Copper oxide heterojunction hollow sphere as well as preparation method and application thereof

Abstract

The invention discloses a copper oxide heterojunction hollow sphere and a preparation method and application thereof, and the method comprises the following steps: dissolving a water-soluble copper salt and an amphiphilic organic ligand containing carboxyl and amino in an alcohol-water solvent, and adjusting the pH value to 5.5-7.5 to form a uniform amphiphilic copper complex solution; placing the amphiphilic copper complex solution in a closed reactor for self-assembly reaction, and washing and drying after the reaction is finished to obtain a precursor; and carrying out gradient oxidation calcination on the precursor to obtain the hollow sphere with the copper oxide-cuprous oxide heterojunction. The complex preparation method of the traditional template method is overcome, the self-assembly behavior of the specific precursor in the solvent is utilized, and the precisely controlled gradient oxidation process is combined, so that the hollow sphere with the heterojunction structure is formed in one step; and the prepared copper oxide heterojunction hollow sphere can be directly used as a catalyst for reaction and has relatively excellent catalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials and relates to a copper oxide heterojunction hollow sphere, its preparation method and application. Background Technology

[0002] In recent years, heterojunctions of cuprous oxide with semiconductors such as titanium dioxide, cerium dioxide, and tungsten trioxide have become a research hotspot. The heterojunction between different semiconductors leads to high catalytic activity. Among semiconductor catalysts, cuprous oxide and copper oxide are stable, abundant, inexpensive, and environmentally friendly p-type semiconductors with direct band gaps of 2.2 and 1.2 eV, respectively. Copper oxides (cuprous oxide and copper oxide) have become important catalysts for the photocatalytic degradation of organic pollutants due to their high light absorption coefficients. Because the conduction band and valence band of cuprous oxide have more negative potentials than those of copper oxide, at the interface between cuprous oxide and copper oxide, photogenerated electrons from the conduction band of cuprous oxide are injected into the conduction band of copper oxide, while photogenerated holes from the valence band of copper oxide are injected into the conduction band of cuprous oxide. This synergistic reaction, formed by the mutual filling of photogenerated electrons and holes, greatly enhances the catalytic activity of the catalyst material. This has also led to increased attention on heterostructures in the field of catalytic reactions. In the application of CO catalytic oxidation, the cuprous oxide and copper oxide composite structure exhibits a synergistic effect as a catalyst for the low-temperature oxidation of CO. Cuprous oxide and copper oxide provide active sites for oxygen dissociation and CO oxidation, respectively. The atomic-scale distance between cuprous oxide and copper oxide facilitates the rapid migration of oxygen adsorption atoms on cuprous oxide and copper oxide to fill oxygen vacancies on copper oxide.

[0003] Furthermore, material morphology also has a crucial impact on catalytic performance. Previous studies have prepared hollow cuprous oxide microspheres with porous layers composed of multiple nanocrystals, exhibiting a hollow, multi-layered cuprous oxide intermediate template assembly. Currently, methods using surfactants, complexing agents, and reducing agents are common, but excessive addition of reagents can lead to difficulties in removal. Therefore, by reducing the initial intermediate with a complex structure to the final phase, a higher-order structure can be obtained. Because the special morphology and microstructure of the intermediate phase influence the hierarchical evolution of the final phase, the resulting cuprous oxide material exhibits a high-level hierarchical hollow spherical morphology. In summary, developing a low-cost, easy-to-operate new method is of great significance for the preparation and application of copper oxide heterostructure hollow spheres.

[0004] CN104192889A discloses a method for preparing monodisperse cuprous oxide hollow spheres, characterized by the direct preparation of monodisperse cuprous oxide hollow spheres without the use of surfactants, which overcomes the drawbacks of using surfactants. This method utilizes the addition of hydrazine hydrate as a reducing agent, which is difficult to completely remove, and increases the operational steps and cost of preparing cuprous oxide hollow spheres. Furthermore, it is not applicable to the field of CO catalytic oxidation.

[0005] CN106082301A discloses a method for preparing hollow cuprous oxide nanospheres, characterized by the direct synthesis of cuprous oxide nanomaterials from a copper complex solution. This method uses not only surfactants but also complexing agents and reducing agents, which increases the cost of material preparation and makes the operation more complex. Furthermore, the prepared hollow cuprous oxide nanospheres are not uniform in size. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a copper oxide heterojunction hollow sphere, its preparation method, and its application. It overcomes the complex preparation method of traditional template methods by utilizing the self-assembly behavior of specific precursors in solvents, combined with a precisely controlled gradient oxidation process, to form a hollow sphere with a heterojunction structure in one step.

