Electrocatalyst, oxygen generating electrode, and method for electrolyzing water

Abstract

To provide an electrode catalyst that is less likely to cause an increase in overvoltage during water electrolysis and can stably operate for an extended period of time even at high current densities, and also to provide an oxygen generating electrode equipped with the electrode catalyst and a water electrolysis method.SOLUTION: An electrode catalyst according to the present invention is an electrode catalyst with a catalyst on an electrode substrate, the catalyst containing a sulfide that contains nickel and iron as constituent elements. An oxygen generating electrode according to the present invention includes the electrode catalyst. A water electrolysis method according to the present invention includes a step of using the oxygen generating electrode to electrolyze water. The electrode catalyst according to the present invention, when used as an electrode for water electrolysis, is less likely to cause an increase in overvoltage during water electrolysis and can stably operate for an extended period of time even at high current densities.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrode catalyst, an oxygen generating electrode including the electrode catalyst, and a method for electrolyzing water. [Background technology]

[0002] Water electrolysis (the electrolysis of water) is a promising method for producing hydrogen from water using renewable energy electricity, as it aims to solve environmental and energy resource problems. Because hydrogen production methods using water electrolysis use electricity, it is necessary to reduce production costs, and from this perspective, various water electrolysis technologies are being developed. Among these, alkaline water electrolysis and polymer electrolyte membrane (PEM) water electrolysis are at the practical stage. PEM water electrolysis has a high current density, making it possible to reduce the size of the system compared to alkaline water electrolysis.

[0003] On the other hand, alkaline water electrolysis can achieve low costs because it has a simple structure and can use inexpensive materials. In water electrolysis, the overvoltage of the oxygen evolution reaction at the positive electrode is larger than that of the hydrogen evolution reaction at the negative electrode, which determines the rate of the entire water electrolysis reaction. Therefore, there is a need to develop a highly active catalyst for the positive electrode. For example, Patent Document 1 proposes an electrode catalyst that uses rare metals such as ruthenium and iridium hydroxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-95618 Summary of the Invention [Problem to be solved by the invention]

[0005] However, electrodes using rare metals, as in the technology described in Patent Document 1, are very expensive. In this regard, it is conceivable to use catalysts containing inexpensive metals in electrodes. However, such catalysts tend to become unstable at high current densities during electrolysis, cause an increase in overvoltage, and are prone to poor durability, posing a problem in terms of long-term operation. From this perspective, there has been a strong demand for the development of an electrode catalyst that is less likely to cause an increase in overvoltage during water electrolysis and that can be operated stably for long periods even at high current densities, even when formed from inexpensive metals.

[0006] The present invention has been made in view of the above, and aims to provide an electrode catalyst that is less likely to cause an increase in overvoltage during water electrolysis and that can be operated stably for a long period of time even at a high current density, an oxygen generating electrode including the electrode catalyst, and a method for electrolyzing water. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the inventors have discovered that the above object can be achieved by forming a catalyst from a sulfide containing nickel and iron as constituent elements, and have thus completed the present invention.

[0008] That is, the present invention includes, for example, the subject matter described in the following sections. Item 1 An electrode catalyst comprising a catalyst on an electrode substrate, The catalyst is an electrode catalyst containing a sulfide containing nickel and iron as constituent elements. Section 2 Item 2. The electrode catalyst according to item 1, wherein the catalyst is formed in a sheet shape on the electrode substrate. Section 3 Item 3. The electrode catalyst according to Item 1 or 2, wherein the electrode substrate is a nickel substrate. Section 4 An oxygen generating electrode comprising the electrode catalyst according to any one of items 1 to 3. Section 5 Item 5. A method for electrolyzing water, comprising the step of electrolyzing water using the oxygen generating electrode according to item 4. [Effects of the Invention]

[0009] When the electrode catalyst according to the present invention is used as an electrode for water electrolysis, an increase in overvoltage during water electrolysis is unlikely to occur, and the electrode catalyst can be operated stably for a long period of time even at a high current density. [Brief explanation of the drawings]

