Integrated preparation and synthetic ammonia application of cobalt-ferroferric oxide / ferrous oxide loaded foam iron self-supporting electrode
By preparing a cobalt-doped self-supporting electrode Co-Fe3O4/FeO@IF, the problems of low ammonia yield and Faraday efficiency in the electrocatalytic reduction of nitrate to ammonia were solved, achieving high-efficiency electrocatalytic performance and improving electron conduction rate and reaction selectivity.
Patent Information
- Application Number
- CN202511962491.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-03-17
AI Technical Summary
Existing electrocatalytic nitrate reduction to ammonia synthesis technology suffers from low ammonia yield and low Faraday efficiency, and its kinetics are slow, often accompanied by competition from hydrogen evolution reaction, resulting in an overall energy efficiency that needs to be improved.
Cobalt-doped self-supporting electrodes Co-Fe3O4/FeO@IF were prepared by a hydrothermal method. Co-MOF-74, H4DOBDC and iron foam were dissolved in a solvent, and a cobalt-doped self-supporting electrode precursor Co/Fe-MOF-74@IF was uniformly loaded on iron foam through a one-step hydrothermal method. The cobalt-doped self-supporting electrode Co-Fe3O4/FeO@IF was then generated by calcination in a tube furnace.
Under alkaline conditions, an ammonia yield of 13.14 mg h–1 cm–2 and a Faraday efficiency of 85.53% were achieved, significantly improving the electrocatalytic nitrate reduction performance. This avoids the traditional powder catalyst coating step, maintains the intrinsic microstructure of the catalyst, and increases the contact area between the active sites and the reactants.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalytic nitrate reduction for ammonia synthesis, specifically the integrated preparation and application of a cobalt-iron tetroxide / ferrous oxide supported foamed iron self-supporting electrode in ammonia synthesis. Background Technology
[0002] The widespread use of artificial nitrogen fertilizers and the combustion of nitrogen-containing fossil fuels have severely impacted the global nitrogen cycle balance. Simultaneously, nitrogen oxides from industrial wastewater and vehicle emissions lead to the continuous accumulation of nitrogen oxides in the biosphere, with nitrates becoming one of the major pollutants in drinking water. Among various nitrate pollution control strategies, catalytically converting nitrates into NH3, which has both fertilizer and fuel value, is one of the most promising pathways. Currently, photocatalytic nitrate reduction to ammonia synthesis technology is limited by low ammonia yield and selectivity, making it difficult to meet the needs of large-scale industrial applications. Biocatalysis, on the other hand, suffers from limitations such as demanding reaction conditions and long cycles. In contrast, electrocatalytic nitrate reduction to ammonia (NO3RR) can achieve a relatively efficient ammonia synthesis process under ambient temperature and pressure conditions. However, this reaction involves an eight-electron transfer process, resulting in slow kinetics, and is often accompanied by competition from the hydrogen evolution reaction (HER), leading to room for improvement in its overall energy efficiency. Therefore, developing high-performance electrocatalysts is one of the key technologies for improving the efficiency of this process.
[0003] Non-noble transition metals, due to their abundant resources and significant cost advantages, can meet the needs of large-scale industrial applications and are ideal electrocatalyst materials. Fe3O4 exhibits comprehensive advantages in alkaline electrocatalytic nitrate reduction (NO3RR). Its spinel structure contains Fe... 2+ with Fe 3+ The sites can work synergistically to promote nitrate adsorption and intermediate conversion, effectively accelerating the reaction process. The material's inherent good electronic conductivity provides the necessary kinetics for the multi-electron transfer process. In an alkaline environment, Fe3O4 not only maintains high structural stability and reduces the dissolution of active components, but also inhibits hydrogen evolution side reactions, thereby improving the selectivity and overall reaction efficiency of the ammonia synthesis pathway. FeO exhibits unique catalytic potential in alkaline NO3RR. Its structure is rich in Fe... 2+ Site for nitrate (NO3) - FeO possesses excellent adsorption affinity, providing a crucial starting step for the reaction. The semiconductor properties of FeO allow for the modulation of its electronic structure through defect engineering and other techniques, optimizing the adsorption energy of reaction intermediates and thus improving reaction selectivity. Cobalt doping can effectively modulate the electronic structure of Fe3O4 / FeO, enhancing its adsorption capacity for nitrate and key reaction intermediates by optimizing the d-band center position, thereby significantly improving the efficiency and selectivity of electrocatalytic reduction for ammonia synthesis.
