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CN109368615B - Composite nano carbon material and preparation method thereof - Google Patents

Composite nano carbon material and preparation method thereof Download PDF

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CN109368615B
CN109368615B CN201811510111.1A CN201811510111A CN109368615B CN 109368615 B CN109368615 B CN 109368615B CN 201811510111 A CN201811510111 A CN 201811510111A CN 109368615 B CN109368615 B CN 109368615B
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CN109368615A (en
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杨少明
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Fujian Xinghong New Material Technology Co ltd
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Abstract

The invention discloses a composite nano carbon material and a preparation method thereof, wherein the material comprises nano carbon fibers and nano carbon spheres growing on the nano carbon fibers, the diameter of each nano carbon fiber is 0.1-1 mu m, and the diameter of each nano carbon sphere is 10-1000 nm. The preparation method comprises two chemical vapor deposition steps, firstly, under the action of a carrier type catalyst containing iron, nickel, chromium and magnesium, heating and introducing hydrocarbon and hydrogen to react to grow the carbon nanofibers on a substrate, and then stopping hydrogen supply to reduce the flow of the hydrocarbon and grow carbon nanospheres on the surfaces of the carbon nanofibers. The carbon nano-sphere/carbon nano-fiber composite carbon material is formed by compounding one-dimensional carbon fibers and zero-dimensional carbon nano-spheres, is stable in shape, can be applied to a microelectrode, an ultra-micro capacitor and the like by taking a section of composite carbon nano-sphere/carbon fibers, and can regulate and control the microscopic size of the carbon nano-spheres and the number of the carbon nano-spheres by regulating and controlling reaction conditions.

Description

Composite nano carbon material and preparation method thereof
[ technical field ] A method for producing a semiconductor device
The invention relates to a composite nano carbon material and a preparation method thereof, belonging to the technical field of multifunctional carbon fiber materials.
[ background of the invention ]
In the field of carbon fiber materials, the carbon nanospheres have excellent chemical stability, heat conduction and electric conduction of common carbon materials on one hand, and have higher specific surface area and active sites on the other hand. Particularly, the catalyst has the characteristics of larger specific surface area and pore volume, uniform pore channel structure, controllable morphology, adjustable surface chemical property and the like, and can be applied to various modern technical fields of catalysis, supercapacitors, electrode materials, adsorption separation, energy storage and the like.
In recent 20 years, many techniques for preparing nanocarbon spheres have been disclosed. For example, pyrolysis of camphor vapor with ferrocene at 1000 ℃ gives a spongy carbon material consisting of carbon nanospheres; catalytic cracking of C with kaolin loaded with nickel at 850 deg.C2H2Obtaining black powdery hollow carbon nanospheres; synthesizing carbon nanospheres with the particle size of 400-2000 nm at the temperature of not less than 650 ℃ by using a kaolin loaded transition metal catalyst; ferrocene is used for catalyzing calcium carbide and chloroform to react at 350 ℃ by utilizing a stainless steel high-pressure autoclave, and 50-150 nm of nano carbon spheres with amorphous structure and plush morphology, catalytic pyrolysis gasified kerosene and the like are prepared.
However, the development of nanocarbon spheres with novel structural morphology, the reduction of cost, the improvement of cost performance and the expansion of applications still remain technical problems to be solved in the field, for example, nanocarbon spheres have a broad application prospect in electrode materials of supercapacitors, but the effective specific surface area is lowered due to the accumulation of nanocarbon spheres, so that the development of products with large effective specific surface area is required.
[ summary of the invention ]
The invention aims to overcome the problems in the prior art and provide a composite nano carbon material with two forms, wherein the carbon material is a nano carbon sphere grown on a nano carbon fiber.
The invention also aims to provide a preparation method of the composite nano carbon material.
The invention is realized by the following technical scheme:
a composite nanocarbon material, characterized by comprising a nanocarbon fiber and nanocarbon spheres grown thereon.
The composite nanocarbon material is characterized in that the diameter of the nanocarbon fiber is 0.1-1 μm, the length of the nanocarbon fiber is more than 1 μm, the reaction time for producing the nanocarbon fiber is prolonged, and the reaction time is prolonged, wherein the reaction time is up to 3 mm long in 1-3 hours, preferably 10-500 μm.