[0010] [Figure 1] (a) is a precursor obtained in Comparative Example 2, (b) is an SEM image of the electrode catalyst obtained in Comparative Example 3, (c) is an SEM image of the electrode catalyst obtained in Example 1, and (d) to (g) are EDX element mapping images of the electrode catalyst obtained in Example 1. [Figure 2] (a) shows the results of linear sweep voltammetry measurements, (b) shows the Tafel slope calculated from the linear sweep voltammetry curve shown in (a), and (c) shows the results of electrochemical impedance (EIS) measurements. [Figure 3] (a) shows the multi-current step chronopotentiometry curve, (b) shows the linear sweep voltammetry measurement results after 2000 cycles of testing, and (c) shows the results of a long-term operation test. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0012] 1.Electrode catalyst The electrode catalyst of the present invention comprises a catalyst on an electrode substrate, and the catalyst contains a sulfide containing nickel and iron as constituent elements. Such an electrode catalyst can be suitably used as an electrode for water electrolysis, particularly as an oxygen generating electrode. In particular, when the electrode catalyst of the present invention is used as an electrode for water electrolysis, an increase in overvoltage during water electrolysis is unlikely to occur, and stable operation for a long period of time is possible even at a high current density.

[0013] The type of electrode substrate is not particularly limited, and for example, a wide variety of known conductive substrates can be used. Examples of electrode substrates include substrates used as electrodes for water electrolysis, and specific examples include metal substrates, carbon substrates, and glass substrates.

[0014] Examples of metal substrates include substrates of simple metals such as nickel, titanium, iron, and copper, substrates of nickel-phosphorus alloys, nickel-tungsten alloys, and stainless steel alloys, and various metal foams (e.g., nickel foam and copper foam). Of these, nickel foam is preferred as the metal substrate. In this case, the catalyst can be formed from nickel derived from the substrate.

[0015] Examples of carbon substrates include carbon paper, carbon fiber paper, and carbon rods. Examples of glass substrates include conductive glass. The electrode substrate may be a porous material such as foam.

[0016] The electrode substrate is more preferably a metal substrate, more preferably a nickel substrate, and most preferably nickel foam.

[0017] The electrode substrate can be obtained, for example, by a known manufacturing method, or can be obtained from a commercial product. The shape and size of the electrode substrate are not particularly limited and can be appropriately selected depending on the intended use and required performance. For example, the shape of the electrode substrate can be foam, sheet, plate, rod, mesh, etc., and a foam shape is preferred.

[0018] In the electrode catalyst of the present invention, the catalyst is formed on an electrode substrate as described above. The catalyst contains a sulfide containing nickel and iron as constituent elements. In the sulfide, Ni is, for example, divalent, and Fe is divalent or trivalent.

[0019] The sulfide may be, for example, a compound represented by the following general formula (1): Nia Fe b S x It is a compound represented by the formula:

[0020] Here, 0.01≦a≦9.0, 0≦b≦8, and 0≦x≦8. For example, when a=1, b is preferably 0.1 to 6, more preferably 0.5 to 4, even more preferably 0.7 to 2, and particularly preferably 0.9 to 1.5. Furthermore, when a=1, x is preferably 0.1 to 7, more preferably 0.5 to 6.5, even more preferably 1 to 6, and particularly preferably 2 to 5.

[0021] The sulfide is a composite compound containing Ni, Fe, and S as constituent elements, but may also contain other elements or atomic groups. Examples of other elements or atomic groups include oxygen, hydroxide (OH - ) and oxyhydroxide (OOH).

[0022] The sulfide can be formed only from Ni, Fe, and S, or can be formed only from Ni, Fe, S, and O (oxygen). When the sulfide contains other elements such as oxygen, the content thereof can be 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, based on the total mass of the sulfide.

[0023] The catalyst may contain other elements and / or other compounds in addition to the sulfides. Examples of other elements include oxygen, and examples of other compounds (compounds other than the sulfides) include oxides, hydroxides, etc.

[0024] When the catalyst contains other elements or compounds in addition to the sulfide, the content of these elements or compounds can be 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, based on the total mass of the catalyst. The catalyst may be formed solely from the sulfide. However, in this case, metal elements or compounds inevitably contained in the catalyst are acceptable.

[0025] The catalyst is not particularly limited in terms of the content of Ni, Fe, and S. For example, the catalyst may contain Ni in an amount of 0.0001 to 10 mol%. The catalyst may contain Fe in an amount of 0.0001 to 90 mol%, preferably 0.1 to 80 mol%, and more preferably 1 to 60 mol%. The catalyst may contain S in an amount of 0.0001 to 90 mol%, preferably 0.1 to 80 mol%, and more preferably 1 to 60 mol%.

[0026] In the electrode catalyst, when the electrode substrate is a nickel substrate (e.g., nickel foam), Ni in the sulfide contained in the catalyst can be based on the nickel of the electrode substrate. That is, Ni, Fe, and S of the nickel substrate can react to form the sulfide serving as the catalyst.

