Multistage shell structure catalyst with adjustable surface appearance and preparation method thereof

Abstract

The invention discloses a multistage shell structure catalyst with an adjustable surface appearance and a preparation method thereof, the method comprises the following steps: (1) mixing a metal salt, a ligand and a polyol solvent, carrying out a stirring reaction, and carrying out microwave synthesis on the solution after the stirring reaction to obtain a metal-organic precursor; (2) adding the metal-organic precursor, a precipitant and a structure-directing agent into a polar solvent for stirring reaction, and performing solvothermal reaction on the solution after stirring reaction; (3) a gas-phase reaction source and a product obtained in the step (2) are placed on the upstream and the downstream of the argon atmosphere respectively, the gas-phase reaction source and the product obtained in the step (2) are calcined and naturally cooled, the multistage shell structure catalyst is obtained, and the gas-phase reaction source is one of red phosphorus, sulfur, sodium hypophosphite, selenium powder or tellurium powder. The catalyst provided by the invention shows excellent electrochemical activity and stability in an electrolyte solution.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a multi-level shell structure catalyst with tunable surface morphology and its preparation method. Background Technology

[0002] With the continuous development of modern agriculture and industry, the global demand for urea, as a crucial nitrogen fertilizer and chemical raw material, is increasing daily. However, traditional industrial urea synthesis relies on the energy-intensive and high-emission Haber-Bosch process for ammonia synthesis and subsequent processes, resulting in significant carbon dioxide emissions. Therefore, developing a new route for the direct electrocatalytic co-reduction synthesis of urea from carbon dioxide and nitrogen-containing species such as nitrate under mild conditions is considered a revolutionary strategy for achieving carbon and nitrogen cycling and green chemical synthesis. This technology not only converts greenhouse gases and water pollutants into high-value-added products but also provides new ideas for the storage and conversion of renewable energy.

[0003] However, this electrocatalytic process involves a complex reaction network with multiple proton / electron couplings, facing severe challenges such as slow kinetics, multiple competing reaction pathways, and low selectivity for target products. Currently, although various noble metal-based catalysts (such as gold and palladium-based materials) have shown some potential, their scarcity, high cost, and susceptibility to poisoning and deactivation severely restrict the prospects for large-scale application of this technology.

[0004] In recent years, transition metal phosphides, which are abundant and inexpensive, have attracted much attention in various electrocatalytic reactions due to their unique electronic structure and excellent catalytic activity. Studies have shown that their surfaces can form defect-rich active phases under reaction conditions, potentially exhibiting suitable adsorption capabilities for both carbon- and nitrogen-containing intermediates. However, single-component phosphides often have limited active sites, making it difficult to simultaneously and efficiently activate both carbon dioxide and nitrate substrates. Furthermore, they are prone to structural reconstruction or metal ion dissolution at high overpotentials, resulting in catalytic selectivity, long-term stability, and current efficiency that still fall short of practical application requirements.

[0005] Therefore, designing and preparing an electrocatalyst that can synergistically activate carbon dioxide and nitrate, has high urea Faradaic efficiency, excellent stability, and low cost has become the core bottleneck for promoting the practical application of this green synthesis technology. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-level shell structure catalyst with tunable surface morphology and its preparation method, which exhibits excellent electrochemical activity and stability in electrolyte solutions.

[0007] In one aspect of the present invention, a method for preparing a multi-level shell structure catalyst with tunable surface morphology is proposed. According to an embodiment of the present invention, the method includes the following steps:

[0008] (1) Mix metal salt, ligand and polyol solvent, stir and react, microwave the solution after stirring and react, then centrifuge, wash and dry to obtain metal-organic precursor;

[0009] (2) Add the metal-organic precursor, precipitant and structure directing agent to a polar solvent and stir to react. Perform a solvothermal reaction on the solution after stirring, and then centrifuge, wash and dry.

[0010] (3) The gas phase reaction source and the product of step (2) are placed upstream and downstream of an argon atmosphere, respectively, and the gas phase reaction source and the product of step (2) are calcined and naturally cooled to obtain a multi-level shell structure catalyst. The gas phase reaction source is one of red phosphorus, sulfur, sodium hypophosphite, selenium powder or tellurium powder.