[0007] The technical solution provided by this invention is as follows:

[0008] This invention provides a method for preparing copper oxide heterojunction hollow spheres, the method comprising the following steps: A water-soluble copper salt and an amphiphilic organic ligand containing carboxyl and amino groups were dissolved in an alcohol-water solvent, and the pH was adjusted to 5.5-7.5 to form a homogeneous amphiphilic copper complex solution. The amphiphilic copper complex solution was placed in a closed reactor to carry out a self-assembly reaction. After the reaction was completed, the precursor was obtained by washing and drying. The precursor was subjected to gradient oxidation and calcination to obtain hollow spheres with a copper oxide-cuprous oxide heterostructure.

[0009] Furthermore, the water-soluble copper salt is selected from at least one of copper nitrate trihydrate, copper sulfate, or copper chloride.

[0010] Furthermore, the amphiphilic organic ligand is selected from at least one of iminodiacetic acid, serine, or histidine.

[0011] Furthermore, the molar ratio of copper ions to amphiphilic organic ligands in the amphiphilic copper complex solution is 1:(1.2~2.5).

[0012] Furthermore, the alcohol-water solvent is a mixed system composed of water and C1-C3 alcohol in a volume ratio of 1:(0.5~2).

[0013] Furthermore, the temperature of the self-assembly reaction is 160~180℃, and the reaction time is 36~48 hours.

[0014] Furthermore, the gradient oxidation calcination includes first heating to 100~200℃ and calcining for 0.5~1h, and then heating to 300~500℃ and calcining for 1~3h.

[0015] Furthermore, the pH adjuster used to adjust the pH is an alkaline solution.

[0016] Furthermore, the alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution; the concentration of the alkaline solution is 0.1~0.5M.

[0017] The present invention also provides a copper oxide heterojunction hollow sphere, which is prepared according to the method described above.

[0018] The present invention also provides the application of the above-described copper oxide heterojunction hollow spheres as catalysts in the catalytic oxidation of CO.

[0019] Beneficial effects

[0020] This invention constructs a hollow heterojunction structure through the self-assembly of copper-carboxyl / amino complexes coupled with gradient oxidation, eliminating the need for template addition / removal steps. The prepared copper oxide heterojunction hollow sphere material was used to study the CO catalytic oxidation reaction. The results showed that the copper oxide heterojunction hollow sphere material can completely oxidize CO at relatively low reaction temperatures (below 180℃), indicating that the prepared copper oxide heterojunction hollow spheres can be directly used as catalysts and possess excellent catalytic performance.

[0021] This invention precisely controls the gradient of oxidation conditions to regulate the form of copper in oxide heterojunction hollow spheres. The presence of the heterojunction structure significantly enhances the active oxygen vacancies on the material surface, thereby improving redox activation performance. Ultimately, complete oxidation of CO can be achieved at a relatively low temperature. Furthermore, the one-pot synthesis method for copper oxide heterojunction hollow spheres is simple, low-cost, and allows for excellent control over the morphology, structure, and uniformity of the material. Attached Figure Description

[0022] Figure 1 The image shown is the XRD pattern of the material prepared in Example 1 of this invention.

[0023] Figure 2 This is a STEM image of the material prepared in Example 1 of the present invention;

[0024] Figure 3The diagram shows the CO catalytic oxidation performance of the copper oxide heterojunction hollow spheres prepared in Examples 1, 2, 3, 4, and 5 of this invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0026] This invention provides a method for preparing copper oxide heterojunction hollow spheres, the method comprising the following steps: A water-soluble copper salt and an amphiphilic organic ligand containing carboxyl and amino groups were dissolved in an alcohol-water solvent, and the pH was adjusted to 5.5-7.5 to form a homogeneous amphiphilic copper complex solution. The amphiphilic copper complex solution was placed in a closed reactor to carry out a self-assembly reaction. After the reaction was completed, the precursor was obtained by washing and drying. The precursor was subjected to gradient oxidation and calcination to obtain hollow spheres with a copper oxide-cuprous oxide heterostructure.

[0027] In this embodiment, the water-soluble copper salt is selected from at least one of copper nitrate trihydrate, copper sulfate, or copper chloride.

[0028] In this embodiment, the amphiphilic organic ligand is selected from at least one of iminodiacetic acid, serine, or histidine.

[0029] In this embodiment, the molar ratio of copper ions to amphiphilic organic ligands in the amphiphilic copper complex solution is 1:(1.2~2.5).

[0030] In this embodiment, the alcohol-water solvent is a mixed system composed of water and C1-C3 alcohol in a volume ratio of 1:(0.5~2).

[0031] In this embodiment, the temperature of the self-assembly reaction is 160~180℃, and the reaction time is 36~48 hours.

