Electrode for water electrolysis and method for manufacturing same

Abstract

The present invention relates to an electrode for water electrolysis and a method for manufacturing same, the electrode comprising a metal substrate and a catalyst layer formed on at least one surface of the metal substrate, wherein the catalyst layer includes CoxFeyO4 (0≤x≤4, 0≤y≤3) and satisfies formula 1.

Description

Electrode for water electrolysis and method for manufacturing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0121089, filed September 5, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to an electrode for electrolysis of water having excellent electrolysis performance due to low overvoltage and excellent durability, and a manufacturing method for manufacturing the same.

[0005] As carbon reduction policies become more active, the use of renewable energy as a substitute for existing carbon-based energy sources is gradually increasing. However, renewable energy production is unstable and fluctuates depending on the surrounding environment, raising the question of how to handle the excess energy produced.

[0006] Traditionally, surplus energy has been stored in energy storage systems (ESS) as electrical energy, which is then used as needed. However, due to the high cost of ESS itself and safety concerns, its widespread use has been limited.

[0007] To address this, a new Power-to-Gas (P2G) strategy is emerging, utilizing excess energy to convert it into hydrogen through electrolysis. Various electrolysis methods are known, including polymer electrolyte membrane electrolysis (PEM), alkaline electrolysis (AEC), anion exchange membrane electrolysis (AEM), and solid oxide electrolysis (SOEC). While PEM is known to be superior in terms of performance, the high cost of the catalysts and cation exchange membranes used makes alkaline electrolysis the most widely used in industrial applications.

[0008] Alkaline electrolysis, which uses an alkaline electrolyte to electrolyze water, is the oldest commercially available technology among various electrolysis methods. Therefore, it can reliably electrolyze water. Furthermore, because it uses a non-precious metal catalyst, the unit cost of electrolysis is low, making it suitable for mass production.

[0009] Meanwhile, anodes used in alkaline water electrolysis primarily utilize nickel as a single element. While nickel is suitable as an alkaline water electrolysis anode among single elements, it suffers from relatively poor performance and durability at the commercial stage. In particular, when applying the surplus renewable energy described above to water electrolysis, load fluctuations can occur during the electrolysis process, making it crucial to ensure sufficient durability against load fluctuations and the potential reverse currents that may arise in such situations. However, nickel-only anodes lack sufficient durability for these situations.

[0010] Therefore, there is a need to develop a new electrolysis electrode, especially an anode, that has excellent performance and can exhibit excellent durability even in load fluctuations and reverse current situations that may occur when applying surplus renewable energy to electrolysis.

[0011] The purpose of the present invention is to provide a new electrode for water electrolysis and a method for manufacturing the same, which can simultaneously achieve superior performance and durability compared to a nickel single element anode conventionally used as an anode in alkaline water electrolysis.

[0012] In order to solve the above-mentioned problem, the present invention provides an electrode for electrolysis of water and a method for manufacturing the same.

[0013] More specifically, (1) the present invention includes a metal substrate and a catalyst layer formed on at least one surface of the metal substrate, wherein the catalyst layer is Co x Fe y Provided is an electrode for water electrolysis, characterized in that it includes O4(0≤x≤4, 0≤y≤3) and satisfies the following equation 1:

[0014] [Formula 1]

[0015] D1 / D2 ≤ 0.321

[0016] In the above equation 1,

[0017] The above D1 means the distance between the point where the content of the metal element of the above-mentioned substrate is 70 wt% and the point where the content is 30 wt% in the element distribution graph obtained through SEM-EDS line scanning analysis of the electrolysis electrode,

[0018] The above D2 refers to the distance between the point where the content of the metal element of the above-mentioned substrate is 90 wt% and the point where it is 10 wt%.

[0019] (2) The present invention provides an electrolysis electrode in the above (1), wherein x:y is 1:1 to 1:9.

[0020] (3) The present invention provides an electrode for electrolysis of water, wherein the catalyst layer comprises a crystal phase in the above (1) or (2).

[0021] (4) The present invention provides an electrode for water electrolysis, characterized in that, in any one of the above (1) to (3), the catalyst layer has a peak in at least one region among a region having a 2θ value of 17.5° to 19.5°, a region having a 2θ value of 30.5° to 32°, a region having a 2θ value of 35° to 36°, a region having a 2θ value of 36° to 37.5°, a region having a 2θ value of 42° to 44°, a region having a 2θ value of 52.5° to 54.5°, a region having a 2θ value of 56° to 58°, and a region having a 2θ value of 61.5° to 63.5° in a graph obtained through XRD analysis.

[0022] (5) The present invention provides an electrolysis electrode in which D1 is 0.4㎛ or less in any one of the above (1) to (4).

[0023] (6) The present invention provides an electrode for electrolysis of water, wherein D2 is 0.2 µm or more and 1.5 µm or less, in any one of the above (1) to (5).

