z -hmh has an atomic ratio of Ni/Fe/Co of 0.1 to 0.9/0.1 to 0.9/0.1 to 0.9 [ 1]
  • the alkaline water electrolysis method according to any one of [6].
  • the present invention provides the following anode for alkaline water electrolysis, which is useful when applied to the alkaline water electrolysis method.
  • a hybrid nickel-iron-cobalt hydroxide Ni and a catalyst layer containing x Fe y Co z -hmh
  • an anode for alkaline water electrolysis that generates oxygen.
  • a conductive substrate having a surface made of nickel or a nickel-based alloy, and a composition formula of Li x Ni 2-x O 2 (0.02 ⁇ x ⁇ 0.5) formed on the surface of the conductive substrate.
  • a hybrid nickel-iron-cobalt hydroxide Ni x Fe y and a catalyst layer comprising Co z -hmh
  • anode for alkaline water electrolysis that generates oxygen.
  • the electrolysis performance is less likely to deteriorate during the electrolysis operation, and the excellent catalytic activity is more stable over a long period of time. It is possible to provide an anode for alkaline water electrolysis (anode for oxygen generation) that generates oxygen efficiently and with excellent durability. Further, according to the present invention, a simple means of supplying a common electrolytic solution to the anode chamber and the cathode chamber, or a simple method of supplying an electrolytic solution in which a specific catalyst is dispersed to the anode chamber as required.
  • the electrolysis performance of the oxygen generating anode is less likely to deteriorate, particularly when electric power with large output fluctuations is used as the power source, and it is possible to perform more stable alkaline water electrolysis over a long period of time.
  • An industrially useful alkaline water electrolysis method can be provided.
  • the material used in the present invention which constitutes the catalyst layer of the anode for alkaline water electrolysis that provides the above-described excellent effects, is highly versatile, and can be easily used in electrolysis at constant current to produce a large amount of By forming (depositing) the catalyst in a short time, the formation of the catalyst layer can be performed more efficiently, especially the self-healing of the catalyst layer can be stably and efficiently performed. expensive.
  • the above-mentioned excellent effects are obtained by using a catalyst layer containing a hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh) of a metal hydroxide and an organic substance newly proposed by the present inventors.
  • FIG. 1 is a diagram schematically showing the molecular structure of layered Ni x Fe y Co z -Tris-NH 2 having tripodal ligands, which is an example of a catalyst component used in the present invention.
  • FIG. 2 is a diagram schematically showing a needle-shaped tunnel-structured substance of Ni x Fe y Co z -Tris-NH 2 having tripodal ligands, which is an example of a catalyst component used in the present invention.
  • FIG. 4B is a graph showing the relationship between catalyst deposition time and catalyst deposition amount (deposition amount) obtained using the peak areas of FIGS. 4A and 4B ;
  • FIG. 4B is a graph showing the relationship between catalyst deposition time and catalyst deposition amount (deposition amount) obtained using the peak areas of FIGS. 4A and 4B ;
  • FIG. 4 is a graph showing changes in electrolysis characteristics when each catalyst component is used in an accelerated test performed in Study Example 1.
  • FIG. 4 is a graph showing changes in electrolysis characteristics when each catalyst component is used in a test of continuous electrolysis at constant current conducted in Examination Example 2.
  • FIG. 4 is a graph showing changes in electrolysis characteristics when each catalyst component is used in an accelerated endurance test conducted in Examination Example 3.
  • FIG. 1 is a transmission electron micrograph showing a state in which Fe-hmh particles, which are an example of a catalyst component that produces the effects of the present invention, are dispersed in an electrolytic solution and deposited on the surface of a Ni substrate by electrolysis.
  • FIG. Field emission type scanning electrons showing a state in which Fe-hmh particles, which are an example of a catalyst component capable of obtaining the effect of the present invention, are dispersed in an electrolytic solution coexisting with Co-ns particles, and deposited on the surface of a Ni substrate by electrolysis.
  • FIG. 3 is a view of a microscope (FE-SEM);
  • FIG. 11B is a field-emission scanning electron microscope (FE-SEM) showing the deposited state in a different field of view than FIG. 11A. Changes in electrolytic characteristics when using an electrolytic solution in which Fe-hmh particles are dispersed and an electrolytic solution in which a catalyst component in which Fe-hmh particles and Co-ns particles coexist are dispersed, respectively, which was performed in Study Example 4.
  • Electrolysis was performed with the electrolytic solution in which the catalyst component in which Fe-hmh particles and Co-ns particles coexisted at different ratios, which was performed in Study Example 5, was dispersed, and the amount of Fe deposited relative to the amount of Co deposited and the amount of electrolysis obtained after electrolysis. 4 is a graph showing changes in characteristics; Electrolysis was performed with each electrolytic solution in which the catalyst components of Fe-hmh particles and Co-ns particles were coexisting and dispersed at different ratios as in Study Example 5, and the Co deposition amount and Fe deposition amount obtained after electrolysis were calculated. It is a graph showing.
  • Non-Patent Document 4 it was reported for the first time that the electrolyte solution in which the self-repairing catalyst Co-ns for the anode is dispersed improves the performance of the anode while having almost no effect on the cathode electrode. .
  • the present inventors have so far proposed new self-repairing catalysts for anodes, there is still room for improvement in anode performance. I found that there is a problem to be solved.
  • the NiFe-ns proposed so far has poor dispersibility in an alkaline aqueous solution, and for this reason, when used in an electrolytic solution, it is difficult to form a sufficient catalyst layer in an electrolytic cell in a short time.
  • Development of a useful technique for recovering (restoring) electrolytic performance more efficiently and stably has been desired.
  • the hybrid nickel-iron-cobalt hydroxide Ni x Fe y Co z -hmh
  • the hybrid nickel-iron-cobalt hydroxide has the high durability that is the object of the present invention. can function more effectively as a self-repairing electrode catalyst, and by using this composite, it is possible to solve the above-described problems in the prior art at a higher level. Completed.
  • Ni x Fe y Co z -hmh nickel-iron-cobalt hydroxide
  • Ni x Fe y Co z -hmh acts as a catalyst and an anti-corrosion coating, and improves the durability of Ni-based anodes against potential fluctuations, and the previously proposed Co-ns as a catalyst.
  • Ni x Fe y Co z -hmh acts as a catalyst and an anti-corrosion coating, and improves the durability of Ni-based anodes against potential fluctuations, and the previously proposed Co-ns as a catalyst.
  • it can be significantly improved over the anodes utilized in the prior art.
  • Ni x Fe y Co z -hmh when used as a catalyst, a larger amount of catalyst is formed on the anode surface in a shorter time during electrolysis than when NiFe-ns is used as the previously proposed catalyst ( It was found that Ni x Fe y Co z -hmh is a useful material that can recover electrolytic performance more efficiently and more stably.
  • the present inventors also found that, even in the case of an anode using Fe-hmh, in which the metal ions are only general-purpose metal iron, as a catalyst, the durability of the Ni-based anode against potential fluctuations We have found that the previously proposed Co-ns can be improved over the catalyzed anode. Furthermore, as a result of intensive studies to improve the practicality of using Fe-hmh as a catalyst, the present inventors have found that the following configuration provides a higher effect.
  • Fe-hmh and Co-ns are separately produced, and even in the case of an anode having a structure in which a deposit in which these are coexisted is used as a catalyst, the durability of the Ni-based anode against potential fluctuations is improved.
  • Fe-hmh alone can be improved over anodes catalyzed by Fe-hmh.
  • FIG. 1 is a cross-sectional view schematically showing one embodiment of an anode for alkaline water electrolysis that generates oxygen, used in the method for alkaline water electrolysis of the present invention.
  • the anode for alkaline water electrolysis has a structure in which the intermediate layer 4 shown in FIG. 1 is formed. It is formed between the substrate 2 and the catalyst layer 6 and is not an essential component.
  • the conductive substrate 2 is a conductor that conducts electricity for electrolysis, and is a member that functions as a carrier for depositing the intermediate layer 4 and the catalyst layer 6 .
  • At least the surface of the conductive substrate 2 (the surface on which the intermediate layer 4 is formed) is made of nickel or a nickel-based alloy. That is, the conductive substrate 2 may be entirely made of nickel or a nickel-based alloy, or only the surface thereof may be made of nickel or a nickel-based alloy.
  • the conductive substrate 2 may be, for example, a metal material such as iron, stainless steel, aluminum, or titanium coated with nickel or a nickel-based alloy by plating or the like.
  • the thickness of the conductive substrate 2 is preferably about 0.05-5 mm.
  • the shape of the conductive substrate is preferably a shape having openings for removing generated bubbles of oxygen, hydrogen, or the like.
  • an expanded mesh or a porous expanded mesh can be used as the conductive substrate 2 .
  • the opening ratio of the conductive substrate is preferably 10 to 95%.
  • the oxygen generating anode used in the water electrolysis method of the present invention can be obtained, for example, by forming an intermediate layer 4 and a catalyst layer 6 on the surface of the conductive substrate 2 as described below. .
  • the conductive substrate 2 is preferably chemically etched in advance in order to remove contaminant particles such as metals and organic substances on the surface. It is preferable that the amount of consumption of the conductive substrate by the chemical etching process is about 30 g/m 2 or more and 400 g/m 2 or less.
  • the intermediate layer 4 is a layer formed on the surface of the conductive substrate 2 .
  • the intermediate layer suppresses corrosion of the conductive substrate, etc., and stably adheres the catalyst layer 6 to the conductive substrate.
  • the intermediate layer also plays a role of rapidly supplying current to the catalyst layer.
  • the intermediate layer may be made of, for example, a lithium-containing nickel oxide represented by the composition formula Li x Ni 2-x O 2 (0.02 ⁇ x ⁇ 0.5). If x in the above composition formula is less than 0.02, the conductivity will be insufficient. On the other hand, when x exceeds 0.5, the physical strength and chemical stability decrease.
  • the intermediate layer 4 formed of the lithium-containing nickel oxide represented by the above compositional formula has sufficient electrical conductivity for electrolysis and exhibits excellent physical strength and chemical stability even when used for a long period of time.
  • the thickness of the intermediate layer is preferably 0.01 ⁇ m or more and 100 ⁇ m or less, more preferably 0.1 ⁇ m or more and 10 ⁇ m or less. If the thickness of the intermediate layer is less than 0.01 ⁇ m, the functions described above are not exhibited. On the other hand, even if the thickness of the intermediate layer exceeds 100 ⁇ m, the voltage loss due to the resistance of the intermediate layer becomes large, and the above-described functions may not be exhibited, and there may be a slight disadvantage in terms of manufacturing cost and the like.
  • a precursor aqueous solution containing lithium ions and nickel ions is applied to the surface of the conductive substrate 2 .
  • the intermediate layer is formed by a so-called pyrolytic method.
  • an aqueous solution of the precursor for the intermediate layer is prepared.
  • a precursor containing a lithium component known precursors such as lithium nitrate, lithium carbonate, lithium chloride, lithium hydroxide and lithium carboxylate can be used.
  • Lithium carboxylates include lithium formate and lithium acetate.
  • Nickel carboxylates include nickel formate and nickel acetate.
  • the heat treatment temperature when forming the intermediate layer by thermal decomposition can be set as appropriate. Considering the decomposition temperature of the precursor and the production cost, the heat treatment temperature is preferably 450° C. or higher and 600° C. or lower, more preferably 450° C. or higher and 550° C. or lower. For example, the decomposition temperature of lithium nitrate is about 430.degree. C., and the decomposition temperature of nickel acetate is about 373.degree. By setting the heat treatment temperature to 450° C. or higher, each component can be decomposed more reliably. If the heat treatment temperature exceeds 600° C., the oxidation of the conductive substrate is likely to proceed, which may increase the electrode resistance and lead to an increase in voltage loss.
  • the heat treatment time may be appropriately set in consideration of the reaction rate, productivity, oxidation resistance of the catalyst layer surface, and the like.
  • the thickness of the intermediate layer to be formed can be controlled by appropriately setting the number of times the aqueous solution is applied in the above-described application step.
  • the application and drying of the aqueous solution may be repeated for each layer, and the whole may be heat-treated after forming the uppermost layer.
  • the whole may be heat treated.
  • the pretreatment temperature and the overall heat treatment temperature may be the same or different.
  • the pretreatment time is preferably shorter than the total heat treatment time.
  • the oxygen generating anode used in the alkaline water electrolysis method of the present invention has a form in which a catalyst layer 6 made of a specific catalyst component is formed on the outermost surface of the conductive substrate 2, so that when applied to alkaline water electrolysis, Remarkable effects of the present invention are exhibited.
  • the catalyst layer which is important for obtaining the remarkable effects of the present invention, will be described below.
  • Hybrid nickel-iron-cobalt (Ni x Fe y Co z -hmh), which is a composite of a metal hydroxide and an organic substance, which is used in the present invention and is a catalyst component that characterizes the present invention, is, for example, as follows.
  • NixFeyCoz - hmh is produced, for example, by mixing an aqueous solution of tripodal ligand tris(hydroxymethyl)aminomethane (Tris- NH2 ) with an aqueous solution of NiCl2 , FeCl2 and CoCl2 , and It can be synthesized by time reaction.
  • Tris- NH2 tripodal ligand tris(hydroxymethyl)aminomethane
  • the reaction product synthesized above is separated as a gel by filtering and washing with pure water, and this is subjected to ultrasonic treatment in pure water to obtain Ni used in the electrolytic solution in the alkaline water electrolysis method of the present invention.
  • x Fe y Co z -hmh dispersions are readily obtained.
  • the concentration of Ni x Fe y Co z -hmh in the dispersion is preferably about 5 to 100 g/L. In test examples of the present invention, which will be described later, a dispersion having a concentration of 5 g/L was used.
  • NiFeCo-hmh dispersion the dispersion in which the Ni x Fe y Co z -hmh catalyst is dispersed, which is used for preparing the electrolytic solution.
  • the “NiFeCo-hmh dispersion” obtained by the production method described above was used as the electrolytic solution in which the catalyst Ni x Fe y Co z -hmh used in the present invention was dispersed.
  • the catalyst was adjusted so as to have an appropriate addition concentration.
  • Tris-NH 2 shown in FIG. 2A was used as a representative example of the tripodal ligand, but the tripodal ligand is not particularly limited, and Tris-NH 2 Any material having a molecular structure similar to that of
  • Ni x Fe y Co z -hmh has a composite structure in which a metal hydroxide and a tripodal ligand are covalently fixed. Some have an amorphous structure.
  • the layered Ni x Fe y Co z -hmh has a layered Ni x Fe y Co z -Tris-NH 2 molecular structure with tripodal ligands, for example, as schematically illustrated in FIG. 2A. and consists of a brucite layer in which the Tris molecules are covalently immobilized. Modification with Tris-NH 2 enhances the ability to exfoliate and disperse in layered nickel-iron-cobalt hydroxide electrolytes.
  • the molecular structure of the Ni x Fe y Co z -hmh obtained above has a thickness of about 1.3 nm and a lateral size of about 10 to 100 nm, similar to the previously proposed "NiFe-ns". It was confirmed by a TEM image that a nanosheet-like substance having a layered molecular structure with a size of . It was also confirmed by XRD that Ni x Fe y Co z -hmh has a layered structure with an enlarged basal plane spacing.
  • FIG. 9 shows a transmission electron micrograph of Fe-hmh as an example of a substance with such a structure.
  • Fe-hmh is used alone as a catalyst, and when Fe-hmh and Co-ns are used together as a catalyst, the durability of the Ni-based anode against potential fluctuations is improved. performance can be improved over previously proposed Co-ns-only catalyzed anodes.
  • Ni x Fe y Co z -hmh of the catalyst constituting the present invention is a substance with a size within the range of 1 to 200 nm.
  • the abundance of the above substances in the reaction product is affected by the atomic ratio of Ni/Fe/Co.
  • the Fe content was 70 mol % or less, the material tended to have a nanosheet-like structure with a layered structure.
  • the Fe content was more than 70 mol %, there was a tendency to form a particulate substance with an amorphous structure.
  • the electrolysis performance of the oxygen generating anode of the present invention using Ni x Fe y Co z -hmh as a catalyst is superior to that of the prior art using Ni x Fe y -ns as a catalyst. Therefore, the degree of influence due to the difference in the atomic ratio of Ni/Fe/Co is small, and there is a tendency to exhibit stable electrolysis performance.
  • the resulting reaction product was also dispersed in water, sonicated and tested for water dispersibility.
  • the dispersions used in the electrolyte were prepared from hydrogels obtained by filtration.
  • a dispersion could be prepared even from its dry powder.
  • the NiFeCo-hmh dispersions utilized in the electrolyte can of course also be prepared from hydrogels obtained by filtration, as with Ni x Fe y -ns catalysts.
  • the present inventors believe that this difference in dispersibility is the factor behind the difference in the amount of the catalyst layer formed (deposited) on the surface of the oxygen generating anode by constant electrolysis, which will be described later. That is, it is thought that the amount of substances that can contribute to the formation (deposition) of the catalyst layer (the amount that can be effectively used) in the electrolytic solution in which the catalyst is dispersed increases when a catalyst that exhibits good dispersibility is used. Because of this , the present invention using Ni x Fe y Co z -hmh as a catalyst produces a greater amount of It is inferred that the formation (deposition) of the catalyst layer was achieved.
  • the electrolytic solution in which the Ni x Fe y Co z -hmh catalyst having excellent dispersibility is dispersed in this way, the electrolytic performance is less likely to deteriorate, which is the object of the present invention, and the alkaline water is more stable over a long period of time. It is considered that the provision of a more excellent oxygen generating anode capable of performing electrolysis and a method of electrolyzing alkaline water using the same has been realized.
  • Ni x Fe y Co z -hmh that can be suitably used for the purpose of the present invention has a Ni/Fe/Co atomic ratio of (0.1 to 0.9)/(0.1 to 0.9) / (0.1 to 0.9). Further, the Ni/Fe/Co atomic ratio is more preferably (0.1 to 0.7)/(0.3 to 0.8)/(0.05 to 0.2) (see FIG. 7 ). As described above, when used in the alkaline water electrolysis method of the present invention, the Ni x Fe y Co z -hmh substance preferably has a length (major diameter) in the range of 1 to 200 nm.
  • Ni x Fe y Co z -hmh that can be used as a catalyst suitable for the purpose of the present invention includes a sheet-like substance having a layered molecular structure, a needle-like substance having a tunnel structure, and a particulate substance having an amorphous structure. Examples include those having at least one of them.
  • the Ni/Fe/Co atomic ratio is (0.0)/(1.0)/( 0.0).
  • Fe-hmh has a morphological feature of having a “needle-shaped material with a tunnel structure”.
  • the Ni/Fe/Co atomic ratio is (0.0)/(0.1 to 0.9)/(0.1 to 0.9), and is made of a material containing metal ions of Fe and Co. Structural ones are also included.
  • Fe-hmh which has high activity, is used as a catalyst in the presence of a Co component, which occurs when Fe-hmh and Co-ns are used together as a catalyst. It was found that -hmh is characterized by more precipitation than when it is used alone as a catalyst. This point will be described later.
  • the catalyst component that forms the catalyst layer of the anode for alkaline water electrolysis and is contained in the electrolytic solution which characterizes the present invention, is a composite of a metal hydroxide and an organic substance.
  • Ni x Fe y Co z -hmh nickel-iron-cobalt
  • the present inventors have so far proposed a technology utilizing hybrid cobalt hydroxide nanosheets (Co-ns) A better effect can be obtained compared to Specifically, each of the above composites is used to form an anode catalyst layer, the obtained anode is used, and an electrolytic solution containing each of the above different composites as a catalyst is supplied to the anode chamber to perform electrolysis.
  • Ni x Fe y Co z -hmh used as a catalyst component in the present invention can be synthesized by a simple method from general-purpose materials and has excellent dispersibility as described above. There is also an industrially extremely important advantage that it is easy to use as a dispersion in which is dispersed or an electrolytic solution prepared using the dispersion.
  • a method for forming the catalyst layer 6 will be described.
  • a 1.0 M KOH aqueous solution was used as an electrolytic solution.
  • potential manipulation in the electrolytic solution For example, potential cyclic operation (-0.5 to 0.5 V vs. RHE, 200 mV/s, 200 cycles) is performed.
  • a 1.0 M KOH aqueous solution containing the NiFeCo-hmh dispersion obtained as described above at an additive concentration of 1 mL/L was prepared and used as an electrolytic solution.
  • Ni x Fe y Co z -hmh on the Ni substrate surface, constant current electrolysis was performed eight times at 800 mA/cm 2 for 30 minutes. In this electrolysis operation, the dispersibility of Ni x Fe y Co z -hmh is reduced on the electrode surface by oxidation of the hydroxide layer and oxidative decomposition of the surface organic group, and Ni x Fe y Co z -hmh is formed on the electrode surface. was deposited.
  • the concentration of the "NiFeCo-hmh dispersion" added to the electrolytic solution is preferably in the range of 0.1 to 10 mL/L, more preferably 0.1 to 8 mL/L. According to the studies of the present inventors, if the concentration is higher than this, the dispersion of Ni x Fe y Co z -hmh in the electrolytic solution becomes insufficient, and homogeneous deposition may not be obtained in electrolysis. I don't like it. On the other hand, if the concentration is lower than this, a sufficient amount cannot be obtained within a practical time in electrolytic deposition.
