Water electrolysis electrode and method for manufacturing water electrolysis electrode

Abstract

This water electrolysis electrode comprises a substrate and a catalyst portion. The catalyst portion includes Raney nickel particles and metal particles that contain nickel as a main component. The metal particles are in contact with the Raney nickel particles and include aluminum. The ratio of the total number of moles of aluminum to the total number of moles of nickel in the Raney nickel particles is greater than the ratio of the total number of moles of aluminum to the total number of moles of nickel in the metal particles.

Description

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

[0001] The present disclosure relates to an electrode for water electrolysis and a method for producing the electrode for water electrolysis.

[0002] Water electrolysis is the electrolysis of water into hydrogen and oxygen, and is used, for example, as a technology for producing hydrogen. A water electrolysis device for generating hydrogen includes, for example, an electrolytic cell containing an electrolyte solution such as alkaline water, and an anode and a cathode disposed in the electrolytic cell with a separator sandwiched therebetween. In the water electrolysis device, oxygen is generated at the anode and hydrogen is generated at the cathode by passing a current between the anode and the cathode.

[0003] Japanese Patent Laid-Open Publication No. 53-54174 (Patent Document 1) discloses an electrode for water electrolysis in which an oxide obtained by oxidizing an alkali-soluble component eluted from a powdered Raney nickel alloy is bound with a binder.

[0004] Japanese Unexamined Patent Publication No. 53-54174

[0005] There is a demand for electrodes for water electrolysis that are highly active and have a longer life (improved durability). The electrode for water electrolysis described in Patent Document 1 has room for improvement, particularly in terms of increasing activity.

[0006] An object of the present disclosure is to provide a water electrolysis electrode that exhibits high activity and a method for producing the water electrolysis electrode.

[0007] The electrode for electrolysis that solves the above-mentioned problems includes a substrate and a catalyst portion, the catalyst portion includes Raney nickel particles and metal particles containing nickel as a main component, the metal particles are in contact with the Raney nickel particles, and the metal particles contain aluminum, and the ratio of the total number of moles of aluminum to the total number of moles of nickel in the Raney nickel particles is greater than the ratio of the total number of moles of aluminum to the total number of moles of nickel in the metal particles.

[0008] The water electrolysis electrode includes a substrate and a catalytic portion. The catalytic portion includes Raney nickel particles and metal particles containing nickel as a main component. The Raney nickel particles have high activity. The metal particles act as a binder that binds the Raney nickel particles to the substrate. When the catalytic portion includes Raney nickel particles and metal particles, improved activity is expected. Furthermore, when the Raney nickel particles and metal particles satisfy the above specific relationship, further improved activity is expected.

[0009] The method for producing an electrode for water electrolysis includes a mixing step of mixing a raw material for Raney nickel particles, a raw material for metal particles containing nickel as a main component, and a solvent to obtain a slurry; a forming step of an electrode precursor for water electrolysis by applying the slurry to a substrate to obtain an electrode precursor for water electrolysis; and an alkali treatment step of treating the electrode precursor for water electrolysis with an alkaline substance to obtain an electrode for water electrolysis containing Raney nickel particles, wherein the number of moles of aluminum contained in the raw material for Raney nickel particles is greater than the number of moles of nickel contained in the raw material for Raney nickel particles.

[0010] According to the present disclosure, a highly active water electrolysis electrode and a method for producing the water electrolysis electrode can be obtained.

[0011] FIG. 1 is an example of a cross-sectional SEM image of a water electrolysis electrode according to the present disclosure. FIG. 2 is an example of an elemental mapping image of the SEM image of FIG. 1 by EDX. FIG. 3 is a graph showing the results of evaluation of the activity of the water electrolysis electrode in Test Example 2. FIG. 4 is a graph showing the results of evaluation of the durability of the water electrolysis electrode in Test Example 2. FIG. 5 is a graph showing the results of evaluation of the activity of the water electrolysis electrode in Test Example 3. FIG. 6 is a graph showing the results of evaluation of the durability of the water electrolysis electrode in Test Example 3. FIG. 7 is a graph showing the results of evaluation of the activity of the water electrolysis electrode in Test Example 4. FIG. 8 is a graph showing the results of evaluation of the durability of the water electrolysis electrode in Test Example 4. FIG. 9 is a graph showing the results of evaluation of the activity of the water electrolysis electrode in Test Example 5. FIG. 10 is a graph showing the results of evaluation of the durability of the water electrolysis electrode in Test Example 5.

[0012] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") and an example of the present disclosure (hereinafter may be abbreviated as "the present example") will be described. However, the present embodiment and the example do not limit the technical scope of the present disclosure.

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

[0014] The average particle size of the Raney alloy refers to the particle size at 50% of the cumulative value in the particle size distribution determined by a laser diffraction / scattering method. The average particle size of the raw metal particles refers to the particle size measured by the Fischer method. The average particle size of the Raney nickel particles and the average particle size of the metal particles refer to the arithmetic mean of the minor axis diameters of 100 randomly selected Raney nickel particles and 100 randomly selected metal particles extracted from SEM images obtained by a scanning electron microscope (SEM).

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

[0016] The water electrolysis electrode of this embodiment may be a water electrolysis electrode in which the catalytic portion is dispersed in a substrate, or may be a water electrolysis electrode in which a layer of the catalytic portion is formed on the surface of a substrate. Furthermore, the water electrolysis electrode of this embodiment can be obtained by applying a slurry containing raw materials for Raney nickel particles and raw materials for metal particles to a substrate, and then performing an alkali treatment, as described in the production method described below.

[0017] <<Substrate>> The substrate of this embodiment is a conductor capable of conducting electricity. The substrate is not particularly limited as long as it is conductive, and examples thereof include Ni-containing metals such as nickel metal and nickel alloys. The substrate may be formed entirely of nickel metal or nickel alloy, or only the surface may be formed of nickel metal or nickel alloy. When only the surface of the substrate is formed of nickel metal or nickel alloy, the surface of a metal material such as iron or stainless steel may be coated with nickel metal or nickel alloy. The substrate preferably contains nickel metal or nickel alloy as a main component. In terms of durability in the usage environment, the substrate is preferably made of nickel metal with a high Ni purity. Note that "containing nickel metal or nickel alloy as a main component" means that the Ni content of the nickel metal or nickel alloy in the substrate is greater than 50 mass%.

