A perovskite ultrathin graphite phase carbon nitride heterojunction photocatalyst, a preparation method and application thereof

Abstract

The application discloses a perovskite ultrathin graphite phase carbon nitride heterojunction photocatalyst and a preparation method and application thereof, and the preparation method comprises the following steps: under inert gas, ball milling boron-doped nitrogen-defect graphite phase carbon nitride, dimethylamine hydrobromide and a tin source with a substance amount ratio of (1-9):(1-9):(1-12) to obtain the perovskite ultrathin graphite phase carbon nitride heterojunction photocatalyst. The photocatalyst has excellent photocatalytic water decomposition performance, good dispersibility and stable storage, the whole preparation process can be realized at room temperature, the operation is simple, controllability is strong, repeatability is good, raw materials are cheap and widely sourced, no organic solvent is involved in the reaction process, environmental pollution can be avoided to a certain extent, the photocatalyst is green, safe, environment-friendly, beneficial to large-scale preparation and practical application, and can be widely used in the fields of photocatalytic water decomposition, artificial photosynthesis, organic pollutant degradation and gas oxidation / reduction.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, and specifically relates to a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] Inspired by natural photosynthesis, semiconductor-based Z-type heterojunction systems are considered one of the most efficient systems for achieving photocatalytic water splitting. This system consists of two semiconductors with matched band structures: a semiconductor with a lower conduction band potential is used for photocatalytic hydrogen production, while a semiconductor with a higher valence band potential is used for photocatalytic oxygen production. Charge carriers are directionally transported through the interface at the junction of the two semiconductors, achieving an ordered oxidation / reduction reaction cycle. This Z-type system divides the water splitting process into two steps, overcoming the kinetic and thermodynamic bottlenecks of single-semiconductor photocatalysts in the water splitting process, and has therefore attracted widespread research attention. To date, several Z-type photocatalytic systems have been successfully developed, such as strontium titanate / bismuth vanadate (J. Am. Chem. Soc. 2017, 139, 1675-1683), strontium titanate / tungsten trioxide (J. Phys. Chem. C 2017, 121, 9691-9697), tantalum nitride / tungsten trioxide (Chem. Sci. 2017, 8, 437-443), metal sulfide / titanium dioxide (J. Am. Chem. Soc. 2015, 137, 604-607), and black phosphorus / bismuth vanadate (Angew. Chem. Int. Ed. 2018, 57, 2160-2164). These Z-type systems have a certain ability to completely split water, but due to problems such as slow carrier transport and low driving force for redox reactions, the performance of completely splitting water still needs to be improved. Furthermore, most of these Z-type systems contain transition metals, resulting in high preparation costs and a tendency to cause heavy metal pollution. Therefore, in the field of photocatalytic water splitting, Z-type systems composed of abundant non-metallic elements are gradually demonstrating great potential and attracting significant research interest. Summary of the Invention

[0003] To overcome the problems of high cost and metal contamination in the preparation of Z-type systems using transition metals in the existing technology, the purpose of this invention is to provide a low-cost, large-scale production-suitable perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst, its preparation method, and its application. This method has low preparation cost and does not contain heavy metals.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst includes the following steps:

[0006] In an inert gas atmosphere, boron-doped nitrogen-defective graphitic carbon nitride, dimethylamine hydrobromic acid, and a tin source in a molar ratio of (1-9):(1-9):(1-12) are ball-milled to obtain a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst.

[0007] A further improvement of the present invention is that the inert gas is argon, nitrogen or helium.

[0008] A further improvement of the present invention is that the molar ratio of boron-doped nitrogen-defective graphitic carbon nitride, dimethylamine hydrobromic acid and tin source is 2:1:1, 1:1:3, 1:1:9, 9:9:1 or 1:1:12.

[0009] A further improvement of this invention is that the tin source is stannous bromide.