  • the electrolysis conditions for the deposition are 1.2 V to 1.8 V vs. the conductive substrate. It is preferable to keep it in the potential range of RHE. The precipitation reaction does not proceed at less than 1.2 V, and if the voltage exceeds 1.8 V, oxygen evolution proceeds simultaneously, inhibiting precipitation, which is not preferable.
  • a transmission electron micrograph is shown as an example of the deposit when the catalyst was deposited on the Ni substrate by electrolysis under the above conditions for 4 hours using the electrolytic solution in which Fe-hmh was dispersed.
  • the Ni substrate surface was found to be covered with a fibrous substance network in which Fe-hmh was bundled.
  • FIGS. 11A and 11B show the state of precipitates deposited on the surface of the Ni substrate by electrolysis by dispersing both Fe-hmh particles and Co-ns particles, which are examples of catalyst components, in an electrolytic solution.
  • a picture of an emission scanning electron microscope (FE-SEM) is shown.
  • the electrode surface was uniformly covered with a catalyst layer, and it was found from FIG. 11B and its enlarged image (not shown) that the microstructure was aggregates of nanosheets (Co-ns).
  • FIG. 11A it was confirmed from another view that the Fe-hmh particles were elongated particles and were incorporated into aggregates.
  • the cathode (negative electrode) and the diaphragm are not particularly limited, and those used in conventional alkaline water electrolysis may be appropriately used. These will be described below.
  • the cathode it is preferable to select and use a substrate made of a material that can withstand alkaline water electrolysis and a catalyst with a small cathode overvoltage.
  • a nickel substrate or a nickel substrate coated with an active cathode can be used.
  • Examples of the shape of the cathode substrate include a plate shape, an expanded mesh, a porous expanded mesh, and the like.
  • Cathode materials include porous nickel having a large surface area and Ni--Mo based materials.
  • Raney nickel materials such as Ni--Al, Ni--Zn and Ni--Co--Zn
  • sulfide materials such as Ni--S
  • hydrogen storage alloy materials such as Ti.sub.2 Ni.
  • the catalyst those having properties such as low hydrogen overvoltage, high short-circuit stability, and high poisoning resistance are preferred.
  • metals such as platinum, palladium, ruthenium, iridium, and oxides thereof are preferred.
  • any conventionally known membrane such as asbestos, nonwoven fabric, ion exchange membrane, porous polymer membrane, and composite membrane of inorganic substance and organic polymer can be used.
  • an ion-permeable membrane having an organic fiber cloth embedded in a mixture of a hydrophilic inorganic material such as a calcium phosphate compound and calcium fluoride and an organic binding material such as polysulfone, polypropylene, and polyvinylidene fluoride. can be used.
  • film-forming mixtures of particulate inorganic hydrophilic substances such as antimony and zirconium oxides and hydroxides and organic binders such as fluorocarbon polymers, polysulfones, polypropylene, polyvinyl chloride, and polyvinyl butyral.
  • organic binders such as fluorocarbon polymers, polysulfones, polypropylene, polyvinyl chloride, and polyvinyl butyral.
  • an ion-permeable diaphragm with an internal stretched organic fiber cloth can be used.
  • a high-concentration alkaline aqueous solution can be electrolyzed by using an alkaline water electrolysis cell comprising the oxygen generating anode that characterizes the present invention.
  • aqueous solutions of alkali metal hydroxides such as potassium hydroxide (KOH) and sodium hydroxide (NaOH) are preferable.
  • the concentration of the alkaline aqueous solution is preferably 1.5% by mass or more and 40% by mass or less. Further, it is preferable that the concentration of the alkaline aqueous solution is 15% by mass or more and 40% by mass or less, because the electric conductivity is high and the power consumption can be suppressed.
  • the concentration of the alkaline aqueous solution is preferably 20% by mass or more and 30% by mass or less.
  • the catalyst layer 6 constituting the anode for alkaline water electrolysis described above can be formed by performing electrolysis in the following manner before incorporation into an electrolytic cell.
  • Ni x Fe y Co z ⁇ which is a component forming the catalyst layer 6 characterizing the present invention, is added to the common electrolytic solution supplied to the anode chamber and the cathode chamber constituting the electrolytic cell.
  • the alkaline water electrolysis technology of the present invention it is possible to recover the performance of an electrolytic cell whose performance has deteriorated due to operation without the trouble of dismantling the electrolytic cell, and stably maintain the performance of the catalyst layer for a long time. can be maintained. Therefore, the alkaline water electrolysis technology of the present invention is practical and has great industrial merit.
  • Ni x Fe y Co z -hmh which is a catalyst component characterizing the present invention
  • Ni x Fe y Co z -hmh which is a catalyst component characterizing the present invention
  • Example 1 The electrolysis operation was performed using a three-electrode cell made of PFA, which is a fluororesin. A Ni wire etched with boiling hydrochloric acid for 6 minutes was used as the working electrode, a reversible hydrogen electrode (RHE) was used as the reference electrode, a Ni coil was used as the counter electrode, and 250 mL of a 1.0 M KOH aqueous solution was used as the electrolyte. . First, as a pretreatment, cyclic voltammetry (0.5 to 1.5 V vs. RHE, 200 mV/s, 200 cycles) was performed without adding the NiFeCo-hmh dispersion to the electrolytic solution. The electrolytic solution used in this study example was prepared as follows.
  • the dispersion was mixed with the electrolytic solution used for the pretreatment to obtain a dispersion. was adjusted to a concentration of 8 mL/L to prepare an electrolytic solution in which the catalyst was dispersed.
  • electrolysis was performed at a constant current of 800 mA/cm 2 for 30 minutes with this electrolytic solution.
  • Ni x Fe y Co z -hmh which is a catalyst component, is oxidized on the electrode surface, and the hydroxide layer of Ni x Fe y Co z -hmh is oxidized and the surface organic groups are oxidatively decomposed.
  • the dispersibility was reduced by , and Ni x Fe y Co z -hmh was deposited on the electrode surface to obtain an anode with a unique catalyst layer formed thereon.
  • FIG. 4A shows changes in cyclic voltammetry in the process of forming a catalyst layer with Ni 11.5 Fe 70.5 Co 18 -hmh.
  • An oxidation peak was observed in RHE. These can be attributed to the reactions of Co 2+ /Co 3+ and Ni 2+ /Ni 3+ , respectively, and are considered to be derived from the precipitated catalyst.
  • FIG. 4B shows changes in cyclic voltammetry during the catalyst layer formation process with Ni 61.5 Fe 38.5 -ns. After 30 minutes of electrolysis and 240 minutes of electrolysis, 1.40 V vs. An oxidation peak was observed in RHE, but unlike in FIG. 4A, the peak height did not increase any further. This suggests that the amount of catalyst deposited on the electrode is smaller when the NiFe-ns catalyst is used than when the NiFeCo-hmh catalyst constituting the present invention is used.
  • Ni 11.5 Fe 70.5 Co 18 -hmh used as a catalyst in the present invention as shown in FIG. 4A, the peak area has increased significantly.
  • Ni 11.5 Fe 70.5 Co 18 -hmh used as a catalyst in the present invention has improved dispersibility compared to the NiFe-ns catalyst. It is believed that this facilitates the formation (deposition) of the catalyst layer on the electrode.
  • FIG. 4C shows a graph of the relationship between catalyst deposition time and catalyst deposition amount obtained using the peak areas of FIGS. 4A and 4B. As shown in FIG. 4C, more catalyst layers can be deposited by using NiFeCo-hmh, which constitutes the present invention, as compared to the case of using Ni x Fe y -ns of the prior art as a catalyst. It could be confirmed.
  • FIG. 5 shows the overpotential at current density of 100 mA/cm 2 versus catalyst deposition time for tests conducted with Ni 11.5 Fe 70.5 Co 18 -hmh and Ni 61.5 Fe 38.5 -ns. showed change.
  • Ni 11.5 Fe 70.5 Co 18 -hmh was used as a catalyst, an overvoltage lower than that of Ni 61.5 Fe 38.5 -ns was obtained from a small amount of precipitation. .
  • an acceleration test for potential fluctuation was performed under the following conditions using an electrolytic solution in which various catalysts were dispersed. Accelerated test for potential fluctuation is 0.5 to 1.7 V vs. RHE, 2000 cycles of cyclic voltammetry at 500 mV/s and electrode performance measurements of 0.5-1.8 V vs. RHE, 2 cycles at 5 mV/s and 0.5-1.5 V vs. Two cycles of cyclic voltammetry were performed at RHE, 50 mV/s. Co-ns, Fe-hmh, Ni 11.5 Fe 70.5 Co 18 -hmh, and Ni 61.5 Fe 38.5 -ns were used as catalysts dispersed in the electrolytic solution. For comparison, a test was performed using an electrolytic solution in which no catalyst was dispersed, and this was designated as "Bare Ni". Each of the above operations was repeated 20 times, and the test was conducted up to a total of 40000 cycles.
  • FIG. 6 shows the results of the accelerated endurance test with respect to the potential fluctuations described above.
  • an increase in overvoltage was observed after 10000 cycles, whereas in the examples using the electrolytic solution in which the catalyst was dispersed, the increase in overvoltage was suppressed in all cases. . This is presumably because the catalyst re-deposited (self-healing) from the electrolytic solution due to constant-current electrolysis every 2000 cycles.
  • Ni 61.5 Fe 38.5 -ns Ni 11.5 Fe 70.5 Co 18 -hmh and Fe-hmh as catalysts
  • bare Ni and Co-ns maintained a smaller overvoltage than with
  • the initial activity was the highest.
  • a slight increase in overvoltage was observed from 4000 to 8000 cycles, the increase in overvoltage was stably suppressed thereafter.
  • Fe-hmh is inferior to Ni 61.5 Fe 38.5 -ns or Ni 11.5 Fe 70.5 Co 18 -hmh as a catalyst, good characteristics are also obtained when using Fe-hmh. Got.
  • FIG. 7 shows changes in overvoltage when electrolysis is continuously performed at a current density of 100 mA/cm 2 with various catalyst components dispersed in the electrolytic solution.
  • Electrolysis was performed using the electrolyte solution obtained in the same manner as in Examination Example 1, using the following catalysts as catalysts dispersed in the electrolyte solution. Specifically, Ni—Fe binary system samples (catalysts) were Ni 83.6 Fe 16.3 -ns, Ni 76.6 Fe 23.5 -ns, Ni 61.5 Fe 38.5 -ns. and Ni 58.8 Fe 41.2 -ns were used.
  • Ni--Fe--Co ternary system samples (catalysts) constituting the present invention Ni 65.6 Fe 33.7 Co 0.6 -hmh, Ni 11.5 Fe 70.5 Co 18 -hmh and Ni 8.2 Fe 85 Co 6.8 -hmh was used.
  • tests were also conducted in the case of using Co-ns and Fe-hmh as catalysts.
  • the smallest overvoltage was obtained with Ni 11.5 Fe 70.5 Co 18 -hmh as a catalyst among the Ni—Fe—Co ternary system samples constituting the present invention. was used for In addition, when the Ni-Fe-Co ternary system samples constituting the present invention are used, any sample is stable at a small overvoltage, and most of the samples use Co-ns. A smaller overvoltage was obtained. Among the Ni-Fe-Co ternary system samples, the overvoltage was slightly higher for the composition with the cobalt content as low as 0.6 compared to the case where Co-ns was used, but it was not inferior. was as much as possible.
  • Ni anodes Four types of Ni anodes and three types of anodes each having a different catalyst layer formed on the Ni substrate were used for each, and durability tests were performed according to the above procedure, and the results obtained are shown in FIG. Specifically, a Ni anode, a Ni anode with a Co-ns catalyst layer formed thereon, an anode with a Ni-Co spinel oxide catalyst layer formed by a pyrolysis method, and a Fe-hmh catalyst layer were formed. Four kinds of Ni anodes (an example in which the effect of the present invention was obtained) were used. As shown in FIG.
  • the electrode composition of the latter was found to be a composition ratio of Fe 55 Co 45 -hmh from ICP analysis of an aqueous solution in which these were dissolved.
  • FIG. 12 shows changes in overvoltage when electrodes were prepared by depositing catalyst layers having different structures as described above and electrolysis was continuously performed at a current density of 100 mA/cm 2 . As shown in FIG. 12, the electrode produced by coexisting the Fe-hmh component and the Co-ns component yielded a lower overvoltage than the electrode of the single component of Fe-hmh. In order to show the effect of the above configuration, FIG. 12 also shows the test results when the Co-ns component was dispersed alone in the electrolytic solution.
  • FIG. 13 using an electrolytic solution having a structure in which the above-mentioned two different catalyst components are dispersed at different addition ratios, electrodes with different catalyst layers deposited on each electrode are produced, and the resulting electrode is obtained after electrolysis.
  • the amount of Fe deposited with respect to the amount of Co deposited, and changes in overvoltage when electrolyzed at a current density of 100 mA/cm 2 are shown.
  • " ⁇ " in FIG. 13 indicates the amount of Fe deposited with respect to the amount of Co deposited, and " ⁇ " in FIG. 13 indicates the change in overvoltage.
  • the electrode with an increased Co-ns component deposition amount had an increased Fe-hmh deposition amount and at the same time a decreased overvoltage.
  • Example 1 As the anode substrate, a nickel expanded mesh (10 cm ⁇ 10 cm, LW ⁇ 3.7 SW ⁇ 0.9 ST ⁇ 0.8 T) was subjected to a chemical etching treatment by being immersed in 17.5% by mass hydrochloric acid for 6 minutes near the boiling point. Using. This expanded mesh was blasted (0.3 MPa) with 60-mesh alumina particles, immersed in 20% by mass hydrochloric acid, and chemically etched for 6 minutes near the boiling point. An aqueous solution containing a precursor component of lithium-containing nickel oxide was applied to the surface of the anode substrate after the chemical etching treatment with a brush, and then dried at 80° C. for 15 minutes. Then, heat treatment was performed at 600° C. for 15 minutes in an air atmosphere. The above-described treatments from application of the aqueous solution to heat treatment were repeated 20 times to obtain an intermediate having an intermediate layer (composition: Li 0.5 Ni 1.5 O 2 ) formed on the surface of the anode substrate.
  • NiFeCo-hmh dispersion as described in Examination Example 1 was used, and the dispersion was added to the electrolytic solution described in Examination Example 1 so that the concentration of the dispersion added was 1 mL / L.
  • An electrolytic solution in which the catalyst used in this example is dispersed was prepared by adjusting as follows. Then, using this electrolytic solution, the same electrolysis operation as described in Examination Example 1 was performed to form a catalyst layer composed of Ni x Fe y Co z -hmh on the surface of the intermediate formed as described above. A formed Ni anode (anode for oxygen evolution) was obtained.
  • Alkaline water electrolysis was performed using the zero-gap electrolysis cell obtained as described above. At that time, a 25 mass % KOH aqueous solution in which the above NiFeCo-hmh dispersion used for forming the catalyst layer of the Ni anode was added at a concentration of 1 mL/L was used as the electrolyte. Then, the electrolytic solution was supplied to each of the anode chamber and the cathode chamber constituting the electrolytic cell, and electrolysis was performed for 6 hours at a current density of 6 kA/m 2 . Then, the anode and cathode were short-circuited (0 kA/m 2 ) and stopped for 15 hours. A shutdown test was conducted in which the operation from electrolysis to stop described above is one cycle. As a result, it was confirmed that the voltage was kept stable in 20 shutdown tests.
  • An example of the application of the present invention is a uniquely configured oxygen evolution anode using a hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh ) for the catalyst layer. Then, using the oxygen-evolving anode, an electrolytic solution in which Ni x Fe y Co z -hmh is dispersed is supplied at least to the anode chamber, and electrolysis is performed in a usual manner. can be deposited in a short time, it is possible to effectively recover the catalytic activity of the catalyst layer.
  • NixFeyCoz - hmh hybrid nickel-iron-cobalt hydroxide
  • an electrolytic solution in which Fe-hmh made of a very general-purpose material is dispersed, or a large amount of Fe-hmh in which Fe-hmh and Co-ns are dispersed and coexisted are deposited. and an oxygen-evolving anode in which a catalyst layer is formed using an electrolytic solution that has been confirmed to be

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Abstract

Provided is an electrolysis technique by which it is possible to form a large amount of catalysts in a short time in a simple manner with constant current electrolysis so as to more efficiently form a catalyst layer, and which has a high practical value due to an exceedingly durable anode for alkaline water electrolysis that lowers susceptibility to deterioration in electrolysis performance during electrolytic operation even if power having large output fluctuations is used as the power source, and that more stably and efficiently maintains excellent catalytic activity over a long period of time.　Provided are an anode for alkaline water electrolysis and an alkaline water electrolysis method in which an electrolyte solution, in which hybrid nickel/iron/cobalt hydroxide (NixFeyCoz-hmh) of a complex of metal hydroxide and organic matter is dispersed, is supplied as a catalyst to at least an anode chamber of an electrolysis cell, electrolytic precipitation of NiFeCo-hmh is performed in the electrolysis cell during operation, and electrolytic precipitation and deposition of NixFeyCoz-hmh is performed on a surface of a conductive substrate obtained by forming a catalyst layer and constituting an oxygen generating anode, thereby recovering and improving electrolysis performance.

Description

アルカリ水電解方法及びアルカリ水電解用アノードAlkaline water electrolysis method and anode for alkaline water electrolysis
　本発明は、アルカリ水電解方法及びアルカリ水電解用アノードに関する。詳しくは、特に、電解セルを構成する少なくともアノード室に、良好な分散性を示す特有の構成の触媒を分散させた電解液を、必要に応じて供給するという簡便な手段によって、多量の触媒を短時間で形成することを可能にして、酸素発生用アノードの触媒活性を長期間にわたって維持させることを実現し、これにより、再生可能エネルギーなどの出力変動の大きい電力を動力源とした場合であっても、電解性能が劣化しにくく、長期間にわたってより安定したアルカリ水電解を行うことができる技術に関する。 The present invention relates to an alkaline water electrolysis method and an anode for alkaline water electrolysis. Specifically, a large amount of the catalyst can be added to at least the anode chamber constituting the electrolytic cell by a simple means of supplying, as needed, an electrolytic solution in which a catalyst having a unique structure exhibiting good dispersibility is dispersed. It is possible to form the catalyst in a short time and maintain the catalytic activity of the oxygen generating anode for a long period of time. The present invention relates to a technology that makes it possible to perform more stable alkaline water electrolysis over a long period of time without deteriorating the electrolysis performance.
　水素は、貯蔵及び輸送に適しているとともに、環境負荷が小さい二次エネルギーであるため、水素をエネルギーキャリアに用いた水素エネルギーシステムに関心が集まっている。現在、水素は主に化石燃料の水蒸気改質などにより製造されている。しかし、地球温暖化や化石燃料枯渇の問題の観点から、基盤技術の中でも、太陽光発電や風力発電といった再生可能エネルギーからの水電解による水素製造が重要になってきている。水電解は、低コストで大規模化に適しており、水素製造の有力な技術である。 Hydrogen is a secondary energy that is suitable for storage and transportation and has a small environmental impact, so there is growing interest in hydrogen energy systems that use hydrogen as an energy carrier. Currently, hydrogen is mainly produced by steam reforming of fossil fuels. However, from the viewpoint of global warming and the depletion of fossil fuels, hydrogen production by water electrolysis from renewable energies such as solar power and wind power has become important among the basic technologies. Water electrolysis is low cost and suitable for large-scale production, and is a promising technology for hydrogen production.
　現状の実用的な水電解は大きく２つに分けられる。１つはアルカリ水電解であり、電解質に高濃度アルカリ水溶液が用いられている。もう１つは、固体高分子型水電解であり、電解質に固体高分子膜（ＳＰＥ）が用いられている。大規模な水素製造を水電解で行う場合は、高価な貴金属を多量に用いた電極が必要な固体高分子型水電解よりも、ニッケル等の鉄系金属などの安価な材料を用いるアルカリ水電解の方が適していると言われている。 Current practical water electrolysis can be roughly divided into two types. One is alkaline water electrolysis, in which a high-concentration alkaline aqueous solution is used as an electrolyte. The other is solid polymer type water electrolysis, in which a solid polymer membrane (SPE) is used as an electrolyte. Alkaline water electrolysis that uses inexpensive materials such as iron-based metals such as nickel, rather than solid polymer type water electrolysis that requires electrodes that use a large amount of expensive precious metals, when large-scale hydrogen production is performed by water electrolysis. is said to be more suitable.
　高濃度アルカリ水溶液は、温度上昇に伴って電導度が高くなるが、腐食性も高くなる。このため、アルカリ水電解の操業温度の上限は８０～９０℃程度に抑制されている。近年、高温及び高濃度のアルカリ水溶液に耐える、電解槽の構成材料や各種配管材料の開発、低抵抗隔膜、及び、表面積を拡大し触媒を付与した電極の開発により、電解セル電圧は、電流密度０．６Ａｃｍ－２において２Ｖ以下にまで向上している。 A high-concentration alkaline aqueous solution increases in conductivity as the temperature rises, but also in corrosiveness. For this reason, the upper limit of the operating temperature of alkaline water electrolysis is suppressed to about 80 to 90°C. In recent years, due to the development of electrolytic cell constituent materials and various piping materials that can withstand high temperatures and high concentrations of alkaline aqueous solutions, the development of low-resistance diaphragms, and the development of electrodes with enlarged surface areas and catalysts, the electrolysis cell voltage is reduced to the current density. It is improved to 2V or less at 0.6 Acm −2 .
