In-situ growth MOG carbon nanofiber catalyst as well as preparation method and application thereof

Abstract

The invention discloses an in-situ growth MOG carbon nanofiber catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: stirring and mixing a nanofiber polymer and a solvent to form a uniform spinning solution; performing electrostatic spinning to obtain a nanofiber membrane; the preparation method comprises the following steps: adding metal salt, a nitrogen-containing compound and resorcinol into water, and slowly dropwise adding formaldehyde into a mixed solution to obtain an in-situ growth solution of metal organic gel MOG; putting the nanofiber membrane into an in-situ growth solution, adjusting the pH value, and heating for in-situ growth to obtain an MOG nanofiber membrane material; the MOG nanofiber membrane material and urea are subjected to high-temperature pyrolysis nitrogen doping in an inert atmosphere, and the MOG-CNF catalyst is obtained. The catalyst can effectively reduce the overpotential of ORR and OER reactions, improves the catalytic stability, and shows stable and excellent bifunctional electro-catalytic performance. Through a nano structure and a synergistic catalytic effect, the material has a wide application prospect in the field of fuel cell energy storage and conversion.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of non-noble metal catalyst materials for fuel cells, and provides a preparation method of in-situ grown metal organic gel carbon nanofiber catalyst and its application in the field of fuel cells. BACKGROUND

[0002] Zinc-air battery is a kind of fuel cell with metal zinc as fuel and oxygen in air as oxidant. It is usually composed of alkaline electrolyte, negative zinc electrode, diaphragm and positive air electrode. Because of the low price of zinc, it has high theoretical energy density, is environmentally friendly and non-polluting, and at the same time, the inherent low reaction temperature and strong stability of zinc in aqueous electrolyte enable it to be used continuously in the field of emerging energy storage. However, during the charging and discharging process of zinc-air battery, the slow kinetics of oxygen reduction (ORR) and oxygen evolution (OER) reactions at the air electrode side leads to high electrode polarization and poor electrode reversibility of zinc-air battery. The free energy and active site requirements of ORR and OER are different, which makes it difficult for ordinary catalysts to simultaneously exhibit excellent electrochemical performance of both. In addition, the corrosion of electrolyte and high potential during battery operation seriously affects the stability and service life of the catalyst. Therefore, designing efficient and structurally stable dual-function oxygen catalyst is particularly important for accelerating the reaction kinetics and reducing the overpotential of charging and discharging, and improving the service life of the catalyst.

[0003] The nanofiber membrane material prepared by electrospinning has the characteristics of large specific surface area, developed pore structure and uniform active site distribution, which is beneficial to the rapid transmission and diffusion of ions and molecules, making it an ideal catalyst support material. Among them, electrospun PAN nanofibers have uniform diameter and are insoluble in water. One-dimensional PAN fibers can be interwoven to form a three-dimensional network structure, and their unique flexibility and water-resistant appearance stability provide important protection for the structure and activity stability of the catalyst for long-term use. Metal organic gel (MOG) is a kind of material formed by self-assembly of metal ions and organic ligands under the assistance of coordination and supramolecular forces. Because MOG has the characteristics of low density, high specific surface area, open active site, high yield and hierarchical porous structure, it has attracted much attention in the field of electrocatalysis. Metal organic gel is amorphous and flexible in structure, which makes it adaptable and able to adjust its pore size and porosity by changing the synthesis conditions. It can be compounded according to different needs to exhibit excellent electrochemical performance.

[0004] Patent No. 2025100536055, the title of the invention is a kind of composite carbon nanofiber catalyst and its preparation method and use, MOG material is mixed into the spinning solution, and a composite catalyst is prepared by integrated spinning. Although a certain catalytic effect is obtained, since most of the active sites in the MOG carbon material are covered by the spinning material, they cannot be fully exposed, making it difficult for the reactants to access, thereby affecting the full play of the catalytic performance. SUMMARY

[0005] To solve the above-mentioned defects in the prior art, the purpose of the present application is to provide a preparation method of in-situ grown metal organic gel carbon nanofiber catalyst, which utilizes the porous network structure in the electrospun nanofiber membrane to provide abundant anchoring sites for MOG in-situ growth, making its active sites in-situ anchored and uniformly distributed, and showing stable and excellent bifunctional electrocatalytic performance. The catalyst can effectively reduce the overpotential of ORR and OER reactions under alkaline conditions, improve the catalytic stability, and show excellent bifunctional catalytic performance.

[0006] The present application is realized by the following technical solutions.

[0007] In one aspect of the present application, a preparation method of in-situ grown MOG carbon nanofiber catalyst is provided, comprising the following steps:

[0008] a. Nanofiber polymer and solvent are stirred and mixed into a uniform spinning solution according to a mass ratio of 1:(3-20);

[0009] b. According to the electrospinning method, the spinning solution is transferred to a syringe, the injection rate of the syringe is controlled, and the nanofiber membrane is collected after vacuum drying by electrospinning;

[0010] c. According to the molar ratio of metal salt, nitrogen-containing compound and m-dihydroxybenzene of 1:(1-10):(10-100), the metal salt, nitrogen-containing compound and m-dihydroxybenzene are added to water to obtain a mixed solution, and then formaldehyde is slowly added to the mixed solution according to the molar ratio of formaldehyde to m-dihydroxybenzene of 2:1 to obtain an in-situ growth solution of metal organic gel MOG;

[0011] d. The nanofiber membrane is placed in the in-situ growth solution, immersed at room temperature, and then ammonia water is added to adjust the pH value. Heat and stir to grow in-situ, until the solution becomes gelatinous, take out the fiber membrane, rinse and dry to obtain MOG nanofiber membrane material;

[0012] e. According to the mass ratio of 1:(1-10), the MOG nanofiber membrane material and urea are doped with nitrogen by high-temperature pyrolysis in an inert atmosphere, and then ground after cooling to obtain MOG-CNF catalyst.

