A nanocomposite material and its preparation method and application

Abstract

The present invention relates to the technical field of nanomaterials, and discloses a nanocomposite material. The nanocomposite material is composed of γ-Fe2O3 nanomaterials and carbon-based materials, and the carbon-based materials account for at least 4% of the mass of the γ-Fe2O3 nanomaterials; the preparation method of the nanocomposite material is as follows: (1) A ferrous salt solution, carbon-based materials and an oxidant are mixed to obtain a mixed solution; (2) The mixed solution is mixed with an alkaline solution, and after aging and post-treatment, a nanocomposite material is obtained; assuming the number of types of carbon-based materials is n, then the value of n is an integer greater than 0. The preparation process flow provided by the present invention is simple. The target product can be prepared in one step only through a simple liquid-phase precipitation reaction, and the reaction conditions are mild. It only needs to react at normal temperature and pressure, and the target product can be obtained without passing through an autoclave or high-temperature calcination and without preparing a precursor.

Description

Technical Field

[0001] The invention relates to the technical field of nano materials, and in particular to a nano gamma-Fe2O3 / carbon-based composite material and a preparation method and application thereof. Background Art

[0002] Supercapacitor is a new type of energy storage device between ordinary capacitors and batteries. Compared with traditional capacitors, it has higher capacitance and energy density, and higher power density than energy storage batteries. Supercapacitors also have faster charging and discharging speeds, a wider operating temperature range and a longer service life. They have good application value and development prospects in many fields.

[0003] As a transition metal oxide, Fe2O3 has a high theoretical specific capacitance, is environmentally friendly, has abundant resources and is inexpensive, and has shown a very high application prospect as a supercapacitor electrode material. However, due to its strong magnetism, it often agglomerates during the preparation process, resulting in a significant reduction in its specific surface area and porosity, which directly limits its electrochemical performance. Carbon-based supported materials usually refer to carbon-based materials such as carbon nanotubes and graphene as carriers, and other substances such as metal nanoparticles and catalysts are loaded on the surface or inside of the carbon carrier. Carbon-based supported materials have important application value in the fields of catalysis, energy storage, sensors, etc. Therefore, loading nano-sized Fe2O3 on different carbon-based materials such as carbon nanotubes, graphene oxide, and reduced graphene oxide can improve the agglomeration problem of nano-Fe2O3, and these carbon-based materials have the characteristics of large specific surface area, strong adsorption performance and excellent conductivity, which can greatly enhance the electrochemical performance of Fe2O3.

[0004] At present, people have conducted some research on the preparation of nano-γ-Fe2O3 composite materials. For example, the invention patent with publication number CN108257793A provides a method for preparing a carbon nanotube / ferric oxide composite material, but the composite solution needs to be heated, and the minimum heating temperature is 90°C, which consumes a lot of energy, and the operation process is complicated, and the optimal electrochemical performance is only 318F / g. In the invention patent with publication number CN112670094A, a method for preparing a carbon fiber composite material modified with ferric oxide nanoflowers is proposed, and the preparation process is complicated and needs to be carried out under high temperature and high pressure, which is difficult to operate, dangerous, and consumes a lot of energy, and the specific capacitance is only 337F / g.

[0005] Therefore, how to provide a Fe2O3 / carbon-based composite material with a simple preparation process and excellent electrochemical performance is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0006] In view of this, the present invention provides a nano-composite material and a preparation method thereof to solve the problems of the existing nano-γ-Fe2O3 composite material having a complex preparation process, high energy consumption, poor safety and poor electrochemical performance.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] In a first aspect of the present invention, a nanocomposite material is provided. The nanocomposite material is composited from a γ-Fe2O3 nanomaterial and a carbon-based material, wherein the carbon-based material accounts for at least 4% of the mass of the γ-Fe2O3 nanomaterial.

[0009] Preferably, the carbon-based material includes at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, single-layer graphene oxide, multi-layer graphene oxide, single-layer reduced graphene oxide, multi-layer reduced graphene oxide, activated carbon, and carbon nanofibers.

[0010] In a second aspect of the present invention, there is provided a method for preparing the nanocomposite material described in any one of the above, comprising the following steps:

[0011] (1) mixing a ferrous salt solution, a carbon-based material and an oxidant to obtain a mixed solution;

[0012] (2) mixing the mixed solution with an alkaline solution, aging and post-treating, to obtain a nanocomposite material;

[0013] The number of types of carbon-based materials is set to n, and the value of n is an integer greater than 0.

[0014] Preferably, when n=1, step (1) is: mixing the ferrous salt solution with the carbon-based material and then ultrasonicating to obtain a mixed solution A, and then mixing the mixed solution A with the oxidant to obtain a mixed solution. In this mixing method, the ferrous salt solution and the carbon-based material are first mixed and then ultrasonicated so that the ferrous salt is uniformly and fully attached to the carbon-based material, and then the potential of the solution is increased by dripping the oxidant, providing an oxidizing environment for the preparation process, and oxidizing the divalent iron to the trivalent iron.

[0015] Preferably, when n=1, step (1) is: mixing the ferrous salt solution with the oxidant to obtain a mixed solution B, and then mixing the mixed solution B with the carbon-based material and ultrasonicating to obtain a mixed solution. In this mixing method, the ferrous salt solution is first mixed with the oxidant to obtain an oxidation reaction liquid, the potential of the solution is increased, and the divalent iron is oxidized to trivalent iron, and then the carbon-based material is added and fully mixed and ultrasonicated, so that the trivalent iron is uniformly and fully attached to the carbon-based material.

[0016] Preferably, when the value of n is an integer greater than 1, step (1) is: mixing the ferrous salt solution with a portion of the carbon-based material and then sonicating to obtain a mixed solution A, then mixing the mixed solution A with the oxidant, continuing to add the remaining portion of the carbon-based material, mixing and then sonicating to obtain a mixed solution.

[0017] Preferably, when the value of n is an integer greater than 1, step (1) is: mixing the ferrous salt solution with all the carbon-based materials and then ultrasonicating to obtain a mixed solution A, and then mixing the mixed solution A with the oxidant to obtain a mixed solution.

[0018] Preferably, the ferrous salt solution includes any one or more of ferrous oxalate solution, ferrous sulfate solution, and ferrous chloride solution.

