Mesoporous / macroporous three-dimensional graphene-like structure carbon-based electrochemical oxygen catalyst and preparation method thereof

Abstract

The application discloses a kind of meso-macroporous three-dimensional graphene structure carbon-based electrochemical oxygen catalyst, catalyst is transition metal and sulfur nitrogen co-doped meso-macroporous three-dimensional graphene structure, carbon has clear graphite strip, transition metal is in the form of single atom distribution constitutes M-Nx Active center, transition metal single atom is dispersed on the surface of three-dimensional graphene carbon matrix, the specific surface area of catalyst is 300-600, average pore volume is 0.5-1.5, pore size size distribution is 2-200 nm.The catalyst of the application is composed of transition metal, carbon, nitrogen and sulfur, the material transition metal is in the form of single atom distribution constitutes M-Nx Active center, with mesoporous and macroporous three-dimensional graphene structure and highly graphitized.Simultaneously, the introduction of S makes the material have more surface defects, good conductivity, high bifunctional oxygen electrocatalytic activity, good cycle stability and other characteristics.Transition metal is abundant in reserves, low in price, simple in preparation method, can be mass-produced, and can be widely used in zinc-oxygen battery material field.

Description

Technical Field

[0001] This invention relates to the field of electrochemical new energy catalytic materials, and in particular to a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst and its preparation method. Background Technology

[0002] Modern society urgently needs to develop efficient, safe, and economical energy storage and conversion devices for electric vehicles, portable electronic devices, and fixed power grid applications. Zinc-oxygen rechargeable batteries, with their advantages of low cost, good safety, high theoretical energy density, and environmental friendliness, have become a promising energy storage technology in recent years. However, the electrochemical performance of zinc-oxygen batteries is still unsatisfactory at present, suffering from low actual energy density, large battery polarization, and poor cycle stability. The sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as the poor stability of the air cathode catalyst, are the main reasons for these limitations. Currently, highly efficient bifunctional oxygen catalysts still largely rely on noble metal-based catalysts such as platinum and iridium, but their high cost and unbalanced bifunctional ORR / OER catalytic performance limit their large-scale application. Therefore, the design and development of low-cost, highly active bifunctional oxygen electrocatalysts is urgently needed.

[0003] In recent years, various materials have been proposed as alternatives to Pt-based and Ir-based electrocatalysts to improve ORR and OER, including metal-free heteroatom-doped carbon and transition metal-modified carbon [J. Electroanal. Chem. 998 (2025)119516; Adv. Funct. Mater. (2025 Early Access) e202525448]. Currently, single-atom catalysts based on transition metals (Fe, Co, Mn and Cu) are considered a promising alternative due to their near 100% atom utilization, tunable electronic properties, competitive performance, and significantly reduced battery costs [Nat. Catal.4(7) (2021) 615-622]. Unfortunately, the M-Nx sites have a strong adsorption strength for oxygen intermediates, making desorption difficult and limiting their overall ORR and OER activities [Adv. Mater. 34(7) (2022) 2107421; Angew.Chem. Int. Edit. 60(6) (2021) 3212-3221].

