Preparation method and application of lignin carbon-based bifunctional oxygen electrode catalyst

Abstract

The application discloses a lignin carbon-based bifunctional oxygen electrode catalyst and a preparation method and application thereof, and belongs to the technical field of zinc-air batteries. The preparation method comprises the following steps: according to a mass ratio of 1: (3-5): (1.5-2.5), lignin, sodium chloride and a nitrogen source are added into water, according to a single metal element and lignin ratio of 0.3-0.5 mmol / g, two of copper source, iron source and nickel source are added, and a precursor solution is obtained; the precursor solution is frozen to-200 to-150 DEG C, and is dehydrated to obtain a lignin-based self-assembled precursor; pyrolysis is carried out in a protective atmosphere; and after acid immersion, cleaning and drying are carried out. The microstructure and pore structure of the lignin-derived carbon are controlled through a salt template assisted pyrolysis strategy, FeN4 / CuN4 double single-atom sites and FeCu atomic clusters are obtained, the activity and stability of ORR / OER reactions are improved, and the energy storage characteristics of the rechargeable zinc-air battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of zinc-air battery technology, specifically relating to a method for preparing and applying a lignin-based carbon-based bifunctional oxygen electrode catalyst. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Aqueous rechargeable zinc-air batteries (ZABs) utilize an electrolyte system with water as the solvent, offering high safety. Based on a zinc anode and an air cathode, their theoretical energy density is high. Furthermore, zinc is abundant in the Earth's crust and relatively inexpensive, making this system a focus of ongoing research. From an energy strategy and technology development perspective, current policies encourage the development of inherently safe, cost-effective, and resource-sufficient energy storage technologies to support the clean energy transition and the construction of new power systems. Against this backdrop, aqueous zinc-air batteries, due to their potential safety and resource advantages, have become a key area of ​​research. However, further improvements in battery performance face several technical challenges, particularly the oxygen reduction / oxygen evolution reaction (ORR / OER) on the air electrode, which involves multiple electron and proton transfers, resulting in complex reaction pathways, typically slow kinetics, and requiring high overpotentials for activation. This not only reduces the battery's energy conversion efficiency but also affects its long-term cycle stability. Currently used high-performance electrocatalysts, such as platinum, iridium, and ruthenium-based materials, have shown good catalytic activity in laboratory studies. However, their high cost, limited natural reserves, and potential activity degradation under long-term cycling conditions fall short of the core requirements of low cost, high reliability, and supply chain security in practical applications. Therefore, developing efficient and stable bifunctional catalysts based on non-precious metals or abundant elements is one of the key research and development goals to drive the advancement of this technology.

[0004] Lignocellulose, a solid waste generated during bio-oil refining and pulping / papermaking, is often simply incinerated as a low-calorific-value fuel to recover heat energy, placing a heavy burden on the environment. Lignin, as a component of lignocellulose, is characterized by its high carbon content and rich aromatic structure. How to efficiently utilize lignin in ZABs to improve their performance is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] Based on the current state of technology, the purpose of this invention is to provide a method for preparing and applying a lignin-based carbon-based bifunctional oxygen electrode catalyst. This catalyst possesses lignin-derived carbon-supported atomic sites and coupled atomic clusters, which can improve the efficiency of 4e...- While improving the activity and selectivity of the ORR reaction, it also reduces the overpotential of the OER reaction, thereby enhancing its reactivity and improving the energy storage characteristics and stability of the rechargeable zinc-air battery.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a lignin-based carbon-based bifunctional oxygen electrode catalyst, comprising the following steps: S1. Add lignin, sodium chloride and nitrogen source to water at a mass ratio of 1:(3~5):(1.5~2.5); add two of copper source, iron source and nickel source at a ratio of 0.3~0.5mmol / g of a single metal element to lignin, and dissolve to obtain a precursor solution. S2. Freeze the precursor solution to -200~-150℃ and dehydrate to obtain a lignin-based self-assembled precursor; S3. The lignin-based self-assembled precursor is processed into powder and then pyrolyzed at 750~850℃ in a protective atmosphere. S4. The pyrolysis product is acid-leached, then washed and dried to obtain the lignin-carbon-based bifunctional oxygen electrode catalyst.

[0007] Secondly, the lignin-based bifunctional oxygen electrode catalyst prepared by the above-mentioned method is a lignin-based bifunctional oxygen electrode catalyst.