[0024] (7) The present invention provides an electrode for electrolysis of water, wherein the metal substrate comprises at least one metal selected from the group consisting of Ni, Fe, Co, and Ti, in any one of the above (1) to (6).

[0025] (8) The present invention provides an electrolysis electrode according to any one of the above (1) to (7), wherein the electrolysis electrode is an anode.

[0026] (9) The present invention provides a method for manufacturing an electrode for electrolysis, comprising the steps of: preparing a coating composition containing a cobalt precursor and an iron precursor (S1); applying the coating composition to a metal substrate, drying it, and performing a first firing at a temperature of 200°C or higher and 450°C or lower (S2); and performing a second firing at a temperature higher than the temperature at which the first firing is performed (S3).

[0027] (10) The present invention provides a method for manufacturing an electrode for water electrolysis, wherein, in the above (9), the cobalt precursor is at least one selected from the group consisting of Co(OAc)2, Co(NO3)2, CoCl2, Co(acac)2, Co(acac)3, CoCO3, and CoSO4.

[0028] (11) The present invention provides a method for manufacturing an electrode for electrolysis, wherein in the above (9) or (10), the iron precursor is at least one selected from the group consisting of iron carbonate, Fe(acac)3, Fe(OAc)2, Fe(NO3)3, FeCl3, FeCl2 and FeSO4.

[0029] (12) The present invention provides a method for manufacturing an electrode for electrolysis of water, wherein the coating composition comprises at least one solvent selected from the group consisting of water and alcohol, in any one of the above (9) to (11).

[0030] (13) The present invention provides a method for manufacturing an electrode for electrolysis, wherein in any one of the above (9) to (12), the drying includes room temperature drying and high temperature drying, and the high temperature drying is performed at a temperature of 50°C or higher and 100°C or lower.

[0031] (14) The present invention provides a method for manufacturing an electrode for electrolysis, wherein the secondary calcination is performed at a temperature of 500°C or higher and 700°C or lower in any one of the above (9) to (13).

[0032] The electrolysis electrode of the present invention can simultaneously secure excellent activity for electrolysis reaction and excellent durability in electrolysis under alkaline conditions.

[0033] Figure 1 is an element distribution graph obtained through SEM-EDS line scanning analysis of an electrolysis electrode according to Example 1 of the present invention.

[0034] Figure 2 is an element distribution graph obtained through SEM-EDS line scanning analysis of an electrolysis electrode according to Example 2 of the present invention.

[0035] Figure 3 is an element distribution graph obtained through SEM-EDS line scanning analysis of an electrolysis electrode according to Comparative Example 5 of the present invention.

[0036] Figure 4 is a graph showing the results of analyzing the crystal structure in the catalyst layer of the electrolysis electrode according to Example 1 of the present invention and the electrolysis electrode according to Comparative Examples 2 and 4.

[0037] Figures 5 and 6 show cross-sections of an electrode for electrolysis according to Example 1 of the present invention.

[0038] Figures 7 and 8 show cross-sections of an electrode for electrolysis according to Comparative Example 2 of the present invention.

[0039] Figure 9 is a graph showing the results of performance deterioration evaluation of the electrolysis electrodes of Examples 1 to 5 and Comparative Examples 1 to 5 of the present invention.

[0040] Hereinafter, the present invention will be described in more detail.

[0041] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0042]

[0043] Electrode for water electrolysis

[0044] The present invention comprises a metal substrate and a catalyst layer formed on at least one surface of the metal substrate, wherein the catalyst layer is Co x Fe y A water electrolysis electrode is provided, characterized in that it includes O4(0≤x≤4, 0≤y≤3) and satisfies the following equation 1.

[0045] [Formula 1]

[0046] D1 / D2 ≤ 0.321

[0047] In the above equation 1,

[0048] The above D1 means the distance between the point where the content of the metal element of the above-mentioned substrate is 70 wt% and the point where the content is 30 wt% in the element distribution graph obtained through SEM-EDS line scanning analysis of the electrolysis electrode,

[0049] The above D2 refers to the distance between the point where the content of the metal element of the above-mentioned substrate is 90 wt% and the point where it is 10 wt%.

[0050]

[0051] The electrolysis electrode of the present invention comprises a catalyst layer formed on a conductive metal substrate, wherein the catalyst layer is Co x Fe y By including O4(0≤x≤4, 0≤y≤3), the durability and performance of the electrode can be secured simultaneously.

[0052]

[0053] Co corresponding to the active ingredient included in the above catalyst layer x Fe y O4(0≤x≤4, 0≤y≤3) can increase the activity for water electrolysis reaction, and the catalyst layer including the above component can more strongly bond with the substrate to provide excellent durability. The above x:y may be 1:1 to 1:9, preferably 1:1.5 to 1:4, and particularly preferably 1:1.8 to 1:3. When the molar ratio between cobalt and iron satisfies the above-described condition, the synergistic effect between the two components can be maximized.

