A dual-site coupled Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst and preparation method and application thereof

Abstract

The application discloses a dual-site coupling Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst, a preparation method thereof and application, and belongs to the technical field of electrochemical energy materials. The preparation method comprises the following steps: (1) refluxing and stirring zinc source and an organic ligand in a polar solvent aqueous solution to construct a precursor; (2) dispersing the precursor in a dispersion system composed of a non-polar and strong-polar organic solvent, and dropwise adding a metal salt solution formed by an iron source and a cobalt source to perform controlled adsorption to obtain a metal precursor; and (3) performing staged pyrolysis on the metal precursor to obtain the dual-site coupling Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst. The catalyst can realize the dual-function synergistic promotion of ORR and OER, the active center can be controlled to be constructed, the Janus structure is stable, the mass transfer and conductivity advantages are obvious, and the catalyst is used in a zinc-air battery and exhibits excellent output capacity and long cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy materials technology, specifically relating to a dual-site coupled Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst, its preparation method and application. Background Technology

[0002] Zinc-air batteries are considered promising energy storage devices due to their high energy density, low cost, and environmental friendliness. However, the intrinsic kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) involved in the air electrode are slow, and the reaction pathways and intermediate adsorption characteristics differ significantly during charge-discharge cycles. This can easily lead to increased battery polarization, reduced energy efficiency, and accelerated performance degradation, thus placing a demand on air electrode catalysts that can achieve both ORR and OER dual functionality and long-cycle stability.

[0003] Currently, while noble metal systems (such as Pt-based systems for ORR and Ru / Ir oxides for OER) exhibit high catalytic activity, their high cost and resource scarcity hinder large-scale applications. Therefore, non-noble metal MNC-type oxygen electrocatalysts (where M represents Fe, Co, etc.) have become an important research direction. Fe-N x While bifunctional sites typically exhibit good ORR activity, their OER capacity is relatively insufficient. To achieve bifunctional catalysis, most methods employ the introduction of a second metal (such as Co) into the carbon support to modulate the electronic structure and adsorption behavior, forming the FeCo-NC system. Various strategies have been developed, including diatomic sites, single-atom sites, alloy / nanounits, and defect modulation. Nevertheless, existing FeCo-NC bifunctional catalysts still generally suffer from the following prominent problems:

[0004] (1) Difficulty in achieving a "compromise" between dual functions and unstable synergy: ORR and OER have different requirements for the optimal adsorption strength and electronic structure of the active center. Many materials perform well in a single reaction, but it is difficult to achieve simultaneous optimization of ORR and OER in the same catalyst. In particular, the performance is more prone to degradation under the round-trip working conditions of zinc-air batteries.

[0005] (2) The active site has a complex morphology but insufficient controllability: In the existing routes, Fe / Co may exist in the form of diatomic coordination centers, single atomic sites, or metal / alloy nano species; the "division of labor and cooperation" between different morphologies often depends on the local structure formed by chance, lacking a repeatable and scalable directional construction path, which leads to limited batch consistency and durability.

[0006] (3) The cycle stability of zinc-air batteries is still weak: Under the conditions of strong alkaline electrolyte and gas-liquid-solid three-phase interface, active sites are prone to migration, aggregation, reconstruction or interface mismatch, which leads to a decrease in round-trip efficiency and a shortened cycle life. It is also clearly pointed out that existing bifunctional electrocatalysts have problems such as "single structure, insufficient synergistic effect of active sites and poor cycle stability of zinc-air batteries".

[0007] Therefore, there is an urgent need for a non-precious metal bifunctional catalyst for the air electrode of zinc-air batteries and its preparation method, which can achieve controllable dual-site construction and stable coupling in a carbon matrix, thereby improving OER performance while ensuring ORR activity, and significantly improving the round-trip efficiency and long-cycle stability of zinc-air batteries, so as to solve the above-mentioned existing technical problems. Summary of the Invention

[0008] To address the common issues of insufficient structural / site controllability in existing bifunctional FeCo-NC catalysts, Fe-N... x To address the issues of insufficient synergy with FeCo species and poor cycle stability in zinc-air batteries, this invention aims to provide a dual-site coupled Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst and its preparation method are applied to zinc-air batteries, achieving synergistic catalysis of ORR and OER in a non-noble metal system and improving the cycle life of zinc-air batteries.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] In a first aspect, the present invention provides a dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0011] (1) Precursor construction: The precursor was constructed by using a zinc source and an organic ligand. The zinc source and the organic ligand were dissolved in a mixed solution of a polar organic solvent and water, respectively. After reflux and stirring, the product was centrifuged, washed, and vacuum dried to obtain a white solid powder.

[0012] (2) Bimetallic controlled adsorption: Bimetallic precursors are constructed by ion adsorption. White solid powder is dispersed in a mixed solution of nonpolar organic solvent and strong polar organic solvent to form the first solution.