　アルカリ水電解用の陽極（アノード）として、高濃度アルカリ水溶液中で安定なニッケル系材料が使用されており、安定な動力源を用いたアルカリ水電解の場合、ニッケル系アノードは、数十年以上の寿命を有することが報告されている（非特許文献１及び２）。しかし、再生可能エネルギーを動力源とすると、激しい起動停止や負荷変動などの過酷な条件となる場合が多く、ニッケル系アノードの性能の劣化が問題とされている（非特許文献３）。 As anodes for alkaline water electrolysis, nickel-based materials that are stable in highly concentrated aqueous alkaline solutions are used. In alkaline water electrolysis using a stable power source, nickel-based anodes have been used for decades or more. (Non-Patent Documents 1 and 2). However, when renewable energy is used as a power source, there are many cases where severe conditions such as severe start-up and stoppages and load fluctuations occur, and deterioration of the performance of nickel-based anodes is a problem (Non-Patent Document 3).
　ニッケル酸化物の生成反応、及び、生成したニッケル酸化物の還元反応は、いずれも金属表面にて進行する。このため、これらの反応に伴い、金属表面に形成された電極触媒の脱離が促進される。電解のための電力が供給されなくなると、電解が停止し、ニッケル系アノードは、酸素発生電位（１．２３Ｖ　ｖｓ．ＲＨＥ）より低い電位、かつ、対極である水素発生用の陰極（カソード）（０．００Ｖ　ｖｓ．ＲＨＥ）より高い電位に維持される。電解セル内では、種々の化学種による起電力が発生しており、電池反応の進行によりアノード電位は低く維持され、ニッケル酸化物の還元反応が促進される。 Both the production reaction of nickel oxide and the reduction reaction of the produced nickel oxide proceed on the metal surface. Therefore, these reactions promote detachment of the electrode catalyst formed on the metal surface. When the power for electrolysis is no longer supplied, the electrolysis stops, and the nickel-based anode has a potential lower than the oxygen generation potential (1.23 V vs. RHE) and the counter electrode, the cathode for hydrogen generation (cathode) ( 0.00 V vs. RHE). Electromotive force is generated by various chemical species in the electrolytic cell, and the anode potential is kept low as the cell reaction progresses, promoting the reduction reaction of nickel oxide.
　電池反応によって生じた電流は、例えば、アノード室とカソード室等の複数のセルを組み合わせた電解槽の場合、セル間を連結する配管を介してリークする。このような電流のリークを防止する対策としては、例えば、停止時に微小な電流を流し続けるようにするなどの方法がある。しかし、停止時に微小な電流を流し続けるには、特別な電源制御が必要になるとともに、酸素及び水素を常に発生させることになるため、運用管理上、過度の手間がかかる。また、逆電流状態を意図的に避けるために、停止直後に液を抜いて電池反応を防止することは可能であるが、再生エネルギーのような出力変動の大きい電力での稼動を想定した場合は、適切な処置であるとは言い難い。 For example, in the case of an electrolytic cell that combines multiple cells such as an anode chamber and a cathode chamber, the current generated by the battery reaction leaks through the piping that connects the cells. As a countermeasure for preventing such current leakage, for example, there is a method of continuing to flow a very small current when the device is stopped. However, in order to continue to flow a minute current when stopped, special power supply control is required, and oxygen and hydrogen are always generated, which requires an excessive amount of time and effort in terms of operation management. In addition, in order to intentionally avoid a reverse current state, it is possible to prevent the battery reaction by removing the liquid immediately after stopping, but if you assume operation with power with large output fluctuations such as renewable energy, , is not an appropriate measure.
　ここで、従来、アルカリ水電解に使用される酸素発生用アノードの触媒（陽極触媒）として、白金族金属、白金族金属酸化物、バルブ金属酸化物、鉄族酸化物、ランタニド族金属酸化物などが利用されている。その他のアノード触媒としては、Ｎｉ－Ｃｏ、Ｎｉ－Ｆｅなど、ニッケルをベースにした合金系；表面積を拡大したニッケル；スピネル系のＣｏ３Ｏ４、ＮｉＣｏ２Ｏ４、ペロブスカイト系のＬａＣｏＯ３、ＬａＮｉＯ３などの導電性酸化物（セラミック材料）；貴金属酸化物；ランタニド族金属と貴金属からなる酸化物なども知られている（非特許文献３）。 Here, conventionally, the oxygen generating anode catalyst (anode catalyst) used in alkaline water electrolysis includes platinum group metals, platinum group metal oxides, valve metal oxides, iron group oxides, lanthanide group metal oxides, and the like. is used. Other anode catalysts include nickel-based alloy systems such as Ni—Co, Ni—Fe; nickel with increased surface area; spinel-based Co 3 O 4 , NiCo 2 O 4 , perovskite-based LaCoO 3 , LaNiO; Conductive oxides (ceramic materials) such as 3 ; noble metal oxides; and oxides composed of lanthanide group metals and noble metals are also known (Non-Patent Document 3).
　近年、高濃度アルカリ水電解に使用される酸素発生用アノードとして、種々の構成のものが提案されている。例えば、リチウムとニッケルを所定のモル比で含むリチウム含有ニッケル酸化物触媒層をニッケル基体表面に形成した、アルカリ水電解用陽極（特許文献１）や、ニッケルコバルト系酸化物と、イリジウム酸化物又はルテニウム酸化物とを含む触媒層をニッケル基体表面に形成した、アルカリ水電解用陽極（特許文献２）が提案されている。 In recent years, various configurations have been proposed as oxygen generating anodes used in high-concentration alkaline water electrolysis. For example, an anode for alkaline water electrolysis in which a lithium-containing nickel oxide catalyst layer containing lithium and nickel at a predetermined molar ratio is formed on the surface of a nickel substrate (Patent Document 1); An anode for alkaline water electrolysis is proposed in which a catalyst layer containing ruthenium oxide is formed on the surface of a nickel substrate (Patent Document 2).
　本発明者らは、上記で提案されている従来技術の課題を解決する技術として、既に、従来にない構成の酸素発生用アノードを提案している。具体的には、表面がニッケル又はニッケル基合金からなる導電性基体の表面上に、金属水酸化物と有機物との複合体のハイブリッド水酸化コバルトナノシート（Ｃｏ－ｎｓ）を含んでなる触媒層を設けてなる酸素発生用アノードを提案した。さらに、この酸素発生用アノードを用い、前記触媒層の形成成分であるハイブリッド水酸化コバルトナノシート（Ｃｏ－ｎｓ）を分散させた電解液を、電解セルを構成するアノード室とカソード室に供給し、各室での電解に共通して用いるアルカリ水電解方法を提案した（特許文献３、非特許文献４）。 The present inventors have already proposed an oxygen generating anode with an unprecedented structure as a technique for solving the problems of the conventional techniques proposed above. Specifically, a catalyst layer comprising hybrid cobalt hydroxide nanosheets (Co-ns), which is a composite of a metal hydroxide and an organic substance, is placed on the surface of a conductive substrate whose surface is made of nickel or a nickel-based alloy. An anode for oxygen evolution is proposed. Furthermore, using this oxygen generating anode, an electrolytic solution in which hybrid cobalt hydroxide nanosheets (Co-ns), which is a component of the catalyst layer, is dispersed is supplied to the anode chamber and the cathode chamber constituting the electrolytic cell, We proposed an alkaline water electrolysis method commonly used for electrolysis in each chamber (Patent Document 3, Non-Patent Document 4).
　また、上記電解方法により形成された電極の性能には改良する余地があったため、ナノシート成分についてさらなる検討を行い、下記の技術を提案した。具体的には、金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄ナノシート（ＮｉＦｅ－ｎｓ）を含んでなる触媒層を設けてなる酸素発生用アノードが、より電極性能に優れていることを見出し、ＮｉＦｅ－ｎｓを分散させた電解液を、電解セルを構成するアノード室とカソード室に供給し、各室での電解に共通して用いるアルカリ水電解方法を提案した（特許文献４）。 In addition, since there was room for improvement in the performance of the electrodes formed by the above electrolysis method, we further studied the nanosheet components and proposed the following technology. Specifically, an oxygen generating anode provided with a catalyst layer containing hybrid nickel hydroxide/iron nanosheets (NiFe-ns), which is a composite of a metal hydroxide and an organic substance, has excellent electrode performance. Therefore, the inventors proposed an alkaline water electrolysis method in which an electrolytic solution in which NiFe-ns is dispersed is supplied to an anode chamber and a cathode chamber that constitute an electrolytic cell, and is commonly used for electrolysis in each chamber (Patent document 4).
特開２０１５－８６４２０号公報JP 2015-86420 A 特開２０１７－１９０４７６号公報JP 2017-190476 A 再表２０２０／１８４６０７号公報Retable 2020/184607 特開２０２１－１３９０２７号公報JP 2021-139027 A
　しかしながら、本発明者らの検討によれば、前記した特許文献４の技術では、ＮｉＦｅ－ｎｓのアルカリ水溶液における分散性が劣り、電解セル内で十分な触媒層を短時間で形成することが困難であるという新たな課題があった。この点は実用上の障害となる懸念があり、解決すべき重要な課題である。ここで、先に述べた特許文献３のＣｏ－ｎｓを利用した技術、この技術を進展させた特許文献４のＮｉＦｅ－ｎｓを利用した技術によれば、いずれも優れた電極触媒活性が得られる。しかし、本発明者らの検討によれば、ＮｉＦｅ－ｎｓを触媒に利用した、より効果的であるアルカリ水電解用アノードであっても、さらなる進展が求められる。具体的には、これらの技術が目的としている、従来のアルカリ水電解用アノードは、再生可能エネルギーなどの出力変動の大きい電力を動力源とした場合に、電解性能が低下（劣化）しやすく、長期間にわたって安定的に使用することが困難であるとした技術課題に対し、未だ十分であるとは言い難かった。すなわち、上記技術課題を十分に解決するためには、激しい起動停止や電位負荷変動による電位変動に対して、使用する酸素発生用アノードの性能の低下が生じた場合に、より速やかに電解性能を回復、向上させることができる高耐久化が求められる。なお、本願の明細書では、酸素発生を行うアルカリ水電解用アノードのことを「酸素発生用アノード」とも呼ぶ。 However, according to the studies of the present inventors, the technique of Patent Document 4 described above has poor dispersibility of NiFe-ns in an alkaline aqueous solution, and it is difficult to form a sufficient catalyst layer in an electrolytic cell in a short time. There was a new problem of This is an important problem to be solved because there is a concern that this point will become an obstacle in practical use. Here, according to the technology using Co-ns of Patent Document 3 described above and the technology using NiFe-ns of Patent Document 4, which is an advanced version of this technology, excellent electrode catalyst activity can be obtained. . However, according to the study of the present inventors, further development is required even for more effective anodes for alkaline water electrolysis using NiFe-ns as a catalyst. Specifically, the conventional anode for alkaline water electrolysis, which is the target of these technologies, is likely to deteriorate (degrade) in electrolysis performance when powered by electric power with large output fluctuations such as renewable energy. It was difficult to say that it was still sufficient for the technical problem that it was difficult to use it stably over a long period of time. In other words, in order to fully solve the above technical problems, it is necessary to improve the electrolysis performance more quickly when the performance of the oxygen generating anode used decreases due to potential fluctuations due to sudden start-up and stoppages and potential load fluctuations. High durability that can be recovered and improved is required. In the specification of the present application, the anode for alkaline water electrolysis that generates oxygen is also referred to as the "oxygen generating anode".
　本発明は、このような従来技術に鑑みてなされたものであり、その課題とするところは、再生可能エネルギーなどの出力変動の大きい電力を動力源とした場合であっても、電解性能が劣化しにくく、優れた触媒活性が長期間にわたって、より安定して維持される耐久性に優れる有用な電解用電極を提供することにある。また、本発明が最終的に課題とするところは、上記の優れた電解用電極を用いることで、出力変動の大きい電力を動力源とした場合であっても、電解性能が劣化しにくく、長期間にわたって、より安定したアルカリ水電解を行うことを実現したアルカリ水電解の運転方法を提供することにある。 The present invention has been made in view of such conventional technology, and its problem is that even when power sources such as renewable energy with large output fluctuations are used as power sources, the electrolytic performance deteriorates. To provide a useful electrode for electrolysis which is difficult to degrade, maintains excellent catalytic activity more stably over a long period of time, and has excellent durability. In addition, the final object of the present invention is that by using the above-described excellent electrode for electrolysis, even when the power source is an electric power with large output fluctuations, the electrolysis performance is less likely to deteriorate, and the electrolysis can be performed for a long time. To provide an operating method of alkaline water electrolysis that realizes more stable alkaline water electrolysis over a period of time.
　したがって、本発明の目的は、先に挙げた本発明者らが開発した技術をさらに進展させて、工業上、より効果的に利用できる技術にすることにある。具体的には、触媒に、Ｃｏ－ｎｓや、ＮｉＦｅ－ｎｓを利用した従来技術の場合よりも、出力変動の大きい電力を動力源とした場合に、電解性能が劣化しにくく、劣化した電解性能を効率よく回復させることができる（すなわち、触媒層が電解によって自己修復する）、優れた触媒活性がより長期間にわたって安定して維持される、耐久性により優れた酸素発生用アノードを開発することである。また、このような優れた効果が得られる酸素発生用アノードの触媒層を、より汎用性の高い材料で、しかも簡便な電解方法で、効率よく長期間にわたって形成することができる技術を開発することにある。 Therefore, the purpose of the present invention is to further develop the above-mentioned technology developed by the inventors and make it a technology that can be used more effectively industrially. Specifically, compared to the conventional technology using Co-ns or NiFe-ns as a catalyst, when electric power with large output fluctuation is used as a power source, the electrolysis performance is less likely to deteriorate, and the electrolysis performance deteriorates. (i.e., the catalyst layer is self-repairing by electrolysis), excellent catalytic activity is stably maintained for a longer period, and a more durable anode for oxygen evolution is developed. is. Also, to develop a technology that can efficiently form the catalyst layer of the oxygen generating anode that provides such excellent effects over a long period of time, using a more versatile material and using a simple electrolysis method. It is in.
　上記の目的は、下記の本発明によって達成される。すなわち、本発明は、以下のアルカリ水電解方法を提供する。なお、本発明において使用する「ｈｍｈ」の表示は、「ｈｙｂｒｉｄ　ｍｅｔａｌ　ｈｙｄｒｏｘｉｄｅ」の略である。
［１］金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒を分散させた電解液を、電解セルを構成するアノード室とカソード室に供給し、各室での電解に共通して用いることを特徴とするアルカリ水電解方法。 The above objects are achieved by the present invention described below. That is, the present invention provides the following alkaline water electrolysis method. The expression "hmh" used in the present invention is an abbreviation for "hybrid metal hydroxide".
[1] An electrolytic cell is composed of an electrolytic solution in which a catalyst containing hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh ), which is a composite of a metal hydroxide and an organic substance, is dispersed. An alkaline water electrolysis method characterized by supplying an anode chamber and a cathode chamber and using it in common for electrolysis in each chamber.
［２］金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒を分散させた電解液を、電解セルを構成する少なくともアノード室に供給し、運転中に、前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈの電解析出を前記電解セル内にて行い、酸素発生用アノードを構成する、表面に触媒層が形成されてなる導電性基体の表面に、前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈを電解析出させることで、電解性能を回復、向上させることを特徴とするアルカリ水電解方法。 [2] An electrolytic cell is composed of an electrolytic solution in which a catalyst containing hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh ), which is a composite of a metal hydroxide and an organic substance, is dispersed. The Ni x Fe y Co z -hmh is supplied to at least the anode chamber, and during operation, the Ni x Fe y Co z -hmh is electrolytically deposited in the electrolysis cell to constitute the anode for oxygen generation, and a catalyst layer is formed on the surface. A method of electrolyzing alkaline water, comprising electrolytically depositing the Ni x Fe y Co z -hmh on the surface of a conductive substrate to recover and improve electrolysis performance.
　上記したアルカリ水電解方法の好ましい形態として、下記のものが挙げられる。
［３］前記電解液の供給を、間欠的に行う［１］又は［２］に記載のアルカリ水電解方法。
［４］前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈが、いずれも１～２００ｎｍの範囲内の大きさの物質である、層状の分子構造を有するシート状の物質、トンネル構造の針状形状の物質及びアモルファス構造の粒子状の物質の少なくともいずれかを有する［１］～［３］に記載のアルカリ水電解方法。
［５］前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈを導電性基体の表面に電解析出させる条件が、前記導電性基体を、１．２Ｖ～１．８Ｖ　ｖｓ．ＲＨＥの電位範囲に保持することである［２］～［４］に記載のアルカリ水電解方法。
［６］前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈを分散させた電解液として、濃度が５～１００ｇ／ＬであるＮｉｘＦｅｙＣｏｚ－ｈｍｈ分散液を用い、該ＮｉｘＦｅｙＣｏｚ－ｈｍｈ分散液の電解液への添加濃度が０．１～８ｍＬ／Ｌの範囲内になるように調整したものを用いる［１］～［５］のいずれかに記載のアルカリ水電解方法。
［７］前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈは、Ｎｉ／Ｆｅ／Ｃｏの原子比が、０．１～０．９／０．１～０．９／０．１～０．９である［１］～［６］のいずれか１項に記載のアルカリ水電解方法。 Preferred embodiments of the alkaline water electrolysis method described above include the following.
[3] The alkaline water electrolysis method according to [1] or [2], wherein the electrolytic solution is supplied intermittently.
[4] The Ni x Fe y Co z -hmh is a substance having a size within the range of 1 to 200 nm, a sheet-like substance having a layered molecular structure, a needle-like substance having a tunnel structure, and The alkaline water electrolysis method according to [1] to [3], which contains at least one of particulate substances having an amorphous structure.
[5] The condition for electrolytically depositing the Ni x Fe y Co z -hmh on the surface of the conductive substrate is 1.2 V to 1.8 V vs. The alkaline water electrolysis method according to [2] to [4], wherein the potential range of RHE is maintained.
[6] As the electrolytic solution in which the Ni x Fe y Co z -hmh is dispersed, a Ni x Fe y Co z -hmh dispersion having a concentration of 5 to 100 g/L is used, and the Ni x Fe y Co z - The alkaline water electrolysis method according to any one of [1] to [5], wherein the concentration of the hmh dispersion added to the electrolytic solution is adjusted to be within the range of 0.1 to 8 mL/L.
[7] Ni x Fe y Co z -hmh has an atomic ratio of Ni/Fe/Co of 0.1 to 0.9/0.1 to 0.9/0.1 to 0.9 [ 1] The alkaline water electrolysis method according to any one of [6].
　また、本発明は、別の実施形態として、上記アルカリ水電解方法に適用した場合に有用な、以下のアルカリ水電解用アノードを提供する。
［８］表面がニッケル又はニッケル基合金からなる導電性基体と、該導電性基体の表面上に形成された、金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒層と、を備えてなることを特徴とする酸素発生を行うアルカリ水電解用アノード。
［９］表面がニッケル又はニッケル基合金からなる導電性基体と、該導電性基体の表面上に形成された、組成式ＬｉｘＮｉ２－ｘＯ２（０．０２≦ｘ≦０．５）で表されるリチウム含有ニッケル酸化物からなる中間層と、該中間層の表面上に形成された、金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒層と、を備えてなることを特徴とする酸素発生を行うアルカリ水電解用アノード。 In another embodiment, the present invention provides the following anode for alkaline water electrolysis, which is useful when applied to the alkaline water electrolysis method.
[8] A hybrid nickel-iron-cobalt hydroxide (Ni and a catalyst layer containing x Fe y Co z -hmh), and an anode for alkaline water electrolysis that generates oxygen.
[9] A conductive substrate having a surface made of nickel or a nickel-based alloy, and a composition formula of Li x Ni 2-x O 2 (0.02≦x≦0.5) formed on the surface of the conductive substrate. and a hybrid nickel-iron-cobalt hydroxide (Ni x Fe y and a catalyst layer comprising Co z -hmh), and an anode for alkaline water electrolysis that generates oxygen.
