Preparation method of Fe / Cu / N doped porous carbon nanotubes and application of Fe / Cu / N doped porous carbon nanotubes in electrocatalytic oxygen reduction reaction

Abstract

This invention discloses a method for preparing Fe / Cu / N-doped porous carbon nanotubes and their application in the electrocatalytic oxygen reduction reaction. The method involves immersing electrospun fibers of H3BTC and PAN in a trimetallic salt solution of zinc, copper, and iron, followed by etching away polyacrylonitrile. The resulting Zn@Fe@Cu-BTC trimetallic nanotubes are then annealed at high temperature to obtain the Fe / Cu / N-doped porous carbon nanotube material. The preparation method of this invention is simple, low-cost, and yields a high-quality product with uniform structure. The resulting conductive carbon framework coated with iron and copper nanoparticles at a high nitrogen doping level exhibits high activity and stability, demonstrating excellent catalytic performance in the oxygen reduction reaction.

Description

Technical Field

[0001] This invention belongs to the field of functional nanomaterials technology, specifically relating to a method for preparing Fe / Cu / N doped porous carbon nanotubes and their application in electrocatalytic oxygen reduction reactions. Background Technology

[0002] Due to increasingly serious environmental problems and rapid growth in global energy demand, developing new clean energy devices is considered an effective strategy to alleviate the energy crisis and environmental pollution. Among these, fuel cells and metal-air batteries have become hot topics. Although platinum-based metal (PGM) catalysts exhibit significant catalytic performance for the electrocatalytic oxygen reduction reaction (ORR), their high cost severely limits large-scale commercialization. Therefore, developing efficient, long-lasting, and low-cost ORR catalysts is of great significance for reducing the platinum load on fuel cells and for their practical application.

[0003] Metal-organic frameworks (MOFs) are crystalline materials with ultra-high porosity and extremely high surface area, and have been widely developed as sources of various controllable structural nanomaterials for electrochemical devices. MOFs not only combine with metal nodes bridged by organic ligands to provide the transition metals (TMs), carbon, and heteroatoms required for catalysis, but also possess controlled periodicity, making them important precursors for preparing highly efficient MNC catalysts for ORR processes. In recent years, Zn-MOFs have been considered suitable precursors for preparing carbon-based materials, possessing various surface geometries, large surface areas, and abundant pores. Fe-NC catalysts have attracted widespread attention due to their excellent ORR activity in both alkaline and acidic solutions. They are often formed with Zn to form bimetallic organic frameworks, followed by high-temperature annealing and zinc source evaporation, which induces abundant defects on the carbon support and endows Fe-NC with a porous structure. However, the carbon materials formed by this method still have some shortcomings in terms of durability, and their electrocatalytic oxygen reduction performance needs further improvement. Cu, second only to platinum in the volcano diagram, is a promising electrocatalytic oxygen reduction raw material among transition metals. Introducing Cu into a zinc-iron bimetallic organic framework can suppress the generation of H2O2 during electrocatalytic oxygen reduction. Simultaneously, the electronegativity difference between Fe and Cu can induce electron transfer between them, thereby optimizing the electronic structure of Fe and the bonding strength between reaction intermediates and active sites. However, Cu-based carbon materials obtained through pyrolysis often suffer from self-aggregation, irreversible integration, and surface oxidation due to their large ion diffusion coefficient. Furthermore, current research on the application of Fe@Cu-NC in electrocatalysis primarily involves co-doping iron and copper nanoparticles onto a zero-dimensional carbon framework. Therefore, a low-cost and simple preparation method is needed to obtain carbon materials with unique structures, ensuring good stability and high yield for their electrocatalytic applications. This invention aims to synthesize one-dimensional trimetallic MOF tubes and, by controlling the content of Zn, Fe, and Cu and the post-treatment method, to regulate the composition and structure of the carbon nanotubes, ultimately improving the electrocatalytic oxygen reduction performance of Fe@Cu-NC materials. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a method for preparing Fe / Cu / N-doped porous carbon nanotube materials with excellent electrocatalytic oxygen reduction capabilities, wherein the morphology is nitrogen-doped porous carbon nanotubes with iron and copper nanoparticles embedded in them.

