Preparation method for precisely constructing transition-rare earth bimetallic monatomic material based on confinement strategy of soft-hard acid-base theory and application of transition-rare earth bimetallic monatomic material in lithium-oxygen battery

Abstract

The invention relates to the technical field of electrode catalytic materials, in particular to a preparation method for precisely constructing a transition-rare earth bimetallic monatomic material based on a confinement strategy of a soft-hard acid-base theory and application of the transition-rare earth bimetallic monatomic material in a lithium-oxygen battery. The preparation method comprises the following steps: S1, selecting transition metal salt, rare earth metal salt, an organic ligand of an oxygen-containing donor and a nitrogen-containing donor; s2, preparing a heteronuclear metal complex; s3, in-situ confinement encapsulation of the complex; and S4, performing high-temperature pyrolysis to form the diatomic catalyst. According to the method disclosed by the invention, molecular pre-constraint under the guidance of a soft-hard acid-base theory is creatively combined with a space confinement effect of ZIF-8, so that the core technical problems of precise pairing of metal atoms and structural stability at a high temperature in synthesis of the heteronuclear diatomic catalyst are successfully solved, and precise, controllable and macro-quantity preparation of heteronuclear diatomic sites such as Co-Gd and the like is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode catalytic materials, and particularly relates to a preparation method of transition-rare earth bimetallic single-atom material based on a soft-hard acid-base theory limited strategy and application thereof in lithium-oxygen batteries. BACKGROUND

[0002] The lithium-oxygen battery is considered as a strong contender for the next generation of high energy density energy storage systems due to its extremely high theoretical energy density, and its electrochemical performance is largely dependent on the catalytic efficiency of the positive electrode catalyst for oxygen reduction reaction and oxygen evolution reaction. Single-atom catalysts can achieve nearly 100% atom utilization, but their single metal active sites are difficult to optimize the adsorption energy of multiple oxygen-containing intermediates, which limits the catalytic activity, and is limited by the linear scaling relationship between the adsorption energies of the reaction intermediates, further restricting the improvement of the catalytic performance.

[0003] To break through the above limitations, bimetallic catalysts have gradually become a research frontier. They inherit the high atom utilization rate of single-atom catalysts, and through the electronic and geometric synergistic effect between the two metal sites, they are expected to break the linear scaling relationship and provide a new idea for designing high-efficiency bifunctional catalysts. However, how to realize the precise and stable pairing of two different metal atoms, especially transition metals and rare earth metals with significant differences in electronic structure and chemical properties, at the atomic scale, is a major challenge in this field. Traditional pyrolysis preparation methods often cannot accurately control the position of metal atoms, and metal migration and aggregation are prone to occur during high-temperature treatment, forming nanoclusters or particles without catalytic activity, so that the successful construction and high-density uniform exposure of heteronuclear bimetallic sites cannot be guaranteed.

[0004] Therefore, the existing technology has the following outstanding defects: first, the metal atoms are prone to migration and aggregation during synthesis, making it difficult to achieve atomic dispersion and stable anchoring of heteronuclear metal pairs; second, the spatial configuration and coordination environment of the bimetallic site are not precisely controlled, which affects the full play of its synergistic catalytic effect; third, the traditional single metal site catalyst is limited by the linear relationship between the oxygen intermediate adsorption energies, which restricts the further improvement of the comprehensive performance of the lithium-oxygen battery. In view of these difficulties, especially the bottleneck of controllable synthesis and structure stabilization of 3d-4f bimetallic catalysts, it is of great significance to develop a synthesis strategy that can accurately regulate the coordination and confinement process according to the chemical properties of metal ions, so as to realize the efficient and controllable construction of transition-rare earth heteronuclear bimetallic single atoms, which promotes the development of bimetallic catalysts and their application in high-performance lithium-oxygen batteries.

[0005] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventors studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0006] This invention relates to the field of electrode catalytic materials technology, and in particular to a method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory, and its application in lithium-oxygen batteries.