　本発明によれば、再生可能エネルギーなどの出力変動の大きい電力を動力源とした場合であっても、電解運転中に電解性能が劣化しにくく、優れた触媒活性が長期間にわたって、より安定して効率よく維持される、より耐久性に優れる酸素発生を行うアルカリ水電解用アノード（酸素発生用アノード）の提供が可能になる。また、本発明によれば、アノード室とカソード室に共通の電解液を供給するという簡便な手段によって、あるいは、アノード室に必要に応じて特有の触媒を分散させた電解液を供給するという簡便な手段によって、より効率よく、酸素発生用アノードの触媒活性を長期間にわたって安定して維持させることが実現可能になる。本発明によれば、特に、出力変動の大きい電力を動力源とした場合に、酸素発生用アノードの電解性能が劣化しにくく、長期間にわたってより安定したアルカリ水電解を行うことが実現可能な、工業上、有用なアルカリ水電解方法を提供することができる。さらに、本発明で利用する、上記の優れた効果が得られるアルカリ水電解用アノードの触媒層を構成する材料は、汎用性の高いものであり、また、定電流の電解で簡便に、多量の触媒を短時間で形成（堆積）して、より効率よく触媒層の形成、特に触媒層の自己修復が安定して効率よくできるので、工業上の利用性により優れており、その実用価値は極めて高い。上記した優れた効果は、本発明者らが新たに提案した、金属水酸化物と有機物とのハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒層を設けてなる酸素発生用アノード、及び、該アノードを用い、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを分散させた電解液で電解を行う新たなアルカリ水電解方法によって容易に得られる。また、極めて汎用な鉄イオンと、有機物とのハイブリッド（Ｆｅ－ｈｍｈ）を含んでなる触媒層を設けてなる酸素発生用アノードによっても、従来技術と比較して、上記したような良好な効果を得ることができることについても確認した。あるいはまた、Ｆｅ－ｈｍｈのみでなく、Ｆｅ－ｈｍｈとＣｏ－ｎｓを共存させた触媒層を設けてなる酸素発生用アノードにした構成にすることで、Ｆｅ－ｈｍｈを単独で含む触媒層の場合、Ｃｏ－ｎｓを単独で含む触媒層の場合のいずれの場合よりも、より良好な性能を示すことを確認した。 According to the present invention, even when power sources such as renewable energy with large output fluctuations are used as the power source, the electrolysis performance is less likely to deteriorate during the electrolysis operation, and the excellent catalytic activity is more stable over a long period of time. It is possible to provide an anode for alkaline water electrolysis (anode for oxygen generation) that generates oxygen efficiently and with excellent durability. Further, according to the present invention, a simple means of supplying a common electrolytic solution to the anode chamber and the cathode chamber, or a simple method of supplying an electrolytic solution in which a specific catalyst is dispersed to the anode chamber as required. This means makes it possible to more efficiently maintain the catalytic activity of the oxygen generating anode stably over a long period of time. According to the present invention, the electrolysis performance of the oxygen generating anode is less likely to deteriorate, particularly when electric power with large output fluctuations is used as the power source, and it is possible to perform more stable alkaline water electrolysis over a long period of time. An industrially useful alkaline water electrolysis method can be provided. Furthermore, the material used in the present invention, which constitutes the catalyst layer of the anode for alkaline water electrolysis that provides the above-described excellent effects, is highly versatile, and can be easily used in electrolysis at constant current to produce a large amount of By forming (depositing) the catalyst in a short time, the formation of the catalyst layer can be performed more efficiently, especially the self-healing of the catalyst layer can be stably and efficiently performed. expensive. The above-mentioned excellent effects are obtained by using a catalyst layer containing a hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh) of a metal hydroxide and an organic substance newly proposed by the present inventors. It can be easily obtained by a new alkaline water electrolysis method in which electrolysis is performed using the provided oxygen generating anode and an electrolytic solution in which Ni x Fe y Co z -hmh is dispersed. In addition, even with an oxygen generating anode provided with a catalyst layer containing a hybrid of iron ions and an organic matter (Fe-hmh), which is extremely versatile, the above-described favorable effects can be obtained as compared with the conventional technology. Also check what you can get. Alternatively, in the case of a catalyst layer containing Fe-hmh alone, by configuring an anode for oxygen generation in which a catalyst layer in which not only Fe-hmh but also Fe-hmh and Co-ns coexist is provided. , Co-ns alone showed better performance than either case.
本発明のアルカリ水電解方法で用いる酸素発生用アノードの一実施形態を模式的に示す断面図である。BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically one Embodiment of the anode for oxygen evolution used with the alkaline water electrolysis method of this invention. 本発明で使用する触媒成分の一例の、三脚型配位子を有する層状のＮｉｘＦｅｙＣｏｚ－Ｔｒｉｓ－ＮＨ２の分子構造を模式的に示す図である。1 is a diagram schematically showing the molecular structure of layered Ni x Fe y Co z -Tris-NH 2 having tripodal ligands, which is an example of a catalyst component used in the present invention. FIG. 本発明で使用する触媒成分の一例の、三脚型配位子を有するＮｉｘＦｅｙＣｏｚ－Ｔｒｉｓ－ＮＨ２の、トンネル構造の針状形状の物質を模式的に示す図である。FIG. 2 is a diagram schematically showing a needle-shaped tunnel-structured substance of Ni x Fe y Co z -Tris-NH 2 having tripodal ligands, which is an example of a catalyst component used in the present invention. 本発明を構成する触媒の製法例の概略と、得られる反応生成物の一例を模式的に示す図である。BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an outline of the manufacturing method example of the catalyst which comprises this invention, and an example of the reaction product obtained typically. 検討例１の電位サイクルにおける、本発明を構成する触媒Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈを利用した場合の電流－電位変化（活性変化）を示すグラフである。2 is a graph showing the current-potential change (activity change) in the potential cycle of Investigation Example 1 when the catalyst Ni 11.5 Fe 70.5 Co 18 -hmh constituting the present invention is used. 検討例１の電位サイクルにおける比較のための、Ｎｉ６１．５Ｆｅ３８．５－ｎｓを触媒に利用した場合の電流－電位変化（活性変化）を示すグラフである。10 is a graph showing current-potential change (activity change) when Ni 61.5 Fe 38.5 -ns is used as a catalyst for comparison in the potential cycle of Investigation Example 1. FIG. 図４Ａと図４Ｂのピーク面積を用いてそれぞれに得た、触媒析出時間と触媒析出量（堆積量）の関係を示したグラフである。4B is a graph showing the relationship between catalyst deposition time and catalyst deposition amount (deposition amount) obtained using the peak areas of FIGS. 4A and 4B ; FIG. 検討例１における、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈを触媒に利用した場合と、Ｎｉ６１．５Ｆｅ３８．５－ｎｓを触媒に利用した場合の、析出時間に対する電解特性の変化を示すグラフである。Changes in electrolysis characteristics with respect to deposition time when Ni 11.5 Fe 70.5 Co 18 -hmh is used as a catalyst and when Ni 61.5 Fe 38.5 -ns is used as a catalyst in Study Example 1 is a graph showing 検討例１で行った加速試験での、それぞれの触媒成分を用いた場合における電解特性の変化を示すグラフである。4 is a graph showing changes in electrolysis characteristics when each catalyst component is used in an accelerated test performed in Study Example 1. FIG. 検討例２で行った定電流で連続電解した試験での、それぞれの触媒成分を用いた場合における電解特性の変化を示すグラフである。4 is a graph showing changes in electrolysis characteristics when each catalyst component is used in a test of continuous electrolysis at constant current conducted in Examination Example 2. FIG. 検討例３で行った加速耐久試験での、それぞれの触媒成分を用いた場合における電解特性の変化を示すグラフである。4 is a graph showing changes in electrolysis characteristics when each catalyst component is used in an accelerated endurance test conducted in Examination Example 3. FIG. 本発明の効果が得られる触媒成分の一例の、Ｆｅ－ｈｍｈ粒子の液中における性状を示す透過型電子顕微鏡写真の図である。FIG. 2 is a transmission electron micrograph showing the properties of Fe-hmh particles in a liquid, which is an example of a catalyst component that produces the effects of the present invention. 本発明の効果が得られる触媒成分の一例であるＦｅ－ｈｍｈ粒子を電解液中に分散させ、電解によりＮｉ基体表面に析出させた状態を示す透過型電子顕微鏡写真の図である。1 is a transmission electron micrograph showing a state in which Fe-hmh particles, which are an example of a catalyst component that produces the effects of the present invention, are dispersed in an electrolytic solution and deposited on the surface of a Ni substrate by electrolysis. FIG. 本発明の効果が得られる触媒成分の一例であるＦｅ－ｈｍｈ粒子をＣｏ－ｎｓ粒子と共存させて電解液中に分散させ、電解によりＮｉ基体表面に析出させた状態を示す電界放射型走査電子顕微鏡(ＦＥ－ＳＥＭ)の図である。Field emission type scanning electrons showing a state in which Fe-hmh particles, which are an example of a catalyst component capable of obtaining the effect of the present invention, are dispersed in an electrolytic solution coexisting with Co-ns particles, and deposited on the surface of a Ni substrate by electrolysis. Fig. 3 is a view of a microscope (FE-SEM); 図１１Ａとは別の視野における析出した状態を示す電界放射型走査電子顕微鏡(ＦＥ－ＳＥＭ)の図である。FIG. 11B is a field-emission scanning electron microscope (FE-SEM) showing the deposited state in a different field of view than FIG. 11A. 検討例４で行った、Ｆｅ－ｈｍｈ粒子を分散させた電解液、Ｆｅ－ｈｍｈ粒子とＣｏ－ｎｓ粒子を共存させた触媒成分を分散させた電解液をそれぞれに用いた場合における電解特性の変化を示すグラフである。Changes in electrolytic characteristics when using an electrolytic solution in which Fe-hmh particles are dispersed and an electrolytic solution in which a catalyst component in which Fe-hmh particles and Co-ns particles coexist are dispersed, respectively, which was performed in Study Example 4. is a graph showing 検討例５で行った、異なった割合でＦｅ－ｈｍｈ粒子とＣｏ－ｎｓ粒子を共存させた触媒成分を分散させた電解液で電解し、電解後に得られたＣｏ析出量に対するＦｅ析出量及び電解特性の変化を示すグラフである。Electrolysis was performed with the electrolytic solution in which the catalyst component in which Fe-hmh particles and Co-ns particles coexisted at different ratios, which was performed in Study Example 5, was dispersed, and the amount of Fe deposited relative to the amount of Co deposited and the amount of electrolysis obtained after electrolysis. 4 is a graph showing changes in characteristics; 検討例５で行った、異なった割合でＦｅ－ｈｍｈ粒子とＣｏ－ｎｓ粒子の触媒成分を共存させて分散させた各電解液で電解し、電解後に得られたＣｏ析出量とＦｅ析出量を示すグラフである。Electrolysis was performed with each electrolytic solution in which the catalyst components of Fe-hmh particles and Co-ns particles were coexisting and dispersed at different ratios as in Study Example 5, and the Co deposition amount and Fe deposition amount obtained after electrolysis were calculated. It is a graph showing.
　以下、好ましい実施の形態を挙げて、本発明について詳細に説明する。前記した非特許文献４において、アノードのための自己修復触媒Ｃｏ－ｎｓを分散させた電解液において、アノードの性能が改善される一方で、カソード電極への影響がほとんどないことが初めて報告された。しかし、先述したように、本発明者らは、これまでにアノードのための新たな自己修復触媒を提案してきたものの、アノード性能にはまだ改善の余地があり、特に実用化にあたって重要になる解決すべき課題があることを見出した。すなわち、これまでに提案したＮｉＦｅ－ｎｓは、アルカリ水溶液における分散性が劣り、このため、電解液に利用した場合に電解セル内で十分な触媒層を短時間で形成することが困難であり、より効率的に安定して電解性能を回復（修復）させる有用な技術の開発が望まれた。本発明者らは、上記課題を解決すべく鋭意検討した結果、第１に、ハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）が、本発明において目的とする高耐久性の自己修復電極触媒として、より効果的に機能し得、この複合体を使用することで、上記した従来技術における課題を、より高いレベルで解決することが可能になることを見出して本発明を完成するに至った。 BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to preferred embodiments. In the above-mentioned Non-Patent Document 4, it was reported for the first time that the electrolyte solution in which the self-repairing catalyst Co-ns for the anode is dispersed improves the performance of the anode while having almost no effect on the cathode electrode. . However, as mentioned above, although the present inventors have so far proposed new self-repairing catalysts for anodes, there is still room for improvement in anode performance. I found that there is a problem to be solved. That is, the NiFe-ns proposed so far has poor dispersibility in an alkaline aqueous solution, and for this reason, when used in an electrolytic solution, it is difficult to form a sufficient catalyst layer in an electrolytic cell in a short time. Development of a useful technique for recovering (restoring) electrolytic performance more efficiently and stably has been desired. As a result of intensive studies by the present inventors to solve the above problems, first, the hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh) has the high durability that is the object of the present invention. can function more effectively as a self-repairing electrode catalyst, and by using this composite, it is possible to solve the above-described problems in the prior art at a higher level. Completed.
　具体的には、本発明者らは、金属水酸化物と有機物の複合体であるハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を、電解液に分散させて用い、自己修復電極触媒として利用することで、ＮｉｘＦｅｙＣｏｚ－ｈｍｈが、触媒及び防食被膜として作用し、電位変動に対してＮｉ系アノードの耐久性を、先に提案したＣｏ－ｎｓを触媒に利用したアノードよりも大幅に向上させることができることを見出した。加えて、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを触媒に利用すると、先に提案した触媒にＮｉＦｅ－ｎｓを利用した場合よりも、電解しながら、より多量の触媒をアノード表面に短時間で形成（堆積）することができ、ＮｉｘＦｅｙＣｏｚ－ｈｍｈは、より効率的に、しかもより安定して電解性能を回復させることができる有用な材料であることを見出した。 Specifically, the present inventors dispersed a hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh), which is a composite of a metal hydroxide and an organic substance, in an electrolytic solution, By using it as a self-repairing electrode catalyst, Ni x Fe y Co z -hmh acts as a catalyst and an anti-corrosion coating, and improves the durability of Ni-based anodes against potential fluctuations, and the previously proposed Co-ns as a catalyst. We have found that it can be significantly improved over the anodes utilized in the prior art. In addition, when Ni x Fe y Co z -hmh is used as a catalyst, a larger amount of catalyst is formed on the anode surface in a shorter time during electrolysis than when NiFe-ns is used as the previously proposed catalyst ( It was found that Ni x Fe y Co z -hmh is a useful material that can recover electrolytic performance more efficiently and more stably.
　また、本発明者らは上記の検討過程で、金属イオンが汎用の金属の鉄のみであるＦｅ－ｈｍｈを触媒に利用したアノードの場合も、電位変動に対してＮｉ系アノードの耐久性を、先に提案しているＣｏ－ｎｓを触媒に利用したアノードよりも向上させることができることを見出した。さらに、上記Ｆｅ－ｈｍｈを触媒に用いた場合の実用性を高めるべく鋭意検討した結果、本発明者らは、下記の構成とすることでより高い効果が得られることを見出した。具体的には、Ｆｅ－ｈｍｈとＣｏ－ｎｓをそれぞれ別個に作製し、これらを共存させた析出物を触媒に利用した構成のアノードの場合も、電位変動に対してＮｉ系アノードの耐久性を、Ｆｅ－ｈｍｈを単独として触媒に利用したアノードよりも向上させることができることを見出した。 In the above study process, the present inventors also found that, even in the case of an anode using Fe-hmh, in which the metal ions are only general-purpose metal iron, as a catalyst, the durability of the Ni-based anode against potential fluctuations We have found that the previously proposed Co-ns can be improved over the catalyzed anode. Furthermore, as a result of intensive studies to improve the practicality of using Fe-hmh as a catalyst, the present inventors have found that the following configuration provides a higher effect. Specifically, Fe-hmh and Co-ns are separately produced, and even in the case of an anode having a structure in which a deposit in which these are coexisted is used as a catalyst, the durability of the Ni-based anode against potential fluctuations is improved. , Fe-hmh alone can be improved over anodes catalyzed by Fe-hmh.
［アノード］
　図１は、本発明のアルカリ水電解方法で用いる、酸素発生を行うアルカリ水電解用アノードの一実施形態を模式的に示す断面図である。図１に示した実施形態の酸素発生用アノード１０は、導電性基体２と、導電性基体２の表面上に形成された中間層４と、中間層４の表面上に形成された触媒層６とを備える。以下、本発明のアルカリ水電解方法で用いる酸素発生用アノードの詳細につき、図面を参照して説明する。なお、下記の説明では、アルカリ水電解用アノードを、図１に示した中間層４を形成した構成としたが、本発明のアルカリ水電解用アノードにおいて中間層４は、必要に応じて導電性基体２と触媒層６との間に形成されるものであり、必須の構成とするものではない。 [anode]
FIG. 1 is a cross-sectional view schematically showing one embodiment of an anode for alkaline water electrolysis that generates oxygen, used in the method for alkaline water electrolysis of the present invention. The oxygen generating anode 10 of the embodiment shown in FIG. and Hereinafter, the details of the oxygen generating anode used in the alkaline water electrolysis method of the present invention will be described with reference to the drawings. In the following description, the anode for alkaline water electrolysis has a structure in which the intermediate layer 4 shown in FIG. 1 is formed. It is formed between the substrate 2 and the catalyst layer 6 and is not an essential component.
＜導電性基体＞
　導電性基体２は、電気分解のための電気を通すための導電体であり、中間層４及び触媒層６を析出する担体としての機能を有する部材である。導電性基体２の少なくとも表面（中間層４が形成される面）は、ニッケル又はニッケル基合金で形成されている。すなわち、導電性基体２は、全体がニッケル又はニッケル基合金で形成されていてもよく、表面のみが、ニッケル又はニッケル基合金で形成されていてもよい。具体的に、導電性基体２は、例えば、鉄、ステンレス、アルミニウム、チタン等の金属材料の表面に、めっき等により、ニッケル又はニッケル基合金のコーティングが施されたものであってもよい。 <Conductive substrate>
The conductive substrate 2 is a conductor that conducts electricity for electrolysis, and is a member that functions as a carrier for depositing the intermediate layer 4 and the catalyst layer 6 . At least the surface of the conductive substrate 2 (the surface on which the intermediate layer 4 is formed) is made of nickel or a nickel-based alloy. That is, the conductive substrate 2 may be entirely made of nickel or a nickel-based alloy, or only the surface thereof may be made of nickel or a nickel-based alloy. Specifically, the conductive substrate 2 may be, for example, a metal material such as iron, stainless steel, aluminum, or titanium coated with nickel or a nickel-based alloy by plating or the like.
　導電性基体２の厚さは、０．０５～５ｍｍ程度であることが好ましい。導電性基体の形状は、生成する酸素や水素等の気泡を除去するための開口部を有する形状であることが好ましい。例えば、エクスパンドメッシュや多孔質エクスパンドメッシュを、導電性基体２として使用することができる。導電性基体が開口部を有する形状である場合、導電性基体の開口率は１０～９５％であることが好ましい。 The thickness of the conductive substrate 2 is preferably about 0.05-5 mm. The shape of the conductive substrate is preferably a shape having openings for removing generated bubbles of oxygen, hydrogen, or the like. For example, an expanded mesh or a porous expanded mesh can be used as the conductive substrate 2 . When the conductive substrate has a shape with openings, the opening ratio of the conductive substrate is preferably 10 to 95%.
　本発明の水電解方法で用いる酸素発生用アノードは、例えば、上記した導電性基体２の表面に、下記のようにして、中間層４と、触媒層６とを形成することで得ることができる。
（前処理工程）
　中間層４、触媒層６の形成工程を行う前に、表面の金属や有機物などの汚染粒子を除去するために、導電性基体２を予め化学エッチング処理することが好ましい。化学エッチング処理による導電性基体の消耗量は、３０ｇ／ｍ２以上、４００ｇ／ｍ２以下程度とすることが好ましい。また、中間層との密着力を高めるために、導電性基体の表面を予め粗面化処理することが好ましい。粗面化処理の手段としては、粉末を吹き付けるブラスト処理や、基体可溶性の酸を用いたエッチング処理や、プラズマ溶射などの方法が挙げられる。 The oxygen generating anode used in the water electrolysis method of the present invention can be obtained, for example, by forming an intermediate layer 4 and a catalyst layer 6 on the surface of the conductive substrate 2 as described below. .
(Pretreatment step)
Before carrying out the steps of forming the intermediate layer 4 and the catalyst layer 6, the conductive substrate 2 is preferably chemically etched in advance in order to remove contaminant particles such as metals and organic substances on the surface. It is preferable that the amount of consumption of the conductive substrate by the chemical etching process is about 30 g/m 2 or more and 400 g/m 2 or less. Moreover, in order to increase the adhesion to the intermediate layer, it is preferable to roughen the surface of the conductive substrate in advance. Examples of means for surface roughening treatment include blasting treatment by spraying powder, etching treatment using base-soluble acid, plasma spraying, and the like.
＜中間層＞
　中間層４は、導電性基体２の表面上に形成される層である。中間層は、導電性基体の腐食等を抑制するとともに、触媒層６を導電性基体に安定的に固着させる。また、中間層は、触媒層に電流を速やかに供給する役割も果たす。中間層は、例えば、組成式ＬｉｘＮｉ２－ｘＯ２（０．０２≦ｘ≦０．５）で表されるリチウム含有ニッケル酸化物で形成するとよい。上記組成式中のｘが０．０２未満であると、導電性が不十分になる。一方、ｘが０．５を超えると、物理的強度及び化学的安定性が低下する。上記組成式で表されるリチウム含有ニッケル酸化物で形成された中間層４は、電解に十分な導電性を有するとともに、長期間使用した場合でも優れた物理的強度及び化学的安定性を示す。 <Middle layer>
The intermediate layer 4 is a layer formed on the surface of the conductive substrate 2 . The intermediate layer suppresses corrosion of the conductive substrate, etc., and stably adheres the catalyst layer 6 to the conductive substrate. The intermediate layer also plays a role of rapidly supplying current to the catalyst layer. The intermediate layer may be made of, for example, a lithium-containing nickel oxide represented by the composition formula Li x Ni 2-x O 2 (0.02≦x≦0.5). If x in the above composition formula is less than 0.02, the conductivity will be insufficient. On the other hand, when x exceeds 0.5, the physical strength and chemical stability decrease. The intermediate layer 4 formed of the lithium-containing nickel oxide represented by the above compositional formula has sufficient electrical conductivity for electrolysis and exhibits excellent physical strength and chemical stability even when used for a long period of time.