[0013] The iron source and the cobalt source are dissolved in water to form a second solution;

[0014] By controlling the dropping rate, the second solution was added dropwise to the first solution, and after adsorption by stirring at room temperature, centrifugation and drying were performed to obtain a light purple metal precursor.

[0015] (3) Reducing segmented pyrolysis: The pale purple metallic precursor was placed in a heating furnace and pyrolyzed in a reducing and inert mixed atmosphere by segmented heating and holding. After cooling to room temperature, a dual-site coupled Janus structure FeN was obtained. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0016] Further, in step (1), the zinc source is a mixture of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O and ZnCl2, the organic ligand is a mixture of 5,6-dimethylbenzimidazole and 2,5-diaminoterephthalic acid, and the polar organic solvent is one or more of methanol, ethanol, ethylene glycol, N,N-dimethylformamide and N-methylpyrrolidone.

[0017] Furthermore, the molar ratio of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O and ZnCl2 is (5-6):(3-4):1;

[0018] The molar ratio of 5,6-dimethylbenzimidazole to 2,5-diaminoterephthalic acid is (0.3-0.4):(0.6-0.7).

[0019] The volume ratio of the polar organic solvent to water is (1-3):1.

[0020] Furthermore, in step (1), the molar ratio of zinc source to organic ligand is (9.8-10.2):1;

[0021] The reflux temperature is 75℃-85℃, the stirring rate is 700rpm / min-900rpm / min, and the reaction time is 6h-10h.

[0022] The centrifugation speed is 8000 rpm / min-9000 rpm / min, the centrifugation time is 4 min-5 min, and the number of centrifugations is 3-5 times;

[0023] The washing process involves first washing with water 2-3 times, and then washing with anhydrous ethanol 2-3 times, ensuring that the precipitate is submerged in water or anhydrous ethanol during each wash.

[0024] Drying is performed in a vacuum drying oven at a temperature of 50℃-70℃ for 6-10 hours.

[0025] Furthermore, in step (2), the mass-to-volume ratio (g:mL) of the white solid powder to the mixed solution of nonpolar organic solvent / strong polar organic solvent is (0.82-1):(50-70);

[0026] The molar ratio of iron source to cobalt source is (2-3):1.

[0027] Further, in step (2), the non-polar organic solvent is one or a combination of n-hexane, cyclohexane or petroleum, and the strong polar organic solvent is one or a combination of dimethyl sulfoxide, N,N-dimethylformamide or acetonitrile; the volume ratio of the non-polar organic solvent to the strong polar organic solvent is (3-4.5):1.

[0028] The iron source is a mixture of Fe(NO3)3·9H2O and Fe(CH3COO)2, with a molar ratio of Fe(NO3)3·9H2O to Fe(CH3COO)2 of 0.02:(0.03-0.06).

[0029] The cobalt source is a mixture of Co(CH3COO)2·4H2O and Co(NO3)2·6H2O; the molar ratio of Co(CH3COO)2·4H2O to Co(NO3)2·6H2O is (0.01-0.03):0.01.

[0030] Furthermore, in step (2), the dropping rate of the second solution onto the first solution is 200 μL / min - 500 μL / min;

[0031] The stirring rate at room temperature was 600 rpm / min-800 rpm / min, and the time was 1.8 h-4.2 h.

[0032] The centrifugation speed is 8000 rpm / min-9500 rpm / min, and the time is 4 min-6 min;

[0033] Drying is performed in a vacuum drying oven at a temperature of 50℃-70℃ for 6-10 hours.

[0034] Furthermore, in step (3), the reducing and inert mixed atmosphere is H2 and Ar, wherein the volume ratio of H2 to Ar is 1:(90-95);

[0035] The pyrolysis process using a segmented heating-holding method involves first heating the temperature to 280℃-300℃ at a rate of 2℃ / min-3℃ / min and holding it for 1.5h-2h; then heating the temperature to 900℃-950℃ at a rate of 5℃ / min-6℃ / min and holding it for 2h-3h.

[0036] Secondly, this invention provides a dual-site coupled Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst, employing the aforementioned dual-site coupled Janus structure FeN x The FeCo@NC-J bifunctional oxygen electrocatalyst was prepared using a specific method. x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0037] Thirdly, this invention provides a dual-site coupled Janus structure FeN x The application of / FeCo@NC-J bifunctional oxygen electrocatalysts combines two-site coupling of Janus structure FeN x An aqueous zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3COO)2 electrolyte, achieving a peak power density ≥205 mW / cm². 2 At a current density of 10 mA / cm 2 At that time, the stable cycle time is more than 1100 hours, and the round-trip efficiency retention rate is ≥59%.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. Dual-function synergistic enhancement: This invention simultaneously constructs atomically dispersed Fe-N in a nitrogen-doped carbon matrix. x The site and FeCo alloy nanounits form a "single atom-alloy" Janus composite active center. Through the synergistic regulation of the metal d-band center by interfacial electrons and the optimization of the adsorption energy of oxygen intermediates, the dual functions of ORR and OER are simultaneously enhanced.

