CN114590804A - Method for efficiently preparing doped graphene through supercritical fluid - Google Patents
Method for efficiently preparing doped graphene through supercritical fluid Download PDFInfo
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- CN114590804A CN114590804A CN202210091430.3A CN202210091430A CN114590804A CN 114590804 A CN114590804 A CN 114590804A CN 202210091430 A CN202210091430 A CN 202210091430A CN 114590804 A CN114590804 A CN 114590804A
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Abstract
The invention discloses a method for efficiently preparing doped graphene through supercritical fluid, which comprises the following steps: preparing graphene oxide, carrying out micro-jet treatment, carrying out low-temperature treatment, and preparing doped graphene. Under the action of an intercalating agent, an active doping element compound invades between graphite layers and is bonded with carbon atoms between the graphite layers, and then the graphite can be effectively sheared and crushed by utilizing the high-speed shearing action of micro-jet processing, the interlayer spacing can be effectively enlarged under the intercalation action of a supercritical fluid, the surface graphite can be effectively stripped by a micelle conversion mechanism, so that the efficient graphene preparation is realized, in addition, the size distribution of the obtained graphene sheet layers can be effectively adjusted by adjusting the pressure of the micro-jet processing, the processing pressure of the supercritical fluid is changed, the number of the layers of the graphene can be adjusted by the intercalation action of the fluid and the reverse micelle conversion mechanism, and the low-temperature graphite slurry is quickly sprayed into a high-temperature environment, so that micro-bursting occurs between graphite particle layers, and a favorable bursting opening is provided for subsequent molecular intercalation.
Description
Technical Field
The invention relates to the technical field of graphene, in particular to a method for efficiently preparing doped graphene through supercritical fluid.
Background
The graphene is sp2The hybridized and connected carbon atoms are tightly packed into a new material with a single-layer two-dimensional honeycomb lattice structure. The graphene has excellent optical, electrical and mechanical properties, has important application prospects in the aspects of materials science, micro-nano processing, energy, biomedicine, drug delivery and the like, and is considered to be a revolutionary material in the future. Therefore, the preparation method of graphene is always a hot point of attention, and the current main synthesis methods include a mechanical stripping method, an epitaxial growth method, a chemical vapor deposition method, a liquid-phase redox method and the like. Although the first three schemes can prepare high-quality graphene, the equipment investment is large, and the cost is high; although the liquid phase redox method has low cost, and the supercritical fluid is a clean, pollution-free, cheap and abundant-source high-efficiency dispersion medium, the liquid phase redox method is generally used for preparing graphene in industrial production.
However, since graphene is a good conductor with a zero band gap, it cannot effectively control its electrical characteristics, and thus cannot be widely used in electronic devices. Therefore, it is necessary to adopt a special means to adjust the band gap of graphene to have semiconductor characteristics, however, one of the most effective methods is to dope impurity atoms into graphene. When impurity atoms are doped into graphene, the graphene needs to be stripped, but the traditional stripping method is low in preparation efficiency, and prepared graphene products are uneven in quality and difficult to control in the number of layers and the size. Therefore, there is a need to provide a new method for improving the existing method for preparing doped graphene by supercritical fluid.
Disclosure of Invention
In view of the above, the present invention is directed to the defects existing in the prior art, and the main object of the present invention is to provide a method for efficiently preparing doped graphene by using a supercritical fluid, wherein the preparation efficiency is high, and the size distribution of graphene sheet layers and the number of graphene layers can be adjusted by adjusting the pressure of the micro-jet treatment and the pressure of the supercritical fluid during the preparation process.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for efficiently preparing doped graphene through supercritical fluid comprises the following steps:
(1) preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 45-60 ℃, continuously stirring for 4-12h, then slowly adding a certain amount of water, heating the reaction system to 85-95 ℃, keeping the temperature for 30-60min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide solution is 3% until bubbling disappears, repeatedly cleaning with a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, then collecting solids through vacuum drying, transferring the collected solids into a quartz tube, pumping out air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite;
(2) microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 100-200MPa for 20-100 times to obtain a material;
(3) low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-30-0 ℃ to obtain low-temperature graphite slurry;
(4) preparation of doped graphene
And (3) injecting supercritical fluid into the sealed autoclave, adjusting the temperature to be 100-260 ℃ and the pressure to be 15-45MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the autoclave, reacting for 1-10h under magnetic stirring, discharging gas through a gas release valve, and taking out a reaction product to obtain the element-doped graphene.
