Iron trioxide@nickel cobalt hollow cube nanomaterial and preparation method thereof

Abstract

The application belongs to the technical field of nanometer materials, and discloses a ferroferric oxide@nickel cobaltate hollow cube nanometer material and a preparation method thereof. The hollow cube nanometer material takes Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 with a hollow cube structure as a precursor, and obtains alpha-Fe2O3@NiCo2O4 composite material with a hollow cube nanometer structure through calcination. The composite material has a porous structure and a large specific surface area, and has potential application value in the fields of gas sensitive sensors and catalytic activation. The preparation method has the advantages of simple cube forming process, low production cost, simple operation, and the like. The method uses ordinary chemical experimental reagents, is low in price, and can produce a core-shell structure without removing a template.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and particularly relates to a ferroferric oxide@nickel cobaltate hollow cube nanomaterial and a preparation method thereof. BACKGROUND

[0002] Metal organic frameworks (MOFs) have high specific surface area and good pore structure, and can be used as precursors / templates for preparing novel porous metal oxide nanostructures. Through high-temperature calcination, metal ions in MOFs can be converted into metal oxides, and C and other elements (such as N and H) can be oxidized into gas. Therefore, due to the release of gas in the calcination process, it is easy to obtain porous oxides with interconnected pores. However, the morphology is prone to collapse during pyrolysis, resulting in a large amount of agglomeration.

[0003] The most optimal way to prepare hollow structures is still to coat the desired material on a removable template, but the process of obtaining the final hollow structure is usually complex and involves the removal of the template. In the process of removing the template, acid and alkali etching, chemical replacement and the like are involved, which inevitably causes problems such as resource waste and environmental pollution. In addition, the morphology of nanomaterials also has a great influence on the catalytic performance. Due to the inhomogeneous morphology, the specific surface area of the nanomaterials is small, which cannot provide a regular channel for electron transfer, thereby leading to a decrease in catalytic performance.

[0004] Among various metal oxides, the N-type semiconductor alpha-Fe2O3 is a widely used material with good electrical conductivity and chemical stability, and the P-type semiconductor NiCo2O4 is well known for its high electrical conductivity and high theoretical capacitance. However, it is difficult to obtain an alpha-Fe2O3@NiCo2O4 heterostructure with a large specific surface area and stable structure by a simple method in the prior art.

[0005] Therefore, it is of great significance to research a preparation method of a ferroferric oxide@nickel cobaltate hollow cube nanomaterial which is simple to operate and green, so that the ferroferric oxide@nickel cobaltate hollow cube nanomaterial has a large specific surface area and good electrical conductivity and chemical stability. SUMMARY

[0006] Therefore, the present application provides a ferroferric oxide@nickel cobaltate hollow cube nanomaterial and a preparation method thereof, and the purpose is to solve the problems of small specific surface area, inhomogeneous morphology and poor catalytic performance of the ferroferric oxide@nickel cobaltate hollow cube nanomaterial prepared by the existing preparation method.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a preparation method of a ferroferric oxide@nickel cobaltate hollow cube nanomaterial, comprising the following steps:

[0009] (1) sequentially mixing, reacting and aging chelating agent, potassium ferricyanide and hydrochloric acid to prepare granule PB;

[0010] (2) sequentially mixing, reacting and aging granule PB, chelating agent, potassium ferricyanide and hydrochloric acid to prepare granule PBPB;

[0011] (3) sequentially mixing, reacting and aging granule PBPB, chelating agent and hydrochloric acid to prepare hollow PB granule;

[0012] (4) mixing hollow PB granule, surfactant, nickel nitrate hexahydrate with water, adding potassium cobaltocyanide solution to react and then aging to prepare Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2;

[0013] (5) calcining Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 to obtain hollow cubic nanomaterial of iron sesquioxide@nickel cobaltate.

[0014] Preferably, in step (1), the mass-volume ratio of chelating agent, potassium ferricyanide and hydrochloric acid is 2-3 g: 113-133 mg: 40 mL; the mixing time is 20-40 min, the reaction temperature is 75-85℃, the reaction time is 16-20 h, and the aging time is 20-26 h.

