Method for preparing ammonia water electrolysis catalyst, and ammonia water electrolysis catalyst prepared using same

Abstract

The present invention relates to a method for preparing an ammonia water electrolysis catalyst, comprising the steps of: (A) using electrophoresis to electrodeposit metal oxide particles on a metal foam support, thereby forming a metal foam support coated with a cocatalyst; (B) immersing, as a working electrode, the metal foam support coated with a cocatalyst in an electrolyte solution containing an active metal precursor; and (C) applying cyclic voltammetry to form active metal crystal particles on the metal foam support coated with a cocatalyst.

Description

Method for manufacturing a catalyst for ammonia water electrolysis and a catalyst for ammonia water electrolysis manufactured thereby

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

[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] Among the previously known technologies for hydrogen production using ammonia, there are the thermal decomposition of ammonia and the electrolytic decomposition of aqueous ammonia solutions as methods for producing hydrogen using ammonia as a raw material. In the case of the thermal decomposition of ammonia, since nitrogen and hydrogen are generated simultaneously, there is a limitation in that high-purity hydrogen must be separated using an expensive palladium membrane, resulting in low productivity and economic feasibility. 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) used platinum as an ammonia oxidation catalyst by electroplating it onto carbon paper via a potential cycling method, but this method has a problem of low catalyst durability due to the decrease in activity caused by catalyst poisoning during the ammonia water electrolysis process.

[0004] The present invention aims to provide a method for manufacturing a catalyst for ammonia water electrolysis having improved catalyst durability and a catalyst for ammonia water electrolysis manufactured thereby.

[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 those skilled in the art from the description below.

[0006] One embodiment of the present invention provides a method for manufacturing a catalyst for ammonia water electrolysis, comprising the steps of: electrodepositing metal oxide particles onto a metal foam support using an electrophoretic method to form a metal foam support coated with a co-catalyst; immersing the metal foam support coated with the co-catalyst as a working electrode in an electrolyte solution containing a precursor of an active metal; and applying a cyclic voltammetry current to form active metal crystal particles on the metal foam support coated with the co-catalyst.

[0007] Another embodiment of the present invention provides a catalyst for electrolysis of ammonia water produced by the above manufacturing method.

[0008] The method for manufacturing a catalyst for ammonia water electrolysis according to the present invention enables high catalyst durability by maintaining the shape of active metal crystal particles formed by electroplating and suppressing catalyst poisoning phenomena through the use of electrophoresis to coat co-catalyst particles onto a metal foam support. Furthermore, by utilizing electrophoresis, the method for manufacturing a catalyst for ammonia water electrolysis according to the present invention allows metal oxide particles to be coated onto a metal foam support without additional processes such as separate heat treatment.

[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 shows SEM images of the surface of the nickel foam support in Comparative Example 1 and the surface of the prepared ammonia water electrolysis catalyst.

[0011] FIG. 2 shows the Y2O3 provided in Comparative Example 2. This shows SEM images of the surface of the nickel foam support and the surface of the prepared ammonia water electrolysis catalyst.

[0012] FIG. 3 shows the Y2O3 provided in Comparative Example 3. This shows SEM images of the surface of the nickel foam support and the surface of the prepared ammonia water electrolysis catalyst.

[0013] FIG. 4 shows the Y2O3 provided in Example 1 This shows SEM images of the surface of the nickel foam support and the surface of the prepared ammonia water electrolysis catalyst.

[0014] Figure 5 shows the ohmic resistance of the ammonia water electrolysis catalyst according to Comparative Examples 1 to 3 and the Example.

[0015] Figure 6 is a graph evaluating the ammonia water electrolysis activity of catalysts for ammonia water electrolysis according to Comparative Examples 1 to 3 and Examples.

[0016] FIG. 7 is a graph evaluating the catalytic durability over time of ammonia water electrolysis catalysts according to Comparative Examples 1 to 3 and Examples.

[0017] 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, if it is determined that a detailed description of related known technology may obscure the essence of the present invention, such detailed description is omitted.

[0018] 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.

[0019] 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.

[0020] In this specification, the unit "parts by weight" may refer to the ratio of weight between each component.

[0021] The present invention will be described in detail below.

[0022] One embodiment of the present invention provides a method for manufacturing a catalyst for ammonia water electrolysis, comprising the steps of: electrodepositing metal oxide particles onto a metal foam support using an electrophoretic method to form a metal foam support coated with a co-catalyst; immersing the metal foam support coated with the co-catalyst as a working electrode in an electrolyte solution containing a precursor of an active metal; and applying a cyclic voltammetry current to form active metal crystal particles on the metal foam support coated with the co-catalyst.

