Method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst on basis of electrostatic spinning method and use of nitrogen-doped bimetallic nanofiber membrane electrocatalyst

Abstract

The present invention belongs to the technical field of OER electrocatalysts. Provided are a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst on the basis of an electrostatic spinning method and the use of the nitrogen-doped bimetallic nanofiber membrane electrocatalyst. The electrocatalyst is prepared from a mixed high-molecular polymer of a metal salt, N,N-dimethylformamide and polyacrylonitrile by means of the coordinated and confined pyrolysis transformation of a one-dimensional porous carbon nanomaterial. The method comprises: S1, preparing a FeCo-NCNF precursor solution; S2, transferring the resulting FeCo-NCNF precursor solution into a plastic injector with a stainless steel needle to perform electrostatic spinning, so as to obtain a nanofiber membrane; and S3, subjecting the obtained nanofiber membrane to high-temperature carbonization and phosphorization in sequence, so as to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst. In the present invention, the nitrogen-doped bimetallic nanofiber membrane electrocatalyst prepared by using the method has the advantages of a large specific surface area, a porous structure, a high nitrogen content, a great number of active sites, etc., and therefore the catalytic performance of the electrocatalyst is improved.

Description

Method and application of constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning Technical Field

[0001] The present invention relates to the technical field of OER electrocatalysts, and in particular to a method and application of constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on an electrospinning method. Background Art

[0002] The operation and development of modern society mainly rely on fossil fuels such as coal, natural gas, and oil. However, fossil fuels are limited and harmful to the environment. The global energy crisis and environmental problems pose a major threat to human society. Hydrogen has high energy capacity and zero carbon emissions, making it an ideal alternative to fossil fuels. Electrocatalytic water splitting is widely considered to be a renewable energy and pollution-free hydrogen production strategy. However, the two half reactions in water splitting, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), require the application of high overpotentials to overcome inherent energy barriers. Currently, commercial catalysts for water splitting are mainly precious metal-based catalysts such as Pt, RuO2, and IrO2. However, low soil reserves, high cost, and poor stability limit their large-scale application. Therefore, finding catalysts with low cost, high electrocatalytic activity, and good stability remains a great challenge.

[0003] Since OER involves 4 electrons, it is generally considered to be the bottleneck of water splitting. At present, first-row transition metal (Fe, Co, Ni, Mn)-based catalysts such as layered hydroxides, perovskites and spinels have been widely studied, and most of them are considered to be well suited for OER. By optimizing the adsorption energy and improving the conductivity of the catalyst, the combination of different metals has become an ideal strategy to improve the catalytic efficiency. At present, some bimetallic catalysts have been widely studied, such as oxides, phosphides, sulfides and layered double hydroxides, but the oxygen evolution performance of these catalysts is also easy to agglomerate, with poor stability and low conductivity, which hinders large-scale application.

[0004] To address these issues, catalysts based on nanoparticles embedded in various carbon materials (i.e., carbon nanotubes, graphite, and graphene) have been widely studied in recent years. Carbon materials offer excellent catalytic properties due to their high conductivity, large surface area, and excellent stability. Metal organic frameworks (MOFs) are composed of inorganic metal centers (metal ions or metal clusters) interconnected by bridging organic ligands through self-assembly. As an emerging nanomaterial, MOFs hold great potential for applications in heterogeneous gas catalysis, sensing, and environmental treatment due to their high surface area, flexible and tunable functionality, rich variety, and highly designable structures. MOFs are composed of metal ions / clusters and organic ligands, and different metal ions / clusters and organic ligands can be paired, resulting in an enormous number of possible combinations. However, MOFs' inherent brittleness, low solubility, difficulty in forming, and incompatibility with other materials pose significant challenges in realizing their functional advantages. Therefore, developing a simple and scalable method to prepare carbon-based electrocatalysts remains a significant challenge.

