A method for synthesizing an active site tunable bimetallic catalyst

Abstract

The present application relates to the technical field of catalyst, in particular to a synthesis method of active site adjustable bimetallic catalyst.The synthesis method of active site adjustable bimetallic catalyst comprises the following steps: synthesizing ligand;preparing bimetallic complex;limiting domain pyrolysis carbonization.The present application first takes p-tert-butylphenol, polyformaldehyde and bis(2-pyridylmethyl)amine as raw materials, reacts in a mixed solvent to synthesize ligand Hbpbp, then sequentially reacts with metal salt in methanol by a stepwise coordination method to construct homonuclear or heteronuclear bimetallic complex, finally uniformly mixes the complex with carbon black and dicyandiamide, and performs programmed temperature carbonization under inert atmosphere to prepare bimetallic catalyst with atomic level dispersion structure, realizes accurate anchoring and stable loading of bimetallic sites on the carbon carrier, and not only has high activity and stability in electrocatalytic carbon dioxide reduction reaction, but also can efficiently activate peroxymonosulfate for pollutant degradation.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and specifically to a method for synthesizing a bimetallic catalyst with tunable active sites. Background Technology

[0002] With the global energy structure transitioning towards cleaner energy, CO2RR has attracted significant attention as a key technology for achieving carbon recycling. However, the large-scale application of this technology is constrained by the development of efficient, stable, and low-cost electrocatalysts. On the other hand, in the field of environmental catalysis, advanced oxidation technologies based on persulfate (PMS) have become a research hotspot due to their enormous potential in treating recalcitrant organic pollutants, and their core also lies in developing catalysts capable of efficiently activating PMS.

[0003] Currently, non-precious metal catalysts, especially MNC materials, are considered ideal substitutes for precious metals in both of the aforementioned fields due to their abundant resources and tunable structures. While atomically dispersed single-atom catalysts possess extremely high atom utilization, their single active site often struggles to simultaneously optimize all reaction steps in multi-step, complex reactions (such as the multi-electron reduction of CO2RR or the heterogeneous activation of PMS), leading to performance limitations. To overcome this bottleneck, research focus is gradually shifting towards biatomic catalysts. By constructing tunable bimetallic sites (M1M2), the electronic structure and coordination environment of the active center can be precisely controlled, thereby optimizing the adsorption behavior of key reaction intermediates, effectively reducing reaction energy barriers, and providing a more flexible catalyst design platform for simultaneously improving the activation performance of CO2RR and PMS.

[0004] Patent CN119243211A discloses a flower-like heteronuclear bimetallic atom catalyst. It successfully prepared a Ru-Mo biatomic catalyst with a flower-like morphology using a process involving organic encapsulation, one-step blending, high-temperature carbonization, and alkaline etching. This catalyst exhibited excellent activity and Tafel kinetics in alkaline HER. However, this method still presents challenges in precisely controlling the metal sites and uniformly regulating the coordination environment, and its structure depends on the self-assembly of specific morphologies and subsequent etching steps.

[0005] Therefore, there is a need to propose a method for synthesizing bimetallic catalysts with tunable active sites that allow for precise anchoring and stable loading of bimetallic sites on carbon supports. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for synthesizing bimetallic catalysts with tunable active sites.

[0007] This invention provides a method for synthesizing a bimetallic catalyst with tunable active sites, comprising the following steps:

[0008] (1) Synthesis of ligands: Under an argon atmosphere, para-substituted phenol derivatives, aldehydes and amines containing pyridine groups are fully reacted in an alcohol-water mixed solvent, and then post-processed to obtain powdered Hbpbp ligands;

[0009] (2) Preparation of bimetallic complexes: The Hbpbp ligands obtained in step (1) are sequentially coordinated with the first metal salt and the second metal salt in an organic solvent to generate complexes containing bimetallic centers.

[0010] (3) Confined domain pyrolysis carbonization: The bimetallic complex obtained in step (2) is mixed with carbon black and dicyandiamide and pyrolyzed under an inert atmosphere to obtain a bimetallic catalyst.

