KR102278529B1 - Porous Ni-Al-Mo Cathode for Alkaline Water Electrolysis - Google Patents

Abstract

The present invention relates to an anode for alkaline water electrolysis with a low overvoltage, chemical stability, excellent durability, and a large specific surface area due to a porous structure, a method for manufacturing the same, and a thermal spray coating material that can be used for manufacturing the catalyst electrode, in more detail relates to an anode for alkaline water electrolysis, characterized in that a porous Ni-Al-Mo alloy catalyst layer is formed on the surface of a conductive substrate.

Description

Porous Ni-Al-Mo Cathode for Alkaline Water Electrolysis

The present invention relates to an anode for alkaline water electrolysis, which has a low overvoltage, is chemically stable, has excellent durability, and has a large specific surface area due to a porous structure.

Research on alternative energy due to global warming and depletion of fossil fuels is being actively conducted, and among them, hydrogen energy is attracting attention as a viable alternative to solving environmental and energy problems. Water is a clean resource that exists anywhere on the planet, and is an ideal hydrogen source with renewable potential that can be used repeatedly with hydrogen and oxygen.

Water electrolysis is a method of producing oxygen and hydrogen from water using electricity, and is divided into polyelectrolyte water electrolysis, alkaline water electrolysis, and high-temperature steam water electrolysis using solid oxides depending on the manufacturing method. Among them, alkaline water electrolysis is a proven technology and is receiving attention as an industrially established method.

Alkaline water electrolysis is a cell composed of a high-concentration alkaline electrolyte of 20-30 wt% KOH or 15-20 wt% NaOH, a diaphragm that selectively passes only OH-, a hydroxide ion, and a cathode and anode that generate hydrogen and oxygen, respectively It is a method of producing hydrogen at a low temperature of 150 ° C or less using When electric energy is applied to the electrolyte, water is electrolyzed at the cathode to generate hydrogen gas and hydroxide ions, and the generated hydroxide ions are transferred to the anode through the diaphragm to generate oxygen and water. Since alkaline water electrolysis can use a non-noble metal-based electrode material and a low-cost diaphragm, the hydrogen production cost is low compared to other water electrolysis processes, and the capacity can be increased.

The theoretical decomposition voltage of water is 1.229 eV, but a higher voltage is actually required due to the resistance of the electrolyzer, the generation of bubbles in the solution, and the resistance associated with the movement of ions between the anode and the cathode in the electrolyte. When the overvoltage is high during water electrolysis, the corresponding electrical energy is lost as heat, so the water electrolysis electrode must have a low overvoltage for oxygen or hydrogen generation and also have excellent corrosion resistance for durability.

As a typical commercial electrode, nickel and stainless steel containing nickel are mainly used, but since there is a problem with a very high overvoltage, various attempts are being made to develop a highly active catalyst electrode. Examples of the cathode catalyst electrode for hydrogen generation in the prior art include noble metals such as platinum and ruthenium, Raney nickel, nickel-cobalt, nickel-copper, nickel-iron, nickel-molybdenum, and the like. As these manufacturing methods, alloy plating method, coating sintering method, stuffing, thermal spraying, etc. are used.

The activity of the electrode in the water electrolysis reaction depends on the specific surface area of the electrode in relation to the reaction area as well as the intrinsic catalytic properties of the electrode material. Nickel-molybdenum (Ni-Mo) electrodes are known to greatly improve the hydrogen generation reaction due to an increase in the bonding force between metals and hydrogen atoms on the electrode surface (Non-Patent Documents 1 and 2). European Patent No. 0769576 discloses a cathode electrode coated with a Ni-Mo alloy having a Mo content of 10 wt% to 35 wt% as a cathode electrode having a low hydrogen evolution overpotential in an aqueous alkali metal chloride solution. The electrode is formed to a thickness of about 20-30 μm on a conductive substrate by an arc discharge ion plating method or a wet plating method. Japanese Patent No. 4085772 discloses that an alloy electrode for hydrogen generation made of a Co-Mo-C alloy or Co-Ni-Mo-C alloy containing 5 to 40 atomic percent molybdenum and 2 to 15 atomic percent carbon exhibits low overvoltage and reported that the electrode can be prepared by plating. However, the coating layer manufactured by the arc discharge ion plating method and the plating method has a disadvantage in that the specific surface area of the electrode is small because the thickness is thin and has a dense microstructure, and since most of the Mo element is present in a dissolved state in the base alloy, high temperature- When operating for a long time in a high-concentration aqueous alkali solution, the electrode activity decreases due to the elution of Mo elements.