[0013] As preferred, the nanofiber polymer is one or more of poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyacrylic acid (PAA), cellulose acetate (CA), polystyrene sulfonate sodium (PSS), polyvinylpyrrolidone (PVP), or polystyrene (PS).

[0014] As preferred, the solvent is one of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), or deionized water.

[0015] As preferred, in step a, the stirring time is 6-24 h, and the stirring temperature is 20-60℃.

[0016] In step b, the needle voltage of electrospinning is 5-20 kV, the injection rate is 0.5-8 ml / h, and the collection rotation speed is 200-800 rpm.

[0017] In step c, the molar concentration of the mixed solution is 10-50 mol / L.

[0018] As preferred, the metal salt is one or more of iron salt, cobalt salt, nickel salt, zinc salt, or copper salt.

[0019] The iron salt is ferric nitrate or ferric chloride.

[0020] The cobalt salt is cobalt nitrate, cobalt chloride, or cobalt sulfate.

[0021] The nickel salt is nickel nitrate or nickel sulfate.

[0022] The zinc salt is zinc sulfate or zinc nitrate.

[0023] The copper salt is copper sulfate, copper chloride, or copper nitrate.

[0024] As preferred, the nitrogen-containing compound is one or more of peptone, urea, melamine, or chitosan.

[0025] As preferred, in step 3), the in-situ growth time is 6-48 h, the pH is 8-13, the heating temperature is 50-75℃, the drying temperature is 50-100℃, and the drying time is 3-7 d.

[0026] As preferred, in step 4), the inert gas is one of Ar, He, or N2; and the gas flow rate of the inert gas is 15-150 ml / min.

[0027] The heating rate of high-temperature carbonization is 5-10℃ / min, the temperature is 700-1100℃, and the time is 2-12 h.

[0028] Another aspect of the present application provides an in-situ growth MOG carbon nanofiber catalyst prepared by the method.

[0029] The present application has the following beneficial effects due to the above technical solutions:

[0030] 1. Compared with the composite catalyst prepared by the existing simple integrated spinning, the in-situ growth MOG carbon nanofiber catalyst prepared by the in-situ growth anchoring method has a significantly reduced ORR and OER overpotential. The porosity of the catalyst prepared by the method is increased by about 32.7%, and the polarization overpotential of the catalyst for ORR and OER is reduced by about 6.38%.

[0031] 2. The in-situ growth MOG carbon nanofiber catalyst prepared by the present application has excellent catalytic stability. This is because, during the preparation of the fiber membrane, by reasonably controlling the key process parameters such as voltage, injection rate and collection speed, the fiber diameter of the fiber membrane is uniform and the void network is regular, providing a large number of accessible anchoring growth points for the in-situ growth of MOG. Under the anchoring support of the fiber membrane, the in-situ growth MOG is combined with the fiber body more strongly. During the high-temperature process, both the MOG and the fiber membrane form carbon materials, and the carbon-carbon covalent bond further enhances the interfacial bonding force, forming a stable carbon composite structure.

[0032] 3. In the application of zinc-air fuel cells, due to the excellent porosity and low overpotential of the catalyst material, when the catalyst is applied to the cathode catalyst of a zinc-air fuel cell, the attenuation rate of the assembled battery is only 6.54% after 200h of charge-discharge operation, the rich void structure provides a fast channel for the rapid transmission of reactants and products, and the stable composite catalyst structure is the key to ensuring the long-term stable operation of the battery. Therefore, the battery has excellent structural stability, catalytic stability and long service life.

[0033] 4. The composite carbon nanofiber catalyst prepared by the present application has significant advantages in porosity improvement and overpotential reduction, and as a non-noble metal catalyst material, it has broad application prospects in the field of energy storage and conversion represented by fuel cells. BRIEF DESCRIPTION OF DRAWINGS

[0034] The drawings described herein are used to provide further understanding of the present application, constitute a part of the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0035] Figure 1 ORR, LSV polarization curve of MOG-CNF of Example 1 and Co-MOG of Comparative Example 1 in 0.1M KOH;

[0036] Figure 2The LSV polarization curve and power density plot of zinc-air battery assembled with MOG-CNF of Example 1 and Co-MOG of Comparative Example 1 as cathode catalyst, respectively;

[0037] Figure 3 The LSV polarization curve and power density plot of zinc-air battery assembled with MOG-CNF of Example 1 and Co-MOG of Comparative Example 1 as cathode catalyst, respectively;

[0038] Figure 4 The LSV polarization curve and power density plot of zinc-air battery assembled with MOG-CNF of Example 1 and Co-MOG of Comparative Example 1 as cathode catalyst, respectively;

[0039] Figure 5 The LSV polarization curve and power density plot of zinc-air battery assembled with MOG-CNF of Example 1 and Co-MOG of Comparative Example 1 as cathode catalyst, respectively; -2 DETAILED DESCRIPTION

[0040] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments, which are used to explain the present application, but not as a limitation of the present application.

