Preparation and application of Fe-N / S co-doped porous carbon material

Abstract

The invention discloses preparation and application of a Fe-N / S co-doped porous carbon material, and belongs to the technical field of battery catalysts. The preparation method of the Fe-N / S co-doped porous carbon material comprises the following steps: mixing a porous carbon matrix, lignosulfonate, ferric salt and a nitrogen-containing compound, and calcining in an inert atmosphere to obtain the Fe-N / S co-doped porous carbon material. The Fe-N / S co-doped porous carbon material prepared by the preparation method disclosed by the invention has a high specific surface area, a hierarchical pore structure, relatively good oxygen reduction activity and high catalytic activity.

Description

Technical Field

[0001] The present invention relates to the technical field of battery catalysts, and particularly to the preparation and application of an Fe-N / S co-doped porous carbon material. Background Art

[0002] With the development of renewable energy technologies, the development of efficient energy storage systems is crucial. Fuel cells have attracted much attention due to their high energy density and environmental friendliness, but their widespread application is limited by the slow kinetics of the oxygen reduction reaction and the stability problem of catalysts; although platinum-based catalysts are effective, they are costly and scarce in resources.

[0003] Biomass-based carbon materials have become potential catalyst substitutes due to their excellent electrical conductivity, large specific surface area, and stable chemical properties. However, the current biomass-based carbon materials are mainly prepared using expensive raw materials such as hardwood and pine, and special treatments are required to prepare biomass-based carbon materials using these raw materials, such as etching with strong acids and alkalis, which not only increases the price of raw materials, but also makes the entire preparation process complex and costly. These factors jointly limit the application and promotion of biomass-based carbon materials in a wider range of fields and pose potential adverse effects on environmental protection, which is not conducive to practical application and environmental protection. Summary of the Invention

[0004] The purpose of the present invention is to provide the preparation and application of an Fe-N / S co-doped porous carbon material to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: A preparation method of an Fe-N / S co-doped porous carbon material, comprising the following steps:

[0007] Mix a porous carbon matrix, lignosulfonate, an iron salt, and a nitrogen-containing compound, and then calcine in an inert atmosphere to obtain the Fe-N / S co-doped porous carbon material.

[0008] Further, the single-point total pore volume of the porous carbon matrix is 1.09 cm 3 / g, and the specific surface area is 2315.21 m 2 / g; the single-point total pore volume of the Fe-N / S co-doped porous carbon material is 0.4 - 2 cm 3 / g, and the specific surface area is 900 - 2600 m 2 / g;

[0009] The mass ratio of the porous carbon matrix, lignosulfonate, and iron salt is 1:1 - 15:0.5 - 1.5;

[0010] The mass ratio of the total mass of the porous carbon matrix, lignosulfonate and iron salt to the mass of the nitrogen-containing compound is 1:15 - 30.

[0011] Further, the heating rate of the calcination is 2 - 5 °C / min, the temperature is 800 - 1100 °C, and the heat preservation time is 1 - 3 h.

[0012] Further, the lignosulfonate includes sodium lignosulfonate;

[0013] The iron salt includes ferric chloride hexahydrate;

[0014] The nitrogen-containing compound is selected from one of ammonium chloride, ammonium phosphate, urea, thiourea or ammonium dihydrogen phosphate.

[0015] Further, the preparation method of the porous carbon matrix includes:

[0016] (1) Mix the biomass material with an alkaline sulfite solution and carry out cooking treatment to obtain a cooking liquid;

[0017] (2) Freeze-dry the cooking liquid and then calcine it in an air atmosphere, pickling, and drying to obtain a carbon precursor;

[0018] The material obtained after drying the cooking liquid is a heteroatom self-doped biomass material, and the main components are one or more of cellulose, hemicellulose, and lignin.

[0019] (3) Mix the carbon precursor with an alkali metal hydroxide and calcine it in an inert atmosphere (to form more active sites on the carbon precursor), pickling, and drying to obtain the porous carbon matrix.

