Preparation method of sea urchin-shaped co3o4 / cuo three-dimensional hierarchical nanostructure and application thereof in catalytic hydrogen production

Abstract

The application discloses a preparation method of a sea urchin-shaped Co3O4 / CuO three-dimensional hierarchical nanostructure, which comprises the following steps: (1) a certain amount of urea is dissolved in water to form a uniform solution by stirring; (2) soluble divalent copper salt and divalent cobalt salt are added into the solution in a certain proportion to form a mixed solution A, and stirring is carried out for 5-15 min; (3) the solution is transferred into a 100mL reaction kettle, and reaction is carried out at 100-140 DEG C for 4-18h; and (4) filtration and washing are carried out, and the collected solid is reacted in a tubular furnace under a nitrogen atmosphere at 300-400 DEG C for 2-6h. The hydrothermal synthesis method is adopted, raw materials are firstly mixed in a certain proportion, urea is used as a homogeneous precipitant, a precursor is generated under the condition that urea exists, and then the Co3O4 / CuO composite is synthesized through calcination. The whole preparation process is simple in operation, environment-friendly, very good in experimental reproducibility, low in cost and easy for industrial production, and the Co3O4 / CuO composite prepared by the method has very high catalytic activity in the ammonia borane alcoholysis hydrogen production reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new material synthesis, in particular to a preparation method of sea urchin-shaped Co3O4 / CuO three-dimensional hierarchical nanostructure and catalytic hydrogen production application thereof. BACKGROUND

[0002] Ammonia borane alcoholysis is a hydrogen production and storage integrated technology with great application prospect, and obtaining a cheap and efficient catalyst is the prerequisite for large-scale application of the technology. At present, researches have confirmed that metal oxide composites have a certain catalytic effect in ammonia borane alcoholysis hydrogen production. However, the activity of the metal oxide composites still needs to be further improved. Traditional metal oxide composites are mostly nanoparticles, and the nanoparticle catalysts are prone to agglomeration during the catalytic reaction, resulting in a decrease in activity. Therefore, it is of great significance to improve the activity and stability of the catalysts by designing the morphology and structure of the catalysts.

[0003] At present, the method for synthesizing three-dimensional hierarchical nanostructure oxides is relatively complex, and templates or surfactants are mostly used, which increases the synthesis cost and the process complexity. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of sea urchin-shaped Co3O4 / CuO three-dimensional hierarchical nanostructure, which has simple operation, is environment-friendly and has lower cost, and catalytic hydrogen production application thereof

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a preparation method of sea urchin-shaped Co3O4 / CuO three-dimensional hierarchical nanostructure, which comprises the following steps: (1) dissolving a certain amount of urea in water to form a uniform solution; (2) adding soluble divalent copper salt and divalent cobalt salt to the above-mentioned solution in a certain proportion to form a mixed solution A, and stirring for 5-15 min; (3) transferring the above-mentioned solution to a 100 mL reaction kettle, and reacting at 100-140℃ for 4-18 h; (4) filtering and washing, and collecting the solid and reacting at 300-400℃ for 2-6 h in a tube furnace under a nitrogen atmosphere.

[0007] When the molar ratio of cobalt to copper is in the range of 2:3 to 4:1, a three-dimensional hierarchical nanostructure composed of nanowires can be obtained; when the ratio is not in this range, the three-dimensional structure cannot be obtained.

[0008] The Co3O4 / CuO catalyst prepared by the above method has high catalytic activity in the ammonia borane alcoholysis hydrogen production reaction, and the TOF value can be as high as 87.5 mol hydrogen min -1 mol cat -1 .

[0009] The present application adopts hydrothermal synthesis method, first mixes raw materials in certain proportion, uses urea as homogeneous precipitator, generates precursor under the condition of urea, and then synthesizes Co3O4 / CuO composite through calcination. This process effectively realizes the set cobalt-copper ratio in raw materials, the whole preparation process is simple, environment-friendly, the experimental reproducibility is very good, the cost is low, and the industrial production is easy. The Co3O4 / CuO composite prepared by the method has high catalytic activity in ammonia borane alcoholysis reaction.

