Catalyst capable of being used for preparing ammonia gas by reducing nitrate as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst capable of being used for preparing ammonia gas by reducing nitrate as well as a preparation method and application of the catalyst. The catalyst comprises a nitrogen-doped carbon carrier and three copper atoms loaded on the nitrogen-doped carbon carrier. The catalyst provided by the invention has excellent electrochemical catalytic nitrate reduction performance, and can be used for reducing nitrate to prepare ammonia gas.

Description

Technical Field

[0001] The present invention belongs to the field of materials, and in particular relates to a catalyst that can be used to reduce nitrate to prepare ammonia, as well as a preparation method and application thereof. Background Art

[0002] Nitrogen is a basic element in living organisms. The nitrogen cycle plays a vital role in maintaining the balance of elements in the biosphere and has a direct impact on human life. However, excessive human intervention and industrial development have led to the accumulation of nitrates (NO3 - ) pollution, gradually destroying the balance of nitrogen cycle mediated by microorganisms. Excessive release of NO3 - It poses a major threat to the ecological environment and public health, for example, NO3 - Accumulation in rivers and lakes can lead to eutrophication, which is harmful to aquatic life; NO3 in drinking water - The presence of NO3 can damage the human endocrine system and lead to serious diseases; - The nitrite (NO2 - ) is a carcinogenic compound. Therefore, removing NO3 from water - is crucial.

[0003] Traditional biological, physical and chemical methods have been used to remove NO3 from water. - However, they produce secondary pollution and require subsequent treatment, which limits the widespread use of traditional methods. Compared with these treatment methods, the electrocatalytic nitrate reduction reaction (NO3RR) is a promising alternative because it uses renewable electricity, operates under mild conditions, and does not produce harmful residues.

[0004] NO3 - As the main nitrogen pollutant in surface and groundwater, converting it into more valuable ammonia (NH3) is an effective way to balance the disturbed nitrogen cycle and has attracted widespread attention from researchers in the past few decades. NO3RR involves the transfer of 9 protons and 8 electrons, which is a kinetically slow process. In addition, byproducts such as NO2 - , hydrazine N2H4 and nitrogen N2, which will affect the selectivity of NH3. In addition, the electrocatalytic hydrogen production HER competes with NO3RR, resulting in low Faradaic efficiency.

[0005] To address these challenges, the development of efficient electrocatalysts with high selectivity for ammonia production is urgently needed. Summary of the Invention

[0006] In response to the shortcomings and deficiencies of the prior art, the present invention uses nitrogen-doped carbon derived from a copper metal-organic framework as a support. Through precursor coordination environment regulation and high-temperature carbonization strategy, a catalyst with different copper species configurations, supported on nitrogen-doped carbon (NC) derived from a copper metal-organic framework (Cu-BTC), is provided for the electrochemical catalytic reduction of nitrates to remove nitrate pollutants from water. To obtain catalysts with different copper species configurations, the amount of copper source and 1,3,5-benzenetricarboxylic acid was regulated. Experiments have shown that this method can be used to simply and efficiently synthesize a catalyst that can be used to reduce nitrate to produce ammonia. The prepared catalyst has good catalytic performance for electrochemical nitrate reduction.

[0007] According to a first aspect of the present invention, a catalyst for reducing nitrate to produce ammonia is provided. The catalyst comprises a nitrogen-doped carbon support and three copper atoms supported on the nitrogen-doped carbon support.

[0008] In some embodiments, the catalyst is a nanosheet structure.

[0009] In some embodiments, the distance between two adjacent copper atoms in the copper triatom is For example, or any value in between.

[0010] In some embodiments, the distance between two adjacent copper atoms in the copper triatoms is and

[0011] In some embodiments, the mass content of copper in the catalyst is 15% to 40%, preferably 15% to 20%. In some embodiments, the mass content of copper in the catalyst is 15%, 16%, 17%, 18%, 19%, 20%, 25%, 30%, 35%, 40%, or any value therebetween.