[0020] Further, in step (1): the concentration of the alkaline substance in the alkaline sulfite solution is 2.5 M, and the concentration of the sulfite is 0.4 M;

[0021] The dosage ratio of the biomass material to the alkaline sulfite solution is 1 g: 3 - 7 mL;

[0022] The temperature of the cooking treatment is 150 - 200 °C, and the heat preservation time is 1 - 3 h;

[0023] The biomass material is eucalyptus wood and / or poplar wood.

[0024] Further, in step (2): the heating rate of the calcination is 1 - 5 °C / min, the temperature is 300 - 400 °C, and the heat preservation time is 1 - 3 h.

[0025] Further, in step (3): the mass ratio of the carbon precursor to the alkali metal hydroxide is 1: (3 - 5);

[0026] The alkali metal hydroxide is potassium hydroxide;

[0027] The heating rate of the calcination is 2 - 5 °C / min, the temperature is 800 - 1100 °C, and the heat preservation time is 1 - 3 h.

[0028] Furthermore, in steps (2) and (3): The acid solution used for pickling is an HCl solution with a concentration of 0 - 2 M (and not 0); the temperature of the pickling is 60 - 100 °C; the temperature of the drying is 65 - 100 °C.

[0029] The biomass material used in the present invention is a renewable hydrocarbon resource, which has the characteristics of environmental protection and easy accessibility. The carbon matrix prepared therefrom has a porous structure, a large number of active sites, a high specific surface area, high adsorption capacity and stability, which helps to improve the electrolyte ion transport efficiency; by doping elements such as N, S, and Fe in the carbon matrix, the specific surface area and surface chemical properties of the material can be improved, enhancing its application performance in electrocatalysis, showing great application potential in the field of electrocatalysis, and providing a new direction for sustainable energy technology.

[0030] The second technical solution of the present invention: A porous carbon material co-doped with Fe-N / S prepared by the above preparation method.

[0031] The third technical solution of the present invention: An application of the above Fe-N / S co-doped porous carbon material in battery electrocatalysis.

[0032] Furthermore, the battery includes a metal-air battery, a hydrogen-oxygen fuel cell, and a methanol fuel cell.

[0033] Furthermore, the metal-air battery is a zinc-air battery.

[0034] The present invention discloses the following technical effects:

[0035] (1) The biomass material used in the Fe-N / S co-doped porous carbon material prepared by the present invention is cheap, easily available, and renewable, making full use of the renewable biomass resources, which conforms to the concept of green and sustainable development; and the preparation method of the present invention is simple, highly practical, and easy to promote.

[0036] (2) The Fe-N / S co-doped porous carbon material prepared by the present invention can be used as a substrate in various catalytic fields such as metal-air batteries, hydrogen-oxygen fuel cells, and methanol fuel cells.

[0037] (3) The Fe-N / S co-doped porous carbon material prepared by the present invention has a high specific surface area, a hierarchical pore structure, and has good oxygen reduction activity and high catalytic activity.

[0038] (4) The Fe-N / S co-doped porous carbon material prepared by the present invention can act as a cathode catalyst in a zinc-air battery to promote the electrocatalytic cathode oxygen reduction reaction. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0040] Figure 1 SEM images of the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2, where a and b are SEM images at different magnifications;

[0041] Figure 2 Nitrogen adsorption and desorption isotherms of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3;

[0042] Figure 3 Raman spectra of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3;

[0043] Figure 4 XRD patterns of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3;

[0044] Figure 5 XPS peak deconvolution spectra of the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2;

[0045] Figure 6 Electrochemical performance of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3, where a is the linear sweep voltammetry curves of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3, b is the cyclic voltammetry curves of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3, c is the time-current curve of the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2 (methanol was added around 500 s), and d is the time-current curve of the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2;

[0046] Figure 7 Performance of the zinc-air battery prepared using the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2, where a is the charge-discharge polarization curve, b is the polarization and energy density curve, and c is the constant current charge-discharge cycle curve. Detailed Description of the Invention

[0047] The various exemplary embodiments of the present invention will be described in detail below. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and implementation schemes of the present invention.

