Copper / nickel-nitrogen-carbon diatomic catalyst, preparation method and application thereof

Abstract

The invention relates to the technical field of carbon material preparation, in particular to a copper / nickel-nitrogen-carbon double-atom catalyst and a preparation method and application thereof.The preparation method includes the steps that copper acetylacetonate and nickel acetylacetonate serve as metal sources, polyacrylonitrile serves as a spinning aid, N, N-dimethylformamide serves as a solvent, polystyrene serves as a pore-foaming agent, the materials are mixed to be uniform and then magnetically stirred for 8 h, and a mixture is obtained; and carrying out electrospinning, placing the obtained film in a carbonization furnace, carrying out air pre-oxidation, and then heating in an argon atmosphere to prepare the copper / nickel-nitrogen-carbon diatomic catalyst. The prepared copper / nickel-nitrogen-carbon double-atom catalyst has an adjustable copper and nickel atom coordination environment, modulation of the copper and nickel metal coordination environment can be achieved by controlling the proportion of copper and nickel metal precursors, and the copper / nickel-nitrogen-carbon double-atom catalyst has excellent catalytic performance.

Description

[0001] This application claims priority to Chinese Patent Application No. 202510909989.6, filed on July 2, 2025, entitled "A copper / nickel-nitrogen-carbon biatom catalyst, preparation method and application thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of carbon material preparation technology, specifically to a copper / nickel-nitrogen-carbon biatom catalyst, its preparation method, and its application. Background Technology

[0003] With the acceleration of industrialization, CO2 emissions have increased year by year, triggering a series of environmental and energy problems. Electrocatalytic CO2 reduction reactions are characterized by mild conditions, a green process, and controllable reaction processes, making them promising for the conversion of CO2 into high-value-added chemicals. Therefore, developing efficient CO2 reduction catalysts is of great significance. In recent years, single-atom catalysts have attracted widespread attention from researchers due to their high atom utilization and excellent catalytic activity. Among them, nickel single atoms have shown high activity in the catalytic reduction of CO2 to CO.

[0004] However, due to the symmetry of the coordination environment, the intrinsic catalytic activity of nickel single-atom catalysts is difficult to further improve, and their catalytic performance at high overpotentials is not ideal. Diatomic catalysts possess asymmetric coordination environments and unique electron cloud arrangements. Copper-based catalysts exhibit unique catalytic activity in electrocatalytic CO2 reduction, and copper single atoms hold promise as promoters for nickel single atoms to further enhance electrocatalytic CO2 reduction activity. However, the coordination environment of nickel / copper diatomic catalysts is difficult to control precisely, which also makes it difficult to establish the structure-activity relationship between it and the electrocatalytic CO2 reduction activity. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of poor catalytic performance caused by the single coordination structure in traditional single-atom catalysts, and to achieve efficient catalysis over a wide potential window. This invention provides a copper / nickel-nitrogen-carbon biatom catalyst, its preparation method, and its application.

[0006] To achieve the above objectives, this invention discloses a method for preparing a copper / nickel-nitrogen-carbon diatomic catalyst, comprising the following steps: S1, Weigh polyacrylonitrile, polystyrene, nickel acetylacetonate, and copper acetylacetonate as solutes, and N,N-dimethylformamide as solvent, mix them evenly and stir to obtain the pre-spinning solution; S2, the pre-spinning solution obtained in step S1 is spun to obtain nanofibers, the nanofibers are placed in a carbonization furnace, heated to 250°C in an air atmosphere, and kept at a constant temperature for 2 h. After the reaction is completed, the air atmosphere is replaced with an argon atmosphere, the temperature is raised to 900°C and kept at a constant temperature for 2 h. After the reaction is completed, the mixture is naturally cooled to room temperature. S3. Take out the product obtained in step S2, wash it with HCl, then wash it with deionized water until neutral, filter and dry to obtain a copper / nickel-nitrogen-carbon biatom catalyst.

[0007] According to the preparation method of a copper / nickel-nitrogen-carbon biatom catalyst provided by the present invention, in step S1, the stirring is carried out by magnetic stirring for a time of 2-8 h.

[0008] According to the preparation method of a copper / nickel-nitrogen-carbon biatom catalyst provided by the present invention, in step S1, the mass ratio of polystyrene to polyacrylonitrile is 1:1, the mass ratio of nickel acetylacetone to polyacrylonitrile is 0.052:1, the mass ratio of copper acetylacetone to polyacrylonitrile is 0.022:1, and the volume mass ratio of N,N-dimethylformamide to polyacrylonitrile is 11.11 mL:1 g.

[0009] According to the preparation method of a copper / nickel-nitrogen-carbon biatom catalyst provided by the present invention, in step S2, spinning is completed in the syringe of an electrospinning machine with a voltage difference of 20 kV, a push speed of 0.1 mm / min, and an ambient temperature of 25℃.