[0041] The present application provides a preparation method of in-situ grown MOG carbon nanofiber catalyst, characterized in that, comprising the following steps:

[0042] Step 1, preparation of nanofiber membrane:

[0043] The nanofiber polymer and the solvent are stirred and mixed according to a mass ratio of 1:(3-20), and stirred for 6-24 h at a temperature of 20-60℃; a uniform spinning solution is formed.

[0044] The nanofiber polymer is left-handed polylactic acid (PLLA), right-handed polylactic acid (PDLA), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyacrylic acid (PAA), cellulose acetate (CA), sodium polystyrene sulfonate (PSS), polyvinylpyrrolidone (PVP), or polystyrene (PS).

[0045] The solvent is one of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), or deionized water.

[0046] Step 2, the spinning solution is transferred to a syringe, the needle voltage of electrospinning is 5-20 kV, the injection rate is 0.5-8 ml / h, and the collection rotation speed is 200-800 rpm; the nanofiber membrane is obtained by electrospinning and vacuum drying.

[0047] ​The three-dimensional network structure in the obtained nanofiber membrane provides abundant growth anchors for in-situ growth of MOG, guarantees uniform distribution and full exposure of active sites, and is conducive to efficient exertion of catalytic activity. The carbon nanofiber structure constructs a high-speed channel for electron transmission at a micro level, enables electrons to shuttle quickly between an electrode and reactants, reduces ohmic polarization, and greatly improves kinetic efficiency of the reaction. The developed pore distribution in the composite structure helps reactants to quickly reach catalytically active sites and products to be timely transported, thereby reducing mass transfer polarization and improving catalytic kinetic efficiency.

[0048] Step 3, preparation of MOG in-situ growth solution:

[0049] Metal salt, nitrogen-containing compound and resorcinol are added into water according to a molar ratio of 1:(1-10):(10-100), and stirred until completely dissolved, to obtain a mixed solution with a molar concentration of 10-50 mol / L; then formaldehyde is slowly added dropwise into the mixed solution according to a molar ratio of formaldehyde to resorcinol of 2:1, to obtain the MOG in-situ growth solution.

[0050] The metal salt is one or more of iron salt, cobalt salt, nickel salt, zinc salt or copper salt.

[0051] The iron salt is ferric nitrate or ferric chloride.

[0052] The cobalt salt is cobalt nitrate, cobalt chloride or cobalt sulfate.

[0053] The nickel salt is nickel nitrate or nickel sulfate.

[0054] The zinc salt is zinc sulfate or zinc nitrate.

[0055] The copper salt is copper sulfate, copper chloride or copper nitrate.

[0056] The nitrogen-containing compound is one or more of peptone, urea, melamine or chitosan.

[0057] Step 4, preparation of MOG nanofiber membrane material:

[0058] The nanofiber membrane material is placed into the in-situ growth solution, and after complete immersion at room temperature, an appropriate amount of ammonia water is added dropwise to make the pH of the system 8-13; the fiber membrane is taken out after the solution becomes gel-like by heating and stirring at a temperature of 50-75℃, washed and dried for in-situ growth for 6-48 h, the drying temperature is 50-100℃, and the drying time is 3-7 d, to obtain the MOG nanofiber membrane material.

[0059] Step 5, preparation of MOG carbon nanofiber (MOG-CNF) catalyst:

[0060] MOG nanofiber membrane material is doped with nitrogen by high-temperature pyrolysis in an inert atmosphere (Ar, He, N2) at a mass ratio of 1:(1-10), the gas flow of the inert gas is 15-150 ml / min, the high-temperature carbonization temperature is 700-1100℃, the time is 2-12 h, the heating rate of high-temperature carbonization is 5-10℃ / min, and the MOG-CNF catalyst is obtained after grinding after cooling.

[0061] Since the sol-gel process of the MOG material synthesis can be regulated by adjusting the pH value, when the monomer material is fully and uniformly impregnated in the fiber membrane gap, the sol-gel reaction is regulated by adjusting the pH value, and the polymerization and growth occur in the fiber membrane gap and the fiber surface, gradually growing into a MOG material in situ embedded and anchored on the fiber membrane surface, forming a stable integrated composite structure. Since MOG and fiber membrane are mainly organic carbon, during the high-temperature carbonization process, the carbon chain in the material breaks and recombines. The interface between the composite materials is tightly fused, and the bonding force is further enhanced. In the initial stage of heating, the CN ring in the fiber membrane generates unsaturated bonds, which undergoes addition or condensation reaction with the organic ligand in the MOG that has not been completely decomposed, forming C-N or C-O covalent bonds; further, the organic phase part of the MOG melts or decomposes into a low-viscosity fluid, which penetrates into the fiber network gap and micropores. As the temperature rises, the carbon skeleton of the MOG interweaves with the carbonized structure of the PAN, forming an "interlocking" structure. The metal nanoparticles formed by the pyrolysis of the MOG penetrate into the interface and enhance the interface bonding force through the metal-carbon bond bridging effect, realizing the tight and stable interface bonding of the composite material at high temperature.

[0062] The following specific different embodiments are given to further illustrate the present application.

