Method for synthesizing carbon fiber loaded copper-iron-nickel multicomponent alloy catalyst based on carbon thermal shock technology and application thereof

Abstract

The invention discloses a method for synthesizing a carbon fiber loaded copper-iron-nickel multi-component alloy catalyst based on a carbon thermal shock technology and application of the carbon fiber loaded copper-iron-nickel multi-component alloy catalyst. Carbon fiber paper is used as a substrate, the carbon fiber loaded copper-iron-nickel multi-element alloy catalyst is successfully prepared by means of a carbon thermal shock technology in a dual-mode heating mode, the carbon fiber loaded copper-iron-nickel multi-element alloy catalyst as a catalyst shows excellent catalytic performance in a reaction system for synthesizing urea through co-reduction of nitrate and carbon dioxide, the Faraday efficiency of urea reaches 78.33% to the maximum, and the carbon fiber loaded copper-iron-nickel multi-element alloy catalyst has a wide application prospect. And the highest yield of the urea reaches 1068.82 [mu] gcm <-2 > h <-1 >. The preparation method of the catalyst has the advantages of being simple, rapid, green, environmentally friendly and the like, and a new method and a new idea are provided for the field of electro-catalytic synthesis of urea.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic co-reduction synthesis of urea from carbon dioxide and nitrate, specifically relating to a method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock and its application. Background Technology

[0002] Urea (CO(NH2)2) is a nitrogen fertilizer containing 46 wt% nitrogen, crucial for promoting rapid crop growth and a key raw material for the production of fine chemical products. However, traditional industrial urea production methods, such as the Haber-Bosch and Bosch-Meiser processes, are plagued by high energy consumption and large amounts of carbon dioxide emissions, deviating from the goals of green economic development. Electrochemical coupling of CO2 and NO3... - Urea production represents a novel approach to achieving green urea synthesis driven by renewable energy. This strategy balances carbon reduction with nitrogen cycle equilibrium, contributing to a lower carbon footprint and reduced nitrogen pollution. Therefore, it offers a significant opportunity for the sustainable transformation of the urea industry. However, the electrocatalytic urea synthesis process involves CO2 and NO3... - Co-reduction is a multi-step proton-coupled electron transfer process that requires 16 electrons from the initial CO2 and NO3. - The transfer to the target product involves electrochemical reactions such as CN coupling, nitrate reduction, carbon dioxide reduction, and hydrogen evolution reaction (HER). Therefore, there is an urgent need to design electrocatalysts with high urea selectivity and high catalytic efficiency.

[0003] Copper-based materials are emerging as promising active catalysts for the electrochemical synthesis of urea due to their moderate adsorption energies for both C and N intermediates. However, single-metal Cu contains only a single active site, limiting its catalytic activity. Designing catalysts with synergistic multiple active sites allows for the tuning of intermediate configurations and catalytic activity, representing an effective strategy for achieving highly selective and catalytically active urea electrosynthesis. In catalyst synthesis technology, the carbon thermal shock method (CTS) is a highly efficient multi-element alloy preparation technique. CTS technology utilizes extremely high heating and cooling rates (up to 10⁻⁶ ppm). 4 -10 5The material synthesis is completed within milliseconds to seconds (K / min), significantly shortening the time-consuming and energy-intensive annealing process in traditional methods and effectively avoiding the problems of catalyst particle sintering and agglomeration. Based on this, this invention, building upon previous research on nitrogen-doped copper-nickel alloys, designed a carbon fiber-supported copper-iron-nickel multi-element alloy catalyst by screening metals, changing synthesis steps, and modifying the thermal shock mode. Multiple active sites enhance the efficiency of CN coupling, and the synergistic effect of these multiple active sites greatly reduces the reaction energy barrier, improving the yield and Faraday efficiency of urea synthesis, and exhibiting good stability during continuous synthesis. Furthermore, during the synthesis of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst, CTS was used to achieve instantaneous heating and cooling within a very short time, effectively preventing the agglomeration of catalyst metal particles. This invention not only provides a highly efficient catalyst for green urea synthesis but also offers a new approach to the design of multi-step coupled electrocatalytic reactions. Currently, there are no related reports in this area.

