ZIF-L derived Fe-N-C oxygen reduction catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemical catalysis, and particularly discloses a ZIF-L derived Fe-N-C oxygen reduction catalyst and a preparation method and application thereof.The preparation method comprises the following steps that water serves as a solvent to prepare an aqueous MOF material ZIF-L, a ferric iron source is introduced in the ZIF-L growth process, and a Fe-ZIF-L precursor is obtained; and calcining the Fe-ZIF-L precursor to obtain the Fe-N-C oxygen reduction catalyst. According to the method, the ZIF-L is prepared by taking water as a solvent, and multiple cheap iron sources are directly doped in the growth process of the ZIF-L to prepare the Fe-ZIF-L precursor, so that the use of an organic solvent in a traditional method is avoided, the preparation cost is remarkably reduced, meanwhile, the environmental pollution is reduced, and the method has good economical efficiency and environmental sustainability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical catalysis, and in particular to a ZIF-L-derived Fe-NC oxygen reduction catalyst and a preparation method and application thereof. Background Art

[0002] Fuel cells and metal-air batteries, as efficient energy conversion devices, have broad application prospects in the field of clean energy. The oxygen reduction reaction (ORR) occurring at the cathode is a key reaction in energy conversion devices such as fuel cells and metal-air batteries. However, the slow kinetics and diverse reaction pathways of the oxygen reduction reaction lead to low energy conversion efficiency. It is usually necessary to use efficient electrocatalysts to accelerate the reaction rate, thereby improving the performance and efficiency of the above-mentioned energy conversion devices. At present, Pt-based catalysts are the most commonly used ORR catalysts. They have excellent ORR catalytic activity and low overpotential, and can effectively reduce the energy barrier of the oxygen reduction reaction. However, their high cost and scarce reserves limit the large-scale use of Pt-based catalysts in the energy field. Therefore, the development of low-cost, highly active non-precious metal catalysts to replace Pt-based catalysts for catalyzing oxygen reduction reactions has become an important research direction in the current field of electrocatalysis.

[0003] In recent years, Fe-NC catalysts have attracted widespread attention due to their excellent ORR catalytic performance and significant cost advantages. This type of catalyst combines Fe atoms with nitrogen-doped carbon substrates to form Fe-N with high ORR activity. x Active sites, showing performance close to or even better than that of Pt-based catalysts. However, the existing preparation methods of Fe-NC catalysts usually require multi-step reactions or complex post-treatment processes (such as acid washing and secondary calcination, etc.), and the synthesis process is cumbersome and costly.

[0004] Zeolitic imidazole framework materials (ZIFs) are a type of porous material formed by self-assembly of metal ions and imidazole ligands. They have a high specific surface area and abundant nitrogen-doped sites, and can be synthesized under mild conditions. Through high-temperature calcination, ZIFs materials can be converted into carbon substrates that are self-doped with nitrogen, which are ideal precursors for preparing Fe-NC catalysts. However, the synthesis of ZIF-8 and ZIF-67 usually requires the use of organic solvents such as methanol and N,N-dimethylformamide, which not only increases production costs, but also produces organic waste liquid and poses a risk of secondary pollution. Therefore, this application intends to develop a ZIF-L-derived Fe-NC oxygen reduction catalyst with low production cost, no organic waste liquid, and no secondary pollution, which provides a new technical approach to achieve efficient, low-cost and sustainable ORR catalyst preparation. Summary of the Invention

[0005] In view of the above-mentioned shortcomings, the present invention provides a ZIF-L-derived Fe-NC oxygen reduction catalyst, a preparation method and application thereof. The present invention avoids the use of organic solvents in traditional methods, significantly reduces the preparation cost, and at the same time reduces environmental pollution, and has good economic efficiency and environmental sustainability. The catalyst prepared by the present invention exhibits excellent catalytic activity for oxygen reduction reactions in both neutral and alkaline systems, and its reduction peak potential and half-wave potential are close to or even better than those of commercial 20% Pt / C catalysts. It has significant catalytic performance advantages and is suitable for practical application scenarios such as fuel cells and metal-air batteries. The present invention has a simple synthesis process, mild reaction conditions, and is easy to mass-produce, and has broad prospects for industrial application.

