CN114804070A - Preparation method of carbon nano hemispherical particles - Google Patents
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Abstract
The invention discloses a preparation method of carbon nano hemispherical particles, which comprises the following steps: adding organic silicon into an ethanol solution, and stirring to uniformly disperse the organic silicon to obtain a solution A; preparing an alkaline water solution, and then adding the alkaline water solution into the solution A to obtain a solution B; heating and stirring the solution B for hydrolysis reaction to obtain a solution C; adding resorcinol and formaldehyde into the solution C to perform phenolic condensation reaction to obtain mixed reaction liquid; centrifugally washing and drying the mixed reaction liquid to obtain a solid, and then grinding the solid to obtain an intermediate product D; calcining at high temperature to completely carbonize the surface coating layer of the intermediate product D to obtain an intermediate product E; placing the intermediate product E in etching liquid, stirring and etching, performing suction filtration, and washing to be neutral to obtain an intermediate product F; and drying the intermediate product F, and grinding to obtain the product carbon nano hemispherical particles. The carbon nano-hemispherical particles are uniformly distributed, have regular shapes, have vacuum structures and particle size range of 300-350 nanometers, and are good catalyst carrier materials.
Description
Technical Field
The invention relates to the field of catalyst preparation, in particular to a particle method of a carbon nano hemispherical material.
Background
With the global combustion of fossil fuels and increasing energy demand, environmental crisis and energy crisis are forcing us to find new energy sources to replace traditional non-renewable energy sources. One of the effective ways to solve this problem is by electrocatalysis. No matter new type electricityThe application of the pool is also electrolytic water and CO for developing new energy and reducing carbon emission 2 The reactions such as electro-reduction and the like all rely on an electrocatalyst with high efficiency temperature. The catalyst support is an important constituent of the supported catalyst. The good catalyst carrier not only has a supporting function for the catalyst, but also can greatly improve the performance of the catalyst. For electrocatalysis, the optimization of the carrier can greatly improve the stability of the catalyst, and simultaneously, the performance of the catalyst can be obviously improved by changing the structural morphology, improving the mass transfer efficiency and improving the intrinsic activity. Therefore, it is important to prepare a suitable electrocatalytic support.
At present, common electrocatalytic carbon carriers comprise carbon fiber cloth, carbon fiber paper and the like, the structure is simple, and more active sites cannot be exposed to the catalyst. And catalyst carriers such as foam nickel, foam cobalt and the like inevitably react when being loaded, so that difficulty is brought to the research of a final catalytic mechanism. Other catalyst supports such as silica-based supports are also difficult to compromise conductivity with high loading. Therefore, the method has very important practical significance for providing the electrocatalyst carrier which can not only keep good stability and conductivity, but also improve the performance of the catalyst by exposing more active sites and improving mass transfer.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a preparation method of carbon nano hemispherical particles; the carbon nano hemispherical powder synthesized by the preparation method has the advantages of uniform particle distribution, uniform size, regular appearance, vacuum structure and particle size range of 300-350 nm; the carbon nano hemisphere has a larger specific surface area while ensuring good conductivity, so that a loaded catalyst exposes more active sites, and mesopores exist to promote mass transfer, so that the carbon nano hemisphere is a good catalyst carrier material.
In order to solve the first technical problem, the invention adopts the following technical scheme:
a preparation method of carbon nano hemispherical particles comprises the following steps:
1) adding organic silicon into an ethanol solution, and stirring to uniformly disperse the organic silicon to obtain a solution A;
2) preparing an alkaline water solution, and then adding the alkaline water solution into the solution A to obtain a solution B;
3) heating and stirring the solution B for hydrolysis reaction, and obtaining a solution C after the solution is changed into milk white; adding resorcinol and formaldehyde into the solution C to perform phenolic condensation reaction, and stirring to uniformly coat the phenolic condensation product on a silicon ball template formed in the solution C to obtain a mixed reaction solution;
4) centrifugally washing the mixed reaction liquid, drying the solid obtained after centrifugal washing in a vacuum drying oven to obtain a reddish brown or light brown solid, and then grinding the reddish brown or light brown solid to obtain an intermediate product D;
5) under the condition of inert atmosphere, the surface coating layer of the intermediate product D is completely carbonized by high-temperature calcination in a tubular furnace to obtain a carbonized intermediate product E;
6) taking out the intermediate product E, placing the intermediate product E in etching liquid, stirring and etching, performing suction filtration after etching, and washing to be neutral to obtain an intermediate product F;
7) and drying the intermediate product F in a vacuum drying oven, and grinding to obtain the product carbon nano hemispherical particles.