[0054]

[0055] Meanwhile, Co included in the catalyst layer x Fe yO4(0≤x≤4, 0≤y≤3) may be a crystalline phase. The crystalline phase may be formed through a secondary calcination process performed in the manufacturing process of the water electrolysis electrode of the present invention, thereby ensuring the durability of the water electrolysis electrode. The crystal size of the crystalline phase may be 5 nm or more and 50 nm or less, and preferably 10 nm or more and 40 nm or less.

[0056] The above Co x Fe y The presence of the O4 crystal phase can be confirmed through XRD analysis of the catalyst layer, and more specifically, in a graph obtained as a result of XRD analysis of the catalyst layer, it can be confirmed through a peak appearing in at least one region among a region having a 2θ value of 17.5° to 19.5°, a region having a 2θ value of 30.5° to 32°, a region having a 2θ value of 35° to 36°, a region having a 2θ value of 36° to 37.5°, a region having a 2θ value of 42° to 44°, a region having a 2θ value of 52.5° to 54.5°, a region having a 2θ value of 56° to 58°, and a region having a 2θ value of 61.5° to 63.5°. More specifically, the electrolysis electrode of the present invention may have a peak in at least one of the following regions, preferably two or more of the eight regions, and more preferably all of the eight regions, among the regions having a 2θ value of 17.5° to 19.5°, the region having a 2θ value of 30.5° to 32°, the region having a 2θ value of 35° to 36°, the region having a 2θ value of 36° to 37.5°, the region having a 2θ value of 42° to 44°, the region having a 2θ value of 52.5° to 54.5°, the region having a 2θ value of 56° to 58°, and the region having a 2θ value of 61.5° to 63.5°, in a graph obtained through XRD analysis of the catalyst layer:

[0057]

[0058] The electrolysis electrode of the present invention can satisfy the following equation 1.

[0059] [Formula 1]

[0060] D1 / D2 ≤ 0.321

[0061] In the above equation 1,

[0062] The above D1 means the distance between the point where the content of the metal element of the above-mentioned substrate is 70 wt% and the point where the content is 30 wt% in the element distribution graph obtained through SEM-EDS line scanning analysis of the electrolysis electrode,

[0063] The above D2 refers to the distance between the point where the content of the metal element of the above-mentioned substrate is 90 wt% and the point where it is 10 wt%.

[0064]

[0065] The electrolysis electrode of the present invention can be manufactured through primary calcination at low temperature and secondary calcination at high temperature as described below, and by performing such secondary calcination, the phenomenon of metal elements of the substrate being diffused into the catalyst layer can be minimized, and thereby the content of effective active ingredients in the catalyst layer can be maximized, thereby improving durability and performance.

[0066] In the above Equation 1, D1 refers to the distance between the points where the content of the metal element of the substrate is 70 wt% and 30 wt% in the element distribution graph obtained through SEM-EDS line scanning analysis of the electrolysis electrode, and D2 refers to the distance between the points where the content of the metal element of the substrate is 90 wt% and 10 wt% in the same graph. In the element distribution graph obtained through SEM-EDS line scanning analysis of the electrolysis electrode of the present invention, the content of the metal element of the substrate appears high on the substrate side, but gradually decreases from the interface between the catalyst layer and the substrate, and the content is minimized in the outermost layer of the catalyst layer. This is because some of the metal elements of the substrate diffuse toward the catalyst layer during the formation of the catalyst layer. If the diffusion of the metal element is small, the content of the metal element decreases over a shorter distance, and conversely, if the diffusion of the metal element is large, the graph is drawn in a form in which the content of the metal element decreases over a longer distance. In other words, the less the diffusion of the metal element, the smaller the D1 appears.

[0067] The electrolysis electrode of the present invention can minimize the diffusion of such metal elements by being manufactured through a two-stage firing process, and the D1 can have a value of 0.321 or less relative to D2. The D1 / D2 value can be 0.321 or less, 0.32 or less, 0.315 or less, 0.31 or less, 0.305 or less, 0.3 or less, 0.295 or less, 0.29 or less, 0.285 or less, or 0.28 or less. Additionally, the D1 / D2 value may be 0.05 or more, 0.1 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, 0.2 or more, 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.3 or more, or 0.31 or more.

[0068] Meanwhile, the above SEM-EDS line scanning analysis can be performed under the following conditions.

[0069] 1) Scan length: 2㎛ or more and 5㎛ or less

[0070] 2) Step size: 0.05㎛ or more and 0.15㎛ or less (10 to 50 steps)

[0071] 3) Scan direction: Metal substrate -> coating layer -> resin (holder)

[0072] 4) Acceleration voltage: 10 to 20 kV

[0073] 5) Measurement time: 1 to 5 minutes

[0074] 6) Analysis elements: C, O, metallic elements of the substrate, Co, Fe

[0075] 7) Line setting conditions: Set the line in an area where there is no gap between the substrate and the coating layer, the thickness of the coating layer is 1㎛ or more, and there are no other components within 0.5㎛ of the line scanning section.