[0006] To achieve the above objectives, the present invention provides a method for preparing a ZIF-L-derived Fe-NC oxygen reduction catalyst, comprising the following steps: preparing an aqueous MOF material ZIF-L using water as a solvent, introducing a trivalent iron source during the growth of the ZIF-L to obtain a Fe-ZIF-L precursor; and calcining the Fe-ZIF-L precursor to obtain a Fe-NC oxygen reduction catalyst.

[0007] According to one aspect of the present invention, the ferric iron source is a soluble ferric iron compound; the soluble ferric iron compound includes at least one of ferric acetylacetonate, potassium ferrocyanide, ammonium ferric oxalate, ferric nitrate, and ferric chloride.

[0008] According to one aspect of the present invention, the calcination is specifically: under the protection of an inert atmosphere, the temperature is raised from room temperature to 850-1050° C. at a rate of 2-10° C. / min and kept at that temperature for 45-90 min.

[0009] According to one aspect of the present invention, the following steps are included:

[0010] S1. Dissolve 2-methylimidazole in ultrapure water with stirring, add an iron source and mix thoroughly to obtain solution A; dissolve zinc nitrate hexahydrate in ultrapure water to obtain solution B; add solution B to solution A and mix thoroughly to obtain solution C;

[0011] S2. Place solution C in a water bath and stir to react to obtain a suspension containing a Fe-ZIF-L precursor; the reaction temperature is 15-40° C. and the reaction time is 12-24 h;

[0012] S3. Centrifuging, washing, drying and calcining the suspension containing the Fe-ZIF-L precursor to obtain a Fe-NC oxygen reduction catalyst.

[0013] According to one aspect of the present invention, in step S1, the concentration of 2-methylimidazole in the solution C is 0.3-1.0 mol / L; the 2-methylimidazole in the solution C and Zn2+ The molar ratio is 6:1-10:1.

[0014] According to one aspect of the present invention, it is characterized in that, in step S1, the Fe 3+ With Zn 2+ The molar ratio is 0.06-0.24:1.

[0015] According to one aspect of the present invention, in step S3, the centrifugation, washing, and drying steps are specifically as follows: the suspension containing the Fe-ZIF-L precursor is divided into centrifuge tubes, and centrifuged at a speed of 3000-10000 rpm for 2-5 minutes to separate the solid product; then, the separated solid product is centrifuged and washed three times with ultrapure water to obtain a pure Fe-ZIF-L precursor; and the pure Fe-ZIF-L precursor is placed in a vacuum drying oven and dried at 50-80°C for 8-24 hours.

[0016] According to one aspect of the present invention, in step S3, the calcination is performed under the protection of an inert atmosphere comprising at least one of nitrogen and argon.

[0017] With the same inventive concept, the present invention also provides a ZIF-L-derived Fe-NC oxygen reduction catalyst prepared by any of the above-mentioned preparation methods.

[0018] Based on the same inventive concept, the present invention also provides the use of the above-mentioned ZIF-L-derived Fe-NC oxygen reduction catalyst in a conversion device of a fuel cell or a metal-air battery to replace a Pt-based catalyst as a cathode oxygen reduction catalyst.

[0019] Beneficial effects of the present invention:

[0020] (1) ZIF-L is prepared using water as a solvent, and a variety of cheap iron sources are directly doped during the growth of ZIF-L to prepare Fe-ZIF-L precursors, which avoids the use of organic solvents in traditional methods, significantly reduces preparation costs, and reduces environmental pollution, with good economic and environmental sustainability. The prepared catalyst exhibits excellent catalytic activity for oxygen reduction reactions in both neutral and alkaline systems. Its reduction peak potential and half-wave potential are close to or even better than those of commercial 20% Pt / C catalysts, with significant catalytic performance advantages and suitable for practical application scenarios such as fuel cells and metal-air batteries. The synthesis process of the present invention is simple, the reaction conditions are mild, and it is easy to scale up production, with broad prospects for industrial application.

[0021] (2) The present invention uses water as a solvent to prepare ZIF-L, and directly dopes a variety of cheap iron sources during the growth process of ZIF-L to prepare a Fe-ZIF-L precursor. During this reaction process, ZIF-L undergoes a second nucleation on the surface of the initial ZIF-L, thereby forming a 3D flower-like structure. Compared with sheet-like ZIF-L, the 3D flower-like ZIF-L has a larger specific surface area and can provide more active sites for oxygen reduction reactions. The Fe-NC catalyst obtained by calcining the Fe-ZIF-L precursor at high temperature well maintains the original 3D flower-like structure of the Fe(acac)3-ZIF-L precursor, which is conducive to the uniform dispersion of Fe. In addition, a small amount of carbon nanotubes can be observed in the Fe-NC catalyst, which is conducive to enhancing the local graphitization degree of the carbon skeleton, thereby enhancing the stability of the Fe-NC catalyst.

