Preparation method and application of a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode

Abstract

The application belongs to the technical field of environmental functional materials, and discloses a preparation method and application of a self-supporting cobalt-doped cuprous oxide double-site cathode electrode. A foam copper is used to prepare a substrate, and a cobalt-doped copper hydroxide nanorod composite is obtained through electrochemical deposition; annealing treatment is performed at a certain temperature and in a nitrogen atmosphere, and a Co-Cu2O / CF electrode is obtained. The preparation method of the three-dimensional self-supporting Co-Cu2O / CF cathode electrode of the application promotes the decomposition of water and the adsorption of nitrate through the synergistic effect between copper and cobalt double sites, so as to improve the selective conversion of nitrate to ammonia. The application provides the application of the cobalt-doped cuprous oxide self-supporting cathode electrode in the electrocatalytic reduction of nitrate to synthesize ammonia, and the electrode has excellent Faraday efficiency and ammonia selectivity and good stability. Meanwhile, the preparation method of the catalyst is simple and easy to implement, the catalyst has high electrocatalytic performance, and has certain potential application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology. The invention relates to a method for preparing and applying a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode. Background Technology

[0002] Ammonia (NH3) is one of the most important chemical raw materials, playing an irreplaceable role in the production of fertilizers, chemicals, and pharmaceuticals. Besides its primary use in fertilizers, ammonia is also an energy carrier in the emerging global hydrogen economy (Hydrogen 2.0) because it can be reliably transported over long distances using existing logistics infrastructure. Currently, the industrial synthesis of NH3 mainly relies on the energy-intensive and carbon-emission Haber-Bosch process, which reacts nitrogen (N2) and hydrogen (H2) under high temperature (350-550℃) and high pressure (150-350 atm) conditions. However, its harsh operating conditions result in high energy consumption and large amounts of carbon dioxide emissions. Therefore, exploring green and economical ammonia synthesis processes is urgently needed.

[0003] Due to industrial wastewater discharge and improper use of fertilizers, nitrates (NO3) are... - Pollutants are widely present in surface water and groundwater aquifers, causing eutrophication, excessive algae growth, harm to aquatic plants, and seriously threatening human health. Nitrate degradation has been a focus of research, with treatment processes including reverse osmosis, ion exchange, and biological denitrification, but these methods have drawbacks such as secondary pollution requiring subsequent treatment.

[0004] In recent years, electrochemical nitrate reduction at room temperature and pressure has shown great promise as an environmentally friendly and efficient method for synthesizing high-value-added NH3. However, current catalytic electrodes in this field are mainly based on noble metals, whose high cost and limited availability significantly restrict their further development and application. Non-noble metal electrodes, due to their advantages of low cost, high activity, and large-scale application potential, have received increasing attention in the field of electrochemical nitrate reduction in recent years. Cu-based electrodes have attracted considerable attention due to their high adsorption capacity for nitrates and the fully filled Cu 3d orbitals, which suppress the competitive hydrogen evolution reaction (HER). However, the accumulation of nitrite during the Cu-based electrode reaction requires prolonged electrolysis and high overpotentials to further reduce NO2. - The reduction to NH3 results in a lower adsorption energy for the reaction intermediate and lower selectivity for NH3. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention aims to address the low selectivity and Faradaic efficiency of non-noble metal electrodes. This invention provides a method for preparing a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode and its application. When the provided electrode is applied to an electrocatalytic nitrate reduction system, in a low-concentration, neutral nitrate solution, the prepared cathode electrode exhibits high NO3RR catalytic activity, with a Faradaic efficiency of 95.98%, a selectivity of 92.45%, and an NH3 yield of 0.4978 mmol / L. -1 cm -2 It has high practical application value.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode includes the following steps:

[0008] S1. Prepare the substrate by pretreating the copper foam by sequentially ultrasonically treating the copper foam with acetone, dilute hydrochloric acid, ethanol and deionized water, washing and then vacuum sealing it for later use as an electrode substrate.

[0009] S2. To prepare Cu(OH)2NRs / CF, the electrode substrate prepared in step S1 is vertically immersed in a solution containing alkaline solution and persulfate. The resulting sky-blue CF is removed from the solution, thoroughly washed with deionized water, and vacuum dried to obtain Cu(OH)2NRs / CF.

[0010] S3. Prepare Co-Cu(OH)2NRs / CF. Place the Cu(OH)2NRs / CF prepared in step S2 into a solution containing cobalt nitrate. At a predetermined temperature, use a three-electrode system and a constant potential method for electrodeposition. Remove, wash, dry and store to obtain Co-Cu(OH)2NRs / CF.