[0010] According to the method for preparing a copper / nickel-nitrogen-carbon diatomic catalyst provided by the present invention, step S2 includes the following steps: Air pre-oxidation: The pre-spinning solution obtained in step S1 is spun into nanofibers. The nanofibers are placed in a carbonization furnace and heated to 250°C in air at a heating rate of 5°C / min, and the reaction is carried out at a constant temperature for 2 hours. Argon pyrolysis and air pre-oxidation reaction were performed. The air atmosphere was replaced with argon atmosphere, and the temperature was increased to 900℃ at a rate of 3℃ / min. The temperature was kept constant for 2 hours. After the reaction was completed, the temperature was naturally cooled to room temperature.

[0011] According to the preparation method of a copper / nickel-nitrogen-carbon biatom catalyst provided by the present invention, in step S3, the HCl concentration is 0.5-3 mol / L and the HCl acid washing time is 4-12 h.

[0012] This invention also discloses a copper / nickel-nitrogen-carbon biatom catalyst prepared by the above method, wherein the copper / nickel-nitrogen-carbon biatom catalyst is a network film composed of interwoven carbon nanofibers with a specific surface area of ​​87 m². 2 / g or more, with a total pore volume of 0.001~0.011cm³. 3 / g.

[0013] The present invention also discloses the application of the above-mentioned copper / nickel-nitrogen-carbon diatomic catalyst in the CO2 electroreduction reaction.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The highly dispersed CuN3-NiN3 catalytic active centers in the copper / nickel-nitrogen-carbon biatom catalyst Ni7Cu3-NC prepared by this invention have high CO2 reduction activity, which lowers the energy barrier for the electroreduction of CO2 to CO. The synergistic effect between the bimetallic sites and the unique electronic structure in CuN3-NiN3 endow it with excellent catalytic activity. 2. The copper / nickel-nitrogen-carbon biatom catalyst prepared by the present invention has a tunable copper and nickel atom coordination environment. By controlling the ratio of copper and nickel metal precursors, the coordination environment of copper and nickel metals can be modulated. 3. The electrocatalytic performance of the copper / nickel-nitrogen-carbon diatomic catalyst prepared in this invention, in an electrolyte of 0.5 mol / L potassium bicarbonate with a nickel / copper acetylacetone mass ratio of 7 / 3, is significantly higher than that of samples with mass ratios of 5 / 5 (Ni5Cu5-NC) and 3 / 7 (Ni3Cu7-NC). The Ni7Cu3-NC sample achieves a Faradaic efficiency of over 93% between -0.8 V and -1.2 V (vs. RHE), and the maximum partial current density for CO reaches 15 mA / cm². 2 The instantaneous switching frequency can reach up to 16,000 h. -1 The above demonstrates excellent catalytic performance; 4. This invention utilizes electrospinning, which has the advantages of simple process and easy industrialization. Attached Figure Description

[0015] Figure 1 The nitrogen adsorption-desorption isotherm of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 2 Scanning electron microscope image of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 3 Aberration-corrected electron microscopy image of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 4 Transmission electron microscopy (TEM) image of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 5The electron paramagnetic resonance spectra of the copper / nickel-nitrogen-carbon biatom catalysts prepared in Examples 1, 2, 6, and 7 of this invention are shown below. Figure 6 The copper / nickel-nitrogen-carbon biatomic sample prepared in Example 1 of this invention and the normalized Ni of the standard sample K -edge X-ray absorption near-edge structure spectrum; Figure 7 The copper / nickel-nitrogen-carbon diatomic sample prepared in Example 1 of this invention and the Ni of the standard sample K -edge Fourier transform X-ray absorption fine structure spectrum; Figure 8 The copper / nickel-nitrogen-carbon diatomic Ni in R space prepared in Example 1 of this invention K -Fitting results of edge Fourier transform X-ray absorption fine structure spectrum; Figure 9 The normalized Cu of the copper / nickel-nitrogen-carbon diatomic sample prepared in Example 1 of this invention and the standard sample K -edge X-ray absorption near-edge structure spectrum; Figure 10 The copper / nickel-nitrogen-carbon diatomic sample prepared in Example 1 of this invention and the Cu of the standard sample K -edge Fourier transform X-ray absorption fine structure spectrum; Figure 11 The copper / nickel-nitrogen-carbon diatomic Cu in R space prepared in Example 1 of this invention K Fitting results of Fourier transform X-ray absorption fine structure spectra of the -edge; Figure 12 The pore size distribution diagram is shown for the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention. Figure 13 The N 1s XPS plot of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 14 The Ni 2p XPS diagram of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 15 The Cu 2p XPS diagram of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; Figure 16 The graph shows the trend of CO Faradaic efficiency of the copper / nickel-nitrogen-carbon diatomic catalyst, nickel-nitrogen-carbon single-atom catalyst and copper-nitrogen-carbon single-atom catalyst prepared in Examples 1-5 of this invention under different applied voltages in an electrolyte of 0.5 mol / L potassium bicarbonate. Figure 17The graph shows the variation trend of CO partial current density of the copper / nickel-nitrogen-carbon diatomic catalyst, nickel-nitrogen-carbon single-atom catalyst and copper-nitrogen-carbon single-atom catalyst prepared in Examples 1-5 of this invention in an electrolyte of 0.5 mol / L potassium bicarbonate under different applied voltages. Detailed Implementation

[0016] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings. Example 1

[0017] The specific preparation process of the copper / nickel-nitrogen-carbon diatomic catalyst Ni7Cu3-NC is as follows: (1) Preparation of pre-spinning solution: Weigh 1.35g polyacrylonitrile, 1.35g polystyrene, 0.07g nickel acetylacetone and 0.03g copper acetylacetone as solutes, measure 15 mL N,N-dimethylformamide as solvent, mix evenly and stir magnetically for 8h.

