Catalytic electrode for ammonia water electrolysis with improved durability and catalytic activity by ultrasonic treatment and method for preparing the same

Abstract

This invention discloses a catalytic electrode for ammonia electrolysis and a method for preparing the electrode. The catalytic electrode for ammonia electrolysis is subjected to ultrasonic treatment for a specific time, which not only synthesizes platinum catalyst seeds, but also inhibits the poisoning of platinum catalyst by forming nickel hydroxide on the surface of a nickel support, thereby improving durability and catalytic activity.

Description

Technical Field

[0001] This invention relates to a catalytic electrode for ammonia electrolysis and its preparation method, and more specifically, to a catalytic electrode for ammonia electrolysis with improved durability and catalytic activity through ultrasonic treatment and its preparation method.

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2023-0172760, filed on December 1, 2023, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Ammonia is the nitrogen compound with the lowest oxidation state. It can be produced directly in various industrial processes or through the nitrogen compound cycle during the treatment of nitrate-based nitrogen compounds. Ammonia can be treated by degassing, biodegradation, chlorination, and electrochemical decomposition. Among these methods, electrochemical oxidation has recently attracted much attention due to its economic efficiency, rapid and convenient operation, and minimal production of secondary products.

[0004] Among the known technologies for producing hydrogen from ammonia, there are methods using ammonia as a raw material, namely the thermal decomposition of ammonia and the electrolytic decomposition of ammonia solution. In the thermal decomposition method, nitrogen and hydrogen are produced simultaneously, thus requiring the use of expensive palladium membranes to separate high-purity hydrogen, resulting in limitations in productivity and economics. Furthermore, research on the electrolytic decomposition of ammonia solution is currently limited, particularly regarding the development of electrodes suitable for ammonia solution electrolysis. Therefore, there is a need to develop electrodes effective for the electrolysis reaction of ammonia solution.

[0005] Furthermore, unlike water electrolysis, which theoretically requires 1.23V, ammonia electrolysis, requiring only 0.06V, is highly anticipated as a hydrogen fuel source. Among currently used catalysts, transition metal catalysts, aside from precious metals like platinum and iridium, suffer from very high overvoltages, hindering their widespread use. However, platinum-based catalysts are prohibitively expensive, making economic viability difficult to ensure.

[0006] In addition, the ammonia electrolysis reaction can be poisoned by nitrogen oxides in the reactants or intermediate products, causing the electrode activity to deactivate within minutes to hours, resulting in a decrease in the durability of the catalytic electrode.

[0007] Korean Patent Publication No. 10-2022-0068566 (May 26, 2022) relates to a hydrogen production apparatus using an ammonia solution, which prepares and uses an electrode deposited on a nickel metal foam, but does not mention a technique for improving the durability and activity of the catalytic electrode through ultrasonic treatment.

[0008] In addition, Yejin Yang et al. (JOURNAL OF MATERIALS CHEMISTRY A, v.9, no.19, May 2021, pp.11571-11579) disclosed a technique for using platinum electrodeposition on carbon paper as an ammonia oxidation catalyst via potential cycling, but similarly did not mention a technique for improving the durability and activity of the catalytic electrode through ultrasonic treatment. Summary of the Invention

[0009] The present invention aims to provide a catalytic electrode for ammonia electrolysis and a method for effectively preparing the electrode. The catalytic electrode for ammonia electrolysis improves durability and activity by removing the oxide layer on the surface of the support and inducing the formation of hydroxides, while simultaneously forming metal catalyst seeds.

[0010] To address the aforementioned issues, the present invention provides a method for preparing a catalytic electrode for ammonia electrolysis, comprising: step (A), ultrasonically treating a support in a solution containing a precursor of an active metal catalyst; and step (B), applying a voltage to the result of step (A) to electroplate the active metal catalyst onto the surface of the support.

[0011] In addition, a method for preparing a catalytic electrode for ammonia electrolysis is provided, characterized in that, in step (A), the frequency of the ultrasonic wave is 10~130kHz and the processing time is 10 seconds~60 minutes.

[0012] In addition, a method for preparing a catalytic electrode for ammonia electrolysis is provided, characterized in that the support comprises one or more materials selected from nickel, iron, aluminum and carbon, and the active metal catalyst is one or more selected from platinum, iridium, rhodium, palladium, ruthenium, iron, nickel and cobalt.

