A photocatalyst and its preparation method and application

Abstract

The present invention relates to a photocatalyst, a preparation method and application thereof, wherein the photocatalyst is a ZnO / ACeVO4 composite material. The preparation method of the photocatalyst comprises the following steps: S1, dispersing ZnO and CeVO4 in an organic solvent to obtain a mixed solution; S2, heating the mixed solution obtained in step S1; S3, washing the precipitate in the solution treated in step S2 with alkali, ultrapure water and an organic solvent, respectively, and obtaining the photocatalyst after drying. The ZnO / ACeVO4 composite material can be used in photocatalytic water decomposition to produce hydrogen, and has a high photocatalytic efficiency. In addition, the photocatalyst of the present invention is a composite material based on ZnO and CeVO4, both of which are relatively inexpensive semiconductor materials, that is, the raw material cost of the photocatalyst of the present invention is also relatively low.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photocatalytic water decomposition to produce hydrogen, and in particular to a photocatalyst and a preparation method and application thereof. Background Art

[0002] With the massive consumption of non-renewable energy sources such as coal, oil, and natural gas, increasingly prominent energy and environmental issues have attracted more attention. Hydrogen, due to its high energy density, renewability, and pollution-free nature, is considered a promising alternative to fossil fuels to alleviate energy shortages and environmental pollution. Photocatalytic hydrogen production is a technology that decomposes abundant water resources into hydrogen under sunlight. Due to its green and environmentally friendly nature, it has become one of the most promising technologies. In recent years, semiconductors with excellent physical, chemical, and electrical properties have been widely used as photocatalysts for the conversion of solar energy to chemical energy, such as TiO2, C3N4, ZnS, CdS, etc.

[0003] Zinc oxide (ZnO) photocatalysts have attracted considerable attention due to their excellent stability, non-toxicity, low cost, wide band gap, strong UV absorption, high refractive index, and excellent photocatalytic performance. ZnO has a wide range of applications in fluorescence, adsorption, thin films, photocatalysis, electrocatalysis, and pollutant degradation. However, in photocatalysis, ZnO suffers from serious photocorrosion, rapid recombination of photogenerated electron-hole pairs, and weak visible light absorption, which limit its application. Improving or overcoming these limitations of ZnO could improve its application in photocatalytic hydrogen production, providing new insights and development directions for developing cost-effective and efficient photocatalysts for hydrogen production. Summary of the Invention

[0004] The purpose of the present invention is to provide a photocatalyst and a preparation method and application thereof, which are low in price and have high hydrogen production efficiency.

[0005] To achieve the above object, the present invention discloses a photocatalyst, which is a ZnO / ACeVO4 composite material.

[0006] Preferably, in the ZnO / ACeVO4 composite material, the molar ratio of ZnO to CeVO4 is 1:(0.07-0.2).

[0007] Preferably, A=0.07 or 0.1 or 0.15 or 0.2.

[0008] The present invention also discloses a method for preparing a photocatalyst, which is used to prepare any of the above-mentioned photocatalysts, and comprises the following steps:

[0009] S1, dispersing ZnO and CeVO4 in an organic solvent to obtain a mixed solution;

[0010] S2, heating the mixed solution obtained in step S1;

[0011] S3. Washing the precipitate in the solution treated in step S2 with alkali, ultrapure water and an organic solvent respectively, and obtaining the photocatalyst after drying.

[0012] Preferably, in step S1, the preparation method of ZnO is: dispersing zinc acetate dihydrate in methanol and stirring for 25 to 35 minutes to obtain solution B; dissolving potassium hydroxide in methanol and stirring for 25 to 35 minutes to obtain solution C; heating solution B at 55 to 65°C, and dripping solution C into solution B to form precipitate B, stirring for 2.8 to 3.2 hours, centrifuging the precipitate B, washing the precipitate B with deionized water and an organic solvent to remove surface impurities, and then drying at 70 to 90°C for 16 to 25 hours, and grinding to obtain ZnO nanomaterials.

