Electrode material and method for manufacturing electrode material

Abstract

To provide a catalyst material for an electrode for water electrolysis which exhibits high activity.SOLUTION: A method for manufacturing an electrode material used for an electrode of a water electrolysis apparatus comprises an alkali treatment step in which Raney nickel is obtained by treating a specific NiAl alloy with an alkali substance thereby eluting aluminum from the specific NiAl alloy. The specific NiAl alloy is an alloy represented by the compositional formula Al3 Ni(n-(x+y))FexCoy (n is 1 or 2, and x and y are values satisfying 0<n-(x+y)<2, 0.005≤x≤0.8, and 0≤y≤0.8).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an electrode material used in electrodes of a water electrolysis device, and a method for producing the electrode material. [Background technology]

[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 has, for example, an electrolytic cell containing an electrolytic solution such as alkaline water, and an anode and a cathode arranged 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] Patent Document 1 discloses a technology that uses Raney nickel as a catalyst for the anode of the water electrolysis device. Raney nickel is nickel that remains after dissolving and removing only aluminum from a NiAl alloy containing nickel and aluminum by alkali treatment. Raney nickel is a porous body with a large specific surface area in which many pores are formed by dissolving aluminum. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 01-028837 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of extensive research, the present inventors have found that Raney nickel obtained from a NiAl alloy of a specific composition exhibits high activity as a catalyst for use in electrodes of a water electrolysis device. [Means for solving the problem]

[0006] The manufacturing method of the electrode material for solving the above problems is a manufacturing method of an electrode material used for an electrode of a water electrolysis device, and has an alkali treatment step of obtaining Raney nickel by eluting aluminum from the NiAl alloy by treating the NiAl alloy with an alkali substance. The NiAl alloy has a composition formula of Al3Ni (n-(x+y)) Fe x Co y (n is 1 or 2, and x and y are values satisfying 0 < n - (x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8.) and is an alloy represented by

[0007] In the above manufacturing method, the NiAl alloy preferably has a composition formula of Al3Ni (2-x) Fe x (x is a value satisfying 0.01 ≤ x ≤ 0.8.) and is an alloy represented by In the above manufacturing method, the NiAl alloy preferably has a composition formula of Al3Ni (1-x) Fe x (x is a value satisfying 0.005 ≤ x ≤ 0.7.) and is an alloy represented by

[0008] In the above manufacturing method, the NiAl alloy preferably has a composition formula of Al3Ni (2-(x+y)) Fe x Co y (x and y are values satisfying 0 < 2 - (x + y) < 2, 0.01 ≤ x ≤ 0.8, and 0 < y ≤ 0.8.) and is an alloy represented by

[0009] In the above manufacturing method, the NiAl alloy preferably has a composition formula of Al3Ni (1-(x+y)) Fe x Co y (x and y are values satisfying 0 < 1 - (x + y) < 1, 0.005 ≤ x ≤ 0.3, and 0 < y ≤ 0.7.) and is an alloy represented by

[0010] In the above manufacturing method, the alkali treatment step includes a treatment of reacting an alkaline aqueous solution, which is an aqueous solution of the alkali substance, with the NiAl alloy at a temperature of 100°C or higher. The alkali substance is an alkali metal hydroxide, and the concentration of the alkaline aqueous solution is preferably 3M or higher.

[0011] In the above manufacturing method, the alkali treatment step includes a treatment of reacting an alkaline aqueous solution, which is an aqueous solution of the alkali substance, with the NiAl alloy at a temperature of 140°C or higher. The alkali substance is an alkali metal hydroxide, and the concentration of the alkaline aqueous solution is preferably 14M or higher.

[0012] In the above manufacturing method, it is preferable to have an oxidation step of oxidizing the surface of the Raney nickel obtained by the alkali treatment step. The electrode material for solving the above problems is an electrode material used for the electrode of a water electrolysis device, and includes Raney nickel in which the molar ratio of nickel, iron, and cobalt (nickel: iron: cobalt) is (n - (x + y)): x: y (n is 1 or 2, and x and y are values satisfying 0 < n - (x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8).

Effects of the Invention

[0013] According to the present invention, a material for an electrode for water electrolysis showing high activity can be obtained.

Brief Description of the Drawings

[0014] [Figure 1] Figure 1 is a graph showing the evaluation results of the catalytic activity in Test 1. [Diagram 2] Figure 2 is a graph showing the evaluation results of the catalytic activity in Test 2.

Modes for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the method for manufacturing the electrode material of the present invention will be described. In this specification, "A to B" described as a numerical range means "A or more and B or less". The electrode material manufactured by the manufacturing method of this embodiment is a catalyst used for the electrodes of a water electrolysis device. Further, the above electrode material can be used for either the oxygen evolution electrode which is the anode of the water electrolysis device or the hydrogen evolution electrode which is the cathode. It is particularly preferable to use the above electrode material for the oxygen evolution electrode which is the anode.

[0016] The method for manufacturing the electrode material of this embodiment includes an alkali treatment step of obtaining Raney nickel from a NiAl alloy, and an oxidation step of oxidizing the surface of the Raney nickel obtained in the alkali treatment step. The oxidation step can be omitted as necessary. Hereinafter, the Raney nickel obtained in the alkali treatment step, that is, the Raney nickel before the oxidation step is performed may be described as the first Raney nickel. And the Raney nickel after the oxidation step is performed may be described as the second Raney nickel.

[0017] <Alkali treatment step> The alkali treatment step is a step of obtaining the first Raney nickel by eluting aluminum from a NiAl alloy (hereinafter referred to as a specific NiAl alloy) having a specific composition by treating the NiAl alloy with an alkali substance.

[0018] (Specific NiAl alloy) The specific NiAl alloy used in the alkali treatment step has the composition formula Al3Ni (n-(x+y)) Fe x Co y is an alloy represented by. In the above formula, n is 1 or 2, and x and y are values satisfying 0 < n - (x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8. In this specification, the composition formula Al3Ni (n-(x+y)) Fe x Co yThe specific NiAl alloy represented by the formula (1) means an alloy of aluminum, nickel, and iron, or an alloy of aluminum, nickel, iron, and cobalt, in which the molar ratio of aluminum, nickel, iron, and cobalt in the entire alloy (aluminum:nickel:iron:cobalt) is 3:(n-(x+y)):x:y. Therefore, the specific NiAl alloy is represented by the formula (1) as follows: Al3Ni (n-(x+y)) Fe x Co y The alloy may be an alloy composed of a single phase, or an alloy composed of multiple phases, for example, an alloy including a main phase and a subphase.