[0012] According to a second aspect of the present invention, there is provided a method for preparing a catalyst that can be used to reduce nitrate to produce ammonia, the method comprising the following steps:

[0013] S1: mixing solution A containing a copper source with solution B containing 1,3,5-benzenetricarboxylic acid and reacting them;

[0014] S2: performing solid-liquid separation and drying on the reaction product obtained in step S1 to obtain a metal organic framework material;

[0015] S3: calcining the mixture of the metal organic framework material obtained in step S2 and dicyandiamide in an inert atmosphere to obtain the catalyst.

[0016] In some embodiments, in step S1, the molar ratio of the 1,3,5-benzenetricarboxylic acid to the copper element in the copper source is 1:(2.2-2.8), for example, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8 or any value therebetween.

[0017] In some embodiments, in step S1, the copper source includes at least one of copper chloride, copper nitrate, copper sulfate, and copper acetate.

[0018] In some embodiments, in step S1, the solvent in the solution A and / or the solution B includes a C1-C3 alcohol compound, preferably one or more of methanol, ethanol, and propanol.

[0019] In some embodiments, in step S1, the reaction temperature is 15-40°C and the reaction time is 10-40 hours. In some embodiments, in step S1, the reaction temperature is 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or any value therebetween. In some embodiments, in step S1, the reaction time is 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, or any value therebetween.

[0020] In some embodiments, in step S2, X-ray diffraction characterization shows that the metal organic framework material has characteristic peaks at 2θ of 5.8°±0.2°, 6.7°±0.2°, 9.5°±0.2°, 11.6°±0.2°, 13.4°±0.2°, 17.5°±0.2° and 19.0°±0.2°.

[0021] In some embodiments, in step S3, the mass ratio of the metal organic framework material to dicyandiamide is 1:(8-15), preferably 1:(8-12). In some embodiments, the mass ratio of the metal organic framework material to dicyandiamide is 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 or any value therebetween.

[0022] In some embodiments, in step S3, the calcination temperature is 700-1000° C., preferably 750-850° C. In some embodiments, the calcination temperature is 700° C., 750° C., 800° C., 850° C., 900° C., 950° C., 1000° C. or any value therebetween.

[0023] In some embodiments, in step S3, the calcination time is 1-5 hours, preferably 1-3 hours. In some embodiments, the calcination time is 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours or any value therebetween.

[0024] In some embodiments, the preparation method further comprises cooling the calcined product and then acid washing and drying it.

[0025] According to a third aspect of the present invention, there is provided use of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in a reaction of electrochemical catalytic reduction of nitrate to produce ammonia.

[0026] In some embodiments, the reaction is carried out in aqueous phase.

[0027] The material synthesis method of the present invention is simple and easy to operate, and the prepared copper triatomic catalyst has excellent electrochemical catalytic nitrate reduction performance. This excellent electrocatalytic NO3RR performance is due to the unique configuration of Cu3 / NC with fully exposed triatomic Cu supported on an ultra-thin NC substrate. This structure gives the catalyst abundant active sites and can promote the rapid deoxygenation and hydrogenation steps in the NO3RR process through the synergistic effect of adjacent Cu sites, avoiding the byproduct NO2 - The accumulation of NH3 / NC also inhibits the competitive HER; at the same time, it adjusts the electronic configuration and d-band center of the catalyst, optimizes the adsorption and desorption ability of reaction intermediates on its surface, and makes Cu3 / NC have excellent NO3RR performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 (a) is a scanning electron microscope image and (b) is an XRD spectrum of Cu-BTC in Example 1 according to the present invention.

[0029] Figure 2 1 is the XRD spectrum of Cu3 / NC in Example 1 according to the present invention.

[0030] Figure 3 2. Transmission electron microscope image (a) and spherical aberration corrected high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) image (b) of Cu3 / NC in Example 1 according to the present invention.

[0031] Figure 4 1 is a high-angle annular dark-field scanning transmission electron microscope image of Cu3 / NC in Example 1 of the present invention and a corresponding element distribution mapping diagram of Cu, C and N.

[0032] Figure 5NH3 production rate (a) at different potentials and NH3 Faraday efficiency FE (b) at different potentials in Example 1 of the present invention.