[0063] Example 1

[0064] (1) Polyacrylonitrile (PAN) was dissolved in dimethylformamide (DMF) at a mass ratio of 1:6, and the mixed solution was magnetically stirred at 20℃ for 24 h to obtain a uniformly mixed spinning solution.

[0065] (2) 5 ml of the above spinning solution was transferred to a syringe for electrospinning, wherein the voltage of the electrospinning needle was 15 kV, the injection rate was 1.0 ml / h, and the collection rotation speed was 450 rpm. The collection was placed in a vacuum dryer to obtain a nanofiber membrane.

[0066] (3) Cobalt nitrate hexahydrate, resorcinol and proteose peptone were dissolved in deionized water at a molar ratio of 1:2:10, and magnetically stirred until the solids were completely dissolved to obtain a mixed solution with a molar concentration of 14 mol / L; formaldehyde was slowly added to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1, and stirred uniformly to obtain a MOG in-situ growth solution.

[0067] (4) The obtained nanofiber membrane was placed in the MOG in-situ growth solution and immersed in a cool place for 24 h. Then, ammonia water (AR, mass concentration 26%) was added under the condition of a 60 °C water bath to adjust the pH value to 9. The solution was stirred until it became gelatinous. The fiber membrane was taken out, washed with deionized water for several times, and then placed in a vacuum drying oven under the condition of 80 °C for 5 d.

[0068] (5) The MOG nanofiber membrane material was carbonized with urea under inert gas N2 according to a mass ratio of 1:4. During the carbonization process, 3 g of urea was placed in another boat for nitrogen-doped pyrolysis at high temperature. The carbonization parameters were as follows: carbonization temperature 800 °C, time 2 h, heating rate 5 °C / min, and inert gas flow rate 80 mL / min. After the carbonization, the obtained carbon nanomaterial was taken out and ground to obtain the MOG carbon nanofiber catalyst (MOG-CNF).

[0069] The overpotential of MOG-CNF (0.88 V) was reduced by 6.38% compared with that of Co-MOG (0.94 V); and the porosity of MOG-CNF was increased by 32.72% compared with that of Co-MOG.

[0070] Example 2

[0071] (1) Polyvinylidene fluoride (PVDF) was dissolved in dimethylformamide (DMF) according to a mass ratio of 1:10. The mixed solution was magnetically stirred at 25 °C for 20 h to obtain a uniformly mixed spinning solution.

[0072] (2) 5 ml of the spinning solution was transferred to a syringe. The voltage of the needle was 10 kV, the injection rate of the syringe was 2.0 ml / h, and the collection rotation speed was 500 rpm. The nanofiber membrane was obtained by vacuum drying.

[0073] (3) Cobalt nitrate hexahydrate, resorcinol and proteose peptone were dissolved in deionized water according to a molar ratio of 1:5:30, and the mixture was magnetically stirred until the solid was completely dissolved to obtain a mixed solution with a molar concentration of 10 mol / L. Formaldehyde was slowly added to the mixed solution according to a molar ratio of formaldehyde to resorcinol of 2:1, and the mixture was stirred uniformly to obtain a MOG in-situ growth solution.

[0074] (4) The obtained nanofiber membrane was placed in the MOG in-situ growth solution and immersed in a cool place for 24 h. Then, ammonia water (AR, mass concentration 26%) was added under the condition of a 60 °C water bath to adjust the pH value to 9. The solution was stirred until it became gelatinous. The fiber membrane was taken out, washed with deionized water for several times, and then placed in a vacuum drying oven under the condition of 80 °C for 5 d.

[0075] (5) The MOG nanofiber membrane material obtained was carbonized with urea under inert gas N2 according to a mass ratio of 1:6. During the carbonization process, 3 g of urea was added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 900°C, time 7 h, heating rate 8°C / min, and inert gas flow rate 100 mL / min. After carbonization, the carbon nanomaterial obtained was taken out and ground, and finally MOG carbon nanofiber catalyst (MOG-CNF-2) was obtained.

[0076] The overpotential of MOG-CNF-2 (0.91 V) was reduced by 3.19% compared with that of Co-MOG (0.94 V); and the porosity of MOG-CNF was increased by 23.65% compared with that of Co-MOG.

[0077] Example 3

[0078] (1) Polyacrylic acid (PAA) was dissolved in dimethylformamide (DMF) according to a mass ratio of 1:20, and the mixed solution was magnetically stirred at 20°C for 24 h to obtain a uniformly mixed spinning solution.

[0079] (2) 5 ml of the spinning solution was transferred to a syringe for electrospinning, wherein the voltage of the electrospinning needle was 5 kV, the injection rate was 3.0 ml / h, and the collection rotation speed was 300 rpm. Vacuum drying gave a nanofiber membrane.

[0080] (3) Iron nitrate nonahydrate, resorcinol and proteose peptone were dissolved in deionized water according to a molar ratio of 1:4:50, and magnetically stirred until the solids were completely dissolved to obtain a mixed solution with a molar concentration of 30 mol / L. Formaldehyde was slowly added to the mixed solution according to a molar ratio of formaldehyde to resorcinol of 2:1, and stirred uniformly to obtain a MOG in-situ growth solution.

[0081] (4) The fiber membrane obtained above was placed in the MOG in-situ growth solution and immersed in a cool place for 12 h. Ammonia water (AR, mass concentration 26%) was added under water bath conditions at 55°C to adjust the pH value to 12, and stirred until the solution became gelatinous. The fiber membrane was taken out, washed with deionized water several times, and then placed in a vacuum drying oven at 90°C for vacuum drying for 5 d.

