Electrode for water electrolysis and method for manufacturing electrode for water electrolysis

Abstract

An electrode for water electrolysis includes a substrate and a catalyst portion, the catalyst portion comprising: Raney nickel particles; and metal particles comprising nickel as a main component, the metal particles being in contact with the Raney nickel particles, the metal particles comprising aluminum, wherein the ratio of the total molar number of aluminum in the Raney nickel particles to the total molar number of nickel is greater than the ratio of the total molar number of aluminum in the metal particles to the total molar number of nickel.

Description

Technical Field

[0001] This disclosure relates to electrodes for water electrolysis and methods for manufacturing electrodes for water electrolysis. Background Technology

[0002] Water electrolysis is the process of electrolyzing water into hydrogen and oxygen, and is used, for example, as a technology for producing hydrogen. A water electrolysis apparatus for hydrogen production includes, for example, an electrolytic cell containing an electrolyte such as alkaline water, and an anode and a cathode sandwiched between separators within the electrolytic cell. In this water electrolysis apparatus, oxygen is produced at the anode and hydrogen is produced at the cathode by flowing current between the anode and cathode.

[0003] Japanese Patent Application Publication No. 53-54174 (Patent Document 1) discloses an electrode for water electrolysis in which an oxide body obtained by oxidizing a substance that is soluble in alkali from powdered Raney nickel alloy is bonded with a binder. Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 53-54174 Summary of the Invention The problem the invention aims to solve

[0005] Electrodes for water electrolysis require high activity and long lifespan (improved durability). In particular, from the viewpoint of improving activity, the water electrolysis electrode described in Patent Document 1 has room for improvement.

[0006] The purpose of this disclosure is to provide an electrode for water electrolysis exhibiting high activity and a method for manufacturing the electrode for water electrolysis. Solution for solving the problem

[0007] An electrolytic electrode for solving the above problems includes a substrate and a catalyst portion, the catalyst portion comprising: Raney nickel particles; and metal particles containing nickel as a main component, the metal particles being in contact with the Raney nickel particles, the metal particles containing aluminum, wherein the ratio of the total moles of aluminum in the Raney nickel particles to the total moles of nickel is greater than the ratio of the total moles of aluminum in the metal particles to the total moles of nickel.

[0008] The electrode for water electrolysis comprises a substrate and a catalyst section. The catalyst section comprises Raney nickel particles and metal particles containing nickel as the main component. Raney nickel particles have high activity. The metal particles act as a binder, bonding the Raney nickel particles to the substrate. By including Raney nickel particles and metal particles in the catalyst section, increased activity is expected. Furthermore, by satisfying the specific relationship described above between the Raney nickel particles and the metal particles, further increased activity is expected.

[0009] A method for manufacturing an electrode for water electrolysis includes: a mixing step, in which raw materials of Raney nickel particles, raw materials of metal particles containing nickel as the main component, and a solvent are mixed to obtain a slurry; a water electrolysis electrode precursor forming step, in which the slurry is coated onto a substrate to obtain a water electrolysis electrode precursor; and an alkali treatment step, in which the water electrolysis electrode precursor is treated with an alkali substance to obtain a water electrolysis electrode containing Raney nickel particles, wherein the raw materials of Raney nickel particles contain more moles of aluminum than the raw materials of Raney nickel particles contain more moles of nickel. Invention Effects

[0010] According to this disclosure, a water electrolysis electrode exhibiting high activity and a method for manufacturing the water electrolysis electrode can be obtained. Attached Figure Description

[0011] Figure 1 This is an example of a cross-sectional SEM image of an electrode used for water electrolysis disclosed herein. Figure 2 It is by Figure 1 An example of an element-mapped image obtained by EDX of a SEM image. Figure 3 This is a coordinate graph showing the evaluation results of the activity of the electrode used for water electrolysis in Experiment Example 2. Figure 4 This is a coordinate graph showing the evaluation results of the durability of the electrodes used for water electrolysis in Test Example 2. Figure 5 This is a coordinate graph showing the evaluation results of the activity of the electrode used for water electrolysis in Experiment Example 3. Figure 6 This is a coordinate graph showing the evaluation results of the durability of the electrodes used for water electrolysis in Test Example 3. Figure 7 This is a coordinate graph showing the evaluation results of the activity of the electrode used for water electrolysis in Experiment Example 4. Figure 8 This is a coordinate graph showing the evaluation results of the durability of the electrodes used for water electrolysis in Test Example 4. Figure 9 This is a coordinate graph showing the evaluation results of the activity of the electrode used for water electrolysis in Experimental Example 5. Figure 10 This is a coordinate graph showing the evaluation results of the durability of the electrodes used for water electrolysis in Test Example 5. Detailed Implementation

[0012] The following describes embodiments of the present disclosure (hereinafter referred to as "the present embodiments") and examples of the present disclosure (hereinafter referred to as "the examples"). However, the present embodiments and examples do not limit the technical scope of the present disclosure.

[0013] The water electrolysis electrode of this embodiment is used as the electrolysis electrode in a water electrolysis apparatus. The water electrolysis electrode of this embodiment is suitable for use in an alkaline water electrolysis apparatus.

[0014] The average particle size of Raney alloys refers to the particle size at which the cumulative value in the particle size distribution, determined by laser diffraction scattering, reaches 50%. The average particle size of the raw material for metallic particles refers to the particle size determined by the Fisher method. The average particle size of Raney nickel particles and the average particle size of metallic particles refer to the arithmetic mean of the minor axis diameters of any 100 Raney nickel particles and metallic particles extracted from SEM images obtained using a scanning electron microscope (SEM).

[0015] <Electrodes for water electrolysis> The electrode for water electrolysis in this embodiment includes a substrate and a catalyst section. The catalyst section includes: Raney nickel particles; and metal particles (hereinafter also simply referred to as "metal particles") containing nickel as a main component. The metal particles are in contact with the Raney nickel particles. The metal particles contain aluminum. The ratio of the total molar number of aluminum in the Raney nickel particles to the total molar number of nickel is greater than the ratio of the total molar number of aluminum in the metal particles to the total molar number of nickel. Furthermore, the ratio of the total molar number of aluminum in the Raney nickel particles to the total molar number of components other than aluminum, including nickel, is greater than the ratio of the total molar number of aluminum in the metal particles to the total molar number of components other than aluminum, including nickel.

[0016] The water electrolysis electrode of this embodiment can be a water electrolysis electrode in which a catalyst portion is dispersed in a substrate, or a water electrolysis electrode in which a layer of catalyst portion is formed on the surface of a substrate. Furthermore, the water electrolysis electrode of this embodiment, as described in the manufacturing method below, is obtained by coating a slurry containing raw materials of Raney nickel particles and metal particles onto a substrate and then subjecting it to alkali treatment.

[0017] Substrate The substrate in this embodiment is a conductor capable of conducting electricity. As long as the substrate is conductive, there are no particular limitations, but examples include nickel metal, nickel alloys, and other metals containing Ni. The substrate can be formed entirely of nickel metal or nickel alloys, or only its surface can be formed of nickel metal or nickel alloys. In the case where only the surface of the substrate is formed of nickel metal or nickel alloys, nickel metal or nickel alloys can be coated onto the surface of a metal material such as iron or stainless steel. Preferably, the substrate contains nickel metal or nickel alloys as a main component. From the perspective of resistance to the operating environment, it is preferable that the substrate is composed of nickel metal with higher Ni purity. Furthermore, "containing nickel metal or nickel alloys as a main component" means that the Ni content in the nickel metal or nickel alloy in the substrate exceeds 50% by mass.

