WO2024063051A1 - Alkaline water electrolysis system, method for alkaline water electrolysis, and method for producing hydrogen - Google Patents

Alkaline water electrolysis system, method for alkaline water electrolysis, and method for producing hydrogen Download PDF

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WO2024063051A1
WO2024063051A1 PCT/JP2023/033920 JP2023033920W WO2024063051A1 WO 2024063051 A1 WO2024063051 A1 WO 2024063051A1 JP 2023033920 W JP2023033920 W JP 2023033920W WO 2024063051 A1 WO2024063051 A1 WO 2024063051A1
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water electrolysis
alkaline water
electrolyte
anode
concentration
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直人 轟
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国立大学法人東北大学
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/042—Electrodes formed of a single material
    • C25B11/046—Alloys
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • 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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  • the present invention relates to an alkaline water electrolysis system, an alkaline water electrolysis method, and a method for producing hydrogen.
  • Hydrogen is a clean energy that does not emit carbon dioxide during its use, and is used, for example, as a fuel for fuel cell vehicles and household fuel cells.
  • Hydrogen which is produced through the electrolytic reaction of water powered by power generation systems that use renewable energies such as solar power, wind power, and hydroelectric power, generates carbon dioxide not only when it is used but also when it is generated. It is called “green hydrogen” because it does not produce hydrogen, and is attracting attention as a fundamental energy for a sustainable social economy.
  • Water electrolysis technologies currently in practical use mainly include alkaline water electrolysis technology that uses a highly concentrated alkaline aqueous solution as an electrolyte (see, for example, Patent Document 1), and solid water electrolysis technology that uses a solid polymer membrane (SPE) as an electrolyte.
  • SPE solid polymer membrane
  • Polymer water electrolysis technology for example, see Patent Document 2 is known.
  • the oxygen generation reaction (4OH ⁇ ⁇ O 2 +2H 2 O+4e ⁇ ) at the anode is the rate-determining step of the water electrolysis reaction.
  • existing alkaline water electrolysis technology uses nickel in the anode, which is relatively stable even in highly concentrated alkaline aqueous solutions.
  • anodes using nickel are required to have improved characteristics.
  • nickel anodes are said to have a lifespan of several decades if a stable power source is used.
  • a power generation system that uses renewable energy with large output fluctuations is used as a power source (power source)
  • catalyst activity and durability tend to decrease.
  • Non-Patent Documents 1 to 3 When stainless steel is used as an anode for alkaline water electrolysis, a nanofiber catalyst layer made of nickel-iron hydroxide is formed on its surface, which suppresses overpotential and realizes highly efficient anode reactions, and also reduces output fluctuations. It is said that low overvoltage can be maintained for a long time even when using renewable energy as a power source.
  • the present invention provides an alkaline water solution that can sustainably generate a highly efficient oxygen generation reaction at the anode even when using a power source with large output fluctuations, and can also improve safety.
  • An object of the present invention is to provide an electrolysis system and an alkaline water electrolysis method. Furthermore, even when using a power supply with large output fluctuations, the present invention can sustainably cause a highly efficient oxygen generation reaction at the anode, and as a result, hydrogen can be generated highly efficiently at the cathode.
  • An object of the present invention is to provide a method for producing hydrogen that can also improve safety.
  • the present inventor has developed an alkaline water electrolysis system using stainless steel as an anode material by incorporating cobalt into the electrolyte and controlling the concentration of cobalt in the electrolyte to a specific concentration.
  • the present invention was completed after further studies based on these findings.
  • An alkaline water electrolysis system that uses stainless steel as an anode and contains cobalt in the electrolyte at a concentration of 3 to 30 ⁇ M.
  • the alkaline water electrolysis system according to [1] which uses a power generation system that uses renewable energy as a power source.
  • An alkaline water electrolysis method which includes performing alkaline water electrolysis using stainless steel as an anode and containing cobalt in an electrolytic solution at a concentration of 3 to 30 ⁇ M.
  • a method for producing hydrogen comprising generating hydrogen at a cathode by using stainless steel as an anode and performing alkaline water electrolysis with cobalt contained in an electrolytic solution at a concentration of 3 to 30 ⁇ M.
  • a numerical range expressed using “ ⁇ ” means a range that includes the numerical values written before and after " ⁇ " as lower and upper limits. For example, when “A to B" is written, the numerical range is "A to B".
  • the alkaline water electrolysis system and alkaline water electrolysis method of the present invention can generate a highly efficient oxygen generation reaction at the anode even when using a power source with large output fluctuations, and can also improve safety. . Furthermore, according to the hydrogen production method of the present invention, even when using a power source with large output fluctuations, a highly efficient oxygen generation reaction can occur at the anode, and as a result, hydrogen can be generated at the cathode with high efficiency. This also makes it possible to improve safety.
  • FIG. 1 is a schematic diagram for explaining a configuration example of an alkaline water electrolysis system.
  • FIG. 2 is a schematic diagram showing an example of the configuration of an electrode used in a potential cycle test. It is a graph showing test results of a potential cycle test. It is a graph showing test results of a potential cycle test.
  • FIG. 1 is a schematic diagram for explaining a configuration example of an alkaline water electrolysis system 10 according to an embodiment of the present invention.
  • the alkaline water electrolysis system 10 includes an anode 11 , a cathode 12 , an electrolytic cell 13 containing an alkaline electrolyte 15 , and a power source 14 .
  • an oxygen generation reaction (4OH ⁇ ⁇ O 2 +2H 2 O+4e ⁇ ) occurs at the anode 11
  • a hydrogen generation reaction (2H 2 O+2e ⁇ ⁇ H 2 +2OH ⁇ ) occurs at the cathode 12.
  • the size (scale) of the alkaline water electrolysis system of the present invention is appropriately set depending on the purpose and business scale. For example, it can be designed as appropriate, from a size that operates at a laboratory level to a scale of a large-scale hydrogen generation system in the field.
  • the anode 11 is an electrode (positive electrode) that causes an oxygen generation reaction in alkaline water electrolysis.
  • Anode 11 is made of stainless steel.
  • the stainless steel that constitutes the anode 11 is not particularly limited. Examples include SUS310S, SUS316, and SUS304, with SUS310S being preferred.
  • the cathode 12 is an electrode (cathode) that causes a hydrogen generation reaction in alkaline water electrolysis, and one used in normal alkaline water electrolysis is appropriately adopted.
  • the cathodes described in JP2022-065484A, JP2022-025951A, or WO2021/184607 can be used without particular limitation.
  • Electrolytic cell 13 contains alkaline electrolyte 15.