[0004] Studies have shown that by designing the microstructure of catalysts and adjusting the electronic structure of the M-Nx sites, the adsorption energy of catalysts for reaction intermediates can be effectively optimized, the reaction mechanism can be adjusted, the electrochemical reaction energy barrier can be reduced, and the ORR / OER activity can be improved. Currently, commonly used methods for adjusting the electronic structure include simultaneously introducing other weakly electronegative heteroatoms (S, P, B, etc.) and introducing a second metal to construct bimetallic sites to optimize the d-band center of the active site. Ji et al. [Adv. Mater. 36(44)(2024) 2410121] introduced phosphorus atoms into the second coordination field of the central metal site iron (Fe-N4), breaking the local symmetry of the electron distribution. This gave it a suitable binding strength with the oxygen intermediate. Under alkaline conditions, the activity and durability of this catalyst have been improved to unprecedented levels. Qin et al. [J. Am. Chem. Soc. 144(5) (2022) 2197-2207] proposed that the electronic configuration of the Ru central site can be tuned by bonding the S anion to the N atom of the second coordination layer of the Ru center. The S anion-coordinated Ru-NC catalyst not only has good ORR activity, but also excellent long-term stability, which is superior to commercial Pt / C and recently reported single-atom catalysts. Liu et al. [Adv. Mater. 34(7) (2022) 2107421] proposed a pre-constrained metal twinning strategy to prepare bimetallic single-atom catalysts. The electrocatalyst exhibits excellent ORR / OER activity. Density functional theory (DFT) calculations show that the synergistic effect of adjacent Co and Fe metals optimizes the d-segment center position of the Co-N4 / Fe-N4 metal center, balancing the The adsorption free energy of the intermediate is improved, thereby enhancing the oxygen electrocatalytic activity. Sun et al. [Nano Res. 17(8) (2024) 6841-6848] reported a highly active CoMn-N / SC electrocatalyst. DFT studies showed that the introduction of Mn and S broke the electronic symmetry of the three-dimensional orbitals of Co, causing the d-band center of Co to shift downward, optimizing the adsorption and desorption of the O intermediate, thereby improving the ORR activity.

[0005] Besides the regulation of electronic structure, a favorable pore structure is also crucial for improving the electrocatalytic performance of catalysts. However, according to previous studies, although MOF-, COF- and other derived catalyst materials have high specific surface areas, they retain a large number of microporous structures, which are detrimental to the accessibility of active sites and limit the contact between reactants and active sites.

[0006] Therefore, it is urgent to find and explore new methods for preparing non-precious metal catalysts to simultaneously adjust the electronic and pore structures of the catalysts in order to promote the development of zinc-oxygen batteries.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst, thereby overcoming the disadvantages of carbon-based catalysts, such as the presence of a large number of microporous structures, unfavorable accessibility of active sites, and limited contact between reactants and active sites.

[0009] Another objective of this invention is to provide a method for preparing a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst.

[0010] To achieve the above objectives, this invention provides a mesoporous / macroporous three-dimensional graphene-like carbon-based electrochemical oxygen catalyst. The catalyst is a mesoporous / macroporous three-dimensional graphene-like structure co-doped with transition metals and sulfur and nitrogen, exhibiting clear graphite striations. The transition metals are distributed in single-atom form, constituting M-Nx active centers. These transition metal single atoms are dispersed on the surface of the three-dimensional graphene-like carbon matrix. The specific surface area of ​​the catalyst is 300-600 nm. The average pore volume is 0.5-1.5. The pore size distribution ranges from 2 to 200 nm;

[0011] A method for preparing the above-mentioned mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst includes the following steps:

[0012] (1) Place aniline organic monomers in an organic solvent, stir to dissolve, add transition metal inorganic salts in proportion, stir to react, and obtain a suspension of transition metal-nitrogen coordination polymers;

[0013] (2) A certain proportion of sodium chloride and polysaccharide were added to the suspension of the transition metal-nitrogen coordination polymer obtained after the reaction in step (1), and the mixture was ground to obtain a mixture;

[0014] (3) The powder obtained by drying and grinding the mixture obtained in step (2) is heated under a protective atmosphere to carry out the first thermal pyrolysis, cooled to room temperature, and the resulting product is acid washed and dried.

[0015] (4) Mix the product obtained after drying in step (3) with sulfur-containing organic matter, grind it, and obtain a mixture;

[0016] (5) The mixture obtained in step (4) is heated under a protective atmosphere to carry out a second thermal pyrolysis, thereby obtaining a carbon-based electrochemical oxygen catalyst with a transition metal single atom embedded with nitrogen and sulfur co-doped mesoporous / macroporous three-dimensional graphene structure.

