Heteronuclear A1 and B2 three-atom catalyst with asymmetric electronic structure and application of heteronuclear A1 and B2 three-atom catalyst

Abstract

The invention relates to a heteronuclear A1 and B2 three-atom catalyst with an asymmetric electronic structure and application thereof.The heteronuclear A1 and B2 three-atom catalyst with the asymmetric electronic structure is prepared through the following steps that a first metal A is packaged in an in-situ self-assembly mode and then pyrolyzed, defect construction is carried out on a carrier through KOH activation, and the heteronuclear A1 and B2 three-atom catalyst with the asymmetric electronic structure is obtained; introducing a second metal species B and carrying out slow two-step carbonization; and finally, controllably synthesizing asymmetrically dispersed A1B2 heteronuclear triatomic sites on the nitrogen-doped carbon carrier. A and B are selected from one of Fe, Co, Ni, Cu and Zn, and A and B are different. The A1B2 three-atom nitrogen-doped carbon material catalyst with asymmetric dispersion is formed by an in-situ self-assembly strategy, shows extraordinary oxygen reduction electrocatalytic activity and stability in alkaline electrolyte and acidic electrolyte, and realizes excellent running performance and excellent durability when being applied to a zinc air battery.

Description

Technical Field

[0001] The present invention relates to an electrocatalyst in the field of energy materials and electrochemical technology, and in particular to a heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure and an application thereof. Background Art

[0002] With the continuous development of society and economy, the problems of energy resource shortage and environmental pollution are becoming increasingly prominent. People's demand for electrochemical solutions to major scientific and engineering technology problems is becoming more and more urgent, and higher requirements are placed on the performance of batteries. Metal-air batteries have attracted much attention due to their high energy density. Zinc-air batteries use zinc as the anode and oxygen in 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). At present, precious metal catalysts (such as Pt / C, RuO2, etc.) have become the preferred materials for cathode catalysts due to their high catalytic activity. However, their low reserves, high costs and poor stability limit their wide application. In addition, precious metals also have problems such as sensitivity to methanol and easy poisoning by trace CO that may be carried in the fuel. Therefore, the development of supported non-precious metal catalysts is one of the development directions in the field of new energy materials.

[0003] In recent years, supported atomically dispersed catalysts have attracted widespread attention due to their maximized atomic utilization efficiency and unique catalytic performance. Compared with traditional metal nanoparticle catalysts, the active sites of supported atomically dispersed catalysts are isolated from each other and have uniform structures, which makes this type of catalyst exhibit higher catalytic activity during electrocatalytic reactions. However, the current loading of single metal atoms is low. Due to the sharp increase in their surface free energy, it is a huge challenge to obtain catalysts with high loading and high stability under reaction conditions. Enhancing the metal-support interaction or confining the active species in a certain space are two common methods to improve the stability of metal atoms. However, too strong metal-support interaction may lead to a significant decrease in reaction activity; microporous confinement of active metal centers may affect reaction mass transfer. Therefore, how to achieve the rational design of high-loading, high-stability and high-activity catalysts is a scientific problem that needs to be solved urgently today. Summary of the invention

[0004] One object of the present invention is to provide a heteronuclear A1, B2 triatom catalyst with an asymmetric electronic structure. This heteronuclear A1, B2 triatom catalyst with an asymmetric electronic structure is used to solve the problem of insufficient catalytic activity and stability of supported non-precious metal catalysts; a second object of the present invention is to provide an application of this heteronuclear A1, B2 triatom catalyst with an asymmetric electronic structure.

