Preparation method and application of foamed nickel loaded phosphating Ni and Co-MOF electrode material

Abstract

The invention discloses a preparation method and application of a foamed nickel loaded phosphating Ni and Co-MOF electrode material, and belongs to the technical field of electro-catalytic materials. The preparation method comprises the following steps: vertically suspending and immersing foamed nickel into an aqueous solution containing cobalt nitrate hexahydrate, nickel oxalate tetrahydrate and terephthalic acid, carrying out a hydrothermal reaction in a reaction kettle, washing and drying to obtain a foamed nickel-loaded Ni and CoMOF composite material, and then phosphorizing the surface of the foamed nickel-loaded Ni and CoMOF composite material in a tubular furnace by using sodium phosphite to obtain the foamed nickel-loaded phosphorized Ni and CoMOF electrode material. The foamed nickel loaded phosphatized Ni and CoMOF electrode material prepared by the invention has the advantages of good nitrate conversion rate, excellent ammonia selectivity, extremely low nitrite generation and ampere-level current.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic materials, and particularly relates to a preparation method and application of a nickel foam supported phosphated Ni,Co-MOF electrode material. Background Art

[0002] Ammonia (NH3), as an indispensable basic chemical material, plays a key role in multiple industries such as refrigeration technology, pharmaceutical manufacturing, and fertilizer production. Its liquid form, due to containing 17.6% hydrogen element and being convenient for storage and transportation, is regarded as a potential hydrogen energy storage medium and a carbon-free fuel option.

[0003] With the rapid development of industry and agriculture, the extensive use of domestic sewage, industrial wastewater, pesticides, and fertilizers has made the problem of groundwater nitrate (NO3 - ) pollution increasingly serious. As a common groundwater pollutant, nitrate can be converted into harmful nitrite through microbial action in the natural environment, which has a potential carcinogenic risk and poses a serious threat to human health. At the same time, the Haber-Bosch process widely used in the industrial field synthesizes ammonia under high temperature and high pressure conditions, and its supporting role in global food production is self-evident, deeply affecting human production activities and living quality. However, the annual energy consumption of this process accounts for about 1% to 2% of the global total energy consumption, and its carbon dioxide emissions account for about 1.5% of the total global greenhouse gas emissions, highlighting the dual challenges of environmental pressure and energy consumption. Therefore, it is particularly urgent to explore a new catalyst material that can effectively convert nitrate pollutants into utilizable ammonia while achieving low energy consumption and zero pollution emissions.

[0004] In recent years, the technology of electrocatalytic reduction of nitrate has gradually emerged, opening up a new way for the conversion of nitrate to ammonia and achieving a series of research progress. However, currently, there are still problems in the nitrate reduction process, such as low ammonia production rate, insufficient selectivity, and high content of by-product nitrite. Summary of the Invention

[0005] In view of the above situation, the purpose of the present invention is to provide a preparation method and application of a nickel foam supported phosphated Ni,Co-MOF electrode material. Compared with the existing research reports on nitrate reduction to ammonia, the nickel foam supported phosphated Ni,Co-MOF electrode material in the present invention has high selectivity for ammonia, and this electrode material reaches an ampere-level current and a Faraday efficiency as high as 95%.

[0006] To achieve the above purpose, the present invention adopts the following technical scheme:

[0007] A preparation method of a nickel foam supported phosphated Ni,Co-MOF electrode material, comprising the following steps:

[0008] Step (1): Clean the nickel foam to remove the surface metal oxides; preferably, ultrasonically treat the nickel foam (2.0×1.0 cm 2 ) with 1.0 M hydrochloric acid and acetone for 30 minutes in sequence to remove the surface oxide layer and organic residues, then wash the nickel foam with pure water and ethanol, and finally place the nickel foam in a vacuum drying oven at 60 °C for 24 hours.

[0009] Step (2): Dissolve and mix cobalt nitrate hexahydrate, nickel oxalate tetrahydrate and terephthalic acid in deionized water according to the molar ratio of (0.8 - 1.2):(0.8 - 1.2):(1.2 - 1.8), and pour it into the inner liner of a hydrothermal reaction kettle containing nickel foam (2.0×1.0 cm 2 ).

[0010] Step (3): Place the hydrothermal reaction kettle in an oven for heating, with the heating temperature being 145 - 155 °C and the heating time being 1100 - 1300 minutes; preferably, the heating temperature is 150 °C and the heating time is 1200 minutes.

