Preparation method and application of multi-site silver-nickel hydroxide / copper nanowire catalyst

Abstract

The invention relates to a preparation method of a multi-site silver (Ag) and nickel hydroxide (Ni (OH) 2) modified copper (Cu) nanowire catalyst (Ag-Ni (OH) 2) / Cu NW) and application of the multi-site silver (Ag) and nickel hydroxide (Ni (OH) 2) modified copper (Cu) nanowire catalyst. A cation exchange and electrodeposition method is adopted to prepare an electrocatalytic nitrate reduction reaction NO3-RR series catalyst with three sites of Ag, Ni (OH) 2 and Cu. Based on the synergistic effect of three sites, Ag in the catalyst promotes conversion from nitrate NO3 <-> to nitrite NO2 <->, Ni (OH) 2 promotes dissociation of water H2O to generate free hydrogen * H, Cu atoms near Ni (OH) 2 accelerate conversion from NO2 <-> to ammonia NH3, and the efficient series catalytic process is achieved. Under the condition of-0.1 V vs. Reversible hydrogen electrode RHE in a 1M potassium hydroxide solution containing 50 mM of potassium nitrate, the NH3 yield of 4.01 mgh <-1 > cm <-2 > and the NH3 Faraday efficiency of 97.3% are obtained, under the condition of 0V vs. RHE, the excellent energy efficiency of 46.5% is achieved, the excellent catalytic activity is kept in a NO3 <-> solution with the wide concentration, and the good sewage treatment capacity is achieved. The invention provides a new design thought for tandem catalysis, and has a wide application prospect in the field of NO3-RR.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of electrocatalytic nitrate reduction reaction for ammonia synthesis, and particularly relates to a preparation method and application of a multi-site silver-nickel hydroxide / copper nanowire catalyst. Background Art

[0002] Ammonia (NH 3 ) plays a key role in the agricultural and chemical industries and has great potential as a next-generation hydrogen-rich fuel. Currently, NH 3 is mainly synthesized from nitrogen (N 2 ) and hydrogen (H 2 ) through the energy- and carbon-intensive Haber-Bosch process under harsh conditions (350 to 450 °C and 100 to 200 bar). The production of NH 3 consumes approximately 1-2% of the global energy supply and accounts for about 1.4% of carbon dioxide (CO 2 ) emissions. Therefore, it is imperative to explore clean and energy-saving sustainable NH 3 synthesis technologies. At the same time, due to the overuse of nitrogen-containing fertilizers and industrial pollution, nitrate (NO 3 - ) ions are widely present in industrial wastewater and contaminated groundwater. The increase in NO 3 - concentrations in surface water and groundwater poses a serious threat to human health and ecological balance. Electrochemical NO 3 - reduction reaction (NO 3 - RR) has become a potential clean approach for sustainable NH 3 synthesis and NO 3 - wastewater treatment. Since NO 3 - RR is a complex 8-electron transfer process and involves multiple intermediates, there are still problems of slow kinetics and low NH 3 selectivity. Therefore, the development of advanced electrocatalysts with high NO 3 - RR activity and NH 3 selectivity remains an urgent task.

[0003] The electroreduction of NO 3 - to NH 3 is achieved by converting NO 3 - to NO 2 - and NO 2 -Converted to NH 3 The cascade process is carried out. Compared with NO 2 - Converted to NH 3 Compared with NO 3 - Converted to NO 2 - Needs to overcome a larger energy barrier, thus severely limiting the reaction rate of NO 3 - RR. In addition, the hydrogenation step of NO 3 - RR requires a certain amount of active hydrogen (*H) to react with the N-containing intermediate. In an alkaline environment, *H mainly comes from the dissociation of H 2 O. Therefore, efficient dissociation of H 2 O to generate *H is also crucial for the rapid generation of NO 3 - RR. Among them, the conversion of NO 3 - to NO 2 - and NO 2 - to NH 3 and the dissociation of H 2 O depend on different catalyst properties, and it is difficult to optimize the reaction kinetics of these three processes simultaneously on a single-site catalyst. Integrating multiple active sites on the catalyst can avoid the adsorption-energy scaling relationship, make full use of the synergistic effect, and promote the generation of ammonia by NO 3 - RR through tandem electrocatalysis. Therefore, designing a multi-site catalyst to separately catalyze the reduction of NO 3 - to NO 2 - and NO 2 - to NH 3 to achieve a tandem catalytic process, thereby accelerating the overall NO 3 - RR kinetics is a new strategy to improve the catalyst activity. Summary of the Invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present disclosure provides a preparation method and application of a multi-site silver-nickel hydroxide / copper nanowire catalyst.

