Photocatalyst, preparation method and application

Abstract

The present invention discloses a photocatalyst, a preparation method and an application, and belongs to the field of photocatalysts. The photocatalyst is a ZnO / APAN composite material, and A is 11.11-42.88. The photocatalyst preparation method is used to prepare the above-mentioned photocatalyst, comprising the following steps: S1: dispersing zinc oxide in an N,N-dimethylformamide solution, ultrasonically obtaining a solution A after 25-40 minutes, and simultaneously taking PAN and dispersing it in another N,N-dimethylformamide solution, ultrasonically obtaining a solution B after 25-40 minutes, mixing solution A and solution B to obtain a mixed solution, S2: stirring the mixed solution obtained in step S1 for 17-19 hours to obtain a mixed solution, S3: centrifuging the mixed solution obtained in step S2 to obtain a precipitate, then washing the precipitate, removing impurities on the surface of the precipitate, and drying it to obtain a ZnO / APAN composite material as a photocatalyst. The present invention forms a photocatalyst with excellent performance in photocatalytic water decomposition and hydrogen production by compounding ZnO and PAN.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysts, and in particular relates to a photocatalyst, a preparation method and an application thereof. Background Art

[0002] The excessive use of fossil fuels has caused air pollution and global warming, and the development of a clean, renewable alternative fuel is urgent. Hydrogen, as a clean energy source that can replace traditional fossil energy, plays an important role in solving global energy shortages and environmental pollution. Photocatalytic hydrogen evolution technology has attracted great interest due to its huge potential in solar energy storage and green energy production. The use of sunlight to catalytically decompose water to produce hydrogen is a very promising technology. Hydrogen is energy-efficient and pollution-free, and hydrogen generates heat during combustion and is converted back into water. Recent studies have shown that semiconductor doping and the formation of heterojunctions are expected to improve the material's utilization of sunlight, effectively promote the separation and transport of electron-hole pairs, inhibit photocorrosion, and thus improve the efficiency of photocatalytic reactions.

[0003] Zinc oxide (ZnO) is a highly competitive catalyst for photocatalytic water splitting to produce hydrogen, with excellent photoelectric properties, adjustable band gap, high electron density and low price. However, the rapid recombination of photogenerated electrons and holes in ZnO, the wide band gap and poor visible light absorption lead to poor photocatalytic performance of ZnO, which affects its practical application. Therefore, it is necessary to modify it to enhance its application value. At the same time, polyacrylonitrile (PAN) is widely used in electrospun fibers due to its excellent mechanical properties, high strength and thermal stability, and exhibits excellent performance in the degradation of environmental pollutants. However, research on polyacrylonitrile (PAN) as a material for photocatalytic water splitting to produce hydrogen is very limited, which provides ideas for further development of new photocatalysts with excellent performance. To the best of our knowledge, there has been no report on the use of composite nanomaterials of ZnO and PAN for photocatalytic hydrogen production. Summary of the Invention

[0004] The purpose of the present invention is to provide a photocatalyst, a preparation method and an application thereof, so as to overcome at least one of the above-mentioned defects in the prior art.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] The photocatalyst provided by the present invention is a ZnO / APAN composite material, and A is 11.11-42.88.

[0007] Preferably, in the ZnO / APAN composite material, the mass ratio of ZnO to PAN is 100:(11.11-42.88).

[0008] Preferably, A is 11.11, 25 or 42.88.

[0009] The present invention also provides a photocatalyst preparation method for preparing the above-mentioned photocatalyst, comprising the following steps: S1: dispersing zinc oxide in an N,N-dimethylformamide solution, and ultrasonicating for 25-40 minutes to obtain a solution A; simultaneously, dispersing PAN in another N,N-dimethylformamide solution, and ultrasonicating for 25-40 minutes to obtain a solution B; mixing solution A and solution B to obtain a mixed solution; S2: stirring the mixed solution obtained in step S1 for 17-19 hours to obtain a mixed solution; and S3: centrifuging the mixed solution obtained in step S2 to obtain a precipitate, then washing the precipitate to remove impurities on the surface of the precipitate, and drying the precipitate to obtain a ZnO / APAN composite material as a photocatalyst.