[0011] The hollow spherical precursor synthesized in step (1) using the "Kirkendall effect" can "enrich" reactants and key intermediates, increase their local concentration, and increase the coupling probability. In step (2), the secondary nanostructure constructed on the surface of the spherical structure greatly increases the contact area between the catalyst and the reactants, provides abundant active sites, and the multi-level structure facilitates the construction of adjacent but electronically different active sites in space, which can efficiently activate carbon dioxide and nitrate respectively and reduce the CN coupling barrier.

[0012] Furthermore, the preparation method of a multi-level shell structure catalyst with tunable surface morphology according to the above embodiments of the present invention may also have the following additional technical features:

[0013] In some embodiments of the present invention, in step (1): the metal salt is one or more of nitrate, chloride, acetate or phosphate; and / or, the metal in the metal salt is selected from one or more of Co, Ni, Fe, Mn, Zn, Mo, W, V; and / or, the ligand is one of ethylene glycol, glycerol, glucose, citric acid, tartaric acid or glycine; and / or, the polyol solvent is one or more of methanol, ethanol, isopropanol, ethylene glycol or propanol.

[0014] In this process, each metal salt provides the metal source; the ligand coordinates with the metal ions, controls the nucleation and growth process, guides anisotropic growth, and is crucial for the formation of hollow spherical structures; the polyol solvent provides a uniform high-temperature reaction environment and reducing power, and assists in controlling the reaction kinetics. During the reaction, different atoms undergo macroscopic movement at the diffusion interface due to their different diffusion rates, thereby forming pores on the side with faster diffusion. This is known as the "Kirkendall effect," which is also the reaction principle of step (1) in this invention.

[0015] In some embodiments of the present invention, in step (1), the molar ratio of each metal salt, ligand, and polyol is 1:(50-80):(80-800).

[0016] In some embodiments of the present invention, in step (1): the stirring reaction time is 0.1-5h, the microwave synthesis reaction temperature is 120-200℃; and / or, the microwave synthesis reaction time is 5-120min, and the power is 50-500W; and / or, the centrifugal washing speed is 1000-5000rpm, and the number of centrifugal washings is 2-8 times; and / or, the drying treatment temperature is 20-65℃, and the drying treatment time is 4-24h.

[0017] Microwave synthesis can directly act on polar molecules, causing the reaction system to heat up uniformly in a very short time, generating a large number of crystal nuclei, thereby obtaining nanoparticles with uniform size and good dispersibility. Within the temperature range of 120-200℃, sufficient reducing power of the polyol can be ensured while avoiding excessive decomposition and carbonization of organic matter.

[0018] In some embodiments of the present invention, in step (2): the precipitant is one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate or urea; and / or, the structure directing agent is one of boric acid, ethylenediamine, sodium citrate, sodium dihydrogen phosphate or ammonium fluoride; and / or, the polar solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, acetone, acetic acid, acetonitrile, hexamethylphosphoric triamine or water.

[0019] In this process, the metal-organic precursor serves as the reaction source; the precipitant provides OH-. - Or other anions, triggering precipitation reactions; the structure-directing agent, as a soft template, guides surface growth and regulates the surface structure of the catalyst, which is the key to surface morphology regulation; the polar solvent system provides an environment for ion or molecular transport, and may also participate in the hydrolysis or alcoholysis of metal-organic functional groups. In step (2), the metal-organic functional group reacts with the precipitant in the polar solvent, transforming into metal hydroxide, and is finely regulated by the structure-directing agent during the regrowth process, thus regulating the mesoscopic structure of the final product.

[0020] In some embodiments of the present invention, in step (2), the mass ratio of the metal-organic precursor, precipitant, structure directing agent and polar solvent is 1:(0.1-100):(0.1-5):(500-1000).

[0021] In some embodiments of the present invention, in step (2): the stirring reaction time is 1-12 h; and / or, the solvothermal reaction temperature is 120-180 °C, and the solvothermal reaction time is 4-12 h; and / or, the centrifugal washing speed is 1000-5000 rpm, and the number of centrifugal washing cycles is 2-7; and / or, the drying treatment temperature is 20-65 °C, and the drying treatment time is 4-24 h. Within the 120-180 °C range, the dissolution-recrystallization process can be promoted while preventing the deactivation of the structure-directing agent or the collapse of the catalyst structure.

