A method for preparing CdS@CoP@NC heterojunction photocatalysts based on ZIF-67 precursor
By preparing a porous CdS@CoP@NC heterojunction photocatalyst, the problems of electron-hole recombination and photocorrosion in the photocatalytic process of CdS were solved, and the high-efficiency photocatalytic water splitting hydrogen production performance of CdS was realized.
Patent Information
- Application Number
- CN202110624446.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-06-04
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2041-06-04
AI Technical Summary
CdS is prone to electron-hole recombination and photocorrosion during photocatalysis, resulting in poor stability. Existing technologies are insufficient to effectively improve its photocatalytic performance.
ZIF-67 material was synthesized by solvothermal method, and CoP@NC composite material was prepared by one-step pyrolysis process. CdS nanosheets were then assembled on its surface to form a porous CdS@CoP@NC heterojunction photocatalyst.
It significantly improved the photocatalytic activity and stability of CdS, thereby enhancing the efficiency of photocatalytic water splitting for hydrogen production.
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Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of visible light catalyst material preparation, specifically relating to a method for preparing CdS@CoP@NC heterojunction photocatalysts based on ZIF-67 precursor. Background Technology
[0002] With the development of human society, the environmental problems caused by the massive consumption of traditional fossil fuels are becoming increasingly serious, making the development and application of clean energy extremely urgent. Currently, hydrogen is considered the most promising energy carrier to replace traditional fossil fuels. Solar photocatalytic water splitting for hydrogen production is one of the most promising green hydrogen production technologies, and the key to improving the efficiency of photocatalytic water splitting for hydrogen production is the development of highly efficient catalysts. As a typical transition metal sulfide, CdS possesses excellent visible light response, suitable redox potential, and a band gap (approximately 2.4 eV), thus becoming one of the important photocatalytic materials. However, CdS is prone to electron-hole recombination and photocorrosion during photocatalysis, exhibiting poor stability. Therefore, developing novel CdS heterojunction photocatalytic materials and improving their photocatalytic performance has become one of the urgent problems to be solved.
[0003] Porous materials, due to their large specific surface area and abundant pore structure, can enhance the absorption of visible light, which is beneficial for accelerating surface mass transfer and diffusion and the transfer of photogenerated electrons, thereby effectively improving photocatalytic activity. Metal-organic frameworks (MOFs), porous coordination polymers composed of metal ions and organic ligands, possess advantages such as tunable structure and pores, large specific surface area, and high porosity, and are considered ideal precursors for preparing porous semiconductor-based heterostructures. Furthermore, transition metal phosphides are a class of non-noble metal cocatalysts that can be used for photocatalytic hydrogen production. Therefore, constructing a CdS / CoP heterojunction photocatalyst based on a porous carbon support using ZIF-67 is expected to significantly improve the performance of CdS-based photocatalytic materials. Summary of the Invention
[0004] To address the above technical issues, ZIF-67 material was first synthesized via a solvothermal method. Using ZIF-67 as a precursor, the carbonization of ZIF-67 and the phosphating of cobalt were simultaneously completed through a one-step pyrolysis process in a nitrogen atmosphere to obtain a CoP@NC composite material. CdS nanosheets were then assembled on its surface to obtain a CdS@CoP@NC heterojunction photocatalyst with a porous structure.
[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution:
[0006] A method for preparing CdS@CoP@NC heterojunction photocatalysts based on ZIF-67 precursor, characterized in that the preparation method includes the following steps:
[0007] (1) Preparation of ZIF-67: 1 mmol of cobalt nitrate and 4 mmol of 2-methylimidazole were dissolved in 25 mL of methanol and ultrasonically dispersed for 10 min. The methanol solution of cobalt nitrate was slowly added to the methanol solution of 2-methylimidazole under stirring for 30 min. After standing for 6 to 12 h, the solid was centrifuged and washed three times each with methanol and deionized water. Then it was dried at 60 °C to obtain the ZIF-67 precursor.
[0008] (2) Preparation of CoP@NC: ZIF-67 precursor and sodium hypophosphite were mixed evenly in a certain proportion. A ceramic boat containing the mixture of ZIF-67 and sodium hypophosphite was placed in a high-temperature tube furnace. High-purity nitrogen was introduced and the temperature was raised to 300-500℃ at a rate of 3℃ / min. The temperature was kept constant for 4-8h. At the same time, the pyrolysis carbonization of ZIF-67 and the phosphating reaction of metallic cobalt were carried out. After the reaction was completed, the mixture was cooled to room temperature and washed three times each with deionized water and anhydrous ethanol. Then it was dried at 60℃ to obtain the CoP@NC composite material.
[0009] (3) Preparation of CdS@CoP@NC: Cadmium acetate and thiourea were dissolved in deionized water in a certain proportion, and a certain volume of diethylenetriamine was added. After mixing evenly, CoP@NC was added and ultrasonically dispersed for 30 min. The mixture was stirred for 6-12 h in an 80℃ water bath, centrifuged, and washed 3 times each with deionized water and anhydrous ethanol. Then, the mixture was dried at 60℃ to obtain the CdS@CoP@NC heterojunction photocatalyst.