[0005] Electrospinning is a simple and versatile synthetic technique for preparing long, continuous nanofibers with large surface area, porous structures, and excellent mechanical properties. It has attracted considerable attention for its low cost and high yield. Its principle involves applying a strong electric field to a polymer solution or melt, causing it to form nanofibers with diameters ranging from 2 nm to several microns under active distribution, which are then coated on a designated substrate. It is a relatively simple method for loading MOFs onto highly porous and flexible nanofibers, overcoming the shortcomings of MOFs and improving their stability. Its cost, operability, and compatibility are also superior to other fabrication methods. By adjusting factors influencing electrospinning, such as the type and concentration of the spinning solution, voltage, conductivity, temperature, and humidity, a variety of electrospun fibers can be produced at the nanoscale. Nitrogen-containing polyacrylonitrile nanofibers are a common product prepared by electrospinning. Studies have reported that nitrogen-doped carbon materials can enhance electrocatalytic activity by modifying electronic states and providing active sites. However, the synthesis of bimetallic alloy nanoparticles embedded in nitrogen-doped nanofibers for water oxidation via simple electrospinning techniques remains limited. Therefore, a simple and scalable method to prepare a series of porous nitrogen-carbon embedded carbon fibers for efficient, cheap, durable and effective catalysts is of great significance in this field. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a method and application of constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning. The prepared nitrogen-doped bimetallic nanofiber membrane electrocatalyst has the advantages of large specific surface area, porous structure, rich nitrogen content, and multiple active sites, thereby improving the catalytic performance of the electrocatalyst.

[0007] To achieve the above objectives, the present invention provides the following solution: a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning, wherein the catalyst is a mixed polymer of a metal salt, N,N-dimethylformamide, and polyacrylonitrile, and is converted into a one-dimensional porous carbon nanomaterial through coordination confined pyrolysis, comprising the following steps:

[0008] S1, preparing FeCo-NCNF precursor solution;

[0009] S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane;

[0010] S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

[0011] Preferably, in step S1, the preparation process of the FeCo-NCNF precursor solution includes the following steps:

[0012] S11, dissolving 5-methyltetrazole in N,N-dimethylformamide, referred to as solution A;

[0013] S12, dissolving ferric nitrate nonahydrate and cobalt nitrate hexahydrate in N,N-dimethylformamide, referred to as solution B;

[0014] S13, adding solution B to solution A to react to obtain solution C;

[0015] S14, adding polyacrylonitrile to solution C to react to obtain solution D;

[0016] S15. After the reaction is completed, the solution D is subjected to ultrasonic stirring and magnetic stirring to obtain the FeCo-NCNF precursor solution.

[0017] Preferably, in step S12, the molar ratio of the ferric nitrate nonahydrate to the cobalt nitrate hexahydrate is 1:1.

[0018] Preferably, the mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate and the polyacrylonitrile is 4:1:40.

[0019] Preferably, in step S15, the reaction conditions for ultrasonic stirring and magnetic stirring are: firstly ultrasonically stirring the solution D after the reaction is completed for 30 minutes, and then magnetically stirring it at room temperature for 12 hours.

[0020] Preferably, in step S2, preparing the nanofiber membrane by electrospinning includes:

[0021] The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then, a high voltage of 20 kV was applied. At an air humidity of 30% RH, electrospinning was performed through a rotating metal collector to obtain a nanofiber membrane.

[0022] Preferably, when preparing the nanofiber membrane, the injection rate of the plastic syringe is 1 ml·h -1 .

[0023] Preferably, in step S3, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

[0024] Preferably, the reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the nanofiber membrane after high-temperature carbonization and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat, respectively, and placed in a heating furnace, and then the furnace temperature of the heating furnace is increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

[0025] The present invention also provides an application of a nitrogen-doped bimetallic nanofiber membrane electrocatalyst prepared by the above-mentioned preparation method in a high-efficiency OER electrocatalyst.

[0026] According to the specific technical solution provided by the present invention, the present invention discloses the following technical effects:

[0027] (1) The present invention produces a FeCo-NCNF precursor solution by ferric nitrate nonahydrate, cobalt nitrate hexahydrate, 5-methyltetrazole and polyacrylonitrile, wherein 5-methyltetrazole provides a planar FeNx center and polyacrylonitrile provides a nitrogen-rich source. Subsequently, a strong electric field is applied to the FeCo-NCNF precursor solution by electrospinning technology to form one-dimensional nanofibers under active distribution. Then, the nanofibers are pyrolyzed at different temperatures in a N2 atmosphere to synthesize nitrogen-doped carbon nanofiber-encapsulated FeCo alloy nanoparticle nanofibers. The overall morphology is well maintained before and after pyrolysis.

[0028] (2) The FeCo-NCNF prepared in the present invention has good catalytic activity due to the synergistic effect of its one-dimensional nanofiber structure and abundant catalytic active sites such as pyridinic-N and pyrrolic-N.

