A method for preparing iron-manganese spinel-loaded tar carbon nanofibers

Abstract

The invention discloses a method for preparing an iron-manganese spinel-loaded tar carbon nanofiber, which is characterized by comprising: dissolving a certain amount of PVP or PAN in DMF at a temperature of 50-70°C and stirring for 6-12 hours to obtain a solution A; uniformly dropping a toluene reagent into a certain amount of liquid tar at a dropping rate of 1 mL / min, a dropping amount of 1-3 mL, a temperature of 50-70°C, stirring for 6-12 hours to completely dissolve the toluene reagent, adding the toluene reagent into the solution A and stirring evenly to obtain a solution B containing tar; respectively taking a certain amount of iron salt, manganese salt and urea and adding them into the solution B, stirring at a constant temperature and uniform speed, injecting the obtained iron-manganese spinel-loaded tar carbon fiber precursor solution into a syringe, using a roller or a flat receiver for electrostatic spinning to obtain an iron-manganese spinel-loaded tar carbon fiber precursor material, and putting the toluene reagent into a tubular furnace for pre-oxidation and carbonization to obtain an iron-manganese spinel-loaded tar carbon nanofiber material.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber materials, and in particular relates to a method for preparing iron-manganese spinel-loaded tar carbon nanofibers. Background Art

[0002] With the development of portable and wearable electronic devices, electrochemical energy storage devices such as supercapacitors have received more and more attention. Electrode materials, as an important component of supercapacitors, are an important factor in determining the performance of supercapacitors. Carbon materials not only contain a variety of allotropes such as fullerenes, graphite, and carbon nanotubes, but also have different structures such as powder, fiber, and foam, so carbon materials are one of the ideal materials for making supercapacitor electrodes.

[0003] Tar is a byproduct generated by the combustion, distillation, pyrolysis, gasification and liquefaction of energy sources such as coal, biomass and oil shale. It has the characteristics of high viscosity, strong corrosiveness, easy condensation and clogging of pipelines. Its harmlessness, reduction and resource utilization are of great significance for industrial low-carbon emission reduction. In recent years, the preparation of carbon materials using tar as a raw material has received widespread attention. Its preparation methods mainly include: high-temperature activation, cross-linking catalysis, condensation polymerization, electrospinning, etc. Electrospinning technology is a process that uses high-voltage electrostatic fields to atomize and spray polymer solutions to prepare nanofiber materials. The carbon nanofibers prepared using this technology have the characteristics of high specific surface area, light weight, good conductivity, excellent stability and adjustable morphology. Therefore, using industrial byproduct tar as a raw material to prepare carbon materials that can be used for supercapacitor electrodes through electrospinning technology can not only achieve high-value conversion and utilization of tar, but also help reduce the production cost of energy storage devices such as supercapacitors.

[0004] CN201510095819.5 discloses a method for preparing a fiber material with antibacterial properties using electrostatic spinning technology using biomass tar and polyacrylonitrile (PAN) as raw materials. The method first obtains dry biomass tar powder, then dissolves it in N, N-dimethylamide (DMF) and stirs vigorously for 24 hours to prepare a tar suspension, which is then mixed with a DMF suspension containing PAN, and a spinning solution is obtained after ultrasonic treatment for 30 minutes. Finally, a fiber material with good antibacterial properties is prepared by electrostatic spinning technology. The tar used in the invention is a solid particle, which requires long-term and vigorous stirring to be evenly dispersed in the spinning solution, and the preparation time is lengthy. In addition, the method only describes the preparation method of the fiber material containing tar, and does not involve the subsequent preparation process of the carbon fiber material with good physical and chemical properties, especially without mentioning its application in electrochemical energy storage devices such as supercapacitors.

