Anode and alkaline water electrolysis apparatus

Abstract

To provide an anode having a low voltage during electrolysis.SOLUTION: The anode of the present invention comprises a conductive substrate, and a covering layer covering the conductive substrate. The covering layer includes a nickel element and a metal element (A) that can take a rutile-type structure when forming an oxide. The oxide of the metal element (A) in a mixture of oxides of metal elements forming the covering layer has a half-value width of 0.45° or more at around 2θ=27.5° attributed to a rutile-type oxide (110) plane as measured by X-ray diffraction using CuKα rays, and has an oxidation electric quantity (CNi) of nickel element of 85 mC / cm2 or more obtained by cyclic voltammetry performed in a 25 mass% KOH aqueous solution in a potential range of 1.34 to 1.47 Vvs.RHE and at a scanning rate of 10 mV / sec.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an anode and an alkaline water electrolysis device. More specifically, the present invention relates to an anode preferably used for alkaline water electrolysis and an alkaline water electrolysis device using the anode.

Background Art

[0002] In recent years, in order to solve problems such as global warming due to CO2 and the depletion of fossil fuel reserves, the spread of renewable energy represented by wind power and solar power has been progressing. However, since renewable energy is greatly affected by weather conditions, there is a problem that the supply is unstable. Therefore, as a method for storing renewable energy, the production of hydrogen using water electrolysis technology has attracted attention. By efficiently converting electrical energy into hydrogen, it becomes easy to store or transport a large amount of energy, and further spread of renewable energy is expected.

[0003] In water electrolysis, oxygen is generated at the anode and hydrogen is generated at the cathode. The main factors of energy loss in electrolysis include the overvoltages of the anode and the cathode. By reducing this overvoltage, it becomes possible to produce hydrogen efficiently. In particular, the overvoltage of the anode is higher than that of the cathode, and research and development for reducing the overvoltage of the anode are widely underway.

[0004] As an anode used for alkaline water electrolysis, for example, an anode in which nickel is used as a conductive substrate and a catalyst containing nickel and cobalt is coated on the conductive substrate (Patent Document 1), and an anode in which a catalyst containing iridium oxide, nickel oxide, and lithium oxide is coated on the conductive substrate (Patent Document 2) are known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] For an anode used in an electrolysis apparatus such as alkaline water electrolysis, it is required that the voltage during electrolysis is low. Therefore, an object of the present invention is to provide an anode with a low voltage during electrolysis. Another object of the present invention is to provide an alkaline water electrolysis apparatus including an anode with a low voltage during electrolysis.

Means for Solving the Problems

[0007] The present invention includes a conductive substrate and a coating layer that coats the conductive substrate. The coating layer contains a nickel element and a metal element (A) that can take a rutile-type structure when forming an oxide. In the mixture of oxides of the metal elements forming the coating layer, the oxide of the metal element (A) has a half-value width of 0.45° or more near 2θ = 27.5° attributed to the (110) plane of the rutile-type oxide measured by X-ray diffraction using CuKα radiation, and is obtained by cyclic voltammetry with a potential scan in a 25 mass% KOH aqueous solution in the potential range of 1.34 to 1.47 V vs. RHE and a scan rate of 10 mV / sec. The oxidation charge (C Ni ) of the nickel element is 85 mC / cm 2 or more. The present invention provides an anode.

[0008] Preferably, the ratio of the lithium element to the total amount of the metal elements in the coating layer is less than 20 mol%.

[0009] The coating layer may contain a cobalt element, and preferably, the total ratio of the nickel element, the metal element (A), and the cobalt element to the total amount of the metal elements in the coating layer is more than 80 mol%.

[0010] The above metal element (A) preferably contains an iridium element and / or a ruthenium element.

[0011] The ratio of the nickel element to the total amount of the metal elements in the coating layer is preferably 20 mol% or more.

[0012] The coating layer preferably contains a cobalt element.

[0013] The anode may have a dendrite structure on its surface.

[0014] The anode is preferably for alkaline water electrolysis.

[0015] The present invention also provides an alkaline water electrolysis apparatus including the above anode.

Advantages of the Invention

[0016] By using the anode of the present invention, electrolysis can be performed at a low voltage. Further, according to the alkaline water electrolysis apparatus of the present invention, electrolysis can be performed at a low voltage.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0018] [Anode] The anode of the present invention includes at least a conductive substrate and a coating layer that coats the conductive substrate. The coating layer is preferably located on the surface of the anode of the present invention, for example, the surface in contact with the electrolytic solution. The anode may be composed of the conductive substrate and the coating layer, or may include other layers other than these.