[0019] In this specification, the main phase of the specific NiAl alloy means one or two specific phases that occupy most of the specific NiAl alloy. The main phase of the specific NiAl alloy can be defined as a phase that satisfies at least one of the volume condition and area condition described below.

[0020] Volume condition: The volume ratio of one specific phase in the entire alloy, or the sum of the volume ratios of two phases with the largest volume ratios in the entire alloy, exceeds 50%. The above value regarding the volume condition may be 60% or more, 70% or more, 80% or more, or 90% or more. The volume of each phase constituting the alloy can be calculated, for example, by Rietveld analysis of the X-ray diffraction (XRD) measurement data of the alloy.

[0021] Area condition: the area ratio of a specific phase in any cross section formed by splitting the alloy, or the sum of the area ratios of two phases with the largest area ratios in the cross section, exceeds 50%. The above numerical value regarding the area condition may be 60% or more, 70% or more, 80% or more, or 90% or more. The area of ​​each phase in the above cross section of the alloy can be calculated by image analysis of elemental mapping data of the alloy cross section obtained by, for example, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX).

[0022] [First NiAl alloy] An example of a specific NiAl alloy is Al3Ni (2-x) Fe xThe alloy (hereinafter referred to as the first NiAl alloy) is represented by the formula: In the above formula representing the first NiAl alloy, x is, for example, a value that satisfies 0.01≦x≦0.8, preferably a value that satisfies 0.03≦x≦0.7, more preferably a value that satisfies 0.05≦x≦0.6, and further preferably a value that satisfies 0.1≦x≦0.4.

[0023] The single phase, the main phase, and the subphase constituting the first NiAl alloy include, for example, Al3Ni (2-x) Fe x The first NiAl alloy may include a main phase of the Al3Ni2 phase, an AlNi phase, and an Al3Fe phase. The first NiAl alloy may also include a subphase that is inevitably formed during manufacturing. The first NiAl alloy may include, for example, an alloy whose main phase is the Al3Ni2 phase and whose molar ratio (aluminum:nickel:iron) is 3:(2-x):x.

[0024] [Second NiAl alloy] An example of a specific NiAl alloy is Al3Ni (1-x) Fe x In the above formula representing the second NiAl alloy, x is, for example, a value that satisfies 0.005≦x≦0.7, preferably a value that satisfies 0.05≦x≦0.3, and more preferably a value that satisfies 0.05≦x≦0.1.

[0025] The single phase, the main phase, and the subphase constituting the second NiAl alloy include, for example, Al3Ni (1-x) Fe x The second NiAl alloy may include, as a subphase, a phase that is inevitably formed during manufacturing. The second NiAl alloy may include, for example, an alloy whose main phase is the Al3Ni1 phase and whose molar ratio (aluminum:nickel:iron) is 3:(1-x):x.

[0026] [Third NiAl alloy] An example of a specific NiAl alloy is Al3Ni(2-(x+y)) Fe x Co y is an alloy represented by (hereinafter referred to as the third NiAl alloy).

[0027] In the above formula representing the third NiAl alloy, x and y are values satisfying, for example, 0 < 2 - (x + y) < 2, 0.01 ≤ x ≤ 0.8, and 0 < y ≤ 0.8. In the above formula, x is preferably a value satisfying 0.03 ≤ x ≤ 0.7, more preferably a value satisfying 0.05 ≤ x ≤ 0.6, and even more preferably a value satisfying 0.1 ≤ x ≤ 0.4. In the above formula, y is preferably a value satisfying 0.1 < y < 0.8, more preferably a value satisfying 0.2 ≤ y ≤ 0.7, and even more preferably a value satisfying 0.2 ≤ y ≤ 0.6. Also, the ratio of cobalt to nickel (y / (2 - (x + y))) is, for example, 0.05 to 1.0, preferably 0.3 to 0.8. The ratio of cobalt to iron (y / x) is, for example, 0.25 to 12.0, preferably 1.0 to 6.0.

[0028] Examples of the single phase, the main phase, and the sub-phase constituting the third NiAl alloy include Al3Ni (2-(x+y)) Fe x Co y phase, Al3Ni2 phase, AlNi phase, Al3Fe phase, and their cobalt-containing substances. Also, the third NiAl alloy may include, as a sub-phase, a phase that is inevitably formed during production. Examples of the third NiAl alloy include an alloy in which the main phases are Al3Ni2 phase and Al4Ni3 phase, and the molar ratio (aluminum:nickel:iron:cobalt) is 3:(2 - (x + y)):x:y.

[0029] [Fourth NiAl alloy] An example of a specific NiAl alloy is an alloy represented by the composition formula Al3Ni (1-(x+y)) Fe x Co y is an alloy (hereinafter referred to as the fourth NiAl alloy).

[0030] In the above formula indicating the fourth NiAl alloy, x and y satisfy, for example, 0 < 1-(x + y) < 1, 0.005 ≤ x ≤ 0.3, and 0 < y ≤ 0.7. x in the above formula preferably satisfies 0.05 ≤ x ≤ 0.3, and more preferably satisfies 0.05 ≤ x ≤ 0.1. y in the above formula preferably satisfies 0.1 ≤ y ≤ 0.6, and more preferably satisfies 0.2 ≤ y ≤ 0.6. Further, the ratio of cobalt to nickel (y / (1-(x + y))) is, for example, 0.1 to 3, and preferably 0.25 to 3.0. The ratio of cobalt to iron (y / x) is, for example, 0.3 to 12.0.