As a preferable scheme, the mass ratio of the reactants in the step (1) is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite (10-40), (1-5), (2-8), (1-5) and 1.
As a preferable mode, the doping element may be any one of nitrogen, boron, phosphorus and sulfur, or any combination thereof.
As a preferable scheme, the doping element is nitrogen, and the active doping element compound is at least one of ammonia, urea, pyrrole, aniline, pyridine, thiophene, dopamine, melamine, ethylenediamine, triethylene tetramine, porphyrin, phthalocyanine, o-phenanthroline, imidazole or thiophene.
Preferably, the doping element is boron, and the active doping element compound is boric acid, borane or an organic boride.
Preferably, the doping element is phosphorus, and the active doping element compound is an organophosphate.
Preferably, the doping element is sulfur, and the active doping element compound is an organic sulfide.
Preferably, the supercritical fluid is one of carbon dioxide, ethanol, ethane, water, ethylene glycol and ethylenediamine.
As a preferable scheme, the mass ratio of the low-temperature graphite slurry to the active doping element compound is (0.1-1): 100.
compared with the prior art, the invention has obvious advantages and beneficial effects, and specifically, the technical scheme includes that:
by adding the intercalating agent, under the action of the intercalating agent, an active doping element compound invades between graphite layers and is bonded with carbon atoms between the graphite layers, and then the intercalation agent is matched with the carbon atoms for combining jet flow treatment and supercritical fluid treatment, the graphite can be effectively sheared and crushed by utilizing the high-speed shearing action of micro-jet flow treatment, the interlayer spacing can be effectively enlarged by the intercalation action of supercritical fluid, a micelle conversion mechanism can effectively strip the surface graphite to realize high-efficiency graphene preparation, in addition, the size distribution of the obtained graphene sheet layers can be effectively adjusted by adjusting the pressure of the micro-jet flow treatment, the treatment pressure of the supercritical fluid is changed, the number of the graphene layers can be adjusted by the intercalation action of fluid and a reverse micelle conversion mechanism, and low-temperature graphite slurry is quickly sprayed into a high-temperature environment, strong thermal shock can be received, and micro-bursting can occur between graphite particle layers, provides favorable breakthrough for subsequent molecular intercalation.
To more clearly illustrate the features and effects of the present invention, the present invention is described in detail below with reference to specific examples.
Detailed Description
The invention discloses a method for efficiently preparing doped graphene through supercritical fluid, which comprises the following steps:
(1) preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 45-60 ℃, continuously stirring for 4-12h, then slowly adding a certain amount of water, heating the reaction system to 85-95 ℃, keeping the temperature for 30-60min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide solution is 3% until bubbling disappears, repeatedly cleaning with a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, then collecting solids through vacuum drying, transferring the collected solids into a quartz tube, pumping out air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite (10-40), (1-5), (2-8), (1-5) and 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 100-200MPa for 20-100 times to obtain the material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-30-0 ℃ to obtain low-temperature graphite slurry; the doping element can be any one of nitrogen, boron, phosphorus and sulfur or any combination thereof; if the doping element is nitrogen, the active doping element compound is at least one of ammonia gas, urea, pyrrole, aniline, pyridine, thiophene, dopamine, melamine, ethylenediamine, triethylene tetramine, porphyrin, phthalocyanine, o-phenanthroline, imidazole or thiophene; if the doping element is boron, the active doping element compound is boric acid, borane or an organic boride; if the doping element is phosphorus, the active doping element compound is an organic phosphide; if the doping element is sulfur, the active doping element compound is an organosulfide.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to be 100-260 ℃ and the pressure to be 15-45MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 1-10h under magnetic stirring, discharging gas through a gas release valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is one of carbon dioxide, ethanol, ethane, water, ethylene glycol and ethylenediamine; the mass ratio of the low-temperature graphite slurry to the active doping element compound is (0.1-1): 100.
