A hybrid BPO4 / g-C3N4 nanocomposite material and its preparation method and application

Abstract

The present invention relates to a hybrid BPO4 / g-C3N4 nanocomposite material and its preparation method and application. The present invention uses urea as a precursor to prepare graphite-like carbon nitride powder, impregnates the graphite-like carbon nitride powder with a configured H3PO4 and H3BO3 aqueous solution, uses an ultrasonic cell crusher for ultrasonic treatment, freeze-drying, and then places it in a muffle furnace for high-temperature calcination to finally obtain a hybrid BPO4 / g-C3N4 nanocomposite material. Compared with the prior art, the present invention increases the specific surface area of ​​carbon nitride and increases its catalytic active sites through an ultrasonic dispersion method; at the same time, hybrid non-metallic BPO4 crystals are dispersed on carbon nitride nanosheets, thereby enhancing the photocatalytic oxidation ability of the BPO4 / g-C3N4 nanocomposite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional composite materials, and in particular relates to a hybrid BPO4 / g-C3N4 nanocomposite material and a preparation method and application thereof. Background Art

[0002] Photocatalyst technology can convert low-density solar energy into high-density chemical energy, such as degrading organic matter, decomposing water to produce hydrogen and oxygen, reducing carbon dioxide, etc. The development of new photocatalysts that can effectively utilize visible light has attracted widespread attention worldwide. Graphitic carbon nitride (g-C3N4, CN) is a very promising metal-free photocatalyst with a suitable band gap (2.7eV), good chemical stability, and good environmental compatibility. However, g-C3N4 prepared by traditional methods has disadvantages such as low visible light utilization efficiency, few active sites, weak oxidation ability, and small specific surface area, which limit its application in photocatalytic degradation of organic matter. CN 108355696 A discloses a black phosphorus / g-C3N4 composite visible light photocatalytic material for visible light degradation of organic pollutants. However, the oxidation ability of black phosphorus and the connection stability with g-C3N4 are relatively weak, and the photocatalytic performance of the composite photocatalytic material still needs to be improved. Summary of the Invention

[0003] The purpose of the present invention is to provide a hybrid BPO4 / g-C3N4 nanocomposite material and its preparation method and application to improve the photocatalytic activity of g-C3N4.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material, characterized by comprising the following steps:

[0006] (1) Calcination of urea to prepare g-C3N4;

[0007] (2) Immersing the prepared g-C3N4 in a mixed solution of H3PO4 and H3BO3, stirring, ultrasonicating, and drying;

[0008] (3) calcining the sample obtained in step (2) to obtain a BPO4 / g-C3N4 nanocomposite photocatalyst.

[0009] Furthermore, in step (1), the calcination temperature is 550-620°C, preferably 550-600°C, and more preferably 600°C.

[0010] Furthermore, in step (1), the heating rate of the calcination is 5-10°C / min, preferably 5°C / min.

[0011] Furthermore, in step (1), the calcination time is 3-4 hours, preferably 3 hours.

[0012] Furthermore, in step (2), the molar concentrations of H3PO4 and H3BO3 in the mixed aqueous solution of H3PO4 and H3BO3 are the same.

[0013] Furthermore, the concentrations of H3PO4 and H3BO3 are both 0.5-1 mol / L, preferably 0.5-0.8 mol / L, and more preferably 0.7 mol / L.

[0014] Furthermore, in step (2), the mass ratio of H3BO3:H3PO4:g-C3N4 is 1:1.6:(2-16).

[0015] Furthermore, in step (2), the stirring time is 1-3 hours, preferably 2 hours.

[0016] Furthermore, in step (2), the stirring speed is 300-500 rpm, preferably 400 rpm.

[0017] Furthermore, in step (2), the ultrasonication time is 1-3 hours, preferably 2 hours.

[0018] Furthermore, the ultrasound is processed using an ultrasonic cell disruptor.

[0019] Furthermore, in step (3), the calcination temperature is 530-580°C, preferably 550-580°C, and more preferably 550°C.

[0020] Furthermore, the heating rate of the calcination is 5-10°C / min, preferably 10°C / min.

[0021] Furthermore, the calcination time is 2-3 hours, preferably 2 hours.