[0018] The shape of the substrate is not particularly limited; it can be porous or non-porous. A porous substrate is preferred, as it can contain Raney nickel particles and Ni-containing metal particles. Examples of such substrate shapes include perforated metal, mesh, foamed metal, and expanded metal. Examples of non-porous substrate shapes include, for example, plates.

[0019] There are no particular restrictions on the thickness of the substrate, as long as it is set to be suitable for the water electrolysis device used.

[0020] Catalyst Department The catalyst section comprises: Raney nickel particles; and metal particles containing Ni as the main component. The catalyst section may also be substantially composed of Raney nickel particles and metal particles. In the catalyst section, the Raney nickel particles and metal particles are in contact. Furthermore, "substantially composed of Raney nickel particles and metal particles" means that the Raney nickel particles and metal particles in the catalyst section account for 95% by mass or more.

[0021] (Raney nickel particles) The Raney nickel particles in this embodiment contain Ni and Al. Raney nickel particles are porous bodies with a large specific surface area and numerous fine pores, exhibiting high activity.

[0022] In this embodiment, the ratio of the total number of moles of Al to the total number of moles of Ni in the Raney nickel particles (hereinafter also referred to as the "first Al / Ni ratio") is 1 or less, preferably 0.6 or less. By making the first Al / Ni ratio 1 or less, an increase in activity is expected. The first Al / Ni ratio can be, for example, 0.005 or more, or 0.01 or more. The first Al / Ni ratio can be confirmed, for example, by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX).

[0023] The Raney nickel particles of this embodiment may also contain a first metal other than Ni and Al. By including a first metal in the Raney nickel particles, it is expected that the activity will be further improved. Examples of such a first metal include magnesium (Mg), silicon (Si), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), silver (Ag), platinum (Pt), and gold (Au). The proportion of the first metal contained in the Raney nickel particles is equal to the proportion of the first metal contained in the raw material of the Raney nickel particles (hereinafter also referred to as "Raney alloy"). When the Raney nickel particles contain a first metal, the molar ratio of Ni to the first metal can be, for example, 1.99:0.01 to 1.15:1.85. The molar ratio of Ni to the first metal is preferably 1.99:0.05 to 1.5:0.5.

[0024] The Raney nickel particles of this embodiment can be an alloy composed of a single phase or an alloy composed of multiple phases. Examples of such phases include a phase composed only of nickel, a phase composed of nickel and aluminum, a phase composed of nickel and a first metal, and a phase composed of nickel, aluminum, and a first metal. The phases constituting the Raney nickel particles and their composition ratios can be identified, for example, by SEM-EDX.

[0025] The BET specific surface area of ​​the Raney nickel particles in this embodiment is, for example, 0.05 m². 2 / g or more and 100m 2 / g or less. Furthermore, BET specific surface area refers to the surface area per unit mass of Raney nickel particles determined by N2 adsorption using the BET method.

[0026] In this embodiment, the average particle size of the Raney nickel particles is 5 μm or more and 100 μm or less. If the average particle size of the Raney nickel particles is less than 5 μm, corrosion may occur in the catalyst section, leading to deterioration in durability. If the average particle size of the Raney nickel particles exceeds 100 μm, the activity may decrease due to the small surface area of ​​the catalyst section. The average particle size of the Raney nickel particles can also be 8 μm or more and 85 μm or less, 10 μm or more and 50 μm or less, 10 μm or more and 30 μm or less, or 15 μm or more and 30 μm or less.

[0027] [Raney Alloy] Raney nickel particles are generally obtained by treating Raney alloys containing Ni and alkali-soluble metal elements with an alkaline substance, thereby dissolving the alkali-soluble metal element from the Raney alloy. Preferably, the alkali-soluble metal element is one with a higher ionization tendency compared to Ni. Examples of alkali-soluble metal elements include amphoteric metals (aluminum (Al), zinc (Zn), tin (Sn), and lead (Pb)).

[0028] The Raney nickel particles of this embodiment are obtained by treating a Raney alloy containing Ni and Al with an alkaline substance to dissolve Al from the Raney alloy. The Raney alloy may also contain a first metal.

[0029] Here, when the proportion of Al in the Raney alloy containing Ni and Al is high, the porosity of the Raney nickel particles obtained by dissolving Al is higher, that is, the specific surface area is higher. Therefore, from the viewpoint of obtaining Raney nickel particles exhibiting higher activity, it is preferable to use a Raney alloy with a higher proportion of aluminum.

[0030] On the other hand, when the proportion of Al in a Raney alloy containing Ni and Al is low, the porosity of the Raney nickel particles obtained by dissolving Al is low, that is, the specific surface area is low. Therefore, from the viewpoint of obtaining Raney nickel particles with high durability (strength), it is preferable to use a Raney alloy with a low proportion of Al.

[0031] In this embodiment, from the viewpoint of obtaining Raney nickel particles that maintain durability and exhibit high activity, it is preferable that the number of moles of Al contained in the Raney alloy is greater than the number of moles of Ni contained in the Raney alloy. Furthermore, from this viewpoint, in this embodiment, it is preferable to use a Raney alloy represented by the following formula (1).

[0032] Al3Ni （2-x）） M x (1) In the above formula (1), M is at least one element selected from Mg, Si, Ti, Cr, Mn, Fe, Co, Cu, Ag, Pt and Au, and x satisfies the relationship 0≤x≤0.2.

[0033] Preferably, element M is at least one element selected from Fe and Co. This is because, in addition to the expected increase in activity, it also allows for the expectation of reduced usage and lower costs. More preferably, element M contains at least Fe. From this point of view, in this embodiment, it is more preferable to use a Raney alloy represented by the following formula (2).

[0034] Al3Ni （2-（y+z）） Fe y Co z (2) In the above equation (2), y and z satisfy the relationship 0≤y≤0.1 and 0≤z≤0.1.

[0035] The Raney alloy is, for example, in powder form. In this embodiment, the average particle size of the Raney alloy is 5 μm or more and 100 μm or less. If the average particle size of the Raney alloy is less than 5 μm, corrosion may occur in the catalyst section, leading to deterioration in durability. If the average particle size of the Raney alloy exceeds 100 μm, the activity may decrease due to the small surface area of ​​the catalyst section. The average particle size of the Raney alloy can also be 8 μm or more and 85 μm or less, 10 μm or more and 50 μm or less, 10 μm or more and 30 μm or less, or 15 μm or more and 30 μm or less.

[0036] There are no particular restrictions on the manufacturing method of Raney alloys, and well-known alloy manufacturing methods can be used. Examples of manufacturing methods for Raney alloys include casting, quenching, mechanical alloying, and sputtering.

[0037] (Metal particles) The metal particles in this embodiment contain Ni as a main component. The metal particles are in contact with Raney nickel particles. Preferably, the metal particles are in contact with multiple Raney nickel particles. The metal particles function as an adhesive to bond the Raney nickel particles dispersed in the water electrolysis electrode to each other or to the substrate. This function will be explained below. Furthermore, "containing Ni as a main component" means that the Ni content in the metal particles exceeds 50% by mass.