[0005] The present invention solves the technical problem by adopting the following technical solution:

[0006] A method for preparing Fe / Cu / N-doped porous carbon nanotube material, characterized by comprising the following steps:

[0007] Step 1: Using N,N-dimethylformamide (DMF) as a solvent, add pyromellitic acid (H3BTC) and polyacrylonitrile (PAN), and stir magnetically until dissolved to obtain an electrospinning solution; then, use the electrospinning solution to form a PAN / H3BTC nanofiber film by electrospinning.

[0008] The PAN / H3BTC nanofiber film was immersed in a trimetallic salt solution of zinc nitrate hexahydrate (Zn(NO3)2·6H2O)), copper nitrate trihydrate (Cu(NO3)2·3H2O)), and iron acetylacetone (Fe(acac)3) dissolved in ethanol. The solution was sealed with plastic wrap, placed in an oven and allowed to stand. The resulting product was then removed, washed with ethanol, and vacuum dried to obtain the PAN / Zn@Fe@Cu-BTC fiber film.

[0009] Step 2: Immerse the PAN / Zn@Fe@Cu-BTC fiber film in N,N-dimethylformamide to etch away the polyacrylonitrile, then wash with ethanol, centrifuge, and freeze-dry to obtain Zn@Fe@Cu-BTC nanotubes.

[0010] Step 3: Place the Zn@Fe@Cu-BTC nanotubes at the lower air outlet of the quartz tube and place dicyandiamine (DCDA) at the upper air outlet. Then transfer them to the Nabor Thermal high-temperature calcination furnace and anneal them at high temperature under an inert atmosphere to obtain Fe / Cu / N doped porous carbon nanotube materials, which are conductive carbon frameworks with high specific surface area and high nitrogen doping content, and embedded in iron and copper bimetals.

[0011] Preferably, in step 1, the mass ratio of DMF, H3BTC and PAN is 13-16 mL: 1.0-1.3 g: 1.0-1.3 g.

[0012] Preferably, in step 1, the magnetic stirring speed is 350-450 rpm and the stirring temperature is between 25°C and 30°C to prevent the spinning solution from crystallizing and precipitating.

[0013] Preferably, in step 1, the voltage of electrospinning is 14-16KV, the amount of spinning solution fed is 0.3-0.5mL / h, and the distance between the needle and the copper mesh receiving plate is 15-20cm.

[0014] Preferably, in step 1, the ratio of the amount of ethanol solution, Zn(NO3)2·6H2O, Fe(acac)3, Cu(NO3)2·3H2O, and PAN / H3BTC nanofiber film is 45-55 mL: 1.40-1.50 g: 0.70-0.80 g: 0.40-0.50 g: 0.06-0.10 g.

[0015] Preferably, in step 1, the oven temperature is 50–70°C and the settling time is 6–7 hours.

[0016] Preferably, in step 2, the etching time is 3 to 10 minutes and the centrifugation speed is 2000 to 3000 rpm.

[0017] Preferably, in step 3, the mass ratio of the Zn@Fe@Cu-BTC nanotubes to dicyandiamine is 1:15 to 25.

[0018] Preferably, in step 3, the inert gas used is nitrogen, the calcination temperature is 900-950℃, and the calcination time is 2-3 hours.

[0019] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0020] This invention provides a method for preparing nitrogen-doped porous carbon nanotube materials embedded with iron-copper nanoparticles for electrocatalytic oxygen reduction reactions. All raw materials are non-precious metals, effectively reducing the cost of oxygen reduction catalysts. The preparation method is simple, yields high-quality products, and exhibits uniform structure. The conductive carbon framework coated with iron-copper nanoparticles obtained by this invention, with a high level of nitrogen doping, possesses high activity and stability, demonstrating excellent catalytic performance in oxygen reduction reactions. Attached Figure Description

[0021] Figure 1 The X-ray diffraction (XRD) patterns of the Zn@Fe@Cu-BTC nanotubes obtained in step 2 of Example 1, and the Fe@Cu-BTC nanotubes and Cu-BTC nanotubes used as comparisons.

[0022] Figure 2 The image shows the XRD pattern of the target product Fe@Cu-NC nanotubes obtained in step 3 of Example 1.

[0023] Figure 3 The images shown are scanning electron microscope (SEM) images of the PAN / H3BTC nanofiber film obtained in step 1 of Example 1, where (a) and (b) correspond to different magnifications.

[0024] Figure 4 The images shown are scanning electron microscope (SEM) images of the PAN / Zn@Fe@Cu-BTC fibers obtained in step 1 of Example 1, where (a) and (b) correspond to different magnifications.