　中間層の厚さは、０．０１μｍ以上１００μｍ以下であることが好ましく、０．１μｍ以上１０μｍ以下であることがさらに好ましい。中間層の厚さが０．０１μｍ未満であると、上述した機能が発現しない。一方、中間層の厚さを１００μｍ超としても、中間層での抵抗による電圧損失が大きくなって、上述の機能が発現しないとともに製造コスト等の面でやや不利になる場合がある。 The thickness of the intermediate layer is preferably 0.01 µm or more and 100 µm or less, more preferably 0.1 µm or more and 10 µm or less. If the thickness of the intermediate layer is less than 0.01 μm, the functions described above are not exhibited. On the other hand, even if the thickness of the intermediate layer exceeds 100 μm, the voltage loss due to the resistance of the intermediate layer becomes large, and the above-described functions may not be exhibited, and there may be a slight disadvantage in terms of manufacturing cost and the like.
（中間層を形成するための塗布工程）
　塗布工程では、リチウムイオン及びニッケルイオンを含有する前駆体水溶液を導電性基体２の表面に塗布する。中間層は、いわゆる熱分解法によって形成される。熱分解法により中間層を形成するに際しては、まず、中間層の前駆体水溶液を調製する。リチウム成分を含む前駆体としては、硝酸リチウム、炭酸リチウム、塩化リチウム、水酸化リチウム、カルボン酸リチウムなど公知の前駆体を使用することができる。カルボン酸リチウムとしては、ギ酸リチウムや酢酸リチウムが挙げられる。ニッケル成分を含む前駆体としては、硝酸ニッケル、炭酸ニッケル、塩化ニッケル、カルボン酸ニッケルなど公知の前駆体を使用することができる。カルボン酸ニッケルとしては、ギ酸ニッケルや酢酸ニッケルが挙げられる。特に、前駆体としてカルボン酸リチウム及びカルボン酸ニッケルの少なくとも一方を用いることにより、後述するように低温で焼成した場合であっても緻密な中間層を形成することができるので特に好ましい。 (Coating step for forming intermediate layer)
In the application step, a precursor aqueous solution containing lithium ions and nickel ions is applied to the surface of the conductive substrate 2 . The intermediate layer is formed by a so-called pyrolytic method. When forming the intermediate layer by the pyrolysis method, first, an aqueous solution of the precursor for the intermediate layer is prepared. As a precursor containing a lithium component, known precursors such as lithium nitrate, lithium carbonate, lithium chloride, lithium hydroxide and lithium carboxylate can be used. Lithium carboxylates include lithium formate and lithium acetate. As a precursor containing a nickel component, known precursors such as nickel nitrate, nickel carbonate, nickel chloride, and nickel carboxylate can be used. Nickel carboxylates include nickel formate and nickel acetate. In particular, it is particularly preferable to use at least one of lithium carboxylate and nickel carboxylate as a precursor, because a dense intermediate layer can be formed even when fired at a low temperature as described later.
　熱分解法で中間層を形成する際の熱処理温度は、適宜に設定することができる。前駆体の分解温度と生産コストとを考慮すると、熱処理温度は、４５０℃以上、６００℃以下とすることが好ましく、４５０℃以上、５５０℃以下とすることがさらに好ましい。例えば、硝酸リチウムの分解温度は４３０℃程度であり、酢酸ニッケルの分解温度は３７３℃程度である。熱処理温度を４５０℃以上とすることにより、各成分をより確実に分解することができる。熱処理温度を６００℃超とすると、導電性基体の酸化が進行しやすく、電極抵抗が増大して電圧損失の増大を招く場合がある。熱処理時間は、反応速度、生産性、触媒層表面の酸化抵抗等を考慮して、適宜に設定すればよい。 The heat treatment temperature when forming the intermediate layer by thermal decomposition can be set as appropriate. Considering the decomposition temperature of the precursor and the production cost, the heat treatment temperature is preferably 450° C. or higher and 600° C. or lower, more preferably 450° C. or higher and 550° C. or lower. For example, the decomposition temperature of lithium nitrate is about 430.degree. C., and the decomposition temperature of nickel acetate is about 373.degree. By setting the heat treatment temperature to 450° C. or higher, each component can be decomposed more reliably. If the heat treatment temperature exceeds 600° C., the oxidation of the conductive substrate is likely to proceed, which may increase the electrode resistance and lead to an increase in voltage loss. The heat treatment time may be appropriately set in consideration of the reaction rate, productivity, oxidation resistance of the catalyst layer surface, and the like.
　前述の塗布工程における水溶液の塗布回数を適宜に設定することで、形成される中間層の厚さを制御することができる。なお、水溶液の塗布と乾燥を一層毎に繰り返し、最上層を形成した後に全体を熱処理してもよく、また、水溶液の塗布及び熱処理（前処理）を一層毎に繰り返し、最上層を形成した後に全体を熱処理してもよい。前処理の温度と全体の熱処理の温度は、同一であってもよく、異なっていてもよい。前処理の時間は、全体の熱処理の時間よりも短くすることが好ましい。 The thickness of the intermediate layer to be formed can be controlled by appropriately setting the number of times the aqueous solution is applied in the above-described application step. The application and drying of the aqueous solution may be repeated for each layer, and the whole may be heat-treated after forming the uppermost layer. The whole may be heat treated. The pretreatment temperature and the overall heat treatment temperature may be the same or different. The pretreatment time is preferably shorter than the total heat treatment time.
＜触媒層＞
　本発明のアルカリ水電解方法で用いる酸素発生用アノードは、導電性基体２の最表面に特有の触媒成分からなる触媒層６を形成した形態としたことで、アルカリ水電解に適用した場合に、本発明の顕著な効果が発現される。以下、本発明の顕著な効果を得るために重要な触媒層について説明する。 <Catalyst layer>
The oxygen generating anode used in the alkaline water electrolysis method of the present invention has a form in which a catalyst layer 6 made of a specific catalyst component is formed on the outermost surface of the conductive substrate 2, so that when applied to alkaline water electrolysis, Remarkable effects of the present invention are exhibited. The catalyst layer, which is important for obtaining the remarkable effects of the present invention, will be described below.
（触媒成分）
　本発明で使用し、本発明を特徴づける触媒成分である、金属水酸化物と有機物との複合体のハイブリッドニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）は、例えば、下記のようにして簡便に製造できる。ＮｉｘＦｅｙＣｏｚ－ｈｍｈは、例えば、三脚型配位子tris(hydroxymethyl)aminomethane（Ｔｒｉｓ－ＮＨ２）水溶液と、ＮｉＣｌ２、ＦｅＣｌ２及びＣｏＣｌ２の水溶液とを混合し、９０℃で２４時間反応させることで合成できる。そして、上記で合成した反応生成物を、ろ過、純水洗浄によりゲルとして分離し、これを純水中で超音波処理することで、本発明のアルカリ水電解方法で、電解液に利用するＮｉｘＦｅｙＣｏｚ－ｈｍｈ分散液が容易に得られる。該分散液中のＮｉｘＦｅｙＣｏｚ－ｈｍｈの濃度は、５～１００ｇ／Ｌ程度とすることが好ましい。後述する本発明の試験例では、濃度が５ｇ／Ｌの分散液を用いた。以下、電解液の調製に用いるＮｉｘＦｅｙＣｏｚ－ｈｍｈ触媒を分散させた分散液のことを「ＮｉＦｅＣｏ－ｈｍｈ分散液」と呼ぶ。本発明で利用する触媒のＮｉｘＦｅｙＣｏｚ－ｈｍｈを分散させた電解液には、上記のような製造方法で得た「ＮｉＦｅＣｏ－ｈｍｈ分散液」を用いた。電解液とする場合には、触媒が適宜な添加濃度になるように調整して用いた。なお、本発明の説明では、三脚型配位子の代表例として、図２Ａに示したＴｒｉｓ－ＮＨ２を用いたが、三脚型配位子は特に限定されるものでなく、Ｔｒｉｓ－ＮＨ２と同じような分子構造を有するものであればよい。 (catalyst component)
Hybrid nickel-iron-cobalt (Ni x Fe y Co z -hmh), which is a composite of a metal hydroxide and an organic substance, which is used in the present invention and is a catalyst component that characterizes the present invention, is, for example, as follows. can be easily manufactured by NixFeyCoz - hmh is produced, for example, by mixing an aqueous solution of tripodal ligand tris(hydroxymethyl)aminomethane (Tris- NH2 ) with an aqueous solution of NiCl2 , FeCl2 and CoCl2 , and It can be synthesized by time reaction. Then, the reaction product synthesized above is separated as a gel by filtering and washing with pure water, and this is subjected to ultrasonic treatment in pure water to obtain Ni used in the electrolytic solution in the alkaline water electrolysis method of the present invention. x Fe y Co z -hmh dispersions are readily obtained. The concentration of Ni x Fe y Co z -hmh in the dispersion is preferably about 5 to 100 g/L. In test examples of the present invention, which will be described later, a dispersion having a concentration of 5 g/L was used. Hereinafter, the dispersion in which the Ni x Fe y Co z -hmh catalyst is dispersed, which is used for preparing the electrolytic solution, is referred to as "NiFeCo-hmh dispersion". The "NiFeCo-hmh dispersion" obtained by the production method described above was used as the electrolytic solution in which the catalyst Ni x Fe y Co z -hmh used in the present invention was dispersed. When used as an electrolytic solution, the catalyst was adjusted so as to have an appropriate addition concentration. In the description of the present invention, Tris-NH 2 shown in FIG. 2A was used as a representative example of the tripodal ligand, but the tripodal ligand is not particularly limited, and Tris-NH 2 Any material having a molecular structure similar to that of
　ＮｉｘＦｅｙＣｏｚ－ｈｍｈは、金属水酸化物と三脚型配位子が共有結合的に固定された複合構造を有し、本発明者らの検討によれば、層状構造、トンネル構造、アモルファス構造のものがある。層状構造のＮｉｘＦｅｙＣｏｚ－ｈｍｈは、例えば、図２Ａに模式的に例示したように、三脚型配位子を有する層状のＮｉｘＦｅｙＣｏｚ－Ｔｒｉｓ－ＮＨ２分子構造を有し、Ｔｒｉｓ分子が、共有結合的に固定化されているブルーサイト層からなる。Ｔｒｉｓ－ＮＨ２による修飾は、層状水酸化ニッケル・鉄・コバルト電解液中での剥離と、分散の能力を高める。上記で得たＮｉｘＦｅｙＣｏｚ－ｈｍｈの分子構造が、先に提案している「ＮｉＦｅ－ｎｓ」と同様な、厚さが１．３ｎｍ程度で、横方向のサイズが１０～１００ｎｍ程度の大きさの、層状の分子構造を有するナノシート状の物質を有することは、ＴＥＭ像によって確認した。また、ＸＲＤより、ＮｉｘＦｅｙＣｏｚ－ｈｍｈは、底面間隔が拡大した層状構造を有することを確認した。 Ni x Fe y Co z -hmh has a composite structure in which a metal hydroxide and a tripodal ligand are covalently fixed. Some have an amorphous structure. The layered Ni x Fe y Co z -hmh has a layered Ni x Fe y Co z -Tris-NH 2 molecular structure with tripodal ligands, for example, as schematically illustrated in FIG. 2A. and consists of a brucite layer in which the Tris molecules are covalently immobilized. Modification with Tris-NH 2 enhances the ability to exfoliate and disperse in layered nickel-iron-cobalt hydroxide electrolytes. The molecular structure of the Ni x Fe y Co z -hmh obtained above has a thickness of about 1.3 nm and a lateral size of about 10 to 100 nm, similar to the previously proposed "NiFe-ns". It was confirmed by a TEM image that a nanosheet-like substance having a layered molecular structure with a size of . It was also confirmed by XRD that Ni x Fe y Co z -hmh has a layered structure with an enlarged basal plane spacing.
　原料の混合液を加熱して反応させることで簡便に得られる反応生成物の、ＮｉｘＦｅｙＣｏｚ－ｈｍｈについて、さらに検討した。その結果、「ＮｉＦｅＣｏ－ｈｍｈ分散液」を構成する分散している物質の中に、図２Ａに示したナノシート状の物質に加えて、トンネル構造に特徴的な針状結晶が存在し、「トンネル構造の針状形状の物質」を有することを見出した。図９に、そのような構造の物質の例として、Ｆｅ－ｈｍｈの透過型電子顕微鏡写真の図を示した。なお、先述したように、Ｆｅ－ｈｍｈは、単独で触媒に利用した場合も、Ｆｅ－ｈｍｈとＣｏ－ｎｓとを併用して触媒に利用した場合も、電位変動に対してＮｉ系アノードの耐久性を、先に提案しているＣｏ－ｎｓを単独で触媒に利用したアノードよりも向上させることができる。このトンネル状構造の物質は、横幅が５ｎｍ程度、長さは、多くが１００ｎｍ以下の針状結晶であり、一部長いものもあるが、大半は２００ｎｍ以下のものであった。また、アモルファス構造に合致する不定形の微粒子も認められた。この微粒子状の物質は、一次粒子についてははっきりと観察されないが、１～５ｎｍ程度であると予想され、実際の存在状態は、このようなサイズの一次粒子が凝集してミクロンオーダーの二次粒子となっていた。したがって、本発明を構成する触媒のＮｉｘＦｅｙＣｏｚ－ｈｍｈは、１～２００ｎｍ範囲内の大きさの物質であるといえる。 Ni x Fe y Co z -hmh, which is a reaction product easily obtained by heating and reacting a mixture of raw materials, was further studied. As a result, in addition to the nanosheet-like substance shown in FIG. It was found that the material has a needle-like shape of the structure. FIG. 9 shows a transmission electron micrograph of Fe-hmh as an example of a substance with such a structure. As described above, Fe-hmh is used alone as a catalyst, and when Fe-hmh and Co-ns are used together as a catalyst, the durability of the Ni-based anode against potential fluctuations is improved. performance can be improved over previously proposed Co-ns-only catalyzed anodes. Most of the substances with this tunnel-like structure were needle-like crystals with a width of about 5 nm and a length of 100 nm or less. In addition, irregularly shaped fine particles matching the amorphous structure were also observed. Although this fine-grained substance is not clearly observed for primary particles, it is expected to be about 1 to 5 nm. It was. Therefore, it can be said that Ni x Fe y Co z -hmh of the catalyst constituting the present invention is a substance with a size within the range of 1 to 200 nm.
　また、本発明者らの検討の結果、反応生成物中における上記の物質の存在量は、Ｎｉ／Ｆｅ／Ｃｏの原子比率によって影響を受けることがわかった。例えば、Ｆｅ含有量が７０ｍｏｌ％以下であると層状構造のナノシート状の物質になる傾向があった。また、Ｆｅ含有量が７０ｍｏｌ％より多いと、アモルファス構造の粒子状の物質になる傾向があった。また、後述するように、触媒にＮｉｘＦｅｙＣｏｚ－ｈｍｈを用いた本発明の酸素発生用アノードの電解性能は、ＮｉｘＦｅｙ－ｎｓを触媒に用いた従来技術の場合と比較して、構成するＮｉ／Ｆｅ／Ｃｏの原子比率の違いによる影響の程度が少なく、安定した電解性能を示す傾向が認められた。 Further, as a result of investigation by the present inventors, it has been found that the abundance of the above substances in the reaction product is affected by the atomic ratio of Ni/Fe/Co. For example, when the Fe content was 70 mol % or less, the material tended to have a nanosheet-like structure with a layered structure. Moreover, when the Fe content was more than 70 mol %, there was a tendency to form a particulate substance with an amorphous structure. In addition, as will be described later, the electrolysis performance of the oxygen generating anode of the present invention using Ni x Fe y Co z -hmh as a catalyst is superior to that of the prior art using Ni x Fe y -ns as a catalyst. Therefore, the degree of influence due to the difference in the atomic ratio of Ni/Fe/Co is small, and there is a tendency to exhibit stable electrolysis performance.
　また、得られた反応生成物を水中に分散させ、超音波処理して水分散性について試験した。まず、これまでに提案したＮｉｘＦｅｙ－ｎｓ触媒を電解液に分散させた場合、乾燥微粉末の状態では、水中に高分散しなかった。このため、電解液に利用する分散液は、濾過により得られたヒドロゲルから調製した。一方、本発明を構成するＮｉｘＦｅｙＣｏｚ－ｈｍｈの場合は、その乾燥粉末からも分散液を調製することができた。電解液に利用するＮｉＦｅＣｏ－ｈｍｈ分散液は、勿論、ＮｉｘＦｅｙ－ｎｓ触媒を用いた場合と同様に、濾過により得られたヒドロゲルから調製することもできる。本発明者らは、この分散性の違いが、後述する、定電解によって酸素発生用アノードの表面に形成（堆積）される触媒層の量の違いの要因であると考えている。すなわち、良好な分散性を示す触媒を用いた方が、触媒を分散させた電解液中における、触媒層の形成（堆積）に寄与できる（実効利用できる）物質の量が多くなると考えられ、このことに起因して、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを触媒に用いた本発明では、従来技術のＮｉｘＦｅｙ－ｎｓを触媒に用いた場合と比較して、長時間にわたって多くの量の触媒層の形成（堆積）が実現できたものと推論している。このように分散性に優れるＮｉｘＦｅｙＣｏｚ－ｈｍｈ触媒を分散させた電解液を用いたことで、本発明が目的としている、電解性能が劣化しにくく、長期間にわたってより安定したアルカリ水電解を行うことが可能な、より優れた酸素発生用アノード、これを用いたアルカリ水電解方法の提供が実現できたものと考えられる。 The resulting reaction product was also dispersed in water, sonicated and tested for water dispersibility. First, when the previously proposed Ni x Fe y -ns catalyst was dispersed in the electrolytic solution, it was not highly dispersed in water in the dry fine powder state. For this reason, the dispersions used in the electrolyte were prepared from hydrogels obtained by filtration. On the other hand, in the case of Ni x Fe y Co z -hmh constituting the present invention, a dispersion could be prepared even from its dry powder. The NiFeCo-hmh dispersions utilized in the electrolyte can of course also be prepared from hydrogels obtained by filtration, as with Ni x Fe y -ns catalysts. The present inventors believe that this difference in dispersibility is the factor behind the difference in the amount of the catalyst layer formed (deposited) on the surface of the oxygen generating anode by constant electrolysis, which will be described later. That is, it is thought that the amount of substances that can contribute to the formation (deposition) of the catalyst layer (the amount that can be effectively used) in the electrolytic solution in which the catalyst is dispersed increases when a catalyst that exhibits good dispersibility is used. Because of this , the present invention using Ni x Fe y Co z -hmh as a catalyst produces a greater amount of It is inferred that the formation (deposition) of the catalyst layer was achieved. By using the electrolytic solution in which the Ni x Fe y Co z -hmh catalyst having excellent dispersibility is dispersed in this way, the electrolytic performance is less likely to deteriorate, which is the object of the present invention, and the alkaline water is more stable over a long period of time. It is considered that the provision of a more excellent oxygen generating anode capable of performing electrolysis and a method of electrolyzing alkaline water using the same has been realized.
　上記した本発明の目的に好適に利用できるＮｉｘＦｅｙＣｏｚ－ｈｍｈとしては、Ｎｉ／Ｆｅ／Ｃｏ原子比率が、（０．１～０．９）／（０．１～０．９）／（０．１～０．９）であるものが挙げられる。また、Ｎｉ／Ｆｅ／Ｃｏ原子比率が、（０．１～０．７）／（０．３～０．８）／（０．０５～０．２）であることがより好ましい（図７参照）。先述したように、本発明のアルカリ水電解方法で使用する場合、ＮｉｘＦｅｙＣｏｚ－ｈｍｈの物質のサイズは、１～２００ｎｍの範囲の長さ（長径）であることが好ましい。本発明者らの検討によれば、これ以上であると、電解析出の効率が低下し、過電圧の改善、修復効果が発現しにくくなる傾向があるので好ましくない。本発明の目的に好適な触媒として利用できるＮｉｘＦｅｙＣｏｚ－ｈｍｈとしては、層状の分子構造を有するシート状の物質、トンネル構造の針状形状の物質及びアモルファス構造の粒子状の物質の少なくともいずれかを有するものが挙げられる。 Ni x Fe y Co z -hmh that can be suitably used for the purpose of the present invention has a Ni/Fe/Co atomic ratio of (0.1 to 0.9)/(0.1 to 0.9) / (0.1 to 0.9). Further, the Ni/Fe/Co atomic ratio is more preferably (0.1 to 0.7)/(0.3 to 0.8)/(0.05 to 0.2) (see FIG. 7 ). As described above, when used in the alkaline water electrolysis method of the present invention, the Ni x Fe y Co z -hmh substance preferably has a length (major diameter) in the range of 1 to 200 nm. According to the investigations of the present inventors, if it is more than this, the efficiency of electrolytic deposition tends to decrease, and it tends to be difficult to develop the effect of overvoltage improvement and restoration, which is not preferable. Ni x Fe y Co z -hmh that can be used as a catalyst suitable for the purpose of the present invention includes a sheet-like substance having a layered molecular structure, a needle-like substance having a tunnel structure, and a particulate substance having an amorphous structure. Examples include those having at least one of them.