[0027] The shape of the catalyst is not particularly limited, and can be, for example, the same shape as that of a catalyst in a known electrode catalyst. For example, the electrode catalyst of the present invention can be formed in the form of a sheet (e.g., 0.1 to 500 μm) on an electrode substrate. In this case, the catalyst is preferably in the form of a nanosheet. When the catalyst is formed in the form of a nanosheet, its thickness is 200 to 500 nm. When the catalyst is formed in the form of a sheet, such a sheet can have a porous structure. Furthermore, the sheet can have not only a single layer but also a laminated structure.

[0028] The catalyst can cover part or all of the electrode substrate, and is preferably disposed in the outermost layer of the electrode catalyst.

[0029] The electrode catalyst of the present invention may be formed only from the electrode substrate and the catalyst, or may be combined with other materials as long as the effects of the present invention are not impaired. For example, the electrode catalyst may be formed directly on the electrode substrate (without any other layer or the like).

[0030] The electrode catalyst of the present invention, which includes the sulfide-containing catalyst, can be suitably used as an electrode for water electrolysis, particularly as an oxygen generating electrode. In particular, when used as an electrode for water electrolysis, the electrode catalyst of the present invention is less likely to cause an increase in overvoltage during water electrolysis, can reduce the Tafel slope, and can operate stably for a long period of time even at a high current density.

[0031] Therefore, the electrode catalyst of the present invention is suitable for use in electrodes for various electrolysis, and in particular, when used as an electrode for water electrolysis, it can provide excellent oxygen generation efficiency, and is therefore suitable as an electrode for oxygen generation (oxygen generating electrode).

[0032] 2. Manufacturing method of electrode catalyst The electrode catalyst of the present invention can be produced by various methods, and is not particularly limited. For example, the method comprises at least the following steps 1 and 2. Step 1: A step of immersing an electrode substrate in a raw material liquid and heat-treating it to obtain a precursor. Step 2: A step of sulfurizing the precursor obtained in step 1 to obtain an electrode catalyst.

[0033] (Process 1) In step 1, the electrode substrate is immersed in a raw material solution and subjected to a heat treatment. By this heat treatment, a precursor of the electrode catalyst is obtained.

[0034] The type of electrode substrate used in step 1 is not particularly limited and is the same as the electrode substrate used in the above-mentioned electrode catalyst. Therefore, examples of the electrode substrate used in step 1 include a metal substrate, a carbon substrate, a glass substrate, etc., and is preferably a metal substrate, more preferably a nickel substrate, and particularly preferably nickel foam.

[0035] The raw material solution used in step 1 contains at least an Fe source. When the electrode substrate used in step 1 is a nickel substrate, the raw material solution does not need to contain a Ni source. However, when the electrode substrate used in step 1 is a substrate other than a nickel substrate or a substrate that does not contain nickel, the raw material solution must contain a Ni source in addition to an Fe source.

[0036] Examples of the Fe source include elemental Fe and compounds containing Fe, and Fe-containing compounds are preferred. Examples of Fe-containing compounds that can be widely used include inorganic acid salts of Fe, organic acid salts of Fe, hydroxides of Fe, and halides of Fe.

[0037] A wide variety of known compounds can be used as inorganic acid salts of Fe, including, for example, one or more selected from the group consisting of Fe nitrates, hydrochlorides, sulfates, carbonates, hydrogencarbonates, phosphates, hydrogenphosphates, etc. A wide variety of known compounds can be used as organic acid salts of Fe, including, for example, one or more selected from the group consisting of Fe acetates, oxalates, formates, succinates, etc.

[0038] The Fe source is preferably a halide of Fe, such as FeCl. One Fe source may be used alone, or two or more Fe sources may be used in combination. The Fe-containing compound may be obtained by a known production method, or a commercially available Fe-containing compound may be used.

[0039] When the raw material solution contains a Ni source, examples of the Ni source include elemental Ni or a compound containing Ni. Examples of compounds containing Ni that can be used include inorganic acid salts of Ni, organic acid salts of Ni, Ni hydroxides, and Ni halides. The types of inorganic acid salts and organic acid salts are the same as those of inorganic acid salts and organic acid salts of Fe.

[0040] The raw material liquid contains a solvent. The solvent is, for example, water, and may also contain a lower alcohol compound. The solvent may be water alone.