[0004] This invention prepares a Co / Fe-MOF-74@IF precursor supported on iron foam (IF) via a hydrothermal method, and further generates a cobalt-doped self-supporting electrode material (Co-Fe3O4 / FeO@IF) by calcination in a tube furnace. This method uses high-specific-surface-area, highly conductive iron foam as a substrate to in-situ grow a cobalt-introduced Fe3O4 / FeO composite catalytic material. The cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF fully utilizes the synergistic effect of Co, Fe3O4, and FeO. Its multi-active-site structure and unique interface significantly improve the performance of nitrate reduction to ammonia synthesis, providing a new pathway for the design of this type of catalyst. Summary of the Invention
[0005] The purpose of this invention is to obtain a cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF for efficient electrocatalytic ammonia synthesis, to solve the problems of low yield and Faraday efficiency in electrochemical nitrate reduction ammonia synthesis, and to provide a method for preparing Co-Fe3O4 / FeO@IF material and its application.
[0006] A method for preparing a cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF for efficient ammonia synthesis includes the following steps:
[0007] 1. Dissolve cobalt nitrate hexahydrate and 2,5-dihydroxyterephthalic acid (H4DOBDC) simultaneously in 50 ml of distilled water, 50 ml of DMF and 50 ml of ethanol, and then stir for a period of time until the solution is clear, resulting in a reddish-brown solution.
[0008] The amount of cobalt nitrate hexahydrate used in step one is 1.5–2.0 g;
[0009] The amount of H4DOBDC used in step one is 0.3–0.7 g;
[0010] 2. Add 50 ml of the reddish-brown reaction solution to a polytetrafluoroethylene (PTFE) reactor and react in the PTFE reactor at 100°C for 24 hours. Then, allow the PTFE reactor to cool naturally to room temperature. Collect the product by centrifugation and wash it three times with methanol. Soak it in methanol at room temperature for three days, changing the solution three times. Finally, place the obtained brown Co-MOF-74 in a vacuum drying oven at 60°C and dry it overnight.
[0011] 3. Dissolve Co-MOF-74 and H4DOBDC simultaneously in 25 ml of DMF, then stir for a period of time to obtain a brown solution.
[0012] The dosage of Co-MOF-74 described in step three is 0.01–0.05 g;
[0013] The amount of H4DOBDC used in step three is 0.03–0.08 g;
[0014] 4. Cut the foam iron to a size of 2×3cm, and then use acetone and 1mol·L⁻¹ to... -1 Rinse with sulfuric acid and deionized water for 5-10 minutes each.
[0015] 5. Add the brown reaction solution to a polytetrafluoroethylene (PTFE) reactor, then add the cleaned foamed iron. React in the PTFE reactor at 110℃ for 12 hours, then allow the PTFE reactor to cool naturally to room temperature. Remove the foamed iron and wash it several times with methanol. Finally, place the resulting black foamed iron in a vacuum drying oven at 60℃ and dry it overnight. Place the dried foamed iron in a tube furnace and heat it at 900℃ for 2 hours under an Ar atmosphere. The resulting light black foamed iron is the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF.
[0016] Cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF was used as an electrocatalyst to electrocatalyze the reduction of nitrate to ammonia.
[0017] Compared with the prior art, this embodiment has the following characteristics:
[0018] I. This invention employs a simple hydrothermal synthesis technique, utilizing Co-MOF-74, H4DOBDC, and iron foam dissolved in a solvent. The iron foam provides the iron source, and a precursor for a cobalt-doped self-supporting electrode, Co / Fe-MOF-74@IF, uniformly loaded onto the iron foam is obtained via a hydrothermal method. Then, the cobalt-doped self-supporting electrode, Co-Fe3O4 / FeO@IF, is successfully prepared by calcination in a tube furnace.