As a further improvement of the technical scheme, in the step 1), the organosilicon is selected from one or more of propyl orthosilicate, tetrapropoxysilane and tetraethyl orthosilicate.
Preferably, in the step 1), the dosage of the organic silicon is 3-12 mL; the dosage of the absolute ethyl alcohol is 70-150 mL.
As a further improvement of the technical scheme, in the step 2), the alkali is selected from concentrated ammonia water, sodium hydroxide or lysine.
Preferably, in step 2), the concentration of the aqueous alkali solution is 25 to 30 wt%, and the amount is 2 to 10 mL.
As a further improvement of the technical scheme, in the step 3), the heating and stirring temperature is 25-40 ℃; and sealing during the reaction.
Preferably, in step 3), the heating and stirring are performed by using a water bath; the heating and stirring time is 10-40 minutes.
Preferably, in the step 3), the formaldehyde is derived from an 18 wt% formaldehyde aqueous solution, wherein the methanol stabilizer is contained in an amount of 5-8 wt%, and the formaldehyde aqueous solution is used in an amount of 0.56-1.4 mL; the resorcinol is used in an amount of 0.4-1 g.
Preferably, in the step 3), the reaction time of the phenolic aldehyde condensation reaction is 3-24 h.
As a further improvement of the technical scheme, in the step 4), the centrifugal washing is ultrasonic washing with deionized water and absolute ethyl alcohol sequentially and centrifugal separation is carried out until the liquid is anhydrous, clear and transparent last time after centrifugation. The rotation speed of the centrifugation is 1000-6000 rpm.
Preferably, in the step 4), the vacuum degree in the vacuum drying oven is 0.08-0.12 MPa.
As a further improvement of the technical solution, in the step 5), the inert atmosphere is nitrogen or helium.
Preferably, in the step 5), the temperature of the high-temperature calcination is 700-.
As a further improvement of the technical solution, in step 6), the etching solution is selected from a sodium hydroxide solution or a hydrofluoric acid solution.
Preferably, in the step 6), when the etching solution is a sodium hydroxide solution, the concentration of the etching solution is 3-5M.
Preferably, in the step 6), the temperature of the stirring etching is 78-82 ℃ and the time is 8-24 h.
As a further improvement of the technical scheme, in the step 7), the vacuum degree in the vacuum drying oven is 0.08-0.12 MPa.
Preferably, in the step 7), the temperature in the vacuum drying oven is 40-70 ℃, and the drying time is 12-24 h.
Any range recited herein is intended to include the endpoints and any number between the endpoints and any subrange subsumed therein or defined therein.
The starting materials of the present invention are commercially available, unless otherwise specified, and the equipment used in the present invention may be any equipment conventionally used in the art or may be any equipment known in the art.
Compared with the prior art, the invention has the following beneficial effects:
the invention synthesizes a novel carbon nano-hemispherical particle by using a template removing method, and the carbon nano-hemispherical particle is used as an electrocatalyst carrier. The overall synthesis idea is to synthesize a silicon dioxide template by alkaline hydrolysis of organic silicon, and coat an organic layer on the silicon dioxide template by utilizing phenolic aldehyde reaction. And carbonizing the organic layer by high-temperature calcination, and etching off the silicon dioxide template to finally form regular and uniform carbon nano hemispheres. The synthesis effect can be well regulated and controlled by changing conditions in the synthesis process. The precise regulation and control of the conditions causes the carbon nanoball to be cracked and collapsed from the middle, and can further increase the loading area of the catalyst. The synthesized carbon nano hemispherical powder particles are uniformly distributed, have uniform size, regular appearance, vacuum structure and 300-350 nm particle size range, and simultaneously, the mesoporous is distributed on the surface of the sphere, so that the catalyst has higher specific surface area and good mass transfer capacity. The method is convenient and simple, and provides a good carrier selection for the research of the electrocatalyst.
