Preparation method and application of N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst

Abstract

The present invention discloses a preparation method and application of an N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst. The product obtained by hydrothermal reaction of iron oxide with glucose and cobalt chloride hexahydrate is ground into powder with trithiocyanuric acid and zinc chloride in an agate mortar, and the above mixture is pyrolyzed at high temperature under the protection of inert gas and then naturally cooled to room temperature; then the product is pickled, washed to neutrality, and dried to obtain the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst. The present invention uses iron oxide as a self-catalyst and iron source, and trithiocyanuric acid as a nitrogen and sulfur source to self-catalytically form nitrogen and sulfur co-doped carbon nanotubes during the high-temperature pyrolysis process. The specific surface area of the Fe, Co bimetal, N, S co-doped carbon oxygen reduction catalyst prepared by the present invention is 574.4 m<supgt;2 < / supgt>g<supgt;−1< / supgt>, and the average pore diameter is 3.88 nm, having excellent oxygen reduction catalytic performance.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis of non-noble metal-doped carbon oxygen reduction catalysts, and specifically relates to a preparation method of a N and S co-doped carbon nanotube-encapsulated FeCo alloy oxygen reduction catalyst and its application in a zinc-air battery. Background Art

[0002] The contradiction between economic development and energy demand has always been mutually reinforcing and counteracting, and global climate anomalies are becoming increasingly obvious. Therefore, it is necessary to develop efficient and environmentally friendly clean energy conversion and storage technologies to ensure national energy security and serve economic construction. Among them, zinc-air batteries have the advantages of safety and reliability, high energy density, simple structure, low price and green environmental protection, which are very in line with the current development needs of new energy. However, the oxygen reduction reaction (ORR) occurring at the air electrode has a slow kinetic process, which greatly limits the practical application of rechargeable zinc-air batteries. At present, Pt-based catalysts can greatly reduce the ORR overpotential, but precious metal materials are expensive, resource-scarce and have poor stability, and cannot meet large-scale production needs. Therefore, there is an urgent need to develop an efficient, stable, economically friendly and low-cost ORR electrocatalyst.

[0003] In the past few decades, inexpensive transition metal Fe / Co-based materials have been demonstrated to be highly efficient non-precious metal catalysts. However, single metal nanoparticles are limited by the volcano plot and lack the appropriate adsorption energy of oxygen and intermediates during the reaction, making them unsuitable for direct use as electrocatalysts. Alloying can adjust the d-band center of the metal and change the adsorption energy of the reactants, thereby achieving excellent performance. Despite the good performance of nanoalloys, how to prevent the dissolution of nanoalloys in alkaline solutions leading to catalyst deactivation remains a severe challenge. Coating a carbon layer on the surface of alloy nanoparticles is an effective strategy to prevent the corrosion of nanoparticles during electrocatalytic reactions in alkaline solutions. Carbon nanotubes are widely used as a durable support for ZAB catalysts due to their excellent chemical stability. It is a wise choice to confine metal nanoparticles in carbon nanotubes, and the metal nanoparticles coated with carbon layers avoid being dissolved and corroded by the electrolyte. In addition, the random stacking of carbon nanotubes provides the catalyst with high porosity, making it easier for the catalyst to enter the catalytic reaction. In addition, metal electrons can be transferred to the surface through the carbon shell, thereby promoting the reaction kinetics. Doping B, F, P, especially N and S in the carbon carrier can improve the electrochemical properties of the carbon material, including hydrophilicity, conductivity and durability. 2 O 3 ) as the autocatalyst and iron source, cobalt chloride hexahydrate as the cobalt source, glucose as the carbon source, and trithiocyanate as the nitrogen and sulfur sources, a high-performance N, S co-doped carbon nanotube-encapsulated FeCo alloy oxygen reduction catalyst was prepared based on the autocatalytic strategy by using the hydrothermal-thermal method. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a preparation method of N, S co-doped carbon nanotubes encapsulating FeCo alloy oxygen reduction catalyst based on an autocatalytic strategy with simple process and relatively low cost. The method uses glucose as a carbon source and trithiocyanate as a nitrogen and sulfur source. In the presence of metallic iron and cobalt, nitrogen and sulfur co-doped carbon nanotubes can be autocatalytically formed during high-temperature pyrolysis, thereby increasing the specific surface area and pore volume of the carbon material, exposing more active sites, and enhancing the oxygen reduction catalytic activity of the carbon material. Finally, a new technology for preparing zinc-air battery electrocatalysts in a simple and efficient manner is developed, and the prepared N, S co-doped carbon nanotubes encapsulating FeCo alloy oxygen reduction catalyst can be well used in zinc-air batteries.