[0011] S4. Preparation of Co-Cu2O / CF: The Co-Cu(OH)2NRs / CF prepared in step S2 is placed in a tube furnace and heated to 300-600℃ under inert gas protection, maintained for 0.5-4h, and then cooled to room temperature to obtain Co-Cu2O / CF.

[0012] Furthermore, in step S1, the size of the foamed copper is 1cm*1cm to 4cm*4cm; the hydrochloric acid concentration is 0.1 to 2M; the ultrasonic time is 10 to 20 minutes; and deionized water is used for washing.

[0013] Furthermore, in step S2, the persulfate is any one of ammonium persulfate, potassium persulfate, or sodium persulfate, with a concentration of 0.05–0.5 M; the alkaline solution is potassium hydroxide or sodium hydroxide, with a concentration of 0.5–4 M.

[0014] Preferably, the persulfate is ammonium persulfate with a concentration of 0.125M, and the alkaline solution is sodium hydroxide with a concentration of 2.5M.

[0015] Furthermore, in step S3, the predetermined temperature is 20–30°C; the drying temperature is 40–60°C; and the drying time is 8–12 hours.

[0016] Furthermore, in step S3, the concentration of the cobalt nitrate solution is 0.01–1 M.

[0017] Furthermore, in step S3, the conditions for electrodeposition using the constant potential method are: deposition potential of -0.6 to -1V; deposition time of 5 to 30 minutes.

[0018] Furthermore, in step S3, the counter electrode of the three-electrode system is any one of a platinum sheet, a platinum mesh, or a stone rod; the reference electrode is any one of Ag / AgCl or a saturated calomel electrode; and the working electrode is Cu(OH)2NRs / CF.

[0019] Furthermore, in step S4, the inert gas is nitrogen or argon.

[0020] Furthermore, in step S4, the heating rate is 5-20℃ / min. Preferably, the heating rate is 5℃ / min.

[0021] This invention also seeks protection for the application of the electrode prepared by the above method in the electrocatalytic reduction of nitrate to prepare NH3.

[0022] The specific application involves using the Co-Cu₂O / CF electrode prepared by the above method as the working electrode, which is assembled together with a Pt sheet electrode and an Ag / AgCl reference electrode in an H-type electrolytic cell. The cathode and anode chambers are separated by a Nafion 117 membrane, and the tests are performed using an electrochemical workstation (Chenhua 660E). The cathode chamber is filled with 80 mL of electrolyte containing 200 mg L⁻¹. -1 NO3 -A 0.5 M Na₂SO₄ solution (pH = 7) containing -N was used, and an equal volume of 0.5 M Na₂SO₄ solution was filled into the anode chamber. Before the test, argon gas was bubbled into the electrolyte for 30 min to eliminate interference from oxygen. Electrolysis was performed for 2 h at a constant potential of -0.7 V vs. RHE at 25 °C with a magnetic stirring rate of 400 rpm. After the reaction, the NH₃ concentration in the catholyte was determined by Nessler's reagent spectrophotometry, and the ammonia yield was calculated to be 0.4978 mmol / L. -1 cm -2 The Faraday efficiency was 95.98%, and the ammonia selectivity reached 92.45%. Ten consecutive cycles of experiments showed that the Co-Cu2O / CF electrode maintained high Faraday efficiency and ammonia yield, demonstrating the electrode's excellent stability.

[0023] The advantages of this invention compared to the prior art are:

[0024] The present invention provides a method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode and its application, which has the following significant advantages compared with the prior art:

[0025] (1) When the self-supporting cobalt-doped cuprous oxide dual-site cathode electrode is applied, no adhesive is required, which effectively inhibits the shedding of active material during the electrocatalytic reduction of nitrate to ammonia.

[0026] (2) The copper active sites of the self-supporting cobalt-doped cuprous oxide dual-site cathode electrode promote NO3- production. - Adsorption and conversion occur on the catalyst surface, and the modulation of the electronic structure of Cu by the cobalt active sites promotes water decomposition, thereby optimizing water decomposition and promoting NO2 decomposition. - It is converted to NH3, and at the same time H ads The adsorption of H2 prevents its release, thus resulting in high electrocatalytic activity of NO3RR.

