Carbon-based Cu-Ni diatomic cluster catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of heterogeneous catalysts, in particular to a carbon-based Cu-Ni diatomic cluster catalyst and a preparation method and application thereof. The preparation method comprises the following steps: mixing an aqueous solution of thiosemicarbazide, magnesium chloride hexahydrate, alkali, nickel salt, copper salt and a carbohydrate, and freeze-drying to obtain a precursor; the precursor is sequentially subjected to preheating treatment, first pyrolysis and second pyrolysis, and the carbon-based Cu-Ni diatomic catalyst is obtained; and preparing the carbon-based Cu-Ni diatomic cluster catalyst into slurry, adhering the slurry to a current collector, and performing in-situ electrolytic treatment to obtain the carbon-based Cu-Ni diatomic cluster catalyst. According to the preparation method, the number of metal atoms in the metal atom cluster can be accurately controlled, reconstruction of Cu-Ni diatomic sites can be achieved, and the problems that in a traditional high-temperature carbonization method, the size of metal particles is difficult to control, and the advantages of an atomic-scale catalyst are difficult to play are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of multiphase catalysts, and in particular to a carbon-based Cu-Ni diatomic cluster catalyst and a preparation method and application thereof. Background Art

[0002] The electrochemical reduction of carbon dioxide technology, driven by renewable energy power generation, is committed to producing high value-added chemicals. In this process, carbon monoxide, as the main product of electrochemical reduction of carbon dioxide, not only occupies a key position in Fischer-Tropsch synthesis, but also exhibits excellent carbon storage efficiency. However, the main challenge facing the current electrochemical reduction of carbon dioxide technology is that the energy efficiency and product selectivity have not yet reached the actual requirements of industrialization. Copper, as an element with abundant reserves on the earth, is regarded as a key element in converting CO2 to CO. 2 Highly efficient catalysts for conversion to hydrocarbons. Cu-based atomic-scale catalysts show great potential to control reaction pathways in complex catalytic processes due to the designability of their electronic properties. Compared with single-atom catalysts, multi-atom catalysts have different coordination environments, geometric configurations, and metal-metal or metal-support interactions.

[0003] Polyatomic cluster catalysts are a new type of heterogeneous catalysts with atomic dispersion. Polyatomic cluster catalysts are between atoms and nanoparticles. They are composed of metal clusters with precise atomic numbers, namely Mn, n=3~20, monodispersed on a carrier. They have the advantages of high atomic utilization, structural diversity and metal synergy, and are regarded as multifunctional boosters for heterogeneous catalysis. In addition to the simple combination of single-atom catalysts, they are also able to improve activity through synergy between adjacent atoms. At the same time, the multiple active sites of the catalytic center diversify their binding modes with adsorbates and provide opportunities for catalyzing complex reactions with multiple products. The coordination microenvironment of the atomic clusters in polyatomic cluster catalysts includes metal type, atomic number, non-metal coordination and aggregation state. Adjusting its microenvironment will lead to significant size effects and polarized charge distribution, thereby improving its catalytic reaction performance.

[0004] At present, the atomic clusters in the multi-atom cluster catalysts obtained by the traditional high-temperature carbonization method have a large diameter, which makes it difficult to give full play to the advantages of atomic-level metals and is not conducive to the identification of true active centers; even if atomic clusters can be directly synthesized, the number and aggregation state of metal atoms in the atomic clusters are relatively random and difficult to control. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a carbon-based Cu-Ni diatomic cluster catalyst and its preparation method and application. The present invention mixes an aqueous solution of thiosemicarbazide, magnesium chloride hexahydrate, alkali, nickel salt, copper salt and sugar compound and freeze-dries to obtain a precursor; then, under an inert atmosphere, the precursor is subjected to preheating treatment, first pyrolysis and second pyrolysis in sequence to obtain a carbon-based Cu-Ni diatomic catalyst; finally, the carbon-based Cu-Ni diatomic catalyst is subjected to in-situ electrolysis treatment to obtain a carbon-based Cu-Ni diatomic cluster catalyst. The present invention realizes the reconstruction of Cu-Ni diatomic sites through in-situ electrolysis treatment, which can not only accurately control the number of metal atoms in the metal atom cluster and effectively reduce the existence of single-atom sites, but also solves the problem that the size of metal particles in the traditional high-temperature carbonization method is difficult to control and it is difficult to give play to the advantages of atomic-level catalysts.

[0006] In order to achieve the above purpose, the technical solution adopted in this application is: The first object of the present invention is to provide a method for preparing a carbon-based Cu-Ni diatomic cluster catalyst, comprising the following steps: S1, mixing an aqueous solution of thiosemicarbazide, magnesium chloride hexahydrate, alkali, nickel salt, copper salt and sugar compound. During the mixing process, thiosemicarbazide and Ni 2+ , Cu 2+ Coordination occurs to form a NiCu complex containing a metal cyanide, which provides a basis for the formation of a NiCu diatomic site; at the same time, magnesium chloride hexahydrate reacts with alkali to generate Mg(OH) 2 and chloride ion salts, while the sugar compound serves as a carbon skeleton to anchor and disperse the NiCu complexes, thereby solving the aggregation of the NiCu complexes and obtaining a mixed hydrogel.