[0005] The present invention adopts the following technical solution to solve the above technical problems, a method for preparing a N and S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst, characterized in that the specific process is:

[0006] Step S1: Ferric chloride hexahydrate (FeCl 3 6H 2 O) and sodium dihydrogen phosphate (NaH 2 PO 4 ) was dissolved in water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor for hydrothermal treatment at 100-110° C. for 24-48 h, the obtained mixture was centrifuged and transferred to a blast drying oven for drying, and after cooling to room temperature, the obtained brick-red product was ground into powder in an agate mortar to obtain material A;

[0007] Step S2: Material A and glucose (C 6 H 12 O 6 ) and cobalt chloride hexahydrate (CoCl 2 6H 2 O) After stirring and mixing thoroughly, transfer to a polytetrafluoroethylene reactor and perform hydrothermal treatment at 160-200° C. for 12-24 hours, wherein material A is used as both a catalyst and an iron source, and then centrifuge the obtained mixture and transfer to a blast drying oven for drying, and then cool to room temperature to obtain material B;

[0008] Step S3: Grind the material B obtained in step S2 and thiocyanate into powder in an agate mortar, then transfer to a tube furnace, and under the protection of inert gas, heat from room temperature to 900° C. over 175 min and maintain at 900° C. for 120 min, then cool naturally to room temperature to obtain material C;

[0009] Step S4: Transfer the material C obtained in step S3 to a container and add an acidic solution to soak for 24 hours, then wash with high-purity water until the filtrate is neutral, and then place it in an 80° C. forced air drying oven to obtain the target product N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst.

[0010] Further preferably, the mass ratio of glucose, cobalt chloride hexahydrate and material A in step S2 is 1.2:1:0.1.

[0011] More preferably, the inert gas in step S3 is one or more of nitrogen or argon.

[0012] More preferably, the acidic solution in step S4 is a hydrochloric acid solution with a concentration of 2M.

[0013] The method for preparing the N and S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst of the present invention is characterized by the following specific steps:

[0014] Step S1: 0.27 g of ferric chloride hexahydrate (FeCl 3 6H 2 O) and 0.45 mmol sodium dihydrogen phosphate (NaH 2 PO 4 ) was dissolved in 50 mL of water and stirred to mix evenly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 105°C for 48 h, the obtained mixture was centrifuged and transferred to a blast drying oven for drying, and after cooling to room temperature, the obtained brick-red product was ground into powder in an agate mortar to obtain material A1;

[0015] Step S2: 50 mg of the material A1 obtained in step S1, 0.7 g of glucose (C 6 H 12 O 6 ) and 0.5 g of cobalt chloride hexahydrate (CoCl 2 6H 2 O) dispersed in water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 180° C. for 20 h, wherein material A is used as both a catalyst and an iron source, and then the obtained mixture is centrifuged and transferred to a blast drying oven for drying, and then cooled to room temperature to obtain material B1;

[0016] Step S3: Grind the material B1 obtained in step S2 and 1 g of thiocyanate into powder in an agate mortar, then transfer to a tube furnace, and under the protection of inert gas, heat from room temperature to 900° C. for 175 min and maintain at 900° C. for 120 min, then cool naturally to room temperature to obtain material C1;

[0017] Step S4: The material C1 obtained in step S3 is transferred to a container and soaked in a 2M hydrochloric acid solution for 24 hours, then washed with high-purity water until the filtrate is neutral, and then dried in a blast drying oven at 80°C to obtain the target product N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst. The specific surface area of ​​the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst is 574.4 m 2 g -1 , and applied it as a cathode material in zinc-air batteries, with excellent oxygen reduction performance and high power density.