[0031] Examples of the single phase, main phase, and sub-phase constituting the fourth NiAl alloy include Al3Ni (1-(x+y)) Fe x Co y phases, Al4Ni3 phase, Al3Ni phase, AlNi phase, Al3Fe phase, Al5FeNi phase, and AlNiFe2 phase. Further, the fourth NiAl alloy may include a phase that is inevitably formed during production as a sub-phase. Examples of the fourth NiAl alloy include an alloy in which the main phase is the Al3Ni1 phase and the molar ratio (aluminum:nickel:iron:cobalt) is 3:(1-(x + y)):x:y.

[0032] Here, Raney nickel used as an electrode material for a water electrolysis device exhibits catalytic activity based on the formation of a composite (oxy)hydroxide during operation. The composite of the composite (oxy)hydroxide means, for example, a composite of at least two or more of Ni(O)OH, Fe(O)OH, Al(O)OH, and Co(O)OH.

[0033] Raney nickel obtained from a specific NiAl alloy in which the proportion of iron is equal to or higher than the lower limit value of each of the above ranges can generate a large amount of highly active Fe(O)OH during the operation of a water electrolysis device, and a core-shell structure relatively rich in Fe(O)OH on the surface side is likely to be formed. Therefore, by setting the proportion of iron to be equal to or higher than the lower limit value of each of the above ranges, Raney nickel exhibiting high activity can be obtained.

[0034] The Raney nickel obtained from the specific NiAl alloy in which the proportion of iron is set to the upper limit value of each of the above ranges or less can suppress the dissolution of iron ions into the electrolyte during operation of the water electrolysis device. Therefore, the increase in resistance caused by the clogging of the separator by the dissolved iron ions can be suppressed. In addition, the dissolved iron ions may react with the oxygen gas generated on the anode side and precipitate as iron oxide (e.g., Fe2O3) on the anode surface. Since this iron oxide has a lower oxygen generation activity than the anode, the precipitation of iron oxide on the anode surface causes a decrease in the activity of the anode. In addition, the dissolved iron ions may cause an internal short circuit by precipitating in the form of dendrites on the cathode surface as iron oxide (e.g., Fe3O4) having electronic conductivity on the cathode side. Therefore, by suppressing the dissolution of iron ions, the decrease in activity on the anode side and the internal short circuit can be suppressed.

[0035] The Raney nickel obtained from the specific NiAl alloy in which the ratio of cobalt is equal to or greater than the lower limit of each of the above ranges can generate a more active complex (acid) hydroxide during the operation of the water electrolysis device, and is also likely to form a structure having many interfaces between NiOOH and CoOOH. Therefore, by setting the ratio of cobalt to equal to or greater than the lower limit of each of the above ranges, a Raney nickel exhibiting high activity can be obtained.

[0036] The Raney nickel obtained from the specific NiAl alloy in which the ratio of cobalt is set to the upper limit value or less of each of the above ranges can suppress the dissolution of cobalt ions into the electrolyte during operation of the water electrolysis device. Therefore, it is possible to suppress the increase in resistance caused by clogging of the separator by the dissolved cobalt ions. In addition, the dissolved cobalt ions may cause an internal short circuit by depositing as metallic cobalt on the cathode surface in the form of dendrites on the cathode side. Therefore, by suppressing the dissolution of cobalt ions, it is possible to suppress a short circuit within the cell.

[0037] In addition, when the proportion of aluminum in the specific NiAl alloy is high, the first Raney nickel obtained by dissolving aluminum has a relatively high porosity, i.e., a high specific surface area. Therefore, in order to obtain a Raney nickel exhibiting higher activity, it is preferable to use a specific NiAl alloy in which n is 1. On the other hand, when the proportion of aluminum in the specific NiAl alloy is low, the first Raney nickel obtained by dissolving aluminum has a relatively low porosity. Therefore, in order to obtain a Raney nickel with high strength, it is preferable to use a specific NiAl alloy in which n is 2.

[0038] The method for producing the specific NiAl alloy is not particularly limited, and any known alloy production method can be used. Examples of the method for producing the specific NiAl alloy include a casting method, a quenching method, a mechanical alloying method, and a sputtering method.

[0039] The specific NiAl alloy subjected to the alkali treatment step is, for example, in the form of a powder. The average particle size of the specific NiAl alloy is, for example, 1 to 150 μm. The average particle size described in this specification means the particle size at an integrated value of 50% in the particle size distribution determined by a laser diffraction / scattering method.

[0040] (Processing conditions) The alkali treatment step is carried out by reacting the specific NiAl alloy with an alkaline aqueous solution containing an alkaline substance. The aluminum in the specific NiAl alloy is dissolved by the reaction with the alkaline aqueous solution, and the first Raney nickel, which is a porous body with a large specific surface area, is obtained. A specific treatment method includes, for example, adding the powdered specific NiAl alloy little by little into the alkaline aqueous solution, and then stirring the alkaline aqueous solution at a predetermined temperature for a predetermined time. In addition, a treatment method may be adopted in which the specific NiAl alloy supported on a predetermined substrate by thermal spraying or the like is reacted with the alkaline aqueous solution.

[0041] The alkaline substance is, for example, an alkali metal hydroxide or an alkali metal salt. 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.

[0042] The treatment temperature in the alkali treatment step is, for example, 100 to 140°C. The treatment time in the alkali treatment step is, for example, 60 to 360 minutes. The amount of the alkaline substance used in the alkali treatment step can be appropriately set depending on the amount of aluminum contained in the specific NiAl alloy. The amount of the alkaline substance may be any amount that is less than, equal to, or excessive to the amount of aluminum contained in the specific NiAl alloy in stoichiometric terms. In addition, the solid-liquid ratio of the specific NiAl alloy to the alkaline aqueous solution in the alkali treatment step (specific NiAl alloy: alkaline aqueous solution) is, for example, 1:10 to 1:500 in mass ratio.

[0043] A preferred example of the treatment conditions for the alkali treatment step is to treat at high temperature using an alkaline aqueous solution of a high concentration of an alkali metal hydroxide. The concentration of the alkaline aqueous solution under the treatment conditions is, for example, 3M or more, preferably 7M or more, and more preferably 14M or more. The concentration of the alkaline aqueous solution under the treatment conditions is 20M or less. The treatment temperature under the treatment conditions is, for example, 100°C or more, preferably 110°C or more, and more preferably 140°C or more. The treatment temperature under the treatment conditions 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 more, the concentration of the alkaline aqueous solution is preferably 3M or more, and when the treatment temperature is 140°C or more, the concentration of the alkaline aqueous solution is preferably 14M or more. The alkali treatment step is preferably performed at normal pressure. In this case, hydrogen generated during the treatment can be easily removed compared to the case of pressurization. In particular, the need for a complex device for removing hydrogen generated during processing can be suppressed.