　本発明の効果が得られ、本発明の目的に好適に利用できるＮｉｘＦｅｙＣｏｚ－ｈｍｈとしては、Ｎｉ／Ｆｅ／Ｃｏ原子比率が、（０．０）／（１．０）／（０．０）である、Ｆｅ以外の金属イオンを含まない、極めて汎用な材料からなる構造のものも挙げられる。先述したように、Ｆｅ－ｈｍｈは、「トンネル構造の針状形状の物質」を有するという形状的な特徴をもつ。また、Ｎｉ／Ｆｅ／Ｃｏ原子比率が、（０．０）／（０．１～０．９）／（０．１～０．９）である、ＦｅとＣｏの金属イオンを含む材料からなる構造のものも挙げられる。本発明者らの検討によれば、Ｆｅ－ｈｍｈとＣｏ－ｎｓとを併用して触媒に利用することで起こる、Ｃｏ成分を共存させた析出においては、高い活性を有するＦｅ－ｈｍｈを、Ｆｅ－ｈｍｈを単独で触媒に利用した場合よりも多く析出させる特徴をもつことがわかった。この点については後述する。 As Ni x Fe y Co z -hmh that can obtain the effect of the present invention and can be suitably used for the purpose of the present invention, the Ni/Fe/Co atomic ratio is (0.0)/(1.0)/( 0.0). As described above, Fe-hmh has a morphological feature of having a “needle-shaped material with a tunnel structure”. In addition, the Ni/Fe/Co atomic ratio is (0.0)/(0.1 to 0.9)/(0.1 to 0.9), and is made of a material containing metal ions of Fe and Co. Structural ones are also included. According to the studies of the present inventors, Fe-hmh, which has high activity, is used as a catalyst in the presence of a Co component, which occurs when Fe-hmh and Co-ns are used together as a catalyst. It was found that -hmh is characterized by more precipitation than when it is used alone as a catalyst. This point will be described later.
　本発明者らの検討によれば、本発明を特徴づける、アルカリ水電解用アノードの触媒層を形成し、電解液中に含有させて利用する触媒成分に、金属水酸化物と有機物との複合体のハイブリッドニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を用いることで、本発明者らがこれまでに提案している、ハイブリッド水酸化コバルトナノシート（Ｃｏ－ｎｓ）を利用した技術に比較して、より優れた効果が得られる。具体的には、上記複合体をそれぞれに利用してアノードの触媒層を形成し、得られたアノードを用い、上記異なる複合体を触媒としてそれぞれ含有させた電解液をアノード室に供給し、電解性能の加速劣化試験を実施して、酸素発生過電圧の電位変動サイクル依存性を調べた。その結果、触媒成分にＣｏ－ｎｓを用いた場合に比べて、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを用いた場合は、明らかに初期の過電圧からの顕著な減少傾向が見られ、耐久に優れることを確認した。詳細については後述する。さらに、本発明で触媒成分に用いるＮｉｘＦｅｙＣｏｚ－ｈｍｈは、汎用の材料から簡便な方法で合成でき、先に述べたように分散性に優れるので、本発明で必要とする、触媒を分散させた分散液や、該分散液を用いて調製する電解液として利用し易いといった、工業上の、極めて重要な利点もある。 According to the studies of the present inventors, the catalyst component that forms the catalyst layer of the anode for alkaline water electrolysis and is contained in the electrolytic solution, which characterizes the present invention, is a composite of a metal hydroxide and an organic substance. By using a hybrid nickel-iron-cobalt (Ni x Fe y Co z -hmh) body, the present inventors have so far proposed a technology utilizing hybrid cobalt hydroxide nanosheets (Co-ns) A better effect can be obtained compared to Specifically, each of the above composites is used to form an anode catalyst layer, the obtained anode is used, and an electrolytic solution containing each of the above different composites as a catalyst is supplied to the anode chamber to perform electrolysis. An accelerated deterioration test of performance was performed to investigate the potential fluctuation cycle dependence of the oxygen generation overvoltage. As a result, compared to the case of using Co-ns as a catalyst component, when Ni x Fe y Co z -hmh is used, a marked decrease in the initial overvoltage is clearly observed, indicating excellent durability. It was confirmed. Details will be described later. Furthermore, Ni x Fe y Co z -hmh used as a catalyst component in the present invention can be synthesized by a simple method from general-purpose materials and has excellent dispersibility as described above. There is also an industrially extremely important advantage that it is easy to use as a dispersion in which is dispersed or an electrolytic solution prepared using the dispersion.
（触媒層の形成方法）
　触媒層６の形成方法について述べる。電解液として１．０ＭのＫＯＨ水溶液を用いた。導電性基体２の表面を清浄化するために、電解液中にて電位操作を行うことが好ましい。例えば、電位サイクリック操作（－０．５～０．５Ｖ　ｖｓ．ＲＨＥ、２００ｍＶ／ｓ、２００サイクル）を行う。その後、先に述べたようにして得たＮｉＦｅＣｏ－ｈｍｈ分散液を、添加濃度１ｍＬ／Ｌで含む、１．０ＭのＫＯＨ水溶液を作製し、これを電解液に用いた。そして、ＮｉｘＦｅｙＣｏｚ－ｈｍｈをＮｉ基体表面に析出させるため、８００ｍＡ／ｃｍ２で３０分の定電流電解を８回行なった。この電解操作で、電極表面で、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを、水酸化物層の酸化や表面有機基の酸化分解により分散性を低下させ、電極表面にＮｉｘＦｅｙＣｏｚ－ｈｍｈを堆積させた。 (Method for forming catalyst layer)
A method for forming the catalyst layer 6 will be described. A 1.0 M KOH aqueous solution was used as an electrolytic solution. In order to clean the surface of the conductive substrate 2, it is preferable to perform potential manipulation in the electrolytic solution. For example, potential cyclic operation (-0.5 to 0.5 V vs. RHE, 200 mV/s, 200 cycles) is performed. Thereafter, a 1.0 M KOH aqueous solution containing the NiFeCo-hmh dispersion obtained as described above at an additive concentration of 1 mL/L was prepared and used as an electrolytic solution. Then, in order to deposit Ni x Fe y Co z -hmh on the Ni substrate surface, constant current electrolysis was performed eight times at 800 mA/cm 2 for 30 minutes. In this electrolysis operation, the dispersibility of Ni x Fe y Co z -hmh is reduced on the electrode surface by oxidation of the hydroxide layer and oxidative decomposition of the surface organic group, and Ni x Fe y Co z -hmh is formed on the electrode surface. was deposited.
　上記において、「ＮｉＦｅＣｏ－ｈｍｈ分散液」の電解液への添加濃度は、０．１～１０ｍＬ／Ｌの範囲内にすることが好ましく、より好ましくは０．１～８ｍＬ／Ｌとする。本発明者らの検討によれば、これよりも濃度が高いと、電解液中におけるＮｉｘＦｅｙＣｏｚ－ｈｍｈの分散が不十分となり、電解において均質な析出が得られない場合があるので好ましくない。また、これよりも濃度が低いと、電解による析出において、実用的な時間内では十分な量が得られない。また、析出のための電解条件としては、導電性基体を１．２Ｖ～１．８Ｖ　ｖｓ．ＲＨＥのポテンシャル範囲で保持することが好ましい。析出反応は、１．２Ｖ未満では進行せず、１．８Ｖを超えると、酸素発生が同時に進行し析出を阻害するので好ましくない。 In the above, the concentration of the "NiFeCo-hmh dispersion" added to the electrolytic solution is preferably in the range of 0.1 to 10 mL/L, more preferably 0.1 to 8 mL/L. According to the studies of the present inventors, if the concentration is higher than this, the dispersion of Ni x Fe y Co z -hmh in the electrolytic solution becomes insufficient, and homogeneous deposition may not be obtained in electrolysis. I don't like it. On the other hand, if the concentration is lower than this, a sufficient amount cannot be obtained within a practical time in electrolytic deposition. In addition, the electrolysis conditions for the deposition are 1.2 V to 1.8 V vs. the conductive substrate. It is preferable to keep it in the potential range of RHE. The precipitation reaction does not proceed at less than 1.2 V, and if the voltage exceeds 1.8 V, oxygen evolution proceeds simultaneously, inhibiting precipitation, which is not preferable.
　Ｆｅ－ｈｍｈを分散させた電解液を用い、上記条件の電解により４時間、Ｎｉ基体上に触媒を析出させたときの析出物の一例として、透過型電子顕微鏡写真の図を示した。図１０に示されている通り、この場合、Ｎｉ基体表面は、Ｆｅ－ｈｍｈが束ねられた繊維状物質のネットワークで覆われた状態になることがわかった。 A transmission electron micrograph is shown as an example of the deposit when the catalyst was deposited on the Ni substrate by electrolysis under the above conditions for 4 hours using the electrolytic solution in which Fe-hmh was dispersed. As shown in FIG. 10, in this case, the Ni substrate surface was found to be covered with a fibrous substance network in which Fe-hmh was bundled.
　図１１Ａ及び図１１Ｂに、触媒成分の一例であるＦｅ－ｈｍｈ粒子とＣｏ－ｎｓ粒子を併用して電解液中に分散させ、電解によりＮｉ基体表面に析出させた析出物の状態を示す、電界放射型走査電子顕微鏡(ＦＥ－ＳＥＭ)の図を示した。電極表面は触媒層で均一に覆われており、図１１Ｂ及びその拡大像（不図示）から、微細構造はナノシート（Ｃｏ－ｎｓ）の凝集体であることがわかった。また、図１１Ａに示したように、別の視野から、Ｆｅ－ｈｍｈ粒子は細長い粒子であり、凝集体の中に取り込まれていることが確認された。分析の結果では、共同析出により、Ｆｅ－ｈｍｈの堆積量が大幅に増加しており（推定としては、Ｆｅ－ｈｍｈを単独で用いた場合に得られる量の６０倍程度）、Ｃｏ－ｎｓ粒子を併用することで、形成される触媒層において、Ｆｅ－ｈｍｈの堆積量が多くなることを見出した。メカニズムはまだ明らかでは無いが、Ｆｅ－ｈｍｈ粒子とＣｏ－ｎｓ粒子を併用して電解液中に分散させたことで、Ｃｏ－ｎｓ成分の析出によりＦｅ－ｈｍｈの析出量が著しく増加し、このことが触媒活性向上の理由であると考えられる。 FIGS. 11A and 11B show the state of precipitates deposited on the surface of the Ni substrate by electrolysis by dispersing both Fe-hmh particles and Co-ns particles, which are examples of catalyst components, in an electrolytic solution. A picture of an emission scanning electron microscope (FE-SEM) is shown. The electrode surface was uniformly covered with a catalyst layer, and it was found from FIG. 11B and its enlarged image (not shown) that the microstructure was aggregates of nanosheets (Co-ns). In addition, as shown in FIG. 11A, it was confirmed from another view that the Fe-hmh particles were elongated particles and were incorporated into aggregates. As a result of the analysis, co-precipitation significantly increases the amount of Fe-hmh deposited (estimated as about 60 times the amount obtained when Fe-hmh is used alone), and Co-ns particles was found to increase the amount of Fe-hmh deposited in the formed catalyst layer. Although the mechanism is not yet clear, by dispersing both Fe-hmh particles and Co-ns particles in the electrolytic solution, precipitation of the Co-ns component significantly increases the amount of Fe-hmh precipitated. This is considered to be the reason for the improvement in catalytic activity.
　本発明のアルカリ水電解方法では、酸素発生用アノードとして、上記した特有の触媒層を有する構成の電極を用いることを要する。一方、カソード（陰極）や、隔膜については、特に限定されず、従来のアルカリ水電解に用いられているものを適宜に使用すればよい。以下、これらについて説明する。 In the alkaline water electrolysis method of the present invention, it is necessary to use an electrode configured to have the above-described specific catalyst layer as the oxygen generating anode. On the other hand, the cathode (negative electrode) and the diaphragm are not particularly limited, and those used in conventional alkaline water electrolysis may be appropriately used. These will be described below.
［カソード］
　カソードとしては、アルカリ水電解に耐え得る材料製の基体と、陰極過電圧が小さい触媒とを選択して用いることが好ましい。カソード基体としては、ニッケル基体、又はニッケル基体に活性陰極を被覆形成したものを用いることができる。カソード基体の形状としては、板状の他、エクスパンドメッシュや、多孔質エクスパンドメッシュなどを挙げることができる。 [Cathode]
As the cathode, it is preferable to select and use a substrate made of a material that can withstand alkaline water electrolysis and a catalyst with a small cathode overvoltage. As the cathode substrate, a nickel substrate or a nickel substrate coated with an active cathode can be used. Examples of the shape of the cathode substrate include a plate shape, an expanded mesh, a porous expanded mesh, and the like.
　カソード材料としては、表面積の大きい多孔質ニッケルや、Ｎｉ－Ｍｏ系材料などがある。その他、Ｎｉ－Ａｌ、Ｎｉ－Ｚｎ、Ｎｉ－Ｃｏ－Ｚｎなどのラネーニッケル系材料；Ｎｉ－Ｓなどの硫化物系材料；Ｔｉ2Ｎｉなど水素吸蔵合金系材料などがある。触媒としては、水素過電圧が低い、短絡安定性が高い、被毒耐性が高い等の性質を有するものが好ましい。その他の触媒としては、白金、パラジウム、ルテニウム、イリジウムなどの金属、及びこれらの酸化物が好ましい。 Cathode materials include porous nickel having a large surface area and Ni--Mo based materials. In addition, there are Raney nickel materials such as Ni--Al, Ni--Zn and Ni--Co--Zn; sulfide materials such as Ni--S; and hydrogen storage alloy materials such as Ti.sub.2 Ni. As the catalyst, those having properties such as low hydrogen overvoltage, high short-circuit stability, and high poisoning resistance are preferred. As other catalysts, metals such as platinum, palladium, ruthenium, iridium, and oxides thereof are preferred.
［隔膜］
　電解用隔膜としては、アスベスト、不織布、イオン交換膜、高分子多孔膜、及び無機物質と有機高分子の複合膜など、従来公知のものをいずれも用いることができる。具体的には、リン酸カルシウム化合物やフッ化カルシウム等の親水性無機材料と、ポリスルホン、ポリプロピレン、及びフッ化ポリビニリデン等の有機結合材料との混合物に、有機繊維布を内在させたイオン透過性隔膜を用いることができる。また、アンチモンやジルコニウムの酸化物及び水酸化物等の粒状の無機性親水性物質と、フルオロカーボン重合体、ポリスルホン、ポリプロピレン、ポリ塩化ビニル、及びポリビニルブチラール等の有機性結合剤とのフィルム形成性混合物に、伸張された有機性繊維布を内在させたイオン透過性隔膜を用いることができる。 [diaphragm]
As the diaphragm for electrolysis, any conventionally known membrane such as asbestos, nonwoven fabric, ion exchange membrane, porous polymer membrane, and composite membrane of inorganic substance and organic polymer can be used. Specifically, an ion-permeable membrane having an organic fiber cloth embedded in a mixture of a hydrophilic inorganic material such as a calcium phosphate compound and calcium fluoride and an organic binding material such as polysulfone, polypropylene, and polyvinylidene fluoride. can be used. Also, film-forming mixtures of particulate inorganic hydrophilic substances such as antimony and zirconium oxides and hydroxides and organic binders such as fluorocarbon polymers, polysulfones, polypropylene, polyvinyl chloride, and polyvinyl butyral. Alternatively, an ion-permeable diaphragm with an internal stretched organic fiber cloth can be used.
　本発明のアルカリ水電解方法においては、本発明を特徴づける酸素発生用アノードを構成要素とするアルカリ水電解セルを用いれば、高濃度のアルカリ水溶液を電解することができる。電解液として用いるアルカリ水溶液としては、水酸化カリウム（ＫＯＨ）、水酸化ナトリウム（ＮａＯＨ）等のアルカリ金属水酸化物の水溶液が好ましい。アルカリ水溶液の濃度は、１．５質量％以上、４０質量％以下であることが好ましい。また、アルカリ水溶液の濃度は、１５質量％以上、４０質量％以下であると、電気伝導度が大きく、電力消費量を抑えることができるため、好ましい。さらに、コスト、腐食性、粘性、操作性などを考慮すると、アルカリ水溶液の濃度は２０質量％以上、３０質量％以下であることが好ましい。 In the alkaline water electrolysis method of the present invention, a high-concentration alkaline aqueous solution can be electrolyzed by using an alkaline water electrolysis cell comprising the oxygen generating anode that characterizes the present invention. As the alkaline aqueous solution used as the electrolytic solution, aqueous solutions of alkali metal hydroxides such as potassium hydroxide (KOH) and sodium hydroxide (NaOH) are preferable. The concentration of the alkaline aqueous solution is preferably 1.5% by mass or more and 40% by mass or less. Further, it is preferable that the concentration of the alkaline aqueous solution is 15% by mass or more and 40% by mass or less, because the electric conductivity is high and the power consumption can be suppressed. Furthermore, considering cost, corrosiveness, viscosity, operability, etc., the concentration of the alkaline aqueous solution is preferably 20% by mass or more and 30% by mass or less.
［運転方法］
　前記したアルカリ水電解用アノードを構成する触媒層６は、下記のようにして電解することで、電解セルに組み込む前に形成することができる。本発明のアルカリ水電解方法では、例えば、電解セルを構成するアノード室とカソード室に供給する共通の電解液に、本発明を特徴づける触媒層６の形成成分であるＮｉｘＦｅｙＣｏｚ－ｈｍを懸濁させ、その状態で電解を開始することで、先に説明したように、触媒成分をアノード表面に多量に析出させ、短時間で堆積させて触媒層を形成することができる。このため、本発明のアルカリ水電解の技術を用いれば、運転によって性能の低下した電解セルの性能回復を、電解セル解体の手間なく行うことができ、安定して長時間にわたり触媒層の性能を維持させることが可能になる。したがって、本発明のアルカリ水電解の技術は、実用的であり、その工業上のメリットは極めて大きい。 [how to drive]
The catalyst layer 6 constituting the anode for alkaline water electrolysis described above can be formed by performing electrolysis in the following manner before incorporation into an electrolytic cell. In the alkaline water electrolysis method of the present invention, for example, Ni x Fe y Co z − , which is a component forming the catalyst layer 6 characterizing the present invention, is added to the common electrolytic solution supplied to the anode chamber and the cathode chamber constituting the electrolytic cell. By suspending hm and starting electrolysis in that state, a large amount of the catalyst component can be deposited on the anode surface and deposited in a short time to form a catalyst layer, as described above. Therefore, by using the alkaline water electrolysis technology of the present invention, it is possible to recover the performance of an electrolytic cell whose performance has deteriorated due to operation without the trouble of dismantling the electrolytic cell, and stably maintain the performance of the catalyst layer for a long time. can be maintained. Therefore, the alkaline water electrolysis technology of the present invention is practical and has great industrial merit.
　次に、実施例、検討例及び比較例を挙げて本発明をさらに具体的に説明する。まず、本発明を特徴づける触媒成分であるＮｉｘＦｅｙＣｏｚ－ｈｍｈを、電解液に分散させて電解した場合における電解表面への堆積の状態と、その効果についての検討を行った。比較のために、触媒成分にＮｉｘＦｅｙ－ｎｓを用いた場合についても、同様の試験を行った。 EXAMPLES Next, the present invention will be described more specifically with reference to examples, study examples, and comparative examples. First, when Ni x Fe y Co z -hmh, which is a catalyst component characterizing the present invention, is dispersed in an electrolytic solution and electrolyzed, the state of deposition on the electrolysis surface and its effect were examined. For comparison, a similar test was conducted using Ni x Fe y -ns as the catalyst component.
