A nano material and its preparation method and application

Abstract

The present invention relates to the technical field of nanomaterials, and discloses a preparation method of nanomaterials, comprising the following steps: (1) mixing and reacting a ferrous salt solution, a strong oxidizing solution and a first additive to obtain a first mixed solution; (2) mixing an alkaline solution and a second additive to obtain a second mixed solution; (3) mixing and stirring the first mixed solution and the second mixed solution and aging, and after post-treatment, obtaining nanomaterials; setting the addition amount of the first additive as x and the addition amount of the second additive as y, wherein the values of x and y satisfy the following conditions: x > 0, y > 0; or x = 0, y > 0; or x > 0, y = 0. The preparation method of the nanomaterials of the present invention has simple process, mild and simple conditions, good repeatability. The obtained nano γ-Fe2O3 has an average size of 20-40 nm, and the morphology is nanoparticles or flakes. Moreover, the obtained nanomaterials have a relatively high specific capacitance and excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of nano material preparation, and in particular to a nano material and a preparation method and application thereof. Background Art

[0002] Fe2O3 nanoparticles are brown or reddish brown, with large specific surface area, good electrical conductivity, high chemical stability and thermal stability, etc. Fe2O3 nanoparticles have diverse properties and are widely used in magnetic materials, supercapacitors, catalysts and environmental materials. As a material with abundant resources, low price and easy access, Fe2O3 has good electrical conductivity and is suitable for use as an electrode material for supercapacitors. Due to its large specific surface area, Fe2O3 can effectively increase the capacitance of supercapacitors, has excellent high temperature resistance and is suitable for various working environments. It has high cycle stability and long life, is non-toxic and harmless, and is environmentally friendly. However, most of the current preparation processes of Fe2O3 nanoparticles need to be carried out at high temperatures, and the preparation time is long and the process flow is complicated.

[0003] Supercapacitor is a new type of energy storage device that stores energy through electrochemical reactions at the electrode / electrolyte interface. It has a large capacitance, between that of electrolytic capacitors and rechargeable batteries. Not only does it have higher power density and energy density than ordinary batteries, but it also has a fast charge and discharge rate and a long service life. This green and clean energy is safe, reliable, and environmentally friendly, and is a device with great development prospects in the field of energy storage.

[0004] Therefore, how to provide a Fe2O3 nanomaterial with a simple preparation process and mild reaction conditions is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a nano material to solve the problems of long preparation time, complex process flow and harsh reaction conditions of existing Fe2O3 nano materials.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a nanomaterial, comprising the following steps:

[0008] (1) mixing a ferrous salt solution, a strong oxidizing solution and a first additive to react to obtain a first mixed solution;

[0009] (2) mixing the alkaline solution and the second additive to obtain a second mixed solution;

[0010] (3) mixing the first mixed solution and the second mixed solution, stirring and aging them, and performing post-treatment to obtain a nanomaterial;

[0011] The amount of the first additive added is set to x, and the amount of the second additive added is set to y, wherein the values ​​of x and y satisfy the following conditions:

[0012] x>0, y>0; or x=0, y>0; or x>0, y=0.

[0013] Preferably, when x=0, y>0, the second additive includes any one or two of N-methylpyrrolidone (NMP), quaternary ammonium salt compounds, and alcohol compounds.

[0014] Preferably, when x>0, y>0 or x>0, y=0, the first additive includes at least N-methylpyrrolidone (NMP); further preferably, the first additive also includes any one or two of quaternary ammonium salt compounds and alcohol compounds.

[0015] Preferably, the quaternary ammonium salt compound includes any one or more of tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylsodium bromide (DTAB), hexadecyltrimethylsodium bromide (CTAB), dodecyldimethylbenzylammonium chloride (DDBAC), N-methylacetamide (NMA), and dimethylacetamide (DMA).

[0016] Preferably, the alcohol compound includes but is not limited to any one or more of ethanol, ethylene glycol (EG), polyvinyl alcohol (PVA), and polyethylene glycol (PEG).

[0017] Preferably, the molar ratio of the strong oxidizing solution to the ferrous salt is (0.01-0.03):0.007.

[0018] Preferably, the molar ratio of the alkaline solution to the ferrous salt is (0.07-0.014):0.007.

[0019] Preferably, the volume ratio of the alkaline solution to any one of the additives is 1:(0-2) and is not zero.