[0022] In some embodiments of the present invention, in step (3), the mass ratio of the gas-phase reaction source to the product of step (2) is 1-10:1. The gas-phase reaction source provides the phosphorus / sulfide elements required for the catalyst, and the product of step (2) serves as the base material for the reaction. These reaction sources can all decompose or volatilize at relatively low temperatures, allowing the catalyst to be fully phosphorus / sulfide-treated.

[0023] In some embodiments of the present invention, in step (3), the protective atmosphere during calcination is argon, the calcination temperature is 300-500℃, the calcination time is 2-4h, and the heating rate is 2-10℃ / min. The active phosphorus / sulfide gaseous molecules generated by the decomposition of the gaseous reaction source will undergo a solid-gas reaction with the precursor, thereby introducing phosphorus or sulfide atoms into the bulk phase of the material and converting them into the corresponding metal phosphides or sulfides. At 300-500℃, amorphous metal hydroxides will be stably converted into metal phosphorus / sulfides, ensuring that the structure does not collapse.

[0024] In another aspect of the present invention, the present invention proposes a multi-level shell structure catalyst with tunable surface morphology prepared by the preparation method described above.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. Using one or more non-precious metals (such as Co, Ni, Fe, Mn, Zn, etc.) as raw materials, which are abundant and inexpensive, fundamentally avoids dependence on precious metals such as gold, platinum, and palladium, thus significantly reducing the cost of large-scale preparation and application of catalysts.

[0027] 2. By precisely controlling the surface morphology of the resulting multi-level structures (such as hollow spheres supporting nanosheets / nanospins), extremely high specific surface areas and abundant pore channels are created. This not only greatly increases the number of exposed active sites and promotes efficient mass transfer between reactants and products, but the integrated multi-level configuration also endows the whole with excellent mechanical and structural stability.

[0028] 3. By regulating the metal composition of the active center, the electronic structure of the active site can be effectively optimized. For multi-metal systems, the electronic interactions between metals can further optimize the adsorption strength of key reaction intermediates.

[0029] 4. The catalyst of the present invention is a metal phosphorus or chalcogenide (such as phosphide, sulfide, selenide, etc.) catalyst. The metal phosphorus or chalcogenide itself has metal-like conductivity, which ensures rapid electron transport. Moreover, the strong covalent bond crystal structure formed after phosphating / chalcogenation sintering is not easily dissolved or reconstructed at high potentials, so that it maintains catalytic activity and structural stability during long-term electrolysis, has a long service life, and has excellent comprehensive performance.

[0030] 5. The catalyst prepared by this invention is a bilevel structure whose hollow core and surface morphology can be precisely controlled by reaction temperature and the type and amount of structure-directing agent. The metal phosphide secondary nanostructures (such as nanosheet arrays) grown on the surface greatly increase the electrochemical active area and expose more active sites. The hollow sphere structure shortens the ion diffusion path, and the surface nanostructure also helps to enhance the local electric field under high current density, promoting the mass transfer of reactants / products, which is crucial for industrial applications. This catalyst exhibits excellent electrochemical activity and stability in electrolyte solutions, and is low in cost and has minimal environmental pollution, showing broad application prospects. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope (SEM) image of the metal-organic precursor prepared in step one of Example 1 of the present invention;

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the product prepared in step two of Example 1 of the present invention;

[0033] Figure 3 This is a scanning electron microscope (SEM) image of the copper-cobalt bimetallic phosphide prepared in step three of Example 1 of the present invention;

[0034] Figure 4 This is a scanning electron microscope (SEM) image of a locally magnified copper-cobalt bimetallic phosphide prepared in step three of Example 1 of the present invention.

[0035] Figure 5 This is an X-ray energy dispersive spectroscopy (EDS) surface scan result of the copper-cobalt bimetallic phosphide prepared in step three of Example 1 of the present invention;

[0036] Figure 6 The graph shows the Faraday efficiency / yield of the copper-cobalt bimetallic phosphide catalyst prepared in Example 1 of this invention as a function of potential.

