A nitrogen-doped porous carbon supported iron-selenium transition metal composite material, a preparation method and application thereof

Abstract

The application belongs to the technical field of battery materials, and discloses a nitrogen-doped porous carbon loaded iron-selenium transition metal composite material and a preparation method and application thereof. The method innovatively introduces Se atoms in Fe single-atom catalysts, and the components are uniformly distributed on the nitrogen-doped carbon-based material. The introduction of Se can adjust the electronic structure and microenvironment of the Fe site through p-d orbital hybridization, thereby optimizing the adsorption / desorption behavior between the active site and the intermediate in the ORR process, not only ensuring the efficient use of the catalyst, but also greatly enhancing the catalytic efficiency through the synergistic effect between iron-selenium particles. In addition, the synthesis method of the composite material is simple and easy to implement, and has high economic efficiency, laying a solid foundation for realizing industrialized mass production. Compared with traditional platinum-carbon catalysts, the composite material catalyst of the application has significant advantages in electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and specifically relates to a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material, its preparation method and application. Background Technology

[0002] Metal-air batteries, a novel energy conversion device that directly converts chemical energy into electrical energy without combustion, have attracted widespread attention due to their high efficiency and environmental friendliness. These batteries can significantly reduce greenhouse gas emissions and environmental pollution, while also effectively improving energy efficiency, offering new possibilities for achieving global energy transition and sustainable development goals. Metal-air batteries possess characteristics such as high specific capacity, low cost, and low pollution, and have broad application prospects. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material; this preparation method has low preparation cost, simple preparation method, and the obtained composite material has excellent oxygen reduction electrocatalytic activity.

[0004] Another objective of this invention is to provide a nitrogen-doped porous carbon-supported iron selenium transition metal composite material prepared by the above-described preparation method.

[0005] Another object of the present invention is to provide an application of the above-mentioned nitrogen-doped porous carbon-supported iron selenium transition metal composite material.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material includes the following steps:

[0008] The magnesium-zinc NC precursor and selenium compound were ground and mixed together, and then placed together with the transition metal iron compound in a tube furnace. The mixture was calcined by vapor deposition under nitrogen or inert gas. The calcined product was ground, acid-washed, filtered, dried, and then calcined a second time to obtain a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material. The molar ratio of the transition metal iron compound to the selenium compound was (0.1-5):(0.1-6); the molar ratio of the transition metal iron compound to the magnesium-zinc NC precursor was (0.01-1):(0.1-5).

[0009] This invention employs a template-based synthesis strategy to form a transition metal single-atom catalyst supported on porous doped carbon materials. Specifically, this invention develops an electrocatalyst containing Fe single-atom doped Se particles on N-doped porous carbon. Due to the synergistic effect between the Fe and Se particles, charge redistribution can be regulated, and the electronic structure and microenvironment optimized, effectively reducing adsorption energy and synergistically improving catalytic activity, significantly promoting the oxygen reduction reaction.

[0010] The magnesium-zinc NC precursor is synthesized from magnesium chloride, p-phenylenediamine, sodium chloride, and zinc chloride, specifically prepared according to the following steps:

[0011] (1) Mix 1 mmol of anhydrous magnesium chloride and 20 mL of methanol with magnetic stirring until completely dissolved to obtain solution A;

[0012] (2) Mix 10 mmol of p-phenylenediamine and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution B;

[0013] (3) Mix 700 mg sodium chloride, 1300 mg zinc chloride and 20 mL deionized water with magnetic stirring until completely dissolved to obtain solution C;

[0014] (4) Add solution A to solution B and stir for 10 min. Then pour solution C into the mixture. Stir the resulting mixture magnetically for more than 6 hours. Then freeze it with liquid nitrogen and freeze-dry it for 36 h. After drying, grind the resulting solid for 10 min. Calcinate the resulting powder particles in a tube furnace at 900 °C for 2 h under a nitrogen atmosphere with a heating rate of 5 °C / min. Grind the calcined powder particles again for 10 min. Then rinse and filter with deionized water to remove soluble salt ions. Acid wash with 0.5 mol / L sulfuric acid for 12 h. Then filter with deionized water. After filtration, dry in an oven at 70 °C for 12 h. Grind the dried sample for 30 min and calcine it again in a tube furnace at 900 °C for 2 h under a nitrogen atmosphere with a heating rate of 5 °C / min to obtain the magnesium-zinc NC precursor.

