Preparation method and application of In2O3 / g-C3N4 heterojunction nanofiber photocatalyst

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method and application of an In2O3 / g-C3N4 heterojunction nanofiber photocatalyst. In2O3 nanofibers prepared by an electrostatic spinning method under high voltage are placed on the upper layer of a porcelain boat with melamine powder laid at the bottom of the porcelain boat, and the In2O3 / g-C3N4 heterojunction nanofiber photocatalyst synthesized by vapor deposition can be applied to the field of hydrogen evolution by photocatalytic decomposition of water. Compared with an existing photocatalyst, the In2O3 / g-C3N4 heterojunction nanofiber photocatalyst has the advantages that the specific surface area is large, more reaction active sites can be provided, and the separation efficiency of current carriers can be further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method and application of an In 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst. Background Art

[0002] The consumption of natural resources such as fossil fuels has a negative impact on the ecosystem, and overuse is the fundamental factor leading to resource depletion. Therefore, the pursuit of renewable resources has received attention. Researchers have found that solar energy is a more cost-effective and environmentally friendly sustainable energy source. Using solar photocatalytic water splitting to produce hydrogen is one of the most promising technologies for developing clean and sustainable hydrogen energy. Therefore, the most crucial goal is to design and manufacture efficient photocatalysts for effective photocatalysis. For photocatalysis, the photocatalyst should have excellent light collection ability, appropriate bandgap width, and high separation efficiency of electrons and holes.

[0003] As a typical n-type semiconductor In 2 O 3 , it has a high permittivity and low resistivity, and has been widely used in gas sensors, solar cells, and photocatalytic water splitting for hydrogen production. However, pure In 2 O 3 faces the problems of poor absorbance and fast carrier recombination. Therefore, synthesizing heterojunctions is an effective method to improve the absorbance of In 2 O 3 and reduce the recombination of electron-hole pairs. The semiconductor to be coupled with it should have appropriate band edge potential to meet the flow direction of interfacial electron water splitting and redox potential. The present invention introduces In 2 O 3 / g-C 3 N 4 to form a heterojunction, which can improve the separation efficiency of photo-generated electron-hole pairs, thereby improving the photocatalytic activity. Summary of the Invention

[0004] To solve the above problems, the present invention provides a preparation method and application of an In 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst.

[0005] The technical solution adopted by the present invention is as follows:

[0006] An In 2 O 3 / g-C 3 N4 Preparation method of heterojunction nanofiber photocatalyst, comprising the following steps:

[0007] 1) Dissolve indium nitrate pentahydrate in a mixed solution of N,N-dimethylformamide and ethanol. After stirring until completely dissolved, add polyvinylpyrrolidone powder to the above mixed solution and stir until the solution becomes colorless and transparent. Electrospinning is carried out at a voltage of 15 kV and a distance of 12 cm from the collecting plate to collect nanofibers;

[0008] 2) Tear the collected nanofibers with scissors and tweezers and place them in a porcelain boat, and calcine them in a muffle furnace to obtain In 2 O 3 nanofibers;

[0009] 3) Grind melamine in a mortar until the powder becomes fine small particles and spread it evenly on the bottom of the porcelain boat; use a piece of porous aluminum foil as a support and place it on the upper layer of the porcelain boat. The distance between the porous aluminum foil and the melamine powder at the bottom of the porcelain boat is 8 mm. Place the In 2 O 3 nanofibers on the porous aluminum foil, cover an empty porcelain boat on it, seal it with two layers of aluminum foil paper, and then transfer it to a muffle furnace for calcination. After the reaction is completed, the sample is preserved to obtain In 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst.

[0010] Further, in the above preparation method, in step 1), the amount of indium nitrate pentahydrate used is 0.8 g, the amount of polyvinylpyrrolidone powder used is 1 g, the amount of N-N-dimethylformamide used is 4 mL, and the amount of ethanol used is 6 mL.

[0011] Further, in the above preparation method, in step 1), the stirring method is to use a magnetic stirrer for stirring.

[0012] Further, in the above preparation method, in step 2), the calcination temperature is 550 °C, the heating rate is 1 °C / min, and the calcination time is 2 h.

[0013] Further, in the above preparation method, in step 3), the calcination temperature is 550 °C, the heating rate is 5 °C / min, and the calcination time is 2 h.

[0014] Further, in the above preparation method, in step 3), the mass ratio of In 2 O 3 nanofibers to melamine is 2.5%, 3.75% or 7.5%.

[0015] In prepared by the preparation method described in any one of the above 2 O 3 / g-C 3 N 4 Application of the heterojunction nanofiber photocatalyst in photocatalytic water splitting for hydrogen evolution.