[0076]

[0077] In the electrolysis electrode of the present invention, the D1 may be 0.4 µm or less, preferably 0.38 µm or less, 0.36 µm or less, 0.35 µm or less, 0.34 µm or less, 0.33 µm or less, 0.32 µm or less, 0.31 µm or less, 0.3 µm or less, 0.29 µm or less, or 0.28 µm or less, and may be 0.05 µm or more, 0.1 µm or more, 0.15 µm or more, 0.17 µm or more, 0.18 µm or more, 0.19 µm or more, 0.2 µm or more, 0.21 µm or more, 0.22 µm or more, or 0.23 µm or more.

[0078] In addition, in the electrolysis electrode of the present invention, the D2 may be 0.2 µm or more and 1.5 µm or less, and preferably 1.5 µm or less, 1.4 µm or less, 1.3 µm or less, 1.2 µm or less, 1.1 µm or less, 1 µm or less, 0.95 µm or less, or 0.9 µm or less, and may be 0.2 µm or more, 0.3 µm or more, 0.4 µm or more, 0.5 µm or more, 0.55 µm or more, 0.6 µm or more, 0.65 µm or more, or 0.7 µm or more.

[0079] Meanwhile, in the SEM-EDS line scanning analysis to obtain the above D1 and D2, when the metal substrate includes multiple elements, the reference metal element may be the metal element included in the largest amount among the multiple elements.

[0080]

[0081] The loading amount per unit area of ​​Co in the above catalyst layer is 0.1 g / m 2 Ideal and 10g / m 2 May be less than, preferably 0.1 g / m 2 Above, 0.5g / m 2 or more than 1g / m 2 Ideally, 10g / m 2 Below 8g / m 2 Below 6g / m 2 Below 5g / m 2 Less than or equal to 4g / m 2 It may be less than or equal to 0.1 g / m. In addition, the loading amount per unit area of ​​Fe in the catalyst layer is 0.1 g / m. 2 Ideal and 10g / m 2 May be less than, preferably 0.1 g / m 2 Above, 0.5g / m 2 or more than 1g / m 2 Ideally, 10g / m 2 Below 8g / m 2 Below 6g / m 2 Below 5g / m 2 Less than or equal to 4g / m 2It may be as follows. When the contents of Co and Fe in the catalyst layer satisfy the conditions described above, the catalytic activity can be maximized.

[0082]

[0083] The thickness of the catalyst layer may be 0.1 ㎛ or more and 10 ㎛ or less, and preferably 0.1 ㎛ or more, 0.5 ㎛ or more, or 1 ㎛ or more, and 10 ㎛ or less, 8 ㎛ or less, 6 ㎛ or less, 5 ㎛ or less, 4 ㎛ or less, 3 ㎛ or less, or 2 ㎛ or less. If the thickness of the catalyst layer is too thick, the efficiency compared to the cost of manufacturing the catalyst may decrease, and if the thickness of the catalyst layer is too thin, the improvement effect by the catalyst layer may be minimal.

[0084]

[0085] The above catalyst layer is Co x Fe y In addition to O4(0≤x≤4, 0≤y≤3), other catalytic components may be included, and more specifically, one or more active components selected from the group consisting of Mn, Zn, and Ni may be further included. The active components may be included in the form of oxides. When the active components are further included, the electrolysis performance can be maximized.

[0086]

[0087] The electrolysis electrode of the present invention may further include a noble metal catalyst layer formed on the catalyst layer. Specifically, the noble metal catalyst layer may include one or more noble metals selected from the group consisting of Ru, Ir, and Pt, or an oxide thereof. The noble metal catalyst layer can maximize the electrolysis performance.

[0088]

[0089] The metal substrate may be conductive, and more specifically, may include one or more metals selected from the group consisting of Ni, Fe, Co, and Ti, and it may be preferable to include Ni in terms of conductivity and durability. In addition, the substrate may have a pore-like form to maximize the contact area with the catalyst layer, and more specifically, may have a form such as a mesh or expanded metal.

[0090]

[0091] The water electrolysis electrode provided by the present invention may be an anode. An oxygen evolution reaction (OER) occurs at the anode during the water electrolysis process, and the water electrolysis electrode of the present invention can exhibit excellent activity for the oxygen evolution reaction.

[0092]

[0093] Method for manufacturing an electrode for water electrolysis

[0094] The present invention provides a method for manufacturing an electrode for water electrolysis as described above.

[0095]

[0096] More specifically, the present invention provides a method for manufacturing an electrode for electrolysis, comprising the steps of: preparing a coating composition containing a cobalt precursor and an iron precursor (S1); applying the coating composition to a metal substrate, drying it, and performing a first firing at a temperature of 200°C or higher and 450°C or lower (S2); and performing a second firing at a temperature higher than the temperature at which the first firing is performed (S3).