[0010] Preferably, in step S2, the solution C in the three-necked flask is heated, and the mixed solution obtained in step S1 is stirred at room temperature at a speed of 500-800 r / min for 17-19 h.

[0011] Preferably, in step S3, the obtained precipitate is washed 2-4 times with water and ethanol respectively to remove surface impurities.

[0012] Preferably, in step S3, drying is performed in a 70-90° C. forced air drying oven for 16-25 hours.

[0013] Preferably, the preparation method of ZnO in step S1 comprises the following steps: dispersing zinc acetate dihydrate in a three-necked flask filled with methanol, stirring for 25-35 minutes to obtain solution C, then dissolving potassium hydroxide in methanol, stirring for 25-35 minutes to obtain solution D, heating solution C in the three-necked flask in an oil bath at 55-65° C., and slowly dripping solution D into solution C to produce precipitation, stirring for 1.8-2.2 hours, centrifuging the precipitate, washing with deionized water and ethanol 2-4 times respectively to remove surface impurities, and then drying in an oven at 70-90° C. for 16-25 hours, and grinding to obtain ZnO nanomaterial.

[0014] The present invention also provides the use of the above-mentioned photocatalyst or the photocatalyst prepared by the above-mentioned photocatalyst preparation method as a photocatalytic water decomposition to produce hydrogen.

[0015] Preferably, 0.30-0.40M Na2S and 0.20-0.30M Na2SO3 solutions are used as sacrificial agents.

[0016] The beneficial effects of the present invention are:

[0017] 1. By compounding ZnO and PAN, a photocatalyst with excellent performance in photocatalytic water decomposition and hydrogen production is formed.

[0018] 2. Doping ZnO with PAN effectively improves charge transfer, inhibits electron-hole pair recombination, and enhances photocatalytic water splitting hydrogen production activity. The heterojunction increases the number of active sites on the photocatalyst, promotes the separation of photogenerated electron-hole pairs, overcomes the photocorrosion effect of a single ZnO catalyst, and exhibits excellent photocatalytic stability. Under the same illumination conditions, the composite material exhibits superior hydrogen production performance compared to pure ZnO and PAN.

[0019] 3. By optimizing the ZnO / APAN composite material, the catalyst with the best photocatalytic performance has a water photolysis hydrogen production rate of 9.8 times and 31.7 times that of ZnO and PAN, respectively.

[0020] 4. It has achieved high-efficiency photocatalytic water decomposition to produce hydrogen and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 These are the XRD patterns of PAN, ZnO, ZnO / 11.1PAN, ZnO / 25PAN, and ZnO / 42.88PAN.

[0022] Figure 2 It is the SEM picture of ZnO of the present invention.

[0023] Figure 3 is a SEM image of PAN of the present invention.

[0024] Figure 4 It is the SEM picture of ZnO / 25PAN of the present invention.

[0025] Figure 5 This is a TEM image of ZnO of the present invention.

[0026] Figure 6 is a TEM image of PAN of the present invention.

[0027] Figure 7 This is a TEM image of ZnO / 25PAN of the present invention.

[0028] Figure 8 This is a high-resolution transmission electron microscope (HR-TEM) image of ZnO / 25PAN of the present invention.

[0029] Figure 9 It is the FTIR spectra of ZnO, PAN and ZnO / APAN of the present invention.

[0030] Figure 10 This is a performance diagram of photocatalytic water decomposition and hydrogen production of PAN, ZnO, ZnO / 11.1PAN, ZnO / 25PAN, and ZnO / 42.88PAN of the present invention.

[0031] Figure 11This is a diagram of the photocatalytic stability of ZnO / APAN of the present invention. DETAILED DESCRIPTION

[0032] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0033] Example 1:

[0034] The photocatalyst provided in this embodiment is a ZnO / APAN composite material, and A is 11.11-42.88. More preferably, A is 11.11, 25, or 42.88. In this embodiment, A is 11.11. The mass ratio of ZnO to PAN in the ZnO / APAN composite material is 100:11.11.