[0019] II. The Co-Fe3O4 / FeO@IF prepared in this invention is an in-situ grown self-supporting electrode. This strategy avoids the traditional step of coating powder catalysts with binders, not only perfectly preserving the intrinsic microstructure of the catalyst and increasing the contact area between active sites and reactants, but also effectively improving the electron conduction rate, thereby significantly promoting the electrocatalytic reduction performance of nitrate. At pH 13, at 0.1 mol·L⁻¹ –1 In a mixed electrolyte of KOH and KNO3, this electrode achieved a concentration of 13.14 mg / h. – 1 cm –2 The ammonia yield and Faraday efficiency of 85.53% demonstrate outstanding application potential.
[0020] This invention can obtain a cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF. Attached Figure Description
[0021] Figure 1 This is a scanning electron microscope (SEM) schematic diagram of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1.
[0022] Figure 2 This is a scanning electron microscope (SEM) schematic diagram of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1.
[0023] Figure 3 This is a schematic diagram of powder X-ray diffraction of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1.
[0024] Figure 4 Infrared spectra of the cobalt-doped self-supporting electrodes Co-MOF-74 and Co / Fe-MOF-74@IF prepared in Example 1;
[0025] Figure 5 The cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 was subjected to 0.1 mol·L⁻¹ – 1 KNO3 and KOH solution and 0.1 mol·L –1 Linear sweep voltammetry curves performed in KOH solution;
[0026] Figure 6 The cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 was used in 0.1 mol·L⁻¹ –1 Electrocatalytic synthesis of ammonia was carried out in KNO3 and KOH solutions, and the UV-Vis absorption spectra of ammonia were detected at different voltages.
[0027] Figure 7 The ammonia yield and Faraday efficiency of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 are shown under different voltages. Detailed Implementation
[0028] The technical solutions of this invention are not limited to the specific embodiments listed below. These specific embodiments are merely illustrative and not intended to limit the technical solutions described in the embodiments of this invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to this invention to achieve the same technical effects. Any modifications or substitutions that meet the usage requirements are within the protection scope of this invention.
[0029] Specific Implementation Method 1: A method for preparing a cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF, comprising the following steps:
[0030] 1. Dissolve cobalt nitrate hexahydrate and H4DOBDC simultaneously in 50ml of distilled water, 50ml of DMF and 50ml of ethanol, and then stir for a period of time until the solution becomes clear, resulting in a reddish-brown solution.
[0031] The amount of cobalt nitrate hexahydrate used in step one is 1.5–2.0 g;
[0032] The amount of H4DOBDC used in step one is 0.3–0.7 g;
[0033] 2. Add 50 ml of the reddish-brown reaction solution to a polytetrafluoroethylene (PTFE) reactor and react in the PTFE reactor at 100°C for 24 hours. Then, allow the PTFE reactor to cool naturally to room temperature. Collect the product by centrifugation and wash it three times with methanol. Soak it in methanol at room temperature for three days, changing the solution three times. Finally, place the obtained brown Co-MOF-74 in a vacuum drying oven at 60°C and dry it overnight.
[0034] 3. Dissolve Co-MOF-74 and H4DOBDC simultaneously in 25 ml of DMF, then stir for a period of time to obtain a brown solution.
[0035] The dosage of Co-MOF-74 described in step three is 0.01–0.05 g;
[0036] The amount of H4DOBDC used in step three is 0.03–0.08 g;
[0037] 4. Cut the foam iron to a size of 2×3cm, and then use acetone and 1mol·L⁻¹ to... -1 Rinse with sulfuric acid and deionized water for 5-10 minutes each.
[0038] 5. Add the brown reaction solution to a polytetrafluoroethylene (PTFE) reactor, then add the cleaned foamed iron. React in the PTFE reactor at 110℃ for 12 hours, then allow the PTFE reactor to cool naturally to room temperature. Remove the foamed iron and wash it several times with methanol. Finally, place the resulting black foamed iron in a vacuum drying oven at 60℃ and dry it overnight. Place the dried foamed iron in a tube furnace and heat it at 900℃ for 2 hours under an Ar atmosphere. The resulting light black foamed iron is the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF.
[0039] Cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF was used as an electrocatalyst to electrocatalyze the reduction of nitrate to ammonia.
