Preparation method and application of iron-nickel doped carbon nanotubes

Abstract

The application relates to the technical field of electrocatalytic materials, in particular to a preparation method and application of iron-nickel doped carbon nanotubes. The preparation method comprises the following steps: (1) using a material containing iron salt, nickel salt and terephthalic acid as raw material, and preparing Fe / Ni-MIL-88B by a hydrothermal method; (2) dispersing the Fe / Ni-MIL-88B in N,N-dimethylformamide, adding polyacrylonitrile to form a spinning solution; (3) spinning the spinning solution to obtain polyacrylonitrile fiber film containing Fe / Ni-MIL-88B; (4) oxidizing the obtained polyacrylonitrile fiber film in air, and then carbonizing the polyacrylonitrile fiber film in a nitrogen atmosphere to obtain the iron-nickel doped carbon nanotube. The Fe / Ni-MIL-88B is assembled into electrospun nanofibers, and the synergistic effect between the two metals can effectively improve the catalytic effect of the catalyst, so that the obtained material has more excellent electrocatalytic performance.

Description

Technical Field

[0001] This invention relates to the field of functional nanomaterials technology, mainly to the field of electrocatalytic materials technology, and specifically to a method for preparing and applying iron-nickel doped carbon nanotubes. Background Technology

[0002] With rapid economic development, fuel cells have received widespread attention. However, the slow kinetics of the oxygen reduction reaction hinder their application. Currently, the most widely used noble metal catalysts in commercial applications are Pt, Ru, Ir, and their oxides. However, their large-scale use is limited by their scarcity, high cost, and susceptibility to poisoning. Therefore, developing inexpensive, efficient, and stable non-noble metal electrocatalysts is of great importance.

[0003] Transition metals have become promising electrocatalysts due to their key advantages of high metal atom utilization efficiency, high intrinsic activity, and low cost. Metal-organic frameworks (MOFs) have attracted widespread attention due to their unique physicochemical properties, such as large specific surface area, high porosity, and precise compositional control. Studies have shown that nickel-based MOFs can serve as excellent electrocatalysts and also as excellent substrate materials for supporting other guest substances, such as metals, metal oxides, and carbon materials. Patent application number 202010878624.9 discloses an invention that provides a method for in-situ growth of Ni-MOF thin film photocatalysts on the surface of nickel foam. This invention enables nickel foam to release nickel ions under voltage, which then self-assemble with 2-methylimidazole in the electrolyte. The resulting photocatalyst can degrade VOCs in the atmosphere under sunlight, exhibiting good photocatalytic activity and stability. The invention patent with application number 202111327404.8 discloses a modulated nickel / cobalt bimetallic MOF-based electrocatalyst, which includes a conductive substrate and a nickel / cobalt bimetallic MOF modulated with ferrocene carboxylic acid supported on its surface, and has excellent electrocatalytic activity for urea oxidation reaction. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for preparing iron-nickel-doped carbon nanotubes. The technical problem to be solved is that existing transition metal-doped carbon nanostructured oxygen reduction electrocatalysts generally suffer from low dispersion and low catalytic activity. The applicant believes that doping nickel into iron-based catalysts can effectively regulate the electronic structure and improve conductivity; however, such catalysts are prone to agglomeration and disordered arrangement during preparation, thus affecting the electrochemical performance and stability of the product. Therefore, designing a transition metal-doped carbon nanostructured catalyst with high dispersion, high performance, and microscopically ordered arrangement is crucial.

[0005] To address the aforementioned technical problems, this invention assembles Fe / Ni-MIL-88B into electrospun nanofibers, followed by pre-oxidation and carbonization to synthesize iron-nickel-doped carbon nanotubes. Fe / Ni-MIL-88B serves as the primary source for the two components, and the synergistic effect between the two components effectively enhances the catalytic effect. The carbon nanotubes derived from the fiber surface enhance the catalyst's conductivity and promote electron transfer. Therefore, the iron-nickel-doped carbon nanotube material of this invention exhibits superior electrocatalytic performance, and the preparation method of this invention has advantages such as low raw material costs and simple operation, making it suitable for large-scale production.

[0006] Specifically, to achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing iron-nickel doped carbon nanotubes, characterized by comprising the following steps:

[0008] (1) Fe / Ni-MIL-88B metal-organic framework material was prepared by hydrothermal method using substances containing iron salts, nickel salts and terephthalic acid as raw materials.

