CN113629260A

CN113629260A - Cobalt and nitrogen co-doped carbon nanosheet material and preparation and application thereof

Info

Publication number: CN113629260A
Application number: CN202110771824.9A
Authority: CN
Inventors: 裴素朋; 孙月阳; 熊霞; 徐康伟; 张维; 韩志越
Original assignee: Shanghai Institute of Technology
Current assignee: Shanghai Institute of Technology
Priority date: 2021-07-08
Filing date: 2021-07-08
Publication date: 2021-11-09

Abstract

The invention relates to a cobalt and nitrogen co-doped carbon nanosheet material and preparation and application thereof, wherein the preparation method specifically comprises the following steps: (a) dissolving lactose monohydrate and a zinc source into water together, and stirring and mixing uniformly to obtain a mixed solution; (b) then heating and evaporating the mixed solution to dryness to obtain a precursor; (c) carbonizing the precursor obtained in the step (b) to obtain the cobalt and nitrogen co-doped carbon nanosheet material. The application is that cobalt and nitrogen co-doped carbon nano sheet material is used as an ORR catalyst. Compared with the prior art, the organic carbon source and the foaming agent used in the invention are cheap and easy to obtain, the preparation method is simple, the large-scale production is easy, the prepared material has obvious oxygen reduction characteristics, and compared with a commercial platinum-carbon catalyst, the preparation method has the advantages of simple preparation process, low cost, good stability and the like.

Description

Cobalt and nitrogen co-doped carbon nanosheet material and preparation and application thereof

Technical Field

The invention belongs to the technical field of electrochemistry, and particularly relates to a cobalt and nitrogen co-doped carbon nanosheet material, and preparation and application thereof.

Background

A fuel cell is a device capable of directly converting chemical energy of fuel into electrical energy. Unlike a general primary battery or secondary battery, an electrode reaction active material of a fuel cell is supplied from the outside of the cell, and is not stored in the inside of the cell. Theoretically, the fuel cell can generate electricity continuously as long as fuel is supplied continuously from the outside. Although the fuel cell operates more like an internal combustion engine, it is not limited by the carnot cycle and has a high energy conversion efficiency (> 80% theoretically) because it generates electricity without undergoing a combustion process. Fuel cells are considered as a preferred power generation technology in the future because of their high energy conversion efficiency, higher energy density and power density than other cells, no need for charging, and no emission of environmentally harmful sulfur and nitrogen oxides during power generation.

The electrocatalytic performance of fuel cells is mainly influenced by the slow kinetics of the cathode Oxygen Reduction Reaction (ORR), which requires the development of an ORR catalyst with high catalytic activity. In the past, Pt-based catalysts have been considered as the best electrocatalysts, but the resources of Pt in the earth are small, the market price is high, and the Pt-based catalysts become a main obstacle for the large-scale commercial application of fuel cells (seal C. the catalyst with platinum [ J ]. Materials Today,2008,11(12): 65-68.). At the same time, Pt-based catalysts also suffer from other problems of insufficient long-term stability, CO deactivation, etc. (Winter M, Brodd R J. What article Batteries, Fuel Cells, and Supercapacitors [ J ]. Chemical Review,2004(104): 4245-. Therefore, it is of great interest to develop an ORR catalyst with low cost, activity comparable to or better than Pt-based catalysts to replace the Pt-based catalyst of conventional fuel cell cathodes.

High surface area, layered pores, uniform doping,High active site density and high conductivity activity are key factors for obtaining good ORR performance of the catalyst. The porous nanocarbon is widely used as a carrier material of nanoparticles of different metals, has the characteristics of large specific surface area, easy surface modification and other excellent catalyst carriers, can be used as a base material doped with carbon and is separated from various derivatives of carbides, and the pore diameter of the porous nanocarbon is easy to adjust, has large specific surface area and can be modified through a synthesis path. At present, nitrogen atoms are generally adopted to modify porous nanocarbon, and after the nitrogen atoms are doped into a porous carbon material, the charge density of the porous carbon material is increased to form an n-type semiconductor, so that the conductivity of the porous carbon material is increased. The porous nano carbon is also modified by adopting metal Co, Co atoms have strong interaction with N and C atoms near a carbon layer, and the structure of N doped with C is adjusted to increase O₂The adsorption energy of (3) and the catalytic activity of the catalyst are improved.

