Hollow cobalt oxide and a method for synthesizing the same

Abstract

The application provides a kind of hollow cobalt oxide and its synthesis method, the synthesis method of the hollow cobalt oxide includes the following steps: (1) mixing cobalt source, carbon material, alcohol solvent, ammonia and water uniformly, then separate, wash and dry treatment;(2) the material obtained in step (1), nano iron oxide, saccharide compound and water are mixed uniformly, evaporate water after roasting treatment, then contact with acid for acid treatment, finally separate, dry;(3) the material obtained in step (2), amine compound and water are mixed for hydrothermal treatment, then separate, dry, calcine to obtain hollow cobalt oxide.The synthesized hollow cobalt oxide has complete crystal structure, and has a hollow shell structure.

Description

Technical Field

[0001] This invention belongs to the field of inorganic synthesis and relates to a method for synthesizing inorganic oxides, specifically to a hollow cobalt oxide and its synthesis method. Background Technology

[0002] Cobalt oxide is an important inorganic compound with a variety of industrial and scientific applications. It can be used as a magnetic material, battery material, catalyst, magnetic pigment, gas sensor, etc., and has broad application prospects.

[0003] CN114130394A discloses a cobalt oxide hollow polyhedral catalyst, its preparation method, and its application. The preparation method includes: A) preparing ZIF-67 material; B) etching the ZIF-67 material with cobalt salt ethanol solutions of different concentrations under ultrasonic conditions; C) calcining the etched catalyst material to obtain a hollow polyhedral cobalt oxide catalyst with a mesoporous structure of 2-5 nm.

[0004] CN113233514A discloses a method for preparing vesicular phosphate ion-functionalized cobalt oxide nanomaterials and their applications. The preparation method involves first adding a deionized aqueous solution containing an organic ligand to a deionized aqueous solution containing a surfactant, and then adding a deionized aqueous solution containing a cobalt salt to obtain a hollow spherical cobalt complex. The hollow spherical cobalt complex is then placed in a tube furnace and calcined in an air atmosphere to obtain a hollow spherical cobalt oxide. The hollow spherical cobalt oxide and sodium dihydrogen phosphate are then placed in two separate ceramic boats and calcined in a tube furnace under a nitrogen atmosphere.

[0005] CN106549153A discloses a hollow hexagonal cobalt hydroxyoxide nanomaterial and its preparation method. The specific process of the preparation method involves continuously introducing an aqueous solution of cobalt nitrate and an aqueous solution of ammonia into a microchannel reactor to carry out a precipitation reaction. After the reaction, the slurry flows into a stirred tank reactor and is aged under certain temperature and stirring conditions. After a certain time, a strong alkaline solution is added, and aging continues. After aging, the material is filtered, washed, and dried to obtain a nanoscale hollow hexagonal cobalt hydroxyoxide material.

[0006] CN107445213A discloses a hollow six-membered cyclic cobalt hydroxyl oxide nanomaterial and its preparation method. The specific preparation process is as follows: (1) Cobalt nitrate aqueous solution and strong alkali aqueous solution are added dropwise to a three-necked flask in parallel flow and reacted for a certain time under an inert atmosphere and stirring; (2) The protective gas is removed, a certain amount of strong oxidant is added, and aging is continued; (3) After aging, the resulting suspension is filtered, washed, and dried to obtain a hollow six-membered cyclic cobalt hydroxyl oxide nanomaterial. This invention has the advantages of simple process flow, mild reaction conditions, and easy large-scale preparation. The obtained product has a narrow particle size distribution, controllable morphology, and good reproducibility, and is expected to be applied in the fields of supercapacitors, lithium-ion batteries, and catalysis.

[0007] CN112635755A discloses a method for preparing hollow Co3O4 nanospheres by in-situ growth of surface coordination polymerization. The preparation method involves dissolving inorganic cobalt salt, sodium citrate, and urea in pure water, heating and reacting, collecting the product after the reaction, washing, and drying to obtain precursor A; dispersing precursor A and 2-methylimidazole in a thickener, then adding pure water and stirring to react, collecting the product after the reaction, washing, and drying to obtain precursor B; and calcining precursor B in air to obtain hollow Co3O4 nanospheres. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a hollow cobalt oxide and its synthesis method. The synthesized hollow cobalt oxide has a complete crystal structure and a hollow shell structure.

