A double-carbon-supported manganese-based bifunctional electrode catalyst and its preparation method and application

Abstract

The present invention relates to a dual-carbon-supported manganese-based bifunctional electrode catalyst, its preparation method, and application. The catalyst uses nitrogen-phosphorus-doped porous carbon (NPAC) and protonated carbon nitride (p-C3N4) as the dual-carbon support, and α-MnO2 as the active agent, and is obtained through hydrothermal self-assembly and solid-phase sintering. The present invention utilizes the layered porous structure and high specific surface area characteristics of the dual-carbon support to form an electrochemical heterogeneous interface composed of a rich carbon support and nanosheets. This facilitates sufficient contact of the active sites with the reactants, while enriching the electron density at the interface and significantly improving the electrocatalytic performance. The zinc-air battery assembled from the catalyst has excellent discharge power density and long-term charge and discharge stability, and has good market application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and in particular relates to a double-carbon-supported manganese-based bifunctional electrode catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Zinc-air batteries (Zn-air batteries) are considered promising candidates for next-generation electrochemical energy conversion devices due to their high specific energy density, widespread availability of zinc resources, and use of non-flammable aqueous electrolytes. However, the development of Zn-air batteries remains limited by the lack of efficient bifunctional air electrodes to enhance the reaction rate of the electrocatalytic oxygen conversion process. Precious metal catalysts Pt / C and RuO2 exhibit high catalytic activity for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively. However, the scarcity and high cost of these precious metal catalysts, particularly their poor stability, have significantly hindered their large-scale application in Zn-air batteries. α-MnO2, with its cost-effectiveness and tunable electrochemical properties, is an ideal candidate for low-cost air electrodes. The MnO6 octahedron in its crystal structure serves as the basic building block for the tunnel-like crystal structure, and the multivalent Mn sites also contribute to its excellent catalytic activity for the electrocatalytic oxygen conversion process.

[0003] In order to prepare efficient air electrodes, the dual functionality of α-MnO2 needs to be further optimized. g Filling theory, when the transition metal e g Transition metal oxides achieve excellent electrocatalytic performance when the orbital occupancy number approaches 1. Specifically, in α-MnO2, trivalent Mn sites exhibit superior bifunctional activity compared to divalent and tetravalent Mn sites. Therefore, bifunctionality can be enhanced by stimulating trivalent Mn sites in α-MnO2. Studies have shown that strategies such as heterostructure construction, anion and cation doping, and morphology control can increase the number of trivalent Mn sites. In addition to these methods, developing simpler activation strategies is essential to achieve high-performance and cost-effective α-MnO2-based electrocatalysts. In addition to these methods, oxygen vacancy engineering is an effective and cost-effective approach to modulating the electrochemical properties of metal oxides. Oxygen atoms on the surface of metal oxides have low energy levels and are easily detached, forming crystal defects. These defects serve as oxygen vacancies that host electrons and form adjacent trivalent Mn sites. Therefore, accelerating molecular transformations by generating trivalent Mn catalytic centers through oxygen vacancies can significantly improve reaction efficiency. However, due to the asymmetric occupation of electrons in the d orbitals of the trivalent Mn sites, the axial tension in the MnO6 octahedron caused by the Jahn-Teller effect changes the Mn-O distance, which in turn causes severe crystal distortion, making it difficult to avoid structural collapse and the accompanying deterioration of activity during long-term catalysis. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a double-carbon supported manganese-based bifunctional electrode catalyst and its preparation method and application, so as to overcome the technical problems such as poor bifunctional activity, insufficient conductivity and poor durability of α-MnO2.

[0005] The present invention provides a dual-carbon supported manganese-based bifunctional electrode catalyst, wherein the catalyst uses nitrogen and phosphorus doped porous carbon NPAC and protonated carbon nitride p-C3N4 as a dual-carbon support, uses α-MnO2 as an active body, and is obtained by hydrothermal self-assembly and solid-phase sintering.

[0006] Preferably, the morphology of the α-MnO2 is nanorods.

[0007] The present invention also provides a method for preparing a dual-carbon supported manganese-based bifunctional electrode catalyst, comprising the following steps:

[0008] (1) Wood powder is mixed with sodium citrate, melamine, and ammonium dihydrogen phosphate, ball-milled, and then heat-treated in a tube furnace. The mixture is cooled to room temperature and then washed and dried to obtain nitrogen-phosphorus-doped porous carbon (NPAC).

