CN111841598B - S-doped Co @ NC composite material with high oxygen evolution catalytic activity and preparation method thereof - Google Patents

Abstract

The invention discloses an S-doped Co@NC composite material with high oxygen evolution catalytic activity and a preparation method thereof. By adjusting the specific surface area and crystal structure of a metal-organic framework, the cobalt element activity in the nitrogen-doped porous carbon material can be adjusted. The composition content, sulfur doping amount, the optimal crystal structure and S/N atomic ratio were found, and S-doped Co@NC composites with excellent electrocatalytic performance were obtained. On the one hand, the particle size of the composites was small. And it has a core-shell structure with a large specific surface area, which is conducive to the full exposure of active sites and has more electrochemical reaction area; on the other hand, the incorporation of S ions can improve the electrical conductivity and interface charge transfer efficiency of the composite material. , so that the material has better OER properties.

Description

A S-doped Co@NC composite with high oxygen evolution catalytic activity and its preparation method

technical field

The invention relates to the technical field of electrocatalysis, in particular to an S-doped Co@NC composite material with high oxygen evolution catalytic activity and a preparation method thereof.

Background technique

Energy is the foundation of national economic and social development. With the development of my country's economy and society, the demand for energy is increasing. Traditional fossil energy will produce a large amount of pollutants, destroy the ecological environment of our earth, and cause serious ecological and environmental problems. In addition, the reserves of traditional fossil energy are limited and increasingly depleted. If alternative energy cannot be found, there will be a serious energy crisis, affecting the development of the national economy and social stability. Therefore, finding a new type of renewable energy as a substitute for traditional energy has become an urgent problem to be solved in today's energy field.

Among the many solutions to the energy crisis, electrocatalysis technology is considered as an energy conversion and storage method with important application prospects, which will provide an important guarantee for the utilization of renewable and clean energy. Electrocatalysts with oxygen reduction, oxygen evolution, and hydrogen evolution reactions have important application prospects in clean energy fields such as metal-air batteries, fuel cells, and water splitting for hydrogen and oxygen production. Efficient electrocatalytic materials with oxygen evolution catalytic activity (OER) play an important role in the process of total water splitting and oxygen production. Electrocatalytic water splitting is highly dependent on the electrocatalyst activity in the oxygen evolution reaction. Therefore, in order to improve the electrocatalytic oxygen evolution efficiency, electrocatalysts with high oxygen evolution reaction activity must be sought. So far, oxides of iridium and ruthenium are considered to be the best oxygen evolution catalysts, however, the high price and scarcity of reserves limit the wide application of such materials in the industrial field. To this end, people are devoted to finding an electrocatalyst with low price, abundant reserves, and high catalytic activity for oxygen evolution.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background art, the present invention proposes an S-doped Co@NC composite material with high oxygen evolution catalytic activity and a preparation method thereof.

A preparation method of an S-doped Co@NC composite material with high oxygen evolution catalytic activity proposed by the present invention includes the following steps:

S1. Dissolve cobalt nitrate hexahydrate, terephthalic acid and triethylenediamine in an organic solvent, first stir at 50-70°C for 20-40min, and then heat at 100-140°C for 20-30h to obtain Co-MOF material, wherein the mass ratio of cobalt nitrate hexahydrate, terephthalic acid, and triethylenediamine is (1.5-2): (0.5-1): (0.2-0.25);

S2, calcining the Co-MOF material in a nitrogen atmosphere at 700-900° C. for 1-3 hours to obtain a Co@NC material;

S3. Disperse the Co@NC material uniformly in an aqueous solution of thiourea, dry it in a nitrogen atmosphere, and keep calcined at 700-900° C. for 1-3 hours to obtain S-doped S-doped material with high oxygen evolution catalytic activity Co@NC composites, in which the mass ratio of Co@NC material to thiourea is 1:(0.5-2).

Preferably, the mass ratio of cobalt nitrate hexahydrate, terephthalic acid and terephthalic acid is 1.8:0.7:0.22.

Preferably, the mass ratio of the Co@NC material to thiourea is 1:1.5.

Preferably, in the step S2, the nitrogen flow rate is 50-100 mL/min.

Preferably, in the step S1, cobalt nitrate hexahydrate, terephthalic acid, and triethylenediamine are dissolved in an organic solvent, first stirred at 60°C for 30 minutes, and then heated at 120°C for 24 hours.