[0029] (3) The FeCo-NCNF prepared in the present invention can be used as a highly efficient OER electrocatalyst and has excellent electrochemical performance under alkaline conditions (0.1 M KOH).

[0030] (4) The preparation process adopted by the present invention is simple, easy to reproduce, and convenient for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] FIG1 is a flow chart of a preparation method provided in Example 1 of the present invention;

[0033] FIG2 is a SEM image of the catalyst prepared in Example 1 of the present invention;

[0034] FIG3 is a TEM image of the catalyst prepared in Example 1 of the present invention;

[0035] FIG4 is an EDS graph of the catalyst prepared in Example 1 of the present invention;

[0036] FIG5 is an XRD pattern of the FeCo-NCNF precursor solution in Example 1 of the present invention;

[0037] FIG6 is an XPS overall spectrum of the FeCo-NCNFs precursor solution in Example 1 of the present invention;

[0038] FIG7 is an LSV curve of a FeCo-NCNF precursor solution in a 0.1 mol / L KOH solution according to Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] The purpose of the present invention is to provide a method and application of constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning. The prepared nitrogen-doped bimetallic nanofiber membrane electrocatalyst has the advantages of large specific surface area, porous structure, rich nitrogen content, and multiple active sites, thereby improving the catalytic performance of the electrocatalyst.

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] In a specific embodiment of the present invention, ferric sulfate nonahydrate, cobalt nitrate hexahydrate and N,N-dimethylformamide were purchased from Shanghai MacLean Biochemical Co., Ltd.; 5-methyltetrazole and polyacrylonitrile were purchased from Shanghai Aladdin Reagent Co., Ltd.; all chemicals and reagents in the embodiment were of analytical grade and did not require further purification, and millipore water was used in the preparation experiments.

[0043] In addition, the scanning electron microscope (SEM) of the test devices used in the specific embodiments of the present invention was purchased from Kunshan Ultrasonic Instrument Co., Ltd.; the transmission electron microscope (TEM, JEM2100F) was purchased from JEOL; the X-ray photoelectron spectrometer (XPS, 250xi) was purchased from Thermo Fisher; the X-ray diffractometer (XRD, Smartlab SE) was purchased from Rigaku; the energy dispersive spectrometer (EDS) was purchased from Shimadzu; and the electrochemical workstation was purchased from Shanghai Chenhua Instrument Co., Ltd.

[0044] Example 1

[0045] As shown in FIG1 , this embodiment provides a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning, comprising the following steps:

[0046] S1, preparing FeCo-NCNF precursor solution;

[0047] S11. Dissolve 50 mg of 5-methyltetrazole in 5 ml of N,N-dimethylformamide, referred to as solution A.

[0048] S12. Dissolve 101 mg of ferric nitrate nonahydrate and 75 mg of cobalt nitrate hexahydrate in 5 ml of N,N-dimethylformamide (solution B).

[0049] S13, adding solution B to solution A to react to obtain solution C;

[0050] S14, adding 1 g of polyacrylonitrile to solution C, and reacting to obtain solution D;

[0051] S15, stirring the solution D after the reaction until it is completely dissolved, first ultrasonically stirring the solution D for 30 minutes to form a clear and transparent solution, and then stirring it under magnetic stirring for 12 hours to obtain the FeCo-NCNF precursor solution;

[0052] S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane;

[0053] The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then a high voltage of 20 kV was applied. At an air humidity of about 30% RH, the injection rate of the plastic syringe was 1 ml h. -1 , electrospinning was performed on a rotating metal collector to obtain a nanofiber membrane.

[0054] S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

[0055] Among them, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

[0056] The reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the high-temperature carbonized nanofiber membrane and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat, respectively, and placed in a heating furnace. The furnace temperature is then increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

[0057] As can be seen in Figure 2, the nanofibers intertwine to form a network structure. The fibers are uniform and continuous, with an average diameter of approximately 200 nm. The surface of the nanofibers is rough, uneven, and has certain pores. Some metal nanoparticles and pitted structures caused by corrosion cracking can be observed. The attachment of metal particles to the nanofiber surface increases the roughness of the fiber surface. The metal Fe and Co particles also enhance the etching effect of N2, thereby promoting the preferential etching of carbon species at the junction of the nanofiber carbon fibers and the metal nanoparticles, thereby improving the OER performance of the nanofiber membrane electrocatalyst.