[0040] 2. Controllable construction of active centers and stable structure: The preparation method of this invention adopts a process chain of "precursor construction - bimetallic controlled adsorption - reducing segmented pyrolysis", which is conducive to the stable acquisition of the target Janus structure and reduces site randomness, thereby improving the reproducibility and structural stability of the material.

[0041] 3. Significant advantages in mass transfer and conductivity: The catalyst of this invention has a hierarchical porous structure and an effective conductive network, which can simultaneously improve the mass transfer and electron transport conditions at the gas-liquid-solid three-phase interface, thereby reducing polarization, improving rate performance and reaction kinetics under actual operating current.

[0042] 4. When the catalyst of this invention is applied to the air cathode of a zinc-air battery, the peak power density of the battery can reach 205 mW / cm³. 2 Above; at 10mA / cm 2 Under current density conditions, it can cycle stably for more than 1100 hours with a round-trip efficiency retention rate of more than 59%. This catalyst demonstrates excellent output capability and long-term cycle stability when used in zinc-air batteries. Attached Figure Description

[0043] Figure 1 The two-site coupled Janus structure FeN was prepared in Example 1. xScanning electron microscope (SEM) image of FeCo@NC-J bifunctional oxygen electrocatalyst;

[0044] Figure 2 Example 1: Two-site coupled Janus structure FeN x Power density curve of zinc-air battery assembled with / FeCo@NC-J bifunctional oxygen electrocatalyst as air cathode. Detailed Implementation

[0045] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0046] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0047] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0048] The zinc source and organic ligand were dissolved in a mixed solution of a polar organic solvent and water at a molar ratio of (9.8-10.2):1. The zinc source was a mixture of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O, and ZnCl2 with a molar ratio of (5-6):(3-4):1. The organic ligand was a mixture of 5,6-dimethylbenzimidazole and 2,5-diaminoterephthalic acid with a molar ratio of (0.3-0.4):(0.6-0.7). The polar organic solvent was methanol, ethanol, ethylene glycol, N,N-dimethylformamide, or N-methylpyrrolidone. One or more of the following are used: a polar organic solvent and water in a volume ratio of (1-3):1; reflux and stir at 75℃-85℃ and 700rpm / min-900rpm / min for 6h-10h; centrifuge the product at 8000rpm / min-9000rpm / min for 4min-5min, repeating the centrifugation operation 3-5 times; wash with water 2-3 times, and then wash with anhydrous ethanol 2-3 times, ensuring that the precipitate is submerged in water or anhydrous ethanol each time; dry in a vacuum drying oven at 50℃-70℃ for 6h-10h to obtain a white solid powder.

[0049] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0050] The white solid powder was dispersed in a mixed solution of a nonpolar organic solvent (the nonpolar phase used to form the first solution) and a strongly polar organic solvent (the polar phase used to regulate the migration / adsorption of metal salts) at a mass-to-volume ratio of (0.82-1) g:(50-70) mL. The volume ratio of the nonpolar organic solvent to the strongly polar organic solvent was (3-4.5):1. The nonpolar organic solvent was one or more of n-hexane, cyclohexane, or petroleum, and the strongly polar organic solvent was one or more of dimethyl sulfoxide, N,N-dimethylformamide, or acetonitrile to form the first solution.

[0051] Iron and cobalt sources were dissolved in water at a molar ratio of (2-3):1 to form a second solution. The iron source was a mixture of Fe(NO3)3·9H2O and Fe(CH3COO)2 with a molar ratio of 0.02:(0.03-0.06), and the cobalt source was a mixture of Co(CH3COO)2·4H2O and Co(NO3)2·6H2O with a molar ratio of (0.01-0.03):0.01. The dropping rate was controlled at 200 μL / min-500 μL / min. The second solution was added dropwise to the first solution and stirred at 600 rpm / min-800 rpm / min for 1.8 h-4.2 h at room temperature. After adsorption was completed, the mixture was centrifuged at 8000 rpm / min-9500 rpm / min for 4 min-6 min and dried in a vacuum drying oven at 50℃-70℃ for 6 h-10 h to obtain a light purple metal precursor.