[0035] This embodiment also provides a photocatalyst preparation method, which is used to prepare the above-mentioned photocatalyst, comprising the following steps:

[0036] Preparation of ZnO nanomaterials:

[0037] Zinc acetate dihydrate was dispersed in a three-necked flask containing 30 ml of methanol and stirred for 30 minutes to obtain solution C. Potassium hydroxide was then dissolved in 30 ml of methanol and stirred for 30 minutes to obtain solution D. Solution C in the three-necked flask was heated in an oil bath at 60°C, and solution D was slowly dripped into solution C. A white precipitate appeared. After stirring for 2 hours, the white precipitate was centrifuged and washed three times with deionized water and ethanol respectively to remove surface impurities. It was then dried in an oven at 80°C for 24 hours and ground to obtain ZnO nanomaterials.

[0038] Preparation of ZnO / 11.11PAN composite nanomaterials:

[0039] S1: Disperse 100 mg of zinc oxide in 25 ml of N,N-dimethylformamide (DMF) solution and sonicate for 30 minutes to obtain solution A. Simultaneously, disperse 11.11 mg of PAN in another 25 ml of N,N-dimethylformamide solution and sonicate for 30 minutes to obtain solution B. Solution A and solution B are mixed to obtain a mixed solution.

[0040] S2: The mixed solution obtained in step S1 was vigorously stirred at room temperature at a speed of 700 r / min for 18 h to obtain a mixed solution.

[0041] S3: The mixed solution obtained in step S2 was centrifuged to obtain a white precipitate, which was then washed three times with water and ethanol respectively to remove impurities on the surface of the white precipitate. The precipitate was dried in a forced air drying oven at 80° C. for 24 h to obtain a ZnO / 11.11PAN composite material as a photocatalyst.

[0042] This embodiment also provides an application of the above-mentioned photocatalyst or the photocatalyst prepared by the above-mentioned photocatalyst preparation method as a photocatalytic water decomposition hydrogen production method. 0.35M Na2S and 0.25M Na2SO3 solutions are used as sacrificial agents.

[0043] Example 2:

[0044] Preparation of ZnO / 25PAN composite nanomaterials:

[0045] S1: Disperse 100 mg of zinc oxide in 25 ml of N,N-dimethylformamide (DMF) solution and sonicate for 30 minutes to obtain solution A. Simultaneously, disperse 25 mg of PAN in another 25 ml of N,N-dimethylformamide solution and sonicate for 30 minutes to obtain solution B. Mix solutions A and B to obtain a mixed solution.

[0046] S2: The mixed solution obtained in step S1 was vigorously stirred at room temperature at a speed of 700 r / min for 18 h to obtain a mixed solution.

[0047] S3: The mixed solution obtained in step S2 was centrifuged to obtain a white precipitate, which was then washed three times with water and ethanol respectively to remove impurities on the surface of the white precipitate. The precipitate was dried in a forced air drying oven at 80° C. for 24 h to obtain a ZnO / 25PAN composite material as a photocatalyst.

[0048] Example 3:

[0049] Preparation of ZnO / 42.88PAN composite nanomaterials:

[0050] S1: Disperse 100 mg of zinc oxide in 25 ml of N,N-dimethylformamide (DMF) solution and sonicate for 30 minutes to obtain solution A. Simultaneously, disperse 42.88 mg of PAN in another 25 ml of N,N-dimethylformamide solution and sonicate for 30 minutes to obtain solution B. Mix solutions A and B to obtain a mixed solution.

[0051] S2: The mixed solution obtained in step S1 was vigorously stirred at room temperature at a speed of 700 r / min for 18 h to obtain a mixed solution.

[0052] S3: The mixed solution obtained in step S2 was centrifuged to obtain a white precipitate, which was then washed three times with water and ethanol respectively to remove impurities on the surface of the white precipitate. The precipitate was dried in a forced air drying oven at 80° C. for 24 h to obtain a ZnO / 42.88PAN composite material as a photocatalyst.