[0058] TEM was then used to further verify the internal structure of the nanofibers, as shown in Figure 3. The FeCo-NCNF electrocatalyst exhibits a fibrous morphology with a diameter of approximately 200 nm. Iron and cobalt nanoparticles of varying sizes can also be observed attached to the fibers, which is consistent with the SEM observations.

[0059] As shown in the EDS diagram of Figure 4, C, N, O, Fe and Co are present in the FeCo-NCNF nanofibers, and all elements are evenly distributed along the nanofibers, indicating that an effective catalyst is prepared using the above preparation method.

[0060] The prepared catalyst was then subjected to XRD testing. As shown in Figure 5, the peak at 2θ=26° in the XRD spectrum of FeCo-NCNF is the characteristic peak of FeC (PDF#03-0411) (002) crystal plane, and no diffraction peaks corresponding to elemental iron and elemental cobalt are observed. The peak at 44° is attributed to the (100) crystal plane of Fe3C (PDF# 06-0686), and the characteristic peak at 65° is attributed to the (110) crystal plane of CoFe (PDF#49-1567), indicating that the corresponding compounds have been synthesized. The results show that after high-temperature carbonization and phosphating, with the growth and catalytic action of FeCo alloy particles, the crystallinity and graphitization degree of the electrocatalyst increase, and the electrocatalytic performance of OER is improved.

[0061] Subsequently, the types and contents of chemical elements on the surface of the prepared nitrogen-doped bimetallic nanofiber membrane electrocatalyst were detected by X-ray photoelectron spectroscopy (XPS). As shown in Figure 6, the overall spectrum of FeCo-NCNF showed the coexistence of C, N, O, Fe and Co elements.

[0062] Finally, commercial RuO2 and FeCo-NCNF were tested in 0.1 mol / L KOH solution, and the LSV curves were obtained after iR correction. As shown in Figure 7, during the OER catalytic process, the LSV polarization curves of RuO2 and FeCo-NCNF both showed a trend of increasing current density with increasing potential. Compared with RuO2 (1.56 V), FeCo-NCNF showed a trend of increasing current density with increasing potential at a current density of 10 mA / cm -2 The results show that FeCo-NCNF outperforms the commercial RuO2 catalyst in OER catalysis and exhibits better OER performance, which proves that the nitrogen-doped bimetallic nanofiber membrane electrocatalyst prepared by the present invention can be used as an OER electrocatalyst.

[0063] Example 2

[0064] This embodiment provides a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on an electrospinning method, comprising the following steps:

[0065] S1, preparing FeCo-NCNF precursor solution;

[0066] S11. Dissolve 50 mg of 5-methyltetrazole in 5 ml of N,N-dimethylformamide, referred to as solution A.

[0067] S12. Dissolve 202 mg of ferric nitrate nonahydrate and 75 mg of cobalt nitrate hexahydrate in 5 ml of N,N-dimethylformamide (solution B).

[0068] S13, adding solution B to solution A to react to obtain solution C;

[0069] S14, adding 1 g of polyacrylonitrile to solution C, and reacting to obtain solution D;

[0070] S15, stirring the solution D after the reaction until it is completely dissolved, first ultrasonically stirring the solution D for 30 minutes to form a clear and transparent solution, and then stirring it under magnetic stirring for 12 hours to obtain the FeCo-NCNF precursor solution;

[0071] S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane;

[0072] The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then a high voltage of 20 kV was applied. At an air humidity of about 30% RH, the injection rate of the plastic syringe was 1 ml h. -1 , electrospinning was performed on a rotating metal collector to obtain a nanofiber membrane.

[0073] S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

[0074] Among them, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

[0075] The reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the high-temperature carbonized nanofiber membrane and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat, respectively, and placed in a heating furnace. The furnace temperature is then increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

[0076] Example 3

[0077] This embodiment provides a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on an electrospinning method, comprising the following steps:

[0078] S1, preparing FeCo-NCNF precursor solution;

[0079] S11. Dissolve 50 mg of 5-methyltetrazole in 5 ml of N,N-dimethylformamide, referred to as solution A.

[0080] S12. Dissolve 202 mg of ferric nitrate nonahydrate and 150 mg of cobalt nitrate hexahydrate in 5 ml of N,N-dimethylformamide (solution B).