Preferably, in the step S2, the Co-MOF material is calcined at a temperature of 800° C. for 2 hours in a nitrogen atmosphere.

Preferably, in the step S3, the Co@NC material is uniformly dispersed in an aqueous solution of thiourea, dried and calcined at 800° C. for 2 hours in a nitrogen atmosphere.

Preferably, the ratio of the mass of the cobalt nitrate hexahydrate to the volume of the organic solvent is (3-5) g: 100mL; preferably, the ratio of the mass of the cobalt nitrate hexahydrate to the volume of the organic solvent is 3.6g: 100mL; preferably; the organic solvent is N,N-dimethylformamide.

Preferably, the concentration of the aqueous solution of thiourea is 5-20 g/L; preferably, the concentration of the aqueous solution of thiourea is 15 g/L.

Preferably, in the step S2, heating to 700-900°C at a heating rate of 5-15°C/min; preferably, in the step S2, heating to 800°C at a heating rate of 10°C/min.

Preferably, in the step S3, heating to 700-900°C at a heating rate of 5-15°C/min; preferably, in the step S3, heating to 800°C at a heating rate of 10°C/min.

Preferably, in the step S1, after heating, cooling to room temperature is further included, and the product is washed and then dried, the drying temperature is 60°C, and the drying time is 24h.

Preferably, in the step S3, the drying temperature is 60°C and the drying time is 12h.

An S-doped Co@NC composite material with high oxygen evolution catalytic activity is prepared by the preparation method.

The beneficial effects of the present invention are as follows:

The invention finds out the optimal crystal structure and S/N atomic ratio by adjusting the specific surface area and crystal structure of the metal organic framework, adjusting the content of the active component of cobalt element and the doping amount of sulfur element in the nitrogen-doped porous carbon material, and obtaining The S-doped Co@NC composites with excellent electrocatalytic performance were developed. On the one hand, the composites have small particle size and core-shell structure with large specific surface area, which is conducive to the full exposure of active sites, and has more The electrochemical reaction area; on the other hand, the incorporation of S ions can improve the electrical conductivity and interfacial charge transfer efficiency of the composite material, making the material have better OER properties. In addition, the method of the present invention has the advantages of simple equipment, simple process, low preparation cost and the like.

Description of drawings

FIG. 1 is the XRD pattern of the S-doped Co@NC composite material prepared in Example 1 of the present invention.

FIG. 2 is an SEM image of the S-doped Co@NC composite prepared in Example 1 of the present invention.

FIG. 3 is the XPS spectrum of the S-doped Co@NC composite prepared in Example 1 of the present invention.

FIG. 4 is the Raman spectrum of the S-doped Co@NC composite prepared in Example 1 of the present invention.

5 is the OER polarization curve, stability test curve and impedance spectrum of the S-doped Co@NC composite prepared in Example 1 of the present invention.

Detailed ways

Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments.

Example 1

Preparation of S-doped Co@NC composites:

S1. Weigh 1.8g of cobalt nitrate hexahydrate, 0.7g of terephthalic acid and 0.22g of triethylenediamine, dissolve them in 50mL of N,N-dimethylformamide, and stir in a constant temperature water bath at 60°C for 30min. It was transferred to a 100 mL autoclave, and then the autoclave was heated in a blast drying oven at 120 °C for 24 h. The product was washed twice with DMF and ethanol, and then placed in a vacuum drying oven, and dried at 60 °C for 24 h to obtain Co. - MOF material;

S2. Put the Co-MOF material in a corundum boat, in a nitrogen atmosphere, heat up to 800°C at a heating rate of 10°C/min, keep calcined for 2h, wherein the nitrogen flow rate is 80mL/min, and cool to room temperature to obtain Co@ NC material;

S3. Dissolve 300 mg of thiourea in 20 mL of deionized water to obtain an aqueous solution of thiourea with a concentration of 15 g/L, then add 200 mg of Co@NC material into the aqueous solution of thiourea obtained above, disperse uniformly by ultrasonic for 15 min, and put it into a blast drying oven , dried at 60°C for 12h, then heated to 800°C at a heating rate of 10°C/min in a corundum boat in a nitrogen atmosphere, kept calcined for 2h, and cooled to room temperature.