[0005] According to the first aspect of the present disclosure, there is provided a preparation method of a multi-site silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH) 2 / Cu NW, characterized by comprising the following steps:

[0006] (1) Clean the copper foam with isopropyl alcohol solution and dilute hydrochloric acid solution in sequence to remove the grease and oxide layer on the surface of the copper foam;

[0007] (2) Immerse the cleaned copper foam in a mixed solution containing sodium hydroxide and ammonium persulfate for 5 hours to prepare copper hydroxide nanowires supported by the copper foam skeleton;

[0008] (3) After washing the copper hydroxide nanowires with deionized water for multiple times, soak them in silver nitrate solution for 30 min at room temperature through the cation exchange method to obtain Ag / Cu(OH) 2 NW; Then, using the silver - copper hydroxide nanowire catalyst Ag / Cu(OH) 2 NW as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, perform an electrochemical deposition process in a 30 mM nickel sulfate hexahydrate solution to obtain Ag - Ni(OH) 2 / Cu(OH) 2 NW;

[0009] (4) Anneal the Ag - Ni(OH) 2 / Cu(OH) 2 NW obtained in step (3) at 160 °C for 30 min in a tubular furnace to obtain silver - nickel hydroxide / cupric oxide nanowires Ag - Ni(OH) 2 / CuO NW. Subsequently, perform an electro - reduction treatment on the Ag - Ni(OH) 2 / CuO NW in 1 M potassium hydroxide solution to finally obtain a silver - nickel hydroxide / copper nanowire Ag - Ni(OH) 2 / Cu NW catalyst.

[0010] Preferably, the concentration of the dilute hydrochloric acid solution in step (1) is 0.1 M.

[0011] Preferably, the concentration of the sodium hydroxide solution in the mixed solution in step (2) is 1 M, and the concentration of the ammonium persulfate solution is 0.05 M.

[0012] Preferably, during the cation exchange process in step (3), the concentration of the silver nitrate solution is 1 mM; the parameters of the electrochemical deposition process are: the deposition current density is - 10 mAcm -2 , and it is maintained for 1 min.

[0013] Preferably, in step (4), immerse the Ag - Ni(OH) 2 / CuO NW in 1 M potassium hydroxide solution with Ag - Ni(OH) 2Using / CuO NW as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode for electroreduction treatment, with a current density of -30 mA cm -2 and a treatment time of 1 h.

[0014] According to the second aspect of the present disclosure, there is provided an application of a silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH) 2 / Cu NW, characterized in that the catalyst is used for electrocatalytic nitrate reduction reaction to synthesize ammonia.

[0015] Preferably, the application of the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH) 2 / Cu NW is characterized by including the following steps:

[0016] (1) Using an Ivium-n-Stat electrochemical workstation, adopting a three-electrode system, performing electrochemical performance tests in an H-type electrolytic cell, wherein the prepared silver-nickel hydroxide / copper nanowire catalyst and the silver / silver chloride electrode are respectively used as the working electrode and the reference electrode, and placed in the cathode chamber of the H-type electrolytic cell; a high-purity platinum sheet is used as the counter electrode and placed in the anode chamber of the H-type electrolytic cell; the anode and cathode chambers of the H-type electrolytic cell are separated by a Nafion 117-type proton exchange membrane, and 1 M potassium hydroxide (KOH) solution containing 50 mM potassium nitrate is added to both the anode and cathode chambers as the electrolyte, and high-purity argon gas is introduced before the test starts to remove impurity gases;

