Method for producing electrode material

Abstract

This method for producing an electrode material used for an electrode of a water electrolysis device includes a step for obtaining Raney nickel contained in the electrode material. The step for obtaining Raney nickel includes an alkali treatment step for eluting aluminum from a NiAl alloy using an alkali substance. The component composition of the NiAl alloy, excluding inevitable impurities, is represented by the compositional formula Al3.00Ni(2.00 − x)Cux (x is a value satisfying 0.00 < x < 0.30).

Description

Method for manufacturing electrode materials

[0001] This disclosure relates to a method for manufacturing electrode materials, etc.

[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 includes, for example, an electrolytic cell containing an electrolyte such as alkaline water, and an anode and a cathode arranged in the electrolytic cell with a separator in between. In such a water electrolysis apparatus, alkaline water is electrolyzed by passing an electric current between the anode and the cathode, generating oxygen at the anode and hydrogen at the cathode.

[0003] Patent document 1 (JP P. 01-028837) discloses the use of Raney nickel as the anode in a water electrolysis apparatus. Raney nickel is obtained by dissolving aluminum from a NiAl alloy containing nickel and aluminum using an alkaline substance. Numerous pores are formed in Raney nickel due to the dissolution of aluminum.

[0004] Special Publication No. 01-028837

[0005] There is a need for electrode materials for water electrolysis devices that exhibit excellent water electrolysis performance.

[0006] This disclosure aims to provide a method for manufacturing electrode materials having excellent water electrolysis performance in water electrolysis devices.

[0007] The method for manufacturing an electrode material is a method for manufacturing an electrode material used in an electrode of a water electrolysis apparatus, and includes a step of obtaining Raney nickel contained in the electrode material, the step of obtaining Raney nickel includes an alkali treatment step of dissolving aluminum from a NiAl alloy with an alkaline substance, and the component composition of the NiAl alloy excluding unavoidable impurities is the composition formula Al ３．００ Ni （２．００－ｘ） Cu ｘ (x is a value that satisfies 0.00 < x < 0.30.)

[0008] The raw material of the electrode material is the raw material of the electrode material used for the electrode of the water electrolysis device. The electrode material contains Raney nickel, and the raw material is the raw material of the Raney nickel and contains a NiAl alloy in which aluminum elutes by an alkaline substance. The component composition excluding inevitable impurities of the NiAl alloy is represented by the compositional formula Al ３．００ Ni （２．００－ｘ） Cu ｘ (x is a value satisfying 0.00 < x < 0.30.)

[0009] According to the manufacturing method of the electrode material and the raw material of the electrode material of the present disclosure, an electrode that exhibits excellent water electrolysis performance in a water electrolysis device can be obtained.

[0010] It is a flowchart showing an example of the manufacturing method of the electrode material according to an embodiment.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In this specification, numerical ranges such as "m to n" include upper and lower limit values and represent a numerical range of "m or more and n or less" unless otherwise specified.

[0012] <Manufacturing method of electrode material> Fig. 1 is a flowchart showing an example of the manufacturing method of the electrode material according to an embodiment. The electrode material manufactured by the manufacturing method of the electrode material of the present embodiment (hereinafter, also referred to as "this manufacturing method") can be used as a catalyst for the electrode of the water electrolysis device. The water electrolysis device is preferably an alkaline water electrolysis device.

[0013] This manufacturing method is a manufacturing method of an electrode material used for an electrode of a water electrolysis device and includes a step of obtaining Raney nickel contained in the electrode material. The step of obtaining Raney nickel includes an alkali treatment step of eluting aluminum (Al) from a NiAl alloy with an alkaline substance. In this manufacturing method, the component composition excluding inevitable impurities of the NiAl alloy is represented by the following compositional formula (I). Al ３．００ Ni （２．００－ｘ） Cu ｘ (x is a value satisfying 0.00 < x < 0.30.) (I)

[0014] As described above, the electrode material obtained by this manufacturing method contains Raney nickel obtained using a NiAl alloy whose component composition, excluding unavoidable impurities, is represented by compositional formula (I) (hereinafter also referred to as "NiAl alloy (I)"). By using this electrode material containing Raney nickel, electrodes that exhibit excellent water electrolysis performance in a water electrolysis apparatus can be obtained. More specifically, in a water electrolysis apparatus, a cathode exhibiting high catalytic activity for hydrogen generation and an anode exhibiting high catalytic activity for oxygen generation can be obtained.

[0015] The electrode material obtained by this manufacturing method can be used as either the cathode (hydrogen-generating electrode) or the anode (oxygen-generating electrode) of a water electrolysis device. Since the electrode material tends to have higher catalytic activity for hydrogen generation than for oxygen generation, it is preferable to use it as the cathode.

[0016] The NiAl alloy (I) used in this manufacturing method and each step of this manufacturing method will be described in detail below.