[0007] S2. Freeze-drying the mixed hydrogel. During freeze-drying, the water in the mixed hydrogel sublimates, leaving a porous structure to obtain a precursor. Compared with freeze-drying, other heating drying methods will cause the mixed hydrogel to agglomerate, resulting in a reduction in the pore structure, thereby reducing the pore structure of the precursor, which is not conducive to mass transfer in the catalytic process.

[0008] S3, preheating the precursor in an inert atmosphere, and then performing the first pyrolysis. During the preheating and the first pyrolysis, the thiosemicarbazide in the precursor decomposes and interacts with the sugar compound to be transformed into a porous carbon skeleton. At the same time, Mg(OH) 2 The decomposition forms the template MgO, which provides an ordered support structure for the NiCu complex; at the same time, the chloride ion salt is reconstructed. MgO and chloride ion salt can decompose Ni and Cu, preventing them from directly forming single substances, and generate NiCu diatomic loaded porous carbon on the MgO template and dispersed in the porous carbon skeleton to obtain NiCu diatomic porous carbon.

[0009] S4. The NiCu diatomic porous carbon is subjected to acid washing treatment to remove MgO and chloride ion salts and excess metal particles or metal oxides to obtain an intermediate.

[0010] S5. The intermediate is placed in an inert atmosphere for a second pyrolysis to remove oxygen-containing functional groups on the surface of the intermediate, while increasing the conductivity of the intermediate and promoting the rearrangement and aggregation of Cu atoms and Ni atoms on the porous carbon skeleton to obtain a carbon-based Cu-Ni diatomic catalyst.

[0011] S6. The carbon-based Cu-Ni catalyst is formulated into a slurry, adhered to a current collector, and subjected to in-situ electrolysis. During the in-situ electrolysis, the Cu-Ni diatomic sites in the NiCu complex are reconstructed, that is, the Cu ions are reduced to metallic Cu atoms under a negative potential, and are separated from the Cu-Ni diatomic coordination structure to become Cu-Ni diatomic cluster sites enriched with Cu atoms, thereby obtaining a carbon-based Cu-Ni diatomic cluster catalyst.

[0012] Preferably, the in-situ electrolysis treatment conditions are: electrolysis at -0.5V~-1.2V for 2h~4h; wherein, the negative increase in voltage is conducive to the increase in the number of metal atoms; copper atoms have a higher reduction potential, i.e., Cu 2+ / Cu 0 +0.34V, Cu + / Cu 0 =+0.52V. Under negative potential, copper ions are preferentially reduced to metallic Cu atoms. This process weakens the adsorption force between Cu atoms and carbon substrates, which in turn triggers the migration of copper atoms and causes them to detach from the original Cu-Ni coordination structure. The role of the electric field is that it accelerates the migration and collision of Cu atoms or Cu ions through the action of electrostatic force. The Cu atoms that are separated from the original carrier will spontaneously agglomerate due to the reduction of surface energy, thereby forming Cu-based nanoclusters. On the other hand, in the water electrolysis system, when a lower voltage is applied, active hydrogen radicals are generated on the cathode surface. These free radicals attack the Cu-Ni coordination structure, thereby weakening the anchoring effect of the carrier on Cu atoms and further promoting the migration of Cu atoms. However, when the voltage is low, the surface energy of copper will decrease accordingly, which will aggravate the Ostwald ripening process, that is, smaller particles dissolve and redeposit on larger particles, which is not conducive to the stable existence of copper atoms.

[0013] Preferably, the mass ratio of thiosemicarbazide, nickel salt and copper salt in the mixed hydrogel is 1-3: 0.2-0.6: 0.1-0.6, the mass ratio of thiosemicarbazide and sugar compound is 1-3: 0.3-1, and the mass ratio of thiosemicarbazide, magnesium chloride hexahydrate and alkali is 1-3: 0.5-2: 0.5-2.

[0014] Preferably, the nickel salt is selected from nickel acetylacetonate, nickel acetate, nickel nitrate or nickel sulfate.

[0015] Preferably, the pickling agent is selected from nitric acid or sulfuric acid, and the pickling time is 10h~15h.

[0016] Preferably, the concentration of the pickling agent is 0.5 mol / L to 3 mol / L; if the concentration is too low, the MgO template will not be completely removed, and metal particles will remain; if the concentration is too high, it will cause excessive metal corrosion, resulting in a significant decrease in metal loading.

[0017] Preferably, the preheating conditions are: heating to 350°C~450°C at a heating rate of 2°C / min~5°C / min for preheating for 1h~3h; wherein, if the heating rate is too fast or the temperature is too high, a large amount of thiosemicarbazide will easily volatilize.

[0018] Preferably, the conditions for the first pyrolysis are: heating to 800°C~1000°C at a heating rate of 4°C / min~10°C / min and then pyrolyzing for 1h~3h; wherein, the first pyrolysis causes the precursor to be quickly and fully carbonized into a porous carbon skeleton; when the temperature is higher than 1000°C, the pore structure of the NiCu diatomic porous carbon will become less, and the metal will agglomerate into a single substance; and when the temperature is lower than 800°C, the conductivity of the NiCu diatomic porous carbon is low.

