CN110391091B - Mn7O13·5H2O/α-Fe2O3Preparation method, product and application of composite material - Google Patents

Mn7O13·5H2O/α-Fe2O3Preparation method, product and application of composite material Download PDF

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CN110391091B
CN110391091B CN201910779351.XA CN201910779351A CN110391091B CN 110391091 B CN110391091 B CN 110391091B CN 201910779351 A CN201910779351 A CN 201910779351A CN 110391091 B CN110391091 B CN 110391091B
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CN110391091A (en
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孟淑娟
苏琼
张平
孙万虹
王彦斌
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Northwest Minzu University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • H01G11/46—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 discloses Mn7O13·5H2O/α‑Fe2O3The invention discloses a preparation method of a composite material, which relates to the technical field of material preparation and capacitor electrode material application, and comprises the following steps: (1) hexagonal alpha-Fe2O3Preparing a nano sheet; (2) hexagonal alpha-Fe2O3Crystallizing the nanosheets; (3) mn7O13·5H2O/α‑Fe2O3And (3) preparing the nano sheet composite material. The invention also provides Mn prepared by the preparation method7O13·5H2O/α‑Fe2O3Composite material and application of the composite material in super capacitor electrodes. The invention has the beneficial effects that: mn prepared by the invention7O13·5H2O/α‑Fe2O3The composite material has good capacitance characteristic, shows excellent electrochemical performance under a three-electrode system, and can be widely applied to electrode materials of super capacitors.

Description

Mn7O13·5H2O/α-Fe2O3Preparation method, product and application of composite material
Technical Field
The invention relates to the technical field of material preparation and application of electrode materials of a super capacitor, in particular to Mn7O13·5H2Oα-Fe2O3A preparation method, a preparation product and application of the composite material.
Background
With the rapid development of current socioeconomic power, the demand of human energy is increasing, and the limited and unregulated exploitation and use of fossil energy reserves on earth causes the human beings to face two very serious problems: energy crisis and environmental pollution. The development of new clean energy sources such as water energy, wind energy, nuclear energy and the like is a sustainable method for effectively solving the energy crisis and environmental pollution.
These new energy sources are usually stored by conversion into electric energy to be utilized by human beings. Supercapacitors are widely used in today's social life as a class of energy storage devices. Supercapacitors can be classified into electric double layer capacitors and pseudocapacitance capacitors according to their energy storage mechanism. Wherein, the electrode material of the pseudocapacitance capacitor is generally an oxide capable of faradaic oxidation-reduction reaction, such as MnO2、 RuO2And some hydroxides, such as Ni (OH)2And the like. However, these material systems are all based on electron transfer between cations and electrolyte ions when redox reaction occurs, and only one electron can be transferred at a time, so that the efficiency is low. And multiple electrons can be transferred between metal cations with multiple oxidation states and electrolyte ions and between cations in different oxidation states, so that the electron transfer efficiency can be obviously improved, and the capacitance performance can be improved.
Patent CN201810050299.X discloses a NiCo2O4@MnO2Foamed nickel/MnO2A preparation method of the composite electrode material of the super capacitor; comprises subjecting foamed nickel to ultrasonic treatment with hydrochloric acid and deionized water, vacuum drying, and adding Ni (NO)3)2·6H2O、Co(NO3)2·6H2O、CO(NH2)2Adding absolute ethyl alcohol and deionized water, and stirring to obtain pink solution; adding the foamed nickel and the pink solution into a reaction kettle, washing, drying and carrying out heat treatment after reaction to obtain NiCo2O4Foaming nickel, then adding NiCo2O4Foamed nickel and KMnO4The aqueous solution is sequentially placed in a polytetrafluoroethylene lining reaction kettle, and the foam nickel after reaction is washed and dried by absolute ethyl alcohol and deionized water to obtain NiCo2O4@MnO2Foamed nickel/MnO2A composite electrode material.
Mn7O13·5H2The Mn element in O has multiple oxidation states, and can realize multi-electron transfer. At present, the performance of the supercapacitor made of the hydrated manganese oxide is rarely researched, and Mn is prepared7O13·5H2The method of O adopts an electrochemical deposition method, and has the defects of time and labor consumption, high energy consumption and complex operation. Therefore, a novel technology which is time-saving, simple, easy to operate and low in energy consumption is developed to prepare Mn7O13·5H2O is a difficult problem to be solved urgently.