example 1
(1) Preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 45 ℃, continuously stirring for 12 hours, slowly adding a certain amount of water, heating the reaction system to 85 ℃ and keeping the temperature for 60min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide aqueous solution is 3% until bubbling disappears, repeatedly cleaning the system by using a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, collecting solids by vacuum drying, transferring the collected solids into a quartz tube, pumping air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite 10:1:2:1: 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 100MPa for 100 times to obtain the material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-10 ℃ to obtain low-temperature graphite slurry; the doping element is nitrogen, and the active doping element compound is at least one of ammonia gas, urea, pyrrole, aniline, pyridine, thiophene, dopamine, melamine, ethylenediamine, triethylene tetramine, porphyrin, phthalocyanine, o-phenanthroline, imidazole or thiophene.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to 160 ℃ and the pressure to 25MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 3 hours under magnetic stirring, then, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is carbon dioxide; the mass ratio of the low-temperature graphite slurry to the active doping element compound is 0.5: 100.
example 2
(1) Preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 60 ℃, continuously stirring for 4 hours, slowly adding a certain amount of water, heating the reaction system to 95 ℃ and keeping the temperature for 30min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide aqueous solution is 3% until bubbling disappears, repeatedly cleaning the system by using a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, collecting solids by vacuum drying, transferring the collected solids into a quartz tube, pumping air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite 40:5:8:5: 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 200MPa for 20 times to obtain the material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-20 ℃ to obtain low-temperature graphite slurry; the doping element is boron; the active doping element compound is boric acid, borane or organic boride.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to 120 ℃ and the pressure to 35MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 4 hours under magnetic stirring, then, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is ethanol; the mass ratio of the low-temperature graphite slurry to the active doping element compound is 0.3: 100.
example 3
(1) Preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 55 ℃, continuously stirring for 7 hours, slowly adding a certain amount of water, heating the reaction system to 88 ℃ and keeping the temperature for 42min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide aqueous solution is 3% until bubbling disappears, repeatedly cleaning the system by using a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, collecting solids by vacuum drying, transferring the collected solids into a quartz tube, pumping air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite 26:4:4:2: 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 150MPa for 40 times to obtain the material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-30-0 ℃ to obtain low-temperature graphite slurry; the doping element is phosphorus; the active doping element compound is organic phosphide.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to 100 ℃ and the pressure to 45MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 1h under magnetic stirring, then, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is ethane; the mass ratio of the low-temperature graphite slurry to the active doping element compound is 0.1: 100.
example 4
(1) Preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 53 ℃, continuing to stir for 11 hours, then slowly adding a certain amount of water, heating the reaction system to 92 ℃ and keeping the temperature for 57 minutes, then adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide aqueous solution is 3% until bubbling disappears, repeatedly cleaning the system by using a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, then collecting solids by vacuum drying, transferring the collected solids into a quartz tube, pumping air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 minutes; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite 33:2:2:4: 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out microjet treatment on the raw material mixed solution at the pressure of 170MPa for 80 times to obtain a material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-30 ℃ to obtain low-temperature graphite slurry; the doping element is sulfur; the active doping element compound is organic sulfide.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to 255 ℃ and the pressure to 35MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 10 hours under magnetic stirring, then, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is water; the mass ratio of the low-temperature graphite slurry to the active doping element compound is 0.9: 100.
example 5
(1) Preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 45 ℃, continuously stirring for 12 hours, slowly adding a certain amount of water, heating the reaction system to 85 ℃ and keeping the temperature for 60min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide aqueous solution is 3% until bubbling disappears, repeatedly cleaning the system by using a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, collecting solids by vacuum drying, transferring the collected solids into a quartz tube, pumping air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite 16:2:6:3: 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 180MPa for 90 times to obtain the material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to 0 ℃ to obtain low-temperature graphite slurry; the doping elements can be nitrogen and boron; the active doping element compound is ammonia gas, urea, pyrrole, aniline, pyridine, thiophene, dopamine, melamine, ethylenediamine, triethylene tetramine, porphyrin, phthalocyanine, o-phenanthroline, imidazole, thiophene, boric acid, borane or an organic boride.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to 260 ℃ and the pressure to 15MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 1h under magnetic stirring, then, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is ethylene glycol; the mass ratio of the low-temperature graphite slurry to the active doping element compound is 0.1: 100.
example 6
(1) Preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 60 ℃, continuously stirring for 6 hours, slowly adding a certain amount of water, heating the reaction system to 90 ℃ and keeping the temperature for 40min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide aqueous solution is 3% until bubbling disappears, repeatedly cleaning the system by using a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, collecting solids by vacuum drying, transferring the collected solids into a quartz tube, pumping air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite; the mass ratio of each reactant is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite 40:5:2:1: 1.
