Double-monatomic redox catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of battery preparation, and particularly relates to a double-monatomic redox catalyst and a preparation method and application thereof. The double-monatomic redox catalyst is prepared by compounding the RMF polymer and the ZIF-8, so that structural collapse and metal agglomeration in a pyrolysis process are effectively prevented, and high dispersion of metal diatoms containing Fe atoms is realized. On the basis, the oxidation-reduction catalyst shows excellent ORR activity in both acidic and alkaline media, the half-wave potential in the acidic medium can reach 0.728 V, and the half-wave potential in the alkaline medium can reach 0.788 V.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, specifically relating to a dual single-atom redox catalyst, its preparation method, and its application. Background Technology

[0002] In the process of restructuring the global energy system driven by the goal of "carbon peaking and carbon neutrality," proton exchange membrane fuel cells (PEMFCs) and rechargeable zinc-air batteries have become key electrochemical technologies supporting the clean energy transition due to their high energy conversion efficiency, environmental friendliness, and modular integration advantages. The performance and lifespan of both types of devices are highly dependent on the cathode oxygen electrode reaction kinetics: PEMFCs are limited by the slow rate of the oxygen reduction reaction (ORR) in acidic environments, while rechargeable zinc-air batteries need to simultaneously achieve efficient bidirectional catalysis of both ORR and oxygen evolution reaction (OER) in alkaline electrolytes. Currently, commercial systems generally use platinum-based and other precious metal catalysts, but these catalysts have inherent drawbacks such as high cost and scarce resources. Furthermore, they are prone to deactivation phenomena such as particle growth, dissolution and redeposition, and carbon support corrosion under acidic / high-potential conditions, making it difficult to balance high activity and long lifespan, severely restricting their large-scale commercial application.

[0003] To overcome the bottleneck of reliance on precious metals, single-atom catalysts (SACs) significantly improve metal atom utilization by dispersing metal centers atomically on the support surface. However, their metal loading is limited by thermodynamic aggregation tendencies, resulting in insufficient effective site density. Simultaneously, the metal-support interaction is weak, making them prone to structural degradation and metal leaching in harsh electrochemical environments. Diatom catalysts (DACs), as an extension of the single-atom catalysis concept, regulate the adsorption behavior of reaction intermediates through the synergistic effect of dual-metal sites, potentially breaking through the performance limits of single-center catalysts and achieving higher metal loading, becoming an important direction for next-generation electrocatalysts. However, existing DAC preparation technologies have significant limitations: methods such as physical vapor deposition rely on ultra-high vacuum conditions, resulting in high equipment costs and difficulty in scaling up; traditional wet chemical methods require extremely dilute precursor concentrations to suppress aggregation, sacrificing yield, and the resulting metal-support interface interaction is limited, leading to the deactivation of active sites during long-term cycling.

[0004] Therefore, there is an urgent need in this field to develop a simple, structurally precise, and scalable method for synthesizing diatomic catalysts to construct diatomic electrocatalysts with high site density, high dispersion, and excellent structural stability. Such catalysts must simultaneously meet the requirements of high intrinsic activity and durability in both acidic and alkaline media, thereby supporting the commercialization of key energy devices such as proton exchange membrane fuel cells and rechargeable zinc-air batteries, and providing core technological support for achieving the goal of "carbon peaking—carbon neutrality." Summary of the Invention

[0005] Based on this, the present invention provides a dual single-atom redox catalyst, its preparation method, and its application. This dual single-atom redox catalyst exhibits excellent catalytic activity in both acidic and alkaline electrolyte systems, and its preparation method is simple.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions: The present invention provides a method for preparing a dual-monoatomic redox catalyst, the method comprising: (1) mixing a metal-organic framework material solution with a dual-amine-aldehyde polymer solution to obtain a mixed solution; (2) subjecting the mixed solution to a hydrothermal reaction to obtain a reaction product; and (3) subjecting the reaction product to pyrolysis to obtain a dual-monoatomic redox catalyst; wherein, the method for preparing the dual-amine-aldehyde polymer solution comprises: mixing an amino compound, an aldehyde compound, a phenolic compound, an iron source and other metal sources in a solvent to obtain a dual-amine-aldehyde polymer solution; the other metal sources are selected from any one of copper, manganese, cerium or chromium sources.

[0007] Preferably, in the above preparation method, the molar ratio of the total metals in the iron source and other metal sources to the metal elements in the metal-organic framework material solution is (0.01-0.5):1; and / or the mass ratio of iron in the iron source to the metals in other metal sources is 1:(0.8-1.2).

[0008] More preferably, in the above preparation method, the molar ratio of the total metals in the iron source and other metal sources to the metal elements in the metal-organic framework material solution is (0.04 to 0.19):1; and / or the mass ratio of iron in the iron source to the metals in other metal sources is 1:1.

[0009] Preferably, the above preparation method satisfies one or more of the following conditions: (a1) the metal-organic framework material is selected from ZIF-8; (b1) the amino compound is selected from one or more of melamine, urea or aniline; (c1) the aldehyde compound is selected from one or more of formaldehyde, acetaldehyde, furfural or benzaldehyde; (d1) the phenolic compound is selected from one or more of resorcinol, phenol, hydroquinone, catechol, phenolphthalein or tannic acid; (e1) the iron source or other metal source is independently selected from one or more of the corresponding metal inorganic salt, metal organometallic acid salt or organometallic complex; (f1) the solvent is selected from one or more of polar organic solvents; or the solvent is selected from one or more of polar organic solvents and water.