[0005] CN202210332656.8 discloses a method for preparing energy storage electrode materials using biomass pyrolysis oil. The biochar obtained after hydrothermal carbonization of biomass pyrolysis tar is mixed evenly with KOH powder, then placed in a tubular furnace for activation, and then repeatedly rinsed with dilute hydrochloric acid and deionized water until neutral, and then the black thick slurry mixed with activated carbon material, polyvinylidene fluoride and acetylene is dripped on a highly conductive graphite paper, placed in an oven for baking to obtain a working electrode. In this invention, it is necessary to undergo hydrothermal carbonization, surface activation modification, multiple rinses and other processes to obtain carbon materials with good performance. The technology is relatively cumbersome, and the carbon material obtained in this method needs to add a binder such as polyvinylidene fluoride in the process of making an electrode, which increases economic cost and time cost, and easily causes a decrease in the conductivity of the electrode material.

[0006] CN202110286961.3 discloses a method for preparing a cobalt and nickel doped / graphene / fabric supercapacitor electrode material. First, the obtained cotton cloth / graphene oxide composite material is impregnated in a precursor solution containing nickel and cobalt, and then a strong reducing agent is added for reduction reaction. After the reaction is completed, it is dried to obtain a supercapacitor electrode material doped with cobalt and nickel. In this invention, metal components are loaded on a fabric substrate by impregnation to prepare a metal-loaded electrode material. Although the metal loading method of this method is relatively simple, problems such as weak cross-linking between metal particles and fiber materials, loss of metal component load, and easy detachment of metal particles are prone to occur during the material preparation process, affecting the material performance.

[0007] Based on the above-mentioned comparative literature, it can be seen that the existing technology can prepare industrial byproduct tar into fiber materials through electrospinning technology for use as electrode materials for electrochemical energy storage devices such as supercapacitors. However, the existing electrospinning fiber material preparation method is complicated and the procedures are cumbersome. The electrochemical performance of the carbon fiber material is poor and cannot meet the actual industrial production needs. Therefore, it is urgent to solve the defects of the existing electrospinning fiber material preparation method. So far, there has been no scientific and reasonable preparation method, easy to operate and control, low preparation cost, good quality, and iron-manganese spinel-loaded tar carbon nanofibers that are particularly suitable for use as electrode materials for electrochemical energy storage devices such as supercapacitors. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a preparation method that is scientific and reasonable, easy to operate and control, has low preparation cost and good quality, and is particularly suitable for iron-manganese spinel-loaded tar carbon nanofibers as electrode materials for electrochemical energy storage devices such as supercapacitors.

[0009] The technical solution adopted to achieve the above purpose is a method for preparing iron-manganese spinel-supported tar-carbon nanofibers, characterized in that the method comprises the following steps:

[0010] A certain amount of polyvinyl pyrrolidone (PVP) or polyacrylonitrile (PAN) is dissolved in 10 mL of N,N-dimethylformamide (DMF) at a temperature of 50 to 70°C and a stirring time of 6 to 12 hours. After sufficient stirring, a solution A is obtained;

[0011] A certain amount of liquid tar is added to solution A, and toluene is uniformly added dropwise during constant temperature stirring, the rate of adding toluene reagent is 1 mL / min, the amount of adding is 1-3 mL, and the temperature is 50-70°C, and the stirring is performed for 6-12 hours to obtain a solution B containing tar;

[0012] Weigh a certain amount of iron salt, manganese salt and urea respectively, add them to solution B, and stir at a constant temperature and uniform speed to obtain an iron-manganese spinel-supported tar carbon fiber precursor solution;

[0013] Inject a certain amount of the iron-manganese spinel-loaded tar carbon fiber precursor solution into a syringe, and use a roller or a flat receiver to start electrospinning to obtain an iron-manganese spinel-loaded tar carbon fiber precursor material;

[0014] The iron-manganese spinel-loaded tar carbon fiber precursor material is placed in a tubular furnace for pre-oxidation and carbonization to obtain an iron-manganese spinel-loaded tar carbon nanofiber material.

[0015] Preferably, the solution A is a 10% PVP solution in DMF.

[0016] Preferably, the liquid tar is at least one of biomass tar, coal tar and oil shale tar.

[0017] Preferably, the mass of the liquid tar is 20% to 100% of the mass of the PVP.

