Methods for preparing catalyst powder for electrolysis of aqueous ammonia and for preparing catalyst electrode for electrolysis of aqueous ammonia

Abstract

The present invention relates to a method for preparing catalyst powder for electrolysis of aqueous ammonia, comprising the steps of: (A) immersing a metal foam support as a working electrode in an electrolyte solution containing a precursor of an active metal; (B) forming active metal crystal particles on the metal foam support by applying cyclic voltage and current, to form a metal foam-catalyst composite; and (C) physically pulverizing the metal foam-catalyst composite to form metal foam-catalyst composite powder.

Description

Method for manufacturing ammonia water electrolysis catalyst powder and ammonia water electrolysis catalyst electrode

[0001] The present invention relates to a catalyst powder for ammonia water electrolysis and a method for manufacturing a catalyst electrode for ammonia water electrolysis.

[0002] Ammonia is the nitrogen compound with the lowest oxidation state and can be generated directly in various industrial processes or through the circulation cycle of nitrogen compounds during the treatment of nitrate nitrogen compounds. Ammonia can be treated by degassing, biological decomposition, chlorine decomposition, and electrochemical decomposition. Among these, the electrochemical oxidation treatment method has recently been receiving much attention due to its economic efficiency, rapid and simple operation, and minimal secondary generation.

[0003] Existing technologies related to hydrogen production using ammonia include the thermal decomposition of ammonia and the electrolytic decomposition of aqueous ammonia solutions as methods for producing hydrogen using ammonia as a raw material. The thermal decomposition of ammonia has limitations in terms of low productivity and economic feasibility because nitrogen and hydrogen are generated simultaneously, requiring the use of expensive palladium membranes to separate high-purity hydrogen. Furthermore, regarding the electrolytic decomposition of aqueous ammonia solutions, there has not been much research conducted. Yejin Yang et al. (JOURNAL OF MATERIALS CHEMISTRY A, v.9, no.19, May 2021, pp.11571-11579) disclosed a technology using platinum as an ammonia oxidation catalyst by electrodepositing it onto carbon paper via a potential cycling method; however, this involved manufacturing the catalyst at a lab scale and has the problem that it is impossible to scale up to a large area using the same method. In other words, there is a complete lack of research on manufacturing large-area electrodes for the electrolysis of large volumes of aqueous ammonia solutions.

[0004] The present invention aims to provide a method for manufacturing ammonia water electrolysis catalyst powder and a method for manufacturing an ammonia water electrolysis catalyst electrode for manufacturing a large-area ammonia water electrolysis catalyst electrode.

[0005] However, the technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0006] One embodiment of the present invention provides a method for manufacturing a catalyst powder for ammonia water electrolysis, comprising: (A) immersing a metal foam support as a working electrode in an electrolyte solution containing a precursor of an active metal; (B) applying a cyclic voltammetry current to form active metal crystal particles on the metal foam support to form a metal foam-catalyst composite; and (C) physically crushing the metal foam-catalyst composite to form a metal foam-catalyst composite powder.

[0007] Another embodiment of the present invention provides a method for manufacturing an ammonia water electrolysis catalyst electrode, comprising the steps of: mixing an ammonia water electrolysis catalyst powder and a binder prepared according to the above manufacturing method to prepare an electrode-binder mixture; and applying the electrode-binder mixture on one surface of a porous support.

[0008] The method for manufacturing a catalyst powder for ammonia water electrolysis according to the present invention can provide a catalyst powder for manufacturing a large-area ammonia water electrolysis catalyst electrode. Furthermore, since the ammonia water electrolysis catalyst electrode using the above-mentioned ammonia water electrolysis catalyst powder can be made large-area and can be applied as an electrode of a Membrane Electrode Assembly (MEA), it has the advantage of possessing various possibilities as a catalyst for the commercialization of ammonia water electrolysis.

[0009] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below.

[0010] Figure 1 is a graph showing the current density according to voltage in the ammonia oxidation reaction of the catalyst electrode according to Example 1 and Comparative Examples 1 to 3.

[0011] Figure 2 is a graph showing the current density according to voltage in the ammonia oxidation reaction of the catalyst electrode according to Examples 1 to 3.