Preparation of working electrode: Take 10 mg of the S-doped Co@NC composite prepared above, 25 μL of DuPont membrane solution and 400 μL of isopropanol, mix them and then ultrasonically treat them for 60 min, and apply the resulting mixture evenly to carbon paper (1.0 × 1.0 cm), the coating amount is 3 mg/cm ² per square centimeter, and then put it into a 60°C incubator to dry for 10 hours.

The structure and properties of the S-doped Co@NC composite prepared in Example 1 were characterized, and the results were as follows:

Figure 1 is the XRD pattern of the S-doped Co@NC composite prepared in Example 1. It can be seen that the pattern is at 2θ=29.8°, 31.2°, 39.6°, 47.6°, 52.1°, 61.2°, 73.2° The diffraction peaks corresponding to the Co ₉ S ₈ (311), (222), (331), (511), (440), (533), (731) and (800) crystal planes appear at and 76.8°. , and diffraction peaks corresponding to the CoS (100), (101), (102) and (110) crystal planes appear at 2θ=30.5°, 35.2°, 46.9°, and 54.3°. Figure 2 is the SEM image of the S-doped Co@NC composite prepared in Example 1. It can be seen that the composite has a loose nanostructure, and a large number of Co and S compound nanoparticles are wrapped or embedded in the loose nanostructure. On the nanostructure, the structure helps to improve the catalytic activity of the material. Figure 3 shows the high-resolution XPS spectra of Co2p and S2p of the S-doped Co@NC composite prepared in Example 1, wherein the XPS peaks at 162.1 eV and 169.0 eV correspond to S 2p _1/2 of S ^2- ions, respectively and the binding energy of S 2p _1/2 of SO ₃ ^2- or SO ₄ ^2- . The XPS peak centered at 781.9 eV corresponds to the binding energy of Co 2p3/2 for Co ²⁺ ions, and its companion peaks at 785.5 eV are derived from Co ²⁺ and Co ³⁺ ions. The XPS peak centered at 798.2 eV corresponds to the binding energy of Co2p1/2 for Co ²⁺ ions, and its corresponding companion peaks at 803.1 eV also originate from Co ²⁺ and Co ³⁺ ions. Fig. 4 is the Raman spectrum of the S-doped Co@NC composite prepared in Example 1. It can be seen that there are two Raman scattering peaks at 1345 and 1574 cm ^-1 in the Raman spectrum, corresponding to carbon D and G peaks of the material, this result indicates the occurrence of graphitized carbon in the composite.

Figure 5a shows the OER test results of the S-doped Co@NC composite obtained in Example 1 under alkaline conditions, wherein the OER test adopts a traditional three-electrode system, and the CHI660E electrochemical workstation is used to test the sample in 1M KOH solution The LSV curve of , the scanning voltage is 1.3-1.8 V (relative to the reversible hydrogen electrode), and the scanning speed is 10 mV s ^-1 . It can be seen that the overpotential of this sample at 10 mA cm ^-2 is 189mV (vs. RHE), which is much smaller than the overpotential of Co@NC without S doping, indicating that S doping helps to improve its OER properties . Figure 5b shows the current density-time curve of the S-doped Co@NC composite obtained in Example 1. The results show that the current density value of the curve does not fluctuate greatly, indicating that the material has stable OER characteristics. Figure 5c is the impedance spectrum of the S-doped Co@NC composite obtained in Example 1. The curve was fitted according to the equivalent circuit model, and the charge transfer resistance (R _ct ) of the catalyst was obtained as 5.01×10 ^-6 Ω , it can be seen that the charge transfer resistance is very small, indicating that the charge is relatively easy to pass through the two-phase interface of the electrode and the electrolyte.

Example 2

Preparation of S-doped Co@NC composites:

S1. Weigh 1.8g of cobalt nitrate hexahydrate, 0.7g of terephthalic acid and 0.22g of triethylenediamine, dissolve them in 50mL of N,N-dimethylformamide, and stir in a constant temperature water bath at 60°C for 30min. It was transferred to a 100 mL autoclave, and then the autoclave was heated in a blast drying oven at 120 °C for 24 h. The product was washed twice with DMF and ethanol, and then placed in a vacuum drying oven, and dried at 60 °C for 24 h to obtain Co. - MOF material;

S2. Put the Co-MOF material in a corundum boat, in a nitrogen atmosphere, heat up to 800°C at a heating rate of 10°C/min, keep calcined for 2h, wherein the nitrogen flow rate is 80mL/min, and cool to room temperature to obtain Co@ NC material;

S3. Dissolve 400 mg of thiourea in 20 mL of deionized water to obtain an aqueous solution of thiourea with a concentration of 15 g/L, then add 200 mg of Co@NC material into the aqueous solution of thiourea obtained above, disperse evenly by ultrasonic for 15 min, and put it into a blast drying oven , dried at 60°C for 12h, then heated to 800°C at a heating rate of 10°C/min in a corundum boat in a nitrogen atmosphere, kept calcined for 2h, and cooled to room temperature.