[0025] Figure 5 The image shows a scanning electron microscope (SEM) image of the Zn@Fe@Cu-BTC nanotubes obtained in step 2 of Example 1.

[0026] Figure 6 The image shows a transmission electron microscope (TEM) image of the Zn@Fe@Cu-BTC nanotubes obtained in step 2 of Example 1.

[0027] Figure 7 The image shows a scanning electron microscope (SEM) image of the target product Fe@Cu-NC nanotubes obtained in step 3 of Example 1.

[0028] Figure 8 The image shows a transmission electron microscope (TEM) image of the target product Fe@Cu-NC nanotubes obtained in step 3 of Example 1.

[0029] Figure 9 The images shown are transmission electron microscope (TEM) images (a) and scanning electron microscope (SEM) images (b) of the target product obtained in step 3 of Example 2.

[0030] Figure 10 The images shown are transmission electron microscope (TEM) images (a) and scanning electron microscope (SEM) images (b) of the target product obtained in step 3 of Example 3.

[0031] Figure 11 The images shown are transmission electron microscope (TEM) images (a) and scanning electron microscope (SEM) images (b) of the target product obtained in step 3 of Example 4.

[0032] Figure 12 The LSV curves of the target products obtained in the various embodiments and comparative examples of the present invention in O2-saturated 0.1M KOH are shown.

[0033] Figure 13 This is a bar chart comparing the half-wave potential of the target products obtained from various embodiments and comparative examples of the present invention. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the instruments, reagents, materials, etc. used in the following embodiments can be obtained commercially.

[0035]

[0036]

[0037] The medicines used in the following examples were purchased and used directly without any treatment.

[0038] Example 1

[0039] In this embodiment, Fe / Cu / N-doped porous carbon nanotubes were prepared according to the following steps:

[0040] Step 1: Take 16 mL of DMF as solvent and place it in a 20 mL glass bottle. Weigh 1.28 g of H3BTC and dissolve it in DMF by sonication for 10 min. Then, add 1.2 g of PAN under magnetic stirring. The stirring speed is 300 rpm, the stirring time is 20 h, and the stirring temperature is maintained between 25℃ and 30℃ to prevent crystallization of the spinning solution. After complete dissolution, an electrospinning solution is obtained. The electrospinning solution is then used to prepare PAN / H3BTC nanofiber films by electrospinning. The electrospinning voltage is 15 kV, the spinning solution feed rate is 0.4 mL / h, and the distance between the needle and the copper mesh receiving plate is 18 cm.

[0041] 0.07 g of PAN / H3BTC nanofiber film was immersed in 50 mL of a trimetallic salt solution containing 1.418 g Zn(NO3)2·6H2O, 0.48 g Cu(NO3)2·3H2O, and 0.706 g Fe(acac)3 dissolved in ethanol. The solution was covered and sealed with plastic wrap and placed in an oven at 60 °C for 7 h. The product was then removed, washed with ethanol, and dried under vacuum at 60 °C to obtain PAN / Zn@Fe@Cu-BTC fiber film.

[0042] Step 2: Immerse the PAN / Zn@Fe@Cu-BTC fiber film in 20 mL of LDMF for 5 min to etch away the polyacrylonitrile, then wash with ethanol, centrifuge, and freeze dry to obtain Zn@Fe@Cu-BTC nanotubes.

[0043] Step 3: Place the Zn@Fe@Cu-BTC nanotubes at the lower air outlet of the quartz tube and place the dicyandiamine (DCDA) at the upper air outlet. The mass ratio of Zn@Fe@Cu-BTC nanotubes to dicyandiamine is 1:18. Then, transfer it to a Nabor Thermal high-temperature calcination furnace and heat it to 950°C at a heating rate of 5°C / min under a nitrogen atmosphere. Hold it at this temperature for 3 hours to obtain Fe / Cu / N doped porous carbon nanotube material, denoted as Fe@Cu-NC.

[0044] Figure 1 The X-ray diffraction (XRD) patterns of the Zn@Fe@Cu-BTC nanotubes obtained in step 2 of this embodiment, and the Fe@Cu-BTC nanotubes and Cu-BTC nanotubes for comparison, are shown in the figure. It can be seen from the figure that all three XRD patterns have a distinct peak at around 12° (2θ), indicating that the three have similar crystal structures.

[0045] Figure 2 This is the XRD pattern of the target product Fe@Cu-NC nanotubes obtained in step 3 of this embodiment. The figure shows that the product after calcination is CuFeO2 and FeN. 0.0324 、Fe3C.