[0008] Thirdly, the application of the above-mentioned lignin-carbon-based bifunctional oxygen electrode catalyst in rechargeable zinc-air batteries includes: loading the lignin-carbon-based bifunctional oxygen electrode catalyst onto the surface of an air electrode.

[0009] The beneficial effects of this invention are as follows: 1. In the preparation method of the lignin-carbon-based bifunctional oxygen electrode catalyst of the present invention, the microstructure and pore structure of the lignin-derived carbon are controlled by a salt template-assisted pyrolysis strategy, which greatly increases the specific surface area of ​​the lignin-derived carbon. Before the pyrolysis operation, the precursor aqueous solution is frozen by liquid nitrogen, which can "fix" the uniform mixing state of lignin, metal salt and NaCl template by rapid freezing, preventing salt migration, recrystallization and agglomeration due to water evaporation during the subsequent drying process, thereby ensuring that porous carbon with uniform pore size and regular structure is finally obtained. By adjusting the type and content of the added metal salt, electrocatalysts with different forms such as single atom, double single atom and double single atom coupled atomic clusters can be obtained respectively.

[0010] 2. The lignin-based bifunctional oxygen electrode catalyst provided by this invention fully exposes the active sites on the surface of the carbon material and promotes mass transfer and charge transfer processes. It has FeN4 / CuN4 dual single-atom sites and FeCu atomic clusters. Through the synergistic effect between the two, it regulates the surface electronic structure of the material, thereby significantly improving the adsorption of active species for ORR / OER reaction by the active sites, improving the activity and stability of ORR / OER reaction, and further improving the energy storage characteristics of rechargeable zinc-air batteries. Attached Figure Description

[0011] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0012] Figure 1 These are characterization results of the lignin-carbon-based bifunctional oxygen electrode catalyst prepared in Example 1 of the specific embodiments of the present invention, where (A) is a SEM image and (B) is a TEM image.

[0013] Figure 2 This is a HAADF-STEM image of the lignin-carbon-based bifunctional oxygen electrode catalyst prepared in Example 1 of this invention.

[0014] Figure 3 These are catalytic activity data graphs for different embodiments and comparative examples in the specific implementation of the present invention, wherein (A) is a performance data graph for catalyzing the ORR reaction, and (B) is a performance data graph for catalyzing the OER reaction.

[0015] Figure 4 These are bifunctional catalytic activity data graphs for different embodiments and comparative examples in the specific implementation of this invention.

[0016] Figure 5 These are the performance test results of the zinc-air battery prepared in Example 4 of the specific embodiments of the present invention, wherein (A) is the battery open circuit potential diagram, (B) is the discharge polarization curve and the corresponding power density curve, and (C) is the cycle charge-discharge curve. Detailed Implementation

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] A typical embodiment of the present invention provides a method for preparing a lignin-based carbon-based bifunctional oxygen electrode catalyst, comprising the following steps: S1. Add lignin, sodium chloride and nitrogen source to water at a mass ratio of 1:(3~5):(1.5~2.5); add two of copper source, iron source and nickel source at a ratio of 0.3~0.5mmol / g of a single metal element to lignin, and dissolve to obtain a precursor solution. S2. Freeze the precursor solution to -200 ~ -150°C and dehydrate to obtain a lignin-based self-assembled precursor; S3. The lignin-based self-assembled precursor is processed into powder and then pyrolyzed at 750~850℃ in a protective atmosphere. S4. The pyrolysis product is acid-leached, then washed and dried to obtain the lignin-carbon-based bifunctional oxygen electrode catalyst.