[0038] When Raney alloy (Raney nickel particles) and metal particles contain metals other than Ni (hereinafter also referred to as "added elements"), applying heat to them causes impurity diffusion, where the added elements are considered impurities. That is, if the atoms of the added element undergo thermal vibration due to heat applied through processes such as sintering, the added element diffuses from the Raney alloy to the metal particle raw material (or from Raney nickel particles to metal particles) due to the concentration gradient of the added element between the Raney alloy and the metal particle raw material (or between Raney nickel particles and metal particles). Therefore, even between different substances such as metal particles and Raney nickel particles (or between Raney alloy and metal particle raw materials), if they are in contact, the added element will undergo surface diffusion, resulting in adhesion between the Raney alloy and the metal particle raw material (or between Raney nickel particles and metal particles). This increases the surface area of ​​the catalyst section, and an increase in the activity of the electrode for water electrolysis can be expected. Furthermore, since the Raney alloy is firmly bonded to the raw materials of the metal particles (or Raney nickel particles and metal particles), detachment from the substrate is suppressed, and as a result, the durability of the electrodes for water electrolysis can also be expected to be improved.

[0039] The metal particles in this embodiment contain Al. That is, in this embodiment, the Al concentration gradient is used as the driving force, and Al atoms diffuse from Raney nickel particles (or from Raney alloy to metal particle raw materials) where the amount of Al is greater than that of the metal particles (or the raw materials of metal particles). Furthermore, by including Al in the metal particles (or the raw materials of metal particles), the function of the metal particles as a binder is improved, resulting in the formation of a stronger electron conduction path, which is expected to further enhance the activity of the electrode for water electrolysis. In addition, since the Raney nickel particles are more firmly bonded to the metal particles (or Raney alloy to metal particle raw materials), the durability of the electrode for water electrolysis is also expected to be improved.

[0040] In this embodiment, the ratio of the total number of moles of Al to the total number of moles of Ni in the metal particles (hereinafter also referred to as the "second Al / Ni ratio") is 0.4 or less, preferably 0.35 or less. By making the second Al / Ni ratio 0.4 or less, an increase in activity is expected. The second Al / Ni ratio can, for example, be 0.005 or more, or 0.01 or more. The second Al / Ni ratio can be confirmed, for example, by SEM-EDX.

[0041] Preferably, the metal particles contain Al on their surface. By containing Al on the surface of the metal particles, it is expected that the function of the metal particles as an adhesive for bonding Raney nickel particles to each other or to a substrate will be further enhanced.

[0042] Preferably, the average particle size of the metal particles is smaller than that of the Raney nickel particles. When the average particle size of the metal particles is smaller than that of the Raney nickel particles, the metal particles can penetrate into the gaps between the Raney nickel particles. As a result, the metal particles and Raney nickel particles can be in closer contact, and the function of the metal particles as a binder is expected to be further improved. The average particle size of the metal particles can be more than 5 times smaller than that of the Raney nickel particles, or more than 10 times smaller. The average particle size of the metal particles is 1 μm or more and 10 μm. The average particle size of the metal particles can also be 1 μm or more and 5 μm or less, 1.5 μm or more and 3.5 μm or less, or 2 μm or more and 3 μm or less. Preferably, the average particle size of the metal particles is 2 μm or more and 3 μm or less. When the average particle size of the metal particles is 2 μm or more and 3 μm or less, improved durability is expected. Furthermore, through the bonding of the metal particles with each other, sometimes the average particle size of the metal particles is larger than that of the Raney nickel particles.

[0043] [Raw materials for metal particles] The preferred raw material for metal particles contains fewer moles of Al than that in the Raney alloy. When the raw material for metal particles contains fewer moles of Al than that in the Raney alloy, in the manufacturing method of the water electrolysis electrode described later, Al diffuses from the Raney alloy to the raw material for metal particles due to the concentration gradient, becoming metal particles. As a result, a more robust electron conduction path is formed, and improvements in the activity and durability of the water electrolysis electrode are expected.

[0044] The raw material for the metal particles can also be substantially composed of nickel, that is, nickel metal with Ni as the main component, such as pure nickel. Nickel metal is an alkali-resistant metal, therefore, it does not corrode even during use. As a result, improvements in the activity and durability of electrodes used in water electrolysis can be expected. Furthermore, "substantially composed of nickel" and "composed of nickel metal with Ni as the main component, such as pure nickel" refer to a Ni content of 95% by mass or more in the metal particles.

[0045] The raw material for the metal particles is, for example, in powder form. Preferably, the average particle size of the raw material is smaller than the average particle size of the Raney alloy. When the average particle size of the raw material is smaller than that of the Raney alloy, the metal particles can penetrate the gaps between the Raney nickel particles obtained from these raw materials, thus improving the binder properties of the metal particles. The average particle size of the raw material can be at least 5 times smaller than the average particle size of the Raney nickel particles, or at least 10 times smaller. The average particle size of the raw material can also be 1 μm or more and 5 μm or less, 1.5 μm or more and 3.5 μm or less, or 2 μm or more and 3 μm or less. Preferably, the average particle size is 2 μm or more and 3 μm or less. When the average particle size is 2 μm or more and 3 μm or less, improved durability is expected.

[0046] The first Al / Ni ratio and the second Al / Ni ratio The first Al / Ni ratio is greater than the second Al / Ni ratio. That is, the Raney nickel particles contain more moles of Al than the metal particles. This improved binding effect of the metal particles results in a more robust electronic conduction pathway, leading to potentially enhanced activity of the electrode used in water electrolysis. Furthermore, the stronger bond between the Raney nickel particles and the metal particles also suggests improved durability of the electrode for water electrolysis.

[0047] The Al-to-Ni ratio in electrodes used for water electrolysis Preferably, the ratio of the total number of moles of Al to the total number of moles of Ni in the water electrolysis electrode of this embodiment (hereinafter also referred to as the "third Al / Ni ratio") is 0.006 or more and 0.45 or less. When the third Al / Ni ratio is within the above range, an improvement in the activity of the water electrolysis electrode can be expected. Furthermore, the total number of moles of Ni in the water electrolysis electrode is the total number of moles of Ni contained in the substrate, Raney nickel particles, and Ni-containing metal particles, and the total number of moles of Al is the total number of moles of Al contained in the Raney nickel particles and Ni-containing metal particles.

[0048] Cross-sectional observation Figure 1 This is an example of a cross-sectional SEM image of the electrode used for water electrolysis in this embodiment. Figure 2 It is by Figure 1 An example of an elemental mapping image obtained by EDX of a SEM image. Furthermore, in this water electrolysis electrode, raw materials are used, including a substrate 1 composed of Ni, a Raney alloy composed of Al3Ni2, and metal particles composed of Ni.

[0049] from Figure 1 and 2 The images confirm that metal particles 3 function as a binder to prevent Raney nickel particles 2 from detaching from the substrate 1. Furthermore, it can be confirmed that trace amounts of Al are present in the Ni-containing metal particles 3. That is, it is conceivable that Al contained in the Raney alloy, the raw material for the Raney nickel particles, diffuses into the raw material of the metal particles, thus becoming metal particles 3.