[0004] Patent document CN202510674763.2 discloses a method for synthesizing carbon fiber-supported nitrogen-doped copper-nickel alloy catalysts based on Joule heating technology and its application. Using carbon paper as a substrate, a carbon fiber-supported nitrogen-doped copper-nickel alloy catalyst was successfully prepared using Joule heating technology. As a catalyst, it exhibited excellent catalytic performance in the urea synthesis reaction system of nitrate and carbon dioxide co-reduction, achieving a Faraday efficiency of 68% and a catalytic efficiency of 544 μg / cm³ at -0.5V vs. RHE. -2 h -1 The urea yield is high, but its Faraday efficiency and urea yield still need to be further improved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalysts based on carbon thermal shock technology, which has readily available raw materials, simple process, low cost, and high product stability. This carbon fiber-supported copper-iron-nickel multi-element alloy catalyst exhibits excellent catalytic performance in the field of catalytic co-reduction of nitrate and carbon dioxide to synthesize urea.

[0006] To achieve the above objectives, the technical solution adopted in this invention is as follows: a method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalysts based on carbothermal shock technology. The carbon fiber-supported copper-iron-nickel multi-element alloy catalyst contains uniformly distributed metal elements and uniformly dispersed nanoparticles. It contains multiple active sites with a synergistic coupling effect, promoting the formation of nitrogen-containing and carbon-containing intermediates respectively, thereby improving the efficiency of coupling to generate key CN-coupled intermediates. Simultaneously, the synergistic coupling effect of multiple active sites effectively reduces the reaction energy barrier for urea synthesis, increasing the yield and Faraday efficiency of urea synthesis. It exhibits good stability and catalytic activity in the continuous catalytic co-reduction synthesis of urea from nitrate and carbon dioxide. The XRD pattern of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst shows metal diffraction peaks at 43.62° and 50.78°; the XPS pattern shows binding energies near 933.10 eV, 881.02 eV, 713.90 eV, 532 eV, 400 eV, and 285 eV, respectively, thus proving the presence of Cu, Ni, Fe, O, N, and C in the catalyst. The specific preparation process of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst is as follows: Step S1: Cut the carbon paper and then perform a hydrophilic treatment; Step S2: Prepare an ethanolic mixed solution of copper nitrate trihydrate, ferric nitrate nonahydrate and nickel nitrate hexahydrate to obtain metal precursor solution A. The molar ratio of copper ions, iron ions and nickel ions in metal precursor solution A is 4:1:1. Step S3: Prepare an ethanol solution of 1,2-dimethylimidazole to obtain precursor solution B; Step S4: 1 mL of precursor solution B obtained in step S3 is uniformly drop-coated onto the carbon paper after hydrophilic treatment in step S1, blow-dried and then vacuum-dried. Then, 1 mL of metal precursor solution A obtained in step S2 is drop-coated onto the vacuum-dried carbon paper, blow-dried and then vacuum-dried to obtain material C. Step S5: Place the material C obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture. Perform a three-inlet, three-outlet gas purging on the Joule heating device to ensure that there is no residual air in the Joule heating device cavity. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device cavity at 0.04~0.05MPa. Set the carbon thermal shock temperature to a programmable heating mode for the first stage and a rapid heating mode for the second stage. Set the temperature of the second stage to 1100~1200℃. The programmable heating mode in the first stage is used to achieve full fusion of multiple metals. The rapid heating mode in the second stage is used to effectively prevent metal agglomeration through instantaneous heating and cooling. Finally, the target product, carbon fiber supported copper-iron-nickel multi-element alloy catalyst, is obtained.

[0007] Further specifying, the specific process of the hydrophilic treatment in step S1 is to place the cut carbon paper in the outer flame of an alcohol lamp for sintering for 1 to 2 minutes, so that the subsequent precursor solution can more easily penetrate into the carbon paper and be more evenly dispersed.