[0037] Figure 7This is a stability test diagram of the copper-cobalt bimetallic phosphide catalyst prepared in Example 1 of the present invention;

[0038] Figure 8 The graph shows the Faraday efficiency / yield of the copper-chromium bimetallic sulfide catalyst prepared in Example 4 of this invention as a function of potential. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] A method for preparing a copper-cobalt bimetallic phosphide catalyst material with a coral-like hollow sphere multi-level shell structure includes the following steps:

[0042] Step 1: Preparation of metal-organic precursors

[0043] Copper nitrate hexahydrate and cobalt nitrate hexahydrate were added to a mixed solvent of glycerol and isopropanol according to the specified ratio and stirred for 0.5 h. The molar ratio of copper nitrate hexahydrate to cobalt nitrate hexahydrate was 1:1, the molar ratio of glycerol to isopropanol was 1:7, and the molar ratio of metal salt to mixed solvent was 1:500. The solution after stirring was subjected to microwave synthesis reaction. The microwave synthesis reaction time and temperature were 20 min and 180 °C, respectively, and the power was 450 W. The solution after solvothermal reaction was centrifuged and washed 4 times at a speed of 3500 rpm. The product after centrifugation and washing was dried at 55 °C for 24 h to obtain the metal-organic precursor.

[0044] Step 2: Catalyst Surface Morphology Reconstruction

[0045] The metal-organic precursor was added to the aqueous solvent according to the formula and stirred for 2 hours. The mass ratio of the metal-organic precursor, sodium hydroxide, ammonium fluoride and water was 1:0.1:0.1:700. The solution after stirring was subjected to a solvothermal reaction for 7 hours and 150°C. The solution after the solvothermal reaction was centrifuged and washed 4 times at 3250 rpm. The product after centrifugation and washing was dried at 55°C for 24 hours.

[0046] Step 3: Preparation of Coral-like Hollow Sphere Multi-level Structure Copper-Cobalt Bimetallic Phosphate Catalyst Material

[0047] NaH2PO2 and the product from step two were placed upstream and downstream of an argon atmosphere, respectively, with a mass ratio of 10:1. In the argon atmosphere, NaH2PO2 and the product from step two were heated to 300℃ at a heating rate of 5℃ / min and then calcined for 4 hours. After natural cooling, a coral-like hollow sphere multi-level structure copper-cobalt bimetallic phosphide catalyst material was obtained.

[0048] The products prepared in the above steps were subjected to performance testing and morphological characterization:

[0049] (1) The microstructure of the three products prepared in steps one, two, and three of this embodiment was characterized by thermal field emission scanning electron microscopy. 0.5 mg of sample was placed in 10 ml of ethanol and sonicated for 1 h. The supernatant was placed on a polished silicon wafer, dried at 40 °C for 0.2 h, and then tested. The results are shown in [reference]. Figure 1 , Figure 2 , Figure 3 , Figure 4 Energy dispersive spectroscopy (EDS) was performed on it, and the results are shown in [reference needed]. Figure 5 .like Figure 1 As shown in the scanning electron microscope (SEM) image of the metal-organic precursor prepared in step one of Example 1, it can be seen that the catalyst precursor has a regular hollow sphere structure. This structural framework greatly accelerates the diffusion of electrolyte ions and the discharge of reaction products, ensuring that the reaction can still proceed efficiently under high current density and avoiding a sharp drop in performance due to limited mass transfer.

[0050] Figure 2 The scanning electron microscope (SEM) image of the product prepared in step two of exemplary embodiment 1 of the present invention shows that a uniform array of nanosheets is grown on the surface of the regular hollow sphere structure. Figure 3 This is a scanning electron microscope (SEM) image of the copper-cobalt bimetallic phosphide prepared in step three of exemplary embodiment 1 of the present invention. Figure 4 The scanning electron microscope (SEM) image of the copper-cobalt bimetallic phosphide prepared in step three of exemplary embodiment 1 of the present invention shows that the nanosheet array on the spherical surface is transformed into an irregular coral-like structure. This complex surface morphology can provide more active sites for electrochemical reactions. Figure 5 This is an X-ray energy dispersive spectroscopy (EDS) surface scan result of the copper-cobalt bimetallic phosphide prepared in step three of exemplary embodiment 1 of the present invention, wherein, Figure 5 In the diagram, (b), (c), and (d) represent the surface scan results for Cu, Co, and P elements, respectively; for example... Figure 5 As shown, the copper-cobalt bimetallic phosphide catalyst is composed of Cu, Co, and P elements, and the Co and P elements are uniformly distributed on the polyhedral structure, which makes the catalytic active sites uniformly dispersed and the catalytic performance higher.