Therefore, in order to maximize the hydrogen evolution reaction of the Mo-containing alloy coating layer and secure the electrode durability for a long time, the electrode and the electrode of a new composition having a porous structure with a large specific surface area, excellent hydrogen generation activity in aqueous alkali solution and chemically stable It is necessary to develop a method that can be economically manufactured.

European Patent No. 0769576 Japanese Patent No. 4085772

X. Tang, L. Xiao. C. Yang, J. Lu, L. Zhuang, International Journal of Hydrogen Energy, 39 (2014) 3055-3060. F. Safizadeh, E. Ghali, G. Houlachi, International Journal of Hydrogen Energy, 40 (2015) 256-274.

In order to solve the problems of the prior art as described above, the present invention is to provide an anode for alkaline water electrolysis with a low overvoltage of the catalyst layer, excellent catalytic activity, chemical stability, excellent durability, and a large specific surface area due to a porous structure. do.

The present invention for achieving the above object relates to an anode for alkaline water electrolysis, characterized in that a porous Ni-Al-Mo alloy catalyst layer is formed on the surface of a conductive substrate.

In the anode for alkaline water electrolysis of the present invention, the Ni-Al-Mo alloy catalyst layer has a low overvoltage for hydrogen generation and excellent catalytic activity. In addition, in the Ni-Al-Mo alloy catalyst layer, a binary Ni (Al, Mo) phase in which Al and Mo are partially dissolved in Ni and a ternary Ni _0.55 Al _7.2 Mo _2.25 phase are mixed, and Mo is present in a simple solid solution state. It has excellent corrosion resistance compared to the Mo alloy of the prior art, so that the elution of Mo elements is small even when operating for a long time in a high-temperature-high-concentration aqueous alkali solution, so that the electrode activity is maintained for a long time.

In the present invention, any conductive substrate may be used as long as it is generally used in the manufacture of an anode for alkaline water electrolysis. For example, nickel or stainless steel may be used, but the present invention is not limited thereto. The present invention is characterized by the configuration of the catalyst layer coated on the surface of the substrate, and does not relate to the substrate itself, so a detailed description thereof will be omitted.

In the Ni-Al-Mo alloy catalyst layer, the atomic ratio of Ni:Al:Mo is preferably 30-50:40-50:10-30. When the Al and Mo content is too high or too low, the ratio of the Ni(Al, Mo) phase is high, and corrosion resistance and catalytic activity are deteriorated.

The activity of the Ni-Al-Mo alloy catalyst layer is also affected by the specific surface area. For example, the specific surface area of the Ni-Al-Mo alloy catalyst layer is preferably 30 m 2 /g or more. The higher the specific surface area, the higher the catalytic activity in the water electrolysis process and thus a low hydrogen generation voltage is required. Therefore, it is more preferably 50 m 2 /g or more, and it is meaningless to set the upper limit of the preferred specific surface area.

Another aspect of the present invention comprises the steps of (A) forming a Ni-Al-Mo alloy coating layer by thermal spray coating on the surface of the conductive substrate; (B) heat-treating the conductive substrate on which the Ni-Al-Mo alloy coating layer is formed; and (C) treating the heat-treated substrate with an aqueous alkali solution.

Hereinafter, each step will be described in detail.

The step (A) is a step of forming a Ni-Al-Mo alloy layer, which is a cathode catalyst of an alkaline water electrolysis reaction, by thermal spray coating on the surface of the conductive substrate.

As described above, as the conductive substrate in this step, a substrate typically used for an electrode for alkaline water electrolysis may be used, and a detailed description thereof will be omitted.