[0018] The shape of the substrate is not particularly limited and may be porous or non-porous. The substrate is preferably porous so that it can contain Raney nickel particles and Ni-containing metal particles inside. Examples of the shape of such a substrate include punched metal, mesh, foam metal, and expanded metal. Examples of the shape of a non-porous substrate include a plate shape.

[0019] The thickness of the substrate is not particularly limited, and may be selected to be suitable for the water electrolysis device to be used.

[0020] <<Catalyst portion>> The catalyst portion includes Raney nickel particles and metal particles containing Ni as a main component. The catalyst portion may essentially consist of Raney nickel particles and metal particles. The catalyst portion may also consist of Raney nickel particles and metal particles. In the catalyst portion, the Raney nickel particles and metal particles are in contact with each other. Note that "consisting essentially of Raney nickel particles and metal particles" means that the content of Raney nickel particles and metal particles in the catalyst portion is 95 mass% or more.

[0021] (Raney Nickel Particles) The Raney nickel particles of this embodiment contain Ni and Al. The Raney nickel particles are porous bodies with a large specific surface area in which many pores are formed, and are highly active.

[0022] The ratio of the total number of moles of Al to the total number of moles of Ni in the Raney nickel particles of this embodiment (hereinafter also referred to as the "first Al / Ni ratio") is 1 or less, and preferably 0.6 or less. When the first Al / Ni ratio is 1 or less, improvement in activity is expected. The first Al / Ni ratio may 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 microscope-energy dispersive X-ray spectroscopy (SEM-EDX).

[0023] The Raney nickel particles of this embodiment may 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 first metals 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 the "Raney alloy"). When the Raney nickel particles contain a first metal, the molar ratio of Ni to the first metal may 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 may be an alloy composed of a single phase or an alloy composed of multiple phases. Examples of such phases include a phase consisting of only nickel, a phase consisting of nickel and aluminum, a phase consisting of nickel and the first metal, and a phase consisting of nickel, aluminum, and the first metal. The phases constituting the Raney nickel particles and their composition ratios can be confirmed, for example, by SEM-EDX.

[0025] The BET specific surface area of ​​the Raney nickel particles of this embodiment is, for example, 0.05 m ２ / g or more 100m ２ / g or less. The BET specific surface area is the N ２ It means the surface area per unit mass of Raney nickel particles measured by adsorption.

[0026] The average particle size of the Raney nickel particles in this embodiment 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 catalytic portion, resulting in a deterioration in durability. If the average particle size of the Raney nickel particles is more than 100 μm, the surface area of ​​the catalytic portion may be small, resulting in a decrease in activity. The average particle size of the Raney nickel particles may 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 a Raney alloy containing Ni and an alkali-soluble metal element with an alkaline substance to elute the alkali-soluble metal element from the Raney alloy. The alkali-soluble metal element is preferably a metal element with a higher ionization tendency than 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 a Raney alloy containing Ni and Al is high, the porosity of the Raney nickel particles obtained by eluting Al becomes high, i.e., the specific surface area becomes large. Therefore, from the viewpoint of obtaining Raney nickel particles that exhibit higher activity, it is preferable to use a Raney alloy with a high proportion of aluminum.

[0030] On the other hand, when the proportion of Al in a Raney alloy containing Ni and Al is small, the porosity of the Raney nickel particles obtained by dissolving Al is low, i.e., 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 exhibit high activity while maintaining durability, 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. From this viewpoint, it is preferable to use a Raney alloy represented by the following formula (1):

[0032] Al ３ Ni （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] The M element is preferably at least one element selected from Fe and Co. This is because, in addition to improving activity, a reduction in the amount used and a reduction in costs are expected. The M element more preferably includes at least Fe. From this viewpoint, in this embodiment, it is more preferable to use a Raney alloy represented by the following formula (2):

[0034] Al ３ Ni （２－（ｙ＋ｚ）） Fe ｙ Co ｚ (2) In the above formula (2), y and z satisfy the relationships 0≦y≦0.1 and 0≦z≦0.1.

[0035] The Raney alloy is, for example, in powder form. The average particle size of the Raney alloy of this embodiment 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 portion, resulting in a deterioration in durability. If the average particle size of the Raney alloy is more than 100 μm, the surface area of ​​the catalyst portion may be small, resulting in a decrease in activity. The average particle size of the Raney alloy may 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] The method for producing a Raney alloy is not particularly limited, and any known alloy production method can be applied, such as casting, quenching, mechanical alloying, and sputtering.

[0037] (Metal Particles) The metal particles of 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 a plurality of Raney nickel particles. The metal particles function as a binder that binds the Raney nickel particles dispersed in the water electrolysis electrode together and between the Raney nickel particles and the substrate. This function is explained as follows. Note that "containing Ni as a main component" means that the Ni content in the metal particles is more than 50 mass%.

[0038] When a Raney alloy (Raney nickel particles) and metal particles contain a metal other than Ni (hereinafter also referred to as an "additive element"), impurity diffusion occurs when thermal energy is applied to them, with the additive element considered as an impurity. That is, when thermal energy is applied by firing or the like and the atoms of the additive element undergo thermal vibration, the additive element diffuses from the Raney alloy to the raw material for the metal particles (or from the Raney nickel particles to the metal particles) due to the concentration gradient of the additive element between the Raney alloy and the raw material for the metal particles (or between the Raney nickel particles and the metal particles). Therefore, even between dissimilar substances such as metal particles and Raney nickel particles (or between the Raney alloy and the raw material for the metal particles), if they are in contact with each other, the additive element diffuses through the surface, bonding the Raney alloy and the raw material for the metal particles (or between the Raney nickel particles and the metal particles). This is expected to increase the surface area of ​​the catalyst portion and improve the activity of the water electrolysis electrode. Furthermore, the Raney alloy and the raw materials of the metal particles (or the Raney nickel particles and the metal particles) are firmly bound together, which inhibits them from falling off from the base material, and as a result, improvement in the durability of the water electrolysis electrode is also expected.