[0013] Preferably, in step S1, the preparation method of CeVO4 is: dissolving Ce(NO3)3·6H2O in deionized water to obtain solution D; dissolving NH4VO3 in deionized water to obtain solution E; dripping solution D into solution E to obtain a mixed solution F, and storing the mixed solution F at 80-100°C for 2-4 hours to obtain a precipitate C; after natural cooling, washing the precipitate C with an organic solvent and distilled water, and then drying it at 70-90°C to obtain CeVO4.

[0014] Preferably, in step S1, the organic solvent is ethanol; while the ZnO and CeVO4 are dispersed in the organic solvent, ultrasonic treatment is performed for 15 to 60 minutes; and in step S2, the heating step is performed by stirring the mixed solution obtained in step S1 in an oil bath at 80 to 100°C for 1 to 3 hours.

[0015] Preferably, in step S3, the precipitate in the solution treated in step S2 is washed 2 to 4 times with NaOH, ultrapure water and ethanol respectively, with the concentration of NaOH being 0.1 to 1 mol / L; the washed precipitate is dried in a forced air drying oven for 12 to 36 hours at a temperature of 70 to 90°C.

[0016] In addition, the present invention also discloses the use of any of the above-mentioned photocatalysts or the photocatalyst prepared by the above-mentioned method for preparing the photocatalyst in photocatalytic water decomposition to produce hydrogen.

[0017] Preferably, when the photocatalyst described in any one of the above items or the photocatalyst prepared by the preparation method of any one of the above items is used for photocatalytic water decomposition to produce hydrogen, 0.30-0.40M Na2S and 0.20-0.30MNa2SO3 solutions are used as sacrificial agents.

[0018] The present invention has the following beneficial effects:

[0019] 1. The photocatalyst of the present invention can be used for photocatalytic decomposition of water to produce hydrogen.

[0020] 2. The photocatalyst of the present invention is a composite material based on ZnO and CeVO4. Both materials are relatively cheap semiconductor materials, that is, the raw material cost of the photocatalyst of the present invention is also relatively low.

[0021] 3. The present invention combines ZnO and CeVO4, significantly improving the photocatalytic hydrogen production performance by adjusting the CeVO4 content. Compared to pure catalysts, the nanocomposite ZnO / ACeVO4 exhibits superior photocatalytic hydrogen production activity. Furthermore, during the composite process, ZnO and CeVO4 form a Z-shaped heterojunction with strong electronic interaction and rich oxygen vacancies, accelerating the separation and migration of electron-hole pairs. The photocatalyst of the present invention has a photocatalytic performance of up to 7.9 times that of ZnO and 31.7 times that of CeVO4.

[0022] 4. The present invention achieves high-efficiency photocatalytic water decomposition to produce hydrogen and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 These are the XRD patterns of ZnO, CeVO4 and ZnO / ACeVO4 prepared in the present invention.

[0024] Figure 2 These are scanning and transmission electron microscope morphologies of ZnO, CeVO4 and ZnO / ACeVO4 prepared in the present invention.

[0025] Figure 3 This is a test chart of the photocatalytic water decomposition and hydrogen production performance of the ZnO, CeVO4, and ZnO / ACeVO4 composite materials prepared in the present invention under full-spectrum illumination of a 300W xenon lamp with Na2S and Na2SO3 as sacrificial agents.

[0026] Figure 4 This is a stability test chart of the ZnO / ACeVO4 composite material prepared in the present invention under full-spectrum illumination, using Na2S and Na2SO3 as sacrificial agents, to photocatalytically decompose water to produce hydrogen. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] The present invention discloses a photocatalyst comprising a ZnO / ACeVO4 composite material, wherein the molar ratio of ZnO to CeVO4 is 1:(0.07-0.2), i.e., A = 0.07-0.2. The present invention utilizes a one-step synthesis method to prepare the ZnO / ACeVO4 composite material, as illustrated below by specific examples.