[0017] (2) Using chronoamperometry for electrochemical tests, the test potential range is +0.2 to -0.2 V vs. the reversible hydrogen electrode RHE, the potential interval is 0.1 V vs. RHE, the test time at each potential is 1 hour, and then the electrolyte in the cathode chamber is collected;

[0018] (3) Using the indophenol blue colorimetric method to color the electrolyte after the reaction, and then testing and calculating the ammonium ion concentration in the electrolyte by an ultraviolet-visible spectrophotometer, and calculating the NH 3 yield and NH 3 Faraday efficiency FE of the catalyst.

[0019] The object of the present disclosure is to prepare a multi-site Ag-Ni(OH) 2 / Cu NW catalyst and apply it to the electrocatalytic nitrate reduction reaction to synthesize NH 3 . Ag promotes the conversion of NO 3 - to NO 2 - , Ni(OH) 2 promotes the dissociation of H 2 O to generate *H, while Cu accelerates NO2 - to NH 3 The conversion of. This multi-site cooperative tandem catalysis method accelerates the overall reaction kinetic process, thus improving the catalytic activity.

[0020] The innovation of the present disclosure lies in:

[0021] (1) The preparation process of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in the present disclosure is simple, safe and controllable, and can be mass-produced;

[0022] (2) The NO 2 of the Ag-Ni(OH) 3 - RR of the / Cu NW catalyst prepared in the present disclosure proceeds through a tandem catalytic process, in which Ag promotes the conversion of NO 3 - to NO 2 - , Ni(OH) 2 promotes the dissociation of H 2 O to generate *H, and Cu accelerates the conversion of NO 2 - to NH 3 , improves the reaction kinetics, and obtains excellent catalytic activity;

[0023] (3) The Ag-Ni(OH) 2 / Cu NW catalyst prepared in the present disclosure has excellent long-term stability and high catalytic activity in a wide range of nitrate concentrations, and is suitable for applications in sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Combined with the accompanying drawings and referring to the following detailed description, the above and other features, advantages and aspects of the embodiments of the present disclosure will become more obvious. The drawings are used to better understand the solution and do not constitute a limitation to the present disclosure. In the drawings, the same or similar reference numerals represent the same or similar elements, where:

[0025] Figure 1 Scanning electron microscope (SEM) image of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1.

[0026] Figure 2 Transmission electron microscope (TEM) image of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1.

[0027] Figure 3 The Ag-Ni(OH)2 XRD pattern of Ag-Ni(OH) / Cu NW catalyst.

[0028] Figure 4 Ag-Ni(OH) prepared in Example 1 2 SEM-EDS pattern of Ag-Ni(OH) / Cu NW catalyst.

[0029] Figure 5 Ag-Ni(OH) prepared in Example 1 2 Ag-Ni(OH) / Cu NW catalyst prepared in Example 1, Cu NW catalyst prepared in Comparative Example 1, Ni(OH) / Cu NW catalyst prepared in Comparative Example 2 2 and Ag / Cu NW catalyst prepared in Comparative Example 3 were used for NO RR NH 3 - yield test results pictures in the potential range of +0.2~-0.2V vs. RHE. 3

[0030] Figure 6 Ag-Ni(OH) prepared in Example 1 2 Ag-Ni(OH) / Cu NW catalyst prepared in Example 1, Cu NW catalyst prepared in Comparative Example 1, Ni(OH) / Cu NW catalyst prepared in Comparative Example 2 2 and Ag / Cu NW catalyst prepared in Comparative Example 3 were used for NO RR NH 3 - yield test results pictures in the potential range of +0.2~-0.2V vs. RHE. 3 FE test results pictures.