[0009] (2) Disperse Fe / Ni-MIL-88B in N,N-dimethylformamide, add polyacrylonitrile to form a spinning solution;

[0010] (3) Spinning the spinning solution to obtain a polyacrylonitrile fiber film containing Fe / Ni-MIL-88B;

[0011] (4) The obtained polyacrylonitrile fiber film is oxidized in air and then carbonized in a nitrogen atmosphere to obtain the iron-nickel doped carbon nanotubes.

[0012] Preferably, in the above preparation method, in step (1), the Fe / Ni-MIL-88B metal-organic framework material is prepared by a method comprising the following steps:

[0013] A substance containing iron salt, nickel salt and terephthalic acid is added to N,N-dimethylformamide as a raw material and mixed evenly to form a mixture. Sodium hydroxide solution is added and mixed evenly to obtain a reaction solution. After hydrothermal reaction at 100-150℃, Fe / Ni-MIL-88B metal-organic framework material is obtained.

[0014] Preferably, in the above preparation method, the molar ratio of iron to nickel in the raw materials is (0.5-2.5):1, more preferably (0.5-1.3):1, and even more preferably (1.0-1.3):1.

[0015] Preferably, in the above preparation method, the molar ratio of the total amount of iron and nickel to terephthalic acid in the raw materials is (2-3.5):1, more preferably (2.0-2.5):1.

[0016] Preferably, in the above preparation method, in step (1), the molar ratio of the sum of iron and nickel to sodium hydroxide is (2.5-4.5):1, more preferably (2.5-4.0):1.

[0017] Preferably, in the above preparation method, in step (1), the iron salt is selected from ferric chloride; the nickel salt is selected from nickel chloride or nickel nitrate.

[0018] Preferably, in the above preparation method, in step (1), the concentration of iron salt in the mixture is 0.05-0.12 g / mL, preferably 0.05-0.06 g / mL.

[0019] Preferably, in the above preparation method, in step (1), the concentration of nickel salt in the mixture is 0.040-0.10 g / mL, preferably 0.045-0.05 g / mL.

[0020] Preferably, in the above preparation method, in step (1), the concentration of terephthalic acid in the mixture is 0.03-0.05 g / mL.

[0021] Preferably, in the above preparation method, the hydrothermal reaction temperature is 100-150℃ and the reaction time is 3-15h; more preferably, it is 100-120℃ and the reaction time is 3-5h.

[0022] Preferably, in the above preparation method, in step (2), the ratio of polyacrylonitrile, N,N-dimethylformamide and Fe / Ni-MIL-88B is 1g:(8-10)mL:(1-2)g, preferably 1g:(9-10)mL:(1.4-1.6)g.

[0023] Preferably, in the above preparation method, step (2) includes the following steps: dispersing Fe / Ni-MIL-88B in N,N-dimethylformamide, adding polyacrylonitrile, and stirring at 300rpm to 500rpm for 10 to 15h to prepare a spinning solution.

[0024] Preferably, in the above preparation method, step (3) includes the following steps: drawing the spinning solution into the syringe of the spinning machine for spinning; wherein the voltage of the spinning process is 15-20kV (preferably 19kV), the distance from the syringe needle to the collecting copper mesh is 10-20cm (preferably 15cm), and the speed of the syringe is 0.5-0.8mL / h.

[0025] Preferably, in the above preparation method, in step (4), the temperature of the oxidation process is 200-300℃, preferably 240-260℃, the oxidation time is 1-3h, and the obtained sample is cooled to room temperature after oxidation.

[0026] Preferably, in the above preparation method, step (4) includes the following steps:

[0027] The oxidized sample was placed downstream of a tube furnace, melamine was placed upstream, nitrogen gas was introduced, and calcination was carried out at 700–900°C to complete the carbonization process.

[0028] Preferably, in the above preparation method, the mass ratio of melamine to the sample obtained after oxidation is (5-20):1, more preferably (8-10):1.

[0029] Preferably, in the above preparation method, the carbonization process is carried out at a temperature of 700-900℃, more preferably 700-800℃, for a time of 2-4 hours.

[0030] Preferably, in the above preparation method, in step (4), the heating rate of the oxidation process is 1-5℃ / min, preferably 1-2℃ / min, and the heating rate of the carbonization process is 1-5℃ / min, preferably 4-5℃ / min.

[0031] The present invention also provides an iron-nickel doped carbon nanotube, characterized in that it is prepared by the above method.

[0032] Preferably, the above-mentioned iron-nickel doped carbon nanotubes contain carbon, nitrogen, oxygen, iron, and nickel, wherein the atomic percentage of iron is 0.85–1.20 at%, preferably 1.00–1.20 at%, and the atomic percentage of nickel is 0.90–1.50 at%, preferably 0.90–1.10 at%.