[0018] The invention discloses an application of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst as a cathode material for zinc-air batteries.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. Fe of the present invention 2 O 3 It is both an iron source and a self-catalyst, forming FeCo alloy sites, exposing more active sites and enhancing the oxygen reduction catalytic activity of carbon materials;

[0021] 2. The present invention uses thiocyanate as the nitrogen and sulfur source to explore the intrinsic relationship between nitrogen and sulfur dual doping and the degree of graphitization and performance of carbon materials;

[0022] 3. The FeCo alloy encapsulated in the N, S co-doped carbon nanotube oxygen reduction catalyst prepared by the present invention has a high specific surface area and a mesoporous structure, and exhibits excellent oxygen reduction activity, cycle stability and methanol tolerance under alkaline conditions. It is applied as a cathode material to zinc-air batteries, and has excellent oxygen reduction performance and a large power density, providing a theoretical basis and technical support for the practical application of zinc-air batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst D1 prepared in Example 1;

[0024] Figure 2 The nitrogen adsorption-desorption isotherm diagram of the N, S co-doped carbon nanotube-encapsulated FeCo alloy oxygen reduction catalyst D1 prepared in Example 1 (the inset is the pore size distribution diagram of D1);

[0025] Figure 3 The X-ray photoelectron spectrum (full spectrum) of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst D1 prepared in Example 1;

[0026] Figure 4The Raman spectrum of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst D1 prepared in Example 1;

[0027] Figure 5 Cyclic voltammetry curves of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst D1 and products D2-D5 prepared in Example 1;

[0028] Figure 6 Linear sweep voltammetric curves of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst D1 and products D2-D5 prepared in Example 1;

[0029] Figure 7 Power density diagram of N, S co-doped carbon nanotubes encapsulated FeCo alloy oxygen reduction catalyst D1 and Pt / C+IrO2 prepared in Example 1. DETAILED DESCRIPTION

[0030] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0031] Example 1

[0032] Step S1: 0.27 g of ferric chloride hexahydrate (FeCl 3 6H 2 O) and 0.45 mmol sodium dihydrogen phosphate (NaH 2 PO 4 ) was dissolved in 50 mL of water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 105°C for 48 h, the obtained mixture was centrifuged and transferred to a forced air drying oven and dried at 80°C, and after cooling to room temperature, the obtained brick red product was ground into powder in an agate mortar to obtain material A1;

[0033] Step S2: 50 mg of the material A1 obtained in step S1, 0.7 g of glucose (C 6 H 12 O 6 ) and 0.5 g of cobalt chloride hexahydrate (CoCl 2 6H 2 O) dispersed in water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 180° C. for 20 h, wherein material A is used as both a catalyst and an iron source, and then the obtained mixture is centrifuged and transferred to a blast drying oven and dried at 80° C., and then cooled to room temperature to obtain material B1;

[0034] Step S3: Grind the material B1 obtained in step S2 and 1 g of thiocyanate into powder in an agate mortar, then transfer to a tube furnace, and under the protection of inert gas, heat from room temperature to 900° C. for 175 min and maintain at 900° C. for 120 min, then cool naturally to room temperature to obtain material C1;

[0035] Step S4: The material C1 obtained in step S3 is transferred to a container and soaked in 2M hydrochloric acid solution for 24 hours, then washed with high-purity water until the filtrate is neutral, and then dried in a 80° C. forced air drying oven to obtain the target product N, S co-doped carbon nanotube-encapsulated FeCo alloy oxygen reduction catalyst D1.