[0023] The method for manufacturing a catalyst for ammonia water electrolysis according to the present invention is characterized by electrodepositing metal oxide particles, which serve as co-catalysts, onto a metal foam support using an electrophoretic method. Specifically, by utilizing an electrophoretic method, the present invention allows for the direct electrodeposition of metal oxide particles, which serve as co-catalysts, onto a metal foam support. This offers the significant advantage of eliminating the conventional heat treatment process required for the formation of metal oxide particles. The present invention also offers the advantage of avoiding changes in physical properties, such as a decrease in electrical conductivity caused by oxidation of the metal foam support during the heat treatment process. Furthermore, when metal oxide particles are physically attached to a support using a binder, the metal oxide particles may not adhere uniformly, which negatively affects the formation of active metal crystal particles formed through electroplating. Consequently, there is a problem in that a catalyst with low activity is formed.

[0024] Furthermore, the present invention minimizes changes in the shape of active metal crystal particles formed by electroplating by electrodepositing metal oxide particles onto a metal foam support using electrophoresis. Specifically, the shape of active metal crystal particles formed by electroplating without electrodeposition of metal oxide particles and the shape of active metal crystal particles formed according to the present invention can be substantially the same.

[0025] According to one embodiment of the present invention, the electrophoretic method in step (A) may involve metal oxide particles dispersed in a dispersion medium moving by an electric field and electrodepositing onto the metal foam support. Specifically, the metal oxide particles within the dispersion medium may carry an electric charge and move in a certain direction by the applied electric field. At this time, the dispersion medium may include a solvent and a charging additive. The solvent may be applied without limitation as long as it allows the metal oxide particles to be effectively dispersed, and may be, for example, an organic solvent such as ethanol, hexane, toluene, chloroform, acetone, methine ethyl ketone, etc. The charging additive may impart a charge to the metal oxide particles so that they can be more effectively affected by the electric field in the electrophoretic method. The charging additive may include at least one selected from alkali metal salts and alkaline earth metal salts. The charging additive may include at least one of magnesium nitrate, sodium chloride, and potassium chloride. For example, the charge aid may be dissolved in the dispersion medium, and metal ions from the charge aid may attach to the surface of the metal oxide particles, allowing the metal oxide particles to easily move to the metal foam support by an electric field. Alternatively, the charge aid may oxidize an organic solvent, so that cations derived from the organic solvent attach to the surface of the metal oxide particles, allowing the metal oxide particles to easily move to the metal foam support by an electric field.

[0026] More specifically, the electrophoretic method may involve immersing the metal foam support and the counter electrode as working electrodes in a dispersion medium in which the metal oxide particles are dispersed, and then applying a voltage. The counter electrode may be any electrode that is conductive and capable of performing the function of a counter electrode, such as a carbon electrode or a metal electrode. Additionally, the counter electrode may be identical to the metal foam support serving as the working electrode. Through the electrophoretic method, the metal oxide particles can be uniformly electrodeposited onto the metal foam support serving as the working electrode without the need for a separate binder and / or firing process.

[0027] According to one embodiment of the present invention, the step of forming a metal foam support coated with the co-catalyst may include immersing the metal foam support in a dispersion containing the metal oxide particles and then applying a voltage of -10 V to -30 V. Within the voltage range, the metal oxide particles may be uniformly electrodeposited on the metal foam support. If the absolute value of the applied voltage exceeds the above range, the metal oxide particles may be electrodeposited unevenly, which may have a negative effect on the growth of the active metal crystal thereafter. Additionally, if the absolute value of the applied voltage is below the above range, the mobility of the metal oxide particles within the dispersion medium may be reduced, and a sufficient amount of metal oxide particles may not be electrodeposited.

[0028] According to one embodiment of the present invention, the metal oxide particles may include at least one selected from the group consisting of yttrium oxide particles, lanthanum oxide particles, cerium oxide particles, titanium oxide particles, aluminum oxide particles, zirconium oxide particles, and niobium oxide particles. The metal oxide particles can prevent catalyst poisoning of the active metal crystal particles, which are the main catalyst, thereby maintaining the stable activity of the catalyst.