[0008] Further specified, the total concentration of copper nitrate trihydrate, ferric nitrate nonahydrate, and nickel nitrate hexahydrate in the metal precursor solution A in step S2 is 0.3 mol / L; the concentration of 1,2-dimethylimidazole in the precursor solution B in step S3 is 0.8 mol / L.

[0009] Further specifying, the vacuum drying temperature in step S4 is 60°C.

[0010] Further specifying, in step S5, the current is set to 13A and the time is set to 3s in the programmable heating mode; in the rapid heating mode, the temperature is set to 1160℃, the time is set to 1s, the voltage is set to 40V, and the current is set to 40A.

[0011] Further specifying, the volume ratio of hydrogen to argon in the hydrogen-argon mixture in step S5 is 1:9.

[0012] The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to the present invention comprises the following specific preparation steps: Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a metal precursor solution A with a total concentration of 0.3 mol / L, consisting of copper nitrate trihydrate, ferric nitrate nonahydrate, and nickel nitrate hexahydrate, wherein the molar ratio of copper ions, iron ions, and nickel ions is 4:1:1, and the solvent is 8 mL of ethanol solution. Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B obtained in step S3 using a 1000 μL pipette and drop it evenly onto the hydrophilic carbon paper after step S1. After drying with a hair dryer, place it in a vacuum drying oven and dry for 3 hours. Then take 1 mL of the metal precursor solution A obtained in step S2 using a 1000 μL pipette and drop it evenly onto the dried carbon paper after step S2. After drying with a hair dryer, place it in a vacuum drying oven and dry for 6 hours to obtain material C. Step S5: Place the material C obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture to ensure that there is no residual air in the Joule heating device to avoid the generation of oxides. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device chamber at 0.045 MPa. Use dual-mode heating, where the time is set to 3s and the current is set to 13A in the programmable heating mode, and the time is set to 1s, the temperature is set to 1160℃, the current is set to 40A, and the voltage is set to 40V in the rapid heating mode, to achieve a rapid carbon thermal shock process and finally obtain the target product, carbon fiber supported copper-iron-nickel multi-element alloy catalyst.

[0013] The application of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst described in this invention in the catalytic co-reduction synthesis of urea from carbon dioxide and nitrate is as follows: The carbon fiber-supported copper-iron-nickel multi-element alloy catalyst is placed in a Pt sheet electrode holder as the working electrode, with Ag / AgCl as the reference electrode, and the Pt sheet as the counter electrode. A 0.1M KNO3 + 0.1M KHCO3 mixture is used as the electrolyte, forming a three-electrode system. CO2 is passed through the electrolyte for 30 minutes to saturate it. Afterwards, the working electrode undergoes CV activation pretreatment for 1500 s. This carbon fiber-supported copper-iron-nickel multi-element alloy catalyst exhibits excellent catalytic performance. During LSV testing, the scan rate is set to 5 mV / s, and the potential range is 0.1V to -0.9V vs. RHE. During iterative testing, the potential range is -0.05V to -0.25V vs. RHE, and the time is 1800 s. The highest Faraday efficiency reaches 78.33%, and the highest urea yield reaches 1068.82 μgh. -1 cm -2 .

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention employs carbon thermal shock technology to prepare carbon fiber-supported copper-iron-nickel multi-element alloy catalysts. This method features ultra-fast synthesis speed, unique flash heating and cooling rates, and a unique dual-mode heating to achieve carbon thermal shock, which helps to achieve uniform distribution of multiple metal elements and uniform dispersion of nanoparticles. It surpasses traditional heating methods such as muffle furnaces, tube furnaces, and hydrothermal reactions, shortens the preparation cycle, improves production efficiency, and provides a new approach for synthesizing nano-multi-element alloy catalysts.