[0010] More preferably, in the above preparation method, the inorganic metal salt is selected from one or more of metal chloride salts, metal sulfide salts, or metal nitrate salts; and / or the organometallic acid salt is selected from one or more of metal acetate salts, metal oxalate salts, or metal citrate salts; and / or the organometallic complex is selected from one or more of metallocene compounds, metal porphyrins, or metal phthalocyanines.

[0011] Preferably, the above preparation satisfies one or more of the following conditions: (a2) In step (1), the pH of the mixed solution is adjusted to be alkaline before hydrothermal reaction; (b2) In step (1), the mixed solution is preheated before hydrothermal reaction, the preheating temperature is 40℃~80℃; and / or the preheating time is 0.5h~1.5h; (c2) In step (2), the hydrothermal reaction temperature is 120℃~160℃; and / or the hydrothermal reaction time is 6h~10h; (d2) In step (3), the pyrolysis temperature is 800℃~1000℃; and / or the pyrolysis time is 1.5h~2.5h; and / or the heating rate is 4℃ / min~6℃ / min; (e2) In step (3), acid washing is performed after pyrolysis to obtain a dual single-atom redox catalyst.

[0012] More preferably, in the above preparation method, step (3) includes acid washing: soaking the pyrolysis product in an acid solution at 50℃~70℃ for 6h~10h.

[0013] In another aspect, the present invention provides a dual single-atom redox catalyst, which is prepared by the above-described preparation method.

[0014] In another aspect, the present invention provides a positive and / or negative electrode for a fuel cell, comprising positive and / or negative electrode active materials and the aforementioned dual single-atom redox catalyst.

[0015] In another aspect, the present invention provides a fuel cell comprising the above-described positive and / or negative electrodes of the fuel cell, wherein the electrolyte of the fuel cell is an alkaline electrolyte.

[0016] The beneficial effects of this invention include: (1) The dual single-atom redox catalyst provided by the present invention is prepared by composite of RMF polymer and ZIF-8, which effectively prevents structural collapse and metal agglomeration during pyrolysis and achieves high dispersion of metal diatoms containing Fe atoms. Based on this, the redox catalyst exhibits excellent ORR activity in both acidic and alkaline media, with a half-wave potential of 0.728V in acidic media and 0.788V in alkaline media.

[0017] (2) The peak power density of a single proton exchange membrane fuel cell (PEMFC) assembled with the dual single-atom redox catalyst provided by this invention can reach 387.20 mW·cm⁻¹. -2 The assembled rechargeable zinc-air battery can achieve a peak power density of 160.47 mW·cm³. -2 This indicates excellent electrochemical performance.

[0018] (3) The method for preparing the redox catalyst provided by the present invention adopts conventional hydrothermal synthesis and pyrolysis processes, which do not require complex equipment and harsh reaction conditions, and are suitable for large-scale production. Attached Figure Description

[0019] Figure 1 Scanning electron microscope (SEM) images of the different composite materials prepared in Examples 1, 3, 5 and 7; Figure 2 The elemental distribution of the composite material prepared in Example 1 is shown in the energy dispersive X-ray spectroscopy (EDS) spectrum. Figure 3 Transmission electron microscope (TEM) image of the composite material prepared in Example 1; Figure 4 Comparison of X-ray diffraction (XRD) patterns of different composite materials prepared in Examples 1, 3, 5 and 7; Figure 5 X-ray photoelectron spectroscopy (XPS) analysis of the composite material prepared in Example 1; Figure 6 Linear sweep voltammetry (LSV) polarization curves of different composite materials prepared for Examples 1, 3, 5 and 7 as redox catalysts under acidic conditions; Figure 7 Linear sweep voltammetry (LSV) polarization curves of different composite materials prepared in Examples 1, 3, 5 and 7 and Comparative Examples 1 to 5 as redox catalysts under alkaline conditions; Figure 8 Polarization curves and power density curves of different composite materials prepared in Examples 1 and 5 as redox catalysts in proton exchange membrane fuel cells; Figure 9 Polarization curves and power density curves of the different composite materials prepared for Examples 1 and 5 as redox catalysts in zinc-air batteries. Detailed Implementation

[0020] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0022] In a first aspect, embodiments of the present invention provide a method for preparing a dual single-atom redox catalyst, the method comprising: (1) A mixed solution is obtained by mixing and reacting a metal-organic framework material solution with a diatomic amine-aldehyde polymer solution; (2) The mixed solution is subjected to a hydrothermal reaction to obtain the reaction product; (3) The reaction products are pyrolyzed to obtain a dual single-atom redox catalyst; The preparation method of the diatomic amine-aldehyde polymer solution includes: mixing an amino compound, an aldehyde compound, a phenolic compound, an iron source, and other metal sources in a solvent to obtain the diatomic amine-aldehyde polymer solution; the other metal sources are selected from any one of copper, manganese, cerium, or chromium sources.

[0023] It should be noted that the preparation method of the dual single-atom redox catalyst provided by this invention adopts conventional hydrothermal synthesis and pyrolysis processes, which do not require complex equipment and harsh reaction conditions, making it suitable for large-scale production. Furthermore, the terms "hydrothermal" and "pyrolysis" in the above preparation method are well-known operations in the art and have no particular meaning. Additionally, amine-aldehyde polymers (such as RMF polymers) provide abundant nitrogen sources and carbon skeletons, while metal-organic framework materials provide a regular pore structure and additional nitrogen coordination environment. The synergistic effect of both optimizes the coordination environment of the dual single atoms (Fe and other metal atoms). Moreover, the composite design of metal-organic framework materials and RMF polymers effectively prevents structural collapse during high-temperature pyrolysis, maintaining a high specific surface area and hierarchical pore structure. Furthermore, the Fe-Nx active sites (Fe-Nx active sites are an atomic-level structure embedded in the functional material "nitrogen-doped porous carbon". This structure is composed of iron atoms as the catalytic center, nitrogen atoms as anchoring points, and carbon matrix as a conductive and supporting framework, which together achieve highly efficient oxygen reduction catalytic activity) have a suitable electronic structure, which is beneficial to the adsorption and activation of O2 and the conversion of intermediates.