[0010] A further improvement of the present invention is that the ball milling speed is 100-400 rpm and the ball milling time is 6-24 hours; the ball milling is carried out by a method of milling for 0.5-2 hours and then stopping for 0.25-1 hour.

[0011] A further improvement of this invention is that boron-doped nitrogen-defective graphitic carbon nitride is prepared through the following process:

[0012] NaBH4 and polymer carbon nitride nanosheets were mixed evenly and then calcined at 300-550℃ under an inert gas to obtain boron-doped nitrogen-defect graphitic carbon nitride.

[0013] A further improvement of the present invention is that the polymer carbon nitride nanosheets are prepared by the following process:

[0014] Melamine, cyanuric acid, urea, biuret or Milleramine are calcined at 450-600℃ for 2-6 hours to obtain graphitic carbon nitride.

[0015] Graphitic carbon nitride was added to water, sonicated, centrifuged, and the suspension was freeze-dried to obtain polymer carbon nitride nanosheets.

[0016] A further improvement of this invention is that the ultrasonic power is 800-1800W, the ultrasonic time is 2-8 hours, and the ultrasonic process is performed by cycling for 1-4 seconds and stopping for 1-4 seconds.

[0017] A perovskite ultrathin graphitic carbon nitride heterostructure.

[0018] Application of a perovskite ultrathin graphitic carbon nitride heterojunction in photocatalytic water splitting, artificial photosynthesis, degradation of organic pollutants, or gas oxidation / reduction.

[0019] Compared with existing technologies, the present invention has the following advantages:

[0020] This invention utilizes boron-doped nitrogen-defective graphitic carbon nitride, dimethylamine hydrobromic acid, and a tin source as raw materials to prepare a heterojunction photocatalyst through ball milling. XRD characterization of the obtained perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst clearly shows that it retains the characteristic peaks of dimethylamine tin bromide (DMASnBr3) and boron-doped nitrogen-defective graphitic carbon nitride (BDCN). This photocatalyst exhibits excellent photocatalytic water splitting performance, good dispersibility, and stable storage. The entire preparation process can be carried out at room temperature, is simple to operate, highly controllable, and reproducible. The raw materials are inexpensive and widely available. The absence of organic solvents in the reaction process helps to avoid environmental pollution to a certain extent, making it green, safe, and environmentally friendly, and conducive to large-scale preparation and practical applications.

[0021] Furthermore, boron-doped nitrogen-defective graphitic carbon nitride was synthesized using thermal polymerization, and ultrathin polymeric carbon nitride nanosheets were synthesized using a two-step ultrasonic-calcination method. These nanosheets were then rapidly calcined under an inert gas environment to synthesize boron-doped nitrogen-defective graphitic carbon nitride. The preparation method is simple and easy to implement.

[0022] Furthermore, freeze-drying allows the perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst to possess a large specific surface area and excellent dispersibility, providing abundant surface active sites for the catalytic reaction and contributing to higher reaction activity. The entire preparation process of this invention is simple to operate, highly controllable, and reproducible. The raw materials are inexpensive and widely available, making it green, safe, and environmentally friendly, suitable for large-scale production.

[0023] Due to the non-toxic nature of carbon nitride, perovskite ultrathin graphitic carbon nitride heterojunction photocatalysts can be widely used in photocatalytic water splitting, artificial photosynthesis, and degradation of organic pollutants. In perovskite ultrathin graphitic carbon nitride heterojunction photocatalysts, DMASnBr3 / BDCN... 450 At a mass ratio of 1:3, it exhibits excellent photocatalytic water splitting efficiency, with the highest hydrogen and oxygen generation rates reaching 100 and 50 μmol h⁻¹, respectively. -1 DMASnBr3 / BDCN 325 At a mass ratio of 1:3, it exhibits excellent photocatalytic phenyl bromination reaction, with the highest hydrogen-to-5,5'-dibromo-2,2'-dianthiophene formation rates reaching 367 and 351 μmol h⁻¹, respectively. -1 For the degradation of nitro pollutants, such as p-nitrophenol, DMASnBr3 / BDCN 450 At a mass ratio of 3:1, it exhibits excellent photocatalytic degradation efficiency of nitro pollutants, achieving a degradation rate of 98% in 3 hours for a 10 mmol / L p-nitrophenol simulated solution. Attached Figure Description