Patent CN108970577A discloses a Co/N Co-doped mesoporous carbon nanosheet, a preparation method and application thereof, and relates to a carbon nanosheet, a preparation method and application thereof. The invention aims to solve the problem that the adsorption quantity of the existing water treatment adsorbent to antibiotics is low. A Co/N Co-doped mesoporous carbon nanosheet is prepared from a template, a cobalt source, a nitrogen source and hexamethylenetetramine. The method comprises the following steps: firstly, preparing a reaction solution; secondly, reacting the reaction solution at the temperature of 75-85 ℃; and thirdly, annealing to obtain the Co/N codoped mesoporous carbon nanosheet. A Co/N Co-doped mesoporous carbon nanosheet is used for adsorbing antibiotics in organic pollutant wastewater. The adsorption capacity of the Co/N codoped mesoporous carbon nanosheet on tetracycline hydrochloride is 336.39-344.83 mg/g. The Co/N Co-doped mesoporous carbon nanosheet can be obtained. Patent CN108970577A proposes a Co/N codoped mesoporous carbon nanosheet and preparation thereof, aiming at solving the problem that the existing water treatment adsorbent is low in adsorption capacity to antibiotics. Reaction liquid involved in the preparation of the nano-sheets involved in the patent needs to react for 20-28h in a closed environment, vacuum drying needs to be carried out for 10-14h, the required raw materials and additives are complex, the reaction time is long, and the interference of uncontrollable factors is greatly increased in the experimental processes. The raw materials required by the invention are low in price and easy to obtain, and the preparation method is simple and has short reaction time.

Patent CN111151283A discloses a nitrogen-cobalt co-doped porous carbon loaded CoxZnS catalytic material, and a preparation method and application thereof. The nitrogen-cobalt co-doped porous carbon loaded CoxZnS catalytic material is prepared from protein-metal ions (Zn)²⁺/Co²⁺) The complex is obtained after pyrolysis and acid washing. The nitrogen-cobalt co-doped porous carbon loads a CoxZnS catalytic material. Patent CN111151283A proposes that nitrogen-cobalt co-doped porous carbon loaded CoxZnS catalytic material is prepared from protein-metal ions (Zn)²⁺/Co²⁺) The complex is obtained after pyrolysis and acid washing. The preparation material protein has strict requirements on a protein storage method and high requirements on temperature conditions, and may be subjected to microbial contamination, protein inactivation and oxidation, and may influence the uniformity of experimental data. If disulfide bonds are present in the protein molecule, they should be stored in an oxidizing environment to ensure their integrity. In addition, proteins stored for more than one month are considered to be discarded. And the synthesis can be carried out only under the condition of low temperature, and the influence of the temperature is large. In addition, it cannot emphasize the catalytic performance of the synthesized catalytic material in which catalytic field is better, and cannot compare with commercial catalysts. The carbon source and the nitrogen source used in the invention have low prices, do not need to consider the problem of preservation too much, have mild reaction conditions, are easy to operate and are easy for large-scale production. Compared with the commercial Pt/C catalyst, the cobalt and nitrogen co-doped carbon nanosheet catalyst prepared by the invention has better initial potential, half-wave potential and limiting current density, and simultaneously shows more excellent stability and methanol tolerance than the commercial Pt/C catalyst. Therefore, the catalyst is an oxygen reduction catalyst with application prospect.

Disclosure of Invention

The first purpose of the invention is to provide a preparation method of a cobalt and nitrogen co-doped carbon nanosheet material.

The second purpose of the invention is to provide a cobalt and nitrogen co-doped carbon nanosheet material.

