In-situ growth of mog carbon nanofiber catalyst, preparation method and application thereof

Abstract

The application discloses an in-situ growth MOG carbon nanofiber catalyst and a preparation method and application thereof, and comprises the following steps: stirring and mixing a nanofiber polymer and a solvent to obtain a uniform spinning liquid; performing electrostatic spinning to obtain a nanofiber membrane; adding a metal salt, a nitrogen-containing compound and resorcinol into water, slowly adding formaldehyde into the mixed solution to obtain an in-situ growth solution of a metal organic gel MOG; placing the nanofiber membrane into the in-situ growth solution to adjust a pH value, and performing in-situ growth by heating to obtain a MOG nanofiber membrane material; and performing high-temperature pyrolysis of the MOG nanofiber membrane material and urea in an inert atmosphere to dope nitrogen, thereby obtaining the MOG-CNF catalyst. The catalyst can effectively reduce overpotential of ORR and OER reactions, improve catalytic stability, and present stable and excellent dual-function electrocatalytic performance. Through a nano structure and a synergistic catalytic effect, the catalyst has a wide application prospect in the field of fuel cell energy storage and conversion.

Description

Technical Field

[0001] This invention belongs to the field of preparation of non-precious metal catalyst materials for fuel cells, and provides a method for preparing in-situ grown metal-organic gel carbon nanofiber catalysts and their application in the field of fuel cells. Background Technology

[0002] Zinc-air batteries are fuel cells that use metallic zinc as fuel and oxygen from the air as an oxide. They typically consist of an alkaline electrolyte, a negative zinc electrode, a separator, and a positive air electrode. Zinc is inexpensive, has a high theoretical energy density, and is environmentally friendly. Furthermore, zinc's inherently low reaction temperature and strong stability in aqueous electrolytes allow for continuous recycling, making it a highly valued technology in the emerging energy storage field. However, during charge and discharge, the slow kinetics of oxygen reduction (ORR) and oxygen evolution (OER) reactions on the air electrode side lead to high electrode polarization and poor electrode reversibility. The different free energies and active site requirements of ORR and OER make it difficult for ordinary catalysts to simultaneously exhibit both excellent electrochemical properties. In addition, electrolyte erosion and high-potential corrosion during battery operation severely affect catalyst stability and lifespan. Therefore, designing efficient and structurally stable bifunctional oxygen catalysts is crucial for accelerating reaction kinetics, reducing overpotentials during charge and discharge, and improving catalyst lifespan.

[0003] Nanofiber membranes prepared by electrospinning possess large specific surface area, well-developed pore structure, and uniform distribution of active sites, which facilitates the rapid transport and diffusion of ions and molecules, making them ideal catalyst support materials. Among them, electrospun PAN nanofibers have uniform diameter and are insoluble in water. One-dimensional PAN fibers can interweave to form a three-dimensional network structure, and their unique flexibility and water-reactive morphological stability provide important guarantees for the structural and activity stability of catalysts during long-term use. Organometallic gels (MOGs) are a class of materials formed through the self-assembly of metal ions and organic ligands with the assistance of coordination and supramolecular forces. Due to their low density, high specific surface area, open active sites, high yield, and hierarchical porous structure, MOGs have attracted much attention in the field of electrocatalysis. Organometallic gels are amorphous and flexible, making them highly adaptable. Their pore size and porosity can be modified by controlling the synthesis conditions, allowing for composite formulations to exhibit excellent electrochemical performance according to different needs.

[0004] Patent number 2025100536055, entitled "A Composite Carbon Nanofiber Catalyst and Its Preparation Method and Use," describes the preparation of a composite catalyst by incorporating MOG material into a spinning solution and spinning it in an integrated manner. While some catalytic effect is achieved, the active sites in the MOG carbon material are mostly covered by the spinning material and cannot be fully exposed, making it difficult for reactants to reach them and thus affecting the full realization of catalytic performance. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a method for preparing an in-situ grown metal-organic gel carbon nanofiber catalyst. This method utilizes the porous network structure in the electrospun nanofiber membrane to provide abundant anchoring sites for the in-situ growth of MOGs, ensuring that the active sites are anchored in situ and uniformly distributed, resulting in stable and excellent bifunctional electrocatalytic performance. Under alkaline conditions, this catalyst can effectively reduce the overpotential of ORR and OER reactions, improve catalytic stability, and exhibit excellent bifunctional catalytic performance.

