CN111554520A - Cobaltosic oxide quantum dot @ carbon composite electrode material and preparation method thereof - Google Patents
Cobaltosic oxide quantum dot @ carbon composite electrode material and preparation method thereof Download PDFInfo
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- UBEWDCMIDFGDOO-UHFFFAOYSA-N cobalt(2+);cobalt(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[Co+2].[Co+3].[Co+3] UBEWDCMIDFGDOO-UHFFFAOYSA-N 0.000 title claims abstract description 148
- 239000002131 composite material Substances 0.000 title claims abstract description 51
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 41
- 239000007772 electrode material Substances 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
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- 239000011148 porous material Substances 0.000 claims description 9
- 239000011259 mixed solution Substances 0.000 claims description 8
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 claims description 7
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 5
- 238000000137 annealing Methods 0.000 claims description 5
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- QAHREYKOYSIQPH-UHFFFAOYSA-L cobalt(II) acetate Chemical compound [Co+2].CC([O-])=O.CC([O-])=O QAHREYKOYSIQPH-UHFFFAOYSA-L 0.000 claims description 3
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- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
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- GPKIXZRJUHCCKX-UHFFFAOYSA-N 2-[(5-methyl-2-propan-2-ylphenoxy)methyl]oxirane Chemical compound CC(C)C1=CC=C(C)C=C1OCC1OC1 GPKIXZRJUHCCKX-UHFFFAOYSA-N 0.000 description 1
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
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- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 1
- 229910001429 cobalt ion Inorganic materials 0.000 description 1
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 1
- XLJKHNWPARRRJB-UHFFFAOYSA-N cobalt(2+) Chemical compound [Co+2] XLJKHNWPARRRJB-UHFFFAOYSA-N 0.000 description 1
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- RPZHFKHTXCZXQV-UHFFFAOYSA-N mercury(I) oxide Inorganic materials O1[Hg][Hg]1 RPZHFKHTXCZXQV-UHFFFAOYSA-N 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/46—Metal oxides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The invention provides a preparation method of cobaltosic oxide quantum dot @ carbon composite electrode material, which comprises the following steps: A) mixing and grinding a carbon material and a cobalt salt to obtain mixed powder, wherein the melting point of the cobalt salt is lower than the thermal decomposition temperature; B) and under the condition of protective atmosphere, heating and melting the mixed product, and then continuing to heat for pyrolysis to obtain the cobaltosic oxide quantum dot @ carbon composite electrode material. The invention solves the problems of poor conductivity, volume expansion, low actual specific capacity, poor cycling stability and the like of the traditional cobaltosic oxide electrode. The prepared cobaltosic oxide quantum dot @ carbon composite electrode realizes the limited-domain growth of cobaltosic oxide, and the cobaltosic oxide quantum dot uniformly wrapped in the carbon nano cavity is obtained. The extremely small nano size ensures the full play of the oxidation-reduction reaction, and the specific capacitance of the electrode is greatly improved. The unique confinement structure inhibits the volume expansion of the electrode in the charging and discharging processes, so that the overall cycle stability of the supercapacitor is improved.
Description
Technical Field
The invention belongs to the technical field of super capacitors, and particularly relates to a cobaltosic oxide quantum dot @ carbon composite electrode material and a preparation method thereof.
Background
Supercapacitors have been widely used in the automotive and electronic fields due to their high energy and power density, fast charge and discharge performance, long cycle life, and environmentally friendly characteristics. There are three main electrode materials currently used in supercapacitors: carbon materials, transition metal oxides and conductive polymers. Compared with the carbon material, the transition metal oxide and the electrolyte can undergo a rapid and reversible redox reaction, so that the specific capacitance is higher. The cobaltosic oxide has low cost, environmental protection and higher theoretical specific capacity (3560F g)-1) And is considered to be a promising candidate material for improving the energy density of the super capacitor. However, it has the disadvantages of high resistance and volume expansion, like other transition metal oxides. The research on cobaltosic oxide is mainly focused on the reduction of the nano size and the compounding with carbon materials. Based on an energy storage mechanism, the particle size of the cobaltosic oxide is reduced, so that more active sites can be exposed, and the electrochemical performance of the cobaltosic oxide is improved. The carbon material serving as an electrode material with high conductivity can not only make up the disadvantage of high resistance of the cobaltosic oxide, but also provide a large amount of dispersion space for the precursor due to the high specific surface area, so that the size of the cobaltosic oxide nano particles can be adjusted.