[0082] (5) The MOG nanofiber membrane material obtained was carbonized with urea under inert gas Ar according to a mass ratio of 1:5. During the carbonization process, 3 g of urea was added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 700°C, time 7 h, heating rate 10°C / min, and inert gas flow rate 40 mL / min.

[0083] (6) After carbonization, the obtained carbon nanomaterial is taken out and ground, and finally a MOG carbon nanofiber catalyst (MOG-CNF-3) is obtained.

[0084] The overpotential of MOG-CNF-3 (0.84 mV) is reduced by 10.64% compared with that of Co-MOG (0.94 V); the porosity of MOG-CNF is increased by 28.56% compared with that of Co-MOG.

[0085] Example 4

[0086] (1) Acetic acid fiber (CA) is dissolved in dimethyl sulfoxide (DMSO) at a mass ratio of 1:15, and the mixed solution is magnetically stirred at 20°C for 20h to obtain a uniformly mixed spinning solution.

[0087] (2) 5ml of the above spinning solution is transferred to a syringe for electrospinning, wherein the voltage of the electrospinning needle is 20kV, the injection rate is 8.0ml / h, and the collection rotation speed is 200rpm. A nanofiber membrane is obtained by vacuum drying.

[0088] (3) Nickel nitrate hexahydrate, resorcinol and proteose peptone are dissolved in deionized water at a molar ratio of 1:5:70, and magnetically stirred until the solids are completely dissolved to obtain a mixed solution with a molar concentration of 35mol / L; formaldehyde is slowly added to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1, and stirred uniformly to obtain a MOG in-situ growth solution.

[0089] (4) The obtained fiber membrane is placed in the MOG in-situ growth solution and immersed in a cool place for 15h. Ammonia (AR, mass concentration 26%) is added under the condition of 70°C water bath to adjust the pH value to 11, and stirred until the solution becomes gelatinous. The fiber membrane is taken out and washed with deionized water several times, and then placed in a vacuum drying oven at 70°C for 6d.

[0090] (5) The obtained MOG nanofiber membrane material is carbonized with urea under inert gas N2 at a mass ratio of 1:1. During carbonization, 3g of urea is added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters are as follows: carbonization temperature 600°C, time 8h, heating rate 6°C / min, and inert gas flow rate 90mL / min. After carbonization, the obtained carbon nanomaterial is taken out and ground, and finally a MOG carbon nanofiber catalyst (MOG-CNF-4) is obtained.

[0091] The overpotential (0.87V) of MOG-CNF-4 is reduced by 7.45% compared with that (0.94V) of Co-MOG; the porosity of MOG-CNF is increased by 27.45% compared with that of Co-MOG.

[0092] Example 5

[0093] (1) Dissolve polylactic acid (PLLA) in dimethylformamide (DMF) at a mass ratio of 1:10, magnetically stir the mixed solution at 20°C for 18h to obtain a mixed uniform spinning solution.

[0094] (2) Take 5ml of the above spinning solution and transfer it to a syringe, perform electrospinning, the voltage of the needle is 20kV, the injection rate is 6.0ml / h, the collection rotation speed is 200rpm, and vacuum drying is performed to obtain a nanofiber membrane.

[0095] (3) Dissolve zinc sulfate heptahydrate, resorcinol and proteose peptone+urea in deionized water at a molar ratio of 1:3.5:60, magnetically stir until the solids are completely dissolved to obtain a mixed solution with a molar concentration of 50mol / L; slowly add formaldehyde to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1, stir uniformly to obtain a MOG in-situ growth solution.

[0096] (4) Put the above obtained fiber membrane into the MOG in-situ growth solution, immerse it in a cool place for 10h, then add ammonia water (AR, mass concentration of 26%) under the condition of 65°C water bath, adjust the pH value to 10, and stir until the solution becomes gelatinous. Take out the fiber membrane, rinse it with deionized water several times, and then put it into a vacuum drying oven, dry at 90°C for 4d.

[0097] (5) Carbonize the obtained MOG nanofiber membrane material with urea under inert gas Ar at a mass ratio of 1:8. During the carbonization process, add 3g of urea to another boat for high temperature pyrolysis of nitrogen doping. The carbonization parameters are as follows: carbonization temperature 1100°C, time 10h, heating rate 9°C / min, and inert gas flow rate 30mL / min. After carbonization, grind the obtained carbon nanomaterial to obtain MOG carbon nanofiber catalyst (MOG-CNF-5).

[0098] The overpotential (0.92V) of MOG-CNF-5 is reduced by 2.13% compared with that (0.94V) of Co-MOG; the porosity of MOG-CNF is increased by 30.85% compared with that of Co-MOG.

[0099] Example 6

[0100] (1) According to the mass ratio of 1:5, dissolving the poly-L-lactic acid (PLLA) in N-methyl-2-pyrrolidone (NMP), magnetically stirring the mixed solution at 25℃ for 20h to obtain a mixed uniform spinning solution.

[0101] (2) Transferring 5ml of the above spinning solution to a syringe, electrospinning, the voltage of the needle is 12kV, the injection rate is 4ml / h, the collection rotation speed is 800rpm, vacuum drying to obtain a nanofiber membrane.