[0019] Preferably, the oxidant is a hydrogen peroxide solution. Hydrogen peroxide is selected as the oxidant in order not to introduce other metal impurities into the entire preparation system and affect the formation of the final target product. If potassium permanganate is selected as the oxidant, manganese metal ions will be introduced, and impure target products are likely to be obtained.

[0020] Preferably, the carbon-based material includes at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, single-layer graphene oxide, multi-layer graphene oxide, single-layer reduced graphene oxide, multi-layer reduced graphene oxide, activated carbon, and carbon nanofibers.

[0021] Preferably, the molar ratio of the ferrous salt solution to the oxidant is 0.007:(0.01-0.03).

[0022] Preferably, the mass ratio of the ferrous salt to the carbon-based material is 1:(0.0176-0.0528), more preferably 1:0.044.

[0023] Preferably, the ferrous salt solution is prepared with ferrous salt as solute and water or additive as solvent, and the mass ratio of the ferrous salt to water or additive is no more than 1:28.

[0024] Preferably, the additive includes any one or more of N-methylpyrrolidone (NMP), quaternary ammonium salt compounds, and alcohol compounds.

[0025] Preferably, the quaternary ammonium salt compound includes, but is not limited to, any one or more of tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylsodium bromide (DTAB), hexadecyltrimethylsodium bromide (CTAB), dodecyldimethylbenzylammonium chloride (DDBAC), N-methylacetamide (NMA), and dimethylacetamide (DMA).

[0026] Preferably, the alcohol compound includes but is not limited to any one or more of ethanol, ethylene glycol (EG), polyvinyl alcohol (PVA), polyethylene glycol (PEG)

[0027] Preferably, the molar ratio of the ferrous salt solution to the alkaline solution is 0.007:(0.014-0.07).

[0028] Preferably, the volume ratio of the alkaline solution to the additive is 1:(0-2), more preferably 1:2.

[0029] Preferably, in steps (1)-(2), the mixed reaction temperature is 20-80°C.

[0030] Preferably, in step (2), the drying temperature is 70-90° C. and the drying time is 2-4 h.

[0031] In a third aspect of the present invention, there is provided a use of the nanocomposite material described in any one of the above items and / or the nanocomposite material prepared by the method described in any one of the above items in a supercapacitor.

[0032] The present invention provides a nanocomposite material, which has the following beneficial effects compared with the prior art:

[0033] The present invention obtains different types of γ-Fe2O3 composite materials by compounding one or more carbon-based materials, so as to optimize the electrochemical performance of the composite materials as supercapacitor electrode materials, thereby further improving the specific capacitance thereof.

[0034] The preparation process provided by the present invention is simple, and the target product can be prepared in one step through a simple liquid phase precipitation reaction, and the reaction conditions are mild. The target product can be obtained by reacting at room temperature and pressure without going through an autoclave or high-temperature calcination, and without preparing a precursor.

[0035] The average size of the gamma-Fe2O3 in the composite material prepared by the present invention is 10-20nm, the appearance is in the form of nanoparticles, it is fully and evenly distributed on the carbon-based material, has good dispersibility, and the recovery rate is about 80% to 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1The XRD pattern of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 1 of the present invention;

[0038] Figure 2 This is the XRD pattern of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 2 of the present invention;

[0039] Figure 3 The XRD pattern of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 3 of the present invention;

[0040] Figure 4 This is the XRD pattern of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 4 of the present invention;

[0041] Figure 5 This is the XRD pattern of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 5 of the present invention;

[0042] Figure 6 This is the XRD pattern of the nano-γ-Fe2O3 / single-layer rGO composite prepared in Example 6 of the present invention;

[0043] Figure 7 This is the XRD pattern of the nano-γ-Fe2O3 / multilayer rGO composite prepared in Example 7 of the present invention;

[0044] Figure 8 This is the XRD pattern of the nano-γ-Fe2O3 / multilayer GO composite prepared in Example 8 of the present invention;

[0045] Fig. 9 This is the XRD pattern of the nano-γ-Fe2O3 / activated carbon composite prepared in Example 9 of the present invention;

[0046] Fig.10 This is the XRD pattern of the nano γ-Fe2O3 / carbon nanofiber composite prepared in Example 10 of the present invention;

[0047] Fig.11 This is the XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 11 of the present invention;

[0048] Fig.12 This is the XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 12 of the present invention;

[0049] Fig.13 This is the XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 13 of the present invention;

[0050] Fig.14This is the XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 14 of the present invention;

[0051] Fig.15 The XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention with TTAB as the additive;

[0052] Fig.16 The XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 16 of the present invention with the additive being PVA;

[0053] Fig.17 The XRD pattern of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 17 of the present invention with the additive being NMP;

[0054] Fig.18 This is the Raman image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 1 of the present invention;

[0055] Fig.19 This is a Raman image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 2 of the present invention;

[0056] Fig. 20 This is the Raman image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 3 of the present invention;

[0057] Fig.21 This is the Raman image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 4 of the present invention;

[0058] Fig. 22 This is the Raman image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 5 of the present invention;

[0059] Fig.23 This is the Raman image of the nano-γ-Fe2O3 / single-layer rGO composite prepared in Example 6 of the present invention;

[0060] Fig.24 This is a Raman image of the nano-γ-Fe2O3 / multilayer rGO composite prepared in Example 7 of the present invention;

[0061] Fig.25 This is a Raman image of the nano-γ-Fe2O3 / multilayer GO composite prepared in Example 8 of the present invention;

[0062] Fig.26 This is a Raman image of the nano-γ-Fe2O3 / activated carbon composite prepared in Example 9 of the present invention;

[0063] Fig. 27 This is a Raman image of the nano-γ-Fe2O3 / carbon nanofiber composite prepared in Example 10 of the present invention;

[0064] Fig.28 This is the Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 11 of the present invention;

[0065] Fig.29 This is the Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 12 of the present invention;

[0066] Fig.30 This is the Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 13 of the present invention;

[0067] Fig.31 This is the Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 14 of the present invention;

[0068] Fig.32 This is a Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention with TTAB as the additive;

[0069] Fig.33 This is a Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 16 of the present invention with PVA as the additive;

[0070] Fig.34 This is a Raman image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 17 of the present invention with NMP as the additive;