[0020] In the above process, lignin forms amorphous carbon with certain conductivity and porous structure during high-temperature pyrolysis, providing an anchoring substrate for active sites such as FeN4 / CuN4 and a conductive pathway for electron transport. NaCl acts as a template agent, providing the porous structure. At 800℃, close to the melting point of NaCl, a semi-molten state is formed, inducing the formation of carbon edge defects. These defect locations are favorable positions for anchoring metal atoms. Nitrogen atoms generated by the pyrolysis of the nitrogen source are incorporated into the lattice of the carbon substrate, strongly chelating metal ions and forming single-atom sites such as FeN4 / CuN4. By further adjusting the amount of copper and iron sources added, the ratio of a single metal element to lignin was increased from 0.3 mmol / g to 0.5 mmol / g. With a concentration of mmol / g, catalysts with FeN4 / CuN4 dual single-atom sites coupled to FeCu clusters can be efficiently prepared (if the amount of Fe and Cu elements added is greater than 0.5 mmol / g, that is, the total amount of metal elements is greater than 1 mmol / g, it is difficult to obtain atomic-scale catalysts); and by freezing the precursor aqueous solution with liquid nitrogen before the pyrolysis operation, the uniform mixing state of lignin, metal salt and NaCl template can be "fixed" by rapid freezing, preventing salt migration, recrystallization and agglomeration due to water evaporation during the subsequent drying process, thereby ensuring that porous carbon with uniform pore size and regular structure is finally obtained; Optionally, in S1, the lignin includes one or more of lignin sulfonate, alkali lignin, and enzymatically hydrolyzed lignin, with a lignin concentration of 0.03~0.05 g / mL; the nitrogen source includes one or more of melamine and urea.

[0021] Optionally, in S1, the method for obtaining the precursor solution includes: magnetic stirring for 12-14 hours.

[0022] Optionally, the copper source in S1 includes one or more of copper nitrate, copper chloride, and copper sulfate; the iron source includes one or more of ferric nitrate, ferrous nitrate, and ferric chloride; and the nickel source includes one or more of nickel nitrate, nickel chloride, and nickel sulfate; nitrate (NO3) - The oxidizing atmosphere released during the inert atmosphere pyrolysis process can etch the carbon skeleton, further increase defects, and promote the entry of metal atoms into defect sites.

[0023] Optionally, in S2, the dehydration method includes: vacuum freeze drying for 48~60h, with the cold trap temperature of the vacuum freeze dryer set to -55~-45℃ and the vacuum degree to 0~5 Pa; during the dehydration process, NaCl crystals will precipitate and be evenly distributed in the lignin matrix, acting as a template agent.

[0024] Optionally, in S3, the heating rate is 5~10℃ / min, and the pyrolysis time is 4~6h. During the pyrolysis process, the carbon atoms of lignin rearrange and form amorphous carbon with certain conductivity and porous structure under the action of the template agent. Nitrogen forms coordinate bonds with metal atoms, becoming double single-atom sites with Fe-N4 and Cu-N4 configurations. By further adjusting the amount of copper and iron sources added, the ratio of a single metal element to lignin can be increased from 0.3 mmol / g to 0.5 mmol / g, thus preparing a catalyst with FeN4 / CuN4 double single-atom site coupled FeCu cluster structure.

[0025] Optionally, in S3, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere. For the preparation of functional carbon materials, the use of an inert protective atmosphere is an essential condition in the carbonization process of lignin. Its purpose is to create an oxygen-deficient reducing / neutral environment to ensure that the carbon skeleton can be preserved and transformed in an orderly manner.

[0026] Optionally, in S4, the acid leaching method includes: immersing in a 1M H2SO4 solution for 12-14 hours; during the process, the template agent and unstable metals on the surface are washed away, so that the FeN4 / CuN4 active sites are fully exposed.

[0027] A typical embodiment of the present invention provides a lignin-carbon-based bifunctional oxygen electrode catalyst prepared by the above-mentioned method.

[0028] It includes a uniformly nitrogen-doped carbon matrix phase, serving as a conductive carrier and anchoring point; FeN4 / CuN4 single-atom phases anchored at nitrogen-doped sites, concentrated in the carbon framework and surrounding areas of clusters; while FeCu alloy atom clusters are spatially adjacent to the dense single-atom region, and the atom clusters can act as powerful "anchoring points," stabilizing adjacent single atoms through chemical bonding and "pinning" them to the carrier, thereby greatly improving the stability of the single-atom components. The unique local geometry and electronic structure formed by the atom clusters and adjacent single atoms can precisely control the adsorption strength and configuration of key reaction intermediates, thereby guiding the reaction path to the target product and suppressing side reactions.

[0029] A typical embodiment of the present invention provides the application of the above-mentioned lignin-carbon-based bifunctional oxygen electrode catalyst in a rechargeable zinc-air battery, comprising: loading the lignin-carbon-based bifunctional oxygen electrode catalyst onto the surface of conductive carbon paper to prepare an air electrode.