[0010] Furthermore, in step (2), the mass ratio of ZIF-67 to sodium hypophosphite is 1:1 to 1:5.
[0011] Furthermore, in step (3), the molar ratio of cadmium acetate to thiourea is 1:2 to 1:4.
[0012] Furthermore, in step (3), the volume ratio of the aqueous solution of cadmium acetate and thiourea to diethylenetriamine is 1:2 to 1:4.
[0013] Furthermore, in step (3), the mass ratio of CoP@NC to CdS is 1:2 to 1:7.
[0014] The CdS@CoP@NC heterojunction photocatalyst prepared according to the above method can be used in the photocatalytic water splitting reaction to produce hydrogen.
[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:
[0016] (1) A porous CoP@NC composite material was obtained by one-step pyrolysis carbonization and phosphating of ZIF-67 precursor. The original porous structure of the precursor ZIF-67 was maintained, and it had a large specific surface area and highly dispersed CoP cocatalyst.
[0017] (2) Further CdS nanosheets were assembled on the surface of CoP@NC composite material, with uniform morphology and good dispersion.
[0018] (3) The band gap of CdS is reduced by the heterojunction formed by CdS nanosheets and CoP, which can effectively separate and transfer photogenerated electron-hole pairs.
[0019] (4) The prepared CdS@CoP@NC heterojunction photocatalyst has excellent activity and stability when used for photocatalytic water splitting to produce hydrogen. Attached Figure Description
[0020] Figure 1 Scanning electron microscope image of CdS@CoP@NC prepared in Example 3.
[0021] Figure 2 The XRD spectra are for CdS, CoP@NC, and CdS@CoP@NC.
[0022] Figure 3 The photocatalytic water splitting performance of CdS and CdS@CoP@NC for hydrogen production. Detailed Implementation
[0023] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.
[0024] Example 1
[0025] Preparation of flake CdS: 0.27 g (1 mmol) cadmium acetate and 0.28 g (3.5 mmol) thiourea were dispersed in a mixed solution of 20 ml deionized water and 40 ml diethylenetriamine, sonicated for 30 min, and then stirred in an 80 °C water bath for 12 h. The product was washed with deionized water and ethanol and centrifuged. Finally, it was dried to obtain flake CdS.
[0026] Example 2
[0027] Preparation of ZIF-67 precursor: 0.29 g (1 mmol) cobalt nitrate and 0.34 g (4 mmol) 2-methylimidazole were dissolved in 25 mL of methanol and sonicated for 10 min. Then, the methanol solution of cobalt nitrate was slowly added to the methanol solution of 2-methylimidazole under stirring for 30 min. After standing for 12 h, the mixture was centrifuged and the recovered solid was washed three times each with methanol and deionized water. The solid was then dried at 60 °C to obtain the ZIF-67 precursor.
[0028] Preparation of CoP@NC: ZIF-67 and sodium hypophosphite were mixed uniformly at a mass ratio of 1:5 and transferred into a ceramic boat. The ceramic boat containing the ZIF-67 and sodium hypophosphite mixture was placed in a high-temperature tube furnace, and high-purity nitrogen was introduced. The temperature was increased to 350℃ at a rate of 3℃ / min and held at a constant temperature for 4 hours. After the reaction was completed, the mixture was cooled to room temperature and washed three times each with deionized water and anhydrous ethanol. Then, it was dried at 60℃ to obtain the CoP@NC composite material.
[0029] Example 3
[0030] Preparation of ZIF-67 precursor: Same as in Example 2.
[0031] CoP@NC preparation: Same as in Example 2.
[0032] Preparation of CdS@CoP@NC: 0.27 g cadmium acetate and 0.28 g thiourea were added to 20 mL deionized water, followed by 40 mL diethylenetriamine. After thorough mixing, 0.07 g CoP@NC was added and ultrasonically dispersed for 30 min. The beaker was then placed in a water bath at 80 °C and stirred for 12 h. The mixture was centrifuged, washed three times each with deionized water and anhydrous ethanol, and then dried at 60 °C to obtain the CdS@CoP@NC-1 heterojunction photocatalyst. Its morphology and structure are shown below. Figure 1 As shown.
[0033] Example 4
[0034] Preparation of ZIF-67 precursor: Same as in Example 2.
[0035] CoP@NC preparation: Same as in Example 2.
[0036] Preparation of CdS@CoP@NC: 0.27 g cadmium acetate and 0.28 g thiourea were added to 20 mL deionized water, followed by 40 mL diethylenetriamine. After thorough mixing, 0.11 g CoP@NC was added and ultrasonically dispersed for 30 min. The beaker was then placed in a water bath at 80 °C and stirred for 12 h. After centrifugation, the mixture was washed three times each with deionized water and anhydrous ethanol, and then dried at 60 °C to obtain the CdS@CoP@NC-2 composite photocatalyst.