[0018] Detailed explanation: Interactions of components in the formulation and solution state In the preparation method, polyacrylonitrile and polystyrene, as polymeric auxiliaries and pore-forming agents, are dissolved together with the metal sources nickel acetylacetonate and copper acetylacetonate in the polar organic solvent N,N-dimethylformamide. These solutes exist primarily in N,N-dimethylformamide through physical dissolution and coordination: polyacrylonitrile and polystyrene are dissolved by N,N-dimethylformamide through polar interactions to form a high-viscosity, homogeneous polymeric solution; Ni(acac)₂ and Cu(acac)₂ can coordinate with N,N-dimethylformamide or disperse in the solvent, but do not undergo chemical reactions to form new compounds. The resulting pre-spinning solution is uniformly dispersed and stable, without visible precipitation or stratification, and possesses good conductivity and viscosity, making it suitable for electrospinning. Compared to traditional pre-spinning solutions containing only a single polymer, this solution, by simultaneously introducing polystyrene (as a removable pore template) and metal precursors, achieves the advantages of a porous structure and uniform metal doping in the precursor, resulting in a final fiber / carbide with a high specific surface area and a uniform distribution of metal sites.

[0019] Purpose and function of magnetic stirring During the preparation process, magnetic stirring is used to continuously agitate the mixed solution, primarily to ensure thorough mixing and uniform dispersion of all components. Strong and continuous stirring prevents the precipitation or aggregation of metal precursors (Ni(acac)₂, Cu(acac)₂) and also facilitates the complete integration of polystyrene and polyacrylonitrile, resulting in a polymer-metal composite solution with entangled chains. A homogeneous solution ensures that each nanofiber contains the same proportion of metal and polymer during electrospinning, leading to a catalyst structure with more uniform metal dispersion and a more consistent distribution of reactive sites during subsequent carbonization. Furthermore, thorough stirring accelerates the dissolution process, improves solution stability, prevents precipitation, and enhances the reproducibility of the spinning process and the quality of the final material.

[0020] (2) Preparation of copper / nickel-nitrogen-carbon biatom catalyst: The pre-spinning solution obtained in step (1) was transferred into the syringe of an electrospinning machine for electrospinning. The obtained nanofibers were placed in a carbonization furnace and heated to 250°C at a heating rate of 5°C / min under an air atmosphere and held at that temperature for 2 h. Then, the air atmosphere was replaced with an argon atmosphere and the temperature was increased to 900°C at a heating rate of 3°C / min and held at that temperature for 2 h. After the reaction was completed, the product was naturally cooled to room temperature and taken out. It was then washed with HCl for 8 h, washed with deionized water until neutral, filtered, and dried to obtain the copper / nickel-nitrogen-carbon biatom catalyst. The acetylacetone ligand was thermally decomposed to generate carbonaceous residues and release CO / CH4, etc. These released metal atoms (Ni, Cu) were captured and coordinated by the nitrogen-containing carbon-based framework formed after the carbonization of polyacrylonitrile to generate Ni–N. x and Cu–N y Single-atom structure. Unlike existing Ni-Cu composite catalysts (such as Ni-Cu alloys or Ni single atoms + Cu nanoparticles), the catalyst of this invention has Ni and Cu each coordinated and fixed by nitrogen atoms (which can be regarded as Ni-N-C and Cu-N-C dual sites), and Ni and Cu atoms can be linked by metallic bonds or the proximity effect to exhibit synergistic activity. In short, this system forms a bimetallic single-atom C-N-Ni···Cu-N-C structure with adjacent sites, which is different from traditional Ni-Cu alloy catalysts or simple Ni / Cu composites.