[0033] Figure 6 According to Example 1 of the present invention, NO3 in the solution at -0.8V - 、NO2 - and NH4 + The concentration changes with time.

[0034] Figure 7 NH3 production rate and Faradaic efficiency FE of Cu3 / NC in Example 1 according to the present invention after 7 cycles at -0.8V.

[0035] Figure 8 2 is the XRD pattern of Cu1 / NC in Example 2 according to the present invention.

[0036] Figure 9 2 are a transmission electron microscope image (a) and a spherical aberration corrected HAADF-STEM image (b) of Cu1 / NC in Example 2 according to the present invention.

[0037] Figure 10 2. HAADF-STEM image of Cu1 / NC corrected for spherical aberration and the corresponding mapping diagram according to Example 2 of the present invention.

[0038] Figure 11 NH3 production rate (a) at different potentials and NH3 Faraday efficiency FE (b) at different potentials in Example 2 of the present invention.

[0039] Figure 12 is the Cu in Example 3 according to the present invention p / NC XRD spectrum.

[0040] Figure 13 is the Cu in Example 3 according to the present invention p Transmission electron microscopy image (a) and HRTEM image (b) of / NC.

[0041] Figure 14 3. HAADF-STEM image and corresponding mapping diagram after spherical aberration correction according to Example 3 of the present invention.

[0042] Figure 15 NH3 production rate (a) at different potentials and NH3 Faraday efficiency FE (b) at different potentials in Example 3 of the present invention. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. The specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention in any way. In addition, descriptions of known structures and techniques are omitted in the following description to avoid unnecessary confusion about the concepts of the present disclosure. Such structures and techniques are also described in many publications.

[0044] In the present invention, "copper triatoms" refer to three adjacent copper atoms supported on a nitrogen-doped carbon support. These three copper atoms are bound together by electrostatic attraction to form a metallic bond. The distance between two adjacent copper atoms is

[0045] The reagents and / or drugs used in the following examples are commercially available or can be synthesized by known methods.

[0046] The detection methods used in the following examples are as follows:

[0047] (1) Detection of NH3 yield and Faraday efficiency FE

[0048] The NO₃RR process was performed in an H-type electrolytic cell. 50 mL of 1 M KOH solution was poured into one side as the anolyte, and 50 mL of 1 M KOH + 0.1 M KNO₃ solution was poured into the other side as the catholyte. The anodic and cathodic compartments were separated by a Nafion membrane. A platinum electrode served as the counter electrode in the anodic compartment, while a Hg / HgO electrode and a catalyst-loaded carbon paper sandwiched between stainless steel electrodes served as the reference and working electrodes, respectively. The reaction was performed on a CHI760E electrochemical workstation. The NO₃RR process was driven by an I2C (IT) system with a reaction time of 30 minutes and a set voltage. The post-reaction solution was sampled and subsequently diluted, developed, and measured for UV absorbance to determine the NH₃ yield and Faradaic efficiency (FE) of the catalyst.

[0049] (2) NO3 - 、NO2 - and NH4 +The concentration detection of NO3RR process was carried out in an H-type electrolytic cell. 50mL of 1M KOH solution was poured into one side as the anode solution, and 50mL of 1M KOH+0.1M KNO3 solution was poured into the other side as the cathode solution. The anode chamber and the cathode chamber were separated by a Nafion membrane. A platinum electrode was inserted into the anode chamber as the counter electrode, and a Hg / HgO electrode and a carbon paper loaded with a catalyst sandwiched between stainless steel electrodes were inserted into the cathode chamber as the reference electrode and the working electrode, respectively. The reaction was carried out on a CHI760E electrochemical workstation. The NO3RR process was driven by it, and the reaction time and reaction voltage were set to 8h, and samples were taken every 1h. All solutions after the reaction were diluted, colored, and tested for ultraviolet absorbance to obtain NO3 - 、NO2 - and NH4 + concentration.