[0009] The first aspect of this invention provides a method for synthesizing hollow cobalt oxide, the method comprising the following steps:

[0010] (1) Mix cobalt source, carbon material, alcohol solvent, ammonia and water, and then separate, wash and dry them;

[0011] (2) The material obtained in step (1), nano iron oxide, sugar compound and water are mixed evenly, the water is evaporated and then roasted, then contacted with acid for acid treatment, and finally separated and dried.

[0012] (3) The material obtained in step (2), amine compounds and water are mixed and subjected to hydrothermal treatment, and then separated, dried and calcined to obtain hollow cobalt oxide.

[0013] Furthermore, as some specific implementations, the cobalt source in step (1) is a cobalt salt, which can specifically be at least one of cobalt nitrate, cobalt chloride, and cobalt isopropoxide.

[0014] Furthermore, as some specific embodiments, the alcohol solvent in step (1) is an alcohol with 1-4 carbon atoms, and more preferably it can be at least one of ethanol, propanol, and butanol.

[0015] Furthermore, as some specific implementations, the carbon material in step (1) has a particle size of 1 to 6 μm and a spherical or near-spherical shape.

[0016] Furthermore, as some specific implementation methods, the mass ratio of cobalt source, carbon material, water, alcohol solvent and ammonia in step (1) is 0.1-1.1:1:80-220:80-220:0.8-6, preferably 0.2-1:1:100-200:100-200:1-5.

[0017] Furthermore, as some specific implementation methods, there are no special restrictions on the mixing process of cobalt source, carbon material, water, alcohol solvent and ammonia in step (1). For example, all materials can be prepared and added together for mixing, or the carbon material, water, alcohol solvent and ammonia can be mixed evenly first, and then the cobalt source can be added to the above mixture. Furthermore, the cobalt source can be added to the above mixture slowly, such as by dripping.

[0018] Furthermore, as some specific implementation methods, the separation in step (1) can be carried out by any of the existing solid-liquid two-phase separation methods in the art, such as filtration, which usually includes multiple filtrations, generally 1 to 10 times.

[0019] Furthermore, as some specific implementation methods, the washing in step (1) is a series of water washes, generally until the filtrate is neutral.

[0020] Furthermore, as some specific implementation methods, the drying temperature in step (1) is 100-150°C and the drying time is 1-20h.

[0021] Furthermore, as some specific implementations, the carbohydrate compound in step (2) can be at least one of sucrose, glucose, fructose, maltose, and lactose, preferably at least one of sucrose and glucose.

[0022] Furthermore, as some specific implementation methods, the particle size of the nano-iron oxide in step (2) is 2 to 15 nm, preferably 5 to 10 nm.

[0023] Furthermore, as some specific implementation methods, the mass ratio of the material obtained in step (1) in step (2), the carbohydrate compound, the nano iron oxide, and the water is 1:1 to 7.5: 0.08 to 0.6: 80 to 310, preferably 1:2 to 7: 0.1 to 0.5: 100 to 300.

[0024] Furthermore, as some specific implementation methods, the evaporation temperature of the water evaporated in step (2) is 80 to 160°C, preferably 100 to 150°C.

[0025] Furthermore, as some specific implementation methods, the calcination treatment in step (2) is carried out under an inert atmosphere, the calcination temperature is 200-400℃, preferably 300-350℃, and the calcination time is 1-12h, preferably 2-10h. The inert atmosphere can be at least one of nitrogen, argon, helium, etc., preferably nitrogen. The calcination treatment under the inert atmosphere can dehydrate and dehydrogenate sugars into carbonaceous materials, and encapsulate cobalt-carbon core-shell materials within them.

[0026] Furthermore, as some specific implementation methods, the acid treatment in step (2) involves mixing the calcined solid material with an acid solution (the mass ratio of the calcined solid material to the acid solution is 1:80-210, preferably 1:100-200), and treating it at 10-40°C for 5-35 minutes, preferably 10-30 minutes. The purpose of acid treatment is to remove iron oxide from the solid material, thereby leaving mesoporous channels in the carbon material, which facilitates the passage of raw materials through the carbon layer to participate in the chemical reaction in subsequent reaction processes. The acid used in the acid treatment is an inorganic acid, specifically at least one of hydrochloric acid, nitric acid, and sulfuric acid. The mass concentration of the acid solution is 0.5%-5.5%, preferably 1.0%-5.0%.