[0039] The metal particles of this embodiment contain Al. That is, in this embodiment, Al atoms diffuse from the Raney nickel particles, which have a higher Al content than the metal particles (or the raw material for the metal particles), to the metal particles (or from the Raney alloy to the raw material for the metal particles), driven by the Al concentration gradient. The inclusion of Al in the metal particles (or the raw material for the metal particles) improves the binder function of the metal particles, thereby forming a stronger electron conduction path, which is expected to further improve the activity of the water electrolysis electrode. Furthermore, the stronger binding between the Raney nickel particles and the metal particles (or the Raney alloy and the raw material for the metal particles) is expected to improve the durability of the water electrolysis electrode.

[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, and preferably 0.35 or less. When the second Al / Ni ratio is 0.4 or less, improved activity is expected. The second Al / Ni ratio may be, for example, 0.005 or more, or 0.01 or more. The second Al / Ni ratio can be confirmed, for example, by SEM-EDX.

[0041] The metal particles preferably contain Al on their surfaces, which is expected to further improve the function of the metal particles as a binder that binds the Raney nickel particles together and the Raney nickel particles to the substrate.

[0042] The average particle size of the metal particles is preferably 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 the Raney nickel particles can be in closer contact with each other, and the binder function of the metal particles is expected to be improved. The average particle size of the metal particles may be 5 times or more smaller than that of the Raney nickel particles, or 10 times or more smaller. The average particle size of the metal particles is 1 μm or more to 10 μm. The average particle size of the metal particles may be 1 μm or more to 5 μm or less, 1.5 μm or more to 3.5 μm or less, or 2 μm or more to 3 μm or less. The average particle size of the metal particles is preferably 2 μm or more to 3 μm or less. When the average particle size of the metal particles is 2 μm or more to 3 μm or less, improved durability is expected. Note that bonding of the metal particles to each other may result in the average particle size of the metal particles being larger than that of the Raney nickel particles.

[0043] [Raw material for metal particles] The number of moles of Al in the raw material for metal particles is preferably smaller than the number of moles of Al in the Raney alloy. When the number of moles of Al in the raw material for metal particles is smaller than the number of moles of Al in the Raney alloy, Al diffuses from the Raney alloy into the raw material for metal particles due to a concentration gradient in the method for producing a water electrolysis electrode described below, and is converted into metal particles. As a result, a stronger electron conduction path is formed, and improvement in the activity and durability of the water electrolysis electrode is expected.

[0044] The raw material of the metal particles may consist essentially of nickel, i.e., may consist of nickel metal containing Ni as the main component, such as pure nickel. Nickel metal is an alkali-resistant metal and therefore does not corrode during use, which is expected to result in improved activity and durability of the water electrolysis electrode. Note that "consisting essentially of nickel" and "consisting of nickel metal containing Ni as the main component, such as pure nickel" mean that the Ni content in the metal particles is 95 mass% or more.

[0045] The raw material for the metal particles is, for example, in powder form. The average particle size of the raw material for the metal particles is preferably smaller than the average particle size of the Raney alloy. When the average particle size of the raw material for the metal particles is smaller than the average particle size of the Raney alloy, the metal particles can penetrate into the gaps between the Raney nickel particles obtained from these raw materials, and it is expected that the function of the metal particles as a binder will be further improved. The average particle size of the raw material for the metal particles may be 5 times or more smaller than the average particle size of the Raney nickel particles, or 10 times or more smaller. The average particle size of the raw material for the metal particles may 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. The average particle size of the metal particles is preferably 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, it is expected that the durability will be improved.

[0046] <<First Al / Ni Ratio and Second Al / Ni Ratio>> The first Al / Ni ratio is greater than the second Al / Ni ratio. That is, the number of moles of Al contained in the Raney nickel particles is greater than the number of moles of Al contained in the metal particles. As a result of the improved function of the metal particles as a binder, a stronger electron conduction path is formed, which is expected to further improve the activity of the water electrolysis electrode. Furthermore, since the Raney nickel particles and the metal particles are more firmly bound together, the durability of the water electrolysis electrode is also expected to improve.

[0047] <<Ratio of Al to Ni in Water Electrode>> 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 preferably 0.006 or more and 0.45 or less. When the third Al / Ni ratio is within the above range, improved activity of the water electrolysis electrode is expected. Note that the total number of moles of Ni in the water electrolysis electrode is the total number of moles of Ni contained in the base material, the Raney nickel particles, and the 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 the Ni-containing metal particles.

[0048] <<Cross-Section Observation>> Fig. 1 is an example of a cross-sectional SEM image of the electrode for water electrolysis according to the present embodiment, and Fig. 2 is an example of an element mapping image of the SEM image of Fig. 1 by EDX. The water electrolysis electrode has a substrate 1 made of Ni and an Al ３ Ni ２ A Raney alloy having the composition and a raw material of metal particles made of Ni were used as raw materials.

[0049] 1 and 2, it can be seen that the metal particles 3 function as a binder to prevent the Raney nickel particles 2 from falling off the substrate 1. It can also be seen that the Ni-containing metal particles 3 contain a trace amount of Al. In other words, it is thought that the Al contained in the Raney alloy, which is the raw material for the Raney nickel particles, diffuses into the raw material for the metal particles, thereby forming the metal particles 3.

[0050] <<Anode for Water Electrolysis>> The electrode for water electrolysis according to this embodiment may be used as an anode for water electrolysis.

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

[0052] <<Cathode for Water Electrolysis>> The electrode for water electrolysis according to this embodiment may be used as a cathode for water electrolysis.

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

[0054] <Method for producing electrode for water electrolysis> The method for producing an electrode for water electrolysis according to this embodiment includes at least (a) a mixing step, (b) a step of forming an electrode precursor for water electrolysis, and (c) an alkali treatment step. The (b) step of forming an electrode precursor for water electrolysis may further include (b-1) a drying step and (b-2) a firing step. The (b) step of forming an electrode precursor for water electrolysis may also include (b-3) a leveling step and (b-4) a pressing step. Furthermore, the (c) alkali treatment step may be followed by (d) an oxidation step.

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

[0056] The slurry may further contain a thickener, such as carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF).