[0041] The raw material solution may contain other additives, such as a pH adjuster. The type of pH adjuster is not particularly limited, and a wide range of known pH adjusters can be used. An example of a pH adjuster is NaNO3. When the raw material solution contains a pH adjuster, the pH value at the time of hydrolysis of ferric iron can be lowered. In addition, when a nickel substrate such as nickel foam is used as an electrode substrate, the pH value can be lowered. 2+ It can act as an etchant to generate ions.

[0042] The raw material liquid is, for example, a solution or a dispersion, preferably a solution, and more preferably an aqueous solution.

[0043] The concentration of the raw material solution is not particularly limited, and the total concentration of the Fe source and the Ni source contained as needed is preferably 1 to 200 mmol, more preferably 5 to 150 mmol, and even more preferably 10 to 100 mmol per 100 mL of solvent. When the raw material solution contains a pH adjuster, the concentration of the pH adjuster is preferably 1 to 200 mmol, more preferably 5 to 150 mmol, and even more preferably 10 to 100 mmol per 100 mL of solvent.

[0044] The heat treatment method in step 1 can be, for example, a so-called hydrothermal synthesis method in which the electrode substrate is immersed in the raw material solution in a container, the container is sealed, and the container is heated. This hydrothermal synthesis method causes a reaction such as hydrolysis, and a hydrothermal reaction product is formed on the electrode substrate. Such a hydrothermal reaction product is, for example, a double hydroxide of Ni and Fe.

[0045] When the electrode base material is a nickel base material, the nickel in the nickel base material is involved in the reaction by the heat treatment (hydrothermal synthesis), and a double hydroxide of Ni derived from the nickel base material and Fe derived from the Fe source contained in the raw material liquid is produced on the electrode base material.

[0046] In step 1, the temperature inside the container during the heat treatment is not particularly limited and can be, for example, 50 to 250°C, preferably 70 to 200°C, more preferably 80 to 180°C, and even more preferably 90 to 150°C. The heating time is also not particularly limited and can be determined appropriately depending on the heating temperature, for example, 30 minutes to 5 hours. The pressure inside the container during the heat treatment can also be set appropriately.

[0047] A precursor of the electrode catalyst is obtained by the heat treatment (hydrothermal synthesis) in step 1. This precursor is formed by forming a double hydroxide containing Ni and Fe on an electrode substrate.

[0048] (Process 2) In step 2, the precursor obtained in step 1 is sulfurized to obtain the target electrode catalyst. The method of sulfurization is not particularly limited, and for example, any known sulfurization method can be widely used.

[0049] A sulfurizing agent can be used for the sulfurization treatment. A wide variety of known compounds capable of sulfurization can be used as the sulfurizing agent, including sodium sulfide (NaS), sulfur, thioacetamide (CHCSNH), thiourea, sodium thiosulfate, and ammonium sulfide.

[0050] The sulfurizing agent can be used, for example, in the form of a solution, particularly in the form of an aqueous solution. The concentration of the sulfurizing agent solution is not particularly limited, and for example, an aqueous sulfurizing agent solution having a concentration of 0.1 to 1 M can be used. Furthermore, the sulfurizing agent solution may contain a pH adjuster such as urea, if necessary. When urea is used, the sulfurization reaction can be accelerated. Furthermore, when the sulfurizing agent is used, the sulfurization reaction can be accelerated by the following formulas (a), (b), and (c), CO(NH2)2 + H2O → 2NH3 + CO2(a) NH3+H2O → NH 4+ +OH - (b) CO2+H2O → 2H + +CO3 2- (c) As shown, the Ksp (solubility constant) of sulfide is - ) and carbonate (CO3 2- ), so the precursor is S 2- can be replaced by

[0051] The method of sulfurization treatment in step 2 is not particularly limited, and an example thereof is a method in which the precursor obtained in step 1 is immersed in a solution (aqueous solution) containing a sulfurizing agent.

[0052] When the precursor is immersed in the solution, the temperature of the solution is not particularly limited and is, for example, 10 to 100° C., preferably 15 to 80° C., and more preferably 20 to 50° C. When the precursor is immersed in the solution, the immersion time can be, for example, 30 minutes to 1 hour.

[0053] The sulfurization treatment causes sulfurization of the double hydroxide in the precursor to form a sulfide, thereby obtaining the electrode catalyst of the present invention.

[0054] The electrode catalyst of the present invention can be obtained, for example, by a production method including the above steps 1 and 2, that is, it can be produced by a simple method.