[0024] In some specific examples, in the above preparation method, the molar ratio of the total metals in the iron source and other metal sources to the metal elements in the metal-organic framework material solution is (0.01 to 0.5): 1.

[0025] It should be noted that the preferred molar ratio of the total metal content in the iron source and other metal sources to the metal elements in the metal-organic framework material solution is (0.01–0.5):1 (0.01–0.5):1, for example, 0.05:1, 0.1:1, 0.2:1, 0.3:1, or 0.4:1. Specifically, excessively low active metal content leads to insufficient active sites, while excessively high active metal content causes metal agglomeration, reducing single-atom yield. Furthermore, the metal-organic framework material in this invention is well-known in the art, and the metal elements therein are also well-known in the art, such as zinc.

[0026] In some specific examples, in the above preparation method, the molar ratio of the total metals in the iron source and other metal sources to the metal elements in the metal-organic framework material solution is (0.04–0.19):1.

[0027] It should be noted that the molar ratio of the total metals in the iron source and other metal sources to the metal elements in the metal-organic framework material solution in this invention can be further preferably (0.04-0.19):1, for example 0.05:1, 0.1:1, 0.15:1 or 0.17:1, etc.; the redox catalyst prepared under this ratio has the best catalytic activity and stability.

[0028] In some specific examples, in the above preparation method, the mass ratio of iron in the iron source to metal in other metal sources is 1:(0.8-1.2).

[0029] It should be noted that the mass ratio of iron in the iron source and metal in the other metal source in this invention can preferably be 1:(0.8-1.2), such as 1:0.9, 1:1 or 1:1.1, etc., and more preferably 1:1. The electrochemical performance of the dual single-atom redox catalyst prepared by this mass ratio is more excellent.

[0030] In some specific examples, the above preparation method satisfies one or more combinations of the following conditions: (a1) The metal-organic framework material is selected from ZIF-8; specifically, the metal-organic framework material in this invention is known in the art, and ZIF-8 is preferred in this invention, as the redox catalyst prepared by this framework material has better performance. (b1) The amino compound is selected from one or more combinations of melamine, urea or aniline; specifically, the amino compound and aldehyde compound in this invention form an organic resin that forms a nitrogen-rich carbon skeleton in subsequent pyrolysis, the skeleton being used to anchor iron single atoms; the amino compound in this invention is known in the art, such as the amino compounds listed above. (c1) The aldehyde compound is selected from one or more combinations of formaldehyde, acetaldehyde, furfural or benzaldehyde; specifically, as described above, the aldehyde compound and amino compound of the present invention form an organic resin that forms a nitrogen-rich carbon skeleton in subsequent pyrolysis; the aldehyde compound of the present invention is known in the art, such as the aldehyde compounds listed above. (d1) The phenolic compound is selected from one or more combinations of resorcinol, phenol, hydroquinone, catechol, phenolphthalein, or tannic acid; specifically, the role of the phenolic compound is to copolymerize with the organic resin formed by the amino compound and the aldehyde compound, which can regulate the microstructure, pore size distribution and hydrophilicity / hydrophobicity of the final composite material; the phenolic compound in this invention is known in the art, such as the phenolic compounds listed above; (e1) The iron source or other metal source shall be selected independently from one or more combinations of corresponding inorganic metal salts, organometallic acid salts or organometallic complexes; specifically, the iron source or other metal source in this invention is an inorganic metal salt, organometallic acid salt or organometallic complex known in the art, such as an iron-containing inorganic salt, an iron-containing organometallic acid salt or an organoiron complex, etc., which can be selected as needed; (f1) The solvent is selected from one or more combinations of polar organic solvents; or the solvent is selected from one or more combinations of polar organic solvents and water. Specifically, the solvent in this invention is known in the art, preferably a polar organic solvent. The polar organic solvent is known in the art, such as alcohol solvents, amide solvents, ketone solvents, ether solvents, or sulfoxide solvents; in addition, alcohol solvents include, but are not limited to: methanol, ethanol, n-propanol, isopropanol, n-butanol, or ethylene glycol; amide solvents include, but are not limited to: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), or N-methylpyrrolidone (NMP); ketone solvents include, but are not limited to: acetone or butanone; ether solvents include, but are not limited to: tetrahydrofuran (THF) or dioxane; sulfoxide solvents include, but are not limited to: dimethyl sulfoxide (DMSO). Furthermore, the solvent may also be a mixture of a polar organic solvent and water.

[0031] In some specific examples, in the above preparation method, The inorganic metal salt is selected from one or more of the following: metal chloride salts, metal sulfide salts, or metal nitrate salts; and / or Organometallic acid salts are selected from one or more of metal acetate, metal oxalate, or metal citrate; and / or Organometallic complexes are selected from one or more of metallocene compounds, metal porphyrins, or metal phthalocyanines.

[0032] It should be noted that the iron source in this invention can preferably be any of the metal inorganic salts, metal organometallic acid salts, or organometallic complexes listed above. In addition, it should be understood that the metal inorganic salts mentioned above can be those known in the art. For example, for iron, the metal inorganic salts can be ferric chloride, ferric sulfate, ferric nitrate, ferrous chloride, or ferrous sulfate containing their hydrates. For example, ferric chloride can be ferric chloride hexahydrate (FeCl3·6H2O), and does not simply refer to anhydrous ferric chloride.