[0006] The present invention is achieved through the following technical solution.

[0007] One aspect of the present invention provides a method for preparing an in-situ grown MOG carbon nanofiber catalyst, comprising the following steps:

[0008] a. Mix the nanofiber polymer with the solvent at a mass ratio of 1:(3-20) to form a uniform spinning solution;

[0009] 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.

[0010] 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.

[0011] 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;

[0012] 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.

[0013] Preferably, the nanofiber polymer is polylactic acid (PLLA), polylactic acid (PDLA), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyacrylic acid (PAA), cellulose acetate (CA), sodium polystyrene sulfonate (PSS), polyvinylpyrrolidone (PVP), or polystyrene (PS).

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

[0015] Preferably, in step a, the stirring time is 6 to 24 hours and the stirring temperature is 20 to 60°C;

[0016] 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.

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

[0018] Preferably, the metal salt is one or more selected from 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] Preferably, the nitrogen-containing compound is one or more of peptone, urea, melamine, or chitosan.

[0025] Preferably, in step 3), 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.

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

[0027] 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.

[0028] In another aspect, the present invention provides an in-situ grown MOG carbon nanofiber catalyst prepared by the method described above.

[0029] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0030] 1. Compared to existing composite catalysts prepared by simple integrated spinning, the in-situ grown MOG carbon nanofiber catalyst prepared by this invention using an in-situ growth and anchoring method exhibits significantly reduced ORR and OER overpotentials. The catalyst prepared by this method shows an approximately 32.7% increase in porosity and a reduction of approximately 6.38% in catalytic ORR and OER polarization overpotentials.

[0031] 2. The in-situ grown MOG carbon nanofiber catalyst prepared by this invention exhibits excellent catalytic stability. This is because, during the fiber membrane preparation process, by rationally controlling key process parameters such as voltage, injection rate, and collection rotation speed, the fiber membrane achieves uniform fiber diameter and a well-organized interwoven pore network, providing numerous accessible anchoring growth points for in-situ MOG growth. Under the anchoring support of the fiber membrane, the in-situ grown MOG is strongly bonded to the fiber matrix. During the high-temperature process, both MOG and the fiber membrane form carbon materials, and the carbon-carbon covalent bonds further enhance the interfacial bonding force, forming a stable carbon composite structure.

[0032] 3. In zinc-air fuel cell applications, due to the excellent porosity and low overpotential of the catalyst material, when applied as the cathode catalyst, the assembled battery exhibits a degradation rate of only 6.54% after 200 hours of charge-discharge operation. The abundant porosity provides a fast channel for the rapid transport of reactants and products, and the stable composite catalyst structure is key to ensuring long-term stable operation of the battery. Therefore, the battery possesses excellent structural stability, catalytic stability, and a long service life.

[0033] 4. The composite carbon nanofiber catalyst prepared by this invention has significant advantages in terms of porosity improvement and overpotential reduction. As a non-precious metal catalytic material, it has broad application prospects in the field of energy storage and conversion, represented by fuel cells. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

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

[0036] Figure 2The OER and LSV polarization curves of MOG-CNF in Example 1 and Co-MOG in Comparative Example 1 in 1M KOH are shown.

[0037] Figure 3 The MOG-CNF of Example 1 and the Co-MOG of Comparative Example 1 are the discharge polarization curves and power density diagrams of zinc-air batteries assembled with cathode catalysts, respectively.

[0038] Figure 4 The charge-discharge polarization curves are shown for the zinc-air battery assembled with MOG-CNF as the cathode catalyst in Example 1 and the Co-MOG battery in Comparative Example 1.