[0012] Figure 3 is a graph showing the current density as a function of voltage in the ammonia oxidation reaction of the catalyst electrode according to Examples 1 and 4.

[0013] The present invention is susceptible to various modifications and may have various embodiments, and specific embodiments are to be described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. In describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention.

[0014] In this specification, when a part is described as "comprising" a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0015] In this specification, when a member is described as being located "on" another member, this includes not only cases where a member is in contact with another member, but also cases where another member exists between the two members.

[0016] Conventional catalysts for ammonia water electrolysis disclose the use of catalysts prepared by electrodeposition at the lab scale. However, when these are manufactured over a large area, problems arise, such as a decrease in catalytic activity due to the detachment of the deposited metal catalyst and the formation of non-uniform catalyst particles during large-area electrodeposition. In other words, it was impossible to manufacture large-area ammonia water electrolysis catalyst electrodes for commercial application using previously known methods for manufacturing ammonia water electrolysis catalysts. Accordingly, the inventors have completed the present invention by researching means for manufacturing large-area ammonia water electrolysis catalyst electrodes.

[0017] The present invention will be described in detail below.

[0018] One embodiment of the present invention provides a method for manufacturing a catalyst powder for ammonia water electrolysis, comprising: (A) immersing a metal foam support as a working electrode in an electrolyte solution containing a precursor of an active metal; (B) applying a cyclic voltammetry current to form active metal crystal particles on the metal foam support to form a metal foam-catalyst composite; and (C) physically crushing the metal foam-catalyst composite to form a metal foam-catalyst composite powder.

[0019] Step (A) may be a preparation step for electrodepositing an active metal on the metal foam support using a potential cycling method. Specifically, Step (A) may be a preparation step for a three-electrode system of a reference electrode, a counter electrode, and a working electrode, and the counter electrode and the reference electrode may be further immersed in the electrolyte solution. The counter electrode and reference electrode, etc., not described herein may be appropriately used according to the purpose, in configurations applied to three-electrode systems known in the art. The active metal crystal particles formed using the potential cycling method may be formed in a crystalline phase such as a dendritic or flower-like shape, thereby having a very high specific surface area and enabling high catalytic activity.

[0020] The metal foam support above provides a large catalytic active area due to its three-dimensional porous structure and, furthermore, enables smooth mass transfer of liquid and gas during the ammonia water electrolysis reaction, thereby enabling high catalytic activity. Furthermore, the metal foam support above has high electrical conductivity, which enables high electrolysis efficiency to be achieved in the ammonia water electrolysis.

[0021] According to one embodiment of the present invention, the material of the metal foam support may be selected from the group consisting of nickel, iron, and aluminum. Specifically, the material of the metal foam support may be nickel. That is, the metal foam support may be a nickel foam support, in which case more stable support of active metal particles and effective catalytic activity of the active metal particles can be achieved.

[0022] According to one embodiment of the present invention, the active metal may be selected from the group consisting of platinum, iridium, rhodium, palladium, ruthenium, iron, nickel, cobalt, and manganese. The active metal may be one or more metals selected from the group consisting of precious metal catalysts such as platinum, iridium, rhodium, palladium, and ruthenium, and non-precious metal catalysts such as iron, nickel, and cobalt. In terms of promoting the adsorption of ammonia in the ammonia oxidation reaction and significantly improving the electrolysis efficiency of an aqueous ammonia solution, the active metal may be platinum.

[0023] According to one embodiment of the present invention, the precursor of the active metal may include at least one of the sulfur oxide, nitrogen oxide, hydroxide, chloride, and acetate of the active metal. For example, when the active metal is platinum, the precursor of the active metal may be chloroplatinic acid (H2PtCl6), platinum chloride (PtCl2, PtCl4), platinum sulfate (Pt(SO4)2), platinum acetate (Pt(C2H3O2)2), or platinum nitrate (Pt(NO3)2). However, it is not limited thereto, and various precursors known for electroplating may be used depending on the desired active metal.

[0024] According to one embodiment of the present invention, the active metal precursor may be included at a concentration of 0.5 to 20 mM, and specifically at a concentration of 1 to 5 mM. If the active metal precursor is less than the concentration range, the amount of deposited active metal catalyst is insufficient, and thus the ammonia electrolytic activity may decrease; and if the concentration of the active metal precursor is higher than the concentration range, the mass activity may decrease due to the excessive formation of aggregated metal particles.

