Porous electrode and manufacturing method thereof

Abstract

The present invention relates to a porous electrode with an increased specific surface area and a method for manufacturing same, and to: a method for manufacturing a water electrolysis electrode having an apparent specific gravity of 2.0 g / cm3 to 2.5 g / cm3, the method comprising a step for filling a mold manufactured in the shape of an electrode with metal powders including a filament-shaped nickel powder, a step for applying pressure to the filled metal powders to manufacture a compressed molded body, and a step for heat-treating the compressed molded body in a reducing atmosphere; and a water electrolysis electrode manufactured by the method of the present invention, wherein the water electrolysis electrode has an apparent specific gravity of 2.0 g / cm3 to 2.5 g / cm3.

Description

porous electrode and method for manufacturing the same

[0001] The present invention relates to a porous electrode and a method for manufacturing the same, and more specifically, to an electrode manufactured using a specific type of nickel powder to allow gas to be easily discharged, and a method for manufacturing the same.

[0002] Efforts to reduce carbon dioxide emissions due to global warming and to use clean hydrogen as fuel are being made worldwide, and in particular, water electrolysis technology, which produces green hydrogen by electrolyzing water using renewable energy, is gaining attention as the most desirable method for producing clean hydrogen.

[0003] Methods used for water electrolysis include high-temperature electrolysis, which produces hydrogen by decomposing steam under high-temperature operating conditions, and low-temperature electrolysis, which decomposes water at low temperatures. Since high-temperature electrolysis operates at temperatures exceeding 700°C, it presents a high level of technical difficulty, and thus, it can be considered to be in the early stages of commercialization. Although there are concerns regarding the use of precious metals such as Pt and Ir as electrode catalysts and a short lifespan due to strong corrosiveness, a low-temperature electrolysis technology known as polymer electrolyte electrolysis, commercialization has recently begun. Meanwhile, alkaline electrolysis is a method in which electrodes come into contact with an alkaline electrolyte to electrolyze water. It has the advantages of not requiring the use of expensive precious metals, operating at low temperatures, making manufacturing and maintenance relatively easy, and having low equipment costs; consequently, it has been commercialized for a long time, with the largest capacity facilities distributed worldwide.

[0004] Nickel, which is stable even in high-concentration alkaline aqueous solutions, is the most widely used electrode material for such alkaline water electrolysis, and nickel-plated stainless steel is also used. Various electrode shapes, such as plate, mesh, porous plate, and foam types, are commonly used. Korean Patent Application No. 10-2022-0109869 discloses a technology for manufacturing an electrode with excellent specific surface area and porosity by forming a dendritic porous composite metal structure on a conductive substrate.

[0005] However, if a technology is provided that can maintain electrode strength while having an increased specific surface area, it is expected to be widely applied in related fields.

[0006] [Prior Art Literature]

[0007] [Patent Document](Patent Document 1) Republic of Korea Application No. 10-2022-0109869

[0008] According to one embodiment of the present invention, a method for manufacturing an electrode capable of providing improved water electrolysis performance can be provided.

[0009] According to another embodiment of the present invention, an electrode with an increased specific surface area capable of providing improved water electrolysis performance may be provided.

[0010] A method for manufacturing a water electrolysis electrode according to one embodiment of the present invention comprises the steps of: filling a mold formed in the shape of an electrode with metal powder including filament-shaped nickel powder; applying pressure to the filled metal powder to produce a compressed molded body; and heat-treating the compressed molded body in a reducing atmosphere, wherein the apparent specific gravity is 2.0 g / cm³ 3 Up to 2.5 g / cm² 3 It may be a method for manufacturing a water electrolysis electrode for manufacturing a phosphorus electrode.

[0011] The above filament-shaped nickel powder may have an aspect ratio of 1.5 to 10.

[0012] The above filament-shaped nickel powder may have a cross-sectional diameter of 1 to 3 μm and a length of 5 to 10 μm.

[0013] The above-mentioned pressing step is 100 to 900 kg / cm² 2 It may be performed within the pressure range.

[0014] The heat treatment step may be performed in a temperature range of 650 to 950°C.