[0029] According to one embodiment of the present invention, the metal oxide particles may be electrodeposited in an amount of 1 mg / cm² or more and 13 mg / cm² or less. The electrodeposited amount of the metal oxide particles can be controlled by controlling the amount of metal oxide particles in the dispersion medium and / or the voltage application time during the performance of the electrophoresis method. If the electrodeposited amount of the metal oxide particles exceeds the above range, it interferes with the formation of active metal crystal particles, which may cause a decrease in the activity of the catalyst being produced. Furthermore, if the electrodeposited amount of the metal oxide particles is less than the above range, the action of the metal oxide particles as a co-catalyst is weak, and there may be a problem in that the catalyst poisoning phenomenon cannot be suppressed.

[0030] Step (B) 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.

[0031] According to one embodiment of the present invention, the active metal crystal particles 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] According to one embodiment of the present invention, the precursor of the active metal may be included at a concentration of 0.5 to 20 mM, and specifically at a concentration of 1 to 5 mM. If the amount of the precursor of the active metal is less than the above concentration range, the amount of deposited active metal is insufficient, and thus the ammonia electrolytic activity may decrease; and if the concentration of the metal catalyst precursor is higher than the above concentration range, the mass activity may decrease due to the excessive formation of aggregated metal particles.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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 above range is exceeded, the reaction proceeds excessively 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 above range is lower, the oxidation of the metal foam support in the electrolyte solution proceeds excessively rapidly, which may significantly lower the mechanical properties of the catalyst for ammonia water electrolysis.

[0041] According to one embodiment of the present invention, the active metal crystal particles may be formed in an amount of 15 mg / cm² or more and 30 mg / cm² or less. The amount of active metal crystal particles formed can be controlled by adjusting the time of application of circulating current and / or the potential range in step (C). Within the range of the amount of active metal crystal particles formed, the activity of the ammonia water electrolysis catalyst being manufactured can be maximized. If the range is exceeded, the manufacturing cost increases without an increase in catalyst activity, which may result in reduced economic feasibility.

[0042] Another embodiment of the present invention provides a catalyst for ammonia water electrolysis manufactured by the above manufacturing method. The ammonia water electrolysis catalyst has improved ammonia water electrolysis efficiency and can have improved long-term durability by suppressing catalyst poisoning. As described above, the above effects can be achieved by electrodepositing metal oxide particles, which serve as co-catalysts, onto a metal foam support using electrophoresis. Specifically, the metal foam support on which the co-catalyst is deposited using electrophoresis has almost no effect on the shape of the active metal crystal particles formed by the potential cycling method, thereby maximizing the surface area of ​​the active metal crystal particles. Furthermore, the co-catalyst particles provided on the metal foam support can effectively suppress catalyst poisoning of the active metal crystal particles, which serve as the main catalyst, thereby improving the long-term stability of the catalyst.

[0043] 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.

[0044] [Comparative Example 1]

[0045] 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 1 cm 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 catalyst for ammonia water electrolysis.

[0046] Figure 1 shows SEM images of the surface of the nickel foam support in Comparative Example 1 and the surface of the prepared ammonia water electrolysis catalyst.

[0047] [Comparative Example 2]

[0048] A solution was prepared by mixing 100 µl of Nafion and 10 mg of Y2O3 powder, then coated onto a nickel foam support prepared as in Comparative Example 1, and then platinum particles were electrodeposited in the same manner as in Comparative Example 1 to produce a catalyst for ammonia water electrolysis.

[0049] FIG. 2 shows the Y2O3 provided in Comparative Example 2. This shows SEM images of the surface of the nickel foam support and the surface of the prepared ammonia water electrolysis catalyst.

[0050] [Comparative Example 3]

[0051] A nickel foam support prepared as in Comparative Example 1 and 20 ml of an aqueous solution containing 2 g of yttrium hexahydrate (Aldrich) and 0.261 g of urea were introduced into an autoclave, and hydrothermal synthesis was performed at a temperature of approximately 140 °C for approximately 12 hours to synthesize Y(OH)CO3, and yttrium oxide was formed on the nickel foam support through a calcination process at a temperature of 600 °C for approximately 5 hours. Then, platinum particles were electrodeposited in the same manner as in Comparative Example 1 to prepare a catalyst for ammonia water electrolysis.

[0052] FIG. 3 shows the Y2O3 provided in Comparative Example 3. This shows SEM images of the surface of the nickel foam support and the surface of the prepared ammonia water electrolysis catalyst.