[0033] Preferably, in the above-mentioned iron-nickel doped carbon nanotubes, the atomic percentage of nitrogen is 7.0-8.0 at%, more preferably 7.2-7.8 at%.

[0034] Preferably, the iron-nickel doped carbon nanotubes are loaded with an iron-nickel alloy, wherein the molar ratio of iron to nickel in the iron-nickel alloy is 0.64:0.36.

[0035] Preferably, in the above preparation method, the length of the Fe / Ni-MIL-88B metal-organic framework material obtained in step (1) is 200-300 nm and the width is 100-150 nm.

[0036] The present invention also provides an oxygen reduction reaction electrode, characterized in that it comprises an oxygen reduction reaction electrocatalyst, wherein the electrocatalyst comprises iron-nickel doped carbon nanotubes.

[0037] The present invention also provides the application of the above-mentioned iron-nickel doped carbon nanotubes or the above-mentioned oxygen reduction reaction electrode in the field of electrocatalytic oxygen reduction reaction.

[0038] The advantages of this invention are: This invention assembles Fe / Ni-MIL-88B into electrospun nanofibers, and then calcines them to obtain iron-nickel-doped carbon nanotubes. The synergistic effect between the bimetals effectively enhances the catalytic effect of the catalyst, and the carbon nanotubes derived from the fiber surface enhance the conductivity of the catalyst and promote electron transfer. Therefore, the iron-nickel-doped carbon nanotube material of this invention has superior electrocatalytic performance, and the preparation method of this invention has advantages such as low raw material cost and simple operation, making it applicable to large-scale production. Attached Figure Description

[0039] Figure 1 This is a transmission electron microscope (TEM) image of the Fe / Ni-MIL-88B particles obtained in Example 1.

[0040] Figure 2 The image shows the XRD pattern of the Fe / Ni-MIL-88B particles obtained in Example 1.

[0041] Figure 3 This is a transmission electron microscope (TEM) image of the PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofibers obtained in Example 1.

[0042] Figure 4 This is a scanning electron microscope image of the iron-nickel doped carbon nanotube material obtained in Example 1.

[0043] Figure 5 This is a transmission electron microscope (TEM) image of the iron-nickel-doped carbon nanotube material obtained in Example 1.

[0044] Figure 6 The image shows the XRD pattern of the iron-nickel doped carbon nanotube material obtained in Example 1.

[0045] Figure 7 The image shows the LSV curve of the iron-nickel doped carbon nanotube material obtained in Example 1.

[0046] Figure 8 This is a transmission electron microscope (TEM) image of the iron-nickel-doped carbon nanotube material obtained in Example 5. Detailed Implementation

[0047] Given that existing transition metal-doped carbon nanostructured oxygen reduction electrocatalysts have low dispersion and their catalytic activity needs to be improved, this invention provides an iron-nickel-doped carbon nanotube that can be used as a catalyst in the electrocatalytic oxygen reduction process, such as being fabricated into an oxygen reduction reaction electrode.

[0048] In a preferred embodiment, the preparation method of the iron-nickel doped carbon nanotubes of the present invention includes the following steps:

[0049] (1) Fe / Ni-MIL-88B was prepared in N,N-dimethylformamide solvent by hydrothermal method;

[0050] (2) Disperse Fe / Ni-MIL-88B in N,N-dimethylformamide, then add polyacrylonitrile and stir evenly to form a spinning solution;

[0051] (3) Spin the obtained spinning solution to obtain a PAN / Fe / Ni-MIL-88B polyacrylonitrile fiber film;

[0052] (4) The obtained fiber film was calcined in an inert gas atmosphere to obtain iron-nickel doped carbon nanotubes.

[0053] Further, in step (1) above, the preparation method of Fe / Ni-MIL-88B includes the following steps: iron salt, nickel salt, and terephthalic acid are added to N,N-dimethylformamide and stirred evenly to obtain a reaction solution; the reaction solution is subjected to hydrothermal reaction at 100-150℃ for 3-15 hours (preferably 100℃ for 3 hours) to obtain Fe / Ni-MIL-88B; in the reaction solution: the concentration of iron salt is 0.054-0.108 g / mL (preferably 0.054 g / mL), the concentration of nickel salt is 0.0474-0.0948 g / mL (preferably 0.0474 g / mL), and the concentration of terephthalic acid is 0.033 g / mL. The iron salt is preferably ferric chloride hexahydrate, and the nickel salt is preferably nickel chloride hexahydrate. In step (4), the carbonization rate is 1-5℃ / min, preferably 4-5℃ / min.