[0015] The molar ratio of the transition metal iron compound to the selenium compound is 1:1; the molar ratio of the transition metal iron compound to the magnesium zinc NC precursor is (0.01-0.5):(0.5-3).

[0016] The drying is carried out in an oven at a temperature of 20–100°C, preferably 75°C.

[0017] The calcination temperature is 600–1100℃, and the time is 0.5–3 hours.

[0018] The secondary calcination temperature is 900℃ and the time is 2 hours.

[0019] A nitrogen-doped porous carbon-supported iron-selenium transition metal composite material prepared by the above preparation method, wherein iron atoms and selenium atoms are uniformly distributed on the nitrogen-doped carbon-based material in the composite material.

[0020] The above-mentioned nitrogen-doped porous carbon-supported iron-selenium transition metal composite material is used in metal-air batteries.

[0021] A metal-air battery cathode material, the cathode material comprising the above-mentioned nitrogen-doped porous carbon-supported iron-selenium transition metal composite material.

[0022] The present invention has the following advantages and beneficial effects compared with the prior art:

[0023] (1) This invention provides a method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material. This method uses a template synthesis strategy to prepare an electrocatalyst containing Fe single-atom-doped Se particles on N-doped porous carbon. This catalyst innovatively introduces Se atoms into the Fe single-atom catalyst, with the components uniformly distributed on the nitrogen-doped carbon-based material. The introduction of Se allows for pd orbital hybridization to regulate the electronic structure and microenvironment of the Fe sites, thereby optimizing the adsorption / desorption behavior between the active sites and intermediates during the ORR process. This not only ensures efficient catalyst utilization but also significantly enhances catalytic efficiency and promotes the oxygen reduction reaction through the synergistic effect between the iron-selenium particles.

[0024] (2) The nitrogen-doped porous carbon-supported iron-selenium transition metal composite material prepared in this invention exhibits excellent oxygen reduction electrocatalytic activity, comparable to that of Pt / C catalysts in alkaline electrolytes, with a half-wave potential reaching 0.89 V (vs. RHE), and demonstrates higher power density and superior 5 mA cm⁻¹ performance compared to commercial Pt / C. -2 Long-term discharge performance and step discharge performance. Attached Figure Description

[0025] Figure 1 XRD patterns of Fe-Se / NC, Fe / NC, Se / NC, and NC obtained in Examples 1-4 of this invention;

[0026] Figure 2 SEM image of Fe-Se / NC prepared in Example 1 of this invention;

[0027] Figure 3 TEM of Fe-Se / NC obtained in Example 1 of this invention;

[0028] Figure 4 The oxygen reduction activity test graphs are for Fe-Se / NC, Fe / NC, Se / NC, NC and commercial Pt / C prepared in Examples 1 to 4 of this invention;

[0029] Figure 5 The graph shows the power test results of the magnesium metal air battery provided in Embodiment 7 of the present invention.

[0030] Figure 6 The 10mA cm of the magnesium metal air battery provided in Embodiment 7 of the present invention -2 Graph of constant current discharge test results;

[0031] Figure 7 The figure shows the step discharge test results of the magnesium metal air battery provided in Embodiment 7 of the present invention.

[0032] Figure 8 The graph shows the power test results of the zinc metal air battery provided in Embodiment 8 of the present invention;

[0033] Figure 9 The 10mA cm of the zinc metal air battery provided in Embodiment 8 of the present invention -2 Graph of constant current discharge test results;

[0034] Figure 10 The figure shows the step discharge test results of the zinc metal air battery provided in Embodiment 8 of the present invention. Detailed Implementation

[0035] The following specific embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention.

[0036] Example 1

[0037] This embodiment describes the preparation of a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material, Fe-Se / NC. The specific preparation steps are as follows:

[0038] Solution A: Mix 1 mmol of anhydrous magnesium chloride and 20 mL of methanol, and stir magnetically until completely dissolved to obtain solution A;

[0039] Solution B: Mix 10 mmol of p-phenylenediamine and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution B;

[0040] Solution C: Mix 700 mg sodium chloride, 1300 mg zinc chloride and 20 mL deionized water, and stir magnetically until completely dissolved to obtain solution C.