[0005] The technical solution adopted by the present invention to solve the technical problem is: the heteronuclear A1, B2 triatomic catalyst with asymmetric electronic structure is prepared by the following method: the first metal A is encapsulated in situ by self-assembly and then pyrolyzed, activated with KOH to construct defects on the carrier, and then the second metal species B is introduced and slowly carbonized in two steps, and finally asymmetrically dispersed A1B2 heteronuclear triatomic sites are controllably synthesized on the nitrogen-doped carbon carrier; 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 comprises the following steps: Step 1: encapsulating a transition metal complex in a zeolite imidazole framework to form a complex; dissolving a zinc metal salt and a compound of a transition metal A in a mixed solution of methanol and N,N-dimethylformamide, dissolving by ultrasonication, and stirring for 1-2 hours to dissolve the metal salt to form a homogeneous solution 1; the molar ratio of zinc ions to transition metal A ions is 15:1 to 20:1; Step 2: adding white powder 2-methylimidazole to another mixed solution of methanol and N,N-dimethylformamide, dispersing by ultrasonication, and performing a self-assembly process under stirring to obtain a mixed solution 2; Step 3: under ultrasonic conditions, the mixed solution 2 formed in step 2 is quickly added to the homogeneous solution 1 formed in step 1, ultrasonically dispersed, and self-assembly is performed under stirring conditions; the molar ratio of the compound of transition metal A to 2-methylimidazole is 1:3 to 1:8; Step 4: centrifuge the sample obtained in step 3, wash it with methanol, and vacuum dry it to obtain a solid powder; Step 5: pyrolyze the sample obtained in the above step 4 at high temperature in an inert atmosphere to obtain a nitrogen-doped carbon material A / NC loaded with metal A; Step 6: Grind the obtained solid powder A1 / NC and KOH or mix them, and pyrolyze them under an inert atmosphere to activate the M1 / NC material and form defects near the metal active sites to obtain A1 / NC-def; the mass ratio of A1 / NC to KOH is 1:8 to 1:12; Step 7, placing the A1 / NC-def prepared in step 6 in deionized water, stirring for 3-5 hours, centrifuging, washing, and vacuum drying; Step 8: The solid powder A1 / NC-def obtained above is mixed with another compound of transition metal B, and then a nitrogen source is added and ground evenly; the molar amount of transition metal B is 2 to 3 times the molar amount of transition metal A, and the molar amount of the nitrogen source is 2 to 4 times the molar amount of transition metal B; Step nine: subjecting the solid powder obtained in step eight to two-step programmed temperature pyrolysis in an inert atmosphere, and calcining to obtain a heteronuclear A1, B2 triatom catalyst A1B2 / NC having an asymmetric electronic structure.

[0006] In step 1 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.

[0007] In the above scheme, the molar concentration of the metal ion of the transition metal compound A in step 1 is 0.006-0.010 mol / L, the molar concentration of the Zn ion in the zinc metal salt solution is 0.10-0.17 mol / L; the molar ratio of zinc ion to transition metal A ion is 16:1-18:1.

[0008] In the above scheme, the molar concentration of 2-methylimidazole in step 2 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.

[0009] In step 5 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.

[0010] In step 6 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.

[0011] In the above scheme, the nitrogen source is melamine or dicyandiamide; the transition metal B is an acetylacetone-type metal organic compound; 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.

[0012] In step nine of the above scheme, the temperature is programmed to rise, the first stage calcination temperature is 550-650︒C, the calcination time is 1-2 hours, and the heating rate during calcination is 2-3︒C / min; the second stage calcination temperature is 900-950︒C, the time is maintained for 2 hours, the heating rate is 3-4︒C / min, and the inert gas used in both calcinations is 99.9% Ar; cooling to room temperature and grinding for 10-20 min to obtain the heteronuclear A1, B2 three-atom catalyst A1B2 / NC with an asymmetric electronic structure. The heteronuclear A1, B2 three-atom catalyst with an asymmetric electronic structure has excellent oxygen reduction reaction activity, the half-wave potential reaches 0.93-0.95 V under alkaline conditions, and reaches 0.86-0.88 V under acidic conditions, and has good resistance to methanol poisoning.

[0013] In the above scheme, the stirring time in step 3 is 24 hours; in step 4, the mixture is washed with deionized water 3 times, washed with methanol 2 times, and vacuum dried at 80°C for 12 hours; in step 5, the heating rate during calcination is 5°C / min, and the calcination time is 2 to 3 hours.

[0014] The heteronuclear A1 and B2 triatomic catalysts with asymmetric electronic structures in the above scheme are used in zinc-air batteries. In the zinc-air battery performance test, the peak power density reaches 270 mW cm -2 The above results show that it still has excellent charge and discharge cycle stability at high current density, and the charge and discharge round-trip efficiency is between 53.5% and 55.5%. Beneficial Effects

[0015] 1. The present invention uses transition metal ions to encapsulate and then pyrolyze anchor metal A through in-situ self-assembly, and then functionalizes the second metal B through KOH activation and a slow two-step carbonization process, and can controllably synthesize asymmetrically dispersed A1B2 heteronuclear triatomic sites on nitrogen-doped carbon carriers, and exhibits high oxidation reaction performance in the acidic to alkaline pH range. The catalyst breaks the intermediate adsorption association limitation based on single-nuclear sites in the electrocatalytic oxygen reduction reaction, retains the high atomic utilization of traditional single-atom supported catalysts, and optimizes the multi-step proton-coupled electron transfer process by adjusting the heteronuclear electronic structure properties, thereby exhibiting high oxidation reaction performance in the acidic to alkaline pH range.

