Pentacoordinated iron monatomic catalyst, its preparation method and application

Abstract

This invention belongs to the field of catalysts, specifically relating to a five-coordinate iron single-atom catalyst, its preparation method, and its application. The method includes the following steps: mixing carbon materials with an inorganic acid and heating in a water bath to obtain activated carbon materials; dispersing the activated carbon materials at a mass ratio of 1:(3-5) with a nitrogen-containing precursor in an alcohol-water mixed solution, and performing a high-temperature hydrothermal reduction reaction to obtain a nitrogen-doped activated carbon support; dispersing the nitrogen-doped activated carbon support at a mass ratio of 1:(0.05-0.2) with a four-coordinate iron compound in an alcohol solution, and performing high-temperature pyrolysis under an inert atmosphere to obtain the five-coordinate iron single-atom catalyst. This invention achieves controllable doping of nitrogen in carbon materials through a high-temperature hydrothermal reduction reaction, adsorbs and disperses the four-coordinate iron compound on the surface of the nitrogen-doped activated carbon support, and obtains the five-coordinate iron single-atom catalyst through calcination activation. This catalyst is used in the ethylbenzene oxidation reaction and exhibits high activity and selectivity for the selective oxidation of the C(sp3)-H bonds of ethylbenzene.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to the preparation and application of single-atom catalyst materials, and more specifically to a five-coordinate iron single-atom catalyst, its preparation method, and its application. Background Technology

[0002] Noble metal catalysts are widely used in energy conversion, chemical production, and environmental remediation processes. However, the scarcity and high price of precious metals themselves severely restrict their large-scale practical application. Therefore, there is an urgent need to develop efficient and stable supported non-precious metal catalysts to replace them. Among them, MNC materials (where M is a former transition metal such as Co / Fe / Ni) have shown excellent performance in ORR, CO2 electroreduction, HER, and fine chemical synthesis, and are considered a very promising class of non-precious metal catalysts that can replace precious metals.

[0003] Typically, MNC materials are prepared by high-temperature calcination of transition metal salts, nitrogen sources, and carbon supports, resulting in multiphase complex structures and compositions. Therefore, determining the structure of catalytic active sites in MNC catalysts has always been a challenge in the research of this type of non-noble metal catalyst. The main reason for the difficulty in elucidating the active sites of MNC catalysts is the non-uniform particle size and composition of currently synthesized MNC materials. Nanoparticles, metal oxides, nitrides, carbides, and single-atom dispersed M-Nx species coexist in a single catalyst, making it difficult to identify the active centers of the MNC.

[0004] On the other hand, single-atom catalysts are a class of heterogeneous catalysts in which the active metal is dispersed as a single atom. Because single-atom catalysts are free from interference from other metal species, they facilitate the identification of active site structures. Therefore, the preparation of MNC single-atom catalysts holds promise as a breakthrough for elucidating the active sites of MNC catalysts. However, although MNC single-atom catalysts have been widely used in electrocatalytic processes, they have rarely been used in organic synthesis reactions, especially the highly challenging activation of CH bonds.

[0005] In existing research, reference 1 (Liu, W. et al. J. Am. Chem. Soc. 2017, 139, 10790-10798) successfully prepared an atomically dispersed self-supporting Fe-NC catalyst using nano-MgO as a sacrificial template. All Fe atoms were atomically dispersed, and the density of single-atom sites depended on the pyrolysis temperature. This Fe-NC catalyst exhibited excellent catalytic performance in the selective oxidation of ethylbenzene via the CH bond. Poisoning experiments and spectroscopic characterization revealed that the Fe-NC catalyst contained multiple coordination structures for ferric ions (FeN...). xAmong the five-coordinate Fe-N5 structures (x = 4, 5, 6), the spin-based five-coordinate Fe-N5 structure exhibits the highest catalytic activity, yet it only accounts for 18% of the total, indicating significant room for improvement in the activity of the Fe-NC catalyst. Reference 2 (Denget al. Sci. Adv. 2015, 1(11), e1500462) reports a four-coordinate Fe-NC single-atom catalyst. This catalyst was prepared by high-energy ball milling of iron phthalocyanine and graphene nanosheets, achieving single-atom dispersion of four-coordinate FeN4 centers on a graphene substrate. In this system, the unsaturated coordinated FeN4 centers are highly dispersed and stable within the graphene substrate, thereby enhancing the activity and stability of benzene oxidation to phenol. This reaction can proceed effectively at room temperature, and even at temperatures as low as 0°C. However, the conversion frequency (TOF) of this catalyst for the selective oxidation of benzene is relatively low, and its intrinsic activity needs further improvement.