Preparation of working electrode: Take 10 mg of the S-doped Co@NC composite prepared above, 25 μL of DuPont membrane solution and 400 μL of isopropanol, mix them and then ultrasonically treat them for 60 min, and apply the resulting mixture evenly to carbon paper (1.0 × 1.0 cm), the coating amount is 3 mg/cm ² per square centimeter, and then put it into a 60°C incubator to dry for 10 hours.

The structure and properties of the S-doped Co@NC composite prepared in Example 2 were characterized, and the results were as follows:

The XRD pattern obtained in Example 2 is similar to the XRD pattern measured in Example 1, and appears at 2θ=29.8°, 31.2°, 39.6°, 47.6°, 52.1°, 61.2°, 73.2° and _76.8 °. ₈ Diffraction peaks corresponding to (311), (222), (331), (511), (440), (533), (731) and (800) crystal planes, at 2θ=30.5°, 35.2°, 46.9 °, and 54.3° appear diffraction peaks corresponding to the CoS (100), (101), (102) and (110) crystal planes. The composite material in Example 2 also has a large number of nano-sized particles, but the dispersibility is poor, and the nanostructure may affect its catalytic activity. The Raman spectrum of the S-doped Co@NC composite prepared in Example 2 shows that the Raman spectrum also has two Raman scattering peaks at 1345 and 1574 cm ^-1 , corresponding to the D peak and G peak, this result indicates the presence of graphitized carbon in the composite. The OER results of the S-doped Co@NC composite obtained in Example 2 under alkaline conditions show that the overpotential of the sample at 10 mA cm ^-2 is 299 mV (vs. RHE), which is also smaller than that of the undoped Co@NC composite. The overpotentials of S-infused Co@NCs indicate that S doping helps to improve its OER properties. By fitting the impedance spectrum obtained in this example according to the equivalent circuit model, it is obtained that the charge transfer resistance (R _ct ) of the catalyst is 3.27Ω.

Example 3

Preparation of S-doped Co@NC composites:

S1. Weigh 1.8g of cobalt nitrate hexahydrate, 0.7g of terephthalic acid and 0.22g of triethylenediamine, dissolve them in 50mL of N,N-dimethylformamide, and stir in a constant temperature water bath at 60°C for 30min. It was transferred to a 100 mL autoclave, and then the autoclave was heated in a blast drying oven at 120 °C for 24 h. The product was washed twice with DMF and ethanol, and then placed in a vacuum drying oven, and dried at 60 °C for 24 h to obtain Co. - MOF material;

S2. Put the Co-MOF material in a corundum boat, in a nitrogen atmosphere, heat up to 800°C at a heating rate of 10°C/min, keep calcined for 2h, wherein the nitrogen flow rate is 80mL/min, and cool to room temperature to obtain Co@ NC material;

S3. Dissolve 100 mg of thiourea in 20 mL of deionized water to obtain an aqueous solution of thiourea with a concentration of 15 g/L, then add 200 mg of Co@NC material into the aqueous solution of thiourea obtained above, disperse uniformly by ultrasonic for 15 min, and put it into a blast drying oven , dried at 60°C for 12h, then heated to 800°C at a heating rate of 10°C/min in a corundum boat in a nitrogen atmosphere, kept calcined for 2h, and cooled to room temperature.

Preparation of working electrode: Take 10 mg of the S-doped Co@NC composite prepared above, 25 μL of DuPont membrane solution and 400 μL of isopropanol, mix them and then ultrasonically treat them for 60 min, and apply the resulting mixture evenly to carbon paper (1.0 × 1.0 cm), the coating amount is 3 mg/cm ² per square centimeter, and then put it into a 60°C incubator to dry for 10 hours.