[0017] Preferably, in the above technical solution, step (1) of the aniline organic monomer includes one or more of aniline, benzidine, 3,3'-diaminobenzidine, polyaniline, aniline sulfate, 2,2'-diaminobenzidine, 3,3'-dihydroxybenzidine, and 3,3'-dimethoxybenzidine.

[0018] Preferably, in the above technical solution, the organic solvent includes one or more of anhydrous ethanol, methanol, ethylene glycol, toluene, isopropanol, benzene, pyridine, or n-butanol.

[0019] Preferably, in the above technical solution, the transition metal inorganic salt in step (1) includes one or more of the following: nitrate, chloride, sulfate or acetate containing cobalt ions, iron ions, manganese ions, zinc ions, copper ions or nickel ions; the molar ratio of added amino group and transition metal ion is 1-3:1-3, and the reaction is carried out at room temperature for 8-12 hours.

[0020] Preferably, in the above technical solution, the polysaccharide in step (2) includes one or more of chitosan, glucose, glycogen, starch, cellulose, sodium alginate, and alginic acid; the mass ratio of aniline organic monomer to polysaccharide is 1:2-20, the mass ratio of aniline monomer to sodium chloride is 1:10-60, and grinding is carried out for 6-12 hours.

[0021] Preferably, in the above technical solution, the heating in steps (3) and (5) is heating to 700-1200 ℃ and holding for 1-2 hours, with a heating rate of 5-10 ℃ / min; the protective atmosphere is one of argon, nitrogen, helium or ammonia atmosphere.

[0022] Preferably, in the above technical solution, the acid washing and drying in step (3) is to soak the sample in 0.1-1 mol / L sulfuric acid solution or 0.2-2 mol / L hydrochloric acid at a temperature of 80-100℃ for 10-20 hours, filter and wash with water multiple times, and then vacuum dry the sample at 80-120℃ for 10-24 hours.

[0023] Preferably, in the above technical solution, the sulfur-containing organic compound in step (4) includes one or more of 2-aminodiphenyl sulfide, thiourea, 3-pyridinethiourea, N-methylthiourea, 2,5-dithiourea, 2,2'-diaminodiphenyl sulfide, 2,2'-diaminodiphenyl disulfide or 2-aminobenzothiazole.

[0024] Based on the above-mentioned mesoporous / macroporous three-dimensional graphene structure carbon-based electrochemical oxygen catalyst, it is applied to the zinc-oxygen battery cathode bifunctional oxygen catalyst.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention relates to a mesoporous / macroporous three-dimensional graphene-like carbon-based electrochemical oxygen catalyst and its preparation method. The catalyst is composed of transition metals, carbon, nitrogen, and sulfur. The transition metals in this material are distributed in single-atom form to constitute M-Nx active centers, possessing a mesoporous and macroporous three-dimensional graphene-like structure and being highly graphitized. Simultaneously, the introduction of sulfur gives the material numerous surface defects, good electrical conductivity, high bifunctional oxygen-electric (oxygen reduction and oxygen evolution reactions) catalytic activity, and good cycle stability. Furthermore, transition metals are abundant and inexpensive; the preparation method is simple and can be mass-produced, enabling its widespread application in the field of zinc-oxygen battery materials. Attached Figure Description

[0026] Figure 1 These are the nitrogen adsorption-desorption isotherms and pore size distribution diagrams of the carbon materials prepared by the method of this invention.

[0027] Figure 2 This is the XRD pattern of the cobalt single-atom embedded nitrogen-sulfur co-doped carbon material prepared by the method of Example 1 of this invention.

[0028] Figure 3 These are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the cobalt single-atom embedded nitrogen-sulfur co-doped carbon material prepared by the method of Example 1 of this invention.