[0053] Phase characterization of prepared ZnO, ZnO / APAN and PAN:

[0054] Figure 1The XRD patterns of PAN, ZnO, ZnO / 11.1PAN, ZnO / 25PAN, and ZnO / 42.88PAN are shown. PAN exhibits a strong diffraction peak at 16.3° and a weak diffraction peak at 29.3°, which are attributed to the (100) and (110) crystal plane diffraction of PAN, respectively. Pure ZnO exhibits relatively sharp diffraction peaks at 31.3°, 34.6°, 36.1°, 47.7°, 56.2°, 62.9°, and 67.7°, corresponding to the (100), (002), (101), (102), (110), (103), and (112) crystal plane diffraction of hexagonal ZnO (JCPDS No. 36-1451). No impurity peaks are found, indicating good crystallinity and high purity. Due to the weak diffraction intensity, high dispersion and low concentration of PAN, the PAN / ZnO composite material only shows obvious diffraction of pure ZnO, and no diffraction peak of PAN is observed.

[0055] Morphological characterization of prepared ZnO, ZnO / APAN and PAN:

[0056] The micromorphology and fine structure of ZnO, PAN and ZnO / 25PAN were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 2 and Figure 3 It can be seen that the morphology of ZnO and PAN samples are both irregular granular, with similar stacking phenomenon, and the size of ZnO particles is obviously much smaller than that of PAN particles. Figure 4 The morphology of the composite sample shows that the morphology has changed and has become more uniformly shaped nanoparticles. This may be due to the collision and close combination of ZnO nanoparticles and PAN nanoparticles during the composite process. The fine structure of the sample was further studied by TEM. Figure 5 and Figure 6 It can be seen that ZnO is in the form of smaller nanoparticles, while PAN exists in the form of irregular nanoparticles. Combined with XRD test, poor crystallinity is the main reason for the uneven morphology of PAN. Figure 7 As shown in Figure 2, the nanoparticle morphology of the sample is consistent with the SEM analysis results. Two distinguishable lattice fringes were observed by high-resolution transmission electron microscopy (HR-TEM), with crystal spacing of 0.247 and 0.260 nm, corresponding to the (101) and (001) crystal planes of hexagonal ZnO ( Figure 8 ). In addition, the EDS mapping of the ZnO / 25PAN sample shows the distribution of Zn, O, C, and N elements in the heterojunction, verifying the uniform distribution of Zn, O, C, and N elements in the composite material, further confirming the successful preparation of the ZnO / PAN photocatalyst.

[0057] Fourier transform infrared spectra of the prepared ZnO, ZnO / APAN and PAN:

[0058] Figure 9 The FTIR spectra of ZnO, PAN, and ZnO / APAN are shown. As can be seen from the figure, PAN has a peak at about 2941 cm -1 (—CH2 stretching), 2250cm -1 (C≡N stretching), 1729cm -1 (C=O stretching) and 1458 cm -1 There is an obvious infrared spectrum signal at (-CH2 bending). The FTIR spectrum of the composite sample is at 2941, 2250, 1729, 1458 cm -1 The FTIR peak of PAN is shown at 37°, but due to the low content of PAN in the synthesized ZnO / APAN composite, the FTIR peak intensity of PAN is weak. Therefore, the FTIR analysis results show that ZnO / APAN contains ZnO and PAN, proving that the two are successfully composited.

[0059] Photocatalytic water decomposition and hydrogen production performance test of the prepared ZnO, ZnO / APAN and PAN under simulated sunlight:

[0060] The photocatalytic water splitting activity of the ZnO / APAN nanocomposite for hydrogen evolution was investigated by photocatalytic water splitting under full-spectrum illumination. The photocatalytic hydrogen production experiments were conducted on top of a quartz bottle (250 mL) under simulated low-temperature solar irradiation. Typically, 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 repeatedly 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 a 300 W xenon lamp for 3 hours, and hydrogen production was monitored every 30 minutes using a gas chromatograph (GC-9790II, Ar, TCD detector).

[0061] Depend on Figure 10-11 It can be seen that under simulated sunlight, a series of ZnO / APAN samples have good photocatalytic performance for hydrogen production from water.

[0062] Specific: Through Figure 10 It can be seen that ZnO / 25PAN has the best photocatalytic performance.