[0081] S13, adding solution B to solution A to react to obtain solution C;

[0082] S14, adding 1 g of polyacrylonitrile to solution C, and reacting to obtain solution D;

[0083] S15, stirring the solution D after the reaction until it is completely dissolved, first ultrasonically stirring the solution D for 30 minutes to form a clear and transparent solution, and then stirring it under magnetic stirring for 12 hours to obtain the FeCo-NCNF precursor solution;

[0084] S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane;

[0085] The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then a high voltage of 20 kV was applied. At an air humidity of about 30% RH, the injection rate of the plastic syringe was 1 ml h. -1 , electrospinning was performed on a rotating metal collector to obtain a nanofiber membrane.

[0086] S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

[0087] Among them, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

[0088] The reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the high-temperature carbonized nanofiber membrane and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat, respectively, and placed in a heating furnace. The furnace temperature is then increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

[0089] Example 4

[0090] This embodiment provides a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on an electrospinning method, comprising the following steps:

[0091] S1, preparing FeCo-NCNF precursor solution;

[0092] S11. Dissolve 100 mg of 5-methyltetrazole in 5 ml of N,N-dimethylformamide (solution A).

[0093] S12. Dissolve 101 mg of ferric nitrate nonahydrate and 75 mg of cobalt nitrate hexahydrate in 5 ml of N,N-dimethylformamide (solution B).

[0094] S13, adding solution B to solution A to react to obtain solution C;

[0095] S14, adding 1 g of polyacrylonitrile to solution C, and reacting to obtain solution D;

[0096] S15, stirring the solution D after the reaction until it is completely dissolved, first ultrasonically stirring the solution D for 30 minutes to form a clear and transparent solution, and then stirring it under magnetic stirring for 12 hours to obtain the FeCo-NCNF precursor solution;

[0097] S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane;

[0098] The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then a high voltage of 20 kV was applied. At an air humidity of about 30% RH, the injection rate of the plastic syringe was 1 ml h. -1 , electrospinning was performed on a rotating metal collector to obtain a nanofiber membrane.

[0099] S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

[0100] Among them, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

[0101] The reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the high-temperature carbonized nanofiber membrane and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat, respectively, and placed in a heating furnace. The furnace temperature is then increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

[0102] Example 5

[0103] This embodiment provides a method for constructing a nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on an electrospinning method, comprising the following steps:

[0104] S1, preparing FeCo-NCNF precursor solution;

[0105] S11. Dissolve 100 mg of 5-methyltetrazole in 5 ml of N,N-dimethylformamide (solution A).

[0106] S12. Dissolve 202 mg of ferric nitrate nonahydrate and 75 mg of cobalt nitrate hexahydrate in 5 ml of N,N-dimethylformamide (solution B).

[0107] S13, adding solution B to solution A to react to obtain solution C;

[0108] S14, adding 1 g of polyacrylonitrile to solution C, and reacting to obtain solution D;

[0109] S15, stirring the solution D after the reaction until it is completely dissolved, first ultrasonically stirring the solution D for 30 minutes to form a clear and transparent solution, and then stirring it under magnetic stirring for 12 hours to obtain the FeCo-NCNF precursor solution;

[0110] S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane;

[0111] The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then a high voltage of 20 kV was applied. At an air humidity of about 30% RH, the injection rate of the plastic syringe was 1 ml h. -1 , electrospinning was performed on a rotating metal collector to obtain a nanofiber membrane.

[0112] S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

[0113] Among them, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

[0114] The reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the high-temperature carbonized nanofiber membrane and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat, respectively, and placed in a heating furnace. The furnace temperature is then increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

[0115] The electrochemical properties of the samples were characterized on a CHI760D electrochemical workstation in a three-electrode system. 1 mg of the sample obtained in the experiment was weighed, 60 μl of conductive solution was added, and ultrasonication was performed for 30 minutes to completely disperse it. The sample suspension was evenly drop-casted onto a graphite electrode (1 cm × 1 cm) twice, 30 μl each time, and then the graphite electrode was placed in an oven and baked at 80 ° C for 2 hours. Using platinum foil as the counter electrode and Hg / HgO as the reference electrode, a three-electrode system was completed to verify the application of the prepared catalyst in OER electrocatalysts.