[0053] [Example 1]

[0054] 100 mg of Y2O3 powder and 100 mg of Mg(NO3)2 were added to 200 ml of ethanol and stirred thoroughly to prepare a dispersion. The dispersion was placed in a container, and a nickel foam support prepared as in Comparative Example 1 was immersed on one side of the container, and the same nickel foam support was immersed on the opposite side as a counter electrode. Then, a voltage of approximately -20 V was applied for approximately 15 minutes to electrodeposit yttrium oxide onto the nickel foam support at an amount of approximately 11.7 mg / cm² using electrophoresis. Then, platinum particles were electrodeposited in the same manner as in Comparative Example 1 to prepare a catalyst for ammonia water electrolysis.

[0055] FIG. 4 shows the Y2O3 provided in Example 1 This shows SEM images of the surface of the nickel foam support and the surface of the prepared ammonia water electrolysis catalyst.

[0056] Comparing Figures 1 and 4, it was confirmed that in the case of Example 1 using electrophoresis, the shape of the platinum particles was very similar to that of Comparative Example 1, in which platinum particles were electrodeposited without separate treatment. Through this, it was confirmed that Y2O3 provided on the nickel foam support via electrophoresis did not significantly affect the formation of platinum particles.

[0057] In contrast, in the case of Comparative Example 2 using an ionomer, it was confirmed that the size of the formed platinum particles was significantly reduced, resulting in a significantly lower specific surface area. This is presumed to be due to the ionomer being coated on the nickel foam support and changing the surface characteristics of the nickel foam support.

[0058] In addition, in Comparative Example 3 using hydrothermal synthesis, Y2O3 covered the surface of the nickel foam support, and it was confirmed that platinum particles overgrow only on the partially exposed surface of the nickel foam support. Furthermore, in Comparative Example 3, oxidation of the nickel foam support proceeded through hydrothermal synthesis, causing a decrease in the electrical conductivity of the nickel foam support, which prevented the electrodeposition of platinum particles from proceeding smoothly.

[0059] The ohmic resistance of the ammonia water electrolysis catalysts according to Comparative Examples 1 to 3 and Example 1 was measured through EIS analysis and is shown in Fig. 5. According to Fig. 5, it was confirmed that Comparative Example 3, which utilized hydrothermal synthesis, exhibited particularly high resistance values. This is presumed to be due to the decrease in electrical conductivity of the nickel foam support caused by oxidation of the nickel foam support due to hydrothermal synthesis and the unevenly grown platinum particles.

[0060] Furthermore, the ammonia water electrolysis catalysts according to Comparative Examples 1 to 3 and Example 1 were immersed in an aqueous electrolyte solution of 2 M NH3 and 5 M KOH, and then a constant current of 300 mA / cm² was applied to evaluate the ammonia water electrolysis activity and catalyst durability.

[0061] FIG. 6 is a graph evaluating the ammonia water electrolytic activity of catalysts for ammonia water electrolysis according to Comparative Examples 1 to 3 and Example 1. Specifically, according to the results of FIG. 6, in the case of Comparative Example 1, which does not contain Y2O3, 1.2 V RHE It exhibited a current density of approximately 1.5 A / cm², and in the case of Example 1, in which Y2O3 was electrodeposited using electrophoresis, it exhibited the same ammonia oxidation performance as Comparative Example 1. This may mean that the shape of the platinum particles in the ammonia water electrolysis catalyst prepared according to Example 1 is substantially the same as the shape of the platinum catalyst of Comparative Example 1.

[0062] In contrast, Comparative Examples 2 and 3 exhibited reduced activity of approximately 30% and 70%, respectively, compared to Comparative Example 1. Specifically, in the Non-Faradaic current region (0 - 0.4 V RHE The specific surface area of ​​platinum can be indirectly compared through this comparison, and it was found that Comparative Example 2 using hydrothermal synthesis and Comparative Example 3 using an ionomer had a negative effect on the electrodeposition of platinum particles. This was consistent with the results of the SEM image analysis reviewed earlier.

[0063] Figure 7 is a graph evaluating the catalytic durability over time of the ammonia water electrolysis catalysts according to Comparative Examples 1 to 3 and Example 1. Specifically, Figure 7 evaluates the long-term stability of the catalyst by measuring the time until the ammonia oxidation reaction is converted to the water oxidation reaction due to poisoning of the ammonia water electrolysis catalyst. Specifically, in the case of the example using electrophoresis, catalytic activity was maintained for about 8.5 hours, which was an improvement of about 26% compared to Comparative Example 1, which showed catalytic activity of about 6.7 hours. That is, it was confirmed that the ammonia water electrolysis catalyst according to Example 1 has catalytic activity equivalent to Comparative Example 1, which does not have a separate co-catalyst, while having improved catalytic durability. In contrast, Comparative Example 2 using an ionomer maintained catalytic activity for only about 5.7 hours, and Comparative Example 3 using hydrothermal synthesis maintained catalytic activity for only about 2 minutes.