[0050] (3) Detection of NH3 yield and Faraday efficiency FE after 7 cycles

[0051] The NO3RR process was performed in an H-type electrolytic cell. 50 mL of 1 M KOH solution was poured into one side as the anolyte, and 50 mL of 1 M KOH + 0.1 M KNO3 solution was poured into the other side as the catholyte. The anodic and cathodic compartments were separated by a Nafion membrane. A platinum electrode served as the counter electrode in the anodic compartment, while a Hg / HgO electrode and a catalyst-loaded carbon paper sandwiched between stainless steel electrodes served as the reference and working electrodes, respectively. The reaction was performed on a CHI760E electrochemical workstation. The NO3RR process was driven by an iterative reaction (IT) with a reaction time of 30 minutes and a set voltage. After the reaction, a sample was retained, and the catholyte and anolyte solutions were replaced with 50 mL of 1 M KOH + 0.1 M KNO3 solution for the catholyte and 50 mL of 1 M KOH for the anolyte. The iterative reaction was repeated, and a sample of the post-reaction solution was retained. After seven cycles, the retained sample was diluted, developed, and measured for UV absorbance to determine the NH3 yield and Faradaic efficiency (FE) of the catalyst.

[0052] Example 1 Preparation of Nitrogen-doped Carbon-supported Copper Triatoms Cu3 / NC Catalyst

[0053] (1) Synthesis of Cu-BTC:

[0054] 4.832g of Cu(NO3)2·3H2O (0.02mol) was dissolved in 100mL of methanol to form solution A; 1.681g of 1,3,5-benzenetricarboxylic acid (BTC) (0.008mol) was dissolved in 100mL of methanol to form solution B. Solution A was then slowly added to solution B, mixed, and stirred at 400rpm for 10 minutes to obtain a blue solution. The blue solution was left at room temperature for 24 hours. Subsequently, the solid was washed with methanol by centrifugation at 8000rpm for 5 minutes each time, and the obtained solid was the Cu-BTC precursor. Finally, the Cu-BTC precursor was freeze-dried.

[0055] (2) Synthesis of Cu3 / NC:

[0056] A Cu-BTC precursor and dicyandiamide were mixed in a 1:10 mass ratio and directly carbonized at 800°C under an argon flow at a heating rate of 5°C / min. After holding for 2 hours, the mixture was naturally cooled to room temperature. Subsequently, the product was immersed in 5 wt.% hydrochloric acid for 4 hours with stirring and then washed with ethanol by centrifugation at 8000 rpm for 5 minutes each. Finally, the Cu3 / NC was freeze-dried.

[0057] like Figure 1 As shown in a, the scanning electron microscope image shows that the precursor Cu-BTC has a clear octahedral morphology. The XRD spectrum of Cu-BTC is consistent with the fitting results ( Figure 1 b), there are typical peaks at 2θ = 5.8° (111), 6.7° (200), 9.5° (220), 11.6° (222), 13.4° (400), 17.5° (511) and 19.0° (440), indicating its successful synthesis.

[0058] Figure 2 The diffraction pattern of Cu3 / NC was shown to be similar to a broad graphitic peak, indicating that no metal or oxide nanocrystals were formed.

[0059] exist Figure 3 In a, Cu3 / NC exhibits a nanosheet structure. Spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image ( Figure 3 b) shows that in Cu3 / NC, the adjacent three-atom structure is clearly visible. The raster image in the illustration directly shows the three representative metal atoms in the blue box area. The distance between the two adjacent atoms is and

[0060] from Figure 4 From the element distribution map of Cu3 / NC, we can see that Cu, C, and N elements are evenly distributed on the surface of the material.

[0061] Figure 5 a shows the NH3 production rate in the voltage range of -0.6 V to -1.0 V. It can be seen from the figure that the NH3 production rate increases as the applied potential shifts negatively from -0.6 V and reaches a maximum of 24816 μg h at -0.8 V. -1 mg -1 , and then slightly decreased with the continued increase of the applied potential. This may be because the more negative applied potential promotes the competitive hydrogen evolution reaction, thereby reducing the yield of NH3. The highest ammonia yield achieved at -0.8V is better than that of most reported materials (5000-15000μgh -1 mg -1 between).