[0029] Figure 4 The polarization curve is the oxygen-electro-catalyzed bifunctional reaction in 0.1M potassium hydroxide saturated with oxygen, of the cobalt single-atom embedded nitrogen-sulfur co-doped carbon material prepared by the method of Example 1 of this invention.

[0030] Figure 5 The charge-discharge curves are shown for the cobalt single-atom embedded nitrogen-sulfur co-doped carbon material prepared by the method of Example 1 of this invention, when used as the cathode catalyst of a zinc-oxygen battery. Detailed Implementation

[0031] The following detailed description of specific embodiments is provided in conjunction with the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0032] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0033] Unless otherwise specified, all raw materials and reagents used in the examples are commercially available. Example 1

[0034] A method for preparing a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst, the specific operation steps of which are as follows:

[0035] (1) Place 10 mmol of 3,3'-diaminobenzidine into a 150 mL flat-bottomed flask, add 60 mL of anhydrous ethanol to the flask, and stir until the 3,3'-diaminobenzidine dissolves. Add the ethanol according to a molar ratio of amino to Co of 2:1. 5 mmol, stirred at room temperature for 12 hours;

[0036] (2) Transfer the turbid liquid obtained after the reaction in step (1) to a ball mill jar, add 0.5 mol of sodium chloride and 10 g of chitosan, ball mill at 500 rpm for 6 hours, dry and grind;

[0037] (3) Place the powder obtained after drying and grinding in step (2) into a high-temperature tube furnace, introduce nitrogen gas, purge the air from the furnace, and heat it to 800 / 900 / 1000 / 1100 ℃ respectively at a heating rate of 5℃ / min, and hold for 2 hours for the first thermal pyrolysis. Allow it to cool naturally to room temperature to obtain product comparison samples at the four temperatures. Grind the samples obtained from the thermal pyrolysis thoroughly, and place the resulting material into 500 ml of 0.5 mol / L [solution / concentration]. The sample was immersed in the solution at 80 °C for 12 hours, filtered, and washed with deionized water until the filtrate was neutral. The sample was then dried in a vacuum drying oven at 80 °C for 24 hours.

[0038] (4) Place 0.25 g of the sample obtained after drying in step (3) into a mortar, add 0.25 g of 2,5-dithiourea, and grind evenly;

[0039] (5) Place the mixture obtained in step (4) in a tube furnace again, heat it under nitrogen to 800 / 900 / 1000 / 1100 ℃ and keep it at that temperature for 2 hours for a second thermal decomposition, and then cool it naturally to room temperature to obtain cobalt single-atom embedded nitrogen-sulfur co-doped meso / macroporous three-dimensional graphene-like carbon materials after decomposition at different temperatures, namely Co-N,SC electrochemical oxygen catalyst. Example 2

[0040] A method for preparing a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst, the specific operation steps of which are as follows:

[0041] (1) Place 10 mmol of 2,2'-diaminobenzidine into a 150 mL flat-bottomed flask, add 60 mL of anhydrous ethanol to the flask, stir until benzidine dissolves, and add amino to Fe at a molar ratio of 2:1. 5 mmol, stirred at room temperature for 12 hours;

[0042] (2) Transfer the turbid liquid obtained after the reaction in step (1) to a ball mill jar, add 0.5 mol of sodium chloride and 12 g of sodium alginate, ball mill at 400 rpm for 6 hours, dry and grind;

[0043] (3) Place the powder obtained after drying and grinding in step (2) into a high-temperature tube furnace, introduce nitrogen gas, purge the air from the furnace, and heat it to 800 / 900 / 1000 / 1100 ℃ respectively at a heating rate of 5 ℃ / min, and hold for 2 hours for the first thermal pyrolysis. Allow it to cool naturally to room temperature to obtain product comparison samples at the four temperatures. Grind the samples obtained from the thermal pyrolysis thoroughly, and place the resulting material into 500 mL of 0.5 mol / L [solution / concentration]. The sample was immersed in the solution at 80 °C for 12 hours, filtered, and washed with deionized water until the filtrate was neutral. The sample was then dried in a vacuum drying oven at 80 °C for 24 hours.