[0019] Preferably, the conditions for the second pyrolysis are: heating to 800°C~1200°C at a heating rate of 2°C / min~5°C / min, and then pyrolyzing for 1h~3h; re-carbonizing the intermediate and effectively decomposing the oxygen-containing functional groups, improving the conductivity of the carbon-based Cu-Ni diatomic catalyst, and enhancing the coordination and anchoring effect of the NiCu diatoms on the porous carbon skeleton; when the temperature is higher than 1200°C, the metal will agglomerate into a single substance; and when the temperature is lower than 800°C, the oxygen-containing functional groups will not be completely eliminated.

[0020] Preferably, the mixing treatment conditions are: stirring at 55° C. to 95° C. for 3 h to 4 h.

[0021] The second object of the present invention is to provide a carbon-based Cu-Ni diatomic cluster catalyst prepared by the above preparation method.

[0022] Preferably, the number of metal atoms in the carbon-based Cu-Ni diatomic cluster catalyst is 4 to 9.

[0023] Preferably, in the carbon-based Cu-Ni diatomic cluster catalyst, the diameter of the Cu-Ni diatomic cluster is less than 2 nm.

[0024] The third object of the present invention is to provide the above-mentioned carbon-based Cu-Ni diatomic cluster catalyst for preparing electrocatalytic CO 2Application in reduction reaction catalysts.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a method for preparing a carbon-based Cu-Ni diatomic cluster catalyst, comprising mixing an aqueous solution of thiosemicarbazide, magnesium chloride hexahydrate, an alkali, a nickel salt, a copper salt and a carbohydrate compound to obtain a mixed hydrogel; then freeze-drying the mixture to obtain a precursor; preheating the precursor under an inert atmosphere, and then performing a first pyrolysis to obtain NiCu diatomic porous carbon, which is then acid-washed to obtain an intermediate; placing the intermediate under an inert atmosphere and performing a second pyrolysis to obtain a carbon-based Cu-Ni diatomic catalyst; formulating the carbon-based Cu-Ni diatomic catalyst into a slurry, adhering the slurry to a current collector, and performing an in-situ electrolysis treatment, wherein during the in-situ electrolysis, Cu ions are reduced to metallic Cu atoms under a negative potential, and are separated from the Cu-Ni coordination structure to become Cu-Ni diatomic cluster sites enriched with Cu atoms, thereby obtaining a carbon-based Cu-Ni diatomic cluster catalyst. The present invention is based on the method of in-situ electrolysis treatment. By adjusting the applied voltage to adjust the in-situ electrolysis parameters, it not only achieves precise control of the number of metal atoms in the metal atom cluster, but also effectively reduces the presence of single-atom sites, thereby simplifying the types of metal active sites and improving their purity and efficiency. In addition, the present invention also effectively solves the problem that the size of metal particles is difficult to control and it is difficult to give full play to the advantages of atomic-level catalysts in the traditional high-temperature carbonization method.

[0026] 2. The carbon-based Cu-Ni diatomic cluster catalyst of the present invention exists in an atomic-level precision and ligand-protected manner, forming a nanocluster structure with a diameter of less than 2nm. The number of metal atoms in these nanoclusters is clear and controlled between 4 and 9. In addition, the carbon-based Cu-Ni diatomic cluster catalyst also significantly enhances the catalytic activity and stability of the carbon-based Cu-Ni diatomic cluster, showing excellent catalytic performance.

[0027] 3. The carbon-based Cu-Ni diatomic cluster catalyst of the present invention can not only solve the problem of lack of metal synergy and poor catalytic activity of conventional atomic-level catalysts, but also promote electrocatalytic CO 2 Restore performance.

[0028] At a potential of -0.9 V vs. RHE, the carbon-based Cu-Ni diatomic catalyst reorganizes into a carbon-based Cu-Ni diatomic cluster catalyst composed of 4 to 6 Cu atoms and 1 Ni atom, with a CO Faraday efficiency of up to 96.9% and a stability of up to 120 h. When the applied potential is -1.2 V vs. RHE, the nanoclusters of the carbon-based Cu-Ni diatomic cluster catalyst are upgraded to 6 to 8 Cu atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are the XRD patterns of carbon-based Cu-Ni diatomic catalyst, carbon-based Ni single-atom catalyst and carbon-based Cu single-atom catalyst.

[0030] Figure 2 These are the Raman images of carbon-based Cu-Ni diatomic catalysts, carbon-based Ni single-atom catalysts, and carbon-based Cu single-atom catalysts.

[0031] Figure 3 This is the SEM image of the carbon-based Cu-Ni diatomic catalyst.

[0032] Figure 4 TEM image of carbon-based Cu-Ni diatomic catalyst.

[0033] Figure 5 HAADF-STEM images of the carbon-based Cu-Ni diatomic catalyst and the carbon-based Cu-Ni diatomic cluster catalysts prepared in Example 1 and Example 4, wherein (a) is the HAADF-STEM image of the carbon-based Cu-Ni diatomic catalyst, (b) is the HAADF-STEM image of the carbon-based Cu-Ni diatomic cluster catalyst prepared in Example 4; (c) is the HAADF-STEM image of the carbon-based Cu-Ni diatomic cluster catalyst prepared in Example 1.