Thermal spray coating is coating by spraying a powder-type material in a molten state using a high-temperature heat source such as flame or plasma, and vacuum plasma spraying, atmospheric plasma spraying, high-speed flame spraying, flame spraying, or low-temperature spraying can be used. , it is not limited to a specific spraying method. However, considering the cost of the coating process, the ease of operation and the porosity of the coating layer, atmospheric plasma spraying is more preferable. Atmospheric plasma thermal spraying is easy to control the heat flowing into the substrate, and since relatively low heat is introduced, thermal deformation of the substrate can be minimized. In addition, large-area coating is possible, the thickness of the coating layer can be easily controlled, a strong bonding force between the coating layer and the substrate is formed, and the pores/fine defects of the coating layer can be controlled through optimization of process conditions.

At this time, in order to increase the adhesion between the conductive substrate and the Ni-Al-Mo alloy coating layer, the method may further include roughening the conductive substrate so that the surface roughness (Ra) of the conductive substrate becomes 0.5 to 5.0 μm before thermal spray coating. More preferably, the surface roughness of the conductive substrate is 2.0-3.0 ㎛. If the surface roughness is too high, damage and deformation may occur to the conductive substrate during the roughening process, and if the surface roughness is too low, the roughening effect cannot be exhibited. Examples of the roughening treatment method include, but are not limited to, blasting treatment and chemical etching using an acid. During blasting, it is recommended to control the particle size and pressure so as not to cause deformation of the conductive substrate.

In the Ni-Al-Mo alloy coating layer, an atomic ratio of Ni: Al: Mo is preferably 1: 2 to 8: 0.2 to 1.5. The change in the Al content aims to increase the specific surface area of the catalyst coating layer in the chemical leaching step and chemical stability in the KOH electrolyte solution of the catalyst coating layer, and the change in the Mo content is to improve the catalytic activity of the electrode in the hydrogen evolution reaction. to be. If the content of Al and Mo is too small or too large, the specific gravity of the phase in which Al and Mo are partially dissolved in Ni among the Ni-Al-Mo alloy layers produced by thermal spray coating increases, so that the durability of the prepared catalyst layer may decrease. can

The thickness of the Ni-Al-Mo alloy coating layer can be easily controlled according to the thermal spray coating conditions and time, and can be formed to a thickness of 50 to 300 μm. If the thickness of the coating layer is too thin, loss may occur in the subsequent aqueous alkali solution treatment step, and if the thickness is too thick, the cost may increase.

In the following examples, the Ni-Al-Mo alloy coating layer prepared by atmospheric plasma spraying generally has a porosity of about 2-5%, but the porosity of the coating layer is not limited in the present invention. In addition, the NiAl _x Mo _y coating layer formed by atmospheric plasma spraying is about 1-10% It may contain a volume fraction of oxide, but there is no problem in using it as an anode coating electrode for water electrolysis.

Step (B) is a step of heat-treating the conductive substrate on which the Ni-Al-Mo alloy coating layer is formed in step (A).

Preferably, the heat treatment is performed at 500 to 800° C. for 0.2 to 3 hours. In the heat treatment process of this step, the diffusion reaction between unmelted Mo particles and Ni or Al in the Ni-Al-Mo alloy coating layer is promoted, and the fraction of the ternary Ni-Al-Mo alloy phase with high hydrogen generating activity is increased. As can be seen in the following examples, when the heat treatment process was not performed, the catalytic activity and corrosion resistance for the hydrogen evolution reaction were greatly reduced. When the heat treatment temperature is too low, the heat treatment effect is not sufficiently exhibited, and when the heat treatment temperature is too high, the coating layer becomes excessively dense, making it difficult to convert to a porous catalyst coating layer in the alkali aqueous solution treatment step of step (C). It goes without saying that the heat treatment time may be appropriately adjusted according to the heat treatment temperature, and may be treated for 1 to 3 hours in general.