(2) Microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 195MPa for 40 times to obtain the material.
(3) Low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-10 ℃ to obtain low-temperature graphite slurry; the doping elements are phosphorus and sulfur; the active doping element compound is organic phosphide and organic sulfide.
(4) Preparation of doped graphene
Injecting supercritical fluid into a sealed high-pressure kettle, adjusting the temperature to 260 ℃ and the pressure to 45MPa to enable the supercritical fluid to reach a supercritical state, then, quickly spraying the low-temperature graphite slurry obtained in the step (3) into the high-pressure kettle, reacting for 1h under magnetic stirring, then, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene; the supercritical fluid is ethylenediamine; the mass ratio of the low-temperature graphite slurry to the active doping element compound is 1: 100.
performance testing
Mixing and grinding an active material (the element-doped graphene prepared in the examples 1-6), acetylene black and polyvinylidene fluoride (PVDF) according to a mass ratio of 80:10:10, dropwise adding a proper amount of N-methylpyrrolidone (NMP) solution, stirring and diluting the mixture into uniform paste, and coating the paste on foamed nickel to form a negative plate. And (3) drying the pole piece in a vacuum drying oven at 80 ℃, tabletting on a tabletting machine under the pressure of 10MPa, and drying the pole piece in a vacuum drying oven at 120 ℃ for 12 hours. And transferring the dried pole piece into a glove box, taking a metal lithium piece as a counter electrode, and assembling the metal lithium piece into a simulated button cell in the glove box filled with dry argon. The diaphragm is a porous polypropylene film, the electrolyte is 1mol/L LiPF6 solution, and the electrolyte solvent is a mixed solvent of Ethylene Carbonate (EC) and diethyl carbonate (DEC). And testing the charge and discharge performance of the battery under different conditions by using a Land battery tester. The charging and discharging voltage test range is 0-3V, the cycle number is 100 cycles, and the test results are shown in Table 1.
TABLE 1
The design of the invention is characterized in that: by adding the intercalating agent, under the action of the intercalating agent, an active doping element compound invades between graphite layers and is bonded with carbon atoms between the graphite layers, and then the intercalation agent is matched with the carbon atoms for combining jet flow treatment and supercritical fluid treatment, the graphite can be effectively sheared and crushed by utilizing the high-speed shearing action of micro-jet flow treatment, the interlayer spacing can be effectively enlarged by the intercalation action of supercritical fluid, a micelle conversion mechanism can effectively strip the surface graphite to realize high-efficiency graphene preparation, in addition, the size distribution of the obtained graphene sheet layers can be effectively adjusted by adjusting the pressure of the micro-jet flow treatment, the treatment pressure of the supercritical fluid is changed, the number of the graphene layers can be adjusted by the intercalation action of fluid and a reverse micelle conversion mechanism, and low-temperature graphite slurry is quickly sprayed into a high-temperature environment, strong thermal shock can be received, and micro-bursting can occur between graphite particle layers, provides favorable breakthrough for subsequent molecular intercalation.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the technical scope of the present invention.