[0024] Figure 1 The images shown are data from the perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst prepared in Example 1 of this invention, where (a) is a transmission electron microscope image of DMASnBr3; (b) is a BDCN image. 325 Transmission electron microscope image; (c) DMASnBr3 / BDCN 325 Transmission electron microscope image; (d) is DMASnBr3 / BDCN 325 High-resolution transmission electron microscope image.

[0025] Figure 2 The images show the XRD data of the perovskite ultrathin graphite phase carbon nitride heterojunction photocatalysts prepared in Examples 1-5 and 8-9 of this invention.

[0026] Figure 3 The perovskite ultrathin graphitic carbon nitride heterojunction photocatalysts prepared in Examples 1-5 of this invention under standard AM1.5 illumination (100 mW cm⁻¹) -2 The data is shown in the following figure, where Figure a is DMASnBr3:BDCN. t The heterojunction photocatalytic water splitting performance is at a ratio of 9:1; Figure b shows the DMASnBr3:BDCN ratio. t The heterojunction photocatalytic water splitting performance at a ratio of 3:1; Figure c shows the DMASnBr3:BDCN ratio. t The heterojunction photocatalytic water splitting performance is shown at a 1:1 ratio; Figure d shows the DMASnBr3:BDCN ratio. t The heterojunction photocatalytic water splitting performance is 1:3; Figure e shows the DMASnBr3:BDCN ratio. t The heterojunction photocatalytic water splitting performance at a ratio of 1:9. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] The present invention discloses a method for preparing a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst, comprising the following steps:

[0029] S1. Place 2g of precursor (melamine, cyanuric acid, urea, biuret or Milleramine, etc.) in a covered alumina crucible made of ceramic, corundum, etc. Calcine in air at 450-600℃ for 2-6 hours with a heating rate of 2-10℃ / min. After cooling to room temperature, yellow blocky graphitic carbon nitride, i.e., PCN, is obtained and then pulverized.

[0030] Add 0.05-5g PCN to 40-4000mL of deionized water, stir under high-power ultrasound for 6 hours, centrifuge, and freeze-dry the suspension for 24-72 hours to obtain solid A; wherein, the power of high-power ultrasound is 800-1800W, the stirring time is 2-8 hours, and the stirring is carried out by circulating for 1-4 seconds and stopping for 1-4 seconds.

[0031] S2, 0.04-1.6 g NaBH4 and 0.1-4 g solid A are mixed and ground finely. Then, in an inert gas (nitrogen) environment, the mixture is heated to 300-550 °C at a heating rate of 10-50 °C / s and calcined for 0.5-2 hours. After cooling to room temperature, the mixture is filtered and washed repeatedly with ethanol and deionized water to remove unreacted NaBH4. The mixture is then freeze-dried for 24-72 hours to obtain boron-doped nitrogen-defective graphitic carbon nitride, i.e., solid B, denoted as BDCN. t , where t is the calcination temperature, for example, calcination temperature is 450℃.

[0032] S3, in an inert gas environment (argon, nitrogen, or helium), solid B, DMABr (dimethylamine hydrobromic acid), and SnBr2 in a molar ratio of (1-9):(1-9):(1-12) (preferably 2:1:1, 1:1:3, 1:1:9, 9:9:1, or 1:1:12) are placed in a container and ground by ball milling to obtain the target product, a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst, denoted as DMASnBr3 / BDCN. t Where t is the calcination temperature. The ball milling method uses a rotation speed of 100-400 rpm and a grinding time of 6-24 hours, employing a method of grinding for 0.5-2 hours and stopping after 0.25-1 hour. The ball / reagent mass ratio is 1:40.