[0019] (Conductive substrate) The above-mentioned conductive substrate is not particularly limited as long as it is composed of a material having conductivity. When the anode of the present invention is used for alkaline water electrolysis, the material of the above-mentioned conductive substrate is preferably a material having conductivity and a certain chemical stability with respect to the alkaline aqueous solution which is the electrolytic solution. For example, stainless steel (stainless steel), nickel, nickel-based alloys, iron, materials containing nickel and / or iron such as nickel-plated iron materials, etc. may be mentioned. It is preferable that at least the surface of the above-mentioned conductive substrate is nickel and / or a nickel-based alloy. The material constituting the above-mentioned conductive substrate may use only one kind, or may use two or more kinds.

[0020] The above-mentioned conductive substrate preferably has openings for the purpose of removing the generated oxygen bubbles. For example, expanded mesh, perforated plate, wire mesh, etc. are preferable. The above-mentioned opening ratio is preferably 10 to 95%, more preferably 20 to 60%, and even more preferably 30 to 50%.

[0021] The thickness of the above-mentioned conductive substrate is preferably 0.05 to 5 mm, more preferably 0.1 to 3 mm, and even more preferably 0.5 to 1 mm.

[0022] From the viewpoint of excellent adhesion between the surface of the above-mentioned conductive substrate and the coating layer or the layer in contact with the above-mentioned conductive substrate, it is preferable that the surface area is increased. Examples of the method for increasing the surface area include blasting using cut wire, steel grid, alumina grid, etc., and acid treatment using sulfuric acid or hydrochloric acid. The above-mentioned increase treatment may be performed by combining a plurality of treatments. Among them, it is preferable to perform a combination of blasting treatment and acid treatment. It is preferable to form irregularities on the surface of the conductive substrate by blasting treatment and then perform acid treatment.

[0023] (Coating layer) The coating layer contains at least a nickel element and a metal element that can form a rutile-type structure when forming an oxide. In this specification, the metal element that can form a rutile-type structure when forming the oxide may be referred to as "metal element (A)". The metal element contained in the coating layer may be contained as a simple metal or as a metal compound such as a metal oxide. Among them, it is preferably contained as a metal oxide.

[0024] Examples of the oxide of the nickel element (nickel oxide) include NiO.

[0025] Examples of the metal element (A) include, for example, titanium element, tin element, vanadium element, manganese element, cesium element, germanium element, silver element, copper element, lead element, iridium element, ruthenium element, etc. Among them, the metal element (A) is preferably an iridium element and / or a ruthenium element. The metal element (A) may be used alone or in combination of two or more.

[0026] Examples of the rutile-type structure oxide that the metal element (A) can form include, for example, vanadium oxide such as VO2, manganese oxide such as β-MnO2, cesium oxide such as CsO2, germanium oxide such as GeO2, silver oxide such as AgO2, copper oxide such as CuO2, lead oxide such as PbO2, iridium oxide such as IrO2, ruthenium oxide such as RuO2, etc.

[0027] The coating layer may contain other metal elements other than the nickel element and the metal element (A). Examples of the other metal elements include cobalt element, iron element, molybdenum element, bismuth element, etc. For example, the cobalt element is presumed to function as a catalyst in alkaline electrolysis and also tends to contribute to improving the durability of the catalyst. The other metal elements may be used alone or in combination of two or more.

[0028] In the mixture of metal element oxides forming the coating layer, the oxide of metal element (A) has a half-value width near 2θ = 27.5° attributed to the rutile-type oxide (110) plane measured by X-ray diffraction using CuKα radiation, which is 0.45° or more, preferably 0.60° or more, more preferably 0.70° or more, still more preferably 0.80° or more, particularly preferably 0.90° or more, and may be 1.00° or more, 1.10° or more, 1.20° or more, or 1.30° or more. There is a correlation between the half-value width near 2θ = 27.5° attributed to the rutile-type oxide (110) plane and the cell voltage. When the half-value width is 0.45° or more, the cell voltage is significantly reduced, and thus the durability of the anode tends to be improved. Note that the half-value width is, for example, 2.80° or less.

[0029] The above half-value width is a parameter indicating crystallinity. The smaller the half-value width, the higher the crystallinity, and the larger the half-value width, the lower the crystallinity (i.e., more amorphous) tends to be. Therefore, the larger the half-value width near 2θ = 27.5° attributed to the rutile-type oxide (110) plane, the stronger the tendency for the oxide of metal element (A) to be amorphous, and it is presumed that the catalytic ability (especially the oxygen evolution ability in alkaline water electrolysis) can be improved and the cell voltage can be lowered in electrolysis.