[0011] Further, the phenolic compound is selected from one or more of phenol, p-cresol, p-tert-butylphenol, p-tert-octylphenol, p-nonylphenol, and 2,4-di-tert-butylphenol; the aldehyde compound is selected from formaldehyde, paraformaldehyde, trioxyformaldehyde, acetaldehyde, or glyoxal; and the amine compound containing a pyridine group is di(2-pyridylmethyl)amine or a derivative thereof.

[0012] Furthermore, the first metal salt and the second metal salt are each independently selected from nitrates, halides (chlorides, bromides, iodides), sulfates, perchlorates, acetates, acetylacetones, or trifluoromethanesulfonates of transition metals including Fe, Co, Ni, Cu, Mn, Zn, Cr, V, or noble metals including Ru, Rh, Pd, Ir, Pt, Ag, Au.

[0013] Furthermore, the organic solvent is selected from one or a mixture of C1-C4 alcohols (such as methanol, ethanol, isopropanol), acetonitrile, acetone, tetrahydrofuran, N,N-dimethylformamide, and dimethyl sulfoxide.

[0014] Further, the mass ratio of the bimetallic complex, carbon black and dicyandiamide is (0.01-0.5):1:(5-30).

[0015] Further, the mass ratio of the bimetallic complex, carbon black and dicyandiamide is (0.02-0.2):1:(10-20).

[0016] Further, the pyrolysis treatment in step (3) includes: pre-carbonization stage: holding at 250-600℃ for 0.5-5 hours to achieve thermal cross-linking of ligands and preliminary anchoring of metal sites; main carbonization stage: holding at 650-1000℃ for 1-10 hours to complete the graphitization reconstruction of carbon skeleton and the final formation of active sites; heating rate: controlling the heating rate at 1-20 ℃ / min between each stage.

[0017] Further, the pyrolysis treatment in step (3) includes: pre-carbonization stage: holding at 300-500 ℃ for 0.5-5 hours to achieve thermal cross-linking of ligands and preliminary anchoring of metal sites; main carbonization stage: holding at 700-900 ℃ for 1-10 hours to complete the graphitization reconstruction of carbon skeleton and the final formation of active sites; heating rate: controlling the heating rate at 2-10 ℃ / min between each stage.

[0018] Furthermore, the bimetallic catalyst comprises a nitrogen-doped carbon substrate and bimetallic active centers anchored thereon.

[0019] Furthermore, the bimetallic active centers exist in an atomically dispersed form and do not contain any metallic elemental or metallic compound crystalline phases that can be detected by X-ray diffraction; characterization by high-angle annular dark-field scanning transmission electron microscopy shows that more than 50% of the visible metal species exhibit a paired morphology.

[0020] The present invention has the following advantages:

[0021] 1. This invention first uses p-tert-butylphenol, paraformaldehyde, and di(2-pyridylmethyl)amine as raw materials to synthesize the ligand Hbpbp in a mixed solvent. Then, it reacts sequentially with metal salts in methanol via a stepwise coordination method to construct homonuclear or heteronuclear bimetallic complexes. Finally, the complexes are uniformly mixed with carbon black and dicyandiamide and carbonized under a programmed temperature rise in an inert atmosphere to obtain an M1 / M2-NC catalyst with an atomically dispersed structure. This achieves precise anchoring and stable loading of bimetallic sites on a carbon support, resulting in a catalyst with high activity and stability in electrocatalytic carbon dioxide reduction reactions and efficient activation of persulfate for pollutant degradation. It also has advantages such as precise and controllable structure, high atomic utilization, and low cost.

[0022] 2. This invention first constructs a well-defined bimetallic complex through stepwise coordination. Then, it uses carbon black and dicyandiamide for hierarchical coating and gradient carbonization treatment to successfully transform it into an atomically dispersed M1 / M2-NC catalyst. This approach has significant advantages in terms of atomic precision, controllability of metal sites, and uniformity of coordination environment. It can not only effectively avoid metal agglomeration, but also achieve precise construction and synergistic control of bimetallic sites, providing an innovative solution to overcome the problem of structural controllability of biatomic catalysts. Attached Figure Description

[0023] Figure 1 The figures show the XRD patterns of the bimetallic catalyst precursor (Cu-Cu-Hbpbp) and different types of catalysts obtained in Example 1; in the figure, a) is the XRD pattern of Cu-Cu-Hbpbp, and b) is the XRD pattern of four samples: Cu-NC, Cu-Cu-NC, Cu-Ni-NC and NC.