[0029] Example 1:

[0030] A method for preparing a photocatalyst (ZnO / 0.07CeVO4 composite material) comprises the following steps:

[0031] S1. Prepare a mixed solution containing ZnO and CeVO4. The specific steps are as follows:

[0032] S1a, preparation of ZnO nanoparticles:

[0033] Disperse zinc acetate dihydrate in a flask containing 30 ml of methanol and stir for 30 minutes to obtain solution B. Dissolve potassium hydroxide in 30 ml of methanol and stir for 30 minutes to obtain solution C. Slowly add solution C dropwise to solution B in a 60°C oil bath, forming a white precipitate. After stirring for 3 hours, precipitate B is centrifuged and washed three times with deionized water and ethanol to remove surface impurities. The precipitate is then dried in an 80°C oven for 24 hours and ground to obtain ZnO nanomaterials.

[0034] S1b, preparation of CeVO4:

[0035] Ce(NO₃)₃·6H₂O was added to a beaker and dissolved in 35 mL of deionized water to obtain a nearly transparent solution D. NH₄VO₃ was added to another beaker and dissolved in 35 mL of deionized water to obtain solution E. Solution D was added dropwise to solution E to obtain mixed solution F. Mixed solution F was heated in a 100 mL hydrothermal autoclave at 90°C for 3 h to obtain precipitate C. After cooling naturally, precipitate C was washed with ethanol and distilled water and then dried in a 90°C oven to obtain CeVO₄.

[0036] S1c, disperse 1 mmol of ZnO and 0.07 mmol of CeVO4 in 50 ml of ethanol solution and ultrasonicate for 30 minutes to obtain a mixed solution.

[0037] S2. Stir the mixed solution obtained in step S1c in an oil bath at 90°C for 1.5 h.

[0038] S3. Wash the precipitate in the solution treated in step S2 three times with 0.5 mol / L NaOH, ultrapure water, and ethanol, respectively, to remove surface impurities. Dry the washed precipitate A in a forced air drying oven at 80° C. for 24 h to obtain a ZnO / 0.07CeVO4 composite material.

[0039] Example 2:

[0040] This embodiment is for preparing a ZnO / 0.1CeVO4 composite material, which differs from the first embodiment in that in step S1c, 1 mmol of ZnO and 0.1 mmol of CeVO4 are dispersed in 50 ml of ethanol solution.

[0041] Example 3:

[0042] This embodiment is for preparing a ZnO / 0.15CeVO4 composite material, which differs from the first embodiment in that in step S1c, 1 mmol of ZnO and 0.15 mmol of CeVO4 are dispersed in 50 ml of ethanol solution.

[0043] Example 4:

[0044] This embodiment is for preparing a ZnO / 0.2CeVO4 composite material, which differs from the first embodiment in that in step S1c, 1 mmol of ZnO and 0.2 mmol of CeVO4 are dispersed in 50 ml of ethanol solution.

[0045] In order to verify the present invention, the prepared ZnO, CeVO4 and ZnO / ACeVO4 nanomaterials were characterized in terms of phase and morphology, and their photocatalytic water decomposition and hydrogen production performance were tested.

[0046] 1. Phase Characterization

[0047] See also Figure 1, which shows the XRD patterns of ZnO, CeVO4, ZnO / 0.07CeVO4, ZnO / 0.1CeVO4, ZnO / 0.15CeVO4, and ZnO / 0.2CeVO4. It can be seen that the XRD spectrum of pure ZnO has very sharp diffraction peaks and no impurity peaks, which is in good agreement with the XRD pattern of ZnO standard card PDF#36-1451, indicating good crystallinity and high purity of ZnO. We also found that pure zinc oxide has a hexagonal wurtzite structure, with diffraction peaks at 31.7°, 34.4°, 36.2°, 47.4°, 56.5°, 62.8°, 66.3°, 68.0°, and 69.1°, corresponding to different ZnO crystal planes. Pure CeVO4 has five obvious characteristic diffraction peaks at 18.2°, 24.1°, 32.5°, 48.1° and 60.5°, corresponding to the (101), (200), (112), (312) and (332) crystal planes of CeVO4, respectively. The XRD pattern of CeVO4 is in good agreement with the XRD pattern of the standard card PDF#84-1457. The diffraction peaks of ZnO and CeVO4 can be observed simultaneously in the XRD pattern of the composite sample, and the relative intensity of the diffraction peaks increases with the increase of CeVO4 content. For example, the diffraction peaks of the (112) and (312) crystal planes are significantly enhanced, indicating the successful doping of CeVO4 and the successful preparation of the photocatalyst. Most importantly, no other impurity peaks were detected in the XRD patterns of all materials, indicating that the prepared samples are of high purity.