[0039] Figure 5 The zinc-air battery assembled using MOG-CNF as the cathode catalyst in Example 1 and the Co-MOG battery in Comparative Example 1 were compared at 10 mA cm⁻¹. -2 Constant current charge-discharge curves under these conditions; Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0041] This invention provides a method for preparing an in-situ grown MOG carbon nanofiber catalyst, characterized by comprising the following steps:

[0042] Step 1, Preparation of nanofiber membranes:

[0043] The nanofiber polymer and solvent are mixed at a mass ratio of 1:(3-20) and stirred at a temperature of 20-60℃ for 6-24 hours to form a uniform spinning solution.

[0044] The nanofiber polymers are polylactic acid (PLLA), 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: Transfer the spinning solution into a syringe. The needle voltage for electrospinning is 5-20kV, the injection rate is 0.5-8ml / h, and the collection speed is 200-800rpm. After electrospinning, collect and vacuum dry to obtain a nanofiber membrane.

[0047] The three-dimensional network structure in the obtained nanofiber membrane provides abundant growth anchors for the in-situ growth of MOGs, ensuring the uniform distribution and full exposure of their active sites, which is conducive to the efficient exertion of catalytic activity. The carbon nanofiber structure constructs high-speed channels for electron transport at the microscopic level, enabling electrons to shuttle rapidly between the electrode and reactants, reducing ohmic polarization and greatly improving the kinetic efficiency of the reaction. The well-developed pore distribution in the composite structure facilitates the rapid arrival of reactants at the catalytic active sites and the timely transport of products, thereby reducing mass transfer polarization and improving catalytic kinetic efficiency.

[0048] Step 3, Preparation of MOG in-situ growth medium:

[0049] Metal salt, nitrogen-containing compound, and resorcinol are added to water at 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 to the mixed solution at a molar ratio of 2:1 to formaldehyde to resorcinol to obtain the MOG in situ growth solution.

[0050] Among them, the metal salt is one or more of iron salt, cobalt salt, nickel salt, zinc salt or copper salt;

[0051] The iron salts are ferric nitrate or ferric chloride;

[0052] The cobalt salts are cobalt nitrate, cobalt chloride, or cobalt sulfate;

[0053] The nickel salt is either nickel nitrate or nickel sulfate;

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

[0055] The copper salts are 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 was placed in the in-situ growth solution and, after complete impregnation at room temperature, an appropriate amount of ammonia was added dropwise to adjust the pH of the system to 8–13. The solution was heated and stirred at 50–75°C until it became gel-like. The fiber membrane was then removed, rinsed, and dried for in-situ growth for 6–48 hours at a temperature of 50–100°C for 3–7 days to obtain the MOG nanofiber membrane material.

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

[0060] MOG nanofiber membrane material and urea were subjected to high-temperature pyrolysis and nitrogen doping in an inert atmosphere (Ar, He, N2) at a mass ratio of 1:(1-10). The inert gas flow rate was 15-150 ml / min, the high-temperature carbonization temperature was 700-1100℃, the time was 2-12 h, and the high-temperature carbonization heating rate was 5-10℃ / min. After cooling, the material was ground to obtain the MOG-CNF catalyst.

[0061] Since the sol-gel process of MOG material synthesis can be controlled by adjusting the pH value, after the monomer material is fully and uniformly impregnated in the pores of the fiber membrane, the pH value is adjusted to induce a sol-gel reaction. Polymerization and growth occur in the pores and surface of the fiber membrane, and the gradually growing MOG material is embedded and anchored in situ on the surface of the fiber membrane, forming a stable integrated composite structure. Because both MOG and the fiber membrane are mainly composed of organic carbon, the carbon chains in the materials break and recombine during high-temperature carbonization. The interfaces between the composite materials are tightly fused, and the bonding force is further enhanced. In the initial stage of heating, unsaturated bonds are generated when CN cyclizes in the fiber membrane, which undergo addition or condensation reactions with the incompletely decomposed organic ligands in MOG to form CN or CO covalent bonds. Furthermore, the organic phase of MOG partially melts or decomposes into a low-viscosity fluid, which permeates into the gaps and micropores of the fiber network. As the temperature increases, the carbon skeleton of MOG intertwines with the carbonized structure of PAN, forming an "interlocking" structure. Metal nanoparticles formed by MOG pyrolysis penetrate into the interface, enhancing the interfacial bonding force through metal-carbon bond bridging, thus achieving a tight and stable interfacial bond in the composite material at high temperatures.