[0020] Preferably, the reaction temperature of steps (1)-(2) is 20-80°C.

[0021] Preferably, the post-treatment includes centrifugation, washing and drying. Specifically, the precipitate obtained after aging is repeatedly washed with deionized water until the supernatant is neutral, and then dried at 60-90° C. for 2-4 hours.

[0022] In a second aspect, the present invention provides a nanomaterial prepared by any of the methods described above.

[0023] In a third aspect, the present invention provides a nanomaterial prepared by any of the above methods or the use of the above nanomaterial in a supercapacitor.

[0024] The present invention provides a method for preparing a nano material and its application. Compared with the prior art, the present invention has the following beneficial effects:

[0025] The preparation method of the nano material of the present invention has simple process, mild and simple conditions and good repeatability. By detecting the XRD of the product, it can be known that its diffraction peak corresponds to the standard card diffraction peak of γ-Fe2O3 one by one. By SEM pictures, it can be known that the average size of the obtained nano γ-Fe2O3 is 20-40nm, and the morphology is nano particles or sheets. And by studying the addition sequence and combination mode of additives, the specific capacitance of the nano material is improved, which can reach up to 1143F / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] Figure 1 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 1 of the present invention;

[0028] Figure 2 This is a SEM image of nano-γ-Fe2O3 prepared in Example 1 of the present invention;

[0029] Figure 3 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 2 of the present invention;

[0030] Figure 4 This is a SEM image of nano-γ-Fe2O3 prepared in Example 2 of the present invention;

[0031] Figure 5 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 3 of the present invention;

[0032] Figure 6 This is a SEM image of nano-γ-Fe2O3 prepared in Example 3 of the present invention;

[0033] Figure 7 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 4 of the present invention;

[0034] Figure 8This is a SEM image of nano-γ-Fe2O3 prepared in Example 4 of the present invention;

[0035] Fig. 9 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 5 of the present invention;

[0036] Fig.10 This is a SEM image of nano-γ-Fe2O3 prepared in Example 5 of the present invention;

[0037] Fig.11 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 6 of the present invention;

[0038] Fig.12 This is a SEM image of nano-γ-Fe2O3 prepared in Example 6 of the present invention;

[0039] Fig.13 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 7 of the present invention;

[0040] Fig.14 This is a SEM image of nano-γ-Fe2O3 prepared in Example 7 of the present invention;

[0041] Fig.15 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 8 of the present invention;

[0042] Fig.16 This is a SEM image of nano-γ-Fe2O3 prepared in Example 8 of the present invention;

[0043] Fig.17 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 9 of the present invention;

[0044] Fig.18 This is a SEM image of nano-γ-Fe2O3 prepared in Example 9 of the present invention;

[0045] Fig.19 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 10 of the present invention;

[0046] Fig. 20 This is a SEM image of nano-γ-Fe2O3 prepared in Example 10 of the present invention;

[0047] Fig.21 This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 11 of the present invention;

[0048] Fig. 22 This is a SEM image of nano-γ-Fe2O3 prepared in Example 11 of the present invention;

[0049] Fig.23This is the XRD pattern of nano-γ-Fe2O3 prepared in Example 12 of the present invention;

[0050] Fig.24 This is a SEM image of nano-γ-Fe2O3 prepared in Example 12 of the present invention;

[0051] Fig.25 This is the GCD diagram of nano-γ-Fe2O3 prepared in Example 11 of the present invention at 0.5A / g;

[0052] Fig.26 This is the CV graph of nano-γ-Fe2O3 prepared in Example 11 of the present invention at 10mV / s;

[0053] Fig. 27 The XRD pattern of the powdered product prepared in Comparative Example 1 of the present invention;

[0054] Fig.28 This is a SEM image of the powdered product prepared in Comparative Example 1 of the present invention;

[0055] Fig.29 The XRD pattern of the powdered product prepared in Comparative Example 2 of the present invention;

[0056] Fig.30 This is a SEM image of the powdered product prepared in Comparative Example 2 of the present invention;

[0057] Fig.31 The XRD pattern of the powdered product prepared in Comparative Example 3 of the present invention;

[0058] Fig.32 This is a SEM image of the powdered product prepared in Comparative Example 3 of the present invention;