[0097]

[0098] The cobalt precursor included in the above coating composition may be at least one selected from the group consisting of Co(OAc)2, Co(NO3)2, CoCl2, Co(acac)2, Co(acac)3, CoCO3, and CoSO4. The iron precursor included in the above coating composition may be at least one selected from the group consisting of iron carboxylate, Fe(acac)3, Fe(OAc)2, Fe(NO3)3, FeCl3, FeCl2, and FeSO4. The cobalt and iron precursors listed above have the advantage of being well soluble in a solvent, thereby allowing a catalyst layer to be uniformly formed on a substrate.

[0099]

[0100] The above coating composition may include one or more solvents selected from the group consisting of water and alcohols, and preferably, the solvent may be water. The solvent components are those capable of dissolving the precursors and additives described above well. When the precursors and additives are uniformly dissolved in the solvent, the uniformity of the catalyst layer ultimately formed also increases, thereby improving durability.

[0101]

[0102] Meanwhile, the concentration of the cobalt precursor in the coating composition may be 0.1 M or more and 2.0 M or less, and preferably 0.2 M or more and 0.8 M or less. In addition, the concentration of the iron precursor in the coating composition may also be 0.1 M or more and 2.0 M or less, and preferably 0.2 M or more and 0.8 M or less.

[0103]

[0104] The coating composition prepared in the previous step can be applied to a substrate, and a catalyst layer can be formed by drying and firing. The substrate can be applied with the same content as described above for the water electrolysis electrode. Meanwhile, the substrate can be a pretreated substrate. The pretreatment is intended to increase the roughness of the substrate surface or remove impurities or oxide films on the substrate surface, and can be mechanical pretreatment or chemical pretreatment. For the mechanical pretreatment, a pretreatment method such as sandblasting can be used, and for the chemical pretreatment, a pretreatment method such as etching using acid can be used. When the substrate is pretreated using the above methods, the coating composition can adhere better to the substrate.

[0105]

[0106] Meanwhile, the drying in step S2 may include room temperature drying and high temperature drying. When the drying is performed separately as room temperature drying and high temperature drying, there may be a technical advantage in that instantaneous evaporation of the solvent can be suppressed, thereby producing a dense catalyst layer. Meanwhile, the room temperature drying may be performed at 10 to 50°C, preferably 20 to 40°C. In addition, the high temperature drying may be performed at a temperature of 50°C or higher and 100°C or lower, preferably 50°C or higher, or 55°C or higher and 100°C or lower, 90°C or lower, 80°C or lower, or 70°C or lower.

[0107] The first firing in the above S2 step may be performed at a temperature of 200°C or higher and 450°C or lower, and preferably 200°C or higher, 220°C or higher, 240°C or higher, 260°C or higher, or 280°C or higher, and 450°C or lower, 430°C or lower, 410°C or lower, 400°C or lower, 380°C or lower, 360°C or lower, 350°C or lower, 330°C or lower, or 320°C or lower.

[0108] When drying and primary calcination are performed within the above-described temperature, a composite oxide of cobalt and iron may be formed. If the temperature of the primary calcination is not appropriate, the crystal size may become larger than necessary, which may result in a deterioration in the water electrolysis performance of the electrode. In addition, the S2 step may be repeated 1 to 10 times, and preferably, it may be repeated 1 or more times, 2 or more times, or 3 or more times and 10 or less times, 7 or less times, or 5 or less times. By repeating the application, drying, and primary calcination of the coating composition, the catalyst content per unit area of ​​the water electrolysis electrode can be increased.

[0109]

[0110] Meanwhile, after completing the application, drying and primary firing of the coating composition, secondary firing can be finally performed. Through secondary firing performed at a higher temperature than the primary firing, Co x Fe y A crystal phase of O4(0≤x≤4, 0≤y≤3) can be formed, and the durability of the catalyst layer can be improved due to the presence of the crystal phase.

[0111] The above secondary calcination may be performed at a temperature of 500°C or higher and 700°C or lower, and preferably, it may be performed at a temperature of 500°C or higher, or 530°C or higher and 700°C or lower, or 650°C or lower, or 600°C or lower. If the secondary calcination temperature is too high, the catalyst component may be damaged due to excessive heat, and if the secondary calcination temperature is too low, the technical advantage of performing the secondary calcination may be small. The above secondary calcination may also be performed repeatedly, and more specifically, it may be performed repeatedly 2 to 10 times.

[0112]

[0113] Hereinafter, the present invention will be described in more detail with examples and experimental examples to specifically explain the present invention. However, the present invention is not limited to these examples and experimental examples. The examples according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those of average skill in the art.