[0018] Preferably, the iron salt and manganese salt are at least one of soluble acetate, nitrate and chlorate.

[0019] Preferably, the molar ratio of the iron salt, manganese salt and urea is Fe:Mn:CO(NH2)2=2:1:25.

[0020] Preferably, the electrospinning process parameters are as follows: needle inner diameter of 0.33-0.5 mm, feed rate of 0.0005-0.0008 mm / s, voltage of 15-20 kV, spinning distance of 17-20 cm, spinning temperature of 20-36°C, relative humidity of 40%-70%, and drying temperature of the obtained spinning membrane of 70°C.

[0021] Preferably, the pre-oxidation temperature of the iron-manganese spinel-loaded tar carbon fiber precursor material is 200-400° C., the air flow rate is 50-200 mL / min, the heating rate is 1-3° C. / min, and the constant temperature time is 1-3 h.

[0022] Preferably, the carbonization temperature of the iron-manganese spinel-supported tar carbon fiber precursor material is 850-1000° C., the nitrogen flow rate is 50-150 mL / min, the heating rate is 3-10° C. / min, and the constant temperature time is 1-5 h.

[0023] The beneficial effects of the present invention are embodied in:

[0024] 1) The present invention overcomes the shortcomings of the traditional tar-containing electrospinning precursor solution, which uses solid tar powder as a raw material and requires physical operations such as vigorous stirring and ultrasonic dispersion to ensure uniform dispersion of the tar. It creatively proposes to directly use liquid tar as a raw material and quickly dissolve the tar by utilizing the compatibility principle of toluene and tar. The obtained tar-containing precursor solution is a homogeneous and unified whole without the existence of solid-liquid two-phase situation;

[0025] 2) The present invention abandons the traditional method of first preparing carbon fiber materials and then loading metal components by impregnation to prepare metal-loaded carbon fiber materials. It proposes to add metal components to the spinning solution, use high-voltage electrostatic field to evenly disperse the metal components inside and outside the tar-containing fiber, and load and form them once after pre-oxidation and carbonization process, which effectively avoids the problem of metal component loading loss, weak cross-linking between metal particles and fiber materials, and easy falling off;

[0026] 3) The preparation method of the present invention is scientific and reasonable, easy to operate and control, has low preparation cost, good quality, and is easy to promote and implement;

[0027] 4) The present invention utilizes spinel manganese ferrite (MnFe2O4) to improve the electrochemical properties of carbon fiber materials, significantly improving the electron and ion transmission capabilities and capacitor storage capabilities of the electrode material for electrochemical energy storage devices, and is an electrode material for electrochemical energy storage devices with good application prospects.

[0028] 5) The application results of the iron-manganese spinel-loaded tar carbon nanofiber material prepared by the present invention as an electrode material in a supercapacitor show that it has the characteristics of high conductivity, large specific capacitance, good cycle stability, high power density and energy density, etc., which provides a new way to prepare green, low-cost, high-performance electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The attached figure shows the iron-manganese spinel-supported tar-carbon nanofibers obtained in Example 1. Figure 1 This is a SEM image of the iron-manganese spinel-supported tar carbon fiber precursor material obtained in step 4) of the embodiment. Figure 2 This is the SEM image of the iron-manganese spinel-supported tar-carbon nanofibers obtained in step 6). DETAILED DESCRIPTION

[0030] The present invention is described in detail below by way of examples.

[0031] The present invention provides a method for preparing iron-manganese spinel-supported tar-carbon nanofibers, comprising the following steps:

[0032] A certain amount of polyvinyl pyrrolidone (PVP) or polyacrylonitrile (PAN) is dissolved in 10 mL of N,N-dimethylformamide (DMF) at a temperature of 50 to 70°C and a stirring time of 6 to 12 hours. After sufficient stirring, a solution A is obtained;

[0033] A certain amount of liquid tar is added to solution A, and toluene is uniformly added dropwise during constant temperature stirring, the rate of adding toluene reagent is 1 mL / min, the amount of adding is 1-3 mL, and the temperature is 50-70°C, and the stirring is performed for 6-12 hours to obtain a solution B containing tar;