[0011] Step (4): Take out the nickel foam, wash it, and dry it to obtain the Ni,CoMOF composite material supported on the nickel foam;

[0012] Step (5): Place the phosphite and the Ni,Co-MOF composite material at the upstream and downstream of the magnetic boat respectively, put them into a tubular furnace, and keep them at 250 - 350 °C for 100 - 140 minutes in an inert gas environment to obtain the phosphated Ni,Co-MOF electrode material supported on the nickel foam.

[0013] Preferably, the molar ratio of cobalt nitrate hexahydrate, nickel oxalate tetrahydrate and terephthalic acid is (1 - 1.2):(1 - 1.2):1.8. When the metal includes both nickel and cobalt, compared with the case of only containing nickel or cobalt, it has higher catalytic activity and ammonia production rate for the electrochemical catalytic reduction of NO3- to NH3.

[0014] Preferably, in the aqueous solution of step (2), the concentrations of cobalt ions (Co 2+ ) and nickel ions (Ni 2+ ) are 0.16 - 0.24 mol / L, and further preferably, the concentrations of cobalt ions (Co 2+ ) and nickel ions (Ni 2+ ) are 0.2 - 0.24 mol / L.

[0015] Preferably, when washing the nickel foam in step (4), rinse the Ni,CoMOF composite material supported on the nickel foam with pure water and absolute ethanol alternately several times until the solution is colorless and transparent, and finally place it in a vacuum oven at 60 °C for 24 hours.

[0016] Preferably, in step (5), the phosphating temperature heating program is to introduce nitrogen at room temperature for 20 - 30 minutes, then increase the temperature to 250 - 300°C at a rate of 2°C per minute, and maintain the high temperature for 120 minutes. During the phosphating reaction, an excessive amount of phosphite is placed upstream of the boat, and the phosphite is any one of potassium phosphite and sodium phosphite.

[0017] Preferably, the size of the nickel foam is 2.0×1.0 cm 2 , and the thickness is 1 - 10 mm.

[0018] The nickel foam supported phosphated Ni,CoMOF electrode material prepared by the above method can be used for electrocatalytic nitrate reduction to ammonia. Using 1 mol / L KOH as the electrolyte, containing a KNO3 solution with a concentration of 0.08 mol / L - 0.12 mol / L, the scanning voltage range is set from -0.1 to -0.6 V relative to the silver chloride electrode. This nickel foam supported phosphated Ni,CoMOF electrode material has a Faraday efficiency as high as 95% and an amperometric current.

[0019] Compared with the existing technology, the present invention has the following advantages:

[0020] (1) The nickel foam supported phosphated Ni,CoMOF electrode material prepared by the present invention has a significantly improved nitrate conversion rate. Compared with traditional catalysts and unphosphated nickel foam supported Ni,CoMOF composite materials, the reaction efficiency is greatly improved, showing excellent ammonia selectivity, greatly reducing side reactions, with the main product being ammonia, increasing ammonia production and purity, and reducing environmental risks and treatment costs;

[0021] (2) It achieves an amperometric current, has a strong current carrying capacity, meets the requirements of large-scale electrocatalytic nitrate reduction to ammonia reactions, and improves the reaction rate and production efficiency. With a Faraday efficiency of 95%, the electric charge in the electrocatalytic process is efficiently used for nitrate reduction to ammonia, reducing energy consumption, and improving the reaction economy and sustainability;

[0022] (3) Compared with existing research, the nickel foam supported phosphated Ni,CoMOF electrode material prepared in the present invention has excellent long-term cycling stability, improving the service life and operation stability of the reaction device;

[0023] (4) The preparation method is simple and green, the raw materials are common, there are no large amounts of toxic and harmful by-products or waste, meeting the requirements of green chemical processes, reducing environmental pollution and resource waste. It efficiently converts nitrate pollutants into valuable ammonia products, realizes the resource utilization of pollutants, reduces the dependence on the traditional Haber–Bosch process, alleviates energy tension and greenhouse gas emission problems, and promotes the sustainable development of the chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1Electrolysis device diagram of Ni, CoMOF electrode material loaded on nickel foam

[0025] Figure 2 SEM image of Ni, CoMOF composite material loaded on nickel foam prepared in Comparative Example 1;

[0026] Figure 3 SEM of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1 Figure 1 ;

[0027] Figure 4 SEM of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1 Figure 2 ;

[0028] Figure 5 Screening diagram of different nitrate concentrations of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1;