[0027] (3) The self-supporting cobalt-doped cuprous oxide dual-site cathode electrode of this invention has a simple fabrication process, high reproducibility, and is easy to scale up. Under neutral conditions, the self-supporting cobalt-doped cuprous oxide dual-site cathode electrode achieves a Faraday efficiency of 95.98% and an ammonia selectivity of 92.45% at -0.7V vs. RHE, with an ammonia yield as high as 0.4978 mmol / h. -1 cm -2 .

[0028] The self-supporting cobalt-doped cuprous oxide dual-site cathode electrode provided by this invention is an innovative method for the electrocatalytic reduction of nitrate to ammonia, providing a new catalytic strategy for the electrocatalytic synthesis of ammonia from nitrate at room temperature and pressure.

[0029] The method for preparing the self-supporting cobalt-doped cuprous oxide dual-site cathode electrode provided by this invention is simple and easy to implement, and achieves high NO3RR catalytic performance, showing certain potential application prospects. Attached Figure Description

[0030] Figure 1 These are the XRD patterns of Co-Cu2O / CF prepared in Example 1 of this invention and Cu2O / CF prepared in Comparative Example 1;

[0031] Figure 2 This is the XPS full spectrum of Co-Cu2O / CF prepared in Example 1 of this invention;

[0032] Figure 3 These are scanning electron microscope (SEM) images of Co-Cu2O / CF prepared in Example 1 and Cu2O / CF prepared in Comparative Example 1 of the present invention; wherein Figure a is a scanning electron microscope image of Cu2O / CF and Figure b is a scanning electron microscope image of Co-Cu2O / CF.

[0033] Figure 4 The following are transmission electron microscope (TEM) and EDS images of Co-Cu2O / CF prepared in Example 1 of this invention; wherein Figure a is a TEM image of Co-Cu2O / CF, Figure b is an EDS image of Cu in Co-Cu2O / CF, Figure c is an EDS image of Co in Co-Cu2O / CF, and Figure d is an EDS image of O in Co-Cu2O / CF.

[0034] Figure 5 This is a diagram of the electrochemical reaction apparatus for the electrocatalytic reduction of nitrate to synthesize ammonia according to the present invention;

[0035] Figure 6 This is a comparison chart of the Faraday efficiency and ammonia yield of the cathode electrode electrocatalytic reduction of nitrate to ammonia in Example 1 of the present invention at different applied potentials.

[0036] Figure 7 Figure a shows the change of nitrate concentration over time and the product percentage of the ammonia synthesis from nitrate via the cathode electrode in Example 1 of this invention, under the optimal applied potential. Figure b shows the change of nitrate concentration over time and the product percentage of the ammonia synthesis from nitrate via the cathode electrode in Example 1, under the optimal applied potential.

[0037] Figure 8 This is an LSV curve of the Co-Cu2O / CF cathode electrode prepared in Example 1 of the present invention with and without nitrate.

[0038] Figure 9The results of 10 consecutive performance tests of the Co-Cu2O / CF cathode electrode prepared in Example 1 of this invention in an H-type reactor are shown in the ammonia yield and Faraday efficiency graphs. Detailed Implementation

[0039] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0040] This invention provides a method for preparing and applying a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode, comprising the following steps: (1) ultrasonically washing copper foam with acetone, dilute hydrochloric acid, ethanol, and deionized water respectively; (2) vertically immersing the cleaned copper foam from step (1) into a mixed solution containing NaOH and (NH4)2SO4 for in-situ wet oxidation; (3) using the copper hydroxide nanorods obtained in step (2) as the working electrode, electrochemically depositing them in a cobalt nitrate solution to obtain a cobalt-doped copper hydroxide nanorod composite material; (4) annealing the composite material obtained in step (3) at a certain temperature and in a nitrogen atmosphere to obtain a Co-Cu2O / CF electrode. The method for preparing the three-dimensional self-supporting Co-Cu2O / CF cathode electrode of this invention optimizes the adsorption of nitrate and promotes the decomposition of water through the synergistic effect between copper and cobalt dual sites, thereby improving the selective conversion of nitrate to ammonia. This invention provides the application of a cobalt-doped cuprous oxide self-supporting cathode electrode in the electrocatalytic reduction of nitrate to ammonia, exhibiting excellent Faraday efficiency and ammonia selectivity, as well as good stability. Meanwhile, the catalyst preparation method is simple and easy to implement, achieves high electrocatalytic performance, and has certain potential application prospects.