[0022] (3) The aqueous ZIF-L derivative material in the preparation method of the present invention has clear restrictions on the iron source. Only trivalent iron compounds can obtain materials with oxygen reduction catalytic activity, while the currently used divalent iron compounds cannot successfully obtain materials with oxygen reduction catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the Fe(acac)3-ZIF-L precursor prepared in Example 1 of the present invention;

[0024] Figure 2 This is a SEM image of the Fe-NC catalyst prepared in Example 1 of the present invention;

[0025] Figure 3 This is the cyclic voltammogram of the Fe-NC catalyst prepared in Example 1 of the present invention under alkaline conditions (commercial 20% Pt / C is used as a reference);

[0026] Figure 4 This is the cyclic voltammogram of the Fe-NC catalyst prepared in Example 1 of the present invention under neutral conditions (commercial 20% Pt / C is used as a reference);

[0027] Figure 5 Cyclic voltammograms of the Fe-NC catalysts prepared in Examples 2 to 5 of the present invention under alkaline conditions (commercial 20% Pt / C is used as a reference);

[0028] Figure 6 Cyclic voltammograms of the Fe-NC catalysts prepared in Examples 2 to 5 of the present invention under neutral conditions (commercial 20% Pt / C is used as a reference);

[0029] Figure 7 Cyclic voltammograms of the powder materials prepared in Comparative Examples 1 to 4 of the present invention under alkaline conditions (commercial 20% Pt / C is used as a reference);

[0030] Figure 8 Cyclic voltammograms of the powder materials prepared in Comparative Examples 1 to 4 of the present invention under neutral conditions (commercial 20% Pt / C is used as a reference);

[0031] Figure 9 This is the linear sweep voltammogram of the Fe-NC catalyst prepared in Example 1 of the present invention under alkaline conditions (commercial 20% Pt / C is used as a reference);

[0032] Figure 10 This is the linear sweep voltammogram of the Fe-NC catalyst prepared in Example 1 of the present invention under neutral conditions (commercial 20% Pt / C is used as a reference);

[0033] Figure 11 Linear sweep voltammograms of the Fe-NC catalysts prepared in Examples 2 to 5 of the present invention under alkaline conditions (commercial 20% Pt / C is used as a reference);

[0034] Figure 12 Linear sweep voltammogram of the Fe-NC catalyst prepared in Examples 2 to 5 of the present invention under neutral conditions (commercial 20% Pt / C is used as a reference)

[0035] Figure 13 Linear sweep voltammograms of the powder materials prepared in Comparative Examples 1 to 4 of the present invention under alkaline conditions (commercial 20% Pt / C is used as a reference);

[0036] Figure 14 Linear sweep voltammograms of the powder materials prepared in Comparative Examples 1 to 4 of the present invention under neutral conditions (commercial 20% Pt / C is used as a reference). DETAILED DESCRIPTION

[0037] To make the present invention easier to understand, the present invention is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by professional and technical personnel in this field; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by known methods.

[0038] In order to solve the problems of high production cost, generation of organic waste liquid, and secondary pollution of the redox catalysts of the cathode oxygen reduction reaction of existing fuel cells and metal-air batteries, the inventors provide a preparation method of a ZIF-L-derived Fe-NC oxygen reduction catalyst, comprising the following steps: preparing an aqueous MOF material ZIF-L using water as a solvent, introducing a trivalent iron source during the growth of ZIF-L to obtain a Fe-ZIF-L precursor; and calcining the Fe-ZIF-L precursor to obtain a Fe-NC oxygen reduction catalyst.

[0039] In some specific embodiments, the ferric iron source is a soluble ferric iron compound; the soluble ferric iron compound includes at least one of ferric acetylacetonate, potassium ferric cyanide, ammonium ferric oxalate, ferric nitrate, and ferric chloride.

[0040] In some specific embodiments, the calcination is specifically: under the protection of an inert atmosphere, the temperature is raised from room temperature to 850-1050° C. at a rate of 2-10° C. / min and kept at that temperature for 45-90 min.