[0015] Preferably, in step (2), the mass-volume ratio of granule PB, chelating agent, potassium ferricyanide and hydrochloric acid is 8-12 mg: 2-3 g: 113-132 mg: 40 mL; the mixing time is 20-40 min, the reaction temperature is 75-85℃, the reaction time is 16-20 h, and the aging time is 20-26 h.

[0016] Preferably, in step (3), the mass-volume ratio of granule PBPB, chelating agent and hydrochloric acid is 19-20 mg: 90-100 mg: 20 mL; the mixing time is 100-120 min, the reaction temperature is 130-140℃, the reaction time is 3-3.5 min, and the aging time is 20-26 h.

[0017] Preferably, in step (4), the mass ratio of hollow PB granule, surfactant, nickel nitrate hexahydrate and potassium cobaltocyanide is 8-12: 260-265: 140-145: 130-135; the mixing time is 20-40 min, the reaction temperature is 55-65℃, the reaction time is 18-24 h, and the aging time is 20-26 h.

[0018] Preferably, in the potassium cobaltocyanide solution, the mass-volume ratio of potassium cobaltocyanide and water is 130-135 g: 20 mL.

[0019] Preferably, the calcination temperature in step (5) is 300-500 DEG C, the calcination time is 2-3h, and the temperature rising rate to the calcination temperature is 1-5 DEG C / min.

[0020] Preferably, the chelating agent is polyvinylpyrrolidone, and the surfactant is sodium citrate dihydrate.

[0021] Preferably, the concentration of hydrochloric acid in step (1) is 0.08-0.12 mol / L, the concentration of hydrochloric acid in step (2) is 0.008-0.012 mol / L, and the concentration of hydrochloric acid in step (3) is 0.8-1.2 mol / L.

[0022] The application further provides the Fe2O3@NiCo2O4 hollow cube nanomaterial prepared by the preparation method of the Fe2O3@NiCo2O4 hollow cube nanomaterial.

[0023] Compared with the prior art, the application has the following beneficial effects through the above technical solution.

[0024] 1) The Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 prepared by the application has high thermal stability and chemical stability, uniform particle size, and obvious advantages in constructing spatial morphology compared with other MOFs.

[0025] 2) The Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 prepared by the application is synthesized by a conventional hydrothermal method without an additional etching step, has uniform size and is not prone to agglomeration, and the core-shell structure alpha-Fe2O3@NiCo2O4 composite material synthesized at a high temperature finally well retains the morphology of the precursor, has a porous structure and a large specific surface area, and has potential application value in the fields of gas sensors and catalytic activation.

[0026] 3) The process for synthesizing the core-shell structure alpha-Fe2O3@NiCo2O4 composite material is simple, the production cost is low, common chemical experimental reagents are used, and the operation is simple.

[0027] 4) The application uses hydrochloric acid with different concentrations as a solvent system in a reaction furnace, avoids potential environmental hazards caused by the use of organic solvents, and also avoids the use of high-temperature and high-pressure reaction conditions for a long time. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on the provided drawings.

[0029] Figure 1 SEM images of the PB particles, PBPB particles, hollow PB particles and Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1, wherein a is the PB particles, b is the PBPB particles, c is the hollow PB particles, and d is the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2;

[0030] Figure 2 SEM images of the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1 and the α-Fe2O3@NiCo2O4 composite materials obtained in Examples 1-3, wherein a is the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1, b is the α-Fe2O3@NiCo2O4 composite material obtained in Example 1, c is the α-Fe2O3@NiCo2O4 composite material obtained in Example 2, and d is the α-Fe2O3@NiCo2O4 composite material obtained in Example 3;

[0031] Figure 3 X-ray diffraction pattern of the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1;

[0032] Figure 4 X-ray diffraction patterns of the α-Fe2O3, NiCo2O4 and α-Fe2O3@NiCo2O4 composite material obtained in Example 1;

[0033] Figure 5 Transmission electron microscope images of the α-Fe2O3@NiCo2O4 composite material obtained in Example 1, wherein a is the electron micrograph with a scale of 200 nm, and b is the electron micrograph with a scale of 100 nm;

[0034] Figure 6 Elemental distribution maps of the α-Fe2O3@NiCo2O4 composite material obtained in Example 1, wherein a is the distribution maps of O, Fe, Co and Ni elements, b is the distribution map of Co element, c is the distribution map of O element, d is the distribution map of Fe element, and e is the distribution map of Ni element. DETAILED DESCRIPTION

[0035] The application provides a preparation method of ferroferric oxide@nickel cobaltate hollow cubic nanomaterials.

