CN115000421B - N, se-doped carbon nanofiber-loaded CoSe organic framework composite material and preparation method and application thereof - Google Patents

N, se-doped carbon nanofiber-loaded CoSe organic framework composite material and preparation method and application thereof Download PDF

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CN115000421B
CN115000421B CN202210829803.2A CN202210829803A CN115000421B CN 115000421 B CN115000421 B CN 115000421B CN 202210829803 A CN202210829803 A CN 202210829803A CN 115000421 B CN115000421 B CN 115000421B
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doped carbon
organic framework
carbon nanofiber
zif
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CN115000421A (en
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卢惠民
刘建学
卢小溪
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Yihang Times Beijing Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M12/00—Hybrid cells; Manufacture thereof
    • H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
    • H01M4/8673—Electrically conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9041—Metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
    • H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
    • H01M2004/8689—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
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    • Y02P20/133—Renewable energy sources, e.g. sunlight

Abstract

The invention provides a N, se doped carbon nanofiber supported CoSe organic framework composite material, which belongs to the technical field of catalysts and comprises N, se doped carbon nanofibers and ZIF-67 pyrolysis derived carbon supported on the surfaces of the N, se doped carbon nanofibers, wherein CoSe particles are supported on the surfaces and the interiors of the ZIF-67 pyrolysis derived carbon. According to the invention, the ZIF-67 pyrolysis derived carbon is used as a dispersion matrix of CoSe particles, so that the ZIF-67 can realize atomic-level dispersion of Co, limit agglomeration of the CoSe particles and improve oxygen reduction catalytic activity of the CoSe particles. According to the invention, N, se doped carbon nanofiber is used as a load matrix, so that good conductivity can be given to the carbon nanofiber, electron transfer in catalysis is facilitated, and catalytic reaction is promoted. When used as the cathode catalyst of the aluminum air battery, the composite material has good oxygen reduction catalytic activity and can be compared favorably with a Pt/C catalyst.

Description

N, se-doped carbon nanofiber-loaded CoSe organic framework composite material and preparation method and application thereof
Technical Field
The invention relates to the technical field of catalysts, in particular to a N, se doped carbon nanofiber supported CoSe organic framework composite material, and a preparation method and application thereof.
Background
The demand of energy is higher and higher in the current society, however, the reserves of fossil energy such as coal, petroleum, natural gas and the like which are relied on by human beings are limited, and the energy crisis is getting severe. In addition, the combustion of the fuel can generate a large amount of greenhouse gases, so that the greenhouse effect of the earth is increased, the environment is polluted, and the development of substitutes for fossil fuels is urgently needed. The emerging energy sources comprise wind energy, water energy, solar energy, geothermal energy and the like, and have the advantages of cleanness, high efficiency, reproducibility, low cost and the like, but also have the defects of dispersibility, intermittence, poor stability and the like, so that the energy sources are difficult to directly utilize, and an energy storage system is usually required to be matched for storage for development and utilization.
The metal aluminum air battery has the characteristics of low cost, high theoretical energy density (2.98 Ah/g) equivalent to lithium (3.86 Ah/g), small environmental pollution and recycling, is known as a '21 st century green energy', and is a powerful substitute for fossil fuel. The catalytic activity of the cathode catalyst is an important factor directly affecting the performance of the aluminum air cell. The most commonly used catalysts with better performance are currently recognized as noble metal catalysts, including metals such as platinum, palladium, gold and silver, but the commercial development of the catalysts is limited by low reserves, high cost and short service life.
The transition metal-based catalyst has high activity and stability, and is attracting high attention in the research field. Among them, transition metal selenide (TMSe) materials have become a highly efficient catalytic material in recent years due to their unique catalytic and electronic properties. However, the transition metal selenide is easy to agglomerate, and the oxygen reduction catalytic activity is not ideal when the transition metal selenide is directly used as a cathode catalyst of an aluminum air battery.
Disclosure of Invention
In view of the above, the invention aims to provide a N, se doped carbon nanofiber supported CoSe organic framework composite material, and a preparation method and application thereof, and the N, se doped carbon nanofiber supported CoSe organic framework composite material provided by the invention has good oxygen reduction catalytic activity.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a N, se doped carbon nanofiber supported CoSe organic framework composite material, which comprises N, se doped carbon nanofibers and ZIF-67 pyrolysis derived carbon supported on the surfaces of the N, se doped carbon nanofibers, wherein CoSe particles are supported on the surfaces and the interiors of the ZIF-67 pyrolysis derived carbon.
Preferably, the mole ratio of Co to Se in the CoSe particles is 0.85:1;
the mass content of the CoSe particles in the N, se doped carbon nanofiber loaded CoSe organic framework composite material is 10-15%.
Preferably, the mass content of the ZIF-67 pyrolysis derived carbon in the N, se doped carbon nanofiber supported CoSe organic framework composite material is 15-35%.
Preferably, the diameter of the N, se doped carbon nanofiber supported CoSe organic framework composite material is 0.5-1 mu m;
the diameter of the N, se doped carbon nanofiber is 100-200 nm;
the particle size of the CoSe particles is 5-10 nm.
The invention provides a preparation method of the N, se doped carbon nanofiber supported CoSe organic framework composite material, which comprises the following steps:
mixing polyacrylonitrile and ZIF-67 organic framework materials with an organic solvent to obtain an electrostatic spinning precursor solution;
carrying out electrostatic spinning on the electrostatic spinning precursor solution, and drying to obtain a spinning fiber film;
heating and oxidizing the spinning fiber film to obtain a pre-oxidized fiber film;
and mixing the pre-oxidized fiber film with selenium powder, and performing pyrolysis to obtain the N, se doped carbon nanofiber-loaded CoSe organic framework composite material.
Preferably, the mass ratio of the polyacrylonitrile to the ZIF-67 organic framework material is 0.55:0.15-0.25.
Preferably, the parameters of the electrospinning include:
the positive high voltage is 12.5-13.5 kV;
the negative high voltage is 1.8-2 kV;
the distance between the needle head and the acquisition plate is 12-14 cm;
the propulsion rate is 0.9-1.1 mLh -1 。
Preferably, the temperature of the heating oxidation is 240-280 ℃, and the heat preservation time is 1-2 h.
Preferably, the mass ratio of the pre-oxidized fiber film to the selenium powder is 1:2-3;
the pyrolysis temperature is 800-850 ℃, and the heat preservation time is 2-3 h.