[0017] (NiAl Alloy (I)) The NiAl Alloy (I) used in the alkali treatment step of this manufacturing method is an alloy whose component composition, excluding unavoidable impurities, is represented by the above compositional formula (I). Compositional formula (I) means that the molar ratio of aluminum (Al), nickel (Ni), and copper (Cu) in the entire alloy, excluding unavoidable impurities, is Al:Ni:Cu = 3.00:(2.00-x):x. NiAl Alloy (I) is Al ３．００ Ni （２．００－ｘ） Cu ｘ The alloy may consist of a single phase, or it may consist of multiple phases with different compositions.

[0018] The multiple phases may include, for example, at least a primary phase and further include secondary phases. In this specification, the primary phase of NiAl alloy (I) means a phase that satisfies at least one of the following volume and area conditions.

[0019] Volume Condition: The main phase of NiAl alloy (I) is defined as one phase whose volume ratio exceeds 50% of the total NiAl alloy (I), or two phases whose combined volume ratio (the volume ratio of the phase with the largest volume ratio and the volume ratio of the next largest phase) exceeds 50% of the total NiAl alloy (I). The volume ratio when there is one main phase, and the combined volume ratio when there are two main phases, may be 60% or more, 70% or more, 80% or more, or 90% or more. The volume of each phase constituting NiAl alloy (I) can be calculated, for example, by performing Rietveld analysis on X-ray diffraction (XRD) measurement data of NiAl alloy (I).

[0020] Area Condition: The main phase of NiAl alloy (I) is defined as one phase whose area ratio to the entire cross-section of the NiAl alloy (I) exceeds 50%, or two phases whose combined area ratio (the area ratio of the phase with the largest area ratio in any cross-section of the NiAl alloy (I) and the area ratio of the next largest phase) exceeds 50%. The area ratio when there is one main phase, and the combined area ratio when there are two main phases, may be 60% or more, 70% or more, 80% or more, or 90% or more. The area of ​​each phase in the cross-section of NiAl alloy (I) can be calculated, for example, by image analysis of elemental mapping data of the cross-section of NiAl alloy (I) obtained by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX).

[0021] The phases contained in NiAl alloy (I), excluding unavoidable impurities, are Al ４ Ni ３ phase, AlNi phase, Al ３ Ni ２ In contrast, Al ３ Ni phase, Al ３ Ni ５ Phase, and AlNi ３ Equivalent Al-Ni base phase; a phase in which some of the Ni in the Al-Ni base phase is replaced with Cu; Al ３ Cu phase, Al ２ Cu phase, AlCu phase, Al ９ Cu １２ In contrast, Al ２ Cu ３ In contrast, Al４ Cu ９ Phase, and AlCu ３ Examples include Al-Cu base phases; and phases in which some of the Cu contained in the Al-Cu base phase is replaced with Ni. NiAl alloy (I) may contain one or more of these phases as the main phase or a secondary phase, and may also contain phases that are inevitably formed during manufacturing. For example, NiAl alloy (I) may have an Al-Cu base phase. ３ Ni ２ It may also be an alloy in which the phase is such that the molar ratio of Al, Ni, and Cu, excluding unavoidable impurities in the entire alloy, is Al:Ni:Cu = 3.00:(2.00-x):x.

[0022] In compositional formula (I), x may be in the range of 0.00 < x < 0.30, but may also be 0.01 ≤ x ≤ 0.29, preferably 0.02 ≤ x ≤ 0.28, 0.03 ≤ x ≤ 0.27, 0.05 ≤ x ≤ 0.25, or 0.07 ≤ x ≤ 0.23.

[0023] In the process of obtaining Raney nickel, an alkali treatment step is used to dissolve Al from the NiAl alloy (I). When the amount of Al in the NiAl alloy increases, the amount of Al that can be dissolved increases, resulting in a larger porosity and specific surface area of ​​Raney nickel. Such Raney nickel tends to exhibit excellent catalytic activity, but its strength and durability tend to decrease. When the amount of Al in the NiAl alloy decreases, the porosity and specific surface area of ​​Raney nickel decrease, so catalytic activity tends to decrease, but strength and durability tend to improve. The amount of Al in NiAl alloy (I) is greater than the amount of Ni and Cu in NiAl alloy (I) in terms of molars, and the content of Al, Ni, and Cu are in the relationship shown in compositional formula (I). Therefore, Raney nickel obtained using NiAl alloy (I) has an appropriate porosity and specific surface area, so it can exhibit good catalytic activity while also having good durability.

[0024] The Raney nickel obtained using the NiAl alloy (I) can exhibit better catalytic activity than the Raney nickel obtained using a Cu-free NiAl alloy. Therefore, by using the electrode material obtained by this production method, an electrode of a water electrolysis device that exhibits excellent water electrolysis performance can be obtained.

