Heteronuclear A1 and B2 triatomic catalysts with asymmetric electronic structures and their applications

Abstract

This invention relates to heteronuclear Al and B2 triatomic catalysts with asymmetric electronic structures and their applications. The heteronuclear Al and B2 triatomic catalysts with asymmetric electronic structures are prepared by the following method: a first metal A is encapsulated and then pyrolyzed in situ through in-situ self-assembly; defects are constructed on a support using KOH activation; a second metal species B is introduced and subjected to slow two-step carbonization; finally, asymmetrically dispersed AlB2 heteronuclear triatomic sites are controllably synthesized on a nitrogen-doped carbon support. A and B are each selected from Fe, Co, Ni, Cu, and Zn, and A and B are different. This invention provides an in-situ self-assembly strategy for forming asymmetrically dispersed AlB2 triatomic nitrogen-doped carbon material catalyst, exhibiting exceptional oxygen reduction electrocatalytic activity and stability in alkaline to acidic electrolytes. Its application in zinc-air batteries achieves excellent operating performance and outstanding durability.

Description

Technical Field

[0001] This invention relates to electrocatalysts in the fields of energy materials and electrochemical technology, specifically to a heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure and its applications. Background Technology

[0002] With the continuous development of society and the economy, energy resource shortages and environmental pollution problems are becoming increasingly prominent. The demand for electrochemistry to solve major scientific and engineering problems is becoming more urgent, placing higher demands on battery performance. Metal-air batteries have attracted much attention due to their high energy density. Zinc-air batteries use zinc as the anode and oxygen from the air or pure oxygen as the cathode active material. The air cathode requires a highly active catalyst to drive the oxygen reduction reaction (ORR). Currently, noble metal catalysts (such as Pt / C, RuO2, etc.) are the preferred cathode catalysts due to their high catalytic activity; however, their low reserves, high cost, and poor stability limit their widespread application. Furthermore, noble metals also suffer from sensitivity to methanol and susceptibility to poisoning by trace amounts of CO that may be carried in fuels. Therefore, developing supported non-noble metal catalysts is one of the development directions in the field of new energy materials.

[0003] In recent years, supported atomized catalysts have attracted widespread attention due to their maximized atom utilization efficiency and unique catalytic performance. Compared with traditional metal nanoparticle catalysts, the active sites of supported atomized catalysts are isolated and structurally homogeneous, resulting in higher catalytic activity during electrocatalytic reactions. However, the current single metal atom loading is relatively low, and due to the sharp increase in surface free energy, obtaining catalysts with high loading while maintaining high stability under reaction conditions remains a significant challenge. Enhancing metal-support interactions or confining active species within a certain space are two common methods to improve the stability of metal atoms. However, excessively strong metal-support interactions may lead to a significant decrease in reaction activity; confining active metal centers in micropores may affect mass transfer. Therefore, how to rationally design catalysts with high loading, high stability, and high activity is a pressing scientific problem that needs to be solved. Summary of the Invention

[0004] One objective of this invention is to provide a heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure, which addresses the problem of insufficient catalytic activity and stability of supported non-noble metal catalysts. A second objective of this invention is to provide applications of this heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: This heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure is prepared by the following method: The first metal A is encapsulated and then pyrolyzed in situ using in-situ self-assembly, and defects are constructed on the support by activation with KOH. Then, a second type of metal species B is introduced and subjected to slow two-step carbonization. Finally, asymmetrically dispersed A1B2 heteronuclear triatomic sites are controllably synthesized on a nitrogen-doped carbon support. A and B are both selected from one of Fe, Co, Ni, Cu, and Zn, and A and B are different. The specific preparation method includes the following steps:

[0006] Step 1: Encapsulate the transition metal complex within a zeolite imidazole framework to form a complex; dissolve a zinc metal salt and a compound of a transition metal A in a mixed solution of methanol and N,N-dimethylformamide, sonicate to dissolve, and stir for 1-2 hours to dissolve the metal salt and form a homogeneous solution 1; the molar ratio of zinc ions to transition metal A ions is 15:1 to 20:1.