[0009] (2) urea is subjected to heat treatment to obtain carbon nitride, which is then placed in a hydrochloric acid solution for hydrothermal protonation treatment, cooled, washed, and dried to obtain protonated carbon nitride p-C3N4;

[0010] (3) dissolving potassium permanganate in a hydrochloric acid solution, subjecting it to hydrothermal treatment after thorough ultrasonication, washing it by centrifugation, drying it, and then subjecting it to heat treatment in a tube furnace, and cooling it to obtain α-MnO2;

[0011] (4) The NPAC, p-C3N4 and α-MnO2 are dispersed in a mixed solution of water and ethanol for hydrothermal treatment, cooled, washed and dried; finally, the product is solid-phase sintered to obtain a dual-carbon supported manganese-based bifunctional electrode catalyst, denoted as MCC.

[0012] Preferably, the mass ratio of wood powder, sodium citrate, melamine and ammonium dihydrogen phosphate in step (1) is 2-4:5-8:1:1.

[0013] Preferably, the ball milling treatment time in step (1) is 1 to 10 hours, and the rotation speed is 200 to 400 rpm.

[0014] Preferably, the heat treatment temperature in step (1) is 800-1000° C., the heat treatment atmosphere is nitrogen, the heating rate is 5-15° C. / min, and the holding time is 1-5 h.

[0015] Preferably, the washing in step (1) is carried out using nitric acid solution and water, wherein the concentration of the nitric acid solution is 3-5M; and the washing time is 12 to 16 hours.

[0016] Preferably, the drying method in step (1) is vacuum drying at 80-90° C. for 12-16 hours.

[0017] Preferably, the heat treatment temperature in step (2) is 500-600° C., the heat treatment atmosphere is air, the heating rate is 5-10° C. / min, and the holding time is 1-5 h.

[0018] Preferably, the mass volume ratio of carbon nitride to hydrochloric acid solution in step (2) is 1-2 g:100 mL.

[0019] Preferably, the concentration of the hydrochloric acid solution in step (2) is 8 to 10M.

[0020] Preferably, the hydrothermal protonation treatment temperature in step (2) is 100-200° C., and the time is 5-10 h.

[0021] Preferably, the washing in step (2) is performed by water washing; and the drying method is freeze drying.

[0022] Preferably, the mass volume ratio of potassium permanganate to hydrochloric acid solution in step (3) is 1.58-3.16 g:100 mL.

[0023] Preferably, the concentration of the hydrochloric acid solution in step (3) is 1-2M.

[0024] Preferably, the post-ultrasonic hydrothermal treatment parameters in step (3) are a temperature of 150 to 180° C. and a time of 8 to 10 hours.

[0025] Preferably, the centrifugal washing in step (3) is performed by water washing and alcohol washing; and the drying method is vacuum drying at 80-90° C. for 8-10 hours.

[0026] Preferably, the heat treatment temperature in step (3) is 300-400°C, the heat treatment atmosphere is nitrogen, the heating rate is 5-10°C / min, and the holding time is 1-5h.

[0027] Preferably, the mass ratio of NPAC, p-C3N4 and α-MnO2 in step (4) is 5:1 to 2:5.

[0028] Preferably, the volume ratio of water to ethanol in the mixed solution of water and ethanol in step (4) is 1:1; the weight volume of α-MnO2 and the mixed solution of water and ethanol is 10 mg:1~5 mL.

[0029] Preferably, the hydrothermal treatment temperature in step (4) is 100-200° C., and the hydrothermal treatment time is 3-5 hours.

[0030] Preferably, the washing in step (4) is performed by water washing and alcohol washing; and the drying method is vacuum drying at 80-90° C. for 8-10 hours.

[0031] Preferably, the solid phase sintering parameters in step (4) are a temperature of 300-400° C., a nitrogen atmosphere, a heating rate of 5-10° C. / min, and a holding time of 1-5 h.

[0032] The present invention also provides an application of a double-carbon supported manganese-based bifunctional electrode catalyst in a zinc-air battery.

