Metal-loaded three-dimensional copper-based catalyst, its preparation method and application

Abstract

The present invention relates to the technical field of electrocatalytic electrode materials, specifically to a metal-loaded three-dimensional copper-based catalyst, its preparation method and application. In the present invention, copper foam is used as the substrate. First, the copper foam is immersed in a mixed solution containing ammonium persulfate and sodium hydroxide, and then taken out. By controlling the drying conditions, while obtaining Cu(OH)2 nanowires on the copper foam, partial dehydration reduction of Cu(OH)2 is achieved to obtain reducible cuprous oxide active sites. Then, cuprous oxide is reacted with metal ions to obtain a metal-loaded three-dimensional copper-based catalyst. The present invention realizes the composite of multiple metal elements and Cu(OH)2 under normal temperature and pressure, overcomes the technical defects existing in the prior art of electrochemical deposition method and high-temperature sintering method, and the obtained metal-loaded three-dimensional copper-based catalyst has non-aggregated metal particles, has the characteristics of efficient mass transfer and charge transfer, and can effectively improve the application efficiency of the metal-loaded three-dimensional copper-based catalyst in electrocatalysis.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic electrode materials, and specifically to a metal-loaded three-dimensional copper-based catalyst, its preparation method and application. Background Art

[0002] Ammonia plays an important role in various fields and is considered a transportable carbon-free energy carrier. Currently, the main industrial method for manufacturing NH3 in the world is still the Haber-Bosch process. However, this process requires reaction under high pressure of 20 MPa to 30 MPa and high temperature of 300 °C to 500 °C, which will lead to a large amount of energy consumption and greenhouse gas emissions. Electrochemical reduction of nitrate to ammonia is a green and environmentally friendly technology. Its mechanism is to convert nitrate, which poses a serious threat to human health and the ecosystem, into ammonia with high economic value by applying an electric current at the cathode, showing an application prospect of "killing two birds with one stone". In this process, the selection of the electrode material is crucial, which directly affects the efficiency and selectivity of the electrocatalytic reduction.

[0003] Copper-based materials have become a research hotspot due to their inherent electrocatalytic performance advantages of good electrical conductivity and weak hydrogen evolution ability for nitrate reduction. Shen et al. confirmed that by means of electrochemical deposition, micron-sized Cu2O / Cu dendrites can be formed on a copper foam mesh in a copper sulfate and sulfuric acid solution, thereby increasing the reduction rate of nitrate from 84% to 98.9%. Specifically disclosed in "ZR Shen, JB Yan, M Wang, LD Xing, et al., Cu / Cu +In "Synergetic Effect in Cu2O / Cu / CF Electrocatalysts for Efficient Nitrate Reduction to Ammonia, ACSSustainable Chem. Eng, 2023, 11(25), 9433 - 9441", Xu et al. demonstrated that by using the impregnation - high - temperature sintering method, a copper - based oxide nanowire array can be formed on copper foam, and by modifying the surface with a conductive polymer, the performance of nitrate reduction to ammonia can be improved, which is specifically disclosed in "Y. Xu, Y. Wen, T. Ren, et al., Engineering the surface chemical microenvironment over CuO nanowire arrays by polyaniline modification for efficient ammonia electrosynthesis from nitrate, Applied Catalysis B: Environmental, 2023, 320, 121981". To further optimize the nitrate adsorption and conversion of the copper - based catalytic electrode and improve the selectivity of ammonia synthesis, composites of Au, Ru, or Pd with the Cu - based can be formed by electrodeposition or high - temperature ion exchange methods, which are specifically disclosed in "Y. K. Zha, M. Liu, J. L. Wang, et al., Electrochemical ammonia synthesis by reduction of nitrate on Au doped Cu nanowires, RSC Adv., 2023, 13, 9839 - 9844"; "F. Y., Wu, Z. Y., Gupta, S., et al., Efficient conversion of low - concentration nitrate sources into ammonia on a Ru - dispersed Cu nanowire electrocatalyst. Nat. Nanotechnol. 2022, 17, 759 - 767"; "W. Gao, J. Sun, G. Zhao, Pd Clusters Loaded with Multivalent Cu Foam for Superior Electrochemical Nitrate Reduction and Selective N≡N Bond Formation.Small, 2024, 20, 2310597”.