[0048] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0049] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0050] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0051] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0052] Example 1

[0053] A preparation method of an Fe-N / S co-doped porous carbon material:

[0054] (1) Mix eucalyptus wood chips with an alkaline sulfite solution (the solution contains 2.5 M NaOH and 0.4 M Na2SO3) at a ratio of 1 g:5 mL, and carry out cooking treatment (the temperature of the cooking treatment is 171 °C, and the heat preservation time is 2 h) to obtain a cooking liquid.

[0055] (2) Freeze-dry the cooking liquor to obtain freeze-dried cooking liquor, grind it for 30 min to reach a uniform and delicate powder, then heat it to 350 °C at a heating rate of 5 °C / min under an air atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a carbon precursor.

[0056] (3) Mix the carbon precursor and potassium hydroxide in water at a mass ratio of 1:4 and stir for 1 h, dry (at a temperature of 65 °C), grind for 30 min to reach a uniform and delicate powder, then heat it to 800 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a porous carbon matrix with a single-point total pore volume of 1.09 cm 3 / g and a specific surface area of 2315.21 m 2 / g.

[0057] (4) Mix the porous carbon matrix, ferric chloride hexahydrate, and sodium lignosulfonate in water at a mass ratio of 1:0.75:10, ultrasonically disperse for 30 min, filter with suction, and dry (at a temperature of 65 °C) to obtain a mixed powder; mix the mixed powder and ammonium chloride at a mass ratio of 1:20, grind for 30 min to reach a uniform and delicate powder, and then heat it to 900 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, calcine for 2 h to obtain a porous activated carbon matrix, sodium lignosulfonate, and ammonium chloride chelating Fe single atoms together to prepare an iron, nitrogen, and sulfur co-doped porous carbon material (i.e., an Fe-N / S co-doped hierarchical porous carbon material, Fe-N / S co-doped porous carbon material - 900) with a single-point total pore volume of 0.40 cm 3 / g and a specific surface area of 904.77 m 2 / g.

[0058] Example 2

[0059] A preparation method of an Fe-N / S co-doped porous carbon material:

[0060] (1) Mix eucalyptus wood chips and an alkaline sulfite solution (the solution contains 2.5 M NaOH and 0.4 M Na2SO3) at a dosage ratio of 1 g:5 mL, and carry out cooking treatment (the cooking treatment temperature is 171 °C and the heat preservation time is 2 h) to obtain cooking liquor.

[0061] (2) Freeze-dry the cooking liquor to obtain freeze-dried cooking liquor, grind it for 30 min to reach a uniform and delicate powder, then heat it to 350 °C at a heating rate of 5 °C / min in an air atmosphere, calcine it for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a carbon precursor.

[0062] (3) Mix the carbon precursor and potassium hydroxide in water at a mass ratio of 1:4 and stir for 1 h, dry (at a temperature of 65 °C), grind for 30 min to reach a uniform and delicate powder, then heat it to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, calcine it for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a porous carbon matrix with a single-point total pore volume of 1.09 cm 3 / g and a specific surface area of 2315.21 m 2 / g.

[0063] (4) Mix the porous carbon matrix, ferric chloride hexahydrate, and sodium lignosulfonate in water at a mass ratio of 1:0.75:10, ultrasonically disperse for 30 min, filter with suction, and dry (at a temperature of 65 °C) to obtain a mixed powder; mix the mixed powder and ammonium chloride at a mass ratio of 1:20 and grind for 30 min to reach a uniform and delicate powder. After grinding, heat it to 1000 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, calcine it for 2 h to obtain a porous activated carbon matrix, sodium lignosulfonate, and ammonium chloride chelating Fe single atoms together to prepare an iron, nitrogen, and sulfur co-doped porous carbon material (i.e., Fe-N / S co-doped hierarchical porous carbon material, Fe-N / S co-doped porous carbon material - 1000) with a single-point total pore volume of 1.66 cm 3 / g and a specific surface area of 2465.31 m 2 / g.

[0064] Example 3

[0065] A preparation method of an Fe-N / S co-doped porous carbon material:

[0066] (1) Mix eucalyptus wood chips and an alkaline sulfite solution (containing 2.5 M NaOH and 0.4 M Na2SO3 in the solution) at a dosage ratio of 1 g:5 mL, and carry out cooking treatment (the cooking treatment temperature is 171 °C and the holding time is 2 h) to obtain cooking liquor.