[0044] In this case, a first Raney nickel exhibiting high activity can be obtained. In particular, due to the high treatment temperature, iron atoms migrate to the surface of the particles in the alkali treatment step, and a first Raney nickel having a core-shell structure containing relatively more iron on the surface side is easily obtained. In addition, the reaction time between the alkaline aqueous solution and the specific NiAl alloy can be shortened. The reaction time between the alkaline aqueous solution and the specific NiAl alloy under the treatment conditions is, for example, 3 hours or more and 6 hours or less when the concentration of the alkaline aqueous solution is 3M or more and the treatment temperature is 100°C or more, and, for example, 1 hour or more and 6 hours or less when the concentration of the alkaline aqueous solution is 14M or more and the treatment temperature is 140°C or more.

[0045] The treatment conditions of the alkali treatment step may be treatment conditions that dissolve all of the aluminum contained in the specific NiAl alloy, or treatment conditions that leave a portion of the aluminum undissolved.

[0046] The first Raney nickel obtained by the above treatment can be recovered by performing a filtration treatment. At that time, a washing treatment may be performed as necessary. As the filtration treatment, a known solid-liquid separation treatment used in the production of Raney nickel can be applied. As the washing treatment, a known washing treatment used in the production of Raney nickel, for example, a water washing treatment, can be applied.

[0047] <Oxidation process> The surface activity of the Raney nickel obtained by the alkali treatment process is high, so it may spontaneously combust in air. Therefore, it is difficult to handle during storage, and it is necessary to store it in a solvent to avoid contact with air.

[0048] The oxidation step is a step of oxidizing the surface of the first Raney nickel obtained by the alkali treatment step. The second Raney nickel, which is the first Raney nickel with an oxidized surface, is suppressed from spontaneously combusting in air. Therefore, the second Raney nickel is easier to handle during storage, etc., than the first Raney nickel.

[0049] An example of the oxidation step is carried out by reacting the first Raney nickel with an acidic aqueous solution containing an acidic substance. A specific treatment method includes, for example, adding powdered first Raney nickel little by little to the acidic aqueous solution, and then stirring the mixture at a predetermined temperature for a predetermined time.

[0050] Examples of the acidic substance include hydrogen peroxide, sodium peroxide, sodium percarbonate, and sodium perborate. Among these, the acidic substance is preferably hydrogen peroxide.

[0051] The concentration of the acidic aqueous solution, as well as the treatment temperature and treatment time in the oxidation step, can be appropriately set. The concentration of the acidic aqueous solution is, for example, 0.7 to 10 M. The treatment temperature in the oxidation step is, for example, 15 to 80 °C. The treatment time in the oxidation step is, for example, 5 to 720 minutes. The solid-liquid ratio (Raney nickel: acidic aqueous solution) of the first Raney nickel and the acidic aqueous solution in the oxidation step is, for example, 1:9 to 1:100 by mass.

[0052] The second Raney nickel obtained by the above treatment can be recovered by performing a filtration treatment. At that time, a washing treatment may be performed as necessary. As the filtration treatment, a known solid-liquid separation treatment used in the production of Raney nickel can be applied. As the washing treatment, a known washing treatment used in the production of Raney nickel, for example, a water washing treatment, can be applied.

[0053] <Raney nickel> The first Raney nickel and the second Raney nickel produced by the above production method (hereinafter, may be referred to as the Raney nickel of the present embodiment) contain nickel and iron in specific ratios, or contain nickel, iron, and cobalt in specific ratios. The ratios of nickel, iron, and cobalt in the Raney nickel of the present embodiment are equal to the ratios of nickel, iron, and cobalt in the specific NiAl alloy used in the production. Therefore, the molar ratio of nickel, iron, and cobalt in the Raney nickel of the present embodiment is (n-(x + y)):x:y. In the above molar ratio, n is 1 or 2, and x and y are values that satisfy 0 < n-(x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8.

[0054] The Raney nickel of the present embodiment may contain aluminum. In this case, the mass ratio of aluminum contained in the Raney nickel of the present embodiment is, for example, 22% by mass or less, preferably 11% by mass or less. Also, the mass ratio of the above aluminum is, for example, 0.6% by mass or more, preferably 1% by mass or more.

[0055] Note that the Raney nickel of the present embodiment is Ni(n-(x+y)) Fe x Co y The alloy may be an alloy composed of a single phase consisting of a phase, or may be an alloy composed of multiple phases, for example, an alloy containing a main phase and a subphase. For example, the Raney nickel of the present embodiment obtained from a specific NiAl alloy containing a main phase and a subphase may have a phase derived from the main phase of the specific NiAl alloy and a phase derived from the subphase of the specific NiAl alloy. The phase derived from the main phase of the specific NiAl alloy is, for example, a phase in which part or all of aluminum is removed from the main phase of the specific NiAl alloy. The phase derived from the subphase of the specific NiAl alloy is, for example, a phase in which part or all of aluminum is removed from the subphase of the specific NiAl alloy.

[0056] The Raney nickel of the present embodiment obtained from the first NiAl alloy is, for example, Ni (2-x) Fe x and alloys in which the main phase is a Ni phase derived from the Al3Ni2 phase and the Al4Ni3 phase and the molar ratio (nickel:iron) is (2-x):x.

[0057] The Raney nickel of the present embodiment obtained from the second NiAl alloy is, for example, Ni (1-x) Fe x and alloys in which the main phase is a Ni phase derived from the Al3Ni1 phase and the molar ratio (nickel:iron) is (1-x):x.

[0058] The Raney nickel of the present embodiment obtained from the third NiAl alloy is, for example, Ni (2-(x+y)) Fe x Co y and alloys in which the main phase is a Ni phase derived from the Al3Ni2 phase and the Al4Ni3 phase and the molar ratio (nickel:iron:cobalt) is (2-(x+y)):x:y.