[0025] According to one embodiment of the present invention, the electrolyte solution may further include a supporting electrolyte. The supporting electrolyte may include at least one selected from H2SO4, HNO3, K2SO4, NaCl, HClO4, KOH, NaOH, and HCl. Specifically, the supporting electrolyte may be an acidic supporting electrolyte, and more specifically, may be H2SO4, HNO3, HClO4, or HCl.

[0026] According to one embodiment of the present invention, the supporting electrolyte may be included at a concentration of 0.5 to 5000 mM, specifically at a concentration of 5 to 3000 mM or at a concentration of 100 to 1000 mM. If the electrolyte is less than the above concentration range, the amount of supported metal catalyst may not be sufficient, and if the electrolyte is higher than the above concentration range, agglomeration of the supported active metal may occur, which may reduce the ammonia electrolytic activity.

[0027] According to one embodiment of the present invention, the potential range when the cyclic voltage current is applied may be -0.8 V to 0.8 V, -0.8 V to 0.5 V, or -0.7 V to 0.3 V based on the Ag / AgCl potential. As the absolute value of the negative value increases, the amount of reduction of the active metal increases, and as the absolute value of the positive value increases, the amount of oxidation of the metal foam support may increase.

[0028] According to one embodiment of the present invention, the voltage scan speed when the cyclic voltage current is applied may be 50 mV / s to 500 mV / s. Specifically, the voltage scan speed may be 150 mV / s to 250 mV / s. While a faster voltage scan speed has the advantage of reducing the reaction time, if the voltage scan speed exceeds the above range, the reaction proceeds too rapidly compared to the chemical reaction on the surface of the metal foam support, and the active metal may not grow and electrodeposit properly. Furthermore, if the voltage scan speed is below the above range, the oxidation of the metal foam support in the electrolyte solution proceeds too rapidly, which may significantly lower the mechanical properties of the metal foam-catalyst composite.

[0029] According to one embodiment of the present invention, the active metal crystal particles provided in the metal foam-catalyst composite may be crystal particles having a dendritic or flower-like shape. Since the active metal crystal particles have a dendritic or flower-like shape with a very high specific surface area, there is an advantage in that a high ammonia decomposition rate can be achieved during ammonia water electrolysis.

[0030] According to one embodiment of the present invention, the physical grinding may utilize at least one physical grinding method selected from the group consisting of a ball mill, a planetary ball mill, a roller mill, a hammer mill, a jet mill, a pin mill, and a disk mill.

[0031] According to one embodiment of the present invention, the average particle size of the metal foam-catalyst composite powder may be 0.5 μm to 5 μm. The average particle size is D 50The particle size may be measured by photographing the particles with an electron microscope such as an SEM and then analyzing the particle size through image processing software. If the average particle size of the metal foam-catalyst composite powder is below the above range, the structure of the crystal particles having a dendritic or flower-like shape may collapse, and the catalytic activity may be reduced. In addition, if the average particle size of the metal foam-catalyst composite powder exceeds the above range, the dispersion may not be uniform during the manufacture of a large-area electrode, which may result in reduced activity of the catalytic electrode or a problem in which the active metal crystal particles easily detach from the crushed metal foam support.

[0032] According to one embodiment of the present invention, the method may further include the step of (A-1) ultrasonically treating an electrolyte solution in which a metal foam support is immersed. By the ultrasonically treating, a hydroxide of the metal constituting the metal foam support is formed on the surface of the metal foam support, thereby preventing poisoning caused by nitrogen oxides generated in the ammonia water electrolysis reaction, which improves durability. Furthermore, a seed of the active metal is formed on the surface of the metal foam support, which can improve the loading rate of the active metal through the potential cycling method.

[0033] According to one embodiment of the present invention, the frequency of the ultrasonic treatment may be 10 to 130 kHz, and the treatment time may be 10 seconds to 60 minutes. In terms of maximizing the durability and activity of the catalyst electrode for ammonia water electrolysis, the electrolyte solution may be treated at a frequency of 20 to 100 kHz for 30 seconds to 40 minutes, and more specifically, at a frequency of 30 to 80 kHz for 1 minute to 20 minutes. Meanwhile, if the frequency of the ultrasonic treatment falls outside the above range, the metal foam support may be damaged and its durability may decrease; if the ultrasonic treatment time is less than 10 seconds, the effect of enhancing durability and activity may be negligible; and if the ultrasonic treatment time exceeds 60 minutes, a decrease in the physical durability of the metal foam support may occur.

