A method for preparing an h-BN / Fe-ZnO / porous g-C3N4 composite photocatalyst

Abstract

This invention discloses a method for preparing an h-BN / Fe-ZnO / g-C3N4 composite photocatalyst. The preparation method includes the following steps: first, mixing an iron source and zinc acetate dihydrate, titrating with an alkaline solution, filtering, washing, vacuum drying, and grinding to obtain a Fe-ZnO precursor; then mixing the Fe-ZnO precursor with urea, h-BN, and ascorbic acid in a covered alumina crucible and calcining in a muffle furnace to obtain a solid material; finally, grinding the solid material to obtain the h-BN / Fe-ZnO / g-C3N4 composite photocatalyst. The h-BN / Fe-ZnO / g-C3N4 composite photocatalyst prepared by this invention can effectively separate electron-hole pairs, reduce the electron-hole recombination rate, and thus effectively improve photocatalytic activity. This material exhibits excellent degradation performance for Rhodamine B water pollutants. Using 40 mg h-BN / Fe-ZnO / g-C3N4 composite photocatalyst under a 300W xenon lamp with a wavelength λ≥420 nm to simulate visible light, 100 mL of Rhodamine B with a concentration of 20 mg / L was degraded. After 90 minutes, the degradation efficiency reached 98.4%, and after five cycles, the degradation rate still reached 80.1%, demonstrating good reusability.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, specifically relating to h-BN / Fe-ZnO / g-C3N4 composite photocatalysts, their preparation methods, and applications. Background Technology

[0002] With industrial development, environmental pollution has become increasingly serious, especially the treatment of organic pollutants in water bodies, which has become a major challenge. To address this problem, researchers have begun to focus on photocatalysis, a green technology that uses light energy to decompose organic pollutants.

[0003] ZnO exhibits high photocatalytic activity, but it also has certain limitations, such as poor stability, a wide photocatalytic bandgap (3.37 eV), and rapid recombination of photogenerated electron-hole pairs. Through Fe... 3+ Doping reduces the band gap and increases the visible light absorption range. While g-C3N4 has advantages such as good stability and a wide visible light response range, its activity is relatively low in practical applications. Therefore, urea is co-fired with ascorbic acid to form oxygen-deficient carbon nitride, which inhibits electron-hole recombination. Compared with ZnO and g-C3N4, hexagonal boron nitride (h-BN) has a wider band gap, larger specific surface area, and better chemical and thermal stability. To fully utilize the advantages of these three materials, a composite of Fe-ZnO, g-C3N4, and h-BN can be formed. This can alter the electronic structure and electron transfer pathway, improve the quantum efficiency of the photocatalyst, capture electrons, inhibit electron-hole recombination, and enhance photocatalytic activity.

[0004] Furthermore, selective degradation of organic pollutants can be achieved by adjusting the composition and structure of the composite material. In summary, the technological background for the degradation of organic pollutants using the h-BN / Fe-ZnO / g-C3N4 composite photocatalyst is the severity of environmental pollution and the demand for green technologies. This technology, by combining the advantages of the three materials, improves photocatalytic activity, stability, and visible light response range, providing an effective means to solve environmental pollution problems.

[0005] Patent CN113457704A discloses a Fe2O3-ZnO / g-C3N4 composite material, its preparation method, and its application. The method involves calcining urea at 550℃ to form g-C3N4. Dimethylimidazole dissolved in methanol is slowly added dropwise to a methanol solution containing a mixture of Zn(NO3)2·6H2O and Fe(NO3)3·9H2O to form a precipitate, which is then mixed with the g-C3N4 and dried. The dried precipitate is then uniformly ground and transferred to a tube furnace, heated to 550℃ in air, and calcined to obtain the final product. This method requires two calcinations, resulting in high energy consumption and high preparation costs. Patent CN109225307A discloses an Eu... 3+The process involves dissolving zinc nitrate and europium nitrate in water, adding selenium-containing hydrazine hydrate, stirring for 30-45 min, then heating to 160-180℃ and reacting for 12-16 h. After natural cooling to room temperature, the mixture is filtered, and the precipitate is washed with deionized water and dried. The resulting precipitate is then ground evenly with melamine in a mortar and placed in a muffle furnace. The temperature is increased to 500℃ at a rate of 10℃ / min, held for 2 hours, and then naturally cooled to room temperature to obtain the desired Eu content. 3+ Se co-doped ZnO / g-C3N4 materials. Summary of the Invention

[0006] The purpose of this invention is to provide a simple, low-cost, and highly efficient method for preparing an h-BN / Fe-ZnO / g-C3N4 composite photocatalyst. The aim is to utilize h-BN, g-C3N4, and Fe... 3+ Compared to pure g-C3N4, the doped ZnO composite provides more active sites, a larger specific surface area, and superior photocatalytic activity, laying a certain theoretical foundation for the treatment of organic dye wastewater.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A highly efficient visible light-catalyzed catalyst for the degradation of methylene blue—h-BN / Fe-ZnO / g-C3N4—is obtained by co-firing Fe-ZnO precursor, urea, h-BN, and ascorbic acid in a covered crucible. The resulting composite material exhibits highly efficient photocatalytic activity.