[0030] The half-value width near 2θ = 27.5° attributed to the rutile-type oxide (110) plane can be adjusted by the form of the metal forming the electrode such as nickel element, metal element (A), and other metal elements used as raw materials (types of simple substances or compounds, etc.), the types of metal element (A) and other metals, the mixing ratio of the metals forming the electrode, etc. Also, the half-value width can be specifically measured under the measurement conditions measured in the examples. The object of measurement of the half-value width is the coating layer. Specifically, for example, X-ray diffraction of the above oxide can be performed on a sample in which the above coating layer is formed on the surface of a substrate (for example, a metal plate constituting the above conductive base material) from the viewpoint of obtaining stable measurement results.

[0031] The molar ratio of the nickel element to the metal element (A) in the coating layer [nickel element / metal element (A)] is preferably from 20 / 80 to 90 / 10. As one embodiment, the molar ratio is preferably more than 50 / 50 (for example, more than 50 / 50 and less than or equal to 90 / 10), more preferably from 60 / 40 to 80 / 20, and particularly preferable when the metal element (A) contains an iridium element. As another embodiment, the molar ratio is preferably 40 / 60 or more (for example, from 40 / 60 to 80 / 20), more preferably more than 40 / 60 (for example, more than 40 / 60 and less than or equal to 80 / 20), still more preferably 45 / 55 or more (for example, from 45 / 55 to 75 / 25), and particularly preferable when the metal element (A) contains a ruthenium element.

[0032] The proportion of the nickel element in the coating layer is preferably 20 mol% or more, more preferably 27 mol% or more, still more preferably 35 mol% or more, and particularly preferably 40 mol% or more, based on the total amount (100 mol%) of the metal elements forming the coating layer. When the proportion is 20 mol% or more, the catalytic ability (for example, the oxygen generation ability in alkaline water electrolysis) becomes higher. Also, the proportion is, for example, 90 mol% or less, preferably 80 mol% or less.

[0033] The proportion of the metal element (A) (particularly, the iridium element and / or the ruthenium element) in the coating layer is preferably 10 mol% or more, and may be 20 mol% or more, 30 mol% or more, or 40 mol% or more, based on the total amount (100 mol%) of the metal elements forming the coating layer. When the proportion is 10 mol% or more, the catalytic ability (for example, the oxygen generation ability in alkaline water electrolysis) becomes higher. Also, the proportion is, for example, 70 mol% or less, preferably 60 mol% or less.

[0034] The proportion of nickel element in the coating layer is preferably 10% by mass or more, more preferably 36% by mass or more, still more preferably 40% by mass or more, and particularly preferably 50% by mass or more with respect to the total amount (100% by mass) of the metal elements forming the coating layer. When the proportion is 36% by mass or more, the catalytic ability (for example, oxygen generation ability in alkaline water electrolysis) becomes higher. Also, the proportion is, for example, 90% by mass or less, preferably 80% by mass or less.

[0035] The proportion of the metal element (A) (particularly, iridium element and / or ruthenium element) in the coating layer is preferably 30% by mass or more, more preferably 57% by mass or more, still more preferably 60% by mass or more, and particularly preferably 65% by mass or more with respect to the total amount (100% by mass) of the metal elements forming the coating layer. When the proportion is 10% by mass or more (particularly 36% by mass or more), the catalytic ability (for example, oxygen generation ability in alkaline water electrolysis) becomes higher. Also, the proportion is, for example, 90% by mass or less, preferably 80% by mass or less.

[0036] In particular, it is preferable that at least one of the proportion of the nickel element in the coating layer and the proportion of the metal element (A) (particularly, iridium element and / or ruthenium element) satisfies the above proportion.

[0037] The total proportion of the nickel element and the metal element (A) (particularly, iridium element and / or ruthenium element) in the coating layer is preferably 50 mol% or more, more preferably more than 50 mol%, still more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 90 mol% or more with respect to the total amount (100 mol%) of the metal elements forming the coating layer, and may be 98 mol% or more, 99 mol% or more, 99.5 mol% or more. When the proportion is 50 mol% or more, the catalytic ability (for example, oxygen generation ability in alkaline water electrolysis) is high and the cell voltage tends to be low.

[0038] The total proportion of nickel element, metal element (A) (especially iridium element and / or ruthenium element), and cobalt element in the above coating layer is preferably more than 80 mol%, more preferably 90 mol% or more, still more preferably 98 mol% or more, still more preferably 99 mol% or more, and particularly preferably 99.5 mol% or more with respect to the total amount (100 mol%) of the metal elements forming the above coating layer. When the above coating layer does not contain cobalt element, the above proportion refers to the total proportion of nickel element and metal element (A). When the above proportion is more than 80 mol%, the catalytic ability (for example, oxygen generation ability in alkaline water electrolysis) is high and the cell voltage tends to be low.