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Example 1 A lignin-based carbon-based bifunctional oxygen electrode catalyst, the preparation method of which includes: S1. Weigh 1 g of lignin sulfonate, 4 g of NaCl, and 2 g of melamine, dissolve them in 25 mL of deionized water, add 0.5 mmol Cu(NO3)2 and 0.5 mmol Fe(NO3)3, stir on a magnetic stirrer for 12 h, filter to obtain the precursor solution, and set aside for later use.

[0032] S2. The precursor solution was rapidly frozen using liquid nitrogen to an ultra-low temperature of -196℃, and then dehydrated at -50℃ for 48 hours in a low-temperature vacuum freeze dryer to obtain a lignin-based self-assembled precursor.

[0033] S3. Grind the lignin-based self-assembled precursor into a uniform powder with a particle size of less than 100 μm, place the ground powder in a tube furnace, raise the temperature to 800℃ at a rate of 5℃ / min under nitrogen protection, and maintain the temperature at 800℃ for 4 hours to obtain the pyrolysis product.

[0034] S4. Pour the pyrolysis product into 1M sulfuric acid and stir with a magnetic stirrer for 12 hours. Then, wash with deionized water by centrifugation at 6000 rpm for 10 minutes. Dry the washed sample under vacuum at 60°C to obtain the lignin carbon-based bifunctional oxygen electrode catalyst.

[0035] The lignin-based bifunctional oxygen electrode catalyst obtained in this embodiment was characterized, and the SEM images are shown below. Figure 1As shown in (A), the SEM image is as follows: Figure 1 As shown in (B) in the figure: the sample exhibits a three-dimensional porous nanosheet morphology, and no obvious nanoparticles are observed. HAADF-STEM characterization results are as follows: Figure 2 As shown, isolated, uniformly intense bright spots indicate the presence of numerous Fe / Cu single-atom sites on the carbon material surface, while small clusters composed of several (usually 3-10) tightly aggregated bright spots demonstrate that the carbon material surface is loaded with FeCu alloy atomic clusters, thus revealing the presence of numerous single-atom / cluster sites on the sample surface.

[0036] Example 2 A lignin-based bifunctional oxygen electrode catalyst is prepared in a manner that differs from that in Example 1. In S1, 1 g of lignin sulfonate, 4 g of NaCl, and 2 g of melamine are weighed and dissolved in 25 mL of deionized water. 0.3 mmol of Cu(NO3)2 and 0.3 mmol of Fe(NO3)3 are added, and the mixture is stirred on a magnetic stirrer for 12 h. After filtration, a precursor solution is obtained.

[0037] That is, the ratio of Cu(NO3)2 and Fe(NO3)3 to lignin sulfonate is 0.3 mmol / g, and the other raw materials and steps are the same as in Example 1.

[0038] Comparative Example 1 A lignin-based bifunctional oxygen electrode catalyst is prepared in a manner that differs from that in Example 1. In S1, 1 g of lignin sulfonate, 4 g of NaCl, and 2 g of melamine are weighed and dissolved in (25 mL) of deionized water. 0.5 mmol of Fe(NO3)3 is added, and the mixture is stirred on a magnetic stirrer for 12 h. After filtration, a precursor solution is obtained.

[0039] That is, without adding Cu(NO3)2, the other raw materials and steps are the same as in Example 1; lignin-derived carbon modified with FeN4 sites is obtained.

[0040] Comparative Example 2 A lignin-based bifunctional oxygen electrode catalyst is prepared in a manner that differs from that in Example 1. In S1, 1 g of lignin sulfonate, 4 g of NaCl, and 2 g of melamine are weighed and dissolved in (25 mL) of deionized water. 0.5 mmol of Cu(NO3)2 is added, and the mixture is stirred on a magnetic stirrer for 12 h. After filtration, a precursor solution is obtained.

[0041] That is, without adding Fe(NO3)3, the other raw materials and steps are the same as in Example 1; CuN4 site modified lignin-derived carbon is obtained.

[0042] Comparative Example 3 A lignin-based bifunctional oxygen electrode catalyst is prepared in a manner that differs from that in Example 1. In S1, 1 g of lignin sulfonate, 4 g of NaCl, and 2 g of melamine are weighed and dissolved in (25 mL) of deionized water. The mixture is stirred on a magnetic stirrer for 12 h and then filtered to obtain a precursor solution.