[0004] However, as can be seen from the above, the existing methods for preparing the composite material of multi-metal elements - Cu(OH)₂ are mostly electrochemical deposition method and high-temperature sintering method. Among them, the electrochemical deposition method depends on the composition, pH value, temperature and current density of the electrolyte, so real-time regulation is required, and the operation is inconvenient; the high-temperature sintering method needs to provide high-temperature conditions, has high requirements for equipment, and requires inert gas assistance, which will generate a large amount of energy consumption and a large amount of CO₂ emissions during large-scale industrial production, and is not conducive to the optimization of the green energy system; in addition, both of them have a common defect, that is, the obtained metal particles are easy to aggregate, resulting in few active sites, thus making the surface activity of the metal low and affecting the catalytic performance of the metal.

[0005] Based on the above reasons, it can be seen that it is of great significance to provide a new method to develop a new composite material of multi-metal elements - Cu(OH)₂. Summary of the Invention

[0006] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides a metal-loaded three-dimensional copper-based catalyst, its preparation method and application. The present invention uses copper foam as the substrate, first immerses the copper foam in a mixed solution containing ammonium persulfate and sodium hydroxide, and then takes it out and controls the drying conditions to obtain Cu(OH)₂ nanowires on the copper foam while realizing the dehydration reduction of a small part of Cu(OH)₂ and obtaining reducible cuprous oxide, and then reacts the cuprous oxide with metal ions to obtain a metal-loaded three-dimensional copper-based catalyst. The present invention realizes the composite of multi-metal elements and Cu(OH)₂ under normal temperature and pressure, overcomes the technical defects of the existing electrochemical deposition method and high-temperature sintering method, and the metal-loaded three-dimensional copper-based catalyst obtained by the method of the present invention has non-aggregated metal nanoparticles and has the characteristics of efficient mass transfer and charge transfer, and can effectively improve the application efficiency of the metal-loaded three-dimensional copper-based catalyst in electrocatalysis.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A preparation method of a metal-loaded three-dimensional copper-based catalyst, comprising the following steps:

[0009] Immerse the copper foam into a mixed solution containing ammonium persulfate and sodium hydroxide, then take it out and vacuum dry it at 30°C to 90°C for 12h to 24h. Under this drying condition, Cu(OH)₂ nanowires grow on the copper foam, and a part of Cu(OH)₂ undergoes dehydration reduction to obtain Cu₂O-Cu(OH)₂ nanowire-copper foam; if the vacuum drying temperature is lower than 30°C and the drying time is too long, it will affect the production cycle; if the vacuum drying temperature is higher than 90°C, it will cause electrode ablation.

[0010] Immerse the Cu2O-Cu(OH)2 nanowire-foamed copper into a metal solution and mix them. Use the reducing Cu2O to undergo an oxidation-reduction reaction with metal ions in the metal solution to reduce the metal ions to metal, obtaining a metal-loaded three-dimensional copper-based catalyst. The entire preparation process of the present invention is carried out at normal temperature and pressure. By controlling the drying conditions to obtain Cu2O, and then using Cu2O to reduce metal ions, a metal-loaded three-dimensional copper-based catalyst is obtained.

[0011] Preferably, the metal ions in the metal solution are selected from Pd 2+ , Ru 3+ , Au 3+ or one or more of them.

[0012] Preferably, the molar concentration of metal ions in the metal solution is 2 mmol / L to 5 mmol / L. When it is lower than 2 mmol / L, no metal particles are observed in the Cu(OH)2 nanowires; when it is higher than 5 mmol / L, the structure of the Cu(OH)2 nanowires collapses and the catalytic performance decreases.

[0013] Preferably, the time for the Cu2O-Cu(OH)2 nanowire-foamed copper to be immersed in the metal solution is 5 min to 30 min. The oxidation-reduction reaction between Cu2O and metal ions in the metal solution is an instantaneous reaction, and with the change of the immersion time, the size of metal particles and the structure of the catalytic electrode will change significantly. Therefore, the optimal time for the oxidation-reduction reaction is 5 min to 30 min.