[0054] In another preferred embodiment, the method for preparing iron-nickel doped carbon nanotubes of the present invention includes the following steps:

[0055] (1) Fe / Ni-MIL-88B was prepared in N,N-dimethylformamide solvent by hydrothermal method;

[0056] (2) Disperse Fe / Ni-MIL-88B in N,N-dimethylformamide by ultrasonication, then add polyacrylonitrile and stir evenly to form a spinning solution;

[0057] (3) Spin the obtained spinning solution to obtain a PAN / Fe / Ni-MIL-88B polyacrylonitrile fiber film;

[0058] (4) The obtained fiber film was first oxidized in air and then carbonized in an inert atmosphere to obtain iron-nickel doped carbon nanotubes.

[0059] Further, in step (1) above, the preparation method of Fe / Ni-MIL-88B includes the following steps: adding iron salt, nickel salt, and terephthalic acid to N,N-dimethylformamide and stirring evenly to obtain a mixed solution; then adding NaOH solution and stirring evenly to obtain a reaction solution; subjecting the reaction solution to a hydrothermal reaction at 100-150℃ for 3-15 hours to obtain Fe / Ni-MIL-88B; in the mixed solution: the concentration of iron salt is 0.05-0.06 g / mL, the concentration of nickel salt is 0.045-0.05 g / mL, and the concentration of terephthalic acid is 0.033 g / mL.

[0060] Furthermore, in step (2) above, the ratio of polyacrylonitrile, N,N-dimethylformamide and Fe / Ni-MIL-88B is 1g:8-10mL:1-2g, preferably 1g:10mL:1.5g.

[0061] Furthermore, in step (3) above, the spinning voltage is 15-20kV (preferably 19kV), and the distance from the spinning needle to the collecting copper mesh is 10-20cm (preferably 15cm).

[0062] Furthermore, in step (4) above, the inert gas used is nitrogen. The calcination is divided into two steps: first, the temperature is raised from 30°C to 200-300°C in air and kept at that temperature for 1-3 hours, and then the temperature is raised from 30°C to 700-900°C in nitrogen and kept at that temperature for 2-4 hours.

[0063] In another preferred embodiment, the present invention also provides an oxygen reduction reaction electrode, which is prepared from iron-nickel-doped carbon nanotubes; preferably, the electrode is a glassy carbon electrode coated with the iron-nickel-doped carbon nanotube material.

[0064] In this invention, electrospinning technology is widely used due to its unique three-dimensional structure and advantages such as high aspect ratio, large specific surface area, and high flexibility. Studies have shown that when a catalyst contains two metals, the synergistic effect between the active sites of the two metals can enhance catalytic activity. Meanwhile, different types of metal-organic frameworks produce different pore structures after pyrolysis. By adjusting the ratio of different metal salts, the microstructure and active sites of the derived material can be effectively controlled, thereby improving the catalytic performance of the material; even with the same ratio of metal salts, the pyrolysis temperature will have a significant impact on its structure. Therefore, this invention provides a method for preparing iron-nickel-doped carbon nanotubes, mainly comprising: assembling metal-organic frameworks into nanofibers by electrospinning, followed by pyrolysis to prepare porous carbon nanofiber materials. During pyrolysis, the volatilization of organic matter generates pore structures, increasing the specific surface area and active sites of the material. In summary, this preparation method is low-cost, and the resulting product has a high specific surface area, porous structure, and more active sites, which can significantly improve catalytic performance.

[0065] In this invention, Fe / Ni-MIL-88B refers to a MIL-type metal-organic framework material synthesized from iron salts, nickel salts, and terephthalic acid, exhibiting a one-dimensional rod-like structure.

[0066] The following specific embodiments further illustrate the iron-nickel doped carbon nanotubes, their preparation methods, and applications described in this invention.

[0067] In the examples below, all reagents used were purchased from Sinopharm Reagents.

[0068] The information of the instruments used in the embodiments is shown in the table below:

[0069] Table 1 Instrument Information Sheet

[0070] Reagents / Instruments Specifications / Model Manufacturer / Source Electric constant temperature drying oven DHG-9145A Shanghai Jinghong Experimental Equipment Co., Ltd. Magnetic stirrer 85-2B Guangzhou Yike Laboratory Technology Co., Ltd. spinning machine E05-001 Foshan Light Zinc Tubular furnace OTF-1200X Hefei Kejing Scanning electron microscope Zeiss Supra 40 Carl Zeiss, Germany X-ray diffraction instrument X'Pert PRO MPD Panaco, Netherlands X-ray photoelectron spectroscopy ESCALAB250Xi Thermo USA