[0046] Figure 3The images shown are scanning electron microscope (SEM) images of the PAN / H3BTC nanofiber film obtained in step 1 of this embodiment, where (a) and (b) correspond to different magnifications. It can be seen that the fiber surface is relatively smooth, with a diameter of approximately 200–300 nm.

[0047] Figure 4 The images show scanning electron microscope (SEM) images of the PAN / Zn@Fe@Cu-BTC fibers obtained in step 1 of this embodiment, where (a) and (b) correspond to different magnifications. As can be seen from the images, the fibers are tightly wrapped with a layer of (Zn, Fe, Cu)-BTC particles with a slightly increased radius.

[0048] Figure 5 and Figure 6 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the Zn@Fe@Cu-BTC nanotubes obtained in step 2 of this embodiment. A distinct hollow tubular structure is visible, with a thickness of approximately 5–10 nm, and the structure remains well-preserved with minimal collapse.

[0049] Figure 7 and Figure 8 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the target product Fe@Cu-NC nanotubes obtained in step 3 of the example. It can be seen that a large number of bamboo-like carbon nanotubes grow outside the tubes.

[0050] Example 2

[0051] This embodiment is similar to Embodiment 1, except that in step 1, an iron-copper bimetallic MOF is synthesized, and in step 3, a DCDA is not placed at the upwind vent. The detailed process is as follows:

[0052] Step 1: Take 16 mL of DMF as solvent and place it in a 20 mL glass bottle. Weigh 1.28 g of H3BTC and dissolve it in DMF by sonication for 10 min. Then, add 1.2 g of PAN under magnetic stirring. The stirring speed is 300 rpm, the stirring time is 20 h, and the stirring temperature is maintained between 25℃ and 30℃ to prevent crystallization of the spinning solution. After complete dissolution, an electrospinning solution is obtained. The electrospinning solution is then used to prepare PAN / H3BTC nanofiber films by electrospinning. The electrospinning voltage is 15 kV, the spinning solution feed rate is 0.4 mL / h, and the distance between the needle and the copper mesh receiving plate is 18 cm.

[0053] 0.07 g of PAN / H3BTC nanofiber film was immersed in 50 mL of a bimetallic salt solution containing 0.48 g of Cu(NO3)2·3H2O and 0.706 g of Fe(acac)3 dissolved in ethanol. The solution was covered and sealed with plastic wrap and placed in an oven at 60 °C for 7 h. The product was then removed, washed with ethanol, and dried under vacuum at 60 °C to obtain PAN / Fe@Cu-BTC fiber film.

[0054] Step 2: Immerse the PAN / Fe@Cu-BTC fiber film in 20 mL of LDM for 5 min to etch away the polyacrylonitrile, then wash with ethanol, centrifuge, and freeze dry to obtain Fe@Cu-BTC nanotubes.

[0055] Step 3: Place the Fe@Cu-BTC nanotubes in a quartz tube and then transfer them to a Nabtech high-temperature calcination furnace. Under a nitrogen atmosphere, heat the material to 950°C at a heating rate of 5°C / min and hold for 3 hours to obtain Fe / Cu / N doped porous carbon nanotube material with low nitrogen doping content, denoted as Fe@Cu-NC.

[0056] Figure 9 The images show transmission electron microscopy (TEM) images (a) and scanning electron microscopy (SEM) images (b) of the target product obtained in step 3 of this embodiment. It can be seen from the images that no bamboo-like carbon nanotubes grow on the Fe@Cu-NC tube when it is not calcined with DCDA.

[0057] Example 3

[0058] This embodiment is similar to Embodiment 1, except that zinc and iron bimetallic MOFs are synthesized in step 1. The detailed process is as follows:

[0059] Step 1: Take 16 mL of DMF as solvent and place it in a 20 mL glass bottle. Weigh 1.28 g of H3BTC and dissolve it in DMF by sonication for 10 min. Then, add 1.2 g of PAN under magnetic stirring. The stirring speed is 300 rpm, the stirring time is 20 h, and the stirring temperature is maintained between 25℃ and 30℃ to prevent crystallization of the spinning solution. After complete dissolution, an electrospinning solution is obtained. The electrospinning solution is then used to prepare PAN / H3BTC nanofiber films by electrospinning. The electrospinning voltage is 15 kV, the spinning solution feed rate is 0.4 mL / h, and the distance between the needle and the copper mesh receiving plate is 18 cm.