[0036] (1) sequentially mixing, reacting and aging a chelating agent, potassium ferricyanide and hydrochloric acid to obtain particles PB;

[0037] (2) sequentially mixing, reacting and aging the particles PB, a chelating agent, potassium ferricyanide and hydrochloric acid to obtain particles PBPB;

[0038] (3) sequentially mixing, reacting and aging the particles PBPB, a chelating agent and hydrochloric acid to obtain hollow PB particles;

[0039] (4) mixing the hollow PB particles, a surfactant, nickel nitrate hexahydrate and water, adding a potassium cobalt cyanide solution to react and then aging to obtain Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2;

[0040] (5) calcining the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 to obtain ferroferric oxide@nickel cobaltate hollow cubic nanomaterials.

[0041] In the application, in steps (1)-(4), the rotation speed of the mixing is preferably 400-600 rpm, further preferably 450-550 rpm, and more preferably 480-520 rpm.

[0042] In the application, in steps (1)-(4), the aged solution is sequentially centrifuged, washed and dried after aging, the centrifugation is preferably performed 3-5 times, further preferably 4 times, the rotation speed of the centrifugation is preferably 8000-10000 rpm, further preferably 8500-9500 rpm, and more preferably 8800-9200 rpm, the centrifugation time is preferably 8-10 min, further preferably 9 min, the washing is preferably sequential washing with anhydrous ethanol and water, and the washing is preferably performed three times, the drying temperature is preferably 58-62 DEG C, further preferably 59-61 DEG C, and more preferably 60 DEG C, and the drying time is preferably 880-920 min, further preferably 885-910 min, and more preferably 895-905 min.

[0043] In the present application, the mass-volume ratio of the chelating agent, potassium ferricyanide and hydrochloric acid in step (1) is preferably 2-3 g: 113-133 mg: 40 mL, further preferably 2.2-2.8 g: 120-130 mg: 40 mL, more preferably 2.4-2.6 g: 123-128 mg: 40 mL; the mixing time is preferably 20-40 min, further preferably 22-38 min, more preferably 24-26 min, the reaction temperature is preferably 75-85℃, further preferably 78-82℃, more preferably 79-81℃, the reaction time is preferably 16-20 h, further preferably 17-19 h, more preferably 17.5-18 h, and the aging time is preferably 20-26 h, further preferably 21-25 h, more preferably 22-24 h.

[0044] In the present application, the mass-volume ratio of the chelating agent, potassium ferricyanide and hydrochloric acid in step (1) is preferably 2-3 g: 113-133 mg: 40 mL, further preferably 2.2-2.8 g: 120-130 mg: 40 mL, more preferably 2.4-2.6 g: 123-128 mg: 40 mL; the mixing time is preferably 20-40 min, further preferably 22-38 min, more preferably 24-26 min, the reaction temperature is preferably 75-85℃, further preferably 78-82℃, more preferably 79-81℃, the reaction time is preferably 16-20 h, further preferably 17-19 h, more preferably 17.5-18 h, and the aging time is preferably 20-26 h, further preferably 21-25 h, more preferably 22-24 h.

[0045] In the present application, the mass-volume ratio of the chelating agent, potassium ferricyanide and hydrochloric acid in step (1) is preferably 2-3 g: 113-133 mg: 40 mL, further preferably 2.2-2.8 g: 120-130 mg: 40 mL, more preferably 2.4-2.6 g: 123-128 mg: 40 mL; the mixing time is preferably 20-40 min, further preferably 22-38 min, more preferably 24-26 min, the reaction temperature is preferably 75-85℃, further preferably 78-82℃, more preferably 79-81℃, the reaction time is preferably 16-20 h, further preferably 17-19 h, more preferably 17.5-18 h, and the aging time is preferably 20-26 h, further preferably 21-25 h, more preferably 22-24 h.