[0034] According to one embodiment of the present invention, (B-1) a step of heat-treating the metal foam-catalyst composite may be further included. By the heat treatment, an oxide of the metal forming the metal foam support within the metal foam-catalyst composite is formed, thereby preventing poisoning caused by nitrogen oxides generated in the ammonia water electrolysis reaction, which has the advantage of improving durability.

[0035] According to one embodiment of the present invention, the temperature range during the heat treatment may be 50 ℃ to 250 ℃. Specifically, the temperature range during the heat treatment may be 70 ℃ to 230 ℃, or 90 ℃ to 210 ℃. If the temperature during the heat treatment is below the above range, the effect of enhancing the durability of the metal foam-catalyst composite may be negligible, and if the temperature during the heat treatment exceeds the above range, a clumping phenomenon of the active metal may occur, reducing the exposure of the active site and thereby reducing the ammonia electrolytic activity.

[0036] According to one embodiment of the present invention, the material of the metal foam support is nickel, and the active metal is platinum. In this case, the ratio of nickel oxide (NiO) and nickel hydroxide (Ni(OH)2) in the metal foam-catalyst composite through the heat treatment may be 1:4 to 1:9. If the ratio of nickel oxide (NiO) and nickel hydroxide (Ni(OH)2) deviates from the above range, the hydrophilicity of the metal foam-catalyst composite may change. If the ratio of nickel oxide is high, the adsorption of the reactant ammonia is not smooth due to the low surface hydrophilicity, which may lead to a decrease in ammonia decomposition performance. Additionally, as the ratio of nickel oxide increases through the high-temperature heat treatment process, aggregation of the active metal may occur, which may also reduce the ammonia electrolytic durability. If the ratio of nickel hydroxide is high, the adsorption of ammonia is smooth and the ammonia decomposition performance is improved, but durability may be reduced due to excessive adsorption of ammonia.

[0037] The method for manufacturing a catalyst powder for ammonia water electrolysis according to the present invention can produce a particulate ammonia water electrolysis catalyst by physically grinding a metal foam-catalyst composite having excellent catalytic efficiency, and the ammonia water electrolysis catalyst powder can have a catalytic efficiency equivalent to that of the ammonia water electrolysis efficiency of the metal foam-catalyst composite. Therefore, it has the advantage of being able to manufacture a large-area ammonia water electrolysis catalyst electrode using this, and also has the advantage of being applicable as a large-area MEA (Membrane Electrode Assembly) electrode.

[0038] Another embodiment of the present invention provides a method for manufacturing an ammonia water electrolysis catalyst electrode, comprising the steps of: mixing an ammonia water electrolysis catalyst powder and a binder prepared according to the above manufacturing method to prepare an electrode-binder mixture; and applying the electrode-binder mixture on one surface of a porous support.

[0039] The porous support may be a conductive porous support, and may be, for example, a carbon porous body such as carbon paper, carbon cloth, or glass-shaped carbon, or a metal porous body such as metal mesh or foamed metal. However, it is not limited thereto, and commercially available materials or products used as gas diffusion layers may be appropriately applied according to the purpose of the present invention.

[0040] According to one embodiment of the present invention, the method of applying the electrode-binder mixture may utilize drop casting, spray casting, or a doctor blade. However, it is not limited thereto, and any method capable of applying uniformly at a predetermined thickness may be appropriately applied according to the purpose of the present invention.

[0041] According to one embodiment of the present invention, the electrode-binder mixture may further include a solvent, and the solvent may serve to dissolve the binder and evenly disperse the ammonia water electrolytic catalyst powder. The solvent may be a water-soluble solvent, such as water or alcohol, but is not limited thereto; any material that has the properties to evenly disperse the ammonia water electrolytic catalyst powder and dissolve the binder, and can be removed without residue through drying, etc., may be applied without limitation.