If oxygen is present in the heat treatment process of this step, oxidation of the catalyst metal may occur and catalytic activity may decrease, so that the heat treatment is more preferably performed in an inert gas atmosphere, a reducing atmosphere, or a vacuum atmosphere.

Step (C) is a step of treating the substrate heat-treated in step (B) with an aqueous alkali solution.

In this step, the aqueous alkali solution penetrates into the coating layer along the splat boundary pore layer of the Ni-Al-Mo thermal spray coating layer and selectively leaches Al and some Mo elements from the Al-rich phases to the Ni-Al-Mo alloy coating layer. Gives porosity. As the specific surface area of the Ni-Al-Mo catalyst layer is greatly increased by this step, the catalytic activity for hydrogen generation by alkaline water electrolysis is greatly increased.

The alkali aqueous solution treatment in this step may be, for example, 10 to 30% by weight of sodium hydroxide or potassium hydroxide aqueous solution at 50 to 100 ℃ 12 to 100 hours treatment.

According to the chemical composition of the powder material, the Ni-Al-Mo catalyst coating layer finally formed by the aqueous alkali solution treatment in this step has a Ni content of 30-50 at%, an Al content of 40-50 at%, and an Al content of 10-30 at%. It has a chemical composition of Mo content, and is composed of a Ni(Al,Mo) phase in which Al and Mo are partially dissolved in Ni and a ternary Ni _0.55 Al _7.2 Mo _2.25 phase, and thus has excellent corrosion resistance. In addition, due to the porous structure, the specific surface area is 30 m ² /g or more, and catalytic activity is high, which is advantageous for hydrogen generation reaction by alkaline water electrolysis.

Conventional metal powder is produced through atomization and subsequent solidification by colliding a molten liquid metal stream with a high-pressure inert gas jet, but manufacturing equipment is expensive, powder production cost is very high, alloy composition is changed, or a small amount is produced not suitable for In particular, when the melting point difference between alloying elements is large, such as the Ni-Al-Mo alloy of the present invention, it is very difficult to prepare a coating material having a uniform composition.

Accordingly, another aspect of the present invention relates to a Ni-Al-Mo thermal spray coating material, and more specifically (A) 1.0 to 5.0 by milling by adding a mixture of Ni, Al and Mo metal or alloy powder to a liquid solvent. crushing into fine particles in the ㎛ range; (B) preparing a slurry by adding a dispersant and a binder to the mixed solution; and (C) spraying the slurry into micron-sized droplets by centrifugal spray drying and drying at a high temperature to prepare a granular powder; it's about

In order to use the thermal spray coating material for manufacturing the above-mentioned alkaline water electrolysis negative electrode, the atomic ratio of Ni: Al: Mo in the mixture of metal or alloy powder in step (A) is 1: 2-8: 0.3-1.5 is preferable. However, the present invention is not limited thereto. Metal or alloy powder refers to each metal such as "Ni, Al and Mo", or an alloy of one or more metals selected from the group consisting of Ni, Al and Mo, such as _{NiAl 2.17 of the following examples, can be used.} means there is At this time, it is preferable that the initial raw material powder has a purity of 98 wt% or more and a particle size of 5.0 μm or less. The smaller the particle size, the more advantageous it is to prepare a uniform mixture. However, the smaller the particle size, the lower the economic feasibility, so it is more preferable to have a particle size of 1.0 to 5.0 μm. The crushed raw material powder, binder, and dispersant are added in a liquid solvent, and ball milling is performed to make a uniformly mixed liquid slurry. The slurry mixture solution is sprayed into droplets by a high-pressure gas atomizer or a centrifugal atomizer using a high-speed rotating disk to remove the solvent in a high-temperature atmosphere, thereby producing a Ni-Al-Mo alloy thermal spray coating material in the form of agglomerated raw powders. do.

The particle size of the Ni-Al-Mo alloy thermal spray coating material is preferably a spherical shape of 5 to 100 ㎛. If the particle size of the powder is smaller than 5㎛ or is not spherical, uniform spraying is difficult during thermal spray coating due to reduced fluidity of the powder. On the other hand, if the powder particle size is larger than 100㎛, it is difficult to form a uniform coating layer. there is a problem. If the strength of the spray-dried granular powder is weak and cannot be used in the thermal spraying process, heat treatment may be performed in an inert gas atmosphere or vacuum at 500 to 1000° C., but it is not necessary. When the heat treatment temperature is too high, sintering may occur between the granular powders.