[0007] One objective of this invention is to provide a method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory, comprising the following steps: Selection of S1 transition metal salts, rare earth metal salts, oxygen-containing organic ligands, and nitrogen-containing donors: Based on the differentiated coordination guided by the HSAB theory, transition metals of soft acids or boundary acids and rare earth metals of hard acids are selected as dual ligands; polycarboxylic acids with hard base sites are selected as organic ligands containing oxygen donors; and 1,10-phenanthroline or its derivatives are selected as nitrogen donors. Preparation of S2 heteronuclear metal complex: The selected transition metal salt, rare earth metal salt, oxygen-containing organic ligand and nitrogen-containing organic ligand selected in S1 were dissolved in ethanol solution in a molar ratio of 15:10:100:16. After adjusting the pH with alkali solution, the heteronuclear metal complex was crystallized by solvothermal reaction to obtain single crystals. In-situ confined encapsulation of S3 complex: The heteronuclear metal complex obtained in S2, zinc salt and surfactant are dissolved in methanol to form solution A, and 2-methylimidazole is dissolved in methanol to form solution B. Solution A is added dropwise to solution B under stirring. Through a self-assembly process, the heteronuclear metal complex is in-situ encapsulated in the channels of the ZIF-8 frame. After centrifugation, washing and drying, the precursor is obtained. S4 High-temperature pyrolysis to form a biatomic catalyst: The precursor obtained from S3 is subjected to programmed temperature rise heat treatment under an inert atmosphere, and after cooling, a transition-rare earth bimetallic single-atom catalyst supported on nitrogen-doped porous carbon is obtained.

[0008] According to a preferred embodiment, in S2, the transition metal salt is a cobalt salt, an iron salt, or a nickel salt. Preferably, in S1, the transition metal salt is cobalt nitrate, ferric nitrate, or nickel nitrate.

[0009] According to a preferred embodiment, in S2, the rare earth metal salt is a gadolinium salt, a cerium salt, or a samarium salt. Preferably, in S1, the rare earth metal salt is gadolinium nitrate, europium nitrate, terbium nitrate, dysprosium nitrate, or samarium nitrate.

[0010] According to a preferred embodiment, in S2, the oxygen-containing donor ligand is 2,3-dichlorobenzoic acid or other polycarboxylic acids.

[0011] According to a preferred embodiment, in S2, the nitrogen-containing donor ligand is 1,10-phenanthroline.

[0012] According to a preferred embodiment, in step S2, the alkaline solution is sodium hydroxide. The pH is adjusted to 2-4. Preferably, the pH is adjusted to 3.

[0013] According to a preferred embodiment, in S2, the temperature of the solvothermal reaction is 140°C and the reaction time is 4 days.

[0014] According to a preferred embodiment, in S3, the surfactant is hexadecyltrimethylammonium bromide (CTAB).

[0015] According to a preferred embodiment, in step S3, the molar ratio of the heteronuclear metal complex to the zinc salt is 1:20-25. Preferably, the molar ratio of the heteronuclear metal complex to the zinc salt is 1:23. More preferably, the molar ratio of the heteronuclear metal complex to the zinc salt is 1:24.

[0016] Preferably, in S3, the molar ratio of CTAB to the heteronuclear metal complex is 20:13.

[0017] According to a preferred embodiment, in S4, the heat treatment involves heating to 900°C at a rate of 5°C / min and holding at this temperature for 2-3 hours.

[0018] According to a preferred embodiment, in the method for preparing the catalyst, the centrifugation conditions are: a rotation speed of 10,000 rpm and a stirring time of 5 min.

[0019] According to a preferred embodiment, in the method for preparing the catalyst, the drying conditions are: drying at 60-75°C for 8-14 hours.

[0020] One of the objectives of this invention is to provide a confinement strategy based on soft-hard acid-base theory for the precise construction of transition-rare earth bimetallic single-atom materials, which are prepared by the above-mentioned preparation method.

[0021] One of the objectives of this invention is to provide the application of the material prepared by the above preparation method in transition-rare earth bimetallic single-atom catalysts.

[0022] According to a preferred embodiment, a transition-rare earth bimetallic single-atom catalyst is used in a lithium-oxygen battery cathode catalyst.

[0023] One of the objectives of this invention is to provide the application of the material prepared by the above preparation method in the cathode catalyst of lithium-oxygen batteries.

[0024] The beneficial effects of this technical solution are: This invention innovatively combines molecular pre-constraint guided by soft-hard acid-base theory with the spatial confinement effect of ZIF-8, successfully solving the core technical challenges of precise metal atom pairing and high-temperature structural stability in the synthesis of heteronuclear diatomic catalysts. This enables the precise, controllable, and large-scale preparation of heteronuclear diatomic sites such as Co-Gd. The direct objective of this technical solution is to provide a reliable method for the universal synthesis of "transition-rare earth heteronuclear bimetallic single-atom catalysts" and to verify their excellent performance as highly efficient bifunctional cathode catalysts in lithium-oxygen batteries. The resulting beneficial effects are reflected in both practical applications and theoretical exploration. In practical applications, the prepared M1M2-DAC catalyst exhibits excellent overall performance in lithium-oxygen batteries. It can significantly reduce the charge-discharge overpotential of the battery, thereby improving its energy conversion efficiency; it can greatly extend the cycle life of the battery, enhancing its practical potential; and it can effectively accelerate the kinetics of oxygen reduction and oxygen evolution reactions, improving the power characteristics of the battery.