[0034] Weigh a certain amount of iron salt, manganese salt and urea respectively, add them to solution B, and stir at a constant temperature and uniform speed to obtain an iron-manganese spinel-supported tar carbon fiber precursor solution;

[0035] Inject a certain amount of the iron-manganese spinel-loaded tar carbon fiber precursor solution into a syringe, and use a roller or a flat receiver to start electrospinning to obtain an iron-manganese spinel-loaded tar carbon fiber precursor material;

[0036] The iron-manganese spinel-loaded tar carbon fiber precursor material is placed in a tubular furnace for pre-oxidation and carbonization to obtain an iron-manganese spinel-loaded tar carbon nanofiber material.

[0037] The solution A is a 10% PVP DMF solution.

[0038] The liquid tar is at least one of biomass tar, coal tar and oil shale tar.

[0039] The mass of the liquid tar is 20% to 100% of the mass of the PVP.

[0040] The iron salt and manganese salt are both soluble in at least one of acetate, nitrate and chlorate.

[0041] The molar ratio of the iron salt, manganese salt and urea is Fe:Mn:CO(NH2)2=2:1:25.

[0042] The electrospinning process parameters are as follows: the inner diameter of the needle is 0.33-0.5 mm, the feed rate is 0.0005-0.0008 mm / s, the voltage is 15-20 kV, the spinning distance is 17-20 cm, the spinning temperature is 20-36° C., the relative humidity is 40%-70%, and the drying temperature of the obtained spinning membrane is 70° C.

[0043] The pre-oxidation temperature of the iron-manganese spinel-loaded tar carbon fiber precursor material is 200-400° C., the air flow rate is 50-200 mL / min, the heating rate is 1-3° C. / min, and the constant temperature time is 1-3 hours.

[0044] The carbonization temperature of the iron-manganese spinel-loaded tar carbon fiber precursor material is 850-1000° C., the nitrogen flow rate is 50-150 mL / min, the heating rate is 3-10° C. / min, and the constant temperature time is 1-5 h.

[0045] Embodiment 1:

[0046] The method for preparing iron-manganese spinel-supported tar-carbon nanofibers provided in Example 1 includes the following steps:

[0047] 1) PVP was dissolved in 10 mL of DMF to obtain a DMF solution of PVP with a mass concentration of 10%, and the solution was obtained by constant temperature stirring at 60° C. for 8 h;

[0048] 2) Weigh 1g of liquid biomass tar and add it to solution A. Stir at a constant temperature of 60°C. During the stirring process, add toluene at a uniform rate of 1mL / min and a drop amount of 1mL. Dissolve the tar quickly and fully. Continue stirring for 8h to obtain a precursor solution B containing tar.

[0049] 3) Weigh 0.2 mmol of ferric nitrate, 0.1 mmol of manganese nitrate and 2.5 mmol of urea respectively and add them to solution B, and stir for 30 min to obtain a precursor solution;

[0050] 4) Inject a certain amount of iron manganese spinel-loaded tar carbon fiber precursor solution into a 10 mL syringe, use a needle with an inner diameter of 0.413 mm, set the propulsion speed of the injection pump to 0.00056 mm / s, use a roller or flat receiver, the voltage is 20 kV, the spinning distance is 17 cm, the spinning temperature is 20 ° C, the relative humidity is 60%, start electrospinning, and dry at 70 ° C to obtain an iron manganese spinel-loaded tar carbon fiber precursor material;

[0051] 5) Pre-oxidizing the iron-manganese spinel-loaded tar carbon fiber precursor material obtained in step 4), heating to 300° C. at a heating rate of 1° C. / min, with an air flow rate of 50 mL / min and a constant temperature time of 1 h.

[0052] 6) The carbonization process is to heat the temperature to 1000° C. at a heating rate of 3° C. / min, with a nitrogen flow rate of 50 mL / min and a constant temperature time of 2 h to obtain iron-manganese spinel-loaded tar carbon nanofibers.