[0102] (3) According to the molar ratio of 1:10:90, dissolving the cobalt sulfate hexahydrate, resorcinol and chitosan in deionized water, magnetically stirring until the solid is completely dissolved to obtain a mixed solution with a molar concentration of 21mol / L; slowly adding formaldehyde to the mixed solution according to the molar ratio of formaldehyde to resorcinol 2:1, stirring uniformly to obtain a MOG in-situ growth solution.

[0103] (4) Placing the above obtained fiber membrane into the MOG in-situ growth solution, immersing in a cool place for 12h, then adding ammonia water (AR, mass concentration of 26%) under the condition of 60℃ water bath, adjusting the pH value to 13, stirring until the solution becomes gelatinous. Taking out the fiber membrane, washing with deionized water for several times, then placing it into a vacuum drying box, vacuum drying at 60℃ for 4d.

[0104] (5) According to the mass ratio of 1:3, the obtained MOG nanofiber membrane material and urea are treated by carbonization under inert gas Ar. During the carbonization process, 3g of urea is added to another boat for high temperature pyrolysis of nitrogen doping. The carbonization specific parameters are as follows: carbonization temperature 750℃, time 12h, heating rate 5℃ / min, inert gas flow rate 40mL / min. After carbonization, the obtained carbon nanomaterial is taken out and ground to obtain MOG carbon nanofiber catalyst (MOG-CNF-6).

[0105] The overpotential of MOG-CNF-6 (0.83V) is reduced by 11.70% compared with that of Co-MOG (0.94V); the porosity of MOG-CNF is increased by 27.91% compared with that of Co-MOG.

[0106] Example 7

[0107] (1) According to the mass ratio of 1:15, dissolving the polyvinylpyrrolidone (PVP) in dimethylformamide (DMF), magnetically stirring the mixed solution at 25℃ for 24h to obtain a mixed uniform spinning solution.

[0108] (2) Transferring 5ml of the above spinning solution to a syringe, electrospinning, the voltage of the needle is 18kV, the injection rate is 0.5ml / h, the collection rotation speed is 200rpm, vacuum drying to obtain a nanofiber membrane.

[0109] (3) Copper sulfate pentahydrate, resorcinol and melamine were dissolved in deionized water according to the molar ratio of 1:8:40, and magnetic stirring was performed until the solids were completely dissolved to obtain a mixed solution with a molar concentration of 13 mol / L. Formaldehyde was slowly added to the mixed solution according to the molar ratio of formaldehyde to resorcinol of 2:1, and the molar ratio of resorcinol to formaldehyde was 1:2. After uniform stirring, the MOG in-situ growth solution was obtained.

[0110] (4) The fiber membrane obtained above was placed in the MOG in-situ growth solution and immersed in a cool place for 32 h. Then, ammonia water (AR, mass concentration of 26%) was added under the condition of a water bath at 50°C to adjust the pH value to 9. After stirring until the solution became gel-like, the fiber membrane was taken out, washed with deionized water several times, and then placed in a vacuum drying oven for drying at 100°C for 4 d.

[0111] (5) The obtained MOG nanofiber membrane material was carbonized with urea under inert gas Ar according to the mass ratio of 1:10. During the carbonization process, 5 g of urea was placed in another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 650°C, time 3 h, heating rate 8°C / min, and inert gas flow rate 20 mL / min. After carbonization, the carbon nanomaterial obtained was taken out and ground, and finally the MOG carbon nanofiber catalyst (MOG-CNF-7) was obtained.

[0112] The overpotential of MOG-CNF-7 (0.86 V) was reduced by 8.51% compared with that of Co-MOG (0.94 V); and the porosity of MOG-CNF was increased by 24.85% compared with that of Co-MOG.

[0113] Example 8

[0114] (1) Sodium polystyrene sulfonate (PSS) was dissolved in deionized water according to the mass ratio of 1:3. The mixed solution was magnetically stirred at 20°C for 18 h to obtain a uniformly mixed spinning solution.

[0115] (2) 5 ml of the spinning solution obtained above was transferred to a syringe for electrospinning. The voltage of the needle was 8 kV, the injection rate was 0.8 ml / h, and the collection rotation speed was 400 rpm. After vacuum drying, a nanofiber membrane was obtained.

[0116] (3) Zinc sulfate heptahydrate, resorcinol and urea were dissolved in deionized water according to the molar ratio of 1:9:100, and magnetic stirring was performed until the solids were completely dissolved to obtain a mixed solution with a molar concentration of 25 mol / L. Formaldehyde was slowly added to the mixed solution according to the molar ratio of formaldehyde to resorcinol of 2:1, and the molar ratio of resorcinol to formaldehyde was 1:2. After uniform stirring, the MOG in-situ growth solution was obtained.

[0117] (4) The obtained fiber membrane was placed in a MOG in-situ growth solution and immersed in a cool place for 48 h. Then, ammonia water (AR, mass concentration 26%) was added to adjust the pH value to 10 under the condition of a water bath at 75 °C. The solution was stirred until it became gel. The fiber membrane was taken out, washed with deionized water for several times, and then placed in a vacuum drying oven at 50 °C for 7 d.