[0060] 0.07 g of PAN / H3BTC nanofiber film was immersed in 50 mL of a bimetallic salt solution containing 1.418 g of Zn(NO3)2·6H2O and 0.706 g of Fe(acac)3 dissolved in ethanol. The solution was covered and sealed with plastic wrap and placed in an oven at 60 °C for 7 h. The product was then removed, washed with ethanol, and dried under vacuum at 60 °C to obtain PAN / Zn@Fe-BTC fiber film.

[0061] Step 2: Immerse the PAN / Zn@Fe-BTC fiber film in 20 mL of LDM for 5 min to etch away the polyacrylonitrile, then wash with ethanol, centrifuge, and freeze dry to obtain Zn@Fe-BTC nanotubes.

[0062] Step 3: Place the Zn@Fe-BTC nanotubes at the lower air outlet of the quartz tube and place the dicyandiamine (DCDA) at the upper air outlet, wherein the mass ratio of Zn@Fe-BTC nanotubes to dicyandiamine is 1:20. Then transfer it to the Nabother high-temperature calcination furnace and heat it to 950°C at a heating rate of 5°C / min under a nitrogen atmosphere, and hold it at that temperature for 3 hours to obtain Fe-NC, a Fe / N-doped porous carbon nanotube material with a high nitrogen doping content.

[0063] Figure 10 The images show transmission electron microscopy (TEM) (a) and scanning electron microscopy (SEM) (b) of the target product obtained in step 3 of this embodiment. It can be seen from the images that a large number of bamboo-like carbon nanotubes grow on the Fe-NC tube, but the tubular morphology is poorly maintained.

[0064] Example 4

[0065] This embodiment is similar to Embodiment 1, except that a DCDA is not placed at the upwind vent in step 3. The detailed process is as follows:

[0066] Step 1: Take 16 mL of DMF as solvent and place it in a 20 mL glass bottle. Weigh 1.28 g of H3BTC and dissolve it in DMF by sonication for 10 min. Then, add 1.2 g of PAN under magnetic stirring. The stirring speed is 300 rpm, the stirring time is 20 h, and the stirring temperature is maintained between 25℃ and 30℃ to prevent crystallization of the spinning solution. After complete dissolution, an electrospinning solution is obtained. The electrospinning solution is then used to prepare PAN / H3BTC nanofiber films by electrospinning. The electrospinning voltage is 15 kV, the spinning solution feed rate is 0.4 mL / h, and the distance between the needle and the copper mesh receiving plate is 18 cm.

[0067] 0.07 g of PAN / H3BTC nanofiber film was immersed in 50 mL of a trimetallic salt solution containing 1.418 g Zn(NO3)2·6H2O, 0.48 g Cu(NO3)2·3H2O, and 0.706 g Fe(acac)3 dissolved in ethanol. The solution was covered and sealed with plastic wrap and placed in an oven at 60 °C for 7 h. The product was then removed, washed with ethanol, and dried under vacuum at 60 °C to obtain PAN / Zn@Fe@Cu-BTC fiber film.

[0068] Step 2: Immerse the PAN / Zn@Fe@Cu-BTC fiber film in 20 mL of LDM for 5 min to etch away the polyacrylonitrile, then wash with ethanol, centrifuge, and freeze dry to obtain Zn@Fe@Cu-BTC nanotubes.

[0069] Step 3: Place Zn@Fe@Cu-BTC nanotubes inside a quartz tube, then transfer them to a Nabtec high-temperature calcination furnace. Under a nitrogen atmosphere, heat the temperature to 950°C at a rate of 5°C / min and hold for 3 hours for high-temperature annealing to obtain Fe / Cu / N doped porous carbon nanotube materials with low nitrogen doping content.

[0070] Figure 11 The images show transmission electron microscopy (TEM) images (a) and scanning electron microscopy (SEM) images (b) of the target product obtained in step 3 of this embodiment. It can be seen from the images that the trimetallic particles are small and uniformly distributed on the tube after calcination, but there is no growth of fine bamboo-like carbon nanotubes outside the tube.