[0040] Compared with the prior art, this embodiment has the following characteristics:
[0041] I. This invention employs a simple hydrothermal synthesis technique, utilizing Co-MOF-74, H4DOBDC, and iron foam dissolved in a solvent. The iron foam provides the iron source, and a precursor for a cobalt-doped self-supporting electrode, Co / Fe-MOF-74@IF, uniformly loaded onto the iron foam is obtained through a one-step hydrothermal method. Then, the cobalt-doped self-supporting electrode, Co-Fe3O4 / FeO@IF, is successfully prepared by calcination in a tube furnace.
[0042] II. The Co-Fe3O4 / FeO@IF prepared in this invention is an in-situ grown self-supporting electrode. This strategy avoids the traditional step of coating powder catalysts with binders, not only perfectly preserving the intrinsic microstructure of the catalyst and increasing the contact area between active sites and reactants, but also effectively improving the electron conduction rate, thereby significantly promoting the electrocatalytic nitrate reduction performance. In a 0.1 mol·L⁻¹ KOH and KNO₃ mixed electrolyte at pH 13, this electrode achieved a nitrate reduction efficiency of 13.14 mgh⁻¹. cm The ammonia yield of -2 and the Faraday efficiency of 85.53% demonstrate outstanding application potential.
[0043] This invention can obtain a cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF.
[0044] Specific Implementation Method Two: The difference between this implementation method and Specific Implementation Method One is that the amount of cobalt nitrate used is 1.78g. All other steps are the same as in Specific Implementation Method One.
[0045] Specific Implementation Method 3: The difference between this implementation method and one of Specific Implementation Methods 1 and 2 is that the amount of H4DOBDC used is 0.54g. The other steps are the same as in Specific Implementation Method 1 or 2.
[0046] Specific Implementation Method Four: The difference between this implementation method and one of Specific Implementation Methods One to Three is that the amount of Co-MOF-74 used is 0.03g. The other steps are the same as those in Specific Implementation Methods One, Two, or Three.
[0047] Specific Implementation Method Five: The difference between this implementation method and one of Specific Implementation Methods One to Four is that the mass ratio of Co-MOF-74 to H4DOBDC is 1:2. The other steps are the same as those in Specific Implementation Methods One to Four.
[0048] Specific Implementation Method Six: In this implementation method, the black foamed iron obtained is the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF, which is directly used as the working electrode to electrocatalyze the reduction of nitrate to ammonia.
[0049] At pH = 13, 0.1 mol·L⁻¹ –1 In KOH and KNO3 solution, the ammonia yield was 13.14 mg / h.-1 cm -2 The Faraday efficiency reached 85.53%.
[0050] The beneficial effects of the present invention are verified using the following embodiments:
[0051] Example 1: The preparation method of cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF is carried out according to the following steps:
[0052] 1. Dissolve cobalt nitrate hexahydrate and H4DOBDC simultaneously in 50ml of distilled water, 50ml of DMF and 50ml of ethanol, and then stir for a period of time until the solution is clear, resulting in a reddish-brown solution.
[0053] The amount of cobalt nitrate used in step one is 1.5–2.0 g;
[0054] The amount of H4DOBDC used in step one is 0.3–0.7 g;
[0055] 2. Add 50 ml of the reddish-brown reaction solution to a polytetrafluoroethylene (PTFE) reactor and react in the PTFE reactor at 100°C for 24 hours. Then, allow the PTFE reactor to cool naturally to room temperature. Collect the product by centrifugation and wash it three times with methanol. Soak it in methanol at room temperature for three days, changing the solution three times. Finally, place the obtained brown Co-MOF-74 in a vacuum drying oven at 60°C and dry it overnight.
[0056] 3. Dissolve Co-MOF-74 and H4DOBDC simultaneously in 25 ml of DMF, then stir for a period of time to obtain a brown solution;
[0057] The dosage of Co-MOF-74 described in step three is 0.01–0.05 g;
[0058] The amount of H4DOBDC used in step three is 0.03–0.08 g;
[0059] 4. Cut the foam iron to a size of 2×3cm, and then use acetone and 1mol·L⁻¹ to... -1 Rinse with sulfuric acid and deionized water for 5-10 minutes each.