[0022] The present invention also provides a hybrid BPO4 / g-C3N4 nanocomposite material obtained by the above preparation method.

[0023] The present invention also provides an application of a hybrid BPO4 / g-C3N4 nanocomposite material in the field of photocatalytic oxidation, specifically in the photocatalytic treatment of organic pollutants, preferably rhodamine B and levofloxacin.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention combines non-metallic boron phosphate (BPO4) with strong oxidizing ability and excellent thermal stability with g-C3N4 to form a nanocomposite material, which overcomes the shortcomings of g-C3N4 itself, such as low oxidation potential and weak oxidizing ability, and greatly improves the photocatalytic activity of carbon nitride.

[0026] (2) The boron (B) in the non-metallic boron phosphate (BPO4) used in the present invention is always in an oxidation state of +3 and has a strong oxidizing ability. After chemical reaction with g-C3N4, a covalent bond is formed to connect the two. The formation of this covalent bond can increase the interfacial stability between the two materials. In addition, the boron atoms can also change the local electronic structure of the carbon nitride structure, increase the accurate positioning of electrons and the ability to capture photogenerated holes. This can effectively prevent the recombination of electrons and holes, improve the efficiency of electron-hole separation, and further promote the degradation of organic matter.

[0027] (3) The present invention uses an ultrasonic cell crusher to further disperse g-C3N4, thereby increasing the interlayer spacing of g-C3N4 and further increasing the specific surface area, which can expose more active sites and is more conducive to the loading of hybrid BPO4 and the exposure of active sites, thereby increasing the overall oxidation capacity and photocatalytic activity of the BPO4 / g-C3N4 nanocomposite material.

[0028] (4) The present invention does not require the introduction of metal elements, which reduces the metal element content in the photocatalytic organic pollutants, and the preparation process and catalytic degradation process are more environmentally friendly; at the same time, the preparation method of the present invention is simple and easy to implement, and has broad application prospects in the field of photocatalytic degradation of organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the hybrid BPO4 / g-C3N4 prepared in Example 1.

[0030] Figure 2 Schematic diagram of the energy dispersive spectrometer (EDS) of the hybrid BPO4 / g-C3N4 prepared in Example 4.

[0031] Figure 3 X-ray diffraction (XRD) patterns of the hybrid BPO4 / g-C3N4 composite photocatalyst prepared in Example 1 and g-C3N4 prepared in Comparative Example 1.

[0032] Figure 4 These are the photocatalytic degradation curves of Rhodamine B by different samples prepared in Examples 1-4 and Comparative Examples 1-2.

[0033] Figure 5 These are the photocatalytic degradation curves of levofloxacin by different samples prepared in Examples 1-4 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Unless otherwise specified, the reagents, methods, instruments, and equipment used in the present invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples were commercially available and of analytical grade. Phosphoric acid (≥85 wt%), boric acid, and urea were purchased from Sinopharm Chemical Reagent Co., Ltd., rhodamine B and levofloxacin were purchased from Shanghai Titan Technology Co., Ltd., and the ultrasonic cell disruptor was a Xinzhi JY88-IIN.

[0036] Example 1:

[0037] 20 g of urea was placed in a crucible and calcined at 600°C in a muffle furnace for 3 h (heating rate of 5°C / min) to produce g-C3N4. A 0.7 mol / L mixed aqueous solution of H3PO4:H3BO3 was prepared at a molar ratio of 1:1. 0.5 g of g-C3N4 was dispersed in 30 mL of deionized water. The H3PO4-H3BO3 mixture was pipetted dropwise into the g-C3N4 suspension at a mass ratio of 1:1.6:2 for H3BO3:H3PO4:g-C3N4. After stirring at 400 rpm for 2 h at room temperature, the mixture was sonicated for 2 h using an ultrasonic cell disrupter. The treated sample was freeze-dried in a vacuum oven (-80°C, pressure <0.05 MPa) and then calcined again at 550°C in a muffle furnace for 2 h at a heating rate of 10°C / min to produce BPO4 / g-C3N4.