[0057] In this step, it is preferable to use a substrate with a low basis weight and a high-viscosity (high-concentration) slurry. By using such a substrate and slurry, the slurry can easily penetrate into the substrate in the coating step described below. This is thought to be due to the following reasons. That is, the lower the basis weight, the higher the porosity of the substrate. The higher the porosity of the substrate, the greater the amount of slurry supported (amount of catalyst part supported), and therefore higher activity is expected. Furthermore, the higher the viscosity (high concentration) of the slurry, the greater the concentration of catalyst part in the slurry, which facilitates contact between Raney nickel particles and metal particles, and therefore improved durability is expected. Furthermore, by using a substrate with a low basis weight, the interior of the water electrolysis electrode can maintain a high porosity even when a high-viscosity slurry is penetrated, and therefore high activity is expected. Note that "low basis weight" refers to, for example, a substrate with a porosity of 100 g / m ２ More than 600g / m ２ Preferably 200 g / m or less ２ More than 400g / m ２ The term "high viscosity" refers to, for example, a situation in which the proportion of the solvent in the slurry is 10% by mass or more and 50% by mass or less, and preferably 20% by mass or more and 45% by mass or less.

[0058] (b) Step of forming an electrode precursor for water electrolysis In the step of forming an electrode precursor for water electrolysis, the slurry obtained in the mixing step is applied to a substrate to obtain an electrode precursor for water electrolysis.

[0059] In this step, the slurry is applied to the surface of the substrate using any coating device. The application of the slurry may be carried out using a known coating device such as a die coater, roll coater, knife coater, blade coater, bar coater, spray coater, or screen printing device, or by immersing the substrate in the slurry. The slurry may be applied to the entire surface of the substrate, or may be applied to a portion of the surface of the substrate. When the substrate is plate-shaped, the slurry may be applied to one or both sides of the substrate. When the substrate is a porous substrate, the slurry may be impregnated into the pores of the substrate by, for example, pressing the substrate to which the slurry has been applied. When the substrate is a porous substrate, the slurry remaining on the surface of the substrate without impregnating the pores may be scraped off using a spatula or the like.

[0060] (b-1) Drying Step In the drying step, the base material (electrode precursor for water electrolysis) containing the slurry is dried. For example, the slurry may be dried using a hot air drying oven, an infrared dryer, a hot plate, or the like. The drying temperature may be, for example, 40°C or higher and 120°C or lower. The drying time may be, for example, 1 minute or higher and 300 minutes or lower.

[0061] (b-2) Calcination Step In the calcination step, the electrode precursor for water electrolysis after the drying step is calcined (heat treated). Calcination allows the slurry to uniformly penetrate the entire substrate, making it possible to prevent unevenness in the thickness of the substrate. Furthermore, calcination allows Al contained in the Raney alloy to diffuse into the raw material for metal particles due to a concentration gradient, and can form metal particles.

[0062] The firing temperature may be, for example, 600° C. or higher and 900° C. or lower. The firing time may be, for example, 1 hour or higher and 24 hours or lower.

[0063] (b-3) Leveling Step In the leveling step, the slurry remaining on the surface of the substrate is leveled off. For example, a spatula or the like may be used for leveling. The leveling step may be performed before or after the pressing step described below, and whether or not the step is performed can be adjusted as appropriate.

[0064] (b-4) Pressing Step In the pressing step, the substrate (electrode precursor for water electrolysis) containing the slurry is pressed. The pressing step may be performed at any time during the electrode precursor for water electrolysis formation step. The thickness of the substrate is adjusted by pressing. The pressure may be appropriately adjusted depending on the desired thickness of the substrate and the amount of slurry supported on the substrate.

[0065] (c) Alkali Treatment Step In the alkali treatment step, the water electrolysis electrode precursor is treated with an alkaline substance. The alkali treatment causes aluminum to be eluted from the Raney alloy, thereby obtaining Raney nickel particles. That is, a water electrolysis electrode containing Raney nickel particles is obtained.

[0066] A specific treatment method includes, for example, adding the electrode precursor for water electrolysis to an alkaline aqueous solution containing an alkaline substance, and then stirring the alkaline aqueous solution at a predetermined temperature for a predetermined time. Examples of the alkaline substance include alkali metal hydroxides and alkali metal salts. Examples of the alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Examples of the alkali metal salts include sodium carbonate, potassium carbonate, and lithium carbonate. The alkaline substance is preferably an alkali metal hydroxide.

[0067] The treatment temperature is, for example, 100° C. or higher and 140° C. or lower. The treatment time is, for example, 1 hour or higher and 9 hours or lower. The amount of alkaline substance used in this step can be adjusted as appropriate.

[0068] This step is preferably carried out at a high temperature using an alkaline aqueous solution of a high concentration of alkali metal hydroxide. 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 treatment temperature is, for example, 100°C or more, preferably 110°C or more, and more preferably 125°C or more. The treatment temperature is, for example, 148°C or less. In order to increase the treatment temperature, it is necessary to increase the concentration of the alkaline aqueous solution so that the boiling point of the alkaline aqueous solution is equal to or higher than the treatment temperature. For example, when the treatment temperature is 100°C or higher, the concentration of the alkaline aqueous solution is preferably 3 mol / L or more, and when the treatment temperature is 125°C or higher, the concentration of the alkaline aqueous solution is preferably 14 mol / L or more. This step is also preferably carried out at normal pressure. In this case, hydrogen generated during the treatment can be more easily removed than when pressurized.

[0069] By carrying out this step under such 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 more and the treatment temperature is 100°C or more, and is, for example, 1 hour to 8 hours when the concentration of the alkaline aqueous solution is 14 mol / L or more and the treatment temperature is 125°C or more.

[0070] In this step, all of the Al contained in the Raney alloy may be eluted, or a portion of the Al may be left uneluted.

[0071] (d) Oxidation Step: The Raney nickel particles (Raney nickel particle-containing substrate) obtained by the alkali treatment step have a high surface activity and may spontaneously combust in air. Therefore, handling during storage, etc. is difficult, and they must be handled by storing them in a solvent or the like to avoid contact with air.