  • an electrolytic cell used for normal alkaline water electrolysis such as an electrochemical cell
  • the alkaline electrolyte 15 is, for example, an alkaline aqueous solution, and this alkaline electrolyte 15 contains cobalt at a specific concentration.
  • Examples of the alkaline aqueous solution include a potassium hydroxide aqueous solution and a sodium hydroxide aqueous solution, with a potassium hydroxide aqueous solution being preferred.
  • the concentration of the alkaline aqueous solution may be appropriately set depending on the purpose, and can be, for example, 3 to 10 M (mol/L).
  • the cobalt contained in the alkaline electrolyte may be derived from a cobalt-containing compound (preferably a cobalt salt) added to the alkaline electrolyte.
  • a cobalt-containing compound preferably a cobalt salt
  • it may be derived from cobalt - containing compounds such as Co ( NO3 ) 2.6H2O , and ( CH3COO ) 2Co.3H2O , CoSO4.7H2O .
  • concentration of cobalt (molar concentration of cobalt atoms) in the alkaline electrolyte is 3 to 30 ⁇ M ( ⁇ mol/L).
  • the concentration of cobalt in the alkaline electrolyte is within the above range, the elution of harmful chromium from the anode made of stainless steel into the alkaline electrolyte 15 can be significantly suppressed.
  • the reason for this is not clear, but it is thought that one reason is that cobalt ions dissolved at a specific concentration in the alkaline electrolyte exhibit a sacrificial anticorrosion effect that suppresses the elution reaction of chromium and iron.
  • the cobalt concentration in the alkaline electrolyte is preferably 3 to 25 ⁇ M, more preferably 3.5 to 20 ⁇ M, even more preferably 4 to 18 ⁇ M, and 4. Particularly preferred is 5 to 16 ⁇ M.
  • a power source used for normal alkaline water electrolysis such as a battery
  • power source 14 may be a renewable energy power generation system that powers an alkaline water electrolysis system.
  • Examples of power generation systems that utilize renewable energy include solar power generators, wind power generators, hydroelectric power generators, biomass power generators, and geothermal power generators.
  • the anode 11 used in the present invention can continuously generate a highly efficient oxygen generation reaction over a long period of time even when a power generation system using renewable energy with large output fluctuations is used as a power source.
  • leaching of chromium derived from stainless steel into the electrolyte can be effectively suppressed. Therefore, by operating the alkaline water electrolysis system of the present invention using a power generation system that utilizes renewable energy, it becomes possible to produce so-called green hydrogen with high efficiency and greater safety.
  • alkaline water electrolysis method and hydrogen production method In relation to the alkaline water electrolysis system described above, the present invention provides the following alkaline water electrolysis method.
  • An alkaline water electrolysis method that involves performing alkaline water electrolysis using stainless steel as an anode and containing cobalt in an electrolytic solution at a concentration of 3 to 30 ⁇ M.
  • the present invention provides the following hydrogen production method.
  • a method for producing hydrogen which includes generating hydrogen at the cathode by using stainless steel as the anode and performing alkaline water electrolysis with cobalt contained in the electrolyte at a concentration of 3 to 30 ⁇ M.
  • normal alkaline water electrolysis is performed by the alkaline water electrolysis system 10. That is, by supplying electrons from the power source 14 to the cathode 12, water (H 2 O) in the alkaline electrolyte 15 is reduced and hydrogen (H 2 gas) is generated. At the anode 11, hydroxide ions (OH ⁇ ) generated by a reduction reaction on the cathode 12 side are oxidized to generate oxygen (O 2 gas).
  • the oxygen generation reaction at the anode 11 can be performed stably with high efficiency over a long period of time. It can be caused by Furthermore, by containing cobalt in the above-described specific concentration in the alkaline electrolyte 15, it is possible to effectively suppress harmful chromium from leaching into the electrolyte from the stainless steel that constitutes the anode. Therefore, environmental load is reduced, safety is improved in alkaline water electrolysis or hydrogen production using it, and hydrogen production efficiency is also improved.
  • Example 1 A SUS310S stainless steel plate (12 mm x 12 mm, thickness: 0.5 mm) was mirror-polished in order with Emily paper (#600, #1000, #1500) and alumina paste (particle size 0.3 ⁇ m, particle size 0.05 ⁇ m), Further, the electrode was washed with ultrapure water and acetone, and insulated and coated so that the exposed area to the electrolytic solution was 0.5 cm 2 per side to obtain an electrode. Specifically, as shown in FIG.
  • the surface of the mirror-polished SUS310S stainless steel plate is partially covered with an insulating coating 21 made of an alkali-resistant insulating resin, and the surface not covered with the insulating coating 21 is
  • the electrode 20 was obtained by setting the area of the surface (exposed portion 22) to 0.5 cm 2 per side.
  • three types of Emily papers with different abrasive grain sizes were used, changing from one with a large abrasive grain size (#600) to one with a small abrasive grain size (#1500).
  • Polishing was carried out, and further polishing was performed using two types of alumina pastes with different particle sizes, changing the particle size from a large one (0.3 ⁇ m) to a small one (0.05 ⁇ m).
  • this electrode was used as a working electrode (anode)
  • a Pt wire was used as a counter electrode
  • a PTFE (polytetrafluoroethylene) three-electrode electric wire was used as a reference electrode.
  • the entire electrode including the insulating coating was immersed in an electrolytic solution, and alkaline water electrolysis was performed at room temperature (25° C.).
  • a KOH aqueous solution (7 mol/L as KOH) containing CoSO 4 .7H 2 O (5 ⁇ mol/L as Co) was used as the electrolytic solution.
  • a potential cycle test was conducted using a protocol that simulates the start-stop environment of an electrolytic cell when using variable power in a power generation system that uses renewable energy. That is, a potential cycle test was conducted 20,000 times at a sweep rate of 1 V/s, with one cycle ranging from 0.5 V to 1.8 V (reversible hydrogen electrode reference).
  • overvoltage refers to the difference between the standard electrode potential of a thermodynamically determined reaction and the actually measured potential of the electrode when the reaction actually proceeds in an electrochemical reaction. It is preferable that this difference is smaller, since energy loss during electrolysis is smaller.
  • Example 2 A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 10 ⁇ mol/L. The results are shown in FIGS. 3 and 4.
  • Example 3 A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 30 ⁇ mol/L. The results are shown in FIGS. 3 and 4.
  • the elution of Cr into the electrolyte is significantly suppressed compared to the alkaline water electrolysis system according to the comparative example.