[0038] Example 2:

[0039] 20 g of urea was weighed into a crucible and calcined in a muffle furnace at 600°C for 3 h (heating rate of 5°C / min) to produce g-C3N4. A 0.7 mol / L mixed aqueous solution was prepared with a 1:1 molar ratio of H3PO4:H3BO3. 0.5 g of g-C3N4 was dispersed in 30 mL of deionized water. The mixed solution was pipetted and added dropwise to the g-C3N4 suspension using a H3BO3:H3PO4:g-C3N4 mass ratio of 1:1.6:4. After stirring at 400 rpm for 2 h at room temperature, the mixture was sonicated for 2 h using an ultrasonic cell disrupter. The treated sample was freeze-dried in a vacuum oven (-80°C, pressure <0.05 MPa) and then calcined again in a muffle furnace at 550°C for 2 h at a heating rate of 10°C / min to produce BPO4 / g-C3N4.

[0040] Example 3:

[0041] 20 g of urea was placed in a crucible and calcined at 600°C in a muffle furnace for 3 h (heating rate of 5°C / min) to produce g-C3N4. A 0.7 mol / L mixed aqueous solution was prepared with a 1:1 molar ratio of H3PO4:H3BO3. 0.5 g of g-C3N4 was dispersed in 30 mL of deionized water. The mixed solution was pipetted and added dropwise to the g-C3N4 suspension using a H3BO3:H3PO4:g-C3N4 mass ratio of 1:1.6:8. After stirring at 400 rpm for 2 h at room temperature, the mixture was sonicated for 2 h using an ultrasonic cell disrupter. The treated sample was freeze-dried in a vacuum oven (-80°C, pressure <0.05 MPa) and then calcined again at 550°C in a muffle furnace for 2 h at a heating rate of 10°C / min to produce BPO4 / g-C3N4.

[0042] Example 4:

[0043] 20 g of urea was placed in a crucible and calcined at 600°C in a muffle furnace for 3 h (heating rate of 5°C / min) to produce g-C3N4. A 0.7 mol / L mixed aqueous solution was prepared with a 1:1 molar ratio of H3PO4:H3BO3. 0.5 g of g-C3N4 was dispersed in 30 mL of deionized water. The mixed solution was pipetted and added dropwise to the g-C3N4 suspension using a H3BO3:H3PO4:g-C3N4 mass ratio of 1:1.6:16. After stirring at 400 rpm for 2 h at room temperature, the mixture was sonicated for 2 h using an ultrasonic cell disrupter. The treated sample was freeze-dried in a vacuum oven (-80°C, pressure <0.05 MPa) and then calcined again at 550°C in a muffle furnace for 2 h at a heating rate of 10°C / min to produce BPO4 / g-C3N4.

[0044] Comparative Example 1:

[0045] Weigh 20g of urea into a crucible and calcine in a muffle furnace at 600°C for 3h (heating rate of 5°C / min), followed by sonication for 2h using an ultrasonic cell disruptor. The sonicated sample was freeze-dried in a vacuum (-80°C, pressure <0.05MPa) to obtain g-C3N4 powder.

[0046] Comparative Example 2:

[0047] Dissolve 0.02 mol of H3PO4 and 0.02 mol of H3BO3 in 30 ml of deionized water, evaporate using a rotary evaporator, dry at 70°C for 12 h, and then calcine at 550°C in a muffle furnace for 2 h at a heating rate of 10°C / min to obtain BPO4 powder.

[0048] The present invention performs the following tests on Examples 1-4 and Comparative Examples 1-2:

[0049] (1) The surface morphology of Example 1 was characterized using a scanning electron microscope (S-4800) and a transmission electron microscope (JEM-2100).

[0050] (2) The elements of BPO4 / g-C3N4 prepared in Example 4 were analyzed using an X-ray spectrometer (Bruker D8 ADVANCE).

[0051] (3) X-ray diffraction (Bruker D8 ADVANCE) was used to characterize the material composition of Example 1 and Comparative Example 1.

[0052] (4) Photocatalytic degradation performance test: 50 mg of the sample of the embodiment or comparative example was weighed and dispersed in 50 mL of a rhodamine B or levofloxacin solution with an initial concentration of 10 mg / L to test its photocatalytic performance. The magnetic stirrer was turned on and dark adsorption was performed for 30 min to allow the catalyst and the target degradation product to reach adsorption-desorption equilibrium. Subsequently, a 500 W xenon lamp was turned on and 3.5 mL of the sample was sampled every 30 min and centrifuged at 9000 r / min for 5 min to remove the catalyst particles. The supernatant was taken and the absorbance of the solution was measured at the maximum absorption wavelength (554 nm for rhodamine B and 284 nm for levofloxacin) using a UV-3100 ultraviolet-visible spectrophotometer.