In recent years, different carbon materials are combined to construct a cobaltosic oxide nano structure, so that cobaltosic oxide is uniformly dispersed in the carbon material in small particles, and the cobaltosic oxide/carbon composite electrode material with high electrochemical performance is prepared. For example, patent 201610302686.9 discloses different ratios of graphene oxide to Co3O4The precursor is fully mixed in different solvents, and then the graphene @ ultramicro Co is prepared under different pulse laser conditions3O4A particulate composite material. There are also tricobalt tetraoxide nanoparticles supported on carbon nanoplatelets obtained in a one-step pyrolysis process, as in patent 201811576714.1.
In the previous research on cobaltosic oxide electrodes, carbon materials with high specific surface area such as graphene can provide a large amount of dispersion space for cobalt salt, but the open planar structure of the carbon materials hardly plays a good role in limiting the agglomeration and growth of nanoparticles. In the conventional synthesis method, liquid phase mixing is difficult to eliminate the hydrophobicity of the carbon material, the affinity between composite interfaces is insufficient, and it is difficult to ensure that a large amount of cobalt ions dissolved in the solution are all in pores, so that cobaltosic oxide remains outside the carbon material. In the long-term charge and discharge process, the structural stability is difficult to guarantee, and the nano particles are easy to fall off from the surface of the carbon material, so that the electrochemical performance is rapidly attenuated. In addition, in the current cobaltosic oxide/carbon composite electrode material, the size of cobaltosic oxide is difficult to break through to less than 5nm, active components in particles cannot be in contact with an electrolyte, and the electrochemical performance of cobaltosic oxide is difficult to be exerted to the maximum.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a preparation method of a cobaltosic oxide quantum dot @ carbon composite electrode material, wherein the electrode material prepared by the present invention realizes the limited-domain growth of cobaltosic oxide, and cobaltosic oxide quantum dots uniformly wrapped in carbon nano cavities are obtained. The extremely small nano size ensures the full play of the oxidation-reduction reaction, and the specific capacitance of the electrode is greatly improved. The unique confinement structure inhibits the volume expansion of the electrode in the charging and discharging processes, so that the overall cycle stability of the supercapacitor is improved.
The invention provides a preparation method of cobaltosic oxide quantum dot @ carbon composite electrode material, which comprises the following steps:
A) mixing and grinding a carbon material and a cobalt salt to obtain mixed powder, wherein the melting point of the cobalt salt is lower than the thermal decomposition temperature;
B) and under the condition of protective atmosphere, heating and melting the mixed product, and then continuing to heat for pyrolysis to obtain the cobaltosic oxide quantum dot @ carbon composite electrode material.
Preferably, the cobalt salt is selected from one or more of cobalt nitrate hexahydrate, cobalt acetate and cobalt oxalate.
Preferably, the preparation method of the carbon material comprises the following steps:
mixing phosphoric acid aqueous solution with melamine to obtain mixed solution;
heating the mixed solution to remove the solvent to obtain mixed powder;
and annealing the mixed powder under the condition of protective atmosphere to obtain the carbon material.
Preferably, the mass ratio of the carbon material to the cobalt salt is 1: (0.9-2.7).
Preferably, the protective atmosphere conditions are selected from argon.
Preferably, the temperature-increasing melting method comprises: heating to 55-70 ℃ at a heating rate of 1-3 ℃/min, and preserving heat for 1-3 h.
Preferably, the pyrolysis method comprises the following steps: heating to 300-600 ℃ at a heating rate of 1-10 ℃/min, and preserving heat for 1-10 h.
The invention also provides a cobaltosic oxide quantum dot @ carbon composite electrode material prepared by the preparation method, which is characterized in that the cobaltosic oxide quantum dot is 2-5nm in size and is uniformly distributed in pores of a carbon material.