[0013] In addition, a method for preparing a catalytic electrode for ammonia electrolysis is provided, characterized in that an electrolyte is further included in the solution of step (A) for ultrasonic treatment.

[0014] In addition, a method for preparing a catalytic electrode for ammonia electrolysis is provided, characterized in that the electrolyte is an acidic electrolyte.

[0015] In addition, a method for preparing a catalytic electrode for ammonia electrolysis is provided, characterized in that the support contains nickel, the active metal catalyst is platinum, and the catalytic electrode for ammonia electrolysis is loaded with 20-60% by weight of platinum and contains 1-50% by weight of nickel hydroxide by ultrasonic treatment.

[0016] To address the aforementioned problem, the present invention provides a catalytic electrode for ammonia electrolysis prepared according to the above method.

[0017] The present invention includes the steps of placing a carrier in an active metal precursor solution and treating it with an ultrasonic disperser. By treating it with an ultrasonic disperser for a specific time, hydroxides and metal catalyst seeds can be formed on the surface of the carrier. The formed hydroxides inhibit poisoning and improve durability, while the formed metal catalyst seeds increase the amount of active metal deposited. This provides a catalytic electrode for ammonia electrolysis with improved ammonia electrolysis activity. Attached Figure Description

[0018] Figure 1 This is a photograph showing the results of SEM analysis of the nickel support of Example 1 in this invention.

[0019] Figure 2 This is a photograph showing the results of SEM analysis of the nickel support of Comparative Example 1 in this invention.

[0020] Figure 3 This is a photograph showing the results of SEM analysis of the catalytic electrode for ammonia electrolysis prepared according to Example 1 in this invention.

[0021] Figure 4 This is a photograph showing the results of SEM analysis of the catalytic electrode for ammonia electrolysis prepared according to Comparative Example 1 in this invention.

[0022] Figure 5 This is a graph showing the results of measuring the platinum content of the nickel carriers in Examples 1, 2 and Comparative Example 1 in this invention.

[0023] Figure 6 This is a graph showing the results of measuring the platinum content of the catalytic electrodes for ammonia electrolysis prepared according to Examples 1, 2 and Comparative Example 1 in this invention.

[0024] Figure 7 This is a graph showing the results of surface chemical species and chemical binding energy analysis of the catalytic electrode for ammonia electrolysis prepared according to Example 1 in this invention.

[0025] Figure 8 The graph represents the results of surface chemical species and chemical binding energy analysis of the nickel support of Comparative Example 1 in this invention.

[0026] Figure 9 The graph shows the results of surface chemical species and chemical binding energy analysis of the catalytic electrode for ammonia electrolysis prepared according to Comparative Example 1 in this invention.

[0027] Figure 10The graph shows the results of measuring the ammonia oxidation characteristics of the catalytic electrode for ammonia electrolysis prepared according to the Examples and Comparative Example 1 in this invention.

[0028] Figure 11 The graph represents the results of evaluating the electrochemical stability of the catalytic electrode for ammonia electrolysis prepared according to the Examples and Comparative Example 1 in this invention. Detailed Implementation

[0029] The present invention will now be described in detail through preferred embodiments. Prior to this, the terms or words used in this specification and claims should not be limited to their conventional or dictionary meanings, but should be interpreted as conforming to the meaning and concept of the technical idea of ​​the present invention, based on the principle that the inventors may appropriately define the concepts of terms to best illustrate their invention. Therefore, the structures of the embodiments described in this specification are merely one of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. It should be understood that various equivalents and modifications may exist to replace these embodiments at the time of filing this application.

[0030] This invention discloses a method for preparing a catalytic electrode for ammonia electrolysis, comprising: step (A), ultrasonically treating a support in a solution containing a precursor of an active metal catalyst; and step (B), applying a voltage to the result of step (A) to electroplate the active metal catalyst onto the surface of the support.

[0031] The support may contain at least one material selected from nickel, iron, aluminum, and carbon. The support functions as a substrate for forming the active metal catalyst, and is preferably made of nickel.