The invention provides application of the N, se doped carbon nanofiber supported CoSe organic framework composite material as an aluminum air battery cathode catalyst.
The invention provides a N, se doped carbon nanofiber supported CoSe organic framework composite material, which comprises N, se doped carbon nanofibers and ZIF-67 pyrolysis derived carbon supported on the surfaces of the N, se doped carbon nanofibers, wherein CoSe particles are supported on the surfaces and the interiors of the ZIF-67 pyrolysis derived carbon. According to the invention, the ZIF-67 pyrolysis derived carbon is used as a dispersion matrix of CoSe particles, and the ZIF-67 can realize atomic-level dispersion of Co and limit agglomeration of the CoSe particles, so that the oxygen reduction catalytic activity of the CoSe particles is improved. According to the invention, N, se doped carbon nanofiber is used as a load matrix, and Se has a larger covalent bond length (120 pm) which is much larger than that of C (73 pm) and N (71 pm), so that large defect deformation can be introduced into a carbon nanofiber lattice, and charge localization and chemical adsorption to oxygen are accelerated; the Se atoms can also introduce a pi conjugated system into the carbon nanofiber matrix, so that a high-efficiency electron transfer path is provided for the carbon nanofiber, interface charge transfer impedance is reduced, good conductivity is provided for the carbon nanofiber, electron transfer in catalysis is facilitated, and the smooth progress of the catalytic reaction is promoted. The example result shows that when the N, se doped carbon nanofiber supported CoSe organic framework composite material provided by the invention is used as an aluminum air battery cathode catalyst, the composite material has good oxygen reduction catalytic activity and can be compared favorably with a Pt/C catalyst; durability tests show that under the action of 5000 CV cycles, the initial potential of the composite material provided by the invention is hardly changed, which indicates that the oxygen reduction reaction activity of the composite material has long-term stability.
According to the preparation method of the N, se doped carbon nanofiber-loaded CoSe organic framework composite material, electrostatic spinning is carried out on an electrostatic spinning precursor solution containing ZIF-67 organic framework materials, the ZIF-67 organic framework materials are loaded on the surfaces of carbon nanofibers, thermal oxidation stabilization is achieved through heating oxidation, and through mixing pyrolysis with selenium powder, a part of selenium is doped into the carbon nanofibers in the pyrolysis process, a part of selenium and Co in the ZIF-67 organic framework materials form CoSe particles, and due to atomic-level dispersion of Co in the ZIF-67 organic framework materials, the ZIF-67 organic framework materials block high Wen Qianyi agglomeration of Co in the selenization process, so that the increase of the particle size of the CoSe particles is limited, and the oxygen reduction catalytic activity of the CoSe particles is guaranteed. In the invention, the selenization and the pyrolytic carbonization are synchronously carried out, which is different from the high-temperature process of carbonizing first and then selenizing in the prior art, shortens the high-temperature process time of the composite material, and avoids the further growth of CoSe particles. Meanwhile, the preparation method provided by the invention is simple to operate, low in cost and suitable for industrial mass production.
Drawings
FIG. 1 is a schematic illustration of a process for preparing a N, se doped carbon nanofiber supported CoSe organic matrix composite;
FIG. 2 is a microscopic topography of ZIF-67;
FIG. 3 is a graph of the microtopography of the resulting fibrous membrane after spinning with a pure PAN/DMF system;
FIG. 4 is a graph of the microscopic morphology of N, se-CNFs;
FIG. 5 is Co 0.85 Microcosmic topography of Se/C;
FIG. 6 is Co 0.85 Se@N,Se-CNFs、N,Se-CNFs、ZIF-67、Co 0.85 XRD pattern of Se/C;
FIG. 7 is Co 0.85 Scanning test results of SEM and TEM of Se@N, se-CNFs;
FIG. 8 is Co 0.85 EDS component analysis results of Se@N and Se-CNFs are proportional to element content;
FIG. 9 is Co 0.85 XPS scan of Se@N, se-CNFs;
FIG. 10 is Co 0.85 X-ray absorption spectrum of Se@N, se-CNFs;
FIG. 11 is Co 0.85 Visual model of Se lattice;
FIG. 12 Co 0.85 Raman spectra of se@n, se-CNFs;
FIG. 13 Co 0.85 N of Se@N, se-CNFs samples 2 Adsorption-desorption isothermal curves and BJH pore size distribution;
FIG. 14 is Co 0.85 Se@N, se-CNFs thermal decomposition curve and decomposition product XRD curve;
FIG. 15 Co 0.85 Oxygen reduction reaction test results of Se@N, se-CNFs;
FIG. 16 shows the Co pairs by chronoamperometry and CV cycling 0.85 Test results of Se@N, se-CNFs;
FIG. 17 is a transmission electron microscope characterization of a durability test sample;
FIG. 18 is an EDS facial sweep analysis of a durability test sample;
FIG. 19 is a graph of density functional theory versus Co 0.85 Analyzing results of electrocatalytic reaction process of Se@N, se-CNFs samples;
FIG. 20 Co 0.85 Electrochemical impedance test results of Se@N, se-CNFs;
FIG. 21 is Co 0.85 The practical discharge performance test result of the aluminum air fuel cell when Se@N and Se-CNFs are used as an air cathode catalyst;
FIG. 22 shows two assembled Co 0.85 And the Se@N, se-CNFs are used as an aluminum air single cell of the cathode catalyst to light the LED small lamp bead physical image in series.
Detailed Description
The invention provides a N, se doped carbon nanofiber supported CoSe organic framework composite material, which comprises N, se doped carbon nanofibers and ZIF-67 pyrolysis derived carbon supported on the surfaces of the N, se doped carbon nanofibers, wherein CoSe particles are supported on the surfaces and the interiors of the ZIF-67 pyrolysis derived carbon.
In the present invention, the diameter of the N, se doped carbon nanofiber is preferably 100 to 200nm, more preferably 150nm. In the N, se doped carbon nanofiber, the atomic ratio of Se to C is preferably 1.5 to 2%, more preferably 1.6 to 1.8%. In the invention, se has larger covalent bond length (120 pm) which is much larger than C (73 pm) and N (71 pm), so that large defect deformation can be introduced into the carbon nanofiber crystal lattice, and charge localization and chemical adsorption to oxygen are accelerated; se atoms can also introduce pi conjugated systems into the carbon nanofiber matrix, so that a high-efficiency electron transfer path is provided, and interface charge transfer impedance is reduced. Se atoms with higher polarizability can produce a fast response with reactants in the electrolyte than N, P and S.