[0016] 2. The single-atom catalyst preparation method described in the present invention is simple to operate and has a stable structure, which increases the loading capacity of existing supported metal single-atom catalysts and can also be expanded to prepare various heteronuclear triatomic nitrogen-doped carbon catalysts. The raw materials are abundant, economical and easy to obtain, and they show excellent activity and stability in electrocatalytic reactions, especially in acidic electrolytes. It still has rare cycle stability and promotes the further development of fuel cells.

[0017] 3. The heteronuclear A1 and B2 triatomic catalysts with asymmetric electronic structures described in the present invention improve the abundance of active sites by in-situ self-assembly and pyrolysis of transition metal ions to form triatomic nitrogen-doped carbon materials, and there is no obvious detachment or deactivation of metal active sites after the reaction. Under alkaline conditions, it shows better methanol poisoning resistance and corrosion resistance than commercial Pt / C.

[0018] 4. The heteronuclear triatomic catalyst described in the present invention is applied to metal zinc-air batteries, which have ultra-long cycle life and high energy density, solve the common problems of zinc-air batteries such as poor round-trip efficiency and short cycle life, and provide more possibilities for the practical application of zinc-air batteries.

[0019] 5. The present invention designs and synthesizes a high-load, high-stability A1B2 / NC heteronuclear triatomic catalyst on a porous carbon carrier derived from a zeolite imidazolate framework material (ZIF-8) by regulating the metal-carrier interaction. The catalyst breaks the intermediate adsorption association limitation based on a single nuclear site in the electrocatalytic oxygen reduction reaction, retains the high atomic utilization of traditional single-atom supported catalysts, and promotes the multi-step elementary reaction electron transfer process by regulating the electronic structure characteristics, showing high catalytic performance from acidic to alkaline pH ranges.

[0020] 6. The present invention aims to provide an in-situ self-assembly strategy to form an A1B2 triatom nitrogen-doped carbon material catalyst with asymmetrical dispersion. The prepared catalyst exhibits extraordinary oxygen reduction electrocatalytic activity and stability in alkaline to acidic electrolytes. It is applied to zinc-air batteries to achieve excellent operating performance and outstanding durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD spectrum of the heteronuclear tri-atom catalyst prepared according to Example 1 of the present invention; Figure 2 This is a SEM image of the heteronuclear tri-atom catalyst prepared according to Example 1 of the present invention; Figure 3 TEM spectrum of the heteronuclear single-atom catalyst prepared according to Example 1 of the present invention; 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; 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; Figure 6 1 is the linear sweep cyclic voltammetry curve of the catalyst prepared in Example 1 and the comparative sample in 0.1 M KOH.

[0022] Figure 7 1 is the linear sweep cyclic voltammetry curve of the catalyst prepared in Example 1 and the comparative sample in 0.5 M H2SO4.

[0023] Figure 8 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 DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings: The preparation method of this asymmetric dispersion of A1 and B2 triatomic catalyst is as follows: transition metal ions form heteronuclear triatomic nitrogen-doped carbon materials through an in-situ self-assembly strategy. By encapsulating and pyrolyzing the first metal (A), and then activating with KOH and functionalizing the second metal (B) through a slow two-step carbonization process, asymmetrically dispersed A1B2 heteronuclear triatomic sites can be controllably synthesized on a nitrogen-doped carbon support. This catalyst breaks the intermediate adsorption association limitation based on single-nuclear sites in the electrocatalytic oxygen reduction reaction, retains the high atomic utilization of traditional single-atom supported catalysts, and optimizes the multi-step proton-coupled electron transfer process by adjusting the electronic structure of the heteronuclear triatomic sites, thereby showing high oxidation reaction performance in the acidic to alkaline pH range. The preparation method is easy to obtain and has universality. The obtained catalyst material has unique electronic structure properties and has very broad application prospects in the fields of energy storage and energy conversion. Example

[0025] 1. Dissolve 1.290 g Zn(NO3)2·6H2O and 0.089 g 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.

[0026] 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 ultrasonicate for 1 hour to obtain solution 2.