[0059] Fig.33 The XRD pattern of the powdered product prepared in Comparative Example 4 of the present invention;

[0060] Fig.34 This is a SEM image of the powdered product prepared in Comparative Example 4 of the present invention;

[0061] Fig.35 This is the XRD pattern of the powdered product prepared in Comparative Example 5 of the present invention;

[0062] Fig.36 This is a SEM image of the powdered product prepared in Comparative Example 5 of the present invention;

[0063] Fig.37 The XRD pattern of the powdered product prepared in Comparative Example 6 of the present invention;

[0064] Fig.38 This is a SEM image of the powdered product prepared in Comparative Example 6 of the present invention;

[0065] Fig.39 The XRD pattern of the powdered product prepared in Comparative Example 7 of the present invention;

[0066] Fig.40 This is a SEM image of the powdered product prepared in Comparative Example 7 of the present invention;

[0067] Fig.41 This is the XRD pattern of the powdered product prepared in Comparative Example 8 of the present invention;

[0068] Fig.42 This is a SEM image of the powdered product prepared in Comparative Example 8 of the present invention;

[0069] Fig.43 This is the XRD pattern of the powdered product prepared in Comparative Example 9 of the present invention;

[0070] Fig.44 This is a SEM image of the powdered product prepared in Comparative Example 9 of the present invention. DETAILED DESCRIPTION

[0071] 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.

[0072] Example 1

[0073] (1) Add 5 mL of water to 0.007 mol of ferrous oxalate at room temperature and stir magnetically to make it evenly dispersed.

[0074] (2) A 1 mol / L H2O2 solution was prepared with deionized water. 10 mL of the H2O2 solution was taken according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h. Magnetic stirring was performed during the dropping process.

[0075] (3) According to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, 14 mL of KOH solution was mixed with 28 mL of tetradecyltrimethylammonium bromide solution (TTAB) in a volume ratio of 1:2 to obtain a mixed solution, which was slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring was performed during the dropping process, and the mixture was aged for 1 h after the addition was completed.

[0076] (4) The reaction solution obtained in step (3) is centrifuged and washed with deionized water until the pH value of the supernatant is 7, and the precipitate is dried in a forced air drying oven at 80° C. for 2-4 h to obtain γ-Fe2O3 nanoparticles.

[0077] Example 2

[0078] Example 2 is basically the same as Example 1, except that step (3) is as follows: 14 mL of KOH solution and 28 mL of N-methylpyrrolidone solution (NMP) are mixed at a volume ratio of 1:2 at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0079] Example 3

[0080] Example 3 is basically the same as Example 1, except that step (3) is as follows: 14 mL of KOH solution and 28 mL of polyvinyl alcohol solution (PVA) are mixed at a volume ratio of 1:2 at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0081] By comparing the XRD patterns of the products of Examples 1-3 with the standard cards of γ-Fe2O3, it can be seen that, when other conditions remain unchanged, the final products obtained by adding three different additives (TTAB, NMP, PVA) to the KOH solution are all γ-Fe2O3, and the particle size of the products is 20-40nm; by testing the electrochemical properties of the three products, the results show that at a current density of 0.5A / g, the specific capacitances of the three products are 737F / g, 315F / g, and 557F / g, respectively.

[0082] On this basis, in order to further improve the electrochemical properties of γ-Fe2O3, the combination and addition order of the three additives (TTAB, NMP, PVA) were changed while the other experimental parameters and conditions remained unchanged, and the effects of the combination and addition order of different additives on the specific capacitance of the product were explored. For specific operations, please refer to Examples 4-12 and Comparative Examples 1-9.

[0083] Example 4

[0084] Example 4 is basically the same as Example 1, except that step (3) is as follows: 14 mL of KOH solution is mixed with 28 mL of TTAB solution and 28 mL of NMP solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0085] Example 5

[0086] Example 5 is basically the same as Example 1, except that step (3) is as follows: 14 mL of KOH solution is mixed with 28 mL of TTAB solution and 28 mL of PVA solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0087] Example 6

[0088] Example 6 is basically the same as Example 1, except that steps (2) to (3) are:

[0089] (2) A 1 mol / L H2O2 solution was prepared with deionized water. 10 mL of the H2O2 solution was mixed with 28 mL of the TTAB solution and 28 mL of the NMP solution at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol to obtain a mixed solution. The mixed solution was slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h. Magnetic stirring was performed during the dropping process.

