CN114855210B - Molten salt method in-situ synthesis carbon-based single-atom nanosheet and preparation method and application thereof - Google Patents

Molten salt method in-situ synthesis carbon-based single-atom nanosheet and preparation method and application thereof Download PDF

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CN114855210B
CN114855210B CN202210332320.1A CN202210332320A CN114855210B CN 114855210 B CN114855210 B CN 114855210B CN 202210332320 A CN202210332320 A CN 202210332320A CN 114855210 B CN114855210 B CN 114855210B
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杨彬
林丹
侯阳
李中坚
雷乐成
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Zhejiang University ZJU
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Abstract

The invention discloses a preparation method for in-situ synthesis of carbon-based single-atom nanosheets by a molten salt method, which comprises the following steps: mixing ferrocene and 2-methylimidazole to obtain a first mixture, mixing zinc oxide, sodium chloride and calcium chloride, grinding to obtain a second mixture, and placing the first mixture and the second mixture in a container at intervals; blowing the first mixture into the second mixture through argon, simultaneously, carrying out gradient calcination on the first mixture and the second mixture in the container, and cooling to obtain the carbon-based single-atom nanosheet containing the mixed salt of sodium chloride/calcium chloride; washing and stirring the carbon-based monatomic nanosheets by deionized water, performing suction filtration and vacuum drying to obtain the carbon-based monatomic nanosheets synthesized in situ by a molten salt method. The method can obtain CO with higher electro-catalytic reduction by one-step method 2 An active catalyst. The invention also provides the carbon-based single-atom nanosheet prepared by the method, and application of the carbon-based single-atom nanosheet in electrocatalysis of CO 2 And (4) application to reduction.

Description

Molten salt method in-situ synthesis carbon-based single-atom nanosheet and preparation method and application thereof
Technical Field
The invention relates to the technical field of nano material preparation, in particular to a molten salt method in-situ synthesis carbon-based single-atom nanosheet and a preparation method and application thereof.
Background
In recent years, with rapid development of cities and industries, atmospheric CO 2 The concentration of the carbon dioxide is increased sharply, the carbon circulation system of the earth is damaged, a series of serious environmental problems are caused, and the survival and development of human beings are selectedFighting. Therefore, there is a need to find a solution to reduce CO in the atmosphere 2 To avoid further deterioration of the environment. Reduction of atmospheric CO 2 On one hand, the concentration of the carbon dioxide is mainly started from two aspects, on the other hand, the use of fossil fuel is reduced by using clean energy such as solar energy, wind energy and the like for energy supply, and CO is reduced from the source 2 Production and discharge of (d); another aspect is to the CO already present in the atmosphere 2 And (4) carrying out capture, separation and conversion to finally generate a compound with high added value.
In CO 2 Electrocatalytic reduction of CO in conversion 2 Obtaining high value added fuels is one of the most interesting conversion processes. Electrocatalytic reduction of CO 2 The electric energy provided by renewable energy sources such as wind energy, hydrogen energy and the like is utilized to drive the electric catalyst to CO 2 Reducing to finally generate carbon monoxide, methane, formic acid, methanol and C 2 Products and even carbon-rich products. The process not only utilizes clean energy to supply power and generate electricity, thereby reducing CO at the source 2 And CO occurs over the electrocatalyst driven by electricity 2 The processes of adsorption activation, electron transfer, protonation, product desorption and the like are finally converted into fossil fuel with high added value, and CO in the atmosphere is reduced 2 The concentration of (c). Therefore, the method has great research value and development prospect. But CO 2 Medium C = O having large bond energy (806 kJ mol) -1 ) The reaction process needs higher energy to break the bond to form an intermediate with C-O bond or C-H bond and the like, and CO is electrochemically reduced 2 Is a process involving multiple electron transfer, proton coupling, so CO 2 Conversion efficiency is generally limited and single product selectivity is not high. Therefore, the electrocatalytic CO with high selectivity, high catalytic activity and good stability is developed 2 Reducing the catalyst is a challenge to the scientists at present.
The carbon-based material serving as the carrier of the electrocatalyst is cheap and easy to obtain, has good chemical stability and electrical conductivity, and the surface of the carbon skeleton is easy to modify and dope, so that the improvement and promotion of the performance of the catalyst are facilitated. In addition, the carbon-based material may be assembled into various sizes and structures, such as zero-dimensional carbon nanodots, one-dimensional carbon nanotubes and nanofibers, two-dimensional carbon nanoplatelets, three-dimensional carbon foams, and the like. Two-dimensional materials have been widely studied by researchers because of their excellent optical, electrical, magnetic and structural properties, and because the structure and electronic properties of the flakes can be adjusted by varying the thickness of the nanosheets or by doping.