[0043] That is, without adding Fe(NO3)3 and Cu(NO3)2, the other raw materials and steps are the same as in Example 1; lignin-derived carbon without FeN4 / CuN4 site modification is obtained.

[0044] Comparative Example 4 A lignin-based bifunctional oxygen electrode catalyst is prepared by means of: the difference from Example 1 is that: in S1, 1 g of lignin sulfonate, 4 g of NaCl, and 2 g of melamine are weighed and dissolved in (25 mL) deionized water, 1.0 mmol of Fe(NO3)3 is added, and the mixture is stirred on a magnetic stirrer for 12 h. After filtration, a precursor solution is obtained.

[0045] That is, Cu element is replaced with an equimolar amount of Fe element, and other raw materials and steps are the same as in Example 1; FeN4 coupled Fe atom cluster site modified lignin-derived carbon is obtained; compared with Comparative Example 1, the catalyst is changed from FeN4 site modified lignin-derived carbon to FeN4 coupled Fe atom cluster site modified lignin-derived carbon.

[0046] Comparative Example 5 A lignin-based carbon-based bifunctional oxygen electrode catalyst is prepared in a method that differs from that in Example 1 in that: in S2, the precursor solution is frozen to -18°C and then dehydrated at -50°C for 48 hours in a low-temperature vacuum freezer to obtain a lignin-based self-assembled precursor.

[0047] That is, freezing is carried out at a temperature higher than the ultra-low temperature caused by liquid nitrogen, and other raw materials and steps are the same as in Example 1.

[0048] Comparative Example 6 A mixture of commercial Pt / C and RuO2 was prepared in a Pt / Ru molar ratio of 1:1 to serve as a bifunctional electrocatalyst.

[0049] Test case The activity and selectivity of the lignin-derived carbon-based bifunctional oxygen electrode catalysts prepared in different examples and comparative examples for electrocatalytic ORR as a function of applied potential were tested using a rotating ring disk electrode. The tests were performed using a PINE 636A testing system (USA). The test conditions were: room temperature and atmospheric pressure. O2 was introduced into the electrolyte beforehand to saturate the dissolved oxygen concentration. The polarization curves of the lignin-derived carbon-supported atomic sites coupled to atomic clusters prepared in different examples and the comparative examples for electrocatalytic OER were tested using an electrochemical workstation. The tests were performed using a Bio-Logic VSP-300 multichannel electrochemical workstation. The test conditions were: room temperature and atmospheric pressure.

[0050] The results are as follows Figure 3 As shown, where, Figure 3 (A) in the text represents the catalyst 4e. - Performance data of the ORR reaction: Example 1 showed the best ORR reaction activity, with its half-wave potential (E) 1 / 2 =0.822 V) and limiting current density (5.04 mA cm⁻¹) -2 It is superior to Example 2 (E) 1 / 2 =0.74 V, J L =5.31 mA cm -2 Comparative Example 1 (E) 1 / 2 =0.73 V, J L =3.95 mA cm -2 Comparative Example 2 (E) 1 / 2 =0.67 V, J L =3.06 mA cm -2 Comparative Example 3 (E) 1 / 2 =0.71 V, J L =1.06 mA cm -2 Comparative Example 4 (E) 1 / 2 =0.64 V, J L =2.60 mA cm -2 ) and Comparative Example 5 (E 1 / 2 =0.55 V, J L =0.54 mA cm -2 ), even superior to commercial Pt / C (E) as a comparison ratio of 6. 1 / 2 =0.53 V, J L =4.44 mA cm -2 ); Figure 3 (B) in the figure represents the performance data of the catalytic OER reaction; Example 1 requires only a low overpotential of 309 mV to achieve 10 mA cm⁻¹. -2The current density is superior to that of Example 2 (350 mV), Comparative Example 1 (370 mV), Comparative Example 2 (380 mV), Comparative Example 3 (380 mV), Comparative Example 4 (380 mV) and Comparative Example 5 (400 mV), and even superior to commercial RuO2 (317 mV) as Comparative Example 6.