[0033] The present invention combines α-MnO2 with a nanocarbon support to stabilize the crystal structure and induce the formation of oxygen vacancies through catalyst-support interactions. The carbon support enriches the charge distribution on the catalyst surface and can also serve as a highway for electron transport to improve electrocatalytic performance. Through reasonable nano-micro design and close interface contact, the stability and activity in the long-term catalytic process will be improved. The rigid nanostructure will also prevent the catalyst from degrading during the battery cycle. Through a dual-carbon strategy, that is, the interaction between two carbon supports and the combination of metal oxides, the micromorphology and the electron distribution of active Mn sites can be controlled to prepare a bifunctional carbon-supported manganese-based catalyst with high activity and long life.

[0034] Beneficial effects

[0035] (1) The present invention is a ternary carbon-supported manganese-based catalyst that combines two carbon supports with manganese oxide. In order to address the shortcomings of α-MnO2, such as low electronic conductivity, poor catalytic stability, and poor bifunctional catalytic activity, nitrogen-phosphorus-doped porous carbon is used as a supporting support, protonated carbon nitride is used as a structural reinforcement module, and manganese dioxide is used as a catalytically active material to prepare a dual-carbon-supported manganese-based bifunctional electrode catalyst, thereby overcoming the problems of performance degradation caused by poor performance and insufficient stability of manganese dioxide in traditional air electrodes.

[0036] (2) The present invention adopts a hydrothermal assembly method to construct a ternary carbon-supported manganese-based composite material, forming an electrochemical heterogeneous interface composed of a three-dimensional carbon carrier, a two-dimensional nanosheet, and a one-dimensional nanorod. The porous characteristics of the three-dimensional nitrogen-phosphorus doped porous carbon ensure that it has a large specific surface area, which is beneficial to gas transmission during the catalytic reaction and allows it to combine with fully exposed catalytic active sites, thereby promoting the reaction. The two-dimensional protonated carbon nitride nanosheets are combined with the one-dimensional manganese dioxide nanorods to induce the formation of oxygen vacancies and adjacent trivalent Mn sites on the oxide surface, which serve as efficient catalytic active centers to improve the dual-functional charge and discharge performance of the air electrode.

[0037] (3) The present invention effectively combines the dual-carbon support carrier and manganese dioxide nanorods, further enriching the electron density of the electrochemical heterogeneous interface, modulating the intrinsic catalytic performance of the Mn site, helping to alleviate the polarization phenomenon of the material during the reaction process, and improving the mass-charge transfer performance, thereby significantly improving the bifunctional catalytic performance of the air electrode prepared by the present invention.

[0038] (4) The catalyst of the present invention has a half-wave potential of up to 0.88 V in the ORR catalytic process and 10 mA cm in the OER process. -2 The lower potential is 1.64 V. MCC is directly used in zinc-air batteries and exhibits a high performance of 452 mW / cm 2 The peak discharge power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 These are SEM images of the materials prepared in Comparative Example 1(a), Comparative Example 2(b), Comparative Example 3(c), and Example 1(d).

[0040] Figure 2 1 is a comparison diagram of the electron spin resonance (EPR) curves of Example 1 and Comparative Examples 2 and 3.

[0041] Figure 3a The figure is a comparison of the ORR polarization curves of Example 1, Comparative Examples 2 and 3, and Pt / C-RuO2.

[0042] Figure 3b It is a comparison diagram of the OER polarization curves of Example 1, Comparative Examples 2, 3 and Pt / C-RuO2.

[0043] Figure 4 2 is a comparison chart of the discharge power of Example 1, Comparative Example 3 and Pt / C-RuO2. DETAILED DESCRIPTION

[0044] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0045] The micromorphology of the product was determined using a scanning transmission electron microscope (SEM, Hitachi S-4800). Electron spin resonance curves were measured using a Bruker EMX Plus paramagnetic resonance spectrometer. Half-cell performance and battery discharge performance were measured using a Chenhua CHI760 series electrochemical workstation.

[0046] Example 1

[0047] This embodiment provides a method for preparing a dual-carbon supported manganese-based bifunctional electrode catalyst (MCC), comprising the following steps:

[0048] Step 1): Mix 2g of wood powder (waste wood powder may be used) with 5g of sodium citrate, 1g of melamine, and 1g of ammonium dihydrogen phosphate;

[0049] Step 2): The mixed powder in step 1) was transferred to a ball mill and ball milled at 300 rpm for 5 h;

[0050] Step 3): The fully ball-milled powder was placed in a corundum boat, and then heat-treated in a tube furnace at 850° C. under nitrogen protection, with a heating rate of 10° C. / min and a holding time of 2 h.