[0071] The oxygen reduction performance of the target products obtained in the above embodiments was tested as follows: 5 mg of each target product was taken, 490 μL of ethanol was added, and after ultrasonic dissolution for half an hour, 10 μL of naphthol reagent was added, and ultrasonication continued for 5 hours to obtain the catalytic material. 20 μL of the catalytic material was coated onto the glassy carbon surface using a microsyringe. Electrochemical tests were performed on an electrochemical workstation using a three-electrode system. The working electrode was a glassy carbon disk electrode with a diameter of 5 mm (disk area 0.196 cm²). 2 The reference electrode was a saturated Ag / AgCl electrode, the counter electrode was a carbon electrode, and the electrolyte was a 0.1 mol / L KOH solution. Before the test, O2 was bubbled into the electrolyte for at least half an hour to saturate it with oxygen. During the oxygen reduction test, the rotating disk electrode was set to 1600 rpm, the LSV scan rate was 5 mV / s, and the scan range was 0-1.1 V (voltage relative to the standard hydrogen electrode).

[0072] Figure 12 The LSV curves of the target products obtained in each embodiment in O2-saturated 0.1M KOH are shown. The half-wave potential of its oxygen reduction electrocatalysis can be calculated using formula (1), where E (RHE) As a reversible hydrogen electrode, E Ag / AgCl Silver / silver chloride electrode, pH 13:

[0073] E (RHE) =E Ag / AgCl +0.059×PH+0.198 (1)

[0074] like Figure 13 As shown, the half-wave potentials of Examples 1 to 4 are 0.870V, 0.534V, 0.762V, and 0.824V respectively, while the half-wave potential of the 20wt% Pt / C material used as a reference is 0.840V.

[0075] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing Fe / Cu / N-doped porous carbon nanotubes, characterized in that, Includes the following steps: Step 1: Using N,N-dimethylformamide (DMF) as a solvent, add trimesic acid (H3BTC) and polyacrylonitrile (PAN), and stir magnetically until dissolved to obtain an electrospinning solution; then, use the electrospinning solution to form a PAN / H3BTC nanofiber film by electrospinning. The PAN / H3BTC nanofiber film was immersed in a trimetallic salt solution of zinc nitrate hexahydrate (Zn(NO3)2·6H2O), copper nitrate trihydrate (Cu(NO3)2·3H2O), and iron acetylacetone (Fe(acac)3) dissolved in ethanol. The solution was sealed and placed in an oven to stand. The resulting product was then removed, washed with ethanol, and vacuum dried to obtain the PAN / Zn@Fe@Cu-BTC fiber film. The ratio of ethanol solution, Zn(NO3)2·6H2O, Fe(acac)3, Cu(NO3)2·3H2O, and PAN / H3BTC nanofiber film was 45~55 mL: 1.40~1.50 g: 0.70~0.80 g: 0.40~0.50 g: 0.06~0.10 g. Step 2: Immerse the PAN / Zn@Fe@Cu-BTC fiber film in N,N-dimethylformamide to etch away the polyacrylonitrile, then wash with ethanol, centrifuge and freeze dry to obtain Zn@Fe@Cu-BTC nanotubes; Step 3: Place the Zn@Fe@Cu-BTC nanotubes at the lower air outlet of the quartz tube, and place dicyandiamide (DCDA) at the upper air outlet. Then transfer them to a Nabor thermal high-temperature calcination furnace and anneal at 900~950℃ for 2~3 hours under an inert atmosphere to obtain Fe / Cu / N doped porous carbon nanotubes. The mass ratio of Zn@Fe@Cu-BTC nanotubes to dicyandiamide is 1:15~25.

2. The preparation method according to claim 1, characterized in that: In step 1, the ratio of DMF, H3BTC and PAN is 13~16 mL: 1.0~1.3 g: 1.0~1.3 g.

3. The preparation method according to claim 1, characterized in that: In step 1, the magnetic stirring speed is 350~450 rpm, and the stirring temperature is between 25℃ and 30℃.

4. The preparation method according to claim 1, characterized in that: In step 1, the electrospinning voltage is 14~16 KV, the spinning solution feed rate is 0.3~0.5 mL / h, and the distance between the needle and the copper mesh receiving plate is 15~20 cm.

5. The preparation method according to claim 1, characterized in that: In step 1, the oven temperature is 50~70℃ and the settling time is 6~7 h.

6. The preparation method according to claim 1, characterized in that: In step 3, the inert gas used is nitrogen.

7. A Fe / Cu / N doped porous carbon nanotube obtained by the preparation method according to any one of claims 1 to 6.

8. The application of the Fe / Cu / N doped porous carbon nanotubes of claim 7 in the electrocatalytic oxygen reduction reaction.

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