[0071] Example 1

[0072] In this embodiment, the preparation process of iron-nickel doped carbon nanotubes is as follows:

[0073] (1) Weigh 3.24g FeCl3·6H2O, 2.844g NiCl2·6H2O, 1.99g terephthalic acid (H2BDC) and 60mL DMF and mix them. Stir at 400rpm for 10 minutes. Add 4.8mL 2M NaOH solution to the above solution and stir at 400rpm for 15 minutes. Pour into a 100mL autoclave and keep in an oven at 100℃ for 3 hours. Then cool to room temperature and centrifuge at 6000rpm for 5 minutes. Wash with DMF and anhydrous ethanol respectively, centrifuge, and dry in a vacuum drying oven at 70℃ for 12 hours to obtain Fe / Ni-MIL-88B material.

[0074] (2) Weigh 1.5g Fe / Ni-MIL-88B and add it to 10mL DMF. Disperse by sonication for 2h. Add 1g polyacrylonitrile (PAN) and stir overnight at 400rpm to prepare spinning solution.

[0075] (3) The obtained spinning solution was drawn into the syringe of the spinning machine. The distance between the needle and the collection network was 15cm. The spinning voltage was 19kV. The spinning syringe speed was 0.5mL / h. The spinning film was collected once every two hours to obtain PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofiber film.

[0076] (4) The obtained PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofiber film was first oxidized and then calcined under an inert gas: First, it was heated to 260°C in air at a heating rate of 1°C / min and held for 2 hours. After cooling to room temperature, the obtained sample was placed in the downstream part of a tube furnace, and melamine was placed upstream. The mass ratio of melamine to sample was 10:1. Nitrogen gas was introduced, and the temperature was increased from 30°C to 800°C at a heating rate of 5°C / min and held for 2 hours. After grinding the product, the iron-nickel doped carbon nanotube material was obtained.

[0077] The reaction mechanism of this embodiment is as follows: small nanorods are installed into fibers through electrospinning technology. Organic matter is evaporated at high temperature, leaving only metal and nitrogen and carbon doped nanofiber materials, which are then used to produce iron-nickel doped carbon nanotube materials.

[0078] Figure 1 The image shows a transmission electron microscope (TEM) image of the Fe / Ni-MIL-88B particles obtained in this embodiment. It can be seen that the overall structure is a long rod-shaped structure with a length of 200-300 nm and a width of 100-150 nm.

[0079] The Fe / Ni-MIL-88B particles obtained in this embodiment were subjected to XRD analysis. The analysis conditions were: Cu target, Kα = 1 / 1.54056, scanning angle 2θ = 5-80°, and scanning speed 5°min. -1 .

[0080] Figure 2 The XRD pattern of the Fe / Ni-MIL-88B particles obtained in step (1) of this embodiment is shown. Comparison with the standard Fe-MIL-88B pattern shows that the material obtained in step (1) of this embodiment is Fe / Ni-MIL-88B material.

[0081] Figure 3The image shown is a transmission electron microscope (TEM) image of the PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofibers obtained in this embodiment. It can be seen that the spun surface is relatively rough, mainly due to the roughness caused by the incorporation of nanorods.

[0082] Figure 4 The image shown is a scanning electron microscope image of the iron-nickel doped carbon nanotube material obtained in this embodiment. It can be seen that after calcination of the fibrous spinning, the main morphology still maintains a thin rod shape, and there are carbon nanotubes on the surface.

[0083] Figure 5 The image shown is a transmission electron microscope (TEM) image of the iron-nickel doped carbon nanotube material obtained in this embodiment. It can be clearly seen that there are particles and voids inside, mainly due to the volatilization of organic matter in the spun fibers, and carbon nanotubes derived on the surface.

[0084] Figure 6 The XRD pattern of the iron-nickel doped carbon nanotube material obtained in this embodiment is shown in standard card PDF#47-1405, i.e., Fe 0.64 Ni 0.36 As can be seen from the comparison, the iron-nickel doped carbon nanotubes obtained in this embodiment contain Fe alloy. 0.64 Ni 0.36 .

[0085] The iron-nickel doped carbon nanotube material obtained in this embodiment was subjected to X-ray photoelectron spectroscopy (XPS) detection. The detection results showed that the product was composed of C, N, O, Fe, and Ni elements, with an atomic percentage of 83.43 at for carbon, 7.49 at for nitrogen, 6.95 at for oxygen, 1.17 at for iron, and 0.96 at for nickel.