[0021] Reaction process and evolution of diatomic sites during carbonization The carbonization process consists of two steps: low-temperature air pre-oxidation and high-temperature argon atmosphere pyrolysis. In the air pre-oxidation stage (approximately 250°C), the nitrile groups in the polyacrylonitrile polymer undergo oxidative coupling and cyclization reactions, forming a thermally stable heterocyclic polymer structure. The polyacrylonitrile fibers are "fixed" into an infusible structure, retaining their fibrous morphology. Meanwhile, polystyrene gradually begins to thermally decompose into volatile products within this temperature range. Subsequently, when the temperature is raised to approximately 900°C in an inert argon atmosphere, the main carbonization reactions occur: polyacrylonitrile and its crosslinking products lose nitrogen and hydrogen, forming nitrogen-rich carbides; the residual components of polystyrene are almost completely burned off, leaving only pores in the carbides; Ni(acac)₂ and Cu(acac)₂ decompose at high temperature, and the acetylacetone ligands are decomposed into carbonaceous residues and small molecules (CO, CO₂, CH₄, etc.), forming transition metal atoms encapsulated on the carbon matrix. Literature reports that when metal acetylacetone is pyrolyzed in an inert atmosphere, it converts the ligands into a carbonaceous layer and promotes metal reduction, and the generated CO / CH₄ can partially reduce the metal. Ultimately, Ni and Cu atoms exist dispersedly in the form of coordination with nitrogen atoms in the carbon framework. In this patent, the catalyst obtained after acid washing to remove large particles was confirmed by X-ray absorption spectroscopy analysis to contain Ni and Cu in atomically dispersed Ni–N and Cu–N forms. Therefore, the carbon source during carbonization is mainly polyacrylonitrile (and a small amount of carbon residue from polystyrene), and the product is a nitrogen-rich carbon fiber structure in which Ni and Cu atoms gradually evolve and are firmly anchored in the carbon-nitrogen framework, forming bimetallic single-atom cooperative sites.

[0022] The role of air atmosphere pretreatment The introduction of air (oxygen) in the pre-oxidation stage is to promote the stabilization of polyacrylonitrile (PAC). Air oxidation can induce cyclization and dehydrogenation reactions in the PAC molecular chains, forming conjugated aromatic structures and crosslinking with oxygen to generate thermally stable polymer structures, thus maintaining the fiber morphology and preventing melting during subsequent high-temperature carbonization. Without oxygen, heating only in an inert atmosphere will cause PAC to lose its fiber morphology and break down or clump upon melting. In short, the air pre-oxidation stage fixes the backbone of the polymer precursor fibers and may partially oxidize polystyrene and metal ligands, forming a more uniform and stable precursor structure, creating conditions for subsequent high-temperature carbonization. For example, this method explicitly involves first heating to 250°C in an air atmosphere to crosslink the PAC, and then switching to argon for further heating.

[0023] Process considerations for a heating rate of 5℃ / min Choosing a slower heating rate (approximately 5°C / min) during the air pre-oxidation stage ensures the uniformity and controllability of the heat treatment process. A slower heating rate avoids thermal runaway or violent dehydrogenation caused by sudden temperature increases, ensuring synchronous cyclization and cross-linking of polyacrylonitrile across the entire fiber cross-section, thus preserving the intact fiber morphology and structure. Slow heating also helps to evenly distribute the heat of the oxidation reaction, preventing localized overheating that could lead to fiber cracking. Furthermore, low-rate heating facilitates control of reaction kinetics, ensuring that polystyrene gradually decomposes to form pores without causing structural collapse.

[0024] Competitive metal coordination and etching-induced strategies In this invention, a competitive metal coordination and etching-induced strategy is used to construct tunable diatomic active sites. This strategy combines competitive metal coordination with etching-induced microenvironment control to build a Ni / Cu diatomic catalyst with a tunable electronic structure. Heterogeneous coordination units are generated by simultaneously adjusting the Ni:Cu ratio and nitrogen vacancy density in the nitrogen-doped carbon matrix through electrospinning and controlled pyrolysis. Nitrogen vacancies reduce local coordination saturation and form defect-rich anchoring sites, thus affecting the adsorption of Ni and Cu. Under competitive binding, different structural units are stabilized: the Ni-rich (Ni7Cu3-NC) composition favors the coordination of unsaturated M-N3 sites, while the relatively balanced Ni / Cu (Ni5Cu5-NC) composition tends to form M-N4 sites. Polystyrene etching exacerbates these differences: Ni7Cu3-NC forms more defect pores, exposing M-N3 sites; while the etching of Ni5Cu5-NC is more uniform, preserving the M-N4 configuration, thereby achieving precise control over the active sites.

[0025] The necessity of an argon atmosphere An inert gas (argon) atmosphere is used during the high-temperature carbonization stage to prevent the oxidation of the carbon matrix and metal. At temperatures of approximately 900°C, the carbon material will burn in the presence of oxygen or other oxidants, and Ni / Cu will easily oxidize to form metal oxides and become deactivated. Inert argon provides an inert, non-reactive environment, allowing organic matter to pyrolyze and deposit as carbon, while Ni and Cu are not oxidized and can even be partially reduced back to their metallic state by the carbonization atmosphere. Furthermore, the reducing gases such as CO / CH4 produced by the decomposition of acetylacetone ligands in the argon atmosphere can partially reduce Ni and Cu, promoting the formation of single-atom sites. In summary, the use of argon ensures a chemically reducing environment during the carbonization process, contributing to the formation of a uniform metal-nitrogen coordination structure.