[0033] The perovskite ultrathin graphitic carbon nitride heterojunction prepared by the method exhibits excellent photocatalytic water splitting performance, with the highest hydrogen and oxygen generation rates reaching 100 and 50 μmol h⁻¹, respectively. -1 It exhibits good dispersibility in water and can be stably stored for 1-2 years. The entire preparation process of this invention is simple to operate, highly controllable, and reproducible. The raw materials are inexpensive and widely available, making it green, safe, and suitable for large-scale production.

[0034] The application of the perovskite ultrathin graphitic carbon nitride heterojunction in photocatalytic water splitting, artificial photosynthesis, degradation of organic pollutants, or gas oxidation / reduction.

[0035] Among them, DMASnBr3 / BDCN 450 At a mass ratio of 1:3, it exhibits excellent photocatalytic water splitting efficiency, with the highest hydrogen and oxygen generation rates reaching 100 and 50 μmol h⁻¹, respectively. -1 .

[0036] This invention discloses a method for preparing a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The method employs a safe and easy-to-operate three-step process of ultrasonication, calcination, and ball milling to prepare the perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The resulting heterojunction photocatalyst exhibits a novel structure, excellent photocatalytic water splitting performance, good dispersibility, and stable storage. The entire preparation process is characterized by short reaction time, low reaction temperature, simple operation, strong controllability, good reproducibility, inexpensive and widely available raw materials, and is environmentally friendly and suitable for large-scale preparation and practical applications. This invention enriches the research field of heterojunction photocatalysts and accumulates valuable experience for the development of high-efficiency photocatalysts.

[0037] The preparation method of this invention includes synthesizing bulk PCN using thermal polymerization, synthesizing ultrathin polymerized carbon nitride nanosheets using a two-step ultrasonic-calcination method, then rapidly calcining boron-doped and nitrogen-deficient PCN nanosheets in an inert gas environment, synthesizing DMASnBr3 using ball milling, and finally constructing DMASnBr3 / BDCN using the same ball milling method. t Heterogeneous structures were used to obtain perovskite ultrathin graphitic carbon nitride heterojunction photocatalysts.

[0038] The present invention will now be described in detail with reference to the accompanying drawings and several preferred embodiments.

[0039] Example 1

[0040] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0041] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0042] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 325 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0043] 4) Under argon atmosphere, solid B, DMABr, and SnBr2 were placed in a container at a mass ratio of 1:1:9 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40, yielding a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst contained DMASnBr3:BDCN. t The ratio is 9:1, and the property parameters are as follows: Figure 3 As shown in Figure c, the highest hydrogen production rate reached 18 μmol / h. -1 The oxygen production rate reached a maximum of 8 μmol / h. -1 .

[0044] Example 2

[0045] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0046] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0047] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 325 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0048] 4) Under argon atmosphere, solid B, DMABr, and SnBr2 were placed in a container at a mass ratio of 1:1:3 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40, yielding a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst contained DMASnBr3:BDCN. t The ratio is 3:1, and the property parameters are as follows: Figure 3 As shown in Figure c, the highest hydrogen production rate reached 23 μmol / h. -1The oxygen production rate reached a maximum of 11 μmol / h. -1 .

[0049] Example 3

[0050] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0051] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0052] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 325 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0053] 4) Under argon atmosphere, solid B, DMABr, and SnBr2 were placed in a container at a mass ratio of 1:1:1 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40, yielding a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst contained DMASnBr3:BDCN. t The ratio is 1:1, and the property parameters are as follows: Figure 3 As shown in Figure c, the highest hydrogen production rate reaches 50 μmol / h. -1 The oxygen production rate reached a maximum of 25 μmol / h. -1 .

[0054] from Figure 1 From (a)-(d), we can see that DMASnBr3 successfully anchored to BDCN. 325 Furthermore, the grain boundary between the two can be clearly observed using a high-resolution transmission electron microscope.