[0086] The electrocatalytic performance of the iron-nickel-doped carbon nanotubes obtained in the examples was tested as follows: Electrochemical tests were performed using a three-electrode system on an electrochemical workstation. The working electrode was a 5 mm diameter glassy carbon disk electrode (disk area 0.196 cm²). 2 The reference electrode was an Hg / HgO electrode, and the carbon rod electrode served as the counter electrode. 5 mg of the obtained nanofibers were dispersed in 490 μL of ethanol, and 10 μL of naphthol solution was added. The mixture was sonicated for 3 hours, and then 15 μL was applied to the glassy carbon surface using a microsyringe. Before testing, O2 was bubbled into the electrolyte (0.1 M KOH solution) for at least half an hour to saturate the electrolyte with O2. During the test, the rotating disk electrode was set to 1600 rpm, the scan rate to 5 mV / s, and the test voltage to -0.9 to 0.3 V (Hg / HgO). The CV curve was tested for ten cycles before testing the catalyst performance.

[0087] Figure 7The image shows the LSV curve of the iron-nickel doped carbon nanotubes obtained in Example 1. It can be seen that the half-wave potential of the target product obtained in Example 1 is 0.87V, indicating that the obtained iron-nickel doped carbon nanotubes have excellent electrocatalytic performance and can be used as an electrocatalyst for oxygen reduction reaction.

[0088] Example 2

[0089] This comparative example prepared iron-nickel-doped carbon nanotubes using a similar method to Example 1, except that step (1) was:

[0090] Weigh 3.24g FeCl3·6H2O, 5.688g NiCl2·6H2O, 1.99g terephthalic acid (H2BDC), and 60mL DMF and mix them. Stir at 400rpm for 10 minutes. Add 4.8mL 2M NaOH solution to the above solution and stir at 400rpm for 15 minutes. Pour the mixture into a 100mL autoclave and keep it in an oven at 100℃ for 3 hours. After cooling to room temperature, centrifuge at 6000rpm for 5 minutes. Wash with DMF and anhydrous ethanol respectively, centrifuge, and dry in a vacuum drying oven at 70℃ for 12 hours to obtain Fe / Ni-MIL-88B material.

[0091] The LSV curves of the samples were tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in Example 2 had a half-wave potential of 0.82 V when used as an electrocatalyst.

[0092] Example 3

[0093] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (1) is as follows:

[0094] Weigh out 6.48g FeCl3·6H2O, 2.844g NiCl2·6H2O, 1.99g terephthalic acid (H2BDC), and 60mL DMF, mix them, and stir at 400rpm for 10 minutes. Add 4.8mL of 2M NaOH solution to the above solution, stir at 400rpm for 15 minutes, pour into a 100mL autoclave, and keep in an oven at 100℃ for 3 hours. After cooling to room temperature, centrifuge at 6000rpm for 5 minutes. Wash with DMF and anhydrous ethanol respectively, centrifuge, and dry in a vacuum drying oven at 70℃ for 12 hours to obtain Fe / Ni-MIL-88B material.

[0095] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.79V when used as an electrocatalyst.

[0096] Example 4

[0097] This embodiment prepares iron-nickel doped carbon nanotubes using a method similar to that in Example 1, the difference being that steps (1) and (4) are respectively:

[0098] (1) Weigh 3.24g FeCl3·6H2O, 3.48g Ni(NO3)2·6H2O, 1.99g terephthalic acid (H2BDC) and 60mL DMF and mix them. Stir at 400rpm for 10 minutes. Add 4.8mL 2M NaOH solution to the above solution and stir at 400rpm for 15 minutes. Pour into a 100mL autoclave and keep in an oven at 120℃ for 3 hours. Then cool to room temperature and centrifuge at 6000rpm for 5 minutes. Wash with DMF and anhydrous ethanol respectively, centrifuge, and dry in a vacuum drying oven at 70℃ for 12 hours to obtain Fe / Ni-MIL-88B material.

[0099] (4) The obtained PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofiber film was first oxidized and then calcined under an inert gas: First, it was heated to 200°C in air at a heating rate of 1°C / min and held for 3 hours. After cooling to room temperature, the obtained sample was placed in the downstream part of a tube furnace, and melamine was placed upstream. The mass ratio of melamine to sample was 8:1. Nitrogen gas was introduced, and the temperature was increased from 30°C to 800°C at a heating rate of 5°C / min and held for 2 hours. After grinding the product, the iron-nickel doped carbon nanotube material was obtained.

[0100] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.81V when used as an electrocatalyst.