In the invention, the mass content of the ZIF-67 pyrolytic derived carbon in the N, se doped carbon nanofiber supported CoSe organic framework composite material is preferably 15-35%, and more preferably 20-25%. In the present invention, the particle diameter of the ZIF-67 pyrolysis-derived carbon is preferably 140 to 160nm, more preferably 150nm, and the ZIF-67 pyrolysis-derived carbon has a cubic structure. In the invention, the ZIF-67 pyrolytic derived carbon is preferably connected in series in a bead shape in N, se doped carbon nanofiber, and the structure can promote the transmission of reactants and accelerate the electrochemical reaction process.
In the present invention, the molar ratio of Co to Se in the CoSe particles is preferably 0.85:1; the mass content of the CoSe particles in the N, se doped carbon nanofiber supported CoSe organic framework composite material is preferably 10-15%, and more preferably 13-14%. In the present invention, the particle diameter of the CoSe particles is preferably 5 to 10nm, more preferably 6 to 8nm. In the present invention, the CoSe particles have a hexagonal crystal structure. According to the invention, the ZIF-67 pyrolysis derived carbon is used as a dispersion matrix of CoSe particles, and the ZIF-67 can realize atomic-level dispersion of Co and limit agglomeration of the CoSe particles, so that the oxygen reduction catalytic activity of the CoSe particles is improved.
In the invention, the diameter of the N, se doped carbon nanofiber supported CoSe organic framework composite material is preferably 0.5-1 μm, and more preferably 0.6-0.8 μm.
The invention provides a preparation method of the N, se doped carbon nanofiber supported CoSe organic framework composite material, which comprises the following steps:
mixing polyacrylonitrile and ZIF-67 organic framework materials with an organic solvent to obtain an electrostatic spinning precursor solution;
carrying out electrostatic spinning on the electrostatic spinning precursor solution, and drying to obtain a spinning fiber film;
heating and oxidizing the spinning fiber film to obtain a pre-oxidized fiber film;
and mixing the pre-oxidized fiber film with selenium powder, and performing pyrolysis to obtain the N, se doped carbon nanofiber-loaded CoSe organic framework composite material.
According to the invention, polyacrylonitrile and ZIF-67 organic framework materials are mixed with an organic solvent to obtain an electrostatic spinning precursor solution. In the present invention, the molecular weight of the Polyacrylonitrile (PAN) is preferably 140000 ～ 150000. In the present invention, the organic solvent is preferably Dimethylformamide (DMF).
In the invention, the organic ligand of the ZIF-67 organic framework material is 2-methylimidazole, and the coordination ion is cobalt ion. In the invention, the preparation method of the ZIF-67 organic framework material preferably comprises the following steps:
mixing soluble bivalent cobalt salt, 2-methylimidazole and a surfactant with water, and carrying out coordination reaction to obtain the ZIF-67 organic framework material.
In the present invention, the surfactant is preferably cetyl trimethylammonium bromide (CTAB). In the present invention, the soluble divalent cobalt salt is preferably cobalt nitrate; the molar ratio of the soluble divalent cobalt salt to the 2-methylimidazole is preferably 1:70 to 80, more preferably 1:75.
In the present invention, the temperature of the coordination reaction is preferably room temperature, and the time is preferably 1h.
In the invention, the mass ratio of the polyacrylonitrile to the ZIF-67 organic framework material is preferably 0.55:0.15-0.25, and more preferably 0.55:0.2. In the present invention, the mass concentration of polyacrylonitrile in the electrospinning precursor solution is preferably 10 to 12%, more preferably 11%. In the invention, the ZIF-67 has a large amount of metal ions on the surface, and can be bonded with-C.ident.N groups contained in PAN after the PAN/DMF system is added.
After the electrostatic spinning precursor solution is obtained, the invention performs electrostatic spinning on the electrostatic spinning precursor solution, and the spinning fiber film is obtained after drying. In the present invention, the parameters of the electrospinning preferably include:
the positive high voltage is preferably 12.5 to 13.5kV, more preferably 13kV;
the negative high voltage is preferably 1.8-2 kV, more preferably 1.9kV;
the distance between the needle and the acquisition plate is preferably 12-14 cm, more preferably 13cm;
the propelling speed is preferably 0.9-1.1 mL h -1 More preferably 1mL h -1 。
In the present invention, the drying temperature is preferably 60 to 80 ℃, more preferably 70 ℃; the time is preferably 10 to 12 hours, more preferably 11 hours.
After the spinning fiber film is obtained, the invention carries out heating oxidation on the spinning fiber film to obtain the pre-oxidized fiber film. In the present invention, the heating and oxidizing atmosphere is preferably an air atmosphere. In the present invention, the temperature of the thermal oxidation is preferably 240 to 280 ℃, more preferably 260 to 280 ℃; the holding time is preferably 1 to 2 hours, more preferably 1.5 hours. In the present invention, the heating rate to the heating oxidation temperature is preferably 1 to 3 ℃/min, more preferably 2 ℃/min. In the invention, after electrostatic spinning film formation, pre-oxidation is carried out in an aerobic atmosphere, cyclization and other reactions can occur, so that chain PAN molecules are converted into a heat-resistant trapezoid structure, and preparation is carried out for forming a continuous high-quality carbonized film in subsequent carbonization.
After the pre-oxidized film is obtained, the pre-oxidized fiber film is mixed with selenium powder and pyrolyzed to obtain the N, se doped nano carbon fiber loaded CoSe organic framework composite material. In the invention, the mass ratio of the pre-oxidized fiber film to the selenium powder is preferably 1:2-3, and more preferably 1:2.5.
In the present invention, the atmosphere for pyrolysis is preferably H 2 Mixed gas with Ar, H in the mixed gas 2 The volume content of (2) is preferably 5 to 7%, more preferably 6%. In the present invention, the pyrolysis temperature is preferably 800 to 850 ℃, more preferably 820 to 840 ℃; the holding time is preferably 2 to 3 hours, more preferably 2.5 hours. In the present invention, the heating rate to the pyrolysis temperature is preferably 1 to 3 ℃/min, more preferably 2 ℃/min. According to the invention, through pyrolysis, PAN fibers in the pre-oxidized film are converted into carbon fibers, and ZIF-67 organic framework materials are converted into ZIF-67 pyrolysis derived carbon. Meanwhile, in the pyrolysis process, the selenium powder is changed into steam, so that selenium doping of the carbon fiber and generation of CoSe particles are realized.