[0052] (3) Reducing segmental pyrolysis: The light purple metallic precursor was placed in a heating furnace and heated to 280℃-300℃ for 1.5h-2h under a mixed atmosphere of H2 and Ar with a volume ratio of 1:(90-95). Then, the temperature was increased to 900℃-950℃ at a heating rate of 2℃ / min-3℃ / min and held for 2h-3h. After cooling to room temperature, the two-site coupled Janus structure FeN was obtained. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0053] A dual-site coupled Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst, employing the aforementioned dual-site coupled Janus structure FeN x The FeCo@NC-J bifunctional oxygen electrocatalyst was prepared using a specific method. x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0054] A dual-site coupled Janus structure FeN xThe application of / FeCo@NC-J bifunctional oxygen electrocatalysts combines two-site coupling of Janus structure FeN x An aqueous zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3COO)2 electrolyte, achieving a peak power density ≥205 mW / cm². 2 At a current density of 10 mA / cm 2 At that time, the stable cycle time is more than 1100 hours, and the round-trip efficiency retention rate is ≥59%.

[0055] Example 1

[0056] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0057] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0058] A zinc source consisting of 5 mmol Zn(CH3COO)2·2H2O, 4 mmol Zn(NO3)2·6H2O, and 1 mmol ZnCl2 was dissolved in a mixture of methanol, N,N-dimethylformamide (30 mL in any proportion), and water (30 mL in total) with an organic ligand consisting of 0.30 mmol 5,6-dimethylbenzimidazole and 0.7 mmol 2,5-diaminoterephthalic acid. The resulting mixture had a molar ratio of zinc source to organic ligand of 10:1. The mixture was refluxed and stirred at 85 °C and 900 rpm / min for 10 h. The reaction product was centrifuged at 8500 rpm / min for 4.8 min, and the centrifugation was repeated 4 times. The product was washed 3 times with water and then 2 times with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 70 °C for 10 h to obtain a white solid powder.

[0059] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0060] 0.88 g of white solid powder was dispersed in 50 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 3.3:1), and this solution was designated as the first solution.

[0061] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.03 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.0067 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 3:1, and this solution is designated as the second solution.

[0062] The dropping rate was controlled at 400 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 800 rpm / min for 2.41 h at room temperature for ion adsorption. The mixture was then centrifuged at 9500 rpm / min for 6 min to collect the solid product. The solid product was dried at 60 °C for 10 h in a vacuum drying oven to obtain a light purple metal precursor.

[0063] (3) Reducing segmental pyrolysis: The pale purple metal precursor was placed in a heating furnace and heated to 300℃ at a heating rate of 2.6℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:90. The temperature was held for 2 h, and then heated to 950℃ at a heating rate of 5℃ / min. The temperature was held for 3 h and then cooled to room temperature to obtain FeN with a dual-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0064] The two-site coupled Janus structure FeN prepared in Example 1 of this embodiment is shown in Figure 1. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix. SEM measurements were performed, such as... Figure 1 As shown, FeNx / FeCo@NC-J exhibits a polyhedral morphology. Its rough surface structure is beneficial for increasing the specific surface area and exposing more metal active sites, thereby promoting the mass-charge transport process.

[0065] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3COO)2 electrolyte. Its charge-discharge cycle performance curve is shown below. Figure 2 As shown, at a current density of 10 mA / cm² 2 At that time, the peak power density of the battery reached 220 mW / cm². 2 It can stably cycle for 1255 hours with a round-trip efficiency retention rate of 61.8%, demonstrating excellent rate performance and cycle stability.

[0066] Example 2

[0067] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0068] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0069] A zinc source consisting of 5.2 mmol of Zn(CH3COO)2·2H2O, 3.6 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of 40 mL of ethanol and 20 mL of water, with an organic ligand consisting of 0.4 mmol of 5,6-dimethylbenzimidazole and 0.6 mmol of 2,5-diaminoterephthalic acid. The resulting mixed solution had a molar ratio of zinc source to organic ligand of 9.8:1. The mixture was refluxed and stirred at 75 °C and 700 rpm / min for 6 h. The reaction product was centrifuged at 8000 rpm / min for 5 min, and the centrifugation was repeated 3 times. The product was washed twice with water and then twice with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 50 °C for 6 h to obtain a white solid powder.

[0070] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0071] 1 g of white solid powder was dispersed in 70 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 3:1), and this solution was designated as the first solution.

[0072] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.045 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.015 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2.6:1, and this solution was designated as the second solution.

[0073] The dropping rate was controlled at 200 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 620 rpm / min for 1.83 h at room temperature for ion adsorption. Then, the mixture was centrifuged at 8000 rpm / min for 4 min to collect the solid product. The solid product was dried at 60 °C for 6 h in a vacuum drying oven to obtain a light purple metal precursor.

[0074] (3) Reducing segmental pyrolysis: The light purple metal precursor was placed in a heating furnace and heated to 280°C at a heating rate of 2°C / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:90. The temperature was held for 2 h, and then heated to 900°C at a heating rate of 5°C / min. The temperature was held for 3 h, and then cooled to room temperature to obtain FeN with a dual-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0075] The two-site coupled Janus structure FeN prepared in Example 2 of this embodiment is shown in Figure 2. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0076] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3COO)2 electrolyte. The battery operated at a current density of 10 mA / cm². 2 At that time, the battery's peak power density reached 208 mW / cm². 2 It can stably cycle for 1180 hours with a round-trip efficiency retention rate of 61.5%, demonstrating excellent rate performance and cycle stability.