[0027] 3. Add solution 2 to solution 1 under ultrasonic conditions and stir at room temperature for 24 hours.

[0028] Fourth, the obtained sample was centrifuged, washed with deionized water and ethanol, and dried in a vacuum drying oven at 80°C for 12 hours.

[0029] 5. The synthesized precursor was carbonized in a tube furnace at 1000 °C for 2 h under argon atmosphere with a heating rate of 5 °C / min, and the obtained sample Fe / NC was collected after grinding.

[0030] 6. Grind 250 mg Fe / NC and 2 g KOH solid to make them evenly mixed, and pyrolyze them in a tube furnace at 800 °C for 2 h under argon atmosphere with a heating rate of 5 °C / min. Collect the obtained sample Fe1 / NC-def after washing and drying.

[0031] 7. Take 200 mg of the Fe1 / NC-def sample prepared above, grind it with 0.993 g of cobalt acetylacetonate and 1.60 g of melamine for 30 min and mix them evenly.

[0032] 8. The powder obtained in step 7 was calcined by two-stage program heating. 1) Calcination in a 600 °C tube furnace for 1 h, with a heating rate of 3 °C / min. 2) Calcination in a 900 °C tube furnace for 2 h, with a heating rate of 3 °C / min, to obtain the catalyst Fe1Co2 / NC.

[0033] Zn was used as the negative electrode, the prepared catalyst was used as the positive electrode, the electrolyte was 6 mol / L KOH and 0.2 mol / L zinc acetate solution, and a zinc-air battery was assembled.

[0034] The catalyst obtained in the above example was subjected to a series of structural characterizations to verify its structure.

[0035] like Figure 1 The figure shows the XRD characterization of the catalyst of Example 1. The figure shows two diffraction peaks at about 24° and 44°, which are the (002) and (101) crystal planes of graphite carbon respectively. No characteristic diffraction peaks of metal nanoparticles are found.

[0036] like Figure 2 The SEM image of the catalyst in Example 1 is shown, which proves that the catalyst obtained in Example 1 is a deformed regular dodecahedron, and the catalyst diameter is 300-400 nm.

[0037] like Figure 3 The TEM image of the catalyst of Example 1 is shown, indicating that there is no metal atom aggregation in the catalyst obtained in Example 1. There are densely distributed and atomically dispersed bright spots in the entire carbon support, and most of the atomic dispersion is triangular three-atomic sites.

[0038] like Figure 4 Shown is the Fe K-edge XANES spectrum of the catalyst of Example 1, showing the valence state of a single Fe atom in a three-atom site.

[0039] like Figure 5 Shown is the Co K-edge XANES spectrum of the catalyst of Example 1, showing the valence state of the Co atom in the three-atom site. Example

[0040] The only difference between this embodiment and embodiment 1 is that in this embodiment, the amount of Zn(NO3)2 6H2O added in step 1 is 3.8 mmol and the amount of Fe(OAc)2 is 0.22 mmol. Example

[0041] The difference between this embodiment and embodiment 1 is that in this embodiment, 30 mL of solution is added in step 1, wherein the volume ratio between the N,N-dimethylimidazole solution and the methanol solution is 3:1. Example

[0042] The difference between this embodiment and embodiment 1 is that, in this embodiment, 0.96 g of diammonium cyanide is added in step eight. Example

[0043] The difference between this embodiment and embodiment 1 is that in this embodiment, 250 mg of A / NC and 2.2 g of KOH are mixed and ground in step 6. Example

[0044] The difference between this embodiment and embodiment 1 is that, in this embodiment, 1.50 g of 2-methylimidazole is added to 30 mL of a mixed solution of N,N-dimethylformamide and ethanol (volume ratio 4:1). Example

[0045] The only difference between this embodiment and embodiment 1 is that in this embodiment, the calcination temperature in step 5 is 980 °C and the heating rate is 4.5 °C / min. Example

[0046] The only difference between this embodiment and embodiment 1 is that in this embodiment, the first calcination temperature in step eight is 650° C. and the time is maintained for 1.5 hours. Example

[0047] The only difference between this embodiment and embodiment 1 is that in this embodiment, the second step calcination temperature in step eight is 950 °C and the time is maintained for 1.5 hours.

[0048] Embodiment 10: The difference between this embodiment and embodiment 1 is that in this embodiment, in step 7, Fe1 / NC-def is ground with 0.984 g of nickel acetylacetonate and 1.60 g of melamine for 30 min to be uniformly mixed.