Compared with the prior art, the invention provides a preparation method of cobaltosic oxide quantum dot @ carbon composite electrode material, which comprises the following steps: A) mixing and grinding a carbon material and a cobalt salt to obtain mixed powder, wherein the melting point of the cobalt salt is lower than the thermal decomposition temperature; B) and under the condition of protective atmosphere, heating and melting the mixed product, and then continuing to heat for pyrolysis to obtain the cobaltosic oxide quantum dot @ carbon composite electrode material. The invention solves the problems of poor conductivity, volume expansion, low actual specific capacity, poor cycling stability and the like of the traditional cobaltosic oxide electrode. The prepared cobaltosic oxide quantum dot @ carbon composite electrode realizes the limited-domain growth of cobaltosic oxide, and the cobaltosic oxide quantum dot uniformly wrapped in the carbon nano cavity is obtained. The extremely small nano size ensures the full play of the oxidation-reduction reaction, and the specific capacitance of the electrode is greatly improved. The unique confinement structure inhibits the volume expansion of the electrode in the charging and discharging processes, so that the overall cycle stability of the supercapacitor is improved.
Drawings
FIG. 1 is a transmission electron micrograph of a composite prepared in example 2;
FIG. 2 is a high resolution Co2p XPS spectrum of the composite prepared in example 2;
FIG. 3 shows the results of electrochemical performance tests on the composite material prepared in example 2;
FIG. 4 is a transmission electron micrograph of a composite prepared according to the comparative example;
fig. 5 is an electrochemical performance of the composite electrode prepared in the comparative example.
Detailed Description
The invention provides a preparation method of cobaltosic oxide quantum dot @ carbon composite electrode material, which comprises the following steps:
A) mixing and grinding a carbon material and a cobalt salt to obtain mixed powder, wherein the melting point of the cobalt salt is lower than the thermal decomposition temperature;
B) and under the condition of protective atmosphere, heating and melting the mixed product, and then continuing to heat for pyrolysis to obtain the cobaltosic oxide quantum dot @ carbon composite electrode material.
The invention takes carbon material and cobalt salt as raw materials for preparing the carbon material.
Wherein the melting point of the cobalt salt is required to be lower than the thermal decomposition temperature. In the present invention, the cobalt salt is selected from one or more of cobalt nitrate hexahydrate, cobalt acetate and cobalt oxalate.
In the present invention, the carbon material is prepared by the following steps:
mixing phosphoric acid aqueous solution with melamine to obtain mixed solution;
heating the mixed solution to remove the solvent to obtain mixed powder;
and annealing the mixed powder under the condition of protective atmosphere to obtain the carbon material.
Specifically, dissolving phosphoric acid in deionized water, heating, stirring and dissolving, then adding melamine powder for mixing, and gradually changing the solution from milky white suspension to colorless transparent liquid to obtain a mixed solution;
then continuously heating and stirring the mixed solution to be in an anhydrous state, and drying to obtain mixed powder;
and then, transferring the dried white mixed powder into a crucible, and annealing for 2-6 hours in a tubular furnace at the temperature rising rate of 2-10 ℃ per minute from room temperature to 900-1100 ℃ by using Ar gas as protective gas to obtain the carbon material.
After obtaining a carbon material, the carbon material and a cobalt salt are mixed and ground to obtain a mixed powder.
Wherein the mass ratio of the carbon material to the cobalt salt is 1: (0.9 to 2.7), preferably 1: (1.0-2.0).
And then, under the condition of protective atmosphere, heating and melting the mixed product, and then continuing to heat for pyrolysis to obtain the cobaltosic oxide quantum dot @ carbon composite electrode material.
Specifically, the mixed powder is placed in a container, sealed and then transferred to a tube furnace, and the mixed powder is heated and melted under the condition of protective atmosphere, wherein the heating and melting method comprises the following steps: heating to 55-70 ℃ at a heating rate of 1-3 ℃/min, preferably 2-3 ℃/min, preferably 60-65 ℃, and keeping the temperature for 1-3 h, preferably 2-3 h.
And then, continuously raising the temperature to carry out pyrolysis on the molten mixture to obtain a pyrolysis product. The pyrolysis method comprises the following steps: heating to 300-600 ℃ at a heating rate of 1-10 ℃/min, preferably 5-10 ℃/min, preferably 400-500 ℃, and keeping the temperature for 1-10 h, preferably 2-8 h.
And then ultrasonically cleaning the pyrolysis product in an acid solution, and repeatedly cleaning the pyrolysis product by using deionized water to obtain the cobaltosic oxide quantum dot @ carbon composite material. The acid solution is selected from strong acid solutions that can dissolve cobaltosic oxide. The ultrasonic cleaning process of the acid solution is to remove cobaltosic oxide particles which are easy to fall off from the surface of the carbon material.