[0036] Example 2

[0037] Step S1: 0.27 g of ferric chloride hexahydrate (FeCl 3 6H 2 O) and 0.45 mmol sodium dihydrogen phosphate (NaH 2 PO 4 ) was dissolved in 50 mL of water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 105°C for 48 h, the obtained mixture was centrifuged and transferred to a forced air drying oven and dried at 80°C, and after cooling to room temperature, the obtained brick red product was ground into powder in an agate mortar to obtain material A2;

[0038] Step S2: 50 mg of the material A2 obtained in step S1, 0.7 g of glucose (C 6 H 12 O 6 ) and 0.5 g of cobalt chloride hexahydrate (CoCl 2 6H 2 O) dispersed in water and stirred and mixed thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 180° C. for 20 h, wherein material A simultaneously served as a catalyst and an iron source, and then the obtained mixture was centrifuged and transferred to a blast drying oven and dried at 80° C., and then cooled to room temperature to obtain material B2;

[0039] Step S3: Grind the material B2 obtained in step S2 and 1 g of melamine into powder in an agate mortar, then transfer to a tube furnace, and under the protection of inert gas, heat from room temperature to 900° C. for 175 min and maintain at 900° C. for 120 min, then cool naturally to room temperature to obtain material C2;

[0040] Step S4: Transfer the material C2 obtained in step S3 to a container and add a 2M hydrochloric acid solution to soak for 24 hours, then wash with high-purity water until the filtrate is neutral, and then place it in an 80°C forced air drying oven to dry to obtain product D2.

[0041] Example 3

[0042] Step S1: 0.27 g of ferric chloride hexahydrate (FeCl 3 6H 2 O) and 0.45 mmol sodium dihydrogen phosphate (NaH 2 PO 4 ) was dissolved in 50 mL of water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 105°C for 48 h, the obtained mixture was centrifuged and transferred to a forced air drying oven and dried at 80°C, and after cooling to room temperature, the obtained brick red product was ground into powder in an agate mortar to obtain material A3;

[0043] Step S2: 50 mg of material A3 obtained in step S1, 0.7 g of glucose (C 6 H 12 O 6 ) and 0.5 g of cobalt chloride hexahydrate (CoCl 2 ·6H2O) was dispersed in water and stirred to mix thoroughly, and then transferred to a polytetrafluoroethylene reactor for hydrothermal treatment at 180°C for 20h, wherein material A was used as both a catalyst and an iron source, and the obtained mixture was centrifuged and transferred to a blast drying oven for drying at 80°C, and then cooled to room temperature to obtain material B3;

[0044] Step S3: Grind the material B3 obtained in step S2 into powder in an agate mortar, then transfer it to a tube furnace, and under the protection of inert gas, heat it from room temperature to 900° C. for 175 min and keep it at 900° C. for 120 min, then cool it naturally to room temperature to obtain material C3;

[0045] Step S4: The material C3 obtained in step S3 is transferred to a container and added with a 2M hydrochloric acid solution for immersion for 24 hours, then washed with high-purity water until the filtrate is neutral, and then placed in an 80° C. forced drying oven to obtain product D3.

[0046] Example 4

[0047] Step S1: 0.27 g of ferric chloride hexahydrate (FeCl 3 6H 2 O) and 0.45 mmol sodium dihydrogen phosphate (NaH 2 PO 4 ) was dissolved in 50 mL of water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 105°C for 48 h, the obtained mixture was centrifuged and transferred to a forced air drying oven and dried at 80°C, and after cooling to room temperature, the obtained brick red product was ground into powder in an agate mortar to obtain material A4;

[0048] Step S2: 50 mg of the material A4 obtained in step S1 and 0.7 g of glucose (C6 H 12 O 6 ) are dispersed in water and stirred to mix thoroughly, and then transferred to a polytetrafluoroethylene reactor for hydrothermal treatment at 180° C. for 20 h, wherein material A is used as both a catalyst and an iron source, and the obtained mixture is centrifuged and transferred to a blast drying oven for drying at 80° C., and then cooled to room temperature to obtain material B4;

[0049] Step S3: Grind the material B4 obtained in step S2 and 1 g of thiocyanate into powder in an agate mortar, then transfer to a tube furnace, and under the protection of inert gas, heat from room temperature to 900° C. for 175 min and maintain at 900° C. for 120 min, then cool naturally to room temperature to obtain material C4;

[0050] Step S4: The material C4 obtained in step S3 is transferred to a container and added with a 2M hydrochloric acid solution for immersion for 24 hours, then washed with high-purity water until the filtrate is neutral, and then placed in an 80° C. forced air drying oven to obtain product D4.