[0046] In the present application, the mass ratio of hollow PB particles, surfactant, nickel nitrate hexahydrate and potassium cobalt cyanide in step (4) is preferably 8-12: 260-265: 140-145: 130-135, further preferably 9-11: 261-264: 141-144: 131-134, more preferably 10: 262-263: 142-143: 132-133; the mixing time is preferably 20-40 min, further preferably 25-35 min, more preferably 28-32 min, the reaction temperature is preferably 55-65 DEG C, further preferably 58-62 DEG C, more preferably 59-61 DEG C, the reaction time is preferably 18-24 h, further preferably 19-23 h, more preferably 20-22 h, and the aging time is preferably 20-26 h, further preferably 21-25 h, more preferably 22-24 h.

[0047] In the present application, the mass-volume ratio of potassium cobalt cyanide to water in the potassium cobalt cyanide solution is preferably 130-135 g: 20 mL, further preferably 131-134 g: 20 mL, more preferably 132-133 g: 20 mL.

[0048] In the present application, the calcination temperature in step (5) is preferably 300-500 DEG C, further preferably 350-450 DEG C, more preferably 380-420 DEG C, the calcination time is preferably 2-3 h, further preferably 2.2-2.8 h, more preferably 2.4-2.6 h, and the heating rate to the calcination temperature is preferably 1-5 DEG C / min, further preferably 2-4 DEG C / min, more preferably 3 DEG C / min.

[0049] In the present application, the calcination temperature plays a crucial role, as the temperature gradient between the surface and the interior of the precursor increases with the increase of the calcination temperature, so that the diffusion rates of the internal and external substances are different, and when the surface has completed crystallization, the internal substances preferentially diffuse to the surface for crystallization, thereby forming a hollow structure, but too high a temperature will cause the collapse of the structure. Therefore, considering the influence of the calcination temperature on the morphology and the crystallization level of the sample, when the calcination temperature is 300-500 DEG C, the composite material obtained can not only retain a good morphology, but also has good crystallinity.

[0050] In the present application, the chelating agent is preferably polyvinylpyrrolidone, and the surfactant is preferably sodium citrate dihydrate.

[0051] In the present application, the sodium citrate dihydrate as a surfactant plays a role in stabilizing the morphology size, controlling the diffusion rate of Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 on the template, so that the α-Fe2O3@NiCo2O4 composite material after calcination retains the morphology of the precursor, and the morphology is regular, porous, and has a large specific surface area, forming a unique core-shell structure.

[0052] In the application, the sodium citrate dihydrate is used in combination with hydrochloric acid, so that the prepared Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 is not easy to agglomerate.

[0053] In the application, the concentration of the hydrochloric acid solution is the key to ensure high yield; the concentration of the hydrochloric acid in step (1) is preferably 0.08-0.12 mol / L, further preferably 0.09-0.11 mol / L, and more preferably 0.1 mol / L; the concentration of the hydrochloric acid in step (2) is preferably 0.008-0.012 mol / L, further preferably 0.009-0.011 mol / L, and more preferably 0.01 mol / L; and the concentration of the hydrochloric acid in step (3) is preferably 0.8-1.2 mol / L, further preferably 0.9-1.1 mol / L, and more preferably 1 mol / L.

[0054] In the application, the preparation method uses Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 with a hollow cubic structure as a precursor, and obtains α-Fe2O3@NiCo2O4 composite material with a hollow cubic nanostructure through simple calcination.

[0055] The application further provides the Fe2O3@NiCo2O4 hollow cubic nanomaterial prepared by the preparation method of the Fe2O3@NiCo2O4 hollow cubic nanomaterial.

[0056] The technical solutions provided by the application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the application.

[0057] Example 1

[0058] 3 g of polyvinylpyrrolidone and 113 mg of potassium ferricyanide were placed in 40 mL of hydrochloric acid with a concentration of 0.1 mol / L, mixed and stirred at a speed of 400 rpm for 30 min, and then reacted at 80℃ for 20 h. The solution after reaction was aged for 24 h, and finally the aged solution was centrifuged at a speed of 8000 rpm for 10 min, and the centrifugation was repeated five times. The precipitate obtained by centrifugation was sequentially washed with anhydrous ethanol and water for three times, and the washed product was dried at 60℃ for 15 h to obtain granular PB.