[0051] Step 4): After cooling to room temperature, washing with 4M nitric acid aqueous solution for 12 h, then washing with water, and vacuum drying at 85° C. for 12 h to obtain nitrogen-phosphorus-doped porous carbon NPAC;

[0052] Step 5): 20 g of urea was placed in a ceramic crucible and heat-treated at 550° C. in an air atmosphere using a muffle furnace at a heating rate of 5° C. / min and a holding time of 4 h to obtain carbon nitride;

[0053] Step 6): 1 g of carbon nitride was placed in 100 mL of 8 M hydrochloric acid solution for hydrothermal protonation treatment at 100 ° C for 7 h, and then cooled, washed with water, and freeze-dried for 12 h to obtain protonated carbon nitride p-C3N4;

[0054] Step 7): 1.58 g of potassium permanganate was dissolved in 100 mL of 1 M hydrochloric acid solution, and after thorough ultrasonic dissolution, the mixture was hydrothermally treated at 160° C. for 9 h, washed with water and alcohol three times each by centrifugation, and dried in vacuo at 85° C. for 8 h. The mixture was then heat-treated at 350° C. in a tube furnace under nitrogen protection at a heating rate of 5° C. / min and a holding time of 1 h. After cooling, α-MnO2 was obtained;

[0055] Step 8): 100 mg, 40 mg, and 100 mg of the products obtained in steps 4), 6), and 7) were respectively dispersed in 60 mL of a hydroalcoholic solution consisting of 30 mL of water and 30 mL of ethanol, and hydrothermally treated at 160° C. for 4 h;

[0056] Step 9): After cooling, the product was washed with water and alcohol three times each, and vacuum dried at 85° C. for 8 h. The product was placed in a ceramic crucible and heat-treated in a tube furnace at 350° C. in a nitrogen atmosphere at a heating rate of 5° C. / min and a holding time of 1 h. MCC was obtained after cooling. Figure 1d shows that under the conditions of Example 1, MCC exhibits a layered porous cross-linked interconnected structure, presenting a bird's nest-like morphology. This unique structure is conducive to the full exposure of active sites and material transport and transportation, alleviating mass transfer polarization. The close combination of oxides and porous carbon is conducive to the rapid electron transfer process and slows down ohmic polarization.

[0057] Comparative Example 1

[0058] This comparative example provides a method for preparing an α-MnO2 catalytic material, and the specific preparation steps are as follows:

[0059] Step 1): Dissolve 1.58 g of potassium permanganate in 100 mL of 1 M hydrochloric acid solution;

[0060] Step 2): The hydrochloric acid solution after sufficient sonication was hydrothermally treated at 160° C. for 9 h, centrifuged and washed with water and alcohol three times each, and vacuum dried at 85° C. for 8 h;

[0061] Step 3): Heat treatment was performed at 350°C in a tubular furnace under nitrogen protection, with a heating rate of 5°C / min and a holding time of 1h. After cooling, α-MnO2 was obtained, and its micromorphology was as follows: Figure 1 As shown in a.

[0062] Comparative Example 2

[0063] This comparative example provides a method for preparing nitrogen and phosphorus doped porous carbon NPAC, and the specific preparation steps are as follows:

[0064] Step 1): 2 g of wood powder was mixed with 5 g of sodium citrate, 1 g of melamine, and 1 g of ammonium dihydrogen phosphate;

[0065] Step 2): The mixed powder in step 1) was transferred to a ball mill and ball milled at 300 rpm for 5 h;

[0066] Step 3): The fully ball-milled powder was placed in a corundum boat, and then pyrolyzed in the corundum boat using a tube furnace under nitrogen protection at 850°C, with a heating rate of 10°C / min and a holding time of 2h;

[0067] Step 4): After cooling to room temperature, wash with 4M nitric acid solution for 12 hours, wash with water and vacuum dry at 85°C for 12 hours to obtain nitrogen and phosphorus doped porous carbon NPAC, the micromorphology of which is as follows Figure 1 As shown in b.