（検討例１）
　電解操作は、フッ素樹脂であるＰＦＡ製の三電極セルを用いて行った。作用極に沸騰塩酸で６分間エッチングしたＮｉワイヤー、参照極に可逆水素電極（ＲＨＥ）、対極にＮｉコイル、電解液に１．０ＭのＫＯＨ水溶液２５０ｍＬをそれぞれ用いて、３０±１℃で実施した。まず、前処理として、上記電解液にＮｉＦｅＣｏ－ｈｍｈ分散液を加えずに、サイクリックボルタンメトリー（０．５～１．５Ｖ　ｖｓ．ＲＨＥ、２００ｍＶ／ｓ、２００サイクル）を行った。本検討例で使用した電解液は、下記のようにして調製した。具体的には、先に説明したと同様の方法で得た濃度が５ｇ／ＬのＮｉＦｅＣｏ－ｈｍｈ分散液を用い、該分散液を、上記前処理に用いた電解液に混合して、分散液の添加濃度が８ｍＬ／Ｌの割合となるように調整して、触媒を分散させた電解液とした。そして、この電解液で、前処理した上記三電極セルを用い、８００ｍＡ／ｃｍ２、３０分間の定電流の電解を行った。このようにして電解することで、電極表面で、触媒成分のＮｉｘＦｅｙＣｏｚ－ｈｍｈが酸化され、ＮｉｘＦｅｙＣｏｚ－ｈｍｈの水酸化物層の酸化や表面有機基の酸化分解により分散性を低下させ、電極表面にＮｉｘＦｅｙＣｏｚ－ｈｍｈを堆積させて、特有の触媒層が形成されたアノードを得た。 (Examination example 1)
The electrolysis operation was performed using a three-electrode cell made of PFA, which is a fluororesin. A Ni wire etched with boiling hydrochloric acid for 6 minutes was used as the working electrode, a reversible hydrogen electrode (RHE) was used as the reference electrode, a Ni coil was used as the counter electrode, and 250 mL of a 1.0 M KOH aqueous solution was used as the electrolyte. . First, as a pretreatment, cyclic voltammetry (0.5 to 1.5 V vs. RHE, 200 mV/s, 200 cycles) was performed without adding the NiFeCo-hmh dispersion to the electrolytic solution. The electrolytic solution used in this study example was prepared as follows. Specifically, using a NiFeCo-hmh dispersion having a concentration of 5 g/L obtained by the same method as described above, the dispersion was mixed with the electrolytic solution used for the pretreatment to obtain a dispersion. was adjusted to a concentration of 8 mL/L to prepare an electrolytic solution in which the catalyst was dispersed. Using the pretreated three-electrode cell, electrolysis was performed at a constant current of 800 mA/cm 2 for 30 minutes with this electrolytic solution. By performing electrolysis in this manner, Ni x Fe y Co z -hmh, which is a catalyst component, is oxidized on the electrode surface, and the hydroxide layer of Ni x Fe y Co z -hmh is oxidized and the surface organic groups are oxidatively decomposed. The dispersibility was reduced by , and Ni x Fe y Co z -hmh was deposited on the electrode surface to obtain an anode with a unique catalyst layer formed thereon.
　図４Ａに、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈでの触媒層形成過程におけるサイクリックボルタンメトリーの変化を示した。電解３０分では、１．３３Ｖ及び１．４０Ｖ　ｖｓ．ＲＨＥに酸化ピークが観測された。これらはそれぞれ、Ｃｏ２＋／Ｃｏ３＋、Ｎｉ２＋／Ｎｉ３＋の反応に帰属可能であり、析出された触媒由来と考えられる。２４０分、６００分と電解時間の増加に伴い、これらの各ピークの高電位側へのシフト、ピーク面積の増加が確認された。これらの様子から、電解時間の増加に伴い電極上への触媒堆積量が増えたことが示唆された。 FIG. 4A shows changes in cyclic voltammetry in the process of forming a catalyst layer with Ni 11.5 Fe 70.5 Co 18 -hmh. At 30 minutes of electrolysis, 1.33 V and 1.40 V vs. An oxidation peak was observed in RHE. These can be attributed to the reactions of Co 2+ /Co 3+ and Ni 2+ /Ni 3+ , respectively, and are considered to be derived from the precipitated catalyst. As the electrolysis time increased to 240 minutes and 600 minutes, it was confirmed that each of these peaks shifted to the high potential side and the peak area increased. These results suggested that the amount of catalyst deposited on the electrode increased as the electrolysis time increased.
　比較検討のため、従来技術のＮｉ６１．５Ｆｅ３８．５－ｎｓ触媒を分散させた電解液を用いたこと以外は上記と同様にして定電流の電解を行って、触媒層が形成されたアノードを得た。図４Ｂに、Ｎｉ６１．５Ｆｅ３８．５－ｎｓでの触媒層形成過程におけるサイクリックボルタンメトリーの変化を示した。電解３０分、電解２４０分に、１．４０Ｖ　ｖｓ．ＲＨＥに酸化ピークが観察されたが、図４Ａの場合と異なり、ピーク高さはこれ以上増加しなかった。このことは、本発明を構成するＮｉＦｅＣｏ－ｈｍｈ触媒を用いた場合に比較して、ＮｉＦｅ－ｎｓ触媒を用いた場合は、電極上への触媒堆積量が少量にとどまることを示唆している。すなわち、本発明で触媒に利用するＮｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈでは、図４Ａに示した通り、組成にＣｏを含まない触媒を利用した図４Ｂの場合と比較して、ピーク面積が非常に大きく増加した。本発明で触媒に利用するＮｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈは、ＮｉＦｅ－ｎｓ触媒と比べて分散性が向上したことから、組成にＣｏを含むことで触媒の分散性が向上し、このことに起因して電極上への触媒層の形成（堆積）が容易になったと考えられる。図４Ｃに、図４Ａと図４Ｂのピーク面積を用いて得た、触媒析出時間と触媒析出量の関係グラフを示した。図４Ｃに示した通り、従来技術のＮｉｘＦｅｙ－ｎｓを触媒に利用した場合に比べて、本発明を構成するＮｉＦｅＣｏ－ｈｍｈを触媒に利用することで、触媒層をより多く堆積できることが確認できた。 For comparative examination, constant-current electrolysis was performed in the same manner as above, except that an electrolytic solution in which a conventional Ni 61.5 Fe 38.5 -ns catalyst was dispersed, to form a catalyst layer. Anode was obtained. FIG. 4B shows changes in cyclic voltammetry during the catalyst layer formation process with Ni 61.5 Fe 38.5 -ns. After 30 minutes of electrolysis and 240 minutes of electrolysis, 1.40 V vs. An oxidation peak was observed in RHE, but unlike in FIG. 4A, the peak height did not increase any further. This suggests that the amount of catalyst deposited on the electrode is smaller when the NiFe-ns catalyst is used than when the NiFeCo-hmh catalyst constituting the present invention is used. That is, in the case of Ni 11.5 Fe 70.5 Co 18 -hmh used as a catalyst in the present invention, as shown in FIG. 4A, the peak area has increased significantly. Ni 11.5 Fe 70.5 Co 18 -hmh used as a catalyst in the present invention has improved dispersibility compared to the NiFe-ns catalyst. It is believed that this facilitates the formation (deposition) of the catalyst layer on the electrode. FIG. 4C shows a graph of the relationship between catalyst deposition time and catalyst deposition amount obtained using the peak areas of FIGS. 4A and 4B. As shown in FIG. 4C, more catalyst layers can be deposited by using NiFeCo-hmh, which constitutes the present invention, as compared to the case of using Ni x Fe y -ns of the prior art as a catalyst. It could be confirmed.
　図５に、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈとＮｉ６１．５Ｆｅ３８．５－ｎｓを用いて行った試験での、触媒析出時間に対する電流密度１００ｍＡ／ｃｍ２での過電圧の変化を示した。図５に示した通り、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈを触媒に利用した場合は、析出量の小さい範囲からＮｉ６１．５Ｆｅ３８．５－ｎｓより小さい過電圧が得られた。 FIG. 5 shows the overpotential at current density of 100 mA/cm 2 versus catalyst deposition time for tests conducted with Ni 11.5 Fe 70.5 Co 18 -hmh and Ni 61.5 Fe 38.5 -ns. showed change. As shown in FIG. 5, when Ni 11.5 Fe 70.5 Co 18 -hmh was used as a catalyst, an overvoltage lower than that of Ni 61.5 Fe 38.5 -ns was obtained from a small amount of precipitation. .
　次に、各種の触媒を分散させた電解液を用いて、下記の条件で、電位変動に対する加速試験を行った。電位変動に対する加速試験は、０．５～１．７Ｖ　ｖｓ．ＲＨＥ、５００ｍＶ／ｓで２０００サイクルのサイクリックボルタンメトリーと、電極性能測定として、０．５～１．８Ｖ　ｖｓ．ＲＨＥ、５ｍＶ／ｓで２サイクル、及び、０．５～１．５Ｖ　ｖｓ．ＲＨＥ、５０ｍＶ／ｓで２サイクルのサイクリックボルタンメトリーを行った。電解液に分散させる触媒に、Ｃｏ－ｎｓ、Ｆｅ－ｈｍｈ、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈ、Ｎｉ６１．５Ｆｅ３８．５－ｎｓをそれぞれ用いた。比較のために、触媒を分散させない電解液を用いた試験を行い、これを「Ｂａｒｅ　Ｎｉ」と表示した。上記した操作をそれぞれ２０回繰り返して、計４００００サイクルまでの試験を行った。 Next, an acceleration test for potential fluctuation was performed under the following conditions using an electrolytic solution in which various catalysts were dispersed. Accelerated test for potential fluctuation is 0.5 to 1.7 V vs. RHE, 2000 cycles of cyclic voltammetry at 500 mV/s and electrode performance measurements of 0.5-1.8 V vs. RHE, 2 cycles at 5 mV/s and 0.5-1.5 V vs. Two cycles of cyclic voltammetry were performed at RHE, 50 mV/s. Co-ns, Fe-hmh, Ni 11.5 Fe 70.5 Co 18 -hmh, and Ni 61.5 Fe 38.5 -ns were used as catalysts dispersed in the electrolytic solution. For comparison, a test was performed using an electrolytic solution in which no catalyst was dispersed, and this was designated as "Bare Ni". Each of the above operations was repeated 20 times, and the test was conducted up to a total of 40000 cycles.
　図６に、上記した電位変動に対する加速耐久試験の結果を示した。図６に示した通り、Ｂａｒｅ　Ｎｉでは１００００サイクル以降、過電圧の増加が見られたのに対して、触媒を分散させた電解液を用いた例では、いずれの場合も過電圧の増加が抑制された。これは、２０００サイクル毎の定電流電解により触媒が電解液から再堆積（自己修復）したためと考えられる。触媒に、Ｎｉ６１．５Ｆｅ３８．５－ｎｓ、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈ及びＦｅ－ｈｍｈを用いた例では、いずれの場合も、Ｂａｒｅ　Ｎｉや、触媒にＣｏ－ｎｓを用いた場合よりも小さい過電圧を維持した。特に、本発明を構成するＮｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈを触媒に用いた場合は、初期活性が最も高かった。また、４０００～８０００サイクルにかけて若干の過電圧の増大が見られたものの、その後、安定して過電圧の増加が抑制された。なお、触媒に、Ｎｉ６１．５Ｆｅ３８．５－ｎｓや、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈを用いた場合よりも劣るものの、Ｆｅ－ｈｍｈを用いた場合も良好な特性が得られた。 FIG. 6 shows the results of the accelerated endurance test with respect to the potential fluctuations described above. As shown in FIG. 6, in Bare Ni, an increase in overvoltage was observed after 10000 cycles, whereas in the examples using the electrolytic solution in which the catalyst was dispersed, the increase in overvoltage was suppressed in all cases. . This is presumably because the catalyst re-deposited (self-healing) from the electrolytic solution due to constant-current electrolysis every 2000 cycles. In the examples using Ni 61.5 Fe 38.5 -ns, Ni 11.5 Fe 70.5 Co 18 -hmh and Fe-hmh as catalysts, in all cases, bare Ni and Co-ns maintained a smaller overvoltage than with In particular, when Ni 11.5 Fe 70.5 Co 18 -hmh constituting the present invention was used as the catalyst, the initial activity was the highest. Also, although a slight increase in overvoltage was observed from 4000 to 8000 cycles, the increase in overvoltage was stably suppressed thereafter. It should be noted that although Fe-hmh is inferior to Ni 61.5 Fe 38.5 -ns or Ni 11.5 Fe 70.5 Co 18 -hmh as a catalyst, good characteristics are also obtained when using Fe-hmh. Got.
（検討例２）
　図７に、電解液に分散させる触媒成分を種々に変えて、電流密度１００ｍＡ／ｃｍ２で連続的に電解したときの過電圧の変化を示した。電解液に分散させる触媒に下記の触媒をそれぞれに用い、検討例１の場合と同様にして得た電解液を用い、電解を行った。具体的には、Ｎｉ－Ｆｅの２元系試料（触媒）として、Ｎｉ８３．６Ｆｅ１６．３－ｎｓ、Ｎｉ７６．６Ｆｅ２３．５－ｎｓ、Ｎｉ６１．５Ｆｅ３８．５－ｎｓ及びＮｉ５８．８Ｆｅ４１．２－ｎｓを用いた。また、本発明を構成するＮｉ－Ｆｅ－Ｃｏの３元系試料（触媒）として、Ｎｉ６５．６Ｆｅ３３．７Ｃｏ０．６－ｈｍｈ、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈ及びＮｉ８．２Ｆｅ８５Ｃｏ６．８－ｈｍｈを用いた。また、触媒に、Ｃｏ－ｎｓを用いた場合、Ｆｅ－ｈｍｈを用いた場合についても試験した。 (Examination example 2)
FIG. 7 shows changes in overvoltage when electrolysis is continuously performed at a current density of 100 mA/cm 2 with various catalyst components dispersed in the electrolytic solution. Electrolysis was performed using the electrolyte solution obtained in the same manner as in Examination Example 1, using the following catalysts as catalysts dispersed in the electrolyte solution. Specifically, Ni—Fe binary system samples (catalysts) were Ni 83.6 Fe 16.3 -ns, Ni 76.6 Fe 23.5 -ns, Ni 61.5 Fe 38.5 -ns. and Ni 58.8 Fe 41.2 -ns were used. Further, as Ni--Fe--Co ternary system samples (catalysts) constituting the present invention, Ni 65.6 Fe 33.7 Co 0.6 -hmh, Ni 11.5 Fe 70.5 Co 18 -hmh and Ni 8.2 Fe 85 Co 6.8 -hmh was used. In addition, tests were also conducted in the case of using Co-ns and Fe-hmh as catalysts.
　図７に示した通り、最も小さい過電圧が得られたのは、本発明を構成するＮｉ－Ｆｅ－Ｃｏの３元系試料の中の、Ｎｉ１１．５Ｆｅ７０．５Ｃｏ１８－ｈｍｈを触媒に利用した場合であった。また、本発明を構成するＮｉ－Ｆｅ－Ｃｏの３元系試料を用いた場合は、いずれの試料を用いた場合も小さい過電圧で安定しており、殆どの試料でＣｏ－ｎｓを用いた場合よりも小さい過電圧が得られた。Ｎｉ－Ｆｅ－Ｃｏの３元系試料の中で、コバルトの量が０．６と少ない組成のものについてはＣｏ－ｎｓを用いた場合と比べて過電圧が若干大きくなったが、遜色がないとできる程度であった。これに対し、Ｎｉ－Ｆｅの２元系の試料を用いた場合は、Ｃｏ－ｎｓを触媒に用いた場合よりも小さい過電圧で安定している場合もあったものの、試料の違いによって、生じる過電圧の変動が大きい傾向が認められた。このことは、Ｎｉ－Ｆｅの２元系の触媒を用いた場合に比べて、本発明で新たに見出したＮｉ－Ｆｅ－Ｃｏの３元系複合体の触媒を用いた方が、安定して小さい過電圧が得られる効果的な連続電解をより簡便に実現できることを示唆している。 As shown in FIG. 7, the smallest overvoltage was obtained with Ni 11.5 Fe 70.5 Co 18 -hmh as a catalyst among the Ni—Fe—Co ternary system samples constituting the present invention. was used for In addition, when the Ni-Fe-Co ternary system samples constituting the present invention are used, any sample is stable at a small overvoltage, and most of the samples use Co-ns. A smaller overvoltage was obtained. Among the Ni-Fe-Co ternary system samples, the overvoltage was slightly higher for the composition with the cobalt content as low as 0.6 compared to the case where Co-ns was used, but it was not inferior. was as much as possible. On the other hand, when a binary Ni—Fe sample was used, it was stable at a lower overvoltage than when Co-ns was used as a catalyst in some cases, but the overvoltage generated was different depending on the difference in the sample. A tendency toward large fluctuations was observed. This means that the Ni—Fe—Co ternary composite catalyst newly found in the present invention is more stable than the Ni—Fe binary catalyst. This suggests that effective continuous electrolysis with small overvoltage can be realized more easily.
（検討例３）
　次に、シャットダウンに基づく耐久性試験を、下記の手順で実施した。まず、試験する陽極を（１）０．６Ａ／ｃｍ２で１分間酸素発生を行った後、（２）５００ｍＶ／ｓの速度で陽極電位を０．５Ｖ　ｖｓ．ＲＨＥまで卑にシフトさせ、次に（３）０．５Ｖ　ｖｓ．ＲＨＥの電位に１分間保持する、（１）～（３）からなる工程を繰り返し、このときの０．１Ａ／ｃｍ２酸素発生電位の変化を特性値として測定した。上記工程の繰り返し数を、ＡＤＴ（加速寿命テスト、Ａｄｖａｎｃｅｄ　Ｄｕｒａｂｉｌｉｔｙ　Ｔｅｓｔの略）サイクルと呼ぶ。なお、この加速寿命テストでは、先に述べた図６に結果を示した電位変動に対する加速耐久試験と比べて、より少ないサイクル数で劣化が進むことが知られている。 (Examination example 3)
Next, a durability test based on shutdown was performed in the following procedure. First, the anode to be tested was (1) subjected to oxygen generation at 0.6 A/cm 2 for 1 minute, and then (2) the anode potential was changed to 0.5 V vs. 0.5 V at a rate of 500 mV/s. RHE to base shift, then (3) 0.5V vs. The steps (1) to (3) of holding the RHE potential for 1 minute were repeated, and the change in the 0.1 A/cm 2 oxygen generation potential at this time was measured as a characteristic value. The number of repetitions of the above steps is called an ADT (abbreviation for Advanced Durability Test) cycle. It is known that in this accelerated life test, deterioration progresses in a smaller number of cycles than in the accelerated endurance test with respect to potential fluctuations whose results are shown in FIG.
　Ｎｉ陽極、Ｎｉ基体上に異なる触媒層がそれぞれ形成されている３種類の陽極の４種をそれぞれに用いて、上記の手順で耐久試験を行い、得られた結果を図８に示した。具体的には、Ｎｉ陽極、Ｃｏ－ｎｓの触媒層を形成したＮｉ陽極、熱分解法で作製したＮｉ－Ｃｏ系スピネル酸化物の触媒層を形成した陽極、Ｆｅ－ｈｍｈの触媒層を形成したＮｉ陽極（本発明の効果が得られた例）の４種類の陽極を用いた。図８に示したように、Ｎｉの陽極では、わずかなＡＤＴサイクルで酸素発生電位の増加が観察され、Ｎｉ－Ｃｏ系スピネル酸化物の触媒層を形成した陽極でも、１０００回の繰り返しで酸素発生電位の増加が観察された。また、Ｃｏ－ｎｓの触媒層を形成したＮｉ陽極では、２７００回まででわずかに電位上昇の傾向が見られた。上記した結果に対し、Ｎｉ基体上にＦｅ－ｈｍｈの触媒層を形成した陽極（Ｎｉアノード）を用いた例では、４０００回の繰り返しでも安定的な電位が観察され、アノードとしての有効性が確認された。 Four types of Ni anodes and three types of anodes each having a different catalyst layer formed on the Ni substrate were used for each, and durability tests were performed according to the above procedure, and the results obtained are shown in FIG. Specifically, a Ni anode, a Ni anode with a Co-ns catalyst layer formed thereon, an anode with a Ni-Co spinel oxide catalyst layer formed by a pyrolysis method, and a Fe-hmh catalyst layer were formed. Four kinds of Ni anodes (an example in which the effect of the present invention was obtained) were used. As shown in FIG. 8, with the Ni anode, an increase in the oxygen evolution potential was observed after only a few ADT cycles, and even with the anode formed with the Ni—Co spinel oxide catalyst layer, oxygen evolution was observed after 1000 repetitions. An increase in potential was observed. Also, in the Ni anode on which the Co-ns catalyst layer was formed, a slight increase in potential was observed up to 2700 cycles. In contrast to the above results, in an example using an anode (Ni anode) in which a Fe-hmh catalyst layer was formed on a Ni substrate, a stable potential was observed even after 4000 repetitions, confirming its effectiveness as an anode. was done.