[0027] Furthermore, as some specific implementation methods, the separation in step (2) can be carried out by any of the existing solid-liquid two-phase separation methods in the art, such as filtration, which usually includes multiple filtrations, generally 1 to 10 times.

[0028] Furthermore, as some specific implementation methods, the drying temperature in step (2) is 100-150°C and the drying time is 1-20h.

[0029] Furthermore, as some specific implementation methods, the amine compound in step (3) is at least one of n-butylamine, ethylenediamine, and hexamethylenediamine.

[0030] Furthermore, as some specific implementation methods, the mass ratio of the material obtained in step (2) in step (3), the amine compound, and the water is 1 to 12: 1 to 12: 100, preferably 2 to 10: 2 to 10: 100.

[0031] Furthermore, as some specific implementation methods, the hydrothermal treatment temperature in step (3) is 90-210°C, preferably 100-200°C; the hydrothermal treatment time is 8-21h, preferably 10-20h.

[0032] Furthermore, as some specific implementation methods, the separation in step (3) can be carried out by any of the existing solid-liquid two-phase separation methods in the art, such as filtration, which usually includes multiple filtrations, generally 1 to 10 times.

[0033] Furthermore, as some specific implementation methods, the drying temperature in step (3) is 100-150°C and the drying time is 1-20h.

[0034] Furthermore, as some specific implementation methods, the calcination in step (3) is carried out in an oxygen-containing atmosphere, wherein the volume content of oxygen in the oxygen-containing atmosphere is 20% to 100%; the oxygen-containing atmosphere can be at least one of oxygen, air, or a mixture of oxygen and other inert atmospheres; the inert atmosphere can be nitrogen and / or an inert gas. The calcination temperature in step (3) is 400 to 600°C, and the calcination time is 1 to 10 hours.

[0035] A second aspect of the present invention provides hollow cobalt oxide obtained by the above-described synthesis method, wherein the hollow cobalt oxide has an irregular spherical or block shape with a cavity in the center, and the particle size of the hollow cobalt oxide is 1 to 5 μm; wherein the shell thickness is 200 to 1200 nm.

[0036] Furthermore, the specific surface area of ​​the hollow cobalt oxide is 50–120 m². 2 / g.

[0037] The hollow cobalt oxide material provided by this invention can be used as a magnetic material, battery material, catalyst, magnetic pigment, gas sensor, etc.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] This invention provides a novel preparation route for hollow shell cobalt oxide. Traditional hollow materials use polystyrene spheres as templates, then the shell material is applied to the outer surface of the polystyrene spheres, and finally the polystyrene spheres are removed, leaving a hollow cobalt oxide shell. This route uses relatively expensive polystyrene spheres, resulting in high preparation costs. Furthermore, a significant amount of cobalt material cannot effectively cover the outer surface of the polystyrene spheres, failing to ultimately form a hollow shell, leading to low production efficiency.

[0040] This invention first prepares a cobalt-carbon core-shell material to form a cobalt oxide shell; then, a carbon layer is coated onto this material to form a more complex hierarchical structure; finally, the material is treated in a hydrothermal environment to improve the physicochemical properties of the cobalt oxide and enhance the mechanical strength of the hollow cobalt oxide. The cobalt oxide shell is confined between the two carbon materials. Due to this spatial constraint, the cobalt oxide can resist the violent impact of water during the intense hydrothermal reaction, preventing damage to the cobalt oxide shell. Therefore, high-quality hollow cobalt oxide can be prepared. Attached Figure Description

[0041] Figure 1 The image shown is a scanning electron microscope image of the sample obtained in Example 1.

[0042] Figure 2 The image shown is a scanning electron microscope image of the sample obtained in Example 1.

[0043] Figure 3 Scanning electron microscope images of the sample obtained for Comparative Example 1. Detailed Implementation

[0044] The technical solutions and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments.

[0045] The pore structure of the material of this invention was characterized by N2 adsorption-desorption using a physical adsorption instrument from Micron Technology, USA. Before measurement, the sample was vacuum-treated at 300℃ for at least 4 hours. Parameters such as specific surface area were calculated using the BET formula.

[0046] The microcrystalline morphology of the material of this invention was characterized by scanning electron microscopy (SEM) using a JSM-6 301F scanning electron microscope (equipped with an Oxford EDS) from Nippon Electronics Corporation. The operating voltage was 20 kV, the working distance was 15 mm, and the resolution was 1.5 nm.