[0033] In some specific examples, in the above preparation method, melamine is selected as the amino compound, formaldehyde is selected as the aldehyde compound, resorcinol is selected as the phenolic compound, ferric chloride hexahydrate (FeCl3·6H2O) is selected as the iron source, and metal chloride salts are also selected as other metal sources.

[0034] It should be noted that, in the above preparation method, the selections mentioned above can be further optimized, and the redox catalyst prepared based on the above-preferred amino compounds, aldehyde compounds, phenolic compounds, iron sources and other metal sources has better performance.

[0035] In some specific examples, the above preparation satisfies one or more combinations of the following conditions: (a2) In step (1), the pH value of the mixed solution is adjusted to alkaline before the hydrothermal reaction is carried out; specifically, adjusting the pH value of the mixed solution to alkaline before the hydrothermal reaction can better control the dispersion of the iron source. If the pH value is not adjusted, the iron ions are easily hydrolyzed and precipitated or agglomerated into large particles in the hydrothermal reaction, which affects the dispersion of single atoms. (b2) In step (1), the mixed solution is preheated before the hydrothermal reaction is carried out. The preheating temperature is 40℃~80℃; and / or the preheating time is 0.5h~1.5h. Specifically, preheating the mixed solution before the hydrothermal reaction can better control the iron source dispersion. (c2) In step (2), the temperature of the hydrothermal reaction is 120℃~160℃; and / or the hydrothermal reaction time is 6h~10h; specifically, the hydrothermal reaction temperature in this invention can be 120℃~160℃, for example 130℃, 140℃ or 150℃, and the reaction time at this temperature can be 6h~10h, for example 7h, 8h or 9h, etc. (d2) In step (3), the pyrolysis temperature is 800℃~1000℃; and / or the pyrolysis time is 1.5h~2.5h; and / or the heating rate is 4℃ / min~6℃ / min; specifically, the pyrolysis temperature in this invention can be 800℃~1000℃, for example 850℃, 900℃ or 950℃, etc., and the pyrolysis time at this temperature can be 1.5h~2.5h, for example 1.7h, 2h or 2.3h, etc.; the heating rate can be 4℃ / min~6℃ / min, for example 4.5℃ / min, 5℃ / min or 5.5℃ / min, etc.; (e2) In step (3), acid washing is performed after pyrolysis to obtain a double single-atom redox catalyst. Specifically, in this invention, acid washing is further performed after pyrolysis. Acid washing can remove substances such as metallic iron, iron carbide, and iron oxide nanoparticles. If these substances are not removed, they will dissolve, leading to rapid degradation of catalyst performance and poor stability. In addition, acid washing can also remove metals from metal-organic framework materials to prevent pore blockage. Furthermore, acid washing can also clear pores and activate impurities that block pores and amorphous carbon covering active sites, thereby increasing the catalytic activity of the redox catalyst.

[0036] In some specific examples, in the above preparation method, step (3) includes acid washing: soaking the pyrolysis product in an acid solution at 50℃~70℃ for 6h~10h.

[0037] Secondly, embodiments of the present invention provide a dual single-atom redox catalyst, which is prepared by the above-described preparation method.

[0038] It should be noted that by combining the RMF polymer with a metal-organic framework (MOF) material (such as ZIF-8), the present invention can effectively prevent structural collapse and metal agglomeration during pyrolysis, achieving high dispersion of the two atoms, thereby preparing a dual single-atom redox catalyst with excellent catalytic performance.

[0039] Thirdly, embodiments of the present invention provide a positive electrode and / or negative electrode for a fuel cell, comprising positive electrode and / or negative electrode active materials and the aforementioned dual single-atom redox catalyst.

[0040] It should be noted that the dual single-atom redox catalyst in this invention has excellent redox activity and can be coated on the surface of the positive and / or negative electrode active materials to prepare fuel cell positive and / or negative electrodes with excellent electrochemical performance; in addition, the fuel cell positive and / or negative electrodes are well known in the art.

[0041] Fourthly, embodiments of the present invention provide a fuel cell, which includes the above-mentioned positive electrode and / or negative electrode of the fuel cell, and the electrolyte of the fuel cell is an alkaline electrolyte.

[0042] It should be noted that the positive and / or negative electrodes of the fuel cell described in this invention can be used to fabricate fuel cells. The resulting fuel cells, based on the excellent electrochemical performance of the positive and / or negative electrodes, also exhibit excellent electrochemical performance, especially in alkaline electrolytes. This allows for better utilization in fields such as new energy vehicles, stationary power generation, and portable power supplies. Furthermore, the fuel cells described in this invention are known in the art, such as rechargeable zinc-air batteries or proton exchange membrane fuel cells.