[0007] Step 2: Add the white powder 2-methylimidazole to another mixed solution of methanol and N,N-dimethylformamide, disperse it by ultrasonication, and carry out the self-assembly process under stirring to obtain mixed solution 2;

[0008] Step 3: Under ultrasonic conditions, the mixed solution 2 formed in Step 2 is rapidly added to the homogeneous solution 1 formed in Step 1, and ultrasonically dispersed. The self-assembly process is carried out under stirring conditions; the molar ratio of the transition metal A compound to 2-methylimidazole is 1:3 to 1:8.

[0009] Step 4: Centrifuge the sample obtained in Step 3 above, wash it with methanol, and vacuum dry it to obtain a solid powder;

[0010] Step 5: The sample obtained in Step 4 is pyrolyzed at high temperature in an inert atmosphere to obtain nitrogen-doped carbon material A / NC supported by metal A.

[0011] Step 6: Grind the obtained solid powder Al / NC with KOH or a mixture thereof, and pyrolyze it under an inert atmosphere to activate the Al / NC material and form defects near the metal active sites, thereby obtaining Al / NC-def; the mass ratio of Al / NC to KOH is 1:8 to 1:12;

[0012] Step 7: Place the Al / NC-def obtained in Step 6 into deionized water and stir for 3-5 hours, centrifuge, wash, and vacuum dry.

[0013] Step 8: Mix the obtained solid powder Al / NC-def with another transition metal B compound evenly, then add a nitrogen source and grind evenly; the number of moles of transition metal B is 2 to 3 times the number of moles of transition metal A, and the amount of nitrogen source is 2 to 4 times the amount of moles of transition metal B.

[0014] Step 9: The solid powder obtained in Step 8 is subjected to two-step temperature-increasing pyrolysis under an inert atmosphere to obtain a heteronuclear A1, B2 triatomic catalyst A1B2 / NC with an asymmetric electronic structure.

[0015] In step one of the above scheme, the compound of transition metal A is an acetylacetone compound, the metal salt of zinc is zinc nitrate, and the volume ratio of N,N-dimethylformamide to methanol solution is 3:1 to 5:1.

[0016] In the above scheme, the molar concentration of metal ions of transition metal compound A in step one is 0.006-0.010 mol / L, the molar concentration of Zn ions in the zinc metal salt solution is 0.10-0.17 mol / L, and the molar ratio of zinc ions to transition metal A ions is 16:1-18:1.

[0017] In the above scheme, the molar concentration of 2-methylimidazole in step two is 0.5 to 0.7 mol / L, and the volume ratio between N,N-dimethylimidazole solution and methanol solution is 3:1 to 5:1.

[0018] In step five of the above scheme, the high-temperature pyrolysis temperature is 950-1000°C, the heating rate is 4-5°C / min, and the calcination time is 2-3 hours.

[0019] In step six of the above scheme, the mass ratio of A / NC to KOH is 1:8 to 1:12; the calcination temperature is 700 to 900 °C / min, the heating rate is 4 to 5 °C / min, and the calcination time is 1 to 2 hours.

[0020] In the above scheme, the nitrogen source is melamine or dicyandiamide; the transition metal B is an organometallic compound of the acetylacetone class; the molar ratio of the transition metal A compound to 2-methylimidazole is 1:4 to 1:6; and the volume ratio of N,N-dimethylformamide to methanol solution is 4:1.

[0021] In step nine of the above scheme, the temperature is programmed. The first stage of calcination is at 550-650°C for 1-2 hours, with a heating rate of 2-3°C / min. The second stage of calcination is at 900-950°C for 2 hours, with a heating rate of 3-4°C / min. Both stages of calcination use 99.9% Ar as the inert gas. After cooling to room temperature and grinding for 10-20 minutes, the heteronuclear Al and B2 triatomic catalyst A1B2 / NC with an asymmetric electronic structure is obtained. This heteronuclear Al and B2 triatomic catalyst with an asymmetric electronic structure exhibits excellent oxygen reduction reaction activity, with a half-wave potential of 0.93-0.95 V under alkaline conditions and 0.86-0.88 V under acidic conditions. It also has good resistance to methanol poisoning.