As described above, according to the anode for alkaline water electrolysis of the present invention and its manufacturing method, it is possible to provide an anode for alkaline water electrolysis with a low overvoltage of the catalyst layer, excellent catalytic activity, chemical stability, excellent durability, and a large specific surface area due to its porous structure. Therefore, it can be usefully used for hydrogen generation by alkaline water electrolysis.

In addition, the thermal spray coating material of the present invention can produce a uniform powder economically by using simpler equipment for various chemical compositions, so it is effective in fields requiring thermal spray coating of Ni-Al-Mo alloys, including the anode for alkaline water electrolysis. can be used as

1 is an electron microscope image showing a cross-sectional microstructure of _{a NiAl x} Mo _y powder material formed by an embodiment of the present invention.
Figure 2 is an electron microscope image showing the cross-sectional microstructure of _{the plasma sprayed NiAl x} Mo _y coating layer formed according to an embodiment of the present invention.
Figure 3 is an electron microscope image showing the surface and cross-sectional microstructure of the porous Ni-Al-Mo coating layer formed according to an embodiment of the present invention.
Figure 4 is an X-ray diffraction spectrum of the porous Ni-Al-Mo coating layer formed according to an embodiment of the present invention.
5a to 5c are graphs showing the potential polarization curves for the hydrogen evolution reaction of the porous Ni-Al-Mo coating layer formed according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying examples. However, these embodiments are merely examples for easily explaining the content and scope of the technical idea of the present invention, and thereby the technical scope of the present invention is not limited or changed. It will be natural for those skilled in the art that various modifications and changes can be made within the scope of the technical spirit of the present invention based on these examples.

[Example]

Example 1: NiAl _x Mo _y Manufacture of thermal spray coating material

Chemical composition of metal components in the mixture of NiAl _2.17 (average particle size 23 μm, Yakuri Pure Chemical, Japan), Al (average particle size 3 μm, High Purity Chemicals, Japan) and Mo (average particle size 5 μm, Seokwang Metal, Korea) powder particles After weighing so that this NiAl _x Mo _0.66 (x = 2, 4, 6 or 8) or NiAl ₆ Mo _y (y = 0.33, 0.66, 1.00 or 1.33), it is mixed with an ethanol solvent and a slurry having a solid phase ratio of 10% by volume was prepared. In order to prepare a thermal sprayed coating material having an at% of Ni and Al of 1:2, Ni powder was additionally mixed in a ratio. The slurry was crushed into fine particles using high-energy attrition milling. A slurry solution was prepared by adding 1 wt% and 2 wt% of a dispersant and a binder to the crushed powder mixture solution, respectively, with respect to the powder mixture solution. For Ni-Al-Mo slurry solutions of different chemical compositions, granular powders having an average particle size of about 40 μm were prepared using a centrifugal spray drying device (DJSD-1500, Dongjin Machinery).

1 is a scanning electron microscope image of the cross-sectional microstructure _{of the NiAl 6} Mo _0.66 powder material prepared in the present invention. The prepared powder is a roughly spherical granular powder, showing that three kinds of NiAl _2.17 , Al and Mo particles are aggregated and distributed inside.

Example 2: NiAl _x Mo _y Preparation of catalyst electrode

1) NiAl by atmospheric plasma spray coating _x Mo _y Preparation of coating layer

A surface roughness of about Ra = 3 μm was formed on a 0.6 mm thick Ni substrate by grit blasting using 200 mesh alumina particles. At this time, blasting was performed with a low injection pressure of ^{3 kg/cm 2} so as not to deform the thin substrate. A coating layer having a thickness of about 100 μm was formed on the blast-treated Ni substrate _{by using the NiAl x} Mo _y thermal spray coating material prepared in Example 1 with an atmospheric plasma spraying equipment SG-100 (Praxair, USA). Atmospheric plasma spraying conditions using Ar-He plasma gas were a plasma jet output of 24 kW, a spraying distance of 120 mm, a powder supply amount of 30 g/min, and a powder supply gas pressure of 3.5 kg/cm ² .