[0031] Figure 7 Ag-Ni(OH) prepared in Example 1 2 Ag-Ni(OH) / Cu NW catalyst prepared in Example 1, Cu NW catalyst prepared in Comparative Example 1, Ni(OH) / Cu NW catalyst prepared in Comparative Example 2 2 and Ag / Cu NW catalyst prepared in Comparative Example 3 were used for NO RR NH 3 - yield test results pictures in the potential range of +0.2~-0.2V vs. RHE. 3 Energy efficiency (EE) test results pictures.

[0032] Figure 8 Ag-Ni(OH) prepared in Example 1 2 H nuclear magnetic resonance spectrum of Ag-Ni(OH) / Cu NW catalyst 1 ( 1 H NMR).

[0033] Figure 9Ag-Ni(OH) prepared for Example 1 2 / Cu NW catalyst in different concentrations of NO 3 - solution for NO 3 - RR test result picture.

[0034] Figure 10 Ag-Ni(OH) prepared for Example 1 2 / Cu NW catalyst in sewage treatment capacity test results picture under the initial condition of 1000 ppm NO close to the sewage environment 3 -

[0035] Figure 11 Ag-Ni(OH) prepared for Example 1 2 / Cu NW catalyst cyclic stability test result picture.

[0036] Figure 12 Ag-Ni(OH) prepared for Example 1 2 / Cu NW catalyst SEM picture after 25-hour cyclic stability test.

[0037] Figure 13 Ag-Ni(OH) prepared for Example 1 2 / Cu NW catalyst X-ray diffraction (XRD) pattern after 25-hour cyclic stability test. Detailed implementation manners

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are some but not all of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0039] Example 1

[0040] First, clean the copper foam (1×1 cm 2 ) with isopropyl alcohol, and then clean its surface with 0.1M hydrochloric acid solution. Then, soak the copper foam in a mixed solution containing 1M sodium hydroxide and 0.05M ammonium persulfate at room temperature for 5h to form copper hydroxide nanowires Cu(OH) 2 NW supported by a copper Cu skeleton. The prepared Cu(OH) 2 ​After the NW was washed multiple times with deionized water, it was immersed in a 1 mM silver nitrate solution at room temperature for 30 min, and the silver - copper hydroxide nanowire catalyst Ag / Cu(OH) 2 NW was obtained through a cation exchange process. Then, using the Ag / Cu(OH) 2 NW as the working electrode, a platinum sheet Pt electrode as the counter electrode, and a silver / silver chloride Ag / AgCl electrode as the reference electrode, an electrochemical deposition process was carried out in a 30 mM nickel sulfate hexahydrate solution, where the electrodeposition time was 1 min, and the silver - nickel hydroxide / copper hydroxide nanowire Ag - Ni(OH) 2 / Cu(OH) 2 NW was obtained. Subsequently, the Ag - Ni(OH) 2 / Cu(OH) 2 NW was annealed in air at 160 °C for 30 min, and then electrochemically reduced at a constant current of - 30 mA cm -2 for 1 h, and finally the silver - nickel hydroxide / copper nanowire catalyst Ag - Ni(OH) 2 / Cu NW was obtained.

[0041] Comparative Example 1

[0042] Cu(OH) 2 NW was synthesized according to the steps of Example 1. Subsequently, it was annealed in air at 160 °C for 30 min, and then electrochemically reduced at a constant current of - 30 mA cm -2 for 1 h, and finally Cu NW was obtained.

[0043] Comparative Example 2

[0044] Cu(OH) 2 NW was synthesized according to the steps of Example 1. Then, using Cu(OH) 2 NW as the working electrode, a Pt electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode, an electrochemical deposition process was carried out in a 30 mM nickel sulfate hexahydrate solution, where the electrodeposition time was 1 min, and Ni(OH) 2 / Cu(OH) 2 NW was obtained. Subsequently, it was annealed in air at 160 °C for 30 min, and then electrochemically reduced at a constant current of - 30 mA cm -2 for 1 h, and finally Ni(OH) 2 / Cu NW was obtained.