[0024] Figure 2 This is a SEM image of the bimetallic catalyst (Cu-Cu-NC) obtained in Example 1.

[0025] Figure 3 The image shows the HAADF-STEM characterization of the bimetallic catalyst (Cu-Cu-NC) obtained in Example 1; in the image, a) is the HAADF-STEM image, with red ellipses marking the Cu double sites; in the image, b) is the distance distribution of site 1 and site 2, with Cu-Cu spacings of 2.72 Å and 2.61 Å, respectively.

[0026] Figure 4 The image shows the EDS-mapping elemental distribution of the bimetallic catalyst (Cu-Cu-NC) obtained in Example 1; the elemental mapping of the corresponding regions shows that Cu species are uniformly dispersed in the C and N matrices.

[0027] Figure 5 The image shows the XPS spectra of the bimetallic catalyst obtained in Example 1; in the image, a) is the C 1s fine spectrum and b) is the N 1s fine spectrum.

[0028] Figure 6 The figure shows the synchrotron radiation spectrum of the bimetallic catalyst obtained in Example 1; in the figure a) are the normalized XANES spectra of Cu foil, Cu2O, CuO and Cu-Cu-NC; in the figure b) are the corresponding XANES spectra. 3 Weighted EXAFS Fourier transform spectrum.

[0029] Figure 7 The graph shows the electrocatalytic performance data of the bimetallic catalyst obtained in Example 1; that is, the product distribution and current density of Cu-Cu-NC and Cu-NC at different potentials; in the figure, a) is Cu-Cu-NC; and b) is Cu-NC.

[0030] Figure 8 Figure 1 shows the data of pollutant degradation by activated PMS using the bimetallic catalyst obtained in Example 1; Figure a) shows the degradation curves (I / I0 - time) of the target pollutant by Cu-Cu-NC, Cu-NC, and NC; Figure b) shows the removal rate and apparent rate constant (I) of Cu-Cu-NC for different pollutants. obs )statistics. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0032] Example 1: A method for synthesizing a bimetallic catalyst with tunable active sites, comprising the following steps:

[0033] (1) Under argon protection, 6 g of p-tert-butylphenol and 2.90 g of paraformaldehyde were added to a 500 mL three-necked flask, followed by the addition of a mixed solvent of 210 mL of anhydrous ethanol and 90 mL of deionized water. The mixture was stirred until homogeneous, and 17.09 g of di(2-pyridylmethyl)amine was slowly added. The reaction mixture was heated to reflux and stirred continuously at this temperature for 4 days. After the reaction was completed, most of the solvent was removed by vacuum evaporation. The remaining aqueous phase was extracted three times with 100 mL of dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate for 3 hours, and then filtered. The filtrate was concentrated under vacuum to obtain a light brownish-yellow oil. The oil was then dissolved in a small amount of dichloromethane, and n-hexane was added. The product was precipitated by rotary evaporation. The solid was collected by filtration, washed with acetonitrile, and finally recrystallized from dichloromethane and n-hexane to obtain a white powder of Hbpbp ligand.

[0034] (2) Dissolve 286 mg of Hbpbp synthesized in step (1) in 2 mL of methanol to obtain Hbpbp solution. Then dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the Hbpbp solution while stirring at room temperature. The solution immediately turns light blue. Continue stirring vigorously for 3 hours to generate mononuclear Cu-Hbpbp intermediate. Then, dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the above mononuclear Cu-Hbpbp intermediate solution to form Cu-Cu bimetallic center. After the addition is complete, the reaction system is stirred overnight at room temperature to ensure complete reaction. Add 20 mL of ethyl acetate to the reaction mixture and let it stand for several days to precipitate crystals. Filter and collect the crystals, wash with cold methanol, and dry to obtain bimetallic complex (copper-copper precursor) Cu-Cu-Hbpbp.