[0015] 2. The carbon fiber-supported copper-iron-nickel multi-element alloy catalyst prepared in this invention contains multiple active sites with synergistic coupling effects, which respectively promote the formation of nitrogen-containing and carbon-containing intermediates, thereby improving the efficiency of coupling to form the key CN coupling intermediate, effectively reducing the reaction energy barrier of urea synthesis, and improving reaction activity and efficiency. The carbon fiber-supported copper-iron-nickel multi-element alloy catalyst is placed in a Pt sheet electrode holder as the working electrode, with Ag / AgCl as the reference electrode, the Pt sheet as the counter electrode, and a 0.1M KNO3 + 0.1M KHCO3 mixture as the electrolyte, forming a three-electrode system with a urea yield reaching a maximum of 1068.82 μg / g. -1 cm -2 The Faraday efficiency reached a maximum of 78.33%. Furthermore, the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst prepared in this invention exhibited good stability and catalytic activity during continuous urea synthesis, indicating that this alloy catalyst has broad practical application prospects in the field of urea synthesis. Attached Figure Description

[0016] Figure 1 The image shows a scanning electron microscope (SEM) image of product D1 prepared in Example 1.

[0017] Figure 2 The X-ray diffraction patterns are of products D1-D4 prepared in Example 1 and Comparative Examples 1-3.

[0018] Figure 3 Linear sweep voltammetry curves of product D1 prepared in Example 1 in 0.1M KNO3 + 0.1M KHCO3 electrolyte under saturated carbon dioxide and argon atmospheres, respectively.

[0019] Figure 4 Linear sweep voltammetry curves of products D1-D4 prepared in Example 1 and Comparative Examples 1-3 in 0.1M KNO3 + 0.1M KHCO3 electrolyte.

[0020] Figure 5 The graph shows the Faraday efficiency and yield of the product D1 prepared in Example 1 during the stability test of nitrate and carbon dioxide co-reduction synthesis of urea.

[0021] Figure 6 The product D1 prepared in Example 1 exhibits the Faraday efficiency and yield of urea synthesis at different potentials during the co-reduction of nitrate and carbon dioxide.

[0022] Figure 7 The X-ray photoelectron spectrum of product D1 prepared in Example 1 is shown.

[0023] Figure 8 The image shows a scanning electron microscope (SEM) image of product D5 prepared in Comparative Example 4. Detailed Implementation

[0024] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Example 1

[0025] Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a metal precursor solution A1 with a total concentration of 0.3 mol / L, consisting of copper nitrate trihydrate, ferric nitrate nonahydrate, and nickel nitrate hexahydrate, wherein the molar ratio of copper ions, iron ions, and nickel ions is 4:1:1, and the solvent is 8 mL of ethanol solution. Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B1, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B1 obtained in step S3 and drop it evenly onto the carbon paper after hydrophilic treatment in step S1 in small amounts. After drying with a hair dryer, place it in a vacuum drying oven and dry for 3 hours. After it is completely dried, take 1 mL of the metal precursor solution A1 obtained in step S2 and drop it evenly onto the carbon paper in small amounts. After drying with a hair dryer, place it in a vacuum drying oven and dry for 6 hours to obtain material C1. Step S5: Place the material C1 obtained in step S4 into a Joule heating device (refer to patent CN202311111434.4, a multifunctional and convenient reaction chamber for electrically triggered Joule heating device and its operation method, hereinafter the same) and continuously introduce a hydrogen-argon mixture (the volume ratio of hydrogen to argon is 1:9) to ensure that there is no air residue in the Joule heating device chamber to avoid the generation of oxides. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device chamber at 0.045MPa. A carbothermic shock reaction is achieved through dual-mode heating. The time of the programmable heating mode is set to 3s, the current is set to 13A, and the time of the rapid heating mode is set to 1s, the temperature is set to 1160℃, the current is set to 40A, and the voltage is set to 40V to achieve a rapid carbothermic shock process to obtain product D1.