[0006] Based on the deficiencies and problems existing in the above-mentioned research, this invention designs a novel uniform five-coordinate Fe-NC single-atom catalyst, explores its application potential in the field of CH bond activation, and aims to resolve the long-standing debate on the difficulty in identifying active sites in MNC materials by using targeted characterization techniques. Summary of the Invention

[0007] The purpose of this invention is to solve the aforementioned problems in the prior art, and to propose a five-coordinate iron single-atom catalyst, its preparation method, and its application. Controllable doping of nitrogen in carbon materials is achieved through a high-temperature hydrothermal reduction reaction. Subsequently, a pre-prepared four-coordinate iron compound is adsorbed and dispersed on the surface of a nitrogen-doped activated carbon support, and then calcined and activated at a certain temperature to obtain the final product, a five-coordinate single-atom iron catalyst. This catalyst is applied to the selective oxidation reaction of ethylbenzene. In the ethylbenzene oxidation application, it significantly improves the C(sp) content of ethylbenzene. 3 The selective oxidation of the -H bond has high activity and selectivity.

[0008] The technical solution of this invention is:

[0009] 1. A method for preparing a five-coordinate iron single-atom catalyst, comprising the following steps:

[0010] (1) Mix carbon material with inorganic acid and heat in a water bath at 50-95°C for 2-4 hours to obtain activated carbon material;

[0011] (2) The activated carbon material with a mass ratio of 1:(3~5) and the nitrogen-containing precursor are dispersed in an alcohol-water mixed solution and subjected to a high-temperature hydrothermal reduction reaction at 150~400℃ for 2~10h to obtain a nitrogen-doped activated carbon carrier.

[0012] (3) A nitrogen-doped active carbon support with a mass ratio of 1:(0.05~0.2) and a tetracoordinated iron compound are dispersed in an alcohol solution, dried, and then pyrolyzed at 300~900℃ for 1~5h under an inert atmosphere to obtain a pentacoordinated iron single-atom catalyst.

[0013] Furthermore, the tetracoordinated iron compound is one or more of tetraphenylporphyrin iron, o-phenanthroline iron, Schiff base iron, urea iron, and phthalocyanine iron.

[0014] Furthermore, the carbon material is one or more of carbon fiber, carbon nanotubes, carbon black, graphene, and graphite, and the inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, boric acid, and carbonic acid.

[0015] Furthermore, the nitrogen-containing precursor is one or more of p-nitroaniline, dicyandiamide, triethylamine, aminocyanide, and melamine.

[0016] Furthermore, in step (1), after heating in a water bath, the material is condensed and refluxed, cooled to room temperature, then separated by filtration with alcohol or water, washed 3 to 5 times, dried at 55 to 65°C for 5 to 7 hours, and ground to obtain activated carbon material.

[0017] Preferably, the water bath heating temperature is 70-90℃ and the heating time is 3 hours.

[0018] In step (1), there is no specific ratio between the amount of carbon material and inorganic acid added; it is sufficient to control the amount of inorganic acid added to cover the carbon material.

[0019] Furthermore, in the alcohol-water mixed solution of step (2), the volume ratio of alcohol to water is 1:(0.5-3);

[0020] The activated carbon material and nitrogen-containing precursor are dispersed in an alcohol-water mixed solution, stirred to ensure uniform mixing, and then subjected to a high-temperature hydrothermal reduction reaction for 20-40 minutes.

[0021] After the reaction, the mixture was cooled to room temperature, washed 2-5 times by centrifugation with ethanol and water, dried at 55-65℃ for 10-14 hours, and then ground to obtain a nitrogen-doped activated carbon support.

[0022] Furthermore, in step (3), the nitrogen-doped activated carbon support is first added to an alcohol solution and dissolved by ultrasonication; then the tetracoordinated iron compound is added to an alcohol solution and dissolved by ultrasonication; then the two are mixed and stirred at 380-420 rpm for 25-35 min, dried by rotary evaporation, dried at 55-65℃ for 5.5-6.5 h, and pyrolyzed at high temperature under an inert atmosphere to obtain a five-coordinated iron single-atom catalyst.