[0035] (3) The bimetallic complex obtained in step (2) is physically mixed with carbon black and dicyandiamide at a mass ratio of 0.1:1:10 and ground thoroughly. Then, it is placed in a tube furnace and heated to 400°C at a rate of 5°C / min under an argon atmosphere and held at this temperature for 1 hour (pre-carbonization). Then, the temperature is raised to 800°C at the same rate and held for 2 hours (main carbonization). After naturally cooling to room temperature, the target bimetallic catalyst Cu-Cu-NC (Cu-DACs) is obtained.

[0036] Example 2, a method for synthesizing a bimetallic catalyst with tunable active sites, includes the following steps:

[0037] (1) Under argon protection, 6 g of p-tert-butylphenol and 2.90 g of paraformaldehyde were added to a 500 mL three-necked flask, followed by the addition of a mixed solvent of 210 mL of anhydrous ethanol and 90 mL of deionized water. The mixture was stirred until homogeneous, and 17.09 g of di(2-pyridylmethyl)amine was slowly added. The reaction mixture was heated to reflux and stirred continuously at this temperature for 4 days. After the reaction was completed, most of the solvent was removed by vacuum evaporation. The remaining aqueous phase was extracted three times with 100 mL of dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate for 3 hours, and then filtered. The filtrate was concentrated under vacuum to obtain a light brownish-yellow oil. The oil was then dissolved in a small amount of dichloromethane, and n-hexane was added. The product was precipitated by rotary evaporation. The solid was collected by filtration, washed with acetonitrile, and finally recrystallized from dichloromethane and n-hexane to obtain a white powder of Hbpbp ligand.

[0038] (2) Dissolve 286 mg of Hbpbp synthesized in step (1) in 2 mL of methanol to obtain Hbpbp solution. Then dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the Hbpbp solution while stirring at room temperature. The solution immediately turns light blue. Continue stirring vigorously for 3 hours to generate mononuclear Cu-Hbpbp intermediate. Then dissolve 183 mg of Ni(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the above mononuclear Cu-Hbpbp intermediate solution. The solution color changes from light blue to dark green, indicating that heteronuclear Cu-Ni bimetallic center is formed. After the dropwise addition is completed, the reaction system is stirred overnight at room temperature to ensure complete reaction. Add 20 mL of ethyl acetate to the reaction mixture and let it stand for several days to precipitate crystals. Filter and collect the crystals, wash with cold methanol, and dry to obtain bimetallic complex (copper-nickel precursor) Cu-Cu-Hbpbp.

[0039] (3) The bimetallic complex obtained in step (2) is physically mixed with carbon black and dicyandiamide at a mass ratio of 0.1:1:10 and ground thoroughly. Then it is placed in a tube furnace and heated to 400°C at a rate of 5°C / min under an argon atmosphere and held at this temperature for 1 hour (pre-carbonization). Then it is heated to 800°C at the same rate and held for 2 hours (main carbonization). After naturally cooling to room temperature, the target bimetallic catalyst Cu-Ni-NC is obtained.

[0040] Example 3, a method for synthesizing a bimetallic catalyst with tunable active sites, comprising the following steps:

[0041] (1) Under argon protection, 6 g of p-tert-butylphenol and 2.90 g of paraformaldehyde were added to a 500 mL three-necked flask, followed by the addition of a mixed solvent of 210 mL of anhydrous ethanol and 90 mL of deionized water. The mixture was stirred until homogeneous, and 17.09 g of di(2-pyridylmethyl)amine was slowly added. The reaction mixture was heated to reflux and stirred continuously at this temperature for 4 days. After the reaction was completed, most of the solvent was removed by vacuum evaporation. The remaining aqueous phase was extracted three times with 100 mL of dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate for 3 hours, and then filtered. The filtrate was concentrated under vacuum to obtain a light brownish-yellow oil. The oil was then dissolved in a small amount of dichloromethane, and n-hexane was added. The product was precipitated by rotary evaporation. The solid was collected by filtration, washed with acetonitrile, and finally recrystallized from dichloromethane and n-hexane to obtain a white powder of Hbpbp ligand.