[0072] In the oxidation step, the surface of the Raney nickel particles obtained in the alkali treatment step is oxidized. The Raney nickel particles with oxidized surfaces (hereinafter also referred to as "oxidized Raney nickel particles") are suppressed from spontaneously combusting in air. Therefore, the oxidized Raney nickel particles are easier to handle during storage, etc., than Raney nickel particles.

[0073] This step is carried out, for example, by reacting Raney nickel particles with an acidic aqueous solution containing an acidic substance. Specific examples of the treatment method include introducing the water electrolysis electrodes after the alkali treatment step into the acidic aqueous solution and stirring the mixture at a predetermined temperature for a predetermined time.

[0074] Examples of the acidic substance include hydrogen peroxide, sodium peroxide, sodium percarbonate, and sodium perborate. Among these, the acidic substance is preferably hydrogen peroxide.

[0075] The concentration of the acidic aqueous solution is, for example, 0.1 mol / L or more and 10 mol / L or less. The treatment temperature is, for example, 15°C or more and 80°C or less. The treatment time is, for example, 5 minutes or more and 720 minutes or less. The solid-liquid ratio of the 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 (water electrolysis electrode containing Raney nickel oxide particles) obtained by the above treatment may be washed, if necessary. As the washing treatment, a known washing treatment used in the production of Raney nickel particles, such as a water washing treatment, can be applied.

[0077] The method for producing electrodes for water electrolysis according to the present embodiment is merely an example, and is not intended to be limiting. For example, a catalyst layer including Raney nickel particles and metal particles may be formed on the surface of a substrate by applying a slurry to the surface of the substrate.

[0078] <Raw Materials> The materials used in this example are as follows.

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

[0080] <<Raney alloy>> B1: Composition formula Al ３ Ni ２ B1: Nickel-aluminum alloy (manufactured by Japan Metals and Chemical Industries, Ltd., average particle size: 23 μm) B2: Composition formula Al ３ Ni １．９５ Fe ０．０５ B1: Nickel-aluminum-iron alloy (manufactured by Japan Metals and Chemical Industries, Ltd., average particle size: 23 μm) B2: Nickel-aluminum alloy (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Raney nickel particles, approximately 50%) (average particle size: 19 μm) B3: Nickel-aluminum alloy (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Raney nickel particles, approximately 50%) (average particle size: 19 μm) B4: Composition formula Al ３ Ni １．９５ Fe ０．０５ B5: Nickel-aluminum-iron alloy (manufactured by Japan Metals and Chemical Industries, Ltd., average particle size: 8.3 μm) ３ Ni １．９５ Fe ０．０５ B6: Nickel-aluminum-iron alloy (manufactured by Japan Metals and Chemical Industries, Ltd., average particle size: 16 μm) ３ Ni １．９５ Fe ０．０５ B7: Nickel-aluminum-iron alloy (manufactured by Japan Metals and Chemical Industries, Ltd., average particle size: 38 μm) ３ Ni １．９５ Fe ０．０５ Nickel-aluminum-iron alloy (manufactured by Japan Metals and Chemical Industries, Ltd., average particle size: 85 μm). Note that B3 contains Ni and Al in a mass ratio of approximately 1:1.

[0081] <<Metal Particle Raw Materials>> C1: Nickel particles (Ni (NIE10PB) manufactured by Kojundo Chemical Laboratory Co., Ltd.) (average particle size: 2-3 μm) C2: Nickel particles (NIE11PB manufactured by Kojundo Chemical Laboratory Co., Ltd.) (average particle size: 3-5 μm)

[0082] Other: Thickener: CMC (Cellogen EP, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Solvent: Water

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

[0084] The above slurry was applied by a die coater to both sides of the substrate A. After application, the slurry remaining on the surface of the substrate A was smoothed off with a spatula.

[0085] Substrate A containing the slurry was dried at 80° C. for 60 minutes.

[0086] The dried substrate A was fired at 700° C. for 2 hours.

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

[0088] (No. 2) An electrode for water electrolysis No. 2 was prepared in the same manner as No. 1, except that Raney alloy B3 was used.

[0089] (Nos. 3 to 10) Electrodes for water electrolysis Nos. 3 to 10 were prepared in the same manner as No. 1, except that the mixing ratio of the Raney alloy B1 and the metal particle raw material C1 was changed to the ratio shown in Table 1 and that the dried substrate A was pressed to a thickness of 0.4 mm.

[0090] (No. 11) Electrode No. 11 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B2 was used, the mixing ratio of Raney alloy B2 and raw material C1 for metal particles was changed to the ratio shown in Table 1, and the dried substrate A was pressed to a thickness of 0.4 mm.

[0091] (Nos. 12 to 18) Water electrolysis electrodes Nos. 12 to 18 were prepared in the same manner as No. 1, except that the mixing ratio of the Raney alloy B1 and the raw material C1 for the metal particles was changed to the ratio shown in Table 1.

[0092] <Analysis> The first Al / Ni ratio and the second Al / Ni ratio of each No. of water electrolysis electrodes were determined. Specifically, a portion of the water electrolysis electrode was embedded in resin, and the surface was processed using a cross-section polisher, followed by analysis of the cross section by SEM-EDX. The results are shown in Table 1. The results in Table 1 represent the average values ​​obtained by arbitrarily selecting three points on the cross section.

[0093]

[0094] Test Example 1 In Test Example 1, the following evaluations were carried out on Nos. 1, 2, and 7, which were mixtures of Raney alloy and raw materials of metal particles in the same mass ratio.

[0095] <Evaluation> A potential fluctuation durability test was conducted to evaluate the performance of the resulting water electrolysis electrodes as anodes for water electrolysis. Specifically, a 7 mol / L aqueous potassium hydroxide solution was used as the electrolyte, and a nickel mesh counter electrode and each of the water electrolysis electrodes No. 1, 2, and 7 were immersed in the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode and connected to the electrolyte via a liquid junction. Before and after the potential fluctuation durability test, the potential of the working electrode relative to the reference electrode was swept at 1 mV / s to measure the oxygen generating current versus electrode potential. The current value when the anode potential was 1.5 V (vs. reversible hydrogen electrode) was read and used as an index of oxygen generating activity. The potential fluctuation durability test consisted of holding the electrode at 1.5 V (vs. reversible hydrogen electrode) for 1 minute, followed by holding it at 0 V (vs. reversible hydrogen electrode) for 1 minute, and this cycle was repeated 1,500 times.