[0071] Fig.35 This is a SEM image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 1 of the present invention;

[0072] Fig.36 This is a SEM image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 2 of the present invention;

[0073] Fig.37 This is a SEM image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 3 of the present invention;

[0074] Fig.38 This is a SEM image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 4 of the present invention;

[0075] Fig.39This is a SEM image of the nano-γ-Fe2O3 / MWCNTs composite prepared in Example 5 of the present invention;

[0076] Fig.40 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO composite prepared in Example 6 of the present invention;

[0077] Fig.41 This is a SEM image of the nano-γ-Fe2O3 / multilayer rGO composite prepared in Example 7 of the present invention;

[0078] Fig.42 This is a SEM image of the nano-γ-Fe2O3 / multilayer GO composite prepared in Example 8 of the present invention;

[0079] Fig.43 This is a SEM image of the nano-γ-Fe2O3 / activated carbon composite prepared in Example 9 of the present invention;

[0080] Fig.44 This is a SEM image of the nano-γ-Fe2O3 / carbon nanofiber composite prepared in Example 10 of the present invention;

[0081] Fig.45 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 11 of the present invention;

[0082] Fig.46 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 12 of the present invention;

[0083] Fig.47 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 13 of the present invention;

[0084] Fig.48 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 14 of the present invention;

[0085] Fig.49 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention, in which the additive is TTAB;

[0086] Fig.50 This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 16 of the present invention, in which the additive is PVA;

[0087] Fig.51This is a SEM image of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 17 of the present invention, in which the additive is NMP;

[0088] Fig.52 The charge-discharge (GCD) diagram of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention and with TTAB as the additive at a current density of 0.5 A / g;

[0089] Fig.53 The CV graph of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention with TTAB as the additive at a scanning rate of 10 mV / s;

[0090] Fig.54 The charge-discharge (GCD) diagram of the nano-γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention and with TTAB as the additive at different current densities;

[0091] Fig.55 The charge-discharge cycle performance diagram of the nano γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 of the present invention and with TTAB as the additive, after 500 cycles of testing at a current density of 2A / g;

[0092] Fig.56 is the XRD pattern of the nano γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite prepared in Example 18 of the present invention;

[0093] Fig.57 This is a Raman graph of the nano γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite prepared in Example 18 of the present invention;

[0094] Fig.58 This is a SEM image of the nano γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite prepared in Example 18 of the present invention;

[0095] Fig.59 This is a charge-discharge (GCD) diagram of the nano γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite prepared in Example 18 of the present invention at a current density of 0.5 A / g;

[0096] Fig.60 This is a CV graph of the nano γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite prepared in Example 18 of the present invention at a scanning rate of 10 mV / s;

[0097] Fig.61The XRD pattern of the powdered product prepared in Comparative Example 1 of the present invention;

[0098] Fig.62 The XRD pattern of the powdered product prepared in Comparative Example 2 of the present invention;

[0099] Fig.63 The XRD pattern of the powdered product prepared in Comparative Example 3 of the present invention;

[0100] Fig.64 is the XRD pattern of the powdered product prepared in Comparative Example 4 of the present invention;

[0101] Fig.65 This is the Raman graph of the powdered product prepared in Comparative Example 2 of the present invention;

[0102] Fig.66 This is the Raman graph of the powdered product prepared in Comparative Example 3 of the present invention;

[0103] Fig.67 is the Raman graph of the powdered product prepared in Comparative Example 4 of the present invention;

[0104] Fig.68 This is a SEM image of the powdered product prepared in Comparative Example 1 of the present invention;

[0105] Fig.69 This is a SEM image of the powdered product prepared in Comparative Example 2 of the present invention;

[0106] Fig.70 This is a SEM image of the powdered product prepared in Comparative Example 3 of the present invention;

[0107] Fig.71 This is a SEM image of the powdered product prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0108] Embodiments of the present invention are described in detail below, and the examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by reference to the accompanying drawings are exemplary, are only used to explain the present invention, and are not to be construed as limitations of the present invention. In the embodiments, if specific techniques or conditions are not indicated, the techniques or conditions described in the literature in this area or the product specifications are carried out. The reagents used or the instruments that are not indicated by the manufacturer are all conventional products that can be obtained commercially.

[0109] In one aspect of the present invention, a nanocomposite material is provided. The nanocomposite material is composited from a γ-Fe2O3 nanomaterial and a carbon-based material, wherein the carbon-based material accounts for at least 4% of the mass of the γ-Fe2O3 nanomaterial.

[0110] In some embodiments of the present invention, the carbon-based material includes at least one of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), single-layer graphene oxide (single-layer GO), multi-layer graphene oxide (multi-layer GO), single-layer reduced graphene oxide (single-layer rGO), multi-layer reduced graphene oxide (multi-layer rGO), activated carbon, and carbon nanofibers, preferably single-layer reduced graphene oxide.

[0111] Optionally, the nanocomposite material is assumed to be composed of γ-Fe2O3 nanomaterial and n carbon-based materials, then the total mass of the carbon-based materials accounts for (4-12%)n, preferably (7-12%)n, and more preferably 10%*n, of the mass of the γ-Fe2O3 nanomaterial, that is, each carbon-based material accounts for 4-12%, preferably 7-12%, and more preferably 10% of the mass of the γ-Fe2O3 nanomaterial.

[0112] In one aspect of the present invention, a method for preparing a nanocomposite material is provided, which will be described below through specific examples.

[0113] Example 1

[0114] (1) Add 28 ml of deionized water to 0.007 mol of ferrous oxalate at room temperature, mix, and then place on a stirrer for magnetic stirring to make it evenly dispersed.

[0115] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the ferrous oxalate system. The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process.

[0116] (3) Weigh 44 mg of multi-walled carbon nanotubes (MWCNTs) according to 10% of the theoretical mass of γ-Fe2O3 obtained, pour it into the solution obtained in (2), stir it with a glass rod, and then put it into an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0117] (4) Take 14 ml of KOH solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, and slowly add the KOH solution dropwise to the solution obtained in (3). The dropping time is controlled to 25 min. Magnetic stirring is performed during the dropping process. After the dropping is completed, the solution is aged for 1 h.