The third purpose of the invention is to provide an application of the cobalt and nitrogen co-doped carbon nanosheet material.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a cobalt and nitrogen co-doped carbon nanosheet material specifically comprises the following steps:

(a) dissolving lactose monohydrate and zinc source which are low in price and stable in property into water, and uniformly stirring and mixing to obtain a mixed solution;

(b) heating and foaming the mixed solution to obtain a precursor;

(c) and (c) carbonizing the precursor obtained in the step (b) (in order that the sample is heated and decomposed in an inert atmosphere) to obtain the cobalt and nitrogen co-doped carbon nanosheet material, wherein the boiling point of zinc is about 900 ℃, so that zinc is completely volatilized from the system in the roasting and carbonizing stage.

In the step (a), a cobalt source, lactose monohydrate and a zinc source are dissolved in water together.

In the step (a), the zinc source is zinc nitrate hexahydrate, and the cobalt source is cobalt nitrate hexahydrate.

In the step (a), when the mixed solution does not contain a cobalt source, the mass ratio of the lactose monohydrate to the zinc nitrate hexahydrate is (2-2.5): 1.

In the step (a), when the mixed solution contains a cobalt source, the mass ratio of the lactose monohydrate, the zinc nitrate hexahydrate and the cobalt nitrate hexahydrate is (2-2.5): 1, (0.04-0.18).

In the step (a), the mass ratio of the lactose monohydrate to the water is 1 (5-10).

In step (a), the three are mixed at room temperature.

In the step (b), the heating and evaporating process specifically comprises the following steps: and (3) placing the mixed solution in a forced air drying oven, rapidly heating to 200-260 ℃, preferably 220 ℃, and preserving heat for 20-50 min.

In the step (c), the carbonization process specifically comprises: and under the inert atmosphere, heating the precursor to 700-950 ℃, carbonizing for 60-240 min, and then cooling to room temperature.

The inert atmosphere adopts nitrogen, and the heating rate is 2 ℃ for min^-1。

Preferably, in step (c), the carbonization process is specifically: and under the inert atmosphere, heating the precursor to 800-950 ℃, carbonizing for 120-240 min, and cooling to room temperature.

The cobalt and nitrogen co-doped carbon nanosheet material is characterized in that the carbon doping amount of the cobalt and nitrogen co-doped carbon nanosheet material is 87.44-94.51 wt%, the cobalt doping amount is 0-1.53 wt%, the oxygen doping amount is 3.11-8.62 wt%, and the nitrogen doping amount is 1.57-3.17 wt%. Specifically, when the material contains cobalt, the doping amount of carbon is 87.44 wt% -93.76 wt%, the doping amount of cobalt is 0.51 wt% -1.53 wt%, the doping amount of oxygen is 4.16 wt% -8.62 wt%, and the doping amount of nitrogen is 1.57 wt% -3.17 wt%.

The material has oxygen reduction performance, the initial potential is-0.0533-0.0197V, and the half-potential is-0.2153-0.1783V.

Compared with the prior art, the invention has the beneficial effects that:

(1) the preparation method is simple: and pyrolyzing the mixture by using a blast drying box, and calcining and carbonizing the mixture in a tubular furnace to obtain the nanosheet.

(2) The lactose monohydrate used by the method can be used as an organic carbon source and a foaming agent, has the advantages of large specific surface area, high porosity and good conductivity after the porous structure is adjusted and the lactose monohydrate is carbonized with other reagents, thereby playing an excellent role in the performance and the appearance of the catalyst and reducing the cost.

(3) The catalyst used has excellent oxygen reduction activity under alkaline conditions and has better stability than commercial Pt/C catalysts.