The preparation process of the N, se doped carbon nanofiber supported CoSe organic framework composite material is shown in figure 1.
The invention provides an application of the N, se doped carbon nanofiber supported CoSe organic framework composite material or serving as an aluminum air battery cathode catalyst. The composite material provided by the invention can avoid agglomeration of CoSe particles and has good oxygen reduction catalytic activity.
The N, se doped carbon nanofiber supported CoSe organic framework composite material, the preparation method and the application thereof provided by the invention are described in detail below by combining with examples, but the N, se doped carbon nanofiber supported CoSe organic framework composite material is not to be construed as limiting the protection scope of the invention.
Example 1
(1) Preparation of cube ZIF-67: 700mg Co (NO) 3 ) 2 ·6H 2 O and 5mg CTAB were dissolved in 10mL deionized water, then 15g of 2-methylimidazole was dissolved in 100mL deionized water, then both were thoroughly mixed and stirring was continued at room temperature for 1h. And then carrying out centrifugal dehydration, cleaning the obtained purple powder for 3 times, and drying for standby.
(2) Preparing a spinning precursor solution; 0.55g of PAN was dissolved in 5.5mL of DMF with stirring and stirred well to a uniform transparency, followed by the addition of 0.2g of ZIF-67.
(3) Preparing an electrostatic spinning film: the purple precursor solution was introduced into a 10mL plastic syringe, and electrospun. Setting a positive high voltage of 13kV and a negative high voltage of 1.9kV. The distance between the needle head and the collecting plate is kept 13cm, and the pushing speed is 1mL h -1 And after spinning, putting the film into a drying oven to be dried for 10 hours at 60 ℃ for standby.
(4) Preoxidation and pyrolysis: transferring the electrostatic spinning film into a glass tube of a tube furnace, raising the temperature from room temperature to 280 ℃ at 2 ℃/min under the air atmosphere, and preserving the temperature for 1h to complete the thermo-oxidative stabilization process. And then carrying out high-temperature pyrolysis on the pre-oxidized film and the selenium powder together, wherein the mass ratio of the pre-oxidized film to the selenium powder is 1:2.5. Setting the high-temperature atmosphere as H 2 Ar (5 vol.%) is heated to 800 ℃ at a heating rate of 2 ℃/min and is kept for 2 hours to obtain N, se doped carbon nanofiber loaded CoSe organic framework composite material, which is denoted as Co 0.85 Se@N,Se-CNFs。
And (3) omitting the addition of ZIF-67 in the step (2), and carrying out the rest operation identically to obtain the N, se doped carbon nanofiber, which is marked as N, se-CNFs.
Mixing ZIF-67 with selenium powder, and performing high-temperature pyrolysis in the mode of step (4) to obtain CoSe organic skeleton pyrolytic carbon material, denoted as Co 0.85 Se/C。
Structural characterization
The micro-morphology of ZIF-67 is shown in FIG. 2. It can be seen that ZIF-67 has a cubic structure.
The microstructure of the fiber film obtained after spinning of the pure PAN/DMF system is shown in figure 3, the microstructure of N, se-CNFs is shown in figure 4, co 0.85 The micro-topography of Se/C is shown in FIG. 5.
Co 0.85 Se@N,Se-CNFs、N,Se-CNFs、ZIF-67、Co 0.85 The XRD pattern of Se/C is shown in FIG. 6, in which (a) is Co 0.85 XRD curves of Se@N, se-CNFs, N, se-CNFs and ZIF-67; (b) Is Co 0.85 XRD profile of Se/C. As can be seen from FIG. 6, the peak spectrum of the comparison standard card shows that the ZIF-67 prepared by the invention is the ZIF-67 particles; the diffraction peak of N, se-CNFs at 24 deg. corresponds to the (002) peak of graphitized carbon-based material; co (Co) 0.85 Se@N, se-CNFs and Co 0.85 Diffraction peaks of Se/C at 33.2 degrees, 44.9 degrees, 50.4 degrees, 60.3 degrees and 61.8 degrees correspond to (101), (102), (110), (103) and (201) crystal planes in PDF#04-8806, and the fact that hexagonal Co is truly contained in the material is proved 0.85 Se。
Co 0.85 SEM and TEM scan test results of Se@N, se-CNFs are shown in FIG. 7. The picture shown in fig. 7 a is an SEM image of an electrospun film incorporating ZIF-67, and it can be seen that ZIF-67 particles were successfully connected in series by PAN fibers during spinning to form a network morphology of intertwined and staggered fibers. Through thermo-oxidation stabilization and mixed selenium high temperature pyrolysis, the Co is obtained 0.85 SEM pictures of Se@N and Se-CNFs are shown as b in FIG. 7, and the sizes of the cubic carbonized particles derived from ZIF-67 at high temperature are about 150nm and are consistent with the sizes of particles obtained by pyrolysis of the pure ZIF-67 mixed selenium powder in FIG. 5; and under the coating of PAN, the appearance of the cubic particles derived from ZIF-67 at high temperature is more regular. These particles are serially interwoven into a 3D network-like structure by PAN-derived high aspect ratio 1D carbon fibers; such a structure can promote the transport of reactants and accelerate the progress of the electrochemical reaction. FIG. 7 c shows Co 0.85 TEM images of Se@N, se-CNFs whose selected area diffraction patterns prove that the material contains hexagonal Co 0.85 The Se crystal is clearly seen in the figure, and the cubic morphology derived from ZIF-67 is seen, so that ZIF-67 does not collapse and collapse greatly under the wrapping action of PAN during high-temperature pyrolysis. The faces exposed at the fiber edges may undergo a greater magnitude of deformation collapse due to the lesser amount of cladding PAN. Thus can be ensuredThe basic morphology of the ZIF-67 is kept so that particles in the ZIF-67 are not excessively aggregated and grown when the ZIF-67 collapses, more active particles can be exposed to the outside, and more catalytic reaction active sites are provided for electrochemical reaction. In FIG. 7 d is Co 0.85 HRTEM images of Se@N, se-CNFs show microscopic morphology of particles in the fiber midbody, and analysis shows that the interplanar spacing is 0.27nm, which belongs to Co 0.85 The (101) crystal plane of Se crystal. In FIG. 7 e is Co 0.85 SEM pictures of Se@N, se-CNFs. In FIG. 7 f is Co 0.85 The C, co, N, se element facial scan of Se@N, se-CNFs shows that C is the matrix component of the sample, N is predominantly distributed on the carbon matrix, co and Se are predominantly distributed in the cubic particles, and the Se content of the fiber fraction is relatively low. This is mainly due to the fact that Co element is only present in the cubes derived from ZIF-67 at high temperature, whereas Co is formed in pyrolysis 0.85 The Se element content in the cube is also more after Se. The Se atoms have larger diameters and cannot enter the carbon matrix in a large amount, so the content of the carbon fibers is small.