[0118] (5) The reaction solution obtained in step (4) was repeatedly washed with deionized water and centrifuged, and the obtained precipitate was dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black product.

[0119] Example 2

[0120] (1) 44 mg of multi-walled carbon nanotubes (MWCNTs) weighed at 10% of the theoretical mass of γ-Fe2O3 to be obtained and 28 ml of deionized water were added to 0.007 mol of ferrous oxalate at room temperature and stirred with a glass rod. The mixture was then placed in an ultrasonic cleaner at a working frequency of 50 kHz and ultrasonicated for 20 min.

[0121] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the mixed solution obtained in (1). The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process.

[0122] (3) Prepare a 1 mol / L KOH solution with deionized water. Take 14 ml of KOH solution according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol. Slowly add the KOH solution dropwise to the solution obtained in (2). The addition time is controlled to 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixture is aged for 1 h.

[0123] (4) The reaction solution obtained in step (3) is repeatedly washed with deionized water and centrifuged, and the obtained precipitate is dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black product.

[0124] Example 3

[0125] Example 3 is basically the same as Example 1, with the only difference being that step (3) is as follows: 17.6 mg of multi-walled carbon nanotubes (MWCNTs) weighed at 4% of the theoretical mass of Fe2O3 is poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0126] Example 4

[0127] Example 4 is basically the same as Example 1, with the only difference being that step (3) is as follows: 30.8 mg of multi-walled carbon nanotubes (MWCNTs) weighed at 7% of the theoretical mass of Fe2O3 are poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0128] Example 5

[0129] Example 5 is basically the same as Example 1, with the only difference being that step (3) is as follows: 52.8 mg of multi-walled carbon nanotubes (MWCNTs) are weighed according to 12% of the theoretical mass value of Fe2O3 obtained, poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0130] The products prepared in Examples 1-5 were subjected to XRD and Raman detection, SEM image analysis, and electrochemical performance tests were performed on the products at a current density of 0.5 A / g. The results are shown in Table 1.

[0131] Table 1

[0132]

[0133]

[0134] Through XRD and Raman detection of the products of Examples 1-5, it can be seen that the diffraction peaks in the XRD of the products are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of MWCNTs (C) are present. However, through Raman, it can be obtained that the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 (D belt) and 1594cm -1 (G band) is the characteristic peak of MWCNTs (C), and the ratio of D band to G band is obtained by calculation. D / I G (I D / I G The larger the ratio, the more defects the composite represents, which is more conducive to the migration of electrons. As shown in the table, it can be shown that the product is a γ-Fe2O3 / MWCNTs composite. From the SEM image, it can be observed that γ-Fe2O3 is relatively evenly distributed on the MWCNTs, and γ-Fe2O3 is a nanoparticle with a particle size of 16-20 nm.

[0135] Compared with the experimental results of Examples 1-2, the composite prepared by the composite method of Example 1 exhibits better electrochemical performance at a current density of 0.5 A / g. Therefore, on this basis, the present invention controls other experimental parameters and conditions unchanged, and obtains Examples 3-5 by adjusting the addition ratio of carbon-based materials, and explores the effect of different addition ratios of carbon-based materials on the specific capacitance of the composite material.

[0136] The experimental result of comparative example 1,3,4,5, the product of preparation is γ-Fe2O3 / MWCNTs composite, detect its specific capacitance size at 0.5A / g, when the composite ratio of carbon-based material is 4%(17.6mg)-10%(44mg), its specific capacitance increases to 600F / g by 267F / g. Along with the increase of composite ratio, its specific capacitance size also increases thereupon, but when composite ratio is from 10%(44mg)-12%(52.8mg), its specific capacitance decreases to 393F / g by 600F / g, this may be due to excessive addition of carbon-based material, γ-Fe2O3 is wrapped in carbon-based material, γ-Fe2O3 is reduced with electrolyte contact area, thereby causes electrochemical performance to reduce, so the best carbon-based material addition ratio is 10%(44mg).

[0137] On the basis of Examples 1-5, the present invention controls other experimental parameters and conditions unchanged, obtains Examples 6-10 by changing the type of carbon-based materials, explores the effect of different carbon-based materials on the specific capacitance of the composite material, and thus obtains the best carbon-based material.

[0138] Example 6

[0139] Example 6 is basically the same as Example 1, with the only difference being that step (3) is as follows: 44 mg of a single-layer reduced graphene oxide (single-layer rGO) weighed at 10% of the theoretical mass of the obtained γ-Fe2O3 is poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0140] Through XRD and Raman detection of the product, it can be seen that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of single-layer reduced graphene oxide (C) are shown. However, through Raman, the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 The peak at the center is the characteristic peak of monolayer reduced graphene oxide (C). The ratio of the D band to the G band is calculated to be 1.51, so it can be said that the product is a γ-Fe2O3 / single-layer rGO composite. From the SEM image, it can be observed that γ-Fe2O3 is relatively evenly distributed on the monolayer reduced graphene oxide and that γ-Fe2O3 is a nanoparticle with a particle size of 17 nm.

[0141] Example 7

[0142] Example 7 is basically the same as Example 1, with the only difference being that step (3) is as follows: 44 mg of multilayer reduced graphene oxide (multilayer rGO) weighed at 10% of the theoretical mass of γ-Fe2O3 is poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0143] Through XRD and Raman detection of the product, it can be seen that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of multilayer reduced graphene oxide (C) are shown. However, through Raman, the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 The peak at the center is the characteristic peak of multilayer reduced graphene oxide (C). The ratio of the D band to the G band is calculated to be 1.58, so it can be said that the product is a γ-Fe2O3 / multilayer rGO composite. The SEM image shows that γ-Fe2O3 is relatively evenly distributed on the multilayer reduced graphene oxide, and γ-Fe2O3 is a nanoparticle with a particle size of 18 nm.

[0144] Example 8

[0145] Example 8 is basically the same as Example 1, with the only difference being that step (3) is as follows: 44 mg of multilayer graphene oxide (multilayer GO) weighed at 10% of the theoretical mass of γ-Fe2O3 is poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0146] Through XRD and Raman detection of the product, it can be seen that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of multilayer graphene oxide (C) are present. However, through Raman, it can be obtained that the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 The peak at the center is the characteristic peak of multilayer graphene oxide (C). The ratio of the D band to the G band is calculated to be 1.29, so it can be said that the product is a γ-Fe2O3 / multilayer GO composite. From the SEM image, it can be observed that γ-Fe2O3 is relatively evenly distributed on the multilayer graphene oxide, and γ-Fe2O3 is a nanoparticle with a particle size of 18 nm.