[0025] The Raney nickel contained in the electrode material of this production method is considered to exhibit catalytic activity by generating a composite (oxy)hydroxide during the operation of the water electrolysis device. The composite (oxy)hydroxide refers to at least two or more of the (oxy)hydroxides of Ni(O)OH, Cu(O)OH, and Al(O)OH being combined. Since x in the composition formula (I) is greater than 0, the electrode obtained using the electrode material of this production method is likely to generate a composite (oxy)hydroxide that exhibits high activity during the operation of the water electrolysis device and is likely to exhibit high catalytic activity. Since x in the composition formula (I) is less than 0.30, the electrode obtained using the electrode material of this production method can suppress the elution of copper ions into the electrolyte when used in a water electrolysis device. The copper ions eluted into the electrolyte can cause an increase in resistance due to clogging of the separator, and can also cause an internal short circuit by depositing as a metal or compound on the electrode surface. The electrode obtained using the electrode material of this production method is likely to suppress an increase in resistance and an internal short circuit in a water electrolysis device.

[0026] The NiAl alloy (I) usually contains unavoidable impurities. The unavoidable impurities are impurities derived from the raw materials of the NiAl alloy (I) or impurities unavoidably mixed in the manufacturing process. Examples of the unavoidable impurities include elements other than the above-mentioned elements (Al, Ni, and Cu) contained in the NiAl alloy (I), such as one or more selected from the group consisting of magnesium (Mg), silicon (Si), titanium (Ti), chromium (Cr), manganese (Mn), cobalt (Co), zinc (Zn), tin (Sn), and lead (Pb). The content of the unavoidable impurities contained in the NiAl alloy (I) may be a content that does not affect the catalytic properties of the Raney nickel obtained from the NiAl alloy (I).

[0027] The method for manufacturing the NiAl alloy (I) is not particularly limited, and it can be manufactured by known alloy manufacturing methods such as casting, rapid solidification, mechanical alloying, and sputtering methods.

[0028] (Step of obtaining Raney nickel) The step of obtaining Raney nickel includes the above-described alkali treatment step (FIG. 1). By this alkali treatment step, Al, which is a component soluble in an alkaline substance, is eluted from the NiAl alloy (I). Therefore, in this manufacturing method, an electrode material containing Raney nickel having a porous structure with a large specific surface area in which a large number of pores are formed can be manufactured.

[0029] The step of obtaining Raney nickel may further include an oxidation step of oxidizing the surface of the porous body obtained by the alkali treatment step (FIG. 1). As long as the step of obtaining Raney nickel includes the alkali treatment step, the oxidation step may or may not be included.

[0030] (Alkali treatment step) The alkali treatment step is carried out by bringing the NiAl alloy (I) into contact with an alkaline substance. When the NiAl alloy (I) comes into contact with the alkaline substance, the NiAl alloy (I) and the alkaline substance react, and Al in the NiAl alloy (I) elutes to obtain a porous body. This porous body may be used as the Raney nickel contained in the electrode material. The alkali treatment step may elute all of the Al contained in the NiAl alloy (I), but a part of the NiAl alloy (I) may remain without eluting as long as a porous body can be formed.

[0031] Examples of the alkaline substance include a solution of an alkali metal compound, and preferably an aqueous solution of an alkali metal compound. Examples of the alkali metal compound include alkali metal hydroxides and alkali metal salts. Examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Examples of the alkali metal salt include sodium carbonate, potassium carbonate, and lithium carbonate. The alkaline substance is preferably an alkali metal hydroxide.

[0032] The method for eluting Al from NiAl alloy (I) is not particularly limited as long as the NiAl alloy (I) and the alkaline substance are brought into contact so that the NiAl alloy (I) reacts with the alkaline substance. If the alkaline substance is a solution, the NiAl alloy (I) and the alkaline substance may be brought into contact by spraying the alkaline substance onto the NiAl alloy (I) or by immersing the NiAl alloy (I) in the alkaline substance. If the NiAl alloy (I) is in powder form, the NiAl alloy (I) and the alkaline substance may be brought into contact by adding it to a solution of the alkaline substance and stirring.

[0033] The shape and form of the NiAl alloy (I) in contact with the alkaline substance are not particularly limited. The NiAl alloy (I) may be, for example, a powder, or it may be a NiAl alloy (I) supported on a first substrate. The first substrate only needs to support at least the NiAl alloy (I), and may also support components other than the NiAl alloy (I) (hereinafter, the components such as the NiAl alloy (I) supported on the first substrate will be collectively referred to as "supported components").

[0034] The average particle size of the powdered NiAl alloy (I) is, for example, 1 to 150 μm, but may also be 5 to 100 μm or 5 to 50 μm. The average particle size of NiAl alloy (I) refers to the particle size at 50% of the cumulative value in the particle size distribution determined by laser diffraction and scattering.