[0026] The purpose of controlling the heating rate of 3℃ / min In argon atmosphere, the temperature was slowly increased from approximately 250°C to 900°C at a rate of approximately 3°C / min. This was primarily to precisely control the decomposition and nucleation processes of the metal precursor, further suppressing the aggregation of metal atoms. The extremely slow heating allows the decomposition gases from polyacrylonitrile and polystyrene to escape gradually, reducing fiber breakage. It also allows Ni and Cu atoms to be released at extremely low concentrations and gradually diffuse into the carbon matrix, making them more easily anchored as single atoms by N ligands, rather than rapidly forming large particles. This slow heating strategy is similar to gradient heating in the preparation of conventional single-atom catalysts, which helps to obtain highly dispersed metal single atoms. This indicates that this embodiment uses a heating rate of 3°C / min to 900°C. Therefore, slow heating is beneficial for forming uniformly dispersed Ni–N and Cu–N sites at 900°C, preventing premature aggregation of metals into nanoparticles.

[0027] The copper / nickel-nitrogen-carbon diatomic catalyst Ni7Cu3-NC:CO achieves a Faradaic efficiency of up to 96.6%, with a partial current density of up to 19.6 mA cm⁻¹. -2 The instantaneous conversion frequency for CO generation can reach up to 16583 h. -1 The Tafel slope is 147.7 mV dec -1 . Example 2

[0028] The specific preparation process of the copper / nickel-nitrogen-carbon diatomic catalyst Ni5Cu5-NC is as follows: (1) Preparation of pre-spinning solution: Same as in Example 1, except that 0.05g of nickel acetylacetone and 0.05g of copper acetylacetone reactants are added.

[0029] (2) Preparation of copper / nickel-nitrogen-carbon diatomic catalyst: Same as in Example 1. Preparation of copper / nickel-nitrogen-carbon diatomic catalyst Ni5Cu5-NC. Performance: The highest Faraday efficiency for CO is 96.3%, and the partial current density for CO is 14.6 mA cm⁻¹. -2 The Tafel slope is 199.7 mV dec -1 . Example 3

[0030] The specific preparation process of the copper / nickel-nitrogen-carbon diatomic catalyst Ni3Cu7-NC is as follows: (1) Preparation of pre-spinning solution: Same as in Example 1, except that 0.03g of nickel acetylacetone and 0.07g of copper acetylacetone reactants are added.

[0031] (2) Preparation of copper / nickel-nitrogen-carbon biatom catalyst: same as in Example 1.

[0032] Performance of the copper / nickel-nitrogen-carbon diatomic catalyst Ni3Cu7-NC: The highest Faraday efficiency for CO is 68%, and the partial current density for CO is only 2.9 mA cm⁻¹. -2 The Tafel slope is 434.60 mV dec -1 . Example 4

[0033] The specific preparation process of the nickel-nitrogen-carbon single-atom catalyst Ni-NC is as follows: (1) Preparation of pre-spinning solution: Same as in Example 1, except that only 0.1g of nickel acetylacetone reactant is added, and copper acetylacetone reactant is not added.

[0034] (2) Preparation of nickel-nitrogen-carbon single-atom catalyst: same as in Example 1.

[0035] Performance of the nickel-nitrogen-carbon single-atom catalyst Ni-NC: The highest Faraday efficiency for CO is 90.1%, and the partial current density for CO is 8.9 mA cm⁻¹. -2 The Tafel slope is 294.2 mV dec. -1 . Example 5

[0036] The specific preparation process of the copper-nitrogen-carbon single-atom catalyst Cu-NC is as follows: (1) Preparation of pre-spinning solution: Same as in Example 1, except that only 0.1g of copper acetylacetone reactant is added, and nickel acetylacetone reactant is not added.

[0037] (2) Preparation of copper-nitrogen-carbon single-atom catalyst: Same as in Example 1.

[0038] Performance of the copper-nitrogen-carbon single-atom catalyst Cu-NC: The highest Faraday efficiency for CO is 18.6%, and the partial current density for CO is only 0.39 mA cm⁻¹. -2 The Tafel slope is 507.1 mV dec. -1 . Example 6

[0039] The specific preparation process of the copper / nickel-nitrogen-carbon diatomic catalyst Ni7Cu3-NC (polystyrene-free) is as follows: (1) Preparation of pre-spinning solution: Weigh 1.35g polyacrylonitrile, 0.07g nickel acetylacetonate and 0.03g copper acetylacetonate as solutes, measure 10 mL N,N-dimethylformamide as solvent, mix evenly and stir magnetically for 8h.

[0040] (2) Preparation of copper / nickel-nitrogen-carbon diatomic catalyst Ni7Cu3-NC (polystyrene-free): Same as in Example 1 Performance of the copper / nickel-nitrogen-carbon diatomic catalyst Ni7Cu3-NC (polystyrene-free): The highest Faradaic efficiency for CO is 7.6%, and the partial current density for CO is only 4.9 mA cm⁻¹. -2 The Tafel slope is 467.1 mV dec -1 . Example 7

[0041] The specific preparation process of the copper / nickel-nitrogen-carbon diatomic catalyst Ni5Cu5-NC (polystyrene-free) is as follows: (1) Preparation of pre-spinning solution: Weigh 1.35g polyacrylonitrile, 0.05g nickel acetylacetonate and 0.05g copper acetylacetonate as solutes, measure 10 mL N,N-dimethylformamide as solvent, mix evenly and stir magnetically for 8h.