[0090] (3) 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 (2). The dropping speed is controlled at 100 mL / h. Magnetic stirring is performed during the dropping process. After the dropping is completed, the mixture is aged for 1 h.

[0091] Example 7

[0092] Example 7 is basically the same as Example 6, except that step (2) is as follows: a 1 mol / L H2O2 solution is prepared with deionized water, 10 mL of the H2O2 solution is mixed with 28 mL of an NMP solution and 28 mL of a PVA solution at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h, with magnetic stirring performed during the dropping process.

[0093] Example 8

[0094] Example 8 is basically the same as Example 6, with the only difference being that step (2) is as follows: a 1 mol / L H2O2 solution is prepared with deionized water, 10 mL of the H2O2 solution is mixed with 28 mL of NMP solution, 28 mL of PVA solution and 28 mL of TTAB solution at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h, with magnetic stirring performed during the dropping process.

[0095] Example 9

[0096] Example 9 is basically the same as Example 1, except that step (2) is as follows: a 1 mol / L H2O2 solution is prepared with deionized water, 10 mL of the H2O2 solution is mixed with 28 mL of the NMP solution at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h, and magnetic stirring is performed during the dropping process.

[0097] Example 10

[0098] Example 10 is basically the same as Example 9, except that step (3) is as follows: 14 mL of KOH solution is mixed with 28 mL of TTAB solution and 28 mL of PVA solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0099] Embodiment 11

[0100] Example 11 is basically the same as Example 6, except that step (3) is as follows: 14 mL of KOH solution and 28 mL of PVA solution are mixed at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0101] Example 12

[0102] Example 12 is basically the same as Example 7, except that step (3) is as follows: 14 mL of KOH solution and 28 mL of TTAB solution are mixed at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0103] Comparative Example 1

[0104] Comparative Example 1 is basically the same as Example 1, except that step (3) is as follows: 14 mL of KOH solution is mixed with 28 mL of TTAB solution, 28 mL of NMP solution and 28 mL of PVA solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring is performed during the dropping process, and the mixture is aged for 1 h after the dropping is completed.

[0105] Comparative Example 2

[0106] Comparative Example 2 is basically the same as Example 6, except that step (2) is as follows: a 1 mol / L H2O2 solution is prepared with deionized water, and 10 mL of the H2O2 solution is mixed with 28 mL of a TTAB solution and 28 mL of a PVA solution at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol to obtain a mixed solution, and the mixed solution is slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h, and magnetic stirring is performed during the dropping process.

[0107] Comparative Example 3

[0108] Comparative Example 3 is substantially the same as Example 9, except that steps (2) to (3) are:

[0109] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Mix 10 mL of the H2O2 solution with 28 mL of the TTAB solution at a molar ratio of 0.01 mol:0.007 mol for H2O2 and FeC2O4·2H2O. Slowly drop the mixed solution into the ferrous oxalate system at a rate of 60 mL / h. Perform magnetic stirring during the dropwise addition.

[0110] (3) 14 mL of KOH solution was mixed with 28 mL of NMP solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, which was slowly added dropwise to the solution obtained in (2) at a dropping rate of 100 mL / h. Magnetic stirring was performed during the dropping process. After the dropping was completed, the mixture was aged for 1 h.

[0111] Comparative Example 4

[0112] Comparative Example 4 is substantially the same as Example 11, except that step (2) is:

[0113] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Mix 10 mL of the H2O2 solution with 28 mL of the TTAB solution at a molar ratio of 0.01 mol:0.007 mol for H2O2 and FeC2O4·2H2O. Slowly drop the mixed solution into the ferrous oxalate system at a rate of 60 mL / h. Perform magnetic stirring during the dropwise addition.

[0114] Comparative Example 5

[0115] Comparative Example 5 is substantially the same as Example 12, except that steps (2) to (3) are:

[0116] (2) Prepare a 1 mol / L H2O2 solution with deionized water, and mix 10 mL of the H2O2 solution with 28 mL of the PVA solution at a molar ratio of 0.01 mol:0.007 mol for H2O2 and FeC2O4·2H2O. Slowly drop the mixed solution into the ferrous oxalate system at a rate of 60 mL / h, with magnetic stirring during the dropwise addition.