The structure and properties of the S-doped Co@NC composite prepared in Example 3 were characterized, and the results were as follows:

Compared with Example 1, the X-ray diffraction spectrum obtained in Example 3 appears at 2θ=29.8°, 31.2°, 47.6°, 52.1° and 76.8°, which is similar to Co ₉ S ₈ (311), (222), (511) , the diffraction peaks corresponding to the (440) and (800) crystal planes, and no diffraction peaks related to CoS were observed. The composite material obtained in Example 3 is also composed of a large number of nano-sized particles, but the dispersibility is poor, and the nano-structure may affect its catalytic activity. Raman characteristic peaks were still observed at 1345 and 1574 cm ^-1 , corresponding to the D peak and G peak of the carbon material, respectively, which indicated that graphitized carbon appeared in the composite material. The OER test results of the composite obtained in Example 3 under alkaline conditions show that the overpotential of the sample at 10 mA cm ^-2 is 275 mV (vs. RHE), which is also smaller than that of Co@NC without S incorporation. overpotential, indicating that S doping helps to improve its OER properties. According to the impedance spectrum obtained by the equivalent circuit model in this example, the charge transfer resistance (R _ct ) of the catalyst was obtained as 0.302Ω.

Example 4

Preparation of S-doped Co@NC composites:

S1. Weigh 1.5g of cobalt nitrate hexahydrate, 0.5g of terephthalic acid and 0.2g of triethylenediamine, dissolve them in 50mL of N,N-dimethylformamide, and stir in a constant temperature water bath at 50°C for 20min. It was transferred to a 100 mL autoclave, and then the autoclave was heated in a blast drying oven at 100 °C for 20 h. The product was washed twice with DMF and ethanol, and then placed in a vacuum drying oven, and dried at 60 °C for 24 h to obtain Co. - MOF material;

S2. Put the Co-MOF material in a corundum boat, in a nitrogen atmosphere, heat up to 700 °C at a heating rate of 5 °C/min, keep calcined for 1 h, wherein the nitrogen flow rate is 50 mL/min, and cool to room temperature to obtain Co@ NC material;

S3. Dissolve 100 mg of thiourea in 20 mL of deionized water to obtain an aqueous solution of thiourea with a concentration of 5 g/L, then add 200 mg of Co@NC material into the aqueous solution of thiourea obtained above, disperse uniformly by ultrasonic for 15 min, and put it into a blast drying oven , dried at 60°C for 12h, and then heated to 700°C at a heating rate of 5°C/min in a corundum boat in a nitrogen atmosphere, calcined for 1h, and cooled to room temperature.

Example 5

Preparation of S-doped Co@NC composites:

S1. Weigh 2g of cobalt nitrate hexahydrate, 1g of terephthalic acid and 0.25g of triethylenediamine and dissolve them in 40mL of N,N-dimethylformamide. Transfer to a 100mL autoclave, then put the autoclave into a blast drying oven and heat at 140°C for 30h, wash the product twice with DMF and ethanol respectively, put it into a vacuum drying oven, and dry it at 60°C for 24h to obtain Co-MOF Material;

S2. Put the Co-MOF material in a corundum boat, in a nitrogen atmosphere, raise the temperature to 900°C at a heating rate of 15°C/min, keep calcined for 3h, wherein the nitrogen flow rate is 100mL/min, and cool to room temperature to obtain Co@ NC material;

S3. Dissolve 100 mg of thiourea in 20 mL of deionized water to obtain an aqueous solution of thiourea with a concentration of 15 g/L, then add 200 mg of Co@NC material into the aqueous solution of thiourea obtained above, disperse uniformly by ultrasonic for 15 min, and put it into a blast drying oven , dried at 60°C for 12h, then heated to 900°C at a heating rate of 15°C/min in a corundum boat in a nitrogen atmosphere, kept calcined for 3h, and cooled to room temperature.

Comparative Example 1

Preparation of S-doped Co@NC composites:

S1. Weigh 1.8g of cobalt nitrate hexahydrate, 0.7g of terephthalic acid and 0.22g of triethylenediamine, dissolve them in 50mL of N,N-dimethylformamide, and stir in a constant temperature water bath at 60°C for 30min. It was transferred to a 100 mL autoclave, and then the autoclave was heated in a blast drying oven at 120 °C for 24 h. The product was washed twice with DMF and ethanol, and then placed in a vacuum drying oven, and dried at 60 °C for 24 h to obtain Co. - MOF material;

S2. Put the Co-MOF material in a corundum boat, in a nitrogen atmosphere, heat up to 800°C at a heating rate of 10°C/min, keep calcined for 2h, wherein the nitrogen flow rate is 80mL/min, and cool to room temperature to obtain Co@ NC composites.