[0041] Example 1

[0042] A method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode includes the following steps:

[0043] (1) Before electrode preparation, copper foam (CF) was cut to a size of 2.5cm*2.0cm and ultrasonically cleaned for 15min in sequence with 10mL acetone, 10mL 1.0M hydrochloric acid, 10mL anhydrous ethanol and deionized water to remove surface oil and oxide layer. Then the substrate was dried in a vacuum oven at 60℃ for 4h and used as electrode substrate.

[0044] (2) Immerse the electrode substrate obtained in step (1) vertically into a solution containing 2.5 mol·L⁻¹ -1 NaOH and 0.125 mol·L -1The substrate was placed in an alkaline solution of (NH4)2S2O8 and allowed to stand at room temperature for 30 min. Then, the resulting sky-blue electrode substrate was removed from the solution, thoroughly washed with deionized water, and dried in a vacuum oven at 60 °C for 12 h. This yielded Cu(OH)2NRs / CF.

[0045] (3) Dissolve 0.4365g (0.05M) cobalt nitrate in 30mL of deionized water and stir thoroughly until completely dissolved. This solution is used as the electrodeposition precursor solution.

[0046] (4) Place the Cu(OH)2NRs / CF obtained in step (2) into the electrodeposition precursor solution obtained in step (3), and use a three-electrode system at 25°C, with a platinum sheet as the counter electrode, an AgCl / Ag electrode as the reference electrode, and the Cu(OH)2NRs / CF obtained in step (2) as the working electrode. Use the constant potential method at -0.8V for 15 min for electrodeposition. After taking it out, wash it several times, dry it and store it to obtain Co-Cu(OH)2NRs / CF.

[0047] (5) The Co-Cu(OH)2NRs / CF obtained in step (4) was placed in a ceramic boat in a tube furnace and heated at 550°C for 2 hours under a N2 atmosphere at a heating rate of 5°C / min. Since the key operation in this step is to control the oxygen-free environment, the tube furnace was pre-ventilated for 30 minutes before heating to remove any residual air. Finally, it was cooled to ambient temperature under a N2 atmosphere to obtain a self-supporting Co-Cu2O / CF dual-site cathode electrode, which can be used as the working electrode for the electrocatalytic nitrate reduction to ammonia synthesis system.

[0048] Example 2

[0049] (1) Cut copper foam (CF) to a size of 2.5cm*2.0cm, and ultrasonically clean it for 15min in sequence with 10mL acetone, 10mL 1.0M hydrochloric acid, 10mL anhydrous ethanol and deionized water to remove surface oil and oxide layer. Then dry the substrate in a vacuum oven at 60℃ for 4h to prepare it as an electrode substrate.

[0050] (2) The electrode substrate CF obtained in step (1) is vertically immersed in a solution containing 2.5 mol·L⁻¹ -1 NaOH and 0.125 mol·L -1 The solution was placed in an alkaline solution of (NH4)2S2O8 and allowed to stand at room temperature for 30 min. Then, the resulting sky-blue CF was removed from the solution, thoroughly washed with deionized water, and dried in a vacuum oven at 60 °C for 12 h. This yielded Cu(OH)2NRs / CF.

[0051] (3) Dissolve 0.087 g (0.01 M) cobalt nitrate in 30 mL of deionized water and stir thoroughly until completely dissolved to obtain the electrodeposition precursor solution.

[0052] (4) Place the Cu(OH)2NRs / CF obtained in step (2) into the electrodeposition precursor solution obtained in step (3), and use a three-electrode system at 25°C, with a platinum sheet as the counter electrode, an AgCl / Ag electrode as the reference electrode, and the Cu(OH)2NRs / CF obtained in step (2) as the working electrode. Use the constant potential method at -0.8V for 15 min for electrodeposition. After taking it out, wash it several times, dry it and store it to obtain Co-Cu(OH)2NRs / CF.

[0053] (5) The Co-Cu(OH)2NRs / CF obtained in step (4) was placed in a ceramic boat in a tube furnace and heated at 550°C for 2 hours under a N2 atmosphere at a heating rate of 5°C / min. Since the key operation in this step is to control the oxygen-free environment, the tube furnace was pre-ventilated for 30 minutes before heating to remove any residual air. Finally, it was cooled to ambient temperature under a N2 atmosphere to obtain a self-supporting Co-Cu2O / CF dual-site cathode electrode, which can be used as the working electrode for the electrocatalytic nitrate reduction to ammonia synthesis system.

[0054] Example 3

[0055] (1) Cut copper foam (CF) to a size of 2.5cm*2.0cm, and ultrasonically clean it for 15min in sequence with 10mL acetone, 10mL 1.0M hydrochloric acid, 10mL anhydrous ethanol and deionized water to remove surface oil and oxide layer. Then dry the substrate in a vacuum oven at 60℃ for 4h to prepare it as an electrode substrate.