[0064] Furthermore, in order to confirm the performance of the ammonia water electrolysis catalyst according to the amount of metal oxide particles deposited, the ammonia water electrolysis catalyst was prepared as shown in the following examples and reference examples by proceeding with different electrophoresis times than in Example 1, and then the catalyst durability was evaluated in the manner described above.

[0065] [Example 2]

[0066] A catalyst for ammonia water electrolysis was prepared in the same manner as in Example 1, except that the voltage application time of the electrophoresis method was adjusted to 4 minutes and yttrium oxide was electrodeposited on a nickel foam support in an amount of about 3.6 mg / cm².

[0067] [Example 3]

[0068] A catalyst for ammonia water electrolysis was prepared in the same manner as in Example 1, except that the voltage application time of the electrophoresis method was adjusted to 10 minutes and yttrium oxide was electrodeposited on a nickel foam support in an amount of about 8.7 mg / cm².

[0069] [Reference Example]

[0070] A catalyst for ammonia water electrolysis was prepared in the same manner as in Example 1, except that the voltage application time of the electrophoresis method was adjusted to 20 minutes and yttrium oxide was electrodeposited on a nickel foam support in an amount of about 14.2 mg / cm².

[0071] Figure 8 is a graph evaluating the catalytic durability over time of ammonia water electrolysis catalysts according to Comparative Example 1, Examples 1 to 3, and Reference Example. Specifically, according to Figure 8, it was confirmed that Examples 1 to 3, which utilized the electrophoresis method, all exhibited higher catalytic stability compared to Comparative Example 1, which did not have separate metal oxide particles. However, when metal oxide particles were electrodeposited in an excessive amount, as in the Reference Example, it was confirmed that the excess metal oxide particles interfered with the formation of platinum crystal particles, which are the main catalyst, thereby reducing catalytic activity and catalytic stability. As a result of the experiment, it was found that the best catalytic activity and catalytic stability could be secured when metal oxide particles were electrodeposited in an amount of approximately 12 mg / cm² using the electrophoresis method, as in Example 1.

Claims

1. (A) A step of forming a metal foam support coated with a co-catalyst by electrodepositing metal oxide particles onto a metal foam support using an electrophoretic method; (B) a step of immersing a metal foam support coated with the co-catalyst as a working electrode in an electrolyte solution containing a precursor of an active metal; and (C) a step of forming active metal crystal particles on a metal foam support coated with the co-catalyst by applying a cyclic voltammetry current; comprising, Method for manufacturing a catalyst for ammonia water electrolysis.

2. In Claim 1, A method for manufacturing a catalyst for ammonia water electrolysis, wherein the step of forming a metal foam support coated with the above-mentioned co-catalyst comprises immersing the metal foam support in a dispersion containing the above-mentioned metal oxide particles and then applying a voltage of -10 V to -30 V.

3. In Claim 1, A method for preparing a catalyst for ammonia water electrolysis, wherein the above electrophoresis method is performed for a period of time of 1 minute or more and less than 20 minutes.

4. In Claim 1, A method for manufacturing a catalyst for ammonia water electrolysis, wherein the potential range when the above-mentioned cyclic voltage and current are applied is -0.8 V to 0.8 V based on the Ag / AgCl potential.

5. In Claim 1, A method for manufacturing a catalyst for ammonia water electrolysis, wherein the voltage scan rate when the above-mentioned cyclic voltage and current are applied is 50 mV / s to 500 mV / s.

6. In Claim 1, A method for manufacturing a catalyst for ammonia water electrolysis, wherein the metal oxide particles are electrodeposited in an amount of 1 mg / cm² or more and 13 mg / cm² or less.

7. In Claim 1, A method for manufacturing a catalyst for ammonia water electrolysis, wherein the above active metal crystal particles are formed in an amount of 15 mg / cm² or more and 30 mg / cm² or less.

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

9. In Claim 1, A method for manufacturing a catalyst for ammonia water electrolysis, wherein the metal oxide particles comprise at least one selected from the group consisting of yttrium oxide particles, lanthanum oxide particles, cerium oxide particles, titanium oxide particles, aluminum oxide particles, zirconium oxide particles, and niobium oxide particles.

10. In Claim 1, A method for manufacturing a catalyst 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.

11. A catalyst for electrolytic ammonia water produced by the manufacturing method of Claim 1.

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