[0043] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0044] Example 1 (1) Add 3.0g zinc nitrate hexahydrate ([Zn(NO3)2·6H2O]) and 6.5g 2-methylimidazole to 20mL methanol and stir magnetically for 1 hour at room temperature until completely dissolved. The solution is clear after dissolution, which is the ZIF-8 precursor solution. Add 1.0g melamine, 1.5mL formaldehyde solution (37wt.%) and 0.88g resorcinol to 20mL ethanol, and then add 0.125g ferric chloride hexahydrate ([FeCl3·6H2O]) and 0.125g copper chloride dihydrate ([CuCl2·2H2O]) as metal sources. Stir magnetically for 1 hour at room temperature. During the stirring process, the solution color gradually darkens and eventually turns brownish-red, which is the FeCu-RMF polymer precursor solution. (2) The obtained ZIF-8 precursor solution was slowly added to the obtained FeCu-RMF polymer precursor solution and mixed thoroughly to obtain a mixed solution; the pH value of the mixed solution was adjusted to 8.5 using 1M NaOH solution; the pH-adjusted mixed solution was heated to 60°C on a heating plate and kept for 1 hour with continuous stirring to obtain a preheated mixed solution. (3) Transfer the preheated mixed solution to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in an oven. Perform a hydrothermal reaction at 140℃ for 8 hours. After the reaction is completed, obtain the reaction product (solid-liquid mixture). Allow the reaction product to cool naturally to room temperature. (4) The solid product of the reaction product was washed three times with deionized water and ethanol alternately, and centrifuged after each washing (8000 rpm, 10 minutes); after washing, the solid product was placed in a vacuum drying oven and dried at 60°C for 16 hours; the dried product was ground into fine powder with an agate mortar and pestle to obtain the FeCu-ZIF-8 / RMF composite material precursor. (5) The FeCu-ZIF-8 / RMF composite precursor was placed in a tube furnace and pyrolyzed under nitrogen protection (flow rate 100 mL / min) to obtain pyrolysis products; the pyrolysis temperature program was as follows: the temperature was increased from room temperature to 900℃ at a rate of 5℃ / min, held at 900℃ for 2 hours, and then naturally cooled to room temperature. (6) The pyrolysis product was acid-leached with 0.5M sulfuric acid solution and stirred at 60°C for 8 hours. After acid leaching, it was repeatedly rinsed with deionized water until the pH of the washing solution was close to neutral. Then, centrifugation was performed (8000 rpm, 10 minutes). The product obtained by centrifugation was freeze-dried for 24 hours to obtain Fe0.125Cu0.125 / ZRMF composite material.

[0045] Example 2 Example 2 is largely the same as Example 1, except that the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and copper chloride dihydrate ([CuCl2·2H2O]) used are different. Otherwise, they are the same as in Example 1, and Fe0.25Cu0.25 / ZRMF composite material is prepared. In Example 2, the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and copper chloride dihydrate ([CuCl2·2H2O]) used are 0.25g each.

[0046] Example 3 Example 3 is largely the same as Example 1, except that 0.125g of manganese chloride tetrahydrate ([MnCl2·4H2O]) is used in Example 3 to replace 0.125g of copper chloride dihydrate ([CuCl2·2H2O]) in Example 1. Otherwise, the same as Example 1 is used to prepare Fe0.125Mn0.125 / ZRMF composite material.

[0047] Example 4 Example 4 is largely the same as Example 3, except that the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and manganese chloride tetrahydrate ([MnCl2·4H2O]) used are different. Otherwise, they are the same as in Example 1, and Fe0.25Mn0.25 / ZRMF composite material is prepared. In Example 4, the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and manganese chloride tetrahydrate ([MnCl2·4H2O]) used are 0.25g each.

[0048] Example 5 Example 5 is largely the same as Example 1, except that 0.125g of cerium chloride hexahydrate ([CeCl3·6H2O]) was used in Example 5 to replace 0.125g of copper chloride dihydrate ([CuCl2·2H2O]) in Example 1. Otherwise, the same as Example 1 was used to prepare Fe0.125Ce0.125 / ZRMF composite material.

[0049] Example 6 Example 6 is largely the same as Example 5, except that the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and cerium chloride hexahydrate ([CeCl3·6H2O]) used are different. Otherwise, they are the same as in Example 1, and Fe0.25Ce0.25 / ZRMF composite material is prepared. In Example 6, the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and cerium chloride hexahydrate ([CeCl3·6H2O]) used are 0.25 g each.

[0050] Example 7 Example 7 is largely the same as Example 1, except that 0.125g of chromium chloride hexahydrate ([CrCl3·6H2O]) is used in Example 7 instead of 0.125g of copper chloride dihydrate ([CuCl2·2H2O]) in Example 1. Otherwise, the same as in Example 1 is used to prepare Fe0.125Cr0.125 / ZRMF composite material.

[0051] Example 8 Example 8 is largely the same as Example 7, except that the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and chromium chloride hexahydrate ([CrCl3·6H2O]) used are different. Otherwise, they are the same as in Example 1, and Fe0.25Cr0.25 / ZRMF composite material is prepared. In the comparative example, the amounts of ferric chloride hexahydrate ([FeCl3·6H2O]) and chromium chloride hexahydrate ([CeCr3·6H2O]) used are 0.25 g each.

[0052] Comparative Example 1 Comparative Example 1 is largely the same as Example 2, except that copper chloride dihydrate ([CuCl2·2H2O]) was not added in Comparative Example 1. Otherwise, it is the same as Example 2, and Fe0.25 / ZRMF is prepared.

[0053] Comparative Example 2 Comparative Example 2 is largely the same as Example 2, except that ferric chloride hexahydrate ([FeCl3·6H2O]) was not added in Comparative Example 1. Otherwise, it is the same as Example 2, and Cu0.25 / ZRMF is prepared.

[0054] Comparative Example 3 Comparative Example 3 is largely the same as Example 4, except that ferric chloride hexahydrate ([FeCl3·6H2O]) was not added in Comparative Example 1. Otherwise, it is the same as Example 2, and Mn0.25 / ZRMF is prepared.

[0055] Comparative Example 4 Comparative Example 4 is largely the same as Example 6, except that ferric chloride hexahydrate ([FeCl3·6H2O]) was not added in Comparative Example 1. Otherwise, it is the same as Example 2, and Ce0.25 / ZRMF is prepared.

[0056] Comparative Example 5 Comparative Example 5 is largely the same as Example 8, except that ferric chloride hexahydrate ([FeCl3·6H2O]) was not added in Comparative Example 1. Otherwise, it is the same as Example 2, and Cr0.25 / ZRMF is prepared.