[0062] The present invention is further illustrated below with specific embodiments.

[0063] Example 1

[0064] (1) Polyacrylonitrile (PAN) was dissolved in dimethylformamide (DMF) at a mass ratio of 1:6. The mixture was magnetically stirred at 20°C for 24 hours to obtain a uniform spinning solution.

[0065] (2) Take 5 ml of the above spinning solution and transfer it into a syringe for electrospinning. The voltage of the electrospinning needle is 15 kV, the injection rate is 1.0 ml / h, the collection speed is 450 rpm, and the collected solution is placed in a vacuum to dry, thus obtaining a nanofiber membrane.

[0066] (3) Dissolve cobalt nitrate hexahydrate, resorcinol and peptone in deionized water at a molar ratio of 1:2:10 and stir magnetically until the solid is completely dissolved to obtain a mixed solution with a molar concentration of 14 mol / L; slowly add formaldehyde to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1 and stir until homogeneous to obtain MOG in situ growth solution.

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

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

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

[0070] Example 2

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

[0072] (2) Take 5 ml of the above spinning solution and transfer it into a syringe. The voltage of the needle is 10 kV, the injection rate of the syringe is 2.0 ml / h, the collection speed is 500 rpm, and vacuum drying is used to obtain a nanofiber membrane.

[0073] (3) Dissolve cobalt nitrate hexahydrate, resorcinol and peptone in deionized water at a molar ratio of 1:5:30 and stir magnetically until the solids are completely dissolved to obtain a mixed solution with a molar concentration of 10 mol / L; slowly add formaldehyde to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1 and stir until homogeneous to obtain MOG in situ growth solution.

[0074] (4) The fiber membrane obtained above was placed in the MOG in-situ growth solution and soaked in a cool place for 6 hours. Then, ammonia water (AR, mass concentration of 26%) was added under a water bath at 60°C to adjust the pH to 8, and the solution was stirred until it became gel-like. The fiber membrane was then removed, rinsed several times with deionized water, and placed in a vacuum drying oven at 100°C for 72 hours.

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

[0076] The overpotential of MOG-CNF-2 (0.91V) was 3.19% lower than that of Co-MOG (0.94V); the porosity of MOG-CNF was 23.65% higher than that of Co-MOG.

[0077] Example 3

[0078] (1) Polyacrylic acid (PAA) was dissolved in dimethylformamide (DMF) at a mass ratio of 1:20. The mixture was magnetically stirred at 20°C for 24 hours to obtain a uniform spinning solution.

[0079] (2) Take 5 ml of the above spinning solution and transfer it into a syringe for electrospinning. The voltage of the electrospinning needle is 5 kV, the injection rate is 3.0 ml / h, the collection speed is 300 rpm, and the nanofiber membrane is obtained by vacuum drying.

[0080] (3) Dissolve ferric nitrate nonahydrate, resorcinol and peptone in deionized water at a molar ratio of 1:4:50 and stir magnetically until the solid is completely dissolved to obtain a mixed solution with a molar concentration of 30 mol / L; slowly add formaldehyde to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1 and stir until homogeneous to obtain 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 hours. Then, ammonia water (AR, mass concentration of 26%) was added under a 55°C water bath to adjust the pH to 12, and the solution was stirred until it became gel-like. The fiber membrane was then removed, rinsed several times with deionized water, and placed in a vacuum drying oven at 90°C for 5 days.

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

[0083] (6) After carbonization, the obtained carbon nanomaterials are removed and ground to obtain MOG carbon nanofiber catalyst (MOG-CNF-3).