[0059] Take 10 mg of granular PB, 3 g of polyvinylpyrrolidone and 113 mg of potassium ferricyanide into 40 mL of 0.01 mol / L hydrochloric acid, mix and stir at a speed of 400 rpm for 30 min, then react at 80℃ for 20 h, let the solution stand for 24 h, finally centrifuge the solution at a speed of 8000 rpm for 10 min, repeat the centrifugation for five times, wash the precipitate obtained by centrifugation with anhydrous ethanol and water in turn, the washing times are three times, dry the washed product at 60℃ for 15 h, and granular PBPB is prepared.

[0060] Take 20 mg of granular PBPB and 100 mg of polyvinylpyrrolidone into 20 mL of 1 mol / L hydrochloric acid, mix and stir at a speed of 400 rpm for 120 min, then react at 135℃ for 3 h, let the solution stand for 24 h, finally centrifuge the solution at a speed of 8000 rpm for 10 min, repeat the centrifugation for five times, wash the precipitate obtained by centrifugation with anhydrous ethanol and water in turn, the washing times are three times, dry the washed product at 60℃ for 15 h, and hollow PB particles are prepared.

[0061] Take 10 mg of hollow PB particles, 264.7 mg of sodium citrate dihydrate and 144.3 mg of nickel nitrate hexahydrate into 20 mL of water, mix and stir at a speed of 400 rpm for 20 min to obtain a mixed solution A; take 133 mg of potassium cobalticyanide into 20 mL of water, mix and stir at a speed of 400 rpm for 20 min to obtain a mixed solution B; add the mixed solution B to the mixed solution A with a stirring speed of 500 rpm, and stir at the same speed for 10 min, then react at 60℃ for 24 h, let the solution stand for 24 h, finally centrifuge the solution at a speed of 8000 rpm for 10 min, repeat the centrifugation for five times, wash the precipitate obtained by centrifugation with anhydrous ethanol and water in turn, the washing times are three times, dry the washed product at 60℃ for 15 h, and Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 particles are prepared.

[0062] The Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 particles are heated to 500℃ at a heating rate of 1℃ / min, and calcined at 500℃ for 3 h to obtain α-Fe2O3@NiCo2O4 composite material.

[0063] Example 2

[0064] The calcination temperature of the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 particles in Example 1 is changed to 400℃, and the others are the same as in Example 1.

[0065] Example 3

[0066] The calcination temperature of the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2particles in Example 1 was changed to 300°C, and the other conditions were the same as in Example 1.

[0067] Example 4

[0068] 2.6 g of polyvinylpyrrolidone and 130 mg of potassium ferricyanide were placed in 40 mL of 0.1 mol / L hydrochloric acid, mixed and stirred at a rotation speed of 600 rpm for 40 min, and then reacted at 80°C for 19 h. The solution after the reaction was aged for 24 h, and finally the aged solution was centrifuged at a rotation speed of 8000 rpm for 8 min, and the centrifugation was repeated four times. The precipitate obtained by centrifugation was sequentially washed with anhydrous ethanol and water, and the washing was performed three times. The washed product was dried at 60°C for 15 h, and particles PB were prepared.

[0069] 10 mg of particles PB, 2.8 g of polyvinylpyrrolidone, and 130 mg of potassium ferricyanide were placed in 40 mL of 0.01 mol / L hydrochloric acid, mixed and stirred at a rotation speed of 400 rpm for 40 min, and then reacted at 80°C for 19 h. The solution after the reaction was aged for 24 h, and finally the aged solution was centrifuged at a rotation speed of 10000 rpm for 8 min, and the centrifugation was repeated four times. The precipitate obtained by centrifugation was sequentially washed with anhydrous ethanol and water, and the washing was performed three times. The washed product was dried at 60°C for 15 h, and particles PBPB were prepared.

[0070] 19 mg of particles PBPB and 98 mg of polyvinylpyrrolidone were placed in 20 mL of 1 mol / L hydrochloric acid, mixed and stirred at a rotation speed of 450 rpm for 110 min, and then reacted at 135°C for 3 h. The solution after the reaction was aged for 24 h, and finally the aged solution was centrifuged at a rotation speed of 8800 rpm for 8 min, and the centrifugation was repeated four times. The precipitate obtained by centrifugation was sequentially washed with anhydrous ethanol and water, and the washing was performed three times. The washed product was dried at 60°C for 15 h, and hollow PB particles were prepared.