[0055] 3. Oxygen Evolving Electrode The electrode catalyst of the present invention is suitable as an oxygen generating electrode. The oxygen generating electrode may be composed of, for example, only the electrode catalyst of the present invention, or may be formed by combining the electrode catalyst of the present invention with other components as necessary.

[0056] Since the oxygen generating electrode comprises the electrode catalyst of the present invention, an increase in overvoltage during water electrolysis can be suppressed, water electrolysis can be performed stably, and oxygen can be generated efficiently. Furthermore, since the oxygen generating electrode comprises the electrode catalyst of the present invention, water electrolysis can also be performed stably for a long period of time.

[0057] 4.Water electrolysis method The method for electrolyzing water of the present invention may include, for example, a step of electrolyzing water using the oxygen generating electrode. By such a method for electrolyzing water, oxygen or hydrogen can be produced.

[0058] In the water electrolysis method, the oxygen generating electrode is used as an anode.

[0059] On the other hand, in the water electrolysis method of the present invention, an electrode generally used as a cathode in water electrolysis can be used as the cathode. For example, a carbon rod or a platinum wire can be used, and the electrode catalyst of the present invention can also be used as the cathode.

[0060] In the water electrolysis method of the present invention, the aqueous solution used in the electrolysis can be an aqueous solution containing components commonly used in water electrolysis. The aqueous solution can also contain halogens such as iodine and bromine, sulfate ions, etc. When an aqueous solution containing iodine is used, iodate ions are generated at the anode. The aqueous solution may be in the acidic, neutral, or alkaline range. For example, in the alkaline range, aqueous solutions of KOH, NaOH, etc. can be used; in the acidic range, aqueous solutions of hydrochloric acid, sulfuric acid, etc. can be used; and in the neutral range, PBS (phosphate buffered saline), etc. can be used. [Example]

[0061] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] Example 1 The size is 2 x 2 cm 2The nickel foam (nickel foam) was treated with 1M hydrochloric acid, ethanol, and deionized water, successively, under ultrasonic conditions for 1 hour, and then dried in a vacuum oven at 60°C for 1 hour to pretreat the electrode substrate. This nickel foam was immersed in a raw material solution of 50 ml of aqueous solution (distilled water) containing 0.5 mmol of FeCl3 (hexahydrate) and 2.5 mmol of NaNO3, and heated at 100°C for 2 hours (Step 1). This heat-treated nickel foam was obtained as a precursor. The precursor surface was gold in color.

[0063] The precursor was washed three times each with distilled water and ethanol, and then dried in a vacuum oven at 60°C for 12 hours. The dried precursor was sulfurized by immersing it in a solution containing 1 g of NaS and 10 mmol of urea at 25°C for one hour. The electrode catalyst obtained by this sulfurization treatment was dried in a vacuum oven at 60°C for 12 hours. The obtained electrode catalyst was black in color.

[0064] (Comparative Example 1) The nickel foam used in Example 1 was prepared without any treatment.

[0065] (Comparative Example 2) A precursor was prepared without carrying out the sulfurization treatment of Example 1.

[0066] (Comparative Example 3) The size is 2 x 2 cm 2 The electrode substrate was pretreated by treating the nickel foam (nickel foam) with 1M hydrochloric acid, ethanol, and deionized water, successively, under ultrasonic conditions for 1 hour, and then drying in a vacuum oven at 60°C for 1 hour. This nickel foam was then sulfurized by immersing it in a solution containing 1g of NaS and 10mmol of urea at 25°C for 1 hour. The electrode catalyst obtained by this sulfurization treatment was then dried in a vacuum oven at 60°C for 12 hours.

[0067] Figure 1 shows an SEM image and an EDX elemental mapping image of the surface of the electrode catalyst obtained in Example 1, along with SEM images of each substrate prepared in the comparative examples. Specifically, in Figure 1, (a) is an SEM image of the precursor obtained in Comparative Example 2, (b) is an SEM image of the electrode catalyst obtained in Comparative Example 3, and (c) is an SEM image of the electrode catalyst obtained in Example 1. Figures 1(d) to (g) are EDX elemental mapping images of the electrode catalyst obtained in Example 1, showing the distribution of Ni, Fe, S, and O elements, respectively.