[0044] (4) Place 0.25 g of the sample obtained after drying in step (3) into a mortar, add 0.25 g of thiourea, and grind evenly;

[0045] (5) Place the mixture obtained in step (4) in a tube furnace again, heat it under nitrogen to 800 / 900 / 1000 / 1100 ℃ and keep it at that temperature for 2 hours for a second thermal decomposition, and then cool it naturally to room temperature to obtain iron single atom embedded nitrogen sulfur co-doped meso / macroporous three-dimensional graphene-like carbon materials after decomposition at different temperatures, namely Fe-N,SC electrochemical oxygen catalyst. Example 3

[0046] A method for preparing a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst, the specific operation steps of which are as follows:

[0047] (1) Place 10 mmol of benzidine into a 150 mL flat-bottomed flask, add 60 mL of anhydrous ethanol to the flask, stir until the benzidine dissolves, and add the ethanol according to a molar ratio of amino to Fe of 2:1. 10 mmol, stirred at room temperature for 12 hours;

[0048] (2) Transfer the turbid liquid obtained after the reaction in step (1) to a ball mill jar, add 0.5 mol of sodium chloride and 10 g of cellulose, ball mill at 400 rpm for 6 hours, dry and grind;

[0049] (3) Place the powder obtained after drying and grinding in step (2) into a high-temperature tube furnace, introduce nitrogen gas, purge the air in the furnace, and heat it to 800 / 900 / 1000 / 1100 ℃ respectively at a heating rate of 5 ℃ / min and hold for 2 hours for the first thermal pyrolysis. Cool it naturally to room temperature to obtain product comparison samples at four temperatures. Grind the samples obtained by thermal pyrolysis thoroughly, put the obtained substance into 500 ml of 0.5 mol / L H2SO4 solution, and soak it at 80 ℃ for 12 hours. After filtration and washing with deionized water until the filtrate is neutral, dry the obtained sample in a vacuum drying oven at 80 ℃ for 24 hours.

[0050] (4) Place 0.25 g of the sample obtained after drying in step (3) into a mortar, add 0.25 g of 2,2'-diaminodiphenyl sulfide, and grind evenly;

[0051] (5) Place the mixture obtained in step (4) in a tube furnace again, heat it under nitrogen to 800 / 900 / 1000 / 1100 ℃ and keep it at that temperature for 2 hours for a second thermal decomposition, and then cool it naturally to room temperature to obtain manganese single atom embedded nitrogen sulfur co-doped meso / macroporous three-dimensional graphene-like carbon materials after decomposition at different temperatures, namely Mn-N,SC electrochemical oxygen catalyst. Detection

[0052] The Co-N and SC samples prepared in Example 1 were used as bifunctional oxygen catalysts in half-cells and full-cells (zinc-oxygen cells), respectively, and their catalytic activity was tested.

[0053] Take 5 mg of the prepared Co-N,SC material (or commercial Pt / C) and add 1 mL of 0.1 wt% perfluorosulfonic acid ethanol solution. Disperse the solution ultrasonically in ice water for 20 min to obtain an ink-like slurry. Take 20 μl of the slurry and drop it evenly onto the surface of a ring-shaped electrode (5.6 mm in diameter). Allow it to air dry for 1 hour. Perform electrochemical tests using a three-electrode system, with a reversible hydrogen electrode (RHE) as the reference electrode and a graphite rod as the counter electrode. The electrolyte is a 0.1 M potassium hydroxide solution. First, at 100... Activation was performed at a scan rate within the potential range of 0-1.1V (vs RHE) until the CV curves stably overlapped. Under saturated oxygen conditions, the scan rate was 5. The oxygen reduction (ORR) polarization curve was tested at a scanning potential range of 0–1.1 V (vs RHE) and a rotation speed of 1600 rpm. ORR background polarization curves were also tested under the same settings in saturated nitrogen. Under saturated oxygen, the scan rate was 5 mV·s. -1 The oxygen evolution (OER) polarization curve was tested at a scanning potential range of 1.2-1.8V vs RHE and a rotation speed of 1200-1600 rpm.