[0039] The proportion of lithium element in the above coating layer is preferably less than 20 mol%, more preferably 10 mol% or less, still more preferably 5 mol% or less, and particularly preferably less than 1 mol% with respect to the total amount (100 mol%) of the metal elements forming the above coating layer. When the above proportion is less than 20 mol%, the catalytic ability (for example, oxygen generation ability in alkaline water electrolysis) is high and the cell voltage tends to be low.

[0040] The thickness of the above coating layer is preferably 0.1 to 5.0 μm, more preferably 0.3 to 0.5 μm. When the thickness of the above coating layer is 0.1 μm or more, it is easy to maintain high initial electrolysis performance. When the thickness is 1.0 μm or less, it is economically excellent.

[0041] (Preferred embodiment of the anode) The anode of the present invention is the oxidation electric quantity of nickel element (hereinafter referred to as C Ni and expressed as such.) obtained by cyclic voltammetry with a potential range of 1.34 to 1.47 V vs. RHE and a scanning speed of 10 mV / sec in a 25 mass% KOH aqueous solution, which is 85 mC / cm 2 or more, preferably 90 mC / cm 2 or more, more preferably 100 mC / cm 2 or more, still more preferably 120 mC / cm 2 or more, and particularly preferably 160 mC / cm 2 or more. The above CNi and there is a correlation with the cell voltage, and the above C Ni is 90 mC / cm 2 or more, the cell voltage is significantly reduced. Incidentally, the above C Ni is, for example, 500 mC / cm 2 or less. The above C Ni is the amount of oxidation electricity from divalent (2+) to trivalent (3+) of nickel element.

[0042] The above C Ni can be adjusted by the form of the metal (type of simple substance or compound, etc.) forming the electrode such as nickel element, metal element (A), and the other metal elements used as raw materials for the coating layer, the type of metal element (A) and the other metals, the mixing ratio of the metal forming the electrode, and further the type and mixing ratio of the metals constituting the conductive metal. Further, the above C Ni can be specifically measured under the measurement conditions measured in the examples.

[0043] The anode of the present invention preferably has a dendrite structure on its surface. When having a dendrite structure, the catalytic ability (for example, oxygen generation ability in alkaline water electrolysis) is high and the cell voltage tends to be low. The above dendrite structure can be confirmed by generation with, for example, a scanning electron microscope (SEM). Specifically, in a field of view within a 25 μm × 25 μm square, the generation of the dendrite structure can be confirmed by confirming that there are a plurality of branched crystal forms in a magnified image at 5,000 to 15,000 times.

[0044] The above dendrite structure may be formed when an anode is manufactured using an iridium element as the metal element (A).

[0045] The anode of the present invention is preferably for alkaline water electrolysis. When the anode of the present invention is used as such an electrode, particularly, the voltage during electrolysis is low.

[0046] The anode of the present invention can be manufactured by the method for manufacturing the anode of the present invention described below, but is not limited to such a method, and can also be manufactured by known or conventional methods.

[0047] [Method for manufacturing anode] The method for manufacturing the anode of the present invention includes, for example, a step of forming a coating layer on a conductive substrate. The formation of the coating layer may be performed by any method as long as the coating layer can be provided on the conductive substrate. As an example, the coating layer can be formed through firing. Specifically, a raw material solution corresponding to a coating layer precursor is applied to the conductive substrate and dried, and then fired to form the coating layer. Specifically, the coating layer can be formed by applying the raw material solution for forming the coating layer on the conductive substrate, drying it, and then subjecting it to firing.

[0048] The above raw material solution is merely an example, and at least includes a metal element constituting the coating layer, and a solvent such as an organic solvent and / or water for dissolving it. The metal element constituting the coating layer includes a nickel element and a metal element (A). The metal element may be these metal simple substances or metal compounds. The metal compound is not particularly limited, and examples thereof include metal salts such as oxides, chloride salts, nitrates, sulfates, metal alkoxides, hydrides, and hydrates thereof.

[0049] The organic solvent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, propanol (n-propyl alcohol, isopropyl alcohol), butyl alcohol (n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol); ketones such as methyl ethyl ketone and methyl isobutyl ketone (MIBK); terpenes such as α-terpineol, β-terpineol, and γ-terpineol; ethylene glycol monoalkyl ethers; ethylene glycol dialkyl ethers; diethylene glycol monoalkyl ethers; diethylene glycol dialkyl ethers; ethylene glycol monoalkyl ether acetates; ethylene glycol dialkyl ether acetates; diethylene glycol monoalkyl ether acetates; diethylene glycol dialkyl ether acetates; propylene glycol monoalkyl ethers; propylene glycol dialkyl ethers; propylene glycol monoalkyl ether acetates, and the like. The above organic solvent may be used alone or in combination of two or more. In addition, an additive (such as an inorganic acid, which is only one example) may be added to the above raw material liquid.