[0053] The specific surface area of ​​the obtained fiber was 425m2 / g, and the average pore size is 2.57nm.

[0054] Embodiment 2:

[0055] The method for preparing iron-manganese spinel-supported tar-carbon nanofibers provided in Example 2 includes the following steps:

[0056] 1) dissolving polyacrylonitrile (PAN) in 10 mL of DMF to obtain a DMF solution of PAN with a mass concentration of 10%, and stirring at a constant temperature of 60° C. for 12 h to obtain a solution A;

[0057] 2) Weigh 0.5g of liquid tar and add it to solution A. Stir at a constant temperature of 60°C. During the stirring process, add toluene at a uniform rate of 1mL / min and a drop amount of 2mL. Dissolve the tar quickly and fully. Continue stirring for 6h to obtain a precursor solution B containing tar.

[0058] 3) Weigh 0.4 mmol of ferric nitrate, 0.2 mmol of manganese nitrate and 5 mmol of urea respectively and add them to solution B, and stir for 30 min to obtain a precursor solution;

[0059] 4) Inject a certain amount of iron manganese spinel-loaded tar carbon fiber precursor solution into a 5 mL syringe, use a needle with an inner diameter of 0.413 mm, set the propulsion speed of the injection pump to 0.0003 mm / s, use a roller or flat receiver, the voltage is 18 kV, the spinning distance is 17 cm, the spinning temperature is 20 ° C, the relative humidity is 60%, start electrospinning, and dry at 70 ° C to obtain an iron manganese spinel-loaded tar carbon fiber precursor material;

[0060] 5) Pre-oxidizing the iron-manganese spinel-loaded tar carbon fiber precursor material obtained in step 4), heating to 300° C. at a heating rate of 1° C. / min, with an air flow rate of 50 mL / min and a constant temperature time of 3 h.

[0061] 6) The carbonization process is to heat the temperature to 1000° C. at a heating rate of 3° C. / min, a nitrogen flow rate of 100 mL / min, and a constant temperature time of 2 h to obtain carbon nanofibers loaded with MnFe2O4 spinel particles.

[0062] The specific surface area of ​​the obtained fiber was 416 m 2 / g, and the average pore size is 3.24nm.

[0063] Embodiment 3:

[0064] The method for preparing iron-manganese spinel-supported tar-carbon nanofibers provided in Example 3 includes the following steps:

[0065] 1) PVP was dissolved in 10 mL of DMF to obtain a DMF solution of PVP with a mass concentration of 10%, and the solution was obtained by constant temperature stirring at 60° C. for 8 h;

[0066] 2) Weigh 1g of liquid tar and add it to solution A. Stir at a constant temperature of 60°C. During the stirring process, uniformly add toluene at a rate of 1mL / min and a drop amount of 1mL. Dissolve the tar quickly and fully. Continue stirring for 8h to obtain a precursor solution B containing tar.

[0067] 3) Weigh 0.2 mmol of ferric acetate, 0.1 mmol of manganese acetate and 2.5 mmol of urea respectively and add them to solution B, and stir for 30 min to obtain a precursor solution;

[0068] 4) Inject a certain amount of iron manganese spinel-loaded tar carbon fiber precursor solution into a 10 mL syringe, use a needle with an inner diameter of 0.413 mm, set the propulsion speed of the injection pump to 0.00056 mm / s, use a roller or flat receiver, the voltage is 20 kV, the spinning distance is 17 cm, the spinning temperature is 20 ° C, the relative humidity is 60%, start electrospinning, and dry at 70 ° C to obtain an iron manganese spinel-loaded tar carbon fiber precursor material;

[0069] 5) Pre-oxidizing the iron-manganese spinel-loaded tar carbon fiber precursor material obtained in step 4), heating to 300° C. at a heating rate of 1° C. / min, with an air flow rate of 100 mL / min and a constant temperature time of 3 h.