[0026] Comparative Example 1 Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a metal precursor solution A2 with a total concentration of 0.25 mol / L of copper nitrate trihydrate and nickel nitrate hexahydrate, wherein the molar ratio of copper ions to nickel ions is 4:1, and the solvent is 8 mL of ethanol solution. Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B2, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B2 obtained in step S3 and drop it evenly onto the hydrophilic carbon paper treated in step S1 in small amounts multiple times. After drying with a hair dryer, place it in a vacuum drying oven and dry for 3 hours. After it is completely dried, take 1 mL of the metal precursor solution A2 obtained in step S2 and drop it evenly onto the dried carbon paper in small amounts multiple times. After drying with a hair dryer, place it in a vacuum drying oven and dry for 6 hours to obtain material C2. Step S5: Place the material C2 obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture (volume ratio of hydrogen to argon is 1:9) to ensure that there is no residual air in the Joule heating device to avoid the generation of oxides. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device at 0.045MPa. A carbothermal shock reaction is achieved through dual-mode heating. The time of the programmable heating mode is set to 3s and the current is set to 13A. The time of the rapid heating mode is set to 1s, the temperature is set to 1160℃, the current is set to 40A, and the voltage is set to 40V to achieve a rapid carbothermal shock process to obtain product D2.

[0027] Comparative Example 2 Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a metal precursor solution A3 with a total concentration of 0.25 mol / L of copper nitrate trihydrate and ferric nitrate nonahydrate, wherein the molar ratio of copper ions to iron ions is 4:1, and the solvent is 8 mL of ethanol solution. Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B3, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B3 obtained in step S3 and drop it evenly onto the hydrophilic carbon paper after step S1 in small amounts. After drying with a hair dryer, place it in a vacuum drying oven and dry for 3 hours. After it is completely dried, take 1 mL of the metal precursor solution A3 obtained in step S2 and drop it evenly onto the dried carbon paper in small amounts. After drying with a hair dryer, place it in a vacuum drying oven and dry for 6 hours to obtain material C3. Step S5: Place the material C3 obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture (volume ratio of hydrogen to argon is 1:9) to ensure that there is no residual air in the Joule heating device to avoid the generation of oxides. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device at 0.045MPa. A carbothermal shock reaction is achieved through dual-mode heating. The time of the programmable heating mode is set to 3s and the current is set to 13A. The time of the rapid heating mode is set to 1s, the temperature is set to 1160℃, the current is set to 40A, and the voltage is set to 40V to achieve a rapid carbothermal shock process and obtain product D3.

[0028] Comparative Example 3 Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a 0.2 mol / L copper nitrate trihydrate metal precursor solution A4 using 8 mL of ethanol solution as the solvent; Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B4, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B4 obtained in step S3 and drop it evenly onto the hydrophilic carbon paper after step S1 in small amounts. After drying with a hair dryer, place it in a vacuum drying oven and dry for 3 hours. After it is completely dried, take 1 mL of the metal precursor solution A4 obtained in step S2 and drop it evenly onto the dried carbon paper in small amounts. After drying with a hair dryer, place it in a vacuum drying oven and dry for 6 hours to obtain material C4. Step S5: Place the material C4 obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture (volume ratio of hydrogen to argon is 1:9) to ensure that there is no residual air in the Joule heating device to avoid the generation of oxides. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device at 0.045 MPa. A carbothermal shock reaction is achieved through dual-mode heating. The time of the programmable heating mode is set to 3s and the current is set to 13A. The time of the rapid heating mode is set to 1s, the temperature is set to 1160℃, the current is set to 40A, and the voltage is set to 40V to achieve a rapid carbothermal shock process to obtain product D4.

[0029] Comparative Example 4 Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a precursor metal solution A5 with a total concentration of 0.3 mol / L, consisting of copper nitrate trihydrate, ferric nitrate nonahydrate, and nickel nitrate hexahydrate, wherein the concentration ratio of copper, iron, and nickel ions is 4:1:1, and the solvent is 8 mL of ethanol solution. Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B5, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B5 obtained in step S3 and drop it evenly onto the carbon paper in small amounts multiple times. After drying with a hair dryer, place it in a vacuum drying oven to dry for 3 hours. After it is completely dried, take 1 mL of the metal precursor solution A5 obtained in step S2 and drop it evenly onto the carbon paper in small amounts multiple times. After drying with a hair dryer, place it in a vacuum drying oven to dry for 6 hours to obtain material C5. Step S5: Place the material C5 obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture (hydrogen to argon volume ratio of 1:9) to ensure that there is no residual air in the Joule heating device chamber to avoid oxide generation. Maintain a vacuum of 0.045 MPa in the Joule heating device chamber while introducing the hydrogen-argon mixture. A carbothermal shock reaction is achieved through single-mode heating, where the programmable heating mode is set to a time of 3 seconds, a current of 13 A, and a temperature of 1160°C to obtain product D5. Figure 8 It can be seen that the D5 particles prepared in this comparative example exhibit severe agglomeration. Furthermore, the direct rapid heating mode may result in uneven loading of the nano-alloy particles. To better fuse metals with different melting and boiling points into an alloy and improve the catalytic performance of the prepared catalyst, a programmable heating mode is added before the rapid heating mode to effectively address the aforementioned issues.