[0050] Anodes for water electrolysis The electrode for water electrolysis in this embodiment can also be used as the anode for water electrolysis.

[0051] In this embodiment, the ratio of the metal particles in the anode for water electrolysis to the total of the Raney alloy and the metal particles can be, for example, 27% by mass or more and 95% by mass or less. When the ratio of Raney nickel particles to the total of Raney nickel particles and the metal particles is within the above-mentioned range, an anode for water electrolysis exhibiting higher activity can be obtained. The ratio of metal particles to the total of Raney nickel particles and the metal particles can also be 33% by mass or more, and can also be 40% by mass or more. The ratio of Raney nickel particles to the total of Raney nickel particles and the metal particles can also be 92% by mass or less, and can also be 85% by mass or less.

[0052] Cathode for water electrolysis The electrode for water electrolysis in this embodiment can also be used as a cathode for water electrolysis.

[0053] In this embodiment, the ratio of metal particles to the total of Raney nickel particles and metal particles in the cathode for water electrolysis can be, for example, 27% by mass or more and 95% by mass or less. When the ratio of Raney nickel particles to the total of Raney nickel particles and metal particles is within the above-mentioned range, a cathode for water electrolysis exhibiting higher activity can be obtained. The ratio of metal particles to the total of Raney nickel particles and metal particles can also be 30% by mass or more, and even 35% by mass or more. The ratio of Raney nickel particles to the total of Raney nickel particles and metal particles can also be 95% by mass or less, and even 90% by mass or less.

[0054] <Manufacturing Method of Electrodes for Water Electrolysis> The method for manufacturing an electrode for water electrolysis according to this embodiment includes at least (a) a mixing step, (b) a precursor formation step for an electrode for water electrolysis, and (c) an alkali treatment step. The precursor formation step for an electrode for water electrolysis further includes (b-1) a drying step and (b-2) a calcination step. The precursor formation step for an electrode for water electrolysis may also include (b-3) a scraping step and (b-4) a pressing step. Additionally, an oxidation step may be included after the alkali treatment step (c).

[0055] (a) Mixed Process In the mixing process, a slurry is obtained by mixing a Raney alloy, a raw material containing Ni-containing metal particles as the main component, and a solvent. The Raney alloy, the Ni-containing metal particles, and the substrate are as described above. Examples of solvents include water, N-methyl-2-pyrrolidone (NMP), and N-ethyl-2-pyrrolidone (NEP).

[0056] The slurry may also contain thickeners. Examples of thickeners include carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF).

[0057] In this process, a substrate with a low basis weight and a high viscosity (high concentration) slurry are preferably used. By using such a substrate and slurry, the slurry can easily penetrate the substrate in the coating process described later. This is likely due to the following reasons: The lower the basis weight, the higher the porosity of the substrate. Higher substrate porosity leads to a higher slurry loading (catalyst loading), thus allowing for higher activity. Furthermore, a higher viscosity (higher concentration) slurry increases the concentration of the catalyst in the slurry, making it easier for Raney nickel particles to contact the metal particles, thus allowing for improved durability. Moreover, by using a low basis weight substrate, even when a high viscosity slurry has been used for impregnation, a high porosity can be maintained inside the water electrolysis electrode, thus allowing for high activity. "Low basis weight" refers to, for example, 100 g / m³. 2 Above and 600g / m 2 The preferred value is 200g / m³. 2 Above and 400g / m 2 The term "high viscosity" refers to, for example, a slurry containing a solvent concentration of 10% by mass or more and 50% by mass or less, preferably 20% by mass or more and 45% by mass or less.

[0058] (b) Electrode precursor formation process for water electrolysis In the process of forming an electrode precursor for water electrolysis, the slurry obtained in the mixing process is coated onto a substrate to obtain an electrode precursor for water electrolysis.

[0059] In this process, a slurry is applied to the surface of the substrate using any coating apparatus. The slurry can be applied using known coating apparatus such as a die coater, roller coater, knife coater, doctor blade coater, bar coater, spray coater, or screen printing apparatus, or by immersing the substrate in the slurry. The slurry can be applied to the entire surface of the substrate or only a portion thereof. If the substrate is plate-shaped, the slurry can be applied to one or both sides. If the substrate is porous, the slurry can be pressed or pressed to allow it to penetrate into the pores of the substrate. If the substrate is porous, any slurry remaining on the surface that has not penetrated into the pores can be scraped off using a doctor blade.

[0060] (b-1) Drying Process In the drying process, the substrate containing the slurry (electrode precursor for water electrolysis) is dried. For example, the slurry can be dried using a hot air dryer, an infrared dryer, a hot plate, etc. The drying temperature can be, for example, above 40°C and below 120°C. The drying time can be, for example, above 1 minute and below 300 minutes.

[0061] (b-2) Firing Process In the firing process, the electrode precursor for water electrolysis after the drying process is fired (heat treated). Firing allows the slurry to penetrate the entire substrate evenly, reducing unevenness in the substrate thickness. Furthermore, firing allows the Al contained in the Raney alloy to diffuse into the raw material of the metal particles due to the concentration gradient, thus forming the metal particles themselves.

[0062] The firing temperature can be, for example, above 600℃ and below 900℃. The firing time can be, for example, above 1 hour and below 24 hours.

[0063] (b-3) Scraping Process In the scraping process, the residual paste on the surface of the substrate is scraped off. Scraping can be performed using, for example, a scraper. The scraping process can also be performed before or after the pressing process described later; the specific timing can be adjusted accordingly.

[0064] (b-4) Pressing Process In the pressing process, the substrate containing the slurry (electrode precursor for water electrolysis) is pressed. The pressing process can be performed at any time during the formation of the electrode precursor for water electrolysis. Through pressing, the thickness of the substrate is adjusted. The pressure can be appropriately adjusted according to the desired substrate thickness and slurry loading.

[0065] (c) Alkali Treatment Process In the alkaline treatment process, an alkaline substance is used to treat the electrode precursor for water electrolysis. Through alkaline treatment, aluminum can be dissolved from the Raney alloy to obtain Raney nickel particles. That is, an electrode for water electrolysis containing Raney nickel particles can be obtained.

[0066] As a specific processing method, one example is to immerse the electrode precursor for water electrolysis into an alkaline aqueous solution containing an alkaline substance, then maintain the temperature of the alkaline aqueous solution at a specified temperature and stir for a specified time. Examples of alkaline substances include alkali metal hydroxides and alkali metal salts. Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Examples of alkali metal salts include sodium carbonate, potassium carbonate, and lithium carbonate. Alkali metal hydroxides are preferred as the alkaline substance.

[0067] The processing temperature is, for example, above 100°C and below 140°C. The processing time is, for example, above 1 hour and below 9 hours. The amount of alkaline substance used in this process can be adjusted appropriately.

[0068] Preferably, this process uses a high-concentration alkaline aqueous solution of alkali metal hydroxide at a high temperature. The concentration of the alkaline aqueous solution is, for example, 3 mol / L or more, preferably 7 mol / L or more, and more preferably 14 mol / L or more. The concentration of the alkaline aqueous solution is 20 mol / L or less. The processing temperature is, for example, 100°C or more, preferably 110°C or more, and more preferably 125°C or more. The processing temperature is, for example, 148°C or less. Furthermore, to increase the processing temperature, it is necessary to increase the concentration of the alkaline aqueous solution so that its boiling point is above the processing temperature. For example, when the processing temperature is 100°C or more, the concentration of the alkaline aqueous solution is preferably 3 mol / L or more; when the processing temperature is 125°C or more, the concentration of the alkaline aqueous solution is preferably 14 mol / L or more. Additionally, this process is preferably carried out at atmospheric pressure. Under this condition, compared to pressurized conditions, hydrogen generated during processing can be removed more easily.