[0147] Example 9

[0148] Example 9 is basically the same as Example 1, with the only difference being that step (3) is as follows: 44 mg of activated carbon weighed at 10% of the theoretical mass of the γ-Fe2O3 obtained is poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0149] Through XRD and Raman detection of the product, it can be seen that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of activated carbon (C) are present. However, through Raman, it can be obtained that the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 The peak at the center is the characteristic peak of activated carbon (C). The ratio of the D band to the G band is calculated to be 1.05, so it can be said that the product is a γ-Fe2O3 / activated carbon composite. From the SEM image, it can be observed that γ-Fe2O3 is relatively evenly distributed on the activated carbon and that γ-Fe2O3 is nanoparticles with a particle size of 16 nm.

[0150] Example 10

[0151] Example 10 is basically the same as Example 1, with the only difference being that step (3) is as follows: 44 mg of carbon nanofibers (CNFs) weighed at 10% of the theoretical mass of γ-Fe2O3 are poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0152] Through XRD and Raman detection of the product, it can be seen that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of carbon nanofibers (C) are shown. However, through Raman, the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 The peak at the center is the characteristic peak of carbon nanofiber (C). The ratio of the D band to the G band is calculated to be 0.59, so it can be said that the product is a γ-Fe2O3 / carbon nanofiber composite. The SEM image shows that γ-Fe2O3 is relatively evenly distributed on the carbon nanofiber, and γ-Fe2O3 is a nanoparticle with a particle size of 16 nm.

[0153] The products prepared in Examples 6-10 were subjected to XRD and Raman detection, SEM image analysis, and electrochemical performance testing at a current density of 0.5 A / g. The results are shown in Table 2.

[0154] Table 2

[0155]

[0156] By comparing the experimental results of Examples 1, 6-10, it can be seen that the γ-Fe2O3 / single-layer rGO composite prepared in Example 6 has the largest specific capacitance at a current density of 0.5 A / g, so the preferred carbon-based material is single-layer reduced graphene oxide (single-layer rGO).

[0157] In order to further improve the electrochemical properties of the composite, the two best carbon-based materials were selected for composite, namely, single-layer reduced graphene oxide (single-layer rGO) and multi-walled carbon nanotubes (MWCNTs), and the effects of different composite methods on the formation and electrochemical properties of γ-Fe2O3 / single-layer rGO-MWCNTs composite materials were further explored. The specific operations are as shown in Examples 11-14.

[0158] Embodiment 11

[0159] (1) 44 mg of monolayer reduced graphene oxide (single-layer rGO) weighed at 10% of the theoretical mass of γ-Fe2O3 was added to 0.007 mol of ferrous oxalate at room temperature and 28 ml of deionized water and stirred with a glass rod. The mixture was then placed in an ultrasonic cleaner at a working frequency of 50 kHz and ultrasonicated for 20 min.

[0160] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the mixed solution obtained in (1). The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process.

[0161] (3) Weigh 44 mg of multi-walled carbon nanotubes (MWCNTs) according to 10% of the theoretical mass of γ-Fe2O3 obtained, pour it into the solution obtained in (2), stir it with a glass rod, and then put it into an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0162] (4) Prepare a 1 mol / L KOH solution with deionized water. Take 14 ml of KOH solution according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol. Slowly add the KOH solution dropwise to the solution obtained in (3). The addition time is controlled to 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixture is aged for 1 h.

[0163] (5) The reaction solution obtained in step (4) was repeatedly washed with deionized water and centrifuged, and the obtained precipitate was dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black product.

[0164] Example 12

[0165] (1) 44 mg of multi-walled carbon nanotubes (MWCNTs) weighed at 10% of the theoretical mass of γ-Fe2O3 to be obtained and 28 ml of deionized water were added to 0.007 mol of ferrous oxalate at room temperature and stirred with a glass rod. The mixture was then placed in an ultrasonic cleaner at a working frequency of 50 kHz and ultrasonicated for 20 min.

[0166] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the mixed solution obtained in (1). The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process.

[0167] (3) Weigh 44 mg of monolayer reduced graphene oxide (single-layer rGO) according to 10% of the theoretical mass of γ-Fe2O3 obtained, pour it into the solution obtained in (2), stir it with a glass rod, and then put it into an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0168] (4) Prepare a 1 mol / L KOH solution with deionized water. Take 14 ml of KOH solution according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol. Slowly add the KOH solution dropwise to the solution obtained in (3). The addition time is controlled to 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixture is aged for 1 h.

[0169] (5) The reaction solution obtained in step (4) was repeatedly washed with deionized water and centrifuged, and the obtained precipitate was dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black product.

[0170] Embodiment 13

[0171] (1) 44 mg of monolayer reduced graphene oxide (single-layer rGO) and 44 mg of multi-walled carbon nanotubes (MWCNTs) were weighed at 10% of the theoretical mass of γ-Fe2O3 to 0.007 mol of ferrous oxalate at room temperature, and 28 ml of deionized water were added and stirred with a glass rod. The mixture was then placed in an ultrasonic cleaner at a working frequency of 50 kHz for 20 min.

[0172] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the mixed solution obtained in (1). The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process.

[0173] (3) Prepare a 1 mol / L KOH solution with deionized water. Take 14 ml of KOH solution according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol. Slowly add the KOH solution dropwise to the solution obtained in (2). The addition time is controlled to 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixture is aged for 1 h.

[0174] (4) The reaction solution obtained in step (3) is repeatedly washed with deionized water and centrifuged, and the obtained precipitate is dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black product.

[0175] Embodiment 14

[0176] (1) 44 mg of monolayer reduced graphene oxide (single-layer rGO) and 44 mg of multi-walled carbon nanotubes (multi-walled CNTs) weighed at 10% of the theoretical mass of γ-Fe2O3 were added to 0.007 mol of ferrous oxalate at room temperature, and the mixture was stirred with a glass rod. The mixture was then placed in an ultrasonic cleaner at an operating frequency of 50 kHz and ultrasonicated for 20 min.