[0014] Preferably, in the mixed solution, the concentration of sodium hydroxide is 0.8 mol / L to 1.5 mol / L, and the concentration of ammonium persulfate is 0.03 mol / L to 0.07 mol / L.

[0015] Preferably, the solvents of the mixed solution and the metal solution are both ultrapure water, and the resistivity of the ultrapure water is 18.25 MΩ·cm. The resistivity of the ultrapure water is the industry standard requirement for electrochemical experiments.

[0016] Preferably, the time for the foamed copper to be immersed in the mixed solution is 25 min to 35 min. If the immersion time is too short, Cu(OH)2 nanowires cannot be formed; if the immersion time is too long, the structure of the Cu(OH)2 nanowires collapses.

[0017] Preferably, the foamed copper also undergoes pickling before use to remove impurities and oxides on the foamed copper.

[0018] The present invention also protects the metal-loaded three-dimensional copper-based catalyst prepared by the above preparation method. In the metal-loaded three-dimensional copper-based catalyst, Cu(OH)2 nanowires are distributed on the copper foam, and one or several metal nanoparticles of Au, Ru, Pd are located on the surface of the Cu(OH)2 nanowires.

[0019] The present invention also protects the application of the metal-loaded three-dimensional copper-based catalyst in the preparation of an electrode material for electrocatalytic reduction of nitrate to ammonia.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The present invention prepares a metal-loaded three-dimensional copper-based catalyst at normal temperature and pressure by adopting a simple impregnation method. Specifically: using copper foam as the substrate, first soaking the copper foam in a mixed solution containing ammonium persulfate and sodium hydroxide, then taking it out and controlling the drying conditions to perform vacuum drying at 30°C to 90°C. While obtaining Cu(OH)2 nanowires on the copper foam, local dehydration reduction of Cu(OH)2 is achieved, and cuprous oxide with reducibility is formed. At this time, the Cu(OH)2 nanowires grow in-situ on the copper foam, and then an oxidation-reduction reaction is carried out between cuprous oxide and metal ions in the metal solution. The oxidation-reduction reaction equation is: Cu2O + M 2+ + H2O → 2Cu 2+ + 2OH - + M, 3 / 2Cu2O + H + + M 3+ + 1 / 2H2O → 3Cu 2+ + 2OH - + M, to obtain a metal-loaded three-dimensional copper-based catalyst.

[0022] Compared with the prior art electrochemical deposition method and high-temperature sintering method, the present invention provides a completely new preparation principle. Under this technical principle, the preparation of a composite material of multi-metal elements - Cu(OH)2 at normal temperature and pressure is realized, overcoming the technical defects existing in the electrochemical deposition method and high-temperature sintering method; and the present invention provides general and mild preparation conditions, with the advantages of simple process, low cost, controllable operation, high yield, environmental friendliness and high repeatability, which is convenient for subsequent industrial application.

[0023] The present invention prepares a metal-loaded three-dimensional copper-based catalyst, where Cu(OH)2 nanowires are distributed on copper foam, and one or several metal nanoparticles of Au, Ru, and Pd are located on the surface of the Cu(OH)2 nanowires. During the vacuum drying process, small local Cu2O is generated, and metal ions undergo redox reactions on Cu2O to form metal nanoparticles with a size of 20 nm to 100 nm. Since the overall synthesis process does not involve high-temperature sintering, the metal nanoparticles riveted in the area where Cu2O exists will not migrate and agglomerate. Additionally, in the metal-loaded three-dimensional copper-based catalyst, zero-dimensional metal nanoparticles are used to activate the chemisorption active sites of catalytic reactants, one-dimensional Cu(OH)2 nanowires are used to enhance the proton and charge co-regulation process during the reaction, and three-dimensional copper foam is used as a metal electrode to optimize the reaction physical space and charge conduction ability. The prepared metal-loaded three-dimensional copper-based catalyst has the characteristics of high mass and charge transfer performance, making it have more excellent electrocatalytic performance. Description of the Drawings

[0024] Figure 1 is a macroscopic view, Figure 1 Figure (a) in [reference] is Cu2O-Cu(OH)2 nanowires - copper foam of Example 1, Figure 1 Figure (b) in [reference] is the Ru-loaded three-dimensional copper-based catalyst of Example 1, Figure 1 Figure (c) in [reference] is the Pd-loaded three-dimensional copper-based catalyst of Example 2, Figure 1 Figure (d) in [reference] is the Au-loaded three-dimensional copper-based catalyst of Example 3, Figure 1 Figure (e) in [reference] is the macroscopic view of the Au / Ru-loaded three-dimensional copper-based catalyst of Example 4.