Drawings

Fig. 1 is a scanning electron microscope image of the cobalt and nitrogen co-doped carbon nanosheet material prepared in example 1;

FIG. 2 is a drawing showing nitrogen adsorption desorption of the cobalt and nitrogen co-doped carbon nanosheet material prepared in example 1;

FIG. 3 is an X-ray photoelectron spectroscopy analysis chart of the cobalt and nitrogen co-doped carbon nanosheet material prepared in example 1;

FIG. 4 is a graph comparing the chronoamperometric curves of the cobalt and nitrogen co-doped carbon nanosheet material prepared in example 1 and a commercial Pt/C catalyst (specifically: the percent loss in current density of the catalyst after 9000s at a constant voltage of-0.35V at 1600 rpm);

FIG. 5 is a comparison graph of cyclic voltammograms of five cobalt and nitrogen co-doped carbon nanosheets prepared in examples 1-5;

fig. 6 is a graph comparing the linear scan curves of the cobalt and nitrogen co-doped carbon nanosheet materials prepared in examples 1-5 with the commercial Pt/C catalyst at 1600 rpm.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The methods described in the examples of the present invention are conventional methods unless otherwise specified. The starting materials are commercially available from the public unless otherwise specified.

The model of the instrument or equipment used in the embodiments of the present invention and the information of the manufacturer are as follows:

air-blast drying oven, model DHG-9920A, manufacturer: Shanghai-Hengchang scientific instruments, Inc.;

scanning Electron Microscope (SEM), model Phenom Pro X, manufacturer: the united states;

transmission Electron Microscope (TEM), model: JEM-2010HT, manufacturer: japan electronics corporation;

x-ray photoelectron spectrometer, model: AXIS UltraDLD, manufacturer: shimadzu, Japan;

electrochemical workstation, model: autolab PGSTAT302N, manufacturer: wantong Switzerland;

full-automatic specific surface area and aperture analyzer, model: ASAP260, manufacturer: microphone instruments inc.

In the embodiment of the invention, the cyclic voltammetry curve of the sample is measured in an Autolab PGSTAT302N electrochemical workstation, and the specific test conditions are as follows: in a three-electrode system, Ag/AgCl is used as a reference electrode, a platinum wire is used as a counter electrode, a glassy carbon electrode loaded with a cobalt and nitrogen co-doped carbon nanosheet material is used as a working electrode, and the scanning speed is 10 mV/s; the preparation process of the working electrode comprises the following steps: dissolving 5mg of cobalt and nitrogen co-doped carbon nanosheet material in 1mL of ethanol and 50 mu L of mixed solution of Nafion (5% solution, purchased from DuPont, USA), performing ultrasonic dispersion, then dropwise adding 10 mu L of the mixture onto a glassy carbon electrode, and drying at room temperature to obtain the working electrode. When the cyclic voltammetry curve test is carried out, nitrogen and oxygen are respectively introduced into 0.1M KOH electrolyte solution to create a nitrogen/oxygen atmosphere. The electrodes were subjected to 10 cycles in electrolyte solution to activate the electrodes before testing.

In the embodiment of the invention, the linear sweep voltammetry curve of the sample is measured in an Autolab PGSTAT302N electrochemical workstation under the following test conditions: in a three-electrode system, Ag/AgCl is used as a reference electrode, a platinum sheet is used as a counter electrode, a rotating disc electrode loaded with a cobalt and nitrogen co-doped carbon nanosheet material or a commercial Pt/C catalyst is used as a working electrode, 0.1M KOH is used as an electrolyte solution, and the scanning speed is 10 mV/s; the preparation process of the working electrode comprises the following steps: dissolving 5mg of cobalt and nitrogen co-doped carbon nanosheet material or a commercial Pt/C catalyst in a mixed solution of 1mL of ethanol and 50 mu L of ethanol (5% solution purchased from DuPont, USA), performing ultrasonic dispersion, dropwise adding 10 mu L of the solution onto a rotating disc electrode, and drying at room temperature to obtain the working electrode. When the linear sweep voltammetry test is carried out, nitrogen and oxygen are respectively introduced into 0.1M KOH electrolyte solution to create a nitrogen/oxygen atmosphere. The electrodes were subjected to 10 cycles in electrolyte solution to activate the electrodes before testing. When the test is carried out in an oxygen atmosphere, the linear sweep voltammetry curves of the test electrode are under different rotating speeds (400-.