[0067] (2) Freeze-dry the cooking liquor to obtain freeze-dried cooking liquor, grind it for 30 min to reach a uniform and delicate powder state, then heat it to 350 °C at a heating rate of 5 °C / min under an air atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a carbon precursor.

[0068] (3) Mix the carbon precursor and potassium hydroxide in water at a mass ratio of 1:4 and stir for 1 h, dry (at a temperature of 65 °C), grind for 30 min to reach a uniform and delicate powder state, then heat it to 800 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a porous carbon matrix with a single-point total pore volume of 1.09 cm 3 / g and a specific surface area of 2315.21 m 2 / g.

[0069] (4) Mix the porous carbon matrix, ferric chloride hexahydrate, and sodium lignosulfonate in water at a mass ratio of 1:0.75:10, ultrasonically disperse for 30 min, filter with suction, and dry (at a temperature of 65 °C) to obtain a mixed powder; mix the mixed powder and ammonium chloride at a mass ratio of 1:20, grind for 30 min to reach a uniform and delicate powder state, and then heat it to 1100 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, calcine for 2 h to obtain a porous activated carbon matrix, sodium lignosulfonate, and ammonium chloride co-chelating Fe single atoms to prepare an iron, nitrogen, and sulfur co-doped porous carbon material (i.e., Fe-N / S co-doped hierarchical porous carbon material, Fe-N / S co-doped porous carbon material - 1100) with a single-point total pore volume of 1.99 cm 3 / g and a specific surface area of 2463.69 m 2 / g.

[0070] Comparative Example 1

[0071] A preparation method of an Fe / S co-doped porous carbon material:

[0072] (1) Mix eucalyptus wood chips and an alkaline sulfite solution (containing 2.5 M NaOH and 0.4 M Na2SO3 in the solution) at a ratio of 1 g:5 mL, and perform a cooking treatment (the temperature of the cooking treatment is 171 °C and the holding time is 2 h) to obtain a cooking liquor.

[0073] (2) Freeze-dry the cooking liquor to obtain freeze-dried cooking liquor, grind it for 30 min to reach a uniform and delicate powder state, then heat it to 350 °C at a heating rate of 5 °C / min under an air atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a carbon precursor.

[0074] (3) Mix the carbon precursor and potassium hydroxide in water at a mass ratio of 1:4 and stir for 1 h, dry (at a temperature of 65 °C), grind for 30 min to reach a uniform and delicate powder state, then heat it to 800 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a porous carbon matrix, with a single-point total pore volume of 1.09 cm 3 / g and a specific surface area of 2315.21 m 2 / g.

[0075] (4) Mix the porous carbon matrix, ferric chloride hexahydrate, and sodium lignosulfonate in water at a mass ratio of 1:0.75:10, ultrasonically disperse for 30 min, filter with suction, and dry (at a temperature of 65 °C) to obtain a mixed powder; grind the mixed powder for 30 min to reach a uniform and delicate powder state, heat it to 1000 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, and calcine for 2 h to obtain an iron and sulfur co-doped porous carbon material prepared by co-chelation of Fe single atoms with a porous activated carbon matrix and sodium lignosulfonate (i.e., Fe / S-anchored hierarchical porous carbon material, Fe / S co-doped porous carbon material - 1000), with a single-point total pore volume of 1.10 cm 3 / g and a specific surface area of 922.44 m 2 / g.

[0076] Comparative Example 2

[0077] A preparation method of an N / S co-doped porous carbon material:

[0078] (1) Mix eucalyptus wood chips and an alkaline sulfite solution (containing 2.5 M NaOH and 0.4 M Na2SO3 in the solution) at a dosage ratio of 1 g:5 mL, and carry out cooking treatment (the temperature of the cooking treatment is 171 °C and the holding time is 2 h) to obtain a cooking liquor.

[0079] (2) Freeze-dry the cooking liquor to obtain freeze-dried cooking liquor, grind it for 30 min to reach a uniform and delicate powder state, then heat it to 350 °C at a heating rate of 5 °C / min under an air atmosphere, calcine for 2 h, then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a carbon precursor.