[0041] Solution A was slowly added to solution B, and after stirring for 10 minutes, solution C was slowly poured in as well. The resulting mixture was magnetically stirred for more than six hours, then frozen with liquid nitrogen, and then freeze-dried in a freeze dryer for 36 hours. After drying, the resulting solid was ground for 10 minutes, and the resulting powder particles were calcined in a tube furnace at 900°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min. The calcined powder particles were ground again for 10 minutes, then washed and filtered with a large amount of deionized water to remove soluble salt ions. The powder particles were then acid-washed with 0.5 mol / L sulfuric acid for 12 hours, and then filtered with a large amount of deionized water. After filtration, the powder particles were dried in an oven at 70°C for 12 hours. The dried sample was ground for 30 minutes, and then calcined a second time in a tube furnace at 900°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min, to obtain the magnesium-zinc NC precursor.

[0042] Magnesium-zinc NC precursor and diphenyldiselenic ether were ground and mixed at a molar ratio of 20:1 for 10 min. Then, ferrocene (the molar ratio of ferrocene to magnesium-zinc NC precursor was 1:20) was weighed and placed together in a tube furnace for calcination using vapor deposition at 950℃ under a nitrogen atmosphere for 2 h at a heating rate of 5℃ / min. The resulting sample was ground for 10 min and then acid-washed with 0.5 mol / L sulfuric acid for 12 h. Afterward, it was filtered with a large amount of deionized water and dried in an oven at 70℃ for 12 h. The dried and ground sample was then calcined a second time at 900℃ under a nitrogen atmosphere in a tube furnace for 2 h at a heating rate of 5℃ / min to obtain a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material, denoted as Fe-Se / NC.

[0043] Example 2

[0044] This embodiment describes the preparation of nitrogen-doped porous carbon-supported iron transition metal composite material Fe / NC. The specific preparation steps are as follows:

[0045] Solution A: Mix 1 mmol of anhydrous magnesium chloride and 20 mL of methanol, and stir magnetically until completely dissolved to obtain solution A;

[0046] Solution B: Mix 10 mmol of p-phenylenediamine and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution B;

[0047] Solution C: Mix 700 mg sodium chloride, 1300 mg zinc chloride and 20 mL deionized water, and stir magnetically until completely dissolved to obtain solution C.

[0048] Solution A was slowly added to solution B, and after stirring for 10 minutes, solution C was slowly poured in as well. The resulting mixture was magnetically stirred for more than six hours, then frozen with liquid nitrogen, and then freeze-dried in a freeze dryer for 36 hours. After drying, the resulting solid was ground for 10 minutes, and the resulting powder particles were calcined in a tube furnace at 900°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min. The calcined powder particles were ground again for 10 minutes, then washed and filtered with a large amount of deionized water to remove soluble salt ions. The powder particles were then acid-washed with 0.5 mol / L sulfuric acid for 12 hours, and then filtered with a large amount of deionized water. After filtration, the powder particles were dried in an oven at 70°C for 12 hours. The dried sample was ground for 30 minutes, and then calcined a second time in a tube furnace at 900°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min, to obtain the magnesium-zinc NC precursor.

[0049] Ferrocene and the aforementioned magnesium-zinc NC precursor were weighed at a molar ratio of 1:20 and calcined together in a tube furnace using vapor deposition at 950°C under a nitrogen atmosphere for 2 hours at a heating rate of 5°C / min. The resulting sample was then ground for 10 minutes and acid-washed with 0.5 mol / L sulfuric acid for 12 hours. Afterward, it was filtered with a large amount of deionized water and dried in an oven at 70°C for 12 hours. The dried and ground sample was then calcined a second time in a tube furnace at 900°C under a nitrogen atmosphere for 2 hours at a heating rate of 5°C / min to obtain a nitrogen-doped porous carbon-supported iron transition metal composite material, denoted as Fe / NC.