  • the amount of Fe eluted into the electrolyte is inversely correlated with the Co concentration in the electrolyte (FIG. 4).
  • the elution behavior of Cr from the anode made of stainless steel into the electrolyte is heterogeneous.
  • the effect of suppressing the elution of Cr into the electrolyte is limited whether the Co concentration in the electrolyte is low or high, and the Co concentration in the electrolyte is controlled within a specific range.

Abstract

This alkaline water electrolysis system uses stainless steel as an anode and contains cobalt at a concentration of 3 to 30 µM in the electrolyte.

Description

アルカリ水電解システム、アルカリ水電解方法、及び水素の製造方法Alkaline water electrolysis system, alkaline water electrolysis method, and hydrogen production method
　本発明は、アルカリ水電解システム、アルカリ水電解方法、及び水素の製造方法に関する。 The present invention relates to an alkaline water electrolysis system, an alkaline water electrolysis method, and a method for producing hydrogen.
　水素は、その使用段階において二酸化炭素を排出しないクリーンなエネルギーであり、例えば、燃料電池自動車や家庭用燃料電池の燃料として使用されている。太陽光発電、風力発電、及び水力発電などの再生可能エネルギーを利用する発電システムを電源とする水の電解反応により生成される水素は、その使用時だけでなく、生成時においても二酸化炭素を発生しないため「グリーン水素」と呼ばれ、サステイナブルな社会経済の基盤エネルギーとして注目されている。 Hydrogen is a clean energy that does not emit carbon dioxide during its use, and is used, for example, as a fuel for fuel cell vehicles and household fuel cells. Hydrogen, which is produced through the electrolytic reaction of water powered by power generation systems that use renewable energies such as solar power, wind power, and hydroelectric power, generates carbon dioxide not only when it is used but also when it is generated. It is called "green hydrogen" because it does not produce hydrogen, and is attracting attention as a fundamental energy for a sustainable social economy.
　現在実用化されている水電解技術としては、主に、電解質に高濃度のアルカリ水溶液を用いるアルカリ水電解技術（例えば、特許文献１参照）と、電解質に固体高分子膜（ＳＰＥ）を用いる固体高分子水電解技術（例えば、特許文献２参照）が知られている。 Water electrolysis technologies currently in practical use mainly include alkaline water electrolysis technology that uses a highly concentrated alkaline aqueous solution as an electrolyte (see, for example, Patent Document 1), and solid water electrolysis technology that uses a solid polymer membrane (SPE) as an electrolyte. Polymer water electrolysis technology (for example, see Patent Document 2) is known.
　アルカリ水電解技術では、アノード（陽極）における酸素発生反応（４ＯＨ－→Ｏ２＋２Ｈ２Ｏ＋４ｅ－）が、水電解反応の律速段階となっている。既存のアルカリ水電解技術では、アノードに、高濃度のアルカリ水溶液中でも比較的安定なニッケルが使用されている。しかし、アノードにおける酸素発生反応のさらなる高効率化の点で、ニッケルを用いたアノードには特性の向上が求められている。また、ニッケルを用いたアノードは、安定した出力の電源を用いれば数十年もの寿命があるとされる。しかしながら、出力変動が大きい再生可能エネルギーを利用する発電システムを電源（動力源）として用いると、触媒活性や耐久性が低下しやすい。
　これらの問題に対処した技術として、アノードの材料にステンレス鋼を用いることが提案されている（非特許文献１～３）。ステンレス鋼をアルカリ水電解のアノードとして用いると、その表面にニッケル鉄水酸化物からなるナノファイバ触媒層が形成され、過電圧（Ｏｖｅｒｐｏｔｅｎｔｉａｌ）を抑えて高効率なアノード反応を実現でき、また、出力変動が大きい再生可能エネルギーを電源としても、低い過電圧を長期に亘り維持できるとされる。 In alkaline water electrolysis technology, the oxygen generation reaction (4OH − →O 2 +2H 2 O+4e − ) at the anode is the rate-determining step of the water electrolysis reaction. Existing alkaline water electrolysis technology uses nickel in the anode, which is relatively stable even in highly concentrated alkaline aqueous solutions. However, in order to further increase the efficiency of the oxygen generation reaction at the anode, anodes using nickel are required to have improved characteristics. Additionally, nickel anodes are said to have a lifespan of several decades if a stable power source is used. However, when a power generation system that uses renewable energy with large output fluctuations is used as a power source (power source), catalyst activity and durability tend to decrease.
As a technique for dealing with these problems, it has been proposed to use stainless steel as the material for the anode (Non-Patent Documents 1 to 3). When stainless steel is used as an anode for alkaline water electrolysis, a nanofiber catalyst layer made of nickel-iron hydroxide is formed on its surface, which suppresses overpotential and realizes highly efficient anode reactions, and also reduces output fluctuations. It is said that low overvoltage can be maintained for a long time even when using renewable energy as a power source.
国際公開第２０２０／１８４６０７号International Publication No. 2020/184607 特開２０２０－１２２１７２号公報Japanese Patent Application Publication No. 2020-122172
　本発明者は上記の非特許文献１～３の技術を基礎としてさらに検討を重ねた結果、アノードの材料としてステンレス鋼を用いてアルカリ水電解を行うと、特に、出力変動が大きい電源を用いた場合に、ステンレス鋼からクロムなどの構成元素が多量に溶出してしまうことが明らかとなってきた。クロムはアルカリ環境で有毒な六価クロムを生成するため、ステンレス鋼をアノードとして用いるアルカリ水電解技術を、現状で実用化するのは問題がある。 As a result of further studies based on the techniques of the above-mentioned non-patent documents 1 to 3, the present inventor found that when alkaline water electrolysis is performed using stainless steel as the anode material, especially when using a power source with large output fluctuations. It has become clear that in some cases, large amounts of constituent elements such as chromium are leached from stainless steel. Since chromium generates hexavalent chromium, which is toxic in an alkaline environment, it is problematic to put alkaline water electrolysis technology, which uses stainless steel as an anode, into practical use at present.
　上述した事情に鑑み、本発明は、出力変動が大きい電源を用いた場合でも、アノードにおいて高効率の酸素発生反応を持続的に生じさせることができ、かつ安全性も高めることが可能なアルカリ水電解システム及びアルカリ水電解方法を提供することを課題とする。また、本発明は、出力変動が大きい電源を用いた場合でも、アノードにおいて高効率の酸素発生反応を持続的に生じさせることができ、その結果、カソードにおいて高効率に水素を生成することができ、かつ安全性も高めることが可能な水素の製造方法を提供することを課題とする。 In view of the above-mentioned circumstances, the present invention provides an alkaline water solution that can sustainably generate a highly efficient oxygen generation reaction at the anode even when using a power source with large output fluctuations, and can also improve safety. An object of the present invention is to provide an electrolysis system and an alkaline water electrolysis method. Furthermore, even when using a power supply with large output fluctuations, the present invention can sustainably cause a highly efficient oxygen generation reaction at the anode, and as a result, hydrogen can be generated highly efficiently at the cathode. An object of the present invention is to provide a method for producing hydrogen that can also improve safety.