[0080] (3) Mix the carbon precursor and potassium hydroxide at a mass ratio of 1:4 in water, stir for 1 h, dry (at a temperature of 65 °C), grind for 30 min to obtain a uniform and delicate powder. Then, under a nitrogen atmosphere, heat it to 800 °C at a heating rate of 5 °C / min, calcine for 2 h, and then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a porous carbon matrix with a single-point total pore volume of 1.09 cm 3 / g and a specific surface area of 2315.21 m 2 / g.

[0081] (4) Mix the porous carbon matrix and sodium lignosulfonate at a mass ratio of 1:10 in water, disperse them by ultrasonic wave for 30 min, filter with suction, and dry (at a temperature of 65 °C) to obtain a mixed powder; mix the mixed powder and ammonium chloride at a mass ratio of 1:20, grind for 30 min to obtain a uniform and delicate powder. Then, under a nitrogen atmosphere, heat it to 1000 °C at a heating rate of 5 °C / min, calcine for 2 h to obtain a nitrogen and sulfur co-doped hierarchical porous carbon material (i.e., N / S anchored porous carbon material, N / S co-doped porous carbon material - 1000) with a single-point total pore volume of 1.42 cm 3 / g and a specific surface area of 2471.32 m 2 / g.

[0082] Comparative Example 3

[0083] A preparation method of an Fe / N co-doped porous carbon material:

[0084] (1) Mix eucalyptus wood chips and an alkaline sulfite solution (containing 2.5 M NaOH and 0.4 M Na2SO3 in the solution) at a dosage ratio of 1 g:5 mL, and carry out cooking treatment (the temperature of the cooking treatment is 171 °C, and the heat preservation time is 2 h) to obtain a cooking liquid.

[0085] (2) Carry out freeze-drying treatment on the cooking liquid to obtain a freeze-dried cooking liquid, grind for 30 min to obtain a uniform and delicate powder. Then, under an air atmosphere, heat it to 350 °C at a heating rate of 5 °C / min, calcine for 2 h, and then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a carbon precursor.

[0086] (3) Mix the carbon precursor and potassium hydroxide at a mass ratio of 1:4 in water, stir for 1 h, dry (at a temperature of 65 °C), grind for 30 min to obtain a uniform and delicate powder. Then, under a nitrogen atmosphere, heat it to 800 °C at a heating rate of 5 °C / min, calcine for 2 h, and then pickle it with a 1 M HCl solution at 80 °C, filter with suction, wash with water, and dry (at a temperature of 65 °C) to obtain a porous carbon matrix with a single-point total pore volume of 1.09 cm 3 / g, the specific surface area is 2315.21 m 2 / g.

[0087] (4) Mix the porous carbon matrix and ferric chloride hexahydrate in water at a mass ratio of 1:0.75, ultrasonically disperse for 30 min, filter by suction, and dry (temperature is 65 °C) to obtain a mixed powder; mix the mixed powder and ammonium chloride at a mass ratio of 1:20 and grind for 30 min until it reaches a uniform and delicate powdery state. Then, heat it to 1000 °C at a heating rate of 5 °C / min under a nitrogen atmosphere and calcine for 2 h to obtain a hierarchically porous carbon material with multiple chelations of Fe single atoms by the porous activated carbon matrix and ammonium chloride, i.e., Fe-N co-doped hierarchically porous carbon material (i.e., Fe / N-anchored porous carbon material, Fe / N co-doped porous carbon material - 1000). The single-point total pore volume is 1.76 cm 3 / g, the specific surface area is 2583.19 m 2 / g.

[0088] Effect Example 1

[0089] Structure Characterization and Performance Testing:

[0090] (1) The SEM images of the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2 are shown in Figure 1 , Figure 1 Figure a (2 μm) and Figure b (1 μm) in it are SEM images at different magnifications.

[0091] As can be seen from Figure 1 , the Fe-N / S co-doped porous carbon material - 1000 prepared in Example 2 exhibits a rich pore structure with uniform pore distribution. This is because during the process of mixing and calcining the carbon precursor with potassium hydroxide, potassium hydroxide is fixed in the carbon matrix, and then the pore structure left after removing potassium hydroxide by pickling; many nanopores also appear on the surface of the sample pyrolyzed from ammonium chloride and ferric chloride hexahydrate, because ammonium chloride and ferric chloride hexahydrate can introduce rich micropore and mesopore structures as activators.