[0077] Example 3

[0078] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0079] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0080] A zinc source consisting of 5.8 mmol of Zn(CH3COO)2·2H2O, 3.4 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of 50 mL of ethylene glycol and 20 mL of water, with an organic ligand consisting of 0.38 mmol of 5,6-dimethylbenzimidazole and 0.62 mmol of 2,5-diaminoterephthalic acid. The resulting mixed solution had a molar ratio of zinc source to organic ligand of 10.2:1. The mixture was refluxed and stirred at 80 °C and 800 rpm / min for 8 h. The reaction product was centrifuged at 9000 rpm / min for 4 min, and the centrifugation was repeated 5 times. The product was washed 3 times with water and then 3 times with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 60 °C for 8 h to obtain a white solid powder.

[0081] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0082] 0.85 g of white solid powder was dispersed in 55 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 4:1), and this solution was designated as the first solution.

[0083] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.045 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.015 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2.6:1, and this solution was designated as the second solution.

[0084] The dropping rate was controlled at 500 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 650 rpm / min for 3.61 h at room temperature for ion adsorption. The mixture was then centrifuged at 9000 rpm / min for 4 min to collect the solid product. The solid product was dried in a vacuum drying oven at 55 °C for 8 h to obtain a light purple metal precursor.

[0085] (3) Reducing segmental pyrolysis: The light purple metallic precursor was placed in a heating furnace and heated to 300℃ at a heating rate of 3℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:95. The temperature was held for 1.5h, and then heated to 950℃ at a heating rate of 6℃ / min. The temperature was held for 2h and then cooled to room temperature to obtain FeN with a dual-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0086] The two-site coupled Janus structure FeN prepared in Example 3 of this embodiment is shown in Figure 3. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-Nx Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0087] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3COO)2 electrolyte. The battery operated at a current density of 10 mA / cm². 2 At that time, the battery's peak power density reached 209 mW / cm². 2 It can stably cycle for 1250 hours with a round-trip efficiency retention rate of 60.3%, demonstrating excellent rate performance and cycle stability.

[0088] Example 4

[0089] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0090] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0091] A zinc source consisting of 5.9 mmol of Zn(CH3COO)2·2H2O, 3 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of 35 mL of N,N-dimethylformamide and 12 mL of water, along with an organic ligand consisting of 0.4 mmol of 5,6-dimethylbenzimidazole and 0.6 mmol of 2,5-diaminoterephthalic acid. The resulting mixed solution contained a zinc source to organic ligand molar ratio of 9.9:1. The mixture was refluxed and stirred at 80 °C and 800 rpm / min for 7 h. The reaction product was centrifuged at 8200 rpm / min for 4.8 min, and the centrifugation was repeated 4 times. The product was washed twice with water and then twice with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 60 °C for 8 h to obtain a white solid powder.

[0092] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0093] 0.95 g of white solid powder was dispersed in 65 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 4.2:1), and this solution was designated as the first solution.

[0094] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.052 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.02 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2.4:1, and this solution was designated as the second solution.

[0095] The dropping rate was controlled at 300 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 670 rpm / min for 1.93 h at room temperature for ion adsorption. Then, the mixture was centrifuged at 9000 rpm / min for 4 min to collect the solid product. The solid product was dried at 60 °C for 8 h in a vacuum drying oven to obtain a light purple metal precursor.

[0096] (3) Reducing staged pyrolysis: The light purple metallic precursor was placed in a heating furnace and heated to 285℃ at a heating rate of 2.2℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:93. The temperature was held for 1.7h, and then heated to 910℃ at a heating rate of 5.2℃ / min. The temperature was held for 2.8h and then cooled to room temperature to obtain FeN with a two-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0097] The two-site coupled Janus structure FeN prepared in Example 4 of this embodiment is shown. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0098] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3OO)2 electrolyte. The battery operated at a current density of 10 mA / cm². 2 At that time, the battery's peak power density reached 218 mW / cm². 2 It can stably cycle for 1210 hours with a round-trip efficiency retention rate of 59.2%, demonstrating excellent rate performance and cycle stability.

[0099] Example 5

[0100] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0101] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0102] A zinc source consisting of 5.1 mmol of Zn(CH3COO)2·2H2O, 4 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of 45 mL of N-methylpyrrolidone and 18 mL of water, along with an organic ligand consisting of 0.35 mmol of 5,6-dimethylbenzimidazole and 0.65 mmol of 2,5-diaminoterephthalic acid. The resulting mixed solution contained a zinc source to organic ligand molar ratio of 10.1:1. The mixture was refluxed and stirred at 80 °C and 800 rpm / min for 8 h. The reaction product was centrifuged at 8800 rpm / min for 4.2 min, and the centrifugation was repeated 5 times. The product was washed 3 times with water and then 3 times with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 60 °C for 8 h to obtain a white solid powder.