[0034] Figure 6 The Faraday efficiency diagrams are of the carbon-based Cu-Ni diatomic cluster catalysts prepared in Examples 1 to 8, the Ni-NCs of Comparative Examples 1 to 8, and the Cu-NCs of Comparative Examples 9 to 16.

[0035] Figure 7 The current density diagrams are of the carbon-based Cu-Ni diatomic cluster catalysts prepared in Examples 1 to 8, the Ni-NCs of Comparative Examples 1 to 8, and the Cu-NCs of Comparative Examples 9 to 16.

[0036] Figure 8 This is a stability diagram of the carbon-based Cu-Ni diatomic cluster catalyst prepared in Example 4.

[0037] Fig. 9 The in-situ XAFS graphs of the Cu element in the carbon-based Cu-Ni diatomic cluster catalysts prepared in Examples 1 to 7, wherein a is the structural spectrum, b is the extended spectrum, and the inset in Figure a is a local enlarged view of the absorption edge of the Cu element.

[0038] Fig.10 The in-situ XAFS graphs of the Ni element in the carbon-based Cu-Ni diatomic cluster catalysts prepared in Examples 1 to 7, wherein a is the structural spectrum, b is the extended spectrum, and the inset in Figure a is a local enlarged view of the absorption edge of the Ni element.

[0039] Fig.11 1 and 2 are the extended XAFS fitting graphs of the carbon-based Cu-Ni diatomic catalyst and the carbon-based Cu-Ni diatomic cluster catalysts prepared in Example 1, Example 4 and Example 6, a is the carbon-based Cu-Ni diatomic catalyst, b is the extended XAFS fitting graph of Example 6, c is the extended XAFS fitting graph of Example 4, and d is the extended XAFS fitting graph of Example 1. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in combination with the data in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The following experimental methods and detection methods, unless otherwise specified, are conventional methods; the following reagents and raw materials, unless otherwise specified, are commercially available reagents and raw materials.

[0042] In the prior art, the synthesis method of multi-atom cluster catalysts mainly relies on the traditional high-temperature carbonization method, but the diameter of the atomic clusters in the multi-atom cluster catalysts obtained by this method is relatively large, which makes it difficult to give full play to the advantages of atomic-level metals and is not conducive to the identification of true active centers. At the same time, even if the atomic clusters can be directly synthesized, the number and aggregation state of metal atoms in the atomic clusters are relatively random, making it difficult to achieve precise control.

[0043] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a carbon-based Cu-Ni diatomic cluster catalyst, comprising the following steps: mixing an aqueous solution of thiosemicarbazide, magnesium chloride hexahydrate, an alkali, a nickel salt, a copper salt and a carbohydrate compound to obtain a mixed hydrogel, and then freeze-drying to obtain a precursor; preheating the precursor under an inert atmosphere, and then performing a first pyrolysis to obtain NiCu diatomic porous carbon, and then performing an acid wash treatment to obtain an intermediate; placing the intermediate under an inert atmosphere and performing a second pyrolysis to obtain a carbon-based Cu-Ni diatomic catalyst; formulating the carbon-based Cu-Ni diatomic catalyst into a slurry, adhering it to a current collector, and performing an in-situ electrolysis treatment. During the in-situ electrolysis, Cu ions are reduced to metallic Cu atoms under a negative potential, and are separated from the Cu-Ni coordination structure to become Cu-Ni diatomic cluster sites enriched with Cu atoms, thereby obtaining a carbon-based Cu-Ni diatomic cluster catalyst.

[0044] The preparation method of the present invention can not only accurately control the number of metal atoms in the metal atom cluster, but also effectively reduce the existence of single-atom sites, thereby simplifying the types of metal active sites and improving their purity and efficiency. At the same time, the reconstruction of Cu-Ni diatomic sites is achieved through in-situ electrolysis treatment, which solves the problem that the size of metal particles is difficult to control and the advantages of atomic-level catalysts are difficult to exert in the traditional high-temperature carbonization method.

[0045] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0046] The carbon-based Cu-Ni diatomic catalyst in the embodiment of the present invention is prepared according to the following method: Method 1: S1. Weigh 2 g of thiosemicarbazide and transfer it to a three-necked flask containing 40 mL of water; then, place the three-necked flask in an oil bath, heat to 55°C and stir for 20 min; then, weigh 1.34 g of magnesium chloride hexahydrate, 1.18 g of potassium hydroxide, 0.4 g of nickel acetate and 0.32 g of copper acetate, add them to the three-necked flask in sequence, and continue stirring at 85°C for 30 min; finally, add 0.53 g of chitosan and continue stirring for 2 h to obtain a mixed hydrogel.

[0047] S2. After the mixed hydrogel is naturally cooled to room temperature, it is placed in a -50°C environment for vacuum drying for 20 hours to obtain a precursor.