[0041] In some specific embodiments, the steps include:

[0042] S1. Dissolve 2-methylimidazole in ultrapure water with stirring, add an iron source and mix thoroughly to obtain solution A; dissolve zinc nitrate hexahydrate in ultrapure water to obtain solution B; add solution B to solution A and mix thoroughly to obtain solution C;

[0043] S2. Place solution C in a water bath and stir to react to obtain a suspension containing a Fe-ZIF-L precursor; the reaction temperature is 15-40° C. and the reaction time is 12-24 h;

[0044] S3. Centrifuging, washing, drying and calcining the suspension containing the Fe-ZIF-L precursor to obtain a Fe-NC oxygen reduction catalyst.

[0045] In some specific embodiments, in step S1, the concentration of 2-methylimidazole in the solution C is 0.3-1.0 mol / L; the 2-methylimidazole in the solution C and Zn 2+ The molar ratio is 6:1-10:1.

[0046] In some specific embodiments, it is characterized in that, in step S1, the Fe 3+ With Zn 2+ The molar ratio is 0.06-0.24:1.

[0047] In some specific embodiments, in step S3, the centrifugation, washing, and drying steps are specifically as follows: the suspension containing the Fe-ZIF-L precursor is divided into centrifuge tubes, and centrifuged at a speed of 3000-10000 rpm for 2-5 minutes to separate the solid product; then, the separated solid product is centrifuged and washed three times with ultrapure water to obtain a pure Fe-ZIF-L precursor; and the pure Fe-ZIF-L precursor is placed in a vacuum drying oven and dried at 50-80°C for 8-24 hours.

[0048] In some specific embodiments, in step S3, the calcination is performed under the protection of an inert atmosphere comprising at least one of nitrogen and argon.

[0049] The present invention also provides a ZIF-L-derived Fe-NC oxygen reduction catalyst prepared by any of the above-mentioned preparation methods.

[0050] The present invention also provides the use of the ZIF-L derived Fe-NC oxygen reduction catalyst as a cathode oxygen reduction catalyst in a conversion device of a fuel cell or a metal-air battery, replacing a Pt-based catalyst.

[0051] The following is further described with reference to specific embodiments and comparative examples.

[0052] Example 1

[0053] A method for preparing a ZIF-L-derived Fe-NC oxygen reduction catalyst comprises the following steps:

[0054] (1) 0.08 mol of 2-methylimidazole was stirred and dissolved in 80 mL of ultrapure water, and 0.0012 mol of ferric acetylacetonate (Fe(acac)3) was added to form solution A; 0.01 mol of zinc nitrate hexahydrate was stirred and dissolved in 40 mL of ultrapure water to form solution B; solution B was added to solution A and stirred to mix uniformly to prepare reaction solution C. The concentration of 2-methylimidazole in solution C was 0.67 mol / L, and the reaction mixture of 2-methylimidazole and Zn 2+ The molar ratio of Fe(acac)3 and Zn is 8:1. 2+ The molar ratio is 0.12:1.

[0055] (2) Solution C was placed in a 30°C water bath and stirred for 24 h to prepare a suspension containing the Fe(acac)3-ZIF-L precursor.

[0056] (3) The suspension was divided into centrifuge tubes and centrifuged at a speed of 3000-10000 rpm for 2-5 minutes to separate the solid product; then, the separated solid product was centrifuged and washed three times with ultrapure water to obtain a pure Fe(acac)3-ZIF-L precursor, which was placed in a vacuum drying oven and dried at 60°C for 24 hours; the dried Fe(acac)3-ZIF-L precursor was placed in a tubular furnace and, under the protection of a N2 atmosphere, the temperature was raised from room temperature to 900°C at a rate of 5°C / min and kept warm for 60 minutes, and then naturally cooled to room temperature to obtain a Fe-NC catalyst.

[0057] Example 2

[0058] The difference between this embodiment and embodiment 1 is that ferric acetylacetonate (Fe(acac)3) is replaced by potassium ferrocyanide (K3[Fe(CN)6]). Other steps and parameters are the same as those in embodiment 1.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is that ferric acetylacetonate (Fe(acac)3) is replaced by ammonium ferric oxalate ((NH4)3[Fe(C2O4)]). Other steps and parameters are the same as those in embodiment 1.

[0061] Example 4

[0062] The difference between this embodiment and embodiment 1 is that ferric acetylacetonate (Fe(acac)3) is replaced by ferric nitrate (Fe(NO3)3). Other steps and parameters are the same as those in embodiment 1.