[0047] The crystal phase structure and crystallinity of the material of this invention were characterized by X-ray diffraction using a Rigaku D / max2500 X-ray diffractometer (Japan), with a Cu target, Kα radiation source, graphite monochromator, tube voltage of 40kV, tube current of 80mA, scanning range of 5° to 40°, step size of 0.1°, and scanning speed of 1° / min.

[0048] All chemical reagents used in this article are analytical reagents and can be obtained by purchasing commercially available products.

[0049] In the context of this specification, the carbon material in step (1) is prepared by the following method: a carbon source, formaldehyde, and water are mixed evenly and then treated, followed by separation, washing, drying, and heat treatment to obtain the carbon material. The carbon source is at least one of glucose and sucrose, and the mass ratio of the carbon source, formaldehyde, and water is 1:0.2–1.5:8–50, preferably 1:0.3–1.3:10–40. The treatment temperature is 150–210°C, preferably 160–200°C; the treatment time is 4–22 h, preferably 5–20 h. Separation can be performed by filtration, typically involving multiple filtrations, generally 1–10 times. The heat treatment is carried out under an inert atmosphere, with a heat treatment temperature of 700–1100°C, preferably 800–1000°C; and a heat treatment time of 3–9 h, preferably 4–8 h. The inert atmosphere can be nitrogen and / or an inert gas.

[0050] Example 1

[0051] (1) Mix glucose, formaldehyde and distilled water and stir for 1 hour, wherein the mass ratio of glucose, formaldehyde and water is 1:1.2:38; then put it into a reaction vessel and treat it at 175°C for 11 hours; then wash the solid product with distilled water to neutralize it, dry it at 120°C for 12 hours, and then treat it at 800°C for 5 hours under nitrogen atmosphere to obtain carbon material.

[0052] (2) Mix the carbon material, water, ethanol and ammonia obtained in step (1) evenly, and then introduce cobalt nitrate, wherein the mass ratio of cobalt nitrate, carbon material, water, ethanol and ammonia obtained in step (1) is 0.53:1:130:150:3.5. Then wash the solid product with distilled water until neutral, and then dry it at 120°C for 12 hours.

[0053] (3) Mix the material obtained in step (2), water, nano-iron oxide particles and glucose, wherein the mass ratio of the material obtained in step (2), glucose, nano-iron oxide and water is 1:3.3:0.31:135. Then evaporate the water at 100℃; then treat at 310℃ for 5h in a nitrogen atmosphere; then mix with hydrochloric acid solution (2wt% hydrochloric acid, the mass ratio of material and acid solution after calcination is 1:120) for 20min; then filter the obtained sample 4 times, and then place it in an oven to dry at 110℃ for 12h.

[0054] (4) The material obtained in step (3), ethylenediamine and water are mixed (the mass ratio of the material obtained in step (3), ethylenediamine and water is 6.6:7.5:100) and then loaded into the reactor and treated at 126°C for 12 hours; the obtained sample is then filtered 3 times, and then placed in an oven to dry at 110°C for 12 hours, and finally calcined in air at 500°C for 7 hours. The obtained sample is numbered A1.

[0055] Figure 1 These are scanning electron microscope images of the prepared samples, produced by... Figure 1 It can be seen that the obtained sample is an irregular hollow sphere. Figure 2 These are scanning electron microscope images of the prepared sample after grinding. Figure 2 It can be seen that after grinding, the sample structure is destroyed, producing spherical shell fragments.

[0056] Example 2

[0057] (1) Mix glucose, formaldehyde and distilled water and stir for 1 hour, wherein the mass ratio of glucose, formaldehyde and water is 1:0.3:10; then place it in a reaction vessel and treat it at 160°C for 20 hours; then wash the solid product with distilled water until neutral, dry it at 120°C for 12 hours, and then treat it at 800°C in a nitrogen atmosphere for 8 hours to obtain carbon material.

[0058] (2) Mix the carbon material, water, ethanol and ammonia obtained in step (1) evenly, and then introduce cobalt nitrate, wherein the mass ratio of cobalt nitrate, carbon material, water, ethanol and ammonia obtained in step (1) is 0.2:1:200:200:5. Then wash the solid product with distilled water until neutral, and then dry it at 120°C for 12 hours.