　本発明者は上記課題に鑑み鋭意検討を重ねた結果、ステンレス鋼をアノード材料として用いたアルカリ水電解システムにおいて、電解液にコバルトを含有させ、かつ電解液中のコバルトの濃度を特定の濃度に制御することで、出力変動が大きい電源を用いて長期に亘りアルカリ水電解を行っても、アノードからのステンレス鋼の構成成分であるクロムの溶出を格段に抑制できることを見出した。本発明はこれらの知見に基づきさらに検討を重ねて完成されるに至ったものである。 As a result of extensive studies in view of the above problems, the present inventor has developed an alkaline water electrolysis system using stainless steel as an anode material by incorporating cobalt into the electrolyte and controlling the concentration of cobalt in the electrolyte to a specific concentration. We have discovered that by controlling this, it is possible to significantly suppress the elution of chromium, a constituent of stainless steel, from the anode even when alkaline water electrolysis is performed over a long period of time using a power source with large output fluctuations. The present invention was completed after further studies based on these findings.
　すなわち、上記の課題は以下の手段により解決される。
［１］
　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させたアルカリ水電解システム。
［２］
　再生可能エネルギーを利用する発電システムを電源として用いる、［１］に記載のアルカリ水電解システム。
［３］
　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させてアルカリ水電解を行うことを含む、アルカリ水電解方法。
［４］
　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させてアルカリ水電解を行うことにより、カソードにおいて水素を生成することを含む、水素の製造方法。
［５］
　再生可能エネルギーを利用する発電システムを電源として用いる、［３］又は［４］に記載の方法。 That is, the above problem is solved by the following means.
[1]
An alkaline water electrolysis system that uses stainless steel as an anode and contains cobalt in the electrolyte at a concentration of 3 to 30 μM.
[2]
The alkaline water electrolysis system according to [1], which uses a power generation system that uses renewable energy as a power source.
[3]
An alkaline water electrolysis method, which includes performing alkaline water electrolysis using stainless steel as an anode and containing cobalt in an electrolytic solution at a concentration of 3 to 30 μM.
[4]
A method for producing hydrogen, comprising generating hydrogen at a cathode by using stainless steel as an anode and performing alkaline water electrolysis with cobalt contained in an electrolytic solution at a concentration of 3 to 30 μM.
[5]
The method according to [3] or [4], which uses a power generation system that uses renewable energy as a power source.
　本発明及び本明細書において、「～」を用いて表される数値範囲は、「～」の前後に記載される数値を下限値及び上限値として含む範囲を意味する。例えば、「Ａ～Ｂ」と記載されている場合、その数値範囲は、「Ａ以上Ｂ以下」である。 In the present invention and this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits. For example, when "A to B" is written, the numerical range is "A to B".
　本発明のアルカリ水電解システム及びアルカリ水電解方法は、出力変動が大きい電源を用いた場合でも、アノードにおいて高効率の酸素発生反応を生じさせることができ、かつ安全性も高めることが可能となる。また、本発明の水素の製造方法によれば、出力変動が大きい電源を用いた場合でも、アノードにおいて高効率の酸素発生反応を生じさせることができ、その結果、カソードにおいて高効率に水素を生成することができ、かつ安全性も高めることが可能となる。 The alkaline water electrolysis system and alkaline water electrolysis method of the present invention can generate a highly efficient oxygen generation reaction at the anode even when using a power source with large output fluctuations, and can also improve safety. . Furthermore, according to the hydrogen production method of the present invention, even when using a power source with large output fluctuations, a highly efficient oxygen generation reaction can occur at the anode, and as a result, hydrogen can be generated at the cathode with high efficiency. This also makes it possible to improve safety.
アルカリ水電解システムの構成例を説明するための模式図である。FIG. 1 is a schematic diagram for explaining a configuration example of an alkaline water electrolysis system. 電位サイクル試験に用いられる電極の構成例を示す模式図である。FIG. 2 is a schematic diagram showing an example of the configuration of an electrode used in a potential cycle test. 電位サイクル試験の試験結果を示すグラフである。It is a graph showing test results of a potential cycle test. 電位サイクル試験の試験結果を示すグラフである。It is a graph showing test results of a potential cycle test.
　以下、図面を参照しながら、本発明の好適な実施形態を説明する。なお、本発明は、本発明で規定すること以外は、以下に示す形態に限定されるものではない。 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the forms shown below except as specified in the present invention.
［アルカリ水電解システム］
　図１は、本発明の一実施形態に係るアルカリ水電解システム１０の構成例を説明するための模式図である。アルカリ水電解システム１０は、アノード１１と、カソード１２と、アルカリ電解液１５を収容する電解槽１３と、電源１４とを有する。電流が流れると、アノード１１において酸素発生反応（４ＯＨ－→Ｏ２＋２Ｈ２Ｏ＋４ｅ－）が生じ、カソード１２では水素発生反応（２Ｈ２Ｏ＋２ｅ－→Ｈ２＋２ＯＨ－）が生じる。本発明のアルカリ水電解システムのサイズ（スケール）は、目的や事業規模に応じて適宜に設定されるものである。例えば、実験室レベルで作動させるサイズから、フィールドにおける大規模水素生成システムのスケールまで、適宜に設計することができる。 [Alkaline water electrolysis system]
FIG. 1 is a schematic diagram for explaining a configuration example of an alkaline water electrolysis system 10 according to an embodiment of the present invention. The alkaline water electrolysis system 10 includes an anode 11 , a cathode 12 , an electrolytic cell 13 containing an alkaline electrolyte 15 , and a power source 14 . When current flows, an oxygen generation reaction (4OH − →O 2 +2H 2 O+4e − ) occurs at the anode 11, and a hydrogen generation reaction (2H 2 O+2e − →H 2 +2OH − ) occurs at the cathode 12. The size (scale) of the alkaline water electrolysis system of the present invention is appropriately set depending on the purpose and business scale. For example, it can be designed as appropriate, from a size that operates at a laboratory level to a scale of a large-scale hydrogen generation system in the field.