[0009] The preparation method of the above-mentioned h-BN / Fe-ZnO / g-C3N4 composite photocatalyst includes the following steps:

[0010] Step 1: Mix the iron source and zinc acetate dihydrate, titrate with an alkaline solution while stirring continuously until the precipitate is completely formed, filter, wash, vacuum dry, and grind to obtain the Fe-ZnO precursor.

[0011] Step 2: The Fe-ZnO precursor obtained in Step 1 is mixed with urea, h-BN and ascorbic acid and placed in a covered alumina crucible. The mixture is then calcined in a muffle furnace to obtain a solid material. After grinding, the solid material is used to obtain an h-BN / Fe-ZnO / g-C3N4 composite photocatalyst.

[0012] In step 1, the iron source is one of FeCl3•6H2O, Fe(NO3)3•9H2O, or Fe2(SO4)3•6H2O, the alkaline solution is NaOH solution, the molar ratio of the iron source to zinc acetate dihydrate is 0.01~0.1:1, and the stirring time is 2h.

[0013] In step 1, the alkaline solution is NaOH solution or KOH solution.

[0014] In step 2, the crucible is a 50 mL covered crucible, and the calcination temperature in the muffle furnace is from room temperature to 500℃ at a heating rate of 10℃ / min, and the calcination time at 500℃ is 2 hours.

[0015] In step 2, the mass ratio of h-BN, urea, ascorbic acid and Fe-ZnO precursor is 2:400:0~1:0~3.

[0016] The above-mentioned h-BN / Fe-ZnO / g-C3N4 composite photocatalyst can be used for the catalytic degradation of organic dye pollutants under visible light. The organic dye pollutant is Rhodamine B.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The h-BN / Fe-ZnO / g-C3N4 composite photocatalyst provided by this invention facilitates effective separation of photogenerated electrons and holes, reduces the recombination rate, and can effectively improve photocatalytic activity.

[0019] 2. The preparation method of the h-BN / Fe-ZnO / g-C3N4 composite photocatalyst provided by the present invention uses inexpensive and readily available raw materials, is simple and convenient to operate, greatly reduces costs, and the prepared composite photocatalyst is environmentally friendly, realizing green chemistry.

[0020] 3. The 40 mg 100FZ-OBCN provided by this invention was added to 100 mL of a 20 mg / L Rhodamine B solution. After sonication for 30 minutes in the dark, it was irradiated with a 300 W xenon lamp to simulate visible light (λ ≥ 420 nm). After irradiation for 90 minutes, the degradation rate of Rhodamine B reached 98.4%, and after five cycles, the degradation rate could still reach 80.1%, showing good reusability. Attached Figure Description

[0021] Figure 1 The image shows a TEM image of the 100FZ-OBCN prepared in Example 5.

[0022] Figure 2 SEM image of 100FZ-OBCN prepared in Example 5. From Figure 2It can be seen that 100FZ-OBCN exhibits a loose porous structure and a sheet-like structure, which is beneficial for providing more adsorption sites and improving photocatalytic performance.

[0023] Figure 3 These are FT-IR images of CN, BCN, OCN, 100FZ-BCN, and 100FZ-OBCN prepared in Examples 1-5.

[0024] Figure 4 XRD patterns of CN, BCN, OCN, 100FZ-BCN and 100FZ-OBCN prepared in Examples 1-5.

[0025] Figure 5 The visible light catalytic degradation efficiency of Rhodamine B by CN, BCN, OCN, 100FZ-BCN and 100FZ-OBCN prepared in Examples 1-5 is shown in the figure.

[0026] Figure 6 The visible light catalytic degradation cycle diagram of Rhodamine B by 100FZ-OBCN prepared in Example 5 is shown. Detailed Implementation

[0027] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0028] Example 1

[0029] (1) Weigh 20 g of urea and place it in a 100 mL alumina crucible and cover it with the crucible lid. Heat it in a muffle furnace and raise the temperature from room temperature to 500 ℃ at a rate of 10 ℃ / min under an air atmosphere. Hold the temperature for 2 h and then cool it with the furnace. Finally, grind it to obtain a light yellow g-C3N4 powder sample (CN).

[0030] (2) Weigh 40 mg CN and add it to 100 mL of a 20 mg / L Rhodamine B solution. After sonicating in the dark for 30 minutes, irradiate with a 300 W xenon lamp simulating visible light (λ ≥ 420 nm). Take 3 mL of the solution every 15 minutes to test the degradation rate of Rhodamine B. For example... Figure 5 The degradation efficiency of CN was 62.2% after 90 minutes of light exposure.