[0059] (3) Mix the material obtained in step (2), water, nano-iron oxide particles, and glucose, wherein the mass ratio of the material obtained in step (2), glucose, nano-iron oxide, and water is 1:2:0.5:100. Then evaporate the water at 100℃; then treat at 300℃ for 2 hours in a nitrogen atmosphere; then mix with hydrochloric acid (2wt% hydrochloric acid, the mass ratio of the material to the acid solution after calcination is 1:125) for 20 minutes; then filter the resulting sample multiple times, and then dry it in an oven at 110℃ for 12 hours.

[0060] (4) Mix the material obtained in step (3), n-butylamine, and water, wherein the mass ratio of the material obtained in step (3), n-butylamine, and water is 2:2:100. Put the mixture into a reactor and treat it at 100°C for 10 hours; then filter the resulting sample multiple times, and then dry it in an oven at 110°C for 12 hours. Finally, calcine it in air at 600°C for 7 hours. The resulting sample is numbered A2.

[0061] Example 3

[0062] (1) Mix sucrose, formaldehyde and distilled water and stir for 1 hour. The mass ratio of sucrose, formaldehyde and water is 1:1.3:40. Then put it into a reaction vessel and treat it at 200°C for 5 hours. Then wash the solid product with distilled water to neutralize it, dry it at 120°C for 12 hours, and then treat it at 1000°C in a nitrogen atmosphere for 4 hours to obtain carbon material.

[0063] (2) Mix the carbon material obtained in step (1), water, ethanol, and ammonia evenly, and then introduce cobalt nitrate, wherein the mass ratio of cobalt nitrate, carbon material obtained in step (1), water, ethanol, and ammonia is 1:1:100:100:1. Then wash the solid product with distilled water until neutral and dry it at 120°C for 12 hours.

[0064] (3) Mix the material obtained in step (2), water, nano-iron oxide particles, and glucose, wherein the mass ratio of the material obtained in step (2), glucose, nano-iron oxide, and water is 1:7:0.1:300. Then evaporate the water at 100℃; then treat at 350℃ for 10h in a nitrogen atmosphere; then mix with hydrochloric acid (2wt% hydrochloric acid, the mass ratio of the material to the acid solution after calcination is 1:190) for 20min; then filter the resulting sample 4 times, and then dry it in an oven at 110℃ for 12h.

[0065] (4) Mix the material obtained in step (3), n-butylamine, and water, wherein the mass ratio of the material obtained in step (3), n-butylamine, and water is 10:10:100. Put the mixture into a reactor and treat it at 200℃ for 20h; then filter the resulting sample 4 times, then place it in an oven to dry at 110℃ for 12h, and finally calcine it in air at 520℃ for 7h. The resulting sample is numbered A3.

[0066] Example 4

[0067] (1) Mix sucrose, formaldehyde and distilled water and stir for 1 hour. The mass ratio of sucrose, formaldehyde and water is 1:1.1:33. Then put it into a reaction vessel and treat it at 166°C for 11 hours. Then wash the solid product with distilled water until neutral, dry it at 120°C for 12 hours, and then treat it at 820°C for 5 hours in a nitrogen atmosphere to obtain carbon material.

[0068] (2) Mix the carbon material obtained in step (1), water, ethanol, and ammonia evenly, and then introduce cobalt chloride, wherein the mass ratio of cobalt chloride, carbon material obtained in step (1), water, ethanol, and ammonia is 0.43:1:135:165:4.5. Then wash the solid product with distilled water until neutral and dry it at 120°C for 12 hours.

[0069] (3) Mix the material obtained in step (2), water, nano-iron oxide particles, and glucose, wherein the mass ratio of the material obtained in step (2), glucose, nano-iron oxide, and water is 1:2.6:0.33:165. Then, evaporate the water at 100℃; then treat at 330℃ for 5 hours in a nitrogen atmosphere; then mix with hydrochloric acid (2wt% hydrochloric acid, the mass ratio of the material to the acid solution after calcination is 1:195) for 20 minutes; then filter the resulting sample 4 times, and then dry it in an oven at 110℃ for 12 hours.

[0070] (4) Mix the material obtained in step (3), ethylenediamine, and water, wherein the mass ratio of the material obtained in step (3), ethylenediamine, and water is 6.8:5.5:100. Put the mixture into a reactor and treat it at 135°C for 12 hours; then filter the resulting sample four times, and then dry it in an oven at 110°C for 12 hours. Finally, calcine it in air at 510°C for 7 hours. The resulting sample is numbered A4.