[0070] 6) The carbonization process is to heat the material to 950°C at a heating rate of 3°C / min, with a nitrogen flow rate of 100 mL / min and a constant temperature time of 2 h to obtain carbon nanofibers loaded with MnFe2O4 spinel particles.

[0071] The specific surface area of ​​the obtained fiber was 345m 2 / g, and the average pore size is 2.75nm.

[0072] Embodiment 4:

[0073] Embodiment 4 provides a method for preparing iron-manganese spinel-supported tar-carbon nanofibers, which includes the following steps:

[0074] 1) 0.5 g PVP and 0.5 g PAN were dissolved in 10 mL DMF and stirred at 60 °C for 8 h to obtain solution A;

[0075] 2) Weigh 1 g of liquid tar and add it to solution A, and stir at a constant temperature of 60° C. for 8 h to obtain a precursor solution B containing tar;

[0076] 3) Weigh 0.2 mmol of ferric nitrate, 0.1 mmol of manganese nitrate and 2.5 mmol of urea respectively and add them to solution B, and stir for 30 min to obtain a precursor solution;

[0077] 4) Inject a certain amount of iron manganese spinel-loaded tar carbon fiber precursor solution into a 10 mL syringe, use a needle with an inner diameter of 0.413 mm, set the propulsion speed of the injection pump to 0.00056 mm / s, use a roller or flat receiver, the voltage is 20 kV, the spinning distance is 17 cm, the spinning temperature is 20 ° C, the relative humidity is 60%, start electrospinning, and dry at 70 ° C to obtain an iron manganese spinel-loaded tar carbon fiber precursor material;

[0078] 5) Pre-oxidizing the iron-manganese spinel-loaded tar carbon fiber precursor material obtained in step 4), heating to 300° C. at a heating rate of 1° C. / min, with an air flow rate of 50 mL / min and a constant temperature time of 1.5 h.

[0079] 6) The carbonization process is to heat the material to 800°C at a heating rate of 5°C / min, with a nitrogen flow rate of 50 mL / min and a constant temperature time of 2 h to obtain carbon nanofibers loaded with MnFe2O4 spinel particles.

[0080] The specific surface area of ​​the obtained fiber was 318m 2 / g, and the average pore size is 5.26nm.

[0081] Comparative Example 1:

[0082] 1) Dissolve 1g PVP or 1g PAN and 1g tar in 10mL N,N-dimethylformamide and stir at 40-70℃ for 8-12h;

[0083] 2) Inject the obtained precursor spinning solution into a 10mL syringe, and use a roller receiver or a flat plate receiver. Set the distance between the needle and the collector to 17-20cm. A high voltage of 15-20kV is used to start electrospinning, and the feed rate of the precursor solution is 0.0003-0.0006mm / s. The obtained nanofiber membrane is dried at 50-70℃;

[0084] 3) Dissolve 0.5-2 mmol of soluble iron salt, 0.5-1 mmol of soluble manganese salt and 1-3 mmol of urea in deionized water (or ethanol, methanol, ethylene glycol), and continue stirring for 15-40 minutes;

[0085] 4) Metal loading by immersion method: The nanofiber membrane obtained in 2) is immersed in the solution obtained in 3) and kept for more than 12 hours.

[0086] 5) In an air atmosphere (flow rate of 50-200 mL / min), the obtained fiber membrane is heated to 300-500°C at a heating rate of 1-3°C / min in a tube furnace and kept at the constant temperature for 1-3 hours. Then, in a nitrogen atmosphere (flow rate of 50-200 mL / min), the temperature is raised to 850-1000°C at a heating rate of 3-5°C / min and kept at the constant temperature for 1-3 hours.

[0087] Comparative Example 2:

[0088] 1) Dissolve 1g PVP and 1g tar in 10mL N,N-dimethylformamide and stir at 40-70℃ for 8-12h.