[0031] Example 2

[0032] (1) Weigh 20 g of urea and 50 mg of ascorbic acid, mix them evenly in a 100 mL alumina crucible and cover the crucible. Heat treat in a muffle furnace, raise the temperature from room temperature to 500 ℃ at a rate of 10 ℃ / min in air atmosphere, and hold for 2 h. Then cool with the furnace and finally grind to obtain a gray-black g-C3N4 powder sample (OCN).

[0033] (2) Weigh 40 mg OCN and add it to 100 mL of a 20 mg / L Rhodamine B solution. After sonicating in the dark for 30 minutes, irradiate with a 300 W xenon lamp simulating visible light (λ ≥ 420 nm). Take 3 mL of the solution every 15 minutes to test the degradation rate of Rhodamine B. For example... Figure 5 The degradation efficiency of OCN was 71.5% after 90 minutes of light exposure.

[0034] Example 3

[0035] (1) Weigh 20 g of urea and 100 mg of h-BN and mix them evenly in a 100 mL alumina crucible and cover it with the crucible lid. Heat treat it in a muffle furnace. Under an air atmosphere, heat the temperature from room temperature to 500 °C at a rate of 10 °C / min and hold it for 2 h. Then cool it with the furnace and finally grind it to obtain a light yellow h-BN / g-C3N4 powder sample (BCN).

[0036] (2) Weigh 40 mg BCN and add it to 100 mL of a 20 mg / L Rhodamine B solution. After sonicating in the dark for 30 minutes, irradiate with a 300 W xenon lamp simulating visible light (λ ≥ 420 nm). Take 3 mL of the solution every 15 minutes to test the degradation rate of Rhodamine B. For example... Figure 5 The degradation efficiency of BCN was 68.2% after 90 minutes of light exposure.

[0037] Example 4

[0038] (1) Weigh 9.5 g (0.0433 mol) zinc acetate dihydrate and 0.62 g (0.0023 mol) ferric chloride hexahydrate, keeping their molar mass fraction constant at 0.0456 mol. Add the weighed reagents to 85 ml of deionized water and stir for 1 h to obtain a homogeneous mixed solution. Weigh 2.8 g of sodium hydroxide and dissolve it in 15 ml of deionized water while stirring continuously to obtain a sodium hydroxide solution. Place the obtained sodium hydroxide solution in a separatory funnel and slowly and uniformly add it dropwise to the above-mentioned continuously stirred mixed solution. As the sodium hydroxide solution is added, precipitates continuously form in the solution. After stirring for 1 h, filter and separate the precipitate, and wash the precipitate multiple times with deionized water and anhydrous ethanol. Dry the washed product in a vacuum at 80 °C for 24 h, then grind it to obtain the Fe-ZnO precursor (FZ).

[0039] (2) Weigh 20 g of urea, 100 mg of Fe-ZnO precursor and 100 mg of h-BN, mix them evenly and place them in a 100 mL alumina crucible and cover the crucible. Heat treat in a muffle furnace. Under air atmosphere, heat from room temperature to 500 ℃ at a heating rate of 10 ℃ / min and hold for 2 h. Then cool with the furnace and finally grind to obtain a light gray h-BN / Fe-ZnO / g-C3N4 composite photocatalyst (100FZ-BCN).

[0040] (3) Weigh 40 mg of 100FZ-BCN and add it to 100 mL of a 20 mg / L Rhodamine B solution. After sonicating in the dark for 30 minutes, irradiate with a 300 W xenon lamp simulating visible light (λ ≥ 420 nm). Take 3 mL of the solution every 15 minutes to test the degradation rate of Rhodamine B. For example... Figure 5 The degradation efficiency of 100FZ-BCN was 93.4% after 90 minutes of light exposure.

[0041] Example 5

[0042] (1) Weigh 9.5 g (0.0433 mol) zinc acetate dihydrate and 0.62 g (0.0023 mol) ferric chloride hexahydrate, keeping their molar mass fraction constant at 0.0456 mol. Add the weighed reagents to 85 ml of deionized water and stir for 1 h to obtain a homogeneous mixed solution. Weigh 2.8 g of sodium hydroxide and dissolve it in 15 ml of deionized water while stirring continuously to obtain a sodium hydroxide solution. Place the obtained sodium hydroxide solution in a separatory funnel and slowly and uniformly add it dropwise to the above-mentioned continuously stirred mixed solution. As the sodium hydroxide solution is added, precipitates continuously form in the solution. After stirring for 1 h, filter and separate the precipitate, and wash the precipitate multiple times with deionized water and anhydrous ethanol. Dry the washed product in a vacuum at 80 °C for 24 h, then grind it to obtain the Fe-ZnO precursor (FZ).