Disclosure of Invention
One of the technical problems to be solved by the invention is to provide a method for simply preparing Mn7O13·5H2O/α-Fe2O3A method of compounding a material.
The invention adopts the following technical scheme to solve the technical problems:
the invention provides Mn7O13·5H2O/α-Fe2O3The preparation method of the composite material comprises the following steps:
(1)α-Fe2O3preparing a nano sheet: mixing and stirring trivalent ferric salt, absolute ethyl alcohol and deionized water, then adding acetate, stirring, pouring into a reaction kettle, reacting at a certain temperature, cooling, centrifuging, drying a product obtained by centrifuging at 60-90 ℃ for 12-24 h, and preparing alpha-Fe2O3Nanosheets;
(2)α-Fe2O3crystallization of the nanosheets: alpha-Fe prepared in the step (1)2O3Mixing the nanosheets and the metal salt, grinding the nanosheets and the metal salt in an agate mortar, and calcining and crystallizing the ground mixture under the protection of inert gas to obtain crystallized alpha-Fe2O3Nanosheets;
(3)Mn7O13·5H2O/α-Fe2O3preparing the nano-sheet composite material: the crystallized alpha-Fe prepared in the step (2)2O3Adding the nanosheets into 0.5-2 mol/L inorganic acid aqueous solution, performing ultrasonic dispersion, heating to a certain temperature, adding manganese salt, continuously stirring for reaction, centrifuging a reaction product, washing with deionized water to be neutral, and performing freeze drying to obtain Mn7O13·5H2O/α-Fe2O3A nanosheet composite.
Has the advantages that: the invention adopts a simple synthesis method to synthesize alpha-Fe2O3Nanosheet and Mn7O13·5H2O is assembled into Mn7O13·5H2O/α-Fe2O3A heterojunction structure capable of effectively increasing Mn7O13·5H2The energy storage property of O. In the invention, alpha-Fe is prepared2O3nanosheet/Mn7O13·5H2In O composite, Mn is synthesized7O13·5H2The O method has the characteristics of simple operation, time and labor saving and low energy consumption; in addition, since Mn is produced7O13·5H2O and alpha-Fe2O3The nano-sheet method is a chemical wet method and a hydrothermal method respectively, and the yield of the synthetic material of the method depends on the size of the volume of a reaction kettle, so that the composite material has the potential of large-scale production through reasonable popularization.
Preferably, the ferric salt in step (1) is one of ferric nitrate, ferric chloride and ferric sulfate.
Preferably, the acetate in step (1) is one of potassium acetate, lithium acetate and sodium acetate.
Preferably, the mass ratio of the acetate to the ferric iron salt in the step (1) is 1: 1-3.
Preferably, the adding mass of the absolute ethyl alcohol in the step (1) is 5-15 times of that of the acetate, and the adding volume of the absolute ethyl alcohol is 5-10 times of that of the deionized water.
Preferably, the reaction kettle in the step (1) is a polytetrafluoroethylene reaction kettle, the reaction temperature is 150-200 ℃, and the reaction time is 7-10 hours.
Preferably, the metal salt in step (2) is NaCl, KCl, LiCl, Na2CO3、K2CO3One or more of (a).
Preferably, the metal salt is reacted with alpha-Fe in the step (2)2O3The mass ratio of the nano sheets is 50: 1.
Preferably, the inert gas in step (2) is one of nitrogen, argon and helium.
Preferably, the calcination temperature-increasing conditions in the step (2) are as follows: heating to 400-500 ℃ at a heating rate of 2 ℃/min, and preserving heat for 30-60 min.
Preferably, the manganese salt in step (3) is one of potassium permanganate, sodium permanganate, ammonium permanganate, manganese chloride, manganese sulfate and manganese nitrate.
Preferably, the inorganic acid in step (3) is one of sulfuric acid, hydrochloric acid, nitric acid and perchloric acid.
Preferably, the concentration of the inorganic acid in the step (3) is 0.5-2 mol/L.
Preferably, the inorganic acid and the crystallized alpha-Fe in the step (3)2O3The mass ratio of the nano sheets is 1: 5.5-588.
Preferably, the ultrasonic dispersion time in the step (3) is 30-120 min, and the heating temperature is 80-90 ℃.
Preferably, the crystallized alpha-Fe in the step (3)2O3The mass ratio of the nanosheets to the manganese salt is 1: 5-20, and the reaction time is 10-60 min.
Preferably, the freeze-drying temperature in the step (3) is-80 ℃ to-150 ℃.