[0015] A water electrolysis electrode according to another embodiment of the present invention is manufactured by the method of the present invention and has an apparent specific gravity of 2.0 g / cm³ 3 Up to 2.5 g / cm² 3 Phosphorus is a water electrolysis electrode.

[0016] The total thickness of the electrode may be 0.1 mm to 1 mm.

[0017] According to the present invention, an electrode is provided in which the specific surface area of ​​the electrode is widened so that an electrolytic solution can easily penetrate the electrode, and according to the present invention, the size of the pores can be easily controlled so that hydrogen and oxygen gases formed by the electrolysis of water on the surface of the electrode can be easily discharged.

[0018] Figure 1 is a photograph of the shape of the nickel powder used in the present invention using a scanning electron microscope.

[0019] Figure 2 shows scanning electron microscope images of the surface of each molded body heat-treated in Preparation Example 1, taken at low magnification (×1000) and high magnification (×3000), respectively, compared according to the heat treatment temperature.

[0020] Figure 3 is a graph showing the results of comparing the hydrogen generation activity of each electrode obtained in Preparation Example 1.

[0021] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0022] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0023] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0024] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0025] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0026] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0027] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0028] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0029] Description of the invention

[0030] According to the present invention, an electrode in which the porosity and pore size are controlled by controlling the apparent specific gravity, and a method for manufacturing the same are provided.

[0031] More specifically, the method for manufacturing a water electrolysis electrode of the present invention comprises the steps of: filling a mold formed in the shape of an electrode with a metal powder including filament-shaped nickel powder; applying pressure to the filled metal powder to produce a compressed molded body; and heat-treating the compressed molded body in a reducing atmosphere, wherein the apparent specific gravity is 2.0 g / cm³ 3 Up to 2.5 g / cm² 3 It is for manufacturing phosphorus electrodes.

[0032] At this time, in the step of filling the metal powder, the metal powder containing nickel powder is evenly fed into a mold suitable for the size and shape of the electrode to be manufactured, and then compression molded using a press machine.

[0033] The above pressing step is 100 to 900 kg / cm²2 It may be performed within a pressure range of, for example, 700 kg / cm² 2 Below, 500 kg / cm² 2 Below, preferably 100 to 200 kg / cm² 2 It is performed within the pressure range.

[0034] Meanwhile, the heat treatment step may be performed in a temperature range of 650 to 950°C, for example, in a temperature range of 650 to 850°C. Sintering may be performed by the heat treatment step, and if the sintering is performed at a temperature below 650°C, the bonding force between nickel powder particles may be insufficient, and if it is performed at a temperature above 950°C, the apparent density may increase and the pore fraction may decrease excessively due to over-sintering.

[0035] The above heat treatment step may be performed in a reducing atmosphere, and the reducing atmosphere may be an atmosphere containing hydrogen (H₂) gas, for example, under an inert mixed gas containing 5 to 40 v / v% or 10 to 30 v / v% of hydrogen. The inert gas may be, for example, argon, but is not limited thereto.

[0036] Meanwhile, the metal powder comprises filament-shaped nickel powder, wherein the filament-shaped nickel powder may have an aspect ratio of 1.5 to 10, for example, 1.7 to 10, where the length of the filament is divided by the cross-sectional diameter. By using such filament-shaped nickel powder, the filament shape is advantageous for forming a three-dimensional network structure, so a pore structure can be formed stably and uniformly. As a result, the electrolyte can diffuse more easily into the electrode, thereby improving electrolyte accessibility. Additionally, release pathways for hydrogen and / or oxygen are efficiently formed, increasing gas release efficiency. Furthermore, since the filament shape shrinks more uniformly throughout the entire particle than spherical particles during the heat treatment process, the stability of the formed structure can be ensured compared to spherical particles, which can increase the mechanical strength of the electrode.

[0037] When the aspect ratio of the filament-shaped nickel powder, calculated by dividing the length of the filament by the cross-sectional diameter, is less than 1.5, the effect caused by the filament formation described above may be minimal, and when the aspect ratio exceeds 10, dispersibility may be reduced, making it difficult to form a uniform molded body during the manufacturing process, and as a result, the stability of the electrode structure may be reduced.