[0037] Example 5
[0038] Preparation of ZIF-67 precursor: Same as in Example 2.
[0039] CoP@NC preparation: Same as in Example 2.
[0040] Preparation of CdS@CoP@NC: 0.27 g cadmium acetate and 0.28 g thiourea were added to 20 mL deionized water, followed by 40 mL diethylenetriamine. After thorough mixing, 0.16 g CoP@NC was added and ultrasonically dispersed for 30 min. The beaker was then placed in a water bath at 80 °C and stirred for 12 h. After centrifugation, the mixture was washed three times each with deionized water and anhydrous ethanol, and then dried at 60 °C to obtain the CdS@CoP@NC-3 composite photocatalyst.
[0041] Example 6
[0042] Preparation of ZIF-67 precursor: Same as in Example 2.
[0043] CoP@NC preparation: Same as in Example 2.
[0044] Preparation of CdS@CoP@NC: 0.27 g cadmium acetate and 0.28 g thiourea were added to 20 mL deionized water, followed by 40 mL diethylenetriamine. After thorough mixing, 0.27 g CoP@NC was added and ultrasonically dispersed for 30 min. The beaker was then placed in a water bath at 80 °C and stirred for 12 h. After centrifugation, the mixture was washed three times each with deionized water and anhydrous ethanol, and then dried at 60 °C to obtain the CdS@CoP@NC-4 composite photocatalyst.
[0045] The photocatalytic hydrogen production performance of the catalysts prepared in Examples 1-6 was tested. The specific reaction conditions were as follows: 10 mg of photocatalyst was added to 30 ml of a 25% (v / v) lactic acid solution, sonicated for 30 min, and then transferred to a quartz glass reactor. The reactor was evacuated, and circulating water at 5°C was used to maintain a constant reactor temperature. An LED lamp was used as the light source, and illumination was maintained for 3 h at a stirring rate of 400 r / min. Online gas chromatography was used to analyze the hydrogen production curve of photocatalytic water splitting over time. The results are shown in [Figure 1]. Figure 3 It can be seen that the hydrogen production rate is significantly improved after CdS is combined with the cocatalyst CoP@NC. When the mass fraction of CoP@NC is 20 wt%, the hydrogen production rate of CdS@CoP@NC-3 reaches 48.76 mmol / h. -1 g -1 It improved by 46 times compared to unmodified CdS.
[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.
Claims
1. A method for preparing CdS@CoP@NC heterojunction photocatalysts based on ZIF-67 precursor, characterized in that: The preparation method comprises the following steps: (1) Preparation of ZIF-67: 1 mmol of cobalt nitrate and 4 mmol of 2-methylimidazole were dissolved in 25 mL of methanol and ultrasonically dispersed for 10 min. The methanol solution of cobalt nitrate was slowly added to the methanol solution of 2-methylimidazole under stirring. The mixture was stirred for 30 min and allowed to stand for 6–12 h. The solid was centrifuged and washed three times each with methanol and deionized water. The solid was then dried at 60 °C to obtain the ZIF-67 precursor. (2) Preparation of CoP@NC: ZIF-67 precursor and sodium hypophosphite were mixed evenly in a certain proportion. A ceramic boat containing the mixture of ZIF-67 and sodium hypophosphite was placed in a high-temperature tube furnace. High-purity nitrogen was introduced and the temperature was raised to 300-500℃ at a rate of 3℃ / min. The temperature was kept constant for 4-8h. At the same time, the pyrolysis carbonization of ZIF-67 and the phosphating reaction of metallic cobalt were carried out. After the reaction was completed, the mixture was cooled to room temperature and washed three times each with deionized water and anhydrous ethanol. Then it was dried at 60℃ to obtain the CoP@NC composite material. (3) Preparation of CdS@CoP@NC: Cadmium acetate and thiourea were dissolved in deionized water in a certain proportion, and a certain volume of diethylenetriamine was added. After mixing evenly, CoP@NC was added and ultrasonically dispersed for 30 min. The mixture was stirred for 6-12 h in an 80℃ water bath, centrifuged, and washed 3 times each with deionized water and anhydrous ethanol. Then, the mixture was dried at 60℃ to obtain the CdS@CoP@NC heterojunction photocatalyst.
2. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of ZIF-67 to sodium hypophosphite is 1:1 to 1:
5.
3. The preparation method according to claim 1, characterized in that: In step (3), the molar ratio of cadmium acetate to thiourea is 1:2 to 1:
4.
4. The preparation method according to claim 1, characterized in that: In step (3), the volume ratio of the aqueous solution of cadmium acetate and thiourea to diethylenetriamine is 1:2 to 1:
4.
5. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of CoP@NC to CdS is 1:2 to 1:
7.
6. A method for preparing CdS@CoP@NC heterojunction photocatalyst based on ZIF-67 precursor according to any one of claims 1 to 5, characterized in that, The prepared catalyst can be used in the photocatalytic water splitting reaction to produce hydrogen.