The second technical problem to be solved by the present invention is to provide a Mn7O13·5H2O/α-Fe2O3A composite material.
The invention adopts the following technical scheme to solve the technical problems:
the invention provides Mn prepared by the preparation method7O13·5H2O/α-Fe2O3A composite material.
The third technical problem to be solved by the invention is to provide Mn7O13·5H2O/α-Fe2O3The application of the composite material in the electrode of the super capacitor.
Has the advantages that: mn prepared by the invention7O13·5H2O/α-Fe2O3The composite material has good capacitance characteristic and is very good under a three-electrode test systemExcellent electrochemical performance, and current density of 1 A.g-1When the specific capacitance reaches 1376.9F g-1Therefore, the method can be widely applied to electrode materials of the super capacitor.
Preferably, the preparation method of the supercapacitor electrode comprises the following steps: adding Mn7O13·5H2O/α-Fe2O3Mixing and grinding the composite material, the carbon black and the polytetrafluoroethylene fully according to the mass ratio of 8:1:1, and then coating the mixture on 0.5 multiplied by 0.5cm2Compacting the foamed nickel, and drying for 12 hours at 100 ℃.
Preferably, the mass of the mixture coated on the nickel foam is 1-2 mg.
The invention has the beneficial effects that:
(1) alpha-Fe prepared by the invention2O3In the shape of quasi-hexagonal nanosheet, with a diameter of about 90-180 nm and a thickness of about 12nm, and alpha-Fe2O3The nano sheet is loaded on Mn7O13·5H2The surface of O or the inside of O is wrapped;
(2) mn prepared by the invention7O13·5H2O/α-Fe2O3The composite material is in a reticular quasi-spherical shape, and the diameter of the composite material is between 550nm and 750 nm;
(3) the invention adopts a simple synthesis method to synthesize alpha-Fe2O3Nanosheet and Mn7O13·5H2O is assembled into Mn7O13·5H2O/α-Fe2O3A heterojunction structure capable of effectively increasing Mn7O13·5H2The energy storage property of O. In the invention, alpha-Fe is prepared2O3nanosheet/Mn7O13·5H2In O composite, Mn is synthesized7O13·5H2The O method has the characteristics of simple operation, time and labor saving and low energy consumption; in addition, since Mn is produced7O13·5H2O and alpha-Fe2O3The method for preparing the nano-sheet is a chemical wet method and a hydrothermal method respectively, the yield of the synthetic material of the method depends on the size of the volume of a reaction kettle, and therefore, the method can be reasonably pushedThe composite material has the potential of large-scale production;
(4) mn prepared by the invention7O13·5H2O/α-Fe2O3The composite material has good capacitance characteristic, has very excellent electrochemical performance under a three-electrode test system, and has current density of 1 A.g-1When the specific capacitance reaches 1376.9F g-1Therefore, the method can be widely applied to electrode materials of the super capacitor.
Drawings
FIG. 1 shows crystallized α -Fe prepared in example 1 of the present invention2O3XRD spectra of the nanosheets;
FIG. 2 shows Mn prepared in example 1 of the present invention7O13·5H2O/α-Fe2O3An XRD (X-ray diffraction) spectrum of the nano-sheet composite material;
FIG. 3 shows crystallized α -Fe prepared in example 1 of the present invention2O3Scanning electron microscope images of the nanosheets;
FIG. 4 shows Mn prepared in example 1 of the present invention7O13·5H2O/α-Fe2O3Scanning electron microscope images of the nano-sheet composite material;
FIG. 5 shows Mn in example 1 of the present invention7O13·5H2Transmission electron microscopy of O;
FIG. 6 shows Mn in example 1 of the present invention7O13·5H2A selected area electron diffraction pattern of O;
FIG. 7 Mn prepared in example 1 of the present invention7O13·5H2O/α-Fe2O3Transmission electron microscopy of the composite;
FIG. 8 shows Mn in example 1 of the present invention7O13·5H2O/α-Fe2O3The cyclic voltammetry characteristic curve of the supercapacitor electrode prepared from the composite material under different voltage scanning rates;
FIG. 9 shows Mn in example 1 of the present invention7O13·5H2O/α-Fe2O3Supercapacitor electrodes prepared from composite materials at different currentsConstant current charge and discharge curve at density;
FIG. 10 shows Mn in example 1 of the present invention7O13·5H2O/α-Fe2O3The multiplying power performance curve of the supercapacitor electrode prepared from the composite material;
FIG. 11 shows Mn in example 1 of the present invention7O13·5H2O/α-Fe2O3And (3) an electrochemical impedance spectrogram of the supercapacitor electrode prepared from the composite material.