In the embodiment of the invention, the timing current curve of the sample is measured in an Autolab PGSTAT302N electrochemical workstation, and the test conditions are as follows: in a three-electrode system, Ag/AgCl is used as a reference electrode, a platinum sheet is used as a counter electrode, a rotating disc electrode loaded with a cobalt and nitrogen co-doped carbon nanosheet material or a commercial Pt/C catalyst is used as a working electrode, 0.1M KOH is used as an electrolyte solution, and the scanning speed is 10 mV/s. The preparation process of the working electrode comprises the following steps: dissolving 5mg of cobalt and nitrogen co-doped carbon nanosheet material or a commercial Pt/C catalyst in a mixed solution of 1mL of ethanol and 50 mu L of ethanol (5% solution purchased from DuPont, USA), performing ultrasonic dispersion, dropwise adding 10 mu L of the solution onto a rotating disc electrode, and drying at room temperature to obtain the working electrode. The test conditions for the chronoamperometric curve were: the current was tested over time at a constant potential of-0.35V at 1600rpm for 9000 s.

Example 1

The carbon doping amount of the cobalt and nitrogen co-doped carbon nanosheet material is 87.44 wt%, the cobalt doping amount is 0.99 wt%, the oxygen doping amount is 8.4 wt%, and the nitrogen doping amount is 3.17 wt%.

The preparation method comprises the following steps:

weighing 1g of lactose monohydrate, 0.5g of zinc nitrate hexahydrate and 43.8mg of cobalt nitrate hexahydrate, dissolving in 5ml of deionized water, stirring and mixing uniformly without obvious particle suspended matters, putting the mixture into a forced air drying box, rapidly heating to 220 ℃, keeping the temperature for 20min to obtain a brownish black foam sample, putting the sample into a ceramic boat, putting the ceramic boat into a tube furnace, and keeping the temperature for 2 min in a nitrogen atmosphere^-1Calcining at the heating rate of 800 ℃, preserving heat for 120min, and cooling to room temperature to obtain the cobalt and nitrogen co-doped carbon nanosheet material.

As can be seen from FIG. 1, the sample has a sheet structure with a thickness of about 5-10um, and also shows good catalytic activity in the back side electrochemical performance test.

A typical IV-type mesoporous curve in fig. 2 proves that the synthesized cobalt and nitrogen co-doped carbon nanosheet material has a good mesoporous structure.

As shown in fig. 3, the cobalt and nitrogen co-doped carbon nanosheet material contains four elements, and the contents of carbon, nitrogen, oxygen and cobalt are 87.44%, 3.17%, 8.4% and 0.99%, respectively.

As can be seen from fig. 4, after 9000s, the current density of the cobalt and nitrogen co-doped carbon nanosheet material remained 93.32%, while that of the commercial platinum-carbon catalyst was 84.74%, indicating that the material had better durability than the commercial platinum-carbon catalyst.

As can be seen from fig. 5, at a voltage of-0.1573V, the cyclic voltammetry curve has a significant concave peak influenced by the oxygen reduction performance, i.e., the cobalt and nitrogen co-doped carbon nanosheet material has a significant oxygen reduction performance.

As can be seen from FIG. 6, the initial potential of the cobalt and nitrogen co-doped carbon nanosheet material is 0.0197V, the initial potential of the commercial platinum-carbon catalyst is-0.0113V, only the difference is 0.031V, the half-wave potential is-0.1783V, the initial potential of the commercial platinum-carbon catalyst is-0.188V, only the difference is 0.0097V, and the material has better oxygen reduction performance.