[0030] The XRD pattern of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst showed metal diffraction peaks at 43.62° and 50.78°; the XPS pattern showed binding energies around 933.10 eV, 881.02 eV, 713.90 eV, 532 eV, 400 eV, and 285 eV, respectively, thus proving the presence of Cu, Ni, Fe, O, N, and C in the catalyst.

[0031] Figure 1 The image shows a scanning electron microscope (SEM) image of product D1 prepared in Example 1, which shows the uniform loading of catalyst nanoparticles.

[0032] Figure 2 The X-ray diffraction patterns of products D1-D4 prepared in Example 1 and Comparative Examples 1-3 are shown in the figure. As can be seen from the figure, with the incorporation of iron-nickel metal, the diffraction angle of XRD gradually shifts to the positive and the lattice spacing gradually decreases.

[0033] Figure 3The linear sweep voltammetry curves of product D1 prepared in Example 1 in 0.1M KNO3 + 0.1M KHCO3 electrolyte under saturated carbon dioxide and argon conditions are shown in the figure. As can be seen from the figure, the current density is higher in the saturated carbon dioxide electrolyte, indicating that the electrocatalytic activity is higher in the saturated carbon dioxide electrolyte during the synthesis of urea.

[0034] Figure 4 The figure shows the linear sweep voltammetry curves of products D1-D4 prepared in Example 1 and Comparative Examples 1-3 in 0.1M KNO3 + 0.1M KHCO3 electrolyte. As can be seen from the figure, compared with other samples, sample D1 has the highest current density, indicating that it has the highest electrochemical activity.

[0035] Figure 5 The graph shows the Faradaic efficiency and yield of product D1 prepared in Example 1 during the stability test of urea synthesis by co-reduction of nitrate and carbon dioxide. As can be seen from the graph, the yield and Faradaic efficiency of the catalyst remained stable after ten cycles, indicating that the catalyst exhibits good stability in the continuous catalytic synthesis of urea.

[0036] Figure 6 Product D1 prepared in Example 1 exhibits the Faradaic efficiency and yield of urea synthesis at different potentials during the co-reduction of nitrate and carbon dioxide. As shown in the figure, the highest Faradaic efficiency of 78.33 is obtained at -0.15 V vs. RHE catalyst, and the highest efficiency of 1068.82 μgh is obtained at -0.2 V vs. RHE catalyst. -1 cm -2 The highest yield.

[0037] Figure 7 The image shows the full X-ray photoelectron spectroscopy spectrum of product D1 prepared in Example 1. As can be seen from the image, the catalyst contains elements such as copper, nickel, iron, oxygen, nitrogen, and carbon.

[0038] Figure 8 The image shows a scanning electron microscope (SEM) image of product D5 prepared in Comparative Example 5. As can be seen from the image, the prepared product D5 exhibits severe particle aggregation.