2 is an electron microscope image showing a cross-sectional microstructure of a representative Ni-Al-Mo coating layer formed on a Ni substrate by atmospheric plasma spraying. Regardless of the chemical composition of the powder material, the plasma spray Ni-Al-Mo coating layer had a similar microstructure. From Fig. 2, the plasma thermal sprayed Ni-Al-Mo coating layer was formed with good interfacial bonding without interfacial separation with the Ni substrate, and the coating layer was composed of some unmelted/partially melted droplets and pores and splat boundary pores along with completely molten splat lamination can confirm. In some regions of the Ni-Al-Mo coating layer, about 1-2% by volume of oxide was included, but it was at a level that did not significantly affect the electrical conductivity of the electrode for alkaline water electrolysis.

2) NiAl _x Mo _y Heat treatment of coating layer

_{In 1), the substrate on which the NiAl x} Mo _y coating layer was formed by atmospheric plasma spraying was heat-treated in a hydrogen atmosphere at 750° C. for 1 hour.

3) Heat-treated NiAl _x Mo _y Chemical leaching of the coating layer

Chemical leaching of Al alloy elements was performed by immersing the heat-treated NiAl _x Mo _y coated substrate in an aqueous alkali solution (30% KOH + 10% K Na tartrate hydrate) at 80 ° C. for more than 24 hours.

3 is an electron microscope image of the surface (a) and cross-section (b) microstructure of the _{NiAl 6} Mo _0.66 coating layer after chemical leaching in an aqueous alkali solution. FIG. 3 shows that the surface unevenness is greatly increased by chemical leaching, and a porous microstructure is formed throughout the inside of the coating layer. It is believed that the aqueous alkali solution penetrates into the coating layer along the splat boundary porous layer of the plasma spray coating layer and selectively leaches Al and some Mo elements from the Al-rich phases to increase the porosity.

4 is an X-ray diffraction analysis result of a porous Ni-Al-Mo catalyst coating layer after chemical leaching in an aqueous alkali solution. It can be seen that the porous Ni-Al-Mo catalyst coating layer is _{composed of a Ni(Al,Mo) phase and a Ni 0.55} Al _7.2 Mo _2.25 phase, which are two kinds of metal-based compounds after chemical leaching. As the Mo content in the NiAl ₆ Mo _y coating layer increased, the fraction of the _{Ni 0.55} Al _7.2 Mo _2.25 phase increased compared to the Ni(Al,Mo) phase. In addition _{, as the Al content in the NiAl x} Mo _0.66 coating layer increased, the fraction of the _{Ni 0.55} Al _7.2 Mo _2.25 phase increased compared to the Ni (Al, Mo) phase. The atomic ratio of Ni: Al: Mo in the coating layer was measured by EDS (Energy Dispersive X-ray Spectroscopy), and as a result, regardless of the composition of the thermal spray coating material, all were in the range of 30-50: 40-50: 10-30, and the composition of the thermal spray coating material No definite correlation was found with In order to quantitatively evaluate the micropores of the catalyst coating layer, the specific surface area was measured using a BET specific surface area measuring device (Belsorp-max, BEL Japan Inc.). As a result, the specific surface area of the prepared catalyst coating layer was 60-80 m ² /g is shown.

Example 3: NiAl _x Mo _y Evaluation of Hydrogen Generation Characteristics of Catalyst Electrodes

In order to evaluate the hydrogen generation characteristics of the porous Ni-Al-Mo catalyst electrode prepared in Example 2, a potentiostatic polarization test of water electrolysis in an aqueous alkali solution was performed. A three-electrode electrochemical cell was constructed using the catalyst electrode prepared in Example 2 as the working electrode, the Ni electrode as the counter electrode, and the Hg/HgO electrode as the reference electrode, and experiments were conducted. 1M KOH aqueous solution at 25°C was used as the electrolyte solution. A polarization curve was obtained by applying a potential from -0.8V to 1.5V at a scanning speed of 0.1 mV/s from Metrohm's Autolab equipment for the electrostatic polarization test. Corrosion current density and corrosion rate were calculated through Tafel extrapolation.