[0103] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0104] 0.82 g of white solid powder was dispersed in 52 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 3.8:1), and this solution was designated as the first solution.

[0105] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.036 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.01 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2.8:1, and this solution was designated as the second solution.

[0106] The dropping rate was controlled at 450 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 700 rpm / min for 4.2 h at room temperature to allow for ion adsorption. The mixture was then centrifuged at 9000 rpm / min for 5 min to collect the solid product. The solid product was dried at 70 °C for 8 h in a vacuum drying oven to obtain a light purple metal precursor.

[0107] (3) Reducing staged pyrolysis: The pale purple metal precursor was placed in a heating furnace and heated to 295℃ at a heating rate of 2.8℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:94. The temperature was held for 1.6h, and then heated to 940℃ at a heating rate of 5.8℃ / min. The temperature was held for 2.2h and then cooled to room temperature to obtain FeN with a two-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0108] The two-site coupled Janus structure FeN prepared in Example 5 of this embodiment is shown in Figure 5. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0109] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3OO)2 electrolyte. The battery operated at a current density of 10 mA / cm². 2 At that time, the battery's peak power density reached 212 mW / cm². 2 It can stably cycle for 1150 hours with a round-trip efficiency retention rate of 59.5%, demonstrating excellent rate performance and cycle stability.

[0110] Example 6

[0111] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0112] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0113] A zinc source consisting of 5.4 mmol of Zn(CH3COO)2·2H2O, 3.5 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of methanol, ethanol (38 mL in any proportion), and water (14 mL in total) with an organic ligand consisting of 0.36 mmol of 5,6-dimethylbenzimidazole and 0.64 mmol of 2,5-diaminoterephthalic acid. The resulting mixed solution had a molar ratio of zinc source to organic ligand of 9.9:1. The mixture was refluxed and stirred at 80 °C and 800 rpm / min for 8 h. The reaction product was centrifuged at 8300 rpm / min for 4.7 min, and the centrifugation was repeated 3 times. The product was washed twice with water and then three times with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 60 °C for 8 h to obtain a white solid powder.

[0114] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0115] 0.92 g of white solid powder was dispersed in 62 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 4.5:1), and this solution was designated as the first solution.

[0116] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.037 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.01 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2.85:1, and this solution was designated as the second solution.

[0117] The dropping rate was controlled at 250 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 720 rpm / min for 2.42 h at room temperature for ion adsorption. Then, the mixture was centrifuged at 9000 rpm / min for 4 min to collect the solid product. The solid product was dried at 60 °C for 8 h in a vacuum drying oven to obtain a light purple metal precursor.

[0118] (3) Reducing staged pyrolysis: The light purple metallic precursor was placed in a heating furnace and heated to 282℃ at a heating rate of 2.3℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:91. The temperature was held for 1.9h, and then heated to 905℃ at a heating rate of 5.3℃ / min. The temperature was held for 2.7h and then cooled to room temperature to obtain FeN with a dual-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0119] The two-site coupled Janus structure FeN prepared in Example 6 of this embodiment is shown in Figure 6. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0120] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3OO)2 electrolyte. The battery operated at a current density of 10 mA / cm². 2 At that time, the peak power density of the battery reached 205 mW / cm³. 2 It can stably cycle for 1100 hours with a round-trip efficiency retention rate of 59%, demonstrating excellent rate performance and cycle stability.

[0121] Example 7

[0122] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0123] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0124] A zinc source consisting of 5.15 mmol of Zn(CH3COO)2·2H2O, 4 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of methanol, ethanol, ethylene glycol (32 mL in any proportion), and 11 mL of water, respectively. The molar ratio of zinc source to organic ligand in the resulting mixed solution was 10.15:1. The mixture was refluxed and stirred at 80 °C and 800 rpm / min for 9 h. The reaction product was centrifuged at 8700 rpm / min for 4.3 min, and the centrifugation was repeated 4 times. The product was washed 3 times with water and then 2 times with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 60 °C for 8 h to obtain a white solid powder.

[0125] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0126] 0.88 g of white solid powder was dispersed in 58 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 3.2:1), and this solution was designated as the first solution.

[0127] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.06 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.03 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2:1, and this solution was designated as the second solution.

[0128] The dropping rate was controlled at 400 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 750 rpm / min for 2.42 h at room temperature for ion adsorption. The mixture was then centrifuged at 9000 rpm / min for 5 min to collect the solid product. The solid product was dried at 65 °C for 8 h in a vacuum drying oven to obtain a light purple metal precursor.