At present, the synthesis technology mainly comprises methods such as stripping, chemical deposition, solvothermal, hydrothermal and the like. The molten salt method is used as a rapid, simple, high-yield and low-cost synthesis method, and is more and more widely applied to the preparation of materials. For example, chinese patent document No. CN111974435A, the method includes weighing magnesium citrate, potassium citrate, and ammonium oxalate according to a certain proportion, placing the weighed materials in a corundum boat under nitrogen gas condition for pyrolysis, after the reaction is completed, performing acid washing and water washing to obtain N-doped carbon nanosheets, immersing the N-doped carbon nanosheets in a copper nitrate aqueous solution by an impregnation method to obtain a precursor, and finally calcining the N-doped carbon nanosheets at low temperature in a hydrogen/nitrogen mixed gas atmosphere to obtain Cu/N-doped carbon nanosheets. Compared with the existing preparation method, the method has the advantages of low synthesis temperature, cheap and easily-obtained raw materials, uniform product structure and uniform appearance. However, the preparation process is relatively complex, the N-doped carbon nanosheet needs to be synthesized first, and then the active metal is loaded, so that the synthesis process can be further simplified through an innovative method.
Disclosure of Invention
The invention provides a preparation method for in-situ synthesis of carbon-based monatomic nanosheets by a molten salt method, which can be used for obtaining CO with high electro-catalytic reduction by a one-step method 2 An active catalyst.
A preparation method for in-situ synthesis of carbon-based monatomic nanosheets by a molten salt method comprises the following steps:
(1) Mixing ferrocene and 2-methylimidazole to obtain a first mixture, mixing zinc oxide, sodium chloride and calcium chloride, grinding to obtain a second mixture, and placing the first mixture and the second mixture in a container at intervals;
(2) Introducing argon into the container, blowing the first mixture into the second mixture through the argon, simultaneously, calcining the first mixture and the second mixture in the container in a gradient manner, and cooling to obtain initial carbon-based single-atom nanosheets containing sodium chloride/calcium chloride mixed salts;
(3) Washing and stirring the initial carbon-based monatomic nanosheet through deionized water, performing suction filtration, and performing vacuum drying to obtain the molten salt method in-situ synthesis carbon-based monatomic nanosheet.
According to the invention, fe-N active sites are distributed in the carbon-based nanosheets with large specific surface areas through a one-step method, so that the Fe-N active sites are exposed as much as possible, and the catalytic activity is enhanced.
In the step (1), the molar ratio of the 2-methylimidazole to the ferrocene is 60-70.
In the step (1), in order to prevent the calcium chloride from absorbing water and deliquescing in the grinding process, the sodium chloride and the zinc oxide are put into an agate mortar according to a molar ratio of 6-7 for uniform grinding, then the calcium chloride is added for continuous grinding until the calcium chloride is uniform, and as the sodium chloride/calcium chloride with different ratios can affect the eutectic point of the mixed salt, in order to ensure that the carbon material forms nanosheets and the loss is low in the pyrolysis process, the mixed salt is required to reach a lower melting temperature, so that the molar ratio of the sodium chloride to the calcium chloride is 7.
In the step (1), the first mixture and the second mixture are separated by a distance of 1-2cm, the distance is crucial to the formation of Fe-N sites, if the distance is too large, part of the first mixture can cool down and sink before being blown to the second mixture, and the Fe-N sites are reduced; if the pitch is too small, ferrocene tends to accumulate in a partial region to form iron particles.
In the step (1), the container is a corundum boat or a porcelain boat.
In the step (2), the purity of the argon is 95-99.999%, and the gas flow rate of the argon is 10-20mL/min. The concentration of argon has important significance for protecting the material in the calcining process, and the higher the purity of argon is, the better the protection effect of the material in the calcining process is.
In the step (2), the parameters of the gradient calcination are as follows: firstly heating to 300-400 ℃ at a heating rate of 2-5 ℃/min, staying for 0.5-2h, then heating to 500-600 ℃ at a heating rate of 2-5 ℃/min, staying for 0.5-2h, finally heating to 700-1000 ℃ at a heating rate of 1-10 ℃/min, and calcining for 0.5-3h.