[0056] (2) The electrode substrate CF obtained in step (1) is vertically immersed in a solution containing 2.5 mol·L⁻¹ -1 NaOH and 0.125 mol·L -1 The solution was placed in an alkaline solution of (NH4)2S2O8 and allowed to stand at room temperature for 30 min. Then, the resulting sky-blue CF was removed from the solution, thoroughly washed with deionized water, and dried in a vacuum oven at 60 °C for 12 h. This yielded Cu(OH)2NRs / CF.

[0057] (3) Dissolve 0.8731 g (0.1 M) cobalt nitrate in 30 mL of deionized water and stir thoroughly until completely dissolved to obtain the electrodeposition precursor solution.

[0058] (4) Place the Cu(OH)2NRs / CF obtained in step (2) into the electrodeposition precursor solution obtained in step (3), and use a three-electrode system at 25°C, with a platinum sheet as the counter electrode, an AgCl / Ag electrode as the reference electrode, and the Cu(OH)2NRs / CF obtained in step (2) as the working electrode. Use the constant potential method at -0.8V for 15 min for electrodeposition. After taking it out, wash it several times, dry it and store it to obtain Co-Cu(OH)2NRs / CF.

[0059] (5) The Co-Cu(OH)2NRs / CF obtained in step (4) was placed in a ceramic boat in a tube furnace and heated at 550°C for 2 hours under a N2 atmosphere at a heating rate of 5°C / min. Since the key operation in this step is to control the oxygen-free environment, the tube furnace was pre-ventilated for 30 minutes before heating to remove any residual air. Finally, it was cooled to ambient temperature under a N2 atmosphere to obtain a self-supporting Co-Cu2O / CF dual-site cathode electrode, which can be used as the working electrode for the electrocatalytic nitrate reduction to ammonia synthesis system.

[0060] Example 4

[0061] (1) Cut copper foam (CF) to a size of 2.5cm*2.0cm, and ultrasonically clean it for 15min in sequence with 10mL acetone, 10mL 1.0M hydrochloric acid, 10mL anhydrous ethanol and deionized water to remove surface oil and oxide layer. Then dry the substrate in a vacuum oven at 60℃ for 4h to prepare it as an electrode substrate.

[0062] (2) The electrode substrate CF obtained in step (1) is vertically immersed in a solution containing 2.5 mol·L⁻¹ -1 NaOH and 0.125 mol·L -1 The solution was placed in an alkaline solution of (NH4)2S2O8 and allowed to stand at room temperature for 30 min. Then, the resulting sky-blue CF was removed from the solution, thoroughly washed with deionized water, and dried in a vacuum oven at 60 °C for 12 h. This yielded Cu(OH)2NRs / CF.

[0063] (3) Dissolve 0.4365g (0.05M) cobalt nitrate in 30mL of deionized water and stir thoroughly until completely dissolved. This solution is used as the electrodeposition precursor solution.

[0064] (4) Place the Cu(OH)2NRs / CF obtained in step (2) into the electrodeposition precursor solution obtained in step (3), and use a three-electrode system at 25°C, with a platinum sheet as the counter electrode, an AgCl / Ag electrode as the reference electrode, and the Cu(OH)2NRs / CF obtained in step (2) as the working electrode. Use the constant potential method at -1V for 15 min, remove and wash several times, dry and store to obtain Co-Cu(OH)2NRs / CF.

[0065] (5) The Co-Cu(OH)2NRs / CF obtained in step (4) was placed in a ceramic boat in a tube furnace and heated at 550°C for 2 hours under a N2 atmosphere at a heating rate of 5°C / min. Since the key operation in this step is to control the oxygen-free environment, the tube furnace was pre-ventilated for 30 minutes before heating to remove any residual air. Finally, it was cooled to ambient temperature under a N2 atmosphere to obtain a self-supporting Co-Cu2O / CF dual-site cathode electrode, which can be used as the working electrode for the electrocatalytic nitrate reduction to ammonia synthesis system.

[0066] Comparative Example 1

[0067] The preparation of a Co-free catalyst control sample includes the following steps:

[0068] (1) Before electrode preparation, copper foam (CF) was cut to a size of 2.5cm*2.0cm and ultrasonically cleaned for 15min in sequence with 10mL acetone, 10mL 1.0M hydrochloric acid, 10mL anhydrous ethanol and deionized water to remove surface oil and oxide layer. Then the substrate was dried in a vacuum oven at 60℃ for 4h and used as electrode substrate.