[0025] At the theoretical science level, this method creates a clearly structured, precisely definable and characterizable "heteronuclear dual single-atom" model catalyst system. This provides an ideal platform for in-depth research at the atomic / molecular scale on the electronic synergistic effects between two different metals (especially 3d-4f metals), as well as the adsorption and activation mechanisms of reaction intermediates during catalysis.

[0026] Specifically, addressing the challenges of metal atom migration and aggregation, uncontrollable site configuration, and the difficulty of overcoming the scaling limitations of oxygen intermediate adsorption energy in the synthesis of heteronuclear diatomic catalysts, this strategy achieves precise synthesis of the entire chain from initial design to final stability through the dual effects of "molecular pre-constraint" and "spatial confinement." First, based on the soft-hard acid-base principle, the strong coordination tendencies between transition metal ions and nitrogen-containing ligands, and between rare earth metal ions and oxygen-containing ligands, are utilized to directionally construct heteronuclear complexes with defined Co1Gd1 cores at the molecular level, achieving pre-organization and precise pairing of the two metal atoms. Then, the well-defined nanopores of ZIF-8 molecular sieves are used for in-situ encapsulation and confinement of this heteronuclear complex. During subsequent high-temperature pyrolysis, this host-guest confinement structure forms effective steric hindrance, strongly inhibiting the thermal migration and aggregation of metal atoms, thus ensuring that Co and Gd in the final product are stably anchored on the nitrogen-doped carbon support in an atomically dispersed heteronuclear pair form.

[0027] Thanks to the precise structure constructed by this strategy, the resulting heteronuclear diatomic sites generate a unique asymmetric electronic bipolar structure through 3d-4f orbital coupling. This electronic structure effectively breaks the limitations of traditional catalyst adsorption energy scaling for oxygen-containing intermediates (such as OOH, LiO2, and Li2O2), inducing O2 molecules to bind in a more easily activated bridge adsorption mode. Simultaneously, the bimetallic sites, with their differentiated adsorption capabilities, can synergistically regulate the formation pathway of the discharge product Li2O2, making it tend to form a loose and porous composite morphology of thin films and sheets through a combination of surface-mediated and solution-phase growth. This morphology greatly promotes electron / ion transport and reactant mass transfer during battery operation and significantly optimizes the decomposition kinetics of Li2O2, thereby conferring lower overpotential, higher energy efficiency, and longer cycle life to the lithium-oxygen battery as a whole. Attached Figure Description

[0028] Figure 1 Selective coordination tendency of metal ions and ligands verified for molecular electrostatic potential (MESP) distribution; Figure 2 X-ray diffraction (PXRD) pattern to confirm the coordination mode of bimetallic atoms in heteronuclear complexes; Figure 3 The XRD patterns are of the stable diatomic catalysts obtained in Examples 1-3 of this invention. Figure 4 These are SEM images of the stable diatomic catalysts obtained in Examples 1-3 of this invention; Figure 5 AC-HAADF-STEM image of the stable diatomic catalyst obtained in Example 1 of this invention; Figure 6 The stable diatomic catalyst obtained in Example 1 of this invention has (a) a Co-K edge. k 3 Weighted EXAFS spectrum; (b) Gd-R edge k 3 Weighted EXAFS spectrum; Figure 7 These are test graphs of the deep discharge curves of the lithium-oxygen batteries prepared in Examples 1-5 of this invention; Figure 8 The graphs show the cycle performance test curves of the lithium-oxygen batteries prepared in Examples 1-5 of this invention. Detailed Implementation

[0029] In the description of this invention, terminology is used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0030] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials, reagents, or instruments used, unless otherwise specified by the manufacturer, are all commercially available; the conditions not specified in the examples are all performed under conventional conditions or conditions recommended by the manufacturer. Furthermore, this invention does not limit the source of the raw materials used; unless otherwise specified, the raw materials used in this invention are all commercially available products in this technical field. In this application, all proportions not explicitly stated are molar ratios.