[0042] (2) Dissolve 286 mg of Hbpbp synthesized in step (1) in 2 mL of methanol to obtain Hbpbp solution. Then dissolve 183 mg of Ni(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the Hbpbp solution while stirring at room temperature. The solution immediately turns light green. Continue stirring vigorously for 3 hours to generate mononuclear Ni-Hbpbp intermediate. Then dissolve 256 mg of Fe(ClO4)3·9H2O in 5 mL of methanol and slowly add it dropwise to the above light green solution. The solution color changes from light green to dark green, indicating that heteronuclear bimetallic center is formed. After the addition is complete, continue stirring at room temperature overnight to ensure complete reaction. Add 20 mL of ethyl acetate to the reaction mixture and let it stand for several days to precipitate crystals. Filter and collect the crystals, wash with cold methanol, and dry to obtain bimetallic complex (iron-nickel precursor) Fe-Ni-Hbpbp.

[0043] (3) The bimetallic complex obtained in step (2) is physically mixed with carbon black and dicyandiamide at a mass ratio of 0.1:1:10 and ground thoroughly. Then it is placed in a tube furnace and heated to 400°C at a rate of 5°C / min under an argon atmosphere and held at this temperature for 1 hour (pre-carbonization). Then it is heated to 800°C at the same rate and held for 2 hours (main carbonization). After naturally cooling to room temperature, the target bimetallic catalyst Fe-Ni-NC is obtained.

[0044] Example 4, a method for synthesizing a bimetallic catalyst with tunable active sites (precursor ratio control), comprising the following steps:

[0045] (1) Under argon protection, 6 g of p-tert-butylphenol and 2.90 g of paraformaldehyde were added to a 500 mL three-necked flask, followed by the addition of a mixed solvent of 210 mL of anhydrous ethanol and 90 mL of deionized water. The mixture was stirred until homogeneous, and 17.09 g of di(2-pyridylmethyl)amine was slowly added. The reaction mixture was heated to reflux and stirred continuously at this temperature for 4 days. After the reaction was completed, most of the solvent was removed by vacuum evaporation. The remaining aqueous phase was extracted three times with 100 mL of dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate for 3 hours, and then filtered. The filtrate was concentrated under vacuum to obtain a light brownish-yellow oil. The oil was then dissolved in a small amount of dichloromethane, and n-hexane was added. The product was precipitated by rotary evaporation. The solid was collected by filtration, washed with acetonitrile, and finally recrystallized from dichloromethane and n-hexane to obtain a white powdery Hbpbp ligand bimetallic complex (copper-copper precursor) Cu-Cu-Hbpbp.

[0046] (2) Dissolve 286 mg of Hbpbp synthesized in step (1) in 2 mL of methanol to obtain Hbpbp solution. Then dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the Hbpbp solution while stirring at room temperature. The solution immediately turns light blue. Continue stirring vigorously for 3 hours to generate a mononuclear Cu-Hbpbp intermediate. Then dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the above mononuclear Cu-Hbpbp intermediate solution to form Cu-Cu bimetallic center. After the addition is complete, the reaction system is stirred overnight at room temperature to ensure complete reaction. Add 20 mL of ethyl acetate to the reaction mixture and let it stand for several days to precipitate crystals. Filter and collect the crystals, wash with cold methanol, and dry to obtain bimetallic complex.

[0047] (3) The bimetallic complex obtained in step (2) is physically mixed with carbon black and dicyandiamide at a mass ratio of 0.2:1:10 and ground thoroughly. Then it is placed in a tube furnace and heated to 400°C at a rate of 5°C / min under an argon atmosphere and held at this temperature for 1 hour (pre-carbonization). Then it is heated to 800°C at the same rate and held for 2 hours (main carbonization). After naturally cooling to room temperature, the target bimetallic catalyst Cu-Cu-NC is obtained.

[0048] Example 5, a method for synthesizing a bimetallic catalyst with tunable active sites (temperature control of black carbide), comprising the following steps:

[0049] (1) Under argon protection, 6 g of p-tert-butylphenol and 2.90 g of paraformaldehyde were added to a 500 mL three-necked flask, followed by the addition of a mixed solvent of 210 mL of anhydrous ethanol and 90 mL of deionized water. The mixture was stirred until homogeneous, and 17.09 g of di(2-pyridylmethyl)amine was slowly added. The reaction mixture was heated to reflux and stirred continuously at this temperature for 4 days. After the reaction was completed, most of the solvent was removed by vacuum evaporation. The remaining aqueous phase was extracted three times with 100 mL of dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate for 3 hours, and then filtered. The filtrate was concentrated under vacuum to obtain a light brownish-yellow oil. The oil was then dissolved in a small amount of dichloromethane, and n-hexane was added. The product was precipitated by rotary evaporation. The solid was collected by filtration, washed with acetonitrile, and finally recrystallized from dichloromethane and n-hexane to obtain a white powder of Hbpbp ligand.