The composite nanocarbon material is characterized in that the diameter of the nanocarbon sphere is 10-1000nm, preferably 10-900 nm; preferably, the diameter of the nano carbon sphere is 10-800 nm; preferably, the diameter of the nano carbon sphere is 10-700 nm; preferably, the diameter of the nano carbon sphere is 10-600 nm; preferably, the diameter of the nano carbon sphere is 10-500 nm; preferably, the diameter of the nano carbon sphere is 10-400 nm; preferably, the diameter of the nano carbon sphere is 10-300 nm; preferably, the diameter of the nano carbon sphere is 10-200 nm; preferably, the diameter of the nano carbon sphere is 10-100 nm; preferably, the diameter of the nano carbon sphere is 100-1000 nm; preferably, the diameter of the nano carbon sphere is 200-1000 nm; preferably, the diameter of the nano carbon sphere is 300-1000 nm; preferably, the diameter of the nano carbon sphere is 400-1000 nm; preferably, the diameter of the nano carbon sphere is 500-1000 nm; preferably, the diameter of the nano carbon sphere is 600-1000 nm; preferably, the diameter of the nano carbon sphere is 700-1000 nm; preferably, the diameter of the nano carbon sphere is 800-1000 nm; preferably, the diameter of the nano carbon sphere is 900-1000 nm; preferably, the diameter of the nano carbon sphere is 100-900 nm; preferably, the diameter of the nano carbon sphere is 200-800 nm; preferably, the diameter of the nano carbon sphere is 350-650 nm; preferably, the diameter of the nano carbon sphere is 450-550 nm.
By extending the reaction time of step b, the size of the carbon spheres can be increased to more than 1 micron. However, it is more preferably 0.1 to 1 μm because the carbon spheres are easily enlarged to cause the connection.
The surface of the nano carbon fiber and the nano carbon sphere in the invention is of a graphite lamellar structure, and the interior of the nano carbon fiber and the nano carbon sphere is of a disordered layer structure of graphite microcrystals.
The preparation method of the composite nano carbon material is characterized by comprising two Chemical Vapor Deposition (CVD) steps:
a. introducing hydrocarbon and hydrogen to react at the temperature of 650-880 ℃ under the action of a carrier type catalyst containing iron, nickel, chromium and magnesium on a reactor substrate, and growing carbon nanofibers on the substrate;
b. and (b) keeping the reaction temperature unchanged, reducing the flow of the hydrocarbon to 20-50% of the original flow, stopping hydrogen supply for reaction, and growing carbon nanospheres on the surface of the carbon nanofiber generated in the step (a) to obtain the carbon nanosphere/carbon nanofiber composite material.
Wherein the carrier of the carrier-type catalyst is silicon dioxide, or alumina, or molecular sieve, the particle diameter is not more than 0.5 μm, and the specific surface area is not less than 50m2Per g, preferably, the particle diameter is not more than 0.5 μm and the specific surface area is not less than 100m2/g。
The invention is realized by a two-step chemical vapor deposition method (CVD method). Specifically, the present invention uses a carrier-type composite catalyst to crack hydrocarbons into carbon particles at a high temperature in a hydrogen atmosphere, to deposit and grow nanocarbon fibers, and then, nanocarbon spheres are grown on the surface of the nanocarbon fibers, thereby obtaining the nanocarbon sphere/nanocarbon fiber composite material as shown in fig. 1.
The preparation of the supported composite catalyst is realized by the following steps: the catalyst is prepared by loading a catalyst at least containing iron, nickel and chromium and a small amount of salt or oxide of a catalytic promoter magnesium on a catalyst carrier, uniformly mixing by ball milling, and calcining in a hydrogen atmosphere. Wherein the nickel accounts for 10-30% of the mole number of the iron; the mole number of the chromium is 0.5-7% of the total mole number of the nickel and the iron, and the mole ratio of the magnesium is 0.5-3% of the total mole number of the nickel, the iron and the chromium.