[0031] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0032] In this scheme, the heteronuclear diatomic construction based on the HSAB theory is achieved through stepwise coordination and molecular pre-assembly. Specifically, it utilizes rare earth metal ions (such as Gd) 3+ 、Sm 3+ Eu 3+ As a hard acid, it preferentially coordinates with oxygen-containing donor ligands (e.g., 2,3-dichlorobenzoic acid) to form a stable rare-earth-carboxylic acid unit; subsequently, this unit, as a whole, coordinates with transition metal ions (e.g., Co) that are soft acids. 2+ Fe 2+ Ni 2+The transition metal ion and nitrogen-containing donor ligand (e.g., 1,10-phenanthroline) are further reacted in a suitable solvent. Utilizing the selective coordination tendency of soft-hard acids and bases, the transition metal ion binds to the nitrogen atom, while the rare earth unit is linked to the ligand backbone via oxygen atoms, thereby directionally synthesizing a heteronuclear bimetallic complex with a defined Co1Ln1 core structure and spatial arrangement at the molecular level. Once confirmed by characterization (e.g., X-ray diffraction), this complex can be used as a precise precursor for subsequent confinement and pyrolysis steps, ultimately transforming into a heteronuclear diatomic catalytic site anchored on a support with a fixed atomic spacing.

[0033] Taking the structural formula of Example 1 as an example, such as Figure 1 As shown, the selective coordination tendency of metal ions with ligands was verified by the molecular electrostatic potential (MESP) distribution. Figure 2 As shown, the formation and spatial location of this structure were jointly verified by multi-scale characterization: the X-ray diffraction (PXRD) pattern directly confirmed the coordination mode of the bimetallic atoms in the heteronuclear complex.

[0034] The inventiveness of this invention lies in the precise control of the two-atom spatial binding sites achieved through molecular pre-constraint guided by HSAB theory and ZIF-8 confined encapsulation. The ligand screening conditions form the structural basis for the universality of the catalyst preparation method and the optimization of its performance.

[0035] This invention identifies the following five bimetallic ligand combinations for catalysts by following the rules of "selecting transition metals of soft or boundary acids and rare earth metals of hard acids as biligands; selecting polycarboxylic acids with hard base sites as organic ligands containing oxygen donors; and selecting 1,10-phenanthroline or its derivatives as nitrogen donors." The corresponding preparation methods and results confirm that the above-mentioned screening conditions form the structural basis for the universality of catalyst preparation methods and performance optimization.

[0036] Example 1 This embodiment involves the design, preparation, and effectiveness verification of the catalyst.

[0037] (I) Preparation of CoGd-DAC catalyst (1) Preparation of the complex CoGdL: A mixture of Co(NO3)2·6H2O (0.15 mmol, 43.7 mg), Gd(NO3)3·nH2O (0.10 mmol, 45.1 mg), 2,3-dichlorobenzoic acid (1.00 mmol, 191.0 mg), and 1,10-phenanthroline (0.16 mmol, 28.8 mg) was added to a mixed solvent of water (5 mL) and ethanol (1 mL). Then, 5 mL of 0.1 mol / L NaOH aqueous solution was added. The mixture was sealed in a 25 mL polytetrafluoroethylene-lined stainless steel reactor and heated in an oven at 140 °C for 4 days. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, yielding purple blocky crystals. These crystals were washed three times with deionized water and dried, and named CoGdL.

[0038] (2) Preparation of CoGdL@ZIF precursor: Zn(NO3)2·6H2O (1.4 mmol, 416.0 mg), CoGdL (0.06 mmol) prepared in the above steps, and CTAB (0.039 mmol, 14.2 mg) were dissolved in methanol (14 mL) and sonicated for 1 h to obtain solution A. 2-Methylimidazole (0.075 mmol, 10.2 g) was dissolved in methanol (98 mL) to form transparent solution B. Solution A was slowly added dropwise to solution B under vigorous stirring. After the addition was complete, the mixture was stirred continuously at room temperature for 12 hours. After the reaction was complete, the resulting purple precipitate was collected by centrifugation and washed five times each with deionized water and methanol to remove unreacted raw materials. Finally, the product was dried overnight in a vacuum oven at 60 °C to obtain the precursor, denoted as CoGdL@ZIF.