[0049] Comparative Example 1: The difference between this comparative example and Example 1 is that in this example, transition metal A is no longer added in step 1.

[0050] Comparative Example 2: The difference between this comparative example and Example 1 is that in this example, the second transition metal B is not added in step eight.

[0051] Comparative Example 3: The difference between this embodiment and embodiment 1 is that in this embodiment, transition metals A and B are not added in step 1 and step 8.

[0052] Comparative Example 4: In this example, 5 mg of commercial Pt / C (Pt content is 20%) catalyst was ultrasonically dispersed for 30 minutes to obtain a solution.

[0053] In order to test the catalytic performance of the single-atom electrocatalyst of the present application, the present application also provides application examples and catalyst performance tests.

[0054] Catalyst catalytic oxygen reduction reaction and zinc-air battery performance evaluation: 5 mg of catalyst was added to 40 uL of 5% Nafion and 960 uL of isopropanol solution, and ultrasonic dispersion was performed to obtain a solution. 11 uL of the solution was drop-coated on the rotating disk electrode, and the catalyst loading was 0.28 mg cm -2 After being dried naturally, a thin film electrode was obtained; a three-electrode system with an Ag / AgCl electrode as a reference electrode and a Pt wire as a counter electrode was formed. Linear voltammetry tests were performed using an electrochemical workstation in an oxygen-saturated 0.1 mol / L KOH or 0.5 M H2SO4 solution at room temperature, with a scan rate of 10 mV / s and an electrode rotation speed of 1600 r.

[0055] like Figure 6 The figure shows the LSV curves of the catalyst of Example 1 and other comparative samples measured in an alkaline environment. Under alkaline conditions, the oxygen reduction starting potential is 1.07 V and the half-wave potential is 0.94 V. The test shows that the oxygen reduction starting potential and half-wave potential are 0.08 V better than those of commercial platinum carbon, and the cycle performance is also better than that of platinum carbon, showing excellent oxygen reduction catalytic activity and stability.

[0056] like Figure 7 The LSV curves of the catalyst of Example 1 and other comparative samples measured in an acidic environment are shown. Under acidic conditions, the oxygen reduction starting potential is 0.98 V and the half-wave potential is 0.88 V. Therefore, the heteronuclear triatomic electrocatalyst prepared by the present invention has the potential to be applied to the cathode reaction of fuel cells.

[0057] A zinc-air battery was assembled using Zn as the negative electrode, Preparation Example 1 as the positive electrode, and 6 mol / L KOH and 0.2 mol / L zinc acetate solution as the electrolyte.

[0058] like Figure 8 Shown are the polarization curves and power density diagrams of the catalyst of Example 1 and Comparative Example 1 and commercial Pt / C. It can be seen from the figure that the power density of the prepared single-atom catalyst is far superior to that of commercial Pt / C, and has excellent development prospects.

[0059] The non-precious metal catalyst prepared by the present invention has an electrocatalytic oxygen reduction performance in alkaline electrolyte comparable to that of commercial Pt / C. When applied to zinc-air batteries, its peak power density exceeds that of most non-precious metal catalysts. In addition, the catalyst has excellent charge and discharge cycle stability when used in zinc-air batteries, and its performance remains stable after more than 1,000 cycles.

[0060] The above is a detailed introduction to the preparation method and application of a triatomic catalyst with asymmetrical dispersion of A1 and B2 disclosed in the embodiment of the present application. The implementation methods of the present application are described in detail using specific examples herein. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. The catalyst is mainly used in zinc-air batteries to catalyze the ORR reaction of cathode oxygen during battery discharge. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. At the same time, for those skilled in the art, according to the idea of ​​this application, there will be changes in the specific implementation and scope of application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention. In summary, the content of this specification should not be understood as a limitation on this application.