[0059] The Raney nickel of the present embodiment obtained from the fourth NiAl alloy may be, for example, Ni (1-(x+y)) Fe x Co yand alloys in which the main phase is a Ni phase derived from the Al3Ni1 phase and the molar ratio (nickel:iron:cobalt) is (1-(x+y)):x:y.

[0060] The BET specific surface area of ​​the Raney nickel of this embodiment is, for example, 5 to 100 m 2 The BET specific surface area means the surface area per unit mass of Raney nickel measured by N2 adsorption using the BET method.

[0061] The average particle size of the Raney nickel in this embodiment is, for example, 0.1 to 100 μm. <effect> Next, the operation of this embodiment will be described.

[0062] According to the production method of this embodiment, Raney nickel containing iron in a specific ratio or Raney nickel containing iron and cobalt in specific ratios can be obtained. When the Raney nickel of this embodiment is used as an electrode material for a water electrolysis device, i.e., as an electrode catalyst, it exhibits high catalytic activity based on the generation of a highly active complex (acid) hydroxide during operation.

[0063] In particular, the Raney nickel of this embodiment shows high activity when applied as a material for the anode of a water electrolysis device, that is, as a catalyst for oxygen generation reaction. Specifically, the Raney nickel of this embodiment has a Tafel gradient of, for example, 50 to 226 mV / dec. when applied as a catalyst for oxygen generation reaction. The Tafel gradient is obtained from a Tafel plot in which the horizontal axis is the logarithm of the oxygen generation current and the vertical axis is the overvoltage, which is the value obtained by subtracting the theoretical decomposition potential of the oxygen generation reaction from the working electrode potential. The Tafel gradient obtained from the Tafel plot in which the horizontal axis is the logarithm of the oxygen generation current, is the voltage required to increase the oxygen generation current by 10 times, and the smaller the absolute value, the higher the catalytic activity for oxygen generation.

[0064] In detail, the composition formula is Al3Ni (2-x) Fe xThe Raney nickel of the present embodiment obtained from a specific NiAl alloy represented by, for example, has a Tafel slope of 121 to 226 mV / dec. Composition formula: Al3Ni (1-x) Fe x The Raney nickel of the present embodiment obtained from a second specific NiAl alloy represented by, for example, has a Tafel slope of 75 to 120 mV / dec. Composition formula: Al3Ni (2-(x+y)) Fe x Co y The Raney nickel of the present embodiment obtained from a third specific NiAl alloy represented by, for example, has a Tafel slope of 86 to 126 mV / dec. Composition formula: Al3Ni (1-(x+y)) Fe x Co y The Raney nickel of the present embodiment obtained from a fourth specific NiAl alloy represented by, for example, has a Tafel slope of 50 to 91 mV / dec. The Tafel slope can be measured by the measurement method described in the examples.

[0065] <Effect> Next, the effects of the present embodiment will be described. (1) The manufacturing method of the electrode material used for the electrode of the water electrolysis device has an alkali treatment step of obtaining Raney nickel by eluting aluminum from a specific NiAl alloy by treating the specific NiAl alloy with an alkali substance. The specific NiAl alloy has a composition formula of Al3Ni (n-(x+y)) Fe x Co y (n is 1 or 2, and x and y are values that satisfy 0 < n-(x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8.)

[0066] According to the above configuration, Raney nickel showing high catalytic activity can be manufactured when used as the electrode material of the water electrolysis device. The manufactured Raney nickel shows high oxygen evolution activity when used as the anode material of the water electrolysis device, and shows high hydrogen evolution activity when used as the cathode material.

[0067] (2) The alkali treatment step includes a treatment in which an alkaline aqueous solution, which is an aqueous solution of an alkaline substance, is reacted with the specific NiAl alloy at a temperature of 100°C or higher. The alkaline substance is an alkali metal hydroxide. The concentration of the alkaline aqueous solution is 3M or higher. According to the above configuration, in the alkali treatment step, iron atoms migrate to the surface of the particles, making it easier to obtain Raney nickel with a core-shell structure that contains a relatively large amount of iron on the surface side. In addition, the reaction time between the alkaline aqueous solution and the specific NiAl alloy can be shortened.

[0068] (3) The alkaline treatment step includes a process of reacting an alkaline aqueous solution, which is an aqueous solution of an alkaline substance, with the specific NiAl alloy at a temperature of 140°C or higher. The alkaline substance is an alkali metal hydroxide. The concentration of the alkaline aqueous solution is 14M or higher. According to the above configuration, the effect of (2) above is further improved.

[0069] (4) A method for producing an electrode material used in an electrode of a water electrolysis device includes an oxidation step of oxidizing the surface of the Raney nickel obtained by the alkali treatment step. According to the above configuration, spontaneous combustion of the obtained Raney nickel in air can be suppressed. This makes it possible to obtain Raney nickel that is easy to handle during storage, etc. EXAMPLES

[0070] Hereinafter, a more specific embodiment of the above embodiment will be described. <Test 1> In test 1, the catalytic activity of Raney nickel obtained from the first NiAl alloy containing iron was evaluated.

[0071] (Preparation of Raney Nickel) A mixture of predetermined amounts of aluminum, nickel, and iron is heated and melted at 1600℃ in a high-frequency melting furnace, and then cooled to produce a material with a main phase of Al3Ni2 and a composition formula of Al3Ni (2-x) Fe xThe alloy ingots were prepared by mixing the above-mentioned alloy ingots with x being 0, 0.05, 0.1, 0.2, 0.4, and 0.7. The alloy ingots were pulverized to obtain NiAl alloy powder of the above-mentioned composition. The average particle size of the obtained powder was measured by a laser diffraction / scattering method and was found to be in the range of 40 to 60 μm.

[0072] Next, the obtained NiAl alloy powder (2 g) was immersed in a 14 M aqueous sodium hydroxide solution (30 g) and subjected to an alkali treatment for 3 hours at 140° C. After that, a filtration treatment and a washing treatment with water were performed to obtain a first Raney nickel in which aluminum was dissolved from the NiAl alloy.