Furthermore, if the catalyst contains a small amount of introduced niobium or molybdenum, the molar content of which is respectively close to that of chromium, the combination of the two is beneficial to increasing the number of carbon spheres, and the size of the nano particles can be controlled by further controlling the reaction time of the step b, so that the nano fibers are not arranged too crowded.
Further adding molybdenum is beneficial to increasing the carbon deposition rate, so that the surface of the carbon nanosphere is rougher, the specific surface area is beneficial to improving, and the production capacity is improved.
Similar effects can be obtained by substituting magnesium with other elements of the second main group.
The substrate in the present invention is a graphite or metal substrate. The reactor is preferably provided with a transverse reaction tube so as to grow the composite carbon nanospheres/carbon fibers in a large area, the top of the reaction tube is provided with an air guide tube so as to introduce raw material gas capable of cracking to obtain carbon, nitrogen is continuously introduced from two ends of the reaction tube so as to prevent a large amount of air from entering the reaction tube, and the pressure in the reaction tube is atmospheric pressure.
In the preparation method of the invention, the introduced hydrocarbon is acetylene, propane or natural gas, preferably acetylene.
The introduction flow rate of the hydrocarbon compound is 0.5 to 3sccm per square centimeter of the substrate area, and the ratio of the introduction amount of the hydrogen gas and the hydrocarbon compound in the carbon fiber growth stage is (0.5 to 3): 1, the ratio of the introduction amount of nitrogen to the introduction amount of hydrogen at the start of the reaction is (0.5 to 1): 1. if hydrogen exists all the time, only the carbon nanofibers can be obtained, and the carbon nanofiber ball deposition cannot be observed.
The mass ratio of the catalyst to the carrier is (0.05-0.3): 1. the carrier catalyst is used in an amount of 15-35 mg/cm on the reaction substrate2. The excessively low use amount can affect the reaction yield and even the catalytic effect; on the contrary, too high an amount may result in waste and even aggregation of catalyst particles into larger particles, which may not result in the product of the present invention. The catalyst is loaded on the carrier powder, so that the catalyst particles are prevented from being entangled into large particles to a certain extent and are reformed into a certain form under the action of hydrogen, the specific surface area of the catalyst can be increased by the catalyst carrier, and the carriers often provide larger specific surface area, so that the catalyst forms a catalytic center on the surface of the carrier, adsorbs reaction substances, provides good contact opportunity for the catalyst and gas-phase active substances (produced by thermal cracking), provides good contact opportunity, accelerates the deposition speed of carbon, ensures that catalytic seed crystals are used as growth tips and are continuously away from the carrier, and enables the carbon nanofibers to continuously grow.
The temperature of the reaction in the reaction tube is controlled to be 650-880 ℃, preferably 750-820 ℃, and the nano carbon fiber and the nano carbon spheres can not be obtained when the temperature is too high or too low.
In the invention, the reaction time of the step a is 10-60min, the nano carbon fibers grow along with the prolonging of time, but the nano carbon fibers are mutually wound or mutually covered due to too long time, so that a part of nano carbon fibers and a part of nano carbon spheres/nano carbon fibers are obtained; the reaction time of the step b is 10-60min, and if the reaction time is too long, the carbon spheres are too large and even connected with each other.
The invention improves the yield of the composite carbon nanosphere/carbon fiber by the modulation of the composite catalyst and the optimization synergistic effect of the composite catalyst, the gas condition, the reaction temperature and the reaction time. The purity of the composite carbon nanospheres/carbon fibers in the product is more than 95 percent; the production rate can be controlled by controlling the amount of the catalyst and the total flow rate of the gas.
Under the appropriate reaction temperature and reactant concentration, carbon precipitated on the crystal face of the catalyst becomes carbon fiber. And b, continuously introducing carbon source gas, stopping introducing hydrogen, enabling carbon not to grow in the one-dimensional direction, and enabling carbon nanospheres to grow on the surface of the carbon fiber. If only iron and nickel catalysts are used, carbon nanospheres cannot be obtained.
Compared with the prior art, the invention has the following advantages:
the carbon nano-sphere/carbon nano-fiber composite carbon material is formed by compounding one-dimensional carbon fibers and zero-dimensional carbon nano-spheres, is stable in shape, can be applied to a microelectrode, an ultra-micro capacitor and the like by taking a section of composite carbon nano-sphere/carbon fibers, and can regulate and control the microscopic size of the carbon nano-spheres and the number of the carbon nano-spheres by regulating and controlling reaction conditions.