Drawings
The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings
FIG. 1 is a BJH pore size distribution curve of a sample prepared in example 1;
FIG. 2 is a transmission electron microscope photograph of a sample prepared in example 1;
FIG. 3 is an XRD spectrum of a sample prepared in example 1;
FIG. 4 is a transmission electron microscope photograph of a sample prepared in comparative example 1;
FIG. 5 is a scanning electron microscope photograph of a sample prepared in comparative example 2;
FIG. 6 is a TEM spectrum of a sample prepared in comparative example 2;
FIG. 7 is a SEM image of a sample prepared in comparative example 3;
FIG. 8 is a TEM spectrum of a sample prepared in comparative example 5.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
As one aspect of the present invention, the present invention provides a method for preparing carbon nano hemispherical particles, comprising the steps of:
1) adding organic silicon into an ethanol solution, and stirring to uniformly disperse the organic silicon to obtain a solution A;
2) preparing an alkaline water solution, and then adding the alkaline water solution into the solution A to obtain a solution B;
3) heating and stirring the solution B for hydrolysis reaction, and obtaining a solution C after the solution is changed into milk white; adding resorcinol and formaldehyde into the solution C to perform phenolic condensation reaction, and stirring to uniformly coat the phenolic condensation product on a silicon ball template formed in the solution C to obtain a mixed reaction solution;
4) centrifugally washing the mixed reaction liquid, drying the solid obtained after centrifugal washing in a vacuum drying oven to obtain a reddish brown or light brown solid, and then grinding the reddish brown or light brown solid to obtain an intermediate product D;
5) under the condition of inert atmosphere, the surface coating layer of the intermediate product D is completely carbonized by high-temperature calcination in a tubular furnace to obtain a carbonized intermediate product E;
6) taking out the intermediate product E, placing the intermediate product E in etching liquid, stirring and etching, performing suction filtration after etching, and washing to be neutral to obtain an intermediate product F;
7) and drying the intermediate product F in a vacuum drying oven, and grinding to obtain the product carbon nano hemispherical particles.
As a further improvement of the technical scheme, in the step 1), the organosilicon is selected from one or more of propyl orthosilicate, tetrapropoxysilane and tetraethyl orthosilicate. Preferably, the organosilicon is propyl orthosilicate, tetraethyl orthosilicate is used as a silicon source, the control is more favorable, the silicon dioxide crystallization is accelerated by increasing the using amount of the tetraethyl orthosilicate, and the inner diameter of the finally formed carbon nano hemisphere is increased.
Preferably, in the step 1), the dosage of the organic silicon is 3-12 mL; the dosage of the absolute ethyl alcohol is 70-150 mL.
As a further improvement of the technical scheme, in the step 2), the alkali is selected from concentrated ammonia water, sodium hydroxide or lysine.
Preferably, in step 2), the concentration of the aqueous alkali solution is 25 to 30 wt%, and the amount is 2 to 10 mL.
As a further improvement of the technical scheme, in the step 3), the heating and stirring temperature is 25-40 ℃; and sealing in the reaction process; sealing helps prevent silicone evaporation.
Preferably, in the step 3), the heating and stirring are performed by using a water bath kettle, so that the synthesis process is more controllable; the heating and stirring time is 10-40 minutes. The heating and stirring time can affect the hydrolysis and crystallization degree of the silicic acid, and further affect the particle size of the silicon ball template and the subsequent carbon balls.
Preferably, in the step 3), the formaldehyde is derived from an 18 wt% formaldehyde aqueous solution, wherein the methanol stabilizer is contained in an amount of 5-8 wt%, and the formaldehyde aqueous solution is used in an amount of 0.56-1.4 mL; the resorcinol is used in an amount of 0.4-1 g. After resorcinol and formaldehyde are added successively, the color of the solution is changed from clear and transparent initially to milky white, then slowly changed to reddish brown and finally to dark brown, so that the condensation reaction is completely well regulated, and the thickness of the finally formed carbon layer can be regulated by changing the using amounts of the formaldehyde and the resorcinol in different proportions.
Preferably, in the step 3), the reaction time of the phenolic aldehyde condensation reaction is 3-24 h.
As a further improvement of the technical scheme, in the step 4), the centrifugal washing is ultrasonic washing with deionized water and absolute ethyl alcohol sequentially and centrifugal separation is carried out until the liquid is anhydrous, clear and transparent last time after centrifugation.
Preferably, in the step 4), the vacuum degree in the vacuum drying oven is 0.08-0.12 MPa.
In certain embodiments, in step 5), the inert atmosphere is nitrogen or helium.
In some embodiments, in step 5), the temperature of the high-temperature calcination is 700-.
In some embodiments, in step 6), the etching solution is selected from a sodium hydroxide solution or a hydrofluoric acid solution.