[0042] (2) Preparation of copper / nickel-nitrogen-carbon diatomic catalyst Ni5Cu5-NC (polystyrene-free): Same as in Example 1 Performance of the copper / nickel-nitrogen-carbon diatomic catalyst Ni5Cu5-NC (polystyrene-free): The highest Faradaic efficiency for CO is 1.2%, and the partial current density for CO is only 0.86 mA cm⁻¹. -2 The Tafel slope is 667.1 mV dec -1 .

[0043] Comparative Example 1 See Hao J, Zhuang Z, Hao J, et al. Strain Relaxation in MetalAlloy Catalysts Steers the Product Selectivity of Electrocatalytic CO2Reduction [J]. ACS Nano, 2022, 16(2): 3251-3263. The prepared s-PdNi / CNFs-800 adopts an alloy strain control strategy. However, PdNi alloy has a strain relaxation effect at high temperature, which leads to limited control of surface electronic structure. Although it can improve CO2 activation ability, it is not economical due to the high proportion of precious metals, high cost and large overpotential.

[0044] Comparative Example 2 See the literature Zhu Z, Li Z, Wang J, et al. Improving NiN Xand Pyridinic NActive Sites with Space-confined Pyrolysis for Effective CO2 Electroreduction[J]. eScience, 2022, 2(4): 445-452. The prepared Ni–N–C has a single Ni–N4 coordination structure, and its electronic environment is symmetrical, making it difficult to simultaneously take into account the adsorption of *COOH and the desorption of *CO, resulting in a high reaction energy barrier.

[0045] Comparative Example 3 See Hao J, Zhuang Z, Hao J, et al. Interatomic Electronegativity Offset Dictates Selectivity When Catalyzing the CO2 Reduction Reaction[J].Advanced Energy Materials, 2022, 12(26): 2200579. The CNFs prepared are simple carbon nanofiber carriers, lacking metal active centers, only providing a conductive network structure, and have extremely low CO2 reduction activity.

[0046] Comparative Example 4 See Hao J, Zhu H, Li Y, et al. Tuning the Electronic Structure of AuNi Homogeneous Solid-solution Alloy with Positively Charged Ni Center for Highly Selective Electrochemical CO2 Reduction[J]. Chemical Engineering Journal, 2021, 404126523. The prepared Au1Ni1 / CNF achieved partial electronic structure regulation through an alloying strategy. Although it can improve the charge state of Ni, the large difference in d-band energy levels between Au and Ni and the uneven electron transfer at the interface limit the stability and economy of the catalyst.

[0047] Comparative Example 5 See the literature Yu W, Zhu J, Chen S, et al. Coupling Ni–Cu atomic pair topromote CO2 electroreduction with near-unity CO selectivity[J]. Environmental Science and Pollution Research, 2023, 51876–51886. NiCu@NCNPs were prepared and Ni–Cu composite sites were constructed through MOF derivatization strategy to achieve local electronic structure regulation. Although this can improve CO selectivity, metal clusters are easy to form and the sites are unstable, which leads to limited long-term catalytic performance.

[0048] Comparative Example 6 See the literature Cheng H, Wu X, Feng M, et al. Atomically Dispersed Ni / Cu DualSites for Boosting the CO2 Reduction Reaction[J]. ACS Catalysis, 2021, 12673−12681. The Ni / Cu-NC prepared by constructing atomically dispersed Ni / Cu dual sites through MOF confinement can achieve atomic-level electronic control. Although it can improve the atomic utilization rate, the site density is limited, resulting in insufficient activity under high current conditions.

[0049] Comparative Example 7 See the literature Wang D, Wang J, Wang Z, et al. Supported Cu / Ni BimetallicCluster Electrocatalysts Boost CO2 Reduction[J]. Precision Chemistry, 2024, 96-102. Cu / Ni-NC was prepared and Cu–Ni bimetallic clusters were constructed by impregnation-heat treatment to achieve bimetallic synergistic effect. Although it can improve the reaction rate, the cluster size is large, the side reactions are enhanced, and the CO selectivity is reduced.

[0050] Comparative Example 8 See the literature Cao X, Hu Y, Hui D, et al. Hydrophobic Nitrogen-Doped Nanocarbon with Cu−Ni Alloy Sites as a Catalyst for CO2 Electroreduction[J].ACS Applied Nano Materials, 2024, 16264-16273. The Cu-Ni / NC prepared by alloying strategy to construct Cu–Ni alloy sites and achieve interfacial electronic structure regulation can improve CO2 mass transfer, but the alloy is prone to reconstruction, which leads to limited catalytic stability.

[0051] Comparative Example 9 See Hao J, Zhuang Z, Hao J, et al. Interatomic Electronegativity Offset Dictates Selectivity When Catalyzing the CO2 Reduction Reaction[J].Advanced Energy Materials, 2022, 12(26): 2200579. CuNi-DSA / CNFs were prepared by constructing CuNi diatomic sites through electrospinning combined with pyrolysis to achieve differential electronegativity control. Although this can optimize the adsorption of intermediates, the coordination environment is difficult to control, resulting in fluctuations in catalytic performance.