[0177] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution to the mixed solution obtained in (1). The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixed solution is placed in an ultrasonic cleaner with an operating frequency of 50 KHz and ultrasonicated for 20 min.

[0178] (3) Prepare a 1 mol / L KOH solution with deionized water. Take 14 ml of KOH solution according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol. Slowly add the KOH solution dropwise to the solution obtained in (2). The addition time is controlled to 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixture is aged for 1 h.

[0179] (4) The reaction solution obtained in step (3) is repeatedly washed with deionized water and centrifuged, and the obtained precipitate is dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black product.

[0180] The products prepared in Examples 11-14 were subjected to XRD and Raman detection, SEM image analysis, and electrochemical performance tests were performed on the products at a current density of 0.5 A / g. The results are shown in Table 3.

[0181] Table 3

[0182]

[0183] Through XRD and Raman detection of the products of Examples 11-14, it can be seen that the XRD diffraction peaks of the prepared products correspond to the (002) crystal plane and (100) crystal plane diffraction peaks of C and the (220), (311), (422)(511), and (440) crystal plane diffraction peaks of γ-Fe2O3 respectively; through Raman, it can be obtained that there is no characteristic peak of γ-Fe2O3, but at 1333cm -1 (D belt) and 1594cm -1 The characteristic peak of C is shown at (G band), and the ratio of D band to G band is calculated to be I D / I G , it can be explained that the products of Examples 11-14 are all γ-Fe2O3 / single-layer rGO-MWCNTs composites; and through the SEM images of Examples 11-14, it can be observed that γ-Fe2O3 is relatively evenly distributed on the single-layer rGO-MWCNTs.

[0184] Analysis of the data of Examples 11-14 shows that the four composite methods can prepare γ-Fe2O3 / single-layer rGO-MWCNTs composites, and the γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared by the composite method in Example 13 has the largest specific capacitance at a current density of 0.5A / g. Compared with Example 13, the specific capacitance of Example 14 at 0.5A / g is lower, which may be due to the continued ultrasound after the addition of H2O2, which shakes off the γ-Fe2O3 originally composited on the single-layer rGO-MWCNTs, resulting in a decrease in electrochemical performance.

[0185] In order to further improve the electrochemical performance of the composite, the above optimal composite method for preparing the γ-Fe2O3 / single-layer rGO-MWCNTs composite was selected for subsequent experiments. Different additives were added to improve the agglomeration of γ-Fe2O3 on the carbon-based material, thereby further optimizing the electrochemical performance of the composite. See Examples 15-17 for details.

[0186] It should be noted that three or more carbon-based materials can be selected to be compounded with γ-Fe2O3, and different compounding methods can be selected for compounding. For example, one carbon-based material is added in step (1) and then ultrasonically treated, and the other two carbon-based materials are added after the strong oxidizing solution is dropped in step (2), and then ultrasonically treated after stirring; or two carbon-based materials are added in step (1) and then ultrasonically treated, and the remaining one carbon-based material is added after the strong oxidizing solution is dropped in step (2), and then ultrasonically treated after stirring.

[0187] Embodiment 15

[0188] Example 15 is basically the same as Example 13, with the only difference being that step (1) is as follows: 44 mg of monolayer reduced graphene oxide (single-layer rGO), 44 mg of multi-walled carbon nanotubes (MWCNTs) and 28 ml of tetradecyltrimethylammonium bromide (TTAB) weighed at 10% of the theoretical mass of γ-Fe2O3 to 0.007 mol of ferrous oxalate at room temperature are added and stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0189] Through XRD and Raman detection of the product, it can be seen that the XRD of the prepared product does not show obvious diffraction peaks, but through Raman, it can be obtained that the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 It is the characteristic peak of single-layer rGO-MWCNTs (C). The ratio of D band to G band is calculated to be 1.93, which indicates that the product is a γ-Fe2O3 / single-layer rGO-MWCNTs composite. The SEM image shows that γ-Fe2O3 is uniformly distributed on the single-layer rGO-MWCNTs.

[0190] Example 16

[0191] Example 16 is basically the same as Example 13, with the only difference being that step (1) is as follows: 44 mg of monolayer reduced graphene oxide (single-layer rGO), 44 mg of multi-walled carbon nanotubes (MWCNTs) and 28 ml of polyvinyl alcohol (PVA) weighed at 10% of the theoretical mass value of γ-Fe2O3 are added to 0.007 mol of ferrous oxalate at room temperature and stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0192] XRD and Raman tests on the product show that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of single-layer rGO-MWCNTs (C) are present. However, Raman results show that the diffraction peaks at 290, 415, 500, and 659 cm -1 It shows the characteristic peak of γ-Fe2O3 at 1333cm -1 and 1594cm -1 It is the characteristic peak of single-layer rGO-MWCNTs (C). The ratio of D band to G band is calculated to be 1.30, which indicates that the product is a γ-Fe2O3 / single-layer rGO-MWCNTs composite. The SEM image shows that γ-Fe2O3 is uniformly distributed on the single-layer rGO-MWCNTs.

[0193] Embodiment 17

[0194] Example 17 is basically the same as Example 13, with the only difference being that step (1) is as follows: 44 mg of single-layer reduced graphene oxide (single-layer rGO), 44 mg of multi-walled carbon nanotubes (multi-walled CNTs) and 28 ml of N-methylpyrrolidone (NMP) weighed at 10% of the theoretical mass value of γ-Fe2O3 are added to 0.007 mol of ferrous oxalate at room temperature and stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0195] XRD and Raman tests on the product show that the diffraction peaks of the prepared product correspond to the (002) and (100) crystal plane diffraction peaks of C and the (220), (311), (422), (511), and (440) crystal plane diffraction peaks of γ-Fe2O3. Raman results show that there is no characteristic peak of γ-Fe2O3, but at 1333cm -1 (D belt) and 1594cm -1 (G band) shows a characteristic peak of C, and the ratio of D band to G band is calculated to be 1.64, which shows that the product is a γ-Fe2O3 / single-layer rGO-MWCNTs composite; from the SEM image, it can be observed that γ-Fe2O3 is uniformly distributed on the single-layer rGO-MWCNTs.