FIG. 12 shows Mn7O13·5H2O, cyclic voltammetry characteristic curves under different voltage scanning rates;
FIG. 13 shows Mn7O13·5H2O constant current charge-discharge curve under different current densities;
FIG. 14 shows Mn7O13·5H2A rate performance curve of O;
FIG. 15 shows Mn7O13·5H2Electrochemical impedance spectrum of O.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples of the specification.
Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.
Example 1
Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3Preparation of nanosheet composite
(1) Quasi-hexagonal alpha-Fe2O3Preparation of nanosheets
Weighing 20mmol of ferric nitrate (9 crystal water) and placing in a round-bottom flask, adding 40ml of absolute ethyl alcohol and 5ml of deionized water, mechanically stirring for 1h, then adding 2.8g of sodium acetate, and stirring for 0.5 h; pouring the mixed liquid into a 50ml polytetrafluoroethylene lining reaction kettle, and reacting for 8 hours at 180 ℃;cooling, centrifuging, washing with deionized water and anhydrous ethanol repeatedly, and drying in 60 deg.C forced air drying oven for 12 hr to obtain alpha-Fe2O3Nanosheets;
(2) quasi-hexagonal alpha-Fe2O3Crystallization of nanosheets
0.2g of quasi-hexagonal alpha-Fe2O3Mixing the nanosheets with 10g of analytical pure NaCl, fully and uniformly grinding the nanosheets in an agate mortar, putting the uniformly ground mixture into a ceramic crucible, and putting the ceramic crucible into a tubular furnace in a N mode2Calcining and crystallizing under protection.
The temperature rise conditions were as follows: heating to 450 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 30 min.
After naturally cooling to room temperature, dissolving NaCl in water, centrifuging, and washing with deionized water for several times; drying at 60 deg.C for 24 h; obtaining crystallized alpha-Fe2O3Nanosheets;
(3)Mn7O13·5H2o/quasi-hexagonal alpha-Fe2O3Preparation of nanosheet composite
Weighing 20mg of crystallized quasi-hexagonal nanosheet alpha-Fe2O3Added into 60ml of 1mol/L H2SO4Dispersing in water solution with ultrasound for 30min, heating to 90 deg.C, and slowly adding 200mg KMnO4Stirring at 90 deg.C for 20min, centrifuging, washing with deionized water repeatedly to neutrality, and freeze drying at-80 deg.C or below.
The preparation method of the supercapacitor electrode comprises the following steps: mn prepared in the step (3)7O13·5H2O/α-Fe2O3Mixing and grinding the composite material, carbon black and polytetrafluoroethylene according to the mass ratio of 8:1:1 fully, and then coating 1mg of the mixture on 0.5 multiplied by 0.5cm2Compacting the foamed nickel, and drying for 12 hours at 100 ℃.
The composite and supercapacitor electrodes prepared in this example were tested:
(1) XRD spectrum analysis: XRD was used to treat the crystallized alpha-Fe prepared in this example2O3Nanosheet and Mn7O13·5H2O/quasi-hexagonalα-Fe2O3And (5) identifying the nano sheet composite material.
FIG. 1 is a crystallized alpha-Fe prepared by hydrothermal method2O3XRD pattern of the nanosheets, from which it was found that the resulting product was α -Fe with good crystallinity2O3Without any other impurities. FIG. 2 is the alpha-Fe prepared2O3/Mn7O13·5H2XRD pattern of O composite material, from which alpha-Fe can be seen2O3And Mn7O13·5H2Diffraction peak of O proves that alpha-Fe is successfully prepared2O3/Mn7O13·5H2And (3) an O composite material.
(2) Scanning electron microscopy characterization
Characterization of crystallized alpha-Fe by scanning Electron microscope2O3Nanosheet and Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3Morphology of the nanosheet composite.
FIG. 3 shows crystallized α -Fe2O3Scanning electron microscope image of the nanosheet, FIG. 4 is Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3Scanning electron microscope image of the nano-sheet composite material shows that the crystallized alpha-Fe2O3In a quasi-hexagonal nanosheet shape, wherein quasi-hexagonal means a shape approximating a regular hexagon, but not a standard hexagon; thickness of about 12nm, alpha-Fe2O3The diameter of the nano-sheet is about 170nm, Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3The nano-sheet composite material is in a reticular quasi-spherical shape, and the size of the nano-sheet composite material is distributed between 550nm and 750 nm.