[0050] Examples of the method for applying the above raw material liquid to the surface of the above conductive substrate include a dip method in which the conductive substrate is immersed in the above raw material liquid, a method in which the above raw material liquid is applied to the surface of the conductive substrate with a brush, a roll method in which the conductive substrate is passed through a sponge-like roll impregnated with the above raw material liquid, and an electrostatic coating method in which the conductive substrate and the above raw material liquid are charged with opposite charges and spray spraying is performed. Among them, from the viewpoint of excellent industrial productivity, the roll method and the electrostatic coating method are preferred.

[0051] On the conductive substrate, the coating layer precursor formed by applying the raw material liquid is subjected to drying to reduce it by vaporization of the solvent. Therefore, the coating layer precursor may be subjected to drying at a high temperature, or the coating layer precursor may be placed under reduced pressure or in a vacuum. When performing drying at a high temperature, for example, it is preferable to subject the coating layer precursor to drying temperature conditions of about 80 to 200 ° C (one example is 100 ° C to 150 ° C) under atmospheric pressure for about 2 to 40 minutes. When placed under reduced pressure or in a vacuum, it is preferable to place the coating layer precursor under reduced pressure or in a vacuum of, for example, 7.0 to 0.1 Pa. If necessary, "under reduced pressure or in a vacuum" and "heat treatment" may be combined. As an example of a more specific mode of subjecting to drying temperature conditions, the drying of the coating layer precursor can be performed by using an appropriate dryer (for example, an explosion-proof dryer manufactured by Daido Kogyo Co., Ltd., "DBO3-450", etc.). After being subjected to such drying, the coating layer precursor is subjected to firing.

[0052] When firing the coating layer precursor in an oxygen-containing atmosphere, the firing temperature can be appropriately selected according to the composition of the raw material liquid and the type of solvent, but 300 to 650 ° C is preferable. The firing time is preferably longer, but from the viewpoint of the productivity of the electrode, the thermal decomposition time per time is preferably 5 to 60 minutes. Incidentally, if necessary, the cycle of coating, drying, and firing of the raw material liquid can be repeated to make the thickness of the coating layer thicker. Furthermore, after forming the coating layer, if necessary, long-time firing can be performed to improve the stabilization of the coating layer.

[0053] In addition, in the above manufacturing method, the half-value width near 2θ = 27.5 ° attributed to the (110) plane of the rutile-type oxide is 0.45 ° or more, and the above C Ni is 85 mC / cm 2Select the conditions as described above. Examples of the above conditions include the type of metal element (A); the type of the other metal elements; the molar ratios of the nickel element, the metal element (A), and the other metal elements; the form of the raw material metal elements used, for example, whether a single substance or a compound is used as the raw material, and in the case of a compound, its type (metal compounds such as oxides, chlorides, hydrides, nitrates, etc. and their hydrates, etc.), and firing conditions such as the firing temperature and time, etc.

[0054] (X-ray diffraction analysis) X-ray diffraction analysis may be performed on the coating layer thus obtained. By the above X-ray diffraction analysis, it is possible to determine whether or not the half-value width near 2θ = 27.5° attributed to the rutile-type oxide (110) plane measured by X-ray diffraction using CuKα rays of the oxide of the metal element (A) in the mixture of the metal element oxides forming the coating layer is 0.45° or more.

[0055] (Cyclic voltammetry) Cyclic voltammetry may be performed on the conductive substrate with the coating layer thus obtained. By the above cyclic voltammetry, the oxidation charge amount (C Ni ) of the nickel element obtained by cyclic voltammetry with a potential scan in a 25 mass% KOH aqueous solution in the potential range of 1.34 to 1.47 V vs. RHE and a scan rate of 10 mV / sec 2 is 85 mC / cm

[0056] As described above, the anode of the present invention can be manufactured.

[0057] When electrolysis is carried out using the anode of the present invention, electrolysis can be carried out at a low voltage. Further, according to the method for manufacturing the anode of the present invention, an anode capable of performing electrolysis at a low voltage can be easily manufactured. Therefore, the anode of the present invention can be used for various electrolyses. In particular, it is more preferably used as an anode for alkaline water electrolysis. By using the anode of the present invention as an anode for alkaline water electrolysis, an alkaline aqueous solution (for example, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, etc.) can be electrolyzed to generate oxygen and hydrogen.

[0058] [Electrolytic cell] An electrolytic cell can be provided using the anode of the present invention. The above electrolytic cell includes at least an anode, a cathode, and a diaphragm disposed between the anode and the cathode. The anode of the present invention is used as the above anode. The above electrolytic cell can be used for various electrolyses. Hereinafter, as a representative example, an electrolytic cell (alkaline water electrolysis device) used for electrolysis of an alkaline aqueous solution will be described.