[0025] Figure 2 Figure (a) in [reference] is the SEM image of the Ru-loaded three-dimensional copper-based catalyst of Example 1, Figure 2 Figure (b) in [reference] is the particle size distribution diagram of Ru nanoparticles in the Ru-loaded three-dimensional copper-based catalyst of Example 1, Figure 2 Figure (c) in [reference] is the EDX image of the Ru-loaded three-dimensional copper-based catalyst of Example 1.

[0026] Figure 3 Figure (a) in [reference] is the SEM image of the Pd-loaded three-dimensional copper-based catalyst of Example 2, Figure 3 Figure (b) in [reference] is the particle size distribution diagram of Pd nanoparticles in the Pd-loaded three-dimensional copper-based catalyst of Example 2, Figure 3 Figure (c) in [reference] is the EDX image of the Pd-loaded three-dimensional copper-based catalyst of Example 2.

[0027] Figure 4 Figure (a) in [reference] is the SEM image of the Au-loaded three-dimensional copper-based catalyst of Example 3, Figure 4Figure (b) in it is the particle size distribution diagram of Au nanoparticles in the Au-loaded three-dimensional copper-based catalyst of Example 3. Figure 4 Figure (c) in it is the EDX diagram of the Au-loaded three-dimensional copper-based catalyst of Example 3.

[0028] Figure 5 Figure (a) in it is the SEM diagram of the Au / Ru-loaded three-dimensional copper-based catalyst of Example 4. Figure 5 Figure (b) in it is the particle size distribution diagram of Au and Ru nanoparticles in the Au / Ru-loaded three-dimensional copper-based catalyst of Example 4. Figure 5 Figure (c) in it is the EDX diagram of the Au / Ru-loaded three-dimensional copper-based catalyst of Example 4.

[0029] Figure 6 Figure (a) in it is the nitrate conversion rate diagram of the Ru-loaded three-dimensional copper-based catalyst of Example 1, the Pd-loaded three-dimensional copper-based catalyst of Example 2, the Au-loaded three-dimensional copper-based catalyst of Example 3, the Au / Ru-loaded three-dimensional copper-based catalyst of Example 4, and copper foam. Figure 6 Figure (b) in it is the synthetic ammonia production diagram of the Ru-loaded three-dimensional copper-based catalyst of Example 1, the Pd-loaded three-dimensional copper-based catalyst of Example 2, the Au-loaded three-dimensional copper-based catalyst of Example 3, the Au / Ru-loaded three-dimensional copper-based catalyst of Example 4, and copper foam.

[0030] Figure 7 Figure (a) in it is the SEM diagram of the Au-loaded three-dimensional copper-based catalyst of Example 5. Figure 7 Figure (b) in it is the particle size distribution diagram of Au nanoparticles in the Au-loaded three-dimensional copper-based catalyst of Example 5. Figure 7 Figure (c) in it is the nitrate conversion rate diagram of the Au-loaded three-dimensional copper-based catalyst of Example 5. Figure 7 Figure (d) in it is the synthetic ammonia production diagram of the Au-loaded three-dimensional copper-based catalyst of Example 5.

[0031] Figure 8 Figure (a) in it is the SEM diagram of the Ru-loaded three-dimensional copper-based catalyst of Comparative Example 1. Figure 8 Figure (b) in it is the nitrate conversion rate diagram of the Ru-loaded three-dimensional copper-based catalyst.