[0010] The present application adopts a simple synthesis method to prepare a three-dimensional hierarchical Co3O4 / CuO nanometer structure hydrogen catalyst for ammonia borane alcoholysis. First, the three-dimensional hierarchical structure usually has high specific surface area and high density of catalytically active centers, which is beneficial to the adsorption and activation of the reaction substrate. Second, the hydrogen production by ammonia borane hydrolysis occurs at the catalyst-reaction medium-hydrogen three-phase interface, and the three-dimensional hierarchical structure can provide a rich solid-liquid-gas three-phase active interface area and diffusion channel for the reaction substrate / gaseous product, which is beneficial to reduce the kinetic barrier of the reaction. Third, cobalt-based, nickel-based and iron-based catalysts commonly used in ammonia borane hydrolysis system are prone to agglomeration due to their inherent magnetism, while the three-dimensional hierarchical structure can effectively avoid the activity decline caused by agglomeration and maintain stable activity due to its large steric hindrance. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 XRD spectra of examples 1-6 of the present application;

[0012] Figure 2 SEM photos of the samples corresponding to example 1(a), example 2(b), example 3(c), example 4(d, e), example 5(f), and example 6(g, h) of the present application;

[0013] Figure 3 SEM photo of the sample corresponding to example 7 of the present application;

[0014] Figure 4 TOF values of Co3O4 / CuO composite with different Co / Cu ratios in catalyzing ammonia borane alcoholysis to produce hydrogen. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application, but do not constitute a limitation on the protection scope of the present application.

[0016] The present application makes full use of the growth characteristics of Co3O4 and CuO in urea solution, and obtains the urchin-like Co3O4 / CuO three-dimensional hierarchical nanostructure by accurately controlling the ratio of cobalt salt and copper salt (cobalt-copper molar ratio is 2:3 to 4:1) in the synthesis process. Specifically, Co3O4 tends to one-dimensional growth in urea solution, and is easy to obtain nanowires or nanorods; while CuO tends to three-dimensional growth, and obtains microspheres, when the ratio of cobalt salt and copper salt is reasonably set and the reaction conditions are controlled, the three-dimensional hierarchical nanostructure Co3O4 / CuO composite can be obtained.

[0017] In the conventional synthesis of three-dimensional hierarchical nanostructure oxides, templates, surfactants, complexing agents, etc. are usually used, while in the present application, the reagents used are only urea and metal salt, and no additives are included, so the synthesis cost is significantly reduced. In addition, the synthesis only involves two steps of hydrothermal reaction and calcination, which is very simple and easy to scale up production.

[0018] Example 1

[0019] 1.6 grams of urea was dissolved in 80 milliliters of water, stirred for 5-10 minutes; 1 mmol of copper nitrate was added to the above solution and stirred for 5 minutes to form a mixed solution; the above solution was transferred to a 100 mL reaction kettle, and reacted at 120°C for 8h; the collected solid was washed by suction filtration and calcined at 350°C for 4h in a tube furnace under nitrogen atmosphere. The CuO catalyst prepared by the above method has a certain catalytic activity in the ammonia borane alcoholysis reaction for hydrogen production, and the TOF value can reach 6.3mol hydrogen min -1 mol cat -1 .

[0020] Example 2

[0021] 1.6 grams of urea was dissolved in 80 milliliters of water, stirred for 5-10 minutes; 0.8 mmol of copper nitrate and 0.2 mmol of cobalt nitrate were added to the above solution and stirred for 5 minutes to form a mixed solution; the above solution was transferred to a 100 mL reaction kettle, and reacted at 120°C for 8h; the collected solid was washed by suction filtration and calcined at 350°C for 4h in a tube furnace under nitrogen atmosphere. The Co3O4 / CuO catalyst prepared by the above method has a higher catalytic activity in the ammonia borane alcoholysis reaction for hydrogen production, and the TOF value can reach 16.9mol hydrogen min -1 mol cat -1 .

[0022] Example 3

[0023] 1.6 g of urea was dissolved in 80 mL of water and stirred for 5-10 minutes; 0.6 mmol of copper nitrate and 0.4 mmol of cobalt nitrate were added to the above solution and stirred for 5 minutes to form a mixed solution; the above solution was transferred to a 100 mL reaction kettle, and reacted at 120°C for 8h; the collected solid was reacted at 350°C for 4h in a tube furnace under nitrogen atmosphere. The Co3O4 / CuO catalyst prepared by the above method has high catalytic activity in the hydrogen production reaction of ammonia borane alcoholysis, and its TOF value can reach 42.7mol hydrogen min -1 mo l cat -1 .

[0024] Example 4

[0025] 1.6 g of urea was dissolved in 80 mL of water and stirred for 5-10 minutes; 0.4 mmol of copper nitrate and 0.6 mmol of cobalt nitrate were added to the above solution and stirred for 5 minutes to form a mixed solution; the above solution was transferred to a 100 mL reaction kettle, and reacted at 120°C for 8h; the collected solid was reacted at 350°C for 4h in a tube furnace under nitrogen atmosphere. The Co3O4 / CuO catalyst prepared by the above method has high catalytic activity in the hydrogen production reaction of ammonia borane alcoholysis, and its TOF value can reach 87.5mol hydrogen min -1 mo l cat -1 .