[0038] For example, the filament-shaped nickel powder may have a cross-sectional diameter of 1 to 3 μm and a length of 5 to 10 μm.

[0039] The total thickness of the water electrolysis electrode according to the present invention may be 0.1 mm to 1 mm, for example, 0.4 to 0.7 mm.

[0040] The water electrolysis electrode of the present invention obtained by such a method has an apparent specific gravity of 2.0 g / cm³ 3 Up to 2.5 g / cm² 3 It may be, and the total thickness of the electrode may be 0.1 mm to 1 mm.

[0041] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0042] Examples

[0043] 1. Manufacturing of electrodes

[0044] Preparation Example 1

[0045] Nickel powder in the form of filaments with a thickness of 1 to 3 μm and a length of 5 to 10 μm was used.

[0046] The above powder is filled into a mold measuring 40mm × 40mm × 3mm, and then molded using a press at a pressure of 100~120 kg / cm² 2 Compression molding was performed within the specified range. The concept of apparent specific gravity was used to select the target molding conditions. In this case, apparent specific gravity was defined as the value obtained by dividing the weight of the molded body by its volume.

[0047] As a result of repeated testing, the apparent specific gravity according to this embodiment is 1.8 to 2.0 g / cm³ 3 It was possible to manufacture a human molded body.

[0048] Figure 1 is a photograph of the shape of the nickel powder used in the present invention using a scanning electron microscope.

[0049] The molded body obtained in this way was heat-treated in a reducing gas atmosphere in which hydrogen was mixed with argon at 10 v / v% to prevent oxidation. The heating rate was set to 10℃ / min, and the target temperatures were changed to 650℃, 750℃, 900℃, 950℃, 1000℃, and 1100℃, respectively, while the holding time for each was fixed at 1 hour. The electrodes obtained therefrom are referred to as the electrodes of Examples 1, 2, 3, and 4, and Comparative Examples 1, 2, and 3, respectively.

[0050] Figure 2 shows a comparison of scanning electron microscope images of the surface of a heat-treated molded body taken at low magnification (×1000) and high magnification (×3000), respectively, according to the heat treatment temperature. As the heat treatment temperature increases, the pore size decreases and nickel particles can be observed to grow by aggregating, and it can be seen that the pores decrease rapidly at temperatures above 950°C.

[0051] Comparative Manufacturing Example 1

[0052] An electrode was prepared by the same process as in Preparation Example 1, except that spherical nickel powder with an average particle size of 5 μm was used instead of filament-shaped nickel powder, and heat-treated at 750°C. The electrode obtained therefrom is referred to interchangeably with Comparative Example 4.

[0053] 2. Evaluation of Electrode Characteristics

[0054] (1) Apparent specific gravity

[0055] Apparent specific gravity was defined as the value obtained by dividing the weight of the molded body by its volume.

[0056] Table 1 below shows the change in apparent specific gravity of the molded electrode according to the heat treatment temperature.

[0057] As described in Preparation Example 1, the apparent specific gravity of the initial molded body is 1.8 to 2.0 g / cm³ 3 However, as the nickel particles sintered due to heat treatment, the volume contracted, and as shown in Comparative Examples 1 to 3 of Table 1, it was confirmed that the apparent specific gravity tended to increase as the heat treatment temperature increased. Meanwhile, in the case of Comparative Example 4, it was confirmed that the apparent specific gravity was high even when the heat treatment temperature was appropriate, by using the electrode of Comparative Example 1.

[0058] Electrode heat treatment temperature (°C) Apparent specific gravity (g / cm³) 3Porosity (%) Example 1 Manufacturing Example 1650 2.0677 Example 2750 2.2575 Example 3900 2.3573 Example 4950 2.4972 Comparative Example 11000 2.5671 Comparative Example 21050 2.7369 Comparative Example 31100 2.8268 Comparative Example 4 Comparative Manufacturing Example 1750℃ 2.7569

[0059] At this time, the porosity is 8.845 g / cm³, where nickel specific gravity is 8.845 g / cm³ 3 Porosity (%) = 100 × (1 - Apparent Specific Gravity / 8.845)… Equation (1)

[0060] (2) Evaluation of hydrogen generation characteristics

[0061] To evaluate the hydrogen generation characteristics of the porous nickel powder sintered electrodes prepared according to Examples 1 to 4 and Comparative Examples 1 to 3, a potentiodynamic polarization test of the water electrolysis reaction in an alkaline aqueous solution was performed.