[0092] (2) The nitrogen adsorption-desorption isotherms of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3 are shown in Figure 2 .

[0093] As can be seen from Figure 2 , the Fe-N / S co-doped hierarchically porous carbon material has a high adsorption capacity at 1000 °C carbonization, indicating that it has a large specific surface area; the large specific surface area can provide more catalytic active sites.

[0094] (3) The Raman spectra of the materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3 are shown in Figure 3 ; the XRD spectra are shown in Figure 4。

[0095] From Figure 3 and Figure 4 it can be seen that the materials prepared in Examples 1-3 and Comparative Examples 1-3 have similar ID / IG values and similar crystal structures.

[0096] (4) The XPS peak deconvolution spectrum of the Fe-N / S co-doped porous carbon material-1000 prepared in Example 2 is shown in Figure 5 。

[0097] From Figure 5 it can be seen that the Fe-N / S co-doped porous carbon material-1000 prepared in Example 2 has a relatively high nitrogen element content. By performing peak deconvolution on the N spectrum, it can be known that at 398.3, 399.5, 400.4, 400.9, and 401.7 eV, they correspond to pyridine nitrogen, Fe-N x , pyrrole nitrogen, graphitic nitrogen, and oxidized nitrogen respectively.

[0098] (5) The method for electrochemical performance testing using a three-electrode system is as follows: The electrolyte is a 0.1 M KOH solution saturated with N2 or O2. A platinum foil is used as the counter electrode, and an Ag / AgCl electrode is used as the reference electrode. All potential values are provided relative to the reversible hydrogen electrode (RHE).

[0099] The preparation method of the working electrode is as follows: Mix 5 mg of the catalyst (the final product prepared in the example or comparative example) with 1 mL of a 2.0 vol% Nafion / ethanol solution and sonicate for 30 min to prepare a uniform ink. Then, uniformly coat 10 μL of the ink on a glassy carbon electrode with a diameter of 5 mm, and the catalyst loading is approximately 0.255 mg cm -2 。

[0100] During the electrochemical testing process, the electrochemical performance is tested in a 0.1 M KOH solution saturated with N2 or O2. The cyclic voltammetry (CV) is obtained at a scanning rate of 50 mV s -1 on a rotating ring-disk (RRDE) electrode. The linear sweep voltammetry (LSV) is collected at a scanning rate of 10 mV s -1 on a rotating ring-disk (RRDE) electrode in a 0.1 M KOH solution saturated with O2 at 400, 625, 900, 1225, 1600, and 2025 rpm respectively. Among them, the stability of the catalyst is tested at 0.4 V vs. RHE in a 0.1 M KOH solution saturated with O2 at 900 rpm. During the testing process, 1 M CH3OH is added to the 0.1 M KOH solution saturated with O2 after 500 s to evaluate the methanol tolerance of the catalyst. The results are shown in Figure 6 。

[0101] The linear sweep voltammetry curves of the materials prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Figure 6 Figure a of Figure 6 The cyclic voltammetry curves of the materials prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Figure 6 Figure b of Figure 6 The time-current curve (methanol was added around 500 s) of the Fe-N / S co-doped porous carbon material-1000 prepared in Example 2 is shown in

[0102] From Figure 6 Figures a and b of

[0103] From Figure 6 Figure c of

[0104] From Figure 6 Figure d of

[0105] (6) The Fe-N / S co-doped porous carbon material-1000 prepared in Example 2 was used as a zinc-air battery electrode catalytic material to prepare a zinc-air battery, and the performance of the zinc-air battery was tested. The results are shown in Figure 7 , Figure 7 In which, a is the charge-discharge polarization curve, b is the polarization and energy density curve of the zinc-air battery, and c is the constant current charge-discharge cycle curve.