[0089] 2) Inject the obtained precursor spinning solution into a 10mL syringe, and use a roller receiver or a flat plate receiver. Set the distance between the needle and the collector to 17-20cm. A high voltage of 15-20kV is used to start electrospinning, and the feed rate of the precursor solution is 0.0003-0.0006mm / s. The obtained nanofiber membrane is dried at 50-70℃;

[0090] 3) Hydrothermal metal loading: Add 0.5-1 mmol soluble iron salt and 0.5-1 mmol soluble manganese salt to ethylene glycol, stir for 15-40 min, use a reactor with a polytetrafluoroethylene liner, immerse the carbon nanofibers obtained in 2) in the bimetallic solution, and react at 120-180°C for 10-18 h.

[0091] 4) In an air atmosphere, the obtained fiber membrane is heated to 300-500°C in a tube furnace at a heating rate of 1-3°C / min and kept at the constant temperature for 1-3 hours. Then, in a nitrogen atmosphere, the temperature is raised to 850-1000°C at a heating rate of 3-5°C / min and kept at the constant temperature for 1-3 hours.

[0092] Comparative Example 3:

[0093] 1) Dissolve 0.5-1 g PVP or PAN and 0.1-3 g tar in 10 mL DMF and stir at 40-70 °C for 8-12 h;

[0094] 2) Inject the obtained precursor spinning solution into a 10mL syringe, and use a roller receiver or a flat plate receiver. Set the distance between the needle and the collector to 17-20cm. A high voltage of 15-20kV is used to start electrospinning, and the feed rate of the precursor solution is 0.0003-0.0006mm / s. The obtained nanofiber membrane is dried at 50-70℃;

[0095] 3) In an air atmosphere, the obtained fiber membrane is heated to 300-500°C in a tube furnace at a heating rate of 1-3°C / min and kept at the constant temperature for 1-3 hours. Then, in a nitrogen atmosphere, the temperature is raised to 850-1000°C at a heating rate of 3-5°C / min and kept at the constant temperature for 1-3 hours.

[0096] 4) Immersion method: add 0.5-1 mmol of soluble iron salt and 0.5-1 mmol of soluble manganese salt to 30-40 mL of methanol solution, continue stirring for 15-40 min, and immerse the carbon nanofiber membrane obtained in 3) in the above solution for more than 10 h;

[0097] Comparative Example 4:

[0098] 1) Dissolve 0.5-1g PVP (or PAN) and 0.1-3g tar in 10mL DMF and stir at 40-70°C for 8-12h;

[0099] 2) Add 0.5-2 mmol of soluble magnesium salt and 0.5-2 mmol of soluble zinc salt to the solution obtained in step 1), and continue stirring for 30 minutes.

[0100] 3) Inject the obtained precursor spinning solution into a 10mL syringe, and use a roller receiver or a flat plate receiver. Set the distance between the needle and the collector to 17-20cm. A high voltage of 15-20kV is used to start electrospinning, and the feed rate of the precursor solution is 0.0003-0.0006mm / s. The obtained nanofiber membrane is dried at 50-70℃;

[0101] 4) In an air atmosphere, the obtained fiber membrane is heated to 300-500°C in a tube furnace at a heating rate of 1-3°C / min and kept at the constant temperature for 1-3 hours. Then, in a nitrogen atmosphere, the temperature is raised to 850-1000°C at a heating rate of 3-5°C / min and kept at the constant temperature for 1-3 hours.

[0102] Application Example 1:

[0103] The electrochemical properties of the carbon nanofiber membrane in the embodiment were tested using a three-electrode system. The prepared carbon nanofiber membrane was cut into a square film with a side length of about 1 cm and a thickness of about 100 μm, and was clamped in a platinum sheet working electrode clamp as a working electrode. The three-electrode system consists of a reference electrode (Ag / AgCl), a counter electrode (Pt wire) and a working electrode, and a 2M KOH solution is used as an electrolyte.