[0057] Characterization test The Fe0.125Cu0.125 / ZRMF composite materials prepared in Example 1, Example 3, Example 5, and Example 7 were observed using scanning electron microscopy (SEM). The results are as follows: Figure 1 As shown, the results indicate that the Fe0.125Ce0.125 composite material exhibits a filamentous agglomerate structure; the particle size of the other three composite materials is significantly reduced, and the surface becomes rough.

[0058] In addition, the EDS elemental composition of the Fe0.125Cu0.125 / ZRMF composite material prepared in Example 1 was analyzed, and the results are as follows: Figure 2 As shown, the results indicate that the C, N, Fe, and Cu elements in Fe0.125Cu0.125 / ZRMF are uniformly distributed, with no obvious element aggregation.

[0059] Furthermore, the microstructure of the Fe0.125Cu0.125 / ZRMF composite material prepared in Example 1 was observed by transmission electron microscopy (TEM), and the results are as follows: Figure 3As shown, the results indicate that Fe0.125Cu0.125 has a porous structure with hierarchical pores, which is beneficial for mass transfer and reaction. Fe0.125Cu0.125 / ZRMF exhibits good Fe and Cu dispersion, with no obvious metal agglomeration observed, indicating that atomic-level dispersion has been achieved. Fe0.125Cu0.125 / ZRMF has a stable carbon matrix: the nitrogen-doped carbon structure provides a stable support environment for Fe and Cu atoms. The particle size of Fe0.125Cu0.125 / ZRMF is moderate and the structure is uniform, which is beneficial for electrochemical applications.

[0060] The above structural characterization well explains the excellent performance of Fe0.125Cu0.125 / ZRMF composite material in oxygen reduction reaction, providing a solid structural basis for its application in proton exchange membrane fuel cells.

[0061] Furthermore, the X-ray diffraction (XRD) patterns of the Fe0.125Cu0.125 / ZRMF composite materials prepared in Example 1, Example 3, Example 5, and Example 7 are shown below. Figure 4 As shown, the results indicate that CeC metal carbides are present in the Fe0.125Ce0.125 catalyst powder, and the Ce aggregates into large nanoparticles on the NC substrate. The other three diatomic catalysts only contain diffraction peaks of graphitized carbon and no diffraction peaks of metal species, indicating that Cr, Mn and Cu do not aggregate into large nanoparticles on the NC substrate.

[0062] In addition, the XPS analysis results of the Fe0.125Cu0.125 / ZRMF composite material prepared in Example 1 are as follows: Figure 5 As shown, the results indicate that the Fe0.125Cu0.125 / ZRMF composite material contains C, N, Fe, Cu and O elements.

[0063] Performance testing (1) Electrochemical test under acidic conditions The ORR performance of the composite material prepared in the example was tested using a three-electrode system in 0.1M HClO4 solution. The specific test method referred to the "Electrocatalysis-Consortium-Test-Protocols" issued by the US Department of Energy (DOE) Fuel Cell Technologies Office, as follows: Ink preparation: Accurately weigh 4.0 mg of catalyst powder, add 1.0 mL of isopropanol, add 30 µL of Nafion® solution (5 wt%), and treat in an ultrasonic water bath for 1 hour to form a uniform catalyst ink; Electrode coating: Using a micropipette, accurately transfer 8.0 µL of catalyst ink and drop it onto the polished and clean surface of a rotating disk electrode (RDE, diameter 5.0 mm, area 0.196 cm²). Allow it to air dry naturally to form a catalyst film. Calculate the catalyst loading: (4.0 mg / 1.03 mL) × 0.008 mL / 0.196 cm² ≈ 0.158 mg / cm².

[0064] The electrolyte is a 0.1M HClO4 solution, the working electrode (WE) is the catalyst electrode prepared above, the counter electrode (CE) is a platinum sheet, and the reference electrode (RE) is a saturated Ag / AgCl electrode. Electrode pretreatment / activation: Immerse the electrode in an electrolyte that has been purged with nitrogen (N2) for 30 minutes; perform cyclic voltammetry (CV) scans at a rate of 100 mV / s for 50 cycles within a potential window of 0.05 V to 1.1 V vs. RHE until the CV curve stabilizes.

[0065] ORR performance test: The electrode rotation speed was set to 1600 rpm; the atmosphere was changed to oxygen (O2) and continuously introduced into the electrolyte for 30 minutes to ensure saturation, and the oxygen atmosphere on the liquid surface was maintained during the test; the ORR linear sweep voltammetry (LSV) polarization curve was recorded from 1.2V to 0.2V vs. RHE at a scan rate of 5 mV / s.

[0066] Test results are as follows Figure 6 As shown in Table 1, the data statistics are listed below.

[0067] Table 1. ORR performance of different composite materials tested under acidic conditions using a three-electrode system.

[0068] Depend on Figure 6 As shown in Table 1, in 0.1M HClO4 acidic electrolyte, the onset potential of Fe0.125Cu0.125 / ZRMF reaches 0.83V vs. RHE, the half-wave potential is 0.728V vs. RHE, and the limiting current density reaches 4.1mA / cm². 2Compared with the Fe0.125Mn0.125 / ZRMF, Fe0.125Ce0.125 / ZRMF, and Fe0.125Cr0.125 / ZRMF prepared in Example 3, the catalyst activity showed an increasing trend, with Fe0.125Cu0.125 / ZRMF achieving the best performance, indicating that the bimetallic atom catalyst composed of Fe and Cu has excellent oxygen reduction reaction activity. In addition, the onset potential and half-wave potential of the 0.25g content bimetallic atom ZRMF catalyst both decreased, which is due to the partial agglomeration caused by excess metal atoms. The half-wave potential of Fe0.25Cu0.25 / ZRMF decreased by 0.128 V vs. RHE. The above results indicate that the synergistic effect of Fe and Cu metal biatoms is the best, significantly improving the catalyst activity.