[0106] The preparation method of the positive electrode membrane electrode in the zinc-air battery is as follows: 20 mg of the Fe-N / S co-doped porous carbon material-1000 catalyst prepared in Example 3 was dispersed in 4 mL of 2.0 vol% naphthol ethanol solution and ultrasonically dispersed for 30 min to obtain a catalyst-containing slurry. Subsequently, the slurry was drop-coated on carbon cloth, and the catalyst loading was 2 mg cm -2 to obtain a membrane electrode. Assembly of the zinc-air battery: The membrane electrode was used as the air positive electrode, the zinc foil was used as the negative electrode, and the electrolyte solution was 6 M potassium hydroxide + 0.2 M zinc acetate.

[0107] From Figure 7It can be seen that the voltage gap between charge and discharge of the zinc-air battery assembled with Fe-N / S co-doped porous carbon material-1000 as the cathode catalyst of the zinc-air battery is very small, indicating its excellent charge and discharge capabilities and a relatively large power density of 253.3 mW cm -2 . Under the condition of charge and discharge cycling at a current density of 5 mA cm -2 , when the 0.2 mm thick zinc sheet was completely consumed, the cycle was maintained for 1586 h with good charge and discharge efficiency.

[0108] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of an Fe-N / S co-doped porous carbon material, characterized in that, It includes the following steps: Mix a porous carbon matrix, lignosulfonate, iron salt and nitrogen-containing compound, and then calcine them under an inert atmosphere to obtain the Fe-N / S co-doped porous carbon material.

2. The preparation method according to claim 1, wherein The single-point total pore volume of the porous carbon matrix is 1.09 cm 3 / g, and the specific surface area is 2315.21 m 2 / g; The single-point total pore volume of the Fe-N / S co-doped porous carbon material is 0.4 - 2 cm 3 / g, and the specific surface area is 900 - 2600 m 2 / g; And / or, the mass ratio of the porous carbon matrix, lignosulfonate and iron salt is 1:1-15:0.5-1.5; And / or, the mass ratio of the total mass of the porous carbon matrix, lignosulfonate and iron salt to the nitrogen-containing compound is 1:15-30.

3. The preparation method according to claim 1, characterized in that, The heating rate of the calcination is 2-5 °C / min, the temperature is 800-1100 °C, and the heat preservation time is 1-3 h.

4. The preparation method according to claim 1, characterized in that, The lignosulfonate includes sodium lignosulfonate; And / or, the iron salt includes ferric chloride; And / or, the nitrogen-containing compound is selected from one of ammonium chloride, ammonium phosphate, urea, thiourea or ammonium dihydrogen phosphate.

5. The preparation method according to claim 1, characterized in that, The preparation method of the porous carbon matrix includes: (1) Mix a biomass material with an alkaline sulfite solution and perform cooking treatment to obtain a cooking liquor; (2) Freeze-dry the cooking liquor, then calcine it under an air atmosphere and perform pickling to obtain a carbon precursor; (3) Mix the carbon precursor with an alkali metal hydroxide, calcine it under an inert atmosphere and perform pickling to obtain the porous carbon matrix.

6. The preparation method according to claim 5, characterized in that, In step (1): the concentration of the alkaline substance in the alkaline sulfite solution is 2.5 M, and the concentration of the sulfite is 0.4 M; And / or, the dosage ratio of the biomass material to the alkaline sulfite solution is 1 g:3-7 mL; And / or, the temperature of the cooking treatment is 150-200 °C, and the heat preservation time is 1-3 h; And / or, the biomass material is eucalyptus and / or poplar.

7. The preparation method according to claim 5, wherein In step (2): the heating rate of the calcination is 1-5 °C / min, the temperature is 300-400 °C, and the heat preservation time is 1-3 h.

8. The preparation method according to claim 5, characterized in that, In step (3): the mass ratio of the carbon precursor to the alkali metal hydroxide is 1:(3-5); And / or, the alkali metal hydroxide is potassium hydroxide; And / or, the heating rate of the calcination is 2-5 °C / min, the temperature is 800-1100 °C, and the heat preservation time is 1-3 h.

9. An Fe-N / S co-doped porous carbon material prepared by the preparation method according to any one of claims 1-8.

10. An application of the Fe-N / S co-doped porous carbon material according to claim 9 in battery electrocatalysis.

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