[0023] This invention also protects a five-coordinate iron single-atom catalyst, prepared by the above-described method. The five-coordinate iron single-atom catalyst comprises an active metal component, a ligand, and a support. The active metal component is loaded on the support in a single-atom dispersed state. The support is a nitrogen-doped active carbon support, and the nitrogen content in the support is 20-50 wt%.

[0024] This invention also protects the application of the five-coordinated iron single-atom catalyst in the ethylbenzene oxidation reaction.

[0025] The beneficial effects of this invention are:

[0026] (1) This invention achieves controllable doping of nitrogen ligands in carbon materials through a hydrothermal doping strategy to obtain nitrogen-doped active carbon support. A five-coordinate iron single-atom catalyst with uniform sites is synthesized by covalent adsorption of a well-defined four-coordinate iron compound with the nitrogen-doped active carbon support. The synthesis method is simple, easy to scale up, and can be industrialized. The five-coordinate iron single-atom catalyst can be used for ethylbenzene oxidation reaction and has excellent performance for ethylbenzene oxidation. The catalyst has the advantages of high catalytic efficiency, good cycle effect, and low cost.

[0027] (2) In this invention, metallic iron is loaded onto a carbon material support as the active metal, and a nitrogen-containing precursor is modified onto the support. After calcination and activation treatment, a five-coordinate iron single-atom catalyst is prepared. Unlike the iron single-atom sites that are generally mixed with three-coordinate, four-coordinate and five-coordinate in existing studies, this invention can synthesize very uniform five-coordinate iron single atoms (characterized by Mössler spectrum). The five-coordinate iron single atoms can be uniformly dispersed on the catalyst surface. This catalyst has excellent catalytic performance in the selective oxidation reaction of CH bonds of ethylbenzene, that is, it has high catalytic activity, selectivity and stability.

[0028] (3) The five-coordinate iron single-atom catalyst prepared by the present invention can remain inactive for a long time in an air atmosphere, and the catalyst synthesis steps are simple; the single-atom catalyst is easy to recover and has excellent recycling performance. Attached Figure Description

[0029] Figure 1 Aberration-corrected electron micrograph of the Fe-NC-1-1# catalyst provided in Example 1 of this invention;

[0030] Figure 2 The image shows the Mössler spectrum of the Fe-NC-1-1# catalyst provided in Example 1 of this invention. Detailed Implementation

[0031] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments, and the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a five-coordinated iron single-atom catalyst for use in the oxidation reaction of ethylbenzene, and also provides a method for preparing the catalyst, comprising the following steps:

[0033] A mixed solution of carbon material and inorganic acid is heated in a water bath at 50–95°C for 2–4 hours, maintained under reflux, and cooled to room temperature. The mixture is then separated by filtration with alcohol or water, washed 3–5 times, dried at 55–65°C for 5–7 hours, and ground to obtain activated carbon material. The activated carbon material (mass ratio 1:(3–5)) and a nitrogen-containing precursor are dispersed in an alcohol-water mixed solution (volume ratio 1:(0.5–3)). The mixture is stirred for 20–40 minutes to ensure homogeneity and then transferred to a hydrothermal reactor for a high-temperature hydrothermal reduction reaction at 150–400°C. After reacting for 2–10 hours, the mixture is cooled to room temperature, washed 2–5 times by centrifugation with ethanol and water, and then dried at 55–65°C. After drying for 10–14 h, the sample was removed and ground to obtain a nitrogen-doped activated carbon support. The nitrogen-doped activated carbon support with a mass ratio of 1:(0.05–0.2) was mixed with a tetracoordinated iron compound and placed in an alcohol solution for ultrasonic treatment. The mixture was stirred at 380–420 rpm for 25–35 min, and the tetracoordinated iron compound was strongly adsorbed onto the surface of the nitrogen-doped activated carbon support through metal-nitrogen covalent interactions. Subsequently, the solution was dried by rotary evaporation at 55–65 °C to obtain a black powder, which was then transferred to a tube furnace and pyrolyzed at 300–900 °C for 1–5 h under an inert atmosphere to obtain a five-coordinated iron single-atom catalyst.