Co 0.85 The EDS component analysis result and the element content ratio of Se@N, se-CNFs are shown in FIG. 8. As can be seen from FIG. 8, the atomic ratio of Co to Se in the material is about 88.78%, and Co 0.85 The theoretical atomic ratio of 0.85:1 in Se is very close. These analytical results are also mutually confirmed by XRD profile analysis.
Co 0.85 An XPS scan of Se@N, se-CNFs is shown in FIG. 9, where (a) full spectrum scan, (b) C1s, (C) N1 s, (d) Co 2p, and (e) Se 3d are shown in FIG. 9. As can be seen from FIG. 9, co 0.85 The Se@N, se-CNFs sample only contains Co, se, C, N, O atoms. Wherein the high resolution peak of C1s is formed by superposition of C-C, C = C, C-N, C-Se, indicating successful doping of N and Se atoms in the carbon matrix. The high resolution peak of N1 s can be subdivided into pyridine N, pyrrole N, graphite N, and N-oxide containing groups. These modified N atoms can increase the conductivity of the matrix and increase the number of reactive sites. Co 2p can be seen to contain Co after peak separation 2+ With Co 3 + Ions, which are located in the active center in the catalytic reaction. In the Se 3d high resolution peak, se-C/O bonds and Co 3p peaks therein are clearly visible. The appearance of Se-C/O bond indicates successful Se dopingIs hybridized into the carbon matrix, and corresponds to the C-N bond in C1 s. Se has a larger covalent bond length (120 pm), is much larger than C (73 pm) and N (71 pm), can introduce large defect deformations into the carbon lattice, and accelerates charge localization and chemisorption of oxygen. The modified Se atoms can also introduce pi conjugated systems into the carbon matrix, so that a high-efficiency electron transfer path is provided, and interface charge transfer impedance is reduced. Se atoms with higher polarizability can produce a fast response with reactants in the electrolyte than N, P and S.
Co 0.85 The X-ray absorption spectrum of Se@N, se-CNFs is shown in FIG. 10, and in FIG. 10, the K-edge of Co (a) and Se (b) are standardized to X-ray absorption near-edge structures; FT-EXAFS spectra of Co (c) and Se (d) corresponding to the K-edge near-edge absorption spectra; extended X-ray acquisition fine structures of Co (e) and Se (f). Co (Co) 0.85 The X-ray near-edge structure of the K edge of the Co element in Se@N, se-CNFs is shown as a in FIG. 10, and meanwhile, the data of 4 standard samples are compared: co (Co) 3 O 4 、Co 2 O3, coO and Co foils, co is clearly visible in the figure 0.85 The structure before the edge of the Se@N, se-CNFs sample is located in the Co foil (Co 0) and can be respectively assigned to Co-N/C and Se-N/C coordination. This also illustrates Co 0.85 There is this strong bond between Se and the carbon matrix. In addition, the least squares curves (e in fig. 10 and f in fig. 10) show the fitting results of the K-edge structures of Co and Se. Co and Se atoms can be analyzed on Co by fitting 0.85 Structural configuration in Se@N, se-CNFs samples. The fitting results of the Co element K-edge extended X-ray absorption fine structure are shown in Table 1, and the fitting results of the Se element K-edge extended X-ray absorption fine structure are shown in Table 2.
Table 1 Co fitting results of K-edge extended X-ray absorption fine Structure
Table 2 Se fitting results of K-edge extended X-ray absorption fine Structure
Note that: in tables 1 and 2, N is the coordination number, R is the atomic distance, σ 2 As a disorder factor, deltaE 0 The energy origin is displaced and R-factor is the root mean square fit difference (i.e., R factor) between the test value and the fit value.
As shown in tables 1 and 2, the calculated number of coordination number of Co atom (Co-Se bond) was 2.9, which is higher than that of Se atom (2.8, se-Co bond), confirming that sample Co 0.85 Cationic vacancies exist in Se@N, se-CNFs.
To sum up, co 0.85 Ordered Co vacancies, co, exist in Se@N, se-CNFs 0.85 An intuitive model of the Se crystal lattice can be seen in fig. 11, where the red spheres show the position of vacancies in the crystal lattice.
Co 0.85 The Raman spectrum of Se@N, se-CNFs is shown in FIG. 12. The Co-Se bonds are found in FIGS. 12 at 190.73, 476.42, 513.55 and 675cm -1 Characteristic peaks appear there. And at 1354.6cm -1 (D peak) and 1593.2cm -1 The presence of (G peak) then confirms the presence of graphitized carbon skeleton in the sample. The intensity ratio of D peak to G peak was ID/ig=1.89, indicating Co 0.85 The Se@N, se-CNFs sample has a large number of disordered carbon atoms and defects in the graphitized carbon structure. Wherein the graphitized structure can enhance the conductivity of the whole sample and accelerate the activity of Co-Se clusters in the reaction.
Co 0.85 N of Se@N, se-CNFs samples 2 The adsorption-desorption isothermal curve and BJH pore size distribution are shown in FIG. 13, wherein a in FIG. 13 is Co 0.85 N of Se@N, se-CNFs 2 Adsorption-desorption isothermal curve, b is BJH aperture distribution curve. The calculated specific surface area is 153.10m 2 g -1 The method comprises the steps of carrying out a first treatment on the surface of the It can also be seen that the pore diameters are distributed on different grades, including micropores and mesopores, and the pore diameter distribution of most of the pores is less than or equal to 4nm. Such a hierarchical structure can contact more electrolyte, thereby exposing more active sites, and can promote rapid oxygen reduction reaction.