Example 2

The cobalt and nitrogen co-doped carbon nanosheet material is characterized in that the carbon doping amount of the cobalt and nitrogen co-doped carbon nanosheet material is 94.51 wt%, the nitrogen doping amount is 2.38 wt%, the oxygen doping amount is 3.11 wt%, and the cobalt doping amount is 0 wt%. The preparation method comprises the following steps:

weighing 1g of lactose monohydrate and 0.5g of zinc nitrate hexahydrate, dissolving in 5ml of deionized water, stirring and mixing uniformly without obvious particle suspended matters, putting the mixture into a blast drying oven, rapidly heating to 220 ℃, keeping the temperature for 30min to obtain a brownish black foam sample, putting the sample into a ceramic boat, putting the ceramic boat into a tube furnace, and putting the ceramic boat into the tube furnace in a nitrogen atmosphere at 2 ℃ for min^-1Calcining at the heating rate of 850 ℃, keeping the temperature for 200min, and cooling to room temperature to obtain the cobalt and nitrogen co-doped carbon nanosheet material. As can be seen from fig. 5, the cyclic voltammetry curve has a significant depression at a voltage of-0.2003V, i.e., the cobalt and nitrogen co-doped carbon nanosheet material has a significant oxygen reduction performance. As can be seen from FIG. 6, the initial potential and half-wave potential of the material are 0.0097V and-0.2113V respectively, which indicates that the catalyst has certain oxygen reduction performance.

Example 3

The cobalt and nitrogen co-doped carbon nanosheet material is prepared by adopting the following steps of, by weight, 93.76% of carbon doping amount, 1.57% of nitrogen doping amount, 4.16% of oxygen doping amount and 0.51% of cobalt doping amount:

weighing 1g of lactose monohydrate, 0.5g of zinc nitrate hexahydrate and 21.9mg of cobalt nitrate hexahydrate, dissolving in 5ml of deionized water, stirring and mixing uniformly without obvious particle suspended matters, putting the mixture into a forced air drying box, rapidly heating to 220 ℃, keeping the temperature for 40min to obtain a brownish black foam sample, putting the sample into a ceramic boat, putting the ceramic boat into a tubular furnace, keeping the ceramic boat in a nitrogen atmosphere,at 2 ℃ for min^-1Calcining at the heating rate of 900 ℃, preserving the heat for 240min, and cooling to room temperature to obtain the cobalt and nitrogen co-doped carbon nanosheet material. As can be seen from fig. 5, the cyclic voltammetry curve has a significant depression at a voltage of-0.1973V, i.e., the cobalt and nitrogen co-doped carbon nanosheet material has a significant oxygen reduction performance. As can be seen from FIG. 6, the initial potential and half-wave potential of the material are-0.0533V and-0.1783V respectively, which shows that the catalyst has certain oxygen reduction performance.

Example 4

The cobalt and nitrogen co-doped carbon nanosheet material is prepared by adopting the following steps of, by weight, 87.56% of carbon doping amount, 2.71% of nitrogen doping amount, 8.62% of oxygen doping amount and 1.11% of cobalt doping amount in the cobalt and nitrogen co-doped carbon nanosheet material:

weighing 1g of lactose monohydrate, 0.5g of zinc nitrate hexahydrate and 65.7mg of cobalt nitrate hexahydrate, dissolving in 5ml of deionized water, stirring and mixing uniformly without obvious particle suspended matters, putting the mixture into a forced air drying box, rapidly heating to 220 ℃, keeping the temperature for 50min to obtain a brownish black foam sample, putting the sample into a ceramic boat, putting the ceramic boat into a tube furnace, and keeping the temperature for 2 min in a nitrogen atmosphere^-1Calcining at the heating rate of 950 ℃, preserving the heat for 200min, and cooling to room temperature to obtain the cobalt and nitrogen co-doped carbon nanosheet material. As can be seen from fig. 5, the cyclic voltammetry curve has a significant depression at a voltage of-0.1843V, i.e., the cobalt and nitrogen co-doped carbon nanosheet material has a significant oxygen reduction performance. As can be seen from FIG. 6, the initial potential and half-wave potential of the material are-0.0133V and-0.1863V respectively, which shows that the material has certain oxygen reduction performance.