[0016] Furthermore, for the above application, the method is as follows: Take In 2 O 3 / g-C 3 N 4 The heterojunction nanofiber photocatalyst is uniformly dispersed in a mixed solution of deionized water, triethanolamine and chloroplatinic acid, and then argon is continuously introduced into the container containing the mixed solution at a constant flow rate to obtain a relatively vacuum environment, and photocatalytic water splitting for hydrogen evolution is carried out under visible light irradiation.

[0017] Even further, for the above application, according to the solid-liquid ratio, In 2 O 3 / g-C 3 N 4 Heterojunction nanofiber photocatalyst: deionized water: triethanolamine: chloroplatinic acid = 20 mg: 18 mL: 2 mL: 15 μL.

[0018] The beneficial effects of the present invention are:

[0019] 1. The In 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst prepared by the present invention using the electrospinning method and the vapor deposition method has an ultra-long one-dimensional structure, which can improve the separation efficiency of carriers and enhance the photocatalytic activity.

[0020] 2. The In 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst prepared by the present invention has a stronger ability to absorb visible light, which is an effective way to improve the visible light photocatalytic activity.

[0021] 3. The In 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst prepared by the present invention has good photocatalytic hydrogen evolution performance, and the method is simple to prepare, environmentally friendly, non-toxic, low-cost, and conducive to large-scale production. Description of the Drawings

[0022] Figure 1 For In 2 O 3 、g-C3 N 4 、 In 2 O 3 / g-C 3 N 4 X-ray diffraction pattern of In₂O₃ / g-C₃N₄ heterojunction nanofiber photocatalyst.

[0023] Figure 2 For In 2 O 3 、 g-C 3 N 4 、 In 2 O 3 / g-C 3 N 4 Hydrogen production amount - time curve of In₂O₃ / g-C₃N₄ heterojunction nanofiber photocatalyst for water splitting. Detailed implementation method

[0024] Example 1

[0025] In 2 O 3 / g-C 3 N 4 The preparation method of In₂O₃ / g-C₃N₄ heterojunction nanofiber photocatalyst is as follows:

[0026] 1) Dissolve 0.8 g of indium nitrate pentahydrate in a mixed solution of 4 mL of N, N-dimethylformamide (DMF) and 6 mL of ethanol, stir magnetically until completely dissolved, and add 1 g of polyvinylpyrrolidone powder (PVP) and stir until it becomes colorless and transparent. Draw the obtained solution into a plastic syringe, perform electrospinning, apply a voltage of 15 kV, and the distance between the needle tip and the collector is 12 cm. Collect a dense nanofiber on the aluminum foil with tweezers. Cut the dense nanofiber into a rectangular sheet of 5 cm × 8 cm with scissors, put it into a porcelain boat, and calcine it in a muffle furnace at 550 °C for 2 h (heating rate is 1 °C / min) to obtain In₂O₃ nanofiber. Grind 0.8 g of melamine with a mortar until the powder becomes fine small particles, and spread it evenly on the bottom of the porcelain boat; use a piece of porous aluminum foil as a support and place it on the upper layer of the porcelain boat. The distance between the porous aluminum foil and the melamine powder at the bottom of the porcelain boat is 8 mm. Place 30 mg of In₂O₃ nanofiber on the porous aluminum foil, cover an empty porcelain boat above the porcelain boat, seal it with two layers of aluminum foil paper, and then place it in a muffle furnace and calcine it at 550 °C at a rate of 5 °C / min for 2 h. Wait for it to cool naturally to room temperature to obtain In₂O₃ / g-C₃N₄ heterojunction nanofiber photocatalyst, denoted as In₂O₃ / g-C₃N₄. 2 O 3 Nanofibers. Grind 0.8 g of melamine with a mortar until the powder becomes fine small particles, and spread it evenly on the bottom of the porcelain boat; use a piece of porous aluminum foil as a support and place it on the upper layer of the porcelain boat. The distance between the porous aluminum foil and the melamine powder at the bottom of the porcelain boat is 8 mm. Place 30 mg of In₂O₃ 2 O 3 Nanofibers on the porous aluminum foil, cover an empty porcelain boat above the porcelain boat, seal it with two layers of aluminum foil paper, and then place it in a muffle furnace and calcine it at 550 °C at a rate of 5 °C / min for 2 h. Wait for it to cool naturally to room temperature to obtain In₂O₃ 2 O 3 / g-C 3 N 4 Heterojunction nanofiber photocatalyst, denoted as In₂O₃ / g-C₃N₄. 2 O3 / g-C 3 N 4 -2.

[0027] 2) Preparation method of g-C 3 N 4 : Grind 0.8 g of melamine in a mortar until the powder becomes fine small particles, spread it evenly on the bottom of a porcelain boat and calcine it in a muffle furnace at 550 °C for 2 h (heating rate: 5 °C / min).