[0039] Testing procedure: The prepared products (D1 / D2 / D3 / D4) were placed in the Pt sheet electrode holder as working electrodes (area 0.25 cm²). 2The electrochemical assay employed Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and a mixed solution of 0.1M KNO3 and 0.1M KHCO3 as the electrolyte. All electrochemical tests utilized a three-electrode system. Before testing, the electrolyte was saturated with CO2 for 30 minutes. Following this, the working electrode underwent CV activation pretreatment for 1500 s. Subsequently, products D1–D4 were subjected to linear sweep voltammetry (LSV), constant voltage electrolysis (it), and electrochemical active surface area (ECSA) tests. For LSV testing, the scan rate was set to 5 mV / s, with a potential range of 0.1 V to -0.9 V vs. RHE. For it testing, the potential range was -0.05 V to -0.25 V vs. RHE, with a time of 1800 s. The collected test solutions were colorimetrically analyzed using the diacetyl oxime detection method, and urea was detected using a UV-Vis spectrophotometer to determine the final urea concentration in the electrolyte.

[0040] The product D1 prepared in Example 1 exhibited excellent electrocatalytic activity as an electrocatalyst in the co-reduction of carbon dioxide and nitrate to urea, with a Faradaic efficiency of 78.33% and a urea yield of 1068.82 μgh. -1 cm -2 Meanwhile, product D1 exhibited good stability and catalytic activity during the continuous catalytic synthesis of urea, indicating that this multi-element alloy catalyst has broad practical application prospects in the field of urea synthesis by co-reduction of nitrate and carbon dioxide.

[0041] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalysts based on carbon thermal shock technology, characterized in that: The carbon fiber-supported copper-iron-nickel multi-element alloy catalyst exhibits uniform distribution of metal elements and uniform dispersion of nanoparticles. It contains multiple active sites with synergistic coupling effects, promoting the formation of nitrogen-containing and carbon-containing intermediates, thereby improving the efficiency of coupling and generating key CN-coupled intermediates. Simultaneously, the synergistic coupling effect of multiple active sites effectively lowers the reaction energy barrier for urea synthesis, increasing the yield and Faraday efficiency. It demonstrates good stability and catalytic activity in the continuous catalytic co-reduction synthesis of urea from nitrate and carbon dioxide. The XRD pattern of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst shows metal diffraction peaks at 43.62° and 50.78°; the XPS pattern shows binding energies around 933.10 eV, 881.02 eV, 713.90 eV, 532 eV, 400 eV, and 285 eV, respectively. The specific preparation process of the carbon fiber-supported copper-iron-nickel multi-element alloy catalyst is as follows: Step S1: Cut the carbon paper and then perform a hydrophilic treatment; Step S2: Prepare an ethanolic mixed solution of copper nitrate trihydrate, ferric nitrate nonahydrate and nickel nitrate hexahydrate to obtain metal precursor solution A. The molar ratio of copper ions, iron ions and nickel ions in metal precursor solution A is 4:1:

1. Step S3: Prepare an ethanol solution of 1,2-dimethylimidazole to obtain precursor solution B; Step S4: 1 mL of precursor solution B obtained in step S3 is uniformly drop-coated onto the carbon paper after hydrophilic treatment in step S1, blow-dried and then vacuum-dried. Then, 1 mL of metal precursor solution A obtained in step S2 is drop-coated onto the vacuum-dried carbon paper, blow-dried and then vacuum-dried to obtain material C. Step S5: Place the material C obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture. Perform a three-inlet, three-outlet gas purging on the Joule heating device to ensure that there is no residual air in the Joule heating device cavity. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device cavity at 0.04~0.05MPa. Set the carbon thermal shock temperature to a programmable heating mode for the first stage and a rapid heating mode for the second stage. Set the temperature of the second stage to 1100~1200℃. The programmable heating mode in the first stage is used to achieve full fusion of multiple metals. The rapid heating mode in the second stage is used to effectively prevent metal agglomeration through instantaneous heating and cooling. Finally, the target product, carbon fiber supported copper-iron-nickel multi-element alloy catalyst, is obtained.

2. The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to claim 1, characterized in that: The specific process of hydrophilic treatment in step S1 is to place the cut carbon paper in the outer flame of an alcohol lamp for sintering for 1 to 2 minutes, so that the subsequent precursor solution can more easily penetrate into the carbon paper and be more evenly dispersed.