Example 5

The carbon doping amount of the cobalt and nitrogen co-doped carbon nanosheet material is 89.81 wt%, the nitrogen doping amount is 2.91 wt%, the oxygen doping amount is 5.75 wt%, and the cobalt doping amount is 1.53 wt%. The preparation method comprises the following steps:

1g of lactose monohydrate, 0.5g of zinc nitrate hexahydrate and 87.6mg of cobalt nitrate hexahydrate are weighed and dissolved in 5ml of deionized water, stirred and mixed uniformly without obvious particle suspended matters, and the mixture is put into a blast drying oven to be rapidly driedHeating to 220 deg.C, maintaining the temperature for 30min to obtain brown black foam sample, placing the sample in ceramic boat, placing in tube furnace under nitrogen atmosphere at 2 deg.C for 2 min^-1Calcining at the heating rate of 900 ℃, preserving heat for 120min, and cooling to room temperature to obtain the cobalt and nitrogen co-doped carbon nanosheet material. As can be seen from fig. 5, the cyclic voltammetry curve has a significant depression at a voltage of-0.1873V, i.e., the cobalt and nitrogen co-doped carbon nanosheet material has a significant oxygen reduction performance. As can be seen from FIG. 6, the initial potential and half-wave potential of the material are-0.0273V and-0.2153V, respectively, indicating that the material has certain oxygen reduction performance.

Comparative example 1

A commercially available commercial Pt/C catalyst was used as a comparative example, and the chronoamperometric graph, cyclic voltammogram, and linear sweep curve of the commercial Pt/C catalyst are shown in fig. 4 and 6, respectively.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The preparation method of the cobalt and nitrogen co-doped carbon nanosheet material is characterized by comprising the following steps:

(a) dissolving lactose monohydrate and a zinc source into water together, and stirring and mixing uniformly to obtain a mixed solution;

(b) then heating and evaporating the mixed solution to dryness to obtain a precursor;

(c) carbonizing the precursor obtained in the step (b) to obtain the cobalt and nitrogen co-doped carbon nanosheet material.

2. The method for preparing a cobalt and nitrogen co-doped carbon nanosheet material according to claim 1, wherein in step (a), a cobalt source, lactose monohydrate, and a zinc source are dissolved in water together.

3. The preparation method of the cobalt and nitrogen co-doped carbon nanosheet material as claimed in claim 2, wherein in step (a), the zinc source is zinc nitrate hexahydrate, and the cobalt source is cobalt nitrate hexahydrate;

in the step (a), when the mixed solution does not contain a cobalt source, the mass ratio of the lactose monohydrate to the zinc nitrate hexahydrate is (2-2.5): 1;

4. The preparation method of the cobalt and nitrogen co-doped carbon nanosheet material according to claim 1, wherein in the step (a), the mass ratio of lactose monohydrate to water is 1 (5-5.5).

5. The method according to claim 1, wherein in step (a), the cobalt-nitrogen-codoped carbon nanosheet material is mixed at room temperature.

6. The method for preparing a cobalt and nitrogen co-doped carbon nanosheet material according to claim 1, wherein in the step (b), the heating and evaporating process specifically comprises: and rapidly heating the mixed solution to 200-260 ℃, and preserving the temperature for 20-50 min.

7. The method for preparing a cobalt and nitrogen co-doped carbon nanosheet material according to claim 1, wherein in step (c), the carbonization process specifically comprises: and under the inert atmosphere, heating the precursor to 700-950 ℃, carbonizing for 60-240 min, and then cooling to room temperature.

8. The method for preparing cobalt and nitrogen co-doped carbon nanosheet material according to claim 7, wherein the method comprisesThe inert atmosphere adopts nitrogen, and the heating rate is 2 ℃ for min^-1。

9. A cobalt and nitrogen co-doped carbon nanosheet material prepared by the preparation method of any one of claims 1-8.

10. Use of the cobalt and nitrogen co-doped carbon nanosheet material of claim 9 as an oxygen reduction catalyst.