According to the preparation method provided by the invention, the cobalt salt is uniformly dispersed in the nano cavity of the carbon material, so that the interface affinity is enhanced. The high specific surface area of the carbon material provides a large amount of dispersion space for cobalt salt, the narrow carbon nano cavity limits the agglomeration and growth of cobaltosic oxide particles, cobaltosic oxide quantum dots below 3nm are synthesized, more active sites are exposed due to the extremely small nano size, and the ultrahigh specific capacitance can be exerted. The carbon material not only improves the electronic conductance in the electrode material, but also ensures the structural stability in the long-term circulation process due to the unique confinement structure. The method for preparing the cobaltosic oxide quantum dot @ carbon composite electrode solves the problems of poor conductivity, volume expansion, low actual specific capacity, poor cycle stability and the like of the traditional cobaltosic oxide electrode.
The invention also provides a cobaltosic oxide quantum dot @ carbon composite electrode material prepared by the preparation method, wherein the cobaltosic oxide quantum dot is 2-4nm in size and is uniformly distributed in pores of a carbon material.
According to the invention, the porous carbon material with a limited domain structure and a high specific surface area is synthesized, the porous carbon material and a cobalt precursor are compounded to prepare the cobaltosic oxide quantum dot/carbon composite electrode material, and on the basis that the high specific surface area provides a high dispersion space, cobalt salt is dispersed into a carbon nano cavity so as to accurately control the cobaltosic oxide nano particles, and more active sites are exposed by utilizing the cobaltosic oxide nano particles, so that the redox reaction between the cobaltosic oxide nano particles and electrolyte is greatly released. Meanwhile, the carbon material with the limited domain structure can effectively limit the growth and agglomeration of cobaltosic oxide nanoparticles while improving the conductivity of the composite material, and avoids the possibility of particle shedding, thereby ensuring the structural stability of the electrode material in the long-term charge and discharge process.
The invention has the following beneficial effects:
1. the cobaltosic oxide quantum dot @ carbon composite electrode prepared by the method can solve the problems of poor conductivity, easy agglomeration and the like when cobaltosic oxide is used as a supercapacitor electrode material, and the performance of a supercapacitor is improved.
2. The adopted nano cavity carbon substrate with high specific surface provides a large amount of space for the dispersion of the cobalt precursor, effectively limits the particle size of the cobaltosic oxide and provides possibility for the improvement of electrochemical performance. The limited domain structure avoids the agglomeration and falling off of nano particles, and ensures the cycling stability of the electrode material in the long-term charge and discharge process.
3. The solid-phase melting pyrolysis method provided by the invention is simple and easy to operate, not only avoids the influence caused by the hydrophobicity of the carbon material, provides stronger interface affinity, but also can ensure the uniform dispersion of the nano particles. In the early slow heating process, the molten cobalt salt can be immersed in the pores as much as possible. The closed container can prevent water from being rapidly evaporated and keep a precursor molten state form, and along with the rise of temperature, pyrolysis product water and nitrogen oxide in the container slowly escape to push the balance to develop towards the growth direction of cobaltosic oxide crystals, until the decomposition temperature of cobalt nitrate is reached, cobaltosic oxide particles are directly precipitated from the molten state. The slow temperature rise rate can generate less seed crystal density in carbon pores to ensure the extremely small nano size of the cobaltosic oxide nanoparticles, and provide possibility for excellent electrochemical performance.
4. The invention can accurately control the mass ratio of the cobaltosic oxide to the carbon material, thereby realizing the preparation of the cobaltosic oxide quantum dot @ carbon composite electrode with controllable load capacity, adjustable particle size and excellent electrochemical performance.
In order to further understand the present invention, the cobaltosic oxide quantum dots @ carbon composite electrode material and the preparation method thereof provided by the present invention are described below with reference to the following examples, and the scope of the present invention is not limited by the following examples.
Example 1
3g of phosphoric acid are weighed out and dissolved in 200g of deionized water, stirred in a water bath at 90 ℃, and then 4g of melamine powder is slowly added and uniformly mixed, and the solution gradually changes from milky white suspension to colorless transparent liquid. After the above liquid was continuously heated and stirred to an anhydrous state, the mixture was transferred to a blast furnace at 80 ℃ and dried overnight. And transferring the dried white powder to an alumina crucible, and annealing for 2 hours in a tubular furnace at the temperature rising rate of 5 ℃ per minute from room temperature to 900 ℃ by using Ar gas as protective gas to obtain the base carbon material.