[0039] (3) Preparation of CoGd-DAC catalyst: The CoGdL@ZIF precursor powder obtained above was placed in a ceramic boat and then transferred to a tube furnace. Under the protection of flowing nitrogen (flow rate of 100 sccm), it was heated to 900℃ at a heating rate of 5℃ / min and held at this temperature for 2 hours for pyrolysis. After pyrolysis, the tube furnace was allowed to cool naturally to room temperature to obtain the final cobalt-gadolinium heteronuclear dual single-atom catalyst, denoted as CoGd-DAC.

[0040] Example 2 (I) Preparation of CoSm-DAC catalyst (1) Preparation of the complex CoSmL: A mixture of Co(NO3)2·6H2O (0.15 mmol, 43.7 mg), Sm(NO3)3·6H2O (0.10 mmol, 44.4 mg), 2,3-dichlorobenzoic acid (1.00 mmol, 191.0 mg), and 1,10-phenanthroline (0.16 mmol, 28.8 mg) was added to a mixed solvent of water (5 mL) and ethanol (1 mL). Then, 5 mL of 0.1 mol / L NaOH aqueous solution was added. The mixture was sealed in a 25 mL polytetrafluoroethylene-lined stainless steel reactor and heated in an oven at 140 °C for 4 days. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, yielding purple blocky crystals. These crystals were washed three times with deionized water and dried, and named CoSmL.

[0041] (2) Preparation of CoGdL@ZIF precursor: Zn(NO3)2·6H2O (1.4 mmol, 416.0 mg), CoSmL (0.06 mmol) prepared in the above steps, and CTAB (0.039 mmol, 14.2 mg) were dissolved in methanol (14 mL) and sonicated for 1 h to obtain solution A. 2-Methylimidazole (0.075 mmol, 10.2 g) was dissolved in methanol (98 mL) to form transparent solution B. Solution A was slowly added dropwise to solution B under vigorous stirring. After the addition was complete, the mixture was stirred continuously at room temperature for 12 hours. After the reaction was complete, the resulting purple precipitate was collected by centrifugation and washed five times each with deionized water and methanol to remove unreacted raw materials. Finally, the product was dried overnight in a vacuum oven at 60 °C to obtain the precursor, denoted as CoSmL@ZIF.

[0042] (3) Preparation of CoSm-DAC catalyst: The CoSmL@ZIF precursor powder obtained above was placed in a ceramic boat and then transferred to a tube furnace. Under the protection of flowing nitrogen (flow rate of 100 sccm), the temperature was increased to 900℃ at a heating rate of 5℃ / min and held at this temperature for 2 hours for pyrolysis. After pyrolysis, the tube furnace was allowed to cool naturally to room temperature to obtain the final cobalt-samarium heteronuclear dual single-atom catalyst, denoted as CoGd-DAC.

[0043] Example 3 (I) Preparation of CoEu-DAC catalyst (1) Preparation of the complex CoGdL: A mixture of Co(NO3)2·6H2O (0.15 mmol, 43.7 mg), Eu(NO3)3·nH2O (0.10 mmol, 44.6 mg), 2,3-dichlorobenzoic acid (1.00 mmol, 191.0 mg), and 1,10-phenanthroline (0.16 mmol, 28.8 mg) was added to a mixed solvent of water (5 mL) and ethanol (1 mL). Then, 5 mL of 0.1 mol / L NaOH aqueous solution was added. The mixture was sealed in a 25 mL polytetrafluoroethylene-lined stainless steel reactor and heated in an oven at 140 °C for 4 days. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, yielding purple blocky crystals. These crystals were washed three times with deionized water and dried, and named CoEuL.

[0044] (2) Preparation of CoEuL@ZIF precursor: Zn(NO3)2·6H2O (1.4 mmol, 416.0 mg), CoEuL (0.06 mmol) prepared in the above steps, and CTAB (0.039 mmol, 14.2 mg) were dissolved in methanol (14 mL) and sonicated for 1 h to obtain solution A. 2-Methylimidazole (0.075 mmol, 10.2 g) was dissolved in methanol (98 mL) to form transparent solution B. Solution A was slowly added dropwise to solution B under vigorous stirring. After the addition was complete, the mixture was stirred continuously at room temperature for 12 hours. After the reaction was complete, the resulting purple precipitate was collected by centrifugation and washed five times each with deionized water and methanol to remove unreacted raw materials. Finally, the product was dried overnight in a vacuum oven at 60 °C to obtain the precursor, denoted as CoEuL@ZIF.

