A method for preparing hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material and its application in catalytic hydrolysis of ammonia borane for hydrogen production.

Abstract

This invention discloses a method for preparing hexagonal cobalt tetroxide-cobalt nitride composite materials, comprising: (1) dissolving soluble cobalt salt in ultrapure water to prepare a mixed salt solution A; (2) dissolving trisodium citrate, a complexing agent, in ultrapure water to prepare a solution B; (3) slowly adding solution B dropwise to solution A under magnetic stirring to form solution C; (4) slowly adding an alkaline solution dropwise to solution C; (5) transferring to a reaction vessel, reacting at 100-180℃ for 6-12 hours, filtering and washing, collecting the product, and drying; (6) calcining the sample in a muffle furnace at 350℃ for 2 hours, and collecting the sample after the reaction is completed; (7) using urea as an ammonia source, placing the sample from step (6) upstream of a tubular furnace, and calcining it at 300-400℃ under a nitrogen atmosphere for 0.1-5 hours for partial nitriding treatment. This invention successfully prepares hexagonal cobalt tetroxide-cobalt nitride composite materials using a simple hydrothermal synthesis method and post-calcination nitriding treatment.

Description

Technical Field

[0001] This invention belongs to the field of catalytic hydrogen production, and particularly relates to a method for preparing a hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material and its application in the catalytic hydrolysis of ammonia borane to produce hydrogen. Background Technology

[0002] The extensive use of traditional fossil fuels has triggered an energy crisis and caused various environmental problems, making the development of renewable green energy extremely important. Hydrogen, as a clean new energy source, has attracted widespread attention. The rapid release of hydrogen using hydrogen storage materials has become a research hotspot in the hydrogen energy field in recent years. Among numerous hydrogen storage materials, ammonia borane (NH3BH3, abbreviated as AB) has attracted widespread research interest due to its high hydrogen content, high heat release during combustion, and zero CO2 emissions. Ammonia borane can release hydrogen through hydrolysis. However, this reaction requires a suitable catalyst, therefore, developing cost-effective, high-performance catalysts is key to realizing hydrogen production from ammonia borane hydrolysis. Research shows that precious metals are good catalysts for hydrogen production from ammonia borane, but their high cost hinders their large-scale application. In recent years, non-precious metal catalysts have attracted widespread research interest due to their price advantage. Developing efficient and inexpensive non-precious metal catalysts is of great significance.

[0003] Previous studies have shown that Co3O4 can catalyze the hydrolysis of ammonia borane to release hydrogen, exhibiting good catalytic performance and attracting widespread attention from researchers. However, the Co3O4-catalyzed hydrogen release from ammonia borane hydrolysis has a certain induction period, resulting in a relatively slow reaction rate in the initial stage and hindering the rapid progress of the reaction. Therefore, reducing the reaction induction period is of great significance for improving catalytic performance. Many studies have shown that constructing heterojunctions can produce a synergistic promoting effect, potentially reducing the initial induction period. Transition metal nitrides, such as cobalt nitride (CoN), exhibit certain catalytic activity in various catalytic reactions due to their good electrical conductivity. Preliminary research results show that the catalytic activity of mono-component cobalt nitride and cobalt tetroxide remains relatively low. Establishing heterojunctions between these two compounds is expected to produce a significant synergistic effect, promoting the reaction rate.

[0004] Therefore, the problem that this invention aims to solve is to develop a method for producing a high-purity cobalt tetroxide-cobalt nitride binary nitride composite that utilizes the interfacial effect of cobalt tetroxide-cobalt nitride to synergistically enhance the catalytic performance of ammonia borane hydrolysis for hydrogen production. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing hexagonal cobalt tetroxide-cobalt nitride composite materials. This invention has the advantages of simple synthesis methods, mild conditions, and uniform dispersion and regular morphology of the obtained cobalt tetroxide-cobalt nitride target product.