Weighing 90mg of cobaltous nitrate hexahydrate and 100mg of substrate carbon material, adding the weighed materials into an agate mortar, uniformly grinding for 10min to obtain mixed black powder, transferring the black powder into a polytetrafluoroethylene container, sealing the container by using a sealing film, transferring the container into a tubular furnace, slowly heating the container from room temperature to 55 ℃ at the heating rate of 1 ℃ per minute under the Ar atmosphere, keeping the temperature for 3h, heating the container to 300 ℃ at the heating rate of 1 ℃ per minute, keeping the temperature for 2h, dissolving a pyrolysis product in a nitric acid solution, carrying out ultrasonic treatment for 10min, and repeatedly cleaning the pyrolysis product for 3 times by using deionized water to obtain the cobaltosic oxide quantum dot @ carbon composite material.
The transmission electron microscope detection of the composite material prepared in the embodiment 1 of the invention shows that: the size of the cobaltosic oxide quantum dots prepared by the method is 2-3nm, and the cobaltosic oxide quantum dots are uniformly distributed in pores of the carbon material.
The composite material prepared in the embodiment 1 of the invention, the conductive carbon black and polyvinylidene fluoride (PVDF) are mixed according to a mass ratio of 8: 1: 1 are mixed to prepare the electrode material.
The composite material prepared in the example 1 of the invention is subjected to high-resolution Co2p XPS spectrum detection, and the result shows that Co is3O4But also implies Co3O4Strong interaction with the PNC interface, which contributes to the long-term stability of the composite material as an electrode material.
The method comprises the steps of adopting KOH of alkaline liquid 6M as electrolyte, adopting the composite material prepared in the embodiment 1 of the invention as a working electrode, adopting a platinum sheet as a counter electrode and adopting mercury-mercurous oxide as a reference electrode to assemble a three-electrode system, carrying out charge-discharge test in a voltage range of 0-0.5V, and measuring that the voltage of the three-electrode system is 0.5Ag by using a 1470E electrochemical workstation with strong output-1Current density of 842F g-1。
Example 2
The preparation method comprises the steps of preparing a substrate carbon material according to the method of example 1, weighing 180mg of cobaltous nitrate hexahydrate and 100mg of the substrate carbon material, adding the weighed materials into an agate mortar, uniformly grinding for 10min to obtain mixed black powder, transferring the black powder into a polytetrafluoroethylene container, sealing the container by using a sealing film, transferring the container into a tubular furnace, slowly heating the container from room temperature to 60 ℃ at a heating rate of 2 ℃ per minute for 2h under Ar atmosphere, keeping the temperature for 2h, heating the container to 450 ℃ at a heating rate of 5 ℃ per minute for 6h, dissolving a pyrolysis product in a nitric acid solution, carrying out ultrasonic treatment for 10min, and repeatedly cleaning the pyrolysis product for 3 times by using deionized water to obtain the cobaltosic oxide quantum dot @ carbon composite material.
The composite material prepared in the embodiment 2 of the present invention is detected by a transmission electron microscope, as shown in fig. 1, it can be known from fig. 1 that: the size of the cobaltosic oxide quantum dots prepared by the method is 2-4nm, and the cobaltosic oxide quantum dots are uniformly distributed in pores of the carbon material.
The results of high resolution Co2p XPS spectroscopy on the composite prepared in example 2 of the invention are shown in fig. 2, where fig. 2 shows that the fine spectrum of Co2p can be fitted by six typical peak fits using a gaussian fitting method, and the fitted data shows four main peaks (780.0, 783.4, 795.3 and 797.2eV) in addition to two satellite peaks, corresponding to Co and its compounds (Co-C, Co-O or Co-N), respectively. It not only shows Co3O4But also implies Co3O4Strong interaction with the PNC interface, which contributes to the long-term stability of the composite material as an electrode material.
The electrode material prepared in example 2 was tested for electrochemical properties according to the method of example 1, as shown in FIG. 3, and was found to be 0.5A g-1Current density of 1310 (g) and discharge specific capacitance of 1310 (g) 1310F g (g)-1And at 5A g-1After 5000 cycles of circulation under high current density, the specific capacitance retention rate is up to 91.9%.