And blowing the gasified 2-methylimidazole to the second mixture by argon gas flow when the flash point temperature of the 2-methylimidazole reaches 155 ℃, carrying out coordination chemical reaction on nitrogen elements in the 2-methylimidazole and zinc in zinc oxide to form a zeolite imidazole framework material (ZIF-8) with Zn-N bonds, diffusing sublimed ferrocene to a ZIF-8 carrier when the temperature is raised to 300-400 ℃, and combining the decomposed ferrocene with nitrogen of the ZIF-8 to replace Zn to form Fe-N bonds.
When the temperature reaches 500-600 deg.C, the melting point temperature of the mixed salt is reached, and the molten salt solution diffuses into the carbonized product to prevent van der Waals force from forming, thereby further inhibiting sp 2 The coordinated carbon layers are stacked along the z axis to form graphene-shaped carbon nano sheets, the graphene-shaped carbon nano sheets can be kept at the temperature for enough time, not only can the graphene-shaped carbon nano sheets be completely formed in the product be guaranteed, but also Fe-N bonds can be formed in molten salt as much as possible, as pyridine nitrogen and pyrrole nitrogen can be converted into graphite nitrogen along with the increase of the temperature, so that the coordination capacity with Fe is lost, and molten salt solution formed at the temperature can completely wrap the product, so that the subsequent loss of N and the reduction of Fe-N active sites caused by the increase of the temperature are reduced.
When the temperature reaches 700-1000 ℃, further carbonizing, and improving the graphitization degree.
In the step (3), the stirring is magnetic stirring, and the stirring parameters are as follows: the stirring speed is 300-600rpm, and the stirring time is 2-4h.
Further, the mole ratio of the ferrocene, the zinc oxide and the 2-methylimidazole is 2-3:80-90:150-200, the molar ratio of sodium chloride to zinc oxide is 6-1.6, the molar ratio of sodium chloride to calcium chloride is 2.
Further preferably, the molar ratio of the sodium chloride to the calcium chloride is 2.
The amount of zinc oxide is higher than that of ferrocene, so that enough Zn-N sites are ensured to exchange with the ferrocene, but the amount of zinc oxide is not too high, otherwise, zn atoms cannot be completely removed during high-temperature calcination, and a Zn-N structure remains in the material; the amount of ferrocene cannot be too high, so that iron particles rather than single atoms are formed in the calcining process, and too low, the Fe-N active sites are reduced, and the activity of the catalyst is reduced; the amount of the mixed salt is also required to be higher than that of the dimethyl imidazole, so that the molten salt solution can completely wrap the product to enable the product to grow in two dimensions to form a nano sheet, and although the amount of the mixed salt is very high, a two-dimensional nano sheet structure can also be formed, unnecessary resource waste and energy consumption can be caused.
The preparation principle of the carbon-based monatomic nanosheet catalyst synthesized in situ by the molten salt method provided by the invention is as follows: when the temperature of the tubular furnace rises to 155 ℃ of the flash point of the 2-methylimidazole, the 2-methylimidazole is sublimated and diffuses to the rear end of the corundum boat along with argon gas flow, and nitrogen in the 2-methylimidazole and zinc in zinc oxide undergo a coordination chemical reaction to form a zeolite imidazole framework material (ZIF-8). When the temperature reached 300-400 ℃, ferrocene sublimed and diffused into the ZIF-8 carrier began to decompose and bond with nitrogen in ZIF-8 to form Fe-N bonds. When the temperature reaches 500-600 deg.C, above the melting point of the mixed salt, the salt solution in molten state diffuses into the carbonized product to prevent the formation of van der Waals forces, thereby further inhibiting sp 2 The coordinated carbon layers are stacked along the z-axis to form graphene-like carbon nanoplatelets. When the temperature reaches 800-1000 ℃, the carbonization degree of the product is further improved. When the temperature at the end of the pyrolysis process drops to room temperature, white mixed salt crystals are distributed in the black product, due to the precipitation of the carbonized product from the mixed salt during cooling. And finally, washing the heat-treated material by using deionized water to completely remove mixed salts to obtain the carbon-based single-atom nanosheet material.
The carbon-based monatomic nanosheet is prepared by a molten salt method through a preparation method for in-situ synthesis of the carbon-based monatomic nanosheet through a molten salt method.
The thickness of the carbon-based single-atom nanosheet synthesized in situ by the molten salt method is 2-5nm.
Hair brushThe invention also provides the application of the fused salt method for in-situ synthesis of the carbon-based single-atom nanosheet catalyst in the electrocatalytic reduction of CO 2 The application of (1).