[0104] Table 1

[0105]

[0106] As can be seen from Table 1, the iron-manganese spinel-loaded tar carbon nanofiber prepared in the embodiment of the present invention has a higher specific capacity as a supercapacitor carbon nanofiber electrode material than the comparative example, and is also much higher than the common electrode material prepared based on tar, indicating that the iron-manganese spinel-loaded tar carbon nanofiber matrix prepared by electrospinning soluble salt in the present invention provides spinel growth skeleton and spinel particle attachment sites, so that when it is used as an electrode material, it can generate pseudocapacitance at the electrode material interface through the electrochemical reaction of metal ions, and the formed ion channel is more stable and conducive to the transmission of charge and electrons; and the carbon material has good cycle stability during the charge and discharge process; the holes formed on the carbon nanofiber by the decomposition of PVP and tar during the carbonization process are conducive to increasing the surface area of ​​the carbon nanofiber, thereby increasing the contact area with the electrolyte. The iron-manganese spinel-loaded tar carbon nanofiber prepared by the present invention has a large specific capacitance as a supercapacitor carbon nanofiber electrode material, high stability and excellent electrochemical properties, so it is of great significance to the research and preparation of electrode materials.

[0107] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing iron-manganese spinel-supported tar-carbon nanofibers, characterized in that: The method comprises the following steps: A certain amount of polyvinylpyrrolidone (PVP) was dissolved in 10 mL of N,N-dimethylformamide (DMF) at a temperature of 50 to 70°C and a stirring time of 6 to 12 hours. After sufficient stirring, a solution A was obtained; A certain amount of liquid tar is added to solution A, and toluene is uniformly added dropwise during constant temperature stirring, the rate of adding toluene reagent is 1 mL / min, the amount of adding is 1-3 mL, and the temperature is 50-70°C, and the stirring is performed for 6-12 hours to obtain a solution B containing tar; Weigh a certain amount of iron salt, manganese salt and urea respectively, add them to solution B, and stir at a constant temperature and uniform speed to obtain an iron-manganese spinel-supported tar carbon fiber precursor solution; Inject a certain amount of the iron-manganese spinel-loaded tar carbon fiber precursor solution into a syringe, and use a roller or a flat receiver to start electrospinning to obtain an iron-manganese spinel-loaded tar carbon fiber precursor material; Putting the iron-manganese spinel-loaded tar carbon fiber precursor material into a tubular furnace for pre-oxidation and carbonization to obtain an iron-manganese spinel-loaded tar carbon nanofiber material; The molar ratio of the iron salt, manganese salt and urea is Fe:Mn:CO(NH2)2=2:1:25; The pre-oxidation temperature of the iron-manganese spinel-loaded tar carbon fiber precursor material is 200-400° C., the air flow rate is 50-200 mL / min, the heating rate is 1-3° C. / min, and the constant temperature time is 1-3 h; The carbonization temperature of the iron-manganese spinel-loaded tar carbon fiber precursor material is 1000° C., the nitrogen flow rate is 50 mL / min, the heating rate is 3° C. / min, and the constant temperature time is 2 h.

2. The method for preparing iron-manganese spinel-supported tar-carbon nanofibers according to claim 1, characterized in that: The solution A is a 10% PVP DMF solution.

3. The method for preparing iron-manganese spinel-supported tar-carbon nanofibers according to claim 1, characterized in that: The liquid tar is at least one of biomass tar, coal tar and oil shale tar.

4. The method for preparing iron-manganese spinel-supported tar-carbon nanofibers according to claim 1, characterized in that: The mass of the liquid tar is 20% to 100% of the mass of the PVP.

5. The method for preparing iron-manganese spinel-supported tar-carbon nanofibers according to claim 1, characterized in that: The iron salt and manganese salt are both soluble in at least one of acetate, nitrate and chlorate.

6. The method for preparing iron-manganese spinel-supported tar-carbon nanofibers according to claim 1, characterized in that: The electrospinning process parameters are as follows: the inner diameter of the needle is 0.33-0.5 mm, the feed rate is 0.0005-0.0008 mm / s, the voltage is 15-20 kV, the spinning distance is 17-20 cm, the spinning temperature is 20-36° C., the relative humidity is 40%-70%, and the drying temperature of the obtained spinning membrane is 70° C.

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