[0035] The first substrate supporting the NiAl alloy (I) is, for example, a conductor, and preferably contains Ni or a Ni alloy. The first substrate may be entirely made of Ni or a Ni alloy, or it may have a core layer and a surface layer, the surface layer may be made of Ni or a Ni alloy, and the core layer may be made of a material other than Ni and a Ni alloy. For example, the first substrate may have a core layer of iron or stainless steel with a surface layer coated with Ni or a Ni alloy. The first substrate is preferably Ni or a Ni alloy, and more preferably Ni. The first substrate may also be a material that constitutes part of the electrodes of a water electrolysis device.

[0036] The first substrate may be a porous substrate or a non-porous substrate. Examples of porous substrates include perforated metal, mesh, foamed metal, and expanded metal. Examples of non-porous substrates include metal foil and metal plate. Preferably, the first substrate is a porous substrate capable of supporting the supported component within its pores.

[0037] The method for supporting the supporting component on the first substrate is not particularly limited. For example, the NiAl(I) alloy may be supported on the first substrate by thermal spraying. Plasma spraying is one example of a thermal spraying method. Alternatively, the step of obtaining Raney nickel may further include a step of applying a first slurry containing NiAl alloy(I) and a first solvent to the first substrate, and this application step may cause the supporting component such as NiAl alloy(I) to be supported on the first substrate. Examples of the first solvent include water, N-methyl-2-pyrrolidone (NMP), and N-ethyl-2-pyrrolidone (NEP).

[0038] The first slurry may be applied 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 it may be applied by immersing the first substrate in the first slurry. The first slurry may be applied to the entire surface of the first substrate, or to a part of the surface of the first substrate. If the first substrate is in the form of a plate, the first slurry may be applied to one or both sides of the first substrate. If the first substrate is a porous substrate, the first slurry may be impregnated into the pores of the first substrate by pressing the first substrate to which the first slurry has been applied. If the first substrate is a porous substrate, any first slurry that has not impregnated into the pores and remains on the surface of the first substrate may be scraped off using a spatula or the like.

[0039] The first substrate on which the supporting component is carried may be obtained by coating the first slurry onto the first substrate and drying it, or by firing after coating and drying. The drying of the first slurry coated onto the first substrate can be carried out using known drying equipment such as a hot air drying oven, an infrared drying oven, and a hot plate. The drying temperature is, for example, 40 to 120°C, and may be 50 to 100°C. The drying time is, for example, 1 to 300 minutes, and may be 30 to 200 minutes. After the drying of the first slurry, the first substrate coated with the first slurry may be pressed.

[0040] The first slurry, applied to the first substrate and dried, may be fired. This firing helps to suppress unevenness in the thickness of the first substrate supporting the supported component, and if the first substrate is a porous substrate, it makes it easier to uniformly penetrate the supported component into the first substrate. If the supported component contains a metal whose main component is Ni (a binder metal described later), firing makes it easier to bond the NiAl alloy (I) to each other and / or to the first substrate.

[0041] If the first substrate has a supported component, the alkali treatment step only requires eluting Al from the NiAl alloy (I) contained in the supported component supported on the first substrate. As described above, if the step of obtaining Raney nickel includes a step of thermal spraying NiAl alloy (I) onto the first substrate, or if the step of obtaining Raney nickel includes a step of applying the first slurry to the first substrate, the NiAl alloy (I) treated in the alkali treatment step may be supported on the first substrate. In the alkali treatment step, for example, Al can be eluted from the NiAl alloy (I) by immersing the entire first substrate supporting the supported component in an alkaline solution. This makes it possible to obtain a first substrate with a porous body supported on it.

[0042] The NiAl alloy (I) contained in the first slurry is preferably in powder form. The average particle size of the powdered NiAl alloy (I) can be within the range described above.

[0043] The first slurry may further contain a metal whose main component is Ni (hereinafter also referred to as "binder metal"). Having Ni as the main component means that the Ni content in the binder metal is more than 50% by mass. The Ni content in the binder metal may be 60% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more. The metal content in the binder metal can be determined, for example, by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX).

[0044] The binder metal can function as a binder that binds NiAl alloy (I) particles together and / or NiAl alloy (I) particles together with the first substrate by firing the first substrate coated with the first slurry. As a result, an electrode material can be obtained in which Raney nickel particles together and / or Raney nickel particles together with the first substrate.

[0045] The binder metal may contain metals other than Ni, for example, one or more selected from the group consisting of Al, Cu, Mg, Si, Ti, Cr, Mn, Co, Zn, Sn, Pb, Fe, Ag, Pt, and Au. When the binder metal contains metals other than Ni, the binder metal is an alloy that is not a NiAl alloy (I), that is, an alloy whose component composition, excluding unavoidable impurities, is not represented by compositional formula (I), and more specifically, an alloy in which the amount of Al (moles) contained in the binder metal is less than the amount of Ni (moles).