（検討例４）
　電解液に分散させる成分として、Ｆｅ－ｈｍｈを単独で用いた場合と、Ｆｅ－ｈｍｈ成分とＣｏ－ｎｓ成分を、質量比が１：１になるように電解液に添加して用いた場合について検討した。その際、Ｆｅ－ｈｍｈ成分とＣｏ－ｎｓ成分を併用する電解液を調製する場合は、これらの成分の合量の添加濃度が検討例１と同様に８ｍＬ／Ｌの分散液となるようにした。そして、上記した分散した触媒成分が異なる２種類の電解液をそれぞれに用いて、検討例１に記載の方法に従い、８００ｍＡ／ｃｍ２で３０分の定電流電解を１０回行なった。後者の電極組成は、これらを溶解させた水溶液のＩＣＰ分析からＦｅ５５Ｃｏ４５－ｈｍｈの組成比であった。図１２に、上記した異なる構成の触媒層をそれぞれに析出させた電極を作製して、電流密度１００ｍＡ／ｃｍ２で連続的に電解したときの過電圧の変化を示した。図１２に示した通り、Ｆｅ－ｈｍｈ成分とＣｏ－ｎｓ成分を共存させて作製した電極では、Ｆｅ－ｈｍｈの単独成分の電極より小さい過電圧が得られた。なお、図１２中に、上記構成の効果を示すため、電解液にＣｏ－ｎｓ成分を単独で分散させた場合の試験結果についても合わせて記載した。 (Examination example 4)
Regarding the case where Fe-hmh is used alone as a component to be dispersed in the electrolytic solution, and the case where the Fe-hmh component and the Co-ns component are added to the electrolytic solution so that the mass ratio is 1:1. investigated. At that time, when preparing an electrolytic solution using both the Fe-hmh component and the Co-ns component, the total concentration of these components was adjusted to be 8 mL / L dispersion as in Examination Example 1. . Then, using the above-mentioned two types of electrolytic solutions with different dispersed catalyst components, according to the method described in Examination Example 1, constant current electrolysis was performed 10 times at 800 mA/cm 2 for 30 minutes. The electrode composition of the latter was found to be a composition ratio of Fe 55 Co 45 -hmh from ICP analysis of an aqueous solution in which these were dissolved. FIG. 12 shows changes in overvoltage when electrodes were prepared by depositing catalyst layers having different structures as described above and electrolysis was continuously performed at a current density of 100 mA/cm 2 . As shown in FIG. 12, the electrode produced by coexisting the Fe-hmh component and the Co-ns component yielded a lower overvoltage than the electrode of the single component of Fe-hmh. In order to show the effect of the above configuration, FIG. 12 also shows the test results when the Co-ns component was dispersed alone in the electrolytic solution.
（検討例５）
　電解液に分散させる成分として、Ｆｅ－ｈｍｈ粒子とＣｏ－ｎｓ粒子を下記の異なった割合で用い、検討例４で行ったと同様の濃度で共存させた触媒成分を分散させた電解液を調製した。得られた各電解液で電解し、電解後に得られた、Ｃｏ－ｎｓ成分（以下、Ｃｏとも表示）の析出量に対するＦｅ－ｈｍｈ成分（以下、Ｆｅとも表示）の析出量及び電解特性について検討した。具体的には、ＦｅとＣｏが、質量比で、Ｆｅ：Ｃｏ＝５：１（Ｃｏ／Ｆｅ＝０．２）、Ｆｅ：Ｃｏ＝１０：１（Ｃｏ／Ｆｅ＝０．１）、Ｆｅ：Ｃｏ＝１：５（Ｃｏ／Ｆｅ＝５）、Ｆｅ：Ｃｏ＝１：１０（Ｃｏ／Ｆｅ＝１０）の割合でそれぞれ共存するように、Ｆｅ－ｈｍｈ成分とＣｏ－ｎｓ成分を添加した電解液をそれぞれ調製した。そして、上記した分散した触媒成分の構成割合が異なる複数の電解液をそれぞれに用いて、検討例１に記載の方法に従い、８００ｍＡ／ｃｍ２で３０分の定電流電解を１０回行なった。その結果、図１４に示したように、ＦｅとＣｏを共存させた触媒成分を分散させた電解液を用いることで、Ｆｅ及びＣｏの析出量をいずれも増加させる効果が得られることを確認した。なお、図１４中に、検討例４で用いたＦｅ：Ｃｏ＝１：１（Ｃｏ／Ｆｅ＝１）の添加割合で触媒成分を分散させた電解液で電解した場合の析出量についても、合わせて示した。 (Examination example 5)
Fe-hmh particles and Co-ns particles were used as components to be dispersed in the electrolytic solution at the following different ratios, and an electrolytic solution was prepared in which the catalyst components were dispersed in the same concentration as in Examination Example 4. . Each electrolytic solution obtained was electrolyzed, and the deposition amount of the Fe-hmh component (hereinafter also referred to as Fe) relative to the deposition amount of the Co-ns component (hereinafter also referred to as Co) obtained after electrolysis and the electrolytic characteristics were examined. bottom. Specifically, the mass ratio of Fe to Co is Fe:Co=5:1 (Co/Fe=0.2), Fe:Co=10:1 (Co/Fe=0.1), Fe: Electrolyte solution to which Fe-hmh component and Co-ns component are added so as to coexist in ratios of Co=1:5 (Co/Fe=5) and Fe:Co=1:10 (Co/Fe=10) were prepared respectively. Then, according to the method described in Investigation Example 1, constant current electrolysis was performed 10 times at 800 mA/cm 2 for 30 minutes using a plurality of electrolytic solutions having different composition ratios of the dispersed catalyst components. As a result, as shown in FIG. 14, it was confirmed that the use of an electrolytic solution in which catalyst components in which Fe and Co coexist are dispersed has the effect of increasing the amounts of both Fe and Co precipitated. . In addition, in FIG. 14, the amount of precipitation when electrolysis is performed with an electrolytic solution in which the catalyst component is dispersed at the addition ratio of Fe:Co=1:1 (Co/Fe=1) used in Study Example 4 is also shown. indicated.
　図１３に、上記した異なる２種の触媒成分を、添加割合を変えて分散させた構成の電解液を用いて、構成の異なる触媒層をそれぞれに析出させた電極を作製し、電解後に得られたＣｏ析出量に対するＦｅ析出量、及び、電流密度１００ｍＡ／ｃｍ２で電解したときの過電圧の変化を示した。図１３中の「○」は、Ｃｏ析出量に対するＦｅ析出量を示し、図１３中の「□」は、過電圧の変化を示す。図１３に示した通り、Ｃｏ－ｎｓ成分の析出量の増加した電極ほど、Ｆｅ－ｈｍｈ析出量が増加し、同時に過電圧が減少した。 In FIG. 13, using an electrolytic solution having a structure in which the above-mentioned two different catalyst components are dispersed at different addition ratios, electrodes with different catalyst layers deposited on each electrode are produced, and the resulting electrode is obtained after electrolysis. The amount of Fe deposited with respect to the amount of Co deposited, and changes in overvoltage when electrolyzed at a current density of 100 mA/cm 2 are shown. "○" in FIG. 13 indicates the amount of Fe deposited with respect to the amount of Co deposited, and "□" in FIG. 13 indicates the change in overvoltage. As shown in FIG. 13, the electrode with an increased Co-ns component deposition amount had an increased Fe-hmh deposition amount and at the same time a decreased overvoltage.
（実施例１）
　陽極基体として、１７．５質量％塩酸中に、沸点近傍で６分間浸漬して化学エッチング処理を行ったニッケルエクスパンドメッシュ（１０ｃｍ×１０ｃｍ、ＬＷ×３．７ＳＷ×０．９ＳＴ×０．８Ｔ）を用いた。このエクスパンドメッシュを、６０メッシュのアルミナ粒子でブラスト処理（０．３ＭＰａ）した後、２０質量％塩酸に浸漬し、沸点近傍で、６分間化学エッチング処理した。そして、化学エッチング処理後の陽極基体の表面に、リチウム含有ニッケル酸化物の前駆体となる成分を含んだ水溶液を刷毛で塗布した後、８０℃で１５分間乾燥させた。次いで、大気雰囲気下、６００℃で１５分間熱処理した。上記した水溶液の塗布から熱処理までの処理を２０回繰り返して、陽極基体の表面上に中間層（組成：Ｌｉ０．５Ｎｉ１．５Ｏ２）が形成された中間体を得た。 (Example 1)
As the anode substrate, a nickel expanded mesh (10 cm × 10 cm, LW × 3.7 SW × 0.9 ST × 0.8 T) was subjected to a chemical etching treatment by being immersed in 17.5% by mass hydrochloric acid for 6 minutes near the boiling point. Using. This expanded mesh was blasted (0.3 MPa) with 60-mesh alumina particles, immersed in 20% by mass hydrochloric acid, and chemically etched for 6 minutes near the boiling point. An aqueous solution containing a precursor component of lithium-containing nickel oxide was applied to the surface of the anode substrate after the chemical etching treatment with a brush, and then dried at 80° C. for 15 minutes. Then, heat treatment was performed at 600° C. for 15 minutes in an air atmosphere. The above-described treatments from application of the aqueous solution to heat treatment were repeated 20 times to obtain an intermediate having an intermediate layer (composition: Li 0.5 Ni 1.5 O 2 ) formed on the surface of the anode substrate.
　次に、先に検討例１で説明したと同様のＮｉＦｅＣｏ－ｈｍｈ分散液を用い、該分散液を、検討例１で説明した電解液に対して、分散液の添加濃度が１ｍＬ／Ｌとなるように調整して、本実施例で使用する触媒を分散した電解液を調製した。そして、この電解液を用いて、検討例１で説明したと同様の電解操作をして、上記のようにして形成した中間体の表面に、ＮｉｘＦｅｙＣｏｚ－ｈｍｈからなる触媒層を形成したＮｉアノード（酸素発生用アノード）を得た。そして、得られたＮｉアノードと、隔膜Ｚｉｒｆｏｎ（商品名、ＡＧＦＡ社製）と、ＲｕとＰｒ酸化物からなる触媒層を形成した活性カソードとを用い、中性隔膜を用いた小型のゼロギャップ型電解セルを作製した。電極面積は１９ｃｍ２とした。 Next, the same NiFeCo-hmh dispersion as described in Examination Example 1 was used, and the dispersion was added to the electrolytic solution described in Examination Example 1 so that the concentration of the dispersion added was 1 mL / L. An electrolytic solution in which the catalyst used in this example is dispersed was prepared by adjusting as follows. Then, using this electrolytic solution, the same electrolysis operation as described in Examination Example 1 was performed to form a catalyst layer composed of Ni x Fe y Co z -hmh on the surface of the intermediate formed as described above. A formed Ni anode (anode for oxygen evolution) was obtained. Then, using the obtained Ni anode, a diaphragm Zirfon (trade name, manufactured by AGFA), and an active cathode formed with a catalyst layer composed of Ru and Pr oxide, a small zero-gap type using a neutral diaphragm An electrolytic cell was produced. The electrode area was 19 cm 2 .
　上記のようにして得たゼロギャップ型電解セルを用いて、アルカリ水電解を行った。その際、Ｎｉアノードの触媒層の形成に用いた上記のＮｉＦｅＣｏ－ｈｍｈ分散液を、添加濃度が１ｍＬ／Ｌとなる割合で添加した２５質量％のＫＯＨ水溶液を電解液に用いた。そして、該電解液を、電解セルを構成するアノード室とカソード室の各室に供給し、電流密度６ｋＡ／ｍ２でそれぞれ６時間電解した。次いで、アノードとカソードを短絡状態（０ｋＡ／ｍ２）とし、１５時間停止させた。上記の電解から停止までの操作を１サイクルとするシャットダウン試験を行った。その結果、２０回のシャットダウン試験において、電圧が安定に保たれることを確認した。 Alkaline water electrolysis was performed using the zero-gap electrolysis cell obtained as described above. At that time, a 25 mass % KOH aqueous solution in which the above NiFeCo-hmh dispersion used for forming the catalyst layer of the Ni anode was added at a concentration of 1 mL/L was used as the electrolyte. Then, the electrolytic solution was supplied to each of the anode chamber and the cathode chamber constituting the electrolytic cell, and electrolysis was performed for 6 hours at a current density of 6 kA/m 2 . Then, the anode and cathode were short-circuited (0 kA/m 2 ) and stopped for 15 hours. A shutdown test was conducted in which the operation from electrolysis to stop described above is one cycle. As a result, it was confirmed that the voltage was kept stable in 20 shutdown tests.
（比較例１）
　実施例１で作製したゼロギャップ型電解セルを構成するアノード室とカソード室の各室に供給する電解液に、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを添加しない電解液を用いたこと以外は実施例１と同様にしてアルカリ水電解を行った。具体的には、実施例１で用いたと同様の電解セルで、実施例１で行ったと同様のシャットダウン試験を行った。その結果、停止回数の増加とともにセル電圧も徐々に増加したことを確認した。このことから、実施例１におけるＮｉｘＦｅｙＣｏｚ－ｈｍｈを分散した電解液を用いたアルカリ水電解方法における優位性が確認できた。 (Comparative example 1)
Examples except that the electrolytic solution to which Ni x Fe y Co z -hmh was not added was used as the electrolytic solution supplied to each of the anode chamber and the cathode chamber constituting the zero-gap electrolytic cell produced in Example 1. Alkaline water electrolysis was performed in the same manner as in 1. Specifically, the same electrolytic cell as used in Example 1 was used, and the same shutdown test as in Example 1 was performed. As a result, it was confirmed that the cell voltage gradually increased as the number of stops increased. From this, the superiority of the alkaline water electrolysis method using the electrolytic solution in which Ni x Fe y Co z -hmh was dispersed in Example 1 was confirmed.
　本発明の活用例としては、触媒層にハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を用いた特有の構成の酸素発生アノードが挙げられる。そして、該酸素発生アノードを用い、ＮｉｘＦｅｙＣｏｚ－ｈｍｈを分散させた電解液を、少なくともアノード室に供給して通常の方法で電解するという極めて簡便な方法によって、簡便に多量の触媒を短時間で堆積させることができるので、触媒層の触媒活性を効果的に回復させることが可能になる。このため、再生可能エネルギーなどの出力変動の大きい電力を動力源とした場合にも、電解性能が劣化しにくく、より長期間にわたってより安定して電解性能が維持できる、工業的に実用価値の高いアルカリ水電解方法の実現が期待される。また、本発明の活用例としては、極めて汎用の材料からなるＦｅ－ｈｍｈを分散させた電解液、あるいは、Ｆｅ－ｈｍｈとＣｏ－ｎｓを分散させて共存させたＦｅ－ｈｍｈの堆積量が多くなることが確認された電解液、を用いて触媒層を形成した酸素発生アノードが挙げられる。 An example of the application of the present invention is a uniquely configured oxygen evolution anode using a hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh ) for the catalyst layer. Then, using the oxygen-evolving anode, an electrolytic solution in which Ni x Fe y Co z -hmh is dispersed is supplied at least to the anode chamber, and electrolysis is performed in a usual manner. can be deposited in a short time, it is possible to effectively recover the catalytic activity of the catalyst layer. For this reason, even when using electricity with large output fluctuations such as renewable energy as a power source, the electrolysis performance is less likely to deteriorate, and the electrolysis performance can be maintained more stably for a longer period of time, making it highly practical industrially. Realization of an alkaline water electrolysis method is expected. In addition, as an example of utilization of the present invention, an electrolytic solution in which Fe-hmh made of a very general-purpose material is dispersed, or a large amount of Fe-hmh in which Fe-hmh and Co-ns are dispersed and coexisted are deposited. and an oxygen-evolving anode in which a catalyst layer is formed using an electrolytic solution that has been confirmed to be
　２：導電性基体
　４：中間層
　６：触媒層
　１０：アルカリ水電解用アノード

  2: Conductive substrate 4: Intermediate layer 6: Catalyst layer 10: Anode for alkaline water electrolysis

Claims (9)

  1. 　金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒を分散させた電解液を、電解セルを構成するアノード室とカソード室に供給し、各室での電解に共通して用いることを特徴とするアルカリ水電解方法。 An electrolytic solution in which a catalyst containing a hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh), which is a composite of a metal hydroxide and an organic substance, is dispersed in an anode chamber constituting an electrolytic cell. A method of electrolyzing alkaline water, characterized in that it is supplied to a cathode chamber and used in common for electrolysis in each chamber.
  2. 　金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒を分散させた電解液を、電解セルを構成する少なくともアノード室に供給し、運転中に、前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈの電解析出を前記電解セル内にて行い、酸素発生用アノードを構成する、表面に触媒層が形成されてなる導電性基体の表面に、前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈを電解析出させることで、電解性能を回復、向上させることを特徴とするアルカリ水電解方法。 An electrolytic solution containing a hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh), which is a composite of a metal hydroxide and an organic substance, is dispersed in at least an anode chamber constituting an electrolytic cell. During operation, the Ni x Fe y Co z -hmh is electrolytically deposited in the electrolysis cell to constitute an oxygen evolution anode, a conductive substrate having a catalyst layer formed on the surface A method for electrolyzing alkaline water, wherein the Ni x Fe y Co z -hmh is electrolytically deposited on the surface of the alkaline water electrolysis method, wherein the electrolysis performance is recovered and improved.
  3. 　前記電解液の供給を、間欠的に行う請求項１又は２に記載のアルカリ水電解方法。 The alkaline water electrolysis method according to claim 1 or 2, wherein the electrolytic solution is supplied intermittently.
  4. 　前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈが、いずれも１～２００ｎｍの範囲内の大きさの物質である、層状の分子構造を有するシート状の物質、トンネル構造の針状形状の物質及びアモルファス構造の粒子状の物質の少なくともいずれかを有する請求項１又は２に記載のアルカリ水電解方法。 The Ni x Fe y Co z -hmh is a sheet-like substance having a layered molecular structure, a needle-like substance having a tunnel structure, and an amorphous structure, all of which have a size within the range of 1 to 200 nm. 3. The alkaline water electrolysis method according to claim 1, wherein at least one of particulate matter is included.
  5. 　前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈを導電性基体の表面に電解析出させる条件が、前記導電性基体を、１．２Ｖ～１．８Ｖ　ｖｓ．ＲＨＥの電位範囲に保持することである請求項２に記載のアルカリ水電解方法。 The condition for electrolytically depositing the Ni x Fe y Co z -hmh on the surface of the conductive substrate is 1.2 V to 1.8 V vs. 3. The alkaline water electrolysis method according to claim 2, wherein the potential range of RHE is maintained.
  6. 　前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈを分散させた電解液として、濃度が５～１００ｇ／ＬであるＮｉｘＦｅｙＣｏｚ－ｈｍｈ分散液を用い、該ＮｉｘＦｅｙＣｏｚ－ｈｍｈ分散液の電解液への添加濃度が０．１～８ｍＬ／Ｌの範囲内になるように調整したものを用いる請求項１又は２に記載のアルカリ水電解方法。 As the electrolytic solution in which the Ni x Fe y Co z -hmh is dispersed, a Ni x Fe y Co z -hmh dispersion having a concentration of 5 to 100 g/L is used, and the Ni x Fe y Co z -hmh dispersion is 3. The alkaline water electrolysis method according to claim 1 or 2, wherein the concentration of added to the electrolytic solution is adjusted to be within the range of 0.1 to 8 mL / L.
  7. 　前記ＮｉｘＦｅｙＣｏｚ－ｈｍｈは、Ｎｉ／Ｆｅ／Ｃｏの原子比が、０．１～０．９／０．１～０．９／０．１～０．９である請求項１又は２に記載のアルカリ水電解方法。 1 or _ 2. The alkaline water electrolysis method according to 2.
  8. 　表面がニッケル又はニッケル基合金からなる導電性基体と、
    　該導電性基体の表面上に形成された、金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒層と、
    を備えてなることを特徴とする酸素発生を行うアルカリ水電解用アノード。     a conductive substrate having a surface made of nickel or a nickel-based alloy;
    a catalyst layer comprising hybrid nickel-iron-cobalt hydroxide ( NixFeyCoz - hmh), a composite of a metal hydroxide and an organic material, formed on the surface of the conductive substrate ;
    An anode for alkaline water electrolysis that generates oxygen, comprising:
  9. 　表面がニッケル又はニッケル基合金からなる導電性基体と、
    　該導電性基体の表面上に形成された、組成式ＬｉｘＮｉ２－ｘＯ２（０．０２≦ｘ≦０．５）で表されるリチウム含有ニッケル酸化物からなる中間層と、
    　該中間層の表面上に形成された、金属水酸化物と有機物との複合体のハイブリッド水酸化ニッケル・鉄・コバルト（ＮｉｘＦｅｙＣｏｚ－ｈｍｈ）を含んでなる触媒層と、
    を備えてなることを特徴とする酸素発生を行うアルカリ水電解用アノード。

          a conductive substrate having a surface made of nickel or a nickel-based alloy;
    an intermediate layer formed on the surface of the conductive substrate and made of a lithium-containing nickel oxide represented by a composition formula Li x Ni 2-x O 2 (0.02≦x≦0.5);
    a catalyst layer comprising hybrid nickel-iron-cobalt hydroxide (Ni x Fe y Co z -hmh), which is a composite of a metal hydroxide and an organic material, formed on the surface of the intermediate layer;
    An anode for alkaline water electrolysis that generates oxygen, comprising:
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WO2020184607A1 (en) * 2019-03-12 2020-09-17 デノラ・ペルメレック株式会社 Alkaline water electrolysis method and alkaline water electrolysis anode
JP2021139027A (en) * 2020-03-09 2021-09-16 デノラ・ペルメレック株式会社 Alkaline water electrolysis method and anode for alkaline water electrolysis
CN113502487A (en) * 2021-08-05 2021-10-15 先进能源产业研究院(广州)有限公司 Preparation method of high-activity bifunctional oxygen electrocatalyst
CN113666427A (en) * 2021-09-01 2021-11-19 中国地质大学（武汉） Transition metal layered double hydroxide modified by phytic acid and preparation method and application thereof

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WO2020184607A1 (en) * 2019-03-12 2020-09-17 デノラ・ペルメレック株式会社 Alkaline water electrolysis method and alkaline water electrolysis anode
JP2021139027A (en) * 2020-03-09 2021-09-16 デノラ・ペルメレック株式会社 Alkaline water electrolysis method and anode for alkaline water electrolysis
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