[0051] (2) The urea production capacity of the copper-cobalt bimetallic phosphide catalyst prepared in this embodiment was tested at different potentials using an electrochemical workstation in a three-electrode system. The results are shown in [reference needed]. Figure 6 Urea production capacity testing was conducted on an electrochemical workstation using a three-electrode system. Carbon paper coated with copper-cobalt bimetallic phosphide catalyst served as the working electrode, saturated calomel as the reference electrode, and a carbon rod as the counter electrode. 5 mg of copper-cobalt bimetallic phosphide catalyst material (hereinafter referred to as CuCoP), 50 μL of 20 wt% Nafion solution, and 450 μL of isopropanol were added to 500 μL of deionized water and sonicated for 1 h to obtain electrode catalyst ink. 18 μL of this ink was coated onto carbon paper, and the test was then conducted in a carbon dioxide-saturated 0.1 mol / L solution of potassium bicarbonate and potassium nitrate.

[0052] like Figure 6 As shown in the figure, the Faraday efficiency / yield of the copper-cobalt bimetallic phosphide catalyst prepared in this embodiment varies with potential. It can be seen that the Faraday efficiency of urea is the highest at -0.4 V, which is 33%; and the yield of urea is the highest at -0.5 V, which is 2 μg / mL.

[0053] (3) The stability of the copper-cobalt bimetallic phosphide catalyst prepared in this embodiment was tested using an electrochemical workstation in a three-electrode system. The results are shown in [reference needed]. Figure 7 Stability testing was conducted on an electrochemical workstation using a three-electrode system. Carbon paper coated with copper-cobalt bimetallic phosphide catalyst served as the working electrode, saturated calomel as the reference electrode, and a carbon rod as the counter electrode. 5 mg CuCoP, 50 μL of 20 wt% Nafion solution, and 450 μL of isopropanol were added to 500 μL of deionized water and sonicated for 1 h to obtain electrode catalyst ink. 18 μL of this ink was coated onto carbon paper, and the test was then performed in a carbon dioxide-saturated 0.1 mol / L solution of potassium bicarbonate and potassium nitrate.

[0054] like Figure 7 As shown in the stability test diagram of the copper-cobalt bimetallic phosphide catalyst prepared in this embodiment, the yield of the copper-cobalt bimetallic phosphide catalyst material (hereinafter referred to as CuCoP) is stable during the 15-hour cycle test, and the Faraday efficiency decreases slightly with the change of current.

[0055] Example 2

[0056] A method for preparing a nanosheet-hollow sphere hierarchical structured copper-iron bimetallic phosphide catalyst material includes the following steps:

[0057] Step 1: Preparation of metal-organic precursors

[0058] Copper nitrate hexahydrate and ferric nitrate hexahydrate were added to a mixed solvent of glycerol and isopropanol according to the specified ratio and stirred for 0.5 h. The molar ratio of copper nitrate hexahydrate to ferric nitrate hexahydrate was 1:1, the molar ratio of glycerol to isopropanol was 1:7, and the molar ratio of metal salt to mixed solvent was 1:500. The solution after stirring was subjected to microwave synthesis reaction. The microwave synthesis reaction time and temperature were 20 min and 180 °C, respectively, and the power was 450 W. The solution after solvothermal reaction was centrifuged and washed 4 times at a speed of 3500 rpm. The product after centrifugation and washing was dried at 55 °C for 24 h to obtain the metal-organic precursor.

[0059] Step 2: Catalyst Surface Morphology Reconstruction

[0060] The metal-organic precursor was added to an aqueous solvent according to the specified ratio and stirred for 2 hours. The mass ratio of the metal-organic precursor, sodium hydroxide, ammonium fluoride, and water was 1:10:0.1:700. The solution after stirring was subjected to a solvothermal reaction for 7 hours and 150°C. The solution after the solvothermal reaction was centrifuged and washed 4 times at 3250 rpm. The product after centrifugation and washing was dried at 55°C for 24 hours.