In Comparative Example 1, a catalyst electrode prepared in the same manner as in Example 2 was used, except that a _{commercial NiAl 2.17} powder material was used as a thermal spray coating material instead of a _{NiAl x} Mo _{y thermal spray coating material.} In Comparative Example 2, a catalyst electrode prepared in the same manner as in Example 2 was used except that a thermal treatment process was omitted while using a thermal spray coating material _{of NiAl 6} Mo _0.66.

5a to 5b are co-potential polarization curves of a porous Ni-Al-Mo catalyst electrode of the present invention according to changes in Mo content and Al content, and FIG. 5c is a co-potential polarization of a catalytic electrode manufactured with or without a heat treatment process. It is a curve. The hydrogen evolution overvoltage and Tafel slope obtained therefrom are summarized in Table 1 below.

As can be seen in Table 1, the catalyst electrodes of all compositions of the present invention showed superior hydrogen generation activity and corrosion resistance compared to the _{NiAl 2.17 catalyst electrode of Comparative Example in which Mo was not added.} For the activity and corrosion resistance of the catalyst electrode, the Al content (x) and Mo content (y) _{in the NiAl x} Mo _{y coating layer showed optimal values.} That is, _{when the Al content in the NiAl x} Mo _0.66 coating layer increased from 2 to 6, the overvoltage decreased and the activity and corrosion resistance of the catalyst electrode gradually improved. When the Al content increased from 6 to 8, the catalytic activity and corrosion resistance decreased again. did. Mo content also showed a similar pattern, and the highest catalytic activity and corrosion resistance were exhibited when the Mo content was 0.66 in the _{NiAl 6} Mo _{y coating layer.}

In addition, even if the same thermal spray coating material is used, the NiAl ₆ Mo _0.66 catalyst electrode manufactured by omitting the heat treatment process has significantly reduced catalytic activity and corrosion resistance, confirming the importance of the heat treatment process in the manufacturing process of the catalyst electrode. Heat treatment promotes the diffusion reaction between unmelted Mo particles and Ni or Al in the NiAl _x Mo _y coating layer, increases the fraction of the ternary Ni-Al-Mo alloy phase with high hydrogen generating activity, and porous catalyst in the subsequent chemical leaching process It is believed to facilitate the conversion to the coating layer.

Claims (5)

(A) forming a Ni-Al-Mo alloy coating layer having an atomic ratio of Ni: Al: Mo of 1: 2-8: 0.66-1.0 by thermal spray coating on the surface of the conductive substrate;
(B) heat-treating the conductive substrate on which the Ni-Al-Mo alloy coating layer is formed at 500-800° C. in an inert gas atmosphere, a reducing atmosphere, or a vacuum atmosphere for 0.2 to 3 hours; and
(C) treating the heat-treated substrate with an aqueous alkali solution;
By being manufactured, including
A porous Ni-Al-Mo alloy catalyst layer having an atomic ratio of Ni: Al: Mo of 30-50: 40-50: 10-30 is formed on the surface of the conductive substrate,
Anode for alkaline water electrolysis, characterized in that the hydrogen generation overvoltage at 25°C, 1M KOH aqueous solution, and 400mA/cm2 is 73 mV or more and 141 mV or less.
delete delete The method of claim 1,
The Ni-Al-Mo alloy catalyst layer is a cathode for alkaline water electrolysis, characterized in that it consists of a binary Ni (Al, Mo) phase in which Al and Mo are partially dissolved in Ni and a ternary Ni _0.55 Al _7.2 Mo _{2.25 phase.}
The method of claim 1,
The anode for alkaline water electrolysis, characterized in that the specific surface area of the Ni-Al-Mo alloy catalyst layer is 30 m 2 /g or more.

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