[0054] The zinc-oxygen battery was tested using a two-electrode system, with a zinc sheet as the anode and carbon paper loaded with the aforementioned Co-N,SC catalyst as the cathode. Charge-discharge tests were conducted, with the discharge voltage range being open circuit voltage ~0.3 V and the charging voltage range being open circuit voltage ~2.8 V.

[0055] Figure 1 These are the nitrogen adsorption-desorption isotherms and pore size distribution diagrams of Co-N,SC, Fe-N,SC, and Mn-N,SC materials obtained in Examples 1 / 2 / 3 at a pyrolysis temperature of 900 °C. The nitrogen adsorption-desorption test results show that the specific surface areas of the Co-N,SC, Fe-N,SC, and Mn-N,SC samples are 563, 527, and 489, respectively. All three carbon matrices exhibit a hierarchical pore structure consisting of mesoporous and macroporous components. The pore volume ranges from 0.5 to 1.5 pores. The pore size distribution ranges from 2 to 200 nm. This indicates that the carbon material obtained in this invention has abundant mesopores / macropores, providing a good pathway for the transfer of oxygen intermediates during electrocatalysis.

[0056] Figure 2 The image shows the XRD pattern of the Co-N,SC material obtained in Example 1 at a pyrolysis temperature of 900 °C. The image shows a strong graphitized carbon peak (PDF card PDF#41-1487) and no diffraction peak of metallic cobalt, indicating that the single-atom Co-N,SC material was successfully prepared.

[0057] Figure 3 These are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the Co-N,SC material obtained in Example 1 at a pyrolysis temperature of 900 °C. From SEM image (a) and TEM image (b), it can be seen that the material consists of interwoven nanosheets with a three-dimensional graphene-like structure. From the high-resolution transmission electron microscopy (HRTEM) image (c), it can be seen that the Co-N,SC carbon material prepared in this invention has clear graphite striations of carbon with a lattice spacing of approximately 0.34 nm, indicating good graphitization. From image (d), it can be seen that the surface of the graphitized carbon has single-atom dispersed metallic Co.

[0058] Figure 4 The polarization curves for oxygen reduction and oxygen evolution reactions of the Co-N,SC material obtained in Example 1 at a pyrolysis temperature of 900 °C were obtained using a three-electrode system. The onset potential of oxygen reduction was approximately 1.05 V, and the half-wave potential was 0.91 V, significantly better than that of commercial Pt / C catalysts. The oxygen evolution overpotential was 293 mV, significantly better than that of commercial iridium oxide catalysts. Simultaneously, the potential difference of the oxygen-electrochemical bifunctional reaction of the Co-N,SC material was also shown. The value of 0.63 V is significantly better than The value of 0.76V indicates that the material has a good bifunctional catalytic effect on oxygen reduction and oxygen evolution.

[0059] Figure 5 This is the charge-discharge curve of a self-assembled zinc-oxygen battery using Co-N,SC material obtained at a pyrolysis temperature of 900 °C as the cathode catalyst, as shown in Example 1. The curve is displayed at a charge-discharge current density of 100... The voltage difference at that time was 1.34 V, which is significantly better than that of commercial products. (1.49 V) Mixed catalyst. Furthermore, the zinc-oxygen battery assembled with this catalyst material achieves an energy density as high as 871.41 kJ / L. .

[0060] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst, characterized in that, The catalyst is a mesoporous / macroporous three-dimensional graphene-like structure co-doped with transition metals and sulfur and nitrogen, exhibiting clear graphite striations. The transition metals are distributed in single-atom form, constituting M-Nx active centers. These transition metal single atoms are dispersed on the surface of the three-dimensional graphene-like carbon matrix. The specific surface area of ​​the catalyst is 300-700. The pore volume is 0.5-1.