[0052]

[0053]

[0054] As shown in Tables 1, 2, and 3, compared to other methods, this invention employs an electrospinning confinement-dual precursor synergistic carbonization process. By precisely controlling the ratio of copper acetylacetonate and nickel acetylacetonate in the spinning system, Cu–Ni diatomic active centers form a CuN3–NiN3 heterocoordination structure within the carbon framework (Ni7Cu3-NC sample). This results in a significant electronic coupling effect and charge redistribution, breaking the linear correlation between the adsorption energies of *COOH and *CO intermediates, improving the activation efficiency of CO2 molecules, and significantly reducing the reaction energy barrier for CO formation. Furthermore, the cross-linked porous carbon nanofiber network constructed using electrospinning technology provides excellent electron conduction and gas diffusion channels, enabling active sites to participate in the reaction efficiently.

[0055] Therefore, the strategy of intermetallic competitive coordination and etching-induced local environment regulation adopted in this invention has the advantages of low cost, high stability and high atomic utilization, which significantly improves the CO2 reduction performance of the catalyst in a wide potential range. Its Faraday efficiency and current density are higher than those of the catalysts shown in Comparative Examples 1 to 9, demonstrating the unique structural design and electronic regulation advantages.

[0056] Figure 1 The figure shows the nitrogen adsorption-desorption isotherm of the copper / nickel-nitrogen-carbon diatomic catalyst prepared in Example 1 of this invention; as can be seen from the figure, the catalyst has a large specific surface area.

[0057] Figure 2 The image shows a scanning electron microscope (SEM) image of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; as can be seen from the image, the catalyst is composed of interwoven nanofibers.

[0058] Figure 3 The image shows a spherical aberration electron microscope image of the copper / nickel-nitrogen-carbon diatomic catalyst prepared in Example 1 of this invention; as can be seen from the image, the catalyst contains a large number of uniformly distributed diatomic sites.

[0059] Figure 4 The image shows a transmission electron microscope (TEM) image of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention. As can be seen from the image, the catalyst has a nanofiber structure and contains axially interconnected channels.

[0060] Figure 5 The electron paramagnetic resonance spectra of the copper / nickel-nitrogen-carbon biatom catalysts prepared in Examples 1, 2, 6 and 7 of this invention are shown in the figure. As can be seen from the figure, Ni7Cu3-NC has the highest nitrogen vacancy content, followed by Ni5Cu5-NC, and both are higher than the polystyrene-free sample.

[0061] Figure 6 The copper / nickel-nitrogen-carbon biatomic sample prepared in Example 1 of this invention and the normalized Ni of the standard sample K -edge X-ray absorption near-edge structure spectrum indicates that the valence state of Ni in Ni7Cu3-NC is between 0 and +2; Figure 7 The copper / nickel-nitrogen-carbon diatomic sample prepared in Example 1 of this invention and the Ni of the standard sample K -edge Fourier transform X-ray absorption fine structure spectrum indicates that Ni species in Ni7Cu3-NC exist in atomically dispersed Ni-N form; Figure 8 The copper / nickel-nitrogen-carbon diatomic Ni in R space prepared in Example 1 of this invention KThe fitting results of the edge Fourier transform X-ray absorption fine structure spectrum show good agreement between the modeling data and the experimental results, indicating the effectiveness of the fitting results.

[0062] Depend on Figure 6-8 The results show that the catalyst contains a Ni-N coordination structure and does not contain Ni particles.

[0063] Figure 9 The normalized Cu of the copper / nickel-nitrogen-carbon diatomic sample prepared in Example 1 of this invention and the standard sample K -edge X-ray absorption near-edge structure spectrum indicates that the valence state of Cu in Ni7Cu3-NC is between 0 and +2; Figure 10 The copper / nickel-nitrogen-carbon diatomic sample prepared in Example 1 of this invention and the Cu of the standard sample K -edge Fourier transform X-ray absorption fine structure spectrum indicates that Cu species in Ni7Cu3-NC exist in the form of atomically dispersed Cu-N; Figure 11 The copper / nickel-nitrogen-carbon diatomic Cu in R space prepared in Example 1 of this invention K The fitting results of the Fourier transform X-ray absorption fine structure spectrum of the -edge showed good agreement between the modeling data and the experimental results, indicating the effectiveness of the fitting results.

[0064] Depend on Figure 9-11 The results show that the catalyst contains a Cu-N coordination structure and does not contain Cu particles.

[0065] Figure 12 The figure shows the pore size distribution of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention; as can be seen from the figure, the catalyst contains a large number of mesoporous structures.

[0066] Figure 13 The N 1s XPS diagram of the copper / nickel-nitrogen-carbon biatom catalyst prepared in Example 1 of this invention is shown in the figure. As can be seen from the figure, the catalyst contains oxidized nitrogen, graphitic nitrogen, pyrrole nitrogen, metallic nitrogen and pyridine nitrogen.