[0022] In the above scheme, the stirring time in step three is 24 hours; in step four, the product is washed three times with deionized water and twice with methanol, and then vacuum dried at 80 ℃ for 12 hours; in step five, the heating rate during calcination is 5 ℃ / min, and the calcination time is 2-3 hours.

[0023] The heteronuclear A1 and B2 triatomic catalysts with asymmetric electronic structures described above were used in zinc-air batteries, achieving a peak power density of 270 mW / cm² in performance tests. -2 In addition, it still exhibits excellent charge-discharge cycle stability under high current density, with a charge-discharge round-trip efficiency between 53.5% and 55.5%. Beneficial effects

[0024] 1. This invention involves encapsulating transition metal ions in situ via self-assembly, followed by pyrolysis to anchor metal A. A second metal B is then functionalized using KOH activation and a slow two-step carbonization process. This allows for the controllable synthesis of asymmetrically dispersed A1B2 heteronuclear triatomic sites on a nitrogen-doped carbon support, exhibiting high oxidation performance across a pH range from acidic to alkaline. This catalyst overcomes the limitations of mononuclear site-based intermediate adsorption in electrocatalytic oxygen reduction reactions. It retains the high atom utilization rate of traditional single-atom supported catalysts and optimizes the multi-step proton-coupled electron transfer process by adjusting the heteronuclear electronic structure, thus demonstrating high oxidation performance across a pH range from acidic to alkaline.

[0025] 2. The single-atom catalyst preparation method described in this invention is simple to operate and structurally stable, improving the loading capacity of existing supported metal single-atom catalysts. It can also be extended to the preparation of various heteronuclear triatomic nitrogen-doped carbon catalysts. The raw materials are abundant, economical, and readily available. It exhibits excellent activity and stability in electrocatalytic reactions, especially demonstrating remarkable cycle stability even in acidic electrolytes, thus promoting the further development of fuel cells.

[0026] 3. The heteronuclear Al and B2 triatomic catalyst with asymmetric electronic structure described in this invention enhances the abundance of active sites by forming triatomic nitrogen-doped carbon materials through in-situ self-assembly and pyrolysis of transition metal ions. Furthermore, there is no obvious loss or deactivation of metal active sites after the reaction. Under alkaline conditions, it exhibits better resistance to methanol poisoning and corrosion resistance than commercial Pt / C.

[0027] 4. Applying the heteronuclear triatomic catalyst described in this invention to zinc-air batteries results in ultra-long cycle life and high energy density, solving the common problems of poor round-trip efficiency and short cycle life in zinc-air batteries, and providing more possibilities for the practical application of zinc-air batteries.

[0028] 5. This invention designs and synthesizes a high-loading, high-stability AlB2 / NC heteronuclear triatomic catalyst on a porous carbon support derived from zeolite imidazole ester framework material (ZIF-8) by regulating metal-support interactions. This catalyst breaks through the limitation of intermediate adsorption correlation based on mononuclear sites in the electrocatalytic oxygen reduction reaction, retains the high atom utilization rate of traditional single-atom supported catalysts, and promotes the electron transfer process of multi-step elementary reactions by regulating electronic structure characteristics, exhibiting high catalytic performance across the pH range from acidic to alkaline.

[0029] 6. The present invention aims to provide an in-situ self-assembly strategy to form an AlB2 triatomic nitrogen-doped carbon material catalyst with asymmetric dispersion. The catalyst obtained exhibits extraordinary oxygen reduction electrocatalytic activity and stability in alkaline to acidic electrolytes. When applied to zinc-air batteries, it achieves excellent operating performance and outstanding durability. Attached Figure Description

[0030] Figure 1 The XRD pattern of the heteronuclear triatomic catalyst prepared according to Example 1 of the present invention;

[0031] Figure 2 The SEM image of the heteronuclear triatomic catalyst prepared according to Example 1 of the present invention;

[0032] Figure 3 The TEM image of the heteronuclear single-atom catalyst prepared according to Example 1 of the present invention;

[0033] Figure 4 The X-ray near-edge absorption structure spectrum of Fe in the heteronuclear triatomic catalyst prepared according to Example 1 of the present invention is shown.