[0059] The configuration of the above electrolytic cell is not particularly limited. For example, it may be a monopolar type or a bipolar type. The electrodes may be arranged with an appropriate interval provided between the partition wall and the anode, but it can also be used without problems even if the anode and the partition wall are arranged in contact with each other. Further, the cathode is generally arranged with an appropriate interval provided from the partition wall, but it can also be used without problems even in a contact type electrolytic cell (zero-gap type electrolytic cell) without this interval.

[0060] As the cathode, a known one can be adopted. For example, a cathode in which a coating layer is formed on a conductive substrate can be mentioned. As the metal constituting the conductive substrate, mild steel, stainless steel, nickel, and nickel-based alloys are preferable. The coating layer of the cathode preferably has a high hydrogen generation ability, and examples thereof include nickel, cobalt, iron, or platinum group elements. Specifically, as the coating layer, Raney nickel, a Raney alloy composed of a combination of a plurality of materials such as nickel and aluminum, or nickel and tin, a porous film produced by a plasma spraying method using a nickel compound or a cobalt compound as a raw material, an alloy or composite compound of nickel and an element selected from cobalt, iron, molybdenum, silver, copper, etc., a metal or oxide of a platinum group element such as platinum or ruthenium, and a mixture of a metal or oxide of these platinum group elements and a compound of another platinum group element such as iridium or palladium or a compound of a rare earth metal such as lanthanum or cerium, a carbon material such as graphene, etc. can be mentioned.

Example

[0061] Hereinafter, an embodiment of the present disclosure will be described in more detail based on examples.

[0062] Production Example 1 (Ni / Ir) Ni(NO3)2·6H2O and H2IrCl6·6H2O were mixed so that the Ni / Ir (molar ratio) = 5 / 5, 7 / 3, or 9 / 1, and these were put into ion-exchanged water and stirred to prepare a raw material solution.

[0063] Production Example 2 (Ni / Ir / Co) Ni(NO3)2·6H2O, H2IrCl6·6H2O, and Co(NO3)2·6H2O were mixed so that the Ni / Ir / Co (molar ratio) = 5 / 3 / 2 or 5 / 4 / 1, and these were put into ion-exchanged water and stirred to prepare a raw material solution.

[0064] Production Example 3 (Ni / Ir / Ru) Ni(NO3)2·6H2O, H2IrCl6·6H2O, and Ru(NO3)3·6H2O were mixed so that the molar ratio of Ni / Ir / Ru = 5 / 1 / 4, 5 / 3 / 2, or 5 / 4 / 1, and these were added to ion-exchanged water and stirred to prepare a raw material solution.

[0065] Production Example 4 (Ni / Ru) Ni(NO3)2·6H2O and RuCl3·3H2O were mixed so that the molar ratio of Ni / Ru = 5 / 5, 7 / 3, or 8 / 2, and these were added to ion-exchanged water and stirred to prepare a raw material solution.

[0066] Production Example 5 (Ni / Ru / Co) Ni(NO3)2·6H2O, RuCl3·3H2O, and Co(NO3)2·6H2O were mixed so that the molar ratio of Ni / Ru / Co = 2 / 3 / 5, and these were added to ion-exchanged water and stirred to prepare a raw material solution.

[0067] Example 1 (Manufacture of Anode for Alkaline Water Electrolysis) Nickel lath (size: 100 mm × 100 mm × 1 mm, lath standard: SW4.5LW10.0) for use as a conductive substrate was prepared. Next, the nickel lath was immersed in a 20% by mass hydrochloric acid aqueous solution at 80°C for 30 minutes, then washed with water until the surface of the nickel plate became neutral and dried to obtain a conductive substrate. Next, in the air, each raw material solution obtained in Production Examples 1 to 5 was respectively applied to the surface of the conductive substrate, and a series of steps of drying and firing (thermal decomposition) were repeated until the coating amount reached a specified amount (5 g / m 2 ) as the metal component to obtain an anode in which a film containing a metal oxide was formed on the surface of the conductive substrate. The exact coating amount is as shown in "Coating Amount" in Table 1. The application of the raw material solution was carried out using a brush, the drying was carried out at 120°C for 10 minutes, and the firing was carried out at 500°C for 10 minutes. ※1

[0068] Example 2 (Preparation of Sample for X-ray Diffraction Measurement) A nickel plate (size: 100 mm x 100 mm x 1 mm) was prepared for use as a conductive substrate. Next, the nickel plate was immersed in a 20% by mass aqueous hydrochloric acid solution at 80°C for 30 minutes, and then washed with water until the surface of the nickel plate became neutral and dried to obtain a conductive substrate. Next, each of the raw material solutions obtained in Production Examples 1 to 5 was applied to the surface of the conductive substrate in air, followed by a series of steps of drying and baking (thermal decomposition) until the coating amount was a specified amount (5 g / m2) of metal component. 2 The coating amount was then calculated as follows: ※2 The coating of the raw material liquid was performed using a brush, the drying was performed at 120°C for 10 minutes, and the baking was performed at 500°C for 10 minutes.