[0048] S3, place the precursor in a nitrogen-filled 2 In a tubular furnace with a low temperature atmosphere, the temperature was heated to 350°C at a rate of 2°C / min, and preheated at this temperature for 1 h; then the temperature was further raised to 950°C at a rate of 10°C / min, and the first pyrolysis was carried out at this temperature for 2 h to obtain NiCu diatomic porous carbon.

[0049] S4. Soak the Cu-Ni diatomic porous carbon in 1 mol / L HNO 3 The solution is leached at 80°C for 12 hours; thereafter, it is repeatedly washed with deionized water until it becomes neutral; it is then filtered with ethanol and dried to obtain an intermediate.

[0050] S5. Place the intermediate in a well-filled N 2 The temperature was heated to 950 °C at 5 °C / min in a tubular furnace with an atmosphere of 5 °C / min, and a second pyrolysis was carried out at this temperature for 3 h to obtain a carbon-based Cu-Ni diatomic catalyst, which was recorded as Cu / Ni-NC.

[0051] Method 2: S1. Weigh 1 g of thiosemicarbazide and transfer it to a three-necked flask containing 40 mL of water. Subsequently, place the three-necked flask in an oil bath, heat it to 55 °C and stir for 20 min. Then, weigh 0.5 g of magnesium chloride hexahydrate, 0.5 g of potassium hydroxide, 0.2 g of nickel acetate and 0.1 g of copper acetate, and add them to the three-necked flask in sequence, and continue to stir at 55 °C for 30 min. Finally, add 0.3 g of chitosan and continue to stir for 4 h to obtain a mixed hydrogel.

[0052] S2. After the mixed hydrogel is naturally cooled to room temperature, place it in an environment of -50 °C for vacuum drying for 20 h to obtain a precursor.

[0053] S3. Place the precursor in a tubular furnace filled with N 2 atmosphere, heat the temperature to 350 °C at a rate of 2 °C / min, and preheat it at this temperature for 1 h. Then continue to heat up to 800 °C at a rate of 4 °C / min and carry out the first pyrolysis at this temperature for 3 h to obtain NiCu dual-atom porous carbon.

[0054] S4. Immerse the Cu-Ni dual-atom porous carbon in a 0.5 mol / L HNO 3 solution, and carry out leaching treatment at 80 °C for 12 h. Then, wash it repeatedly with deionized water until it is neutral. Then carry out filtration treatment with ethanol and drying treatment to obtain an intermediate.

[0055] S5. Place the intermediate in a tubular furnace filled with N 2 atmosphere, heat the temperature to 800 °C at a rate of 2 °C / min, and carry out the second pyrolysis at this temperature for 3 h to obtain a carbon-based Cu-Ni dual-atom catalyst.

[0056] Method 3: S1. Weigh 3 g of thiosemicarbazide and transfer it to a three-necked flask containing 40 mL of water. Subsequently, place the three-necked flask in an oil bath, heat it to 55 °C and stir for 20 min. Then, weigh 2 g of magnesium chloride hexahydrate, 2 g of potassium hydroxide, 0.6 g of nickel acetate and 0.6 g of copper acetate, and add them to the three-necked flask in sequence, and continue to stir at 95 °C for 30 min. Finally, add 1 g of chitosan and continue to stir for 3 h to obtain a mixed hydrogel.

[0057] S2. After the mixed hydrogel is naturally cooled to room temperature, place it in an environment of -50 °C for vacuum drying for 20 h to obtain a precursor.

[0058] S3. Place the precursor in a tubular furnace filled with N 2In a tubular furnace with an atmosphere, the temperature was heated to 450°C at a rate of 5°C / min, and preheated at this temperature for 3 hours; then the temperature was further raised to 1000°C at a rate of 10°C / min, and the first pyrolysis was carried out at this temperature for 1 hour to obtain NiCu diatomic porous carbon.

[0059] S4. Soak the Cu-Ni diatomic porous carbon in 3 mol / L HNO 3 The solution is leached at 80°C for 12 hours; thereafter, it is repeatedly washed with deionized water until it becomes neutral; it is then filtered with ethanol and dried to obtain an intermediate.

[0060] S5. Place the intermediate in a well-filled N 2 The temperature was heated to 1200°C at 5°C / min in a tubular furnace with a low temperature atmosphere, and a second pyrolysis was carried out at this temperature for 1 h to obtain a carbon-based Cu-Ni diatomic catalyst.

[0061] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments, wherein the Cu-Ni-NC in Examples 1 to 8 are all prepared by Method 1.

[0062] Example 1 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was injected into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.2 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -1.2 V-Cu 7 / Ni-NC; the average number of Cu atoms is 7.

[0063] Example 2 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.1 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -1.1 V-Cu / Ni-NC.

[0064] Example 3 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.0 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -1.0 V-Cu / Ni-NC.

[0065] Example 4 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.9 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -0.9 V-Cu 5 / Ni-NC; the average number of Cu atoms is 5.

[0066] Example 5 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.8 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -0.8 V-Cu / Ni-NC.

[0067] Example 6 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.7 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -0.7 V-Cu 3 / Ni-NC; the average number of Cu atoms is 3.

[0068] Example 7 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.6 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -0.6V-Cu / Ni-NC.