[0063] pass Figure 11 It can be seen that the photocatalyst provided by the present invention has stable photocatalytic performance.

[0064] In this embodiment, the optimal hydrogen production rate of ZnO / 25PAN is 7.53 mmol·h -1 ·g -1 , which are 9.8 times and 31.7 times of pure ZnO and PAN respectively. The photocatalyst is a ZnO / APAN composite material.

[0065] The ZnO / 25PAN photocatalyst has a wider light absorption spectrum and can more fully absorb sunlight. The present invention uses a physical stirring method to synthesize the ZnO / PAN heterojunction photocatalyst. By introducing PAN, the separation of photogenerated electrons and holes in ZnO is improved, the light absorption range of ZnO is expanded, and more excellent photocatalytic performance is achieved. The construction of the heterojunction provides more active sites for the reactant molecules, enhancing the rapid generation and separation of electron-hole pairs, while providing a good transfer path for carriers, better avoiding photocorrosion. The composite material ZnO / APAN has superior photocatalytic water decomposition and hydrogen production performance compared to pure ZnO or PAN.

[0066] Doping ZnO with PAN effectively improves charge transfer, inhibits electron-hole pair recombination, increases specific surface area, and enhances photocatalytic hydrogen production activity. The heterojunction increases the number of active sites on the photocatalyst, promotes the separation of photogenerated electron-hole pairs, overcomes the photocorrosion effect of a single ZnO catalyst, and demonstrates excellent photocatalytic stability and sustainability. Under the same illumination conditions, the composite material exhibits superior hydrogen production performance compared to pure ZnO and PAN.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An application of a photocatalyst in photocatalytic water decomposition to produce hydrogen, characterized by: The photocatalyst is a ZnO / PAN composite material, wherein the mass ratio of ZnO to polyacrylonitrile (PAN) is 100:(11.11-42.88); The preparation method of the photocatalyst comprises the following steps: S1: Disperse zinc oxide in N,N-dimethylformamide solution and sonicate for 25-40 minutes to obtain solution A. Simultaneously, disperse polyacrylonitrile (PAN) in another N,N-dimethylformamide solution and sonicate for 25-40 minutes to obtain solution B. Mix solution A and solution B to obtain a mixed solution. S2: Stir the mixed solution obtained in step S1 for 17-19 hours to obtain a mixed solution; S3: The mixed solution obtained in step S2 is centrifuged to obtain a precipitate, which is then washed to remove impurities on the surface of the precipitate, and then dried to obtain a ZnO / PAN composite material, which is a photocatalyst.

2. The use according to claim 1, characterized in that 0.30-0.40M Na2S and 0.20-0.30MNa2SO3 solutions were used as sacrificial agents.

3. The use according to claim 1, characterized in that: In the ZnO / PAN composite material, the mass ratio of ZnO to PAN is 100:11.11, 100:25 or 100:42.

88.

4. The use according to claim 1, characterized in that: In step S2, the mixed solution obtained in step S1 is stirred at room temperature at a speed of 500-800 r / min for 17-19 hours.

5. The use according to claim 1, characterized in that: In step S3, the obtained precipitate is washed with water and ethanol 2-4 times respectively to remove surface impurities.

6. The use according to claim 1, characterized in that: In step S3, drying is performed in a 70-90° C. forced air drying oven for 16-25 hours.

7. The use according to claim 1, characterized in that: The preparation method of ZnO in step S1 comprises the following steps: Disperse zinc acetate dihydrate in a three-necked flask filled with methanol and stir for 25-35 minutes to obtain solution C. Then, dissolve potassium hydroxide in methanol and stir for 25-35 minutes to obtain solution D. Heat solution C in the three-necked flask in an oil bath at 55-65°C, and slowly drop solution D into solution C to produce a precipitate. After stirring for 1.8-2.2 hours, the precipitate is centrifuged and washed with deionized water and ethanol for 2-4 times respectively to remove surface impurities. Then, the precipitate is dried in an oven at 70-90°C for 16-25 hours and ground to obtain ZnO nanomaterials.

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