[0118] (5) The obtained MOG nanofiber membrane material was mixed with urea at a mass ratio of 1:9, and carbonization treatment was performed under inert gas He. During the carbonization process, 4 g of urea was added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 850 °C, time 4 h, heating rate 10 °C / min, and inert gas flow rate 150 mL / min. After the carbonization was completed, the obtained carbon nanomaterial was taken out and ground, and finally the MOG carbon nanofiber catalyst (MOG-CNF-8) was obtained.

[0119] The overpotential of MOG-CNF-8 (0.81 V) was reduced by 13.83% compared with that of Co-MOG (0.94 V); and the porosity of MOG-CNF was increased by 26.56% compared with that of Co-MOG.

[0120] Comparative Example 1

[0121] Cobalt nitrate hexahydrate, resorcinol and proteose peptone were dissolved in deionized water, and magnetic stirring was performed until the solids were completely dissolved. Then, formaldehyde was slowly added to the mixed solution at a molar ratio of resorcinol to formaldehyde of 1:2. After uniform stirring, drying was performed in a vacuum drying oven. The molar ratio of metal salt, nitrogen-containing component, resorcinol and water was 1:2:10:50.

[0122] The obtained solid was subjected to carbonization treatment under inert gas N2. During the carbonization process, 3 g of urea was added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 800 °C, time 2 h, heating rate 5 °C / min, and inert gas flow rate 80 mL / min. After the carbonization was completed, the obtained material was taken out and ground, and finally the Co-MOG catalyst material was obtained.

[0123] Comparative Example 2

[0124] Nickel nitrate hexahydrate, resorcinol and proteose peptone were dissolved in deionized water, and magnetic stirring was performed until the solids were completely dissolved. Then, formaldehyde was slowly added to the mixed solution at a molar ratio of resorcinol to formaldehyde of 1:2. After uniform stirring, drying was performed in a vacuum drying oven. The molar ratio of metal salt, nitrogen-containing component, resorcinol and water was 1:2:10:50.

[0125] The obtained solid was subjected to carbonization treatment under inert gas N2. During the carbonization process, 3 g of urea was added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 800℃, time 2 h, heating rate 6℃ / min, and inert gas flow rate 70 mL / min. After the carbonization was completed, the obtained material was taken out and ground, and finally a Ni-MOG catalyst material was obtained.

[0126] Comparative Example 3

[0127] Iron nitrate nonahydrate, resorcinol and proteose peptone were dissolved in deionized water, and magnetic stirring was performed until the solids were completely dissolved. Then, formaldehyde was slowly added to the mixed solution at a molar ratio of resorcinol to formaldehyde of 1:2. After uniform stirring, the mixture was placed in a vacuum drying oven for drying. The molar ratio of metal salt, nitrogen-containing component, resorcinol and water was 1:2:10:50.

[0128] The obtained solid was subjected to carbonization treatment under inert gas N2. During the carbonization process, 3 g of urea was added to another boat for high-temperature pyrolysis of nitrogen doping. The carbonization parameters were as follows: carbonization temperature 800℃, time 2 h, heating rate 6℃ / min, and inert gas flow rate 70 mL / min. After the carbonization was completed, the obtained material was taken out and ground, and finally a Fe-MOG catalyst material was obtained.

[0129]

[0130]

[0131] The present application utilizes electrospinning and in-situ growth technology to introduce MOG into a nanoporous fiber membrane in-situ, and constructs an in-situ growth MOG carbon nanofiber catalyst. The three-dimensional interwoven porous network structure in the nanofiber membrane not only provides abundant anchoring sites for the in-situ growth of MOG, but also helps the in-situ anchoring of active sites to make the interface combination more closely and more uniformly distributed. At the same time, the nanofiber can provide a large number of mass transfer and conduction channels to help the efficient transmission of substances and the rapid transfer of electrons. Thus, the excellent microstructure basis is provided for the stable and excellent bifunctional electrocatalytic performance of the MOG-CNF catalyst.

[0132] The ORR and LSV polarization curves of the MOG-CNF of Example 1 and the Co-MOG of Comparative Example 1 in 0.1 mol / L KOH solution are shown in Figure 1 The OER polarization curves of the MOG-CNF of Example 1 and the Co-MOG of Comparative Example 1 in 1 mol / L KOH solution are shown in Figure 2 The discharge polarization curves and power density maps of the zinc-air batteries assembled with the MOG-CNF of Example 1 and the Co-MOG of Comparative Example 1 as cathode catalysts are shown in Figure 3As shown; the charge-discharge polarization curves of zinc-air batteries assembled with MOG-CNF from Example 1 and Co-MOG from Comparative Example 1 as cathode catalysts are shown in the figure. Figure 4 As shown; the zinc-air battery assembled using MOG-CNF as the cathode catalyst in Example 1 and the Co-MOG battery in Comparative Example 1, at 10 mA cm⁻¹ -2 The constant current charge-discharge curve is shown below. Figure 5 As shown.