[0050] Example 3

[0051] This embodiment describes the preparation of a nitrogen-doped porous carbon-supported selenium transition metal composite material (Se / NC). The specific preparation steps are as follows:

[0052] Solution A: Mix 1 mmol of anhydrous magnesium chloride and 20 mL of methanol, and stir magnetically until completely dissolved to obtain solution A;

[0053] Solution B: Mix 10 mmol of p-phenylenediamine and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution B;

[0054] Solution C: Mix 700 mg sodium chloride, 1300 mg zinc chloride and 20 mL deionized water, and stir magnetically until completely dissolved to obtain solution C.

[0055] Solution A was slowly added to solution B, and after stirring for 10 minutes, solution C was slowly poured in as well. The resulting mixture was magnetically stirred for more than six hours, then frozen with liquid nitrogen, and then freeze-dried in a freeze dryer for 36 hours. After drying, the resulting solid was ground for 10 minutes, and the resulting powder particles were calcined in a tube furnace at 900°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min. The calcined powder particles were ground for 10 minutes, then washed with a large amount of deionized water and filtered to remove soluble salt ions. Then, the powder was acid-washed with 0.5 mol / L sulfuric acid for 12 hours, and then filtered with a large amount of deionized water. After filtration, the powder was dried in an oven at 70°C for 12 hours. The dried sample was ground for 30 minutes and then calcined a second time in a tube furnace at 900°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min, to obtain the magnesium-zinc NC precursor.

[0056] Magnesium-zinc NC precursor and diphenyldiselenic ether were ground and mixed at a molar ratio of 20:1 for 10 min, then calcined in a tube furnace at 950℃ under a nitrogen atmosphere for 2 h at a heating rate of 5℃ / min. The resulting sample was ground for 10 min and then acid-washed with 0.5 mol / L sulfuric acid for 12 h. It was then filtered with a large amount of deionized water and dried in an oven at 70℃ for 12 h. The dried and ground sample was then calcined a second time in a tube furnace at 900℃ under a nitrogen atmosphere for 2 h at a heating rate of 5℃ / min to obtain a nitrogen-doped porous carbon-supported selenium transition metal composite material, denoted as Se / NC.

[0057] Example 4

[0058] This embodiment describes the preparation of the precursor NC. The specific preparation steps are as follows:

[0059] Solution A: Mix 1 mmol of anhydrous magnesium chloride and 20 mL of methanol, and stir magnetically until completely dissolved to obtain solution A;

[0060] Solution B: Mix 10 mmol of p-phenylenediamine and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution B;

[0061] Solution C: Mix 700 mg sodium chloride, 1300 mg zinc chloride and 20 mL deionized water, and stir magnetically until completely dissolved to obtain solution C.

[0062] Solution A was slowly added to solution B, and after stirring for 10 minutes, solution C was slowly poured in as well. The resulting mixture was magnetically stirred for more than six hours, then frozen with liquid nitrogen, and then freeze-dried in a freeze dryer for 36 hours. After drying, the resulting solid was ground for 10 minutes, and the resulting powder particles were calcined in a tube furnace under a nitrogen atmosphere at 900°C for 2 hours at a heating rate of 5°C / min. The calcined powder particles were then ground for 10 minutes, followed by rinsing and filtration with a large amount of deionized water to remove soluble salt ions. The powder was then acid-washed with 0.5 mol / L sulfuric acid for 12 hours, followed by filtration with a large amount of deionized water. After filtration, the powder was dried in an oven at 70°C for 12 hours. The dried sample was ground for 30 minutes, and then calcined a second time in a tube furnace under a nitrogen atmosphere at 900°C for 2 hours at a heating rate of 5°C / min to obtain the magnesium-zinc NC precursor, denoted as NC.

[0063] Example 5

[0064] 1. The Fe-Se / NC, Fe / NC, Se / NC and NC obtained in Examples 1-4 were characterized by XRD, and the results are as follows: Figure 1 As shown.

[0065] like Figure 1 As shown, Fe-Se / NC, Fe / NC, Se / NC, and NC were successfully prepared in Examples 1-4. The main phases of Fe-Se / NC are FeSe and FeC phases; the main phases of Fe / NC and Se / NC are FeC and SeC phases, respectively; and the main phase of NC is C phase.

[0066] 2. The Fe-Se / NC prepared in Example 1 was characterized by SEM and TEM, and the results are as follows: Figure 2 , 3 As shown.