[0034] Figure 5 The X-ray near-edge absorption structure spectrum of Co in the heteronuclear triatomic catalyst prepared according to Example 1 of the present invention is shown.

[0035] Figure 6The linear sweep cyclic voltammetry curves of the catalyst prepared in Example 1 and the control sample in 0.1 M KOH are shown.

[0036] Figure 7 The linear sweep cyclic voltammetry curves of the catalyst prepared in Example 1 and the control sample in 0.5 M H2SO4 are shown.

[0037] Figure 8 The figures show the polarization curves and power density diagrams of zinc-air batteries using the catalyst prepared in Example 1 and the comparative sample Pt / C as the positive electrode. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings:

[0039] The preparation method of this asymmetrically dispersed Al and B2 triatomic catalyst involves the formation of heteronuclear triatomic nitrogen-doped carbon materials by transition metal ions through an in-situ self-assembly strategy. The second metal (B) is functionalized by encapsulating and pyrolyzing the first metal (A), followed by activation with KOH and a slow two-step carbonization process. This allows for the controllable synthesis of asymmetrically dispersed AlB2 heteronuclear triatomic sites on a nitrogen-doped carbon support. This catalyst overcomes the limitations of mononuclear site-based intermediate adsorption in electrocatalytic oxygen reduction reactions, retaining the high atomic utilization of traditional monoatomic supported catalysts. Furthermore, by adjusting the electronic structure of the heteronuclear triatomic sites, the multi-step proton-coupled electron transfer process is optimized, resulting in high oxidation performance across a pH range from acidic to alkaline. The preparation method utilizes readily available and universally applicable materials, and the resulting catalyst material possesses unique electronic structure properties, showing great promise for applications in energy storage and energy conversion. Example

[0040] 1. Dissolve 1.290 g of Zn(NO3)2·6H2O and 0.089 g of Fe(acac)3 solid powder in 30 mL of a mixed solution of N,N-dimethylformamide and ethanol (volume ratio 4:1) to form a homogeneous solution 1.

[0041] 2. Add 1.62 g of 2-methylimidazole to 30 mL of a mixed solution of N,N-dimethylformamide and ethanol (volume ratio 4:1), and sonicate for 1 hour to obtain solution 2.

[0042] 3. Under ultrasonic conditions, add solution 2 to solution 1 and stir at room temperature for 24 hours.

[0043] 4. Centrifuge the obtained sample, wash with deionized water and ethanol, and dry in a vacuum drying oven at 80 °C for 12 hours.

[0044] 5. The synthesized precursor was carbonized in a tube furnace at 1000 °C for 2 h under an argon atmosphere with a heating rate of 5 °C / min. The Fe / NC sample was then collected after grinding.

[0045] 6. Take 250 mg Fe / NC and 2 g KOH solid, grind them to make them uniform, and pyrolyze them in a tube furnace at 800 °C for 2 h under argon atmosphere with a heating rate of 5 °C / min. After washing and drying, collect the obtained sample Fe1 / NC-def.

[0046] 7. Take 200 mg of the sample Fe1 / NC-def prepared above, grind it with 0.993 g of cobalt acetylacetone and 1.60 g of melamine for 30 min and mix them evenly.

[0047] 8. The powder obtained in step 7 is calcined through a two-stage heating process. 1) Calcination in a tube furnace at 600 °C for 1 h, with a heating rate of 3 °C / min. 2) Calcination in a tube furnace at 900 °C for 2 h, with a heating rate of 3 °C / min, to obtain the catalyst Fe1Co2 / NC.

[0048] Zn was used as the negative electrode, the prepared catalyst was used as the positive electrode, and the electrolyte was a solution of 6 mol / L KOH and 0.2 mol / L zinc acetate to assemble a zinc-air battery.

[0049] The catalysts obtained in the above examples were subjected to a series of structural characterizations to verify their structures.