[0028] Figure 1 The In prepared in Example 1 2 O 3 / g-C 3 N 4 X-ray diffraction pattern of the heterojunction nanofiber photocatalyst. Characteristic diffraction peaks appear at 2θ = 21.6°, 30.8°, 35.5°, 51.0° and 60.9° in the figure, corresponding to the (211), (222), (400), (440) and (622) crystal planes, which is consistent with the In 2 O 3 PDF standard card (PDF#88-2160). Characteristic diffraction peaks appear at 2θ = 13.2° and 27.3° in the figure, corresponding to the (100) and (002) crystal planes, which is consistent with the g-C 3 N 4 PDF standard card (PDF#85-1726). After the two are combined, it can be seen from Figure 1 that the peaks of both substances appear in the composite sample In 2 O 3 / g-C 3 N 4 , indicating that the two substances are successfully combined.

[0029] Example 2

[0030] At normal temperature and pressure, take 20 mg of the In prepared in Example 1 2 O 3 / g-C 3 N 4 heterojunction nanofiber photocatalyst and disperse it evenly in a mixed solution of 18 mL of deionized water, 2 mL of TEOA (triethanolamine) and 15 μL of chloroplatinic acid. Then, continuously introduce argon into the container containing the mixed solution at a constant flow rate (40 mL / min) to create a relatively vacuum environment. Then, irradiate it with a xenon lamp. After every 30 min of light irradiation reaction, draw the upper gas from the container with a syringe and measure the hydrogen concentration in the upper gas with a gas chromatograph.

[0031] Figure 2It is a graph of the hydrogen production amount - time for photocatalytic water splitting of the sample. It can be seen that after 150 minutes of light irradiation reaction, the hydrogen production amount of In 2 O 3 / g-C 3 N 4 is 2338.09 μmol / g, which is 209.23 times that of pure In 2 O 3 and 4.61 times that of pure g-C 3 N 4 in terms of hydrogen production amount.

Claims

1. A method for preparing In2O3 / g-C3N4 heterojunction nanofiber photocatalyst, characterized in that: The steps include: 1) dissolving indium nitrate tetrahydrate in a mixed solution of N,N-dimethylformamide and ethanol, stirring until completely dissolved, adding polyvinyl pyrrolidone powder to the mixed solution, stirring until the solution is colorless and transparent, and performing electrospinning at a voltage of 15 kV and a distance of 12 cm from a collecting plate to collect nanofibers; 2) The collected nanofibers are torn with scissors and tweezers and placed in a porcelain boat, which is then placed in a muffle furnace for calcination to obtain In2O3 nanofibers; 3) Grind melamine with a mortar until the powder becomes fine small particles and evenly spread on the bottom of the porcelain boat; use a piece of porous aluminum foil as a support and place it on the upper layer of the porcelain boat, with the distance between the porous aluminum foil and the melamine powder at the bottom of the porcelain boat being 8 mm; place In2O3 nanofibers on the porous aluminum foil, put an empty porcelain boat on it, seal it with two layers of aluminum foil, and then transfer it to a muffle furnace for calcination. After the reaction is completed, store the sample to obtain In2O3 / g-C3N4 heterojunction nanofiber photocatalyst.

2. The preparation method according to claim 1, characterized in that: In step 1), the amount of indium nitrate tetrahydrate is 0.8 g, the amount of polyvinyl pyrrolidone powder is 1 g, the amount of NN-dimethylformamide is 4 mL, and the amount of ethanol is 6 mL.

3. The preparation method according to claim 1, characterized in that: In step 1), the stirring method is to use a magnetic stirrer for stirring.

4. The preparation method according to claim 1, characterized in that: Step 2), the calcination temperature is 550°C, the heating rate is 1°C / min, and the calcination time is 2h.

5. The preparation method according to claim 1, characterized in that: Step 3), the calcination temperature is 550°C, the heating rate is 5°C / min, and the calcination time is 2h.

6. The preparation method according to claim 1, characterized in that: In step 3), the mass ratio of In2O3 nanofibers to melamine is 2.5%, 3.75% or 7.5%.

7. Use of the In2O3 / g-C3N4 heterojunction nanofiber photocatalyst prepared by the preparation method according to any one of claims 1 to 6 in photocatalytic water decomposition and hydrogen evolution.

8. The use according to claim 7, characterized in that: The method is as follows: In2O3 / g-C3N4 heterojunction nanofiber photocatalyst is uniformly dispersed in a mixed solution of deionized water, triethanolamine and chloroplatinic acid, and argon gas is continuously introduced into the container containing the mixed solution at a constant flow rate to obtain a relatively vacuum environment, and water is photocatalytically decomposed to release hydrogen under visible light irradiation conditions.

9. The use according to claim 8, characterized in that: According to the solid-liquid ratio, In2O3 / g-C3N4 heterojunction nanofiber photocatalyst: deionized water: triethanolamine: chloroplatinic acid = 20 mg: 18 mL: 2 mL: 15 μL.

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