[0006] The inventors of this application have discovered that combining cobalt tetroxide and cobalt nitride to form a cobalt tetroxide-cobalt nitride composite for use in catalytic reactions can produce a synergistic catalytic effect and enhance reaction activity. Therefore, the present invention aims to solve the problem of developing a method for preparing a cobalt tetroxide-cobalt nitride composite that is simple in process, low in cost, and has excellent product performance and can be applied to the industrial production of cobalt tetroxide-cobalt nitride composite.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material, comprising the following steps:

[0008] (1) Dissolve soluble cobalt salt in ultrapure water to prepare mixed salt solution A;

[0009] (2) Dissolve the complexing agent trisodium citrate in ultrapure water to prepare solution B;

[0010] (3) Under magnetic stirring, solution B is slowly added dropwise to solution A to form solution C;

[0011] (4) Slowly add an alkaline solution to solution C; the alkaline solution is selected from one or more of urea, sodium hydroxide, potassium hydroxide, ammonia, and hexamethylenetetramine;

[0012] (5) Transfer to a reaction vessel, react at 100-180℃ for 6-12 hours, filter and wash, collect the product, and dry.

[0013] (6) Place the sample in a muffle furnace and calcine at 350°C for 2 hours. After the reaction is complete, collect the sample.

[0014] (7) Using urea as the ammonia source, place the sample from step (6) on the upper part of a tube furnace and calcine it at 300-400°C in a nitrogen atmosphere for 0.1-5 hours for partial nitriding treatment.

[0015] Preferably, the soluble cobalt salt in step (1) is selected from one or more of cobalt acetate tetrahydrate, cobalt sulfate hexahydrate, cobalt nitrate hexahydrate, and cobalt chloride hexahydrate.

[0016] Preferably, the amount of trisodium citrate added in step (2) is 0.5 to 4 times that of the metal ions.

[0017] Preferably, the amount of alkali added in step (4) is 10 to 50 times that of the metal ions.

[0018] The present invention also discloses the application of the hexagonal cobalt tetroxide-cobalt nitride composite material prepared by the above method in the catalytic hydrolysis of ammonia borane to produce hydrogen.

[0019] In summary, the preparation method of the present invention has the following beneficial effects:

[0020] 1. The preparation method of this invention is simple. Trisodium citrate is selected as a complexing agent, and the reaction rate of the synthesis process is precisely controlled to synthesize a regular hexagonal nanosheet structure with good dispersion.

[0021] 2. By precisely adjusting the nitriding time, cobalt tetroxide-cobalt nitride composite catalysts with different ratios can be obtained.

[0022] 3. The hexagonal cobalt tetroxide-cobalt nitride composite material prepared by the present invention has obvious interface effect and exhibits synergistic catalytic performance in the hydrolysis of ammonia borane to produce hydrogen.

[0023] 4. This invention employs a simple hydrothermal synthesis method and stepwise calcination with partial nitriding treatment to successfully prepare hexagonal cobalt tetroxide-cobalt nitride composite materials. By controlling the nitriding time, the ratio of cobalt tetroxide to cobalt nitride in the target product can be effectively set. The entire preparation process is simple to operate, environmentally friendly, exhibits excellent experimental reproducibility, is low-cost, and easy to industrialize, enabling the large-scale production of hexagonal cobalt tetroxide-cobalt nitride composite materials. Attached Figure Description

[0024] Figure 1 Here is a SEM image of the cobalt tetroxide-cobalt nitride composite material prepared in this invention;

[0025] Figure 2 The XRD pattern of the cobalt tetroxide-cobalt nitride composite material prepared in this invention;

[0026] Figure 3 The FT-IR image of the cobalt tetroxide-cobalt nitride composite material prepared in this invention;

[0027] Figure 4 The BET diagram of the cobalt tetroxide-cobalt nitride composite material prepared in this invention;

[0028] Figure 5 The diagram shows the catalytic hydrogen production performance of the cobalt tetroxide-cobalt nitride composite material prepared in this invention. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the invention to the following embodiments. Various substitutions, modifications, and improvements made based on common technical knowledge and conventional methods in the art without departing from the technical concept of the present invention should be included within the scope of the present invention.