　アノード１１は、アルカリ水電解において酸素発生反応を生じる電極（陽極）である。アノード１１はステンレス鋼で構成されている。アノード１１を構成するステンレス鋼は特に制限されない。例えば、ＳＵＳ３１０Ｓ、ＳＵＳ３１６、及びＳＵＳ３０４などが挙げられ、ＳＵＳ３１０Ｓが好ましい。 The anode 11 is an electrode (positive electrode) that causes an oxygen generation reaction in alkaline water electrolysis. Anode 11 is made of stainless steel. The stainless steel that constitutes the anode 11 is not particularly limited. Examples include SUS310S, SUS316, and SUS304, with SUS310S being preferred.
　カソード１２は、アルカリ水電解において水素発生反応を生じる電極（陰極）であり、通常のアルカリ水電解に用いられるものが適宜に採用される。例えば、特開２０２２－０６５４８４号公報、特開２０２２－０２５９５１号公報、又は国際公開第２０２１／１８４６０７号に記載のカソードなどを、特に制限なく用いることができる。 The cathode 12 is an electrode (cathode) that causes a hydrogen generation reaction in alkaline water electrolysis, and one used in normal alkaline water electrolysis is appropriately adopted. For example, the cathodes described in JP2022-065484A, JP2022-025951A, or WO2021/184607 can be used without particular limitation.
　電解槽１３はアルカリ電解液１５を収容する。電解槽１３は、電気化学セルなどの通常のアルカリ水電解に用いられるものが適宜採用される。アルカリ電解液１５は、例えばアルカリ水溶液であり、このアルカリ電解液１５はコバルトを特定濃度で含む。アルカリ水溶液としては、例えば、水酸化カリウム水溶液、又は水酸化ナトリウム水溶液などが挙げられ、水酸化カリウム水溶液が好ましい。アルカリ水溶液の濃度（水中の水酸化物の濃度）は目的に応じて適宜に設定すればよく、例えば、３～１０Ｍ（ｍｏｌ／Ｌ）とすることができる。アルカリ電解液に含まれるコバルトは、アルカリ電解液に添加されたコバルト含有化合物（好ましくはコバルト塩）由来のものであってよい。例えば、Ｃｏ（ＮＯ３）２・６Ｈ２Ｏ、及び（ＣＨ３ＣＯＯ）２Ｃｏ・３Ｈ２Ｏ、ＣｏＳＯ４・７Ｈ２Ｏなどのコバルト含有化合物由来のものであってよい。アルカリ電解液中のコバルトの濃度（コバルト原子のモル濃度）は、３～３０μＭ（μｍｏｌ／Ｌ）である。アルカリ電解液中のコバルトの濃度が上記範囲内であることにより、ステンレス鋼で構成されたアノードからアルカリ電解液１５中への有害なクロムの溶出を格段に抑えることができる。この理由は定かではないが、アルカリ電解液中に特定濃度で溶解したコバルトイオンがクロムや鉄の溶出反応を抑制する犠牲防食作用を示すことが一因と考えられる。クロムの溶出をより抑える観点から、アルカリ電解液中のコバルト濃度は３～２５μＭであることが好ましく、３．５～２０μＭであることがより好ましく、４～１８μＭであることがさらに好ましく、４．５～１６μＭであることが特に好ましい。 Electrolytic cell 13 contains alkaline electrolyte 15. As the electrolytic cell 13, an electrolytic cell used for normal alkaline water electrolysis, such as an electrochemical cell, is appropriately employed. The alkaline electrolyte 15 is, for example, an alkaline aqueous solution, and this alkaline electrolyte 15 contains cobalt at a specific concentration. Examples of the alkaline aqueous solution include a potassium hydroxide aqueous solution and a sodium hydroxide aqueous solution, with a potassium hydroxide aqueous solution being preferred. The concentration of the alkaline aqueous solution (concentration of hydroxide in water) may be appropriately set depending on the purpose, and can be, for example, 3 to 10 M (mol/L). The cobalt contained in the alkaline electrolyte may be derived from a cobalt-containing compound (preferably a cobalt salt) added to the alkaline electrolyte. For example, it may be derived from cobalt - containing compounds such as Co ( NO3 ) 2.6H2O , and ( CH3COO ) 2Co.3H2O , CoSO4.7H2O . The concentration of cobalt (molar concentration of cobalt atoms) in the alkaline electrolyte is 3 to 30 μM (μmol/L). When the concentration of cobalt in the alkaline electrolyte is within the above range, the elution of harmful chromium from the anode made of stainless steel into the alkaline electrolyte 15 can be significantly suppressed. The reason for this is not clear, but it is thought that one reason is that cobalt ions dissolved at a specific concentration in the alkaline electrolyte exhibit a sacrificial anticorrosion effect that suppresses the elution reaction of chromium and iron. From the viewpoint of further suppressing the elution of chromium, the cobalt concentration in the alkaline electrolyte is preferably 3 to 25 μM, more preferably 3.5 to 20 μM, even more preferably 4 to 18 μM, and 4. Particularly preferred is 5 to 16 μM.
　電源１４は、バッテリーなどの通常のアルカリ水電解に用いられるものが適宜採用される。あるいは、電源１４は、アルカリ水電解システムに電力を供給する、再生可能エネルギーを利用する発電システムであってもよい。再生可能エネルギーを利用する発電システムとしては、例えば、太陽光発電機、風力発電機、水力発電機、バイオマス発電機、及び地熱発電機などが挙げられる。本発明に用いるアノード１１は、出力変動が大きい再生可能エネルギーを利用する発電システムを電源として用いても、高効率の酸素発生反応を長期に亘り持続的に生じさせることができる。また、その間、ステンレス鋼由来のクロムの電解液中への浸み出しを効果的に抑えることができる。したがって、再生可能エネルギーを利用する発電システムを用いて本発明のアルカリ水電解システムを作動させることにより、いわゆるグリーン水素を、高効率に、より高い安全性の下で製造することが可能となる。 As the power source 14, a power source used for normal alkaline water electrolysis, such as a battery, is appropriately employed. Alternatively, power source 14 may be a renewable energy power generation system that powers an alkaline water electrolysis system. Examples of power generation systems that utilize renewable energy include solar power generators, wind power generators, hydroelectric power generators, biomass power generators, and geothermal power generators. The anode 11 used in the present invention can continuously generate a highly efficient oxygen generation reaction over a long period of time even when a power generation system using renewable energy with large output fluctuations is used as a power source. In addition, during this time, leaching of chromium derived from stainless steel into the electrolyte can be effectively suppressed. Therefore, by operating the alkaline water electrolysis system of the present invention using a power generation system that utilizes renewable energy, it becomes possible to produce so-called green hydrogen with high efficiency and greater safety.