[0042] According to one embodiment of the present invention, the binder may be an ion-conducting polymer. Specifically, the binder may be a polymer that is completely or partially fluorinated, or comprises a sulfonate, a sulfonimide, a phosphate, a phosphonic acid group, and / or a sulfonic group. For example, the ionomer may be perfluorosulfonic acid (PSFA) (e.g., Nafion®), perfluoroalkyl sulfonimide ionomer (PFSI), polytetrafluoroethylene (PTFE) (e.g., Teflon®), polyvinylidene fluoride (PVDF), polystyrene sulfonic acid (PSSA), poly(trifluoromethanesulfonic acid) (PTFMSA), poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), poly(vinyl alcohol-sodium acrylate copolymer) (poly(vinyl alcohol-co-sodium acrylate)), polybenzimidazole (PBI), FLEMION®, SELEMION®, and / or Sustainion®.

[0043] According to one embodiment of the present invention, the content of the binder may be 5 to 10 parts by weight with respect to the ammonia water electrolysis catalyst powder. When the content of the binder is within the above range, the clumping of the ammonia water electrolysis catalyst electrode is minimized, and detachment from the porous support can be prevented.

[0044] According to one embodiment of the present invention, the ammonia water electrolysis catalyst powder may be supported on the porous support in an amount of 5 mg / cm² to 50 mg / cm². When the amount of the ammonia water electrolysis catalyst powder supported is within the above range, electron transfer is smooth, making it easy for the reactant to approach the catalyst electrode, and thereby enabling high ammonia water electrolysis efficiency.

[0045] The above-described catalyst electrode for ammonia water electrolysis may be applied directly as an ammonia water electrolysis catalyst, or it may be applied as an electrode of a Membrane Electrode Assembly (MEA) for ammonia water electrolysis. As described above, when using the ammonia water electrolysis catalyst powder prepared according to the present invention, a large-area catalyst electrode for ammonia water electrolysis can be easily manufactured, and this can achieve significantly improved ammonia water electrolysis efficiency compared to commercial ammonia water electrolysis catalysts.

[0046] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0047] [Example 1]

[0048] An electrolyte solution was prepared by dissolving 2 mM H2Cl6Pt·6H2O (Sigma Aldrich) in 200 ml of 0.05 M sulfuric acid (H2SO4, manufacturer: Sigma Aldrich). Then, a 1 cm x 2 cm porous nickel foam support (nickel main component thickness 1.6 mm, manufacturer: MTI Korea, porosity: ≥ 95%) to be used as the working electrode was washed with acetone, ultrasonically cleaned in approximately 1 M HCl for about 10 minutes, rinsed with water, and dried. A three-electrode cell system was constructed by immersing the nickel foam support as the working electrode, an (Ag / AgCl) electrode as the reference electrode, and a carbon rod as the counter electrode in the electrolyte solution. Furthermore, a cyclic voltammetry current was applied at a voltage scan rate of 200 mV / s under voltage conditions of 0.2 V to -0.4 V (vs. Ag / AgCl) to electrodeposit platinum particles on the nickel foam support, thereby producing a metal foam-catalyst composite.

[0049] Then, the manufactured metal foam-catalyst composite is ground by a ball mill to an average particle size of about 2 μm (D 50 A catalyst powder having ) was obtained. 50 mg of the above catalyst powder and 2.5 mg of Nafion (5 parts by weight relative to the catalyst powder) as a binder were added to 1 ml of ethanol and ultrasonically dispersed to prepare an electrode dispersion. The electrode dispersion was loaded onto a 1 cm x 1 cm carbon paper by a drop casting method so that the loading amount of the catalyst powder was approximately 50 mg / cm², and dried to produce a catalyst electrode for ammonia water electrolysis.

[0050] An ammonia oxidation experiment was performed using the ammonia water electrolytic catalyst electrode prepared as described above. Specifically, an Ivium-n-Stat instrument (Ivium Technologies) was used, and measurements were taken in an Ar-purged 1 M KOH electrolyte at room temperature, followed by measurements in Ar-purged 5 M KOH and 2 M NH3 electrolytes. The electrochemical test was conducted in a three-electrode system in a sealed glass beaker without a membrane (to prevent ammonia evaporation), using an Hg / HgO electrode (1 M KOH) and a Pt mesh as the reference electrode and counter electrode, respectively. The catalyst performance in the ammonia oxidation reaction was measured by cyclic voltammetry (CV) of the catalyst, applying a voltage within a potential range of -0.2 V to 1.2 V relative to the RHE.