[0073] The obtained first Raney nickel powder (1.5 g) was immersed in a 5 mass% hydrogen peroxide aqueous solution (14 g) and subjected to an oxidation treatment for 10 hours at 20° C. Thereafter, a filtration treatment and a washing treatment with water were performed to obtain a second Raney nickel powder with an oxidized surface.

[0074] (Evaluation of catalytic activity) The oxygen evolution activity of the obtained second Raney nickel was evaluated using a three-electrode electrochemical measurement device.

[0075] A slurry was prepared by dispersing powder of 2-Raney nickel, Ketjen black, and 20% Nafion (registered trademark) dispersion (DE2020CS type: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in a mixed solvent of water and ethanol. The prepared slurry was applied to a glassy carbon substrate to obtain an electrode body. The amount of 2-Raney nickel supported in the electrode body was 0.05 mg / cm. 2 It was decided.

[0076] A 7 mol / L aqueous potassium hydroxide solution was used as the electrolyte, and the platinum coil (counter electrode) and the working electrode were immersed in the electrolyte. A mercury-mercury oxide electrode was used as the reference electrode, and it was connected to the electrolyte via a liquid junction. The potential of the working electrode relative to the reference electrode was swept at 10 mV / s, and the oxygen evolution current versus the electrode potential was measured at room temperature.

[0077] Next, a Tafel plot was created with the logarithm of the measured oxygen generating current (A) on the horizontal axis and the overvoltage (V), which is the value obtained by subtracting the theoretical decomposition potential of the oxygen generating reaction from the working electrode potential, on the vertical axis, and the Tafel gradient (mV / dec.) was obtained from the created Tafel plot. The overvoltage was calculated assuming that the theoretical decomposition voltage of the oxygen generating reaction is 1.23 V. The results are shown in the graph in Figure 1. As described above, the Tafel gradient obtained by plotting the logarithm of the oxygen generating current on the horizontal axis is the amount of change in potential required to increase the oxygen generating current by 10 times. The smaller the absolute value of the Tafel gradient, the higher the catalytic activity for oxygen generation.

[0078] Table 1 below is a table summarizing the Fe ratio and the Tafel slope at each point in the graph shown in FIG. 1. The relative evaluation column of oxygen generating activity in Table 1 also shows the evaluation of the oxygen generating activity for each example with different Fe ratios. This evaluation is a relative evaluation with the Tafel slope value when the Fe ratio is "0" as the reference value. The evaluation criteria are as follows:

[0079] "=": The Tafel slope value is 98% or more and 102% or less with respect to the above reference value, and the oxygen generating activity is equivalent to that when the Fe ratio is "0". "◯": The Tafel slope value is 85% or more and less than 98% of the above reference value, and the oxygen generating activity is higher than when the Fe ratio is "0".

[0080] "Excellent": The Tafel slope value is less than 85% of the above reference value, and the oxygen generating activity is significantly higher than when the Fe ratio is "0".

[0081] [Table 1] As shown in Figure 1 and Table 1, the Tafel slope is (2-x) Fe x As the iron ratio x (Fe ratio) in the NiAl alloy increases, the curve becomes convex downward. From this result, it can be seen that Raney nickel obtained from NiAl alloys containing iron in the range of iron ratio x being 0.8 or less has higher oxygen evolution activity than Raney nickel obtained from NiAl alloys not containing iron. In addition, the Tafel slope has a minimum value when the iron ratio x is in the vicinity of 0.2. From this result, it can be seen that, among NiAl alloys containing iron, the Raney nickel obtained from the composition formula Al3Ni (2-x) Fe x It can be seen that Raney nickel obtained from the NiAl alloy represented by the formula (x is a value satisfying 0.1≦x≦0.4) exhibits particularly high oxygen evolution activity.

[0082] <Test 2> In test 2, the catalytic activity of Raney nickel obtained from a second NiAl alloy containing iron was evaluated.

[0083] (Preparation of Raney Nickel) A mixture of predetermined amounts of aluminum, nickel, and iron is heated and melted at 1550℃ in a high-frequency melting furnace, and then cooled to produce a product with a main phase of Al3Ni1 and a composition formula of Al3Ni (1-x) Fe x The alloy ingots were prepared by mixing the above-mentioned alloy ingots with x being 0, 0.05, 0.1, 0.2, 0.3, and 0.7. The alloy ingots were pulverized to obtain NiAl alloy powder of the above-mentioned composition. The average particle size of the obtained powder was measured by a laser scattering method and was in the range of 50 to 70 μm.

[0084] Next, the obtained NiAl alloy powder was subjected to the same alkali treatment and oxidation treatment as in Test 1 to obtain a second Raney nickel powder. (Evaluation of catalytic activity) The oxygen generating activity of the obtained second Raney nickel was evaluated in the same manner as in Test 1. The results are shown in the graph of FIG. 2. Table 2 below is a table summarizing the Fe ratio and the Tafel slope at each point in the graph shown in FIG. 2. The relative evaluation column of oxygen generating activity in Table 2 also shows the evaluation of the oxygen generating activity of each example with different Fe ratios. This evaluation is a relative evaluation with the Tafel slope value when the Fe ratio is "0" as the reference value. The evaluation criteria are as follows:

[0085] "=": The Tafel slope value is 98% or more and 102% or less with respect to the above reference value, and the oxygen generating activity is equivalent to that when the Fe ratio is "0". "◯": The Tafel slope value is 85% or more and less than 98% of the above reference value, and the oxygen generating activity is higher than when the Fe ratio is "0".

[0086] "Excellent": The Tafel slope value is less than 85% of the above reference value, and the oxygen generating activity is significantly higher than when the Fe ratio is "0".

[0087] [Table 2] As shown in Figure 2 and Table 2, the Tafel slope is (1-x) Fe x As the iron ratio x (Fe ratio) in the NiAl alloy increases, the curve becomes convex downward. From this result, it can be seen that Raney nickel obtained from NiAl alloys containing iron in the range of iron ratio x being 0.8 or less has higher oxygen evolution activity than Raney nickel obtained from NiAl alloys not containing iron. In addition, the Tafel slope has a minimum value when the iron ratio x is in the vicinity of 0.1. From this result, it can be seen that, among NiAl alloys containing iron, the Raney nickel obtained from the composition formula Al3Ni (1-x) Fe x (x is a value satisfying 0.05≦x≦0.3) shows that Raney nickel obtained from the NiAl alloy shown in (x) exhibits particularly high oxygen evolution activity.