[0032] Figure 9 It is the macroscopic diagram of the Au-loaded three-dimensional copper-based catalyst of Comparative Example 2. Detailed implementation manners

[0033] The specific embodiments of the present invention will be described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0034] Compared with the existing high-temperature sintering method, the present invention realizes the preparation of Cu-based hydroxide nanowires loaded with various metals without the assistance of reducing agents and surfactants under normal temperature and pressure, and further realizes the application of the three-dimensional copper-based catalyst loaded with metals as a highly active electrocatalytic reduction nitrate electrode. In addition, the experimental process does not involve high-temperature sintering above 100 °C. While reducing energy consumption, it not only avoids the aggregation and growth of metal nanoparticles during high-temperature sintering, but also avoids the coating of organic surfactants, significantly increasing the adsorption active sites for reactants during the catalytic process and effectively improving the ammonia production efficiency of the three-dimensional copper-based catalyst loaded with metals.

[0035] Compared with the existing electrochemical deposition method, the present invention avoids the use of a large amount of high-concentration (>10 mmol / L) metal ion solutions as electrolytes, thus effectively reducing the preparation cost of the three-dimensional copper-based catalyst loaded with metals. On the other hand, through the redox reaction between Cu2O microdomains and metal ions, controlled by the size of the Cu2O microdomains, compared with the formation of micron-sized large dendrites by electrochemical deposition, the control of particle miniaturization size is achieved.

[0036] The technical solutions of the present invention are studied by using examples and comparative examples below, and the specific research methods and results are as follows:

[0037] Example 1

[0038] A preparation method of a three-dimensional copper-based catalyst loaded with metals includes the following steps:

[0039] S1. After pickling 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for 30 min, it is rinsed with ultrapure water and then dried at 60 °C for 6 h, and taken out to obtain clean copper foam.

[0040] S2. The clean copper foam is immersed in a mixed solution containing 0.05 mol / L ammonium persulfate and 1 mol / L sodium hydroxide for 30 min. The volume of the mixed solution is 8 mL, and then taken out and vacuum dried at 30 °C for 20 h to obtain Cu2O-Cu(OH)2 nanowire-copper foam, denoted as Cu2O-Cu(OH)2NW-CuCF.

[0041] S3. Immerse the Cu2O-Cu(OH)2 NW-CuCF in 5 mL of a 2 mmol / L metal solution, where the solute in the metal solution is RuCl2. After shaking the reaction for 30 min, rinse with ultrapure water and then vacuum dry at 40 °C for 36 h to obtain a Ru-loaded three-dimensional copper-based catalyst, denoted as Ru-Cu(OH)2 NW-CuCF.

[0042] Example 2

[0043] A method for preparing a metal-loaded three-dimensional copper-based catalyst, comprising the following steps:

[0044] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for pickling for 30 min, then rinse with ultrapure water and dry at 60 °C for 6 h, and take out to obtain clean copper foam.

[0045] S2. Immerse the clean copper foam in a mixed solution containing 0.03 mol / L ammonium persulfate and 0.8 mol / L sodium hydroxide for 30 min. The volume of the mixed solution is 8 mL, then take out and vacuum dry at 45 °C for 12 h to obtain Cu2O-Cu(OH)2 nanowire-copper foam, denoted as Cu2O-Cu(OH)2 NW-CuCF.

[0046] S3. Immerse the Cu2O-Cu(OH)2 NW-CuCF in 5 mL of a 2 mmol / L metal solution, where the solute in the metal solution is PdCl2. After shaking the reaction for 30 min, rinse with ultrapure water and then vacuum dry at 40 °C for 36 h to obtain a Pd-loaded three-dimensional copper-based catalyst, denoted as Pd-Cu(OH)2 NW-CuCF.

[0047] Example 3

[0048] A method for preparing a metal-loaded three-dimensional copper-based catalyst, comprising the following steps:

[0049] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for pickling for 30 min, then rinse with ultrapure water and dry at 60 °C for 6 h, and take out to obtain clean copper foam.

[0050] S2. Immerse the clean copper foam in a mixed solution containing 0.04 mol / L ammonium persulfate and 0.9 mol / L sodium hydroxide for 30 min. The volume of the mixed solution is 8 mL, then take out and vacuum dry at 30 °C for 24 h to obtain Cu2O-Cu(OH)2 nanowire-copper foam, denoted as Cu2O-Cu(OH)2 NW-CuCF.