[0071] Example 5

[0072] (1) Mix sucrose, formaldehyde and distilled water and stir for 1 hour. The mass ratio of sucrose, formaldehyde and water is 1:0.8:28. Then put it into a reaction vessel and treat it at 155°C for 12 hours. Then wash the solid product with distilled water until neutral, dry it at 120°C for 12 hours, and then treat it at 780°C for 5.5 hours in a nitrogen atmosphere to obtain carbon material.

[0073] (2) Mix the carbon material obtained in step (1), water, propanol, and ammonia evenly, and then introduce cobalt chloride, wherein the mass ratio of cobalt chloride, carbon material obtained in step (1), water, propanol, and ammonia is 0.51:1:120:125:2.5. Then wash the solid product with distilled water four times until neutral, and dry it at 120°C for 12 hours.

[0074] (3) Mix the material obtained in step (2), water, nano-iron oxide particles and sucrose, wherein the mass ratio of the material obtained in step (2), sucrose, nano-iron oxide and water is 1:4.3:0.41:185. Then evaporate the water at 100℃; then treat at 310℃ for 5h in a nitrogen atmosphere; then mix with hydrochloric acid (2wt% hydrochloric acid, the mass ratio of the material and acid after calcination is 1:175) for 20min; then filter the obtained sample several times, and then place it in an oven to dry at 110℃ for 12h.

[0075] (4) Mix the material obtained in step (3), n-butylamine and water, wherein the mass ratio of the material obtained in step (3), n-butylamine and water is 5.6:9.5:100; put it into a reactor and treat it at 120°C for 12 hours; then filter the obtained sample multiple times, and then place it in an oven to dry at 110°C for 12 hours, and finally calcine it in an air atmosphere at 500°C for 7 hours. The obtained sample is numbered A5.

[0076] Comparative Example 1

[0077] (1) Mix glucose, formaldehyde and distilled water and stir for 1 hour, wherein the mass ratio of glucose, formaldehyde and water is 1:1.2:38; then put it into a reaction vessel and treat it at 175°C for 11 hours; then wash the solid product with distilled water to neutralize it, dry it at 120°C for 12 hours, and then treat it at 800°C for 5 hours under nitrogen atmosphere to obtain carbon material.

[0078] (2) Mix the carbon material, water, ethanol and ammonia obtained in step (1) evenly, and then introduce cobalt nitrate, wherein the mass ratio of cobalt nitrate, carbon material, water, ethanol and ammonia obtained in step (1) is 0.53:1:130:150:3.5. Then wash the solid product with distilled water until neutral, and then dry it at 120°C for 12 hours.

[0079] (3) The material obtained in step (3), ethylenediamine and water are mixed (the mass ratio of the material obtained in step (3), ethylenediamine and water is 6.6:7.5:100) and then loaded into the reactor and treated at 126°C for 12 hours; the obtained sample is then filtered 3 times, and then placed in an oven to dry at 110°C for 12 hours, and finally calcined in air at 500°C for 7 hours. The obtained sample is numbered D1.

[0080] Figure 3 These are scanning electron microscope images of the prepared sample (after grinding), by... Figure 3 It can be seen that the obtained samples are blocky and strip-shaped crystals. No broken spherical particles were found after grinding, indicating that no hollow structure was formed.

[0081] Comparative Example 2

[0082] The experiment was basically the same as in Example 1, except that in step (2), the acid concentration used for the acid treatment was 10 wt%, and the resulting sample was numbered D2. The amount of solid product collected by this method was too low to obtain the target product, and the experiment failed.

[0083] Comparative Example 3

[0084] The experiment was basically the same as in Example 1, except that the acid treatment in step (2) was performed at a temperature of 80°C, and the resulting sample was numbered D3. The amount of solid product collected by this method was too low to obtain the target product, and the experiment failed.

[0085] Comparative Example 4

[0086] The sample is basically the same as in Example 1, except that the carbon material in step (1) is a conventional activated carbon material. The carbon material particles are not uniform in shape and size, and the particles are irregular shapes such as strips and blocks. The particle size ranges from tens of nanometers to several micrometers. The sample obtained is numbered D4.