[0196] The products prepared in Examples 15-17 were subjected to XRD and Raman detection, SEM image analysis, and electrochemical performance testing at a current density of 0.5 A / g. The results are shown in Table 4.

[0197] Table 4

[0198]

[0199] Analysis of the data of Examples 15-17 shows that the best additive is tetradecyltrimethylammonium bromide (TTAB), and the electrochemical size of its composite is as high as 1211 F / g at a current density of 0.5 A / g.

[0200] In order to further explore the excellent electrochemical performance of the γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15, its specific capacitance at different current densities was measured. The results showed that at 1A / g, the specific capacitance was 851F / g, at 2A / g, the specific capacitance was 780F / g, and at 5A / g, the specific capacitance was 680F / g. Fig.54 As can be seen from the charge and discharge diagram, even if the current density is increased from 0.5A / g to 5A / g, the specific capacitance remains at 56% of the original value. Fig.55As shown in the figure, the cycle performance diagram of 500 cycles at a current density of 2A / g was measured. The results show that after 500 cycles of charge and discharge, the specific capacity retention rate is 57%, reflecting its excellent rate performance and stability. Fig.55 The illustration in the figure is the charge-discharge diagram for the first 15 times. The shape does not change significantly and the charge and discharge are symmetrical, indicating that the electron migration rate is relatively stable. In summary, compared with other composites or γ-Fe2O3 / single-layer rGO-MWCNTs composites prepared by other methods, the specific capacitance retention rate of the γ-Fe2O3 / single-layer rGO-MWCNTs composite prepared in Example 15 at different current densities and the specific capacitance retention rate after 500 cycles at 2A / g can illustrate the superiority of its electrochemical performance.

[0201] Embodiment 18

[0202] Example 18 is basically the same as Example 13, with the only difference being that step (1) is as follows: 44 mg of single-layer reduced graphene oxide (single-layer rGO) weighed at 10% of the theoretical mass of γ-Fe2O3, 44 mg of multi-walled carbon nanotubes (MWCNTs), 44 mg of carbon nanofibers and 28 ml of deionized water are added to 0.007 mol of ferrous oxalate at room temperature and stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0203] Through XRD and Raman detection of the product, it can be seen that the XRD diffraction peaks of the prepared product correspond to the diffraction peaks of the (002) crystal plane, (511) crystal plane, and (100) crystal plane of C and the diffraction peaks of the (220), (311), (422), (511), and (440) crystal planes of γ-Fe2O3. Raman analysis shows that there is no characteristic peak of γ-Fe2O3, but at 1333cm -1 (D belt) and 1594cm -1 (G band) shows a characteristic peak of C, and the ratio of D band to G band is calculated to be 1.82. In summary, it is fully demonstrated that the product is a γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite; through the SEM image, it can be observed that γ-Fe2O3 is evenly distributed on the single-layer rGO-MWCNTs-carbon nanofiber; and then the electrochemical performance test was carried out, and the results showed that at a current density of 0.5A / g, its specific capacitance is 1916F / g.

[0204] Comparative Example 1

[0205] Comparative Example 1 is basically the same as Example 1, with the only difference being that step (3) is as follows: 4.4 mg of carbon nanotubes are weighed according to 1% of the theoretical mass value of Fe2O3 obtained, poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 KHz for 20 minutes.

[0206] Through XRD and SEM detection of the product, it can be seen that the diffraction peak in the XRD of the prepared product is highly consistent with the γ-Fe2O3 standard card, but no diffraction peak of multi-walled carbon nanotubes (C) is present. In addition, only nano-particle-shaped γ-Fe2O3 is observed in the SEM image, and multi-walled carbon nanotubes are not observed. In summary, when the addition ratio of multi-walled carbon nanotubes is 1% (4.4 mg), only γ-Fe2O3 is obtained, and no γ-Fe2O3 / carbon-based material composite is obtained.

[0207] Comparative Example 2

[0208] (1) Add 28 ml of deionized water to 0.007 mol of ferrous oxalate at room temperature, mix, and then place on a stirrer for magnetic stirring to make it evenly dispersed.

[0209] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the ferrous oxalate system. The addition time is controlled manually for 10 min. Magnetic stirring is performed during the addition process.

[0210] (3) Weigh 44 mg of monolayer reduced graphene oxide (single-layer rGO) and 44 mg of multi-walled carbon nanotubes (MWCNTs) according to 10% of the theoretical mass of γ-Fe2O3, pour them into the solution obtained in (2), stir with a glass rod, and then put it into an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0211] (4) Prepare a 1 mol / L KOH solution with deionized water. Take 14 ml of KOH solution according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol. Slowly add the KOH solution dropwise to the solution obtained in (3). The addition time is controlled to 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the mixture is aged for 1 h.

[0212] (5) The reaction solution obtained in step (4) is repeatedly washed with deionized water, and the precipitate obtained by centrifugation is dried in a forced air drying oven at 80° C. for 2-4 hours to obtain a brown-black powder solid sample.

[0213] The difference between this comparative example and Example 13 is that the order of adding the carbon-based material and the oxidant is different. Through XRD and Raman detection of the product, it can be seen that the diffraction peak in the XRD of the prepared product is highly consistent with the γ-Fe2O3 standard card, but it does not show the diffraction peak of the single-layer rGO-MWCNTs (C). Through Raman, it can be obtained that there is no diffraction peak at 290, 415, 500, 659 cm -1 The characteristic peak of γ-Fe2O3 is shown at 1333cm -1 and 1594cm -1 The peak at the bottom is the characteristic peak of single-layer rGO-MWCNTs (C). The ratio of D band to G band is calculated to be 1.55, and only nanoparticulate γ-Fe2O3 and a very small amount of single-layer reduced graphene oxide and multi-walled carbon nanotubes are observed in the SEM image. In summary, the composite method of adding an oxidant before adding the carbon-based material cannot obtain a γ-Fe2O3 / single-layer rGO-MWCNTs composite.

[0214] Comparative Example 3

[0215] (1) Add 28 ml of deionized water to 0.007 mol of ferrous oxalate at room temperature, mix, and then place on a stirrer for magnetic stirring to make it evenly dispersed.