[0101] Example 5

[0102] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (1) is as follows:

[0103] Weigh 3.24g FeCl3·6H2O, 2.844g NiCl2·6H2O, 1.99g terephthalic acid (H2BDC), and 60mL DMF and mix them. Stir at 400rpm for 10 minutes. Add 4.8mL 2M NaOH solution to the above solution and stir at 400rpm for 15 minutes. Pour the mixture into a 100mL autoclave and keep it in an oven at 100℃ for 15 hours. After cooling to room temperature, centrifuge at 6000rpm for 5 minutes. Wash with DMF and anhydrous ethanol, centrifuge, and dry in a vacuum drying oven at 70℃ for 12 hours to obtain Fe / Ni-MIL-88B material.

[0104] Figure 8The image shows a transmission electron microscope (TEM) image of the Fe / Ni-MIL-88B material obtained in this embodiment. As can be seen from the image, the obtained MOF material is in the shape of a long rod with a length of 800 nm to 1.5 μm and a width of 100-200 nm.

[0105] Example 6

[0106] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (1) is as follows:

[0107] Weigh out 3.24 g FeCl3·6H2O, 2.844 g NiCl2·6H2O, 1.99 g terephthalic acid (H2BDC), and 60 mL DMF, mix them, and stir at 400 rpm for 10 minutes. Add 4.8 mL of 2 M NaOH solution to the above solution, stir at 400 rpm for 15 minutes, pour into a 100 mL autoclave, and keep in an oven at 150 °C for 5 hours. After cooling to room temperature, centrifuge at 6000 rpm for 5 minutes. Wash with DMF and anhydrous ethanol respectively, centrifuge, and dry in a vacuum drying oven at 70 °C for 12 hours to obtain Fe / Ni-MIL-88B material.

[0108] Transmission electron microscopy (TEM) images of the Fe / Ni-MIL-88B material obtained in this embodiment show that the obtained MOF material is in the shape of a long rod, with a length of 1.0 μm to 1.5 μm and a width of 100-200 nm.

[0109] Example 7

[0110] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (2) is as follows:

[0111] Weigh 1.0g Fe / Ni-MIL-88B and add it to 9mL DMF. Disperse by sonication for 2 hours. Add 1g polyacrylonitrile (PAN) and stir overnight at 400rpm to prepare the spinning solution.

[0112] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.83V when used as an electrocatalyst.

[0113] Example 8

[0114] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (2) is as follows:

[0115] Weigh 2.0g of Fe / Ni-MIL-88B and add it to 10mL of DMF. Disperse by sonication for 2 hours. Add 1g of polyacrylonitrile (PAN) and stir overnight at 400rpm to prepare the spinning solution.

[0116] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.84V when used as an electrocatalyst.

[0117] Example 9

[0118] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (4) is:

[0119] The obtained PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofiber film was first oxidized and then calcined under an inert gas: First, the temperature was raised to 260℃ in air at a heating rate of 1℃ / min and held for 2 hours, then cooled to room temperature. The obtained sample was then placed in the downstream part of a tube furnace, with melamine placed upstream at a mass ratio of 10:1 to the sample. Nitrogen gas was introduced, and the temperature was raised from 30℃ to 700℃ at a heating rate of 5℃ / min and held for 2 hours. After grinding the product, the iron-nickel doped carbon nanotube material was obtained.

[0120] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.86V when used as an electrocatalyst.

[0121] Example 10

[0122] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (4) is:

[0123] The obtained PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofiber film was first oxidized and then calcined under an inert gas: First, the temperature was raised to 260℃ in air at a heating rate of 1℃ / min and held for 2 hours, then cooled to room temperature. The obtained sample was then placed in the downstream part of a tube furnace, with melamine placed upstream at a mass ratio of 10:1 to the sample. Nitrogen gas was introduced, and the temperature was raised from 30℃ to 900℃ at a heating rate of 5℃ / min and held for 2 hours. After grinding the product, the iron-nickel doped carbon nanotube material was obtained.

[0124] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.85V when used as an electrocatalyst.

[0125] Example 11

[0126] This embodiment prepares iron-nickel-doped carbon nanotubes using a method similar to that in Example 1, except that step (4) is:

[0127] The obtained PAN / Fe / Ni-MIL-88B polyacrylonitrile nanofiber film was first oxidized and then calcined under an inert gas: First, the temperature was raised to 260℃ in air at a heating rate of 1℃ / min and held for 2h. After cooling to room temperature, the obtained sample was placed in the downstream part of a tube furnace, and melamine was placed upstream. The mass ratio of melamine to sample was 10:1. Nitrogen gas was introduced, and the temperature was raised from 30℃ to 800℃ at a heating rate of 2℃ / min and held for 2h. After grinding the product, the iron-nickel doped carbon nanotube material was obtained.