[0045] (3) Preparation of CoEu-DAC catalyst: The CoEuL@ZIF precursor powder obtained above was placed in a ceramic boat and then transferred to a tube furnace. Under the protection of flowing nitrogen (flow rate of 100 sccm), it was heated to 900℃ at a heating rate of 5℃ / min and held at this temperature for 2 hours for pyrolysis. After pyrolysis, the tube furnace was allowed to cool naturally to room temperature to obtain the final cobalt-europium heteronuclear dual single-atom catalyst, denoted as CoEu-DAC.

[0046] Example 4 (I) Preparation of CoTb-DAC catalyst (1) Preparation of the complex CoTbL: A mixture of Co(NO3)2·6H2O (0.15 mmol, 43.7 mg), Tb(NO3)3·nH2O (0.10 mmol, 45.3 mg), 2,3-dichlorobenzoic acid (1.00 mmol, 191.0 mg), and 1,10-phenanthroline (0.16 mmol, 28.8 mg) was added to a mixed solvent of water (5 mL) and ethanol (1 mL). Then, 5 mL of 0.1 mol / L NaOH aqueous solution was added. The mixture was sealed in a 25 mL polytetrafluoroethylene-lined stainless steel reactor and heated in an oven at 140 °C for 4 days. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, yielding purple blocky crystals. These crystals were washed three times with deionized water and dried, and named CoGdL.

[0047] (2) Preparation of CoTbL@ZIF precursor: Zn(NO3)2·6H2O (1.4 mmol, 416.0 mg), CoGdL (0.06 mmol) prepared in the above steps, and CTAB (0.039 mmol, 14.2 mg) were dissolved in methanol (14 mL) and sonicated for 1 h to obtain solution A. 2-Methylimidazole (0.075 mmol, 10.2 g) was dissolved in methanol (98 mL) to form transparent solution B. Solution A was slowly added dropwise to solution B under vigorous stirring. After the addition was complete, the mixture was stirred continuously at room temperature for 12 hours. After the reaction was complete, the resulting purple precipitate was collected by centrifugation and washed five times each with deionized water and methanol to remove unreacted raw materials. Finally, the product was dried overnight in a vacuum oven at 60 °C to obtain the precursor, denoted as CoTbL@ZIF.

[0048] (3) Preparation of CoTb-DAC catalyst: The CoTbL@ZIF precursor powder obtained above was placed in a ceramic boat and then transferred to a tube furnace. Under the protection of flowing nitrogen (flow rate of 100 sccm), it was heated to 900℃ at a heating rate of 5℃ / min and held at this temperature for 2 hours for pyrolysis. After pyrolysis, the tube furnace was allowed to cool naturally to room temperature to obtain the final cobalt-terbium heteronuclear dual single-atom catalyst, denoted as CoTb-DAC.

[0049] Example 5 (I) Preparation of CoDy-DAC catalyst (1) Preparation of the complex CoDyL: A mixture of Co(NO3)2·6H2O (0.15 mmol, 45.6 mg), Tb(NO3)3·nH2O (0.10 mmol, 45.3 mg), 2,3-dichlorobenzoic acid (1.00 mmol, 191.0 mg), and 1,10-phenanthroline (0.16 mmol, 28.8 mg) was added to a mixed solvent of water (5 mL) and ethanol (1 mL). Then, 5 mL of 0.1 mol / L NaOH aqueous solution was added. The mixture was sealed in a 25 mL polytetrafluoroethylene-lined stainless steel reactor and heated in an oven at 140 °C for 4 days. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, yielding purple blocky crystals. These crystals were washed three times with deionized water and dried, and named CoDyL.

[0050] (2) Preparation of CoDyL@ZIF precursor: Zn(NO3)2·6H2O (1.4 mmol, 416.0 mg), CoGdL (0.06 mmol) prepared in the above steps, and CTAB (0.039 mmol, 14.2 mg) were dissolved in methanol (14 mL) and sonicated for 1 h to obtain solution A. 2-Methylimidazole (0.075 mmol, 10.2 g) was dissolved in methanol (98 mL) to form transparent solution B. Solution A was slowly added dropwise to solution B under vigorous stirring. After the addition was complete, the mixture was stirred continuously at room temperature for 12 hours. After the reaction was complete, the resulting purple precipitate was collected by centrifugation and washed five times each with deionized water and methanol to remove unreacted raw materials. Finally, the product was dried overnight in a vacuum oven at 60 °C to obtain the precursor, denoted as CoDyL@ZIF.