[0088] <Test 3> In Test 3, the catalytic activity of Raney nickel obtained from the second NiAl alloy containing iron and the fourth NiAl alloy containing iron and cobalt was evaluated. In this test, the Fe ratio of 0.1, which showed the highest oxygen evolution activity in Test 2, was adopted.

[0089] (Preparation of Raney Nickel) A mixture of predetermined amounts of aluminum, nickel, iron, and cobalt was heated and melted at 1550°C using a high-frequency melting furnace, and then cooled to obtain NiAl alloys (Test Example 1) whose main phase is the Al3Ni1 phase and whose composition is Al3Ni 0.9 Fe 0.1 The NiAl alloy (Test Example 2) shown in the following formula has a main phase of Al3Ni1 and a composition formula of Al3Ni 0.75 Co 0.25 and a NiAl alloy (Test Example 3) having a main phase of Al3Ni1 phase and a composition formula of Al3Ni 0.7 Fe 0.1 Co 0.2 The alloy ingots thus obtained were pulverized to obtain NiAl alloy powders. The average particle size of the obtained powders was measured by a laser scattering method and was in the range of 40 to 60 μm.

[0090] Next, the obtained NiAl alloy powder was subjected to the same alkali treatment and oxidation treatment as in Test 1 to obtain a second Raney nickel powder. (Evaluation of catalytic activity) The oxygen generating activity of the obtained second Raney nickel was evaluated in the same manner as in Test 1. The results are shown in Table 3.

[0091] [Table 3] As shown in Table 3, the Raney nickel obtained from the NiAl alloy containing iron (Test Example 2) has a smaller Tafel gradient value than the Raney nickel obtained from the NiAl alloy containing cobalt (Test Example 3). This result shows that it is effective to add iron to the NiAl alloy to increase the oxygen generating activity, compared to other metals such as cobalt. In addition, the Raney nickel obtained from the NiAl alloy containing both iron and cobalt (Test Example 4) has a smaller Tafel gradient value than the NiAl alloy containing iron (Test Example 2). This result shows that it is effective to use both iron and cobalt in combination as metals to be added to the NiAl alloy to increase the oxygen generating activity.

[0092] <Test 4> In Test 4, the catalytic activity of Raney nickel obtained from the third NiAl alloy containing iron and cobalt was evaluated. In this test, the iron ratio in the NiAl alloy was kept constant. In this test, the Fe ratio was fixed at 0.2, which was the Fe ratio that showed the highest oxygen evolution activity in Test 1, and the Co ratio was changed.

[0093] (Preparation of Raney Nickel) A mixture of predetermined amounts of aluminum, nickel, iron, and cobalt is heated and melted at 1600℃ in a high-frequency melting furnace, and then cooled to produce a material with the main phases of Al3Ni2 and Al4Ni3 and the composition formula Al3Ni (1.8-y) Fe 0.2 Co y The alloy ingots were prepared by mixing 0, 0.1, 0.2, 0.4, and 0.6 in the above formula. The alloy ingots were pulverized to obtain NiAl alloy powder of the above composition. The average particle size of the obtained powder was measured by a laser scattering method and was in the range of 50 to 70 μm.

[0094] Next, the obtained NiAl alloy powder was subjected to the same alkali treatment and oxidation treatment as in Test 1 to obtain a second Raney nickel powder. (Evaluation of catalytic activity) The oxygen generating activity of the obtained Raney nickel powder was evaluated in the same manner as in Test 1. The results are shown in Table 4. The details of the evaluation shown in the relative evaluation column of oxygen generating activity in Table 4 are the same as those shown in Table 1. The relative evaluation column of oxygen generating activity in Table 4 also shows the evaluation of the oxygen generating activity of each example with different Co ratios. The evaluation is a relative evaluation with the Tafel slope value when both the Fe ratio and the Co ratio are "0" as the reference value. The evaluation criteria are as follows:

[0095] "=": The Tafel slope value is 98% or more and 102% or less with respect to the above reference value, and the oxygen generating activity is equivalent to that when the Fe ratio is "0". "◯": The Tafel slope value is 85% or more and less than 98% of the above reference value, and the oxygen generating activity is higher than when the Fe ratio is "0".

[0096] "◎1": The Tafel slope value is 50% or more and less than 85% of the above reference value, and the oxygen generating activity is significantly higher than when the Fe ratio is "0". "A2": The Tafel slope value is less than 50% of the above reference value, and the oxygen generating activity is significantly higher than when the Fe ratio is "0".

[0097] [Table 4] As shown in Table 4, the Tafel gradient of Raney nickel obtained from NiAl alloy containing both iron and cobalt is lower than that when the Fe ratio and the cobalt ratio (Co ratio) are 0 (when the NiAl alloy does not contain iron and cobalt), and is approximately equal to or lower than that when the Fe ratio is 0.2 and the Co ratio is 0. In particular, when cobalt is contained in a Co ratio range of 0.2 to 0.6, the Tafel gradient is an extremely small value. From these results, it can be seen that even when cobalt is used in combination, the effect of improving oxygen generating activity can be obtained by including iron, and that a Co ratio of 0.2 to 0.6 is effective in improving oxygen generating activity.