[0043] (2) Weigh 20 g of urea, 100 mg of Fe-ZnO precursor, 50 mg of ascorbic acid and 100 mg of h-BN, mix them evenly and place them in a 100 mL alumina crucible and cover the crucible. Heat treat in a muffle furnace. Under air atmosphere, heat from room temperature to 500 °C at a heating rate of 10 °C / min and hold for 2 h. Then cool with the furnace and finally grind to obtain a light gray h-BN / Fe-ZnO / g-C3N4 composite photocatalyst (100FZ-OBCN).

[0044] (3) Weigh 40 mg of 100FZ-OBCN and add it to 100 mL of a 20 mg / L Rhodamine B solution. After sonicating in the dark for 30 minutes, irradiate with a 300 W xenon lamp simulating visible light (λ ≥ 420 nm). Take 3 mL of the solution every 15 minutes to test the degradation rate of Rhodamine B. Figure 5 After 90 minutes of light exposure, the degradation efficiency of 100FZ-OBCN was 98.2%.

[0045] Figure 3 These are the FT-IR spectra of CN, BCN, OCN, 100FZ-BCN, and 100FZ-OBCN prepared in Examples 1-5. CN, BCN, and OCN did not show significant changes in absorption peaks, while 100FZ-BCN and 100FZ-OBCN showed a peak at 2043 cm⁻¹ after FZ addition. -1 The appearance of a peak caused by the -N=C=N asymmetric stretching vibration is due to zinc cyanamide, a byproduct produced during the calcination of zinc oxide and urea, which indirectly indicates the successful composite of FZ and OBCN.

[0046] Figure 4 The XRD patterns of CN, BCN, OCN, 100FZ-BCN and 100FZ-OBCN prepared in Examples 1-5 are shown. According to the standard card comparison, the 100FZ-OBCN showed that h-BN, FZ and OCN were successfully compounded.

[0047] Figure 5 The visible light photocatalytic degradation efficiency of Rhodamine B by CN, BCN, OCN, 100FZ-BCN, and 100FZ-OBCN prepared in Examples 1-5 is shown in the graphs. The photocatalytic performance gradually improves with the addition of h-BN, ascorbic acid, and FZ. Finally, 100FZ-OBCN exhibits the best photocatalytic effect.

[0048] Example 6

[0049] 40 mg of 100FZ-OBCN (prepared in Example 5) was weighed and added to 100 mL of a 20 mg / L Rhodamine B solution. After sonication for 30 minutes in the dark, the solution was irradiated with a 300 W xenon lamp simulating visible light (λ ≥ 420 nm) for 90 minutes. After the reaction was complete, the solution was separated by centrifugation, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 4 hours. The recovered 100FZ-OBCN was used in the next catalytic cycle. The cycle results are as follows: Figure 6 After five cycles, the photocatalytic degradation efficiency of 100FZ-OBCN still reached 80.1%.

[0050] The above description is only a preferred embodiment of the present invention. Any modifications and substitutions made within the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. The use of an h-BN / Fe-ZnO / g-C3N4 composite photocatalyst in the catalytic degradation of organic dye pollutants under visible light, characterized in that, The preparation method of the composite photocatalyst comprises the following steps: Step 1, mixing an iron source and zinc acetate dihydrate, titrating with an alkaline solution, and continuously stirring until the precipitate is completely precipitated, and then filtering, washing, vacuum drying, and grinding to obtain a Fe-ZnO precursor; the iron source is one of FeCl3·6H2O, Fe(NO3)3·9H2O, and Fe2(SO4)3·6H2O, and the molar ratio of the iron source to zinc acetate dihydrate is 0.01-0.1:1; Step 2, mixing the Fe-ZnO precursor obtained in Step 1 with urea, h-BN, and ascorbic acid in an alumina crucible with a cover, and calcining in a muffle furnace to obtain a solid material, and then grinding the solid material to obtain a h-BN / Fe-ZnO / g-C3N4 composite photocatalyst; the mass ratio of h-BN, urea, ascorbic acid, and the Fe-ZnO precursor is 2:400:0-1:0-3; wherein the mass of neither ascorbic acid nor the Fe-ZnO precursor is 0.

2. Use according to claim 1, characterized in that: In Step 1, the stirring time is 2 h.

3. Use according to claim 1, characterized in that: In Step 1, the alkaline solution is any one of a NaOH solution or a KOH solution.

4. Use according to claim 1, characterized in that: In Step 2, the crucible is a 100 mL crucible with a cover, the calcination temperature in the muffle furnace is room temperature to 500℃, the temperature rising rate is 10℃ / min, and the calcination time at 500℃ is 2 h.

5. The use according to claim 1, characterized in that, The organic dye pollutant is rhodamine B.

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