[0029] Figure 6 Linear sweep voltammetry (LSV) comparison diagram of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1 and Ni, CoMOF composite material loaded on nickel foam prepared in Comparative Example 1 in 1M KOH + 0.1M KNO3 and 1M KOH;

[0030] Figure 7 XRD comparison diagram of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1 and Ni, CoMOF composite material prepared in Comparative Example 1;

[0031] Figures 8 - 10 X-ray photoelectron spectroscopy (XPS) diagram of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1;

[0032] Figure 11 Conversion of nitrate and kinetic curve of ammonia generation of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1;

[0033] Figure 12 For the Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1 15 Nuclear magnetic resonance comparison diagram after electrochemical reduction of potassium nitrate labeled with N isotope and unlabeled potassium nitrate as electrolyte;

[0034] Figure 13 Cyclic stability performance diagram of Ni, CoMOF electrode material loaded on nickel foam prepared in Example 1;

[0035] Figure 14 Standard curve diagram of ammonia by indophenol blue spectrophotometry;

[0036] Figure 15 Standard curve of nitrite by Griess method. Detailed implementation mode

[0037] The nickel foam supported Ni,CoMOF composite material obtained in the present invention has advantages such as a large specific surface area, rich surface functional groups, excellent electrochemical properties, etc., and has an ampere-level current. The disclosed Ni,CoMOF composite material for phosphating has significantly improved performance in electrocatalytic nitrate reduction to ammonia.

[0038] The technical solutions of the present invention are further explained and illustrated below in conjunction with several preferred embodiments, but the experimental conditions and set parameters therein should not be regarded as limitations to the basic technical solutions of the present invention. And the protection scope of the present invention is not limited to the following embodiments. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments can be obtained by commercial means; the specific operation methods and test methods involved are all conventional techniques.

[0039] In the present invention, the electrode substrate used is nickel foam, and the nickel foam will be ultrasonically cleaned with acetone and 1.0 M hydrochloric acid before use, and the size is 2.0×1.0 cm 2 , and the thickness is 1 mm; then the nickel foam is cleaned with pure water and ethanol, and finally the nickel foam is placed in a vacuum drying oven at 60°C for 24 hours.

[0040] Example 1

[0041] At room temperature, 0.012 mol of cobalt nitrate hexahydrate, 0.012 mol of nickel oxalate tetrahydrate and 0.018 mol of terephthalic acid are weighed, and then 50 ml of deionized water is added to dissolve. This solution is poured into the inner liner of the reaction kettle containing nickel foam (2.0×1.0 cm 2 ). It is placed in an oven and set at 150°C for 1200 minutes. After 1200 minutes, the Ni,CoMOF material is taken out from the hydrothermal reaction kettle, and then rinsed several times alternately with pure water and absolute ethanol until the solution is colorless and transparent. Finally, it is placed in a vacuum oven at 60°C for 24 hours to finally obtain the nickel foam supported Ni,CoMOF composite material.

[0042] At room temperature, about 500 mg of sodium phosphite and the nickel foam supported Ni,CoMOF composite material (2.0×1.0 cm 2 ) are placed upstream and downstream of the magnetic boat respectively, and then the magnetic boat is placed in a tubular furnace. Nitrogen is passed at room temperature for 25 minutes, and then heated to 300°C at a rate of 2°C per minute, and then maintained at 300°C for 120 minutes. Finally, the nickel foam supported phosphated Ni,CoMOF electrode material is obtained, which can be used as a catalytic electrode for nitrate reduction to ammonia.

[0043] Example 2

[0044] At room temperature, 0.01 mol of cobalt nitrate hexahydrate, 0.01 mol of nickel oxalate tetrahydrate and 0.018 mol of terephthalic acid were weighed, and then 50 ml of deionized water was added for dissolution. This solution was poured into the inner liner of a reaction kettle containing nickel foam (2.0×1.0 cm 2 ). It was placed in an oven and set at 155 °C for 1100 minutes. After 1100 minutes, the Ni,CoMOF material was taken out from the hydrothermal reaction kettle, and then rinsed several times alternately with pure water and absolute ethanol until the solution was colorless and transparent. Finally, it was placed in a vacuum oven at 60 °C and dried for 24 hours to finally obtain the Ni,CoMOF composite material supported on nickel foam.