[0050] (2) Dissolve 286 mg of Hbpbp synthesized in step (1) in 2 mL of methanol to obtain Hbpbp solution. Then dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the Hbpbp solution while stirring at room temperature. The solution immediately turns light blue. Continue stirring vigorously for 3 hours to generate mononuclear Cu-Hbpbp intermediate. Then, dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the above mononuclear Cu-Hbpbp intermediate solution to form Cu-Cu bimetallic center. After the addition is complete, the reaction system is stirred overnight at room temperature to ensure complete reaction. Add 20 mL of ethyl acetate to the reaction mixture and let it stand for several days to precipitate crystals. Filter and collect the crystals, wash with cold methanol, and dry to obtain bimetallic complex (copper-copper precursor) Cu-Cu-Hbpbp.

[0051] (3) The bimetallic complex obtained in step (2) is physically mixed with carbon black and dicyandiamide at a mass ratio of 0.1:1:10 and ground thoroughly. Then it is placed in a tube furnace and heated to 400°C at a rate of 5°C / min under an argon atmosphere and held at this temperature for 2 hours (pre-carbonization). Then it is heated to 800°C at the same rate and held for 4 hours (main carbonization). After naturally cooling to room temperature, the target bimetallic catalyst Cu-Cu-NC is obtained.

[0052] Example 6, a method for synthesizing a bimetallic catalyst with tunable active sites (carbonization temperature control), comprising the following steps:

[0053] (1) Under argon protection, 6 g of p-tert-butylphenol and 2.90 g of paraformaldehyde were added to a 500 mL three-necked flask, followed by the addition of a mixed solvent of 210 mL of anhydrous ethanol and 90 mL of deionized water. The mixture was stirred until homogeneous, and 17.09 g of di(2-pyridylmethyl)amine was slowly added. The reaction mixture was heated to reflux and stirred continuously at this temperature for 4 days. After the reaction was completed, most of the solvent was removed by vacuum evaporation. The remaining aqueous phase was extracted three times with 100 mL of dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate for 3 hours, and then filtered. The filtrate was concentrated under vacuum to obtain a light brownish-yellow oil. The oil was then dissolved in a small amount of dichloromethane, and n-hexane was added. The product was precipitated by rotary evaporation. The solid was collected by filtration, washed with acetonitrile, and finally recrystallized from dichloromethane and n-hexane to obtain a white powder of Hbpbp ligand.

[0054] (2) Dissolve 286 mg of Hbpbp synthesized in step (1) in 2 mL of methanol to obtain Hbpbp solution. Then dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the Hbpbp solution while stirring at room temperature. The solution immediately turns light blue. Continue stirring vigorously for 3 hours to generate mononuclear Cu-Hbpbp intermediate. Then, dissolve 185 mg of Cu(ClO4)2·6H2O in 5 mL of methanol and slowly add it dropwise to the above mononuclear Cu-Hbpbp intermediate solution to form Cu-Cu bimetallic center. After the addition is complete, the reaction system is stirred overnight at room temperature to ensure complete reaction. Add 20 mL of ethyl acetate to the reaction mixture and let it stand for several days to precipitate crystals. Filter and collect the crystals, wash with cold methanol, and dry to obtain bimetallic complex (copper-copper precursor) Cu-Cu-Hbpbp.

[0055] (3) The bimetallic complex obtained in step (2) is physically mixed with carbon black and dicyandiamide at a mass ratio of 0.1:1:10 and ground thoroughly. Then it is placed in a tube furnace and heated to 300°C at a rate of 5°C / min under an argon atmosphere and held at this temperature for 1 hour (pre-carbonization). Then it is heated to 800°C at the same rate and held for 2 hours (main carbonization). After naturally cooling to room temperature, the target bimetallic catalyst Cu-Cu-NC is obtained.