[0069] By carrying out this process under these conditions, the reaction time between the alkaline aqueous solution and the Raney alloy can be shortened. The reaction time is, for example, 3 hours to 9 hours when the concentration of the alkaline aqueous solution is 3 mol / L or higher and the processing temperature is 100°C or higher; and, for example, 1 hour to 8 hours when the concentration of the alkaline aqueous solution is 14 mol / L or higher and the processing temperature is 125°C or higher.

[0070] In addition, this process can either dissolve all the Al contained in the Raney alloy, or it can leave a portion of the Al undissolved.

[0071] (d) Oxidation Process Raney nickel particles obtained through an alkaline treatment process (substrate containing Raney nickel particles) have high surface activity and may spontaneously ignite in air. Therefore, handling such as storage is difficult, and they need to be stored in solvents or handled in a way that prevents contact with air.

[0072] In the oxidation process, the surface of the Raney nickel particles obtained through the alkali treatment process is oxidized. The surface-oxidized Raney nickel particles (hereinafter also referred to as "oxidized Raney nickel particles") suppress spontaneous combustion in air. Therefore, compared to Raney nickel particles, oxidized Raney nickel particles are easier to handle, such as during storage.

[0073] This process is carried out, for example, by reacting Raney nickel particles with an acidic aqueous solution containing an acidic substance. A specific treatment method could be described as follows: after immersing the water electrolysis electrode from the alkali treatment process into the acidic aqueous solution, stirring at a specified temperature for a specified time.

[0074] Examples of acidic substances include hydrogen peroxide, sodium peroxide, sodium percarbonate, and sodium perborate. Among these, hydrogen peroxide is preferred.

[0075] The concentration of the acidic aqueous solution is, for example, 0.1 mol / L or higher and 10 mol / L or lower. The treatment temperature is, for example, 15°C or higher and 80°C or lower. The treatment time is, for example, 5 minutes or higher and 720 minutes or lower. The solid-liquid ratio of Raney nickel particles to the acidic aqueous solution (Raney nickel particles: acidic aqueous solution) is, for example, 1:2 to 1:100 by mass.

[0076] The Raney nickel oxide particles obtained through the above treatment (electrodes for water electrolysis containing Raney nickel oxide particles) can also be cleaned as needed. As a cleaning process, known cleaning processes used in the manufacture of Raney nickel particles, such as water washing, can be applied.

[0077] Furthermore, the method for manufacturing the electrode for water electrolysis described above is merely an example and is not limited thereto. For instance, a catalyst layer composed of Raney nickel particles and metal particles can also be formed on the surface of a substrate by coating a slurry onto the substrate surface. Example

[0078] <Raw Materials> The materials used in this embodiment are shown below.

[0079] Substrate A: Nickel-based porous metal (manufactured by Sumitomo Electric Industries, Ltd., CELMET (registered trademark), product number #8) (size: 50mm x 50mm, thickness: 1.2mm)

[0080] Raney Alloy B1: Nickel-aluminum alloy with Al3Ni2 composition (manufactured by Japan Heavy Chemical Industry Co., Ltd., average particle size: 23μm) B2: Composition Al3Ni 1.95 Fe 0.05 Nickel-aluminum-iron alloy (manufactured by Japan Heavy Chemical Industry Co., Ltd., average particle size: 23μm) B3: Nickel-aluminum alloy (manufactured by Fujifilm and Koichi Pure Chemical Industries, Ltd., Raney nickel particles, approximately 50%) (average particle size: 19 μm) B4: Composition Al3Ni 1.95 Fe 0.05 Nickel-aluminum-iron alloy (manufactured by Japan Heavy Chemical Industry Co., Ltd., average particle size: 8.3μm) B5: Composition Al3Ni 1.95 Fe 0.05 Nickel-aluminum-iron alloy (manufactured by Japan Heavy Chemical Industry Co., Ltd., average particle size: 16μm) B6: Composition Al3Ni 1.95 Fe 0.05 Nickel-aluminum-iron alloy (manufactured by Japan Heavy Chemical Industry Co., Ltd., average particle size: 38μm) B7: Composition Al3Ni 1.95 Fe 0.05 Nickel-aluminum-iron alloy (manufactured by Japan Heavy Chemical Industry Co., Ltd., average particle size: 85μm) In addition, B3 contains Ni and Al in a mass ratio of approximately 1:1.

[0081] Raw Materials for Metal Particles C1: Nickel particles (manufactured by High Purity Chemical Research Institute, Inc., Ni nickel (NIE10PB)) (average particle size: 2-3 μm) C2: Nickel particles (manufactured by High Purity Chemical Research Institute, Co., Ltd., NIE11PB) (average particle size: 3-5 μm)

[0082] "other" Thickener: CMC (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., CELLOGEN EP) Solvent: Water

[0083] <Electrodes for water electrolysis> (No.1) A slurry was prepared by mixing Raney alloy B1, raw material C1 of metal particles, CMC, and water. The mass ratio of Raney alloy B1 to raw material C1 of metal particles is as shown in Table 1, “B:C (wt%)”. The proportion of solvent in the slurry is 24% by mass or more and 40% by mass or less.

[0084] The above-mentioned slurry is applied to both sides of substrate A using a die-coating machine. After application, any remaining slurry on the surface of substrate A is scraped off with a scraper.

[0085] Dry substrate A containing the slurry at 80°C for 60 minutes.

[0086] The dried substrate A is fired at 700℃ for 2 hours.

[0087] The fired substrate A was immersed in a 14 mol / L sodium hydroxide aqueous solution at 125°C for 3 hours. Then, substrate A was washed with water and oxidized with hydrogen peroxide water to produce the No.1 water electrolysis electrode.

[0088] (No.2) Except for the use of Raney alloy B3, the water electrolysis electrode for No.2 was made using the same method as No.1.

[0089] (No. 3-10) Except for changing the mixing ratio of Raney alloy B1 and raw material C1 of metal particles to the ratio described in Table 1, and pressing the dried substrate A in such a way that the thickness is 0.4 mm, the water electrolysis electrodes No. 3 to 10 were manufactured using the same method as No. 1.

[0090] (No. 11) Except for the use of Raney alloy B2, the change of the mixing ratio of Raney alloy B2 and raw material C1 of metal particles to the ratio described in Table 1, and the pressing of the dried substrate A in such a way that the thickness is 0.4 mm, the water electrolysis electrode of No.11 was manufactured using the same method as No.1.

[0091] (No. 12-18) Except for changing the mixing ratio of Raney alloy B1 and raw material C1 of metal particles to the ratio described in Table 1, electrodes for water electrolysis No. 12 to 18 were manufactured using the same method as No. 1.