[0114]

[0115] Example 1

[0116] A coating composition was prepared by mixing 3 mL of a 0.4 M Co(OAc)2 aqueous solution and 6 mL of a 0.4 M Fe(NO3)3 aqueous solution. The prepared coating composition was applied to an expanded nickel mesh substrate using a brush, dried at room temperature for 10 minutes, and then dried in an oven at 60°C for 10 minutes. After that, the composition was first fired at 300°C for 10 minutes using a kiln, and immediately after the firing was completed, it was taken out of the kiln and cooled in the air. This process of coating, drying, and first firing was repeated a total of 4 times, and finally, second firing at 550°C was performed twice to manufacture an electrode for water electrolysis.

[0117]

[0118] Example 2

[0119] An electrode for water electrolysis was manufactured in the same manner as in Example 1 above, except that the temperature of the first firing was set to 400°C.

[0120]

[0121] Example 3

[0122] An electrode for electrolysis was manufactured in the same manner as in Example 1 above, except that the number of coatings was changed to 8.

[0123]

[0124] Example 4

[0125] In the above Example 1, an electrode for water electrolysis was manufactured by performing the same procedure except that the total molar number of Co and Fe was maintained the same, but the molar ratio between Co and Fe was changed to Co:Fe = 1:9.

[0126]

[0127] Example 5

[0128] In the above Example 1, an electrode for water electrolysis was manufactured by performing the same procedure except that the total molar number of Co and Fe was maintained the same, but the molar ratio between Co and Fe was changed to Co:Fe = 1:1.

[0129]

[0130] Comparative Example 1

[0131] The expanded nickel mesh itself used in the above example was used as an electrode for water electrolysis.

[0132]

[0133] Comparative Example 2

[0134] In the above Example 1, a coating composition was prepared and used using 3 mL of a 0.4 M Co(NO3)2 aqueous solution as a cobalt precursor, and an electrode for water electrolysis was manufactured in the same manner as in Example 1, except that secondary calcination was not performed.

[0135]

[0136] Comparative Example 3

[0137] In the above Example 1, a coating composition was prepared and used using 3 mL of a 0.4 M Co(NO3)2 aqueous solution as a cobalt precursor, and an electrode for water electrolysis was manufactured in the same manner as in Example 1 except that the temperature of the first firing was 500°C and the second firing was not performed.

[0138]

[0139] Comparative Example 4

[0140] An electrode for electrolysis was manufactured in the same manner as in Example 1 above, except that secondary calcination was not performed.

[0141]

[0142] Comparative Example 5

[0143] An electrode for water electrolysis was manufactured in the same manner as in Example 1 above, except that the secondary firing was omitted and the primary firing temperature was set to 500°C.

[0144]

[0145] The calcination temperature and precursor type during the manufacturing process of the water electrolysis electrode manufactured in the above examples and comparative examples are summarized in Table 1 below.

[0146]

[0147] Cobalt precursorIron precursor1st calcination(℃)2nd calcination(℃)Coating timesCo:FeExample 1Co(OAc)2Fe(NO3)330055041:2Example 2Co(OAc)2Fe(NO3)340055041:2Example 3Co(OAc)2Fe(NO3)330055081:2Example 4Co(OAc)2Fe(NO3)330055041:9Example 5Co(OAc)2Fe(NO3)330055041:1Comparative example 1Catalyst layer XComparative example 2Co(NO3)2Fe(NO3)3300-41:2Comparative example 3Co(NO3)2Fe(NO3)3500-41:2Comparative example 4Co(OAc)2Fe(NO3)3300-41:2Comparative example 5Co(OAc)2Fe(NO3)3500-41:2

[0148] Experimental Example 1. SEM-EDS line scanning analysis of the manufactured water electrolysis electrode.

[0149] SEM-EDS line scanning analysis was performed on the electrolysis electrodes of Example 1 and Comparative Example 5. The specific analysis conditions are as follows.

[0150] 1) Preparation of the specimen: 1 x 1 cm electrode for electrolysis 2After cutting, fix the sample with a clip, and mount it using epoxy resin. After the epoxy resin has cured, observe the specimen after polishing.

[0151] 2) SEM equipment: Regulus 8220 FE-SEM (Hitachi)

[0152] 3) EDS line scanning conditions:

[0153] - Equipment name: Oxford Ultim

[0154] - Scan length: 3.5㎛

[0155] - Step size: 0.117㎛ (30 steps)

[0156] - Scan direction: Nickel substrate -> coating layer -> resin (holder)

[0157] - Acceleration voltage: 15kV

[0158] - Measurement distance: 15mm

[0159] - Measurement time: 3 minutes

[0160] - Elements analyzed: C, O, Ni, Co, Fe

[0161] - Line setting conditions: The line was set as an area where there was no gap between the substrate and the coating layer, the coating layer had a thickness of 1㎛ or more, and no other components were present within 0.5㎛ of the line scanning section. Line scanning was performed to measure the substrate at least 0.5㎛ and the epoxy resin at least 0.5㎛ together to ensure that the coating layers were clearly distinguished.