[0030] Example 1

[0031] 5 mmol of cobalt nitrate was dissolved in 5 mL of ultrapure water to obtain solution A; 10 mmol of trisodium citrate was dissolved in 40 mL of deionized water to obtain solution B; and 100 mmol of NaOH was dissolved in 20 mL of ultrapure water to obtain solution C. Under magnetic stirring, solution B was slowly added dropwise to solution A, followed by dropwise addition of solution C to solution A, with continued magnetic stirring for 5 min. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 6 h. After the reaction, the sample was collected, washed 2-3 times with water and 2-3 times with ethanol, and dried. The sample was calcined in a muffle furnace at 350 °C for 2 h. After the reaction, the sample was collected. 0.1 g of sample Co3O4 was placed in a ceramic boat and placed in a tube furnace. 1 g of urea was placed upstream of the sample as an ammonia source. The sample was calcined in a tube furnace at 350 °C under a nitrogen atmosphere for 0.5 h to obtain the target product, a hexagonal cobalt tetroxide-cobalt nitride composite catalyst.

[0032] Example 2

[0033] 5 mmol of cobalt nitrate was dissolved in 5 mL of ultrapure water to obtain solution A; 10 mmol of trisodium citrate was dissolved in 40 mL of water to obtain solution B; and 100 mmol of NaOH was dissolved in 20 mL of ultrapure water to obtain solution C. Under magnetic stirring, solution B was slowly added dropwise to solution A, followed by solution C, which was then added dropwise to solution A. Magnetic stirring was continued for 5 min. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 6 h. After the reaction, the sample was collected, washed 2-3 times with water and 2-3 times with ethanol, and dried. The sample was calcined in a muffle furnace at 350 °C for 2 h. After the reaction, the sample was collected. 0.1 g of sample Co3O4 was placed in a porcelain boat and placed in a tube furnace. 1 g of urea was placed upstream of the sample as an ammonia source. The sample was calcined in a tube furnace at 350 °C under a nitrogen atmosphere for 1 h to obtain the target product, a hexagonal cobalt tetroxide-cobalt nitride composite catalyst.

[0034] Example 3

[0035] 5 mmol of cobalt nitrate was dissolved in 5 mL of ultrapure water to obtain solution A; 10 mmol of trisodium citrate was dissolved in 40 mL of water to obtain solution B; and 100 mmol of NaOH was dissolved in 20 mL of ultrapure water to obtain solution C. Under magnetic stirring, solution B was slowly added dropwise to solution A, followed by solution C being added dropwise to solution A, with continued magnetic stirring for 5 min. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 6 h. After the reaction, the sample was collected, washed 2-3 times with water and 2-3 times with ethanol, and dried. The sample was calcined in a muffle furnace at 350 °C for 2 h. After the reaction, the sample was collected. 0.1 g of sample Co3O4 was placed in a porcelain boat and placed in a tube furnace. 1 g of urea was placed upstream of the sample as an ammonia source. The sample was calcined in a tube furnace at 350 °C under a nitrogen atmosphere for 1.5 h to obtain the target product, a hexagonal cobalt tetroxide-cobalt nitride composite catalyst.

[0036] Example 4

[0037] 5 mmol of cobalt nitrate was dissolved in 5 mL of ultrapure water to obtain solution A; 10 mmol of trisodium citrate was dissolved in 40 mL of water to obtain solution B; and 100 mmol of NaOH was dissolved in 20 mL of ultrapure water to obtain solution C. Under magnetic stirring, solution B was slowly added dropwise to solution A, followed by solution C, which was then added dropwise to solution A. Magnetic stirring was continued for 5 min. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 6 h. After the reaction, the sample was collected, washed 2-3 times with water and 2-3 times with ethanol, and dried. The sample was calcined in a muffle furnace at 350 °C for 2 h. After the reaction, the sample was collected. 0.1 g of sample Co3O4 was placed in a porcelain boat and placed in a tube furnace. 1 g of urea was placed upstream of the sample as an ammonia source. The sample was calcined in a tube furnace at 350 °C under a nitrogen atmosphere for 2 h to obtain the target product, a hexagonal cobalt tetroxide-cobalt nitride composite catalyst.