[0067] Figure 14 The image shows the Ni 2p XPS diagram of the copper / nickel-nitrogen-carbon diatomic catalyst prepared in Example 1 of this invention. As can be seen from the figure, the valence state of Ni species in this catalyst is between 0 and +2.

[0068] Figure 15 The image shows the Cu 2p XPS diagram of the copper / nickel-nitrogen-carbon diatomic catalyst prepared in Example 1 of this invention. As can be seen from the figure, the valence state of Cu species in this catalyst is between 0 and +2.

[0069] Figure 16The graph shows the trend of CO Faradaic efficiency of the copper / nickel-nitrogen-carbon diatomic catalyst, nickel-nitrogen-carbon single-atom catalyst, and copper-nitrogen-carbon single-atom catalyst prepared in Examples 1, 2, 3, 4, and 5 of this invention under different applied voltages in an electrolyte of 0.5 mol / L potassium bicarbonate. As can be seen from the graph, the Ni7Cu3-NC catalyst in Example 1 has the highest CO Faradaic efficiency at high overpotential.

[0070] Figure 17 The graph shows the variation trend of the CO partial current density of the copper / nickel-nitrogen-carbon diatomic catalyst, nickel-nitrogen-carbon single-atom catalyst, and copper-nitrogen-carbon single-atom catalyst prepared in Examples 1, 2, 3, 4, and 5 of this invention in an electrolyte of 0.5 mol / L potassium bicarbonate under different applied voltages. As can be seen from the graph, the Ni7Cu3-NC catalyst in Example 1 has the highest CO partial current density.

[0071] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A method for preparing a copper / nickel-nitrogen-carbon biatomic catalyst, characterized by, It comprises the following steps: S1, taking polyacrylonitrile, polystyrene, nickel acetylacetone, copper acetylacetone as solute, N, N-dimethylformamide as solvent, stirring after mixing uniformly to obtain a spinning solution; S2, the nanofiber obtained by spinning the spinning solution obtained in step S1 is placed in a carbonization furnace, heated to 220-280℃ under air atmosphere, constant temperature for 1-3 h reaction, after the reaction is completed, the air atmosphere is changed to argon atmosphere, continue to heat to 900℃, constant temperature for 1-3 h, after the reaction is completed, natural cooling to room temperature; S3, the product obtained in step S2 is taken out, washed with HCl acid, then washed with deionized water to neutral, filtered and dried to obtain copper / nickel-nitrogen-carbon double atom catalyst.

2. The method for preparing a copper / nickel-nitrogen-carbon biatom catalyst as described in claim 1, characterized in that, In the step S1, magnetic stirring is used for stirring, and the stirring time is 2-8 h.

3. The method for preparing a copper / nickel-nitrogen-carbon diatomic catalyst as described in claim 1, characterized in that, In the step S1, the mass ratio of polystyrene to polyacrylonitrile is 1:1, the mass ratio of nickel acetylacetone to polyacrylonitrile is 0.052~0.022:1, the mass ratio of copper acetylacetone to polyacrylonitrile is 0.022~0.052:1, and the volume mass ratio of N, N-dimethylformamide to polyacrylonitrile is 11.11 mL:1 g.

4. The method for preparing a copper / nickel-nitrogen-carbon diatomic catalyst as described in claim 1, characterized in that, In the step S2, the spinning is completed in the needle cylinder of the electrospinning machine, the voltage difference is 20 kV, the injection speed is 0.1 mm / min, and the environmental temperature is 25℃.

5. The method for preparing a copper / nickel-nitrogen-carbon biatom catalyst as described in claim 1, characterized in that, In the step S2, it comprises the following steps: Air pre-oxidation, the nanofiber obtained by spinning the spinning solution obtained in step S1 is placed in a carbonization furnace, heated to 250℃ at a heating rate of 5℃ / min under air atmosphere, constant temperature for 2 h reaction; Argon pyrolysis, after the air pre-oxidation reaction is completed, the air atmosphere is changed to argon atmosphere, heated to 900℃ at a heating rate of 3℃ / min, constant temperature for 2 h, after the reaction is completed, natural cooling to room temperature.

6. The method for preparing a copper / nickel-nitrogen-carbon biatom catalyst as described in claim 1, characterized in that, In the step S3, the concentration of HCl is 0.5-3 mol / L, and the HCl acid washing time is 4~12 h.

7. A copper / nickel-nitrogen-carbon bi-metallic atomic catalyst prepared by the method of any one of claims 1 to 6, wherein the copper / nickel-nitrogen-carbon bi-metallic atomic catalyst is characterized by: The copper / nickel-nitrogen-carbon bi-atomic catalyst is a reticular film composed of interlaced carbon nanofibers, with a specific surface area of 87 m 2 / g or more and a total pore volume of 0.001 to 0.011 cm 3 / g.

8. The copper / nickel-nitrogen-carbon double atom catalyst of claim 7 in the application of CO2 electro-reduction reaction.

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