[0067] like Figure 2 , 3 As shown, the Fe-Se / NC material exhibits a large number of uniformly distributed pores, demonstrating its highly porous nature. Furthermore, TEM images reveal that Fe-Se / NC possesses a very large surface area, which facilitates the anchoring of individual atoms and positively contributes to promoting contact between target molecules and active sites.

[0068] Example 6

[0069] The oxygen reduction activity of Fe-Se / NC, Fe / NC, Se / NC, and NC prepared in Examples 1-4, and commercial Pt / C was tested. The specific preparation steps are as follows:

[0070] Weigh 8 mg of the samples prepared in Examples 1-4 into sample vials, add 1 ml of ethanol, 1 ml of deionized water, and 80 μl of Nafion, and sonicate for 30 minutes to obtain a solution. After sonication, use a pipette to drop 12.5 μL of the solution onto a glassy carbon electrode and dry the water and alcohol with an infrared lamp (catalyst loading: 0.4 mg / cm³). 2 Using a glassy carbon electrode as the working electrode, graphite and Ag / AgCl as the counter and reference electrodes, respectively, and 0.1M KOH solution as the electrolyte, linear voltammetry was performed at a rotation speed of 1600 rpm, with a scan range of 0.2–1.0 V (vs. RHE). The test results are as follows. Figure 4 As shown.

[0071] like Figure 4 As shown, the oxygen reduction activities of Fe-Se / NC, Fe / NC, Se / NC and NC catalysts are similar to those of Pt / C catalysts, but the best performance is that of Fe-Se / NC catalyst, with a half-wave potential of 0.88V (vs. RHE).

[0072] Example 7

[0073] The metal-air battery is assembled as follows: The solution preparation process is the same as that in Example 6 above. A 6.5*2cm piece of hydrophilic and hydrophobic carbon cloth is cut, and 562.5μL of the prepared solution is evenly added to a 1.5*1.5cm area on the hydrophilic side (carbon cloth catalyst loading: 1mg / cm). 2 After drying, an air electrode is obtained. An air battery is assembled using a specific mold, with a magnesium sheet as the negative electrode, coated with 1 mg / cm³ of... 2 Fe-Se / NC and Pt / C carbon cloth are used as positive electrodes, and an appropriate amount of 6M KOH is added as the electrolyte.

[0074] The magnesium-air batteries assembled according to the above method were used to perform power tests on Fe-Se / NC and Pt / C batteries. The test results are as follows: Figure 5 As shown.

[0075] like Figure 5 As shown, the maximum power density of Fe-Se / NC is 53.73 mW / cm². -2 36.82 mW cm⁻¹ higher than Pt / C -2 This further demonstrates the excellent oxygen reduction performance of Fe-Se / NC.

[0076] The magnesium-air battery assembled according to the above method was used to test Fe-Se / NC and Pt / C at a current density of 10 mA / cm². -2 Constant current discharge test. The test results are as follows: Figure 6 As shown.

[0077] like Figure 6 As shown, the specific capacity of Fe-Se / NC is 1213 mAh g. -1 Compared to the 1140mAh g of commercial Pt / C - high.

[0078] The batteries assembled according to the above method were subjected to step discharge tests on Fe-Se / NC and Pt / C batteries. The test results are as follows: Figure 7 As shown.

[0079] like Figure 7 As shown, Fe-Se / NC at open circuit, 2, 5, and 10 mA / cm² -2 The voltage values ​​below are all higher than Pt / C.

[0080] Example 8

[0081] The metal-air battery is assembled as follows: The solution preparation process is the same as that in Example 6 above. A 6.5*2cm piece of hydrophilic and hydrophobic carbon cloth is cut, and 562.5μL of the prepared solution is evenly added to a 1.5*1.5cm area on the hydrophilic side (carbon cloth catalyst loading: 1mg / cm). 2 After drying, an air electrode is obtained. An air battery is assembled using a specific mold, with a zinc sheet as the negative electrode, coated with 1 mg / cm³ of zinc oxide. 2 Fe-Se / NC and Pt / C carbon cloth are used as positive electrodes, and an appropriate amount of 3.5wt% NaCl is added as the electrolyte.