[0045] Comparative Example 3

[0046] Cu(OH) 2 NW was synthesized according to the steps of Example 1. At room temperature, it was immersed in a 1 mM silver nitrate solution for 30 min, and the Ag / Cu(OH) 2NW. Then it was washed and dried, and annealed in air at 160 °C for 30 min, and then electrochemically reduced at a constant current of -30 mA cm -2 for 1 h, and finally Ag / Cu NW was obtained.

[0047] Figure 1 It is the SEM image of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1. As shown in the figure, the morphology of the Ag-Ni(OH) 2 / Cu NW catalyst is a nanowire structure with a diameter between 80 and 150 nm growing on the copper foam skeleton.

[0048] Figure 2 It is the high-resolution transmission electron microscope image of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1. The figure shows Ag clusters with a diameter of 2 - 5 nm and amorphous Ni(OH) with a certain crystallite domain observed 2 . The high-resolution TEM image shows lattice spacings of 0.235 nm, 0.209 nm, and 0.252 nm, corresponding to the (111), (200), and (220) planes of Ag(111), Cu(111), and Ni(OH) 2 (110) crystal planes, respectively.

[0049] Figure 3 It is the XRD pattern of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1. The catalyst has three strong diffraction peaks at 43.32°, 50.45°, and 74.12°, corresponding to the (111), (200), and (220) planes of face-centered cubic Cu (JCPDS 85 - 1326), respectively. There is a weak diffraction peak at 38.11° corresponding to the (111) plane of face-centered cubic Ag (JCPDS 04 - 0783). No diffraction peak of Ni(OH) 2 is observed, which is consistent with the amorphous nature of Ni(OH)2.

[0050] Figure 4 It is the SEM-EDS pattern of the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1, and this characterization can determine the content of metal elements in the catalyst. Among them, the atomic ratio of Cu:Ni:Ag in the Ag-Ni(OH) 2 / Cu NW catalyst is 86.2:10.9:2.9.

[0051] Example 2

[0052] The Ag-Ni(OH) 2 / Cu NW catalyst, Cu NW catalyst prepared in Comparative Example 1, Ni(OH) prepared in Comparative Example 2 2 / Cu NW catalyst, and Ag / Cu NW catalyst prepared in Comparative Example 3 were subjected to electrocatalytic NO 3 - RR test. Using an Ivium-n-Stat electrochemical workstation, electrochemical performance tests were carried out in a three-electrode system in an H-type electrolytic cell. The prepared catalyst and the silver / silver chloride electrode were used as the working electrode and the reference electrode respectively, and placed in the cathode chamber of the H-type electrolytic cell; a high-purity platinum sheet was used as the counter electrode and placed in the anode chamber of the H-type electrolytic cell; the anode and cathode chambers of the H-type electrolytic cell were separated by an N117-type proton exchange membrane, and 1M potassium hydroxide solution containing 50 mM potassium nitrate was added to both the anode and cathode chambers as the electrolyte, and high-purity argon gas was introduced before the test to remove impurity gases; then electrochemical tests were carried out using chronoamperometry, the test potential range was +0.2 to -0.2 V vs. reversible hydrogen electrode (RHE), the potential interval was 0.1 V vs. RHE, the test time at each potential was 1 hour, and then the electrolyte in the cathode chamber was collected.

[0053] Example 3

[0054] Weigh 0.8 g of sodium hydroxide, 1.156 g of salicylic acid, and 1.155 g of trisodium citrate dihydrate, and dissolve them fully in 20 mL of deionized water to obtain Color Reagent 1; absorb 900 μL of sodium hypochlorite solution (available chlorine content: 7.5%, free alkali content: 0.1 - 1%), and dissolve it fully in 30 mL of deionized water to obtain Color Reagent 2; weigh 0.2 g of sodium nitroprusside, and dissolve it fully in 20 mL of deionized water to obtain Color Reagent 3.

[0055] Example 4

[0056] Take the cathode electrolyte after NO 3 - RR in Example 2. After diluting it with 1M potassium hydroxide solution by an appropriate multiple, take 2 mL of the electrolyte, and successively add 2 mL of Color Reagent 1, 1 mL of Color Reagent 2, and 0.2 mL of Color Reagent 3. After shaking well, let it stand in the dark at room temperature for 2 hours, and then measure the absorbance at a wavelength of 655 nm by a UV-visible spectrophotometer, and calculate the ammonium ion concentration in the electrolyte according to the fitted standard curve, and further calculate the NH 3 yield and NH 3 FE.