(3) TEM characterization
Using transmission electron microscope to measure Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3And (5) characterizing the nano-sheet composite material. FIG. 5 shows Mn7O13·5H2O, it can be observed that the morphology is mainly in the form of clusters of stacked very thin, wrinkled sheets. FIG. 6 shows the selected area of the sampleDaughter diffractogram, which can be seen to have a number of diffuse ring compositions, illustrating Mn7O13·5H2The crystallinity of O is very low, consistent with the very weak diffraction peaks observed in its XRD pattern. FIG. 7 shows Mn7O13·5H2O/α-Fe2O3The transmission electron microscope picture of the composite material can see a great deal of alpha-Fe2O3The nano sheet is loaded on Mn7O13·7H2The surface of the O sample is wrapped in the O sample.
(4) Electrochemical performance test
In the three-electrode measurement system, 6M KOH is used as electrolyte, a platinum mesh is used as a counter electrode, an Hg/HgO electrode is used as a reference electrode, a super capacitor electrode is used as a working electrode, and a test voltage window is-0.4V.
FIG. 8 shows Mn7O13·5H2O/α-Fe2O3The cyclic voltammetry characteristic curves of the supercapacitor electrodes made of the composite material are respectively represented by the curves of which black dashed arrows sequentially pass through from the innermost to the outermost in a voltage scanning rate of 3mV s-1,5mV s-1,10mV s-1,20mV s-1,30mV s-1,50mV s-1,70mV s-1And 100mV s-1And (5) collecting a cyclic voltammetry characteristic curve. It can be observed that all curves are quasi-rectangular, indicating that the composite system exhibits good capacitive properties. A distinct redox peak can be observed between-0.1 and 0.1V, indicating that the material system stores and releases charges mainly through Faraday redox reactions.
FIG. 9 is a constant current charge-discharge curve of the material system, wherein the current density from left to right of the curve is 1A g-1、2A·g-1、3A·g-1、4A·g-1、5A·g-1The current density of the upper right-hand curve from left to right in the figure is 10A g-1、7A·g-1It can be seen that the charge and discharge curves are quasi-triangular under small current density, and there is almost no voltage drop, which indicates that the conductivity of the material is very good.
By calculating specific capacitance at different current densities, e.g.Shown in FIG. 10, at 1A · g-1The specific capacitance can reach 1376.9F g at the current density of (2)-1The current density increased to 10A g-1When the specific capacitance reaches 333.3F g-1. Fig. 11 is an electrochemical impedance spectrogram of the composite material, in which the equivalent series resistance and the charge transfer resistance are 0.77 Ω and 1 Ω, respectively, which shows that the material has a small resistance, is favorable for electron transmission and ion diffusion, and effectively improves the capacitance performance.
Mn as described above7O13·5H2O/α-Fe2O3In the preparation process of the composite material, the quasi-two-dimensional hexagonal alpha-Fe is prepared2O3The Fe source can be ferric nitrate, ferric chloride and ferric sulfate containing iron salt with or without water, the function of sodium acetate can be replaced by potassium acetate and lithium acetate to prepare Mn7O13·5H2The Mn source of O can be potassium permanganate, sodium permanganate, ammonium permanganate, manganese chloride, manganese sulfate and manganese nitrate, and the sulfuric acid can be replaced by hydrochloric acid, nitric acid and perchloric acid. High temperature crystallization of alpha-Fe2O3The salt can be NaCl, KCl, LiCl, Na2CO3、K2CO3Provided that its melting point is below 500 ℃ and that it does not react with alpha-Fe in this temperature range2O3The reaction can be carried out as a mixed salt. The invention can prepare the composite material with the same shape and structure by using proper raw materials as long as the conditions allow. The term "conditional permission" as used herein means that certain restrictive conditions need to be satisfied, such as: iron salts are soluble in water, manganese salts are soluble in water, auxiliary growth regulators such as sodium acetate are soluble in water, and acids include strong and weak acids soluble in water.