[0051] S3. Immerse the Cu2O-Cu(OH)2 NW-CuCF in 5 mL of a 2 mmol / L metal solution with the solute in the metal solution being HAuCl4. After shaking the reaction for 30 min, rinse it with ultrapure water and then vacuum dry it at 40 °C for 36 h to obtain a three-dimensional copper-based catalyst loaded with Au, denoted as Au-Cu(OH)2 NW-CuCF.

[0052] Example 4

[0053] A preparation method of a metal-loaded three-dimensional copper-based catalyst includes the following steps:

[0054] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for pickling for 30 min, then rinse it with ultrapure water and dry it at 60 °C for 6 h, and take it out to obtain clean copper foam.

[0055] S2. Immerse the clean copper foam in a mixed solution containing 0.06 mol / L ammonium persulfate and 1.1 mol / L sodium hydroxide for 30 min. The volume of the mixed solution is 8 mL, then take it out and vacuum dry it at 35 °C for 18 h to obtain Cu2O-Cu(OH)2 nanowire-copper foam, denoted as Cu2O-Cu(OH)2 NW-CuCF.

[0056] S3. Immerse the Cu2O-Cu(OH)2 NW-CuCF in 5 mL of a 2 mmol / L metal solution with the solute in the metal solution being RuCl2 and HAuCl4. After shaking the reaction for 30 min, rinse it with ultrapure water and then vacuum dry it at 40 °C for 36 h to obtain a metal-loaded three-dimensional copper-based catalyst, denoted as Au / Ru-Cu(OH)2 NW-CuCF.

[0057] Example 5

[0058] A preparation method of a metal-loaded three-dimensional copper-based catalyst includes the following steps:

[0059] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for pickling for 30 min, then rinse it with ultrapure water and dry it at 60 °C for 6 h, and take it out to obtain clean copper foam.

[0060] S2. Immerse the clean copper foam in a mixed solution containing 0.04 mol / L ammonium persulfate and 0.9 mol / L sodium hydroxide for 30 min. The volume of the mixed solution is 8 mL, then take it out and vacuum dry it at 90 °C for 12 h to obtain Cu2O-Cu(OH)2 nanowire-copper foam, denoted as Cu2O-Cu(OH)2 NW-CuCF.

[0061] S3. Immerse the Cu2O-Cu(OH)2 NW-CuCF in 5 mL of a 2 mmol / L metal solution with the solute in the metal solution being HAuCl4. After shaking for 30 min, rinse with ultrapure water and then vacuum dry at 40 °C for 36 h to obtain the Au-loaded three-dimensional copper-based catalyst, denoted as Au-Cu(OH)2 NW-CuCF-90.

[0062] Example 6

[0063] A method for preparing a metal-loaded three-dimensional copper-based catalyst, comprising the following steps:

[0064] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for 30 min, then rinse with ultrapure water and dry at 60 °C for 6 h, and take out to obtain clean copper foam.

[0065] S2. Immerse the clean copper foam in an 8 mL mixed solution containing 0.07 mol / L ammonium persulfate and 1.5 mol / L sodium hydroxide for 30 min, then take out and vacuum dry at 60 °C for 14 h to obtain Cu2O-Cu(OH)2 nanowire - copper foam, denoted as Cu2O-Cu(OH)2 NW-CuCF.

[0066] S3. Immerse the Cu2O-Cu(OH)2 NW-CuCF in 5 mL of a 5 mmol / L metal solution with the solute in the metal solution being PdCl2 and RuCl2. After shaking for 5 min, rinse with ultrapure water and then vacuum dry at 40 °C for 36 h to obtain the Pd / Ru-loaded three-dimensional copper-based catalyst.

[0067] Comparative Example 1

[0068] A method for preparing a metal-loaded three-dimensional copper-based catalyst, comprising the following steps:

[0069] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for 30 min, then rinse with ultrapure water and dry at 60 °C for 6 h, and take out to obtain clean copper foam.

[0070] S2. Immerse the clean copper foam in an 8 mL mixed solution containing 0.05 mol / L ammonium persulfate and 1 mol / L sodium hydroxide for 30 min, then take out and vacuum dry at 25 °C for 36 h to obtain an intermediate.