Claims

1. A heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure, characterized in that: The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure is prepared by the following method: encapsulating the first metal A in situ by self-assembly and then pyrolyzing it, activating it with KOH to construct defects on the carrier, introducing the second metal species B and performing a slow two-step carbonization, and finally controllably synthesizing asymmetrically dispersed A1B2 heteronuclear triatomic sites on the nitrogen-doped carbon carrier; 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: Step 1: encapsulating a transition metal complex in a zeolite imidazole framework to form a complex; dissolving a zinc metal salt and a compound of a transition metal A in a mixed solution of methanol and N,N-dimethylformamide, dissolving by ultrasonication, and stirring for 1-2 hours to dissolve the metal salt to form a homogeneous solution 1; the molar ratio of zinc ions to transition metal A ions is 15:1 to 20:1; Step 2: adding white powder 2-methylimidazole to another mixed solution of methanol and N,N-dimethylformamide, dispersing by ultrasonication, and performing a self-assembly process under stirring to obtain a mixed solution 2; Step 3: under ultrasonic conditions, the mixed solution 2 formed in step 2 is quickly added to the homogeneous solution 1 formed in step 1, ultrasonically dispersed, and self-assembly is performed under stirring conditions; the molar ratio of the compound of transition metal A to 2-methylimidazole is 1:3 to 1:8; Step 4: centrifuge the sample obtained in step 3, wash it with methanol, and vacuum dry it to obtain a solid powder; Step 5: pyrolyze the sample obtained in the above step 4 at high temperature in an inert atmosphere to obtain a nitrogen-doped carbon material A / NC loaded with metal A; Step 6: Grind the obtained solid powder A1 / NC and KOH or mix them, and pyrolyze them under an inert atmosphere to activate the M1 / NC material and form defects near the metal active sites to obtain A1 / NC-def; the mass ratio of A1 / NC to KOH is 1:8 to 1:12; Step 7, placing the A1 / NC-def prepared in step 6 in deionized water, stirring for 3-5 hours, centrifuging, washing, and vacuum drying; Step 8: The solid powder A1 / NC-def obtained above is mixed with another compound of transition metal B, and then a nitrogen source is added and ground evenly; the molar amount of transition metal B is 2 to 3 times the molar amount of transition metal A, and the molar amount of the nitrogen source is 2 to 4 times the molar amount of transition metal B; Step nine: subjecting the solid powder obtained in step eight to two-step programmed temperature pyrolysis in an inert atmosphere, and calcining to obtain a heteronuclear A1, B2 triatom catalyst A1B2 / NC having an asymmetric electronic structure.

2. The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 1, characterized in that: In the step 1, 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.

3. The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 2, characterized in that: In the step 1, the molar concentration of the metal ions of the transition metal compound A is 0.006-0.010 mol / L, the molar concentration of the 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.

4. The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 3, characterized in that: In the step 2, the molar concentration of 2-methylimidazole is 0.5-0.7 mol / L, and the volume ratio of N,N-dimethylimidazole solution to methanol solution is 3:1-5:

1.

5. The heteronuclear A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 4, characterized in that: In the step 5, 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 A1, B2 triatomic catalyst with an asymmetric electronic structure according to claim 5, characterized in that: In step 6, 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 A1, 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 acetylacetone-type metal organic compound; the molar ratio of the transition metal A compound to 2-methylimidazole is 1:4-1:6; and 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 the step nine, the temperature is programmed to rise, the first stage calcination temperature is 550-650︒C, the calcination time is 1-2 hours, and the heating rate during calcination is 2-3︒C / min; the second stage calcination temperature is 900-950︒C, the time is maintained for 2 hours, the heating rate is 3-4︒C / min, and the inert gas used in both calcinations is 99.9% Ar; cooling to room temperature and grinding for 10-20 minutes to obtain the heteronuclear A1, B2 three-atom catalyst A1B2 / NC with an asymmetric electronic structure, the heteronuclear A1, B2 three-atom catalyst with an asymmetric electronic structure has excellent oxygen reduction reaction activity, the half-wave potential reaches 0.93-0.95 V under alkaline conditions, and reaches 0.86-0.88 V under acidic conditions, and 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 3, the stirring time is 24 hours; in step 4, the mixture is washed with deionized water for 3 times, washed with methanol for 2 times, and vacuum dried at 80°C for 12 hours; in step 5, the heating rate during calcination is 5°C / min, and the calcination time is 2 to 3 hours.

10. Use of a heteronuclear A1, B2 triatomic catalyst having an asymmetric electronic structure according to any one of claims 1 to 9, characterized in that: The heteronuclear A1 and B2 triatomic catalysts with asymmetric electronic structures are used in zinc-air batteries. In the performance test of zinc-air batteries, the peak power density reaches 270 mW cm -2 The above results show that it still has excellent charge and discharge cycle stability at high current density, and the charge and discharge round-trip efficiency is between 53.5% and 55.5%.

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