[0128] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.77V when used as an electrocatalyst.

[0129] Comparative Example 1

[0130] This comparative example prepared iron-nickel-doped carbon nanotubes in a similar manner to Example 1, except that Fe / Ni-MIL-88B was not added to the spinning solution. That is, step (2) was: weigh 1g of polyacrylonitrile and disperse it in 10mL of N,N-dimethylformamide solution, stir overnight, and prepare the spinning solution.

[0131] Transmission electron microscopy (TEM) images of the carbon nanotubes obtained in Comparative Example 1 show that they contain only a carbon framework structure. The LSV curves of the samples were analyzed using the same method as in Example 1. The results indicate that the iron-nickel doped carbon nanotubes obtained in this example, when used as an electrocatalyst, have a half-wave potential of 0.73 V.

[0132] Comparative Example 2

[0133] This comparative example prepared iron-nickel-doped carbon nanotubes using a similar method to Example 1, except that NiCl2·6H2O was not added; only FeCl3·6H2O was added. That is, step (1) is:

[0134] Weigh 3.24 g FeCl3·6H2O, 1.99 g terephthalic acid (H2BDC), and 60 mL DMF and mix them. Stir at 400 rpm for 10 minutes. Add 4.8 mL 2 M NaOH solution to the above solution and stir at 400 rpm for 15 minutes. Pour the mixture into a 100 mL autoclave and keep it in an oven at 100 °C for 3 hours. After cooling to room temperature, centrifuge at 6000 rpm for 5 minutes. Wash with DMF and anhydrous ethanol, centrifuge, and dry in a vacuum drying oven at 70 °C for 12 hours to obtain Fe-MIL-88B material.

[0135] The LSV curve of the sample was tested using the same method as in Example 1. The results showed that the iron-nickel doped carbon nanotubes obtained in this example had a half-wave potential of 0.77V when used as an electrocatalyst.

[0136] Therefore, it can be seen that the assembly of an iron-nickel bimetallic organic framework structure in electrospun fibers can effectively improve the electrocatalytic performance of the material.

[0137] 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 iron-nickel-doped carbon nanotubes, characterized in that, Includes the following steps: (1) A substance containing iron salt, nickel salt and terephthalic acid is added to N,N-dimethylformamide as a raw material, mixed evenly to form a mixture, sodium hydroxide solution is added, mixed evenly to obtain a reaction solution, and after hydrothermal reaction at 100-120℃, Fe / Ni-MIL-88B metal-organic framework material is obtained. In the raw materials, the molar ratio of iron to nickel is (1.0-1.3):1, the molar ratio of the total amount of iron and nickel to terephthalic acid is (2.0-2.5):1, and the hydrothermal reaction time is 3-5 hours. (2) Disperse Fe / Ni-MIL-88B in N,N-dimethylformamide, add polyacrylonitrile to form a spinning solution; the ratio of the amount of polyacrylonitrile, N,N-dimethylformamide and Fe / Ni-MIL-88B is 1g: (9-10)mL: (1.4-1.6)g; (3) Spinning the spinning solution to obtain a polyacrylonitrile fiber film containing Fe / Ni-MIL-88B; (4) The obtained polyacrylonitrile fiber film is oxidized in air, and the oxidized sample is placed downstream of a tube furnace. Melamine is placed upstream, nitrogen is introduced, and calcination is carried out at 700-900℃ to complete the carbonization process and obtain the iron-nickel doped carbon nanotubes. The mass ratio of melamine to the oxidized sample is (8-10):1, the heating rate of the oxidation process is 1-2℃ / min, and the heating rate of the carbonization process is 4-5℃ / min.

2. A type of iron-nickel doped carbon nanotube, characterized in that, It is prepared by the method described in claim 1.

3. The iron-nickel doped carbon nanotube according to claim 2, wherein, The iron-nickel doped carbon nanotubes contain carbon, nitrogen, oxygen, iron, and nickel, with the iron having an atomic percentage of 0.85–1.20 at% and the nickel having an atomic percentage of 0.90–1.50 at%.

4. An oxygen reduction reaction electrode, characterized in that, It includes an oxygen reduction reaction electrocatalyst, said electrocatalyst comprising the iron-nickel doped carbon nanotubes of claim 2 or 3.

5. The application of the iron-nickel doped carbon nanotubes of claim 2 or 3, or the oxygen reduction reaction electrode of claim 4, in the field of electrocatalytic oxygen reduction reaction.

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