[0092] <Analysis> The first Al / Ni ratio and the second Al / Ni ratio for each numbered (No.) water electrolysis electrode were determined. Specifically, a portion of the water electrolysis electrode was embedded in resin, and the cross-sections that had undergone surface processing using a cross-section polishing machine were analyzed by SEM-EDX. The results are shown in Table 1. The results in Table 1 show the average value obtained from any three points extracted from the above cross-sections.

[0093] [Table 1]

[0094] <Experimental Example 1> In Test Example 1, the following evaluations were conducted on No. 1, 2, and 7, in which raw materials of Raney alloy and metal particles were mixed in the same mass ratio.

[0095] "evaluate" To evaluate the performance of the obtained water electrolysis electrodes as anodes, a potential variation durability test was conducted. Specifically, a 7 mol / L potassium hydroxide aqueous solution was used as the electrolyte, and the nickel mesh as the counter electrode and the No. 1, 2, and 7 water electrolysis electrodes were immersed in the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode, connected to the electrolyte using a liquid junction. Before and after the potential variation durability test, the potential of the active electrode was scanned at 1 mV / s for the reference electrode, and the oxygen generation current relative to the electrode potential was measured. The current value at an anode potential of 1.5 V (vs. reversible hydrogen electrode) was used as an indicator of oxygen generation activity. As part of the potential variation durability test, 1500 cycles were repeatedly performed, maintaining 1.5 V (vs. reversible hydrogen electrode) for 1 minute followed by 0 V (vs. reversible hydrogen electrode) for 1 minute.

[0096] (Current density) Before and after the end of the potential variation durability test, the oxygen generation current was measured, and the current value was read when the anode potential was 1.5V (vs. reversible hydrogen electrode). The results are shown in Table 2. A higher current density indicates higher activity as an anode for water electrolysis.

[0097] (Catalyst residue rate) Let X (mg / cm³) be the weight per unit area of ​​the water electrolysis electrode before the potential variation durability test. 2 The weight per unit area of ​​the water electrolysis electrode after the potential variation durability test is set as Y (mg / cm²). 2 The catalyst residue rate after the potential variation durability test was calculated based on Equation (i). The results are shown in Table 2. A catalyst residue rate of less than 100% indicates that the catalyst has detached, meaning that durability has deteriorated. A catalyst residue rate of 100% shows no reduction in catalyst residue before and after the potential variation durability test, indicating excellent durability. Furthermore, if a portion of the catalyst is oxidized during the potential variation durability test, the catalyst residue rate may exceed 100%, but the catalyst remains intact and does not detach, thus not affecting durability. Catalyst residue rate = Y / X × 100 (i)

[0098] [Table 2]

[0099] "result" As shown in Table 2, regarding the current density after the potential variation durability test, No. 1 exhibited a larger value than No. 2 for electrodes of the same thickness. This can be attributed to the structure of the Raney nickel particles contained in the water electrolysis electrode. Specifically, the Raney nickel particles in No. 1 were made from Raney alloy B1, which has the composition Al3Ni2 and a higher proportion of Al than Ni, while the Raney nickel particles in No. 2 were made from Raney alloy B3, which contains Ni and Al in almost the same proportion. The Raney nickel particles are produced by dissolving Al from the Raney alloy; the higher the proportion of Al in the Raney alloy, the higher the porosity of the Raney nickel particles after Al dissolution, and thus the higher their activity as a catalyst.

[0100] Furthermore, as shown in Table 1, the second Al / Ni ratios of No. 1 and No. 2 are almost identical. On the other hand, regarding the first Al / Ni ratio, No. 1 has a lower ratio than No. 2, suggesting that No. 1 dissolves more Al than No. 2. Therefore, regarding the porosity of the Raney nickel particles after Al dissolution, No. 1 has a higher porosity than No. 2, as also shown in Table 2, resulting in higher catalyst activity (current density after testing). Moreover, generally, even for water electrolysis electrodes with the same unit area weight, if the thickness of the water electrolysis electrode increases, the porosity also increases, thus increasing the specific surface area. As a result, the catalyst activity of the water electrolysis electrode increases, and its current density also increases. Therefore, it is conceivable that No. 7, which is thinner than No. 1 and No. 2, has the lowest current density.

[0101] Furthermore, in No.1 and No.7, the catalyst residue exceeded 100%. Therefore, it can be assumed that No.1 and No.7 have excellent durability.

[0102] <Experimental Example 2> In Experiment 2, Nos. 3 to 11 were used, and the following evaluations were conducted.

[0103] "evaluate" To evaluate the performance of the obtained water electrolysis electrode as an anode for water electrolysis, a potential variation durability test was conducted. The test method was the same as in Test Example 1.

[0104] (Current density) The current density was measured before and after the potential variation durability test. See Table 3 and... Figure 3 The results are shown below. At a current density of 150 mA / cm². 2 Under the above conditions, the electrode is considered to exhibit good activity for water electrolysis.

[0105] (Catalyst residue rate) The catalyst residue rate after the potential variation durability test was calculated based on the above equation (i). See Table 3 and... Figure 4 The results are shown in the figure.

[0106] [Table 3]

[0107] "result" As shown in Table 3 and Figure 3 As shown, in Nos. 4–8 and 11, the current density before and / or after the potential variation durability test is 150 mA / cm². 2 That's all. Furthermore, in Nos. 5–8 and 11, the current density after the potential variation durability test was greater than the current density before the test, or the current density remained the same after the test. Moreover, in Nos. 5–8 and 11, the current density before and after the potential variation durability test was even better, reaching 200 mA / cm². 2 above.

[0108] Additionally, as shown in Table 3 and Figure 4 As shown, in Nos. 5–8 and 11, the catalyst residue exceeded 100%. Based on the above, it can be inferred that Nos. 5–8 and 11 exhibit good activity and excellent durability.

[0109] <Experimental Example 3> In Experiment 3, No.1 and 12-18 were used, and the following evaluations were conducted.

[0110] "evaluate" To evaluate the performance of the obtained water electrolysis electrodes as cathodes, a potential variation durability test was conducted. Specifically, a 7 mol / L potassium hydroxide aqueous solution was used as the electrolyte, and the nickel mesh serving as the counter electrode and the No. 1 and 12-18 water electrolysis electrodes were immersed in the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode and connected to the electrolyte using a liquid junction. Before and after the potential variation durability test, the potential of the active electrode was scanned at 1 mV / s for the reference electrode, and the hydrogen generation current relative to the electrode potential was measured. The current value at a cathode potential of -0.15 V (vs. reversible hydrogen electrode) was read and used as an indicator of hydrogen generation activity. As part of the potential variation durability test, 1000 cycles of holding at -0.1 V (vs. reversible hydrogen electrode) for 1 minute followed by holding at 0.4 V (vs. reversible hydrogen electrode) for 1 minute were repeatedly performed.

[0111] (Current density) The current density was measured before and after the potential variation durability test. See Table 4 and... Figure 5The results are shown below. At a current density of 200 mA / cm². 2 Under the above conditions, the electrode is considered to exhibit good activity for water electrolysis.

[0112] (Catalyst residue rate) Based on the above equation (i), the catalyst residue rate after the potential variation durability test was calculated. (See Table 4 and...) Figure 6 The results are shown in the figure.

[0113] [Table 4]

[0114] "result" As shown in Table 4 and Figure 5 As shown, in No. 1 and 12–18, the current density before and / or after the potential variation durability test is 200 mA / cm². 2 That's all. Furthermore, in No. 1 and 13-17, the current density before and after the potential variation durability test was even better, at 200 mA / cm². 2 above.