[0051] Furthermore, the bifunctional electrocatalytic activity of ORR and OER can be evaluated by the value of the potential difference ΔE, such as... Figure 4 As shown, in Example 1 The E value was the smallest, at 0.717 V, which was better than the commercial RuO2 used as comparative example 6. E value is 0.794 V) and any other comparative examples.

[0052] Example 4 The application of lignin-carbon-based bifunctional oxygen electrode catalysts in zinc-air batteries is specifically as follows: An air electrode for a zinc-air battery is prepared using the aforementioned lignin-carbon-based bifunctional oxygen electrode catalyst. This includes cutting hydrophobic carbon paper into 1cm × 1cm pieces, sequentially ultrasonically treating them with deionized water, ethanol, acetone, and isopropanol, and then drying them for pretreatment. A catalyst slurry is prepared by mixing 5 mg of lignin-carbon-based bifunctional oxygen electrode catalyst powder, 485 μL of anhydrous ethanol, 485 μL of water, and 30 μL of Nafion solution, followed by ultrasonication. The catalyst slurry is then drop-coated onto the pretreated hydrophobic carbon paper, with a bifunctional catalyst loading of 1 mg / cm². 2 The air electrode is obtained by naturally drying it at room temperature.

[0053] The bifunctional catalyst powders mentioned above are selected from Example 1 or Comparative Example 6.

[0054] Test results are as follows Figure 5 As shown, where, Figure 5 (A) in the diagram is the open-circuit potential of the battery, which shows that the battery has a high energy density and that the oxygen reduction reaction at the positive electrode is thermodynamically very favorable. Figure 5 (B) shows the discharge polarization curve and the corresponding power density curve, indicating that the zinc-air battery assembled using Example 1 as the air electrode catalyst exhibits a higher peak power density. Figure 5 (C) in the figure represents the charge-discharge cycle curve, which shows that the zinc-air battery assembled using Example 1 as the air electrode catalyst can maintain a stable charge-discharge voltage during long-term and repeated use, indicating that the battery has a good lifespan. It can be seen that the zinc-air battery assembled based on Example 1 exhibits superior performance in terms of open circuit potential, peak power density, and cycle stability.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lignin-based carbon-based bifunctional oxygen electrode catalyst, characterized in that, Includes the following steps: S1. Add lignin, sodium chloride and nitrogen source to water at a mass ratio of 1:(3~5):(1.5~2.5); add two of copper source, iron source and nickel source at a ratio of 0.3~0.5mmol / g of a single metal element to lignin, and dissolve to obtain a precursor solution. S2. Freeze the precursor solution to -200~-150℃ and dehydrate to obtain a lignin-based self-assembled precursor; S3. The lignin-based self-assembled precursor is processed into powder and then pyrolyzed at 750~850℃ in a protective atmosphere. S4. The pyrolysis product is acid-leached, then washed and dried to obtain the lignin-carbon-based bifunctional oxygen electrode catalyst.

2. The preparation method of the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, In S1, lignin includes one or more of lignin sulfonate, alkali lignin, and enzymatically hydrolyzed lignin, with a lignin concentration of 0.5~1.5 g / mL; the nitrogen source includes one or more of melamine and urea.

3. The method for preparing the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, In S1, the copper source includes one or more of copper nitrate, copper chloride, and copper sulfate; the iron source includes one or more of ferric nitrate, ferrous nitrate, and ferric chloride; and the nickel source includes one or more of nickel nitrate, nickel chloride, and nickel sulfate.

4. The method for preparing the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, In S1, the method for obtaining the precursor solution includes: magnetic stirring for 12-14 hours.

5. The preparation method of the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, In S2, the dehydration method includes: vacuum freeze drying for 48~60 hours.

6. The method for preparing the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, In S3, the heating rate is 5~10℃ / min, and the pyrolysis time is 4~6h.

7. The method for preparing the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, In S3, the protective atmosphere is either nitrogen or argon.

8. The method for preparing the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 1, characterized in that, The acid leaching method includes immersing the sample in a 1M H2SO4 solution for 12-14 hours.

9. A lignin-carbon-based bifunctional oxygen electrode catalyst prepared by a method according to any one of claims 1-8.

10. The application of the lignin-carbon-based bifunctional oxygen electrode catalyst as described in claim 9 in a rechargeable zinc-air battery, characterized in that, The lignin-based bifunctional oxygen electrode catalyst described above is loaded onto the surface of the air electrode.

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