[0069] Example 8 A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst comprises the following steps: 5 mg of Cu-Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.5 V was applied for in-situ electrolysis for 2 h to obtain a carbon-based Cu-Ni diatomic cluster catalyst, which was recorded as -0.5V-Cu / Ni-NC.

[0070] The present invention provides a method for preparing a carbon-based Ni single-atom catalyst, comprising the following steps: S1. Weigh 2 g of thiosemicarbazide and transfer it to a three-necked flask containing 40 mL of water; then, place the three-necked flask in an oil bath, heat to 55°C and stir for 20 min; then, weigh 1.34 g of magnesium chloride hexahydrate, 1.18 g of potassium hydroxide and 0.4 g of nickel acetate, add them to the three-necked flask in sequence, and continue stirring at 85°C for 30 min; finally, add 0.53 g of chitosan and continue stirring for 2 h to obtain a mixed hydrogel.

[0071] S2. After the mixed hydrogel is naturally cooled to room temperature, it is placed in a -50°C environment for vacuum drying for 20 hours to obtain a precursor.

[0072] S3, place the precursor in a nitrogen-filled 2In a tubular furnace with an atmosphere, the temperature was heated to 350°C at a rate of 2°C / min, and preheated at this temperature for 1 h; then the temperature was further raised to 950°C at a rate of 10°C / min, and the first pyrolysis was carried out at this temperature for 2 h to obtain Ni porous carbon.

[0073] S4. Soak the Ni porous carbon in 1 mol / L HNO 3 The solution is leached at 80°C for 12 hours; thereafter, it is repeatedly washed with deionized water until it becomes neutral; it is then filtered with ethanol and dried to obtain an intermediate.

[0074] S5. Place the intermediate in a well-filled N 2 The temperature was heated to 950 °C at 5 °C / min in a tubular furnace with an atmosphere of 5 °C / min, and a second pyrolysis was carried out at this temperature for 3 h to obtain a carbon-based Ni single-atom catalyst, which was recorded as Ni-NC.

[0075] Based on the Ni-NC obtained by the above preparation method, taking Ni-NC as an example, an in-situ electrolysis treatment is performed, as shown in Comparative Examples 1 to 8: Comparative Example 1 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.2 V was applied for in-situ electrolysis treatment for 2 h.

[0076] Comparative Example 2 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.1 V was applied for in-situ electrolysis treatment for 2 h.

[0077] Comparative Example 3 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.0 V was applied for in-situ electrolysis treatment for 2 h.

[0078] Comparative Example 4 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.9 V was applied for in-situ electrolysis treatment for 2 h.

[0079] Comparative Example 5 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.8 V was applied for in-situ electrolysis treatment for 2 h.

[0080] Comparative Example 6 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.7 V was applied for in-situ electrolysis treatment for 2 h.

[0081] Comparative Example 7 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.6 V was applied for in-situ electrolysis treatment for 2 h.

[0082] Comparative Example 8 An in-situ electrolytic treatment method for a carbon-based Ni single-atom catalyst comprises the following steps: 5 mg of Ni-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and then ultrasonicated for 30 min to obtain a slurry. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.5 V was applied for in-situ electrolysis treatment for 2 h.

[0083] The present invention provides a method for preparing a carbon-based Cu single-atom catalyst, comprising the following steps: S1. Weigh 2 g of thiosemicarbazide and transfer it to a three-necked flask containing 40 mL of water; then, place the three-necked flask in an oil bath, heat to 55°C and stir for 20 min; then, weigh 1.34 g of magnesium chloride hexahydrate, 1.18 g of potassium hydroxide and 0.32 g of cupric acetate, add them to the three-necked flask in sequence, and continue stirring at 85°C for 30 min; finally, add 0.53 g of chitosan and continue stirring for 2 h to obtain a mixed hydrogel.

[0084] S2. After the mixed hydrogel is naturally cooled to room temperature, it is placed in a -50°C environment for vacuum drying for 20 hours to obtain a precursor.

[0085] S3, place the precursor in a nitrogen-filled 2 In a tubular furnace with an atmosphere, the temperature was heated to 350°C at a rate of 2°C / min, and preheated at this temperature for 1 h; then the temperature was further raised to 950°C at a rate of 10°C / min, and the first pyrolysis was carried out at this temperature for 2 h to obtain Cu porous carbon.

[0086] S4. Soak the Cu porous carbon in 1 mol / L HNO 3 The solution is leached at 80°C for 12 hours; thereafter, it is repeatedly washed with deionized water until it becomes neutral; it is then filtered with ethanol and dried to obtain an intermediate.

[0087] S5. Place the intermediate in a well-filled N 2 The temperature was heated to 950 °C at 5 °C / min in a tubular furnace with an atmosphere of 5 °C / min, and a second pyrolysis was carried out at this temperature for 3 h to obtain a carbon-based Cu single-atom catalyst, which was recorded as Cu-NC.

[0088] Based on the Cu-NC obtained by the above preparation method, taking Cu-NC as an example, an in-situ electrolysis treatment is performed, as shown in Comparative Examples 9 to 16: Comparative Example 9 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.2 V was applied for in-situ electrolysis treatment for 2 h.

[0089] Comparative Example 10 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.1 V was applied for in-situ electrolysis treatment for 2 h.