[0061] Step 3: Preparation of nanosheet-hollow sphere multi-level structured copper-iron bimetallic phosphide catalyst material

[0062] NaH2PO2 and the product from step two were placed upstream and downstream of an argon atmosphere, respectively, with a mass ratio of 10:1. In the argon atmosphere, NaH2PO2 and the product from step two were heated to 300℃ at a heating rate of 5℃ / min and then calcined for 4 hours. After natural cooling, a nanosheet-hollow sphere multi-level structure copper-iron bimetallic phosphide catalyst material was obtained.

[0063] Example 3

[0064] A method for preparing a nanorod-hollow sphere hierarchical copper-nickel bimetallic selenide catalyst material includes the following steps:

[0065] Step 1: Preparation of metal-organic precursors

[0066] Copper nitrate hexahydrate and nickel nitrate hexahydrate were added to a mixed solvent of glycerol and isopropanol according to the specified ratio and stirred for 0.5 h. The molar ratio of copper nitrate hexahydrate to nickel nitrate hexahydrate was 1:1, the molar ratio of glycerol to isopropanol was 1:7, and the molar ratio of metal salt to mixed solvent was 1:500. The solution after stirring was subjected to microwave synthesis reaction. The microwave synthesis reaction time and temperature were 20 min and 180 °C, respectively, and the power was 450 W. The solution after solvothermal reaction was centrifuged and washed 4 times at a speed of 3500 rpm. The product after centrifugation and washing was dried at 55 °C for 24 h to obtain the metal-organic precursor.

[0067] Step 2: Catalyst Surface Morphology Reconstruction

[0068] The metal-organic precursor was added to an aqueous solvent according to the specified ratio and stirred for 2 hours. The mass ratio of the metal-organic precursor, sodium hydroxide, ammonium fluoride, and water was 1:20:2:700. The solution after stirring was subjected to a solvothermal reaction for 7 hours and 150°C. The solution after the solvothermal reaction was centrifuged and washed 4 times at a speed of 3250 rpm. The product after centrifugation and washing was dried at 55°C for 24 hours.

[0069] Step 3: Preparation of copper-nickel bimetallic selenide catalyst material with nanorod-hollow sphere hierarchical structure

[0070] Selenium powder and the product from step two were placed upstream and downstream of an argon atmosphere, respectively, with a mass ratio of 10:1. In the argon atmosphere, the selenium powder and the product from step two were heated to 300°C at a heating rate of 5°C / min and then calcined for 4 hours. After natural cooling, a nanorod-hollow sphere multi-level structure copper-nickel bimetallic selenide catalyst material was obtained.

[0071] Example 4

[0072] A method for preparing a copper-chromium bimetallic sulfide catalyst material with a nanoneedle-hollow sphere hierarchical structure includes the following steps:

[0073] Step 1: Preparation of metal-organic precursors

[0074] Copper nitrate hexahydrate and chromium nitrate hexahydrate were added to a mixed solvent of glycerol and isopropanol according to the specified ratio and stirred for 0.5 h. The molar ratio of copper nitrate hexahydrate to chromium nitrate hexahydrate was 1:1, the molar ratio of glycerol to isopropanol was 1:7, and the molar ratio of metal salt to mixed solvent was 1:500. The solution after stirring was subjected to microwave synthesis reaction. The microwave synthesis reaction time and temperature were 20 min and 180 °C, respectively, and the power was 450 W. The solution after solvothermal reaction was centrifuged and washed 4 times at a speed of 3500 rpm. The product after centrifugation and washing was dried at 55 °C for 24 h to obtain the metal-organic precursor.

[0075] Step 2: Catalyst Surface Morphology Reconstruction

[0076] The metal-organic precursor was added to an aqueous solvent and stirred for 2 hours according to the specified ratio. The mass ratio of the metal-organic precursor, sodium hydroxide, ammonium fluoride, and water was 1:50:2:700. The solution after stirring was subjected to a solvothermal reaction for 7 hours and 150°C. The solution after the solvothermal reaction was centrifuged and washed 4 times at 3250 rpm. The product after centrifugation and washing was dried at 55°C for 24 hours.