[0084] The overpotential of MOG-CNF-3 (0.84 mV) was 10.64% lower than that of Co-MOG (0.94 V); the porosity of MOG-CNF was 28.56% higher than that of Co-MOG.

[0085] Example 4

[0086] (1) Dissolve cellulose acetate (CA) in dimethyl sulfoxide (DMSO) at a mass ratio of 1:15. Stir the mixture magnetically for 20 h at 20 °C to obtain a uniform spinning solution.

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

[0088] (3) Dissolve nickel nitrate hexahydrate, resorcinol and peptone in deionized water at a molar ratio of 1:5:70 and stir magnetically until the solid is completely dissolved to obtain a mixed solution with a molar concentration of 35 mol / L; slowly add formaldehyde to the mixed solution at a molar ratio of formaldehyde to resorcinol of 2:1 and stir until homogeneous to obtain MOG in situ growth solution.

[0089] (4) The fiber membrane obtained above was placed in the MOG in-situ growth solution and immersed in a cool place for 15 hours. Then, ammonia water (AR, mass concentration of 26%) was added under a 70°C water bath to adjust the pH to 11, and the solution was stirred until it became gel-like. The fiber membrane was then removed, rinsed several times with deionized water, and placed in a vacuum drying oven at 70°C for 6 days.

[0090] (5) The obtained MOG nanofiber membrane material and urea were carbonized under an inert gas N2 at a mass ratio of 1:1. During the carbonization process, 3g of urea was added to another boat for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 600℃, time 8h, heating rate 6℃ / min, and inert gas flow rate 90mL / min. After carbonization, the obtained carbon nanomaterial was removed and ground to obtain the MOG carbon nanofiber catalyst (MOG-CNF-4).

[0091] The overpotential of MOG-CNF-4 (0.87V) was 7.45% lower than that of Co-MOG (0.94V); the porosity of MOG-CNF was 27.45% higher than that of Co-MOG.

[0092] Example 5

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

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

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

[0096] (4) The fiber membrane obtained above was placed in the MOG in-situ growth solution and immersed in a cool place for 10 hours. Then, ammonia water (AR, mass concentration of 26%) was added under a 65°C water bath to adjust the pH to 10, and the solution was stirred until it became gel-like. The fiber membrane was then removed, rinsed several times with deionized water, and placed in a vacuum drying oven at 90°C for 4 days.

[0097] (5) The obtained MOG nanofiber membrane material and urea were carbonized under an inert gas Ar at a mass ratio of 1:8. During the carbonization process, 3g of urea was added to another boat for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 1100℃, time 10h, heating rate 9℃ / min, and inert gas flow rate 30mL / min. After carbonization, the obtained carbon nanomaterial was removed and ground to obtain the MOG carbon nanofiber catalyst (MOG-CNF-5).

[0098] The overpotential of MOG-CNF-5 (0.92V) was 2.13% lower than that of Co-MOG (0.94V); the porosity of MOG-CNF was 30.85% higher than that of Co-MOG.

[0099] Example 6

[0100] (1) Dissolve polylactic acid (PLLA) in N-methyl-2-pyrrolidone (NMP) at a mass ratio of 1:5. Stir the mixture magnetically for 20 h at 25 °C to obtain a uniform spinning solution.

[0101] (2) Take 5 ml of the above spinning solution and transfer it into a syringe for electrospinning. The voltage of the needle is 12 kV, the injection rate is 4 ml / h, the collection speed is 800 rpm, and the nanofiber membrane is obtained by vacuum drying.

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

[0103] (4) The fiber membrane obtained above was placed in the MOG in-situ growth solution and immersed in a cool place for 12 hours. Then, ammonia water (AR, mass concentration of 26%) was added under a 60°C water bath to adjust the pH to 13, and the solution was stirred until it became gel-like. The fiber membrane was then removed, rinsed several times with deionized water, and placed in a vacuum drying oven at 60°C for 4 days.

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

[0105] The overpotential of MOG-CNF-6 (0.83V) was 11.70% lower than that of Co-MOG (0.94V); the porosity of MOG-CNF was 27.91% higher than that of Co-MOG.