A carbon-based single-atom nanosheet catalyst synthesized in situ by a molten salt method is attached to carbon paper to serve as a working electrode, ag/AgCl serves as a reference electrode, a platinum wire serves as a counter electrode, and a three-electrode system is formed to carry out electro-catalytic reduction on CO 2 。
According to the invention, the carbon-based single-atom nanosheet catalyst is prepared by combining low-temperature gas diffusion, high-temperature calcination carbonization and molten salt product morphology control, so that the Fe-N coordination active center is well fixed in the two-dimensional carbon nanosheet structure with higher specific surface area, and the electric catalysis CO is improved due to the clear coordination structure 2 Selectivity for CO reduction.
Compared with the prior art, the invention has the beneficial effects that:
(1) In the temperature programming process, gas diffusion is generated during low-temperature calcination to obtain an iron atom-loaded carbon material, and then the carbon material is subjected to temperature rise to change the morphology in molten salt and further generate carbonization, so that the molten salt method in-situ synthesis carbon-based single-atom nanosheet catalyst has a nano-sheet structure and good structural stability; meanwhile, the preparation method is simple and efficient, low in cost, high in controllability, good in reproducibility and suitable for industrial production.
(2) In the preparation process of the material, the mixed salt sodium chloride/calcium chloride serves as a sealed reactor in a molten state, the carbon material which is calcined at low temperature to form Fe-N bonds can be dissolved in molten salt for further pyrolysis, more nitrogen is doped on carbon, and the longitudinal growth of the carbon material is inhibited due to the acting force of the molten salt, so that the nanosheet with the large specific surface area is formed. Due to high N doping amount, fe-N coordination active sites and high specific surface area, the catalyst shows excellent electrocatalytic performance, and the faradaic efficiency of CO reaches 95% when the potential is-0.5V (relative to a reversible hydrogen electrode).
(3) Because the mixed salt used in the method is easy to dissolve in water, only deionized water is needed in the washing process for removing the mixed salt after the synthesis is finished, and the washing process is simple, convenient and effective. The method solves the problem that inorganic salt is difficult to remove quickly and efficiently in the molten salt synthesis method.
(4) According to the invention, by the method of combining low-temperature gas diffusion, high-temperature calcination and carbonization and fused salt control of product morphology, the fused salt method is used for preparing the carbon-based monatomic nanosheet catalyst in-situ synthesis, so that the Fe-N coordination active center is well fixed in the two-dimensional carbon nanosheet structure with higher specific surface area, and the clear coordination structure improves the electrocatalysis of CO 2 Selectivity for CO reduction.
Drawings
FIG. 1 is an SEM image of a carbon-based monatomic nanosheet catalyst prepared in example 1 and synthesized in situ by a molten salt method;
FIG. 2 is a TEM image of an in-situ synthesized carbon-based monatomic nanosheet catalyst prepared in example 1 by a molten salt method;
FIG. 3 is an AFM image of a molten salt method for in-situ synthesis of a carbon-based monatomic nanosheet catalyst prepared in example 1;
FIG. 4 is an XRD pattern of the catalysts prepared in examples 1 and 2 and comparative example 1;
FIG. 5 is a graph showing electrochemical polarization curves of the catalysts prepared in examples 1 and 2 and comparative example 1 in a three-electrode reaction cell in 0.5M potassium bicarbonate electrolyte;
figure 6 is a graph of faradaic efficiency of CO in a three electrode reaction cell, 0.5M potassium bicarbonate electrolyte, for catalysts prepared in examples 1, 2 and comparative example 1.
Detailed Description
The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Experimental procedures without specific conditions noted in the following examples, generally according to conventional conditions, or according to conditions recommended by the manufacturer.
Example 1
A preparation method of a carbon-based single-atom nanosheet catalyst synthesized in situ by a molten salt method comprises the following steps:
the method comprises the following steps: 60mg of ferrocene and 1.707g 2-methylimidazole are weighed on an electronic balance and placed at 1/4 of one end of a corundum boat.
Step two: 0.6512g of zinc oxide and 2.922g of sodium chloride are weighed on an electronic balance and put into an agate mortar for even grinding, 8.3235g of calcium chloride is weighed and put into the agate mortar for even mixing and grinding, and the ground powder is placed at the other end 2/3 of the corundum boat, namely, at a distance of 1cm from the mixture of ferrocene and 2-methylimidazole.