5. The pore size distribution ranges from 2 to 200 nm.

2. A method for preparing a mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst as described in claim 1, characterized in that, Includes the following steps: (1) Take aniline organic monomers and place them in an organic solvent, stir to dissolve, add transition metal inorganic salts in proportion, stir to react, and obtain a suspension of transition metal-nitrogen coordination polymers; (2) A certain proportion of sodium chloride and polysaccharide were added to the suspension of the transition metal-nitrogen coordination polymer obtained after the reaction in step (1), and the mixture was ground to obtain a mixture; (3) The powder obtained by drying and grinding the mixture obtained in step (2) is heated under a protective atmosphere to carry out the first thermal pyrolysis, cooled to room temperature, and the resulting product is acid washed and dried. (4) Mix the product obtained after drying in step (3) with sulfur-containing organic matter, grind it, and obtain a mixture; (5) The mixture obtained in step (4) is heated under a protective atmosphere to carry out a second thermal pyrolysis, thereby obtaining a carbon-based electrochemical oxygen catalyst with a transition metal single atom embedded with nitrogen and sulfur co-doped mesoporous / macroporous three-dimensional graphene structure.

3. The preparation method according to claim 2, characterized in that, Step (1) Aniline organic monomers include one or more of aniline, benzidine, 3,3'-diaminobenzidine, polyaniline, aniline sulfate, 2,2'-diaminobenzidine, 3,3'-dihydroxybenzidine, and 3,3'-dimethoxybenzidine.

4. The preparation method according to claim 2, characterized in that, The organic solvent includes one or more of anhydrous ethanol, methanol, ethylene glycol, toluene, isopropanol, benzene, pyridine, or n-butanol.

5. The preparation method according to claim 2, characterized in that, In step (1), the transition metal inorganic salt includes one or more of the following: nitrates, chlorides, sulfates or acetates containing cobalt ions, iron ions, manganese ions, zinc ions, copper ions or nickel ions; the molar ratio of added amino groups and transition metal ions is 1-3:1-3, and the reaction is carried out at room temperature for 8-12 hours.

6. The preparation method according to claim 2, characterized in that, Step (2) The polysaccharide includes one or more of chitosan, glucose, glycogen, starch, cellulose, sodium alginate, and alginic acid; the mass ratio of aniline organic monomer to polysaccharide is 1:2-20, the mass ratio of aniline monomer to sodium chloride is 1:10-60, and grinding is carried out for 6-12 hours.

7. The preparation method according to claim 2, characterized in that, The heating in steps (3) and (5) is 700-1200 ℃ and held for 1-2 hours, with a heating rate of 5-10℃ / min; the protective atmosphere is one of argon, nitrogen, helium or ammonia.

8. The preparation method according to claim 2, characterized in that, The acid washing and drying in step (3) are as follows: soaking in 0.1-1 mol / L sulfuric acid solution or 0.2-2 mol / L hydrochloric acid at a temperature of 80-100℃ for 10-20 hours, followed by filtration and multiple water washings. The sample obtained after washing is then vacuum dried at 80-120℃ for 10-24 hours.

9. The preparation method according to claim 2, characterized in that, Step (4) The sulfur-containing organic compounds include one or more of 2-aminodiphenyl sulfide, thiourea, 3-pyridinethiourea, N-methylthiourea, 2,5-dithiodiurea, 2,2'-diaminodiphenyl sulfide, 2,2'-diaminodiphenyl disulfide or 2-aminobenzothiazole.

10. The mesoporous / macroporous three-dimensional graphene-structured carbon-based electrochemical oxygen catalyst according to any one of claims 1-9 is applied to the zinc-oxygen battery cathode bifunctional oxygen catalyst.

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