[0063] Example 5

[0064] The difference between this embodiment and embodiment 1 is that ferric acetylacetonate (Fe(acac)3) is replaced by ferric chloride (FeCl3). Other steps and parameters are the same as those in embodiment 1.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that no iron source is added. Other steps and parameters are the same as those in Example 1.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that ferrous acetylacetonate (Fe(acac)3) is replaced by ferrous sulfate (FeSO4). Other steps and parameters are the same as those in Example 1.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 1 is that iron acetylacetonate (Fe(acac)3) is replaced by iron phthalocyanine (FePc). Other steps and parameters are the same as those in Example 1.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 1 is that ferric acetylacetonate (Fe(acac)3) is replaced by ferrous chloride (FeCl2). Other steps and parameters are the same as those in Example 1.

[0073] Performance testing and result analysis:

[0074] Microscopic morphology detection:

[0075] The Fe(acac)3-ZIF-L precursor prepared in step (2) of Example 1 was subjected to scanning electron microscopy (SEM) analysis, and the results are as follows: Figure 1 As shown. Figure 1 The Fe(acac)3-ZIF-L precursor prepared in Example 1 exhibits a 3D flower-like structure composed of an orderly combination of sheet-like structures. This is related to the secondary nucleation and growth of ZIF-L on the surface of the initial ZIF-L during the reaction. Compared with sheet-like ZIF-L, the 3D flower-like ZIF-L has a larger specific surface area and can provide more active sites for the oxygen reduction reaction.

[0076] The Fe-NC catalyst prepared in step (3) of Example 1 was subjected to scanning electron microscopy (SEM) analysis, and the results were as follows: Figure 2 As shown. Figure 2 The Fe-NC catalyst prepared in Example 1 of the present invention maintains the original 3D flower-like structure of the Fe(acac)3-ZIF-L precursor, facilitating uniform dispersion of Fe. Furthermore, a small amount of carbon nanotubes is observed in the Fe-NC catalyst, enhancing the localized graphitization of the carbon skeleton and thus the stability of the Fe-NC catalyst.

[0077] Electrochemical performance test:

[0078] (1) Cyclic voltammetry test

[0079] The commercial 20% Pt / C catalyst, the materials finally prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to cyclic voltammetry tests in an O2-saturated 0.1 mol / L KOH solution (alkaline conditions) and a 0.05 mol / L phosphate buffer solution (acidic conditions). The cyclic voltammetry tests were performed on a Donghua DH7000 electrochemical workstation using a three-electrode system, wherein the working electrode was a glassy carbon electrode with a diameter of 3 mm, the counter electrode was a square platinum electrode with a side length of 10 mm, and the reference electrode was a silver-silver chloride electrode; the catalyst loading on the working electrode was 0.354 mg / cm 2Under alkaline conditions, the cyclic voltammetry test potential range is 1.17 ~ 0.17V (vs. RHE) with a scan rate of 10mV / s; under neutral conditions, the cyclic voltammetry test potential range is 1.03 ~ -0.17V (vs. RHE) with a scan rate of 10mV / s. The results are as follows Figure 3-8 As shown in Table 1.

[0080] (2) Linear sweep voltammetry test

[0081] The commercial 20% Pt / C catalyst, the materials finally prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to linear voltammetric sweep tests in an O2-saturated 0.1 mol / L KOH solution (alkaline conditions) and a 0.05 mol / L phosphate buffer solution (neutral conditions). The linear voltammetric sweep tests were performed on a Metrohm Autolab PGSTAT204 electrochemical workstation (Switzerland) using a three-electrode system, wherein the working electrode was a rotating disk electrode with a diameter of 5 mm, the counter electrode was a carbon rod electrode, and the reference electrode was a silver-silver chloride electrode; the catalyst loading on the working electrode was 0.354 mg / cm 2 Under alkaline conditions, the cyclic voltammetry test potential range is 1.17 ~ 0.07V (vs. RHE) with a scan rate of 10mV / s; under neutral conditions, the cyclic voltammetry test potential range is 1.02 ~ -0.18V (vs. RHE) with a scan rate of 10mV / s. The rotating disk electrode speed is 1600rpm. The results are as follows Figure 9-14 and as shown in Table 1.