[0129] (3) Reducing staged pyrolysis: The light purple metallic precursor was placed in a heating furnace and heated to 288℃ at a heating rate of 2.6℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:92. The temperature was held for 1.7h, and then heated to 930℃ at a heating rate of 5.6℃ / min. The temperature was held for 2.4h and then cooled to room temperature to obtain FeN with a two-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0130] The two-site coupled Janus structure FeN prepared in Example 7 of this embodiment is shown. x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0131] Two-site coupled Janus structure FeN x A water-based zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3OO)2 electrolyte. The battery operated at a current density of 10 mA / cm². 2 At that time, the peak power density of the battery reached 220 mW / cm². 2 It can stably cycle for 1230 hours with a round-trip efficiency retention rate of 60.2%, demonstrating excellent rate performance and cycle stability.

[0132] Example 8

[0133] A dual-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst includes the following steps:

[0134] (1) Precursor construction: Precursors were constructed using zinc source and organic ligand.

[0135] A zinc source consisting of 6 mmol of Zn(CH3COO)2·2H2O, 3 mmol of Zn(NO3)2·6H2O, and 1 mmol of ZnCl2 was dissolved in a mixed solution of 30 mL of methanol and 10 mL of water, with an organic ligand consisting of 0.3 mmol of 5,6-dimethylbenzimidazole and 0.7 mmol of 2,5-diaminoterephthalic acid. The resulting mixed solution had a molar ratio of zinc source to organic ligand of 10:1. The mixture was refluxed and stirred at 80 °C and 800 rpm / min for 8 h. The reaction product was centrifuged at 8500 rpm / min for 4.5 min, and the centrifugation was repeated 4 times. The product was washed 3 times with water and then 3 times with anhydrous ethanol (the precipitate was submerged in water or anhydrous ethanol during each wash). The product was then dried in a vacuum drying oven at 60 °C for 8 h to obtain a white solid powder.

[0136] (2) Controlled adsorption of bimetals: Ion adsorption to construct bimetallic precursors

[0137] 0.9 g of white solid powder was dispersed in 60 mL of a mixed solution of n-hexane and dimethyl sulfoxide (volume ratio 3.5:1), and this solution was designated as the first solution.

[0138] An iron source consisting of 0.02 mmol Fe(NO3)3·9H2O and 0.05 mmol Fe(CH3COO)2, and a cobalt source consisting of 0.018 mmol Co(CH3COO)2·4H2O and 0.01 mmol Co(NO3)2·6H2O, were dissolved in deionized water to form a metal salt solution. The molar ratio of the iron source to the cobalt source was 2.5:1, and this solution was designated as the second solution.

[0139] The dropping rate was controlled at 350 μL / min. The second solution was slowly added dropwise to the first solution. The mixture was stirred at 600 rpm / min for 2.86 h at room temperature for ion adsorption. The mixture was then centrifuged at 9000 rpm / min for 4 min to collect the solid product. The solid product was dried at 60 °C for 8 h in a vacuum drying oven to obtain a light purple metal precursor.

[0140] (3) Reducing staged pyrolysis: The light purple metallic precursor was placed in a heating furnace and heated to 290℃ at a heating rate of 2.5℃ / min under the protection of a mixed atmosphere of H2 and Ar with a volume ratio of 1:92. The temperature was held for 1.8h, and then heated to 920℃ at a heating rate of 5.5℃ / min. The temperature was held for 2.5h and then cooled to room temperature to obtain FeN with a dual-site coupled Janus structure. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

[0141] The dual-site coupled Janus structure FeN prepared in Example 8 x / FeCo@NC-J bifunctional oxygen electrocatalyst, Fe-N x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

[0142] Couple the two-site Janus structure FeN x An aqueous zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3OO)2 electrolyte, achieving a peak power density of 215 mW / cm³. 2 At a current density of 10 mA / cm 2 It can stably cycle for 1200 hours with a round-trip efficiency retention rate of up to 62%, demonstrating excellent rate performance and cycle stability.

Claims

1. A two-site coupled Janus structure FeN x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, Includes the following steps: (1) Precursor construction: The precursor was constructed by using a zinc source and an organic ligand. The zinc source and the organic ligand were dissolved in a mixed solution of a polar organic solvent and water, respectively. After reflux and stirring, the product was centrifuged, washed, and vacuum dried to obtain a white solid powder. (2) Bimetallic controlled adsorption: Bimetallic precursors are constructed by ion adsorption. White solid powder is dispersed in a mixed solution of nonpolar organic solvent and strong polar organic solvent to form the first solution. The iron source and the cobalt source are dissolved in water to form a second solution; By controlling the dropping rate, the second solution was added dropwise to the first solution, and after adsorption by stirring at room temperature, centrifugation and drying were performed to obtain a light purple metal precursor. (3) Reducing segmented pyrolysis: The pale purple metallic precursor was placed in a heating furnace and pyrolyzed in a reducing and inert mixed atmosphere by segmented heating and holding. After cooling to room temperature, a dual-site coupled Janus structure FeN was obtained. x / FeCo@NC-J bifunctional oxygen electrocatalyst.