[0082] The zinc-air batteries assembled according to the above method were used to perform power tests on Fe-Se / NC and Pt / C batteries. The test results are as follows: Figure 8 As shown.

[0083] like Figure 8 As shown, the maximum power density of Fe-Se / NC is 114.5 mW / cm². -2 58.4 mW cm⁻¹ higher than Pt / C -2 This further demonstrates the excellent oxygen reduction performance of Fe-Se / NC.

[0084] The zinc-air battery assembled according to the above method was used to test Fe-Se / NC and Pt / C at a current density of 10 mA / cm². -2 Constant current discharge test. The test results are as follows: Figure 9 As shown.

[0085] like Figure 9 As shown, the specific capacity of Fe-Se / NC is 818.9 mAh g. -1 Compared to the 696.5mAh g of commercial Pt / C - high.

[0086] The batteries assembled according to the above method were subjected to step discharge tests on Fe-Se / NC and Pt / C batteries. The test results are as follows: Figure 10 As shown.

[0087] like Figure 10 As shown, Fe-Se / NC at open circuit, 2, 5, 10, 15 and 20 mA cm⁻¹ -2 The voltage values ​​below are all higher than Pt / C.

[0088] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material, characterized in that... The following steps are included: The magnesium-zinc NC precursor and selenium compound were ground and mixed together, and then placed together with the transition metal iron compound in a tube furnace. Under nitrogen or inert gas, the mixture was calcined at 600~1100℃ for 0.5~3 h using a vapor deposition method. The calcined product was ground, acid-washed, filtered, and dried, and then subjected to a second calcination at 900℃ for 2 h to obtain a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material. The molar ratio of the transition metal iron compound to the selenium compound was (0.1~5):(0.1~6); the molar ratio of the transition metal iron compound to the magnesium-zinc NC precursor was (0.01~1):(0.1~5). The magnesium-zinc NC precursor was prepared according to the following steps: (1) Mix 1 mmol of anhydrous magnesium chloride and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution A; (2) Mix 10 mmol of p-phenylenediamine and 20 mL of methanol with a magnetic stirrer until completely dissolved to obtain solution B; (3) Mix 700 mg sodium chloride, 1300 mg zinc chloride and 20 mL deionized water with magnetic stirring until completely dissolved to obtain solution C; (4) Add solution A to solution B, stir for 10 minutes, and then pour in solution C as well. The resulting mixed solution was magnetically stirred for more than 6 hours, then frozen with liquid nitrogen, and then freeze-dried for 36 hours. After drying, the resulting solid was ground for 10 minutes, and the resulting powder particles were calcined in a tube furnace under a nitrogen atmosphere at 900℃ for 2 hours with a heating rate of 5℃ / min. The calcined powder particles were ground again for 10 minutes, then washed with deionized water and filtered to remove soluble salt ions. The powder particles were then acid-washed with 0.5 mol / L sulfuric acid for 12 hours, and then filtered with deionized water. After filtration, the powder particles were dried in an oven at 70℃ for 12 hours. The dried sample was ground for 30 minutes and then calcined a second time in a tube furnace under a nitrogen atmosphere at 900℃ for 2 hours with a heating rate of 5℃ / min to obtain the magnesium-zinc NC precursor.

2. The method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material according to claim 1, characterized in that: The molar ratio of the transition metal iron compound to the selenium compound is 1:1; the molar ratio of the transition metal iron compound to the magnesium-zinc NC precursor is (0.01~0.5):(0.5~3).

3. The method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material according to claim 1, characterized in that: The drying is carried out in an oven at a temperature of 20-100°C.

4. The method for preparing a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material according to claim 3, characterized in that: The drying temperature is 75°C.

5. A nitrogen-doped porous carbon-supported iron selenium transition metal composite material prepared by the preparation method according to any one of claims 1 to 4, characterized in that: In the composite material, iron atoms and selenium atoms are uniformly distributed on nitrogen-doped carbon-based materials.

6. The application of the nitrogen-doped porous carbon-supported iron-selenium transition metal composite material according to claim 5 in metal-air batteries.

7. A metal-air battery cathode material, characterized in that; The cathode material includes the nitrogen-doped porous carbon-supported iron selenium transition metal composite material as described in claim 5.

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