[0057] Figure 5 、 Figure 6 and Figure 7 are Ag-Ni(OH) prepared in Example 1 2 / Cu NW catalyst and the Cu NW catalyst prepared in Comparative Example 1, Ni(OH) prepared in Comparative Example 2 2 / Cu catalyst, and the electrocatalytic NO 3 - RR performance comparison with that of the Ag / Cu NW catalyst prepared in Comparative Example 3. As can be seen from the figure, the Ag-Ni(OH) 2 / Cu NW catalyst has higher NH 3 yield, NH 3 FE, and energy conversion efficiency (EE) of NH 3 than those of Cu NW, Ag / Cu NW, and Ni(OH) 2 / Cu catalyst. At a test potential of -0.1 V vs. RHE, the NH 3 yield, NH 3 FE, and energy conversion efficiency of NH 3 are 4.01 mg h -1 cm -2 -2, 97.3%, and 44.8% respectively.

[0058] Example 5

[0059] In this example, the isotope labeling method was used to explore the source of the product NH 3 . As Figure 8 shown, when 15 KNO 3 is used as the reactant, two sets of signal peaks corresponding to 1 NH 15 can be detected by 4 + H NMR; when 14 KNO 3 is used as the reactant, three sets of signal peaks corresponding to 1 NH 14 can be detected by 4 + H NMR; the above results prove that the NH 3 in the reaction product comes from NO 3 - in the electrolyte, rather than from external contamination.

[0060] Example 6

[0061] Prepare 1 M potassium hydroxide solutions containing 5 mM, 10 mM, 30 mM, 50 mM, and 100 mM potassium nitrate as electrolytes. Other operating steps are the same as those in Example 2. Test the Ag-Ni(OH) 2 / Cu NW catalyst at different concentrations of NO 3- NO in 3 - RR catalytic activity.

[0062] Example 7

[0063] Prepare an electrolyte solution close to the nitrate concentration in sewage (1000 ppm NO 3 - ), and evaluate the NO removal ability of Ag-Ni(OH) 2 / Cu NW at -0.1 V vs. RHE potential. 3 - Removal ability.

[0064] Figure 9 The Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1 was used to test the NO 3 - NO in 3 - RR catalytic activity. As shown in the figure, the Ag-Ni(OH) 2 / Cu NW catalyst maintained excellent catalytic activity in a wide concentration range of NO 3 - electrolyte solution. In addition, as Figure 10 shown, after 150 min, the concentrations of NO 3 - and NO 2 - decreased to 1.76 and 0.52 ppm respectively, both lower than the WHO drinking water standards (NO 3 - -N < 11.3 ppm and NO 2 - -N < 0.91 ppm), indicating that the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1 has broad application prospects in the fields of NH 3 synthesis and wastewater treatment.

[0065] Example 8

[0066] Using a 1 M potassium hydroxide solution containing 50 mM potassium nitrate as the electrolyte, the Ag-Ni(OH) 2 / Cu NW catalyst prepared in Example 1 was tested for cyclic stability at a test potential of -0.1 V vs. RHE. As Figure 11 shown, the catalyst maintained stable NH 3 yield and NH 3 FE after 25 hours of cyclic testing. Figure 12 AndFigure 13 The SEM images and XRD patterns of showed that the catalyst maintained the nanowire structure and good crystal structure after the cyclic test, indicating that the catalyst had excellent stability.