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

[0097] (Catalyst Residual Rate) The catalyst residual rate after the potential fluctuation durability test was determined by multiplying the basis weight of the water electrolysis electrode before the potential fluctuation durability test by X (mg / cm ２ ), and the basis weight of the water electrolysis electrode after the potential fluctuation durability test was Y (mg / cm ２) was calculated based on the following formula (i). The results are shown in Table 2. When the catalyst portion remaining rate is less than 100%, it means that the catalyst portion has fallen off, i.e., durability is poor. When the catalyst portion remaining rate is 100%, it means that no decrease in the catalyst portion is observed before and after the potential fluctuation durability test, and durability is excellent. Note that if a portion of the catalyst portion is oxidized in the potential fluctuation durability test, the catalyst portion remaining rate may be 100% or more, but the catalyst portion is maintained without falling off, and this does not affect durability. Catalyst portion remaining rate = Y / X x 100 (i)

[0098]

[0099] <<Results>> As shown in Table 2, when No. 1 and No. 2 had the same thickness, the current density after the potential fluctuation durability test was higher in No. 1 than in No. 2. This is thought to be due to the structure of the Raney nickel particles contained in the water electrolysis electrode. That is, the Raney nickel particles contained in No. 1 have the composition formula Al ３ Ni ２ The Raney nickel particles in No. 1 and No. 2 are made from Raney alloy B1, which has a higher proportion of Al than Ni, while the Raney nickel particles in No. 2 are made from Raney alloy B3, which has almost equal proportions of Ni and Al. The Raney nickel particles are made by eluting Al from the Raney alloy, and the higher the proportion of Al in the Raney alloy, the higher the porosity of the Raney nickel particles after elution of Al and the higher the activity as a catalyst portion.

[0100] Furthermore, as shown in Table 1, the second Al / Ni ratios of No. 1 and No. 2 were almost the same. On the other hand, the first Al / Ni ratio of No. 1 was lower than that of No. 2, suggesting that more Al was eluted from No. 1 than from No. 2. Therefore, the porosity of the Raney nickel particles after Al elution was higher in No. 1 than in No. 2, and as shown in Table 2, the activity as a catalytic part (current density after the test) was higher in No. 1. Furthermore, even for water electrolysis electrodes with the same basis weight, generally, as the thickness of the water electrolysis electrode increases, the porosity increases, and therefore the specific surface area increases. As a result, the catalytic activity of the water electrolysis electrode increases, and the current density also increases. Therefore, No. 7, which was thinner than Nos. 1 and 2, is thought to have had the smallest current density.

[0101] Furthermore, the catalyst portion remaining rate exceeded 100% in Nos. 1 and 7. Therefore, Nos. 1 and 7 are considered to have excellent durability.

[0102] <Test Example 2> In Test Example 2, the following evaluations were performed using Nos. 3 to 11.

[0103] <Evaluation> To evaluate the performance of the obtained water electrolysis electrode as an anode for water electrolysis, a potential fluctuation durability test was carried out. The test method was the same as in Test Example 1.

[0104] (Current Density) The current density was measured before and after the potential fluctuation durability test. The results are shown in Table 3 and Figure 3. When the current density was 150 mA / cm ２ In the above cases, the electrode was deemed to have good activity for water electrolysis.

[0105] (Catalyst Residual Rate) After the potential fluctuation durability test, the catalyst residual rate was calculated based on the above formula (i). The results are shown in Table 3 and FIG.

[0106]

[0107] <<Results>> As shown in Table 3 and FIG. 3, in Nos. 4 to 8 and 11, the current density before and / or after the potential fluctuation durability test was 150 mA / cm ２In addition, in Nos. 5 to 8 and 11, the current density after the potential fluctuation durability test was greater than the current density before the potential fluctuation durability test or the current density was maintained even after the potential fluctuation durability test was completed. Furthermore, in Nos. 5 to 8 and 11, the current density before and after the potential fluctuation durability test was 200 mA / cm ２ It was better than the above.

[0108] 4, the catalyst portion remaining rate exceeded 100% in Nos. 5 to 8 and 11. From the above, it is believed that Nos. 5 to 8 and 11 exhibit good activity and are also excellent in durability.

[0109] Test Example 3 In Test Example 3, Nos. 1 and 12 to 18 were used to carry out the following evaluations.

[0110] <Evaluation> A potential fluctuation durability test was conducted to evaluate the performance of the resulting water electrolysis electrodes as cathodes for water electrolysis. Specifically, a 7 mol / L aqueous potassium hydroxide solution was used as the electrolyte, and the nickel mesh counter electrode and each of the water electrolysis electrodes No. 1 and No. 12 to No. 18 were immersed in the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode and connected to the electrolyte via a liquid junction. Before and after the potential fluctuation durability test, the potential of the working electrode relative to the reference electrode was swept at 1 mV / s, and the hydrogen generation current versus electrode potential was measured. The current value when the cathode potential was −0.15 V (vs. reversible hydrogen electrode) was read and used as an index of hydrogen generation activity. The potential fluctuation durability test consisted of holding the electrode at −0.1 V (vs. reversible hydrogen electrode) for 1 minute, followed by holding it at 0.4 V (vs. reversible hydrogen electrode) for 1 minute, and this cycle was repeated 1,000 times.

[0111] (Current Density) The current density was measured before and after the potential fluctuation durability test. The results are shown in Table 4 and FIG. 5. When the current density was 200 mA / cm ２ In the above cases, the electrode was deemed to have good activity for water electrolysis.

[0112] (Catalyst Residual Rate) After the potential fluctuation durability test, the catalyst residual rate was calculated based on the above formula (i). The results are shown in Table 4 and FIG.

[0113]

[0114] <<Results>> As shown in Table 4 and Fig. 5, in Nos. 1 and 12 to 18, the current density before and / or after the potential fluctuation durability test was 200 mA / cm ２ In addition, in Nos. 1 and 13 to 17, the current density before and after the potential fluctuation durability test was 200 mA / cm ２ It was better than the above.