[0162] The element distribution graphs obtained for each of Example 1, Example 2, and Comparative Example 5 through the above process are shown in Figures 1, 2, and 3, respectively, and the x-axis values ​​of points where the content of nickel, an element of the metal substrate, is 10 wt%, 30 wt%, 70 wt%, and 90 wt%, respectively, and the distances therebetween (unit: ㎛) are summarized in Table 2 below.

[0163] 10 wt%30 wt%70 wt%90 wt%D1D2D1 / D2Example 11.8641.4091.1330.9780.2760.8860.311Example 21.6261.3111.0770.8940.2340.7300.320Comparative Example 52.2231.9051.5431.1020.3621.1210.323

[0164] In summary of the results of FIGS. 1 to 3 and the results of Table 2 above, in the case of the electrode of Comparative Example 5 manufactured through only a single firing at a relatively high temperature of 500°C, the D1 / D2 value is outside the range of the present invention as nickel, which is a metal substrate element, diffuses into the catalyst layer in a relatively large amount, whereas the electrolysis electrodes of Examples 1 and 2 manufactured through two-stage firing at low and high temperatures have low D1 / D2 values ​​due to minimized nickel diffusion. This difference in D1 / D2 values ​​affects the performance and durability of the electrolysis electrode, as will be described later.

[0165]

[0166] Experimental Example 2. Analysis of the crystal structure within the manufactured water electrolysis electrode catalyst layer.

[0167] The crystal structures within the catalyst layers of the above-mentioned manufactured Examples 1, Comparative Examples 2, and 4 were analyzed by XRD. More specifically, measurements were performed using a Bruker D8 Endeavor device, with the samples fixed on a glass plate and measured in the range of 10 to 90° based on 2 theta. The results are shown in Fig. 4.

[0168] As confirmed through Fig. 4, the crystal phase of CoFe2O4 was confirmed only in the electrode catalyst layer of Example 1, which means that the crystal phase was formed through the secondary calcination at 550°C. More specifically, the crystal phase of CoFe2O4 can be confirmed from the presence of peaks appearing in the region indicated by the vertical solid line in Fig. 2, and only Example 1 exhibited peaks in the region of 2θ = 18.5°, 31.3°, 35.6°, 36.9°, 43.2°, 53.6°, 57.0°, and 62.6°. From the above results, it was confirmed that a secondary calcination process performed after the primary calcination is absolutely necessary in order to manufacture an electrode for water electrolysis including the crystal phase of the present invention.

[0169]

[0170] Experimental Example 3. Cross-sectional observation of a water electrolysis electrode

[0171] The cross-sections of the electrolysis electrode manufactured in Example 1 and the electrolysis electrode manufactured in Comparative Example 2 were observed. Specifically, electrode specimens were manufactured using a focused ion beam device (TFS HELIOS 5UX) and the cross-sections were observed. The results of Example 1 are shown in Figs. 5 and 6, and the results of Comparative Example 2 are shown in Figs. 7 and 8.

[0172] In Figs. 5 and 6, it can be confirmed that the bonding of each layer structure has been achieved, whereas in Figs. 7 and 8, it can be seen that the layer structures have been formed but that the bonding between them has not been completely achieved. From this, it can be seen that by going through the secondary firing process, the bonding force between the catalyst layer and the substrate is improved, thereby improving the durability of the electrode.

[0173]

[0174] Experimental Example 4. Performance and Durability Evaluation Results of Electrodes for Water Electrolysis

[0175] Performance evaluations were performed using the electrolysis electrodes of Examples 1 to 5 and the electrolysis electrodes of Comparative Examples 1 to 5. First, a full cell was configured using the electrolysis electrodes of Examples and Comparative Examples as the anode, a Ru-based noble metal electrode as the cathode, a 30 wt% KOH aqueous solution as the electrolyte, and zirfon 500 as the separator, and the voltage under specific current conditions at a temperature of 80°C was measured.

[0176] The results are summarized in Table 3 below.

[0177] Voltage (V @ 6kA / m) 2 )Example 11.78Example 21.78Example 31.82Example 41.80Example 51.84Comparative Example 11.84Comparative Example 21.78Comparative Example 31.95Comparative Example 41.76Comparative Example 51.87

[0178] The above results show that the electrolysis electrode of the present invention exhibits low overvoltage and excellent performance. On the other hand, in the case of Comparative Example 3, although a catalyst layer was formed, the first calcination was performed at a high temperature. In the case of calcination at such a high temperature, the performance was lower than that of Comparative Example 1, which used only the nickel substrate itself as the electrolysis electrode. Accordingly, it was confirmed that the temperature conditions of the first calcination affect the performance of the electrolysis electrode that is ultimately manufactured.