For Co 0.85 The se@n, se-CNFs samples were subjected to thermogravimetric analysis, i.e. heated from room temperature to above 800 ℃ under an air atmosphere, to obtain their thermal decomposition profile and decomposition product XRD profile, as shown in fig. 14. In FIG. 14, a is Co 0.85 And (3) calcining the TGA curve at high temperature in an air atmosphere of Se@N, se-CNFs, wherein b is the XRD curve of a decomposition product. As can be seen from FIG. 14, co 0.85 Se@n, se-CNFs samples lost little below 300 ℃, which may be the result of only small molecule gases or water adsorbed on the sample surface; the weight of the sample is drastically reduced to below 30 percent at the temperature of 300-500 ℃, and the main carbide material of the sample can be burnt to generate CO 2 Escaping; while at higher temperatures up to 800 ℃, the sample eventually formed a black powder. In order to confirm the phase structure of the powder, X-ray scanning was performed to obtain a curve as shown in FIG. 14b, belonging to Co 3 O 4 (PDF # 43-1003). It can be seen that Co when heated to 800 DEG C 0.85 Se reacts in high temperature air to produce Co 3 O 4 The residual amount was 24.75wt.%. From this, co 0.85 Co in Se@N, se-CNFs samples 0.85 Se content was 13.26wt.%.
Example 2 Co 0.85 Electrochemical test of oxygen reduction catalytic activity of Se@N, se-CNFs composite material
(1)Co 0.85 Oxygen reduction reaction test of Se@N, se-CNFs
To further test Co 0.85 Se@N,Se-CNFs，N,Se-CNFs，Co 0.85 The electrochemical properties of Se/C and Pt/C were tested by the present invention by first testing the CV curves of the samples in an oxygen saturated 0.1M KOH solution with the same experimental parameters, and the results are shown in FIG. 15. In FIG. 15, a is Co 0.85 Se@N,Se-CNFs、Co 0.85 CV curve of Se/C, N, se-CNFs and Pt/C, b being Co 0.85 Se@N,Se-CNFs、Co 0.85 LSV curve of Se/C, N, se-CNFs and Pt/C1600 rpm, C is Co 0.85 LSV curve of Se@N, se-CNFs at 400-1600 rpm, d is according to Co 0.85 K-L equation fitting curve collected by LSV curve of Se@N, se-CNFs and transferred electron number n. The obvious oxygen reduction peak, especially Co, is seen in FIG. 15 a 0.85 Se@N, se-CNFs with peaks at 0.85 At V vs. RHE, the reduction peak to peak value of Pt/C is even exceeded. And Co 0.85 The CV curve of Se/C, N, se-CNFs shows lower peak voltage and much lower peak current of oxygen reduction peaks.
To go deep into Co 0.85 Se@N,The reaction process of Se-CNFs sample in oxygen reduction catalysis is that the sample is prepared into a membrane electrode, RDE test is developed under multiple rotating speeds, limiting currents corresponding to different potentials are calculated by a K-L equation, and the kinetic parameters of oxygen reduction reaction are analyzed by using a fitted curve of the limiting currents, as shown in b-d in fig. 15. As can be seen from FIG. 15 b, co at 1600rpm in an oxygen saturated 0.1M KOH solution 0.85 The LSV curve of Se@N, se-CNFs sample has an initial voltage of 0.93V, a half-wave potential of 0.87V, and performance slightly higher than Pt/C (initial potential of 0.92V, half-wave potential of 0.84V).
As can be seen from FIG. 15 c, co is used at 400-2500 rpm 0.85 The initial potential of Se@N, se-CNFs sample is basically constant at 0.93V, and the limiting diffusion current is continuously increased along with the increase of the rotating speed.
Using these curve data, a straight line can be fitted according to the K-L equation, and the path (4 e-path or 2e - A path). As can be seen from the analysis d in FIG. 15, at 0.3V, 0.4V, 0.5V and 0.6V, the calculated n values are 3.88, 3.91, 3.89 and 3.95, respectively, and the oxygen reduction reaction process is 4e - A path.
(2)Co 0.85 Durability test of Se@N, se-CNFs
The durability of the oxygen reduction catalyst is a key point in determining the life of the cathode of an aluminum air battery, which in turn affects the practical performance and cost of the battery. For this purpose, the invention adopts a chronoamperometry and a CV circulation method for Co 0.85 Se@N, se-CNFs samples were tested and the results obtained are shown in FIG. 16, where a is Co in FIG. 16 0.85 I-t curves for Se@N, se-CNFs and Pt/C; b is Co 0.85 LSV curves at 1600rpm for Se@N, se-CNFs were compared before and after 5000 CV cycles.
It can be seen from FIG. 16 a that Co is present in the oxygen reduction history for up to 10h 0.85 The current of the reaction under the catalysis of Se@N, se-CNFs sample is only slowly lost by 2.8% at the beginning of the reaction, which indicates that the reaction durability is very high; while the Pt/C catalyst is up to 47.6%, the current is greatly reduced at the beginning of the reaction, and the stability of the Pt/C catalyst is not good in continuous reduction although the subsequent process is stable. In addition, in the case of the optical fiber,the invention also relates to Co 0.85 Se@N, se-CNFs samples were scanned for up to 5000 CV cycles and LSV scans were performed before and after them to evaluate 5000 CV cycles, co 0.85 Attenuation of Se@N, se-CNFs reactivity. As can be seen from FIG. 16 b, the initial potential was hardly changed, only slightly shifted, and the limiting diffusion current density was almost the same, and the two curves were considered to be almost the same except for the influence of uncontrollable factors on the reaction in the test. To sum up, co 0.85 The oxygen reduction reactivity of Se@N, se-CNFs has long-term stability.
Although durability tests demonstrated Co 0.85 The stability of Se@N, se-CNFs is very good, but these data only indicate little change in the reduction current of the catalytic reaction of the sample. To investigate whether the chemical composition and the microscopic morphology are changed by the influence of the reaction, the present invention performed transmission electron microscope characterization on the samples after the durability test, as shown in fig. 17. In FIG. 17, a is Co 0.85 TEM image and diffraction pattern, bCo, of Se@N, se-CNFs after durability test 0.85 HRTEM images of se@n, se-CNFs after durability testing.
A TEM image of the sample after the durability test is shown in fig. 17 a, the visible material is still a fiber tandem cube structure. The diffraction pattern of the selected area is calibrated to be Co 0.85 Diffraction rings of (101), (102), (110) crystal planes of Se. While FIG. 17 b shows an image of the crystals in the sample cube, which is measured to have a interplanar spacing of about 0.27nm, which should be Co 0.85 The (101) crystal plane of Se.