[0090] Comparative Example 11 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -1.0 V was applied for in-situ electrolysis treatment for 2 h.

[0091] Comparative Example 12 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.9 V was applied for in-situ electrolysis treatment for 2 h.

[0092] Comparative Example 13 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.8 V was applied for in-situ electrolysis treatment for 2 h.

[0093] Comparative Example 14 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.7 V was applied for in-situ electrolysis treatment for 2 h.

[0094] Comparative Example 15 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.6 V was applied for in-situ electrolysis treatment for 2 h.

[0095] Comparative Example 16 An in-situ electrolytic treatment method for a carbon-based Cu single-atom catalyst comprises the following steps: 5 mg of Cu-NC was dispersed in a mixed solution consisting of 700 μL of ethanol, 300 μL of water and 60 μL of Nafion, and a slurry was obtained after ultrasonic treatment for 30 min. Subsequently, 120 μL of the slurry was evenly coated on a hydrophobic carbon paper and used as a working electrode. At the same time, Ag / AgCl was used as a reference electrode and a platinum mesh was used as a counter electrode to assemble a conventional three-electrode system. 0.5 mol / L CO was introduced into the three-electrode system. 2 Saturated KHCO 3 The solution was used as the electrolyte; the assembled three-electrode system was connected to the electrochemical workstation, and a voltage of -0.5 V was applied for in-situ electrolysis treatment for 2 h.

[0096] observe Figure 1 It was concluded that the crystal structure of the catalyst was tested by X-ray diffractometer, and the results showed that the peaks at about 22° and 44° belonged to the (002) and (100) planes of graphite carbon with a lower degree of crystallinity, which indicated that the prepared carbon-based Cu-Ni diatomic catalyst did not have large metal particles, further indicating that the atomic-level sites could be reconstructed into atomic clusters by applying a negative voltage; on the contrary, if large metal particles were formed, the carbon-based Cu-Ni diatomic catalyst would be very stable and difficult to further process into atomic-level clusters.

[0097] Combination Figure 2 , Figure 3 and Figure 4 The results show that the carbon-based Cu-Ni diatomic catalyst presents a porous granular morphology with rich pore structure, low graphitization degree and more defective structures. Specifically, these defective structures exist in the form of a large number of mesopores and micropores, accompanied by the distribution of metal sites; further indicating that the carbon-based Cu-Ni diatomic catalyst is rich in structural defects and no large metal particles are observed.

[0098] observe Figure 5 Figure a shows that the carbon-based Cu-Ni diatomic catalyst has many diatomic bright spots evenly distributed on its entire porous carbon skeleton. The diatomic metal spacing represented by these bright spots is between 0.19nm and 0.24nm, as shown in Figure 2. Figure 5 In addition, Figure 5 No aggregation of large particles or nanoclusters was observed in Figure a, which fully demonstrates the successful formation of Cu-Ni diatomic sites in the carbon-based Cu-Ni diatomic catalyst.

[0099] Depend on Figure 5 Figure b shows that under the condition of in-situ electrolysis treatment potential of -0.9 V, the Cu-Ni diatomic sites in the carbon-based Cu-Ni diatomic catalyst were reconstructed, accompanied by the aggregation of metal atoms, forming a carbon-based Cu-Ni diatomic cluster catalyst composed of 5 to 7 metal atoms; further, when the voltage was reduced to -1.2 V and reconstruction was performed, as shown in Figure 5 In Figure c, the Cu-Ni diatomic sites in the carbon-based Cu-Ni diatomic catalyst continue to be reconstructed, and the cluster size is upgraded to form a Cu-Ni diatomic cluster composed of 8 to 10 metal atoms.

[0100] By comparison Figure 5 Figure b in Figure 5 and Figure c in Figure 5 show that the diatomic cluster size of -1.2V-Cu-Ni-NC reconstructed at -1.2V is slightly larger than that of -0.9V-Cu-Ni-NC reconstructed at -0.9V. The yellow circles are used to mark diatomic pairs, the red circles are used to mark diatomic clusters with slightly smaller sizes, and the blue circles are used to mark clusters with larger sizes.

[0101] Combination Figure 6 and Figure 7 The data analysis in the literature shows that when the in-situ electrolysis treatment potential of Cu-Ni-NC is -0.9 V, its selectivity for CO is excellent, up to 96.9%; at the same time, the partial current density of CO is 18 mA / cm 2 When the potential is further reduced to -1.2 V, the current density of the obtained -1.2 V-CuNi-NC increases accordingly, specifically 30 mA / cm 2 .

[0102] observe Figure 8 It was concluded that the Cu-Ni diatomic cluster catalyst prepared in Example 4 could operate stably for 120 h at a constant voltage of -0.9 V, and during this period, its selectivity for CO did not show a significant decrease, which fully proved that the carbon-based Cu-Ni diatomic cluster catalyst of the present invention has excellent catalytic stability.

[0103] from Fig. 9 Figure a shows that as the potential of the in-situ electrolysis treatment moves negatively, the valence of the Cu element shows a trend of gradually decreasing; Fig. 9 Figure b shows that as the potential of the in-situ electrolysis treatment continues to move negatively, the N coordination number of the Cu element gradually decreases. At the same time, the metal coordination effect gradually increases, indicating that the Cu metal is gradually aggregating.