For quasi-hexagonal alpha-Fe2O3The preparation of the nano-sheet has the basic reaction principle that Fe is dissolved after ferric salt is dissolved3+With acetate anion (CH) in acetate salt3COO-) Combined and then further converted to alpha-Fe2O3The nano-sheet, and the anion in the iron salt combines with the cation in the acetate to form the corresponding halide salt, such as Na2SO4NaCl and NaNO3And the like. Thus, different anions in the trivalent iron saltThe different cations in the iron salt and the acetate do not influence the shape and the size of the final product, so that the quasi-hexagonal alpha-Fe with the same shape and size can be prepared by different ferric iron salts and different acetate shape regulators2O3Nanosheets.
For quasi-hexagonal alpha-Fe2O3High temperature crystallization of the nanoplatelets, NaCl was used in example 1. Sufficient NaCl and alpha-Fe2O3The purpose of the sufficient mixing of the nano-sheets is to enable alpha-Fe2O3The nano-sheets are fully dispersed in NaCl to prevent alpha-Fe in the high-temperature crystallization process2O3The interconnection and fusion between the nanoplatelets form large particles. Therefore, the alpha-Fe is not decomposed and not reacted with the alpha-Fe as long as the melting point is below 500 ℃ and the alpha-Fe is heated in the air below 500 DEG C2O3Salts of the nanosheet reaction can be used as dispersants. The melting points of several salts selected by us are above 500 ℃ and the salts are not decomposed by self heating and are not mixed with alpha-Fe2O3The nanosheets react and therefore can be used as dispersants. In addition, the crystallization temperature is selected primarily in consideration of the melting point of the selected salt and the ability to increase the α -Fe2O3In the temperature range of the crystallization degree of the nano sheet, the excessive high temperature can cause the melting of salts to cause the loss of the function of the dispersing agent, and the excessive low temperature can cause the alpha-Fe2O3The degree of crystallization of the nanoplatelets is insufficient and it is therefore very important to select a suitable temperature interval.
For Mn7O13·5H2Preparation of O, MnO being involved in the reaction4 -And Mn2+Ions, and reducing the higher valent manganese ions is H+Independent of the cations in the manganese salt and the anions in the acid, several manganese salts and acids can be selected for the preparation of Mn7O13·5H2O。
Example 2
Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3Preparation of nanosheet composite
(1) Quasi-hexagonal alpha-Fe2O3Nano-sheetPreparation of
Weighing 20mmol of ferric chloride, placing in a round-bottom flask, adding 40ml of absolute ethyl alcohol and 5ml of deionized water, mechanically stirring for 1h, then adding 2.8g of potassium acetate, and stirring for 0.5 h; pouring the mixed liquid into a 50ml reaction kettle with a polytetrafluoroethylene lining, and reacting for 8h at 180 ℃. Cooling, centrifuging, washing with deionized water and anhydrous ethanol repeatedly, and drying in a forced air drying oven at 60 deg.C for 12 hr;
(2) quasi-hexagonal alpha-Fe2O3Crystallization of nanosheets
0.2g of quasi-hexagonal alpha-Fe2O3Nanosheet and 10g of analytically pure Na2CO3Mixing, fully and uniformly grinding in an agate mortar, putting the uniformly ground mixture into a ceramic crucible, and calcining and crystallizing under the protection of Ar gas in a tubular furnace. The temperature rise conditions were as follows: heating to 480 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 40 min;
after naturally cooling to room temperature, adding water to the Na2CO3Dissolving, centrifuging, washing with deionized water for several times, and drying at 60 deg.C for 24 hr to obtain crystallized alpha-Fe2O3Nanosheets;
(3)Mn7O13·5H2o/quasi-hexagonal alpha-Fe2O3Preparation of nanosheet composite
Weighing 20mg of crystallized quasi-hexagonal nanosheet alpha-Fe2O3Adding into 60ml of 2mol/L HCl aqueous solution, ultrasonically dispersing for 30min, heating to 90 ℃, and slowly adding 200mg NaMnO4Stirring at 90 deg.C for 20min, centrifuging, washing with deionized water repeatedly to neutrality, and freeze drying at-80 deg.C. Crystallized alpha-Fe2O3Nanosheet, Mn7O13·5H2O、Mn7O13·5H2O/α-Fe2O3Characterization of the nanosheet composite Using example 1 as an example, the crystallized α -Fe prepared in this example2O3Nanosheet, Mn7O13·5H2O、Mn7O13·5H2O/α-Fe2O3The characterization of the nanoplatelet composites is essentially the same as in example 1.