[0069] (2) Immerse the electrode substrate obtained in step (1) vertically into a solution containing 2.5 mol·L⁻¹ -1 NaOH and 0.125 mol·L -1 The substrate was placed in an alkaline solution of (NH4)2S2O8 and allowed to stand at room temperature for 30 min. Then, the resulting sky-blue electrode substrate was removed from the solution, thoroughly washed with deionized water, and dried in a vacuum oven at 60 °C for 12 h. This yielded Cu(OH)2NRs / CF.

[0070] (3) The Cu(OH)2NRs / CF obtained in step (2) is placed in a ceramic boat in a tube furnace and heated at 550°C for 2 hours under N2 atmosphere with a heating rate of 5°C / min to obtain Cu2O / CF, which is used for electrochemical tests related to the electrocatalytic reduction of nitrate to synthesize ammonia.

[0071] The phase composition of Example 1 and Comparative Example 1 was characterized using X-ray diffraction, and the results are as follows: Figure 1As shown, the horizontal axis represents twice the diffraction angle (degree), and the vertical axis represents the intensity (au) of the diffraction peaks. Characteristic peaks of Cu and Cu₂O are clearly visible in the figure, while no obvious characteristic peaks of cobalt are observed. Elemental analysis of the material surface using XPS yielded the following results: Figure 2 As shown, this demonstrates that cobalt was successfully doped into Cu₂O. The morphology and structure of the composite material obtained in Example 1 were characterized using scanning electron microscopy, and the results are as follows. Figure 3 As shown, the irregular nanorod shape demonstrates the successful synthesis of Co-Cu2O. Figure 4 The high-resolution transmission electron microscope image and elemental distribution map of Example 1 show that Cu, Co, and O elements are uniformly distributed on the material surface.

[0072] Comparative Example 2

[0073] Cut the copper foam into pieces measuring 1×2cm. -2 The surface oil and oxide layer were removed by ultrasonic cleaning with 10 mL of acetone, 10 mL of 1.0 M hydrochloric acid, 10 mL of anhydrous ethanol, and deionized water for 15 min in sequence, and then dried at room temperature for later use. 3.2 g of sodium hydroxide was dissolved in 22 mL of deionized water, and 0.89 g of ammonium persulfate was dissolved in 8 mL of deionized water. The two solutions were then mixed and stirred. The treated foam was soaked and stirred in the mixed solution for 30 min. It was washed several times with deionized water and anhydrous ethanol, and then vacuum dried overnight at 60 °C to obtain Cu(OH)2 / CF. Cu(OH)2 / CF was then placed in a tube furnace and calcined at 250 °C for 180 min under air atmosphere. After natural cooling, CuO / CF material was obtained.

[0074] Comparative Example 3

[0075] Cut the nickel foam into pieces measuring 1×3cm. -2 The electrodes were ultrasonically cleaned sequentially with 10 mL of acetone, 10 mL of 1.0 M hydrochloric acid, 10 mL of anhydrous ethanol, and deionized water for 15 min to remove surface oil and oxide layer, and dried at room temperature for later use. The treated nickel foam was then transferred to a polytetrafluoroethylene liner containing 60 mL of 4.5 wt.% hydrogen peroxide aqueous solution and 8 mg of copper chloride, assembled into a reaction vessel, placed in an oven, and reacted at 160 °C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, the foam electrode was removed, washed with water, and dried to obtain Cu-Ni(OH)2 / CF.

[0076] Application examples

[0077] The cathode electrodes prepared in Examples 1, 2, 3, and 4 were used in the electrocatalytic reduction of nitrates to synthesize ammonia, as detailed below:

[0078] The electrocatalytic nitrate reduction synthesis experiment was conducted using an electrochemical workstation (Chenhua 660E). A three-electrode system was employed, with a 1cm*1cm platinum sheet as the counter electrode. Electrodes obtained in Examples 1, 2, 3, and 4 were used as working electrodes, and an Ag / AgCl reference electrode was used. The experiment was carried out in an H-type electrolytic cell, with the cathode and anode chambers separated by a Nafion 117 membrane. 5.682g of anhydrous sodium sulfate (analytical grade) and 0.0971g of sodium nitrate (analytical grade) were dissolved in 80mL of deionized water as the electrolyte for the cathode chamber. The molar concentrations of sulfate and nitrate (calculated as nitrogen) were 0.5M and 200mg / L, respectively. -1 The electrolyte in the anode chamber was a 0.5M Na2SO4 solution. Before the test, argon gas was introduced into the electrolyte for 30 minutes to ensure an oxygen-free environment and eliminate any interference from oxygen in the reaction process.