[0032] In this invention, the shape of the carrier is not particularly limited and can be foam, plate, fabric, foil, or felt, preferably a metal foam carrier. When the carrier is a metal foam carrier, it can effectively improve the stability of the electrode, the catalyst loading, the fluidity of the electrolyte, and increase the surface area of ​​electrode catalyst particles such as platinum particles, thereby improving the electrode activity.

[0033] In one specific embodiment of the present invention, the metal foam support may be a nickel-based foam support. When the metal foam support is a nickel-based foam support, it can exhibit more stable loading of active metal particles and more effective catalytic activity of the active metal particles.

[0034] In this invention, the active metal catalyst supported on the support is not particularly limited as long as it is a metal catalyst that functions as a catalyst for the ammonia water electrolysis oxidation reaction. For example, it can be one or more catalysts selected from noble metal catalysts such as platinum, iridium, rhodium, palladium, and ruthenium, as well as non-noble metal catalysts such as iron, nickel, and cobalt. Moreover, from the perspective of promoting the adsorption of ammonia in the ammonia oxidation reaction and greatly improving the electrolysis efficiency of ammonia water solution, platinum catalyst is preferred.

[0035] Furthermore, the precursor of the active metal catalyst is a compound containing active metal catalysts such as platinum, iridium, rhodium, palladium, ruthenium, iron, nickel, and cobalt. For example, chloroplatinic acid (H2PtCl6xH2O) can be used as a precursor for electroplating platinum active metals.

[0036] Furthermore, the concentration of the precursor of the active metal catalyst contained in the solution of step (A) can be 0.5~20 mM, preferably 1~5 mM. If the precursor of the active metal catalyst deviates from the above concentration range, it may damage the support.

[0037] In this invention, in the step of ultrasonically treating the support in a solution containing an active metal catalyst precursor, the ultrasonic treatment forms hydroxides of the metal constituting the support on the surface of the support, thereby preventing poisoning caused by nitrogen oxides generated in the ammonia electrolysis reaction and improving durability. Moreover, the ultrasonic treatment forms seeds of the active metal catalyst on the surface of the support, thereby improving the loading rate and catalytic activity of the active metal catalyst in the subsequent electroplating process. Therefore, step (A) plays a role in improving the durability and activity of the catalytic electrode for ammonia electrolysis prepared in this invention.

[0038] As specific conditions for the ultrasonic treatment, the frequency can be set to 10~130kHz and the treatment time can be 10 seconds to 60 minutes. From the perspective of maximizing the durability and activity of the catalytic electrode for ammonia electrolysis, it is preferable to set the frequency to 20~100kHz and the treatment time can be 30 seconds to 40 minutes. More preferably, the frequency can be set to 30~80kHz and the treatment time can be 1 minute to 20 minutes.

[0039] On the other hand, if the frequency of the ultrasound deviates from the above range, it may damage the carrier, resulting in a decrease in durability. If the ultrasound treatment time is less than 10 seconds, the effect of improving durability and activity may not be obvious. If the ultrasound treatment time exceeds 60 minutes, it may lead to a decrease in the physical durability of the carrier.

[0040] Step (B) is to apply a voltage to the result of step (A) to electroplate the active metal catalyst onto the surface of the support. Even with a small amount of active metal catalyst, it can be uniformly deposited on a large surface area, thereby enabling excellent ammonia oxidation reactions to occur at more active sites.

[0041] In the electroplating process of step (B), the voltage can be -1.0 to 1.0V, preferably -0.5 to 0.8V, more preferably -0.2 to 0.4V, and the electroplating time can be 600 to 5400 seconds, preferably 1200 to 4800 seconds, more preferably 2400 to 4200 seconds. In particular, if the electroplating time is less than 600 seconds, the amount of deposited active metal catalyst may be insufficient; if the electroplating time exceeds 5400 seconds, the amount of deposited active metal catalyst may be excessive, which may reduce the economic efficiency of preparing the catalytic electrode for ammonia electrolysis.

[0042] Furthermore, the present invention provides a method for preparing a catalytic electrode for ammonia electrolysis, characterized in that the solution in step (A) further contains an electrolyte for ultrasonic treatment.

[0043] There are no particular restrictions on the electrolyte as long as it is a salt that enables the active metal catalyst to migrate from the active metal catalyst precursor to the support for electroplating. For example, NaCl, KCl, KOH, LiCl, HClO4, HCl, H2SO4, etc. can be used. Considering the deposition efficiency, catalytic activity and the stability of the catalytic electrode, acidic electrolytes such as HClO4, HCl, and H2SO4 are preferred, and HClO4 is even more preferred.