[0051] [Comparative Example 1]

[0052] A commercial Pt catalyst (Pt on carbon black 40 wt%, alfa aesar) was prepared, and the catalytic performance in the ammonia oxidation reaction was measured in the same way as in Example 1.

[0053] [Comparative Example 2]

[0054] A commercial Ni catalyst (Ni nanoparticle, < 100 nm, sigma aldrich) was prepared, and the catalytic performance in the ammonia oxidation reaction was measured in the same manner as in Example 1.

[0055] [Comparative Example 3]

[0056] 100 mg of Ni nanoparticles (Ni nanoparticle, < 100 nm, sigma aldrich) were dispersed in 300 ml of distilled water and then mixed with 100 mL of a 0.44 M aqueous solution of Pt precursor, H2Cl6Pt·6H2O (sigma aldrich). A galvanic reaction was then carried out using the mixed solution to prepare a Pt-Ni alloy catalyst, and the catalytic performance in the ammonia oxidation reaction was measured in the same manner as in Example 1.

[0057] FIG. 1 is a graph showing the current density according to voltage in the ammonia oxidation reaction of the catalyst electrodes according to Example 1 and Comparative Examples 1 to 3. According to FIG. 1, unlike conventional commercial catalysts and Ni-Pt alloy catalysts, it can be confirmed that the catalyst electrode for ammonia water electrolysis according to the present invention exhibits a very high current density value, and through this, it can be seen that very high ammonia oxidation efficiency is achieved.

[0058] Furthermore, to investigate the catalytic performance in the ammonia oxidation reaction according to the loading amount on the catalyst electrode for ammonia water electrolysis, the following experiment was additionally conducted.

[0059] [Example 2]

[0060] A catalyst electrode for ammonia water electrolysis was prepared in the same manner as in Example 1, except that the loading amount of catalyst powder was about 25 mg / cm², and the catalytic performance in the ammonia oxidation reaction was measured.

[0061] [Example 3]

[0062] A catalyst electrode for ammonia water electrolysis was prepared in the same manner as in Example 1, except that the loading amount of catalyst powder was about 5 mg / cm², and the catalytic performance in the ammonia oxidation reaction was measured.

[0063] [Reference Example 1]

[0064] A catalyst electrode for ammonia water electrolysis was prepared in the same manner as in Example 1, except that the loading amount of catalyst powder was about 100 mg / cm², and the catalytic performance in the ammonia oxidation reaction was measured.

[0065] Figure 2 is a graph showing the current density as a function of voltage in the ammonia oxidation reaction of the catalyst electrodes according to Examples 1 to 3. According to Figure 2, it was confirmed that Example 2, with a catalyst powder loading of approximately 25 mg / cm², exhibited catalytic performance similar to Example 1, but in the case of Example 3, with a catalyst powder loading of approximately 5 mg / cm², it was confirmed that it exhibited significantly lower catalytic performance compared to Example 1. In the case of Example 3 as well, it was confirmed that it exhibited very high catalytic performance compared to commercial catalysts; however, due to the low catalyst loading, it showed lower catalytic performance compared to Examples 1 and 2. For reference, in the case of Reference Example 1, where the catalyst powder loading was adjusted to approximately 100 mg / cm², the thickness of the catalyst electrode became excessively thick, causing catalyst detachment during the ammonia oxidation reaction, making measurement impossible.

[0066] In addition, the following experiment was conducted to investigate the catalytic performance in the ammonia oxidation reaction according to the binder content in the catalytic electrode for ammonia water electrolysis.

[0067] [Example 4]

[0068] A catalyst electrode for ammonia water electrolysis was prepared in the same manner as in Example 1, except that 5 mg of Nafion (10 parts by weight relative to the catalyst powder) was applied as a binder, and the catalytic performance in the ammonia oxidation reaction was measured.

[0069] [Reference Example 2]

[0070] A catalyst electrode for ammonia water electrolysis was prepared in the same manner as in Example 1, except that 0.5 mg of Nafion (2 parts by weight relative to the catalyst powder) was applied as a binder, and the catalytic performance in the ammonia oxidation reaction was measured.