[0179] In addition, accelerated degradation evaluation was performed using the electrolysis electrodes of Examples 1 to 5 and the electrolysis electrodes of Comparative Examples 1 to 5. Specifically, a three-electrode cell was constructed in which the working electrode was composed of the electrode of the Example or Comparative Example, the counter electrode was composed of nickel, and the reference electrode was composed of Hg / HgO, and then the evaluation was performed under the following conditions.

[0180] 1) Durability evaluation conditions

[0181] Cyclic Voltammetry range: 0.5 to 1.8 V RHE

[0182] Scan Rate: 1 V / s

[0183] Number of cycles: 40,000

[0184] 2) Performance measurement conditions

[0185] Cyclic Voltammetry range: 0.5 to 1.8 V RHE

[0186] Scan Rate: 5 mV / s

[0187] Number of Cycles: 5

[0188] The results are shown in Figure 9.

[0189]

[0190] As can be seen from Figure 9, the electrolysis electrodes of Comparative Examples 2 and 4 showed a decrease in performance as the cycle progressed, which means that the electrolysis electrodes of Comparative Examples 2 and 4 had low durability.

[0191] Meanwhile, the electrodes of Comparative Examples 3 and 5 were confirmed to have high durability, but their performance was confirmed to be poor due to high overvoltage. On the other hand, the water electrolysis electrodes of Examples 1 to 5 of the present invention were confirmed to have excellent durability and relatively low overvoltage, and thus to be able to maintain excellent performance for a long period of time.

Claims

1. Metal substrate; and A catalyst layer formed on at least one surface of the metal substrate; The above catalyst layer is Co x Fe y Includes O4(0≤x≤4, 0≤y≤3), An electrode for electrolysis characterized by satisfying the following equation 1: [Formula 1] D1 / D2 ≤ 0.321 In the above equation 1, The above D1 means the distance between the point where the content of the metal element of the above-mentioned substrate is 70 wt% and the point where the content is 30 wt% in the element distribution graph obtained through SEM-EDS line scanning analysis of the electrolysis electrode, The above D2 refers to the distance between the point where the content of the metal element of the above-mentioned substrate is 90 wt% and the point where it is 10 wt%.

2. In paragraph 1, The above x:y is an electrode for electrolysis in a ratio of 1:1 to 1:

9.

3. In paragraph 1, An electrode for water electrolysis, wherein the catalyst layer comprises a crystal phase.

4. In paragraph 1, An electrode for water electrolysis, wherein the catalyst layer has a peak in at least one region among a region having a 2θ value of 17.5° to 19.5°, a region having a 2θ value of 30.5° to 32°, a region having a 2θ value of 35° to 36°, a region having a 2θ value of 36° to 37.5°, a region having a 2θ value of 42° to 44°, a region having a 2θ value of 52.5° to 54.5°, a region having a 2θ value of 56° to 58°, and a region having a 2θ value of 61.5° to 63.5° in a graph obtained through XRD analysis.

5. In paragraph 1, The above D1 is an electrode for electrolysis of 0.40㎛ or less.

6. In paragraph 1, The above D2 is an electrode for water electrolysis having a size of 0.2㎛ or more and 1.5㎛ or less.

7. In paragraph 1, An electrode for water electrolysis, wherein the metal substrate comprises at least one metal selected from the group consisting of Ni, Fe, Co, and Ti.

8. In paragraph 1, The above-mentioned electrolysis electrode is an anode.

9. Step (S1) of preparing a coating composition containing a cobalt precursor and an iron precursor; Step (S2) of applying the coating composition to a metal substrate, drying it, and performing a first firing at a temperature of 200°C or higher and 450°C or lower; and A method for manufacturing an electrode for electrolysis, comprising a step (S3) of performing a second firing at a temperature higher than the temperature at which the first firing is performed.

10. In paragraph 9, A method for manufacturing an electrode for water electrolysis, wherein the cobalt precursor is at least one selected from the group consisting of Co(OAc)2, Co(NO3)2, CoCl2, Co(acac)2, Co(acac)3, CoCO3, and CoSO4.

11. In paragraph 9, A method for manufacturing an electrode for water electrolysis, wherein the iron precursor is at least one selected from the group consisting of iron carbonate, Fe(acac)3, Fe(OAc)2, Fe(NO3)3, FeCl3, FeCl2 and FeSO4.

12. In paragraph 9, A method for manufacturing an electrode for electrolysis of water, wherein the coating composition comprises at least one solvent selected from the group consisting of water and alcohol.

13. In paragraph 9, The above drying includes room temperature drying and high temperature drying, A method for manufacturing an electrode for electrolysis, wherein the above high-temperature drying is performed at a temperature of 50°C or higher and 100°C or lower.

14. In paragraph 9, A method for manufacturing an electrode for electrolysis, wherein the above secondary firing is performed at a temperature of 500°C or higher and 700°C or lower.

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