[0050] like Figure 1 The figure shows the XRD characterization of the catalyst in Example 1. The figure shows two diffraction peaks at around 24° and 44°, which are the (002) and (101) crystal planes of graphite carbon, respectively. No characteristic diffraction peaks of metal nanoparticles were found.

[0051] like Figure 2 The image shown is a SEM image of the catalyst from Example 1, demonstrating that the catalyst obtained in Example 1 is a deformed dodecahedron with a diameter of 300-400 nm.

[0052] like Figure 3 The image shown is a TEM image of the catalyst from Example 1, indicating that the catalyst obtained in Example 1 does not exhibit any metal atom aggregation. Densely distributed and atomically dispersed bright spots are present throughout the carbon support, with most of the atomic dispersion consisting of triangular triatomic sites.

[0053] like Figure 4 The image shows the Fe K-side XANES pattern of the catalyst in Example 1, which reveals the valence state of the Fe single atom at the three-atom site.

[0054] like Figure 5The image shows the Co K-side XANES pattern of the catalyst in Example 1, which reveals the valence state of the Co atom at the three-atom site. Example

[0055] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the amount of Zn(NO3)2 6H2O added in step one is 3.8 mmol and the amount of Fe(OAc)2 is 0.22 mmol. Example

[0056] The only difference between this embodiment and Embodiment 1 is that in this embodiment, 30 mL of solution is added in step one, wherein the volume ratio between N,N-dimethylimidazole solution and methanol solution is 3:1. Example

[0057] The only difference between this embodiment and Embodiment 1 is that in this embodiment, 0.96 g of dicyandiamide is added in step eight. Example

[0058] The only difference between this embodiment and Embodiment 1 is that in this embodiment, 250 mg A / NC and 2.2 g KOH are mixed and ground in step six. Example

[0059] The difference between this embodiment and Example 1 is that in this embodiment, 1.50 g of 2-methylimidazole is added to a 30 mL mixed solution of N,N-dimethylformamide and ethanol (volume ratio 4:1). Example

[0060] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the calcination temperature in step five is 980 °C and the heating rate is 4.5 °C / min. Example

[0061] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the calcination temperature in the first step of step eight is 650 °C and the time is maintained for 1.5 hours. Example

[0062] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the calcination temperature in the second step of step eight is 950 °C, and the time is maintained for 1.5 hours.

[0063] Example 10:

[0064] The only difference between this embodiment and Embodiment 1 is that in this embodiment, Fe1 / NC-def is ground and mixed evenly with 0.984g of nickel acetylacetone and 1.60g of melamine for 30 minutes in step seven.

[0065] Comparative Example 1:

[0066] The only difference between this comparative example and Example 1 is that in this example, transition metal A is no longer added in step one.

[0067] Comparative Example 2:

[0068] The only difference between this comparative example and Example 1 is that in this example, the second transition metal B is not added in step eight.

[0069] Comparative Example 3:

[0070] The difference between this embodiment and Embodiment 1 is that, in this embodiment, transition metals A and B are not added in steps one and eight.

[0071] Comparative Example 4:

[0072] In this example, 5 mg of a commercial Pt / C catalyst (Pt content of 20%) was ultrasonically dispersed for 30 min to obtain a solution.

[0073] To test the catalytic performance of the single-atom electrocatalyst of this application, this application also provides application examples and catalyst performance tests.

[0074] Catalytic oxygen reduction reaction and zinc-air battery performance evaluation: 5 mg of catalyst was added to a solution containing 40 μL of 5% Nafion and 960 μL of isopropanol, and the mixture was ultrasonically dispersed to obtain a solution. 11 μL of this solution was drop-coated onto a rotating disk electrode, with a catalyst loading of 0.28 mg / cm³. -2 After air drying, a thin-film electrode was obtained; a three-electrode system was formed with an Ag / AgCl electrode as the reference electrode and a Pt wire as the counter electrode. Linear voltammetry was performed at room temperature in oxygen-saturated 0.1 mol / L KOH or 0.5 M H₂SO₄ solution using an electrochemical workstation, with a scan rate of 10 mV / s and an electrode rotation speed of 1600 r.