[0082] Table 1 Comparison of the performance of the materials finally prepared from commercial 20% Pt / C, Examples 1-5 and Comparative Examples 1-4 under cyclic voltammetry and linear sweep voltammetry tests under alkaline and neutral conditions, respectively

[0083]

[0084] Depend on Figure 3-14 As shown in Table 1, under neutral conditions, the Fe-NC catalysts obtained in Examples 1-5 all exhibited oxygen reduction catalytic activity superior to that of commercial 20% Pt / C. Under alkaline conditions, the Fe-NC catalysts obtained in Examples 1-5 all exhibited oxygen reduction catalytic activity, with the catalysts in Examples 2 and 3 exhibiting significantly better activity than commercial 20% Pt / C. The powdered materials obtained in Comparative Examples 1-4 exhibited no significant oxygen reduction catalytic activity under either alkaline or neutral conditions, indicating that the aqueous ZIF-L-derived materials prepared using this method have clear limitations on the iron source. Only trivalent iron compounds can produce materials with oxygen reduction catalytic activity, while currently used divalent iron compounds are incapable of successfully producing materials with oxygen reduction catalytic activity.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a ZIF-L-derived Fe-NC oxygen reduction catalyst, characterized in that: The following steps are involved: The aqueous MOF material ZIF-L was prepared using water as the solvent. A trivalent iron source was introduced during the growth process of ZIF-L to obtain a Fe-ZIF-L precursor; the Fe-ZIF-L precursor was calcined to obtain a Fe-NC oxygen reduction catalyst.

2. The method for preparing the ZIF-L derived Fe-NC oxygen reduction catalyst according to claim 1, wherein The ferric iron source is a soluble ferric iron compound; the soluble ferric iron compound includes at least one of ferric acetylacetonate, potassium ferrocyanide, ammonium ferric oxalate, ferric nitrate, and ferric chloride.

3. The method for preparing the ZIF-L derived Fe-NC oxygen reduction catalyst according to claim 1, wherein The calcination is specifically as follows: under the protection of an inert atmosphere, the temperature is raised from room temperature to 850-1050° C. at a rate of 2-10° C. / min and kept at that temperature for 45-90 minutes.

4. The method for preparing the ZIF-L-derived Fe-NC oxygen reduction catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Dissolve 2-methylimidazole in ultrapure water with stirring, add an iron source, and mix thoroughly to obtain solution A. Dissolve zinc nitrate hexahydrate in ultrapure water to obtain solution B; add solution B to solution A and mix well to obtain solution C; S2. Place solution C in a water bath and stir to react to obtain a suspension containing a Fe-ZIF-L precursor; the reaction temperature is 15-40° C. and the reaction time is 12-24 h; S3. Centrifuging, washing, drying and calcining the suspension containing the Fe-ZIF-L precursor to obtain a Fe-NC oxygen reduction catalyst.

5. The method for preparing the ZIF-L derived Fe-NC oxygen reduction catalyst according to claim 4, characterized in that: In step S1, the concentration of 2-methylimidazole in the solution C is 0.3-1.0 mol / L; the 2-methylimidazole in the solution C and Zn 2+ The molar ratio is 6:1-10:

1.

6. The method for preparing the ZIF-L derived Fe-NC oxygen reduction catalyst according to claim 4, characterized in that: In step S1, the Fe in the solution C 3+ With Zn 2+ The molar ratio is 0.06-0.24:

1.

7. The method for preparing the ZIF-L derived Fe-NC oxygen reduction catalyst according to claim 4, characterized in that: In step S3, the centrifugation, washing, and drying steps are specifically as follows: the suspension containing the Fe-ZIF-L precursor is divided into centrifuge tubes, and centrifuged at a speed of 3000-10000 rpm for 2-5 minutes to separate the solid product; then, the separated solid product is centrifuged and washed three times with ultrapure water to obtain a pure Fe-ZIF-L precursor; and the pure Fe-ZIF-L precursor is placed in a vacuum drying oven and dried at 50-80°C for 8-24 hours.

8. The method for preparing the ZIF-L-derived Fe-NC oxygen reduction catalyst according to claim 4, wherein: In step S3, the calcination is performed under the protection of an inert atmosphere comprising at least one of nitrogen and argon.

9. A ZIF-L derived Fe-NC oxygen reduction catalyst prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the ZIF-L derived Fe-NC oxygen reduction catalyst as claimed in claim 9 as a cathode oxygen reduction catalyst in a conversion device of a fuel cell or a metal-air battery, replacing a Pt-based catalyst.

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