[0068] Comparative Example 3

[0069] This comparative example provides a preparation method of NPAC loaded α-MnO2, and the specific preparation steps are as follows:

[0070] Step 1): 2 g of wood powder was mixed with 5 g of sodium citrate, 1 g of melamine, and 1 g of ammonium dihydrogen phosphate;

[0071] Step 2): The mixed powder in step 1) was transferred to a ball mill and ball milled at 300 rpm for 5 h;

[0072] Step 3): The fully milled powder was placed in a corundum boat, and then placed in a corundum tube and pyrolyzed at 850°C in a tube furnace under nitrogen protection, with a heating rate of 10°C / min and a holding time of 2h;

[0073] Step 4): After cooling to room temperature, washing with 4M nitric acid aqueous solution for 12 h, washing with water and vacuum drying at 85°C for 12 h to obtain nitrogen-phosphorus-doped porous carbon NPAC;

[0074] Step 5): 1.58 g of potassium permanganate was dissolved in 100 mL of 1 M hydrochloric acid solution, and the mixture was hydrothermally treated at 160° C. for 9 h after thorough ultrasonication, washed three times with water and alcohol, and dried in vacuo at 85° C. for 8 h. The mixture was then heat-treated in a tubular furnace at 350° C. under nitrogen protection at a heating rate of 5° C. / min and a holding time of 1 h. After cooling, α-MnO2 was obtained;

[0075] Step 6): 100 mg of each of the products obtained in steps 4) and 5) was dispersed in 60 mL of a hydroalcoholic solution consisting of 30 mL of water and 30 mL of ethanol, and hydrothermally treated at 160° C. for 4 h;

[0076] Step 7): After cooling, washing with water and alcohol for 3 times each, and vacuum drying at 85°C for 8 hours, the product was placed in a ceramic crucible and heat treated at 350°C in a nitrogen atmosphere using a tube furnace for 1 hour, with a heating rate of 5°C / min and a holding time of 1 hour. After cooling, MC was obtained, and its micromorphology was as follows: Figure 1 As shown in c.

[0077] SEM was used to examine the micromorphology of the MCC prepared in Example 1, as well as the NPAC, α-MnO2, and MC catalytic materials prepared in Comparative Examples 1, 2, and 3. NPAC has a honeycomb-like porous feature, and α-MnO2 is a rod-like nanostructure. By combining NPAC and α-MnO2 to construct the MC material, the MC exhibits severe nanorod accumulation, which is not conducive to the contact between the active sites and the reactants. The addition of p-C3N4 as a structural modulation framework greatly slows down the occurrence of the accumulation phenomenon, and constructs an MCC catalyst with a porous structure. This unique bird's nest structure can greatly enhance oxygen transport and electrolyte penetration during the reaction, further improving the discharge performance of the MCC catalyst in zinc-air batteries.

[0078] Example 2

[0079] 100 mg of samples prepared in Example 1 and Comparative Examples 2 and 3 were taken and placed in a quartz container for electron spin resonance property testing. The test results are shown in Figure 2. Figure 2 As shown, the EPR curves of MCC, MC, and MnO2 all show a signal characteristic peak of oxygen vacancies at g of 2.003, confirming that all three materials contain oxygen vacancies. By comparison, it can be found that MCC exhibits a higher signal intensity, indicating that it contains a higher oxygen vacancy concentration and content. After the addition of carbon nitride, more oxygen atoms are detached from the MnO2 surface in MCC, which increases the number of oxygen vacancies, that is, more trivalent Mn sites are formed on the MCC surface. At the same time, it also improves the electronic distribution characteristics of the carbon-manganese interface, so that the trivalent Mn site can be used as an efficient bifunctional catalytic site to promote the rapid progress of ORR and OER reactions.

[0080] Example 3

[0081] 10 mg of the samples prepared in Example 1 and Comparative Examples 2 and 3 and the commercial Pt / C-RuO2 catalyst were respectively dissolved in a solution consisting of 2 mL of ethanol and 5% Nafion, and ultrasonicated for 30 minutes to form a uniform slurry. The obtained slurry was then drop-coated on the glassy carbon surface of a rotating disk electrode (with a loading of 0.1 mg / cm 2 ), and after being fully dried, it was used as the working electrode to form a three-electrode system with a platinum wire counter electrode and a saturated calomel reference electrode. Potassium hydroxide solution was used as the alkaline electrolyte. The test was carried out using the CHI760 series electrochemical workstation of Chenhua Company, and the linear voltammetry method (scan rate of 5 mV / s) was adopted to investigate the ORR and OER performances.