[0060] 5. Add the brown reaction solution to a polytetrafluoroethylene (PTFE) reactor, then add the cleaned foamed iron. React in the PTFE reactor at 110℃ for 12 hours, then allow the PTFE reactor to cool naturally to room temperature. Remove the foamed iron and wash it several times with methanol. Finally, place the resulting black foamed iron in a 60℃ vacuum drying oven and dry it overnight. Place the dried foamed iron in a tube furnace and heat it at 900℃ for 2 hours under an Ar atmosphere. The resulting light black foamed iron is the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF.
[0061] Scanning electron microscopy (SEM) was performed on the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 to obtain the SEM image of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1.
[0062] Figure 1 This is a scanning electron microscope (SEM) schematic diagram of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1.
[0063] Depend on Figure 1 It can be seen that the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF composite material prepared in Example 1 is uniformly and densely distributed on the foamed iron.
[0064] Figure 2 This is a scanning electron microscope (SEM) schematic diagram of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1.
[0065] Depend on Figure 2 It can be seen that the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF material prepared in Example 1 has a polyhedral morphology.
[0066] X-ray diffraction (XRD) was performed on the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1, and the X-ray diffraction pattern of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 was obtained, as shown below. Figure 3 As shown.
[0067] Figure 3 X-ray diffraction diagram of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1;
[0068] Figure 3In the diagram, 1 represents the diffraction peak of the Fe standard card, corresponding to standard card number 87–0722. The diffraction peaks 2θ = 44.76° and 82.53° point to the (110) and (211) crystal planes of the Fe phase; 2 represents the diffraction peak of the FeO standard card, corresponding to standard card number 88–2153. The diffraction peaks 2θ = 36.20°, 42.05°, and 60.98° point to the (111), (200), and (220) crystal planes of the FeO phase; 3 represents the diffraction peak of the Fe3O4 standard card, corresponding to standard card number 75–0449. The diffraction peaks 2θ = 30.36°, 35.76°, 37.41°, 43.47°, 53.94°, 57.51° and 63.17° point to the (220), (311), (222), (400), (422), (511) and (440) crystal planes of the Fe3O4 phase; 4 is the actual diffraction peak of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF, which is consistent with the peak positions of the standard cards of Fe3O4, FeO and IF. It can be determined that the material obtained in the experiment is the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF composed of Co, Fe3O4, FeO and IF, and the purity of the material is high.
[0069] Infrared spectroscopy was performed on the Co-MOF-74 and Co / Fe-MOF-74@IF self-supporting electrodes prepared in Example 1. The infrared spectra of the Co-MOF-74 and Co / Fe-MOF-74@IF self-supporting electrodes prepared in Example 1 were obtained, as shown below. Figure 4 As shown;
[0070] Figure 4 In the diagram, 1 and 2 represent the stretching vibrations of C=O and the benzene ring, respectively; 3 and 4 represent the stretching vibrations of CO; and 5 and 6 represent the stretching vibrations of CH on the benzene ring. This confirms that the experiment successfully synthesized Co-MOF-74 and Co / Fe-MOF-74@IF self-supporting electrodes.
[0071] Linear sweep voltammetry was performed on the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1, and the linear sweep voltammetry curve of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 was obtained, as shown in the figure. Figure 5 As shown;
[0072] from Figure 5 It can be seen that the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF prepared in Example 1 was tested at 0.1 mol·L⁻¹. -1 KNO3 and KOH solution, 0.1 mol·L -1Linear sweep voltammetry curves of KOH solution showed that, within the same voltage range, the reduction current density of Co-Fe3O4 / FeO@IF in nitrate-containing electrolyte was significantly higher than that in electrolyte without nitrate, indicating that the Co-Fe3O4 / FeO@IF catalyst has good electrocatalytic ability to reduce nitrate to ammonia.
[0073] Figure 6 The image shows a cobalt-doped self-supporting electrode, Co-Fe3O4 / FeO@IF, at 0.1 mol·L⁻¹. -1 The ammonia synthesis reaction is carried out in KNO3 and KOH solutions. The UV-Vis absorption spectra at different voltages are shown below. Figure 6 As shown, with the increase of voltage, the absorbance of the electrolyte that underwent color development after the catalytic test also gradually increased with the voltage in the absorbance test.