[0034] Example 1

[0035] Weigh 1.0g of carbon fiber, dissolve it in 100mL of nitric acid, heat it in a water bath at 90℃ for 3h, reflux it, cool it to room temperature, wash it 4 times by alcohol filtration, dry it in an oven at 60℃ for 6h, and then grind it to obtain activated carbon material, labeled as C-1#.

[0036] Weigh 200 mg C-1#, 20 mL anhydrous ethanol, 20 mL water and 760 mg p-nitroaniline and stir for 30 min to mix well. Add to a hydrothermal reactor and heat in an oven at 200 °C for 6 h. After taking it out, wash it three times with ethanol and water respectively. Then transfer it to a vacuum drying oven and dry it at 60 °C for 12 h. After taking it out, grind it to obtain nitrogen-doped activated carbon support, labeled as NC-1-1#.

[0037] Weigh 100 mg of N-C-1-1# and place it in a beaker. Add 40 mL of methanol to dissolve the catalyst and sonicate for 20 min. Dissolve 10 mg of o-phenanthroline iron in 2 mL of methanol and sonicate for 10 min. Add the dissolved 10 mg of phenanthroline iron to a flask and place it on a magnetic stirrer. Stir at 400 rpm for 30 min. After rotary evaporation to dry the catalyst, place it in a vacuum drying oven at 60 °C for 6 h. Then, place it in a tube furnace and purge with nitrogen gas at 500 °C for 1 h to obtain a five-coordinate iron single-atom catalyst, labeled Fe-NC-1-1#.

[0038] The aberration-corrected electron microscopy image of the five-coordinate iron single-atom catalyst Fe-NC-1-1# is shown below. Figure 1 As shown, its Mu spectrum is as follows Figure 2 As shown.

[0039] Example 2

[0040] Weigh 1.0g of carbon nanotubes, dissolve them in 100mL of hydrochloric acid, heat in a water bath at 70℃ for 2h, reflux, cool to room temperature, wash three times with water by vacuum filtration, dry in an oven at 55℃ for 5.5h, and grind to obtain activated carbon material, labeled C-2#.

[0041] Weigh 200 mg C-2#, 20 mL anhydrous ethanol, 40 mL water and 600 mg dicyandiamide and stir for 20 min to mix well. Add to a hydrothermal reactor and heat in an oven at 150 °C for 3 h. After taking it out, wash it twice with ethanol and water respectively. Then transfer it to a vacuum drying oven and dry it at 55 °C for 10 h. After taking it out, grind it to obtain nitrogen-doped activated carbon support, labeled as NC-2-1#.

[0042] Weigh 100 mg of N-C-2-1# and place it in a beaker. Add 40 mL of methanol to dissolve the catalyst and sonicate for 20 min. Dissolve 15 mg of tetraphenylporphyrin iron in 2 mL of methanol and sonicate for 10 min. Add the dissolved catalyst to a flask and place it on a magnetic stirrer. Stir at 3800 rpm for 25 min. After rotary evaporation to dry the catalyst, place it in a vacuum drying oven at 55 °C for 6 h. Then, place it in a tube furnace, purge with nitrogen, and heat at 300 °C for 2 h to obtain a five-coordinate iron single-atom catalyst, labeled Fe-NC-2-1#.

[0043] Example 3

[0044] Weigh 1.0g of carbon black, dissolve it in 100mL of sulfuric acid, heat it in a water bath at 95℃ for 4h, reflux it, cool it to room temperature, wash it 5 times by alcohol filtration, dry it in an oven at 65℃ for 6.5h, and then grind it to obtain activated carbon material, labeled as C-3#.

[0045] Weigh 200 mg C-3#, 20 mL anhydrous ethanol, 60 mL water and 1000 mg triethylamine and stir for 40 min to mix well. Add to a hydrothermal reactor and heat in an oven at 400 °C for 10 h. After taking it out, wash it 5 times with ethanol and water respectively. Then transfer it to a vacuum drying oven and dry it at 65 °C for 14 h. After taking it out, grind it to obtain nitrogen-doped activated carbon support, labeled as NC-3-1#.