3. The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to claim 1, characterized in that: In step S2, the total concentration of copper nitrate trihydrate, ferric nitrate nonahydrate, and nickel nitrate hexahydrate in the metal precursor solution A is 0.3 mol / L; in step S3, the concentration of 1,2-dimethylimidazole in the precursor solution B is 0.8 mol / L.

4. The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to claim 1, characterized in that: The vacuum drying temperature in step S4 is 60°C.

5. The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to claim 1, characterized in that: In step S5, the current is set to 13A and the time is set to 3s in the programmable heating mode; in the rapid heating mode, the temperature is set to 1160℃, the time is set to 1s, the voltage is set to 40V, and the current is set to 40A.

6. The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to claim 1, characterized in that: In step S5, the volume ratio of hydrogen to argon in the hydrogen-argon mixture is 1:

9.

7. The method for synthesizing carbon fiber-supported copper-iron-nickel multi-element alloy catalyst based on carbon thermal shock technology according to claim 1, characterized in that... The specific preparation steps are as follows: Step S1: Cut the carbon paper into rectangles of the required size of 1cm × 10cm and place the rectangular carbon paper in the outer flame of an alcohol lamp for 1 minute to perform hydrophilic treatment; Step S2: Prepare a metal precursor solution A with a total concentration of 0.3 mol / L, consisting of copper nitrate trihydrate, ferric nitrate nonahydrate, and nickel nitrate hexahydrate, wherein the molar ratio of copper ions, iron ions, and nickel ions is 4:1:1, and the solvent is 8 mL of ethanol solution. Step S3: Prepare a 0.8 mol / L 1,2-dimethylimidazole solution to obtain precursor solution B, wherein the solvent is 8 mL of ethanol solution; Step S4: Take 1 mL of the precursor solution B obtained in step S3 using a 1000 μL pipette and drop it evenly onto the hydrophilic carbon paper after step S1. After drying with a hair dryer, place it in a vacuum drying oven and dry for 3 hours. Then take 1 mL of the metal precursor solution A obtained in step S2 using a 1000 μL pipette and drop it evenly onto the dried carbon paper after step S2. After drying with a hair dryer, place it in a vacuum drying oven and dry for 6 hours to obtain material C. Step S5: Place the material C obtained in step S4 into a Joule heating device and continuously introduce a hydrogen-argon mixture to ensure that there is no residual air in the Joule heating device to avoid the generation of oxides. When introducing the hydrogen-argon mixture, maintain the vacuum degree in the Joule heating device chamber at 0.045 MPa. Use dual-mode heating, where the time is set to 3s and the current is set to 13A in the programmable heating mode, and the time is set to 1s, the temperature is set to 1160℃, the current is set to 40A, and the voltage is set to 40V in the rapid heating mode, to achieve a rapid carbon thermal shock process and finally obtain the target product, carbon fiber supported copper-iron-nickel multi-element alloy catalyst.

8. The application of the carbon fiber supported copper-iron-nickel multi-element alloy catalyst prepared by the method according to any one of claims 1 to 7 in the catalytic co-reduction synthesis of urea from carbon dioxide and nitrate.

9. The application according to claim 8, characterized in that... The specific process is as follows: A carbon fiber-supported copper-iron-nickel multi-electrode alloy catalyst is placed within a Pt sheet electrode holder as the working electrode, with Ag / AgCl as the reference electrode and the Pt sheet as the counter electrode. A 0.1M KNO3 + 0.1M KHCO3 mixture is used as the electrolyte, forming a three-electrode system. CO2 is passed through the electrolyte for 30 minutes to saturate it. Afterward, the working electrode undergoes CV activation pretreatment for 1500 s. This carbon fiber-supported copper-iron-nickel multi-electrode alloy catalyst exhibits excellent catalytic performance. During LSV testing, the scan rate is set to 5 mV / s, and the potential range is 0.1V to -0.9V vs. RHE. During IT testing, the potential range is -0.05V to -0.25V vs. RHE, and the time is 1800 s. The highest Faraday efficiency reaches 78.33%, and the highest urea yield reaches 1068.82 μg / h. -1 cm -2 .

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