[0087] Comparative Example 5

[0088] The results were essentially the same as in Example 1, except that the hot alkaline treatment in step (4) was omitted. The resulting sample was designated D5, and its properties are shown in Table 1. Granular cobalt oxide particles were obtained; no hollow structure was obtained. This indicates that the prepared hollow cobalt oxide decomposed during the preparation process, thus failing to yield hollow cobalt oxide.

[0089] Table 1. Physicochemical properties of samples obtained from each embodiment and comparative example.

[0090]

[0091] Note: The sample obtained in Example 1 is used as a reference in this invention, and its crystallinity is set to 100%. The relative crystallinity of all other samples is obtained by comparing it with the crystallinity of the reference.

Claims

1. A method for synthesizing hollow cobalt oxide, the method comprising the following steps: (1) Mix cobalt source, carbon material, alcohol solvent, ammonia and water, and then separate, wash and dry them; (2) Mix the material obtained in step (1), nano iron oxide, sugar compound and water evenly, evaporate the water and then calcine, then contact with acid for acid treatment, and finally separate and dry; (3) Mix the material obtained in step (2), amine compound and water for hydrothermal treatment, and then separate, dry and calcine to obtain hollow cobalt oxide.

2. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The cobalt source in step (1) is a cobalt salt, which is at least one of cobalt nitrate, cobalt chloride, and cobalt isopropoxide.

3. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The alcohol solvent in step (1) is an alcohol with 1-4 carbon atoms, and the alcohol is selected from at least one of ethanol, propanol, and butanol.

4. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The carbon material in step (1) has a particle size of 1 to 6 micrometers and is spherical or quasi-spherical in shape.

5. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The mass ratio of cobalt source, carbon material, water, alcohol solvent and ammonia in step (1) is 0.1-1.1:1:80-220:80-220:0.8-6, preferably 0.2-1:1:100-200:100-200:1-5.

6. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The carbohydrate compound in step (2) is at least one of sucrose, glucose, fructose, maltose, and lactose, preferably at least one of sucrose and glucose.

7. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The size of the nano-iron oxide particles in step (2) is 2-15 nm, preferably 5-10 nm.

8. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, In step (2), the mass ratio of the material obtained in step (1), the carbohydrate compound, the nano iron oxide, and the water is 1:1 to 7.5: 0.08 to 0.6: 80 to 310, preferably 1:2 to 7: 0.1 to 0.5: 100 to 300.

9. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The evaporation temperature for evaporating water in step (2) is 80-160℃, preferably 100-150℃.

10. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The calcination process in step (2) is carried out under an inert atmosphere, the calcination temperature is 200-400℃, preferably 300-350℃, and the calcination time is 1-12h, preferably 2-10h.

11. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The acid treatment in step (2) involves mixing the calcined solid with an acid solution and treating it at 10–40°C for 5–35 min, preferably 10–30 min; the acid is an inorganic acid selected from at least one of hydrochloric acid, nitric acid, and sulfuric acid; the mass concentration of the acid solution is 0.5%–5.5%, preferably 1.0%–5.0%.

12. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The amine compound in step (3) is at least one of n-butylamine, ethylenediamine, and hexamethylenediamine.

13. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The mass ratio of the material obtained in step (2) in step (3), the amine compound, and the water is 1-12:1-12:100, preferably 2-10:2-10:

100.

14. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The hydrothermal treatment temperature in step (3) is 90-210℃, preferably 100-200℃; the hydrothermal treatment time is 8-21h, preferably 10-20h.

15. The method for synthesizing hollow cobalt oxide according to claim 1, wherein, The roasting in step (3) is carried out in an oxygen-containing atmosphere, wherein the volume content of oxygen in the oxygen-containing atmosphere is 20% to 100%; the oxygen-containing atmosphere is at least one of oxygen, air, or a mixture of oxygen and other inert atmospheres; the inert atmosphere is nitrogen and / or an inert gas; the roasting temperature in step (3) is 400 to 600°C.

16. A hollow cobalt oxide, wherein the hollow cobalt oxide is obtained by the synthesis method described in any one of claims 1-15.

17. The hollow cobalt oxide according to claim 16, wherein, Hollow cobalt oxide has an irregular spherical or block shape with a hollow center. The particle size of hollow cobalt oxide is 1 to 5 micrometers, and the shell thickness is 200 to 1200 nm.

18. The hollow cobalt oxide according to claim 16, wherein, The specific surface area of ​​hollow cobalt oxide is 50–120 m². 2 / g.

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