2. The dual-site coupled Janus structure FeN as described in claim 1 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, In step (1), the zinc source is a mixture of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O and ZnCl2, the organic ligand is a mixture of 5,6-dimethylbenzimidazole and 2,5-diaminoterephthalic acid, and the polar organic solvent is one or more of methanol, ethanol, ethylene glycol, N,N-dimethylformamide and N-methylpyrrolidone.

3. A dual-site coupled Janus structure FeN as described in claim 2 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, The molar ratio of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O and ZnCl2 is (5-6):(3-4):1; The molar ratio of 5,6-dimethylbenzimidazole to 2,5-diaminoterephthalic acid is (0.3-0.4):(0.6-0.7). The volume ratio of the polar organic solvent to water is (1-3):

1.

4. A two-site coupled Janus structure FeN as described in claim 1 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, In step (1), the molar ratio of zinc source to organic ligand is (9.8-10.2):1; The reflux temperature is 75℃-85℃, the stirring rate is 700rpm / min-900rpm / min, and the reaction time is 6h-10h. The centrifugation speed is 8000 rpm / min-9000 rpm / min, the centrifugation time is 4 min-5 min, and the number of centrifugations is 3-5 times; The washing process involves first washing with water 2-3 times, and then washing with anhydrous ethanol 2-3 times, ensuring that the precipitate is submerged in water or anhydrous ethanol during each wash. Drying is performed in a vacuum drying oven at a temperature of 50℃-70℃ for 6-10 hours.

5. A two-site coupled Janus structure FeN as described in claim 1 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, In step (2), the mass-to-volume ratio (g:mL) of the white solid powder to the mixed solution of nonpolar organic solvent / strong polar organic solvent is (0.82-1):(50-70); The molar ratio of iron source to cobalt source is (2-3):

1.

6. A two-site coupled Janus structure FeN as described in claim 1 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, In step (2), the non-polar organic solvent is one or a combination of n-hexane, cyclohexane or petroleum, and the strong polar organic solvent is one or a combination of dimethyl sulfoxide, N,N-dimethylformamide or acetonitrile; the volume ratio of the non-polar organic solvent to the strong polar organic solvent is (3-4.5):

1. The iron source is a mixture of Fe(NO3)3·9H2O and Fe(CH3COO)2, with a molar ratio of Fe(NO3)3·9H2O to Fe(CH3COO)2 of 0.02:(0.03-0.06). The cobalt source is a mixture of Co(CH3COO)2·4H2O and Co(NO3)2·6H2O; the molar ratio of Co(CH3COO)2·4H2O to Co(NO3)2·6H2O is (0.01-0.03):0.

01.

7. A two-site coupled Janus structure FeN as described in claim 1 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, In step (2), the dropping rate of the second solution onto the first solution is 200 μL / min - 500 μL / min; The stirring rate at room temperature was 600 rpm / min-800 rpm / min, and the time was 1.8 h-4.2 h. The centrifugation speed is 8000 rpm / min-9500 rpm / min, and the time is 4 min-6 min; Drying is performed in a vacuum drying oven at a temperature of 50℃-70℃ for 6-10 hours.

8. A two-site coupled Janus structure FeN as described in claim 1 x The preparation method of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by, In step (3), the reducing and inert mixed atmosphere is H2 and Ar, wherein the volume ratio of H2 to Ar is 1:(90-95); The pyrolysis process using a segmented heating-holding method involves first heating the temperature to 280℃-300℃ at a rate of 2℃ / min-3℃ / min and holding it for 1.5h-2h; then heating the temperature to 900℃-950℃ at a rate of 5℃ / min-6℃ / min and holding it for 2h-3h.

9. A two-site coupled Janus structure FeN x / FeCo@NC-J bifunctional oxygen electrocatalyst, characterized in that... FeN using the dual-site coupled Janus structure as described in claim 1 x The FeCo@NC-J bifunctional oxygen electrocatalyst was prepared using a specific method. x Atomic sites and FeCo alloy nanounits form an asymmetrically coupled Janus active interface in a nitrogen-doped carbon matrix.

10. A two-site coupled Janus structure FeN x The application of / FeCo@NC-J bifunctional oxygen electrocatalyst is characterized by... The two-site coupled Janus structure FeN as described in claim 9 x An aqueous zinc-air battery was assembled using FeCo@NC-J bifunctional oxygen electrocatalyst as the air cathode and zinc sheet as the anode in a 6 mol / L KOH + 0.2 mol / L Zn(CH3COO)2 electrolyte, achieving a peak power density ≥205 mW / cm². 2 At a current density of 10 mA / cm 2 At that time, the stable cycle time is more than 1100 hours, and the round-trip efficiency retention rate is ≥59%.

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