Claims (9)
1. A method for efficiently preparing doped graphene through supercritical fluid is characterized by comprising the following steps: the method comprises the following steps:
(1) preparation of thermally reduced expanded graphite
Adding graphite and an intercalator into a mixture of strong oxidation acid and nitrate, uniformly mixing, adding a potassium-containing strong oxidant, heating the system to 45-60 ℃, continuously stirring for 4-12h, then slowly adding a certain amount of water, heating the reaction system to 85-95 ℃, keeping the temperature for 30-60min, adding water and a certain amount of hydrogen peroxide, wherein the concentration of the hydrogen peroxide solution is 3% until bubbling disappears, repeatedly cleaning with a dilute acid solution and deionized water after fully stirring and reacting, removing various ions in the system, then collecting solids through vacuum drying, transferring the collected solids into a quartz tube, pumping out air in the quartz tube, slowly introducing argon, and keeping the argon flowing for 2 min; then placing the quartz tube into a tube furnace preheated to 1050 ℃ and placing for 30s to obtain thermally reduced expanded graphite;
(2) microfluidic processing
Mixing the thermally reduced expanded graphite obtained in the step (1) with a surfactant, water and ethanol to obtain a raw material mixed solution, and carrying out micro-jet treatment on the raw material mixed solution at the pressure of 100-200MPa for 20-100 times to obtain a material;
(3) low temperature treatment
Primarily mixing the material obtained in the step (2) with an active doping element compound, transferring the mixture into a low-temperature container, and cooling to-30-0 ℃ to obtain low-temperature graphite slurry;
(4) preparation of doped graphene
And (4) injecting supercritical fluid into the sealed autoclave, adjusting the temperature to be 100-260 ℃ and the pressure to be 15-45MPa to enable the supercritical fluid to reach a supercritical state, then quickly spraying the low-temperature graphite slurry obtained in the step (3) into the autoclave, reacting for 1-10 hours under magnetic stirring, deflating through a deflation valve, and taking out a reaction product to obtain the element-doped graphene.
2. The method for preparing doped graphene efficiently by supercritical fluid according to claim 1, wherein: the mass ratio of reactants in the step (1) is strong oxidizing acid: nitrate salt: potassium-containing strong oxidizing agent: hydrogen peroxide: graphite (10-40), (1-5), (2-8), (1-5) and 1.
3. The method for preparing doped graphene efficiently by supercritical fluid according to claim 1, wherein: the doping element may be any one of nitrogen, boron, phosphorus and sulfur or any combination thereof.
4. The method for preparing doped graphene efficiently by supercritical fluid according to claim 1, wherein: the doping element is nitrogen, and the active doping element compound is at least one of ammonia gas, urea, pyrrole, aniline, pyridine, thiophene, dopamine, melamine, ethylenediamine, triethylene tetramine, porphyrin, phthalocyanine, o-phenanthroline, imidazole or thiophene.
5. The method for efficiently preparing doped graphene by supercritical fluid according to claim 1 or 3, wherein: the doping element is boron, and the active doping element compound is boric acid, borane or an organic boride.
6. The method for efficiently preparing doped graphene by supercritical fluid according to claim 1 or 3, wherein: the doping element is phosphorus, and the active doping element compound is organic phosphide.
7. The method for efficiently preparing doped graphene by supercritical fluid according to claim 1 or 3, wherein: the doping element is sulfur, and the active doping element compound is organic sulfide.
8. The method for preparing doped graphene efficiently by supercritical fluid according to claim 1, wherein: the supercritical fluid is one of carbon dioxide, ethanol, ethane, water, ethylene glycol and ethylenediamine.
9. The method for preparing doped graphene efficiently by supercritical fluid according to claim 1, wherein: the mass ratio of the low-temperature graphite slurry to the active doping element compound is (0.1-1): 100.
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| CN104229787A (en) * | 2014-09-18 | 2014-12-24 | 上海交通大学 | Method for increasing yield of graphene prepared by supercritical fluid through pretreatment of natural graphite |
| CN105366668A (en) * | 2015-11-04 | 2016-03-02 | 福建翔丰华新能源材料有限公司 | Method for preparing graphene through supercritical fluid |
| CN105366667A (en) * | 2015-11-04 | 2016-03-02 | 福建翔丰华新能源材料有限公司 | Method for preparing doped graphene from supercritical fluid |
| CN110759337A (en) * | 2019-12-09 | 2020-02-07 | 中国科学院兰州化学物理研究所 | Preparation method of graphene |
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| CN104229787A (en) * | 2014-09-18 | 2014-12-24 | 上海交通大学 | Method for increasing yield of graphene prepared by supercritical fluid through pretreatment of natural graphite |
| CN105366668A (en) * | 2015-11-04 | 2016-03-02 | 福建翔丰华新能源材料有限公司 | Method for preparing graphene through supercritical fluid |
| CN105366667A (en) * | 2015-11-04 | 2016-03-02 | 福建翔丰华新能源材料有限公司 | Method for preparing doped graphene from supercritical fluid |
| CN110759337A (en) * | 2019-12-09 | 2020-02-07 | 中国科学院兰州化学物理研究所 | Preparation method of graphene |
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