[0069] (2) Test system under alkaline conditions The ORR performance of the composite materials prepared in Examples 1, 3, 5, and 7, as well as Comparative Examples 1 to 5, was tested using a three-electrode system in a 0.1M KOH aqueous solution. Specific testing methods were based on the "Electrocatalysis-Consortium-Test-Protocols" published by the U.S. Department of Energy's Fuel Cell Technologies Office, as follows: Electrolyte: The electrolyte is a 0.1M KOH aqueous solution; Test Procedure: The ORR half-cell test under alkaline conditions was conducted in a three-electrode system, using a rotating disk electrode (RDE) as the working electrode and a platinum sheet as the counter electrode. The Hg / HgO ratio was 1 mol·L⁻¹. -1 The KOH electrode was used as the reference electrode; high-purity oxygen (O2) was bubbled into the electrolyte for 30 minutes before the test to achieve oxygen saturation; in the control experiment, high-purity nitrogen (N2) was bubbled into the electrolyte to eliminate the influence of oxygen; linear sweep voltammetry was performed at room temperature, with a scan potential range of, for example, 0.2V–1.1V (relative to the reversible hydrogen electrode RHE), and a scan rate of 5V·s. -1 –10mV·s -1 The rotational speed is 1600 r·min -1 .

[0070] Test results are as follows Figure 7 As shown in Table 2, the data statistics are listed below.

[0071] Table 2. ORR performance of different composite materials tested using a three-electrode system in 0.1M KOH solution.

[0072] Depend on Figure 7 As shown in Table 2, in 0.1M KOH alkaline electrolyte, the onset potential of Fe0.125Mn0.125 / ZRMF reaches 0.89 V vs. RHE, the half-wave potential is 0.788 V vs. RHE, and the limiting current density reaches 4.26 mA / cm². Compared with the comparative example, Fe0.125Mn0.125 / ZRMF achieves the best performance, indicating that the bimetallic atom catalyst composed of Fe and Mn has excellent oxygen reduction reaction activity. In addition, compared with the acidic environment, Fe0.125Mn0.125 / ZRMF tested in the alkaline environment shows better overall oxygen reduction reaction activity, which is of great significance to the development of zinc-air batteries.

[0073] (3) Performance testing of a single proton exchange membrane fuel cell (PEMFC) To verify the performance of the catalyst in actual devices, Fe from Example 1 was used. 0.125 Cu 0.125 / ZRMF and Fe prepared in Example 5 0.125 Ce 0.125 / ZRMF were used as cathode catalysts, assembled into an active area of ​​25 cm². 2 A membrane electrode assembly (MEA) measuring 5cm × 5cm was constructed, and single-cell testing was performed. Details are as follows: (3-1) Preparation of cathode catalyst ink: Accurately weigh 10.0 mg of Fe 0.125 Cu 0.125 / ZRMF and Fe 0.125 Ce 0.125 / ZRMF was placed in clean glass bottles; then 400 μL of isopropanol, 580 μL of deionized water and 20 μL of 5 wt.% Nafion® D-521 dispersion were added to obtain different mixtures; the different mixtures were treated in an ultrasonic (ultrasonic power 160 W, ultrasonic frequency 40 kHz, temperature 40 °C) water bath for 60 minutes to form a uniform and stable catalyst ink. (3-2) Coating of the cathode catalyst layer: The pre-cut gas diffusion layer (GDL, Sigrette 29BC, area 25 cm²) is coated onto the cathode catalyst layer. 2 The cathode catalyst ink was fixed on a heating plate and the temperature was set to 60°C. Using a doctor blade, the prepared cathode catalyst ink was uniformly coated onto the gas diffusion layer. Through multiple coating and drying processes, the cathode catalyst loading was precisely achieved at 3.0 mg / cm³. 2 The prepared cathode gas diffusion electrode (GDE) was dried in a vacuum oven at 60°C for 2 hours for later use.

[0074] (3-3) Preparation of the anode gas diffusion electrode: A commercial platinum-carbon (Pt / C) catalyst (Johnson Matthey Hispec 4000, 40 wt.% Pt) was used as the anode catalyst; catalyst ink was prepared using the same method as the cathode and coated onto the gas diffusion layer, so that the noble metal platinum (Pt) loading of the anode was 0.1 mg / cm³. 2 .

[0075] (3-4) Hot-press assembly of membrane electrode: The Nafion® 212 proton exchange membrane was pretreated in deionized water at 80°C for 1 hour, then treated in 0.5M sulfuric acid solution at 80°C for 1 hour, and finally washed several times in deionized water at 80°C. The pretreated proton exchange membrane was placed between the cathode GDE and the anode GDE, ensuring that the catalyst layer faced the proton exchange membrane. This "sandwich" structure was then placed in a hot press and hot-pressed at 135°C and 1.5MPa for 3 minutes to obtain an active area of ​​25cm². 2 A membrane electrode (MEA) measuring 5cm x 5cm.

[0076] The test conditions were as follows: battery temperature 80℃, anode / cathode humidification temperature 80℃ (100%RH), anode / cathode gas H2 / air, and back pressure 150kPa. Before the test, the battery voltage was kept constant at 0.6V for 1 hour to fully wet the proton exchange membrane and activate the catalyst surface. After the battery was fully activated, its polarization curve and power density curve were recorded.

[0077] Test results are as follows Figure 8 As shown, the results indicate that the fuel cell using the composite material prepared in Example 1 as the catalyst has a high open-circuit voltage and peak power density (387.20 mW·cm⁻¹). -2 The results show that the electrochemical performance of the fuel cell using the composite material prepared in Example 1 as a catalyst is better than that of the fuel cell using the composite material prepared in Example 5 as a catalyst.