[0079] Electrochemical testing process:

[0080] Linear sweep voltammetry (LSV) was used at 5 mV s. -1 The scanning rate was conducted within a certain voltage range, and the catalyst activity was initially tested based on the current density. Chorometric galvanometry (it) was used to record the changes in current density over time when different potentials were applied to the working electrode, in order to obtain the reaction products and calculate relevant indicators. Cyclic stability was tested by constant potential testing at a certain voltage for a certain period of time, with a fresh electrolyte after each test. The concentrations of nitrate, nitrite, and ammonia nitrogen after the reaction were measured using a UV spectrophotometer to understand the distribution of total nitrogen. The potential window for LSV scanning was selected as +0.2V to -0.8V (vs RHE), and the scanning rate was set to 5mV / s. The distribution of nitrogen species in the products was measured at five points: -0.5V, -0.6V, -0.7V, -0.8V, and -0.9V, and the Faraday efficiency was calculated. The test results are shown in Table 1.

[0081] Ammonia yield calculation formula:

[0082] NH3 yield rate = (C NH3 ×V) / (M NH3 ×t×S)

[0083] Ammonia selectivity:

[0084] Selectivity = C product / ΔC NO3- ×100%

[0085] Faraday efficiency:

[0086] FE NH3 = (8F×C) NH3×V) / (M NH3 ×Q)

[0087] Where C NH3 M is the mass concentration of the NH3 aqueous solution, V is the volume of the electrolyte in the cathode chamber (80 mL), and M is the mass concentration of the NH3 aqueous solution. NH3 t is the molar mass of NH3, t is the electrolysis time (2h), and S is the geometric area of ​​the working electrode (1cm²). -2 ), ΔC NO3- NO3 before and after electrolysis - The concentration difference, C0 is NO3 - The initial concentration, C product It is the concentration of ammonia or nitrite formed, and F is the Faraday constant (96485 Cmol). -1 Q is the total charge through the electrodes.

[0088] Application of comparative examples

[0089] The undoped cobalt cathode electrode prepared in Comparative Example 1 was used in the electrocatalytic reduction of nitrate to synthesize ammonia, as follows:

[0090] The electrocatalytic reduction synthesis of nitrate was conducted using an electrochemical workstation (Chenhua 660E) with a three-electrode system. A 1cm*1cm platinum sheet was used as the counter electrode, Cu₂O (from Comparative Example 1) was used as the working electrode, and an Ag / AgCl reference electrode was used. The experiment was carried out in an H-type electrolytic cell, with the cathode and anode chambers separated by a Nafion 117 membrane. 5.682g of anhydrous sodium sulfate (analytical grade) and 0.0971g of sodium nitrate (analytical grade) were dissolved in 80mL of deionized water as the electrolyte for the cathode chamber. The molar concentrations of sulfate and nitrate (based on nitrogen) were 0.5M and 200mg / L, respectively. -1 The electrolyte in the anode chamber is a 0.5M Na2SO4 solution. Before the test, argon gas was introduced into the electrolyte for 30 minutes to ensure an oxygen-free environment for the electrolyte and to eliminate the interference of oxygen on the reaction process.

[0091] Choriometry (IT) was used to record the changes in current density over time when different potentials were applied to the working electrode, in order to obtain the reaction products and calculate relevant indicators. Ultraviolet spectrophotometry was used to determine the concentrations of nitrate, nitrite, and ammonia nitrogen after the reaction to understand the distribution of total nitrogen changes. The results are shown in Table 1.