[0069] <Evaluation> The anode obtained in Example 1 and the sample obtained in Example 2 were evaluated as follows.

[0070] (1) X-ray diffraction measurement X-ray diffraction measurements were performed on each sample obtained in Example 2 to obtain an X-ray diffraction pattern, and analysis software was used to calculate the half-width at about 2θ=27.5°, which is assigned to the rutile oxide (110) plane. The conditions for the X-ray diffraction measurements and analysis software are as follows. Table 1 shows the half-widths for each sample. [X-ray diffraction] Equipment: Rigaku Corporation, horizontal sample multipurpose X-ray diffraction instrument "Ultima IV" X-ray source: CuKα ray Tube voltage: 40kV Tube current: 40mA Scan speed: 3° / min. [Analysis software] Qualitative analysis: PDXL Database:ICDD

[0071] (2) Cell voltage measurement Using the equipment shown in FIG. 1, a 25% by mass KOH aqueous solution was used as the electrolyte, and the temperature was 80°C and the current density was 6 kA / m 2Electrolysis was carried out under the following conditions, and the cell voltage at that time was measured. The results are shown in Table 1. The cell voltage was measured with a tester between the anode and cathode plates. Fig. 1(a) shows the overall configuration, Fig. 1(b) shows the exploded view (cross-sectional view) of the electrolysis cell, and Fig. 1(c) shows the anode plate and the cathode plate (top view), respectively. In Fig. 1, 11 is the electrolysis cell, 12 is the electrolyte circulation tank, 13 is the gas line, 14 is the liquid line, 21 is the anode chamber (PTFE), 22 is the cathode chamber (PTFE), 23 is the anode plate, 24 is the cathode plate, 25 is the diaphragm, 26 is the cathode top mesh, 27 is the elastic body, 28a - d are gaskets, 31 is the opening, 32 is the anode or cathode, and 33 is the bolt hole, respectively. The anode or cathode 32 is welded to the frame having the opening 31.

[0072] (3) Observation of the Anode Surface The surface of the anode prepared in Example 2 was observed under the following conditions using a scanning electron microscope ("JSM-IH500HR" manufactured by JEOL Ltd.). The obtained SEM image is shown in Fig. 2. Acceleration voltage: 20 kV Irradiation current: 50 μA W.D.: 15 mm

[0073] (4) Cyclic Voltammetry A three-electrode cell was used, a platinum plate was used as the counter electrode, Pd-H was used as the reference electrode, and it was calibrated based on the RHE standard. The anode obtained in Example 1 was used as the working electrode. As the electrolyte, a 25 mass% KOH aqueous solution (25 °C) was used. As a pretreatment, scanning was performed 10 times at a scanning rate of 100 mV / sec in the potential range of -0.20 to 1.51 V vs. RHE, and then the scanning rate was set to 10 mV / sec in the same potential range. The cyclic voltammogram is shown in Fig. 3. The electrochemical measurement conditions for cyclic voltammetry are shown below. Electrolyte: 25 mass% KOH aqueous solution Electrolysis area: 1 cm 2 Temperature: 25 °C Reference electrode: Pd-H (the potential is calibrated based on the RHE standard) Counter electrode: Pt Analysis device: "HSV-110" manufactured by Hokuto Denko Corporation

[0074] (5)C Ni Calculation method In the cyclic voltammogram measured in (4), in the oxidation wave of nickel element from divalent (2+) to trivalent (3+) observed at 1.34 to 1.47 V vs. RHE, C was calculated by time integration of the oxidation current density Ni was calculated

[0075]

Table 1

[0076] As shown in Table 1, when an anode with a full width at half maximum near 2θ = 27.5° attributed to the rutile-type oxide (110) plane is 0.45° or more and C Ni is 85 mC / cm 2 or more is used, the cell voltage is about 1.78 V or less, and it was evaluated that a low cell voltage can be achieved. On the other hand, no dendrite formation was confirmed for anodes with a full width at half maximum near 2θ = 27.5° attributed to the rutile-type oxide (110) plane of less than 0.45°