To further characterize the composition and distribution of the fiber structure of the durability test samples, EDS facial scan analysis was further performed by the present invention, as shown in FIG. 18. In the visible fiber, co element and Se element and C element are mainly distributed on the fiber outside the cube, and N element is distributed almost in the whole fiber range. This also fully demonstrates that the material maintains Co in the carbon fiber supported cubic particles prior to the oxygen reduction durability test 0.85 The structure and the component distribution of Se are not changed. Visible Co 0.85 Se@N, se-CNFs have very good propertiesThe durability of the oxygen reduction reaction is maintained, and the composition is unchanged and the structure is stable after long-time testing.
(3)Co 0.85 Theoretical calculation and research on Se@N, se-CNFs activity
To go deep into Co 0.85 The invention utilizes density functional theory to react with Co at the oxygen reduction reactive site of Se@N, se-CNFs sample 0.85 The electrocatalytic reaction process of Se@N, se-CNFs samples is subjected to corresponding theoretical calculation and discussion analysis, as shown in FIG. 19. In theoretical computational analysis, the present invention primarily discusses a variety of oxygen reduction reactive sites that may be present in the sample, including: 1) N-containing active sites in pure N, se-CNFs nanofibers; 2) Co active sites in pure CoSe nanoparticles; 3) Co0 .85 N-containing active sites in Se@N, se-CNFs; 4) Co, co 0.85 Active sites containing Se in Se@N, se-CNFs; 5) Co, co 0.85 Co active sites in Se@N, se-CNFs. And further calculate and discuss the free energy variation courses of the oxygen reduction process of the electrocatalytic reaction active centers, and the analysis considers that the main processes are as follows: * +O2→ +OOH→ +O→OH, as shown in FIG. 19 a. Wherein eta ORR Is of overpotential (eta) ORR ＝1.23V-E ORR ) The smaller the number, the higher the oxygen reduction reactivity of the catalyst material. Numerical analysis showed that Co 0.85 Co in Se@N, se-CNFs samples 0.85 The Co atom of the outermost layer of Se is the site with the highest catalytic reactivity, and the reaction history model is shown in fig. 19 a. As shown in FIGS. 19 b-d, the present work also compares Co by numerical analysis 0.85 The oxygen reduction reaction activity of Se@N, se-CNFs, N, se-CNFs and CoSe (001) 3 different material surfaces shows that the eta of the CoSe material ORR After CoSe is combined with N, se-CNFs, the voltage is reduced from 0.45V to 0.36V, the root of which is probably the speed control step of oxygen reduction reaction, namely OH, in Co 0.85 Se@N, se-CNFs surface Co 0.85 When the Co atom of Se goes through the OH step, the free energy becomes lower than for simple CoSe (001).
In order to further study how the synergistic effect of CoSe particles and N, se-CNFs in oxygen reduction reaction improves the electrocatalytic reaction performance, the invention continuously calculates and analyzes Co 0.85 Se@N,Se-The state Density (DOS) and charge density differences of the CNFs and pure CoSe surfaces were examined for changes in the electronic structure of the material before and after the introduction of N, se-CNFs, as shown in FIG. 19 e. Numerical results demonstrate that after introducing N, se-CNFs to CoSe, the adsorption energy of OH by the CoSe surface is indeed significantly reduced. The decrease in adsorption energy can be attributed to Co 0.85 Co in Se@N, se-CNFs 0.85 The electron energy level of the 3d layer of Co atoms in Se is closer to the Fermi level. In conclusion, the combination of N, se-CNFs can obviously reduce the adsorption free energy of the sample in the oxygen reduction reaction and strengthen the oxygen reduction reaction activity, so that Co in 3 materials 0.85 Se@N, se-CNFs have the highest electrocatalytic activity.
(4)Co 0.85 Impedance study of Se@N, se-CNFs
For in-depth analysis of Co 0.85 The charge transfer capability of Se@N, se-CNFs sample in reaction, the work performs electrochemical impedance test and compares N, se-CNFs with Co 0.85 Se/C samples are shown in FIG. 20. Visible Co 0.85 The reaction interface charge transfer impedance of Se@N and Se-CNFs is minimum, so that the catalytic reaction is facilitated, and the oxygen reduction activity of the sample is improved. Due to Co 0.85 Se@N, se-CNFs sample was prepared from Co 0.85 And compared with ZIF-67 derived carbon particles, the Se-combined carbon nano-fiber has higher electron transport capacity, so that the charge transfer impedance is minimum. The solid-liquid interface electrochemical impedance of N, se-CNFs in the reaction is the largest. Co (Co) 0.85 The electrochemical impedance of Se/C is Co 0.85 Se@N, se-CNFs and N, se-CNFs.
Example 3 Co 0.85 Application of Se@N, se-CNFs in aluminum air battery
To detect Co 0.85 The actual discharge performance of the aluminum air fuel cell with the se@n, se-CNFs samples as the air cathode catalyst was tested for the redox performance of the catalyst using a single cell test die, and the results are shown in fig. 21. In FIG. 21, a is the assembled Co 0.85 The principle sketch of an aluminum air battery taking Se@N and Se-CNFs as a cathode catalyst; b is 50mA cm at room temperature -2 Co at discharge 0.85 Se@N,Se-CNFs、Co 0.85 Discharge capacity of Se/C or Pt/C assembled aluminum air cells; c is greater thanf Co fitting at different temperatures 0.85 Dynamic constant current discharge polarization curve of an aluminum air cell with se@n, se-CNFs as cathode catalyst: wherein c is 20-50 ℃, d is 0 ℃ or 10 ℃, e is-20 ℃ or-10 ℃, and f is-40 or-30 ℃; g-h is the Co assembled at different temperatures 0.85 Voltage/power density versus current density curves for aluminum air cells with se@n, se-CNFs as cathode catalysts: wherein g is-20-50 ℃, h is-40 ℃ or-50 ℃; i is a monolithic cathode of 50mA cm in an aluminum air battery -2 Voltage and power density change curves in the process of switching a plurality of aluminum anodes during discharge, wherein the inset shows Co 0.85 Performance comparison of se@n, se-CNFs with Pt/C catalysts.