[ description of the drawings ]
FIG. 1 is a scanning electron microscope image of a segment of composite nanocarbon sphere/carbon fiber according to the present invention;
FIG. 2 is an electron microscope image of the reaction product of comparative example 1 with iron and nickel, with hydrogen, and without chromium and magnesium;
FIG. 3 is an electron microscope image of the reaction product of comparative example 2 with iron and nickel only, no hydrogen, no chromium and no magnesium;
FIG. 4 is an electron micrograph of the reaction product of comparative example 3 with no hydrogen, magnesium and chromium.
[ detailed description ] embodiments
A composite nano carbon material, which comprises nano carbon fibers and nano carbon spheres growing on the nano carbon fibers, wherein the diameter of the nano carbon fibers is 0.1-1 mu m, and the length of the nano carbon fibers is limited by the reaction time in the step a; the diameter of the carbon nanospheres is 10-1000nm, and the carbon nanospheres are influenced by the reaction time in the step b, and the preparation method of the composite carbon nanomaterial comprises the following steps:
preparation of a Supported catalyst: the particle diameter is not more than 0.5 μm, and the specific surface area is not less than 50m2Putting a catalyst carrier in a ball milling tank in a per gram mode, mixing salts or oxides of magnesium or strontium and salts or oxides containing ferric nitrate, nickel nitrate, magnesium nitrate, chromium nitrate, molybdenum nitrate and niobium nitrate into a powder catalyst in batches, and uniformly dispersing the powder catalyst in silicon dioxide carrier powder, wherein the mass ratio of the catalyst to the carrier is (0.05-0.2): 1, ball milling and mixing, and calcining in a hydrogen atmosphere to obtain the carrier type catalyst. The salt or oxide of magnesium or strontium is used as a catalytic promoter, which is helpful for regulating and controlling the quantity of the nano-catalyst required for generating nano-carbon spheres on the nano-carbon fiber.
Step a, synthesizing nanometer by CVD methodCarbon fiber: the carrier type catalyst is added according to the ratio of 60-20 mg/cm2The amount of the carbon fiber is flatly laid on the surface of a substrate which is flatly placed in a reactor, the reactor is heated to 720 to 880 ℃ in nitrogen atmosphere, preferably 760 to 820 ℃, gaseous hydrocarbon and hydrogen are introduced, the reaction is maintained for 10 to 60min, and the hydrocarbon is catalytically cracked into carbon fiber in hydrogen atmosphere;
step b, synthesizing the carbon nanospheres in situ by a CVD method: b, maintaining the reaction temperature unchanged, reducing the quantity of the hydrocarbon to 20-50% of the original quantity, stopping hydrogen supply, starting the carbon nanospheres to grow on the surface of the carbon nanofiber generated in the step a, and maintaining the reaction for 10-60min to form a graphite crystal layer on the surface of the carbon nanospheres;
wherein the hydrocarbon is acetylene, natural gas or propane, the introduction flow rate is 0.5-3 sccm per square centimeter of the substrate area, and the ratio of the introduction amount of the hydrogen to the hydrocarbon is (0.5-3): 1, the ratio of the introduction amount of nitrogen to the introduction amount of hydrogen is (0.5 to 1): 1.
the present invention will be described in further detail with reference to specific examples.
Example 1:
mixing the components in a weight ratio of 3: 0.3: 0.23: 0.11: 0 of ferric nitrate, nickel nitrate, chromium nitrate, magnesium nitrate and niobium nitrate are mixed into a powder catalyst, the particle size is not more than 0.5 mu m, and the specific surface area is not less than 50m2Putting an alumina carrier in a ball milling tank, putting a powder catalyst in the ball milling tank, wherein the ratio of the catalyst to the carrier is 0.2: 1, ball milling and mixing to uniformly disperse the catalyst on the micro surface of the carrier powder to form the carrier type catalyst.