[0071] [Reference Example 3]

[0072] A catalyst electrode for ammonia water electrolysis was prepared in the same manner as in Example 1, except that 12.5 mg of Nafion (25 parts by weight relative to the catalyst powder) was applied as a binder, and the catalytic performance in the ammonia oxidation reaction was measured.

[0073] Figure 3 is a graph showing the current density as a function of voltage in the ammonia oxidation reaction of the catalyst electrodes according to Examples 1 and 4. According to Figure 3, it can be seen that Example 4, in which 10 parts by weight of binder were applied to the catalyst powder, exhibits slightly lower catalytic performance compared to Example 1, in which 5 parts by weight of binder were applied to the catalyst powder. This may be due to a decrease in the catalyst contact area of ​​the reactants caused by the increased amount of binder. For reference, in Reference Example 2, in which 2 parts by weight of binder were applied to the catalyst powder, the amount of binder was excessively small, causing catalyst detachment during the ammonia oxidation reaction and making measurement impossible. Additionally, in Reference Example 3, in which 25 parts by weight of binder were applied to the catalyst powder, the amount of binder was excessively large, causing the thickness of the catalyst electrode to become excessively thick, which caused catalyst detachment during the ammonia oxidation reaction and made measurement impossible.

[0074] By referring to the results in the above examples and reference examples, it can be confirmed that in the present invention, when the loading amount of catalyst powder and the content of the binder are appropriately controlled, a catalyst electrode for ammonia water electrolysis with very superior efficiency compared to existing commercial catalysts can be manufactured, and furthermore, it can be easily understood that it can be easily scaled up to a large area.

Claims

1. (A) A step of immersing a metal foam support as a working electrode in an electrolyte solution containing a precursor of an active metal; (B) a step of forming active metal crystal particles on the metal foam support by applying cyclic voltammetry to form a metal foam-catalyst composite; and (C) a step of physically crushing the metal foam-catalyst composite to form a metal foam-catalyst composite powder; comprising Method for manufacturing ammonia water electrolysis catalyst powder.

2. In Claim 1, (A-1) A step of ultrasonically treating an electrolyte solution in which a metal foam support is immersed; a method for manufacturing a catalyst powder for ammonia water electrolysis, further comprising.

3. In Claim 1, (B-1) A step of heat-treating the metal foam-catalyst composite; further comprising a method for manufacturing a catalyst powder for ammonia water electrolysis.

4. In Claim 2, A method for manufacturing a catalyst powder for ammonia water electrolysis, wherein the vibration frequency during the above ultrasonic treatment is 10 to 130 kHz and the treatment time is 10 seconds to 60 minutes.

5. In Claim 3, A method for manufacturing a catalyst powder for ammonia water electrolysis, wherein the temperature range during the heat treatment is 50 ℃ to 250 ℃.

6. In Claim 1, A method for manufacturing ammonia water electrolysis catalyst powder, wherein the material of the metal foam support is selected from the group consisting of nickel, iron, and aluminum.

7. In Claim 1, A method for manufacturing a catalyst powder for ammonia water electrolysis, wherein the active metal is selected from the group consisting of platinum, iridium, rhodium, palladium, ruthenium, iron, nickel, cobalt, and manganese.

8. In Claim 1, A method for manufacturing a catalyst powder for ammonia water electrolysis, wherein the average particle size of the metal foam-catalyst composite powder is 0.5 μm to 5 μm.

9. A step of preparing an electrode-binder mixture by mixing an ammonia water electrolytic catalyst powder and a binder prepared according to the manufacturing method of Claim 1; and A step comprising applying the electrode-binder mixture on one surface of a porous support; Method for manufacturing a catalyst electrode for ammonia water electrolysis.

10. In Claim 9, A method for manufacturing an ammonia water electrolysis catalyst electrode, wherein the content of the binder is 5 to 10 parts by weight with respect to the ammonia water electrolysis catalyst powder.

11. In Claim 9, A method for manufacturing an ammonia water electrolysis catalyst electrode, wherein the ammonia water electrolysis catalyst powder is supported on the porous support at a content of 5 mg / cm² to 50 mg / cm².

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