[0074] Figure 7 The image shows a cobalt-doped self-supporting electrode, Co-Fe3O4 / FeO@IF, at 0.1 mol·L⁻¹. -1 The ammonia synthesis reaction is carried out in KNO3 and KOH solutions, and the ammonia yield and Faraday efficiency are plotted under different voltages. Figure 7 As shown, at a potential of -0.74V vs. RHE, the best Faraday efficiency of 85.53% is achieved, corresponding to an ammonia production of 13.14 mg h⁻¹. –1 cm –2 Cobalt-doped self-supporting electrodes (Co-Fe3O4 / FeO@IF) exhibit excellent performance in the electrocatalytic reduction of nitrate. Therefore, cobalt-doped self-supporting electrodes can serve as highly efficient electrocatalytic catalysts for the reduction of nitrate to ammonia.
[0075] In summary, the results of Example 1 demonstrate that the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF exhibits excellent nitrate reduction performance in alkaline media. Its high activity and high Faradaic efficiency jointly prove the practical value and broad application prospects of this material as a highly efficient electrocatalyst.
Claims
1. A method for preparing a cobalt-ferroferric oxide / ferrous oxide loaded iron foam self-supporting electrode, comprising the following steps: I. Dissolving cobalt nitrate hexahydrate and H4DOBDC into 50 ml of distilled water, 50 ml of DMF and 50 ml of ethanol at the same time, then stirring for a period of time until the solution is transparent to obtain a reddish-brown solution; The amount of cobalt nitrate hexahydrate described in step I is 1.5-2.0 g; The amount of H4DOBDC described in step I is 0.3-0.7 g; II. Adding 50 ml of the reddish-brown reaction solution into a polytetrafluoroethylene reaction kettle, reacting in the polytetrafluoroethylene reaction kettle at a temperature of 100°C for 24 h, and then naturally cooling the polytetrafluoroethylene reaction kettle to room temperature. Centrifuging to collect the product, and washing with methanol for 3 times, soaking in methanol at room temperature for 3 days with liquid change for 3 times, and finally drying the obtained brown Co-MOF-74 in a vacuum drying oven at 60°C overnight; III. Dissolving Co-MOF-74 and H4DOBDC into 25 ml of DMF at the same time, then stirring for a period of time to obtain a brown solution; The amount of Co-MOF-74 described in step III is 0.01-0.05 g; The amount of H4DOBDC described in step III is 0.03-0.08 g; IV. The foam iron was cut to a size of 2 x 3 cm, and sequentially cleaned with acetone, 1 mol / L HCl, deionized water, 1 mol / L H2SO4, and deionized water for 5-10 min each. -1 deionized water for 5-10 min each. V. Adding the brown reaction solution into a polytetrafluoroethylene reaction kettle, then adding the cleaned iron foam, reacting in the polytetrafluoroethylene reaction kettle at a temperature of 110°C for 12 h, and then naturally cooling the polytetrafluoroethylene reaction kettle to room temperature. Taking out the iron foam and washing with methanol for multiple times, and finally drying the obtained black iron foam in a vacuum drying oven at 60°C overnight. Placing the dried iron foam in a tube furnace, heating at 900°C under Ar atmosphere for 2 h, and obtaining the light black iron foam as the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF.
2. The preparation method of the cobalt-doped self-supporting electrode Co-Fe304 / FeO@IF for high-efficiency ammonia synthesis according to claim 1, characterized in that The amount of cobalt nitrate described in step I is 1.78 g.
3. The preparation method of the cobalt-doped self-supporting electrode Co-Fe304 / FeO@IF for high-efficiency ammonia synthesis according to claim 1, characterized in that The amount of H4DOBDC described in step I is 0.54 g.
4. The preparation method of the cobalt-doped self-supporting electrode Co-Fe304 / FeO@IF for high-efficiency ammonia synthesis according to claim 1, characterized in that The amount of Co-MOF-74 described in step I is 0.03 g.
5. The preparation method of the cobalt-doped self-supporting electrode Co-Fe304 / FeO@IF for efficient ammonia synthesis according to claim 1, characterized in that The mass ratio of Co-MOF-74 to H4DOBDC described in step I is 1:
2.
6. The application of the cobalt-doped self-supporting electrode Co-Fe3O4 / FeO@IF according to claim 1, characterized in that the catalyst Co-Fe3O4 / FeO@IF is directly used as a working electrode to electrocatalyze the reduction of nitrate to ammonia.