[0048] 2. Morphology Characterization

[0049] The morphologies of pure ZnO, pure CeVO4 and composite catalyst ZnO / 0.1CeVO4 samples were measured by scanning electron microscopy (SEM). Figure 2 As shown in a, ZnO is a nanoparticle with a small particle size and is easy to accumulate; in addition, Figure 2 b It can be seen that CeVO4 exists in the form of irregular nanoparticles with large particle size. Figure 2 c. In the ZnO / 0.1CeVO4 composite, the morphology of the sample clearly changes. The CeVO4 nanoparticles accumulate into nanosheets, and the ZnO is evenly distributed on the CeVO4 surface, forming a strong attachment. The close bond between ZnO and CeVO4 accelerates the transfer of electron and hole pairs.

[0050] Figure 2 d, 2e, and 2f are transmission electron microscopy (TEM) images of ZnO, CeVO4, and ZnO / 0.1CeVO4, respectively. ZnO, CeVO4, and ZnO / 0.1CeVO4 exhibit a granular structure consistent with the SEM image. HR-TEM further studied the surface morphology of ZnO / 0.1CeVO4, such as Figure 2 As shown in Figure g, the lattice stripes with a lattice spacing of 0.247 nm correspond to the ZnO (101) crystal plane, and the lattice stripes with a lattice spacing of 0.367 nm correspond to the ZnO (200) crystal plane. In addition, the energy dispersive spectroscopy (EDS) technique was used to detect the elements of ZnO / 0.1CeVO4. From the morphology of ZnO / 0.1CeVO4 ( Figure 2 g) and the distribution of elements in ZnO / 0.1CeVO4 ( Figure 2 i) It can be seen that the four elements Zn, O, Ce, and V are evenly distributed, indicating that the preparation of the composite photocatalyst is successful.

[0051] 3. Photocatalytic water splitting and hydrogen production performance test under full spectrum illumination

[0052] The photocatalytic hydrogen evolution activity of ZnO / ACeVO4 nanocomposites was investigated under full-spectrum illumination. Photocatalytic hydrogen production experiments were conducted in a quartz vial (250 mL) under 300 W xenon lamp irradiation. 10 mg of the photocatalyst was ultrasonically dispersed in an aqueous solution containing Na2S (0.35 M, 50 mL) and Na2SO3 (0.25 M, 50 mL) as sacrificial agents. Before illumination, the sampler was evacuated three times to completely remove the air inside, and 20 mL of argon (99.9%) was added to the photocatalytic reactor. Throughout the reaction, the temperature was maintained at 5°C using a circulating cooling system. The catalyst was irradiated under the xenon lamp for 3 hours, and hydrogen production was monitored every 30 minutes using a gas chromatograph (GC-9790II, Ar, TCD detector).

[0053] Depend on Figure 3 and Figure 4 It can be seen that a series of ZnO / ACeVO4 samples have good performance in photocatalytic water splitting and hydrogen production. Figure 3 It can be seen that ZnO / 0.1CeVO4 has the best photocatalytic performance. Figure 4 It can be seen that the photocatalyst provided by the present invention has stable photocatalytic performance.

[0054] In the above tests, the optimal hydrogen production rate of ZnO / 0.1CeVO4 composite material was 1288.7 μmol·h −1 ·g −1 , which are 7.9 times that of pure ZnO and 31.7 times that of CeVO4.