[0117] (3) 14 mL of KOH solution was mixed with 28 mL of NMP solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, which was slowly added dropwise to the solution obtained in (2) at a dropping rate of 100 mL / h. Magnetic stirring was performed during the dropping process. After the dropping was completed, the mixture was aged for 1 h.

[0118] Comparative Example 6

[0119] Comparative Example 6 is substantially the same as Example 12, except that step (2) is as follows: a 1 mol / L H2O2 solution is prepared with deionized water, and 10 mL of the H2O2 solution is mixed with 28 mL of the PVA solution at a molar ratio of 0.01 mol:0.007 mol of H2O2 to FeC2O4·2H2O. The mixed solution is slowly added dropwise to the ferrous oxalate system at a dropping speed of 60 mL / h, and magnetic stirring is performed during the dropping process.

[0120] Comparative Example 7

[0121] Comparative Example 7 is substantially the same as Example 11, except that steps (2) to (3) are:

[0122] (2) Prepare a 1 mol / L H2O2 solution with deionized water, and mix 10 mL of the H2O2 solution with 28 mL of the PVA solution at a molar ratio of 0.01 mol:0.007 mol for H2O2 and FeC2O4·2H2O. Slowly drop the mixed solution into the ferrous oxalate system at a rate of 60 mL / h, with magnetic stirring during the dropwise addition.

[0123] (3) According to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, 14 mL of KOH solution was mixed with 28 mL of TTAB solution and 28 mL of NMP solution to obtain a mixed solution, and the mixed solution was slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring was performed during the dropping process. After the dropping was completed, the mixture was aged for 1 h.

[0124] Comparative Example 8

[0125] Comparative Example 8 is substantially the same as Example 12, except that steps (2) to (3) are:

[0126] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Mix 10 mL of the H2O2 solution with 28 mL of the TTAB solution at a molar ratio of 0.01 mol:0.007 mol for H2O2 and FeC2O4·2H2O. Slowly drop the mixed solution into the ferrous oxalate system at a rate of 60 mL / h. Perform magnetic stirring during the dropwise addition.

[0127] (3) 14 mL of KOH solution was mixed with 28 mL of PVA solution and 28 mL of NMP solution at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, which was slowly added dropwise to the solution obtained in (2) at a dropping speed of 100 mL / h. Magnetic stirring was performed during the dropping process. After the dropping was completed, the mixture was aged for 1 h.

[0128] Comparative Example 9

[0129] Comparative Example 9 is substantially the same as Example 10, except that steps (2) to (3) are:

[0130] (2) Prepare a 1 mol / L H2O2 solution with deionized water. Mix the H2O2 solution with 28 mL of PVA solution and 28 mL of TTAB solution at a molar ratio of 0.01 mol:0.007 mol of H2O2 to FeC2O4·2H2O. Slowly drop the mixed solution into the ferrous oxalate system at a rate of 60 mL / h. Perform magnetic stirring during the dropwise addition.

[0131] (3) 14 mL of KOH solution and 28 mL of NMP solution were mixed at a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol to obtain a mixed solution, which was slowly added dropwise to the solution obtained in (2) at a dropping rate of 100 mL / h. Magnetic stirring was performed during the dropping process. After the dropping was completed, the mixture was aged for 1 h.

[0132] The products prepared in Examples 1-12 and Comparative Examples 1-9 were subjected to XRD and SEM image analysis, and the specific capacitance of the products in Examples 1-12 at a current density of 0.5 A / g was tested. The results are shown in Table 1.

[0133] Table 1

[0134]

[0135]

[0136] The XRD and SEM image analysis results of the products are shown in the attached drawings. By detecting the XRD of the products of Examples 1-12, it can be seen that the diffraction peaks thereof correspond to the diffraction peaks of the γ-Fe2O3 standard card one by one, and the final products are all γ-Fe2O3; it can be seen from the SEM image that the average size of the products of Examples 1-12 is 20-40nm, and the morphology is nanoparticles or sheets. By detecting the XRD of the products of Comparative Examples 1-9, it can be seen that the diffraction peaks thereof differ greatly from the diffraction peaks of the γ-Fe2O3 standard card, so the final products are not γ-Fe2O3; it can be seen from the SEM image that most of the products of Comparative Examples 1-9 are in block form, with only a small number of nanoparticles, while in the SEM image of Comparative Example 8, although there are nanoparticles, they are severely piled up, with poor dispersibility, and most of the morphology is block products.