[0115] Additionally, as shown in Table 4 and Figure 6 As shown, in No.1 and 14-18, the catalyst residue exceeded 100%. Based on the above, it can be inferred that No.1 and 14-18 exhibited good activity and excellent durability.

[0116] <Experimental Example 4> In Experiment 4, the following evaluation was conducted using the following water electrolysis electrodes.

[0117] (No. 19) Aside from using Raney alloy B4, changing the mixing ratio of Raney alloy B4 and raw material C1 of metal particles to 22:78, and pressing the dried substrate A to a thickness of 0.6 mm, the water electrolysis electrode of No.19 was manufactured using the same method as No.1.

[0118] (No. 20) Except for the use of Raney alloy B5, the change of the mixing ratio of Raney alloy B5 and raw material C1 of metal particles to 22:78, and the pressing of the dried substrate A to make the thickness 0.6 mm, the water electrolysis electrode of No. 20 was made using the same method as No. 1.

[0119] (No. 21) Aside from using Raney alloy B2, changing the mixing ratio of Raney alloy B2 and raw material C1 of metal particles to 22:78, and pressing the dried substrate A to achieve a thickness of 0.6 mm, the water electrolysis electrode of No. 21 was manufactured using the same method as No. 1.

[0120] (No. 22) Aside from using Raney alloy B7, changing the mixing ratio of Raney alloy B7 and raw material C1 of metal particles to 22:78, and pressing the dried substrate A to achieve a thickness of 0.6 mm, the water electrolysis electrode of No. 22 was manufactured using the same method as No. 1.

[0121] "evaluate" To evaluate the effect of the average particle size of Raney alloy (Raney nickel particles) on the anode used in water electrolysis, a potential variation durability test was conducted. The test method was the same as in Test Example 1.

[0122] (Current density) The current density was measured before and after the potential variation durability test. (See Table 5 and...) Figure 7 The results are shown below. At a current density of 150 mA / cm². 2 Under the above conditions, the electrode is considered to exhibit good activity for water electrolysis.

[0123] (Catalyst residue rate) Based on the above equation (i), the catalyst residue rate after the potential variation durability test was calculated. See Table 5 and... Figure 8 The results are shown in the figure.

[0124] [Table 5]

[0125] "result" As shown in Table 5 and Figure 7 As shown, in Nos. 19–22, the current density before and after the potential variation durability test is 200 mA / cm². 2 That's all. Furthermore, in Nos. 20–22, the current density after the potential variation durability test was higher than the current density before the test. Moreover, in Nos. 20 and 21, the current density before the potential variation durability test was 300 mA / cm². 2 The current density at the end of the potential variation durability test was 400 mA / cm². 2 above.

[0126] Additionally, as shown in Table 5 and Figure 8As shown, in Nos. 19 to 22, the catalyst residue exceeded 100%. Based on the above, it can be seen that by setting the average particle size of the Raney alloy (Raney nickel particles) to an appropriate range, anodes for water electrolysis exhibiting good activity and durability can be obtained.

[0127] <Experimental Example 5> In Experiment 5, the following evaluation was conducted using the following water electrolysis electrodes.

[0128] (No. 23) Except for the use of Raney alloy B5 and the change of the mixing ratio of Raney alloy B5 and raw material C1 of metal particles to 52:48, the water electrolysis electrode of No. 23 was made using the same method as No. 1.

[0129] (No. 24) Except for the use of Raney alloy B2 and the change of the mixing ratio of Raney alloy B2 and raw material C1 of metal particles to 52:48, the water electrolysis electrode of No. 24 was made using the same method as No. 1.

[0130] (No. 25) Except for the use of Raney alloy B6 and the change of the mixing ratio of Raney alloy B6 and raw material C1 of metal particles to 52:48, the water electrolysis electrode of No. 25 was made using the same method as No. 1.

[0131] (No. 26) Except for the use of Raney alloy B7 and the change of the mixing ratio of Raney alloy B7 and raw material C1 of metal particles to 52:48, the water electrolysis electrode of No. 26 was made using the same method as No. 1.

[0132] "evaluate" To evaluate the effect of the average particle size of Raney alloy (Raney nickel particles) on the cathode used in water electrolysis, a potential variation durability test was conducted. The test method was the same as in Test Example 3.

[0133] (Current density) The current density was measured before the potential variation durability test. (See Table 6 and...) Figure 9 The results are shown below. At a current density of 200 mA / cm². 2 Under the above conditions, the electrode is considered to exhibit good activity for water electrolysis.

[0134] (Catalyst residue rate) The catalyst residue rate after the potential variation durability test was calculated based on the above formula (i). See Table 6 and... Figure 10 The results are shown in the figure.

[0135] [Table 6]

[0136] "result" As shown in Table 6 and Figure 9 As shown, in Nos. 23 to 26, the current density before the potential variation durability test was 200 mA / cm². 2 That's all. Additionally, in Nos. 24 and 25, the current density after the potential variation durability test was 800 mA / cm². 2 above.

[0137] Additionally, as shown in Table 6 and Figure 10 As shown, in Nos. 24 to 26, the catalyst residue exceeded 100%. Based on the above, it can be seen that by setting the average particle size of the Raney alloy (Raney nickel particles) to an appropriate range, a cathode for water electrolysis exhibiting good activity and durability can be obtained.

[0138] <Experimental Example 6> In Test Example 6, the following evaluation was conducted using the following water electrolysis electrodes.

[0139] (No. 27) Aside from using Raney alloy B2, changing the mixing ratio of Raney alloy B2 and raw material C1 of metal particles to 52:48, and pressing the dried substrate A to achieve a thickness of 0.6 mm, the water electrolysis electrode for No. 27 was manufactured using the same method as No. 1.

[0140] (No. 28) Except for the use of metal particles as raw material C2, the water electrolysis electrode of No. 28 was made using the same method as No. 27.

[0141] "evaluate" To evaluate the impact of the average particle size of the raw material (metal particles) on the anode used in water electrolysis, a potential variation durability test was conducted. The test method was the same as in Test Example 1.

[0142] (Current density) The current density was measured before and after the potential variation durability test. The results are shown in Table 7. The current density was 150 mA / cm². 2 Under the above conditions, the electrode is considered to exhibit good activity for water electrolysis.

[0143] (Catalyst residue rate) The catalyst residue rate after the potential variation durability test was calculated based on the above equation (i). The results are shown in Table 7.

[0144] [Table 7]

[0145] "result" As shown in Table 7, in No. 27, the current density before and after the potential variation durability test is 200 mA / cm². 2 That's all. On the other hand, in No. 28, the current density before the potential variation durability test was 200 mA / cm². 2 However, the current density decreased significantly after the potential variation durability test was completed.

[0146] Furthermore, as shown in Table 7, in No. 27, the catalyst residue exceeded 100%. On the other hand, in No. 28, there was almost no catalyst residue. Based on the above, it can be seen that by setting the average particle size of the raw material (metal particles) to an appropriate range, an anode for water electrolysis exhibiting good activity and durability can be obtained.

[0147] <Experimental Example 7> In Experiment 7, using No. 27 and 28, the following evaluation was conducted.