0.5g of supported catalyst was laid flat in a reaction tube of 30cm2Heating the reaction tube to 650 ℃ in a nitrogen atmosphere of 120sccm in the reaction tube, introducing 40sccm of acetylene and 120sccm of hydrogen, maintaining the reaction temperature for 1 hour, maintaining the reaction temperature unchanged, adjusting the acetylene to 20sccm, stopping introducing the hydrogen, and carrying out an in-situ reaction for 30 minutes to obtain the composite carbon nanosphere/carbon fiber material.
The average diameter of the carbon fiber of the obtained composite nano carbon sphere/carbon fiber material is 0.6 mu m, the length is 1.2mm, the diameter of the carbon sphere distributed on the carbon sphere is 80-200nm, the purity of the product reaches 98%, and the yield per square centimeter is 20.3 mg. The impurities are carbon particles which are connected together in a small amount and carbon fibers which have the diameter of about 1 micron and have no carbon nanospheres on the surface.
Example 2:
mixing the components in a weight ratio of 3: 0.7: 0.15: 0.1: 0.1 of ferric nitrate, nickel nitrate, chromium nitrate, magnesium nitrate and molybdenum nitrate are mixed into a powder catalyst, the particle size is not more than 0.5 mu m, and the specific surface area is not less than 50m2Putting a silicon dioxide carrier in a ball milling tank, putting a powder catalyst in the ball milling tank, wherein the mass ratio of the catalyst to the carrier is 0.3: 1, ball milling and mixing to uniformly disperse the catalyst on the micro surface of the carrier powder to form the carrier type catalyst.
The supported catalyst was spread flat at 1.0g in a reaction tube of 30cm2Heating the reaction tube to 750 ℃ in a nitrogen atmosphere of 180sccm in the reaction tube, introducing 80sccm of acetylene and 200sccm of hydrogen, maintaining the reaction temperature for 1 hour, maintaining the reaction temperature, adjusting the acetylene to 30sccm, stopping introducing the hydrogen, and carrying out an in-situ CVD reaction for 30 minutes to obtain the composite carbon nanosphere/carbon fiber.
The average diameter of the carbon fiber of the obtained composite nano carbon sphere/carbon fiber is 0.5 mu m, the length is 0.8mm, the average diameter of the nano carbon sphere is 250nm, and the yield is 20.3mg per square centimeter. The purity of the product reaches 95.5 percent, and impurities are a small amount of carbon particles and coarse carbon fibers without nano carbon spheres on the surface.
Example 3:
mixing the components in a weight ratio of 3: 0.3: 0.21: 0.11 of ferric nitrate, nickel nitrate, chromium nitrate and magnesium nitrate are mixed into a powder catalyst, the particle size is not more than 0.5 mu m, and the specific surface area is not less than 50m2Putting an alumina carrier in a ball milling tank in a/g mode, putting a powder catalyst in the ball milling tank, wherein the mass ratio of the catalyst to the carrier is 0.2: 1, ball milling and mixing to uniformly disperse the catalyst on the micro surface of the carrier powder to form the carrier type catalyst.
0.7g of supported catalyst was laid flat in a reaction tube of 30cm2The surface of a rectangular flat plate substrate is treated by (step a) introducing 150sccm of nitrogen into a reaction tubeHeating the reaction tube to 700 ℃ in a gas atmosphere, introducing 150sccm of acetylene and 150sccm of hydrogen, maintaining the reaction temperature for 1 hour, (b) maintaining the reaction temperature unchanged, adjusting the acetylene to 50sccm, then stopping introducing the hydrogen, and carrying out an in-situ CVD reaction for 30 minutes to obtain the composite carbon nanosphere/carbon fiber.
The average diameter of the carbon fiber of the obtained composite nano carbon sphere/carbon fiber is 0.6 mu m, the length is 1.0mm, the average diameter of the nano carbon sphere is 200-300 nm, and the yield is 17.6mg per square centimeter. The purity of the product reaches 97.4 percent, and impurities are the nano carbon fibers without nano carbon spheres on the surface.