[0044] The concentration of the electrolyte contained in the solution of step (A) can be 0.5~5000 mM, preferably 5~3000 mM, and more preferably 100~1000 mM. If the electrolyte deviates from the above concentration range, the amount of supported metal catalyst may be insufficient or the support may be damaged.

[0045] Furthermore, according to a specific example of the present invention, a method for preparing a catalytic electrode for ammonia electrolysis can be provided, characterized in that, in step (A), the support comprises nickel and is treated by the ultrasonic disperser, the surface of the catalytic electrode for ammonia electrolysis comprises 1-50% by weight of nickel hydroxide, and the active metal catalyst electroplated in step (B) is platinum, the amount of platinum loaded on the catalytic electrode for ammonia electrolysis is 20-60% by weight.

[0046] On the other hand, if the nickel hydroxide falls outside the above range, the catalytic activity may decrease, and if the platinum content is higher than the above range, the economics may be reduced.

[0047] Furthermore, surface chemical species analysis of the following test examples confirmed that the nickel hydroxide content can be increased to approximately 90% of the platinum content by the ultrasonic disperser treatment. The amount of nickel hydroxide contained in the catalytic electrode can be 1 to 50% by weight, preferably 10 to 45% by weight, and more preferably 30 to 45% by weight, from the perspective of maximizing the durability and catalytic activity of the catalytic electrode.

[0048] Furthermore, the present invention can provide a catalytic electrode for ammonia electrolysis prepared by the above preparation method, thereby improving durability and catalytic activity.

[0049] That is, according to the present invention, before electroplating the active metal catalyst onto the support, the support is treated with the ultrasonic disperser. During this treatment, the support is immersed in a precursor solution of the active metal catalyst, and ultrasonic treatment is performed at a specific frequency and for a specific time, thereby forming hydroxides and seeds of the active metal catalyst on the surface of the support. Therefore, the hydroxides prevent poisoning caused by nitrogen oxides, improving electrode durability, and the active metal catalyst can be electroplated more actively around the seeds. This provides a catalytic electrode for ammonia electrolysis with improved loading and catalytic activity of the active metal catalyst compared to the same electroplating process time.

[0050] The present invention will now be described in more detail through specific embodiments and comparative examples.

[0051] Example 1

[0052] A nickel support (MTI Korea, nickel thickness 1600 μm, porosity 50~98%) with a transverse dimension of 1 cm and a longitudinal dimension of 1 cm was placed in a solution containing 2 mM chloroplatinic acid (H2PtCl6xH2O) as an active metal catalyst precursor and 100 mM electrolyte HClO4. The solution was treated with an ultrasonic disperser (UCP-20, JEIO TECH) at a frequency of 40 kHz for 7 minutes.

[0053] After the ultrasonic treatment, a voltage of -0.2 to 0.4 V is applied to the solution for 4200 seconds to deposit a platinum catalyst on the surface of a nickel support, thereby preparing a catalytic electrode for ammonia electrolysis.

[0054] Example 2

[0055] Except for the ultrasonic treatment for 2 minutes as in Example 1, the catalytic electrode for ammonia electrolysis was prepared using the same method as in Example 1.

[0056] Example 3

[0057] Except for the ultrasonic treatment for 15 minutes as in Example 1, the catalytic electrode for ammonia electrolysis was prepared using the same method as in Example 1.

[0058] Example 4

[0059] Except that 0.05M H2SO4 was used as the electrolyte in Example 1, the catalytic electrode for ammonia electrolysis was prepared using the same method as in Example 1.

[0060] Example 5

[0061] Except that 0.1M KOH was used as the electrolyte in Example 1, the catalytic electrode for ammonia electrolysis was prepared using the same method as in Example 1.

[0062] Comparative Example 1

[0063] Except that an ultrasonic disperser was not used for ultrasonic treatment in Example 1, the catalytic electrode for ammonia electrolysis was prepared using the same method as in Example 1.

[0064] Comparative Example 2

[0065] Except that no electrolyte was added in Example 1, the catalytic electrode for ammonia electrolysis was prepared using the same method as in Example 1.