[0051] (3) Preparation of CoDy-DAC catalyst: The CoDyL@ZIF precursor powder obtained above was placed in a ceramic boat and then transferred to a tube furnace. Under the protection of flowing nitrogen (flow rate of 100 sccm), it was heated to 900℃ at a heating rate of 5℃ / min and held at this temperature for 2 hours for pyrolysis. After pyrolysis, the tube furnace was allowed to cool naturally to room temperature to obtain the final cobalt-dysprosium heteronuclear dual single-atom catalyst, denoted as CoDy-DAC.

[0052] Test case (I) Microstructure observation The catalysts prepared in Examples 1-3 were observed using X-ray diffraction and scanning electron microscopy. The X-ray diffraction patterns and scanning electron microscopy images are shown below. Figure 3 , Figure 4 As shown. From Figure 3As can be seen, the XRD test curves of the stable supported heteronuclear diatomic catalysts obtained using the methods of Examples 1-3 show that only at 25... ~30 and 43 The broad peaks that appeared should be attributed to the (002) and (101) diffraction peaks of graphite carbon, respectively; the above results indicate that the M1M2 elements were successfully doped into the ZIF-8 derived N-doped C matrix. Figure 4 The SEM images obtained in Examples 1-3 are from... Figure 4 We can see that its particles are dodecahedral with a particle size of about 50nm.

[0053] (ii) Atomic spatial positioning Aberration-corrected high-angle annular dark-field scanning electron microscopy (AC-HAADF-STEM) was used to investigate the atomic forms present in the catalyst prepared in Example 1. Figure 5 As shown, numerous well-isolated, paired bright spots are uniformly dispersed on the ZIF-8 derived carbon support. These bright spots are designated as metal atom pair sites based on their contrast differences. Histograms show that over 80% of the metal pair spacings in the CoGd-DAC are controlled within the 2.6–2.8 Å range, confirming the Co-Gd pathway: adjacent Co and Gd atoms coexist as dual-site single-atom centers. The consistency between atomic distribution intensity and interatomic spacing demonstrates the significant potential of the HSAB-based pre-constraint-encapsulation strategy for customizing diatomic structures.

[0054] The atomic-scale coordination configuration of the catalyst prepared in Example 1 was further analyzed in R space using Fourier transform extended X-ray absorption fine structure (FT-EXAFS) spectroscopy, providing convergent evidence for the identification of atomic pairs. Figure 6As shown in Figure a, the Co K-edge EXAFS spectra in the CoGd-DAC generally exhibit waveforms similar to those of Co3O4, but with significant changes in oscillation frequency and amplitude. This indicates an adjustment in the local coordination environment around the Co atoms. The amplification of the Co-N (1.20–1.80 Å) bond length corresponds to an enhancement of the Co-N covalent interaction in the first coordination shell, and also reflects a faster electron transfer process between the supports. Compared to the reference sample, the Co-NM (2.40–2.50 Å) peak intensity is relatively weak, indicating that the Co-NM coordination environment is somewhat separated. This phenomenon is further verified by the absence of the Co-Co (2.20 Å) scattering path, confirming that Co in the CoGd-DAC mainly exists in a dispersed and isolated single-atom form. Similarly, the Gd-L3 edge of the CoGd-DAC can be deciphered in a similar context. The positive shift of the Gd-O scattering path compared to the reference sample indicates a change in the coordination environment of the Gd atoms. The strong peak at 1.95 Å can be attributed to the main scattering of Gd-N, while the signal in the 2.0–3.0 Å region corresponds to the scattering contribution of Gd-NM coordination. Furthermore, the absence of the Gd-Gd (2.55 Å) scattering pathway further confirms that Gd exists in a dispersed and isolated single-atom state in the CoGd-DAC system. These results collectively demonstrate that in the CoGd-DAC structure, Co / Gd is firmly anchored to the ZIF framework via MN bonds, thus revealing the unique structural characteristics of this catalytic system.

[0055] (iii) Applicability of materials in batteries The catalysts prepared in Examples 1-5 were used as positive electrode materials to assemble coin-type lithium-oxygen batteries for testing. The electrolyte was a 0.5 M LiCF3SO3 TEGDME solution.

[0056] The full charge-discharge capacity of the lithium-oxygen battery assembled with the catalysts obtained in Examples 1-5 is as follows: Figure 7 As shown, the Li-O2 cell based on the CoGd-DAC cathode operates at 250 mA g. -1 It exhibits 46560 mAh g at current density -1 High discharge capacity.

[0057] The catalysts prepared in Examples 1-5 were used as positive electrode materials to assemble coin-type lithium-oxygen batteries for testing. The electrolyte was a 0.5 M LiCF3SO3 TEGDME solution.