[0115] 6, the catalyst portion remaining rate exceeded 100% in Nos. 1 and 14 to 18. From the above, it is believed that Nos. 1 and 14 to 18 exhibit good activity and are also excellent in durability.

[0116] Test Example 4 In Test Example 4, the following water electrolysis electrodes were used and the following evaluations were carried out.

[0117] (No. 19) Electrode No. 19 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B4 was used, the mixing ratio of Raney alloy B4 to raw material C1 for metal particles was changed to 22:78, and the dried substrate A was pressed to a thickness of 0.6 mm.

[0118] (No. 20) Electrode No. 20 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B5 was used, the mixing ratio of Raney alloy B5 to raw material C1 for metal particles was changed to 22:78, and the dried substrate A was pressed to a thickness of 0.6 mm.

[0119] (No. 21) Electrode No. 21 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B2 was used, the mixing ratio of Raney alloy B2 to raw material C1 for metal particles was changed to 22:78, and the dried substrate A was pressed to a thickness of 0.6 mm.

[0120] (No. 22) Electrode No. 22 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B7 was used, the mixing ratio of Raney alloy B7 to metal particle raw material C1 was changed to 22:78, and the dried substrate A was pressed to a thickness of 0.6 mm.

[0121] <<Evaluation>> A potential fluctuation durability test was carried out to evaluate the influence of the average particle size of the Raney alloy (Raney nickel particles) on the anode for water electrolysis. The test method was the same as in Test Example 1.

[0122] (Current Density) The current density was measured before and after the potential fluctuation durability test. The results are shown in Table 5 and FIG. 7. When the current density was 150 mA / cm ２ In the above cases, the electrode was deemed to have good activity for water electrolysis.

[0123] (Catalyst Residual Rate) After the potential fluctuation durability test, the catalyst residual rate was calculated based on the above formula (i). The results are shown in Table 5 and FIG.

[0124]

[0125] <<Results>> As shown in Table 5 and Fig. 7, in Nos. 19 to 22, the current density before and after the potential fluctuation durability test was 200 mA / cm ２ In addition, in Nos. 20 to 22, the current density after the potential fluctuation durability test was higher than the current density before the potential fluctuation durability test. Furthermore, in Nos. 20 and 21, the current density before the potential fluctuation durability test was 300 mA / cm ２ or more, and the current density after the potential fluctuation durability test was 400 mA / cm ２ That was all.

[0126] 8, the catalytic portion residual rate exceeded 100% in Nos. 19 to 22. From the above, it is considered that by adjusting the average particle size of the Raney alloy (Raney nickel particles) to an appropriate range, an anode for water electrolysis exhibiting good activity and durability can be obtained.

[0127] Test Example 5 In Test Example 5, the following water electrolysis electrodes were used and the following evaluations were carried out.

[0128] (No. 23) An electrode for water electrolysis No. 23 was prepared in the same manner as No. 1, except that Raney alloy B5 was used and the mixing ratio of Raney alloy B5 to raw material C1 for metal particles was changed to 52:48.

[0129] (No. 24) Electrode No. 24 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B2 was used and the mixing ratio of Raney alloy B2 to raw material C1 for metal particles was changed to 52:48.

[0130] (No. 25) Electrode No. 25 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B6 was used and the mixing ratio of Raney alloy B6 to raw material C1 for metal particles was changed to 52:48.

[0131] (No. 26) Electrode No. 26 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B7 was used and the mixing ratio of Raney alloy B7 to raw material C1 for metal particles was changed to 52:48.

[0132] <<Evaluation>> A potential fluctuation durability test was carried out to evaluate the influence of the average particle size of the Raney alloy (Raney nickel particles) on the cathode for water electrolysis. The test method was the same as in Test Example 3.

[0133] (Current Density) The current density was measured before the potential fluctuation durability test. The results are shown in Table 6 and FIG. 9. When the current density was 200 mA / cm ２ In the above cases, the electrode was deemed to have good activity for water electrolysis.

[0134] (Catalyst Residual Rate) The catalyst residual rate after the potential fluctuation durability test was calculated based on the above formula (i). The results are shown in Table 6 and FIG.

[0135]

[0136] <<Results>> As shown in Table 6 and FIG. 9, in Nos. 23 to 26, the current density before the potential fluctuation durability test was 200 mA / cm ２ In addition, in Nos. 24 and 25, the current density after the potential fluctuation durability test was 800 mA / cm ２That was all.

[0137] 10 , the catalytic portion residual rate exceeded 100% in Samples Nos. 24 to 26. From the above, it is considered that a cathode for water electrolysis exhibiting good activity and durability can be obtained by adjusting the average particle size of the Raney alloy (Raney nickel particles) to an appropriate range.

[0138] Test Example 6 In Test Example 6, the following water electrolysis electrodes were used and the following evaluations were carried out.

[0139] (No. 27) Electrode No. 27 for water electrolysis was prepared in the same manner as No. 1, except that Raney alloy B2 was used, the mixing ratio of Raney alloy B2 to raw material C1 for metal particles was changed to 52:48, and the dried substrate A was pressed to a thickness of 0.6 mm.

[0140] (No. 28) An electrode for water electrolysis No. 28 was prepared in the same manner as No. 27, except that raw material C2 for metal particles was used.

[0141] <Evaluation> A potential fluctuation durability test was conducted to evaluate the influence of the average particle size of the raw material (metal particles) of the metal particles on the anode for water electrolysis. The test method was the same as in Test Example 1.

[0142] (Current Density) The current density was measured before and after the potential fluctuation durability test. The results are shown in Table 7. When the current density was 150 mA / cm ２ In the above cases, the electrode was deemed to have good activity for water electrolysis.

[0143] (Catalyst Residual Rate) After the potential fluctuation durability test, the catalyst residual rate was calculated based on the above formula (i). The results are shown in Table 7.

[0144]

[0145] <<Results>> As shown in Table 7, in No. 27, the current density before and after the potential fluctuation durability test was 200 mA / cm ２ On the other hand, in No. 28, the current density before the potential fluctuation durability test was 200 mA / cm ２However, the current density after the potential fluctuation durability test was significantly reduced.