［アルカリ水電解方法及び水素の製造方法］
　上述したアルカリ水電解システムに関連し、本発明は、次のアルカリ水電解方法を提供するものである。 [Alkaline water electrolysis method and hydrogen production method]
In relation to the alkaline water electrolysis system described above, the present invention provides the following alkaline water electrolysis method.
　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させてアルカリ水電解を行うことを含む、アルカリ水電解方法。 An alkaline water electrolysis method that involves performing alkaline water electrolysis using stainless steel as an anode and containing cobalt in an electrolytic solution at a concentration of 3 to 30 μM.
　また、上述したアルカリ水電解システムないしアルカリ水電解方法に関連し、本発明は、次の水素の製造方法を提供するものである。 Furthermore, in relation to the above-mentioned alkaline water electrolysis system or alkaline water electrolysis method, the present invention provides the following hydrogen production method.
　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させてアルカリ水電解を行うことにより、カソードにおいて水素を生成することを含む、水素の製造方法。 A method for producing hydrogen, which includes generating hydrogen at the cathode by using stainless steel as the anode and performing alkaline water electrolysis with cobalt contained in the electrolyte at a concentration of 3 to 30 μM.
　本発明のアルカリ水電解方法、及び水素の製造方法の一実施形態では、アルカリ水電解システム１０により通常のアルカリ水電解が実施される。すなわち、電源１４からカソード１２に電子が供給されることによりアルカリ電解液１５中の水（Ｈ２Ｏ）が還元されて水素（Ｈ２ガス）が生成する。アノード１１では、カソード１２側の還元反応により生じた水酸化物イオン（ＯＨ－）が酸化されることで酸素（Ｏ２ガス）が生成する。
　ここで、アノードをステンレス鋼で構成することにより、電源として、出力変動の大きな再生可能エネルギーを利用する発電システムを適用しても、アノード１１において酸素発生反応を、高効率に、長期に亘り安定して生じさせることができる。さらに、アルカリ電解液１５にコバルトを上記の特定濃度で含有させることにより、アノードを構成するステンレス鋼から有害なクロムが電解液中に溶出することを効果的に抑制することができる。それゆえ、環境負荷が低減し、アルカリ水電解ないしそれを利用した水素の製造において安全性が向上し、水素の製造効率も向上する。 In an embodiment of the alkaline water electrolysis method and hydrogen production method of the present invention, normal alkaline water electrolysis is performed by the alkaline water electrolysis system 10. That is, by supplying electrons from the power source 14 to the cathode 12, water (H 2 O) in the alkaline electrolyte 15 is reduced and hydrogen (H 2 gas) is generated. At the anode 11, hydroxide ions (OH − ) generated by a reduction reaction on the cathode 12 side are oxidized to generate oxygen (O 2 gas).
By configuring the anode with stainless steel, even if a power generation system that uses renewable energy with large output fluctuations is applied as a power source, the oxygen generation reaction at the anode 11 can be performed stably with high efficiency over a long period of time. It can be caused by Furthermore, by containing cobalt in the above-described specific concentration in the alkaline electrolyte 15, it is possible to effectively suppress harmful chromium from leaching into the electrolyte from the stainless steel that constitutes the anode. Therefore, environmental load is reduced, safety is improved in alkaline water electrolysis or hydrogen production using it, and hydrogen production efficiency is also improved.
　以下に、本発明を実施例に基づき詳細に説明するが、本発明は、本発明で規定すること以外はこれらの実施例に限定されるものではない。 The present invention will be described in detail below based on Examples, but the present invention is not limited to these Examples except for what is specified in the present invention.
［アルカリ水電解システムの構築と評価］
　＜実施例１＞
　ＳＵＳ３１０Ｓステンレス鋼板(１２ｍｍ×１２ｍｍ、厚み：０．５ｍｍ)をエミリー紙(♯６００、♯１０００、♯１５００)及びアルミナペースト(粒径０．３μｍ、粒径０．０５μｍ)で順次に鏡面研磨し、さらに、超純水及びアセトンで洗浄し、電解液への露出面積が片面につき０．５ｃｍ２となるように絶縁被覆して電極を得た。具体的には、上記鏡面研磨されたＳＵＳ３１０Ｓステンレス鋼板の表面を、図２に示されるように、耐アルカリ絶縁樹脂からなる絶縁被覆部２１で部分的に覆い、絶縁被覆部２１で覆われていない当該表面（露出部２２）の面積を片面につき０．５ｃｍ２として電極２０を得た。なお、上記鏡面研磨の際には、砥粒径が異なる３種のエミリー紙を、砥粒径が大きいもの（♯６００）から小さなもの（♯１５００）へと取り換えながら３段階の砥粒径で研磨し、さらに、粒径が異なる２種のアルミナペーストを、粒径が大きいもの（０．３μｍ）から小さなもの（０．０５μｍ）へと取り換えながら２段階の粒径で研磨した。
　次いで、この電極を作用極（アノード）に用い、Ｐｔワイヤーを対極、Ｈｇ／ＨｇＯ(ＫＯＨ水溶液（ＫＯＨとして７ｍｏｌ／Ｌ）)を参照極としたＰＴＦＥ（ポリテトラフルオロエチレン）製の３電極式電気化学セルを用い、絶縁被覆部を含む電極全体を電解液に浸漬させ、室温（２５℃）下で、アルカリ水電解を行なった。電解液はＣｏＳＯ４・７Ｈ２Ｏ（Ｃｏとして５μｍｏｌ／Ｌ）を含むＫＯＨ水溶液（ＫＯＨとして７ｍｏｌ／Ｌ）を用いた。
　具体的には、再生可能エネルギーを利用する発電システムの変動電力を利用したときの電解槽の起動停止環境を模擬したプロトコルで電位サイクル試験を行った。すなわち０．５Ｖから１．８Ｖ（可逆水素電極基準）を１サイクルとして、掃引速度１Ｖ／ｓで２００００回の電位サイクル試験を行なった。この電位サイクルの前後において、１．２Ｖ－２．４Ｖ ｖｓ ＲＨＥ（水素電極）の範囲で分極曲線を測定し、交流インピーダンス法で測定した溶液抵抗値を用いてｉＲ損を補正した分極曲線を作成した。得られた曲線から１００ｍＡ・ｃｍ－２の値の過電圧を求め、電極特性を評価した。結果を図３に示す。
　また、上記電位サイクル試験後の電解液を誘導結合プラズマ質量分析法で分析し、Ｃｒ及びＦｅの溶出量を評価した。結果を図４に示す。なお、上記した「過電圧」とは、電気化学反応において、熱力学的に求められる反応の標準電極電位と、実際に反応が進行するときの電極の実測電位との差を意味する。この差は小さい方が電気分解におけるエネルギー損失が少なく好ましい。 [Construction and evaluation of alkaline water electrolysis system]
<Example 1>
A SUS310S stainless steel plate (12 mm x 12 mm, thickness: 0.5 mm) was mirror-polished in order with Emily paper (#600, #1000, #1500) and alumina paste (particle size 0.3 μm, particle size 0.05 μm), Further, the electrode was washed with ultrapure water and acetone, and insulated and coated so that the exposed area to the electrolytic solution was 0.5 cm 2 per side to obtain an electrode. Specifically, as shown in FIG. 2, the surface of the mirror-polished SUS310S stainless steel plate is partially covered with an insulating coating 21 made of an alkali-resistant insulating resin, and the surface not covered with the insulating coating 21 is The electrode 20 was obtained by setting the area of the surface (exposed portion 22) to 0.5 cm 2 per side. In addition, during the mirror polishing described above, three types of Emily papers with different abrasive grain sizes were used, changing from one with a large abrasive grain size (#600) to one with a small abrasive grain size (#1500). Polishing was carried out, and further polishing was performed using two types of alumina pastes with different particle sizes, changing the particle size from a large one (0.3 μm) to a small one (0.05 μm).