[0045] At room temperature, approximately 500 mg of sodium phosphite and the Ni,CoMOF composite material supported on nickel foam (2.0×1.0 cm 2 ) were placed upstream and downstream of a magnetic boat respectively, and then the magnetic boat was placed in a tubular furnace. Nitrogen was introduced at room temperature for 25 minutes, then heated to 300 °C at a rate of 2 °C per minute, and then maintained at 350 °C for 110 minutes. Finally, the Ni,CoMOF electrode material supported on nickel foam phosphated was obtained, which can be used as a catalytic electrode for nitrate reduction to ammonia.

[0046] Example 3

[0047] At room temperature, 0.012 mol of cobalt nitrate hexahydrate, 0.012 mol of nickel oxalate tetrahydrate and 0.018 mol of terephthalic acid were weighed, and then 50 ml of deionized water was added for dissolution. This solution was poured into the inner liner of a reaction kettle containing nickel foam (2.0×1.0 cm 2 ). It was placed in an oven and set at 145 °C for 1300 minutes. After 1300 minutes, the Ni,CoMOF material was taken out from the hydrothermal reaction kettle, and then rinsed several times alternately with pure water and absolute ethanol until the solution was colorless and transparent. Finally, it was placed in a vacuum oven at 60 °C and dried for 24 hours to finally obtain the Ni,CoMOF composite material supported on nickel foam.

[0048] At room temperature, approximately 500 mg of sodium phosphite and the Ni,CoMOF composite material supported on nickel foam (2.0×1.0 cm 2 ) were placed upstream and downstream of a magnetic boat respectively, and then the magnetic boat was placed in a tubular furnace. Nitrogen was introduced at room temperature for 25 minutes, then heated to 250 °C at a rate of 2 °C per minute, and then maintained at 250 °C for 140 minutes. Finally, the Ni,CoMOF electrode material supported on nickel foam phosphated was obtained, which can be used as a catalytic electrode for nitrate reduction to ammonia.

[0049] Comparative Example 1

[0050] At room temperature, 0.01 mol of cobalt nitrate hexahydrate, 0.01 mol of nickel oxalate tetrahydrate and 0.018 mol of terephthalic acid were weighed, and then 50 ml of deionized water was added to dissolve them. This solution was poured into the inner liner of a reaction kettle containing nickel foam (2.0×1.0 cm 2 ). It was placed in an oven and set at 155 °C for 1100 minutes. After 1100 minutes, the Ni,CoMOF material was taken out from the hydrothermal reaction kettle, and then rinsed several times alternately with pure water and absolute ethanol until the solution was colorless and transparent. Finally, it was placed in a vacuum oven at 60 °C and dried for 24 hours to finally obtain the Ni,CoMOF composite material supported on nickel foam.

[0051] Example 4

[0052] The Ni,CoMOF electrode material supported on nickel foam prepared in Example 1 was used as a catalytic electrode for nitrate reduction to ammonia, and was used for electrocatalytic nitrate reduction to ammonia. It was tested by an electrochemical workstation (model Chenhua CHI660E). Before the test, the working electrode clamp was connected to the catalytic electrode for nitrate reduction to ammonia, the counter electrode was connected to a platinum mesh, and a silver chloride electrode was used as the reference electrode, as Figure 1 shown. After assembly, 1 mol / L KOH was used as the electrolyte and 0.1 mol / L KNO3 was used as the electrolytic substance. The linear voltammetric scanning curve was tested, and the scanning potential range was -0.1~-0.6 V (relative to the silver chloride electrode). The constant voltage scanning curve was tested, and the voltage range was -0.1~-0.6 V (relative to the silver chloride electrode).

[0053] Test example 1 for Example 4:

[0054] The detection method for ammonia in the laboratory is the indophenol blue spectrophotometry.

[0055] The preparation method of solution A is as follows: 4 g of NaOH was added to 100 mL of water, stirred evenly, 5 g of sodium salicylate was added, and then 5 g of potassium sodium tartrate was added. After stirring evenly, the solution was recorded as A.

[0056] The preparation method of solution B is as follows: 3.5 mL of 10%-15% sodium hypochlorite was added to 96.5 mL of pure water and recorded as solution B.

[0057] The preparation method of solution C is as follows: 0.2 g of sodium nitroprusside was weighed and added to pure water. After stirring evenly, the obtained solution was recorded as C.

[0058] To determine the ammonia content, 2 mL of the electrolyte was taken, 2 mL of solution A was added first, then 1 mL of solution B was added, and finally 0.2 mL of solution C was added and mixed evenly. It was placed in the dark for 2 hours, and the ultraviolet-visible absorption spectrum was measured, and the absorbance at 655 nm was recorded.