[0082] The test results are as follows Figure 3a , b, as shown by Figure 3a It can be found that the limiting current density of MCC in the ORR catalytic process is close to 6 mA / cm 2 The half-wave potential is 0.88V, which is better than the half-wave potential of commercial noble metal catalysts and very close to the limiting current density of noble metal materials. It is better than the ORR catalytic performance of NPAC, MnO2, and MC prepared in the comparative example. Figure 3b It can be seen that the limiting current density of MCC in the OER catalytic process is the largest, and at a current density of 10 mA / cm 2 The overpotential at 420 mV is lower than that of the comparative materials and close to that of commercial precious metal catalysts. The effective combination of the dual carbon support and MnO2 forms a heterogeneous interface with rich electron density. A widely distributed three-dimensional electron transport network within the internal structure helps reduce the material's inherent impedance and improve its electronic conductivity. This significantly enhances the electrocatalytic bifunctionality of MCC, demonstrating optimal bifunctionality.

[0083] Example 4

[0084] 10 mg of the samples prepared in Example 1 and Comparative Example 3 and commercial Pt / C-RuO2 powder were dispersed in ethanol and 5% Nafion solution, and ultrasonicated for 30 minutes to form a uniform catalyst slurry, which was sprayed on a hydrophobic carbon paper with a gas diffusion layer (loading 1 mg / cm 2 ) and, after thorough drying, the resulting air electrode was used as the positive electrode. A zinc sheet was then used as the negative electrode, and a 6M potassium hydroxide solution was used as the electrolyte. These components were then assembled into a zinc-air battery. Discharge power density measurements were performed using an electrochemical workstation equipped with a current amplifier (scan rate 5mV / s).

[0085] The test results are as follows Figure 4 As shown in the figure, the discharge power density comparison of different embodiments is shown. It can be found that the zinc-air battery assembled using MCC shows an extremely high peak discharge power density of 452mW / cm during the test. 2 , which is better than the power density of MC material assembled battery 373mW / cm 2 , and precious metal materials assembled battery power density 256mW / cm 2 , reflecting the excellent discharge performance of MCC electrode catalyst.

[0086] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention in any form or substance. It should be noted that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a dual-carbon supported manganese-based bifunctional electrode catalyst, comprising the following steps: (1) Wood powder is mixed with sodium citrate, melamine and ammonium dihydrogen phosphate, ball-milled and then heat-treated in a tube furnace, cooled to room temperature, washed and dried to obtain nitrogen-phosphorus-doped porous carbon (NPAC); wherein, The mass ratio of the wood powder, sodium citrate, melamine and ammonium dihydrogen phosphate is 2-4:5-8:1:1; (2) urea is heat-treated to obtain carbon nitride, which is then placed in a hydrochloric acid solution for hydrothermal protonation treatment, cooled, washed, and dried to obtain protonated carbon nitride p-C3N4; (3) Potassium permanganate is dissolved in a hydrochloric acid solution, subjected to hydrothermal treatment after thorough ultrasonication, washed by centrifugation and dried, and then placed in a tube furnace for heat treatment, and α-MnO2 is obtained after cooling; (4) The NPAC, p-C3N4 and α-MnO2 are dispersed in a mixed solution of water and ethanol for hydrothermal treatment, cooled, washed and dried; finally, the product is solid-phase sintered to obtain a dual-carbon-supported manganese-based bifunctional electrode catalyst; wherein the mass ratio of the NPAC, p-C3N4 and α-MnO2 is 5:1~2:

5.

2. The preparation method according to claim 1, wherein: The ball milling treatment time in step (1) is 1-10 hours, and the rotation speed is 200-400 rpm.

3. The preparation method according to claim 1, wherein: The heat treatment temperature in step (1) is 800-1000°C, the heat treatment atmosphere is nitrogen, the heating rate is 5-15°C / min, and the holding time is 1-5h.

4. The preparation method according to claim 1, wherein: The heat treatment temperature in step (2) is 500-600°C, the heat treatment atmosphere is air, the heating rate is 5-10°C / min, and the holding time is 1-5h.

5. The preparation method according to claim 1, wherein: The hydrothermal protonation treatment temperature in step (2) is 100-200° C. and the time is 5-10 h.

6. The preparation method according to claim 1, wherein: The heat treatment temperature in step (3) is 300-400°C, the heat treatment atmosphere is nitrogen, the heating rate is 5-10°C / min, and the holding time is 1-5h.

7. A dual-carbon-supported manganese-based bifunctional electrode catalyst obtained by the preparation method according to claim 1.

8. Use of the dual-carbon-supported manganese-based bifunctional electrode catalyst as claimed in claim 7 in a zinc-air battery.

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