Preparation of working electrode: Take 10 mg of the Co@NC composite material prepared above, 25 μL of DuPont membrane solution and 400 μL of isopropanol, mix them, and then ultrasonically treat them for 60 min. ), the coating amount is 3mg/cm ² per square centimeter, and then put it into a 60°C incubator to dry for 10h.

The structure and properties of the Co@NC composites prepared in Comparative Example 1 were characterized, and the results were as follows:

The test results of X-ray diffraction spectrum show that the sample has diffraction peaks corresponding to Co ₉ S ₈ (311), (440) and (800) crystal planes at 2θ=29.8°, 52.1° and 76.8°. Diffraction peaks corresponding to Co(111), (200) and (220) crystal planes appeared at =44.2°, 51.6° and 75.9°, and no diffraction peaks related to CoS were observed. Raman characteristic peaks were observed at 1345 and 1574 cm ^-1 in the sample, corresponding to the D peak and G peak of the carbon material, respectively, but the peak intensity was relatively weak, indicating that the degree of graphitization of carbon in the composite material was weak. The composite material is composed of a large number of nanoparticles and has a loose nanostructure, and a large number of Co compound nanoparticles are covered by the loose carbon nanostructure. The OER test results of the composite material obtained in this example under alkaline conditions show that the overpotential of the sample at 10 mA cm ^-2 is 323 mV (vs. RHE). According to the equivalent circuit model of the impedance spectrum obtained in this example After fitting, the charge transfer resistance (R _ct ) of the catalyst was obtained as 2.68×10 ⁹ Ω.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (9)

1. A preparation method of an S-doped Co @ NC composite material with high oxygen evolution catalytic activity is characterized by comprising the following steps:

s1, dissolving cobalt nitrate hexahydrate, terephthalic acid and triethylene diamine in an organic solvent, stirring for 20-40min at 50-70 ℃, and heating for 20-30h at 100-140 ℃ to obtain a Co-MOF material, wherein the mass ratio of the cobalt nitrate hexahydrate to the terephthalic acid to the triethylene diamine is (1.5-2): (0.5-1): (0.2-0.25);

s2, calcining the Co-MOF material in a nitrogen atmosphere at 700-900 ℃ for 1-3h to obtain a Co @ NC material;

s3, uniformly dispersing the Co @ NC material in an aqueous solution of thiourea, drying, and calcining at 700-900 ℃ for 1-3h in a nitrogen atmosphere to obtain the S-doped Co @ NC composite material with high oxygen evolution catalytic activity, wherein the mass ratio of the Co @ NC material to the thiourea is 1: (0.5-2).

2. The preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity according to claim 1, wherein the mass ratio of the cobalt nitrate hexahydrate, the terephthalic acid and the triethylene diamine is 1.8:0.7:0.22.

3. the preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity as claimed in claim 1 or 2, characterized in that the mass ratio of the Co @ NC material to thiourea is 1.5.

4. The preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity as claimed in claim 1 or 2, characterized in that the ratio of the mass of the cobalt nitrate hexahydrate to the volume of the organic solvent is (3-5) g:100mL.

5. The preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity as claimed in claim 1 or 2, characterized in that the organic solvent is N, N-dimethylformamide.

6. The preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity as claimed in claim 1 or 2, characterized in that in the step S2, the nitrogen flow is 50-100mL/min.

7. The preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity according to claim 1 or 2, characterized in that the concentration of the thiourea aqueous solution is 5-20g/L.

8. The preparation method of the S-doped Co @ NC composite material with high oxygen evolution catalytic activity as claimed in claim 1 or 2, characterized in that, in the step S2, the S-doped Co @ NC composite material is heated to 700-900 ℃ at a heating speed of 5-15 ℃/min; in the step S3, the mixture is heated to 700-900 ℃ at a heating speed of 5-15 ℃/min.

9. An S-doped Co @ NC composite material with high oxygen evolution catalytic activity, which is characterized by being prepared by the preparation method of any one of claims 1-8.

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