[0066] Experimental Example 1

[0067] To confirm the changes on the nickel carrier surface caused by ultrasonic treatment in this invention, scanning electron microscopy (SEM) analysis was performed on the nickel carrier before electroplating in Example 1 and Comparative Example 1, and the results are shown below. Figure 1 and Figure 2 .

[0068] Reference Figure 1 and Figure 2 It can be confirmed that the nickel carrier surface in Example 1, which underwent ultrasonic treatment (refer to...) Figure 1 Platinum catalyst seeds were formed on the surface, which is different from Comparative Example 1 (refer to) that did not undergo ultrasonic treatment. Figure 2 )different.

[0069] Furthermore, to confirm the changes on the surface of the catalytic electrode for ammonia electrolysis caused by ultrasonic treatment in this invention, SEM analysis was performed on the catalytic electrodes for ammonia electrolysis prepared according to Example 1 and Comparative Example 1, and the results are shown below. Figure 3 and Figure 4 .

[0070] Reference Figure 3 and Figure 4 The shape of the platinum catalyst electroplated on the surface of the catalytic electrode for ammonia electrolysis prepared according to Example 1 was confirmed (refer to...). Figure 3 The shape of the platinum catalyst electroplated on the surface of the catalytic electrode for ammonia electrolysis prepared according to Comparative Example 1 (see reference). Figure 4 Similar to [the previous description of the platinum catalyst]. This confirms that ultrasonic treatment does not affect the shape of the platinum catalyst during electroplating.

[0071] Experimental Example 2

[0072] To confirm the change in platinum content of the nickel carrier caused by ultrasonic treatment in this invention, ICP (Inductively Coupled Plasma) analysis was performed on the nickel carriers in Examples 1, 2, and Comparative Example 1 before electroplating to determine the platinum content, and the results are presented below. Figure 5 .

[0073] Reference Figure 5 Almost no platinum content was detected in the nickel support of Comparative Example 1, which is consistent with the results of Test Example 1, confirming that the platinum content of the nickel support of Example 1 was 340% higher than that of Example 2.

[0074] It is evident that, through ultrasonic treatment, a galvanic displacement reaction occurs, in which platinum, which has a higher standard reduction potential than nickel, is reduced. Furthermore, it is observed that the platinum content on the nickel support surface increases with increasing ultrasonic treatment time.

[0075] Furthermore, to confirm the change in platinum content in the catalytic electrode for ammonia electrolysis caused by ultrasonic treatment in this invention, ICP (Inductively Coupled Plasma) analysis was performed on the catalytic electrodes for ammonia electrolysis prepared according to Examples 1, 2, and Comparative Example 1 to determine the deposited platinum content, and the results are shown below. Figure 6 .

[0076] Reference Figure 6 It was confirmed that the platinum content of the catalytic electrode for ammonia electrolysis prepared according to Example 2 was 140% higher than that of Comparative Example 1, and the platinum content of the catalytic electrode for ammonia electrolysis prepared according to Example 1 was 190% higher than that of Example 2.

[0077] Therefore, it can be seen that the amount of platinum catalyst deposited during electroplating is proportional to the amount of platinum seeds formed by the ultrasonic treatment.

[0078] Experimental Example 3

[0079] To confirm the factor contributing to the improved durability of the ammonia electrolysis catalytic electrode resulting from ultrasonic treatment in this invention, the changes in the oxidation numbers of platinum and nickel on the surfaces of the ammonia electrolysis catalytic electrode prepared according to Example 1, the nickel support before electroplating in Comparative Example 1, and the ammonia electrolysis catalytic electrode prepared according to Comparative Example 1 were analyzed by X-ray photoelectron spectroscopy, and the results are shown below. Figures 7 to 9 In addition, Figures 7 to 9 The surface chemical species and chemical binding energies corresponding to the peak values ​​in each figure are shown in Tables 1 to 3 below.