[0104] from Fig.10 Figure a shows that as the potential of the in-situ electrolysis treatment moves negatively, the valence state of the Ni element changes relatively little and remains relatively stable; Fig.10 Figure b shows that during the negative movement of the potential in the in-situ electrolysis treatment, the coordination of the Ni element did not change significantly, and only a slight enhancement of the metal peak was observed, which indicates that the Ni atoms did not undergo an obvious reconstruction process.

[0105] Combination Fig. 9 and Fig.10 It was concluded that the metal reconstruction phenomenon in carbon-based Cu-Ni diatomic catalysts is mainly concentrated on the Cu element.

[0106] In order to gain a deeper understanding of the dynamic reconstruction mechanism of Cu-Ni-NC, in situ X-ray absorption fine structure technique was used to monitor the changes in the electronic structure and coordination environment of Ni and Cu under electrochemical CO reduction test conditions.

[0107] By observation Fig.11 The dynamic evolution process of Cu-Ni-NC is as follows: the initial stage is Cu-S 1 N 3 / Ni-S 1 N 3 ,like Fig.11 As shown in Figure a; then, at a potential of -0.7 V, its structure transforms into Ni-S 1 N 3 / Cu3-S 1 N 3 The configuration, such as Fig.11 As shown in Figure b; then, when the potential reaches -0.9V, it further evolves into Ni-S 1 N 3 / Cu5-S 1 N 3 The configuration, such as Fig.11 As shown in Figure c; then, at a potential of -1.2 V, Ni-S 1 N 3 / Cu7-S 1 N 1 The configuration, such as Fig.11This series of changes shows that the preparation method of the present invention can enable Cu-Ni-NC to achieve continuous and orderly structural transformation.

[0108] Although the preferred embodiments of the present invention have been described, those skilled in the art will be able to make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0109] 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 their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a carbon-based Cu-Ni diatomic cluster catalyst, characterized in that: The following steps are involved: An aqueous solution of thiosemicarbazide, magnesium chloride hexahydrate, alkali, nickel salt, copper salt and a sugar compound are mixed to obtain a mixed hydrogel, and then freeze-dried to obtain a precursor; The precursor is preheated in an inert atmosphere, and then pyrolyzed for the first time to obtain NiCu diatomic porous carbon, which is then acid-washed to obtain an intermediate; The intermediate is placed in an inert atmosphere for a second pyrolysis to obtain a carbon-based Cu-Ni diatomic catalyst; The carbon-based Cu-Ni diatomic catalyst is formulated into a slurry, adhered to a current collector, and subjected to in-situ electrolysis. During the in-situ electrolysis, Cu ions are reduced to metallic Cu atoms under a negative potential and detached from the Cu-Ni coordination structure to become Cu-Ni diatomic cluster sites enriched with Cu atoms, thereby obtaining a carbon-based Cu-Ni diatomic cluster catalyst.

2. The method for preparing a carbon-based Cu-Ni diatomic cluster catalyst according to claim 1, characterized in that: The conditions for in-situ electrolysis are: in-situ electrolysis at -0.5V~-1.2V for 2h~4h.

3. The method for preparing the carbon-based Cu-Ni diatomic cluster catalyst according to claim 1, characterized in that: In the mixed hydrogel, the mass ratio of thiosemicarbazide, nickel salt and copper salt is 1~3:0.2~0.6:0.1~0.6, the mass ratio of thiosemicarbazide and sugar compound is 1~3:0.3~1, and the mass ratio of thiosemicarbazide, magnesium chloride hexahydrate and alkali is 1~3:0.5~2:0.5~2.

4. The method for preparing a carbon-based Cu-Ni diatomic cluster catalyst according to claim 1, characterized in that: The preheating conditions are: preheating at 350°C~450°C for 1h~3h.

5. The method for preparing the carbon-based Cu-Ni diatomic cluster catalyst according to claim 1, characterized in that: The conditions for the first pyrolysis are: pyrolysis at 800°C~1000°C for 1h~3h.

6. The method for preparing the carbon-based Cu-Ni diatomic cluster catalyst according to claim 1, characterized in that: The conditions for the second pyrolysis are: pyrolysis at 900°C~1200°C for 1h~3h.

7. A carbon-based Cu-Ni diatomic cluster catalyst, characterized in that: The carbon-based Cu-Ni diatomic cluster catalyst is prepared by the preparation method according to any one of claims 1 to 6.

8. The carbon-based Cu-Ni diatomic cluster catalyst according to claim 7, characterized in that: The total number of Cu and Ni metal atoms in the carbon-based Cu-Ni diatomic cluster catalyst is 4 to 9.

9. The carbon-based Cu-Ni diatomic cluster catalyst according to claim 7, characterized in that: In the carbon-based Cu-Ni diatomic cluster catalyst, the diameter of the Cu-Ni diatomic cluster is less than 2nm.

10. Use of the carbon-based Cu-Ni diatomic cluster catalyst according to claim 7 in preparing a catalyst for electrocatalytic CO2 reduction reaction.

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