[0032] In this embodiment, the gradient oxidation calcination includes first heating to 100~200℃ and calcining for 0.5~1h, and then heating to 300~500℃ and calcining for 1~3h.

[0033] In this embodiment, the pH adjuster used to adjust the pH is an alkaline solution.

[0034] In this embodiment, the alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution; the concentration of the alkaline solution is 0.1~0.5M.

[0035] This invention also provides a copper oxide heterojunction hollow sphere, prepared according to the method described above.

[0036] This invention also provides the application of the aforementioned copper oxide heterojunction hollow spheres as catalysts in the catalytic oxidation of CO.

[0037] The following examples illustrate the present invention, which provides a copper oxide heterojunction hollow sphere, its preparation method, and its application. Figures 1-3 The following descriptions are provided, but they should not be construed as limiting the scope of protection of this invention.

[0038] Example 1

[0039] First, weigh 2.0 g of copper nitrate trihydrate and 1.566 g of serine (copper ion to ligand molar ratio of 1:1.8) and dissolve them in 150 ml of a water / ethylene glycol mixed solvent, with 75 ml of water and 75 ml of ethylene glycol. Adjust the pH to 6.5 with 0.1 M NaOH and stir thoroughly for 1 h to ensure complete dissolution of copper nitrate trihydrate and iminodiacetic acid. Transfer the solution to a 200 mL autoclave and react at 160 °C for 48 h. After the reaction is complete, cool to room temperature and collect the precipitate by centrifugation and washing. Finally, place the dried precipitate in a muffle furnace, maintain the temperature at 160 °C for 0.5 h, and then calcine it at 300 °C for 1 h to obtain the copper oxide heterojunction hollow sphere material.

[0040] from Figure 1 The diffraction peaks of both cuprous oxide and copper oxide phases can be seen, which proves that the copper oxide (copper oxide-cuprous oxide) heterojunction material prepared at the gradient oxidation temperature is a copper oxide (copper oxide-cuprous oxide) heterojunction material. Figure 2 It exhibits a hollow spherical structure and a rough surface, which may be due to the heterojunction structure where cuprous oxide and copper oxide coexist.

[0041] Example 2

[0042] Weigh 2.0 g of copper nitrate trihydrate and 1.044 g of serine (copper ion to ligand molar ratio of 1:1.2), and dissolve them in 150 ml of a water / ethylene glycol mixed solvent, with 75 ml of water and 75 ml of ethylene glycol. Adjust the pH to 6.5 with 0.1 M NaOH, and stir thoroughly for 1 h to ensure complete dissolution of copper nitrate trihydrate and iminodiacetic acid. Transfer the solution to a 200 mL autoclave and react at 160 °C for 48 h. After the reaction is complete, cool to room temperature and collect the precipitate by centrifugation and washing. Finally, place the dried precipitate in a muffle furnace, maintain the temperature at 160 °C for 0.5 h, and then calcine it at 300 °C for 1 h to obtain the copper oxide heterojunction hollow sphere material.

[0043] Example 3

[0044] Weigh 2.0 g of copper nitrate trihydrate and 2.175 g of serine (copper ion to ligand molar ratio of 1:2.5), and dissolve them in 150 ml of a water / ethylene glycol mixed solvent, with 75 ml of water and 75 ml of ethylene glycol. Adjust the pH to 6.5 with 0.1 M NaOH, and stir thoroughly for 1 h to ensure complete dissolution of copper nitrate trihydrate and iminodiacetic acid. Transfer the solution to a 200 mL autoclave and react at 160 °C for 48 h. After the reaction is complete, cool to room temperature and collect the precipitate by centrifugation and washing. Finally, place the dried precipitate in a muffle furnace, maintain the temperature at 160 °C for 0.5 h, and then calcine it at 300 °C for 1 h to obtain the copper oxide heterojunction hollow sphere material.

[0045] Example 4

[0046] Weigh 2.0 g of copper nitrate trihydrate and 2.312 g of histidine (copper ion to ligand molar ratio of 1:1.8), and dissolve them in 150 ml of a water / ethylene glycol mixed solvent, with 75 ml of water and 75 ml of ethylene glycol. Adjust the pH to 6.5 with 0.1 M NaOH, and stir thoroughly for 1 h to ensure complete dissolution of copper nitrate trihydrate and iminodiacetic acid. Transfer the solution to a 200 mL autoclave and react at 160 °C for 48 h. After the reaction is complete, cool to room temperature and collect the precipitate by centrifugation and washing. Finally, place the dried precipitate in a muffle furnace, maintain the temperature at 160 °C for 0.5 h, and then calcine it at 300 °C for 1 h to obtain the copper oxide heterojunction hollow sphere material.