Next, this electrode was used as a working electrode (anode), a Pt wire was used as a counter electrode, and a PTFE (polytetrafluoroethylene) three-electrode electric wire was used as a reference electrode. Using a chemical cell, the entire electrode including the insulating coating was immersed in an electrolytic solution, and alkaline water electrolysis was performed at room temperature (25° C.). As the electrolytic solution, a KOH aqueous solution (7 mol/L as KOH) containing CoSO 4 .7H 2 O (5 μmol/L as Co) was used.
Specifically, a potential cycle test was conducted using a protocol that simulates the start-stop environment of an electrolytic cell when using variable power in a power generation system that uses renewable energy. That is, a potential cycle test was conducted 20,000 times at a sweep rate of 1 V/s, with one cycle ranging from 0.5 V to 1.8 V (reversible hydrogen electrode reference). Before and after this potential cycle, a polarization curve was measured in the range of 1.2V-2.4V vs RHE (hydrogen electrode), and a polarization curve corrected for iR loss was created using the solution resistance value measured by the AC impedance method. did. An overvoltage of 100 mA·cm −2 was determined from the obtained curve, and the electrode characteristics were evaluated. The results are shown in Figure 3.
Further, the electrolytic solution after the potential cycle test was analyzed by inductively coupled plasma mass spectrometry to evaluate the elution amount of Cr and Fe. The results are shown in Figure 4. In addition, the above-mentioned "overvoltage" refers to the difference between the standard electrode potential of a thermodynamically determined reaction and the actually measured potential of the electrode when the reaction actually proceeds in an electrochemical reaction. It is preferable that this difference is smaller, since energy loss during electrolysis is smaller.
　＜実施例２＞
　電解液中のＣｏ濃度が１０μｍｏｌ／Ｌとなるように電解液中にＣｏＳＯ４・７Ｈ２Ｏを添加したこと以外は、実施例１と同様にして電位サイクル試験を行った。結果を図３及び図４に示す。 <Example 2>
A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 10 μmol/L. The results are shown in FIGS. 3 and 4.
　＜実施例３＞
　電解液中のＣｏ濃度が３０μｍｏｌ／Ｌとなるように電解液中にＣｏＳＯ４・７Ｈ２Ｏを添加したこと以外は、実施例１と同様にして電位サイクル試験を行った。結果を図３及び図４に示す。 <Example 3>
A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 30 μmol/L. The results are shown in FIGS. 3 and 4.
　＜比較例１＞
　電解液にＣｏＳＯ４・７Ｈ２Ｏを添加しないこと以外は、実施例１と同様にして電位サイクル試験を行った。結果を図３及び図４に示す。 <Comparative example 1>
A potential cycle test was conducted in the same manner as in Example 1 except that CoSO 4 .7H 2 O was not added to the electrolyte. The results are shown in FIGS. 3 and 4.
　＜比較例２＞
　電解液中のＣｏ濃度が１μｍｏｌ／Ｌとなるように電解液中にＣｏＳＯ４・７Ｈ２Ｏを添加したこと以外は、実施例１と同様にして電位サイクル試験を行った。結果を図３及び図４に示す。 <Comparative example 2>
A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 1 μmol/L. The results are shown in FIGS. 3 and 4.
　＜比較例３＞
　電解液中のＣｏ濃度が５０μｍｏｌ／Ｌとなるように電解液中にＣｏＳＯ４・７Ｈ２Ｏを添加したこと以外は、実施例１と同様にして電位サイクル試験を行った。結果を図３及び図４に示す。 <Comparative example 3>
A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 50 μmol/L. The results are shown in FIGS. 3 and 4.
　＜比較例４＞
　電解液中のＣｏ濃度が１００μｍｏｌ／Ｌとなるように電解液中にＣｏＳＯ４・７Ｈ２Ｏを添加したこと以外は、実施例１と同様にして電位サイクル試験を行った。結果を図３及び図４に示す。 <Comparative example 4>
A potential cycle test was conducted in the same manner as in Example 1, except that CoSO 4 .7H 2 O was added to the electrolyte so that the Co concentration in the electrolyte was 100 μmol/L. The results are shown in FIGS. 3 and 4.