As can be seen from FIG. 21, the temperature is 50mA cm -2 Constant current discharge until the anode aluminum sheet is completely depleted, and the resulting discharge curve and corresponding capacity are shown in fig. 21 b. By Co 0.85 When Se@N, se-CNFs samples are used as the air cathode catalyst, the constant-current discharge electrode polarization curve is stable, the voltage is stabilized at 1.2V, and the discharge capacity is 2867.13mAh g -1 Near the theoretical discharge capacity of Al (2980 mA h g -1 ) The method comprises the steps of carrying out a first treatment on the surface of the When Pt/C is used as the cathode catalyst of the aluminum air battery, the initial value of the constant-current discharge voltage is only slightly higher than 1.1V, the discharge process is continuously reduced, the fluctuation is large, and the battery capacity is only 2618.86mAh g -1 . And Co 0.85 When Se/C is used as a cathode catalyst, the voltage is initially 1.0V during constant-current discharge, and continuously decreases in the discharge process, and the battery capacity is only 2536.27mAh g -1 . It can be seen that Co is assembled 0.85 The discharge performance of Se@N, se-CNFs is obviously better than that of Pt/C and Co 0.85 Se/C. This again demonstrates the Co orientation 0.85 After Se is introduced into N, se-CNFs, the oxygen reduction performance of the material can be obviously improved, and Co is also illustrated 0.85 There is a synergy between Se and N, se-CNFs.
FIG. 21 c shows the assembly Co 0.85 Dynamic constant current discharge electrode polarization curve of an aluminum air cell with Se@N, se-CNFs as oxygen reduction catalyst. When the temperature is 30-50 ℃, the current density is only 1mA cm at the beginning of discharge -2 When the battery voltage is higher than 1.8V; when the current density of constant-current discharge increases in a gradient, the voltage of the battery is continuously increasedDecrease, but until the current density reaches 150mA cm -2 When the voltage is still above 0.3V. At 20 ℃, the discharge voltage at each current density is obviously reduced; at 140mA cm -2 The voltage is already close to 0.3V. The same trend of reduction also occurs in lower temperature (-40 ℃ to 10 ℃) tests. The effect of the temperature decrease on the battery was seen to be greater and greater up to-40℃at 1.3mA cm -2 The voltage is less than 0.2V at the current density of (c). In the long-time discharge process with different current densities, each echelon keeps a stable discharge platform, and Co is visible 0.85 Se@N, se-CNFs have excellent electrochemical reaction stability. Fig. 21g and 21h show the relationship between the power density, voltage and current density at different temperatures in the discharge process, and it is seen that the output power density decreases stepwise with decreasing temperature. The peak value of the power density at 50 ℃ reaches 80mW cm -2 While the peak value of the power density at-40 ℃ is only 0.7mW cm -2 。
The mechanical charging of the aluminum air battery can be realized by manually replacing the metal anode, so that higher requirements are put on the long-life stability of the cathode catalyst. For this reason, the present stack aluminum air cell was subjected to durability testing as shown by i in fig. 21. The same 1 cathode maintains stable voltage in continuous discharge of 4 pieces of different metal aluminum, and the specific capacity of the anode is small. The durability of the cathode catalytic reaction is very excellent, and a powerful guarantee is provided for continuous power supply of the aluminum-air battery.
FIG. 22 shows the composition of Co 0.85 The two monomer aluminum air fuel cells taking Se@N and Se-CNFs as cathode catalysts are connected in series to light LED small lamp beads, so that the catalyst has practical application significance.
To sum up, co 0.85 Such excellent performance of the aluminum air cell imparted by se@n, se-CNFs as cathode catalyst can be attributed to 3 aspects:
1) Co with ordered cation vacancies and 1D-3D porous-level carbon fiber supported structure 0.85 Se；
2) N, se the co-doped carbon matrix can provide more reaction sites for electrochemical reaction, and a powerful synergistic effect is formed;
3) The 1D-3D porous hierarchical structure has small impedance, and provides great convenience for transfer of reactants and electron conduction.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (7)

1. A N, se doped carbon nanofiber supported CoSe organic framework composite material, which comprises N, se doped carbon nanofiber and ZIF-67 pyrolysis-derived carbon supported on the surface of the N, se doped carbon nanofiber, wherein CoSe particles are supported on the surface and the inside of the ZIF-67 pyrolysis-derived carbon;
the molar ratio of Co to Se in the CoSe particles is 0.85:1;
the mass content of the CoSe particles in the N, se doped carbon nanofiber loaded CoSe organic framework composite material is 10-15%;
the mass content of the ZIF-67 pyrolysis derived carbon in the N, se doped carbon nanofiber loaded CoSe organic framework composite material is 15-35%;
the diameter of the N, se doped carbon nanofiber supported CoSe organic framework composite material is 0.5-1 mu m;
the diameter of the N, se doped carbon nanofiber is 100-200 nm;
the particle size of the CoSe particles is 5-10 nm.
2. The method for preparing the N, se doped carbon nanofiber supported CoSe organic framework composite material as set forth in claim 1, comprising the following steps:
mixing polyacrylonitrile and ZIF-67 organic framework materials with an organic solvent to obtain an electrostatic spinning precursor solution;
carrying out electrostatic spinning on the electrostatic spinning precursor solution, and drying to obtain a spinning fiber film;
heating and oxidizing the spinning fiber film to obtain a pre-oxidized fiber film;
and mixing the pre-oxidized fiber film with selenium powder, and performing pyrolysis to obtain the N, se doped carbon nanofiber-loaded CoSe organic framework composite material.
3. The preparation method according to claim 2, wherein the mass ratio of the polyacrylonitrile to the ZIF-67 organic framework material is 0.55:0.15-0.25.
4. A method of preparing according to claim 2 or 3, wherein the parameters of electrospinning comprise:
the positive high voltage is 12.5-13.5 kV;
the negative high voltage is 1.8-2 kV;
the distance between the needle head and the acquisition plate is 12-14 cm;
the propulsion rate is 0.9-1.1 mL h -1 。
5. The preparation method according to claim 2, wherein the temperature of the heating oxidation is 240-280 ℃ and the heat preservation time is 1-2 h.
6. The preparation method according to claim 2, wherein the mass ratio of the pre-oxidized fiber film to the selenium powder is 1:2-3;
the pyrolysis temperature is 800-850 ℃, and the heat preservation time is 2-3 h.
7. Application of the N, se doped carbon nanofiber supported CoSe organic framework composite material as an aluminum air battery cathode catalyst, wherein the N, se doped carbon nanofiber supported CoSe organic framework composite material is prepared by the preparation method as described in any one of claims 2-6.
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