[0047] Example 5

[0048] First, weigh 2.0 g of copper nitrate trihydrate and 1.984 g of iminodiacetic acid (copper ion to ligand molar ratio of 1:1.8) and dissolve them in 150 ml of a water / ethylene glycol mixed solvent, with 75 ml of water and 75 ml of ethylene glycol. Adjust the pH to 6.5 with 0.1 M NaOH and stir thoroughly for 1 h to ensure complete dissolution of copper nitrate trihydrate and iminodiacetic acid. Transfer the solution to a 200 mL autoclave and react at 120 °C for 24 min. After the reaction is complete, cool to room temperature and collect the precipitate by centrifugation and washing. Finally, place the dried precipitate in a muffle furnace, maintain the temperature at 300 °C for 1 h, and then calcine it at 500 °C for 1 h to obtain the copper oxide heterojunction hollow sphere material.

[0049] Evaluation of the catalyst's activity for CO oxidation:

[0050] The catalytic performance of the catalyst for CO oxidation was evaluated in a vertical fixed-bed continuous flow reactor (quartz tube, inner diameter 8.00 mm). The specific method was as follows: 100 mg of catalyst was fixed in the center of the reaction tube with quartz wool. The reaction gas (1% CO, 20% O2, 79% N2) was controlled by a mass flow controller (MFC) at a total flow rate of 50 mL / min (space velocity 30000 mL·g⁻¹). -1 ·h -1 The reaction mixture is introduced into the reactor, and the reaction temperature is monitored in real time using a built-in thermocouple, while the furnace temperature is controlled by an external thermocouple. Activity testing is conducted under programmed temperature ramping (e.g., 50~300℃), and the CO conversion rate of the reaction tail gas is analyzed online using a PerkinElmer GC-680 gas chromatograph equipped with a TCD detector.

[0051] from Figure 3 As can be seen, the copper oxide heterojunction hollow sphere material prepared in Example 1 exhibits the best CO catalytic oxidation performance. Compared with Examples 2 (100% CO conversion at 240℃) and 3 (100% CO conversion at 200℃), Example 1 (100% CO conversion at 160℃) shows differences in the molar ratio of copper ions to ligands under the same ligand type conditions. Compared with Examples 4 (100% CO conversion at 240℃) and 5 (100% CO conversion at 180℃), Example 1 changes the type of ligand under the same copper ion to ligand molar ratio conditions, thus affecting the CO catalytic oxidation performance of the prepared material. This indicates that a suitable ligand type and copper ion to ligand molar ratio can promote the synergistic effect of divalent and monovalent copper in the copper oxide (copper oxide-cuprous oxide) heterojunction structure, thus promoting the improvement of CO catalytic oxidation performance.

[0052] The specific embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited to the above embodiments. For those skilled in the art, various adjustments, modifications, or substitutions can be made to the embodiments without departing from the core principles and spirit of the present invention, but these modifications still fall within the protection scope of the present invention.

Claims

1. A method for preparing copper oxide heterojunction hollow spheres, characterized in that, The method includes the following steps: A water-soluble copper salt and an amphiphilic organic ligand containing carboxyl and amino groups were dissolved in an alcohol-water solvent, and the pH was adjusted to 5.5-7.5 to form a homogeneous amphiphilic copper complex solution. The amphiphilic copper complex solution was placed in a closed reactor to carry out a self-assembly reaction. After the reaction was completed, the precursor was obtained by washing and drying. The precursor was subjected to gradient oxidation and calcination to obtain hollow spheres with a copper oxide-cuprous oxide heterostructure.

2. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The water-soluble copper salt is selected from at least one of copper nitrate trihydrate, copper sulfate, or copper chloride.

3. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The amphiphilic organic ligand is selected from at least one of iminodiacetic acid, serine, or histidine.

4. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The molar ratio of copper ions to amphiphilic organic ligands in the amphiphilic copper complex solution is 1:(1.2~2.5).

5. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The alcohol-water solvent is a mixture of water and C1-C3 alcohol in a volume ratio of 1:(0.5~2).

6. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The self-assembly reaction is carried out at a temperature of 160-180°C for 36-48 hours.

7. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The gradient oxidation calcination includes first heating to 100~200℃ and calcining for 0.5~1h, then heating to 300~500℃ and calcining for 1~3h.

8. The method for preparing copper oxide heterojunction hollow spheres according to claim 1, characterized in that, The pH adjuster used to adjust the pH is an alkaline solution.

9. A copper oxide heterostructure hollow sphere, characterized in that, Prepared by the method according to any one of claims 1-8.

10. The application of the copper oxide heterojunction hollow spheres according to claim 9 as a catalyst in the catalytic oxidation of CO.

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