Example 3
The preparation method comprises the steps of preparing a substrate carbon material according to the method of example 1, weighing 270mg of cobalt nitrate hexahydrate and 100mg of the substrate carbon material, adding the weighed materials into an agate mortar, uniformly grinding for 10min to obtain mixed black powder, transferring the black powder into a polytetrafluoroethylene container, sealing the container by using a sealing film, transferring the container into a tubular furnace, slowly heating the container from room temperature to 70 ℃ at a heating rate of 3 ℃ per minute in an Ar atmosphere, keeping the temperature for 1h, heating the container to 600 ℃ at a heating rate of 10 ℃ per minute, keeping the temperature for 10h, dissolving a pyrolysis product in a nitric acid solution, carrying out ultrasonic treatment for 10min, and repeatedly cleaning the pyrolysis product for 3 times by using deionized water to obtain the cobaltosic oxide quantum dot @ carbon composite material.
The transmission electron microscope detection of the composite material prepared in the embodiment 3 of the invention shows that: the size of the cobaltosic oxide quantum dots prepared by the method is 2-5nm, and the cobaltosic oxide quantum dots are uniformly distributed in pores of the carbon material.
The composite material prepared in the embodiment 3 of the invention is subjected to high-resolution Co2p XPS spectrum detection, and the result shows that Co is3O4But also implies Co3O4Strong interaction with the PNC interface, which contributes to the long-term stability of the composite material as an electrode material.
The electrode material prepared in example 3 was tested for electrochemical properties according to the method of example 1 and found to be at 0.5Ag-1Current density of 1227F g-1。
Comparative example
A base carbon material was prepared in accordance with the method of example 1, and 180mg of cobalt nitrate hexahydrate and 100mg of the base carbon material were added to 200ml of a mixed solvent of deionized water and anhydrous ethanol with vigorous stirring. The mixture was then transferred to a teflon-lined autoclave, which was gradually heated to 450 ℃. And held at this temperature for 6 hours. The black product was collected by centrifugation and washed several times with deionized water and absolute ethanol and then kept in an oven at 60 ℃ for 12 hours. Thus obtaining the cobaltosic oxide/carbon composite material.
The composite material prepared by the comparative example of the present invention was subjected to transmission electron microscopy, as shown in fig. 4, it can be seen from fig. 4 that: the size of the cobaltosic oxide quantum dots prepared by the method is 10-20nm, and the cobaltosic oxide quantum dots are completely dispersed on the surface of a carbon material.
The electrode material prepared in comparative example was tested for electrochemical properties according to the method of example 1, as shown in FIG. 5, and was found to be 0.5A g-1Current density of (2) and discharge specific capacitance of only 365F g-1And is far lower than the specific capacitance of the electrode material prepared in the example.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A preparation method of cobaltosic oxide quantum dot @ carbon composite electrode material is characterized by comprising the following steps:
A) mixing and grinding a carbon material and a cobalt salt to obtain mixed powder, wherein the melting point of the cobalt salt is lower than the thermal decomposition temperature;
B) and under the condition of protective atmosphere, heating and melting the mixed product, and then continuing to heat for pyrolysis to obtain the cobaltosic oxide quantum dot @ carbon composite electrode material.
2. The method according to claim 1, wherein the cobalt salt is selected from one or more of cobalt nitrate hexahydrate, cobalt acetate, and cobalt oxalate.
3. The method according to claim 1, wherein the carbon material is produced by:
mixing phosphoric acid aqueous solution with melamine to obtain mixed solution;
heating the mixed solution to remove the solvent to obtain mixed powder;
and annealing the mixed powder under the condition of protective atmosphere to obtain the carbon material.
4. The production method according to claim 1, wherein the mass ratio of the carbon material to the cobalt salt is 1: (0.9-2.7).
5. The method of claim 1, wherein the protective atmosphere conditions are selected from argon.
6. The preparation method according to claim 1, wherein the temperature-raising melting method comprises: heating to 55-70 ℃ at a heating rate of 1-3 ℃/min, and preserving heat for 1-3 h.
7. The method of claim 1, wherein the pyrolysis is carried out by: heating to 300-600 ℃ at a heating rate of 1-10 ℃/min, and preserving heat for 1-10 h.
8. The cobaltosic oxide quantum dot @ carbon composite electrode material prepared by the preparation method according to any one of claims 1 to 7, wherein the cobaltosic oxide quantum dots have the size of 2-5nm and are uniformly distributed in pores of the carbon material.
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