[0046] Weigh 100 mg of N-C-3-1# and place it in a beaker. Add 40 mL of methanol to dissolve the solution and sonicate for 20 min. Dissolve 20 mg of Schiff base iron in 2 mL of methanol and sonicate for 10 min. Add the solution to a flask and place it on a magnetic stirrer. Stir at 420 rpm for 35 min. After rotary evaporation to dry the solution, place it in a vacuum drying oven at 65 °C for 6 h. Then, place it in a tube furnace and purge with nitrogen at 900 °C for 5 h to obtain a five-coordinate iron single-atom catalyst, labeled Fe-NC-3-1#.

[0047] Example 4

[0048] Weigh 1.0g of graphene, dissolve it in 100mL of boric acid, heat it in a water bath at 50℃ for 3.5h, reflux it, cool it to room temperature, separate it by water filtration, wash it 4 times, dry it in an oven at 60℃ for 6h, and then grind it to obtain activated carbon material, labeled as C-4#.

[0049] Weigh 200 mg C-4#, 20 mL anhydrous ethanol, 50 mL water and 800 mg aminocyanide and stir for 30 min to mix well. Add to a hydrothermal reactor and heat in an oven at 300 °C for 5 h. After taking it out, wash it three times with ethanol and water respectively. Then transfer it to a vacuum drying oven and dry it at 60 °C for 12 h. After taking it out, grind it to obtain nitrogen-doped activated carbon support, labeled as NC-4-1#.

[0050] Weigh 100 mg of NC-4-1# and place it in a beaker. Add 40 mL of methanol to dissolve the NC-4-1# and sonicate for 20 min. Dissolve 7 mg of urea iron in 2 mL of methanol and sonicate for 10 min. Add the urea iron to a flask and place it on a magnetic stirrer. Stir at 400 rpm for 30 min. After rotary evaporation to dry the urea iron, place it in a vacuum drying oven at 60 °C for 6 h. Then, place the urea iron in a tube furnace and purge it with nitrogen. Heat at 600 °C for 3 h to obtain a five-coordinate iron single-atom catalyst, labeled Fe-NC-4-1#.

[0051] Example 5

[0052] Weigh 1.0g of graphite, dissolve it in 100mL of carbonic acid, heat it in a water bath at 80℃ for 3h, reflux it, cool it to room temperature, separate it by alcohol filtration, wash it 4 times, dry it in an oven at 60℃ for 6h, and then grind it to obtain activated carbon material, labeled as C-5#.

[0053] Weigh 200 mg C-5#, 20 mL anhydrous ethanol, 10 mL water and 700 mg melamine and stir for 30 min to mix well. Add to a hydrothermal reactor and heat in an oven at 230 °C for 6 h. After taking it out, wash it three times with ethanol and water respectively. Then transfer it to a vacuum drying oven and dry it at 60 °C for 12 h. After taking it out, grind it to obtain nitrogen-doped activated carbon carrier, labeled as NC-5-1#.

[0054] Weigh 100 mg of N-C-5-1# and place it in a beaker. Add 40 mL of methanol to dissolve the catalyst and sonicate for 20 min. Dissolve 17 mg of iron phthalocyanine in 2 mL of methanol and sonicate for 10 min. Add the dissolved phthalocyanine to a flask and place it on a magnetic stirrer. Stir at 400 rpm for 30 min. After rotary evaporation to dry the catalyst, place it in a vacuum drying oven at 60 °C for 6 h. Then, place it in a tube furnace and purge with nitrogen gas at 700 °C for 4 h to obtain a five-coordinate iron single-atom catalyst, labeled Fe-NC-5-1#.

[0055] Comparative Example 1

[0056] The difference between Comparative Example 1 and Example 1 is that copper acetate is used instead of iron o-phenanthroline, while the other steps are the same as those in Example 1.

[0057] Comparative Example 2

[0058] The difference between Comparative Example 2 and Example 2 is that tetraamminecopper sulfate is used instead of tetraphenylporphyrin iron, while the other steps are the same as those in Example 2.

[0059] Comparative Example 3

[0060] The difference between Comparative Example 3 and Example 3 is that nickel phthalocyanine is used instead of Schiff base iron, while the other steps are the same as those in Example 3.