[0146] Furthermore, as shown in Table 7, the catalytic portion remaining rate exceeded 100% in Sample No. 27. On the other hand, almost no catalytic portion remained in Sample No. 28. From the above, it is considered that an anode for water electrolysis exhibiting good activity and durability can be obtained by adjusting the average particle size of the raw material of the metal particles (metal particles) to an appropriate range.

[0147] Test Example 7 In Test Example 7, the following evaluations were performed using Nos. 27 and 28.

[0148] <Evaluation> A potential fluctuation durability test was conducted to evaluate the influence of the average particle size of the raw material (metal particles) of the metal particles on the cathode for water electrolysis. The test method was the same as in Test Example 3.

[0149] (Current Density) The current density was measured before and after the potential fluctuation durability test. The results are shown in Table 8. When the current density was 200 mA / cm ２ In the above cases, the electrode was deemed to have good activity for water electrolysis.

[0150] (Catalyst Residual Rate) The catalyst residual rate after the potential fluctuation durability test was calculated based on the above formula (i). The results are shown in Table 8.

[0151]

[0152] <<Results>> As shown in Table 8, in No. 27, the current density before and after the potential fluctuation durability test was 200 mA / cm ２ On the other hand, in No. 28, the current density before the potential fluctuation durability test was 200 mA / cm ２ However, the current density after the potential fluctuation durability test was significantly reduced.

[0153] Furthermore, as shown in Table 8, the catalytic portion remaining rate exceeded 100% in Sample No. 27. On the other hand, almost no catalytic portion remained in Sample No. 28. From the above, it is considered that a water electrolysis cathode exhibiting good activity and durability can be obtained by adjusting the average particle size of the raw material of the metal particles (metal particles) to an appropriate range.

[0154] [Aspects] Next, the technical ideas that can be understood from the above-described embodiments will be additionally described below.

[0155] (Aspect 1) An electrode for water electrolysis comprising: a substrate; and a catalyst portion; wherein the catalyst portion comprises Raney nickel particles and metal particles containing nickel as a main component; the metal particles are in contact with the Raney nickel particles; and the metal particles contain aluminum; and a ratio of the total number of moles of aluminum to the total number of moles of nickel in the Raney nickel particles is greater than a ratio of the total number of moles of aluminum to the total number of moles of nickel in the metal particles.

[0156] (Aspect 2) The electrode for electrolysis according to aspect 1, wherein the metal particles have an average particle size smaller than the average particle size of the Raney nickel particles, and the metal particles are in contact with a plurality of the Raney nickel particles.

[0157] (Aspect 3) The electrode for electrolysis according to Aspect 1 or 2, wherein the substrate contains nickel or a nickel alloy as a main component.

[0158] (Aspect 4) A method for producing an electrode for water electrolysis, comprising: a mixing step of mixing a raw material for Raney nickel particles, a raw material for metal particles containing nickel as a main component, and a solvent to obtain a slurry; a forming step of applying the slurry to a substrate to obtain an electrode precursor for water electrolysis; and an alkali treatment step of treating the electrode precursor for water electrolysis with an alkaline substance to obtain an electrode for water electrolysis containing Raney nickel particles, wherein the number of moles of aluminum contained in the raw material for Raney nickel particles is greater than the number of moles of nickel contained in the raw material for Raney nickel particles.

[0159] (Embodiment 5) The raw material of the Raney nickel particles is a compound represented by the following formula (1): Al ３ Ni （２－ｘ）） M ｘ (1) wherein 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] (Aspect 6) The method for producing a water electrolysis electrode according to Aspect 5, wherein M contains at least Fe.

[0161] (Embodiment 7) The raw material of the Raney nickel particles is a compound represented by the following formula (2): Al ３ Ni （２－（ｙ＋ｚ）） Fe ｙ Co ｚ (2) wherein in formula (2), y and z satisfy the relationships 0≦y≦0.1 and 0≦z≦0.1.

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

[0163] (Aspect 9) The method for producing an electrode for water electrolysis according to any one of Aspects 4 to 8, wherein the electrode precursor-forming step further includes a drying step of drying the electrode precursor for water electrolysis; and a firing step of firing the electrode precursor for water electrolysis after the drying step.

[0164] The present embodiment and examples are illustrative in all respects. The present embodiment and examples are not limiting. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the beginning that any configuration may be extracted from the present embodiment and examples and that they may be combined in any desired manner.

[0165] 1 substrate, 2 Raney nickel particles, 3 metal particles.

Claims

1. An electrode for water electrolysis, comprising a substrate and a catalyst part, wherein the catalyst part includes Raney nickel particles and metal particles mainly containing nickel, the metal particles are in contact with the Raney nickel particles, the metal particles contain aluminum, and the ratio of the total number of moles of aluminum to the total number of moles of nickel in the Raney nickel particles is larger than the ratio of the total number of moles of aluminum to the total number of moles of nickel in the metal particles.

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

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

4. A method for manufacturing an electrode for water electrolysis, comprising: a mixing step of mixing a raw material of Raney nickel particles, a raw material of metal particles mainly containing nickel, and a solvent to obtain a slurry; a step of forming a precursor of an electrode for water electrolysis by coating the slurry on a substrate; and an alkali treatment step of treating the precursor of the electrode for water electrolysis with an alkaline substance to obtain an electrode for water electrolysis containing Raney nickel particles, wherein the number of moles of aluminum contained in the raw material of the Raney nickel particles is larger than the number of moles of nickel contained in the raw material of the Raney nickel particles.

5. The raw material of the Raney nickel particles is represented by the following formula (1): Al ３ Ni （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 of 0 ≦ x ≦ 0.

2. The method for manufacturing an electrode for water electrolysis according to claim 4.

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

7. The raw material of the Raney nickel particles is represented by the following formula (2): Al ３ Ni （２－（ｙ＋ｚ）） Fe ｙ Co ｚ (2) In the above formula (2), y and z satisfy the relationship of 0 ≦ y ≦ 0.1 and 0 ≦ z ≦ 0.

1. The method for manufacturing an electrode for water electrolysis according to any one of claims 4 to 6.

8. The 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 material of the Raney nickel particles and the raw material of the metal particles is 27% by mass or more and 95% by mass or less.

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

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