[0092] Table 1 Results of Electrochemical Nitrate Reduction Synthesis of Ammonia

[0093] Material <![CDATA[FE NH3 ]]> <![CDATA[NH3 production rate]]> Example 1 <![CDATA[Co-Cu2O / CF(-0.8V,0.05MCo(NO3)2)]]> 95.98％ <![CDATA[0.498mmolh -1 cm -2 ]]> Example 2 <![CDATA[Co-Cu2O / CF(-0.8V,0.01MCo(NO3)2)]]> 89.75％ <![CDATA[0.392mmolh -1 cm -2 ]]> Example 3 <![CDATA[Co-Cu2O / CF(-0.8V,0.1MCo(NO3)2)]]> 93.67％ <![CDATA[0.448mmolh -1 cm -2 ]]> Example 4 <![CDATA[Co-Cu2O / CF(-1V,0.05MCo(NO3)2)]]> 90.49％ <![CDATA[0.406mmolh -1 cm -2 ]]> Comparative Example 1 <![CDATA[Cu2O / CF]]> 83.32％ <![CDATA[0.358mmolh -1 cm -2 ]]> Comparative Example 2 CuO / CF 75.3％ <![CDATA[0.243mmolh -1 cm -2 ]]> Comparative Example 3 <![CDATA[Cu-Ni(OH)2 / CF]]> 80.2％ <![CDATA[0.294mmolh -1 cm -2 ]]>

[0094] Table 1 compares the removal efficiency and ammonia yield of the electrodes prepared in Examples 1-4 under an applied potential of -0.7V vs. RHE. The electrocatalytic test results are shown in Table 1, indicating that Examples 1-4 achieved an ammonia yield as high as 0.498 mmol / h at -0.7V vs. RHE. -1 cm -2 The value was much higher than that of the pure cuprous oxide electrode in Comparative Example 1, indicating that cobalt metal doping plays an important role in improving the performance of electrocatalytic nitrate reduction to ammonia synthesis.

[0095] The Co-Cu₂O / CF dual-site cathode electrode prepared using the method of this invention can achieve highly efficient conversion of nitrate pollutants at lower potentials, improving the selectivity and Faradaic efficiency of ammonia. Compared with a single undoped Cu₂O catalyst, the Faradaic efficiency of ammonia reaches 95.98%, and the selectivity reaches 92.45%, with low energy consumption for ammonia production. Furthermore, this electrode exhibits good reusability and stability. Figure 9 As shown, it maintains a Daladier efficiency of over 90% even after more than 10 cycles, and has the advantages of simple and easy-to-operate preparation process and no pollution. It can realize the conversion of nitrate and ammonia production in an economical, efficient and environmentally friendly manner, showing potential application value.

[0096] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode, characterized in that, Includes the following steps: S1. Prepare the substrate by pretreating the copper foam by sequentially ultrasonically treating the copper foam with acetone, dilute hydrochloric acid, ethanol and deionized water, washing and then vacuum sealing it for later use as an electrode substrate. S2. To prepare Cu(OH)2 NRs / CF, the electrode substrate prepared in step S1 is vertically immersed in a solution containing alkaline solution and persulfate. The resulting sky-blue CF is removed from the solution, thoroughly washed with deionized water, and vacuum dried to obtain Cu(OH)2 NRs / CF. S3. Preparation of Co-Cu(OH)2 NRs / CF: The Cu(OH)2 NRs / CF prepared in step S2 is placed in a cobalt nitrate solution. At a predetermined temperature, electrodeposition is performed using a three-electrode system and a constant potential method. The electrodepositor is then removed, washed, dried, and stored to obtain Co-Cu(OH)2 NRs / CF. S4. Prepare Co-Cu2O / CF. Place the Co-Cu(OH)2 NRs / CF prepared in step S2 in a tube furnace, heat it to 300~600℃ under inert gas protection, maintain it for 0.5~4 h, and then cool it to room temperature to obtain Co-Cu2O / CF.

2. The method for preparing a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that the steps... In S1, the size of the copper foam is 1cm*1cm to 4cm*4cm; the hydrochloric acid concentration is 0.1 to 2M; the ultrasonic time is 10 to 20 minutes; and deionized water is used for washing.

3. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S2, the persulfate is any one of ammonium persulfate, potassium persulfate, or sodium persulfate, and the concentration is 0.05–0.5 M.

4. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S2, the alkaline solution is potassium hydroxide or sodium hydroxide, with a concentration of 0.5–4 M.

5. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S3, the predetermined temperature is 20–30°C; the drying temperature is 40–60°C; and the drying time is 8–12 h.

6. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S3, the concentration of the cobalt nitrate solution is 0.01~1 M.

7. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S3, the conditions for electrodeposition using the constant potential method are: deposition potential of -0.6 to -1V; deposition time of 5 to 30 minutes.

8. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S4, the heating rate is 5-20 °C / min.

9. The method for fabricating a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode as described in claim 1, characterized in that, In step S4, the inert gas is nitrogen or argon.

10. The application of the electrode prepared by the method for preparing a self-supporting cobalt-doped cuprous oxide dual-site cathode electrode according to any one of claims 1-9 in the electrocatalytic reduction of nitrate to prepare NH3.

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