[0133] The LSV curves of ORR for different catalysts in 0.1M KOH at 1600 rpm are shown below. Figure 1 As shown. Half-wave potential (E) of the ORR polarization curve of the MOG-CNF sample. 1 / 2 The voltage is 0.75V, which is better than Co-MOG(E) 1 / 2 =0.72V), indicating that it possesses excellent ORR electrocatalytic activity characteristic of MOG-CNF. The OER electrocatalytic activity of the catalyst was studied in 1M KOH solution. Figure 2 At 10mAcm -2 At the specified current density, MOG-CNF exhibits an overpotential of 395 mV, significantly lower than that of Co-MOG (428 mV). This indicates that MOG-CNF possesses superior OER catalytic performance compared to Co-MOG. This is likely due to the excellent conductivity and porous structure of the nanofibers, which create a high-speed channel for Co-MOG, allowing electrons to rapidly shuttle between the electrode and reactants, greatly improving the reaction kinetic efficiency and providing satisfactory stability. The discharge polarization curves and power density curves are shown below. Figure 3 As shown, the highest power density of MOG-CNF-based ZAB reaches 119.8 mW / cm². -2 It is significantly higher than that of Co-MOG-based ZAB (109.4 mW cm⁻¹). -2 The battery charge / discharge curve is as follows: Figure 4 As shown, at 20mA cm -2 At the specified current density, the voltage difference of MOG-CNF-based ZABs is 1.146V, which is 42mV less than the charge-discharge voltage difference of Co-MOG-based ZABs (1.188V). At 200mA cm⁻¹ -2 At high current densities, the voltage difference of MOG-CNF-based ZAB was 1.818V, which was 115mV less than that of Co-MOG-based ZAB (1.933V). After 800 hours (approximately 2200 cycles), MOG-CNF-based ZAB showed no significant increase in its charge-discharge voltage range, while Co-MOG-based ZAB exhibited a significant widening of its charge-discharge voltage range around 270 hours. This indicates that MOG-CNF possesses excellent catalytic performance.

[0134] The results of the present example show that the present application mixes the polymer and the solvent to obtain a fiber membrane by electrospinning, grows metal organic gel particles on the fiber membrane by an in-situ growth method, constructs a high-speed channel to enable electrons to shuttle quickly between the electrode and the reactant, greatly improves the kinetic efficiency of the reaction and has satisfactory stability, and thus has important significance for promoting the industrialization development of the zinc-air battery.

[0135] The present application is not limited to the above-mentioned embodiments, and on the basis of the technical solutions disclosed in the present application, those skilled in the art can make some substitutions and modifications to some technical features without creative labor according to the disclosed technical content, and these substitutions and modifications are all within the protection scope of the present application.

Claims

1. A method for preparing an in-situ grown MOG carbon nanofiber catalyst, characterized in that, Includes the following steps: a. Mix the nanofiber polymer with the solvent at a mass ratio of 1:(3-20) to form a uniform spinning solution; b. Following the electrospinning method, the spinning solution is transferred to a syringe, the injection rate of the syringe is controlled, and after electrospinning, the nanofiber membrane is obtained by collecting and vacuum drying. c. Add the metal salt, nitrogen-containing compound and resorcinol to water according to the molar ratio of metal salt, nitrogen-containing compound and resorcinol of 1:(1~10):(10~100) to obtain a mixed solution. Then slowly add formaldehyde to the mixed solution according to the molar ratio of formaldehyde to resorcinol of 2:1 to obtain the in-situ growth solution of metal organogel MOG. d. Place the nanofiber membrane in the in-situ growth solution, soak it thoroughly at room temperature, add ammonia water to adjust the pH value, heat and stir to carry out in-situ growth until the solution becomes gel-like, take out the fiber membrane, rinse and dry to obtain MOG nanofiber membrane material; e. MOG nanofiber membrane material and urea were subjected to high-temperature pyrolysis and nitrogen doping in an inert atmosphere at a mass ratio of 1:(1~10), and then ground after cooling to obtain MOG-CNF catalyst.

2. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, The nanofiber polymer is L-polylactic acid, D-polylactic acid, polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, cellulose acetate, sodium polystyrene sulfonate, polyvinylpyrrolidone, or polystyrene.

3. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, The solvent is one of dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, or deionized water.

4. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, In step a, the stirring time is 6 to 24 hours and the stirring temperature is 20 to 60°C; In step b, the needle voltage for electrospinning is 5–20 kV, the injection rate is 0.5–8 ml / h, and the collection speed is 200–800 rpm. In step c, the molar concentration of the mixed solution is 10–50 mol / L.

5. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, The metal salt is one or more of iron salt, cobalt salt, nickel salt, zinc salt, or copper salt; The iron salt is ferric nitrate or ferric chloride; The cobalt salt is cobalt nitrate, cobalt chloride, or cobalt sulfate; The nickel salt is nickel nitrate or nickel sulfate; The zinc salt is zinc sulfate or zinc nitrate; The copper salt is copper sulfate, copper chloride, or copper nitrate.

6. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, The nitrogen-containing compound is one or more of peptone, urea, melamine, or chitosan.

7. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, In step d, the in-situ growth time is 6–48 h, the pH is 8–13, the heating temperature is 50–75 °C, the drying temperature is 50–100 °C, and the drying time is 3–7 days.

8. The method for preparing the in-situ grown MOG carbon nanofiber catalyst according to claim 1, characterized in that, In step e, the inert gas is one of Ar, He, or N2; the gas flow rate of the inert gas is 15-150 ml / min. The heating rate for high-temperature carbonization is 5–10 °C / min, the temperature is 700–1100 °C, and the time is 2–12 h.

9. An in-situ grown MOG carbon nanofiber catalyst prepared by the method described in claims 1 to 8.

10. The application of an in-situ grown MOG carbon nanofiber catalyst as described in claim 9 in a fuel cell.

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