[0106] Example 7

[0107] (1) Polyvinylpyrrolidone (PVP) was dissolved in dimethylformamide (DMF) at a mass ratio of 1:15. The mixture was magnetically stirred at 25°C for 24 hours to obtain a uniform spinning solution.

[0108] (2) Take 5 ml of the above spinning solution and transfer it into a syringe for electrospinning. The voltage of the needle is 18 kV, the injection rate is 0.5 ml / h, the collection speed is 200 rpm, and the nanofiber membrane is obtained by vacuum drying.

[0109] (3) Dissolve copper sulfate pentahydrate, resorcinol and melamine in deionized water at a molar ratio of 1:8:40 and stir magnetically until the solid is completely dissolved to obtain a mixed solution with a molar concentration of 13 mol / L; slowly add formaldehyde to the mixed solution at a molar ratio of 2:1 for formaldehyde and 1:2 for resorcinol and formaldehyde, and stir evenly to obtain MOG in situ growth solution.

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

[0111] (5) The obtained MOG nanofiber membrane material and urea were carbonized under an inert gas Ar at a mass ratio of 1:10. During the carbonization process, 5g of urea was added to another boat for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 650℃, time 3h, heating rate 8℃ / min, and inert gas flow rate 20mL / min. After carbonization, the obtained carbon nanomaterial was removed and ground to obtain the MOG carbon nanofiber catalyst (MOG-CNF-7).

[0112] The overpotential of MOG-CNF-7 (0.86V) was 8.51% lower than that of Co-MOG (0.94V); the porosity of MOG-CNF was 24.85% higher than that of Co-MOG.

[0113] Example 8

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

[0115] (2) Take 5 ml of the above spinning solution and transfer it into a syringe for electrospinning. The voltage of the needle is 8 kV, the injection rate is 0.8 ml / h, the collection speed is 400 rpm, and the nanofiber membrane is obtained by vacuum drying.

[0116] (3) Dissolve zinc sulfate heptahydrate, resorcinol and urea in deionized water at a molar ratio of 1:9:100 and stir magnetically until the solid is completely dissolved to obtain a mixed solution with a molar concentration of 25 mol / L. Slowly add formaldehyde to the mixed solution at a molar ratio of 2:1 for formaldehyde and 1:2 for resorcinol and formaldehyde, and stir evenly to obtain MOG in situ growth solution.

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

[0118] (5) The obtained MOG nanofiber membrane material and urea were carbonized under an inert gas (He) at a mass ratio of 1:9. During the carbonization process, 4g of urea was added to another vessel for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 850℃, time 4h, heating rate 10℃ / min, and inert gas flow rate 150mL / min. After carbonization, the obtained carbon nanomaterial was removed and ground to obtain the MOG carbon nanofiber catalyst (MOG-CNF-8).

[0119] The overpotential of MOG-CNF-8 (0.81V) was 13.83% lower than that of Co-MOG (0.94V); the porosity of MOG-CNF was 26.56% higher than that of Co-MOG.

[0120] Comparative Example 1

[0121] Cobalt nitrate hexahydrate, resorcinol, and peptone were dissolved in deionized water and magnetically stirred until the solids were completely dissolved. Then, formaldehyde was slowly added to the mixed solution, with a molar ratio of resorcinol to formaldehyde of 1:2. After stirring evenly, 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.

[0122] The obtained solid was carbonized under an inert gas N2 atmosphere. During carbonization, 3g of urea was added to another vessel for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 800℃, time 2h, heating rate 5℃ / min, and inert gas flow rate 80mL / min. After carbonization, the obtained material was removed and ground to obtain the final Co-MOG catalyst material.

[0123] Comparative Example 2

[0124] Nickel nitrate hexahydrate, resorcinol, and peptone were dissolved in deionized water and magnetically stirred until the solids were completely dissolved. Then, formaldehyde was slowly added to the mixed solution, with a molar ratio of resorcinol to formaldehyde of 1:2. After stirring evenly, 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.