[0046] It is preferable that the ratio of the amount of Ni (moles) to the total amount of all elements in the binder metal [mol%] is greater than the ratio of Ni (moles) to the total amount of all elements in the NiAl alloy (I) [mol%]. Also, it is preferable that the ratio of the total amount of metals other than Ni (moles) to the total amount of all elements in the binder metal [mol%] is less than the ratio of Cu (moles) to the total amount of all elements in the NiAl alloy (I) [mol%]. When the first slurry is fired as described above, Al and Cu diffuse from the NiAl alloy (I) to the binder metal at the contact area between the NiAl alloy (I) and the binder metal due to the thermal energy from firing and the elemental concentration gradient. This makes it easier for the NiAl alloy (I) and the binder metal to bond. When NiAl alloy (I) and a binder metal bond together, strong electron conduction paths are more easily formed, making it easier to obtain electrode materials with excellent water electrolysis performance in water electrolysis devices.

[0047] The binder metal is preferably in powder form. The average particle size of the binder metal is, for example, 1 to 10 μm, but may also be 1 to 8 μm or 2 to 5 μm. The average particle size of the binder metal refers to the value measured by the Fischer method.

[0048] When the NiAl alloy (I) and binder metal contained in the first slurry are in powder form, it is preferable that the average particle size of the NiAl alloy (I) is larger than the average particle size of the binder metal. This makes it easier for the binder metal to penetrate the gaps in the NiAl alloy (I), allowing the binder metal to function more effectively as a binder.

[0049] The binder metal content in the first slurry may be 15 to 95% by mass, 20 to 90% by mass, or 25 to 85% by mass, relative to the total amount of NiAl alloy (I) and the binder metal. The solvent content in the first slurry may be 15 to 70% by mass, 20 to 60% by mass, 25 to 55% by mass, or 27 to 50% by mass, relative to the total amount of the first slurry.

[0050] The first slurry may further contain components other than the NiAl alloy (I), the first solvent, and the binder metal. For example, the first slurry may contain a thickening agent to adjust the viscosity of the first slurry. Examples of thickening agents include carboxymethylcellulose (CMC), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVdF).

[0051] The treatment temperature for the alkali treatment step is preferably 90 to 150°C, but may also be 95 to 145°C or 100 to 140°C. If the alkaline substance is a solution, the alkali treatment step may be carried out while the temperature of the solution is adjusted and maintained within the above range. For example, NiAl alloy (I) may be added to an alkaline substance in solution, and then the alkali treatment step may be carried out after heating to the above treatment temperature.

[0052] The processing time for the alkali treatment step is, for example, 60 to 360 minutes, but may also be 100 to 300 minutes or 120 to 240 minutes.

[0053] The amount of alkali substance used in the alkali treatment process should be set according to the amount of Al contained in the NiAl alloy (I). The amount of alkali substance may be less than the stoichiometric amount of Al contained in the NiAl alloy (I), may be the same amount, or may be in excess. The mass ratio of NiAl alloy (I): alkali substance in solution in the alkali treatment process (NiAl alloy (I): alkali substance in solution) may be, for example, 1:10 to 1:500, 1:20 to 1:450, or 1:30 to 1:400.

[0054] When the alkaline substance is a solution of an alkali metal compound, the concentration of the solution may be, for example, 1 to 20 mol / L, 2 to 18 mol / L, or 3 to 15 mol / L.

[0055] The above-mentioned conditions in the alkali treatment process can be combined in any way. For example, if the treatment temperature in the alkali treatment process is 100°C or higher, the concentration of the alkali metal compound solution may be 3 mol / L or higher, and if the treatment temperature in the alkali treatment process is 140°C or higher, the concentration of the alkali metal compound solution may be 14 mol / L or higher. In the alkali treatment process, it is preferable to raise the treatment temperature as the concentration of the alkali metal compound solution increases.

[0056] The alkali treatment process is preferably carried out under atmospheric pressure (10¹³ hPa). This allows for easier removal of hydrogen generated during the alkali treatment process compared to carrying out the process under pressure, thus preventing the need for complex hydrogen removal equipment.

[0057] The porous material obtained through the alkaline treatment process may be washed as needed. Washing can be done with water. If powdered NiAl alloy (I) is immersed in an alkaline solution, the porous material may be recovered by solid-liquid separation such as filtration.