[0216] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Take 10 ml of the H2O2 solution according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the ferrous oxalate system. The addition time is controlled to 10 min. Magnetic stirring is performed during the addition process.

[0217] (3) Weigh 44 mg of monolayer reduced graphene oxide (single-layer rGO) and 44 mg of multi-walled carbon nanotubes (MWCNTs) according to 10% of the theoretical mass of γ-Fe2O3, pour them into the solution obtained in (2), stir with a glass rod, and then put it into an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0218] (4) Take 14 ml of KOH solution prepared at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, and slowly add the KOH solution dropwise to the solution obtained in (3). The dropping time is controlled to 25 min. Magnetic stirring is performed during the dropping process. After the dropping is completed, the mixed solution is placed in an ultrasonic cleaner with an operating frequency of 50 kHz and ultrasonicated for 20 min. After the ultrasonication is completed, it is aged for 1 h.

[0219] (5) The reaction solution obtained in step (4) was repeatedly washed with deionized water, and the precipitate obtained by centrifugation was dried in a forced air drying oven at 80° C. for 2-4 h to obtain a brown-black powder solid sample.

[0220] The difference between this comparative example and Example 14 is that the order of adding the carbon-based material and the oxidant is different. Through XRD and Raman detection of the product, it can be seen that the diffraction peak in the XRD of the prepared product is highly consistent with the γ-Fe2O3 standard card, but it does not show the diffraction peak of the single-layer rGO-MWCNTs (C). Through Raman, it can be obtained that there is no diffraction peak at 290, 415, 500, 659 cm -1 The characteristic peak of γ-Fe2O3 is shown at 1333cm -1 and 1594cm -1 The peak at the center is the characteristic peak of single-layer rGO-MWCNTs (C). The ratio of the D band to the G band is calculated to be 1.54. In the SEM image, only nanoparticulate γ-Fe2O3 was observed, but no single-layer reduced graphene oxide and multi-walled carbon nanotubes were observed. In summary, this composite method did not obtain γ-Fe2O3 / single-layer rGO-MWCNTs.

[0221] Comparative Example 4

[0222] Comparative Example 4 is substantially the same as Comparative Example 3, except that steps (3) to (4) are different:

[0223] (3) 44 mg of single-layer reduced graphene oxide (single-layer rGO), 44 mg of multi-walled carbon nanotubes (MWCNTs), and 44 mg of carbon nanofibers weighed according to 10% of the theoretical mass of γ-Fe2O3 were poured into the solution obtained in (2), stirred with a glass rod, and then placed in an ultrasonic cleaner with an operating frequency of 50 kHz for 20 minutes.

[0224] (4) Take 14 ml of the prepared KOH solution with a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, and slowly add the KOH solution dropwise to the solution obtained in (3). The addition time is controlled to be 25 min. Magnetic stirring is performed during the addition process. After the addition is completed, the solution is aged for 1 h.

[0225] Through XRD and Raman detection of the product, it can be seen that the diffraction peaks in the XRD of the prepared product are highly consistent with the γ-Fe2O3 standard card, but no diffraction peaks of single-layer rGO-MWCNTs (C) are present. Through Raman, it can be seen that the product does not have diffraction peaks at 290, 415, 500, 659 cm -1 The characteristic peak of γ-Fe2O3 is shown at 1333cm -1 and 1594cm -1The peak at the bottom is the characteristic peak of single-layer rGO-MWCNTs (C). The ratio of D band to G band is calculated to be 1.71, and only nano-granular γ-Fe2O3 and a very small amount of multi-walled carbon nanotubes are observed in the SEM image. In summary, this composite method did not obtain a γ-Fe2O3 / single-layer rGO-MWCNTs-carbon nanofiber composite.

[0226] A comprehensive comparison of Example 13 and Example 18 and Comparative Examples 2-4 shows that when compounding multiple (two or more) types of carbon-based materials, the corresponding γ-Fe2O3 / carbon-based composite can only be obtained by adding all or part of the carbon-based materials before adding the oxidant.

[0227] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A nanocomposite material, characterized in that: The nanocomposite material is composited by γ-Fe2O3 nanomaterial and carbon-based material, and the carbon-based material accounts for 10% of the mass of the γ-Fe2O3 nanomaterial; The carbon-based material comprises at least two of multi-walled carbon nanotubes, single-layer reduced graphene oxide, and carbon nanofibers; The nanocomposite material is prepared by a method comprising the following steps: (1) mixing a ferrous salt solution with all carbon-based materials and then ultrasonicating the mixture to obtain a mixed solution A, and then mixing the mixed solution A with an oxidant to obtain a mixed solution; (2) mixing the mixed solution with an alkaline solution, aging and post-treating, to obtain a nanocomposite material; The number of types of carbon-based materials is set to n, and the value of n is an integer greater than 1.

2. A method for preparing the nanocomposite material according to claim 1, characterized in that: The following steps are involved: (1) mixing a ferrous salt solution with all carbon-based materials and then ultrasonicating the mixture to obtain a mixed solution A, and then mixing the mixed solution A with an oxidant to obtain a mixed solution; (2) mixing the mixed solution with an alkaline solution, aging and post-treating, to obtain a nanocomposite material; The number of types of carbon-based materials is set to n, and the value of n is an integer greater than 1.

3. The method for preparing the nanocomposite material according to claim 2, characterized in that: In step (1), the mass ratio of the ferrous salt to the carbon-based material is 1:(0.0176-0.0528).

4. The method for preparing the nanocomposite material according to claim 3, characterized in that: In step (1), the ferrous salt solution is prepared with ferrous salt as solute and water or N-methylpyrrolidone as solvent, and the mass ratio of the ferrous salt to water or N-methylpyrrolidone is no more than 1:

28.

5. The method for preparing the nanocomposite material according to claim 4, characterized in that: In step (2), the molar ratio of the ferrous salt solution to the alkaline solution is 0.007:(0.014-0.07), and the volume ratio of the alkaline solution to N-methylpyrrolidone is 1:(0-2).

6. The method for preparing the nanocomposite material according to claim 2, characterized in that: In steps (1)-(2), the mixed reaction temperature is 20-80°C.

7. Use of the nanocomposite material according to claim 1 or the nanocomposite material prepared by the method according to any one of claims 2 to 6 in a supercapacitor.

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