[0137] In addition, by comparing the experimental results of Examples 1-12, it can be seen that different combinations and addition orders of the three additives have a significant impact on the specific capacitance of the final product, specifically:

[0138] It can be seen from Examples 1-5 that when no additives are added to the strong oxidizing solution, that is, x=0, y>0, at most any two additives among TTAB, NMP, and PVA are added to the alkaline solution, and the XRD image of the final prepared product shows γ-Fe2O3; and as in Comparative Example 1, when no additives are added to the strong oxidizing solution, and the three additives of TTAB, NMP, and PVA are added to the alkaline solution at the same time, the XRD image of the final product shows no obvious crystal form.

[0139] It can be seen from Examples 6-12 that when one or more additives are added to the strong oxidizing solution, that is, x>0, y>0 or x>0, y=0, the type of additive must include NMP. Only in this way can the XRD image of the final product show γ-Fe2O3; and as in Comparative Examples 2-9, when there is no NMP in the additives added to the strong oxidizing solution, the XRD images of the final products do not show γ-Fe2O3.

[0140] in addition, Fig.25 This is a constant current charge and discharge (GCD) test of the electrode sheet prepared from the product obtained in Example 11 at a current density of 0.5 A / g. As can be seen from the figure, the GCD curve of Example 11 shows a longer discharge time, indicating that it has a higher specific capacitance. According to its GCD graph, the specific capacitance of Example 11 is calculated to be 1143 F / g. Fig.26 The cyclic voltammetry (CV) curve of the electrode sheet prepared by the product obtained in Example 11 at a scanning rate of 10 mV / s shows a pair of redox peaks, indicating that the product prepared in Example 11 has good pseudocapacitive performance.

[0141] 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 method for preparing a nanomaterial, characterized in that: The following steps are involved: (1) mixing a ferrous salt solution, a strong oxidizing solution and a first additive to obtain a first mixed solution; (2) mixing the alkaline solution and the second additive to obtain a second mixed solution; (3) mixing the first mixed solution and the second mixed solution, stirring and aging them, and performing post-treatment to obtain a nanomaterial; The amount of the first additive added is set to x, and the amount of the second additive added is set to y, wherein the values ​​of x and y satisfy the following conditions: x>0, y>0; or x=0, y>0; or x>0, y=0; When x>0, y>0, the first additive includes at least N-methylpyrrolidone; the second additive is one or both of a quaternary ammonium salt compound and an alcohol compound; When x=0, y>0, the second additive is at least one of a quaternary ammonium salt compound and an alcohol compound, the quaternary ammonium salt compound is tetradecyltrimethylammonium bromide, and the alcohol compound is polyvinyl alcohol; When x>0 and y=0, the first additive includes three types: N-methylpyrrolidone, quaternary ammonium salt compounds, and alcohol compounds.

2. The method for preparing nanomaterials according to claim 1, characterized in that: When x>0, y>0, the first additive further comprises any one of quaternary ammonium salt compounds and alcohol compounds.

3. The method for preparing the nanomaterial according to claim 1 or 2, characterized in that: When x>0, y>0 or x>0, y=0, the quaternary ammonium salt compound includes any one or more of tetradecyltrimethylammonium bromide, dodecyltrimethylsodium bromide, hexadecyltrimethylsodium bromide, dodecyldimethylbenzylammonium chloride, N-methylacetamide, and dimethylacetamide; The alcohol compound includes any one or more of ethanol, ethylene glycol, polyvinyl alcohol, and polyethylene glycol.

4. The method for preparing nanomaterials according to claim 1, characterized in that: The molar ratio of the strong oxidizing solution to the ferrous salt is (0.01-0.03):0.007; The molar ratio of the alkaline solution to the ferrous salt is (0.07-0.014):0.

007.

5. The method for preparing nanomaterials according to claim 1, characterized in that: The volume ratio of the alkaline solution to any additive is 1:(0-2) and is not zero.

6. The method for preparing nanomaterials according to claim 1, characterized in that: The reaction temperature of steps (1)-(2) is 20-80°C.

7. A nanomaterial prepared by the method according to any one of claims 1 to 6.

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

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