[0056] Comparative Example 1: A single-metal catalyst and its NC synthesis method, comprising the following steps:

[0057] 100 mg of carbon black, 88.7 mg of Cu(NO3)2·6H2O, and 1000 mg of glucose were dispersed in 5 mL of deionized water, followed by sonication for 0.5 hours to form a homogeneous black suspension. This suspension was then freeze-dried to obtain a black flocculent solid, which was then thoroughly ground and mixed with dicyandiamide at a mass ratio of 1:5. The mixture was then pyrolyzed at 800 °C for 2 hours under a flowing argon atmosphere at a heating rate of 5 °C / min to finally obtain the single-metal catalyst Cu-NC. The synthesis of NC was the same except that no metal source (Cu(NO3)2·6H2O) was added.

[0058] Verification example:

[0059] Taking Example 1 and Comparative Example 1 as examples, the performance of the prepared homonuclear bimetallic catalysts was tested, specifically as follows:

[0060] XRD ( Figure 1 The following diagram illustrates the XRD characteristics of the precursor and the pyrolysis sample. a) The Cu-Cu-Hbpbp precursor exhibits sharp diffraction peaks in the low-angle region, indicating its high crystallinity and well-defined long-range ordered structure. b) Cu-NC, Cu-Cu-NC, Cu-Ni-NC, and NC all show broad, diffuse peaks at approximately 20-30° (corresponding to the amorphous / low-graphitization structural characteristics of carbon materials), and only weak, broad peaks in the high-angle region, indicating that the main body after pyrolysis is an amorphous nitrogen-doped carbon framework.

[0061] SEM ( Figure 2 Cu-Cu-NC exhibits a distinct morphology of wrinkled lamellar / thin-walled carbon framework, with the lamellars stacked on top of each other to form open cavities and interconnected gaps. This loose porous structure facilitates electrolyte wetting and reactant diffusion, and provides a large accessible surface area, thereby improving mass transfer and interfacial reaction efficiency in catalytic reactions.

[0062] HAADF-STEM Figure 3 As observed by HAADF-STEM, the bright spots are dispersed in pairs within the carbon matrix, with no obvious large particle aggregation, indicating that the copper species maintain a high degree of dispersion after pyrolysis. The line scan distances of the two representative sites are 2.72 Å and 2.61 Å, respectively, both at the nearest-neighbor diatomic scale, supporting the existence of a stable Cu-Cu dual-site configuration in the sample.

[0063] SEM-EDS elemental mapping of Cu-Cu-NC ( Figure 4 The distribution of C, N, and Cu elements in the corresponding region shows that C and N are continuously distributed in the carbon framework, while the Cu signal is diffuse and dispersed within the field of view, with no obvious local enrichment observed.

[0064] XPS ( Figure 5 In the figure, a) C 1s spectrum, all three samples are expressed as sp. 2 The dominant peak is CC / C=C, accompanied by secondary components such as CN / CO, indicating that a nitrogen-containing carbon support with a carbon skeleton as the main component was formed after pyrolysis. In addition, b) N 1s fitting shows that it can be distributed into components such as pyridine N, pyrrole N, graphitic N and metal coordinated N (M-Nx); among them, the coordinated N signal is more prominent in Cu-Cu-NC, pointing to a more complete Cu-N anchoring effect.

[0065] Cu K edge ( Figure 6 In XANES, the absorption edge of Cu-Cu-NC is located between the Cu foil and the copper oxide reference, indicating that Cu aggregates predominantly in the positive oxidation state rather than the metallic state. The corresponding 𝑘 3 The weighted EXAFS Fourier transform spectrum shows a significant Cu-N coordination peak in the low R region, while a weak Cu-Cu scattering signal is observed in the higher R region, indicating that the sample simultaneously possesses a Cu-N dominant coordination environment and a nearest-neighbor Cu-Cu interaction. This "Cu-N + Cu-Cu" cooperative coordination feature corroborates the nearest-neighbor double copper sites observed in HAADF, supporting the structure of Cu-Cu-NC, which is dominated by atomically dispersed double sites and stabilized by N coordination.