[0098] Next, the technical idea that can be grasped from the above embodiment will be added as follows. [Aspect 1] A method for manufacturing an electrode material used for an electrode of a water electrolysis device, the method having an alkali treatment step of obtaining Raney nickel by eluting aluminum from the NiAl alloy by treating the NiAl alloy with an alkali substance, wherein the NiAl alloy has a composition formula Al3Ni (n-(x+y)) Fe x Co y (n is 1 or 2, and x and y are values satisfying 0 < n - (x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8.) The method for manufacturing an electrode material is characterized in that it is an alloy represented by

[0099] [Aspect 2] The NiAl alloy has a composition formula Al3Ni (2-x) Fe x (x is a value satisfying 0.01 ≤ x ≤ 0.8.) The method for manufacturing an electrode material according to Aspect 1, wherein the alloy is an alloy represented by

[0100] [Aspect 3] The NiAl alloy has a composition formula Al3Ni (1-x) Fe x (x is a value satisfying 0.005 ≤ x ≤ 0.7.) The method for manufacturing an electrode material according to Aspect 1, wherein the alloy is an alloy represented by

[0101] [Aspect 4] The NiAl alloy has a composition formula Al3Ni (2-(x+y)) Fe x Co y (x and y are values satisfying 0 < 2 - (x + y) < 2, 0.01 ≤ x ≤ 0.8, and 0 < y ≤ 0.8.) The method for manufacturing an electrode material according to Aspect 1, wherein the alloy is an alloy represented by

[0102] [Aspect 5] The NiAl alloy has a composition formula Al3Ni (1-(x+y)) Fe x Co yThe manufacturing method of the electrode material according to Embodiment 1, which is an alloy represented by (where x and y are values satisfying 0 < 1 - (x + y) < 1, 0.005 ≤ x ≤ 0.3, and 0 < y ≤ 0.7).

[0103] [Embodiment 6] The alkali treatment step includes a treatment of reacting an alkaline aqueous solution, which is an aqueous solution of the alkali substance, with the NiAl alloy at a temperature of 100°C or higher. The alkali substance is an alkali metal hydroxide, and the concentration of the alkaline aqueous solution is 3M or higher. The manufacturing method of the electrode material according to any one of Embodiments 1 to 5.

[0104] [Embodiment 7] The alkali treatment step includes a treatment of reacting an alkaline aqueous solution, which is an aqueous solution of the alkali substance, with the NiAl alloy at a temperature of 140°C or higher. The alkali substance is an alkali metal hydroxide, and the concentration of the alkaline aqueous solution is 14M or higher. The manufacturing method of the electrode material according to Embodiment 6.

[0105] [Embodiment 8] The manufacturing method of the electrode material according to any one of Embodiments 1 to 7, which has an oxidation step of oxidizing the surface of the Raney nickel obtained by the alkali treatment step.

[0106] [Embodiment 9] An electrode material used for an electrode of a water electrolysis device, having a composition formula Al3Ni (n-(x+y)) Fe x Co y (where n is 1 or 2, and x and y are values satisfying 0 < n - (x + y) < 2, 0.005 ≤ x ≤ 0.8, and 0 ≤ y ≤ 0.8), characterized by containing Raney nickel by eluting aluminum from the NiAl alloy represented by.

[0107] [Embodiment 10] The electrode is an anode, and the Tafel slope is 50 to 226 mV / dec. The electrode material according to Embodiment 9.

Claims

1. A method for producing an electrode material used in an electrode of a water electrolysis device, comprising: an alkali treatment step of treating a NiAl alloy with an alkaline substance to dissolve aluminum from the NiAl alloy, thereby obtaining Raney nickel; The NiAl alloy is Composition formula Al ３ Ni （ｎ－（ｘ＋ｙ）） Fe ｘ Co ｙ (n is 1 or 2, and x and y are values ​​that satisfy 0<n-(x+y)<2, 0.005≦x≦0.4, 0≦y≦0.8), or an alloy represented by the composition formula Al3Ni(2-(x+y))FexCoy (x and y are values ​​that satisfy 0<2-(x+y)<2, 0.01≦x≦0.8, 0<y≦0.8).

2. The NiAl alloy has the composition formula Al ３ Ni （２－ｘ） Fe ｘ 2. The method for producing an electrode material according to claim 1, wherein the alloy is represented by the formula: (x is a value that satisfies 0.01≦x≦0.4).

3. The NiAl alloy has the composition formula Al ３ Ni （１－ｘ） Fe ｘ 2. The method for producing an electrode material according to claim 1, wherein the alloy is represented by the formula: (x is a value that satisfies 0.005≦x≦0.2).

4. The NiAl alloy has the composition formula Al ３ Ni （２－（ｘ＋ｙ）） Fe ｘ Co ｙ 2. The method for producing an electrode material according to claim 1, wherein the alloy is represented by the formula: (x and y are values ​​satisfying 0<2-(x+y)<2, 0.01≦x≦0.8, 0<y≦0.8).

5. The NiAl alloy has the composition formula Al ３ Ni （１－（ｘ＋ｙ）） Fe ｘ Co ｙ 2. The method for producing an electrode material according to claim 1, wherein the alloy is represented by the formula: (x and y are values ​​satisfying 0<1-(x+y)<1, 0.005≦x≦0.3, 0<y≦0.7).

6. the alkaline treatment step includes a treatment of reacting an alkaline aqueous solution, which is an aqueous solution of the alkaline substance, with the NiAl alloy at a temperature of 100°C or higher; the alkaline substance is an alkali metal hydroxide; The method for producing an electrode material according to any one of claims 1 to 5, wherein the concentration of the alkaline aqueous solution is 3M or more.

7. the alkaline treatment step includes a treatment of reacting an alkaline aqueous solution, which is an aqueous solution of the alkaline substance, with the NiAl alloy at a temperature of 140°C or higher; the alkaline substance is an alkali metal hydroxide; 7. The method for producing an electrode material according to claim 6, wherein the concentration of the alkaline aqueous solution is 14M or more.

8. The method for producing an electrode material according to any one of claims 1 to 5, further comprising an oxidation step of oxidizing the surface of the Raney nickel obtained in the alkali treatment step.

9. An electrode material used in an electrode of a water electrolysis device, The molar ratio of nickel, iron, and cobalt (nickel:iron:cobalt) is (n-(x+y)):x:y (n is 1 or 2, and x and y are values ​​that satisfy 0<n-(x+y)<2, 0.005≦x≦0.4, and 0≦y≦0.8), or 1. An electrode material comprising Raney nickel having a structure of (2-(x+y)):x:y (x and y are values ​​satisfying 0<2-(x+y)<2, 0.01≦x≦0.8, and 0<y≦0.8).

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