[0061] Application Example 1

[0062] The catalysts prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to experiments, and the steps are as follows:

[0063] The water bath was heated to 45°C. 5 mg of the catalysts prepared in Examples 1-5 and Comparative Examples 1-3 were weighed and placed in centrifuge tubes. 32 μL of ethylbenzene and 5 mL of water were added, and the tubes were placed in the water bath and allowed to stand for 5 min. 400 μL of tert-butyl hydroperoxide was added, and the mixture was stirred at 400 rpm for 5 min. After stirring was stopped, 8 μL of trimethylbenzene internal standard and 15 mL of ethyl acetate were added for extraction. The mixture was shaken, allowed to stand, and allowed to separate into layers. The upper organic layer was collected, filtered through an organic membrane, and the filtrate was injected into a chromatographic vial for GC-MS analysis. The results are shown in Table 1 below.

[0064] Table 1. GC-MS analysis results of catalysts in Examples 1-5 and Comparative Examples 1-3

[0065]

[0066]

[0067] As shown in Table 1 above, the five-coordinate copper compound cannot oxidize ethylbenzene, while the five-coordinate nickel compound has a low conversion rate of ethylbenzene; the five-coordinate iron compound has the best conversion rate of ethylbenzene and the best selectivity for the product acetophenone.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Use of a penta-coordinated iron-singlet catalyst in the oxidation of ethylbenzene, characterized in that, The preparation method of the five-coordinated iron single atom catalyst comprises the following steps: (1) mixing a carbon material with an inorganic acid, heating in a water bath at 50-95°C for 2-4 h to obtain an activated carbon material; (2) dispersing the activated carbon material and a nitrogen-containing precursor in an alcohol-water mixed solution at a mass ratio of 1: (3-5), and performing a high-temperature hydrothermal reduction reaction at 150-400°C for 2-10 h to obtain a nitrogen-doped active carbon carrier; (3) dispersing the nitrogen-doped active carbon carrier and a four-coordinated iron compound in an alcohol solution at a mass ratio of 1: (0.05-0.2), drying, and then pyrolyzing at 300-900°C in an inert atmosphere for 1-5 h to obtain a five-coordinated iron single atom catalyst; wherein the four-coordinated iron compound is one or more of tetraphenylporphyrin iron, phenanthroline iron, Schiff base iron, urea iron, and phthalocyanine iron; the nitrogen-containing precursor is one or more of p-nitroaniline, dicyandiamide, triethylamine, cyanamide, and melamine.

2. Use according to claim 1, characterized in that, The carbon material is one or more of carbon fiber, carbon nanotube, carbon black, graphene, and graphite, and the inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, boric acid, and carbonic acid.

3. Use according to claim 1, characterized in that, In step (1), after water bath heating, condensation refluxing, and cooling to room temperature, the activated carbon material is obtained by alcohol or water filtration separation, washing 3-5 times, drying at 55-65°C for 5-7 h, and grinding.

4. Use according to claim 1, characterized in that, In the alcohol-water mixed solution of step (2), the volume ratio of alcohol to water is 1: (0.5-3); After the activated carbon material and the nitrogen-containing precursor are dispersed in the alcohol-water mixed solution and stirred to mix uniformly, high-temperature hydrothermal reduction reaction is performed, and the stirring time is 20-40 min; After cooling to room temperature, the nitrogen-doped active carbon carrier is obtained by centrifugal washing with ethanol and water 2-5 times, drying at 55-65°C for 10-14 h, and grinding after removal.

5. The use according to claim 1, characterized in that, In step (3), the nitrogen-doped active carbon carrier is first added to an alcohol solution and ultrasonically dissolved; then the four-coordinated iron compound is added to the alcohol solution and ultrasonically dissolved; and then the two are mixed, stirred at a speed of 380-420 rpm for 25-35 min, dried by rotary evaporation, dried at 55-65°C for 5.5-6.5 h, and pyrolyzed at high temperature in an inert atmosphere to obtain the five-coordinated iron single atom catalyst.

6. Use according to any one of claims 1 to 5, characterized in that, In the five-coordinated iron single atom catalyst prepared by the preparation method, the active metal component is dispersed in a single atom state on the carrier, and the carrier is a nitrogen-doped active carbon carrier, and the content of the doped nitrogen element in the carrier is 20-50 wt%.

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