[0062] Figure 5 b shows the Faraday efficiency FE in the voltage range of -0.6V to -1.0V. It can be seen from the figure that the Faraday efficiency of Cu3 / NC shows a volcanic trend, reaching a maximum of 95.4% at -0.8V. The overall Faraday efficiency is maintained above 70%, indicating that Cu3 / NC has a wide voltage range for NO3 - Degradation to produce ammonia has good energy efficiency.

[0063] like Figure 6 As shown, when the starting NO3 - When the concentration is 100mmol / L, NO3 - After 7 hours, the degradation is almost complete. A small amount of toxic byproduct NO2 is produced after 2 hours of reaction. - However, after 5 hours of reaction, the intermediate product NO2 - Almost all of the conversion is completed, and the final products are all important chemicals such as ammonia and pollution-free nitrogen.

[0064] from Figure 7 It can be seen that after 7 NO3RR cycles at -0.8 V, the NH3 yield and Faradaic efficiency FE did not show a significant attenuation, indicating that Cu3 / NC has good electrocatalytic NO3RR stability.

[0065] Example 2 Preparation of nitrogen-doped carbon-supported single-atom copper Cu1 / NC catalyst:

[0066] 0.966 g of Cu(NO₃)₂·3H₂O (0.004 mol) was dissolved in 100 mL of methanol to form Solution A. 1.681 g of 1,3,5-benzenetricarboxylic acid (0.008 mol) was dissolved in 100 mL of methanol to form Solution B. Solution A was then slowly added to Solution B, mixed, and stirred at 400 rpm for 10 minutes to obtain a blue solution. The blue solution was allowed to stand at room temperature for 24 hours. Subsequently, the solution was washed with methanol by centrifugation at 8000 rpm for five times, each for 5 minutes. The Cu-BTC precursor was freeze-dried.

[0067] The Cu-BTC precursor was then mixed with dicyandiamide in a 1:10 mass ratio and directly carbonized under an argon flow at 800°C at a heating rate of 5°C / min. After a 2-hour hold, the mixture was naturally cooled to room temperature. The product was then immersed in 5 wt.% hydrochloric acid for 4 hours with stirring and then washed with ethanol by centrifugation at 8000 rpm for 5 minutes each. Finally, the Cu1 / NC was freeze-dried.

[0068] The diffraction pattern of Cu1 / NC ( Figure 8 ) is similar to the broad graphitic peak, indicating that there is no formation of metal or oxide nanocrystals.

[0069] Transmission electron microscopy image of Cu1 / NC ( Figure 9 a) HAADF-STEM image showing its nanosheet morphology and spherical aberration correction ( Figure 9 b) can be observed scattered bright spots, corresponding to the dispersed Cu atoms. Figure 10 In the Mapping diagram, we can see that Cu, C, and N elements are evenly distributed on the surface of the material.

[0070] Example 3 Preparation of Nitrogen-doped Carbon-supported Copper Nanoclusters Cu p / NC catalyst:

[0071] Solution A was formed by dissolving 1.82 g of Cu(NO₃)₂·3H₂O (0.0075 mol) in 50 mL of methanol. Solution B was formed by dissolving 0.8575 g of 1,3,5-benzenetricarboxylic acid (0.0041 mol) in 50 mL of methanol. Solution A was slowly added to Solution B while sonicating, forming a blue solution. The precipitate was recovered by centrifugation and washed with methanol at 8000 rpm for five times, each for 5 minutes, to remove any reaction residue. The powder was then freeze-dried.

[0072] Then the powder was mixed with dicyandiamide powder in a mass ratio of 1:10, and directly carbonized under argon flow at 800 ° C with a heating rate of 5 ° C / min. After keeping warm for 2 hours, it was naturally cooled to room temperature to obtain a solid, which is Cu p / NC; Finally, Cu p / NC was freeze-dried.

[0073] like Figure 12 As shown, Cu p / NC exhibits weak diffraction peaks at 43.3°, 50.2°, and 73.6°, corresponding to the (111), (200), and (220) planes of metallic Cu, respectively (PDF 1-1241).