Example 3
Mn7O13·5H2O/quasi-hexagonal alpha-Fe2O3Preparation of nanosheet composite
(1) Quasi-hexagonal alpha-Fe2O3Preparation of nanosheets
Weighing 20mmol of ferric sulfate, placing in a round-bottom flask, adding 40ml of absolute ethyl alcohol and 5ml of deionized water, mechanically stirring for 1h, then adding 2.8g of sodium acetate, and stirring for 0.5 h; pouring the mixed liquid into a 50ml reaction kettle with a polytetrafluoroethylene lining, and reacting for 8h at 180 ℃. Cooling, centrifuging, washing with deionized water and anhydrous ethanol repeatedly, and drying in a forced air drying oven at 60 deg.C for 12 hr;
(2) quasi-hexagonal alpha-Fe2O3Crystallization of nanosheets
0.2g of quasi-hexagonal alpha-Fe2O3Mixing the nanosheets with 10g of analytical grade KCl, fully and uniformly grinding the nanosheets in an agate mortar, putting the uniformly ground mixture into a ceramic crucible, and calcining and crystallizing the uniformly ground mixture in a tubular furnace under the protection of Ar gas. The temperature rise conditions were as follows: heating to 430 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 60 min;
after naturally cooling to room temperature, dissolving KCl in water, centrifuging, washing with deionized water for several times, and drying at 60 ℃ for 24h to obtain crystallized alpha-Fe2O3Nanosheets;
(3)Mn7O13·5H2o/quasi-hexagonal alpha-Fe2O3Preparation of nanosheet composite
Weighing 20mg of crystallized quasi-hexagonal nanosheet alpha-Fe2O3Adding 60ml of 2mol/L HNO3Dispersing in water solution with ultrasound for 30min, heating to 90 deg.C, and slowly adding 200mg KMnO4Stirring at 90 deg.C for 20min, centrifuging, washing with deionized water repeatedly to neutrality, and freeze drying at-80 deg.C. Crystallized alpha-Fe2O3Nanosheet, Mn7O13·5H2O、Mn7O13·5H2O/α-Fe2O3The nanosheet composite is characterized by example 1, which is the present examplePrepared crystallized alpha-Fe2O3Nanosheet, Mn7O13·5H2O、Mn7O13·5H2O/α-Fe2O3The characterization of the nanoplatelet composites is essentially the same as in example 1.
Comparative example
Preparation of Mn7O13·5H2O, the preparation method comprises the following steps:
60ml of 2mol/L HNO3Heating the aqueous solution to 90 deg.C, and adding KMnO 20-30 mg every 2min within 10min4KMnO4 at 200mg, stirring at 90 deg.C for 20min, centrifuging, washing with deionized water repeatedly to neutrality, and freeze drying at-80 deg.C to obtain Mn7O13·5H2O。
Using Mn prepared in this comparative example7O13·5H2O preparing the supercapacitor electrode, wherein the preparation method comprises the following steps:
mn prepared in this comparative example7O13·5H2Mixing and grinding O, carbon black and polytetrafluoroethylene according to the mass ratio of 8:1:1 fully, and then coating the mixture on 0.5 multiplied by 0.5cm2Compacting the foamed nickel, and drying for 12 hours at 100 ℃.
The experimental results are as follows: FIG. 12 is Mn prepared in this comparative example7O13·5H2O is a cyclic voltammetry characteristic curve of a supercapacitor electrode prepared from the electrode material, and curves of which black dashed arrows sequentially pass through from the innermost to the outermost represent the curves at a voltage scanning rate of 5mV s-1,10mV s-1,20mV s-1,30mV s-1,50mV s-1, 70mV s-1,90mV s-1And 100mV s-1And (5) collecting a cyclic voltammetry characteristic curve. It can be seen from the figure that very distinct redox peaks appear in these curves, while Mn is used7O13·5H2O/α-Fe2O3The oxidation reduction peak is not obvious when the composite material is used as an electrode material to prepare the supercapacitor, which shows that the alpha-Fe2O3Is added to promote FaradayThe rapid oxidation-reduction reaction is beneficial to improving the rate capability of the composite material system.
FIG. 13 is Mn7O13·5H2O is a constant current charge-discharge curve of the supercapacitor prepared from the electrode material, and two obvious charge-discharge platforms can be observed from the graph, which indicates that the speed of the Faraday redox reaction is slow.