[0067] Although the embodiments of the present disclosure have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. For those skilled in the art, various changes and modifications can be made to the present disclosure. Any changes, modifications, substitutions, combinations, and simplifications made to the present disclosure shall be equivalent replacement methods and shall be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a multi-site silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW, characterized in that: The following steps are involved: (1) using isopropyl alcohol solution and dilute hydrochloric acid solution to clean the copper foam in turn to remove grease and oxide layer on the surface of the copper foam; (2) soaking the cleaned copper foam in a mixed solution containing sodium hydroxide and ammonium persulfate for 5 hours to prepare copper hydroxide nanowires supported by a copper foam skeleton; (3) After washing the copper hydroxide nanowires with deionized water for multiple times, the copper hydroxide nanowires were immersed in a silver nitrate solution for 30 minutes at room temperature by a cation exchange method to obtain Ag / Cu(OH)2NW; then, an electrochemical deposition process was performed in a 30 mM nickel sulfate hexahydrate solution using the silver-copper hydroxide nanowire catalyst Ag / Cu(OH)2NW as a working electrode, a platinum sheet electrode as a counter electrode, and a silver / silver chloride electrode as a reference electrode to obtain silver-nickel hydroxide / copper hydroxide nanowires Ag-Ni(OH)2 / Cu(OH)2NW; (4) The Ag-Ni(OH)2 / Cu(OH)2NW in step (3) is subjected to tubular furnace annealing at 160 degrees Celsius for 30 minutes to obtain silver-nickel hydroxide / copper oxide nanowires Ag-Ni(OH)2 / CuO NW, and then the Ag-Ni(OH)2 / CuO NW is subjected to electro-reduction treatment in 1M potassium hydroxide solution to finally obtain silver-nickel hydroxide / copper nanowires Ag-Ni(OH)2 / Cu NW catalyst.

2. The method for preparing the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW according to claim 1, characterized in that: The concentration of the dilute hydrochloric acid solution in step (1) is 0.1M.

3. The method for preparing the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW according to claim 1, characterized in that: The concentration of the sodium hydroxide solution contained in the mixed solution in step (2) is 1M, and the concentration of the ammonium persulfate solution is 0.05M.

4. The method for preparing the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW according to claim 1, characterized in that: In the cation exchange process of step (3), the concentration of the silver nitrate solution is 1 mM; the electrochemical deposition process parameters are: the deposition current density is -10 mA cm -2 , hold for 1 minute.

5. The method for preparing the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW according to claim 1, characterized in that: Step (4), the Ag-Ni(OH)2 / CuO NW is electro-reduced in 1M potassium hydroxide solution to -30 mA cm -2 Electroreduction was carried out under constant current for 1 h.

6. The use of the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW according to claim 1, characterized in that: The catalyst is used for synthesizing ammonia through electrocatalytic nitrate reduction reaction.

7. The use of the silver-nickel hydroxide / copper nanowire catalyst Ag-Ni(OH)2 / Cu NW according to claim 6, characterized in that: The following steps are involved: (1) using an Ivium-n-Stat electrochemical workstation and a three-electrode system, an electrochemical performance test was performed in an H-type electrolytic cell, wherein the prepared silver-nickel hydroxide / copper nanowire catalyst and the silver / silver chloride electrode were used as a working electrode and a reference electrode, respectively, and were placed in the cathode chamber of the H-type electrolytic cell; a high-purity platinum sheet was used as a counter electrode and was placed in the anode chamber of the H-type electrolytic cell; the positive and negative chambers of the H-type electrolytic cell were separated by a Nafion 117 proton exchange membrane, and a 1M potassium hydroxide (KOH) solution containing 50mM potassium nitrate was added to both the positive and negative chambers as an electrolyte, and high-purity argon gas was introduced before the test to remove impurity gases; (2) electrochemical testing was performed using a chronoamperometry method, with a test potential range of +0.2 to -0.2 V vs. reversible hydrogen electrode RHE, a potential interval of 0.1 V vs. RHE, and a test time of 1 hour at each potential, followed by collection of the electrolyte in the cathode chamber; (3) The electrolyte after the reaction was developed using the indophenol blue colorimetric method, and then the ammonium ion concentration in the electrolyte was calculated using a UV-visible spectrophotometer to calculate the NH3 yield of the catalyst and the NH3 Faraday efficiency FE.

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