[0055] In summary, the excellent photocatalytic performance of ZnO / ACeVO4 is due to the synergistic effect of the heterojunction structure of the ZnO / ACeVO4 composite material, which is conducive to the absorption of light and the generation, separation and transfer of photogenerated charges, while reducing the recombination of photogenerated charges. ZnO / ACeVO4 has abundant active sites and strong electronic interactions. By adjusting the content of CeVO4, the photocatalytic hydrogen production performance is greatly improved. Compared with pure catalysts, the nanocomposite ZnO / ACeVO4 exhibits excellent photocatalytic activity in the visible light region. In addition, during the composite process, ZnO and CeVO4 form a heterojunction with strong electronic interactions and rich oxygen vacancies, which accelerates the separation and migration of electron-hole pairs.

[0056] Through the above research, the present invention also discloses the application of a photocatalyst, a ZnO / ACeVO4 composite material, in photocatalytic water decomposition to produce hydrogen. When the photocatalyst is used to photocatalytically decompose water to produce hydrogen, 0.30-0.40M Na2S and 0.20-0.30M Na2SO3 solutions are used as sacrificial agents.

[0057] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. An application of a photocatalyst, characterized in that: The photocatalyst is a ZnO / CeVO4 composite material, which is used for photocatalytic decomposition of water to produce hydrogen. In the ZnO / CeVO4 composite material, the molar ratio of ZnO to CeVO4 is 1:(0.07-0.15). The preparation method of the photocatalyst comprises the following steps: S1, dispersing ZnO and CeVO4 in an organic solvent to obtain a mixed solution; S2, heating the mixed solution obtained in step S1; S3. Washing the precipitate in the solution treated in step S2 with alkali, ultrapure water and an organic solvent respectively, and obtaining the photocatalyst after drying.

2. The use according to claim 1, characterized in that: The molar ratio of ZnO to CeVO4 is 1:0.07 or 1:0.1 or 1:0.

15.

3. The use according to claim 1, characterized in that In step S1, the preparation method of ZnO is as follows: dispersing zinc acetate dihydrate in methanol and stirring for 25 to 35 minutes to obtain solution B; dissolving potassium hydroxide in methanol and stirring for 25 to 35 minutes to obtain solution C; heating solution B at 55 to 65°C, and dripping solution C into solution B to form precipitate B, stirring for 2.8 to 3.2 hours, centrifuging the precipitate B, washing the precipitate B with deionized water and an organic solvent to remove surface impurities, and then drying at 70 to 90°C for 16 to 25 hours. After grinding, ZnO nanomaterials are obtained.

4. The use according to claim 1, wherein In step S1, the preparation method of CeVO4 is as follows: dissolving Ce(NO3)3·6H2O in deionized water to obtain solution D; dissolving NH4VO3 in deionized water to obtain solution E; adding solution D dropwise into solution E to obtain a mixed solution F; stirring the mixed solution F at 80-100°C for 2-4 hours to obtain a precipitate C; after natural cooling, washing the precipitate C with an organic solvent and distilled water, and then drying at 70-90°C to obtain CeVO4.

5. The use according to claim 1, characterized in that: In step S1, the organic solvent is ethanol; while ZnO and CeVO4 are dispersed in the organic solvent, ultrasonic treatment is performed for 15 to 60 minutes; and in step S2, heating is performed by stirring the mixed solution obtained in step S1 in an oil bath at 80 to 100°C for 1 to 3 hours.

6. The use according to claim 1, characterized in that: In step S3, the precipitate in the solution treated in step S2 is washed 2 to 4 times with NaOH, ultrapure water and ethanol respectively, with the concentration of NaOH being 0.1 to 1 mol / L; the washed precipitate is dried in a forced air drying oven at a temperature of 70 to 90°C for 12 to 36 hours.

7. The use according to claim 1, characterized in that: When the photocatalyst is used for photocatalytic decomposition of water to produce hydrogen, 0.30-0.40M Na2S and 0.20-0.30M Na2SO3 solutions are used as sacrificial agents.

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