[0058] (Oxidation Process) The oxidation process is a process of oxidizing the surface of the porous material obtained by the alkali treatment process, in which Al is dissolved from the NiAl alloy (I) with an alkaline substance. The surface of the porous material obtained by the alkali treatment process is highly reactive with oxygen and may spontaneously ignite in air, making it difficult to handle during storage, etc. By carrying out the oxidation process to oxidize the surface of the porous material, the reactivity of the porous material with oxygen can be reduced, thereby improving the ease of handling during storage, etc. If part or all of the surface of the porous material is not oxidized, the porous material may be stored in a solvent or the like to suppress contact with air.

[0059] The oxidation process is carried out by bringing the porous material into contact with an acidic substance. When the acidic substance comes into contact with the surface of the porous material, the surface of the porous material is oxidized. The porous material with an oxidized surface may be used as Raney nickel contained in the electrode material. The oxidation process only needs to oxidize at least a portion of the surface of the porous material, but it is preferable to oxidize the entire surface of the porous material.

[0060] Examples of acidic substances include acidic solutions. Examples of acidic solutions include aqueous solutions of hydrogen peroxide, sodium peroxide, sodium percarbonate, and sodium perborate, with aqueous hydrogen peroxide being preferred.

[0061] The shape and form of the porous body that comes into contact with the acidic substance are not particularly limited. The porous body may be, for example, a powdered porous body, or a porous body supported on a first substrate. The porous body supported on the first substrate may be obtained by treating the first substrate supporting the supporting component in an alkali treatment step. The porous body supported on the first substrate may be supported on the first substrate in a state mixed with components other than Raney nickel contained in the electrode material or their raw materials.

[0062] The method for bringing a porous material into contact with an acidic substance is not particularly limited as long as the surface of the porous material is oxidized. If the acidic substance is an acidic solution, the porous material may be brought into contact with the acidic substance by spraying the acidic solution onto the porous material; or by immersing a powdered porous material or a porous material supported on a first substrate in an acidic solution. If the porous material is in powder form, the porous material may be brought into contact with the acidic substance by adding it to an acidic solution and stirring.

[0063] The processing temperature for the oxidation process is, for example, 10 to 80°C, but may also be 15 to 70°C or 15 to 60°C. The processing time for the oxidation process is, for example, 5 to 720 minutes, but may also be 60 to 700 minutes or 120 to 650 minutes. When an acidic solution is used as the acidic substance, the concentration of the acidic solution is, for example, 0.1 to 10 mol / L, but may also be 0.3 to 8 mol / L. The mass ratio of the porous material to the acidic solution (porous material: acidic solution) in the oxidation process is, for example, 1:5 to 1:100, but may also be 1:7 to 1:80 or 1:9 to 1:50.

[0064] The Raney nickel obtained through the oxidation process may be washed if necessary. Washing can be done with water. If the powdered porous material is immersed in an acidic solution, the Raney nickel may be recovered by solid-liquid separation such as filtration.

[0065] <Raw Materials for Electrode Material> The raw materials for the electrode material of this embodiment are used as electrode material for electrodes in a water electrolysis apparatus. The electrode material contains Raney nickel, and the raw materials for the electrode material contain NiAl alloy (I), which is a raw material for Raney nickel and from which Al is eluted by an alkaline substance. Therefore, in this specification, the raw materials for the electrode material refer to the compound or composition before Al is eluted from NiAl alloy (I) by an alkaline substance. By using the raw materials for the electrode material of this embodiment, an electrode material containing Raney nickel obtained using NiAl alloy (I) can be obtained, and thus an electrode that exhibits excellent water electrolysis performance in a water electrolysis apparatus can be obtained.

[0066] Examples of NiAl alloy (I) include those listed above. NiAl alloy (I) can be manufactured by the manufacturing method described above. Examples of alkaline substances and methods for leaching Al from NiAl alloy (I) using alkaline substances include those listed above.

[0067] The raw materials for the electrode material may include NiAl alloy (I) and at least one of a binder metal, a first solvent, and a thickener, and may also include components other than NiAl alloy (I), binder metal, first solvent, and thickener. The raw materials for the electrode material may include NiAl alloy (I) and a first solvent, or NiAl alloy (I), binder metal, and a first solvent, or NiAl alloy (I), binder metal, first solvent, and a thickener. Examples of the binder metal, first solvent, and thickener are those described above, and their content may be within the range described above.

[0068] If the raw material for the electrode material contains a binder metal, the binder metal content may be 15 to 95% by mass, 20 to 90% by mass, or 25 to 85% by mass, relative to the total amount of NiAl alloy (I) and the binder metal.

[0069] If the raw material for the electrode material contains a first solvent, the raw material for the electrode material may be in slurry form. The slurry-like raw material for the electrode material may be the first slurry described above.

[0070] <Method for Manufacturing Electrodes> The method for manufacturing electrodes in this embodiment is a method for manufacturing electrodes for a water electrolysis apparatus. The water electrolysis apparatus is preferably an alkaline water electrolysis apparatus. The electrode may be either a cathode or an anode, but it is preferably a cathode.