[0068] From the SEM image in Figure 1, it can be seen that the electrode catalyst obtained in Example 1 has a nanosheet-like catalyst formed on the electrode substrate as a porous structure, and that the catalyst is uniformly formed on the electrode substrate. Furthermore, the mapping image shows that each element is uniformly present throughout the catalyst, indicating that the catalyst formed on the electrode substrate is a sulfide containing nickel and iron as constituent elements, and further confirming the presence of oxygen. In Comparative Example 2, it was confirmed that nanosheets of Ni and Fe double hydroxide (NiFe-OH) had grown uniformly, but in Comparative Example 3 (nickel sulfide foam), there was no nanosheet state on the nickel foam substrate. From these results, it can be seen that S 2- and OH - It is presumed that the catalyst in the electrode catalyst obtained in Example 1 retains the original form of NiFe—OH due to an effective ion exchange reaction between the catalyst and the NiFe—OH.

[0069] Figure 2(a) shows the results of linear sweep voltammetry measurements using the electrode catalysts obtained in Example 1 and each comparative example. In this measurement, an oxygen evolution (OER) test was performed using the electrode catalysts prepared in Example 1 and each comparative example as the cathode, a carbon rod as the anode, and an Ag / AgCl electrode as the reference electrode. The electrolyte used was a 1 M KOH aqueous solution (pH = 14). In this example, a VersaSTAT4 potentiostat galvanostat electrochemical workstation (USA) was used with a standard three-electrode cell to evaluate electrical characteristics such as linear sweep voltammetry curves.

[0070] Figure 2(b) shows the Tafel slope calculated from the linear sweep voltammetry curve shown in (a). Figure 2(c) shows the electrochemical impedance (EIS) measurement results for the electrode catalysts obtained in Example 1 and each comparative example. The measurements were performed in a 1 M KOH solution by electrochemical impedance spectroscopy (EIS) using a three-electrode electrochemical measurement device. The measurement frequency range was 0.01 Hz to 0.1 MHz, and the measurement voltage was -0.35 V vs. Ag / AgCl. The electrode / electrolyte interfacial resistance can be determined from Figure 2(c).

[0071] Table 1 shows the 10 mA cm of each electrode catalyst derived based on the results of Figures 2(a), (b), and (c). -2 and 100mAcm -2 Overpotential, Tafel slope and charge transfer resistance (R ct ) results are shown.

[0072] [Table 1]

[0073] From the above results, it can be seen that the electrode catalyst obtained in Example 1 can be used at a high current density (100 mAcm -2 ), the overpotential was low, the Tafel slope showed the best performance, and the charge transfer resistance was also the smallest. Therefore, the electrode catalyst obtained in Example 1 can be said to exhibit a good catalytic reaction rate and to be advantageous in improving electronic conductivity.

[0074] FIG. 3(a) shows a multi-current step chronopotentiometry curve when the electrode catalyst obtained in Example 1 was used as the anode, and shows the results at a current density of 10 mA / cm 2 ~400mA / cm 2 Up to 50mA / cm 2 Measurements were taken at intervals (the electrolyte was a 1M KOH solution), and finally at 10 mA / cm 2Figure 3(b) shows the potential-time graph obtained by returning the sample to 100 mA / cm. Figure 3(c) shows the linear sweep voltammetry measurement results after 2000 cycles. 2 The results are shown for a period of 100 hours at a current density of 1 M KOH, after which the solution was replaced with a new 1 M KOH solution and electrolysis continued. The measurement conditions were the same as those used to obtain the linear sweep voltammetry curves, and the measurement was performed using a VersaSTAT4 potentiostat galvanostat electrochemical workstation (USA) together with a two-electrode cell.

[0075] From the results in Figure 3, the electrode catalyst obtained in this example exhibited excellent stability for 100 hours without catalyst dissolution (peel-off), and was able to withstand high current densities (100 mA / cm 2 ) showed no significant change in potential. Furthermore, even after 2000 cycles of cyclic voltammetry in an alkaline medium solution, the LSV curve showed almost no change. Therefore, it was demonstrated that the electrode catalyst obtained in Example 1 can be operated stably for a long period of time even at high current densities, and is suitable for an oxygen generating electrode capable of efficient water electrolysis.

Claims

1. A method for producing an electrode catalyst comprising a catalyst on a nickel substrate, the method comprising: The method comprises: Step 1: immersing a nickel substrate in a raw material solution containing an Fe source and heat-treating the nickel substrate to obtain a precursor; and Step 2: sulfiding the precursor obtained in Step 1 at 15 to 80°C in the presence of a pH adjuster to obtain an electrode catalyst; The catalyst contains a sulfide containing nickel and iron as constituent elements, and further contains oxygen.

2. A method for manufacturing an electrode catalyst as described in claim 1, wherein the catalyst is formed in a sheet form on the nickel substrate.

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