Example 4:
mixing the components in a weight ratio of 3: 0.9: 0.18: 0.1: 0.1 of ferric nitrate, nickel nitrate, chromium nitrate, magnesium nitrate and molybdenum nitrate are mixed into a powder catalyst, the particle size is not more than 0.5 mu m, and the specific surface area is not less than 50m2Putting a silica carrier in a ball milling tank, wherein the mass ratio of the catalyst to the carrier is 0.05: 1, ball milling and mixing to uniformly disperse the catalyst on the micro surface of the carrier powder to form the carrier type catalyst.
The supported catalyst was spread flat at 1.5g in a reaction tube of 30cm2Heating the reaction tube to 880 ℃ in a nitrogen atmosphere of 250sccm in the reaction tube, introducing 90sccm of propane and 200sccm of hydrogen, maintaining the reaction temperature for 1 hour, maintaining the reaction temperature unchanged, adjusting the propane to 40sccm, stopping introducing the hydrogen, and carrying out an in-situ CVD reaction for 30 minutes to obtain the composite carbon nanosphere/carbon fiber.
The average diameter of the carbon fiber of the obtained composite nano carbon sphere/carbon fiber is 0.5 mu m, the length is 0.7mm, the average diameter of the carbon spheres distributed in the diameter of the carbon spheres is 300-550 nm, and the yield is 12.8mg per square centimeter. The purity of the product reaches 90.7 percent, and impurities are linear carbon filaments.
Example 5:
mixing the components in a weight ratio of 3: 0.8: 0.2: 0.1: 0.09 of ferric nitrate, nickel nitrate, chromium nitrate and molybdenum nitrate are mixed into a powder catalyst, the particle size is not more than 0.5 mu m, and the specific surface area is not less than 50m2Putting an alumina carrier in a ball milling tank, wherein the mass ratio of the catalyst to the carrier is 0.1: 1, ball milling and mixingThe catalyst is uniformly dispersed on the micro-surface of the carrier powder to form a carrier type catalyst.
The supported catalyst was spread flat at 1.0g in a reaction tube of 30cm2Heating the reaction tube to 850 ℃ in a nitrogen atmosphere of 180sccm in the reaction tube, introducing 80sccm of natural gas and 200sccm of hydrogen, maintaining the reaction temperature for 1 hour, and (b) keeping the conditions of the reaction temperature and the natural gas unchanged, stopping introducing the hydrogen, and carrying out a CVD reaction for 30 minutes to obtain the composite carbon nanosphere/carbon fiber.
The average diameter of the carbon fiber of the obtained composite nano carbon sphere/carbon fiber is 0.5 mu m, the length is 0.9mm, the average diameter of the carbon spheres distributed in the diameter of the carbon spheres is 200-300 nm, and the yield is 17.6mg per square centimeter. The purity of the product reaches 98 percent, and impurities are linear carbon filaments.
Comparative example 1:
in the catalyst, only iron and nickel were used, and no chromium catalyst and no magnesium as an alkaline earth metal catalyst promoter were used, and as a result of the rest of the synthesis conditions referring to example 1 (hydrogen was introduced in both step a and step b), carbon fibers were obtained, and as shown in FIG. 2, carbon spheres deposited on the carbon fibers as shown in FIG. 1 could not be obtained.
Comparative example 2:
no hydrogen was always passed through, so step b was not present and no chromium catalyst and alkaline earth metal catalyst promoter were added, and the remaining synthesis conditions were as in example 1, resulting in a small amount of carbon particles sticking together, as shown in figure 3.
Comparative example 3:
in the catalyst, only iron, nickel, chromium catalyst, catalyst promoter magnesium were used, and hydrogen was not introduced all the time, and the rest of the synthesis conditions were as in example 1, with the results that: step a can yield carbon fibers and carbon spheres, but carbon nanospheres grown on carbon nanofibers as shown in FIG. 1 cannot be obtained, as shown in FIG. 4.
The application effect evaluation of the invention:
the carbon-based material is the most applied electrode material in the super capacitor in recent years, and in order to enlarge the aperture and the specific surface area of the activated carbon and improve the specific capacitance thereof, there are still many researches on the surface modification of the activated carbon, the preparation of the activated carbon with ultrahigh specific surface area and the mesoporous activated carbon and the research on the preparation of the activated carbon as the electrode material, but still no surprising results are obtained. From the energy storage principle, for the electrode material of the super capacitor, the specific surface area, the pore structure, the electrical conductivity and the surface property are 4 key factors determining the electrochemical properties such as specific capacitance, power density and energy density, and the most important is the specific surface area.