[0059] NH4Cl solutions with concentrations of 0.5, 1, 2, 3, 4, and 5 mg / L were used respectively. The absorbance at the corresponding concentration was obtained by the above test method, and the standard curve method was obtained by linear fitting with Origin software. The standard curve was obtained. Figure 14 Then, the ammonia was determined using the standard curve.

[0060] 5 mL of the electrolytes corresponding to -0.1V, -0.2V, -0.3V, -0.4V, -0.5V, and -0.6V were collected and then diluted 200 times, 400 times, 500 times, 1000 times, 1000 times, 1000 times, and 1000 times respectively. Then, 2 mL of each electrolyte at each potential was taken. First, 2 mL of Solution A was added, then 1 mL of Solution B was added, and finally 0.2 mL of Solution C was added and mixed evenly. It was placed in the dark for 2 hours, and the ultraviolet-visible absorption spectrum was measured, and the absorbance at the 655 nm position was recorded.

[0061] For Test Example 2 of Example 4:

[0062] The quantitative detection of nitrite was determined using Griess reagent. 5 mL of the electrolyte after electrochemical testing was taken, and 0.2 mL of Griess reagent was added to it. Then, it was heated at 100 °C for one minute. After cooling to room temperature, the UV-Vis absorption spectrum was measured, and the absorbance at the 524 nm position was recorded.

[0063] NO2 solutions with concentrations of 0.15625, 0.3125, 0.625, 1.25, and 2.5 mg / L were used respectively. - The absorbance at the corresponding concentration was obtained by the above test method, and the standard curve method was obtained by linear fitting with Origin software. The standard curve was obtained as Figure 15 Then, the nitrite was quantified using the standard curve method.

[0064] 5 mL of the electrolytes corresponding to -0.1V, -0.2V, -0.3V, -0.4V, -0.5V, and -0.6V were collected and then diluted 20 times, 40 times, 50 times, 100 times, 100 times, 100 times, and 10 times respectively. Then, 5 mL of the electrolyte after electrochemical testing of each electrolyte at each potential was taken, and 0.2 mL of Griess reagent was added to it. Then, it was heated at 100 °C for one minute. After cooling to room temperature, the UV-Vis absorption spectrum was measured, and the absorbance at the 524 nm position was recorded.

[0065] The data of Test Example 1 and Test Example 2 for Example 4 above were integrated into an Origin graph as Figure 11As shown, it can be seen that as the voltage drops from -0.1 V to -0.6 V, the ammonia conversion rate continuously increases. At -0.6 V, the conversion ammonia selectivity of nitrate is as high as 95.025%. The cyclic stability of the electrode material was tested at the test voltage of -0.6 V. As Figure 13 shown, during the cyclic test, after one electrolysis experiment of 0.1 mol / L nitrate, the solution after the reaction was poured out, and fresh 0.1 mol / L stock solution was added again to continue the reaction. The test voltage was 0.6 V. After 16 cycles, excellent selectivity and ammonia production rate were still maintained, showing excellent cyclic stability. As Figure 5 shown, at different nitrogen concentrations, the Ni,Co-MOF electrode material supported on nickel foam all showed extremely high ammonia selectivity (test voltage: -0.6 V).

[0066] Test example 3 for Example 4:

[0067] The Ni,CoMOF nickel foam electrode after phosphating was respectively placed into an H-type cell with 15 0.1 mol / L potassium nitrate labeled with N isotope as the electrolyte and 0.1 mol / L potassium nitrate without labeling as the electrolyte, and electrolyzed at a voltage of 0.6 V. The electrolyzed solution was tested with a nuclear magnetic resonance spectrometer (model Bruker 600M). The final nuclear magnetic resonance spectrum is as Figure 12 shown, and it can be seen that the reduction of ammonia directly comes from nitrate.

[0068] Result analysis for Example 1 and Comparative Example 1:

[0069] Except for Figure 10 this, the rest of the attached figures use 0.1 mol / L KNO3 as the electrolyte.

[0070] Figure 2 is the SEM pattern of the Ni,CoMOF composite material supported on nickel foam prepared in Comparative Example 1, Figure 3 and Figure 4 is the SEM pattern of the Ni,Co-MOF electrode material supported on nickel foam after phosphating prepared in Example 1. It can be seen that the surface of the Ni,Co-MOF electrode material after phosphating was modified. Combining with the XRD comparison results in Figure 7 , it can be known that the Ni,Co-MOF electrode material after phosphating prepared in Example 1 grew on nickel foam. Figures 8 - 10 is the X-ray photoelectron spectroscopy (XPS) pattern of the Ni,Co-MOF electrode material supported on nickel foam after phosphating prepared in Example 1. The XPS spectrum shows typical peaks of Ni 2p, Co 2p, and P2p. It shows that the Ni,Co-MOF electrode material supported on nickel foam was phosphated on the outside of the flaky crystals of Ni,CoMOF.