[0078] (4) Performance testing of rechargeable zinc-air batteries To verify the bifunctional properties (ORR and OER) of the composite material as a catalyst, Fe from Example 1 was used. 0.125 Cu 0.125 / ZRMF and Fe prepared in Example 5 0.125 Ce 0.125 ZRMF was used as an air electrode catalyst to assemble a rechargeable zinc-air battery, and then its electrochemical performance was tested. Details are as follows: (4-1) Preparation of catalyst ink: Accurately weigh 10.0 mg of catalyst powder, add 450 μL of isopropanol and 50 μL of 5 wt.% Nafion® solution; sonicate (ultrasonic power 160 W, ultrasonic frequency 40 kHz, temperature 40 °C) for 60 minutes to form a uniform ink. (4-2) Electrode coating: The catalyst ink is uniformly drop-coated onto an area of ​​1.0 cm². 2 An air electrode was obtained by placing the catalyst on carbon paper (TorayTGP-H-060) and allowing it to air dry naturally; the catalyst loading was controlled at 3.0 mg / cm³. 2 The prepared air electrode was dried in a vacuum oven at 60°C for 2 hours for later use. (4-3) Battery assembly: Zinc sheet is used as the anode, and 6.0M KOH solution + 0.2M zinc acetate solution is used as the electrolyte.

[0079] The open-circuit voltage, discharge polarization curve, power density curve, and constant-current charge-discharge cycle stability of the battery were tested. The test results are as follows: Figure 9 As shown, the results indicate that the zinc-air battery assembled using the composite materials prepared in Examples 1 and 5 as catalysts exhibits a high open-circuit voltage, a low charge-discharge voltage, and a peak power density of 160.47 mW·cm⁻¹. -2 (Example 1) and 157.6 mW·cm -2 (Example 5) demonstrates its superior bifunctional catalytic activity and its application value in the field of metal-air batteries.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a dual-atomic single oxidation-reduction catalyst, characterized by, The preparation method comprises: (1) mixing and reacting a metal organic framework material solution and a diatomic-amine aldehyde polymer solution to obtain a mixed solution; (2) performing hydrothermal reaction on the mixed solution to obtain a reaction product; (3) performing pyrolysis on the reaction product to obtain a diatomic-single atomic redox catalyst. The preparation method of the diatomic-amine aldehyde polymer solution comprises: mixing an amino compound, an aldehyde compound, a phenolic compound, an iron source and other metal sources in a solvent to obtain the diatomic-amine aldehyde polymer solution; the other metal sources are selected from any one of a copper source, a manganese source, a cerium source or a chromium source.

2. The preparation method according to claim 1, wherein a molar ratio of a total amount of metals in the iron source and the other metal sources to metal elements in the metal organic framework material solution is (0.01-0.5):1; and / or a mass ratio of iron in the iron source to metals in the other metal sources is 1:(0.8-1.2).

3. The preparation method according to claim 2, wherein a molar ratio of a total amount of metals in the iron source and the other metal sources to metal elements in the metal organic framework material solution is (0.04-0.19):1; and / or a mass ratio of iron in the iron source to metals in the other metal sources is 1:

1. The preparation method satisfies one or more combinations of the following conditions: (a1) the metal organic framework material is selected from ZIF-8; (b1) the amino compound is selected from one or more combinations of melamine, urea or aniline; (c1) the aldehyde compound is selected from one or more combinations of formaldehyde, acetaldehyde, furfural or benzaldehyde; 4. The production method according to any one of claims 1 to 3, characterized by, (d1) the phenolic compound is selected from one or more combinations of resorcinol, phenol, hydroquinone, catechol, phenothalin or tannic acid; (e1) the iron source or the other metal source is independently selected from one or more combinations of a corresponding metal inorganic salt, a metal organic acid salt or an organic metal complex; (f1) the solvent is selected from one or more combinations of polar organic solvents; or the solvent is selected from one or more combinations of polar organic solvents and water.

5. The preparation method according to claim 4, wherein the metal inorganic salt is selected from one or more of metal chloride, metal sulfide or metal nitrate; and / or the metal organic acid salt is selected from one or more of metal acetate, metal oxalate or metal citrate; and / or the organic metal complex is selected from one or more of metallocene compound, metal porphyrin or metal phthalocyanine. The preparation method satisfies one or more combinations of the following conditions: (a2) in step (1), the mixed solution is adjusted to be alkaline before hydrothermal reaction; (b2) in step (1), the mixed solution is preheated before hydrothermal reaction, the preheating temperature is 40-80℃; and / or the preheating time is 0.5-1.5h; (c2) in step (2), the hydrothermal reaction temperature is 120-160℃; and / or the hydrothermal reaction time is 6-10h; (d2) in step (3), the pyrolysis temperature is 800-1000℃; and / or the pyrolysis time is 1.5-2.5h; and / or the heating rate is 4-6℃ / min. ​ ​ 6. The production method according to claim 1, 2, 3 or 5, characterized by, ​ ​ ​ ​ ​ (e2) In step (3), the diatomic redox catalyst is obtained by acid washing after pyrolysis.

7. The production method according to claim 6, wherein In step (3), the acid washing comprises: soaking the pyrolysis product in an acid solution at 50-70°C for 6-10 hours.

8. A diatomic redox catalyst characterized by, The diatomic redox catalyst is prepared by the method of any one of claims 1-7.

9. A fuel cell anode and / or cathode, characterised in that, The diatomic redox catalyst of claim 8 is used in the positive and / or negative active material of a battery.

10. A fuel cell, characterized by The fuel cell positive and / or negative electrode of claim 9 is used in a fuel cell with an alkaline electrolyte.

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