[0080] [Table 1]

[0081]

[0082] [Table 2]

[0083]

[0084] [Table 3]

[0085]

[0086] Reference Figures 7 to 9 And the surface chemical species analysis results of the nickel carrier before electroplating in Comparative Example 1, as shown in Tables 1 to 3 above (refer to Tables 1 to 3 above). Figure 8 In Table 2, the peak values ​​of the chemical binding energies of nickel metal (Ni, 3p 3 / 2) and nickel oxide (NiO, 3p 3 / 2) corresponding to 66.06 eV and 67.64 eV can be confirmed, and the peak intensity of the platinum (Pt) metal phase is confirmed to be 12% of that of nickel oxide, which is significantly lower.

[0087] On the other hand, the surface chemical species analysis results of the catalytic electrode for ammonia electrolysis prepared according to Comparative Example 1 (refer to...) Figure 9 In Table 3), it was confirmed that Pt 0 and Pt 2+ The corresponding peak chemical binding energy is as high as 1:0.03 (Pt:Ni(OH)2) compared to the peak of nickel hydroxide, while the surface chemical species analysis results of the catalytic electrode for ammonia electrolysis prepared according to Example 1 (refer to...) Figure 7 As shown in Table 1), an increase in the peak value of nickel hydroxide (Ni(OH)2, 3p3 / 2) corresponding to a chemical binding energy of 68.08 eV was confirmed. Specifically, on the surface of the catalytic electrode, the peak ratio of platinum metal to nickel hydroxide increased to 1:0.89 (Pt:Ni(OH)2).

[0088] Therefore, it can be seen that through the ultrasonic treatment in Example 1, the content of nickel hydroxide on the surface of the catalytic electrode for ammonia electrolysis increases, specifically confirming that the content of nickel hydroxide can be increased to approximately 90% of the platinum content.

[0089] Test Example 4

[0090] To confirm the change in ammonia oxidation activity of the catalytic electrode for ammonia electrolysis caused by ultrasonic treatment in this invention, the ammonia oxidation characteristics of the catalytic electrodes for ammonia electrolysis prepared according to Examples 1 to 3 and Comparative Example 1 were measured, and the results are shown below. Figure 10 All electrochemical measurements for ammonia oxidation were performed using an electrochemical workstation (Zive, WonATech). Specifically, the measurements were conducted in a 1M NH4OH / 5M KOH electrolyte system, using a three-electrode system in a diaphragm-free, sealed glass beaker (to prevent ammonia evaporation). A Hg / HgO electrode (filling solution: 1.0M KOH) and a Pt mesh were used as the reference and counter electrodes, respectively. Cyclic voltage-current method (CV) curves of the catalyst were obtained at a scan rate of 20 mV / s, ranging from -0.15 to 1.2 V relative to the reversible hydrogen electrode (RHE). Furthermore, under a hydrogen atmosphere, using a Pt mesh as the electrode and Hg / HgO as the reference electrode, all potentials measured for Hg / HgO were converted to the RHE scale as shown in Equation 1 below.

[0091] [Mathematical Expression 1]

[0092] V RHE =V Hg / HgO +0.97 (experimental measurement value)

[0093] Reference Figure 10 The catalytic performance of ammonia oxidation is as follows: the catalytic electrode for ammonia electrolysis prepared according to Comparative Example 1 has a performance of 510 mA / cm². 2 The catalytic electrode for ammonia electrolysis prepared according to Example 3 has a strength of 600 mA / cm². 2 The catalytic electrode for ammonia electrolysis prepared according to Example 2 has a strength of 650 mA / cm². 2 The catalytic electrode for ammonia electrolysis prepared according to Example 1 has a strength of 770 mA / cm². 2 It can be confirmed that the trend of the ammonia oxidation catalytic performance increases in the order of Comparative Example 1, Example 3, Example 2 and Example 1.

[0094] Therefore, it can be seen that in the range where the ultrasonic treatment time is less than 7 minutes, the activity of the ammonia oxidation reaction increases with the increase of ultrasonic treatment time, while when the ultrasonic treatment time exceeds 7 minutes, the activity of the ammonia oxidation reaction decreases.

[0095] Experimental Example 5

[0096] To confirm the stability changes of the catalytic electrode for ammonia electrolysis caused by ultrasonic treatment in this invention, the electrochemical stability of the catalytic electrodes for ammonia electrolysis prepared according to Examples 1 to 3 and Comparative Example 1 was evaluated under the following conditions, and the results are shown below. Figure 11 .

[0097] [Evaluation Criteria]

[0098] - Use 1M NH4OH / 5M KOH electrolyte, stirring at 200 rpm.