[0051] Example 5

[0052] Step S1: 0.7 g glucose (C 6 H 12 O 6 ) and 0.5 g of cobalt chloride hexahydrate (CoCl 2 6H 2 O) dispersed in water and stirred to mix thoroughly, then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 180° C. for 20 h, and then the obtained mixture was centrifuged and transferred to a blast drying oven and dried at 80° C., and then cooled to room temperature to obtain material B5;

[0053] Step S2: Grind the material B5 obtained in step S2 and 1 g of thiocyanate into powder in an agate mortar, then transfer to a tube furnace, and under the protection of inert gas, heat from room temperature to 900° C. for 175 min and maintain at 900° C. for 120 min, then cool naturally to room temperature to obtain material C5;

[0054] Step S4: The material C5 obtained in step S3 is transferred to a container and soaked in a 2M hydrochloric acid solution for 24 hours, then washed with high-purity water until the filtrate is neutral, and then dried in an 80° C. forced drying oven to obtain product D5.

[0055] Example 6

[0056] The catalyst solution consists of the target product D1, 5wt% Nafion solution and aqueous solution, and is ultrasonically treated to form a homogeneous solution. Use a pipette to transfer an appropriate amount of ink-like active substance and drop it on a clean glassy carbon electrode, then dry it naturally at room temperature to prepare a working electrode. The same method is used to prepare working electrodes for products D2, D3, D4, and D5, which are used for comparison with the target product D1. All electrochemical tests use a three-electrode system. In the linear sweep voltammetry (LSV) test, glassy carbon is used as the working electrode (with a diameter of 5mm), Hg / HgO electrode and platinum sheet are used as reference electrode and counter electrode respectively, and the electrolyte is N 2 / O 2 Saturated 0.1 mol·L -1 When testing, a certain volume and concentration of active material (i.e. the prepared ink-like dispersion) is applied on the surface of the working electrode, and the scanning speed is 10mV·s -1 , the rotation speed is 1600 rpm, and the scanning range is -0.8 V to 0.4 V. During the cyclic voltammetry (CV) test, except for the glassy carbon electrode with a working diameter of 3 mm and coated with a certain volume and concentration of active material (the ink dispersion prepared above), the scanning range is -0.8 V to 0.2 V, and the reference electrode, counter electrode, electrolyte and other test conditions are the same as the above LSV conditions.

[0057] The catalytic performance of the samples in all examples is as follows: Figure 5 As shown in FIG. 1 , the cyclic voltammetry curves of the target products D1, D2, D3, D4 and D5 obtained in Example 1 have peak potentials of 0.86 V, 0.83 V, 0.77 V, 0.83 V and 0.80 V, respectively. Figure 6 As shown, the half-wave potentials of samples D1, D2, D3, D4 and D5 of Examples 1-5 under the linear scanning curve of the rotating disk electrode obtained at 1600 rpm are 0.83 V, 0.80 V, 0.74 V, 0.80 V and 0.71 V, respectively. The comparison shows that D1 has the best oxygen reduction activity.

[0058] Liquid zinc-air battery assembly and testing: The catalyst solution consists of the target product D1, 5wt% Nafion solution, and isopropanol solution, which is ultrasonically treated to form a homogeneous solution. The catalyst ink is evenly dropped on the hydrophobic carbon paper (loading amount is 2mgcm -2 ) and dried naturally to serve as the air cathode. The air cathode and Zn sheet anode were mixed in 6.0 M KOH and 0.2 M Zn(CH 3 COO 2 Liquid zinc-air batteries were assembled in electrolyte, and the battery performance tests were carried out using a CHI660E electrochemical workstation at room temperature.