[0071] A method for manufacturing an electrode includes the steps of: obtaining an electrode material by the method for manufacturing an electrode material described above (hereinafter also referred to as "step [i]"); obtaining an electrode material using the raw materials for the electrode material described above (hereinafter also referred to as "step [ii]"); or obtaining an electrode material by the method for manufacturing an electrode material described above and applying a second slurry containing the electrode material and a second solvent to a second substrate (hereinafter also referred to as "step [iii]").

[0072] According to the electrode manufacturing method, since the electrode is manufactured using an electrode material containing Raney nickel obtained using NiAl alloy (I), an electrode that exhibits excellent water electrolysis performance in a water electrolysis apparatus can be obtained.

[0073] Step [i] can be carried out by the method described above for manufacturing the electrode material. When manufacturing an electrode material by supporting a supporting component such as NiAl alloy (I) on a first substrate, the first substrate on which Raney nickel or the like is supported, obtained by the above method for manufacturing the electrode material, may be used as the electrode.

[0074] Step [ii] can be carried out by obtaining an electrode material containing Raney nickel using the raw materials for the electrode material described above. Raney nickel may be a porous body obtained by dissolving Al from the NiAl alloy (I) in the raw materials for the electrode material with an alkaline substance, or it may be obtained by oxidizing the surface of this porous body. The electrode material obtained in step [ii] can be obtained, for example, by the method described in the method for manufacturing the electrode material described above.

[0075] The electrode material obtained in step [iii] is preferably obtained using the electrode material manufacturing method described above, which does not involve supporting NiAl alloy (I) or the like on the first substrate. For example, in step [iii], powdered Raney nickel as an electrode material is obtained from powdered NiAl alloy (I).

[0076] The second solvent contained in the second slurry may include water; alcohols such as methanol, ethanol, and propanol; and mixed solvents of water and alcohol. The second slurry may also contain components other than the electrode material and the second solvent. These components may include conductive porous carbon, ionomers, and conductive oxides. Examples of porous carbon include carbon black such as Ketjenblack and acetylene black, activated carbon, graphite, and carbon nanotubes. Examples of ionomers include fluorine-based resins such as perfluorocarbon sulfonic acid polymers. Examples of conductive oxides include niobium-substituted titanium dioxide.

[0077] The second substrate is, for example, a conductor and can be formed from a carbon material, a metal material, or a polymer electrolyte. The second substrate may be a porous substrate or a non-porous substrate. The second substrate may be one of those described for the first substrate.

[0078] The second slurry can be applied by the method described for the application of the first slurry. The second slurry may be applied to the entire surface of the second substrate, or to a portion of the surface of the second substrate. If the second substrate is in the form of a plate, the second slurry may be applied to one or both sides of the second substrate. If the second substrate is a porous substrate, the second slurry may be impregnated into the pores of the second substrate by pressing the second substrate to which the second slurry has been applied. If the second substrate is a porous substrate, any second slurry that has not impregnated into the pores and remains on the surface of the second substrate may be scraped off using a spatula or the like.

[0079] After applying the second slurry to the second substrate, the second slurry may be dried. The drying of the second slurry can be carried out, for example, using the apparatus, temperature, and time described for drying the first slurry. After drying the second slurry, the second substrate coated with the second slurry may be pressed.

[0080] The present disclosure will be described in more detail below with reference to examples and comparative examples. [Examples 1-3, Comparative Examples 1 and 2] (Preparation of raw materials for electrode material) Aluminum, nickel, and copper (if present) were weighed to obtain a composition with the composition formula shown in Table 1, and these were mixed to obtain a mixture. This mixture was heated and melted at 1600°C using a high-frequency melting furnace, and then cooled to obtain an alloy ingot of NiAl alloy represented by the composition formula shown in Table 1. By crushing the obtained alloy ingot, a powder of NiAl alloy with the above composition was obtained. The average particle size of the obtained powder was measured by laser diffraction and scattering methods and was in the range of 20 to 40 μm in all cases.

[0081] (Preparation of electrode material) Next, NiAl alloy powder (2 g) was immersed in a 14M sodium hydroxide aqueous solution (30 g) and subjected to alkaline treatment at 140°C for 3 hours (alkaline treatment step). Subsequently, a porous body was obtained from which aluminum had leached out of the NiAl alloy by filtration and washing with water.

[0082] A porous material powder (1.5 g) was immersed in a 5% by mass hydrogen peroxide aqueous solution (14 g) and subjected to oxidation treatment at 20°C for 10 hours (oxidation step). Subsequently, by filtration and washing with water, a Raney nickel powder with an oxidized porous material surface was obtained.

[0083] [Evaluation of catalytic activity for hydrogen generation] The hydrogen generation activity of Raney nickel powder was evaluated using a three-electrochemical measuring device.