[0099] - Perform 50mA / cm at room temperature 2 The constant current test was used to determine the time required for water oxidation due to catalyst poisoning.

[0100] Reference Figure 11 The electrochemical stability of the catalytic electrodes was as follows: 5 hours for the catalytic electrode for ammonia electrolysis prepared according to Comparative Example 1, 13 hours for the catalytic electrode for ammonia electrolysis prepared according to Example 2, 44 hours for the catalytic electrode for ammonia electrolysis prepared according to Example 3, and 48 hours for the catalytic electrode for ammonia electrolysis prepared according to Example 1. In particular, the catalytic electrode for ammonia electrolysis prepared according to Example 1 exhibited an electrochemical stability that was 9.6 times higher than that of Comparative Example 1.

[0101] On the other hand, in the case of the catalytic electrode for ammonia electrolysis with a specific ultrasonic treatment time in this invention (Example 1), a significantly improved electrochemical stability was observed compared to the increase rate of platinum catalyst content, and the content of nickel hydroxide on the surface of the catalytic electrode increased. Based on these experimental results, it can be concluded that the catalytic electrode for ammonia electrolysis prepared by the method of this invention, subjected to ultrasonic treatment for a specific time as described above, thereby forming hydroxide on the support surface and preventing poisoning by nitrogen oxides, thus improves electrochemical stability and durability.

[0102] Experimental Example 6

[0103] To confirm the changes in ammonia oxidation activity and stability of the catalytic electrode caused by the pH of the electrolyte in this invention, the ammonia oxidation characteristics and electrochemical stability of the catalytic electrodes for ammonia electrolysis prepared according to Examples 4, 5 and Comparative Example 2 were evaluated in the same manner as in Test Examples 4 and 5, and the results are shown in Table 4 below.

[0104] [Table 4]

[0105]

[0106] Referring to Table 4, it was confirmed that the ammonia oxidation activity and electrochemical stability of the catalytic electrode for ammonia electrolysis using an acidic electrolyte (Example 4) were significantly improved compared to the catalytic electrode for ammonia electrolysis using an alkaline electrolyte (Example 5) and the catalytic electrode for ammonia electrolysis without an electrolyte (Comparative Example 2).

[0107] The preferred embodiments of the present invention have been described in detail above. The description of the present invention is exemplary, and those skilled in the art should understand that it can be easily modified into other specific forms without changing the technical concept or essential features of the present invention.

[0108] Therefore, the scope of the invention should be defined by the claims rather than the foregoing detailed description, and all modifications or variations derived from the meaning, scope and equivalent concepts of the claims should be interpreted as being included within the scope of the invention.

Claims

1. A method for preparing a catalytic electrode for ammonia electrolysis, comprising: Step (A): The support is subjected to ultrasonic treatment in a solution containing a precursor of an active metal catalyst; as well as Step (B) involves applying a voltage to the result of step (A) to electroplate the active metal catalyst onto the surface of the support.

2. The method for preparing the catalytic electrode for ammonia electrolysis according to claim 1, characterized in that, In step (A), the frequency of the ultrasound is 10~130kHz, and the processing time is 10 seconds~60 minutes.

3. The method for preparing the catalytic electrode for ammonia electrolysis according to claim 1, characterized in that, The carrier comprises one or more materials selected from nickel, iron, aluminum, and carbon. The active metal catalyst is selected from one or more of platinum, iridium, rhodium, palladium, ruthenium, iron, nickel and cobalt.

4. The method for preparing the catalytic electrode for ammonia electrolysis according to claim 1, characterized in that, The solution in step (A) further contains an electrolyte for ultrasonic treatment.

5. The method for preparing the catalytic electrode for ammonia electrolysis according to claim 4, characterized in that, The electrolyte is an acidic electrolyte.

6. The method for preparing the catalytic electrode for ammonia electrolysis according to claim 1, characterized in that, The carrier contains nickel. The active metal catalyst is platinum. The ammonia electrolysis catalytic electrode is loaded with 20-60% by weight of platinum and contains 1-50% by weight of nickel hydroxide through the ultrasonic treatment.

7. A catalytic electrode for ammonia electrolysis, prepared according to any one of claims 1 to 6.

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