Step three: the corundum boat is put in argon atmosphere for calcination. Wherein the purity of argon atmosphere is 99.999 percent, the heating rate is 5 ℃/min, the low-temperature calcination temperature is 400 ℃, the retention time is 1h, the medium-temperature calcination temperature is 600 ℃, the retention time is 1h, the high-temperature calcination temperature is 1000 ℃, and the retention time is 2h.
Step four: placing the heat-treated powder sample in deionized water with the resistivity of 18.2M omega cm -1 And magnetically stirring for 4 hours, performing suction filtration on the stirred suspension, then performing acid washing and suction filtration for multiple times by using a 1M hydrochloric acid solution, and finally washing the suspension to be neutral by using deionized water. And (3) putting the filtered sample into a vacuum drying oven, keeping the temperature at 60 ℃, and drying for 12h to obtain the carbon-based monatomic nanosheet catalyst synthesized in situ by the molten salt method.
Fig. 1 shows that the prepared carbon-based monatomic nanosheet catalyst synthesized in situ by the molten salt method has a nanosheet-shaped microstructure; as can be seen from FIG. 2, the nanosheet thickness of the prepared carbon-based monatomic nanosheet catalyst synthesized in situ by the molten salt method is about 2-5nm, and no agglomerated metal particles occur; from fig. 3, it can be further seen that the thickness of the nanosheet of the prepared carbon-based monatomic nanosheet catalyst synthesized in situ by the molten salt method is 4nm; from fig. 4, it can be seen that the prepared carbon-based monatomic nanosheet catalyst synthesized in situ by the molten salt method does not contain metal nanoparticles, and the material has a low degree of crystallization.
Application example 1
Example 1 as electrocatalytic CO 2 Related test methods for cathode materials for the reduction preparation of CO:
the method comprises the following steps: weighing 5mg of the catalyst prepared in the example 1 by using an analytical balance, simultaneously taking 450 mu L of absolute ethyl alcohol and 50 mu L of 0.5wt.% Nafion solution, uniformly mixing the three, putting the mixture into a sample bottle, performing ultrasonic treatment for 2 hours, and performing magnetic stirring for 10-12 hours;
step two: cutting to 1 × 3cm 2 Weighing 100 mu L of the catalyst solution prepared in the step one, and dropwise adding the catalyst solution into the carbon paper to be 1 multiplied by 1cm 2 Drying the carbon paper of the area at room temperature or under the irradiation of infrared light to be used as a working electrode;
step three: adopting Ag/AgCl as reference electrode, platinum wire as counter electrode, forming three-electrode system together with working electrode, placing in sealed H-type electrolytic cell, using 0.5M potassium bicarbonate as electrolyte solution, respectively testing at different potentials, and analyzing CO and H by gas chromatograph 2 The yield of (2).
From fig. 5, the current densities of the catalysts at different potentials can be seen; from fig. 6 it can be seen that the catalyst has CO faradaic efficiency at different potentials, with the highest CO faradaic efficiency being about 95%.
Example 2
The only difference compared to example 1 is that the molten salt treatment was carried out using a different high temperature calcination temperature. The preparation method of the embodiment 1 is adopted, the calcination temperature in the step one is changed from 1000 ℃ to 900 ℃, and the rest steps are not changed, so that the carbon-based single-atom nanosheet catalyst is obtained.
Application example 2
The method comprises the steps of application example 1, and is characterized in that the carbon-based single-atom nanosheet catalyst prepared in example 2 is used as a cathode material to obtain electrocatalytic CO 2 The highest faradaic efficiency of reduction to CO is about 92%.
Comparative example 1
A preparation method of a nitrogen-doped carbon nanosheet catalyst synthesized in situ by a molten salt method comprises the following steps:
the method comprises the following steps: 1.707g2-methylimidazole is weighed on an electronic balance and placed at 1/4 of one end of a corundum boat.
Step two: 0.6512g of zinc oxide and 2.922g of sodium chloride are weighed on an electronic balance and put into an agate mortar for even grinding, 8.3235g of calcium chloride is weighed and put into the agate mortar for even mixing and grinding, and the ground powder is placed at the other end 2/3 of the corundum boat, namely, the distance between the ground powder and the mixture of 2-methylimidazole is 1 cm.
Step three: the corundum boat was calcined in an argon atmosphere. Wherein the purity of argon atmosphere is 99.999 percent, the heating rate is 5 ℃/min, the low-temperature calcination temperature is 400 ℃, the retention time is 1h, the medium-temperature calcination temperature is 600 ℃, the retention time is 1h, the high-temperature calcination temperature is 1000 ℃, and the retention time is 2h.