[0077] As shown in Figure 2, for anodes using Ni / Ir (molar ratio 5 / 5, 7 / 3), Ni / Ir / Co (molar ratio 5 / 4 / 1, 5 / 3 / 2), and Ni / Ir / Ru (molar ratio 5 / 4 / 1, 5 / 3 / 2), in the field of view within a 25 μm × 25 μm square, it was confirmed that dendrites were formed on the surface because there were multiple branched crystal morphologies in the magnified image at 5,000 to 15,000 times. On the other hand, no dendrite formation was confirmed for anodes with a full width at half maximum near 2θ = 27.5° attributed to the rutile-type oxide (110) plane of less than 0.45°

[0078] In the case of Ni / Ir (molar ratio 5 / 5, 7 / 3) and Ni / Ir / Co (molar ratio 5 / 3 / 2, 5 / 4 / 1) with a low cell voltage, as shown in Fig. 3, it was confirmed that dendrites were formed on the anode surface. In these samples, it was found that the oxidation charge of nickel element in the cyclic voltammogram was large and the cell voltage was low.

[0079] Hereinafter, variations of the invention according to the present disclosure will be described. [Appendix 1] A conductive substrate and a coating layer covering the conductive substrate are provided. The coating layer contains a nickel element and a metal element (A) that can take a rutile-type structure when forming an oxide. In the mixture of oxides of the metal elements forming the coating layer, the oxide of the metal element (A) has a half-value width of 0.45° or more near 2θ = 27.5° attributed to the (110) plane of the rutile-type oxide measured by X-ray diffraction using CuKα rays, and the oxidation charge (C Ni ) of the nickel element obtained by cyclic voltammetry with a potential sweep in the potential range of 1.34 to 1.47 V vs. RHE and a scan rate of 10 mV / sec in a 25 mass% KOH aqueous solution is 85 mC / cm 2 or more for the anode. [Appendix 2] The ratio of the lithium element to the total amount of metal elements in the coating layer is less than 20 mol%, and the anode according to Appendix 1. [Appendix 3] The coating layer may contain a cobalt element, and the total ratio of the nickel element, the metal element (A), and the cobalt element to the total amount of metal elements in the coating layer is more than 80 mol%, and the anode according to Appendix 1 or 2. [Appendix 4] The metal element (A) contains an iridium element and / or a ruthenium element, and the anode according to any one of Appendices 1 to 3. [Appendix 5] The ratio of the nickel element to the total amount of metal elements in the coating layer is 20 mol% or more, and the anode according to any one of Appendices 1 to 4. [Appendix 6] The coating layer contains a cobalt element, and the anode according to any one of Appendices 1 to 5. [Appendix 7] The anode according to any one of Appendices 1 to 6, which has a dendrite structure on the surface. [Appendix 8] The anode according to any one of Appendices 1 to 7, which is for alkaline water electrolysis. [Appendix 9] An alkaline water electrolysis device including the anode according to Appendix 8.

Explanation of symbols

[0080] 11 Electrolytic cell 12 Electrolyte circulation tank 13 Gas line 14 Liquid line 21 Anode chamber 22 Cathode chamber 23 Anode plate 24 Cathode plate 25 Diaphragm 26 Cathode top mesh 27 Elastomer 28a - d Gasket 31 Opening 32 Anode or cathode 33 Bolt hole

Claims

1. A conductive substrate and a coating layer covering the conductive substrate, The coating layer contains a nickel element and a metal element (A) that can take a rutile-type structure when an oxide is formed. In the mixture of oxides of the metal element that forms the coating layer, the oxide of the metal element (A) has a half-value width of 0.45° or more near 2θ = 27.5° attributed to the rutile-type oxide (110) plane measured by X-ray diffraction using CuKα radiation, and the oxidation charge amount (C Ｎｉ ) of nickel element obtained by cyclic voltammetry with potential scanning in the potential range of 1.34 to 1.47 V vs. RHE and a scanning rate of 10 mV / sec in 25 mass% KOH aqueous solution is 85 mC / cm ２ or more.

2. The ratio of the lithium element to the total amount of metal elements in the coating layer is less than 20 mol%, and the anode according to Claim 1.

3. The coating layer may contain a cobalt element, and the total ratio of the nickel element, the metal element (A), and the cobalt element to the total amount of metal elements in the coating layer is more than 80 mol%, and the anode according to Claim 1 or 2.

4. The metal element (A) contains an iridium element and / or a ruthenium element, and the anode according to Claim 1 or 2.

5. The ratio of the nickel element to the total amount of metal elements in the coating layer is 20 mol% or more, and the anode according to Claim 1 or 2.

6. The coating layer contains a cobalt element, and the anode according to Claim 1 or 2.

7. The anode according to Claim 1 or 2 having a dendrite structure on the surface.

8. The anode according to Claim 1 or 2 for alkaline water electrolysis.

9. An alkaline water electrolysis device including the anode according to Claim 8.

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