[0038] The structure and properties of the cobalt tetroxide-cobalt nitride composite material prepared in this invention are analyzed and tested below.

[0039] 1. SEM Analysis

[0040] Figure 1 This is a SEM image of the cobalt tetroxide-cobalt nitride composite material prepared in this invention. The SEM image shows that the synthesized cobalt tetroxide-cobalt nitride composite material has a morphology of hexagonal nanosheets with a size of approximately 300 nm.

[0041] 2. XRD Analysis

[0042] Figure 2 XRD analysis of the cobalt tetroxide-cobalt nitride prepared for this invention. The results show that the sample is a composite of Co3O4 (JCPDS43-1003) and CoN (JCPDS16-0116).

[0043] 3. Infrared analysis

[0044] Figure 3 FT-IR test of cobalt tetroxide-cobalt nitride prepared in this invention.

[0045] 4. Pore structure and specific surface area analysis

[0046] Figure 4 BET test of cobalt tetroxide-cobalt nitride prepared in this invention.

[0047] 5. Testing of catalytic hydrogen production performance

[0048] Figure 5To test the performance of cobalt tetroxide-cobalt nitride as a catalyst for the hydrolysis of ammonia borane to produce hydrogen, the following method was used: 3 mmol of NH3BH3, 10 mmol of NaOH, and 10 mg of catalyst. The hydrogen production rate curve of cobalt tetroxide-cobalt nitride was measured at 25 °C.

[0049] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material, characterized in that, Includes the following steps: (1) Dissolve soluble cobalt salt in ultrapure water to prepare mixed salt solution A; (2) Dissolve the complexing agent trisodium citrate in ultrapure water to prepare solution B; (3) Under magnetic stirring, solution B is slowly added dropwise to solution A to form solution C; (4) Slowly add an alkaline solution to solution C; the alkaline solution is selected from one or more of urea, sodium hydroxide, potassium hydroxide, ammonia, and hexamethylenetetramine; (5) Transfer to a reaction vessel, react at 100-180℃ for 6-12 hours, filter and wash, collect the product, and dry. (6) Place the sample in a muffle furnace and calcine at 350°C for 2 hours. After the reaction is complete, collect the sample. (7) Using urea as the ammonia source, place the sample from step (6) on the upper part of a tube furnace and calcine it at 300-400℃ in a nitrogen atmosphere for 0.1-5 hours for partial nitriding treatment.

2. The method for preparing a hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material according to claim 1, characterized in that: The soluble cobalt salt mentioned in step (1) is selected from one or more of cobalt acetate tetrahydrate, cobalt sulfate hexahydrate, cobalt nitrate hexahydrate, and cobalt chloride hexahydrate.

3. The method for preparing a hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material according to claim 1, characterized in that: The amount of trisodium citrate used as the complexing agent in step (2) is 0.5 to 4 times that of the metal ions.

4. The method for preparing a hexagonal nanosheet cobalt tetroxide-cobalt nitride composite material according to claim 1, characterized in that: The amount of alkali added in step (4) is 10 to 50 times that of the metal ions.

5. A nanosheet cobalt tetroxide-cobalt nitride composite material, characterized in that: Prepared by the method described in any one of claims 1-4.

6. The application of the nanosheet cobalt tetroxide-cobalt nitride composite material as described in claim 5 as a catalyst in the catalytic hydrolysis of ammonia borane to produce hydrogen.

Images