[0071] S3. Immerse the intermediate in 5 mL of a 2 mmol / L metal solution. The solute in the metal solution is RuCl2. After reacting on a shaker for 30 min, rinse with ultrapure water and then vacuum dry at 40 °C for 36 h to obtain a Ru-loaded three-dimensional copper-based catalyst, denoted as Ru-Cu(OH)2NW-CuCF-25.

[0072] After vacuum drying at 25 °C for 36 h, water marks were found on the surface of the intermediate and it could not be completely dried.

[0073] Comparative Example 2

[0074] A method for preparing a metal-loaded three-dimensional copper-based catalyst, comprising the following steps:

[0075] S1. Immerse 2 cm × 1 cm copper foam in a 3 mol / L dilute sulfuric acid solution for 30 min, then rinse with ultrapure water and dry at 60 °C for 6 h, and take out to obtain clean copper foam.

[0076] S2. Immerse the clean copper foam in a mixed solution containing 0.05 mol / L ammonium persulfate and 1 mol / L sodium hydroxide for 30 min. The volume of the mixed solution is 8 mL, then take out and vacuum dry at 95 °C for 12 h to obtain Cu2O-Cu(OH)2 nanowire - copper foam, denoted as Cu2O-Cu(OH)2NW-CuCF.

[0077] S3. Immerse Cu2O-Cu(OH)2NW-CuCF in 5 mL of a 2 mmol / L metal solution. The solute in the metal solution is HAuCl4. After reacting on a shaker for 30 min, rinse with ultrapure water and then vacuum dry at 40 °C for 36 h to obtain an Au-loaded three-dimensional copper-based catalyst, denoted as Au-Cu(OH)2NW-CuCF-95.

[0078] In Examples 1 - 6 of the present invention, metal-loaded three-dimensional copper-based catalysts were all prepared. Taking the metal-loaded three-dimensional copper-based catalysts prepared in Examples 1 - 5 as examples, comparative studies were carried out with Comparative Examples 1 - 2. The specific research methods and results are as follows:

[0079] Via Figure 1 It can be seen that after loading different metal nanoparticles on the Cu(OH)2 nanowires, the obtained metal-loaded three-dimensional copper-based catalysts showed different macroscopic color changes, indicating that different metal-loaded three-dimensional copper-based catalysts were formed.

[0080] Figures 2 to 5The results of Figure (a) in [reference] show that the metal-loaded three-dimensional copper-based catalysts obtained in the present invention all have a nanowire structure, and have a multi-dimensional structure of two-dimensional copper-based hydroxide nanowires grown on three-dimensional copper foam and modified with nanoparticles. Figures 2 to 5 The results of Figure (b) in [reference] show that the particle size of Ru nanoparticles is 39.41 nm, the particle size of Pd nanoparticles is 91.92 nm, the particle size of Au nanoparticles is 99.97 nm, the particle size of Au / Ru nanoparticles is 58.75 nm, there are many chemisorption active sites, and the metal nanoparticles do not agglomerate. Figures 2 to 5 The results of Figure (c) in [reference] show that the products of the metal-loaded three-dimensional copper-based catalysts obtained in Examples 1 to 4 are pure and there is no doping with other elements.

[0081] Figure 6 Figure [figure number] shows the catalytic performance diagrams of the metal-loaded three-dimensional copper-based catalysts and copper foam in Examples 1 to 4. The catalytic method is as follows: Using the metal-loaded three-dimensional copper-based catalysts or copper foam in Examples 1 to 4 as the working electrode, Ag / AgCl as the reference electrode, and a platinum mesh as the counter electrode, reactions are carried out in an H-type electrolytic cell. K2SO4 solutions are added to the cathode and anode respectively, and at the same time, a 10 mmol / L KNO3 solution is added to the cathode. An i-t test is carried out for 2 h by providing a voltage of -0.4 V vs. RHE to the working electrode through an electrochemical workstation, and the nitrate conversion rate and ammonia synthesis yield of the working electrode are measured. Figure 6 The results show that the metal-loaded three-dimensional copper-based catalysts obtained in the present invention have good nitrate conversion rates and ammonia synthesis yields, have high performance in electro-reducing nitrate to ammonia, and the performance is significantly better than that of copper foam.