[0062] The experiment was conducted by constructing a 3-electrode electrochemical cell using an electrode prepared under the conditions of the example or comparative example as the working electrode, a platinum electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode.

[0063] A 30 wt% KOH aqueous solution at 70°C was used as the electrolyte. The potential applied to the graph was converted to RHE (Reversible Hydrogen Electrode) and plotted. To compare the relative effects of the fabricated electrodes, the performance of nickel foam was also compared, with a pore size of 450 μm, a thickness of 1.5 mm, and a yield of 420 g / m². 2 A commercial nickel foam with density specifications was used as a control.

[0064] Figure 3 is a graph showing the results of comparing the activity of hydrogen generation. When the same current density is applied, the closer the potential is to 0, the lower the overvoltage, which indicates superior performance. The electrode prepared in Example 1 showed superior performance compared to nickel foam, and it was confirmed that the performance was relatively superior, especially as the heat treatment temperature was lower.

[0065] Meanwhile, Table 2 below shows the current density at 100 mA / cm² 2 This compares the overvoltage of the electrode under the application conditions.

[0066] The overpotential of the nickel foam used as a control was 330 mV, and as the heat treatment temperature of the electrode prepared according to Example 1 decreased, it showed 163 mV at 650°C. However, if the heat treatment temperature is below 600°C, the strength is weak and it is prone to breaking due to the action of gas generation during water electrolysis; therefore, it is desirable to set the heat treatment temperature to 600°C or higher, preferably 650°C or higher. Furthermore, as confirmed in Figure 2, rapid sintering occurs above 950°C, which may degrade electrode performance; therefore, considering this, it can be seen that it is desirable to set the temperature to 950°C or lower.

[0067] Heat Treatment Temperature (°C) Overvoltage (mV) Control Group Nickel Foam - 330 Example 1 Manufacturing Example 1650 163 Example 2750 177 Example 3900 180 Example 4950 196 Comparative Example 11000 209 Comparative Example 31100 221 Comparative Example 4 Comparative Manufacturing Example 1750°C 210

[0068] This phenomenon is due to the fact that when a large number of pores are secured, the reaction area of ​​the electrode increases, as confirmed in Table 1 and Figure 2, and the performance of such an electrode can be explained by the apparent specific gravity as shown in Table 1.

Claims

1. A step of filling a mold made in the shape of an electrode with metal powder containing filament-shaped nickel powder; A step of manufacturing a compressed molded body by applying pressure to filled metal powder; and The method includes the step of heat-treating the compressed molded body in a reducing atmosphere, Apparent specific gravity 2.0 g / cm³ 3 Up to 2.5 g / cm² 3 A method for manufacturing a water electrolysis electrode for manufacturing a phosphorus electrode.

2. A method for manufacturing a water electrolysis electrode according to claim 1, wherein the filament-shaped nickel powder has an aspect ratio of 1.5 to 10.

3. A method for manufacturing a water electrolysis electrode according to claim 1, wherein the filament-shaped nickel powder has a cross-sectional diameter of 1 to 3 μm and a length of 5 to 10 μm.

4. In paragraph 1, the pressing step is 100 to 900 kg / cm² 2 A method for manufacturing a water electrolysis electrode, performed within a pressure range.

5. A method for manufacturing a water electrolysis electrode according to claim 1, wherein the heat treatment step is performed in a temperature range of 650 to 950°C.

6. Apparent specific gravity 2.0 g / cm³ 3 Up to 2.5 g / cm² 3 Phosphorus, water electrolysis electrode.

7. In paragraph 6, a water electrolysis electrode having a total thickness of 0.1 mm to 1 mm.

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