[0059] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. Preparation method of N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst, characterized in that the specific process is as follows: Step S1: Dissolve ferric chloride hexahydrate and sodium dihydrogen phosphate in water, stir and mix well, then transfer to a polytetrafluoroethylene reaction kettle and perform hydrothermal treatment at 100-110 °C for 24-48 h. Centrifuge the obtained mixture and transfer it to a blast drying oven for drying. After cooling to room temperature, grind the obtained brick-red product into powder in an agate mortar to obtain material A; Step S2: Material A, glucose and cobalt chloride hexahydrate obtained in step S1 are stirred and mixed thoroughly, and then transferred to a polytetrafluoroethylene reactor for hydrothermal treatment at 160-200°C for 12-24h, wherein material A is iron oxide, and its chemical formula is Fe 2 O 3 The iron oxide is used as a catalyst and an iron source at the same time, and the obtained mixture is centrifuged and transferred to a forced air drying oven for drying, and then cooled to room temperature to obtain material B; Step S3: Grind the material B obtained in Step S2 and trithiocyanuric acid into powder in an agate mortar, then transfer to a tubular furnace. Under the protection of nitrogen or inert gas, heat from room temperature to 900 °C in 175 min and maintain at 900 °C for 120 min, then naturally cool to room temperature to obtain material C; Step S4: Transfer the material C obtained in Step S3 to a container, add an acidic solution and soak for 24 h, then wash with high-purity water until the filtrate is neutral, and then place in a blast drying oven at 80 °C for drying to obtain the target product N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst.

2. Preparation method of N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst according to claim 1, characterized in that: In Step S2, the feeding mass ratio of glucose, cobalt chloride hexahydrate and material A is 1.2:1:0.

1.

3. Preparation method of N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst according to claim 1, characterized in that: The inert gas in Step S3 is argon.

4. Preparation method of N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst according to claim 1, characterized in that: The acidic solution in Step S4 is a hydrochloric acid solution with a concentration of 2 M.

5. Preparation method of N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst according to claim 1, characterized in that the specific steps are as follows: Step S1: Dissolve 0.27 g of ferric chloride hexahydrate and 0.45 mmol of sodium dihydrogen phosphate in 50 mL of water, stir and mix evenly, then transfer to a polytetrafluoroethylene reaction kettle and perform hydrothermal treatment at 105 °C for 48 h. Centrifuge the obtained mixture and transfer it to a blast drying oven for drying. After cooling to room temperature, grind the obtained brick-red product into powder in an agate mortar to obtain material A1; Step S2: 50 mg of the material A1 obtained in step S1, 0.7 g of glucose and 0.5 g of cobalt chloride hexahydrate were dispersed in water and stirred to mix thoroughly, and then transferred to a polytetrafluoroethylene reactor and hydrothermally treated at 180°C for 20 h, wherein the material A is iron oxide, and its chemical formula is Fe 2 O 3 The iron oxide is used as a catalyst and an iron source at the same time, and the obtained mixture is centrifuged and transferred to a forced air drying oven for drying, and then cooled to room temperature to obtain material B1; Step S3: Grind the material B1 obtained in Step S2 and 1 g of trithiocyanuric acid into powder in an agate mortar, then transfer to a tubular furnace. Under the protection of nitrogen or inert gas, heat from room temperature to 900 °C in 175 min and maintain at 900 °C for 120 min, then naturally cool to room temperature to obtain material C1; Step S4: The material C1 obtained in step S3 is transferred to a container and soaked in a 2M hydrochloric acid solution for 24 hours, then washed with high-purity water until the filtrate is neutral, and then dried in a blast drying oven at 80°C to obtain the target product N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst. The specific surface area of ​​the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst is 574.4 m 2 g −1 , and applied it as a cathode material in zinc-air batteries, with excellent oxygen reduction performance and high power density.

6. Application of the N, S co-doped carbon nanotube encapsulated FeCo alloy oxygen reduction catalyst prepared by the method according to any one of claims 1-5 as a cathode material of a zinc-air battery.

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