[0055] Example 4

[0056] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0057] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0058] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 450 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0059] 4) Under argon atmosphere, solid B, DMABr, and SnBr2 were loaded into a jar at a mass ratio of 1:3:1 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40, yielding a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The resulting perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst contained DMASnBr3:BDCN. t The ratio is 1:3, and the property parameters are as follows: Figure 3 As shown in Figure d, the hydrogen production rate reaches a maximum of 100 μmol / h. -1 The oxygen production rate reached a maximum of 50 μmol / h. -1 .

[0060] Example 5

[0061] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0062] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0063] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 500 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0064] 4) Under argon atmosphere, solid B, DMABr, and SnBr2 were loaded into a jar at a mass ratio of 1:9:1 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40, yielding a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst. The resulting perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst contained DMASnBr3:BDCN. t The ratio is 1:9, and the property parameters are as follows: Figure 3 As shown in Figure e, the highest hydrogen production rate reached 58 μmol / h. -1 The oxygen production rate reached a maximum of 40 μmol / h. -1 .

[0065] Figure 3 a, b, c, d, and e represent the performance parameters of the perovskite ultrathin graphitic carbon nitride heterojunction photocatalysts obtained in Examples 1 to 5. It can be seen that in the perovskite ultrathin graphitic carbon nitride heterojunction photocatalysts obtained by this invention, DMASnBr3:BDCN... t The heterojunction structure is stable, and the highest photocatalytic water splitting hydrogen production rate can reach 100 μmol / h. -1 It exhibits excellent visible light photocatalytic water splitting performance for hydrogen production.

[0066] Example 6

[0067] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0068] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0069] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 375 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0070] 4) Under argon atmosphere, solid B, DMABr and SnBr2 were loaded into a container in a mass ratio of 9:9:1 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40 to obtain perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst.

[0071] Example 7

[0072] 1) Melamine (2g) was calcined in air at 520°C for 4 hours in a covered alumina crucible at a heating rate of 5°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0073] 2) Add 0.5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 6 hours (2 seconds cycle, 2 seconds stop). After centrifugation, freeze-dry the resulting suspension for 48 hours to obtain solid A, weighing approximately 0.26g.

[0074] 3) Grind 0.4 g of solid A and 0.16 g of NaBH4 into a fine powder, and then calcine them at 425 °C in nitrogen at a rate of 20 °C / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0075] 4) Under argon atmosphere, solid B, DMABr and SnBr2 were loaded into a container in a mass ratio of 1:1:12 and ground at 300 rpm for 12 hours (1 hour cycle, 30 minutes stop). The ball / reagent ratio was 1:40 to obtain perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst.

[0076] Example 8

[0077] 1) Melamine (2g) was calcined in air at 450°C for 6 hours in a covered alumina crucible at a heating rate of 2°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0078] 2) Add 0.05 g of the pre-prepared block PCN to a 500 mL glass beaker containing 40 mL of deionized water. Stir the mixture under high-power sonication (1500 W) for 2 hours (1 second cycle, 1 second stop). After centrifugation, freeze-dry the resulting suspension for 24 hours to obtain solid A, weighing approximately 0.26 g.

[0079] 3) Grind 0.04 g of solid A and 0.1 g of NaBH4 into a fine powder, and then calcine them at 300 °C in nitrogen at a rate of 10 °C / s for 2 hours. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0080] 4) Solid B, DMABr and SnBr2 were loaded into a container in a mass ratio of 2:1:1 under argon atmosphere and ground at 100 rpm for 6 hours (0.5 hours of circulation, 60 minutes of stop). The ball / reagent ratio was 1:40 to obtain perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst.