[0058] The lithium-oxygen batteries assembled with the catalysts obtained in Examples 1-5 were cycled at 250 mA g. -1 The test was conducted at a current density with a cutoff capacity of 1000 mAh g. -1.like Figure 8 As shown, the evolution of the terminal voltage during cycling is illustrated. The CoGd-DAC cathode maintained a discharge terminal voltage >2.0 V for over 300 cycles, accumulating a stable operating time of up to 2500 hours. Furthermore, throughout the cycling process, the CoGd-DAC cathode consistently maintained the highest discharge potential and the lowest charge potential. This indicates that the CoGd-DAC system exhibits more stable oxygen catalytic activity and can maintain low polarization over a long period, achieving a dual breakthrough in oxygen electrode reaction kinetics and stability.

[0059] The examples demonstrate that various diatomic combinations, such as Co–Gd, Co–Sm, and Co–Eu, were successfully synthesized and exhibited significant catalytic enhancement, indicating that this method has good versatility for heteronuclear diatomic combinations. In particular, the Co–Gd combination showed the best overall performance in lithium-oxygen batteries due to its unique electronic structure enabling efficient decoupling catalysis of the oxygen intermediate. However, the performance improvements of all combinations are rooted in the precise construction of spatial binding sites. Therefore, the focus of the preferred approach is on the controllable construction of spatial binding sites, rather than being limited to a specific metal combination. This strategy provides a reliable platform for the design and optimization of diverse diatomic catalysts.

[0060] It should be noted that the specific embodiments described above are exemplary, and those skilled in the art can devise various solutions inspired by the disclosure of this invention. These solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory, characterized in that, Includes the following steps: Selection of S1 transition metal salts, rare earth metal salts, oxygen-containing organic ligands, and nitrogen-containing donors: Based on the differentiated coordination guided by the HSAB theory, transition metals of soft acids or boundary acids and rare earth metals of hard acids are selected as dual ligands; polycarboxylic acids with hard base sites are selected as organic ligands containing oxygen donors; and 1,10-phenanthroline or its derivatives are selected as nitrogen donors. Preparation of S2 heteronuclear metal complex: The selected transition metal salt, rare earth metal salt, oxygen-containing organic ligand and nitrogen-containing organic ligand selected in S1 were dissolved in ethanol solution in a molar ratio of 15:10:100:

16. After adjusting the pH with alkali solution, the heteronuclear metal complex was crystallized by solvothermal reaction to obtain single crystals. In-situ confined encapsulation of S3 complex: The heteronuclear metal complex obtained in S2, zinc salt and surfactant are dissolved in methanol to form solution A, and 2-methylimidazole is dissolved in methanol to form solution B. Solution A is added dropwise to solution B under stirring. Through a self-assembly process, the heteronuclear metal complex is in-situ encapsulated in the channels of the ZIF-8 frame. After centrifugation, washing and drying, the precursor is obtained. S4 High-temperature pyrolysis to form a biatomic catalyst: The precursor obtained from S3 is subjected to programmed temperature rise heat treatment under an inert atmosphere, and after cooling, a transition-rare earth bimetallic single-atom catalyst supported on nitrogen-doped porous carbon is obtained.

2. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S2, the transition metal salt is cobalt nitrate, ferric nitrate, or nickel nitrate.

3. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S2, the rare earth metal salts are gadolinium nitrate, europium nitrate, terbium nitrate, dysprosium nitrate, or samarium nitrate.

4. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S2, the oxygen-containing donor ligand is 2,3-dichlorobenzoic acid.

5. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S2, the nitrogen-containing donor ligand is 1,10-phenanthroline.

6. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S3, the surfactant is hexadecyltrimethylammonium bromide.

7. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S3, the molar ratio of the heteronuclear metal complex to the zinc salt is 1:20-25.

8. The method for precisely constructing transition-rare earth bimetallic single-atom materials using a confinement strategy based on soft-hard acid-base theory according to claim 1, characterized in that, In S4, the heat treatment involves heating to 900°C at a rate of 5°C / min and holding at this temperature for 2-3 hours.

9. A confinement strategy based on soft-hard acid-base theory for the precise construction of transition-rare earth bimetallic single-atom materials, characterized in that, The material is prepared based on the preparation method described in claims 1-8.

10. The application of transition-rare earth bimetallic single-atom materials prepared by the preparation method described in claims 1-8 using a confinement strategy based on soft-hard acid-base theory in lithium-oxygen batteries.

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