[0074] Cu p TEM image of NC ( Figure 13 In a), copper clusters aggregated on the nanosheets are seen, and high-resolution transmission electron microscopy (HRTEM) images ( Figure 13 b) shows a 0.21 nm lattice fringe, corresponding to the Cu(111) crystal plane. The obvious white spots on HAADF-STEM are clusters of copper. Figure 14 The mapping diagram shows that Cu is aggregated, while C and N elements are evenly distributed.

[0075] Figure 11 a and 11b show the electrochemical catalytic nitrate reduction performance of Cu1 / NC; Figure 15 a and 15b show Cu p Electrochemical catalytic nitrate reduction performance of / NC.

[0076] according to Figure 5 and Figure 11 、 Figure 15 It can be seen that Cu1 / NC, Cu3 / NC, Cu p / NC can be used for electrochemical catalysis of nitrate to synthesize ammonia, which can effectively convert the pollutant NO3 in water. - .

[0077] The experimental results show that the electrochemical catalytic nitrate reduction performance of the catalyst Cu3 / NC prepared in Example 1 is the best. The Faradaic efficiency can be maintained above 70% in a large voltage range (-0.6V to -1.0V), and can reach a maximum of 95.4% at -0.8V. At the same time, the ammonia yield reaches a maximum of 24816 μg h -1 mg -1 , demonstrating excellent electrocatalytic stability over seven cycles, with no significant degradation in NH3 yield and Faradaic efficiency (FE). Furthermore, the Cu3 / NC preparation method is simple and requires minimal metal, significantly improving atomic utilization, making it suitable for mass production and application.

[0078] In summary, the synthesis method of the catalyst in the present invention is simple and easy to operate, and the prepared Cu3 / NC has excellent electrochemical catalytic nitrate reduction performance.

[0079] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A catalyst for reducing nitrate to produce ammonia, the catalyst comprising a nitrogen-doped carbon support and copper atoms supported on the nitrogen-doped carbon support.

2. The catalyst according to claim 1, characterized in that The catalyst has a nano-sheet structure; and / or In the copper triatoms, the distance between two adjacent copper atoms is Preferably, in the copper triatoms, the distance between two adjacent copper atoms is and 3. The catalyst according to claim 1 or 2, characterized in that In the catalyst, the mass content of copper element is 15% to 40%, preferably 15% to 20%.

4. A method for preparing a catalyst for reducing nitrate to produce ammonia, comprising the following steps: S1: mixing solution A containing a copper source with solution B containing 1,3,5-benzenetricarboxylic acid and reacting them; S2: performing solid-liquid separation and drying on the reaction product obtained in step S1 to obtain a metal organic framework material; S3: calcining the mixture of the metal organic framework material and dicyandiamide obtained in step S2 in an inert atmosphere to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that In step S1, the molar ratio of the 1,3,5-benzenetricarboxylic acid to the copper element in the copper source is 1:(2.2-2.8); and / or In step S1, the copper source includes at least one of copper chloride, copper nitrate, copper sulfate, and copper acetate; and / or In step S1, the solvent in the solution A and / or the solution B comprises a C1-C3 alcohol compound, preferably one or more of methanol, ethanol, and propanol; and / or In step S1, the reaction temperature is 15-40° C. and the reaction time is 10-40 h.

6. The preparation method according to claim 4 or 5, characterized in that In step S2, X-ray diffraction characterization shows that the metal organic framework material has characteristic peaks at 2θ of 5.8°±0.2°, 6.7°±0.2°, 9.5°±0.2°, 11.6°±0.2°, 13.4°±0.2°, 17.5°±0.2° and 19.0°±0.2°.

7. The preparation method according to any one of claims 4 to 6, characterized in that In step S3, the mass ratio of the metal organic framework material to dicyandiamide is 1:(8-15), preferably 1:(8-12); and / or In step S3, the calcination temperature is 700-1000°C, preferably 750-850°C; and / or In step S3, the calcination time is 1-5 hours, preferably 1-3 hours.

8. The preparation method according to any one of claims 4 to 7, characterized in that The preparation method further comprises cooling the calcined product and then acid washing and drying it.

9. Use of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 8 in a reaction of electrochemical catalytic reduction of nitrate to produce ammonia.

10. The use according to claim 9, characterized in that The reaction is carried out in aqueous phase.

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