[0081] Example 9

[0082] 1) Melamine (2g) was calcined in air at 600℃ for 2 hours in a covered alumina crucible at a heating rate of 10℃ / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0083] 2) Add 5g of the pre-prepared block PCN to a 500ml glass beaker containing 400ml of deionized water. Stir the mixture under high-power sonication (1500W) for 8 hours (4 seconds cycle, 4 seconds stop). After centrifugation, freeze-dry the resulting suspension for 72 hours to obtain solid A, weighing approximately 0.26g.

[0084] 3) Grind 0.1g of solid A and 1g of NaBH4 into a fine powder, then calcine them at 550℃ in nitrogen at a rate of 30℃ / s for 0.5 hours. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0085] 4) Solid B, DMABr and SnBr2 were loaded into a container in an argon atmosphere at a mass ratio of 5:3:10 and ground at 400 rpm for 24 hours (1 hour cycle, 25 minutes stop). The ball / reagent ratio was 1:40 to obtain a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst.

[0086] Example 10

[0087] 1) Melamine (2g) was calcined in air at 500°C for 4 hours in a covered alumina crucible at a heating rate of 7°C / min. After cooling to room temperature, the resulting yellow blocky PCN was crushed.

[0088] 2) Add 2g of the pre-prepared block PCN to a 500ml glass beaker containing 200ml of deionized water. Stir the mixture under high-power sonication (1500W) for 5 hours (3 seconds cycle, 3 seconds stop). After centrifugation, freeze-dry the resulting suspension for 60 hours to obtain solid A, weighing approximately 0.26g.

[0089] 3) Grind 1.6g of solid A and 4g of NaBH4 into a fine powder, then calcine them at 400℃ in nitrogen at a rate of 50℃ / s for 1 hour. After cooling to room temperature, wash the powder several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B is obtained.

[0090] 4) Solid B, DMABr and SnBr2 were loaded into a container in a mass ratio of 7:2:5 under argon atmosphere and ground at 200 rpm for 20 hours (2 hours of circulation, 30 minutes of stop). The ball / reagent ratio was 1:40 to obtain perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst.

[0091] Example 11

[0092] Same as Example 1, except that in step 3), 1.6 g of solid A and 4 g of NaBH4 were ground into a fine powder, and then calcined in nitrogen at 350°C for 1 hour at a rate of 40°C / s. After cooling to room temperature, the powder was washed several times with ethanol and deionized water to remove unreacted NaBH4. After a 48-hour freeze-drying process, solid B was obtained.

[0093] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0094] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. The application of a perovskite ultrathin graphite-phase carbon nitride heterojunction photocatalyst in the photocatalytic degradation of p-nitrophenol, characterized in that, The preparation method of the photocatalyst includes the following steps: In an inert gas atmosphere, boron-doped nitrogen-defective graphitic carbon nitride, dimethylamine hydrobromide, and a tin source in a molar ratio of (1-9):(1-9):(1-12) are ball-milled to obtain a perovskite ultrathin graphitic carbon nitride heterojunction photocatalyst; wherein the inert gas is argon or helium, and the tin source is stannous bromide; Among them, boron-doped nitrogen-defective graphitic carbon nitride is prepared through the following process: NaBH4 and polymer carbon nitride nanosheets were mixed evenly and then calcined at 300-550℃ under an inert gas to obtain boron-doped nitrogen-defect graphitic carbon nitride.

2. The application according to claim 1, characterized in that, The ball mill speed is 100-400 rpm, and the ball milling time is 6-24 hours; the ball milling is carried out by grinding for 0.5-2 hours and then stopping for 0.25-1 hour.

3. The application according to claim 1, characterized in that, Polymer carbon nitride nanosheets are prepared through the following process: Melamine, cyanuric acid, urea, biuret or Milleramine are calcined at 450-600℃ for 2-6 hours to obtain graphitic carbon nitride. Graphitic carbon nitride was added to water, sonicated, centrifuged, and the suspension was freeze-dried to obtain polymer carbon nitride nanosheets.

4. The application according to claim 3, characterized in that, The power of the ultrasound is 800-1800 W, and the ultrasound time is 2-8 hours.

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