Mn can be calculated from the constant current charge-discharge curve of FIG. 137O13·5H2O is the specific capacitance of the electrode material at different current densities, as shown in FIG. 14, at 1A · g-1Has a specific capacitance of 429.2 F.g at a current density of (1)-1The current density increased to 10A g-1When the specific capacitance reaches 215.4F g-1. Also, Mn is shown in FIG. 147O13·5H2O/α-Fe2O3The specific capacitance of the composite material under different current densities can be found that the composite material is more pure Mn7O13·5H2The specific capacitance of O is improved by about 2 to 3 times.
FIG. 15 shows pure Mn7O13·5H2The electrochemical impedance spectrogram of the supercapacitor prepared by taking O as the electrode material has equivalent series resistance and charge transfer resistance of 0.85 omega and 4.9 omega respectively, which are both larger than those of the composite material, and more particularly, alpha-Fe2O3The addition of the composite material obviously reduces the equivalent series resistance and the charge transfer resistance of an electrode material system, is more beneficial to electron transmission and ion diffusion, and effectively improves the capacitance performance of the composite material system.
Mn7O13·5H2The electrochemical properties of O are shown in FIGS. 12 to 15, and it can be seen that Mn is present7O13·5H2O/α-Fe2O3Specific capacitance ratio pure Mn of nano-sheet composite material7O13·5H2The specific capacitance of O is about 2 to 3 times higher, which is caused by alpha-Fe2O3Nanosheet and Mn7O13·5H2And the heterojunction structure formed by O promotes the transfer efficiency of electrons in the composite material.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and various process schemes having no substantial difference from the concept of the present invention are within the protection scope of the present invention.

Claims (9)

1. Mn (manganese)7O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: the method comprises the following steps:
(1)α-Fe2O3preparing a nano sheet: mixing and stirring trivalent ferric salt, absolute ethyl alcohol and deionized water, then adding acetate, stirring, pouring into a reaction kettle, reacting at a certain temperature, cooling, centrifuging, drying a product obtained by centrifuging at 60-90 ℃ for 12-24 h, and preparing alpha-Fe2O3Nanosheets;
(2)α-Fe2O3crystallization of the nanosheets: alpha-Fe prepared in the step (1)2O3Mixing the nanosheets and the metal salt, grinding the nanosheets and the metal salt in an agate mortar, and calcining and crystallizing the ground mixture under the protection of inert gas to obtain crystallized alpha-Fe2O3Nanosheets; the metal salt is NaCl, KCl, LiCl, Na2CO3、K2CO3One or more of;
(3)Mn7O13·5H2O/α-Fe2O3preparing the nano-sheet composite material: the crystallized alpha-Fe prepared in the step (2)2O3Adding the nanosheets into 0.5-2 mol/L inorganic acid aqueous solution, performing ultrasonic dispersion, heating to a certain temperature, adding manganese salt, continuously stirring for reaction, centrifuging a reaction product, washing with deionized water to be neutral, and performing freeze drying to obtain Mn7O13·5H2O/α-Fe2O3A nanosheet composite.
2. Mn according to claim 17O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: the ferric iron salt in the step (1) is one of ferric nitrate, ferric chloride and ferric sulfateAnd (4) seed preparation.
3. Mn according to claim 17O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: the acetate in the step (1) is one of potassium acetate, lithium acetate and sodium acetate.
4. Mn according to claim 37O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: the mass ratio of the acetate to the ferric iron salt in the step (1) is 1: 1-3.
5. Mn according to claim 17O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: in the step (1), the adding mass of the absolute ethyl alcohol is 5-15 times of that of the acetate, and the adding volume of the absolute ethyl alcohol is 5-10 times of that of the deionized water.
6. Mn according to claim 17O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: the reaction kettle in the step (1) is a polytetrafluoroethylene reaction kettle, the reaction temperature is 150-200 ℃, and the reaction time is 7-10 hours.
7. Mn according to claim 17O13·5H2O/α-Fe2O3The preparation method of the composite material is characterized by comprising the following steps: the calcination temperature-rising conditions in the step (2) are as follows: raising the temperature to 400-500 ℃ at a rate of 2-5 ℃/min, and keeping the temperature for 30-60 min.
8. Use of Mn according to any of claims 1 to 77O13·5H2O/α-Fe2O3Preparation method of composite material to prepare Mn7O13·5H2O/α-Fe2O3A composite material.
9. Use of Mn according to any of claims 1 to 77O13·5H2O/α-Fe2O3Mn prepared by preparation method of composite material7O13·5H2O/α-Fe2O3The application of the composite material in the electrode of the super capacitor.
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