In some embodiments, in step 6), when the etching solution is a sodium hydroxide solution, the concentration of the etching solution is 3-5M.
In some embodiments, in step 6), the temperature of the stirring etching is 78-82 ℃ and the time is 8-24 h.
In certain embodiments, in step 7), the vacuum degree in the vacuum drying oven is 0.08-0.12 MPa.
In some embodiments, in step 7), the temperature in the vacuum drying oven is 40-70 ℃ and the drying time is 12-24 h.
The invention synthesizes a novel carbon nano hemisphere used as an electrocatalyst carrier by using a template removing method. The synthesis effect can be well regulated and controlled by changing conditions in the synthesis process. The precise control of the conditions allows the carbon nanoball to collapse from the middle by breaking, which in turn can further increase the supported area of the catalyst. The synthesized carbon nano hemispherical powder particles are uniformly distributed, have uniform size, regular appearance, vacuum structure and 300-350 nm particle size range, and simultaneously, the mesoporous is distributed on the surface of the sphere, so that the catalyst has higher specific surface area and good mass transfer capacity. The method is convenient and feasible, and provides a good carrier selection for the research of the electrocatalyst.
Example 1
A preparation method of a carbon nano hemisphere material comprises the following steps:
1) weighing 70mL of absolute ethyl alcohol by using a measuring cylinder, adding the absolute ethyl alcohol into a beaker, transferring 3.5mL of tetraethyl orthosilicate by using a liquid transfer gun, adding the tetraethyl orthosilicate into an ethanol solution, adding magnetons, stirring until the tetraethyl orthosilicate is completely dispersed, and keeping stirring for later use;
2) weighing 3mL of 28 wt% concentrated ammonia water solution, adding into 10mL of deionized water, and carrying out ultrasonic treatment until the solution is uniformly dispersed;
3) adding the ammonia water solution into the ethanol solution of tetraethyl orthosilicate, heating the mixed solution in a water bath kettle, maintaining the temperature at 40 ℃, performing magnetic stirring, and stirring for 20 minutes until the solution is to be milk white. During stirring, sealing the beaker by a sealing film to prevent the volatilization of the toxic tetraethyl orthosilicate. Adding ammonia water, heating and stirring to hydrolyze tetraethyl orthosilicate, wherein the heating and stirring time can influence the particle size of the finally formed silicon dioxide template, and the adjustment is carried out according to the pH value and the silicon source content;
4) weighing 0.8g of resorcinol by using an electronic balance, weighing 1.2mL of formaldehyde solution by using a liquid-moving gun, adding the solution into the mixed solution to perform phenolic condensation reaction, and stirring for 24 hours to uniformly coat the silicon ball template with the solution; after resorcinol and formaldehyde are added successively, the color of the solution is changed from initial clear and transparent to milky white and then slowly changed to reddish brown and finally changed to dark brown, which shows that the silicon dioxide is coated with the phenolic aldehyde condensation after the silicon dioxide is nucleated and crystallized;
5) transferring the mixed solution into a centrifugal tube, centrifuging at 8000rpm, pouring out upper red transparent liquid after centrifugal layering, adding deionized water, performing ultrasonic treatment until dispersion is achieved, and centrifuging again to remove residual ammonia and the like; continuously pouring out the upper layer liquid, adding absolute ethyl alcohol, centrifugally washing to remove residual phenol, aldehyde and the like after ultrasonic dispersion, and repeatedly centrifugally washing the upper layer liquid until the upper layer liquid is transparent and colorless;
6) vacuum drying the lower layer solid preferably after centrifugation at 70 deg.C in a vacuum drying oven for 12 hr, wherein the vacuum degree in the oven is maintained below 0.08-0.12MPa, and the dried lower layer solid is reddish brown or light brown solid. It was ground to a uniform brown powder using a mortar so as to be carbonized uniformly;
7) transferring the powder into a porcelain boat and putting the porcelain boat into a tube furnace, wherein inert gas is firstly introduced into the tube furnace for 1-2h, and carbon can be oxidized and volatilized without discharging internal oxygen. Then heating to 900 ℃ at the rate of 5K/min, keeping for 2h for high-temperature calcination to completely carbonize the material surface coating, cooling to room temperature, and taking out for later use;
8) placing 30.93g of sodium hydroxide in a beaker, adding 250mL of deionized water, adding magnetons, and magnetically stirring until the sodium hydroxide is completely dissolved to prepare a 3mol/L NaOH solution;
9) taking out the carbonized powder, placing the carbonized powder in NaOH solution, heating and stirring at 80 ℃, sealing the beaker by using a sealing film during heating and stirring, and stirring for 24 hours until complete etching;
10) and carrying out suction filtration on the etched mixed solution. Continuously adding deionized water for multiple times of suction filtration and washing until the solution is neutral, and washing to remove residual sodium hydroxide;
11) and drying the filtered sample in a vacuum drying oven at 40 ℃ for 24h, and grinding the dried sample by using a mortar to obtain the carbon nano hemispherical particles.