The specific capacitance of the electrode material of the super capacitor is
Figure BDA0001900509700000111
Since S is the specific surface area and D is the electrode pitch, the specific surface area of the electrode is required to be large, and the specific surface area of the carbon material is required to be fully utilized.
Example 1 the specific surface area of the carbon sphere/filamentous nanocarbon (see FIG. 1) was 185m2In g, the product of comparative example 3 has a specific surface area of 85m2/g。
The carbon nanosphere/carbon nanofiber composite carbon material of example 1 and the carbon nanosphere stack of comparative example 3 were prepared into supercapacitor electrode materials, respectively. Respectively weighing a certain amount of carbon material, adding 5% of Polytetrafluoroethylene (PTFE) as a binder, fully grinding the mixture in an agate mortar to uniformly disperse the binder in the carbon material, and tabletting to obtain an electrode plate with the diameter of 10mm and the thickness of about 0.5 mm. A glass fiber diaphragm is adopted and fixed by a polytetrafluoroethylene die, and the glass fiber diaphragm is assembled into a simulation capacitor in a 6.0mol/L KOH electrolyte system. The specific capacitance of the electrode at a current density of 1A/g reached 157F/g and 113F/g, indicating that example 1 has a much higher effective specific surface area than comparative example 3.
The performance test and application effects of examples 1 to 5 and comparative examples 1 to 3 are shown in Table 1.
Table 1:
item Specific surface area m2/g Specific capacitance F/g
Example 1 185 217
Example 2 153 149
Example 3 113 143
Example 4 163 137
Example 5 149 151
Comparative example 1 85 102
Comparative example 2 67 84
Comparative example 3 93 113

Claims (3)

1. A composite nanocarbon material is characterized by comprising a nanocarbon fiber and nanocarbon spheres growing on the nanocarbon fiber, wherein the diameter of the nanocarbon fiber is 0.5-1 μm, the diameter of the nanocarbon spheres is 80-550 nm, the nanocarbon fiber and the nanocarbon spheres are of a graphite lamellar structure, a disordered layer structure of graphite microcrystals is arranged inside the nanocarbon fiber and the nanocarbon spheres, and the nanocarbon material is prepared through two chemical vapor deposition steps:
a. laying a carrier type catalyst on a reactor substrate, introducing hydrocarbon and hydrogen to react at the temperature of 650-880 ℃, and growing carbon nanofibers on the substrate;
b. maintaining the reaction temperature unchanged, reducing the flow of the hydrocarbon to 20-50% of the original flow, stopping hydrogen supply for reaction, and growing carbon nanospheres on the surface of the carbon nanofiber generated in the step a;
the carrier type catalyst contains iron, nickel, chromium, molybdenum and a second main group element or contains iron, nickel, chromium, niobium and a second main group element;
the preparation method of the carrier type catalyst comprises the following steps: the particle diameter is not more than 0.5 μm, and the specific surface area is not less than 50m2Sieving carrier silicon dioxide in a ball milling tank, uniformly dispersing salts or oxides of a catalyst and a catalytic promoter in batches in silicon dioxide carrier powder, mixing by ball milling, and calcining;
the nickel in the catalyst is 10-30% of the mole number of iron; the mole number of the chromium is 0.5-7% of the total mole number of the nickel and the iron, the mole ratio of the magnesium is 0.5-3% of the total mole number of the nickel, the iron and the chromium, and the mass ratio of the catalyst to the carrier is 0.05-0.3: 1.
2. the composite nanocarbon material of claim 1, wherein the hydrocarbon is acetylene, propane or natural gas.
3. The composite nanocarbon material as claimed in claim 1, wherein the hydrocarbon is introduced at a flow rate of 0.5 to 3sccm per square centimeter of the substrate area in step a, and the ratio of the amount of hydrogen introduced to the amount of hydrocarbon introduced in the stage of growing the nanocarbon fibers is 0.5 to 3: 1, the ratio of the introduced amounts of nitrogen and hydrogen at the start of the reaction is 0.5 to 1: 1.
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