[0066] LSV curve ( Figure 7 In a CO2-saturated 0.5M KHCO3 solution, the product distribution is as follows: at a potential of -0.8V, the main product of Cu-NC is CO (FE ~80%); while the main products of Cu-Cu-NC are converted to ethylene and ethanol (C). 2+ Total FE ~55%. Cu-Cu-NC exhibits greater technological potential and application prospects than Cu-NC.

[0067] PMS activation and degradation performance ( Figure 8 Degradation kinetics: In the experiment of degrading sulfadiazine (SD), Cu-Cu-NC exhibited the highest reaction rate constant (k=0.15 min). -1 ), is Cu-NC (0.04 min -1 It is nearly four times that of ).

[0068] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for synthesizing a bimetallic catalyst with tunable active sites, characterized in that, Includes the following steps: (1) Synthesis of ligands: Under an argon atmosphere, phenolic compounds, aldehyde compounds and amine compounds containing pyridine groups are fully reacted in an alcohol-water mixed solvent, and then powdered Hbpbp ligands are obtained after post-treatment. (2) Preparation of bimetallic complexes: The Hbpbp ligands obtained in step (1) are sequentially coordinated with the first metal salt and the second metal salt in an organic solvent to generate complexes containing bimetallic centers. (3) Confined domain pyrolysis carbonization: The bimetallic complex obtained in step (2) is mixed with carbon black and dicyandiamide and pyrolyzed under an inert atmosphere to obtain a bimetallic catalyst. The phenolic compounds are selected from one or more of phenol, p-cresol, p-tert-butylphenol, p-tert-octylphenol, p-nonylphenol, and 2,4-di-tert-butylphenol; the aldehyde compounds are selected from formaldehyde, paraformaldehyde, triformaldehyde, acetaldehyde, or glyoxal; and the amine compounds containing pyridine groups are di(2-pyridylmethyl)amine or its derivatives.

2. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The first metal salt and the second metal salt are each independently selected from nitrates, halides, sulfates, perchlorates, acetates, acetylacetones, or trifluoromethanesulfonates of transition metals including Fe, Co, Ni, Cu, Mn, Zn, Cr, V or noble metals including Ru, Rh, Pd, Ir, Pt, Ag, Au, and the halides include chlorides, bromides, or iodides.

3. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The organic solvent is selected from at least one of C1-C4 alcohols, acetonitrile, acetone, tetrahydrofuran, N,N-dimethylformamide, and dimethyl sulfoxide, wherein the C1-C4 alcohols include methanol, ethanol, or isopropanol.

4. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The mass ratio of the bimetallic complex, carbon black, and dicyandiamide is (0.01-0.5):1:(5-30).

5. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The mass ratio of the bimetallic complex, carbon black, and dicyandiamide is (0.02-0.2):1:(10-20).

6. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The pyrolysis treatment described in step (3) includes: pre-carbonization stage: holding at 250-600℃ for 0.5-5 hours to achieve thermal cross-linking of ligands and preliminary anchoring of metal sites; main carbonization stage: holding at 650-1000℃ for 1-10 hours to complete the graphitization reconstruction of carbon skeleton and the final formation of active sites; heating rate: controlling the heating rate at 1-20℃ / min between each stage.

7. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The pyrolysis treatment described in step (3) includes: pre-carbonization stage: maintaining at 300-500℃ for 0.5-5 hours to achieve thermal cross-linking of ligands and preliminary anchoring of metal sites; main carbonization stage: maintaining at 700-900℃ for 1-10 hours to complete the graphitization reconstruction of the carbon skeleton and the final formation of active sites; heating rate: controlling the heating rate at 2-10 ℃ / min between each stage.

8. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 1, characterized in that, The bimetallic catalyst comprises a nitrogen-doped carbon substrate and a bimetallic active center anchored thereon.

9. The method for synthesizing a bimetallic catalyst with tunable active sites according to claim 8, characterized in that, The bimetallic active centers exist in an atomically dispersed form and do not contain any elemental or compound crystalline phases that can be detected by X-ray diffraction; characterization by high-angle annular dark-field scanning transmission electron microscopy shows that more than 50% of the visible metal species exhibit a pairwise morphology.

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