[0084] A slurry was prepared by dispersing Raney nickel powder, Ketjenblack, and a 20% Nafion® dispersion (DE2020CS type: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in a mixed solvent of water and ethanol. An electrode was obtained by coating the prepared slurry onto a glassy carbon substrate (second substrate), and this was used as the working electrode.

[0085] The working electrode and the platinum coil (counter electrode) obtained above were immersed in a 7 mol / L potassium hydroxide solution as the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode and connected to the electrolyte via a liquid junction. The potential of the working electrode was swept at 10 mV / s relative to the reference electrode, and the hydrogen generation current relative to the electrode potential was 10 mA / cm². ２ The overpotential [mV] was measured under these conditions. The results are shown in Table 1. A smaller overpotential indicates better catalytic activity for hydrogen generation.

[0086]

[0087] [Example 4, Comparative Example 3] Except that aluminum, nickel, and copper were weighed out to match the composition formula shown in Table 2, raw materials for the electrode material were obtained in the same procedure as in Examples 1 to 3, and using these, electrode material, porous body, and Raney nickel were obtained.

[0088] [Evaluation of catalytic activity for oxygen evolution] The oxygen evolution activity of Raney nickel powder was evaluated using a three-electrochemical measuring device.

[0089] The working electrode was prepared using the procedure described in the evaluation of catalytic activity for hydrogen generation. The working electrode and a platinum coil as the counter electrode were immersed in a 7 mol / L potassium hydroxide solution as the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode and connected to the electrolyte via a liquid junction. The potential of the working electrode was swept at 10 mV / s relative to the reference electrode, and the current value [mA / cm²] at an electrode potential of 1.7 V (vs. reversible hydrogen electrode) was measured. ２ The following was measured. The results are shown in Table 2. A higher current value indicates better catalytic activity for oxygen evolution.

[0090]

[0091] [Note] The exemplary embodiments described above will be understood by those skilled in the art to be specific examples of the following embodiments. (Embodiment 1) A method for manufacturing an electrode material used in an electrode of a water electrolysis apparatus, comprising a step of obtaining Raney nickel contained in the electrode material, wherein the step of obtaining Raney nickel includes an alkali treatment step of dissolving aluminum from a NiAl alloy with an alkaline substance, and the component composition of the NiAl alloy excluding unavoidable impurities is of the composition formula Al ３．００ Ni （２．００－ｘ） Cu ｘ A method for manufacturing an electrode material, represented by (x is a value satisfying 0.00 < x < 0.30). (Aspect 2) The method for manufacturing an electrode material according to aspect 1, wherein x in the composition formula is 0.02 ≤ x ≤ 0.28. (Aspect 3) The method for manufacturing an electrode material according to aspect 1 or 2, wherein the step of obtaining the Raney nickel further includes an oxidation step of oxidizing the surface of the porous body obtained by the alkali treatment step. (Aspect 4) A raw material for an electrode material used in an electrode of a water electrolysis apparatus, wherein the electrode material contains Raney nickel, the raw material contains a NiAl alloy which is a raw material for Raney nickel and from which aluminum is eluted by an alkaline substance, and the component composition of the NiAl alloy excluding unavoidable impurities is the composition formula Al ３．００ Ni （２．００－ｘ） Cu ｘ The raw material for the electrode material, expressed as (where x is a value satisfying 0.00 < x < 0.30).

[0092] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims and not by the foregoing description, and all modifications are intended to be in the meaning and scope equivalent to the claims.

Claims

1. A method for manufacturing an electrode material used in an electrode of a water electrolysis apparatus, comprising a step of obtaining Raney nickel contained in the electrode material, wherein the step of obtaining Raney nickel includes an alkali treatment step of dissolving aluminum from a NiAl alloy with an alkaline substance, and the component composition of the NiAl alloy excluding unavoidable impurities is the composition formula Al ３．００ Ni （２．００－ｘ） Cu ｘ A method for manufacturing electrode materials, expressed as follows: (where x is a value satisfying 0.00 < x < 0.30).

2. The method for manufacturing an electrode material according to claim 1, wherein x in the composition formula is 0.02 ≤ x ≤ 0.

28.

3. The method for producing an electrode material according to claim 1 or 2, wherein the step of obtaining the Raney nickel further includes an oxidation step of oxidizing the surface of the porous body obtained by the alkali treatment step.

4. A raw material for an electrode material used in an electrode of a water electrolysis apparatus, wherein the electrode material contains Raney nickel, the raw material contains a NiAl alloy which is a raw material for Raney nickel and from which aluminum is leached by an alkaline substance, and the component composition of the NiAl alloy, excluding unavoidable impurities, has the composition formula Al ３．００ Ni （２．００－ｘ） Cu ｘ The raw material for the electrode material, expressed as (where x is a value satisfying 0.00 < x < 0.30).

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