[0116] The beneficial effects of the present invention are as follows:

[0117] (1) The present invention produces a FeCo-NCNF precursor solution by ferric nitrate nonahydrate, cobalt nitrate hexahydrate, 5-methyltetrazole and polyacrylonitrile, wherein 5-methyltetrazole provides a planar FeNx center and polyacrylonitrile provides a nitrogen-rich source. Subsequently, a strong electric field is applied to the FeCo-NCNF precursor solution by electrospinning technology to form one-dimensional nanofibers under active distribution. Then, the nanofibers are pyrolyzed at different temperatures in a N2 atmosphere to synthesize nitrogen-doped carbon nanofiber-encapsulated FeCo alloy nanoparticle nanofibers. The overall morphology is well maintained before and after pyrolysis.

[0118] (2) The FeCo-NCNF prepared in the present invention has good catalytic activity due to the synergistic effect of its one-dimensional nanofiber structure and abundant catalytic active sites such as pyridinic-N and pyrrolic-N.

[0119] (3) The FeCo-NCNF prepared in the present invention can be used as a highly efficient OER electrocatalyst and has excellent electrochemical performance under alkaline conditions (0.1 M KOH).

[0120] (4) The preparation process adopted by the present invention is simple, easy to reproduce, and convenient for industrial production.

[0121] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0122] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning, characterized in that: The catalyst is a mixed polymer of metal salt, N,N-dimethylformamide and polyacrylonitrile, which is converted into a one-dimensional porous carbon nanomaterial through coordination confined pyrolysis, including the following steps: S1, preparing FeCo-NCNF precursor solution; S2, transferring the obtained FeCo-NCNF precursor solution into a plastic syringe with a stainless steel needle for electrospinning to obtain a nanofiber membrane; S3. The obtained nanofiber membrane is subjected to high-temperature carbonization and phosphating in sequence to obtain a nitrogen-doped bimetallic nanofiber membrane electrocatalyst.

2. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 1, characterized in that: In step S1, the preparation process of the FeCo-NCNF precursor solution includes the following steps: S11, dissolving 5-methyltetrazole in N,N-dimethylformamide, referred to as solution A; S12, dissolving ferric nitrate nonahydrate and cobalt nitrate hexahydrate in N,N-dimethylformamide, referred to as solution B; S13, adding solution B to solution A to react to obtain solution C; S14, adding polyacrylonitrile to solution C to react to obtain solution D; S15. After the reaction is completed, the solution D is subjected to ultrasonic stirring and magnetic stirring to obtain the FeCo-NCNF precursor solution.

3. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 2, characterized in that: In the step S12, the molar ratio of the ferric nitrate nonahydrate to the cobalt nitrate hexahydrate is 1:

1.

4. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 2, characterized in that: The mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate and the polyacrylonitrile is 4:1:

40.

5. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 2, characterized in that: In step S15, the reaction conditions for ultrasonic stirring and magnetic stirring are: first, ultrasonic stirring is performed on the solution D after the reaction is completed for 30 minutes, and then magnetic stirring is performed at room temperature for 12 hours.

6. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 1, characterized in that: In the step S2, preparing the nanofiber membrane by electrospinning includes: The FeCo-NCNF precursor solution was injected into a plastic syringe with a stainless steel needle, and the plastic syringe was placed on an electrospinning machine. The distance between the stainless steel needle and the rotating metal collector was 10 cm. Then, a high voltage of 20 kV was applied. At an air humidity of 30% RH, electrospinning was performed through a rotating metal collector to obtain a nanofiber membrane.

7. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 6, characterized in that: When preparing nanofiber membranes, the injection rate of the plastic syringe was 1 ml h -1 .

8. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 1, characterized in that: In step S3, the reaction process of high-temperature carbonization of the nanofiber membrane is as follows: the nanofiber membrane is first heated from room temperature to 25°C at a rate of 1°C / min in N2 and kept warm for 2 hours, and then carbonized from 250°C to 800°C at a rate of 5°C / min and kept warm for 1 hour.

9. The method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to claim 8, characterized in that: The reaction process of the nanofiber membrane after high-temperature carbonization and subsequent phosphating is as follows: 40 mg of the high-temperature carbonized nanofiber membrane and 800 mg of NaH2PO2 are placed downstream and upstream of a 10 cm porcelain boat respectively, and placed in a heating furnace, and then the furnace temperature of the heating furnace is increased to 300°C at a heating rate of 2°C / min, and then kept warm for 5 hours under N2 gas flow.

10. Application of the nitrogen-doped bimetallic nanofiber membrane electrocatalyst prepared by the method for constructing nitrogen-doped bimetallic nanofiber membrane electrocatalyst based on electrospinning according to any one of claims 1 to 9 in high-efficiency OER electrocatalyst.

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