[0071] Take 10 mg of hollow PB particles, 263 mg of sodium citrate dihydrate, 142 mg of nickel nitrate hexahydrate into 20 mL of water, and mix and stir at a speed of 500 rpm for 20 min to obtain a mixed solution A; take 133 mg of potassium cobalticyanide into 20 mL of water, and mix and stir at a speed of 400 rpm for 20 min to obtain a mixed solution B; add the mixed solution B into the mixed solution A at a speed of 500 rpm, and stir at the same speed for 10 min, then react at 58℃ for 24 h, age the solution after reaction for 24 h, finally centrifuge the aged solution at a speed of 8500 rpm for 8 min, repeat the centrifugation for four times, wash the obtained precipitate with anhydrous ethanol and water in sequence, and repeat the washing for three times, dry the washed product at 60℃ for 15 h, and obtain Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2particles.

[0072] Take the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2particles, and heat them to 450℃ at a heating rate of 5℃ / min, and calcine at 450℃ for 2 h, to obtain α-Fe2O3@NiCo2O4 composite material.

[0073] The SEM image of the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1 is shown in Figure 1 , wherein a is PB particles, b is PBPB particles, c is hollow PB particles, and d is Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2. Figure 1 It can be seen that the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1 has a smooth surface and a regular cubic structure, and the particles are uniformly distributed and have a uniform particle size of 300-500 nm.

[0074] The SEM images of the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1 and the α-Fe2O3@NiCo2O4 composite material obtained in Examples 1-3 are shown in Figure 2 . It can be seen that Figure 2As can be seen, a) is the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1, b) is the α-Fe2O3@NiCo2O4 composite material obtained in Example 1, c) is the α-Fe2O3@NiCo2O4 composite material obtained in Example 2, and d) is the α-Fe2O3@NiCo2O4 composite material obtained in Example 3. Figure (b) shows that the obtained composite material has a good morphology, and due to the high calcination temperature, the surface pore size of the obtained material is significantly larger. Figure (c) shows that the obtained composite material maintains a similar size and shape to the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 precursor. However, compared with the Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 precursor, the surface of these cubic structures is relatively rough and a large amount of C and H elements are lost during calcination, resulting in a slightly smaller product particle size than the precursor. Figure (d) shows that the morphology of the obtained composite material is well maintained.

[0075] The X-ray diffraction pattern of Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2 obtained in Example 1 is as follows: Figure 3 As shown. By Figure 3 As can be seen, by comparing the main peak intensities of the X-ray diffraction pattern with that of the standard Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2, the corresponding XRD pattern matches well with the pattern of the standard Fe4[Fe(CN)6]3@Ni3[(CN)Co6]2, indicating a high-purity phase structure.

[0076] The X-ray diffraction patterns of the α-Fe₂O₃, NiCo₂O₄ and α-Fe₂O₃@NiCo₂O₄ composite materials obtained in Example 1 are as follows: Figure 4 As shown. By Figure 4 As can be seen, the X-ray diffraction pattern of Example 1 corresponds to the standard PDF cards (α-Fe2O3: JCPDS#40-1139) and (NiCo2O4: JCPDS#20-0781), and is consistent with the structure obtained from the analysis of transmission electron microscopy data, further indicating that the prepared composite material is composed of α-Fe2O3 and NiCo2O4 with good crystallinity.

[0077] The transmission electron microscope image of the α-Fe2O3@NiCo2O4 composite material obtained in Example 1 is shown below. Figure 5 As shown. Where a is an electron micrograph with a scale bar of 200 nm, and b is an electron micrograph with a scale bar of 100 nm, from... Figure 5 As can be seen, the α-Fe2O3@NiCo2O4 composite material obtained in Example 1 is a hollow structure composed of stacked nanoparticles, and the distribution is relatively uniform.