[0075] like Figure 6 The LSV curves of the catalyst in Example 1 and other comparative samples were measured under alkaline conditions. Under alkaline conditions, the oxygen reduction onset potential was 1.07 V and the half-wave potential was 0.94 V. The measured oxygen reduction onset potential and half-wave potential were 0.08 V better than those of commercial platinum carbon, and the cycle performance was also better than that of platinum carbon. It has excellent oxygen reduction catalytic activity and stability.

[0076] like Figure 7The LSV curves of the catalyst in Example 1 and other comparative samples were measured under acidic conditions. Under acidic conditions, the oxygen reduction onset potential was 0.98 V and the half-wave potential was 0.88 V. Therefore, the heteronuclear triatomic electrocatalyst prepared in this invention has the potential to be applied to the cathode reaction of fuel cells.

[0077] Using Zn as the negative electrode and Example 1 as the positive electrode, a zinc-air battery was assembled with a 6 mol / L KOH and 0.2 mol / L zinc acetate solution as the electrolyte.

[0078] like Figure 8 The figures show the polarization curves and power density graphs of the catalyst in Example 1 and Comparative Example 1 with commercial Pt / C. As can be seen from the graphs, the power density of the prepared single-atom catalysts is far superior to that of commercial Pt / C, and they have excellent development prospects.

[0079] The non-precious metal catalyst prepared by this invention has electrocatalytic oxygen reduction performance comparable to commercial Pt / C in alkaline electrolyte. When applied to zinc-air batteries, its peak power density surpasses that of most non-precious metal catalysts. Furthermore, this catalyst exhibits excellent charge-discharge cycle stability in zinc-air batteries, maintaining stable performance even after more than 1000 cycles.

[0080] The preparation method and application of an asymmetric dispersion Al and B2 triatomic catalyst disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the implementation of this application. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this application.

[0081] This catalyst is primarily used in zinc-air batteries to catalyze the ORR reaction of cathode oxygen during battery discharge. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Furthermore, those skilled in the art will recognize that variations in specific implementation methods and application scope may occur based on the ideas of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure, characterized in that: This heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure was prepared by the following method: The first metal A was encapsulated in situ via self-assembly and then pyrolyzed. Defects were constructed on the support using KOH activation. Then, a second metal species B was introduced and subjected to a slow two-step carbonization process. Finally, asymmetrically dispersed A1B2 heteronuclear triatomic sites were controllably synthesized on a nitrogen-doped carbon support. Both A and B are selected from one of Fe, Co, Ni, Cu, and Zn, and A and B are different. The specific preparation method includes the following steps: Step 1: Encapsulate the transition metal complex within a zeolite imidazole framework to form a complex; dissolve a zinc metal salt and a compound of a transition metal A in a mixed solution of methanol and N,N-dimethylformamide, sonicate to dissolve, and stir for 1-2 hours to dissolve the metal salt and form a homogeneous solution 1; the molar ratio of zinc ions to transition metal A ions is 15:1 to 20:

1. Step 2: Add white powder 2-methylimidazole to another mixed solution of methanol and N,N-dimethylformamide, disperse by ultrasonication, and carry out a self-assembly process under stirring to obtain mixed solution 2; Step 3: Under ultrasonic conditions, the mixed solution 2 formed in Step 2 is rapidly added to the homogeneous solution 1 formed in Step 1, and ultrasonically dispersed. The self-assembly process is carried out under stirring conditions; the molar ratio of the transition metal A compound to 2-methylimidazole is 1:3 to 1:

8. Step 4: Centrifuge the sample obtained in Step 3 above, wash it with methanol, and vacuum dry it to obtain a solid powder; Step 5: The sample obtained in Step 4 is pyrolyzed at high temperature in an inert atmosphere to obtain nitrogen-doped carbon material A / NC supported by metal A. Step 6: Grind the obtained solid powder Al / NC with KOH or a mixture thereof, and pyrolyze it under an inert atmosphere to activate the Al / NC material and form defects near the metal active sites, thereby obtaining Al / NC-def; the mass ratio of Al / NC to KOH is 1:8 to 1:12; Step 7: Place the Al / NC-def obtained in Step 6 into deionized water and stir for 3-5 hours, centrifuge, wash, and vacuum dry. Step 8: Mix the obtained solid powder Al / NC-def with another transition metal B compound evenly, then add a nitrogen source and grind evenly; the number of moles of transition metal B is 2 to 3 times the number of moles of transition metal A, and the amount of nitrogen source is 2 to 4 times the amount of moles of transition metal B. Step 9: The solid powder obtained in Step 8 is subjected to a two-step heating process under an inert atmosphere to pyrolyze and calcine it to obtain a heteronuclear A1, B2 triatomic catalyst A1B2 / NC with an asymmetric electronic structure.

2. The heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure according to claim 1, characterized in that: In step one, the transition metal A compound is an acetylacetone compound, the zinc metal salt is zinc nitrate, and the volume ratio of N,N-dimethylformamide to methanol solution is 3:1 to 5:

1.

3. The heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure according to claim 2, characterized in that: In step one, the molar concentration of metal ions in the transition metal A compound is 0.006–0.010 mol / L, and the molar concentration of Zn ions in the zinc metal salt solution is 0.10–0.17 mol / L; the molar ratio of zinc ions to transition metal A ions is 16:1–18:

1.

4. The heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure according to claim 3, characterized in that: In step two, the molar concentration of 2-methylimidazole is 0.5–0.7 mol / L, and the volume ratio between the N,N-dimethylimidazole solution and the methanol solution is 3:1–5:

1.

5. The heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure according to claim 4, characterized in that: In step five, the high-temperature pyrolysis temperature is 950-1000°C, the heating rate is 4-5°C / min, and the calcination time is 2-3 hours.

6. The heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure according to claim 5, characterized in that: In step six, the mass ratio of A / NC to KOH is 1:8 to 1:12; the calcination temperature is 700 to 900 °C / min, the heating rate is 4 to 5 °C / min, and the calcination time is 1 to 2 hours.

7. The heteronuclear Al, B2 triatomic catalyst with an asymmetric electronic structure according to claim 6, characterized in that: The nitrogen source is melamine or dicyandiamide; the transition metal B is an organometallic compound of the acetylacetone class; the molar ratio of the transition metal A compound to 2-methylimidazole is 1:4 to 1:6; the volume ratio of N,N-dimethylformamide to methanol solution is 4:

1.

8. The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 7, characterized in that: In step nine, the temperature is programmed. The first stage of calcination is at 550-650°C for 1-2 hours, with a heating rate of 2-3°C / min. The second stage of calcination is at 900-950°C for 2 hours, with a heating rate of 3-4°C / min. Both stages of calcination use 99.9% Ar as the inert gas. After cooling to room temperature, the mixture is ground for 10-20 minutes to obtain the heteronuclear Al / B2 triatomic catalyst A1B2 / NC with an asymmetric electronic structure. This heteronuclear Al / B2 triatomic catalyst exhibits excellent oxygen reduction reaction activity, with a half-wave potential of 0.93-0.95 V under alkaline conditions and 0.86-0.88 V under acidic conditions. It also has good resistance to methanol poisoning.

9. The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 8, characterized in that: In step three, the stirring time is 24 hours; in step four, the mixture is washed three times with deionized water and twice with methanol, and then vacuum dried at 80 ℃ for 12 hours; in step five, the calcination process involves a heating rate of 5 ℃ / min and a calcination time of 2-3 hours.

10. The application of any one of the heteronuclear A1, B2 triatomic catalysts having an asymmetric electronic structure as claimed in claims 1 to 9, characterized in that: The heteronuclear A1 and B2 triatomic catalyst with an asymmetric electronic structure, when used in zinc-air batteries, achieved a peak power density of 270 mW / cm² in zinc-air battery performance tests. -2 In addition, it still exhibits excellent charge-discharge cycle stability under high current density, with a charge-discharge round-trip efficiency between 53.5% and 55.5%.

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