[0026] Example 5

[0027] 1.6 g of urea was dissolved in 80 mL of water and stirred for 5-10 minutes; 0.2 mmol of copper nitrate and 0.8 mmol of cobalt nitrate were added to the above solution and stirred for 5 minutes to form a mixed solution; the above solution was transferred to a 100 mL reaction kettle, and reacted at 120°C for 8h; the collected solid was reacted at 350°C for 4h in a tube furnace under nitrogen atmosphere. The Co3O4 / CuO catalyst prepared by the above method has high catalytic activity in the hydrogen production reaction of ammonia borane alcoholysis, and its TOF value can reach 25.2mol hydrogen min -1 mo l cat -1 .

[0028] Example 6

[0029] Dissolve 1.6 g of urea in 80 ml of water and stir for 5-10 minutes. Add 1.0 mmol of cobalt nitrate to the solution and stir for 5 minutes to form a mixed solution. Transfer the solution to a 100 mL reactor and react at 120°C for 8 hours. Filter and wash the collected solids, then react at 350°C in a tube furnace under nitrogen for 4 hours. The Co3O4 catalyst prepared by the above method has no catalytic activity in the ammonia borane alcoholysis reaction to produce hydrogen, with a TOF value of 0 mol / L. hydrogen min -1 mo l cat -1 .

[0030] Example 7

[0031] Dissolve 1.6 grams of sodium hydroxide in 80 milliliters of water and stir for 5-10 minutes. Add 0.4 millimoles of copper nitrate and 0.6 millimoles of cobalt nitrate to the solution and stir for 5 minutes to form a suspension. Transfer the solution to a 100-mL reactor and react at 120°C for 8 hours. Filter and wash the collected solids, then react at 350°C in a tube furnace under a nitrogen atmosphere for 4 hours. The Co3O4 / CuO catalyst prepared by the above method has high catalytic activity in the hydrogen production reaction by alcoholysis of ammonia borane, with a TOF value of up to 29.4 mol / L. hydrogen min -1 mo l cat -1 .like Figure 3 As shown, when sodium hydroxide is used instead of urea, nanosheets are obtained.

[0032] The present invention utilizes a simple hydrothermal reaction and, through a calcination process, produces a sea urchin-like Co3O4 / CuO nanostructure composed of nanowires. By optimizing the ratio of cobalt to copper in the Co3O4 / CuO (a cobalt-copper molar ratio of 2:3 to 4:1 yields a three-dimensional hierarchical nanostructure composed of nanowires, corresponding to Examples 3, 4, and 5; a ratio outside this range results in no three-dimensional structure), a high-performance ammonia borane alcoholysis hydrogen production catalyst is obtained, with a turnover frequency (TOF) of up to 87.5 min. -1 , which is much higher than the activity of oxide catalysts reported in recent literature.

[0033] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. Use of sea urchin-shaped Co3O4 / CuO as a catalyst in the alcoholysis of ammonia borane to produce hydrogen, characterized in that: The preparation method of the sea urchin-shaped Co3O4 / CuO catalyst comprises the following steps: (1) Dissolve a certain amount of urea in water and stir to form a uniform solution; (2) adding a soluble divalent copper salt and a divalent cobalt salt to the above solution in proportion to form a mixed solution A, and stirring for 5 to 15 minutes; wherein the molar ratio of cobalt to copper is 2:3 to 3:2; (3) Transfer the above solution to a 100 mL reactor and react at 100-140°C for 4-18 hours; (4) Filter and wash the collected solids, and react them in a tube furnace at 300-400°C under a nitrogen atmosphere for 2-6 hours.

2. The use of the sea urchin-shaped Co3O4 / CuO as claimed in claim 1 as a catalyst in the alcoholysis of ammonia borane to produce hydrogen, characterized in that: The divalent copper salt includes one or both of copper nitrate and copper chloride.

3. The use of the sea urchin-shaped Co3O4 / CuO as claimed in claim 1 as a catalyst in the alcoholysis of ammonia borane to produce hydrogen, characterized in that: The divalent cobalt salt includes one or both of cobalt nitrate and cobalt chloride.

4. The use of the sea urchin-shaped Co3O4 / CuO as claimed in claim 1 as a catalyst in the alcoholysis of ammonia borane to produce hydrogen, characterized in that: The reaction was carried out at 350 °C for 4 h under nitrogen atmosphere.

Images