FIG. 1 shows the BJH pore size distribution curve of the product obtained in this example 1, which shows that the carbon hemisphere particles have good mass transfer capacity due to the micropores and mesopores distributed on the surface thereof, and the BET test also shows that the carbon hemisphere particles have a large specific surface area (550-700 m) 2 /g)。
Fig. 2 is a transmission electron microscope image of the product obtained in this example 1, and through the detection of a low-power transmission microscope, the carbon nano hemispherical material obtained in this example has a uniform size of about 300-350 nm, and a regular and stable structure.
FIG. 3 is a XRD spectrum of a sample prepared in example 1, from which it can be seen that the material is amorphous carbon, indicating that the silicon template has been substantially removed; the carrier is not influenced by silicon and the like, can provide a large amount of surface area and excellent mass transfer capacity, and is an excellent carrier of the electrocatalyst; thus, the applicability of this method is explained.
Example 2
Example 1 was repeated, which did not use only The Propyl Orthosilicate (TPOS) used in step 1).
Example 3
Example 1 was repeated, with the only difference that sodium hydroxide or lysine was used for the pH adjustment in step 2).
Example 4
Example 1 was repeated, with the only difference that etching was carried out using HF in step 8). 5mL of hydrofluoric acid was dissolved in 25mL of deionized water to prepare a solution in a plastic centrifuge tube. 0.5g of carbonized powder is added into the prepared solution and added with magnetons for magnetic stirring. It should be noted that the centrifuge tube was sealed and placed in a vented cabinet during mixing, and no heating was required.
Comparative example 1
Example 1 was repeated except that the resorcinol in step 4) was changed to 0.4g and the formalin solution was changed to 0.56 mL.
As shown in FIG. 4, the carbon sphere catalyst carrier obtained by this method is subjected to irregular collapse due to the excessively thin outer carbon layer, and finally is difficult to support the morphological structure of the hemisphere, as detected by a low-power transmission microscope.
Comparative example 2
Example 1 was repeated except that the amount of resorcinol used in step 4) was increased to 1.6g and the amount of formalin used was 2.4 mL.
As can be seen from the SEM test of fig. 5, a good spherical shape is present at this time. Through the detection of a transmission electron microscope, as shown in fig. 6, regular and uniform carbon nanospheres are formed, and the carbon nanospheres can also be considered as hollow carbon nanosphere electrocatalyst carriers with excellent morphology and structure. But the carbon layer is now thicker, about 50nm, which somewhat constrains the catalyst loading.
Comparative example 3
Comparative example 1 was repeated except that, in step 4), it was left to stand for centrifugal washing after stirring for 3 hours.
As can be seen from the SEM test of fig. 7, the organic layer formed of phenol was difficult to be uniformly coated due to the excessively short stirring time. Indicating that comparative example 2 cannot be optimized by reducing the stirring time, the preferred method is to reduce the amount of phenol and aldehyde.
Through detection, when different samples are taken for detection, the obtained Ag nano particles present different Ag distribution conditions and contents.
Comparative example 4
Example 1 was repeated, except that in step 6), the calcination temperature was changed to 70 ℃ and the calcination was allowed to stand for 1 hour and then allowed to cool naturally.
The powder calcined under this condition often appeared greenish black. It can be concluded that the carbon spheres under these conditions have not yet been fully carbonized, resulting in uncontrollable variations in the loading of the catalyst at the later stage.
Comparative example 5
Example 1 was repeated, with the only difference that, in step 10), the concentration of the NaOH solution was reduced or the heating and stirring were stopped.
The nanoparticles obtained were solid spherical as detected by low power transmission microscopy of fig. 8. It can be concluded that the silicon dioxide template inside the carbon sphere under the condition is not completely etched, the carbon sphere cannot be broken to form a hemisphere, and the performance of the carbon sphere is greatly influenced by the presence of silicon.