　電解液がＣｏを含まない比較例１や、Ｃｏ濃度が本発明で規定するよりも低い比較例２に係るアルカリ水電解システムは、図４に示されるように、電位サイクル試験後において、電解液中にＣｒが相当量溶出する結果となった。また、比較例３及び４に係るアルカリ水電解システムは、電解液中のＣｏ濃度が高いにもかかわらず、電位サイクル試験後においてＣｒが相当量溶出する結果となった。
　これに対し、実施例１～３に係るアルカリ水電解システムでは、図４に示されるように、電解液中へのＣｒの溶出が、比較例に係るアルカリ水電解システムよりも大幅に抑制されることがわかった。ここで、電解液中へのＦｅの溶出量は、電解液中のＣｏ濃度と逆相関することが示されている（図４）。これと対比すると、ステンレス鋼で構成したアノードから電解液中へのＣｒの溶出挙動は異質であることがわかる。つまり、電解液中へのＣｒの溶出抑制効果は、電解液中のＣｏ濃度が低くても、逆に高くしても限定的であり、電解液中のＣｏ濃度を特定の範囲に制御してはじめて、電解液中へのＣｒの溶出抑制効果が飛躍的に高められることがわかる。
　また、実施例及び比較例に係るアルカリ水電解システムは、図３に示されるように、電位サイクル試験前（０ｃｙｃｌｅ）の過電圧と電位サイクル試験後（２００００ｃｙｃｌｅ後）の過電圧との変化量がいずれも同程度であり、これらの過電圧は、現行電極の１つであるＮｉメッシュにＮｉＣｏ酸化物を触媒層として塗布した電極（ＮｉＣｏＯＸ／Ｎｉ）でアノードを構成した場合の過電圧（約０．４２Ｖ）よりも明らかに低いレベルであった。この結果は、アルカリ水電解システムのアノードをステンレス鋼で構成することにより、２００００回の電位サイクル試験を経ても過電圧が十分に抑えられ、かつ、電解液中のＣｏはこのサイクル特性に影響しないことを示している。 As shown in FIG. 4, in the alkaline water electrolysis system according to Comparative Example 1 in which the electrolyte does not contain Co or in Comparative Example 2 in which the Co concentration is lower than that specified in the present invention, after the potential cycle test, the electrolyte As a result, a considerable amount of Cr was eluted inside. Furthermore, in the alkaline water electrolysis systems according to Comparative Examples 3 and 4, a considerable amount of Cr was eluted after the potential cycle test, despite the high Co concentration in the electrolyte solution.
On the other hand, in the alkaline water electrolysis systems according to Examples 1 to 3, as shown in FIG. 4, the elution of Cr into the electrolyte is significantly suppressed compared to the alkaline water electrolysis system according to the comparative example. I understand. Here, it has been shown that the amount of Fe eluted into the electrolyte is inversely correlated with the Co concentration in the electrolyte (FIG. 4). In contrast, it can be seen that the elution behavior of Cr from the anode made of stainless steel into the electrolyte is heterogeneous. In other words, the effect of suppressing the elution of Cr into the electrolyte is limited whether the Co concentration in the electrolyte is low or high, and the Co concentration in the electrolyte is controlled within a specific range. It can be seen for the first time that the effect of suppressing elution of Cr into the electrolytic solution is dramatically enhanced.
In addition, as shown in FIG. 3, in the alkaline water electrolysis systems according to the examples and comparative examples, the amount of change between the overvoltage before the potential cycle test (0 cycles) and the overvoltage after the potential cycle test (after 20,000 cycles) is These overvoltages are about the same, and the overvoltage (approximately 0.42 V) when the anode is configured with one of the current electrodes, an electrode in which NiCo oxide is coated as a catalyst layer on Ni mesh (NiCoO x /Ni). It was clearly at a lower level. These results show that by constructing the anode of an alkaline water electrolysis system with stainless steel, overvoltage can be sufficiently suppressed even after 20,000 potential cycle tests, and that Co in the electrolyte does not affect this cycle characteristic. It shows.
　本発明をその実施態様とともに説明したが、我々は特に指定しない限り我々の発明を説明のどの細部においても限定しようとするものではなく、添付の請求の範囲に示した発明の精神と範囲に反することなく幅広く解釈されるべきであると考える。 Although the invention has been described in conjunction with embodiments thereof, we do not intend to limit our invention in any detail in the description unless otherwise specified and contrary to the spirit and scope of the invention as set forth in the appended claims. I believe that it should be interpreted broadly without any restrictions.
　本願は、２０２２年９月２０日に日本国で特許出願された特願２０２２－１４９１８７に基づく優先権を主張するものであり、これはここに参照してその内容を本明細書の記載の一部として取り込む。 This application claims priority based on Japanese Patent Application No. 2022-149187, which was filed in Japan on September 20, 2022, and the content thereof is incorporated herein by reference. Incorporate it as a part.
　１０…アルカリ水電解システム、１１…アノード、１２…カソード、１３…電解槽、１４…電源、１５…電解液。

  DESCRIPTION OF SYMBOLS 10... Alkaline water electrolysis system, 11... Anode, 12... Cathode, 13... Electrolytic cell, 14... Power supply, 15... Electrolyte solution.

Claims (5)

  1. 　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させたアルカリ水電解システム。 An alkaline water electrolysis system that uses stainless steel as the anode and contains cobalt in the electrolyte at a concentration of 3 to 30 μM.
  2. 　再生可能エネルギーを利用する発電システムを電源として用いる、請求項１に記載のアルカリ水電解システム。 The alkaline water electrolysis system according to claim 1, which uses a power generation system that uses renewable energy as a power source.
  3. 　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させてアルカリ水電解を行うことを含む、アルカリ水電解方法。 An alkaline water electrolysis method that involves performing alkaline water electrolysis using stainless steel as an anode and containing cobalt in an electrolytic solution at a concentration of 3 to 30 μM.
  4. 　ステンレス鋼をアノードとして用い、電解液中にコバルトを濃度３～３０μＭで含有させてアルカリ水電解を行うことにより、カソードにおいて水素を生成することを含む、水素の製造方法。 A method for producing hydrogen, which includes generating hydrogen at the cathode by using stainless steel as the anode and performing alkaline water electrolysis with cobalt contained in the electrolyte at a concentration of 3 to 30 μM.
  5. 　再生可能エネルギーを利用する発電システムを電源として用いる、請求項３又は４に記載の方法。

          The method according to claim 3 or 4, wherein a power generation system using renewable energy is used as a power source.
PCT/JP2023/033920 2022-09-20 2023-09-19 Alkaline water electrolysis system, method for alkaline water electrolysis, and method for producing hydrogen WO2024063051A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
KR20210029605A (en) * 2019-09-06 2021-03-16 한국재료연구원 Electrode for water electrolysis comprising catalyst with three-dimensional dendrite structure, method for preparing same and water electrolyzer comprising same
KR20220073263A (en) * 2020-11-26 2022-06-03 인하대학교 산학협력단 Anodized high brittleness and high durability stainless steel electrode for water electrolysis and preparation method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
KR20210029605A (en) * 2019-09-06 2021-03-16 한국재료연구원 Electrode for water electrolysis comprising catalyst with three-dimensional dendrite structure, method for preparing same and water electrolyzer comprising same
KR20220073263A (en) * 2020-11-26 2022-06-03 인하대학교 산학협력단 Anodized high brittleness and high durability stainless steel electrode for water electrolysis and preparation method thereof

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