[0053] like Figure 1 (a) As shown in the SEM image, the hybrid BPO4 / g-C3N4 is a stacked layer structure, proving that the addition of BPO4 does not change the structure of g-C3N4. Figure 1 (b) TEM image shows that the black part marked with a circle is hybrid BPO4, and it can be seen that hybrid BPO4 is loaded on the g-C3N4 nanosheets.

[0054] like Figure 2 As shown, the EDS map shows the distribution of C, N, B, P, and O elements, further proving the successful preparation of hybrid BPO4 / g-C3N4.

[0055] like Figure 3As shown in the figure, there are two relatively obvious diffraction peaks at around 13.6° and 27.2°, which correspond to the diffraction peaks of the (100) and (002) crystal planes of graphitic carbon nitride, respectively. In addition to the characteristic peaks at around 13.6° and 27.2°, the hybrid BPO4 / g-C3N4 has two new characteristic peaks at around 24.5° and 40°, which correspond to the diffraction peaks of the (101) and (112) crystal planes of BPO4, respectively. This shows that the hybrid BPO4 prepared by the chemical reaction of H3PO4 and H3BO3 has been successfully loaded onto g-C3N4.

[0056] Figure 4 and Figure 5 The photocatalytic degradation curves of rhodamine B and levofloxacin by different samples prepared in Examples 1-4 of the present invention and Comparative Examples 1 and 2 are shown respectively. Figure 4 It can be seen that after 60 minutes of illumination, the degradation rates of Rhodamine B in Examples 1-4 all reached over 96%, while the degradation rates of pure BPO4 and g-C3N4 for Rhodamine B were 52.9% and 57.7%, respectively. Figure 5 As can be seen, after 60 minutes of illumination, the degradation rates of levofloxacin in Examples 1-4 all reached over 96%, while the degradation rates of levofloxacin in pure BPO4 and g-C3N4 were 52.1% and 57.9%, respectively. The above results indicate that the photocatalytic performance of BPO4 / g-C3N4 is significantly improved compared to pure BPO4 and g-C3N4 treated with cell pulverizer ultrasound in the degradation of organic matter. This indicates that under the same reaction conditions, the visible light catalytic performance of BPO4 / g-C3N4 is significantly improved.

[0057] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material, characterized in that: The following steps are involved: (1) Calcination of urea to prepare g-C3N4; (2) Immerse the prepared g-C3N4 in a mixed solution of H3PO4 and H3BO3, stir, ultrasonicate, and dry; (3) calcining the sample obtained in step (2) to obtain a BPO4 / g-C3N4 nanocomposite photocatalyst; In step (2), the mass ratio of H3BO3:H3PO4:g-C3N4 is 1:1.6:(2-16), and ultrasonication is performed using an ultrasonic cell disruptor.

2. The method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material according to claim 1, characterized in that: In step (1), the calcination temperature is 550-620 °C, the calcination heating rate is 5-10 °C / min, and the calcination time is 3-4 h.

3. The method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material according to claim 1, characterized in that: In step (2), the molar concentrations of H3PO4 and H3BO3 in the mixed solution of H3PO4 and H3BO3 are the same, and the concentrations of H3PO4 and H3BO3 are both 0.5-1 mol / L.

4. The method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material according to claim 1, characterized in that: In step (2), the stirring time is 1-3 hours and the rotation speed is 300-500 rpm.

5. The method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material according to claim 1, characterized in that: In step (2), the ultrasonication time is 1-3 hours.

6. The method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material according to claim 1, characterized in that: In step (3), the calcination temperature is 530-580°C, and the calcination heating rate is 5-10°C / min.

7. The method for preparing a hybrid BPO4 / g-C3N4 nanocomposite material according to claim 1, characterized in that: In step (3), the calcination time is 2-3 hours.

8. A hybrid BPO4 / g-C3N4 nanocomposite material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the hybrid BPO4 / g-C3N4 nanocomposite material according to claim 8 in the field of photocatalytic oxidation.

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