Comparative example 6
The solution does not change color after changing into milk white in the stirring process for 24 hours, which shows that the process that the solution slowly changes from milk white into reddish brown and finally changes into dark brown is really the process of phenolic aldehyde condensation coating. And (4) centrifugally washing and drying the solution to obtain a white powder product. The final product was tested as pure silica particles, indicating that no carbon layer could be formed without phenolic condensation coating.
In summary, according to the preparation method of the carbon nano hemispherical material, the selection of the template silicon source, the dosage of the phenolic aldehyde condensation, the vacuum condition, the etching condition, the temperature and time during calcination and carbonization, and the like are coordinated and matched with each other to form a complete technical scheme, so that the carbon nano hemispherical material catalyst required by the invention can be prepared.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Not all embodiments are exhaustive. All obvious changes and modifications which are obvious to the technical scheme of the invention are covered by the protection scope of the invention.
Claims (9)
1. A preparation method of carbon nano hemispherical particles is characterized by comprising the following steps:
1) adding organic silicon into an ethanol solution, and stirring to uniformly disperse the organic silicon to obtain a solution A;
2) preparing an alkaline water solution, and then adding the alkaline water solution into the solution A to obtain a solution B;
3) heating and stirring the solution B for hydrolysis reaction, and obtaining a solution C after the solution is changed into milk white; adding resorcinol and formaldehyde into the solution C to perform phenolic condensation reaction, and stirring to uniformly coat the phenolic condensation product on a silicon ball template formed in the solution C to obtain a mixed reaction solution;
4) centrifugally washing the mixed reaction liquid, drying the solid obtained after centrifugal washing in a vacuum drying oven to obtain a reddish brown or light brown solid, and then grinding the reddish brown or light brown solid to obtain an intermediate product D;
5) under the condition of inert atmosphere, the surface coating layer of the intermediate product D is completely carbonized by high-temperature calcination in a tubular furnace to obtain a carbonized intermediate product E;
6) taking out the intermediate product E, placing the intermediate product E in etching liquid, stirring and etching, performing suction filtration after etching, and washing to be neutral to obtain an intermediate product F;
7) and drying the intermediate product F in a vacuum drying oven, and grinding to obtain the product carbon nano hemispherical particles.
2. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 1), the organic silicon is selected from one or more of propyl orthosilicate, tetrapropoxysilane and tetraethyl orthosilicate;
preferably, in the step 1), the dosage of the organic silicon is 3-12 mL; the dosage of the absolute ethyl alcohol is 70-150 mL.
3. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 2), the alkali is selected from concentrated ammonia water, sodium hydroxide or lysine;
preferably, in step 2), the concentration of the aqueous alkali solution is 25 to 30 wt%, and the amount is 2 to 10 mL.
4. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 3), the heating and stirring temperature is 25-40 ℃; and sealing in the reaction process;
preferably, in step 3), the heating and stirring are performed by using a water bath; the heating and stirring time is 10-40 minutes;
preferably, in the step 3), the formaldehyde is derived from an 18 wt% formaldehyde aqueous solution, wherein the methanol stabilizer is contained in an amount of 5-8 wt%, and the formaldehyde aqueous solution is used in an amount of 0.56-1.4 mL; the using amount of the resorcinol is 0.4-1 g;
preferably, in the step 3), the reaction time of the phenolic aldehyde condensation reaction is 3-24 h.
5. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 4), the centrifugal washing refers to ultrasonic washing by deionized water and absolute ethyl alcohol sequentially and centrifugal separation is carried out until the liquid is anhydrous, clear and transparent last time after centrifugation; the rotation speed of the centrifugation is 1000-6000 rpm;
preferably, in the step 4), the vacuum degree in the vacuum drying oven is 0.08-0.12 MPa.
6. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 5), the inert atmosphere is nitrogen or helium;
preferably, in the step 5), the temperature of the high-temperature calcination is 700-.
7. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 6), the etching solution is selected from a sodium hydroxide solution or a hydrofluoric acid solution;
preferably, in the step 6), when the etching solution is a sodium hydroxide solution, the concentration of the etching solution is 3-5M;
preferably, in the step 6), the temperature of the stirring etching is 78-82 ℃ and the time is 8-24 h.
8. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 7), the vacuum degree in the vacuum drying oven is 0.08-0.12 MPa.
9. The method for preparing carbon nano-hemispherical particles according to claim 1, wherein: in the step 7), the temperature in the vacuum drying oven is 40-70 ℃, and the drying time is 12-24 h.
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