[0077] Step 3: Preparation of copper-chromium bimetallic sulfide catalyst material with nanoneedle-hollow sphere hierarchical structure

[0078] Sodium sulfide and the product from step two were placed upstream and downstream of an argon atmosphere, respectively, with a mass ratio of 10:1. In the argon atmosphere, the sulfur and the product from step two were heated to 300°C at a heating rate of 5°C / min and then calcined for 4 hours. After natural cooling, a nano-needle-hollow sphere hierarchical structure copper-chromium bimetallic sulfide catalyst material was obtained.

[0079] like Figure 8 As shown in the figure, the Faraday efficiency / yield of the copper-chromium bimetallic sulfide catalyst prepared in this embodiment varies with potential. It can be seen that the Faraday efficiency of urea is the highest at -0.5 V, which is 19%.

[0080] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a multi-level shell structure catalyst with tunable surface morphology, characterized in that, Includes the following steps: (1) Mix metal salt, ligand and polyol solvent, stir and react, microwave the solution after stirring and react, then centrifuge, wash and dry to obtain metal-organic precursor; (2) Add the metal-organic precursor, precipitant and structure directing agent to a polar solvent and stir to react. Perform a solvothermal reaction on the solution after stirring, and then centrifuge, wash and dry. (3) The gas phase reaction source and the product of step (2) are placed upstream and downstream of an argon atmosphere, respectively, and the gas phase reaction source and the product of step (2) are calcined and naturally cooled to obtain a multi-level shell structure catalyst. The gas phase reaction source is one of red phosphorus, sulfur, sodium hypophosphite, selenium powder or tellurium powder.

2. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that, In step (1): The metal salt is one or more of nitrates, chlorides, acetates, or phosphates; And / or, the metal in the metal salt is selected from one or more of Co, Ni, Fe, Mn, Zn, Mo, W, and V; And / or, the ligand is one of ethylene glycol, glycerol, glucose, citric acid, tartaric acid, or glycine; And / or, the polyol solvent is one or more of methanol, ethanol, isopropanol, ethylene glycol, and propanol.

3. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that: In step (1), the molar ratio of each metal salt, ligand, and polyol is 1:(50-80):(80-800).

4. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that, In step (1): The stirring reaction time is 0.1-5 hours, and the microwave synthesis reaction temperature is 120-200℃. And / or, the microwave synthesis reaction time is 5-120 min, and the power is 50-500 W; And / or, the centrifugal washing speed is 1000-5000 rpm, and the number of centrifugal washing cycles is 2-8; And / or, the drying temperature is 20-65℃, and the drying time is 4-24h.

5. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that, In step (2): The precipitant is one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, or urea. And / or, the structure directing agent is one of boric acid, ethylenediamine, sodium citrate, sodium dihydrogen phosphate, or ammonium fluoride; And / or, the polar solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, acetone, acetic acid, acetonitrile, hexamethylphosphoric triamine, or water.

6. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that: In step (2), the mass ratio of the metal-organic precursor, precipitant, structure directing agent, and polar solvent is 1:(0.1-100):(0.1-5):(500-1000).

7. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that, In step (2): The stirring reaction time is 1-12 hours; And / or, the temperature of the solvothermal reaction is 120-180℃, and the time of the solvothermal reaction is 4-12h; And / or, the centrifugal washing speed is 1000-5000 rpm, and the number of centrifugal washing cycles is 2-7; And / or, the drying temperature is 20-65℃, and the drying time is 4-24h.

8. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that: In step (3), the mass ratio of the gas phase reaction source to the product of step (2) is 1-10:

1.

9. The method for preparing a multi-level shell structure catalyst with tunable surface morphology according to claim 1, characterized in that: In step (3), the protective atmosphere during calcination is argon atmosphere, the calcination temperature is 300-500℃, the calcination time is 2-4h, and the heating rate is 2-10℃ / min.

10. A multi-level shell structure catalyst with tunable surface morphology prepared by the preparation method according to any one of claims 1-9.

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