[0071] Figure 6 Linear voltammetry (LSV) comparison chart of Ni,CoMOF electrode material supported on nickel foam prepared in Example 1 and Ni,CoMOF composite material supported on nickel foam prepared in Comparative Example 1 in 1M KOH + 0.1M KNO3 and 1M KOH. From the results of linear voltammetry (test voltage: -0.1 to -0.7V), it can be seen that after adding nitrate, the current level increases significantly, indicating that nitrate is reduced on the electrode. The conversion rate of nitrate is particularly important for the reduction of nitrate, and phosphating modification can significantly increase the current of nitrate reduction to ammonia and reach the ampere level, which is of great significance for the study of highly efficient reduction of ammonia from low-concentration nitrate.

[0072] In summary, the Ni,CoMOF electrode material supported on nickel foam prepared in the present invention has excellent nitrate conversion to ammonia efficiency, up to 95.025% and ampere-level current. These excellent properties not only reflect the high efficiency of this electrode in electrochemically reducing nitrate to ammonia, but also demonstrate its great potential in practical applications. Specifically, this electrode can maintain a high ammonia production rate and Faraday efficiency within a wide potential range, and has good stability, providing a highly competitive option for the future fields of nitrate degradation and ammonia synthesis.

Claims

1. A method for preparing a nickel foam loaded with phosphated Ni, Co-MOF electrode material, characterized in that: The following steps are involved: Step (1): cleaning the nickel foam to remove surface metal oxides; Step (2): dissolving and mixing cobalt nitrate hexahydrate, nickel oxalate tetrahydrate and terephthalic acid in a molar ratio of (0.8-1.2):(0.8-1.2):(1.2-1.8) with deionized water, and pouring the mixture into the inner tank of a hydrothermal reactor containing nickel foam; Step (3): placing the hydrothermal reactor in an oven and heating it at a temperature of 145 to 155° C. for a heating time of 1100 to 1300 minutes; Step (4): taking out the nickel foam, washing it, and drying it to obtain a nickel foam-loaded Ni, CoMOF composite material; Step (5): Place the phosphite and the Ni, Co-MOF composite material on the upstream and downstream of the magnetic boat respectively, put them into a tubular furnace, and maintain them at 250-350° C. for 100-140 minutes in an inert gas environment to obtain a nickel foam-loaded phosphated Ni, Co-MOF electrode material.

2. The preparation method according to claim 1, characterized in that: The size of the nickel foam is 2.0×1.0 cm 2 , thickness is 1-10mm.

3. The preparation method according to claim 1, characterized in that: In step (2), the molar ratio of cobalt nitrate hexahydrate, nickel oxalate tetrahydrate and terephthalic acid is (1-1.2):(1-1.2):1.

8.

4. The preparation method according to claim 1, characterized in that: In step (3), the heating temperature of the oven is 150° C. and the heating time is 1200 minutes.

5. The preparation method according to claim 1, characterized in that: The phosphating temperature heating procedure in step (5) is to pass nitrogen at room temperature for 20 to 30 minutes, then increase the temperature to 250 to 300°C at 2°C per minute, and maintain the high temperature for 120 minutes.

6. The preparation method according to claim 1, characterized in that: The phosphite is any one of potassium phosphite and sodium phosphite.

7. A nickel foam loaded with phosphated Ni, CoMOF electrode material prepared by the method according to any one of claims 1 to 6.

8. Use of nickel foam loaded with phosphinated Ni, CoMOF electrode material prepared by the method according to any one of claims 1 to 6 in electrocatalytic nitrate reduction to produce ammonia.

9. The use according to claim 8, characterized in that: The electrolyte for the electrocatalytic reduction of nitrate to produce ammonia contains 0.08 mol / L to 0.12 mol / L of KNO3 solution, and the voltage range of the electrocatalytic reaction is -0.1 to -0.6V.

10. The use according to claim 8, characterized in that: The nickel foam loaded with phosphated Ni and the CoMOF electrode material have a Faradaic efficiency of up to 95% and an ampere-level current.

Images