[0078] The element distribution map of the α-Fe2O3@NiCo2O4 composite material obtained in Example 1 is shown in Figure 2. Figure 6 Wherein a is the distribution map of O, Fe, Co and Ni elements in the composite material, b is the distribution map of Co element in the composite material, c is the distribution map of O element in the composite material, d is the distribution map of Fe element in the composite material, and e is the distribution map of Ni element in the composite material. Figure 6 It can be seen that the α-Fe2O3@NiCo2O4 composite material has an element distribution of obvious hollow structure, and more intuitively indicates that the synthesized sample is a hollow cubic structure of NiCo2O4 nanoparticles coated α-Fe2O3 nanoparticles.

[0079] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A preparation method of ferroferric oxide@nickel cobalt hollow cube nanomaterials, characterized in that, It comprises the following steps: (1) sequentially mixing, reacting and aging the chelating agent, potassium ferricyanide and hydrochloric acid to prepare granular PB; (2) sequentially mixing, reacting and aging the granular PB, chelating agent, potassium ferricyanide and hydrochloric acid to prepare granular PBPB; (3) sequentially mixing, reacting and aging the granular PBPB, chelating agent and hydrochloric acid to prepare hollow PB granules; (4) mixing the hollow PB granules, surfactant, nickel nitrate hexahydrate and water, adding a potassium cobalticyanide solution to react and then aging to prepare Fe4[Fe(CN)6]3@Ni3[Co(CN)6]2; (5) calcining Fe4[Fe(CN)6]3@Ni3[Co(CN)6]2 to obtain the hollow cubic nanomaterial of iron sesquioxide@nickel cobaltate; In the step (3), the reaction time is 3-3.5 h; In the step (5), the calcination time is 2-3 h; In the step (4), the mass ratio of the hollow PB granules, surfactant, nickel nitrate hexahydrate and potassium cobalticyanide is 8-12:260-265:140-145:130-135; the mixing time is 20-40 min, the reaction temperature is 55-65℃, the reaction time is 18-24 h, and the aging time is 20-26 h; In the step (5), the calcination temperature is 300-500℃, and the temperature rising rate to the calcination temperature is 1-5℃ / min; In the step (1), the concentration of the hydrochloric acid is 0.08-0.12 mol / L, in the step (2), the concentration of the hydrochloric acid is 0.008-0.012 mol / L, and in the step (3), the concentration of the hydrochloric acid is 0.8-1.2 mol / L.

2. The method for preparing ferric oxide@nickel cobalt oxide hollow cubic nanomaterials according to claim 1, characterized in that, In the step (1), the mass-volume ratio of the chelating agent, potassium ferricyanide and hydrochloric acid is 2-3 g:113-133 mg:40 mL; the mixing time is 20-40 min, the reaction temperature is 75-85℃, the reaction time is 16-20 h, and the aging time is 20-26 h. 3.The method of claim 1, wherein the method further comprises the step of: adding a cobalt salt to the solution of the step (a). In the step (2), the mass-volume ratio of the granular PB, chelating agent, potassium ferricyanide and hydrochloric acid is 8-12 mg:2-3 g:113-132 mg:40 mL; the mixing time is 20-40 min, the reaction temperature is 75-85℃, the reaction time is 16-20 h, and the aging time is 20-26 h. 4.The method of claim 1, wherein the method further comprises the step of: adding a cobalt salt to the solution of the step (a). In the step (3), the mass-volume ratio of the granular PBPB, chelating agent and hydrochloric acid is 19-20 mg:90-100 mg:20 mL; the mixing time is 100-120 min, the reaction temperature is 130-140℃, and the aging time is 20-26 h. 5.The method of claim 1, wherein the method further comprises, after the step of preparing the iron oxide@nickel cobalt hollow cube nanomaterial, the step of: In the potassium cobalticyanide solution, the mass-volume ratio of potassium cobalticyanide to water is 130-135 mg:20 mL. ​ 6.The preparation method of the ferric oxide@nickel cobalt hollow cube nanomaterial according to any one of claims 1-5, characterized in that, The chelating agent is polyvinylpyrrolidone, and the surfactant is sodium citrate dihydrate.

7. The hollow cubic nanomaterial of iron sesquioxide@nickel cobaltate prepared by the preparation method of claim 1-6.

Images