[0148] "evaluate" To evaluate the impact of the average particle size of the raw material (metal particles) on the cathode used in water electrolysis, a potential variation durability test was conducted. The test method was the same as in Test Example 3.

[0149] (Current density) The current density was measured before and after the potential variation durability test. The results are shown in Table 8. The current density was 200 mA / cm². 2 Under the above conditions, the electrode is considered to exhibit good activity for water electrolysis.

[0150] (Catalyst residue rate) The catalyst residue rate after the potential variation durability test was calculated based on the above equation (i). The results are shown in Table 8.

[0151] [Table 8]

[0152] "result" As shown in Table 8, in No. 27, the current density before and after the potential variation durability test is 200 mA / cm². 2That's all. On the other hand, in No. 28, the current density before the potential variation durability test was 200 mA / cm². 2 However, the current density decreased significantly after the potential variation durability test was completed.

[0153] Furthermore, as shown in Table 8, in No. 27, the catalyst residue exceeded 100%. On the other hand, in No. 28, there was almost no catalyst residue. Based on the above, it can be seen that by setting the average particle size of the raw material (metal particles) of metal particles to an appropriate range, a cathode for water electrolysis exhibiting good activity and durability can be obtained.

[0154] [plan] Next, the technical ideas that can be grasped from the above implementation methods will be summarized below.

[0155] (Option 1) An electrode for water electrolysis, Includes substrate and catalyst sections. The catalyst section comprises: Raney nickel particles; and metal particles containing nickel as the main component. The metal particles are in contact with the Raney nickel particles. The metal particles contain aluminum. The ratio of the total moles of aluminum to the total moles of nickel in the Raney nickel particles is greater than the ratio of the total moles of aluminum to the total moles of nickel in the metal particles.

[0156] (Option 2) According to the electrolysis electrode described in Scheme 1, wherein, The average particle size of the metal particles is smaller than the average particle size of the Raney nickel particles. The metal particles are in contact with the plurality of Raney nickel particles.

[0157] (Option 3) According to the electrolysis electrode described in scheme 1 or 2, wherein, The substrate contains nickel or a nickel alloy as the main component.

[0158] (Option 4) A method for manufacturing an electrode for water electrolysis, comprising: The mixing process involves mixing raw materials of Raney nickel particles, raw materials of metal particles containing nickel as the main component, and solvent to obtain a slurry. A process for forming an electrode precursor for water electrolysis involves coating the slurry onto a substrate to obtain an electrode precursor for water electrolysis; and The alkaline treatment process involves treating the water electrolysis electrode precursor with an alkaline substance to obtain a water electrolysis electrode containing Raney nickel particles. The raw material for the Raney nickel particles contains more moles of aluminum than the raw material for the Raney nickel particles.

[0159] (Option 5) According to the method for manufacturing electrodes for water electrolysis described in Scheme 4, wherein, The raw material for the Raney nickel particles is given by the following formula (1): Al3Ni （2-x）） M x (1) This means that in the above formula (1), M is at least one element selected from Mg, Si, Ti, Cr, Mn, Fe, Co, Cu, Ag, Pt and Au, and x satisfies the relationship 0≤x≤0.2.

[0160] (Option 6) According to the method for manufacturing electrodes for water electrolysis described in Scheme 5, wherein, The M contains at least Fe.

[0161] (Option 7) The method for manufacturing an electrode for water electrolysis according to any one of Schemes 4 to 6, wherein, The raw material for the Raney nickel particles is given by the following formula (2): Al3Ni （2-（y+z）） Fe y Co z (2) This means that in the above equation (2), y and z satisfy the relationship 0≤y≤0.1 and 0≤z≤0.1.

[0162] (Option 8) The method for manufacturing an electrode for water electrolysis according to any one of Schemes 4 to 7, wherein, The ratio of the raw material of the metal particles to the total of the raw materials of the Raney nickel particles and the raw materials of the metal particles is 27% by mass or more and 95% by mass or less.

[0163] (Option 9) The method for manufacturing an electrode for water electrolysis according to any one of Schemes 4 to 8, wherein, The process for forming the electrode precursor for water electrolysis further includes: a drying process for drying the electrode precursor for water electrolysis; and a firing process for firing the electrode precursor for water electrolysis after the drying process.

[0164] This embodiment and embodiment are illustrative in all respects. This embodiment and embodiment are not restrictive. The scope of this disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it was originally intended that arbitrary configurations be extracted from this embodiment and embodiment and combined arbitrarily. Explanation of reference numerals in the attached figures

[0165] 1. Substrate; 2. Raney nickel particles; 3. Metal particles.

Claims

1. An electrode for water electrolysis, characterized in that, Includes substrate and catalyst sections. The catalyst section comprises: Raney nickel particles; and metal particles containing nickel as the main component. The metal particles are in contact with the Raney nickel particles. The metal particles contain aluminum. The ratio of the total moles of aluminum to the total moles of nickel in the Raney nickel particles is greater than the ratio of the total moles of aluminum to the total moles of nickel in the metal particles.

2. The electrode for water electrolysis according to claim 1, wherein, The average particle size of the metal particles is smaller than the average particle size of the Raney nickel particles. The metal particles are in contact with the plurality of Raney nickel particles.

3. The electrode for water electrolysis according to claim 1 or 2, wherein, The substrate contains nickel or a nickel alloy as the main component.

4. A method for manufacturing an electrode for water electrolysis, characterized in that, Include: The mixing process involves mixing raw materials of Raney nickel particles, raw materials of metal particles containing nickel as the main component, and solvent to obtain a slurry. In the process of forming an electrode precursor for water electrolysis, the slurry is coated onto a substrate to obtain an electrode precursor for water electrolysis. as well as The alkaline treatment process involves treating the water electrolysis electrode precursor with an alkaline substance to obtain a water electrolysis electrode containing Raney nickel particles. The raw material for the Raney nickel particles contains more moles of aluminum than the raw material for the Raney nickel particles.

5. The method for manufacturing an electrode for water electrolysis according to claim 4, wherein, The raw material for the Raney nickel particles is given by the following formula (1): Al3Ni （2-x）） M x (1) This means that in the above formula (1), M is at least one element selected from Mg, Si, Ti, Cr, Mn, Fe, Co, Cu, Ag, Pt and Au, and x satisfies the relationship 0≤x≤0.

2.

6. The method for manufacturing an electrode for water electrolysis according to claim 5, wherein, The M contains at least Fe.

7. A method for manufacturing an electrode for water electrolysis according to any one of claims 4 to 6, wherein, The raw material for the Raney nickel particles is given by the following formula (2): Al3Ni （2-（y+z）） Feb y Co z (2) This means that in the above equation (2), y and z satisfy the relationship 0≤y≤0.1 and 0≤z≤0.

1.

8. A method for manufacturing an electrode for water electrolysis according to any one of claims 4 to 7, wherein, The ratio of the raw material of the metal particles to the total of the raw materials of the Raney nickel particles and the raw materials of the metal particles is 27% by mass or more and 95% by mass or less.

9. A method for manufacturing an electrode for water electrolysis according to any one of claims 4 to 8, wherein, The process for forming the electrode precursor for water electrolysis further includes: a drying process for drying the electrode precursor for water electrolysis; and a firing process for firing the electrode precursor for water electrolysis after the drying process.

Images