[0082] Figure 7 The results of Figure (a) in [reference] show that under vacuum drying conditions at 90 °C, the active sites of Cu2O will decrease, and Au nanoparticles are significantly distributed in the defect regions at the tips of Cu(OH)2 nanowires, and the number is significantly reduced; Figure 7 The results of Figure (b) in [reference] show that compared with Example 3, the size of Au nanoparticles increases significantly. Figure 7 The results of Figure (c) and Figure (d) in [reference] show that the nitrate conversion rate and ammonia synthesis yield decrease significantly compared with Example 3.

[0083] Figure 8 The results of Figure (a) in [reference] show that drying at a temperature below 30 °C and then reacting with metal ions will cause the obtained Cu(OH)2 nanowires to react with metal ions to obtain cuprous oxide, and then there is no Cu(OH)2 nanowire structure. Figure 8 Figure (b) in [reference] is the nitrate conversion rate diagram of Ru-Cu(OH)2NW-CuCF-25, indicating that the performance decreases significantly after there is no Cu(OH)2 nanowire.

[0084] Figure 9 The results show that after drying under the condition that the vacuum drying temperature is higher than 90 °C, micro-local Cu network fusing will occur, causing uncontrollable random breakage, affecting the quality of Au-Cu(OH)2NW-CuCF-95, and reducing the catalytic performance.

[0085] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and its equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. Preparation method of metal-loaded three-dimensional copper-based catalyst, characterized in that, It includes the following steps: Immerse the copper foam into a mixed solution containing ammonium persulfate and sodium hydroxide, then take it out and vacuum dry at 30°C to 90°C. Under this drying condition, Cu(OH)2 nanowires grow on the copper foam, and part of the Cu(OH)2 is dehydrated and reduced to Cu2O, obtaining Cu2O-Cu(OH)2 nanowire-copper foam; Immerse the Cu2O-Cu(OH)2 nanowire-copper foam into a metal solution and mix. The Cu2O reduces metal ions to metals, obtaining a metal-loaded three-dimensional copper-based catalyst; The molar concentration of metal ions in the metal solution is 2 mmol / L to 5 mmol / L.

2. The preparation method of the metal-loaded three-dimensional copper-based catalyst according to claim 1, characterized in that, The metal ions in the metal solution are selected from one or more of Pd 2+ , Ru 3+ , Au 3+ .

3. The preparation method of the metal-loaded three-dimensional copper-based catalyst according to claim 1, characterized in that, The time for vacuum drying is 12 h to 24 h.

4. The preparation method of the metal-loaded three-dimensional copper-based catalyst according to claim 1, characterized in that, The time for the Cu2O-Cu(OH)2 nanowire-copper foam to be immersed in the metal solution is 5 min to 30 min.

5. The preparation method of the metal-loaded three-dimensional copper-based catalyst according to claim 1, characterized in that, In the mixed solution, the concentration of sodium hydroxide is 0.8 mol / L to 1.5 mol / L, and the concentration of ammonium persulfate is 0.03 mol / L to 0.07 mol / L.

6. The preparation method of the metal-loaded three-dimensional copper-based catalyst according to claim 1, characterized in that, The solvents of the mixed solution and the metal solution are both ultrapure water, and the resistivity of the ultrapure water is 18.25 MΩ·cm.

7. The preparation method of the metal-loaded three-dimensional copper-based catalyst according to claim 1, wherein, The time for the copper foam to be immersed in the mixed solution is 25 min to 35 min.

8. A metal-loaded three-dimensional copper-based catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that, In the metal-loaded three-dimensional copper-based catalyst, Cu(OH)2 nanowires are distributed on the copper foam, and one or more metal nanoparticles of Au, Ru, Pd are located on the surface of the Cu(OH)2 nanowires.

9. Application of the metal-loaded three-dimensional copper-based catalyst according to claim 8 in the preparation of an electrode material for electrocatalytic reduction of nitrate to ammonia.

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