[0125] The obtained solid was carbonized under an inert gas N2 atmosphere. During carbonization, 3g of urea was added to another vessel for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 800℃, time 2h, heating rate 6℃ / min, and inert gas flow rate 70mL / min. After carbonization, the obtained material was removed and ground to obtain the final Ni-MOG catalyst material.

[0126] Comparative Example 3

[0127] Ferric nitrate nonahydrate, resorcinol, and peptone were dissolved in deionized water and magnetically stirred until the solids were completely dissolved. Then, formaldehyde was slowly added to the mixed solution, with a molar ratio of resorcinol to formaldehyde of 1:2. After stirring evenly, 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 carbonized under an inert gas N2 atmosphere. During carbonization, 3g of urea was added to another vessel for high-temperature pyrolysis and nitrogen doping. The specific carbonization parameters were: carbonization temperature 800℃, time 2h, heating rate 6℃ / min, and inert gas flow rate 70mL / min. After carbonization, the obtained material was removed and ground to obtain the final Fe-MOG catalyst material.

[0129]

[0130]

[0131] This invention utilizes electrospinning and in-situ growth techniques to introduce MOGs in situ into nanoporous fiber membranes, constructing an in-situ grown MOG carbon nanofiber catalyst. The three-dimensional interwoven porous network structure of the nanofiber membrane not only provides abundant anchoring sites for MOG in situ growth, facilitating the in-situ anchoring of active sites and resulting in tighter and more uniform interfacial bonding, but also provides numerous mass transfer and conductivity channels, promoting efficient mass transport and rapid electron transfer. This provides an excellent microstructural basis for the stable and superior bifunctional electrocatalytic performance of the MOG-CNF catalyst.

[0132] The ORR and LSV polarization curves of MOG-CNF in Example 1 and Co-MOG in Comparative Example 1 in 0.1 mol / L KOH solution are shown below. Figure 1 As shown; the OER polarization curves of MOG-CNF in Example 1 and Co-MOG in Comparative Example 1 in 1 mol / L KOH solution are as follows. Figure 2 As shown; the discharge polarization curves and power density diagrams 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 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 this example demonstrate that the present invention, by mixing polymers and solvents and electrospinning to obtain a fiber membrane, and by growing metal-organic gel particles on the fiber membrane through an in-situ growth method, constructs a high-speed channel that allows electrons to shuttle rapidly between the electrodes and reactants, greatly improving the kinetic efficiency of the reaction and possessing satisfactory stability. This is of great significance for promoting the industrialization of zinc-air batteries.

[0135] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

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; the stirring time is 6~24h and the stirring temperature is 20~60℃; 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. The needle voltage for electrospinning is 5~20kV, the injection rate is 0.5~8ml / h, and the collection speed is 200~800rpm; c. Add the metal salt, nitrogen-containing compound, and resorcinol to water at a molar ratio of 1:(1~10):(10~100) to obtain a mixed solution with a molar concentration of 10~50 mol / L. Then, slowly add formaldehyde dropwise to the mixed solution at a 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, and after sufficient immersion at room temperature, add ammonia water to adjust the pH to 8-13. Heat and stir to carry out in-situ growth at a temperature of 50-75℃ for 6-48 hours until the solution becomes gel-like. Remove the fiber membrane, rinse and dry to obtain MOG nanofiber membrane material. The drying temperature is 50~100℃, and the drying time is 3~7 days; e. MOG nanofiber membrane material and urea were subjected to high-temperature pyrolysis and nitrogen doping in an inert gas at a mass ratio of 1:(1~10), and then ground after cooling to obtain MOG-CNF catalyst; The inert gas is either Ar or He; the gas flow rate of the inert gas is 15~150 ml / min; The heating rate for high-temperature pyrolysis is 5~10℃ / min, the temperature is 700~1100℃, and the time is 2~12h.

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, 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.

5. 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.

6. An in-situ grown MOG carbon nanofiber catalyst prepared by the method according to any one of claims 1 to 5.

7. The application of an in-situ grown MOG carbon nanofiber catalyst as described in claim 6 in a fuel cell.

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