Step four: and (3) placing the heat-treated powder sample in deionized water, magnetically stirring for 4 hours, and carrying out suction filtration on the stirred suspension. And putting the filtered sample into a vacuum drying oven, keeping the temperature at 60 ℃, and drying for 12h to obtain the nitrogen-doped carbon nanosheet catalyst synthesized in situ by the molten salt method.
The method comprises the steps of application example 1, and is characterized in that the nitrogen-doped carbon nanosheet catalyst prepared in comparative example 1 through molten salt method in-situ synthesis is used as a cathode material to obtain electrocatalytic CO 2 The highest faradaic efficiency of reduction to CO is about 90%.
It should be noted that the above-mentioned specific implementation methods are described in detail for the technical solutions and application results of the present invention, and it should be understood by the reader that the above-mentioned embodiments are only the most preferred embodiments and are not intended to limit the present invention, and modifications, equivalent substitutions and the like performed by the related technical personnel within the core theory scope of the present invention should be within the protection scope of the present invention.

Claims (9)

1. A preparation method for in-situ synthesis of carbon-based monatomic nanosheets through a molten salt method is characterized by comprising the following steps:
(1) Mixing ferrocene and 2-methylimidazole to obtain a first mixture, mixing zinc oxide, sodium chloride and calcium chloride, grinding to obtain a second mixture, and placing the first mixture and the second mixture in a container at intervals;
(2) Introducing argon into the container, blowing the first mixture into the second mixture through the argon, simultaneously, calcining the first mixture and the second mixture in the container in a gradient manner, and cooling to obtain initial carbon-based single-atom nanosheets containing sodium chloride/calcium chloride mixed salts;
(3) Washing and stirring the initial carbon-based monatomic nanosheet through deionized water, performing suction filtration and vacuum drying to obtain a molten salt method in-situ synthesized carbon-based monatomic nanosheet;
the parameters of the gradient calcination are as follows: firstly heating to 300-400 ℃ at the heating rate of 2-5 ℃/min, staying for 0.5-2h, then heating to 500-600 ℃ at the heating rate of 2-5 ℃/min, staying for 0.5-2h, finally heating to 700-1000 ℃ at the heating rate of 1-10 ℃/min, and calcining for 0.5-3h.
2. The molten salt method for preparing the carbon-based monatomic nanosheet according to claim 1, wherein the molar ratio of 2-methylimidazole to ferrocene ranges from 60 to 1.
3. The preparation method of the carbon-based monatomic nanosheet through in-situ synthesis by the molten salt method according to claim 1, wherein the sodium chloride and the zinc oxide are uniformly ground according to a molar ratio of 6.
4. The method for preparing the carbon-based monatomic nanosheet through in situ synthesis using the molten salt process of claim 1, wherein the first mixture and the second mixture are separated by a distance of 1-2cm.
5. The preparation method of the carbon-based monatomic nanosheet through in-situ synthesis by the molten salt method of claim 1, wherein the argon purity is 95% -99.999% and the gas flow rate of the argon is 10-20mL/min.
6. The molten salt method molten salt in-situ synthesis method for preparing carbon-based monatomic nanosheets of claim 1, wherein the stirring in step (3) is magnetic stirring with stirring parameters of: the stirring speed is 300-600rpm, and the stirring time is 2-4h.
7. The molten salt method in-situ synthesis carbon-based monatomic nanosheet prepared by the preparation method of the carbon-based monatomic nanosheet according to any one of claims 1-6.
8. The molten salt method in-situ synthesis carbon-based monatomic nanosheet prepared by the preparation method for a carbon-based monatomic nanosheet according to claim 7, wherein the molten salt method in-situ synthesis carbon-based monatomic nanosheet has a thickness of 2-5nm.
9. The molten salt method of claim 7 or 8, wherein the molten salt method in-situ synthesized carbon-based monatomic nanosheet prepared by the method for preparing the carbon-based monatomic nanosheet through in-situ synthesis through the molten salt method is used for electrocatalytic reduction of CO 2 The application comprises the following specific steps:
a carbon-based single-atom nanosheet catalyst synthesized in situ by a molten salt method is attached to carbon paper to serve as a working electrode, ag/AgCl is used as a reference electrode, a platinum wire is used as a counter electrode, and a three-electrode system is formed to carry out electrocatalysis on CO 2 And (4) reducing.
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